Bis-THF structures

Model compounds of bis-THF structure prepared for NMR correlation studies observation that H NMR shifts of acetate methyl groups correlate with relative configuration of C(15)/C(16) and C(23)/C(24) in uvaricin (later proven to be correct). 

Addition of anhydrous LiX (X = OH, Cl, Br, 1) to Li[Bu"C(NBu%] in THF afforded laddered aggregates in which two neutral lithium amidinates chelate one LiX unit. When the added salt is Lil, the monomeric laddered aggregate is isolated as a bis-THF adduct. In the case of LiOH, LiCl, and LiBr, the ladders dimerize about their external LiX edges. This process is highlighted in Scheme 10 for LiOH. The molecular structure of the resulting dimeric ladder complex is depicted in Figure 2. °... 

Dihydro-9,10-dialaanthracene derivatives have also been reported. As shown by Bickelhaupt, the reaction of ort/io-phenylenemagnesium 41 with MeAl-CI2 leads to the formation of 9,10-dimethyl-9,10-dihydro-9,10-dialaanthracene as a bis(THF) adduct (42, Scheme 17). When taken out of solution, crystals of this adduct proved unstable toward THF loss so that the crystal structure could not be determined. 

For polyurethane production, Donnelly [109] has carried out the synthesis of copolyurethanes based on mixtures of commercial poly(THF diol)s with glucose. Complex products resulted, which can be represented by mono- or bis(glucoside) structures. From a variety of polyol blends, solid polyurethanes were prepared which ranged from linear, soluble, weak elastomers to polymers of higher transition temperature and stiffness, low solubility, and low extension under tensile load [110]. 

An X-ray crystal structure determination of the bis(thf) adduct of this macrocycle revealed an approximately planar ring of dimensions ca. 12 x 7 A with the thf guests each chelated by two Hg atoms. No structural results relating to the anion-binding properties of these macrocycles have yet been reported. ... 

Bis(indenyl)magnesium has a polymeric strucmre in the solid state, the details of which have been discussed in a previous section. When it is recrystaUized from THF, a discrete monomeric bis-THF adduct, indenyl2Mg(THF)2 (128), is obtained . An X-ray crystal-structure determination shows that the magnesium atom has one relatively short bond [2.256(3) A] with C(l) of each of the indenyl groups, but also interactions with the two adjacent carbon atoms at a much longer distance [Mg-C 2.723(3) and 2.738(3)]. This bonding mode was described as intermediate between r and rf. 

Fig 5. Solid-state structure of the bis-THF adduct of 1,2-C6F4[B(C12F8)]2. 

Finally, two other types of n coordination to sodium documented by crystal structure data will be mentioned. rc-Type bonding interactions between bis(THF)sodium units and the benzene rings of complex aluminate anions derived from naphthalene or anthracene have been found in the compounds [Na(THF)2]2[Me2AlC10H8]2 and [Na(THF)2]2[Me2AlC14H10]2 (46). Even more complex coordination patterns between sodium, transition metals, and n systems have been reported by Jonas and Kruger (5). 

The organometallic chemistry of scandium is generally similar to that of the later lanthanides. It thus forms a cyclopentadienyl ScCps that has mixed mono- and pentahapto-coordination like LuCps. An anionic methyl [Li(tmed)]3[M(CH3)6] is formed by scandium, as by the lanthanides. However, there are often subtle differences that should be borne in mind. The pentamethylcyclopentadienyl compound [ScCp 2Me] is a monomer but the lutetium compound is an asymmetric dimer [Cp 2Lu(/u.-Me)LuCp 2Me]. Similarly, whilst triphenylscandium is obtained as a bis(thf) adduct, [ScPh3(thf)2], which has a TBPY structure with axial thf molecules, the later lanthanides form octahedral [LnPh3(thf)3]. Triphenylscandium and the phenyls of the later lanthanides are made by different routes. 

Compound (97) crystallized as a dimeric, bis-THF-solvated adduct with two different types of lithium atoms, illustrated as (99). ° Compound (98) is a doubly lithium bridged dimer chelated with one TMEDA per lithium atom and roughly depicted as (1(H)).In the solid state, the sodium anion of (101) is monomeric with some of the relevant structural parameters shown in formula (102). ... 

In this latter structure, roughly depicted as (154), there are two different lithium atoms as well as two different anion residues. In one of the residues a lithium is -coordinated and in the other residue the lithium is T) -coordinated. Hie possible origins of the selectivity of the alkylations of the metallated hydiazones are discussed relative to this structure. Hie lithiated hydrazone enolate (155) prepared from (S)-(-)-l-amino-2-(methoxymethyl)pyrrolidine (SAMP) hydrazone of 2-acetylnaphthalene (156) yields the monomeric bis-THF-solvated species (157) as ruby red crystals. Hiis is one of the few examples of the crystallization of a resolved enolate substrate. ... 

The sodium salt of the stabilized enolate derived from the heteroaryl-substituted 2-oxoglutaric acid ester (186) is reported to have the alkene geometry as shown in formula (187). Hnally, Collum et al. have reported the structure of the lithiated anion derived from the A, A -dimethylhydrazone of 2-methoxy-carbonylcyclohexanone (188). This enolate crystallizes as the dimeric, bis-THF-solvated aggregate (189). 

Excluding the a-P-, a-Si-substituted carbanions which are listed in Table 2, there exist relatively few simple a-P-substituted carbanions whose structures are known. References to the crystal structures of some tri (alkyl or aryl) substituted phosphines are listed in Table 4. Few if any of these compounds have been utilized as synthetic reagents. Only two synthetically useful phosphorus-stabilized carbanions of Group la or Ila metal cations have been examined by X-ray diffraction analysis. Hie lithium carbanion of 2-benzyl-2-oxo-l,3,2-diazaphosphorinane (198) crystallizes as a monomeric bis-THF solvate (199) with a tricoordinate lithium atom. The magnesium salt of diethoxyphosphinyl acetone (200) is cluirac-terized as an intramolecularly chelated trimer similar in structure to [Mg(acac)]3. The Cu salt of this 3-keto phosphorus-stabilized anion exists only as a monomer. 

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