New rhenium complexes with phosphinite PPh2OR or phosphonite PPh(OR)2(R = Me, Et or Pri) ligands: synthesis and protonation of various polyhydrides

Abstract

The rhenium complexes [ReOCl₃L₂] and [ReCl₃L₃][L = PPh₂OMe, PPh₂OEt, PPh₂OPrⁱ, PPh(OEt)₂ or PPh(OPrⁱ)₂] were prepared by allowing [ReOCl₃(AsPh₃)₂] to react with the appropriate amount of phosphinite or phosphonite. Treatment of [ReCl₃L₃] with CO and p-MeC₆H₄NC afforded the mer-trans-[ReCl(CO)₃L₂] and [ReCl₂(p-MeC₆H₄NC)₄L]BPh₄ complexes, respectively. Treatment of [ReOCl₃L₂] with NaBH₄ gave [Re₂H₈L₄], but in the presence of phosphinite or phosphonite the trihydrides [ReH₃L₄] were obtained. Treatment of [ReCl₃L₃] with NaBH₄ gave instead pentahydride complexes [ReH₅L₃]. All the multihydrides were characterised as ‘classical’ species by variable-temperature NMR spectroscopy (¹H and ³¹P) and T₁ measurements. Protonation of [Re₂H₈L₄] and [ReH₃L₄] with HBF₄·Et₂O gave the classical hydride cations [Re₂H₉L₄]⁺ and [ReH₄L₄]⁺, respectively, while similar treatment of [ReH₅L₃] gave a species formulated as containing an η²-H₂ ligand, [ReH₄(η²-H₂)L₃]⁺ on the basis of T_1(min) evidence.