Article pubs.acs.org/crystal
Supramolecular Design of the Trinuclear Silver(I) and Copper(I) Metal Pyrazolates Complexes with Ruthenium Sandwich Compounds via Intermolecular Metal−π Interactions Aleksei A. Titov,†,‡ Alexander F. Smol’yakov,†,‡ Oleg A. Filippov,† Ivan A. Godovikov,† Dmitry A. Muratov,† Fedor M. Dolgushin,† Lina M. Epstein,† and Elena S. Shubina*,† †
A.N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, INEOS RAS, 119991 Moscow, Vavilova str. 28, Russia ‡ Peoples’ Friendship University of Russia, 117198, Moscow, Miklukho-Maklaya str. 6, Russia S Supporting Information *
ABSTRACT: The interaction of copper(I) and silver(I) macrocyclic pyrazolates with aromatic ligands of ruthenium sandwiches (Cp*RuInd, CpRuInd, and Ind2Ru) in solution is shown for the first time. The similar mode of coordination of macrocycles to the C6 fragment of indenyl ligand was found both in the solution and in the solid state. Complexation of macrocycles with the nonencumbered sandwiches (CpRuInd, Ind2Ru) leads to the formation of infinite stacks via alternating molecules of macrocycles and sandwich compounds as one-dimensional coordination polymers with a regular structure. Coordination mode of the indenyl ligand is independent of the second part of the ruthenium sandwich as well as of the aromatic ligand coordinated to another face of the macrocycle. The general principle of macrocycle supramolecular packing suggests coordination of two ligands on both faces of the macrocycle.
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containing alternating molecules of macrocycle and π-base ({([ML]3)(arene)}∞).16,19 Variation of crystallization conditions allows the formation of other types of packing like {([ML]3)2(arene)}, {(arene)([ML]3)(arene)}, or {(arene)([ML]3)2(arene)}.16 Nevertheless, complexes of macrocycles with aromatic hydrocarbons have never been observed in solution; moreover, some researchers doubt that they could at all exist in solution.17 On the other hand, to date, there was only one example of formation of macrocycle-π-base complex in solution. For the example of (COT)Fe(CO)3 and {[3,5-(CF3)2Pz]Ag}3, we have shown that π-ligands of organometallic compounds are able to interact with the macrocycles even in solution, and this interaction is retained in the solid state. Our group has recently studied the host−guest complexes of the macrocyclic copper(I) and silver(I) pyrazolates with a wide range of organic and organometallic bases possessing hydride, halide, carbonyl, and π-electronic ligands in solution and solid state.12,19−24 Peculiar features of crystal packing depend on the base type, the complex strength, and the presence of a secondary basic center. These results demonstrate how information on the complexes’ structure and stability in solution can be used to predict and control the supramolecular
INTRODUCTION Weak noncovalent intermolecular interactions such as hydrogen or halogen bonding, π−π stacking play a significant role in supramolecular aggregations.1 Other types of weak intermolecular forces are metal−metal or metal−π interactions. Design of complexes based on metallophilic or dipolar interactions became popular in the past decade.2−4 One of the properties of this type of compound based on its ability to have intermolecular interactions is a high affinity to small molecules of gas5 and liquids,6 making controlled formation of supramolecular systems with assigned structure important in modern coordination chemistry.7 Macrocyclic polydentate Lewis acids are known to form stable complexes with neutral and anionic bases. Such host− guest complexes with transition metal compounds, particularly with macrocyclic Lewis bases8 or metallocenes,9,10 are mainly represented by cyclic trimeric perfluoro-o-phenylenemercury as a Lewis acid. However, there are no data on macrocyclic Lewis acids interactions with sterically hindered organometallic sandwich complexes except of Cp*Fe(η5-E5) (E = P, As), where two aromatic ligands are obviously incomparable.11−13 Trinuclear d10 metal pyrazolates have shown interesting structural features forming infinite stacks due to metal···metal intermolecular interactions.14,15 Copper(I) and silver(I) macrocyclic pyrazolates form stable complexes in the solid state with compounds possessing π-electron density, e.g., with arenes.16−18 The main type of structure is again an infinite stack © 2017 American Chemical Society
Received: September 22, 2017 Revised: October 31, 2017 Published: November 2, 2017 6770
DOI: 10.1021/acs.cgd.7b01351 Cryst. Growth Des. 2017, 17, 6770−6779
Crystal Growth & Design
Article
Ruthenium complexes Ru(η5-C5H5)(η5-C9H7) and Ru(η5-C5Me5)(η5C9H7),25 Ru(η5-C9H7)226 were prepared as described in the literature. Macrocycles were prepared by the modification of the previously described method27 by using ultrasonic irradiation. Synthesis of {[3,5-(CF3)2Pz]Ag}3 (1a). Suspension of Ag2O (50 mg, 0.216 mmol) was added to the solution of 3,5-(CF3)2Pz (78.8 mg, 0.388 mmol) in 10 mL of benzene. Suspension was sonicated for 5 min at 50 °C. Unreacted solid was removed by centrifugation at normal atmosphere, and the solvent was removed in a vacuum. White product was crystallized from boiling hexane by cooling to 5 °C. Yield: 102.6 mg (85%). 1H NMR (CDCl3, ppm) δ = 7.05 (CH pyrazole); 19F NMR (CDCl3, ppm) δ = −61.15 (CF3). Calc. for C15H3F18N6Ag3 (%): C, 19.37; H, 0.34; N, 9.01. Found (%): C, 19.57; H, 0.27; N, 8.9. Synthesis of {[3,5-(CF3)2Pz]Cu}3 (1b). Suspension of Cu2O (30 mg, 0.210 mmol) was added to the solution of 3,5-(CF3)2Pz (76.6 mg, 0.377 mmol) in 10 mL of benzene. Suspension was sonicated for 20 min at 50 °C. Unreacted solid was removed by centrifugation at normal atmosphere, and the solvent was removed in a vacuum. White product was crystallized from DCM/hexane (1:4) solution at 5 °C. Yield 78.4 mg (78%). 1H NMR (CDCl3, ppm) δ = 7.06 (CH); 19F NMR (CDCl3, ppm) δ = −61.09 (CF3). Calc. for C15H3F18N6Cu3 (%): C, 22.5; H, 0.38; N, 10.51. Found (%): C, 22.63; H, 0.58; N, 10.70. Materials and Methods. Crystals of intermolecular complexes suitable for X-ray diffraction analysis were obtained from equimolar hexane/DCM solutions for 2a, 3a, and 3b and from toluene solution in the presence of hexane vapor for 4a. NMR measurements were carried out on Bruker Avance-III-500 spectrometer with CryoProbe Prodigy operating at 500.13 MHz (1H) and 125.76 MHz (13C{1H}) and Bruker Avance 600 spectrometer operating at 600.22 MHz (1H) and 150.93 MHz (13C{1H}). The temperature was controlled using Bruker BVT-3000 accessory; the accuracy of the temperature adjustment and stability was ±1 K. Computation Details. Density functional theory (DFT) calculations were performed by Gaussian 0928 on the BP8629 level applying Grimme D330 dispersion correction with Def2-SVP31 basis set for all atoms accompanied by ECP32 potential in the case of Ru and Ag.
architecture in the solid state. Continuing our research, we present herein the data on the interaction of silver(I) and copper(I) pyrazolates ([ML]3, M = Ag (1a), Cu (1b)) (Scheme 1, left) with organometallic compounds bearing Scheme 1. Structural Schemes of Macrocycles (Left) and Ruthenium Sandwiches (Right)
only aromatic ligands. The main goal was to show the existence of a complexation between macrocycles and aromatic π-bases in solution and to connect the complexation in solution with the solid-state structures. We chose ruthenium sandwich complexes ([Ru(η5-C5Me5)(η5-C9H7)] (2), [Ru(η5-C5H5)(η5-C9H7)] (3), and [Ru(η5-C9H7)2] (4)) (Scheme 1, right). In these complexes indenyl (Ind) and cyclopentadienyl (Cp) ligands have different electronic (basic) properties and can compete for complexation with macrocycles in solution and in the solid state. Influence of steric effects on complexation was elucidated by comparing Cp and Cp* ligands.
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EXPERIMENTAL SECTION
Synthesis. Solvents (benzene, hexane, DCM) were dried by standard procedures and distilled under argon atmosphere prior to use.
Table 1. Crystal Data, Data Collection, and Structure Refinement Parameters for Complexes 2a, 3a, 3b, and 4a formula molecular wt crystal size (mm) temperature (K) crystal syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z Dcalcd (g·cm−3) linear absorption (μ) (cm−1) Tmin/Tmax 2θmax (deg) no. of unique reflns (Rint) no. of obsd reflns (I > 2σ(I)) no. of params R1 (on F for obsd reflns)a wR2 (on F2 for all reflns)b GOFc a
2a
3a
3b
4a
C53H47Ag3F18N6Ru2 1635.71 0.35 × 0.16 × 0.08 120(2) monoclinic P21 11.5088(5) 30.5125(12) 16.3790(7) 90 101.1350(10) 90 5643.4(4) 4 1.925 16.47 0.773/0.879 60 32655 (0.0781) 25966 1490 0.0552 0.1075 1.081
C29H15Ag3F18N6Ru 1214.15 0.16 × 0.12 × 0.10 120(2) triclinic P1̅ 10.0278(6) 13.4422(7) 13.7127(8) 83.5462(10) 80.6886(11) 75.3219(10) 1759.59(17) 2 2.292 21.95 0.762/0.810 60 10248 (0.0958) 7793 508 0.0688 0.1079 1.182
C29H15Cu3F18N6Ru 1081.16 0.30 × 0.20 × 0.10 120(2) triclinic P1̅ 10.0102(14) 13.0318(18) 13.5705(18) 84.938(3) 81.696(3) 78.035(3) 1710.6(4) 2 2.099 24.05 0.601/0.795 54 7450 (0.0940) 4712 523 0.0435 0.0768 0.943
C33H17Ag3F18N6Ru 1264.20 0.32 × 0.23 × 0.18 120(2) monoclinic P21/c 15.0477(6) 13.1270(5) 19.8830(8) 90 107.0790(10) 90 3754.3(3) 4 2.237 20.62 0.558/0.708 58 9942 (0.0461) 9249 534 0.0430 0.1081 1.026
R = Σ||Fo| − |Fc||/Σ|Fo|. bRw = [Σ(w(Fo2 − Fc2)2)/Σ(w(Fo2))]1/2. cGOF = [Σw(Fo2 − Fc2)2/(Nobs − Nparam)]1/2. 6771
DOI: 10.1021/acs.cgd.7b01351 Cryst. Growth Des. 2017, 17, 6770−6779
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Optimization of geometry was performed without any symmetry restrictions in the DCM solution, described by CPCM model. Analysis of noncovalent interactions in the obtained crystals was done with the NCIPLOT program. 33 This method enables identification of noncovalent interactions, and it is based on the peaks that appear in the reduced density gradient (RDG) at low densities. The numerical data for the solid state geometries of complexes were obtained with the promolecular approach of NCIPLOT program. X-ray Diffraction Study. Single-crystal X-ray diffraction experiments were carried out with a Bruker SMART APEX II diffractometer (graphite-monochromated Mo Kα radiation, λ = 0.71073 Å, ω-scan technique). The APEX II software34 was used for collecting frames of data, indexing reflections, determination of lattice constants, integration of intensities of reflections, scaling and absorption correction, while SHELXTL35 and OLEX236 was applied for space group and structure determination, refinements, graphics, and structure reporting. The structures were solved by direct methods and refined by the full-matrix least-squares technique against F2 with anisotropic thermal parameters for all non-hydrogen atoms. The hydrogen atoms were placed geometrically and included in the structure factor calculations in the riding motion approximation. Crystallographic data for complexes 2a, 3a, 3b, 4a are presented in Table 1, and data for 3 are presented in Table S3 (see Supporting Information). Some of the CF3 groups in all structures as well as of two crystallographically independent complexes is 2a are disordered.
increase of the macrocycle excess up to 2 equiv leads to the increase of 5,6 and 8,9 carbons high field shift up to −0.29 and −0.48 ppm. The resonances of other carbon atoms of 2 undergo low field shifts (Δδ = +0.03 ÷ +0.75 ppm) (Figure 1). Complex formation is reversible1H and 13C NMR signal shifts values increase at low temperatures and return back to the initial values with the temperature increase. Typically, η2-type coordination of metal atom to indenyl or naphthalene ligands leads to high field shifts only of two coordinated carbons atoms,37,38 while cooperative coordination of aromatic ligands to the metal atoms in the η5 or η6 fashion leads to the high field shifts of all coordinated carbon atoms resonances.38,39 Therefore, the observed 13C NMR spectral pattern with high field shifts of only 5,6 and 8,9 carbon atoms (Scheme 2) suggests η2,η2 coordination of [ML]3 to the C6 ring of the indenyl ligand. Interaction of 2 with [CuL]3 leads to high field shifts of protons resonances by −0.02 ÷ −0.07 ppm at 290 K and by −0.14 ÷ −0.25 ppm at 200 K. However, changes in the 13C NMR spectra were observed only at low temperatures ( 2. On the other hand, we suppose that the temperature decrease diminishes the entropy effect, allowing the formation of {([AgL]3)n·3m} aggregates with n+m > 2 even in solution. Interaction of 3 with [CuL]3 leads to the nonsignificant high field shifts of proton resonances by −0.02 ÷ −0.05 ppm even at 230 K due to weaker interaction as was shown for complexes with Cp*RuInd. There are no reliable signals in 13C NMR spectra at 230 K due to the intensive precipitation. In the solid state the complexes of [CuL]3 and [AgL]3 macrocycles with CpRuInd are isostructural and have 1:1 composition. They represent infinite stacks formed via alternated molecules of macrocycles and ruthenium sandwiches. As supposed on the basis of spectroscopic studies, both π-
Table 3. 13C NMR Shifts (in ppm) of 2 and 2 in the Presence of 1 equiv. [ML]3, CD2Cl2, 200 K +[CuL]3
+[AgL]3
carbon atom
2, 200 K
δ
Δδ
δ
Δδ
4,7 5,6 8,9 5C(Cp*) 2 1,3 5Me(Cp*)
124.85 120.36 91.28 81.86 76.32 67.66 10.51
124.92 120.32 91.13 82.00 76.52 67.89 10.39
0.07 −0.04 −0.15 0.14 0.20 0.23 −0.12
125.45 120.10 90.62 82.26 77.47 67.72 10.31
0.60 −0.26 −0.66 0.40 1.15 0.06 −0.2
the main site of coordination is C6 fragment of indenyl ligand, and η5 or η6 types of coordination are not observed. Complexation with CpRuInd. At ambient temperature the 1H and 13C NMR spectral changes caused by the interaction of both macrocycles with 3 are similar to those observed for compound 2. That means the modes of coordination of both macrocycles to these sandwiches 2 and 3 are similar in solution at RT. Peculiarities of [AgL]3 interaction with 3 are observed at low temperatures. For the CD2Cl2 solution of 3 mixed with [AgL]3 the temperature decrease leads to the growth of Δδ in 13 C NMR spectra only for 5,6 and 8,9 indenyl carbon atoms, whereas the shift values decrease for other carbon atoms of CpRuInd. This suggests an additional coordination takes place with another side of the sandwich 3 that is the Cp ligand (see structural part). This interaction is significantly weaker, and this correlates with the absence of spectral changes in the solution of [ML]3/Cp2Ru mixture under the same conditions. In contrast to the compound 2, the addition of the macrocycles [ML]3 to the solution of 3 in CD2Cl2 at high 6773
DOI: 10.1021/acs.cgd.7b01351 Cryst. Growth Des. 2017, 17, 6770−6779
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Figure 3. Left: a ball-and-stick diagram of {([AgL]3)(Cp*RuInd)2}, 2a. Right: projection of 2a part showing the position of π-ligands on both sides of macrocycle’s plane (hydrogen atoms are omitted for clarity).
atoms M1 and M3 in macrocycles are η2-coordinated to both aromatic ligands, forming infinite stacks. Metal atom M2 is η3coordinated only to the indenyl ligand. M···C contacts for copper and silver containing macrocycles in both 3a and 3b complexes are in the same narrow range (for example, the six shortest contacts are 3.010(7)−3.185(7) for 3a and 3.100(4)−3.197(4) for 3b). On the other hand, their average values are slightly shorter for [AgL]3 whereas the VdW radii for silver is notably larger than for copper. The most frequently used values of VdW radii of silver and copper, presented in the classic Bondi’s work, are rCu = 1.4 Å, rAg = 1.72 Å, respectively.41 Therefore, it can be assumed that the interaction of compound 1a with ruthenium sandwiches is significantly stronger. That is in agreement with the results of
Table 4. 13C NMR Shifts (in ppm) of 2 and 2 in the Presence of 1 equiv. [AgL]3 at Different Temperatures, CD2Cl2 +[AgL]3
+[AgL]3
carbon atom
3, 293 K
δ
Δδ
3, 256 K
δ
Δδ
4,7 5,6 8,9 2 Cp 1,3
126.59 122.39 92.14 72.47 69.78 65.57
126.81 122.38 91.92 72.81 70 65.65
0.22 −0.01 −0.22 0.34 0.22 0.08
126.68 122.45 92.07 72.61 69.86 65.68
126.82 122.4 91.73 72.92 70.02 65.69
0.14 −0.05 −0.34 0.31 0.16 0.01
aromatic ligands of 3 take part in coordination to macrocycles due to multiple M···C contacts (Figure 4, Figure 5). Metal
Figure 4. A ball-and-stick diagram of {([ML]3)(CpRuInd)} (M = Ag, right and M = Cu, left; hydrogen atoms are omitted for clarity). 6774
DOI: 10.1021/acs.cgd.7b01351 Cryst. Growth Des. 2017, 17, 6770−6779
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Figure 5. Projection of part of the 2a (left) and 2b (right) showing the position of π-ligands on both sides of the macrocycles planes. Hydrogen atoms omitted for clarity.
The average contacts for Ag···C(Cp) and Ag···C(Ind) are 3.14 and 3.22 Å, respectively. Therefore, that the interactions of macrocycles with indenyl and cyclopentadienyl ligands are approximately equal. At the same time, the number of contacts of silver with indenyl ligand is larger than with Cp (7 vs 4). These data correlate with the NMR investigations in solution under conditions of monomers formation also demonstrating the preferable coordination of macrocycles to indenyl ligand in the solution. Further insight into the solid state structures was given by the analysis of noncovalent interactions (NCI).42 Results of the NCI calculations confirm the hapticity of the metal···arene interactions as well as the presence of π-stacking. NCI analysis also confirms that intermolecular interactions in 3b are weaker than in 3a (see Figures S9−S13). DFT optimization of the complexes in the DCM solution confirms the ability of both aromatic ligands of 3 to interact with macrocycle 1a. The interaction with the indenyl ligand is slightly stronger compared to the Cp one (ΔGDCM = −6.0 kcal/ mol for Cp-[AgL]3 interaction and −9.3 kcal/mol for Ind[AgL]3). The calculated M···C distances are very close to those obtained for the solid state structures (Figure 7). Complexation with Ind2Ru. The interaction of bis-indenyl complex 4 with silver macrocycle in DCM-d2 leads to the precipitation of 95% of the complex already at room temperature as evidenced by the 20 times decrease of the integral area of compound signals in reference to the area of the solvent signal. However, the 1H NMR spectra are still informativethe resonances of all protons are slightly shifted to the high field (Δδ = −0.02 ÷ −0.05 ppm) similarly to previous cases. For 13C NMR measurements toluene-d8 was used to increase the solubility of complexes. Under these conditions the complexation of 4 with [ML]3 results in high field shifts of proton resonances (by −0.04 ÷ −0.08 ppm for complex with 1a and by −0.02 ÷ −0.04 ppm for 1b at 298 K) (Table 5). The signals shifts increase upon the temperature decrease to 230 K up to −0.09 ÷ −0.16 ppm for complex with [AgL]3 and to −0.06 ÷ −0.10 for complex with [CuL]3. The 13 C NMR spectral changes observed differ from those for complexes of macrocycles with 2 and 3. The addition of 1a and 1b to the solution of 4 in toluene-d8 leads to the high field shift of resonances of all carbon atoms in the C6 fragment (C4−C9) of the indenyl ligand, evidencing the coordination of these atoms with macrocycles. The resonances of other carbon atoms (C1−C3) shift to lower field, indicating that they are not coordinated. The temperature decrease leads to the growth of
investigation in solution. For example, in the case of interaction of 2 with [CuL]3 the informative 13C NMR spectral changes were detected only at low temperature ( 2 are formed in solution followed by the precipitation of oligomeric complexes. Coordination of the base molecules on both faces of macrocycle is of essentially the same strength and makes the macrocycles more flat in terms of coplanarity of Ag3N6 and Pz rings. Notable is that all described complexes of macrocycles with organometallic π-bases do not reveal the formation of the M···M bonded dimers but only to the alternating macrocycle/base stacks or coordination of bases on both macrocycle’s faces. The first indenyl ligand coordinates mainly to the two metal atoms in a very similar manner for all complexes. Another basic ligand approaches the macrocycle from the opposite side. One metal atom of a macrocycle is coordinated to arene ligands on both faces (type Base-M1-Base’). The other two metal atoms coordinate only one base each (M2-Base- and M3-Base’ interactions); these metal-base contacts are shorter among others. We suggest that this structural motif is general for supramolecular packing of macrocycles complexes.
with CpRuInd and Cp2Fe19 with Ag···C contacts of 2.910(4)− 3.378(4) Å and π(Pz)···π(C6Ind) and π(Pz)···π(C5Ind) contacts of 3.257−3.378 Å in 4a. Distances between the macrocycles Ag3N6 planes and C6 centroids of indenyl ligands coordinated on both macrocycles faces is equal to 3.030 and 3.153 Å, respectively. These data match the corresponding values in complexes of macrocycles with 2 and 3. Moreover, the number of contacts is larger, that in turn allows ranking this complex as the strongest in the series. Neighboring macrocycles molecules are located in a staggered (head-to-head) conformation with the angle between their M3N6 planes of 8.97°. Coordination of macrocycles on both sides of 4 leads to the significant compression of the sandwich molecule through C6 fragments of indenyl ligands. As the result the distance between the C6 centroids (3.500 Å) is significantly smaller than in free complex 4 (3.678 Å).43 Interaction with sandwich compounds leads to a slight elongation of macrocycles’ M−N bonds lengths (for Cu−N Δrav is 0.014 Å and for Ag−N Δrav is 0.015 Å).9 The maximal alteration of bond lengths is observed for the strongest complex 4a. The formation of macrocycles complexes with all sandwich compounds makes the macrocycle more flat in terms of coplanarity of M3N6 and Pz rings. This fact reflects essentially the same strength of interaction of the base molecules at both faces of the macrocycle.
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CONCLUSION Herein we have shown for the first time the interaction of the macrocycles 1 with aromatic ligands of ruthenium sandwiches (Cp*RuInd, CpRuInd, and Ind2Ru) in solution. The formation of complexes of copper(I) and silver(I) macrocyclic pyrazolates with organic aromatic compounds in solution was questioned previously.17 According to the 13C NMR data in solution the main coordination centers are located on carbon atoms in the C6 fragment of the indenyl ligand, which is not bound to ruthenium. The interaction with Cp ligand was observed only at low temperatures. In the solid state the average M···C contacts in coordination with both π-ligands (Ind and Cp) are in the same range (2.9−3.4 Å), but number of contacts of metals with indenyl ligand is larger than with Cp (7 vs 4). For sandwiches with different nonequivalent aromatic ligands, Cp*RuInd and CpRuInd, a similar mode of coordination was shown both in solution and the solid state by means of NMR spectroscopy and X-ray diffraction, respectively. The interaction of [AgL]3 macrocycle with ruthenium sandwiches is significantly stronger than that of [CuL]3 in solution and the solid state. For example, in the case of interaction of 2 with [CuL]3 the detectable changes in the 13C NMR spectra were observed only at low temperatures (
