Aluminates, dimerization

A penta-co-ordinated aluminate dimer x-ray crystal structure, M.C. 

Hydrocarbon resins based on CPD are used heavily in the adhesive and road marking industries derivatives of these resins are used in the production of printing inks. These resins may be produced catalyticaHy using typical carbocationic polymerization techniques, but the large majority of these resins are synthesized under thermal polymerization conditions. The rate constants for the Diels-Alder based dimerization of CPD to DCPD are weU known (49). The abiHty to polymerize without Lewis acid catalysis reduces the amount of aluminous water or other catalyst effluents/emissions that must be addressed from an environmental standpoint. Both thermal and catalyticaHy polymerized DCPD/CPD-based resins contain a high degree of unsaturation. Therefore, many of these resins are hydrogenated for certain appHcations. 

Analogously, pyrazolyl-aluminate and -indate ligands have been prepared <75JCS(D)749) and their chelating properties evaluated with cobalt, nickel, copper and zinc. Gallyl derivatives of pyrazoles and indazoles have been extensively studied by Storr and Trotter e.g. 75CJC2944) who determined several X-ray structures of these compounds. These derivatives exist in the solid state as dimers, such as (212) and (288). A NMR study in acetone solution showed the existence of a slow equilibrium between the dimer (212) and two identical tautomers (289) and (290) (Section 4.04.1.5.1) (81JOM(215)157). 

Alkali and alkaline-earth aluminosilicates are insoluble, and Muller et al. (138) resorted to tetramethylammonium (TMA) aluminosilicates to measure 27A1 chemical shifts in aluminosilicate solutions. Solutions with different Si/Al ratios and the pure TMA aluminate solution were studied. The molar ratio TMAOH Si Al varied from 3 0 2 to 9 6 2. Theoretically there are 15 distinct Q"(mSi) units with Q = Al (n 0-4 m 0-n). However, dimeric aluminate anions are found only in very concentrated solutions and even then in very small quantities, which led the authors to suggest that the Loewenstein rule is obeyed in aluminate and aluminosilicate anions. The exclusion of Al—O—Al linkages limits the number of possibilities to five... 

The oxides and the metals also dissolve in alkali bases as well as in acids. The oxides and hydroxides of In and Tl are, by contrast, basic hydrated T1203 is precipitated from solution even at pH 1 to 2.5. The nature of the aluminate and gallate solutions has been much studied by Raman and nmr spectra. The principal species in solution for Al is [Al(OH)4] only where Na+ is the cation is there evidence for species in solution that may be related to solids that crystallize from aluminate solutions. The latter contain dimeric anions with 4-coordinate Al, [(H0)3A10A1(0H)3]2 , and others with octahedral Al3+. 

Led by the efforts of Westerhausen and coworkers, a variety of heavy alkaline earth metal zincates or aluminates under formation of alkaline earth metal-carbon contacts have been prepared. Examples include the reaction of trialkylalanes with donor-free calcium i)fr-amides to afford dimeric aluminates, shown in Figure 30. Noteworthy is the planar Ca2N2 center of this complex, in addition to close calcium-aluminum contacts, which may indicate the presence of three-center, two-electron bonding. 

Auxiliary agents silanes, titanates fatty acids polymer grafting with maleic anliydride to increase interaction," " stearic acid, nucleating agents octamethylcyclotetrasiloxane amino silane dimeric aluminates acrylic acid "... 

The alkinyl group bridges strongly ". Consequently, RjAlCSCR are dimeric and stable. Although the alumination of alkynes (see 5.3.3.5.2) or the reaction between dialkylaluminum halides and metallated alkynes is the preferred method of preparation, disproportionation of R3AI with (R C=C)3A1 in ether can also be used. ... 

The potential of ILs in liquid-liquid biphasic catalysis for the generation of clean technology has became a reality with the announcement of a commercial process for the dimerization of butenes to isooctenes (Difasol process) by IFF (France) based on nickel complexes immobilized in organo-aluminate imidazolium ILs [138]. 

Some silicate species are more reactive than others. McCormick et al. [20] have shown that in a silicate solution containing the monomer, dimer and cyclic trimer, the latter was the most reactive towards Al incorporation. Van den Berg et al. [21] have shown that the D4R anion does not react with aluminate anion at room temperature. Al is only incorporated in the D4R at higher (90 C) temperatures, where a crystalline phase is formed. 

Conversely to the complex behavior of silicate, aluminate-solution is very simple, it consists of monomeric units only and, so far, all attempts to prove the existence of dimers have failed. 

Several aluminates, (RA1H3] [R = Triph,Mes, (Me2PhSi) 30 ] have been reported, the latter dimer containing an eight-membered (AlHLiH>2 ring. ... 

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