Reactivity of a Phosphinoamidinate-Stabilized Disilylene toward H–X Bonds

Abstract

An efficient method for the preparation of a phosphinoamidinate-supported disilylene was developed, and its reactivity toward H–E bonds (E = elements from Groups 13–15) was studied. With HBpin, transfer of the ligand from silicon to boron was observed to afford (NP)­Bpin. Reaction with a silane (H3SiPh) took place only at elevated temperatures, at which point oxidative addition of the N–P bond of the NP-ligand to one of the silicon atoms of the disilylene occurred prior to Si–H addition involving the remaining silylene center. In contrast, reaction of the disilylene with phosphine, HPPh2 furnished the phosphidosilylene (NP)­SiPPh2 (16) together with a highly transient species that, on the basis of a trapping experiment with H3SiPh, is proposed to be the hydridosilylene (NP)­SiH, 17. Interestingly, 16 reacts with HPPh2 to give the diphosphine (PPh2)2, most likely via a direct σ-bond metathesis process. The aforementioned products have been characterized by multinuclear NMR and single-crystal X-ray diffraction studies.

The Insertion of EII and EIV Chlorides (E=Si, Ge) into the Si−Si Bond of Disilylene

“…For the major isomer, the SiCl 2 fragment resonates at 35.7 ppm, which is shifted downfield from the parent dichlorosilylene IPr⋅SiCl 2 (19.1 ppm). The silylene signal was observed at −39.9 ppm, which is almost the same as in the parent disilylene 6 (−40.2 ppm) [21] . For comparison, for the oxygen‐bridged bis(silylene) 9 (Figure 2), the silylene signal is observed at −16 ppm, in the xanthene‐bridged species 10 it comes at 7.3 ppm, and in the ethylenediyl‐bridged compound 4 , two non‐equivalent silylene centers give rise to singlets at 15.1 and 29.5 ppm.…”

“…Additionally, other chlorosilanes were tested in the reaction with disilylene 6 . Phenyltrichlorsilane did not react at room temperature, while heating resulted in the intramolecular rearrangement of 6 , previously described by our group [21] . Reaction with methyltrichlorsilane started at 50 °C and resulted in the isolation of a complex mixture of products.…”

“…Interestingly, for the minor diastereomer, the phosphorus signals are so close that they produce second‐order roofed doublet signals at 83.3 and 83.8 ppm. For comparison, the 31 P NMR spectrum of disilylene 6 displays a broad signal at room temperature which resolves into two sharp signals at 78.7 and 67.5 ppm at −53 °C, consistent with the presence of two quickly interconverting isomers [21] . In the 29 Si NMR spectrum of 11 , the silyl‐substituted silylene gives rise to an upfield shifted signal at −135.6 ppm (cf.…”

“…The silylene signal was observed at À 39.9 ppm, which is almost the same as in the parent disilylene 6 (À 40.2 ppm). [21] For comparison, for the oxygen-bridged bis(silylene) 9 (Figure 2), the silylene signal is observed at À 16 ppm, in the xanthene-bridged species 10 it comes at 7.3 ppm, and in the ethylenediyl-bridged compound 4, two non-equivalent silylene centers give rise to singlets at 15.1 and 29.5 ppm. Finally, in the related disilylenylsilylium compound 5, the silylene resonates at À 0.53 ppm, whereas the central four-coordinate silicon cation gives rise to a singlet at 2.96 ppm.…”

“…For comparison, the 31 P NMR spectrum of disilylene 6 displays a broad signal at room temperature which resolves into two sharp signals at 78.7 and 67.5 ppm at À 53 °C, consistent with the presence of two quickly interconverting isomers. [21] In the 29 Si NMR spectrum of 11, the silyl-substituted silylene gives rise to an upfield shifted signal at À 135.6 ppm (cf. À 40.2 ppm in 6), whereas the amido-substituted silylene resonates at the much lower field of À 19.9 ppm, consistent with the electron-releasing nature of the silyl vs. amide substituent.…”