Synthesis and characterization of 2-mono- and 1,2-diaminocarba-closo-dodecaborates M[1-R-2-H2N-closo-CB11H10] (R=H, Ph, H2N, CyHN).
The first primary 2-aminocarba-closo-dodecaborates [1-R-2-H(2)N-closo-CB(11)H(10)](-) (R=H (1), Ph (2)) have been synthesized by insertion reactions of (Me(3)Si)(2)NBCl(2) into the trianions [7-R-7-nido-CB(10)H(10)](3-). The difunctionalized species [1,2-(H(2)N)(2)-closo-CB(11)H(10)] (3) and 1-CyHN-2-H(3)N-closo-CB(11)H(10) (H-4) have been prepared analogously from (Me(3)Si)(2)NBCl(2) and 7-H(3)N-7-nido-CB(10)H(12). In addition, the preparation of [Et(4)N][1-H(2)N-2-Ph-closo-CB(11)H(10)] ([Et(4)N]-5) starting from PhBCl(2) and 7-H(3)N-7-nido-CB(10)H(12) is described. Methylation of the [1-Ph-2-H(2)N-closo-CB(11)H(10)](-) ion (2) to produce 1-Ph-2-Me(3)N-closo-CB(11)H(10) (6) is reported. The crystal structures of [Et(4)N]-2, [Et(4)N]-5, and 6 were determined and the geometric parameters were compared to theoretical values derived from DFT and ab initio calculations. All new compounds were studied by NMR, IR, and Raman spectroscopy, MALDI mass spectrometry, and elemental analysis. The discussion of the experimental NMR chemical shifts and of selected vibrational band positions is supported by theoretical data. The thermal properties were investigated by differential scanning calorimetry (DSC). The pK(a) values of 2-H(3)N-closo-CB(11)H(11) (H-1), 1-H(3)N-closo-CB(11)H(10) (H-7), and 1,2-(H(3)N)(2)-closo-CB(11)H(10) (H(2)-3) were determined by potentiometric titration and by NMR studies. The experimental results are compared to theoretical data (DFT and ab initio). The basicities of the aminocarba-closo-dodecaborates agree well with the spectroscopic and structural properties.
Finze
Maik
M
Institut für Anorganische Chemie und Strukturchemie II, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany. maik.finze@uni-duesseldorf.de