Synthesis of Iridium Tetrazolato, Triazolinato, and Triazolato Complexes by [3+2] Cycloaddition of Iridium(III) Azido Complexes with Unsaturated Nitriles

The diazido complexes [Ir(eta(5)-C5Me5)(N-3)(2)-(PPh3)] (1a), [Ir(eta(5)-C5Me5)(N-3)(2){kappa(P)-R2PCH2CH=CH2}] (R = Ph (1b), Pr-i (1c)) have been synthesized and their [3+2] cycloaddition reaction toward tetracyanoethylene and fumaronitrile investigated. Complexes 1a-1c react with tetracyanoethylene, giving single (2a, 2b, 2c) or double (4a, 4b) azide-nitrile cycloadducts. The complexes [Ir(eta(5)-C5Me5){kappa(2)(N-1,N-1)-(N4C)(2)C=C(CN)(2)}(PPh3)] (3a) and [Ir(eta(5)-C5Me5){kappa(2)(N-1,N-1)-(N4C)(2)C=C(CN)(2)}{kappa(P)-Ph2PCH2-CH=CH2}] (3b) have been obtained through the [3+2] cycloaddition reaction involving the azide ligands of complexes 1a,b and two geminal nitrile groups of tetracyanoethylene. Uncommon triazolinato stable complexes [Ir(eta(5)-C5Me5)(N-3)-{kappa(N-1)-N3CH(CN)CH(CN)}(PPh3)] (5a) and [Ir(eta(5)-C5Me5)(N-3){kappa(N-1)-N3CH(CN)CH(CN)}{kappa(P)-Ph2PCH2CH=CH2}] (5b) have been stereoselectively prepared from 1a,b and fumaronitrile through a single [3+2] cycloaddition reaction between the C-C double bond of fumaronitrile and an azide ligand. The treatment of a dichloromethane solution of complexes 5a and 5b with basic alumina gives regioselectively the triazolato complexes 6a and 6b. The structures of complexes 2b, 3a, and 6a have been determined by single-crystal X-ray diffraction analysis.