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Targeting [AuCl2(CN)2]− units as halophilic building blocks in coordination polymers
Accepted Manuscript Targeting [AuCl2(CN)2]- Units as Halophilic Building Blocks in Coordination Polymers Jeffrey S. Ovens, Kimberley N. Truong, Daniel B. Leznoff PII: DOI: Reference:
S0020-1693(13)00051-0 http://dx.doi.org/10.1016/j.ica.2013.02.011 ICA 15330
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Inorganica Chimica Acta
Received Date: Accepted Date:
21 November 2012 1 February 2013
Please cite this article as: J.S. Ovens, K.N. Truong, D.B. Leznoff, Targeting [AuCl2(CN)2]- Units as Halophilic Building Blocks in Coordination Polymers, Inorganica Chimica Acta (2013), doi: http://dx.doi.org/10.1016/j.ica. 2013.02.011
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Targeting [AuCl2(CN)2] – Units as Halophilic Building Blocks in Coordination Polymers Jeffrey S. Ovens, Kimberley N. Truong, Daniel B. Leznoff∗ Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
Abstract Several new [AuCl2 (CN)2 ] – -containing complexes were synthesized with a range of ancillary ligands and first row transition metals. Use of Cu(II) and 1, 10-phenanthroline (phen) and 2, 9-dimethyl-1, 10-phenanthroline (Me2 phen) with [ nBu4 N][AuCl2 (CN)2 ] yielded the ionic compounds [Cu(phen)2 (OHMe)][AuCl2 (CN)2 ]2 (1) and {Cu(Me2 phen)2 [AuCl2 (CN)2 ]}[AuCl2 (CN)2 ] (2). Use of 2, 20 ; 60 , 200 -terpyridine (terpy) and Cu(NO3 )2 · 3 H2 O or Cu(ClO4 )2 · 6 H2 O instead yielded Cu(terpy)[AuCl2 (CN)2 ]2 (3) and Cu(terpy)(µ−ClO4 )[AuCl2 (CN)2 ] (4), respectively. Compound 3 is molecular, with a single terpy ligand and two pendant [AuCl2 (CN)2 ] – units bound to a Cu(II) centre, whereas 4 is a linear 1-D coordination polymer consisting of Cu(II) centres bridged by ClO4– moieties. Using Cu(II) and pyrazine (pyz) generates a 1-D coordination polymer, Cu(pyz)(NCMe)2 [AuCl2 (CN)2 ]2 · 2 MeCN (5) with bridging pyz units and pendant [AuCl2 (CN)2 ] – and NCMe moieties. Upon switching to 4, 40 -bipyridine (bipy), the 3-D coordination polymer, {Cu(bipy)2 [Au(CN)2 ]}[AuCl2 (CN)2 ] (6) results, which is built up of sheets of Cu(II)/bipy units bridged by [Au(CN)2 ] – . Free [AuCl2 (CN)2 ] – anions sit in the network cavities, held by a rare, unsupported Au I ···Au III interaction of 3.4530(10) ˚ A. The in– ability of [AuCl2 (CN)2 ] to act as a bridging unit in any of these ancillary ligand-containing structures is consistent with the behaviour of [AuBr2 (CN)2 ] – in previous studies and shows that [AuCl2 (CN)2 ] – holds no advantages over [AuBr2 (CN)2 ] – in coordination polymer formation. In the absence of ancillary ligands, molecular Mn(OH2 )4 [AuCl2 (CN)2 ]2 (7) and the 1-D coordination polymer Co(OH2 )4 [AuCl2 (CN)2 ] · 2 H2 O (8), the first coordination polymer with [AuCl2 (CN)2 ] – as the primary bridging moiety, were also prepared and structurally characterized. 1. Introduction Coordination polymers have become an increasingly important class of materials due to the ability to rationally design them through the strategic choice of metals, building blocks (bridging moieties) and ancillary ligands.[1, 2, 3, 4, 5, 6, 7] Gold-containing cyanometallate species, specifically linear d10 [Au(CN)2 ] – and square planar d8 [Au(CN)4 ] – have been used in a range of coordination polymer structures with potentially useful properties such as ∗
To whom all correspondence should be addressed. Email address: [email protected] (Daniel B. Leznoff)
Preprint submitted to Inorganica Chimica Acta
February 18, 2013
magnetism,[8, 9, 10, 11, 12, 13] birefringence,[14, 15, 16] and vapochromism.[17, 18, 19, 20, 21] The halophilic [AuBr2 (CN)2 ] – was recently shown to enhance birefringent properties[14] as a result of the polarizable Au–Br bonds, and its propensity to form intermolecular Br···Br interactions that help to align structural units. However, these studies also found that [AuBr2 (CN)2 ] – was weakly Lewis basic, and as a result, it did not readily bridge metals to form coordination polymers, especially when paired with competing chelating ancillary ligands. In this context we investigated the related [AuCl2 (CN)2 ] – unit in terms of its ability to form coordination polymers and the impact of potential Cl···Cl interactions[22, 23] on the resulting structures as a comparison with the Br-analogue. The results, which include the first molecules and coordination polymers incorporating [AuCl2 (CN)2 ] – are reported herein. 2. Results and Discussion 2.1. Structure of [ nBu4 N][AuCl2 (CN)2 ]. The crystal structure of K[AuCl2 (CN)2 ] has been previously described as having separated K+ cations and [AuCl2 (CN)2 ] – ions, with N(cyano) moieties interacting with the K+ cations.[24] Substitution of the K+ cations in K[AuCl2 (CN)2 ] for nBu4 N+ cations resulted in [ nBu4 N][AuCl2 (CN)2 ];[25] the structure also shows separated cations and anions with no Cl···Cl or Au···Cl interactions present (Fig. 1). The [AuCl2 (CN)2 ] – anion features standard Au–Cl and Au–C bonds of 2.284(2)-2.289(2) ˚ A and 2.008(7)-2.038(8) ˚ A, respectively.[14, 24] Typically, νCN stretches in the IR spectrum of cyanoaurate(III) compounds are very weak when compared to those of cyanoaurate(I) compounds.[26, 27, 28] In this case, the IR spectrum of [ nBu4 N][AuCl2 (CN)2 ] is completely devoid of νCN signals – presumably, they are too weak. Therefore, the Raman spectrum was recorded for [ nBu4 N][AuCl2 (CN)2 ] as a comparison to that reported for K[AuCl2 (CN)2 ][28] to confirm the identity of the product. Indeed, the νCN , νAuCl and νAuC stretches are present in spectra for both salts indicating that the [AuCl2 (CN)2 ] – anion is present in both materials. Although the latter two of these signals do not differ significantly as a function of cation, the νCN stretch in [ nBu4 N][AuCl2 (CN)2 ] is red-shifted from 2199 cm−1 for K[AuCl2 (CN)2 ] to 2185 cm−1 for [ nBu4 N][AuCl2 (CN)2 ], consistent with the replacement of K+ cations, which tend to interact with the N(cyano) moieties, for non-bonding nBu4 N+ cations.[24] N(cyano) binding to a Lewis acidic site tends to blue-shift the νCN band.[29] 2.2. Structures of salts with at least one unbound [AuCl2 (CN)2 ] – anion. The addition of [ nBu4 N][AuCl2 (CN)2 ] to a solution of Cu(ClO4 )2 · 6 H2 O and one equivalent of 1, 10-phenanthroline (phen) in MeOH yielded crystals of the salt [Cu(phen)2 (OHMe)][AuCl2 (CN)2 ]2 (1). Single crystal X-ray diffraction revealed an ionic network consisting of [Cu(phen)2 (OHMe)2 ] 2+ cations and unbound [AuCl2 (CN)2 ] – anions (Fig. 2(a)), arranged in alternating layers perpendicular to the a-axis. The Cu(II) centre displays a distorted trigonal bipyramidal geometry with axial Cu–N(phen) distances of 2.001(15) ˚ A, equatorial ˚ Cu–N(phen) distances of 2.074(16) A and an equatorial Cu–O(MeOH) distance of 2.04(3) ˚ A (Table 1).[14] Although there are no Cl···Cl analogous to the Br···Br interactions found in similar [AuBr2 (CN)2 ] – structures (the shortest Cl···Cl contact is 3.724(18) ˚ A, c.f. sum of van der Waals radii of 3.50 ˚ A for two Cl atoms[30]),[14, 31, 24] chains of [AuCl2 (CN)2 ] – 2
Figure 1: Crystal structure of [ nBu4 N][AuCl2 (CN)2 ] (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; N, blue.
units do interact via Au···Cl interactions of 3.348(6) ˚ A (c.f. sum of van der Waals radii of ˚ 3.41 A for Au and Cl[30]) as shown in Fig. 2(b). Between the layers of anions and cations are hydrogen bonds of 2.72(3) ˚ A between the cyano group of the [AuCl2 (CN)2 ] – units and the hydroxy group on the MeOH moiety. These Au···Cl interactions can be compared with similar intermolecular Au–NC interactions in aggregates of [Au(CN)4 ] – where this weak contact was shown to be chemically significant by observing 15N MAS NMR shifts.[32] In order to restrict phen from binding to Cu(II), and thus encourage [AuCl2 (CN)2 ] – coordination, the phen ligands were replaced by 2, 9-dimethyl-1, 10-phenanthroline (Me2 phen), and the synthesis repeated, but this resulted in {Cu(Me2 phen)2 [AuCl2 (CN)2 ]}[AuCl2 (CN)2 ] (2). As with 1, 2 is an ionic salt consisting of Cu(II)-based cations and [AuCl2 (CN)2 ] – anions (Fig. 3(a)), but one set of [AuCl2 (CN)2 ] – anions is bound pendant to the Cu(II) centre in place of the MeOH moiety. The geometry of the Cu(II) centre is again a distorted trigonal bipyramid with standard bond lengths and angles as listed in Table 2. A similar type of layered motif (Fig. 3(b)) is also observed; between cationic layers are groups of three [AuCl2 (CN)2 ] – units (including those bound to the Cu(II) centre) held together by Au···Cl interactions of 3.2604(19) ˚ A and 3.3674(19) ˚ A. Again, there are no Cl···Cl interactions present. For both 1 and 2, despite adding only one equivalent of phen or Me2 phen, the Cu(II) centre accepted two chelating ligands, as was observed for the previously reported Cu/[AuBr2 (CN)2 ] – analogues, where the metal centre was in most cases saturated by the chelating ligand, leaving no open sites for [AuBr2 (CN)2 ] – coordination.[14] 2.3. Structures of coordination complexes and polymers incorporating only bound [AuCl2 (CN)2 ] – . In order to target Cu(II) centres with 3 coordinated donor sites rather than 4 (as in 1 and 2), 2, 20 ; 60 , 200 -terpyridine (terpy) was used as an ancillary ligand. Thus, upon mixing of MeOH solutions of Cu(NO3 )2 · 3 H2 O, terpy and [ nBu4 N][AuCl2 (CN)2 ], crystals of Cu(terpy)[AuCl2 (CN)2 ]2 (3) were generated. Isostructural to the previously reported Cu(terpy)[AuBr2 (CN)2 ]2 ,[14] the Cu(II) centre features a trigonal bipyramidal geometry (Fig. 4), as in 1 and 2. However, in this case 3 is molecular rather than ionic, with two
3
(a)
(b) Figure 2: a) Crystal structure of 1 (H atoms removed for clarity). The hydrogen bond between the MeOH and [AuCl2 (CN)2 ] – units is shown as a dotted line. b) Extended structure produced by Au···Cl interactions (shown as dashed lines). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue; O, red.
equivalents of [AuCl2 (CN)2 ] – bound pendant to the Cu(II) centre. Relevant bond lengths and angles can be found in Table 3. No significant intermolecular interactions are present. Using Cu(ClO4 )2 · 6 H2 O instead of Cu(NO3 )2 · 3 H2 O as a starting salt, Cu(terpy)(ClO4 )[AuCl2 (CN)2 ] (4) was formed. As shown in Fig. 5(a), 4 consists of {Cu(terpy)[AuCl2 (CN)2 ]}+ units bridged together via axial η 2 −µ−ClO4– anions (Cu–O distances of 2.390(6) ˚ A), resulting in an overall octahedral geometry about the Cu(II) centre (Fig. 5(b)) and a 1-D coordination polymer superstructure. Relevant bond lengths and angles can be found in Table 4. Presumably the lower solubility of the ClO4– -containing salt contributes to generating this different product of crystallization compared to 3. The bridging behaviour exhibited by the ClO4– anion in this structure is well precedented, and has been observed in many binding modes such as a single oxygen bridge or a two-oxygen bridge between metal centres. Typical Cu–O distances range from about 2.3 ˚ A to 3.0 ˚ A.[33, 34, 35, 36, 37] Previous studies on the analogous [AuBr2 (CN)2 ] – building block showed that when paired with other bridging units such as pyrazine (pyz) and 4, 40 -bipyridine (bipy), coordination polymers that also incorporated the Au(III) unit could result. In order to compare with the [AuBr2 (CN)2 ] – results, Cu(ClO4 )2 · 6 H2 O, pyz and [ nBu4 N][AuCl2 (CN)2 ] were mixed in a 1:1:2 ratio in a MeCN solution, resulting in crystals of Cu(pyz)(NCMe)2 [AuCl2 (CN)2 ]2 · 2 MeCN (5). X-ray diffraction reveals that 5 is a 1-D coordination polymer linearly bridged by equatorial
4
Table 1: Selected bond lengths and angles in 1a .
Bond Lengths (˚ A) Cu(1)–N(3) 2.074(16) Cu(1)–N(4) 2.001(15) Cu(1)–O(1) 2.04(3) Au(1)–C(1) 2.01(2) Au(1)–C(2) 1.984(16) Au(1)–Cl(1) 2.276(6) Au(1)–Cl(2) 2.277(7) Au(1)· · ·Cl(1)† 3.348(6) O(1)–H(11)· · ·N(2) 2.72(3) Bond Angles (◦ ) N(3)–Cu(1)–N(4) 81.8(6) ‡ N(3)–Cu(1)–N(4) 97.3(6) N(3)–Cu(1)–N(3)‡ 109.1(8) O(1)–Cu(1)–N(3) 105.5(8) ‡ O(1)–Cu(1)–N(3) 145.4(8) O(1)–Cu(1)–N(4) 87.0(10) † Au(1)–Cl(1)· · ·Au(1) 153.3(4) a Symmetry operation: †: −x + 1/2, y + 1/2, −z + 1/2; ‡: −x, y, −z + 1/2. pyz units (Fig. 6(a)), with similar structural features to many other Cu(II)/pyz chains.[38, 39] Although two [AuCl2 (CN)2 ] – units are indeed bound to the Cu(II) centres, they are pendant and thus do not help to increase the coordination polymer dimensionality. The remaining two axial coordination sites on the octahedral Cu(II) centres are filled by MeCN units (The Cu–N distance is 2.449(4) ˚ A; Fig. 6(b)); these units readily desolvate upon removal from the MeCN solution. The 1-D chains in this structure are isostructural to the previously reported [AuBr2 (CN)2 ] – analogue, Zn(pyz)(NCMe)2 [AuBr2 (CN)2 ]2 .[31] Relevant bond lengths and angles can be found in Table 5. 2.4. A mixed-valent Au(I)/Au(III) system. When pyz is replaced by bipy in the synthetic procedure for 5, an immediate blue precipitate forms. Filtering off this (unidentified) precipitate and allowing the filtrate to slowly evaporate resulted in crystals of {Cu(bipy)2 [Au(CN)2 ]}[AuCl2 (CN)2 ] (6), which has a 3-D framework consisting of 2-D sheets of octahedral Cu(II) centres connected by equatorial bridging bipy ligands; the sheets are linked in the third dimension by axially bound, Au(I)-based [Au(CN)2 ] – units (Fig. 7(a) and Table 6). Situated inside the network spaces are one equivalent of uncoordinated [AuCl2 (CN)2 ] – and a second, interpenetrating {Cu(bipy)2 [Au(CN)2 ]}+ framework. These free [AuCl2 (CN)2 ] – units interact with the coordination polymer framework via a rare Au I ···Au III interaction between the Au(III) centre and the Au(I) centre in the [Au(CN)2 ] – bridge of 3.4530(10) ˚ A (c.f. the 3.6 ˚ A cut-off for a Au···Au interacI III tion), as shown in Fig. 7(b). Such Au ···Au interactions, when observed, are generally either found in structures which impose close proximity between Au(I) and Au(III) centres such as the 2.8874(4) ˚ A bond in [Au I (µ-2-C6 H4 PPh2 )2 Au III (CH3 )2 ][40] and the 3.061(2) ˚ A 5
Table 2: Selected bond lengths and angles in 2.
Bond Lengths (˚ A) Cu(1)–N(4) 2.037(5) Cu(1)–N(5) 1.991(5) Cu(1)–N(6) 2.181(5) Cu(1)–N(7) 2.102(5) Cu(1)–N(8) 1.998(5) Au(1)–C(1) 2.024(8) Au(2)–C(2) 2.016(8) Au(3)–C(3) 1.988(7) Au(3)–C(4) 2.010(7) Au(1)–Cl(1) 2.2183(18) Au(2)–Cl(2) 2.2770(17) Au(3)–Cl(3) 2.2804(18) Au(3)–Cl(4) 2.2777(17) Au(2)· · ·Cl(3) 3.3674(19) Au(3)· · ·Cl(1) 3.2604(19) ◦ Bond Angles ( ) N(5)–Cu(1)–N(4) 83.7(2) N(5)–Cu(1)–N(6) 80.7(2) N(5)–Cu(1)–N(7) 98.34(19) N(8)–Cu(1)–N(4) 88.9(2) N(8)–Cu(1)–N(6) 110.69(19) N(8)–Cu(1)–N(7) 81.7(2) N(4)–Cu(1)–N(6) 111.6(2) N(4)–Cu(1)–N(7) 141.5(2) N(6)–Cu(1)–N(7) 106.60(18) Au(1)–Cl(1)· · ·Au(3) 120.15(7) Au(3)–Cl(3)· · ·Au(2) 92.71(6)
6
Table 3: Selected bond lengths and angles in 3.
Bond Lengths (˚ A) Cu(1)–N(1) 2.226(6) Cu(1)–N(3) 1.976(5) Cu(1)–N(5) 2.005(4) Cu(1)–N(6) 1.925(4) Cu(1)–N(7) 2.019(5) Au(1)–C(1) 1.986(6) Au(1)–C(2) 2.000(6) Au(2)–C(3) 1.992(6) Au(2)–C(4) 1.988(6) Au(1)–Cl(1) 2.2810(17) Au(1)–Cl(2) 2.2769(16) Au(2)–Cl(3) 2.2869(18) Au(2)–Cl(4) 2.268(2) Bond Angles (◦ ) N(1)–Cu(1)–N(3) 88.1(2) N(1)–Cu(1)–N(5) 93.7(2) N(1)–Cu(1)–N(6) 107.7(2) N(1)–Cu(1)–N(7) 94.4(2) N(3)–Cu(1)–N(5) 100.6(2) N(3)–Cu(1)–N(7) 96.80(19) N(6)–Cu(1)–N(5) 80.19(18) N(6)–Cu(1)–N(7) 81.01(19)
7
Table 4: Selected bond lengths and angles in 4.
Bond Lengths (˚ A) Cu(1)–N(2) 1.944(12) Cu(1)–N(3) 2.035(9) Cu(1)–N(4) 1.895(10) Cu(1)–N(5) 2.022(9) Cu(1)–O(3) 2.390(6) Au(1)–C(1) 1.997(15) Au(1)–C(2) 2.004(14) Au(1)–Cl(1) 2.271(3) Au(1)–Cl(2) 2.282(3) Bond Angles (◦ ) O(3)–Cu(1)–N(2) 94.1(2) O(3)–Cu(1)–N(3) 81.0(2) O(3)–Cu(1)–N(4) 85.9(2) O(3)–Cu(1)–N(5) 97.61(18) N(2)–Cu(1)–N(3) 99.4(4) N(2)–Cu(1)–N(5) 99.4(4) N(4)–Cu(1)–N(3) 80.9(4) N(4)–Cu(1)–N(5) 80.4(4)
Table 5: Selected bond lengths and angles in 5a .
Bond Lengths (˚ A) Cu(1)–N(2) 1.996(3) Cu(1)–N(3) 2.010(3) Cu(1)–N(4) 2.449(4) Au(1)–C(1) 1.981(4) Au(1)–C(2) 2.009(4) Au(1)–Cl(1) 2.2888(10) Au(1)–Cl(2) 2.2763(11) † Au(1)· · ·Cl(1) 3.44861(18) Bond Angles (◦ ) N(2)–Cu(1)–N(4) 94.50(15) ‡ N(2)–Cu(1)–N(4) 85.50(15) † Au(1)–Cl(1)· · ·Cl(1) 87.086(17) a Symmetry operation: †: −x + 1/2, −y + 1/2, −z; ‡: −x, −y, −z.
8
(a)
(b) Figure 3: a) Crystal structure of 2 (H atoms removed for clarity). b) Extended structure produced by Au···Cl interactions (interactions shown as dashed lines; aromatic systems belonging to Me2 phen ligands removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue.
bond in [Au(CH2 )2 PPh2 ]Br2 ,[41] or where the Au(I) and Au(III) centres belong to attractive cation and anion pairs such as the 3.54-3.73 ˚ A contacts in [AuCl(bis(2-pyridylmethyl)˚ amine)]PF6 and the 3.34 A interaction in [AuCl(bis(2-pyridylmethyl)-amine)][AuCl2 ].[42] Unlike these examples, the charges of the Au(I) and Au(III)-containing moieties in 6 are of the same sign, and not connected by any kind of ’support’ ligand. Few examples of this type of Au I ···Au III interaction have been observed. In the case of the recently reported K5 [Au(CN)2 ]4 [AuI2 (CN)2 ] · 2 H2 O, an unsupported Au I ···Au III interaction of 3.5697(5) ˚ A – – was observed, linking [Au(CN)2 ] and [AuI2 (CN)2 ] anions together in the solid state structure. The Au I ···Au III interaction seen in 6 is significantly shorter. What is the source of the [Au(CN)2 ] – units? We have recently reported the thermally induced reductive elimination of Br2 from [AuBr2 (CN)2 ] – at elevated temperatures. This reduction process is clearly operative here too (perhaps induced photochemically),[43] bringing 9
Figure 4: Crystal structure of 3 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue.
(a)
(b) Figure 5: a) Supramolecular 1-D, ClO4– -bridged chains of 4. b) Close-up view of 4 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue; O, red.
Au(III)-based [AuCl2 (CN)2 ] – to Au(I)-based [Au(CN)2 ] – in situ; the fact that this reaction 10
(a)
(b) Figure 6: a) Supramolecular 1-D, pyrazine-bridged chains of 5. b) Close-up view of 5 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue.
is non-negligible even at room temperature for the chloro-analogue suggests that it is relatively unstable as compared with [AuBr2 (CN)2 ] – . Upon generation, [Au(CN)2 ] – , which is a much stronger Lewis-base than most Au(III)-based cyanoaurates, then preferentially binds to the Cu(II) centres, generating the insoluble material 6, which effectively traps this mixed Au(I)/Au(III) product. 2.5. Structures of [AuCl2 (CN)2 ] – -based coordination complexes and polymers without ancillary ligands. The above results demonstrated that [AuCl2 (CN)2 ] – is a weak Lewis base which cannot effectively compete with ancillary heterocyclic amine ligands. In order to encourage [AuCl2 (CN)2 ] – -based coordination polymer formation, ancillary ligand-free reactions were targeted. To start, the previously reported Au(I)-based coordination polymers M(OH2 )2 [Au(CN)2 ]2 (M = Mn, Co)[11, 12] were synthesized as in situ precursors. Cl2 gas was then bubbled through a suspension of the Au(I)-containing materials in MeOH, generating [AuCl2 (CN)2 ] – in situ by oxidative addition of Cl2 to the Au(I) centres. As a result, M(OH2 )4 [AuCl2 (CN)2 ]2 · xH2 O products were formed. Crystallographic examination of the Mn-analogue, Mn(OH2 )4 [AuCl2 (CN)2 ]2 (7), reveals a molecular species (Fig. 8) despite the absence of added ancillary ligands; however the [AuCl2 (CN)2 ] – units are both bound to the Mn(II) centre. The structure consists of an octahedral Mn(II) center bound equatorially by aqua ligands and by axial trans-[AuCl2 (CN)2 ] – units. The molecules interact primarily through intermolecular hydrogen bonds 11
(a)
(b) Figure 7: a) Supramolecular 3-D network of 6 bridged in two dimensions by 4, 40 -bipyridine and in the other by [Au(CN)2 ] – . b) One cage section of 6 showing the interactions between [AuCl2 (CN)2 ] – and [Au(CN)2 ] – units (H atoms and interpenetrated structure removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue.
between the aqua ligands and the N(cyano) atoms, and Au···Cl interactions of 3.391(3)3.509(3) ˚ A. When Co(OH2 )2 [Au(CN)2 ]2 undergoes the conversion to an Au(III)-based material, Co(OH2 )4 [AuCl2 (CN)2 ]2 · 2 H2 O (8) is formed (Fig. 9). Compound 8 is a 1-D linear coordination polymer bridged by one equivalent of [AuCl2 (CN)2 ] – units, thus representing the first coordination polymer with [AuCl2 (CN)2 ] – as the bridging moiety. To the Co(II) centers are also bound four equatorial aqua ligands (Fig. 9(b)). These 1-D chains are then linked together via hydrogen bonding to the N(cyano) groups of free [AuCl2 (CN)2 ] – units located between the chains (Table 7). This structure resembles the analogous [Au(CN)4 ] – -containing M(OH2 )4 [Au(CN)4 ]2 · 4 H2 O (M = Mn, Co, Ni, Cu, Zn) systems,[13] which form 1-D linear 12
Table 6: Selected bond lengths and angles in 6a .
˚) Bond Lengths (A Cu(1)–N(1) 2.464(10) Cu(1)–N(4) 2.026(8) † Cu(1)–N(5) 2.043(8) Au(1)–C(1) 1.972(12) Au(3)–C(3) 2.02(2) Au(3)–Cl(3) 2.309(6) Au(1)· · ·Au(3) 3.4530(10) Bond Angles (◦ ) N(1)–Cu(1)–N(4) 88.98(16) † N(1)–Cu(1)–N(5) 91.04(16) N(4)–Cu(1)–N(5)‡ 90.5(3) N(4)–Cu(1)–N(4)∗ 90.8(4) N(5)0 –Cu(1)–N(5)‡ 88.2(4) a Symmetry operation: †: x + 1/2, y + 1/2, z, ‡: −x + 1/2, y + 1/2, z, ∗: −x, y, z.
Figure 8: Crystal structure of 7 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Mn, lt. purple; N, blue; O, red.
chains of [M(OH2 )4 ] 2+ centres bridged by [Au(CN)4 ] – (analogous to 8), connected by weak interactions such as hydrogen bonding and Au···NC interactions between the chains and unbound [Au(CN)4 ] – units. 3. Conclusions In this study, the ability of [AuCl2 (CN)2 ] – to form coordination polymers when combined with some first row transition metals and with or without a variety of heterocyclic amine ancillary ligands was investigated, and compared to the analogous [AuBr2 (CN)2 ] – . In the presence of ancillary ligands, most complexes formed contained metal centres nearly saturated by the ancillary ligand, leaving little or no room for the [AuCl2 (CN)2 ] – units to bind. In the cases where [AuCl2 (CN)2 ] – was able to bind, it was not in a bridging fashion. This clearly demonstrates the weak Lewis basicity of the N(cyano) groups on the [AuCl2 (CN)2 ] – units, thereby imparting no significant advantage over [AuBr2 (CN)2 ] – as a primary bridging unit in coordination polymer formation. In the case of 6, the in situ generation of [Au(CN)2 ] – units, likely via reductive elimination of Cl2 from [AuCl2 (CN)2 ] – indicates that [AuCl2 (CN)2 ] – is unstable in solution as compared to [AuBr2 (CN)2 ] – . A Au I ···Au III interaction in 6, especially unusual in that it occurs between anionic fragments, is particularly noteworthy. 13
Table 7: Selected bond lengths and angles in 7 and 8a .
7 (M = Mn) Bond Lengths (˚ A) M(1)–N(1) 2.161(7) M(1)–O(1) 2.131(7) M(1)–O(2) 2.199(9) Au(1)–C(1) 1.983(7) Au(1)–C(2) 2.005(8) Au(2)–C(2) – Au(1)–Cl(1) 2.286(2) Au(1)–Cl(2) 2.273(2) Au(2)–Cl(2) – † Au(1)· · ·Cl(1) 3.391(3), 3.509(3) Au(2)· · ·Cl(1) – O(2)–H(21)· · ·N(2)‡ – Bond Angles (◦ ) O(1)–M(1)–N(1) 89.8(3) O(2)–M(1)–N(1) 85.7(3) O(1)–M(1)–O(2) 88.3(4) O(1)–M(1)–O(2)† 91.7(4) Au(1)–Cl(1)· · ·Au(1)† 88.87(8), 84.21(8) Au(1)–Cl(1)· · ·Au(2) – a Symmetry operation: †: −x, −y, −z;
14
8 (M = Co) 2.083(4) 2.147(4) 2.032(4) 1.999(5) – 2.009(6) 2.2843(18) – 2.2828(17) – 3.4824(16) 2.815(8) 87.32(16) 89.23(16) 90.27(16) 89.73(16) – 104.4(2) ‡: x, y, z.
(a)
(b) Figure 9: a) 3-D network of 8 showing 1-D, [AuCl2 (CN)2 ] – -bridged, chains linked together by uncoordinated [AuCl2 (CN)2 ] – units via hydrogen bonds (shown as dashed lines). b) Close-up view of 8 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Co, dk. blue; N, blue; O, red.
When the ancillary ligands were eliminated, binding of the [AuCl2 (CN)2 ] – units occurred much more easily, as evidenced by the formation of 7 and 8. Specifically, 8 is the first coordination polymer reported with [AuCl2 (CN)2 ] – as the primary bridging unit, which clearly shows the impact of removing competing ligands from the reaction mixture. Despite this, however, 7 crystallized as a molecular species, suggesting that the energy difference between the two structural motifs is quite small. In many compounds containing [AuBr2 (CN)2 ] – (ionic, molecular and coordination polymer alike), Br···Br interactions played an important structural role. In contrast, halophilic Cl···Cl interactions are not observed in any of 1-8. Instead, the structural outcome and dimensionality is more significantly affected by intermolecular Au···Cl interactions. Overall, considering its weak Lewis basicity and propensity to form only weak intermolecular interactions, the anion [AuCl2 (CN)2 ] – is in practice very similar in behaviour to its counterpart [AuBr2 (CN)2 ] – . 4. Experimental 4.1. General Procedures Caution! Perchlorate salts are potentially explosive and are powerful oxidants. Although no difficulties have been experienced, they should be handled with care. Chlorine should only be used in a well-ventilated fumehood. All reactions were performed in air. K[AuCl2 (CN)2 ],[44, 28] Mn(OH2 )2 [Au(CN)2 ]2 [12] and Co(OH2 )2 [Au(CN)2 ]2 [12] were synthesized as previously reported. All other reagents were obtained from commercial sources and used as received.
15
Infrared spectra were measured on a Thermo Nicolet Nexus 670 FT-IR spectrometer equipped with a Pike MIRacle attenuated total reflection (ATR) sampling accessory (4000700 cm−1 ). Raman spectra were measured on a Renishaw inVia Raman microscope equipped with a 785 nm and a 514 nm laser (as specified). Microanalyses (C, H, N) were performed by Frank Haftbaradaran or Paul Mulyk at Simon Fraser University on a Carlo Erba EA 1110 CHN elemental analyzer. 4.2. Synthetic Procedures [ nBu4 N][AuCl2 (CN)2 ]. [ nBu4 N][AuCl2 (CN)2 ] was synthesized using a modification of a literature procedure.[25] A 10 mL aqueous solution of [ nBu4 N]NO3 (91 mg; 0.30 mmol) was added to a 10 mL colourless aqueous solution of K[AuCl2 (CN)2 ] (75 mg; 0.21 mmol), resulting in a white precipitate of [ nBu4 N][AuCl2 (CN)2 ]. The white powder was collected by vacuum filtration and air dried overnight (96 mg, 81% yield). IR (cm−1 ): 2962 (vs), 2931 (m), 2873 (s), 1485 (s), 1463 (w), 1382 (m), 1153 (w), 1107 (w), 1029 (w), 880 (m), 800 (w), 741 (m). Raman (cm−1 ; 514 nm): 2185 (s; νCN ), 1450 (w), 1324 (w), 1152 (vw), 1132 (vw), 1051 (w), 910 (w), 446 (m; νAuC ), 340 (vs; νAuCl ), 257 (w), 134 (m; δClAuC ).[28] Anal. Calcd. for C18 H36 N3 AuCl2 : C 38.44%, H 6.45%, N: 7.47%; Found: C 38.77%, H 6.48%, N 7.55%. X-ray quality crystals of [ nBu4 N][AuCl2 (CN)2 ] were obtained by slow evaporation of an EtOAc solution. [Cu(phen)2 (OHMe)][AuCl2 (CN)2 ]2 (1). A 5 mL MeOH solution of 1, 10-phenanthroline (phen; 20 mg; 0.10 mmol) was added to a 5 mL faint blue MeOH solution of Cu(ClO4 )2 · 6 H2 O (36 mg; 0.097 mmol), resulting in a light blue solution. To this, a 10 mL colourless MeOH solution of [ nBu4 N][AuCl2 (CN)2 ] (113 mg; 0.20 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After four days, turquoise plate-shaped crystals of [Cu(phen)2 (OHMe)][AuCl2 (CN)2 ]2 (1) formed and were collected by vacuum filtration (25 mg; 24% yield). IR (cm−1 ): 2232 (w; νCN ), 2200 (w; νCN ), 2176 (w; νCN ); 3070 (w), 1606 (w), 1587 (mw), 1519 (m), 1428 (s), 1229 (w), 1149 (mw), 1108 (m), 998 (m), 874 (mw), 849 (s), 785 (w), 722(s). Anal. Calcd. for C29 H20 N8 Au2 Cl4 CuO · 2 H2 O: C 30.77%, H 2.14%, N 9.90%; Found: C 30.87%, H 2.48%, N 9.96%. {Cu(Me2 phen)2 [AuCl2 (CN)2 ]}[AuCl2 (CN)2 ] (2). A 5 mL MeOH solution of 2, 9-dimethyl-1, 10-phenanthroline (Me2 phen; 19 mg; 0.091 mmol) was added to a 5 mL faint blue MeOH solution of Cu(ClO4 )2 · 6 H2 O (38 mg; 0.10 mmol), resulting in a green solution. To this, a 10 mL colourless MeOH solution of [ nBu4 N][AuCl2 (CN)2 ] (116 mg; 0.21 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After three days, green plate-shaped crystals of {Cu(Me2 phen)2 [AuCl2 (CN)2 ]}[AuCl2 (CN)2 ] (2) formed and were collected by vacuum filtration (16 mg; 16% yield). IR (cm−1 ): 2227 (w, νCN ); 1624 (w), 1597 (m), 1503 (m), 1434 (m), 1362 (w), 1298 (w), 1162 (w), 1090 (s, br), 1033 (w), 857 (m), 780(w), 727 (w). Anal. Calcd. for C32 H24 N8 Au2 Cl4 Cu: C 34.32%, H 2.16%, N 10.01%; Found: C 35.41%, H 2.33%, N 9.74%.
16
Cu(terpy)[AuCl2 (CN)2 ]2 (3). A 5 mL MeOH solution of 2, 20 ; 60 , 200 -terpyridine (terpy; 24 mg; 0.10 mmol) was added to a 5 mL faint blue MeOH solution of Cu(NO3 )2 · 3 H2 O (25 mg; 0.10 mmol), resulting in a turquoise solution. To this, a 10 mL colourless MeOH solution of [ nBu4 N][AuCl2 (CN)2 ] (115 mg; 0.21 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After one day, blue needle-shaped crystals of Cu(terpy)[AuCl2 (CN)2 ]2 (3) formed and were collected by vacuum filtration (58 mg; 62% yield). IR (cm−1 ): 2228 (w; νCN ), 2215 (w; νCN ), 2182 (w; νCN ); 3082 (w), 1598 (m), 1578 (m), 1479 (s), 1449(s), 1408 (m), 1329 (m), 1253 (w), 1164 (m), 1027 (s), 780 (vs), 732 (m). Anal. Calcd. for C19 H11 N7 Au2 Cl4 Cu: C 24.36%, H 1.18%, N 10.47%; Found: C 24.51%, H 1.30%, N 10.30%. Cu(terpy)(ClO4 )[AuCl2 (CN)2 ] (4). A 5 mL MeOH solution of 2, 20 ; 60 , 200 -terpyridine (terpy; 22 mg; 0.094 mmol) was added to a 5 mL faint blue MeOH solution of Cu(ClO4 )2 · 6 H2 O (38 mg; 0.10 mmol), resulting in a light blue solution. To this, a 10 mL colourless MeOH solution of [ nBu4 N][AuCl2 (CN)2 ] (110 mg; 0.20 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After four days, blue plate-shaped crystals of Cu(terpy)(ClO4 )[AuCl2 (CN)2 ] (4) formed and were collected by vacuum filtration (48 mg; 71% yield). IR (cm−1 ): 2239 (w; νCN ); 3093 (w), 1600 (mw), 1580 (mw), 1479 (m), 1446 (m), 1327 (mw), 1252 (w), 1092 (s), 1053 (s, br), 1025 (s), 779 (s). Anal. Calcd. for C18 H11 N5 AuCl3 CuO4 : C 28.51%, H 1.55%, N 9.78%; Found: C 28.83%, H 1.46%, N 9.89%. Cu(NCMe)2 (pyz)[AuCl2 (CN)2 ]2 · 2 MeCN (5). A 5 mL MeCN solution of pyrazine (pyz; 9 mg; 0.11 mmol) was added to a 5 mL faint blue MeCN solution of Cu(ClO4 )2 · 6 H2 O (37 mg; 0.10 mmol), resulting in a light blue suspension. The addition of 2 mL of H2 O dissolved the suspended solid, resulting in a light blue solution. To this, a 10 mL colourless MeCN solution of [ nBu4 N][AuCl2 (CN)2 ] (113 mg; 0.20 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After four days, blue needle-shaped crystals of Cu(NCMe)2 (pyz)[AuCl2 (CN)2 ]2 · 2 MeCN (5) formed. These crystals desolvate very rapidly upon removal from the mother liquor, precluding IR and elemental analyses. Rapid transfer of crystals of 5 to a coldstream facilitated single crystal X-ray analysis. {Cu(bipy)2 [Au(CN)2 ]}[AuCl2 (CN)2 ] (6). A 5 mL MeCN solution of 4, 40 -bipyridine (bipy; 16 mg; 0.10 mmol) was added to a 5 mL faint blue MeCN solution of Cu(NO3 )2 · 3 H2 O (25 mg; 0.10 mmol), resulting in a purple precipitate. The addition of 5 mL of H2 O dissolved the precipitate, resulting in a faint blue solution. To this, a 10 mL colourless MeCN solution of [ nBu4 N][AuCl2 (CN)2 ] (114 mg; 0.20 mmol) was added, which resulted in a light blue suspension. This suspension was allowed to settle overnight and was removed by vacuum filtration. The remaining faint blue filtrate was then partially covered and set aside. After one day, blue block-shaped crystals of {Cu(bipy)2 [Au(CN)2 ]}[AuCl2 (CN)2 ] (6) formed (ca. 5-10 mg; 5-10% yield). The solution was removed and the crystals were rinsed several times with clean MeCN. Raman (cm−1 ; 785 nm): 2288 (w; νCN ), 2185 (w; νCN ), 2166 (s, νCN ), 1625 (s), 1523 (m), 1298 (vs), 1244 17
(w), 1087 (w), 1036 (s), 780 (m), 658 (m), 573 (vw), 445 (w), 334 (vs), 316 (m), 153 (s). Contamination of the cyrstals with the primary light blue suspension precluded accurate IR and elemental analyses as well as an accurate determination of the yield. Mn(OH2 )4 [AuCl2 (CN)2 ]2 (7). Cl2 gas was bubbled through a 20 mL MeOH suspension of Mn(OH2 )2 [Au(CN)2 ]2 (57 mg; 0.097 mmol) for 2 min resulting in a yellow solution. N2 gas was then bubbled through this solution for 5 min to dissipate any dissolved Cl2 remaining, resulting in a colourless solution. Any remaining solid was removed by gravity filtration. A white solid of Mn(OH2 )4 [AuCl2 (CN)2 ]2 (7) was collected by rotary evaporation to dryness of the remaining filtrate (34 mg; 45% yield). IR (cm−1 ): 2221 (m, νCN ); 3468 (s, br), 1365 (mw), 1103 (w), 1006 (vs). Raman (cm−1 ; 785 nm): 2227 (m; νCN ), 2190 (mw; νCN ), 499 (m), 461 (vw), 440 (w), 369 (vw), 341 (vs), 306 (w), 177 (mw), 144 (s). Anal. Calcd. for C4 H8 N4 Au2 Cl4 MnO4 : C 6.27%, H 1.05%, N 7.31%; Found: C 6.38%, H 1.13%, N 7.02%. X-ray quality crystals of 7 were obtained by slow evaporation of a MeOH solution. Co(OH2 )4 [AuCl2 (CN)2 ]2 · 2 H2 O (8). Cl2 gas was bubbled through a 20 mL MeOH suspension of Co(OH2 )2 [Au(CN)2 ]2 (65 mg; 0.11 mmol) for 5 min resulting in a green solution. N2 gas was bubbled through this solution for 5 min to dissipate any dissolved Cl2 remaining, resulting in a green solution. Any remaining solid was removed by gravity filtration. A blue solid of Co(OH2 )4 [AuCl2 (CN)2 ]2 · 2 H2 O (8) was collected by rotary evaporation to dryness of the remaining filtrate (36 mg; 42% yield). IR (cm−1 ): 2221 (m; νCN ); 3468 (s), 1365 (w), 1103 (w), 1006 (s). Raman (cm−1 ; 785 nm): 2233 (m; νCN ), 2190 (mw; νCN ), 507 (m), 441 (w), 368 (vw), 339 (vs), 315 (mw), 201 (w), 145 (s). Anal. Calcd. for C4 H12 N4 Au2 Cl4 CoO6 : C 5.95%, H 1.50%, N 6.94%; Found: C 5.92%, H 1.30%, N 7.08%. X-ray quality crystals of 8 were obtained by slow evaporation of a MeOH solution. 4.3. X-ray Crystallographic Analysis Crystals of 1 to 4 and 6 were mounted on glass fibers using epoxy adhesive. X-ray data for these compounds was collected at room temperature. Crystals of 5 desolvate rapidly, therefore they were mounted on MiTeGen dual-thickness MicroMounts using paratone oil and the data were collected at 150 K. Crystals of 7 and 8 were also mounted on MiTeGen sample holders, however the data were collected at room temperature as it was found that these crystals do not desolvate. X-ray data were collected on a Bruker Apex II diffractometer equipped with a Mo Kα (λ = 0.71073 nm) source and an Oxford Cryosystems coldstream. Additional crystallographic information can be found in Tables 8 and 9. All diffraction data were processed with the Bruker Apex II software suite. The structures were solved with Sir92 direct methods and subsequent refinements were performed in CRYSTALS.[45] Compounds 1 and 7 crystallized as twins. Twinning was accounted for using Rotax analysis in CRYSTALS. Diagrams were made using ORTEP-3[46] and POV-ray.[47]
18
Table 8: Crystallographic data for [ nBu4 N][AuCl2 (CN)2 ] and compounds 1 to 4. empirical formula formula weight (g·mol−1 ) crystal system space group a (˚ A) b (˚ A) c (˚ A) α (deg) β (deg) γ (deg) V (˚ A3 ) Z T (K) ρcalcd (g·cm−3 ) µ (mm−1 ) R, Rw [I0 ≥ 2.50σ(I0 )]a goodness of fit reflections [I0 ≥ 2.50σ(I0 )] a
[ nBu4 N][AuCl2 (CN)2 ] C18 H36 AuCl2 N3 562.38 monoclinic P 21 /n 14.672(2) 8.9189(14) 198.432(3) 90 109.062(2) 90 2403.4(6) 4 296(2) 1.554 6.348 0.0322, 0.0307 1.1218 2737
1 C29 H20 Au2 Cl4 CuN8 O 1095.82 monoclinic C 2/c 23.2596(9) 7.8186(3) 17.9766(3) 90 96.244(3) 90 3249.8(2) 4 296(2) 2.240 10.022 0.0601, 0.0830 1.0239 2194
2 C32 H24 Au2 Cl4 CuN8 1119.89 triclinic P ¯ 1 10.2610(8) 10.7330(9) 17.0463(14) 96.691(5) 104.985(5) 105.427(5) 1713.2(3) 2 296(2) 2.171 9.506 0.0348, 0.0293 1.0722 5365
3 C19 H11 Au2 Cl4 CuN7 936.63 monoclinic P 21 /c 7.6389(2) 15.9784(5) 20.5561(6) 90 94.064(2) 90 2502.72(13) 4 296(2) 2.486 12.987 0.0269, 0.0319 0.9640 3863
4 C17 H15 AuCl3 CuN5 O4 720.21 orthorhombic P n m a 21.7786(18) 6.9551(6) 14.5185(14) 90 90 90 2199.2(3) 4 296(2) 2.175 8.030 0.0340, 0.0385 1.1889 1492
Function minimized: Σw(|Fo | − |Fc |)2 , where w−1 = [σ 2 (Fo ) + (n · P )2 + m · P ], with n = 0.02, m = 0 for [ nBu4 N][AuCl2 (CN)2 ], 3 and 4, n = 0, m = 0.6 for 1 and n = 0.01, m = 0 for 2, and where P = 1 (Fo + 2Fc ). R = Σ||Fo | − |Fc ||/Σ|Fo | and 3 1
Rw = [Σw(|Fo | − |Fc |)2 /Σw|Fo |2 ] 2 .
Table 9: Crystallographic data for compounds 5 to 8. empirical formula formula weight (g·mol−1 ) crystal system space group a (˚ A) b (˚ A) c (˚ A) α (deg) β (deg) γ (deg) V (˚ A3 ) Z T (K) ρcalcd (g·cm−3 ) µ (mm−1 ) R, Rw [I0 ≥ 2.50σ(I0 )]a goodness of fit reflections [I0 ≥ 2.50σ(I0 )] a
5 C16 H16 Au2 Cl4 CuN10 947.66 monoclinic C 2/m 19.2613(6) 6.8059(2) 13.9284(7) 90 132.9070(10) 90 1337.38(9) 2 150(2) 2.353 12.155 0.0261, 0.0272 1.1924 2790
6 C24 H16 Au2 Cl2 CuN8 944.83 orthorhombic C m c m 15.1343(4) 16.3411(4) 11.1500(3) 90 90 90 2757.52(12) 4 296(2) 2.276 11.602 0.0280, 0.0370 1.1793 1149
7 C4 H8 Au2 Cl4 MnN4 O4 766.81 triclinic P ¯ 1 6.6722(3) 6.7949(3) 9.6371(4) 70.780(2) 87.154(2) 89.710(2) 412.03(3) 1 296(2) 3.058 19.170 0.0426, 0.0618 1.0835 2815
8 C4 H12 Au2 Cl4 CoN4 O6 806.84 triclinic P ¯ 1 5.2333(2) 9.2120(3) 9.4271(3) 83.557(2) 85.408(2) 89.333(2) 450.15(3) 1 296(2) 2.961 17.782 0.0267, 0.0334 1.0195 2261
Function minimized: Σw(|Fo | − |Fc |)2 , where w−1 = [σ 2 (Fo ) + (n · P )2 + m · P ], with n = 0.01, m = 0 for 5, n = 0.01, m = 0.7 for 6, n = 0.05, 1 m = 0 for 7 and n = 0.02, m = 0 for 8, and where P = 1 (Fo + 2Fc ). R = Σ||Fo | − |Fc ||/Σ|Fo | and Rw = [Σw(|Fo | − |Fc |)2 /Σw|Fo |2 ] 2 . 3
5. acknowledgement The authors thank NSERC of Canada for financial support. JSO is grateful to NSERC for a PGS-D doctoral scholarship and to Natural Resources Canada for an internship. References [1] S. R. Batten, S. M. Neville, D. R. Turner, Coordination Polymers: Design, Analysis and Applications, Royal Society of Chemistry, London, UK, 2009. [2] L. R. MacGillivray, Metal-Organic Frameworks: Design and Application, Wiley, New Jersey, USA, 2010. [3] M.-C. Hong, Chen, Design and Construction of Coordination Polymers, Wiley, Hoboken, USA, 2009. [4] A. Laguna (Ed.), Modern Supramolecular Gold Chemistry, Wiley-VCH, Weinheim, 2008.
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Highlights: Eight new [AuCl2(CN)2]–‐based materials were synthesized and structurally characterized Structures included 4 new ionic and molecular species and 4 new coordination polymers Co(OH2)4[AuCl2(CN)2]2 2H2O is the first coordination polymer with the [AuCl2(CN)2]– building block A rare AuI AuIII interaction of 3.4530(10) Å was observed in one case
S0020-1693(13)00051-0 http://dx.doi.org/10.1016/j.ica.2013.02.011 ICA 15330
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Inorganica Chimica Acta
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21 November 2012 1 February 2013
Please cite this article as: J.S. Ovens, K.N. Truong, D.B. Leznoff, Targeting [AuCl2(CN)2]- Units as Halophilic Building Blocks in Coordination Polymers, Inorganica Chimica Acta (2013), doi: http://dx.doi.org/10.1016/j.ica. 2013.02.011
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Targeting [AuCl2(CN)2] – Units as Halophilic Building Blocks in Coordination Polymers Jeffrey S. Ovens, Kimberley N. Truong, Daniel B. Leznoff∗ Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
Abstract Several new [AuCl2 (CN)2 ] – -containing complexes were synthesized with a range of ancillary ligands and first row transition metals. Use of Cu(II) and 1, 10-phenanthroline (phen) and 2, 9-dimethyl-1, 10-phenanthroline (Me2 phen) with [ nBu4 N][AuCl2 (CN)2 ] yielded the ionic compounds [Cu(phen)2 (OHMe)][AuCl2 (CN)2 ]2 (1) and {Cu(Me2 phen)2 [AuCl2 (CN)2 ]}[AuCl2 (CN)2 ] (2). Use of 2, 20 ; 60 , 200 -terpyridine (terpy) and Cu(NO3 )2 · 3 H2 O or Cu(ClO4 )2 · 6 H2 O instead yielded Cu(terpy)[AuCl2 (CN)2 ]2 (3) and Cu(terpy)(µ−ClO4 )[AuCl2 (CN)2 ] (4), respectively. Compound 3 is molecular, with a single terpy ligand and two pendant [AuCl2 (CN)2 ] – units bound to a Cu(II) centre, whereas 4 is a linear 1-D coordination polymer consisting of Cu(II) centres bridged by ClO4– moieties. Using Cu(II) and pyrazine (pyz) generates a 1-D coordination polymer, Cu(pyz)(NCMe)2 [AuCl2 (CN)2 ]2 · 2 MeCN (5) with bridging pyz units and pendant [AuCl2 (CN)2 ] – and NCMe moieties. Upon switching to 4, 40 -bipyridine (bipy), the 3-D coordination polymer, {Cu(bipy)2 [Au(CN)2 ]}[AuCl2 (CN)2 ] (6) results, which is built up of sheets of Cu(II)/bipy units bridged by [Au(CN)2 ] – . Free [AuCl2 (CN)2 ] – anions sit in the network cavities, held by a rare, unsupported Au I ···Au III interaction of 3.4530(10) ˚ A. The in– ability of [AuCl2 (CN)2 ] to act as a bridging unit in any of these ancillary ligand-containing structures is consistent with the behaviour of [AuBr2 (CN)2 ] – in previous studies and shows that [AuCl2 (CN)2 ] – holds no advantages over [AuBr2 (CN)2 ] – in coordination polymer formation. In the absence of ancillary ligands, molecular Mn(OH2 )4 [AuCl2 (CN)2 ]2 (7) and the 1-D coordination polymer Co(OH2 )4 [AuCl2 (CN)2 ] · 2 H2 O (8), the first coordination polymer with [AuCl2 (CN)2 ] – as the primary bridging moiety, were also prepared and structurally characterized. 1. Introduction Coordination polymers have become an increasingly important class of materials due to the ability to rationally design them through the strategic choice of metals, building blocks (bridging moieties) and ancillary ligands.[1, 2, 3, 4, 5, 6, 7] Gold-containing cyanometallate species, specifically linear d10 [Au(CN)2 ] – and square planar d8 [Au(CN)4 ] – have been used in a range of coordination polymer structures with potentially useful properties such as ∗
To whom all correspondence should be addressed. Email address: [email protected] (Daniel B. Leznoff)
Preprint submitted to Inorganica Chimica Acta
February 18, 2013
magnetism,[8, 9, 10, 11, 12, 13] birefringence,[14, 15, 16] and vapochromism.[17, 18, 19, 20, 21] The halophilic [AuBr2 (CN)2 ] – was recently shown to enhance birefringent properties[14] as a result of the polarizable Au–Br bonds, and its propensity to form intermolecular Br···Br interactions that help to align structural units. However, these studies also found that [AuBr2 (CN)2 ] – was weakly Lewis basic, and as a result, it did not readily bridge metals to form coordination polymers, especially when paired with competing chelating ancillary ligands. In this context we investigated the related [AuCl2 (CN)2 ] – unit in terms of its ability to form coordination polymers and the impact of potential Cl···Cl interactions[22, 23] on the resulting structures as a comparison with the Br-analogue. The results, which include the first molecules and coordination polymers incorporating [AuCl2 (CN)2 ] – are reported herein. 2. Results and Discussion 2.1. Structure of [ nBu4 N][AuCl2 (CN)2 ]. The crystal structure of K[AuCl2 (CN)2 ] has been previously described as having separated K+ cations and [AuCl2 (CN)2 ] – ions, with N(cyano) moieties interacting with the K+ cations.[24] Substitution of the K+ cations in K[AuCl2 (CN)2 ] for nBu4 N+ cations resulted in [ nBu4 N][AuCl2 (CN)2 ];[25] the structure also shows separated cations and anions with no Cl···Cl or Au···Cl interactions present (Fig. 1). The [AuCl2 (CN)2 ] – anion features standard Au–Cl and Au–C bonds of 2.284(2)-2.289(2) ˚ A and 2.008(7)-2.038(8) ˚ A, respectively.[14, 24] Typically, νCN stretches in the IR spectrum of cyanoaurate(III) compounds are very weak when compared to those of cyanoaurate(I) compounds.[26, 27, 28] In this case, the IR spectrum of [ nBu4 N][AuCl2 (CN)2 ] is completely devoid of νCN signals – presumably, they are too weak. Therefore, the Raman spectrum was recorded for [ nBu4 N][AuCl2 (CN)2 ] as a comparison to that reported for K[AuCl2 (CN)2 ][28] to confirm the identity of the product. Indeed, the νCN , νAuCl and νAuC stretches are present in spectra for both salts indicating that the [AuCl2 (CN)2 ] – anion is present in both materials. Although the latter two of these signals do not differ significantly as a function of cation, the νCN stretch in [ nBu4 N][AuCl2 (CN)2 ] is red-shifted from 2199 cm−1 for K[AuCl2 (CN)2 ] to 2185 cm−1 for [ nBu4 N][AuCl2 (CN)2 ], consistent with the replacement of K+ cations, which tend to interact with the N(cyano) moieties, for non-bonding nBu4 N+ cations.[24] N(cyano) binding to a Lewis acidic site tends to blue-shift the νCN band.[29] 2.2. Structures of salts with at least one unbound [AuCl2 (CN)2 ] – anion. The addition of [ nBu4 N][AuCl2 (CN)2 ] to a solution of Cu(ClO4 )2 · 6 H2 O and one equivalent of 1, 10-phenanthroline (phen) in MeOH yielded crystals of the salt [Cu(phen)2 (OHMe)][AuCl2 (CN)2 ]2 (1). Single crystal X-ray diffraction revealed an ionic network consisting of [Cu(phen)2 (OHMe)2 ] 2+ cations and unbound [AuCl2 (CN)2 ] – anions (Fig. 2(a)), arranged in alternating layers perpendicular to the a-axis. The Cu(II) centre displays a distorted trigonal bipyramidal geometry with axial Cu–N(phen) distances of 2.001(15) ˚ A, equatorial ˚ Cu–N(phen) distances of 2.074(16) A and an equatorial Cu–O(MeOH) distance of 2.04(3) ˚ A (Table 1).[14] Although there are no Cl···Cl analogous to the Br···Br interactions found in similar [AuBr2 (CN)2 ] – structures (the shortest Cl···Cl contact is 3.724(18) ˚ A, c.f. sum of van der Waals radii of 3.50 ˚ A for two Cl atoms[30]),[14, 31, 24] chains of [AuCl2 (CN)2 ] – 2
Figure 1: Crystal structure of [ nBu4 N][AuCl2 (CN)2 ] (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; N, blue.
units do interact via Au···Cl interactions of 3.348(6) ˚ A (c.f. sum of van der Waals radii of ˚ 3.41 A for Au and Cl[30]) as shown in Fig. 2(b). Between the layers of anions and cations are hydrogen bonds of 2.72(3) ˚ A between the cyano group of the [AuCl2 (CN)2 ] – units and the hydroxy group on the MeOH moiety. These Au···Cl interactions can be compared with similar intermolecular Au–NC interactions in aggregates of [Au(CN)4 ] – where this weak contact was shown to be chemically significant by observing 15N MAS NMR shifts.[32] In order to restrict phen from binding to Cu(II), and thus encourage [AuCl2 (CN)2 ] – coordination, the phen ligands were replaced by 2, 9-dimethyl-1, 10-phenanthroline (Me2 phen), and the synthesis repeated, but this resulted in {Cu(Me2 phen)2 [AuCl2 (CN)2 ]}[AuCl2 (CN)2 ] (2). As with 1, 2 is an ionic salt consisting of Cu(II)-based cations and [AuCl2 (CN)2 ] – anions (Fig. 3(a)), but one set of [AuCl2 (CN)2 ] – anions is bound pendant to the Cu(II) centre in place of the MeOH moiety. The geometry of the Cu(II) centre is again a distorted trigonal bipyramid with standard bond lengths and angles as listed in Table 2. A similar type of layered motif (Fig. 3(b)) is also observed; between cationic layers are groups of three [AuCl2 (CN)2 ] – units (including those bound to the Cu(II) centre) held together by Au···Cl interactions of 3.2604(19) ˚ A and 3.3674(19) ˚ A. Again, there are no Cl···Cl interactions present. For both 1 and 2, despite adding only one equivalent of phen or Me2 phen, the Cu(II) centre accepted two chelating ligands, as was observed for the previously reported Cu/[AuBr2 (CN)2 ] – analogues, where the metal centre was in most cases saturated by the chelating ligand, leaving no open sites for [AuBr2 (CN)2 ] – coordination.[14] 2.3. Structures of coordination complexes and polymers incorporating only bound [AuCl2 (CN)2 ] – . In order to target Cu(II) centres with 3 coordinated donor sites rather than 4 (as in 1 and 2), 2, 20 ; 60 , 200 -terpyridine (terpy) was used as an ancillary ligand. Thus, upon mixing of MeOH solutions of Cu(NO3 )2 · 3 H2 O, terpy and [ nBu4 N][AuCl2 (CN)2 ], crystals of Cu(terpy)[AuCl2 (CN)2 ]2 (3) were generated. Isostructural to the previously reported Cu(terpy)[AuBr2 (CN)2 ]2 ,[14] the Cu(II) centre features a trigonal bipyramidal geometry (Fig. 4), as in 1 and 2. However, in this case 3 is molecular rather than ionic, with two
3
(a)
(b) Figure 2: a) Crystal structure of 1 (H atoms removed for clarity). The hydrogen bond between the MeOH and [AuCl2 (CN)2 ] – units is shown as a dotted line. b) Extended structure produced by Au···Cl interactions (shown as dashed lines). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue; O, red.
equivalents of [AuCl2 (CN)2 ] – bound pendant to the Cu(II) centre. Relevant bond lengths and angles can be found in Table 3. No significant intermolecular interactions are present. Using Cu(ClO4 )2 · 6 H2 O instead of Cu(NO3 )2 · 3 H2 O as a starting salt, Cu(terpy)(ClO4 )[AuCl2 (CN)2 ] (4) was formed. As shown in Fig. 5(a), 4 consists of {Cu(terpy)[AuCl2 (CN)2 ]}+ units bridged together via axial η 2 −µ−ClO4– anions (Cu–O distances of 2.390(6) ˚ A), resulting in an overall octahedral geometry about the Cu(II) centre (Fig. 5(b)) and a 1-D coordination polymer superstructure. Relevant bond lengths and angles can be found in Table 4. Presumably the lower solubility of the ClO4– -containing salt contributes to generating this different product of crystallization compared to 3. The bridging behaviour exhibited by the ClO4– anion in this structure is well precedented, and has been observed in many binding modes such as a single oxygen bridge or a two-oxygen bridge between metal centres. Typical Cu–O distances range from about 2.3 ˚ A to 3.0 ˚ A.[33, 34, 35, 36, 37] Previous studies on the analogous [AuBr2 (CN)2 ] – building block showed that when paired with other bridging units such as pyrazine (pyz) and 4, 40 -bipyridine (bipy), coordination polymers that also incorporated the Au(III) unit could result. In order to compare with the [AuBr2 (CN)2 ] – results, Cu(ClO4 )2 · 6 H2 O, pyz and [ nBu4 N][AuCl2 (CN)2 ] were mixed in a 1:1:2 ratio in a MeCN solution, resulting in crystals of Cu(pyz)(NCMe)2 [AuCl2 (CN)2 ]2 · 2 MeCN (5). X-ray diffraction reveals that 5 is a 1-D coordination polymer linearly bridged by equatorial
4
Table 1: Selected bond lengths and angles in 1a .
Bond Lengths (˚ A) Cu(1)–N(3) 2.074(16) Cu(1)–N(4) 2.001(15) Cu(1)–O(1) 2.04(3) Au(1)–C(1) 2.01(2) Au(1)–C(2) 1.984(16) Au(1)–Cl(1) 2.276(6) Au(1)–Cl(2) 2.277(7) Au(1)· · ·Cl(1)† 3.348(6) O(1)–H(11)· · ·N(2) 2.72(3) Bond Angles (◦ ) N(3)–Cu(1)–N(4) 81.8(6) ‡ N(3)–Cu(1)–N(4) 97.3(6) N(3)–Cu(1)–N(3)‡ 109.1(8) O(1)–Cu(1)–N(3) 105.5(8) ‡ O(1)–Cu(1)–N(3) 145.4(8) O(1)–Cu(1)–N(4) 87.0(10) † Au(1)–Cl(1)· · ·Au(1) 153.3(4) a Symmetry operation: †: −x + 1/2, y + 1/2, −z + 1/2; ‡: −x, y, −z + 1/2. pyz units (Fig. 6(a)), with similar structural features to many other Cu(II)/pyz chains.[38, 39] Although two [AuCl2 (CN)2 ] – units are indeed bound to the Cu(II) centres, they are pendant and thus do not help to increase the coordination polymer dimensionality. The remaining two axial coordination sites on the octahedral Cu(II) centres are filled by MeCN units (The Cu–N distance is 2.449(4) ˚ A; Fig. 6(b)); these units readily desolvate upon removal from the MeCN solution. The 1-D chains in this structure are isostructural to the previously reported [AuBr2 (CN)2 ] – analogue, Zn(pyz)(NCMe)2 [AuBr2 (CN)2 ]2 .[31] Relevant bond lengths and angles can be found in Table 5. 2.4. A mixed-valent Au(I)/Au(III) system. When pyz is replaced by bipy in the synthetic procedure for 5, an immediate blue precipitate forms. Filtering off this (unidentified) precipitate and allowing the filtrate to slowly evaporate resulted in crystals of {Cu(bipy)2 [Au(CN)2 ]}[AuCl2 (CN)2 ] (6), which has a 3-D framework consisting of 2-D sheets of octahedral Cu(II) centres connected by equatorial bridging bipy ligands; the sheets are linked in the third dimension by axially bound, Au(I)-based [Au(CN)2 ] – units (Fig. 7(a) and Table 6). Situated inside the network spaces are one equivalent of uncoordinated [AuCl2 (CN)2 ] – and a second, interpenetrating {Cu(bipy)2 [Au(CN)2 ]}+ framework. These free [AuCl2 (CN)2 ] – units interact with the coordination polymer framework via a rare Au I ···Au III interaction between the Au(III) centre and the Au(I) centre in the [Au(CN)2 ] – bridge of 3.4530(10) ˚ A (c.f. the 3.6 ˚ A cut-off for a Au···Au interacI III tion), as shown in Fig. 7(b). Such Au ···Au interactions, when observed, are generally either found in structures which impose close proximity between Au(I) and Au(III) centres such as the 2.8874(4) ˚ A bond in [Au I (µ-2-C6 H4 PPh2 )2 Au III (CH3 )2 ][40] and the 3.061(2) ˚ A 5
Table 2: Selected bond lengths and angles in 2.
Bond Lengths (˚ A) Cu(1)–N(4) 2.037(5) Cu(1)–N(5) 1.991(5) Cu(1)–N(6) 2.181(5) Cu(1)–N(7) 2.102(5) Cu(1)–N(8) 1.998(5) Au(1)–C(1) 2.024(8) Au(2)–C(2) 2.016(8) Au(3)–C(3) 1.988(7) Au(3)–C(4) 2.010(7) Au(1)–Cl(1) 2.2183(18) Au(2)–Cl(2) 2.2770(17) Au(3)–Cl(3) 2.2804(18) Au(3)–Cl(4) 2.2777(17) Au(2)· · ·Cl(3) 3.3674(19) Au(3)· · ·Cl(1) 3.2604(19) ◦ Bond Angles ( ) N(5)–Cu(1)–N(4) 83.7(2) N(5)–Cu(1)–N(6) 80.7(2) N(5)–Cu(1)–N(7) 98.34(19) N(8)–Cu(1)–N(4) 88.9(2) N(8)–Cu(1)–N(6) 110.69(19) N(8)–Cu(1)–N(7) 81.7(2) N(4)–Cu(1)–N(6) 111.6(2) N(4)–Cu(1)–N(7) 141.5(2) N(6)–Cu(1)–N(7) 106.60(18) Au(1)–Cl(1)· · ·Au(3) 120.15(7) Au(3)–Cl(3)· · ·Au(2) 92.71(6)
6
Table 3: Selected bond lengths and angles in 3.
Bond Lengths (˚ A) Cu(1)–N(1) 2.226(6) Cu(1)–N(3) 1.976(5) Cu(1)–N(5) 2.005(4) Cu(1)–N(6) 1.925(4) Cu(1)–N(7) 2.019(5) Au(1)–C(1) 1.986(6) Au(1)–C(2) 2.000(6) Au(2)–C(3) 1.992(6) Au(2)–C(4) 1.988(6) Au(1)–Cl(1) 2.2810(17) Au(1)–Cl(2) 2.2769(16) Au(2)–Cl(3) 2.2869(18) Au(2)–Cl(4) 2.268(2) Bond Angles (◦ ) N(1)–Cu(1)–N(3) 88.1(2) N(1)–Cu(1)–N(5) 93.7(2) N(1)–Cu(1)–N(6) 107.7(2) N(1)–Cu(1)–N(7) 94.4(2) N(3)–Cu(1)–N(5) 100.6(2) N(3)–Cu(1)–N(7) 96.80(19) N(6)–Cu(1)–N(5) 80.19(18) N(6)–Cu(1)–N(7) 81.01(19)
7
Table 4: Selected bond lengths and angles in 4.
Bond Lengths (˚ A) Cu(1)–N(2) 1.944(12) Cu(1)–N(3) 2.035(9) Cu(1)–N(4) 1.895(10) Cu(1)–N(5) 2.022(9) Cu(1)–O(3) 2.390(6) Au(1)–C(1) 1.997(15) Au(1)–C(2) 2.004(14) Au(1)–Cl(1) 2.271(3) Au(1)–Cl(2) 2.282(3) Bond Angles (◦ ) O(3)–Cu(1)–N(2) 94.1(2) O(3)–Cu(1)–N(3) 81.0(2) O(3)–Cu(1)–N(4) 85.9(2) O(3)–Cu(1)–N(5) 97.61(18) N(2)–Cu(1)–N(3) 99.4(4) N(2)–Cu(1)–N(5) 99.4(4) N(4)–Cu(1)–N(3) 80.9(4) N(4)–Cu(1)–N(5) 80.4(4)
Table 5: Selected bond lengths and angles in 5a .
Bond Lengths (˚ A) Cu(1)–N(2) 1.996(3) Cu(1)–N(3) 2.010(3) Cu(1)–N(4) 2.449(4) Au(1)–C(1) 1.981(4) Au(1)–C(2) 2.009(4) Au(1)–Cl(1) 2.2888(10) Au(1)–Cl(2) 2.2763(11) † Au(1)· · ·Cl(1) 3.44861(18) Bond Angles (◦ ) N(2)–Cu(1)–N(4) 94.50(15) ‡ N(2)–Cu(1)–N(4) 85.50(15) † Au(1)–Cl(1)· · ·Cl(1) 87.086(17) a Symmetry operation: †: −x + 1/2, −y + 1/2, −z; ‡: −x, −y, −z.
8
(a)
(b) Figure 3: a) Crystal structure of 2 (H atoms removed for clarity). b) Extended structure produced by Au···Cl interactions (interactions shown as dashed lines; aromatic systems belonging to Me2 phen ligands removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue.
bond in [Au(CH2 )2 PPh2 ]Br2 ,[41] or where the Au(I) and Au(III) centres belong to attractive cation and anion pairs such as the 3.54-3.73 ˚ A contacts in [AuCl(bis(2-pyridylmethyl)˚ amine)]PF6 and the 3.34 A interaction in [AuCl(bis(2-pyridylmethyl)-amine)][AuCl2 ].[42] Unlike these examples, the charges of the Au(I) and Au(III)-containing moieties in 6 are of the same sign, and not connected by any kind of ’support’ ligand. Few examples of this type of Au I ···Au III interaction have been observed. In the case of the recently reported K5 [Au(CN)2 ]4 [AuI2 (CN)2 ] · 2 H2 O, an unsupported Au I ···Au III interaction of 3.5697(5) ˚ A – – was observed, linking [Au(CN)2 ] and [AuI2 (CN)2 ] anions together in the solid state structure. The Au I ···Au III interaction seen in 6 is significantly shorter. What is the source of the [Au(CN)2 ] – units? We have recently reported the thermally induced reductive elimination of Br2 from [AuBr2 (CN)2 ] – at elevated temperatures. This reduction process is clearly operative here too (perhaps induced photochemically),[43] bringing 9
Figure 4: Crystal structure of 3 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue.
(a)
(b) Figure 5: a) Supramolecular 1-D, ClO4– -bridged chains of 4. b) Close-up view of 4 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue; O, red.
Au(III)-based [AuCl2 (CN)2 ] – to Au(I)-based [Au(CN)2 ] – in situ; the fact that this reaction 10
(a)
(b) Figure 6: a) Supramolecular 1-D, pyrazine-bridged chains of 5. b) Close-up view of 5 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue.
is non-negligible even at room temperature for the chloro-analogue suggests that it is relatively unstable as compared with [AuBr2 (CN)2 ] – . Upon generation, [Au(CN)2 ] – , which is a much stronger Lewis-base than most Au(III)-based cyanoaurates, then preferentially binds to the Cu(II) centres, generating the insoluble material 6, which effectively traps this mixed Au(I)/Au(III) product. 2.5. Structures of [AuCl2 (CN)2 ] – -based coordination complexes and polymers without ancillary ligands. The above results demonstrated that [AuCl2 (CN)2 ] – is a weak Lewis base which cannot effectively compete with ancillary heterocyclic amine ligands. In order to encourage [AuCl2 (CN)2 ] – -based coordination polymer formation, ancillary ligand-free reactions were targeted. To start, the previously reported Au(I)-based coordination polymers M(OH2 )2 [Au(CN)2 ]2 (M = Mn, Co)[11, 12] were synthesized as in situ precursors. Cl2 gas was then bubbled through a suspension of the Au(I)-containing materials in MeOH, generating [AuCl2 (CN)2 ] – in situ by oxidative addition of Cl2 to the Au(I) centres. As a result, M(OH2 )4 [AuCl2 (CN)2 ]2 · xH2 O products were formed. Crystallographic examination of the Mn-analogue, Mn(OH2 )4 [AuCl2 (CN)2 ]2 (7), reveals a molecular species (Fig. 8) despite the absence of added ancillary ligands; however the [AuCl2 (CN)2 ] – units are both bound to the Mn(II) centre. The structure consists of an octahedral Mn(II) center bound equatorially by aqua ligands and by axial trans-[AuCl2 (CN)2 ] – units. The molecules interact primarily through intermolecular hydrogen bonds 11
(a)
(b) Figure 7: a) Supramolecular 3-D network of 6 bridged in two dimensions by 4, 40 -bipyridine and in the other by [Au(CN)2 ] – . b) One cage section of 6 showing the interactions between [AuCl2 (CN)2 ] – and [Au(CN)2 ] – units (H atoms and interpenetrated structure removed for clarity). Au, gold; C, gray; Cl, lt. green; Cu, lt. blue; N, blue.
between the aqua ligands and the N(cyano) atoms, and Au···Cl interactions of 3.391(3)3.509(3) ˚ A. When Co(OH2 )2 [Au(CN)2 ]2 undergoes the conversion to an Au(III)-based material, Co(OH2 )4 [AuCl2 (CN)2 ]2 · 2 H2 O (8) is formed (Fig. 9). Compound 8 is a 1-D linear coordination polymer bridged by one equivalent of [AuCl2 (CN)2 ] – units, thus representing the first coordination polymer with [AuCl2 (CN)2 ] – as the bridging moiety. To the Co(II) centers are also bound four equatorial aqua ligands (Fig. 9(b)). These 1-D chains are then linked together via hydrogen bonding to the N(cyano) groups of free [AuCl2 (CN)2 ] – units located between the chains (Table 7). This structure resembles the analogous [Au(CN)4 ] – -containing M(OH2 )4 [Au(CN)4 ]2 · 4 H2 O (M = Mn, Co, Ni, Cu, Zn) systems,[13] which form 1-D linear 12
Table 6: Selected bond lengths and angles in 6a .
˚) Bond Lengths (A Cu(1)–N(1) 2.464(10) Cu(1)–N(4) 2.026(8) † Cu(1)–N(5) 2.043(8) Au(1)–C(1) 1.972(12) Au(3)–C(3) 2.02(2) Au(3)–Cl(3) 2.309(6) Au(1)· · ·Au(3) 3.4530(10) Bond Angles (◦ ) N(1)–Cu(1)–N(4) 88.98(16) † N(1)–Cu(1)–N(5) 91.04(16) N(4)–Cu(1)–N(5)‡ 90.5(3) N(4)–Cu(1)–N(4)∗ 90.8(4) N(5)0 –Cu(1)–N(5)‡ 88.2(4) a Symmetry operation: †: x + 1/2, y + 1/2, z, ‡: −x + 1/2, y + 1/2, z, ∗: −x, y, z.
Figure 8: Crystal structure of 7 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Mn, lt. purple; N, blue; O, red.
chains of [M(OH2 )4 ] 2+ centres bridged by [Au(CN)4 ] – (analogous to 8), connected by weak interactions such as hydrogen bonding and Au···NC interactions between the chains and unbound [Au(CN)4 ] – units. 3. Conclusions In this study, the ability of [AuCl2 (CN)2 ] – to form coordination polymers when combined with some first row transition metals and with or without a variety of heterocyclic amine ancillary ligands was investigated, and compared to the analogous [AuBr2 (CN)2 ] – . In the presence of ancillary ligands, most complexes formed contained metal centres nearly saturated by the ancillary ligand, leaving little or no room for the [AuCl2 (CN)2 ] – units to bind. In the cases where [AuCl2 (CN)2 ] – was able to bind, it was not in a bridging fashion. This clearly demonstrates the weak Lewis basicity of the N(cyano) groups on the [AuCl2 (CN)2 ] – units, thereby imparting no significant advantage over [AuBr2 (CN)2 ] – as a primary bridging unit in coordination polymer formation. In the case of 6, the in situ generation of [Au(CN)2 ] – units, likely via reductive elimination of Cl2 from [AuCl2 (CN)2 ] – indicates that [AuCl2 (CN)2 ] – is unstable in solution as compared to [AuBr2 (CN)2 ] – . A Au I ···Au III interaction in 6, especially unusual in that it occurs between anionic fragments, is particularly noteworthy. 13
Table 7: Selected bond lengths and angles in 7 and 8a .
7 (M = Mn) Bond Lengths (˚ A) M(1)–N(1) 2.161(7) M(1)–O(1) 2.131(7) M(1)–O(2) 2.199(9) Au(1)–C(1) 1.983(7) Au(1)–C(2) 2.005(8) Au(2)–C(2) – Au(1)–Cl(1) 2.286(2) Au(1)–Cl(2) 2.273(2) Au(2)–Cl(2) – † Au(1)· · ·Cl(1) 3.391(3), 3.509(3) Au(2)· · ·Cl(1) – O(2)–H(21)· · ·N(2)‡ – Bond Angles (◦ ) O(1)–M(1)–N(1) 89.8(3) O(2)–M(1)–N(1) 85.7(3) O(1)–M(1)–O(2) 88.3(4) O(1)–M(1)–O(2)† 91.7(4) Au(1)–Cl(1)· · ·Au(1)† 88.87(8), 84.21(8) Au(1)–Cl(1)· · ·Au(2) – a Symmetry operation: †: −x, −y, −z;
14
8 (M = Co) 2.083(4) 2.147(4) 2.032(4) 1.999(5) – 2.009(6) 2.2843(18) – 2.2828(17) – 3.4824(16) 2.815(8) 87.32(16) 89.23(16) 90.27(16) 89.73(16) – 104.4(2) ‡: x, y, z.
(a)
(b) Figure 9: a) 3-D network of 8 showing 1-D, [AuCl2 (CN)2 ] – -bridged, chains linked together by uncoordinated [AuCl2 (CN)2 ] – units via hydrogen bonds (shown as dashed lines). b) Close-up view of 8 (H atoms removed for clarity). Au, gold; C, gray; Cl, lt. green; Co, dk. blue; N, blue; O, red.
When the ancillary ligands were eliminated, binding of the [AuCl2 (CN)2 ] – units occurred much more easily, as evidenced by the formation of 7 and 8. Specifically, 8 is the first coordination polymer reported with [AuCl2 (CN)2 ] – as the primary bridging unit, which clearly shows the impact of removing competing ligands from the reaction mixture. Despite this, however, 7 crystallized as a molecular species, suggesting that the energy difference between the two structural motifs is quite small. In many compounds containing [AuBr2 (CN)2 ] – (ionic, molecular and coordination polymer alike), Br···Br interactions played an important structural role. In contrast, halophilic Cl···Cl interactions are not observed in any of 1-8. Instead, the structural outcome and dimensionality is more significantly affected by intermolecular Au···Cl interactions. Overall, considering its weak Lewis basicity and propensity to form only weak intermolecular interactions, the anion [AuCl2 (CN)2 ] – is in practice very similar in behaviour to its counterpart [AuBr2 (CN)2 ] – . 4. Experimental 4.1. General Procedures Caution! Perchlorate salts are potentially explosive and are powerful oxidants. Although no difficulties have been experienced, they should be handled with care. Chlorine should only be used in a well-ventilated fumehood. All reactions were performed in air. K[AuCl2 (CN)2 ],[44, 28] Mn(OH2 )2 [Au(CN)2 ]2 [12] and Co(OH2 )2 [Au(CN)2 ]2 [12] were synthesized as previously reported. All other reagents were obtained from commercial sources and used as received.
15
Infrared spectra were measured on a Thermo Nicolet Nexus 670 FT-IR spectrometer equipped with a Pike MIRacle attenuated total reflection (ATR) sampling accessory (4000700 cm−1 ). Raman spectra were measured on a Renishaw inVia Raman microscope equipped with a 785 nm and a 514 nm laser (as specified). Microanalyses (C, H, N) were performed by Frank Haftbaradaran or Paul Mulyk at Simon Fraser University on a Carlo Erba EA 1110 CHN elemental analyzer. 4.2. Synthetic Procedures [ nBu4 N][AuCl2 (CN)2 ]. [ nBu4 N][AuCl2 (CN)2 ] was synthesized using a modification of a literature procedure.[25] A 10 mL aqueous solution of [ nBu4 N]NO3 (91 mg; 0.30 mmol) was added to a 10 mL colourless aqueous solution of K[AuCl2 (CN)2 ] (75 mg; 0.21 mmol), resulting in a white precipitate of [ nBu4 N][AuCl2 (CN)2 ]. The white powder was collected by vacuum filtration and air dried overnight (96 mg, 81% yield). IR (cm−1 ): 2962 (vs), 2931 (m), 2873 (s), 1485 (s), 1463 (w), 1382 (m), 1153 (w), 1107 (w), 1029 (w), 880 (m), 800 (w), 741 (m). Raman (cm−1 ; 514 nm): 2185 (s; νCN ), 1450 (w), 1324 (w), 1152 (vw), 1132 (vw), 1051 (w), 910 (w), 446 (m; νAuC ), 340 (vs; νAuCl ), 257 (w), 134 (m; δClAuC ).[28] Anal. Calcd. for C18 H36 N3 AuCl2 : C 38.44%, H 6.45%, N: 7.47%; Found: C 38.77%, H 6.48%, N 7.55%. X-ray quality crystals of [ nBu4 N][AuCl2 (CN)2 ] were obtained by slow evaporation of an EtOAc solution. [Cu(phen)2 (OHMe)][AuCl2 (CN)2 ]2 (1). A 5 mL MeOH solution of 1, 10-phenanthroline (phen; 20 mg; 0.10 mmol) was added to a 5 mL faint blue MeOH solution of Cu(ClO4 )2 · 6 H2 O (36 mg; 0.097 mmol), resulting in a light blue solution. To this, a 10 mL colourless MeOH solution of [ nBu4 N][AuCl2 (CN)2 ] (113 mg; 0.20 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After four days, turquoise plate-shaped crystals of [Cu(phen)2 (OHMe)][AuCl2 (CN)2 ]2 (1) formed and were collected by vacuum filtration (25 mg; 24% yield). IR (cm−1 ): 2232 (w; νCN ), 2200 (w; νCN ), 2176 (w; νCN ); 3070 (w), 1606 (w), 1587 (mw), 1519 (m), 1428 (s), 1229 (w), 1149 (mw), 1108 (m), 998 (m), 874 (mw), 849 (s), 785 (w), 722(s). Anal. Calcd. for C29 H20 N8 Au2 Cl4 CuO · 2 H2 O: C 30.77%, H 2.14%, N 9.90%; Found: C 30.87%, H 2.48%, N 9.96%. {Cu(Me2 phen)2 [AuCl2 (CN)2 ]}[AuCl2 (CN)2 ] (2). A 5 mL MeOH solution of 2, 9-dimethyl-1, 10-phenanthroline (Me2 phen; 19 mg; 0.091 mmol) was added to a 5 mL faint blue MeOH solution of Cu(ClO4 )2 · 6 H2 O (38 mg; 0.10 mmol), resulting in a green solution. To this, a 10 mL colourless MeOH solution of [ nBu4 N][AuCl2 (CN)2 ] (116 mg; 0.21 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After three days, green plate-shaped crystals of {Cu(Me2 phen)2 [AuCl2 (CN)2 ]}[AuCl2 (CN)2 ] (2) formed and were collected by vacuum filtration (16 mg; 16% yield). IR (cm−1 ): 2227 (w, νCN ); 1624 (w), 1597 (m), 1503 (m), 1434 (m), 1362 (w), 1298 (w), 1162 (w), 1090 (s, br), 1033 (w), 857 (m), 780(w), 727 (w). Anal. Calcd. for C32 H24 N8 Au2 Cl4 Cu: C 34.32%, H 2.16%, N 10.01%; Found: C 35.41%, H 2.33%, N 9.74%.
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Cu(terpy)[AuCl2 (CN)2 ]2 (3). A 5 mL MeOH solution of 2, 20 ; 60 , 200 -terpyridine (terpy; 24 mg; 0.10 mmol) was added to a 5 mL faint blue MeOH solution of Cu(NO3 )2 · 3 H2 O (25 mg; 0.10 mmol), resulting in a turquoise solution. To this, a 10 mL colourless MeOH solution of [ nBu4 N][AuCl2 (CN)2 ] (115 mg; 0.21 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After one day, blue needle-shaped crystals of Cu(terpy)[AuCl2 (CN)2 ]2 (3) formed and were collected by vacuum filtration (58 mg; 62% yield). IR (cm−1 ): 2228 (w; νCN ), 2215 (w; νCN ), 2182 (w; νCN ); 3082 (w), 1598 (m), 1578 (m), 1479 (s), 1449(s), 1408 (m), 1329 (m), 1253 (w), 1164 (m), 1027 (s), 780 (vs), 732 (m). Anal. Calcd. for C19 H11 N7 Au2 Cl4 Cu: C 24.36%, H 1.18%, N 10.47%; Found: C 24.51%, H 1.30%, N 10.30%. Cu(terpy)(ClO4 )[AuCl2 (CN)2 ] (4). A 5 mL MeOH solution of 2, 20 ; 60 , 200 -terpyridine (terpy; 22 mg; 0.094 mmol) was added to a 5 mL faint blue MeOH solution of Cu(ClO4 )2 · 6 H2 O (38 mg; 0.10 mmol), resulting in a light blue solution. To this, a 10 mL colourless MeOH solution of [ nBu4 N][AuCl2 (CN)2 ] (110 mg; 0.20 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After four days, blue plate-shaped crystals of Cu(terpy)(ClO4 )[AuCl2 (CN)2 ] (4) formed and were collected by vacuum filtration (48 mg; 71% yield). IR (cm−1 ): 2239 (w; νCN ); 3093 (w), 1600 (mw), 1580 (mw), 1479 (m), 1446 (m), 1327 (mw), 1252 (w), 1092 (s), 1053 (s, br), 1025 (s), 779 (s). Anal. Calcd. for C18 H11 N5 AuCl3 CuO4 : C 28.51%, H 1.55%, N 9.78%; Found: C 28.83%, H 1.46%, N 9.89%. Cu(NCMe)2 (pyz)[AuCl2 (CN)2 ]2 · 2 MeCN (5). A 5 mL MeCN solution of pyrazine (pyz; 9 mg; 0.11 mmol) was added to a 5 mL faint blue MeCN solution of Cu(ClO4 )2 · 6 H2 O (37 mg; 0.10 mmol), resulting in a light blue suspension. The addition of 2 mL of H2 O dissolved the suspended solid, resulting in a light blue solution. To this, a 10 mL colourless MeCN solution of [ nBu4 N][AuCl2 (CN)2 ] (113 mg; 0.20 mmol) was added, which resulted in no discernable colour change. This solution was partially covered and set aside. After four days, blue needle-shaped crystals of Cu(NCMe)2 (pyz)[AuCl2 (CN)2 ]2 · 2 MeCN (5) formed. These crystals desolvate very rapidly upon removal from the mother liquor, precluding IR and elemental analyses. Rapid transfer of crystals of 5 to a coldstream facilitated single crystal X-ray analysis. {Cu(bipy)2 [Au(CN)2 ]}[AuCl2 (CN)2 ] (6). A 5 mL MeCN solution of 4, 40 -bipyridine (bipy; 16 mg; 0.10 mmol) was added to a 5 mL faint blue MeCN solution of Cu(NO3 )2 · 3 H2 O (25 mg; 0.10 mmol), resulting in a purple precipitate. The addition of 5 mL of H2 O dissolved the precipitate, resulting in a faint blue solution. To this, a 10 mL colourless MeCN solution of [ nBu4 N][AuCl2 (CN)2 ] (114 mg; 0.20 mmol) was added, which resulted in a light blue suspension. This suspension was allowed to settle overnight and was removed by vacuum filtration. The remaining faint blue filtrate was then partially covered and set aside. After one day, blue block-shaped crystals of {Cu(bipy)2 [Au(CN)2 ]}[AuCl2 (CN)2 ] (6) formed (ca. 5-10 mg; 5-10% yield). The solution was removed and the crystals were rinsed several times with clean MeCN. Raman (cm−1 ; 785 nm): 2288 (w; νCN ), 2185 (w; νCN ), 2166 (s, νCN ), 1625 (s), 1523 (m), 1298 (vs), 1244 17
(w), 1087 (w), 1036 (s), 780 (m), 658 (m), 573 (vw), 445 (w), 334 (vs), 316 (m), 153 (s). Contamination of the cyrstals with the primary light blue suspension precluded accurate IR and elemental analyses as well as an accurate determination of the yield. Mn(OH2 )4 [AuCl2 (CN)2 ]2 (7). Cl2 gas was bubbled through a 20 mL MeOH suspension of Mn(OH2 )2 [Au(CN)2 ]2 (57 mg; 0.097 mmol) for 2 min resulting in a yellow solution. N2 gas was then bubbled through this solution for 5 min to dissipate any dissolved Cl2 remaining, resulting in a colourless solution. Any remaining solid was removed by gravity filtration. A white solid of Mn(OH2 )4 [AuCl2 (CN)2 ]2 (7) was collected by rotary evaporation to dryness of the remaining filtrate (34 mg; 45% yield). IR (cm−1 ): 2221 (m, νCN ); 3468 (s, br), 1365 (mw), 1103 (w), 1006 (vs). Raman (cm−1 ; 785 nm): 2227 (m; νCN ), 2190 (mw; νCN ), 499 (m), 461 (vw), 440 (w), 369 (vw), 341 (vs), 306 (w), 177 (mw), 144 (s). Anal. Calcd. for C4 H8 N4 Au2 Cl4 MnO4 : C 6.27%, H 1.05%, N 7.31%; Found: C 6.38%, H 1.13%, N 7.02%. X-ray quality crystals of 7 were obtained by slow evaporation of a MeOH solution. Co(OH2 )4 [AuCl2 (CN)2 ]2 · 2 H2 O (8). Cl2 gas was bubbled through a 20 mL MeOH suspension of Co(OH2 )2 [Au(CN)2 ]2 (65 mg; 0.11 mmol) for 5 min resulting in a green solution. N2 gas was bubbled through this solution for 5 min to dissipate any dissolved Cl2 remaining, resulting in a green solution. Any remaining solid was removed by gravity filtration. A blue solid of Co(OH2 )4 [AuCl2 (CN)2 ]2 · 2 H2 O (8) was collected by rotary evaporation to dryness of the remaining filtrate (36 mg; 42% yield). IR (cm−1 ): 2221 (m; νCN ); 3468 (s), 1365 (w), 1103 (w), 1006 (s). Raman (cm−1 ; 785 nm): 2233 (m; νCN ), 2190 (mw; νCN ), 507 (m), 441 (w), 368 (vw), 339 (vs), 315 (mw), 201 (w), 145 (s). Anal. Calcd. for C4 H12 N4 Au2 Cl4 CoO6 : C 5.95%, H 1.50%, N 6.94%; Found: C 5.92%, H 1.30%, N 7.08%. X-ray quality crystals of 8 were obtained by slow evaporation of a MeOH solution. 4.3. X-ray Crystallographic Analysis Crystals of 1 to 4 and 6 were mounted on glass fibers using epoxy adhesive. X-ray data for these compounds was collected at room temperature. Crystals of 5 desolvate rapidly, therefore they were mounted on MiTeGen dual-thickness MicroMounts using paratone oil and the data were collected at 150 K. Crystals of 7 and 8 were also mounted on MiTeGen sample holders, however the data were collected at room temperature as it was found that these crystals do not desolvate. X-ray data were collected on a Bruker Apex II diffractometer equipped with a Mo Kα (λ = 0.71073 nm) source and an Oxford Cryosystems coldstream. Additional crystallographic information can be found in Tables 8 and 9. All diffraction data were processed with the Bruker Apex II software suite. The structures were solved with Sir92 direct methods and subsequent refinements were performed in CRYSTALS.[45] Compounds 1 and 7 crystallized as twins. Twinning was accounted for using Rotax analysis in CRYSTALS. Diagrams were made using ORTEP-3[46] and POV-ray.[47]
18
Table 8: Crystallographic data for [ nBu4 N][AuCl2 (CN)2 ] and compounds 1 to 4. empirical formula formula weight (g·mol−1 ) crystal system space group a (˚ A) b (˚ A) c (˚ A) α (deg) β (deg) γ (deg) V (˚ A3 ) Z T (K) ρcalcd (g·cm−3 ) µ (mm−1 ) R, Rw [I0 ≥ 2.50σ(I0 )]a goodness of fit reflections [I0 ≥ 2.50σ(I0 )] a
[ nBu4 N][AuCl2 (CN)2 ] C18 H36 AuCl2 N3 562.38 monoclinic P 21 /n 14.672(2) 8.9189(14) 198.432(3) 90 109.062(2) 90 2403.4(6) 4 296(2) 1.554 6.348 0.0322, 0.0307 1.1218 2737
1 C29 H20 Au2 Cl4 CuN8 O 1095.82 monoclinic C 2/c 23.2596(9) 7.8186(3) 17.9766(3) 90 96.244(3) 90 3249.8(2) 4 296(2) 2.240 10.022 0.0601, 0.0830 1.0239 2194
2 C32 H24 Au2 Cl4 CuN8 1119.89 triclinic P ¯ 1 10.2610(8) 10.7330(9) 17.0463(14) 96.691(5) 104.985(5) 105.427(5) 1713.2(3) 2 296(2) 2.171 9.506 0.0348, 0.0293 1.0722 5365
3 C19 H11 Au2 Cl4 CuN7 936.63 monoclinic P 21 /c 7.6389(2) 15.9784(5) 20.5561(6) 90 94.064(2) 90 2502.72(13) 4 296(2) 2.486 12.987 0.0269, 0.0319 0.9640 3863
4 C17 H15 AuCl3 CuN5 O4 720.21 orthorhombic P n m a 21.7786(18) 6.9551(6) 14.5185(14) 90 90 90 2199.2(3) 4 296(2) 2.175 8.030 0.0340, 0.0385 1.1889 1492
Function minimized: Σw(|Fo | − |Fc |)2 , where w−1 = [σ 2 (Fo ) + (n · P )2 + m · P ], with n = 0.02, m = 0 for [ nBu4 N][AuCl2 (CN)2 ], 3 and 4, n = 0, m = 0.6 for 1 and n = 0.01, m = 0 for 2, and where P = 1 (Fo + 2Fc ). R = Σ||Fo | − |Fc ||/Σ|Fo | and 3 1
Rw = [Σw(|Fo | − |Fc |)2 /Σw|Fo |2 ] 2 .
Table 9: Crystallographic data for compounds 5 to 8. empirical formula formula weight (g·mol−1 ) crystal system space group a (˚ A) b (˚ A) c (˚ A) α (deg) β (deg) γ (deg) V (˚ A3 ) Z T (K) ρcalcd (g·cm−3 ) µ (mm−1 ) R, Rw [I0 ≥ 2.50σ(I0 )]a goodness of fit reflections [I0 ≥ 2.50σ(I0 )] a
5 C16 H16 Au2 Cl4 CuN10 947.66 monoclinic C 2/m 19.2613(6) 6.8059(2) 13.9284(7) 90 132.9070(10) 90 1337.38(9) 2 150(2) 2.353 12.155 0.0261, 0.0272 1.1924 2790
6 C24 H16 Au2 Cl2 CuN8 944.83 orthorhombic C m c m 15.1343(4) 16.3411(4) 11.1500(3) 90 90 90 2757.52(12) 4 296(2) 2.276 11.602 0.0280, 0.0370 1.1793 1149
7 C4 H8 Au2 Cl4 MnN4 O4 766.81 triclinic P ¯ 1 6.6722(3) 6.7949(3) 9.6371(4) 70.780(2) 87.154(2) 89.710(2) 412.03(3) 1 296(2) 3.058 19.170 0.0426, 0.0618 1.0835 2815
8 C4 H12 Au2 Cl4 CoN4 O6 806.84 triclinic P ¯ 1 5.2333(2) 9.2120(3) 9.4271(3) 83.557(2) 85.408(2) 89.333(2) 450.15(3) 1 296(2) 2.961 17.782 0.0267, 0.0334 1.0195 2261
Function minimized: Σw(|Fo | − |Fc |)2 , where w−1 = [σ 2 (Fo ) + (n · P )2 + m · P ], with n = 0.01, m = 0 for 5, n = 0.01, m = 0.7 for 6, n = 0.05, 1 m = 0 for 7 and n = 0.02, m = 0 for 8, and where P = 1 (Fo + 2Fc ). R = Σ||Fo | − |Fc ||/Σ|Fo | and Rw = [Σw(|Fo | − |Fc |)2 /Σw|Fo |2 ] 2 . 3
5. acknowledgement The authors thank NSERC of Canada for financial support. JSO is grateful to NSERC for a PGS-D doctoral scholarship and to Natural Resources Canada for an internship. References [1] S. R. Batten, S. M. Neville, D. R. Turner, Coordination Polymers: Design, Analysis and Applications, Royal Society of Chemistry, London, UK, 2009. [2] L. R. MacGillivray, Metal-Organic Frameworks: Design and Application, Wiley, New Jersey, USA, 2010. [3] M.-C. Hong, Chen, Design and Construction of Coordination Polymers, Wiley, Hoboken, USA, 2009. [4] A. Laguna (Ed.), Modern Supramolecular Gold Chemistry, Wiley-VCH, Weinheim, 2008.
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Highlights: Eight new [AuCl2(CN)2]–‐based materials were synthesized and structurally characterized Structures included 4 new ionic and molecular species and 4 new coordination polymers Co(OH2)4[AuCl2(CN)2]2 2H2O is the first coordination polymer with the [AuCl2(CN)2]– building block A rare AuI AuIII interaction of 3.4530(10) Å was observed in one case