Ligand coordination in [Re2(CO)9(NCMe)] and [H3Re3(CO)11(NCMe)] by triphenylantimony: Reactivity studies and Sb–Ph bond cleavage to give new antimony-containing di- and trirhenium complexes

Abstract The reactions of the MeCN-substituted compounds [Re2(CO)9(NCMe)] and [H3Re3(CO)11(NCMe)] with SbPh3 are described. Treatment of [Re2(CO)9(NCMe)] with SbPh3 in refluxing benzene furnished [Re2(CO)9(SbPh3)] (1) in good yield. Complex 1 reacts with SbPh3 in the presence of Me3NO in acetonitrile to give [Re2(CO)8(σ-C6H5)(µ-SbPh2)(NCMe)] (2), which on further reaction with additional SbPh3 in refluxing benzene afforded the known complex [Re2(CO)8(σ-C6H5)(µ-SbPh2)(SbPh3)] (3). Heating 1 with SbPh3 at 110 °C yields 3, which on prolonged heating at 110 °C in the presence of SbPh3 furnished the known stibene-bridged compound [Re2(CO)7(µ-SbPh2)2(SbPh3)] (4). Complex 2 is a rare example of a dirhenium complex containing a sigma-bonded phenyl group and a labile acetonitrile ligand in the same molecule. The stibene-bridged dirhenium complexes (2−4) result from the cleavage of antimony-carbon and Re–Re bonds. Heating [H3Re3(CO)11(NCMe)] with SbPh3 in refluxing toluene afforded the new compounds [H3Re3(CO)11(SbPh3)] (5), [H2Re3(CO)11(µ-SbPh2)(SbPh3)] (6), and [HRe2(CO)6(µ-SbPh2)(SbPh3)2] (8) together with previously reported compound [HRe2(CO)7(µ-SbPh2)(SbPh3)] (7). Compound 5 is a simple monosubstituted product, while 6 contains a terminally coordinated SbPh3 ligand and a bridging SbPh2 group formed by Sb–Ph bond scission. Compound 8 results from cluster fragmentation and SbPh3 ligand activation by Sb–Ph bond cleavage. A series of separate thermolysis experiments have been performed in order to establish the relationship between the different products. Compounds 1, 2, 5, 6, and 8 have been structurally characterized by X-ray crystallography. The bonding in these new compounds has been investigated by electronic structure calculations.