含多芽氮配位基與雙鉬金屬化合物之研究

Dimolybdenum Complexes Containing Polydentate Nitrogen Ligands

吳英彥(Ying-Yann Wu)

指導教授 ： 陳志德

中原大學/理學院/化學研究所/博士(2002年)

https://doi.org/10.6840/cycu200200395

摘要

本論文主要探討含formamidine之多芽氮配位基與羧酸配位基與雙鉬金屬四重鍵化合物之化學。
經由m-anisidine或o-anisidine在triethyl orthoformate中加熱，進行縮合反應，可分別獲得N,NS-di(3-methoxyphenyl)formamidine (m-HDMophF)與N,NS-di(2-methoxyphenyl)formamidine (o-HDMophF)，o-HDMophF久置於空氣中，會因為空氣中的水分而進行水解反應，分別產生o-formanisidide與o-anisidine，而其結構皆由X-ray單晶繞射鑑定出。
以Mo(CO)6為起始物，與過量的m-HDMophF在o-dichloro-benzene中反應，獲得黃色化合物Mo2(m-DMophF)4, 1，m-DMophF{配位基以橋接的形式配位方式，形成s-cis, s-trans與s-trans, s-trans的構形，並由1H NMR中計算反磁的不均性(diamagnetic anisotropy, )為4920 b 17 e 10-34 m3/molecule。將化合物1與Me3OBF4在CH3CN中反應，產生化合物cis-[Mo2(m-DMophF)2(CH3CN)4][BF4]2, 2，形成在中心結構具Mo2(2-L)2(CH3CN)4型式化合物中最短的Mo-Mo距離2.1281(6) Å，其m-DMophF{配位基形成s-cis, s-trans與s-trans, s-trans的構形。利用化合物[Mo2(CH3CN)10][BF4]4與m-HDMophF在CH3CN中反應的產物與CH3OH合成養晶，獲得化合物cis-[Mo2(m-DMophF)2]2(-OCH3)4, 3，其具有四個橋接的CH3O{配位基，連接兩個四重鍵單位，其m-DMophF{配位基為s-trans, s-trans的構形。
將Mo2(O2CCH3)4與Mo2(O2CCF3)4和o-HDMophF反應，可獲得化合物Mo2(O2CCH3)3(o-DMophF), 4與trans-Mo2(O2CCF3)2(o-DMophF)2, 5。而將Mo2(O2CPrn)4與Mo2(O2CCH3)4和o-LiDMophF反應，則分別獲得trans-Mo2(O2CPrn)2(o-DMophF)2, 6和trans-Mo2(O2CCH3)2(o-DMophF)2, 7。再以化合物7為起始物，分別與4-pyridinecarboxylic acid (p-pyacidH)和3-pyridinecarboxylic acid (m-pyacidH)反應，獲得化合物trans-Mo2(p-pyacid)2(o-DMophF)2, 8和trans-Mo2(m-pyacid)2(o-DMophF)2, 9。化合物5 ~ 9上的o-DMophF{配位基皆為s-cis, s-trans的構形，形成較短的Mo---O距離(2.576(5), 5；2.602(2), 6；2.602(5), 2.608(5), 7；2.579(3), 8；2.553(3), 2.542(3) Å, 9)，這些化合物為第一個同時含有橋接羧酸基與橋接formamidine配位基之雙鉬金屬化合物。化合物5 ~ 9具有類似的雙橋接羧酸基與雙橋接formamidine配位基結構，但因具有不同酸性的羧酸基，造成不同的四重鍵長與不同的反磁不均性影響，另外於化合物5 ~ 9的單晶結構中，具有Mo---O的作用力，而在溶劑中此作用並不存在。而化合物8和9因強度借用(intensity-borrowing)效應，具有異常的莫耳吸收度()，分別為14430與14381 M{1cm{1。
以化合物7為起始物，分別與N,NS-di(2-pyridyl)formamidine (HDpyF)、N,NS-di(2-pyrimidyl)formamidine (HDpmF)和N,NS-di(6-methyl-2-pyridyl)formamidine (HDMepyF)在CH2Cl2中迴流反應，獲得化合物trans-Mo2(O2CCH3)(DpyF)(o-DMophF)2, 10、trans-Mo2-(O2CCH3)(DpmF)(o-DMophF)2, 11和trans-Mo2(O2CCH3)(DMepyF)(o-DMophF)2, 12，化合物10與11之o-DMophF{配位基為s-cis, s-trans的構形，因此形成較短的Mo---O距離(2.889(3), 2.861(2), 10；2.880(3), 3.024(4) Å, 11)，而10中的DpyF{亦為s-cis, s-trans的構形，而因化合物11具有嘧啶環，拉電子的能力較強，形成較化合物10為長的Mo-Mo距離，亦形成較長的Mo-N距離。化合物10 ~ 12的的結構相近，形成第一個三種配位基之四橋接雙鉬金屬化合物，而將7與HDMepyF在CH3CN中迴流反應，會同時獲得化合物trans-Mo2(O2CCH3)(DMepyF)2(o-DMophF), 13,和trans-Mo2(DMepyF)2-
(o-DMophF)2, 14，在此反應中發現獨特的重排反應機制。化合物13與14上的o-DMophF{配位基皆為罕見的s-cis, s-cis構形，而DMepyF{配位基形成則s-cis, s-trans的構形。
利用相同的起始物7，在CH2Cl2與THF溶劑中依序加入Me3SiCl和PMe3，可獲得紫紅色的化合物Mo2(O2CCH3)(o-DMophF)Cl2(PMe3)2, 15，藉由31P{1H} NMR的研究得知經由四重鍵的P-P偶合常數3JP-Mo-Mo-P = 16 b 1 Hz，並可由13C{1H} NMR光譜之3JC-P麆蒂X常數分析，可以確定在雙鉬四重鍵化合物中，單芽磷配位基與橋接羧酸基或類似配位基的相關位置。

關鍵字

多芽氮配位基 ； 四重鍵 ； 雙鉬金屬

並列摘要

The content of this dissertation pertains to the chemistry of dinuclear compounds containing quadruply bonded pairs of molybdenum atoms that ligated by formamidine and carboxylate ligands.
Heating m-anisidine and o-anisidine with triethyl orthoformate produced N,NS-di(3-methoxyphenyl)formamidine (m-HDMophF) and N,NS-di(2-methoxyphenyl)formamidine (o-HDMophF), respectively. o-HDMophF undergoes hydrolysis if exposed to air and then degenerates into o-formanisidide and o-anisidine. The structures of these compounds were identified by single crystal X-ray diffraction.
The reaction of Mo(CO)6 with excess m-HDMophF in o-dichloro-benzene afforded the yellowish compound Mo2(m-DMophF)4, 1. Its structure reveals that the ligands bridge the two metal centers, forming s-cis, s-trans and s-trans, s-trans conformations. The diamagnetic aniso-tropy, , of the Mo-Mo quadruple bond is calculated as 4920 b 17 e 10{34 m3/molecule. Compound 1 reacted with Me3OBF4 in CH3CN to produce cis-[Mo2(m-DMophF)2(CH3CN)4][BF4]2, 2. Its Mo-Mo distance, 2.1281(6) Å, is the shortest among the compounds having Mo2(2-L)2(CH3CN)4 core structure. The ligands in this compound form the s-cis, s-trans and s-trans, s-trans conformations. The reaction of [Mo2-(CH3CN)10][BF4]4 with m-HDMophF in CH3CN afforded the tetranuclear complex cis-[Mo2(m-DMophF)2]2(-OCH3)4, 3. The molecule bears four bridging CH3O{ that link two quadruply bonded moieties. The ligands adopts the s-trans, s-trans conformation.
The reactions of Mo2(O2CCH3)4 and Mo2(O2CCF3)4 with o-HDMophF afforded the complexes Mo2(O2CCH3)3(o-DMophF), 4 and trans-Mo2(O2CCF3)2(o-DMophF)2, 5, respectively. The reactions of Mo2(O2CPrn)4 and Mo2(O2CCH3)4 with o-LiDMophF produced trans-Mo2(O2CPrn)2(o-DMophF)2, 6, and trans-Mo2(O2CCH3)2(o-DMophF)2, 7, respectively. Compound 7 reacted with 4-pyridinecarboxylic acid (p-pyacidH) and 3- pyridinecarboxylic acid (m-pyacidH) to give trans-Mo2(p-pyacid)2(o-DMophF)2, 8, and trans-Mo2(m-pyacid)2(o-DMophF)2, 9, respectively. All the o-DMophF{ ligands in compounds 5 ~ 9 adopted the s-cis, s-trans conformation with a short Mo---O distance (2.576(5), 5; 2.602(2), 6; 2.602(5), 2.608(5), 7; 2.579(3), 8; 2.553(3), 2.542(3) Å, 9). These complexes can be envisaged as the intermediates of the stepwise decarboxylation of Mo2(O2CR)4 to form Mo2(form)4, where form is a generic formamidine. Compounds 5 ~ 9 are the first dimolybdenum complexes containing a pair of carboxylate and a pair of formamidine ligands. Compound 5 ~ 9 possess similar ligand structure of doubly bridged carboxylate and formamidinate, however, the quadruple bond lengths and the extent of diamagnetic anisotropy differ from each other on account of different acidity of the carboxylate ligand. The Mo---O interaction which was observed in the solid state disappeared in solution. Compound 8 and 9 have anomalous molar absorbance () owing to intensity-borrowing effect (14430 and 14381 M{1cm{1, respectively).
Another series of experiments start with compound 7. Three products, trans-Mo2(O2CCH3)(DpyF)(o-DMophF)2, 10, trans-Mo2(O2CCH3)-(DpmF)(o-DMophF)2, 11 and trans-Mo2(O2CCH3)(DMepyF)(o-DMophF)2, 12, were prepared by refluxing compound 7 with N,NS-di(2-pyridyl)formamidine (HDpyF)、N,NS-di(2-pyrimidyl)formamidine (HDpmF) and N,NS-di(6-methyl-2-pyridyl)formamidine (HDMepyF), respectively, in CH2Cl2. The o-DMophF{ ligands in these complex adopt the s-cis, s-trans conformation. The Mo---O distances for 10 and 11 are 2.889(3) and 2.861(2) and 2.880(3) and 3.024(4) Å, respectively. The DpyF{ ligand in 10 also adopted an s-cis, s-trans conformation. The Mo-Mo distance in 11 is longer than 10 owing to its pyrimidine ring that contributes more electron-withdrawing capacity, and the same factor also lengthens the distance of Mo-N. Compounds 10 ~ 12 are the first dimolybdenum complexes containing mixed formamidinate ligands. Compound 7 reacted with HDMepyF in CH3CN to give trans-Mo2-(O2CCH3)(DMepyF)2(o-DMophF), 13, and trans-Mo2(DMepyF)2(o-DMophF)2, 14, which were obtained through a unique rearrangement mechanism. The o-DMophF{ ligands in 13 and 14 adopt a rare s-cis, s-cis conformation while DMepyF{ assumes an s-cis, s-trans conformation.
The reaction of 7 with Me3SiCl and PMe3 gave purple compound Mo2(O2CCH3)(o-DMophF)Cl2(PMe3)2, 15. The study on 31P{1H} NMR spectrum of 15 concluded that the through metal-metal quadruple bonding coupling 3JP-Mo-Mo-P is about 16 b 1 Hz. The position of the monodentate phosphine ligand, i.e. cis or trans to the acetate or similar ligands, can be determined by evaluating the 3JC-P coupling constant.

並列關鍵字

Dimolybdenum Metal ； Polydentate Nitrogen Ligands ； Quadruply Bond

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