低配位、低價數擴展的金屬鏈與金屬-金屬鍵之合成、反應性和形成機制的探討

去質子化的雙胺配基Li4[Me2Si(NDipp)2]2 (Dipp = 2,6-iPrC6H3)和氯化錳(MnCl2)或氯化鎘(CdCl2)反應，可以得到雙錳、雙鎘錯合物Mn2{m2-Me2Si(NDipp)2}2 (3)和Cd2{m-k2-Me2Si(NDipp)2}2 (4)。錯合物3，可以經過兩個電子的分段還原反應，分離出錯合物[(THF)2K⊂18-crown-6][Mn2{m-h2-Me2Si(NDipp)2}2] (18-crwon-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; THF = tetrahydrofuran) ([(THF)2K⊂18-crown-6][5])、[K⊂222-cryptand]2[Mn2{k2-Me2Si(NDipp)2}2] (222-cryptand = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) ([K⊂222-cryptand]2[6])和[K2⊂6]。 [K⊂222-cryptand]2[6]和[K2⊂6]皆具有[Mn22+]核心，兩者都是利用4s軌域形成錳-錳鍵鍵結。另外，錯合物4經過一個電子的還原可以得到四核鎘金屬化合物[(THF)2K⊂18-crown-6]2[{k2-Me2Si(NDipp)2}Cd{m-Me2Si(NDipp)2}Cd]2 ([(THF)2K⊂18-crown-6]2[7])，其中兩個鎘原子之間具有鎘-鎘單鍵。藉由錯合物3和4隨著還原反應的結構變化，我們可以證實理論計算中雙鋅金屬錯合物Zn2{m-k2-Me2Si(NDipp)2}2 (1)隨著還原反應得到具有鋅-鋅鍵的雙核鋅(I)金屬錯合物[{k2-Me2Si(NDipp)2}Zn-Zn{k2-Me2Si(NDipp)2}]2- (2)，所預測產生的兩個中間體。去質子化的吡啶雙胺配基2,6-(DippN)2-4-MeC5H4N (N2N)與溴化鋅(ZnBr2)和氯化鎘(CdCl2)反應，可以得到雙鋅錯合物[Zn(THF)(m-k3-N2N)]2 (8)和雙鎘錯合物[Cd(m-k3-N2N)]2 (9)。將錯合物8和9與鹼金屬還原劑(如鉀石墨和銣金屬)進行還原反應，可以分離出新奇的三核金屬團簇化合物[K(THF)n(18-crown-6)][(MKM)(N2N)2] (10: M = Zn, n = 0; 11: M = Cd, n = 1)、[Rb(THF)(18-crown-6)][(ZnRbZn)(N2N)2] (12)，錯合物10、11和12具有很短的M-A鍵結(M = Zn, A = K, Rb; M = Cd, A = K)；錯合物9與銣金屬反應，只能分離出[Rb(18-crown-6)2]{Cd(THF)[2-2,6-(DippN)2-4-MeC5H4N][2-2-(DippN)-6-(DippNH)-4-MeC5H4N]} (13)。而錯合物10和碘化鎂反應，可以產生Zn-K-Zn被氧化的產物[K(18-crown-6)][{Zn(m-I)Zn}(N2N)2] (16)；錯合物12分別與碘化鉀與碘化鈉反應，卻只能對陽離子銣(I)進行離子交換反應，分別得到錯合物[K(18-crown-6)][(ZnRbZn)(N2N)2] (14)和[Na(THF)2(18-crown-6)][(ZnRbZn)(N2N)2] (15)。因此，錯合物10、11和12具有未曾發表過的M(I)-A(I)-M(I)共價鍵結(M = Zn, Cd; A = K, Rb)，也展現了很高的還原能力。吡啶雙胺配基與三氯化鉻(CrCl3)反應後，再直接以鉀石墨進行還原反應，可以分離出新穎的雙鉻(I)金屬錯合物{(OEt2)KCr(1:2-N2N)}2 (26)，具有鉻-鉻五重鍵。而利用18-冠-6-醚以四氫呋喃或苯為溶劑下與錯合物26進行反應，可以得到[K(18-crown-6)(THF)2][(THF)KCr(m-k1:k2-N2N)2] (27)和[K(18-crown-6)(THF)2]2[Cr2(m-k2-N2N)2(m-k2:k2-C6H6)] (28)，發現具有所謂的親芳烴性(Arene-philic)和取代基效應(Substitution effect)，且第三個具有配位能力的氮原子確實會影響雙鉻之間鍵結的形成。除此之外，利用雙氮基脒、a-雙亞胺和吡啶雙胺配基與鈮的氯化物NbCl3(DME)反應，可以得到(m-Cl)3[Li(THF)2(m-Cl)2][Nb(k2-HC(N-2,6-iPr2C6H3)]2 (30)、Cl3Nb(k2-o,o’-iPr2C6H3-DAB) (o,o’-iPr2C6H3-DAB = 2,3-dimethyl-1,4-bis-(2,6-iPr2C6H3)-1,4-diaza-1,3-butadiene)) (31)和[NbCl(m-k3-N2N)]2 (32)，其中錯合物30和32具有鈮=鈮雙鍵。錯合物31可以用鋅粉繼續進行兩個電子的還原反應，得到錯合物[ClNb(m-Cl)2Nb(THF)][k2-o,o’-iPr2C6H3-DAB]2 (33)，具有鈮-鈮單鍵。當氯化物NbCl3(DME)與鉀石墨先進行還原反應，再與雙氮基脒配基反應，卻可以產生新穎的蝴蝶構形四核鈮金屬錯合物[{(THF)Nb}(m-Cl)2{Nb(THF)Cl}]2[m-k2-HC(N-2,6-iPr2C6H3)2]2 (29)。鋅-鋅和錳-錳鍵可以催化有機疊氮化合物氮-氮的耦合反應。將K2[{k2-Me2Si(NDipp)2}Zn-Zn{k2-Me2Si(NDipp)2}]¬¬ (17)或[{HC(CMeNAr)2}Mn]2 (Ar = 2,6-iPr2C6H3) (18)與一系列有機疊氮化合物R-N3 (R = 1-adamantly, p-tolyl, trimethylsilyl)進行反應，可以分別分離出錯合物[K(18-crown-6)(THF)]2{[k2-Me2Si(NDipp)2]Zn(m-k4-RNN2NR)Zn[k2-Me2Si(NDipp)2]} (R = p-tolyl) (19a)、[K(18-crown-6)(THF)2]2 {[k2-Me2Si(NDipp)2]Zn(m-NSiMe3)Zn[k2-Me2Si(NDipp)2]} (20)、(m-h2:h2-RN6R)[Mn(Nacnac)]2 (Nacnac = HC(C(Me)N-2,6-iPr2C6H3)2 (21: R = 1-adamantyl; 22: R = p-tolyl)和[(Nacnac)Mn(μ-N3)]3 (23)。錯合物19a具有一個橋接反式四氮烯基RNN2NR (R = p-tolyl)，我們認為反應機制是先形成類似錯合物20的中間體，再與另一當量的甲苯疊氮化合物反應，得到錯合物19a。錯合物20和21具有橋接式六氮烯基RNN4NR，錯合物23則為三核錳金屬錯合物，具有三個疊氮基橋接著三個錳原子。當使用矽基橋聯雙氮基脒(Silyl-linked bis(amidinate))配基與碘化銅(CuI)和三氯化鉻(CrCl3)反應，可以分別得到錯合物Cu4{m-h4-Me2Si[NC(C6H5)N(2,6-iPr2C6H3)]2}2 (34)和[Cl(m-Cl)2(THF)Cr]2{m-h4-Me2Si[NC(C6H5)N(2,6-iPr2C6H3)]2} (35)。錯合物35可以進一步用經過兩個電子的還原，得到錯合物[Cl(THF) Cr]2{m-h4-Me2Si[NC(C6H5)N(2,6-iPr2C6H3)]2} (36)。雙鉻金屬錯合物35和36其鉻與鉻之間沒有任何鍵結作用力存在，錯合物34為四核銅金屬錯合物，每個銅之間存在著很強的d10-d10交互作用力。以上所有合成出來的產物，皆已經過核磁共振光譜和元素分析鑑定。透過單晶X-ray繞射解析，我們也清楚了解其分子結構。

關鍵字

多重鍵；五重鍵；氮-氮耦合反應；多金屬鏈錯合物；錳-錳單鍵；鎘-鎘單鍵

並列摘要

The reaction between diamido ligand, Li4[Me2Si(NDipp)2]2 (Dipp = 2,6-iPrC6H3), and MCl2 (M = Mn and Cd) yields Mn2{2-Me2Si(NDipp)2}2 (3) and Cd2{-2-Me2Si(NDipp)2}2 (4). After stepwise reduction of Complex 3, we could separate [(THF)2K⊂18-crown-6][Mn2{-2-Me2Si(NDipp)2]2 (18-crwon-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; THF = tetrahydrofuran ([(THF)2K⊂18-crown-6][5]), [K⊂222-crptand]2[Mn2{2-Me2Si(NDipp)2]2 (222-cryptand = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) ([K⊂222-cryptand]2[6]) and [K2⊂6]. Both Complex [K⊂222-cryptand]2[6] and [K2⊂6] possess [Mn22+] core with Mn-Mn single bond. The addition of KH to Complex 4 leads the isolation of tetranuclear cadmium complex, [(THF)2K⊂18-crown-6]2[{2-Me2Si(NDipp)2}Cd{-Me2Si(NDipp)2}Cd]2 ([(THF)2K⊂18-crown-6]2[7]), with Cd-Cd single bond. The isolation of these compounds corroborate the existence of the intermediates anticipated in structural transformations between Zn2{-2-Me2Si(NDipp)2}2 (1) and [{2-Me2Si(NDipp)2}Zn-Zn{2-Me2Si(NDipp)2}]2- (2) by theoretical calculations. A series of stable molecules containing unprecedented three-center, two-electron M-A-M bonds (M = Zn, Cd; A = K, Rb) were prepared. Reduction of dinuclear Zn(II) and Cd(II) compounds, [Zn(THF)(-3-N2N)]2 (N2N = 2,6-(DippN)2-4-MeC5H4N) (8) and [Cd(-3-N2N)]2 (9), by potassium graphite or elemental rubidium with the presence of 18-crown-6 ether afforded thermally stable compounds [K(THF)n(18-crown-6)][(MKM)(N2N)2] (10: M = Zn, n = 0; 11: M = Cd, n = 1) and [Rb(THF)(18-crown-6)][(ZnRbZn)(N2N)2] (12). The A-M bond lengths are surprisingly short (Zn-Kavg = 2.474 Å, Cd-Kavg = 2.606 Å, and Zn-Rbavg = 2.532 Å). The M-Rb-M three-center, two-electron covalent bonding is also supported by the fact that the bridging alkali metals cannot be replaced by other Group 1 metal ions via ion exchange reactions. Complex 10 shows highly reducting potential in view of the reaction between 10 and MgI2. Treatment of pyridyl diamido ligand, Li2[N2N](OEt2), with CrCl3 and subsequently reduced by 2.5 equiv of potassium graphite gives a novel quintuply-bonded dichromium complex, {(OEt2)KCr(1:2-N2N)}2 (26). We also found the arene-philic and substitution effect on the formation of Cr-Cr quintuple bond. In addition, the reaction of NbCl3(DME) and different type of ligands, such as amidinates, pyridyl diamido ligand, and -dimine ligand, leads to the isolation of (-Cl)3[Li(THF)2(-Cl)2][Nb(2-HC(N-2,6-iPr2C6H3)]2 (30), Cl3Nb(2-o,o’-iPr2C6H3-DAB) (o,o’-iPr2C6H3-DAB = 2,3-dimethyl-1,4-bis-(2,6-iPr2C6H3)-1,4-diaza-1,3-butadiene)) (31), and [ClNb (-3-N2N)]2 (32). Complex 30 and 32 have Nb=Nb doble bond. Redution of Complex 31 with zinc powder gives dinioubium complex, [ClNb(-Cl)2Nb(THF)](2-o,o’-iPr2C6H3-DAB)2 (33), with Nb-Nb single bond. However, addition of 0.25 equiv of amidinates ligand to the precursor, reduced by potassium graphite from NbCl3(DME), leads to the isolation of tetranuclear niobium(II) complex, [{(THF)Nb}(-Cl) 2{Nb(THF)Cl}]2[-2-HC(N-2,6-iPr2C6H3)2]2 (29). It’s an unprecedented butter-fly conformation. We also present N-N coupling reactions mediated by univalent Zn–Zn and Mn–Mn bonds. Treatment of the Zn–Zn bonded complex K2[{2-Me2Si(NDipp)2}Zn-Zn{2-Me2Si(NDipp)2}]¬¬ (17) with 2 equiv of p-tolylazide or azidotrimethylsilane in presence of 18-crwon-6 ether gives [K(18-crown-6)(THF)]2{[2-Me2Si(NDipp)2]Zn(-4-RNN2NR)Zn[2-Me2Si(NDipp)2]} (R = p-tolyl) (19a) with a bridging trans-tetrazene ligand [(p-tolyl)NN2N(p-tolyl)] and [K(18-crown-6)(THF)2]2 {[2-Me2Si(NDipp)2]Zn(-NSiMe3)Zn[2-Me2Si(NDipp)2]} (20), respectively. However, addition of 2 equiv of organic azides RN3 (R = 1-adamantyl, p-tolyl) to the Mn–Mn bonded complex [Mn(Nacnac)]2 (Nacnac = HC[C(Me)N(2,6-iPr2C6H3)]2 (18) also induces N-N coupling to give (-2:2-RN6R)[Mn(Nacnac)]2 (20: R = adamantyl; 21: R = p-tolyl). Both 20 and 21 feature essentially the same core with a bridging hexazene ligand (RNN4NR). Interestingly, a trinuclear manganese complex [(Nacnac)Mn(μ-N3)]3 (22), where three manganese atoms are linked together via three bridging azido ligands, is obtained if 18 is treated with 2 equiv of azidotrimethylsilane. Furthermore, the reaction of Silyl-linked bis(amidinate) ligand, [Li(THF)4][Li3{3-4-Me2Si[NC(C6H5)N(2,6-iPr2C6H3)]2}2] and CuI leads to the isolation of Cu4{-4-Me2Si[NC(C6H5)N(2,6-iPr2C6H3)]2}2 (34) with the d10-d10 interactions between four copper atoms. Finally, addition of the same ligand to CrCl3 gives [Cl(-Cl)(THF)Cr]2{-4-Me2Si[NC(C6H5)N(2,6-iPr2C6H3)]2} (35). [Cl(THF) Cr]2{-4-Me2Si[NC(C6H5)N(2,6-iPr2C6H3)]2} (36) is prepared by further reduced by 2 equiv of potassium graphite from complex 35. There is no bonding interactions between two dichormium atoms of Comples 34 and 35. All the synthesized products are characterized by NMR spectroscopy and elemental analysis and their molecular structures are determined by single crystal X-ray crystallography.

並列關鍵字

Multiple Bonds ； Quintuple Bonds ； N-N Coupling reaction ； Extended Metal Atom Chains ； Manganese-Manganese Bond ； Cadmium-Cadmium Bond

參考文獻

(115) 黃于倫, 國立清華大學化學研究所碩士論文, 2008.

(117) 許家瑋, 國立清華大學化學研究所碩士論文, 2008.

(95) 林冠銘, 國立清華大學化學研究所碩士論文, 2008.

(131) 楊凡陞, 國立清華大學化學研究所碩士論文, 2010.

(59) (a) 呂端晏, 國立清華大學化學研究所碩士論文, 2005. (b) Bardaji, M.; Laguna, A. J. Chem. Educ. 1999, 76, 201.

國際替代計量

低配位、低價數擴展的金屬鏈與金屬-金屬鍵之合成、反應性和形成機制的探討

主題瀏覽