Formation of hydride, formyl, hydroxymethyl, dimetal ketone, and ethylene-bridged species from small-molecule substrate reactions with rhodium complexes of an N-4 nonmacrocyclic ligand

Reactions of the rhodium(II) dimer [(dbpb)-Rh](2) (1) ((dbpb)H-2 (2) = 4,5-dimethyl-1,2-bis((4-(1-butylpentyl))pyridine-2-carboxamido)benzene) with H-2, CO, and CH2=CH3 produce a rhodium(III) hydride, (dbpb)Rh-H (3), dirhodium hetone, (dbpb)Rh-C(O)-Rh(dbpb) (4), and an ethylene-bridged complex, (dbpb)-Rh-CH2CH2-Rh(dbpb) (5), respectively. The rhodium-(III) hydride (3) reacts with CO and H2CO to produce formyl, (dbpb)Rh-CHO (6), and hydroxymethyl, (dbpb)-Rh-CH2OH (7) complexes. Equilibrium thermodynamic studies for reactions of 1 with hydrogen and ethene and the observed substrate reactions of 1 and 3 indicate that the (dbpb)Rh-H and (dbpb)Rh-C bond dissociation enthalpies are comparable to those for rhodium porphyrin complexes.