Crystal Structure and Spectroscopic and Magnetic Properties of the Manganese(II) and Copper(II) Azido-Tetramethylammonium Systems.

The compounds [N(CH(3))(4)][Cu(N(3))(3)] (1) and [N(CH(3))(4)][Mn(N(3))(3)] (2) have been synthesized and characterized. Compound 1 crystallizes in the monoclinic P2(1)/n space group, with Z = 4, a = 7.473(2) Å, b = 15.780(2) Å, c = 9.321(2) Å, and beta = 92.59(2) degrees. Compound 2 crystallizes in the monoclinic P2(1) space group, with Z = 2, a = 6.264(3) Å, b = 13.150(6) Å, c = 6.375(3) Å, and beta = 90.00(6) degrees. At high temperature, compound 2 undergoes a structural phase transition toward a pseudocubic phase with a = 6.446(4) Å. The nature of the metallic ion remarkably influences the molecular structure of both compounds. Thus, while compound 1 is one-dimensional, with the copper(II) ions bridged by one end-on (EO) and two end-to-end (EE) azido ligands, the structural arrangement in compound 2 is three-dimensional, the manganese(II) ions being bridged by EE azido ligands. In both cases, tetramethylammonium cations stabilize the negative charge of the [M(N(3))(3)](-) fragments. Magnetic susceptibility measurements show antiferromagnetic couplings for compounds 1 and 2. The obtained exchange parameters are J/k = -3.6 K, g = 2.10 and J/k = -2.5 K, g = 2.01 for compounds 1 and 2, respectively.