The rate of transmetalation reaction of unsymmetrical organotrimethyltin or organotributyltin (R1SnR3) followed the order of R1
PhC≡C > PrC≡C > PhCH=CH, CH2=CH > Ph > PhCH2 > CH3OCH2 > CH3 >
Bu, Et > i-Pr.30 This trend makes sense since these groups have to be able to stabilize the developing negative charge in the transition state.