Synthesis,Characterization And Catalytic Performances Of DI (Pyrazoly) Borate Complexes

Three bis?pyrazolyl?borate ligands were slected to react with CoCl2,NiCl2,Ni?acac?₂,CuCl₂,Cu?PPh₃?₂NO₃?I?,ZnCl2,ZrCl₄ and TiCl₄ to produce corresponding complexes,respectively.Eight compounds were characterized by single-crystal X-ray diffraction.All of them show weak intramolecular C-H···M interactions which can be assigned as agostic or anagostic and preagostic interactions.In the past decades,transition metal organometallic complexes have been found to show some unusual bonding modes.One typical example is the agostic interaction.In addition,non-agostic and anagostic or preagostic are complementary terms used to describe systems that,while showing similar close C-H···M proximity,are not considered truly agostic in nature.Agostic interactions are often used to active inert C-H bonds,and thus facilitate new reactions.The dissertation demonstrates the first example of designed catalysts based on the agostic interaction and the catalytic property of three new copper?I?complexes.It mainly includes the following parts:A novel methodology is reported for the highly yield synthesis of bis?pyrazolyl?borate ligands [?BBN?BpR]–?R= H,Me,iPr?through one-pot reactions by mixing commercially available 9-BBN dimer?BBN = 9-borabicyclo[3.3.1]nonane?,HpzR?3-substitued pyrazole?and metal hydrides?sodium hydride or potassium hydride?.Bis?pyrazolyl?borate ligand [?BBN?Bp]-?1?reacted with Ni?acac?₂,CuCl₂ and ZnCl2 at 2:1 molar ratio leading to bis?pyrazolyl?borate complexes Ni[?BBN?Bp]2?4?,Cu[?BBN?Bp]2?5?and Zn[?BBN?Bp]2?6?in high yields,respectively.The reactions of?BBN?Bp?1?with 1 equiv.of ZrCl₄ or,TiCl₄ in THF affords the complex [?BBN?Bp]ZrCl3·THF?9?or,[?BBN?Bp]Ti Cl3?10?.Treatment of 1 with Cu?PPh₃?₂NO₃?I?in toluene at room temperature gave the copper complex [?BBN?Bp]Cu?PPh₃?2?7?.1 reacted with Ni?acac?₂,Ni?acac?₂ and Napz at 1:1:1 molar ratio in CH2Cl2 resulting in binuclear complex Ni2[?BBN?Bp]2?pz?2?11?.All complexes are characterized by elemental analyses,NMR,and IR.Complexes 4-7 and 11 were characterized by single-crystal X-ray diffraction.Treatment of bis?pyrazolyl?borate ligand [?BBN?BpMe]-?2?with Cu?PPh₃?₂NO₃?I?in toluene at room temperature gives the copper complex [?BBN?BpMe]Cu?PPh₃??8?.2 reacted with CoCl2 and ZnCl2 in 2:1 molar to produce bis?pyrazoly?borate complexes Co2[?BBN?BpMe]2?pzMe?2?12?and Zn2[?BBN?BpMe]2?pzMe?2?13?in good yield,respectively.Complexes 8 and 12 were characterized by single-crystal X-ray diffraction.The reaction of [?BBN?BpiPr]-?3?with 1 equiv.of Cu?CH3CN?4PF6 in toulene afforded the complex Cu2[?BBN?BpiPr]2?14?which were characterized by single-crystal X-ray diffraction.In addition to X-ray diffraction analysis,we also identified all the above compounds by NMR analyses,infrared spectroscopy,elemental analyses and mass spectrometry.Single crystal studies of the three compounds 7,8 and 14 show weak intramolecular C?H···Cu interactions which can be assigned as agostic or anagostic interactions.Catalytic studies of these complexes toward carbenoid insertion into N-H bonds indicate these weak interactions act as a “switch” which will be turned “on” if interacting with the substrate and “off” if eliminating the substrate and regenerating the weak interaction.The process of the “swith” turning “on” or “off”,which is related to the catalytic effect,is found to be influenced by both steric effects and the solvent: a less sterically hindered catalyst in non-coordinating benzene results in high yield,while a more sterically hindered catalyst in coordinating THF results in relatively low yield.