Transition metal derivatives of arenediazonium ions XV. The synthesis, chemistry and X-ray crystallographic characterisation of molybdenum(0) and tungsten(0) complexes containing the cis-[M(NO)(N2Ar)]2+ structural unit

Synthetic procedures and preliminary chemical studies are described for four new types of Group VIa nitrosyl-arenediazo complex: (η-C5H5)M(NO)(N2Ar)Cl (VII), (HBpz3)M(NO)(N2Ar)Cl (VIII). [(HCpz3)M(NO)(N2Ar)Cl]+ (IX) and [(η-C5H5)M(NO)(N2Ar)(PPh3)]+ (XIII). These complexes complete the homologous series containing the isoelectronic and quasi-isostructural fragments [M(NO)2]2+, [M(NO)(N2Ar)]2+ and [M(N2Ar)2]2+ (M = Group VIa metal). IR spectroscopic studies of VII and VIII suggest that the hydrotris-(1-pyrazolyl)borato ligand in these complexes is a better π-acceptor than cyclopentadienide. Two of the new complexes have been characterised by X-ray crystallographic methods. Crystals of (HBpz3)Mo(NO)(N2C6H4F-p)Cl (VIIIb) are triclinic, space group P1 with four molecules in a unit cell of dimensions a = 13.053(3), b = 18.275(3), c = 8.954(2) Å, α = 97.18(2), β = 106.50(2), γ = 88.53(2)°. Crystals of [(η-C5H5)Mo(NO)(N2C6H4F-p)(PPh3)]PF6, [(XIIIc)]PF6, are also triclinic, space group P1, with two formula units in a unit cell of dimensions a = 11.526(1), b = 13.875(2), c = 10.873(2) Å, α = 108.37(2), β = 105.82(10, γ = 103.00(1)°. Both structures were determined by the heavy-atom method and refined to final R values of 0.030 (for 3812 observed reflections, VIIb) and 0.028 (for 3560 observed reflections [(XIIIc)]PF6). There are two independent molecules of VIIIb in the asymmetric unit. Principal bond lengths are: VIIIb: MoN(nitrosyl) 1.767(4) and 1.789(4), MoN(arenediazo) 1.857(3) and 1.877(3), MoN(Pz) 2.158–2.200(4), MoCl 2.424(1) and 2.428(1) Å; [(XIIIc)]PF6: MoN(nitrosyl) 1.802(3), MoN(arenediazo) 1.876(3), MoP 2.487(1), MoC(C5H5) 2.318–2.371(4) Å.