Zirconium Complexes of Diamine−Bis(phenolate) Ligands:  Synthesis, Structures, and Solution Dynamics

Abstract

A family of new organometallic and coordination compounds supported by the diamine−bis(phenolate) ligands O2NN‘Me and O2NN‘tBu are reported [H2O2NN‘R = (2-C5H4N)CH2N(CH2-2-HO-3,5-C6H2R2)2, where R = Me (1a) or tBu (1b)]. Reaction of H2O2NN‘R with sodium hydride in THF gives the corresponding sodium salts Na2O2NN‘R (R = Me (2a) or tBu (2b)). Reaction of H2O2NN‘R with Zr(CH2SiMe3)2Cl2(Et2O)2 gives the cis-dichloride derivatives ZrCl2(O2NN‘R) (R = Me (3a) or tBu (3b)), which exist as two isomers (possessing either C 1 (major) or C s symmetry) in dynamic equilibrium with each other in solution. The compound 3b can also be prepared from Na2O2NN‘tBu and ZrCl4(THF)2, but reaction of Na2O2NN‘Me with either ZrCl4 in benzene or ZrCl4(THF)2 in THF gives mixtures of 3a and the eight-coordinate bis(diamine−bis(phenolate)) complex Zr(O2NN‘Me)2 (4a). The latter can also be prepared from 2 equiv of H2O2NN‘Me and Zr(CH2SiMe3)4. Treatment of Zr(NMe2)4 with H2O2NN‘tBu leads to the bis(dimethylamide) derivative Zr(NMe2)2(O2NN‘tBu) (5b). Similar protonolysis reactions between ZrR‘4 (R‘ = CH2SiMe3, CH2CMe3, or CH2Ph) give the corresponding organometallic alkyl or benzyl compounds ZrR‘2(O2NN‘R) [R‘ = CH2SiMe3 (8a, 8b), CH2CMe3 (9a, 9b), or CH2Ph (10a, 10b); R = Me (suffix a) or tBu (suffix b)]. The dichloride complexes ZrCl2(O2NN‘R) (3a, 3b) are also precursors to new organometallic derivatives, and treatment with LiR‘ (R‘ = Me or CH2SiMe3) or R‘MgCl (R‘ = CH2Ph or C3H5) yields ZrR‘2(O2NN‘R) [R‘ = Me (6a, 6b), η3-C3H5 (7b), CH2SiMe3 (8a, 8b), CH2Ph (10a, 10b)]. The thermally unstable bis(η3-allyl) complex 7b is highly fluxional in solution. Reaction of the dibenzyl compound 10a or 10b with B(C6F5)3 in the presence of THF gives the cationic complexes [Zr(CH2Ph)(THF)(O2NN‘R)]+ as the [PhCH2B(C6F5)3]- salts (11a, 11b). The X-ray crystal structures of the compounds 3a, 3b, 4a, 5b, 6a, 6b, and 10a are described.

A zirconium dichloro complex supported by an ancillary stereorigid tetradentate bis(phenoxo-imino) Schiff-base-donor ligand: Evidence for a conformational equilibrium between two solution stereoisomers

“…At room temperature, complex 3b interconverted slowly but appreciably in toluene solution into complex 3a when dissolved in a Teflon valved NMR tube. Addition of N n Bu 4 Cl [38] as a chloride ion source, has no significant influence on the 3a:3b molar ratio, suggesting that chloro dissociation is not involved in the ligand isomerization, which more probably occurs via an intramolecular reaction. Recently, Mountford and coworkers studied [38] the interconversion of C s -and C 1 -symmetry dichloro zirconium complexes bearing an pyridinoamino-diphenoxo-Kol-type ligand and demonstrated that the reaction proceeds through an intramolecular exchange.…”

High Molecular Weight Atactic Polypropylene prepared by Zirconium Complexes of an Amine Bis(phenolate) Ligand

“…Interestingly, the crystal structure of a dichloro zirconium complex of a ligand of this family (bearing a pyridine donor on a sidearm) was recently published by Mountford and coworkers and found to exhibit a cis geometry between the phenolate groups resulting in an overall C 1 -symmetry. 29 As described above, independently of the overall symmetry, this tetradentate [ONNO]-type ligand forces a cis relationship between the two labile groups in the respective octahedral complex, as is evident from a Cl-Zr-Cl angle of 103.2 deg. In general, the structure of 3 resembles that of 1, however, it is somewhat more compact.…”

Synthesis, Structure, and C–C Cross‐Coupling Activity of (Amine)bis(phenolato)iron(acac) Complexes

“…Previously, these compounds have been prepared in refluxing methanol. [9,10,[71][72][73][74] The use of water as a reaction medium proves much more effective at generating the desired compounds in higher yield and requires shorter heating times. [75,76] While the preparation of H 2 [L5] by this method has previously been reported, no spectroscopic characterization was given.…”