Organic group adducts

In contrast to these trends observed for the stibine adducts, the H-NMR spectra of the bismuthine adducts R3M—BiR without exception show almost the same chemical shifts due to the organic groups as the starting trialkylalanes, -gallanes and -bismuthines, again indicating very weak acid-base interactions in solution. 

Since there are many more carbene-transition-metal complexes known than main-group adducts this chapter is organized by the synthetic methods that lead to the complexes rather than by the metal itself, Applications of these complexes to catalysis and materials science will be discussed in separate chapters of this article. 

That the chlorotriorganotin(IV) adducts with carbonyl (Table 23) are invariably five-coordinate rather than six-coordinate has been attributed to steric crowding by the organic groups attached to the tin atom253,422a. Structural study on the R3SnCI L adducts, L =... 

In contrast to the existence of numerous stable ionic triorganosilylonium complexes, there is no well-defined pentacoordinate molecular 1 1 adduct of acyclic structure of a triorganohalosilane with an uncharged nucleophile. This implies a higher thermodynamic stability of the ionic silylonium complexes than their molecular isomers for the open chain triorganosilyl structure [Eq. (53)]. Stable penta- or hexacoordinate 2 1 nucleophile-silane open chain complexes with three organic groups bound to... 

In Table 19, selected bond distances and angles are reported for intermolecular N SnRsX complexes. All adducts have a distorted TBP configuration with the organic groups in the equatorial position and the more electronegative nitrogen and halide or pseudohalide in the axial positions. The smallest N Sn distance, and hence the strongest donor... 

The addition of tribromoborane to acetylene first may give a cw-adduct, which then isomerizes to the tmns-i omer during its isolation. This two-step procedure is useful for achieving a formal carboboration of alkynes with a variety of organic groups. 

Haloboranes add to terminal alkynes in a cis /in-Markovnikov manner however, the bromoboration of acetylene itself exceptionally provides a trans adduct [28] (eq (17)). A sequence of haloboration with boron tribromide and then cross-coupling with organozincs is useful for a formal carboboration of alkynes with various organic groups. Addition of boron triboromide to allene is convenient for the synthesis of (2-bromo-2-propeny])borate [29] (eq (18)). 

Boronic acids submit the organic groups to o-alkynylaryl isocyanates to afford 3-alkylideneoxindoles, the incoming group being cw-related to the carbonyl function. Bis(pinacolato)diboron reacts similarly, and apparently the cyclic adducts are available for Suzuki coupling to generate a library of oxindoles. ... 

Many biomolecules are Lewis adducts with central metal ions. Most often, O and N atoms of organic groups, with their lone pairs, serve as the Lewis bases. Chlorophyll is a Lewis adduct of a Mg " ion and four N atoms in an organic ring system. Vitamin B12 has a similar structure with a central Co, and so does heme, but with a central Fe ". Several other metal ions, such as Zn ", Mo ", and Cu ", are bound at the active sites of enzymes and function as Lewis acids in the enzymes catalytic action. 

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