Synthesis and Characterisation of New Nickel‐Iron Complexes with an S4 Coordination Environment around the Nickel Centre

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AbstractThe nickel complex [Ni(xbsms)] [H2xbsms is α,α′‐bis(4‐mercapto‐3,3‐dimethyl‐2‐thiabutyl)‐o‐xylene] was reacted with FeCl2, [Fe2(CO)9], [Fe(CO)2(NO)2] and [Fe(CO)4I2]. The reaction with FeCl2 gives the heterotetranuclear nickel−iron complex [Ni(xbsms)FeCl2]2. The complex was characterised by analytical, spectroscopic and electrochemical methods and by X‐ray diffraction. [Ni(xbsms)FeCl2]2 crystallises in the monoclinic space group P21/c, with the dimer located on the inversion centre. The nickel ions are in a square‐planar S2S′2 environment, comprised of two thioether and two thiolate sulfur atoms. The thiolate sulfur atoms form a bridge between the nickel ion and the iron centre. The iron ions are in a pseudo square‐pyramidal S2Cl3 environment, with two chloride ions forming a bridge between the two iron centres. The Ni−Fe distance is 3.0403(3) Å. The reaction with [Fe2(CO)9], [Fe(CO)2(NO)2] or [Fe(CO)4I2] gives the heterodinuclear complexes [Ni(xbsms)Fe(CO)4], [Ni(xbsms)Fe(NO)2] and [Ni(xbsms)Fe(CO)2I2], respectively. These complexes were characterised by analytical, spectroscopic and electrochemical methods. In [Ni(xbsms)Fe(CO)4], one thiolate group bridges the Ni and Fe centres, whereas in [Ni(xbsms)Fe(NO)2] and [Ni(xbsms)Fe(CO)2I2], two thiolate groups form a bridge between the centres. These newly synthesised nickel−iron complexes appear to be suitable complexes for new structural models for [NiFe]‐hydrogenases. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)