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The bi-acidic properties of the low-coordinated 2- phosphorus in the stable 1,3-azaphosphole substructure might be strengthened compared to benzazaphospholes by anellation with electron- withdrawing heterocycles. Pyridine-anellated 1,3- azaphospholes without N-bridgehead are not yet known to the best of our knowledge. The unsymmetric bi- charge density distribution in pyrido-anellated heterocycles may lower the kinetic stability and thus increase the reactivity, as indicated by the easier thermal decomposition of pyrido- as compared to benzo-anellated N-heterocyclic silylenes, germylenes and stannylenes. Therefore, the chemistry of electron-withdrawing anellation should be studied by means of pyridine anellation and additionally symmetric electron-withdrawing anellation with a quinoxaline ring. Anellated 1,3-azaphospholes of this type, which should present efficient bi- acceptor ligands, are still unknown to the best of our knowledge in sznthesis, coordination chemical behaviour and finally in catalysis.

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Dr. Adam is a lecturer and researcher in inorg. organometallic chemistry in Chemistry Department, Faculty of Science, Sohag University, Egypt. He got a PhD scholarship form DAAD in Institut für Biochemie, EMA-Universität Greifswald, Germany and obtained his PhD in 2008 under supervision of Prof. Dr. Joachim W. Heinicke.

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