Experimental Section General Procedures. Manipulations were done using standard Schlenk-and glove... more Experimental Section General Procedures. Manipulations were done using standard Schlenk-and glovebox techniques (O 2 level < 0.1 ppm; N 2 as inert gas). Solvents were dried using an MBraun Solvent Purification System and stored under nitrogen over 4 Å molecular sieves. C 6 D 6 was prepared through freeze-pump-thaw procedures and stored under nitrogen over 4 Å molecular sieves. 1 H NMR spectra were recorded on a Bruker 500 MHz Avance spectrometer at 25 ºC. 1 H chemical shifts are referenced to the residual protons of the deuterated solvent (C 6 D 6 : δ 7.15). Diphenylsila[1]molybdarenophane (1), 1 [Mo(C 6 H 6) 2 ] 1 and [Mo(LiC 6 H 5) 2 ] • tmeda, 2 were synthesized as described in the literature. Me 2 SiCl 2 and iPr 2 SiCl 2 were purchased from Sigma-Aldrich and deoxygenated via a flask-to-flask condensation. Karstedt's catalyst, [{[(H 2 C=CH)Me 2 Si] 2 O}Pt(0)], was purchased from Sigma-Aldrich and use as received. Reaction of 1 with Karstedt's catalyst. Karstedt's catalyst (3 wt% in xylenes, 153 μL, 6.9 mol%) was added dropwise to a solution of 1 (64 mg, 0.15 mmol) in toluene (3 mL) at ambient temperature inside a glovebox. The color of the reaction mixture was changed from brownish yellow to dark brown within 2 h and an aliquot (1 mL) was transferred into a NMR tube. All volatiles were removed from the NMR sample under high vacuum, resulting in a dark brown paste which was dissolved in C 6 D 6 (0.5 mL). The 1 H NMR spectrum showed new product peaks and some residual amounts of 1. The reaction mixture
Bis(cyclopentadienyl)aluminum and-gallium species of the type (Pytsi)ECp 2 [E = Al (2a), Ga (2b);... more Bis(cyclopentadienyl)aluminum and-gallium species of the type (Pytsi)ECp 2 [E = Al (2a), Ga (2b); Pytsi = C(SiMe 3) 2 SiMe 2 (2-C 5 H 4 N)] have been prepared from NaCp and respective dichlorides (Pytsi)ECl 2 in isolated yields of 65% (2a) and 83% (2b). In addition to applying standard methods of characterization (NMR spectroscopy, CHN analysis, and MS), the molecular structures of both compounds were solved by single-crystal X-ray crystallography. Reactions between 2a or 2b with Zr(NMe 2) 4 in benzene, followed by addition of an excess of ClSiMe 3 , gave the first ansa-zirconocene dichlorides with aluminum (4a) or gallium (4b) in bridging position. The gallium compound 4b was isolated in a yield of 40% and characterized by NMR spectroscopy, CHN analysis, and mass spectrometry. The aluminum species 4a could not be obtained in an analytically pure form; it was characterized by NMR spectroscopy, and its molecular structure was determined by single-crystal X-ray analysis. The angle between the two planes of the Cp ligands in 4a was found to be 57.17(11)°, which is larger than in Cp 2 ZrCl 2 (R = 53.5°) and smaller than in silicon-bridged ansa-zirconocene dichlorides (e.g., Me 2 Si(C 5 H 4) 2 ZrCl 2 : R = 60.1°). Crystallization attempts of 4a from DCCl 3 solutions gave crystals of the new species (Pytsi)AlCl[(C 5 H 4)ZrCp] (7), which was characterized by NMR spectroscopy and single-crystal X-ray analysis. In comparison to the Pytsi-containing species 2a and 2b, the less sterically protected compound [2-(Me 2 NCH 2)C 6 H 4 ]AlCp 2 (6), which was prepared from NaCp and [2-(Me 2 NCH 2)C 6 H 4 ]AlCl 2 in yields of 94% and characterized by standard methods (NMR, CHN, and MS), reacted with Zr(NMe 2) 4 to give the known Cp 2 Zr(NMe 2) 2. The targeted ansa-species was not formed, as judged by 1 H NMR spectroscopy. The gallium-bridged compound 4b and Cp 2 ZrCl 2 , respectively, had been tested for polymerizations of ethylene utilizing MAO as an activator (300 equiv of MAO; 5 or 10 μmol of precatalyst; 15 or 70 psi), resulting in activities of 637 to 1080 for 4b and of 640 to 2601 kg PE (mol Zr)-1 h-1 atm-1 for Cp 2 ZrCl 2 .
ABSTRACT Two new [1]ruthenocenophanes, Ru(η5-C5H4)2E(Me2Ntsi) (Me2Ntsi = C(SiMe3)2SiMe2NMe2; E = ... more ABSTRACT Two new [1]ruthenocenophanes, Ru(η5-C5H4)2E(Me2Ntsi) (Me2Ntsi = C(SiMe3)2SiMe2NMe2; E = Al, Ga), bridged by aluminum (3a) and gallium (3b), were synthesized by reaction of dilithioruthenocene with (Me2Ntsi)ECl2 in good to moderate yields (3a, 80%; 3b, 36%). Both species were analyzed by standard techniques (multinuclear NMR spectroscopy, elemental analysis, UV−vis, MS), and their molecular structures were deduced from single-crystal X-ray analysis. Compared to the analogous [1]ferrocenophanes 2a,b, compounds 3a,b showed an increased ring tilt as indicated by the tilt angle α (2a, α = 14.33(14)°; 3a, α = 20.31(19)°; 2b, α = 15.83(19)°; 3b, α = 20.91(19)°). Ring-opening polymerization (ROP) with previously published aluminum- and gallium-bridged [1]ferrocenophanes Fe(η5-C5H4)2E(Pytsi) (Pytsi = C(SiMe3)2SiMe2(2-C6H4N); E = Al (1a), Ga (1b)) and Fe(η5-C5H4)2E(Me2Ntsi) (E = Al (2a), Ga (2b)) and the [1]ruthenocenophanes 3a,b (this paper) has been shown to be very sluggish or unsuccessful. Only the ROP of 1b with [Pd(dba)2] (2 mol %, toluene, 25 °C, 48 h) resulted in polymeric material (GPC analysis: Mw = 2.11 × 104, PDI = 3.0).
Aluminum-and gallium-bridged [1]ferrocenophanes (4a, 4b), [1]chromarenophanes (5a, 5b), and [1]va... more Aluminum-and gallium-bridged [1]ferrocenophanes (4a, 4b), [1]chromarenophanes (5a, 5b), and [1]vanadarenophanes (6a, 6b) were synthesized from the respective dilithiated sandwich compounds with element dichlorides (Me 2 Ntsi)ECl 2 [E) Al, Ga; Me 2 Ntsi) C(SiMe 3) 2 (SiMe 2 NMe 2)] in moderate to high isolated yields (54-97%). The new intramolecularly stabilized aluminum compound (Me 2 NCH 2tsi)AlCl 2 (2a) was synthesized, but was proven to be unreactive with respect to [Fe(LiC 5 H 4) 2 ]‚2/3TMEDA. The diamagnetic species 2a, 4a, 4b, 5a, and 5b were characterized by NMR spectroscopy (1 H, 13 C, 27 Al), CHN elemental analysis, and mass spectrometry, whereas the paramagnetic compounds 6a and 6b were characterized by IR spectroscopy, CHN elemental analysis, and mass spectrometry. In addition, the molecular structures of compounds 2a, 4a, 4b, 5a, 5b, 6a, and 6b were determined by single-crystal X-ray analysis. All [1]cyclophanes are strained species, as revealed by the following tilt angles R [deg]: 14.33(14) (4a), 15.83(19) (4b), 11.81(9) (5a), 13.24(13) (5b), 14.65(14) (6a), and 15.63(14) (6b).
The first example of a [1]ferrocenophane with a heavier group 13 element in the bridging position... more The first example of a [1]ferrocenophane with a heavier group 13 element in the bridging position is described. The [1]aluminaferrocenophane, with the aluminum atom equipped with a bulky and intramolecularly stabilizing ligand, has been synthesized and structurally characterized by NMR spectroscopy and singlecrystal X-ray analysis. In 1975 Osborn and Whiteley described the first [1]ferrocenophane, a strained organometallic compound that contained silicon in the bridging position (ER x) SiPh 2 ; Figure 1). 1 Three decades later, Manners et al. discovered that ring-opening polymerization (ROP) of [1]silaferrocenophanes provides access to poly(ferrocenylsilanes) with high molecular weights. 2 Today, [1]ferrocenophanes with main-group elements in the bridging position are known from group 16 (S, Se), 3,4 15 (P, As), 5-8 14 (Si, Ge, Sn), 1,2,5,6,9-11 and 13 (B) 12,13 elements, with the [1]boraferrocenophanes being the most recent examples in this series (ER x) BN(SiMe 3) 2 , BN(SiMe 3)-tBu, BNiPr 2). However, [1]ferrocenophanes with heavier bridging group 13 elements are unknown today. Surprisingly, even simpler compounds such as ferrocenyl-alanes 14,15 or gallanes are very rare, with some interesting ferrocenylgallanes being characterized recently. 16-18 Within this report we describe the synthesis and structural characterization of the first [1]aluminaferrocenophane. On the basis of our experience with organic ligands that are capable of intramolecular donation, 19-21 we decided to attach a trisyl ligand 22 in which one of the methyl groups is replaced by a 2-pyridyl group to aluminum (trisyl) tris(trimethylsilyl)methyl, C(SiMe 3) 3 ; commonly denoted as Tsi). The ligand C(SiMe 3) 2-(SiMe 2 C 5 H 4 N-2) was described for the first time in 2000, 23 and since then, investigations have been published dealing with new compounds equipped with this ligand. 23-27 Very recently, the first compounds with group 13 elements containing this unique ligand were reported, including the two alanes (Pytsi)AlCl 2 and (Pytsi)AlMe 2 (Pytsi) C(SiMe 3) 2 (SiMe 2 C 5 H 4 N-2)). 28 In-† Dedicated to Professor Peter Paetzold on the occasion of his 70th birthday.
Salt metathesis reaction between Li(thf)(Me 2 Ntsi) [Me 2 Ntsi) C(SiMe 3) 2 SiMe 2 NMe 2 ] and In... more Salt metathesis reaction between Li(thf)(Me 2 Ntsi) [Me 2 Ntsi) C(SiMe 3) 2 SiMe 2 NMe 2 ] and InX 3 gave the new indium dihalides (Me 2 Ntsi)InX 2 [X) Cl (2a), I (2b); isolated yields 34% (2a) and 44% (2b)]. Single-crystal X-ray analysis revealed that 2a is a Cl-bridged dimer, while 2b is monomeric. Salt metathesis reaction between dilithioferrocene and 2a and 2b, respectively, gave the new indium-bridged [1.1]ferrocenophane [(Me 2 Ntsi)In(η 5-C 5 H 4) 2 Fe] 2 (3). Only when 2a was used, could analytically pure 3 be isolated (45%). Revealed by a single-crystal X-ray analysis, compound 3 crystallized as an anti isomer (C i symmetry). The diinda[1.1]ferrocenophane 3 showed fluxional behavior in solution. The proton NMR spectrum of 3 revealed only five singlets at ambient temperature (500 MHz, 25°C, C 6 D 6 or C 7 D 8): one singlet for SiMe 2 , SiMe 3 , and NMe 2 each and two singlets for the 16 Cp protons. These facts can be rationalized by assuming a fast degenerate isomerization from one anti isomer to another anti isomer (time-averaged D 2h symmetry). The two singlets at 4.43 and 4.45 ppm (500 MHz, 25°C, C 7 D 8) of the Rand-protons broadened at lower temperature and coalesced at 5°C. By lowering the temperature further, two sets of signals emerged and became clearly visible at-30°C, with each set consisting of four singlets for the Cp protons of equal intensity. Consistent with the splitting of the Cp signals, all other signals split in two sets of three singlets, indicating C s symmetric Me 2 Ntsi moieties. These data show that the [1.1]ferrocenophane 3 exists as a mixture of two isomers in toluene solutions (2:1 ratio at-30°C). Assuming that the thermodynamically favored isomer was found in the crystal lattice, the most intense set of signals was assigned to the anti isomer of 3, while the less intense set of signals was assigned to a syn isomer. The already known diinda[1.1]ferrocenophane {[2-(Me 2 NCH 2)C 6 H 4 ]In(η 5-C 5 H 4) 2 Fe} 2 (1c) was revisited. Compound 1c did not reveal any fluxional behavior in 1D 1 H NMR spectra at ambient temperature, but EXSY spectroscopy revealed an occurring anti-to-anti isomerization of 1c in solution. A cyclic voltammogram of 3 in thf/0.1 M [Bu 4 N][PF 6 ] showed only an irreversible oxidation. A rationale is given why the reaction of (Me 2 Ntsi)InX 2 [X) Cl (2a), I (2b)] with dilithioferrocene gave a [1.1]ferrocenophane, as similar reactions of (Me 2 Ntsi)ECl 2 (E) Al, Ga) with dilithioferrocene gave strained [1]ferrocenophanes.
On the basis of our previous results with aluminum, we herein report the synthesis of the first g... more On the basis of our previous results with aluminum, we herein report the synthesis of the first gallium-bridged [1]ferrocenophane. The attempt to synthesize the respective indium compound resulted in an unusual ferrocenophane containing an In−(μ-Cl)2−In group in the bridging position. All compounds have been characterized by NMR spectroscopy and single-crystal X-ray structural determination.
The first [1]molybdarenophanes were synthesized and structurally characterized. The aluminum and ... more The first [1]molybdarenophanes were synthesized and structurally characterized. The aluminum and gallium compounds [(Me2Ntsi)Al(η 6-C6H5)2Mo] (2a) and [(Me2Ntsi)Ga(η 6-C6H5)2Mo] (2b) [Me2Ntsi) C(SiMe3)2(SiMe2NMe2)] were obtained from [Mo(LiC6H5)2]‚TMEDA and (Me2Ntsi)ECl2 [E) Al, Ga] in analytical pure form with isolated yields of 74% (2a) and 52% (2b). The silicon-bridged species [Ph2Si-(η 6-C6H5)2Mo] (2c) was synthesized from [Mo(LiC6H5)2]‚TMEDA and Ph2SiCl2. Compound 2c was isolated as a crystalline material in an approximately 90% overall purity, from which a single crystal was used for X-ray analysis. The molecular structures of all three [1]molybdarenophanes 2a-c were determined by singlecrystal X-ray analysis. The ring-tilt angle R was found to be 18.28(17), 21.24(10), and 20.23(29)°for 2a, 2b, and 2c, respectively. Variable temperature NMR measurements of 2a and 2b (-80 to 80°C; 500 MHz) showed a dynamic behavior of the gallium species 2b but not of compound 2a. The dynamic behavior of 2b was rationalized by assuming that the Ga-N donor bond breaks, inversion at the nitrogen atom occurs, and a rotation of the Me 2Ntsi ligand takes place followed by a reformation of the Ga-N bond on the other side of the gallium atom. The analysis of the signals of meta and ortho protons of 2b gave approximate values of ∆G * of 59.6 and 59.1 kJ mol-1 , respectively. Compound 2b reacted with [Pt(PEt3)3] to give the ring-open product [(η 6-C6H6)Mo{η 6-C6H5[GaPh(Me2Ntsi)]}] (3b). The molecular structure of 3b was deduced from a single-crystal X-ray determination. The formation of the unexpected platinum-free product 3b can be rationalized by assuming that benzene reacted with 2b in a 1:1 ratio. Through a series of 1 H NMR experiments with 2b it was shown that small amounts of donor molecules (e.g., THF) in benzene are needed to form 3b; in the absence of a donor molecule, 2b is thermally stable.
The synthesis and structural characterization of the first [1.1]chromarenophanes and the first [1... more The synthesis and structural characterization of the first [1.1]chromarenophanes and the first [1.1]molybdarenophanes are described. A salt-metathesis reaction of [2-(Me 2NCH 2)C 6H 4]AlCl 2 with freshly prepared [Cr(LiC 6H 5) 2].TMEDA (TMEDA = N, N, N&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;, N&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-tetramethylethylenediamine) resulted in the dialumina[1.1]chromarenophane [{2-(Me 2NCH 2)C 6H 4}Al(eta (6)-C 6H 5) 2Cr] 2 ( 2a). The poor solubility of 2a in organic solvents prompted us to synthesize the new intramolecularly coordinated aluminum- and gallium dichlorides [5- tBu-2-(Me 2NCH 2)C 6H 3]ECl 2 [E = Al ( 3a), Ga ( 3b)] in which the phenyl group was equipped with a tert-butyl group. Salt-metathesis reactions of 3a and 3b, respectively, with freshly prepared [M(LiC 6H 5) 2].TMEDA (M = Cr, Mo) resulted in four new [1.1]metallarenophanes of the general type [{5- tBu-2-(Me 2NCH 2)C 6H 3}E(eta (6)-C 6H 5) 2M] 2 [E = Al, M = Cr ( 4a); E = Ga, M = Cr ( 4b); E = Al, M = Mo ( 5a); E = Ga, M = Mo ( 5b)]. 2a, 4a, b, and 5a, b have been structurally characterized by single-crystal analysis [ 2a.1/2C 6H 12: C 48H 56Al 2Cr 2N 2, monoclinic, P2 1/ c, a = 9.9117(9) A, b = 19.9361(16) A, c = 10.638(2) A, alpha = 90 degrees , beta = 112.322(5) degrees , gamma = 90 degrees , Z = 2; 4a.2C 6H 6: C 62H 72Al 2Cr 2N 2, monoclinic, P2 1/ c, a = 10.9626(9) A, b = 19.3350(18) A, c = 12.4626(9) A, alpha = 90 degrees , beta = 100.756(5) degrees , gamma = 90 degrees , Z = 2; 4b.2C 6H 6: C 62H 72Cr 2Ga 2N 2, monoclinic, P2 1/ c, a = 10.8428(2) A, b = 19.4844(4) A, c = 12.4958(2) A, alpha = 90 degrees , beta = 100.6187 degrees , gamma = 90 degrees , Z = 2; 5a.2C 6H 6: C 62H 72Al 2Mo 2N 2, triclinic, P1, a = 10.4377(4) A, b = 11.6510(4) A, c = 11.6514(4) A, alpha = 73.545(3) degrees , beta = 89.318(2) degrees , gamma = 76.120(2) degrees , Z = 1; 5b.2C 6H 6: C 62H 72Ga 2Mo 2N 2, triclinic, P1, a = 10.3451(5) A, b = 11.6752(6) A, c = 11.6900(5) A, alpha = 73.917(3) degrees , beta = 89.550(3) degrees , gamma = 76.774(2) degrees , Z = 1]. All five [1.1]metallarenophanes 2a, 4a, b, and 5a, b crystallize as anti isomers with both Me 2N donor groups in exo positions ( C i point group symmetry). The new [1.1]metallarenophanes show NMR spectra that can be interpreted as being caused by time-averaged C 2 h symmetrical species, which is consistent with the findings of their molecular structures in the solid state. Variable-temperature (1)H NMR measurements for 4a, b and 5a, b (500 MHz; -90 to 90 degrees C) revealed only peak broadening in the lower temperature range of -70 to -90 degrees C. (1)H NMR saturation transfer difference experiments did not show an expected anti-to-anti isomerization, rendering the new [1.1]metallacyclophanes rigid on the NMR time scale. Electrochemical measurements were performed for 4a, b and 5a, b. However, reproducible cyclic voltammograms could only be obtained for the two gallium species 4b and 5b, revealing the expected weak communication between the two transition-metal atoms in both compounds (class II).
Five new intramolecularly coordinated aluminum species, whose molecular structures have been eluc... more Five new intramolecularly coordinated aluminum species, whose molecular structures have been elucidated in solution by NMR spectroscopy and in the solid state by single crystal X-ray analysis, are described. All species are equipped with a trisyl-based ligand with a pyridyl donor group [Pytsi stands for -C(SiMe3)2SiMe2(2-C5H4N)]. While the compound (Pytsi)AlMeCl was accessible either from Li(THF)(Pytsi) and MeAlCl2 or from (Pytsi)AlCl2 and LiMe, the tert-butyl derivative (Pytsi)AltBuCl could only be obtained from Li(THF)(Pytsi) and tBuAlCl2. Attempted synthesis of (Pytsi)AltBuCl from (Pytsi)AlCl2 and LitBu or from (Pytsi)AlCl2 and tBuMgCl failed. Three other compounds (3-5) were synthesized and can be described as derivatives of (Pytsi)AlMe2 with additional groups in the ortho position of the pyridyl group. Compound 3 carried a Me group in the ortho position, while compounds 4 and 5 were equipped with Ph and 2,6-diisopropylphenyl moieties, respectively.Key words: aluminum, trisyl li...
Acta Crystallographica Section E Structure Reports Online, 2005
The structure of the title compound, bis(-ferrocene-1,1 0-diyl)bis[chloro(N,N,N 0 N 0-tetramethyl... more The structure of the title compound, bis(-ferrocene-1,1 0-diyl)bis[chloro(N,N,N 0 N 0-tetramethylethylenediamine)aluminium], [Al 2 Fe 2 Cl 2 (C 5 H 4) 4 (C 6 H 16 N 2) 2 ], possesses a center of inversion and an anti conformation. Bound to each Al atom in the bridging position are one Cl atom and one molecule of N,N,N 0 N 0-tetramethylethylenediamine (TMEDA). The angle between the least-squares planes of the two cyclopentadienyl (Cp) ligands is 3.6 (3). The five C atoms in the Cp rings are staggered on average at an angle of 10.3 (5). Comment Recently, we synthesized the first [1]aluminaferrocenophane, (I), by a metathesis reaction of 1,1 0-dilithioferroceneÁ0.67-TMEDA and (Pytsi)AlCl 2 [Pytsi = C(SiMe 3) 2 SiMe 2 (2-C 5 H 4 N) and TMEDA = N,N,N 0 ,N 0-tetramethylethylenediamine] using toluene as a solvent. Compound (I) was isolated as a crystalline material with one half-molecule of ferrocene (FeCp 2) in the asymmetric unit (Schachner et al., 2005). We assume that FeCp 2 results from the protolysis of 1,1 0-dilithioferrocene, with toluene being the source of protons. Consequently, we substituted toluene by the less acidic solvent hexane with the intention of optimizing the synthesis of (I). However, the title compound, (II), was the only isolable product from this reaction (isolated yield 9%). Compound (II) is a [1.1]dialuminaferrocenophane in which each Al atom still carries one Cl atom and is coordinated by one molecule of TMEDA. So far, we could neither clarify how compound (II) is formed nor optimize its synthesis by a rational approach starting from 1,1 0-dilithioferroceneÁ0.67
Experimental Section General Procedures. Manipulations were done using standard Schlenk-and glove... more Experimental Section General Procedures. Manipulations were done using standard Schlenk-and glovebox techniques (O 2 level < 0.1 ppm; N 2 as inert gas). Solvents were dried using an MBraun Solvent Purification System and stored under nitrogen over 4 Å molecular sieves. C 6 D 6 was prepared through freeze-pump-thaw procedures and stored under nitrogen over 4 Å molecular sieves. 1 H NMR spectra were recorded on a Bruker 500 MHz Avance spectrometer at 25 ºC. 1 H chemical shifts are referenced to the residual protons of the deuterated solvent (C 6 D 6 : δ 7.15). Diphenylsila[1]molybdarenophane (1), 1 [Mo(C 6 H 6) 2 ] 1 and [Mo(LiC 6 H 5) 2 ] • tmeda, 2 were synthesized as described in the literature. Me 2 SiCl 2 and iPr 2 SiCl 2 were purchased from Sigma-Aldrich and deoxygenated via a flask-to-flask condensation. Karstedt's catalyst, [{[(H 2 C=CH)Me 2 Si] 2 O}Pt(0)], was purchased from Sigma-Aldrich and use as received. Reaction of 1 with Karstedt's catalyst. Karstedt's catalyst (3 wt% in xylenes, 153 μL, 6.9 mol%) was added dropwise to a solution of 1 (64 mg, 0.15 mmol) in toluene (3 mL) at ambient temperature inside a glovebox. The color of the reaction mixture was changed from brownish yellow to dark brown within 2 h and an aliquot (1 mL) was transferred into a NMR tube. All volatiles were removed from the NMR sample under high vacuum, resulting in a dark brown paste which was dissolved in C 6 D 6 (0.5 mL). The 1 H NMR spectrum showed new product peaks and some residual amounts of 1. The reaction mixture
Bis(cyclopentadienyl)aluminum and-gallium species of the type (Pytsi)ECp 2 [E = Al (2a), Ga (2b);... more Bis(cyclopentadienyl)aluminum and-gallium species of the type (Pytsi)ECp 2 [E = Al (2a), Ga (2b); Pytsi = C(SiMe 3) 2 SiMe 2 (2-C 5 H 4 N)] have been prepared from NaCp and respective dichlorides (Pytsi)ECl 2 in isolated yields of 65% (2a) and 83% (2b). In addition to applying standard methods of characterization (NMR spectroscopy, CHN analysis, and MS), the molecular structures of both compounds were solved by single-crystal X-ray crystallography. Reactions between 2a or 2b with Zr(NMe 2) 4 in benzene, followed by addition of an excess of ClSiMe 3 , gave the first ansa-zirconocene dichlorides with aluminum (4a) or gallium (4b) in bridging position. The gallium compound 4b was isolated in a yield of 40% and characterized by NMR spectroscopy, CHN analysis, and mass spectrometry. The aluminum species 4a could not be obtained in an analytically pure form; it was characterized by NMR spectroscopy, and its molecular structure was determined by single-crystal X-ray analysis. The angle between the two planes of the Cp ligands in 4a was found to be 57.17(11)°, which is larger than in Cp 2 ZrCl 2 (R = 53.5°) and smaller than in silicon-bridged ansa-zirconocene dichlorides (e.g., Me 2 Si(C 5 H 4) 2 ZrCl 2 : R = 60.1°). Crystallization attempts of 4a from DCCl 3 solutions gave crystals of the new species (Pytsi)AlCl[(C 5 H 4)ZrCp] (7), which was characterized by NMR spectroscopy and single-crystal X-ray analysis. In comparison to the Pytsi-containing species 2a and 2b, the less sterically protected compound [2-(Me 2 NCH 2)C 6 H 4 ]AlCp 2 (6), which was prepared from NaCp and [2-(Me 2 NCH 2)C 6 H 4 ]AlCl 2 in yields of 94% and characterized by standard methods (NMR, CHN, and MS), reacted with Zr(NMe 2) 4 to give the known Cp 2 Zr(NMe 2) 2. The targeted ansa-species was not formed, as judged by 1 H NMR spectroscopy. The gallium-bridged compound 4b and Cp 2 ZrCl 2 , respectively, had been tested for polymerizations of ethylene utilizing MAO as an activator (300 equiv of MAO; 5 or 10 μmol of precatalyst; 15 or 70 psi), resulting in activities of 637 to 1080 for 4b and of 640 to 2601 kg PE (mol Zr)-1 h-1 atm-1 for Cp 2 ZrCl 2 .
ABSTRACT Two new [1]ruthenocenophanes, Ru(η5-C5H4)2E(Me2Ntsi) (Me2Ntsi = C(SiMe3)2SiMe2NMe2; E = ... more ABSTRACT Two new [1]ruthenocenophanes, Ru(η5-C5H4)2E(Me2Ntsi) (Me2Ntsi = C(SiMe3)2SiMe2NMe2; E = Al, Ga), bridged by aluminum (3a) and gallium (3b), were synthesized by reaction of dilithioruthenocene with (Me2Ntsi)ECl2 in good to moderate yields (3a, 80%; 3b, 36%). Both species were analyzed by standard techniques (multinuclear NMR spectroscopy, elemental analysis, UV−vis, MS), and their molecular structures were deduced from single-crystal X-ray analysis. Compared to the analogous [1]ferrocenophanes 2a,b, compounds 3a,b showed an increased ring tilt as indicated by the tilt angle α (2a, α = 14.33(14)°; 3a, α = 20.31(19)°; 2b, α = 15.83(19)°; 3b, α = 20.91(19)°). Ring-opening polymerization (ROP) with previously published aluminum- and gallium-bridged [1]ferrocenophanes Fe(η5-C5H4)2E(Pytsi) (Pytsi = C(SiMe3)2SiMe2(2-C6H4N); E = Al (1a), Ga (1b)) and Fe(η5-C5H4)2E(Me2Ntsi) (E = Al (2a), Ga (2b)) and the [1]ruthenocenophanes 3a,b (this paper) has been shown to be very sluggish or unsuccessful. Only the ROP of 1b with [Pd(dba)2] (2 mol %, toluene, 25 °C, 48 h) resulted in polymeric material (GPC analysis: Mw = 2.11 × 104, PDI = 3.0).
Aluminum-and gallium-bridged [1]ferrocenophanes (4a, 4b), [1]chromarenophanes (5a, 5b), and [1]va... more Aluminum-and gallium-bridged [1]ferrocenophanes (4a, 4b), [1]chromarenophanes (5a, 5b), and [1]vanadarenophanes (6a, 6b) were synthesized from the respective dilithiated sandwich compounds with element dichlorides (Me 2 Ntsi)ECl 2 [E) Al, Ga; Me 2 Ntsi) C(SiMe 3) 2 (SiMe 2 NMe 2)] in moderate to high isolated yields (54-97%). The new intramolecularly stabilized aluminum compound (Me 2 NCH 2tsi)AlCl 2 (2a) was synthesized, but was proven to be unreactive with respect to [Fe(LiC 5 H 4) 2 ]‚2/3TMEDA. The diamagnetic species 2a, 4a, 4b, 5a, and 5b were characterized by NMR spectroscopy (1 H, 13 C, 27 Al), CHN elemental analysis, and mass spectrometry, whereas the paramagnetic compounds 6a and 6b were characterized by IR spectroscopy, CHN elemental analysis, and mass spectrometry. In addition, the molecular structures of compounds 2a, 4a, 4b, 5a, 5b, 6a, and 6b were determined by single-crystal X-ray analysis. All [1]cyclophanes are strained species, as revealed by the following tilt angles R [deg]: 14.33(14) (4a), 15.83(19) (4b), 11.81(9) (5a), 13.24(13) (5b), 14.65(14) (6a), and 15.63(14) (6b).
The first example of a [1]ferrocenophane with a heavier group 13 element in the bridging position... more The first example of a [1]ferrocenophane with a heavier group 13 element in the bridging position is described. The [1]aluminaferrocenophane, with the aluminum atom equipped with a bulky and intramolecularly stabilizing ligand, has been synthesized and structurally characterized by NMR spectroscopy and singlecrystal X-ray analysis. In 1975 Osborn and Whiteley described the first [1]ferrocenophane, a strained organometallic compound that contained silicon in the bridging position (ER x) SiPh 2 ; Figure 1). 1 Three decades later, Manners et al. discovered that ring-opening polymerization (ROP) of [1]silaferrocenophanes provides access to poly(ferrocenylsilanes) with high molecular weights. 2 Today, [1]ferrocenophanes with main-group elements in the bridging position are known from group 16 (S, Se), 3,4 15 (P, As), 5-8 14 (Si, Ge, Sn), 1,2,5,6,9-11 and 13 (B) 12,13 elements, with the [1]boraferrocenophanes being the most recent examples in this series (ER x) BN(SiMe 3) 2 , BN(SiMe 3)-tBu, BNiPr 2). However, [1]ferrocenophanes with heavier bridging group 13 elements are unknown today. Surprisingly, even simpler compounds such as ferrocenyl-alanes 14,15 or gallanes are very rare, with some interesting ferrocenylgallanes being characterized recently. 16-18 Within this report we describe the synthesis and structural characterization of the first [1]aluminaferrocenophane. On the basis of our experience with organic ligands that are capable of intramolecular donation, 19-21 we decided to attach a trisyl ligand 22 in which one of the methyl groups is replaced by a 2-pyridyl group to aluminum (trisyl) tris(trimethylsilyl)methyl, C(SiMe 3) 3 ; commonly denoted as Tsi). The ligand C(SiMe 3) 2-(SiMe 2 C 5 H 4 N-2) was described for the first time in 2000, 23 and since then, investigations have been published dealing with new compounds equipped with this ligand. 23-27 Very recently, the first compounds with group 13 elements containing this unique ligand were reported, including the two alanes (Pytsi)AlCl 2 and (Pytsi)AlMe 2 (Pytsi) C(SiMe 3) 2 (SiMe 2 C 5 H 4 N-2)). 28 In-† Dedicated to Professor Peter Paetzold on the occasion of his 70th birthday.
Salt metathesis reaction between Li(thf)(Me 2 Ntsi) [Me 2 Ntsi) C(SiMe 3) 2 SiMe 2 NMe 2 ] and In... more Salt metathesis reaction between Li(thf)(Me 2 Ntsi) [Me 2 Ntsi) C(SiMe 3) 2 SiMe 2 NMe 2 ] and InX 3 gave the new indium dihalides (Me 2 Ntsi)InX 2 [X) Cl (2a), I (2b); isolated yields 34% (2a) and 44% (2b)]. Single-crystal X-ray analysis revealed that 2a is a Cl-bridged dimer, while 2b is monomeric. Salt metathesis reaction between dilithioferrocene and 2a and 2b, respectively, gave the new indium-bridged [1.1]ferrocenophane [(Me 2 Ntsi)In(η 5-C 5 H 4) 2 Fe] 2 (3). Only when 2a was used, could analytically pure 3 be isolated (45%). Revealed by a single-crystal X-ray analysis, compound 3 crystallized as an anti isomer (C i symmetry). The diinda[1.1]ferrocenophane 3 showed fluxional behavior in solution. The proton NMR spectrum of 3 revealed only five singlets at ambient temperature (500 MHz, 25°C, C 6 D 6 or C 7 D 8): one singlet for SiMe 2 , SiMe 3 , and NMe 2 each and two singlets for the 16 Cp protons. These facts can be rationalized by assuming a fast degenerate isomerization from one anti isomer to another anti isomer (time-averaged D 2h symmetry). The two singlets at 4.43 and 4.45 ppm (500 MHz, 25°C, C 7 D 8) of the Rand-protons broadened at lower temperature and coalesced at 5°C. By lowering the temperature further, two sets of signals emerged and became clearly visible at-30°C, with each set consisting of four singlets for the Cp protons of equal intensity. Consistent with the splitting of the Cp signals, all other signals split in two sets of three singlets, indicating C s symmetric Me 2 Ntsi moieties. These data show that the [1.1]ferrocenophane 3 exists as a mixture of two isomers in toluene solutions (2:1 ratio at-30°C). Assuming that the thermodynamically favored isomer was found in the crystal lattice, the most intense set of signals was assigned to the anti isomer of 3, while the less intense set of signals was assigned to a syn isomer. The already known diinda[1.1]ferrocenophane {[2-(Me 2 NCH 2)C 6 H 4 ]In(η 5-C 5 H 4) 2 Fe} 2 (1c) was revisited. Compound 1c did not reveal any fluxional behavior in 1D 1 H NMR spectra at ambient temperature, but EXSY spectroscopy revealed an occurring anti-to-anti isomerization of 1c in solution. A cyclic voltammogram of 3 in thf/0.1 M [Bu 4 N][PF 6 ] showed only an irreversible oxidation. A rationale is given why the reaction of (Me 2 Ntsi)InX 2 [X) Cl (2a), I (2b)] with dilithioferrocene gave a [1.1]ferrocenophane, as similar reactions of (Me 2 Ntsi)ECl 2 (E) Al, Ga) with dilithioferrocene gave strained [1]ferrocenophanes.
On the basis of our previous results with aluminum, we herein report the synthesis of the first g... more On the basis of our previous results with aluminum, we herein report the synthesis of the first gallium-bridged [1]ferrocenophane. The attempt to synthesize the respective indium compound resulted in an unusual ferrocenophane containing an In−(μ-Cl)2−In group in the bridging position. All compounds have been characterized by NMR spectroscopy and single-crystal X-ray structural determination.
The first [1]molybdarenophanes were synthesized and structurally characterized. The aluminum and ... more The first [1]molybdarenophanes were synthesized and structurally characterized. The aluminum and gallium compounds [(Me2Ntsi)Al(η 6-C6H5)2Mo] (2a) and [(Me2Ntsi)Ga(η 6-C6H5)2Mo] (2b) [Me2Ntsi) C(SiMe3)2(SiMe2NMe2)] were obtained from [Mo(LiC6H5)2]‚TMEDA and (Me2Ntsi)ECl2 [E) Al, Ga] in analytical pure form with isolated yields of 74% (2a) and 52% (2b). The silicon-bridged species [Ph2Si-(η 6-C6H5)2Mo] (2c) was synthesized from [Mo(LiC6H5)2]‚TMEDA and Ph2SiCl2. Compound 2c was isolated as a crystalline material in an approximately 90% overall purity, from which a single crystal was used for X-ray analysis. The molecular structures of all three [1]molybdarenophanes 2a-c were determined by singlecrystal X-ray analysis. The ring-tilt angle R was found to be 18.28(17), 21.24(10), and 20.23(29)°for 2a, 2b, and 2c, respectively. Variable temperature NMR measurements of 2a and 2b (-80 to 80°C; 500 MHz) showed a dynamic behavior of the gallium species 2b but not of compound 2a. The dynamic behavior of 2b was rationalized by assuming that the Ga-N donor bond breaks, inversion at the nitrogen atom occurs, and a rotation of the Me 2Ntsi ligand takes place followed by a reformation of the Ga-N bond on the other side of the gallium atom. The analysis of the signals of meta and ortho protons of 2b gave approximate values of ∆G * of 59.6 and 59.1 kJ mol-1 , respectively. Compound 2b reacted with [Pt(PEt3)3] to give the ring-open product [(η 6-C6H6)Mo{η 6-C6H5[GaPh(Me2Ntsi)]}] (3b). The molecular structure of 3b was deduced from a single-crystal X-ray determination. The formation of the unexpected platinum-free product 3b can be rationalized by assuming that benzene reacted with 2b in a 1:1 ratio. Through a series of 1 H NMR experiments with 2b it was shown that small amounts of donor molecules (e.g., THF) in benzene are needed to form 3b; in the absence of a donor molecule, 2b is thermally stable.
The synthesis and structural characterization of the first [1.1]chromarenophanes and the first [1... more The synthesis and structural characterization of the first [1.1]chromarenophanes and the first [1.1]molybdarenophanes are described. A salt-metathesis reaction of [2-(Me 2NCH 2)C 6H 4]AlCl 2 with freshly prepared [Cr(LiC 6H 5) 2].TMEDA (TMEDA = N, N, N&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;, N&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-tetramethylethylenediamine) resulted in the dialumina[1.1]chromarenophane [{2-(Me 2NCH 2)C 6H 4}Al(eta (6)-C 6H 5) 2Cr] 2 ( 2a). The poor solubility of 2a in organic solvents prompted us to synthesize the new intramolecularly coordinated aluminum- and gallium dichlorides [5- tBu-2-(Me 2NCH 2)C 6H 3]ECl 2 [E = Al ( 3a), Ga ( 3b)] in which the phenyl group was equipped with a tert-butyl group. Salt-metathesis reactions of 3a and 3b, respectively, with freshly prepared [M(LiC 6H 5) 2].TMEDA (M = Cr, Mo) resulted in four new [1.1]metallarenophanes of the general type [{5- tBu-2-(Me 2NCH 2)C 6H 3}E(eta (6)-C 6H 5) 2M] 2 [E = Al, M = Cr ( 4a); E = Ga, M = Cr ( 4b); E = Al, M = Mo ( 5a); E = Ga, M = Mo ( 5b)]. 2a, 4a, b, and 5a, b have been structurally characterized by single-crystal analysis [ 2a.1/2C 6H 12: C 48H 56Al 2Cr 2N 2, monoclinic, P2 1/ c, a = 9.9117(9) A, b = 19.9361(16) A, c = 10.638(2) A, alpha = 90 degrees , beta = 112.322(5) degrees , gamma = 90 degrees , Z = 2; 4a.2C 6H 6: C 62H 72Al 2Cr 2N 2, monoclinic, P2 1/ c, a = 10.9626(9) A, b = 19.3350(18) A, c = 12.4626(9) A, alpha = 90 degrees , beta = 100.756(5) degrees , gamma = 90 degrees , Z = 2; 4b.2C 6H 6: C 62H 72Cr 2Ga 2N 2, monoclinic, P2 1/ c, a = 10.8428(2) A, b = 19.4844(4) A, c = 12.4958(2) A, alpha = 90 degrees , beta = 100.6187 degrees , gamma = 90 degrees , Z = 2; 5a.2C 6H 6: C 62H 72Al 2Mo 2N 2, triclinic, P1, a = 10.4377(4) A, b = 11.6510(4) A, c = 11.6514(4) A, alpha = 73.545(3) degrees , beta = 89.318(2) degrees , gamma = 76.120(2) degrees , Z = 1; 5b.2C 6H 6: C 62H 72Ga 2Mo 2N 2, triclinic, P1, a = 10.3451(5) A, b = 11.6752(6) A, c = 11.6900(5) A, alpha = 73.917(3) degrees , beta = 89.550(3) degrees , gamma = 76.774(2) degrees , Z = 1]. All five [1.1]metallarenophanes 2a, 4a, b, and 5a, b crystallize as anti isomers with both Me 2N donor groups in exo positions ( C i point group symmetry). The new [1.1]metallarenophanes show NMR spectra that can be interpreted as being caused by time-averaged C 2 h symmetrical species, which is consistent with the findings of their molecular structures in the solid state. Variable-temperature (1)H NMR measurements for 4a, b and 5a, b (500 MHz; -90 to 90 degrees C) revealed only peak broadening in the lower temperature range of -70 to -90 degrees C. (1)H NMR saturation transfer difference experiments did not show an expected anti-to-anti isomerization, rendering the new [1.1]metallacyclophanes rigid on the NMR time scale. Electrochemical measurements were performed for 4a, b and 5a, b. However, reproducible cyclic voltammograms could only be obtained for the two gallium species 4b and 5b, revealing the expected weak communication between the two transition-metal atoms in both compounds (class II).
Five new intramolecularly coordinated aluminum species, whose molecular structures have been eluc... more Five new intramolecularly coordinated aluminum species, whose molecular structures have been elucidated in solution by NMR spectroscopy and in the solid state by single crystal X-ray analysis, are described. All species are equipped with a trisyl-based ligand with a pyridyl donor group [Pytsi stands for -C(SiMe3)2SiMe2(2-C5H4N)]. While the compound (Pytsi)AlMeCl was accessible either from Li(THF)(Pytsi) and MeAlCl2 or from (Pytsi)AlCl2 and LiMe, the tert-butyl derivative (Pytsi)AltBuCl could only be obtained from Li(THF)(Pytsi) and tBuAlCl2. Attempted synthesis of (Pytsi)AltBuCl from (Pytsi)AlCl2 and LitBu or from (Pytsi)AlCl2 and tBuMgCl failed. Three other compounds (3-5) were synthesized and can be described as derivatives of (Pytsi)AlMe2 with additional groups in the ortho position of the pyridyl group. Compound 3 carried a Me group in the ortho position, while compounds 4 and 5 were equipped with Ph and 2,6-diisopropylphenyl moieties, respectively.Key words: aluminum, trisyl li...
Acta Crystallographica Section E Structure Reports Online, 2005
The structure of the title compound, bis(-ferrocene-1,1 0-diyl)bis[chloro(N,N,N 0 N 0-tetramethyl... more The structure of the title compound, bis(-ferrocene-1,1 0-diyl)bis[chloro(N,N,N 0 N 0-tetramethylethylenediamine)aluminium], [Al 2 Fe 2 Cl 2 (C 5 H 4) 4 (C 6 H 16 N 2) 2 ], possesses a center of inversion and an anti conformation. Bound to each Al atom in the bridging position are one Cl atom and one molecule of N,N,N 0 N 0-tetramethylethylenediamine (TMEDA). The angle between the least-squares planes of the two cyclopentadienyl (Cp) ligands is 3.6 (3). The five C atoms in the Cp rings are staggered on average at an angle of 10.3 (5). Comment Recently, we synthesized the first [1]aluminaferrocenophane, (I), by a metathesis reaction of 1,1 0-dilithioferroceneÁ0.67-TMEDA and (Pytsi)AlCl 2 [Pytsi = C(SiMe 3) 2 SiMe 2 (2-C 5 H 4 N) and TMEDA = N,N,N 0 ,N 0-tetramethylethylenediamine] using toluene as a solvent. Compound (I) was isolated as a crystalline material with one half-molecule of ferrocene (FeCp 2) in the asymmetric unit (Schachner et al., 2005). We assume that FeCp 2 results from the protolysis of 1,1 0-dilithioferrocene, with toluene being the source of protons. Consequently, we substituted toluene by the less acidic solvent hexane with the intention of optimizing the synthesis of (I). However, the title compound, (II), was the only isolable product from this reaction (isolated yield 9%). Compound (II) is a [1.1]dialuminaferrocenophane in which each Al atom still carries one Cl atom and is coordinated by one molecule of TMEDA. So far, we could neither clarify how compound (II) is formed nor optimize its synthesis by a rational approach starting from 1,1 0-dilithioferroceneÁ0.67
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