Organometalic Chemistry

Catalysis is an important field in both academic and industrial research because it leads to more efficient reactions in terms of energy consumption and waste production. The common feature of these processes is a catalytically active species which forms reactive intermediates by coordination of an organic ligand and thus decreases the activation energy. Formation of the product should occur with regeneration of the catalytically active species. The efficiency of the catalyst can be described by its turnover number, providing a measure of how many catalytic cycles are passed by one molecule of catalyst.

Heterometallic alkoxides are those alkoxides having two or more different metals linked via bridging alkoxy groups, via oxo-groups or sometimes metal-metal bonding. The large majority of heterometallic alkoxides corresponds to derivatives in which one of the metals is either an alkali or alkaline earth metal.

ABSTRACT
The solid complexes of Fe(II), Cr(III), Co(II), Ni(II), andCu(II)) with Synthesis of [Butanal(5-ethyl-1,3,4-oxadiazol-
2-yl)hydrazone]have been synthesized and characterized by using the spectroscopic IR,1HNMR, Mass as
well as by elemental analyses C,H,N and Molar conductance the were studied.It may be concluded that the
ligand coordinate through Nitrogen atoms shown in Scheme (2). For all the complexes. The ligand acts as a
didentate ligand coordinating through the oxadiazole nitrogen and the nitrogen of C=N group .This view is
further supported by the appearance of a band corresponding to the metal–nitrogen stretching vibration at
513–540 cm–1 in the complexes. The physicochemical data suggest the octahedral geometry for all complexes
except for Ni and Cu complexes which were tetrahedral respectively.
KEYWORDS: PREPARATION. CHARACTERISATION. COMPLEXES. HYDRAZONE. ETHYL.

The palladium−nickel binary nanocluster is reported
as a new catalyst system for Suzuki−Miyaura cross-coupling of orthoheterocycle-
tethered sterically hindered aryl bromides. The inferior
results obtained with the reported Pd/Ni salts/complexes or
individual Pd/Ni nanoparticles as catalyst reveal the cooperative
catalytic effect of the Pd and Ni nanoparticles in the Pd−Ni
nanocluster. The broad substrate scope with respect to variation of
the 2-arylbenzoxazole moiety and boronic acids, which offers a means for diversity generation and catalyst recyclability, marks a
distinct advantage.

Antimicrobial resistance is an ever-increasing problem throughout the world and has already reached severe proportions. Bacteria can develop ways to render traditional antibiotics ineffective, raising a crucial need to find new antimicrobials with novel mode of action. We demonstrate here a novel class of pyrazine functionalized Ag(I) and Au(I)-NHC complexes as antibacterial agents against human pathogens that are resistant to several antibiotics. Complete synthetic and structural studies of Au(I) and Ag(I) complexes of 2-(1methylimidazolium) pyrimidinechloride (L-1), 2,6-bis(1-methylimidazol)pyrazinechloride (L-2) and 2,6-bis(1-methyl imidazol) pyrazinehexa-fluorophosphate (L-3) are reported herein. Chloro[2,6-bis(1-methyl imidazol)pyrazine]gold(I), 2b and chloro [2,6-bis(1methyl imidazol)pyrazine]silver(I), 2a complexes are found to have more potent antimicrobial activity than other synthesized compounds and several conventionally used antibiotics. Complexes 2b and 2a also inhibit the biofilm formation by Gram-positive bacteria, Streptococcus mutans and Gram-negative bacteria, Escherichia coli, causing drastic damage to the bacterial cell wall and increasing membrane permeability. Complexes 2b and 2a strongly binds to both Lys and Dap-Type peptidoglycan layers, which may be the reason for damage to the bacterial cell wall. Theoretical studies of all the complexes reveal that 2b and 2a are more reactive than other complexes, and this may be the cause of differences in antibacterial activity. These findings will pave the way towards developing a new class of antibiotics against different groups of conventional antibiotic-resistant bacteria.

The palladium-nickel binary nanocluster is reported as a new catalyst system for Suzuki-Miyaura cross-coupling of ortho-heterocycle-tethered sterically hindered aryl bromides. The inferior results obtained with the reported Pd/Ni salts/complexes or individual Pd/Ni nanoparticles as catalyst reveal the cooperative catalytic effect of the Pd and Ni nanoparticles in the Pd-Ni nanocluster. The broad substrate scope with respect to variation of the 2-arylbenzoxazole moiety and boronic acids, which offers a means for diversity generation and catalyst recyclability, marks a distinct advantage.

The syntheses, structures and optical properties of polymethylene-vaulted trans-bis(2-aminotroponato) palladium(II) complexes are described. A series of Pd complexes incorporating nona-, deca-, undeca-and dodecamethylene bridges (1a: n ¼ 9; 1b: n ¼ 10; 1c: n ¼ 11; 1d: n ¼ 12) was newly prepared by reacting Pd(OAc) 2 with the corresponding N,N'-[alkane-1,u-diylbis(azanediyl)]ditropone. NMR and single-crystal X-ray diffraction analyses unequivocally established the specific structures of these complexes, including trans-coordination and three-dimensional vaulted structures. The photophysical properties of 1a ed exhibit a significant linker length dependence in 2-methyl-2,3,4,5-tetrahydrofuran, such that the absorption wavelengths in the vicinity of 420 nm are red-shifted as the linker length is decreased. This trend is the opposite to that observed in the corresponding vaulted trans-bis(salicylaldiminato)Pd(II) analogues 2aed under similar conditions. The mechanistic rationale for the specific linker-dependence of the absorption wavelengths of 1 is discussed in comparison with that of 2, based on molecular structures and electronic configurations.