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

Abstract

Abstract The nickel complex [Ni(xbsms)] [H 2 xbsms is α,α′‐bis(4‐mercapto‐3,3‐dimethyl‐2‐thiabutyl)‐ o ‐xylene] was reacted with FeCl 2 , [Fe 2 (CO) 9 ], [Fe(CO) 2 (NO) 2 ] and [Fe(CO) 4 I 2 ]. The reaction with FeCl 2 gives the heterotetranuclear nickel−iron complex [Ni(xbsms)FeCl 2 ] 2 . The complex was characterised by analytical, spectroscopic and electrochemical methods and by X‐ray diffraction. [Ni(xbsms)FeCl 2 ] 2 crystallises in the monoclinic space group P 2 1 / c , with the dimer located on the inversion centre. The nickel ions are in a square‐planar S 2 S′ 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 S 2 Cl 3 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 [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) 4 ], one thiolate group bridges the Ni and Fe centres, whereas in [Ni(xbsms)Fe(NO) 2 ] and [Ni(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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)