Organogold(III) complexes. Structure of monomethyldibromogold

Phosphanchalkogenide und ihre Metallkomplexe. IV. Halogenierungsprodukte der Gold(I)halogenidkomplexe einiger Diphosphanmonochalkogenide

Diphosphanegold(I) complexes of the form dppmEAuX [dppm = bis(diphenylphosphano)methane, E = S, Se; X = Br, I], dppeEAuX [dppe = 1,2-bis(diphenylphosphano)ethane; E = O, S; X = Br, I] and dppbzEAuX [dppbz = 1,2-bis(diphenylphosphano)benzene; E = S, Se, X = Br, I] were treated with elemental X2. With dppm, the three products [dppmEAuX2]+X3 – (E = S, X = Br (1), I (2); E = Se, X = I (3) were obtained in quantitative yield. These are gold(III) complexes involving a five-membered ring . With dppe, the only related product was [dppeEAuBr2]+Br3 – (4), in which the central ring is six-membered with two carbon atoms. These dppe systems are very sensitive to oxidation/hydrolysis of the ligand, and several such unintended products were isolated and identified. The reaction of dppbzSAuBr with bromine leads to [dppbzS]2+[AuBr4]–Br– (5), the dication of which is formally 1,1,3,3-tetraphenylbenzo[d]-2-thia-1, 3-diphosphol-1,3-diium and contains a central five-membered ring . The dications are associated with the bromide anions via S…Br contacts of ca. 3.1 Å to form inversion-symmetric S2Br2 rings. The halogenation of the dppbzSe derivatives leads to loss of selenium and formation of dppbzAuBr3 (6), with [4+1] coordination at gold, or the known compound [dppbzAuI2]+I3 – (7). All products 1–6 were subjected to X-ray diffraction analyses, as were four hydrolysis products 4a–d and two further by-products [5(thtBr+)·2Br3 –·3(AuBr4 –)] (1a) and (tht)AuBr3 (1b). Compound 1a displays unusually short Br…Br contacts of 3.2398(8) Å between neighbouring tetrabromidoaurate(III) ions.

C-C coupling reactivity of an alkylgold(III) fluoride complex with arylboronic acids

Previously, alkylgold(III) fluorides have been proposed as catalytic intermediates that undergo C-C coupling with reagents such as arylboronic acids in Au(I)/Au(III) cross-coupling reactions. Here is reported the first experimental evidence for this elementary mechanistic step. Complexes of the type (NHC)AuMe (NHC = N-heterocyclic carbene) were oxidized with XeF(2) to yield cis-(NHC)AuMeF(2) products, which were found to be in equilibrium with their fluoride-dissociated, dimeric [(NHC)AuMe(μ-F)](2)[F](2) forms. In one case, a monomeric cis-(NHC)AuMeF(2) complex was favored exclusively in solution, and it was found to react with a variety of ArB(OH)(2) reagents to yield Ar-CH(3) products.