From monomeric to polymeric manganese complexes bearing bis(imino)pyridine and related ligands

Article abstract of DOI:10.1039/b207384f

Reactions of MnX₂ with the tridentate nitrogen donor ligands [2,6-{(2,4,6-Me₃C₆H₂)N=CMe}₂C ₅H₃N], [2,6-{(Me)-(Ph)NN=CMe}₂C ₅H₃N] and [2-{(2,6-Pi₂ⁱC ₆H₃)N=CH}-6-{(2,6-Pr₂ⁱC ₆H₃)NHCH(Me)}C₅H₃N] in refluxing acetonitrile yield the high spin divalent monometallic manganese complexes, [2,6-{(2,4,6-Me₃C₆H₂)N=CMe}₂C ₅H₃N]-MnX₂ (X = Br 1), [2,6-{(Me)(Ph)NN=CMe} ₂C₅H₃N]MnX₂ (X = Cl 2) and [2-{(2,6-Pi₂ⁱC₆H₃)N=CH}-6-{(2,6- Pi₂ⁱ-C₆H₃)NHCH(Me)}C ₅H₃N]MnX₂ (X = Cl 3), respectively, in good yield. Crystallographic studies on 1-3 reveal all three complexes to be pentacoordinate with geometries that can be best described as distorted trigonal bipyramidal (1, 2) or square pyramidal (3). Conversely, treatment of MnCl ₂ with [2-{(2″-H₂NC₆H₄-C ₂H₄-2″-C₆H₄)N=CMe}6-{O=CMe} C₅H₃N] (prepared from the incomplete condensation reaction of the diamine [{2,2″-(NH₂)C₆H₄}2- (CH₂CH₂)] with 2,6-diacetylpyridine) under similar reaction conditions results in self-assembly to afford the antiferromagnetically coupled polymetallic salt [{2,6-{(2′,2″-C₆H ₄-CH₂)₂(N=CMe)₂}₂(C ₅H₃N)₂}Mn₂Cl₃(NCMe) ₂]-[{2,6-{(2′,2″-C₆H₄-CH ₂)₂(N=CMe)₂}₂(C₅H ₃N)₂}Mn₂Cl₃(MnCl₄)] _n (4). The molecular structure of 4 shows a discrete dimanganese cation and polymeric manganese anion with each ionic unit supported by a 26-membered macrocyclic hexadentate nitrogen donor ligand. The Royal Society of Chemistry 2003.

Full text of DOI:10.1039/b207384f

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From monomeric to polymeric manganese complexes bearing
bis(imino)pyridine and related ligands
Vernon C. Gibson,* Stuart McTavish, Carl Redshaw, Gregory A. Solan, Andrew J. P. White
and David J. Williams
Department of Chemistry, Imperial College, South Kensington, London, UK SW7 2AY.
E-mail: V.Gibson@ic.ac.uk
Received 29th July 2002, Accepted 8th November 2002
First published as an Advance Article on the web 12th December 2002
Reactions of MnX with the tridentate nitrogen donor ligands [2,6-{(2,4,6-Me C H )N᎐CMe} C H N], [2,6-{(Me)-
᎐
2
3
6
2
2
5
3
(Ph)NN᎐CMe} C H N] and [2-{(2,6-Pri C H )N᎐CH}-6-{(2,6-Pri C H )NHCH(Me)}C H N] in refluxing
᎐
᎐
2
5
3
2
6
3
2
6
3
5
3
acetonitrile yield the high spin divalent monometallic manganese complexes, [2,6-{(2,4,6-Me C H )N᎐CMe} C H N]-
᎐
3
6
2
2
5
3
MnX (X = Br 1), [2,6-{(Me)(Ph)NN᎐CMe} C H N]MnX (X = Cl 2) and [2-{(2,6-Pri C H )N᎐CH}-6-{(2,6-Pri -
᎐
᎐
2
2
5
3
2
2
6
3
2
C6H3)NHCH(Me)}C5H3N]MnX2 (X = Cl 3), respectively, in good yield. Crystallographic studies on 1–3 reveal all
three complexes to be pentacoordinate with geometries that can be best described as distorted trigonal bipyramidal
(1, 2) or square pyramidal (3). Conversely, treatment of MnCl with [2-{(2Љ-H NC H –C H –2Љ-C H )N᎐CMe}-
᎐
2
2
6
4
2
4
6
4
6-{O᎐CMe}C H N] (prepared from the incomplete condensation reaction of the diamine [{2,2Љ-(NH )C H } -
᎐
5
3
2
6
4 2
(CH2CH2)] with 2,6-diacetylpyridine) under similar reaction conditions results in self-assembly to afford the
antiferromagnetically coupled polymetallic salt [{2,6-{(2Ј,2Љ-C H –CH ) (N᎐CMe) } (C H N) }Mn Cl (NCMe) ]-
᎐
6
4
2
2
2
2
5
3
2
2
3
2
[{2,6-{(2Ј,2Љ-C H –CH ) (N᎐CMe) } (C H N) }Mn Cl (MnCl )] (4). The molecular structure of 4 shows a discrete
᎐
6
4
2
2
2
2
5
3
2
2
3
4
n
dimanganese cation and polymeric manganese anion with each ionic unit supported by a 26-membered macrocyclic
hexadentate nitrogen donor ligand.
iminopyridine manganese complexes [2,6-{(2,4,6-Me C H )N᎐
Introduction
᎐
3
6
2
CMe}2C5H3N]MnBr2 (1), [2,6-{(Me)(Ph)NN᎐CMe} C H N]-
᎐
2
5
3
In recent years there has been much interest in the discovery
and development of new catalysts for olefin polymerisation.
While cyclopentadienyl-based systems have largely led the way,1
the potential for non-cyclopentadienyl metal catalysts, and
especially for new systems featuring late transition metals, has
been realised.2–4 In this regard, divalent iron (d6) and cobalt (d7)
complexes stabilised by sterically demanding bis(imino)pyrid-
ine ligands (type A in Fig. 1) have allowed access to highly active
MnCl2 (2) and [2-{(2,6-Pri C H )N᎐CH}-6-{(2,6-Pri C H )N-
᎐
2
6
3
2
6
3
HCH(Me)}C5H3N]MnCl2 (3) have been prepared in good yield
(ca. 40–77%) as air stable orange solids by reaction of the corre-
sponding ligand with MnX2 in refluxing acetonitrile (Scheme 1).
All the complexes have been characterised by mass spectro-
metry, infrared spectroscopy, EPR, microanalysis and from
magnetic measurements (see Experimental). In addition, 1–3
have been the subject of single crystal X-ray diffraction studies.
Orange crystals of 1 suitable for an X-ray crystal structure
determination were grown from acetonitrile at room temper-
ature. The molecular structure is shown in Fig. 2; selected bond
Fig. 1 Bis(imino)pyridine (A), bis(hydrazone)pyridine (B) and amino-
iminopyridine (C) complexes.
catalysts for ethylene polymerisation.5,6 Subsequent advances
have shown that active systems can also be prepared containing
the bis(hydrazone)pyridine (type B in Fig. 1)7 and the amino-
iminopyridine (type C in Fig. 1)8 complexes, albeit with lower
productivities.
By contrast, manganese (d5) derivatives of complexes A–C
(Fig. 1) exhibit no or very poor ethylene polymerisation activ-
ities upon activation with excess methylaluminoxane (MAO),
possibly a result of reduction of the Mn() centres.5c,9 The
recent report by Gambarotta and co-workers9 on the bis(imino)-
pyridine manganese system prompts us to disclose our results
on the synthesis and characterisation of Mn() complexes con-
taining bis(imino)pyridine, and closely related bis(hydrazone)-
pyridine and aminoiminopyridine, ligands.
Fig. 2 The molecular structure of 1.
lengths and angles are listed in Table 1. The manganese com-
plex 1 crystallises with two independent molecules in the
asymmetric unit, both having molecular Cs symmetry and a
trigonal bipyramidal geometry for the manganese centre. This
geometry is similar to that observed for the related complex
[2,6-{(C H )N᎐CMe} C H N]MnBr .10 The Mn–N and Mn–Br
᎐
6
5
2
5
3
2
distances are unexceptional (Table 1). The principal difference
between the two molecules is in the displacement of the metal
centre out of the plane of the bis(imino)pyridine unit. In one
molecule the manganese lies only 0.08 Å out of the plane of the
ligand backbone, which is planar to within 0.04 Å, whereas in
the other the metal is displaced by 0.24 Å out of the ligand
plane (which is planar to within 0.06 Å). In the isostructural
Results and discussion
Synthesis of ligands and complexes
The bis(imino)pyridine, bis(hydrazone)pyridine and the amino-
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 3
D a l t o n T r a n s . , 2 0 0 3 , 2 2 1 – 2 2 6
221

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Table 1 Selected bond lengths (Å) and angles (Њ) for 1
Molecule A
Molecule B
Molecule A
Molecule B
Mn–Br(1)
Mn–N(1)
Mn–N(9)
C(9)–N(9)
2.497(2)
2.202(7)
2.330(6)
1.292(10)
2.498(2)
2.207(6)
2.345(6)
1.277(10)
Mn–Br(2)
Mn–N(7)
C(7)–N(7)
2.485(2)
2.330(7)
1.270(10)
2.483(2)
2.322(6)
1.272(10)
N(1)–Mn–N(9)
N(9)–Mn–N(7)
N(9)–Mn–Br(2)
N(1)–Mn–Br(1)
N(7)–Mn–Br(1)
71.2(2)
142.6(2)
99.3(2)
122.2(2)
100.8(2)
71.2(2)
141.3(2)
101.0(2)
117.6(2)
103.0(2)
N(1)–Mn–N(7)
N(1)–Mn–Br(2)
N(7)–Mn–Br(2)
N(9)–Mn–Br(1)
Br(2)–Mn–Br(1)
71.3(2)
125.3(2)
100.9(2)
100.2(2)
112.51(6)
70.6(2)
130.6(2)
99.3(2)
99.5(2)
111.79(6)
Table 2 Selected bond lengths (Å) and angles (Њ) for 2
Mn–Cl(1)
Mn–N(1)
Mn–N(11)
N(8)–N(9)
N(11)–N(12)
2.353(2)
2.173(4)
2.321(4)
1.396(6)
1.387(6)
Mn–Cl(2)
Mn–N(8)
C(7)–N(8)
C(10)–N(11)
2.332(2)
2.330(4)
1.290(7)
1.285(7)
N(1)–Mn–N(11)
N(11)–Mn–N(8)
N(11)–Mn–Cl(2)
N(1)–Mn–Cl(1)
N(8)–Mn–Cl(1)
71.9(2)
143.0(2)
99.65(12)
109.25(12)
97.18(12)
N(1)–Mn–N(8)
N(1)–Mn–Cl(2)
N(8)–Mn–Cl(2)
N(11)–Mn–Cl(1)
Cl(2)–Mn–Cl(1)
71.2(2)
122.96(13)
97.91(13)
97.35(12)
127.77(7)
Fig. 3 The molecular structure of 2.
Scheme
1
Reagents and conditions: (i) [2,6-{(2,4,6-Me3C6H2)N᎐
᎐
CMe}2C5H3N], MeCN, heat; (ii) [2,6-{(Me)(Ph)NN᎐CMe}2C5H3N],
᎐
MeCN, heat; (iii) [2-{(2,6-Pri2C6H3)N᎐CH}-6-{(2,6-Pri2C6H3)NHCH-
᎐
(Me)}C5H3N], MeCN, heat.
(though not isomorphous) iron complex5b the metal lies 0.15 Å
out of the ligand plane. In both independent molecules the
mesityl ring planes are oriented approximately orthogonally to
the plane of the bis(imino)pyridine unit (interplanar angles in
the range 80–89Њ). There are no intermolecular packing features
of interest.
The molecular structure of 2 is shown in Fig. 3; selected bond
lengths and angles are listed in Table 2. Crystals of 2 were
grown from acetonitrile at room temperature. Compound 2 has
a solid state structure that is isomorphous with its iron ana-
logue,7 having molecular Cs symmetry and a distorted trigonal
bipyramidal geometry at the manganese atom, though with the
Mn–Cl(1) distance still being significantly longer than that to
Cl(2); the Mn–N distances are unexceptional. The bis(imino)-
pyridine unit, together with N(9) and N(12), is planar to within
0.08 Å, the manganese atom being displaced by 0.16 Å out of
the plane in the direction of Cl(1). There are no intermolecular
packing interactions of note.
Fig. 4 The molecular structure of 3.
isomorphous with the previously reported iron and cobalt
analogues.8 The geometry at manganese is square pyramidal
with the metal atom lying 0.53 Å out of the basal plane cf.
0.43 Å for the iron species. The aminoiminopyridine unit is
planar to within 0.07 Å with the manganese centre lying 0.16 Å
out of this plane in the direction of Cl(1). The planes of the
The molecular structure of 3 is shown in Fig. 4; selected
bond lengths and angles are collected in Table 3. A single
crystal X-ray analysis shows the manganese complex 3 to be
D a l t o n T r a n s . , 2 0 0 3 , 2 2 1 – 2 2 6
222

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Table 3 Selected bond lengths (Å) and angles (Њ) for 3
Mn–Cl(1)
Mn–N(1)
Mn–N(9)
C(9)–N(9)
2.327(2)
2.206(4)
2.294(4)
1.268(6)
Mn–Cl(2)
Mn–N(7)
C(7)–N(7)
2.2967(12)
2.386(4)
1.480(6)
N(1)–Mn–N(9)
N(9)–Mn–Cl(2)
N(9)–Mn–Cl(1)
N(1)–Mn–N(7)
Cl(2)–Mn–N(7)
73.35(13)
103.30(10)
106.12(12)
71.63(14)
N(1)–Mn–Cl(2)
N(1)–Mn–Cl(1)
Cl(2)–Mn–Cl(1)
N(9)–Mn–N(7)
Cl(1)–Mn–N(7)
144.11(12)
103.98(12)
111.05(7)
144.16(14)
89.58(12)
100.51(10)
C(10)- and C(22)-containing 2,6-diisopropylphenyl rings are
inclined by ca. 88 and 78Њ to the aminoiminopyridine unit
respectively. The most noticeable feature of the pattern of
bonding to manganese is the very long Mn–N distance to the
amino nitrogen N(7) [2.386(4) Å] cf. that to the imino nitrogen
N(9) [2.294(4) Å], a very similar asymmetry to that seen in the
iron complex. There are no noteworthy intermolecular packing
interactions.
Fig. 5 The structure of one of the repeat units of the anionic [{2,6-
{(2Ј,2Љ-C6H4–CH2)2(N᎐CMe)2}2(C5H3N)2}Mn2Cl3(MnCl4)]n polymer
᎐
chains present in the crystals of 4.
Complexes 1–3 are all paramagnetic with magnetic moments
falling between 5.6 and 5.8 µB (Evans balance at ambient tem-
perature) indicating a high spin d5 electronic configuration for
the divalent manganese centres. The X-band EPR spectra of
1–3, recorded at ambient temperature in toluene display single
broad featureless resonances at ca. g = 2.0; no hyperfine struc-
ture is evident. The IR spectra of 1–3 display absorption bands
for the imine C᎐N stretches ca. 1590 cmϪ1 and for 3 an addi-
᎐
tional band at 3270 cmϪ1 is observed for the ν(N–H). In the
FAB mass spectra of 1–3 molecular ion peaks are seen along
with peaks corresponding to loss of halide ligands from the
molecular ions.
With the intent of generating complexes with the bis(imino)-
pyridine motif (type A in Fig. 1) incorporated into a
macrocyclic unit, we set about examining the reaction of 2,6-
diacetylpyridine with the ortho-bridged diamine [{2,2Ј-(NH2)-
C6H4}2(CH2CH2)]. However, the acid catalysed condensation in
ethanol at elevated temperature afforded [2-{(2Ј-H2NC6H4–
C H –2Љ-C H )N᎐CMe}-6-{O᎐CMe}C H N] as a yellow solid,
᎐
᎐
2
4
6
4
5
3
in which only one amine group had undergone condensation
and the other amine remained unreacted. Spectroscopic data
(see Experimental) are consistent with the formulation depicted
in Scheme 2. The 1H NMR spectrum of [2-{2Ј-H2NC6H4–
Fig. 6 Part of the one of the MnCl4-linked anionic polymer chains
of
[{2,6-{(2Ј,2Љ-C6H4–CH2)2(N᎐CMe)2}2(C5H3N)2}Mn2Cl3(MnCl4)]n
᎐
present in the crystals of 4, showing the continuous –Mn–Cl–Mn–Cl–
C H –2Љ-C H N᎐CMe}-6-{O᎐CMe}C H N] in CDCl exhibits
᎐
᎐
2
4
6
4
5
3
3
backbone.
resonances in the regions characteristic of the imine (δ 2.41)
and ketone (δ 2.80) CMe protons along with three more down-
field signals (δ 8.61–7.95) being observed for the inequivalent
pyridine protons. In the infrared spectrum absorption bands for
the imine and ketone are clearly visible at 1696 and 1638 cmϪ1
respectively and the molecular ion peak is observed in the EI
mass spectrum.
Complete condensation can, nevertheless, be achieved on
reaction of MnCl2 with [2-{2Ј-H NC H –C H –2Љ-C H N᎐
᎐
2
6
4
2
4
6
4
CMe}-6-{O᎐CMe}C H N] in refluxing acetonitrile to
᎐
5
3
afford the air stable orange crystalline salt [LMn2Cl3(NCMe)2]-
[LMn2Cl3(MnCl4)]n (4) [where L = 2,6-{(2Ј,2Љ-C6H4–CH2)2-
(N᎐CMe) } (C H N) ] (Scheme 2).
᎐
2
2
5
3
2
Single crystals of 4 suitable for an X-ray crystal determin-
ation were grown by slow cooling of a hot acetonitrile solution
of 4. The molecular structure indicates that co-crystallisation
of two distinct molecular species has occurred. One of these is
an anionic polymer in which macrocyclic LMn2Cl3 moieties
(Fig. 5) are linked by MnCl4 dianions to form chains having a
continuous –Mn–Cl–Mn–Cl– backbone (Fig. 6). The other,
in contrast, comprises discrete [LMn2Cl3(NCMe)2] cations
(Fig. 7).
Fig. 7 One of the monomeric [{2,6-{(2Ј,2Љ-C6H4–CH2)2(N᎐CMe)2}2-
᎐
(C5H3N)2}Mn2Cl3(NCMe)2] cations present in the crystals of 4.
In both cases the LMn2Cl3 cores have crystallographic C2
symmetry and essentially the same geometry, the manganese,
nitrogen and equivalent chlorine atoms fitting to within 0.16 Å.
The geometry at each manganese of the LMn2Cl3 units is
distorted octahedral with cis angles ranging between 72.0(1)
and 110.9(1)Њ in the polymer and 71.0(1) and 108.9(1)Њ in the
monomer (Table 4). In both the polymer and monomer the
distances from the manganese to the “axial” chlorine atoms are
D a l t o n T r a n s . , 2 0 0 3 , 2 2 1 – 2 2 6
223

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Table 4 Selected bond lengths (Å) and angles (Њ) for 4a
Mn(1)–Cl(1)
Mn(1)–Cl(2)
Mn(1)–N(1)
Mn(1)–N(9)
Mn(2)–Cl(3A)
Mn(2)–Cl(4A)
C(9)–N(9)
Cl(5)–Mn(3A)
Mn(3)–N(31)
Mn(3)–N(37)
C(37)–N(37)
2.5935(9)
Cl(1)–Mn(1A)
Mn(1)–Cl(3)
Mn(1)–N(7)
Mn(2)–Cl(3)
Mn(2)–Cl(4)
C(7)–N(7)
Mn(3)–Cl(5)
Mn(3)–Cl(6)
Mn(3)–N(39)
Mn(3)–N(60)
C(39)–N(39)
2.5935(9)
2.716(2)
2.295(4)
2.3806(14)
2.352(2)
1.291(6)
2.5333(8)
2.3627(13)
2.298(4)
2.388(5)
1.280(6)
2.3491(13)
2.168(4)
2.295(4)
2.3806(14)
2.352(2)
1.262(6)
2.5333(8)
2.201(4)
2.336(4)
1.280(6)
N(1)–Mn(1)–N(9)
N(9)–Mn(1)–N(7)
N(9)–Mn(1)–Cl(2)
N(1)–Mn(1)–Cl(1)
N(7)–Mn(1)–Cl(1)
N(1)–Mn(1)–Cl(3)
N(7)–Mn(1)–Cl(3)
Cl(1)–Mn(1)–Cl(3)
Cl(4)–Mn(2)–Cl(3A)
Cl(4)–Mn(2)–Cl(3)
Cl(3A)–Mn(2)–Cl(3)
Mn(1)–Cl(3)–Mn(2)
N(31)–Mn(3)–N(37)
N(31)–Mn(3)–Cl(6)
N(37)–Mn(3)–Cl(6)
N(39)–Mn(3)–N(60)
Cl(6)–Mn(3)–N(60)
N(39)–Mn(3)–Cl(5)
Cl(6)–Mn(3)–Cl(5)
Mn(3)–Cl(5)–Mn(3A)
71.96(14)
143.92(14)
110.87(11)
88.76(10)
96.65(10)
80.39(11)
91.56(10)
163.70(5)
114.61(5)
111.57(5)
99.94(8)
129.74(6)
71.27(14)
170.79(11)
107.70(10)
85.7(2)
N(1)–Mn(1)–N(7)
N(1)–Mn(1)–Cl(2)
N(7)–Mn(1)–Cl(2)
N(9)–Mn(1)–Cl(1)
Cl(2)–Mn(1)–Cl(1)
N(9)–Mn(1)–Cl(3)
Cl(2)–Mn(1)–Cl(3)
Cl(4)–Mn(2)–Cl(4A)
Cl(4A)–Mn(2)–Cl(3A)
Cl(4A)–Mn(2)–Cl(3)
Mn(1)–Cl(1)–Mn(1A)
N(31)–Mn(3)–N(39)
N(39)–Mn(3)–N(37)
N(39)–Mn(3)–Cl(6)
N(31)–Mn(3)–N(60)
N(37)–Mn(3)–N(60)
N(31)–Mn(3)–Cl(5)
N(37)–Mn(3)–Cl(5)
N(60)–Mn(3)–Cl(5)
72.06(14)
174.58(10)
104.78(10)
85.19(10)
96.04(5)
79.93(10)
95.43(5)
104.89(8)
111.57(5)
114.61(5)
156.71(8)
71.00(14)
142.06(14)
108.87(11)
80.1(2)
84.1(2)
90.74(12)
86.97(10)
99.15(5)
90.05(11)
96.92(10)
169.20(12)
159.75(8)
a Equivalent atoms labelled ‘A’ are related to their unique counterparts by the crystallographic C2 axis.
Scheme 2 Reagents and conditions: (i) [{2,2Љ-(NH2)C6H4}2(CH2CH2)], EtOH, Hϩ, heat; (ii) MnCl2, MeCN, heat.
longer than those to their equatorial counterparts. In the
polymer, however, the linkage to the chlorine atom of the
MnCl4 dianion is significantly longer [2.716(2) Å] than to
that linking the two octahedra [2.594(1) Å]. There is no distinct
pattern of differences (monomer vs. polymer) in the bonding to
the bis(imino)pyridine ligand. In the monomer the bis(imino)-
pyridine unit is planar to within 0.07 Å with the manganese
atom lying 0.14 Å out of plane and the phenyl rings are
both inclined, in the same sense (C2 rather than Cs symmetric),
by ca. 63Њ. In the polymer the bis(imino)pyridine unit is
slightly more distorted, being planar to only 0.10 Å but with the
manganese atom lying within this plane; the phenyl rings are
again inclined in the same sense, here by ca. 63 and 71Њ. The
anions and cations pack to form alternating layers within the
crystal. A number of transition metal complexes have been
prepared that contain the aryl-substituted bis(imino)pyridine
D a l t o n T r a n s . , 2 0 0 3 , 2 2 1 – 2 2 6
224

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motif (type A in Fig. 1) incorporated into a macrocyclic
ligand11 but none have been reported that incorporate the
ortho-bridged diamine [{2,2Ј-(NH2)C6H4}2(CH2CH2)]. A tetra-
manganese complex involving chloride-bridged bimetallic units
each sandwiched into a macrocycle has been described12 as
has an infinite polymer based on chloride-bridged [bis(imino)-
pyridine]Mn units.13
elsewhere.5,7,8,16 Compound [{2,2Ј-(NH2)C6H4}2(CH2CH2)] was
obtained as its diphosphate salt and extracted from aqueous
alkaline solution into ethyl acetate, dried (MgSO4) and
recrystallised from isopropyl alcohol. All other chemicals were
obtained commercially and used as received unless stated
otherwise.
Complex 4 shows antiferromagnetic coupling; the magnetic
moment, based on the composition of the complex being
the cation–anion pair [LMn2Cl3(NCMe)2][LMn2Cl3(MnCl4)],
drops from 13.7 µB at 300 K to 6.0 µB at 6 K as indicated in Fig.
8. The FAB mass spectrum of 4 shows peaks corresponding to
Preparations
[2-{(2Ј-H NC H –C H –2Љ-C H )N᎐CMe}-6-{O᎐CMe}-
᎐
᎐
2
6
4
2
4
6
4
C5H3N]. To a solution of 2,6-diacetylpyridine (1.00 g, 6.13
mmol) in absolute ethanol (25 cm3) was added [{2,2Ј-(H2N)-
C6H4}2(C2H4)] (1.30 g, 6.13 mmol). After addition of a few
drops of glacial acetic acid the solution was refluxed for 6 h.
Volatiles were removed under reduced pressure and the solid
was washed with cold ethanol and dried to give [2-{(2Ј-
H NC H –C H –2Љ-C H )N᎐CMe}-6-{O᎐CMe}C H N] as a
᎐
᎐
2
6
4
2
4
6
4
5
3
yellow solid. Yield: 1.12 g, 51%. EI mass spectrum, m/z 357
1
3
[Mϩ]. H NMR (CDCl3): δ 8.61 [d, J(HH) 7.6, Py–Hm, 1H],
8.15 [d, 3J(HH) 7.6, Py–Hm, 1H], 7.95 [app. t, Py–Hp, 1H], 7.3–
6.5 [m, Ph, 8H], 3.45 [s, br, NH, 2H], 2.80 [s, MeC᎐O, 3H], 2.78
᎐
[s, CH CH , 4H] and 2.41 [s, MeC᎐N, 3H]. IR (Nujol mull,
᎐
2
2
cmϪ1): ν(N–H) 3441, ν(C᎐O) 1696, ν(C᎐N) 1638. Anal. Calcd.
᎐
᎐
For C23H23N3O: C, 77.31; H, 6.44; N, 11.76. Found: C, 77.59;
H, 6.71; N, 11.45%.
[2,6-{(2,4,6-Me C H )N᎐CMe} C H N]MnBr (1). The lig-
᎐
3
6
2
2
5
3
2
and [2,6-{(2,4,6-Me C H )N᎐CMe} C H N] (1.00 g, 2.52
᎐
3
6
2
2
5
3
mmol) and MnBr2 (0.54 g, 2.52 mmol) were heated at reflux in
acetonitrile (50 cm3) for 12 h. Following filtration, 1 was
obtained as an orange crystalline solid on prolonged standing
at ambient temperature. Yield: 1.19 g, 77%. Anal. Calcd. for
C27H31Br2N3Mn: C, 52.96; H, 5.07; N, 6.86. Found: C, 53.10; H,
5.21; N, 6.71%. FAB mass spectrum, m/z 612 [Mϩ], 532 [Mϩ Ϫ
Fig. 8 Plot of magnetic moment against temperature for [{2,6-
{(2Ј,2Љ-C6H4–CH2)2(N᎐CMe)2}2(C5H3N)2}Mn2Cl3(NCMe)2][{2,6-
᎐
{(2Ј,2Љ-C6H4–CH2)2(N᎐CMe)2}2(C5H3N)2}Mn2Cl3(MnCl4)] (4).
᎐
the fragments LMn2Cl3 and LMn. In the infrared spectrum
absorption bands for the C᎐N stretch are seen ca. 1595 cmϪ1
.
᎐
Br]. IR (cmϪ1) ν(C᎐N) 1591. µeff 5.67 µB. EPR (toluene, 298 K):
᎐
Microanalytical data support the empirical formula given for 4.
In conclusion, four manganese complexes based on ligands
either containing or derived from the bis(imino)pyridine motif
have been prepared and characterised. All the mononuclear
complexes (1–3) are paramagnetic while the polymetallic com-
plex 4 exhibits antiferromagnetic behaviour. It is worthy of note
that, while iron and cobalt analogues of 1–3 can be prepared,
iron and cobalt analogues of 4 have not proved accessible.
g = 2.00.
[2,6-{(Me)(Ph)NN᎐CMe} C H N]MnCl (2). As for 1, but
᎐
2
5
3
2
using [2,6-{(Me)(Ph)NN᎐CMe} C H N] (1.00 g, 2.68 mmol)
᎐
2
5
3
and MnCl2 (0.33 g, 2.62 mmol) gave 2 as orange blocks. Yield:
0.53 g, 40%. Anal. Calcd. for C23H25Cl2N5Mn: C, 55.53; H,
5.03; N, 14.08. Found: C, 55.71; H, 5.16; N, 13.97%. FAB mass
spectrum, m/z 498 [Mϩ], 463 [Mϩ Ϫ Cl]. IR (cmϪ1) ν(C᎐N)
᎐
1592. µeff 5.69 µB. EPR (toluene, 298 K): g = 2.00.
Experimental
[2-{(2,6-Pri C H )N᎐CH}-6-{(2,6-Pri C H )NHCH(Me)}-
᎐
2
6
3
2
6
3
General
C5H3N]MnCl2 (3). As for 1, but using [2-{(2,6-Pri2C6H3)-
N᎐CH}-6-{(2,6-Pri C H )NHCH(Me)}C H N] (1.00 g, 2.13
All manipulations were carried out under an atmosphere of
nitrogen using standard Schlenk and cannula techniques or in a
conventional nitrogen-filled glove-box. Solvents were refluxed
over an appropriate drying agent, and distilled and degassed
prior to use. Elemental analyses were performed by the micro-
analytical services of the Department of Chemistry at Imperial
College and Medac Ltd. NMR spectra were recorded on a
Bruker spectrometer at 250 MHz (1H) and 62.9 MHz (13C) at
293 K; chemical shifts are referenced to the residual protio
impurity of the deuterated solvent; coupling constants are
quoted in Hz. IR spectra (Nujol mulls) were recorded on Per-
kin-Elmer 577 and 457 grating spectrophotometers. Mass spec-
tra were obtained using either fast atom bombardment (FAB)
or electron impact (EI). Magnetic susceptibility studies were
performed using an Evans balance (Johnson Matthey) at room
temperature. The magnetic moment was calculated following
standard methods14 and corrections for underlying diamagnet-
ism were applied to data.15
᎐
2
6
3
5
3
mmol) and MnCl2 (0.27 g, 2.15 mmol) gave 3 as orange blocks.
Yield: 0.95 g, 75%. Anal. Calcd. for C32H43Cl2N3Mn: C, 64.54;
H, 7.23; N, 7.06. Found: C, 64.81; H, 7.56; N, 6.95%. FAB mass
spectrum, m/z 596 [Mϩ], 561 [Mϩ Ϫ Cl]. IR (cmϪ1) ν(N–H)
3270, ν(C᎐N) 1591. µeff 5.71 µB. EPR (toluene, 298 K): g = 2.00.
᎐
[{2,6-{(2Ј,2Љ-C H –CH ) (N᎐CMe) } (C H N) }Mn Cl -
᎐
6
4
2
2
2
2
5
3
2
2
3
(NCMe) ][{2,6-{(2Ј,2Љ-C H –CH ) (N᎐CMe) } (C H N) }Mn -
᎐
2
6
4
2
2
2
2
5
3
2
2
Cl3(MnCl4)]n (4). As for 1, but using [2-{(2Ј-H2NC6H4–C2H4–2Љ-
C H )N᎐CMe}-6-{O᎐CMe}C H N] (1.00 g, 2.80 mmol) and
᎐
᎐
6
4
5
3
MnCl2 (0.35 g, 2.78 mmol) gave 4 as orange blocks. Yield: 0.37
g, 32% (based on Mn). Anal. Calcd. for C96H90Cl10N14Mn5:
C, 55.71; H, 4.35; N, 9.48. Found: C, 55.02; H, 3.95; N, 8.51%.
FAB mass spectrum, m/z 895 [{2,6-{(2Ј,2Љ-C6H4–CH2)2-
(N᎐CMe) } (C H N) }Mn Cl ], 732 [{2,6-{(2Ј,2Љ-C H –CH ) -
᎐
᎐
2
2
5
3
2
2
3
6
4
2 2
(N᎐CMe) } (C H N) }Mn]. IR (cmϪ1) ν(C᎐N) 1595.
᎐
2
2
5
3
2
X-Ray crystal structure determinations
Materials
Table 5 provides a summary of the crystallographic data for
compounds 1–4. Data were collected on Siemens P4 diffract-
ometers using ω-scans. The structures were solved by direct
methods and they were refined based on F 2 using the
The syntheses of [2,6-{(2,4,6-Me C H )N᎐CMe} C H N], [2,6-
᎐
3
6
2
2
5
3
{(Me)(Ph)NN᎐CMe} C H N] and [2-{(2,6-Pri C H )N᎐CH}-
᎐
᎐
2
5
3
2
6
3
6-{(2,6-Pri2C6H3)NHCH(Me)}C5H3N] have been reported
D a l t o n T r a n s . , 2 0 0 3 , 2 2 1 – 2 2 6
225

View Online
Table 5 Crystal data, data collection and refinement parameters for compounds 1–4a
Data
1
2
3
4
Formula
C27H31N3Br2Mn
C23H25N5Cl2Mn
C32H43N3Cl2Mn
[(C46H42N6Cl3Mn2)(MeCN)2]
[(C46H42N6Cl3Mn2)(MnCl4)]
6MeCN
Solvent
MeCN
MeCN
—
Formula weight
Colour, habit
Crystal size/mm
Temperature/K
Crystal system
Space group
a/Å
653.4
538.4
595.5
2315.3
Yellow plates
0.50 × 0.27 × 0.03
293
Orange plates
0.20 × 0.20 × 0.05
293
Orange prisms
0.33 × 0.28 × 0.22
293
Orthorhombic
P212121 (no. 19)
13.463(1)
13.559(1)
18.694(1)
—
Orange prisms
0.63 × 0.23 × 0.12
173
Monoclinic
P2/c (no. 13)
12.796(1)
17.298(1)
25.167(1)
94.43(1)
Monoclinic
P21/n (no. 14)
16.842(1)
15.156(1)
23.431(2)
92.04(1)
5977.1(5)
8b
Monoclinic
P21/c (no. 14)
13.737(1)
13.211(1)
15.181(1)
101.91(1)
2695.5(3)
4
b/Å
c/Å
β/Њ
V/Å3
3412.3(4)
4
Cu-Kα
5553.6(7)
Z
2c
Radiation used
Cu-Kα
6.90
Cu-Kαd
5.99
Cu-Kαd
µ/mmϪ1
4.75
7.15
No. of unique reflections
measured
8194
5248
Lamina
677
0.059, 0.133
3982
2650
Ellipsoidal
284
0.059, 0.121
3176
2691
Ellipsoidal
348
0.041, 0.090
8230
5746
Empirical
674
0.052, 0.108
observed, |Fo| > 4σ(|Fo|)
Absorption correction
No. of variables
e
R1, wR2
a Details in common: graphite monochromated radiation, refinement based on F 2. b There are two crystallographically independent molecules in the
asymmetric unit. c The complex has crystallographically C2 symmetry. d Rotating anode source. e R1 = Σ||Fo| Ϫ |Fc||/Σ|Fo|; wR2 = {Σ[w(Fo Ϫ Fc2)2]/
2
Σ[w(Fo )2]}1/2; wϪ1 = σ2(Fo ) ϩ (aP)2 ϩ bP.
2
2
SHELXTL program system.17 The structure of 3 was shown to
be a partial racemic twin by a combination of R-factor tests
[R1ϩ = 0.0549, R1Ϫ = 0.0603] and by use of the Flack parameter
[xϩ = ϩ0.45(5), xϪ = ϩ0.55(5)]—the refinements using the Flack
parameter gave the substantially lower residuals quoted in the
table.
G. A. Solan, BP Chemicals Ltd, WO patent 99/12981, 1999; (Chem.
Abstr., 1999, 130, 252–793).
6 (a) B. L. Small, M. Brookhart and A. M. A. Bennett, J. Am. Chem.
Soc., 1998, 120, 4049; (b) B. L. Small and M. Brookhart, J. Am.
Chem. Soc., 1998, 120, 7143.
7 G. J. P. Britovsek, V. C. Gibson, B. S. Kimberley, S. Mastroianni,
C. Redshaw, G. A. Solan, A. J. P. White and D. J. Williams,
J. Chem. Soc., Dalton Trans., 2001, 1639.
CCDC reference numbers 190871–190874.
8 (a) G. J. P. Britovsek, V. C. Gibson, S. Mastroianni, D. C. H. Oakes,
C. Redshaw, G. A. Solan, A. J. P. White and D. J. Williams,
Eur. J. Inorg. Chem., 2001, 431; (b) V. C. Gibson, B. S. Kimberley
and G. A. Solan, BP Chemicals Ltd., WO patent 00/20427, 2000;
(Chem. Abstr., 2000, 132, 279–649f).
9 D. Reardon, G. Aharonian, S. Gambarotta and G. P. A. Yap,
Organometallics, 2002, 21, 786.
10 D. A. Edwards, M. F. Mahon, W. R. Martin, K. C. Molloy,
P. E. Fanwick and R. A. Walton, J. Chem. Soc., Dalton Trans., 1990,
3161.
11 See, for example, (a) N. W. Alcock, D. C. Liles, M. McPartlin and
P. A. Tasker, J. Chem. Soc., Chem. Commun., 1974, 727; (b) L.
Valencia, H. Adams, R. Bastida, A. de Blas, D. E. Fenton,
A. Macias, A. Rodriguez and T. Rodriguez-Blas, Inorg. Chim. Acta,
2000, 300, 234; (c) D. C. Liles, M. McPartlin and P. A. Tasker,
J. Chem. Soc., Dalton Trans., 1987, 1631; (d ) D. E. Fenton,
R. W. Matthews, M. McPartlin, B. P. Murphy, I. J. Scowen and
P. A. Tasker, J. Chem. Soc., Chem. Commun., 1994, 1391; (e) R. W.
Matthews, M. McPartlin and I. J. Scowen, J. Chem. Soc., Dalton
Trans., 1997, 2861.
See http://www.rsc.org/suppdata/dt/b2/b207384f/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
BP Chemicals Ltd and the Leverhulme Trust (Special
Research Fellowship to CR) are thanked for financial support.
Dr E.K. Brechin (University of Manchester) and Dr D. Oswald
(Queen Mary and Westfield, University of London) are
thanked for SQUID and EPR measurements respectively.
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D a l t o n T r a n s . , 2 0 0 3 , 2 2 1 – 2 2 6
226