The octaamino cryptand, L2, obtained by tetrahydroborate reduction of the [2+3] condensation product of tris(2-ethy1amino)amine with terephthalaldehyde, acts as a host for pairs of protons or first-series transition-metal cations. An X-ray crystallographic structure determination of [ H,L2I4+ reveals a pair of protons held at opposite ends of the molecule by strong intramolecular hydrogen bonding of each proton to two of the amino nitrogen atoms. Pairs of transition-metal cations co-ordinated to the amino N-donors accommodate mono-and tri-atomic bridging ligands, such as OHor imidazolate, generating weak to moderate antiferromagnetic interaction. Dicopper( 11) p-azido complexes have been prepared where the combination of a large zero-field splitting in t h e ESR spectrum and a near Curie-law dependence of -3.84 (t) 360 183 7.&7.5 (m) 8.40 (s) -3.84 (br s) 183 6.67 (s) 3.53 (br s) 1.55 (br s) 2.53 (br s) L2 CD,CI, 360 298 6.89 (s, 4 H) 3.67 (s, 4 H) 2.0 (br s, 2 H) 2.65 (t, 4 H) CH4L21CCF3S031, (CD,),SO 400 298 7.45 (s, 4 H) 2.80 (s, 4 H) 8.65 (br s) 4.22 (s, 4 H) [Ag,LZ][CF,S03]2 CD3CN 500 298 7.12 (s, 4 H) 2.78 (4 H) 2.9 (br) 3.78' (4 H) 338 7.12 (s, 4 H) 2.80 (4 H) 2.92 3.78' (4 H) [Cu2LZ][CF3S03], CD3CN 500 338 6.89 (4 H) 2.80 2.90 3.90, 3.65 Chemical shifts 6 relative to SiMe,. Overlapped. Assigned on the basis of comparison with the copper(1) spectrum. 323 7.22 (s) 2.90(br s) --3.97 (s) 298 2.80 (s) 2.85 (m) 3.95 (d), 3.53 (1) H E 2.83 (br s) 3.4, 2.1 (br) 2.65 (br s) 2.81 (t, 4 H) 2.61 (t, 4 H) 2.71 (t) 2.95 3.00 (4 H) 3.28, 2.95 3.35 (br t), 2.95 (d) Table 2 Torsion angles (")in [H,L2][CF,S0,], C( 3 1 )-C( 30)-N( 1 )-C( 10) 128.9 C(3O)-N( 1)-C( 10)-C( 11) C( 3 1 )-C( 30)-N( 1 j C ( 23 *) -58.4 -99.2 C(30)-N( 1 )-C(23*)-C(22*) 167.0 C(ll)--C(lO)-N(l)-C(23*) 175.0 C( 10)-N( l)-C(23*)-C(22*) -66.5 N( 1 )-C( 10)-C( 1 1)-N( 12) C( 1 0)-C( 1 1 )-N( 12)-C( 1 3) C( 1 1 )-N( 12)-C( 13)-C( 14) N(12)-C(13)-C(14)-C(15) C( 13)-C( 14)-C( 15)-C( 16) C( 16)-C( 17)-C(20)-N(2 1) C( 20)-N( 2 1 )-C( 22)-C(23) C( 17)-C(20)-N(21)-C(22) N(21)4'(22)-C(23)-N(l*) N(l)-C(3O)-C(31)-N(32) C( 30)-C(3 1 )-N(32)-C(3 3) C(3 1 )-N(32)-C(33)-C(34) N(32)-C(33)-C(34)-C(35) * Symmetry operation +x , y , 1z.-50.1 -167.3 -172.9 115.7 173.4 -112.4 178.4 -153.2 -66.9 -76.9 178.6 106.9 -49.6 L1 *6H,O 70.2 -118.1 -178.6 2.6 -177.1
2-Phenylethnylpyridine reacted with dimethyl acetylenedicarboxylate (DMAD) in the presence of a proton source such as an alcohol to give indolizines having methoxycarbonyl groups at the 2-or 2,3-positions in high yields.
A hexaimino cryptand L1 has been obtained by condensation of tris(2-aminoethy1)amine with terephthalaldehyde without template. An X-ray crystal structure determination has been carried out on L1-6H,0 and shows a divergent conformation for the macrocycle in which all six imine nitrogen atoms form hydrogen bonds to water molecules positioned outside the macrobicycle. In the presence of Cu' and Ag' a convergent form of the macrocycle which allows encapsulation of a pair of cations is adopted. Tetra-and di-thiocyanato derivatives [M,L'(NCS),(CIO,),] ( x = 2 or 4, y = 2 or 0) have also been prepared with M = Co, Ni or Cu. In these molecules the thiocyanate ligand adopts a terminal rather than bridging mode. Molecular mechanics and molecular dynamics calculations indicate that at least four different conformations of L1 are likely to be found. Conformational preferences of L' have been established in the gas phase, in water and in the presence of metal ions.
THE method described by Blom and Edelhausenl for determining carbon dioxide, involving absorption in acetone or pyridine followed by titration with sodium methoxide in methanolpyridine solution with thymol blue as indicator, has several disadvantages. These include the obnoxious nature of pyridine, the necessity for purifying it before use2 and the inflammability of acetone, particularly since it may be used in the vicinity of combustion furnaces. Moreover, the high proportion of methanol in the titrant interferes with the sharpness of the end-point because of its acidic behaviour in non-aqueous media.Fritz3 has discussed the merits of other compounds, such as formdimethylamide, ethylenediamine and n-butylamine, as solvents for acidic substances in general, and concludes that formdimethylamide is an excellent solvent for many acids and for their sodium and potassium salts, is suitable for use in titrations with visual indicators and is superior to either ethylenediamine or n-butylamine.Fritz and Keen4 have proposed alkaline methoxide in benzenemethanol solution as titrant for acids dissolved in non-aqueous media. The amount of methanol is kept to the minimum required to give a homogeneous solution and, since potassium methoxide requires less methanol for this, it gives sharper end-points than sodium methoxide.It is commercially available of sufficient purity to require no further treatment and is much less inflammable than acetone. The use of potassium methoxide in benzenemethanol as titrant and the replacement of thymol blue by the one-colour indicator, thymolphthalein, has considerably improved the
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