Dialkylcyanamides are more reactive substrates toward metal-mediated nucleophilic addition than alkylcyanides

Abstract

The dialkylcyanamide complexes Q[PtCl₃(NCNR₂)] (Q = Ph₃PCH₂Ph, R₂ = Me₂1, Et₂2, C₅H₁₀3, C₄H₈O 4; Q = NMe₄, R₂ = Me₂5; Q = NEt₄, R₂ = Me₂6) were synthesized either by dissolving Q₂[Pt₂(μ-Cl)₂Cl₄] in neat NCNR₂ (1–4) or by substitution of a NCNR₂ ligand with Cl⁻ in [PtCl₂(NCNR₂)₂] by its treatment with QCl (5, 6). Nucleophilic addition of dibenzylhydroxylamine, HON(CH₂Ph)₂, to 1–6 results in the formation of the complexes Q[PtCl₃{NHC(NR₂)ON(CH₂Ph)₂}] (Q = Ph₃PCH₂Ph, R₂ = Me₂, 7; Et₂, 8; C₅H₁₀, 9; C₄H₈O, 10; Q = Me₄N, R₂ = Me₂11; Q = Et₄N, R₂ = Me₂, 12) that further convert at room temperature in the solid state (1–24 h) or in a solution (0.5–2 h) to the imine complexes Q[PtCl₃{N(CH₂Ph)C(H)Ph}] (Q = Ph₃PCH₂Ph, 13; Me₄N, 14; Et₄N, 15) and the corresponding dialkylureas H₂NC(O)NR₂. The competitive reactivity study of the nucleophilic addition of HON(CH₂Ph)₂ to (Ph₃PCH₂Ph)[PtCl₃(NCR′)] (R′ = Ph, NR₂, CH₂Ph) indicated that the reactivity of the coordinated NCNR₂ is comparable to NCPh, while NCCH₂Ph appeared to be much less reactive than the former two ligands. Compounds 1–6 and 13 were fully characterized by elemental analyses (C, H, N), high resolution ESI-MS, IR, and ¹H and ¹³C{¹H} NMR spectroscopy. The structure of 1 was additionally verified by a single-crystal X-ray diffraction.