metal-organic compounds
Bromido(2,2′:6′,2′′-terpyridine)platinum(II) dibromidoaurate(I) dimethyl sulfoxide solvate
aChemistry Department, Boston University, 590 Commonwealth Ave., Boston, Massachusetts 02215, USA, bDepartment of Chemistry and Biochemistry, University of Massachusetts–Dartmouth, North Dartmouth, Massachusetts 02747, USA, and cDepartment of Chemistry and Biochemistry, University of California–San Diego, 9500 Gilman Drive, MC 0358, La Jolla, California 92093, USA
*Correspondence e-mail: doerrer@bu.edu
The 15H11N3)][AuBr2]·(CH3)2SO, exhibits infinite chains of {PtAuPt}∞ metallophilic interactions along the b axis. Two cations and one anion stack in a trimer with a unique Pt⋯Au distance of 3.3361 (5) Å and Pt⋯Pt contacts of 3.4335 (6) Å. The remaining [AuBr2]− anion forms no close contacts.
of the title compound, [PtBr(CRelated literature
For the related chloride structure, [Pt(tpy)Cl][AuCl2] (tpy=2,2′:6′,2"-terpyridine), see Hayoun et al. (2006). For the related [Pt(tpy)I][AuI2] complex, see Angle et al. (2007). For a review of double salts with metallophilic interactions, see Doerrer (2008). The synthesis of [Pt(tpy)X]X complexes (X = Cl, Br, I) is discussed in Annibale et al. (2004), and the preparation of [AuX2]− in Braunstein & Clark (1973). For background to metallophilic interactions, see: Pyykkö (1997). For a description of the Cambridge Structural Database, see: Allen (2002).
Experimental
Crystal data
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Data collection: SMART (Bruker, 2005); cell SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
Supporting information
10.1107/S1600536809033248/cv2602sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809033248/cv2602Isup2.hkl
[Pt(tpy)Br]Br, prepared according to the literature (Annibale et al., 2004), was mixed with potassium tetrabromoaurate, KAuBr4. Dry acetone was added to the mixture to reduce the gold(III) in KAuBr4 to gold(I) in [AuBr2]-, as expected from the literature (Braunstein and Clark, 1973). This resulted in a maroon solution which turned light orange after stirring for three minutes at 30°C. The solution was allowed to mix at 30°C for four h, resulting in KBr, bromoacetone, and the orange powder [Pt(tpy)Br]+ [AuBr2]- (in 66% yield) as the products. The orange powder [Pt(tpy)Br]+ [AuBr2]- was dissolved in DMSO and layered with chloroform to form red block-like crystals.
The crystal was mounted on a CryoLoop with Paratone-N oil and immediately placed under a stream of N~2~ on a Bruker SMART APEX CCD system. All H atoms were positioned geometrically (C—H = 0.94–0.97 Å), and allowed to ride on their parent atoms, with Uĩso~ = 1.2–1.5 U~eq~(C). The highest residual peak [2.01 e Å-3] and deepest hole [-4.13 e Å-3] are situated 0.11 and 0.87 Å from Pt1, respectively.
Data collection: SMART (Bruker, 2005); cell
SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).[PtBr(C15H11N3)][AuBr2]·C2H6OS | Z = 2 |
Mr = 943.18 | F(000) = 852 |
Triclinic, P1 | Dx = 2.962 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 8.1463 (11) Å | Cell parameters from 5521 reflections |
b = 10.0930 (14) Å | θ = 2.5–28.2° |
c = 13.9624 (19) Å | µ = 19.31 mm−1 |
α = 81.905 (2)° | T = 208 K |
β = 87.675 (2)° | Block, red |
γ = 68.532 (3)° | 0.30 × 0.20 × 0.15 mm |
V = 1057.6 (3) Å3 |
Bruker SMART CCD area-detector diffractometer | 4826 independent reflections |
Radiation source: fine-focus sealed tube | 4312 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.019 |
ϕ and ω scans | θmax = 28.2°, θmin = 1.5° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2000) | h = −8→10 |
Tmin = 0.068, Tmax = 0.160 | k = −13→10 |
7511 measured reflections | l = −18→17 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.039 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.103 | H-atom parameters constrained |
S = 1.01 | w = 1/[σ2(Fo2) + (0.0756P)2] P = (Fo2 + 2Fc2)/3 |
4826 reflections | (Δ/σ)max = 0.001 |
249 parameters | Δρmax = 2.01 e Å−3 |
0 restraints | Δρmin = −4.14 e Å−3 |
[PtBr(C15H11N3)][AuBr2]·C2H6OS | γ = 68.532 (3)° |
Mr = 943.18 | V = 1057.6 (3) Å3 |
Triclinic, P1 | Z = 2 |
a = 8.1463 (11) Å | Mo Kα radiation |
b = 10.0930 (14) Å | µ = 19.31 mm−1 |
c = 13.9624 (19) Å | T = 208 K |
α = 81.905 (2)° | 0.30 × 0.20 × 0.15 mm |
β = 87.675 (2)° |
Bruker SMART CCD area-detector diffractometer | 4826 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2000) | 4312 reflections with I > 2σ(I) |
Tmin = 0.068, Tmax = 0.160 | Rint = 0.019 |
7511 measured reflections |
R[F2 > 2σ(F2)] = 0.039 | 0 restraints |
wR(F2) = 0.103 | H-atom parameters constrained |
S = 1.01 | Δρmax = 2.01 e Å−3 |
4826 reflections | Δρmin = −4.14 e Å−3 |
249 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > σ(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
Au1 | 1.0000 | 0.5000 | 1.0000 | 0.03631 (12) | |
Au2 | 0.5000 | 0.5000 | 0.5000 | 0.03754 (12) | |
Pt1 | 0.01155 (3) | 0.82805 (2) | −0.005856 (15) | 0.02023 (9) | |
Br1 | −0.25578 (8) | 0.87221 (7) | 0.08893 (5) | 0.03042 (15) | |
Br2 | 0.98737 (9) | 0.44194 (7) | 1.17203 (6) | 0.03918 (18) | |
Br3 | 0.75978 (12) | 0.32173 (10) | 0.45033 (6) | 0.0514 (2) | |
S1 | 0.3410 (3) | 1.1786 (2) | 0.55776 (14) | 0.0477 (5) | |
N1 | 0.1935 (6) | 0.7291 (5) | 0.1004 (4) | 0.0220 (10) | |
N3 | −0.0990 (6) | 0.9177 (5) | −0.1372 (4) | 0.0212 (9) | |
N2 | 0.2244 (6) | 0.7937 (5) | −0.0823 (4) | 0.0196 (9) | |
O1 | 0.3110 (10) | 1.0395 (7) | 0.5756 (6) | 0.079 (2) | |
C1 | 0.1657 (9) | 0.6989 (7) | 0.1947 (5) | 0.0292 (13) | |
H1A | 0.0493 | 0.7257 | 0.2172 | 0.035* | |
C2 | 0.3038 (10) | 0.6292 (8) | 0.2598 (5) | 0.0363 (15) | |
H2A | 0.2809 | 0.6086 | 0.3256 | 0.044* | |
C3 | 0.4751 (10) | 0.5900 (8) | 0.2277 (5) | 0.0356 (15) | |
H3A | 0.5700 | 0.5420 | 0.2713 | 0.043* | |
C4 | 0.5057 (9) | 0.6221 (7) | 0.1305 (5) | 0.0313 (14) | |
H4A | 0.6216 | 0.5976 | 0.1072 | 0.038* | |
C5 | 0.3634 (8) | 0.6908 (6) | 0.0682 (4) | 0.0239 (12) | |
C6 | 0.3808 (8) | 0.7276 (7) | −0.0365 (5) | 0.0275 (13) | |
C7 | 0.5327 (8) | 0.7028 (6) | −0.0895 (5) | 0.0274 (13) | |
H7A | 0.6440 | 0.6568 | −0.0592 | 0.033* | |
C8 | 0.5184 (8) | 0.7467 (7) | −0.1880 (5) | 0.0307 (14) | |
H8A | 0.6215 | 0.7295 | −0.2249 | 0.037* | |
C9 | 0.3560 (8) | 0.8153 (7) | −0.2337 (4) | 0.0270 (12) | |
H9A | 0.3475 | 0.8453 | −0.3008 | 0.032* | |
C10 | 0.2060 (8) | 0.8385 (6) | −0.1780 (4) | 0.0237 (12) | |
C11 | 0.0209 (8) | 0.9105 (6) | −0.2094 (4) | 0.0241 (12) | |
C12 | −0.0334 (9) | 0.9673 (7) | −0.3032 (5) | 0.0306 (14) | |
H12A | 0.0508 | 0.9637 | −0.3519 | 0.037* | |
C13 | −0.2089 (9) | 1.0288 (7) | −0.3261 (5) | 0.0344 (15) | |
H13A | −0.2470 | 1.0662 | −0.3903 | 0.041* | |
C14 | −0.3288 (9) | 1.0348 (8) | −0.2530 (5) | 0.0356 (15) | |
H14A | −0.4502 | 1.0775 | −0.2672 | 0.043* | |
C15 | −0.2725 (8) | 0.9788 (6) | −0.1592 (5) | 0.0270 (13) | |
H15A | −0.3559 | 0.9833 | −0.1100 | 0.032* | |
C16 | 0.2828 (11) | 1.2500 (9) | 0.4364 (5) | 0.0473 (19) | |
H16A | 0.3572 | 1.1838 | 0.3945 | 0.071* | |
H16B | 0.2987 | 1.3414 | 0.4222 | 0.071* | |
H16C | 0.1603 | 1.2642 | 0.4255 | 0.071* | |
C17 | 0.1620 (13) | 1.3074 (11) | 0.6114 (7) | 0.063 (3) | |
H17A | 0.1799 | 1.2924 | 0.6809 | 0.094* | |
H17B | 0.0525 | 1.2965 | 0.5969 | 0.094* | |
H17C | 0.1560 | 1.4035 | 0.5856 | 0.094* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Au1 | 0.02295 (18) | 0.0324 (2) | 0.0533 (3) | −0.00747 (15) | −0.00103 (16) | −0.01197 (17) |
Au2 | 0.0434 (2) | 0.0484 (2) | 0.0243 (2) | −0.02176 (18) | −0.00643 (16) | 0.00001 (16) |
Pt1 | 0.01865 (13) | 0.02448 (13) | 0.01805 (14) | −0.00871 (9) | 0.00074 (9) | −0.00222 (9) |
Br1 | 0.0254 (3) | 0.0345 (3) | 0.0311 (3) | −0.0109 (3) | 0.0069 (2) | −0.0054 (3) |
Br2 | 0.0306 (3) | 0.0323 (3) | 0.0542 (5) | −0.0095 (3) | −0.0011 (3) | −0.0097 (3) |
Br3 | 0.0499 (5) | 0.0579 (5) | 0.0436 (5) | −0.0160 (4) | −0.0025 (4) | −0.0072 (4) |
S1 | 0.0383 (9) | 0.0678 (13) | 0.0308 (10) | −0.0188 (9) | −0.0043 (8) | 0.0137 (9) |
N1 | 0.021 (2) | 0.027 (2) | 0.019 (2) | −0.0096 (19) | −0.0004 (19) | −0.0027 (19) |
N3 | 0.017 (2) | 0.022 (2) | 0.022 (2) | −0.0041 (18) | −0.0033 (18) | −0.0013 (19) |
N2 | 0.018 (2) | 0.021 (2) | 0.020 (2) | −0.0077 (18) | 0.0020 (18) | −0.0030 (19) |
O1 | 0.081 (5) | 0.057 (4) | 0.079 (5) | −0.020 (4) | 0.013 (4) | 0.033 (4) |
C1 | 0.034 (3) | 0.035 (3) | 0.021 (3) | −0.017 (3) | 0.003 (3) | −0.002 (3) |
C2 | 0.042 (4) | 0.045 (4) | 0.023 (3) | −0.020 (3) | −0.001 (3) | 0.005 (3) |
C3 | 0.039 (4) | 0.038 (4) | 0.029 (4) | −0.015 (3) | −0.012 (3) | 0.006 (3) |
C4 | 0.030 (3) | 0.034 (3) | 0.032 (4) | −0.013 (3) | −0.004 (3) | −0.004 (3) |
C5 | 0.023 (3) | 0.025 (3) | 0.024 (3) | −0.011 (2) | 0.000 (2) | −0.001 (2) |
C6 | 0.024 (3) | 0.030 (3) | 0.028 (3) | −0.010 (2) | −0.001 (2) | −0.003 (3) |
C7 | 0.023 (3) | 0.029 (3) | 0.029 (3) | −0.008 (2) | −0.002 (2) | −0.004 (3) |
C8 | 0.024 (3) | 0.036 (3) | 0.032 (4) | −0.011 (3) | 0.007 (3) | −0.005 (3) |
C9 | 0.027 (3) | 0.035 (3) | 0.020 (3) | −0.013 (3) | 0.002 (2) | −0.002 (2) |
C10 | 0.025 (3) | 0.023 (3) | 0.025 (3) | −0.010 (2) | 0.001 (2) | −0.003 (2) |
C11 | 0.022 (3) | 0.026 (3) | 0.025 (3) | −0.008 (2) | −0.001 (2) | −0.007 (2) |
C12 | 0.036 (3) | 0.029 (3) | 0.026 (3) | −0.013 (3) | −0.003 (3) | 0.001 (3) |
C13 | 0.035 (3) | 0.036 (3) | 0.029 (4) | −0.010 (3) | −0.009 (3) | 0.001 (3) |
C14 | 0.027 (3) | 0.042 (4) | 0.035 (4) | −0.010 (3) | −0.010 (3) | 0.002 (3) |
C15 | 0.022 (3) | 0.030 (3) | 0.029 (3) | −0.009 (2) | −0.003 (2) | −0.003 (3) |
C16 | 0.057 (5) | 0.060 (5) | 0.028 (4) | −0.025 (4) | 0.001 (3) | −0.001 (3) |
C17 | 0.070 (6) | 0.084 (7) | 0.049 (5) | −0.040 (5) | 0.016 (5) | −0.025 (5) |
Au1—Br2i | 2.3981 (9) | C4—H4A | 0.9400 |
Au1—Br2 | 2.3981 (9) | C5—C6 | 1.471 (9) |
Au2—Br3 | 2.3753 (9) | C6—C7 | 1.375 (9) |
Au2—Br3ii | 2.3753 (9) | C7—C8 | 1.381 (9) |
Pt1—N2 | 1.944 (5) | C7—H7A | 0.9400 |
Pt1—N3 | 2.015 (5) | C8—C9 | 1.383 (9) |
Pt1—N1 | 2.018 (5) | C8—H8A | 0.9400 |
Pt1—Br1 | 2.4320 (7) | C9—C10 | 1.385 (8) |
S1—O1 | 1.497 (7) | C9—H9A | 0.9400 |
S1—C16 | 1.757 (8) | C10—C11 | 1.468 (8) |
S1—C17 | 1.782 (9) | C11—C12 | 1.376 (9) |
N1—C1 | 1.338 (8) | C12—C13 | 1.365 (9) |
N1—C5 | 1.369 (7) | C12—H12A | 0.9400 |
N3—C15 | 1.348 (7) | C13—C14 | 1.376 (10) |
N3—C11 | 1.366 (8) | C13—H13A | 0.9400 |
N2—C6 | 1.342 (7) | C14—C15 | 1.376 (9) |
N2—C10 | 1.345 (8) | C14—H14A | 0.9400 |
C1—C2 | 1.382 (10) | C15—H15A | 0.9400 |
C1—H1A | 0.9400 | C16—H16A | 0.9700 |
C2—C3 | 1.379 (10) | C16—H16B | 0.9700 |
C2—H2A | 0.9400 | C16—H16C | 0.9700 |
C3—C4 | 1.385 (9) | C17—H17A | 0.9700 |
C3—H3A | 0.9400 | C17—H17B | 0.9700 |
C4—C5 | 1.380 (9) | C17—H17C | 0.9700 |
Br2i—Au1—Br2 | 180.0 | C6—C7—H7A | 120.7 |
Br3—Au2—Br3ii | 180.000 (1) | C8—C7—H7A | 120.7 |
N2—Pt1—N3 | 80.7 (2) | C7—C8—C9 | 121.5 (6) |
N2—Pt1—N1 | 80.8 (2) | C7—C8—H8A | 119.2 |
N3—Pt1—N1 | 161.5 (2) | C9—C8—H8A | 119.2 |
N2—Pt1—Br1 | 179.63 (16) | C8—C9—C10 | 118.2 (6) |
N3—Pt1—Br1 | 98.95 (14) | C8—C9—H9A | 120.9 |
N1—Pt1—Br1 | 99.58 (14) | C10—C9—H9A | 120.9 |
O1—S1—C16 | 107.0 (4) | N2—C10—C9 | 118.9 (5) |
O1—S1—C17 | 106.8 (4) | N2—C10—C11 | 113.0 (5) |
C16—S1—C17 | 97.3 (4) | C9—C10—C11 | 128.2 (6) |
C1—N1—C5 | 118.9 (5) | N3—C11—C12 | 120.8 (6) |
C1—N1—Pt1 | 127.8 (4) | N3—C11—C10 | 114.7 (5) |
C5—N1—Pt1 | 113.3 (4) | C12—C11—C10 | 124.4 (6) |
C15—N3—C11 | 119.1 (5) | C13—C12—C11 | 120.3 (7) |
C15—N3—Pt1 | 127.2 (4) | C13—C12—H12A | 119.8 |
C11—N3—Pt1 | 113.6 (4) | C11—C12—H12A | 119.8 |
C6—N2—C10 | 123.9 (5) | C12—C13—C14 | 118.4 (6) |
C6—N2—Pt1 | 118.2 (4) | C12—C13—H13A | 120.8 |
C10—N2—Pt1 | 117.9 (4) | C14—C13—H13A | 120.8 |
N1—C1—C2 | 121.7 (6) | C13—C14—C15 | 120.6 (6) |
N1—C1—H1A | 119.2 | C13—C14—H14A | 119.7 |
C2—C1—H1A | 119.2 | C15—C14—H14A | 119.7 |
C3—C2—C1 | 119.7 (6) | N3—C15—C14 | 120.7 (6) |
C3—C2—H2A | 120.1 | N3—C15—H15A | 119.7 |
C1—C2—H2A | 120.1 | C14—C15—H15A | 119.7 |
C2—C3—C4 | 119.2 (6) | S1—C16—H16A | 109.5 |
C2—C3—H3A | 120.4 | S1—C16—H16B | 109.5 |
C4—C3—H3A | 120.4 | H16A—C16—H16B | 109.5 |
C5—C4—C3 | 118.9 (6) | S1—C16—H16C | 109.5 |
C5—C4—H4A | 120.5 | H16A—C16—H16C | 109.5 |
C3—C4—H4A | 120.5 | H16B—C16—H16C | 109.5 |
N1—C5—C4 | 121.6 (6) | S1—C17—H17A | 109.5 |
N1—C5—C6 | 115.0 (5) | S1—C17—H17B | 109.5 |
C4—C5—C6 | 123.4 (6) | H17A—C17—H17B | 109.5 |
N2—C6—C7 | 119.0 (6) | S1—C17—H17C | 109.5 |
N2—C6—C5 | 112.7 (5) | H17A—C17—H17C | 109.5 |
C7—C6—C5 | 128.3 (6) | H17B—C17—H17C | 109.5 |
C6—C7—C8 | 118.6 (6) |
Symmetry codes: (i) −x+2, −y+1, −z+2; (ii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [PtBr(C15H11N3)][AuBr2]·C2H6OS |
Mr | 943.18 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 208 |
a, b, c (Å) | 8.1463 (11), 10.0930 (14), 13.9624 (19) |
α, β, γ (°) | 81.905 (2), 87.675 (2), 68.532 (3) |
V (Å3) | 1057.6 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 19.31 |
Crystal size (mm) | 0.30 × 0.20 × 0.15 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2000) |
Tmin, Tmax | 0.068, 0.160 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7511, 4826, 4312 |
Rint | 0.019 |
(sin θ/λ)max (Å−1) | 0.665 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.039, 0.103, 1.01 |
No. of reflections | 4826 |
No. of parameters | 249 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 2.01, −4.14 |
Computer programs: SMART (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), SHELXTL (Sheldrick, 2008).
Cl | Br | I | |||
Au—Pt | 3.2684 (1) | 3.3361 (5) | 4.2546 (4) | ||
Pt—X | 2.305 (3) | 2.4319 (8) | 2.5930 (5) | ||
Au—X | 2.271 (3) | 2.3984 (9) | 2.5581 (5) | ||
Pt—Pt | 3.4535 (7) | 3.4335 (6) | 3.5278 (3) | ||
Cl | Br | ||||
X2—Au1—Pt1 | 88.63 (7) | 81.70 (2) | |||
91.37 (7) | 98.30 (2) | ||||
X1—Pt1—Au1 | 97.62 (7) | 84.08 (2) | |||
Au1—Pt1—Pt1(1-x, 2-y, -z) | 165.10 (2) | 173.94 (1) |
Acknowledgements
We thank Boston University and the National Science Foundation (NSF-CCF 829890 to LHD) for financial support.
References
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
The title compound, (I), is the bromide analog of the previously published chloride (Hayoun et al., 2006) and iodide (Angle et al., 2007) derivatives.
There are no previous structural characterizations of [Pt(tpy)Br]+ (tpy=2,2':6',2"-terpyridine), but the interatomic distances within the [Pt(tpy)]2+ are unexceptional and unperturbed by the intermolecular interactions. According to the Cambridge Structural Database (Version 5.30, May 2009; Allen, 2002), the linear [AuBr2]- anion has been structurally characterized 32 times with an average Au—Br distance of 2.376 (3) Å and Br—Au—Br angle of 179.3 (2)°, with which the anions in (I) compare favorably. The structure of (I) is analogous to that of [Pt(tpy)Cl]+[AuCl2]-, with metallophilic interactions forming among two platinum(II) and one gold(I) centers to form {[Pt(tpy)Br]2[AuBr2]}+ cations (Figure 1). These cations also form metallophilic interactions among each other resulting in an infinite chain of {PtAuPt}∞ metallophilic interactions along the b-axis with the remaining [AuBr2]- counteranion found outside of the chain (Figure 2). A solvent DMSO molecule was also found in the lattice. The bromide ligands are small enough to allow for metallophilic interactions between gold(I) and platinum(II) centers (Figure 1). No extended metallophilic chains exist in the iodide derivative, which exhibits only pairwise contacts between the cations and between the anions.
As seen in Table 1, the Pt(II)···Pt(II) distances in the bromide derivative are the shortest of all three halogenated species, at 3.4335 (6) Å. The chloride and iodide derivatives exhibit 3.4535 (7) and 3.5278 (3) Å Pt···Pt metallophilic distances, respectively. Evidently the bromide ligand promotes shorter Pt···Pt bonds than the chloride or iodide derivatives, consistent with expectations that more electron rich metal centers promote metallophilic interactions (Pyykkö, 1997). As bromide is softer and less electronegative than chloride, its adjacent platinum center is less electron deficient and bromide is small enough to allow stacking for metallophilic bonding. The gold-platinum distances increase slightly with halogen size from Cl to Br. The Au···Pt···Pt angle is more linear in the bromide derivative at 173.9°, compared to the chloride derivative with an angle of 165.1°. These distances and angles, along with other potentially interesting geometrical values, are collected in Table 1.
The structure of compound (I), therefore, completes a study of the [Pt(tpy)X][AuX2] systems and demonstrates that the halide constituent in the [Pt(tpy)X]+ ion has a determining effect on the length of the Pt···Pt metallophilic contacts for steric and electronic reasons.