Synthesis of M/Fe/S Clusters Relevant to Biological Systems and Minerals.

Abstract

The synthesis and characterization of three series of iron sulfur clusters is presented with relevance to biological systems and minerals. The synthesis, crystallographic structures and reactivity of these clusters is presented along with preliminary spectroscopic characterization including magnetic susceptibility measurements, cyclic voltammetry, infra-red and Mössbauer spectroscopy. The first series of compounds includes iron sulfur nitrosyl clusters with tetra-, hexa-, and octanuclear core structures. The interconversions between these three cores and their reactivity are presented. Comparative spectroscopic characterization provides experimental evidence supporting that the best description for iron-bound nitric oxide is NO-. These clusters can serve as model compounds that can help to elucidate the interactions of nitric oxide with iron sulfur proteins in biological systems. The second series of compounds includes heterometalic iron sulfur chloride clusters containing a pentlandite like M8S6 core, with the heterometal being nickel, copper or cobalt. The clusters presented provides several new complexes that can serve as structural and electronic models for the natural occurring pentlandites, and the systematic synthesis provides a methodology for the expansion of the M8S6 core to additional metals. The third series includes metal iron sulfur nitrosyl clusters containing a pentlandite like M8S6 core, with the metal being molybdenum, nickel, cobalt. Both chloro and nitrosyl clusters are compared in terms of synthesis and electronic properties, and the possibility of these clusters to serve as potential building blocks for extended networks that could serve as multi-electron heterogeneous catalysts is discussed.