Synthesis and characterization of trans-[Co(III)(bpb)(amine)2]X (X = NCS, ClO4). X-ray crystal structure of trans-[Co(III)(bpb)(pyrrolidine)2]NCS·0.5H2O containing intermolecular N-H?O=C hydrogen-bonding

Article abstract of DOI:10.1016/S0020-1693(02)00906-4

A series of complexes of the type trans-[Co(III)(bpb)(amine)₂]X (X=NCS, amine=pyrrolidine (prldn) (1), benzylamine (bzlan) (2), and X=ClO₄, amine=pyrrolidine (prldn) (3), benzylamine (bzlan) (4), piperidine (pprdn) (5), morpholine (mrpln) (6), and bpb=N,N′-bis(2-pyridinecarboxamide)-1,2-benzene dianion) have been synthesized and characterized by elemental analyses, IR, UV-Vis, and ¹H NMR spectroscopy. The crystal and molecular structure of 1·0.5H₂O was determined by X-ray crystallography. The compound crystallizes in the triclinic space group P1?, a=9.4059(8) A?, b=11.3047(10) A?, c=12.8451(11) A?, α=81.984(2)°, β=83.761(2)°, γ=85.456(2)°, V=1341.6(2) A?³, Z=2 and final R₁=0.039 (wR₂=0.0625) for 5723 independent reflections with I>2σ(I) and 368 parameters. The structure consists of chains of complexes linked by moderately strong N-H?O=C hydrogen-bonds zig-zagging along the c lattice translation. The IR, UV-Vis, and ¹H NMR spectra of the complexes are also discussed.

Full text of DOI:10.1016/S0020-1693(02)00906-4

Inorganica Chimica Acta 338 (2002) 19ꢁ26
/
www.elsevier.com/locate/ica
Synthesis and characterization of trans-[Co(III)(bpb)(amine)2]X (Xꢀ
/
NCS, ClO4). X-ray crystal structure of trans-
[Co(III)(bpb)(pyrrolidine)2]NCS×
/
0.5H2O containing intermolecular
NÃ
/
HÁ Á ÁOÄ
/
C hydrogen-bonding
Mehdi Amirnasr a,1,*, Kurt J. Schenk b, Soraia Meghdadi c
a Institute of Physical Chemistry, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
b Institut de Cristallographie de l’Universite´ de Lausanne, BSP Dorigny, CH-1015 Lausanne, Switzerland
c Department of Chemistry, Isfahan University of Technology, 84156-83111 Isfahan, Iran
Received 15 October 2001; accepted 15 March 2002
Abstract
A series of complexes of the type trans-[Co(III)(bpb)(amine)2]X (Xꢀ
(2), and XꢀClO4, amineꢀpyrrolidine (prldn) (3), benzylamine (bzlan) (4), piperidine (pprdn) (5), morpholine (mrpln) (6), and
bpbꢀN,N?-bis(2-pyridinecarboxamide)-1,2-benzene dianion) have been synthesized and characterized by elemental analyses, IR,
UVꢁVis, and H NMR spectroscopy. The crystal and molecular structure of 1×
The compound crystallizes in the triclinic space group P 81.984(2)8,
/
NCS, amineꢀ/pyrrolidine (prldn) (1), benzylamine (bzlan)
/
/
/
1
/
/0.5H2O was determined by X-ray crystallography.
˚
˚
˚
/
1; aꢀ
/
9.4059(8) A, bꢀ
/
11.3047(10) A, cꢀ
0.0625) for 5723 independent reflections with
C hydrogen-
/
12.8451(11) A, aꢀ
/
3
˚
bꢀ
I ꢀ
bonds zig-zagging along the c lattice translation. The IR, UVꢁ
# 2002 Elsevier Science B.V. All rights reserved.
/
83.761(2)8, gꢀ
/
85.456(2)8, Vꢀ
/
1341.6(2) A , Zꢀ
/
2 and final R1ꢀ
/
0.039 (wR2ꢀ
/
/
2s(I) and 368 parameters. The structure consists of chains of complexes linked by moderately strong NÃ
/
HÁ Á ÁOÄ
/
1
/
Vis, and H NMR spectra of the complexes are also discussed.
1
Keywords: N4-amido complexes of Co(III); Axial amines; IR, UVꢁ
/
Vis, H NMR; Crystal structure of trans-[Co(bpb)(pyrrolidine)2]NCS×
/
0.5H2O
1. Introduction
mine)2]X (XꢀNCS, ClO4) complexes, to further in-
/
vestigate the role played by the equatorial ligand in the
chemistry of these complexes.
While in trans-[Co(acacen)(amine)2]NCS complexes a
There is a large volume of literature on coordination
compounds containing the thiocyanate ligand [1ꢁ7]. The
/
diversity of the role played by thiocynate in the
structural chemistry and the kinetics of the reactions
[8,9] of this class of complexes is still attracting interest
to their synthesis and characterization. We have recently
synthesized a series of trans-[Co(acacen)(amine)2]NCS
complexes [10] and studied their solid state
NÃ
/
HÁ Á ÁNCS intramolecular hydrogen-bonding exists
between the aminic hydrogen of one of the axial amines
and the thiocyanate anion [10], a moderately strong
intermolecular hydrogen-bonding of the type NÃ
HÁ Á ÁOÄC, between the aminic hydrogen of one molecule
and the CÄO group of the equatorial amide ligand of
another is observed in trans-[Co(bpb)(pyrrolidine)2]-
NCS×0.5H2O (1×0.5H2O), showing a stacked structure,
/
/
/
deaminationꢁanation reactions [11]. As an extension
/
/
/
of this work, we have turned our attention to the
synthesis and characterization of trans-[Co(III)(bpb)(a-
Fig. 2. This hydrogen-bonding has an interesting
influence on the decarbonylation of one of the amide
CÄ
/
O groups following the deaminationꢁanation reac-
/
* Corresponding author. Tel.: ꢂ
391-2350
E-mail address: amirnasr@cc.iut.ac.ir (M. Amirnasr).
/
98-311-391-2351; fax: ꢂ98-311-
/
tion in the solid state at high temperatures [12].
We report herein the synthesis and characterization of
trans-[Co(bpb)(amine)2]X complexes (Scheme 1). The
1
On sabbatical leave from the Department of Chemistry, Isfahan
University of Technology, Isfahan 84156-83111, Iran.
X-ray crystal structure of trans-[Co(bpb)(prldn)2]NCS×
/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 0 9 0 6 - 4

20
M. Amirnasr et al. / Inorganica Chimica Acta 338 (2002) 19ꢁ26
/
(2H, m, Hb), 7.84 (2H, AA?XX?, Jmꢀ
7.98 (2H, m, Hc), 8.22 (2H, brd, Jcdꢀ7.9, Hd), 8.56 (2H,
brd, Ja,b 5.0, Ha), 10.20 (2H, br s, Hamidic). The
/
3.5, Joꢀ6.0, He),
/
/
ꢀ
/
chemical shifts match those reported in the literature
[13].
2.3.2. trans-[Co(bpb)(prldn)2]NCS×
(1×0.5H2O)
To a solution of 786 mg (2 mmol) of [Co(II)(bpb)]×
/0.5H2O
/
/
H2O complex in 50 ml methanol was added dropwise
0.67 ml (8 mmol) of pyrrolidine and air was bubbled
through the solution for 3 h. Small portions of methanol
were added during this period to compensate for
evaporation. The final reaction mixture was filtered off
and a solution of 194 mg (2 mmol) potassium thiocya-
nate in methanol was added to the filtrate followed by
25 ml of toluene. Dark green crystals were obtained
after 48 h. These crystals were isolated by filtration and
Scheme 1.
washed with a mixture of ethanolꢁ
dried in vacuo. Yield 85%. Anal. Calc. for
C27H30N7O2SCo×0.5 H2O (584.58): C, 55.47; H, 5.34;
N, 16.72. Found: C, 55.53; H, 5.28; N, 16.84%. IR: nmax
cmꢃ1 (KBr): 3165(m, NÃ
H), 2045(s, NCNCS), 1628(s,
CÄO), 1596(s, CÄC), 1566(s, CÃ
N). 1H NMR (200
MHz, CD3CN): pyrrolidine, [dꢀ1.27 (8H, m,
C3H2C4H2), 1.52 (4H, m, NC2,5H), 2.05 (4H, m,
NC2,5H), 3.33 (2H, br s, NH)], bpb, [dꢀ
7.10 (2H,
/
ether (1:9 v/v), and
0.5H2O is also reported. The details of thermal
deaminationꢁanation, and decarbonylation of these
complexes have been published in a separate report [12].
/
/
/
/
/
/
2. Experimental
/
2.1. Chemicals
/
AA?XX, Jmꢀ
(2H, dd, Jmꢀ
(2H, AA?XX?, Jmꢀ
Jꢀ5.7, Ha)].
/
3.4, Joꢀ
/
6.1, Hf), 8.00 (2H, m, Hb), 8.28
1,2-Phenylenediamine was recrystallized from hot
ethanol before use. Piperidine (pprdn) (Aldrich), benzyl-
amine (bzlan), morpholine (mrpln), pyrrolidine (prldn)
(Merck) were distilled under reduced pressure. All other
chemicals were of commercial reagent grade and used as
received from Aldrich and Merck.
/
1.7, Joꢀ
/
7.6, Hd), 8.39 (2H, m, Hc), 8.88
/
3.5, Joꢀ6.1, He), 9.48 (2H, br d,
/
/
2.3.3. trans-[Co(bpb)(bzlan)2]NCS (2)
This complex was synthesized as described for 1
except that 0.8 ml (8 mmol) benzylamine was added as
the amine, and 25 ml ethanol instead of toluene was
added to the final solution for crystallization. The
resulting dark green crystals were isolated and washed
2.2. Physical measurements
1H NMR spectra were obtained on a BRUKER AC-
200 MHz and a BRUKER AVANCE DRX500 (500
MHz) spectrometer. Proton chemical shifts are reported
in parts per-million (ppm) relative to an internal
standard of Me4Si. IR spectra were recorded as KBr
with a mixture of ethanolꢁether (1:5 v/v) and dried in
/
vacuo. Yield 90%. Anal. Calc. for C33H30N7O2sco
(647.64): C, 61.20; H, 4.67, N, 15.14. Found: C, 61.30;
H, 4.60; N, 15.60%. IR: nmax cmꢃ1 (KBr): 3198, 3105(m,
pellets on a Shimadzu 435 instrument. UVꢁVis spectra
/
NÃ
1563(s, CÃ
mine, [dꢀ
6.69 (4H, m, ArH), 7.08 (6H, m, ArH)], bpb, [dꢀ
(2H, AA?XX?, Jmꢀ3.4, Joꢀ5.60, Hf), 7.91 (2H, m, Hb),
8.18 (2H, dd, Jmꢀ1.7, Joꢀ7.6, Hd), 8.32 (2H, m, Hc),
8.87 (2H, AA?XX?, Jmꢀ3.5, Joꢀ6.2, He), 9.38 (2H, br
d, Jꢀ5.2, Ha)].
/
H), 2055(s, NCNCS), 1628(s, CÄ
/
O), 1601(s, CÄ
N). H NMR (200 MHz, CD3CN): benzyla-
2.70 (4H, m, C7H2), 2.89 (4H, br s, NH2),
7.04
/
C),
1
were obtained on a Shimadzu UV-240 spectrophot-
ometer. Elemental analyses were performed by using a
Heraeus CHNO-RAPID elemental analyzer.
/
/
/
/
/
2.3. Synthesis
/
/
/
/
2.3.1. H2bpb ligand and [Co(II)(bpb)]×
N,N?-bis[(2?-pyridinecarboxamide)-1,2-benzene]ꢀ
H2O were prepared as de-
/H2O Complex
/
/
H2bpb and [Co(II)(bpb)]×
/
2.3.4. trans-[Co(bpb)(prldn)2]ClO4 (3)
To a solution of 786 mg (2 mmol) of [Co(bpb)]×
1
scribed in the literature [13]. The assignment of the H
/H2O
1
NMR spectrum of H2bpb is quite straightforward; H
NMR (200 MHz, CD3CN, assignments as in Scheme 1):
in 50 ml methanol was added dropwise 0.54 ml (6 mmol)
of pyrrolidine and air was bubbled through the solution
for 3 h. Several portions of methanol were added during
[dꢀ
/
7.33 (2H, AA?XX?, Jmꢀ
/
3.5, Joꢀ6.1, Hf), 7.57
/

M. Amirnasr et al. / Inorganica Chimica Acta 338 (2002) 19ꢁ
/26
21
this period to compensate for evaporation. The final
reaction mixture was filtered off and a solution of 280
hydrogen-bonds (normalized lengths are 1.899 and
˚
1.919 A and angles 164 and 1678). There exists a
void (channel) between four neighboring chains within
which lie the disordered perchlorate anions. They hold
mg (2 mmol) of NaClO4×/H2O in methanol was added to
the filtrate. Dark green crystals were obtained after 48 h.
The product was isolated by filtration and washed with
cold ethanol and ether and finally recrystallized from
the chains together by means of weak CÃ
/
HÁ Á ÁO
hydrogen-bonds the lengths of which lie between 2.35
˚
and 2.68 A.
acetonitrileꢁethanol (1:2 v/v). The resulting dark green
/
crystals were collected, washed with cold ethanol and
ether and dried in vacuo. Yield 74%. Anal. Calc. for
C26H30ClN6O6Co (616.94): C, 50.62; H, 4.90, N, 13.62.
Found: C, 50.30; H, 4.80; N, 13.50%. IR: nmax cmꢃ1
2.3.7. trans-[Co(bpb)(mrpln)2]ClO4 (6)
This complex was prepared by a procedure similar to
that for 3, except that morpholine (0.54 ml, 6 mmol) was
used as the amine ligand and the product was recrys-
(KBr): 3164(m, NÃ
/
H), 1628(s, CÄ
N). H NMR (500 MHz, CD3CN): pyrroli-
1.28 (8H, m, C3H2C4H2), 1.53 (4H, m,
NC2,5H), 2.10 (4H, m, NC2,5H), 3.23 (2H, br s, NH)],
bpb, [dꢀ 3.4, Joꢀ6.1, Hf), 7.99
7.11 (2H, AA’XX’, Jmꢀ
(2H, m, Hb), 8.28 (2H, dd, Jmꢀ1.7, Joꢀ7.6, Hd), 8.40
(2H, m, Hc), 8.89 (2H, AA?XX?, Jmꢀ3.5, Joꢀ6.1, He),
9.45 ( 2H, br d, Jꢀ5.7, Ha)].
/
O), 1595 (s, CÄ
/
C),
1
1566(s, CÃ
/
dine, [dꢀ
/
tallized from acetonitrileꢁ
/
methanolꢁethanol (4:8:1 v/v).
/
Yield 70%. Anal. Calc. for C26H30ClN6O8Co (648.94):
C, 48.12; H, 4.66, N, 12.95. Found: C, 48.10; H, 4.60; N,
/
/
/
/
/
/
/
13.00%. IR: nmax cmꢃ1 (KBr): 3130(m, NÃ
/
H), 1620(s,
N). 1H NMR (200
1.65 (4H, m, NCHax),
1.95 (4H, br d, NCHeq), 2.98 (2H, br t, NH), 3.2 (8H, m,
/
CÄ
/
O), 1600 (s, CÄ
/
C), 1560(s, CÃ
/
MHz, CD3CN): morpholine, [dꢀ
/
2.3.5. trans-[Co(bpb)(bzlan)2]ClO4 (4)
This complex was prepared by a procedure similar to
that for 3, except that benzylamine (0.63 ml, 6 mmol)
was used as the amine ligand. Yield 85%. Anal. Calc. for
C32H30ClN6O6Co (689.00): C, 55.78; H, 4.39, N, 12.20.
Found: C, 55.60; H, 4.40; N, 12.20%. IR: nmax cmꢃ1
OCH2], bpb, [dꢀ
Hf), 8.05 (2H, m, Hb), 8.37 (2H, dd, Jmꢀ
Hd), 8.47 (2H, m, Hc), 8.92 (2H, AA?XX?, Jmꢀ
Joꢀ6.2, He), 9.43 (2H, br d, Jꢀ5.7, Ha)].
/
7.13(2H, AA?XX?, Jmꢀ
/
3.6, Joꢀ
/
6.1,
7.1,
3.6,
/
1.8, Joꢀ
/
/
/
/
(KBr): 3200, 3105 (m, NÃ
C), 1560 (s, CÃ
N). 1H NMR (200 MHz, CD3CN):
benzylamine, [dꢀ
2.72 (4H, m, C7H2), 2.89 (4H, br s,
NH2), 6.71 (4H, m, ar H), 7.14 (6H, m, ar H)], bpb, [dꢀ
7.07 (2H, AA?XX?, Jmꢀ3.3, Joꢀ6.0, Hf), 7.94 (2H, m,
Hb), 8.20 (2H, dd, Jmꢀ1.7, Joꢀ7.8, Hd), 8.34 (2H, m,
Hc), 8.88 (2H, AA?XX?, Jmꢀ3.3, Joꢀ6.1, He), 9.40
(2H, br d, Jꢀ5.7, Ha)].
/
H),1628 (s, CÄ
/
O), 1602 (s, CÄ
/
/
2.4. X-ray crystallography
Dark green crystals of 1×
evaporation of a methanolic solution mixed with toluene
/
/
/
0.5H2O were grown by slow
/
/
/
/
at room temperature (r.t.). A parallelepipede of approx-
/
/
imate dimensions 0.30ꢄ
/
0.23ꢄ0.17 mm was mounted
/
/
in the orifice of a glass capillary with the help of a high
viscosity oil and cooled to 90 K with an Oxford
2.3.6. trans-[Co(bpb)(pprdn)2]ClO4 (5)
This complex was prepared by a procedure similar to
that for 3, except that piperidine (0.6 ml, 6 mmol) was
used as the amine ligand and the product was recrys-
tallized from methanol-acetone-ethanol (1:5:5 v/v).
Yield 65%. Anal. Calc. for C28H34ClN6O6Co (645.00):
C, 52.14; H, 5.31, N, 13.03. Found: C, 51.00; H, 5.20; N,
Cryostream. Diffraction measurements were made on
˚
0.71073 A).
a Stoe IPDS using Mo Ka radiation (lꢀ
/
The intensities were corrected for Lp effects and an
absorption correction based on crystal habitus was
carried out as well. The decay during the measurement
was negligible.
The structure was easily solved with the help of
DIRDIF-96 [14], and refined by means of SHELXTL5.5
13.00%. IR: nmax cmꢃ1 (KBr): 3150 (m, NÃ
/
H), 1625 (s,
N). H NMR (200
0.95 (2H, m, CHax of
1.20 (10H, m, CH2CHCH2), 1.80 (4H, br d,
11.8, NCHax), 1.93 (4H, br d, Jꢀ12.1, NCHeq), 2.29
(2H, br s, NH)], bpb, [dꢀ7.11 (2H, AA?XX?, Jmꢀ
Joꢀ6.0, Hf), 7.99 (2H, m, Hb), 8.33 (2H, dd, Jmꢀ
Joꢀ
Jmꢀ
1
CÄ
MHz, CD3CN): piperidine, [dꢀ
C4), 1.05ꢁ
Jꢀ
/
O), 1600 (s, CÄ
/
C), 1565 (s, CÃ
/
/
[15]. All non-hydrogen atoms of 1×/0.5H2O were refined
/
anisotropically, but the amine hydrogens and the water
hydrogens were refined isotropically. The remaining
hydrogens were made to ride on their associated carbon
atoms. The water hydrogens were difficult to find in
difference maps, but surprisingly easy to refine to very
reasonable positions and IDPs (Table 3). Crystallo-
graphic data for the structure determination are listed in
Table 1. Selected bond lengths and bond angles are
presented in Table 2, and the hydrogen-bond lengths
and angles are given in Table 3.
/
/
/
/3.2,
/
/1.8,
/
8.0, Hd), 8.43 (2H, m, Hc), 8.89 (2H, AA?XX?,
/
3.2, Joꢀ6.0, He), 9.38 (2H, br d, Jꢀ6.1, Ha)].
/
/
Compound 5 crystallizes in the triclinic space group
1 with lattice constants 10.021(2), 11.330(2), 13.472(3)
A and 78.61(3), 83.46(3), 85.33(3)8. The structure
consists of endless chains of complexes along [001].
P
˚
/
These are connected by quite strong NÃ
/
HÁ Á ÁOÄ
/C

22
M. Amirnasr et al. / Inorganica Chimica Acta 338 (2002) 19ꢁ26
/
Table 1
Crystallographic data for trans-[Co(bpb)(prldn)2]NCS×0.5H2O
(1×0.5H2O)
3. Results and discussion
3.1. Synthetic study
Formula
C27H30N7O2SCo×0.5H2O
584.58
Triclinic
Six new complexes (1ꢁ
oxidation of [Co(II)(bpb)]×
appropriate amine in methanol. A vigorous stream of
air was passed through a solution of [Co(II)(bpb)]×H2O
/
6) were prepared through the
Formula weight
Crystal system
Space group
Crystal size (mm)
Morphology
/H2O in the presence of the
P/1/
0.30ꢄ0.23ꢄ0.17
{100}, {0.10}, {00.1} pinacoids
9.4059(8)
/
in methanol to which was gradually added excess amine.
˚
a (A)
˚
The air oxidation was continued for a period of 3 h
b (A)
11.3047(10)
12.8451(11)
81.984 (2)
83.761 (2)
85.456 (2)
1341.6(2)
˚
c (A)
during which the color changed from redꢁ
green. Dark green crystals of these complexes were
obtained in good yield (65ꢁ90%). The presence of excess
/brown to
a (8)
b (8)
g (8)
/
3
˚
amine is especially important in the synthesis of 1 and 2
having NCSꢃ as the counterion. This is due to the fact
that thiocyanate, as a strong nucleophile, can compete
with the amine ligand and result in the formation of
trans-[Co(bpb)(amine)(NCS)] complex as a byproduct.
In fact, preparation of the diamine complexes of
piperidine, and morpholine with NCSꢃ counterion
was encountered with the formation of a mixture of
the diamine and amineisothiocyanato complexes. This
critical dependence of the composition of compounds in
the cobalt thiocyanate systems on reaction conditions
has been noted before [16].
V (A )
Z
2
1.469
Dc (mg mꢃ3
Radiation (l, A)
)
˚
Mo Ka, 0.71073
55.72
90 (1)
2Umax (8)
Temperature (K)
m (mmꢃ1
F(000)
Index ranges
)
0.761
620
ꢃ125h 512, ꢃ145k 514,
ꢃ165l 516
12 399
Reflections collected
Independent reflections
Absorption correction
5723 [Rintꢀ0.0398]
Integration
Max. and min. transmission 0.9737 and 0.9579
Refinement method
Data/restraints/parameters 5694/0/368
Full-matrix least-squares on F2
3.2. Description of structure of trans-
Goodness-of-fit on F2
4.505
Final R indices [I ꢀ2s(I)] R1ꢀ0.0390, wR2ꢀ0.0625
[Co(bpb)(prldn)2]NCS Hemihydrate (1×
/
0.5H2O)
R indices (all data)
Weights
R1ꢀ0.0504, wR2ꢀ0.1605
[s2(Fo2)]ꢃ1
Only a few cobalt(III) amide complexes have been
reported in the literature [17ꢁ19]. To our knowledge,
this is the first reported structure of a Co(III)(bpb)(N)2
ꢃ3
˚
Largest difference peak and 0.802 and ꢃ0.465 e A
hole
/
complex containing neutral N-donor axial ligands. Fig.
0.5H2O together with
Table 2
1 shows an ORTEP drawing of 1×
/
˚
Selected bond lengths (A) and angles (8) for 1×0.5H2O
the atomic numbering scheme. The structure exhibits a
distorted octahedral environment around cobalt, with
the bpb ligand occupying the four equatorial positions.
The four N-donor atoms define an almost perfect plane,
with an average deviation from the least-square plane of
Bond lengths
CoÃN(1)
CoÃN(11)
CoÃN(2)
CoÃN(12)
CoÃN(5)
CoÃN(6)
1.885(2)
1.8910(13)
2.0039(13)
1.981(2)
1.987(2)
2.008(2)
˚
0.056 A, the most offending atom being O(1) with a
˚
0.102 A. The two axial positions are
deviation of ꢃ
/
occupied by two pyrrolidine ligands, adopting a puck-
ered geometry in the envelope conformation. Despite
some rotational dispersion in diffraction figure (indicat-
ing some minor degree of intergrowth) most of the
structural parameters are well within literature values
[20]. The internal coordinates of thiocyanate anion are
Bond angles
N(1)ÃCoÃN(11)
N(1)ÃCoÃN(12)
N(11)ÃCoÃN(12)
N(1)ÃCoÃN(5)
N(11)ÃCoÃN(5)
N(12)ÃCoÃN(5)
N(1)ÃCoÃN(2)
N(11)ÃCoÃN(2)
N(12)ÃCoÃN(2)
N(5)ÃCoÃN(2)
N(1)ÃCoÃN(6)
N(11)ÃCoÃN(6)
N(12)ÃCoÃN(6)
N(5)ÃCoÃN(6)
N(2)ÃCoÃN(6)
83.82(6)
166.93(6)
83.13(6)
92.07(6)
89.48(6)
88.58(6)
82.61(6)
166.42(7)
110.44(6)
90.50(6)
89.73(7)
90.85(6)
89.69(7)
178.19(7)
89.60(6)
˚
1.657(5), 1.148(4) A, and 178.52(3)8 as compared with
˚
1.630(14), 1.155(12) A. Even the water molecule internal
˚
˚
coordinates (0.92(4) A, 0.86(3) A and 117(4)8) lie
delectably close to the values from neutron data (0.957
˚
A and 104.58) [21].
Of the four CoÃ
CoÃNamide bond distances to N(1) [1.885(2) A] and
N(11) [1.8910(13) A], being comparable to the CoÃ
Namine values, are indicative of strong bonds of the
/N bonds in the equatorial plane, the
˚
/
˚
/

M. Amirnasr et al. / Inorganica Chimica Acta 338 (2002) 19ꢁ
/26
23
Table 3
Hydrogen-bond lengths (A) and angles (8) for 1×0.5H2O
˚
˚
Hydrogen-bond length (A)
˚
H distance (A)
Acceptor. . .H-Donor
Hydrogen-bond angle (8)
N
H1
H2
Hi6i
O
2.139
2.136
2.155
2.573
1.891
2.869
2.797
2.831
2.877
2.948
2.980
2.66
158
164
162
124
157
105
121
140
157
132
126
135
0.918
0.863
0.841
0.960
1.005
0.960
0.960
0.960
0.930
0.960
0.960
0.960
Ni
O1
O1
O11
O11
O11
O11
S
O
Ni6i
ii
ii
62
Ni5ii
iii
54
iii
52
iv
53
C5v
H
C
62a
Hi5ii
iii
54b
H
C
iii
H
H
C
52b
iv
C
53a
H5v
S
H51a
vi
C51
vi
64
vii
62
S
H
C
64a
vii
O
H
62b
C
Symmetry transformations used to generate equivalent atoms: (i) 1ꢃx, 2ꢃy, 1ꢃz; (ii) ꢃx, 1ꢃy, ꢃz; (iii) ꢃx, 1ꢃy, 1ꢃz; (iv) 1ꢂx, y, z; (v)
1ꢃx, 1ꢃy, ꢃz; (vi) x, 1ꢂy, z; (vii) ꢃx, ꢃy, 1ꢃz.
sphere due to the rigid geometry of the ligand. All cis-
Nax bond angles are within 28 of the idealized
N(6) unit with a bond
NeqÃ
/
CoÃ
/
right angle. The trans-N(5)Ã
/
CoÃ
/
angle of 178.19(7)8 is almost linear. The distances
between the cobalt atom and the two axial nitrogen
˚
N(5)ꢀ1.987(2) A
donor atoms differ only slightly [CoÃ
/
/
˚
2.008(2) A] and compare well with the
and CoÃ
CoÃN distances found in cobalt amine complexes
[10,22,23] (e.g. [Co(NH3)6]Cl3 (CoÃ
However, these two CoÃNax bond distances in 1×
0.5H2O are slightly shorter than those observed for
trans-[Co(acacen)(piperidine)2]NCS (mean CoÃNaxꢀ
2.042(2) A) [10]. Considering similar donor-abilities for
pyrrolidine (pKaꢀ11.27) and piperidine (pKaꢀ11.12)
[24], the shorter CoÃNax in 1×0.5H2O is indicative of a
/
N(6)ꢀ
/
/
˚
Nꢀ1.963 A [23]).
/
/
/
/
/
/
˚
/
/
/
/
stronger interaction between the cobalt atom and the
axial amine ligands. In fact, it is expected that the
weaker electron donating character of the equatorial
Fig. 1. ORTEP plot of trans-[Co(bpb)(pyrrolidine)2]NCS Hemihydrate
0.5H2O) with displacement ellipsoids drawn at the 50% level and a
partial labelling scheme for the sake of clarity.
bpb ligand (relative to acacen) in complexes 1ꢁ6 to be
/
(1×
/
compensated for by the stronger axial amine interaction
with cobalt atom. This also correlates well with the
higher activation energies estimated for the dissociative
deaminationꢁanation process in 1, 2, and 5 complexes
in the solid state relative to those for the corresponding
acacen complexes [12].
/
deprotonated amide nitrogens to cobalt. This is in
agreement with the fact that the deprotonated amide
nitrogen is a very strong s-donor. The deprotonated
mode of coordination of the amide nitrogens is also
evident from the absence of the amidic proton signal
An interesting feature of the structure of 1×
/0.5H2O is
the intermolecular hydrogen-bonding between adjacent
molecules. The structure consists of chains of molecules
1
from the H NMR spectrum of complex 1 (vide infra).
The bond lengths to the pyridine nitrogens N(2)
linked by rather strong NÃ
zig-zagging along the c lattice translation (Fig. 2). These
main hydrogen-bonds are furthermore complicated by
/
HÁ Á ÁOÄ
/
C hydrogen-bonds
˚
˚
[2.0039(13) A] and N(12) [1.981(2) A] are relatively
longer than those to CoÃN(1) and CoÃN(11), which is
in accord with the lower donorability of the pyridine
nitrogens. The nitrogenÃcobaltÃnitrogen bond angles in
the equatorial plane comprise one angle which is larger
than 908 (N(2)ÃCoÃN(12)Ä110.448) and three smaller
than 908 (N(1)ÃCoÃN(2)ꢀ82.618, N(1)ÃCoÃN(11)ꢀ
83.828, and N(11)ÃCoÃN(12)ꢀ83.138). This indicates
that there might be some strain in the coordination
/
/
weak CÃ
/
HÁ Á ÁOÄ
/
C hydrogen-bonds. There is a subtle,
but interesting difference between the two carbonyl
groups: While the secondary bond for O(1) is moder-
/
/
˚
ately strong, 2.57 A (Table 3), there are three very weak
/
/
/
bonds for O(11), with the additional feature that one of
these reaches out to the chain in the next layer (Fig. 2).
/
/
/
/
/
/
/
/
/
The chains are held together by weak CÃ
/
HÁ Á ÁS (parallel

24
M. Amirnasr et al. / Inorganica Chimica Acta 338 (2002) 19ꢁ26
/
Table 4
Spectral properties of cobalt(III) carboxamido complexes in acetoni-
trile solution
Complex
lmax, nm (omax, Mꢃ1 cmꢃ1
)
LF
ILCT
[Co(bpb)(prldn)2]NCS (1)
[Co(bpb)(bzlan)2]NCS (2)
[Co(bpb)(prldn)2]ClO4 (3)
[Co(bpb)(bzlan)2]ClO4 (4)
[Co(bpb)(pprdn)2]ClO4 (5)
[Co(bpb)(mrpln)2]ClO4 (6)
632 (160)
604 (200)
630 (157)
600 (202)
675 (179)
699 (168)
411 (5806)
411 (6148)
412 (5816)
410 (6241)
410 (5856)
409 (6208)
505 (IL)
a
[Co(II)(bpb)×H2O]
735 (dꢁp*)
/
a
[13], Diffuse reflectance spectrum.
spectra of the new trans-[Co(III)(bpb)(amine)2]X com-
plexes show a low intensity (157Bo B202) ligand field
/
/
band which, depending on the axial amine ligand field
strength, appears in the region between 600 nm for
benzylamine and 699 nm for morpholine. An intense
intraligand charge-transfer band appears at around 410
nm in the spectra of all new Co(III) complexes. Similar
spectral changes have been observed in the oxidative
Fig. 2. Hydrogen-bonding scheme in compound (1×0.5H2O).
/
to (110)) and moderately strong NÁ Á ÁHÃ
dicular to (110)) hydrogen-bonds. The intermolecular
NÃHÁ Á ÁOÄC hydrogen-bonds play a significant role in
controlling the solid state deaminationꢁanation and
/
OÃ/H (perpen-
conversion of a planar Co(II)L complex (Lꢀa tetra-
/
dentate ligand with delocalized p system) to an octahe-
dral complex with two amines in the axial positions
[22,26].
The 1H NMR spectral data for the free ligand H2bpb
/
/
/
decarbonylation processes of complex 1 at high tem-
peratures [12].
and cobalt(III) complexes 1ꢁ
There are three important features in the spectra of the
complexes: (1) The absence of the amidic (dꢀ10.2)
/6 are given in Section 2.
3.3. Spectroscopic properties
/
proton signal, which clearly indicates that the equatorial
amide ligand is coordinated in a deprotonated form. (2)
The expansion, toward downfield chemical shifts, of the
aromatic proton signals range. These signals in the
spectrum of the free H2bpb ligand are located between
Three main features are observed in the IR spectra of
the new Co(III) complexes: (1) The vibrations due to the
equatorial ligand including three main bands due to the
CÄ
/
O, CÄ
/
C, and CÃ
/
N stretching vibrations. These
bands which appear at 1615, 1595, and 1560 cmꢃ1
respectively, are common to all six complexes. (2) The
7.30 and 8.60 (Ddꢀ
/
1.30 ppm), while in the spectra of
the complexes they lie between 7.15 and 9.50 ppm (Ddꢀ
/
bands corresponding to the amine NÃ
vibrations, appearing in the 3105ꢁ
3215 cmꢃ1 region.
These vibrations are shifted by about 150ꢁ
300 cmꢃ1
/
H stretching
2.35 ppm), showing a common pattern in all complexes,
Fig. 3. These signals have been assigned by comparison
/
/
with the spectra of closely related complexes [27ꢁ29]
/
relative to the uncoordinated amines, which is in accord
with expectation [25]. (3) The sharp stretching at 2045
cmꢃ1 in 1 and 2055 cmꢃ1 in 2, which clearly indicates
that NCSꢃ acts as a counterion in 1 and 2 [25]. This is
also evident from the X-ray crystal structure of complex
and a number of rules by Kahl et al. [30]. (3) The
appearance of the amine signals which indicate the
coordination of two amine ligands in the axial positions.
Aside from the aromatic protons of benzylamine which
appear at about 6.7ꢁ
of the axial amines appear between about 1.00 and 3.50
ppm. The downfield chemical shift of the amine NÃ
resonance appearing as a broad signal at lower fields
(ca. 3.00ꢁ3.50 ppm) relative to the corresponding
acacen complexes (ca. 2.40ꢁ2.80 ppm) indicates that
the CoÃNÃ C intermolecular hydrogen-bonding
/7.0 ppm, other proton resonances
1×
perchlorate salts 3ꢁ
region [25].
/
0.5H2O. The perchlorate stretching vibrations for the
/6 are observed in the corresponding
/H
The electronic spectral properties of the complexes are
listed in Table 4. There are several overlapping absorp-
tion bands in the spectrum of the Co(II)(bpb) complex
including the two more distinct bands corresponding to
/
/
/
/
HÁ Á ÁOÄ
/
is probably strong enough to retain its character in
the dꢁ
/
p and intraligand (IL) transitions, which appear
at 735 and 505 nm, respectively [13]. The electronic
solution.

M. Amirnasr et al. / Inorganica Chimica Acta 338 (2002) 19ꢁ
/26
25
Fig. 3. 1H NMR spectrum (500 MHz) of trans-[Co(bpb)(pyrrolidine)2]ClO4 (3) in CD3CN solution. The spectrum is labeled as to peak assignments
discussed in the text.
4. Conclusion
well be operative. This remains to be tested by further
theoretical studies on these complexes.
We have reported the synthesis and characterization
of several trans-[Co(bpb)(amine)2]X complexes with
The crystal packing of 1×
/
0.5H2O is mainly determined
by a moderately strong intermolecular NÃ
/
HÁ Á ÁOÄ
/C
hydrogen-bond involving the axial amine nitrogen and
the amido oxygen atom of two adjacent molecules.
From the solid state kinetic data of complex 1 [12], it is
evident that this intermolecular hydrogen-bonding is
one of the major factors affecting the activation para-
bpbꢀ
/
N,N?Ã
/
bis(2Ã
/
pyridinecarboxamide)Ã
/
1,2Ã/benzene
dianion as the equatorial ligand, and part of our
characterization included the single-crystal X-ray struc-
ture analysis of trans-[Co(bpb)(pyrrolidine)2]NCS×
/
0.5H2O (1×0.5H2O). The bpb ligand modifies the
/
meters of the deaminationꢁanation and the decar-
bonylation of this complex at high temperatures.
/
affinity of the cobalt metal center towards the axial
ligands, therefore, a competition between the amines
and NCSꢃ is observed for coordination to the axial
positions. It seems that both the electronic and the steric
effects contribute to this tendency. While all four trans-
[Co(acacen)(amine)2]NCS complexes have been pre-
pared under common experimental conditions [10], the
synthesis of bpb analogues proved to be successful only
5. Supplementary material
Full tables of bond lengths and angles and listing of
atom coordinates, thermal parameters, and details of
least-squares planes have been deposited with the Cam-
bridge Crystallographic Data Center under no. CCDC-
155326. Copies of this information may be obtained free
of charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (Fax: ꢂ44-1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk.
for pyrrolidine (pKaꢀ
(pKaꢀ9.33) (2). Mixtures of trans-[Co(bpb)(am-
ine)2]NCS and trans-[Co(bpb)(amine)(NCS)] complexes
obtained for piperidine (pKaꢀ11.12) and morpholine
(pKaꢀ8.33) indicate that factors other than pure
electronic effect, including the steric effect, might as
/
11.27) (1), and benzylamine
/
/
/
/

26
M. Amirnasr et al. / Inorganica Chimica Acta 338 (2002) 19ꢁ26
/
[13] (a) D.J. Barnes, R.L. Chapman, R.S. Vagg, E.C. Walton, J.
Chem. Eng. Data 23 (1978) 349;
Acknowledgements
(b) R.L. Chapman, R.S. Vagg, Inorg. Chim. Acta 33 (1979) 227.
[14] P.T. Beurskens, G. Beurskens, W.P. Bosman, R. de Gelder, S.
Garcia-Granda, R.O. Gould, R. Israel, M.M. Smits, DIRDIF-96
¨
Financial support from the Isfahan University of
Technology, and the Ministry of Higher Education of
Iran for sabbatical leave at EPFL, Lausanne, is grate-
fully acknowledged by M. A. Strong acknowledgement
System of Programs, Laboratorium voor Kristallografie, Katho-
lieke Universiteit Nijmegen, Nijmegen, 1996.
[15] G.M. Sheldrick, SHELXTL 5.05, Bruker Analytical X-ray Instru-
ments, Inc. Madison, WI, 1996.
is due to Professor Michael Gratzel for providing the
¨
chemicals and the laboratory space during the sabbatical
leave at ICP II, EPFL. The authors would also like to
thank Dr. Md. K. Nazeeruddin of ICP II, EPFL for
helpful discussions.
[16] L.G. Marzilli, R.C. Stewart, L.A. Epps, J.B. Allen, J. Am. Chem.
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Academic Publishers, Dordrecht, 1996
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