Reaktive EC(p‐p)n‐Systeme, XXXVIII. Molekül‐ und Elektronenstruktur des 2‐(Diisopropylamino)‐1λ 3 ‐phosphaethins i Pr 2 NCP

Reactive EC(p‐p)π‐Systems, XXXVIII. — Molecular and Electronic Structure of 2‐(Diisopropylamino)‐1λ 3 ‐phosphaethyne i Pr 2 NCP The molecular structure of 2‐(diisopropylamino)‐1λ 3 ‐phosphaethyne i Pr 2 NCP ( 3 ) has been investigated by X‐ray diffraction using a single crystal grown from the melt at −50.2°C. Bond distances and angles indicative for the electronic structure are: P°C 155.2(2), NC(sp) 131.2(3) pm, PCN 179.2(2)°; with a sum of angles 359‐8° the nitrogen atom has a trigonal‐planar coordination. The reported geometrical parameters of 3 have been reproduced by ab initio calculations (3‐21G and DZP basis), showing that the lengthening of the P°C and the shortening of the CN bond can be rationalized by the interaction of the π system of the triple bond with the 2p orbital at N. The He(I) photoelectron spectrum of 3 confirms the strong interaction.