Bis[μ-1,2-bis­(diphenyl­phosphino)ethane-κ2 P:P′]digold(I)(Au—Au) bis­(trifluoro­methane­sulfonate) acetonitrile disolvate

Christoph E Strasser; Stephanie Cronje; Helgard G Raubenheimer

doi:10.1107/S1600536809025513

. 2009 Jul 11;65(Pt 8):m914. doi: 10.1107/S1600536809025513

Bis[μ-1,2-bis(diphenylphosphino)ethane-κ² P:P′]digold(I)(Au—Au) bis(trifluoromethanesulfonate) acetonitrile disolvate

Christoph E Strasser ^a, Stephanie Cronje ^a, Helgard G Raubenheimer ^a,^*

PMCID: PMC2977105 PMID: 21583372

Abstract

The title compound, [Au₂(C₂₆H₂₄P₂)₂](CF₃SO₃)₂·2CH₃CN, comprises a cyclic cation with a short intramolecular aurophilic interaction of 2.9220 (3) Å. The trifluoromethanesulfonate anions and acetonitrile solvent molecules are located in channels formed by the complex cations that run along the crystallographic c axis. Each counter-anion is also engaged in a C—H⋯O contact with one of the methylene H atoms of a 1,2-bis(diphenylphosphino)ethane (dppe) ligand; another C—H⋯O contact involving an aromatic H atom is also observed.

Related literature

For ³¹P NMR evidence of [Au₂(μ-dppe)₃]²⁺, see: Al-Baker et al. (1985 ▶). For [Au₂(μ-dppm)₂]²⁺, see: de Jongh et al. (2007 ▶). For a related structure, see: Schuh et al. (2001 ▶).

Experimental

Crystal data

[Au₂(C₂₆H₂₄P₂)₂](CF₃SO₃)₂·2C₂H₃N
M _r = 1571.0
Monoclinic,
a = 11.7888 (9) Å
b = 36.998 (3) Å
c = 14.377 (1) Å
β = 113.011 (1)°
V = 5771.6 (8) Å³
Z = 4
Mo Kα radiation
μ = 5.33 mm⁻¹
T = 100 K
0.21 × 0.15 × 0.07 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2002 ▶) T _min = 0.404, T _max = 0.686
36089 measured reflections
13385 independent reflections
10742 reflections with I > 2σ(I)
R _int = 0.048

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.095
S = 1.01
13385 reflections
723 parameters
H-atom parameters constrained
Δρ_max = 2.35 e Å⁻³
Δρ_min = −0.75 e Å⁻³

Data collection: SMART (Bruker, 2002 ▶); cell refinement: SAINT (Bruker, 2003 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: X-SEED (Barbour, 2001 ▶; Atwood & Barbour, 2003 ▶); software used to prepare material for publication: X-SEED.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809025513/im2111sup1.cif

e-65-0m914-sup1.cif^{(42.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809025513/im2111Isup2.hkl

e-65-0m914-Isup2.hkl^{(654.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C212—H212⋯O1ⁱ	0.95	2.45	3.387 (7)	171
C21—H21B⋯O1ⁱ	0.99	2.34	3.268 (7)	155
C11—H11B⋯O4ⁱⁱ	0.99	2.36	3.301 (7)	158

Open in a new tab

Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

We would like to thank the National Research Foundation (NRF) of South Africa for financial support.

supplementary crystallographic information

Comment

Ditopic phosphines can form cyclic cations with gold(I) and especially dppm [bis(diphenylphosphino)methane] readily yields the [Au₂(µ-dppm)₂]²⁺ cation (de Jongh et al., 2007; and references cited therein). However, the tendency of dppe [1,2-bis(diphenylphosphino)ethane] to form cyclic cations is less apparent than that of dppm since only one structural report of a bis(methanol) solvate, [Au₂(µ-dppe)₂](CF₃SO₃)₂.CH₃OH, has been published (Schuh et al., 2001). The two solvates, however are not isomorphous with (I) being monoclinic and the methanol solvate triclinic.

Compound (I) crystallizes as an asymmetric cation with the trifluoromethanesulfonate anions forming two sets of channels running parallel to the crystallographic a axis (for the anion containing S1) and c axis (for the anion containing S2), respectively. The acetonitrile containing N2 is also found in the former channels while another solvent is embedded between the cations.

Compared to the other example of a crystallographically characterized [Au₂(µ-dppe)₂]²⁺ cation in literature, (I) (Figure 1) exhibits a shorter aurophilic interaction and slightly wider P1—Au1···Au2—P2 and P3—Au1···Au2—P4 torsion angles [2.9220 (3) Å, -47.11 (5) and -46.89 (5)° in (I) compared to 2.959 (1) Å, -43.8 (1) and -45.0 (1)°, in the example of Schuh et al.]. The angles at the gold centres in (I) are bent significantly from the linear ideal [P1—Au1—P3 171.77 (5)° and P2—Au2—P4 177.10 (5)°] due to the attractive aurophilic interaction. Other geometric parameters between both structures agree very closely and differences would likely be caused by lattice effects. Another noteworthy feature of (I) is the well defined trifluoromethanesulfonate anions and acetonitrile solvent molecules that do not exhibit disorder despite the fact that the thermal displacement ellipsoids of the acetonitrile containing N1 show higher mobility. Disorder of one trifluoromethanesulfonate anion and methanol molecule each was observed in the crystal structure of the bis(methanol) solvate which may have been enhanced by the higher temperature [223 (2) K] at which data were collected.

The title compound (I) was obtained as the exclusive product in an unsuccessful attempt to structurally characterize the [Au₂(µ-dppe)₃]²⁺ cation that has been previously detected by ³¹P NMR spectroscopy (Al-Baker et al., 1985) and its presence in the mother liquor of (I) can therefore not be completely ruled out.

Experimental

The ditopic phosphine dppe (184 mg, 0.46 mmol) was suspended in 20 ml of acetonitrile, sodium trifluoromethanesulfonate (53 mg, 0.31 mmol) was added and the suspension stirred briefly. [AuCl(tht)] (99 mg, 0.31 mmol; tht = tetrahydrothiophene) and few NaCl crystals (to seed precipitation) were subsequently added. After 1 h the precipitated solids were filtered off, the filtrate was reduced to ca 5 ml and layered with diethyl ether. Colourless blocks of (I) crystallized at 258 K. No other species could be identified in the crystalline phase.