Main Group Element (S and Bi)-Containing Metal Carbonyl Complexes: Synthesis, Transformation, Reactivity, and Applications

Abstract

1.硫/錳系統 當硫粉以及 Mn2(CO)10 以一鍋化方式於 KOH 混合甲醇溶劑加熱回流反應時，可得一罕見的硫–錳含氫配子之羰基團簇物 [(μ-H)Mn3(CO)9(μ3-S)2]2– (1)。由 X-ray 單晶結構鑑定可知化合物 1 係由 S2Mn3 四角錐組成，且其氫配子橋接於一 Mn–Mn 鍵上。有趣的是，藉由質子–氫配子交互方式，1 可與已發表的雙三角錐化合物 [Mn3(CO)9(μ3-S)2]– 進行可逆結構轉換，其中包含著有趣的氫氣產生過程。進一步，當硫粉以及 Mn2(CO)10 以一鍋化方式於莫耳比為 5: 8 的條件下，可生成含硫醇之化合物 [Mn3(CO)9(μ-HS)(μ3-S2)2]2− (3)。由變溫 1H NMR 可知錯合物 3 中的氫配子具有有趣的流動現象。再者，當 3 與 TEMPO 反應時，可得去質子之硫−硫鍵結雙聚物 [{Mn3(CO)9(μ3-S2)(μ3-S2)}2(μ4-S)]4− (9)。由十八電子規則可知，化合物 9 具有 108 個價電子，滿足電子計算。但其卻具有令人意想不到的磁性表現，此表現可藉由固態 EPR 光譜證實。最重要的是，9 可於 UV 燈照下進行氫氣活化，逆反應回化合物 3。最後，此系列含硫之錳羰基錯合物之性質、結構轉換以及氫配子流動特性皆藉由 DFT 理論計算之輔佐進行系統性的討論。 2.鉍/鉻系統 成功合成出過去未知的 4 中心–6π 共振平面三角形錯合物 [Bi{Cr(CO)5}3]– (1)，並藉由 XAS、XPS 以及 DFT 理論計算得知其中心鉍原子為正 3 價。由化合物 1 結構得知，此鉍原子在鍵結上可扮演雙重的提供者與接受者的角色。與過往鉍三價原子之弱路易士酸性不同，化合物 1 中的鉍三價原子為極強路易士酸，其可吸引極弱路易士鹼氟負離子並產生鍵結、展現溶劑化顯色性質、進行有趣的醚化過程以及具有令人訝異的半導體特性。化合物 1 之能隙為 1.02 eV，主要歸因於其於固態下存在著 Bi···O 和 O···O 之弱作用力。此外，Fe4(CO)4 加成之錯合物 [{Fe(CO)4}Bi{Cr(CO)5}3]3– (1-Fe) 可進行選擇性的去金屬化反應，生成等電子數之 BiCr3 錯合物 1 以及 BiCr2Fe 錯合物 [Bi{Cr(CO)5}2{Fe(CO)4}]– (2)。此結果提供了一個新穎的方式來設計一系列異核金屬引入之鉍/鉻平面三角形錯合物。1.S/Mn System When the one-pot reaction of S8 powder with Mn2(CO)10 was conducted in refluxing KOH/MeOH, a rare example of S–Mn hydride carbonyl cluster [(μ-H)Mn3(CO)9(μ3-S)2]2– (1) was formed. X-ray crystallographic analysis of 1 displayed a S2Mn3 square-pyramidal core with one Mn–Mn bond bridged by one hydrogen atom. Interestingly, the hydrogen formation was found in the transformation between 1 and the reported S2Mn3 trigonal-bipyramidal cluster [Mn3(CO)9(μ3-S)2]– through the proton–hydride interaction. In addition, a thiol complex [Mn3(CO)9(μ-HS)(μ3-S2)2]2− (3) could be prepared also from the one-pot reaction of S8 powder with Mn2(CO)10 in the molar ration of 5: 8. The variable-temperature (VT) 1H NMR showed that the hydrogen in 3 exhibited significant fluxionality. Further, when 3 reacted with TEMPO, a deprotonated S−S-bonded dimeric cluster [{Mn3(CO)9(μ3-S2)(μ3-S2)}2(μ4-S)]4− (9) was formed. On the basis of 18-electron rule, 9 is an electron-precise species with 108 valence electrons, however, it showed unexpected magnetic propertied as evidenced by the solid-state EPR. Most importantly, cluster 9 could be reconverted back to 3 via the activation of hydrogen by radiation with UV lamp. Finally, the nature, transformation, and hydride fluxionality of these S−Mn carbonyl complexes were systematically discussed with the aid of DFT calculations.

2.Bi/Cr System The formation of a hitherto unknown 4-center, 6π–conjugated trigonal-planar complex, [Bi{Cr(CO)5}3]– (1), is reported, in which the oxidation state of the Bi atom is +3, as evidenced by XAS, XPS, and DFT calculations. The BiIII atom in 1 has dual donor and acceptor properties in its bonding mode. In contrast to the mild Lewis acidity of BiIII, the central Bi in 1 functions as a prodigious Lewis acid site to exhibit strong affinity toward F– ions, unique solvatochromic properties, intriguing etherification through the C–O bond cleavage of alcohols, and surprising semiconducting characteristics with an ultra-narrow optical band gap of 1.02 eV, which can be attributed to the intermolecular Bi···O and O···O interactions in the solid state. The tetrahedral Fe(CO)4-adduct [{Fe(CO)4}Bi{Cr(CO)5}3]3– (1-Fe) allowed the selective demetallation to afford the isoelectronic multiply bonded BiCr3-complex 1 and the BiCr2Fe-complex, [Bi{Cr(CO)5}2{Fe(CO)4}]– (2), which may open a novel pathway for the design of the heterometal-incorporated trigonal-planar Bi-Cr complexes.