X-ray structure of [Nb(eta(5) -C5H5)(2)(SCH2CH2CH2S]. ECP quantum chemistry of niobium five and six metallacycle complexes
Additional Document Info
[Nb(5-C5H5)2PDT] (1) (PDT= propane-1,3-dithiolate), 5- C5H5 = Cp, in the chair form, was characterized by spectroscopic methods as well as by X-ray crystallography, that indicated a tetrahedral geometry around niobium. Quantum chemistry calculations were performed for 1, for the hypothetical complex containing the five member ring metallacycle [NbCp2EDT], (EDT = ethane-1,2-dithiolate), (2), as well for the cationic complex analog of 2, [NbCp2EDT]+, 2+. The data obtained indicated also a tetrahedral geometry around niobium in 2, with a S-Nb-S angle of 82.1. The five-membered ring adopts a twisted conformation, with the carbon atoms lying 12.5 above and below the S-Nb-S plane, resulting in the conformers and , that are separated by an ROHF/ECP barrier of 8.6 kcal mol-1. For 2+, the S-Nb-S angle was found to increase to 85.6, in agreement with the fact that the single occupied SOMO orbital is expected to keep the L-M-L angle to values close to 80. For complex 1 the obtained theoretical results are in good agreement with parameters obtained from the X-ray crystallographic studies. 2002 Elsevier Science Ltd. All rights reserved.