Photochemistry of tricarbonyl(η⁴-cyclo-octatetraene)iron in a methane matrix at 12 K. Infrared spectroscopic evidence for photoisomerisation and carbon monoxide ejection reactions

Abstract

Fourier-transform infrared spectroscopic evidence, including 3C0 labelling and energy-factored CO force-field fitting, is presented to show that photolysis of [Fe(' tub '-q4-C8H,)(C0)3] in a CH4 matrix at 12 K leads to the formation of a [Fe(' chair'-q4-C8Ha)(C0)3] species via the [Fe(q2-C,H8)(C0)3] intermediate. An additional photoproduct is the co-ordinatively unsaturated species [ Fe(q4-C8H8) (CO),] formed by photoelimination of a CO ligand. The results are related to the fluxional behaviour of [Fe(q4-C8H,) (CO)3] in solution.A single-crystal X-ray diffraction study of tricarbonyl(cyc1o-0ctatetraene)iron showed that the [Fe(CO),] fragment, which has C, symmetry, is bonded to a 1,3-diene fragment of the cyclo-octatetraene (cot) molecule.' There are a number of ways the cot molecule could bind 2-4 (Scheme 1) but the X-ray study and a variety of spectroscopic studies, e.g. infrared and Raman,5 low-temperature 'H n.m.r.,6a7 and Mossbauer: all favour structure (1). This structure is henceforth denoted as [Fe(' tub '-q4-C8H8)(C0),] or [Fe(' tub '-q4-cot)The fluxional behaviour of [Fe(q4-cot)(CO),] in solution and the solid state has been known for many years.' N.m.r. studies ('H and 13C)6*10 are consistent with a rapid interconversion of isomers (6a) * (6b) Fe through 1'2-shifts of (6a) (6b)

Photoluminescence of PtII(cyclooctatetraene)(CN)2 originating from a MLCT triplet

“…In this context, complexes with C 8 H 8 (cyclooctatetraene) as ligand [3,4] should be also of considerable interest. The photoproperties of Fe(C 8 H 8 )(CO) 3 have been studied in quite some detail [5][6][7][8] but it turned out that the C 8 H 8 ligand serves only as a spectator ligand while the lowest excited state which dominates the excited state behavior is of the LF type [8]. In order to avoid this interference we selected the complex Pt II (C 8 H 8 )(CN) 2 for the present study.…”