Complexes of phosphine–phenolate ligands with the [ReO]3+ and [Re(HNNC5H4N)(NNC5H4N)]2+ cores

Abstract

Complexes incorporating the [ReO]³⁺ core have been synthesised with ligands containing the new methyl substituted phosphine–phenolate PO and PO₂ donor sets, (2-hydroxy-5-methylphenyl)diphenylphosphine (H(MePO)) and bis(2-hydroxy-5-methylphenyl)phenylphosphine (H₂(Me₂PO₂)). The analogous tert-butyl ligands, (5-tert-butyl-2-hydroxyphenyl)diphenylphosphine (H(t-BuPO)) and bis(5-tert-butyl-2-hydroxyphenyl)phenylphosphine (H₂(t-Bu₂PO₂)), were also prepared. Reaction of either mer-[ReOCl₃(PPh₃)₂] or [NH₄][ReO₄] in CH₃OH with H(MePO) led to formation of [ReOCl(MePO)₂] (1) in good yield. Reaction of [NH₄][ReO₄] with H₂(Me₂PO₂) in CH₃OH afforded [ReO(Me₂PO₂)(H(Me₂PO₂))] (2), also in good yield. X-Ray crystallographic analyses of 1 and 2 demonstrated that both complexes are neutral and octahedral, and contain the oxo moiety. Two complexes have been structurally characterised from the reaction of (o-hydroxyphenyl)diphenylphosphine (HPO) with [Re(Hhypy)(hypyH)Cl₃]: [Re(Hhypy)(hypy)(PO)(HPO)]Cl (3) and [ReCl(Hypy)(hypy)(PO)] (4) (hypy = NNC₅H₄N, Hhypy = HNNC₅H₄N, hypyH = NNC₅H₄NH). X-Ray crystallography demonstrated that both are Re(III) complexes; 3 is monocationic with an N₃OP₂ coordination sphere while 4 is neutral with a ClN₃OP coordination sphere. [Re(Hhypy)(hypy)(HPO₂)(H₂PO₂)]Cl (5) and [Re(Hhypy)(hypy)(H(Me₂PO₂))(H₂(Me₂PO₂))]Cl (6) were synthesised by reaction of [Re(Hhypy)(hypyH)Cl₃] in CH₃OH with bis(o-hydroxyphenyl)phenylphosphine (H₂PO₂) and H₂(Me₂PO₂) respectively. Compounds 5 and 6 were shown by ¹H and ³¹P NMR spectroscopies to have the same N₃OP₂ coordination sphere as [Re(Hhypy)(hypy)(PO)(HPO)]Cl, with the addition of several uncoordinated, protonated phenolic donors.