Nouveaux complexes pinces POCOP, NHCCOP, PIMCOP et PIMIOCOP, et complexes cyclométallés de Ni(II) : synthèse, caractérisation et réactivité
This thesis describes the chemistry of Ni (II) pincer and cyclonickelated complexes bearing at least one phosphinite moiety. The content is divided into three parts. A first study concerns the synthesis, the characterization, the mechanism of formation and the reactivity of nickel complexes bearing a ligand POCOP (1,3-(i- Pr2PO)2C6H4). New ligands R-(POCOP) = κP,κC,κP-{Rn-2,6-( R'2PO)2C6H3-n}; Rn = 4-OMe, 4-Me, 4-CO2Me, 3-OMe, 3-CO2Me, 3,5-t-Bu2 ; R' = i-Pr, t-Bu have been synthesized by addition of chlorophosphine in presence of base in a resorcinol or derivatives solution. The synthesis of R-(POCOP)Ni(Br) complexes occurred by reacting the corresponding ligand in presence of base and{NiBr2(NCiPr)}n. This new nickel precursor is synthesized in isobutyronitrile with bromine and metallic nickel powder. It is stable under inert atmosphere and its solubility in polar solvents allowed the study of those complexes in homogenous solution. Mechanism of formation of complexes bearing pincer ligands (PCsp3P) 1,3-(i-Pr2PCH2CH2)2CH2, (POCsp3OP) 1,3-(i-Pr2POCH2)2CH2, (PCsp2P) 1,3-(i-Pr2PCH2)2C6H4, Rn-(POCsp2OP) 1,3-(i- Pr2PO)2C6H4-n via C-H nickelation has been investigated by a method of competition reactions. The nickelation step was determined to be electrophilic. New {Rn-2,6-( R'2PO)2C6H4-n} ligands and corresponding nickel bromine complexes were characterized including linear correlation between 13C NMR chemical shift of ipso carbon (Cipso) and oxidation potential Eox. A new greener methodology for the one pot synthesis of (POCOP)Ni(Cl) from metallic nickel has been developed. Reacting at 75 °C at mixture of resorcinol, chlorodiisopropylphosphine and nickel power gives (POCsp2OP)Ni(Cl) up to 93 %. Reactivity of this complex has been investigated for fluorination and trifluoromethylation of benzyl halides. Synthesis of (POCOP)Ni(F) occurred starting from (POCOP)Ni(X) (X=Br, Cl) with excess of silver fluoride AgF. This complex catalyzes the fluorination of benzyl bromide and can be converted into (POCOP)Ni(CF3) using Ruppert reagent Me3SiCF3. Reaction of (POCOP)Ni(CF3) with benzyl bromide leads to its complete conversion into (POCOP)Ni(Br) and to the unexpected benzylation of the used aromatic solvent. The second part concerns the synthesis of new unsymmetrical complexes bearing imidazolo-phosphine moiety (PIMCOP) 3-[2-(R2P)-C3H2N2]-(R2PO)-C6H3, imidazoliophosphine (PIMIOCOP) 3-[2-(R2P)-3-(CH3)-C3H2N2]-(R2PO)-C6H3] and N-heterocyclique carbene (NHCCOP). (PIMCOP) ligands were synthesized by double deprotonation of 3-hydroxyphenyl-imidazole followed by addition of two equivalents of chlorodiphenylphosphine. Nickelation occured in a similar route as (POCOP)Ni. Methylation of the imidazole moiety of (PIMCOP)Ni(Br) using MeOTf leads the (PIMIOCOP)Ni(Br) complex. The latter can be converted into (NHCCOP)Ni(Br) after addition of tetraethylamonium chloride NEt4Cl. Analogs PiPr2 of those complexes are synthesized replacing ClPPh2 by ClPiPr2. Cationic species [(PIMCOP)Ni(NCCH3)][OTf], [(PIMIOCOP)Ni(NCCH3)][OTf]2 et [(NHCCOP)Ni(NCCH3)][OTf] are obtained reacting their bromo homologue complexes with silver triflate in acetonitrile. Those species are used to catalyze amidine synthesis from benzonitrile with various aliphatic amines. Finally orthonickellated complexes trans-Ni[(ĸ2-P,C-P(OC6H4)-(iPr2)( iPr2P(OC6H5))]Br, and dimeric specie {Ni(μ-Br){κ2-P,C-PiPr2(OC6H4)}}2 have been synthesized and characterized. Phosphinite ligand was synthesized reacting phenol and ClPiPr2 in presence of base. Nickellation occured heating in solution {NiBr2(NCiPr)}n and base. An intermediate trans-[NiBr2{PiPr2(OC6H5)}2] of this reaction has been isolated. Ortho-functionalization of diisopropyl phosphinite can be achieved by reacting dimeric complex with electrophilic species.
Nickel Pincer complexes C-H activation Cyclometalated Complexes Fluoration Fluorination