SYNTHESES AND X-RAY CRYSTAL-STRUCTURES OF THE COMPOUNDS [2,4,6-(TERT-BU)3C6H2PAS]2 AND [2,4,6-(TERT-BU)3C6H2PAS]2 - P2AS2-SUBSTITUTED AND P2SB2-SUBSTITUTED ANALOGS OF BICYCLO[1.1.0]BUTANE

The syntheses and X-ray crystal structures of the new bicyclo compounds [ArPAs]2,1, and [ArPSb]2, 2 (Ar = 2,4,6-(t-Bu)3C6H2) are reported. Both 1 and 2 represent the first well-characterized examples of their type to be described. They are analogues of the bicyclotetraphosphanes [P4{N(SiMe3)2}2], 3, and [P4Ar2], 4, which were recently reported. The P2As2 compound 1 adopts a structure similar to those of 3 and 4 with the aryl groups in the exo‒exo orientation. In addition the bridgehead As‒As bond is somewhat short averaging 2.383 (1) Å. In sharp contrast the P2Sb2 compound 2 adopts the exo,endo configuration with a significantly larger fold angle of 103.2° than those in 1, 3, and 4, which average near 95°. The bridgehead Sb‒Sb bond length is 2.723 (1) Å and is also significantly shorter than the sum of the covalent radii for antimony. Crystal data with Mo Kα (λ = 0.71069 Å) radiation at 130 K are as follows: 1, a = 20.777 (5) Å, b = 16.024 (2) Å, c = 25.958 (4) Å, β = 100.20 (1)°, Z = 8, monoclinic, space group P21/n, Rw = 0.063; 2, a = 10.126 (3) Å, b = 13.770 (3) Å, c = 15.250 (4) Å, α = 66.09 (2)°, β = 85.97 (2)°, γ = 77.71 (2)°, Z = 2, triclinic, space group P1, Rw = 0.041. © 1990, American Chemical Society. All rights reserved.