REACTIVE E=C(P-P)PI-SYSTEMS .38. MOLECULA R AND ELECTRONIC-STRUCTURE OF 2-(DIISOPROPYLAMINO)-1-LAMBDA-3-PHOSPHAETHYNE IPR2NC-EQUIVALENT-TO-P

The molecular structure of 2-(diisopropylamino)-1lambda3-phosphaethyne iPr2NC=P (3) has been investigated by X-ray diffraction using a singl e crystal grown from the melt at -50.2-degrees-C. Bond distances and a ngles indicative for the electronic structure are: P=C 155.2(2), N-C(s p) 131.2(3) pm, P-C-N 179.2(2)degrees; with a sum of angles 359.8-degr ees the nitrogen atom has a trigonal-planar coordination. The reported geometrical parameters of 3 have been reproduced by ab initio calcula tions (3-21G and DZP basis), showing that the lengthening of the P=C a nd the shortening of the C-N bond can be rationalized by the interacti on of the pi system of the triple bond with the 2p orbital at N. The H e(I) photoelectron spectrum of 3 confirms the strong interaction.