Please use this identifier to cite or link to this item:
|Title:||Spectral resolution of fluxional organometallics. The observation and FTIR characterization of all-terminal [Rh 4(CO) 12]|
|Citation:||Allian, A.D., Garland, M. (2005-06-07). Spectral resolution of fluxional organometallics. The observation and FTIR characterization of all-terminal [Rh 4(CO) 12]. Dalton Transactions (11) : 1957-1965. ScholarBank@NUS Repository. https://doi.org/10.1039/b500044k|
|Abstract:||In situ FTIR spectroscopy at 1 cm -1 resolution was conducted on n-hexane solutions of the bridged [Rh 4(CO) 9-(μ-CO) 3] in the interval T = 268-288 K and P T = 0.1-7.0 MPa using either helium or carbon monoxide as dissolved gas. Analysis of the spectral data sets was conducted using band-target entropy minimization (BTEM), in order to recover the pure component spectra. A new spectral pattern was recovered with terminal vibrations at 2075, 2069.8, 2044.6 and 2042 cm -1. The new spectrum is consistent with an all-terminal [Rh 4(CO) 12] species with a C 3v anticubeoctahedron structure where 2 different [Rh(CO) 3] moieties exist, although the presence of some T d structure can not be entirely excluded. The equilibrium between all-terminal [Rh 4(CO) 12] and the bridged [Rh 4(CO) 9(μ-CO) 3] was determined in the presence of both helium and CO. The equilibrium constant K eq = [Rh 4(CO) 12]/[Rh 4(CO) 9-(μ-CO) 3] at 275 K was ca. 0.011 and the determined equilibrium parameters were Δ rG = 12.63 ± 4.8 kJ mol -1, Δ rH = -21.45 ± 2.3 kJ mol -1 and Δ rS = -114.3 ± 8.35 J mol -1 K -1. The free energy indicates a very small difference between the bridged and terminal geometry, and the lower entropy is consistent with a higher symmetry. This finding helps to address a long-standing issue concerning the existence of various [M 4(CO) 12] symmetries. In a more general context, the present study illustrates the considerable utility of quantitative infrared spectroscopy (occurring on a fast vibrational timescale) combined with sophisticated deconvolution techniques in order to resolve systems which have been demonstrated to be fluxional on the NMR timescale. © The Royal Society of Chemistry 2005.|
|Source Title:||Dalton Transactions|
|Appears in Collections:||Staff Publications|
Show full item record
Files in This Item:
There are no files associated with this item.
checked on May 18, 2018
WEB OF SCIENCETM
checked on Mar 26, 2018
checked on Mar 11, 2018
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.