Synthesis, Properties, and Reactions of a Series of Stable Dialkyl-Substituted Silicon−Chalcogen Doubly Bonded Compounds

Abstract

The first dialkyl-substituted silicon-chalcogen doubly bonded compounds [R2Si=X; R2=1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl, X = S (4), Se (5), and Te (6)]were synthesized by the reactions of an isolable dialkylsilylene R2Si: (3) with phosphine sulfide, elemental selenium, and elemental tellurium, respectively. Systematic changes of characteristics of silicon-chalcogen double bonds are elucidated by X-ray analysis, UV-vis spectroscopy, and DFT calculations. In the solid state, the unsaturated silicon atom in 4-6 adopts planar geometry and the extent of the shortening of Si=X double bonds from the corresponding Si-X single bonds decreases in the order 4 > 5 > 6. In the absorption spectra of 4-6, pi -->pi* transition bands are observed distinctly in addition to n -->pi* transition bands. Both the n -->pi* and pi -->pi* transitions are red-shifted in the order 4 < 5 < 6, and the difference between the energies of the two transitions is kept almost constant among 4-6. The tendency is explained using the qualitative perturbation theory and is reproduced by the DFT calculations for model silanechalcogenones. Addition reactions of water, methanol, and isoprene to 4-6 are reported.

Synthesis and Characterization of an Amidinate-Stabilized Siladithiocarboxylate and Its Germanium(II) Complex

“…The Si(1)ÀN(1)ÀC(5)ÀN(2) ring is planar and almost perpendicular to the S(1)ÀSi (1) 7 They are shorter than typical SiÀS single bond lengths (average 2.14 Å), but longer than the SidS double bond length in [SdSi{C(SiMe 3 ) 2 -CH 2 CH 2 C(SiMe 3 ) 2 }] (1.9575(7) Å). 9 They are comparable with those in the base-stabilized silanethiones reported by research groups of Driess (1.9854(9)À2.006(1) Å) and Corriu (2.013(3) Å). 10 The results show that the SiÀS bonds in 2 could have some double-bond character or zwitterionic Si þ ÀS À bonding character.…”

N‐Heterocyclic Carbene (NHC)‐Stabilized Silanechalcogenones: NHC→Si(R2)E (E=O, S, Se, Te)

“…[3,4] Even the intramolecular N-donor-supported silanechalcogenones I (dA C H T U N G T R E N N U N G ( 29 Si) = 22.3 ppm) and II (dA C H T U N G T R E N N U N G ( 29 Si) = 29.4 ppm) [2] are less shielded than 3 a,b and 4 a,b, respectively. Apparently, this observation is indicative of greater perturbation of the Si=E (E= O, S, Se, Te) double bonds caused by both the C 3 N 2 p system in the backbone and the NHC moiety, thereby leading to several resonance structures as depicted in Scheme 3.…”

“…Si donor-acceptor bond, [2] several series of stable doubly bonded species have been developed by taking advantage of the kinetic protection from the bulky ligands and/or the thermodynamic stabilization from Lewis donors as well as acceptors. Striking examples, including a series of fascinating stable heavier diarylsilanechalcogenones III (Scheme 1) [3] and dialkylsilanechalcogenones IV (Scheme 1) [4] without intramolecular donor support, were described by Tokitoh, Okazaki et al as well as by Iwamoto and Kira et al, respectively. Recently, a novel bis(silaneselone) with two donorsupported Si=Se double bonds was reported by Müller and West et al [5] Abstract: A series of N-heterocyclic carbene-stabilized silanechalcogenones 2 a,b (Si=O), 3 a,b (Si=S), 4 a,b (Si=Se), and 5 a,b (Si=Te) are described.…”

Recent Advances in Silylene Chemistry: Small Molecule Activation En-Route Towards Metal-Free Catalysis

“…The first examples of dialkylsubstituted silicon double bonds to chalcogen atoms (S, Se and Te) were shown to be easily accessible by reaction of 70 with Me 3 P═S; elemental selenium or elemental tellurium, respectively [73]. These reactions lead from good to excellent yields in the silanethione L H Si═S (78) (72%) (L H ¼ ring cycle attached to Si in 70), silaselone L H Si═Se (79) (92%), and finally silatellone L H Si ¼ Te (80) (99%), respectively.…”