Replacing Mercury: Syntheses of Lanthanoid Pyrazolates from Free Lanthanoid Metals, Pentafluorophenylsilver, and Pyrazoles, Aided by a Facile Synthesis of Polyfluoroarylsilver Compounds

Abstract

The polyfluorophenylsilver complexes [Ag2(C6F4Br‐4)2(py)3] (py = pyridine) (1) and [{Ag2R2(py)2}n] [R = C6F5 (2); C6F4Br‐3 (3); C6F4H‐4 (4)] were prepared in reasonable yields by reactions of silver(I) oxide with the appropriate polyfluorobenzenes in pyridine. This simple and convenient synthesis is selective and does not lead to debromination of C6HF4Br‐(3 or 4). Complex 1 is dinuclear with AgR2 and Ag(py)3 units linked by a bridging polyfluoroaryl group and Ag···Ag interactions, whereas 2–4 are polymeric with alternating AgR2 and Ag(py)2 units similarly linked. The trivalent lanthanoid pyrazolates, [Ln(Ph2pz)3(py)2]·2thf (Ph2pz = 3,5‐diphenylpyrazolate; Ln = Yb, 5, Er, 6, Dy, 7, Lu, 8; thf = tetrahydrofuran), [Ho(Ph2pz)3(py)(thf)] (9), [Ln(Ph2pz)3(py)(dme)]·solv (Ln = Tb, solv = 1.75PhMe, 10, Gd, solv = 1.5dme, 11; dme = 1,2‐dimethoxyethane; PhMe = toluene), [Ln(Ph2pz)3(thf)3] (Ln = La, 12, Ce, 13, Nd, 14), [Ln(tBu2pz)3(py)2] (tBu2pz = 3,5‐di‐tert‐butylpyrazolate; Ln = Yb, 15, Tm, 16, Ho, 17, Dy, 18), [Yb(Phtpz)3(py)2]·PhMe (19) (Phtpz = 3‐Phenyl‐5‐(2′‐thienyl)pyrazolate) and [Nd(ttfpz)3(dme)2] (20) (ttfpz = 3‐(2′‐thienyl)‐5‐(trifluoromethyl)pyrazolate) have been prepared by redox transmetallation/protolysis (RTP) reactions employing lanthanoid metals, pentafluorophenylsilver and the corresponding pyrazoles (pzH) in donor solvents. This is a new synthetic route in which AgC6F5 replaces the more commonly used Hg(C6F5)2 or HgPh2. Yields are good to excellent if long crystallization times are used but the heavier Ln metals require activation with iodine to induce reaction. The monomeric structures exhibit η2‐bound pyrazolate ligands with eight‐coordinate metal atoms for complexes 5–9 and 15–19, nine‐coordinate metal atoms for complexes 10–14, and ten‐coordinate metal atoms for complex 20.