A trimetal chain cocooned by two heptadentate polypyridylamide ligands

Article abstract of DOI:10.1039/b612076h

Compounds of nickel in which a chain of three metal atoms is closely embraced by two interlocking heptadentate dianions derived from a chain of five pyridyl groups linked at the 2, or 2 and 6, positions by four amide nitrogen atoms are reported. This new type of extended metal atom chain (EMAC) compound differs from earlier ones in that ligand exchange at the axial positions cannot occur, because the axial ligands are part of the entire ligand. Four such compounds, all crystallographically characterized, are reported. This work is a proof-of-concept project that will be extended to other metals with these and other homologous ligands. The Royal Society of Chemistry.

Full text of DOI:10.1039/b612076h

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A trimetal chain cocooned by two heptadentate polypyridylamide ligands
F. Albert Cotton,* Hui Chao, Carlos A. Murillo* and Qingsheng Wang
Received 22nd August 2006, Accepted 25th September 2006
First published as an Advance Article on the web 5th October 2006
DOI: 10.1039/b612076h
Compounds of nickel in which a chain of three metal atoms is closely embraced by two interlocking
heptadentate dianions derived from a chain of five pyridyl groups linked at the 2, or 2 and 6, positions
by four amide nitrogen atoms are reported. This new type of extended metal atom chain (EMAC)
compound differs from earlier ones in that ligand exchange at the axial positions cannot occur, because
the axial ligands are part of the entire ligand. Four such compounds, all crystallographically
characterized, are reported. This work is a proof -of -concept project that will be extended to other
metals with these and other homologous ligands.
smallest possible scale. For EMACs to function as molecular
Introduction
scale wires it must be possible to connect them at each end into
The field of extended metal atom chain (EMAC) compounds
molecular scale circuits. From this point of view, the fact that all
began in 1968 when Ni3(dpa)4Cl2 was reported,1 but did not
EMACs to date have had axial positions where anions or other
develop at all, even when the correct structure, Fig. 1, for this
donors could be attached must be viewed as an asset. On the other
compound was recognized.2 It was not until the very last years of
hand, the lability of axial ligands can be a disadvantage in some
the twentieth century that extensive work in several laboratories3,4
circumstance, such as when an oxidation is accompanied by a
began to reveal the breadth and fascination of the field.5 Two major
lines of experimental development have been: (1) the extension to
other metals, i.e., Cr, Co, Cu, Ru and Rh, and (2) the lengthening
of the metal atom chains by the use of longer polypyridylamide
ligands. There have also been some significant theoretical efforts to
elucidate the electronic structures,6 but these molecules are difficult
to treat rigorously. One of the most seductive characteristics of
the EMACs that have been reported so far is their structural
resemblance to an ordinary, everyday electrical wire, but on the
change of axial ligands.7
We considered that a way to avoid this might entail combining
two of the polypyridyl ligands that run along the metal atom chain
and one of the axial ligands into one continuous chain of donor
atoms. Our work so far is a proof -of -concept project, in which we
have shown that the desired type of ligand can be synthesized and
EMACs cocooned inside the ligands can be made, with nickel as
the first metal to be used.
Results and discussion
Ligand syntheses
Several years ago, the ligand I (Chart 1) was reported along
with a linear nonanickel EMAC,8 but the methods of preparation
were not (and so far as we know never have been) presented in
the literature. The trivial name and abbreviation proposed for
this ligand prior to deprotonation were pentapyridyl tetramine,
H4peptea. To avoid unnecessarily complicating the literature, we
shall continue to use this trivial name and its abbreviation. We have
now made H4peptea-type ligands with alkyl substituents (II and
III) and their trimetal complexes by the route shown in Scheme 1,
whichalsoshows how the compounds are numbered. The synthetic
details are given in the experimental section but it should be noted
that no species with nuclearity higher than three were isolated
nor observed in the mass spectra. A previous preparation of 2 in
which ButOK was used as the base gave only an 8% yield.9 None
of the H4peptea derivatives shown in Scheme 1 have been reported
before.
Fig. 1 Structure of Ni3(dpa)4Cl2 (dpa = N,Nꢀ-dipyridylamide).
Syntheses of trinickel compounds
The preparation of the trimetal complexes was carried out in
refluxing diglyme. The ligand was deprotonated by methyllithium
and nickel chloride then added in the stoichiometric amount. It
Department of Chemistry and Laboratory for Molecular Structure and
Bonding, P. O. Box 30012, Texas A & M University, College Station, Texas,
77842-3012, USA. E-mail: cotton@tamu.edu, murillo@tamu.edu
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Chart 1
is necessary to have extremely dry NiCl2, THF and diglyme. For
optimum results, the NiCl2 must be refluxed in thionyl chloride and
the solvent diglyme must be refluxed with Na/K (1/3) overnight
prior to use. It has been found that high temperature is necessary
to obtain these trinickel EMACs. To subsequently replace the
chloride ions, KPF6 and NaBPh4 were used in CH2Cl2, from which
NaCl and KCl precipitated. The desired products remained in
solution, from which they could be crystallized by layering with
isomeric hexanes.
Crystal structures
Crystallographic studies have shown that it is possible to lock
in donor atoms at the axial positions of an EMAC by making
them part of a large polydentate ligand that runs up one side
and down the other of the central metal atom chain, as shown
simplistically in IV. This is an artificially flattened representation
of one heptadentate ligand together with three metal atoms that it
can embrace. When another such ligand is introduced in a plane
perpendicular to the one shown, and oppositely oriented, each
metal atom becomes fully coordinated and a stable compound
results in which the trimetal unit is cocooned. In this type of
molecule each ligand is twisted to form a capped helix in order
Scheme 1 The synthetic routes for preparation of the ligands and trinickel
complexes.
to relieve repulsion between the hydrogen atoms shown in bold in
IV.
Selected bond distances and angles for compounds 7, 8, 9, 10
are listed in Table 1. For the compound [Ni3(H2epeptea)2]Cl2,
7, which has two ethyl-substituted ligands (4) there are two
◦
˚
Table 1 Selected bond distances (A) and angles ( )
7·4CH3OH·0.5H2Oa
8·0.75C3H6O·0.5H2Oa
9·3C3H6O
10·3CH2Cl2
Ni1 · · · Ni2
Ni2 · · · Ni3
Niouter–N(av)
Niinner–N(av)
Ni–Naxial (av)
2.378(2)
2.382(2)
2.056[9]
1.885[8]
1.990[9]
2.343(1)
2.347(1)
2.065[5]
1.887[6]
1.978[8]
2.3527(9)
2.3560(9)
2.057[4]
1.888[5]
1.986[6]
2.382(1)
2.386(1)
2.068[6]
1.888[7]
2.015[9]
Ni1 · · · Ni2 · · · Ni3
N14–Ni1 · · · Ni2
N5–Ni3 · · · Ni2
178.57(7)
179.2(2)
178.3(2)
179.54(5)
178.8(2)
179.7(2)
179.26(4)
179.2(1)
179.6(1)
178.96(6)
179.2(2)
179.2(2)
a Only data for one of the two crystallographically independent molecules in 7 and 8 are provided because they are very similar.
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¯
crystallographically independent, but chemically equivalent
molecules. This compound crystallizes in the monoclinic space
group P21/c, and the structure of the cation is shown in Fig. 2.
The Ni · · · Ni separations in one of the independent molecules
8 has PF6 anions and crystallizes in the triclinic space group P1
with two crystallographically independent molecules and 9, which
has BPh4 anions, crystallizes in the monoclinic space group P21/c.
The structure of the cation in 9 is shown in Fig. 3. The Ni · · · Ni
separations are slightly different in these cations, 2.3527(9) and
˚
are 2.378(2), and 2.382(2) A and similar to those in the other
molecule. The Ni · · · Ni · · · Ni unit is essentially linear, having an
angle of 178.57(7)◦. The coordination about the Ni atoms differs
depending on whether they are at the outer edges of the molecular
wire, or inside the wire. The former are square pyramidal while the
latter is square planar. Because of such difference in coordination,
the average Ni–N bond length on the central nitrogen atom is
˚
˚
2.3560(9) A for 9 and 2.343(1) and 2.347(1) A for one of the
crystallographically independent molecules in 8. It is noteworthy
that the latter are the shortest separations between nickel atoms
6+
among all Ni3 species reported to date. Though these distances
are rather short, no bond is expected between the nickel atoms.
˚
∼0.17 A shorter than those for the outer Ni atoms. For the terminal
˚
Ni atoms, the axial Ni–N bond length is ∼0.07 A shorter than
the equatorial Ni–N bond lengths. Compound 10, which also
crystallizes in the monoclinic space group P21/c, has the same
cation as 7 and differs only in the nature of the anions.
Fig. 3 Side view (top) and end view (bottom) for the cation in
[Ni3(mpeptea)2](BPh4)2, 9. Displacement ellipsoids are drawn at the 40%
probability level. Hydrogen atoms are omitted for clarity. The cation in 8,
which has hexafluorophosphate counter-anions is similar.
In all cocooned compounds (7–10), the Ni · · · Ni · · · Ni angles
are very close to 180◦. The trinickel chain is symmetrical, having
roughly D2 symmetry. In comparing the structures of 7–10 with
those having Ni3(dpa)4X2 units, the most obvious difference is that
7–10 are helically wrapped by only two long chain ligands instead
of four dpa ligands.
Fig. 2 Side view (top) and end view (bottom) for the cation in
[Ni3(H2epeptea)2]Cl2, 7. Displacement ellipsoids are drawn at the 40%
probability level. Hydrogen atoms are omitted for clarity. The cation in 10,
which has tetraphenylborate counter-anions is similar.
Conclusion
The concept of having two long, polydentate ligands coordinate
to form a protective cocoon around an EMAC has been shown to
be feasible in the simplest case, where there are only three metal
atoms in the chain, and with nickel as the metal. The ligands
Another pair of salts whose cations are the same,
[Ni3(mpeptea)2]2+, but differ in the nature of the anions is 8 and
9. The ligand mpeptea is derived from 5 in Scheme 1. Compound
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and the complexes have been made in respectable yields and on
a useful scale. With this proof -of -concept successfully completed,
there are now two next steps to take. One is to make analogues of
the complexes reported here with other metals, such as Cr, Co and
Cu, and the other is to try to make EMACs of this new type with
five metal atoms in the chain.
in THF (30 mL), and the mixture stirred for 30 min. A solution
of 2,6-dibromopyridine (14.2 g, 60.0 mmol) in THF (60 mL) was
added to give a greenish grey suspension, which was refluxed at
70 ◦C under a nitrogen atmosphere for 36 h, resulting in a brown
solution. After cooling to room temperature, the solution was
filtered and the solvent was removed under reduced pressure. The
residue was further washed with NH4Cl solution and CH2Cl2. The
grey solid was collected on a frit and air-dried. Yield: 4.04 g, 48%.
1H NMR (DMSO-d6, 300 MHz, d): 9.86 (s, 2H), 7.86 (d, 2H), 7.58
(t, 3H), 7.06 (d, 2H), 7.03 (d, 2H). ESI+ (m/z): 421.8 [M + H]+.
Experimental
General procedures
N,Nꢀ-bis(6ꢀ-bromopyrid-2ꢀ-yl)bismethyl-2,6-
All manipulations were carried out under dry nitrogen us-
ing standard Schlenk techniques. All solvents were either dis-
tilled over appropriate drying agents in a nitrogen atmosphere
or purified by means of a Glass Contour solvent system.
Sodium tetraphenylborate was purchased from Strem. Anhy-
drous nickel chloride, 2,6-dibromopyridine, methylamine (40 wt%
solution in water), sodium hydride, 2-aminopyridine, bis(2-
methoxyethyl) ether, potassium hexafluorophosphate, Pd2(dba)3,
2,2ꢀ-bis(diphenylphosphino)-1,1ꢀ-binaphthyl (BINAP), 18-crown-
6, ButOK and methyllithium (1.6 M in diethyl ether) were
purchased from Aldrich Chemical Co.; methylamine was diluted
to 25 wt% with water before use, and anhydrous nickel chloride,
2,6-dibromopyridine, sodium tetraphenylborate and potassium
hexafluorophosphate were dried overnight under dynamic vacuum
at 70 ◦C prior to use. Other chemicals were used as received;
2-amino-4-ethylpyridine was prepared according to a published
method.10
Synthesis
of
diaminopyridine, 3. A solution of 2,6-dimethylaminopyridine
(1.37 g, 10.0 mmol) in THF (20 mL) was added to a white
suspension of NaH (0.76 g, 30.0 mmol) in THF (20 mL). After
stirring for 30 min, 2,6-dibromopyridine (7.11 g, 30.0 mmol) in
THF (40 mL) was transferred by cannula to give a grey–white
suspension, which was refluxed at 70 ◦C under a nitrogen
atmosphere for 36 h, resulting in a brown suspension. After
cooling to room temperature, the solvent was removed under
reduced pressure to give a pale brown oil. Addition of isomeric
hexanes (50 mL) to the oil precipitated a pale yellow product.
After washing with water (3 × 50 mL) and hexanes (3 × 50 mL),
the pale yellow solid was collected on a frit. Yield: 3.12 g, 69%.
1H NMR (DMSO-d6, 300 MHz, d): 7.71 (t, 1H), 7.53 (t, 2H), 7.23
(d, 2H), 7.10 (d, 2H), 6.94 (d, 2H), 3.44 (s, 6H). Mass spectrum,
ESI+ (m/z): 450.0 [M + H]+.
Synthesis of N,Nꢀ-bis[6ꢀ-(4ꢀꢀ-ethylpyrid-2ꢀꢀ-yl)aminopyrid-2ꢀ-yl]-
2,6-diaminopyridine (H4epeptea), 4. N,Nꢀ-Bis(6ꢀ-bromopyrid-2ꢀ-
yl)-2,6-diaminopyridine (1.68 g, 4.0 mmol) and Pd2(dba)3 (0.13 g,
12 mol %) in dry benzene (60 mL) were placed in a 250 mL round-
bottom flask, and the mixture was stirred for 30 min. Then 2,2ꢀ-
bis(diphenylphosphino)-1,1ꢀ-binaphthyl (BINAP, 0.152 g, 24 mol
%), 18-crown-6 (2.11 g, 8.0 mmol) and ButOK (2.24 g, 20.0 mmol)
in dry benzene (30 mL) were added to the reaction mixture by can-
nula. After stirring for another 30 min, 2-amino-4-ethylpyridine
(1.46 g, 12.0 mmol) in dry benzene (10 mL) was added. The
resulting mixture was stirred and refluxed at 80 ◦C under a nitrogen
atmosphere for 3 days. The reaction mixture was cooled to room
temperature and then quenched with NH4Cl (2.04 g) in aqueous
solution (20 mL). Two phases separated. The organic phase was
saved, and the aqueous phase was extracted twice with chloroform
(2 × 30 mL). The extracts were combined and dried over MgSO4,
and the solvent was removed under vacuum to give the crude
product as a black–red oil, which was further purified by column
chromatography over silica gel (hexanes–ethyl acetate, 3 : 2). The
solvent was removed under reduced pressure, giving a grey powder.
Physical measurements
1H NMR spectra were obtained on a Mercury 300 NMR
spectrometer with chemical shifts referenced to DMSO (d =
2.49 ppm). The 19F NMR spectrum was obtained on an Inova 300
NMR spectrometer (CFCl3, d = 0.0 ppm). Mass spectrometry data
were recorded at the Laboratory for Biological Mass Spectrometry
at Texas A & M University. UV-vis spectra were measured on
a Shimadzu UV-2501PC spectrophotometer in dichloromethane
solutions. Elemental analyses were performed by Robertson
Microlit Laboratories, Madison, NJ.
Synthesis of 2,6-dimethylaminopyridine, 1. This compound
was made by a modification of a literature procedure.11 A mixture
of 2,6-dibromopyridine (9.48 g, 40.0 mmol) and a 25% aqueous
solution of methylamine (200 mL, 160 mmol) was sealed in a
pressure reactor (Parr bomb) under a nitrogen atmosphere, and
heated at 190 ◦C for 10 h. The reaction mixture was cooled to room
temperature, diluted with 150 mL of water, filtered, and then 50 mL
of 40% NaOH solution was added to the mixture to neutralize the
acid. Petroleum ether was used to extract the product from the
aqueous solution (4 × 250 mL). The ether extracts were combined
and dried over anhydrous K2CO3. The solvent was removed under
reduced pressure and the white needle solid was collected. Yield:
2.87 g, 52%. 1H NMR (DMSO-d6, 300 MHz, d): 7.04 (t, 1H), 5.83
(q, 2H), 5.54 (d, 2H), 2.67 (d, 6H).
1
Yield: 0.54 g, 27%. H NMR (DMSO-d6, 300 MHz, d): 9.28 (s,
2H), 9.05 (s, 2H), 8.09 (d, 2H), 7.67 (s, 2H), 7.50 (t, 3H), 7.33 (d,
2H), 7.18 (d, 2H), 7.13 (d, 2H), 6.75 (d, 2H), 2.61–2.55 (q, 4H),
1.18 (t, 6H). Mass spectrum, ESI+ (m/z): 504.3 [M + H]+.
Synthesis of N,Nꢀ-bis[(6ꢀ-pyrid-2ꢀꢀ-yl)aminopyrid-2ꢀ-yl]bismethyl-
2,6-diaminopyridine (H2mpeptea), 5. N,Nꢀ-Bis(6ꢀ-bromopyrid-
2ꢀ-yl)bismethyl-2,6-diaminopyridine (1.80 g, 4.0 mmol) and
Pd2(dba)3 (0.13 g, 12 mol %) in dry benzene (60 mL) were
placed in a 250 mL round-bottom flask and the mixture was
Synthesis of N,Nꢀ-bis(6ꢀ-bromopyrid-2ꢀ-yl)-2,6-diaminopyridine,
2. A solution of 2,6-diaminopyridine (2.18 g, 20.0 mmol) in THF
(30 mL) was added to a suspension of NaH (1.51 g, 60.0 mmol)
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stirred for 30 min. To this mixture 2,2ꢀ-bis (diphenylphosphino)-
1,1ꢀ-binaphthyl (BINAP, 0.15 g, 24 mol %), 18-crown-6 (2.11 g,
8.0 mmol) and ButOK (2.24 g, 20.0 mmol) in dry benzene (30 mL)
were added to the reaction mixture by cannula. After stirring
for another 30 min, 2-aminopyridine (1.13 g, 12.0 mmol) in dry
benzene (10 mL) was added. The resulting mixture was stirred
and refluxed at 80 ◦C under a nitrogen atmosphere for 3 days.
After cooling to room temperature, the reaction mixture was
quenched with NH4Cl (2.04 g) aqueous solution (20 mL). Two
phases were formed. The organic phase was saved, and the aqueous
phase was extracted twice with chloroform (2 × 30 mL). The
combined extracts were dried over MgSO4, and the solvent was
then evaporated under vacuum to give a black–red oil, which
was further purified by column chromatography over silica gel
(hexanes–ethyl acetate, 3 : 2, with CH2Cl2 5%). The solvent was
then removed and a pale yellow powder was obtained. Large
crystals were obtained by slow evaporation of a CH2Cl2 solution
of the product. Yield: 0.43 g, 23%. Anal. Calc. for C27H26N9O
(H2mpeptea·H2O): C, 65.82; H, 5.32; N, 25.60%. Found: C, 65.92;
room temperature, during which time a white precipitate of KCl
had formed. This deep purple solution was filtered through Celite
to remove KCl. The dichloromethane was removed under vacuum,
the remaining dark purple solid was re-dissolved in methanol
(3 mL) and further purified on an aluminium oxide column
using methanol–diethyl ether (1 : 2) as the eluent. The product
was then recrystallized in a mixture of acetone–hexanes (5: 20),
producing deep purple plate-like crystals of 8·0.75C3H6O·0.5H2O
after one week. Yield: 32 mg, 88%. Mass spectrum, ESI+ (m/z):
561.1 [Ni3(mpeptea)2]2+. 19F NMR (DMSO-d6, 300 MHz): d =
−
−70.93 ppm (d) (conforming the presence of PF6 anions). UV-
vis (CH2Cl2) kmax/nm (e/M−1 cm−1): 555 (1000).
Preparation of [Ni3(mpeptea)2](BPh4)2, 9. To a mixture of
[Ni3(mpeptea)2]Cl2 (60 mg, 0.05 mmol) and an excess of NaBPh4
(40 mg, 0.12 mmol), was added 15 mL of dichloromethane, giving
a purple solution. The resulting solution was stirred overnight
at room temperature, during which time a white precipitate,
presumably NaCl, had formed. This deep purple solution was
filtered through Celite. The dichloromethane was removed under
vacuum; the remaining dark purple solid was redissolved in
methanol (5 mL) and further purified on an aluminum oxide
column using methanol–diethyl ether (1 : 2) as the eluent. Large
block deep purple crystals of 9·3C3H6O were obtained by slow
diffusion of hexanes (20 mL) into an acetone solution of the
product (5 mL) within a week. Yield: 79 mg, 82%. Anal. Calc. for
C111H104B2N18Ni3O3 (Ni3(mpeptea)2(BPh4)2·3C3H6O): C, 68.87; H,
5.32; N, 13.02%. Found: C, 69.09; H, 5.12; N, 13.01%. Mass
spectrum, ESI+ (m/z): 561.1 [Ni3(mpeptea)2]2+. UV-vis (CH2Cl2)
kmax/nm (e/M−1 cm−1): 555 (950).
1
H, 4.83; N, 25.88%. H NMR (DMSO-d6, 300 MHz, d): 9.52 (s,
2H), 8.19 (d, 2H), 7.75 (d, 2H), 7.61–7.51 (m, 5H), 7.20 (d, 2H),
6.83 (t, 2H), 6.74 (t, 4H), 3.51 (s, 6H). Mass spectrum, ESI+ (m/z):
476.2 [M + H]+.
Preparation of [Ni3(mpeptea)2]Cl2, 6. N,Nꢀ-Bis[(6ꢀ-pyrid-2ꢀꢀ-
yl)aminopyrid-2ꢀ-yl]bismethyl-2,6-diaminopyridine (H2mpeptea,
0.19 g, 0.40 mmol) was dissolved in 15 mL of THF to give a pale
yellow solution. This solution was cooled in a dry ice/acetone
bath, and 0.5 mL of 1.6 M MeLi in diethyl ether (0.8 mmol)
was added slowly. The mixture was allowed to warm to room
temperature to give a yellow suspension, which was transferred
to a flask containing anhydrous NiCl2 (0.078 g, 0.60 mmol) by
cannula. The resulting deep brown suspension was stirred at
room temperature for 2 h, and the solvent was removed under
vacuum. After addition of 15 mL of bis(2-methoxyethyl) ether
(diglyme), the mixture was stirred and refluxed overnight at 180 ◦C
under nitrogen to give a deep purple precipitate. The solvent was
decanted and the remaining precipitate was washed with toluene
(2 × 10 mL), THF (2 × 10 mL), diethyl ether (2 × 10 mL),
hexanes (2 × 10 mL), and then dried under vacuum for 1 h. The
crude product was dissolved in methanol and further purified on
an aluminum oxide column using methanol–diethyl ether (1 : 1)
as the eluent. A purple band was collected and the solvent was
removed under vacuum. The complex was then recrystallized from
CH2Cl2–hexanes. Small deep purple crystals of 6·CH2Cl2·H2O
were formed after one week. Yield: 60 mg, 26%. Anal. Calc.
for C55H50N18Ni3Cl4O (Ni3(mpeptea)2Cl2·CH2Cl2·H2O): C, 50.93;
H, 3.99; N, 19.44%. Found: C, 50.74; H, 4.48; N, 19.40%. Mass
spectrum, ESI+ (m/z): 561.1 [Ni3(mpeptea)2]2+. UV-vis (CH2Cl2)
kmax/nm (e/M−1 cm−1): 556 (1050).
Preparation of [Ni3(H2epeptea)2](BPh4)2, 10. This compound
was synthesized similarly to 9, and the product was recrystallized
from CH2Cl2–hexanes.
X-Ray crystallography
In each case, a suitable crystal attached at the end of a quartz
fiber with a small amount of stopcock grease was placed on
a goniometer head. X-Ray diffraction data for 5, 6·CH2Cl2·
H2O, 7·4CH3OH·0.5H2O, 8·0.75C3H6O·0.5H2O, 9·3C3H6O and
10·3CH2Cl2 were collected at 213 K on a BRUKER SMART 1000
CCD area detector system.12 Data reduction and integration were
performed with the software SAINTPLUS,13 while the absorption
corrections were applied using the program SADABS.14 All the
structures were solved by direct methods and refined using the
SHELXL-97 program.15 In all structures, hydrogen atoms were
added at calculated positions based on a riding model. Some
interstitial molecules and PF6− anions were found to be disordered.
Crystal data are given in Table 2. A displacement ellipsoid plot of
5 is given in Fig. 4.
Preparation of [Ni3(H2epeptea)2]Cl2, 7. This compound was
synthesized similarly to 6, and the product was recrystallized from
methanol–diethyl ether.
Preparation of [Ni3(mpeptea)2](PF6)2, 8. A flask containing
[Ni3(mpeptea)2]Cl2 (30 mg, 0.025 mmol) and a 20% molar excess
of KPF6 (11 mg, 0.06 mmol) was charged with 15 mL of
dichloromethane. The suspended solids slowly dissolved, giving
a purple solution. The resulting solution was stirred overnight at
CCDC reference numbers 618416 (5), 618417 (7·4CH3OH·
0.5H2O), 618491 (8·0.75C3H6O·0.5H2O), 618490 (9·3C3H6O) and
618418 (10·3CH2Cl2).
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b612076h
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Table 2 Crystallographic data
5
7·4CH3OH·0.5H2O
8·0.75C3H6O·0.5H2O
9·3C3H6O
10·3CH2Cl2
Formula
Mr
C27H25N9
C62H71Cl2N18Ni3O4.50
1387.39
Monoclinic
P21/c
21.001(5)
44.077(11)
13.966(3)
90
98.094(5)
90
12799(5)
8
213
0.71073
1.439
0.0755, 0.1718
0.1478, 0.2092
C56.25H50.50F12Ni3N18O1.25P2
1464.72
Triclinic
¯
P1
C111H104B2N18Ni3O3
1936.88
Monoclinic
P21/c
25.708(5)
15.112(3)
26.789(5)
90
109.406(3)
90
9816(3)
4
213
C109H100B2Cl6N18Ni3
2072.52
Monoclinic
P21/c
23.186(4)
15.723(3)
28.092(4)
90
100.041(3)
90
10084(3)
4
213
0.71073
1.365
0.0929, 0.2216
0.1563, 0.2625
475.56
Orthorhombic
Fdd2
17.578(3)
25.708(5)
10.673(2)
90
90
90
4823(2)
8
213
Crystal system
Space group
˚
a/A
13.986(7)
14.116(7)
31.151(15)
85.761(8)
78.517(8)
80.128(9)
5933(5)
4
213
0.71073
1.656
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
3
˚
V/A
Z
T/K
˚
k/A
0.71073
1.310
0.0435, 0.1097
0.0529, 0.1168
0.71073
1.311
0.0600, 0.1454
0.1206, 0.1776
Dc/g cm−3
R1,a wR2b (I > 2rI)
0.0617, 0.1457
0.1109, 0.1767
R1,a wR2b (all data)
ꢀ
ꢀ
ꢀ
ꢀ
a R1 = ꢁFo| − |Fcꢁ/ |Fo|. b wR2 = [ [w(Fo − Fc2)2]/ [w(Fo2)2]]1/2
.
2
C.-Y. Yeh, G.-H. Lee, J.-M. Fang and S.-M. Peng, Dalton Trans., 2006,
2106; (j) C.-H Chien, J.-C. Chang, C.-Y. Yeh, G.-H. Lee, J.-M. Fang, Y.
Song and S.-M. Peng, Dalton Trans., 2006, 3249.
4 (a) F. A. Cotton, L. M. Daniels, C. A. Murillo and I. Pascual, J. Am.
Chem. Soc., 1997, 119, 10223; (b) F. A. Cotton, L. M. Daniels, G. T.
Jordan, IV and C. A. Murillo, J. Am. Chem. Soc., 1997, 119, 10377;
(c) F. A. Cotton, C. A. Murillo and X. Wang, J. Chem. Soc., Dalton
Trans., 1999, 3327; (d) R. Cle´rac, F. A. Cotton, L. M. Daniels, K. R.
Dunbar, K. Kirschbaum, C. A. Murillo, A. A. Pinkerton, A. J. Schultz
and X. Wang, J. Am. Chem. Soc., 2000, 122, 6226; (e) R. Cle´rac, F. A.
Cotton, K. R. Dunbar, C. A. Murillo, I. Pascual and X. Wang, Inorg.
Chem., 1999, 38, 2655; (f) F. A. Cotton, L. M. Daniels, T. Lu, C. A.
Murillo and X. Wang, J. Chem. Soc., Dalton Trans., 1999, 517; (g) F. A.
Cotton, L. M. Daniels, C. A. Murillo and X. Wang, Chem. Commun.,
1999, 2461; (h) F. A. Cotton, L. M. Daniels, C. A. Murillo and I.
Pascual, Inorg. Chem. Commun., 1998, 1, 1; (i) R. Cle´rac, F. A. Cotton,
L. M. Daniels, K. R. Dunbar, C. A. Murillo and I. Pascual, Inorg.
Chem., 2000, 39, 752; (j) R. Cle´rac, F. A. Cotton, K. R. Dunbar, T.
Lu, C. A. Murillo and X. Wang, J. Am. Chem. Soc., 2000, 122, 2272;
(k) J. F. Berry, F. A. Cotton and C. A. Murillo, Organometallics, 2004,
23, 2503; (l) J. F. Berry, F. A. Cotton, P. Lei, T. Lu and C. A. Murillo,
Inorg. Chem., 2003, 42, 3534; (m) F. A. Cotton, L. M. Daniels and G. T.
Jordan IV, Chem. Commun., 1997, 421; (n) F. A. Cotton, L. M. Daniels,
C. A. Murillo and X. Wang, Chem. Commun., 1998, 39; (o) F. A. Cotton,
C. A. Murillo and X. Wang, Inorg. Chem., 1999, 38, 6294; (p) R. Cle´rac,
F. A. Cotton, L. M. Daniels, K. R. Dunbar, C. A. Murillo and I.
Pascual, Inorg. Chem., 2000, 39, 748; (q) R. Cle´rac, F. A. Cotton, K. R.
Dunbar, T. Lu, C. A. Murillo and X. Wang, Inorg. Chem., 2000, 39,
3065; (r) R. Cle´rac, F. A. Cotton, L. M. Daniels, K. R. Dunbar, C. A.
Murillo and X. Wang, J. Chem. Soc., Dalton Trans., 2001, 386; (s) R.
Cle´rac, F. A. Cotton, L. M. Daniels, K. R. Dunbar, C. A. Murillo and
X. Wang, Inorg. Chem., 2001, 40, 1256; (t) R. Cle´rac, F. A. Cotton,
S. P. Jeffery, C. A. Murillo and X. Wang, Inorg. Chem., 2001, 40, 1265;
(u) J. F. Berry, F. A. Cotton, C. S. Fewox, T. Lu, C. A. Murillo and X.
Wang, Dalton Trans., 2004, 2297.
Fig. 4 Structure of compound 5. Displacement ellipsoids are drawn
at the 40% probability level. N(5)–C(51) 1.337(2), N(4)–C(51) 1.393(2),
N(4)–C(35) 1.420(2), N(4)–C(4) 1.451(3), N(3)–C(31) 1.334(3), N(3)–
C(35) 1.340(2), N(2)–C(31) 1.381(2), N(2)–C(15) 1.393(2), N(1)–C(15)
˚
1.345(3), N(1)–C(11) 1.340(3) A, N(5)–C(51)–N(4) 114.8(2), N(3)–C(35)–
N(4) 115.4(2), N(3)–C(31)–N(2) 119.7(2), N(1)–C(15)–N(2) 112.5(2)◦.
Acknowledgements
We thank the Robert A. Welch Foundation and Texas A & M
University for financial support and Mr Z. Li, Dr C. Y. Liu, Dr
X. Wang and Ms Q. Zhao for help with crystallography.
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