Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 86. Aikylidyne(carbaborane)molybdenum–gold, –rhodium and –iron complexes; crystal structure of [NEt4][MoFe2(µ3-CC6H4Me-4)(µ-σ : σ′ : η5C2B9H7Me2)(CO)8

Abstract

The alkylidyne–molybdenum complex [NEt4][Mo(CC6H4Me-4)(CO){P(OMe)3}(η5-C2B9H9Me2)] has been prepared, and used to prepare compounds with bonds between molybdenum and gold, rhodium, and iron. Reactions of the molybdenum compound with [AuCl(PPh3)],[Rh(cod)(PPh3)2][PF6](cod = cyclo-octa-1,5-diene), and [Fe2(CO)9] afford, respectively, the complexes [MoAu(µ-CC6H4Me-4)(CO){P(OMe)3}(PPh3)(η5-C2B9H9Me2)], [MoRh(µ-CC6H4Me-4)(µ-CO){P(OMe)3}(PPh3)2(η5-C2B9H9Me2)], and [NEt4][MoFe2(µ3-CC6H4Me-4)(µ-σ : σ′ : η5-C2B9H7Me2)(CO)8]. The structure of the latter has been established by X-ray diffraction. There are two crystallographically independent anions with their associated cations in the asymmetric unit but with overall very similar geometries. In the anions a triangle of metal atoms is symmetrically capped on one side by the alkylidyne ligand. On the other side of the triangle the molybdenum atom is η5-ligated by the C2B9cage, but two boron atoms in the pentagonal face are σ bonded to the two iron atoms. The molybdenum carries two carbonyl groups and each of the iron atoms is bonded by three of these ligands. The reaction between [Fe2(CO)9] and [NEt4][Mo(CC6H4Me-4)(CO){P(OMe)3}(η5-C2B9H9Me2)] also affords the novel mononuclear molybdenum compound [NEt4][Mo{σ,η5-CH (C6H4Me-4)C2B9H8Me2}(CO)3]. Protonation (HBF4·Et2O) of CO-saturated CH2Cl2solutions of the latter gives the neutral complex [Mo(CO)4{η5-C2B9H8(CH2C6H4Me-4)Me2}]. Protonation in the presence of an excess of PMe3 gives a mixture of the two compounds [Mo(CO)3(L){η5-C2B9H8(CH2C6H4Me-4)Me2}](L = PMe3 or CO). The n.m.r. data (1H, 13C-{1H},11B-{1H}, and 31P-(1H}) for the new compounds are reported and discussed.