The reaction behavior of trimethylsilyl phosphanimine, Me3SiNPPh3, toward the pseudohalogen species XCN (X = Cl, Br, and I), especially the intermediate formation of [Me3SiN(PPh3). XCN] adduct complexes, was investigated in solution. Only the ICN adduct was shown to be metastable in solution, with respect to further reaction into Ph3PNCN and Me3SiX, and can be intercepted. Raman and X-ray data of the ICN adduct revealed a very labile donor-acceptor complex with the iodine atom of the ICN moiety loosely bound to the nitrogen atom of Me3SiNPPh3. There are two distinct rather long N . . .I bonds with bond lengths of 2.634(1) and 2.739(14) Angstrom. The structure and bonding are discussed on the basis of natural bond orbital analysis and valence bond considerations.