UEBERGANGSMETALL-METHYLEN-KOMPLEXE LXI. UEBERGANGSMETALL-VINYLIDEN-KOMPLEXE: NEUARTIGE SYNTHESE AUS DIAZOALKEN-VORSTUFEN

Article abstract of DOI:10.1016/0022-328X(85)80422-8

The diazoolefines of composition N2=C=CR2 (R/R = CH3/CH3 and (-CH2-)5) are suitable precursors of the corresponding vinylidene ligands C=CR2.Thus, treatment of the Rh=Rh complex <(η⁵-C5Me5)Rh(μ-CO)>2 (1) with the N-nitrosourethanes 2a and 2b, resp., in the presence of lithium t-butoxide yields the otherwise inaccessible μ-vinylidene complexes (μ-C=CR2)<(η⁵-C5Me5)Rh(CO)>2 (R = CH3 (3a), R,R = (-CH2-)5 (3b)).The analogous cobalt compound (μ-CCMe2)<(η⁵-C5Me5)Co(CO)>2 (5a) is obtained similarly.This procedure extends the well-documented diazoalkane method for the synthesis of μ-alkylidene complexes to the less stable diazoalkenes.A single-crystal X-ray diffraction study of the dimethylvinylidene derivative 3a shows the C=CMe2 ligand to adopt an almost symmetrically metal-bridging position (d(Rh-C) 197.8(1) and 204.3(1) pm), with a rhodium-rhodium single bond completing a three-membered Rh2C-metallacycle (d(Rh-Rh) 268.4(0) pm) analogous with cyclopropane.