Redox transmetallation reactions between trimethyltin com

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The dimeric complex [Li(Ph2pz)(OEt2)]2 (1) and tetrameric cluster [Na(Ph2pz)(thf)]4 (2) were prepared by treatment of alkali-metal reagents (nBuLi and Na{N(SiMe3)2}, respectively) with 3,5-diphenylpyrazole (Ph2pzH) in Et2O (1) or THF (2). The polymer [Na(tBu2pz)]n (3) was obtained from reaction at elevated temperature in a sealed tube between Na metal and 3,5-di-tert-butylpyrazole (tBu2pzH). The complex [Na4(tBu2pz)2(thf)3(obds)]2 (4; obds = (OSiMe2)2O) was obtained as a minor product from prolonged treatment of tBu2pzH with elemental sodium in a silicone-greased flask. All four alkali-metal pyrazolato complexes were characterized by IR and 1H NMR spectroscopy and X-ray crystallography.The Li dimer 1 displays mu-eta(2):eta(1) lithium-pyrazolato binding, in which both lithium atoms are four-coordinate. Room- and variable-temperature NMR studies (1H, 13C, and 7Li) of 1 suggest similar behavior in solution, with peaks coalescing at low temperatures. Complexes 2 and 4 display distorted cubane structures. In 2, all the sodium atoms are five-coordinate, whereas 4 contains two sodium/pyrazolate/thf clusters (4:2:3 ratio) bridged by two obds(2-) units, as well as two four-coordinate and two five-coordinate sodium atoms. Compound 3 is composed of two independent chains with the unusual coordination modes mu3-eta(5):eta(2):eta(2), mu3-eta(5):eta(2):eta(1), and mu3-eta(4):eta(2):eta(1), with five-, six-, and seven-coordinate sodium atoms. Two oxo-centered M8 cage complexes [(tBu2pz)6Li8O] (5) and [(tBu2pz)6Na8O] (6) were obtained as by-products from attempted preparation of [Li(tBu2pz)] and [Na(tBu2pz)], respectively, and their structures were determined.

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The complex [Yb(Ph2pz)3(LiOBu)]2 (1) (Ph2pz = 3,5‐diphenylpyrazolate), fortuitously obtained from reaction of Yb metal with a lithium containing sample of [SnMe3(Ph2pz)] at elevated temperatures forms a centrosymmetric butoxy‐ and pyrazolate‐bridged open box structure. Each ytterbium atom is eight coordinate with one chelating Ph2pz ligand, one μ‐η2:η2 bridging pyrazolate, one μ‐η2(Yb):η4(Li) Ph2pz group and two bridging butoxide ligands. Each lithium atom is unsymmetrically chelated by an η2‐Ph2pz group, η4(N,C(pz)C2(Ph)) bonded by another pyazolate group, and bridged through a butoxide oxygen atom to two ytterbium atoms. The type of η4‐pyrazolate coordination is unprecedented and is the first observation of interactions to a metal by the Ph rings of the Ph2pz ligand. The complex [Li(dme)3][Eu(Ph2pz)3(dme)] (2) obtained from reaction of Eu metal with the same sample of [SnMe3(Ph2pz)] in dme at room temperature is a charged separated species with the first anionic pyrazolatolanthanoidate(II) complex in which europium is eight coordinate with three chelating Ph2pz ligands and a chelating dme.