Sentence:  The reactions of "trans"-[Pt(Mef)Br(PPh<sub>3</sub>)<sub>2</sub>] with AgBF<sub>4</sub> and Ph<sub>3</sub>ECHC(O)R (E = P, R = Me, OMe, Ph; E = As, R = Me) afford only "trans"-[Pt(Mef){OC(=CHEPh<sub>3</sub>)R}(PPh<sub>3</sub>)<sub>2</sub>] because the "C"-alkyl/"C"-ylide <WSD>transphobia</WSD> is greater than the "C"-alkyl/"O"-ylide <WSD>transphobia</WSD> and also because of the lower steric requirement of the "O"-ylide ligand. 
Meaning of the word marked with <WSD> tags:  The preference of pairs of high-trans effect soft ligands to avoid being mutually trans by becoming cis and having other low-trans effect hard ligands trans to themselves.