SYNTHESES AND REACTIONS OF IRON AND RUTHENIUM COMPLEXES OF AN OPTICALLY PURE FUSED CYCLOPENTADIENYL LIGAND

Optically pure (lR)-(-)-9,9-dimethyltricyClo[6.1.1.0(2,6)]deca-2,5-diene (HPCp) reacts with Fe-(CO)5 and Ru3(CO)12, in the presence of the hydrogen acceptor norbornene, to form the isomorphic and isostructural complexes Cis-[PCPM(CO)2]2 (M = Fe (t), Ru (8)), in which the metal is coordinated exclusively to the exo face of PCp. These complexes react with iodine to form PCPM(CO)2I (M = Fe(2), Ru(9)) Complex 2 reacts with 1-phenyl-3,4-dimethylphosphole (DMPP), diphenylvinylphosphine (DPVP), and phenyldivinylphosphine (DVPP) to form two diastereomers of PCpFe(CO)(DMPP)l (3a,b), PCpFe(CO)(DPVP)I, (4a,b), and PCpFe(CO)-(DVPP)I (5a,b), respectively. Complex 9 reacts with DMPP to form two diastereomers of PCpRu(CO)(DMPP)l (10a,b). Complexes 4a and 4b react with DPVP and DVPP to undergo sequential ligand substitution and intramolecular [4 + 2] Diels-Alder cycloaddition forming four and five diastereomers of [PCpFe(CO)(DMPP)(DPVP)]I (6a-d) and [PCpFe(CO)(DMPP)-(DVPP)]I (7a-e), respectively. Complexes 10a and 10b similarly react with DPVP and AgBF4 to form four diastereomers of the [4 + 2] Diels-Alder adducts [PCpRu(CO)(DMPP)(DPVP)] BF4 (11a-d). Little asymmetric induction is observed in these metal-promoted intramolecular [4 + 2] Diels-Alder cycloadditions. New complexes were characterized by elemental analyses, infrared spectroscopy, and H-1, C-13{H-1}, and where appropriate P-31{H-1} NMR spectroscopy. The structures of 8 and 9 were confirmed by X-ray crystallography. Both compounds crystallized in the acentric space group P2(1)2(1)2, in unit cells with the following dimensions. 8: a = 12.082(2) angstrom, b = 18.689(5) angstrom, c = 11.156(2) angstrom, V = 2519.o(9) angstrom3, Z = 4. 9: a = 20.061(5) angstrom, b = 7.166(2) angstrom, c = 10.323(2) angstrom, v = 1483.9(6) angstrom3, Z = 4. Refinements converged to R(F) = 0.054 and 0.045 for 3561 and 2185 independent observed (I > 4sigma(I)) reflections. In both compounds ruthenium coordinates to the less sterically hindered exo face of the PCp ligand, anti to the gem-dimethyl groups.