含十六族元素 (硒、碲) 之錳團簇化合物的合成、轉換關係、化性及物性之探討

Abstract

Te−Mn−CO 系統 將 Mn2(CO)10 與 Te powder 以莫耳比 1: 1.6 的比例於 2 M KOH/MeOH 反應可得四邊形錯合物 [Te2Mn2(CO)8]2− (1)。此外化合物 1 可作為良好的建構單元，於適當的條件與 Mn2(CO)10 反應，可形成螺環形 (spiro) 錯合物 [TeMn4(CO)16]2− (3) 或已發表之八面體結構團簇物 [Te2Mn4(CO)12]2−。另一方面，化合物 1 與 Te powder 進行擴核反應生成似啞鈴型團簇物 [Te10Mn6(CO)18]4− (5)或籃子型團簇物 [Te4Mn3(CO)10]−。同樣地，錯合物 3 以及團簇物 [Te4Mn3(CO)10]− 於高溫加入足量 Te powder 可進一步擴核成團簇物 5。除此之外，若團簇物 5 與 2 當量或 4.5 當量的 Mn2(CO)10 反應，則可轉換得到含氫配子之團簇物 [HTe2Mn3(CO)9]2− (2) 或雙魚型化合物 [Te6Mn6(CO)18]4− (4)；相反地，團簇物 2 或 4 透過引入足量之 Te powder 可擴核成化合物 5。值得一提的是，當團簇物 2 與 HCl 反應，可生成已知雙三角錐化合物 [Te2Mn3(CO)9]−，並伴隨 H2 的產生。除此之外，將 2 依序與 CO 和 O2 反應，可得含氫配子之共邊二聚物 [H2Te4Mn6(CO)20]2‒ (6)。再者，當化合物 6 加入過量強酸 HBF4•Et2O 溶液時，則意外得到 CH2CH3+ 片段加成之化合物 [H2Te4Mn6(CO)20(CH2CH3)]– (7)。最後，此系列化合物之轉換關係及電化學分析之結果皆搭配理論計算來進行探討。 Se−Mn−CO 系統 將 Mn2(CO)10 與 Se powder 以莫耳比 1: 5.4 於 40 oC 之 2 M KOH/ MeOH/MeCN 混合溶劑下反應，可得似啞鈴型 (dumbbell-like) 二聚物 [Se10Mn6(CO)18]4‒ (1)；然而，當反應溫度改由 0 oC 回室溫，則可得化合物 1 之單體 [Se5Mn3(CO)9]2‒ (1′)。當團簇物 1 與 2 當量 CH3I 反應，可得到 –CH3 片段加成於 Se10Mn6 之化合物 [Se10Mn6(CO)18(CH3)2]2‒ (2)。同樣地，當團簇物 1 加入雙鹵烷試劑 CH2X2 (X = Cl, Br) 或 Br(CH2)2Br 於室溫反應，可分別得到有機片段加成之化合物[Se10Mn6(CO)18(CH2Cl)2]2‒ (3)、[Se10Mn6(CO)18(CH2Br)2]2‒ (4) 及 [Se10Mn6(CO)18{(CH2)2Br}2]2‒ (5)。特別的是，當化合物 1 與過量 CH2Br2 反應長時間，則可得到兩個相似結構 (isostructural) 之四核錳化合物 [Se8Mn4(CO)18(Se)(CH2)]2‒ (6) 與 [Se8Mn4(CO)12(CH2)2]2‒ (7)。此外，化合物 3 進一步加入過量 AgBF4，同樣地可生成化合物 6 及 7。除此之外，若化合物 5 與 Br(CH2)2Br 反應長時間，則可得到化合物 [Se8Mn4(CO)18(Se)2]2‒ (8)，再者，當化合物 1 與碳鏈較長的鹵烷試劑 Br(CH2)4Br 反應，可同樣地生成化合物 8。有趣的是，當化合物 8 與 CH2Cl2 在高溫下加熱迴流反應長時間，可成功單離相似結構之化合物 7，由此反應過程發現化合物 8 之末端 Se 原子可被等電子的 ‒CH2 片段置換。此外，藉由 SQUID 分析可知化合物 4 為一逆磁性物種，化合物 8 則透過 Evans’ method 以及電子順磁共振光譜探討其磁性以及未成對電子的表現。除此之外，藉由 X-ray 電子能譜儀、電化學、液態及固態紫外光譜，探討化合物 4、5 和 8 之錳價數對磁性表現的影響。最後上述之結果亦搭配密度泛函數理論 (DFT) 之理論計算加以佐證。Te−Mn−CO System The square complex, [Te2Mn2(CO)8]2− (1), was obtained from the reaction of Te powder with Mn2(CO)10 in KOH/MeOH solutions. This Te2Mn2 complex 1 was found to function as a useful synthon to prepare the spiro complex [TeMn4(CO)16]2− (3), dumbbell-like cluster [Te10Mn6(CO)18]4− (5), picnic-basket-like cluster [Te4Mn3(CO)10]2−, and octahedral complex [Te2Mn4(CO)12]2− under appropriate conditions. In addition, complex 3 and [Te4Mn3(CO)10]− could undergo cluster-expansion reaction to form 5 upon the addition of Te powder. Besides, cluster 5 could successfully transform into hydride-bridged cluster [HTe2Mn3(CO)9]2− (2) or [Te6Mn6(CO)18]4− (4) upon the treatment with 2 or 4.5 equivalents of Mn2(CO)10, respectively. Conversely, clusters 2 and 4 could be reconverted into 5 by the addition of Te powder in MeCN. Importantly, when 2 was treated with HCl at room temperature, the reported trigonal-bipyramidal complex [Te2Mn3(CO)9]– was produced, accompanied with the formation of H2. Further, when CO was bubbled into cluster 2 in MeCN at 0 oC, an intermediate [HTe2Mn3(CO)10]2− (2′) was formed which was detected by HR-MS, and then, upon addition of O2 into this reaction, a final stable product [H2Te4Mn6(CO)20]2−(6) was obtained in high yield. Interestingly, when the reaction of 6 with excess HBF4∙Et2O was carried out, an unexpected ethylated product [H2Te4Mn6(CO)20(CH2CH3)]− (7) was yielded. Finally, the nature, structural transformation, and electrochemical properties of these Te–Mn–CO clusters were elucidated by the density functional theory calculations. Se−Mn−CO System The reaction of Se powder and Mn2(CO)10 in appropriate ratios in refluxing 2 M KOH/MeOH/MeCN solutions led to the formation of the dumbbell-like cluster [Se10Mn6(CO)18]4− (1). The similar reaction in MeCN at 0 oC was allowed to warm up to room temperature, yielding the momeric of cluster 1, [Se5Mn3(CO)9]2‒ (1′), detected by FT-IR. Cluster 1 was treated with 2 equiv of CH3I to give the functionalized product [Se10Mn6(CO)18(CH3)2]2− (2). Moreover, cluster 1 could also undergo the –CH2X (X = Cl ,Br) and –(CH2)2Br fragments addition to give rise to [Se10Mn6(CO)18(CH2Cl)2]2‒ (3), [Se10Mn6(CO)18(CH2Br)2]2‒ (4), and [Se10Mn6(CO)18{(CH2)2Br}2]2‒ (5), respectively. Importantly, cluster 1 with CH2Br2 in a long-time reaction led to the formation of isostructural complexes [Se8Mn4(CO)18(Se)(CH2)]2− (6) and [Se8Mn4(CO)12(CH2)2]2− (7), as evidenced by ESI-MS and FT-IR. Complex 4 could also be transformed into complexes 6 and 7 upon the addition of excess AgBF4. Furthermore, when cluster 1 was treated with Br(CH2)nBr (n = 2, 4) in long time, complex [Se8Mn4(CO)18(Se)2]2‒ (8) was obtained. Interestingly, complex 8 was reconverted into the isostructural cluster 7 upon treatment with CH2Cl2 solutions. The diamagnetic properties of complex 4 and paramagnetic behavior of complex 8 were evidence by SQUID analysis and Evans’ method, respectively. The oxidation state of manganese atoms of complexes 4, 5, and 8 can be further determined by HR-XPS. Finally, the nature, structural transformation, and electrochemical properties of these Se–Mn–CO clusters were elucidated by the density functional theory calculations.