The first homologous series of self-assembled aryl bromo- and aryl cyanocuprates, -argentates, and -aurates; MLi2XAr2 (M = CuI, AgI, AuI; X = Br, C≡N; Ar = [C6H4CH2N(Et)CH2 CH2NEt2-2]-)

Article abstract of DOI:10.1021/ja026945t

Reaction of 2 molar equiv of the diamine chelated aryllithium dimers Li₂(C₆H₄{CH₂N(Et) CH₂-CH₂NEt₂}-2)₂ (Li₂Ar₂) with the appropriate metal bromide allows the synthesis of the first homologous series of monomeric group 11 bromoate complexes of type MLi₂BrAr₂ (M = Cu (7), Ag (8), Au (9)). Both in the solid state and in solution, the bromocuprate 7 is isostructural with the bromoargentate 8. The crystal structures of 7 and 8 consist of a MLi₂ core, and each of the two aryl ligands bridges via electron-deficient bonding between the group 11 metal and one Li atom (d(C_ipso-M) = 1.941(4) (mean) and 2.122(4) (mean) A, for 7 and 8, respectively). The bromine atom exclusively bridges between the two lithium atoms. Each of the ortho-CH₂N(Et)CH₂CH₂NEt₂ moieties is N,N′-chelate bonded to one lithium (d(N-Li) = 2.195(5) and 2.182(0) (mean) A for 7 and 2.154(8) and 2.220(1) (mean) A for 8). Although the MLi₂BrAr₂ compounds are neutral higher-order -ate species, the structure can also be regarded as consisting of a contact ion pair consisting of two ionic fragments, [Li-Br-Li]⁺ and [Ar₂M]^-, which are interconnected by both Li-N,N′-chelate bonding and a highly polar C_ipso-Li interaction. On the basis of NMR and cryoscopic studies, the structural features of the bromoaurate 9 are similar to those of 7 and 8. A multinuclear NMR investigation shows that the bonding between the [Li-Br-Li] and [Ar₂M] moieties is intermediate between ionic and neutral with an almost equally polarized C_ipso-Li bond in 7, 8, and 9. Similar reactions between M(C≡N) and 2 molar equiv of LiAr yield the analogous 2:1 cyanoate complexes of type MLi₂(C≡N)Ar₂ (M = Ag (10), Au (11)). Multinuclear NMR studies show that the cyanoate complexes 10 and 11 are isostructural with the bromoate complexes 7, 8, and 9. This paper illustrates that these cyanoaurates may serve as excellent model complexes to gain more insight into the structure of 2:1 cyanocuprates in solution.

Full text of DOI:10.1021/ja026945t

Published on Web 09/04/2002
The First Homologous Series of Self-Assembled Aryl Bromo-
and Aryl Cyanocuprates, -Argentates, and -Aurates; MLi2XAr2
(M ) CuI, AgI, AuI; X ) Br, CtN;
Ar ) [C6H4CH2N(Et)CH2CH2NEt2-2]-)
Claudia M. P. Kronenburg,† Johann T. B. H. Jastrzebski,† Jaap Boersma,†
Martin Lutz,‡ Anthony L. Spek,#,‡ and Gerard van Koten*,†
Contribution from the Debye Institute, Department of Metal-Mediated Synthesis,
Utrecht UniVersity, Padualaan 8, 3584 CH Utrecht, The Netherlands, and BijVoet Center for
Biomolecular Research, Crystal and Structural Chemistry, Utrecht UniVersity,
Padualaan 8, 3584 CH Utrecht, The Netherlands
Received May 17, 2002
Abstract: Reaction of 2 molar equiv of the diamine chelated aryllithium dimers Li2(C6H4{CH2N(Et)CH2-
CH2NEt2}-2)2 (Li2Ar2) with the appropriate metal bromide allows the synthesis of the first homologous series
of monomeric group 11 bromoate complexes of type MLi2BrAr2 (M ) Cu (7), Ag (8), Au (9)). Both in the
solid state and in solution, the bromocuprate 7 is isostructural with the bromoargentate 8. The crystal
structures of 7 and 8 consist of a MLi2 core, and each of the two aryl ligands bridges via electron-deficient
bonding between the group 11 metal and one Li atom (d(Cipso-M) ) 1.941(4) (mean) and 2.122(4) (mean)
Å, for 7 and 8, respectively). The bromine atom exclusively bridges between the two lithium atoms. Each
of the ortho-CH2N(Et)CH2CH2NEt2 moieties is N,N′-chelate bonded to one lithium (d(N-Li) ) 2.195(5) and
2.182(0) (mean) Å for 7 and 2.154(8) and 2.220(1) (mean) Å for 8). Although the MLi2BrAr2 compounds
are neutral higher-order -ate species, the structure can also be regarded as consisting of a contact ion pair
consisting of two ionic fragments, [Li-Br-Li]+ and [Ar2M]-, which are interconnected by both Li-N,N′-
chelate bonding and a highly polar Cipso-Li interaction. On the basis of NMR and cryoscopic studies, the
structural features of the bromoaurate 9 are similar to those of 7 and 8. A multinuclear NMR investigation
shows that the bonding between the [Li-Br-Li] and [Ar2M] moieties is intermediate between ionic and
neutral with an almost equally polarized Cipso-Li bond in 7, 8, and 9. Similar reactions between M(CtN)
and 2 molar equiv of LiAr yield the analogous 2:1 cyanoate complexes of type MLi2(CtN)Ar2 (M ) Ag
(10), Au (11)). Multinuclear NMR studies show that the cyanoate complexes 10 and 11 are isostructural
with the bromoate complexes 7, 8, and 9. This paper illustrates that these cyanoaurates may serve as
excellent model complexes to gain more insight into the structure of 2:1 cyanocuprates in solution.
extensive, ongoing discussions in the literature.5,6 We have set
out to concentrate our synthetic and structural studies on haloaryl
and cyanoaryl cuprates containing monoanionic, ortho-mono-,
and -diamine chelating aryl ligands; see Scheme 1. The use of
these ortho-amine aryl ligands allows the formation of stable,
well-defined organocopper aggregates of which the neutral
Introduction
Organocopper(I) complexes, especially cuprates [CuLinRn+1
]
and [CuLinXRn] (n ) 1,2), are widely used, often as in situ
prepared reagents, in organic synthesis.1 Along with the
development of synthetic applications, interest in the structural
features both in the solid state and in solution is increasing as
well. Although a number of pure halocuprates (X ) Cl, Br, I)2
and cyanocuprates3,4 have been reported, particularly the
structural aspects of cyanocuprates (X ) CN) are subject to
(2) (a) Hope, H.; Oram, D.; Power, P. P. J. Am. Chem. Soc. 1984, 106, 1149.
(b) Hope, H.; Olmstead, M. M.; Power, P. P.; Sandell, J.; Xu, X. J. Am.
Chem. Soc. 1985, 107, 4337. (c) Villacorte, G. M.; Pulla Rao, Ch.; Lippard,
S. J. J. Am. Chem. Soc. 1988, 110, 3175. (d) Hwang, C.-S.; Power, P. P.
Organometallics 1999, 18, 697.
(3) Kronenburg, C. M. P.; Jastrzebski, J. T. B. H.; Spek, A. L.; van Koten, G.
J. Am. Chem. Soc. 1998, 120, 9688.
(4) Boche, G.; Bosold, F.; Marsch, M.; Harms, K. Angew. Chem. 1998, 110,
1779.
(5) (a) Bertz, S. H. J. Am. Chem. Soc. 1990, 112, 4031. (b) Lipshutz, S. H.;
Sharma, S.; Elsworth, E. L. J. Am. Chem. Soc. 1990, 112, 4032. (c) Bertz,
S. H.; Nilsson, K.; Davidsson, O.; Snyder, J. P. Angew. Chem., Int. Ed.
1998, 37, 314. (d) Gerold, A.; Jastrzebski, J. T. B. H.; Kronenburg, C. M.
P.; Krause, N.; van Koten, G. Angew. Chem., Int. Ed. Engl. 1997, 36, 755.
(e) Gschwind, R. M.; Xie, X.; Rajamohanan, P. R.; Auel, C.; Boche, G. J.
Am. Chem. Soc. 2001, 123, 7299. (f) Mobley, T. A.; Mu¨ller, F.; Berger, S.
J. Am. Chem. Soc. 1998, 120, 1333. (g) Huang, H.; Liang, C. H.; Penner-
Hahn, J. E. Angew. Chem., Int. Ed. 1998, 37, 1564.
* To whom correspondence should be addressed. E-mail: g.vankoten@
chem.uu.nl. Fax: +31 30 252 3615.
# To whom correspondence on crystallographic studies should be
addressed.
† Debye Institute, Utrecht University.
‡ Bijvoet Center, Utrecht University.
(1) (a) Posner, G. H. An Introduction to Synthesis using Organocopper
Regeants; John Wiley & Sons: New York, 1980. (b) Lipshutz, B. H.;
Wilhelm, R. S. J. Am. Chem. Soc. 1981, 103, 7672. (c) Lipshutz, B. H.;
Sengupta, S. Org. React. 1992, 41, 139. (d) Bertz, S. H.; Fairchild, E. H.
Encyclopedia of Reagents for Organic Synthesis; Wiley: New York, 1995.
(e) Krause, N.; Gerold, A. Angew. Chem., Int. Ed. Engl. 1997, 36, 186.
9
10.1021/ja026945t CCC: $22.00 © 2002 American Chemical Society
J. AM. CHEM. SOC. 2002, 124, 11675-11683
11675

A R T I C L E S
Kronenburg et al.
Scheme 1
bromocuprate [CuLi2Br(C6H4{CH2N(Me)CH2CH2NMe2}-2)2]
(2a) (vide infra, Scheme 1) is an interesting example.7 In the
complexes 1 and 2, the ortho-amine substituents represent
suitably positioned donor atoms8 which contribute, by forming
additional N-Li or N-Cu bonds, to the overall (thermody-
namic) stability of the resulting cuprate aggregate. Recently,
we have also reported the synthesis and characterization of a
stable, polymeric 2:1 cyanocuprate [Cu(C6H4{CH2NMe2}-2)2]-
[Li2(CN)‚(THF)4]+ (3) (vide infra, Scheme 1).3 The solid-state
structure of 3 reveals an ionic structure comprising distinct,
anionic [R2Cu]- moieties with a linear C-Cu-C arrangement
and [Li2(CN)]+ countercations. In this structure, the amino-to-
Li coordination occurs between both ionic species.
studies;6b-f see Figure 1. The synthesis of the corresponding
argentate(I) and aurate(I) complexes would give the first series
of homologous 2:1 heteroate complexes in group 11 organo-
metallic chemistry. An early example of such a series in group
11 alkyl and aryl chemistry is the neutral 1:1 homoate complexes
[Li2M2(C6H4{CH2NMe2}-2)4] for M ) CuI (1a),9 AgI (1b),10
and AuI (1c)11 (cf., Scheme 1).12
The present study describes the synthesis and isolation of
the homologous series of aryl bromo- and cyanoate complexes
[MLi2X(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (M ) CuI, X ) Br
(7); M ) AgI, X ) Br (8); M ) AuI, X ) Br (9); M ) AgI, X
) CN (10); and M ) AuI, X ) CN (11)).21 These are the first
Despite the disclosure of this solid-state structure of a 2:1
cyanocuprate, the structures of such cuprates in solution remain
uncertain. Recent NMR studies by Gschwind et al.5e reveal that
organocuprates exist in solution either as contact ion pairs (CIP)
or as solvent-separated ion pairs (SSIP), depending on the nature
of the solvent. The neutral bromocuprates 2 (achiral, 2a,
enantiomerically pure, 2b, and racemic, 2c), which we recently
reported, may be regarded as comprising [R2Cu]- and [Li2Br]+
ionic fragments (vide infra).5,7 They occur as discrete neutral
monomers CuLi2BrR2, both in the solid state and in apolar
solutions; see Figure 1.7 This unique feature prompted us to
attempt the synthesis of the corresponding aryl cyanocuprate,
-argentate, and -aurate complexes. The resulting [MLi2(CN)-
R2] species, when accessible, may serve as model complexes
for an important class of organo cyanocuprates (M ) CuI) which
has been used as a starting point in a number of computational
(6) (a) Krause, N. Angew. Chem., Int. Ed. 1999, 38, 79. (b) Nakamura, E.;
Mori, S. J. Am. Chem. Soc. 1998, 120, 8273. (c) Nakamura, E.; Yamanaka,
M. J. Am. Chem. Soc. 1999, 121, 8941. (d) Mori, S.; Nakamura, E.
Tetrahedron Lett. 1999, 40, 5319. (e) Mori, S.; Nakamura, E. Chem.-Eur.
J. 1999, 5, 1534. (f) Nakamura, E.; Yamanaka, M.; Mori, S. J. Am. Chem.
Soc. 2000, 122, 1826. (g) Nakamura, E.; Yamanaka, M.; Yoshikai, N.;
Mori, S. Angew. Chem., Int. Ed. 2001, 40, 1935.
(7) Kronenburg, C. M. P.; Amijs, C. H. M.; Jastrzebski, J. T. B. H.; Lutz, M.;
Spek, A. L.; van Koten, G. Organometallics 2002, in press.
(8) In many cases of unsubtituted aryl-ate compounds, the compound is
stabilized by coordination of solvent molecules to the metal.
(9) (a) van Koten, G.; Noltes, J. G. J. Chem. Soc. 1972, 941. (b) van Koten,
G.; Jastrzebski, J. T. B. H.; Muller, F.; Stam, C. H. J. Am. Chem. Soc.
1985, 107, 697.
(10) Leusink, A. J.; van Koten, G.; Marsman, J. W.; Noltes, J. G. J. Organomet.
Chem. 1973, 55, 419.
(11) van Koten, G.; Jastrzebski, J. T. B. H. J. Am. Chem. Soc. 1984, 106, 1880.
(12) Although a large number of organogold(I) complexes are known,13-16
examples of well-defined organosilver(I) complexes are relatively
scarce.10,17-19 This has been attributed to their lack of thermal stability and
their tendency to decompose photolytically.20 The synthesis and charac-
terization of a series of 1:2 hetero-ate complexes in group 11 would
therefore give more insight into organosilver complexes as well.
(13) Review: Parish, R. V. Gold Bull. 1997, 30, 55; Parish, R. V. Gold Bull.
1998, 31, 14.
(14) (a) Lang, H.; Ko¨hler, K.; Zsolnai, L. Chem. Commun. 1996, 2043. (b)
Crespo, O.; Gimeno, M. C.; Jones, P. G.; Ahrens, B.; Laguna, A. Inorg.
Chem. 1997, 36, 495. (c) Tzeng, B.-C.; Schier, A.; Schmidbauer, H. Inorg.
Chem. 1999, 38, 3978.
(15) Togni, A.; Pastor, S. D. J. Org. Chem. 1990, 55, 1649.
(16) Puddephatt, R. J. In ComprehensiVe Organometallic Chemistry; Wilkinson,
G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, 1982; Vol. II,
Chapter 14, p 765.
(17) Lettko, L.; Rausch, M. D. Organometallics 2000, 19, 4060.
(18) Hwang, C.-S.; Power, P. P. J. Organomet. Chem. 1999, 589, 234.
(19) Eaborn, C.; Hitchcock, P. B.; Smith, J. D.; Sullivan A. C. J. Chem. Soc.,
Chem. Commun. 1984, 870.
(20) (a) Hayashi, N.; Fujiwara, K.; Marai, A. Synlett 1997, 7, 793. (b) Omura,
K. J. Org. Chem. 1998, 63, 10031. (c) Muller, A. A.; Vogt, C.; Sewald, N.
Synthesis 1998, 6, 837.
Figure 1. Schematic representations of organocuprates. a, homocuprates;
b, heterocuprates.
9
11676 J. AM. CHEM. SOC. VOL. 124, NO. 39, 2002

Self-Assembled Aryl Bromo- and Aryl Cyanocuprates
A R T I C L E S
Scheme 2
compounds that substantiate the CuLi2XR2 structural motif that
has been discussed in computational studies.6b-f In fact, the
structural similarities of the heterocuprate 7, heteroargentate 8,
and the bromocopper compound 4 show that the [R2Cu]-,
[R2Ag]-, and [R2Au]- building blocks can self-assemble with
any suitable [M2X]+ cation to give stable, overall neutral species.
moisture-sensitive. The powder readily turns dark brown-to-
black upon exposure to light for periods ranging from several
minutes to 1 h. The aryl bromoaurate 9 is obtained as a pink/
white solid which is slightly light sensitive; after exposure to
light for a period of 6 h, its color had slowly changed to purple/
black. The argentate 8 is easily soluble in THF but only slightly
so in benzene and toluene. It is almost insoluble in diethyl ether,
pentane, and hexane. Aurate 9 shows the same solubility
behavior as cuprate 7 (vide supra).
Results
Syntheses. N-(2-Bromobenzyl)-N,N′,N′-triethyl-1,2-diamino-
ethane [C6H4BrCH2N(Et)CH2CH2NEt2-2] (5) was prepared via
amination of 2-bromobenzyl bromide with (HN(Et)CH2CH2-
NEt2) analogous to the synthesis of [C6H4BrCH2N(Me)CH2-
CH2NMe2-2].22 Lithiation of 5 by slow addition of an equimolar
amount of n-BuLi in pentane at -78 °C gave dimeric [Li-
(C6H4{CH2N(Et)CH2CH2NEt2}-2)]2 (6) in 85% yield. The
heterogeneous reaction of 6 in diethyl ether with insoluble
copper(I) bromide resulted in selective formation of the neutral
aryl bromocuprate [CuLi2Br(C6H4{CH2N(Et)CH2CH2NEt2}-2)2]
(7) (Scheme 2). Compound 7, which was isolated as a colorless
solid in 85% yield, is air- and moisture-sensitive, and crystalline
material immediately turns green upon exposure to air. It is very
soluble in benzene, toluene, and THF and slightly soluble in
diethyl ether, pentane, and hexane. A successful cuprate
synthesis requires following a strict synthetic protocol, and the
synthesis of 7 is no exception. The temperature at which the
cuprate formation begins should be below -30 °C. At higher
temperatures, cuprate formation is accompanied by reductive
side reactions giving metallic copper particles which are known
to cause subsequent autocatalytic decomposition.23-25 As the
formation of copper metal cannot be completely avoided, its
removal from the cuprate solution via a quick filtration through
Celite is essential (details can be found in the Experimental
Section). In the absence of metallic copper, the cuprate 7 is
relatively stable. Also, the stoichiometry of the starting materials,
that is, the Li:Cu atomic ratio, must be exactly 2:1.
The reaction of 6 with silver(I) or gold(I) cyanide in diethyl
ether affords the analogous aryl cyanoargentate [AgLi2(CtN)-
(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (10) or -aurate [AuLi2-
(CtN)(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (11) as the major
reaction products (Scheme 2). Both 10 and 11 are highly air-,
moisture-, and light-sensitive white solids, which are soluble
in benzene, toluene, and diethyl ether and slightly soluble in
pentane and hexane. The similar reaction of 6 with copper(I)
cyanide resulted in the formation of a solid material that partially
redissolved in all common solvents after separation (vide infra).
Crystallographic Studies of -Ate Complexes 7 and 8.
Suitable crystals for X-ray diffraction were grown by vapor
diffusion of pentane into benzene solutions of 7 and 8 at room
temperature and at 0 °C, respectively. Both compounds appeared
to be isomorphous in the solid state, which implies that they
crystallize in the same monoclinic space group P21/c with
essentially the same cell parameters and atomic positions. The
small deviations observed can be explained by the different
measurement temperatures of 150 K for 7 and 125 K for 8, and
by the slightly different radii of the CuI and AgI atom (0.60
versus 0.81 Å, for coordination number 226). Isomorphism is a
common phenomenon among CuI and AgI compounds (for
examples, see refs 27, 28).
In the crystal structures of 7 and 8, part of the Li sites are
occupied by Cu and Ag atoms, respectively. The occupancies
were refined as 9 and 4% Cu in 7 on positions Li1 and Li2,
respectively, and 2.3 and 2.9% Ag in 8, on positions Li1 and
Li2. This implies that the corresponding Cu3 and Ag3 complexes
also have to be isomorphous, which is a prerequisite for the
formation of such substitutional solid solutions. We can assume
that the N,N′-chelated site can be occupied by Li, Cu, and Ag
in any ratio without changing the crystal structure. This
interpretation of the electron density is supported by the
knowledge that tetrahedral geometries are quite common in CuI
and AgI complexes.32
The analogous aryl bromoargentate [AgLi2Br(C6H4{CH2N(Et)-
CH2CH2NEt2}-2)2] (8) and -aurate [AuLi2Br(C6H4{CH2N(Et)CH2-
CH2NEt2}-2)2] (9) were prepared by reacting equimolar amounts
of 6 with AgBr or AuBr(PPh3), using similar synthetic
procedures (Scheme 2). In both cases, the -ate formation should
begin at or below -78 °C. Argentate 8 was obtained in
reasonable yield as a cream-colored powder which is air- and
(21) So far, all attempts to prepare suitable crystals of the corresponding
arylcyanocuprate of 2 for an X-ray structure determination had failed. For
this reason, we decided to replace the methyl groups in the ortho-diamine
chelating substituent of the aryl ligand in 2 by ethyl groups which enhance
the Lewis basicity of the N-donor sites leading to a stronger N-Li
coordination.
The molecules are discrete, neutral [MLi2BrR2] species in
the solid state (Figure 2). The bond lengths and angles given
(22) Rietveld, M. H. P.; Wehman-Ooyevaar, I. C. M.; Kapteijn, G. M.; Grove,
D. M.; Smeets, W. J. J.; Kooijman, H.; Spek, A. L.; van Koten, G.
Organometallics 1994, 13, 3782.
(23) van Koten, G.; Noltes, J. G. In ComprehensiVe Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford,
1981; Vol. II, Chapter 14, p 709.
(24) Papasergio, R. I.; Raston, C. L.; White, A. H. J. Chem. Soc., Dalton Trans.
(1972-1999) 1987, 3085.
(25) van Koten, G.; James, S. L.; Jastrzebski, J. T. B. H. In ComprehensiVe
Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G.,
Eds.; Pergamon: Oxford, 1995; Vol. III, Chapter 2, p 57.
(26) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
(27) Masciocchi, M.; Moret, M.; Cairati, P.; Sironi, A.; Ardizzoia, G. A.; La
Monica, G. J. Am. Chem. Soc. 1994, 116, 7668.
(28) Engelhardt, L. M.; Pakawatchai, C.; White, A. H.; Healy, P. C. J. Chem.
Soc., Dalton Trans. (1972-1999) 1985, 125.
(29) Meyer, E. M.; Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C.
Organometallics 1989, 8, 1067.
(30) Edwards, D. A.; Harker, R. M.; Mahon, M. F.; Molloy, K. C. J. Chem.
Soc., Dalton Trans. (1972-1999) 1997, 3509.
(31) Chiang, M. Y.; Bohlen, E.; Bau, R. J. Am. Chem. Soc. 1985, 107, 1679.
9
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A R T I C L E S
Kronenburg et al.
Figure 2. Displacement ellipsoid plot (50% probability level) of 7. The position of Li1 is occupied by 91% Li and 9% Cu. The position of Li2 is occupied
by 96% Li and 4% Cu. The crystal structures of the Cu compound 7 and the Ag compound 8 are isostructural. A schematic Newman projection along the
Cu-Br axis is depicted as well. Torsion C1-Cu3-Br-Li2, 155.72(19)°.
Table 1. Selected Bond Distances, Angles, and Torsion Angles
for Li are averaged, including the contribution of Cu and Ag,
respectively. The transition-metal atom is bonded to both anionic
for 7 and 8a
7; M) Cu
8; M) Ag
aryl units and is therefore two-coordinate ( Cipso-M-Cipso
)
C1-M3
1.940(4)
1.942(4)
2.621(3)
2.807(4)
3.6702(7)
2.197(4)
2.193(4)
2.159(5)
2.203(5)
2.408(3)
2.412(4)
2.402(5)
2.361(5)
2.118(4)
2.126(3)
2.789(5)
2.828(5)
3.6632(5)
2.154(6)
2.155(6)
2.220(6)
2.218(5)
2.417(5)
2.395(5)
2.502(6)
2.369(6)
165.13(15)° for 7 and 168.08(14)° for 8). The two-coordinate
bromide anion links the two lithium centers ( Li1-Br-Li2 )
94.53(12)° and 99.97(17)° for 7 and 8, respectively). Additional
chelate bonding of the two amine-nitrogen atoms of the ortho-
diamine substituent and Cipso of the same aryl group completes
the coordination environment of each of the lithium centers,
which is best described as distorted tetrahedral. In particular,
the N-Li-N angles (85.41(16)° and 86.6(2)° for Li1 in 7 and
8, respectively) are significantly distorted by chelate-ring
formation and much smaller than the ideal tetrahedral value.
Table 1 summarizes the geometrical details of the molecular
structures of 7 and 8.
The molecules can be considered to consist of a cationic
[Li-Br-Li]+ fragment and an anionic [Ar-Cu-Ar]- (7) or
[Ar-Ag-Ar]- (8) fragment, which are connected by chelate
N,N′-Li binding to form a neutral molecule with approximate,
noncrystallographic C2 symmetry. Deviations from C2 symmetry
are mainly caused by conformational differences between the
ethyl groups.
Upon coordination of the benzylic NEt atoms to lithium, these
nitrogen groups become stereogenic. The centrosymmetric
structures of both 7 and 8 contain the RNRN/SNSN enantiomeric
pair in the unit cell. The alternative RNSN/SNRN stereoisomers
are not only absent from the solid state but also from solution
as appears from variable-temperature NMR experiments (vide
infra). The bonding of the ipso-carbon atom of the aryl group
to the two metals is highly asymmetric; the bonds to the lithium
atoms are significantly longer (C-Li 2.402(5) and 2.361(5) Å
in 7, C-Li 2.502(6) and 2.396(6) Å in 8) than the bonds to the
group 11 metal (C-Cu 1.940(4) and 1.942(4) in 7, 2.118(4)
and 2.126(3) in 8). The Cipso-Cu and -Ag bonds are in the
expected range for σ Csp2-M bonds.29,30 Monoanionic [Ag3-
Li2Ph6]-31, in which the lithium atoms are only coordinating to
aryl anions, contains significantly shorter C-Li distances
(2.188-2.332 Å). The Cipso-Cu bond distances are comparable
to those found in the neutral homocuprate [Cu2Li2(C6H4CH2-
NMe2-2)4] (1a) (d(mean) ) 1.942 Å)32 and in [CuLi2Br-
C16-M3
Li1b-M3
Li2c-M3
M3-Br
N1-Li1b
N2-Li1b
N3-Li2c
N4-Li2c
Li1b-Br
Li2c-Br
Li1b-C1
Li2c-C16
C1-M3-C16
Li1b-Br-Li2c
Li1b-M3-Li2c
N1-Li1b-N2
N3-Li2c-N4
C2-C1-C6
165.13(15)
94.53(12)
81.35(11)
85.41(16)
85.84(19)
114.7(3)
168.08(14)
99.97(17)
82.02(14)
86.6(2)
84.2(2)
114.8(3)
114.9(3)
C17-C16-C21
115.0(3)
N1-C10-C11-N2
N3-C25-C26-N4
59.3(5)
62.2(4)
53.1(6)
62.2(4)
a The estimated standard deviations are given in parentheses. b 9%
occupation of Cu1 for 7 and 2.9% of Ag1 for 8. c 4% occupation of Cu2
for 7 and 2.3% of Ag2 for 8.
(C6H4{CH2N(Me)CH2CH2NMe2}-2)2] (2a) (d(mean) ) 1.928
Å).7 Also, the trinuclear neutral heteroorganocopper compound
[Cu3Br(C6H4{CH2N(Me)CH2CH2NMe2}-2)2] (4),32 which is
structurally closely related to 7, shows similar Cipso-Cu bond
lengths (d(mean) ) 1.968 Å). These structures, 1a, 2a, 4, and
7, have asymmetric CipsoCuLi bonding in common, which
suggests the presence of 3c-2e bonding or 2c-2e Cipso-Cu
bonding complemented by a polar Cipso-Li interaction. It is
interesting to note that the Cipso-Cu bond distances in the ionic
cyanocuprate [CuLi2(CtN)(C6H4{CH2NMe2}-2)2(THF)4] (3),
which only contains 2c-2e C-Cu bonds, are slightly shorter
(d(mean) ) 1.917 Å).3 Finally, the Ag-Cipso and Ag-Li
distances in 8 are about 0.1 Å longer than the corresponding
Cu-Cipso and Cu-Li distances in 7, which is in agreement with
the smaller ionic radius of CuI (0.60 Å) versus AgI (0.81 Å).
Structure of the Aryl Bromoate Complexes 7, 8, and 9 in
Solution. Molecular weight determinations by cryoscopy in
(32) Janssen, M. D.; Corsten, M. A.; Spek, A. L.; Grove, D. M.; van Koten, G.
Organometallics 1996, 15, 2810.
9
11678 J. AM. CHEM. SOC. VOL. 124, NO. 39, 2002

Self-Assembled Aryl Bromo- and Aryl Cyanocuprates
A R T I C L E S
benzene showed that all three complexes exist in solution as
distinct neutral species with stoichiometry MLi2BrAr2. This
indicates that the MLi2BrAr2 stoichiometry found in the solid
state has been retained in benzene solution.
coupling observed for the aryl bromocuprate 7. However, the
line width of each of the two signals (31 Hz) is in agreement
with a J(13C-7Li) coupling of about 7.8 Hz (vide supra).
Unambiguous proof for the bridging of the aryl group via the
The 1H NMR spectra of these -ate complexes are more
complex than those reported earlier for the corresponding
complex 2,7 which contains the [C6H4{CH2N(Me)CH2CH2-
NMe2}-2]- ligand. This is due to the presence of N-bound Et
Cipso atom between one Ag and one Li nucleus in 8 is obtained
from the Li NMR spectrum (benzene-d6, 298 K). A single
6
broadened doublet resonance is observed. This multiplicity is
2
characteristic for a silver-lithium coupling J(6Li-107,109Ag)
groups. H, 13C, and Li NMR spectra in toluene-d8 in the
temperature range from 193 to 378 K provided unambiguous
evidence that these MLi2BrAr2 compounds have identical
connectivity patterns between M (Cu, Ag, or Au), Li, and Cipso
of 1.3 Hz (average). Further evidence for connectivities in the
1
6
1
1
AgLi2Br core is provided by H NMR experiments. In the H
NMR spectrum, at 298 K a triplet of doublets is observed for
the ortho-H (i.e., H(6)) of the aryl ring. The triplet splitting
(6.6 Hz) arises from the coupling of H(6) with both H(5) and
107,109Ag. Evidence for the silver-proton coupling is provided
by proton spin-decoupling. Irradiation at H(5) results in collapse
of the H(6) pattern to a doublet resulting from the proton-silver
1
of the Ar ligand. The H and 13C NMR spectra of solutions of
7, 8, and 9 in the temperature range from 233 to 378K showed
for all compounds only one single resonance pattern for the
two [C6H4CH2N(Et)CH2CH2NEt2]- ligands. The 1H NMR
spectra below 233 K show a rigid coordination of the Li-NEt2
units on the NMR time scale, as two distinct resonances are
observed for the CH3 groups of the NEt2 units, and also at this
temperature an AB pattern is observed for the benzylic CH2
groups in both 7 and 9. Unfortunately, the solubility of aryl
bromoargentate 8 in toluene-d8 was too low to record 1H NMR
spectra below 253 K. At this temperature, the CH3 groups of
the NEt2 units are still observed as two very broad resonances.
3
coupling J(1H - 107,109Ag) of 6.6 Hz (average).10,33-35
The 13C NMR spectrum (benzene-d6, 283 K) of the aryl
bromoaurate 9 shows a relatively sharp Cipso resonance at 176.0
1
ppm with a line width of 16 Hz. This indicates a J(13C-7Li)
coupling constant of ∼5 Hz, which is considerably smaller that
those in 7 and 8. The chemical shifts of the Cipso resonances of
7, 8, and 9 closely match those of the previously reported -ate
compounds of type [M2Li2(C6H4{CH2NMe2}-2)4] (M ) Cu
(168.1 ppm); Ag (ca. 170 ppm); and Au (174.4 ppm)).9-11
These NMR experiments show that all three MLi2BrAr2
compounds, 7, 8, and 9, have a MLi2Br core which is rigid on
the NMR time scale as intermolecular exchanges between
similar cores or aggregates with different compositions would
remove the coupling information. In particular, the 13C-
107,109Ag coupling is extremely sensitive to that.34
Structural Aspects of the ortho-Diamine Chelated Aryl
Cyanoate Complexes 10 and 11 in Solution. Solid 12 obtained
from the synthesis of the cuprate redissolves only partly in
solvents such as diethyl ether, benzene, or toluene. This
hampered meaningful NMR analysis and cryoscopic molecular
weight determinations. Unfortunately, so far, also attempts to
obtain suitable single crystals for the X-ray determination of
cyanocuprate 12, cyanoargentate 10, and cyanoaurate 11 failed.
However, the molecular weight determination of cyanoargentate
10 by cryoscopy in benzene was successful and indicated that
this compound exists in solution as a species with R2MLi2-
(CtN) stoichiometry.
1H and 13C NMR studies (toluene-d8, 213-373 K) of the
cyanoargentate 10 and the cyanoaurate 11 revealed that these
compounds have structural features in common with bromo-
argentate 8 and bromoaurate 9. The 13C NMR spectra of 10
and 11 both contain a resonance at 168 ppm, which indicates
the presence of a CN group in the structure. The same shift
value of a CtN group has been found earlier in cyanocuprate
3,3 in which the cyanide anion bridges exclusively between two
Li centers and has no further contact with Cu-sites. The coupling
patterns of the Cipso atoms in both 10 and 11 are equal to those
found for the bromo analogues 8 and 9, vide supra. For example,
the line width of the 13Cipso resonance (ca. 13 Hz) of cyanoaurate
11 closely resembles that found for the bromoaurate 9 (16 Hz).
1
The H NMR spectra in benzene-d6 at 298 K of 7, 8, and 9
show one broad signal for the CH3 groups of the NEt2 groupings,
indicating a Li-N bond dissociation/association process which
is in the intermediate exchange limit. Above 333 K, this process
becomes faster as indicated by sharpening of the (triplet)
resonance of the CH3 moieties of these NEt2 units. At room
temperature, the ArCH2N methylene hydrogen atoms are
diastereotopic and still appear as an AB pattern which unam-
biguously proves that NEt-Li coordination is present and renders
the NEt center stereogenic. At 373 K, the coordination of the
NEt group is still rigid (and inert) on the NMR time scale,
although the AB pattern has broadened slightly. These observa-
tions show that the MLi2Br core has C2 symmetry along the
axis through Br and Cu atoms (see Newman projection in Figure
2) and only one of the possible stereoisomeric pairs, that is,
RNRN/SNSN, is present in solution.7
The 13C NMR spectra of 7 in benzene-d6 at room temperature
showed the expected quartet multiplicity (equal intensity) for
the Cipso carbon resonance as a result of the 13C-7Li coupling
1
(1J(13C-7Li) ) 6.9 Hz) (cf., J(13C-7Li) ) 7.0 Hz for [Cu2-
Li2(C6H4{CH2NMe2}-2)4]).9 The 6Li NMR spectrum shows one
singlet resonance at -1.08 ppm, which is in agreement with
the presence of two structurally equivalent Li nuclei in the
molecule.
Because of the low solubility of 8 in toluene, spectra with
only partly resolved fine structures were obtained. However,
the 13C NMR spectrum of 8 in toluene-d8 at 253 K shows clearly
two (broad) Cipso resonances at 168.7 and 170.5 ppm. This can
13
be explained by coupling of
C
with both isotopes 107Ag
ipso
and 109Ag (J(13C-107,109Ag)), resulting in an average value of
135 Hz (gyromagnetic ratio: 107Ag/109Ag ) 1.14). The 107Ag
and 109Ag couplings are not resolved (natural abundances:
107Ag ) 51.8%; 109Ag ) 48.2%).33 Likewise, the quartet
multiplicity resulting from the corresponding J(13C-7Li) cou-
pling in 8 is not resolved, cf., the well-resolved 13C-7Li
(34) Brevard, C.; van Stein, G. C.; van Koten, G. J. Am. Chem. Soc. 1981, 103,
6746.
(35) van Koten, G.; Jastrzebski, J. T. B. H.; Stam, C. H.; Brevard, C. In Copper
Coordination Chemistry; Biochemical and Inorganic PerspectiVes; Karlin,
K. D., Zubieta, J., Eds.; Adenine Press: Guilderland, New York, 1985; p
267.
(33) Mason, J., Ed. Multinuclear NMR; Plenum Press: New York, 1987.
9
J. AM. CHEM. SOC. VOL. 124, NO. 39, 2002 11679

A R T I C L E S
Kronenburg et al.
IR spectra of 10 in the solid state (recorded in Nujol) showed
a weak νCN at 2149 cm-1 which is similar to that found for 10
in benzene solution (2150 cm-1). In contrast, when 10 is
dissolved in a polar solvent like THF, the νCN shifts consider-
ately to lower frequencies (2114 cm-1, sh 2146 cm-1). The latter
value is the same as that found for a THF solution of
cyanocuprate 3 (νCN ) 2114 cm-1), which in THF is a solvent-
separated ion pair (SSIP) comprising [Li-CtN-Li]+ cations.3
A possible reason for a structural difference between the
cyanoargentate, -aurate, and -cuprate and therefore for the low
stability of 3 may be the larger ionic radii of AgI and AuI as
compared with that of CuI.37 As a consequence of this, the
distance between the N,N′-chelating donor atoms in the ArMAr
anion which coordinate the [Li(X)Li]+ cationionic unit will vary
and, in the case of the cyanocuprate, is too small to accom-
modate the [Li(X)Li] cation for X ) CN, whereas for X ) Br
this cation fits well (cf., 8).
Discussion
The bonding mode of the cyanide anion can be either end-
on (via N or C) or side-on (linearly, N,C-bridged). The latter
CtN bonding mode is present in the solid-state structure of
the related ionic 2:1 cyanocuprates 33 and [(t-Bu)2Cu]- [Li2-
(CtN)pmdeta2(THF)2]+.4 Because no distinct difference is
found between the cyanide 13C NMR resonances in 10 and 11,
we believe that the cyanide is side-on bonded between the two
lithium atoms. This idea is corroborated by our IR results.
Previous IR studies of cyanocuprates reported that there is a
significant difference between νCN of an end-on coordinated
CtN group (2034 cm-1) and a side-on bonded CtN group
(2163 cm-1).39 The differences observed in our data (in benzene
versus in THF) may result from the fact that in THF, solvated
[(THF)nLi-CtN-Li(THF)n]+ ions are present with five-
coordinated Li atoms (n ) 4). This high coordination number
may lower the νCN by 20-40 cm-1 for each added ligand to
the metal.39 It has to be noted that in benzene the Li atoms of
10 (νCN 2149 cm-1 in Nujol and benzene) are four coordinated
(cf., the structure of 7).
The bonding types found in bromoaurate 9 and cyanoaurate
11 can be best described as contact ion pair (CIP) for 9 and
solvent-separated ion pair (SSIP) for 11 (Figure 3). In 11, the
nitrogen atoms can be seen as the solvent molecules, and the
[Li-(CtN)-Li]+ is captured in the cavity formed by these four
nitrogen atoms. Earlier results by Boche et al. demonstrated
that in polar (i.e., well-solvating) solvents, lithium cuprates are
present as solvent-separated ion pairs, whereas in poorly
solvating solvents such as diethyl ether and benzene they are
present as contact ion pairs.5e,40 The NMR results presented in
this paper and those reported earlier by Van Koten et al.9-11
provide evidence that in less polar solvents such as diethyl ether
and benzene, the ionic units as identified in neutral ortho-amine
chelated aryllithium cuprates and argentates are not separated
from each other. The strongest evidence is provided by the
observation of both the Li-C and the Li-Ag couplings in the
corresponding argentates.
The formation of a homologous series of aryl bromoate
complexes 7, 8, and 9 and their silver and gold cyano analogues
10 and 11, by reacting 2 equiv of aryllithium compound 6 with
1 equiv of the appropriate metal salt, shows that in solution
stable and unique aggregates are formed. This can be seen as
an example of ligand-directed self-assembling because only one
type of thermodynamically stable aggregate is formed indepen-
dent of the nature of metal (Cu, Ag, or Au) in the precursor
salt. The 13C NMR spectra of the bromoate complexes illustrate
changes in the nature of the metal-Cipso bond within a series.
The Cipso atoms of bromocuprate 7 and bromoargentate 8 both
show an upfield shift (7, 167.1 ppm; 8, 169.5 ppm) as compared
to that of Cipso in the bromoaurate 9 (176 ppm). This suggests
a more covalent bonding of Au with Cipso
.
Similar effects are found in the solid-state structure of the
known aurate [Au2Li2(C6H4CH2NMe2-2)4], where the lithium
and gold atoms are bridged by the Cipso carbon.11 The bridge
bond in this aurate is more asymmetric (d(Au-Cipso) ) 2.06
Å; d(Li-Cipso) ) 2.58 Å) than that in the analogous cuprate 1
6
(vide supra). Furthermore, the Li NMR spectrum of aurate 9
shows a larger upfield shift (-1.67 ppm) than that found for
cuprate 7 and argentate 8 (-1.08 and -1.17 ppm, respectively),
1
while the J(13C-7Li) for 9 is smaller (4 Hz) than that for 7
and 8 (7.0 and 7.8 Hz, respectively). A similar trend has been
reported by Van Koten et al. for homoate compounds of type
[M2Li2(C6H4{CH2NMe2}-2)4] (M ) Cu, Ag, Au).35 It is
suggested that these differences largely originate from the
differences of the M-Cipso (M ) Cu, Ag, Au) bond character;
that is, the Cu-Cipso and Ag-Cipso bonds are more ionic than
the Au-Cipso bond.36
The 1H, 13C, and 6Li NMR spectra of cyanoargentate 10 show
related coupling patterns indicating an electron-deficient type
of bonding mode of the Li-Cipso-Ag unit as is found for 8.
The coupling constants between 13C and 7Li (7.3 Hz) still imply
a bonding with considerable s character between Cipso with
6
lithium. This is also supported by the Li-107,109Ag coupling
Experimental Section
observed in the Li spectrum of 10. For cyanoaurate 11, an even
7
smaller line width (ca. 13 Hz) for the Li-13C coupling has
General Data. All experiments were carried out under a strictly
dry, oxygen-free nitrogen atmosphere, using standard Schlenk tech-
niques. Solvents were dried and distilled prior to use. All standard
been found, suggesting a further distortion of the unsymmetrical
electron-deficient bonding mode in the direction of a more
covalent bonding between Cipso and Au. This observation
suggests that the extent of charge separation between the
[ArAuAr] and [Li(X)Li] (X ) Br, 9; CN, 11) increases going
from 9 to 11.
A further interesting aspect of the ethyl-substituted C∧N∧N
ligand is that it allows the formation of distinct cyanoate
complexes 10 and 11. So far, no clear indication has been
obtained about the nature of the cyanocopper species formed.
(37) Recently, it was found that the ionic radius of gold(I) is ca. 7% smaller
than that of silver.38 Therefore, one would assume less interaction between
Li and Ag/Cipso as compared with Li and Au/Cipso in the bromo- and
cyanoate compounds 10 and 11. The results presented in this paper are not
consistent with this earlier finding.38 However, they are in close agreement
with the findings presented by our group in 1985.35
(38) Zank, J.; Schier, A.; Schmidbauer, H. J. Chem. Soc., Dalton Trans. (1972-
1999) 1999, 415.
(39) Huang, H.; Alvarez, K.; Lui, Q.; Barnhart, T. M.; Snyder, J. P.; Penner-
Hahn, J. E. J. Am. Chem. Soc. 1996, 118, 8808.
(40) (a) John, M.; Auel, C.; Behrens, C.; Marsch, M.; Harms, K.; Bosold, F.;
Gschwind, R. M.; Rajamohanan, P. R.; Boche, G. Chem.-Eur. J. 2000, 6,
3060. (b) Gschwind, R. M.; Rajamohanan, P. R.; John, M.; Boche, G.
Organometallics 2000, 19, 2868.
(36) One of the reviewers is thanked for his work which has been based on the
results of a series of calculated structures.6g
9
11680 J. AM. CHEM. SOC. VOL. 124, NO. 39, 2002

Self-Assembled Aryl Bromo- and Aryl Cyanocuprates
A R T I C L E S
Figure 3. Schematic representation of the structures of 7, 8, 9, 10, and 11. For compound 11, both the intramolecular [Li-(CN)-Li]+ moiety located within
the cavity of the aryldiamine framework and the [Ar2Au]- fragment are framed.
chemicals were purchased from ACROS and Aldrich Chemical Co.
and used as received. The starting materials [AuCl(PPh3)]41 and water-
free CuIBr42 were prepared according to literature procedures, and CuI-
Br was stored in a nitrogen atmosphere. 1H, 13C, and 6Li NMR spectra
were recorded at 300 MHz at ambient temperature unless otherwise
stated, and a full description of the NMR data can be found in the
Supporting Information. Chemical shifts (δ) for 1H and 13C spectra are
given in ppm relative to the internal standard SiMe4. Coupling constants
(m, 3H, ArH(3,4,5)), 8.32 (bs, 1H, ArH(6)). 13C NMR (C6D6, 75.469
MHz, 298 K): δ (in ppm) 8.12 (CH2N(CH2CH3)), 10.1 (b, 2 ×
N(CH2CH3)2), 45.3 (b, 2 × N(CH2CH3)2), 45.6, 46.0 (2 × NCH2CH2N),
51.7 (CH2N(CH2CH3)), 68.8 (ArCH2N), 124.0 (2×), 125.8, 142.9, 150.9
(Ar(2,3,4,5)), (ArCipso not observed, probably too broad). Anal. Calcd
for C15H25N2Li: C, 74.97; H, 10.49; N, 11.66. Found: C, 77.06; H,
10.72; N, 11.88.
[CuLi2Br(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (7). To a stirred
solution of 6 (2.00 g, 8.32 mmol of monomer) in Et2O (80 mL) at
-78 °C was added CuBr (0.60 g, 4.16 mmol) as a solid. After the
reaction mixture had been stirred between -40 and -30 °C for 1.5 h,
the suspension was allowed to warm slowly to room temperature. After
the suspension had been stirred for 1.5 h at ambient temperature, all
volatiles were removed in vacuo. The remaining slightly white/brownish
solid was dissolved in toluene (40 mL) and filtered over a glass filter
covered with dry Celite (to remove Cu0), leaving an almost colorless
solution. Warning: The Celite has to be thoroughly dried. Evaporation
of the solvent in vacuo and subsequently washing with pentane (2 ×
15 mL) yielded 1.60 g of 7 as a cream-colored powder (2.56 mmol,
62%). Suitable crystals for X-ray diffraction were obtained by crystal-
6
are given in Hz. Chemical shifts (δ) for Li spectra are given in ppm
relative to LiCl (1.0 M in D2O) as an external standard. Melting points
are uncorrected. Elemental analyses were obtained from Dornis und
Kolbe Mikroanalytisches Laboratorium, Mu¨lheim a.d. Ruhr, Germany.
Cryoscopic measurements were carried out using a S2541 thermolyzer
and a metal-mantled Pt-100 sensor. For calibration purposes, naphtha-
lene was used to calculate the cryoscopic constant Kf (5.54 K Kg mol-1).
IR measurements were recorded on a Mattson Galaxy FTIR 5000
spectrometer and on a Mettler Toledo ReactIR 1000 FTIR spectrometer
with a K6 conduit, 6 bounce SiComp probe, Nickelson Interferometer
and MCT Midband detector. All reactions involving silver(I) and gold-
(I) chemistry were carried out under exclusion of light by wrapping
the Schlenk flasks in aluminum foil.
1
lization from benzene/pentane at room temperature. H NMR (C6D6,
[C6H4BrCH2N(Et)CH2CH2NEt2-2] (5). To a solution of N,N,N′-
triethylethanediamine (10.0 mL, 55.73 mmol) and triethylamine (25
mL) in C6H6 (80 mL) was added a solution of 2-bromobenzyl bromide
(13.73 g, 54.94 mmol) in C6H6 (60 mL) dropwise. After 5 h, the
resulting white suspension (indicating the formation of HNEt3Br) was
filtered off and extracted with C6H6 (25 mL). The filtrate was
concentrated by removal of the solvent in vacuo. The crude product
was obtained as a yellow oil, which was purified by a short-path
distillation at reduced pressure to yield 1 as a colorless oil, yield 12.94
g (75%). 1H NMR (C6D6, 300.105 MHz, 298 K): δ (in ppm) 0.86 (dt,
9H, N(CH2CH3)2 and CH2N(CH2CH3)), 2.32 (q, 4H, N(CH2CH3)2), 2.50
(m, 6H, CH2N(CH2CH3)CH2CH2N(Et2)), 3.65 (s, 2H, ArCH2N(Et)),
6.73 (t, 1H, 2J ) 7.80 Hz, ArH(4)), 7.02 (t, 1H, 2J ) 7.80 Hz, ArH(5)),
7.35 (d, 1H, 2J ) 7.80 Hz, ArH(3)), 7.60 (d, 1H, 2J ) 7.80 Hz, ArH(6)).
13C NMR (C6D6, 75.469 Hz, 298 K): δ (in ppm) 12.4 (CH2N-
(CH2CH3)), 12.5 (N(CH2CH3)2), 47.8 (N(CH2CH3)2), 48.6 (CH2N(CH2-
CH3)), 52.0, 52.6 (NCH2CH2N(Et2)), 58.6 (ArCH2), 124.2, 128.1, 128.2,
130.7, 132.6 (Ar(2-6)), 140.3 (Ar(1)). Anal. Calcd for C15H25BrN2:
C, 57.50; H, 8.04; N, 8.94. Found: C, 57.63; H, 8.11; N, 9.04.
[Li(C6H4{CH2N(Et)CH2CH2NEt2}-2)]2 (6). This was prepared
according to a published procedure for the synthesis of [Li-
(C6H4{CH2N(Me)CH2CH2NMe2}-2)]2,22 starting from 5 (6.71 g; 21.44
mmol) in pentane and n-BuLi (13.6 mL of a 1.6 M solution in hexane;
21.8 mmol), yield 85% (4.38 g; 18.22 mmol). 1H NMR (C6D6, 300.105
MHz, 298 K): δ (in ppm) 0.59-1.20 (bm, 9H, CH2N(CH2CH3) and
N(CH2CH3)2), 1.54-3.00 (bm, 8H, N(CH2CH3)2 and CH2N(Et)-
CH2CH2N(Et)2), 3.00-3.15 (bm, 2H, CH2N(CH2CH3)), 3.48 (d, 1H,
2J ) 11.4 Hz, ArCH2), 4.22 (d, 1H, 2J ) 11.4 Hz, ArCH2), 7.13-7.30
300.105 MHz, 298 K): δ (in ppm) 0.68 (bs, 12H, N(CH2CH3)2), 1.20-
1.40 (bm, 4H, N(CH2CH3)2), 1.51 (t, 6H, CH2N(CH2CH3)), 1.86 (m,
2H, NCH2CH2N(Et2)), 2.10 (dm, 4H, NCH2CH2N(Et2)), 2.49 (m, 2H,
NCH2CH2N(Et2)), 2.73 (m, 4H, CH2N(CH2CH3) and N(CH2CH3)2), 2.87
(m, 2H, N(CH2CH3)2), 2.91 (d, 2H, 2J ) 11.4 Hz, ArCH2N), 3.06 (m,
2
2H, CH2N(CH2CH3)), 4.47 (d, 2H, J ) 11.4 Hz, ArCH2N), 7.00 (d,
3
3
2H, J ) 7.50 Hz, ArH(3)), 7.14 (t, 2H, J ) 7.50 Hz, ArH(4)), 7.22
(t, 2H, 3J ) 7.2 Hz, ArH(5)), 8.30 (d, 2H, 3J ) 6.90 Hz, ArH(6)). 13
C
NMR (C6D6, 75.469 MHz, 298 K): δ (in ppm) 6.77, 8.85 (2 × b,
N(CH2CH3)2), 11.9 (CH2N(CH2CH3)), 42.4, 45.2 (2 × b, N(CH2CH3)2),
47.6, 48.2 (2 × NCH2CH2N), 52.2 (CH2N(CH2CH3)), 67.4 (ArCH2N),
125.4, 128.0, 143.7, 149.9 (Ar(2,3,4,5)), 167.2 (ArCipso). 6Li NMR
(C6D6, 44.165 MHz, 298 K): δ (in ppm) -1.08 (s, 2Li). Mp. (dec)
150-155 °C. Anal. Calcd for C30H50BrCuLi2N4: C, 57.74; H, 8.08;
N, 8.98. Found: C, 57.59; H, 7.96; N, 8.88. Molecular weight
determination by cryoscopy (0.40 g (0.64 mmol) in 12.98 g of C6H6).
Calcd for C30H50BrCuLi2N4 (7): 624.09. Found: 699.70.
[AgLi2Br(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (8). To a stirred
solution of 6 (1.70 g, 7.07 mmol of monomer) in Et2O (80 mL) at
-78 °C was added solid AgBr (0.66 g, 3.54 mmol). After the reaction
mixture had been stirred at -78 °C for 45 min, the suspension was
allowed to warm slowly to room temperature and was subsequently
stirred for 1.5 h at ambient temperature, after which all volatiles were
removed in vacuo. The slightly gray solid obtained was dissolved in
toluene (40 mL) and filtered over a glass filter filled with dry Celite
(to remove Ag0), leaving a light brown solution. Evaporation of the
solvent in vacuo and subsequent washing with pentane (2 × 15 mL)
gave 1.58 g of 8 as a light brown powder (2.36 mmol, 67%). Suitable
crystals for X-ray diffraction were obtained by a slow diffusion of
pentane into a solution of 8 in benzene at 0 °C. 1H NMR (C6D6, 300.105
MHz, 298 K): δ (in ppm) 0.62 (bs, 12H, N(CH2CH3)2), 1.10-1.43
(41) Kaesz, H. D., Ed. Inorganic Syntheses; John Wiley & Sons: New York,
1989; Vol. 26, p 325.
(42) Fernelius, W. C., Ed. Inorganic Syntheses; McGraw-Hill: New York, 1946;
Vol. 2, p 3.
9
J. AM. CHEM. SOC. VOL. 124, NO. 39, 2002 11681

A R T I C L E S
Kronenburg et al.
3
Table 2. Experimental Data for the X-ray Diffraction Studies of 7
and 8
(bm, 4H, N(CH2CH3)2), 1.50 (t, 6H, J ) 6.90 Hz, CH2N(CH2CH3)),
1.79 (m, 2H, NCH2CH2N(Et2)), 1.94 (m, 2H, NCH2CH2N(Et2)), 2.06
(m, 2H, NCH2CH2N(Et2)), 2.37 (m, 2H, NCH2CH2N(Et2)), 2.45 (m,
4H, CH2N(CH2CH3) and N(CH2CH3)2), 2.61 (m, 2H, N(CH2CH3)2),
7
8
formula
formula weight
crystal system
space group
crystal size
[mm3]
C30H50BrCu1.13Li1.87N4
631.29
monoclinic
P21/c (No. 14)
0.32 × 0.28 × 0.03
C30H50Ag1.05BrLi1.95N4
673.70
monoclinic
P21/c (No. 14)
0.51 × 0.12 × 0.06
2
2.81 (d, 2H, J ) 11.4 Hz, ArCH2N), 2.93 (m, 2H, CH2N(CH2CH3)),
4.30 (d, 2H, 2J ) 11.4 Hz, ArCH2N), 7.03 (d, 2H, 3J ) 7.80 Hz, ArH-
3
3
(3)), 7.12 (t, 2H, J ) 7.50 Hz, ArH(4)), 7.24 (t, 2H, J ) 6.90 Hz,
3
3
ArH(5)), 8.26 (t, 2H, J
) 6.60 Hz, JHAg ) 7.3 Hz, ArH(6)). 13C
HH
NMR (C6D6, 75.469 MHz, 298 K): δ (in ppm) 6.80, 10.7 (2 × b,
crystal color
temp [K]
λ [Å]
colorless
150
0.71073
12.6266(5)
31.1512(11)
8.6751(4)
109.3060(7)
3220.3(2)
4
colorless
125
0.71073
12.6609(3)
31.2622(8)
8.5488(2)
107.7146(10)
3223.24(14)
4
N(CH2CH3)2), 12.4 (CH2N(CH2CH3)), 42.3, 45.3 (2 × b, N(CH2CH3)2),
50.8, 50.9 (2 × NCH2CH2N), 52.3 (CH2N(CH2CH3)), 67.7 (d, 3JCAg
)
2
ca. 4 Hz, ArCH2N), 125.1 (d, JCAg ) 6.7 Hz, Ar(6)), 125.6, 127.1,
145.1 (Ar(3,4,5)), 150.1 (d, 2JCAg ) 4.2 Hz, Ar(2)), 168.7, 170.5 (2 ×
b, 1JCAg ) 135 Hz, ArCipso). 6Li NMR (C6D6, 44.165 MHz, 298 K): δ
a [Å]
b [Å]
c [Å]
â [°]
2
(in ppm) -1.17. (d, 2Li, JLiAg ) 1.30 Hz). mp. (dec) 165-170 °C.
V [Å3]
Anal. Calcd for C30H50BrAgLi2N4: C, 53.91; H, 7.54; N, 8.38. Found:
C, 54.06; H, 7.63; N, 8.31. Molecular weight determination by
cryoscopy (0.51 g (0.76 mmol) in 17.00 g of C6H6). Calcd for C30H50-
BrAgLi2N4 (8): 668.41. Found: 608.80.
Z
D
calc [g/cm3]
1.302
2.03
1.388
1.92
µ [mm-1
]
abs. correction
transmission
range
PLATON (MULABS)
0.66-0.94
PLATON (MULABS)
0.82-0.91
[AuBr(PPh3)]. To a stirred solution of [AuCl(PPh3)] (0.36 g, 0.78
mmol) in 10 mL of CH3Cl was added 22 mL of a saturated solution of
NaBr in a mixture of EtOH/H2O (1:1 v/v). The solution was stirred for
2 h at ambient temperature, after which all solvents were removed by
rotary evaporation at 50 °C. The remaining solid was extracted with
CH2Cl2 (6 × 25 mL). The CH2Cl2 fractions were collected, dried over
Na2CO3, and concentrated to ca. 10 mL. Next, an equal amount of
hexane was added. Crystallization from this solvent mixture at -30
°C afforded 0.25 g (0.46 mmol, 59% (first batch of crystals)) of [AuBr-
(PPh3)] as colorless crystals. 31P NMR (C6D6/CDCl3 (1:1 v/v), 88.016
MHz, 298 K): δ (in ppm) 35.76.43,44
[AuLi2Br(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (9). The synthetic
procedure is identical to that described for the argentate 8, starting from
6 (0.23 g, 0.95 mmol of monomer) in Et2O (30 mL) and [AuBr(PPh3)]
(0.24 g, 0.47 mmol). Yield 0.28 g of 9 as slightly pink powder (0.38
mmol, 80%). 1H NMR (C6D6, 300.105 MHz, 298 K): δ (in ppm) 0.62
(t, 3J ) 6.90 Hz, 12H, N(CH2CH3)2), 1.44 (bm, 2H, N(CH2CH3)2), 1.47
(t, 6H, 3J ) 6.90 Hz, CH2N(CH2CH3)), 1.84 (m, 4H, NCH2CH2N-
(Et2)), 2.02 (dm, 6H, NCH2CH2N(Et2) and N(CH2CH3)2), 2.38 (m, 4H,
NCH2CH2N(Et2) and CH2N(CH2CH3)), 2.67 (m, 4H, N(CH2CH3)2), 2.75
sin(θ/λ)max
0.57
0.65
[Å-1
]
refl. meas./
20 853/5044
24 973/7340
unique
Rint
0.078
343/0
0.056
351/0
param./
restraints
R1 (obs./
all refl.)
wR2 (obs./
all refl.)
GOF
0.0445/0.0594
0.1127/0.1305
0.0448/0.0734
0.0938/0.1056
1.085
1.045
F (min/max)
-1.25/0.82
-0.77/1.20
[e/Å3]
2
3
CH3)2), 4.33 (d, 2H, J ) 11.7 Hz, ArCH2N), 7.03 (d, 2H, J ) 7.50
3
3
Hz, ArH(3)), 7.13 (t, 2H, J ) 7.20 Hz, ArH(4)), 7.27 (t, 2H, J )
6.90 Hz, ArH(5)), 8.33 (t, 2H, 3J HH ) 6.9 Hz, 2JHAg ) 7.6 Hz, ArH(6)).
13C NMR (C6D6, 75.469 MHz, 298 K): δ (in ppm) 7.49, 10.1 (2 × b,
N(CH2CH3)2), 12.4 (CH2N(CH2CH3)), 42.4, 45.3 (2 × b, N(CH2CH3)2),
50.4, 50.8 (2 × NCH2CH2N), 51.8 (CH2N(CH2CH3)), 67.1 (ArCH2N),
125.12 (d, 2JCAg ) 7.3 Hz, Ar(6)), 125.5, 128.9, 145.2 (Ar(3,4,5)), 149.8
2
(d, 2H, J ) 11.4 Hz, ArCH2N), 3.02 (m, 2H, CH2N(CH2CH3)), 4.61
(d, 2H, 2J ) 11.4 Hz, ArCH2N), 7.01 (d, 2H, ArH(3)), 7.31 (m, ArH-
(4,5)), 8.14 (d, 2H, J ) 6.90 Hz, ArH(6)). 13C NMR (C6D6, 75.469
3
(d, 2JCAg ) 4.2 Hz, Ar(2)), 168.5 (CtN), 169.9, 171.7 (2 × b, 1JCLi
)
MHz, 283 K): δ (in ppm) 6.70, 10.7 (2 × b, N(CH2CH3)2), 12.2 (CH2N-
(CH2CH3)), 43.0, 47.8 (2 × b, N(CH2CH3)2), 50.5, 50.8 (2× NCH2CH2N),
52.6 (CH2N(CH2CH3)), 66.1 (ArCH2N), 125.2, 126.1, 129.4, 143.9,
149.0 (Ar(2,3,4,5)), 176.0 (ArCipso). 6Li NMR (C6D6, 44.165 MHz, 298
K): δ (in ppm) -1.67 (s, 2Li). mp. 188-190 °C. Anal. Calcd for
C30H50BrAuLi2N4: C, 47.57; H, 6.65; N, 7.40. Found: C, 47.63; H,
6.64; N, 7.28. Molecular weight determination by cryoscopy (0.20 g
(0.26 mmol) in 11.20 g of C6H6). Calcd for C30H50BrAuLi2N4 (9):
757.55. Found: 638.20.
1
6
7.3 Hz, JCAg ) 134 Hz, ArCipso). Li NMR (C6D6, 44.165 MHz, 298
2
K): δ (in ppm) -1.85 (d, 2Li, JLiAg ) 1.30 Hz). IR (solid): CtN
2149 cm-1; (C6H6): CtN 2150 cm-1; (THF): CtN 2114 cm-1. Anal.
Calcd for C31H50AgLi2N5: C, 60.59; H, 8.20; N, 11.40. Found: C,
60.68; H, 8.16; N, 11.40. Molecular weight determination by cryoscopy
(0.43 g (0.70 mmol) in 13.45 g C6H6). Calcd for C31H50AgLi2N5 (10):
614.52. Found: 598.05.
[AuLi2(CtN)(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (11). The syn-
thetic procedure is identical to that described for the argentate 8, starting
from 6 (0.36 g, 1.50 mmol of monomer) in Et2O (30 mL) and AuCN
(167 mg, 0.75 mmol). Yield 0.27 g of 11 as a white powder (0.38
mmol, 51%). 1H NMR (toluene-d8, 300.105 MHz, 298 K): δ (in ppm)
0.59 (bs, 12H, N(CH2CH3)2), 1.43 (t, 6H, 3J ) 6.90 Hz, CH2N-
(CH2CH3)), 1.85 (m, 2H, NCH2CH2N(Et2)), 1.98 (m, 2H, NCH2CH2N-
(Et2)), 2.06 (m, 2H, NCH2CH2N(Et2)), 2.37-2.44 (m, 2H, NCH2CH2N-
(Et2)); 2.55-2.80 (m, 6H, CH2N(CH2CH3) and N(CH2CH3)2), 2.70 (d,
2H, ArCH2N), 2.94 (m, 2H, N(CH2CH3)2), 4.55 (d, 2H, 2J ) 11.4 Hz,
[AgLi2(CtN)(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (10). The syn-
thetic procedure is identical to that described for the argentate 8, starting
from 6 (1.22 g, 5.08 mmol of monomer) in Et2O (30 mL) and AgCN
(340 mg, 2.54 mmol). Yield 1.12 g of 10 as a white powder (1.83
mmol, 72%). 1H NMR (C6D6, 300.105 MHz, 298 K): δ (in ppm) 0.56
(bs, 12H, N(CH2CH3)2), 1.10-1.60 (bm, 4H, N(CH2CH3)2), 1.51 (t,
6H, J ) 6.90 Hz, CH2N(CH2CH3)), 1.73 (m, 2H, NCH2CH2N(Et2)),
1.85 (m, 2H, NCH2CH2N(Et2)), 1.97 (m, 2H, NCH2CH2N(Et2)), 2.20-
2.60 (m, 2H, NCH2CH2N(Et2); m, 6H, CH2N(CH2CH3) and N(CH2-
3
2
ArCH2N), 7.07 (bm, 4H, ArH(3,4)), 7.33 (m, 2H, ArH(5)), 8.03 (d,
CH3)2), 2.79 (d, 2H, J ) 11.7 Hz, ArCH2N), 2.84 (m, 2H, N(CH2-
3
2H, J
) 6.90 Hz, ArH(6)). 13C NMR (toluene-d8, 75.469 MHz,
HH
(43) The 31P NMR spectrum of [AuCl(PPh3)] in CDCl3 showed a singlet at
33.84 ppm, which is in accordance with literature values. A mixture of
248 K): δ (in ppm) 6.71, 10.6 (2 × b, N(CH2CH3)2), 12.5 (CH2N-
(CH2CH3)), 41.5, 45.1 (2 × b, N(CH2CH3)2), 50.3, 50.5 (2 ×
NCH2CH2N), 51.8 (CH2N(CH2CH3)), 65.1 (ArCH2N), 125.7, 129.4,
143.7 (Ar(3,4,5)), 148.6 (Ar(2)), 167.8 (CtN), 175.8 (ArCipso). Anal.
[AuBr(PPh3)] and [AuCl(PPh3)] showed two singlet resonances in the 31
P
NMR spectrum, indicating that the single resonance in 5 can be assigned
to pure [AuBr(PPh3)] and not a mixture of the Cl and Br compounds.
9
11682 J. AM. CHEM. SOC. VOL. 124, NO. 39, 2002

Self-Assembled Aryl Bromo- and Aryl Cyanocuprates
A R T I C L E S
Calcd for C31H50AuLi2N5: C, 52.92; H, 7.16; N, 9.95. Found for (11):
C, 53.06; H, 7.05; N, 9.86.
anisotropic displacement parameters; hydrogen atoms were refined as
rigid groups. The drawings, structure calculations, and checking for
higher symmetry were performed with the program PLATON.47 The
lithium positions in both structures were partially occupied by copper
atoms (compound 7) or silver atoms (compound 8). The lithium atoms
and the heavy atom were constrained to the same coordinates and the
same anisotropic displacement parameters. The corresponding partial
occupancies were then refined with the criterion that the total occupancy
remains 1.0. Further experimental details are given in Table 2.
We have tried to prepare the copper analogue of 10 and 11, [CuLi2-
(CtN)(C6H4{CH2N(Et)CH2CH2NEt2}-2)2] (12), by the same procedure
as has been described for 7, that is, starting from 6 (1.07 g, 4.46 mmol
of monomer) in Et2O and CuCN (199 mg, 2.23 mmol). However, a
suspension was formed, which was not fully soluble in benzene or
toluene. A NMR spectrum of the reaction mixture in benzene-d6 showed
a mixture of at least four complex resonance patterns.
X-ray Crystal Structure Determinations of 7 and 8. Intensities
were measured on a Nonius Kappa CCD diffractometer with rotating
anode (Mo KR). The structures were solved by Patterson methods
(DIRDIF-9745) and refined with the program SHELXL-9746 against F2
of all reflections. Non-hydrogen atoms were refined freely with
Acknowledgment. This work was supported in part (M.L.,
A.L.S.) by the Council for Chemical Sciences of The Nether-
lands Organization for Scientific Research (CW-NWO).
Supporting Information Available: X-ray crystallographic
data 7 and 8 (CIF). This material is available free of charge via
the Internet at http://pubs.acs.org.
(44) Bruce, M. I.; Nicholson, B. K.; Bin Shawkataly, O. Inorg. Synth. 1987,
26, 325.
(45) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; Garcia-
Granada, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The DIRDIF
Program System. Technical report of the Crystallography Laboratory;
University of Nijmegen, The Netherlands, 1997.
JA026945T
(46) Sheldrick, G. M. SHELXL-97, Program for crystal structure refinement;
University of Go¨ttingen, Germany, 1997.
(47) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht
University, The Netherlands, 2000.
9
J. AM. CHEM. SOC. VOL. 124, NO. 39, 2002 11683