ISSN:
0009-2940
Keywords:
Tetraphosphorus ligands
;
Bond cleavage in P4, stepwise
;
Rhodium P4 complexes
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Pn Ligands with Maximum Electron-Donor Capacity, 7. - Three-Component Reaction of P4-Phosphorus with [CpxRh(CO)2] in the Presence of [Cr(CO)5THF] or [CpMn(CO)2THF]. - A Method of Studying the Pathway from Tetrahedral P4 to the Planar cyclo-P4 LigandHerrn Professor Gerhard Fritz zum 75. Geburtstag gewidmet.The reaction of P4 with [CpxRh(CO)2] (Cpx = Cp′, Cp′′; Cp′ = η5-C5H4tBu, Cp′′ = η5-C5H3tBu2-1,3) in the presence of [Cr(CO)5THF] leads to [CpxRh(CO)(η1:1-P4){Cr(CO)5}4] (1a, b), [Cp′′Rh(η4-P4){Cr(CO)5}3] (2b), and [Cp′Rh(η4-P4){Cr-(CO)5}4] (3a). In the corresponding reaction with [CpMn-(CO)2THF] no P4 takes part, and [(Cp′′RhCO)(CpMnCO)(μ-CO)2] (4) is formed. An X-ray structure determination of [CpxRh(CO)(η1:1-P4){Cr(CO)5}4] (1) and [Cp′Rh(η4-P4)-{Cr(CO)5}4] (3a) indicates a stepwise (PP) bond cleavage as the transformation pathway from the P4 tetrahedron to the cyclo-P4 ligand by passing a bicyclotetraphosphane. In the cyclo-P4 ligand complex 3a all P atoms are able to coordinate to [Cr(CO)5] groups. However, in [Cp′′Rh(η4-P4){Cr(CO)5}3] (2b) the additional tBu group at the Cpx ligand sterically influences the coordination behavior of the P atoms, and only three of them are able to coordinate to [Cr(CO)5] units. In these syntheses the [Cr(CO)5] moieties promote the reaction and stabilise intermediates along the reaction pathway. Variable-temperature 31P{1H}-NMR measurements indicate for 2b the freezing of the Cp′′ rotation at low temperature and reveals a ΔG≠c (at the coalescence temperature) of 36 kJ mol-1. Surprisingly, in [(Cp′′RhCO)(CpMnCO)(μ-CO)2]-(Rh-Mn) (4) the Cpx ligands are cis-oriented whereas in [(Cp*RhCO)(CpMnCO)(μ-CO)2](Rh-Mn) a trans arrangement is observed. This indicates the unusual behavior of the Cp′′ ligand as a “rod” and not as an “enlarged disk” like Cp* in the crystal lattice of these compounds.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19951280308
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