In order to extend existing ideas on isotropic spin transfer mechanisms in bipyridine-metal complexes, a series of unsymmetrical methyl-substituted bipyridine ligands, and their nickel(I1) and cobalt(I1) complexes, have been prepared, and their IH nmr isotropic shifts measured experimentally. Simulating different electron spin density transfer mechanisms, from direct 0-electron density transfer to indirect rr-mechanisms involving spin polarization or hyperconjugation, various INDO calculations have been performed on model cations and anions of the free ligand, producing good agreement with the experimental results.T. L. JOSEPH HUANG et DOUGLAS G. BREWER. Can. J. Chem. 59, 1689 (1981). Dans le but d'ktendre les concepts existants relatifs aux mkcanismes de transfert isotrope de spin dans les complexes bipyridine-metal on a prepare une serie de ligands bipyridines non symktriques portant des substituants methyles ainsi que leurs complexes de Ni(I1) et de Co(I1) et on a mesure experimentalement leurs dtplacements isotropes en rmn du 'H. Simulant divers mecanismes de transfert de densite de spin Clectronique, allant du transfert direct de la densite d'electron 0 jusqu'a des mecanismes rr indirects impliquant la polarisation du spin ou I'hyperconjugaison, on a realise divers calculs INDO sur des modkles de cations et d'anions du ligand libre et I'on a obtenu un bon accord avec les rksultats expkrimentaux.[Traduit par le journal]
The heterometallic compound Os 3 (CO) 10 (µ-H)(µ-η 3 -C(dCHPh)CtCW(O) 2 (C 5 Me 5 )) (1), which possesses a bridging hydride and a CtCCdCHPh ligand, is obtained on addition of the diynyl complex (C 5 Me 5 )W(O) 2 (CtCCtCPh) to Os 3 (µ-H) 2 (CO) 10 . 1 H NMR spectra show the occurrence of three isomers at equilibrium in solution, of which two isomers have been unambiguously characterized by an X-ray diffraction study. During subsequent tests of reactivity we isolated Os 3 (CO) 10 (µ-σ:η 2 -CtCCHCHPh)(µ-H) (2) and (C 5 Me 5 )W(µ-O) 2 Os 3 (CO) 9 (µ-σ:η 2 -CtCCHCHPh) (3) through two distinct processes initiated by removal of the (C 5 Me 5 )W(O) 2 fragment and decarbonylation, respectively.
Experimental SectionGeneral Information and Materials. Infrared spectra were recorded on a Perkin-Elmer 2000 FT-IR spectrometer. 1 H and 13 C NMR spectra were recorded on a Bruker AM-400
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