Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 32. Reactions of the rhodium–tungsten complex [RhW(µ-CC6H4Me-4)(CO)3(η-C5H5)(η-C9H7)] with alkynes; X-ray crystal structure of [RhW{µ-C(C6H4Me-4)C(Ph)C(Ph)}(CO)2(η-C5H5)(η-C9H7)]

The bimetal compound [RhW(µ-CR)(CO)3(η-C5H5)(η-C9H7)](R = C6H4Me-4, C9H7= indenyl) reacts with the alkynes R1CCR2(R1= R2= Ph or Me; R1= Ph, R2= H or Me) in toluene at ca. 50–80 °C to give the bridged complexes [RhW{µ-C(R)C(R1)C(R2)}(CO)2(η-C5H5)(η-C9H7)]. The molecular structure of the species obtained from PhCCPh was established by a single-crystal X-ray diffraction study. A Rh–W bond [2.754(1)A] is bridged by a three-carbon chain [mean C–C 1.439(8)A]. Whereas all the atoms of the chain are bound to the rhodium [2.105(6), 2.135(6), and 2.103(5)A], only the two end carbons are attached to the tungsten [2.175(5) and 2.196(6)A]. The tungsten atom carries two essentially orthogonal terminal carbonyl groups, as well as the cyclopentadienyl ring. The indenyl group is asymmetrically attached to the rhodium atom, with three short Rh–C [2.185(7), 2.198(7), and 2.204(7)A] and two long Rh–C [2.334(7) and 2.330(7)A] separations to the C5 ring, implying slippage towards an η3-bonding mode. Formation of [RhW{µ-C(R)C(Ph)C(Ph)}(CO)2(η-C5H5)(η-C5Me5)] from [RhW(µ-CR)(CO)3(η-C5H5)(η-C5Me5)] and PhCCPh requires forcing conditions (100 °C, 5 d in toluene), and side-reactions occur to yield hexaphenylbenzene, [Rh(CO)2(η-C5Me5)], and the tetraphenylcyclopentadienone complex [Rh(µ-C4Ph4CO)(η-C5Me5)]. The reaction between [RhW(µ-CR)(CO)3(η-C5H5)(η-C9H7)] and [W(CR)(CO)2(η-C5H5)] has also been investigated. With heptane as solvent, the products are the trimetal complex [Rh2W(µ3-CR)(µ-CO)(CO)2(η-C5H5)(η-C9H7)2], the alkyne-bridged complex [W2(µ-RC2R)(CO)4(η-C5H5)2], and a compound formulated as [W2{µ-C(R)C(O)C(R)}(CO)4(η-C5H5)2]. Spectroscopic data (i.r., 1H and 13C-{1H} n.m.r.) for the new compounds are reported and discussed.