Synthesis,structures And Reactivities Of Organic Alkali-metal(Li,Na,K)Alkyl Magnesiates And Zincates

Binuclear metal compounds have been vastly invested and applied in stoichiometric or catalytic reactions and building ordered macroporous nanomaterials due to their unique reactivities and catalysis caused by metal-metal synergic effects.Especially,new bimetallic systems,which combine an alkali-metal with a more electronegative metal such as Mg,Zn and Al,has emerged as a family of versatile and efficient reagents that can effectively promote many cornerstone organic transformations.By switching on metal-metal cooperativity,these reagents can exhibit greatly enhanced performances over traditional single-metal systems,allowing the use of milder reaction conditions,and enabling in some cases synergic regioselectivities,which cannot be replicated by their monometallic components.Though these studies hint at the enormous potential of these bimetallic reagents in organic synthesis,so far their use has been limited to stoichiometric transformations.Thus,developing new bimetallic compounds and expansion of their applied ranges will be the key targets.In this work,we will synthesize a series of novel bimetallic compounds containing substituted aminopyrrolyl ligand with more flexible coordination modes,and to improve the low selectivities and limited substrate availability of catalytic crossed Tishchenko reaction through their synergistic effects.The main research contents are described as follows:(1)Five alkali-metal alkyl magnesiates containing bidentate pyrrolyl ligands,[Li2(THF)4Mg{C4H3N(2-CH2NtB u)}2](2a),[Li2(TMEDA)4Mg{C4H3N(2-CH2NtBu)}2](2b),[Na(THF)(Et2O)Na{C4H3N(2-CH2N(tBu)MgnBu)}2]?(2c),[Na(TMEDA)Na{C4H3N(2-CH2N(tBu)MgnBu)}2](2d)and[K(THF)2K{C4H3N(2-CH2N(tBu)MgnBu)}2]?(2e)were synthesized,wherein 2a-2d obtains single crystal structure and characterized by 1H,13C NMR.The single crystal structure of 2e was not obtained and characterized by 1H,13C NMR.The structure is diversity due to the coordination number and the size of different alkali metal ions which induce a greater covalent character.Compounds 2a-2e were used to catalyze the crossed-Tishchenko reaction between different aldehydes.The results showed that compound 2c have the best catalytic effect and highest selectivity under the same conditions in the cross-Tishchenko reaction.Therefore,we can better understand the mechanism of the cross-Tishchenko reaction and may contribute to further advances in the area of binuclear compounds.(2)Four alkali-metal alkyl zincates containing bidentate pyrrolyl ligands,[Li(TMEDA)2]+[Li{C4H3N(2-CH2NCBu)ZnC2H5)}2]-(3a),[Na(TMEDA)Na{C4H3N(2-CH2N(tBu)ZnC2H5)}2]?(3b),[Na(THF)2Na {C4H3N(2-CH2N(tBu)ZnC2H5)}2]?(3c)and[K(THF)2{C4H3N(2-CH2N(tBu)ZnC2H5)}2K]?(3d)were synthesized,wherein the single crystal structure of 3a-3d was obtained and characterized by 1H,13C NMR and elemental analysis.The structure ranging from molecular eomplexes to more coordination polymers.The new types of alkali-metal alkyl zincates shed new light on pyrrolyl-based complexes and could provide useful tools in the field of bimetallic cooperativity.