The synthesis, isolation, and reactivity of a cationic, geometrically constrained σ 3 -P compound in the hexaphenylcarbodiphosphoranyl-based pincer-type ligand (1 + ) are reported. 1 + reacts with electron-poor fluoroarenes via an oxidative additiontype reaction of the C−F bond to the P III -center, yielding new fluorophosphorane-type species (P V ). This reactivity of 1 + was used in the catalytic hydrodefluorination of Ar−F bonds with PhSiH 3 , and in a catalytic C−N bond-forming cross-coupling reactions between fluoroarenes and aminosilanes. Importantly, 1 + in these catalytic reactions closely mimics the mode of action of the transition metal-based catalysts.
The chlorination of Si-H bonds often requires stoichiometric amounts of metal salts in conjunction with hazardous reagents, such as tin chlorides, Cl , and CCl . The catalytic chlorination of silanes often involves the use of expensive transition-metal catalysts. By a new simple, selective, and highly efficient catalytic metal-free method for the chlorination of Si-H bonds, mono-, di-, and trihydrosilanes were selectively chlorinated in the presence of a catalytic amount of B(C F ) or Et O⋅B(C F ) and HCl with the release of H as a by-product. The hydrides in di- and trihydrosilanes could be selectively chlorinated by HCl in a stepwise manner when Et O⋅B(C F ) was used as the catalyst. A mechanism is proposed for these catalytic chlorination reactions on the basis of competition experiments and density functional theory (DFT) calculations.
In contrast to the well-known reductive cleavage of the alkyl− O bond, the cleavage of the alkenyl−O bond is much more challenging especially using metal-free approaches. Unexpectedly, alkenyl−O bonds were reductively cleaved when enol ethers were reacted with Et 3 SiH and a catalytic amount of B(C 6 F 5 ) 3 . Supposedly, this reaction is the result of a B(C 6 F 5 ) 3 -catalyzed tandem hydrosilylation reaction and a silicon-assisted βelimination. A mechanism for this cleavage reaction is proposed based on experiments and density functional theory (DFT) calculations.
The chlorination of Si−H bonds often requires stoichiometric amounts of metal salts in conjunction with hazardous reagents, such as tin chlorides, Cl2, and CCl4. The catalytic chlorination of silanes often involves the use of expensive transition‐metal catalysts. By a new simple, selective, and highly efficient catalytic metal‐free method for the chlorination of Si−H bonds, mono‐, di‐, and trihydrosilanes were selectively chlorinated in the presence of a catalytic amount of B(C6F5)3 or Et2O⋅B(C6F5)3 and HCl with the release of H2 as a by‐product. The hydrides in di‐ and trihydrosilanes could be selectively chlorinated by HCl in a stepwise manner when Et2O⋅B(C6F5)3 was used as the catalyst. A mechanism is proposed for these catalytic chlorination reactions on the basis of competition experiments and density functional theory (DFT) calculations.
The difference in reactivity of 1,2-dibenzoyl-o-carborane (2) and its analogue with an aromatic
backbone
and two C6F5 electron withdrawing groups, C6H4(CO(C6F5))2 (5), in cyclization reactions with R3SiH (R = Et,
Ph (a)) with or without a catalytic amount of B(C6F5)3 was studied. In contrast to the
reaction of 2 with R3SiH, which directly leads
to the cyclic hydrofurane products 3 and 4, 5 and R3SiH do not react without a catalytic
amount of B(C6F5)3. However, in the
presence of a catalytic amount of B(C6F5)3, 5 reacts with R3SiH forming through
hydrofurane-type products 9, 9a, isobenzofuran 6. 2, on the other hand, reacts with R3SiH in the presence of a catalytic amount of B(C6F5)3 giving stable products 10, 10a. 10, 10a in the presence of
B(C6F5)3 transform over time to a
mixture of diastereomers 3′, 3a′. The mechanisms leading to these reactions are proposed on the basis
of experimental and computational investigation.
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