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)Å] is spanned by an alkylidene group C(H)C₆H₄Me-4 [µ-C–Fe 2.153(5), µ–C–W 2.172(5)Å], and a carbonyl ligand [µ-C(O)–Fe 2.021(4), µC(O)–W 2.172(5)Å; 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)Å], capped on one side by the phenylmethylidyne group [µ₃–C–Fe 2.06(1), µ₃-C–W 2.029(8)Å]. 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)Å]. 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.