Tetramers molecular structure

Figure 4.17 Crystal and molecular structure of (LiMe)4 showing (a) the unit cell of lithium methyl, (b) the LijCj skeleton of the tetramer viewed approximately along one of the threefold axes, (c) the 7-coordinate environment of each C atom, and (d) the (4 -I- 3 -I- 3)-coordinate environment of each Li atom. After ref. 93, modified to include Li—H contacts.

Jackman and Szeverenyi were the first to systematically correlate the quadrupoiar interaction with molecular structure, i.e. with the aggregation of lithium enolates ". They noted that a tetrameric aggregate had a smaller QSC than a dimeric aggregate, ca 135 kHz compared to an estimate of 230 kHz for the dimer. The QSC of the tetramer was shown to be of the same magnitude in three different ethereal solvents. 

The brief account in this section is based mainly on Ref. 20 but also Ref. 19, having 78 and 47 literature citations, respectively, the majority being from the groups of West and Gehrhus/Lappert. Molecular structures were established by electron diffraction for 2 and X-ray diffraction for 3 and 4. In solution, 4 was in dynamic equilibrium. Equation (9.2) the tetramer 7 was X-ray-characterised. 

Fig. 14. Molecular structure of the complexed iminolithium tetramer, (PI12C—NLipy-ridine)4 (7).

It is exceedingly difficult to determine the molecular structure of a synthetic macromolecule. X-ray diffraction—the ultimate structural tool for small-molecule studies—yields only limited information for most synthetic high polymers, and crucial data about bond lengths and bond angles are difficult to obtain.47 However, that same information can be obtained relatively easily from single crystal X-ray diffraction studies of cyclic trimers, tetramers, and short-chain linear phosphazene oligomers. The information obtained may then be used to help solve the structures of the high polymeric counterparts. 

Molecular structure of (a) methyllithium tetramer (Li4Me4) (H atoms have been omitted) and (b) vinyllithium-THF tetramer (LiHC=CH2-THF)4 (THF ligands have been omitted). 

Higuchi, T., and A. Shimada The Crystal and Molecular Structure of the Dehydrated Tetramer of 1,2-Dimethyldisilantetraol, (CH3)8Si3Os. Bull, chem. Soc. Japan 39, 1316—1322 (1966). 

Figure 5 Molecular structure of phenyltellurium iodide 11 tetramer.17...

Figure 21-5. The molecular structure of tetramers GCAT and GCXT (X = stable abasic site) (Figure 1 of ref. [26]. Reprinted with permission. Copyright 2004 by the American Physical Society.)...

Janczak, J. and Kubiak, R. (1992). Crystal and molecular structures of metal-free phthalocyanines, 1,2-dicyanobenzene tetramers. II. a Form. J. Alloys Compd, 190, 121. [270]... 

Figure 7.12. Molecular structure of a hairpin pyrrole-imidazole tetramer.

Platinum(V) fluoride is a tetramer (structurally like 22.5) PtFg is a red solid and has a molecular structure consisting of octahedral molecules neutron powder diffraction data confirm little deviation from an ideal octahedral structure. The hexafluoride is a very powerful oxidizing agent (equation 22.127, and see Section 5.16) and attacks glass. The oxidizing power of the second row rZ-block hexafluorides... 

The reaction between AuC " and dithioacetic acid gives the tetramer [Au(S2CMe)]4. The molecular structure consists of a square of gold atoms with the dithioacetato ligands bridging above and below the AU4 plane as shown in (7). 

Constable, E.C. Eeese. T.A. Tocher, D.A. Polynuclear 7E intermediates in the synthesis of cyclometallated complexes and molecular structure of (2-pyridylphenyl)mer-cury(II) chloride tetramer. J. Chem. Soc., Dalton Trans. 

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