Bidentate phosphinophenol R2POH ligands. Oxo and imido Re(V) complexes of 2-diphenylphosphinomethyl-4-methylphenol (POH). Crystal structure of ReOCl(PO)2

The PPh3 ligands were displaced and ReOCl3(POH)2 (1) was formed when ReOCl3(PPh3)2 and 2 equiv. of the title ligand (POH) were refluxed in acetonitrile. In the presence of the proton quencher NEt3, ligand deprotonation took place and the bis-chelate complex ReOCl(PO)2 (2) was isolated. Under similar conditions, ReO(OEt)(PO)2 (3) was obtained from ReO(OEt)Cl2(PPh3)2. NMR data are consistent with the trans-O–ReO-cis-P,P ‘twisted’ octahedral geometry for these species. The corresponding phenylimido complex Re(NPh)Cl(PO)2 (4), similarly prepared from Re(NPh)Cl3(PPh3)2, adopts the trans-O–Re–NPh-trans-P,P arrangement. The structure of 2 was confirmed by X-ray diffraction. The methylene group in the side-arm imparts flexibility to the chelate ring and allows the bond angles to be closer to the ideal octahedral values than in the corresponding diphenylphosphinophenolato compound. The six-membered rings adopt a flattened boat conformation bringing the phenolate unit out of the coordination plane and making the overall van der Waals envelope substantially different from that of the diphenylphosphinophenol-based complex.