Dilithium

Chirlian, P. M., 1981. Microsoft FORTRAN. Dilithium Press, Beaverton, OR. 

If one of the groups R is Ph or SR, the abstraction of the second proton is much faster. Allenes give the same dilithium compounds as their acetylenic isomers . 

If two equivalents of the reagents are used, disubstitution to ECeC-CH(E)R occurs in most cases, but interestingly the reaction of LiCeCCH(Li)R with an excess of COj gives mainly the allenic dicarboxylic acids. These are probably the result of a rapid isomerization of the primary dilithium salt of the acetylenic diacid during the work-up or during the reaction of the dilithio compound with COj ... 

Aromatic radical anions, such as lithium naphthalene or sodium naphthalene, are efficient difunctional initiators (eqs. 6,7) (3,20,64). However, the necessity of using polar solvents for their formation and use limits their utility for diene polymerization, since the unique abiUty of lithium to provide high 1,4-polydiene microstmcture is lost in polar media (1,33,34,57,63,64). Consequentiy, a significant research challenge has been to discover a hydrocarbon-soluble dilithium initiator which would initiate the polymerization of styrene and diene monomers to form monomodal a, CO-dianionic polymers at rates which are faster or comparable to the rates of polymerization, ie, to form narrow molecular weight distribution polymers (61,65,66). 

The methodology for preparation of hydrocarbon-soluble, dilithium initiators is generally based on the reaction of an aromatic divinyl precursor with two moles of butyUithium. Unfortunately, because of the tendency of organ olithium chain ends in hydrocarbon solution to associate and form electron-deficient dimeric, tetrameric, or hexameric aggregates (see Table 2) (33,38,44,67), attempts to prepare dilithium initiators in hydrocarbon media have generally resulted in the formation of insoluble, three-dimensionally associated species (34,66,68—72). These precipitates are not effective initiators because of their heterogeneous initiation reactions with monomers which tend to result in broader molecular weight distributions > 1.1)... 

Soluble analogues of these difunctional initiators have been prepared either by addition of small amounts of weakly basic additives such as triethylamine (73) or anisole (74) which have relatively minor effects on diene microstmcture (37). Another method to solubilize these initiators is to use a seeding technique, whereby small amounts of diene monomer are added to form a hydrocarbon-soluble, oligomeric dilithium-initiating species (69,75). 

The stoichiometric reaction of y -diisopropenylbenzene [3748-13-8] with two moles of j -butyUithium in the presence of triethylamine has been reported to produce a useful, hydrocarbon-soluble dilithium initiator because of the low ceiling temperature of the monomer (78,79) which is analogous in stmcture to a-methylstyrene however, other studies suggest that oligomerization occurs to form initiators with functionahties higher than two (80). 

Dilithium tetraborate trihydrate, 3H2O or Li20 2B2O2 3H20, has a density of 1.88 g/mL. It crystallines with difficulty from a... 

Dicaesium acetylide Copper(ll) acetylide Dicopper(l) acetylide Silver acetylide Caesium acetylide Potassium acetylide Lithium acetylide Sodium acetylide Rubidium acetylide Lithium acetylide-ammonia Dipotassium acetylide Dilithium acetylide Disodium acetylide Dirubidium acetylide Strontium acetylide Silver trifluoromethylacetylide Sodium methoxyacetylide Sodium ethoxyacetylide... 

More recently, Bhattacharjya and Hortmann have condensed the dilithium salt of 1,3-propanedithiol with 2,5-bischloromethylthiophene at high dilution (aqueous THF). The product (8) shown in Eq. (6.7) was obtained in only 2.5% yield . 

A characteristic reaction of sulfmylimines RNSO is the quantitative addition of R Li reagents to form adducts of the type Li[RNS(R )NR]. ° The structures of these sulfmimidinates are discussed in Section 10.4.4." The reactions of RNSO derivatives with two equivalents of lithium tert-butylamide result in the formation of diazasulfite anions [OSNR(N Bu)] (9.12) (Eq. 9.12)." The dilithium derivatives of these dianions form hexameric thirty-six atom (Lii2Ni206S6) clusters with structures that are dependent on the nature of the R group. 

The dilithium triimidochalcogenites [Ei2 E(N Bu)3 ]2 form dimeric structures in which two pyramidal [E(N Bu)3] dianions are bridged by four lithium cations to form distorted, hexagonal prisms of the type 10.13. A fascinating feature of these cluster systems is the formation of intensely coloured [deep blue (E = S) or green (E = Se)] solutions upon contact with air. The EPR spectra of these solutions (Section 3.4), indicate that one-electron oxidation of 10.13a or 10.13b is accompanied by removal of one Ei" ion from the cluster to give neutral radicals in which the dianion [E(N Bu)3] and the radical monoanion [E(N Bu)3] are bridged by three ions. ... 

Dilithium octaphenyltetraphosphafulvalene with [(i -Cp)Fe(i -],4-Me2C6H4](PFg) gives the 17 -coordinated species 203, which is unstable with respect to oxidants but can be stabilized by reacting with [ rf-nbd)Cr(CO)4] (92AGE1031). The latter affords the chelate complex 204. 

Dilithium phthctlocyanine (PcLi2) can be prepared by the method of Linstead.59 Lithium metal is added to pentan-l-ol and heated to dissolve the metal. Then, the phthalonitrile is added and the mixture is refluxed for some hours. Due to its lability toward water and acid, both have to be excluded during the reaction and purification.79131132... 

Disodium phthalocyanine (PcNa2) can be prepared in the same way as the dilithium compound by reacting sodium pentoxide in pentan-l-ol with phthalonitrile. It is more sensitive towards moisture and even alcohol than the dilithium phthalocyanine and is readily demeta-lated.58... 

Dipotassium phthalocyanine (PcK2) can be prepared analogously to the dilithium compound by refluxing phthalonitrile and potassium pentoxide in pentan-l-ol.58 With additional oxygen-donor ligands (e.g., crown ethers) it forms crystals with the potassium bulging outside of the phthalocyanine ring.133134... 

Calcium phthalocyanine (PcCa) can be prepared by the reaction of calcium oxide with phthalonitrile58 or by the reaction of dilithium phthalocyanine and calcium chloride in ethanol.59... 

Lead(II) phthalocyanine can be prepared by heating lead(II) oxide with the respective phthalonitrile without solvent150-159 or in 1-chloronaphthatene.154 Addition of anhydrous lead(II) acetate to a solution of dilithium phthalocyanine in anhydrous alcohol gives a precipitate of lead phthalocyanine.59 Lead phthalocyanine can also be obtained by electrosynthesis.160... 

Arsenic phthalocyanine (PcAsCl) can be prepared by metal exchange starting from dilithium phthalocyanine and arsenic(lll) chloride in dimethylformamide.163... 

The exchange of lithium in a dililhium phthalocyanine is a useful tool to prepare metal (e.g., zinc) or metal-free phthalocyanines. For this purpose, the dilithium phthalocyanine is prepared by reaction of phthalonitrile and lithium alkoxide in an alcohol, e.g. pentan-l-ol. In most cases, the lithium phthalocyanine is not separated but directly converted into the respective phthalocyanine by treatment with metal salts or, in the case of metal-free phthalocyanine, with acid or water. 

Dilithium phthalocyanines are readily converted to metal-free phthalocyanines on hydrolysis. To prepare 1,8,15,22-tetrasubstituted phthalocyanines 4 the corresponding 3-monosubstituted phthalonitriles 3 have to be used. 

In the preparation of lutetium(III) 2,9,16,23-tetra-ter -butylbis(phthalocyanine) from lutetium(III) acetate, dilithium phthalocyanine and dilithium 2,9,16,23-tetra-terr-butyl-phthalocyaninc in refluxing 1 -chloronaphthalene for one hour, only one of the phthalocyanine moieties carries all of the substituents (yield 20%).185... 

Chloroindium(III) phthalocyanine 16 can be synthesized from dilithium phthalocyanine 15 in 19% yield.432... 

Lu(OAc)j (20 mg, 0.05 mol) was added to a solution of dilithium 2,3-naphthalocyanine (17 72 mg, 0.1 mmol) in quinoline (10 mL), previously deaerated with N2. The refluxing medium was stirred, under Nj, for 3 h. After cooling, the mixture was poured on top of an alumina column (20 g). The purple band, containing 2,3-Nc2Lu (18) associated with quinoline, was rapidly eluted with CH,C12. After complete removal of the solvents, the desired product was obtained as a dark solid yield 38 mg (47%). 

The isomerization of acetylenic oxiranes cis- and trows-91 to allenic ketone 94 has recently been described (Scheme 5.18). It is proposed that the rearrangement proceeds via a dilithium ynenolate [33]. 

Metalated epoxides can react with organometallics to give olefins after elimination of dimetal oxide, a process often referred to as reductive alkylation (Path B, Scheme 5.2). Crandall and Lin first described this reaction in their seminal paper in 1967 treatment of tert-butyloxirane 106 with 3 equiv. of tert-butyllithium, for example, gave trans-di-tert-butylethylene 110 in 64% yield (Scheme 5.23), Stating that this reaction should have some synthetic potential , [36] they proposed a reaction pathway in which tert-butyllithium reacted with a-lithiooxycarbene 108 to generate dianion 109 and thence olefin 110 upon elimination of dilithium oxide. The epoxide has, in effect, acted as a vinyl cation equivalent. 

Small amounts of lithium phenolate or dilithium-2,2 biphenyldiolate, whose anodic decomposition starts at about 3.2 V versus Li and thus before anodic decomposition of the borates begins, prevent the anodic decomposition of benzenediolatoborate anions in PC. The behavior of the solution is then determined by the additive. 

Chiral modification of diorganomagnesium compounds with the dilithium salt oi (S)-l,l -bi-naphthalene-2,2 -diol gave reagents with the empirical formula 30. Good to excellent enantiose-lectivities were observed in addition reactions of aliphatic and aromatic reagents to aromatic aldehydes30,31, however, the selectivities were not satisfactory with allylic, vinylic and acetylenic reagents. 

The organometallic reagent was prepared by adding the diorganomagnesium compound to the dilithium salt of (S)-l,1 -binaph-thalcnc-2.2 -diol, itself prepared by addition of 2 equivalents of BuLi to the chiral diol. b n.r. = not reported. 

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