Heteroaromatic Substituted Phosphoranes with Enhanced Hemilabile Character

New ligands with enhanced hemilabile character compared to iminophosphoranes known in the literature are presented. When diphenyl-2-picolylphosphane was oxidized with elemental sulfur or gray selenium, the new ligands Ph2P(S)(CH2Py) (1) and Ph2P(Se)(CH2Py) (2) were obtained. In addition, the calcium complex [(thf)2Ca{(PyCH)(Se)PPh2}2] (3), based on 2, is presented. This is only the second example of a molecular structure displaying a direct calcium−selenium contact. A structural comparison of the parent ligands and the related motifs in the organometallic complex reveals the bonding to the central phosphorus atom to be mostly strengthened by electrostatic means rather than by any double bonding. The spectroscopic data of 3 show features similar to those of iminophosphoranes, despite small differences in electronegativity. All of the compounds presented are accessible in good yields and high purity. The DTA analysis of 3 points to possible CVD applications to form CaSe from the gas phase.