Cationic Five‐Coordinate Bis(guanidinato)silicon(IV) Complexes with SiN₄El Skeletons (El=S, Se): “Heterolytic Activation” of S−S and Se−Se Bonds

Abstract

The donor-stabilized silylene [iPrNC(NiPr2 )NiPr]2 Si (2) reacts with PhEl-ElPh (El=S, Se) to form the respective cationic five-coordinate bis(guanidinato)silicon(IV) complexes {[iPrNC(NiPr2 )NiPr]2 SiSPh}(+) PhS(-) (4) and {[iPrNC (NiPr2 )NiPr]2 SiSePh}(+) PhSe(-) (5). Compounds 4 and 5 were characterized by crystal structure analyses and NMR spectroscopic studies in the solid state.

Chalcogen-atom transfer and exchange reactions of NHC-stabilized heavier silaacylium ions

“…1a) the Si=Se bond lengths are 2.1516(9) Å and 2.1571(8), which are similar to Lewis base stabilized tetra-coordinated Si=Se double bonded compounds (2.13 to 2.16 Å), 7a,7b,7e,7k but significantly shorter than the cationic Si-Se single bond length (2.308 Å) in {[iPrNC(NiPr2)NiPr]2SiSePh} + PhSe -. 18 Similarly, the Si=Te bond length of 4 (Fig. 1b) is 2.3941(6) Å and falls in the range of other neutral tetra-coordinated Si=Te compounds (2.38 to 2.39 Å).…”

“…The Si … Cl distances in 2, 3 and 4 are well above 5 Å, suggesting no direct contact between the silicon and the chlorine atom. In compound 2 (see SI), the Si=S lengths are 2.013(1) Å and 2.018(1) Å for the two independent molecules, which is shorter than the cationic Si-S single bond (2.160 Å) in {[iPrNC(NiPr2)NiPr]2SiSPh} + PhS -, 18 and nearly close to NHC or donor stabilized neutral or cationic Si=S bonds reported before (1.96 -2.00 Å). 7b,7d,7e,7k,8 In compound 3 (Fig.…”