to further downfield shifts for the N(15)–H resonance (to dH
9.39, 9.55 and 9.65 on addition of 1, 2 and 3 equivalents of
nBu4NNO3, respectively) consistent with anion binding in
solution. Significantly, addition of [nBu4N][NO3] to L2 does not
shift the N(15)–H resonance; therefore, anion binding to L2 can
only occur once cation binding within the macrocyclic cavity
and concomitant cleavage of the internal H-bonding takes place,
thus affording an element of cooperativity to this system.
Compound 4 has also been prepared and characterised.†‡
In conclusion, we have confirmed that the combination of
thioether macrocycles with functionalised acylurea lariat arms
affords heteroditopic receptors that have a wide applicability for
the complexation of transition metal salts. These results have
important implications for the extraction and transport of
transition metal salts, especially at low pH where thioether
crowns can still function as avid metal cation receptors.
This work was supported by the EPSRC (UK) and Avecia
plc.
Fig. 2 View of structure of [CuCl(L2)]2CuCl4.
Neither 1 or 2 allow for NMR studies on solution complexa-
tion. However, the reaction between AgNO3 and L2 yields
[Ag(NO)3(L2)], 3,†‡ which is soluble in CD3CN. The solid state
Notes and references
‡ For 1: Anal. Found: C, 38.70; H, 5.77; N, 9.92. C26H50Cl2N6O4PdS4
requires: C, 38.30; H, 6.25; N, 10.32%; 1H NMR (CD3OD): dH 8.40 (br s,
1H, NH), 3.9–3.0 (br m’s, 28H, macrocycle H/ CH2), 1.37 (s, 18H, But); MS
(FAB, +ve NBA matrix): m/z 744 (M+ 2 2Cl 100%). For 2: Anal. Found:
C, 30.74; H, 4.95; N, 7.58. C30H58Cl6Cu3N6O4S6 requires: C, 30.99; H,
5.03; N, 7.23%; MS (FAB, +ve NBA matrix): m/z 477 {[CuCl(L2)]+ 45},
442 {[Cu(L2)]+ 50%}. For 3: Anal. Found: C, 33.17; H, 5.39; N, 10.64.
C15H29AgN4O5S3 requires: C, 32.79; H, 5.32; N, 10.20%; 1H NMR
(CD3CN): dH 8.85 (brs, 1H, NH), 8.08 (br s, 1H, NH), 3.40 (s, 2H, CH2),
2.85 (br m’s, 16H, macrocyclic CH2’s), 1.35 (s, 9H, CMe3); MS (FAB, +ve
NBA matrix): m/z 488 (M+ 2 NO3, 100%); IR (KBr disc): n/cm21 3449
(vbr, m), 3299 (br, m), 1712 (s), 1348 (vs). For 4: Anal. Found: C, 32.71; H,
4.97; N, 8.00. C15H29Cl2N3O2PdS3 requires: C, 32.35; H, 5.25; N, 7.54%.
1H NMR (CD3OD): dH 4.2–3.2 (br m’s, 18H, macrocycle H/ CH2), 1.38 (s,
9H, But). 1H NMR (CD3CN): dH 8.30 (br s, 1H, NH), 8.15 (br s, 1H, NH),
3.70–2.80 (m’s, 18H, macrocyclic H), 1.36 (s, 9H, But). MS (FAB, +ve
NBA matrix): m/z 522 (M+ 2 Cl, 65), 484 (M+ 2 2Cl, 70%).
structure of 3§ confirms that the Ag( ) cation is complexed by
I
the azathiocrown with the anion receptor arm extending radially
(Fig. 3). Inspection of the extended structure reveals a bond
between Ag(
I
) and a S-donor of a second cation [Ag–S(4A)
2.496(2) Å], so completing a five-coordinate, square pyramidal
geometry at Ag( ) and affording an overall two-dimensional
I
step-polymeric motif. Although displaying two-fold rotational
2
disorder, the NO3 anion is clearly H-bonded to the pendant
arm via the urea N(15), interacting in varying degrees with
O(2), O(2A) and O(1) [N(15)–O(2) 3.27(3), N(15)–O(2A)
2.50(2), N(15)–O(1) 3.43(3) Å].
suppdata/cc/b1/b109486f/ for crystallographic data in CIF or other
electronic format.
1 For recent overview on anion binding, see: P. D. Beer and P. A. Gale,
Angew. Chem., Int. Ed., 2001, 40, 486.
2 J. E. Redman, P. D. Beer, S. W. Dent and M. G. B. Drew, Chem.
Commun., 1998, 231; P. D. Beer and S. W. Dent, Chem. Commun.,
1998, 825.
3 D. M. Rudkevich, Z. Brzozka, M. Palys, H. C. Visser, W. Verboom and
D. N. Reinhoudt, Angew. Chem., Int. Ed. Engl., 1993, 33, 467; D. M.
Rudkevich, J. D. Mercer-Chalmers, W. Verboom, R. Ungaro, F. de Jong
and D. N. Reinhoudt, J. Am. Chem. Soc., 1995, 117, 6124.
4 E. A. Arafa, K. I. Kinnear and J. C. Lockhart, J. Chem. Soc., Chem.
Commun., 1992, 61.
5 M. T. Reetz, C. M. Niemeyer and K. Harms, Angew. Chem., Int. Ed.
Engl., 1991, 30, 1472; M. T. Reetz, C. M. Niemeyer and K. Harms,
Angew. Chem., Int. Ed. Engl., 1991, 30, 1474. See also ref. 6 for an
energy minimised structure of a metal salt complex.
6 D. M. Rudkevich, A. N. Shivanayuk, Z. Brzozka, W. Verboom and D.
N. Reinhoudt, Angew. Chem., Int. Ed. Engl., 1995, 34, 2124.
7 P. D. Beer, P. K. Hopkins and J. D. McKinney, Chem. Commun., 1999,
1253.
8 D. J. White, N. Laing, H. Miller, S. Parsons, S. Coles and P. A. Tasker,
Chem. Commun., 1999, 2077; S. Ghosh, M. Mukherjee, A. K.
Mukherjee, S. Mohanta and M. Helliwell, Acta Crystallogr., Sect C.,
1993, 50, 1204.
Fig. 3 View of structure of [Ag(NO3)(L2)].
Addition of AgNO3 to a solution of L2 in MeCN leads
initially to an upfield shift for the N(15)–H proton from dH 9.01
in L2 to 8.65 on addition of 0.4 equivalents of AgNO3. This
upfield shift reflects the breaking of the internal H-bonding in
free L2 (confirmed by structural studies) on complexation to
Ag( ) (Scheme 2). On further addition of AgNO3, this resonance
I
shows the expected downfield shift to dH 8.85 for 3 reflecting H-
bonding of the acylurea arm to the nitrate anion as confirmed by
the crystal structure of 3. Addition of [nBu4N][NO3] to 3 leads
9 A. J. Blake and M. Schröder, Adv. Inorg. Chem., 1990, 35, 1 and
references therein; T. F. Baumann, J. G. Reynolds and G. A. Fox, Chem.
Commun., 1998, 1637.
10 For example of an acyl-O to M interaction see: T. Okuno, S. Ohba and
Y. Nishida, Polyhedron, 1997, 16, 3765.
11 K. E. Halvorson, C. Patterson and R. D. Willet, Acta Crystallogr., Sect.
B, 1990, 46, 508 and references therein.
Scheme 2 Cleavage of internal H-bonding in L2 on binding to AgNO3.
Chem. Commun., 2001, 2678–2679
2679