Transition-metal derivatives of arenediazonium ions. Part 12. Complexes derived from pyrazole-4-diazonium and 3-pyrazolin-5-one-4-diazonium cations. X-Ray crystallographic characterisation of a sterically distorted organodiazenido-complex: dicarbonyl(3,5-dimethylpyrazol-4-yl-diazenido)tris(pyrazol-1-yl)methanemolybdenum(II) tetrafluoroborate–diethyl ether (1/1)

Abstract

Reaction of the 3,5-dimethylpyrazole-4-diazonium cation, [(3,5Me₂-pz)N₂]⁺(1), or the antipyrene-4-diazonium cation (2,3-dimethyl-1-phenyl-3-pyrazolin-5-one-4-diazonium), [(ap)N₂]⁺(2), with the appropriate transition-metal substrates yields the complexes [Mo(CO)₂{N₂(3,5Me₂pz)}{HC(pz)₃}] BF₄·Et₂O (3), [Mo(CO)₂{N₂(ap)}{HC(pz)₃}] BF₄, [Mo(CO)₂{N₂(3,5Me₂pz)}{HB(pz)₃}], [Mo(CO)₂{N₂(ap)}{HB(pz)₃}](pz = pyrazol-1-yl), [Mo(CO)₃{N₂(ap)}(bipy)] BF₄, (bipy = 2,2′-bipyridyl), [Mo(CO)₃{N₂(ap)}(phen)] BF₄(phen = 1,10-phenanthroline), and [Fe(CO)₂{N₂(ap)}(PPh₃)₂] BF₄, the first organodiazenido complexes derived from heterocyclic diazonium cations. Crystals of (3) are monoclinic, space group C2, with four formula units in a unit cell of dimensions a= 18.326(2), b= 9.185(2), c= 16.886(2)Å, and β= 91.387(6)Å. The structure was solved by the heavy-atom method and refined by least-squares calculations to R= 0.034 for 1 145 reflections with I > 3σ(I). The molybdenum atom has a slightly distorted octahedral co-ordination with Mo–N(pz) 2.21(1)–2.28(2), Mo–C(CO) 1.92(2) and 1.95(2), Mo–N (organodiazenido) 1.84(1), and N–N (organodiazenido) 1.22(2)Å. Steric interaction between the organodiazenido ligand and the tris(pyrazol-1-yl)methane ligand causes the former to deviate significantly from the idealised ‘singly-bent’ geometry: Mo–N–N 164.5(8), N–N–C(pz) 124.4(10)°. The antipyrene-4-diazonium cation (2) degrades [Ni(CO)₂(PPh₃)₂] with the formation of an azophosphonium salt [PPh₃{N₂(ap)}] BF₄ but reacts with [Mn(CO)₂(thf)(η-C₅H₄Me)](thf = tetrahydrofuran) at –50 °C to yield [Mn(CO)₂{N₂(ap)}(η-C₅H₄Me)] BF₄.