The synthesis of the first indenylnickel chelate complexes with a pendant phosphane ligand is described. In contrast to earlier attempts by others directed to chelates with a tethered diphenylphosphino ligand in our hands, the synthesis was successful with a di-tert-butylphosphino ligand. The anionic ligand system was generated by a nucleophilic ring-opening of spiroindene 3 with lithium di-tert-butylphosphide, a reaction that was significantly accelerated by microwave irradiation. Alternatively, the borane-protected ligand was obtained by using the lithiated borane adduct of di-tert-butylphosphane. Reaction of the anionic ligand with nickel(II) chloride gave chloro chelate 8, which was transformed to azido, cyano, and isothiocyanato complexes 9−11, the cationic acetonitrile complex 12, and representatives containing nickel−carbon bonds, including the methyl and the ethynyl derivatives 13 and 18. A crystal structure analysis of methyl chelate 13 is also included. The 13C NMR data of a quarternized 2-pyridylethynyl derivative 20 suggest a significant contribution of the respective allenylidene resonance formulas 21 and 22. Finally, bimetallic ferrocenylethynyl complex 23 has been included as a bimetallic representative. Some of the complexes were characterized by cyclovoltammetry.

The syntheses, characterization, and some reactions of (phosphanylethyl)cyclopentadienyl chelate complexes of cobalt, rhodium, iridium, nickel, and chromium with unsymmetrical substitution at the phosphorus atom are described. The ligand systems were prepared by nucleophilic ring opening of spiro[2.4]hepta-4,6-diene with lithium tert-butylphenylphosphide or lithium tert-butylcyclohexylphosphide. The anionic ligands give the respective chelate complexes by treatment with metal halide reagents. In three cases it was possible to obtain X-ray crystal structure analyses. The cobalt chelate complex undergoes oxidative addition with a dihydrosilane, the reaction results in the formation of products with three stereogenic centers at phosphorus, cobalt, and silicon, which show dynamic behavior as indicated by VTNMR. The rhodium chelate complex undergoes oxidative addition of iodomethane with diastereoselective formation of the respective Rh(III) chelate. While diastereoselectivity caused by a planar chiral indenyl ligand or by a stereogenic carbon center in the chelate backbone has earlier been observed, this is the first case of a stereoinduction by the stereogenic phosphorus ligand. Activation energies for the rotation of cobalt and rhodium chelates have also been determined by VTNMR.

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