Late transition metal .mu.-oxo and .mu.-imido complexes. Part 3. Sequential insertion of carbon monoxide into rhodium-nitrogen .mu.-imido/amido bonds. Formation of isocyanate and dimetallocycloimide complexes

Catalytic carbonylations of organoazides and nitroaryls are frequently postulated to proceed via metal imido intermediates. In support of this proposal imido complexes have been isolated from reactions of metal complexes with organoazides, nitroaryls, and nitrosoaryls. In the catalytic processes the formation of nitrogen-carbon bonds is a key step. In most cases, isocyanate (formed by coupling of the imido ligand and CO) is the final product or is a probable precursor to the final product. However, until recently the isolated imido complexes have given little, if any, isocyanates or products derived from isocyanates when treated with CO under mild conditions. This communication reports the facile formation of isocyanate and dimetallocycloimide complexes and free isocyanates and ureas by the formal single and double insertion of CO into the metal-nitrogen bonds of rhodium {mu}-imido/amido A-frame complexes.