Oxo-rhenium(V) complexes containing bridging phosphito ligands. The synthesis, characterisation and X-ray crystal structures of [ReOCl{μ-OP(OR) 2}{OCMe 2CMe 2OP(OCMe 2CMe 2O)}] 2 (R=Me or CMe 2)

Abstract

The oxo-rhenium(V) complexes [ReOCl 2(P∼O)L] (P∼O=(OCMe 2CMe 2O)POCMe 2CMe 2O −), L=py ( 1), PPh 3 ( 2) or OPPh 3 ( 3)) react with P(OMe) 3 or spirophosphorane HP(OCMe 2CMe 2O) 2 (HP∼O) affording the related μ-phosphito(1−) bridged dimeric compounds [ReOCl{μ-OP(OR) 2}(P∼O)] 2 (R=Me ( 4) or CMe 2 ( 5)). The μ-phosphito ligands result from Arbuzov-like dealkylation reactions. Complexes 4 and 5 were characterised by NMR, IR, UV–VIS spectroscopic methods. In solution, both the light brown complexes 4 and 5 remain dimeric and comprise two equivalent six-coordinated monomeric subunits stereochemically rigid at ambient temperature. The complexes appeared to be rather inert in attempted substitution reactions. In the crystal state, in spite of the molecular C i symmetry of 4, complex 5 reveals a distorted pseudocentrosymmetric C 1 geometry. The multiply bonded terminal oxo ligands (ReO 1.681(5) Å ( 4), 1.684(5) and 1.691(5) Å ( 5)) are in cis arrangements to two phosphito bridges. Two different phosphito bridged cores Re{μ-OP(OR) 2} 2Re (R=Me ( 4), CMe 2 ( 5)) adopt the chair conformation.