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.

We have first studied the reactions of monoanions [(μ-RE)(μ-E)Fe 2 (CO) 6 ] -(A, E=Se; B, E=S) with electrophile PhC(Cl)dNPh or dianions [(μ-E) 2 Fe 2 (CO) 6 ] 2-(C, E=Se; D, E=S) with electrophiles PhC(Cl)dNR 0 (R 0 =Ph, p-MeC 6 H 4 ). While monoanion A was found to react with PhC(Cl)d NPh to give expected complexes (μ-RSe)[μ-SeC(Ph)dNPh]Fe 2 (CO) 6 (1, R=Me; 2, R=Et; 3, R= m-MeC 6 H 4 ), monoanion B was found to react with PhC(Cl)dNPh to afford unexpected complexes (μ-RS)[η 1 -SC(Ph)dNPh-η 1 ]Fe 2 (CO) 6 (4, R=Me; 5, R=Et). Furthermore, while dianion C reacted with PhC(Cl)dNR 0 (R 0 =Ph, p-MeC 6 H 4 ) to give expected complexes [μ-SeC(Ph)dNR 0 ] 2 Fe 2 (CO) 6 (6, R 0 = Ph; 7, R 0 = p-MeC 6 H 4 ), dianion D was found to react with PhC(Cl)dNR 0 (R 0 = Ph, p-MeC 6 H 4 ) to afford unexpected complexes [μ-SC(Ph)dNR 0 ][η 1 -C(Ph)dNR 0 -η 1 ]Fe 2 (CO) 6 (8, R 0 = Ph; 9, R 0 = p-MeC 6 H 4 ). All the new complexes 1-9 were characterized by elemental analysis and spectroscopy, and complexes 1 and 4-8 were further structurally confirmed by X-ray crystallography.