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

Abstract

2-[Bis(ethoxyethyl)phosphino]phenol P 1–OH reacts in basic refluxing solvents with ReOCl 3(PPh 3) 2, in a 2/1 molar ratio, to give the green ReOCl(P 1–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)Cl 3(PPh 3) 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 2 J PP coupling constants. Only cis-PP-Re(NPh)Cl(P 1–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 P 1–OH with NiCl 2 gives Ni(P 1–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.