Synthesis, characterisation and crystal structure of hydroxylamido-κ2N,O(iodo)[tris(3,5-dimethylpyrazol-1-yl)borato]nitrosylmolybdenum(II)

The unusual 18e seven-coordinate Mo(II) complex [Mo(NO)(H2NO-κ2N,O)(TpMe2)I] (1; [TpMe2]− is hydrotris(3,5-dimethylpyrazol-1-yl)borate) has been synthesised and characterised by IR, 1H NMR and ESI-MS spectroscopies and by a single crystal X-ray diffraction study. The complex has a distorted pentagonal bipyramid structure with equatorial κ2-NH2O− ligand (dN–O = 1.387 Å, dMo–N and dMo–O equal 2.049 and 2.092 Å, respectively). In the solid state 1 exists as a dimer (the point group Ci) due to the formation of two NH⋯O hydrogen bonds (dN–H⋯O = 2.064 Å) between the adjacent NH2O− ligands, whilst in solution at/or above RT it resolves itself giving a monomer, which readily isomerises to more thermodynamically stable diastereoisomer.