Preparation and characterisation of a series of cationic monometallated, and neutral and cationic tridentate dimetallated, tri-o-tolyl phosphite iridium(III) complexes

Abstract

Stoicheiometric additions of P(OC₆H₄Me-o)₃ to [{IrCl(cod)}₂](cod = cyclo-octa-1,5-diene) in various solvents have given the internally metallated complexes [Ir(P–C)(cod){P(OC₆H₄Me-o)₃}][P–C = P(OC₆H₃Me-o)-(OC₆H₄Me-o)₂], [IrCl(P–C)₂{P(OC₆H₄Me-o)₃}], and a complex analysing for [Ir₂Cl₂{P(OC₆H₄Me-o)₃}₃]. Chemical attempts to fully characterise the last product afforded the dimers [lr₂Cl₂(P–C₂)₂L(L′)][P–C₂= P(OC₆H₃Me-o)₂(OC₆H₄Me-o); L = P(OC₆H₄Me-o)₃, L′= MeCN; L = L′= MeCN, EtOH, PrⁿOH, CO, or SbPh₃]. Bridge fission of [Ir₂Cl₂(P–C₂)₂(CO)₂] with 4-methylpyridine gives [IrCl(P–C₂)(CO)(4Me-py)]. The complex [Ir₂Cl₂{P(OC₆H₄Me-o)₃)₃] is an excellent precursor for the preparation of: (i)[IrCl(P–C₂) L₂][L = 4Me-py, py, PMePh₂, PMe₂Ph, AsMe₂Ph, P[(OCH₂)₃CMe], or PEt₃; L₂= 2,2′-bipyridyl] from ethanol {addition of Na[BPh₄] to the mother liquors of these reactions gives the salts [IrCl(P–C)L₃][BPh₄]}; and (ii) the salts [Ir(P–C₂(NCMe)₃]A (A = PF₆ or BPh₄) from EtOH-MeCN mixtures. Further substitution of this salt produces [Ir(P–C₂)(NCMe)L₂]A (L₂= Ph₂PCH₂CH₂PPh₂; L = PMePh₂ or PMe₂Ph). Relevant aspects of the X-ray crystallo-graphic determination of [IrCl(P–C₂)(4Me-py)₂] are briefly discussed together with i.r. and ¹H n.m.r. data for all the complexes prepared.