IRIDIUM ETA-4-1,5-CYCLOOCTADIENE AND 1,2-ETA-2,6-SIGMA-CYCLOOCTA-1,4-DIENYL COMPLEXES - DEPROTONATION OF COORDINATED 1,5-CYCLOOCTADIENE BY STRONG AND WEAK BASES

The reaction of [lr(eta4-1,5-cyclooctadiene)Cl]2 With 2 equiv of triphos [(Ph2PCH2CH2)2PPh] in methylene chloride yields [lr(triphos)(eta4-1,5-cyclooctadiene)] [CI] (1), which upon reaction with various bases [KOH, NaOCH3, NaOC6H5, NaOC6H4-P-CH3, NaOC6H4-P-C(CH3)3, N(C2H5)3, pyridine,N,N,N,N'-tetramethyl-1,8-naphthalenediamine (Proton Sponge)] in tetrahydrofuran solutions affords the neutral deprotonated complex, Ir(triphos) (1,2-eta2,6-sigma-cycloocta-1,4-dienyl) (2). X-ray structure determinations of 1 and 2 were undertaken. Complex 1 crystallizes in the monoclinic space group P2(1)/c with a = 15.165(2) angstrom, b = 10.791(2) angstrom, c = 23.488(2) angstrom, v = 3843(2) angstrom3, Z = 4, and D(calc) = 1.535 g/cm3. The structure was refined to R = 0.029 and R(w) = 0.038 for 428 variables and 4043 observations. Complex 2 crystallizes in monoclinic space group Cc with a = 9.5782(8) angstrom, b = 39.313(5) angstrom, c = 11.252(2) angstrom, V = 3911(4) angstrom3, Z = 4, and D(calc) = 1.560 g/cm3. The structure was refined to R = 0.027 and R(w) = 0.034 for 425 variables and 2301 observations. The mechanism of formation of 2 by deprotonation of 1 is discussed.