Competitive Molecular Rearrangements in Hexacoordinate Cyano-Silicon Dichelates

Abstract

Pentacoordinate siliconium chloride or neutral hexacoordinate silicon complexes with imino-nitrogen donor groups react with cyanotrimethylsilane in two competing reactions, leading either to addition of the cyano group to the imino carbon or to hexacoordinate cyano-silicon complexes. The latter may further transform to a rearranged tricyclic pentacoordinate complex. The common driving force for these reactions seems to be the conversion of one of the two initial NfSi dative bonds, present in the starting complexes, to a shorter formal covalent bond.

Photo‐Driven Si‐C Bond Cleavage in Hexacoordinate Silicon Complexes

“…As soon as Si−X bonds other than Si-Halide are getting activated by Sihypercoordination, the groups X may exhibit reactivities of camouflaged nucleophiles, i.e., group X may attack electrophilic centres in the ligand backbone such as carbonyl and imine carbon atoms. Such reactivity was shown for hexacoordinate silacyclobutanes [4], allylsilanes [5], disilanes [6], cyanosilanes [7] and H-silanes [8]. Even an unexpected alkyl group shift towards an imine ligand was reported recently [9].…”

Cyanidosilikate – Synthese und Struktur

“…Über neutrale binäre Si‐CN‐Verbindungen (z. B. Si‐CN und Si(CN) 2 ), die in einer Argonmatrix untersucht oder in der Hülle eines Sterns beobachtet wurden, weiß man wenig, obwohl cyanidhaltige Silane, wie das Cyantrimethylsilan (Me 3 Si‐CN), in der organischen Chemie für ihre vielseitige Verwendung als Cyanosilylierungsreagens in Kombination mit Lewis‐Säuren oder ‐Basen bekannt sind . Das höher substituierte Dicyandimethylsilan kann als Schutzgruppe verwendet werden, während das Tricyanmethylsilan noch nicht isoliert, aber vermutlich in situ in einer Reaktion von MeSiCl 3 mit KCN gebildet wird .…”

Tp*Cu(i)–CN–SiL2–NC–Cu(i)Tp* – a hexacoordinate Si-complex as connector for redox active metals via π-conjugated ligands

“…14,15 Cyanide and thiocyanate are known to behave as ambidentate ligands 16,17 and might thus give rise to possible coordination isomerism. 14,15 Cyanide and thiocyanate are known to behave as ambidentate ligands 16,17 and might thus give rise to possible coordination isomerism.…”

“…Out of this series, the chloro complex 1 (Scheme 2, 29 Si CP/ MAS NMR δ = −171.0 ppm) 13 was chosen as starting material for ligand exchange with Me 3 SiX (X = CN, NCS). These reagents, which already have proven to be suitable cyano and thiocyanato synthons in hypercoordinate silicon chemistry, 14,15 afforded the desired complexes 2 and 3 (Scheme 2, 29 Si CP/ MAS NMR δ = −198.4 and −194.0 ppm, respectively). Their molecular structures, confirmed by single-crystal X-ray diffraction, reveal the target configuration all-trans (Fig.…”