SYNTHESIS OF 2-PYRROLYL COMPLEXES OF RUTHENIUM AND OSMIUM VIA HYDROLYSIS OF A CHLORO(PYRROLYL)CARBENE LIGAND OR VIA TRANSMETALATION REACTIONS USING (2-PYRROLYL)MERCURIC CHLORIDE

The chloro(2-pyrrolyl)carbene complex Ru(=C[Cl]-2-C4H3NH)Cl2(CO)(Pph3)2 (1) undergoes hydrolysis and rearrangement to give the sigma-bound 2-pyrrolyl complex Ru(2-C4H3NH)Cl(CO)2(Pph3)2(2). Compound 2, and the osmium analogue Os(2-C4H3NH)Cl-(CO)2(Pph3)2 (4), can be prepared by reaction of (2-pyrrolyl)mercuric chloride (3) with the low-oxidation-state compounds M(CO)2(Pph3)3 (M = Ru, Os), respectively. Key steps in the synthesis of compound 3 involve protection of the pyrrolic nitrogen atom with a lithiocarboxylate function followed by selective lithiation and then mercuration in the ring 2-position.