J. Am. Chem. SOC. 1995,117, 9367-9368
9367
In the meantime we have learned how to design further examples of polyionic self-organization3limited by the van der Waals interactions4 in the space-filling and slightly bonding4 hydrocarbon skin and to crystallize them under aprotic conditions. A prototype example is tert-butylcalix[4]arene, the ''CI~.. perimeter of which shows an average diameter of 630 pm and holds four " H O cation-docking sites with 0.* -0distances of about 280 pm?
Crystallization and Structure of {(Hs3C,043-)[Li+6(NH3)~l(3-04C,H~3)1, an Edge-Shared Li+a Double Tetrahedron between Calix[4]arenetrianion Half-Shells: Another Self-organized and Lipophilically-Wrapped Polyion Aggregate Hans Bock,* Andreas John, Christian NBther,Ib and Zdenek Havlaslc
9
Department of Chemistry, University of Frankjirt Marie-Curie-Strasse 11. 0-60439 FrankfurdMain, Germany Received March 13, 1995 Revised Manuscript Received July 21, 1995 The first two examplesIa of novel lipophilically-wrapped polyion aggregates? in which a cluster of cations and anions provides thermodynamical stability and a kinetically persistent impenetrable hydrocarbon skin, have both been discovered serendipitously: the (octahedron prismane) polyhedron (1) crystallized after addition of n-butyllithium to the solution obtained from dissolving barium metal in tert-butyl alcohol (I), and the hexameric sodium imido diphosphonate was prepared by reacting the tetrapheuoxydiphospbonate imine with NaH in benzene (2):
+
Reaction with lithium amide in aprotic toluene6 yields ammonia and colorless prisms of the title compound. Its structure, determined at 150 K (Figure I), shows an edge-shared (Li+6) double tetrahedron fixed to each three O s in both of the calix[4]arene ligands and to an additional ammonia, which covers the open space between their four (H,C),CH?C6 subunits. The view from the center of inversion between the two half-shells (3) shows the hydrogen bond (1)06----H-O(4) of the unreacted fourth hydroxyl group to an adjacent O*- center (Figure 1, la. 4a). The polyion aggregate [Lit60-6(H0)2(NH3)2] in between the calix[4]arene hydrocarbon (C44Hn) half-shells (Figure I ) contains twice three different Li+ and 0- centers, two hydrogen bonds O---*H-O and two NH3 ligands (3). Altogether 35 short contact distances can be recognized, of which 11 are Li+.**Li+, f
(I) (a) Receding examples are the tert-butanolate-wrapped cluster [Bas(Back. H.: Hauck, T.; Nlher. C.: Rbsch. N.; Staufer, M.: Lii021t Haberlen, 0. D.Angew. Chem. 1995, 107, 1439; 181. Ed. Engl. 1995, 34, 1353) and the phenaxy-covered sodium imidodiphasphonate hexamer (Bock, H.; Schbdel. H.; Havlas, Z.; Hemann, E. Angew. Chem. 1995. 107, 1441: Inr. Ed. Enyl. 1995.34, 1355). (b) Part of Ph.D. thesis: N2ther. C. University of Frankfurt. 1994. (c) On leave from Czech Academv of Sciences, Flemingovo Nam, CZ, 16610 Prague. (2) Despite considerable effort, a global search for analogous lipophilically-wrapped polyion aggregates in the Cambridge StNCtUrd Database omvided no evidence for selected classes of comvounds. The followine kports are pointed out: (a) S- and Se-containing thsitian metal dusted a& reviewid Fenske, 0.;Longini. G.; Schmid, G. In Clusters ond Colloids-From Theory to Applications Schmid, G..Ed.: VCH Verlag: Weinheim. Gemanv. I994 D 89-298. fb) Alkali metal oxides such as Rb902 or Csc203 wkh O-fill;d metal act&drans are known since 1971 (cf. Simon, A. Stnrct. Bonding 1W9, 36, 81. (c) Individual compounds
''
(2) ((HsC~),,IOPN-PONa?,)
For the hexabarium-trilithium-dioxide-undecacation (l), a relativistic density functional calculation comprising 33 centers with 460 electrons substantiated the polyion cluster [Ba2+&i+302-z] and predicted a force constant f i 2 0.1 mdyn/A for the O(1)-O(2) coupling.Ia The interactions in the hydrocarbon skin have been analyzed statistically for the 24 phenoxy groups in the hexameric sodium phosphate (2) using centroid distances as well as interplanar angles and enthalpy contributions of ahout -50 kJ mol-', i.e. about one-hundredth of the Coulombic stabilization in the (Na+O"& core."
-
rert-butandlate [(HIC)ICO-N~+]~ (Davies, 1. E.; Kopf, 1.; Weiss, E. Acta Cry,~ldlogr., Sect. B 1982,38,2251), of which the (LicO-)a cubane is more lipophilically covered than the (Na+O-)g, a double hexagon. (3) Examples quoted are hexamenc aci-9-nitrofluorene potassium, { ( H ~ ( C , ~ C = N I O ~ ~ K ' l a ( O C ~ H ~ ) ~ ( Owith ~ C ~ aH ~K)'}n,0 " ~ nucleus (Bock, H.; Dienelt, R.; Schadel. H.;Havlas, Z. Terrahedron Lett., submitted) or lithium-aluminium-bis(catecholate)-pentaki~(dim~th~~y~th~"~), {(HaCas)[Li+rAI'+iO-~O,~]],containing a "LibA12018.. string (Bock, H.; Beck. R.: Schbdel. H.: Havlas. 2. Unvublished results. Cf. Beck. R. Master
.. .. , .. ., . . ..
(5) Reviews on calixarenes containing StNCtUral details: Bbhmer, V.: Mckervey. M. A. Chem-Zrg. 1991, 25, 195-207 or Gutsche, D.: Igbal, M.; Nam. K. S.; See. K. A,; Alam, I. Pure Appl. Chem. 1988, 60, 483488. For known metal complexes. cf. e.g.: Hmowfield 1. M.; Ogden M. I.: White. A. H. J. Chem. Soc.. Dalton Trans. 1991. 2625 and (together with Richmond. W. R.) J. Chem. Soc., Chem. Commun. 1991, 1159 or Atwood. 1. L.; Bott, S. G.; Jones. C.; Raston C. L. Ibid. 1992, 1344 and references within.
0002-7863/95/1517-9367$09.00/00 1995 American Chemical Society
9368 J. Am. Chem. Soc., Vol. 117, No. 36, I995
Communications to the Editor
20 Li+-..O-, two Li+***N,and two extremely short hydrogen bridges with distances 0 . ( H ) O of only 250(1) pm (!)? Based on the structural coordinates determined at 150 K6 (Figure I), MNDO calculations' have been performed to gather more detailed information. The MNDO charges for the individual centers, which range from +0.16 t o +0.24 for Li*+ and from -0.27 to -0.44 for O*-, possibly underestimate the ionic character, including the Li+n.'b.-N-o.ll coordination and the 0-0.M-..H+31-0-Q.27hydrogen bond. The MNDO enthalpy of = -63 W mol-(, can be subdivided into formation, three consecutive steps?(i) The formation of the [Li6+]6cluster in its edge-shared double-tetrahedral arrangement which should require AAHH1MND0= +9810 kl mol-(-including the sum of six ionizations 6Li 6 Li' 6e-, 6AHFNDo= 6(656) = 3936 kJ mol-', and allowing for all the individual, distancedependent Lid+/Lid+Coulomb repulsions. (ii) The fixation of the cluster [Li+]6 at the 0 centers of the t w o calix[4]arenehalfshells without the O*-***H-O bridges, {Hs3CM043-)yields the negative enthalpy difference [Li+1&04C~Hs,)}. AAH?Noo = -10960 W mol-', or an averaged enthalpy of -550 W mol-' for each of the 20 contacts Lid+** ad-, which
-
+
compares with the experimentally determined9 value AHdLi20) = -591 W mol-'). (iii) For the NH3 complexation a t t w o of the [Li+l6centers, AAH,J'"Do = -653 W mol-' is estimated? In the summary, the energetically favorable, largely ionic bonds Lidi**.O*- add considerably t o the thermodynamical stability of the title compound-as did the Ba2+.*.0- and Li+**.O- Coulombic interactions in our first, serendipitously discovered lipophilically-wrapped polyion aggregate ( I ) with its [Ba2+&i+3O2-1nucleus.la Other structures are now known,' and there will be many more examples in the future t o further substantiate the self-organization principle, based on an energetically advantageous ionic core and limited by van der Waals interactions in its lipophilic hydrocarbon skin. (6) Preparation and Crystallization of Trilithium-4-tert-Butylcalix[4]arene: To 0.5 g (0.77 mmol) of 4-1ert-butylcalix[4]arenesuspended in 15 mL of purified toluene at room temperature and under argon are added 0.07 g (3.05 mmol) of lithium amide and 10 mL of purified toluene. After being stirred for 45 min, the mixture is heated to reflux until a clear solution results. The hot solution is filtered under argon over a Schlenk frit, and
Figure 1. Single crystal structure (150 K16 of the polyion aggregate
[ L ~ + O ~ ( H O ) ~ ( N Hbetween I ) ~ ] two ren-butylcalix[4]arene hydmcarbn (CMHIZ)trianion half-shells. Upper left: Side view of the edge-shared double tetrahedron (Li+)dLi+)*(Li+)iwith all Li+ fixed to three of the four calixarene 0 centers (with the fourth HO(4) group hydrogen. ..... .= 1.134 g cm". triclinic. P i (No. 2). Z = I, Siemens P4 four-cycle bonded to (1) O*-) and to one NHI ligand in each of the caiix[4larene diffractometer, Mo K a irradiation, p = 0.07 mm-'. 5773 measured cavities (OLi+; 0 0 ,O N , OC). Selected bond lengths (pm) and angles reflections between 3" < 28 < 45*. of which 5456 indenendent and S4S2 r~~~~~~~~ ~~~~. .~ (deg): Li(llLi(2a), 257(1); Li(l)Li(2), 309(1); Li(2)Li(2a), 260(1); Liused far refinement. StNCtUre solu&n by direct methods and difference (2)Li(3). 276(l); Li(l)Li(3), 283(l); Li(2a)Li(3). 286(l); Li(i)0(2a), Fourier technique (SHELXS-86), refinement YS P(SHELXL-93). 577 parameters, w = I / [ d ( F o 2 ) (0.0544P)2 1.76P1, R for 3690 F, > 40190(1); Li(l)0(3), 184(i); Li(1)0(4), 185(1); Li(2)0(1), 192(1); Li(Fa]= 0.053I, wR2 for all 5456 data = 0.1403. GOF = 1.042. rest electron (2)0(2), 203(l); Li(2)0(2a). i91(1]; Li(2a)0(3), 191(1); Li(3)N. 205density 0.22/-0.23 el,&'. The Li, C, N, and 0 positions are anisotropically (I); O(l)(H)0(4), 250(1); Li(Za)Li(l)Li(2), 53.6(2); Li(Za)Li(l)Li(3), refined. The H centers Were set in the geometrical ideal msitions and refined 63.6(2); Li(2a)Li(Z)Li(l), 52.9(2); Li(2a)Li(2)Li(3), 64.4(2); Li(2a)Li(3)Li(2), 55.0(2); Li(i)O(3)Li(3), 95.2(3); Li(1)0(3)Li(2a), 86.7(3); Li(Za)O(3)Li(3), 93.9(3). Right: space-filling representation of the with respect to two orientations and, therefore. have been refined using a lipophilically-wrapped lithium plane between the two terr-butylcaiixsplit madel and isotropic displacement parameters. [4larene half-shells. Bottom: Unit cell (monoclinic P i , Z = 2) in (7) Cf.: Elmsley, 1. Very Stmng Hydrogen Bonding. Chem. Soc. Re". 1980, 9, 91 references within. X-direction. The crystal contains four toluene solvent molecules per (81The MNDO calculations were performed using the program package formula unit, which fill interlattice positions with contact distances SCAMP IVII (Dr. T. Clark, University of Erlangen) on our work station ,370 pm to nearest centers. IBM RISC 6000l320. An additional test of the Li parameten yields a satisfactory reproduction of the first vertical ionization energy Li Lit Acknowledgment. Our investigations are generously sponsored by e- by 495 kJ mol-' = 5.13 eV vs the experimental value IE," = 5.39 eV.8 the State of Hesse, the Adolf Messer Foundation, the Deutsche For a methoxy-substitutedcluster model [Lii)a(-OCH3s(HOCH~)*(NH,)~l, Forschungsgemeinschaft, and the Fonds der Chemischen Industrie. an enthalpy Of formation AH?" = -1823 kJ mol-' is calculated for dissociation at the individual Li+ centers, ('Li +...-OCH3) >Lit -0CH3. Dissociation enthalpies AHdin between -634 and -809 W mol-' Supporting Information Available: Tables of atomic coordinates. are approximated, and for methanol split-off, (>Li+.,O(H]CH,) >Li+ isotropic and anisotropic thermal parameters, bond lengths and angles, + HOCH,, AHMNDo= 175 kl mol-'. Far the campexation LI+ NH, at and crystal data (1 I pages). This material is contained in many libraries an optimized distance d(Li+...N) = 207 pm. an enthalpy difference on microfiche, immediately follows this article in the microfilm version AAH?" = - 145 kJ mol-( results. For the addition of NHI to the complex of the journal, can be ordered from the ACS, and can be downloaded (Li+]a(calix[4larene)based on the structural data determined (Figure 1). from the Intemet; see any current masthead page for ordering surprisingly, a small repulsion is calculated, which indicates some spatial overcrowding. information and Internet access instructions. (9) Wiberg. N. Hollemann/Wiberg: Lehrbuch der Anorganischen Chemie. 91-100. de Gruyter: BerlinNew York, 1985; p 954. 1A950816D
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