Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Aryl-(4-arylimino-4H-pyrido[1,2-a]pyrazine-3-yl)amines-Synthesis, Complex Formation with Molybdenum(0) and OxygenationThe synthesis of p-tolyl(4-p-tolylimino-4H-pyrido [1,2-a]pyrazine-3-yl)amine 8 (TTPPA) is achieved by the reaction of 2-pyridylmethylamine with oxalic acid bis(p-tolylimidoyl)chloride. The ion-pair [Na(THF)3][(TTPPAH)Mo(CO)4] 4 is obtained by the reaction of the NH-acidic compound 8 with sodium bis(trimethylsilyl)amide and (nor)Mo(CO)4 (nor = norbornadiene) dissolved in THF. The bidentate ligand anion TTPPA-H is related to the 1,4-diazadienes, but its n-donor effect is dominating. Its trans-influence results in different Mo-CO-bond lengths of 4 : 1.901 and 1.951 Å (trans-positions); 2.003 and 2.031 Å (cis-positions). In the cationic part of 4 the sodium is five-coordinate (distorted tetragonal pyramidal structure). Donor atoms are the three THF, N3 of TTPPA-H, and the oxygen atom of one CO of the moiety Mo(CO)4.8 is oxygenated by hydrogen peroxide or by dioxygen on heating. In the course of a ring transformation of the 6-membered pyrazine to the 5-membered imidazole cycle 3-p-tolyl-5-p-tolylimino-2-pyridine-2-yl-2,3-dihydro-imidazol-4-one 9 is formed. In THF two isomers 9 and 9a are observed in a molar ratio of about 1:1.4 and 9 have been characterized by single crystal x-ray diffraction.
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