Although cobalt(I) bis-phosphine complexes have been implicated in many selective C–C bond-forming reactions, until recently relatively few of these compounds have been fully characterized or have been shown to be intermediates in catalytic reactions. In this paper we present a new practical method for the synthesis and isolation of several cobalt(I)-bis-phosphine complexes and their use in Co(I)-catalyzed reactions. We find that easily prepared (in situ generated or isolated) bis-phosphine and (2,6-N-aryliminoethyl)pyridine (PDI) cobalt(II) halide complexes are readily reduced by 1,4-bis-trimethylsilyl-1,4-dihydropyrazine or commercially available lithium nitride (Li₃N), leaving behind only innocuous volatile byproducts. Depending on the structures of the bis-phosphines, the cobalt(I) complex crystallizes as a phosphine-bridged species [(P∼P)(X)Co^I[μ-(P∼P)]Co^I(X)(P∼P)] or a halide-bridged species [(P∼P)Co^I[μ-(X)]₂Co^I(P∼P)]. Because the side-products are innocuous, these methods can be used for the in situ generation of catalytically competent Co(I) complexes for a variety of low-valent cobalt-catalyzed reactions of even sensitive substrates. These complexes are also useful for the synthesis of rare cationic [(P∼P)Co^I-η⁴-diene]⁺ X⁻ or [(P∼P)Co^I-η⁶-arene]⁺ X⁻ complexes, which are shown to be excellent single-component catalysts for the following regioselective reactions of dienes: heterodimerizations with ethylene or methyl acrylate, hydroacylation and hydroboration. The reactivity of the single-component catalysts with the in situ generated species are also documented.

中文翻译：

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用于 1,3-二烯的区域和对映选择性异二聚化和加氢酰化反应的无活化剂单组分 Co(I)-催化剂。[L]Co(I)-络合物合成的新还原程序及与原位生成催化剂的比较

尽管钴 ( I ) 双膦配合物与许多选择性的 C-C 键形成反应有关，但直到最近，这些化合物中很少有人被完全表征或被证明是催化反应的中间体。在本文中，我们提出了一种新的实用方法，用于合成和分离几种钴 ( I )-双膦配合物及其在 Co( I ) 催化反应中的应用。我们发现容易制备（原位产生或分离）的双膦和 ( 2,6- N-芳基亚氨基乙基)吡啶 (PDI) 钴 ( II ) 卤化物配合物很容易被 1,4-双-三甲基甲硅烷基-1,4 还原-二氢吡嗪或市售的氮化锂（Li ₃N)，只留下无害的挥发性副产物。取决于双膦的结构，钴（I）配合物结晶为膦桥物种 [( P∼P )(X)Co ^I [μ-( P∼P )]Co ^I (X)( P ∼P )] 或卤化物桥接物种 [( P∼P )Co ^I [μ-(X)] ₂ Co ^I ( P∼P )]。由于副产物无害，这些方法可用于原位生成具有催化活性的 Co( I) 配合物，适用于甚至敏感底物的各种低价钴催化反应。这些配合物也可用于合成稀有的阳离子 [( P∼P )Co ^{I -η 4} -diene ] ⁺ X ^-或 [( P∼P )Co ^I -η ⁶ -arene] ⁺ X ^-配合物，它们是被证明是用于二烯的以下区域选择性反应的优异单组分催化剂：与乙烯或丙烯酸甲酯的异二聚化、氢化酰化和硼氢化。还记录了单组分催化剂与原位产生的物质的反应性。