1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphosphal-1,2-diborolane and 1,2-bis(dimethylamino)-3,4,5,6-tetra-rbutyl-3,4,5,6-tetraphospha-1,2-diborine: Synthesis and structure as well as calculations on the molecular structure

Article abstract of DOI:10.1002/zaac.19966220906

The diphosphides K₂[(C₆H₅)P-(C₆H ₅)P-P(C₆H₅)], 4 or K₂[tBuP)-(tBuP)₂-P(tBu)], 5, react with (ClBNMe₂)₂ to form the binary 5-membered ring system 1,2-bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolane (C₆H₅P)₃(BNMe₂)₂, 2a, and the 6-membered ring system 1,2-bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborine, (tBuP)₄(BNMe₂)₂, 3a, respectively. 2a and 3a could be obtained in a pure form and characterized NMR spectroscopically and by X-ray structure analyses. The two ring systems are folded; 2 a exists in the envelope - 3a in the boat -conformation. Ab initio computations for 3,4,5-triphospha-1,2-diborolane M5 show that the global minimum is characterized by one B - P double bond. The parent compound geometry M6 is characterized by transannular bonding in the PH - BH - BH - PH moiety which differs in character from those in the four- and five-membered rings (BH)₂(PH)₂ and (BH)₂(PH)₃ M5d, respectively. Explicit calculation of the influence of amino substituents on boron improved agreement of the bond length between computed and X-ray data. Johann Ambrosius Barth 1996.