Hydrido-oxo complexes of rhenium(V): synthesis, structure, spectroscopic properties, and reactions with acids and bases

The reaction of [ReH4(η2-H2)(Cyttp)]X (X=SbF6 (1(SbF6)), OTf (1OTf)); Cyttp=PhP(CH2CH2CH2PCy2)2, OTf=O3SCF3) with neat acetone at reflux temperature affords the dihydrido-oxo complex [ReH2(O)(Cyttp)]X (X=SbF6 (2(SbF6)), OTf (2(OTf))). The isotopomers [ReH2(18O)(Cyttp)]SbF6 (2-18O(SbF6)), [ReD2(O)(Cyttp)]SbF6 (2-d2(SbF6)), and [ReD2(18O)(Cyttp)]SbF6 (2-d2,18O(SbF6)) were prepared, respectively, by treatment of 2(SbF6) with H218O, D2 under photolysis, and D2 followed by H218O. The structure of 2 (as 2(SbF6)·3/4MeOH) was determined by single-crystal X-ray diffraction analysis and shown to contain a meridionally-coordinated Cyttp and an oxo ligand approximately cis to each of the three phosphorus donor atoms (Re–O=1.732(7) Å). The hydrido ligands were not located; however, their presence in the positions essentially cis and trans to the oxide in a severely distorted coordination octahedron of the metal is suggested by the elucidated molecular structure. The 1H NMR signals at δ −1.04 (tt) and −12.62 (dtd) and the IR ν(ReH) absorptions at 2030 and 1716 cm−1 provide strong evidence for this assignment. The IR ν(Re16O) band of 2(SbF6) at 923 cm−1 surprisingly shifts to 897 cm−1 in 2-d2(SbF6). Similarly, the ν(Re18O) of 2-18O(SbF6) at 887 cm−1 moves to 854 cm−1 in 2-d2,18O(SbF6). Changes are also observed for one of the δ(ReH) absorptions of 2(SbF6) at 817 cm−1, which appears at 810 cm−1 in 2-18O(SbF6). A simple analysis of the ν(ReO) and δ(ReH or ReD) vibrational frequencies suggests that a resonance interaction occurs between the ν(ReO) and one of the δ(ReH) modes. Complex 2(OTf) reacts at low temperature with KOH–pyridine to form [Re(O)2(py)(Cyttp)]OTf, and with Li[BEt3H] in excess to give ReH5(Cyttp). Treatment of 2(OTf) with aqueous HCl in benzene yields a green solid which is formulated as [ReH2(OH)Cl(Cyttp)]OTf from spectroscopic evidence.