Reactivity of a silylsilylene bearing a functionalized diaminochlorosilyl substituent

The reactivity of the silylsilylene [{PhC(NtBu)₂}SiSi(Cl){(NtBu) ₂C(H)Ph}] (2) towards diphenylacetylene, azobenzene, 2,6-diisopropylphenyl azide, sulfur, and selenium is described. The reaction of 2 with one equivalent of azobenzene in toluene afforded compound 3, which is the first example of a 1,2-diaza-3,4-disilacyclobutane containing a pentacoordinate silicon center. The formation of 3 can be explained by a [1+2] cycloaddition of the divalent Si center in 2 with PhN=NPh to form a diazasilacyclopropane intermediate, which then undergoes a 1,2-chlorine shift to release the ring strain to form 3. Similarly, the reaction of 2 with one equivalent of diphenylacetylene in toluene afforded the 1,2-disilacyclobutene 4, which contains a pentacoordinate silicon center. The reaction of 2 with 1.6equivalents of 2,6-diisopropylphenylazide in toluene afforded the silaimine [LSi(=NAr)N(Ar)L′] (5, L=PhC(NtBu)₂, L′=Si(Cl){(NtBu) ₂C(H)Ph}, Ar=2,6-iPr₂C₆H₃). The formation of 5 can be explained by an oxidative addition of the divalent Si center in 2 with ArN₃ to afford a silaimine intermediate, which then reacts with another molecule of ArN₃ to give compound 5. The reaction of 2 with elemental sulfur in toluene afforded the chlorosilanethione [LSi(S)Cl] (6) and dithiodisiletane [{Ph(H)C(NtBu)₂}Si(μ-S)] ₂ (7). Treatment of 2 with elemental selenium in THF afforded the di(silaneselone) [LSi(Se)Si(Se)L] (8). Evidently, the divalent Si center in 2 undergoes oxidative addition with chalcogens to afford a silylsilanechalcogenone intermediate, which then displaces ":Si{(NtBu)₂C(H)Ph}" and "ClSi{(NtBu)₂C(H)Ph}" to form 6 and 8, respectively. Moreover, compound 8 was synthesized by the reaction of [{PhC(NtBu) ₂}Si:]₂ (10) with elemental selenium in THF. The results show that the reactions of 2 are initiated by oxidative addition of the divalent silicon center, and then the intermediate formed undergoes a rearrangement involving the diaminochlorosilyl substituent to form compounds 3-8. These products have been characterized by NMR spectroscopy and X-ray crystallography. Stable silylenes: The reactivity of the silylsilylene 1 towards diphenylacetylene, azobenzene, 2,6-diisopropylphenyl azide, sulfur, and selenium is reported. The results show that the reactions of 1 are initiated by oxidative addition of the divalent silicon center, and then the intermediate formed undergoes a rearrangement that involves the diaminochlorosilyl substituent (see scheme). The diaminochlorosilyl substituent in 1 can undergo a 1,2-chlorine shift, and it also serves as a leaving group in the reactions.