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Reactivity of a Dinuclear PdI Complex [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] with PPh3: Implications for Cross-Coupling Catalysis Using the Ubiquitous Pd(OAc)2/nPPh3 Catalyst System
Organometallics ( IF 2.5 ) Pub Date : 2021-08-19 , DOI: 10.1021/acs.organomet.1c00347 Neil W J Scott 1 , Mark J Ford 2 , David R Husbands 1 , Adrian C Whitwood 1 , Ian J S Fairlamb 1
Organometallics ( IF 2.5 ) Pub Date : 2021-08-19 , DOI: 10.1021/acs.organomet.1c00347 Neil W J Scott 1 , Mark J Ford 2 , David R Husbands 1 , Adrian C Whitwood 1 , Ian J S Fairlamb 1
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[PdI2(μ-PPh2)(μ2-OAc)(PPh3)2] is the reduction product of PdII(OAc)2(PPh3)2, generated by reaction of ‘Pd(OAc)2’ with two equivalents of PPh3. Here, we report that the reaction of [PdI2(μ-PPh2)(μ2-OAc)(PPh3)2] with PPh3 results in a nuanced disproportionation reaction, forming [Pd0(PPh3)3] and a phosphinito-bridged PdI-dinuclear complex, namely [PdI2(μ-PPh2){κ2-P,O-μ-P(O)Ph2}(κ-PPh3)2]. The latter complex is proposed to form by abstraction of an oxygen atom from an acetate ligand at Pd. A mechanism for the formal reduction of a putative PdII disproportionation species to the observed PdI complex is postulated. Upon reaction of the mixture of [Pd0(PPh)3] and [PdI2(μ-PPh2){κ2-P,O-μ-P(O)Ph2}(κ-PPh3)2] with 2-bromopyridine, the former Pd0 complex undergoes a fast oxidative addition reaction, while the latter dinuclear PdI complex converts slowly to a tripalladium cluster, of the type [Pd3(μ-X)(μ-PPh2)2(PPh3)3]X, with an overall 4/3 oxidation state per Pd. Our findings reveal complexity associated with the precatalyst activation step for the ubiquitous ‘Pd(OAc)2’/nPPh3 catalyst system, with implications for cross-coupling catalysis.
中文翻译：
双核 PdI 复合物 [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] 与 PPh3 的反应性：使用无处不在的 Pd(OAc)2/nPPh3 催化剂系统对交叉偶联催化的影响
[Pd I 2 (μ-PPh 2 )(μ 2 -OAc)(PPh 3 ) 2 ] 是Pd II (OAc) 2 (PPh 3 ) 2的还原产物，由'Pd(OAc) 2 '反应生成具有两当量的 PPh 3。在这里，我们报告 [Pd I 2 (μ-PPh 2 )(μ 2 -OAc)(PPh 3 ) 2 ] 与 PPh 3 的反应导致细微的歧化反应，形成 [Pd 0 (PPh 3 ) 3] 和膦基桥连的 Pd I -双核复合物，即 [Pd I 2 (μ-PPh 2 ){κ 2 -P,O-μ-P(O)Ph 2 }(κ-PPh 3 ) 2 ]。后一种配合物被提议通过从 Pd 处的乙酸盐配体中提取氧原子来形成。假定一种将推定的 Pd II歧化物质正式还原为观察到的 Pd I复合物的机制。[Pd 0 (PPh) 3 ]和[Pd I 2 (μ-PPh 2 ){κ 2 -P,O-μ-P(O)Ph 2 }(κ-PPh 3) 2 ] 与 2-溴吡啶，前者的 Pd 0 配合物经历快速氧化加成反应，而后者的双核 Pd I 配合物缓慢转化为 [Pd 3 (μ-X)(μ-PPh 2 ) 2 (PPh 3 ) 3 ]X，每个Pd的总氧化态为4/3 。我们的研究结果揭示了与普遍存在的“Pd(OAc) 2 ”/nPPh 3催化剂体系的催化剂前活化步骤相关的复杂性，对交叉偶联催化有影响。
更新日期：2021-09-13
中文翻译：
双核 PdI 复合物 [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] 与 PPh3 的反应性：使用无处不在的 Pd(OAc)2/nPPh3 催化剂系统对交叉偶联催化的影响
[Pd I 2 (μ-PPh 2 )(μ 2 -OAc)(PPh 3 ) 2 ] 是Pd II (OAc) 2 (PPh 3 ) 2的还原产物，由'Pd(OAc) 2 '反应生成具有两当量的 PPh 3。在这里，我们报告 [Pd I 2 (μ-PPh 2 )(μ 2 -OAc)(PPh 3 ) 2 ] 与 PPh 3 的反应导致细微的歧化反应，形成 [Pd 0 (PPh 3 ) 3] 和膦基桥连的 Pd I -双核复合物，即 [Pd I 2 (μ-PPh 2 ){κ 2 -P,O-μ-P(O)Ph 2 }(κ-PPh 3 ) 2 ]。后一种配合物被提议通过从 Pd 处的乙酸盐配体中提取氧原子来形成。假定一种将推定的 Pd II歧化物质正式还原为观察到的 Pd I复合物的机制。[Pd 0 (PPh) 3 ]和[Pd I 2 (μ-PPh 2 ){κ 2 -P,O-μ-P(O)Ph 2 }(κ-PPh 3) 2 ] 与 2-溴吡啶，前者的 Pd 0 配合物经历快速氧化加成反应，而后者的双核 Pd I 配合物缓慢转化为 [Pd 3 (μ-X)(μ-PPh 2 ) 2 (PPh 3 ) 3 ]X，每个Pd的总氧化态为4/3 。我们的研究结果揭示了与普遍存在的“Pd(OAc) 2 ”/nPPh 3催化剂体系的催化剂前活化步骤相关的复杂性，对交叉偶联催化有影响。
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