The reactions of boron trifluoride with the organostannylene RSnCl {R = 4-tBu-2,6-[P(O)(OiPr)(2)](2)C6H2} and the organosilane RSiMe3 provided the corresponding 1:1 and 1:2 complexes, respectively, through the formation of P=OB interactions. In the former reaction, even with excess BF3OEt2, no SnB complexation involving the lone electron pair at the tin(II) center was observed. The experimental results are supported by DFT calculations.