From an Isolable Acyclic Phosphinosilylene Adduct to Donor‐Stabilized SiE Compounds (E=O, S, Se)

Abstract

Reaction of the arylchlorosilylene-NHC adduct ArSi(NHC)Cl [Ar=2,6-Trip2C6H3; NHC=(MeC)2(NMe)2C:] 1 with one molar equiv of lithium diphenylphosphanide affords the first stable NHC-stabilized acyclic phosphinosilylene adduct 2 (ArSi(NHC)PPh2), which could be structurally characterized. Compound 2, when reacted with one molar equiv selenium and sulfur, affords the silanechalcogenones 4 a and 4 b (ArSi(NHC)(=E)PPh2, 4 a: E=Se, 4 b: E=S), respectively. Conversion of 2 with an excess of Se and S, through additional insertion of one chalcogen atom into the Si=P bond, leads to 3 a and 3 b (ArSi(NHC)(=E)-E-P(=E)Ph2, 3 a: E=Se, 3 b: E=S), respectively. Additionally, the exposure of 2 to N2O or CO2 yielded the isolable NHC-stabilized silanone 4 c, Ar(NHC)(Ph2P)Si=O.

A Stabilized Bisphosphanylsilylene and Its Heavier Congeners

“…In benzene solution the latter shows a 29 Si resonance at −72.5 ppm with a triplet splitting of 1 J SiP =45 Hz corresponding to a 31 P chemical shift of −33.8 ppm. Related NHC–silylene donor adducts with only one phosphanyl group at silicon show 29 Si resonances at substantially lower field with an additional C‐substituent (−39.2 ppm) or N ‐substituent (+4.2 ppm) . The signal of the carbene carbon atom in 8 shows coupling to the phosphorus nuclei (t, 2 J PC =8.1 Hz) and its chemical shift at 168.5 ppm is significantly shielded compared with that of the uncoordinated carbene in the same solvent (benzene, δ ( 13 C=212.7 ppm).…”

“…The signal of the carbene carbon atom in 8 shows coupling to the phosphorus nuclei (t, 2 J PC =8.1 Hz) and its chemical shift at 168.5 ppm is significantly shielded compared with that of the uncoordinated carbene in the same solvent (benzene, δ ( 13 C=212.7 ppm). The carbene resonance in 8 is very close to that in the monophosphanylsilylene adducts of Driess (166.7 ppm, 2 J CP =5.8 Hz) and Cui et al. (166.25 ppm, 14.67 Hz) .…”

“…Single crystals suitable for X‐ray diffraction have been obtained for 8 (Figure ). In the molecular structure of 8 the Si‐P distances of 2.3369(8) and 2.3275(8) Å are elongated compared with the tetravalent dihalosilanes Fe(C 5 H 4 P t Bu) 2 SiX 2 (X=Cl, Br, I; 2.2380(5)–2.2548(8) Å) and the recently published tetraphosphanyldisilene (2.2666(8)‐2.2392(8) Å) but are very similar to those in NHC adducts of monophosphanyl substituted silylenes ((2.3460(11) Å, 2.3748(7) Å)). One might be tempted to attribute this elongation to hyperconjugative electron donation from the σ PSiP orbital to the electron acceptor N ‐heterocycle, but second order perturbation theory analysis on the NBO basis reveals only weak (2–3 kcal mol −1 ) interactions between the P−Si bonds and the antibonding orbitals of the NHC unit.…”

S–H Bond Activation in Hydrogen Sulfide by NHC-Stabilized Silyliumylidene Ions

“…Also, we could demonstrate the recovery of silyliumylidene A from VIIIa-c by the treatment with AuI as well as chalcogen transfer reactions. dihydrophosphasilene reported by Driess and coworkers in 2015 [56,57] as well as the reaction towards diazoalkanes and azides presented by Filippou and coworkers [58] remain as the only reports regarding the reactivity of this species.…”

“…Subsequently, the mTer iPr -chlorosilylene was employed as the precursor for the preparation of a silylidyne complex Cp(CO) 2 Mo≡Si(mTer iPr ) [55]. The conversion of those chlorosilylenes with lithium diphenylphosphine and LiPH 2 to the corresponding phosphinosilylene and 1,2-dihydrophosphasilene reported by Driess and coworkers in 2015 [56,57] as well as the reaction towards diazoalkanes and azides presented by Filippou and coworkers [58] remain as the only reports regarding the reactivity of this species.…”