Facile Access to Mono- and Dinuclear Heteroleptic N‑Heterocyclic Silylene Copper Complexes

Reaction of the heteroleptic N-heterocyclic chlorosilylene L­(Cl)­Si: (1; L = PhC­(NtBu)2) with [Cu­(tmeda)­(CH3CN)]­[OTf] (2; tmeda = N,N,N′,N′-tetramethylethylenediamine, OTf = OSO2CF3 (triflate)) affords the Cu­(I) complex [L­(Cl)­Si:→Cu­(tmeda)]­[OTf] (3) in high yield as the first example of a heteroleptic N-heterocyclic silylene copper complex. Similarly, the reaction of L­(OtBu)­Si: (4; L = PhC­(NtBu)2) with 2 affords [L­(OtBu)­Si: → Cu­(tmeda)]­[OTf] (5) and that of L­(NMe2)­Si: (6) with 2 leads to [L­(NMe2)­Si:→Cu­(tmeda)]­[OTf] (7). Complex 3 shows a rather strong interaction in the solid state between the O atom of the triflate anion and the three-coordinate Cu­(I) center with a Cu···O distance of 2.312 Å. In contrast, complex 7 features only a weak interaction (ca. 3.28 Å), while in complex 5 the cation and anion are fully separated. Strikingly, the reaction of the chelating oxo-bridged silylene :Si­(L)­(μ2-O)­(L)­Si: (8) with the copper source [Cu­(CH3CN)4]­[OTf] (9) affords the dinuclear complex salt [Cu2{η1:η1-LSi­(μ2-O)­SiL}2]­[OTf]2 (10), featuring a novel metallacyclooctane dication, selectively in a good yield. Complex 10 also exhibits a very strong interaction between the copper centers in the dication and the oxygen atoms of triflate anions in the solid state, evidenced by a Cu···O separation of only 2.141 Å. All complexes were fully characterized.