Unsymmetrical sp²‐sp³ Disilenes

Abstract

Disilenes with differently coordinated silicon atoms are not known. Here, we have shown the high yield synthesis of a range of disilenes (2–4 and 6) upon reaction of a hypersilyl silylene PhC(NtBu)2SiSi(SiMe3)3 (1) with aliphatic chlorophosphines. The most striking characteristic of these disilenes is the presence of two differently coordinated Si atoms (one is three‐coordinated, the other four‐coordinated). The analogous reaction with Ph2PCl did not afford the desired disilene, but, surprisingly, led to the first tetraphosphinosilane (8). DFT calculations were performed to understand the bonding in disilenes and differences in reactivity of the complexes.

The Hypersilyl Substituent in Heavier Low‐Valent Group 14 Chemistry

“…The high reactivity of the Si=Si bond was anticipated from the HOMO-LUMO gap of 2.67 eV. The expectation was confirmed from the stereospecific trans-hydrogenation (18) of the Si=Si bond of 17, upon reacting with dihydrogen.…”

“…Similarly, the reaction with PMes 2 Cl resulted in a penta‐coordinate silane ( 51 ) possibly via 51’ (Scheme 18). [18] …”

“…From the hypersilylsilylene 26 we were able to generate a series of unsymmetrical sp 2 -sp 3 disilene 44-47 (Scheme 15). [18] Scheme 10. Synthesis and reactivity of hypersilylsilylene 26.…”

“…Similarly, the reaction with PMes 2 Cl resulted in a pentacoordinate silane (51) possibly via 51' (Scheme 18). [18] The electronic ground state of carbenes can be either singlet or triplet depending on the electronic and steric characteristics of the substituents on the carbene center. The analogous silylene in contrast, prefers a singlet ground state and the existence of a triplet silylene is still a question.…”

“…[8] Subsequently, some groundbreaking works came from the groups of Inoue [9][10][11][12] and Rivard [13,14] who have exploited hypersilyl group to realize several exotic compounds with low-valent silicon atoms. In our part, we have used this moiety in benzamidinate Si(II) system and were able to isolate several silicon compounds, including several unsymmetrical disilenes, [15][16][17][18] which were not accessible from the typical benzamidinate Si(II) system with a π-donor substituent. By looking at the increasing interest in the hypersilyl group as a substituent, we realize that it is the time to review the recent developments on the low-valent group 14 chemistry using hypersilyl moiety.…”