1-D coordination polymers containing benzenedicarboxylate

Crystal Engineering 4 (2001) 25–36 www.elsevier.com/locate/cryseng

1-D coordination polymers containing benzenedicarboxylate Susan A. Bourne a,*, Arunendu Mondal b, Michael J. Zaworotko b b

a Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa Department of Chemistry, University of South Florida, 4202 E Fowler Ave, Tampa, FL 33620, USA

Received 31 October 2000; accepted 22 January 2001 (Refereed)

Abstract The preparation and crystal structures of [Cu(1,3-bdc)(py)3].11/2 H2O (1), [Cu(1,3bdc)(py)3].H2O.CH3OH (2), [Co(1,3-bdc)(py)3(H2O)] (3), [Co(1,3-bdc)(py)3(CH3OH)].H2O (4), [Cu(1,3-bdc)(py)2] (5), [Co(1,3-bdc)(CH3OH)4] (6) and [Ni(1,3-bdc)(CH3OH)4] (7) are described (1,3-bdc=1,3-benzenedicarboxylic acid; py=pyridine). 1–4 form straight-chain 1-D coordination polymers with interdigitated pyridyl ligands that are engaged in C-H···π hydrogen bonds. 6 and 7 form similar 1-D polymeric chains, but the smaller methanol ligands allow the bdc groups to stack to form π···π interactions. 5 forms a rectangular 2-D grid structure with insufficient space for guest inclusion.  2001 Elsevier Science Ltd. All rights reserved. Keywords: Inorganic compounds; Coordination polymers; Crystal structure

1. Introduction The field of crystal engineering is continuously expanding and its ability to offer rational design of solids is receiving ever-increasing recognition, so much so that the design of solid-state architectures based on “node-and-spacer” type methodology has become an accepted practice [1,2]. Over the past few years a large number of coordination polymers have been prepared using these methods. Typically the “spa* Corresponding author. E-mail address: [email protected] (S.A. Bourne). 1463-0184/01/$ - see front matter  2001 Elsevier Science Ltd. All rights reserved. PII: S 1 4 6 3 - 0 1 8 4 ( 0 1 ) 0 0 0 0 7 - 7

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cers” used are bifunctional rod-like ligands such as 4,4⬘-bipyridine or pyrazine, chosen to function as linear building blocks. Depending on the metal node that is used, 1-D, 2-D and 3-D polymers have been prepared with potential application in molecular recognition [3], magnetic materials [4], non-linear optics [5] or catalysis [6]. A number of 1-D coordination polymers containing 4,4⬘-bipyridine have been reported and have been found to form one of three “network geometries” (scheme 1): zigzag chains [7–11] and straight-chain structures [12–15] are frequently seen, but a number of stair-step structures [16,17] and even helices [18] have also been reported. The 0-D “square box” consisting of four metal nodes and four linear spacers [19,20] are also supramolecular “isomers” of these 1-D coordination polymers. We have recently become interested in preparing new structures using ligands which have a built-in coordination angle other than 180°, such as 1,3-benzenedicarboxylic acid. In this paper we report a number of 1-D coordination polymers that have been prepared using cobalt and copper as the metal nodes. An analysis of structures in the CSD [21] containing a bdc coordinated to at least one transition metal at each carboxyl group revealed that there are seven such compounds. In five of these the bdc acts as a bridging ligand between metal terminating groups. The other two (ROLVET and RUQKIX) form 2-D coordination polymers with each carboxyl group of the bdc coordinating to two metal ions. In this paper we report the structures of 1-D coordination polymers formed by bdc with copper, cobalt and nickel in which the carboxyl groups of the bdc are singly coordinated to metal ions as well as a 2-D coordination polymer of copper in which the bdc acts as a bridging ligand between metal centres.

2. Experimental 2.1. Preparation of [Cu(1,3-bdc)(py)3].11/2H2O (1) and [Co(1,3-bdc)(py)3(H2O)] (3) In a typical reaction, a solution of Cu(NO3)2.21/2H2O (0.232 g, 1 mmol) and 1,3benzenedicarboxylic acid (0.166 g, 1 mmol) was prepared in a mixture of 2 cm3 pyridine and 7 cm3 DMSO with stirring at room temperature. Slow evaporation of solvent gave blue crystals of 1. A methanolic solution (10 cm3) of Co(NO3)2.6H2O (0.290 g, 1 mmol) and 1,3benzenedicarboxylic acid (0.166 g, 1 mmol) in 2 cm3 of pyridine was refluxed for about 30 minutes. Slow evaporation of the resulting clear solution gave pink crystals of 3. 2.2. Preparation of [Cu(1,3-bdc)(py)3].H2O.CH3OH (2) and [Co(1,3bdc)(py)3(CH3OH)].H2O (4) Solutions of Cu(NO3)2.21/2H2O (0.125 g, 0.5 mmol) in methanol(5 cm3) and 1,3benzenedicarboxylic acid (0.174 g, 1.1 mmol) in methanol (5 cm3) and pyridine (1

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cm3) were mixed giving dark blue rods of 2 overnight. Pink needles of 4 were prepared in the same manner, using Co(NO3)2.6H2O (0.147 g, 0.5 mmol) in 5 cm3 methanol in place of the copper solution. 2.3. Preparation of [Cu(1,3-bdc)(py)2] (5), [Co(1,3-bdc)(CH3OH)4] (6) and [Ni(1,3-bdc)(CH3OH)4] (7) Blue crystals of 5 were prepared in the same manner as described for 1, using DMF as solvent instead of DMSO. Compound 6 was synthesized by slow diffusion of a methanolic solution (5 cm3) of Co(NO3)2.6H2O (0.290 g, 1 mmol) into a solution of 1,3-benzenedicarboxylic acid (0.166 g, 1 mmol) in 7 cm3 methanol and 2 cm3 2,6-lutidine. 7 was prepared in the same manner, using Ni(NO3)2.6H2O (0.290 g, 1 mmol) instead of Co(NO3)2.6H2O. 2.4. Crystal structure determination Data were collected using a Bruker Smart APEX diffractometer (173 K, Mo Kα ˚ ). Corrections for Lorentz, X-ray radiation, graphite monochromator, l=0.7107 A polarisation and absorption effects were applied. Details of crystal data and intensity collection are summarised in Table 1. The structures were solved by direct methods Table 1 Crystallographic data

Formula CCDC deposit no. Molecular weight Temperature (K) Crystal size (mm) Crystal system Space group ˚) a (A ˚) b (A ˚) c (A b (°) ˚ 3) V (A Z F(000) GOF on F2 R1 (on F, I⬎2sI) wR2 (on F2, all data) ˚ ⫺3) ⌬rmax,min (e A

1

2

3

4

5

C23 H22 Cu N3 O5.5 1294/191 491.98 173 0.15×0.20 ×0.25 monoclinic

C24 H25 Cu N3 O6 1294/192 515.01 173 0.20×0.20 ×0.20 orthorhombic Pna21 16.301(2) 16.144(2) 9.010(1)

C23 H21 Co N3 O5 1294/193 478.36 173 0.10×0.10 ×0.20 monoclinic

C24 H22 Co N3 O5 1294/194 491.38 173 0.15×0.15 ×0.15 monoclinic

C18 H14 Cu N2 O4 1294/195 385.85 173 0.20×0.20 ×0.30 monoclinic

P21/n 9.068(1) 15.069(2) 16.648(2) 91.772(2) 2273.7(5) 4 988 1.198 0.0523 0.1709 1.258, ⫺0.604

P21/n 8.992(1) 14.804(2) 16.959(2) 91.191(2) 2257.1(5) 4 1016 0.772 0.0452 0.1387 0.603, ⫺0.575

P21/n 9.0525(7) 15.231(1) 15.973(1) 92.487(2) 2200.0(3) 4 1016 0.625 0.0413 0.1145 0.698, ⫺0.540

2371.0(4) 4 1068 0.599 0.0360 0.0963 0.592, ⫺0.334

6

7

C12 H20 C12 H20 Co O8 Ni O8 1294/196 1294/197 351.21 350.99 173 173 0.10×0.10 0.10×0.20 ×0.15 ×0.20 monomonoclinic clinic P21/n C2/c C2/c 9.912(1) 16.829(2) 16.927(5) 11.226(1) 13.161(1) 13.026(4) 15.626(2) 7.292(1) 7.304(2) 101.344(2) 108.009(2)109.176(6) 1704.7(3) 1535.8(3) 1521.0(8) 4 4 4 788 732 736 0.541 0.954 0.779 0.0384 0.0436 0.0449 0.1077 0.1144 0.1075 0.540, 1.171, 0.977, ⫺0.384 ⫺0.853 ⫺0.408

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and refined using full-matrix least-squares on all F2 data, using SHELX97 [22]. All non-hydrogen atoms were refined anisotropically; hydrogen atoms were included in calculated positions and refined with isotropic thermal parameters of 1.2 times (or 1.5 times for methanol protons) the isotropic thermal parameter of their parent atom. Hydrogens involved in hydrogen bonding were not placed in calculated positions, but only included in the model (with independent thermal parameters) if they could be located in the difference electron density map. 1 consists of a [Cu(1,3-bdc)(py)3] unit hydrogen bonded to a water molecule; there is another water molecule close to, but not on, a centre of inversion at (1/2, 1/2, 1/2). Attempting to model this peak at the origin gives rise to unacceptably high negative electron density at that point. 2 has the same building unit as 1, but the second water molecule is replaced by a methanol in a general position. 3 is unusual in these complexes as it contains only a [Co(1,3-bdc)(py)3(H2O)] unit, with no guest solvent. 4 is very similar to 3, but the coordinated water has been replaced by a methanol ligand. There is a water guest molecule in 4 which was found to be disordered over two positions. The hydrogen atoms on the guest water molecules in 1 and 4 could not be found and were omitted from the final model. 5 consists of a copper ion linked to another by two bridging bdc molecules; the metal is also singly coordinated to another bdc and to two pyridyl ligands. 6 and 7 consist of a metal ion coordinated to one bdc and four methanol ligands. The metal adopts octahedral symmetry and is located on a centre of inversion. Atomic coordinates and thermal parameters for all compounds have been deposited and CCDC numbers are given in Table 1. Selected bond lengths and angles for all four complexes are listed in Table 2.

Table 2 ˚ ) and angles (°) Selected bond distances (A

M-N(21) M-N(31) M-N(11) M-O(1) M-O(3) M-O(5) N(21)-M-N(31) O(1)-M-O(3) O(5)-M-N(11) a b c d e

1e (M=Cu)

2 (M=Cu)

3 (M=Co)

4 (M=Co)

5 (M=Cu)

6 (M=Co)

7 (M=Ni)

2.019(2) 2.030(2) 2.286(2) 1.953(2) 1.947(2) – 170.6(1) 177.6(1) –

2.043(4) 2.043(4) 2.273(3) 1.965(3) 1.956(3) – 168.9(1) 179.3(1) –

2.180(3) 2.153(3) 2.155(2) 2.043(2) 2.036(2) 2.109(2) 179.5(1) 177.4(1) 175.7(1)

2.155(2) 2.162(2) 2.184(2) 2.040(2) 2.075(2) 2.150(2) 179.1(1) 172.1(1) 170.4(1)

2.016(2) – 2.044(2) 1.972(2) 1.952(2) 2.271(2)a 175.6(1) 159.81(8) –

– – – 2.053(2) 2.083(2)b 2.115(2)c

– – – 2.014(3) 2.050(3)b 2.082(3)c

d

d

M-O(4). M-O(11). M-O(12). O-M-O bond angles all 180°, by symmetry. ˚. O(5)···O(6) distance in compound 1 is 2.67 A

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3. Results and discussion 3.1. Structures The structures of the metal environment of 1 and 2 are shown in Fig. 1, which also indicates the atomic labelling used. Both of these copper complexes adopt a 5coordinate geometry in the form of an incomplete octahedron, with one pyridine (containing N(11)) and both bdc oxygens in a plane with the copper and water oxy-

Fig. 1. Molecular structures and atom labelling schemes for compounds 1–7.

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Fig. 1. (continued)

gen, while the other two pyridine ligands perpendicular to this plane have slightly shorter Cu-N bond lengths. The bdc ligands on either side of the metal are in the syn- conformation, so that both the unbound oxygen atoms can accept a hydrogen ˚ (1) and 3.59 A ˚ (2) the bond from an uncoordinated water molecule. (At 3.67 A copper–oxygen distance to this water is too long to be a bond) The water molecule also acts as a hydrogen bond acceptor for a water (1) or methanol (2) solvent molecule. Details of the hydrogen bonding are given in Table 3.

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Table 3 Hydrogen bonding parametersd

1 O(5)-H(5AO)···O(2) O(5)-H(5BO)···O(4) C(22)-H(22)···centroid(N31-C35)a C(24)-H(24)···centroid(N31-C35)b 2 O(5)-H(5AO)···O(2) O(5)-H(5BO)···O(4) O(6)-H(6O)···O(5) C(22)-H(22)···centroid(N31-C35)c C(24)-H(24)···centroid(N31-C35)c 3 O(5)-H(5AO)···O(2) O(5)-H(5BO)···O(4) C(22)-H(22)···centroid(N31-C35)e C(24)-H(24)···centroid(N31-C35)f 4 O(5)-H(5O)···O(4) C(32)-H(32)···centroid(N21-C25)e C(34)-H(34)···centroid(N21-C25)f 5 C(3)g-H(3)g···O(2) C(25)-H(25)···O(2) 6 O(11)-H(11)···O(2)h O(12)-H(12)···O(2) 7 O(11)-H(11)···O(2)h O(12)-H(12)···O(2) a b c d e f g h

via via via via via via via via

˚) D-H (A

˚) D···A (A

˚) H···A (A

D-H···A (°)

0.903(2) 0.935(2) 0.950 0.950

2.796(3) 2.811(3) 3.623(2) 3.488(2)

1.883(3) 1.941(2) 2.834 2.660

161.2(5) 164.8(4) 141.1 145.9

0.987(2) 0.927(3) 0.902(2) 0.950 0.949

2.738(5) 2.784(4) 2.690(5) 3.613(2) 3.412(2)

1.848(4) 1.885(4) 1.815(3) 2.762 2.579

148.3(5) 162.8(3) 162.8(5) 149.5 146.6

0.830(3) 0.847(3) 0.950 0.950

2.661(4) 2.686(4) 3.704(2) 3.648(2)

1.889(2) 1.982(2) 2.910 2.862

154.3(2) 140.0(2) 141.9 140.7

1.10(3) 0.949 0.950

2.587(3) 3.780(2) 3.707(2)

1.491(3) 3.008 2.951

173.8(5) 139.4 137.5

0.950 0.950

3.074(4) 3.204(4)

2.297 2.442

138.5 137.1

0.961(3) 0.918(3)

2.627(3) 2.600(3)

1.700(3) 1.794(4)

160.7(4) 145.0(5)

0.934(3) 0.904(3)

2.638(4) 2.600(4)

1.904(3) 1.763(5)

177.3(4) 162.6(4)

x⫺0.5, 1.5⫺y, z⫺0.5. x⫺1, y, z. 0.5⫺x, 0.5+y, 0.5+z. x, y, 1+z. x+0.5, 0.5⫺y, 0.5+z. 1+x, y, z. 0.5⫺x, 0.5+y, 0.5⫺z. 0.5⫺x, y⫺0.5, 0.5⫺z.

Its d 9 configuration makes the copper(II) ion subject to Jahn–Teller distortion in the cubic environment, so this ion is seldom observed in a regular octahedral or tetrahedral geometry. More commonly, the octahedron is distorted to give four short bonds in a plane and two long trans bonds (eg. [Cu(H2O)2(NH3)4] has four Cu-N ˚ ) [23]. The bonds at 2.05, one Cu-O bond at 2.59 and one Cu-O bond at 3.37 A geometry observed in compounds 1 and 2 is consistent with this observation. The crystal structures of 1 and 2 consist of a benzenedicarboxylate bridged chain which runs approximately parallel to [1 0 1¯ ] (in 1) and to [0 1 1¯ ] (in 2), with the

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Fig. 2.

1-D coordination polymer structure of 2.

deprotonated carboxyl groups each coordinated to a copper(II) ion. This difference in orientation is expected as 2 crystallises in the orthorhombic space group Pna21 with similar cell parameters to the monoclinic space group P21/n which is observed ˚ axis in 2 is consequently c not a as it is in the other three for 1, 3 and 4. The 9 A structures. The chain is illustrated (for 2) in Fig. 2, showing that the metal centres are aligned in an approximately straight line. The chains pack together by perpendicular stacking of the “axial” pyridines (Fig. 3 shows this for 1). This interdigitated chain packing results in the formation of edge-to-face C-H···π hydrogen bonds between pyridine ligands (details given in Table 3). Cobalt frequently forms octahedral complexes, especially with non-sterically hindered ligands [23], and this is the case for 3 and 4, illustrated in Fig. 1. Again, the bdc ligands are syn- allowing for hydrogen bond formation with the coordinated water (in 3) or methanol ligand in 4. Compound 3 has no guest but compound 4 includes a disordered water molecule. 1-D chains similar to those seen for 1 and 2

Fig. 3. An illustration of how adjacent chains pack to allow C-H···π interactions between pyridyl ligands (shown here for 1) Guest molecules have been omitted.

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are formed — one such chain from 3 is illustrated in Fig. 4. The chains in turn interdigitate to give perpendicular stacking of the “axial” pyridines with C-H···π hydrogen bonds between them (details given in Table 3). Viewed perpendicular to the hydrogen-bonded bdc–water–bdc unit (i.e. along the axial pyridine axis), the chains of 1, 3 and 4 pack with hydrophilic regions facing one another. This can be seen in Fig. 5(a) which shows a packing diagram of 1 ˚ axis. This form of packing allows the formation of viewed down [1 0 0], the 9 A a small “cavity” into which the water guest fits. In 2, the second chain is inverted, allowing the methanol guest to fit into a hydrophobic pocket between phenyl and bdc groups (Fig. 5(b)). This subtle change is also the cause of the change of space group seen for this compound — having adjacent chains not related by a centre of symmetry prevents the compound from crystallizing in P21/n and forces it into a polar space group instead. The CSD search carried out showed that of seven complexes involving a transition metal and bdc, five (HAMTEU, REYSIX, RUFTOH, SOMLIP and VAVKUY) are discrete complexes. Only one structure of a complex with bdc and copper (REYSIX) has been reported. In this structure, the bdc bridges two (2-pyridylcarbonyl)amidato copper(II) moieties, with square planar copper ions. There are no reported structures containing a complex of bdc and cobalt. Compounds 5, 6 and 7 illustrate the influence of the other ligands beside bdc. At first sight, 5 closely resembles 1 and 2, with two pyridine ligands rather than three (Fig. 1). The copper ion geometry remains a distorted octahedron, but with no pseudo-ligand occupying the 6th coordination site. In this structure, the bdc acts as a bridge between adjacent copper ions; all but one of the carboxyl oxygens is involved in a Cu-O bond. The exception (O(2)) accepts weak C-H···O hydrogen bonds from nearby pyridine rings (Table 3). The resulting network is therefore a 2D rectangular polymer as shown in Fig. 6. There is insufficient space between the organic ligands to allow this structure to act as a host compound. 6 and 7 are analogous compounds to 1–4 in that they each contain a bdc ligand singly coordinated to a metal ion (cobalt in 6, nickel in 7), but in these compounds there are no pyridyl ligands, only four coordinated methanols. The molecular structures are shown in Fig. 1. The octahedral geometry causes two methanols to be in plane with the carboxyl groups of the bdc, allowing for O-H···O interactions (Table 3). The 1-D polymer propagates in the [1 0 1] direction. Methanol is smaller than pyridine, so the chains can pack closely without including solvent; adjacent chains stack (Fig. 7, showing structure 6) with aromatic groups offset to allow π···π interac˚ in 6 and 3.861 A ˚ in 7). tions (centroid–centroid distance is 3.864 A

Fig. 4.

1-D coordination polymer structure of 3.

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˚ axis, showing how the hydrophilic regions face one another and Fig. 5. (a) 1 viewed along the 9 A allow inclusion of a water molecule. The same type of packing obtains in 3 and 4. (b) 2 viewed along ˚ axis. The orientation of adjacent chains is reversed to allow the methyl group of the guest to fit the 9 A into a hydrophobic pocket.

These results indicate the utility and reliability of the benzenedicarboxylate moiety as a spacer ligand in forming coordination polymers. Variation of the other ligands coordinated to the central metal ion profoundly influences the packing modes of the polymer chains. Structure 2 (compared to the analogous 4) shows the influence of the guest molecule in determining the orientation of adjacent polymer chains. The methyl group on the methanol guest (in 2) appears to encourage the inversion of adjacent polymer chains to form a hydrophobic guest cavity, whereas guest water

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Fig. 6. 2-D coordination polymer structure of 5. The grid is a distorted rectangle with metal···metal ˚. distances of between 8 and 10 A

Fig. 7. Packing diagram of 6, showing π···π stacking between adjacent polymer chains.

molecules (in 4) are accommodated in a hydrophilic cavity, probably facilitated by their participation in the hydrogen bonding network.

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