Orbital Interaction and Electron Density Transfer in PdII([9]aneB2A)L2 Complexes: Theoretical Approaches

Abstract

Abstract:The geometric structures of Pd-complexes {Pd ([9]aneB 2 A)L 2 and Pd ([9]aneBAB)L 2 where A = P, S; B = N; L = PH 3 , P(CH 3 ) 3 , Cl − }, their selective orbital interaction towards equatorial or axial (soft A…Pd) coordination of macrocyclic [9]aneB 2 A tridentate to PdL 2 , and electron density transfer from the electron-rich trans L-ligand to the low-lying unfilled a 1g (5s)-orbital of PdL 2 were investigated using B3P86/lanl2DZ for Pd and 6-311+G** for other atoms. The pentacoordinate endo- [Pd([9]complex with an axial (soft A--Pd) quasi-bond was optimized for stability. The fifth (soft A--Pd) quasi-bond between the σ-donor of soft A and the partially unfilled a 1g (5s)-orbital of PdL 2 was formed. The pentacoordinate endo-Pd ([9]aneB 2 A)(L-donor) 2 ] 2+ complex has been found to be more stable than the corresponding tetracoordinate endo-Pd complexes. Except for the endo-Pd pentacoordinates, the tetracoordinate Pd([9]aneBAB)L 2 complex with one equatorial (soft A-Pd) bond is found to be more stable than the Pd([9]aneB 2 A)L 2 isomer without the equatorial (A-Pd) bond. In particular, the geometric configuration of endo- [Pd([9]anePNP)(L-donor) 2 ] 2+ could not be optimized.

Hemilabile bonding of 1-oxa-4,7-dithiacyclononane in cyclometallated palladium(ii) complexes

“…DFT calculations on related systems have been used previously to study the relative energies of energies of endo and exodentate bonding modes of 9-membered tridentate macrocycles and the effects of axial donor atoms. 42,43 The thermodynamically more stable exo form is consistent with the obtained X-ray structure of 4b (exodentate). The endo conformer, however, is less stable by only 2.2 kcal mol −1 .…”