Rearrangement of the Mo/Fe/S Cluster under the Reducing Conditions;Alternative Synthesis of MoFe_4S_6(PEt_3)_4Cl Cluster from [(Cl_4-cat)Mo(MeCN)Fe_3S_4Cl_3](Et_4N)_2

摘要

Synthetic model compounds for FeMo-cofactor have been pursued persistently by synthetic inorganic chemists.Continuous efforts resulted in P-cluster analogs of [(Tp)_2Mo_2Fe_6S_9(SH)_2]~(3-) and [(Fe_4S_3)_2(mu_6-S)]~(4+) clusters,recently.Our ongoing efforts to synthesize FeMo-cofactor model compounds has produced many new Mo/Fe/S clusters,including (Cl_4-cat)_2Mo_2Fe_6S_8(PR_3)_6 (R = Et,~nPr,and ~nBu),Fe(DMF)Cl(Cl_4-cat)_2Mo_2Fe_2S_4(PEt_3)_2ClFe_4S_4(PEt_3)_3(CO)_6Cl,[(Cl_4-cat)_2Mo_2Fe_2S_3O(PEt_3)_3Cl]~+,(Cl_4-cat)_2Mo_2Fe_3S_5(PEt_3)_5,and (Cl_4-cat)LMoFe_3S_3(PR_3)n(CO)_m (L = none,PR_3,Pyridine,or O,n = 2 or 3,m = 4,5 or 6,R = Et or ~nPr).These Mo/Fe/S clusters are synthesized by rational synthetic designs instead of so-called spontaneous self-assembly (SSA).One of the established methods to prepare high nuclearity Mo/Fe/S clusters is the reductive coupling of the Fe_2S_2 and MoFeS_2 rhombic building blocks in the presence of S~(2-)-scavenging trialkylphosphine.Reductive coupling rationale can also explain reactivity of many Mo/Fe/S clusters in the presence of CO and trialkylphosphine.This approach has advantage over SSA method because the product can be predicted and explained,while SSA method cannot be.For examples,high pressure CO reaction of [Fe_4S_4(PcHex_3)_4](BPh_4) cluster produces the Fe_3S_2(CO)_7-(PcHex_3)_2 cluster and Fe_4S_4(P~tBu_3)_4 cluster couples itself to form Fe_(16)S_(16)(P~tBu_3)_8 cluster.