Do Metal-Metal Multiply-Bonded "Ligands" Have a trans Influence? Structural and Magnetic Comparisons of Heterometallic Cr Cr center dot center dot center dot Co and Mo Mo center dot center dot center dot Co Interactions
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
Reported here are two new compounds containing either a Cr=CrCo [1, CrCrCo(dpa)4Cl2, dpa = 2,2-dipyridylamide] or a Mo=MoCo [2, MoMoCo(dpa)4Cl2] framework both having a multiply-bonded unit (Cr=Cr in 1, Mo=Mo in 2) in close proximity to the Co2+ ion and trans to a Co-Cl bond. Variable temperature magnetic susceptibility measurements reveal 1 to have a temperature-dependent spin equilibrium between a low-spin (S = 1/2) and high-spin (S = 3/2) state, whereas the Co2+ ion in 2 exists solely in its high-spin state. The crystal structures of 1 and 2 were determined. Variable temperature crystallographic data of 1 at 100 K and at room temperature reveal that the spin-transition affects not only the Co-ligand bond lengths but also the terminal Cr-ligand bond lengths. Whereas the CrCo distance becomes shorter by 0.13 in the low-spin form, the Co-Cl distance becomes longer by 0.2 . These observations, along with the crystal structure of 2, suggest that the multiply-bonded M=M group has a trans influence on the Co2+ ion. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
