1420299-97-3

Upstream product

• 1420299-69-9 [2,6-η6:η1-bis(2,4,6-trimethylphenyl)phenylthiolato]tris(4-fluorophenyl)phosphineruthenium(II)tetrakis[3,5-bis(trifluoromethyl)phenyl]borate 
• 597-50-2 triethylphosphine oxide 
• 1420299-89-3 C₅₅H₅₁F₃PRuSSi⁽¹⁺⁾*C₃₂H₁₂BF₂₄^(1-) 
• 758-21-4 dimethylethylsilane 
• 1420299-84-8 [2,6-η6:η1-bis(2,4,6-trimethylphenyl)phenylthiolato]chlorido[tris(4-fluorophenyl)phosphine]ruthenium(II) 

Relevant academic research and scientific papers

A Neutral RuII Hydride Complex for the Regio- and Chemoselective Reduction of N-Silylpyridinium Ions

A detailed experimental analysis of the 1,4-selective reduction of pyridine with hydrosilanes catalyzed by a coordinatively unsaturated RuII thiolate complex is reported. The previously suggested intermediates, N-silylpyridinium ions and a neutral RuII hydride, have been independently synthesized and do indeed participate in the catalytic cycle. The resting state is not the cationic RuII complex initially used as the catalyst but its pyridine-coordinated congener. All RuII complexes, including the one resulting from hydrosilane activation, are in equilibrium with each other. The N-silylated 1,4-dihydropyridine together with the cationic RuII complex convert back into the corresponding N-silylpyridinium ion and the neutral RuII hydride (retro-hydrosilylation), followed by further backward reaction into the hydrosilane and the pyridine adduct of the cationic complex. These steps prove the overall reversibility of the transformation.

Mechanism of the cooperative Si-H bond activation at Ru-S bonds

The nature of the hydrosilane activation mediated by ruthenium(ii) thiolate complexes of type [(R3P)Ru(SDmp)]+[BArF4]- is elucidated by an in-depth experimental and theoretical study. The combination of various ruthenium(ii) thiolate complexes and tertiary hydrosilanes under variation of the phosphine ligand and the substitution pattern at the silicon atom is investigated, providing detailed insight into the activation mode. The mechanism of action involves reversible heterolytic splitting of the Si-H bond across the polar Ru-S bond without changing the oxidation state of the metal, generating a ruthenium(ii) hydride and sulfur-stabilized silicon cations, i.e. metallasilylsulfonium ions. These stable yet highly reactive adducts, which serve as potent silicon electrophiles in various catalytic transformations, are fully characterized by systematic multinuclear NMR spectroscopy. The structural assignment is further verified by successful isolation and crystallographic characterization of these key intermediates. Quantum-chemical analyses of diverse bonding scenarios are in excellent agreement with the experimental findings. Moreover, the calculations reveal that formation of the hydrosilane adducts proceeds via barrierless electrophilic activation of the hydrosilane by sterically controlled η1 (end-on) or η2 (side-on) coordination of the Si-H bond to the Lewis acidic metal center, followed by heterolytic cleavage of the Si-H bond through a concerted four-membered transition state. The Ru-S bond remains virtually intact during the Si-H bond activation event and also preserves appreciable bonding character in the hydrosilane adducts. The overall Si-H bond activation process is exergonic with ΔGr0 ranging from -20 to -40 kJ mol-1, proceeding instantly already at low temperatures.

C(sp3)-F bond activation of CF3-substituted anilines with catalytically generated silicon cations: Spectroscopic evidence for a hydride-bridged Ru-S dimer in the catalytic cycle

Heterolytic splitting of the Si-H bond mediated by a Ru-S bond forms a sulfur-stabilized silicon cation that is sufficiently electrophilic to abstract fluoride from CF3 groups attached to selected anilines. The ability of the Ru-H complex, generated in the cooperative activation step, to intramolecularly transfer its hydride to the intermediate carbenium ion (stabilized in the form of a cationic thioether complex) is markedly dependent on the electronic nature of its phosphine ligand. An electron-deficient phosphine thwarts the reduction step but, based on the Ru-S catalyst, half of an equivalent of an added alkoxide not only facilitates but also accelerates the catalysis. The intriguing effect is rationalized by the formation of a hydride-bridged Ru-S dimer that was detected by 1H NMR spectroscopy. A refined catalytic cycle is proposed.