One step formation of amino derivatives of the closo-decaborate anion with exo-polyhedral benzimidazole groups during cadmium(ii) complexation

Abstract

The possibility of the formation of amino-substituted derivatives [B₁₀H₉N(MBzim)CH₂MBzim]²⁻ (MBzim is 1-methylbenzimidazole) and [B₁₀H₉N⁺H(MBzim)CH₂Bzid⁻]²⁻ (Bzid is benzimidazolide) during the cadmium(II) complexation with N,1-bis(1-methylbenzimidazol-2-yl)methanimine (L¹) and N-(benzimidazol-2-yl)-1-(1-methylbenzimidazol-2-yl)methanimine (L²) with a –CHN– linker group in the presence of a closo-decaborate anion has been demonstrated for the first time. The substitution likely results from the metal-promoted formation of the carbocation [Cd(MBzim)HC⁺–N⁻R]²⁺ (R = MBzim or Bzim), which acts as an electrophilic inducer in the EINS reaction with the [B₁₀H₁₀]²⁻ anion. As a result, binuclear complexes {Cd(CH₃CN)[B₁₀H₉N(MBzim)CH₂MBzim]}₂ and {Cd(DMF)[B₁₀H₉N⁺H(MBzim)CH₂Bzid⁻]}₂ have been obtained and characterized. A method for obtaining soluble salts Cat₂[B₁₀H₉N(MBzim)CH₂MBzim] and Cat₂[B₁₀H₉N⁺H(MBzim)CH₂Bzid⁻] (Cat = Na⁺, Bu₄N⁺) has been proposed. The heteroleptic complex {CdL²(DMF)[B₁₀H₁₀-κ³B1,B2,B3]}, in which the benzimidazole derivative acts only as a ligand, has been obtained and characterized as a result of complexation with 1-isopropyl-N-((1-methyl-1H-benzo[d]imidazol-2-yl)methyl)-1H-benzo[d]imidazol-2-amine (L³) with a –CH₂–NH– linker group. X-ray diffraction analysis revealed the structural features of the synthesized compounds, namely the coordination of bis(benzimidazoles) resulting in the formation of a seven-membered chelate ring, and the facial coordination of the closo-decaborate anion, which is rare for cadmium(II).