Formation and Cleavage of P-C, Mo-C, and C-H Bonds Involving Arylphosphinidene and Cyclopentadienyl Ligands at Dimolybdenum Centers
Formation and Cleavage of P-C, Mo-C, and C-H Bonds Involving Arylphosphinidene and Cyclopentadienyl Ligands at Dimolybdenum Centers
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涉及二钼中心芳基膦和环戊二烯基配体的 P-C、Mo-C 和 C-H 键的形成和断裂
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发表时间：
2006
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通讯作者：
J. Jeffery
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作者：
I. Amor;M. E. García;Miguel A. Ruiz;David Sáez;H. Hamidov;J. Jeffery
膦配位桥联配合物[Mo 2 Cp 2（μ-PR*）（CO）4 ]（R = 2，4，6-C6 H2 tBu 3）在β-二甘醇二甲醚中发生分子内C-H键断裂，生成膦氢化物[Mo 2 -Cp 2（μ-H）{μ-P（CH 2CMe 2）C6 H2 tBu 2 }（CO）4 ]。438 K）或暴露于近UV-可见光下。相比之下，其暴露于紫外光下产生两种不同的二羰基衍生物，取决于反应条件，三键[Mo 2 Cp 2（μ-PR*）（μ-CO）2 ]（Mo-Mo = 2.5322（3）A）或其异构体[Mo 2 Cp 2（μ-κ 1：κ 1，η 6 -PR*）（CO）2 ]，其中亚膦配体不对称地桥接金属中心，同时以η 6 -方式将其芳基结合到钼原子之一上。后一种配合物经历质子催化的互变异构反应，得到环戊二烯基-膦叉衍生物[Mo 2 Cp（μ-κ 1：κ 1，η 5 -PC 5 H 4）（η 6 -R*H）（CO）2]。η 6 -亚膦配合物的羰基化反应通过η 4 -三羰基配合物[Mo 2 Cp 2（μ-κ 1：κ 1，η 4 -PR*）（CO）3 ]逐步进行，然后得到起始的四羰基化合物，而其与CN t Bu的反应仅产生η 4 -配合物[Mo 2 Cp 2（μ-κ 1：κ 1，η 4 -PR*）（CN t Bu）（CO）2 ]，其通过X射线研究表征。在四氢呋喃中，η 4 -三羰基物种与CN tBu反应，得到金属-金属键合衍生物[Mo 2Cp 2（μ-PR*）（CN tBu）（CO）3 ].然而，在石油醚中，该反应生成双（异氰化物）衍生物[Mo 2 Cp 2（μ-PR*）（CN t Bu）2（CO）3 ]，它具有不对称的三角膦桥，没有金属-金属键。上述结果可以通过假设[Mo 2Cp 2（μ-PR*）（CO）4 ]光解过程中的两个主要过程来解释，其中一个过程涉及膦配体从三角（四电子给体）到金字塔（两电子给体）配位模式的价态互变异构. CuCl的存在促进了η 6络合物的羰基化反应，形成了三金属物种[CuMo 2（Cl）Cp 2（μ-κ 1：κ 1：κ 1，η 6 -PR*）（CO）2 ]和[CuMo 2（Cl）-Cp 2（μ-κ 1：κ 1：κ 1，η 4 -PR*）（CO）3].后者的配合物，其特征在于还通过单晶X-射线研究。
The phosphinidene-bridged complex [Mo 2 Cp 2 (μ-PR*)(CO) 4 ] (R = 2,4,6- C 6 H 2 t Bu 3 ) experiences an intramolecular C-H bond cleavage from a t Bu group to give the phosphide-hydride derivative [Mo 2 -Cp 2 (μ-H){μ-P(CH2CMe2)C 6 H 2 t Bu 2 }(CO) 4 ] in refluxing diglyme (ca. 438 K) or under exposure to near-UV-visible light. In contrast, its exposure to UV light yields two different dicarbonyl derivatives depending on the reaction conditions, either the triply bonded [Mo 2 Cp 2 (μ-PR*)(μ-CO) 2 ] (Mo-Mo = 2.5322(3) A) or its isomer [Mo 2 Cp 2 (μ-κ 1 :κ 1 ,η 6 -PR*)(CO) 2 ], in which the phosphinidene ligand bridges asymmetrically the metal centers while binding its aryl group to one of the molybdenum atoms in a η 6 -fashion. The latter complex experiences a proton-catalyzed tautomerization to yield the cyclopentadienylidene-phosphinidene derivative [Mo 2 Cp(μ-κ 1 :κ 1 ,η 5 -PC 5 H 4 )(η 6 -R*H)(CO)2]. Carbonylation of the η 6 -phosphinidene complex proceeds stepwise through the η 4 -tricarbonyl complex [Mo 2 Cp 2 (μ-κ 1 :κ 1 ,η 4 -PR*)(CO) 3 ] and then to the starting tetracarbonyl compound, whereas its reaction with CN t Bu yields only the η 4 -complex [Mo 2 Cp 2 (μ-κ 1 :κ 1 ,η 4 -PR*)(CN t Bu)(CO) 2 ], which was characterized through an X-ray study. The η 4 -tricarbonyl species reacts with CN t Bu in tetrahydrofuran to give the metal-metal bonded derivative [Mo 2 Cp 2 (μ-PR*)(CN t Bu)(CO) 3 ]. In petroleum ether, however, this reaction yields the bis(isocyanide) derivative [Mo 2 Cp 2 (μ-PR*)(CN t Bu)2(CO) 3 ], which has an asymmetric trigonal phosphinidene bridge and no metal-metal bond. All the above results can be explained by assuming the operation of two primary processes in the photolysis of [Mo 2 Cp 2 (μ-PR*)(CO) 4 ], one of them involving a valence tautomerization of the phosphinidene ligand, from the trigonal (four-electron donor) to the pyramidal (two-electron donor) coordination mode. The carbonylation reaction of the η 6 -complex is accelerated by the presence of CuCl, due to the formation of the trimetal species [CuMo2(Cl)Cp 2 (μ-κ 1 :κ 1 :κ 1 ,η 6 -PR*)(CO) 2 ] and [CuMo 2 (Cl)-Cp 2 (μ-κ 1 :κ 1 :κ 1 ,η 4 -PR*)(CO)3]. The latter complexes were also characterized by single-crystal X-ray studies.