ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The fluxionality of [Ir4(CO)8(μ2-CO)3L] (L = Br-, I-, SCN-, NO2-, P(4-ClC6H4)3, PPh3, P(4-MeOC6H4)3, P(4-Me2NC6H4)3), as studied by 2D-13C-NMR in solution, is due to two successive scrambling processes: the merry-go-round of six basal CO's and CO bridging to alternative faces of the Ir4 tetrahedron. The basicity of the ligand L has no significant effect on the activation parameters. The scrambling process of lowest activation energy in [Ir4(CO)7(μ2-CO)3(PMePh2)2] correspond to the two possible synchronous CO bridging about a unique face of the metal tetrahedron swapping the relative axial and radial positions of the ligands L. The disubstituted clusters [Ir4(CO)10(μ2-L—L)] with one edge-bridging ligand have a ground-state geometry with three edge-bridging CO's (L—L = bis(diphenylphosphino)methane, bis(diphenylarsino)methane, bis(diphenylphosphino)propane) or with all terminal CO's (L—L = CH3SCH2SCH3). In all cases, the fluxional process of lowest activation energy in the merry-go-round of six CO's about a unique triangular face. For the P and As donor ligands, this process is followed by the rotation of terminal CO's bonded to two Ir-atoms residing on the mirror plane of the unbridged intermediate.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19930760605
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