Nitridomolybdenum Complexes of Tris(3,5-dimethylpyrazol-1-yl)Hydroborate and the X-Ray Crystal-Structure of {HB(3,5-Me₂C₃N₂H)₃)MoN(N₃)₂

Abstract

The reaction of (NEt₄)₂[MoNCl₅] and K{HB(Me₂pz)₃}[HB(Me₂pz)₃^- = tris (3,5- dimethylpyrazol-1-yl) hydroborate anion] produces both purple, diamagnetic {HB(Me₂pz)₃}MoNCl₂ (1) and yellow, paramagnetic Net₄ [{HB(Me₂pz)₃}MoNCl₂] (2) (e.s.r.: {g} 1.961, {a}(⁹⁵Mo) 57×10^-4 cm^-1), which have been separately isolated under different conditions. In contrast, the reaction of [ MoN (N₃)₄]- with Na{HB(Me₂pz)₃} results in the exclusive formation of red {HB(Me₂pz)₃} MoN (N₃)₂ (3). Crystals of (3) are monoclinic and belong to space group P2₁/n with a 16.440(2), b 8.787(2), c 16.754(2) Ǻ,β 112.47(1)°, V 2236.4 Ǻ³, and Z 4. The structure was solved by Patterson and Fourier methods, followed by least-squares refinement, using 3208 reflections, to a conventional R value of 0.032 ( Rw 0.047). In the distorted octahedral complex the molybdenum(VI) atom is coordinated by a facial HB(Me₂pz)₃^- ligand , a terminal nitrido ligand with a Mo-N bond distance of 1.646(4)Ǻ, and two azide ligands. All complexes have been characterized by elemental analysis, infrared, ¹H n.m.r. or e.s.r. spectroscopy, and mass spectrometry. Improved syntheses for the starting materials (NEt₄)₂ [MoNCl₅] and (NEt₄)₂ [MoNCl₄] are also reported.