in diethyl ether; toluene Ar atmosphere, addn. of 2-butyne to complex in toluene (-30°C), stirring, addn. of PC-t-Bu in Et2O (during 10 min, 0°C), stirring (1 h); volatiles removal (1E-3 Torr, darkness), redissoln., (pentane/Et2O 1:1), filtn. (Celite), crystn. on cooling (78°C, 48 h), drying (1E-3 Torr); elem. anal.;