Phenylcyclopropane reacts with trans- lrCI(N2)(PPh3)2or “lrCI(PPh3)2” to yield IrCIH [η3-C3H4(l-Ph)](PPh3)2. This complex is also obtained from similar reactions with allylbenzene or trans-β-methylstyrene. A series of analogous complexes is formed from the reaction of allylbenzene, [lrCI(COT)2]2(COT = cyclooctene), and the appropriate donor ligand in which PPh3 (Ph = C6H5) is replaced by P(p-Tol)3(p-Tol = 4-tolyl), AsPh3, As(p-Tol)3, or SbPh3. These η3-allyl hydride complexes do not exhibit dynamic behavior in solution as judged by their variable-temperature NMR spectra. They possess unusual thermal stability and are not highly air sensitive. Chloroform solutions of the η3-a11y1 hydride complexes do not effect the conversions of cyclopropane to olefin or primary to internal olefin. The complex IrCIH[η3-C3H4(l-Ph)](PPh3)2reacts with CO or PF3 to liberate β-methylstyrene, which also results from the extended exposure of the complex to O2. Reaction with HCI yields a mixture of products from which a new isomer of lrCl2H(CO)(PPh3)2is obtained upon treatment with CO. Similar reaction with HBr causes total substitution of chlorine. Spectroscopic data indicate that IrClH [η3-C3H4(1-Ph](PPh3)2adopts a geometry in which the phosphine ligands are mutually cis, hydrido and chloro ligands are trans, and the allyl group occupies two coordination sites. This structure is substantiated by a single-crystal X-ray diffraction study. The complex crystallizes in space group C2,9-Pn21a with four formula units in a cell of dimensions a = 14.902 (2), b = 11.016 (2). and c = 22.456 (4) Å. Based on 3738 unique reflections having F02>3σ(F02), the structure was refined by full-matrix least-squares techniques to conventional agreement indices (on F) of R = 0.029 and = 0.041. The hydride and allyl hydrogen atoms were located and refined. The lr-Cl bond length is long, 2.549 (2) Å, as a result of the trans influence of the hydrido ligand. The geometry of the allyl group, including hydrogen atoms, is similar to that found in other η3-allyl complexes. The implications of the isolation of these η3-ally 1 hydride complexes to catalytic transformations of cyclopropanes and olefins are discussed.
ASJC Scopus subject areas
- Colloid and Surface Chemistry