Synthesis and characterisation of new nickel-iron complexes with an S4 coordination environment around the nickel centre

The nickel complex [Ni(xbsms)] [H(2)xbsms is alpha,alpha'-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)-o-xylene] was reacted with FeCl2, [Fe-2(CO)(9)], [Fe(CO)(2)(NO)(2)] and [Fe(CO)(4)I-2]. 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 P2(1)/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) Angstrom. The reaction with [Fe-2(CO)(9)], [Fe(CO)(2)(NO)(2)] or [Fe(CO)(4)I-2] gives the heterodinuclear complexes [Ni(xbsms)Fe(CO)(4)], [Ni(xbsms)Fe(NO)(2)] and [Ni(xbsms)Fe(CO)(2)I-2], respectively. These complexes were characterised by analytical, spectroscopic and electrochemical methods. In [Ni(xbsms)Fe(CO)41, one thiolate group bridges the Ni and Fe centres, whereas in [Ni(xbsms)Fe(NO)(2)] and tNi(xbsms)Fe(CO)(2)I-2], 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. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).