Trimethylamine metal complexes

A series of metal complexes containing trimethylamine boranecarboxylato ionligand [103904-11-6], (CH3)3N BH COO, have been prepared with Co (III), Co (II), Zn(II), Ca(II), Cr(III), and Fe(III) (39,40). This ligand, derived from the boron analogue of the amino acid glycine, behaves similady to organic carboxylato ligands. 

The first class of reactions, direct transfer of an oxygen atom from the oxidant to carbon monoxide, has not been commonly observed as a reaction catalyzed by metal complexes in solution. One example, derived from a preparative procedure developed to substitute carbonyls with other ligands (90), is the reaction of trimethylamine oxide, Me3NO, with carbonyl clusters such as Os3(CO)12 in the presence of excess CO. The net reaction is shown as (27). 

Although trimethylamine should form more stable metal complexes than ammonia, steric repulsion between methyl groups becomes important when there is more than one trimethylamine coordinated to a metal ion. Comparatively, ethylenediamine does not show this steric repulsion although the alkylation of the nitrogens by the ethylene bridge is nearly as great as would be the case for two methylamines. Thus the formation of an ethylene bridge is sterically efficient. 

The strength of the metal-amide bond in yttrium complex 57 (Scheme 6.6) allowed Arnold et al. to monitor the reactivity of the NHC-metal bond via Jyc coupling in NMR. Triphenylphosphane or trimethylamine A-oxide did not displace the carbene, showing again that the NHC moiety has stronger donating properties than most other donors. Only tmeda and triphenylphosphane oxide successfully dissociated the carbene to form the corresponding metal complexes with pendant NHCs. 

Bitumen Ionomers. Moisture-resistant asphalts (qv) have been prepared by reaction of metal oxides with acid-functionalized bitumens (75). Maleic anhydride or sulfur trioxide/trimethylamine complexes have been used successfully for introduction of acid groups into asphaltic bitumens. 

Its molecular structure (Figure 37) consists of a centrosymmetric dimer with a bridging H2Al(OR)( U-OR)2Al(OR)H2 entity. The Ta atoms are approximately square pyramidal, with the four phosphorus atoms forming the basal plane (Ta lies 0.64 A out of it). The relatively short Ta—A1 distances are comparable to those found in other transition metal aluminum complexes (Ta—Al 2.79-3.13 A). The hydrogen atoms have not been located, but were evidenced by chemical and spectroscopic techniques (IR 1605, 1540 cm 1 HNMR 16.30p.p.m.). The Ta—(ju-H2)A1 unit is relatively stable, and (54) is inert to carbon monoxide or trimethylamine. It is a poor catalyst in the isomerization of 1-pentene. Formation of complexes analogous to (54) may explain the low yields often obtained from alkoxoaluminohy-drides and metal halides. 

The residue from sublimation of the complex with dioxane is explosive, and the complex should not be dried by heating. The trimethylamine complex may also explode on sublimation [1]. Triethynylaluminium or its complex with diethyl ether may decompose explosively on heating. Sublimation is not therefore advised as a purification method [2]. See other METAL ACETYLIDES... 

As a first approximation, the reactions of pyridines with electrophiles can be compared with those of trimethylamine and benzene. Thus, pyridine reacts easily at the nitrogen atom with reagents such as proton acids, Lewis acids, metal ions, and reactive halides to form salts, coordination compounds, complexes, and quaternary salts, respectively. Under much more vigorous conditions it reacts at ring carbons to form C-substitution products in nitration, sulfonation, and halogenation reactions. 

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