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

Abstract

Four- and three-coordinate iron(ii) bis(silyl) complexes were prepared and their catalytic performance in hydrosilylation reactions was investigated.

Planar three-coordinate iron(ii) complexes supported by sterically demanding –Si(SiMe3)2(SiMe2tBu) ligands

“…1; 2.4923(11)/2.5209(12) Å), presumably due to the steric repulsion induced by Me CAAC in B . 4 Moreover, the Fe–Si bonds in 2 are comparable to those in Tilley's anionic iron( ii ) disilyl complex A (Fe–Si: 2.488(6)/2.491(6) Å). 3…”

“…In stark contrast, when four-coordinate 1 was used, 1 h was required for the full conversion of acetophenone in the reaction with Ph 2 SiH 2 (entry 1). 4,5 Moreover, complete conversion of acetophenone was confirmed after 1 h by 0.1 mol% of 3 (entry 3). These reactions were monitored by 1 H NMR spectrum, and the time course of these reaction was summarized in the ESI †.…”

“…Subsequently, we performed the hydrosilylation of acetophenone with TMDS using 0.5 mol% of 2 at room temperature for 24 h, which resulted in 60% conversion of acetophenone (entry 8), whereas the conversion reached only 30% using 1 as the catalyst under otherwise identical reaction conditions. 4,5 A slight increase in conversion (81%) was observed when 3 was used as the catalyst under otherwise identical reaction conditions (entry 9). Thus, it can be concluded that substitution of one of the three SiMe 3 groups on the –Si(SiMe 3 ) 3 ligand with a SiMe 2 t Bu moiety leads to highly active iron catalysts.…”

“…, THF, pyridine, or an N-heterocyclic carbenes (NHC) on “Fe[Si(SiMe 3 ) 3 ] 2 ” and its analogous fragment exclusively afford four-coordinate complexes. 4,5 Therefore, rational synthetic strategies for the construction of coordinatively unsaturated three-coordinate iron-silyl complexes remain elusive so far §§Tilley et al have obtained Fe[Si(SiMe 3 ) 3 ] 2 (L) (L = Et 2 O, THF) from the reaction of anionic {Fe(Cl)[Si(SiMe 3 ) 3 ] 2 } − with Me 3 SiOSO 2 CF 3 in Et 2 O or THF; however, a crystallographic analysis has not yet been reported for these complexes; for details, see ref.…”

“…In our previous paper, we reported that tetrahedral four-coordinate complex 1 and the aforementioned four-coordinate planar complex trans -Fe[Si(SiMe 3 ) 3 ] 2 (MeIM Me ) 2 show good catalytic performance in the hydrosilylation of acetophenone. 4,5 Thus, the catalytic performance of 2 and 3 was examined in the hydrosilylation of acetophenone using the hydrosilanes, Ph 2 SiH 2 and 1,1,3,3-tetramethyldisiloxane (TMDS). 9…”