Synthesis and reactivity of half-sandwich (η5-C5Me5)Ir(iii) complexes of a cyclometallated aryl phosphine ligandThis paper is dedicated with much appreciation to Professor Didier Astruc, on the occasion of his 65th birthday, in recognition of his fundamental contributions to Inorganic and Organometallic Chemistry.CIF files for compounds 1-Cl, 1-SCN, 2-Hand 3. CCDC reference numbers 817784–817787. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c1nj20244h

Reaction of the Ir(iii) dimer [(η5-C5Me5)IrCl2]2with PMeXyl2(Xyl = 2,6-C6H3Me2), in the presence of the poorly coordinating base 2,2,6,6-tetramethyl piperidine, gives a chloride complex 1-Cl, resulting from hydrogen chloride elimination involving one of the phosphine benzylic hydrogen atoms and concomitant cyclometallation. Related compounds containing other halide or pseudohalide ligands, 1-Br, 1-Cl, 1-SCN, can be made, the latter featuring S-coordination of the ambidentate thiocyanate to the soft Ir(iii) Lewis acid centre, as suggested by IR data and demonstrated by X-ray crystallography. Hydride 2-H, and alkyl derivatives 3(Me) and 4(CH2SiMe3) can also be prepared from 1-Cland appropriate hydride and alkylating reagents. An interesting H/D exchange chemistry that occurs in the presence of CD3OD has been disclosed for 1-Cl, 1-Brand 2-H. For the halide derivatives, deuterium incorporation takes place into the methylene and methyl sites of their cyclometallated ligand, whereas for 2-Honly the hydride and methylene (Ir–CH2) protons participate in the exchange, which is strikingly accelerated by catalytic amounts of acids. [ABSTRACT FROM AUTHOR]