MODELING THE N-N BOND-CLEAVAGE STEP IN THE REDUCTION OF MOLECULAR NITROGEN TO AMMONIA - PROTONATION AND ELECTRON-TRANSFER REACTIONS OF DINITROGEN, NITROGEN HYDRIDE, AND ORGANONITROGEN COMPLEXES OF MOLYBDENUM AND TUNGSTEN

Organic-substituted hydrazido(2-) complexes of molybdenum and tungsten are investigated as possible reaction analogues of the nitrogen-nitrogen bond cleavage step during the reduction of molecular nitrogen to ammonia. The reactions of [WC12(NNR2)-(PMe2Ph)3], 1 (R = Ph) and 2 (R = Me) with HCl in CH2Cl2 Produce a secondary amine (ca. 0.62 mol/mol W) and ammonia (ca. 0.20 mol/mol W). The reaction of 1 with water in CH2Cl2 Produces 0.98 mol of Ph2NH and 0.30 mol of ammonia, respectively. These nitrogen balances approach those obtained in the form of ammonia from reactions of unsubstituted hydrazido(2-) complexes that are prepared directly from dinitrogen complexes. The crystal structures of 1 and 2 have been determined. Although the relative positions of the atoms and orientations of the phenyl rings are the same in 1 and 2 there are significant differences in the W-N, W-Cl and W-P bond distances.