Activation of small molecules by cationic rhenium complexes

Thesis (Ph. D.)--University of Washington, 1997Thermolysis of ReX(CO)\sb5 (X = CH\sb3 or H) with PPh\sb3 and P\rm\sp{i}PrPh\sb2 in toluene generates trans-mer-Re(X)(PR\rm\sb3)\sb2(CO)\sb3 complexes. Protonation of trans-mer-Re(X)(PR\rm\sb3)\sb2(CO)\sb3 with (H(Et\rm\sb2O)\sb2\rbrack B(Ar\sp\prime)\sb4\ (Ar\sp\prime=3,5(CF\sb3)\sb2C\sb6H\sb3) under an H\sb2 atmosphere generates stable dihydrogen complexes, (\rm Re(H\sb2)(PR\sb3)\sb2(CO)\sb3\rbrack B(Ar\sp\prime)\sb4\ (PR\sb3=PPh\sb3 (4a), \rm P\sp{i}PrPh\sb2 (4b)). The large J\sb{\rm HD} values (4a = 32 Hz, 4b = 30 Hz) and short T\rm\sb{1min} values (4a = 10.3 ms, 4b = 10.5 ms) at 300 MHz are consistent with a dihydrogen formulation. The hydrogen ligand can be removed in solution or the solid state by exposing to vacuum or argon to generate a ligand deficient product, (Re(PR\rm\sb3)\sb2(CO)\sb3\rbrack B(Ar\sp\prime)\sb4 (5). Complexes 4 and 5 react with a variety of small molecules to form (ReL(PR\rm\sb3)\sb2(CO)\sb3\rbrack B(Ar\sp\prime)\sb4\ (L=H\sb2O,\ NH\sb3,\ C\sb2H\sb4,\ N\sb2,\ CO, Cl\sp-,\ PPh\sb3,\ THF). (\rm Ph\sb3C\rbrack B(Ar\sp\prime)\sb4 reacts with \rm Cp\sb2ReCH\sb3 and \rm Cp\sb2ReCH\sb2CH\sb3 to abstract an $\alpha$-hydride from the alkyl ligand to generate carbene complexes, (\rm Cp\sb2Re=CH\rm\sb2\rbrack B(Ar\sp\prime)\sb4 (1) and (Cp\sb2Re=CH(CH\rm\sb3)\rbrack B(Ar\sp\prime)\sb4 (3). Both complexes 1 and 3 decompose to \rm\lbrack Cp\sb2Re(C\sb2H\sb4)\rbrack\sp+ and \rm\lbrack Cp\sb2Re(NCCD\sb3)\rbrack\sp+ in acetonitrile upon addition of BF\sb{4\sp-} salts or thermolysis of the solutions at 50\sp\circC for two weeks. \rm\lbrack Cp\sb2Re(CH\sb3)H\rbrack B(Ar\sp\prime)\sb4 eliminates methane at 0\sp\circC in \rm CH\sb2Cl\sb2 to generate \rm\lbrack Cp\sb2Re(CH\sb2Cl)Cl\rbrack B(Ar\sp\prime)\sb4. Addition of (Me\rm\sb3O\rbrack BF\sb4 to \rm Cp\sb2ReR\ (R=CH\sb3,\ CH\sb2CH\sb3,\ CH\sb2SiMe\sb3) in acetonitrile forms stable bis-alkyl complexes, \rm\lbrack Cp\sb2Re(CH\sb3)R\rbrack BF\sb4. (Cp\sb2Re=CH\rm\sb2\rbrack B(Ar\sp\prime)\sb4 (1) reacts with triphenylphosphine and pyridine to generate ylide complexes. Complex 1 reacts with Cl\rm\sb2,\ Br\sb2,\ I\sb2 by 1,2-addition across the Re-C double bond to form halomethyl halide complexes. Complex 1 has also been shown to react with oxygen, sulfur and carbene donor reagents to form \eta\sp2-formaldehyde, \eta\sp2-thioformaldehyde and \eta\sp2-olefin complexes.The addition of \rm Me\sb2SiCl\sb2 or \rm(Me\sb2Si)\sb2Cl\sb2 to a THF solution of (\eta\sp5-C\rm\sb5H\sb4Li)\sb2ReCH\sb3 gives ansa-bridged complexes with a single or double silicon linker. A X-ray diffraction study was undertaken to confirm the structure of (\eta\sp5-\rm C\sb5H\sb4-SiMe\sb2-\eta\sp5-\rm C\sb5H\sb4)ReCH\sb3. Substituted derivatives of \rm Cp\sb2ReX\ (X=H,\ CH\sb3) have also been synthesized with Me or SiMe\sb3 groups on each cyclopentadienyl ring. Several methyl hydride rhenocene complexes have been generated by protonation and characterized at low temperature by NMR spectroscopy. Methane elimination from these complexes occurs at ambient temperature, although ((\eta\sp5-\rm C\sb5H\sb4-SiMe\sb2-\eta\sp5-\rm C\sb5H\sb4)Re(CH\sb3)H\rbrack B(Ar\sp\prime)\sb4 has been observed to be more stable at room temperature then analogous complexes

Reversible Ethylene Cycloaddition Reactions of Cationic Aluminum 'beta'-Diketiminate Complexes

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