Exploring the Coordination Chemistry of N2 with Technetium PNP Pincer-Type Complexes

Dinitrogen (N2) complexes of technetium (99Tc) are rare, and only two examples have been reported. To complement this important class of complexes also for 99Tc, two different pincer-type complexes of 99Tc were studied to assess their abilities for coordinating dinitrogen. The reactions of the 99TcIII complex [99TcCl3(PPh3)2(NCCH3)] with the pincer ligands PNP tBu and PyrPNP tBu respectively gave [99Tc­(PNP tBu)­Cl2] and [99Tc­(PyrPNP tBu)­Cl3], the first structurally characterized 99Tc complexes with mer-coordinated pincer ligands. Reductions with [Co­(Cp*)2] under N2 gave the mononuclear bis-dinitrogen complex [99TcI(PNP tBu)­(N2)2] and the dinuclear complex [99TcI(PyrPNP tBu)­(N2)­Cl]2(μ-N2) with both a bridging and a terminal N2 ligand. Spectroscopy and crystal structures confirm their identities. The complexes are stable under a dinitrogen atmosphere, and the N2 ligands are tightly bound. The results for the complexes with the PNP tBu pincer allow a comparison to its rhenium homologue, which has recently been shown to split the N2 ligand with the formation of a nitrido complex.