Dirhenium(II) complexes containing monodentate and polydentate nitrile ligands

The complex Re2Cl4(μ-dppa)2 (dppa=Ph2PNHPPh2) has been reacted with EtCN and PhCN to afford the complexes [Re2Cl3(μ-dppa)2(NCR)2]PF6 (R=Et or Ph), [Re2Cl3(μ-HN2C2Et2)(μ-dppa)2(NCEt)]Cl and [Re2Cl3(μ-HN2C2Et2)(μ-dppa)2(NCEt)](PF6)2 which are derivatives of the [Re2]4+, [Re2]5+ and [Re2]6+ cores, respectively. This behaviour is similar to the reactions of Re2Cl4(μ-dppm)2 (dppm=Ph2PCH2PPh2) with monodentate nitriles. The reactions of Re2Cl4(μ-dppm)2 with the polydentate nitrile ligands 1,4-dicyanobenzene (1,4-DCB), 1,4-dicyanobut-2-ene (1,4-DCBE) and tris(2-cyanoethyl)phosphine (CEP) also give complexes of this same type in which the nitrile ligand utilizes only one of its CN groups. This is confirmed by an X-ray crystal structure determination of [Re2Cl3(μ-dppm)2(1,4-DCB)2]PF6, in which the ReRe bond is retained (Re–Re distance 2.2637(12) Å) and the 1,4-DCB ligands are monodentate.