Synthesis, structure, and absolute configuration of chiral, pseudooctahedral perfluoroalkyl-substituted dimethylphosphonate complexes

Article abstract of DOI:10.1021/om00044a018

The substitution-labile complexes η⁵-CpCo(X)(PPh₂N(R)C*H(Me)Ph)(I), 6(a,b)(α,β), react with trimethyl phosphite to afford η⁵-CpCo(X)(PPh₂N(R)C*H(Me)Ph)(P(O)(OMe) ₂), 7(a,b)α, and θ⁵;-CpCo(X)(P(OMe)₃)(I), 8a,b (a, X = CF₃; b, X = n-C₃F₇; α, R = H; β, R = Me). Arbuzov dealkylation to give 7 occurs only for R = H and requires intramolecular P=O?H-N hydrogen bonding, which develops early in the transition state to anchor the aminophosphine ligand. The chiral, Co-epimeric Arbuzov products were separated and characterized. The absolute configuration of (+)₄₃₆-7bα was determined crystallographically. (+)₄₃₆-7bα crystallizes in the monoclinic system P2₁ with a = 11.0941 (20) A?, b = 16.9200 (22) A?, c = 16.927 (3) A?, β = 91.241 (15)°, V = 3176.6 (9) A?³, Z= 4, and R_f = 8.4% (R_w = 5.1%) for 1638 reflections with I > 2.5σI and was found to contain two independent molecules in the asymmetric unit. Absolute configurations of (-)₄₃₆-7bα, (-)₄₃₆-7aα, and (+)₄₃₆-7aα were assigned on the basis of chiroptical evidence. P=O?H-N hydrogen bonding establishes a pseudoboat conformation with pseudoaxial η⁵-Cp and pseudoequatorial n-C₃F₇ in the solid state. Nuclear Overhauser difference (NOED) spectra show that the solid-state conformation persists in solution.