Abstract:

The first preparation and full characterization of highly insoluble [\eta(5)-Cp\CoS2N2H][BF4] is reported. Proof of structure and composition is established from a single-crystal X-ray diffraction experiment at 173 K, which determined a crystal structure containing two independent cations and two independent anions in the asymmetric unit. The site of protonation is the terminal N of the S-N-S-N2- ligand which is coordinated to cobalt in the metallacycle. The crystal lattice contains numerous interatomic interactions, of which the most important are formed from multiple hydrogen bonds that link four [\eta(5)-Cp\CoS2N2H](+) ions and two [BF4](-) ions into a tetrameric cluster. The second kind of [BF4](-) is not involved in intermolecular bonding. Short S center dot center dot center dot S' interactions link such tetramers into planes; the resulting double-layer planes are described by the (101) Miller planes. DFT calculations using the B3PW91/6-311+G(3df)(2p) and B3LYP/6-311+G(3df)(2p) methods are in excellent agreement with the structure of the title cation from crystallography. Comparison to newly calculated and literature-reported DFT calculations on the neutral starting material [\eta(5)-Cp\CoS2N2] and to a recent low-temperature crystal structure of the latter shows that there are only minor changes (<= 3%) in the bond lengths within the CoS2N2 ring upon protonation, whereas the bond angles change by up to 9%. The B3PW91 functional is shown to be superior to B3LYP for computing the molecular structures of these formally Co-III metallacycles.