Synthesis, molecular structure, and spectroscopic properties of tris[trans-diazidobis(2,2-dimethylpropane-1,3-diamine)chromium(III)]bis[tertaazido(2,2-dimethylpropane-1,3-diamine)chromium(III)] perchlorate

A new double complex, [trans-Cr(N3)2(Me2tn)2]3[Cr(N3)4(Me2tn)]2ClO4 (Me2tn = 2,2-dimethylpropane-1,3-diamine), was prepared, and its structure determined through single-crystal X-ray diffraction at 100 K. The complex crystallizes in the space group C2/c of the monoclinic system with a = 34.255 (7), b = 11.067 (2), c = 24.137 (5) Å, and β = 120.64 (3)o. The asymmetric unit contains one half of a centrosymmetric trans-anti-[Cr(N3)2(Me2tn)2]+ cation, one independent trans-syn-[Cr(N3)2(Me2tn)2]+ cation, one cis-[Cr(N3)4(Me2tn)]- anion, and one half of a perchlorate anion. In two independent complex cations, the CrIII ions are each coordinated by four N atoms of two chelating Me2tn and two N atoms of the azido group in a distorted octahedral geometry, whereas the CrIII ion in cis-[Cr(N3)4(Me2tn)]- has a distorted octahedral coordination with two N atoms of one Me2tn and four N atoms of the azido group. Interestingly, the six-membered rings in two trans-[Cr(N3)2(Me2tn)2]+ cations adopt anti and syn chair-chair conformations, independently. The CrN (Me2tn) bond lengths vary from 2.0556 (15) to 2.0992 (19) Å, whereas the CrN (azido) bond lengths range from 2.0205 (16) to 2.0428 (16) Å. The perchlorate anion is disordered over two sets of sites, and has a distorted tetrahedral geometry. The crystal lattice is stabilized through hydrogen bonding interactions between the nitrogen of N3− and the NH groups of the Me2tn ligand. The IR and electronic absorption spectral properties are also discussed herein.