Synthesis and reactions of a nucleophilic bis(μ-dimethylphosphido)dicobalt complex. The crystal and molecular structure of [C5H5Co(μ-PMe2)]2 and [(C5H5Co)2(μ-H)(μ-PMe2)2]BPh4 |
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Authors: | H. Werner W. Hofmann R. Zolk L.F. Dahl J. Kocal A. Kühn |
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Affiliation: | 1. Institut für Anorganische Chemie der Universität Würzburg, Am Hubland, D-8700 Würzburg F.R.G.;2. Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706 U.S.A. |
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Abstract: | The bis(μ-dimethylphosphido)dicobalt complex [C5H5Co(μ-PMe2)]2 (II) has been prepared from Co(C5H5 and PMe2H on almost quantitative yield. It has also been made by reduction of [C5H5Co(PMe2H)3]I2 (IV) with NaH and from the reaction of [C5H5(PMe3)Co(μ-CO)2Mn(CO)C5H4Me] with PMe2H. Protonation of II with CF3CO3H in the presence of NH4PF6 produces the PF6? salt of the (μ-hydrido)dicobalt cation [(C5H5Co)2(μ-H)(μ-PMe2)2]+ (V) which reacts with aqueous NaOH to give II. Similar treatment of [C5H5Co(μ-SMe]2 with CF3CO2H/NH4PF6 leads to the formation of [(C5H5Co)2(μ-SMe)3]PF6 (VI). The nucleophilic character of complex II has also been demonstrated in the reaction with SO2, which gives [(C5H5Co)2 (μ-PMe2)2(μ-SO2)] (VII). The crystal and molecular structures of II, the corresponding bis(μ-diphenylphosphido) compound [C5H5Co(μ-PPh2)]2 (III) and the BPh4? salt of V have been determined. In both neutral complexes the Co2P2 cores are similarly puckered, as reflected in the dihedral angle between the CoP2 and P2Co′ planes of 108.1 and 105.0° for R = Me and Ph, respectively. The CoCo bond length and the PP interatomic separations are essentially identical for both dimers. The CoCo bond length in V, 2.517(1) Å, is lower than that in II, 2.542(2) Å. The only obvious structural variation between the unprotonated and the protonated species is the large difference in the degree of canting of the C5H5 rings with respect to each other. The angles between the C5(ring)-centroid and the CoCo line are ca. 150 and 167° in II and V, respectively, which reflects the influence of the bridging hydride ligand in the cationic complex. |
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