CO Substitution Reactions of Diiron Complexes [{(μ-SCH2)2X}Fe2(CO)6] and [{(μ-SeCH2)2X}Fe2(CO)6] (X = O, CH2) with Ph2PCl/Me3NO To Give Ph2PCl-, Ph2PNMe2-, and Ph2PP(=O)Ph2-Substituted Complexes Related to [ FeFe] Hydrogenases

Diiron carbonyl complex [{(-SCH2)(2)O}Fe-2(CO)(6)] (A) reacted with Ph2PCl and Me3NO in MeCN at room temperature to give the expected and unexpected Ph2PCl-, Ph2PNMe2-, and Ph2PP(=O)Ph-2-substituted complexes [{(-SCH2)(2)O}Fe-2(CO)(5)L] [1, L = Ph2PCl; 2, L = Ph2PNMe2; 3, L = Ph2PP(=O)Ph-2], whereas complex [{(-SCH2)(2)CH2}Fe-2(CO)(6)] (B) reacted with Ph2PCl and Me3NO under similar conditions to afford only the unexpected complexes [{(-SCH2)(2)CH2}Fe-2(CO)(5)L] [4, L = Ph2PNMe2; 5, L = Ph2PP(=O)Ph-2]. Similarly, complex [{(-SeCH2)(2)O}Fe-2(CO)(6)] (C) reacted with Ph2PCl and Me3NO in MeCN at room temperature to give the unexpected complexes [{(-SeCH2)(2)O}Fe-2(CO)(5)L] [6, L = Ph2PNMe2; 7, L = Ph2PP(=O)Ph-2], and the corresponding unexpected complexes [{(-SeCH2)(2)CH2}Fe-2(CO)(5)L] [8, L = Ph2PNMe2; 9, L = Ph2PP(=O)Ph-2] were produced by the reaction of complex [{(-SeCH2)(2)CH2}Fe-2(CO)(6)] (D) with Ph2PCl and Me3NO under similar conditions. The structures of 1-9 were characterized by elemental analysis and spectroscopy, and for 1-5 and 7-9 by X-ray crystallography. Possible pathways for the formation of the functionalized phosphine-substituted complexes 1-9 have been suggested. Complexes 1-9 can be regarded as models for [FeFe] hydrogenases as their structures are similar to the active site of [FeFe] hydrogenases, and some have been found to be catalysts for proton reduction to hydrogen in the presence of HOAc.