in dichloromethane; acetone under N2 or Ar, addn. of diene to Ir-complex in CH2Cl2, then addn. of AgBF4 in acetone, soln. is stirred for 20 min; filtn. through Celite, addn. of THF to the filtrate, concn., filtn. of deep red crystals, washed with THF, air-dried;