Bis-organoamide complexes of nitrosyl[tris(3,5-dimethylpyrazolyl)borato]molybdenum and -tungsten. The crystal and molecular structure of [Mo(NO){HB(Me2pz)3}(NHBun)2]

Abstract

The reaction between [MO(NO)L(I)(NHR¹)][L = tris(3,5-dimethylpyrazolyl)borate, HB(Me₂pz)₃^–; R¹= Et, Prⁿ, or Buⁿ] and R¹NH^– afforded [Mo(NO)L(NHR¹)₂] but did not provide a route to derivatives in which R¹= aryl. A similar approach using [W(NO)L(Cl)(NHR¹)] and R¹NH^– afforded the tungsten analogues [W(NO)L(NHR¹)₂](R¹= Et, Prⁿ, or Buⁿ). The reaction of [Mo(NO)L(I)(NHR¹)](R¹= Et, Ph, or C₆H₄Me-p) with NaC₁₀H₈ in tetrahydrofuran, followed by the addition of R²NH₂(R²= Ph or C₆H₄Me-p), led to the formation of the arylamide derivatives [Mo(NO)L(NHR¹)(NHR²)](R¹= R²= Ph or C₆H₄Me-p; R¹= C₆H₄Me-p, R²= Ph; and R¹= Et, R²= C₆H₄Me-p). Bis-arylamide derivatives of tungsten could not be prepared in this manner but [W(NO)L(NHEt)(NHC₆H₄Me-p)] was prepared from the reaction of NHC₆H₄Me-p^– and [W(NO)L(Cl)(NHEt)]. The electrochemistry of the new complexes has been investigated and, while the bis-arylamide derivatives exhibited reversible reduction behaviour, the alkylamide complexes reduced irreversibly. The molecular structure of [Mo(NO){HB(Me₂pz)₃}(NHBuⁿ)₂] has been determined by a single-crystal X-ray diffraction study and was found to contain a linear nitrosyl ligand. The average Mo–N(butylamido) distance was 1.940 Å and the average Mo–N–Buⁿ angle 129.9°.