Substituted N-picorylethylenediamines of the type (ArNHCH 2CH2)-{(2-C5H4N)CH2}NR [R = Me, 4-CH2=CH(C6H4)CH2, (2-C 5H4N)CH2] and their transition metal(II) halide complexes

Article abstract of DOI:10.1039/b505763a

Alkylation of (ArNHCH₂CH₂){(2-C₅H ₄N)CH₂}NH with RX [RX = Mel, 4-CH₂=CH(C ₆H₄)CH2Cl) and (2-C₅H₅N)CH ₂Cl] in the presence of base has allowed access to the sterically demanding multidentate nitrogen donor ligands, {(2,4,6-Me₃C ₆H₂)NHCH₂CH₂}{(2-C₅H ₄N)CH₂}NMe (L1), {(2,6-Me₃C₆H ₃)NHCH₂CH₂}{(2-C₅H ₄N)-CH₂}NCH₂(C₆H₄)-4-CH= CH₂ (L2) and (ArNHCH₂CH₂){(2-C ₅H₄N)CH₂}₂N (Ar = 2,4-Me ₂C₆H₃ L3a, 2,6-Me₂C ₆H₃ L3b) in moderate yield. L3 can also be prepared in higher yield by the reaction of (NH₂CH₂CH ₂)-{(2-C₅H₄N)CH₂}₂N with the corresponding aryl bromide in the presence of base and a palladium(0) catalyst. Treatment of L1 or L2 with MCl₂ [MCl₂ = CoCl₂·6H₂O or FeCl₂(THF)_1.5] in THF affords the high spin complexes [(L1)MCl₂] (M = Co 1a, Fe 1b) and [(L2)MCl₂] (M = Co 2a, Fe 2b) in good yield, respectively; the molecular structure of 1a reveals a five-coordinate metal centre with L1 bound in a facial fashion. The six-coordinate complexes, [(L3a)MCl₂] (M = Co 3a, Fe 3b, Mn 3c) are accessible on treatment of tripodal L3a with MCl ₂. In contrast, the reaction with the more sterically encumbered L3b leads to the pseudo-five-coordinate species [(L3b)MCl₂] (M = Co 4a, Fe 4b) and, in the case of manganese, dimeric [(L3b)MnCl(μ-Cl)]₂ (4c); in 4a and 4b the aryl-substituted amine arm forms a partial interaction with the metal centre while in 4c the arm is pendant. The single crystal X-ray structures of 1a, 3b·MeCN, 3c·MeCN, 4b·MeCN and 4c are described as are the solution state properties of 3b and 4b. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b505763a

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F U L L P A P E R
Substituted N-picolylethylenediamines of the type (ArNHCH2CH2)-
=
{(2-C5H4N)CH2}NR [R = Me, 4-CH2 CH(C6H4)CH2,
(2-C5H4N)CH2] and their transition metal(II) halide complexes
Christopher J. Davies,a John Fawcett,a Richard Shuttb and Gregory A. Solan*a
a Department of Chemistry, University of Leicester, University Road, Leicester, UK LE1 7RH.
E-mail: gas8@leicester.ac.uk
b ExxonMobil Chemical Europe, Hermeslaan 2, B-1831 Machelen, Belgium
Received 25th April 2005, Accepted 20th June 2005
First published as an Advance Article on the web 4th July 2005
=
Alkylation of (ArNHCH2CH2){(2-C5H4N)CH2}NH with RX [RX = MeI, 4-CH2 CH(C6H4)CH2Cl) and
(2-C5H5N)CH2Cl] in the presence of base has allowed access to the sterically demanding multidentate nitrogen donor
ligands, {(2,4,6-Me3C6H2)NHCH2CH2}{(2-C5H4N)CH2}NMe (L1), {(2,6-Me3C6H3)NHCH2CH2}{(2-C5H4N)-
=
CH2}NCH2(C6H4)-4-CH CH2 (L2) and (ArNHCH2CH2){(2-C5H4N)CH2}2N (Ar = 2,4-Me2C6H3 L3a,
2,6-Me2C6H3 L3b) in moderate yield. L3 can also be prepared in higher yield by the reaction of (NH2CH2CH2)-
{(2-C5H4N)CH2}2N with the corresponding aryl bromide in the presence of base and a palladium(0) catalyst.
Treatment of L1 or L2 with MCl2 [MCl2 = CoCl2·6H2O or FeCl2(THF)1.5] in THF affords the high spin complexes
[(L1)MCl2] (M = Co 1a, Fe 1b) and [(L2)MCl2] (M = Co 2a, Fe 2b) in good yield, respectively; the molecular
structure of 1a reveals a five-coordinate metal centre with L1 bound in a facial fashion. The six-coordinate
complexes, [(L3a)MCl2] (M = Co 3a, Fe 3b, Mn 3c) are accessible on treatment of tripodal L3a with MCl2. In
contrast, the reaction with the more sterically encumbered L3b leads to the pseudo-five-coordinate species
[(L3b)MCl2] (M = Co 4a, Fe 4b) and, in the case of manganese, dimeric [(L3b)MnCl(l-Cl)]2 (4c); in 4a and 4b the
aryl-substituted amine arm forms a partial interaction with the metal centre while in 4c the arm is pendant. The
single crystal X-ray structures of 1a, 3b·MeCN, 3c·MeCN, 4b·MeCN and 4c are described as are the solution state
properties of 3b and 4b.
Alternatively, an additional donor group could be introduced
to augment the denticity of the ligand.
1
Introduction
The emergence in recent years of tridentate nitrogen donor
ligand frames that can act as compatible supports for both
early (Ti, Zr, V, Cr)1–4 and late (Fe, Co)5,6 transition metal-
based olefin polymerisation catalysts has fuelled a considerable
research activity directed towards the design of alternative ligand
frameworks.7 In many cases the N,N,N-chelates are symmetri-
cally disposed [e.g., bis(imino)pyridines,3–6 bis(amido)pyridines,2
bis(amido)amines1] with the exterior nitrogen donors possessing
aryl substituents which impart, through both steric and elec-
tronic variation, considerable control on the resultant catalyst
performance.
This manuscript is concerned, in the first instance, with
the synthesis of methylated L1, pendant arm-containing L2
and tripodal L3 (Fig. 1). Secondly, the synthesis and de-
tailed characterisation of paramagnetic metal chloride com-
plexes supported by L1-L3 is described including X-ray
structural characterisation of cobalt, iron and manganese
complexes.
2
Results and discussion
2.1 Derivatised N-Picolylethylenediamine ligands
Recently we have reported the synthesis of both iron and
cobalt halide complexes containing the highly flexible (both
mer- and fac-configurations accessible) mono-aryl-substituted
N-picolylethylenediamine frame (Fig. 1) which, on activation
with MAO, are active catalysts for the oligomerisation of
ethylene.8 These type of ligands are of added interest due to the
scope for further functionalisation such as at the central nitrogen
atom. This functionalisation could, for example, include the
introduction of simple alkyl groups (to modify the electronic
properties) through to the incorporation of a polymerisable
side arm9 to allow immobilisation on an organic support.
=
The reaction of RX [RX = MeI, 4-CH2 CH(C6H4)CH2Cl
and (2-C5H5N)CH2Cl] with the corresponding aryl-
substituted N-picolylethylenediamine, (ArNHCH2CH2){(2-
C5H4N)CH2}NH,8 in the presence of excess K2CO3 gives
{(2,4,6-Me3C6H2)NHCH2CH2}{(2-C5H4N)CH2}NMe (L1),
{(2,6-Me2C6H3 )NHCH2CH2 }{(2-C5H4N)CH2 }NCH2(C6H4 )-
=
4-CH CH2 (L2) and (ArNHCH2CH2){(2-C5H4N)CH2}2N
(Ar = 2,4-Me2C6H3 L3a, 2,6-Me2C6H3 L3b) in yields between
38–63% (Scheme 1). Also identified as by-products in the
formation of L1–L3 are the corresponding ammonium salts
Fig. 1 N-picolylen and its derivatives (L1,L2 and L3) reported in this study.
2 6 3 0
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

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Scheme 1 Reagents and conditions: (i) Ar–Br, NaOBut, Pd2(dba)3 (0.2 mol%), rac-BINAP, toluene, heat;8 (ii) RX, xs. K2CO3, MeCN, −10 to 20 ◦C
(L1), 80 ◦C (L2) or 55 ◦C (L3).
Scheme 2 Reagents and conditions: (i) N-tosylaziridine, CH3CN, heat; (ii) conc. H2SO4, heat; (iii) Ar–Br, NaOBut, Pd2(dba)3 (0.2 mol%), rac-BINAP,
toluene, heat.
which can be readily separated following chromatography on
alumina.
Alternatively, L3 can be prepared in two steps from N,N-
bis(2-picolyl)amine (dpa).10 Firstly, dpa can be converted to
N,N-dipicolylethylenediamine (dpea) using previously reported
procedures11 or by reacting dpa with N-tosylaziridine12 followed
by tosyl deprotection under acidic conditions (Scheme 2).
Secondly, treatment of dpea with one equivalent of the cor-
responding aryl bromide in the presence of a catalytic amount
of Pd2(dba)3 gave L3a and L3b as the sole products in good
1
yield.13 All the new ligands have been characterised by IR, H
and 13C NMR spectroscopy and ES mass spectrometry (see
Experimental section).
2.2 Complexes of L1–L3
Treatment of MCl2 [MCl2 = CoCl2·6H2O, FeCl2(THF)1.5] with
one equivalent of L1 or L2 in tetrahydrofuran at room temper-
ature affords [(L1)MCl2] (M = Co 1a, Fe 1b) and [(L2)MCl2]
(M = Co 2a, Fe 2b) in good yield (Scheme 3). All the complexes
have been characterised by mass spectrometry, IR spectroscopy
and magnetic measurements (Table 1). In addition, 1a has been
the subject of a single crystal X-ray diffraction study.
Purple crystals of 1a suitable for the X-ray diffraction study
were grown by slow cooling of a hot acetonitrile solution of 1a.
The molecular structure of 1a is depicted in Fig. 2; selected bond
distances and bond angles are listed in Table 2.
The structure of 1a consists of a single cobalt atom surrounded
by a facially bound tridentate nitrogen donor ligand and two
monodentate chloride ligands. The coordination geometry can
be best described as distorted trigonal bipyramidal with the
equatorial plane being defined by N(1)pyridyl, N(3)arylamine, Cl(2)
[N(1)–Co(1)–N(3) 104.82(16)◦, N(1)–Co(1)–Cl(2) 110.09(13)◦,
N(3)–Co(1)–Cl(2) 139.68(12)◦] and the axial sites by N(2) and
Cl(1) [N(2)–Co(1)–Cl(1) 166.88(12)◦]. The N-aryl group is
oriented such that the ortho-methyl groups [C(16) and C(18)]
are positioned above and below the plane defined by N(2)–
Co(1)–N(3)–C(9) [max. deviation from plane N(3) 0.0232 A]
Scheme 3 Reagents and conditions: (i) MCl2 [MCl2 = CoCl2·6H2O or
FeCl2(THF)1.5], THF, room temperature; (ii) MCl2, n-BuOH, 90 ◦C.
˚
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0
2 6 3 1

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Table 1 Spectroscopic and analytical data for the new complexes 1–4
Microanalysis (%)c
Compound leff/BMa
v(N–H)/cm−1b
FAB mass spectrum
C
H
N
1a
1b
2a
2b
3a
3b
3c
4a
4b
4c
4.09
5.11
4.16
5.09
4.26
5.22
5.76
3.97
5.31
8.04
3278
3281
3263
3274
3290
3279
3311, 3261
3241
3238
789 [2M − Cl]+, 412 [M]+, 377 [M − Cl]+
785 [2M − Cl]+, 410 [M]+, 374 [M − Cl]+
967 [2M − Cl]+, 465 [M − Cl]+
52.63 (52.30) 6.16 (6.05) 10.09 (10.17)
52.91 (52.69) 6.23 (6.10) 10.11 (10.24)
60.01 (59.89) 5.95 (5.79)
8.47 (8.38)
d
d
d
960 [2M − Cl]+, 462 [M − Cl]+
917 [2M − Cl]+, 440 [M/2 − Cl]+
910 [2M − Cl]+, 472 [M]+, 437 [M − Cl]+
909 [2M − Cl]+, 436 [M − Cl]+
55.71 (55.46) 5.62 (5.46) 11.69 (11.76)
55.80 (55.84) 5.59 (5.54) 11.67 (11.84)
55.73 (55.95) 5.67 (5.55) 11.67 (11.86)
917 [2M − Cl]+, 440 [M − Cl]+, 405 [M − 2Cl]+ 55.29 (55.46) 5.41 (5.46) 11.51 (11.76)
909 [2M − Cl]+, 472 [M]+ 437 [M − Cl]+
55.67 (55.84) 5.46 (5.54) 12.00 (11.84)
55.81 (55.95) 5.37 (5.55) 11.88 (11.86)
3312, 3261
909 [M − Cl]+, 436 [M/2 − Cl]+
a Recorded on an Evans Balance at room temperature b Recorded on a Perkin-Elmer Spectrum One FT-IR spectrometer on solid samples c Calculated
values are shown in parentheses d The microanalytical data for 2b were repeatedly incorrect.
o
˚
˚
Table 2 Selected bond distances (A) and angles ( ) for 1a
however, contracted by 0.044(4) and 0.045(1) A, respectively. In
contrast, the Co–N(pyridyl) distance is essentially the same in
both structures as is the Cl–Co–Cl angle at [103.48(6)◦ (1a) vs.
103.11(3)◦]. Due to the centric nature of the space group, both
R/R and S/S forms are present for the two chiral centres at N(2)
and N(3) in the crystal of 1a, a relative configuration that is also
observed in [{(ArNHCH2CH2){(2-C5H4N)CH2}NH}CoCl2]
(Ar = 2,6-Me2C6H3, 2,4,6-Me3C6H2).8
Co(1)–N(1)
Co(1)–N(2)
Co(1)–N(3)
2.093(4)
2.254(4)
2.170(4)
Co(1)–Cl(1)
Co(1)–Cl(2)
2.3107(15)
2.3159(15)
N(1)–Co(1)–N(2)
N(1)–Co(1)–N(3)
N(2)–Co(1)–N(3)
N(1)–Co(1)–Cl(1)
N(2)–Co(1)–Cl(1)
76.42(17)
104.82(16)
79.45(16)
97.73(13)
166.88(12)
N(3)–Co(1)–Cl(1)
N(1)–Co(1)–Cl(2)
N(2)–Co(1)–Cl(2)
N(3)–Co(1)–Cl(2)
Cl(1)–Co(1)–Cl(2)
90.95(12)
110.09(13)
89.59(12)
139.68(12)
103.48(6)
The FAB mass spectrum for 1a, along with those for 1b, 2a
and 2b, give molecular ion peaks and/or fragmentation peaks
corresponding to the loss of chloride ions from the molecular
ion and, in addition, minor peaks that can be attributed to
dimeric species. In their IR spectra the t(N–H) absorption
bands are seen at ca. 3274 cm−1 and shifted (by ca. 75 cm−1)
to a lower wavenumber in comparison with that observed
with the C(18)o-Me group pointing in a similar direction
to Cl(2). The three Co–N distances are inequivalent with
the Co–N(pyridyl) distance being the shortest [Co(1)–
N(1) 2.093(4) A] and the distance involving the central
tertiary amine the longest [Co(1)–N(2) 2.254(4) A]. In
comparison with the non-methylated analogue, [{{(2,4,6-
Me3C6H2 )NHCH2CH2 }{(2-C5H4N)CH2 }NH}CoCl2 ],8 the
presence of the central methyl-substituted tertiary nitrogen
donor in 1a has the effect of elongating both the Co–N bond
[by 0.065(4) A] and the Co–Cl(axial) bond [by 0.028(1) A];
the Co–N(arylamine) and the Co–Cl(equatorial) bonds are,
˚
=
in the corresponding free ligands. The t(C C) band for 2a
and 2b is seen at ca. 1626 cm−1 and shows little variation in
wavenumber when compared to that found in free L2. The
magnetic susceptibility measurements for the cobalt complexes,
1a and 2a, reveal magnetic moments of ca. 4.13 BM (Evans
Balance at ambient temperature) which are consistent with high
spin configurations possessing three unpaired electrons (S =
3/2). On the other hand, 1b and 2b exhibit moments of ca. 5.1
˚
˚
˚
Fig. 2 Molecular structure of 1a. All hydrogen atoms except for H1 have been omitted for clarity.
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0
2 6 3 2

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Fig. 3 Molecular structure of 3b. All hydrogen atoms except for H4 have been omitted for clarity.
BM, consistent with high spin configurations possessing four
unpaired electrons (S = 2).
alone. The structures of 3b and 3c are essentially identical,
both containing two unique molecules (A and B) differing
mainly in the inclination of the aryl groups; only one of the
unique molecules in 3b will be discussed in any detail. The
molecular structure of 3b is shown in Fig. 3 while selected bond
distances and bond angles for both 3b and 3c (molecules A
and B for each) are listed in Table 3. The structure comprises
a single iron atom surrounded by a N,N,N,N-tripod and two
monodentate chloride ligands so as to complete a distorted
octahedral environment. One of the two pyridyl donors in the
N,N,N,N-tripod is located trans to Cl(2) [N(3)–Fe(1)–Cl(2)
165.55(18)◦] while the other is trans to the 2,4-Me2Ph-substituted
amine [N(1)–Fe(1)–N(4) 150.9(2)◦] leaving the tertiary amine
atom and Cl(1) mutually trans [N(2)–Fe(1)–Cl(1) 167.69(19)◦].
Of the four M–N bond distances the two involving the pyridyl
nitrogen atoms are the shortest [Fe(1)–N(1) 2.191(7), Fe(1)–
Interaction of anhydrous MCl2 with one equivalent of L3a
at 90 ◦C in n-butanol gives [(L3a)MCl2] (M = Co 3a, Fe 3b,
Mn 3c) while reaction of MCl2 with L3b affords [(L3b)MCl2]
(M = Co 4a, Fe 4b) and [(L3b)MnCl(l-Cl)]2 (4c) in high yield
(Scheme 3). All the compounds have been characterised by FAB
mass spectrometry, magnetic susceptibility measurements, IR
spectroscopy and elemental analysis (Table 1). Furthermore,
crystals of 3b, 3c, 4b and 4c have been the subject of single
crystal X-ray diffraction studies.
Yellow crystals of 3b and clear crystals of 3c suitable for
the X-ray studies were grown by either slow cooling of a hot
acetonitrile solution containing the complex or by layering
an acetonitrile solution with hexane, respectively. Despite the
apparent immiscibility of acetonitrile and hexane, we have
found that crystals of 3c could not be grown from acetonitrile
˚
N(3) 2.169(7) A], followed by the one involving the tertiary
◦
˚
Table 3 Selected bond distances (A) and angles ( ) for 3b·MeCN and 3c·MeCN
3b·MeCN (M = Fe)
3c·MeCN (M = Mn)
Molecule A
Molecule B
Molecule A
Molecule B
M(1)–N(1)
M(1)–N(2)
M(1)–N(3)
M(1)–N(4)
M(1)–Cl(1)
M(1)–Cl(2)
2.191(7)
2.249(6)
2.169(7)
2.303(6)
2.337(2)
2.468(2)
2.175(7)
2.231(7)
2.192(7)
2.319(6)
2.299(2)
2.536(2)
2.272(7)
2.344(7)
2.279(7)
2.400(6)
2.400(2)
2.472(2)
2.252(7)
2.340(7)
2.285(7)
2.383(7)
2.369(2)
2.529(2)
N(1)–M(1)–N(2)
N(1)–M(1)–N(3)
N(1)–M(1)–N(4)
N(2)–M(1)–N(3)
N(2)–M(1)–N(4)
N(3)–M(1)–N(4)
N(1)–M(1)–Cl(1)
N(2)–M(1)–Cl(1)
N(3)–M(1)–Cl(1)
N(4)–M(1)–Cl(1)
N(1)–M(1)–Cl(2)
N(2)–M(1)–Cl(2)
N(3)–M(1)–Cl(2)
N(4)–M(1)–Cl(2)
Cl(1)–M(1)–Cl(2)
74.2(2)
95.0(2)
150.9(2)
76.7(2)
77.2(2)
83.6(2)
100.28(18)
167.69(19)
93.02(18)
108.82(16)
90.55(18)
91.99(17)
165.55(18)
85.08(16)
99.15(8)
73.8(2)
91.6(2)
152.2(2)
77.1(2)
78.6(2)
85.7(2)
99.17(19)
169.09(18)
95.13(19)
108.68(17)
94.81(18)
90.23(17)
163.57(19)
81.55(17)
98.75(8)
71.7(2)
93.7(2)
146.7(2)
74.4(2)
75.3(2)
81.3(2)
101.38(18)
163.86(17)
91.95(18)
111.61(16)
92.01(17)
93.15(17)
163.80(18)
85.62(17)
101.77(8)
71.7(2)
90.1(3)
148.0(2)
74.3(2)
76.4(2)
83.8(2)
99.40(18)
164.94(19)
93.98(18)
112.32(17)
95.54(19)
90.95(18)
161.72(19)
82.23(17)
102.18(9)
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0
2 6 3 3

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Fig. 4 Molecular structure of 4b. All hydrogen atoms except for H4 have been omitted for clarity.
˚
amine [Fe(1)–N(2) 2.249(6) A] and the most elongated distance
as a response to the steric interactions between a pyridyl
group and one ortho-Me group (C22) with the result that
N4 forms only a weak interaction with Fe(1) [Fe(1) · · · N(4)
˚
involving the aryl-substituted amine [Fe(1)–N(4) 2.303(6) A].
This cis-arrangement of the pyridyl donors in 3b is in contrast
to the trans-configuration observed for [(dpea)Fe(NCS)2]11a but
resembles the configuration seen in [(dpea)Mn(l-O)]2(ClO4)3.14
The M–Cl bond distances are inequivalent, presumably due
to the differing trans effects imposed on each chloride ligand
(tert-amine vs. pyridyl) with M(1)–Cl(2) bond distance being
˚
2.5580(16) cf. Fe(1)–N(4) 2.303(6) A (3b)]. This weak interaction
is likely to be further supplemented by a hydrogen-bonding
˚
interaction between H(4) and Cl(2) [ca. 2.358 A]. As a con-
sequence the geometry of the metal centre can be described
as somewhere between octahedral and square pyramidal. It
is noteworthy that a similar elongation has been observed
in the related mesityl-substituted ferrous complex [{((2,4,6-
Me3C6H2)NHCH2CH2)2{(2-C5H4N)CH2}N}FeCl2]15 in which
˚
the longest [2.468(2) A].
The FAB mass spectra of 3a–c gave molecular ion peaks
and/or fragmentation peaks corresponding to the loss of
chloride ions from their [M]+ peaks. As with 1 and 2, 3a–c all
show minor peaks corresponding to the loss of a chloride from
a dimeric species. The magnetic susceptibility measurements
(Evans Balance at ambient temperature) for 3a–c indicate high
spin configurations are present in each case giving magnetic
moments consistent with three (3a), four (3b) and five (3c)
unpaired electrons. In the IR spectra of 3a–c, characteristic
pyridyl ring deformation bands at ca. 1600 cm−1 are observed
along with absorption bands for the bound N(Ar)–H groups
(ca. 3280 cm−1).
Golden crystals of 4b suitable for the X-ray diffraction study
were grown by slow cooling of a hot acetonitrile solution
containing the complex. The molecular structure of 4b is
shown in Fig. 4; selected bond distances and bond angles
are listed in Table 4. The structure resembles 3b with a
single iron centre surrounded by a N,N,N,N-tripod and two
monodentate chloride ligands. However, effective coordination
of the 2,6-Me2Ph-substituted amine (N4) donor is impeded
˚
the corresponding Fe · · · N distance is 2.597(5) A. The elon-
gation in 4b seems to have a minimal effect on the MCl2 unit
with the Cl(1)–Fe(1)–Cl(2) angle [97.20(2) vs. 99.15(8)o (3b)] and
the M–Cl bond distances [Fe(1)–Cl(1), 2.3203(6) vs. 2.337(2)o
(3b); Fe(1)–Cl(2), 2.4627(6) vs. 2.468(2)◦ (3b)] similar to that
in 3b. Conversely, the coordinated M–N distances in 4b vary
considerably with Fe–N(tert-amine) being compressed by ca.
˚
0.078 A, while Fe–N(pyridyl) distances are lengthened and most
significantly for the pyridyl donor trans to the loosely bound
˚
aryl-substituted amine (ca. 0.073 A). As with 3b, the Fe–N
˚
bond distances are all >2.0 A, characteristic of high spin ferrous
complexes.16
Clear crystals of 4c were grown by layering of an acetonitrile
solution with hexane. The molecular structure of 4c is shown
in Fig. 5; selected bond distances and bond angles are listed
in Table 5. Unlike 4b, the structure of 4c consists of a
dimeric unit generated through a crystallographically imposed
◦
˚
Table 5 Selected bond distances (A) and angles ( ) for 4c
◦
˚
Table 4 Selected bond distances (A) and angles ( ) for 4b·MeCN
Mn(1)–N(1)
Mn(1)–N(2)
Mn(1)–N(3)
Mn(1)–Cl(1)
2.3907(16) Mn(1)–Cl(2)
2.2876(17) Mn(1)–Cl(2A)
2.2226(16) Mn(1) · · · Mn(1A)
2.4279(6)
2.5706(7)
2.5321(7)
3.795(1)
Fe(1)–N(1)
Fe(1)–N(2)
Fe(1)–N(3)
2.1712(16) Fe(1) · · · N(4)
2.2636(16) Fe(1)–Cl(1)
2.1883(16) Fe(1)–Cl(2)
2.5580(16)
2.3203(6)
2.4627(6)
N(1)–Fe(1)–N(2)
N(1)–Fe(1)–N(3)
N(1)–Fe1) · · · N(4)
N(2)–Fe(1)–N(3)
N(2)–Fe(1) · · · N(4)
N(3)–Fe(1) · · · N(4)
N(1)–Fe(1)–Cl(1)
N(2)–Fe(1)–Cl(1)
74.91(6)
91.02(6)
147.70(5)
77.81(6)
74.41(5)
92.32(5)
103.12(5)
171.15(4)
N(3)–Fe(1)–Cl(1)
93.68(5)
N(1)–Mn(1)–N(3)
N(1)–Mn(1)–N(2)
N(2)–Mn(1)–N(3)
N(1)–Mn(1)–Cl(1) 157.94(4)
N(2)–Mn(1)–Cl(1)
N(3)–Mn(1)–Cl(1)
72.67(6)
70.30(6)
97.18(6)
N(3)–Mn(1)–Cl(2)
N(1)–Mn(1)–Cl(2A)
N(2)–Mn(1)–Cl(2A)
N(3)–Mn(1)–Cl(2A)
Cl(1)–Mn(1)–Cl(2)
Cl(1)–Mn(1)–Cl(2A)
Cl(2)–Mn(1)–Cl(2A)
Mn(1)–Cl(2)–Mn(1A)
87.43(4)
91.92(4)
88.31(4)
160.58(4)
96.75(2)
103.06(2)
83.91(2)
96.09(2)
N(4) · · · Fe(1)–Cl(1) 108.81(5)
N(1)–Fe(1)–Cl(2)
N(2)–Fe(1)–Cl(2)
N(3)–Fe(1)–Cl(2)
N(4) · · · Fe(1)–Cl(2)
Cl(1)–Fe(1)–Cl(2)
92.72(4)
91.53(4)
167.38(5)
78.10(3)
97.20(2)
93.76(4)
95.18(5)
N(1)–Mn(1)–Cl(2) 100.91(4)
N(2)–Mn(1)–Cl(2) 168.11(4)
2 6 3 4
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0

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Fig. 5 Molecular structure of 4c; the atoms labelled with an additional A are generated by symmetry (2 − x, −y, 1 − z). All hydrogen atoms except
for H4 have been omitted for clarity.
inversion centre. The two manganese centres are bridged by
a pair of chloride ligands and bound terminally by both a
chloride and L3b to give a distorted octahedral geometry at
each metal centre. L3b acts as a tridentate ligand and adopts
a facial configuration [N(2)–Mn(1)–N(3) 97.18(6)o] with the
2,6-Me2Ph-substituted amine non-coordinated. The structure
of 4c resembles that of [(Etdpa)MnCl(l-Cl)]2 (Etdpa = ethyl-
substituted dipicolylamine)17 in which the central tertiary amines
are trans to a terminal chloride and the pyridyl groups are trans
to the bridging chlorides. As expected the Mn–N(amine) bond
corresponding to the loss of a chloride ion from the molecular
ion peak along with minor peaks that can be ascribed to dimeric
species. In the FAB mass spectrum of 4c, a [M − Cl]+ peak
is observed along with a peak corresponding to the loss of a
chloride ion from a monomeric species.
Clearly, the steric properties of L3 play a key role on the
ability for the ligand to bind in a tetradentate fashion. While
the presence of a single ortho-methyl group (L3a) on the aryl-
substituted amine arm leads to efficient coordination (3), the
introduction of a second methyl group at the ortho position
(L3b) results in either a loosely bound amine (4b) or in de-
coordination of the amine altogether (4c). Indeed we have
previously suggested that the lability of arylamine arm could
be a factor involved in mer/fac interconversions that are evident
for [(N-picolylen)FeCl2] in solution.8
˚
distance in 4c [Mn(1)–N(1) 2.3907(16) A] is longer than the Mn–
N(pyridyl) bond distances [Mn(1)–N(2) 2.2876(17), Mn(1)–N(3)
˚
2.2226(16) A]. The two Mn–l-Cl bond distances are slightly
˚
different [Mn(1)–Cl(2) 2.5706(7), Mn(1)–Cl(2A) 2.5321(7) A]
and longer than the terminal Mn–Cl bond distances [Mn(1)–
1
˚
Cl(1) 2.4279(6) A]. The ClMn(l-Cl)2MnCl motif has been found
To probe the solution state properties of 3 and 4, the H
in a number of crystallographically characterised complexes
NMR spectra of the iron(II) complexes 3b and 4b were recorded.
The spectra are typical of high spin ferrous species containing
broad paramagnetically shifted resonances. By consideration of
the chemical shifts, relaxation times and comparison with the
spectra of [(tpa)FeCl2] (tpa = tripicolylamine),19 [(dpa)FeCl(l-
Cl)]2,20 [{{(2,6-Me2C6H3)NHCH2CH2}{(2-C5H4N)CH2}NH}-
FeCl2]8 and related polypyridyl iron complexes,16 assignment of
the peaks has been tentatively made (see Table 6). The Py–Ha of
the coordinated pyridyl arms in 3b and 4b are characteristically
the furthest downfield at d = 139.1 and 120.2 with low values for
T1 (0.5 ms and 0.4 ms), respectively. The Py–Hb/b’ and Py–Hc
appear at d = 53.0 (T1 = 11.7 ms), 45.5 (T1 = 10.0 ms) and 27.6
(T1 = 37.9 ms) for 3b, whilst for 4b they are found at d = 51.9
(T1 = 11.4 ms), 51.1 (T1 = 9.3 ms) and 19.3 (T1 = 26.3 ms).
All four sets of methylene protons are assigned for 4b at d =
73.5 (T1 = 1.3 ms), ca. 72 (shoulder of d = 73.5), 28.7 (T1 =
1.0 ms) and 12.2 (T1 = 1.7 ms). In contrast, for 3b only one very
broad methylene peak is assigned at ca. d = 46. In each case
the aromatic peaks are shifted further downfield than their free
ligand counterparts (L3a and L3b) and in 3b they are shifted
more so than 4b.
˚
with the transannular Mn · · · Mn separation of 3.795(1) A falling
in the mid-range.18 While no notable intermolecular interactions
are apparent, there is evidence that weak N(Ar)–H · · · Cl in-
teractions occur intramolecularly between the pendant amine
˚
hydrogen atom and a terminal chloride ligand (ca. 2.654 A).
The IR spectra for 4a–c reflect the ligand coordination
modes within the complexes by exhibiting characteristic pyridyl
ring deformation bands at ca. 1600 cm−1 and N–H stretching
frequencies in the range 3312–3238 cm−1. In 4a and 4b the single
broad N–H absorption bands are seen at the lower end of the
range and shifted by ca. 100 cm−1 with regard to free L3b.
In 4c, however, two bands are seen at 3312 and 3261 cm−1 in
an approximate intensity ratio of 3 : 1, respectively. It is likely
that the higher wavenumber band corresponds to the pendant
N(Ar)–H groups in dimeric 4c while the lower wavenumber
band to a monomeric isomer analogous in structure to 4a and
4b. Interestingly, in 3c two peaks are also observed in the NH
region (3311 and 3261 cm−1); in this case a preference for the
lower wavenumber absorption band is observed (ca. 4 : 1). The
room temperature magnetic susceptibility measurements of 4a–
c all indicate high spin behaviour with three [Co(II), S = 3/2]
and four [Fe(II), S = 2] unpaired electrons present in 4a and 4b
respectively. In dimeric 4c, the magnetic moment of 8.04 BM
is consistent with two non-interacting high spin manganese(II)
centres (using l2 = Rli2, where li is the magnetic moment of
the individual metal centres). The FAB mass spectra of 4a and
4b give either molecular ion peaks and/or fragmentation peaks
Given the similarity in chemical shift for the picolyl protons in
4b with [(dpa)FeCl(l-Cl)]220 (see Table 6), in which the dpa binds
as a tridentate ligand, it would seem reasonable to suggest that
the aryl amine arm in 4b is pendant in solution. Nevertheless,
some degree of interaction seems likely and sufficient enough
to cause the aromatic protons to be paramagnetically shifted
in 4b.
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0
2 6 3 5

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In summary, the N-picolylen ligand frame developed in our
earlier study8 has been shown to be amenable to functionalisa-
tion at the central nitrogen atom with methyl (L1), 4-vinylbenzyl
(L2) and 2-picolyl (L3) derivatives accessible. While L1 and L2
act as tridentate ligands, the introduction of a 2-picolyl group
in L3 has allowed access to a tripodal ligand that can bind to
a range of paramagnetic transition metal chlorides as either a
tridentate or tetradentate ligand; the denticity being dependent
on the steric bulk in the ortho-positions of the aryl groups. The
role of these systems as precatalysts for olefin polymerisation
and other catalytic applications is currently being probed as is
the potential immobilisation of L2 (and its complexes) and will
be published in due course.
3
Experimental
3.1 General
All reactions were carried out under an atmosphere of dry,
oxygen-free nitrogen, using standard Schlenk techniques or in a
nitrogen purged glove box. Solvents were distilled under nitrogen
from appropriate drying agents and degassed prior to use.21 The
infrared spectra were recorded as Nujol mulls between 0.5 mm
NaCl plates on a Perkin Elmer 1600 series. The ES and the
FAB mass spectra were recorded using a micromass Quattra
LC mass spectrometer and a Kratos Concept spectrometer with
methanol or NBA as the matrix, respectively. 1H and 13C NMR
spectra were recorded on a Bruker ARX spectrometer (250
or 300 or 400 MHz) at ambient temperature; chemical shifts
(ppm) are referred to the residual protic solvent peaks; relax-
ation times (T1) are in seconds. Magnetic susceptibility studies
were performed using an Evans Balance (Johnson Matthey)
at room temperature. The magnetic moment was calculated
following standard methods22 and corrections for underlying
diamagnetism were applied to data.23 Elemental analyses were
performed at the Department of Chemistry, University of North
London by Dr S. Boyer.
The reagents, methyl iodide, 4-vinylbenzyl chloride, 2-
picolyl chloride hydrochloride, sodium t-butoxide, the aryl
halides and the metal dichlorides were purchased from
Aldrich Chemical Co. and used without further purification.
rac-BINAP was purchased from Strem Chemical Co. The
compounds, FeCl2(THF)1.5,24 Pd2(dba)3,25 N-tosylaziridine,12
N,N-bis(2-picolyl)amine (dpa),10 and (ArNHCH2CH2){(2-
C5H4N)CH2}NH (Ar = 2,4,6-Me3C6H2, 2,4-Me2C6H3, 2,6-
Me2C6H3)8 were prepared according to previously reported
procedures. All other chemicals were obtained commercially and
used without further purification.
3.2 Synthesis of N,N-dipicolylethylenediamine (dpea)
Prepared via two-step procedure.
(a) (N-tosyl-2-aminoethyl)bis(2-picolyl)amine. To
a 3-
necked round bottom flask equipped with a reflux condenser,
dropping funnel and a magnetic stirrer was added dpa (19.900 g,
100 mmol) dissolved in acetonitrile (250 ml). The yellow solution
was brought to reflux and N-tosylaziridine (19.700 g, 100 mmol)
in acetonitrile (200 ml) was added dropwise over 1 h, to give a
dark red solution, which was heated to reflux for an additional
5 h. The dark red solution was concentrated and dried under
reduced pressure overnight to give (N-tosyl-2-aminoethyl)bis(2-
picolyl)amine as a dark red oil. Yield: 99% (39.204 g, 99.0 mmol).
ES mass spectrum: m/z 397 [M + H]+. 1H NMR (CDCl3,
3
250 MHz): d 2.36 (s, 3H, Me), 2.77 (t, 2H, J(HH) 5.3, CH2),
3.03 (t, 2H, CH2), 3.76 (s, 4H, PyCH2), 7.1–7.2 (m, 6H, Ar–H
and Py–H), 7.57 (d, 2H, 3J(HH) 6.0, Py–H), 7.71 (d, 2H, 3J(HH)
8.0, Py–H) and 8.58 (d, 2H,3J(HH) 4.6, Py–H).
(b) N,N-dipicolylethylenediamine (dpea). To (N-tosyl-2-
aminoethyl)bis(2-picolyl)amine (39.20 g, 99.0 mmol) was added
concentrated H2SO4 (300 ml). The dark red solution was stirred
and heated to 130 ◦C. After 3 days, the reaction mixture
2 6 3 6
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0

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was cooled in an ice bath and diethyl ether (4000 ml) and
absolute ethanol (3000 ml) added dropwise to give a dark
brown precipitate. Caution! The brown precipitate is hygroscopic.
The brown precipitate was filtered and immediately dissolved
in saturated NaOH. The organic layer was extracted with
chloroform (3 × 200 ml) and the organic phases combined
and dried over MgSO4. Following filtration, the solution was
concentrated to give (H2NCH2CH2){(2-C5H4N)CH2}2N as a
red oil. Yield: 73% (17.45 g, 72.0 mmol). ES mass spectrum:
ing solvent mixture to give {(2,6-Me2C6H3)NHCH2CH2}{(2-
=
C5H4N)CH2}N(CH2C6H4CH CH2) (L2) as a yellow oil. Yield:
41% (0.401 g, 1.08 mmol). ES mass spectrum, m/z 372 [M +
+
−1
1
=
H] . IR (cm ), 3361 (N–H), 1629 (C C). H NMR (CDCl3,
300 MHz): d 2.15 (s, 6H, Meo), 2.70 (t, 2H, 3J(HH) 6.2, CH2),
3.07 (t, 2H, CH2), 3.62 (s, 2H, Py–CH2), 3.73 (s, 2H, Styr-
CH2), 5.15 (d, 1H, 3J(HH) 11.0, vinyl-H), 5.65 (d, 1H, 3J(HH)
17.0, vinyl-H), 6.6–6.7 (m, 2H, Ar–H and vinyl-H), 6.87 (d, 2H,
3J(HH) 7.6, Ar–H), 7.07 (m, 1H, Py–H), 7.2–7.3 (m, 4H, Ar–
H), 7.40 (d, 1H,3J(HH) 7.9, Py–CH), 7.57 (dt, 1H, 3J(HH) 7.6,
+
−1
=
m/z 243 [M + H] . IR (cm ) 3360 (N–H), 1590 (C Npyridine).
1H NMR (CDCl3, 250 MHz): d 1.65 (s br, 2H, NH2), 2.67 (t,
2H, 3J(HH) 5.7, CH2), 2.80 (t, 2H, CH2), 3.85 (s, 4H, PyCH2),
7.14 (dd, 2H, 3J(HH) 7.5, 5.0, Py–H), 7.49 (d, 2H,3J(HH) 7.8,
Py–H), 7.65 (dd, 2H, 3J(HH) 7.5, 6.9, Py–H) and 8.53 (d, 2H,
3J(HH) 5.0, Py–H). 13C NMR (CDCl3, 63 MHz,1H composite
pulse decoupled): d 39.9 (s, CH2), 57.8 (s, CH2), 61.1 (s, PyCH2),
122.4 (s, Py–CH), 123.4 (s, Py–CH), 136.8 (s, Py–CH), 149.4 (s,
Py–CH) and 160.0 (s, Py–C).
4J(HH) 1.8, Py–H) and 8.45 (d, 1H, J(HH) 6.0, PyCH). 13C
3
NMR (CDCl3, 75 MHz,1H composite pulse decoupled): d 17.8
(s, Meo), 44.7 (s, CH2), 53.3 (s, CH2), 57.4 (s, Py–CH2), 58.9 (s,
Styr-CH2), 112.5 (s, vinyl-C), 120.0 (s, Py–C), 121.0 (s, Py–C),
122.0 (s, Ar–C), 125.2 (s, Ar–C), 127.3 (s, Ar–C), 127.8 (s, Ar–
C), 128.2 (s, Ar–C), 135.4 (s, Py–C), 135.5 (s, vinyl-C), 137.3 (s,
Ar–C), 145.5 (s, Ar–C), 147.9 (s, Py–C) and 158.5 (s, Py–C).
3.5 Synthesis of {(ArNHCH2CH2}{(2-C5H4N)CH2}2N (L3)
3.3 Synthesis of {(2,4,6-Me3C6H2)NHCH2CH2}{(2-
C5H4N)CH2}NMe (LI)
(a) L3a, Ar = 2,4-Me2C6H3. An oven-dried Schlenk
flask equipped with a magnetic stir bar was evacuated
and backfilled with nitrogen. The flask was charged with
{(2,4-Me2C6H3)NHCH2CH2}{(2-C5H4N)CH2}NH (1.00 g,
3.92 mmol), 2-picolyl chloride hydrochloride (0.965 g,
5.88 mmol), K2CO3 (1.628 g, 11.8 mmol) and acetonitrile
An oven-dried Schlenk flask equipped with a magnetic
stir bar was evacuated and backfilled with nitrogen. The
flask was charged with {(2,4,6-Me3C6H2)NHCH2CH2}{(2-
C5H4N)CH2}NH (0.200 g, 0.74 mmol), K2CO3 (0.154 g,
1.12 mmol) in MeCN (40 ml) and cooled to −10 ◦C. MeI
(0.05 ml, 0.82 mmol) in MeCN (40 ml) was added dropwise
over the course of 1 h before warming of the reaction mixture
to room temperature and stirring for an additional 1 h. The
reaction mixture was filtered and the solvent removed under
reduced pressure to afford an oily residue. The residue was
dissolved in dichloromethane (30 ml) and washed with water
(3 × 30 ml). The organic layer was separated, dried over MgSO4
and the volatiles removed under reduced pressure to give a
brown oil. The crude product was purified via alumina column
chromatography (active neutral Brockmann grade 1) employing
ethyl acetate and hexane (1 : 3) as the eluting solvent mixture
to give {(2,4,6-Me3C6H2)NHCH2CH2}{(2-C5H4N)CH2}NMe
(LI) as a yellow oil. Yield: 63% (0.132 g, 0.47 mmol). ES mass
spectrum, m/z 284 [M + H]+. IR (cm−1), 3356 (N–H). 1H NMR
(CDCl3, 300 MHz): d 2.13 (s, 3H, Mep), 2.18 (s, 6H, Meo), 2.20
◦
(80 ml). The reaction mixture was heated to 55 C and stirred
for a period of 3 days. After cooling to room temperature, the
contents were filtered and the solvent removed under reduced
pressure to afford an oily residue. The residue was dissolved in
dichloromethane (50 ml) and washed with water (3 × 50 ml). The
organic layer was separated, dried over MgSO4 and the volatiles
removed under reduced pressure to give a brown oil. The
crude product was purified via alumina column chromatography
(active neutral Brockmann grade 1) employing ethyl acetate
and hexane (1 : 4) as the eluting solvent mixture to give {(2,4-
Me2C6H3)NHCH2CH2}{(2-C5H4N)CH2}2N (L3a) as a yellow
oil. Yield: 38% (0.515 g, 1.49 mmol). ES mass spectrum, m/z
1
347 [M + H]+. IR (cm−1), 3331 (N − H). H NMR (CDCl3,
250 MHz): d 2.10 (s, 3H, Mep), 2.13 (s, 3H, Meo), 2.83 (t, 2H,
3J(HH) 6.0, CH2), 3.12 (t, 2H, CH2), 3.79 (s, 4H, Py–CH2), 6.35
3
(d, 1H, J(HH) 8.5, Ar–H), 6.79 (m, 2H, Ar–H), 7.05 (t, 2H,
3
(s, 3H, N–Me), 2.61 (t, 2H, J(HH) 6.0, CH2), 3.00 (t, 2H,
3J(HH) 7.6, Py–H), 7.37 (d, 2H,3J(HH) 7.8, Py–H), 7.53 (dt,
CH2), 3.65 (s, 2H, PyCH2), 6.72 (s, 2H, Ar–H), 7.07 (m, 1H,
4
3
2H,3J(HH) 7.5, J(HH) 1.6, Py–H) and 8.45 (d, 2H, J(HH)
4.8, Py–H). 13C NMR (CDCl3, 63 MHz,1H composite pulse
decoupled): d 17.9 (s, Meo), 20.7 (s, Mep), 41.7 (s, CH2), 53.1 (s,
CH2), 60.6 (s, PyCH2), 110.3 (s, Ar–C), 122.5 (s, Ar–C), 122.5 (s,
Py–C), 123.4 (s, Py–C), 126.1 (s, Ar–C), 127.7 (s, Ar–C), 131.2
(s, Ar–C), 136.8 (s, Py–C), 144.7 (s, Ar–C), 149.6 (s, Py–C) and
159.8 (s, Py–C).
3
3
Py–H), 7.39 (d, 1H, J(HH) 7.6, Py–H), 7.67 (dt, 1H, J(HH)
7.5, 4J(HH) 1.6, Py–H) and 8.46 (d, 1H, 3J(HH) 7.5, Py–H). 13
C
NMR (CDCl3, 75 MHz, 1H composite pulse decoupled): d 17.5
(s, Meo), 19.5 (s, Mep), 40.94 (s, N–Me), 44.9 (s, CH2), 56.7 (s,
CH2), 63.3 (s, Py–CH2), 121.0 (s, Py–C), 121.8 (s, Py–C), 127.9
(s, Ar–C), 128.4 (s, Ar–C), 129.6 (s, Ar–C), 135.4 (s, Py–C), 143.0
(s, Ar–C), 148.0 (s, Py–C) and 158.3 (s, Py–C).
(b) L3b, Ar = 2,6-Me2C6H3. Using the same proce-
dure and molar quantities of reagents as above in 3.5(a),
employing {(2,6-Me2C6H3)NHCH2CH2}{(2-C5H4N)CH2}NH
(1.00 g, 3.92 mmol), 2-picolyl chloride hydrochloride (0.965 g,
5.88 mmol), K2CO3 (1.628 g, 11.8 mmol) and ace-
tonitrile (80 ml), afforded {(2,6-Me2C6H3)NHCH2CH2}{(2-
C5H4N)CH2}2N (L3b) as a yellow oil. Yield: 35% (0.48 g,
1.4 mmol). ES mass spectrum, m/z 347 [M + H]+. IR (cm−1),
3354 (N–H). 1H NMR (CDCl3, 250 MHz): d 2.20 (s, 6H, Meo),
3.4 Synthesis of {(2,6-Me2C6H3)NHCH2CH2}{(2-
=
C5H4N)CH2}N(CH2C6H4CH CH2) (L2)
An oven-dried Schlenk flask equipped with a magnetic
stir bar was evacuated and backfilled with nitrogen. The
flask was charged with {(2,6-Me2C6H3)NHCH2CH2}{(2-
C5H4N)CH2}NH (0.667 g, 2.62 mmol), 4-vinylbenzyl chloride
(0.600 g, 0.55 ml, 3.93 mmol), K2CO3 (1.08 g, 7.86 mmol) a◦nd
acetonitrile (60 ml). The reaction mixture was heated to 80 C
and stirred at this temperature for a period of 3 days. After
cooling to room temperature, the contents were filtered and the
solvent removed under reduced pressure to afford an oily residue.
The residue was dissolved in dichloromethane (40 ml) and
washed with water (3 × 40 ml). The organic layer was separated,
dried over MgSO4 and the volatiles removed under reduced
pressure to give a brown oil. The crude product was purified
via alumina column chromatography (active neutral Brockmann
grade 1) employing ethyl acetate and hexane (1 : 4) as the elut-
3
2.80 (t, 2H, J(HH) 6.0, CH2), 3.10 (t, 2H, CH2), 3.80 (s, 4H,
Py–CH2), 6.68 (m, 1H, Ar–H), 6.87 (d, 2H, 3J(HH) 7.4, Ar–H),
7.07 (m, 2H, Py–H), 7.42 (d, 2H,3J(HH) 8.1, Py–H), 7.60 (dt,
2H,3J(HH) 6.0,4J(HH) 1.1, Py–H) and 8.47 (dd, 2H, 3J(HH) 4.8,
4J(HH) 1.6, Py–H). 13C NMR (CDCl3, 63 MHz,1H composite
pulse decoupled): d 19.2 (s, Meo), 46.2 (s, CH2), 55.0 (s, CH2),
60.8 (s, Py–CH2), 121.5 (s, Ar–C), 122.5 (s, Py–C), 123.5 (s, Py–
C), 129.2 (s, Ar–C), 136.8 (s, Py–C), 138.9 (s, Ar–C), 147.0 (s,
Ar–C), 149.6 (s, Py–C) and 159.7 (s, Py–C).
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0
2 6 3 7

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3.6 Alternative synthesis of {(ArNHCH2CH2}{(2-
C5H4N)CH2}2N (L3)
3.9 Synthesis of [{{(2,4-Me2C6H3)NHCH2CH2}{(2-
C5H4N)CH2}2N}}MCl2] (3)
(a) L3a, Ar = 2,4-Me2C6H3. An oven-dried Schlenk flask
equipped with a magnetic stir bar was evacuated and backfilled
with nitrogen. The flask was charged with dpea (3.68 g,
15.2 mmol), 2,4-dimethylphenyl bromide (2.5 ml, 3.36 g,
18.2 mmol), Pd2(dba)3 (0.028 g, 0.030 mmol), rac-BINAP
(0.061 g, 0.10 mmol), NaOBut (1.90 g, 20 mmol) and toluene
(30 ml). The reaction mixture was heated to reflux and stirred
for 4 days. After cooling to room temperature, the solvent was
removed under reduced pressure to afford an oil residue. The
residue was dissolved in diethyl ether, washed with water and
saturated NaCl solution. The organic layer was separated and
dried over MgSO4. The volatiles were removed under reduced
pressure and the residue left under vacuum at 50 ◦C for 24 h
to give {(2,4-Me2C6H3)NHCH2CH2}{(2-C5H4N)CH2}2N (L3a)
as a viscous brown oil. Yield: 74% (4.237 g, 12.25 mmol). The
spectroscopic data were as described in 3.5(a).
(a) 3a, M = Co. An oven-dried Schlenk flask equipped
with a magnetic stir bar was evacuated and backfilled with
nitrogen. The flask was charged with CoCl2 (0.020 g, 0.15 mmol)
in n-BuOH (5 ml) and the reaction stirred at 90 ◦C until
dissolution. L3a (0.052 g, 0.15 mmol) in n-BuOH (2 ml) was
added and the reaction mixture stirred at 90 ◦C for 20 min.
Following concentration of the reaction mixture, hexane was
added to induce precipitation of the product. The suspension
was stirred overnight, filtered, washed with hexane (2 × 30 ml)
and dried under reduced pressure to afford [(L3a)CoCl2] (3a) as
a pale blue solid. Yield: 65% (0.046 g, 0.10 mmol).
(b) 3b, M = Fe. Using an analogous procedure to that
described above in 3.9(a) employing L3a (0.138 g, 0.40 mmol)
and FeCl2 (0.050 g, 0.40 mmol), gave [(L3a)FeCl2] (3b) as a
yellow powder. Recrystallisation from a hot acetonitrile solution
gave 3b as yellow crystals. Yield: 79% (0.151 g, 0.32 mmol).
(b) L3b, Ar = 2,6-Me2C6H3. Using an analogous route to
that outlined in 3.6(a) employing dpea (4.00 g, 16.5 mmol), 2,6-
dimethylphenyl bromide (2.42 ml, 3.36 g, 18.2 mmol), Pd2(dba)3
(0.032 g, 0.034 mmol), rac-BINAP (0.064 g, 0.11 mmol),
NaOBut (1.982 g, 21.0 mmol) and toluene (30 ml) gave {(2,6-
Me2C6H3)NHCH2CH2}{(2-C5H4N)CH2}2N (L3b) as a viscous
oil. Yield: 85% (4.864 g, 14.0 mmol). The spectroscopic data
were as described in 3.5(b).
(c) 3c, M = Mn. Using an analogous procedure to that
described above in 3.9(a) employing L3a (0.194 g, 0.56 mmol)
and MnCl2 (0.070 g, 0.56 mmol), gave [(L3a)MnCl2] (3c) as a
white powder. Layering of an acetonitrile solution with hexane
gave 3c as clear crystals. Yield: 65% (0.170 g, 0.36 mmol).
3.10 Synthesis of [{{(2,6-Me2C6H3)NHCH2CH2}{(2-
C5H4N)CH2}2N}}MCl2]n (4)
(a) 4a, M = Co, n = 1. An oven-dried Schlenk flask
equipped with a magnetic stir bar was evacuated and backfilled
with nitrogen. The flask was charged with CoCl2 (0.022 g,
0.17 mmol) in n-BuOH (5 ml) and the reaction stirred at 90 ◦C
until dissolution of the metal salt. L3b (0.059 g, 0.17 mmol)
in n-BuOH (2 ml) was added and the reaction mixture stirred
3.7 Synthesis of [{((2,4,6-Me3C6H2)NHCH2CH2)((2-
C5H4N)CH2)NMe}MCl2] (1)
(a) 1a, M = Co. An oven-dried Schlenk flask equipped
with a magnetic stir bar was evacuated and backfilled with
nitrogen. The flask was charged with CoCl2·6H2O (0.066 g,
0.28 mmol) in THF (5 ml) at room temperature and L1 (0.080 g,
0.28 mmol) was introduced to form a purple solution. After
being stirred at room temperature for 24 h, the reaction mixture
was concentrated and hexane added to induce precipitation of
[(LI)CoCl2] (1a) as a purple solid. The suspension was stirred
overnight, filtered, washed with hexane (2 × 30 ml) and dried
under reduced pressure. Recrystallisation from hot acetonitrile
gave purple crystals of 1a suitable for single crystal X-ray
structure determination. Yield: 72% (0.087 g, 0.21 mmol).
◦
at 90 C for a further 20 min. Following concentration of the
reaction mixture, hexane was added to induce precipitation
of the product. The suspension was stirred overnight, filtered,
washed with hexane (2 × 30 ml) and dried under reduced
pressure to afford [(L3b)CoCl2] (3b) as a pale blue solid. Yield:
68% (0.055 g, 0.16 mmol).
(b) 4b, M = Fe, n = 1. Using an analogous procedure
and molar ratios to that described in 3.10(a) employing L3b
(0.059 g, 0.17 mmol) and FeCl2 (0.022 g, 0.17 mmol), gave
[(L3b)FeCl2] (4b) as a yellow powder. Recrystallisation from a
hot acetonitrile solution gave 4b as yellow crystals. Yield: 65%
(0.052 g, 0.11 mmol).
(b) 1b, M = Fe. Using an analogous procedure and molar
ratios of reagents to that described above in 3.7(a) employing L1
(0.080 g, 0.28 mmol) and FeCl2(THF)1.5 (0.066 g, 0.28 mmol),
gave [(L1)FeCl2] (3b) as a pale yellow powder. Yield: 66%
(0.076 g, 0.19 mmol).
(c) 4c, M = Mn, n = 2. Using an analogous procedure to
that described in 3.10(a) using MnCl2 (0.076 g, 0.60 mmol) and
L3b (0.208 g, 0.60 mmol) gave [(L3b)MnCl(l-Cl)]2 (4c) as a white
solid. Layering of an acetonitrile solution of 4c with hexane gave
4c as clear crystals. Yield: 71% (0.198 g, 0.21 mmol).
3.8 Synthesis of [{{(2,6-Me2C6H3)NHCH2CH2}{(2-
=
C5H4N)CH2)}N(CH2C6H4CH CH2)}MCl2] (2)
(a) 2a, M = Co. An oven-dried Schlenk flask equipped
with a magnetic stir bar was evacuated and backfilled with
nitrogen. The flask was charged with CoCl2·6H2O (0.022 g,
0.09 mmol) in THF (5 ml) at room temperature and L2 (0.033 g,
0.09 mmol) was introduced to form a blue solution. After being
stirred at room temperature for 24 h, the reaction mixture
was concentrated and hexane added to induce precipitation of
[(L2)CoCl2] (2a) as a blue solid. The suspension was stirred
overnight, filtered, washed with hexane (2 × 30 ml) and dried
3.11 Crystallography
Data for 1a, 3b·MeCN, 3c·MeCN, 4b·MeCN and 4c were
collected on a Bruker APEX 2000 CCD diffractometer. Details
of data collection, refinement and crystal data are listed in
Table 7. The data were corrected for Lorentz and polarisation
effects and empirical absorption corrections applied. Structure
solution by Patterson methods and structure refinement on F2
employed SHELXTL version 6.10.26,27 Hydrogen atoms were
˚
included in calculated positions (C–H = 0.96 A) riding on the
under reduced pressure. Yield: 65% (0.030 g, 0.06 mmol). IR
−1
bonded atom with isotropic displacement parameters set to 1.5
Ueq(C) for methyl H atoms and 1.2 Ueq(C) for all other H atoms.
All non H atoms were refined with anisotropic displacement
parameters.
=
(cm ), 1628 (C C).
(b) 2b, M = Fe. Using an analogous procedure to that
described above in 3.8(a) employing L2 (0.056 g, 0.15 mmol)
and FeCl2(THF)1.5 (0.035 g, 0.15 mmol), gave [(L1)FeCl2] (3b)
CCDC reference numbers 270047–270051.
as a pale yellow powder. Yield: 63% (0.047 g, 0.09 mmol). IR
See http://dx.doi.org/10.1039/b505763a for crystallographic
data in CIF or other electronic format.
−1
=
(cm ), 1626 (C C).
2 6 3 8
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0

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D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0
2 6 3 9

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Acknowledgements
We thank the EPSRC (to CJD) and ExxonMobil (to CJD) for
financial assistance. Financial and equipment support from the
Department of Chemistry at the University of Leicester and the
Royal Society are gratefully acknowledged. Johnson Matthey
PLC are thanked for their loan of palladium chloride.
12 B. Dietrich, M. W. Hosseini, J.-M. Lehn and R. B. Sessions, Helv.
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2 6 4 0
D a l t o n T r a n s . , 2 0 0 5 , 2 6 3 0 – 2 6 4 0