in dichloromethane N2 atmosphere, addn. of soln. of stannyl compound to soln. of borane at -75 to -65°C (>/= 60 min) with stirring, slow warming to room temp., stirring (room temp., 12 h); NMR-monitoring, not isolated;

in dichloromethane N2 atmosphere, addn. of soln. of stannyl compound to soln. of borane at -75 to -65°C (60 min) with stirring, slow warming to room temp., stirring (room temp., 16-17 h); removement of volatiles (25-40°C, 12 Torr to 1E-5 Torr), NMR-monitoring, not isolated;