Emissive Monocopper Amidophosphine Complexes -and- Lewis Acid-Assisted Reductive Coupling of Carbon Monoxide

Two major themes are presented, in roughly chronological order: the synthesis and characterization of photoluminescent copper complexes are described, followed by studies on the selective conversion of synthesis gas (CO and H2) to oxygenates. With the latter comprising the majority of the work, it is the subject of the introductory Chapter 1. In Chapter 2, the photoluminescent copper chemistry is introduced, and the synthesis and photophysics of monomeric amidophosphine complexes of copper is presented. The copper complexes are exceptional luminophores, with quantum efficiency up to 70% and lifetimes up to 150 &mgr;s. In Chapter 3, homogeneous CO hydrogenation is pursued using a strategy reliant on the incorporation of pendent Lewis acidic groups into the secondary coordination sphere of a metal carbonyl complex. This design feature promotes facile C-H and C-C bond formation, with transition metal hydrides as the hydrogen source. A structure-function study investigating the specific role of the Lewis acid determined that thefirst C-H bond formation is not particularly sensitive to the acid, whereas the second C-H bond formation and C-C coupling are both highly sensitive to the length of the tether between the metal and the borane. In Chapter 4, this chemistry is extended to utilize dihydrogen directly as a reductant, in a "frustrated Lewis pair" (FLP) mechanism. A strong phosphazene base is too bulky to interact with the pendent borane, but can heterolytically cleave dihydrogen in concert with the borane to generate a borohydride that transforms the carbonyl ligands into a metal-bound C2 organic fragment. In Chapter 5, Lewis acidic boranes are again employed as promoters of reductive chemistry, this time for CO2 reduction. The same late transition metal hydrides that were employed for CO reduction, such as [HNi(dmpe) 2][BF4] (dmpe = 1,2-bis(dimethylphosphino)ethane), are able to reduce CO2 gas when used in concert with the appropriate borane, affording a borane-formate adduct. In Chapter 6, the "frustrated Lewis pair" concept is extended to a different problem: the dehydrogenation of amine-boranes, which are candidates for hydrogen storage applications. Treatment of amine-boranes with the FLP tBu3P/B(C6F5) 3 effects rapid and quantitative transfer of H2 from the amine-borane, forming cyclic aminoborane products along with [tBu3PH][HB(C 6F5)3]. Appendices are provided, including early work on Bronsted acid-assisted CO reduction, speciation of trialkylborohydrides, tabulating NMR impurities in deuterated solvents of interest to the organometallic chemist, and crystallographic tables.