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Ion Pairing and Cyclization on Coordinatively Bound Oxalamidines The tetraphenyloxalamidine ligand of complex 8a reacts easily in the presence of bases with elementorganic dichlorides (R2MCl2) to form coordinated metalacycles. The cyclization with phosgene gives the (CO)4Mo-coordinated 1,3-diphenyl-4,5-bis(phenylimino)-2-imidazolidinones 10. In contrast to the reaction forming the piperazine derivative 2, the reaction of 8a with oxalyl chloride also proceeds to 10 by decarbonylation. The product of this cyclization, (CO)4Mo(OCTPOA) (10), and two possible intermediates, the dinuclear sodium salts Na2(THF)8[(CO)4Mo(HTPOA)]2 (11a) and Na(THF)4[(CO)4Mo(EtO2COCTTOA)]2 (15) have been characterized by X-ray analyses. 11a contains the coordinated oxalaminate anion. The structure of the ionic complex 15 shows the simultaneous attack at both sp3-hybridized nitrogen atoms and the selective formation of the five-membered 2-imidazolidinone heterocycle by coordination of the oxalamidine. Both sodium complexes 11a and 15 are dimeric and centrosymmetric ion pairs. Complex 11a contains two CONaOC bridges while compound 15 has a central [Na2O2] four-membered ring consisting of sodium alcoholate bridges. |
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