Nuclearity Control in Molecular Copper Phosphates Derived from a Bulky Arylphosphate: Synthesis, Structural and Magnetic Studies

Abstract

Dedicated to Professor Dietmar Stalke on the occasion of his 65 th birthdayStarting from sterically encumbered 2,6-di-tert-butylphenyl phosphate (dtbppH 2 ) and co-ligand 3,5-dimethyl pyrazole (dmpz), it is possible to isolate either mono-, di-or tetranuclear copper phosphates by varying the copper source and making attendant changes in the reaction conditions. For example, reaction of copper nitrate with dtbppH 2 and dmpz at 60 °C leads to the isolation of the mononuclear copper phosphate [Cu(dtbppH) 2 (dmpz)(MeOH) 2 ] (1) as the only product. However, the use of copper acetate in place of copper nitrate and conducting the reaction at the room temperature leads to the formation of both dinuclear [Cu(dtbpp)(dmpz) 2 ] 2 (2) and tetranuclear [Cu 2 (dtbpp)(dmpz) 2 (OAc)(MeO)] 2 (3) from the same reaction mixture. Compounds 2 and 3 could be isolated in pure form through fractional crystallization. Copper phosphates 1-3 have been characterized by both analytical and spectroscopic methods including EPR and magnetic measurements. The molecular structures of all three compounds were established through single crystal diffraction studies. Dc magnetic measurements indicate antiferromagnetic interactions between the metal centres in all the compounds.

Copper Phosphinate Complexes as Molecular Precursors for Ethanol Dehydrogenation Catalysts

“…Applying molecular precursors to prepare structure-controlled catalysts with homogeneously dispersed catalytic species on the support is a well-known and widely used method. − However, there is a lack of information on applying phosphorus-containing metal complexes (phosphates, phosphonates, and phosphinates) as precursors to nonoxidative ethanol dehydrogenation catalysts. Numerous studies have been conducted on copper phosphates − and phosphonates. − However, the application of phosphinate ligands for the formation of copper complexes has seen limited exploration, with a modest number of copper complexes based on phosphinate ligands present to date. − A small amount of the copper complexes with macrocyclic ligands possessing pendant phosphinate groups are also being studied for potential medical applications. − The formation of insoluble polymeric compounds is commonplace in such systems, which is a factor that limits their potential application as molecular precursors. Typical strategies employed for the isolation of molecular species include the utilization of bulky ligands, ,…”

“…Numerous studies have been conducted on copper phosphates − and phosphonates. − However, the application of phosphinate ligands for the formation of copper complexes has seen limited exploration, with a modest number of copper complexes based on phosphinate ligands present to date. − A small amount of the copper complexes with macrocyclic ligands possessing pendant phosphinate groups are also being studied for potential medical applications. − The formation of insoluble polymeric compounds is commonplace in such systems, which is a factor that limits their potential application as molecular precursors. Typical strategies employed for the isolation of molecular species include the utilization of bulky ligands, , incorporation of additional ancillary ligands, ,,,,, and the exchange of labile ligands within the molecular clusters (cluster expansion). ,,…”

“…94−101 The formation of insoluble polymeric compounds is commonplace in such systems, which is a factor that limits their potential application as molecular precursors. Typical strategies employed for the isolation of molecular species include the utilization of bulky ligands, 34,37 incorporation of additional ancillary ligands, 40,48,49,52,65,73 and the exchange of labile ligands within the molecular clusters (cluster expansion). 51,52,80 The addition of phosphorus into Cu/SiO 2 catalysts prepared by incipient wetness impregnation and ion-exchange method was studied by Yamamoto et al 102 Interestingly, phosphoruscontaining catalysts exhibited a significant increase in formaldehyde productivity during methanol dehydrogenation.…”

“… 23 − 25 However, there is a lack of information on applying phosphorus-containing metal complexes (phosphates, phosphonates, and phosphinates) as precursors to nonoxidative ethanol dehydrogenation catalysts. Numerous studies have been conducted on copper phosphates 26 − 34 and phosphonates. 35 − 53 However, the application of phosphinate ligands for the formation of copper complexes has seen limited exploration, with a modest number of copper complexes based on phosphinate ligands present to date.…”

“… 94 − 101 The formation of insoluble polymeric compounds is commonplace in such systems, which is a factor that limits their potential application as molecular precursors. Typical strategies employed for the isolation of molecular species include the utilization of bulky ligands, 34 , 37 incorporation of additional ancillary ligands, 40 , 48 , 49 , 52 , 65 , 73 and the exchange of labile ligands within the molecular clusters (cluster expansion). 51 , 52 , 80 …”