Syntheses and Structures of a Series of Acyclic Diaminocarbene Palladium(II) Complexes Derived from 3,4-Diaryl-1H-pyrrol-2,5-diimines and Bisisocyanide Palladium(II) Complexes

Reactions of 3,4-diaryl-1H-pyrrol-2,5-diimines with various bisisocyanide palladium(II) complexes were studied. The coupling proceeds with one isocyanide ligand to accomplish the acyclic diaminocarbene complexes. The structure of generated diaminocarbene complexes depends on bulkiness of isocyanide ligand in the bisisocyanide complexes of palladium(II). The imino-group of 3,4-diaryl-1H-pyrrol-2,5-diimine reacts with one isocyanide ligand of cis-[PdCl2(CN-R)(2)] (R = i-Pr, Cy, t -Bu, Bn), and the nitrogen atom of the pyrrole ring is coordinated to the palladium center as the second isocyanide ligand remains intact. In the case of cis-[PdCl2(CN-R)(2)] (R = 2-acyloxyphenyl, 2-sulfonyloxyphenyl), one isocyanide ligand is displaced from the coordination sphere. Structural features of the prepared diaminocarbene complexes have been studied by molecular spectroscopy techniques, cyclic voltammetry, single -crystal X-ray diffraction, and DFT calculations. The photophysical properties of the obtained acyclic diaminocarbene complexes in solution mainly depend on the substituents in the 3,4-diaryl-1H-pyrrol-2,5-diimine moiety.