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alexwang0521银虫 (初入文坛)
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[求助]
求虫友翻译一部分化学相关的英文文献
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Cyanamide (NCNH2) and its conjugate bases, hydrogen cyanamido (NCNH) and cyanoimido (NCN2), have been known for a long time ; however, their coordination chemis-try has not received much attention. Although there are a number of transition-metal complexes of these ligands ; [1–9] usually only structural, vibrational spectroscopy, and mag-netic properties were studied, with little emphasis on the re-activity of the coordinated ligands. Cyanamide has been found to be a substrate of Mo– and V–nitrogenases ; it can be reduced by these enzymes to CH4 ,CH3NH2 , and NH3. [10] It can also be hydrolyzed by cyanamide hydratase, which is a Zn-containing enzyme. [11] These enzymatic reactions most likely involve binding of cyanamide or its bases to a metal center ; hence study of the binding and reactivity of coordi-nated cyanamide is of additional interest. The reaction of the dialkyl cyanamido complexes [(NH3)5CoIIINCN(CH3)2]3 +and cis-or trans-[PtIICl2(NCNR)2](R= Me2,Et 2,C5H 10) with NH3 to generate the corresponding guanidine com-plexes has been reported. [12, 13] Meyer and co-workers have developed a novel synthesisof OsIV=NC N that bears 2,2’ :6 ’ ,2 ’’ -terpyridine (tpy) and 2,2’ -bipyridine (bpy) ligands by direct addition of CN to OsVIN. [14] The Nb of OsIV=NC N exhibits both nucleo-philic and electrophilic reactivity. It reacts readily with vari-ous electrophiles such as H+,Et3O+,CH3I, and (CH3CO)2O; and it also reacts with PPh3 and alkenes (Scheme 1). [14–16] Similar reaction with electrophiles has also been reported for trans-[MoIV(NCN)2(dppe)2] (dppe = 1,2-bis(diphenylphosphino)ethane). [17] In contrast to dialkyl cyanamido complexes, the reactivity of hydrogen cyanamido/cyanoimido complexes reported so far occurs only at the N atom of cyanoimido or hydrogen cyanamido moieties, but not at the C atom. Herein we report the reaction of an osmium(VI) nitrido complex that bears a tridentate Schiff base ligand, [OsVI(N)( L1)(Cl)-(H2O)] (1 ), with CN under various conditions to afford (PPh4) [OsVI(N)( L1)(CN)(Cl)] ( 2 ), (PPh4)2[OsVI(N)( L2)(CN)2]( 3 ), and (PPh4)2[OsIII{N(H)CN}( L3)(CN)3](4 ). Electrophilic attack of 4 on the Nb atom of the hydrogen cyanamide ligand by H+ or MeI readily occurs to produce (PPh4) [OsIII-{NCN(R)2}( L3)(CN) 3 ](R = H(5 ); R = Me (6 )). More signifi-cantly, 4 readily undergoes nucleophilic attack at the C atom of the hydrogen cyanamide ligand by a variety of amines to produce a series of novel osmium guanidine com-pounds (PPh4) [OsIII{N(H)C (NH2 )NR1R2}( L3)(CN)3](R1=R2= H(7 ); R1= H, R2= CH2 CH3（8 ); R1= R 2= CH2CH3 ( 9 )). These compounds have been characterized by different spectroscopic methods. The crystal structures of 1 – 5 and 7 and 8 have been determined by X-ray crystallography. |
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至尊木虫 (职业作家)
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sltmac: 金币+1 2012-04-28 08:05:09
alexwang0521: 金币+70, 翻译EPI+1, ★★★很有帮助 2012-05-02 22:32:32
sltmac: 金币+1 2012-04-28 08:05:09
alexwang0521: 金币+70, 翻译EPI+1, ★★★很有帮助 2012-05-02 22:32:32
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很早以前我们已经知道氰化胺和它的共轭碱。然而，并未引起化学界的足够重视。尽管这类配体和过渡金属形成的复合物很多[1–9]，但通常只有结构，谱图和磁性得到了研究。很少研究与配体协同促进反应性。氰化胺是从一种硝基化合物发现的。通过酶催化甲烷，甲胺和氨气制备。也可以由氢氰酸水解制备，这一反应由锌酶共催化完成。这些酶催化反应大多涉及氰化胺的键合或者与一个金属中心键合。因此氰化胺的反应性与键合的研究渐渐引起了我们的兴趣。化合物[(NH3)5CoIIINCN(CH3)2]3 和 顺或反式的 [PtIICl2(NCNR)2](R= Me2,Et 2,C5H 10) ，反应过程中会产生氨气。 [12, 13]。Meyer和他的同事已经发现了一种新的合成C－N键的方法。.其中的Nb在反应中同时显示出了亲核性和亲电性。它能和许多亲电试剂反应，像H+,Et3O+,CH3I, and (CH3CO)2O，同样它也能与PPh3能及烯烃反应(Scheme 1)[14–16]。 r我们已经报导了反式的-[MoIV(NCN)2(dppe)2] (dppe = 1,2-bis(diphenylphosphino)ethane)参与的许多相似反应[17]。与二烷基的氰化胺相比较，氢化氰的反应性集中在氮和氧两个原子上。在这里，我们报导了四价Os参与的硝化反应。在不同的条件下，我们把(PPh4) [OsVI(N)( L1)(CN)(Cl)] ( 2 ), (PPh4)2[OsVI(N)( L2)(CN)2]( 3 ), and (PPh4)2[OsIII{N(H)CN}( L3)(CN)3](4 )加在一起进行一锅反应，这种化合物能够兼容西弗碱以及配体[OsVI(N)( L1)(Cl)-(H2O)] (1 )。反应一般在氮原子上进行亲电进攻。(PPh4) [OsIII-{NCN(R)2}( L3)(CN)3 ](R = H(5 ); R = Me (6 )).同时也能在氰根的碳原子上进行亲核进攻。这些化合物已由不同的谱图方法鉴定出特征吸收。我们用单晶衍射技术测定了1，5，7和8几种化合物的单晶结构。 |
2楼2012-04-27 23:34:50
