Nitride formation by thermolysis of a kinetically stable niobium dinitrogen complex

The reduction of [P2N2]NbCl (where [P2N2] = PhP(CH2SiMe2NSiMe2CH2)(2)PPh) with KC8 under a dinitrogen atmosphere generates the paramagnetic dinuclear dinitrogen complex ([P2N2]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 [(PH3)(2)(NH2)(2)Nb](2)(mu-N-2) was performed. Thermolysis of ([P2N2]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 [P2N2]Nb(mu-N)Nb[PN3] (3) (where [PN3] = PhPMe(CHSiMe2NSiMe2CH2P(Ph)CH2SiMe2NSiMe2N)). Complex 3 has been characterized in the solid state as well as by variable-temperature magnetic susceptibility measurements. The reaction of ([P2N2]Nb)(2)(mu-N-2) with phenylacetylene displaces the dinitrogen fragment to generate a paramagnetic eta(2)-alkyne complex, [P2N2]Nb(eta(2)-HCCPh) (4).