Two chloro-bridged osmium clusters

Abstract

The molecular structure of the chloro-bridged tetra-osmium cluster, dodecacarbonyl-1κ3C,2κ3C,3κ3 C,4κ3C-μ-chloro-3:4κ3 Cl-tris-μ-hydrido-1: 2κ2H;1:3κ2H;2:4κ2 H-tetraosmium(5 Os-Os), [Os4(μ-Cl)(μ-H)3(CO)12], consists of a 'butterfly' arrangement of Os atoms, just as in the iodo analogue. The chloro bridge in the tetraosmium cluster is symmetric, whereas in the pentaosmium cluster, tetradecacarbonyl-1κ3C,2κ2C,3κ3 C,4κ3C,5κ3-μ-chloro-2:5κ2 Cl-tris-μ-hydrido-1:2κ2H;2:3 κ2H;2:4κ2 H-pentaosmium(8 Os-Os), [Os5(μ-Cl)(μ-H)3(CO)14], it is distinctly asymmetric. This asymmetry is attributed to the trans influence of a carbonyl ligand, which lengthens the trans-Os-Cl bond.