Four- and three-coordinate planar iron(II) complexes supported by bulky organosilyl ligands.

The ligand exchange reaction of (THF) 2 Fe[Si(SiMe 3 ) 3 ] 2 with 2 equivalents of an N-heterocyclic carbene (NHC) led to the formation of a square-planar iron(II) complex with trans -oriented -Si(SiMe 3 ) 3 ligands. Conversely, the introduction of a cis -coordinate bidentate organosilyl ligand instead of -Si(SiMe 3 ) 3 resulted in the formation of a square planar iron(II) complex supported by a cis -coordinate bidentate organosilyl ligand. A three-coordinate planar iron(II) bis(silyl) complex was also synthesized using a cis -coordinate bidentate organosilyl ligand and a cyclic (alkyl)(amino)carbene auxiliary ligand. Investigation of the catalytic performance of these complexes in the hydrosilylation of acetophenone revealed that the square-planar iron(II) complex with trans -oriented -Si(SiMe 3 ) 3 ligands exhibits superior reactivity relative to its tetrahedral precursor.