Elucidation of the structures of the hydridothiolato complexes WH(SC6H2Pri3-2,4,6)3(L)(PMe2Ph), L = PMe2Ph or pyridine, by NMR and X-ray techniques

Abstract

Measurement of the T1 values of the 31P nuclei in the unusual capped trigonal bipyramidal complexes WH(tipt)3(PMe2Ph)2 (1, tipt = SC6H2Pri3-2,4,6) and W(2H)(tipt)3(PMe2Ph)2 allows the determination of the phosphorus–hydride distance of 2.2 ± 0.2 Å and the P-W-H angle of about 62 ± 7°. An approximate location of the hydride on an S2P face is proposed on the basis of steric interactions. The crystal structure of WH(tipt)3-(NC5H5)(PMe2Ph) (2) is reported; the WS3NP core consists of a distorted trigonal bipyramidal system with the phosphine and pyridine ligands axial and the thiolate ligands equatorial. The hydride ligand was not located by X-ray diffraction but can be positioned on an open S2P face at an angle P-W-H of about 65°. The small P-W-H angle results in large 2J(H,P) couplings for 1 and 2. The 1H NMR spectrum of complex 2 is assigned by use of NOE and homodecoupling NMR methods. This complex has the same crowded structure in solution as in the crystalline state. The pyridine ligand, which is sandwiched between two tipt aryl groups, is hindered from rotating around the W—N bond. Keywords: molybdenum, tungsten, thiolate, hydride, NMR, NOE.