Synthesis of tetraborylethenes and 1,1,1 ',1 '-tetra- and hexaborylethanes; Electronic interactions in tetraborylethenes and 1,1,1 ',1 '-tetraborylethanes, and HF-SCF calculations

The catechol-substituted diboranes(4) 1 react with the catechol-substituted diborylacetylenes 2, in the presence of [Pt(PPh3)(2)(C2H4)] or [Pt(PPh3)(4 )], to give tetra- and the hexaborylethane derivatives. When [Pt(cod)(2)] i s used as catalyst, the tetraborylethene 5a is formed exclusively, covers C atalytic hydrogenation of 5a affords the 1,1,1',1'-tetraborylethane 4a, whi ch has been studied by an X-ray structure analysis. Natural Bond Orbital (N BO) analyses for the RHF/3-21G optimized geometries of 4a and 5a reveal int ramolecular stabilization of the boron p(z) orbital. This covers B-O, B-B, and agostic interactions. The photoelectron spectrum of 5a is reported.