Main group fluorides with coordination

SEPPELT Main-Group Fluorides with High Coordination Numbers... 

Comparable recent detailed reviews of the actinide halides could not be found. The structures of actinide fluorides, both binary fluorides and combinations of these with main-group elements with emphasis on lattice parameters and coordination poly-hedra, were reviewed by Penneman et al. (1973). The chemical thermodynamics of actinide binary halides, oxide halides, and alkali-metal mixed salts were reviewed by Fuger et al. (1983), and while the preparation of high-purity actinide metals and compounds was discussed by Muller and Spirlet (1985), actinide-halide compounds were hardly mentioned. Raman and absorption spectroscopy of actinide tri- and tetrahalides are discussed in a review by Wilmarth and Peterson (1991). Actinide halides, reviewed by element, are considered in detail in the two volume treatise by Katzet al. (1986). The thermochemical and oxidation-reduction properties of lanthanides and actinides are discussed elsewhere in this volume [in the chapter by Morss (ch. 122)]. 

Tin forms dihahdes and tetrahahdes with all of the common halogens. These compounds may be prepared by direct combination of the elements, the tetrahalides being favored. Like the halides of tile lower main group 4 elements, all are essentially covalent. Their hydrolysis requires, therefore, an initial step consisting of the coordinative addition of Iwo molecules of water, followed by the loss of one molecule of HX. the process being repeated until the end product ft S111 Oil c is obtained. The most significant commercial tin halides are stannous chloride, stannic chloride, and stannous fluoride. 

The teflate ion, (OTeFs)", plays an important role in synthetic main group chemistry. Its effective electronegativity is similar to that of fluoride. A group of anions with a general formula of [M(OTeF5H)6] (M = As, Sb, Bi, Ti, etc.) have recently been prepared. They are only weakly coordinating and serve to stabilize otherwise unstable cations. 

The main limitations of using organoboronic acids in cross-coupling chemistry are threefold. These compounds are quite reactive towards many nucleophiles and oxidants, which prohibits installation of the boronic acid functional group early in a synthetic sequence. Moreover, purification of boronic acids is often problematic. Finally, since the C—B bond is relatively nonpolar, transmetalation of an organoboron reagent to Pd(ll) will not occur without coordination of an anionic base or a fluoride ion to the boron atom to afford a four-coordinate ate -complex (e.g. 20 shown below). This requirement poses some limitations with respect to transformations of base- or fluoride-sensitive substrates, although these... 

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