Coordination environment friendly silicon in copper(I) chloride π-complexes with tetravinylsilane and dimethyltetravinyldisiloxane

Bridging vs. Chelating Coordination Modes of Vinylsilanes in CuI π‐Complexes: Structure and Stability

“…Certainly, the trigonal bipyramidal environment of Cu I formed in this way is strongly distorted, but L ax –Cu–C α –Si torsion angle (φ) values by far exceed 90° (Table 2). Both the Cu–C α bond shortening and the silicon atom position, may be attributed not only to the (d Si +σ* Si–C ) ←π* C=C ← d Cu conjugation, which we reported earlier,16 but also, probably, to the d Si ← d Cu π‐donation. In addition, the strengthening of the Cu–(C=C) interaction, observed in the series 4 → 3 → 2 (see ω(C α ‐Cu–C β ) values in Table 2) and determined mainly by steric requirements of coligands and ligand substituents, favors more planar orientation of the chelate ring (see maximum deviations from planarity, Δ ring , in Table 2), greatly facilitating the π‐conjugation.…”

“…Here the tin ions act not only as reducing substance, but also as stabilizing agent to prevent premature precipitation of sparingly soluble copper(I) chloride complexes. To test the efficiency of the method, we recently applied it also to growing single crystals of CuCl complexes with tetravinylsilane and dimethyltetravinyldisiloxane 16. Due to the insolubility of complex 1, the deuterated chloroform solutions of CuCl and MTrVS in the molar ratios 1:1 and 2:1 were examined.…”

“…The occurrence of two different sources of separate Cu n Cl n species in the same structure points out that the cuprous halide clusters are highly prone to rearrangement depending on the coordination behavior and steric properties of an unsaturated ligand. For this reason, tetravinylsilane (TVS) bridges two Cu 4 Cl 4 units in the structure of [Cu 4 Cl 4 (TVS)],16 whereas a lack of one of the vinyl groups does not allow self‐assembling of Cu 2 Cl 2 dimers in 1 . On the other hand, tetraallylsilane (TAS), the molecule with a longer spacer arm, was found to be efficient for cross‐linking and formation of four inter‐Cu 5 Cl 5 ‐cluster bridges in the structure of complex [Cu 5 Cl 5 (TAS)] 17.…”

“…Thus, it becomes possible to design optimal copper(I) halide oligomers using the organic component with required electronic properties, molecular symmetry and conformational flexibility. For example, the Cu 4 Cl 4 chair‐like units show in 1 as well as in [Cu 4 Cl 4 (TVS)] the twisting conformation (torsion angles –164.8°, 78.1°, 15.5°, –100.7°) which is partly a result of excellent electron π‐acceptor properties of vinylsilanes 16. Indeed, an increase in π* C=C ← d Cu back bonding interaction promotes the planarity of the Cu I coordination sphere, causing elongation of the Cu ··· Cl lateral bonds (see Cu2–Cl2 bond length in Table 1) and, consequently, distortion of chair‐like tetranuclear clusters.…”

“…All the above‐mentioned facts have encouraged us to direct our attention to the complexation of alkenylsilicon compounds by d 10 metal atoms. We previously showed that a silicon atom acts as an amplifier of copper‐olefin interaction to enhance the thermal stability of organometallic complexes 16. Undoubtedly, these effects will also depend upon the coordination mode of unsaturated silicon containing ligand: bridging or chelating.…”