Reactions of Rh- and Ir-bis(iminophosphoranyl)methanide compounds with electrophiles; a trapped cation-anion complex in the oxidative addition of iodine to a d 8 metal centre and X-ray crystal structure of IrI{CH(PPh 2NC 6H 4CH 3-4) 2}(COD)]I, containing two fused four-membered metallacycles

Abstract

Reaction of square planar M{CH(PPh 2NC 6H 4CH 3-4) 2(COD)] ( 1a: MRh; 1b: MIr), in which the bis-iminophosphoranylmethanide ligand is bidentate N,C-coordinated, with I 2, MeI and MeOSO 2CF 3 yields products resulting from metal or ligand (N atom) centered reactivity. Complexes 1a and 1b react with MeI and MeOSO 2CF 3 to yield mainly cationic N-methyl or N, N′-dimethyl derivatives. The reaction of b1 with I 2 results in the selective formation of the hexacoordinate Ir(III) complex ( OC-6-43)-[ Ir(I)σ-N,σ-N′,σ-C-{ CH(PPh 2 NC 6 H 4 CH 4-4) 2(η 2,η 2- COD] + I − ( 4) . The molecular structure of 4 has beend determined by an X-ray crystal structure study; it crystallizes in space group P2 1/ c with a=21.040(2), b=18.399(2), c=26.075(3) A ̊ and β =102.33(2)° . A total 5243 reflections ( I>2.5 σ( I)) has been used in the refinement which converged, after including a model for observed disorder, to R=0.061 ( R w=0.084). In the cationic part of 4 the N,N′,C ligand is facilly trridentate coordinated to Ir, thus forming a [2.2.0]-bicyclohexane structure containing an Ir, a C, two P and two N atoms. Iodine is in trans position to the methadine carbon atom. Compound 4 represents a trapped cation-anion complex and may be regarded as a model of an intermediate in the polar oxidative addition of I 2 to d 8 transition metal compounds. Instead of coordinating the second iodine atom, stabilization of 4 is achieved by virtue of the adaptation of the bis(iminophosphoranyl)methanide ligand by coordination of the pendant N atom.