Physical and chemical investigations of iron complexes with 1,4,7-trimethyl-1,4,7-triazacyclononane and [2.2.2.2.3]adamanzane

The spin-transition character of several iron(II) complexes is studied in both the solid state and in solution. Iron(II) complexes with 1,4,7-trimethyl-1,4,7-triazacyclononane, Me₃tacn, and 1,4,7-tribenzyl-1,4,7-triazacyclononane were synthesized. The variable temperature X-ray cystallographic data of [Fe(Me₃tacn)(MeCN) ₃](BPh₄)₂ and [Fe(Bn₃tacn)(MeCN) ₃](B₁₂H₁₂) are presented as a way of measuring the high-spin/low-spin character of the complexes in the solid state. Magnetic susceptibility of [Fe(Me₃tacn)(MeCN)₃](BPh₄) ₂ was measured on a SQUID spectrometer. The spin equilibrium and the ligand exchange equilibria of [Fe(Me₃tacn)(MeCN)₃](CF ₃SO₃)₂ in solution was studied using variable temperature paramagnetic 1H and 19F NMR techniques. [Fe((CD₃)₃tacn)(MeCN)₃](CF₃SO ₃)₂ was synthesized and variable temperature 2H NMR was performed on this compound in acetonitrile to further investigate the electron spin and chemical equilibria in solution. These experiments indicated that the triflate salt of the iron (II) me₃tacn complex in solution is involved not only in a spin equilibrium, but is also involved in ligand exchange between the triflate counterion and coordinated acetonitriles. The 19F NMR experiments showed the presence of triflate bridged iron dimers and terminally bound triflates, as well as uncoordinated triflate.; Iron(II) complexes with [2.2.2.2.3]adamanzane and 1,4,7,10-tetraazacyclododecane were synthesized and the spin-transition character of these complexes in solution are studied by uv-vis spectroscopy and 1H NMR spectroscopy. Ligand exchange of the coordinated acetonitriles of [Fe(adamanzane)(MeCN) ₂] (CF₃SO₃)₂ was performed with triphenylacetate and acetate and the x-ray crystallographic data is presented. [Fe(adamanzane)(O ₂CCPh₃)](CF₃SO₃) exhibits an interesting N-H···π-electron hydrogen bonding motif.; A series of non-heme diiron protein model complexes were synthesized with different bridging carboxylates were synthesized and the proton-coupled electron-transfer reactions were studied using cyclic voltammetry. Protonation of the mixed-valent complexes were followed by 2H NMR spectroscopy when (CD₃)₃tacn was used as the macrocyclic ligand.; Oxidation of [Fe(Me₃tacn)(MeCN)₃](CF₃SO ₃)₂ in acetonitrile by N-methylmorpholine-N-oxide (MMNO) resulted in the formation of a very intense blue-green intermediate with a lifetime of hours at −30°C. The formation of this intermediate was followed by UV-Vis spectroscopy. A solid sample of the intermediate was achieved by metathesis with dodecaborate. The intermediate was characterized by IR and Mössbauer spectroscopies. Oxo-transfer catalysis from MMNO to triphenylphosphine was achieved by using [Fe(Me₃tacn)(MeCN) ₃](CF₃SO₃)₂ as the catalyst.