Some unusual iridium complexes formed from (2,6-dimethoxyphenyl) and (2,3-dimethoxyphenyl)-di-t-butylphosphine: crystal structure of [2-di-t-butylphosphino-3-methoxyphenoxo-OP]{2-[(2-hydroxy-6-methoxyphenyl)t-butylphosphino]-2-methylpropanato(2—)-C1PO2}-(methyl isocyanide)iridium(III)

Abstract

The compound PBu^t₂[C₆H₃(OMe)₂-2,6] reacts with iridium trichloride in propan-2-ol to give the purple five-co-ordinate hydride [[graphic omitted]Bu^t₂-2)}₂](1). This hydride in solution is converted by air into the red paramagnetic iridium(II) complex [[graphic omitted]Bu^t₂-2)}₂](3) which can be converted back to (1) when treated with Na[BH₄]. The hydride (1) takes up small ligands (L) such as pyridine or carbon monoxide reversibly to give colourless adducts [[graphic omitted]Bu^t₂-2)}₂]. Complex (3) takes up dioxygen reversibly to give a purple complex, probably [[graphic omitted]Bu^t₂-2)}₂], reacts with NO to give brown diamagnetic [[graphic omitted]Bu^t₂-2)}₂] and with CO to give a pale green complex which in air becomes intensely blue, then red, and finally gives the colourless C-cyclometallated iridium(III) complex [[graphic omitted]}{OC₆H₃(OMe-3)(PBu^t₂-2)}](7; L = CO). The dioxygen adduct is slowly converted into the purple, co-ordinatively unsaturated, C-cyclometallated complex [[graphic omitted]Bu^t₂-2)}](8). Complex (8) takes up small ligands such as CO, pyridine, or MeNC more strongly than (1) to give six-co-ordinate species. The structure of the title complex (7; L = MeNC) has been determined by X-ray diffraction. The crystals are monoclinic, space group P2₁/c, with a= 13.471 (2), b= 16.043(3), c= 16.690(3)Å, and β= 104.22(1)°. The complex has a five-membered IrPC₂O chelate ring bound to a highly strained four-membered IrPC₂ ring. Complex (8) also takes up PMe₂Ph; this addition is reversed on heating and the ³¹P n.m.r. spectrum at 300 K shows that rapid PMe₂Ph exchange occurs (at 233 K exchange does not occur). Treatment of iridium carbonyl chloride solution with PBu^t₂[C₆H₃(OMe)₂-2,6] and PBu^t₂[C₆H₃(OMe)₂-2,3] gives yellow complexes of the type [[graphic omitted]Bu^t₂-2)}₂], isomeric and much more stable than the one described above. Hydrogen-1, ¹³C, and ³¹P n.m.r. and i.r. data are given.