SOME NEW CONCEPTS IN THE CHEMISTRY OF THE P-BLOCK ELEMENTS

Of all elements in the Periodic Table, the chemistry of the First Row Elements of the p-block (i.e. boron to fluorine) is known to follow classical rules of bonding most closely, and it was for these elements that e.g. the Octet Rule (Lewis) and standard coordination numbers and geometries (Van't Hoff, Le Bel) have first been proposed. Only in extreme electron-deficient situations the traditional electron count had to be reconsidered to account for special types of molecular or solid state structures. Recent work has shown, however, that hypercoordination of small First Row Elements can also be detected in simple compounds with the very heavy Late Transition Elements. Though being isolobal analogues of transient species like CH5+, CH62+, NH52+, (PH2+, PH63+), or OH42+, these complexes show stunning stability. The results of detailed spectroscopic investigations and structural work, together with a thorough theoretical treatment including relativistic effects, not only allow a consistent account of the data accumulated to date, but lead also to predictions regarding other novel species.