Cleavage of carbon-nitrogen bond in 1,3,5-tri-tert-butyl-1,3,5-triazacyclohexane by copper(I) bromide

Reactions of CuCl, CuCl2 and CuBr2 with 1,3,5-tri-tert-butyl-1,3,5-triazacyclohexane ((t)Bu(3)tach) resulted in the formation of (((t)Bu(3)tach-H)(+)(CuCl2)] (1), K(t)Bu(3)tach)(CuCl2)] (2) and [((t)Bu(3)tach-H)(+)(CuBr2)] (3) respectively. Interestingly, CuBr was found to mediate the cleavage of the C-N bonds of (t)Bu(3)tach in a vast range of solvents, namely, chloroform, dichloromethane, tetrahydrofuran, acetonitrile and methanol to yield [Cu4Br4((BuNCH2)-Bu-t)(4)] (4) and stands as an example of C-N bond cleavage of 1,3,5-triazacyclohexane rings by copper salts. Compounds 1 and 3 contains amidinium cations and are unstable in solution towards the release of copper. The release of copper from 3 in solution was confirmed by the isolation of the compound, [CuBr(MeCN)] (5). Formation of the amidinium cations [((t)Bu(3)tach-H)(+)] in 1 and 3 may be avoided by the use of PPh3 to yield [((t)Bu(3)tach)Cu(PPh3)1(PF6) (6), while the coordinated N-tert-butyl-methanimine ((BuNCH2)-Bu-t) in 4 could be replaced by PPh3 to yield [Cu4Br4(PPh3)(4)] (7). Complexes 1-7 are characterized by a combination of single crystal X-ray structure determination and/or elemental analysis, NMR, IR, and UV-Vis spectroscopy, and Mass spectrometry. (C) 2016 Elsevier B.V. All rights reserved.