The Coordination of Novel, Hard Ligand Systems to Tantalum(V) and Niobium(V) Metal Centres

Abstract:

The formation reaction of acetylacetone to solvated tantalum pentachloride ([TaCl₅]₂) in methanol, is defined by limiting kinetic behaviour and is indicative of a two-step process. This involves the rapid formation of an intermediate, possibly trans-[TaCl₂(OMe)₃(η¹-acacH)]) with the stability constant, K₁, equal to 2.4 ± 0.3 x 10³ M^-1 at 25 °C. The second order rate constant, k₁, at 25 °C was determined as 3.1 ± 0.1 x 10² M^-1 s^-1. A fit of the data obtained from the UV-Vis study, and describing the total reaction, yielded a value of 1.7 ± 0.2 x 10³ M^-1 s^-1 for K₁, which is in agreement with the value obtained earlier. Comparison of k₁ and k₂ indicates that the first reaction is roughly six orders of magnitude (10⁶) faster than the second rate determining step.

• Periodical: Advanced Materials Research (Volume 1019)
• Pages: 426-432
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1019.426
• Online since: October 2014
• Authors: Renier Koen*, Andreas Roodt, Hendrik Visser
• Keywords: Kinetic, Niobium, Separation, Tantalum

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