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–H⇀Lr 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-H⇀Lr, 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.