Neutral zinc, lower-order zincate and higher-order zincate derivatives of pyrrole: synthesis and structural characterisation of zinc complexes with one, two, three or four pyrrolyl ligands
Neutral zinc, lower-order zincate and higher-order zincate derivatives of pyrrole: synthesis and structural characterisation of zinc complexes with one, two, three or four pyrrolyl ligands
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DOI：
10.1039/c1dt11430a
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发表时间：
2011-01-01
影响因子：
4
通讯作者：
Robertson, Stuart D.
中科院分区：
文献类型：
--
作者：
Garden, Jennifer A.;Kennedy, Alan R.;Robertson, Stuart D.
对重要的五元氮杂环吡咯的锌化学的系统发展，这项工作报告了五个结晶锌吡咯配合物的合成和表征。吡咯基在本文中是指其中发生了N-H键向N-锌键的转化。在TMEDA（TMEDA为N，N，N '，N'-四甲基乙二胺）存在下，二叔丁基锌与不同量的吡咯反应，合成了两种中性配合物[（BuZn）-Bu-t（NC_4 H_4）（TMEDA）中心点HNC_4 H_4]_1和[Zn（NC_4 H_4）（2）（TMEDA）]_2。X射线晶体学研究表明，两者都采用单核结构，前者的显著特征是存在额外的母体质子化吡咯分子，该分子在N-H中心点中心点π C-C相互作用中与其阴离子对应物接合。采用类似的合成方法，但在反应混合物中加入正丁基钠以形成ATE衍生物，得到三种不同的锌酸钠。[{（THF）（2）中心点NaZn（THF）（NC 4 H4）（3）}中的（阴离子锌）化合物（无穷大）] 3、[{（TMEDA）中心点Na}（2）Zn（NC 4 H4）（4）] 4和[{（PMDETA）中心点Na}（2）Zn（NC 4 H4）（4）] 5（PMDETA是N，N，N ′，N ″，N ″-五甲基二亚乙基三胺）。从它们的晶体结构，1：1，Na：Zn络合物3可以被分类为具有三个吡咯基配体结合到锌的聚合物链排列的较低阶锌酸盐，而2：1，Na：Zn络合物4和5是具有由四个吡咯基配体完全饱和的Zn中心的分子高阶锌酸盐。1-5的结构的讨论集中在吡咯基配体和金属中心之间的σ键和π键的相互作用。显示性地，为了比较而制备和表征的不含锌的钠吡咯络合物[{（PMDETA）中心点Na（NC 4 H4）}（2）] 6表明，钠本身更喜欢前一种类型的键合，但当与锌酸盐组合物中更强的刘易斯酸锌结合时，被迫切换到后一种类型。配合物1-6也已在溶液中通过NMR光谱表征。
Towards a systematic development of the zinc chemistry of the important five-membered nitrogen heterocycle pyrrole, this work reports the synthesis and characterisation of five crystalline zinc-pyrrolyl complexes. Pyrrolyl in this context means where conversion of the N-H bond to an N-zinc bond has occurred. Two neutral complexes, [(BuZn)-Bu-t(NC4H4)(TMEDA)center dot HNC4H4] 1 and [Zn(NC4H4)(2)(TMEDA)] 2, containing one and two pyrrolyl ligands, respectively, were synthesised by reacting di-t-butylzinc with different amounts of pyrrole in the presence of TMEDA (TMEDA is N,N,N',N'-tetramethylethylenediamine). X-ray crystallographic studies established that both adopt mononuclear structures with the salient feature of the former the presence of an additional parent protonated pyrrole molecule which engages its anionic counterpart in N-H center dot center dot center dot pi C-C interactions. Employing a similar synthetic approach but adding n-butylsodium to the reaction mixture in attempts to form ate derivatives delivered three distinct sodium zincate (anionic zinc) compounds in [{(THF)(2)center dot NaZn(THF)(NC4H4)(3)}(infinity)] 3, [{(TMEDA)center dot Na}(2)Zn(NC4H4)(4)] 4, and [{(PMDETA)center dot Na}(2)Zn(NC4H4)(4)] 5 (PMDETA is N, N, N', N '', N ''-pentamethyldiethylenetriamine). From their crystal structures, the 1 : 1, Na: Zn complex 3 can be classified as a lower-order zincate having three pyrrolyl ligands bound to zinc in a polymeric chain arrangement, while the 2 : 1, Na:Zn complexes 4 and 5 are molecular higher-order zincates having Zn centres fully saturated by four pyrrolyl ligands. Discussion of the structures of 1-5 focuses on the interplay of sigma-bonding and pi-bonding between the pyrrolyl ligands and the metal centres. Revealingly, the zinc-free sodiopyrrole complex [{(PMDETA)center dot Na(NC4H4)}(2)] 6, made and characterised for comparison, shows that on its own sodium prefers the former type of bonding, but is forced to switch to the latter type when combined with the stronger Lewis acid zinc in the zincate compositions. Complexes 1-6 have also been characterised in solution by NMR spectroscopy.