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

Abstract

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^t₂ )₂] with [Ru(η⁵-P₂SbC₂Bu^t₂ )(η⁵-P₃C₂Bu^t ₂)]. 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^t₂ )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^t₂ )(η⁵-C₅R₅)] (R = H or Me) were prepared by treating [Ru(η⁵-C₅R₅)(MeCN)₃] [PF₆] (R = H or Me) with [P₂SbC₂Bu^t₂]^- . The analogous ferrocene complex [Fe(η⁵-P₂SbC₂Bu^t₂ )(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^t₂ )(η⁵-C₅Me₅)] (M = Ru or Fe) with [W(CO)₅(thf )] (thf = tetrahydrofuran) formed the secondary co-ordination complexes [M(η⁵-P₂SbC₂Bu^t₂ )(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-η⁵ : η⁵-P₂SbC₂Bu^t₂ )Ru(η⁵-C₅Me₅)][PF₆ ] was the product of the reaction of [P₂SbC₂Bu^t₂]^- with 2 equivalents of [Ru(η⁵-C₅Me₅)(MeCN)₃] [PF₆].

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