Synthesis and structures of group 11 metal triazenide complexes: Ligand supported metallophilic interactions

Article abstract of DOI:10.1021/ic901051f

A homologous and homoleptic series of stable Group 11 metal triazenide complexes with the general formula [M(L′)]_n (M = Cu or Au, n=2; M = Ag, n=3) featuring the bulky triazenide ligand N,N-bis(2,6-di- isopropylphenyl)triazene, L′H, have been p

Full text of DOI:10.1021/ic901051f

Inorg. Chem. 2009, 48, 8613–8622 8613
DOI: 10.1021/ic901051f
Synthesis and Structures of Group 11 Metal Triazenide Complexes: Ligand
Supported Metallophilic Interactions
Andrew L. Johnson,* Alexander M. Willcocks, and Stephen P. Richards
Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K.
Received June 1, 2009
A homologous and homoleptic series of stable Group 11 metal triazenide complexes with the general formula [M(L0)]n
(M = Cu or Au, n = 2; M = Ag, n = 3) featuring the bulky triazenide ligand N,N0-bis(2,6-di-isopropylphenyl)triazene, L0H,
have been prepared by the reaction of Li[L0] with the metal chlorides, CuCl, AgCl, and [(THT)AuCl], respectively, in a
1:1 stoichiometric ratio. The compounds [Cu2(L0)2] and [Au2(L0)2] crystallized as dimers with M M separations of
3 3 3
0
˚
˚
2.4458(4) A and 2.6762(4) A, respectively. In comparison, the reaction of AgCl with Li[L ] results in the formation of
the tri-silver complex [Ag3(L0)3] with Ag Ag separations of 3.01184(17) A, 2.95329(17) A, and 2.92745(16) A.
˚
˚
˚
3 3 3
Attempts to react the parent triazene system L0H with [Cu(Mes)] resulted in the formation of the novel tri-copper
system [Cu3(L0)2(Mes)]. In all cases the molecular structures of the resultant complexes have been unambiguously
determined by single crystal X-ray diffraction experiments.
Introduction
similar interactions have now been observed in other closed
shell metal systems such as Cu(I),14-19Ag(I),11,20-23 Ga(I),24
In(I),6,25 Tl(I),7,25-29 Pd(II),30-33 and Pt(II)33-36 systems,
assuming the name of metallophilic interactions. These
metallophilic interactions arise primarily because of weak
dispersive forces but are considerably enhanced by relativistic
Attractive interactions between formally closed shell metal
centers (s2 or d10) have been the subject of considerable
attention for some time,1-3 specifically with respect to the
ability to control such bonding.4-11 Weak attractive closed
shell interactions were first witnessed by Schmidbaur
in gold(I) complexes exhibiting close Au Au contacts
3 3 3
(2.8-3.5 A).12,13 Although first observed in gold(I) complexes,
˚
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*To whom correspondence should be addressed. E-mail: a.l.johnson@
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r
2009 American Chemical Society
Published on Web 07/28/2009
pubs.acs.org/IC

8614 Inorganic Chemistry, Vol. 48, No. 17, 2009
Johnson et al.
Chart 1. General Formula of the Amidinate, Guanidinate, and Tria-
zenide Anions
Chart 2. Generic Bonding Modes and Typical Structures of Triazenide
Complexes
effects in heavier element systems.3,37 In fact, theoretical
studies have shown that the relative strength of these inter-
actions can increase by ∼50% moving from lighter systems
(Cu) to heavier (Au) because of increased relativistic effects,
and are comparable in energetic terms to hydrogen bonding
interactions.37 While bridging ligands have been used suc-
cessfully to promote short metal-metal contacts and control
metallophilic interactions, the existence of true d10-d10
bonding interactions in systems containing copper or silver
have been both supported38 and refuted39 by theoretical
studies. While it is recognized that ligand architecture can
possibly blur the degree of metallophilic interactions, the
Chart 3. Effect of Sterics on N-Orbital Projection in Amidinate, Gua-
nidinate, and Triazenide Ligands
M
M distances in such complexes are often short enough
3 3 3
to raise the question of whether direct M M bonding
might not exist.
3 3 3
Anionic bridging ligands such as guanidinates, amidinates,
and triazenides (Chart 1) have continued to evolve as
versatile N,N0-donor ligands in coordination chemistry.
The attractiveness of both amidinate and guanidinate ligands
in this role is largely due to the large range of derivatives that
are available through substitution at nitrogen.
Amidinate and guanidinate ligands have been used widely
with Group 11 metals to form a range of dimeric and tetra-
meric complexes,40-45 with varying coordination arrange-
ments, and such systems have recently attracted attention as
potential metal deposition precursors,46-48 and as model
systems for the study of spin delocalization super-exchange
pathways.49 In contrast, triazenide ligands [R0NNNR0]-,
have not received the same degree of attention, despite their
relative ease of preparation.50,51 Structurally characterized
examples of triazenide complexes show coordination modes
typical of related amidinate52 and guanidinate53 systems
(Chart 2), as well as alternative coordination modes including
polyhapto π-aromatic interactions with aryl substituents.54
Chart 2 shows the range of oligomeric coordination com-
plexes that Group 11 triazenide complexes typically fall into.
In comparison to amidinate and guanidinate systems, the
propensity of triazenide ligand systems to engage in bridging
coordination modes55 (Chart 2) is, in-part, attributed to the
near parallel projection of the two N-donor atom orbitals: an
effect that is more prevalent because of the lack of steric
perturbation caused by substituent groups, often encoun-
tered in non-cyclic amidinate and guanidinate systems
(Chart 3).51
While reports on the chemistry of Group 11 complexes
containing amidinate and guanidinate ligands are prevalent,
there is a comparative paucity of reports describing Group 11
triazenide complexes. Here we report the synthesis and
structure of a homologous/homoleptic series of Group 11
metal complexes with the sterically encumbered N,N0-bis(2,6-
di-isopropyl)triazenide ligand and have unambiguously de-
termined the solid state structure of the resultant products,
using single crystal X-ray diffraction experimentation.
::
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The triazene system, N,N0-bis(2,6-di-isopropyl)triazene,
L0H was synthesized in a simple one-pot reaction by the
addition of excess iso-pentyl nitrite to 2,6-di-isopropylaniline
in diethyl ether. Subsequent reaction of lithium N,N0-bis(2,6-
di-isopropyl)triazide56 generated in situ, with the cetal
chlorides CuCl, AgCl, or (THT)AuCl, respectively, in a
1:1 stoichiometric ratio, followed by extraction into toluene
and storage at low temperature resulted in the formation of
(44) Mohamed, A., A.; Abdou, H. E.; Irwin, M. D.; Lopez-de-Luzuriaga,
J. M.; Fackler, J. P. Jr. J. Cluster Sci. 2003, 14, 253–266.
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Article
Inorganic Chemistry, Vol. 48, No. 17, 2009 8615
Scheme 1
air and moisture stable crystals which were isolated and
characterized. The 1H NMR spectroscopic data in d2-methy-
lene dichloride obtained for the resultant products were
consistent with simple symmetrical structures in which the
two 2,6-di-isopropyl groups are magnetically equivalent (for
example, in the case of the copper product a single doublet
resonance at δ =1.20 ppm, a single septet resonance at
δ=3.47 ppm with resonances for the aromatic region
The complex [Cu2(L0)2] crystallizes in the monoclinic
space group C2/c and contains two independent halves of
the di-copper complex in the asymmetric unit cell (ASU).
While one-half-molecule is disordered with respect to the
central core, which shows two orientations of the planar
{Cu2N6} unit rotated by 90ꢀ: the second half-molecule shows
no disorder. The molecular structure of the non-disordered
dimer [Cu2(L0)2] is shown in Figure 1a and is taken as
representative of both half-molecules in the ASU. The silver
and gold complexes [Ag3(L0)3] and [Au2(L0)2] both crystallize
in the monoclinic space group P21/c. In the case of the tri-
silver complex [Ag3(L0)3] one whole molecule resides within
the ASU, along with one molecule of toluene of crystal-
lization (Figure 2). In comparison, the ASU for the gold
complex [Au2(L0)2] (Figure 1b) contains one-half of the di-
gold complex, the second half of which is generated by
symmetry. The ASU also contains one molecule of toluene
of crystallization, such that there are two molecules of
toluene per molecule of complex.
1
(δ =7.08-7.17 ppm) are observed in the H NMR spec-
trum). In the case of both the silver and gold products, NMR
spectroscopy (1H and 13C) reveals a similar series of reso-
nances. However, the methyl region for both complexes
shows the presence of two doublets, consistent with restricted
rotation about the phenyl-CHMe2 bond such that the methyl
groups on either side of the plane of the phenyl ring are in
different magnetic environments.
Single crystal X-ray diffraction analysis of the three com-
plexes reveals the solid state structure of the complexes to be a
di-copper complex [Cu2(L0)2], a tri-silver complex [Ag3(L0)3],
and the di-gold complex [Au2(L0)2], respectively. The molec-
ular structure of the complexes [Cu2(L0)2], [Ag3(L0)3], and
[Au2(L0)2] are depicted in Figures 1 ([Cu2(L0)2] and [Au2-
(L0)2]) and 2 ([Ag3(L0)3]), selected bond lengths and angles are
shown in Table 1 ([Cu2(L0)2] and [Au2(L0)2]) and 2 ([Ag3-
(L0)3]). As alluded to earlier, the structures of Group 11
triazenide complexes, typically fall into three classes: dimeric,
tetrameric, or polymeric systems (Chart 2, Scheme 1), the
formation of which is strongly dependent upon the steric
requirements of the nitrogen substituents.57 While dimeric
structures of copper-triazenide complexes have been reported
previously, the dimeric gold complex [Au2(L0)2] represents a
unique example of a structurally characterized gold-triaze-
nide dimer, the only other example of a gold triazenide system
having a tetrameric structure in the solid state.58 Similarly, the
structural elucidation of the tri-silver triazenide complex,
[Ag3(L0)3], represents a unique addition to the structural
range of Group 11 triazenide systems.
The copper and gold complexes [Cu2(L0)2] and [Au2(L0)2]
shown in Figure 1 are isotypic, and share many of the gross
structural features of previously structurally characterized
Cu(I), Ag(I), and Au(I) di-metallic systems (Tables 4 and 5),
consisting of two metal centers bridged by two triazenide
ligands in an μ,η1,η1-fashion, with approximately linear two-
coordinate geometries [N(1)-Cu(1)-N(3A): 172.63(7)ꢀ and
N(1)-Au(1)-N(3A): 168.0(2)ꢀ respectively], with the devia-
tion caused by the metal atoms moving away from each
other. A consequence of the increased separation between the
Au centers in [Au2(L0)2] is the increased N-N-N angle in the
triazenide ligand [N(1)-N(2)-N(3): 119.5(5)ꢀ] compared to
that observed in [Cu2(L0)2], [N(1)-N(2)-N(3): 115.53(15)ꢀ].
Both complexes have essentially planar bi-cyclic cores,
formed by the two N3-ligands and the {M2} unit (M=Cu
or Au) (largest deviation from the least-squares plane:
˚
˚
{Cu2N6} 0.0051(12) A; {Au2N6} 0.0071(28) A). As with
related sterically demanding triazenide N-substituents, the
2,6-di-isopropyl rings are twisted out of the plane of the
central bi-cyclic {M2N6} cores, with angles between the
M(1)-N(1)-N(2)-N(3)-M(1A) plane and the phenyl rings
C(1)-C(6) and C(13)-C(18) approaching perpendicularity
(57) Jiang, X.; Bollinger, J. C.; Lee, D. J. Am. Chem. Soc. 2005, 127,
15678–15679.
::
(58) Beck, J.; Straehle, J. Angew. Chem., Int. Ed. Engl. 1986, 25, 95–96.

8616 Inorganic Chemistry, Vol. 48, No. 17, 2009
Johnson et al.
Figure 1. Diagram showing the centrosymmetric molecular structures of the complexes [Cu2(L0)2] (A) and [Au2(L0)2] (B): Figure 1a shows the molecular
structure of one molecule of [Cu2(L0)2] (50% probability ellipsoids). Hydrogen atoms have been omitted for clarity. Symmetry transformations used to
generate equivalent atoms: -x + 1/2, -y + 1/2, -z.; Figure 1b shows the molecular structure of [Au2(L0)2] (50% probability ellipsoids) Hydrogen atoms
and solvent of crystallization have been omitted for clarity. Symmetry transformations used to generate equivalent atoms: -x, -y + 1, -z + 1.
Table 1. Selected Geometric Data for [Cu2(L0)2] and [Au2(L0)2]
0
˚
[Cu2(L )2], Bond Lengths (A)
Cu(1)-Cu(1A)
Cu(1)-N(1)
Cu(1)-N(3A)
2.4458(4)
1.8811(15) N(2)-N(3)
1.8824(16)
N(1)-N(2)
1.308(2)
1.298(2)
[Cu2(L0)2], Bond Angles (deg)
N(1)-Cu(1)-N(3A) 172.63(7)
Cu(1)-Cu(1A)-N(3) 86.04(5)
N(1)-N(2)-N(3)
115.53(15) Cu(1A)-Cu(1)-N(1) 86.58(5)
Cu(1)-N(1)-N(2)
N(2)-N(3)-Cu(1A)
125.51(12)
126.32(12)
0
˚
[Au2(L )2], Bond Lengths (A)
Au(1)-Au(1A)
Au(1)-N(1)
Au(1)-N(3A)
2.6762(4)
2.046(5)
2.042(5)
N(1)-N(2)
N(2)-N(3)
1.308(7)
1.297(7)
[Au2(L0)2], Bond Angles (deg)
N(1)-Au(1)-N(3A) 168.0(2)
N(1)-N(2)-N(3) 119.5(5)
Au(1)-Au(1A)-N(3) 84.32(14)
Au(1A)-Au(1)-N(1) 83.71(13)
Au(1)-N(1)-N(2)
N(2)-N(3)-Au(1A)
126.4(4)
126.1(4)
Figure 2. Diagram showing the molecular structure of the complex
[Ag3(L0)3] (50% probability ellipsoids). Isopropyl groups, hydrogen
atoms, and solvent of crystallization have been omitted for clarity.
complexes is the presence of relatively short M M intra-
3 3 3
molecular distances. In both complexes, the metal-metal
˚
[{Cu2N3}-{C(1)-C(6)}: 78.85(5)ꢀ, {Cu2N3}-{C(13)-
C(18)}: 78.36(5)ꢀ, {Au2N3}-{C(1)-C(6)}: 89.44(17)ꢀ,
{Au2N3}-{C(13)-C(18)}: 81.37(13)ꢀ].
distances [Cu(1)-Cu(1A): 2.4458(4) A and Au(1)-Au(1A):
˚
2.6762(4) A] are significantly shorter than the sum of the van
der Waals radii59 of Cu (1.40 A) and Au (1.66 A) and are
˚
˚
The Cu-N and Au-N bond distances in both [Cu2(L0)2]
and [Au2(L0)2] are within the expected ranges for terminal
directly comparable to related dimeric complexes listed in
Table 4, and are also significantly shorter than M
interactions observed in related tetrameric complexes.
M
3 3 3
˚
˚
M(I)-N bonds [Cu-N: 1.8811(15) A and 1.8824(16) A;
˚
˚
Au-N: 2.046(5) A and 2.042(5) A]. Similarly the N-N bond
The facile oxidative addition of small molecules, such as
X2, CX4, CH2X2, CH3X, PhICl2 and (PhCO2)2 (X=Cl, Br,
or I), to related di-gold amidinate systems has previously
been shown to result in the formation of the corresponding
˚
lengths within the triazenide ligands [N(1)-N(2): 1.308(2) A,
0
˚
N(2)-N(3): 1.298(2) A in [Cu2(L )2] and0 N(1)-N(2):
˚
˚
1.308(7) A, N(2)-N(3): 1.297(7) A in [Au2(L )2] ] are also
comparable to those observed in related systems. A signifi-
cant point of interest in these dimeric Cu(I) and Au(I)
(59) Bondi, A. J. Phys. Chem. 1964, 68, 441–451.

Article
Inorganic Chemistry, Vol. 48, No. 17, 2009 8617
Table 2. Selected Geometric Data for [Ag3(L0)3]
Table 4. Cu Cu and Au Au Distances in Some Bridged Di-Nuclear Cu(I)
and Au(I) Complexes
3 3 3
3 3 3
˚
Bond Lengths (A)
˚
d(M•••M) (A)
Complex
ref
Ag(1)-Ag(2)
Ag(2)-Ag(3)
Ag(1)-Ag(3)
Ag(1)-N(1)
Ag(1)-N(9)
Ag(2)-N(3)
Ag(2)-N(4)
Ag(3)-N(6)
Ag(3)-N(7)
3.01186(17) N(1)-N(2)
2.95330(17) N(2)-N(3)
2.92748(17) N(4)-N(5)
1.297(2)
1.3017(19)
1.287(2)
1.293(2)
1.2939(19)
1.2922(19)
Copper
2.4405(10)
2.4458(4)
2.4289(12)
2.4571(2)
2.1291(14)
2.1204(13)
2.1245(13)
2.1233(14)
2.0907(13)
2.0963(13)
N(5)-N(6)
N(7)-N(8)
N(8)-N(9)
[Cu2(μ-Ph-NNN-Ph)2]
[Cu2(μ-C6H3(iPr)2-
NNN-C6H3(iPr)2)2]
[Cu2{μ-o-C6H4(CO2Me)-
NNN-o-C6H4-(CO2Me)}2]
[Cu2{μ-C6H3Me2-
94
this work
95
49
NC(Ph)N-C6H3Me2}2]
[Cu2(μ-iPr-NC(Me)N-iPr)2]
[Cu2(μ-sBu-NC(Me)N-sBu)2]
[Cu2(μ-iPr-
Bond Angles (deg)
2.414(1)
2.4031(6)
2.4233(10)
48
47
46
N(1)-Ag(1)-N(9)
N(3)-Ag(2)-N(4)
N(6)-Ag(3)-N(7)
154.60(5)
153.69(5)
157.37(5)
N(1)-Ag(1)-Ag(2) 72.45(4)
N(3)-Ag(2)-Ag(1) 72.18(4)
N(4)-Ag(2)-Ag(3) 77.35(4)
N(6)-Ag(3)-Ag(2) 78.66(4)
N(7)-Ag(3)-Ag(1) 79.90(4)
N(9)-Ag(1)-Ag(3) 78.07(4)
NC(NMe2)N-iPr)2]
[Cu2(μ-iPr-
2.4289(11)
2.4227(12)
46
43
NC(NHiPr)N-iPr)2]
[Cu2(μ-Me3Si-
NC(Ph)N-SiMe3)2]
Ag(3)-Ag(1)-Ag(2) 59.615(4)
Ag(3)-Ag(2)-Ag(1) 58.772(4)
Ag(1)-Ag(1)-Ag(2) 61.613(4)
N(1)-N(2)-N(3)
N(4)-N(5)-N(6)
N(7)-N(8)-N(9)
114.39(13)
116.99(13)
116.05(13)
[Cu4{μ-FC6H4-
NNN-C6H4F}4]
[Cu4{μ-CF3C6H4-
NNN-C6H4CF3}4]
[Cu4{μ-Ph-
2.607(6), 2.738(6)
2.578(11)
96
97
49
Table 3. Selected Geometric Data for [Cu3(L0)2(Mes)]
2.5674(6), 2.6419(7)
NC(Ph)N-Ph}4]
˚
Bond Lengths (A)
Gold
Cu(1)-Cu(2)
Cu(2)-Cu(3)
Cu(3)-Cu(1)
Cu(2)-C(101)
Cu(3)-C(101)
2.7068(4)
2.4393(4)
2.6836(3)
1.975(2)
1.956(2)
Cu(1)-N(1)
Cu(2)-N(3)
Cu(1)-N(4)
Cu(1)-N(6)
1.8911(17)
1.8932(17)
1.8928(18)
1.8828(19)
[Au2(μ-C6H3(iPr)2-
NNN-C6H3(iPr)2)2]
[Au2(μ-Me3Si-NC(Ph)N-
SiMe3)2]
[Au2(μ-C6H3Me2-
NC(H)N-C6H3Me2)2]
2.6762(4)
this work
2.6456(6)
2.711(2)
41
60
Bond Angles (deg)
Cu(1)-Cu(2)-
Cu(3)
Cu(2)-Cu(3)-
Cu(1)
Cu(3)-Cu(1)-
Cu(2)
Cu(2)-C(101)-
Cu(3)
62.610(10)
63.581(10)
53.808(9)
76.71(9)
N(1)-Cu(1)-N(4)
N(1)-N(2)-N(3)
N(4)-N(5)-N(6)
156.50(7)
114.91(16)
114.16(17)
21.58(7)
[Au4(μ-Ph-NNN-Ph)4]
2.848(1), 2.856(1),
2.855(1), 2.842(1)
3.0139(11), 2.9920(9),
2.9944(10), 2.9721(11)
2.968(2), 3.103(2)
58
98
44
44
44
40
40
[Au4(μ-Nap-
NC(H)N-Nap)4]
[Au4(μ-MeC6H4-
NC(H)N-C6H4Me)4]
[Au4(μ-Cl2C6H3-
NC(H)N-C6H2Cl2)4]
[Au4(μ-MeOC6H4-
NC(H)N-C6H4OMe)4]
[Au4(μ-Ph-NC(Me)N-Ph)4]
N(1)-Cu(1)-
Cu(2)-N(3)
N(4)-Cu(1)-
Cu(3)-N(6)
2.8662(14), 2.9699(14)
22.12(8)
2.9016(8), 3.0057(9),
2.9265(9), 2.9447(10)
2.9996(12), 2.9796(13),
2.9078(12), 2.8970(12)
2.982(2), 2.970(18),
2.9252(18), 2.955(2)
Au(II) complexes, which display significantly shorter
Au Au contacts.60,61 While analogous reactions of
[Au4(μ-Ph-NC(Ph)N-Ph)4]
3 3 3
[Au2(L0)2] with halogen containing reagents have not been
performed, it is noteworthy that [Au2(L0)2] displays increased
stability in the presence of chlorinated solvents such as
CD2Cl2 compared to the less sterically encumbered gold
amidinate complex described by Fackler et al., as evidenced
by the observed presence of only one species in the 1H NMR
spectra of [Au2(L0)2] in both CD2Cl2 and CDCl3 solvents.
Surprisingly, and in direct contrast to the formation of the
isotypic complexes [Cu2(L0)2] and [Au2(L0)2], the reaction of
AgCl with Li[L0] in a 1:1 stoichiometric ratio, results in the
formation of the tri-silver complex [Ag3(L0)3], crystals of
which were grown from a cooled toluene solution. The
molecular structure of [Ag3(L0)3] is shown in Figure 2 and
selected bond lengths and angles in Table 2.
˚
˚
3.01186(17) A, Ag(2)-Ag(3): 2.95330(17) A, Ag(3)-Ag(1):
˚
2.92748(17) A]. A comparison of the Ag Ag distances in
[Ag3(L0)3] with related systems in Table 5 shows the distances
3 3 3
to be comparable to those observed in related tri-metallic
systems,48 but appreciably longer than the M M interac-
3 3 3
tions observed in both [Cu2(L0)2] and [Au2(L0)2]. As noted
earlier, it is not unusual for short metal-metal distances to
be observed in complexes with bridging ligands. For this
reason the presence of true metallophilic interactions is
often dubious. What is clear is that purely on the basis
˚
of atomic size differences (van der Waals radii: Cu=1.40 A,
Au=1.66 A, and Ag=1.72 A)59 it might have been expected
˚
˚
˚
that M M distances differ by 0.64 A (Cu Cu vs
3 3 3
3 3 3
The complex is formed from a central {Ag3} triangle
of approximately equilateral geometry [Ag(1)-Ag(2):
˚
˚
Ag Ag), 0.12 A (Au Au vs Ag Ag), and 0.52 A
3 3 3 3 3 3 3 3 3
(Cu Cu vs Au Au), respectively. However, it may
3 3 3
3 3 3
be noted that from a comparison of the M-M distances, only
the Au-Au distance is notably shorter in proportion to
the size of the atoms, though longer than the Cu-Cu distance
(60) Abdou, H. E.; Mohamed, A. A.; Fackler, J. P. Jr. Inorg. Chem. 2005,
44, 166–172.
(61) Abdou, H. E.; Mohamed, A. A.; Fackler, J. P., Jr. Inorg. Chem. 2007,
46, 9692–9699.
˚
˚
(by 0.23 A) and shorter than the Ag-Ag distance (0.29 A) in

8618 Inorganic Chemistry, Vol. 48, No. 17, 2009
Johnson et al.
Table 5. Ag Ag Distances in Some Bridged Di- and Tri-Nuclear Ag(I)
Complexes
triazenide and related systems to form a range of oligomeric
complexes (Chart 1) is well known, lower order oligomers are
typically formed by more sterically demanding ligand-sets,
with the formation of trimeric systems, such as [Ag3(L0)3],
typically limited to complexes in which the directionality of
the donor orbitals of the ligand systems preclude the forma-
tion of dimeric (and higher) oligomers, for example, Group
11 metal pyrazolate complexes [M3(μ-R2-pz)3] (R2-pz = R2-
3,5-N2C3).62-66 However, it is noteworthy that the only other
structurally characterized neutral tri-metallic silver system,
containing a related ligand, is the amidinate complex
[Ag3(iPr-NC(Me)N-iPr)3] reported by Gordon et al.48 which
exists in dynamic equilibrium in solution with its dimeric
congener, [Ag3(iPr-NC(Me)N-iPr)3], an observation that is
not made in the case of [Ag3(L0)3]. Other tri-metallic silver
complexes have been described in the literature, but these are
typically cationic species supported by constrained tripodal
ligand systems67-70 or strong σ-donor polydentate ligands
such as phosphines or N-heterocyclic carbenes.71-76 Despite
the identical steric demands of the ligand system in the three
homoleptic complexes [Cu2(L0)2], [Ag3(L0)3], and [Au2(L0)2],
silver appears to have different bonding requirements, the
reasons for which are not fully understood.77 Reports con-
cerning the synthesis and structure of complete homologous/
homoleptic Cu, Ag, and Au complexes are rare,78-82 but even
with the paucity of data, it is correct to say that in the
instances where evidence exists, there are important differ-
ences between copper, silver, and gold, and these observable
differences in coordination geometry may in-part be a result
of a significant variation in size within the Group 11 metals,77
3 3 3
˚
d(M•••M) (A)
Complex
ref
[Ag2(μ-Ph-NNN-Ph)2]
[Ag2{μ-MeOC6H4-NNN-
C6H4OMe}2]
2.669(1)
2.680(2)
99
100
[Ag2{μ-EtOC6H4-NC(H)N-
C6H4OEt}2
2.7533(4)
45
[Ag2(μ-iPr-NC(Me)N-iPr)2]
[Ag2(μ-Me3Si-NC(Ph)N-
SiMe3)2]
2.6447(5)
2.6548(9)
48
41
[Ag3(μ-C6H3(iPr)2-
3.01184(7),
2.92745(16),
2.95329(17)
2.8599(4),
2.8954(5),
3.2002(4)
this work
48
NNN-C6H3(iPr)2)3]
[Ag3(μ-iPr-NC(Me)N-iPr)3]
[Ag4{μ-FC6H4-NNN-
C6H4F}4]
2.8064(4),
2.8337(4)
96
[Ag4{μ-MeOC6H4-
NNN-C6H4OMe}4]
2.7633(16),
2.7849(12),
2.8174(15),
2.7951(11)
2.8614(6)
101
[Ag4(μ-N2C3H6NC3H6)4]
42
97
[Ag{μ-F3CC6H4-NNN-
C6H4CF3}]¥
2.835(2)
an absolute sense. This observation is consistent with strong
d10-d10 interactions in Au-Au systems (cf. Cu-Cu and Ag-
Ag).1,3,12,13,37
As with the bi-metallic systems described earlier the tria-
zenide ligands in [Ag3(L0)3] bridge the M M edges in
3 3 3
an μ,η1,η1-fashion such that each silver atom is bound
to nitrogen atoms of two different triazenide ligands, with
Ag-N bond lengths (see Table 2) lying within expec-
ted values . The N-Ag-N angles about each silver atom
[N(1)-Ag(1)-N(9): 154.60(5)ꢀ, N(3)-Ag(2)-N(4): 153.69-
(5)ꢀ, N(6)-Ag(3)-N(7): 157.37(5)ꢀ] describe a distorted
linear two-coordinate geometry, such that the silver atoms
deviate from linearity by moving toward each other (cf.
[Cu2(L0)2] and [Au2(L0)2]). As a result of this distortion
away from linearity, the triazenide ligands experience sig-
nificant twisting of the {N3} backbone, while maintaining a
bridging coordination mode. Figure 3 shows the relative
arrangements of the three triazenide ligands about the central
{Ag3} core, and clearly shows two distinct types of triazenide
coordination. The triazenide ligand {N(1)-N(2)-N(3)}
bridging the Ag(1)-Ag(2) edge (Figure 3a) shows a signifi-
cant distortion away from coplanarity with the {Ag3} core,
as indicated by the angle between the two planes [38.18(7)ꢀ]
or the dihedral angle [N(1)-Ag(1)-Ag(2)-N(3): 38.82(6)ꢀ]
(Figure 3b), the origins of which we assume to be the result of
a desire to form close Ag-Ag contacts versus the steric
demands of the bulky 2,6-di-isopropyl substituents. The
remaining two triazenide ligands that bridge the Ag(1)-
Ag(3) and Ag(2)-Ag(3) edges display a significantly
less-distorted coordination geometry [N(4)-Ag(2)-Ag(3)-
N(6): 20.23(6)ꢀ; N(7)-Ag(3)-Ag(1)-N(9): 15.52(6)ꢀ], with
a mutually trans-orientation about the two edges of the
{Ag3} core.
(62) Halcrow, M. A. Dalton Trans. 2009, 2059–2073.
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The energetic consequences of steric bulk, and the role that
this plays in molecular design and control, are well estab-
lished.51,54,57 While the propensity for Group 11 metal

Article
Inorganic Chemistry, Vol. 48, No. 17, 2009 8619
Figure 3. Diagrams showing the core of the complex [Ag3(L0)3]: (A) a view along the approximate N(2)-Ag(3) vector, illustrating the distribution and
orientation of the triazenide ligands about the {Ag3} core; (B) a view along the approximate Ag(1)-Ag(2) vector, illustrating the twisting of the triazenide
ligands. Selected angles: N(1)-Ag(1)-Ag(2)-N(3): 38.82(6)ꢀ, N(7)-Ag(3)-Ag(1)-N(9): 15.52(6)ꢀ, N(4)-Ag(2)-Ag(3)-N(6): 20.23(6)ꢀ, N(4)-Ag(2)-
Ag(1)-N(9): 70.63(7)ꢀ, N(3)-Ag(2)-Ag(1)-N(9): 125.27(6)ꢀ, N(1)-Ag(1)-Ag(2)-N(4): 125.28(7)ꢀ, N(9)-Ag(1)-Ag(3)-N(6): 156.15(6)ꢀ, N(4)-
Ag(2)-Ag(3)-N(7): 148.93(6)ꢀ.
Scheme 2
with computational and experimental data showing the size
order within the group to be Cu<Au<Ag.83-86
During the course of our studies, the potential utility of
[Cu(Mes)]79 as a precursor for metal triazenide complex
formation was investigated. Previous studies by others have
demonstrated that reaction of triazenes with metal alkyl
Figure 4. Diagram showing the molecular structures of the complex
[Cu3(L0)2(Mes)] (50% probabilityellipsoids). Isopropyl groups, hydrogen
atoms, and solvent of crystallization have been omitted for clarity.
and amide complexes such as BuLi, MgBu2, ZnEt2, or
[M{N(SiMe3)2}n] (M=Li or K, n=1; M=Ca, Sr, or Ba,
n=2) result in the formation of the corresponding metal
triazenide complexes51,54,56,87 A stoichiometric reaction
between [CuMes] (Mes = 2,4,6-trimethylphenyl) and the
triazene system L0H in toluene at room temperature as
shown in Scheme 2, resulted in the formation of a complex
determined to be different from the expected di-copper
system [Cu2(L0)2].
Concentration of the reaction mixture followed by stand-
ing at -28 ꢀC, gave colorless crystals, which were isolated in
1
a 60% yield with respect to L0H. H NMR studies clearly
1
show the presence of triazenide ligand within the H NMR
Figure 5. Diagramshowingthe core of[Cu3(L0)2(Mes)]: a view alongthe
approximate Cu(2)-Cu(3) vector, illustrating twisting of the triazenide
ligands. Selected angles: N(1)-Cu(1)-Cu(2)-N(3): 21.58(1)ꢀ, N(4)-Cu-
(1)-Cu(3)-N(6): 22.12(8)ꢀ, N(3)-Cu(2)-Cu(3)-N(6): 24.64(15)ꢀ,
N(1)-Cu(1)-Cu(3)-N(6): 150.28(9)ꢀ, N(4)-Cu(1)-Cu(2)-N(3):
153.63(9)ꢀ.
(83) Bruce, M. I.; Williams, M. L.; Patrick, J. M.; Skelton, B. W.; White,
A. H. J. Chem. Soc., Dalton Trans. 1986, 2557–2567.
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Trans. 1997, 2865–2868.
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Chem. Soc. 1996, 118, 7006–7007.
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Taylor, M. J. Inorg. Chem. 1990, 29, 3593–3607.
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5959.
spectrum: with broad doublet resonances at δ = 0.97 ppm
(12H) and δ=1.20 ppm (36H) in a 1:3 ratio for the iso-
propyl CH3 groups. Single resonances at δ=2.12 ppm (3H),

8620 Inorganic Chemistry, Vol. 48, No. 17, 2009
Johnson et al.
Table 6. Crystallographic Data for the Complexes [Cu2(L0)2], [Ag3(L0)3] Tol, [Au2(L0)2] 2Tol, [Cu3(L0)2(Mes)] 2Tol, and [Cu3(L0)2(Mes)]
3
3
3
[Cu2(L0)2]
[Ag3(L0)3] Tol
[Au2(L0)2] 2Tol
[Cu3(L0)2(Mes)] 2Tol
[Cu3(L0)2(Mes)]
3
3
3
empirical formula
formula weight
T/K
C
857.17
150(2)
monoclinic
C2/c
46.4390(4)
10.43100(10)
21.2250(2)
48H69Cu2N6
C72H102Ag3N9 C7H8 C48H68Au2N6 2(C7H8) C57H79Cu3N6 2(C7H8) C57H79Cu3N6
1223.15
150(2)
3
3
3
1509.37
150(2)
1307.29
150(2)
1038.88
150(2)
crystal system
space group
monoclinic
P21/c
monoclinic
P21/c
triclinic
P1
triclinic
P1
˚
a (A)
19.77800(10)
19.97300(10)
19.96700(10)
12.9430(2)
10.0730(2)
22.5260(5)
11.5430(2)
15.3140(2)
20.2000(3)
71.6040(10)
81.2990(10)
83.8170(10)
3342.43(9)
2
11.9480(3)
15.3420(4)
15.5620(4)
93.0140(10)
99.3270(10)
92.364(2)
2807.42(12)
2
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
V
115.4740(10)
99.5770(10)
102.6100(10)
9281.93(15)
8
1.227
0.954
3656
7777.55(7)
4
2865.98(10)
2
Z
F
calc mg/m-3
1.289
0.794
3152
1.515
5.156
1312
1.215
0.989
1300
1.229
1.166
1100
μ(Mo KR), mm-1
F(000)
crystal size, mm
θ range (deg)
reflections collected
independent reflections [R(int)]
reflections observed [I > 2σ(I)]
max.,min transmission
goodness-of-fit
final R1 (wR2) [I > 2σ(I)]
final R1 (wR2) (all data)
largest diff. peak and hole, e A
0.1 ꢀ 0.25 ꢀ 0.40 0.1 ꢀ 0.13 ꢀ 0.22
0.1 ꢀ 0.17 ꢀ 0.2
8.17 to 27.48
44149
6356 (0.1134)
5154
0.6266 and 0.4253
1.153
0.0504 (0.1220)
0.0668 (0.1398)
4.751 and -4.512
0.2 ꢀ 0.2 ꢀ 0.4
8.53 to 27.56
53645
14779 (0.0528)
10989
0.8267 and 0.6930
1.023
0.0404 (0.0872)
0.0690 (0.0993)
0.784 and -0.500
0.13 ꢀ 0.25 ꢀ 0.25
8.52 to 27.56
53616
12403 (0.0692)
8645
0.8680 and 0.7593
1.021
0.0453 (0.0960)
0.0821 (0.1128)
0.961 and -0.540
3.62 to 27.49
77888
8.17 to 30.50
144388
10630 (0.0492) 23190 (0.0634)
8674 19033
0.9106 and 0.7014 0.9248 and 0.8447
1.071
0.0360 (0.0830)
0.0509 (0.0899)
1.071
0.0300 (0.0665)
0.0431 (0.0737)
-3
˚
0.355 and -0.877 0.936 and -0.666
δ=2.71 ppm (6H) and a multiplet at δ=3.13-3.38 ppm (8H)
can also be observed along with a series of resonances in the
aromatic region, which is consistent with a system containing
triazenide and mesityl ligands in a 2:1 ratio. These observa-
tions are consistent with the potential formation of a system
of the general formula [Cu3(L0)2(Mes)] which experiences
molecular fluxionality at room temperature. Elemental ana-
lysis further supports this assertion. Attempts to resolve the
1H NMR spectrum at low temperature were unsuccessful,
and failed to freeze-out fluxional processes in solution. Simi-
larly, a full assignment of the 13C NMR spectra was also not
possible because of poor resolution of resonances. Attempts
were made to resolve the spectrum by modifying relaxation
delay parameters, extended data collections, and variable
temperature experimentation, but to little avail.
shown in Figure 5 for [Cu3(L0)2(Mes)] and those of [Ag3(L0)3]
(Figure 3), indicate significantly less distortion within the
tri-copper complex [Cu3(L0)2(Mes)]. The mesityl group,
which bridges the shortest Cu-Cu edge, possesses Cu-C
˚
distances [Cu(2)-C(101): 1.975(2) A, Cu(3)-C(101):
˚
1.956(2) A] which are also comparable to those found in
both [Cu(Mes)]79 and the tri-copper system [Cu3(O2CPh)2-
(Mes)],88,89 and is orientated such that the planes defined by
the tri-copper unit and the mesityl ring are approximately
perpendicular [86.32(7)ꢀ], reflecting the three-center two-
electron (3c-2e) bonding between Cu(1), Cu(3) and the
mesityl group (the range for Cu-Cu distances bridged
by 3c-3e bonds has previously been shown to be 2.37-
88
˚
2.53 A ). The ASU also contains two molecules of toluene
of crystallization.
The results of a single crystal X-ray diffraction experiment
demonstrate the product formed from the reaction to
be the unanticipated tri-copper system [Cu3(L0)2(Mes)],
Figure 4. Selected bond lengths and angles are shown in
Table 3. The complex, [Cu3(L0)2(Mes)] crystallizes in the
triclinic space group P1 and is fashioned from a central
tri-copper unit reminiscent of [Ag3(L0)3], of approximately
The synthesis of tri-copper based cluster systems such as
[Cu3(L0)2(Mes)] is currently of interest because of their role in
enzymatic systems,90,91 for example, ascorbate oxidase, cer-
uplasmin, and laccase, since tri-nuclear copper clusters at the
active site of these enzymes have been implicated in the
reduction of O2 to H2O. The complex [Cu3(L0)2(Mes)]
represents a well-defined tri-nuclear copper system which is
presently under investigation in our laboratory with respect
to its ability to activate small molecules such as O2, CO,
and CO2.
Successive attempts to produce the di-copper complex
[Cu2(L0)2] by reacting [Cu(Mes)] with L0H in different
solvents (hexane or tetrahydrofuran) resulted in further
isolation of the tri-copper system [Cu3(L0)2(Mes)], suggesting
that the product is in some way kinetically or thermodyna-
mically stabilized. Attempts to induce complete reaction with
˚
isoscelean geometry [Cu(1)-Cu(2): 2.7068(4) A, Cu(1)-Cu-
˚
˚
(3): 2.6836(3) A, Cu(2)-Cu(3): 2.4393(4) A]. Two triazenide
ligands bridge the Cu-Cu edges with distances that
are significantly longer than that observed in [Cu2(L0)2]
0
˚
[cf. Cu(1)-Cu(1A): 2.4458(4) A]. As with [Cu2(L )2], the
Cu-N distances are in the range expected for comparable
copper-amidinate and -triazenide complexes, [Cu(1)-N(1)
1.8911(17) A; Cu(1)-N(4) 1.8928(18) A; Cu(2)-N(3)
1.8932(17) A; Cu(2)-N(6) 1.8828(12) A].
˚
˚
˚
˚
The bridging triazenide ligands form two twisted five-
membered {Cu2N3} rings (Figure 5), and as with the struc-
turally related tri-silver complex, it is believed that the
triazenide ligands are twisted in such a way as to relieve the
steric interaction between the 2,6-di-isopropyl substituents
on N(1) and N(4). A comparison between the torsion angles
(88) Aalten, H. L.; van Koten, G.; Goubitz, K.; Stam, C. H. J. Chem.
Soc., Chem. Commun. 1985, 1252–1253.
(89) Aalten, H. L.; van Koten, G.; Goubitz, K.; Stam, C. H. Organome-
tallics 1989, 8, 2293–2299.
(90) Chan, S. I.; Yu, S. S. F. Acc. Chem. Res. 2008, 41, 969–979.
(91) Mirica, L. M.; Stack, T. D. P. Inorg. Chem. 2005, 44, 2131–2133.

Article
Inorganic Chemistry, Vol. 48, No. 17, 2009 8621
additional heating of reaction mixtures at reflux tempera-
tures in both tetrahydrofuran and toluene resulted in the
thermal degradation of the product, such that only intract-
able material was isolated. During the course of our investi-
gations, crystals of the tri-copper complex [Cu3(L0)2(Mes)],
which were free of toluene of crystallization, were isolated,
and the molecular structure determined by single crystal X-
ray diffraction, details of which are included in Table 6 for
completeness.
was added. The reaction mixture was allowed to stir for 4 h, after
which the volatiles were removed under reduced pressure, and the
product was extracted into toluene and filtered through Celite. The
resultant filtrate was concentrated, and storage of the material at
-28 ꢀC facilitated the growth of yellow crystals suitable for single
crystal X-ray diffraction (2.84 g, 66%). Elemental analysis: calcd.
(%): C 67.41, H 8.02, N 9.83; Found: C 67.4, H 7.95, N 9.85. 1H
NMR (300 Hz, CD2Cl2): δ = 1.20 (48H, d, CH(CH3)2, J = 6.96
Hz), 3.47 (8H, sept, CH(CH3)2, J = 6.96 Hz), 7.08-7.17 (12H, m,
CH), 13C NMR (75.49 Hz, CD2Cl2): δ = 24.0, 28.72, 123.9, 127.2,
144.0 and 144.7.
Synthesis of [Ag3(L0)3]. Silver(I) chloride (0.287 g, 2.00 mmol),
1,3-bis(2,6-di-isopropyl)triazene (0.731 g, 2.00 mmol), and
lithium bis(trimethylsilyl)amide (0.335 g, 2.00 mmol) were
placed in a dry Schlenk tube under Argon, into which tetrahy-
drofuran (20 mL) was added. The reaction mixture was allowed
to stir for 16 h, after which time the solvent was removed under
reduced pressure. Dry hexane (20 mL) was added to the
resultant residue and left to stir for 15 min, after which time
the hexane was removed under reduced pressure. The process
was repeated twice to remove any residual tetrahydrofuran. The
product was then extracted into hexane and filtered through
Celite. The resultant filtrate was concentrated, and storage of
the material at -28 ꢀC facilitated the growth of yellow crystals
suitable for single crystal X-ray diffraction (0.699 g, 74%).
Elemental analysis: calcd. (%): C 61.12, H 7.27, N 8.92; Found:
C 61.30, H 7.34, N 8.84. 1H NMR (300 Hz, CD2Cl2): δ = 0.85
(36H, d, CH(CH3)2, J = 6.87 Hz), 1.02 (36H, d, CH(CH3)2, J =
6.87 Hz), 3.14 (12H, sept, CH(CH3)2, J = 6.87 Hz), 6.99-7.14
(18H, m, CH) 13C NMR (75.49 Hz, C6D6): δ = 23.2, 24.3, 28.5,
123.9, 127.1, 143.6, and 145.6.
Conclusions
Reported here in are the structures of several novel
Group 11 M(I) complexes containing metal-metal inter-
actions supported by sterically demanding triazenide li-
gands. In contrast to the reactions of the metal chlorides
CuCl, AgCl, and (THT)AuCl with lithium triazenide Li-
[L0], which provide a series of homoleptic complexes,
[M(L0)]n (M=Cu or Au, n=2; M=Ag, n=3), which have
been structurally characterized. Reaction of [Cu(Mes)]
with the triazene system L0H results in the serendipitous
formation of a novel Cu(I) tri-metallic system, [Cu3(L0)2-
(Mes)]. The precise reasons for this difference in reactivity
are not fully understood, but it is possible to speculate that
there is a fine balance between any energetic gain in the
disruption of 3c-2e bonding present in [Cu(Mes)] versus
loss of mesitylene and formation of Cu-N bonds. Such
energetic considerations are not relevant in the case of salt
metathesis reactions.
Synthesis of [Au2(L0)2]. Tetrahydrothiophene gold(I) chloride
(0.317 g, 1.00 mmol), 1,3-bis(2,6-di-isopropyl)triazene (0.366 g,
1.00 mmol), and lithium bis(trimethylsilyl)amide (0.167 g,
1.00 mmol) were placed in a dry Schlenk tube under Argon,
into which tetrahydrofuran (15 mL) was added. The reaction
mixture was allowed to stir for 16 h, after which time the solvent
was removed under reduced pressure and dry hexane (15 mL)
was added to the resultant residue. This was left to stir for
15 min, after which the volatiles were removed under reduced
pressure. The process was repeated twice, to remove any residual
tetrahydrofuran. The product was then extracted into hexane
and filtered through Celite. The resultant filtrate was concen-
trated, and storage of the material at -28 ꢀC facilitated the
growth of pale yellow crystals suitable for single crystal X-ray
diffraction (0.343 g, 61%). Elemental analysis, calcd (%): C
51.31, H 6.11, N 7.49; Found: C 51.0, H 6.19, N 7.16. 1H NMR
(300.22 Hz, CD2Cl2): δ 1.20 (24H, d, CH(CH3)2, J = 6.82 Hz),
1.37 (24H, d, CH(CH3)2, J = 6.82 Hz), 3.66 (8H, sept, CH-
(CH3)2, J = 6.82 Hz), 7.05-7.16 (12H, m, CH); 13C NMR
(75.49 Hz, CD2Cl2): δ = 24.2, 24.4, 28.0, 123.9, 128.0, 143.8 and
146.0.
Synthesis of [Cu3(L0)2(Mes)]. Copper(I) mesitylene (0.914 g,
5.00 mmol) and 1,3-bis(2,6-di-isopropylphenyl)triazene (1.83
g, 5.00 mmol) were placed in a dry Schlenk tube under Argon,
into which toluene (15 mL) was added. The reaction mixture
was allowed to stir for 16 h, after which time the solution
was concentrated and storage of the material at -28 ꢀC
facilitated the growth of colorless crystals suitable for single
crystal X-ray diffraction (0.945 g, 61%). Elemental analysis:
calcd. (%): C 65.90, H 7.66, N 8.09; Found: C 65.70 H 7.49, N
8.09. 1H NMR (300.22 Hz, DCM-d2): 0.97 (12H, d, CH(CH3)2,
J = 6.97 Hz), 1.20 (36H, d, CH(CH3)2, J = 6.97 Hz), 2.12 (3H,
s, Mes-p-CH3), 2.71 (6H, s, Mes-o-CH3), 3.13-3.38 (8H, m,
CH(CH3)2, 6.94 (2H, s, CH), 6.98-7.09 (12H, m, CH). 13C NMR
(75.49 Hz, DCM-d2): 21.7, 21.9, 23.0, 23.6, 23.78, 24.2, 24.4, 28.7,
28.9, 29.2, 123.9, 124.0, 127.4, 127.5, 143.8, 144.2, 144.6, 144.9,
145.2, 155.9.
All the complexes described exhibit bridging triazenide
ligand systems which can be accused of enhancing any
inherent metallophilic interactions. Despite this, there is
no doubt that significant M-M interactions exist in all
four systems that we have described. In fact, our observa-
tions would lead us to conclude that the triazenide ligands
are not solely responsible for M-M contacts in the com-
plexes [Cu2(L0)2], [Ag3(L0)3], [Au2(L0)2], and [Cu3(L0)2-
(Mes)]: empirical analysis of the experimentally deter-
mined M-M distances versus calculated van der Waals
radii would suggest that the bridging nature of the triaze-
nide ligands is actually facilitated by the presence of
significant metallophilic interactions in complexes such
as these.
Experimental Section
General Procedures. Elemental analyses were performed by
1
Elemental Microanalysis Ltd., Okehampton, Devon, U.K. H
and 13C NMR spectra were recorded on a Bruker Avance
300 MHz FT-NMR spectrometer, as saturated solutions in
d2-CD2Cl2; chemical shifts are quoted in units of parts per
million, relative to Me4Si (1H, 13C); coupling constants are in
hertz.
All reactions were carried out under an inert atmosphere
using standard Schlenk techniques. Solvents were dried over
activated alumina columns using an Innovative Technology
solvent purification system (SPS) and degassed under an argon
atmosphere. The ligand system 1,3-bis(2,6-di-isopropyl)tria-
zene51 and [Cu(Mes)]79 were made according to literature
procedures. All other reagents were purchased from commercial
sources.
Synthesis of [Cu2(L0)2]. Copper(I) chloride (0.495 g, 5.00 mmol),
1,3-bis(2,6-di-isopropyl)triazene (1.83 g, 5.00 mmol), and lithium
bis(trimethylsilyl)amide (0.837 g, 5.00 mmol) were placed in a dry
Schlenk tube, under Argon, into which tetrahydrofuran (20 mL)

8622 Inorganic Chemistry, Vol. 48, No. 17, 2009
Johnson et al.
Crystallography
complexes, hydrogen atoms were included at calculated posi-
tions.
Experimental details relating to the single-crystal X-ray
crystallographic studies are summarized in Table 6. For all
structures, data were collected on a Nonius Kappa CCD
The asymmetric unit of [Cu2(L0)2] consists of two indepen-
dent halves of the di-copper complex. One of the two
‘half-molecules’ is disordered with respect to the central
core, which shows two orientations of the planar {Cu2N6}
unit rotated by 90ꢀ. This disorder was modeled such that the
{N3} unit and the Cu centers were modeled over two posi-
tions, in a 19:1 ratio, relative to the 2,6-di-isopropyl rings,
which are not disordered. The major component of the
disorder was refined using anisotropic displacement para-
meters. To obtain a stable convergence, refinement of the
minor component of disorder was refined with isotropic
displacement parameters.
diffractometer at 150(2)
K using Mo KR radiation
˚
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Acknowledgment. We acknowledge the financial support of
the University of Bath and the EPSRC for the award of a CASE
for New Academics (A.M.W.). We thank UMICORE AG &
Co. KG for a generous gift of precious metal compounds. A.L.J.
thanks Prof. P. Raithby (UoB) and Dr. M. S. Hill (UoB) for
helpful comments and fruitful discussions.
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