Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 68. Reactions between nonacarbonyldi-iron and the salts [NEt4][W(CR)(CO)2(η5-C2B9H9Me2)](R = Me, Ph, or C6H4Me-4); crystal structures of [NEt4][FeW{µ-CH(C6H4Me-4)}(µ-σ:η5-C2B9H8Me2)(µ-CO)(CO)5] and [NEt4][Fe2W(µ3-CPh)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8

Abstract

Treatment of the compound [NEt4][W(CMe)(CO)2(η5-C2B9H9Me2)] with [Fe2(CO)9] in tetrahydrofuran at room temperature affords the trimetal compound [NEt4][Fe2W(µ3-CMe)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8]. Similar reactions between [Fe2(CO)9] and the salts [NEt4][W(CR)(CO)2(η5-C2B9H9Me2)](R = Ph or C6H4Me-4) afford mixtures of the di- and tri-metal compounds [NEt4][FeW{µ-CH(R)}(µ-σ:η5-C2B9H8Me2)(µ-CO)(CO)5] and [NEt4][Fe2W(µ3-CR)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8]. The structures of the two species [NEt4][FeW{µ-CH(C6H4Me-4)}(µ-σ:η5-C2B9H8Me2)(µ-CO)(CO)5] and [NEt4][Fe2W(µ3-CPh)(µ-σ:σ′,η5-C2B9H7M2)(CO)8] have been established by X-ray diffraction. In the anion of the former, the Fe–W bond [2.625(1)A] is spanned by an alkylidene group C(H)C6H4Me-4 [µ-C–Fe 2.153(5), µ–C–W 2.172(5)A], and a carbonyl ligand [µ-C(O)–Fe 2.021(4), µC(O)–W 2.172(5)A; W–C–O 149.3(3), Fe–C–O 133.2(3)°]. The tungsten atom carries two terminally bound CO groups, and is η5-co-ordinated by the nido face of the carbaborane cage. The latter is linked to the iron via a σ bond involving a boron atom adjacent to a carbon atom in the face of the cage. The iron is ligated by three terminally bonded CO groups. In the di-irontungsten salt there is an isosceles triangle of metal atoms [Fe–W 2.645(2), Fe–Fe 2.578(2)A], capped on one side by the phenylmethylidyne group [µ3–C–Fe 2.06(1), µ3-C–W 2.029(8)A]. On the opposite side of the triangle a µ3-C2B9H7Me2 ligand is η5-co-ordinated to tungsten with two adjacent boron atoms in the nido face of the carbaborane cage forming σ bonds to the iron atoms [Fe–B 2.12(1) and 2.14(1)A]. There are eight terminally bound carbonyl groups, three attached to each iron atom, and two bonded to the tungsten atom. Treatment of [NEt4][Fe2W(µ3-CMe)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8] in tetrahydrofuran with [AuCl(PPh3)], in the presence of TIPF6, affords a tetranuclear metal cluster complex [AuFe2W(µ3-CMe)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8(PPh3)]. The n.m.r. data (1H, 13C-{1H}, and 11B-{1H}) for the new compounds are reported and discussed.