Other Organo-Metallic Compounds

According to Vobecky et al. [88], the triphenyl derivatives of antimony, bismuth, phosphorus and arsenic and also ditolyl-teUurium isomers can be separated on alumina layers using petrol ether (hR/-values of the first two, 69 and 62 respectively). They may be visualised by spraying with permanganate solution. 

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Reaction of metal salts with other (organo)metallic compounds ... 

The mechanism of initiation of anionic polymerization of vinyl monomers with alkyllithium compotmds and other organo-metallic compounds is complicated by association and cross-association phenomena in hydrocarbon solvents and by the presence of a variety of ionic spedes in polar media. ° The kinetics of initiation are complicated by competing propagation and the occurrence of cross-association of the alkyllithium initiator with the propagating organolithium. Thus, only the initial rates provide reliable kinetic data. 

Organo-metallic compounds, on the other hand, behave very much like organic compounds, e.g. they can be redistilled and may be soluble in organic solvents. A note of caution should be made about handling organo-metallic compounds, e.g. arsines, because of their potential toxicities, particularly when they are volatile. Generally the suppliers of such compounds provide details about their safe manipulation. These should be read carefully and adhered to closely. If in any doubt always assume that the materials are lethal and treat them with utmost care. The same safety precautions about the handling of substances as stated in Chapter 4 should be followed here (see Chapter 1). 

Supported oxide catalysts were discovered at the same time (8-5) as the two-component Ziegler-Natta catalysts (6, 7) in the early 1950 s. The publications on other types of one-component catalysts [supported organo-metallic compounds of transition elements (8, 9, 9a) and titanium dichloride (10) ] appeared quite recently. 

Some examples of specific electron-capture by various organo-metallic compounds in such solvents are summarised in reactions [5]-[10] [refs. (5)-(H)) respectively]. In some cases, the parent anion ( AB ) is detected by e.s.r. spectroscopy, but in others subsequent reactions have occurred. 

It is worth noting that in some cases adducts may be prepared by routes other than those leading directly to adduct formation. Thus Fraenkel and his co-workers139,140 obtained 4,4-dialkyl-substituted adducts from l-ethoxycarbonyI-4,4-dialkyl-l, 4-dihydropyridines by reaction with organo-metallic compounds, R M (M = Li, Na, K, MgX), according to Scheme 7. The NMR spectra of these adducts consisted of an AB system (J = 6.5-8.0 Hz). The chemical shift values were similar (Table XV) to those reported... 

In certain cases it has been shown that the rate of reaction of the a-haloalkyl derivative with a second reagent, such as an olefin or diazoalkane, is dependent upon the concentrations of both reactants (Blanchard and Simmons, 1964 Bethell and Brown, 1967). Such observations are consistent either with a one-step bimolecular reaction of the organo-metallic compound as such and the other reagent or with a rapid preequilibrium forming an intermediate, followed by a slow reaction of this intermediate with the second reactant. The latter alternative is represented in equation (14), in which b[olefin]Rate-determining reaction of an intermediate carbene... 

Structure optimization of main group molecules with generic force fields has the same advantages and problems as similar calculations of organic and organo-metallic compounds on one hand there is no need to fit a specialist force field, on the other is the expectation of lower accuracy[89,126]. The structural results are especially poor for molecules where electronic effects are important, e.g., those with hypervalent or dative bonds. An exception to this is the VALBOND force field which generally leads to excellent results (see above) [78,81l... 

The family of photoreducible dyes (e.g, acridinium, xanthene, thiazinium among other classes of dyes) produce excited states of essentially quinoidal structures which can act as efficient acceptors of electrons. Amines [59], sulfur compounds, especially sulfmate salts [60], heterocycles of low ionization potential [61], alkylcarboxylates and stable enolate anions [62], and several classes of organo-metallic compounds, notably allylic and benzylic organostannanes [63], represent classes of compounds which have proved efficacious as coinitiators in electron transfer sensitization with these dyes. Electron transfer with the organometallics was unambiguously established in a series of model studies involving electron acceptors of the anthracene class [64],... 

OTHER METHODS OF DETERMINING HEATS OF FORMATION 7.2.v5. Organo-metallic Compounds... 

However, the recent increase in literature has somewhat reduced the general utility of this series. To supplement this publication, the Society undertook to prepare a series of Specialist Reports (B6), and among the first of these to appear was Spectroscopic Properties of Inorganic and Organo-metallic Compounds, three volumes of which have now appeared. Other... 

Still one more class of alkyl derivatives should be mentioned in this part of our study. These are compounds of the alkyl radicals with metals, and are known in general as organo-metallic compounds. A large number of metals form compounds of this kind, and the ease of formation seems to have a definite relation to the position of the metal in the periodic system. Compounds of the alkali metals with organic radicals have not been isolated, but they probably exist as intermediate products and also as double compounds with other metallic alkyl compounds. The two groups of these compounds which we shall briefly consider are those of zinc and magnesium. 

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