Monomers, dimers, and trimers of [Au(CN)2]− in a Ba(diaza-18-crown-6)2+ coordination polymer

Christine M Beavers; Latisha Paw U; Marilyn M Olmstead

doi:10.1107/S1600536809005285

. 2009 Feb 21;65(Pt 3):m300–m301. doi: 10.1107/S1600536809005285

Monomers, dimers, and trimers of [Au(CN)₂]⁻ in a Ba(diaza-18-crown-6)²⁺ coordination polymer

Christine M Beavers ^a, Latisha Paw U ^a, Marilyn M Olmstead ^a,^*

PMCID: PMC2968470 PMID: 21582080

Abstract

The structure of the title compound, poly[triaquatetra-μ-cyanido-tetracyanidobis(1,4,10,13-tetraoxa-7,16-diazacyclooctadecane)dibarium(II)tetragold(I)], [Au₄Ba₂(CN)₈(C₁₂H₂₆N₂O₄)₂(H₂O)₃]_n, displays O—H⋯N hydrogen bonding between water molecules and cyano ligands and an unusual pattern of aurophilic interactions that yields a monomer, dimer, and trimer of [Au(CN)₂]⁻ within the same crystal structure. In two of the five Au positions, the atom resides on a center of inversion. The overall arrangement is that of a coordination polymer assisted by aurophilic and hydrogen-bonded interactions.

Related literature

For aurophilic interactions, see: Anderson et al. (2007 ▶); Schmidbaur (1995 ▶); Pathaneni & Desiraju (1993 ▶). For the structure of a related Pt(CN)₄ ²⁻ salt, see: Olmstead et al. (2005 ▶).

Experimental

Crystal data

[Au₄Ba₂(CN)₈(C₁₂H₂₆N₂O₄)₂(H₂O)₃]
M _r = 1849.45
Triclinic,
a = 11.0962 (3) Å
b = 15.9223 (5) Å
c = 16.5480 (5) Å
α = 64.142 (2)°
β = 70.523 (2)°
γ = 79.027 (3)°
V = 2476.90 (13) Å³
Z = 2
Mo Kα radiation
μ = 13.43 mm⁻¹
T = 90 K
0.20 × 0.15 × 0.12 mm

Data collection

Bruker SMART APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.174, T _max = 0.296 (expected range = 0.117–0.200)
46665 measured reflections
15056 independent reflections
13234 reflections with I > 2σ(I)
R _int = 0.028

Refinement

R[F ² > 2σ(F ²)] = 0.021
wR(F ²) = 0.041
S = 1.03
15056 reflections
585 parameters
13 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 1.06 e Å⁻³
Δρ_min = −0.89 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP in SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809005285/pk2153sup1.cif

e-65-0m300-sup1.cif^{(45.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809005285/pk2153Isup2.hkl

e-65-0m300-Isup2.hkl^{(735.9KB, hkl)}

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

Table 1. Selected geometric parameters (Å, °).

Ba1—N1	2.959 (2)
Ba1—N2	2.919 (2)
Ba1—N5	2.889 (3)
Ba1—N6	2.877 (3)
Ba1—O1	2.854 (2)
Ba1—O2	2.827 (2)
Ba1—O3	2.802 (2)
Ba1—O4	2.850 (2)
Ba1—O5	2.764 (2)
Ba2—N9	2.939 (3)
Ba2—N10	2.867 (3)
Ba2—N11	2.929 (3)
Ba2—N12	2.867 (3)
Ba2—O6	2.888 (2)
Ba2—O7	2.884 (2)
Ba2—O8	2.888 (2)
Ba2—O9	2.929 (2)
Ba2—O10	2.859 (2)
Ba2—O11	2.761 (2)
Au1—Au2	3.5655 (2)
Au1—C13	1.978 (3)
Au1—C14	1.991 (3)
Au2—C15	1.986 (3)
Au3—C16	1.985 (3)
Au3—C17	1.990 (3)
Au3—Au4	3.2670 (2)
Au4—C18	1.988 (3)
Au4—C19	1.989 (3)
Au5—C32	1.985 (3)

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C13—Au1—C14	177.12 (14)
C16—Au3—C17	177.40 (13)
C18—Au4—C19	176.60 (12)

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C14—Au1—Au2—C15	53.73 (13)
C13—Au1—Au2—C15	−127.71 (13)
C14—Au1—Au2—C15ⁱ	−126.27 (13)
C13—Au1—Au2—C15ⁱ	52.29 (13)
C16—Au3—Au4—C18	−125.59 (12)
C17—Au3—Au4—C18	54.37 (13)
C16—Au3—Au4—C19	55.81 (12)
C17—Au3—Au4—C19	−124.22 (13)

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Symmetry code: (i) Inline graphic .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O5—H5C⋯N4ⁱ	0.84 (3)	2.19 (2)	2.997 (4)	161 (4)
O5—H5D⋯N3ⁱⁱ	0.84 (3)	1.98 (3)	2.804 (4)	168 (3)
O10—H10C⋯N8ⁱⁱⁱ	0.83 (4)	2.09 (3)	2.916 (3)	170 (3)
O10—H10D⋯N6	0.84 (4)	2.35 (2)	3.132 (3)	156 (3)
O11—H11C⋯N4^iv	0.84 (4)	2.01 (3)	2.845 (4)	177 (3)
O11—H11D⋯N7^v	0.84 (3)	2.09 (3)	2.920 (4)	176 (4)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

supplementary crystallographic information

Comment

Two coordinate gold(I) compounds often associate through aurophilic interactions that span the range of ca 2.9 - 3.6 Å (Pathaneni & Desiraju, 1993; Schmidbaur, 1995; Anderson et al., 2007). In previous work (Olmstead et al., 2005) we reported a coordination polymer of Ba(18-crown-6)[Pt(CN)₄]^.2H₂O. The title compound represents an extension of that work to the [Au(CN)₂]^- anion, using a diaza-18-crown-6 to complex Ba²⁺. A related coordination polymer with aurophilic association between gold(I) species is the result.

The asymmetric unit of the title compound consists of two Ba(diaza-18-crown-6)²⁺ cations, four dicyanidoaurate anions, and three molecules of water (Fig. 1). There are five gold positions, two of which, Au2 and Au5, are located on centers of inversion. The monomeric dicyanidoaurate is comprised of Au5, linearly coordinated to two cyanide groups. It functions as a linker anion between two Ba2 complexes via N12 of its cyanide group (Fig. 2). It does not participate in any hydrogen bonding nor aurophilic interactions. The closest dicyanidoaurate is that of Au4, at an Au···Au distance of 4.4501 (2) Å. The Au1 and Au2 atoms are involved in the trimer while Au3 and Au4 form the dimer. Distances and angles are reported in Table 1. As shown in Fig. 2, the polymer is connected through a combination of coordination of the [Au(CN)₂]^- nitrogen atoms to barium and aurophilic interactions. All of the hydrogen atoms of the three coordinated waters behave as hydrogen bond donors to N3, N4, N6, N7 and N8 of the cyanide groups (see Table 2). Fig. 3 depicts how a portion of the polymeric structure is supported by these hydrogen bonds.

The bariums, Ba1 and Ba2, have coordination numbers of 9 and 10, respectively. Ba1 is six-coordinated by the diaza-18-crown-6, two [Au(CN)₂]^- anions and one water molecule. It is 0.56 (2) Å out of the N₂O₄ plane of the crown, giving endo and exo faces. One dicyanidoaurate is coordinated to each face while the water molecule coordinates on the exo face. The coordination environment of Ba2 is different. Ba2, which is 0.71 (2) Å out of the N₂O₄ plane of the crown, is also coordinated by two dicyanidoaurates, but both are found on the exo face. Two water molecules are coordinated to Ba2, one on each face. Four of the eight independent cyanide groups are coordinated through their cyanide N atom to a barium (N5, N6, N9, N12). Interestingly, even though the dimer and trimer differ in their Au···Au distances, they show similar C-Au-Au-C torsion angles that are intermediate between eclipsed and staggered. The average value of the two smaller angles is 53° for the trimer and 55° for the dimer (see Table 1 for details).

Experimental

A salt of Ba[Au(CN)₂]₂ was prepared by mixing 162 mg (0.62 mmol) Ba(NO₃)₂ and 288 mg (1.0 mmol) K[Au(CN)₂] in water and heating until both compounds were dissolved. The solution was then put in an ice bath to precipitate out Ba[Au(CN)₂]₂. An excess of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (diaza-18-crown-6), 400 mg (1.5 mmol) was dissolved in methanol and added to the precipitated material. This solution was placed in a 5 mm diameter glass tube and layered with water. After 24 h, suitable prismatic crystals formed.