Redox-catalyzed binding of dinitrogen by molybdenum N-tert-hydrocarbylanilide complexes:: Implications for dinitrogen functionalization and reductive cleavage
Redox-catalyzed binding of dinitrogen by molybdenum N-tert-hydrocarbylanilide complexes:: Implications for dinitrogen functionalization and reductive cleavage
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DOI：
10.1021/ja991435t
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发表时间：
1999-11-03
影响因子：
15
通讯作者：
Cummins, CC
中科院分区：
文献类型：
--
作者：
Peters, JC;Cherry, JPF;Cummins, CC
发现在存在钠汞齐的情况下，Mo（N[R]Ar）（3）（R = C（CD 3）（2）CH 3，Ar = 3，5-C6 H3 Me 2）分解二氮（1 atm，THF，25 ℃）得到2当量的氮化物N=Mo（N[R]Ar）（3）被加速。仔细控制Mo（N[R]Ar）（3）浓度导致阴离子二氮络合物[（THF）（x）Na] [（N-2）Mo（N[R]Ar）（3）]的分离和表征，其中x为0至3。通过电化学实验和合成研究，发现[（THF）（x）Na] [（N-2）Mo（N[R]Ar）（3）]是在汞齐存在下Mo（N[R]Ar）（3）加速N-2裂解的关键中间体。因此，在电子受体的存在下，[（THF）（x）Na] [（N-2）Mo（N[R]Ar）（3）]与Mo（N[R]Ar）（3）反应，得到中性N-2-桥连络合物（mu-N-2）{Mo（N[R]Ar）（3）}（2），其又分裂成2当量的氮化物N=Mo（N[R]Ar）（3）。可以看出，在该体系中，钠汞齐的功能是作为氧化还原催化剂，加速Mo（N[R]Ar）（3）转化为（μ-N-2）{Mo（N[R]Ar）（3）}（2），这是一种不容易失去N-2的双核二氮络合物。[（THF）（x）Na] [（N-2）Mo（N[R]Ar）（3）]的电化学或化学外层氧化导致N-2快速释放，并再生Mo（N[R]Ar）（3），推测是通过中性单核二氮络合物（N-2）Mo（N[R]Ar）（3）。原位生成的[（THF）（x）Na][（N-2）Mo（N[R]Ar）（3）]被ClSiMe 3有效地捕获，得到（Me 3SiNN）Mo（N[R]Ar）（3）。该配合物与三氟甲磺酸甲酯反应得到二甲基肼基阳离子物种[（Me 2NN）Mo（N[R]Ar）（3）] [OTf]。合成了单甲基配合物（MeNN）Mo（N[R]Ar）（3）。设计用于捕获中性单核双氮络合物（N2）Mo（NIR）Ar）3的实验产生了包括（Ph[Bu-t]N）（3）Ti（mu-N-2）Mo（N[R]-Ar）（3）的异双核双氮络合物的有效合成，其也以其N-15（2）-标记形式合成。合成了一个新的N-金刚烷基取代的三配位钼（III）配合物Mo（N[Ad]Ar）（3）（Ad = 1-金刚烷基，Ar = 3，5-C6 H3 Me 2）。发现该络合物在钠汞齐存在下与二氮（1 atm，THF，25 ℃）反应，得到二氮阴离子络合物[（THF）（x）Na] [（N-2）Mo（N[Ad]Ar）（3）];合成不需要仔细调节Mo（N[Ad]Ar）（3）浓度。事实上，在任何条件下都没有观察到Mo（N[Ad]Ar）（3）分裂二氮或产生双核μ-N-2络合物;这与Mo（N[R]Ar）（3）（R = C（CD 3）（2）CH 3）的反应性形成鲜明对比，这归因于1-金刚烷基取代基在Mo处提供的增强的空间保护。
The splitting of dinitrogen (1 atm, THF, 25 degrees C) by Mo(N[R]Ar)(3) (R = C(CD3)(2)CH3, Ar = 3,5-C6H3Me2) giving 2 equiv of nitride N=Mo(N[R]Ar)(3) is found to be accelerated in the presence of sodium amalgam. Careful control of the Mo(N[R]Ar)(3) concentration led to the isolation and characterization of the anionic dinitrogen complex, [(THF)(x)Na] [(N-2)Mo(N[R]Ar)(3)], where x is from 0 to 3. Via electrochemical experiments and synthetic studies, [(THF)(x)Na] [(N-2)Mo(N[R]Ar)(3)] is found to be a key intermediate in the acceleration of N-2 Splitting by Mo(N[R]Ar)(3) in the presence of sodium amalgam. Accordingly, in the presence of an electron acceptor, [(THF)(x)Na] [(N-2)Mo(N[R]Ar)(3)] reacts with Mo(N[R]Ar)(3) to give the neutral N-2-bridged complex (mu-N-2){Mo(N[R]Ar)(3)}(2), which in turn splits to 2 equiv of nitride N=Mo(N[R]Ar)(3). It is seen that the function of sodium amalgam in this system is as a redox catalyst, accelerating the conversion of Mo(N[R]Ar)(3) to (mu-N-2){Mo(N[R]Ar)(3)}(2), a dinuclear dinitrogen complex that does not lose N-2 readily. Electrochemical or chemical outer-sphere oxidation of [(THF)(x)Na] [(N-2)Mo(N[R]Ar)(3)] leads to rapid N-2 evolution with regeneration of Mo(N[R]Ar)(3), presumably via the neutral mononuclear dinitrogen complex (N-2)Mo(N[R]Ar)(3). In situ generated [(THF)(x)Na][(N-2)Mo(N[R]Ar)(3)] was efficiently trapped by ClSiMe3 to give (Me3SiNN)Mo(N[R]Ar)(3) This complex underwent reaction with methyl triflate to give the dimethyl hydrazido cationic species, [(Me2NN)Mo(N[R]Ar)(3)] [OTf]. The synthesis of the monomethyl complex (MeNN)Mo(N[R]Ar)(3) also was achieved. Experiments designed to trap the neutral mononuclear dinitrogen complex (N2)Mo(NIR)Ar)3 gave rise to efficient syntheses of heterodinuclear dinitrogen complexes including (Ph[Bu-t]N)(3)Ti(mu-N-2)Mo(N[R]-Ar)(3), which also was synthesized in its N-15(2)-labeled form. Synthesis and characterization data for the new N-adamantyl-substituted three-coordinate molybdenum(III) complex Mo(N[Ad]Ar)(3) (Ad = 1-adamantyl, Ar = 3,5-C6H3Me2) are presented. The complex is found to react with dinitrogen (1 atm, THF, 25 degrees C) in the presence of sodium amalgam to give the dinitrogen anion complex [(THF)(x)Na] [(N-2)Mo(N[Ad]Ar)(3)]; the synthesis does not require careful regulation of the Mo(N[Ad]Ar)(3) concentration. Indeed, under no conditions has Mo(N[Ad]Ar)(3) been observed to split dinitrogen or to give rise to a dinuclear mu-N-2 complex; this striking contrast with the reactivity of Mo(N[R]Ar)(3) (R = C(CD3)(2)CH3) is attributed to the enhanced steric protection at Mo afforded by the 1-adamantyl substituents.