RESUMO
Diaminocarbocations (or amidinium salts) feature a three-center 4pi electron system with an open planar structure. Their 2pi electron three-membered cyclic valence isomers, in which the carbon atom bears a negative charge, are predicted to be about 541 kilojoules per mole higher in energy than the open form. This isomer has not been identified yet. In contrast, the attempted synthesis of a diphosphorus analog of amidinium salts leads to the cyclic carbanionic form. There is no precedent for such a transformation of a carbocationic center into a carbanionic center, but with the help of heavier main-group elements, numerous examples can be imagined. This approach will enable the preparation of many unknown structural moieties that are difficult or even impossible to access in the corresponding carbon and nitrogen series.
RESUMO
The reactivity of the formyl group in alpha-phosphorus-substituted aldehydes 1 can be tuned by adjusting the coordination number of the phosphorus atom. When X is a lone pair, the formylphosphanes obtained are stable compounds, whereas when X=O a relatively unstable formylphosphane oxide is produced. R=iPr(2)N, cHex(2)N.
RESUMO
As expected for a singlet carbene, the stable phosphanylsilylcarbene 1 possesses an accessible vacant orbital, as shown by reactions with Lewis bases such as phosphanes and a bimetallic complex containing a side-on-coordinated full blockC:full blockP identical withPfull blockC:full block moiety (see the reaction scheme). R=cHex(2)N.
RESUMO
A tetraphosphabenzene analog of the postulated anti-tricyclohexylene, a singlet biradical valence isomer of benzene, has been isolated. The tricyclic derivative features one-electron phosphorus-phosphorus bonds, which result from the pi*-pi* interaction between two diphosphirenyl radicals. Such one-electron bonds may play a wider role in phosphorus chemistry.
