Molekül- und Elektronenstruktur des 2-(Diisopropylamino)-1λ3-phosphaethins iPr2NC≡P (Reaktive E=C(p-p)π-Systeme ; 38)

The molecular structure of 2-{diisopropylamino)·1λ3-phosphaethyne iPr2NC=P (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), N-C(sp) 131.2(3) pm, P-C-N 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 C-N 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.