A Study On Preparation And Properties Of Heteronuclear Fe/S Clusters And Cubane-type Mo/S Clusters With Cp~* As Ancillary Ligands

Nitrogenase is a complex composed of molybdoiron protein and ferroprotein, which can complete biological transformations from inert molecule N2 to NH3 through coorperative actions of many clusters or multi-metallic centers of one cluster. As active sites iron-molybdenum cofactor is an advanced heteronuclear Fe7MoS9X (X=C, N,O) cluster formed by two incomplete cubane-type clusters Fe4S3 and Fe3MoS3 bridged by three S atoms and an unknown X (X=C, N,O) atom. In view of the unique and excellent catalytic properties of nitrogenase in the organisms, the synthesis of novel heteronuclear iron-sulfur clusters and cubane-type molybdenum-sulfur clusters and mimicing of biological metallopreteins have always been a challenging topic for a long time.Recently, some iron-sulfur clusters with Cp* ligands, such as [Cp*Fe(μ-SR)3FeCp*] (R =Me, Et, Ph) can provide well defined bimetallic reaction sites of unique activation of some inactive small molecule including CO, cumulenes (for example:CS2, COS and PhNCS), halohydrocarbon and favourable catalytic conversion of the N-N single bond cleavage of hydrazines. So far, there has been no example of heteronuclear iron-sulfur clusters with Cp* ligands including Group 10 (Ni, Pd, Pt) and 11 (Au, Ag, Cu) atoms, although they are expected to have analogous or different properties with similar subunit to the active sites of nitrogenase, which is a heteronuclear iron-sulfur clusters.Since the 1980s, the synthetic chemistry of cubane-type clusters has been gotten a rapid development from original "one-pot" method to the active building-block assembly. At present, over 100 cubane-type clusters have been reported that include a majority of transition metals in periodic table. Some heteronuclear cubane-type clusters [(Cp*Mo)3M'(μ3-S)4] (M'= Ni, Pd, Ru, etc) show unique transformation of organic substrates such as alkynes, hydrazines, alkynoic acid, aminoalkynes. However, the heteronuclear cubane-type clusters with Group 11 (Au, Ag) atoms have never been studied so far.This thesis describes the preparation and electrochemical properties of novel heteronuclear iron-sulfur clusters and cubane-type clusters with Cp* as ancillary ligands, and a total of 8 new heteronuclear iron-sulfur clusters and 6 cubane-type clusters are fully characterized by IR, 1H NMR,31P NMR spectroscopies, ESI-HRMS and single-crystal X-ray diffraction methods. The detailed contents are as follows: 1. The mononuclear complexes [Cp*FeSEt(CNR)2] (2a, R=tBu;2b, R=Ph; 2c, R=Cy; 2d, R= Bn) can be obtained by the reactions of triply thiolate-bridged diiron complex [Cp*Fe(μ-SEt)3FeCp*] with the isocyanide ligands CNR (R=tBu, Ph, Cy, Bn)2. The reactions of 2 with complex PdCl2(PPh3)2 and AgPF6 can produce new heterobinuclear isocyanide-bridged iron-palladium clusters [Cp*FeCNR(μ-CNR)(μ-SEt)PdCl(PPh3)][PF6] (3a, R=tBu; 3b, R=Ph; 3c, R=Cy; 3d, R=Bn). The iron-palladium clusters with azide ligands [Cp*FeCNtBu(μ-CNtBu)(μ-SEt)PdN3(PPh3)][PF6] (3e) can be obtained by the reaction of 3a with NaN3. Treatment of 2a with complex NiCl2(PPh3)2 and AgPF6 can afford new heterobinuclear iron-nickel cluster [Cp*Fe(CNtBu)2(μ-SEt)NiCl(PPh3)][PF6] (4). The electrochemical CVs of 3a-3d reveal that the conjugated isocyanide ligand CNPh not only increase their reduction potential but also enhance their stability.3. Some new heterotrinuclear iron-sulfur clusters with Group 11 (Au, Ag, Cu) atoms [{Cp*Fe(CNtBu)2(μ-SEt)}2M][PF6] (5a, M=Au; 5b, M=Ag; 5c, M=Cu) are prepared by the reaction of 2a with [(Ph3P)M]+or M+(M=Au, Ag, Cu).4. By the reaction of the incomplete cubane-type cluster [(Cp*Mo)3(μ3-S)(μ-S)3][PF6] with [(R3P)Au]+(R=Ph, Cy, tBu), [(Ph3P)Ag]+and [(Ph3P)Cu]+(or CuI), the heteronuclear cubane-type gold clusters [(Cp*Mo)3(μ3-S)4Au(PR3)]2+(7a:R=Ph; 7b:R=Cy; 7c:R=tBu), cubane-type silver cluster [(Cp*Mo)3(μ3-S)4Ag(PPh3)]2+(8), cubane-type copper clusters [(Cp*Mo)3(μ3-S)4Cu(PPh3)]2+(9a) and [(Cp*Mo)3(μ3-S)4CuI]+(9b) can be prepared, respectivedly. The electrochemical CVs of the heteronuclear cubane-type gold and copper clusters show that the valence states of clusters'Mo atoms have been changed in their two consecutive one-electron reduction process, and yet that of the heterometal Au or Cu are retained.