Development of Highly Efficient Bond Dissociation and Bond Formation Reactions Utilizing Group 6 Organometallic Complexes

已知过渡金属多羟基配合物是配位不饱和物质的有效前体，因为它们在光照射或溶液加热下经常通过还原消除释放二氢。鉴于所生成的配位不饱和中间体对氧化加成反应的高活性，采用[MH_4 (Ph_2PCH_2CH_2PPh_2)_2]（1， M=Mo， W）和[MH_2 (η^5-C_5H_5)_2]（2， M=Mo， W）作为起始配合物，进行了选择性解键和成键的研究。配合物1在辐照或加热时释放1或2摩尔二氢，产生配位不饱和中间体{MoH_2 (Ph_2PCH_2CH_2PPh_2)_2}和/或{Mo (Ph_2P-CH_2CH_2PPh_2)_2}。由此形成的反应中间体可与(1)甲基丙烯酸酯反应生成烯烃C-H键活化，(2)烯丙基羧酸酯反应生成η^2-羧酸配合物，丙烯反应生成C-O键活化，(3)β-二酮和儿茶酚分别生成螯合的二酮和儿茶酚衍生物，(4)环亚胺和酰胺裂解其N-H键生成n -酰基胺配合物。最后(5)芳基硅烷或日耳曼，得到一种新型的氢化硅基或锗基配合物，该配合物具有由P ~ P ~ Si/Ge ~ P ~ P框架组成的五齿配体。最后一种配合物由于其独特的结构而具有反应性，因此进一步进行了研究。配合物2与对甲苯磺酸等酸发生质子化反应，生成阳离子三羟基配合物，可选择性还原羰基和亚胺等有机官能团。该体系还能将烯丙醇还原为丙烷。最后尝试合成了迄今为止未知的辉钼矿卡宾衍生物，并获得了一些新的此类配合物。

Transition metal polyhydrido complexes are known to be potent precursors of the coordinatively unsaturated species because they often release dihydrogen via reductive elimination on light irradiation or heating in solution. In view of the highly reactive nature of the coordinatively unsaturated intermediate thus generated toward oxidative addition reactions, the research program utilizing [MH_4 (Ph_2PCH_2CH_2PPh_2)_2](1, M=Mo, W) and [MH_2 (η^5-C_5H_5)_2](2, M=Mo, W) as starting complexes for the selective bond cleavage and bond formation was undertaken. Complex 1 affords coordinatively unsaturated intermediate {MoH_2 (Ph_2PCH_2CH_2PPh_2)_2} and/or {Mo (Ph_2P-CH_2CH_2PPh_2)_2} on irradiation or heating in solution by releasing one or two moles of dihydrogen. The reactive intermediates thus formed were found to react with (1) methacrylic esters to cause olefinic C-H bond activation, (2) allyl carboxylates to give an η^2-carboxylato complex and propene as a result of C-O bond activation, (3) β-diketones and catechols to give chelated diketonato and catecholato derivatives, respectively, (4) cyclic imines and amides to cleave their N-H bonds to give N-acylamido complexes, or finally (5) aryl silanes or germanes to give a novel hydrido-silyl or-germyl complex which has a quinquedentate ligand comprising of a P〜P〜Si/Ge〜P〜P framework. The last complex was further investigated in view of the reactivity resulting from its unique structure. Complex 2 gives, on protonation with the acid such as p-toluene sulfonic acid, cationic trihydirdo complex, which exhibits selective reduction of organic functional group such as carbonyl and imine. The system was found also to reduce allylic alcohols to propane. Finally synthesis of the hitherto unknown carbene derivatives of molybdenocene was attempted and some new complex of such type were obtained.