Applications of bis and tris(aryloxy)amine ligands to main group and transition metal chemistry.

摘要

Sterically demanding alkoxide ligands have been utilized to support a range of homogenous catalytic reactions including metathesis, polymerization, hydrogenation, C-H bond activation, and small molecule activation. Chelating ligands impart stable, mononuclear complexes that may be functionalized to incorporate substituents that tune the electron density at the metal center. In the last 10 years, considerable attention has been given to the application of poly(aryloxide) ligands. In this regard, we sought to develop the applications of bis and tris aryloxide ligands featuring an amine linker.; In Chapter one, the molecular structures of N(o-C 6H4OH)3 and PhN(o-C6H 4OH)2 are compared, indicating that replacing one of the ortho-OH groups in N(o-C6H4OH) 3 with hydrogen causes a significant change in the geometry of the molecule with respect to the rotation of the aryl rings and to the extent of pyramidalization at N. Specifically, N(o-C6H4OH) 3 exhibits a pyramidal geometry with all three aryl rings twisted into a propeller like conformation, whereas PhN(o-C6H 4OH)2 exhibits a trigonal planar geometry, with the phenyl ring in the plane defined by the ipso carbons. This conformation maximizes the delocalization of the nitrogen lone pair into the phenyl ring compared to the C6H4OR ring, the negative charge on the ortho carbon is destabilized by a pi-interaction with the oxygen lone pair.; In Chapter 2, comparison of the molecular structures of [kappa 4-N(CH2 ArBut 2 O)3]Sb(OSMe2) and [kappa4-N( o-C6H4O)3]Sb(OSMe2) indicates that the Sb-OSMe2 bond length for [kappa4-N(CH 2 ArBut 2 O)3]Sb(OSMe2) [2.97 A] is significantly longer than that for [kappa4-N(o-C6H 4O)3]Sb(OSMe2) [2.31 A], thereby demonstrating that the [kappa4-N(CH2 ArBut 2 O)3] ligand engenders a less Lewis acidic antimony center than does the [kappa4-N(o-C6H 4O)3] ligand, a manifestation of the greater donor character of the nitrogen atom in the former ligand. Also, [kappa4-N(CH 2 ArBut 2 O)3]Sb exhibits diverse reactivity: AcOH cleaves one of the Sb-O bonds to give [kappa3-N(CH2 ArBut 2 O)2(CH2 ArBut 2 OH)]Sb(kappa1-O2CMe), Br2 undergoes oxidative addition to give N(CH2 ArBut 2 O)3]SbBr2, while reaction with Me3NO·2H 2O gives the oxo and hydroxo complexes {lcub}[kappa4-N(CH 2 ArBut 2 O)3]Sb(mu-O){rcub}2, [kappa4-N(CH 2 ArBut 2 O)3]Sb(OH)2, and {lcub}[kappa4-N(CH 2 ArBut 2 O)3]SbVO{rcub}4{lcub}SbIII 4O6{rcub}.; The reactivity of the bis(phenol), PhN(o-C 6H4OH)2 and tris(phenol), N( o-C6H4OH)3 towards electron rich tungsten and molybdenum complexes is described in Chapter 3. Specifically, PhN(o-C6H4OH)2 undergoes a series intramolecular O-H and C-H bond activation reactions of with W(PMe 3)4(eta2-CH2PMe2)H to give products that feature (i) bidentate eta2- OC, and kappa2-O2 (ii) tridentate kappa 3-O2N, and (iii) tetradentate kappa 4-O2CN coordination modes. This conversion of eta2-OC, to kappa 3-O2N is catalyzed by H2, which facilitates the oxidative addition of the second ArO-H via a dihydrogen bonding intermediate. The ortho position on the phenyl moiety may also be C-H activated and this interconversion of kappa3-O2N to kappa4-O2CN is in equilibrium with H2. The tungsten system is contrasted with the reactivity of PhN(o-C6H4OH) 2 towards Mo(PMe3)6, in which only (i) bidentate kappa 2-O2 and (ii) tridentate kappa 3-O2N coordination modes are observed. Also, the reactivity of N(o-C6H 4OH)3 towards W(PMe3)4(eta 2-CH2PMe2)H results in an array of compounds which feature (i) bidentate eta2-OC, (ii) tetradentate kappa4-O3 N, and (iii) tetradentate kappa4-O 2CN coordination modes and (iv) an unusual dinuclear, bicyclometallated compound, which features both the bidentate eta 2-OC, and tetradentate kappa4- O2CN coordination mode.