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The terminal (diphenylalkenyl)alkylidene complexes (C5Me4R)Ta(CHCHCPh2)X2 (R=Me, Et; X=Cl, Br) are formed in moderate yields from the ring-opening reaction of 3,3-diphenylcyclopropene with the organoditantalum(III) halides (η-C5Me4R)2Ta2(μ-X)4. Potassium amalgam reduction of these alkenylalkylidene complexes afforded the alkylidene-tethered tantallanorbornadienes (C5Me4R)Ta[CHCHCPh(σ2-C6H5)], which possess a bent, boat conformation σ2-arene ligand with a fold angle of 19.24(46)° (R=Me) in the solid state. 13C and 1H NMR spectroscopies are consistent with a rapid flip-flop motion that averages the resonances of the σ2-phenyl group to fewer resonances than expected from the solid-state structure. [Copyright &y& Elsevier]

bis[2-(Dimethylaminomethyl)pyrrolyl]tantalum chloride (1) was prepared by treatment of the TaCl5 with 2 equiv. of [2-(dimethylaminomethyl)pyrrolyl]lithium. The solid state structure of 1 shows the seven-coordinated tantalum atom, with a geometry corresponding to a pentagonal bipyramidal structure, in which two chlorine atoms occupy the axial position with the angle of 174.8(2)°. Furthermore, variable-temperature 1H NMR spectra infer the fluxionality of the two chelating pyrrolyl ligands with an estimated energy barrier of 13.8 kcal mol−1. Compound 1 shows no catalytic activity toward ethylene polymerization even activated with MAO. [Copyright &y& Elsevier]

Abstract: A series of Sn(II) and Sn(IV) compounds containing ketiminate ligands were synthesized. Reactions of SnCl2 with 1 or 2equiv. Li[OCMeCHCMeNAr] (where Ar=2,6-diisopropylphenyl) generate [OCMeCHCMeNAr]SnCl (1) and [OCMeCHCMeNAr]2Sn (2) in moderate yield, respectively. Similarly, reacting SnCl4 with 2equiv. Li[OCMeCHCMeNAr] yields a six-coordinated [OCMeCHCMeNAr]2SnCl2 (3). Divalent tin compound 2 can be oxidized with I2 in diethyl ether to generate tetravalent tin compound [OCMeCHCMeNAr]2SnI2 (4) in moderate yield. Compounds 1–4 have been characterized by 1H and 13C NMR spectroscopy and have been analyzed by X-ray crystallography. Theoretical calculation found that the bonding of ketiminate ligands and tin atom in compound 2 has a strong ionic character. [Copyright &y& Elsevier]