Higher‐Coordinate Silicon Compounds withSiO₅andSiO₆Skeletons

Bis(catecholato)silanes: assessing, rationalizing and increasing silicon's Lewis superacidity

“…Pentacoordinate anionic bis(catecholato)silicates were used as hydride or allyl donors to carbonyls,17 and more recently for the photoredox catalytic generation of alkyl radicals 18. The related tris(catecholato) silicate dianions have in fact been known for almost 100 years and serve as a prime example for hexacoordination of silicon 19. Obviously, the Lewis acidity of the underlying catecholatosilanes is decisive for the stability and reactivity of all their adducts.…”

Neutral Hexa- and Pentacoordinate Silicon(IV) Complexes withSiO6andSiO4N Skeletons

“…The chemistry of hexacoordinate silicon(IV) complexes with Si O 6 skeletons is dominated by anionic and cationic species. The most prominent examples are the tris[benzene-1,2-diolato(2−)]silicate dianion and the tris[acetylacetonato(1−)- O , O ‘]silicon cation . We have also contributed to this field of chemistry and have determined the first crystal structures of compounds containing the tris[glycolato(2−)- O 1 , O 2 ]silicate, tris[benzilato(2−)- O 1 , O 2 ]silicate, tris[acetohydroximato(2−)]silicate, tris[benzohydroximato(2−)]silicate, or tris[salicylato(2−)- O 1 , O 3 ]silicate dianions as well as the tris[1-oxopyridin-2-olato(1−)]silicon cation .…”

Neutral and Cationic Bis-Chelate Monoorganosilicon(IV) Complexes of 1-Hydroxy-2-pyridinone

“…Structural, bonding, and reactivity studies of hypercoordinate organosilicon complexes have been explored extensively and continue to be an active area of interest. , In organic synthesis, neutral and charged donor atom complexes of this type are important mediators in carbon–carbon bond forming reactions. In these reactions, the silicon atom acts as the reactive site, and upon expansion of its coordination shell, both its Lewis acidity and reactivity of its carbon substituent as a nucleophile are enhanced.…”

“…Complexes with expanded coordination spheres also serve as models of intermediates and transition states in the mechanisms of substitution processes at tetracoordinate silicon . Pentacoordinate silicon complexes often manifest geometrical and stereochemical flexibility with low energy barriers to isomerization.…”