Stereoselectivity in the complexing of platinum(II) chloride with substituted cyclopropanes

Abstract

A series of mono-substituted cyclopropanes have been shown to displace ethylene from [(C₂H₄)PtCl₂]₂ with formation of substituted (propane- 1,3-diyl)PtCl₂ derivatives, displacement being impeded or inhibited by electron withdrawing substituents. From the ¹H n.m.r. spectra of the bis-pyridine derivatives (RC₃H₅)PtCl₂(py)₂ it is shown that insertion occurs preferentially into the less substituted cyclopropane bond when R = n-C₆H₁₃, PhCH₂, o-NO₂C₆H₄, or Ph, but for R =p-MeC₆H₄ the principal product arises from insertion into the more substituted bond in the cyclopropane. trans-1,2-Diphenyl- and trans-1-methyl-2-n-butyl-cyclopropane undergo insertion of PtCl₂ into the less substituted cyclopropane bond, but cis-1-methyl-2-n-butylcyclopropane and bicyclo[4,1,0]heptane are preferentially isomerised to olefins. 1,2-Dicyclopropylethane yields a bis-PtCl₂ derivative.