in neat (no solvent) dropwise addn. of monomer (-78°C) within 30 min to cyclodimer (kept at 50°C); distn., spectroscopically pure product;

THF in tetrahydrofuran byproducts: CO; Irradiation (UV/VIS); Cr(CO)6 irradn. in THF; soln. warmed up to 50°C and -50°C BuBN(tBu)/THF soln. dropped into it; solvent and not converted Cr(CO)6 vac. evapd. at 40°C; dissolved in warm hexane; crystd. in cold; elem. anal.;

byproducts: Me3SiCl; heating at 530°C in vac., cooling to 0°C, stirring for 2 h; elem. anal.;

in toluene byproducts: C6H12; soln. of Ti-complex in cold toluene at -78°C, addn. of cold borane (with stirring), slowly warmed to room temp. (with stirring); evapn. (oily mixt.), decompn. on further purification (identification by NMR);