Multifunctional Phosphorus Compounds: Molecular Structures of 1,2,4,5‐Tetra(phosphinyl)‐, Tetra(dimethoxyphosphoryl)‐, and Tetra(dihydroxyphosphoryl)benzene

Abstract

1,2,4,5-Tetra(phosphinyl)benzene (1) and -tetrakis(dimethoxyphosphoryl)benzene (4) have molecular structures of point group C i symmetry with conformations largely determined by steric factors. In the crystal of compound 1 there are no discernible effects of intra-or intermolecular PϪH···P hydrogen bonding. By contrast, the crystal structure of the corresponding phosphonic acid, 1,2,4,5-tetrakis(dihydroxyphosphoryl)benzene (3), is governed by a network of hydrogen bonds between PO(OH) 2 groups with monofunctional PϪOH donors and difunctional PϭO acceptors as required for a maximum set of hydrogen bonds under the given stoichiometry. The aggregation of the molecules (C i symmetry) le-2595 ads to narrow channels formed by 14-and 16-membered rings which comprise POH···OP bridges between PϪCCϪP and PϪCCCϪP units, respectively. Accordingly, the crystals of compound 3 are mechanically extremely robust. A tri(phosphinyl)benzene (2) with an interesting 1,2,4-substitution pattern has been obtained as a by-product of the synthesis of the tetra(phosphinyl)benzene (1) where it is formed by reductive PϪC cleavage.

Synthesis of Benzene Derivatives with Multiple Dichlorophosphino Groups

“…The synthesis of 1,2-diphosphinobenzene (5) has already been described above (Scheme 2) and 1,2,4-triphosphinobenzene (8) and 1,2,4,5-tetraphosphinobenzene (9) are accessible via a similar route (Scheme 3). [17,18] Thus, starting from 1,2,4,5-tetrachlorobenzene, four phosphorus atoms can be introduced in a photo-Arbuzov reaction to form the phosphonate 10. In the reduction with in situ generated AlH 3 (from LiAlH 4 and TMSCl), not only the tetraphosphane 9, but also the triphosphane 8 is formed by CÀ P bond cleavage, resulting in release of one equivalent of PH 3 .…”