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40812-B3
Solid-State and Solution Behavior of Lanthanide Scorpionates and Porphyrinoids

Gregory M. Ferrence, Illinois State University

Our lab has been examining the reaction chemistry displayed by the divalent lanthanide complex [(Tp^tBu,Me)Yb(mu-2-H)]₂ where Tp^tBu,Me equals tris(3-tert-butyl-5-methylpyrazolyl)borate. This Tp^tBu,Me scorpionate ligand is particularly well suited for stabilizing low coordinate divalent lanthanide complexes and has shown rich chemical reactivity. The specific sterics provided by the 3-tert-butyl-5-methylpyrazolyl substituents appears to be optimal for preparation of a discrete divalent lanthanide hydride. This spring we reported the synthesis of the related 3-tert-butyl-5-methyl(1,2,4-triazole) as well as the preparation and characterization of several tris(3-tert-butyl-5-methyl(1,2,4-triazolyl)borate, Ttz^tBu,Me, metal complexes. There are few reported tristriazolylborate metal complexes and most utilize less sterically demanding triazoles. Often the complexes isolated are polymeric and difficult to characterize. Results so far show the Ttz^tBu,Me ligand to display chemistry very similar to that of Tp^tBu,Me, including an absence of polymer formation. During the next year we intend to examine the feasibility of preparation of [(Ttz^tBu,Me)Yb(mu-2-H)]₂.

During 2007, one PRF funded undergraduate researcher began examining the coordination chemistry of 3-tert-butyl-5-methyl(1,2,4-triazole), Htz^tBu,Me, and comparing it to the related 3-tert-butyl-5-methylpyrazole, Hpz^tBu,Me. Reaction of [Cp*RuCl]₄ with Hpz^tBu,Me leads to clean formation of (eta⁵-Cp*)Ru(eta⁵-pz^tBu,Me), whereas substitution with Htz^tBu,Me forms a complex mixture. Reaction of two equivalents of Hpz^tBu,Me with PdCl₂ cleanly forms (Hpz^tBu,Me)PdCl₂, which afforded X-ray quality crystals upon crystallization from chloroform-hexanes. In contrast, reaction of two equivalents of Htz^tBu,Me with PdCl₂ affords only an insoluble off-white solid. It appears that tz^tBu,Me will have limited utility as a simple ligand; however, as a tristriazolylborate ligand, it may be quite useful.

Over the past year, one undergraduate researcher has continued preparing benziporphyrins to use as supporting ligands for lanthanide complexes. The benziporphyrins, H₂BZP, are readily deprotonated to form dianionic ligands, making isolation of (BZP)LnL complexes likely. We appear to be making progress towards isolation and characterization of tetraphenylbenziporphyrin supported lanthanide complexes; however, further characterization is necessary to make any formal claims. The PI continues to collaborate with colleague T.D. Lash, an expert in the organic synthesis of novel porphyrinoids, and routinely handles the crystallographic analysis of Lash's porphyrinoids. For example, we recently reported a new class of porphyrinoid metal complexes including the structure of a palladium(II) complex of [22]porphyrin-(3.1.1.3). We also reported the structure of (2³-tert-butyl-5,10,15,20-tetraphenylazuliporphyrinato)palladium(II) dichloromethane solvate.

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