Molybdenum, tungsten and rhodium complexes of nitrogen-oxides.

Abstract

Complexes of the type MX(η²-NO₃)(CO)₂(PPh₃)₂, (M = Mo, X = Cl, Br; M = W, X = Br) were prepared from the reactions of MX₂(CO)₂(PPh₃)₂ with ammonium nitrate in acetone. The complexes were characterized by elemental analyses, ¹⁵N labelling, infrared and NMR spectroscopy. The nitrate ligand is bidentate and the complexes are seven-coordinate. Novel nitrite complexes of molybdenum and tungsten of the type M(NO₂)₂(PPh₃)₂ were prepared. The compounds were characterized by elemental analyses, ¹⁵N labelling, infrared and multinuclear NMR spectroscopy. Both NO₂ ligands are chelating and the two NO₂, PPh₃ and CO ligands are equivalent. Molybdenum dinitrosyl complexes were synthesized by the reduction of nitrate ions. The crystal structure of cis-dinitrosyl-cis-dichloro-trans-bis-(triphenylphosphine)molybdenum(II) was determined by x-ray diffraction. Both the nitrosyl groups are linear. Mo(NO)₂Cl₂(OPPh₃)₂ and Mo(NO)₂Cl(NO₃)(OPPh₃)₂ were synthesized by the reaction of MoCl(η²-NO₃)(CO)₂(PPh₃)₂ with NO in acetone/toluene mixture. The nitrosyl ligands are linear and the phosphineoxide ligands are cis to each other. The dinitrite complex Rh(NO)(NO₂)₂(PPh₃)₂ of the series Rh(NO)X₂(PPh₃)₂ (X - monodentate anions) was prepared as a direct derivative of Rh(NO)Cl₂(PPh₃)₂ by its reaction with sodium nitrite. The complex is square pyramidal with an apical nitrosyl ligand. The two NO₂ groups are present as the nitro and the nitrito group. Rh(NO)(NO₂)₂(PPh₃) reacted with oxygen and formed Rh(NO₃)₃(PPh₃)₂. The reaction of Rh(NO)(NO₂)₂(PPh₃)₂ with CO in acetonitrile produced Rh(CO)(NO₂)(PPh₃)₂. The complex Rh(CO)(NO₂)(PPh₃)₂ is square planar with the phosphine ligands in the trans positions.