Direct Halogenation of TpRu(diene)Cl Preceding Ligand Exchange Reactions and Assessment of the Halogenated Complexes via Oxidation Potentials and Catalysis

The focus of this dissertation centers on the direct on-metal halogenation of trispyrazoyl borate ligand (Tp) in TpRu(diene)Cl. The first chapter begins with the preparation of TpRu(diene)Cl complexes and assessment of their stability under different conditions. TpRu(diene)Cl complexes were halogenated in one step using sulfuryl chloride, NBS, and iodine in the presence of mCPBA and H2O and then also functionalized through Sonogashira coupling reactions. Through this methodology, TpClRu(diene)Cl, TpBrRu(diene)Cl, TpIRu(nbd)Cl, and, TpC≡CHRu(nbd)Cl were synthesized via an unusual strategy. The next chapter encompasses the syntheses of simple di-phosphine complexes (dppm to dppb) and mono-phosphine complexes from the TpXRu(diene)Cl obtained in the previous chapter. By synthesizing the di-phosphine complexes of different P-P linker lengths, changes to the chemical properties of the complexes were investigated. Mono-phosphine complexes TpXPPh3Cl2 were synthesized via a reported reaction reported for TpRuPPh3Cl2, and other mono-phosphine complexes TpXRuPPh3(MeCN)Cl were derived from the counterpart TpXRuPPh3Cl2 with newly devised reaction conditions. These phosphine complexes, in addition to the new diene complexes, were analyzed with cyclic voltammetry. Lastly, the synthesized complexes were subject to evaluation of their catalysis. Two investigatory reactions used were (1) propargylic substitution and furan synthesis from epoxy alkynes. Propargylic substitution reactions gave a mixture of copious compounds from which the product was not isolated. Furan synthesis gave the expected furan, but in an unexpectedly low yield. Increasing the catalyst loading barely enabled a comparison between differently halogenated complexes. In TpXRuPPh3Cl2 catalysis, TpClRuPPh3Cl2 gave a slightly higher yield (17%) than the analogues (14%). On the other hand, TpRuPPh3(MeCN)Cl (26%) and TpIRuPPh3(MeCN)Cl (28%) gave slightly higher yield than the chlorinated (23%) and brominated (22%) complex.