A Novel Reaction of an Overcrowded Germylene with Isothiocyanate Leading to the Formation of 4-Imino-1,3,2-dithiagermetane Ring System

Abstract

A diarylgermylene [Tbt(Tip)Ge:] kinetically stabilized by 2,4,6-tris-[bis(trimethylsilyl)methyl]phenyl (Tbt) and 2,4,6-triisopropylphenyl (Tip) groups was allowed to react with phenyl isothiocyanate to afford a germanium-containing four-membered heterocycle, 4-imino-1,3,2-dithiagermetane derivative via [2+2]cycloaddition reaction of initially formed diarylgermanethione [Tbt(Tip)Ge=S], the intermediacy of which was evidenced by electronic spetrnscopy.Germylenes, i. e. divalent germanium species, are among a most fascinating class of reactive organogermanium compounds, and their high reactivity toward unsaturated bonds enables us to synthesize a variety of germanium-containing novel cyclic system^.^For example, Ando et al. reported the synthesis of the first 3-alkylidene-l,2-thiagermirane derivative by [1+2] cycloaddition reaction of dimesitylgermylene generated by thermolysis of hexamesitylcyclotrigermane with di-r-b~t~lthioketene.3 Although they also described the reactions of less hindered germylenes such as dimethyl-and diphenylgermylenes with di-tbutylthioketene leading to the formation of the corresponding 4-alkylidene-l,2,3-thiadigermetane derivatives,3 there has been no description for cycloaddition of germylenes with other heterocumulenes.Meanwhile, we have already developed new and effective methods for the generation of an extremely hindered diarylgermylene, Tbt(Tip)Ge: (1),4 bearing 2,4,6-tris[bis(trimethylsilyl)methyl]pheny (Tbt) and 2,4,6-triisopropylphenyl (Tip) groups on the germanium atom, and quite recently we reported the reaction of germylene (1) with carbon disulfide which resulted in the first isolation of a novel germaketenedithioacetal derivative (2).5 Here, we present the reaction of the overcrowded germylene (1) with another cycle of full-matrix least-squares refinement was based on 7339 obsewed reflections [I > 3.000(0]and 532 variable parameters.Atomic coordinates, thermal parameters, and the complete tables of bond lengths and angles of 5 have been deposited at