Wavelength-, medium-, and temperature-dependent competition between photosubstitution and photofragmentation in triruthenium dodecacarbonyl and triiron dodecacarbonyl: detection and characterization of coordinatively unsaturated trimetal undecacarbonyl complexes

Nature and Role of Bridged Carbonyl Intermediates in the Ultrafast Photoinduced Rearrangement of Ru3(CO)12

“…It is difficult to extract much useful information from this region as there are a multitude of carbonyl ligands from each photo-excited species that produce a spectrum of overlapping, indistinguishable peaks in solution. 3 The kinetics of the peaks in this region were determined with the trace fitting method and respective time constants are reported in Table 1. In addition, three small peaks at 1815, 1833, and 1857 cm -1 can be discerned and are shown in the inset of Figure 2.…”

“…These peaks originate from bridged CO stretching frequencies which typically appear in the region between 1800 and 1900 cm -1 . 3,10,13 The dynamics of the largest bridging carbonyl peak centered at 1833 cm -1 were determined with the area fitting method to have an exponential rise time of 23 ± 3 ps and a decay of 60 ± 5 ps, shown in Figure 3(a). Figure 3 (b) shows the temporal evolution of the area of the peak centered at 1857 cm -1 .…”

“…1,2 In general, photo-activation of this cluster allows for systematic control in synthetic procedures by breaking only specific types of bonds in the complex when a particular wavelength of light is used. 2,3 A particularly interesting aspect of this system is that it exhibits unique dynamics, due to its trimetal infrastructure, that are not possible in corresponding metal monomers or dimers. The structure of Ru 3 (CO) 12 and of some of its photochemical intermediates, as well as the main reaction channels, have been investigated previously in matrices and solutions using laser flash photolysis in combination with visible or infrared spectroscopy.…”

“…The lifetime of this product depends on its thermodynamic stability with respect to the starting material and the availability of CO to replace the solvent S and reform the original cluster. 3,[7][8][9] Despite the wealth of information provided by previous studies, some particularly important details of the photochemistry of Ru 3 (CO) 12 are unresolved. First, the timescales of formation and decay for the CO loss transient have not been determined and the structures of both bridged carbonyl complexes discussed above are uncertain.…”

“…[6][7][8]16 A few studies have directly observed a bridged carbonyl complex, and each study used a different wavelength of excitation. 3,10,13 It is important to point out that in every study in which a bridged carbonyl complex was observed, only one species could be detected. This is inconsistent with results that suggest multiple photoproducts, derived from multiple bridged carbonyl complexes, are formed at a single excitation wavelength.…”