Houng-Min Shih

Halomethylmetal compounds : XLIX. The insertion of phenyl(bromodichloromethyl)mercury-derived dichlrocarbene into carbonhydrogen bonds: tetraalkylgermanes. Thermolysis of 3-dichloromethyl-1-metallacycloalkanes

Phenyl(bromodichloromethyl)mercury-derived dichlorocarbene was found to insert into βCH bonds of a number of tetraalkylgermanes: into the n-propyl group of Et3GeCH2CH2CH3, the isobutyl group of Et3GeCH2CHMe2, the trimethylene bridges of Et3Ge(CH2)3GeEt3 and 1,1,2,2-tetraethyl-1,2-digermacyclopentane, the tetramethylene bridge of 1,1,2,2-tetraethyl-1,2-digermacyclohexane and the pentamethylene bridge of 1,1-diethyl-1-germacyclohexane. Pyrolysis of these insertion products resulted in γ-elimanation of GeCl to give germyl-substituted chlorocyclopropanes, reactions which served well in confirming the structures of the insertion products. For instance, thermolysis of 1,1-diethyl-3-dichloromethyl-1-germacyclohexane gave 1-chloro-2-(γ-diethylchlorogermylpropyl)cyclopropane. The various insertion products were reduced to the chlorine-free methyl derivatives, e.g., Et3GeCH2C(CCl2H)Me2 to Et3GeCH2CMe3. A competition between Et3GeCH2CHMe2 and Et3SiCH2SiCH2CHMe2 for a deficiency of PhHgCCl2Br showed the germane to be 1.35 times more reactive toward this CCl2 source than the silane. The pyrolysis of 1,1-dimethyl-3-dichloromethyl-1-silacyclopentane and -cyclohexane, as well as of 1,1-dimethyl-3-dichloromethyl-1-stannacyclohexane was also studied.

Crystal structure of methyl 5-bromo-2-oxo-Δ2-1,3,4-oxadiazolin-3-carboxylate

An X-ray crystal structure determination of the title compound has confirmed the cyclic structure and has demonstrated a strong charge-transfer interaction between the carbonyl oxygen and the bromine atoms of adjacent molecules; the medium-dependent i.r. spectra of this molecule are discussed in the light of this finding.