Solid-state and solution structures of [PNP][W(CO)5O2CCH3] and [PNP][W(CO)4(PEt3)O2CCH3] and the carbonyl-labilizing ability of the acetato ligand in these anionic derivatives
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The structures of [PNP] [W(CO)5O2CCH3] (1) and [PNP] [W(CO)4(PEt3)02CCH3] (2) have been determined by single-crystal X-ray investigations. Complex 1 crystallizes in the triclinic space group [formula omitted] with a = 10.544 (2) Å, b = 12.140 (1) Å, c = 17.095 (3) Å, ± = 104.28 (1)°, β = 107.07 (1)°, γ = 91.43 (1)°, and Z = 2. The structure of 1 was refined to values of R1 = 0.035 and R2 = 0.045 for 54 atoms (all anisotropic) and 5528 reflections with I > 3<3σ(I). Complex 2 crystallizes in the monoclinic space group P21/c with a = 17.661 (5) Å, b = 32.502 (4) Å, c = 16.141 (4) Å, β = 90.93 (4)°, and Z = 8. The discrepancy indices for 2 were R1 = 0.052 and R2 = 0.067 for 4542 reflections with I > 2σ(I). The two crystallographically independent formula units are structurally almost identical. The structure of the anion in 2 is best described as a distorted octahedron with a cisoid arrangement of the PEt3 and acetate ligands. The [formula omitted] anion in solution is shown to dissociate equatorial carbon monoxide, readily and stereoselectively, at ambient temperature. In contrast, the [formula omitted] anion under similar conditions is inert toward dissociative CO loss. In part this inertness in 2 might be ascribed to a tightening of the W–C bonds in the ground-state molecule, i.e., W–C (average) in 2 is ca. 0.10 Å shorter than W–C (average) for the equatorial CO groups in 1. © 1982, American Chemical Society. All rights reserved.
author list (cited authors)
Cotton, F. A., Darensbourg, D. J., Kolthammer, B., & Kudaroski, R.