| Abstract
| - The conditions for the stabilization of the Z configuration of the iminoether ligands and the X-ray structures of two of such complexes, one having 4-coordinate square-planar arrangement and the second 6-coordinate octahedral geometry, are described for the first time. The steric clash between the alkoxy group and the platinum center, cis to one another with respect to the CN double bond, is particularly severe, especially in the 6-coordinate PtIV species. How the steric strain can influence the reactivity of these species has also been investigated.
- Platinum complexes with Z configuration iminoether ligands (trans-[PtCl2{HNC(OMe)But}2], 1, and trans-[PtCl4{HNC(OMe)But}2], 2) have been structurally characterized for the first time. The nearly planar Pt−N−C−O−Cchain, all atoms being in gauche conformation, brings the terminal Pt and C atoms very close to one another. Thesteric clash is released by considerably increasing the Pt−N−C, N−C−O, and C−O−C bond angles (133, 124, and121° for 1, respectively; 147, 129, and 127° for 2, respectively), which are well above the expected values (120°for Pt−N−C and N−C−O; less than 120° for C−O−C owing to the repulsive effect exerted by the lone pair ofelectrons on the oxygen atom). In the platinum(II) case the smaller increase of bond angles is accompanied by agreater value of the Pt−N−C−O torsion angle (27.3 and 15.6° for 1 and 2, respectively). The stabilization of theZ configuration, notwithstanding the steric clashes described above, has been achieved by a careful choice of theR substituent in the iminoether moiety (a bulky tert-butyl group). The reactions of the platinum(IV) species (2) inbasic and acidic conditions and with triphenylphosphine have been investigated. Bases and acids both interactwith the coordinated ligand in such a way to weaken the coordinative bond and promote the release of the iminoetherligands. The phosphine promotes a ready and complete reduction of the platinum(IV) complex to the correspondingplatinum(II) species (1). Compound 1 reacts with a stoichiometric amount of phosphine (1:1 molar ratio) to formcis-[PtCl2(PPh3){Z-HNC(OMe)But}] and with excess phosphine to form [PtCl2(PPh3)2] and free iminoether. Thelatter two reactions leading to formation of a mixed phosphine/iminoether platinum species and to free iminoether,which can be used as a synthon for further organic transformations, can be of synthetic utility.
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