Di-organocobalt complexes of macrocyclic ligands

Article abstract of DOI:10.1016/S0020-1693(03)00429-8

Three new di-metallorganic cobalt complexes of the type trans-(Bz) ₂Co(chel), where Bz is a benzyl group σ-bonded to cobalt atom and chel is an equatorial chelating system constituted by an amino-oximic ligand and its conjugated base, were synthesised. The protonated and the unprotonated ligands interact through an O-H?O bridge stabilising the entire structure. The complexes differ in the equatorial moiety which is derived from the following ligands: HLN-py=3-[(2-pyridyl)ethylimino] -butan-2-one oxime), HLN-Ph=3-[(2-phenyl)ethylimino]-butan-2-one oxime and the analogous HLN-PhCl=3-[(2-chlorophenyl)ethylimino]-butan-2-one oxime. Two of these compounds, namely those derived from HLN-py and HLN-PhCl were structurally characterised by means X-ray diffractometry. Data reveal that each complex is characterised by the presence of two unusually long cobalt-carbon bonds which are 2.120(4) A? (mean value) in complex with HLN-py ligand and 2.119(4) A? (mean value) in complex with HLN-PhCl. These data are consistent with a strong mutual trans-influence exerted by one ligand on the other.

Full text of DOI:10.1016/S0020-1693(03)00429-8

Inorganica Chimica Acta 357 (2004) 177–184
www.elsevier.com/locate/ica
Di-organocobalt complexes of macrocyclic ligands
*
Giovanni Tauzher , Renata Dreos, Alessandro Felluga, Nazario Marsich,
Giorgio Nardin, Lucio Randaccio
Dipartimento di Scienze Chimiche, Universitaꢀ di Trieste, via Giorgieri 1, 34127 Trieste, Italy
Received 13 June 2003; accepted 20 June 2003
Abstract
Three new di-metallorganic cobalt complexes of the type trans-(Bz)2Co(chel), where Bz is a benzyl group r-bonded to cobalt
atom and chel is an equatorial chelating system constituted by an amino-oximic ligand and its conjugated base, were syn-
thesised. The protonated and the unprotonated ligands interact through an O–H ꢀ ꢀ ꢀ O bridge stabilising the entire structure. The
complexes differ in the equatorial moiety which is derived from the following ligands: HLN-py ¼ 3-[(2-pyridyl)ethylimino]-bu-
tan-2-one oxime), HLN-Ph ¼ 3-[(2-phenyl)ethylimino]-butan-2-one oxime and the analogous HLN-PhCl ¼ 3-[(2-chlorophe-
nyl)ethylimino]-butan-2-one oxime. Two of these compounds, namely those derived from HLN-py and HLN-PhCl were
structurally characterised by means X-ray diffractometry. Data reveal that each complex is characterised by the presence of two
ꢁ
ꢁ
unusually long cobalt–carbon bonds which are 2.120(4) A (mean value) in complex with HLN-py ligand and 2.119(4) A (mean
value) in complex with HLN-PhCl. These data are consistent with a strong mutual trans-influence exerted by one ligand on the
other.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Dialkyl; Cobalt; Complexes; Tridentate; Ligands
1. Introduction
fewer in number [16–19] and only one, namely
[(Me)2Co(DO)(DOH)pn]0, has been structurally char-
acterised [20]. It has been recognised that only a few
number of ligands, namely (DO)(DOH)pn, tim and cr
(Fig. 1) are capable to stabilise trans di-organocobalt
complexes [21].
The specific properties (steric or electronic or both)
conferring to the ligands this ability are difficult to be
recognised. For instance cr and (DO)(DOH)pn ligands
both give di-organocobalt complexes, despite of the
significant differences in their structure and electronic
properties (a less extensively conjugate electronic system
is present in cr as compared to (DO)(DOH)pn). How-
ever the Co(DH)2 complexes (DH ¼ dimethyl glyoxi-
mate) closely related to the Co(DO)(DOH)pn complexes
have been proved to give only mono-alkyl and not di-
alkyl derivatives.
Compounds with cobalt–carbon bonds have been
known for many years [1]. The realisation that the
porphyrin-like corrin ring was an important factor in
the stabilisation of the cobalt–carbon bond led to the
conviction that other organocobalt complexes could be
prepared employing analogous tetradentate ligands. At
present a number of organocobalt complexes are known
[2–5] and a variety of ligands, such as dioximes [2], im-
ino–oxime [6–9], polyamine [10,11] and Schiff bases de-
rived from diamine and aldehydes [12,13] or chetones
[14,15] have been shown to be effective in the stabilising
the metal–carbon bond. Examples of di-organocobalt
complexes of the type trans-RR0Co(chel), where chel is a
tetradentate equatorial ring and R and R0 are a variety
of identical or different-bonded alkyl or aryl groups, are
The most widely used method in the synthesis of di-
organocobalt complexes is the reaction of Co(I) com-
plexes with electrophiles [21] (Eqs. (1)–(4), Scheme 1).
Scheme 1 shows that trans di-alkylcobalt complexes
formation requires that nucleophilic intermediate
* Corresponding author. Tel.: +39-040-558-3941; fax: +39-040-558-
3903.
E-mail address: tauzher@dsch.univ.trieste.it (G. Tauzher).
0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00429-8

178
G. Tauzher et al. / Inorganica Chimica Acta 357 (2004) 177–184
Me
Me
Me
N
N
Me
Me
Me
Me
Me
N
N
N
N
Me
Me
N
N
N
N
O
N
O
N
H
H
cr
tim
(DO)(DOH)pn
(DO)(DOH)pn = 3,3'-(trimethylene-diimino)bis(butan-2-oneoxime) monoanion
tim = 2,3,9,10-tetramethyl-1,4,8,11-tetraaza-cyclotetradeca-1,3,8,10-tetra-ene
cr = 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.11]-heptadeca-1-(17),2,11,13,15-pentaene
Fig. 1. Structure of chelating ligands that form di-organocobalt complexes.
H
H
H
O
N
O
N
O
N
-
-
-
-
2e
2e
2e
2e
LL'CoIII (chel)
LCoI(chel)
RLCoIII(chel) + X-
RCoI(chel)
RR'CoIII(chel) + X-
+ L’
(1)
(2)
(3)
(4)
Me
Me
Me
Me
Me
Me
LCoI(chel) + RX
RLCoIII(chel)
N
N
N
+ L
Cl
N
RCoI(chel) + R'X
Scheme 1.
HLN-Ph
HLN-PhCl
HLN-py
species of the type RCoI(chel) (Eq. (3)) can be produced
from RLCoIII(chel) (Eq. (3)). These generally unstable
intermediates are, in the majority of cases, generated in
situ. However, in two case [17] they have been isolated in
an oxygen-free atmosphere.
Fig. 2.
2. Results and discussion
Electrochemical studies reveal that alkyl derivatives
undergo two-electron and one-electron reduction at
more negatives potential than those required for the
reduction of the parents non-metallorganic complexes.
In addition CoI alkyl derivative resulting from the
electrochemical reduction are generally short living
species [23,24]. This could justify the exiguous number
of di-alkylcobalt up to day synthesised, since conven-
tional reducing agents such as NaBH4 could be ineffec-
tive in promoting the two-electron reduction process
RLCoIII(chel) ! RCoI(chel).
2.1. Syntheses
In a preceding report we described the synthesis and
structural characterisation of the new benzylcobalt com-
plex [BzCoIII(LN-py)(LrNH-py)]ClO4 (2) (LrNH-py ¼
3-[(2-pyridyl) ethylamino]-butan-2-amino, HLN-py ¼ 3-
[(2-pyridyl)ethylimino]-butan-2-one oxime). Complex 2
(Scheme 2) was obtained directly from the non-metall-
organic mer-[CoIII(LN-py)2]ClO4 complex (LN-py is the
conjugated base derived from HLN-py) by reduction
with NaBH4 and successive addition of BzCl under ni-
trogen atmosphere. The process involves the oxidative
addition of the benzyl halide to the in situ generated CoI
species. In addition a profound change in the nature and
in configuration of the chelating system of the starting
complex occurs. In fact one of tridentate imino/oximic
ligand (HLN-py) undergoes reduction both at level of
oximic function and imine function generating the di-
amino ligand (LrNH-py), which chelates Co in one axial
and one equatorial position through its amino donors.
The unchanged LN-py tridentate ligand co-ordinates Co
in a mer configuration, whereas the r-bonded benzyl
group occupies the remaining axial position.
We are currently interested in the problems con-
cerning the formation and the rupture of the cobalt–
carbon bond. In the past years, on the basis of Eqs. (1)
and (2) in Scheme 1, we prepared some series of stable
mono-alkyl organocobalt complexes starting from non-
metallorganic compounds containing tridentate amino-
oximic and imino-oximic ligands (Fig. 2).
The results indicated that the above ligands are ef-
fective in the stabilising the cobalt–carbon bond in the
same way as the better-known tetradentate ligands [25–
30]. In the present work we show that, under appro-
priate experimental conditions, the above-mentioned
tridentate ligands are capable to stabilise also di-al-
kylcobalt complexes.
In the present work present we shown that, under
slightly modified experimental conditions (see Section 4)

G. Tauzher et al. / Inorganica Chimica Acta 357 (2004) 177–184
179
Scheme 2.
with respect to those above described [27], alkylation of
the mer-[CoIII(LN-py)2]ClO4 complex gives the di-ben-
zyl fac-[(Bz)2CoIII(HLN-py)(LN-py)]0 (1). The reaction
involves the rearrangement of the amino-oximic ligands
of the starting complex to form an equatorial chelating
system stabilised by the presence of a O ꢀ ꢀ ꢀ H–O bridge.
Complex 1 precipitated from the reaction mixture in a
few minutes after the addition of the benzyl halide and
was collected by filtration. By prolonging the reaction
time, the product re-dissolved and a successive reaction
takes place leading to a mono-benzyl derivative, which
was identified, by means elemental analysis and 1H
NMR as complex 2 so far prepared and characterised
[27]. This complex was also obtained by further reduc-
tion with NaBH4 of a sample of the di-benzyl derivative
1 dissolved in methanol. Therefore complex 1 is inter-
mediate in the synthesis of 2 from mer-[CoIII(LN-
py)2]ClO4 as depicted in Scheme 2.
and oxime functions of one ligand to amino groups
which chelates the cobalt atom trough its –NH2 donors.
A possible mechanism for this reaction is depicted in
Scheme 3.
Reaction with MeI, instead of the expected di-meth-
ylcobalt complex gives the mono-methyl [MeCoIII(LN-
py)(LrNH-py)]þ (3), homologous of 2. On the analogy
of that observed in the reaction with BzCl, it could be
suggested that also the reaction with MeI involves a di-
alkyl intermediate, which precedes the formation of 3
(Scheme 3). The failure in the obtaining the di-methyl
derivative may be due to its intrinsic lability.
Attempts of synthesising other di-alkyl complexes in
addition to the di-benzyl derivative using alkylating
agents such as ClCH2I, EtI and CF3CH2I, were unsuc-
cessful.
Two other di-benzyl derivatives have been obtained
using both the 3-[(2-phenyl)ethylimino]-butan-2-one
oxime bidentate ligand (HLN-Ph) and the analogous 3-
[(2-chlorophenyl)ethylimino]-butan-2-one oxime ligand
(HLN-PhCl) in place of HLN-py. Reaction of these
The conversion of di-benzyl derivative 1 to mono-
benzyl derivative 2 involves not only the loss of a benzyl
group from 2 but also the reduction of both the imino
Scheme 3.

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G. Tauzher et al. / Inorganica Chimica Acta 357 (2004) 177–184
ligands with CoCl2 ꢀ 6H2O gave only amorphous un-
identified material instead of the expected non-metall-
organic precursors of di-organocobalt complexes.
However, a mixture of CoCl2 ꢀ 6H2O and of the appro-
priate ligand in a 1:2 ratio in methanol, under nitrogen
atmosphere, treated with NaBH4 and BzCl produced
the di-benzyl derivatives [(Bz)2(HLN-PhCl)(LN-PhCl)]0
(4) and [(Bz)2(HLN-Ph)(LN-Ph)]0 (5), respectively.
Suitable crystals for X-ray analysis were obtained in the
case of complex 4.
C36
C37
C35
C8
C38
C5
C34
C17
C6
C7
C21
C33
N4
C20
C22
C23
C19
C18
C32
O2
O1
C24
Cl1
N3
N2
Cl2
Co
C10
C15
C16
C11
N1
C2
C9
C25
C14
2.2. Structures of complexes 1, 3 and 4
C3
C12
C13
C4
C27
C28
C26
C31
C1
If the orientation of the pendant aromatic moieties is
excluded, the molecular structure of 1 and 4 are very
similar as it appears from the comparison of their cor-
responding ORTEP drawings reported in Figs. 3 and 4,
respectively.
Both molecules have an approximate C2 symmetry,
the twofold axis passing through the Co and the
O1 ꢀ ꢀ ꢀ O2 midpoint. The co-ordination geometries of Co
in 1 and 4 differ only slightly, as shown in Table 1. The
two trans Co–C bonds are equal within the experimental
C30
C29
Fig. 4. An ORTEP view of the complex Bz2Co(HLN-PhCl)(LN-PhCl)
(4) with the atom numbering scheme.
reported for some mono-methyl derivatives [3]
[MeLCo{(DO)(DOH)pn}]þ (L ¼ H2O, aniline, pyridine
and 1-methylimidazole) which range from 1.991(4) to
ꢁ
errors, averaging to 2.120(4) and 2.119(4) A in 1 and 4,
respectively. They are significantly longer by about 0.07
ꢁ
2.003(3) A. The lengthening observed in trans di-alkyl
ꢁ
A than the Co–CH2–Ph distances found in the mono-
complexes can be attributed to the strong mutual trans-
influence exerted by one alkyl group on the other. It is
interesting to observe that the ideally tetrahedral Co–
CH2–Ph angle is significantly opened (Table 1) to relieve
the steric interaction between the benzyl group and the
equatorial moiety.
The four equatorial Co–N distances are very similar
in 1 and 4 (Table 1). The two oximic Co–N2 and Co–N3
are short and the two iminic Co–N1 and Co–N4 are
ꢁ
benzyl derivative [27] (2.044(5) A), in [Bz(H2O)Co
ꢁ
{(DO)(DOH)pn}]þ (2.052(2) A) [5] and in BzCo(DH)2
ꢁ
ꢁ
Py (2.056(3) A) [3]. However, a value of 2.128(8) A in a
less accurate structure (refined with reflection parame-
ters about 4) of BzCo(DH)2(pyrrolidine) was reported
[31]. The lengthening of Co–C bond in di-alkyl deriva-
tives with respect to mono-alkyl ones, was also observed
for the Co–Me distances in (Me)2Co[(DO)(DOH)pn]
ꢁ
ꢁ
(mean value 2.047 A) [20] when compared with those
long, with differences of about 0.1 A. The crystal of 3 are
built up by [MeCo(LrNH-py)(LN-py)]þ cations, ClO4ꢁ
anions and crystallisation water molecules, the latter in a
ratio Co/H2O of 1:2. The ORTEP drawing of the mono-
methyl cation of 3 is given in Fig. 5 and its overall
structure is similar to that found for the mono-benzyl
analogue [27].
On the analogy of mono-benzyl derivative 2, com-
pound 3 can be considered as derived from a hypo-
thetical di-methyl complex by loss of one methyl group
and reduction of one tridentate imino-oximic ligand
(HLN-py) to the di-amino ligand (LrNH-py). The LN-
py tridentate ligand equatorially coordinates Co in a
mer configuration, whereas the r-bonded methyl group
occupies the remaining axial position. The two LrNH-py
and LN-py ligands interact through a relatively strong
C35
C36
C20
C34
C21
C19
C18
C8
C33
C5
C22
C13
N6
C12
C32 C31
C7
C16
C17
N4
C6
C30
C10 C11
N3
C14
O2
Co
C23
N1
C9
N2
C15
N5
C2
O1
C3
C4
C1
C25
C24
ꢁ
H-bond of 2.755 A between O1 and N3 (Fig. 5) which
C26
C29
ꢁ
should be compared with that of 2.724(5) A found in 2.
A part the different r-bonded alkyl group, the only
other significant difference between 3 and 2 lies in the
uncoordinated pyridyl group of the LrNH-py, which in
C28
C27
Fig. 3. An ORTEP view of the complex Bz2Co(HLN-py)(LN-py) (1)
with the atom numbering scheme.
ꢁ
2 is anchored by an intramolecular H-bond of 2.915(5) A

G. Tauzher et al. / Inorganica Chimica Acta 357 (2004) 177–184
181
Table 1
Selected bond lengths and angles for complexes Bz2Co(HLN-py)(LN-py) (1), BzCo(LN-py)(LrNH-py)ClO4 (2), MeCo(LN-py)(LrNH-py)ClO4 (3)
and Bz2Co(HLN-PhCl)(LN-PhCl) (4)
1
4
3
2
Co–Cax
Co–N1
2.124(4), 2.116(4)
1.988(3)
1.875(3)
2.119(4), 2.119(4)
1.966(3)
1.878(3)
1.998(8)
1.893(5)
1.904(5)
1.952(6)
2.032(5)
2.160(5)
2.044(5)
1.909(4)
1.871(5)
1.961(4)
2.014(5)
2.135(4)
Co–N2
Co–N3
1.882(3)
1.977(3)
1.877(3)
1.972(3)
Co–N4
Co–N5
Cax–Co–Cax
Co–CH2–Ph
178.7(2)
116.8(3), 114.6(3)
172.3(2)
118.2(2), 118.5(2)
118.8(4)
addition to methylcobalamin (methylcobalamin b) a
small amount of the so-called methylcobalamin a, a
diastereoisomer in which the methyl group replaces the
3,5-dimethyl benzimidazole in the ‘‘lower’’ position and
water occupies the ‘‘upper’’ axial position [22]. Later,
several other alkylcobalamins with more complicate al-
kyl group have been characterised both in a and in b
form and facile a=b diastereomerism has been demon-
strated to occur in several cases [32,33]. However evi-
dence for di-alkyl cobaloximes has not been reported.
On the other hand, since both the axial co-ordination
positions can be alkylated, it is logical to ask whether
B12 di-alkyl derivatives can exist [34]. The occurrence of
synthetic di-alkyl cobalt compounds may led one to
believe that analogous derivatives may be formed also in
the case of vitamin B12. Data of the present work sup-
port indirect evidence for a di-methyl unstable cobalt
complex. This would lead to the speculation that, even
in absence of any direct evidence for di-alkylcobaloxi-
mes, these species might exist, at least as short-living
species.
C13
C23
C12
C9
C14
C11
C10
C1
C15
C2
N4
Co
N1
C4
N3
C3
O1
N2
C16
C7
N5
C6
C8
C19
C20
C5
C17
C18
N6
C21
C22
O2w
O1w
Fig. 5. An ORTEP view of the complex cation [MeCo(LN-py)(LrNH-
py)]þ (3) with the atom numbering scheme.
between the pyridyl N atom and the axially co-ordinated
amino group. In 3 the pyridyl N6 atom is not involved in
4. Experimental
ꢁ
the intramolecular H-bond, being H-bonded (2.825 A)
to the water molecule QW1.
4.1. Instruments and materials
The co-ordination distances are given in Table 1,
where are compared with those found in 2. Chemically
equivalent distances are similar, whereas, as expected,
1H NMR spectra were recorded with a JEOL EX-400
at 400 MHz from DMSO-d6 or CDCl3 solutions.
Commercially available chemicals were purchased from
Aldrich and used without further purification.
ꢁ
the Co–C bond in 3 is shorter than in 2, by about 0.05 A
as a consequence of the bulk of the methyl group smaller
than that of the benzyl one. However, it falls in the
range of other Co–Me distances [5]. As compared to the
Co–N distances, the axial Co–N5 distance in both 2 and
3 is lengthened because of the strong trans influence of
the alkyl group as compared to the Co–N3 one.
4.2. Syntheses
Caution. Some complexes have been isolated as per-
chlorate salts. Although no problems were encountered
in the present study, perchlorate salts are potentially
explosive and should be handled in small quantities.
3. Concluding remarks
4.2.1. Preparation of Bz2Co(HLN-py)(LN-py) (1)
To a suspension of [Co(LN-py)2]ClO4 [35] (1 g, 1.75
mmol) in 20 ml of 96% EtOH, a drop of a PdCl2 solu-
tion (prepared by addition of concentrated HCl to 1 g of
There are not evidences for the occurrence of di-alkyl
corrinoids. However it has been observed that the re-
action of (CoI) B12s with methyl iodide produces, in

182
G. Tauzher et al. / Inorganica Chimica Acta 357 (2004) 177–184
PdCl2 in 20 ml of water) and some glass splinters were
added. The reaction vessel was placed in an ice bath.
Under nitrogen atmosphere and vigorous magnetic
stirring, NaBH4 (0.8 g, 21 mmol) dissolved in the min-
imum volume of water was added, followed by 2 ml of
BzCl (17.4 mmol). The red–purple Bz2Co(HLN-
py)(LN-py) complex, which was formed, immediately
precipitates. N.B.: The vigorous stirring of the reaction
mixture in presence of glass fragments is necessary to
induce the precipitation of the product from the over
saturated solution. In absence of this care the mono-
benzyl complex 2 was formed (see synthesis 3.4.). The
crude product was collected by filtration, washed many
times with water and air-dried. Purification was made by
dissolving it in a 1:1 (vol.) isopropyl ether/benzene
mixture and then reducing the solution to 1/4 of the
initial volume by a rotary evaporator (40 °C). The pre-
cipitate, which was formed, was filtered off and air-dried
(0.30 g, yield 26%). Suitable crystals for X-ray analysis
were obtained from a saturated solution of complex in
pyridine after addition of isopropyl ether. Anal. Calcd.
for C36H43CoN6O2: C, 66.4; H, 6.66; N, 12.9. Found: C,
d, CH3–CH–NH2); 1.96 (3H, s, CH3–CN–CH2–); 2.50
(3H, s, CH3–CNO); 2.20, 3.20 (10H, m, 2CH2–CH2–,
2CH–CH3); 4.30, 4.74 (2H, dd, –NH2); 5.27 (H, t, –NH–);
7.10 ꢂ 8.81 (13H, 2Py-CH2–, 2Ph-CH2–).
4.2.3. Preparation of MeCo(LN-py)(LrNH-py)ClO4
(3)
To a suspension of [Co(LN-py)2]ClO4 (1 g, 1.75
mmol) in 20 ml of 96% EtOH, a drop of a PdCl2 solution,
previously prepared by addition of concentrated HCl to
1 g of PdCl2 in 20 ml of water, and some glass splinters
were added. The reaction vessel is placed in an ice bath.
Under nitrogen atmosphere with vigorous magnetic
stirring, NaBH4 (0.8 g, 21 mmol), dissolved in the min-
imum volume of water was added followed by 1 ml of
MeI (16.1 mmol). In contrast with that observed during
the synthesis of 1 no precipitate was formed and the
extraction with benzene does not furnished significant
amount of product. To the aqueous phase a concentrated
solution of NaClO4 was added. Red brown crystals that
were formed after a week were collected by filtration and
air-dried (0.25g, yield 25%). Without any further purifi-
cation the crystals were utilised for X-ray analysis. Anal.
Calcd. for C23H36CoN6O5Cl: C, 48.4; H, 6.35; N, 14.7.
1
66.1; H, 6.63; N, 12.7%. H NMR (DMSO-d6): d 1.73
(6H, s, 2CH3–CN–CH2–); 1.98 (6H, s, 2CH3–CNO);
3.10, 3.84 (8H, m, 2-CH2–CH2–); 3.86 (4H, d, 2CH2–
Co); 8.87 (10H, m, 2Ph-CH2–Co); 7.05, 7.17, 7.54, 8.32
(8H, 2Py-CH2–).
1
Found: C, 48.0; H, 6.35; N, 14.8%. H NMR (DMSO-
d6): d 0.99 (3H, s, CH3–Co); 1.07 (3H, d, CH3–CH–NH–);
1.27 (3H, d, CH3–CH–NH2); 1.95 (3H, s, CH3–CN–
CH2–); 2.34 (3H, s, CH3–CNO); 2.41, 3.20 (10H, m, 2-
CH2–CH2–, 2CH–CH3); 4.41, 4.54 (2H, dd, –NH2); 5.08
(H, t, –NH–); 7.22 ꢂ 8.86 (8H, 2Py-CH2–).
4.2.2. Preparation of BzCo(LN-py)(LrNH-py)ClO4 (2)
Method A. A synthetic method slightly differing from
that below described has been previously reported and
structure of the complex has been confirmed by X-ray
analysis [27].
Method B. Complex 2 was formed as final product,
by applying, the synthetic procedure for 1 (preparation
3.1.), but preventing the precipitation of 1. If precipitate
of 1 was formed it was allowed to re-dissolve to give 2.
The complex was identified from its 1H NMR spectrum,
which is identical to that of an authentic sample ob-
tained by utilising Method A.
Method C. To a solution of Bz2Co(HLN-py)(LN-py)
(0.3 g, 0.46 mmol) in 50 ml of MeOH under nitrogen
atmosphere and stirring, NaBH4 (0.4 g, 10.5 mmol)
dissolved in a minimum amount of water and a drop of
PdCl2 solution were added. After 30 min, the solvent
was evaporated to dryness by rotary evaporator. The
solid was dissolved in 10 ml of water and extracted twice
with CH2Cl2. The organic phase was then concentrated,
passed through a chromatographic column of allumine
and eluted with CH2Cl2. Elute was treated drop wise
with isopropyl ether until turbid and allowed to stand
overnight. Red crystals, which were formed, were col-
lected by filtration and air-dried (0.11 g, yield 38%).
Anal. Calcd. for C23H36CoN6O5Cl: C, 48.4; H, 6.35; N,
14.7. Found: C, 48.0; H, 6.35; N, 14.8%. 1H NMR
(DMSO-d6): d 1.08 (3H, d, CH3–CH–NH–); 1.31 (3H,
4.2.4. Preparation of Bz2Co(HLN-Ph)(LN-Ph) (5)
The starting non-organometallic complex could not
been isolated. Therefore in the synthesis of di-benzyl
derivative, a solution of HLN-Ph (1 g, 4.89 mmol) and
CoCl2 ꢀ 6H2O (0.58 g, 2.44 mmol) in 20 ml of EtOH 96%
were used. The reaction mixture was treated with
NaBH4 and BzCl under nitrogen and stirring. Reduc-
tion and alkylation procedures were performed as in
synthesis of complex 1 (0.55 g, yield 45%). The desired
complex precipitated from the reaction solution. The
crude product was collected by filtration, washed many
times with water and air-dried. Crystallisation was per-
formed by addition of isopropyl ether to a saturated
solution of the product in THF. Red crystals were
formed allowing to stand the solution overnight. Anal.
Calcd. for C38H45CoN4O2: C, 70.3; H, 6.99; N, 8.64.
1
Found: C, 69.7; H, 7.27; N, 8.78%. H NMR (DMSO-
d6): d 1.73 (6H, s, 2CH3–CN–CH2–); 1.95 (6H, s, 2CH3–
CNO); 2.93, 3.04, 3.67, 4.06 (8H, m, 2CH2–CH2–); 6.44
(4H, d, 2CH2–Co); 6.80, 7.30 (20H, 2Ph-CH2–Co, 2Ph-
CH2–).
4.2.5. Preparation of Bz2Co(HLN-PhCl)(LN-PhCl) (4)
The synthetic route, and work-up followed in the
above synthesis were followed also in this case. A

G. Tauzher et al. / Inorganica Chimica Acta 357 (2004) 177–184
183
Table 2
Crystal data and structure refinement for 1, 4 and 3
1
4
3
Formula
Fw
C36H43CoN6O2
650.69
C38H43Cl2CoN4O2
717.59
293(2)
C23H40ClCoN6O7
606.99
293(2)
T (K)
293(2)
0.71073
ꢁ
k (A)
Crystal system, space group
0.71073
0.71073
monoclinic, P21=n
7.603(3)
triclinic, P ꢁ 1
7.729(2)
12.415(2)
monoclinic, P21=c
14.176(3)
10.205(3)
20.325(5)
90
ꢁ
a (A)
ꢁ
b (A)
17.624(4)
24.889(5)
90
ꢁ
c (A)
19.026(5)
87.48(2)
a (°)
b (°)
c (°)
98.13(2)
90
81.59(2)
71.88(2)
98.71(3)
90
3
ꢁ
V (A )
3301.5(16)
4, 1.309
0.561
full-matrix l.s. on F 2
1.014
1716.5(7)
2, 1.388
2906.5(13)
4, 1.387
0.733
full-matrix l.s. on F 2
1.070
Z; Dcalc (Mg/m3)
q (mmꢁ1
Refinement method
)
0.696
full-matrix l.s. on F 2
1.029
Goodness-of-fit on F 2
R indices ½I > 2rðIÞꢃ
a
R1 ¼ 0:0563
wR2 ¼ 0:1379
R1 ¼ 0:0985
R1 ¼ 0:0523
wR2 ¼ 0:1395
R1 ¼ 0:0699
wR2 ¼ 0:1522
R1 ¼ 0:0847
wR2 ¼ 0:2318
R1 ¼ 0:1181
wR2 ¼ 0:2710
R indices (all data)a
wR2 ¼ 0:1611
P
P
P
P
2
2
2
2 1=2
a R1 ¼ jjFoj ꢁ jFcjj= jFoj; wR2 ¼ ½ wðjFoj ꢁ jFcj Þ = wjFo2j ꢃ
.
solution of HLN-PhCl (1 g, 4.19 mmol) and
CoCl2 ꢀ 6H2O (0.50 g, 2.09 mmol) in 20 ml of EtOH 96%
(0.76 g, yield 51%) was used. Red crystals were obtained.
Anal. Calcd for C38H43Cl2CoN4O2: C, 63.6; H, 6.04; N,
7.81. Found: C, 61.6; H, 6.44; N, 7.61%. Complex was
characterised by X-ray analysis.
4.3. X-ray crystallographic data collection and refinement
of the structures
Red single needle-shaped crystals of 1, dark red
platelet of 4 and small red cubic crystals of 3 were grown
as reported in Syntheses. X-ray diffraction data were
collected with a Nonius DIP 1030 H system using
4.2.6. Preparation of the ligand HLN-Ph
graphite
monochromated
ꢁ
Mo
Ka
radiation
A suspension of diacethyl monoxime (8.1 g, 79.6
mmol) in 50 ml of isopropyl ether was heated to reflux
with stirring. Phenyl ethylamine (10 ml, 79.6 mmol) was
added drop wise and the heating is protract for 3 h.
Then the solution was poured into a beaker and allowed
to evaporate in air. To the concentrated solution (about
10 ml) n-pentane was added. The white precipitate that
was formed was collected by filtration on sintered glass
funnel and washed with pentane (13.8 g, yield 85%).
Anal. Calcd. for C12H16N2O: C, 70.5; H, 7.89; N, 13.7.
Found: C, 70.2; H, 7.81; N, 13.6%. 1H NMR (CDCl3): d
1.90 (3H, s, CH3–CN–CH2–); 2.10 (3H, d, CH3–CNO);
3.00, 3.70 (4H, t, –CH2–CH2–); 7.15 ꢂ 7.30 (5H, m, Ph-
CH2–).
(k ¼ 0:71070 A). Crystal data and details of structure
refinement are given in Table 2.
For all the structures a total of 30 frames were col-
lected, using XPRESS program [36], over a hemisphere
of reciprocal space with rotation of 6° about the U-axis.
A MAC Science Image Plate (diameter ¼ 300 mm) was
used and the crystal-to-plate distance was fixed at 90
mm. The determination of unit-cell parameters, inte-
gration of intensities and data scaling were performed
using MOSFLM and SCALA from the CCP4 program
suite [37]. The structures were solved by direct method
using SIR-92 [38] and Fourier methods and refined by
the least-square method (on F 2) [39]. In the three
structures, all non-hydrogen atoms were refined aniso-
tropically. Hydrogen atoms were placed at calculated
positions and refined as riding atoms with isotropic
displacement parameters. A suite of programs [40] was
also used in the geometrical and final calculations.
4.2.7. Preparation of the ligand HLN-PhCl
The above-described method (preparation 3.6) was
followed also in this case using as reagents diacethyl
monoxime (7.15 g, 70.7 mmol) and 2-(2-chloro phenyl)
ethyl amine (10 ml, 70.7 mmol) (13.9 g, yield 82%). Anal.
Calcd. for C12H15N2OCl: C, 60.4; H, 6.33; N, 11.7.
Found: C, 60.2; H, 6.10; N, 11.2%. 1H NMR (CDCl3): d
1.93 (3H, s, CH3–CN–CH2–); 2.08 (3H, s, CH3–CNO);
3.12, 3.71 (4H, t, –CH2–CH2–); 7.12 ꢂ 7.37 (4H, m,
ClPh–CH2–).
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 212108 (for 2), 212109 (for 4)

184
G. Tauzher et al. / Inorganica Chimica Acta 357 (2004) 177–184
[16] G. Costa, G. Mestroni, T. Licari, E. Mestroni, Inorg. Nucl. Chem.
Lett. 5 (1969) 561.
and 212110 (for 3). Copies of this information may be
obtained free of charge from: The Director, CCDC, 12
Union Road, Cambridge, CB21EZ, UK (fax: +44-1223-
336033; e-mail: deposit@ccdc.cam.ac.uk or http://
www.ccdc.cam.ac.uk).
[17] K. Farmery, D.H. Busch, Chem. Commun. (1970) 1091.
[18] G.N. Schrauzer, J.A. Seck, T.M. Beckhman, Bioinorg. Chem. 3
(1974) 353.
[19] J.K. Espenson, H.L. Fritz, R.A. Heckman, C. Nicolini, Inorg.
Chem. 15 (1976) 906.
[20] M. Calligaris, J. Chem. Soc., Dalton Trans. (1974) 1628.
[21] M.W. Whitman, J.H. Weber, Inorg. Chim. Acta Rev. 23 (1977)
263.
Acknowledgements
[22] W. Friedrich, J.P. Nordmeyer, Z. Naturforsch. 25b (1970) 972,
979.
We are grateful to CNR (Rome) and MURST
(Rome), PRIN No. MM03185591, for financial support.
[23] J. Halpern, Ann. N.Y. Acad. Sci. 239 (1974) 2.
[24] G. Costa, Coord. Chem. Rev. 8 (1972) 63.
[25] R. Dreos, G. Tauzher, D.H. Trendafilova, G. Nardin, L.
Randaccio, Inorg. Chem. 35 (1996) 2715.
[26] A. Bigotto, A. Felluga, R. Dreos, G. Nardin, L. Randaccio, G.
Tauzher, S. Peressini, C. Tavagnacco, J. Chem. Soc., Dalton
Trans. (2002) 99.
References
[1] G.N. Schrauzer, J. Kohnle, Ber. 97 (1964) 3056.
[2] N. Bresciani-Pakor, M. Forcolin, L.G. Marzilli, L. Randaccio,
M.F. Summers, J.P. Toscano, Coord. Chem. Rev. 63 (1985) 1.
[3] L. Randaccio, N. Bresciani-Pakor, E. Zangrando, L.G. Marzilli,
Chem. Soc. Rev. 18 (1989) 225.
[27] R. Dreos, E. Herlinger, G. Tauzher, S. Vuano, G. Nardin, L.
Randaccio, Organometallic 17 (1998) 2367.
[28] R. Dreos, A. Felluga, G. Nardin, L. Randaccio, P. Siega, G.
Tauzher, Eur. J. Inorg. Chem. (2001) 267.
[29] R. Dreos, A. Felluga, G. Nardin, L. Randaccio, P. Siega, G.
Tauzher, Inorg. Chem. 40 (2001) 5541.
[4] P.J. Toscano, L.G. Marzilli, Prog. Inorg. Chem. 31 (1984) 105.
[5] L. Randaccio, Comments Inorg. Chem. 21 (1999) 327.
[6] G. Costa, G. Mestroni, E. de Savorgnani, Inorg. Chim. Acta 3
(1969) 323.
[30] R. Dreos, A. Felluga, G. Nardin, L. Randaccio, M. Sandri, G.
Tauzher, Inorg. Chem. 41 (2002) 4548.
[31] S.K. Tyrlik, A.T.H. Lenstra, J.F.J. van Loock, H.J. Geise, R.A.
Dommisse, Acta Cryst. C 42 (1986) 553.
[7] G. Costa, G. Mestroni, G. Tauzher, J. Chem. Soc., Dalton Trans.
(1972) 450.
[32] K.L. Brown, M.S.A. Hamza, J. Inorg. Biochem. 70 (1998) 171,
and references therein.
[8] R.G. Finke, B.L. Smith, W.A. McKenna, P.A. Christian, Inorg.
Chem. 20 (1981) 687.
[33] K.L. Brown, D. Zhao, S. Cheng, X. Zou, Inorg. Chem. 36 (1997)
1764, and reference therein.
[9] V.E. Magnuson, J.K. Weber, J. Organometal. Chem. 74 (1974)
135.
[34] D.G. Brown, Prog. Inorg. Chem. 18 (1974) 177.
[35] L. Catalano, R. Dreos, G. Nardin, L. Randaccio, G. Tauzher, S.
Vuano, J. Chem. Soc., Dalton Trans. (1996) 4269.
[36] B. Schierbeek, Nonius, Delft, The Netherlands, 1998.
[37] Collaborative Computational Project, No. 4, Acta Crystallogr. A
46 (1990) 467.
[10] E. Ochiai, K.M. Long, C.R. Sperati, D.H. Busch, J. Am. Chem.
Soc. 91 (1969) 3201.
[11] E. Ochiai, D.H. Busch, Chem. Commun. (1968) 905.
[12] G. Costa, G. Mestroni, L. Stefani, J. Organometal. Chem. 7
(1967) 493.
[13] G. Costa, G. Mestroni, G. Pellizer, J. Organometal. Chem. 11
(1968) 333.
[38] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, J.
Appl. Crystallogr. 26 (1993) 343.
[39] G.M. Sheldrick, SHELXL97 – programs for structure refinement,
[14] G. Costa, G. Mestroni, G. Tauzher, L. Stefani, J. Organometal.
Chem. 6 (1966) 181.
[15] G. Costa, G. Mestroni, J. Organometal. Chem. 11 (1968) 325.
€
Universitat Gottingen: Gottingen, Germany, 1998.
[40] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
€
€