AN AB-INITIO STUDY OF DIARSACYCLOBUTADIENES

Moller-Plesset MP2/6-311G and MP4SDQ/6-311G* calculations have been m ade for the various possible ground state conformers of the simple 1,2 - and 1,3-diarsacyclobutadienes (AsCH)(2), in order to determine their geometries, the nature of the bonding, and the relative stabilities o f different isomers. These calculations revealed some qualitative diff erences between the analogous 1,2- and 1,3-diphosphacyclobutadienes. T he most stable (gas phase) isomeric form of (AsCH)(2) is predicted to be 1,2-diarsatetrahedrane. Additionally, the mono- and di-substituted compounds Bu-t(AsC)(2)H, Bu-t(AsC)(2)Bu-t, Ph(AsC)(2)H and Ph(AsC)(2)P h have been optimized. These indicate that 1,3-diarsacyclobutadienes p refer a planar C-2h-like ring structure with localized single and doub le As-C bonds.