Dihydrobis(tetrazolyl)borate ligands BH2(RCN4)2- were synthesized as the potassium salts in 73-91% yields with hydrogen, methyl, dimethylamino, or diisopropylamino substituents on the ring core carbon atom by heating a solid mixture of KBH4 with two equivalents of the appropriate tetrazole at 100-120 �C. Treatment of the potassium salts with equimolar quantities of 18-crown-6 afforded the corresponding crown ether adducts as colorless crystalline solids in good yields. Formation of the new complexes was confirmed by spectroscopic and analytical methods, and also by X-ray crystallography. The methyl and dimethylamino substituted tetrazolate salts exhibit similar polymeric crystal structures with a network of O-H���N hydrogen bonds, except that the boron is bridged through the 1-nitrogen atoms of the two tetrazolate rings in K[BH2(MeCN4)2], and through the 2-nitrogen atoms in K[BH2(Me2NCN4)2]. K[BH2(MeCN4)2](18-crown-6) contains one 3,4-?2-dihydrobis(tetrazolyl)borate ligand and one ?6-18-crown-6 ligand, whereas K[BH2(iPr2NCN4)2](18-crown-6) exhibits an isomeric structure with one chelating 3,3'-?2-dihydrobis(tetrazolyl)borate ligand and one ?6-18-crown-6 ligand. The crystal structure of K[BH2(iPr2NCN4)2](18-crown-6) shows the first example of a chelating ?3-dihydrobis(tetrazolyl)borate ligand, which is analogous to the chelating stuctures observed for bis(pyrazolyl)borate ligands. The energetic materials properties of the new complexes will be discussed.

Synthesis of dihydrobis(tetrazolyl)borate ligands and their coordination to the [K(18-Crown-6)]<sup>+</sup> fragment: Unexpected isomeric structures

239th National Meeting (2010)

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Synthesis of dihydrobis(tetrazolyl)borate ligands and their coordination to the [K(18-Crown-6)]+ fragment: Unexpected isomeric structures

Synthesis of dihydrobis(tetrazolyl)borate ligands and their coordination to the [K(18-Crown-6)]⁺ fragment: Unexpected isomeric structures