Addition of amines to a carbonyl ligand: Syntheses, characterization, and reactivities of iridium(iii) porphyrin carbamoyl complexes

Article abstract of DOI:10.1021/om500189a

Treatment of (carbonyl)chloro(meso-tetra-p-tolylporphyrinato)iridium(III), (TTP)Ir(CO)Cl (1), with excess primary amines at 23°C in the presence of Na₂CO₃ produces the trans-amine-coordinated iridium carbamoyl complexes (TTP)Ir(NH₂R)[C(O)NHR] (R = Bn (2a), n-Bu (2b), i-Pr (2c), t-Bu (2d)) with isolated yields up to 94%. The trans-amine ligand is labile and can be replaced with quinuclidine (1-azabicyclo[2.2.2]octane, ABCO), 1-methylimidazole (1-MeIm), triethyl phosphite (P(OEt)₃), and dimethylphenylphosphine (PMe₂Ph) at 23°C to afford the hexacoordinated carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (for R = Bn: L = ABCO (3a), 1-MeIm (4a), P(OEt)₃ (5a), PMe₂Ph (6a)). On the basis of ligand displacement reactions and equilibrium studies, ligand binding strengths to the iridium metal center were found to decrease in the order PMe₂Ph > P(OEt)₃ > 1-MeIm > ABCO > BnNH ₂ ? Et₃N, PCy₃. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = RNH₂ (2a,b), 1-MeIm (4a)) undergo protonolysis with HBF₄ to give the cationic carbonyl complexes [(TTP)Ir(NH₂R)(CO)]BF₄ (7a,b) and [(TTP)Ir(1-MeIm)(CO)] BF₄ (8), respectively. In contrast, the carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = P(OEt)₃ (5a), PMe₂Ph (6a,c)) reacted with HBF₄ to afford the complexes [(TTP)Ir(PMe ₂Ph)]BF₄ (9) and [(TTP)IrP(OEt)₃]BF₄ (10), respectively. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = RNH ₂ (2a-d), 1-MeIm (4a), P(OEt)₃ (5b), PMe₂Ph (6c)) reacted with methyl iodide to give the iodo complexes (TTP)Ir(L)I (L = RNH₂ (11a-d), 1-MeIm (12), P(OEt)₃ (13), PMe₂Ph (14)). Reactions of the complexes [(TTP)Ir(PMe₂Ph)]BF₄ (9) and [(TTP)IrP(OEt)₃]BF₄ (10) with [Bu₄N]I, benzylamine (BnNH₂), and PMe₂Ph afforded (TTP)Ir(PMe ₂Ph)I (14), (TTP)Ir[P(OEt)₃]I (13), [(TTP)Ir(PMe ₂Ph)(NH₂Bn)]BF₄ (16), and trans-[(TTP) Ir(PMe₂Ph)₂]BF₄ (17), respectively. Metrical details for the molecular structures of 4a and 17 are reported.