in tetrahydrofuran under N2, mixt. of phosphorane and Pt complex in THF was stirred for 12h, pptn.; volatiles removed in vac., residue washed (10 times hexane, 10 times THF (to dissolve the η2-complex), residue (cis complex) and washing (η2.-complex) pumped dry separately, each heated to 90°C under vac., elem. anal.;