Two-stage formation of chloro (N-o-chlorobenzamido-meso-tetraphenylporphyrinato) zinc(II) methylene chloride solvate: Zn(N-NHCO(o-Cl)C6H4-tpp)Cl · CH2Cl2

Article abstract of DOI:10.1016/j.poly.2007.06.021

The coordinating properties of N-o-chlorobenzamido-meso-tetraphenylporphyrin (N-NHCO(o-Cl)C₆H₄-Htpp; 11) have been investigated for the Zn²⁺ ion. Insertion of Zn results in the formation of the zinc complex Zn(N-NCO(o-Cl)C₆H₄-tpp)(MeOH) · MeOH (12 · MeOH). The diamagnetic 12 · MeOH can be transformed into the diamagnetic Zn(N-NHCO(o-Cl)C₆H₄-tpp)Cl · CH₂Cl₂ (13 · CH₂Cl₂) in a reaction with aqueous hydrogen chloride (2%). X-ray structures for 12 · MeOH and 13 · CH₂Cl₂ have been determined. The coordination sphere around the Zn²⁺ ion in 12 · MeOH is a distorted trigonal bipyramid with N(2), N(4) and O(2) lying in the equatorial plane, whereas for the Zn²⁺ ion in 13 · CH₂Cl₂, it is a square-based pyramid in which the apical site is occupied by the Cl(1) atom.

Full text of DOI:10.1016/j.poly.2007.06.021

Polyhedron 26 (2007) 4602–4608
www.elsevier.com/locate/poly
Two-stage formation of chloro
(N-o-chlorobenzamido-meso-tetraphenylporphyrinato) zinc(II)
methylene chloride solvate: Zn(N-NHCO(o-Cl)C6H4-tpp)Cl Æ CH2Cl2
a
a
a,
b
Chun-Yi Chen , Hua-Yu Hsieh , Jyh-Horung Chen *, Shin-Shin Wang ,
c,
d
Jo-Yu Tung *, Lian-Pin Hwang
a
Department of Chemistry, National Chung Hsing University, Taichung 40227, Taiwan
b
Material Chemical Laboratories ITRI, Hsin-Chu 300, Taiwan
Department of Occupational Safety and Health, Chung Hwai University of Medical Technology, Taiwan
Department of Chemistry, National Taiwan University and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10764, Taiwan
c
d
Received 11 April 2007; accepted 14 June 2007
Available online 4 July 2007
Abstract
The coordinating properties of N-o-chlorobenzamido-meso-tetraphenylporphyrin (N-NHCO(o-Cl)C6H4-Htpp; 11) have been investi-
gated for the Zn2+ ion. Insertion of Zn results in the formation of the zinc complex Zn(N-NCO(o-Cl)C6H4-tpp)(MeOH) Æ MeOH
(12 Æ MeOH). The diamagnetic 12 Æ MeOH can be transformed into the diamagnetic Zn(N-NHCO(o-Cl)C6H4-tpp)Cl Æ CH2Cl2
(13 Æ CH2Cl2) in a reaction with aqueous hydrogen chloride (2%). X-ray structures for 12 Æ MeOH and 13 Æ CH2Cl2 have been determined.
The coordination sphere around the Zn2+ ion in 12 Æ MeOH is a distorted trigonal bipyramid with N(2), N(4) and O(2) lying in the equa-
torial plane, whereas for the Zn2+ ion in 13 Æ CH2Cl2, it is a square-based pyramid in which the apical site is occupied by the Cl(1) atom.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Zinc; X-ray diffraction; Acid hydrolysis; Two-stage process; N-Substituted-N-aminoporphyrin
1. Introduction
(N-NHCO-2-C4H3S-tpp) (7) in 58% yield [4]. Compounds
4–7 are cadmium(II) and mercury(II) complexes of
N-substituted-N-aminoporphyrins. Prompted by these
results, we focused on the synthesis of zinc(II) complexes
of a similar kind. In addition, the intermediate acid
Zn2+ attacks the two N–H protons of 1 [or N-p-
HNCOC6H5NO2-Htpp (8)] and leads to a five-coordinate
distorted trigonal bipyramidal Zn(II) derivative Zn
(N-NCOC6H5-tpp)(MeOH) (9) [or Zn(N-p-NCOC6H5NO2-
tpp)(MeOH) (10)] possessing a nitrene moiety inserted
between the zinc atom and one nitrogen atom, N(4)
[2,5]. In 1, when the ortho proton is replaced by a chloro
ligand, the new free aminated porphyrin is formed,
namely, N-o-chlorobenzamido-meso-tetraphenylporphyrin
[N-NHCO(o-Cl)C6H4-Htpp; 11]. A thorough literature
review reveals that there is no report on a metal complex
The absolute values of hardness g for Zn2+, Cd2+ and
Hg2+ are 10.88, 10.29 and 7.7 eV, respectively [1]. The
softness of acidity increases from Zn2+ to Cd2+ to Hg2+
.
Insertion of Cd(OAc)2 into N-NHCO-C6H5-Htpp (1)
[N-NHCO-2-C4H3O-Htpp (2) or N-NHCO-2-C4H3S-Htpp
(3)] results in the formation of a six-coordinate diamagnetic
complex Cd(N-NHCOC6H5-tpp)(OAc) (4) [Cd(N-NHCO-
2-C4H3O-tpp)(OAc) (5) or Cd(N-NHCO-2-C4H3S-tpp)-
(OAc) (6)] in 54% (55% or 52%) yield [2,3] (Scheme 1).
Mercury (II) is readily inserted into (3) yielding exclu-
sively the four-coordinate diamagnetic complex HgPh-
*
Corresponding authors.
E-mail address: JyhHChen@dragon.nchu.edu.tw (J.-H. Chen).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.06.021

C.-Y. Chen et al. / Polyhedron 26 (2007) 4602–4608
4603
O
O
O
C
C
C
O
S
N
NH
N
NH
N
NH
NH
N
HN
N
HN
N
N
N
N
2
1
3
Cl
O
O
O N
2
C
C
N
NH
N
NH
HN
N
HN
N
N
N
11
8
Scheme 1.
of 11. The lack of study on metal complexes of ligand 11
prompted us to undertake the synthesis and structural
investigations of the zinc(II) complexes. Zn(II) is a dia-
magnetic ion and maintains the d10 electron configuration
which minimizes intrinsic coordination geometry prefer-
ences whilst favoring coordination by ligands of interme-
diate basicity. In this paper, we describe the X-ray
structural investigation on the metallation of 11 leading
to the mononuclear zinc(II) complex (N-o-chlorobenz-
imido-meso-tetraphenylporphyrinato)(methanol)zinc(II)
methanol solvate [Zn(N-NCO(o-Cl)C6H4-tpp)(MeOH) Æ
MeOH; 12 Æ MeOH]. Tsurumaki et al. have reported the
electronic structures of oxidized metalloporphyrin com-
plexes by acid-induced cleaveage of Ni(II) complexes of
tetraarylporphyrin N-oxides at ꢀ25 ꢁC [6]. A similar kind
of acid hydrolysis was reported by Latos-Grazynski and
co-workers for the cleavage of the Ni–O bond in nickel-
(II)-6,11,16,21-tetraphenyl-22-hydroxy-m-benziporphyrin
(TPBPO)NiII, leading to (TPBPOH)NiIICl, and for the
cleavage of the Ni–C bond in nickel(II)-6,11,16,21-tetra-
phenyl-m-benziporphyrin, leading to chloronickel(II)-22-
H-6,11,16,21-tetraphenyl-m-benziporphyrin [7,8]. We tried
to apply acid-hydrolysis to Zn–N bond cleavage in
12 Æ MeOH. The Zn–N bond in 12 Æ MeOH is cleaved by
addition of aqueous HCl (2%) to a CH2Cl2 solution of
the complex leading to the desired complex chloro(N-
o-chlorobenzamido-meso-tetraphenylporphyrinato)zinc(II)
methylene chloride solvate [Zn(N-NHCO(o-Cl)C6H4-
tpp)Cl Æ CH2Cl2; 13 Æ CH2Cl2]. Intramolecular hydrogen
bonding between the ortho chlorine and (o-Cl)benzamido
hydrogen might enhance the formation of complex 13.
Collectively, we describe the two-stage formation of 13
and the spectroscopic properties of complexes 12 and 13.
2. Experimental
2.1. N-NHCO(o-Cl)C6H4-Htpp (11)
Compound 11 was prepared in 32% yield in the same
way as described for N-NHCOC6H5-Htpp using 2-chloro-
benzoyl azide [2]. Compound 11 was dissolved in CH2Cl2
1
and layered with MeOH to give a purple solid. H NMR
(559.95 MHz, CDCl3, 20 ꢁC) d: 9.10 [d, 2H, Hb, 3J(H–
3
H) = 4.2 Hz]; 8.86 [d, 2H, Hb, J(H–H) = 4.8 Hz]; 8.57 [s,
2H, Hb]; 8.15 [s, 2H, Hb]; 8.20 [d, 2H, ortho protons o-H,
3J(H–H) = 6.0 Hz]; 8.10 [d, 2H, o-H, J(H–H) = 6.6 Hz];
3
7.76–7.85 (m, 12H, meta and para protons); 5.94 [t, 1H,
(o-Cl)BA-Ph-H4 (where (o-Cl)BA = the o-chlorobenzam-
3
ido ligand), J(H–H) = 7.5 Hz]; 5.70 [d, 1H, (o-Cl)BA-Ph-
H3, 3J(H–H) = 7.8 Hz]; 5.34 [t, 1H, (o-Cl)BA-Ph-H5,
3J(H–H) = 7.5 Hz]; 2.13 [d, 1H, (o-Cl)BA-Ph-H6, 3J(H–
H) = 7.8 Hz]; ꢀ0.26 [bs, 2H, NH]. Anal. Calc. for
C51H34ClN5O: C, 79.73; H, 4.46; N, 9.12. Found: C,
79.29; H, 4.29; N, 9.05%. MS(FAB): (M)+ 768 (calc. for
C51H34ClN5O: 768). UV–Vis spectrum, k (nm) [e · 10ꢀ3
(Mꢀ1 cmꢀ1)] in CH2Cl2: 429 (213.9), 540 (10.8), 579 (9.7),
637 (7.4). IR (KBr) cmꢀ1: 3052 [m(CH)], 1624 (amide I
band), 1548 (amide II band), 1307 (amide III band), 1594
and 1462 (phenyl ring), 1439 [m(CN)], 754 [m(CCl)].
2.2. Zn(N-NCO(o-Cl)C6H4-tpp)(MeOH) Æ MeOH
(12 Æ MeOH)
Compound 12 was prepared in 75% yield in the same
way as described for Zn(N-NCOC6H5-tpp)(MeOH) Æ
MeOH using N-NHCO(o-Cl)C6H4-Htpp [2], with a reac-
tion temperature of 30 ꢁC and a reaction time of 30 min.

4604
C.-Y. Chen et al. / Polyhedron 26 (2007) 4602–4608
Compound 12 was dissolved in CH2Cl2 and layered with
MeOH to obtain purple crystals for single-crystal X-ray
analysis. 1H NMR (559.95 MHz, CDCl3, 20 ꢁC) d: 9.12
[d, 2H, Hb(2,13), 3J(H–H) = 4.2 Hz]; 8.88 [d, 2H,
Hb(3,12), 3J(H–H) = 4.2 Hz]; 8.78 [s, 2H, Hb(7,8)]; 7.76
[s, 2H, Hb(17,18)]; 8.36 [d, 2H, ortho protons o-H(26,28),
3J(H–H) = 7.8 Hz]; 8.09 [d, 2H, o-H(22,32), 3J(H–
H) = 6.6 Hz]; 8.84 [bs, 2H, ortho protons o0-H(38,40)];
8.21 [bs, 2H, o0-H(34,44)]; 7.72–7.87 (m, 12H, meta and
para protons); 6.10 [t, 1H, (o-Cl)BA-Ph-H4, 3J(H–H) =
d = 7.24 and 13C NMR to the center line of CDCl3 at
d = 77.0. HMQC (heteronuclear multiple quantum coher-
ence) was used to correlate protons and carbon through
one–bond coupling and HMBC (heteronuclear multiple
bond coherence) for two- and three-bond proton–carbon
coupling. Nuclear Overhauser effect (NOE) difference spec-
1
troscopy was employed to determine the H–1H proximity
˚
through space over a distance of up to about 4 A.
The positive-ion fast atom bombardment mass spectrum
(FAB MS) was obtained in a nitrobenzyl alcohol (NBA)
matrix using a JEOL JMS-SX/SX 102A mass spectrome-
ter. UV–Vis spectra were recorded at 20 ꢁC on a HITACHI
U-3210 spectrophotometer. IR spectra were measured at
20 ꢁC in KBr discs on a Bomem, DA8.3 spectrometer. Ele-
mental analyses were obtained using a Heraeus CHN-O-S-
Rapid elemental analyzer.
3
7.2 Hz]; 5.91 [d, 1H, (o-Cl)BA-Ph-H3, J(H–H) = 7.8 Hz];
3
5.69 [t, 1H, (o-Cl)BA-Ph-H5, J(H–H) = 7.8 Hz]; 3.61 [d,
3
1H, (o-Cl)BA-Ph-H6, J(H–H) = 7.8 Hz]. Anal. Calc. for
C53H40ClN5O3Zn: C, 71.06; H, 4.50; N, 7.82. Found: C,
71.03; H, 4.19; N, 7.47%. MS(FAB): (M)+ 832 (calc. for
C51H32ClN5OZn: 832). UV–Vis spectrum,
k
(nm)
[e · 10ꢀ3 (Mꢀ1 cmꢀ1)] in CH2Cl2: 439 (328.1), 607 (18.8).
IR (KBr) cmꢀ1: 3643 [m(OH)], 3051 [m(CH)], 1597 (amide
I band), 1473 (phenyl and methyl), 1384 (methyl), 1439
[m(CN)], 753 [m(CCl)].
2.5. X-ray crystallography
Table 1 presents the crystal data as well as other infor-
mation for 12 Æ MeOH and 13 Æ CH2Cl2. Measurements
were taken on a Bruker AXS SMART-1000 diffractometer
2.3. Zn(N-NHCO(o-Cl)C6H4-tpp)Cl Æ CH2Cl2
(13 Æ CH2Cl2)
˚
using monochromatized Mo Ka radiation (k = 0.71073 A)
at a temperature of 100(2) K for 12 Æ MeOH and 297(2) K
for 13 Æ CH2Cl2. Empirical absorption corrections were
made for both complexes. The structures were solved by
direct methods (SHELXL-97) [9] and refined by the full-
matrix least-squares method. The (o-Cl)BA group within
12 Æ MeOH is disordered with an occupancy factor of
0.55 for Cl, C(46), C(47), C(48), C(49), C(50), C(51) and
Compound 12 (0.06 g, 0.069 mmol) in CH2Cl2 (50 ml)
was extracted with 2% HCl (50 ml). After the CH2Cl2 layer
was concentrated to dryness, the residue was redissolved in
a minimum of CH2Cl2. Removal of the solvent and recrys-
tallization from CH2Cl2–CH3CN [1:1 (v/v)] gave the blue
solid 13 (0.059 g, 0.062 mmol, 90%). Compound 13 was
dissolved in CH2Cl2 and layered with CH3CN to obtain
1
blue crystals for single-crystal X-ray analysis. H NMR
Table 1
(559.95 MHz, CDCl3, 20 ꢁC) d: 9.03 [d, 2H, Hb(2,13),
Crystal data for 12 Æ MeOH and 13 Æ CH2Cl2
3J(H–H) = 4.8 Hz]; 8.89 [s, 2H, Hb(7, 8)]; 8.89 [d, 2H,
Compound
12 Æ MeOH
13 Æ CH2Cl2
3
Hb(3,12), J(H–H) = 4.2 Hz]; 8.38 [s, 2H, Hb(17,18)]; 8.34
Empirical formula
Formula weight
Space group
C53H40ClN5O3Zn C52H35Cl4N5OZn
[s, 2H, ortho protons o-H(26,28)]; 8.12 [s, 2H, o-
H(22,32)]; 8.77 [s, 2H, o0-H(38,40)]; 8.42 [s, 2H, o0-
H(34,44)]; 7.77–7.94 (m, 12H, meta and para protons);
6.45 [t, 1H, (o-Cl)BA-Ph-H4, 3J(H–H) = 7.2 Hz]; 6.23
895.72
P21/n
953.02
P21/c
Crystal system
monoclinic
14.713(4)
16.754(5)
17.433(5)
90
97.933(6)
90
4256(2)
4
monoclinic
13.8993(16)
30.995(4)
11.1975(13)
90
113.451(2)
90
4425.5(9)
4
˚
a (A)
3
˚
b (A)
[t, 1H, (o-Cl)BA-Ph-H5, J(H–H) = 7.8 Hz]; 6.13 [d, 1H,
˚
3
c (A)
(o-Cl)BA-Ph-H3, J(H–H) = 8.4 Hz]; 5.29 [d, 1H, (o-Cl)-
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
BA-Ph-H6, J(H–H) = 8.1 Hz]; ꢀ0.56 [s, 1H, NH]. Anal.
Calc. for C51H33Cl2N5OZn: C, 70.56; H, 3.83; N, 8.07.
Found: C, 69.99; H, 3.28; N, 8.09%. MS(FAB):
(M ꢀ H)+ 867 (calc. for C51H33Cl2N5OZn: 868). UV–Vis
spectrum, k (nm) [e · 10ꢀ3 (Mꢀ1 cmꢀ1)] in CH2Cl2: 440
(306.8), 455 (208.6), 617 (22.2). IR (KBr) cmꢀ1: 3350
[m(NH)], 3053 [m(CH)], 1690 (amide I band), 1574 (amide
II band), 1274 (amide III band), 1596 and 1480 (phenyl
ring), 1441 [m(CN)], 751 [m(CCl)].
3
˚
V (A )
Z
F(000)
1856
1.398
0.692
1952
1.430
0.843
Dcalc (g cmꢀ3
)
l (Mo Ka) (mmꢀ1
)
S
0.961
1.238
Crystal size (mm)
0.25 · 0.15 · 0.10 0.68 · 0.43 · 0.13
h(ꢁ)
28.40
100(2)
26.02
297(2)
8684
T (K)
Number of reflections measured 10496
2.4. Spectroscopy
Number of reflections observed
7046
6585
with [I > 2r(I)]
1H and 13C NMR spectra were recorded at 599.95 and
150.87 MHz, respectively, on Varian Unity Inova-600 spec-
trometers locked on deuterated solvent, and referenced to
R1a
0.0610
0.1514
0.0485
0.1411
wRb2
P
P
a
R1 = [ iFoj ꢀ jFci/ jFoj].
P
P
2
2
1=2
b
1
wR2 ¼ f ½wðF 2o ꢀ F c2Þ ꢁ= ½wðF 2oÞ ꢁg
.
the solvent peak. The H NMR is relative to CDCl3 at

C.-Y. Chen et al. / Polyhedron 26 (2007) 4602–4608
4605
Table 2
but is significantly shorter than the sum of the van der
Waals radii of Zn and O (2.90 A) [10]. This Zn–O(2) con-
˚
Selected bond distances (A) and angles (ꢁ) for compounds 12 Æ MeOH and
13 Æ CH2Cl2
˚
tact may be described as a weak covalent bond. The distor-
tion in five-coordinate complexes can be quantified by the
‘‘degree of trigonality’’ which is defined as s = (b ꢀ a)/60,
where ‘‘b’’ is the largest and ‘‘a’’ the second largest of the
Lbasal–M–Lbasal angles [11]. In 12, we find b = 169.22(9)ꢁ
[N(3)–Zn–N(1)] and a = 131.45(10)ꢁ [N(2)–Zn–N(5)] for
12 Æ MeOH (Table 2) and thus a s value of 0.63 is obtained
for 12 Æ MeOH. Hence, the geometry around Zn(II) in
12 Æ MeOH is best described as a distorted trigonal bipyra-
mid. In 12 Æ MeOH (Fig. 1a), the observed H(3)ꢂ ꢂ ꢂO(1) and
Compound 12 Æ MeOH
˚
Bond lengths (A)
Zn–N(1)
Zn–N(2)
Zn–N(3)
Zn–N(5)
2.073(3)
1.944(2)
2.067(3)
2.013(3)
Zn–O(2)
2.107(2)
1.821(2)
2.609(2)
H(3)ꢂ ꢂ ꢂO(1)
O(1)ꢂ ꢂ ꢂO(3)
Bond angles (ꢁ)
O(2)–Zn–N(1)
O(2)–Zn–N(2)
O(2)–Zn–N(3)
O(2)–Zn–N(5)
Zn–N(5)–N(4)
Zn–O(2)–C(52)
O(3)–H(3)ꢂ ꢂ ꢂO(1)
88.28(9)
111.26(10)
95.29(9)
117.08(9)
95.90(17)
131.1(2)
N(1)–Zn–N(2)
N(1)–Zn–N(3)
N(1)–Zn–N(5)
N(2)–Zn–N(3)
N(2)–Zn–N(5)
N(3)–Zn–N(5)
94.25(10)
169.22(9)
84.77(10)
95.10(10)
131.45(10)
85.03(10)
˚
O(3)ꢂ ꢂ ꢂO(1) distances are 1.821(2) and 2.609(2) A (Table
2), respectively, which fall below those values expected
˚
173.65(9)
from van der Waals distances (2.60 and 2.80 A, respec-
tively). The O(3)–H(3)–O(1) angle is 173.65(9)ꢁ, and its
deviation from linearity is small. Therefore, this intermo-
lecular hydrogen bonding causes an increased polarization
of the carbonyl bond in 12 Æ MeOH. Consequently, the car-
bonyl carbon C(45) in 12 Æ MeOH becomes more positive,
thereby accounting for its NMR downfield shift of
2.8 ppm observed at 20 ꢁC, i.e. from 161.5 ppm for C(45)
in 13 to 164.3 ppm for the same carbonyl carbon in
12 Æ MeOH (Tables S1 and S2).
Compound 13 Æ CH2Cl2
˚
Bond lengths (A)
Zn–N(1)
Zn–N(2)
Zn–N(3)
Znꢂ ꢂ ꢂN(4)
Bond angles (ꢁ)
Cl(1)–Zn–N(1)
Cl(1)–Zn–N(2)
Cl(1)–Zn–N(3)
Cl(1)–Zn–N(4)
N(3)–Zn–N(4)
N(5)–H(5A)ꢂ ꢂ ꢂCl(2)
2.131(2)
2.007(2)
2.138(2)
2.557(2)
Zn–Cl(1)
2.2090(9)
3.138(2)
2.768(2)
N(5)ꢂ ꢂ ꢂCl(2)
H(5A)ꢂ ꢂ ꢂCl(2)
109.81(7)
120.63(7)
108.62(7)
101.04(7)
76.78(9)
N(1)–Zn–N(2)
N(1)–Zn–N(3)
N(1)–Zn–N(4)
N(2)–Zn–N(3)
N(2)–Zn–N(4)
88.65(9)
136.98(9)
77.63(9)
88.05(9)
138.30(9)
3.3. Formation and characterization of 13
107.68(9)
When a solution of 12 in CH2Cl2 is treated with aqueous
hydrogen chloride (2%), a new species is formed that can be
formulated as 13 (Scheme 2). The reaction is reversed by
heating the products in CH2Cl2/MeOH at 30 ꢁC for
10 min (Scheme 2).
0.45 for Cl0, C(460), C(470), C(480), C(490), C(500), C(510).
The phenyl group within 12 Æ MeOH is disordered with
an occupancy factor of 0.5 for C(43), C(44) and 0.5 for
C(430), C(440). O(1) within 12 Æ MeOH is disordered with
an occupancy factor of 0.9 for O(1) and 0.1 for O(10). All
non–hydrogen atoms were refined with anisotropic thermal
parameters, whereas all hydrogen atoms were placed in cal-
culated positions and refined with a riding model. Table 2
lists selected bond distances and angles for complexes
12 Æ MeOH and 13 Æ CH2Cl2.
3.4. Crystal structure of 13 Æ CH2Cl2
The structure of 13 Æ CH2Cl2, determined by an X-ray
diffraction study, is shown in Fig. 1b. The (o-Cl)BA group
lies on the side opposite to the chloride Cl(1) in
13 Æ CH2Cl2. The coordination bond lengths Zn–N(1)
˚
˚
˚
3. Results and discussion
2.131(2) A, Zn–N(2) 2.007(2) A, Zn–N(3) 2.138(2) A and
˚
Zn–Cl(1) 2.090(9) A are within the limit found for zinc(II)
3.1. Formation and characterization of 12
porphyrins. The (o-Cl)BA nitrogen N(5) in 13 Æ CH2Cl2 is
no longer bonded to zinc as indicated by its longer internu-
˚
Insertion of Zn(OAc)2 into 11 in a methylene/methanol
solution results in the formation of a five-coordinate dia-
magnetic complex 12 in 75% yield (Scheme 2).
clear distance, 2.935(2) A for Znꢂ ꢂ ꢂN(5). Moreover, the
˚
Znꢂ ꢂ ꢂN(4) distance of 2.557(2) A for 13 Æ CH2Cl2 is longer
˚
than 2.138(2) A for Zn–N(3) but is significantly shorter
than the sum of the van der Waals radii of Zn and N
˚
3.2. Crystal structure of 12 Æ MeOH
(2.95 A) [10]. This longer Znꢂ ꢂ ꢂN(4) contact in 13 Æ CH2Cl2
may be viewed as a secondary intramolecular interaction.
This kind of secondary interaction was earlier observed
The structure of 12 Æ MeOH, determined in an X-ray dif-
fraction study, is shown in Fig. 1a. The geometry around
Zn in 12 Æ MeOH is described as a distorted trigonal bipyr-
amid with N(2), N(5) and O(2) lying in the equatorial
˚
for Zn(N-Me-tpp)Cl with Znꢂ ꢂ ꢂN1 = 2.530(7) A [12,13].
Most chemists seem to consider this secondary interaction
between the metal ion and the fourth N as a weak bond in
N-substituted porphyrin metal complexes. In the present
case, we find b = 138.30(9)ꢁ [N(2)–Zn–N(4)] and
a = 136.98(9)ꢁ [N(1)–Zn–N(3)] for 13 Æ CH2Cl2 and thus a
s value of 0.02 is obtained for 13 Æ CH2Cl2. Hence, the
˚
plane. The Zn–O(2) bond distance is 2.107(2) A and the
˚
mean Zn-4N distance is 2.024(3) A for 12 Æ MeOH. The
˚
Zn–O(2) (MeOH) distance of 2.107(2) A is slightly longer
than the sum of the covalent radii of Zn and O (1.92 A)
˚

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C.-Y. Chen et al. / Polyhedron 26 (2007) 4602–4608
Cl
Cl
3
Cl
O
1
O
O
4
C
C
C
5
6
N
N
HCl (aq) 2%
N
NH
Zn(OAc)2 2H2O
NH
Zn
N
N
N
HN
N
N
N
Zn
N
CH2Cl2 / MeOH
30 30min
CH2Cl2 / MeOH
30 10min
Cl
N
MeOH
N
N-NHCO(o-Cl)C H -Htpp
6
4
Zn(N-NCO(o-Cl)C6H4-tpp)(MeOH)
Zn(N-NHCO(o-Cl)C6H4-tpp)Cl
(11)
(12)
(13)
Scheme 2.
12 Æ MeOH and 13 Æ CH2Cl2. The zinc ion in 13 Æ CH2Cl2
˚
(or 12 Æ MeOH) is displaced from the 3N plane by 0.75 A
˚
(or 0.09 A) toward the chloride [Cl(1)] [or O(2)(MeOH)]
(Fig. S1). The occurrence of weak intramolecular hydrogen
bonding between the (o-Cl)benzamido hydrogen [H(5A)]
and the chlorine Cl(2) in 13 is reflected in the long N(5)–
˚
H(5A)ꢂ ꢂ ꢂCl(2) bond distance of 2.768(2) A and acute
N(5)–H(5A)ꢂ ꢂ ꢂCl(2) angle of 107.68(9)ꢁ (Table 2). This
weak intramolecular hydrogen bonding might strengthen
the formation of complex 13.
1
3.5. H NMR spectroscopy data of 12 and 13 in CDCl3
In solution, the molecule has an effective Cs symmetry
with a mirror plane running through the N(2)–Zn–N(5)–
N(4) unit for 12 or the N(2)–Zn–N(4)–N(5) unit for 13.
1
As a result, the H NMR spectra will exhibit four pyrrole
resonances [Hb(7,8), Hb(17,18), Hb(3,12), Hb(2,13)] for
these two complexes (Fig. 2). Non-equivalence of the two
sides of the macrocycle will cause each phenyl ring to have
two distinct ortho resonances with one set of ortho protons,
o-H(22,32) and o-H(26,28), for phenyl C(24) and C(30) and
the other set of ortho protons, o0-H(34,42) and o0-H(38,40),
for phenyl C(36) and C(42), unless the rotation around the
Cmeso–C1 [C(5)–C(21), C(10)–C(27) or C(15)–C(33), C(20)–
C(39)] bond is sufficiently fast in these two complexes
(Fig. 2).
The tautomerism exchange between the two NH protons
of 11 in CD2Cl2 is fast on the 1H NMR timescale at both 20
and ꢀ90 ꢁC. Hence only one type of N–H proton signal
was observed for 11 in CD2Cl2 at 20 and ꢀ90 ꢁC. At
ꢀ90 ꢁC, traces of water were frozen from the solution of
11 and 13 in CD2Cl2. Thus, the frozen water inhibits inter-
molecular proton exchange between water and NH protons
of 11 and 13, and allows the observation of a broad singlet
for the NH proton at d = ꢀ0.51 ppm (Dm1/2 = 11.8 Hz) for
11 and d = ꢀ0.69 ppm (Dm1/2 = 9.1 Hz) for 13 at ꢀ90 ꢁC.
In this case, the NH proton signal for 11 and 13 at
ꢀ90 ꢁC is broadened by the quadrupolar interaction of
the 14N nucleus. The signal arising from the NH proton
of 11 in CD2Cl2 was observed as a broad singlet at
d = ꢀ0.29 ppm (Dm1/2 = 23 Hz) at 20 ꢁC. These NMR data
suggest that the NH protons of 11 undergo intermediate
intermolecular proton exchange with water at 20 ꢁC.
Fig. 1. Molecular configuration and atom-labelling scheme for (a)
12 Æ MeOH and (b) 13 Æ CH2Cl2, with ellipsoids drawn at 30% probability
for both complexes. Hydrogen atoms except H(3) in 12 Æ MeOH and
H(5A) in 13 Æ CH2Cl2 are omitted for clarity.
geometry around Zn(II) in 13 Æ CH2Cl2 is best described as
a square-based pyramid with Cl(1) as the apical atom. The
s value of 0.02 obtained for 13 Æ CH2Cl2 is quite close to the
value of 0.05 for Zn(N-Me-tpp)Cl [12,13]. Hence com-
pounds 13 Æ CH2Cl2 and Zn(N-Me-tpp)Cl have a similar
coordination geometry around the Zn2+ ion. We adopt
the plane of three strongly bound pyrrole nitrogen atoms
[i.e. N(1), N(2) and N(3)] as a reference plane 3N for

C.-Y. Chen et al. / Polyhedron 26 (2007) 4602–4608
4607
those protons in the same compound would be still higher.
This observation is corroborated by the doublet at
3.61 ppm for (o-Cl)BA-Ph-H6 in 12 and the doublet at
5.29 ppm for the same Ph-H6 proton in 13, the triplet
at 5.69 ppm for (o-Cl)BA-Ph-H5 in 12 and the triplet at
6.23 ppm for the same Ph-H5 proton in 13, the doublet
at 5.91 ppm for (o-Cl)BA-Ph-H3 in 12 and the doublet at
6.13 ppm for the same Ph-H3 proton in 13, the triplet
at 6.10 ppm for (o-Cl)BA-Ph-H4 in 12 and the triplet at
6.45 ppm for the same Ph-H4 proton in 13 (Fig. 2).
3.6. Solid state IR spectroscopy data of 11, 12 and 13
Compound 12 could be viewed as a tertiary amide and it
displayed a unique amide I band at 1597 cmꢀ1 in the IR
spectrum in the solid state. The two interactions due to a
strong intermolecular hydrogen bond between O(1) and
H(3) and the covalent bond Zn–N(5) reduces the C@O
stretching frequency by 53 cmꢀ1 from 1650 cmꢀ1 for ter-
tiary amides to 1597 cmꢀ1 for 12 [15]. The O–H stretching
and methyl bending bands of MeOH in 12 occur near 3643
and 1384 cmꢀ1, respectively. Moreover, compounds 11 and
13 are classified as secondary amides with bands at 1624,
1548 and 1307 cmꢀ1 (or 1690, 1574 and 1274 cmꢀ1) being
assigned as amide I, II and III bands of 11 (or 13). These
data are quite close to those frequencies of 1680–1630,
1570–1515 and 1300 cmꢀ1 reported for amide I, II and
III bands of secondary amides [15,16]. The band at
3350 cmꢀ1 results from the N(5)–H(5A) stretch of 13.
Fig. 2. The 599.95 MHz 1H NMR spectra in CDCl3 at 20 ꢁC for (a) 12
and (b) 13, where / = Ph (phenyl group).
Moreover, the 1H NMR spectrum of 13 in CD2Cl2 showed
a sharp singlet at d = ꢀ0.58 ppm (Dm1/2 = 2.1 Hz) for the
NH proton at 20 ꢁC (see a similar spectrum shown in
Fig. 2b). This sharp signal (Dm1/2 = 2.1 Hz) is not in agree-
ment with that of Dm1/2 = 9.1 Hz found for 13 in the
absence of any exchange. Hence, these NMR data for 13
indicate that the NH proton [i.e., H(5A)] bound to N(5)
undergoes rapid intermolecular proton exchange with
water at 20 ꢁC. Due to the ring current effect, upfield shifts
for the 1H resonances of (o-Cl)BA-Ph-H6, (o-Cl)BA-Ph-H3,
(o-Cl)BA-Ph-H5 and (o-Cl)BA-Ph-H4 for 13 in CDCl3 at
20 ꢁC are Dd = ꢀ2.48 [from 7.77 (obtained from o-chlorob-
enzamide) to 5.29 ppm], ꢀ1.29 (from 7.42 to 6.13 ppm),
ꢀ1.12 (from 7.35 to 6.23 ppm) and ꢀ0.95 (from 7.40 to
6.45 ppm), respectively (Fig. 2b). As the distance between
the geometrical center (Ct) of the 4N plane and axial pro-
tons gets smaller qualitatively, the shielding effect becomes
larger [14]. In 13, the distance for Ctꢂ ꢂ ꢂ(o-Cl)BA-Ph-H6,
Ctꢂ ꢂ ꢂ(o-Cl)BA-Ph-H3, Ctꢂ ꢂ ꢂ(o-Cl)BA-Ph-H5 and Ctꢂ ꢂ ꢂ(o-Cl)-
4. Conclusion
Two distinct types of zinc complexes, hitherto unre-
ported, have been obtained from N-o-chlorobenzamido-
meso-tetraphenylporphyrin (N-NHCO(o-Cl)C6H4-Htpp;
11). In Zn(N-NCO(o-Cl)C6H4-tpp)(MeOH) (12), the N–
H bond of the o-chlorobenzamido ligand is cleaved and
the o-chlorobenzamido nitrogen participates in bonding
to the zinc ion. In Zn(N-NHCO(o-Cl)C6H4-tpp)Cl (13),
the o-chlorobenzamido [(o-Cl)BA] substituent is left intact
and the zinc(II) ion is coordinated to the three nitrogens of
the macrocycle core. Compound 13 can be synthesized in
the reaction of 12 with aqueous HCl (2%).
Acknowledgements
˚
BA-Ph-H4, increases from 5.615, 6.119, 7.138 to 7.312 A.
The financial support from the National Science Council
of the ROC under Grant NSC 95-2113-M-005-014-MY3
and NSC 95-2113-M-273-002 is gratefully acknowledged.
As the (o-Cl)BA-Ph-H6 proton of 13 is closer to Ct, the
shielding gets larger for this (o-Cl)BA-Ph-H6 proton. A
similar ring current effect is also observed for 12. The
average distance between Ctꢂ ꢂ ꢂ(o-Cl)BA-Ph-H6, Ctꢂ ꢂ ꢂ(o-Cl)-
BA-Ph-H5, Ctꢂ ꢂ ꢂ(o-Cl)BA-Ph-H3 and Ctꢂ ꢂ ꢂ(o-Cl)BA-Ph-H4
Appendix A. Supplementary material
˚
for 12 increases from 3.934, 5.438, 5.684 to 6.166 A. The
CCDC 642339 and 642340 contain the supplementary
crystallographic data for 12 Æ MeOH and 13 Æ CH2Cl2.
These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
fact that all four distances between Ct and (o-Cl)BA-Ph
protons in 12 are shorter than those distances in 13 indi-
cates that the ring current effect of (o-Cl)BA protons in
1
12 would be larger and in turn the H upfield shifts for

4608
C.-Y. Chen et al. / Polyhedron 26 (2007) 4602–4608
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[8] M. Stepien, L. Latos-Grazynski, L. Szterenberg, J. Panek, Z. Latajka,
J. Am. Chem. Soc. 126 (2004) 4566.
[9] G.M. Sheldrick, SHELXL-97: Program for the Refinement of Crystal
Structure from Diffraction Data, University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
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ed., Harper Collins College Publishers, New York, 1993, pp. 117,
292.
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk. Fig. S1 shows the dia-
gram of the porphyrinato (C20N4, Zn, (o-Cl)BA,
O(MeOH), Cl) unit of 12 Æ MeOH and 13 Æ CH2Cl2. Tables
S1 and S2 show the 13C NMR (150.87 MHz) for 12 and 13
in CDCl3 at 20 ꢁC. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.poly.2007.06.021.
[11] A.W. Addison, T.N. Rao, J. Reedijk, J.V. Rijn, G.C. Verschoor, J.
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