Synthesis of Bis(Carboranyl)amides 1,1′-μ-(CH2NH(O)C(CH2)n-1,2-C2B10H11)2 (n=0, 1) and Attempt of Synthesis of Gadolinium Bis(Dicarbollide)

Bis(carboranyl)amides 1,1 '-mu-(CH2NH(O)C(CH2)(n)-1,2-C2B10H11)(2) (n = 0, 1) were prepared by the reactions of the corresponding carboranyl acyl chlorides with ethylenediamine. Crystal molecular structure of 1,1 '-mu-(CH2NH(O)C-1,2-C2B10H11)(2) was determined by single crystal X-ray diffraction. Treatment of bis(carboranyl)amides 1,1 '-mu-(CH2NH(O)C(CH2)(n)-1,2-C2B10H11)(2) with ammonium or cesium fluoride results in partial deboronation of the ortho-carborane cages to the nido-carborane ones with formation of [7,7 '(8 ')-mu-(CH2NH(O)C(CH2)(n)-7,8-C2B9H11)(2)](2-). The attempted reaction of [7,7 '(8 ')-mu-(CH2NH(O)CCH2-7,8-C2B9H11)(2)](2-) with GdCl3 in 1,2-dimethoxy- ethane did not give the expected metallacarborane. The stability of different conformations of Gd-containing metallacarboranes has been estimated by quantum-chemical calculations using [3,3-mu-DME-3,3 '-Gd(1,2-C2B9H11)(2)](-) as a model. It was found that in the most stable conformation the CH groups of the dicarbollide ligands are in anti,anti-orientation with respect to the DME ligand, while any rotation of the dicarbollide ligand reduces the stability of the system. This makes it possible to rationalize the design of carborane ligands for the synthesis of gadolinium metallacarboranes on their base.

Automated summary

Bis(carboranyl)amides were synthesized and characterized, with one of the compounds having its crystal molecular structure determined by X-ray diffraction. Partial deboronation of the compounds upon reaction with ammonium or cesium fluoride, as well as unsuccessful attempted synthesis of a gadolinium metallacarborane, were also investigated. The stability of different conformations of Gd-containing metallacarboranes was estimated using quantum-chemical calculations, providing insights for the design of carborane ligands for synthesis purposes.