Metal polypyrazolylborates XIII. Solution and solid state NMR study of cyano-mercury(II) polypyrazolylborates. X-ray crystal structure of [HB(3,5-Me₂pz) ₃]HgCN

Complexes of the cyanomercury cation with various polypyrazolylborato ligands of the type HB(pz)₃ · Hg-CN or pzB(pz)₃ · Hg-CN (pz = pyrazolyl or substituted pyrazolyl) have been synthesised and characterised by IR, conductivity, ¹H, ¹³C, and ¹⁹⁹Hg NMR spectroscopy. The crystal structure of the cyanomercury hydridotris(1 H-3,5-dimethylpyrazol-l-yl)borate has been resolved (space group P1̄ with a = 7.863(3), b = 11.157(5), c = 13.117(5)Å; α = 89.32(3), β = 78.31(3), γ = 79.13(4)°, V = 1106.22ų, Z = 2) showing a distorted tetrahedral coordination around Hg. The tris(pyrazolyl)borato complexes contain four-coordinated Hg and are rigid in solution at r.t., while the tetrakis(pyrazolyl)borates are fluxional. The ¹⁵N-CPMAS-NMR spectrum of the pzTp · HgCN derivative suggests a tetracoordination around mercury in this complex in the solid state.