Formation of an iridium σ-cyclopropane complex by the intramolecular activation of a cyclopropylphosphine: Rearrangement to a chelating σ-vinyl complex

When (t-Bu)₂PCH₂CHCH₂CH₂ is combined with IrCl(C₈H₁₄)₂]₂ in toluene, the σ-bound cyclopropane complexes

(P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂) (1a, 1b) are formed. Complexes 1a,1b react readily with H₂ to form IrClH₂P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂)₂ (2). In polar solvents 1a,1b isomerize to the σ-vinyl chelated complex $\text{IrClH(P(t-Bu)}{}_2\text{CH}{}_2\text{C(CH}{}_3\text{)C}$H)(P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂) (3). The structure of this 5-coordinate, 16-electron Ir^III complex was deduced from spectroscopic data, reaction chemistry, and from the crystal structure of its CO adduct (4). Compound 4 crystallizes in the monoclinic space group C_2h⁵-P2₁/n (a 15.610(14), b 15.763(16), c 11.973(13) Å, and β 104.74(5)°) with 4 molecules per unit cell. The final agreement indices for 2326 reflections having F_o² > 3σ(F_o²) are R(F) = 0.089 and R_w(F) = 0.095 (271 variables) while R(F²) is 0.148 for the 3423 unique data. Bond lengths in the 5-atom chelate ring $\text{IrPCCC}$ are IrP 2.341(4), PC 1.857(26), CC 1.520(30), CC 1.341(25), and CIr 1.994(21) Å. The IrCl distance is 2.479(5) Å.