Activation of Polymerization Catalysts:  Synthesis and Characterization of Novel Dinuclear Nickel(I) Diimine Complexes

Abstract

The reaction of 1,4-bis(diisopropylphenyl)-aza-1,4-butadienenickel dibromide (1a) with stoichiometric amounts of phenyl Grignard or trimethylaluminum affords the purple Ni(I) complexes 1b and 1c, respectively. Single-crystal X-ray diffraction reveals dinuclear species in the solid state for both compounds. UV/vis spectroscopy supports this rare oxidation state of nickel.

Conversion of imine ligands in allyl–nickel(II) complexes

“…This gave a great impetus to syntheses of a wealth of new diimine ligands and their metallo-complexes with different transition metals [19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Nickel(I) complex as the final product of the sequence of spontaneous transformations in the system Ni(allyl)2-(2,6-diisopropylphenyl)diazabutadiene

“…Although such catalytic systems are currently under intensive study, a question is still open as to whether N containing ligands themselves can be transformed in organometallic complexes. As a result, almost all the mechanisms proposed in the literature for the cat alytic cycle ignore possible changes in the nature of the metal-ligand bond and in the structure of the diimine ligand itself [9][10][11][12][13][14][15]. One can state that this ligand is most often regarded as an unchangeable entity involved in the catalytic cycle as a "guest" that can either be coordinated to the metal center or quit its coordination sphere intact.…”

“…The Ni +2 form is regarded as the second most stable species inferior only to colloidal nickel [9, 13-15]. However, some authors do note the formation of nickel(I) complexes from both nickel(II) complexes with allyl [6] and diimine ligands [10,11].Furthermore, despite much research dealing with allyl complexes of transition metals, the literature data on nickel allyl systems are very scarce because the attention of researchers is mainly focused on allyl complexes of palladium [16]. Obviously, this is due to both the relatively low stability of allyl complexes of nickel and the limited scope of their study by the most commonly used method (NMR spectroscopy) [17].…”

“…The Ni +2 form is regarded as the second most stable species inferior only to colloidal nickel [9,[13][14][15]. However, some authors do note the formation of nickel(I) complexes from both nickel(II) complexes with allyl [6] and diimine ligands [10,11].…”

Intramolecular rearrangement of the imine–amide ligand within the nickel coordination sphere affected by carbon monoxide

“…H NMR (500 MHz, THF-D 8 , 297 K): d ¼ 9.06 (dd, 3 J H1eH2 ¼ 4.30Hz, 4 J H1eH3 ¼ 1.76 Hz, 1H, CH1), 7.58 (dd, 3 J H2eH3 ¼ 8.10 Hz, 3 J H2eH1 ¼ 4.27 Hz, 1H, CH2), 8.25 (dd, 3 J H3eH2 ¼ 8.10 Hz, 4 J H3eH1 ¼ 1.75 Hz, 1H, CH3), 7.75 (d, 3 J H5eH6 ¼ 8.80 Hz, 1H, CH5), 7.76 (d, 3 J H6eH5 ¼ 8.80 Hz, 1H, CH6), 8.19 (d, 3 J H8eH9 ¼ 8.30 Hz, 1H, CH8), 7.66 (d, 3 J H9eH8 ¼ 8.30 Hz, 1H, CH9), 6.84 (dk, 3 J H13eH14 ¼ 15.50 Hz, 4 J H13eH15 ¼ 1.72 Hz, 1H, CH13), 7.17 (dk, 3 J H14eH13 ¼ 15.50 Hz, 3 J H14eH15 ¼ 6.82 Hz 1H, CH14), 2.0 (dd, 3 J H15eH14 ¼ 6.77 Hz, 4 J H15eH13 ¼ 1.75 Hz, 3H, CH 315) ppm(Fig. 7) 13.…”