High Electrophilicity at Silicon in η³-Silane σ-Complexes: Lewis Base Adducts of a Silane Ligand, Featuring Octahedral Silicon and Three Ru–H–Si Interactions

Abstract

New η(3)-silane σ-complexes [PhBP(Ph)(3)]RuH(η(3)-H(2)SiRR') (RR' = PhMe, Ph(2)) were synthesized. Lewis bases [THF, 4-(dimethylamino)pyridine, and PMe(3)] coordinate to the silicon centers of these complexes to form stable adducts. The base adducts, [PhBP(Ph)(3)]Ru(μ-H)(3)SiRR'(base), feature three nonclassical Ru-H-Si interactions and hexacoordinate silicon centers, as determined by multinuclear NMR spectroscopy, X-ray crystallography, and computational investigations.

Silane–Isocyanide Coupling Involving 1,1-Insertion of XylNC into the Si–H Bond of a σ-Silane Ligand

“…3,4 It might also be possible for Si−H σ-complexes to bind substrates at silicon without Si−H bond cleavage, and this was suggested by our recent discovery that η 3 -H 2 SiRR′ σ-complexes [PhBP Ph 3 ] -RuH(η 3 -H 2 SiRR′) (R,R′ = Me,Ph 1a; R,R′ = Ph 2 1b, eq 1) add Lewis bases to form stable adducts of the type {[PhBP Ph 3 ]Ru[(μ-H) 3 SiRR′(base)]} (base = THF, PMe 3 , 4-dimethylaminopyridine). 5 In these adducts, the donor atom of the base is in close proximity to the hydride ligands, and in principle this could favor uncommon 1,1-hydrosilation reactions. Thus, it is important to examine the role that 1a,b might play in activations of unusual substrates and in new hydrosilation reactions.…”

Beyond Triphos – New hinges for a classical chelating ligand

“…Ph )] (R,R' = Me,Ph (154); Ph 2 (155)), featuring a rarely observed η 3 -H 2 Si coordination mode (Scheme 24, reaction ii) [33]. This differs from the reactivity observed for iridium in that the silicon moiety still contains directly bound hydrogens.…”

“…It was hoped that by implementing 2 as the ligand, the high electron-donating ability of the di-isopropylphosphino groups would facilitate the loss of anthracene with concomitant nitride transfer to generate the desired Ni N subunit, but this did not occur. More recent work has focused on second row transition metals such as rhodium [31,32] and ruthenium [32,33]. Rhodium derivatives have displayed a wide range of chemistry, with many reported complexes (64-76, Scheme 12) [32,34,35].…”

“…These complexes have displayed a rich chemistry for the stabilization of reactive species via activation of small molecules, as well as mediating their subsequent reactivity. The activation chemistry of primary, secondary and tertiary silanes to generate catalytically important silylene fragments has been developed on both iridium [61] and ruthenium centered complexes [33,62]. Catalytic and stoichiometric reactions of organosilanes are thought to occur via intermediate silylene complexes (e.g.…”

“…This differs from the reactivity observed for iridium in that the silicon moiety still contains directly bound hydrogens. The electrophilic character of the silicon atom in 154 and 155 is evident from the reaction of these complexes with Lewis bases such as THF (156) and 4-(dimethylamino)pyridine (DMAP) (157 and 158) which resulted in adduct formation (Scheme 24, reaction iii) [33]. The reactivity of 154 and 155 was further studied by reaction with 2,6-xylylisocyanide (Scheme 24, reaction iv) [63] and 2,6-xylylsilane (Scheme 24, reaction v) [62], the former resulting in silane-isocyanide coupling (159 and 160), and the latter in formation of a dimeric species featuring an extremely rare central η 4 ,η 4 -[SiH 6 ] 2-moiety [{Ru(κ 3 -PhBP 3 Ph )} 2 {μ-η 4 ,η 4 -H 6 Si}] (161) [62].…”