Linear Pentanuclear Complexes Containing a Chain of Metal Atoms: [Co(5-tpda)4(NCS)2] und [Ni(5-tpda)4Cl2]

COMMUNICATIONS

Depending on the donor ligand the average F e - 0 distances

in the double octahedron are about 1.93

A

(FpP(Mes)O,),

2.011(7)

A

(MesPO,), and 2.123(7)

8,

(p3-OH). The equatorial

angles 02-Fe2-010 and 08-Fe2-08a were determined to be

98.9(3) and 81.7(2)", respectively. The atoms Fe2,08, Fe2a and

0 8 a lie in one plane and form a rhombus with the acute angle

at the iron atoms; thus, a bonding interaction between Fe2 and

Fe2a i s

not possible (distance Fe2-Fe2a

=

3.212 Aj. The trigo-

nal-bipyramidal coordination of Fe4 is slightly distorted. The

longest F e - 0 distance in

2 was determined for Fe4-08(apical)

to be 2.168(7)A, the shortest for Fe4-0, (equatorial) to be

about 1.895

A.

The equatorial bridges

04,05,

and O l a are bent

slightly out of the ideal plane. The Fe4-Cl1 distance is

2.346(3)

A.

The bond angles at the

0 bridges lie between

124.5(4) and 146.7(4)", those at the P atoms (103.8(4)-

113.1(3)") have values close to the tetrahedron angle. The sum

of angles Fe-0-Fe a t the trigonal-pyramidal pu,-OH

bridges is

345.3'; the p,-OH hyrogen atom does not participate

in any

hydrogen bonding.

Temperature-dependent magnetic measurements for

2

re-

vealed antiferromagnetic behavior with

a Nee1 temperature of

40 K ; the bond lengths (Fe-0) and angles (Fe-0-Fe) of the

four central Fe"'

ions (Fe2, Fe2a, Fe4, Fe4a) allow super-

exchange and spin orientation. At 300K the

peff

value was

5.48 BM.[61

The mild aerial oxidation of the diferriophosphonium salt

l a

leads to many (sometimes drastic) changes in the functionality

at both the iron and phosphorus atoms: We find both retention

and elimination

of the CpFe(CO), groups as well as complete

oxidation to give iron(in) centers, and oxidation of the phospho-

nium building blocks to give p,-phosphinato and p3-phospho-

nato ligands. This wide palette of new building blocks finally

readily combines to form

2.

The new molecular framework of

2

is illustrated by the polyhedral representation in Figure 2. The

structure contains a central double octahedron (FeO,(OH)),

,

two trigonal bipyramids ( F e 0 3 ( 0 H)Cl), and six tetrahedrons

(four Fp(Mes)PO, and two MesPO,). Compound

2

is an ex-

ample for the unusual combination of classic (in the corej and

organometallic complex chemistry (at the periphery). We are

currently investigating similar organometalated sulfonium

salts,['' which also may be converted to similar coordination

polyhedrons with sulfenato, sulfinato, and sulfonato ligands by

aerial oxidation.

Experimental Section

Synthesis of l a see reference [3].

2: l a (200 mg, 0.37 mmol) was dissolved in acetonitrile (12 mL) and this solution was exposed to air for three days. Small yellow crystals formed on the inside glass surface. They were collected and washed with acetone. Yield: 30 mg (22.4%). Ad- ditional quantities of 2 remained ~n the mother liquor; however, these could not be isolated in a pure f o m ; correct elemental analysis. Compound 2 is soluble only in dimethyl sulfoxide (DMSO)

Received: May 20. 1996 Revised version: September 26, 1996 [Z9132IE] German version: Angeir.. Chem. 1997, 109, 55-56

Keywords: cage compounds

*

iron

-

magnetic properties

P ligands

-

self-assembly

[I] A. Miiller, K. Hovemeier, E. Krickemeyer, H. Bocke, Angew. Chem. 1995,107, 856; Angew. Chem. In[. Ed. Engl. 1995,34,779; further examples for molecular self-assembly can be found in J.-M. Lehn, Supermolecular Chemisrry: Concepts

and Perspectives, VCH, New York, 1995.

[2] a) W. Pohl. I.-P. Lorenz, H. Noth, M. Schmidt, Z. Naturforsch. 5 1995, SO, 1485; b) I.-P Lorenz, P. Miirschel, W. Pohl,

K .

Polborn, Chern. Ber. 1995,128, 441; c) I.-P. Lorenz, W. Pohl,

K.

Polborn, ihid. 1996, 129, 11.

[3] ILP. Lorenz. W. Pohl, H. Noth, M. Schmidt. .IOrganornet. Chem. 1994, 47S, 211.

[4] W. Pohl, PhD Thesis, University of Miinchen, 1995.

[ S ] X-ray structure analysis of 2: C8,H8,CI,Fe,02,P,, brown plates, 0.30 x 0.26 x

0.1 mm', triclinic, space group P , u = 12.991(7), b = 14.660(7), c = 14.7?6(7)

A,

1.581 p =1.476mm-l, F(OO0) =1104, diffractometer: Siemens P4,

Mo,, (1. = 0.71073 A), T = 213 K, 28 = 3.24-47.00, w scan, scan range (0)

1.2'. reflections: 5241 measured, 4967 of which were independent (R(int) = 0.1251), 3022 observed [F>4o(F)]. The structure was solved with the programs XS (Siemens) and SHELXL (G. M. Sheldrick, Gottingen, 1993) by direct methods and refined by full-matrix least squares refinement. The hydro- gen atoms were refined as riding atoms with fixed isotropic temperature parame- ters. 553 refined parameters, R = 0.0693, nR2 = 0.1308, GOOF = 1.049. Fur- ther details of the crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen (Germany), on quoting the depository number CSD-405885.

161 The measurements of magnetic susceptability were made between 10-300 K with 20 mg of microcrystalline 2 on a Quantum Design MPMS Squid magne- tometer at a field strength of 2 T Calculations (without diamagnetic correction) were made with one molecule of CH,CN per molecule of 2.

[?I

1:P. Lorem, K . Thurow, J Orgunornrc. Cliem. 1995,496, 191.

x=119.25(1), 8=106.41(2), ~=94.88(1)', 2 = 2 , V=2270(2)A3, pcSicd=

Linear Pentanuclear Complexes Containing a

Chain of

Metal Atoms: [Co:'(pu,-tpda),(NCS),]

und [Ni:'(p5-tpda),C1,1**

Shen-Jye Shieh, Chin-Cheng Chou,

Gene-Hsiang Lee, Chih-Chieh Wang, and

Shie-Ming Peng*

Metal-metal bonding

in dinuclear metal complexes is well

understood.['

-

31

Our efforts to extend dinuclear metal complex-

es to form trinuclear metal complexes with a

syn-syn

bis-

[*I

Prof. S.-M. Peng, Dr. S.-J. Shieh, C.-C. Chou, G.-H. Lee, Dr. C.-C. Wang Department of Chemistry

National Taiwan University

Taipei, Taiwan, 107 (Republic of China) Fax: Int. code

+

(2)3636359

(H,tpdd = N,N'-bis(i-pyridyl)-2,6-diaminopyridine). Figure 2. Polyhedral representation of 2, consisting of two edge-shared octa-

hedrons ([FeO,(OH)],), two trigonal bipyramids (FeO,(OH)CI), and six tetra- hedrons (four Fp(Mes)PO, and two MesPO,).

["I

This research was supported by the National Science Council of Taiwan.

COMMUNICATIONS

(wpyridy1)amido ligand have been r e~ 0r t e d. I ~ .

51

In order

to achieve a further extension to pentanuclear metal com-

plexes a new ligand,

N,N'-bis(a-pyridyl)-2,6-diaminopy-

ridine (the common name in our system is tripyridyldi-

amine abbreviated as H,tpda), was synthesized. It was

found that the ligand can bind metal

ions

in two confor-

mations, the anti-anti-anti-anti

form

I and the

syn-

syn-syn-syn

form

XI.

In

I the ligand is tridentate and coordinates to metal ion

through the nitrogen atoms of pyridine moieties. The ligand can

be either neutral or dianionic. [Co"(H,tpda)Cl,] illustrates this

coordination mode.

In I1 the ligands have been deprotonated

and act as bridging pentadentate ligands. The unprecedented

linear pentanuclear nickel(r1) and cobalt(1r) complexes ([M5(p5-

tpda),X,],

M

=

Ni, X

=

C1, and

M

=

Co, X

=

NCS) are re-

ported here.

The ligand was synthesized by treating

2.5

equivalents

of

2-bromopyridine with

1

equivalent

of 2,6-diaminopyridine

un-

der basic conditions. Remaining 2,6-diaminopyridine and N-(a-

pyridyl)-2,6-diaminopyridine

were washed away with water.

The crude product of N,N'-bis(2-pyridyl)-2,6-diaminopyridine

was recrystallized from dichloromethane and methanol. The

cobalt complex of type

I was synthesized by treating equimolar

amounts of CoC12.6H,0 with H,tpda

in

dichloromethane. The

crystal structure of the neutral complex [Co(H,tpda)Cl,] reveals

that the coordination geometry around the cobalt@) ion is trig-

onal bipyramidal with two chloride ions and the nitrogen atom

of the central pyridine as the basal plane and two nitrogen atoms

of the terminal pyridine group as the apex. The ligand H,tpda

is planar and coordinates to cobalt ion in anti-anti-anti-anti

conformation.

The pentanuclear cobalt(I1) complex was synthesized similar-

ly to the trinuclear metal complex.[4-

']

It was characterized by

various spectroscopic methods, in particular mass spectrometry

(FAB) and X-ray diffraction. The parent peak of

[Cos(ps-

tpda),(NCS),J

is

clearly assigned and peaks of the fragments of

[Co,(p-tpda),], and [Co,(p-tpda),] are observed. The structure

of the complex, obtained by X-ray single crystal diffraction

study, has several uncommon features (Figure

1).

First, the pen-

tacobalt metal chain is helically wrapped by four

syn-syn-syn-

syn

type ligands. The complex exhibits approximate

D,

symme-

try. Secondly, the five cobalt(r1) ions are collinear, linked by

multicentered

Co-Co

IS

bonding. The Co-Co distances are

2.277(2), 2.232(2), 2.229(2), and 2.274(2)

A,

which are com-

parable with those of dinuclear cobalt complexes.[*] The prelim-

inary MO analyses indicate there are two

CT

bonds among five

cobalt(I1) ions, and the HOMO is of nonbonding character and

singly occupied. The average Col -N(py) (1.97(1)), C02-

N(amido) (1.90( I ) ) , Co3

-

N(py) (1.93(1)), Co4-N(amido)

(1.90(1)), and Co5-N(py) distances (1.97(1)

A)

are consistent

with a

low spin

state for the cobalt@) ion

(p

=

1.9

pB

and tem-

perature-independent)

.

Thirdly, the negative charges

of

the an-

[CO ~(PL-~P ~~ ),(NCS )J

1

[ C o & - t ~ d a ) J > [Co,(~-tpda),(NCS)1,

Figure 1. Top: Crystal structure of [Co,(ps-tpda),(NCS),l (ORTEP view) Perti- nent bond lengths

(A)

and angles

r):

Col -C02 2.277(2), Co2-Co3 2.232(2), c 0 3 - c o 4 2.229(2), Co4-CoS 2.274(2), Col -N21 2.07(1), Col --N(py) (averaged) 1.97(1), Co2-N (averaged) 1.90(1), Co3-N (averaged) 1.93(1), Co4-N (averaged) 1.90(1), CoS -N(py) (averaged) 1.97( l ) , CoS -N22 2.06( l ) , N21 -Col -C02 178.8(3), N22 179.3(3), N(py)-Col-CoZ (averaged) 86(1), N-Co2-Co3 (averaged) 89(1), N-Co3-Co4 (averaged) 90(1), N-Co4-Co3 (averaged) 89(1), N(py)-CoS-Co4 (averaged) 86(1). Center: Illustration of the helical ligands wrapped around the linear metal chain (along the metal chain axis). The three carbon atoms of

pyridine rings are omitted for clarity. Bottom: Another illustration down the metal chain axis.

COl-cO2-CO3 178.7(1), CO2-Co3-Co4 179.9(1), C O ~ - C O ~ - C O S 178 8 ( 1 ) , CO4-CO5-

ionic ligand are delocalized

on the five nitrogen atoms of the

ligand. The observed bond pattern is qualitatively consistent

with the delocalization model.

The pentanuclear nickel(I1) complex has also been synthesized

similarly to the trinuclear metal complexes.[4

71

The parent

peak of [Ni,(ps-tpda),C1,]

is clearly assigned, and peaks of the

[Ni,(p-tpda),] and [Ni,(p-tpda),Cl] fragments are also ob-

served. The single-crystal X-ray diffraction study of [Niy(p5-

tpda),Cl,] reveals that the asymmetric unit contains half of the

complex and two dichloromethane molecules. The complex is

located at the crystallographic center of inversion. The atomic

positions are averaged, because right-turn and left-turn helical

complexes are disordered in the crystal. Eight nitrogen atoms

from amido groups that are coordinated to nickel ions (Ni2,

occupancy factor

0.5)

and the a-carbon atoms of the pyridyl

groups have high

anisotropic

thermal parameters.

One

of

the helical forms

is

shown

in

Figure2. The pentanuclear

COM NI

U

N

ICATIONS

^, n C28

Figure 2. Crystal structure of pi,(p,-tpda),CI,] (ORTEP view) Pertinent bond lengths

(A)

and angles

r):

Nil-CI 2.346(3), Nil -Ni2 2.385(2), Ni2-Ni3 2.305(1), Nil - N (averaged) 2.11 1(9), Ni2- N (averaged) 1.897(1 S), Ni?- N 1.904(8), CI-Nil- Ni2 l79.1(1), Nil-Ni2-Ni3 179.5(1), Ni2-Ni3-Ni2 180, N-Ni3-N2 (averaged) 90. N-Ni2-Ni3 (averaged) 88(1), N-Nil-Ni2 (averaged) 82(1).

linear metal chain is helically wrapped by four

syn-syn-syn-

syn type ligands. The five nickel ions and two chloride ions are

collinear (Cl-Nil-Ni2 179.1(1)", Nil-Ni2-Ni3 179.5(1)", and

Ni2-Ni3-NiY 180"). The Ni-Ni distances are very short (Nil

-

Ni2 2.385(2); Ni2-Ni3 2.306(2)

A).

The latter

is the shortest

known Ni-Ni distance.[9-"] According to

MO analyses, no

bonding interactions exist between the nickel ions, which is con-

sistent with the magnetic data (see below).

The average Ni2-N (1.897(15)

A)

and Ni3-N distances

(1.904(8)

A)

are short, consistent with a square-planar, diamag-

netic arrangement of nickel(I1) ions. The terminal Ni" ions (Nil)

are in a square-pyramidal environment and exhibit a long Nil -

C1 bond (2.346(3)

A)

and long Nil -N bonds (av. 2.1 1 l(9)

A),

consistent with high-spin nickel(I1) ions ( S

=

1,

p

=

2.8

pB).

A

temperature-dependent magnetic study

o f the complex (Fig-

ure 3) indicates the antiferromagnetic interaction of terminal

high-spin nickel ions with

J

=

-

14.6 cm-'. This interaction

is

one order of magnitude smaller than those of similar trinuclear

nickel(I1) complexes.[',

Attempts to isolate other linear pentanuclear metal complex-

es and demonstration of their potential application as molecular

wires are under way.

0.018 0 O o Z o t 016

j

0

I

0.012 xM/emu mol-' 0.010 0 008 0.006 50 1 0 0 150 200 250 300 TIK-

Figure 3. Magnetic data for [Ni,(p,-tpda),CI,]. Solid curves represent calculation based on the equation

5,

= C(2e2"

+

10eb=)/(l

+

3eZ'

+

Se'"). C = Ng2f12/ kT,x = J/kT, 2 = - 2 J S , - S , (S, = S, = S, = 0, S, = S, =1) and pert =

2.84((,T)"2. o is the observed xhl and the observed perr.

Experimental Sect ion

H,tpda: Under a nitrogen atmosphere 2-bromopyridine (36 mL) was added to a solution of 2.6-diaminopyridine (10 g, 0.09 mol) and fBuOK (30.24 g. 0.27 mol) in T H F ( 1 50 mL). The reaction mixture was heated under reflux for 24 h. After cool- ing to room temperature, the solvent was removed by rotary evaporator. Then the mixture was extracted with dichloromethane, and the solvent removed under re- duced pressure. Unchanged 2.6-diaminopyridine and N-(a-pyridyl)-2,6-diaminopy- ridine were rinsed away with water. The crude product of N.N'-bis(2-pyridyl)-2.6- diaminopyridine was recrystallized from dichloromethane and hexane(Yie1d 26%). IR (KBr)

V

= 3442.31 80 cm -

'

(NH). UV/Vis (CH,CI,): i.,,(6:) ,= 268 (3.76 x I 0,). 321 n m ( 4 . 1 3 ~ lo3). MS(FAB):m/~(%)264(60)[M+l]~. 186(100) [C,oNaHJ+, 77 (20) [C,H,N]'.

[Co(H,tpda)CI,]: CoCI, 6H,O (23 mg, 0.09 mmol) was added to a solution of H,tpda (25 mg, 0.09 mmol) in CH,CI, (30 mL). The yellow solution was stirred for 6 h A green precipitate was formed, filtered off, washed with ether, and air-dried. Green prismatic crystals were formed by slow diffusion of diethyl ether into a CH,CN/DMF solution of the compound (yield 70%). IR (KBr): 3 = 3397, 3316, 3203 c m - ' (NH). UV/Vis ( D M F ) i,,( 6 ) ,= 330 (3.34 x lo4). MS (FAB): m/z (%) 321 (40) [ M

-

Cl]'

[Co,(p,-tpda),(SCN),]: CoCI,.6H,O (0.936 g, 4 mmol) and H,tpda (1.02 g, 4 mmol) were placed in an Erlenmeyer flask, and naphthalene (7.2 g) was added. The mixture was heated (about 160-180°C) for 10min to remove water. Then n-butanol(3 mL) was added to the heated mixture, and heating was continued until the n-butanol had almost completely evaporated. A solution of potassium n-butox- ide (0.88 g, 8 mmol)n-butanol(20 mL) wasadded dropwise. Heating was continued until the remaining n-butanol had evaporated completely, after which an excess of sodium thiocyanate (1.0 g) was added. After the mixture had cooled. n-hexane was added to wash out naphthalene. The remaining solid was extracted with CH,CI, and recrystallized from CH,Cl,/n-hexane solution. Deep brown crystals were ob- tained (yield 5 % ) . I R (KBr) i = 2058 (CN), 1594, 1565, 1536 (C=C). UV/Vis (CH,CI,) i,,, ( 6 ) = 279 (1.13 x lo5), 338 (6.21 x lo4), 393 ( 5 . 8 4 ~ lo4), 513 ( 9 . 7 5 ~ lo'). 725cm-' (1.01 x lo3). MS (FAB): mi;

(YO)

1455 (2) [MI', 1397 (4)

[M - SCN]+. 1339 ( I ) (Co,(p-tpda),]', 1077 (6) [Co,(p-tpda),SCN]+, 1019 (4) ICo&-tpda)J+.

[Ni,(p,-tpda),CI,]: NiCI;6H,O (0.948 g, 4 mmol) and H,tpda (1.02 g, 4 mmol) were placed in an Erlenmeyer flask, and naphthalene (7.2 g) was added. The mixture was heated (about 160-180") for 10min to remove water. Then n-butanol (3 mL) was added to the heated mixture, and heating was continued until the n-butanol had almost completely evaporated. A solution ofpotassium n-butoxide (0.88 g, 8 mmol, in 20 mL n-butanol) was added dropwise. Heating was continued until the remain- ing n-butanol had evaporated completely. After the mixture had cooled, n-hexane was added to wash out naphthalene. The remaining solid was extracted with CH,CI, and recrystallized from CH,Cl,/n-hexane solution Deep purple crystals were obtained (yield 50%). IR (KBr) V ~ 1 5 9 1 , 1562, 1541 cm-' (C=C). UV/Vis (CH,CI,) i.,,, (E) = 253(1.02 x lo5). 293(1.28 x lo5), 37311.55 x lo5), 592 nm (1.28 x lo4). MS (FAB): m/z (YO) 1408 (4) [MI', 1373 (3). [ M - Cll'. 1017 (10) [Ni&-tpda)J+, 698 (10) [Ni,(p-tpda),]'

Crystal data for [Co"(H,tpda)CI,I: Monoclinic, space group C2/c, a = 7.482(1). 2 = 4; CAD4 diffractometer with graphite-monochromated Mo,, radiation, Y - scan absorption correction (0.91

-

1 .OO); of 1406 unique reflections (20< SO0) mea- sured, 1125 with I > 2 u ( I ) were used in the refinement. R = 0.027, Rn, = 0 026 (133 variables)

Crystal data for [Ni~(p,-tpda),CI,](CH,C12)4: Monoclinic, space group P2,/n,

u = 13.416(3), V = 3578(1) A3,

p = 1.623 gcm-'.Z = 4; Y-scanabsorptioncorrection(0.92-1.00);of6280unique reflections (20i50") measured, 3188 with I>Zu(I) were used in the refinement.

R = 0.072, R n = 0.071 (485 variables).

Crystal data for [Co~(pt,-tpda),(SCN),I-CH,CI,-(C~H,O), ;(H,O), 5 : Triclinic,

space group P i . a = 11.802(1), b =14.631(7), c = 20.184(4)

A,

a =73.42(3), b=77.77(1),g=87.56(3)", V = 3 2 6 4 ( 2 ) A 3 , p = 1 . 6 1 5 g c m - ' , Z = 2 ; Y-scan ab- sorption correction (0.83- 1 .OO); of 8645 unique reflections (20i45') measured, 3400 with I > 2 u ( I ) were used in the refinement. R = 0.049, R n = 0 046 (847 vari- ables)

Crystallographic data (excluding structure factors) for the structure(s) reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-179-145 Copies of the data can be ob- tained free of charge on application to The Director, CCDC, 12 Union Road, Cambridge CB2 IEZ, UK (fax: Int. code

+

(1223) 336-033; e-mail: teched(rlchemcrys.cam.ac.uk).

5=17.172(3), c = i 2 . 8 3 3 ( i ) A , ~ = i o 4 . i ( i ) " , v = i 5 9 8 8 ( 4 ) A 3 , =1.633gcm-',

h =16.894(3), c = 15.8807(4)

A,

= 92.54(2)",

Received: July 12, 1996 Revised version: October 8, 1996 [Z9328IEJ German version: Angew. Chem. 1997. 109, 57-59

Keywords:

cobalt

*

helical structures

-

magnetic properties

nickel

.

N ligands

COMMUNICATIONS

[I] F. A. Cotton. G. Wilkinson. Advanced Inorganic Chemistry, 5th ed., Wiley,

[2] F. A. Cotton. R. A. Walton. Multiple Bonds Between Meral Atoms, 2nd ed., 131 Metul-Meiul Bonds C1u.ster.s in Cl?emi.rtrv nnd Cataljsis, Plenum, New York, [4] E C. Yang, M C. Cheng. M. S . Tsai. S. M. Peng, J Chem. Soc. Chem. Com- [5] J. T Sheu. C. C . Lin. I. Chao. C. C. Wang, S. M. Peng, Chem. Commun. 1996, [6] L. P. Wu. P. Field. T. Morrissey, C. Murphy, P. Nagle, B. Hathway, J Chem.

[7] S Aduldecha. 8. Hathway. J Chem. Soc. Dalton Trans. 1991, 993. [XI F. A. Cotton. R . Poli. lnorx Chrin. 1987, 26, 3653. Co-Co = 2.265(2) 8, in

[Co','(triaz),] (rriaz = di-p-tolytriazenato)

[9] 0 Jarchow. H Schultz. R. Nast, Angeu.. Chern. 1970, 614. 43. Angew. Chem. I n ! Ed Engl. 1970, 9, 71. Ni-Ni = 2.32 8, in [Ni:(CN),]"-.

[lo] L. Sacconi. C. Mealli. D. Gatteschi. Inorg. Chem. 1974, 13, 1985. Ni- Ni = 2 42 8, in [N~:-~(napy),Br,]' (napy = 1.8-naphthyridine).

[ l l ] M. Corbett.

B.

Hoskins, Chem. Commun. 1969, 1602. Ni-Ni = 2.38 8, in [Niy(PhN,Ph),] (PhN,Ph = diphenyltriazenato).

[12] C. Lin, C. Chou, S. Peng, unpublished. The J for [Ni,(p3-dpa),X,l"+ idpa = dipyridylamido ion) is - 96. -122 and - SSOcm-' for X = C1- i n = 0 ) . X = KCS- ( n = 0) and X = NCMe ( n = 2). respectively. New York. 1988, Chap. 23.

Clarendon Press. Oxford, 1993. 1989.

miin. 1994. 2377. 315.

so<..

Daiton Ti.un.\ 1990. 3835.

An Interwoven Supramolecular

Cage**

Peter

R.

Ashton, Andrew N. Collins,

Matthew C. T. Fyfe, Peter

T.

Glink, Stephan Menzer,

J. Fraser Stoddart,* and David J. Williams

Dedicated to Professor Vincenzo Balzani

on the occasion of his 60th birthday

In recent times, supramolecular, noncovalent synthesis"] has

provided the chemist convenient access t o some remarkable

su-

perstructures, many of which are produced with a high degree of

architectural control and have the potential to perform specific

functions. One of the most challenging domains within this field

of

endeavor involves s e l f - a ~ s e m b l i n g [ ~ ~

discrete supramolecular

cages that are held together by intermolecular intera~tions[~1

and can act as synthetic receptors. However, none of the systems

reported to date involve interlocked o r interwoven structures.[41

We have designed such

a

system (Scheme I ) , which relies upon

the simultaneous threading of two secondary dialkylammonium

ions through the cavity of a ditopic crown ether, namely bis-p-

phenylene[34]crown-10 (BPP34C10)

.[51

The trifurcated trisam-

monium ion

[1-H,I3'

has three secondary ammonium centers in

branches radiating from a central polyaromatic core. Each

branch can insert itself through the cavity

of

a

BPP34C10

molecule, but then utilizes only half of the potential receptor

[*I Prof J F. Stoddart, P. R. Ashton, M. C. T. Fyfe, Dr. P. T. Glink School of Chemistry, University of Birmingham

Edgbaston. GB-Birmingham B15 2TT (UK)

F a x : Int. code +(121)414-3531 e-mail. J f.stodddrt(a bham.ac.uk Dr. S Menzer. Prof. D. J. Williams

Chemical Crystallography Laboratory, Imperial College. London (UK) Dr. A N Collins

ZENECA Specialities, Manchester (UK)

[**I This research was sponsored in the UK by an Engineering and Physical Sciences Research Council CASE Award (to M.C.T.F) and also by the Biotech- nology and Biological Sciences Research Council.

Scheme 1. Schematic representation of the anticipated [3

+

21 self-assembly be- tween two [1-HJ3+ ions and three BPP34C10 macrocycles to form a n interwoven supramolecular cage.

sites. The vacant receptor sites remaining in each of the cavities

of

the three macrocyclic polyethers are then free to accept an-

other branch from

a

second trication, which leads to

a

cagelike

supermolecule. Here we report the synthesis of the trifurcated

trisammonium salt l-H3.3PF, and the self-assembly of a five-

component interwoven supramolecular cage in the solid state

from the [1-H,I3+ ion and BPP34C10.

The trisammonium ion [1-H3I3+ was prepared as its hexa-

fluorophosphate salt in good overall yield: condensation

of

1,3,5-tris(4-f0rmylphenyl)benzene[~~

with benzylamine, fol-

lowed by reduction of the resultant trisaldimine. gave the tri-

furcated trisamine

1,3,5-tris[(4-benzylaminomethyl)phenyl]-

benzene, which afforded 1-H,.3

PF,

after treatment with hy-

drochloric acid and counterion exchange from chloride to hexa-

fluorophosphate.

Single crystals suitable for X-ray analysis were obtained when

a MeNO, solution containing BPP34C10 (3 equiv) and

1-

H;3

PF,

(2 equiv) was layered with Et,O. Gratifyingly, the

crystallographic analysis of one of these crystals (Figure 1) re-

v e a l ~ [ ~ ]

the formation of a highly symmetrical cagelike super-

structure in which two [1-HJ3+ ions are threaded through three

BPP34ClO macrocycles.['] The supermolecule has

D,

symme-

try, and the principal axis passes through the centers of the two

1,3,5-triarylbenzene rings,[71 which have a mean interplanar sep-

aration of about 4.0 A

(Figure 2). The three pura-phenylene

rings of each trication are rotated by about 37" out of the plane

Angeu Chwn Inr Ed Engl 1997. 36. N o 112

0

VCH Verlagsgesellschuft mbH, 0.69451 Wemherm, 1997 OS7O-O833~97/36Ol-OOS9$ 15 0#+ 2 0 0

59