Neutral and cationic main group element cages of germanium(ii) with pyrazolyl ligands: solid state structures, DFT calculations and advanced solution NMR investigations

Abstract

Two equivalents of 3,5-bis(trifluoromethyl)pyrazole or 5-methyl-3-(trifluoromethyl)pyrazole react with [Ge{N(SiMe₃)₂}₂] to give dimeric homoleptic germanium(II) compounds [{Ge(3,5-RR′pz)₂}₂] (R = R′ = CF₃ (1); R = Me, R′ = CF₃ (2)), which provide cationic triply pz-bridged cages of the general formula [Ge(μ₂-3,5-RR′pz)₃Ge]⁺[OTf]⁻ (R = R′ = CF₃ (3); R = Me, R′ = CF₃ (4)) upon treatment with one equivalent of triflic acid (HOTf, HSO₃CF₃). The compounds were studied using the pulsed field gradient spin-echo (PGSE) NMR technique and ¹⁹F,¹H-HOESY NMR methods. Single crystal X-ray structure determinations of all compounds are reported. The results obtained are verified by density functional theory calculations.