Reactivity of a Silylsilylene Bearing a Functionalized Diaminochlorosilyl Substituent

The reactivity of the silylsilylene [{PhC(N t Bu) 2 }SiSi(Cl){(N t Bu) 2 C(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 PhNNPh 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 1.6 equivalents of 2,6‐diisopropylphenylazide in toluene afforded the silaimine [LSi(NAr)N(Ar)L′] ( 5 , L=PhC(N t Bu) 2 , L′=Si(Cl){(N t Bu) 2 C(H)Ph}, Ar=2,6‐ i Pr 2 C 6 H 3 ). The formation of 5 can be explained by an oxidative addition of the divalent Si center in 2 with ArN 3 to afford a silaimine intermediate, which then reacts with another molecule of ArN 3 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(N t Bu) 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{(N t Bu) 2 C(H)Ph}” and “ClSi{(N t Bu) 2 C(H)Ph}” to form 6 and 8 , respectively. Moreover, compound 8 was synthesized by the reaction of [{PhC(N t Bu) 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.