Early-late heterobimetallic (ELHB) complexes have polar metal-metal bonds, making them very different from homobimetallic systems in terms of reactivity. The combination of a Lewis acidic early transition metal with an electron rich late transition metal is expected to result in enhanced redox activity. It is also plausible that two different metals can act in a cooperative way to activate small molecules. Moreover, well defined ELHB complexes enable us to model metal alloys, clusters and magnetic materials. Our group has been interested in the design, synthesis and characterization of tris(phosphinoamide)-linked C3-symmetric early-late heterobimetallic complexes to investigate their chemical, magnetic and electronic properties, and activity towards small molecule activation and electron transfer processes. Our early studies proved that a heterobimetallic Zr-Co complex supported by a tris(phosphinoamide) ligand system could undergo facile multielectron redox chemistry and activate CO2. Further studies to explore this type of chemistry using first row transition metal early-late heterobimetallic complexes have also showed that these complexes can activate a variety of small molecules. In the context of designing well defined and characterized heterobimetallic complexes, we were interested in extending this chemistry from zirconium to niobium. We previously reported the synthesis and characterization of a Nb-Co complex with an imido fragment on the niobium atom that limited the metal-metal interactions and reactivity possible with this molecule. More recently, we have synthesized and characterized Cl-Nb(iPrNPPh2)3M-Br (M = Fe, Co, Cu) complexes through two independent routes starting from Nb(IV) and Nb(V) trisphosphinoamide precursors in order to study the metal-metal interactions, redox properties, and reactivity of these complexes in the absence of an imido fragment. Details of the syntheses of these complexes and their characterization by NMR, IR, UV-Vis, and Mössbauer spectroscopies will be presented, along with their redox potentials and analyses of their geometric and electronic structures.

Synthesis, characterization, and reactivity of Cl-Nb(iPrNPPh2)3M-Br complexes (M = Fe, Co, Cu)

252nd National Meeting (2016)

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