CHEMICAL-SHIFT ANISOTROPY OF ORGANOMETALLIC CARBON

Principal values of C-13 chemical shift tensors have been measured in 19 compounds containing carbon sigma-bonded to transition metals, name ly, PtMe(2)(cod), PtMe(2)(nbd), PtMe(2)(bpy), PtMe(2)(tmeda), cis-PtMe (2)(dmso)(2), PtClMe(cod), PtClMe(bpy), Pt(CH(2)SiMe(3))(2)(cod), Pt(C H(2)SiMe(3))(2)(nbd), cis-Pt(CH(2)SiMe(3))(2)(dmso)(2), Pt(C=C-(t)Bu)( 2)(cod), Pt(4-(t)Bu-phenyl)(2)(nbd), [Me(3)PtI](4), [Me(3)PtOH](4), (M e(3)Pt)(2)SO4, PdMe(2)(tmeda), Fe(Cp)(CO)(2)Me, Mo(Cp)(CO)(3)Me, and M o(Cp)(CO)(3)Et. A range of behaviours is observed, the most striking o f which is a strong dependence of anisotropy on the nature of the othe r ligands in the complex. A very large anisotropy is induced by the pr esence of a chelating diolefin on the same metal center. The low-frequ ency isotropic shifts generally observed for metal-bound carbon are fo und to result mainly from a single low-frequency component.