Spin state control on four-coordinate cobalt(II)

The spin state of transition metal complexes can control the kinetics of reactivity for first row ions and has generated interest recently due to their potential magnetic device applications. Because it is difficult to predict and alter the spin state for first row transition metal complexes systematically, we set out to synthesize a cobalt(ll) model system where low-spin, high-spin, and spincrossover complexes are readily accessible through exchange of a single monodentate ligand. The tripodal ligand [PhBP_3] ([PhBP_3]=[PhB(CH_2PPh_2)_3]-) allows for simple pseudo-tetrahedral complexes to be prepared from [PhBP_3]CoX (X=I, Cl) via metathesis of aryl oxides, arylthiol oxides, or siloxides. These complexes have been characterized both as solids and in solution by utilizing NMR, EPR, SQUID and X-ray diffraction. The magnetic and structural properties of these complexes will be discussed