Molecular and electronic structure of nitridocyanometalates of chromium(V)and manganese(V): A combined experimental and DFT study

The six-coordinate complexes [M(N)(CN)(5)](3-) (M = Cr, Mn) have been isola ted as salts of robust rhodium amine complexes. [Rh(en)(3)][Mn(N)(CN)(5)]. H2O (1) and [Rh(tn)(3)] [Cr(N)(CN)(5)]. 2H(2)O (2) have been characterized by single-crystal X-ray crystallography: 1 crystallizes in the hexagonal sp ace group P6(3) with a = b = 15.810(2) Angstrom, c = 13.844(3) Angstrom, V = 2996.8(8) Angstrom(3), and Z = 6; 2 crystallizes in the orthorhombic spac e group Pbcn with a = 9.723(1) Angstrom, b = 14.564(2) Angstrom, c = 31.498 (4) Angstrom, V = 4460.3(8) Angstrom(3), and Z = 8, In 1, all the anions ar e oriented with their Mn=N directions almost coparallel to the crystallogra phic S-fold axis. Polarized single-crystal UV-vis spectroscopy of 1 confirm s the validity of the Jorgensen-Ballhausen-Gray d-orbital splitting scheme with the lowest energy transition being d(xy) --> {d(yz),d(zx)}. Single-cry stal EPR spectroscopy of [Cr(N)(CN)(5)](3-) diluted into 1 shows the hyperf ine (Cr-53) and super-hyperfine (N-14) tensors to be quite anisotropic with different major axes, For the hyperfine interaction we observe A(parallel to) > A(perpendicular to), whereas, for the super-hyperfine interaction to the terminal nitrido ligand, the reverse ordering is found: A(perpendicular to) > A(parallel to). The complexes [M(N)(CN)(5)](3-), trans-[M(N)(CN)(4)( py)(2-), and [M(N)(CN)(4)](2-) (M = CI, Mn) were investigated by DFT method s. Good reproduction of the molecular structures, vibrational, and W-vis sp ectra was obtained. However, pronounced differences between local density a nd gradient corrected functionals were observed in the description of the w eak bonding to the ligands trans to the nitrido ligand. For the five-coordi nate TM(N)(CN)(4)](2-) complexes the LUMO is predicted to be a strongly adm ired d(z)(2)(M)-p(z)(M) hybrid.