Synthesis and physicochemical characterization of oxo and phenylimido Re(V), Re(III) and Ni(II) complexes with the 2-[bis(ethoxyethyl)phosphino]phenolato ligand and derivatives

2-[Bis(ethoxyethyl)phosphino]phenol P1–OH reacts in basic refluxing solvents with ReOCl3(PPh3)2, in a 2/1 molar ratio, to give the green ReOCl(P1–O)2 complex. Structure elucidation by 31P NMR is consistent with a cis-PP “twisted” octahedral complex, which is the preferred conformation on electronic grounds. The complex is unique in toluene while several species were present in ethanol. When the reaction is performed with Re(NPh)Cl3(PPh3)2, a mixture of trans-PP (major) and cis-PP(minor) species in a 3/1 ratio is obtained. These geometric isomers were distinguished by their 2JPP coupling constants. Only cis-PP-Re(NPh)Cl(P1–O)2, less soluble, could be isolated and its molecular structure determined by physicochemical measurements. This is the first example of cis-PP phosphinophenolato complex with the [ReNPh]3+ core, thus illustrating the importance of the steric demand of the phosphine substituent. Reaction of P1–OH with NiCl2 gives Ni(P1–O)2 as an orange oily solid with a cis-PP square planar structure. This structure is the most probable based on the 31P, 13C NMR data.