Complexes transition metal/metalloids

Infrared Intensities of Metal Carbonyl Stretching Vibrations, 10, 199 Infrared and Raman Studies of w-Complexes, 1, 239 Insertion Reactions of Compounds of Metals and Metalloids, 5, 225 Insertion Reactions of Transition Metal-Carbon o-Bonded Compounds I Carbon Monoxide Insertion, 11, 88... 

The complex of tartaric acid and antimony (emetic) was described three centuries ago. Nevertheless, the structure of this compound has been elucidated these last fifteen years by X-ray diffraction ( 1 ). In fact, emetic presents a binuclear cyclic structure. Many authors mentioned similar complex with transition metals (vanadium (2), chromium (3)) or metalloids (arsenic (4), bismuth (5)). Emetic with phosphorus was not mentioned. Nevertheless, tartaric acid or alkyl tartrates has been utilized in phosphorus chemistry tartaric acid reacts with trialkyl phosphites giving heterocyclic phosphites (6). Starting from alkyl tartrates, we prepared spirophosphoranes with a P-H bond and sixco-ordinated compounds (7). With unprotected tartaric acid, many possibilities appear condensation as a diol, as a di(oc-hydro-xyacid), or even as a 8-hydroxyacid. 

The jS-diketones are a versatile class of ligand with many known modes of coordination, some of which are shown in Figure 3. 0,0 -chelation (11) of the monoanion is by far the most common mode, being found for almost all of the metallic and metalloid elements. Compounds of the stoichiometry M(dike)3 and M(dike)2 are the most common. The former generally have an almost octahedral distribution of the six oxygen atoms when M is a main group or transition metal. These compounds have been used extensively in studies of the mechanism of the racemization of trischelate complexes. 

Complexes containing bonds between Transition Metals and Main Group Metals metalloids)... 

Alternatively, the ligand may occupy a terminal site, as shown in 4 or 5 (X=S). The tendency for the new ligand formed as a result of aminometallation to behave in a bidentate fashion, as in 3, 6, or 7, depends on whether the metal or metalloid has adequate Lewis acidity and is otherwise coordinatively unsaturated. Consequently, among main group elements M, chelation or bridging is most frequently found among the s-block, group IIIB, or electropositive (e.g., Sn", raher than SP) elements and is commonly encountered in transition metal complexes. 

Inherently, whether a coordination compound involves metal or metalloid elements is immaterial to the basic concept. However, one factor that distinguishes the chemistry of the majority of metal complexes is an often incomplete d (for transition metals) or f... 

Heteronuclear M—M Bonds. The transition metals, especially in their carbonyl-type compounds, form many bonds to the non-transitional metal or metalloidal atoms. This is particularly true for the elements Zn, Cd, Hg, Cu, Ag, Au, Tl, Ge, Sn and Pb. These are nearly always 2c-2e bonds which require no special comment. However, there are cases where mixed metal clusters of a more complex nature are formed. Examples of these are trigonal-bipyramidal Sn2Pt3 species and tetrahedral Ge2Co2 species. 

The borderline cations comprise the first row of transition metals, in their common oxidation states, as well as Ga, In " ", Cd, Sn " ", and Pb ". The hydrogen ion and the metalloid ions As(III) and Sb(III) are also included in this category (Nieboer and Richardson 1980). They are able to form stable complexes with numerous ligands, and preference for a given donor group... 

Organometallic compounds are those in which there is a metal-carbon bond. According to this definition, in the case of transition metals, this group of compounds includes not only metal carbonyls, olefin complexes, cyclopentadienyl, and other 7r-complexes, but also cyanide and fulminate compounds. Certain difficulties arise in defining the metal of the main group elements. Usually, organometallic compounds are comprised not only of compounds of typical metals, but also of metalloids such as boron, silicon, phosphorus, arsenic, selenium, etc. In compounds of metals as well as in those of metalloids, the bond is generally polarized as follows C. Consequently, the... 

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