Diphosphanyl- and Diarsanyl-Suhstituted Carbene Homologues: Germanediyls, Stannanediyls, and Piumbanediyis with Remarkable Electronic Structures

摘要

Compounds with multiple bonds (pi-electron systems) and subvalem compounds (carbene analogues) of the heavy main group elements (period > 3) differ fundamentally from those of the elements of the second period with respect to then electronic slructure. This is illustrated impressively, to: example, by car-bene homologues which, in contrast to methanediyll, have a singlet ground state (S_0). The synthesis of thermally stable compounds of the form :EX_2 with eta~1-bound liganda X (ger-manediyls, stannanediyls, and plumbanediyls) has enabled extensive preparative and theoretical investigations. The focus of these studies has been the influence ot the electronic-structure (singlet triplet (S T) separation) on the reactivity (dimerization and cycloaddition behavior). The results have demonstrated that the carbene homoiogues are monomenc and show no tendency to oligimerize when they have a relatively large S T separation and the ligands X are particularly bulky and or function as intramolecular donor centers.