Change of the coordination type for the phospholyl ligand under nucleophilic attack of H 2O on phosphorus atom in 2,5-diphenylphosphacymantrene promoted by aliphatic amines

Abstract

η 5-2,5-Diphenylphosphacymantrene ( 1) in benzene or CH 2Cl 2 solution does not react with amines. However, with amines NHEt 2, NEt 3, NEt(i-Pr) 2 in excess and in the presence of small amounts of water 1 reacts to form anionic complexes [(CO) 3Mn(η 4-Ph 2H 2C 4P( O)H] − A +, where cation A = H 2 NEt 2 + ( 2a), HNEt 3 + ( 2b), HN(Et) ( Pr i ) 2 + ( 2c). Probably, first an unstable intermediate with Р–ОН bond is formed as a result of the attack by the activated H 2O molecule at the P atom. Afterwards, the rapid rearrangement occurs with migration of H from O to P which leads to the ligand 2,5-diphenyl-1- Н-phosphol-1-oxide, Ph 2H 2C 4P( O)H. Salts 2а– с have been characterized by 1H, 31P, 13C NMR- and IR-spectra and the structures of 2a and 2c established by single crystal X-ray diffraction analyses. The phosphoryl ligand in anions 2a and 2c has the “envelope” conformation and is η 4-coordinated with Mn(CO) 3. The phosphorus atom is not involved in the coordination with Mn because the Mn–P distances (2.7670(4) and 2.7732(8) Å) are greater than the sum of covalent radii of P and Mn.