Abstract The reaction of [(COD) PtCl 2] with biphen (QPiPr)(Q′ PiPr)(Q, Q′= O, CH 2 O) yields cis-[{biphen (QPiPr)(Q′ PiPr)} PtCl 2]. Treatment of trans-[PtCl 2 (ethene)(py)] with biphen (QPiPr)(Q′ PiPr)(Q, Q′= O, CH 2 O) gives trans-[{biphen (QPiPr)(Q′ PiPr)} PtCl 2] for Q or Q′≠ O. No trans/cis isomerization can be observed for these compounds after 24 h at 105 C in [D 8] toluene. In the case of Q= Q′= O a trans/cis isomerization takes place at ...