1. Instability of Square Planar N<INF>3</INF>-Ligand Iridium(I) Ethene Complexes
- Author
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Thewissen, S., Reijnders, M. D. M., Smits, J. M. M., and Bruin, B. de
- Abstract
New, five-coordinate, iridium(I) bis-ethene complexes [fac-(bpa-R)IrI(ethene)
2 ]+ (1 +: R = H,2 +: R = Me,3 +: R = Bz; bpa-H = N,N-di(2-pyridylmethyl)amine, bpa-Me = N-methyl-N,N-di(2-pyridylmethyl)amine, bpa-Bz = N-benzyl-N,N-di(2-pyridylmethyl)amine) were prepared. In contrast to their previously reported rhodium analogues, these iridium species do not readily lose one of their two ethene fragments to form square planar mono-ethene complexes [mer-(bpa-R)IrI(ethene)]+. Heating complex1 + results in N−H activation at the bpa-H ligand and formation of the dinuclear iridium(III) species [{(mer-μ2 -bpa#)IrIII(ethyl)(MeCN)}2 ]2+ (4 2+) with bridging amides (bpa# = bpa-H deprotonated at NHamine ). Heating bpa-Bz complex3 + results in aromatic C−H activation of the ligand benzyl group to form dinuclear iridium(III) species [{(bpa-Bz#)IrIII(μ2 -H)}2 ]2+ (5 2+) with unsupported hydride bridges (bpa-Bz# = bpa-Bz cyclometalated at the benzylic C2-position). The dimeric structure of5 2+ easily breaks up in MeCN, giving the mononuclear species [(bpa-Bz#)IrIII(H)(MeCN)]+ (6 +). Complex5 2+ is also light-sensitive: glass-filtered daylight converts it to a geometrical isomer,7 2+, in which the cyclometalated benzyl functionality of one of the two ligands has switched its position with a pyridyl donor.- Published
- 2005