Monoxidised sulfur and selenium derivatives of 1,8-bis(diphenylphosphino)naphthalene: Synthesis and coordination chemistry

Treatment of 1,8-bis(diphenylphosphino)naphthalene (dppn, 1) with stoichiom etric amounts of sulfur or selenium in toluene at 80 degreesC selectively a fforded the diphosphine monochalcogenides 1-Ph2P(C10H6)-8-P(:S)Ph-2 (dppnS, 2a) and 1-Ph2P(C10H6)-8-P(:Se)Ph-2 (dppnSe, 2b), The P-31{H-1} NMR spectru m of 2b showed an unusually large (5)J(P-Se) value, which indicates a signi ficant through-space coupling component. The monosulfide acted as a bidenta te P,S-ligand towards platinum(II) (3a), whereas the corresponding monosele nide complex (3b') lost elemental selenium with formation of the previously reported complex [PtCl2(dppn)P:P'] (3). Treatment of dppnSe with [(nor)Mo( CO)(4)] (nor = norbornadiene) led to formation of [(dppnSe)Mo(CO)P,Se] (3b) . Solutions of the latter slowly deposited Se with formation of [(dppn)Mo(C O)(4)-P,P'] (4) which was also obtained by independent synthesis from 1 and [(nor)Mo(CO)(4)]. All isolated new compounds were characterised by a combi nation of P-31, H-1, C-13 and Se-77 (2b) NMR spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis. Single-crystal X-ray structure d eterminations were performed for dppnSe (2b), [PtCl2(dppnS)-P,S] (3a), [(dp pnSe)Mo(CO)(4)-P,Se] (3b) and [(dppn)Mo(CO)(4)-P,P'] (4). In 2b steric effe cts cause the naphthalene ring to be distorted and force the phosphorus ato ms by 65 and 59 pm to opposite sides of the best naphthalene plane. In the metal complexes 3a, 3b and 4 the phosphino-phosphinochalcogenyl systems act as bidentate ligands through the P and the chalcogen atoms. The naphthalen e systems are again distorted. The two independent molecules of 4 differ in their conformations.