Differently from typical iminoboranes, the iminoboryl complex trans-[(PCy3)(2)Pt(B equivalent to NSiMe3)(Br)] (2) displays remarkable stability against oligomerization. Its clean reactivity toward Lewis acids led to the synthesis of the neutral platinum borylene complex trans-[(PCy3)(2)Pt{BN(SiMe3)(AlCl3)}(Br)], through coordination of AlCl3 to the nitrogen atom of the iminoboryl ligand. Surprising stability of the Pt-B linkage in 2 is further manifested in its reaction with MeOH, yielding the alkoxy(amino)boryl species trans-[(PCy3)(2)Pt{B(OMe)(N(H)SiMe3)}(Br)].