Synthesis and structural analysis of mono-oxo Re(V) complexes with phosphino-carboxylato ligands

[nBu4N][Re(O)Cl4] or [Re(O)Cl2(OEt)(PPh3)2] react with PCOOH (2-(diphenylphosphanyl)benzoic acid) in different stoichiometries leading to the mono-substituted complexes [nBu4N][Re(O)Cl3(PCOO)] (2) and [Re(O)Cl2(PCOO)(PPh3)] (5), respectively. In CH2Cl2–MeOH, 2 rearranges partially into the neutral [Re(O)Cl2(PCOO)(MeOH)] (3). The mixed [Re(O)(OCH2CH2O)(PCOO)(MeOH)] (4) is obtained by reacting [nBu4N][Re(O)Cl4], ethylene glycol and PCOOH. The [PCOO]− ligand is bidentate and the coordination geometry around rhenium is distorted octahedral, as shown by the X-ray structural analysis of 2 and 3. In these complexes the phosphorus and the oxygen atoms of the phosphino-carboxylato ligand occupy an equatorial and an axial position, respectively.