Nitride formation by thermolysis of a kinetically stable niobium dinitrogen complex

The reduction of P(2)N(2)]NbCl (where P(2)N(2)] = PhP(CH(2)SiMe(2)NSiMe(2)CH(2))(2)PPh) with KC(8) under a dinitrogen atmosphere generates the paramagnetic dinuclear dinitrogen complex (P(2)N(2)]Nb)(2)(mu-N(2)) (2). Complex 2 has been characterized crystallographically and by EPR spectroscopy. Variable-temperature magnetic susceptibility measurements indicate that 2 displays antiferromagnetic coupling between two Nb(IV) (d(1)) centers. A density functional theory calculation on the model complex (PH(3))(2)(NH(2))(2)Nb](2)(mu-N(2)) was performed. Thermolysis of (P(2)N(2)]Nb)(2)(mu-N(2)) in toluene generates the paramagnetic bridging nitride species where one N atom of the dinitrogen ligand inserts into the macrocycle backbone to form P(2)N(2)]Nb(mu-N)NbPN(3)] (3) (where PN(3)] = PhPMe(CHSiMe(2)NSiMe(2)CH(2)P(Ph)CH(2)SiMe(2)NSiMe(2)N)). Complex 3 has been characterized in the solid state as well as by variable-temperature magnetic susceptibility measurements. The reaction of (P(2)N(2)]Nb)(2)(mu-N(2)) with phenylacetylene displaces the dinitrogen fragment to generate a paramagnetic eta(2)-alkyne complex, P(2)N(2)]Nb(eta(2)-HCCPh) (4).