Polyhetero-ferrocenes and -ruthenocenes derived from the 1,4,2-diphosphastibolyl ring anion [P₂SbC₂Bu^t₂]^-

The complex [RuCl₂(PPh₃)₃] reacted with the 1,4,2-diphosphastibolyl ring anion [P₂SbC₂Bu^t₂]^- (containing ca. 25% of the 1,2,4-triphospholyl anion [P₃C₂Bu^t₂]^-) to produce a cocrystallised mixture (crystal structure) of two isomers of [Ru(η⁵-P₂SbC₂Bu^t ₂)₂] with [Ru(η⁵-P₂SbC₂Bu^t₂)]. Variable-temperature ³¹P-{¹H} NMR studies on the mixture show one of the isomers and the last complex to be fluxional at room temperature. It is believed that an interring Sb ⋯ Sb interaction in the other isomer restricts its fluxionality in solution. The reaction of [P₂SbC₂Bu^t₂]^- with FeCl₂ yielded only one isomer of the heteroferrocene complex [Fe(η⁵-P₂SbC₂Bu^t ₂)₂] which is also non-fluxional in solution and has a similar oxidation potential to that of ferrocene itself. The heteroruthenocene complexes [Ru(η⁵-P₂SbC₂Bu^t ₂)(η⁵-C₅R₅)] (R = H or Me) were prepared by treating [Ru(η⁵-C₅R₅)(MeCN)₃][PF ₆] (R = H or Me) with [P₂SbC₂Bu^t₂]^-. The analogous ferrocene complex [Fe(η⁵-P₂SbC₂Bu^t ₂)-(η⁵-C₅Me₅)] (crystal structure) was synthesized by treating a 1:1 mixture of [P₂SbC₂Bu^t₂]^- and Li(C₅Me₅) with half an equivalent of FeCl₂. Treatment of [M(η⁵-P₂SbC₂Bu^t ₂)(η⁵-C₅Me₅)] (M = Ru or Fe) with [W(CO)₅(thf)] (thf = tetrahydrofuran) formed the secondary co-ordination complexes [M(η⁵-P₂SbC₂Bu^t ₂)(η⁵-C₅Me₅){W(CO)₅}] (M = Ru or Fe) in which the W(CO)₅ fragment is η¹ ligated to the phosphorus centre adjacent to the ring antimony centre. A diphosphastibolyl-bridged cationic triple-decker complex [(η⁵-C₅Me₅)Ru(μ-η ⁵:η⁵-P₂SbC₂Bu^t ₂)Ru(η⁵-C₅Me₅)][PF₆] was the product of the reaction of [P₂SbC₂Bu^t₂]^- with 2 equivalents of [Ru(η⁵-C₅Me₅)(MeCN)³][PF ₆].