ChemInform Abstract: SPECTROSCOPIC STUDIES ON C2 HYDROCARBON FRAGMENTS. PART 1. VIBRATIONAL STUDIES OF CLUSTER‐BOUND VINYL AND VINYLIDENE LIGANDS

Abstract

Vibrational assignments of the vinyl and vinylidene groups in [Os3(CO)10(µ-H)(µ-η2-CHCH2)](1) and [Os3(CO)9(µ-H)2(µ3-η2-CCH2)](3) respectively have been made on the basis of normal co-ordinate analyses of the Os3(C2Hn)(n= 2 or 3) fragments and [2H] substitution. π-Co-ordination caused the lowering of the principal ν(CC) vibration to 1 311 and 1 331 cm–1 in (1) and (3) respectively. The vinyl group frequencies could largely be transferred to assign partially the spectrum of another vinyl complex [Ru2(CO)3(η5-C5H5)2(µ-η2-CHCH2)]BF4(2) with the same co-ordination mode. The vinylidene frequencies in (3) were quite distinct from those of another complex, [Ru2(CO)3(η5-C5H5)2(µ-CCH2)](4) which has a different co-ordination mode; a band at 1 586 cm–1 in (4) is assigned as consisting largely of the ν(CC) mode. Analysis was also made of the Os(µ-H) group in (1) and showed strong mixing between the symmetric ν(Os–H) and out-of-plane bend giving rise to the i.r. active vibrations at 1 285 and 710 cm–1; the asymmetric ν(Os–H) stretch occurs at 1 394 cm–1.