REACTIONS OF COORDINATED DINITROGEN .25. REACTIONS OF MONO(DINITROGEN) COMPLEXES OF MOLYBDENUM - ISOLATION AND CHARACTERIZATION OF HYDRAZIDO(2-) AND MONOHYDRIDE AND DIHYDRIDE COMPLEXES - CRYSTAL-STRUCTURE OF MOBR[PHP(CH2CH2PPH2)2](ME2PCH2PME2).1/2C5H12

The reactions of a series of mono(dinitrogen) complexes of molybdenum Mo(N2)(dpepp)(L2) [where dpepp = PhP(CH2CH2PPh2)2and L2= 2 PMe2Ph (1), Me2PCH2PMe2(dmpm) (2), 1,2-(Me2As)2C6H4(diars) (3), Ph2PCH2PPh2(dppm) (4), Ph2PCH2CH2PPh2(dppe) (5)] with acids are reported. Reactions of 1 with excess HX (X = Br, C1) in the solid state or HX (2 mol) in toluene led to the isolation of the hydrazido(2-) complexes [MoX(NNH2)(η2-dpepp)(PMe2Ph)2]X [6 (X = C1) and 7 (X = Br)] in which dpepp is bidentate. Similar results were obtained with CF3SO3H. Heating a toluene solution of 7 led to the loss of one PMe2Ph and reincorporation of the pendant phosphine to form mer-[MoBr(NNH2)(dpepp)(PMe2Ph)]Br. Complexes 6 and 7 yielded ammonia and hydrazine when treated with HCl and HBr. The pendant phosphine can be protonated (HBr) and alkylated. Complex 1 reacted with HBr (1 mol) to initially (0.25 h) produce an equimolar mixture of 1 and 7. These two complexes reacted (15 h) to give an almost quantitative yield of Mo(H)Br(dpepp)(PMe2Ph) (10). With HBr (1 mol), 10 produced Mo(H)2Br2(dpepp)(PMe2Ph). Solid 2 reacted with excess HX (X = Br, Cl, SO3CF3) to produce the unstable hydrazido(2-) dication [Mo(NNH2)(dpepp)(dmpm)]2+without loss of a ligand. In solution the stability of the dication increased with decreasing basicity of the anion: Cl < Br < SO3CF3. [Mo(NNH2)(dpepp)(dmpm)] [SO3CF3]2was isolated. Decomposition of the dication in solution led to loss of N2and formation of a pair of isomeric eight-coordinate dihydrides, [Mo(H)2Cl(dpepp)(dmpm)][HCl2] (16). Reaction of 2 with HBr (1 mol) in benzene led to the isolation of [Mo(H)2Br(dpepp)(dmpm)]Br (13, single isomer), MoBr(dpepp)(dmpm) (14), and Mo(H)Br(dpepp)(dmpm) (15, single isomer). A similar reaction with HCl produced Mo(H)-Cl(dpepp)(dmpm) (17) as a pair of isomers. Complex 14 crystallizes with 0.5 mol of pentane in the monoclinic space group P21/c with a = 12.452 (2) Å, b = 15.738 (2) Å, c = 21.677 (3) Å, β = 98.94 (1)°, and Z = 4. Complexes 3–5 gave evidence of hydrazido(2-) formation upon treatment with acid, but in solution N2was rapidly evolved and hydrides were formed. Structural assignments of new complexes are based upon 31P and 1H NMR spectral data. Dpepp is shown to adopt both fac and mer configurations. The protonation of metal-N2complexes is discussed. © 1990, American Chemical Society. All rights reserved.