ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The monosubstituted [Ir4(CO)11L] clusters (L = P(OPh)3, 1; L = P(OMe)3, 2; L = P(OCH2)3CEt, 3) were obtained in good yields by the reaction of [Ir4(CO)11I]- with the corresponding phosphite. In the solid state, cluster 3 has a Cs geometry with all terminal ligands as shown by an X-ray analysis. Three isomers are present in solution: one with terminal ligands (A) and two with three edge-bridging CO's and with L in axial (B) or radial (C) position (see Scheme). The thermodynamic and kinetic parameters of isomerisations B ⇌ A and A ⇌ C were determined by simulation of the variable-temperature 31P-NMR spectra. The three isomers correspond to three minima on the kinetic pathway of CO scrambling, whose relative energies vary independently within a small range (1-9 kJ mol-1 at 298 K). At low temperature, isomer C is always the least stable and is not observed for 1 which bears the most bulky phosphite ligand. The isomerisations are due to two intramolecular merry-go-rounds of CO groups about two unequivalent faces of the unbridged species A.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19930760816
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