Photoredox Catalysis Mediated by Tungsten(0) Arylisocyanides
Photoredox Catalysis Mediated by Tungsten(0) Arylisocyanides
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DOI：
10.1021/jacs.1c07617
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发表时间：
2021-11-24
影响因子：
15
通讯作者：
Gray, Harry B.
中科院分区：
文献类型：
--
作者：
Fajardo, Javier, Jr.;Barth, Alexandra T.;Gray, Harry B.
W（CNAr）（6）（CNAr =芳基异氰）光还原剂催化氘代苯中1-（2-碘苄基）-吡咯的碱促均裂芳香取代反应（BHAS）。中到高效率与在单光子445 nm激发时的W（CNAr）（6）激发态还原电位相关，其中10 mol %负载的最强光还原剂W（CNDipp）（6）（CNDipp = 2，6-二异丙基苯基异氰）和W（CNDippPh（OMe 3））（6）（CNDippPh（OMe 3）= 4-（3，4，5-三甲氧基苯基）-2，6-二异丙基苯基异氰）提供几乎完全的转化。Stern-Volmer猝灭实验表明，催化是由底物还原脱卤引发的。利用W（CNAr）（6）配合物大的双光子吸收截面（TPA），我们发现飞秒脉冲810 nm激发可以驱动双光子吸收。对于单光子和双光子激发，通过形成七配位的W-II-diiodo [WI 2（CNAr）（5）]络合物来终止双光子激发。值得注意的是，我们发现W（CNDipp）（6）可以通过溶液中存在过量配体的WI 2（CNDipp）（5）的化学还原来再生。
W(CNAr)(6) (CNAr = arylisocyanide) photoreductants catalyze base-promoted homolytic aromatic substitution (BHAS) of 1-(2-iodobenzyl)-pyrrole in deuterated benzene. Moderate to high efficiencies correlate with W(CNAr)(6) excited-state reduction potentials upon one-photon 445 nm excitation, with 10 mol % loading of the most powerful photoreductants W(CNDipp)(6) (CNDipp = 2,6-diisopropylphenylisocyanide) and W(CNDippPh(OMe3))(6) (CNDippPh(OMe3) = 4-(3,4,5-trimethoxyphenyl)-2,6-diisopropylphenylisocyanide) affording nearly complete conversion. Stern-Volmer quenching experiments indicated that catalysis is triggered by substrate reductive dehalogenation. Taking advantage of the large two-photon absorption (TPA) cross sections of W(CNAr)(6) complexes, we found that photocatalysis can be driven with femtosecond-pulsed 810 nm excitation. For both one- and two-photon excitation, photocatalysis was terminated by the formation of seven-coordinate W-II-diiodo [WI2(CNAr)(5)] complexes. Notably, we discovered that W(CNDipp)(6) can be regenerated by chemical reduction of WI2(CNDipp)(5) with excess ligand present in solution.