COPPER(I) AND SILVER(I) COMPLEXES OF OLEFINS, ALKYNES, AND CYCLOPROPENES AND THEIR APPLICATIONS

Abstract

Poly(pyrazolyl)borates are very popular ligands in organometallic chemistry due to their attractive properties. It is easy to modify the steric and electronic properties of these ligands by changing the pyrazolyl substituents. Fluorinated tris(pyrazolyl)borates are used to stabilize many reactive metal ions. The metal complexes of them are used for multiple applications. These ligands are extensively used to isolate and stabilize many coinage metal complexes (Cu, Ag, and Au). We have synthesized comparably less explored fluorinated bis(pyrazolyl)borate ligands and utilized them to isolate several π-ligands (olefin, alkyne, and cyclopropene) complexes of copper(I) and silver(I). Chapter 2 of this research work focuses on ethylene/ethane separation technology and the development of novel pentafluorosulfanyl supported bis(pyrazolyl)borate ligands. The copper(I) bis(pyrazolyl)borate trimer, {[H2B(3,5-(CF3)2Pz)2]Cu}3, reversibly coordinate ethylene and forms [H2B(3,5-(CF3)2Pz)2]Cu(C2H4). We have studied the chemistry of this transformation both in the solution and solid phase and also how efficiently it can separate ethylene from a mixture of ethylene and ethane. The second part of this chapter focuses on the development of a novel pentafluorosulfanyl supported bis(pyrazolyl)borate ligand, [Ph2B(3-(SF5))Pz)2]-. We have synthesized copper(I) and silver(I) ethylene complexes using this ligand and compared it to the metal complexes of the CF3 analog [Ph2B(3-(CF3)Pz)2]- in a structure and bonding study and also as a catalyst in cyclopropanation reactions. Chapter 3 discusses the synthesis and characterization of several copper(I) and silver(I) alkyne complexes including the rare complexes with acetylene. We have compared the ligand and metal effect on acetylene complexes using various characterization methods such as NMR, Raman, XRD, etc. We have also performed computational studies to support our experimental results. We have utilized one of our copper(I) complexes as a catalyst for the azide-alkyne cycloaddition reaction of various alkynes including acetylene. Chapter 4 describes the synthesis and isolation of novel copper(I) bis(pyrazolyl)borate cyclopropene complexes. These cyclopropane complexes are the first examples of copper(I) η2-cyclopropene complexes. The studies show how the backbonding due to metal coordination effects ring angle and bond lengths of highly strained cyclopropenes. We have shown a copper(I) catalyzed method to synthesize cyclopropenes from alkynes using ethyl diazoacetate.