Molekül- und Kristallstruktur des Tetramethyldiphosphans und -diarsans (Element-Element-Bindungen ; 4)

Abstract

The molecular and crystal structures of the isotypic compounds tetramethyldiphosphane 1 and -diarsane 2 have been determined by single crystal X-ray diffraction (monoclinic; C2/m; Z = 2; 1/2: -155/-144 ·C°; a = 540.6(2)/555.8(2); b = 1131.0(6)/1136.7(6); c = 602.5(2)/612.8(2) pm;β = 97.31(3)/95.24(3)"; P-P 221.2(1)/As-As242.9(1) pm). In accordance with the crystallographically imposed symmetry 2/m, the molecules adopt antiperiplanar conformation. Their crystal structures are c10sely related to those of the homologues tetramethyldistibane 3 [1] and -dibismuthane 4 [3]. As found for the latter compounds, the E-E units (E = P, As) are also aligned in linear chains, but the intermolecular E···E contacts (P...P 381/As...As 370 pm) do not allow any extended interaction between molecules, which otherwise would result in thermochromic effects.