Pyrolytic Synthesis And Structural Characterization Of Triazine Alkyne-coordinated Ruthenium Carbonyl Clusters

Transition metal carbonyl clusters are a kind of important aggregates of atomic metals,which play an important role as a bridge between homogeneous catalysis and heterogeneous catalysis in the study of transition metal catalytic mechanism.In recent years,ruthenium carbonyl cluster Ru3(CO)12 has successfully achieved the activation and transformation of inert chemical bonds including hydrocarbon bond,carbon carbon double bond,triple bond and carbon heterobond.However,the structure and coordination activation mode of related catalytically active metal species have always lacked necessary research.Aiming at the nitrogen heteroatom-oriented ruthenium carbonyl catalytic system,a series of alkyne ligands containing triazine functional groups are designed to capture the highly active metal cluster skeleton structure produced during the activation of alkyne by carbonyl ruthenium clusters in this paper,which provides a coordination molecular model for further understanding the catalytic conversion of transition metal activated inert bonds.1.A safe and efficient gas free synthesis method of Ru3(CO)12 was developed by using iron pentacarbonyl as carbonyl donor.It was found that potassium carbonate could promote the decomposition of carbonyl iron and release carbon monoxide in isopropanol solution.Carbon monoxide in situ can be rapidly coordinated with ruthenium atoms to form ruthenium carbonyl products.Compared with the traditional synthesis method,the reaction conditions are mild,the solvent is green,and it gets rid of the limitation of the highly toxic carbon monoxide gas on the reaction device,and greatly improves the safety of the carbonylation reaction.It is a user-friendly laboratory preparation method for carbonyl metal compounds.2.Using 1,3,5-triazine as heterocyclic directing group,a series of triazine conjugated molecules with aryl and alkyl alkynes were designed and synthesized.The results of catalytic experiments show that,regioselective alkynylation of 4,6-triazine dichloride can be achieved in PdCl2/PhCl/PPh3 system.Under the optimal coupling reaction conditions(reaction temperature was 60?,acetonitrile as solvent and N,N-diisopropylamine as base),the coupling of aryl,alkyl and ferrocenyl alkynes with triazine chlorides was successfully realized in this catalytic system.The yield of alkynes was 53%by gram order reaction.3.The pyrolytic reaction of Ru3(CO)12 with triazine alkyne conjugated molecules was systematically studied.The multinuclear carbonyl metal skeleton structure produced by the activation of carbon carbon triple bond and hydrocarbon bond was isolated and identified.Ruthenium carbonyl can react with 2-chloro-4-methoxy-6-phenylethynyl-1,3,5-triazine(1)to form a unique trinuclear ruthenium "ruthenole" cluster structure 1b and 1c under pyrolysis conditions.Single crystal structure analysis shows that the triazine heterocyclic coordination stabilizes a ruthenium carbonyl unit and stabilizes the carbon carbon triple bond coupling product together with the classical Binuclear Ruthenium structure.Interestingly,the stable carbonyl ruthenium unit of triazine nitrogen atom is linearly combined with trisruthenium,and the coordination stabilizes the intermediate of alkynyl benzene ring adjacent hydrocarbon bond activation.This unique four metal chain structure provides a new coordination activation model for the long-distance transition metal activated hydrocarbon bond of nitrogen atoms.The pyrolysis experiments show that the substituents of triazine heterocycles and alkynes directly affect the reaction activity of these conjugated molecules.The results show that the results show that the triazine and tert-butylene of triazine can not react with ruthenium carbonyl.In this paper,the possible mechanism of this kind of pyrolysis reaction is proposed,which is that triazine alkynes first coordinate with carbonyl ruthenium cap,and then the coupling of trinuclear ruthenium activated carbon carbon triple bond competes with the activation of aryl C-H bond.Finally,dodecarbonyltriruthenium was transformed into stable Ru4 and Ru3 metal skeletons under the guidance of triazine heterocycle and the coordination of carbon carbon triple bond.