二苯胺萘啶、二吡啶胺萘啶配基及其單核、雙核、 六核金屬錯合物之合成與研究

Abstract

本論文是以探討新穎的偶數氮配基： 2,7- 二苯胺-1,8- 萘啶 (2,7-Bis(α-phenylamino)-1,8-naphthyridine, H2bphany)，以及 2,7-二吡啶胺 -1,8-萘啶， (2,7-Bis(α-pyridylamino)-1,8-naphthyridine, H2bpyany)的配位 化學研究。配基的合成， 由2,6-Dichloro-1,8-naphthyridine 與2 當 量的Aniline (或 2-Aminopyridine)， 在強鹼(t-BuOK) 以及Pd 催化 條件下， 即可合成H2bphany(或H2bpyany)。在配基H2bphany 的研究 中，已合成出鉬雙核錯合物[Mo2(Hbphany)3(O2C(R))] (R = CH3,CF3) ，並解出 其晶體結構；我們亦嘗試合成四核金屬錯合物，目前只有從FAB-MS 光譜中 得知已合成出四核鎳金屬串錯合物，[Ni4(µ4-bphany)4](1) ，但是並未得到其 晶體結構。六氮配基，H2bpyany，配位模式至少有the anti-anti form I, the anti-anti-syn-anti-anti form II , and the all-syn form III。在form I 中，配基為雙 芽基，利用吡啶和萘啶上的各一個氮原子來配位金屬離子，已合成出單核之 [Co(H2bpyany)(NCS)2] (2) 及[Ni(H2bpyany)(NCS)2(H2O)] (3)。在form II 中， 配基可配位兩個金屬離子，如錯合物[Cu2(µ4-H2bpyany)(µ-Cl)(µ-OH)Cl2] (4). 我們最感興趣的是form III，我們已合成出鎳、鈷之六核金屬串錯合物 [Ni6(µ6-bpyany)4(X)2]n+ (X= NCS– : n = 2 (5), n = 1 (6); X = Cl–: n = 2 (7), n = 1 (8))及 [Co6(µ6-bpyany)4(X)2]n+ (X= NCS– : n = 1 (9), n = 2 (10); X = OTf –: n = 1 (11), n = 2 (12))。Ni6 系列，由晶體結構與磁性分析結果顯示，脫氫之配基 (bpyany2–)為螺旋型纏繞於金屬串上，鎳(II)排列(Ni(1)…Ni(2)…Ni(3)… Ni(4)…Ni(5)…Ni(6))近乎直線，不考慮軸配位基時，錯合物具D4 對稱。而錯 合物(5) 及(7)的Ni…Ni 之間無鍵結，末端Ni(1)、Ni(6)為四角錐環境，高自 旋態(S = 1)，而內部四個鎳(II)為平方四邊形環境，低自旋態(S = 0)，其磁性 偶合常數J16≒–4 ~ –5 cm–1。錯合物(5)的電化學有一還原對E1/2 = –0.19 V， 顯示Ni6 12+金屬軸為容易還原為Ni6 11+。還原前後錯合物(7)與(8)，鍵長 Ni(3)–Ni(4)由2.281(2) Å(錯合物(7))縮短至2.201(3) Å(錯合物(8))，明顯的縮 短約0.08 Å，Ni(3)–Npy(av) 則從1.903(8) Å 變長為2.009(4) Å，明顯的變長約 4 0.106 Å，我們推測在Ni(3)與Ni(4) 原子上共同發生一個電子的還原，故其 價數依序為Ni+2…Ni+2…Ni+1.5…Ni+1.5…Ni+2…Ni+2。 在鈷金屬串錯合物方面，在空氣下穩定存在還原態錯合物(9)與(11)，氧 化一個電子分別形成錯合物(10) 與(12) ， 而錯合物 [Co6(µ6-bpyany)4(NCS)2](PF6) (9)，Co 的平均價數為+1.83，其磁矩µeff =1.80 µB. (300 K)，為S = 1/2 之電子組態。其電化學顯示在−0.55 V、+0.38 V、 +0.91 V、 +1.18 V，有四對氧化還原對。利用化學方法將錯合物(9)氧化一個電子，產生 錯合物[Co6(µ6-bpyany)4(NCS)2](PF6)2 (10)，磁矩µeff 由0.80 µB (2 K) 逐漸上升 至2.79 µB (300 K)，推測在室溫下符合S = 1 之電子組態。由EHMO 計算得 知，錯合物(10)之SOMO 為 σ*(4)和δ*(6)軌域，其能量差∆E = 0.084 eV 很小。

We report here novel ligands, 2,7-Bis(α-phenylamino)-1,8-naphthyridine (H2bphany) and 2,7-Bis(α-pyridylamino)-1,8-naphthyridine (H2bpyany). H2bphany (or H2bpyany) was synthesized by palladium-catalyzed crosscoupling of treatment of 2,7-Dichloronaphthyridine with aniline (or 2-Aminopyridine). The ligand H2bphany has been used to synthesize the dinuclear molybdenum(II) complexes, [Mo2(Hbphany)3(O2C(R))] (R = CH3,CF3) and a tetranuclear nickel(II) complex, [Ni4(µ4-bphany)4](1). Unfortunately, the crystals of complex (1) have not been good enough for X-ray structural determination until now. The coordination chemistry of the other ligand, H2bpyany, is rich and was found that the H2bpyany ligand can bind metal ions at least in three conformations, the anti-anti form I, the anti-anti-syn-anti-anti form II , and the all syn form III. In I the ligand is bidentate and coordinates to a metal ion through one nitrogen atom of pyridine and of naphthyridine to form [Co(H2bpyany)(NCS)2] (2) and [Ni(H2bpyany)(NCS)2(H2O)] (3). In II the ligand can bind two metal ions, and the complex [Cu2(µ-H2bpyany)(µ-Cl)(µ-OH)Cl2] (4) was obtained. The coordination geometry about each Cu(II) ion is closer to a trigonal bipyramid. Complex 4 has a slight longer Cu(II)…Cu(II) distance of 3.022(1) Å and exhibits ferromagneitc interaction (J = 63.3 cm-1) from magnetic studies. In the last form III, the ligands have been deprotonated to act as hexadentate ones and were helically wrapped the metal ions to form a hexanuclear metal string, structurally similar to previous reports. We have successfully prepared the novel hexametal string complex , [Ni6(µ6-bpyany)4(X)2]n+ (X= NCS– : n=2 (5), n=1 (6);X = Cl–: n=2 (7), n=1 (8)) and [Co6(µ6-bpyany)4(X)2]n+ (X= NCS– : n = 1 (9), n=2 (10); X = OTf –: n=1 (11), n=2 (12)). Ni6 complexes have linear cores of metal arrangements, Ni(1)…Ni(2)…Ni(3)…Ni(4)…Ni(5)…Ni(6), with D4 symmetry without considering axial ligands. For complex (5) and (7), the terminal nickel(II) ions, Ni(1) and Ni(6), are in high-spin states (S = 1) and the inner four ones are in low-spin states (S = 0). The coupling constant (J16) of Ni6 metal string is –4 ~ –5 cm–1. The The complex (5) has a redox couple at E1/2 = – 0.19 V and would 6 be easily reduced by chemical methods. One-electron reduction of complex (7) produces complex (8). Ni(3)–Ni(4) distance is slight shorter 0.08 Å from 2.281(2) Å to 2.201(3) Å with respect to complex (7) and (8). Ni(3)–Npy(av) distance is obviously becoming longer 0.106 Å from 1.903(8) Å to 2.009(4) Å. We propose reduction was occurred at one unit of Ni(3) and Ni(4).The arrangement of the nickel charge are Ni+2…Ni+2…Ni+1.5…Ni+1.5…Ni+2…Ni+2. In cobalt systems, one-electron reduced complexes (9) and (11) are stable in the air. One-electron oxidation of complex (9) and (11) generate complex (10) and (12). Complex [Co6(µ6-bpyany)4(NCS)2](PF6) (9) has +1.83 averaged oxidation state of cobalt and exhibits magnetic moment as 1.80 µB. (300 K) which reveals S = 1/2 electronic configuration. The electrochemistry of the complex (9) displays four redox couples at −0.55 V, +0.38 V, +0.91 V and+1.18 V. One-electron oxidized form, complex [Co6(µ6-bpyany)4(NCS)2](PF6)2 (10) has an unusual magnetic behavior with gradually increasing magnetic moment from 0.80 µB (2 K) to 2.79 µB (300 K). EHMO calculation is consistent with S = 1 electronic configuration at high temperature. These two unpaired electrons fill in SOMO orbitals, namely σ*(4) and δ*(6).