Synthesis and Reactivity of Aluminum Disilacyclopropenes. Cyclic AlSi 2 Delocalized 2π Systems.

The synthesis, structures, and reactivity of the first unsaturated AlSi 2 three-membered ring systems were described. Reactions of dilithiodisilene [(NHB)LiSi═SiLi(NHB)] ( 1 , NHB = diazaborolyl) with aluminum halides AlCl 3 , Ar(SiMe 3 )NAlCl 2 (Ar = 2,6- i Pr 2 C 6 H 3 ), Cp*AlBr 2 (Cp* = C 5 Me 5 ), and TipAlBr 2 ·Et 2 O (Tip = 2,4,6- i Pr 3 C 6 H 2 ) led to the formation of AlSi 2 three-membered ring species, solvated (NHBSi) 2 AlCl(OEt 2 ) ( 2 ) and solvent-free (NHBSi) 2 AlN(SiMe 3 ) Ar ( 3 ), (NHBSi) 2 AlCp* ( 4 ), and (NHBSi) 2 AlTip ( 5 ), in good yields. X-ray diffraction studies and DFT calculations disclosed delocalized AlSi 2 2π electron systems. Methanolysis of 4a resulted in cleavage of the Al-Si σ and Si-Si π bonds, giving trihydrodisilane (NHB)H(MeO)SiSiH 2 (NHB) ( 6 ). Reaction of 4b with 4 equiv of N 2 O and H 2 C═CH 2 resulted in the insertion of four oxygen atoms and four H 2 C═CH 2 π bonds into all of the Al-Si and Si-Si bonds, yielding the O- and CH 2 CH 2 -bridged polycyclic species 7 and 8 , demonstrating the synergistic reactivity of the Al-Si and Si-Si bonds in the AlSi 2 ring system.