Isolation of chloride- and hydride-bridged tri-iron and -zinc clusters in a tris(β-oxo-δ-diimine) cyclophane ligand

Abstract

Chloride- and hydride-bridged tri-iron and -zinc clusters decorated with amine protons were successfully isolated in a cage-type ligand.

Access to Metal Centers and Fluxional Hydride Coordination Integral for CO2 Insertion into [Fe3(μ-H)3]3+ Clusters

“…29 Similar hydride transfer reactivity was also observed for the cobalt and the zinc congeners, leading to a hypothesis that the ligand pocket surrounding the μ-hydride donors strongly influences kinetics and selectivity for CO 2 reduction to formate. 29,34,37 In addition, we also observed reductive elimination (re) of H 2 upon the reaction of 2 with CO. The resultant Fe 3 (μ 3 -H)(CO) 2 L 1 product is competent for the oxidative addition of H 2 at slightly elevated temperatures to regenerate 2.…”

“… − For example, Holland and co-workers synthesized a series of β-diketiminate (or BDI) supported di­(μ-hydrido)­diiron complexes in which the H/D exchange with H 2 /D 2 and between isotopologues, bond metathesis with BEt 3 , insertion reactivity with CO 2 and various other possible electrophiles, and H 2 reductive elimination have been observed. , In contrast to these dimetallics which spontaneously assemble and exist in a monomer–dimer equilibrium, the tri­(μ-hydrido)­triiron complex templated by a tris­(β-diketimine)­cyclophane (i.e., Fe 3 (μ-H) 3 L 1 or 2 ) is remarkably specific for hydride transfer to CO 2 with minimal or no hydride transfer reactivity to other substrates . Similar hydride transfer reactivity was also observed for the cobalt and the zinc congeners, leading to a hypothesis that the ligand pocket surrounding the μ-hydride donors strongly influences kinetics and selectivity for CO 2 reduction to formate. ,, In addition, we also observed reductive elimination (re) of H 2 upon the reaction of 2 with CO. The resultant Fe 3 (μ 3 -H)­(CO) 2 L 1 product is competent for the oxidative addition of H 2 at slightly elevated temperatures to regenerate 2 .…”