DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 111–113 111 Self-assembly of triatomic gold units as supporting frames for a large gold diphenylphosphinite cage molecule† Christian Hollatz, Annette Schier, Jürgen Riede and Hubert Schmidbaur * Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany Received 4th November 1998, Accepted 26th November 1998 A novel hexanuclear cage-type double-decker cation [FB- (OPPh2Au)3Cl3(AuPPh2O)3BF]1 is obtained in high yield as the tetrafluoroborate salt from a dinuclear diphenylphosphinous acid complex [Ph2P(OH)AuCl]2 upon treatment with BF3?OEt2.Intra- and inter-molecular metal–metal contacts between the closed-shell Au(I) centres of two-coordinate gold complexes are now recognized to contribute significantly to the stoichiometry, structure and conformation of all compounds of this type.1–3 The energy associated with these interactions is similar to the energetics of hydrogen bonds,4–9 and therefore this phenomenon has a great influence on the molecular and supramolecular chemistry of gold.10 Small complex molecules are found to associate into pairs, rings, chains, or multidimensional frameworks the structural pattern of which is often solely determined by “aurophilic” Au ? ? ?Au attractions.11 There are also systems where hydrogen bonding and aurophilic bonding are cooperative forces.12,13 We now report another striking case where the build-up of gold–gold contacts induces the formation of large cage-type molecules in which two Au3-triples represent supporting framework units.The reaction of diphenylphosphinous acid with chloro- (dimethyl sulfide)gold(I) in dichloromethane at room temperature gives the 1 : 1 complex [Ph2P(OH)AuCl]2 1, with liberation of dimethyl sulfide [eqn. (1)]. The colourless product (93% 2 (Me2S)AuCl 1 2 Ph2P(O)H CH2Cl2 22 Me2S [Ph2(OH)AuCl]2 (1) 1 yield, mp 128 8C) has been fully characterized by standard analytical and spectroscopic data.‡ In the crystal (triclinic, space group P1� , Z = 4),§ the compound is a dimer the monomeric units of which are tied together by a central Au ? ? ? Au bond [3.1112(7) Å] and two peripheral O–H ? ? ? Cl hydrogen bonds (Fig. 1). It is obvious that the two Cl–Au–P units are bent to allow a close contact of the metal atoms. The structure approaches quite closely non-crystallographic twofold symmetry as shown in Fig. 2. Related structures have recently been found for compounds of the type [R2P(OH)–Au–P(O)R2]2.13 3 [Ph2P(OH)AuCl]2 BF3?OEt2 (excess) 23 HCl/23 HF 1 [FB(OPPh2Au)3Cl3(AuPPh2O)3BF]1BF4 2 (2) 2 Treatment of compound 1 with an excess of BF3?OEt2 in dichloromethane at 20 8C leads to the liberation of HCl and HF, the latter being trapped by the excess BF3 to give HBF4 and BF4 2 counter ions. The net reaction is represented by eqn. (2). The only gold-containing product in this reaction, 2, is isolated almost quantitatively (96% yield) as a colourless, crystalline solid (mp 152 8C with decomposition), soluble in dichloromethane. The solutions are stable only at lower temperatures and the NMR spectra show a singlet resonance for 31P and two singlet 11B resonances (intensity ratio 2 : 1).There is only one set of phenyl 13C and 1H resonances with the expected 1H- and 13C-31P splittings, respectively.‡ These data suggest a very high symmetry for the components of the product in solution.Crystals of 2?3CH2Cl2 (from CH2Cl2–Et2O, hexagonal, space group P63/m, Z = 2) § contain cage-like hexanuclear cations with crystallographically imposed point group C3h symmetry (Fig. 3). At the opposite ends of the cation two BF bridgehead units are each connected to three diphenylphosphinite units via the oxygen atoms. The tentacles of the resulting tripodal donor anions [FB(OPPh2)3]2 are attached via their phosphorus atoms to three V-shaped digoldchloronium groups [Au2Cl]1 to close three 16-membered rings which have only the two BF bridgeheads in common.In the lattice the BF4 2 counter ions are disordered and associated with the CH2Cl2 molecules via weak F ? ? ? H–C hydrogen bonds (virtual C3h symmetry). The structure of the cation is remarkable mainly for two Fig. 1 Molecular structure of compound 1 (ORTEP20 drawing with 50% probability ellipsoids, C–H atoms omitted for clarity). Selected bond lengths (Å) and angles (8): Au(1)–P(1) 2.218(2), Au(1)–Cl(1) 2.306(2), P(1)–O(1) 1.597(5), Au(1) ? ? ?Au(2) 3.1112(7), Au(2)–P(2) 2.224(2), Au(2)–Cl(2) 2.309(2), P(2)–O(2) 1.582(6); P(1)–Au(1)–Cl(1) 169.18(7), P(2)–Au(2)–Cl(2) 170.85(7); hydrogen bridges: O(1)–- H(1) ? ? ? Cl(2): O(1)–H(1) 0.986, H(1) ? ? ? Cl(2) 2.029, O(1) ? ? ? Cl(2) 2.994; O(1)–H(1) ? ? ? Cl(2) 165.6; O(2)–H(2) ? ? ? Cl(1): O(2)–H(2) 0.921, H(2) ? ? ? Cl(1) 2.105, O(2) ? ? ? Cl(1) 3.004; O(2)–H(2) ? ? ? Cl(1) 168.1.Fig. 2 Projection of the molecular structure of compound 1 along the Au(1) ? ? ?Au(2) axis.112 J.Chem. Soc., Dalton Trans., 1999, 111–113 reasons. (1) The gold atoms are arranged in two triangular groups with short Au ? ? ?Au contacts [3.1725(5) Å]. These two units clearly stabilize the framework of the cage like two rings of a barrel. The same phenomenon, but with only one Au3- triple, has recently been observed in the structure of the trinuclear cation [FB(OPPh2AuPPh2O)3BF]1.14 (2) The two triangles of gold atoms, which together form a trigonal prism, are linked through three chloride anions which are thus converted into di(gold)chloronium centres already known in salts of the type [Cl(AuPR3)2]1.15 The Au–Cl–Au angles in 2 [106.51(10)8] are not as small as in open-chain reference compounds [82.7(2)8 for R = Ph],16 but probably still small enough to allow some weak Au ? ? ?Au bonding.The overall double decker arrangement may thus be taken as a hexanuclear gold cluster with three chlorine atoms bridging the three vertical edges of the trigonal prism (Fig. 3 and 4). Triangular Au3 units have previously been encountered with various other tripodal ligands.9,14,17–19 The mechanism of the formation of 2 probably involves stepwise substitution of fluoride in the BF3?OEt2 agent by phosphinite nucleophiles [ClAuPPh2O]2. The second and third steps are increasingly promoted by the opportunity to form pairs and triples of gold atoms. The reaction is terminated by closure of the cluster via only three chloride anions.The prismatic unit Au3Cl3Au3 is remarkably robust and withstands attack by HCl and HBF4, the by-products of the reaction. All P–Au–Cl units are close to linear, but nevertheless bent in the direction required for intimate Au ? ? ?Au interactions. Acknowledgements This work was supported by Deutsche Forschungsgemeinschaft, by Fonds der Chemischen Industrie, and by Degussa AG and Heraeus GmbH. Fig. 3 Molecular structure of the cation of compound 2 (ORTEP drawing with 50% probability ellipsoids, H atoms omitted for clarity). Selected bond lengths (Å) and angles (8): Au(1)–P(1) 2.238(2), Au(1)–Cl(1) 2.357(2), Au(1) ? ? ?Au(1a) 3.1725(5), P(1)–O(1) 1.576(5), O(1)–B(1) 1.464(7), B(1)–F(1) 1.38(2); P(1)–Au(1)–Cl(1) 171.38(8), Au(1)–Cl(1)–Au(1c) 106.51(10), Au(1a) ? ? ?Au(1) ? ? ?Au(1b) 60.0. Fig. 4 Projection of the molecular structure of the cation of compound 2 along the threefold axis.Notes and references † Dedicated to Professor E. Niecke on the occasion of his 60th birthday. ‡ Preparations. 1: (Me2S)AuCl (177 mg, 0.60 mmol) and Ph2P(O)H (121 mg, 0.60 mmol) were dissolved in CH2Cl2 (15 mL) and the resulting mixture was stirred for 2 h at 20 8C. The solvent was evaporated under vacuum to leave a volume of 3 mL, and pentane (30 mL) was added to precipitate a white solid, which was recrystallized from CH2Cl2–pentane to give colourless crystals. Yield 243 mg, 93%; mp 128 8C, stable to air and moisture, soluble in tetrahydrofuran, di- and tri-chloromethane, and insoble in diethyl ether and pentane. 1H NMR (CDCl3, 20 8C): d 8.70 (br s, OH); 7.21–7.91 (m, C6H5). 13C-{1H} NMR (CDCl3, 20 8C): d 134.7 (d, 1JPC = 74.4, i-C6H5), 132.1 (d, 4JPC = 2.3, p-C6H5), 131.4 (d, 2JPC = 16.1, o-C6H5), 128.8 (d, 3JPC = 13.0 Hz, m- C6H5). 31P-{1H} NMR (CDCl3, 20 8C): d 90.4 (s). MS (FAB): m/z 1000 [{Ph2P(OH)}3Au2]1, 833 [2M 2 Cl]1, 601 [{Ph2P(OH)}2Au]1, 399 [M 2 Cl]1, 202 [M 2 AuCl]1 (Found: C, 34.11; H, 2.79.Calc. for C12H11AuClOP?0.125C5H12: C, 34.18; H, 2.84%). 2: a solution of compound 1 (140 mg, 0.32 mmol) in CH2Cl2 (10 mL) was treated with 1 mL of BF3?OEt2 for 2 h at 20 8C. The solvent was evaporated to leave a volume of 2 mL, and Et2O was added to precipitate the product 2, which was recrystallized from CH2Cl2–Et2O at 4 8C to give colourless crystals. Yield 135 mg, 96%; mp 152 8C (decomp.), stable to air and moisture, soluble in tetrahydrofuran and methanol, and insoluble in diethyl ether and pentane.Product 2 decomposes slowly in dichloromethane and rapidly in chloroform, at 20 8C. 1H NMR (CD2Cl2, 20 8C): d 7.25–8.00 (m, C6H5). 13C-{1H} NMR (CD2Cl2, 20 8C): d 132.6 (s, p-C6H5), 131.2 (d, 2JPC = 16.9, o-C6H5), 128.9 (d, 3JPC = 13.8 Hz, m-C6H5), i-C6H5 not detected. 31P-{1H} NMR (CD2Cl2, 20 8C): d 82.3 (s). 11B-{1H} NMR (CD2Cl2, 20 8C): d 20.75 [s, (PO)3BF], 21.05 (s, BF4 2) (Found: C, 32.45; H, 2.44.Calc. for C72H60Au6B3Cl3- F6O6P6: C, 32.74; H, 2.29%). § Crystal structure determinations. Crystal data for C12H11AuClOP 1. Mr = 434.59, colorless crystals (0.45 × 0.35 × 0.30 mm), triclinic, a = 10.357(2), b = 10.806(2), c = 11.689(2) Å, a = 101.18(1), b = 98.49(2), g = 98.00(2)8, space group P1� , Z = 4, V = 1250.2(4) Å3, rcalc = 2.309 g cm23, F(000) = 808; T = 278 8C. Data were corrected for Lorentz, polarization, and absorption eVects [m(Mo-Ka) = 120.83 cm21]. 5436 measured [(sin q/l)max = 0.64 Å21], 5435 unique reflections (Rint = 0.0058); 289 refined parameters, wR2 = 0.0918, R = 0.0361 for 5166 reflections with Fo > 4s(Fo) used for refinement. Crystal data for C75H66Au6B3Cl9F6O6P6 (2?3CH2Cl2), Mr = 2896.38, colorless crystals (0.40 × 0.35 × 0.35 mm), hexagonal, a, b = 15.709(1), c = 23.705(1) Å, space group P63/m, Z = 2, V = 5066.0(5) Å3, rcalc = 1.899 g cm23, F(000) = 2700; T = 277 8C. Data were corrected for Lorentz, polarization, and absorption eVects [m(Mo-Ka) = 90.40 cm21]. 7974 measured [(sin q/l)max = 0.64 Å21], 3755 unique reflections (Rint = 0.0502); 175 refined parameters, wR2 = 0.0954, R = 0.0363 for 3265 reflections with Fo > 4s(Fo) used for refinement. CCDC reference number 186/1260. See http://www.rsc.org/suppdata/dt/1999/111/ for crystallographic files in .cif format. 1 H. Schmidbaur, Chem. Soc. Rev., 1995, 24, 391. 2 A. 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