Zero valent iron and nickel coordination chemistry: metal atoms as direct approach to bis(benzene)chromium bridged N-heterocyclic silylene complexes

Abstract

Synthesis and characterization of iron and nickel metal complexes employing the monodentate N-heterocyclic silylene RSiPh (R = PhC(N^tBu)₂) is reported. The iron complexes were obtained by reacting the 20 valence electron bis(η⁶-toluene)iron sandwich generated in situ by co-condensation of elemental iron and toluene vapor with the silylene ligand. The corresponding nickel complexes are accessible by employing bis(1,5-cyclooctadiene)nickel(0) as a zerovalent nickel source. The N-heterocyclic silylene RSiPh (R = PhC(N^tBu)₂) ligand was tethered in the periphery of bis(benzene)chromium, resulting in the formation of a unique bidentate organometallic pincer ligand with two independent silylene units bridged by a bis-benzene moiety. All complexes were fully characterized by multinuclear NMR spectroscopy, IR spectroscopy, mass spectrometry and a single-crystal X-ray analysis of one of the iron compounds. The results underscore the versatility of silylenes and demonstrate the utility of highly reactive bis(η⁶-toluene)iron as a single-step approach to zerovalent Fe-silylene complexes.