Crystal and molecular structure of di-µ-carbonyl-{µ-carbonyl-bis[(methyldiphenylphosphine)platino]}dicarbonyl(methyldiphenylphosphine)ruthenium(2Ru–Pt)(Pt–Pt). A substituted heteronuclear cluster carbonyl of unexpected asymmetry

Abstract

Crystals of the title compound (l) are triclinic, space group P, with Z= 2 in a unit cell of dimensions : a= 10.694(3), b= 22.424(7), c= 8.938(2)Å, α= 83.41 (2). β= 90.02(2), γ= 92.42(2)°. The structure has been elucidated by conventional heavy-atom methods from 5 002 non-zero intensities measured on a diffractometer, and refined to R 0.100. The three metal atoms are bonded to form a triangle which is bridged on all three sides, approximately symmetrically, by carbonyl groups orientated perpendicular to the corresponding metal-metal bond in a coplanar cyclic system. Each Pt atom carries one phosphine ligand with the Pt–P bond in the equatorial plane. The third phosphine is bonded axially to the ruthenium atom and is trans to one of the two terminal carbonyl groups also attached to Ru. The equatorial carbonyl group, surprisingly, is not symmetrically placed with respect to the two Ru–Pt bonds, probably for steric reasons; in consequence the two Ru–Pt bond lengths are different [2.707(2) and 2.729(2)Å], the longer bond lying opposite to the larger Pt–Ru–CO angle. Pt–Pt Is 2.647(2), and mean Pt–P 2.262(7)Å.