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)Cl-2(PPh3)(2). NMR data are consistent with the tPans-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)Cl-3(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. (C) 2000 Elsevier Science S.A. All rights reserved.