AbstractThe title reactions in all cases lead to the complexes (I)‐(IV) with a 1:1 ratio of Ta to the other metal.

The reaction of Cp/sub 2/TaH/sub 3/ (Cp = eta/sup 5/-C/sub 5/H/sub 5/) with Me/sub n/SnCl/sub 4-n/ (n = 0 to 2) in benzene results in the formation of the heterometallic complexes Cp/sub 2/TaH/sub 2/ (SnMe/sub n/Cl/sub 3-n/). The synthesis of Cp/sub 2/TaH/sub 2/(SnMe/sub 2/Cl) is possible only under conditions which provide for the binding of the HCl generated by triethylamine. According to the data from Moessbauer, IR, and /sup 1/H NMR spectroscopy, the compounds obtained have a symmetric structure with two terminal Ta-H bonds and a central Ta-Sn sigma bond. The complex Cp/sub 2/TaH/sub 2/(SnMeCl/sub 2/) has been studied by x-ray diffraction analysis (a = 7.736(1) b = 10.552(1), c = 16.943(3) A, space group Pcmn, Z = 4, R = 0.0245). The molecule of Cp/sub 2/TaH/sub 2/(SnMeCl/sub 2/) has a symmetry plane passing through the centers of the Cp rings, the Ta and Sn atoms, and the C atom of the methyl group. The Ta-Sn distance is equal to 2.752(1) A, and the Ta-H distance is equal to 1.61(10) A. It has been concluded that the Ta-Sn bond has a highly s character on the basis of the spectroscopic and structural data.

By X-ray structural analysis of the complexes of pyromllitdianilic acid with amide solvents it was found that the character of the system of hydrogen bonds and the structure of the solvates depend on the nature of the amide solvent. It was shown that in the case of polyamic acid solvates, the hydrogen bonds formed in the solid polyamic acid films can be studied by mass-spectrometric thermal analysis; from the obtained data, the mechanism may be determined of the function of additives catalyzing the solid phase cyclodehydration of polyamic acids.

AbstractDie Titelverbindung (I).wird durch Reduktion von FeCl3 mit Bis‐[cyclopentadienyll‐rheniumhydrid in THF dargestellt.