| Autor: |
Zolnhofer EM; Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander University Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany., Wijeratne GB; Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States., Jackson TA; Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States., Fortier S; Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, Indiana 47405, United States., Heinemann FW; Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander University Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany., Meyer K; Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander University Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany., Krzystek J; National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States., Ozarowski A; National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States., Mindiola DJ; Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States., Telser J; Department of Biological, Physical and Health Sciences, Roosevelt University, Chicago, Illinois 60605, United States. |
| Abstrakt: |
Stable coordination complexes of Ti II (3d 2 ) are relatively uncommon, but are of interest as synthons for low oxidation state titanium complexes for application as potential catalysts and reagents for organic synthesis. Specifically, high-spin Ti II ions supported by redox-inactive ligands are still quite rare due to the reducing power of this soft ion. Among such Ti II complexes is trans -[TiCl 2 (tmeda) 2 ], where tmeda = N , N , N ', N '-tetramethylethane-1,2-diamine. This complex was first reported by Gambarotta and co-workers almost 30 years ago, but it was not spectroscopically characterized and theoretical investigation by quantum chemical theory (QCT) was not feasible at that time. As part of our interest in low oxidation state early transition metal complexes, we have revisited this complex and report a modified synthesis and a low temperature (100 K) crystal structure that differs slightly from that originally reported at ambient temperature. We have used magnetometry, high-frequency and -field EPR (HFEPR), and variable-temperature variable-field magnetic circular dichroism (VTVH-MCD) spectroscopies to characterize trans -[TiCl 2 (tmeda) 2 ]. These techniques yield the following S = 1 spin Hamiltonian parameters for the complex: D = -5.23(1) cm -1 , E = -0.88(1) cm -1 , ( E / D = 0.17), g = [1.86(1), 1.94(2), 1.77(1)]. This information, in combination with electronic transitions from MCD, was used as input for both classical ligand-field theory (LFT) and detailed QCT studies, the latter including both density functional theory (DFT) and ab initio methods. These computational methods are seldom applied to paramagnetic early transition metal complexes, particularly those with S > 1/2. Our studies provide a complete picture of the electronic structure of this complex that can be put into context with the few other high-spin and mononuclear Ti II species characterized to date. |
