Aurophilic coordination

The TCNQ molecule in [TR(bzim)]2-TCNQ is sandwiched between two units of [ J,-N, C -bzimAu]3 in a face-to-face manner so that it is best represented by the formula (7t-[ J,-N, C -bzimAu]3)( j,-TCNQ)(7t-[p-N, C -bzimAu]3). The cyanide groups clearly are not coordinated to the gold atoms. The distance between the centroid of TCNQ to the centroid of the AU3 unit is 3.964 A. The packing of [TR(bzim)]2-TCNQ shows a stacked linear-chain structure with a repeat pattern of-(Au3)(Au3)(p-TCNQ) (Au3)(Au3)(p-TCNQ)- an ABBABB repeat The complex [TR(bzim)]2-TCNQ contains two very short intermolecular Au Au distances of 3.152 A (identical for the two aurophilic bonds). The intermolecular Au Au distance is even shorter than the intramolecular distances in the starting compound, which are 3.475, 3.471, and 3.534 A. The adjacent AU3 units in [TR(bzim)]2-TCNQ form a chair-type structure rather than the face-to-face (nearly eclipsed) pattern reported in Balch s studies of the nitro-9-fluorenones adducts with the trinuclear Au(I) alkyl-substituted carbeniate complexes. 

The most straightforward synthesis of compounds (L)AuAr uses the metathesis of (L)AuX precursors with aryllithium reagents, as, for example, executed for the preparation of (Ph3P)AuPh. The crystal structure of this benchmark complex has been determined. The linear coordination geometry is as expected. No aurophilic contacts are discernible in the crystal packing. Short Au- -Au contacts are observed, however, in the dinuclear compound (dppm)(AuPh)2 with an intramolecular intermetallic distance of 3.154(1) A. This complex shows a UV-VIS absorption at 290-300 nm and is luminescent in fluid solution at room temperature.1... 

These were found to have a particularly rich coordination chemistry, because the close proximity of the two gold atoms leads to significant transannular aurophilic interactions, facilitating, for example, the stoichiometric oxidation to compounds with a transannular Au-Au bond with the metal atoms in the rare Au(ii) state (Scheme >9).2,166,168... 

Cations Au+ have been embedded between parallel -C=C-Au-C=C- units connecting two calixarenes (Scheme 82). The symmetrical side-on coordination is slightly distorted to allow for aurophilic bonding.51... 

Information about aurophilicity and chemical situations in which it is observed may be found in different works that may be classified as those which analyse closed shell interactions in general [2], those focused on aurophilicity [1,3], and others which analyze the role of these interactions in coordination [4] and organometallic gold... 

The electron-rich trinudear Au3 (bzim) 3 and Au3 (carb) 3 react with F6 to yield the sandwich clusters [n Au3(bzim)3 2](PF6) 29 and [n Au3(carb)3 2](PF6) 30 [54]. The cation of both compounds contains atom which interacts in a distorted trigonal prismatic coordination with six Au(I) atoms from two cyclic Au3C3N3 moieties at Au- distances ranging from 2.971(1) to 3.107(1) A, indicative of appretiable metal-metal interaction. Two Au(I) atoms on each planar trinudear unit are involved in intermolecular aurophilic bonding interactions [Au-Au 3.109(1)/3.066(1) A in 29 3.059(1)/3.052(1) A in 30], thus resulting in an infinite columnar chain with a BBABBA- pattern (Figure 4.11). 

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