Iridium Carbene and Carbamoyl Complexes Supported by a Tetradentate Pyridine‐Carboxamide Ligand

The nucleophilic attack of an IrIII isocyanide complex bearing a tetradentate pyridine‐carboxamide ligand with amines to give carbene and carbamoyl complexes has been studied. The treatment of Na[Ir(bpb)Cl2] {bpb2– = dianion of 1,2‐bis(2‐pyridinecarboxamido)benzene} with PR3 (R = p‐tolyl) in refluxing glycol gave [Ir(bpb)(PR3)Cl] (1). Chloride abstraction of 1 with silver tosylate (AgOTs) led to isolation of a mixture of [Ir(bpb)(PR3)(OTs)] (2a) and [Ir(bpb)(PR3)(H2O)](OTs) (2b) that reacted with 2,6‐dimethylphenyl isocyanide (CNxyl) and 4‐tert‐butylaniline to give [Ir(bpb)(PR3)(CNxyl)](OTs) (3) and [Ir(bpb)(PR3)(4‐tBuC6H4NH2)](OTs) (4), respectively. The reaction of 4 with AgOTf (OTf– = triflate) yielded an Ir–Ag dimeric complex, [Ir(bpb)(PR3)(4‐tBuC6H4NH2){Ag(H2O)(µ‐OTf)}]2(OTf)2 (5). Whereas nucleophilic attack of 3 with benzylamine (BnNH2) afforded the carbene complex [Ir(bpb)(PR3){C(NHBn)(NHxyl)}](OTs) (6), that with tBuNH2 yielded the carbamoyl complex [Ir(bpb)(PR3){C(O)NHxyl}] (7). The IrIV–IrIII redox potentials for Ir(bpb) complexes have been determined using cyclic voltammetry. The crystal structures of 2a, 2b, and 5–7 have been determined.