Chelation of vinyl acetate and related unsaturated ketones: molecular structure of [Os3(CO)10(CH2CHOCOMe)]

Abstract

The cluster [Os₃H₂(CO)₁₀] reacts with neat vinyl acetate at room temperature to give complexes [Os₃H (CHCH₂)(CO)₁₀](5%) and [Os₃(CO)₁₀(CH₂CHOCOMe)](1)(43%). Complex (1) has also been obtained (30%) from [Os₃(CO)₁₀(MeCN)₂]. The X-ray crystal structure of complex (1) has been determined. Crystals are monoclinic, space group P2₁/n, with a= 17.218(3), b= 13.407(3), c= 8.597(3)Å, β= 93.67(4)°, and Z= 4; the structure has been refined to R= 0.0565 for 2 562 observed reflections. The structure is related to that of [Os₃(CO)₁₂] but with two carbonyl ligands at one osmium atom being replaced by a chelating vinyl acetate. The ester group is co-ordinated axially [ν(CO) 1 622 cm^–1] and the η²-vinyl group equatorially. The triosmium cluster [Os₃(CO)₁₀(CH₂CMeCH₂COMe)][ν(CO) 1 642 cm^–1] obtained from 4-methylpent-3-en-2-one and [Os₃(CO)₁₀(MeCHCHCH₂COMe)][ν(CO) 1 640 cm^–1] obtained from hex-5-en-2-one have been shown by their i.r. and ¹H n.m.r. spectra to be isostructural with complex (1).