Synthesis, characterization and reactivity of new cobalt, palladium and nickel complexes bearing α-diimines and P, O ligands

This work describes the synthesis and characterization of a series of new α-diimine and P,O, β-keto and acetamide phosphines ligands, and their complexation to Ni(II), Co(II),Co(III) and Pd(II) to obtain a series of new compounds aiming to study their structural characteristics and to test their catalytic activity. All the compounds synthesized were characterized by the usual spectroscopic and spectrometric techniques: Elemental Analysis, MALDI-TOF-MS spectrometry, IR, UV-vis, 1H, 13C and 31P NMR spectroscopies. Some of the paramagnetic compounds were also characterized by EPR. For the majority of the compounds it was possible to solve their solid state structure by single crystal X-ray diffraction. Tests for olefin polymerization were performed in order to determine the catalytic activity of the Co(II) complexes. Chapter I presents a brief introduction to homogenous catalysis, highlighting the reactions catalyzed by the type of compounds described in this thesis, namely olefin polymerization and oligomerization and reactions catalyzed by the complexes bearing α-diimines and P,O type ligands. Chapter II is dedicated to the description of the synthesis of new α-diimines cobalt (II) complexes, of general formula [CoX2(α-diimine)], where X = Cl or I and the α-diimines are bis(aryl)acenaphthenequinonediimine) (Ar-BIAN) and 1,4-diaryl-2,3-dimethyl-1,4-diaza-1,3-butadiene (Ar-DAB). Structures solved by single crystal X-ray diffraction were obtained for all the described complexes. For some of the compounds, X-band EPR measurements were performed on polycrystalline samples, showing a high-spin Co(II) (S = 3/2) ion, in a distorted axial environment. EPR single crystal experiments on two of the compounds allowed us to determine the g tensor orientation in the molecular structure. In Chapter III we continue with the synthesis and characterization of more cobalt (II)complexes bearing α-diimines of general formula [CoX2(α-diimine)], with X = Cl or I and α-diimines are bis(aryl)acenaphthenequinonediimine) (Ar-BIAN) and 1,4-diaryl-2,3-dimethyl- 1,4-diaza-1,3-butadiene (Ar-DAB). The structures of three of the new compounds synthesized were determined by single crystal X-ray diffraction. A NMR paramagnetic characterization of all the compounds described is presented. Ethylene polymerization tests were done to determine the catalytic activity of several of the Co(II) complexes described in Chapter II and III and their results are shown. In Chapter IV a new rigid bidentate ligand, bis(1-naphthylimino)acenaphthene, and its complexes with Zn(II) and Pd(II), were synthesized. Both the ligand and its complexes show syn and anti isomers. Structures of the ligand and the anti isomer of the Pd(II) complex were solved by single crystal X-ray diffraction. All the compounds were characterized by elemental analysis, MALDI-TOF-MS spectrometry, and by IR, UV-vis, 1H, 13C, 1H-1H COSY, 1H-13C HSQC, 1H-13C HSQC-TOCSY and 1H-1H NOESY NMR when necessary. DFT studies showed that both conformers of [PdCl2(BIAN)] are isoenergetics and can be obtain experimentally. However, we can predict that the isomerization process is not available in square-planar complex, but is possible for the free ligand. The molecular geometry is very similar in both isomers, and only different orientations for naphthyl groups can be expected. Chapter V describes the synthesis of new P, O type ligands, β-keto phosphine, R2PCH2C(O)Ph, and acetamide phosphine R2PNHC(O)Me, as well as a series of new cobalt(III) complexes namely [(η5-C5H5)CoI2{Ph2PCH2C(O)Ph}], and [(η5- C5H5)CoI2{Ph2PNHC(O)Me}]. Treating these Co(III) compounds with an excess of Et3N, resulted in complexes η2-phosphinoenolate [(η5-C5H5)CoI{Ph2PCH…C(…O)Ph}] and η2- acetamide phosphine [(η5-C5H5)CoI{Ph2PN…C(…O)Me}]. Nickel (II) complexes were also obtained: cis-[Ni(Ph2PN…C(…O)Me)2] and cis-[Ni((i-Pr)2PN…C(…O)Me)2]. Their geometry and isomerism were discussed. Seven structures of the compounds described in this chapter were determined by single crystal X-ray diffraction. The general conclusions of this work can be found in Chapter VI