Dehydrogenative coupling of aromatic thiols with Et₃SiH catalysed by N-heterocyclic carbene nickel complexes

Abstract

A series of new tetramethylcyclopentadienyl-functionalised N-heterocyclic carbene ligands with different wingtip substituents have been prepared and characterised. These ligands have been successfully coordinated to nickel affording complexes of the general type (Cp*-NHC(R))NiX (X = Cl, I). These well-defined nickel complexes selectively catalysed the coupling of aromatic thiols with Et3SiH to give the corresponding silylthioethers (RSSiEt3). The nickel complexes bearing ethyl, iso-butyl, and n-butyl wingtips displayed comparable catalytic efficiency, while the nickel complex bearing a methyl substituent on the wingtip was the worst performing catalyst.

Nickel N-heterocyclic carbene complexes and their utility in homogeneous catalysis

“…In particular, the (533−534), [163] (535), [164] (536), [165] (543−544), [166] (545−546), [167] (548 [168]−557), [169] (558), [51] (559), [71] (560), [161] (561), [170] (562−563), [141] (565), [171] (566−567), [172] (568), [173] (569), [126d] (570−573), [174] (574), [175] (575−576), [176] (577), [177] (578), [178] (579), [106] (580−581), [179] (582−583), [151] (584−585), [180] (586−588), [181] (595−596), [182] (597−599), [183] (600−603), [184] (604), [185] (605−608), [186] (609), [185] (610−613), [187] (614−618), [188] (619−621), [189] (622−623), [185] (624−630), [190] (631), [191] (633−635), [192] (636), [193] (637), [194] (647) [195] and (648) [196] complexes were obtained by this pathway from the treatment of the free or the in situ generated NHC The third route is the oxidation method (Scheme 15) using which the (589−590), [197] (638) …”

“…The following mixed Cp*/NHC nickel complexes (215) and (631−635) carried out the catalytic dehydrogenative coupling of thiols with triethyl silane [192].…”

“…The fourth method (Scheme 16) was used for the preparation of the following complexes (547), [167] (591−592), [78] (593), [191] (594), [194] (632), [192] (640−641) [23] (642−645) [88a] and (650−664) [199].…”

Selective Reduction of Nitroarenes with Silanes Catalyzed by Nickel N‐Heterocyclic Carbene Complexes

“…The catalytic activity of half‐sandwich Ni–NHC complexes 1 and 2 (Scheme ) in the reduction of nitroarenes was tested by using the primary silane PhSiH 3 as reducing agent and 1‐chloro‐4‐nitrobenzene as a model substrate. Initially, the reaction was performed in toluene at 60 °C in the presence of 2 mol % of catalyst and using a PhSiH 3 /substrate ratio of 5:1.…”

Catalytic Formation of Silicon–Heteroatom (N, P, O, S) Bonds

“…A year later, Nolan and co‐workers synthesized a highly stable [RuCl(PPh 3 )2‐(3‐phenylindenyl)] complex that also turned out to be an effective catalyst for the formation of silylthioethers by Si−S dehydrocoupling . Recently, the Royo group has introduced NHC nickel complexes that are also active in the abovementioned transformation . Moreover, several other reports describe the formation of the Si−S bond through silylation in the presence of HMDS by using poly( N ‐bromobenzene‐1,3‐disulfonamide), N , N , N′,N′‐ tetrabromobenzene‐1,3‐disulfonamide, 1,1′‐(ethane‐1,2‐diyl)dipiperidinium bis(tribromide), and 2‐carboxyethyltriphenylphosphonium tribromide as catalysts.…”