Phenyllithium complexes structure

With the aim to obtain additional benchmark values, a larger number of substituted phenyllithium complexes with known solid state structures were included in this study . They range from monomers of different solvation, over dimers and one trimer to different tetramers. The investigated aryl systems are shown in Scheme 2 and the obtained x values are reported in Table 7. 

Wittig l56) and Waack 157) showed ebullioscopically and osmometrically, respectively, that phenyllithium is a dimer in etheral solvents. Thonnes and Weiss, 58) found a TMEDA complexed phenyllithium dimer in the solid state, and calculations performed by Schleyer et al. 159) similarly showed the dimer to be the most stable species. The 13C nmr spectrum of phenyl-6Li in THF shows a quintuplet at —118 °C which also reveals a dimeric aggregate l49,160). Thus experimental investigations of the structure in solution and in the solid state as well as a theoretical study (corresponding to the situation in the gas-phase) lead remarkably to the same result a phenyllithium dimer structure seems to be the most stable one. 

The results from reactions with phenyllithium and phenylsodium indicated that the phosphorus-derived organophosphides were of complex structure (6). The alkyl halide reactions demonstrated the presence of structural units having two phenyl groups bonded to phosphorus, yet only small yields of diphenylphosphine were obtained on hydrolysis. Lithium diphenylphosphide was thus ruled out as an important intermediate, since it hydrolyzes cleanly to diphenylphosphine. Moreover, hydrolysis of the organophosphide from plienylsodium and phosphorus failed to give simple phosphine products at all, but reaction of the sodium... 

Fig. 10.3. The structures of alkyllithium compounds in solution II contact ion pairs, solvent-separated ion pairs or lithium at-complexes. In THF solution sec- and tert-BuLi are present as contact ion pairs in the same way as phenyllithium (A) or (2,6-diisopropylphenyl) lithium (D) are.

There are several recent methods for the reduction of azobenzene to hydrazobenzene in near-quantitative yield. Samarium(II) iodide reduces azobenzene to hydrazobenzene rapidly at room temperature. Hydrogen telluride, generated in situ from aluminum telluride and water, reduces both azobenzene and azoxybenzene to hydrazobenzene a mixture of phenyllithium and tellurium powder has been used to reduce azobenzene. A complex of the coenzyme dihydrolipoamide and iron(II) is also effective for the reduction of azo- and azoxy-benzene to hydrazobenzene the reduction probably involves coordination of the azobenzene to iron(II) as shown in structure (1). Electrochemical reduction has been used to prepare a number of hydrazobenzenes from the corresponding azobenzenes. In the presence of an acylating agent a diacylhydrazine (e.g. the pyridazinedione derivative 2) can be isolated from the electrochemical reduction of azobenzene. 

TT-Allyl compounds are also readily formed via the interaction of more complex polymeric systems. Thus, the cyclic polyene cyclododeca-1,5,9-triene (104) with Ru3(CO),2 gives a good yield (70%) of the ir-allyl species shown in Fig. 14a. This structure is closely related to a complex obtained by Fischer et al. (105) by reaction of phenyllithium with Ru3(CO),2 (Fig. 14b). 

Molecular design and precision synthesis of silicon-containing polymers are described. Polymerizations of substituted silacyclobutanes by phenyllithium and platinum complexes gave poly(carbosilane)s of head to tail regular structure. However, extensive chain transfer seems to have occurred in the polymerization by platinum complexes. 

A number of solid complexes of various organolithium compounds with various bases have been reported, e.g., C4H9Li-S(CH3)2 (56) [( 113)3 CLi]2 THF (55) 9-fluorenyllithium dietherate, a yellow solid (57) phenyllithium dioxanate, a colorless solid of formula 2C(HsLi 3C4Hg02 (58). The structures of none of these compounds are known, but they serve as examples to establish that the alkyllithium compounds do behave as Lewis acids toward n-type bases. 

An intramolecular cyclisation occurs when [Ru(n -C5H5)(CO)2(CH2-2-Br-C(5H4)] is o-deprotonated with butyllithiura followed by electrophilic attack by a tiimethyloxonium salt The metallaindene complex produced, [Ru(Ti -C5H5)(CO)(=C OMe)C6H4CH2-K-C,C,)], reacts with phenyllithium and trimethylsilyl triflate to produce [Ru(Ti5-C5H5)(CO)(=4r Ph)C6H4CH2-K-C,C,)] which was structurally characterised. 212... 

Crystal structures of ethylmagnesium bromide Crystal structure of tetrameric phenyllithium etherate Representation of tt bonding in alkene-transition-metal complexes Mechanisms for addition of singlet and triplet carbenes to alkenes Frontier orbital interpretation of radical substituent effects Chain mechanism for radical addition reactions mediated by trialkylstannyl radicals... 

The simple structures of THF-solvated 2,6-di(l-naphthyl)phenyllithium and 2,6-di(phenyl)phenyhithium have been reported to be respectively mono- and dinuclear. The solid-state structure of (DME Li)2C4(SiMc3)4 has recently been found to incorporate DME-chelated metal centres above and below a four-membered, flat cyclobutadienyl ring (within which mean O-C = 1.495 A). A similar structure has also been revealed for (DME Li)2C4Ph2(SiMe2CH2)2. The two electron reduction of 2,3-bis(dimethylsilyl)-l,l,4,4-tetramethyl-l,4-disila-1,4-dihydronaphthalene using elemental lithium affords a complex in which the two metal centres bridge an isolated C = C bond. In the same way, alkali metal ions reside above and below each of two C=C interactions in the tetrametal salt which results from the treatment of 2,3,6,7-tetrakis(trimethylsilyl)-l,l,4,4,5,5,8,8-octamethyl-1,4,5,8-tetrasila- 1,4,5,8-tetrahydroanthracene with Li(0). ... 

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