Evidence for a preferential intramolecular oxidative addition in Ni-catalyzed cross-coupling reactions and their impact on chain-growth polymerizationsElectronic supplementary information (ESI) available: Experimental details; spectroscopic data; CIF file. CCDC 915793. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3sc00090g

• Main Authors: Bryan, Zachary J, McNeil, Anne J
• Format: Article
• Language: English
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c3sc00090g

Small molecule competition experiments were performed to determine whether Ni-catalyzed Kumada cross-coupling reactions proceed through an intramolecular oxidative addition. Indeed, preferential intramolecular oxidative addition was observed for all four complexes when stoichiometric quantities of competitive agent were present. At higher concentrations of competitive agent, the intramolecular pathway was still preferred when bidentate, electron-rich ligands were utilized, suggesting that these ligands promote the formation and reactivity of the key intermediate. To determine whether a similar pathway is involved in the polymerizations, (4-bromo-2,5-bis(hexyloxy)phenyl)magnesium bromide was polymerized in the presence and absence of competitive agent. The number-average molecular weights were lower and the molecular weight distributions were broadened substantially when competitive agent was present, consistent with the presence of competing intermolecular pathways. Because bidentate, electron-rich ligands suppressed these undesired intermolecular reactions, these ligands should lead to improved polymerization catalysts. Preferential intramolecular oxidative additions are observed in competition experiments, suggesting that Ni-catalyzed Kumada cross-coupling reactions likely proceed through a π-complex intermediate. Bidentate, electron-rich ligands favor the intramolecular pathway and promote chain-growth polymerizations.