Dialkylgermylene Coordinated Low-valent Gold Complexes: Synthesis And Reactivity

Gold is a chemical element with the highest electronegativity(?=2.54)and electron affinity of any metal at 2.28 e V,which is possible to synthesize a stable gold anion species and investigate its chemistry.The development of gold(?1)species remain in tackling the challenges of the construction due to the electronic and steric effects of associated ligands.Germylene(R₂Ge:),as a carbene analogue,which has similar chemical properties and electronic structure to carbene.Compared with N-heterocyclic carbene,the lone pair of electons on central getmanium atom can form a stronger dative bond with gold atom,and the empty p orbitals of germylene can also accept feedback electrons from low-valent gold atoms,so germylene can form stable low-valent gold compounds.In this thesis,a series of gold(I)complexes containing Ge-Au bond were synthestized by the insertion reactions of dialkylgermylene with the speices containing Au-Cl bond.Based on the excellent?electron acceptability of dialkylgermylene,the14-group carbene-coordinated dinuclear gold(?1)complexes were first prepared by reduction of the gold(I)complexes with KC₈.Subsequently,the reactivity and application in catalyzing the trimerization of isocyanate of gold(?1)complexes was also systematically studied.The content of this paper will mainly include the two part:1.The Synthesis of dialkylgermylene coordinated gold(?1)complexs:Some gold(I)complexes are synthesized by insertion reaction of dialkylgermylene with(THT)Au Cl,Me₃PAu Cl,and Et₃PAu Cl.When the ligand coordinated with gold is THT with weak coordination ability,a gold three-membered ring anion compound(cyclic-Au₃^-)was isolated;When the ligand is trimethylphosphine or triethylphosphine with strong coordination ability,the 14-group carbene-coordination dinuclear gold(?1)complexes were first isolated.By varying the temperature by ¹H NMR and X-ray,we discussed low-valent gold compound in the solution and the solid-state structure.2.The reactivity of dialkylgermylene coordinated gold(?1)complexs:Dialkylgermylene coordinated gold(?1)complexe have diverse reactivity.It reacted with PMe₃ for ligand exchange reaction to obtain double gold-coordinated organogermanium complexe and reacted with PPh₄Cl for addition reaction to obtain ionic gold complexe;Substitution reaction with CH₃COCl to obtain mononuclear gold(?1)complexe and nucleophilic reaction with CH₃OTf to obtain methyl germylene-coordinated monovalent gold complexes respectively.And gold(?1)complexe 5 is strong lewis base and can catalyze the cyclotrimerization of aryl isocyanates.