Investigations on Synthesis, Structure, and Properties of New Butterfly [2Fe2Se] Cluster Complexes Relevant to Active Sites of Some Hydrogenases

Abstract

As a continuation of our studies on biomimetic chemistry and butterfly cluster chemistry, two series of "closed" and "open" butterfly [2Fe2Se] cluster complexes have been prepared in satisfactory yields. Thus, treatment of Fe 3 (CO) 12 with (HSeCH 2 ) 2 CHOH in toluene at reflux gave the expected "closed" butterfly [2Fe2Se] cluster complex [(μ-SeCH 2 ) 2 CH(OH)]Fe 2 (CO) 6 (A), whereas the "open" butterfly cluster complex (μ-EtSe)[(μ-SeCH 2 CH(OH)(CH 2 Br)]Fe 2 (CO) 6 (B) was unexpectedly produced along with complex A via a sequential reaction of (μ-Se 2 )Fe 2 (CO) 6 with Et 3 BHLi, followed by treatment with (BrCH 2 ) 2 CHOH. The other "closed" and "open" cluster complexes 1-6 could be further prepared by the hydroxy transformation and CO substitution reactions of complexes A and B. For example, (i) reaction of A with PPh 3 and decarbonylating agent Me 3 NO afforded PPh 3monosubstituted complex [(μ-SeCH 2 ) 2 CH(OH)]Fe 2 (CO) 5 (PPh 3 ) (1), (ii) further reaction of 1 with the acylating agent PhC(O)Cl in the presence of Et 3 N produced the benzoate-functionalized complex [(μ-SeCH 2 ) 2 CH(O 2 CPh)]Fe 2 (CO) 5 (PPh 3 ) (2), (iii) treatment of A with the phosphatizing agent Ph 2 PCl in the presence of Et 3 N or simply with PhPCl 2 yielded the phosphite-functionalized complexes [(μ-SeCH 2 ) 2 CH(OPPh 2 -η 1 )]Fe 2 (CO) 5 ( 3) and [(μ-SeCH 2 ) 2 CH(OPPhCl-η 1 )]Fe 2 (CO) 5 (4), and (iv) treatment of B with 4-pyridinecarboxylic chloride or Ph 2 PCl in the presence of Et 3 N resulted in formation of the "open" butterfly cluster complexes (μ-EtSe)[μ-SeCH 2 CH(CH 2 Br)-(O 2 CC 5 H 4 N-4)]Fe 2 (CO) 6 ( 5) and (μ-EtSe)[μ-SeCH 2 CH(CH 2 Br)(OPPh 2 -η 1 )]Fe 2 (CO) 5 (6). All the new complexes have been characterized by elemental analysis and spectroscopy, as well as for A, 1-4, and 6 by X-ray crystallography. Both 1 H and 77 Se NMR spectral studies demonstrated that complexes B and 5 consist of three isomers of e-Et/a-R, e-Et/e-R, and a-Et/e-R, whereas complex 6 exists only as one isomer of e-Et/a-R. On the basis of an electrochemical study, it was found that the "closed" and "open" complexes A and B can catalyze the proton reduction of TsOH and HOAc to give hydrogen, respectively.

Synthesis and characterisation of polymeric materials consisting of {Fe2(CO)5}-unit and their relevance to the diiron sub-unit of [FeFe]-hydrogenase

“…3, this complex shows largely the structural features found for analogous diiron pentacarbonyl complexes reported in the literature. 4,9,14,24,26,28, 29 But it is noteworthy that the Fe-N bond is trans rather than cis to one of the two sulfur atoms as found in those reported analogues. The triazole ring is co-planar with the one defined by Fe2, S2, C9, C10, and N1 atoms.…”

Effects of Alkane Linker Length and Chalcogen Character in [FeFe]‐Hydrogenase Inspired Compounds

“…Recently, Se homologues of [FeFe]‐hydrogenase active site models with the [2Fe2Se] subunit were reported . Enhancement of the catalytic activity toward proton reduction was observed with strong acid ( p ‐toluenesulfonic acid in CH 3 CN) upon replacement of S atoms by more electropositive Se atoms .…”

A Straightforward Access to Stable β‐Functionalized Alkyl Selenols

“…To the best of our knowledge a limited number of β‐substituted selenols, which are the focus of the present study, have been obtained, either through a multistep procedure by reductive cleavage of Se‐oligomers, or via ring opening of epoxides with hydrogen selenide . However in these studies alkyl selenols were formed in rather low yield, diselenides being usually the products in the largest percentage ,,. Thus, the study of functionalized aliphatic selenols represents an interesting challenge both from a synthetic point of view and for their possible applications.…”