What is the most reasonable explanation for why a mixture of trans-4 and cis-4 is observed? cis-4 and trans-4 interconvert through dissociation and subsequent reassociation of PMe3 Step III. is actually in equilibrium; reconversion of 4 to 2 enables formation of both isomers. 2 is fluxional and rapidly interconverts between two complexes, one having H and CH3 cis and the other having H and CH3 trans. Both convert to 4. 2 undergoes Berry pseudo-rotation to give two isomers, one having phosphines cis and one having phosphines trans. Both of these isomers have H and CH3 in the cis position. 2 undergoes a second reaction (not shown above) that involves loss of CH3CI