Transition metal–carbon bonds. Part 52. Large ring and cyclometallated complexes formed from But2PCH2CH2CHRCH2CH2PBut2(R H or Me) and IrCl3, or [Ir2Cl4(cyclo-octene)4] : crystal structures of the cyclometallated hydride, [IrHCl(But2PCH2CH2CHCH2CH2PBut2)], and the carbene complex [IrCl(But2PCH2CH2CCH2CH2PBut2)]

Abstract

Treatment of Bu^t ₂P(CH₂)₅PBu^t ₂, with iridium trichloride gives a mixture of the 16-atom ring dihydride [lr₂H₂Cl₄{Bu^t ₂P(CH₂)₅PBu^t ₂}₂], a co-ordinatively saturated cyclometallated hydride, [[graphic omitted]Bu^t ₂)])(1b), which is non-fluxional, and an unidentified complex. A better route to the cyclometallated hydride (1b) is to treat [Ir₂Cl₂(C₈H₁₄)₄](C₈H₁₄= cyclo-octene) with the diphosphine. Complex (1b) takes up carbon monoxide to give the six-co-ordinate [[graphic omitted]Bu^t ₂)] and loses dihydrogen on heating [ca. 200 °C (15 mmHg)] to give the very dark carbene/ylide complex [[graphic omitted]Bu^t ₂)](3)/(4). This carbene/ylide complex takes up dihydrogen at 20 °C (1 atm) to give back (1b). The diphosphine Bu^t ₂PCH₂CH₂CHMeCH₂CH₂PBu^t ₂ reacts with IrCl₃ to give the 16-atom ring chelate [Ir₂H₂Cl₄(Bu^t ₂PCH₂CH₂CHMeCH₂CH₂ PBu^t ₂)₂], no cyclometallated product being detected. However, the complex [[graphic omitted]Bu^t ₂)], can be prepared from [Ir₂Cl₂(C₈H₁₄)₄] and the diphosphine. Hydrogen-1, ¹³C, and ³¹P n.m.r. and i.r. data are reported. The crystal structures of (1b) and of the carbene/ylide (3)/(4) have been determined. Cell dimensions are, for (1b), a= 1 231.8(3), b= 1 435.9(3), c= 1 485.4(3) pm, and β= 104.82(2)° and for (3)/(4), a= 1 232.6(3), b= 1 436.2(3), c= 1 480.7(3) pm, and β= 104.87(2)°. The structures are isomorphous, with space group P2₁/c and Z= 4.