PREPARATION AND STRUCTURE OF HEXAKIS[(TRIALKYLPHOSPHANE)AURIO(I)]METHANIUM(2+) SALTS [(LAU)6C]2+(X-)2 WITH L = ET3P, IPR3P AND X = BF4-, B3O3F4-

Hexaaurated carbon complexes of the type [(R3PAu)6C](BF4)2, R = Et (2a), iPr (2b) have been prepared by the reaction of the appropriate (phosphane)gold(I) chlorides R3PAuCl (1 a and 1 b) with tetrakis(dimethoxyboryl)methane, C-13-enriched at the central carbon atom, in the presence of excess of CsF in HMPT at room temperature. The products 2a and 2b are characterized by standard spectroscopic methods including direct detection of the interstitial C atoms by C-13-NMR spectroscopy. The crystal structure of the compound [(iPr3PAu)6C](B3O3F4)2 . 3 CH2Cl2 (3), obtained from partial (anion) hydrolysis has been determined. It contains dications with a central carbon atom surrounded by six (phosphane)gold(I) units. The edges of the CAu6 octahedron represent short Au-Au contacts (aprox. 3.0 angstrom), which strongly contribute to the formation and stability of these hypercoordinated species. Attempts to prepare a corresponding hexaauriomethanium dication starting from tBu3PAuCl (1c) failed owing to the bulkiness of the (tri-tert-butylphosphane)gold(I) unit. The X-ray structure analysis for lc verifies an extremely crowded environment of the gold atom with small Au-P-C angles of only 107-degrees leading to efficient shielding of the metal atom by methyl groups.