Base-Free Iron Hydrosilylene Complexes via an α-Hydride Migration that Induces Spin Pairing

Abstract

Two new base-free hydrosilylene complexes of iron were synthesized using the novel starting material Cp*( PrMeP)FeMes. These Cp*( PrMeP)Fe(H)SiHR (R = DMP, Trip) complexes are in equilibrium with the corresponding iron silyl complexes, Cp*( PrMeP)FeSiHR, which can be trapped and characterized for R = Trip. Unlike the Ru analogues, the Fe silylene complex with R = DMP is observed to undergo an intramolecular C-H activation involving formal addition of a benzylic C-H bond across the Fe-Si bond. This increased activity for bond activations is also observed for reactions with hydrogen, where Fe reacts faster than a Ru analog to form the hydrogenation product, Cp*( PrMeP)HFeSiHDMP.

Efficient and selective alkene hydrosilation promoted by weak, double Si–H activation at an iron center

“…Note that the MECP computed using the uB97X-D3 functional most likely does not reproduce either the energy or geometry of the MECP well, as this functional overstabilizes triplet states in both the present and related systems. 37 Thus, using the B3LYP functional (for which the singlet-triplet gap of I agrees much better with DLPNO-CCSD(T)) the MECP is found to be 4.6 kcal mol À1 above 3 Ph , and still lower in energy than the fully dissociated triplet species. In this structure, the Fe-Si bond has lengthened by ca.…”

Entrapment of THF‐Stabilized Iridacyclic IrIII Silylenes from Double H−Si Bond Activation and H2 Elimination

“…Ageometry optimized at the ZORA-PBE0 [62] -DdsC [63] ). The reaction described above was repeated (À40 8C) for recording 13 Ca nd 2D NMR spectra. 13…”

“…Nonetheless, 1 Ha nd 29 Si chemical shifts that were diagnostic of the structure of [2d] [BArF 24 ]c ould be unambiguously identified (vide infra). 13 Cn uclei could not be assigned with certainty to the product of interest due to the complex nature of the reaction mixture and of the resulting NMR spectrum. 1…”

“…[10] The main methods [1a] for preparing metal silylenes are based on anionic-substituenta bstraction [4f, 11] from am etal hydrosilyl precursor or sequential HÀSi activations [4c, 5a, 12] in the reaction of an RM precursor (e.g.,R = alkyl, aryl) with ah ydrosilane. [13] Althoughe xamples of directf ormation of metal silylenes by double HÀSi bond activation [14,15] are legion, cases in which spontaneous elimination of H 2 followsd ouble SiÀHb ond activationa re relativelys carce. [3a, 4c, 5a, 12, 16] Recently,T illey et al [5a] reportedt hat an Ru silylene [L 3 (H)Ru=SiRR']c an be obtained by reversible H 2 elimination from a[ L 3 (H)Ru(h 3 -H 2 SiRR')] intermediate, which later showed catalytic turnover in ketone hydrosilylation.…”

“…The main methods for preparing metal silylenes are based on anionic‐substituent abstraction from a metal hydrosilyl precursor or sequential H−Si activations in the reaction of an RM precursor (e.g., R=alkyl, aryl) with a hydrosilane . Although examples of direct formation of metal silylenes by double H−Si bond activation are legion, cases in which spontaneous elimination of H 2 follows double Si−H bond activation are relatively scarce .…”