Synthesis and structural characterization of tris[3-trifluoromethyl-5-(2-thienyl)pyrazolyl]hydroborato thallium, Tl[TpCF3,Tn]: a monovalent thallium complex with a highly solvent dependent JTl–F coupling constant, ranging from 0 to 850 Hz

Abstract

The tris[3-trifluoromethyl-5-(2-thienyl)pyrazolyl]hydroborato thallium complex, Tl[Tp^CF₃,Tn], has been prepared via the reaction of 3-trifluoromethyl-5-(2-thienyl)pyrazole with KBH₄ followed by metathesis with TlNO₃. Both ¹⁹F and ²⁰³Tl NMR spectroscopies reveal the presence of an exceptionally large 850 Hz four-bond ⁴J_Tl–F coupling constant for Tl[Tp^CF₃,Tn] in chloroform at room temperature; however, the observed coupling constant is highly solvent dependent and is reduced to 0 Hz in methanol, acetonitrile and dimethyl sulfoxide. The molecular structure of Tl[Tp^CF₃,Tn] has been determined by X-ray diffraction: Tl[Tp^CF₃,Tn] is triclinic, P (no. 2), a = 8.328(1), b = 11.432(2), c = 16.088(3) Å, α = 70.58(2), β = 82.90(2), γ = 77.54(2)°, U = 1408(1) ų, Z = 2.