Synthesis, Characterization, and Structural Analysis of PN ³ (P)-Antimony(III) Complexes and Their Reactivity in Transmetalation with Ni and Co

We report the synthesis and characterization of a new class of antimony(III) complexes supported by the PN3(P)-pincer frameworks, featuring phosphorus–nitrogen donor arms. These complexes exhibit versatile coordination behavior, adopting either bi- or tridentate binding modes depending on the structural features of the specific PN3(P) platform. The complexes were thoroughly characterized in solution (1H, 31P, and 13C NMR spectroscopy) and in the solid state by single-crystal X-ray diffraction analysis (SC-XRD). The antimony complexes can be readily transmetalated to form the corresponding well-defined pincer nickel and cobalt complexes, representing a new example of antimony-to-nickel/cobalt transmetalation. The behavior of the detached arm in the bipyridine complex is influenced by the strength of the P–Sb bond, which affects the rotation of the arm and determines the resulting conformer. This analysis is supported by Wiberg bond orders, the intrinsic bond strength index (IBSI), and the QTAIM analysis.