Unexpected Preparation of Butterfly Fe/S Cluster Complexes Containing a Quaternary Phosphorus Atom via Reactions of the Anions (μ-RS)(μ-S^-)Fe₂(CO)₆ and (μ-RS)(μ-S^-)[Fe₂(CO)₆]₂(μ₄-S) with Diphenylchlorophosphine

Reactions of Monoanions [(μ-RE)(μ-E)Fe2(CO)6]− and Dianions [(μ-E)2Fe2(CO)6]2− (E = Se, S) with N-Substituted Benzimidoyl Chlorides, Leading to Novel Butterfly Fe/E Cluster Complexes

“…At the present stage, we are not clear about the mechanism for formation of the unexpected complexes 4 and 5 . However, according to the familiar nucleophilic mode of monoanion B ,, and the studied results regarding reaction of monoanion B with Ph 2 PCl, we might suggest a possible pathway to account for the formation of complexes 4 and 5 . That is, as shown in Scheme , the initially intermolecular nucleophilic attack of the S-centered monoanion B at the leaving group(Cl − )-attached C atom of electrophile PhC(Cl)NPh would first afford intermediate M 1 .…”

“…Although this pathway is mainly speculative, it seems reasonable. This is because (i) the nucleophilic attack of the S-centered dianion D at various organic halides is known to give symmetrically disubstituted complexes; (ii) the intramolecular isomerization from M 2 to M 3 is similar to that involved in reaction of dianion D with Ph 2 PCl; (iii) although the extrusion of one S atom followed by C coordination in M 3 is unprecedented, the extrusion of one Se atom or one CO followed by the corresponding coordination was previously observed in similar butterfly Fe/E cluster complexes; , and (iv) from the studied reactions byproducts PhC(S)NHPh ( 8′ ) and PhC(S)NHC 6 H 4 Me- p ( 9′ ) were isolated along with products 8 and 9 , respectively (see Experimental Section). Presumably, the two byproducts were generated from the extruded S and excess PhC(Cl)NR′ or some species derived from PhC(Cl)NR′.…”

“…It is well known that the [MgX] + salts of monoanions A and B , and the dilithium salts of dianions C and D − can be prepared in nearly quantitative yields by reductive cleavage of the E−E bond of cluster (μ-E 2 )Fe 2 (CO) 6 with Grignard reagents and Super-Hydride (Et 3 BHLi), respectively, in THF at −78 °C (Scheme ). In addition, these anions have been also demonstrated to be versatile reagents for synthesis of a wide variety of novel butterfly Fe/E cluster complexes. − Recently, we published two papers that described the unexpected production of the butterfly Fe/S/P cluster complexes from reactions of the butterflyFe/S cluster anions B and D with a P-based electrophile, Ph 2 PCl. , Closely related to such studies, we further carried out a study on reactions of anions A − D with another type of electrophile, namely, the N-substituted benzimidoyl chlorides PhC(Cl)NR′, in order to find new reaction modes and to prepare the corresponding butterfly cluster complexes. Interestingly, through this study we found that the Se-centered anions A and C reacted with PhC(Cl)NR′ to give the expected butterfly Fe/Se cluster complexes, whereas reactions of the S-centered anions B and D afforded the unexpected novel butterfly Fe/S cluster complexes.…”

Synthetic and Structural Studies of Butterfly Fe/S/P Cluster Complexes Related to the Active Site of [FeFe]-Hydrogenases. Proton Reduction to H2 Catalyzed by (η1-Ph2PS-η1)2Fe2(CO)6

“…As mentioned above, the single- and double-butterfly complexes 1 − 6 can be prepared by reactions of the BrMg salts of monoanions A (R = Me, Ph) and the lithium salts of monoanions B (R = n -Bu, Ph) with Ph 2 PCl, respectively (Scheme ) . Similarly, we could further prepare the single-butterfly Fe 2 S 2 P complexes 7 − 10 by treatment of the BrMg salts of monoanions A (R = Et, p -MeC 6 H 4 ) (prepared in situ from 1 equiv of (μ-S 2 )Fe 2 (CO) 6 and 1 equiv of the Grignard reagents RMgBr) with 1 equiv of Ph 2 PCl in THF from −78 °C to room temperature (Scheme ).…”

“…This is due to the realization that the active site of [FeFe]-hydrogenases (so-called H-clusters) resembles the archetypal (μ-RS) 2 Fe 2 (CO) 6 derivatives, which consist of a butterfly Fe 2 S 2 cluster core and four unusual ligands: CO, CN − , [Fe 4 S 4 (SCys) 4 ], and a dithiolate (Figure ) . So far, a great variety of butterfly Fe/S cluster complexes that act as structural and functional models of the H-cluster have been prepared and characterized, which has considerably promoted our understanding of the natural enzymes. , Recently, we published a communication that describes the unexpected formation of the Fe/S/P cluster complexes 1 − 6 from reactions of the butterfly Fe/S cluster anions A (R = Me, Ph) and B (R = n -Bu, Ph) with Ph 2 PCl (Scheme ). Since these Fe/S/P complexes contain a butterfly Fe 2 S 2 or Fe 2 S 2 P cluster core that carries a given amount of CO ligands, they might be regarded as the structural analogues of the active site of [FeFe]-hydrogenases .…”