SYNTHESIS AND REACTIVITY OF THE IRIDIUM VINYLIDENE IR=C=CH2[N(SIME2CH2PPH2)2] - FORMATION OF CARBON-CARBON BONDS VIA MIGRATORY INSERTION OF A VINYLIDENE UNIT

The synthesis of the 16-electron iridium vinylidene complex Ir=C=CH2[N(SiMe2CH2PPh2)2] is described by starting from the cyclooctene derivative Ir(eta-2-C8H14)[N(SiMe2CH2PPh2)2] with addition of acetylene. This vinylidene complex reacts with a variety of electrophiles; thus, reaction with AlR3 (R = Me, Et) or GaMe3 leads to the formation of the new derivatives Ir(ER2)CR=CH2[N(SiMe2CH2PPh2)2] (E = Al, R = Me, Et; E = Ga, R = Me). These complexes result from oxidative addition of the ER3 reagent to the coordinatively unsaturated Ir(I) vinylidene followed by migratory insertion to generate the carbon-carbon bond of the substituted vinyl moiety. Oxidative addition of methyl iodide generates as the final product the allyl iodide derivative Ir(eta-3-C3H5)I[N(SiMe2CH2PPh2)2]. This last transformation has been examined in detail using NMR spectroscopy to follow the course of the reaction. A number of intermediates could be observed: the first species is the oxidative adduct Ir=C=CH2(Me)I[N(SiMe2CH2PPh2)2], which undergoes migratory insertion to generate the isopropenyl iodide Ir(CMe=CH2)I[N(SiMe2CH2PPh2)2], which then rearranges to the allyl product. A third intermediate, believed to be an allene-amine derivative of the formula Ir(eta-2-H2C=C=CH2)I[HN(SiMe2CH2PPh2)2] ig observed but was found not to be on the pathway to the allyl complex. Extension to other alkyl halides was attempted; reactions with ethyl iodide and benzyl bromide do proceed, but the resultant product mixtures are complex. Crystallographic data: Ir=C=CH2[N(SiMe2CH2PPh2)2].C6H5CH3, triclinic, a = 11.485 (3) angstrom, b = 115.498 (6) angstrom, c = 11.047 (5) angstrom, alpha = 92.00 (4)-degrees, beta = 103.31 (3)-degrees, gamma = 85.20 (3)-degrees, Z = 2, space group P1BAR; Ir(eta-3-C3H5)I[N(SiMe2CH2PPh2)2], monoclinic, a = 9.571 (4) angstrom, b = 9.267 (6) angstrom, c = 39.262 (5) angstrom, beta = 95.22 (3)-degrees, Z = 4, space group P2(1)/n; Ir(AlMe2)CMe=CH2[N(SiMe2CH2PPh2)2], monoclinic, a = 18.823 (6) angstrom, b = 9.701 (2) angstrom, c = 21.359 (8) angstrom, beta = 111.78 (2)-degrees, Z = 4, space group P2(1)/c; Ir(GaMe2)CMe=CH2[N(SiMe2CH2PPh2)2], monoclinic, a = 18.816 (4) angstrom, b = 9.725 (3) angstrom, c = 21.4429 (4) angstrom, beta = 111.58 (1)-degrees, Z = 4, space group P2(1)/c; IrMeI2[HN(SiMe2CH2PPh2)2].C6H6, orthorhombic, a = 36.250 (5) angstrom, b = 11.368 (12) angstrom, c = 9.892 (8) angstrom, Z = 4, space group Pna2(1). The structures were all solved by heavy-atom methods and were refined by full-matrix least-squares procedures to R = 0.027, 0.026, 0.034, 0.034, and 0.032 for 7795, 5050, 5723, 7025, and 2806 reflections with I greater-than-or-equal-to 3-sigma(I), respectively.