Abstract
Hexacoordinate silicon complexes L2SiX2 (L = a 2-benzoylpyrrol-1-yl derivative, X = CN, NCS) were synthesized from L2SiCl2 by ligand exchange with trimethylsilyl reagents Me3SiX. In the presence of [Tp*CuNCMe] and Me3SiCN the silicon complex L2Si(NC(CuTp*))2 was obtained, which contains a linear Cu-CN-Si-NC-Cu unit (Tp* = hydrotris(3,5-dimethylpyrazolyl)borato).
Highlights
There is considerable interest in the creation and exploration of metal complexes with long-range intramolecular electronic communication.[1,2] Compounds such as Prussian Blue[3] or the Creutz–Taube salt,[4] compounds with C/N ligand backbones served as early motivators
Hypercoordinate silicon chemistry, i.e., the chemistry of silicon compounds with Si coordination numbers greater than four, is another field of coordination chemistry which attracts the interest of various chemists.[5,6]
Exhibits the soft sulphur atom as a terminal group, suitable for binding to a soft transition metal atom, the cyanide in 2 binds to silicon via the rather soft C atom, a coordination mode which might switch to the alternative Si–N coordination as soon as a soft competitor Lewis acid is available
Summary
Our recently reported Si-complexes with 2-benzoylpyrrolyl scaffold offered ideal prerequisites with the tendency of forming all-trans complexes of the type L2SiX′2 (L = 2-benzoylpyrrol-1-yl, X′2 = Cl2, (OTf )[2], ClPh).[13] we started introducing metal complexes into the Si coordination sphere of this type of complexes via Si–N coordination Out of this series, the chloro complex 1 (Scheme 2, 29Si CP/ MAS NMR δ = −171.0 ppm)[13] was chosen as starting material for ligand exchange with Me3SiX (X = CN, NCS). The very long Si–NCS bond of 1.97 Å24 is caused by the influence of the electron releasing trans-substituent, i.e., a methyl group This set of structures of Si6–N2–C2–X compounds reveals even greater variability of the Si–N–C angles, which cover the ranges of 180–146°26 (X = O), 180–151°24 (X = S) and 176° (X = Se25). Even though tetrahedral coordination is frequently encountered with both Cu(I) and Cu(II), the degenerate orbital situation associated with complex 5 and the degenerate SOMO resulting therefrom in case of formation of a Cu(I)/ Cu(II) complex 5+ apparently gives rise to the more positive oxidation potential and supports decomposition upon oxidation
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