Related Experiment Video
Updated: Nov 9, 2025

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry
Published on: February 4, 2017
Exploring the Coordination Chemistry of N2 with Technetium PNP Pincer-Type Complexes
Manuel Luca Besmer1, Henrik Braband1, Sven Schneider2
1Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
Abstract:
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 and PyrPNP respectively gave [99Tc(PNP)Cl2] and [99Tc(PyrPNP)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)(N2)2] and the dinuclear complex [99TcI(PyrPNP)(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 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.
Related Concept Videos
Valence Bond Theory
Coordination Number and Geometry
Coordination Compounds and Nomenclature
Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
Structural Isomerism
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...

