Coordination Chemistry of Dimethylgold Halides with Bidentate Phosphorus and Arsenic Ligands – Revisited

Abstract

Dimethylgold(II1) chloride and bromide, (MezAuX)2, react with bis(diphenylphosphany1)methane (dppm, molar ratio 1 :2) to give the P-monohapto complexes cis-Me,AuX(dppm) (la, b) in quantitative yields. The products are readily oxidized by air to yield the P-hapto P'-monoxides 2a, b. Treatment of la, b with AgN03 affords an ionic nitrate [MezAu(dppm) complexes arose from the discovery that these compounds are surprisingly stable both thermally (e.g. as compared to silver compounds!), and also towards water and oxygen. They are colorless and diamagnetic and feature a characteristic square-planar cis geometry. There are analogies with the cis-diorganoplatinum(I1) complexes, which are important reference systems for catalytically active platinum comFor diorganogold(II1) compounds no catalyst properties could be found, however, and even the attempts to use them as model systems were of limited success. Furthermore, work with R2AuX compounds was often discouraging since all available literature procedures gave yields no higher than 40% even in experienced hands.The recent renewed attention is associated with the use of dialkylgold(II1) compounds as volatile precursors for the deposition of gold metal on substrates ['] and with potential medical applications (in the therapy of rheumatism, arthritis, and cancer)L81. There is also a significant progress to be noted in the synthesis of dimethylgold(lI1) halides by using tetramethyltin as a methylating reagent for HAu-C14(aq) ['].In the recent advances in diorganogold(II1) chemistry the field of complexes with bidentate ligands proved to be most promising. We therefore reexamined some of the simple reactions in order to delineate further their course and their products. As ligands we used mainly bis(dipheny1phosphan-y1)methane (dppm), bis(diphenylphosphany1)amine (dppa), and bis(diphenylarsany1)methane (dpam), which had been studied also in some of our earlier Bis(dipheny1phosphanyl)methane as a Ligand of DimethylgoldQII) Halides and NitrateThe dimers of cis-chloro-and cis-bromodimethylgold(II1) react with two equivalents of dppm in diethyl ether at ambient temperature to give colorless, crystalline products of 1 : 1 stoichiometry (la, b) (Scheme 1). The composition and the molecular mass follow from the analytical data and from the mass spectra. The 31P-NMR spectra of the products in chloroform at room temperature show two broadened doublet signals of an AX pattern in each case, which become sharp as the temperature is lowered to -60°C. It therefore appears that the molecules are fluxional in solution at room temperature with the MezAu unit undergoing site exchange at a monohapto dppm ligand. This is confirmed by the variable-temperature 'H-and I3C-NMR spectra.Complexes 1 a, b undergo decomposition upon heating, predominantly with evolution of ethane (below). Solutions of l a , b were also found to be surprisingly susceptible to oxidation by traces of oxygen at ambient temperature. Both species were converted rapidly and quantitatively into the P-monoxides Za, b, which rea...

Tetrakis(Triphenylphosphine Oxide)Lithium Di(Iodo)Aurate(I)

“…The findings confirm previous observations that gold(I) salts catalyze the oxidation of tertiary phosphines to the corresponding phosphine oxides [24]. It is also again obvious [30] …”

“…However, there is precedent for this phenomenon: 1 : 1 complexes of gold(I) or gold(III) with ditertiary phosphines R 2 P(CH 2 ) n PR 2 are readily converted to complexes of the monoxides R 2 P(CH 2 ) n PR 2 O even with traces of oxygen [24]. As another parallel, the tertiary phosphine ligands R 3 P in the copper(I) cluster complex (R 3 P) 4 [Cu 4 OCl 6 ] were found to be readily oxidized even by traces of oxygen to give the cluster complex (R 3 PO) 4 [Cu 4 OCl 6 ] [7].…”

Gold–Gold Interactions

“…The structure of [Au 3 Cl 2 (dppm) 2 ]PF 6 is based on a triangular Au 3 -core (Figure 2.46d) [260]. Reaction of [AuBr(CH 3 ) 2 (dppm)] with AgNO 3 in methanol affords the tetranuclear species shown in Figure 2.46e [261]. Longer chains afford different features and thus the crystal structures shown by compounds of empirical formula [Au{PPh 2 (CH 2 ) n PPh 2 }] þ consist on rings [Au 2 {PPh 2 (CH 2 ) n PPh 2 } 2 ] 2þ for n ¼ 3 or 5 but a polymer for n ¼ 4 [262].…”

Tris(pentafluorophenyl)[2-(diphenylphosphino)thiophenol-κP]gold(III) dichloromethane solvate

“…A search of the Cambridge Structural Database (Version of October 1998; Allen & Kennard, 1993) indeed revealed that the longest Au III ÐP bonds are formed trans to '-carbon ligands: e.g. cis-[Au(CH 3 ) 2 (PPh 3 )(OPh)] 2.402 (4) A Ê (Sone et al, 1991); cis-[Au(CH 3 ) 2 {Ph 2 P(O)CH 2 PPh 2 }Cl] 2.389 (2) A Ê (Paul & Schmidbaur, 1996); [Au(2-PhNNC 6 H 4 ){3,4,5-(CH 3 O) 3 -C 6 H 2 -COCH 2 }(PPh 3 )Cl] 2.386 and 2.390 (2) A Ê (Vicente et al, 1993). Typical examples without such ligands are [Au(C 6 F 5 )(S 2 -C 6 H 4 )PPh 3 ] 2.340 (1) A Ê (Cerrada et al, 1995); [AuCl 3 (PPh 3 )] 2.335 (4) A Ê (Bandoli et al, 1973); [AuMe 3 (PPh 3 )] 2.350 (6) and 2.347 (6) A Ê (Stein et al, 1981); [Au(SC 6 H 4 PPh 2 ) 2 ]BPh 4 2.325 (4) and 2.332 (4) A Ê (Dilworth et al, 1994).…”