TRIPHOSPHA-FERROCENES AS LIGANDS - CRYSTAL AND MOLECULAR-STRUCTURES OF [FE(ETA(5)-C5ME5)(ETA(5)-C2BUT2P3)CR(CO)5] AND OF THE NOVEL NICKEL-COMPLEX [FE(ETA(5)-C5ME5)(ETA(5)-C2BUT2P3)NI(CO)2]2 CONTAINING 2 INTERLINKED [FE(ETA(5)-C5ME5)(ETA(5)-C2BUT2P3)] SYSTEMS

The lone pair electrons of the two adjacent phosphorus atoms of the C2BUt2P3 ring in the triphospha-ferrocene complex [Fe(eta5-C5Me5)(eta5-C2BUt2P3)] can ligate to other metal centres to afford novel bi- and tetrametallic complexes, whose structures have been elucidated by NMR and single-crystal X-ray studies. In the reaction of [Fe(eta5-C5Me5)(eta5-C2But2P3)] with Ni(CO)4 the tetrametallic complex [Fe(eta5-C5Me5)(C2BUt2P3)Ni(CO)2]2 is formed. This complex is of particular interest because it represents the first example of the intermolecular interlinkage of two phospha-ferrocene units by two metal centres. A six-membered ring consisting of four phosphorus and two nickel atoms forms the core of the molecule and exhibits a boat configuration. The starting material [Fe(eta5-C5Me5)(eta5-C2But2P3)] reacts with Cr(CO)5(thf), W(CO)5(thf) and Fe2(CO)9 to yield the eta1-complexes [Fe(eta5-C5Me5)(eta5-C2BUt2P3)M(CO)n] (M = Cr, W, n = 5; M = Fe, n = 4). Variable-temperature (P{H})-P-31-H-1 NMR studies reveal that these complexes are fluxional in solution.