Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The bis(acetone) complex of tetramethyl rac-3,3,7,7-tetramethyl-trans-5-palladatricyclo[4.1.0.02,4]heptane-1,2,4,6-tetracarboxylate rac-1a was crystallized and investigated by X-ray structure analysis. Unlike in complexes with bidendate ligands in rac-1a · 2(acetone), only a small deviation from the square planar coordination of palladium was observed. Efforts to crystallize the analogous pyridine, acetonitrile and benzonitrile complexes failed; but the labile complexes rac-1a · 2([D5]pyridine) and rac-1a · 2([D3] acetonitrile) as well as rac-1a · 2([D6]acetone) could be characterized by 1H and 13C NMR spectra and a fast ligand exchange was proven by nmr. Then the ability of different 1,2-disubstituted cyclopropenes to form trans-5-pallada-tricyclo[4.1.0.02,4] heptanes 1 was investigated. Only the diesters 5c-e lead to PTHs, with a diester possessing sterically demanding substituents in 3-position of the cyclopropene and with other substituents in 1- respectively 2-position of the cyclopropene either the cyclopropene-formation or the PTH-formation failed.
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