| Abstract
| - Treatment of the tetranuclear gold cluster [Au4{(PPh2)2C2B9H10}2(AsPh3)2] (1), which contains the nido-carborane-diphosphine [7,8-(PPh2)2C2B9H10]-, with various tertiary phosphines leads to derivatives [Au4{(PPh2)2C2B9H10}2(PR3)2] (PR3 = PPh3 (2), P(4-MeC6H4)3 (3), P(4-OMeC6H4)3 (4)). The X-ray crystal structure of complex 4shows a tetrahedral framework of gold atoms, two of which are chelated by the diphosphine, and two are coordinatedto one monophosphine ligand each. These compounds are very stable and are obtained in high yield. MP2calculations suggest that the two types of chemically nonequivalent gold atoms can be formally assigned as Au(I)(those attached to the arsines or phosphines) and Au(0) (those bonded to the anionic diphosphine) and emphasizethe role of correlation in the gold−gold interactions. The compounds are luminescent. The emission is assignedto a gold-centered spin-forbidden transition; the assignment of the oxidation state of the gold centers on this basisleads to results coincident with those obtained by theoretical calculations.
- Substitution of the arsine ligands in [Au4{(PPh2)2C2B9H10}2(AsPh3)2] by tertiary phosphines leads to the new cluster compounds [Au4{(PPh2)2C2B9H10}2(PR3)2]. Structural characterization of the complex [Au4{(PPh2)2C2B9H10}2{P(C6H4OMe)3}2] has been carried out. MP2 calculations suggest that those gold atoms attached to the arsines or phosphines can be formally assigned as Au(I) and those attached to the diphosphine as Au(0). These compounds are luminescent. The emission is assigned to a gold-centered spin-forbidden transition.
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