Investigation of the reactivity of palladium(0) complexes with nitroso compounds: relevance to the palladium-phenanthroline-catalysed carbonylation reactions of nitroarenes

The electron transfer reaction between palladium(0) complexes and RNO compounds afforded different palladium species depending on the aromatic or aliphatic nature of R. When R = Ph a paramagnetic palladium complex 1 was isolated, whereas if R = Bu-t the palladium enolate complex 2 was the unexpected reaction product. Complex 1 reacted with methanol and CO to yield Pd(phen)(C(O)OCH3}(2) 3, which was characterised by single-crystal X-ray structure determination. Compound 3 is a probable intermediate in the reductive carbonylation reaction of organic nitro compounds catalysed by palladium complexes. Nitrobenzene is in fact carbonylated to PhNHCO2Me, by using 3 as a very efficient catalyst.