Cyclopentadienyl chromium and tungsten complexes with halide, methyl and σ-phenylethynyl ligands:: Structures of (η5-C5H5)Cr(NO)2(-CC-C6H5), (η5-C5H5)Cr(NO)2I and [(η5-C5H4)-COOCH3]W(CO)3Cl

With copper(I) iodide as catalyst, sigma-alkynyls, compounds (eta(5)-C5H5) Cr(NO)(2)(C C-C6H5) (5), [(eta(5)-C5H4)COOCH3]Cr(NO)(2)(C C-C6H5) (10), and [(eta(5)-C5H4)-COOCH3]W(CO)(3)(C C-C6H5) (13), were prepared from their corresponding metal chloride 1, 6 and 12. Structures of compound 3, 5 and 12 have been solved by X-ray diffraction studies. In the case of 5, there is an internal mirror plane passing through the phenylethynyl ligand and bisecting the Cp ring. The phenyl group is oriented perpendicularly to the Cp with an eclipsed conformation. The twist angle is 0 degrees and 118.4 degrees for -C C-Ph and two NO ligands, respectively. The orientation is rationalized in terms of orbital overlap between psi(3) of Cp, d pi of Cr atom, and pi* of alkynyl ligand, and complemented by molecular orbital calculation. The opposite correlation was observed on the chemical shift assignments of C(2)-C(5) on Cp ring in compounds 6 and 12, using HetCOR NMR spectroscopy. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of C-13 NMR data and compared with the calculations via density functional B3LYP correlation-exchange method. (C) 2008 Elsevier B.V. All rights reserved.