The Structure of a 2:1 Host Guest Complex between p-Nitroaniline and 18-Crown-6 Gabriela Weber*

The Structure of a 2:1 Host Guest Complex between p-Nitroaniline and 18-Crown-6 Gabriela Weber*

Anorganisch-Chemisches Institut der Universität,

Tammannstraße 4, D-3400 Göttingen Z. Naturforsch. 36b, 896-897 (1981);

received May 6, 1981

Neutral Complexes, Crown Ethers, H Bonds, X-ray

The crown and two nitroaniline molecules are linked by four N - H ••• O interactions leaving the cyclic ether in a strain free conformation of approximate Ü3d symmetry. Partial disorder of one O atom facilitates one more H bond but induces considerable conformational strain in the ligand.

18-crown generally adopts a conformation of approximate Ü3d symmetry both in cationic com- plexes (e.g. [1, 2]) and when hydrogen bonding to guest species [3-6]. This symmetry with exclusively ag±a units of alternating signs is also found in the structure of the present adduct (Fig. 1) which forms readily upon refluxing the crown ether and the aniline [7]: All torsion angles along C-C bonds are gauche average |67.9(5)|°) while those along C - 0 bonds are trans (average |175.9(5)|°). However, a (less accurately determined) alternative site for one 0 atom, namely 0(4') (see Fig. 1), is 14.3(3)%

occupied, resulting in unusual torsion angles 0(l)-C(2)-C(3)-0(4') = 2(1)°,

C(2)-C(3)-0(4')-C(5) = 138(1)°, C(3)-0(4')-C(5)-C(6) = —120(1)° and

0(4')-C(5)-C(6)-0(7) = —13(1)°. The stronger H bond thus formed [0(4) - 1 H(25) = 275.5(7) pm, but 0 ( 4 ' ) - l H ( 2 5 ) = 242.8(22) pm] may compen- sate for these conformational strains. For 0(13), however, a corresponding disorder is not observed;

the 2H(35)•••0(13) distance of 266.1(6) pm is probably too long to allow strong interactions.

Thus only four of the six 0 atoms of the crown [neglecting 0(4')] are involved in the H bonding system linking host and guests, and none of these H bridges is bifurcated. This pattern contrasts with those in complexes of 18-crown-6 with 2,4-dinitro- phenylhydrazine [6] and 2,4-dinitroaniline [8]

respectively, but is consistent with the less acidic amino group in the present structure.

Experimental

Crystal data: C24H36N4O10, M = 540.58, space group P b c a , a = 1506.5(4) pm, b = 1988.7(5) pm, c = 1871.2(5) pm, Z = 8,

= 1.281 Mg m~«, /i(MoKa) = 0.094 mm

. Sparkling yellow crystals were grown from toluene. 2395 unique observed [F > 4cr(F)] diffractometer data, collected between 20 = 7° and 50° with monochromated MoK

radia- tion in a profile fitting procedure [9], were used for solving the structure by direct methods and for anisotropic refinement of non-hydrogen atoms [10].

Figure. A perspective view of the adduct and the numbering scheme adopted. Radii are arbitrary. H ••• O distances [pm] are:

l H ( 2 5 ) - 0 ( 4 ) = 275.5(7), l H ( 2 5 ) - 0 ( 4 ' ) = 242.8(22) l H ( 2 5 ) - 0 ( 7 ) =206.2(6), 2 H ( 2 5 ) - 0 ( 1 ) =232.7(6), 1 H ( 3 5 ) - 0 ( 1 0 ) = 213.9(6), 2 H ( 3 5 ) - 0 ( 1 3 ) = 266.1(6), 2 H ( 3 5 ) - 0 ( 1 6 ) = 210.0(7) [coordinates of the nitro- aniline molecule C(19) to 0(28) given in Table I, are to be transformed by x, 0 . 5 —y , — 0 . 5 + z].

* Reprint requests to Dr. G. Weber.

0340-5087/81/0700-0896/$ 01.00/0

H atoms were located from difference maps and

assigned fixed isotropic temperature factors 1.2 times

the U values of attached atoms. Amine groups

Table I. Atom coordinates ( x 104) and isotropic tem- perature factors (pm2 X 10- 1).

X y z U

0(1) 3258(2) 1354(1) 5823(1) 73(1)*

0(2) 3653(3) 1101(2) 6448(2) 81(2)*

0(3) 4081(3) 1626(2) 6867(2) 82(2)*

0(4) 3517(2) 2086(2) 7152(2) 67(1)*

0(4') 4146(14) 2356(9) 6765(10) 65(8) 0(5) 4000(4) 2640(2) 7472(3) 101(2)*

0(6) 3343(3) 3098(2) 7769(2) 92(2)*

0(7) 2855(2) 3406(1) 7208(1) 92(1)*

0(8) 2164(4) 3816(2) 7446(2) 94(2)*

0(9) 1704(4) 4111(2) 6815(2) 96(2)*

O(10) 1267(2) 3596(1) 6424(1) 86(1)*

0(11) 891(3) 3837(2) 5784(2) 97(2)*

0(12) 381(3) 3298(2) 5417(2) 96(2)*

0(13) 978(2) 2828(1) 5094(1) 74(1)*

0(14) 543(3) 2280(2) 4791(2) 87(2)*

0(15) 1210(4) 1828(2) 4459(2) 86(2)*

0(16) 1727(2) 1533(1) 5013(1) 78(1)*

0(17) 2458(3) 1155(2) 4768(2) 82(2)*

0(18) 2914(3) 840(2) 5385(2) 82(2)*

0(19) 3327(3) 1632(2) 10190(2) 62(1)*

C(20) 3227(3) 1773(2) 9467(2) 79(2)*

0(21) 3458(3) 1319(2) 8957(2) 76(2)*

C(22) 3792(3) 707(2) 9148(2) 65(1)*

0(23) 3913(3) 549(2) 9873(2) 78(2)*

C(24) 3671(3) 1006(2) 10379(2) 78(2)*

N(25) 3129(3) 2089(2) 10697(2) 85(1)*

1H(25) 3053 1935 11180 85

2H(25) 2928 2529 10562 85

N(26) 4040(3) 220(2) 8613(2) 84(1)*

0(27) 4439(3) — 290(1) 8784(2) 128(2)*

0(28) 3854(3) 340(2) 7984(2) 115(2)*

C(29) 1307(3) 1600(2) 7037(2) 61(2)*

C(30) 1380(3) 1785(2) 7752(2) 64(1)*

0(31) 1320(3) 1316(2) 8287(2) 65(1)*

C(32) 1185(3) 653(2) 8113(2) 65(1)*

C(33) 1104(3) 451(2) 7410(2) 71(2)*

0(34) 1159(3) 925(2) 6870(2) 74(2)*

N(35) 1346(3) 2068(2) 6514(2) 79(1)*

1H(35) 1416 2540 6604 77

2H(35) 1436 1893 6042 77

N(36) 1112(3) 159(2) 8683(2) 91(2)*

0(37) 1092(3) 350(2) 9293(2) 155(2)*

0(38) 1056(3) —427(1) 8523(2) 125(2)*

* Equivalent isotropic U calculated from anisotropic U.

Table II. Bond lengths (pm).

0(1) - 0 ( 2 ) 140.6(6) 0(2) - 0 ( 3 ) 145.6(7) 0(3) - 0 ( 4 ) 135.8(7) 0(3) - 0(4') 146.9(19) 0(4) - 0 ( 5 ) 145.1(7) 0(4') - 0 ( 5 ) 145.6(21) 0(5) - 0 ( 6 ) 145.6(8) 0(6) - 0 ( 7 ) 142.1(6) 0(7) - 0 ( 8 ) 139.4(7) 0(8) - 0 ( 9 ) 149.1(7) 0(9) - O(10) 142.1(6) O(10) - C ( l l ) 140.8(6) 0(11) - 0 ( 1 2 ) 148.7(8) 0(12) - 0(13) 143.1(6) 0(13) - 0 ( 1 4 ) 139.3(6) 0(14) - 0 ( 1 5 ) 148.4(8) 0(15) - 0 ( 1 6 ) 142.2(6) 0(16) - 0(17) 141.1(7) 0(17) - 0 ( 1 8 ) 148.2(7) 0(18) - 0 ( 1 ) 140.9(6) 0(19) - C(20) 139.1(7) 0(19) - C(24) 139.4(7) 0(19) - N(25) 134.7(6) 0(20) - 0(21) 135.9(7) 0(21) - 0(22) 136.5(7) 0(22) - 0(23) 140.5(6) 0(22) - N(26) 144.2(6) 0(23) — 0(24) 136.1(7) N(26) - 0 ( 2 7 ) 122.4(6) N(26) - 0 ( 2 8 ) 123.3(6) 0(29) - C(30) 139.2(6) C(29) - C(34) 139.6(6) 0(29) - N(35) 135.2(6) C(30) - 0(31) 137.1(6) 0(31) - C(32) 137.2(6) 0(32) - 0(33) 138.2(7) 0(32) - N(36) 145.5(6) 0(33) - C ( 3 4 ) 138.4(7) N(36) - 0(37) 120.4(6) N(36) - 0(38) 120.5(5)

(N-H = 96 pm, H - N - H = 120°) then were refined as rigid groups; for other H atoms (in ideal positions) a 'riding model' was employed. With refinement of an empirical extinction correction coefficient the final R was 0.064. Atom parameters and bond lengths are given in Tables I and II; bond angles, torsion angles and lists of observed and calculated structure amplitudes are available from "Fach- informationszentrum Energie, Physik, Mathematik, GmbH, D-7514 Eggenstein-Leopoldshafen 2". The Registry-Nr., CSD 50023, the name of the author, and the reference should be given.

The author thanks Dr. W . M. Müller and Prof. F.

Vogtle, Bonn, for providing the sample. This study was financially supported by the Fonds der Chemi- schen Industrie.

[1] J. D. Dunitz, M. Dobler, P. Seiler, and R. P.

Phizackerley, Acta Crystallogr. B 30, 2733 (1974).

[2] O. Nagano, Acta Crystallogr. B 35, 465 (1979).

[3] O. Nagano, A. Kobayashi, and Y . Sasaki, Bull.

Chem. Soc. Jpn. 51, 790 (1978).

[4] I. Goldberg, Acta Crystallogr. B 81, 754 (1975).

[5] R. Kaufmann, A. Knöchel, J. Kopf, J. Oehler, and G. Rudolph, Chem. Ber. 110, 2249 (1977).

[6] R. Hilgenfeld and W . Saenger, Z. Naturforsch.

36b, 242 (1981).

[7] F. Vögtle and W . M. Müller, Chem. Ber. 114, in press.

[8] G. Weber and G. M. Sheldrick, Acta Crystallogr.

B 37, in press.

[9] W. Clegg, Acta Crystallogr. A 37, 22 (1981).

[10] All programs used were written by Prof. G. M.

Sheldrick, Göttingen.