Dimenthyltin(IV) Bis(3,5-diphenylpyrazolate) as a Synthetic Reagent in the Preparation of Rare-Earth Pyrazolate Complexes

Reaction of SnMe2Cl2 with [Li(Ph(2)pz)] (Ph(2)pz = 3,5-diphenylpyrazolate) in diethyl ether in a 1:2 ratio afforded the new transmetallation reagent [SnMe2(Ph(2)pz)(2)]. Treatment of [SnMe2(Ph(2)pz)(2)] with Ln metals in either 1,2-dimethoxyethane (dme) or tetrahydrofuran (thf) provided a new route to the divalent [Ln(Ph(2)pz)(2)(dme)(2)] (Ln = Sm, Eu, Yb) and the trivalent [La(Ph(2)pz)(3)(dme)(2)] and [Yb(Ph(2)pz)(3)(thf)(2)] complexes in comparable yields to those from alternative methods. These reactions enabled isolation of the highly reactive [Sm(Ph(2)pz)(2)(dme)(2)] complex in good yield, in addition to the new cis isomer of [Eu(Ph(2)pz)(2)(dme)(2)], thereby establishing a rare case of geometric isomerism in lanthanoid chemistry. H-1 and Sn-119 NMR spectral studies and EDAX measurements were performed on the reaction mixture and/or residue to identify the tin-containing products and suggest formation of SnMe4, Sn2Me6, tin metal and two other SnMe3 species, which plausibly result from decomposition of unstable '' SnMe2 ''. Treatment of [Yb(Ph(2)pz)(2)(dme)(2)] with [SnMe2(Ph(2)pz)(2)] or [T1(Ph(2)pz)] resulted in the isolation of [Yb(Ph(2)pz)(3)(thf)(2)]center dot 2C(6)D(6) and [Yb(Ph(2)pz)(3)(dme)]center dot 0.5dme com- plexes, the structures of which have eight-coordinate Yb atoms and contrast nine-coordination observed for previous [Ln(Ph(2)pz)(3)(thf or dme)(n)] complexes. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)