Interconversion and reactivity of manganese silyl, silylene, and silene complexes

Abstract

Interconversions between manganese silylene and silene complexes are reported, including those involving the first spectroscopically observed silene complexes with an SiH substituent, and their involvement in ethylene hydrosilylation is discussed.

Reactions of Manganese Silyl and Silylene Complexes with CO2 and C(NiPr)2: Synthesis of Mn(I) Formate and Amidinylsilyl Complexes

“…0.93–0.95). These Mn–Si distances lie at the shorter end of the range observed for Mn­(I) silyl complexes with dmpe co-ligands {e.g., 2.35–2.44 Å in [(dmpe) 2 Mn­(SiH 2 R)­(CNR′)] (R = Ph or n Bu, R′ = o -xylyl or t Bu)}, and are longer than those in related NHC-stabilized silylene hydride complexes {2.26–2.30 Å in [(dmpe) 2 MnH­{SiR­(NHC)}] (R = Ph or n Bu, NHC = 1,3-diisopropylimidazolin-2-ylidene or 1,3,4,5-tetramethyl-4-imidazolin-2-ylidene)} . However, the two C–N distances in the metallacycle are more similar than would be expected for localized single and double bonds.…”

“…The reactions described in this work (Schemes and ) could proceed via a 5-coordinate silyl species ( A ) or a silylene hydride complex ( 2 ); Scheme . Both of these species have previously been shown to be accessible from disilyl hydride complexes 1 R through combined computational studies, high temperature 1 H NMR spectroscopy, and trapping reactions with isonitriles and NHCs . In addition, silyl isomers have been shown to be accessible from isolated silylene hydride complexes 2 R2 by DFT calculations …”

“…Our group has recently reported the manganese disilyl hydride complexes [(dmpe) 2 MnH­(SiH 2 R) 2 ] ( 1 Ph : R = Ph, 1 Bu : R = n Bu) and silylene hydride complexes [(dmpe) 2 MnH­(SiR 2 )] ( 2 Ph2 : R = Ph, 2 Et2 : R = Et). , Exposure of either set of complexes to ethylene resulted in an unprecedented transformation to afford manganese silene hydride complexes [(dmpe) 2 MnH­(RR′SiCHMe)] (Scheme ). , Reaction schemes were proposed for this transform­ation involving either a 5-coordinate silyl complex ( A ; formed from 1 R by hydrosilane elimination, or from 2 R2 by 1,1-insertion) or a silylene hydride complex (formed from 1 R by hydrosilane elimination to form A , followed by α-hydride elimination); Scheme . DFT calculations and trapping experiments were conducted, and demonstrated the thermodynamic and kinetic accessibility of 5-coordinate silyl and silylene hydride species from disilyl hydride complexes 1 R …”

Cooperativity in Transition Metal Tetrylene Complexes

“…The Emslie group has also provided valuable fundamental knowledge on the reactivity of silylenes with alkenes [76,77] . For instance, the reaction of manganese silylene hydride complex cis ‐ 30 with ethylene formed a complex bearing a coordinated silene ligand ( 31 ) (Scheme 12).…”

“…The Emslie group has also provided valuable fundamental knowledge on the reactivity of silylenes with alkenes. [ 76 , 77 ] For instance, the reaction of manganese silylene hydride complex cis ‐ 30 with ethylene formed a complex bearing a coordinated silene ligand ( 31 ) (Scheme 12 ). [76] Direct insertion of ethylene into a Mn−H bond was ruled out, and a [2+2] cycloaddition mechanism was not supported by either calculations or stoichiometric experiments.…”