Organometallic compounds shifts 293

Many organometallic compounds are best prepared by this reaction, which involves replacement of a metal in an organometallic compound by another metal. The compound RM can be successfully prepared only when M is above M in the electromotive series, unless some other way is found to shift the equilibrium. That is, RM is usually an unreactive compound and M is a metal more active than M. Most often, RM is R2Hg, since mercury alkyls are easy to prepare and mercury is far down in the electromotive series." Alkyls of Li, Na, K, Be, Mg, Al, Ga, Zn, Cd, Te, Sn, and so on have been prepared this way. An important advantage of this method over 12-36 is that it ensures that the organometallic compound will be prepared free of any possible halide. This method can be used for the isolation of solid sodium and potassium alkyls." If the metals lie too close together in the series, it may not be... 

C NMR Chemical Shifts and Coupling Constants of Organometallic Compounds, 12, 135... 

Equations 10 and 11 indicate that the redox potential of the HQ/BQ couple is shifted in the negative direction when ti6-chemisorbed but shifted in the positive direction when 2,3-ti2-bonded. This orientation-dependent shift in redox potential is not unexpected by analogy with molecular organometallic compounds. For example, the redox potential for the reversible, one-electron reduction of duroquinone in acetonitrile is shifted from -0.90 V (vs. SCE) to -0.69 V in bis (duroquinone) Ni (0) and to -1.45 V in (1,5 — cyclooctadiene) (duroquinone)Ni (0) (22.) ... 

The usual carbon-) 3 chemical shift range of organic compounds ( 250 ppm) considerably expands in organometallic compounds. Paramagnetic metals in metallocenes (Table 4.72) induce particularly large 13C shift values [476]. 

Chiral Metal Atoms in Optically Active Organo-Transition-Metal Compounds, 18, 151 13C NMR Chemical Shifts and Coupling Constants of Organometallic Compounds, 12, 135 Compounds Derived from Alkynes and Carbonyl Complexes of Cobalt, 12, 323 Conjugate Addition of Grignard Reagents to Aromatic Systems, I, 221 Coordination of Unsaturated Molecules to Transition Metals, 14, 33 Cyclobutadiene Metal Complexes, 4, 95 Cyclopentadienyl Metal Compounds, 2, 365... 

Lamansky S, Thompson ME, Adamovich V, Djurovich PI, Adachi C, Baldo MA, Forrest SR, Kwong R (2005) Organometallic compounds and emission-shifting organic electrophosphorescence. US Patent 6939 624... 

The high sensitivity of the chemical shifts of 73Ge,119Sn and 207Pb to substituent effects calls for a detailed study of the resonance interactions in these organometallic compounds. 

Ge chemical shifts of selected organometallic compounds are given in Table 2. 

TABLE 2. 73Ge Chemical Shifts of Organometallic Compounds... 

TABLE 16. 207Pb chemical shifts of organometallic compounds... 

Fig. 16.17. Mechanism of the carbocupration of acetylene (R = H) or terminal alkynes (R H) with a saturated Gilman cuprate. The unsaturated Gilman cuprate I is obtained via the cuprolithiation product E and the resulting carbolithiation product F in several steps—and stereoselectively. Iodolysis of I leads to the formation of the iodoalkenes J with complete retention of configuration. Note The last step but one in this figure does not only afford I, but again the initial Gilman cuprate A B, too. The latter reenters the reaction chain "at the top" so that in the end the entire saturated (and more reactive) initial cuprate is incorporated into the unsaturated (and less reactive) cuprate (I). - Caution The organometallic compounds depicted here contain two-electron, multi-center bonds. Other than in "normal" cases, i.e., those with two-electron, two-center bonds, the lines cannot be automatically equated with the number of electron pairs. This is why only three electron shift arrows can be used to illustrate the reaction process. The fourth red arrow—in boldface— is not an electron shift arrow, but only indicates the site where the lithium atom binds next.

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