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 31 P 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 31 P, 13 C NMR data.