Bi-X bonds

The broken bonds (boldface = dissociated BDEs (boldface = recommended data reference in parentheses) Methods (reference in  

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Simple arene solvates of bismuth(III) halides and pseudohalides have been structurally characterized, as have adducts prepared in the presence of AlCls. " The sohd-state structures of these compounds show 7t-coordination of the arenes to the bismuth centers, as well as intermolecular Bi- X bonding that produces dimers or polymeric structures. Arene complexes that have been structurally characterized include those of benzene, o-, m- and jo-xylene, mesitylene, and hexamethylbenzene. tt-Coordination of arenes has also been seen in [Bi(OC6F5)3(toluene)]2 and BL4(/r4-0)(/u-OC6F5)6 /r3-OBi(/r-OC6F5)3 -2(C6H5CH3). 5... 

For the preparation of bismuth carboxylates, four methods are available (i) a substitution reaction of Bi-X bonds with carboxylate anions, (ii) the cleavage of Bi-C bonds in Ar3Bi with carboxylic acids, (iii) a ligand-exchange reaction of bismuth carboxylates with different earboxylic acids, (iv) the treatment of Bi203 with carboxylic acids. These four methods (i)-(iv) are denoted in Table 2.19 (i) as method A, (ii) as method B, (iii) and (iv) as method C, respectively. 

In the 1 1 complexes of mesitylene with BiXs (X = Cl and Br) self-assembly leads to formation of two-dimensional sheets containing six-membered BieXg moieties and a complex array of primary Bi-X bonds (three at each bismuth atom, ca. 2.5 A) and secondary Bi- -X bonds (in the range 3.1-4.0 A) [458]. 

For allyl acetate a significant deuterium isotope effect supports the hydrogen abstraction mechanism (Scheme 6,31).183 Allyl compounds with weaker CTT-X bonds (113 X=SR, S02R, Bi etc.) may also give chain transfer by an addition-fragmentation mechanism (Section 6.2.3). 

For bromide and iodide, the nature of the countercation influences the structure of the anionic complex. In fact, when the [(18-C-6)-K]Br and [(18-G-6)-K]I salts are used, the anionic complexes ([ 163—X]—, X = Br, I) remain mononuclear and adopt a T-shaped structure (Figure 11). In both cases, the Hg-X bonds are shorter than those observed in the corresponding dinuclear complexes in agreement with the terminal location of the anion. The reaction of bis(pentafluoro)phenylmercury 164 with [(18-C-6)-K]Br and [(18-C-6)-K]I also afford T-shaped complexes [164-Br] and [164-1]. The Hg-Br (2.93 A) and Hg-I (3.12 A) bonds found in these complexes are longer than those observed in [163-Br] and [ 163—1] indicating that 164 is a weaker Lewis acid than 163.206... 

To date, 15 stibine R3M Sb(R/)3 (M = B, Al, Ga, In) and six bismuthine adducts R3M Bi(R )3 (M = Al, Ga) have been structurally characterized by single crystal X-ray diffraction. Their M-E, M-X and E-X bond lengths as well as X-M-X and X-E-X bond angles are summarized in Tables VI, YII and VIII. Figures 6-9 show the solid state structures of four representative adducts. 

Bismuth phosphine complexes represent a substantial component of the established phosphine complexes of heavier p-block elements, and an excellent overview has presented an important bonding model for these systems (7). The observed structures are considered as trigonal-pyramidal BiX3 units with three secondary trans bonds. If the acceptor orbitals are the Bi-X trans arrangement is expected, as the relationship between the trans X-Bi-P bond distances. The shortest Bi-P distance [2.7614(2) vs 2.866(3) A] is trans to the longer Bi-Br distance [3.403(1) vs 2.9916(1) A], as the only arrangement that will allow the phosphine ligands to occupy trans... 

Attempts were made not only to find an alternative way to replace dimer and to deposit high-quality poly(tetrafluoro-p-xylylene) film, but also to eliminate the dibromide as the precursor because of the difficulty of synthesis. Therefore, the deposition of poly(tetrafluoro-p-xylylene) film by using hexafluoro-p-xylene as the precursor instead of dibromotetrafluoro-p-xylene was tried. However, no polymer film was deposited on the wafer. Effort was expanded and other metal reagents such as nickel or copper were used to react with l,4-bis(trifluoromethyl)-benzene to generate a,a,a, a -tetrafluoro-p-xylylene to deposit poly(tetrafluoro-p-xylylene) film. However, the result showed that no film was deposited, which was not unexpected, because a C—X bond that is weaker than C—F bonding might be necessary to initiate the formation of the desired intermediate. 

Photolysis of vinyl halides can induce both heterolysis of the C-X bond, thereby generating vinyl cations, and homolysis giving vinyl radicals. This competition between the two mechanisms was studied for 3-vinyl halides, 1,2,2-triphenylbromoethane (136) and 1-phenyl-2,2-bis(o-methoxyphenyl)-l-bromoethene and /3-styrene. Incursion of the photo-induced SrnI process, through the intermediate vinyl radical, is verified in the presence of reducing nucleophiles, such as the enolate ions of ketones and in part with (EtO)2PO . Incursion of the heterolytic pathway and the intermediacy of the radical cation, occurs in the presence of weak electron-donor anions, such as N02, Ns and Cl . The vinyl cation of /3-styrene gives phenylacetylene via an El-type elimination. 

Shortened M-Si bonds Long Si-X bonds Si-H contacts of 1.8-2.1A Small Si-M-Si angles in bis(silyl)hydride systems X and H substituents in the apical positions in respect to silicon atom Elongated M-H bonds Elongated M-Si bonds Normal Si-X bonds Si-H contacts of 1.7-1.8 A No regulations No regulations Normal M-H bonds... 

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