Synthesis,Structures And Reactivities Of Guanidinatometal(Lithium And Aluminum) Complexes

Guanidinato ligands can bind to the metals from across the periodic table via N,N?-chelating or bridging model,due to their excellent steric and electronic tunability by changing various groups.Guanidinato metal complexes have an irreplaceable role in coordination chemistry,synthesis,catalysis,and stabilization of complexes of low oxidation state metals.Since the research on guanidinatoaluminium complexes started late and there are few alternative types of carbodiimides for the synthesis,the synthetic amounts of such complexes are relative limited and their properties are far from fully grasped.Therefore,the range of applications of such complexes is very limited.The main content of the thesis can be divided into three parts.The first part focuses on the synthesis of guanidinatoaluminium complexes from various carbodiimides by traditional methods for preparing the type of guanidinates.The second part is about reactivities of aluminium monoguanidinate complexes with oxygen,carbodiimide or water,and application of guanidinatoaluminium complexes in Meerwein-Ponndorf-Verley reduction.The third part describes on synthesis of a biguanidine,and reactivities of the biguanidine ligand with metal alkyls.Three metal guanidinates containing a dianionic guanidinatolithium complex,have been successfully obtained.In addition,a series of dianionic guanidinatolithium complex can be produced by treatment of primary amine with n-Bu Li and carbodiimide,which could provide the further support for synthesis of multinuclear metal guanidinates.The main research contents are described as follows.1.Seven new mononuclear guanidinatoaluminium complexes,[{?Et₂N?C?NCy?-(NPh}₂AlMe]?2c?,[{?Et₂N?C?NPh??NAr?}₂AlMe]?2d?,[{(C₅H₁₀N)C?NPh??NAr?}₂-AlMe]?2e?,[{?Et₂N?C?NPh??NAr?}₂AlCl]?Ar = 2,6-Me₂C₆H₃??2f?,[{?Et₂N?C?NCy?-?NPh?}AlMe₂]?2g?,[{(C₅H₁₀N)C?NCy?₂}AlMe₂]?2h?and [{?Bz?Me?N?C?NCy?₂}Al-Me₂]?2i?,have been synthesized via the reported methods.2c-2f are bisguanidinatoaluminium complexes;while 2g-2i are?mono?guanidinatoaluminium complexes.All of the guanidinatoaluminium complexes were characterized by satisfactory C,H,and N microanalysis,¹H,¹³C NMR spectra and single crystal X-ray diffraction analysis.The experimental results show that the type of carbodiimide as starting material determines the model of the main product,which is?bis?guanidinatoaluminium or?mono?guanidinatoaluminium complex.If carbodiimide CyN=C=NPh is selected as starting material,two types of guanidinatoaluminium complexes can be isolated from the reaction solution.However,carbodiimide CyN=C=NPh or PhN=C=NAr is selected as starting material,only one type of guanidinatoaluminium complex can be obtained.2.The reactivities of the mononuclear?mono?guanidinatoaluminum complexes with O₂,carbodiimide or H₂O were studied.Treatment of?mono?guanidinatoaluminum complex with O₂ afforded five dimeric O-bridging guanidinatoaluminum complexes,[LAlMe??-OMe?]₂?3a-3e,L stands for guanidinato ligand?.Two mononuclear biguanidinatoaluminum complexes,[{N?Ph?C?NR?N?Ph?C?NEt₂?-N?R?}AlMe₂]?R = Cy,3f;R = 2,6-Me₂C₆H₃,3g?,were produced by the treatment of guanidinatoaluminum complex with carbodiimide?CyN=C=NPh or PhN=C=NAr?.While introducing degassing H₂O into the treatment solution,which afford?mono?guanidinatoaluminum complex,two tetranuclear complexes,???and ??? ?Ar = 2,6-Me₂C₆H₃?,were isolated and characterized.In addition,the different guanidinatoaluminum complexes were used as catalysts to catalyze the Meerwein-Ponndorf-Verley reduction,and both of 2g and 3e exhibited good to excellent catalytic activity.The reduction can proceed in toluene for 2 h at 110 oC in the presence of 10 mol% loading,and a range of aldehydes and ketones are rapidly,selectively transferred to the corresponding alcohols in good or excellent yields.3.We demonstrated a simple and efficient method for synthesis of monoanionic biguanidine and dianionic guanidinato ligands,which could provide the further support for synthesis of multinuclear metal guanidinates.Hydrolysis of complex 3g gave the protonated free biguanidinato ligand 4a in good yield meanwhile,the reactivity of 4a with AlMe₃,ZnEt₂,or n-BuLi was also described.Interestingly,treatment of 4a with n-BuLi in the presence of TMEDA afforded a dianionic guanidinatolithium?4d?,which could be synthesized by treatment of primary amine with n-BuLi and carbodiimide in the presence of TMEDA.Besides,reaction of aniline with n-BuLi and carbodiimide?CyN=C=NPh,PhN=C=NAr or CyN=C=NCy?produced guanidinatolithium complexes?4e-4g?.The structures of 4e and 4f are similar to that of 4d,while the structure of 4g is dimeric?mono?guanidinatolithium complex.The experimental results show that the type of guanidinatolithium complex is related to the group bound to N atoms in carbodiimide as starting material.