Pentadienyl-metal-phosphine chemistry. 17. Syntheses, structures, and spectroscopy of pentadienyl-ruthenium-phosphine complexes

Article abstract of DOI:10.1021/om00101a013

The reaction of RuCl₂(PPh₃)₃ with pentadienyltributyltin produces (η⁵-pentadienyl)RuCl(PPh₃)₂ (1), which serves as a convenient starting material for the synthesis of a large family of new pentadienyl-ruthenium-phosphine complexes. Treatment of 1 with 1 equiv of PMe₃, PMe₂Ph, PEt₃, or PEt₂Ph produces the mixed-phosphine complexes (η⁵-pentadienyl)RuCl(PR₃) (PPh₃) (2a, PR₃ = PMe3; 2b, PR₃ = PMe₂Ph; 2c, PR₃ = PEt₃; 2d, PR₃ = PEt₂Ph). Compound 2c crystallizes in the monoclinic space group P2₁/c with a = 11.435 (2) A?, b = 13.770 (4) A?, c = 18.237 (5) A?, β = 109.04 (2)°, V = 2715 (1) A?³, and Z = 4. This complex adopts a pseudooctahedral coordination geometry with the PEt₃ ligand residing under the open mouth of the pentadienyl ligand and the PPh₃ and Cl groups lying under the pentadienyl edges . Treatment of 1 with 2 equiv of PEt₃, PEt₂Ph, or PEtPh₂ produces (η⁵-pentadienyl)RuCl(PR₃)₂ (3c, PR₃ = PEt₃; 3d, PR₃ = PEt₂Ph; 3e, PR₃ = PEtPh₂). (η⁵-Pentadienyl)RuCl(PMe₂Ph)₂ (3b) is obtained cleanly by reacting 2b with one additional equivalent of PMe₂Ph. (η⁵-Pentadienyl)RuCl(PEt₃)₂ (3c) [monoclinic, Cc, a = 28.094 (7) A?, b = 10.003 (2) A?, c = 15.134 (3) A?, β = 98.54 (2)°, V = 4205 (2) A?³, Z = 8] and (η⁵-pentadienyl)RuCl(PEt₂Ph)₂ (3d) [orthorhombic, P2₁2₁2₁, a = 16.848 (7) A?, b = 19.409 (4) A?, c = 7.867 (1) A?, V = 2572 (1) A?³, Z = 4] have been structurally characterized. Both complexes adopt pseudooctahedral coordination geometries in which one phosphine resides under the pentadienyl mouth while the other phosphine and the chloro ligand lie under the pentadienyl edges . Treatment of 1 with 3 equiv of PMe₃ produces (η³-pentadienyl)RuCl(PMe₃)₃ (4a). (η³-Pentadienyl)RuCl(PMe₂Ph)₃ (4b) is obtained upon treatment of 2b with 2 equiv of PMe₂Ph. 4a crystallizes in the monoclinic space group P2₁/n with a = 9.628 (3) A?, b = 13.662 (3) A?, c = 15.667 (4) A?, β = 91.59°, V = 2060 (1) A?³, and Z = 4. 4a's coordination geometry is pseudooctahedral with C1 and C3 of the pentadienyl ligand, the three phosphorus atoms, and the chlorine atom occupying the six coordination sites. The η³-pentadienyl ligand adopts a W-shaped syn geometry. Both 4a and 4b react with Ag⁺O₃SCF₃^- or Me⁺O₃SCF₃^- to yield [(η⁵-pentadienyl)Ru(PR₃)₃] ⁺O₃SCF₃^- (5a, PR₃ = PMe₃; 5b, PR₃ = PMe₂Ph). 5a crystallizes in the monoclinic space group P2₁/m with a = 8.622 (2) A?, b = 11.302 (4) A?, c = 12.676 (2) A?, β = 103.22 (1)°, V = 1202.6 (6) A?³, and Z = 2. It exhibits pseudooctahedral coordination geometry with one PMe₃ ligand under the open pentadienyl mouth and the other PMe₃ ligands under the pentadienyl edges . Compounds 1, 3, and 5 undergo dynamic processes in solution involving rotation of their pentadienyl groups with respect to the metal-ligand framework. ΔG*'s for these processes have been determined from line-shape simulations of the variable-temperature ³¹P NMR spectra.