Coordination behaviour of bis-terdentate N-donor ligands: Double- and single-stranded helicates, mesocates, and cyclic oligomers

Article abstract of DOI:10.1002/ejic.200700715

Three new ligands have been prepared in which two terdentate chelating pyrazolyl-bipyridine units are connected by a central aromatic spacer via methylene "hinges": the spacers are o-phenylene (L^Ph), 2,6-pyridine-diyl (L^Py) and 2,3-n

Full text of DOI:10.1002/ejic.200700715

FULL PAPER
DOI: 10.1002/ejic.200700715
Coordination Behaviour of Bis-Terdentate N-Donor Ligands: Double- and
Single-Stranded Helicates, Mesocates, and Cyclic Oligomers
Nawal K. Al-Rasbi,[a] Harry Adams,[a] Lindsay P. Harding,[b] and Michael D. Ward*[a]
Keywords: Chelating ligands / Coordination chemistry / Helical structures / Self-assembly
Three new ligands have been prepared in which two terdent-
ate chelating pyrazolyl-bipyridine units are connected by a
central aromatic spacer via methylene “hinges”: the spacers
are o-phenylene (LPh), 2,6-pyridine-diyl (LPy) and 2,3-naph-
ligands; [Ag3(Lnaph)2](BF4)3, which contains a linear trinu-
clear array of AgI ions with the two ligands arranged in a
shallow helical twist, each ligand spanning one terminal and
the central metal ion; and [Cd6(Lnaph)6](ClO4)12, a cyclic
thalenediyl (Lnaph). The ligands act as potentially hexaden- hexanuclear helicate with a perchlorate anion in the central
tate bridging ligands, with the central pyridyl N atom of LPy
not involved in coordination. The following complexes were
prepared and structurally characterised: [M2(LPh)2][ClO4]4
(M = Ni, Cu), which are dinuclear double helicates; [Ag2-
(LPh)(MeCN)2][BF4]2, a dinuclear complex with an Ag···Ag
bond in which the ligand adopts a helical twist around the
pair of metal ions; [Ni2(LPy)2][BF4]4, an achiral “mesocate”
with a box-like structure and a face-to-face arrangement of
cavity. Both [Cu2(LPh)2][ClO4]4 and [Cd6(Lnaph)6](ClO4)12
,
which have architecturally similar bridging ligands, show
evidence by electrospray mass spectrometry for formation of
a range of cyclic oligomers in solution up to 11-mers for the
CdII/Lnaph system.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
has used polynuclear helicate complexes to understand and
illustrate the phenomenon of cooperativity in self-assembly
processes,[5] and has used heterodinuclear d/f helicates for
studies on photoinduced energy-transfer between d-block
and f-block luminophores.[6] Nitschke has used structurally
relatively simple dinuclear CuI helicates with different com-
binations of ligands to probe the concept of “valence frus-
tration” which plays an important role in controlling self-
assembly processes.[7] Triple helicates with a pendant hydro-
gen-bonding group attached to each ligand have been found
to bind anions in the resultant pocket, and such anion bind-
ing can control the orientation of the three ligands in the
helical scaffold.[8] Williams and co-workers showed how di-
nuclear helicates can display unusual stepwise spin-cross-
over properties, associated with mechanical coupling be-
tween the two metal centres.[9] Certain anions can template
formation of cyclic helicates in which the anion occupies
the central cavity, and the size of the anion dictates the size
of the metal/ligand circular helical array around it.[10]
We report here the preparation and coordination chemis-
try of a set of three new bis-tridentate ligands LPh, Lpy, and
Lnaph (Scheme 1), in which two terdentate arms, each based
on a pyrazolyl–pyridyl–pyridyl sequence of donors, are con-
nected to various different aromatic spacers (o-phenylene,
pyridine-2,6-diyl, and 2,3-naphthalenediyl, respectively).
Flexibility in the ligand backbone is provided by the meth-
ylene “hinges” which connect the terdentate arms to the
central spacer. These belong to a general class of bridging
Introduction
Complexes with double or triple helical structures (“hel-
icates”) have been of interest in the field of coordination
chemistry for many years. These assemblies have elegantly
demonstrated how the formation of architecturally complex
systems is directed by the interplay between simple param-
eters such as the stereoelectronic preference of the metals
ion and the disposition of the binding sites in the ligand.[1]
Despite that the fact that very many helical complexes
are known, the field remains as popular as ever because of
the development of new research areas which involve them.
These are remarkably diverse as some very recent examples
will illustrate. Hannon and co-workers have shown how rel-
atively simple dinuclear helicates bind to DNA and stabilise
a triple junction.[2] Rice and co-workers have prepared li-
gands in which the degree of twist between the two binding
domains can be controlled by allosteric means, allowing the
assembly of helicate complexes to be controlled by an exter-
nal perturbation.[3] A double helical ligand array has been
used as a scaffold for a dinuclear CuI/CuII complex which
shows unusual electronic delocalisation behaviour.[4] Piguet
[a] Department of Chemistry, University of Sheffield,
Sheffield S3 7HF, UK
Fax: +44-114-2229346
E-mail: m.d.ward@sheffield.ac.uk
[b] Department of Chemical and Biological Sciences, University of
Huddersfield,
Huddersfield HD1 3DH, UK
4770
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4770–4780

Coordination Behaviour of Bis-Terdentate N-Donor Ligands
ligand that we have studied extensively in the last few years M(Lph)(ClO4)2 by elemental analysis, that is 1:1 M2+/LPh
and which have proven to be particularly effective at provid- stoichiometry. X-ray quality crystals could be grown for M
ing polynuclear complexes with elaborate and often unex- = Cu and Ni by diffusion of diethyl ether vapour into
pected structures.[10b,11]
MeCN solutions of the complexes.
Both complexes [M2(LPh)2][ClO4]4 (M = Ni, Cu) proved
to be dinuclear double helicates with two ligands wrapped
around two metal ions; each ligand donates one terdentate
site to each metal ion, and each metal ion is six-coordinate
from coordination by two terdentate fragments, one from
each ligand. Their gross structures are very similar (Fig-
ure 2), with minor differences arising from the distorted co-
ordination environment around CuII due to the Jahn–Teller
effect. Thus the NiII complex has fairly regular coordina-
tion around the NiII ions, with the Ni–N(pyridine) bond
lengths in the range 2.00–2.10 Å and the Ni–N(pyrazole)
distances being slightly longer at 2.12–2.18 Å. The angles
between the two Ni(NNN) planes at Ni(1) and Ni(2) are
92.5° and 94.2°, respectively (Table 1). Areas of overlap be-
tween aromatic rings on adjacent ligands are clear, resulting
in some degree of stabilisation of the structure by π-stack-
Scheme 1.
Results and Discussion
Ligand Syntheses
The new ligands (Scheme 1) were prepared by the reac-
tion of two equivalents of 6-(pyrazol-3-yl)-2,2Ј-bipyr-
idine[12] with the appropriate bis(bromomethyl)-substituted
organic spacer, in the presence of hydroxide ion under
phase-transfer conditions, according to the method we have
used for related ligands in this series.[13] All of the spectro-
scopic and analytical data were consistent with the formula-
tion of the ligands. Needles of LPh suitable for X-ray analy-
sis were obtained by slow evaporation of a dilute dichloro-
methane solution of the ligand. The crystal structure is pre-
sented in Figure 1. Individual bond lengths and angles
within the ligand are unremarkable. The crystal packing
shows an extensive combination of weak CH···N hydrogen
bonds and π–π stacking interactions between adjacent
molecules.
Complexes with LPh
Figure 2. Structures of the double helical complex cations of (a)
Reaction of LPh with perchlorate salts of NiII or CuII in
MeCN afforded crystalline products of empirical formula MeCN, with the ligands shaded differently for clarity.
[Cu2(LPh)2][ClO4]4·2MeCN·0.5H2O and (b) [Ni2(LPh)2][ClO4]4·
Figure 1. Structure of LPh
.
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FULL PAPER
Table 1. Selected bond lengths [Å] and angles [°] for [Ni2(LPh)2][ClO4]4·MeCN.
Ni(1)–N(161)
Ni(1)–N(261)
2.001(4)
2.008(4)
Ni(2)–N(221)
Ni(2)–N(121)
2.005(4)
2.019(4)
Ni(1)–N(171)
Ni(1)–N(271)
2.102(4)
2.110(4)
Ni(2)–N(211)
Ni(2)–N(111)
2.106(4)
2.110(4)
Ni(1)–N(251)
Ni(1)–N(151)
2.118(4)
2.164(4)
Ni(2)–N(131)
Ni(2)–N(231)
2.153(4)
2.180(4)
N(161)–Ni(1)–N(261)
N(161)–Ni(1)–N(171)
N(261)–Ni(1)–N(171)
N(161)–Ni(1)–N(271)
N(261)–Ni(1)–N(271)
N(171)–Ni(1)–N(271)
N(161)–Ni(1)–N(251)
N(261)–Ni(1)–N(251)
N(171)–Ni(1)–N(251)
N(271)–Ni(1)–N(251)
N(161)–Ni(1)–N(151)
N(261)–Ni(1)–N(151)
N(171)–Ni(1)–N(151)
N(271)–Ni(1)–N(151)
N(251)–Ni(1)–N(151)
170.80(17)
78.35(17)
101.28(16)
92.77(17)
78.12(16)
96.67(16)
111.74(17)
77.37(16)
88.42(15)
155.49(16)
76.44(16)
104.76(16)
153.78(16)
91.64(16)
94.25(15)
N(221)–Ni(2)–N(121)
N(221)–Ni(2)–N(211)
N(121)–Ni(2)–N(211)
N(221)–Ni(2)–N(111)
N(121)–Ni(2)–N(111)
N(211)–Ni(2)–N(111)
N(221)–Ni(2)–N(131)
N(121)–Ni(2)–N(131)
N(211)–Ni(2)–N(131)
N(111)–Ni(2)–N(131)
N(221)–Ni(2)–N(231)
N(121)–Ni(2)–N(231)
N(211)–Ni(2)–N(231)
N(111)–Ni(2)–N(231)
N(131)–Ni(2)–N(231)
173.31(16)
78.24(17)
99.81(17)
96.41(15)
77.59(16)
100.81(16)
109.15(16)
76.93(16)
85.73(15)
154.42(16)
76.18(15)
106.46(16)
153.30(16)
89.57(15)
95.47(14)
Table 2. Selected bond lengths [Å] and angles [°] for [Cu2(LPh)2][ClO4]4·2MeCN·0.5H2O.
Cu(1)–N(221)
Cu(1)–N(121)
1.973(4)
2.007(5)
Cu(2)–N(161)
Cu(2)–N(261)
1.980(5)
1.995(5)
Cu(1)–N(211)
Cu(1)–N(231)
2.115(6)
2.170(5)
Cu(2)–N(171)
Cu(2)–N(271)
2.114(6)
2.184(6)
Cu(1)–N(111)
Cu(1)–N(131)
2.233(5)
2.355(7)
Cu(2)–N(151)
Cu(2)–N(252)
2.274(5)
2.438(7)
N(221)–Cu(1)–N(121)
N(221)–Cu(1)–N(211)
N(121)–Cu(1)–N(211)
N(221)–Cu(1)–N(231)
N(121)–Cu(1)–N(231)
N(211)–Cu(1)–N(231)
N(221)–Cu(1)–N(111)
N(121)–Cu(1)–N(111)
N(211)–Cu(1)–N(111)
N(231)–Cu(1)–N(111)
N(221)–Cu(1)–N(131)
N(121)–Cu(1)–N(131)
N(211)–Cu(1)–N(131)
N(231)–Cu(1)–N(131)
N(111)–Cu(1)–N(131)
171.61(11)
79.1(2)
92.79(19)
78.3(2)
N(161)–Cu(2)–N(261)
N(161)–Cu(2)–N(171)
N(261)–Cu(2)–N(171)
N(161)–Cu(2)–N(271)
N(261)–Cu(2)–N(271)
N(171)–Cu(2)–N(271)
N(161)–Cu(2)–N(151)
N(261)–Cu(2)–N(151)
N(171)–Cu(2)–N(151)
N(271)–Cu(2)–N(151)
N(161)–Cu(2)–N(252)
N(261)–Cu(2)–N(252)
N(171)–Cu(2)–N(252)
N(271)–Cu(2)–N(252)
N(151)–Cu(2)–N(252)
176.12(11)
78.8(2)
97.29(19)
102.77(15)
78.32(15)
108.87(13)
77.1(2)
109.7(2)
157.29(10)
105.69(19)
77.7(2)
99.95(16)
88.54(17)
102.05(14)
75.79(15)
91.84(11)
90.43(11)
151.41(12)
106.8(2)
154.84(11)
83.52(14)
104.70(11)
75.08(11)
88.11(11)
150.04(14)
91.14(10)
ing. In the CuII complex in contrast the coordination geom- values of which those at 972.4 and 1508.1 can be assigned
etry about the CuII ions is more distorted (Table 2). Cu(1) as belonging to {Ni4(LPh)4(ClO4)5}3+ and {Ni4(LPh)4-
has a trans-related pair of Cu–N bonds from the same li- (ClO4)6}2+ respectively. Thus, both complexes which were
gand (using a terminal pyridyl ring and the pyrazolyl ring) isolated as dinuclear species in the solid state show evidence
and that are significantly longer than the other four; for for traces of a tetrameric (presumably, cyclic helical) species
Cu(2) in contrast the distortion is expressed as an elong- existing in solution.[10]
ation of both Cu–N(pyrazolyl) bonds, which are cis to one
another.
Reaction of LPh with AgBF4 in MeCN, followed by dif-
fusion of diisopropyl ether vapour into the solution, af-
Electrospray mass spectra of both complexes revealed forded crystals of [Ag2(LPh)(MeCN)2][BF4]2 (Figure 3)
several peaks at the m/z values expected for the dinuclear which, in contrast to the two structures above, is a dinuclear
complexes (see Experimental section). However in both single stranded helicate. The hexadentate ligand LPh is ar-
cases there are very weak peaks identifiable whose m/z val- ranged in a shallow spiral which is wound around a central
ues are consistent with formation of higher oligomers. For axis of two AgI ions; the two metals end up close enough
redissolved crystals of [Cu2(LPh)2][ClO4]4 for example, the together to be considered as having an argentophilic bond
ES mass spectrum has a weak peak at m/z 979.1, assigned between them [Ag(1)···Ag(2), 3.07 Å]. Somewhat surpris-
as {Cu4(LPh)4(ClO4)5}3+
;
and redissolved crystals of ingly, the two AgI ions are in markedly different coordina-
[Ni2(LPh)2][ClO4]4 show numerous weak peaks at high m/z tion environments. It might be expected [cf. the structures
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Coordination Behaviour of Bis-Terdentate N-Donor Ligands
with CuII and NiII, above] that LPh would donate a terdent- of the ligand is bound in its entirety to Ag(2). Thus, LPh
ate pyrazolyl-bipyridine arm to each AgI ion. Instead the acts as a “2+4”-dentate donor [or, possibly, a “2.5+3.5”
partitioning of the ligand into two binding sites occurs donor if N(51) is considered as genuinely bridging] to the
within one of the terdentate units, such that one terdentate two AgI centres, each of which also has one MeCN ligand.
arm of the ligand donates only a bipyridyl unit to Ag(1), The differences in coordination number of Ag(1) and Ag(2)
with the adjacent pyrazolyl donor [N(51)] closer to Ag(2) are reflected in significantly longer average Ag–N bond
(2.43 Å) than to Ag(1) (2.78 Å). Such ambiguous bridging lengths around Ag(2) (see Table 3).
interactions of a single N-donor ligand to a pair of AgI ions
A consequence of the single-stranded helical structure is
is known in other cases.[14] The remaining terdentate arm that the bipyridyl groups at each end of the ligand are over-
lapping and π-stacked with each other. This is emphasised
in Figure 3(b). These two bipyridyl groups are near-parallel,
and the separation between them is ca. 3.3 Å. It is conve-
nient that the separation between the two AgI ions is almost
exactly that required for aromatic ligands coordinated to
them to have an optimal π-stacking separation.
NiII Complex with LPy
Reaction of LPy with Ni(BF4)2 in a 1:1 ratio in nitro-
methane afforded, after crystallisation, [Ni2(LPy)2][BF4]4
which has the structure of a box-like achiral complex, some-
times called a “meso-helicate” or “mesocate”,[15] in which
the two ligands are side-by-side rather than twisted around
one another (Figure 4, Table 4). This suits the coordination
preference of NiII for octahedral geometry as it allows the
Figure 3. Structure of the complex cation of [Ag2(LPh)(MeCN)2]-
[BF4]2 (MeCN ligands are shown shaded differently for clarity).
Table 3. Selected bond lengths [Å] and angles [°] for [Ag2-
(LPh)(MeCN)2][BF4]2.
Ag(1)–N(71)
Ag(1)–Ag(2)
Ag(2)–N(21)
Ag(2)–N(86)
Ag(2)–N(51)
Ag(2)–N(11)
Ag(2)–N(31)
2.386(8)
3.0697(12)
2.344(7)
2.366(9)
2.428(7)
2.451(8)
2.514(8)
N(83)–Ag(1)–N(61)
N(83)–Ag(1)–N(71)
N(61)–Ag(1)–N(71)
N(21)–Ag(2)–N(86)
N(21)–Ag(2)–N(51)
N(86)–Ag(2)–N(51)
N(21)–Ag(2)–N(11)
N(86)–Ag(2)–N(11)
N(51)–Ag(2)–N(11)
N(21)–Ag(2)–N(31)
N(86)–Ag(2)–N(31)
N(51)–Ag(2)–N(31)
N(11)–Ag(2)–N(31)
167.3(3)
112.1(3)
70.6(3)
143.5(3)
129.5(2)
84.2(3)
68.9(3)
91.1(3)
104.9(3)
68.9(3)
120.4(3)
105.9(2)
137.5(2)
Figure 4. Two views of the complex cations of the mesocate
[Ni2(LPy)2][BF4]4·2MeNO2, with the ligands shaded differently for
clarity.
Eur. J. Inorg. Chem. 2007, 4770–4780
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N. K. Al-Rasbi, H. Adams, L. P. Harding, M. D. Ward
FULL PAPER
Table 4. Selected bond lengths [Å] and angles [°] for [Ni2(LPy)2][BF4]4·2MeNO2.
Ni(1)–N(21)
Ni(1)–N(61)
2.009(4)
2.013(4)
Ni(1)–N(11)
Ni(1)–N(51)
2.094(4)
2.154(4)
Ni(1)–N(71)
2.083(4)
Ni(1)–N(31)
2.172(4)
N(21)–Ni(1)–N(61)
N(21)–Ni(1)–N(71)
N(61)–Ni(1)–N(71)
N(21)–Ni(1)–N(11)
N(61)–Ni(1)–N(11)
N(71)–Ni(1)–N(11)
N(21)–Ni(1)–N(51)
N(61)–Ni(1)–N(51)
177.12(16)
104.50(15)
78.20(16)
78.17(16)
102.85(16)
92.20(15)
100.68(14)
76.66(15)
N(71)–Ni(1)–N(51)
N(11)–Ni(1)–N(51)
N(21)–Ni(1)–N(31)
N(61)–Ni(1)–N(31)
N(71)–Ni(1)–N(31)
N(11)–Ni(1)–N(31)
N(51)–Ni(1)–N(31)
154.70(15)
90.63(15)
76.77(15)
102.26(14)
92.46(15)
154.89(15)
95.56(14)
two Ni(NNN) planes to be essentially perpendicular to one complex should be [Ag3(Lnaph)2](BF4)3. This was confirmed
another (89° between them), and also allows a region of by X-ray crystallography; the structure is in Figure 5, and
overlap between parallel and overlapping ligand fragments shows some interesting similarities to that of the simpler
in the space between the two metal ions, involving the pyr- complex [Ag2(LPh)(MeCN)2][BF4]2. The trinuclear complex
azolyl ring of one ligand [N(51)–C(55)] and the non-coordi- cation has C2 symmetry, and consists of a linear sequence
nated central pyridyl ring of the other [N(41A)–C(46A)], of three AgI ions with two ligands each spanning two of
whose mean planes are separated by ca. 3.3 Å. The Ni–N them. Thus one ligand presents four of its six donor atoms
bonds to the two pyrazolyl donors (average 2.16 Å) are (one entire tridentate arm, and the pyrazolyl donor of the
slightly longer than to the four pyridyl donors (average next arm) to the terminal AgI ion, and the remaining two
2.05 Å). Notably, the central pyridyl ring of each ligand (a bipyridyl unit) to the next AgI at the centre of the array.
[containing N(41)] does not participate in coordination but We are seeing again how each ligand is partitioned into a
acts like a meta-phenylene spacer such that the ligand coor- “4+2-dentate” coordination mode rather than the more
dinated only via its terdentate pyrazolyl-bipyridine arms.
natural “3+3” mode which might be expected. The central
AgI ion [Ag(1)] is therefore in a four-coordinate environ-
ment, connected to a terminal bipyridyl fragment from each
of the two ligands; the terminal AgI ions are also four coor-
Complexes with Lnaph
This ligand is architecturally similar to LPh in that it has dinate with all four donors coming from the same ligand
the same geometry spacer (an ortho-disubstituted six-mem- (see Table 5). As with [Ag2(LPh)(MeCN)2][BF4]2, each li-
bered aromatic ring) separating the two fragments. How- gand adopts a shallow monohelical twist such that the bi-
ever, replacement of the 1,2-phenylene spacer by 2,3-naph- pyridyl units at each end of a given ligand overlap with one
thalenediyl spacer results in formation of some quite dif- another. The C2 symmetry of the complex cation means
ferent structural types.
that both ligands have the same helical arrangement as one
Reaction of Lnaph with AgBF4 in MeCN afforded a clear another, so the complex superstructure contains a pair of
solution, from which X-ray quality crystals were obtained mono-helical ligands with the same configuration.
following slow diffusion of diethyl ether vapour into the
The Ag···Ag separations are considerably higher than in
solution. The peak at the highest m/z value in the ES mass dinuclear [Ag2(LPh)(MeCN)2][BF4]2, where it was 3.07 Å.
spectrum was at 1691.2, consistent with the 3:2 Ag/L frag- Actually Ag(2) at the end of the sequence (and its symmetry
ment {[Ag3(Lnaph)2][BF4]2}+, implying that the neutral equivalent at the other end) is disordered over two closely
Figure 5. Structure of the complex cation of [Ag3(Lnaph)2](BF4)3·2MeCN, with the two ligands shaded differently for clarity.
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Coordination Behaviour of Bis-Terdentate N-Donor Ligands
Table 5. Selected bond lengths [Å] and angles [°] for [Ag3(Lnaph)2](BF4)3·2MeCN.
Ag(1)–N(81)
2.216(3)
2.216(3)
2.442(3)
2.442(3)
2.234(3)
Ag(2)–N(31)[b]
2.358(4)
2.571(4)
2.330(5)
2.360(4)
2.454(4)
Ag(1)–N(81)#1[a]
Ag(1)–N(71)#1
Ag(2)–N(11)[b]
Ag(3)–N(11)[c]
Ag(1)–N(71)
Ag(3)–N(61)[c]
Ag(2)–N(61)[b]
Ag(3)–N(21)[c]
Ag(2)–N(21)[b]
2.249(4)
Ag(3)–N(31)[c]
2.590(4)
N(81)–Ag(1)–N(81)#1
N(81)–Ag(1)–N(71)#1
N(81)#1–Ag(1)–N(71)#1
N(81)–Ag(1)–N(71)
N(81)#1–Ag(1)–N(71)
N(71)#1–Ag(1)–N(71)
N(61)–Ag(2)–N(21)
N(61)–Ag(2)–N(31)
N(21)–Ag(2)–N(31)
149.64(16)
133.99(10)
71.15(10)
71.15(10)
133.99(10)
89.64(14)
154.59(11)
117.07(12)
72.34(13)
N(61)–Ag(2)–N(11)
N(21)–Ag(2)–N(11)
N(31)–Ag(2)–N(11)
N(11)–Ag(3)–N(61)
N(11)–Ag(3)–N(21)
N(61)–Ag(3)–N(21)
N(11)–Ag(3)–N(31)
N(61)–Ag(3)–N(31)
N(21)–Ag(3)–N(31)
111.63(13)
67.05(14)
130.67(13)
116.11(14)
67.96(15)
130.54(19)
131.13(15)
104.52(15)
65.20(13)
[a] Symmetry transformations used to generate equivalent atoms: #1 –x + 2, y, –z + 1/2. [b] Ag(2) has a site occupancy of 58%. [c] Ag(3)
has a site occupancy of 42%.
Figure 6. Two views of the structure of the complex cation of [Cd6(Lnaph)6](ClO4)12: (a) a face-on view, with the ligands shaded alternately
dark and light for clarity, emphasising the cyclic helical structure and the encapsulated anion in the centre; (b) an edge-on view showing
the shallow bowl shape of the cation.
Eur. J. Inorg. Chem. 2007, 4770–4780
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4775

N. K. Al-Rasbi, H. Adams, L. P. Harding, M. D. Ward
FULL PAPER
spaced sites, with the Ag(1)···Ag(2) separation being 3.35 Å a single component crystallises preferentially such that so-
and Ag(1)···Ag(2Ј) being 3.88 Å, such that argentophilic in- lid-state studies indicate that only a single product has
1
teractions are clearly much less significant than for formed. Accordingly we examined the H NMR spectrum
[Ag2(LPh)(MeCN)2][BF4]2. The structure of this complex and electrospray mass spectra of redissolved crystals of
1
may be compared with those of other linear polynuclear [Cd6(Lnaph)6](ClO4)12. The H NMR spectrum in CD3CN
complexes of AgI with polypyridine-type ligands.[16]
showed no evidence for a mixture of species being present,
Reaction of Lnaph with Cd(ClO4)2 in MeCN (1:1 ratio), with a clean spectrum being observed indicative of a struc-
followed by diffusion of diethyl ether vapour into the result- ture with all ligands in a chiral twofold symmetric environ-
ant solution, afforded X-ray quality colourless needles. On ment, viz. half of the ligand being unique, and the two CH2
the basis of the common preference of CdII for six-coordi- protons being inequivalent (diastereotopic) and coupled to
nate geometry, we were expecting a dinuclear double helic- one another (AB doublets) as a consequence of the chirality
ate to form similar to what we observed for [M2(LPh)2]- of the helicate.
[ClO4]4 (M = Ni, Cu). Instead however the structure is that
The ES mass spectrum however reveals more compli-
of a circular hexanuclear helicate [Cd6(Lnaph)6](ClO4)12 cated behaviour in solution that is not apparent from the
(Figure 6), in which the 1:1 ratio of metal ions to ligands 1H NMR spectrum (Figure 7). The most intense peak at
ensures that each CdII centre is in a six-coordinate geometry m/z 809.1 is ascribable to the mononuclear fragment
(Cd–N separations lie in the range 2.21–2.41 Å, see {Cd(Lnaph)(ClO4)}+, implying either that dissociation of the
Table 6). There are two significant non-covalent interac- complex occurs in solution, or that fragmentation occurs
tions involved, beyond the metal-ligand bonding, which ap- under mass spectroscopic conditions. The latter explanation
1
pear to play a significant role in the structure. Firstly, each is likely to be correct as the H NMR spectrum shows that
of the six naphthyl units is sandwiched between two pyridyl- the main species in solution is chiral, i.e. at least a
pyrazole chelating units (from different ligands) to form a [Cd2(Lnaph)2]4+ dinuclear double helicate. More interest-
three-layer π-stack with separations of ca. 3.5 Å between ingly, at higher m/z values are numerous much weaker peaks
the approximately parallel layers. Secondly, there is a per- (Ͻ 2% of intensity of the main peak at m/z 809.1) whose
chlorate ion inside the ring which is involved in numerous m/z values match exactly to a range of oligomers ranging
short O···HC contacts with H atoms from the ligands. The from a dimer [the peak at m/z 1717.2 corresponds to
anion is not actually centrally located in the cavity because {Cd2(Lnaph)2(ClO4)3}4+, presumably a double helicate] up
the ring is not planar but slightly bowl-shaped; a view of to an 11-mer [the peak at m/z 3229.2 corresponds to
the structure emphasising this is in Figure 6 (b).
{Cd11(Lnaph)11(ClO4)9}2+, presumably a large cyclic helical
assembly of the same nature as the crystal structure]. Al-
together, peaks corresponding to {Cd(Lnaph)}n oligomers
with n = 2, 4, 5, 7, 8, 10, 11 can be identified unambigu-
ously; and a peak at m/z 2624.2 could correspond to either
the n = 3 species {Cd3(Lnaph)3(ClO4)5}+ or the n = 6 species
{Cd6(Lnaph)6(ClO4)10}2+ (or both, superimposed). It is clear
that in solution an equilibrium mixture of cyclic helicates
species exists.[10b] The fact that this is not apparent in the
NMR spectrum implies either that they all have essentially
Table 6. Selected bond lengths [Å] for [Cd6(Lnaph)6](ClO4)12.
Cd(1)–N(471) 2.301(7)
Cd(1)–N(521) 2.305(6)
Cd(1)–N(531) 2.325(7)
Cd(1)–N(461) 2.331(6)
Cd(1)–N(511) 2.334(6)
Cd(1)–N(481) 2.371(7)
Cd(2)–N(421) 2.294(6)
Cd(2)–N(371) 2.312(6)
Cd(2)–N(411) 2.325(7)
Cd(2)–N(431) 2.343(8)
Cd(2)–N(361) 2.349(7)
Cd(2)–N(381) 2.357(6)
Cd(3)–N(271) 2.229(8)
Cd(3)–N(321) 2.288(7)
Cd(3)–N(261) 2.295(7)
Cd(3)–N(331) 2.309(7)
Cd(3)–N(311) 2.363(6)
Cd(3)–N(281) 2.474(9)
Cd(4)–N(221)
Cd(4)–N(171)
Cd(4)–N(231)
Cd(4)–N(161)
Cd(4)–N(211)
Cd(4)–N(181)
Cd(5)–N(131)
Cd(5)–N(121)
Cd(5)–N(661)
Cd(5)–N(671)
Cd(5)–N(681)
Cd(5)–N(111)
Cd(6)–N(571)
Cd(6)–N(631)
Cd(6)–N(611)
Cd(6)–N(561)
Cd(6)–N(621)
Cd(6)–N(581)
2.271(6)
2.301(7)
2.302(8)
2.346(7)
2.358(8)
2.406(7)
2.213(9)
2.216(9)
2.312(10)
2.317(10)
2.352(11)
2.380(10)
2.208(10)
2.323(9)
2.326(8)
2.338(9)
2.342(9)
2.451(9)
Circular helicates have been reported by several
groups[10,17] and, in addition to their appealing structures,
can have two features of interest. Firstly, there is often an
anion located in the centre of the cavity which has acted
as a template to induce assembly of the metal/ligand array
around it. Thus, use of a differently-sized templating anion
can lead to a larger circular helicate containing more metal
ions and more ligands in the peripheral assembly to accom-
modate a larger anion in the central cavity. Secondly, there
can be a dynamic equilibrium in solution between dif-
Figure 7. Part of the electrospray mass spectrum of redissolved
crystals of [Cd6(Lnaph)6](ClO4)12, showing the presence of a range
ferently-sized assemblies (M3L3, M4L4, M5L5 etc.), even if of cyclic oligomers in solution.
4776
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Eur. J. Inorg. Chem. 2007, 4770–4780

Coordination Behaviour of Bis-Terdentate N-Donor Ligands
identical NMR spectra, or that one species is present in of [Cd6(Lnaph)6](ClO4)12 could include the aromatic π-stack-
abundance and dominates the NMR spectrum, with the ing between the naphthyl units, and the ability of CdII to
minor components being invisible. Either possibility is per- tolerate a more highly distorted coordination environment
fectly plausible.
than CuII or NiII on stereoelectronic grounds.
A final interesting point about these complexes of Lnaph
However, although it is tempting to try and rationalise
is their luminescence spectra. The free ligand has a charac- such structural variations in a facile manner, it is not appro-
teristic intense naphthalene-based fluorescence band at priate to over-do this for two reasons. Firstly, the number
347 nm. For the AgI complex [Ag3(Lnaph)2](BF4)3 in MeCN of variables involved is large: some of the more obvious
solution, the fluorescence is reduced in intensity by about factors include the charge and radius of the metal cation;
90% but remains at exactly the same wavelength. In stereoelectronic preferences arising from partially filled d-
[Cd6(Lnaph)6](ClO4)12 in MeCN solution however the fluo- shells [for CuII and NiII]; the presence of attractive Ag···Ag
rescence is significantly red-shifted, to 363 nm (Figure 8). interactions in the AgI complexes; the nature of the anion,
We ascribe this to the extensive aromatic stacking of the which may exert a templating effect in the hexanuclear CdII
emissive naphthyl units between pyridyl/pyrazolyl units of circular helicate; and the presence of other supramolecular
adjacent ligands in the cyclic helical array (see Figure 6), interactions such as aromatic π-stacking between ligands.
which results in stabilisation of the naphthyl-based π-π* ex- Secondly, the solid-state structures are not necessarily
cited state and hence a red-shift of the emission.[18] Even if thermodynamic minima but may represent kinetically stable
other cyclic oligomers are present in solution, as the ES assemblies which happened to crystallise well; for example
mass spectrum suggests, similar structures are plausible in the ES mass spectroscopic data for [Cd6(Lnaph)6](ClO4)12
which this type of stacking is retained. Thus the red-shifted clearly shows that there is a mixture of oligomers in solu-
luminescence of the ligand is indicative of the nature of the tion. Rationalising the appearance of one kinetic product
self-assembled structure formed in solution.
in the solid state therefore does not tell the whole story.
Experimental Section
General Details: 6-Acetyl-2,2Ј-bipyridine,[19] 6-(pyrazol-3-yl)-2,2Ј-
bipyridine,[12] 2,6-bis(bromomethyl)pyridine,[20] and 2,3-bis(bromo-
methyl)naphthalene[21] were prepared as described previously.
Other organic reagents and metal salts were obtained from Aldrich
and Avocado and used as received. Instrumentation used for spec-
1
troscopic analysis were as follows: H NMR spectra, a Bruker AC
250 spectrometer. EI mass spectra, a VG AutoSpec magnetic sector
instrument; ES mass spectra, a Bruker MicroTOF instrument in
positive ion mode, with capillary exit and first skimmer voltages of
30 V and 60 V respectively. UV/Vis absorption spectra, a Cary 50
spectrophotometer, using MeCN solutions of the complexes.
Figure 8. Luminescence spectra of solutions of (i) [Ag3(Lnaph)2]-
(BF4)3 and (ii) [Cd6(Lnaph)6](ClO4)12 in MeCN, concentration ca.
10–6 ; the solutions had the same optical density at the excitation
wavelength.
Syntheses of Ligands
LPh
:
A
mixture of 1,2-bis(bromomethyl)benzene (0.539 g,
2.04 mmol), 6-(pyrazol-3-yl)-2,2Ј-bipyridine (0.852 g, 3.84 mmol),
10  aqueous NaOH (3 cm3), NBu4OH (3 drops of 40% aqueous
solution) and toluene (15 cm3) was heated with vigorous stirring to
85 °C for 24 h. After cooling, the organic layer was washed with
water and then dried with MgSO4. The solvent was removed to
Conclusions
This series of relatively simple bridging ligands has gen-
erated a range of structures in which the ligands all span
two metal ions – an essential prerequisite for formation of
polynuclear assemblies – resulting in double helicates, a me-
socate, some single-stranded helicates based on AgI, and a
cyclic hexanuclear helicate based on CdII. In some cases
there are obvious factors controlling the structures, such as
the presence of Ag···Ag interactions in the AgI complexes.
In other cases apparently very similar metal/ligand combi-
nations generate quite different structures, cf. the difference
between the dinuclear double helicates [M2(LPh)2][ClO4]4
afford
a pale yellow solid which was purified by column
chromatography (5:95 EtOAc/CH2Cl2 on alumina) to give 0.861 g
(65%) of LPh as a white powder. EI MS: m/z (%) = 546 (3) [M+]
and 324 (35) [M+ – pzbpy]. 1H NMR (250 MHz, CDCl3): δ = 8.67
(d, 2 H, bpy H6Ј), 8.57 (d, 2 H, bpy H3Ј), 8.33 (dd, 2 H, bpy H3),
8.01 (dd, 2 H, bpy H5), 7.76–7.85, (m, 4 H, bpy H5Ј and H4Ј), 7.37
(d, 2 H, pz H5), 7.24–7.33 (m, 4 H, bpy H4 and phenyl H3 and H4),
7.17 (m, 2 H, phenyl H2 and H5), 7.07 (d, 2 H, pz H4) and 5.49 (s,
4 H, CH2) ppm. C34H26N8 (546.63): calcd. C 74.7, H 4.8, N 20.5;
found C 74.9, H 4.7, N 20.3.
Lpy:
2.27 mmol)
A
mixture of 2,6-bis(bromomethyl)pyridine (0.602 g,
and 6-(pyrazol-3-yl)-2,2Ј-bipyridine (1.00 g,
(M
= Ni, Cu) and the cyclic hexanuclear helicate
[Cd6(Lnaph)6](ClO4)12; both of these structural types have
arisen from combination of bis-terdentate ligands (with
similar spacers separating the binding sites) with six-coordi-
4.50 mmol) were reacted in exactly the same manner as described
above for the synthesis of LPh. The crude product was purified by
column chromatography (1% MeOH in CH2Cl2, on alumina) to
nate metal ions. Significant factors favouring the formation give 0.593 g (47%) of Lpy as yellow foam. EI MS: m/z (%) = 547
Eur. J. Inorg. Chem. 2007, 4770–4780
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4777

N. K. Al-Rasbi, H. Adams, L. P. Harding, M. D. Ward
FULL PAPER
(5) [M+] and 325 (100) [M+ – pzbpy]. 1H NMR (250 MHz, CDCl3):
δ = 8.66 (d, 2 H, bipy H6Ј), 8.58 (d, 2 H, bpy H3Ј), 8.32 (dd, 2 H,
bpy H3), 8.02 (dd, 2 H, bpy H5), 7.83 (t, 4 H, bpy H4Ј and H5Ј),
7.61–7.52 (m, 3 H, py H3, H4 and H5), 7.33 (t, 2 H, bpy H4), 7.11
(d, 2 H, pz H5), 6.93 (d, 2 H, pz H4) ppm. C33H25N9·H2O (565.63):
calcd. C 70.1, H 4.8, N 22.3; found C 70.5, H 4.6, N 22.4.
709.1 {[Cu2LPh2](ClO4)2}2+
{[Cu2LPh2]}4+
Cu2C68H52N16Cl4O16·2H2O (1654.19): calcd.
49.4, H 3.4, N 13.5; found C 48.3, H 3.3, N 13.3.
, , 305.1
439.7 {[Cu2LPh2](ClO4)}3+
.
C
[Ag2LPh(MeCN)2](BF4)2: Yield 0.051 g (55%). 1H NMR
(250 MHz, CD3CN): δ = 8.06 (d, 2 H, bpy H6Ј), 7.90–7.97 (m, 4
H, bpy H3Ј, H3), 7.75 (d, 2 H, bpy H5), 7.68 (d, 2 H, bpy H5Ј),
7.56 (d, 4 H, phenyl H2, H3), 7.53 (d, 2 H, pz H5), 7.44 (m, 2 H,
py H4Ј), 7.12 (dt, 2 H, py H4), 6.95 (d, 2 H, pz H4), 5.32 (s, 4 H,
CH2) ppm. UV/Vis (MeCN): λmax/nm (ε, dm3 mol–1 cm–1) = 238
Lnaph: A mixture of 2,3-bis(bromomethyl)naphthalene[9] (0.314 g,
1.00 mmol) and 6-(pyrazol-3-yl)-2,2Ј-bipyridine were reacted in the
same manner as described above for the synthesis of LPh. The crude
solid was purified by column chromatography (0.5% MeOH in
CH2Cl2, on alumina) to give 0.390 g (69%) of yellow powder. EI-
MS: m/z (%) = 596 (5) [M+], 374 (100) M+ – pzBipy]. 1H NMR
(250 MHz, CDCl3): δ = 8.65 (d, 2 H, bipy H6Ј), 8.56 (d, 2 H, bipy
H3Ј), 8.33 (dd, 2 H, bipy H3), 8.04 (dd, 2 H, bipy H5), 7.71–7.85,
(m, 6 H, bipy H5Ј, H4Јand naphthyl H5/H8), 7.59 (s, 2 H, naphthyl
H1/H4) 7.43–7.47 (m, 2 H, naphthyl H6/H7), 7.43 (d, 2 H, pz H5),
7.24 (t, 2 H, bipy H4), 7.10 (d, 2 H, pz H4) and 5.56 (s, 4 H, CH2)
ppm. C38H28N8 (596.69): calcd. C 76.5, H 4.7, N 18.8; found C
76.1, H 4.7, N 18.4.
(40000), 265 (sh), 310 (19400). ES MS: m/z
=
849.0
{[Ag2LPh][BF4]}+, 380.0 {[Ag2LPh]}2+
.
C38H32Ag2B2F8N10
(1018.07): calcd. C 44.8, H 3.2, N 13.8; found C 44.5, H 2.9, N
13.4.
[Ni2Lpy2](BF4)4: Yield 0.035 g (49%). UV/Vis (MeCN): λmax/nm (ε,
dm3 mol–1 cm–1) = 247 (54800), 326 (19600), 845 (83). ES MS: m/z
=
692.2 {[Ni2Lpy2](BF4)2}2+ 433.1 {[Ni2Lpy2](BF4)}3+
, , 302.6
{[Ni2Lpy2]}4+. This sample was hygroscopic and gave variable ele-
mental analyses consistent with the presence of several molecules
of water per complex.
Syntheses of Complexes
[Ag3(Lnaph)2](BF4)3: Yield 0.034 g (46%). UV/Vis (MeCN): λmax/nm
(ε, dm3 mol–1 cm–1) = 227 (160000), 260 (89500), 310 (37100). ES
MS: m/z = 1691.2 {[Ag3(Lnaph)2][BF4]2}+, 899.1 {[Ag2(Lnaph)]-
[BF4]}+. C76H56Ag3B3F12N16·2H2O (1813.42): calcd. C 50.3, H 3.3,
N, 12.4; found C 50.3, H 3.0, N 12.3.
Complexes were prepared by the reaction of the ligand (0.05 g)
with the appropriate metal salt [in a 2:1 metal/ligand ratio for AgI
complexes and in a 1:1 ratio for the NiII, CoII, CuII, and CdII com-
plexes] in nitromethane or acetonitrile. Diffusion of diisopropyl
ether vapour into the resulting solutions afforded single crystals
suitable for X-ray crystallography and other analyses. Characterisa-
tion data for the complexes are as follows.
[Cd6(Lnaph)6](ClO4)12: Yield 0.032 g (42%). 1H NMR (250 MHz,
CD3CN): δ = 8.44 (d, 2 H, bipy H6Ј), 8.43 (br, 2 H, bipy H3), 8.29
(m, 2 H, bipy H3Ј), 8.28 (m, 2 H, bipy H5), 8.13 (s, 2 H, naphthyl
H1/H4), 7.99 (t, 2 H, bipy H5Ј), 7.95 (d, 2 H, naphthyl H5/H8), 7.90
(d, 2 H, pz H5), 7.65–7.68 (2 H, naphthyl H6/H7), 7.52 (dt, 2 H,
bipy H4Ј), 7.31 (dt, 2 H, bipy H4Ј), 7.27 (dt, 2 H, pz H4), 5.38 (d,
2 H, CH2), 5.76 (d, 2 H, CH2) ppm. UV/Vis (MeCN): λmax/nm (ε,
dm3 mol–1 cm–1) = 320 (22800), 268 (30200), 226 (55700). ES MS:
m/z = 809.1 {[Cd(Lnaph)](ClO4)}+, 1717.2 {[Cd2(Lnaph)2](ClO4)3}+,
[Ni2LPh2](ClO4)4: Yield: 0.050 g (68%). UV/Vis (MeCN): λmax/nm
(ε, dm3 mol–1 cm–1) = 245 (32400), 260 (32600), 327 (18800), 340
(16700), 548 (29), 848 (71). ESMS: m/z = 704.1 {[Ni2LPh2]-
(ClO4)2}2+
,
436.4 {[Ni2LPh2](ClO4)}3+
,
302.6 {[Ni2LPh2]}4+
.
Ni2C68H52N16Cl4O16·2H2O (1644.48): calcd. C 49.7, H 3.4, N 13.6;
found C 49.3, H 3.5, N 13.6.
[Cu2LPh2](ClO4)4: Yield 0.046 g (62%). UV/Vis (MeCN): λmax/nm 2624.2 {[Cd3(Lnaph)3](ClO4)5}+, 3532.2 {[Cd4(Lnaph)4](ClO4)7}+,
(ε, dm3 mol–1 cm–1) = 210 (67600), 245 (23000), 686 (69). ES MS:
1717.2 {[Cd4(Lnaph)4](ClO4)6}2+, 2170.2 {[Cd5(Lnaph)5](ClO4)8}2+
2624.2 {[Cd6(Lnaph)6](ClO4)10}2+, 3079.2 {[Cd7(Lnaph)7](ClO4)12}2+
,
,
m/z = 1518.1 {[Cu2LPh2](ClO4)3}+, 979.1 {[Cu4LPh4](ClO4)5}3+
,
Table 7. Crystallographic data.
Complex
LPh
[Ni2(LPh)2][ClO4]4·
MeCN
[Cu2(LPh)2][ClO4]4·
2MeCN·0.5H2O
[Ag2(LPh)(MeCN)2][BF4]2
Empirical formula
Formula mass
T [K]
Crystal system, space group
a [Å]
b [Å]
c [Å]
C34H26N8
546.6
100(2)
monoclinic, P21/n
10.181(5)
23.562(12)
11.711(6)
90
95.079(16)
90
C70H55Cl4N17Ni2O16
1649.53
C72H59Cl4Cu2N18O16.5 C38H32Ag2B2F8N10
1709.25
100(2)
triclinic, P1
13.73(4)
14.37(4)
21.66(6)
1018.1(0)
150(2)
triclinic, P1
12.6315(16)
13.1407(18)
13.6001(16)
72.745(7)
150(2)
triclinic, P1
¯
¯
¯
13.6741(18)
14.3285(19)
21.426(3)
102.679(3)
93.931(3)
113.108(2)
3710.5(9)
α [°]
β [°]
102.22(5)
94.69(3)
83.475(7)
γ [°]
112.83(4)
3786(17)
62.214(6)
1906.4(4)
V [Å3]
2798(2)
Z
4
2
2
2
Dcalcd. [Mg/m3]
µ [mm–1]
1.298
0.081
1.476
0.730
1.499
0.783
1.774
1.112
Crystal size [mm]
Reflections collected
Independent reflections
Data/restraints/parameters
Final R indices[a]
Largest diff. peak/hole [eÅ–3]
0.14ϫ0.06ϫ0.04
25235
4804 (Rint = 0.126)
4804/0/380
0.0576, 0.1518
+0.22/–0.30
0.32ϫ0.14ϫ0.09
32968
13042 (Rint = 0.108)
13042/5/982
0.0644, 0.1675
+0.77/–0.73
0.27ϫ0.20ϫ0.07
83182
14172 (Rint = 0.059)
14172/8/1020
0.0456, 0.1199
+0.92/–0.63
0.35ϫ0.16ϫ0.08
43039
6605 (Rint = 0.0333)
6605/0/543
0.0784, 0.1934
+2.42/–2.19
[a] The first value is R1, based on “observed data” with I Ͼ 2σ(I); the second value is wR2, based on all data.
4778 Eur. J. Inorg. Chem. 2007, 4770–4780
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Coordination Behaviour of Bis-Terdentate N-Donor Ligands
Table 8. Crystallographic data.
Complex
[Ni2(LPy)2][BF4]4·2MeNO2
[Ag3(Lnaph)2](BF4)3·2MeCN
[Cd6(Lnaph)6](ClO4)12
Empirical formula
Formula mass
C68H56B4F16N20Ni2O4
1681.98
C80H62Ag3B3F12N18
1859.52
C228H168Cd6Cl12N48O48
5447.90
T [K]
100(2)
100(2)
100(2)
monoclinic, P21/n
25.350(2)
26.015(2)
41.398(3)
Crystal system, space group
a [Å]
b [Å]
c [Å]
monoclinic, P21/n
12.3638(7)
12.3036(7)
23.4297(13)
90
monoclinic, C2/c
15.1250(9)
23.7334(15)
20.9965(17)
90
α [°]
90
β [°]
97.427(4)
90
3534.2(3)
2
1.581
0.641
103.930(3)
90
7315.4(9)
4
1.688
0.887
95.762(5)
90
27163(4)
4
1.332
0.654
γ [°]
V [Å3]
Z
Dcalcd. [Mg/m3]
µ [mm–1]
Crystal size [mm]
Reflections collected
Independent reflections
Data/restraints/parameters
Final R indices[a]
Largest diff. peak/hole [eÅ–3]
0.18ϫ0.16ϫ0.14
49325
7161 (Rint = 0.0836)
7161/4/514
0.0680, 0.1934
+0.94/–0.72
0.06ϫ0.04ϫ0.03
55542
8612 (Rint = 0.0546)
8612/83/581
0.0457, 0.1267
+1.66/–1.01
0.24ϫ0.16ϫ0.06
304166
47783 (Rint = 0.1166)
47783/1419/2197
0.1195, 0.3615
+2.33/–1.38
[a] The first value is R1, based on “observed data” with I Ͼ 2σ(I); the second value is wR2, based on all data.
2018.8 {[Cd7(Lnaph)7](ClO4)11}3+, 3532.2 {[Cd8(Lnaph)8](ClO4)14}2+
2321.5 {[Cd8(Lnaph)8](ClO4)13}3+, 2927.2 {[Cd10(Lnaph)10](ClO4)17}3+
,
,
disordered over two positions with the same fractional occupancies
(0.58/0.42). None of the other structural determinations presented
3229.2
{[Cd11(Lnaph)11](ClO4)19}3+
.
C228H168Cd6Cl12N48O48· any significant problems.
10H2O (5628.19): calcd. C 48.7, H 3.4, N 11.9; found C 48.0, H
3.0, N 11.4.
CCDC-653275 to -653281 contain the supplementary crystallo-
graphic information for this paper. These data can be obtained free
of charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Crystallography
X-ray crystallographic data are summarised in Tables 7 and 8. In
each case a suitable crystal was coated with hydrocarbon oil and
attached to the tip of a glass fibre and transferred to a Bruker
APEX-2 CCD diffractometer (graphite-monochromated Mo-Kα
radiation, λ = 0.71073 Å) under a stream of cold N2. After collec-
tion and integration the data were corrected for Lorentz and polari-
sation effects and for absorption by semi-empirical methods (SAD-
ABS) based on symmetry-equivalent and repeated reflections.[22]
The structures were solved by direct methods or heavy atom Pat-
terson methods and refined by full-matrix least-squares methods
on F2. Hydrogen atoms were placed geometrically and refined with
a riding model and with Uiso constrained to be 1.2 (1.5 for methyl
groups) times Ueq of the carrier atom. Structures were solved and
refined using the SHELX suite of programs.[23] Significant bond
lengths and angles for the structures of the metal complexes are in
Tables 1–6. Particular problems associated with the refinements are
as follows.
Acknowledgments
We thank theGovernment of the Sultanate of Oman for a PhD
studentship to N. K. A.
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Received: July 9, 2007
Published Online: August 29, 2007
4780
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Eur. J. Inorg. Chem. 2007, 4770–4780