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Des ligands hydrides potentiellement bidentes (possédant un donneur N-hétérocyclique (NHC) associé à un groupement donneur éther ou amine) ainsi que des ligands tritopiques de type pinceur (possédant un groupement (NHC) flanqué de deux types de donneurs azotés différents Nimine et Namine) ont été préparés et utilisés pour la coordination de métaux de transition tels que le Ni, Cr, Cu et Ir. L’influence de la longueur de la chaine alkylée -(CH2)2- ou -(CH2)3- reliant le groupe éther ou amine au groupe hétérocyclique (NHC) a été examinée. Dans le but d’accéder aux complexes des métaux de transition différentes méthodologies ont été adoptées : a) déprotonation préalable du sel d’imidazolium suivie de l’addition des précurseurs métalliques correspondants ; b) transmétallation à partir des complexes (NHC) de l’argent correspondants ; c) réaction d’addition oxydante des sels d’imidazolium ou de leurs sels protonés avec du Ni(0). Une série de complexes du Ni(II) et du Cr(III) a été testée dans la réaction catalytique d’oligomérisation de l’éthylène. / Potentially bidentate hybrid ligands (containing a NHC donor associated with an ether or an amine) and tridentate NCN pincer-type ligands (containing a central NHC donor flancked by two chemically-different nitrogen donors (Nimine and Namine)) have been prepared and used for coordination to transition metals, such as Ni, Cr, Cu, Ir. The influence of the length of the alkyl chain, -(CH2)2- or -(CH2)3- connecting the ether or the amine group to the heterocycle NHC was examined. In order to have access to the transition metal complexes, several methodologies were adopted: a) deprotonation of the corresponding imidazolium salts followed by addition of transition metal precursors; b) transmetalation from NHC silver complexes; c) oxidative-addition reaction of Ni(0) with imidazolium salts or the corresponding protonated salts. A series of Ni(II), Cr(III) complexes were tested in the catalytic ethylene oligomerization reaction.

Le sujet de cette thèse porte sur l’étude de ligands hybrides incorporant un donneur carbène N-hétérocyclique (NHC). Les ligands phosphine-NHC construits sur le motif m-phénylène ont conduit à des complexes di- ou tétranucléaires d’Ag, Cu, Au et Ir, et à des complexes bimétalliques Ag/Cu et Ag/Ir par transmétallation sélective du site NHC. Dans le cas des ligands phosphino-picoline-NHC (PNC), la transmétallation des sels de Li ou K correspondants a permis d’isoler des complexes « pinceurs » dé-aromatisés du Cr, Fe et Co. La déprotonation du ligand bis(phosphinométhyl)pyridine (PNP) a été examinée, et les ligands dé-aromatisés mono- et bis-anioniques correspondants ont été utilisés dans des réactions de transmétallation vers le Cr(II) et Zr(IV). Différents modes de coordination des ligands dé-aromatisés, notamment une métallation de la position alpha-CHP, ont été observés. La substitution de la phosphine dans PNC par une fonction imine conduit à un ligand hybride « rédox non-innocent ». / The purpose of this work is the synthesis and study of hybrid and potentially “pincer” ligands featuring an N-heterocyclic carbene (NHC) donor. The phosphine-NHC ligands based on the m-phenylene framework led to di- or tetranuclear Ag, Cu, Au and Ir complexes, and to bimetallic Ag/Cu and Ag/Ir complexes by selective transmetallation of the NHC. With the phosphino-picoline-NHC (PNC) ligands, transmetallation from the corresponding Li or K salts led to dearomatised Cr, Fe and Co “pincer” complexes. Deprotonation of the bis(phosphinomethyl)pyridine (PNP) ligand was also examined. The corresponding dearomatised mono- and bis-anionic ligands were isolated as Li or K salts and further used in transmetallation reactions towards Cr(II) and Zr(IV). Different coordination modes of the dearomatised ligands, including side-arm metallation, were observed. Substitution of the phosphine group in PNC by an imine donor led to a hybrid and “redox non-innocent” ligand.

The synthesis of a rigid 4,5-bis(triphenylphosphinimino)-2,7-di-tert-butyl-9,9-dimethylxanthene (Ph3PN)2XT (1) ligand is outlined, along with a modified synthesis for previously reported 1,8-bis(triphenylphosphinimino)naphthalene (Ph3PN)2NAP (3). Reaction of neutral (Ph3PN)2XT with [Y(CH2SiMe3)3(THF)2] resulted in double cyclometallation, yielding the base-free monoalkyl complex, [({Ph2(C6H4)PN}2XT)Y(CH2SiMe3)] (2). Layering a concentrated THF solution of 2 with hexanes at −28 °C afforded THF-coordinated [({Ph2(C6H4)PN}2XT) Y(CH2SiMe3)(THF)]·2THF (2-THF·2THF), with a distorted pentagonal bipyramidal geometry and approximately meridional coordination of the pentadentate {Ph2(C6H4)PN}2XT dianion. Similarly, (Ph3PN)2NAP reacted with [Y(CH2SiMe3)3(THF)2] to afford a THF-coordinated monoalkyl complex, [{(Ph2(C6H4)PN)2NAP}Y(CH2SiMe3)(THF)] (4-THF). Layering a DME solution of 4-THF with hexanes at −28 °C afforded X-ray quality crystals of [{(Ph2(C6H4)PN)2NAP}Y(CH2SiMe3)(κ2-DME)]·hexane (4-DME·hexane), with a highly distorted pentagonal bipyramidal geometry and a facial coordination mode of the tetradentate {Ph2(C6H4)PN}2NAP dianion The synthesis of a rigid 4,5-bis(1,3-diisopropylimidazol-2-imine)-2,7,9,9-tetramethylacridan H(AII2) ligand (5) was achieved via a Buchwald-Hartwig cross-coupling reaction. Reaction of the proligand H(AII2) with [M(CH2SiMe3)3(THF)2] (M = Y(6), Sc(8)) yielded the base free dialkyl complexes [(AII2)Y(CH2SiMe3)2] (6) and [(AII2)Sc(CH2SiMe3)2] (8). The reaction of 6 with one equivalent of [CPh3][B(C6F5)4] yielded [(AII2)Y(CH2SiMe3)][B(C6F5)4] (7) in-situ. Complex 7 proved to be a potent intramolecular hydroamination catalyst for a variety of aminoalkane substrates. The attempted synthesis of 4,5-bis(1,3-diisopropylimidazol-2-imine)-2,7-di-tert-butyl-9,9-dimethylxanthene (XII2) via the Staudinger reaction resulted in the isolation of the triazene intermediate 4,5-bis(1,3-diisopropylimidazol-2-yliedene{triazene})-2,7-di-tert-butyl-9,9-dimethylxanthene XIA2 (9). Reaction of XIA2 with one equivalent of [Y(CH2SiMe3)3(THF)2] led to the isolation of [(XIA2)Y(CH2SiMe3)3] (10). Synthesis of XII2 (11) was achieved via a Buchwald-Hartwig cross-coupling reaction. Reaction of XII2 with one equivalent of YCl3(THF)3.5 resulted in the isolation of [(XII2)YCl3] (12). In contrast, the reaction of XII2 with one equivalent of [Y(CH2SiMe3)3(THF)2] led to several unidentified products. Reaction of XII2 with 1 equivalent of [H(Et2O)2][B(C6F5)4] led to the isolation of the precursor [H(XII)2][B(C6F5)4] (13). The reaction of 13 with 1.1 equivalents of [M(CH2SiMe3)3(THF)2] (M = {Y(14), Sc(15)} led to the isolation of the monocationic [(XII)2M(CH2SiMe3)2][B(C6F5)4] complexes. The reaction of [(XII)2Sc(CH2SiMe3)2][B(C6F5)4] with 1.1 equivalents of B(C6F5)3 led to the abstraction of a methyl anion from the silicon center, with concomitant migration of the remaining alkyl group to the positively charged silicon, forming a new CH2SiMe2CH2SiMe3 alkyl group. This process is accompanied by MeB(C6F5)3 anion formation, forming a contact ion pair to afford the dicationic species [(XII)2Sc(CH2SiMe3)][MeB(C6F5)3][B(C6F5)4] 16. In contrast, the reaction of 15 with 1.3 equivalents of [CPh3][B(C6F5)4] in the presence of 5 equivalents of toluene resulted in the synthesis of [(XII)2Sc(CH2SiMe3)(ɳx-toluene)][B(C6F5)4]2 17 in-situ. Complex 17 is a highly potent ethylene polymerization catalyst with an activity of 868 kg/mol·atm·h. The reaction of 15 with [HNMe2Ph][B(C6F5)4] led to the cyclometallation of the resulting NMe2Ph byproduct to yield [(XII2)Sc(C6H4NMe2)][B(C6F5)4]2 (18) in-situ. The synthesis of a rigid, asymmetric 4-(1,3-diisopropylimidazol-2-imine)-5-(2,6-diisopropylanilido)- 2,7-di-tert-butyl-9,9-dimethylxanthene XAI (19) ligand was achieved by a two step Buchwald-Hartwig cross-coupling reaction with initial cross coupling of 1,3-diisopropylimidazol-2-imine followed by the cross-coupling of 2,6-diisoproylaniline. The reaction of XAI with 1.1 equivalents of [Y(CH2SiMe3)3(THF)2] yielded [(XAI)Y(CH2SiMe3)2] (20). Subsequent reaction of [(XAI)Y(CH2SiMe3)2] with 1 equivalent of [CPh3][B(C6F5)4] in the presence of 10 equivalents of toluene resulted in the synthesis of the toluene coordinated [(XAI)Y(CH2SiMe3)(ɳx-toluene)][B(C6F5)4] (21) complex. Similar to 7, complex 21 was highly active for intramolecular hydroamination of various substrates. / Dissertation / Doctor of Philosophy (PhD) / Cationic group 3 alkyl complexes are underreported in comparison to analogous group 4 complexes. The scarcity of these complexes can be attributed to their propensity to engage in undesirable reactions such as ligand redistribution and cyclometallation. To increase the thermal stability of such complexes, design features, such as carefully positioned steric bulk and ligand rigidity are beneficial. Additionally, such ligands must also have considerable donor ability, in order to stabilize inherently electron deficient cationic metal centers. This work details the synthesis of a variety of neutral and monoanionic ligands that incorporate the aforementioned design features, which were utilized in the successful synthesis of a variety of neutral, monocationic and extremely rare dicationic group 3 alkyl complexes. The cationic monoalkyl complex in this work proved to be a highly potent intramolecular hydroamination catalyst. Furthermore, a rare dicationic scandium complex was highly active for ethylene polymerization