Practical Synthetic Routes to Solvates of U(OTf)3: X-ray Crystal Structure of [U(OTf)3(MeCN)3]n, a Unique U(III) Coordination Polymer

Abstract

The reaction of UH3 or U metal with triflic acid results in the formation of a mixture of species including U(OTf)4 and leads to the reproducible isolation of the mononuclear U(IV) hydroxo complex [U(OTf)3(OH)(py)4] (1) and the U(IV) dinuclear mu-oxo-complex [{U(OTf)2(py)3}2{mu-O}{mu-OTf}2] (2). The X-ray crystal structures of these complexes have been determined. Analytically pure complex 1 can be prepared in a 17-27% yield providing a good precursor for the synthesis and study of the reactivity of the hydroxo complexes with different coordination environments. Two practical synthetic methods for the preparation of Lewis base adducts of U(OTf)3 are described. Analytically pure [U(OTf)3(py)4] (4) was easily and reproducibly prepared (50-60% yield) by protonolysis of the amide U{N(SiMe3)2}3 with pyridinium triflate in pyridine. Salt metathesis of UI3(thf)4 with potassium triflate in acetonitrile resulted in the complete substitution of the iodide counterions by triflate producing the acetonitrile solvate [U(OTf)3(MeCN)3]n (3). The solid-state structure of 3 shows the formation of a unique U(III) coordination polymer in which the metal ions are connected by three triflates acting as bidentate bridging ligands to form a 1D chain.