Expanding the Oxidative Addition Route for the Rational Design of Multi-Metallic Dithiolene Complexes

This thesis describes studies on oxidative addition reactions of 1,2,5,6-tetrathiocins to low valent transition metals, yielding an array of multinuclear metal dithiolene complexes. Chapter 1 provides a literature review of metal dithiolene complexes, including their synthesis and applications. Chapter 2 investigates the reaction of Pd2dba3 with tetramethoxydibenzotetrathiocin (1) and a range of monodentate phosphines with different Tolman cone angles. The isostructural series of homo-dimetallic complexes [(dmobdt)Pd(P)]2 [P = PPh2iPr, P(NMe2)3, P(iPr)3, P(m-tol)3, PCy3 and PBn3] (3 – 8) were isolated as the major phosphine-containing metal complex. These were characterized by multinuclear 1H and 31P NMR spectroscopy and X-ray diffraction. The related reaction of Pt(PPh3)4 with tetrathiocin afforded a mixture of monometallic (dmobdt)Pt(PPh3)2 (11) and dimetallic [(dmobdt)Pt(PPh3)]2 (10). Experimental studies revealed that conversion of 11 to 10 appears to require the presence of oxygen and is characterized by formation of free phosphine oxide. Reaction of Pt1.9dba3 with 1 in the presence of the sterically demanding PtBu3 ligand led to the isolation of the homo bimetallic [(dmobdt)Pt(PHtBu2)]2 (13) in which dealkylation of the phosphine occurs as well as characterization of the first hexanuclear homoleptic platinum complex, [Pt(dmobdt)]6 (12). Chapter 3 extends the oxidative addition of tetrathiocins to low valent metals by examining the reactivity of tetrathiocins to CpCo(CO)2. Reaction of tetrathiocin 1 and its benzo-crown-5 analogue 16 with CpCo(CO)2 under microwave conditions afforded the 16e- CoIII organometallic complexes CpCo(dmobdt) (17) and CpCo(b-15-c-5-dt) (18). In the solid state 17 exists as the 18e- dimer [CpCo(dmobdt)]2 whereas 18 can exist in monomeric or dimeric forms depending upon crystallization conditions. Reactivity of 18 towards alkali metal cations afforded a series of 2:1 complexes in which the s-block metal is sandwiched between two benzo crowns. The structures of [M{CpCo(b15c5dt)}2][BPh4] (M = Na, K, Rb, Cs) were determined by X-ray diffraction and ESI mass spectrometry. Reaction with Cu(CF3SO3)2 led to a redox reaction and the isolation of a unique bimetallic complex exhibiting a disulfide S-S bond