The traditional concept of racemates means an exactly 1:1 mixture of two enantiomeric molecules. ... more The traditional concept of racemates means an exactly 1:1 mixture of two enantiomeric molecules. Modern analytical and catalytic/preparative discoveries, first of all the Soai-reaction, make necessary a re-evaluation of this concept. The most important aspect of such a revision is the definition of the amount of an excess of one or of the other enantiomer, originating from statistical fluctuation, which can still be "tolerated" when a substance is defined as racemate. The present paper discusses the statistical view of racemates and some related problems.
Chiral conformations of flexible molecules may develop in a concerted manner if the molecule is c... more Chiral conformations of flexible molecules may develop in a concerted manner if the molecule is crowded enough to assure sufficient level of through-the-space contacts. Higher number (> 4) of groups connected to the same atom, as in many coordination compounds, can be advantageous in this respect. The case study of R,S-[(sec-butoxycarbonyl)methyl]cobalt tricarbonyl triphenylphosphine is presented here. X-ray diffraction shows that the possible number of enantiomeric and diastereomeric conformations is reduced by 75% (from 8 to 2) by concerted development of the molecular conformations in crystalline phase.
with Ni, Mn and dodecaphenylcyclododecasiloxane-dodecaol with Cu was studied. The complexes react... more with Ni, Mn and dodecaphenylcyclododecasiloxane-dodecaol with Cu was studied. The complexes react electrochemically as a unit assembly of the complexed metals.
Abstract Rh2(CO)4(OR)2 complexes (R = Me, Et, Pr, i-pent, Ph, p-chlorophenyl) were prepared from ... more Abstract Rh2(CO)4(OR)2 complexes (R = Me, Et, Pr, i-pent, Ph, p-chlorophenyl) were prepared from Rh2(CO)4Cl2 and sodium alcoholates or phenolates. They are converted by phosphines into the monomeric Rh(CO)(PR′3)2(OR) derivatives (R′ = Bu, Ph) via Rh2(CO)3(PR′3)(OR)2 intermediates.
~2 -LL Co, (CO), P& and (ccz -I& Co2 (CO),P(OR), (R = alkyl, ~1, L = Pz, Asz, acetylene, L = CO a... more ~2 -LL Co, (CO), P& and (ccz -I& Co2 (CO),P(OR), (R = alkyl, ~1, L = Pz, Asz, acetylene, L = CO and but-2-en-4-olid-4-ylidene) compounds were prepared. The Y(C-0) infrared spectra are in agreement with the expected C, or C1 symmetry. The results indicate that the PRs or P(OR)s substituent is in all cases in the axial position. TABLE 1 IR DATA OF ~Co<CO>sPR3 COMPOUNDS Ligands NC-0) values (cm -1 ) L2 PR3 Ul v2 v3 v4 us AV * Co. P and moL wt. values were satisfactory. n-Bu and cycle-C&Hi 1), (C6H13C2H)Co2(CO)5P(OPh)3 (C,O,HH). 233 and Co2 (CO), (P-n-B+)-Note added in proof. After this manuscript had been mailed we became aquainted with the results of Manning end this coworkers (LB. Chic. W.R. CuBen. M. Frenkhn and A.R. M axming. to be published). These authors prepared a series of mono-and di-substituted derivatives of <RCZCR')Co#0)6 complexes with mono-and b&dentate Group V ligands. Their results seem to be in good agreement with those in this paper.
Zeitschrift für anorganische und allgemeine Chemie, Feb 1, 1990
Thiolatecobalt carbonyls RSCo(CO)4, 1 (R = Me, a, Et, b, PhCH2, c, Ph, d) and RSCo(CO)3PPh3, 2 (R... more Thiolatecobalt carbonyls RSCo(CO)4, 1 (R = Me, a, Et, b, PhCH2, c, Ph, d) and RSCo(CO)3PPh3, 2 (R = Et, a, PhCH2, b) were prepared. Complexes 1 were obtained from Co2(CO)8 or ICo(CO)4 and RS− or from Co2(CO)8 and RSSR, complexes 2 were prepared by substitution of 1 by PPh3 or by the reaction of ICo(CO)3PPh3 with RS−. Complexes 1 yield desulfuration products and/or polynuclear sulfur containing cobalt carbonyl clusters. Einkernige Thiolatcobaltcarbonyl-Komplexe Thiolatcobaltcarbonyle RSCo(CO)41 (R = Me, a; Et, b; PhCH2, c; Ph, d) und RSCo(CO)3PPh32 (R = Et, a; PhCH2, b) wurden dargestellt. Die Komplexe 1 wurden von Co2(CO)8 bzw. ICo(CO)4 und RS− oder von Co2(CO)8 und RSSR erhalten; die Komplexe 2 wurden durch Substitution von 1 mit PPh3 oder durch Umsetzung von ICo(CO)3PPh3 mit RS− dargestellt. Die Komplexe 1 ergeben desulfurierte Produkte und/oder mehrkernige schwefelhaltige Cobaltcarbonyl-Cluster.
... In 1943 Quilico left Firenze to go back to Milano, but Carlo Musante and Giovanni Speroni con... more ... In 1943 Quilico left Firenze to go back to Milano, but Carlo Musante and Giovanni Speroni continued in Firenze the chemistry of ... I. Goldberg Chapter 8 Genetic Code: a Self-Referential and Functional Model 83 Romeu Cardoso Guimaraes and Carlos Henrique Costa Moreira ...
Author for correspondence. ** Throughout this paper those alkylcobalt carbonyls are considered in... more Author for correspondence. ** Throughout this paper those alkylcobalt carbonyls are considered in which the forma1 oxidation state of Co is +1 (thus the Co(II1) alkyls will not be included even if they contain CO ligand(s)); on the other hand only those derivatives are treated which contain in addition to the q' alkyl group CO, PR,, P(OR), ligands (thus the NO, isonitrile, etc. complexes reported in the literature are not included). OOlO-8545/84/$10.80 Q 1984 Elsevier Science Publishers B.V. * Two decades ago the cobalt-organic product of reaction (2) was supposed to be the R P-1 acyl-type chelate complex O=C-CH,-C-Co(CO), on the basis of IR spectra of low resolution [4]. 8 ** The hydrocarbon group of (lR, 3R, 4S)-p-menthane-3-01 (menthol) will be denoted as Men in this paper. * In fact the molecular structure of the p-Me derivative could be determined by X-ray diffraction (cf. Section C). * Extensive (mostly kinetic) investigations on the mechanism of the stoichiometric reaction of olefins with HCo(CO), have been published recently [26-301 but none of these works described preparative variants of reaction (7). * These compounds are discussed in this review because of some analogies, in spite of the fact that they are formally acylcobalt complexes. * The local symmetry of the Co(CO), unit will be considered; the actual overall symmetry of the molecule is generally lower. * These compounds were not prepared and characterized (cf. Section B, Table 1). * cf. Ref. 95. * One of the authors (G.P.) acknowledges a discussion with W. Keim and B. Fell (Aachen, G.F.R.) in 1981 which contributed to the formation of this opinion. * The authors are aware that an ab initio investigation of this problem has been recently initiated by F. Bemardi (Bologna, Italy) and his group.
pz-Acetylene)-hexacarbonyldicobalt (Co-co) compounds (1) give a wide variety of reactions of the ... more pz-Acetylene)-hexacarbonyldicobalt (Co-co) compounds (1) give a wide variety of reactions of the coordinated CZ moiety [2], while reactions of the substituents of the acetylene were reported in only a few cases [3]. Haloacetylenic derivatives can be hoped to be reactive starting materials for such studies. We prepared and characterized some dihaloacetylenic derivatives can be hoped to be reactive starting materials for such studies. We prepared and characterized some dihaloacetylene (I) derivatives and studied their reaction with Co2(CO)s or [Co(CO),]-. The results of this study will be reported here.
ChemInform Abstract Durch Umsetzung mit den Alkoholaten (IIa) und (IIb) oder Phenolaten (IIc) und... more ChemInform Abstract Durch Umsetzung mit den Alkoholaten (IIa) und (IIb) oder Phenolaten (IIc) und (IId) k önnen die Chlorbr ücken in (I) durch Alkoxy-oder Aroxy-Br ücken ersetzt werden, wobei (III) entsteht. Durch einen Phosphin-Überschuss k önnen diese in siedendem Hexan in die monomeren Produkte (IV) aufgespalten werden. Voraussichtlich verl äuft diese Reaktion über die im Falle von (IIIb), (IIIc) und (IIId) mit Tributylphosphin-Unterschuss untermilden Bedingungen darstellbaren dimeren Komplexe (VI). (IR-und NMR-Daten).
The traditional concept of racemates means an exactly 1:1 mixture of two enantiomeric molecules. ... more The traditional concept of racemates means an exactly 1:1 mixture of two enantiomeric molecules. Modern analytical and catalytic/preparative discoveries, first of all the Soai-reaction, make necessary a re-evaluation of this concept. The most important aspect of such a revision is the definition of the amount of an excess of one or of the other enantiomer, originating from statistical fluctuation, which can still be "tolerated" when a substance is defined as racemate. The present paper discusses the statistical view of racemates and some related problems.
Chiral conformations of flexible molecules may develop in a concerted manner if the molecule is c... more Chiral conformations of flexible molecules may develop in a concerted manner if the molecule is crowded enough to assure sufficient level of through-the-space contacts. Higher number (> 4) of groups connected to the same atom, as in many coordination compounds, can be advantageous in this respect. The case study of R,S-[(sec-butoxycarbonyl)methyl]cobalt tricarbonyl triphenylphosphine is presented here. X-ray diffraction shows that the possible number of enantiomeric and diastereomeric conformations is reduced by 75% (from 8 to 2) by concerted development of the molecular conformations in crystalline phase.
with Ni, Mn and dodecaphenylcyclododecasiloxane-dodecaol with Cu was studied. The complexes react... more with Ni, Mn and dodecaphenylcyclododecasiloxane-dodecaol with Cu was studied. The complexes react electrochemically as a unit assembly of the complexed metals.
Abstract Rh2(CO)4(OR)2 complexes (R = Me, Et, Pr, i-pent, Ph, p-chlorophenyl) were prepared from ... more Abstract Rh2(CO)4(OR)2 complexes (R = Me, Et, Pr, i-pent, Ph, p-chlorophenyl) were prepared from Rh2(CO)4Cl2 and sodium alcoholates or phenolates. They are converted by phosphines into the monomeric Rh(CO)(PR′3)2(OR) derivatives (R′ = Bu, Ph) via Rh2(CO)3(PR′3)(OR)2 intermediates.
~2 -LL Co, (CO), P& and (ccz -I& Co2 (CO),P(OR), (R = alkyl, ~1, L = Pz, Asz, acetylene, L = CO a... more ~2 -LL Co, (CO), P& and (ccz -I& Co2 (CO),P(OR), (R = alkyl, ~1, L = Pz, Asz, acetylene, L = CO and but-2-en-4-olid-4-ylidene) compounds were prepared. The Y(C-0) infrared spectra are in agreement with the expected C, or C1 symmetry. The results indicate that the PRs or P(OR)s substituent is in all cases in the axial position. TABLE 1 IR DATA OF ~Co<CO>sPR3 COMPOUNDS Ligands NC-0) values (cm -1 ) L2 PR3 Ul v2 v3 v4 us AV * Co. P and moL wt. values were satisfactory. n-Bu and cycle-C&Hi 1), (C6H13C2H)Co2(CO)5P(OPh)3 (C,O,HH). 233 and Co2 (CO), (P-n-B+)-Note added in proof. After this manuscript had been mailed we became aquainted with the results of Manning end this coworkers (LB. Chic. W.R. CuBen. M. Frenkhn and A.R. M axming. to be published). These authors prepared a series of mono-and di-substituted derivatives of <RCZCR')Co#0)6 complexes with mono-and b&dentate Group V ligands. Their results seem to be in good agreement with those in this paper.
Zeitschrift für anorganische und allgemeine Chemie, Feb 1, 1990
Thiolatecobalt carbonyls RSCo(CO)4, 1 (R = Me, a, Et, b, PhCH2, c, Ph, d) and RSCo(CO)3PPh3, 2 (R... more Thiolatecobalt carbonyls RSCo(CO)4, 1 (R = Me, a, Et, b, PhCH2, c, Ph, d) and RSCo(CO)3PPh3, 2 (R = Et, a, PhCH2, b) were prepared. Complexes 1 were obtained from Co2(CO)8 or ICo(CO)4 and RS− or from Co2(CO)8 and RSSR, complexes 2 were prepared by substitution of 1 by PPh3 or by the reaction of ICo(CO)3PPh3 with RS−. Complexes 1 yield desulfuration products and/or polynuclear sulfur containing cobalt carbonyl clusters. Einkernige Thiolatcobaltcarbonyl-Komplexe Thiolatcobaltcarbonyle RSCo(CO)41 (R = Me, a; Et, b; PhCH2, c; Ph, d) und RSCo(CO)3PPh32 (R = Et, a; PhCH2, b) wurden dargestellt. Die Komplexe 1 wurden von Co2(CO)8 bzw. ICo(CO)4 und RS− oder von Co2(CO)8 und RSSR erhalten; die Komplexe 2 wurden durch Substitution von 1 mit PPh3 oder durch Umsetzung von ICo(CO)3PPh3 mit RS− dargestellt. Die Komplexe 1 ergeben desulfurierte Produkte und/oder mehrkernige schwefelhaltige Cobaltcarbonyl-Cluster.
... In 1943 Quilico left Firenze to go back to Milano, but Carlo Musante and Giovanni Speroni con... more ... In 1943 Quilico left Firenze to go back to Milano, but Carlo Musante and Giovanni Speroni continued in Firenze the chemistry of ... I. Goldberg Chapter 8 Genetic Code: a Self-Referential and Functional Model 83 Romeu Cardoso Guimaraes and Carlos Henrique Costa Moreira ...
Author for correspondence. ** Throughout this paper those alkylcobalt carbonyls are considered in... more Author for correspondence. ** Throughout this paper those alkylcobalt carbonyls are considered in which the forma1 oxidation state of Co is +1 (thus the Co(II1) alkyls will not be included even if they contain CO ligand(s)); on the other hand only those derivatives are treated which contain in addition to the q' alkyl group CO, PR,, P(OR), ligands (thus the NO, isonitrile, etc. complexes reported in the literature are not included). OOlO-8545/84/$10.80 Q 1984 Elsevier Science Publishers B.V. * Two decades ago the cobalt-organic product of reaction (2) was supposed to be the R P-1 acyl-type chelate complex O=C-CH,-C-Co(CO), on the basis of IR spectra of low resolution [4]. 8 ** The hydrocarbon group of (lR, 3R, 4S)-p-menthane-3-01 (menthol) will be denoted as Men in this paper. * In fact the molecular structure of the p-Me derivative could be determined by X-ray diffraction (cf. Section C). * Extensive (mostly kinetic) investigations on the mechanism of the stoichiometric reaction of olefins with HCo(CO), have been published recently [26-301 but none of these works described preparative variants of reaction (7). * These compounds are discussed in this review because of some analogies, in spite of the fact that they are formally acylcobalt complexes. * The local symmetry of the Co(CO), unit will be considered; the actual overall symmetry of the molecule is generally lower. * These compounds were not prepared and characterized (cf. Section B, Table 1). * cf. Ref. 95. * One of the authors (G.P.) acknowledges a discussion with W. Keim and B. Fell (Aachen, G.F.R.) in 1981 which contributed to the formation of this opinion. * The authors are aware that an ab initio investigation of this problem has been recently initiated by F. Bemardi (Bologna, Italy) and his group.
pz-Acetylene)-hexacarbonyldicobalt (Co-co) compounds (1) give a wide variety of reactions of the ... more pz-Acetylene)-hexacarbonyldicobalt (Co-co) compounds (1) give a wide variety of reactions of the coordinated CZ moiety [2], while reactions of the substituents of the acetylene were reported in only a few cases [3]. Haloacetylenic derivatives can be hoped to be reactive starting materials for such studies. We prepared and characterized some dihaloacetylenic derivatives can be hoped to be reactive starting materials for such studies. We prepared and characterized some dihaloacetylene (I) derivatives and studied their reaction with Co2(CO)s or [Co(CO),]-. The results of this study will be reported here.
ChemInform Abstract Durch Umsetzung mit den Alkoholaten (IIa) und (IIb) oder Phenolaten (IIc) und... more ChemInform Abstract Durch Umsetzung mit den Alkoholaten (IIa) und (IIb) oder Phenolaten (IIc) und (IId) k önnen die Chlorbr ücken in (I) durch Alkoxy-oder Aroxy-Br ücken ersetzt werden, wobei (III) entsteht. Durch einen Phosphin-Überschuss k önnen diese in siedendem Hexan in die monomeren Produkte (IV) aufgespalten werden. Voraussichtlich verl äuft diese Reaktion über die im Falle von (IIIb), (IIIc) und (IIId) mit Tributylphosphin-Unterschuss untermilden Bedingungen darstellbaren dimeren Komplexe (VI). (IR-und NMR-Daten).
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