Reactions of the dirhenium(III,III) complex cis-Re2(μ-O2CMe)2Cl4(H2O)2 that lead to the dirhenium(III,II) complexes Re2(μ-O2CMe)Cl4(PR3)2 and tetrarheniumcyclodiyne clusters of the type Re4(μ-O)4Cl4(PR3)4

Abstract

The reaction of cis-Re₂(μ-O₂CMe)₂Cl₄(H₂O)₂ 1 with P(C₆H₄OMe-p)₃ gives the tetranuclear complex Re₄(μ-O)₄Cl₄[P(C₆H₄OMe-p)₃]₄ 14 along with the salt [(C₆H₄OMe-p)₃PMe]₂Re₂Cl₈ 15. Compound 14 is the first symmetrical, neutral, tetrarheniumcyclodiyne type cluster that contains phosphine ligands. Complexes of this same type with PPh₃ (16) and PMe₂Ph (17) have been prepared by alternative methods but have poor solubility properties. The paramagnetic complex Re₂(μ-O₂CMe)Cl₄(PPh₃)₂ 2, which is prepared from 1 by reaction with PPh₃, undergoes phosphine substitution reactions when treated with dichloromethane solutions of other phosphines. Simple non-redox reactions can occur upon reaction of 2 with monodentate and bridging bidentate phosphines to afford complexes of the types Re₂(μ-O₂CMe)Cl₄(PR₃)₂ [PR₃ = PBz₃ 3, P(C₆H₄OMe-p)₃ 4 or PMePh₂ 5] and trans-Re₂(μ-O₂CMe)Cl₄(μ-PP)₂ [PP = dppm 9, Ph₂PNHPPh₂ 10 or (Ph₂P)₂CCH₂ 11]. However, reactions that lead either to reduction to dirhenium(II) complexes or Re–Re bond cleavage are encountered in the case of the reactions of 2 with PMePh₂, PMe₂Ph, PCy₃ and dppe; these have led to the isolation of Re₂Cl₄(PMePh₂)₄ 6, Re₂Cl₄(PMe₂Ph)₄ 7, mer-trans-ReOCl₃(PCy₃)₂ 8, α-Re₂Cl₄(dppe)₂ 12, and trans-[ReO₂(dppe)₂]Cl 13. The structures of compounds 3, 8, 13, 14 and 15 have been determined by X-ray crystallography.