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Pitfalls in the supramolecular assembly of silver(I) coordination compounds
Journal
of
MOLECULAR STRUCTURE ELSEVIER
Journal of Molecular
Structure 474 (1999) 91-101
Pitfalls in the supramolecular assembly of silver(I) coordination compounds Christer B. Aakeriiy”,
Alicia M. Beatty
Department of Chemistry, Kansas State University, Manhattan, KS 66506, USA Received
17 December
1997; received in revised form 5 May 1998; accepted
5 May 1998
Abstract
The syntheses and crystal structures of (6-methylnicotinic acid) (6- methylnicotinato)silver(I), di (6-methylnicotinic acid) silver(I) nitrate, (2-chloro-6-methylnicotinato) silver(I), di (2-chloro-6-methylnicotinic acid) silver(I) nitrate, and (2-methylnicotinic acid) (2-methylnicotinato) silver(I) are described. These coordination complexes were synthesized under the same conditions and with very similar ligands but their resulting structures are quite different, in part due to the degree of protonation of the nicotinic acid ligand(s). The structures vary from coordination polymers to hydrogen-bonded coordination dimers, to linear structures linked by anion-carboxylic acid hydrogen bonds. This study illustrates some of the difficulties involved in predicting hydrogen-bonded networks in transition-metal systems which contain carboxylic acid moieties and coordinatively unsaturated metal ions. 0 1998 Elsevier Science B.V. All rights reserved. Keywords:
Coordination
polymers;
Crystal engineering;
Hydrogen bonding; Nicotinic acid; Silver complexes
1. Introduction The predictable and controlled assembly of molecules and ions in the solid state is one of the primary goals of crystal engineering, and the last decade has seen the arrival of several useful tools for synthesizing supramolecular assemblies [l-5]. The hydrogen bond is arguably the most effective intermolecular connector, and hydrogenbonded motifs such as carboxylic acid dimers and amide-amide ribbons have been utilized in the design of extended assemblies in organic molecular solids [6-171. More recently, intermolecular via hydrogen assembly of metal complexes bonding has gained attention, where, rather than * Corresponding author. Tel.: 00 1 913 532 6096; Fax: 00 1 913 532 6666: e-mail: [email protected].
forming the more common coordination polymers using covalent interactions [ 1g-251, neighboring metal complexes are connected and oriented through ligand-ligand hydrogen bonds [26-281. For example, Mingos has used molecular recognition strategies to connect neighboring transitionmetal metal complexes as well as to link complexes to organic molecules using complementary hydrogen-bonding groups [29,30]. Recently we employed various nicotinamide ligands in the assembly of silver(I) complexes, where the pyridine nitrogen atom provides a coordinate covalent interaction with the silver ion. The geometry encoded in these linear silver(I) complexes was then propagated in a predictable manner via amide-amide hydrogen bonds between neighboring cations [3 I-331. The presence of substituents on the pyridine ring did not have a great effect on the overall
0022-2860/98/$ - see front matter 0 1998 Elsevier Science B.V. All rights reserved PII: SOO22-2860(98)00563-8
92
C.B. Aakerfiy,
A.M.
Brcttty /.lo~mul
structure, but the nature of the counterion could significantly influence the assembly and orientation of the cationic motifs. Now we wish to examine whether nicotinic acid, the carboxylic acid analog of nicotinamide, can be used as a reliable connector in the assembly of transition-metal complexes. Carboxylic acid and carboxylate moieties have a well-known ability to generate hydrogen-bonded motifs in organic molecular and ionic solids [34]. Therefore, a potential advantage of a nicotinic acid-nicotinate ligand system would be that a carboxylate moiety can eliminate the need for a counterion in metal complexes, thereby avoiding the structural interference induced by the chemical and steric demands of a counterion. A possible disadvantage of these ligands is that the carboxylate moiety may compete with the pyridine nitrogen atom for the metal center, which would interfere with the design strategy. There is a precedent for using analogs of nicotinic acid in metal complexes: the structure of a silver(I)-iso-nicotinic acid complex has been reported [35], where (iso-nicotinic acid)-(iso-nicotinato) silver(I) tetrahydrate forms a linear complex, with two ligands coordinated through the pyridine nitrogen atoms to silver(I). The complex has no counterion; rather, one of the ligands has lost a proton, and exists as the iso-nicotinate. Therefore, an intermolecular hydrogen bond (between the carboxylic acid unit of one complex and the carboxylate unit of a neighboring complex) results in an infinite chain of silver complexes. In contrast, (nicotinato) silver(I) is a coordination polymer in which the pyridine nitrogen atom and both carboxylate oxygen atoms are coordinated to silver ions, resulting in polymeric sheets [36]. We want to establish whether we can reliably use the carboxylic acid as an intermolecular connector in metal complexes, and to probe this in some detail by attaching substituents on the pyridine ring. To this end, we obtained the X-ray single crystal structures of five new silver(I) complexes: (6-methylnicotinic acid) (6- methylnicotinato) silver(I), 1; di (6-methylnicotinic acid) silver(I) nitrate, 2; (2-chloro-6-methylnicotinato) silver(I), 3; di (2-chloro-6-methylnicotinic acid) silver(I) nitrate, 4; and (2- methylnicotinic acid) (2-methylnicotinato) silver(I), 5.
ofMolucular
Structure
474 (1999)
91-101
2. Experimental 2.1. Preparation of (6methylnicotinic acid) (6 methylnicotinato) silver(l), 1,and di (6 methylnicotinic acid) silver(l) nitrate, 2 Silver nitrate (0.10 g, 0.59 mmol) was dissolved in 20 ml of a 1: 1 ethanol:water mixture. To this solution was added 0.16 g (1.2 mmol) 6-methylnicotinic acid dissolved in 40 ml of a 1: 1 ethanol:water mixture. The solution was briefly stirred, the solvent was allowed to evaporate slowly at ambient temperature, and single crystals of 1 were formed in solution as colorless prisms. The solvent was then allowed to evaporate to dryness at ambient temperature, and single crystals of 2 were formed as colorless prisms. 2.2. Preparation of (2-chloro-Cmethylnicotinato) silver(l), 3, and di (2-chloro-6-methylnicotinic acid) silver(l) nitrate, 4 Silver nitrate (0.10 g, 0.59 mmol) was dissolved in 20 ml of a 1: 1 ethanol:water mixture. To this solution was added 0.20 g (1.2 mmol) 2-chloro-6-methylnicotinic acid dissolved in 40 ml of a 1: 1 ethanol water mixture. The solution was briefly stirred, the solvent was allowed to evaporate slowly at ambient temperature, and single crystals of 3 were formed in solution as colorless prisms. The solvent was then allowed to evaporate to dryness at ambient temperature, yielding single crystals of 4 as colorless rods. 2.3. Preparation of (2-methylnicotinic (2.meth_ylnicotinato) silver(l), 5
acid)
Silver nitrate (0.10 g, 0.59 mmol) was dissolved in 20 ml of a 1: 1 ethanol:water mixture. To this solution was added 0.16 g ( 1.2 mmol) 2-methylnicotinic acid dissolved in 40 ml of a 1: 1 ethanol:water mixture. The mixture was briefly stirred, and the solution was allowed to evaporate slowly at ambient temperature. Single crystals of 5 were formed in solution as colorless prisms. 2.4. X-ray crystallography Single-crystal diffraction data were collected using a Siemens P4 four-circle diffractometer with 0 graphite monochromated MO-Ko (A = 0.71073 A) radiation.
s Weighting function variables
AP,,,~~,,,,~@A-‘)
R/R: (obs data) R/R; (all data)
D,,t, (g cm-‘) 0000) P(Mo-%) (mm-‘) Temperature (K) 0 range (deg.) Range h Range k Range 1 Reflections collected Unique reflections Observed reflections (I > 2aI) Observed data:parameter Refinement
o (deg) P (deg) Y (deg) Volume (A’) Z
fl (A) b (A) c (A, 111.775(7) 1650.8(4) 8 1.787 888 1.264 173 2.66-23.50 - 15too 0 to 8 - 17 to 18 1274 1217 1149 9.99 full-matrix least squares on F’ 0.0233lO.057 1 0.0257/0.0584 0.4361 - 0.470 1.060 g, = 0.0332 & = 3.5710
1362.3(3) 4 1.858 760 1.497 173 I .78-22.49 - 12to I - II to 1 - 12 to 12 1266 1077 1049 5.5 full-matrix least squares on F’ 0.0190/0.0529 0.02OUO.0536 0.365/ - 0.334 I.138 g, = 0.0345 g2 = 2.1056
CMHMN@~A~ 444. I.5 0.40 x 0.37 x 0.29 monoclinic C2lc 14.054(2) 7.666(l) 16.499(2)
2
95.16(l)
CIJHI~NZQIA~ 381.13 0.43 x 0.24 x 0. I8 monoclinic c2 1 I .484(2) 10.367(l) 1 I .488(2)
Empirical formula
‘wv Crystal size (mm) Crystal system Space group
1
Crystal data
Table I Data collection and refinement for l-5
1746.3(2) 8 1.951 1016 1.505 173 2.66-22.48 - It09 - 14to 1 - 16 to 16 1575 1148 1100 8.80 full-matrix least squares on F’ 0.0194/0.0511 0.0204/0.05 17 0.416/ - 0.316 1.265 g, = 0.0239 ,Q = 2.6770
1596.7(2) 8 2.3 17 1072 2.809 173 2.39-22.50 - 13to13 - 12to1 - 11to1 1383 1039 954 8.67 full-matrix least squares on F’ 0.0464/o. 1357 0.0544/O. 1556 1.837/ - 1.463 1.330 g, = 0.000 g2 = 115.2909
full-matrix least squares on F2 0.0224/0.0574 0.0238/0.0582 0.6741 - 0.786 1.175 g, = 0.0276 gz = 0.7221
11.6
Ct~H,~NzQAg 381.13 0.42 x 0.34 x 0.28 triclinic P-l 8.068(7) 8.093(l) 11.353(l) 73.909(7) 72.926(6) 70.746(6) 655.5( 1) 2 1.931 380 I.555 173 I .92-25.00 - 1to9 -9t09 - 13 to 13 2843 2309 2209
C IJH I?N \ 0 ?Cl?Ag 5 13.04 0.48 x 0.36 x 0.36 monoclinic C2lc 8.4333(5) 13.525(l) 15.533(9) 99.7 14(3)
5
4
90.560( 1)
C,HsNO>ClAg 278.44 0.42 x 0.18 x 0.10 monoclinic czlc 12.856(l) 11.419(l) 10.877(i)
3
94
C.B. Aakertiy. A.M. Bratty / Joumul of Molt~ular Structure 474 (1999) 91-101
Table 2 Atomic coordinates ( X 10”) and equivalent parameters (A X 102) for 1 x
Ag(l) N(1) N21) O(7A) O(7B) O(27A) O(27B) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(22) ~(23) ~(24) ~(25) C(26) ~(27) C(28) ~(27) H(2) H(4) H(5) H(8A) H(8B) H(8C) H(22) ~(24) ~(25) H(28A) H(28B) H(28C)
14 14 15 11 12 17 16 13 13 13 13 14 12 14 16 16 16 16 15 16 15 17 13 12 13 14 14 15 15 17 16 15 14 15
680(l) 153(4) 751(4) 918(4) 794(4) 105(4) 845(4) 677(5) 183(5) 195(5) 706(5) 165(5) 584(5) 694(6) 114(4) 535(5) 621(5) 311(5) 861(5) 852(5) 451(5) 290(4) 648(5) 858(5) 667(5) 264(6) 637(6) 385(6) 943(4) 015(5) 499(5) 870(5) 792(5) 536(5)
isotropic displacement
Table 3 Atomic coordinates ( X 104) and equivalent parameters (A X 101) for 2
Y
z
U(cq)
5015(l) 6965(l) 3533(5) 9302(5) 7464(5) 22 I O(4) 43 12(4) 7128(6) 8284(6) 9306(6) 9153(6) 7966(6) 8382(6) 7727(7) 3779(6) 2826(6) 1591(6) 1344(6) 2319(6) 3 178(6) 2090(7) 2355(4) 6277(6) 10 039(6) 10 017(6) 6964(7) 8470(7) 7441(7) 4996(6) 942(6) 5 19(6) 1386(7) 1976(7) 293 l(7)
7867( 1) 8361(4) 7079(4) 10914(4) ll535(3) 3480(3) 3810(3) 9380(5) 969 l(5) 8915(5) 7877(5) 7619(5) 10812(5) 647415) 6001(5) 5314(5) 5749(5) 685 l(5) 7500(5) 41 lO(5) 8672(5) 2638(3) 9767(5) 9166(5) 7187(5) 5993(5) 6001(5) 6801(5) 5823(5) 5427(5) 72 I O(5) 9010(5) X790(5) 9195(5)
28(l)
A@])
0
19(l) 21(l) 39(l) 29(l) 28( 1) 28(l) 21(l)
N(l) N(2) O(7B) O(7A) O(l) O(2) C(2) C(3) C(4) C(5) C(6) C(7) C(8) H(7) H(2) H(4) H(5) W8A) H(8B) H(8C)
455(2) 5000 3254(2) 3035(2) 4176(2) 5000 1353(2) 1727(2) 1136(2) 206(2) - 123(2) 2742(2) - 1126(2) 3594(2) 1791(2) 141 l(2) - 214(2) - 1602(2) - 999(2) - 1373(2)
19(l) 24(l) 23(l) 22(l) 23(l) 30(2) 20(l) l&l) 26(l) 26(2) 20( 1) 20(l) 26(l) 34 25 29 28 36 36 36 24 31 32 32 32 32
Crystal stabilities were monitored by measuring three standard reflections after every 97 reflections, with no significant decay observed. Cell parameters were obtained from 35 accurately centered reflections in the 20 range 10-25. Data were collected using a @29 scanning technique, Lorentz, polarization and Psiscan absorption corrections were applied. The structures were solved using Patterson methods, with the remaining non-hydrogen atoms found by successive full-matrix least-squares refinement on F’ and refined with anisotropic thermal parameters. Hydrogen atom positions were located from difference Fourier maps; and a riding model with fixed thermal parameters
x
4’
z
“(eq)
6497( 1) 6617(3) 2542(5) 4437(3) 5345(3) 1774(3) 4209(4) 5896(4) 5941(4) 6748(4) 7458(4) 7396(4) 5141(4) 8164(4) 493 l(3) 5333(4) 67OQ(4) 8055(4) 8544(4) 9165(4) 7277(4)
2500 3903(2) 7500 5439( 1) 6642( 1) 7330(2) 7500 4401(2) 5301(2) 5707(2) 5198(2) 4295(2) 5789(2) 37 19(2) 6902(l) 4079(2) 6335(2) 5439(2) 4008(2) 3388(2) 3295(2)
24(l) 21(l) 27(l) 39(l) 38(l) 34(l) 41(l) 22(l) 21(l) 24(l) 24(l) 21(l) 25(l) 32(i) 45 26 28 29 38 38 38
Table 4 Atomic coordinates ( X 10J) and equivalent parameters (A X 10’) for 3 x
&(I) Cl(]) N(l) O(7A) O(7B) C(2) C(3) C(4) C(5) C(6) C(7) C(8) H(4) H(5) H(8A) H(8B) H(8C)
4491(l) 2083(3) 927(8) 391 l(7) 3393(7) l746( 10) 2312(10) l942( 10) 105O(ll) 557( 10) 3306( IO) - 361(11) 2309(10) 759( I I) - 581(11) - 176(11) - 918(11)
isotropic displacement
isotropic displacement
Y
z
Weq)
5776(l) 2471(3) 2710(9) 5075(9) 4575(g) 3180(11) 4131(11) 4628( 12) 4187(12) 3210(12) 4607( 12) 2663( 14) 5268( 12) 4566( 12) 1997(14) 2416(14) 3221(14)
1317(l) 2264(3) 4187(10) 4267(9) 2385(g) 3624(12) 4062( 12) 5162(12) 5682( 13) 5199(13) 3517(13) 5780( 14) 5539( 12) 6387( 13) 5306(14) 6597(14) 5818(14)
2](l) 29(l) 20(3) 28(2) 23(2) 17(3) l7(3) 22(3) 25(3) 22(3) 20(3) 32(4) 27 30 38 38 38
C.B. Aakeriiy, A.M. Beatty / Journal of Molecular Structure 474 (1999) 91-101 Table 5 Atomic coordinates ( x IO”) and equivalent parameters (A X 10’) for 4
A&l) Cl(l) N(l)
N(2) O(7A) O(7B) O(1) O(2) C(2) C(3) C(4) C(5) C(6) C(7) C(8) H(7) H(4) H(5) H(8A) H(8B) H(8C)
isotropic displacement
x
4‘
z
Weq)
IO 000 7416(l) 10 497(3) 5000 8550(3) 6667(2) 5000 628 l(2) 9269(3) 9436(3) 11 016(3) 12 303(3) 12 020(3) 8062(3) 13 342(3) 7792(3) II 189(3) 13 424(3) 13 308(3) I3 352(3) 14 136(3)
1285(l) 1164(l) 1191(2) 1385(2) 1252(2) 1444(2) 483(2) 1868(2) 1222(2) I260(2) 1255(2) 1221(2) 1196(2) 1329(2) 1168(2) 1340(2) 1224(2) 1246(2) 1793(2) 593(2) 1237(2)
7500 8696(l) 8930( I ) 12500 I I 616(l) 10 439(l) 12500 12 499(l) 9369(2) IO 271(2) IO 728(2) 10 280(2) 9383(2) IO 766(2) 8853(2) II 909(l) 11 396(2) 10 60X(2) 8392(2) 8492(2) 9092(2)
27(l) 30(l)
21(l) 26(l) 36(l) 35(l) 520) 32(l) 22(l) 21(l) 25(l) 27(l) 24(l) 24(l) 31(l) 43 30 32 38 38 38
[Uij = 1.2Uij(eq) for the atom to which they are bonded] was used for subsequent refinements. The weighting function applied was w-’ = [c?(Fi) + (sip)* + (g2P)] where P = (Fi + 2Fz)/3. The SHELXTL PC and SHELXL-93 packages were used for data reduction and structure solution and refinement [37], and the crystallographic details for compounds l-5 are listed in Table 1. Fractional atomic coordinates for compounds l-51 are listed in Tables 2-6, respectively.
3. Results The reaction of silver(I) nitrate with two equivalents of 6-methylnicotinic acid leads to the formation of (6-methylnicotinic acid) (6-methylnicotinato) silver(I), 1 (Fig. l), where the coordination around the silver ion is approximately linear; LN(l)Ag( l)-N(21), 156.9”. The asymmetric unit contains one (6-methylnicotinic acid) (6- methylnicotinato) silver(I) complex. With two oxygen atoms in close proximity ( = 2.5 A), the silver ion is perhaps most accurately described as being four-coordinate
Table 6 Atomic coordinates ( X 10J) and equivalent parameters (A X IO’) for 5
Ml) N(1) WI) O(7A) O(7B) O(27A) O(27B) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(22) ~(23) c(24) C(25) C(26) C(27) C(28) ~(27) H(4) H(5) H(6) H(8A) H(8B) H(8C) H(24) ~(25) H(26) H(28A) H(28B) H(28C)
3496(l) 2228(3) 5358(3) - 3235(2) - 2441(2) 9991(2) 9052(3) 575(3) - 278(3) 576(3) 2297(4) 3078(3) - 2128(3) - 279(4) 6559(3) 7602(3) 7392(3) 6204(3) 5206(3) 8957(3) 6699(3) 11 056(2) - 50(3) 2832(4) 424 l(3) 164(4) - 1608(4) 5(4) 8112(3) 6007(3) 4342(3) 7761(3) 6892(3) 5617(3)
1496(l) - 678(3) 3 138(3) - 2169(3) - 1864(3) 2308(2) 521 l(3) - 631(3) - 1920(3) - 3221(3) - 3292(3) - 1999(4) - 1970(3) 897(3) 2890(3) 4093(3) 5534(3) 5722(3) 4513(3) 3903(3) 1291(3) 2055(2) - 4035(3) - 4166(3) - 1952(4) 613(3) 1202(3) 1949(3) 6485(3) 6728(3) 4606(3) 289(3) 1584(3) 859(3)
95
isotropic displacement
2693(l) 3503(2) 1723(2) 5179(2) 3111(2) - 1251(2) - 2063(2) 3422(2) 4206(2) 5093(2) 5 128(2) 43 17(2) 4 I80(2) 2489(2) 636(2) 1O(2) 533(2) 1678(2) 2237(2) - 1216(2) 150(2) - 1992(2) 5597(2) 5817(2) 4424(2) 1605(2) 2795(2) 2405(2) - ll(2) 1977(2) 3020(2) 384(2) - 819(2) 576(2)
29(l) 19(l) 16(l) 27(l) 22(l) 21(l) 29(l) 15(l) 15(l) 19(l) 23(l) 23(l) 17(l) 21(l) 15(l) 14(l) 19(l) 20(l) 20(l) 17(l) 20(l) 25 23 28 27 25 25 25 22 24 24 24 24 24
(Table 7, Fig. 1). In addition to the coordinate covalent bonds, an O-H...0 hydrogen bond exists between neighboring carboxylic acid and carboxylate units [rH(27). . .0(7B), 1.445(5) A; r0(27A). . .0(7B), 2.45 l(5) A; L0(27A)-H(27). . .0(7B), 167.9(2)“] (Fig. 2). Although the interaction leads to an infinite chain, the structure is dominated by the Ag-N, Ag-0 interactions, forming a coordination polymer that extends in three dimensions. Further evaporation of the solution which yielded 1 results in the formation of single crystals of di (6methylnicotinic acid) silver(I) nitrate 2 (Fig. 3) where the cationic complex contains a silver ion
C.B. Aukertiy, A.M. Bearty / Jounml
96
Fig. 1. The coordination scheme
Table 7 283Selected
geometry about the silver ion in the coordination
bond lengths (A) and angles (“) for 1”
Ag( 1)-NC1) Ag( 1)-NO 1) Ag( 1)-O(7A) Ag( I)-O(27B) N(I)-Ag(l)-N(21) N( 1)-Ag(l)-O(7A)’ N(21 )-Ag( I)-O(7A)’ N( I)-Ag( l)-O(27B)” N(2 I)-Ag( 1)-O(27B)” 0(7A)‘-A&l)-O(27B)” ’ Symmetry Y, - z + 1.
of Molecular
code: (‘)I + 5/2,y -
2.1990) 2.213(5) 2.5 17(4) 2.590(4) 156.9(2) 84.0(2) I l&9(2) 105.5(2) 82.2( 1) 2938 I .6( 1) l/2, - z + 2; (“) - x + 3, -
Structure
474 (1999) 9/L101
polymer in 1. The inset shows the asymmetric
unit of 1 with labeling
coordinated to two ligands through the pyridyl nitrogen atoms0 in a near-linear fashion [rAg(l)N(l), 2.163(2) A; LN(l)-A&l)-N(lA), 175.1(l)“]. The asymmetric unit contains one-half of the complex (one 6-methylnicotinic acid coordinated to silver, and one-half of the nitrate anion). The shortest silveroxygen distance is > 2.7 A. The 1-D geometry of the complex cation is propagated in the solid state through two symmetry-related O-H.. .O hydrogen bonds [vH(7)...0(2), 1.934(2) A; r0(7A)...0(2), 2.736(2) A; L0(7A)-H(7). . .0(2), 172.9(l)“] between the acid hydroxyl group and an oxygen atom of the nitrate counterion, leading to an infinite chain linked through nitrate ions (Fig. 3). In the structure of (2-chloro-6-methylnicotinato)
C.B. Aakertiy, A.M. Beatty / Journal of Molecular Structure 474 (1999) 91-101
Fig. 2. The linear motif formed by hydrogen-bonding
interactions
silver(I), 3 (Fig. 4), the silver ion is coordinated to three carboxylate oxygen atoms and one pyridine nitrogen atom, resulting in a distorted tetrahedral arrangement (Table 8). The asymmetric unit contains
Fig. 3. The chain formed by carboxylic scheme.
acid-nitrate
in 1. Ag-0
interactions
97
with nearby cations have been omitted for clarity.
one 2-chloro-6-methyl nicotinate ligand coordinated to silver; the tetrahedral coordination is generated through symmetry-related ligands. The bridging carboxylate units lead to a short Ag-Ag distance of
hydrogen bonds in 2. The inset is the linear cation and associated
anion with the labeling
98
C.B. Aakerijv, A.M. Beatty / Jourrzal of Molecular Structure 474 (1999) 91-101
Fig. 4. The bridging carboxylate interactions asymmetric unit of 3 with labeling scheme.
in the coordination
polymer
Table 8 Selected bond lengths (A) and angles (“) for 3” Ag( I)-N( I)” Ag( 1)-O(7B) Ag( l)-O(7A)’ Ag( l)-O(7A)“’ 0(7B)-Ag( I)-O(7A)’ 0(7B)-Ag( I)-N( 1)” 0(7A)‘-Ag( I)-N( 1)’ 0(7B)-Ag( I)-O(7A)“’ 0(7A)‘-Ag( l)-O(7A)“’ N( l)‘-Ag( l)-O(7A)“’
2.34(l) 2.29(9) 2.300(9) 2.54(l) 119.2(4) 122.9(4) 117.9(4) 92.2(3) 83. I(3) 95.2(4)
d Symmetry code: (‘) - x + I,y, - z + l/2; (“) - x + 112,~ + I/ 2, - z + l/2; (“I)& - y + I,z - i/2.
in 3. Hydrogen
atoms have been omitted for clarity. The inset is the
2.87X2) A (Fig. 4). The coordination polymer extends in three dimensions, and there are no acidacid hydrogen bonds, as the carboxylic acid moiety is fully deprotonated. Further evaporation of the solution which yielded 3 results in the formation of single crystals of di (2chloro-6-methylnicotinic acid) silver(I) nitrate, 4 (Fig. 5), where the ligands coordinate through the pyridine nitrogen atoms to the silver ion, [rAg-N, 2.194(2) A; L(Nl)-Ag-(NlA), 173.3(l)“. The asymmetric unit contains one-half of the cation and onehalf of the anion, as in 2. The shortest silver-oxygen distance is > 2.7 A. The 1D geometry of the complex cation is propagated by symmetry-related O-H.. .O
C.B. Aakeriiy, A.M. Beutty / Joumul of Molecular Structure 474 (1999) 91-101
Fig. 5. The chain formed by carboxylic scheme
acid-nitrate
hydrogen
bonds in 4. The inset is the linear cation and associated
hydrogen bonds [rH(7)...0(2), 1.835(3) A; r0(7A). . .0(2), 2.668(3) A; L0(7A)-H(7). . .0(2), 165.08(9)“] leading to an infinite chain linked through nitrate ions similar to that in 2 (Fig. 5). The reaction of silver(I) nitrate with two equivalents of 2-methylnicotinic acid leads to the formation of (2-methylnicotinic acid) (2-methylnicotinato) silver(I), 5 (Fig. 6), where the asymmetric unit contains one (2-methylnicotinic acid) (2-methylnicotinato) silver(I) subunit. The coordinate covalent bonds (Table 9) result in a dimeric species, where two nicotinate ligands bridge two silver(I) ions. Although the coordination geometry around silver is no longer linear, these dimers are assembled into an extended 1D motif by O-H...0 hydrogen bonds [rH(27). . .0(7B), 1.430(2) A; r0(27A)...0(7B), 2.448(2) A; L0(27A)-H(27). . .0(7B), 173.8(l)“] between neighboring ligands (Fig. 6).
4. Discussion An examination of the structures l-5 in the context of predictable supramolecular assemblies demonstrates that, under the reaction conditions used in this study, exceptions are the rule. In fact, in two of the reactions, two different complexes were isolated
99
anion with labeling
(1,2 and 3,4). Only 1 displays an obvious similarity to the aforementioned structure of (iso-nicotinic acid) (iso-nicotinato) silver(I), in which chains are formed through intermolecular carboxylic acid-carboxylate hydrogen bonds. Despite this similarity, the structure of 1 is dominated by coordinate-covalent interactions, and is best described as a three-dimensional coordination polymer. Recurring patterns in this series of compounds are not readily apparent. For example, the molecular structure of 1 and 5 differ only in the position of the methyl substituent on the aromatic ring. However, this small change leads to very different structures, including differences in coordination geometry. The structure of 3 further illustrates the lack of recognizable patterns; the bridging carboxylate motif present in 3 is absent in 1 and 5. It is also important to note that the hydrogen bonding distance between O(7B) and O(27A) is short in 1 and 5 ( = 2.45 A), which is reflected in theOcarboxylate C-O distance: [C(7)0(7A), 1.235(8) A; C(7)-0(7B), 1.271(8) A for 1; [C(7)-0(7A), 1.229(3) A; C(7)-0(7B), 1.285(3) A for 5.1 Even though this is a short O-O contact, the carboxylate and carboxylic acid moieties are crystallographically inequivalent, and the hydrogen atom was located on the carboxylic acid moiety. In 2 and 4, where the nitrate counterion is present,
loo
C.B. Aakertiy, A.M. Bratty / Journrrl of Molecular Srrucrure 474 (1999) 91-101
Fig. 6. The nicotinate ligands bridge silver ions, and hydrogen bonds between dimers form an extended one-dimensional the asymmetric unit of 5 with labeling scheme.
the anion participates in hydrogen bonding interactions between neighboring complexes, interfering with ligand-ligand interactions. The fact that these complexes contain fully protonated ligands can be attributed to the increased acidity of the reaction Table 9 Selected bond lengths “tblfn3” >
43 1)-NC1) Ag( 1)-NO 1) Ag( I)-O(7A)’ N(l)-Ag(l)-N(21) N( I)-Ag( l)-O(7A)’ N(21)-Ag(l)-O(7A)’ ’ Symmetry
(.k) and angles
(“) for 5”rowref
2.17(2) 2.184(2) 2.556(2) 165.49(E) 94.16(7) 92.23(7)
code: (‘) - X, - y, - z + 1
relid =
motif in 5. The inset is
mixture after the precipitation of 1 and 3, respectively. The major difference between the structures of 2 and 4 appears to be the torsion angle about silver, where the two pyridyl rings in 4 are essentially coplanar [C(2)N(l)-Ag( I)-N( 1A) = 1.71”], but are twisted with respect to each other in 2 [C(2)-N( l)-N(lA)C(6A) = 59.4”]. This result is surprising, considering that the nicotinic acid groups in 2 have only one bulky substituent (6-methyl), while those in 4 are di-substituted (2-chloro, 6-methyl).
5. Conclusion The five very different structures described above demonstrate that we cannot always translate the prin-
C.B. AnkerGy. A.M. Batty
/Journal
ciples of organic molecular solids to the assembly of coordination complexes. Difficulties arise due to the formation of the carboxylate anion, which in some cases competes successfully (and unpredictably) for metal coordination sites. Thus, while the role of protonated carboxylates may be identified easily (linear hydrogen-bonding motifs in 2 and 4), the oxygen atoms of non-protonated carboxylate moieties and the pyridine nitrogen atoms compete unpredictably for coordination to the metal ion, resulting in a mixture of bridging and non-bridging coordination environments. Therefore, in order to implement a reliable strategy for the supramolecular assembly of coordination complexes via carboxylic acid hydrogen bonds, we must carefully control the acidity of the reaction mixture, so that we have a consistent set of functional groups for intermolecular interaction. Once consistent ligand-based intermolecular connectors are present, we may further facilitate ligand-ligand interactions by using more non-coordinating anions such as tetrafluoroborate or hexafluorophosphate [38] (in place of hydrogen-bonding nitrate as in 2 and 4.) The unpredictable system described in this paper contrasts with the silver(I) coordination complexes of nicotinamide, where the amide functionality proved to be a reliable connector for supramolecular assemblies [3 l-331.
Acknowledgements We acknowledge the financial support from Kansas State University and NSF-EPSCoR (OSR-9550487).
References 111J.-M. Lehn, Angew. Chem. Int. Ed. Engl. 29 (1990) 1304. 121G.R. Desiraju, Crystal Engineering: The Design of Organic Solids, Elsevier, Amsterdam, 1989. Angew. Chem. Int. Ed. Engl. 34 (1995) 231 I. C.B. Aakeriiy, Acta Crystallogr. Sect. B. 53 (1997) 569. M [51 M.J. Zaworotko, Nature 386 (I 997) 220. [61 S. Coe, J.J. Kane, T.L. Nguyen, L.M. Toledo, E. Wininger, F.W. Fowler. J.W. Lauher, J. Am. Chem. Sot. II9 (1997) 86. J. Am. Chem. Sot. 116 [71 C.B. Aakerliy, M. Nieuwenhuyaen, (1994) 10983. M.J. Zaworotko, C. 181 R.E. Melendez, C.V. Krishnamohan, Bauer, R.D. Rogers, Angew. Chem. Int. Ed. Engl. 35 (1996) 2213. [31 G.R. Desiraju,
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101
[9] 0. Felix, M.W. Hosseini, A. deCian. J. Fischer. Angew. Chem. lnt. Ed. Engl. 36 (1997) 102. [IO] P. Brunet, M. Simard, J.D. Wuest, J. Am. Chem. Sot. 119 (1997) 2737. [ 1 I] A. Marsh, M. Silvestri. J.-M. Lehn, Chem. Commun. (1996) 1527. [12] C.B. Aakeroy, P.B. Hitchcock, J. Mater. Chem. 3 (1993) 1129. [ 131 C.B. Aakeroy, P.B. Hitchcock, K.R. Seddon, J. Chem. Sot. Chem. Commun. (1992) 553. [ 141 J. Zyss, J. Pecaut, J.P. Levy, R. Masse, Acta Crystallogr. Sect. B, 49 (I 993) 334. [ 151 S. Bhattacharaya, P. Dastidar, T.N.G. Row, Chem. Mater. 6 (1994) 531. [ 161 0. Watanabe, T. Noritake, Y. Hirose. A. Okada, T. Kurauchi, J. Mat. Chem. 23 (1993) 32 1. [ 171 S. Hanessian, M. Simard, S. Roelens, J. Am. Chem. Sot. 1 17 (1995)7630. [I81 R. Robson, B.F. Abrahams, S.R. Batten, R.W. Gable, B.F. Hoskins, J. Liu, Supramolecular Architectures, ACS Publication, Washington, DC, 1992, pp. 256-273. [ 191 O.M. Yaghi, G. Li, H. Li, Nature 378 (1995) 703. [20] A.J. Blake, N.R. Champness, S.S.M. Chung, W.-S. Li, M. Schriider, Chem. Commun. (1997) 1005. [21] S. Subramanian, M.J. Zaworotko, Angew. Chem. Int. Ed. Engl. 34 (1995) 2127. [22] EC. Constable, Chem. Commun. (1997) 1073. [23] M. Fujita, Y.J. Kwon, S. Washizu, K. Ogura, J. Am. Chem. Sot. 116 (1994) 1151. 1241 D. Venkataraman, S. Lee, J.S. Moore, P. Zhang, K.A. Hirsch, G.B. Gardner, A.C. Covey, C.L. Prentice, Chem. Mater. 8 (1996) 2030. [25] L. Carlucci, G. Ciani, D.M. Proserpio, A. Sironi, J. Am. Chem. Sot. 117 (1995) 4562. [26] L. Carlucci. G. Ciani, D.M. Proserpio, A. Sironi, J. Chem. Sot. Dalton Trans. (I 997) 1801. [27] A. Hassan. S. Wang, J. Chem. Sot. Dalton Trans. (1997) 2009. [28] C.M. Drain, K.C. Russel, J.-M. Lehn, Chem. Commun. (1996) 337. [29] A.D. Burrows, C.-W. Chan, M.M. Chowdhry, J.E. McGrady, D.M.P. Mingos, Chem. Sot. Rev. Commun. (1995) 329. [30] A.D. Burrows, D.M.P. Mingos, A.J.P. White, D.J. Williams, Chem. Commun. (1996) 97. [31] C.B. Aakerdy, A.M. Beatty, Chem. Commun. (1998) 1067. 1321 C.B. Aakeroy, A.M. Beatty, Cryst. Engng I (1998) 3. [33] C.B. Aakeroy, A.M. Beatty, B.A. Helfrich, J. Chem. Sot. Dalton Trans. (1998) 1943. [34] L. Leiserowitz, M. Tuval, Acta Crystallogr. Sect. B, 34 (1978) 1230. [35] F. Jaber, F. Charbonnier, R. Faure, M. Petit-Ramel, Z. Kristallogr. 209 (1994) 536. [36] G. Smith, A.N. Reddy, K.A. Byriel, C.H.L. Kennard, Polyhedron I3 ( 1994) 2425. [37] G.M. Sheldrick, SHELXL-93, University of Glittingen. [38] C.B. Aakeroy, A.M. Beatty, D.S. Leinen, J. Am. Chem. Sot. 120 (1998) 7383.
of
MOLECULAR STRUCTURE ELSEVIER
Journal of Molecular
Structure 474 (1999) 91-101
Pitfalls in the supramolecular assembly of silver(I) coordination compounds Christer B. Aakeriiy”,
Alicia M. Beatty
Department of Chemistry, Kansas State University, Manhattan, KS 66506, USA Received
17 December
1997; received in revised form 5 May 1998; accepted
5 May 1998
Abstract
The syntheses and crystal structures of (6-methylnicotinic acid) (6- methylnicotinato)silver(I), di (6-methylnicotinic acid) silver(I) nitrate, (2-chloro-6-methylnicotinato) silver(I), di (2-chloro-6-methylnicotinic acid) silver(I) nitrate, and (2-methylnicotinic acid) (2-methylnicotinato) silver(I) are described. These coordination complexes were synthesized under the same conditions and with very similar ligands but their resulting structures are quite different, in part due to the degree of protonation of the nicotinic acid ligand(s). The structures vary from coordination polymers to hydrogen-bonded coordination dimers, to linear structures linked by anion-carboxylic acid hydrogen bonds. This study illustrates some of the difficulties involved in predicting hydrogen-bonded networks in transition-metal systems which contain carboxylic acid moieties and coordinatively unsaturated metal ions. 0 1998 Elsevier Science B.V. All rights reserved. Keywords:
Coordination
polymers;
Crystal engineering;
Hydrogen bonding; Nicotinic acid; Silver complexes
1. Introduction The predictable and controlled assembly of molecules and ions in the solid state is one of the primary goals of crystal engineering, and the last decade has seen the arrival of several useful tools for synthesizing supramolecular assemblies [l-5]. The hydrogen bond is arguably the most effective intermolecular connector, and hydrogenbonded motifs such as carboxylic acid dimers and amide-amide ribbons have been utilized in the design of extended assemblies in organic molecular solids [6-171. More recently, intermolecular via hydrogen assembly of metal complexes bonding has gained attention, where, rather than * Corresponding author. Tel.: 00 1 913 532 6096; Fax: 00 1 913 532 6666: e-mail: [email protected].
forming the more common coordination polymers using covalent interactions [ 1g-251, neighboring metal complexes are connected and oriented through ligand-ligand hydrogen bonds [26-281. For example, Mingos has used molecular recognition strategies to connect neighboring transitionmetal metal complexes as well as to link complexes to organic molecules using complementary hydrogen-bonding groups [29,30]. Recently we employed various nicotinamide ligands in the assembly of silver(I) complexes, where the pyridine nitrogen atom provides a coordinate covalent interaction with the silver ion. The geometry encoded in these linear silver(I) complexes was then propagated in a predictable manner via amide-amide hydrogen bonds between neighboring cations [3 I-331. The presence of substituents on the pyridine ring did not have a great effect on the overall
0022-2860/98/$ - see front matter 0 1998 Elsevier Science B.V. All rights reserved PII: SOO22-2860(98)00563-8
92
C.B. Aakerfiy,
A.M.
Brcttty /.lo~mul
structure, but the nature of the counterion could significantly influence the assembly and orientation of the cationic motifs. Now we wish to examine whether nicotinic acid, the carboxylic acid analog of nicotinamide, can be used as a reliable connector in the assembly of transition-metal complexes. Carboxylic acid and carboxylate moieties have a well-known ability to generate hydrogen-bonded motifs in organic molecular and ionic solids [34]. Therefore, a potential advantage of a nicotinic acid-nicotinate ligand system would be that a carboxylate moiety can eliminate the need for a counterion in metal complexes, thereby avoiding the structural interference induced by the chemical and steric demands of a counterion. A possible disadvantage of these ligands is that the carboxylate moiety may compete with the pyridine nitrogen atom for the metal center, which would interfere with the design strategy. There is a precedent for using analogs of nicotinic acid in metal complexes: the structure of a silver(I)-iso-nicotinic acid complex has been reported [35], where (iso-nicotinic acid)-(iso-nicotinato) silver(I) tetrahydrate forms a linear complex, with two ligands coordinated through the pyridine nitrogen atoms to silver(I). The complex has no counterion; rather, one of the ligands has lost a proton, and exists as the iso-nicotinate. Therefore, an intermolecular hydrogen bond (between the carboxylic acid unit of one complex and the carboxylate unit of a neighboring complex) results in an infinite chain of silver complexes. In contrast, (nicotinato) silver(I) is a coordination polymer in which the pyridine nitrogen atom and both carboxylate oxygen atoms are coordinated to silver ions, resulting in polymeric sheets [36]. We want to establish whether we can reliably use the carboxylic acid as an intermolecular connector in metal complexes, and to probe this in some detail by attaching substituents on the pyridine ring. To this end, we obtained the X-ray single crystal structures of five new silver(I) complexes: (6-methylnicotinic acid) (6- methylnicotinato) silver(I), 1; di (6-methylnicotinic acid) silver(I) nitrate, 2; (2-chloro-6-methylnicotinato) silver(I), 3; di (2-chloro-6-methylnicotinic acid) silver(I) nitrate, 4; and (2- methylnicotinic acid) (2-methylnicotinato) silver(I), 5.
ofMolucular
Structure
474 (1999)
91-101
2. Experimental 2.1. Preparation of (6methylnicotinic acid) (6 methylnicotinato) silver(l), 1,and di (6 methylnicotinic acid) silver(l) nitrate, 2 Silver nitrate (0.10 g, 0.59 mmol) was dissolved in 20 ml of a 1: 1 ethanol:water mixture. To this solution was added 0.16 g (1.2 mmol) 6-methylnicotinic acid dissolved in 40 ml of a 1: 1 ethanol:water mixture. The solution was briefly stirred, the solvent was allowed to evaporate slowly at ambient temperature, and single crystals of 1 were formed in solution as colorless prisms. The solvent was then allowed to evaporate to dryness at ambient temperature, and single crystals of 2 were formed as colorless prisms. 2.2. Preparation of (2-chloro-Cmethylnicotinato) silver(l), 3, and di (2-chloro-6-methylnicotinic acid) silver(l) nitrate, 4 Silver nitrate (0.10 g, 0.59 mmol) was dissolved in 20 ml of a 1: 1 ethanol:water mixture. To this solution was added 0.20 g (1.2 mmol) 2-chloro-6-methylnicotinic acid dissolved in 40 ml of a 1: 1 ethanol water mixture. The solution was briefly stirred, the solvent was allowed to evaporate slowly at ambient temperature, and single crystals of 3 were formed in solution as colorless prisms. The solvent was then allowed to evaporate to dryness at ambient temperature, yielding single crystals of 4 as colorless rods. 2.3. Preparation of (2-methylnicotinic (2.meth_ylnicotinato) silver(l), 5
acid)
Silver nitrate (0.10 g, 0.59 mmol) was dissolved in 20 ml of a 1: 1 ethanol:water mixture. To this solution was added 0.16 g ( 1.2 mmol) 2-methylnicotinic acid dissolved in 40 ml of a 1: 1 ethanol:water mixture. The mixture was briefly stirred, and the solution was allowed to evaporate slowly at ambient temperature. Single crystals of 5 were formed in solution as colorless prisms. 2.4. X-ray crystallography Single-crystal diffraction data were collected using a Siemens P4 four-circle diffractometer with 0 graphite monochromated MO-Ko (A = 0.71073 A) radiation.
s Weighting function variables
AP,,,~~,,,,~@A-‘)
R/R: (obs data) R/R; (all data)
D,,t, (g cm-‘) 0000) P(Mo-%) (mm-‘) Temperature (K) 0 range (deg.) Range h Range k Range 1 Reflections collected Unique reflections Observed reflections (I > 2aI) Observed data:parameter Refinement
o (deg) P (deg) Y (deg) Volume (A’) Z
fl (A) b (A) c (A, 111.775(7) 1650.8(4) 8 1.787 888 1.264 173 2.66-23.50 - 15too 0 to 8 - 17 to 18 1274 1217 1149 9.99 full-matrix least squares on F’ 0.0233lO.057 1 0.0257/0.0584 0.4361 - 0.470 1.060 g, = 0.0332 & = 3.5710
1362.3(3) 4 1.858 760 1.497 173 I .78-22.49 - 12to I - II to 1 - 12 to 12 1266 1077 1049 5.5 full-matrix least squares on F’ 0.0190/0.0529 0.02OUO.0536 0.365/ - 0.334 I.138 g, = 0.0345 g2 = 2.1056
CMHMN@~A~ 444. I.5 0.40 x 0.37 x 0.29 monoclinic C2lc 14.054(2) 7.666(l) 16.499(2)
2
95.16(l)
CIJHI~NZQIA~ 381.13 0.43 x 0.24 x 0. I8 monoclinic c2 1 I .484(2) 10.367(l) 1 I .488(2)
Empirical formula
‘wv Crystal size (mm) Crystal system Space group
1
Crystal data
Table I Data collection and refinement for l-5
1746.3(2) 8 1.951 1016 1.505 173 2.66-22.48 - It09 - 14to 1 - 16 to 16 1575 1148 1100 8.80 full-matrix least squares on F’ 0.0194/0.0511 0.0204/0.05 17 0.416/ - 0.316 1.265 g, = 0.0239 ,Q = 2.6770
1596.7(2) 8 2.3 17 1072 2.809 173 2.39-22.50 - 13to13 - 12to1 - 11to1 1383 1039 954 8.67 full-matrix least squares on F’ 0.0464/o. 1357 0.0544/O. 1556 1.837/ - 1.463 1.330 g, = 0.000 g2 = 115.2909
full-matrix least squares on F2 0.0224/0.0574 0.0238/0.0582 0.6741 - 0.786 1.175 g, = 0.0276 gz = 0.7221
11.6
Ct~H,~NzQAg 381.13 0.42 x 0.34 x 0.28 triclinic P-l 8.068(7) 8.093(l) 11.353(l) 73.909(7) 72.926(6) 70.746(6) 655.5( 1) 2 1.931 380 I.555 173 I .92-25.00 - 1to9 -9t09 - 13 to 13 2843 2309 2209
C IJH I?N \ 0 ?Cl?Ag 5 13.04 0.48 x 0.36 x 0.36 monoclinic C2lc 8.4333(5) 13.525(l) 15.533(9) 99.7 14(3)
5
4
90.560( 1)
C,HsNO>ClAg 278.44 0.42 x 0.18 x 0.10 monoclinic czlc 12.856(l) 11.419(l) 10.877(i)
3
94
C.B. Aakertiy. A.M. Bratty / Joumul of Molt~ular Structure 474 (1999) 91-101
Table 2 Atomic coordinates ( X 10”) and equivalent parameters (A X 102) for 1 x
Ag(l) N(1) N21) O(7A) O(7B) O(27A) O(27B) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(22) ~(23) ~(24) ~(25) C(26) ~(27) C(28) ~(27) H(2) H(4) H(5) H(8A) H(8B) H(8C) H(22) ~(24) ~(25) H(28A) H(28B) H(28C)
14 14 15 11 12 17 16 13 13 13 13 14 12 14 16 16 16 16 15 16 15 17 13 12 13 14 14 15 15 17 16 15 14 15
680(l) 153(4) 751(4) 918(4) 794(4) 105(4) 845(4) 677(5) 183(5) 195(5) 706(5) 165(5) 584(5) 694(6) 114(4) 535(5) 621(5) 311(5) 861(5) 852(5) 451(5) 290(4) 648(5) 858(5) 667(5) 264(6) 637(6) 385(6) 943(4) 015(5) 499(5) 870(5) 792(5) 536(5)
isotropic displacement
Table 3 Atomic coordinates ( X 104) and equivalent parameters (A X 101) for 2
Y
z
U(cq)
5015(l) 6965(l) 3533(5) 9302(5) 7464(5) 22 I O(4) 43 12(4) 7128(6) 8284(6) 9306(6) 9153(6) 7966(6) 8382(6) 7727(7) 3779(6) 2826(6) 1591(6) 1344(6) 2319(6) 3 178(6) 2090(7) 2355(4) 6277(6) 10 039(6) 10 017(6) 6964(7) 8470(7) 7441(7) 4996(6) 942(6) 5 19(6) 1386(7) 1976(7) 293 l(7)
7867( 1) 8361(4) 7079(4) 10914(4) ll535(3) 3480(3) 3810(3) 9380(5) 969 l(5) 8915(5) 7877(5) 7619(5) 10812(5) 647415) 6001(5) 5314(5) 5749(5) 685 l(5) 7500(5) 41 lO(5) 8672(5) 2638(3) 9767(5) 9166(5) 7187(5) 5993(5) 6001(5) 6801(5) 5823(5) 5427(5) 72 I O(5) 9010(5) X790(5) 9195(5)
28(l)
A@])
0
19(l) 21(l) 39(l) 29(l) 28( 1) 28(l) 21(l)
N(l) N(2) O(7B) O(7A) O(l) O(2) C(2) C(3) C(4) C(5) C(6) C(7) C(8) H(7) H(2) H(4) H(5) W8A) H(8B) H(8C)
455(2) 5000 3254(2) 3035(2) 4176(2) 5000 1353(2) 1727(2) 1136(2) 206(2) - 123(2) 2742(2) - 1126(2) 3594(2) 1791(2) 141 l(2) - 214(2) - 1602(2) - 999(2) - 1373(2)
19(l) 24(l) 23(l) 22(l) 23(l) 30(2) 20(l) l&l) 26(l) 26(2) 20( 1) 20(l) 26(l) 34 25 29 28 36 36 36 24 31 32 32 32 32
Crystal stabilities were monitored by measuring three standard reflections after every 97 reflections, with no significant decay observed. Cell parameters were obtained from 35 accurately centered reflections in the 20 range 10-25. Data were collected using a @29 scanning technique, Lorentz, polarization and Psiscan absorption corrections were applied. The structures were solved using Patterson methods, with the remaining non-hydrogen atoms found by successive full-matrix least-squares refinement on F’ and refined with anisotropic thermal parameters. Hydrogen atom positions were located from difference Fourier maps; and a riding model with fixed thermal parameters
x
4’
z
“(eq)
6497( 1) 6617(3) 2542(5) 4437(3) 5345(3) 1774(3) 4209(4) 5896(4) 5941(4) 6748(4) 7458(4) 7396(4) 5141(4) 8164(4) 493 l(3) 5333(4) 67OQ(4) 8055(4) 8544(4) 9165(4) 7277(4)
2500 3903(2) 7500 5439( 1) 6642( 1) 7330(2) 7500 4401(2) 5301(2) 5707(2) 5198(2) 4295(2) 5789(2) 37 19(2) 6902(l) 4079(2) 6335(2) 5439(2) 4008(2) 3388(2) 3295(2)
24(l) 21(l) 27(l) 39(l) 38(l) 34(l) 41(l) 22(l) 21(l) 24(l) 24(l) 21(l) 25(l) 32(i) 45 26 28 29 38 38 38
Table 4 Atomic coordinates ( X 10J) and equivalent parameters (A X 10’) for 3 x
&(I) Cl(]) N(l) O(7A) O(7B) C(2) C(3) C(4) C(5) C(6) C(7) C(8) H(4) H(5) H(8A) H(8B) H(8C)
4491(l) 2083(3) 927(8) 391 l(7) 3393(7) l746( 10) 2312(10) l942( 10) 105O(ll) 557( 10) 3306( IO) - 361(11) 2309(10) 759( I I) - 581(11) - 176(11) - 918(11)
isotropic displacement
isotropic displacement
Y
z
Weq)
5776(l) 2471(3) 2710(9) 5075(9) 4575(g) 3180(11) 4131(11) 4628( 12) 4187(12) 3210(12) 4607( 12) 2663( 14) 5268( 12) 4566( 12) 1997(14) 2416(14) 3221(14)
1317(l) 2264(3) 4187(10) 4267(9) 2385(g) 3624(12) 4062( 12) 5162(12) 5682( 13) 5199(13) 3517(13) 5780( 14) 5539( 12) 6387( 13) 5306(14) 6597(14) 5818(14)
2](l) 29(l) 20(3) 28(2) 23(2) 17(3) l7(3) 22(3) 25(3) 22(3) 20(3) 32(4) 27 30 38 38 38
C.B. Aakeriiy, A.M. Beatty / Journal of Molecular Structure 474 (1999) 91-101 Table 5 Atomic coordinates ( x IO”) and equivalent parameters (A X 10’) for 4
A&l) Cl(l) N(l)
N(2) O(7A) O(7B) O(1) O(2) C(2) C(3) C(4) C(5) C(6) C(7) C(8) H(7) H(4) H(5) H(8A) H(8B) H(8C)
isotropic displacement
x
4‘
z
Weq)
IO 000 7416(l) 10 497(3) 5000 8550(3) 6667(2) 5000 628 l(2) 9269(3) 9436(3) 11 016(3) 12 303(3) 12 020(3) 8062(3) 13 342(3) 7792(3) II 189(3) 13 424(3) 13 308(3) I3 352(3) 14 136(3)
1285(l) 1164(l) 1191(2) 1385(2) 1252(2) 1444(2) 483(2) 1868(2) 1222(2) I260(2) 1255(2) 1221(2) 1196(2) 1329(2) 1168(2) 1340(2) 1224(2) 1246(2) 1793(2) 593(2) 1237(2)
7500 8696(l) 8930( I ) 12500 I I 616(l) 10 439(l) 12500 12 499(l) 9369(2) IO 271(2) IO 728(2) 10 280(2) 9383(2) IO 766(2) 8853(2) II 909(l) 11 396(2) 10 60X(2) 8392(2) 8492(2) 9092(2)
27(l) 30(l)
21(l) 26(l) 36(l) 35(l) 520) 32(l) 22(l) 21(l) 25(l) 27(l) 24(l) 24(l) 31(l) 43 30 32 38 38 38
[Uij = 1.2Uij(eq) for the atom to which they are bonded] was used for subsequent refinements. The weighting function applied was w-’ = [c?(Fi) + (sip)* + (g2P)] where P = (Fi + 2Fz)/3. The SHELXTL PC and SHELXL-93 packages were used for data reduction and structure solution and refinement [37], and the crystallographic details for compounds l-5 are listed in Table 1. Fractional atomic coordinates for compounds l-51 are listed in Tables 2-6, respectively.
3. Results The reaction of silver(I) nitrate with two equivalents of 6-methylnicotinic acid leads to the formation of (6-methylnicotinic acid) (6-methylnicotinato) silver(I), 1 (Fig. l), where the coordination around the silver ion is approximately linear; LN(l)Ag( l)-N(21), 156.9”. The asymmetric unit contains one (6-methylnicotinic acid) (6- methylnicotinato) silver(I) complex. With two oxygen atoms in close proximity ( = 2.5 A), the silver ion is perhaps most accurately described as being four-coordinate
Table 6 Atomic coordinates ( X 10J) and equivalent parameters (A X IO’) for 5
Ml) N(1) WI) O(7A) O(7B) O(27A) O(27B) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(22) ~(23) c(24) C(25) C(26) C(27) C(28) ~(27) H(4) H(5) H(6) H(8A) H(8B) H(8C) H(24) ~(25) H(26) H(28A) H(28B) H(28C)
3496(l) 2228(3) 5358(3) - 3235(2) - 2441(2) 9991(2) 9052(3) 575(3) - 278(3) 576(3) 2297(4) 3078(3) - 2128(3) - 279(4) 6559(3) 7602(3) 7392(3) 6204(3) 5206(3) 8957(3) 6699(3) 11 056(2) - 50(3) 2832(4) 424 l(3) 164(4) - 1608(4) 5(4) 8112(3) 6007(3) 4342(3) 7761(3) 6892(3) 5617(3)
1496(l) - 678(3) 3 138(3) - 2169(3) - 1864(3) 2308(2) 521 l(3) - 631(3) - 1920(3) - 3221(3) - 3292(3) - 1999(4) - 1970(3) 897(3) 2890(3) 4093(3) 5534(3) 5722(3) 4513(3) 3903(3) 1291(3) 2055(2) - 4035(3) - 4166(3) - 1952(4) 613(3) 1202(3) 1949(3) 6485(3) 6728(3) 4606(3) 289(3) 1584(3) 859(3)
95
isotropic displacement
2693(l) 3503(2) 1723(2) 5179(2) 3111(2) - 1251(2) - 2063(2) 3422(2) 4206(2) 5093(2) 5 128(2) 43 17(2) 4 I80(2) 2489(2) 636(2) 1O(2) 533(2) 1678(2) 2237(2) - 1216(2) 150(2) - 1992(2) 5597(2) 5817(2) 4424(2) 1605(2) 2795(2) 2405(2) - ll(2) 1977(2) 3020(2) 384(2) - 819(2) 576(2)
29(l) 19(l) 16(l) 27(l) 22(l) 21(l) 29(l) 15(l) 15(l) 19(l) 23(l) 23(l) 17(l) 21(l) 15(l) 14(l) 19(l) 20(l) 20(l) 17(l) 20(l) 25 23 28 27 25 25 25 22 24 24 24 24 24
(Table 7, Fig. 1). In addition to the coordinate covalent bonds, an O-H...0 hydrogen bond exists between neighboring carboxylic acid and carboxylate units [rH(27). . .0(7B), 1.445(5) A; r0(27A). . .0(7B), 2.45 l(5) A; L0(27A)-H(27). . .0(7B), 167.9(2)“] (Fig. 2). Although the interaction leads to an infinite chain, the structure is dominated by the Ag-N, Ag-0 interactions, forming a coordination polymer that extends in three dimensions. Further evaporation of the solution which yielded 1 results in the formation of single crystals of di (6methylnicotinic acid) silver(I) nitrate 2 (Fig. 3) where the cationic complex contains a silver ion
C.B. Aukertiy, A.M. Bearty / Jounml
96
Fig. 1. The coordination scheme
Table 7 283Selected
geometry about the silver ion in the coordination
bond lengths (A) and angles (“) for 1”
Ag( 1)-NC1) Ag( 1)-NO 1) Ag( 1)-O(7A) Ag( I)-O(27B) N(I)-Ag(l)-N(21) N( 1)-Ag(l)-O(7A)’ N(21 )-Ag( I)-O(7A)’ N( I)-Ag( l)-O(27B)” N(2 I)-Ag( 1)-O(27B)” 0(7A)‘-A&l)-O(27B)” ’ Symmetry Y, - z + 1.
of Molecular
code: (‘)I + 5/2,y -
2.1990) 2.213(5) 2.5 17(4) 2.590(4) 156.9(2) 84.0(2) I l&9(2) 105.5(2) 82.2( 1) 2938 I .6( 1) l/2, - z + 2; (“) - x + 3, -
Structure
474 (1999) 9/L101
polymer in 1. The inset shows the asymmetric
unit of 1 with labeling
coordinated to two ligands through the pyridyl nitrogen atoms0 in a near-linear fashion [rAg(l)N(l), 2.163(2) A; LN(l)-A&l)-N(lA), 175.1(l)“]. The asymmetric unit contains one-half of the complex (one 6-methylnicotinic acid coordinated to silver, and one-half of the nitrate anion). The shortest silveroxygen distance is > 2.7 A. The 1-D geometry of the complex cation is propagated in the solid state through two symmetry-related O-H.. .O hydrogen bonds [vH(7)...0(2), 1.934(2) A; r0(7A)...0(2), 2.736(2) A; L0(7A)-H(7). . .0(2), 172.9(l)“] between the acid hydroxyl group and an oxygen atom of the nitrate counterion, leading to an infinite chain linked through nitrate ions (Fig. 3). In the structure of (2-chloro-6-methylnicotinato)
C.B. Aakertiy, A.M. Beatty / Journal of Molecular Structure 474 (1999) 91-101
Fig. 2. The linear motif formed by hydrogen-bonding
interactions
silver(I), 3 (Fig. 4), the silver ion is coordinated to three carboxylate oxygen atoms and one pyridine nitrogen atom, resulting in a distorted tetrahedral arrangement (Table 8). The asymmetric unit contains
Fig. 3. The chain formed by carboxylic scheme.
acid-nitrate
in 1. Ag-0
interactions
97
with nearby cations have been omitted for clarity.
one 2-chloro-6-methyl nicotinate ligand coordinated to silver; the tetrahedral coordination is generated through symmetry-related ligands. The bridging carboxylate units lead to a short Ag-Ag distance of
hydrogen bonds in 2. The inset is the linear cation and associated
anion with the labeling
98
C.B. Aakerijv, A.M. Beatty / Jourrzal of Molecular Structure 474 (1999) 91-101
Fig. 4. The bridging carboxylate interactions asymmetric unit of 3 with labeling scheme.
in the coordination
polymer
Table 8 Selected bond lengths (A) and angles (“) for 3” Ag( I)-N( I)” Ag( 1)-O(7B) Ag( l)-O(7A)’ Ag( l)-O(7A)“’ 0(7B)-Ag( I)-O(7A)’ 0(7B)-Ag( I)-N( 1)” 0(7A)‘-Ag( I)-N( 1)’ 0(7B)-Ag( I)-O(7A)“’ 0(7A)‘-Ag( l)-O(7A)“’ N( l)‘-Ag( l)-O(7A)“’
2.34(l) 2.29(9) 2.300(9) 2.54(l) 119.2(4) 122.9(4) 117.9(4) 92.2(3) 83. I(3) 95.2(4)
d Symmetry code: (‘) - x + I,y, - z + l/2; (“) - x + 112,~ + I/ 2, - z + l/2; (“I)& - y + I,z - i/2.
in 3. Hydrogen
atoms have been omitted for clarity. The inset is the
2.87X2) A (Fig. 4). The coordination polymer extends in three dimensions, and there are no acidacid hydrogen bonds, as the carboxylic acid moiety is fully deprotonated. Further evaporation of the solution which yielded 3 results in the formation of single crystals of di (2chloro-6-methylnicotinic acid) silver(I) nitrate, 4 (Fig. 5), where the ligands coordinate through the pyridine nitrogen atoms to the silver ion, [rAg-N, 2.194(2) A; L(Nl)-Ag-(NlA), 173.3(l)“. The asymmetric unit contains one-half of the cation and onehalf of the anion, as in 2. The shortest silver-oxygen distance is > 2.7 A. The 1D geometry of the complex cation is propagated by symmetry-related O-H.. .O
C.B. Aakeriiy, A.M. Beutty / Joumul of Molecular Structure 474 (1999) 91-101
Fig. 5. The chain formed by carboxylic scheme
acid-nitrate
hydrogen
bonds in 4. The inset is the linear cation and associated
hydrogen bonds [rH(7)...0(2), 1.835(3) A; r0(7A). . .0(2), 2.668(3) A; L0(7A)-H(7). . .0(2), 165.08(9)“] leading to an infinite chain linked through nitrate ions similar to that in 2 (Fig. 5). The reaction of silver(I) nitrate with two equivalents of 2-methylnicotinic acid leads to the formation of (2-methylnicotinic acid) (2-methylnicotinato) silver(I), 5 (Fig. 6), where the asymmetric unit contains one (2-methylnicotinic acid) (2-methylnicotinato) silver(I) subunit. The coordinate covalent bonds (Table 9) result in a dimeric species, where two nicotinate ligands bridge two silver(I) ions. Although the coordination geometry around silver is no longer linear, these dimers are assembled into an extended 1D motif by O-H...0 hydrogen bonds [rH(27). . .0(7B), 1.430(2) A; r0(27A)...0(7B), 2.448(2) A; L0(27A)-H(27). . .0(7B), 173.8(l)“] between neighboring ligands (Fig. 6).
4. Discussion An examination of the structures l-5 in the context of predictable supramolecular assemblies demonstrates that, under the reaction conditions used in this study, exceptions are the rule. In fact, in two of the reactions, two different complexes were isolated
99
anion with labeling
(1,2 and 3,4). Only 1 displays an obvious similarity to the aforementioned structure of (iso-nicotinic acid) (iso-nicotinato) silver(I), in which chains are formed through intermolecular carboxylic acid-carboxylate hydrogen bonds. Despite this similarity, the structure of 1 is dominated by coordinate-covalent interactions, and is best described as a three-dimensional coordination polymer. Recurring patterns in this series of compounds are not readily apparent. For example, the molecular structure of 1 and 5 differ only in the position of the methyl substituent on the aromatic ring. However, this small change leads to very different structures, including differences in coordination geometry. The structure of 3 further illustrates the lack of recognizable patterns; the bridging carboxylate motif present in 3 is absent in 1 and 5. It is also important to note that the hydrogen bonding distance between O(7B) and O(27A) is short in 1 and 5 ( = 2.45 A), which is reflected in theOcarboxylate C-O distance: [C(7)0(7A), 1.235(8) A; C(7)-0(7B), 1.271(8) A for 1; [C(7)-0(7A), 1.229(3) A; C(7)-0(7B), 1.285(3) A for 5.1 Even though this is a short O-O contact, the carboxylate and carboxylic acid moieties are crystallographically inequivalent, and the hydrogen atom was located on the carboxylic acid moiety. In 2 and 4, where the nitrate counterion is present,
loo
C.B. Aakertiy, A.M. Bratty / Journrrl of Molecular Srrucrure 474 (1999) 91-101
Fig. 6. The nicotinate ligands bridge silver ions, and hydrogen bonds between dimers form an extended one-dimensional the asymmetric unit of 5 with labeling scheme.
the anion participates in hydrogen bonding interactions between neighboring complexes, interfering with ligand-ligand interactions. The fact that these complexes contain fully protonated ligands can be attributed to the increased acidity of the reaction Table 9 Selected bond lengths “tblfn3” >
43 1)-NC1) Ag( 1)-NO 1) Ag( I)-O(7A)’ N(l)-Ag(l)-N(21) N( I)-Ag( l)-O(7A)’ N(21)-Ag(l)-O(7A)’ ’ Symmetry
(.k) and angles
(“) for 5”rowref
2.17(2) 2.184(2) 2.556(2) 165.49(E) 94.16(7) 92.23(7)
code: (‘) - X, - y, - z + 1
relid =
motif in 5. The inset is
mixture after the precipitation of 1 and 3, respectively. The major difference between the structures of 2 and 4 appears to be the torsion angle about silver, where the two pyridyl rings in 4 are essentially coplanar [C(2)N(l)-Ag( I)-N( 1A) = 1.71”], but are twisted with respect to each other in 2 [C(2)-N( l)-N(lA)C(6A) = 59.4”]. This result is surprising, considering that the nicotinic acid groups in 2 have only one bulky substituent (6-methyl), while those in 4 are di-substituted (2-chloro, 6-methyl).
5. Conclusion The five very different structures described above demonstrate that we cannot always translate the prin-
C.B. AnkerGy. A.M. Batty
/Journal
ciples of organic molecular solids to the assembly of coordination complexes. Difficulties arise due to the formation of the carboxylate anion, which in some cases competes successfully (and unpredictably) for metal coordination sites. Thus, while the role of protonated carboxylates may be identified easily (linear hydrogen-bonding motifs in 2 and 4), the oxygen atoms of non-protonated carboxylate moieties and the pyridine nitrogen atoms compete unpredictably for coordination to the metal ion, resulting in a mixture of bridging and non-bridging coordination environments. Therefore, in order to implement a reliable strategy for the supramolecular assembly of coordination complexes via carboxylic acid hydrogen bonds, we must carefully control the acidity of the reaction mixture, so that we have a consistent set of functional groups for intermolecular interaction. Once consistent ligand-based intermolecular connectors are present, we may further facilitate ligand-ligand interactions by using more non-coordinating anions such as tetrafluoroborate or hexafluorophosphate [38] (in place of hydrogen-bonding nitrate as in 2 and 4.) The unpredictable system described in this paper contrasts with the silver(I) coordination complexes of nicotinamide, where the amide functionality proved to be a reliable connector for supramolecular assemblies [3 l-331.
Acknowledgements We acknowledge the financial support from Kansas State University and NSF-EPSCoR (OSR-9550487).
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