Syntheses of Tantalum(V) Complexes Containing Tetramethylpyrrolyl, Pyrrolyl, and Indolyl Ligands

Abstract
The reaction of TaMe3Cl2 with the lithium salt of tetramethylpyrrole (Li−TMP) led to the formation of (η5-TMP)TaMe3Cl (1). Reactions of 1 with a series of anionic ligands have been carried out to form products of the formula (η5-TMP)TaMe3X, where X = SR, Me, pyrrolyl, or indolyl. Crystals of (η5-TMP)TaMe3(indolyl) (5), were isolated in space group P21/c with a = 8.957(2) Å, b = 28.540(6) Å, c = 14.695(3) Å, β = 99.40(3)°, V = 3706.1(14) Å3, and Z = 8. The structure confirmed the η5-bonding mode of the tetramethylpyrrolyl ligand and the η1-N-coordination mode of the indolyl ligand.The derivatives (η5-TMP)TaMe3X showed limited stability, and decomposition products which formed in toluene solutions at room temperature have been identified in some cases. The reaction of (η5-TMP)TaMe3(pyrrolyl) with hydrogen (2−3 atm) in benzene-d6 solution at room temperature was studied. The stoichiometric formation of cyclohexane-d6 by hydrogenation of an equivalent of solvent was confirmed by 1H and 13C NMR and gas chromatographic/mass spectroscopic data. The characteristics and scope of the room temperature arene hydrogenation process are discussed.

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