Nickel-Catalyzed O‑Arylation of Primary or Secondary Aliphatic Alcohols with (Hetero)aryl Chlorides: A Comparison of Ni(I) and Ni(II) Precatalysts

A comparative experimental and computational study examining the interplay of the ancillary ligand structure and Ni oxidation state in the Ni-catalyzed C­(sp2)–O cross-coupling of (hetero)­aryl chlorides and primary or secondary aliphatic alcohols is presented, focusing on PAd-DalPhos (L1)-, CyPAd-DalPhos (L2)-, PAd2-DalPhos (L3)-, and DPPF (L4)-ligated [(L)­NiCl]n (n = 1 or 2) and (L)­Ni­(o-tol)Cl precatalysts. Both L1 and L2 were found to outperform the other ligands examined, with the latter proving to be superior overall. While Ni­(II) precatalysts generally outperformed Ni­(I) species, in some instances the catalytic abilities of Ni­(I) precatalysts were competitive with those of Ni­(II). Density-functional theory calculations indicate the favorability of a Ni(0)/Ni­(II) catalytic cycle featuring turnover-limiting C–O bond reductive elimination over a Ni­(I)/Ni­(III) cycle involving turnover-limiting C–Cl oxidative addition.本研究报道了一项对比实验与计算研究，旨在探究镍催化（杂）芳基氯与伯、仲脂肪醇的C(sp²)–O交叉偶联反应中，辅助配体（ancillary ligand）结构与镍氧化态之间的相互作用。研究重点考察四类配体配位的预催化剂（precatalysts）：分别由PAd-DalPhos（L1）、CyPAd-DalPhos（L2）、PAd₂-DalPhos（L3）与DPPF（L4）配位得到的[(L)NiCl]ₙ（n=1或2）以及(L)Ni(邻甲苯基)Cl配合物。实验结果表明，L1与L2的催化性能均优于其余测试配体，其中L2整体表现更优异。尽管镍(II)预催化剂整体性能优于镍(I)物种，但在部分场景中，镍(I)预催化剂的催化能力可与镍(II)预催化剂相媲美。密度泛函理论（Density-functional theory）计算显示，相较于以C–Cl氧化加成为决速步的Ni(I)/Ni(III)催化循环，以C–O键还原消除为决速步的Ni(0)/Ni(II)催化循环更具热力学优势。