Compounds with bridged structure

The compounds A12(CH3)6, (CH3)2A1(/u,-C6H5)2A1(CH3)2, and (C6H5)2A1(/x-C6H5)2A1(C6H5)2 all have bridged structures, as shown in Figs. 13.6.1 (a), (b) and (c) respectively. The bond distances and angles are listed in Table 13.6.1. 

The bonding in the Al-C-Al bridges involves a 3c-2e molecular orbital formed from essentially sp3 orbitals of the C and A1 atoms. This type of 3c-2e interaction in the bridge necessarily results in an acute Al-C-Al angle (75° to 78°), which is consistent with the experimental data. This orientation is steri-cally favored and places each i/wo-carbon atom in an approximately tetrahedral configuration. 

In the structure of Me2Ga(/x-C=C-Ph)2GaMe2 [Fig. 13.6.1(d)], each alkynyl bridge leans over toward one of the Ga centers. The organic ligand 

Compounds In(Me)3 and Tl(Me)3 are monomeric in solution and the gas phase. In the solid state, they also exist as monomers essentially, but close intermolecular contacts become important. In crystalline In(Me)3, significant In- -C intermolecular interactions are observed, suggesting that the structure can be described in terms of cyclic tetramers, as shown in Fig. 13.6.1(e), with interatomic distances of In-C 218 pm and In- -C 308 pm. The corresponding bond distances in isostructural Tl(Me)3 areTl-C = 230pmandTl- C = 316pm. 

Many organometallic compounds of group 13 are formed by n bonds. The n ligands commonly used are olefins, cyclopentadiene, or their derivatives. 

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As it was shown in [15-18], such compounds, with bridging atoms of deprotonated amino alcohol, are formed when aminoalcoholate complexes of metal (III) react with bivalent 3d-metal ions. Many representatives of these compounds were synthesized in crystalline state the polynuclear compounds were also found to form in aqueous and methanol solutions. The structure of 2Co(III) - Ni(II) tri-nuclear complex, according to [17,18], is shown below in Figure 2. 

The structure of 11a has been established by X-ray diffraction. The compounds 11 are 30-cluster valence-electron (CVE) dimetal species, and are therefore electronically unsaturated. The electron distribution within the W(fi-C)fth rings may be represented by various canonical forms. However, that shown, which implies that the W=C bond in the ( 5-C2B9H9R 2)(OC)2-W=CC6H4Me-4 moiety formally contributes three electrons to the rhodium center (16-electron valence shell), accords with other results from our laboratory involving electronically unsaturated dimetal compounds with bridging alkylidyne ligands 18). 

Chromium-based reagent systems, for pinacol coupling, 11, 63 Chromium carbenes, in ene-yne metathesis, 11, 272 Chromium carbonyl compounds with bridging hydrides, 5, 206 computational studies and spectroscopy, 5, 203 experimentally determined structures, 5, 204 nitro and nitroso compounds, 5, 205 silatropic migrations, 5, 249 with very weakly bonded ligands, 5, 205 Chromium carbonyl hydrides, preparation and characteristics,... 

S-Bridged compounds, with the structure (31) indicated from i.r. measurements, have been synthesized by the action of H2S on K[Pt(am)Cl3](am = NH3 or... 

In the last 10 years, considerable amount of research has been devoted to the development of heterodinuclear cyano-bridged cubic cluster based on the [Feni(Tp)(CN)3]- synthon which directs the formation of cyanide-bridged compounds with interesting structures and magnetic properties. 

The compounds are crystalline and can be sublimed when R and R are methyl groups. The crystalline compound with adamantane structure which can be prepared from dimethylalane and dimethylpropynylalane has a framework containing A1R2A1 bridge bonds and may be called a pseudo-aluminaadamantane ... 

Compound 2c was used as a model system to induce an elimination of hydrochloride in order to create molecular Si/N-compounds with bridging or chelating pseudo-chalcogen structural novelties (Eq. 2). In no case was a successful formation of 5c or oligomers thereof obtained. 

Compounds with bridging N ligands whose structures have been determined during the review period are given in Table 1. As can be seen, all but two compounds contain hydrocarbon ligands and hence are discussed later. 

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