title: Pyrazole complexes as anion receptors.
abstract: The behavior of the receptors [Re(CO)3(Hdmpz)3]BAr'4 (Hdmpz = 3,5-dimethylpyrazole) (1) and [Re(CO)3(HtBupz)3]BAr'4 (HtBupz = 3(5)-tert-butylpyrazole) (2; Ar' = 3,5-bis(trifluoromethyl)phenyl) toward the anions fluoride, chloride, bromide, iodide, hydrogensulfate, dihydrogenphosphate, nitrate, and perrhenate was studied in CD3CN solution. In most cases, the receptors were stable. Anion exchange was fast, and binding constants were calculated from the NMR titration profiles. The structure of the adduct [Re(CO)3(HtBupz)3] x NO3 (3) was determined by X-ray diffraction. Two pyrazole moieties are hydrogen-bonded to one nitrate oxygen atom, and the third pyrazole moiety is hydrogen-bonded to an oxygen atom of an adjacent nitrate, leading to infinite chains. The structure of the adduct [Re(CO)3(Hdmpz)3]BAr'4acetone (4), also determined by X-ray diffraction, showed a similar interaction of two pyrazole N-H groups with the acetone oxygen atom. F- and H2PO4(-) deprotonate the receptors, and HSO4(-) decomposed 1. The structure of one of the decomposition products (5), determined by X-ray diffraction, is consistent with pyrazole protonation and substitution by sulfate.
authors.affiliation: Departamento de Química Orgánica e Inorgánica-IUQOEM, Facultad de Química, Universidad de Oviedo-CSIC, 33006 Oviedo, Spain.
authors.forename: Sonia
authors.initials: S
authors.lastname: Nieto
authors.forename: Julio
authors.initials: J
authors.lastname: Pérez
authors.forename: Lucía
authors.initials: L
authors.lastname: Riera
authors.forename: Víctor
authors.initials: V
authors.lastname: Riera
authors.forename: Daniel
authors.initials: D
authors.lastname: Miguel