Complexes of phosphine–phenolate ligands with the [ReO]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.