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

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