Transition Metal Catalysis in Water

由阴离子芳基碳原子和芳香环2,6位的两个相互反式螯合的配体组成的三元单阴离子有机金属螯合物在催化和材料科学中引起了广泛的兴趣。以反式（4-叔丁基-2,6-二（n-烷基基）苯基）氯（三苯基膦）钯为原料（烷基=正丁基、苄基、环己基、t-丁基、金刚烷基、苯基、4-甲氧基苯基），通过脱水引入相应的烷基基配体基团（配体引入途径），制备了多种NCN螯合钯配合物[4-叔丁基-2,6-二甲酰苯基]氯（三苯基膦）钯，收率高达71-98%。对这一钳形配合物形成途径的核磁共振研究表明，[4-叔-2,6-双（n -烷基基）苯基]氯苯（三苯基膦）钯通过分子内亚胺基和三苯基膦配体的配位/解离与相应的NCN钳形配合物处于平衡状态。硝基甲烷作为Cl亲核试剂被安全地应用于两亲性PS-PEG树脂负载的磷-钯配合物在水中钯催化的对烯丙基取代。在非均相条件下，以5 mol %钯的PS-PEG树脂负载钯-咪唑吲哚膦配合物为催化剂，在水中实现了环烯基酯的不对称硝基甲基化反应，得到了具有高达98% ee的光学活性（环烯基）硝基甲烷。采用两亲性树脂-分散纳米金属（Pd, Pt）颗粒-催化剂，成功地实现了以多种醇为烷基化试剂的醇基好氧氧化和甲基酮的α -烷基化反应。

Organometallic pincer complexes containing terdentate monoanionic ligands composed of an anionic aryl carbon atom and two mutually trans-chelating donosites at the 2,6-positions of the aromatic ring have been attracting widespread interest in catalysis and material science. A wide range of NCN pincer palladium complexes, [4-tert-2,6-bis(N-alkylimino)phenyl]chloropalladium (alkyl = n-butyl, benzyl, cyclohexyl, t-butyl, adamantyl, phenyl, 4-methoxyphenyl), were readily prepared from trans-(4-tert-butyl-2, 6-diformyl-phenyl)chlorobis(triphenylphosphine)palladium via dehydrative introduction of the corre sponding alkylimino ligand groups (ligand introduction route) in excellent yields (71-98%). NMR studies on this route for forming pincer complexes revealed the intermediacy of [4-tert-2,6- bis(N-alkylimino)phenyl]chlorobis(triphenylphosphine)palladium which is in equilibrium with the corresponding NCN pincer complexes via coordination/dissociation of the intramolecular imino groups and triphenylphosphine ligands.Nitromethane was safely applied as a Cl nucleophile for palladium-catalyzed p-allylic substitution in water with amphiphilic PS-PEG resin-supported phosphine-palladium complexes. Catalytic asymmetric nitromethylation of cycloalkenyl esters was achieved in water as a single reaction medium under heterogeneous conditions using 5 mol % palladium of a PS-PEG resin-supported pallad ium-imidazoindolephosphine complex to give optically active (cycloalkenyl) nitromethanes with up to 98% ee. Water-based aerobic oxidation of alcohols and alfa-alkylation of methyl ketones with a variety of alcohols as alkylation reagents were also successfully achieved by using the amphiphilic resin-dispersion of nanometal (Pd, Pt) particle-catalysts.