Beiträge zur Chemie des Phosphors. 122. 1,2,3,4-Tetra-tert-butyl-tetraphosphan,H(PBut)–(PBut)2–(PBut)H – ein stabiles kettenförmiges Tetraphosphan

Contributions to the Chemistry of Phosphorus. 122. 1,2,3,4-Tetra-tert-butyltetraphosphane, H(PBu^t)—(PBu^t)₂—(PBu^t)H — a Stable Chain-type Tetraphosphane The alcoholysis of 1,2,3,4-tetra-tert-butyl-1,4-bis(trimethylsilyl)-tetraphosphane, (Me₃Si)₂(PBu^t)₄, yields the hitherto unknown title compound 1 , which is the first stable partially substituted derivative of n-tetraphosphane(6), n-P₄H₆. 1 can also be obtained in the reaction of 1,4-dipotassium-1,2,3,4-tetra-tert-butyl-tetraphosphide, K₂(PBu^t)₄, with tert-butylchloride. In solution 1 forms the three diastereomers 1d (threo/d,l/threo), 1f (erythro/threo/threo), and 1b (erythro/d,l/erythro) in a ratio of about 10:5:1. Their correlation to the ³¹P-NMR spectroscopically observed spin systems results from the preferred trans arrangement of neighbouring tert-butyl groups as well as from the dependence of the ¹J(PP) coupling constant on dihedral angles and from the ³J(PP) long range coupling constant. The configuration and conformation of the existent isomers is determined by the all-trans arrangement of the tert-butyl groups and by the tendency of vicinal free electron pairs to assume a gauche conformation.