Edward Rosenberg

Carbon-13 nuclear magnetic resonance spectra and mechanism of bridge–terminal carbonyl exchange in di-µ-carbonyl-bis[carbonyl(η-cyclopentadienyl)iron](Fe–Fe)[{(η-C5H5)Fe(CO)2}2]; cd-di-µ-carbonyl-f-carbonyl-ae-di(η-cyclopentadienyl)-b-(triethyl -phosphite)di-iron(Fe–Fe)[(η-C5H5)2Fe2(CO)3P(OEt)3], and some related complexes

A mechanism involving carbonyi-bridge breaking, rotation about the Fe–Fe bond, and bridge reformation is shown to account qualitatively for changes in the carbonyl region of the 13C n.m.r spectrum of the complex [(cp)(OC)[graphic omitted]e(cp){P(OEt)3}] and quantitatively for [(cp)(OC)[graphic omitted]e(CO)(cp)](cp =η-cyclopentadienyl).The activation energy for this process, 49·0 ± 4 kJ mol–1(11·7 ± 1 kcal mol–1), is close to that reported for cis–trans-isomerization of the cp groups, in accord with this mechanism. Variable-temperature 13C n.m.r. spectra of the complexes [(cp)(OC)[graphic omitted]u(CO)(cp)] and [(cp)(OC)[graphic omitted]i(cp)] are also reported.

Carbene complexes. Part III. Carbon-13 nuclear magnetic resonance studies of carbene complexes of 1,3-diorganoimidazolidin-2-ylidenes

13 C N.m.r. data for the series of cis and trans-neutral carbene complexes [MX2(R3′E)([graphic omitted]R)](where M = Pt, Pd; E = P, As; X = Cl, Br, Me; R = Me, Ph; and R′= Et, Prn, Bun), and the related complexes Fe(CO)4 [graphic omitted](CH3) and cis-Cr(CO)4[C(SCH3)2]2 are presented. The chemical shift of the carbene carbon is sensitive to the trans-ligand. Unusual long range 31P–13C couplings to the ring methylene carbon and 195Pt–13Ccarb couplings are reported for four of the complexes studied.