Syntheses, structure and spectroscopic characterization of fac- and mer-Co(aepn)(CN)(3) and of their (CN)-C-13 analogues [aepn = N-(2-aminoethyl)-1,3-propanediamine]

Both facial (1) and meridional. (3) isomers of Co(aepn)(CN)(3) [aepn = N-(2 -aminoethyl)-1,3-propanediamine] and their (CN)-C-13 analogues (facial 2 an d meridional. 4) have been prepared by two different synthetic approaches. I crystallizes in a monoclinic space group, P2(1/c), and has one long and t wo short C equivalent toN bonds. Meanwhile 3 crystallizes with a water of c rystallization in the same space group (P2(1/n)) and has one short and two long C equivalent toN bonds. The C-13 NMR spectrum of 4 shows three well-re solved resonances (delta = 143.53, 142.14, 132.85) for the three mer cyanid e carbon atoms. In contrast, 3 has a single broad resonance in the range of delta = 120-140, suggesting the presence of a dynamic process that is thou ght to be a trigonal twist of the three fac cyanide groups. According to th e analyses of IR and Raman spectra, the Co(CN), moiety of both isomers appe ars to have approximate C, molecular symmetry resulting in three IR- and Ra man-active v(C equivalent toN) modes. Individual assignments of the vibrati onal peaks in the v(C equivalent toN) region have been confirmed by Raman b and polarization measurements and (CN)-C-13 isotope shifts. The stretching and bending modes of the metal-cyano, groups in the low-frequency region ( < 600 cm(-1)) have also been analyzed. (C) 2001 Elsevier Science Ltd. All r ights reserved.