Synthesis of New Bis(amidine)–Cobalt Catalysts and Their Application to Styrene Polymerization

Abstract

Two new bis(amidine) cobalt(II) complexes were rationally designed and efficiently synthesized. The first synthesized cobalt complex was based on a cyclic bis(amidine) ligand with chiral vicinal diphenyl groups. The structure was verified by single-crystal X-ray crystallography. As expected from the ligand structure, the Co−N bonds in this complex were significantly shorter than those found in the corresponding 1,2-diimine cobalt complex. This indicates that the bis(amidine) ligand has better electron-donating capability than the 1,2-diimine ligand. Upon test polymerization of styrene, the complex exhibited a moderate activity of 5.88 × 10 5 g PS/(mol Co h). On the basis of this encouraging result, a new 1,2-diaminobenzene-derived bis(amidine) ligand was efficiently synthesized and used to make the corresponding cobalt(II) complex. When subjected to styrene polymerization, the resulting complex showed unusually high polymerization activity [164 × 10 5 g PS/(mol Co h)] and high conversion (>99%). The resulting polymer was identified as atactic polystyrene by 13 C NMR spectroscopy analysis. The significantly enhanced styrene polymerization activity of the 1,2-diaminobenzene-originated bis(amidine) cobalt(II) complex is attributed to the improved electron-donating capability of the ligand. Article pubs.acs.org/Organometallics

Quinoxaline and Pyrido[x,y‐b]pyrazine‐Based Emitters: Tuning Normal Fluorescence to Thermally Activated Delayed Fluorescence and Emitting Color over the Entire Visible‐Light Range

“…Important intermediates a , b , and c were synthesized according to methods reported in the literature …”

“…Structures and detailed synthetic procedures for all compounds are described in Scheme 1a nd Scheme S1 in the Supporting Information. The importanti ntermediates, 2,3-dichloroquinoxaline (a), [28] [4-(9H-fluoren-9-yl)phenyl]boronic acid (b), [29] 1,2-bis(4-bromophenyl)ethane-1,2-dione (c), [30] 2,3-bis(4-bromophenyl)quinoxaline (d), 2,3-bis(4-bromophenyl)pyrido [3,4-b]pyrazine (e)a nd 2,3-bis(4-bromophenyl)pyrido [2,3-b]pyrazine (f), [31] were synthesized accordingt op reviously reportedm ethods. The Cz-based compound Q-Cz was then prepared in high yield through aS uzuki cross-coupling reactionofi ntermediates a and b.T he other five analogues were synthesized through the Buchwald-Hartwig reactiono fd, e,o rf with DMAC or PXZ in moderate yields of 40-50 %.…”

“…Important intermediates a, b,a nd c were synthesized according to methods reported in the literature. [28][29][30][31] Generalp rocedure for the synthesis of intermediatesd -f…”

A One‐pot Facile Synthesis of 2,3‐Dihydroxyquinoxaline and 2,3‐Dichloroquinoxaline Derivatives Using Silica Gel as an Efficient Catalyst

“…Until now, there are several methods reported in the literature. Traditionally, condensing o ‐phenylenediamine with oxalic acid or diethyl oxalate in the presence of an acid catalyst (usually HCl) is to date one of the most employed methods . However, a large amount of concentrated hydrochloric acid was required in this process.…”

Binary molybdenum-based catalyst for coordination polymerization of styrene

“…However, the number of reports on polymerization processes for styrene (St) is limited. In recent years, there have been considerable reports on coordination polymerization methods of synthesizing PS, [17][18][19][20][21][22][23][24][25][26] most of which are dominated by metallocene (MAO) or rare earth catalytic systems. Unfortunately, the relatively high molecular weight and stereoregularity are strongly dependent on the content of MAO, which ultimately led to high cost of catalyst.…”