in toluene under N2, addn. of I2 soln. to a soln. of W-compound, at -78°C, allowed to warm to -50°C, addn. of MeOH, stirring at room temp. 12 h; vac. evapn., chromy. on silica gel column, a black band (toluene/hexane, 9/1) and a yellow one (CH2Cl2), vac. evapn. of the second fraction , crystn. from toluene/hexane (1/5) at -78°C, elem. anal.;