SYNTHESIS AND CHARACTERIZATION OF BIS(2-PYRIDYLMETHYL)AMINE COMPLEXES OF MANGANESE(II), ZINC(II), AND CADMIUM(II)

Complexes of the general formulation [M(bispicam)2]X2 [where bispicam is bis(2-pyridylmethyl)amine, C12H13N3, and M is Mn(II), Zn(II), or Cd(II)] have been synthesized and characterized by X-ray crystallography and by EPR and C-13 NMR spectroscopy. All of the complexes are facial isomers, but three distinct structural types have been discovered. The manganese complex [Mn(bispicam)2](ClO4)2 (1) crystallizes in the space group C2/c of the monoclinic system with four molecules in a cell of dimensions a = 20.594 (4) angstrom, b = 11.01 1 (2) angstrom, c = 13.715 (3) angstrom, and beta = 114.845 (15)-degrees. The manganese atom in 1 sits on a crystallographic 2-fold axis. The cadmium complex [Cd-(bispicaM)2](ClO4)2 (2) is isomorphous with 1, with cell dimensions a = 20.670 (4) angstrom, b = 10.911 (3) angstrom, c = 13.953 (2) angstrom, and beta = 114.493 (13)-degrees. The zinc complex [Zn(bispicam)2](ClO4)2 (3) also crystallizes in the space group C2/c of the monoclinic system but with eight molecules in a cell of dimensions a = 23.715 (6) angstrom, b = 9.006 (2) angstrom, c = 26.052 (I 1) angstrom, and beta = 91.52 (3)-degrees. There are two crystallographically independent cations in the crystals of 3, in one of which the zinc atom sits on a crystallographic 2-fold axis as in 1 and 2 and in the other of which zinc sits on a crystallographic inversion center. The chloride salt of the zinc complex, [Zn(bispicam)2]Cl2.6H2O (4), crystallizes in the space group P2(1)/c of the monoclinic system with two molecules in a cell of dimensions a = 9.175 (2) angstrom, b = 10.088 (2) angstrom, c = 16.472 (3) angstrom, and beta = 94.540 (I 0)-degrees. The zinc atom in 4 sits on a crystallographic inversion center, so the isomer found here is similar to one of those in 3. The EPR spectrum of Mn doped in the crystals of 2 reveals the presence of the anticipated geometry at Mn, and this spectrum has been very successfully simulated by diagonalization of the energy matrix. The EPR spectrum of Mn doped in the crystals of 3 demonstrates that, at low concentrations, the manganese atoms evidently occupy only the sites of C2 symmetry, the resulting spectrum being very similar to that of Mn doped in 2; this spectrum has also been precisely simulated. The C-13 NMR spectra of the complexes demonstrate that NMR techniques will be of value in distinguishing between the various isomers in this and other diamagnetic zinc and cadmium series.