Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 88. Carbaboranetungsteniridium compounds; crystal structure of the complex [WIr(µ-CC6H4Me-4)(CO)2(PEt3)2(η5-C2B9H9Me2)]

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Abstract
The reaction between the compounds [Ir(PPh3)2(cod)][PF6](cod = cycle-octa-15diene) and [N(PPh3)2][W(CR)(CO)2(η5-C2B9H9Me2)](R = C6H4Me-4) in thf (tetrahydrofuran) at room temperature affords the complex [WIr(µ-CR)(CO)2(PPh3)2(η5-C6B2H9Me2)]. The triphenylphosphine groups in the latter can be displaced with PEt3, P(OPh)3, or P(OMe)3 to give the compounds [WIr(µ-CR)(CO)2L(L′)(η5-C2B9H9Me2)][L = L′= PEt3, P(OPh)3, or P(OMe)3; L = PPh3, L′= P(OMe)3]. In solution several of these products exist as isomeric mixtures. An X- ray diffraction study was carried out on an isomer of [WIr(µ-CR)(CO)2(PEt3)2(η5- C2B9H9Me2)]. The W–lr bond [2.590(1)Å] is spanned by the p-tolylmethylidyne group [µ-C–W 2.06(1), µ-C–Ir 1.95 (1)Å]. The nido-icosahedral fragment C2B9H7Me2 is η5-co-ordinated to the tungsten, but the central boron CCBBB in the pentagonal face of the ligand is attached to the iridium via a two-electron three-centre B–HLr bond. The tungsten atom also carries two terminal CO groups, and the two PEt3 ligands are bonded to the iridium. The co-ordination environment of the iridium is such that the plane defined by the atoms IrP2 is perpendicular to that containing the atoms W, µ-C, and B-HLr, and the midpoint of the cage C–C bond. The reaction between [WIr(µ-CR)(CO)2(PPh3)2(η5-C2B2H8Me2)] and P(OMe)3 also affords the compounds [WIrH(µ-CR)(µ-σ:η5-C2B9H8Me2)(CO)3{P(OMe)3}2] and [WIrH{µ-σ: η5-CH (R)(C2B2H7Me2)}(CO)2{P(OMe)3}4]. Similarly PMe3 displaces the PPh3 groups in the precursor to give [WIrH(µ-CR)(µ-σ:η5-C2B2H8Me2)(CO)2(PMe3)3] and [WlrH{µ-σ: η5-CH(R)(C2B9H7Me2)}(CO)2(PMe3)4]. The reactions between [IrL2(cod)][PF6](L = Ph2PCH2CH2PPh2 or 2,2′- bipyridine) and [N(PPh3)2][W(CR)(CO)2(η5-C2B9H9Me2)] yield tungsten–iridium complexes [WIrH (µ-CR)(µ-σ: η5-C2B9H8Me2)(CO)3L2] with terminal Ir–H bonds, and σ B–Lr linkages to the carbaborane group ligating the tungsten. N.m.r. data (1H, 13C-{1H}, 31P-{1H}, and 11B-{1H}) for the new compounds are reported and discussed.

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