Hydrogen-Bonding Motifs in MS2N2H Metallacycles: A

Dec 19, 2013 - The crystal lattice contains numerous interatomic interactions, of which the most important are formed from multiple hydrogen bonds tha...
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Hydrogen-Bonding Motifs in MS2N2H Metallacycles: A Crystallographic and Computational Study of [CpCoS2N2H][BF4] René T. Boeré*,†,‡ †

Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, Canada T1K 3M4 The Canadian Centre for Research in Advanced Fluorine Technologies, University of Lethbridge, 4401 University Dr W, Lethbridge, AB, Canada T1K 3M4



S Supporting Information *

ABSTRACT: The first preparation and full characterization of highly insoluble [{η5−Cp}CoS2N2H][BF4] is reported. Proof of structure and composition is established from a single-crystal X-ray diffraction experiment at 173 K, which determined a crystal structure containing two independent cations and two independent anions in the asymmetric unit. The site of protonation is the terminal N of the S−N−S−N2− ligand which is coordinated to cobalt in the metallacycle. The crystal lattice contains numerous interatomic interactions, of which the most important are formed from multiple hydrogen bonds that link four [{η5−Cp}CoS2N2H]+ ions and two [BF4]− ions into a tetrameric cluster. The second kind of [BF4]− is not involved in intermolecular bonding. Short S···S′ interactions link such tetramers into planes; the resulting doublelayer planes are described by the (101) Miller planes. DFT calculations using the B3PW91/6-311+G(3df)(2p) and B3LYP/6311+G(3df)(2p) methods are in excellent agreement with the structure of the title cation from crystallography. Comparison to newly calculated and literature-reported DFT calculations on the neutral starting material [{η5−Cp}CoS2N2] and to a recent low-temperature crystal structure of the latter shows that there are only minor changes (≤3%) in the bond lengths within the CoS2N2 ring upon protonation, whereas the bond angles change by up to 9%. The B3PW91 functional is shown to be superior to B3LYP for computing the molecular structures of these formally CoIII metallacycles.



INTRODUCTION In the carbon-mimetic chemistry of the p-block elements, unsaturation and multiple-bonding have been prominent features for investigation.1−17 A key property of unsaturated hydrocarbons is their ability to form π-complexes with low and intermediate valent transition metals, and there is perhaps no more famous example than in η5−cyclopentadienyl coordination compounds. The alternate optionthat the metal inserts into a C−C bond to form “metallocyclobenzenes”is now recognized as entirely plausible, but it is usually less thermodynamically stable than the π-complex alternative.18,19 There are well-documented cases wherein cyclo-MC 5 R 5 complexes (A) isomerize to (η5−C5H5)M (A′).20 The exact inverse applies for unsaturated thiazyl (-SN-) ring compounds. Thus, the unsaturated heterocycle 1,3-S2N2 is known in all cases to insert metals into an S−N bond rather than form an η4-π complex (B).21−24 The resulting cyclo-MS2N2 (B′) are formally derivatives of the S2N2−2 dianion, a ligand that is unknown as the free ion but for which there are many documented complexes with metals in the +2 to +5 oxidation states (M = Sn, Pb, Sb, Ni, Pd, Pt, Co, Rh, Ir).22,25,26 An exhaustive study of the electrochemical reduction of S2N2 found two irreversible electron transfers at −1.0 and −2.2 V versus Fc+/0, only the first of which is consistent with production of a transient monoanion.27,28 Chemical reduction with sodium salts of anthracene or benzophenone in the © 2013 American Chemical Society

presence of crown ethers result exclusively in the formation of salts of the [sym-S3N3]− anion.28 Oxidative addition also predominates for metal complexes of 1,2,3,5-dithiadiazoyl radicals, RCN2S2,29,30 but recently the first π complexes have been reported as η1- and η2-adducts with CpCr(CO)2.31−34

Group 8 metal half-sandwich cyclopentadienyl derivatives of the type {η5−Cp}MS2N2 (M = Co, Rh, Ir) have received repeated attention since the discovery of CpCoS2N2, 1, by Edelmann in 1982 (Chart 1).35 Later, the synthesis of the Cp* analogue 2 was reported,36 followed by the iridium Cp* complex 6 in 2002.37 The missing members of the series, the two rhodium complexes 3 and 4 as well as 5 and the first determination of a crystal structure for 2 were added in 2009.38 Only 1 and 2 have been studied in detail, including an electrochemical study by cyclic and ac voltammetry,39 the chemical reduction of 1 with cobaltocene,39,40 a UV-PES study Received: November 8, 2013 Revised: December 11, 2013 Published: December 19, 2013 814

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RESULTS AND DISCUSSION Synthesis. The salt 9 was prepared by treating a highly dilute ethereal solution of 1 with HBF4-etherate (Scheme 1).

Chart 1

Scheme 1

of their oxidation potentials,36 and several computational investigations.36,38−40 A consensus has developed from these investigations that the CoN2S2 cobaltacycle in this complex shows extensive delocalization and satisfies criteria of metalloaromaticity.40 The degree to which aromaticity is also shared by the Rh and Ir analogues has apparently not received consideration. Nevertheless, in view of the strong interest in aromatic and antiaromatic character in delocalized thiazyl ring compounds, the organometallic series 1−6 are of considerable importance. Compared to the level of physicochemical investigation, the chemical reactivity of this class of compounds has received less attention. Aucott et al. demonstrated that compounds 1, 2, 4, and 6 can be coordinated to Au(I) complexes at N2 (Chart 1).37,41 By contrast, a Cp*IrCl2 adduct of 6 was found to coordinate at N1.38 Van Droogenbroeck et al. predicted on the basis of DFT calculations that if 1 were protonated under thermodynamic control, the site of protonation should be N2, that is, the cation 7 which is predicted to be more stable than the alternative 8 by about 44 kJ·mol−1.40 This theoretical predication has never been substantiated. Herein we report the first structure determination of a protonated salt of an {η5− Cp}MS 2N2 complex, which corroborates the predicted structure of the cation as 7. However, there exist some 23 known crystal structures containing the same MS2N2H ring in other kinds of coordination compounds with the metals CoII, NiII, PdII, PtII, and PtIV. The first-row transition metal complexes (CoII, NiII) are exclusively square-planar cis-M(S2N2)2 complexes, 10a (Chart 2), where either one, 10b, or both, 10c, rings are

Reaction of the substrate with HBF4 is extremely rapid and resulted in the formation of dark powders. IR analysis invariably shows the presence of strong signals from solvent occluded or cocrystallized with product. After much trial and experimentation, we focused on a strategy of making a very dilute solution of 1 in diethyl ether. Then, the neat liquid HBF4-etherate is added very slowly over more than 1 h for a 0.35 mmol-scale reaction. Very small dark-brown plate-like crystals of the BF4− salt 9 then form directly from the mother liquor at RT. The product was characterized by IR spectroscopy, which is consistent with protonation of 1, with ν(NH) bands at 3225 cm−1 (asym. str.) and 3119 cm−1 (sym. str.). Similarly, ν(BF) bands are at 1082 and 1042 cm−1. Such a splitting of the BF4− B−F stretch is diagnostic for C3v coordination of this “weaklycoordinating” anion.43,44 Nevertheless, the spectroscopic methods make it difficult to conclusively identify the protonation site as there are two N atoms in the S2N2 chelate ring. Despite the very thin crystal morphology, we were eventually able to obtain a high-quality X-ray diffraction data set at low temperature. While it is evident that Cp*CoS2N2, 2, also reacts rapidly with HBF4 in CH3CN, CH2Cl2, and Et2O, we were unable to find conditions suitable for crystal growth. Indeed, all our solid samples of putative [Cp*CoS2N2H][BF4] show the presence of occluded solvent. Crystallography. The structure is a reliable determination by the normal criteria with a conventional R1 = 5.8% (see the Experimental Section and Table 4). Constituent ions of 9 are crystallized in the monoclinic space group P21/n with two independent cations and two anions within the asymmetric unit. The interatomic distances and angles obtained from the structure for the two independent cations are in excellent agreement (see below). Figure 1 presents a displacement ellipsoids plot of an asymmetric unit in the crystal structure of 9. The two independent, cationic protonated cobaltacycles form H-bonded dimers to only one of the two crystallographically independent tetrafluoroborate ions, namely, (BF4)2, numbered as B2, F5−8, whereas anion, (BF4)1, numbered B1, F1−4, is not involved in H bonding. As a direct consequence of this structural feature, the displacement ellipsoids in (BF4)2 are small and very welldefined, whereas those of (BF4)1 are large and very distorted. Attempts to define a disorder model for this latter anion failed, but the difference shows that it has considerably more orientational flexibility than (BF4)2. In order to preserve stoichiometry and charge balance, the (BF4)2 anions actually bridge four cobaltacycles in a centrosymmetric manner as is shown at the RHS of Figure 2. There are in all eight NH to F hydrogen bonds of four different kinds (Table 1) and all are on the long end of the accepted range for “moderate” H-bonds. This tetrameric H-bonded cluster lies beside a second such cluster, of which only the rear half is shown on the LHS of

Chart 2

protonated at the nitrogen atoms adjacent to the metal ion. It has also been shown that complexes of type 10c can be derivatized by metals to form bimetallic complexes wherein 10a acts as a “metalloligand”.42 By contrast, many Pd and Pt complexes contain a single S2N2H chelate ring with two (for MII) or four (for MIV) additional ligands attached to the metal. The majority were prepared in the research groups of Woollins and Weiss, and these compounds display a wide variety of Hbonding behaviors. Some show no H-bonding at all, one shows only intramolecular H-bonding, while the remainder display a diverse range of terminal, paired (side-by-side dimeric), or bridging arrangements. This paper includes an analysis of these diverse H-bonding patterns and a detailed investigation of the electronic structure of the protonated cation from hybrid-DFT calculations. 815

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Figure 1. Displacement ellipsoids plot of an asymmetric unit in the crystal structure of 9, showing the atom numbering scheme and the bridging hydrogen bonds that represent the strongest interionic interactions in the lattice. F7 atom of the lower and the F6, 8 atoms of the upper (BF4)2 ions connect to two further cations to form the centrosymmetric cluster portrayed in the abstract. Counterion (BF4)1, top left, does not interact with the cations.

Figure 3. Expanded packing diagram of 9 showing the “double-layer” structure formed by ribbons of {[CpCoS2N2H]4[BF4]2}2+ ions linked by short S1···S3′ contacts to neighboring atoms. View is up the b axis; the double layers with outward facing Cp rings form (101) Miller planes. (BF4)1 anions fit between the facing Cp rings of two adjacent double layers.

ensemble of these interacting species form the horizontal layers clearly visible in Figure 3, parallel with b and perpendicular to the ac bisector and corresponding to (101) Miller planes. The role of the (BF4)1 anions is now shown to be the weak electrostatic “glue” between the layers as they fit between the opposing cyclopentadienyl rings that face each other across the layer gaps (Figure 3). It is thus not surprising that these latter anions have greater orientational flexibility than (BF4)2. The very low solubility of 9 in polar solvents indicates that the multiple H-bonds, even if individually weak, result in relatively strong lattice forces. Hydrogen Bonding Motifs in M(S2N2H) Complexes. Hydrogen bonding is observed in about 90% of the reported structures of MN2S2H complexes (Table 2). All the DA distances listed fit the expected range for the indicated donor (D) and acceptor (A) atom types according to the compilation provided by Wallwork for traditional H-bonds, except those involving the BF4− and PF6− ions,45 for which all the distances are long for an F atom acceptor, as expected for so-called “weakly coordinating” anions. Nevertheless, these interactions most certainly qualify for H-bonding by the more refined definition that is currently accepted by the IUPAC.46−48 The H-bonds for BF4− and PF6− ions are all terminal rather than cluster-forming as observed thus far uniquely in 9. The listed DA distances all fall within the range 2.854(1)−3.253(7) Å for the four different kinds of H-bonds observed for the doubly bridged tetrameric clusters reported here for the crystal lattice of 9. Only two previously reported structures involve bridges. In [(Ph3P)PtII(S2N2H)(SSO3)][H2NPPh3] (Cambridge Structural Database refcode WUWWEP), there is direct NH···O bonding of both an intramolecular and intermolecular nature.49 In addition, the anionic thiosulfate ligands further H-bonds with the protonated phosphonium−imine counterions. This complex behavior comes closest to that observed for the ions of 9 even though there are substantive differences in their chemistry. In [(nBu3P)2PtII(S2N2H)][Cl][PF6] (refcode FEHNIP), two metal complexes are bridged via H-bonding to the single naked chloride anion, and the PF6− is entirely uninvolved;50 thus, this latter example shares with 9 the property of distinct behavior for the two symmetry-inequivalent counteranions.

Figure 2. Expanded H-bonding diagram in the crystal structure of 9 showing at right the centrosymmetric double bridge wherein four CpCoS2N2H+ rings are linked to two (BF4)1 anions. Two cobaltocycles are omitted from the left-hand cluster for sake of clarity; further electrostatic interactions between the (BF4)1 anions of this unit with the CoS2N2 ring of the right-hand cluster serve to link the tetramers into ladder chains.

Table 1. Hydrogen Bonds for [CpCoS2N2][HBF4] [Å and °]a D−H···A

d (D−H)

d (H···A)

d (D···A)

∠ (DHA)

N(2)−H(2N)···F(7)b N(2)−H(2N)···F(8)c N(4)−H(4N)···F(6)d N(4)−H(4N)···F(7)e

0.87(2) 0.87(2) 0.87(2) 0.87(2)

2.45(4) 2.46(6) 2.16(5) 2.47(5)

3.253(7) 3.011(7) 2.854(7) 3.151(7)

152(6) 121(6) 136(5) 135(5)

a

Note: symmetry transformations used to generate equivalent atoms. x + 1/2, −y + 1/2, z − 1/2. c−x + 3/2, y + 1/2, −z + 1/2. dx − 1/2, −y + 1/2, z − 1/2. e−x + 1/2, y + 1/2, −z + 1/2. b

Figure 2. Surprisingly, there are no strong contacts between the pairs of tetramers; rather, there are secondary electrostatic interactions of the bridging (BF4)2 units with the neighboring Co2 metallacycle. These interactions create ribbons (or ladders) along the b direction (Figure 3). These ladders associate with neighboring ladders via a single type of contact, namely, S1···S3′ at 3.504(3) Å, some 3% less than the sums of v.d. Waals’ radii of sulfur (and interestingly not the more common, electrostatically driven, S(δ+)···N(δ−) contacts that are so very often present in sulfur−nitrogen chemistry.) The 816

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Table 2. Crystal Structures of (S2N2H) in the CSD by Type of H-Bonding Observed refcodea

formulab

DA, Å

no H-bonding GELMAL GELMEP GEWZUD intramoleculare NIPDTN terminal FEHNEL FEHNOV GAGJUT GAGKAA GAGKEE GELLUEf DOCZAW DOCZEA VUWYOB paired (side-by-side dimers) CAGLOL FAVWEE GELLUE01f JACMOP JEZLUV KOVKAH MXNSNIe bridging VUWWEPe FEHNIP

chg

counter ion (A)c

ref

Br(PhMe2)PtII(S2N2H) I(PhMe2)PtII(S2N2H) {C,CN}PdII(S2N2H)d

0 0 0

55 55 56

NiII(S2N2H)(S2N2CONHPh)

0

57

3.22(1) 2.882(8), 2.917(9) 3.166(8) 2.995(9) 3.06(1) 2.94(1) 3.14(2) 3.05(1) 3.05(1)

(Et3P)2PtII(S2N2H) CoII(S2N2H)2 (PhMe2)2PtII(S2N2H) (PhMe2)2PtII(S2N2H) (PhMe2)2PdII(S2N2H) α-(PhMe2)2PtIVBr2(S2N2H) (Me3)2PtII(S2N2H) (PhMe2)2PtII(S2N2H) (Et3)2PtII(S2N2H)

+1 0 +1 +1 +1 +1 +1 +1 +1

Cl3SnMe2− (OPh2PCH2−) Cl− PF6− BF4− BF4− PF6− PF6− PF6−

50 50 58 58 58 55 59 59 60

2.840(1) 2.945(6) 3.337(5) 3.022(9) 2.93(1) 3.22(1) 3.021(3)

NiII(S2N2)(S2N2H) NiII(S2N2)(S2N2H) β-(PhMe2)2PtIVBr2(S2N2H) {C,CN}PdII(S2N2H)d (NC)2PtII(S2N2H) Cl2PdII(S2N2H) NiII(S2N2H)(S2N2CH2OMe)

−1 −1 +1 0 −1 −1 0

Ph4As+ (ring N) Me4N+ (ring N) BF4− (Br) (ring N) Et4N+ (NC) Ph4P+ (Cl) (O)

61 62 55 63 64 65 66

2.96(1) 3.116(6), 3.119(7)

(Ph3P)PtII(S2N2H)(SSO3) (nBu3P)2PtII(S2N2H)

−1 +1

H2NPPh3+ (O) (Cl−), PF6−

48 50

a

Cambridge Structural Database indexing code (ref 67). One structure, refcode NISATN, has been omitted as coordinates are not available in the CSD. bOxidation state of metal indicated; for overall charge see next column. cThe actual acceptor A is indicated where there is ambiguity; it is not always part of the counterion. dOne of several kinds of monoanionic cyclometalated imino−benzene ligands. eStructures MXNSNI and VUVWEP also have an intramolecular H-bonding component. fOne of two polymorphs reported for this compound in the same paper.

Table 3. Selected Geometrical Parameters from Experiments and DFT Calculations parameter

mol Aa

mol Bb

av valc

B3PW91d

B3LYPe

neutralf

B3PW91g

B3LYPh

Co−S1 S1−N1 N1−S2 S2−N2 N2−Co Co−Cavi N2−Co−S1 Co−S1−N1 S1−N1−S2 N1−S2−N2 S2−N2−Co Co−N2−H S2−N2−H

2.081(2) 1.645(6) 1.558(8) 1.608(6) 1.816(6) 2.031(1) 89.3(2) 105.4(2) 118.1(4) 105.0(3) 122.1(3) 126(4) 112(4)

2.067(2) 1.640(6) 1.563(6) 1.609(6) 1.806(5) 2.04(2) 89.4(2) 106.3(2) 117.1(4) 105.1(3) 122.1(3) 138(4) 100(4)

(2.074) 1.6425 1.5605 1.6085 1.811 2.035(18) 89.4 (105.9) 117.6 105.1 122.1 132 106

2.1024 1.6268 1.5493 1.6197 1.8194 2.049(15) 88.36 105.73 118.83 104.48 122.61 126.24 111.16

2.1278 1.6331 1.5532 1.6276 1.8343 2.074(16) 88.19 105.30 119.41 104.46 122.64 126.16 111.20

2.0764(6) 1.657(2) 1.597(2) 1.556(1) 1.816(1) 2.053(16) 91.02(4) 107.39(6) 111.22(9) 111.22(9) 112.06(8) n/a n/a

2.0873 1.6403 1.5908 1.5456 1.8033 2.056(10) 89.99 107.47 111.57 111.36 119.61 n/a n/a

2.125 1.661 1.620 1.576 1.804 2.082(9) 90.79 106.35 112.45 110.46 119.96 n/a n/a

a This work: CpCo{S2N2H} cation with Co(1). bThis work: CpCo{S2N2H} with Co(2). cAv value of “A” and “B” for values that do not differ at the 99% confidence level; (values in parentheses) are not equivalent at 99% confidence. dB3PW91/6-311+G(2df,2p) DFT calculation under Cs symmetry and the Cp ring “cis” to the N−H bond. eB3LYP/6-311+G(2df,2p) DFT calculation under Cs symmetry and the Cp ring “cis” to the N− H bond. fSee ref 40. gB3PW91/6-311+G(2df,2p) DFT calculation under Cs symmetry and the Cp ring “cis” to N1. hB3LYP/6-311+G(2df,2p) DFT calculation reported in ref 40. iSince the Cp rings are somewhat skewed in the experimental structures one-to-one correspondence to the DFT calculations is not meaningful. Instead, the average of all five Co−C values has been determined and is reported here. Errors are std dev.

Computational Investigation. Although previous workers determined the relative energies of the cations 7 and 8 using B3LYP/6-311G* hybrid DFT calculations,40 thereby correctly predicting that 7 should be the thermodynamically preferred protonated structure, the geometrical coordinates for the protonated structure have not been published. Here, we report

new calculations comparing the efficacy of the B3PW91 functional with the common B3LYP method for CpCoS2N2 complexes. In addition, we have investigated the preferred orientation of the Cp ring w.r.t. the N−H bond direction. For both functionals, using the same basis set, a slight preference (0.73, 0.69) kJ·mol−1 is afforded by the trans orientation of the 817

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experimental evidence for metalloaromaticity in MS 2 N 2 complexes. The H-bonding motif in crystals of 9 forms a unique two-anion/four-cation cluster, and this seems to be responsible for the unusually low solubility of this salt.

Cp ring, even though the crystal structures of 1 and 9 are both found with the Cp ring closer to cis than trans. Also, only the trans orientation minimizes to local minima (zero imaginary frequencies). The computed cis orientations, as well as a skewed orientation without applied C2 symmetry, are found in all cases we examined to have both slightly higher energy and to possess an imaginary frequency for rotation about the Cp bond axis (for full details and structure coordinates, see the Supporting Information.) We also found that the B3PW91 computed geometries (Table 3) are consistently closer to those observed in the solidstate crystal structures. For example, the average deviation of the calculated CoC bonds from the experimental is twice as high for the B3LYP-generated structure. The deviations in the bond distances around the metallacycle are 50% higher for B3LYP compared to B3PW91. The overall agreement in the geometry for the latter functional confirms that this is a very suitable method for first-row transition element metal complexes. Geometrical Changes upon Protonation. Table 3 also provides comparative experimental and computational data for neutral 1 and protonated cation 7 as found in the structure of 9. The two experimental Co−S1 distances are surprisingly different, but their average value of 2.074 Å is very close to that of the neutral species at 2.0764(6) Å. The DFT calculated values for the two species are also extremely similar, suggesting that this bond, which is remote from the protonation site, is little affected. Bond S1−N1 is found to shorten slightly ( 2σ(I)] R indices (all data)

[C5H5CoS2N2H][BF4] 303.98 173(2) Mo/0.71073 monoclinic P21/n 14.587(3) 7.6483(13) 18.132(3) 102.264(2) 1976.7(6) 8 2.043 2.180 semiempirical from equivalents 0.9785 and 0.5009 1200 0.368 × 0.145 × 0.01 1.632 to 26.010° −17 ≤ h ≤ 17, −9 ≤ k ≤ 9, −22 ≤ l ≤ 22 19617/3886 [Rint = 0.1184] 99.9% 3886/2/279 1.014 R1 = 0.0577, wR2 = 0.1194 R1 = 0.1209, wR2 = 0.1452

(9) Wang, Y.; Robinson, G. H. Organometallics 2007, 26, 2−11. (10) Power, P. P. Organometallics 2007, 26, 4362−4372. (11) Tokitoh, N.; Sasamori, T. Dalton Trans. 2008, 1395−1408. (12) Ottosson, H.; Eklöf, A. M. Coord. Chem. Rev. 2008, 252, 1287− 1314. (13) Scheschkewitz, D. Chem.Eur. J. 2009, 15, 2476−2485. (14) Wang, Y.; Robinson, G. H. Chem. Commun. 2009, 5201−5213. (15) Mizuhata, Y.; Sasamori, T.; Tokitoh, N. Chem. Rev. 2009, 109, 3479−3511. (16) Kira, M. Chem. Commun. 2010, 2893−2903. (17) Jones, C. Coord. Chem. Rev. 2010, 254, 1273−1289. (18) Landorf, C. W.; Haley, M. M. Angew. Chem., Int. Ed. 2006, 45, 3914−3936. (19) Chen, J.; Jia, G. Coord. Chem. Rev. 2013, 257, 2491−2521. (20) Shi, C.; Guo, T.; Poon, K. C.; Lin, X.; Jia, G. Dalton Trans. 2011, 11315−11320. (21) Bénard, M. New J. Chem. 1986, 10, 529−532. (22) Chivers, T.; Edelmann, F. Polyhedron 1986, 5, 1662−1699. (23) Oakley, R. T. Prog. Inorg. Chem. 1988, 36, 299−391. (24) Chivers, T.; Manners, I. Inorganic Rings and Polymers of the pBlock Elements; Royal Society of Chemistry: United Kingdom, 2009; p 82ff. (25) Kelly, P. F.; Woollins, J. D. Polyhedron 1986, 5, 607−632. (26) Kelly, P. F.; Slawin, A. M. Z.; Williams, D. J.; Woollins, J. D. Chem. Soc. Rev. 1992, 245−252. (27) Boeré, R. T.; Chivers, T.; Roemmele, T. L.; Tuononen, H. M. Inorg. Chem. 2009, 48, 7294−7306. (28) Roemmele, T. L.; Konu, J.; Boeré, R. T.; Chivers, T. Inorg. Chem. 2009, 48, 9454−9462. (29) Preuss, K. E. Dalton Trans. 2007, 2357−2369. (30) Banister, A. J.; May, I.; Rawson, J. M.; Smith, J. N. B. J. Organomet. Chem. 1998, 550, 241−253. (31) Lau, H. F.; Ng, V. W. L.; Koh, L. L.; Tan, G. K.; Goh, L. Y.; Roemmele, T. L.; Seagrave, S. D.; Boeré, R. T. Angew. Chem., Int. Ed. 2006, 45, 4498−4501.

and experimental parameters are compiled in Table 4, and selected interatomic distances are available in Table 3. A more detailed crystal structure report is available in the Supporting Information.



ASSOCIATED CONTENT

S Supporting Information *

Full crystallographic data and computational results. This material is available free of charge via the Internet at http:// pubs.acs.org



AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: +14033292045. Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS This work was underwritten by ongoing Discovery Grants from the Natural Sciences and Engineering Research Council (NSERC). The diffractometer at the University of Lethbridge X-ray Diffraction Facility was purchased with funding from NSERC and the University. B. Klassen is thanked for assistance with the synthesis of 9.



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dx.doi.org/10.1021/cg401674w | Cryst. Growth Des. 2014, 14, 814−820