PENTADIENYL-METAL-PHOSPHINE CHEMISTRY .23. PENTADIENYL-IRIDIUM-PHOSPHINE CHEMISTRY - SURVEY OF THE REACTIONS OF PENTADIENIDE REAGENTS WITH CLIRL3 COMPLEXES

A systematic study of the reactions of four ClIrL3 complexes with pentadienide reagents has been carried out. Treatment of ClIr(PEt3)3 with potassium pentadienide produces (1,4,5-eta-pentadienyl)Ir(PEt3)3 (2), while the reaction of ClIr(PMe3)3 with potassium pentadienide yields the analogous trimethylphosphine compound 5. In contrast, treatment of ClIr(PMe3)3 with potassium 2,4-dimethylpentadienide produces an equilibrium mixture of (1,4,5-eta-2,4-dimethylpentadienyl)Ir(PMe3)3 (3) and the metallacyclohexadiene complex fac-(activated IrCH2C(Me) = CHC(Me) = CH)(PMe3)3(H) (4). The formation of 4 involves the intermediacy of 16e- (eta-1-2,4-dimethylpentadienyl)Ir(PMe3)3, which intramolecularly activates a C-H bond on the end of the pentadienyl chain. Vaska's complex, ClIr(PPh3)2(CO), reacts with potassium 2,4-dimethylpentadienide to produce an equilibrium mixture of (1,4,5-eta-2,4-dimethylpentadienyl)Ir(PPh3)2(CO) (6) and (1-3-eta-2,4-dimethylpentadienyl)Ir(PPh3)2(CO) (7). The analogous reaction involving unmethylated pentadienide produces exclusively (1-3-eta-pentadienyl)Ir(PPh3)2(CO) (8). This species undergoes a dynamic process in solution, which involves shuttling between eta-3- and eta-1-pentadienyl bonding modes. Treatment of ClIr(PEt3)2(CO) with potassium 2,4-dimethylpentadienide yields (1,4,5-eta-2,4-dimethylpentadienyl)Ir(PEt3)2(CO) (9), while the analogous reaction involving unmethylated pentadienide produces an equilibrium mixture of (1,4,5-eta-pentadienyl)Ir(PEt3)2(CO) (10) and (1-3-eta-pentadienyl)Ir(PEt3)2(CO) (11). Molecular structures of compounds 2, 3, 6, and 8 have been determined by single-crystal X-ray diffraction studies. Crystal structure data for these compounds are as follows: 2, monoclinic, P2(1)/c, a = 15.489 (5) angstrom, b = 11.453 (5) angstrom, c = 15.769 (4) angstrom, beta = 101.83 (2)-degrees, V = 2738 (2) angstrom 3, Z = 4, R = 0.038 for 3572 reflections with I > 3-sigma(I); 3, monoclinic, P2(1)/n, a = 8.958 (6) angstrom, b = 20.308 (5) angstrom, c = 11.970 (5) angstrom, beta = 93.14 (5)-degrees, V = 2174 (2) angstrom 3, Z = 4, R = 0.037 for 3440 reflections with I > 3-sigma-(I); 6, monoclinic, P2(1)/n, a = 13.518 (5) angstrom, b = 17.862 (6) angstrom, c = 15.417 (5) angstrom, beta = 93.59 (3)-degrees, V = 3715 (2) angstrom 3, Z = 4, R = 0.035 for 5003 reflections with I > 3-sigma-(I); 8, monoclinic, P2(1)/c, a = 17.276 (7) angstrom, b = 23.038 (8) angstrom, c = 18.896 (5) angstrom, beta = 111.92 (2)-degrees, V = 6977 (4) angstrom 3, Z = 8, R = 0.049 for 6353 reflections with I > 3-sigma-(I).