Nitrogenated lewis bases compound

Bis(l-methylboratabenzene)lead 42 is synthesized in 63% yield by the reaction of LifCsHsBMe) with lead(n) chloride. The X-ray structure analysis of 42 reveals some remarkably short intermolecular contacts from the lead atoms to the ortho-carbon atoms of neighboring molecules which create a tetrameric packing unit. Compound 42 forms weak adducts such as 43 with nitrogen Lewis bases like TMEDA or 4,4 -dimethyl-2,2 -bipyridine.71... 

The simplest type of Lewis acid-base reaction is the combination of a Lewis acid and a Lewis base to form a compound called an adduct. The reaction of ammonia and trimethyl boron is an example. A new bond forms between boron and nitrogen, with both electrons supplied by the lone pair of ammonia (see Figure 21-21. Forming an adduct with ammonia allows boron to use all of its valence orbitals to form covalent bonds. As this occurs, the geometry about the boron atom changes from trigonal planar to tetrahedral, and the hybrid description of the boron valence orbitals changes from s p lo s p ... 

After a fluorine/chlorine exchange, a lithiated aminochlorosilane is obtained. Lithium is bound to nitrogen, the strongest Lewis base in this compound. The SiN bond is enlarged (164.2 pm) and the SiNC angle of 138.7° shows the character of the amine.17,18... 

In reactions involving coordination compounds, the metal acts as the Lewis acid (electron-pair acceptor), while the ligand acts as a Lewis base (electron-pair donor). In the reaction above, the ammonia ligand displaced the water ligand from the chromium complex because nitrogen is a better electron-pair donor (less electronegative) than oxygen. 

The picture of the nitrogen atoms in diazadiboretidines acting as Lewis base centers is also supported by the formation of a 1 1 coordination compound with TiCl4 [Eq. (58)] (91). The B-NMR signal of 22.7 ppm indicates a highfield shift, which cannot be due to d-electrons from tetravalent d -titanium. X-Ray structural analysis shows that bridging chlorine atoms provide the observed electronic saturation of the boron atoms. 

Di-/i-chloro(dichloro)bis[77 -T7 -2,7-dimethylocta-2,6-diene-l,8-diyl)diruthenium (compound A) is a purple crystalline compound, that is indefinitely stable at room temperature under a nitrogen atmosphere. For short periods it can also be handled in air. MS (El) m/z 616 (M + ). In the solid state the product shows symmetry Ci, ° but it exists as a mixture of two diastereomers in solution. It reacts with various Lewis bases L to form the monomers Ru(t7 77 -CioHi6)Cl2L and it shows catalytic activity in ROMP polymerization. ... 

Compounds with a high HOMO and LUMO (Figure 5.5c) tend to be stable to selfreaction but are chemically reactive as Lewis bases and nucleophiles. The higher the HOMO, the more reactive. Carbanions, with HOMO near a, are the most powerful bases and nucleophiles, followed by amides and alkoxides. The neutral nitrogen (amines, heteroaromatics) and oxygen bases (water, alcohols, ethers, and carbonyls) will only react with relatively strong Lewis acids. Extensive tabulations of gas-phase basicities or proton affinities (i.e., —AG° of protonation) exist [109, 110]. These will be discussed in subsequent chapters. 

Just as ammonia, NHif is a weak Lewi. base, there is a large group of nitrogen-containing organic compounds that behaves like weak bases and is known as ... 

B is correct. Amines (—NH2) behave as weak Lewis bases and are most similar to ammonia (NH3). A Lewis base is any species that can donate a pair of electrons and form a coordinate covalent bond. Amides contain a carbonyl carbon and therefore are not similar to ammonia. Ether and ethanol are not nitrogen-containing compounds. 

The chemistry and physical properties of various -triazines are summarized in Tables A1 and A2 of the Appendix. The triazines are Lewis bases as the ring nitrogen (N) atoms may donate electron pairs for the formation of covalent bonds. In aqueous systems, triazines exist as either neutral or protonated (cationic) forms depending on the pKa of the compound and the pH of the system. The most basic ring N and the most likely site of protonation are located in the 5 position between the electron-rich alkylamino side chains (Figure 21.1). 

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