Synthesis and Reactivity of New Copper(I) Hydride Dimers

Abstract

The expanded-ring N-heterocyclic carbenes 6Dipp and 7Dipp (6Dipp = 1,3-bis­(2,6-diisopropylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene and 7Dipp = 1,3-bis­(2,6-diisopropylphenyl)-4,5,6,7-tetrahydro-1,3-diazepin-2-ylidene) support isolable neutral copper hydride dimers. [(6Dipp)­CuH]2 reacts with 1-hexene to give (6Dipp)­copper­(I) hexyl by 1,2-insertion and with benzyl isonitrile to afford an η1-formimidoyl by 1,1-insertion.

Experimental and Computational Studies of the Copper Borate Complexes [(NHC)Cu(HBEt3)] and [(NHC)Cu(HB(C6F5)3)]

“…DOSY measurements showed that it was dimeric (Scheme ) . The complex exhibited a low frequency Cu‐H resonance at δ =0.96 ppm, in good agreement with the shifts recently reported for [(6/7Dipp)Cu(μ‐H)] 2 species . However, whereas [(6/7Dipp)Cu(μ‐H)] 2 prove stable for days at 298 K, 2 was stable only below 209 K. Above this temperature, the 1 H NMR resonances began to broaden and at 255 K signals for 3 were present…”

Base Metal Catalyzed Isocyanide Insertions

“…[50] While the mechanism was not fully investigated, the authors proposed aT ype II process involving hydrosilicate intermediate 86 (Scheme 22 b). However, as the insertion of isocyanides into CuÀHb onds is known, [51] a1 ,1migratory insertion following aT ype Ip rocess into copper hydride species 88 cannot be excluded without further studies.…”

Base Metal Catalyzed Isocyanide Insertions

“…While the mechanism was not fully investigated, the authors proposed a Type II process involving hydrosilicate intermediate 86 (Scheme b). However, as the insertion of isocyanides into Cu−H bonds is known, a 1,1‐migratory insertion following a Type I process into copper hydride species 88 cannot be excluded without further studies. Formal enantioselective S N 2′ attack of the organocopper species 87 onto the allylic phosphate 83 affords aldimines 84 in excellent yields with moderate to excellent ee .…”