Structural and electrochemical aspects of tris(ferrocenyl/phenyl-ethynyl) phosphine ligated chalcogen bridged iron carbonyl clusters

Abstract

Room temperature stirring of THF solution of [Fe3Se 2(CO)9] and P(C2R)3 (R = Ph, Fc), in presence of Me3NO·2H2O, yield monosubstituted [Fe3Se2(CO)8{P(C2R)3}] (1, R = Ph; 2, R = Fc) and disubstituted [Fe3Se2(CO) 7{P(C2R)3}2] (3, R = Ph; 4, R = Fc) clusters. Under similar conditions, reactions of [Fe3Te 2(CO)9] yield disubstituted [Fe3Te 2(CO)7{P(C2R)3}2] (5, R = Ph; 6, R = Fc) and [Fe3Te2(CO)8{P(C 2R)3}2] (7, R = Ph; 8, R = Fc), consisting of an adduct of Fe(CO)2{P(C2R)3}2 and Fe2Te2(CO)6 butterfly moieties. Further substitution of 2 with P(C2Ph)3 forms a mixed disubstituted cluster, [Fe3Se2(CO)7P(C 2Fc)3P(C2Ph)3] (9). Crystal structures of disubstituted clusters 3-5 reveal a rare syn orientation of phosphinoalkyne ligands attached to the equatorial position of both basal irons, which is stabilised by an intramolecular CH⋯π interaction. DFT calculations also suggest that syn disubstituted products are thermodynamically most stable. Electrochemistry of tris(ferrocenylethynyl)phosphine containing clusters 2, 4, 8 and 9 has been studied by cyclic voltammetry, which shows cathodically shifted multielectron reversible oxidation of ferrocenyl groups. © 2013 The Royal Society of Chemistry.