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

过渡金属多氢化合物是配位不饱和化合物的有效前体，因为它们在光照或溶液中加热时经常通过还原消除释放二氢。鉴于生成的配位不饱和中间体对氧化加成反应具有很强的反应性，本文开展了以[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)为起始络合物的选择性断裂成键反应的研究。配合物1在溶液中辐射或加热时释放1或2个摩尔二氢，生成配位不饱和中间体{MoH_2(Ph_2PCH_2CH_2PPh_2)_2}和/或{Mo(Ph_2P-CH_2PPh_2)_2}。结果表明，这些反应中间体与(1)甲基丙烯酸酯反应生成烯烃C-H键，(2)烯丙基羧酸盐与C-O键反应生成η^2-羧基配合物和丙烯，(3)β-二酮和邻苯二酚分别生成螯合二酮和儿茶酚衍生物，(4)环亚胺和酰胺裂解N-H键生成N-酰胺基配合物，或(5)芳基硅烷或锗生成具有五齿配体和P~P~Si/Ge~P~P骨架的新型多硅或锗-锗配合物。鉴于其独特的结构所产生的反应性，对最后一个络合物进行了进一步的研究。配合物2与对甲苯磺酸等酸发生质子化反应，得到阳离子三氢络合物，它能选择性地还原有机官能团，如羰基和亚胺。该系统还被发现可以将烯丙醇还原为丙烷。最后，尝试合成了一些迄今未知的茂钼卡宾衍生物，得到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.