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