title: Spin-state diversity in a series of Co(ii) PNP pincer bromide complexes.
abstract: We describe the structural and electronic impacts of modifying the bridging atom in a family of Co(ii) pincer complexes with the formula Co(t-Bu)2PEPyEP(t-Bu)2Br2(Py = pyridine, E = CH2, NH, and O for compounds 1-3, respectively). Structural characterization by single crystal X-ray diffraction indicates that compounds 1 and 3 are 5-coordinate complexes with both bromides bound to the Co(ii) ion, while compound 2 is square planar with one bromide in the outer coordination sphere. The reduction potentials of 1-3, characterized by cyclic voltammetry, are consistent with the increasing electron-withdrawing character of the pincer ligand as the linker (E) between the pyridine and phosphine arms becomes more electronegative. Magnetic property studies of compounds 1 and 2 confirm high- and low-spin behavior, respectively, through a broad temperature range. However, complex 3 features an unusual combination of high spin S = 3/2 Co(ii) and temperature dependent spin-crossover between S = 3/2 and S = 1/2 states. The different magnetic behaviors observed among the three CoBr2pincer complexes reflects the importance of small ligand perturbations on overall coordination geometry and resulting spin state properties.
authors: Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA. j.yang@uci.edu.
authors: David W
authors: DW
authors: Shaffer
authors: Indrani
authors: I
authors: Bhowmick
authors: Arnold L
authors: AL
authors: Rheingold
authors: Charlene
authors: C
authors: Tsay
authors: Brooke N
authors: BN
authors: Livesay
authors: Matthew P
authors: MP
authors: Shores
authors: Jenny Y
authors: JY
authors: Yang