Metal complexes of N-benzamidoporphyrin: (N-benzimido-meso-tetraphenylporphyrinato)(methanol)zinc(II) methanol solvate and (acetato)(N-benzamido-meso-tetraphenylporphyrinato)cadmium(II) benzene solvate

Article abstract of DOI:10.1021/ic0207202

The crystal structures of N-benzamido-meso-tetraphenylporphyrin (NHCOC₆H₅-Htpp; 1), (N-benzimido-meso-tetraphenylporphyrinato)(methanol)zinc(II) [Zn(N-NCOC₆H₅-tpp)(MeOH); 2(MeOH)], and (acetato)(N-benzamido-meso-tetraphenylporphyrinato)cadmium(II) [Cd(N-NHCOC₆H₅-tpp)(OAc); 3] were established. The coordination sphere around Zn²⁺ ion in 2(MeOH) is a distorted trigonal bipyramid with N(2), N(5), and O(2) lying in the equatorial plane, whereas, for Cd²⁺ ion in 3, it is a sitting-atop derivative with a distorted trigonal bipyramidal geometry in which the apical site is occupied by atoms N(2) and O(2). Cd in 3 acquires five-coordination with five strong bonds [Cd(1)-N(1) = 2.319(5) A?, Cd(1)-N(2) = 2.252(5) A?, Cd(1)-N(3) = 2.332(5) A?, Cd(1)-0(2) = 2.292(5) A?, and Cd(1)-O(3) = 2.317(5) A?] and with one secondary intramolecular interaction [Cd(1)?N(4)]. The porphyrin ring in these two complexes is distorted to a large extent. The plane of the three pyrrole nitrogen atoms [i.e., N(1)-N(3)] strongly bonded to Zn²⁺ in 2(MeOH) and to Cd²⁺ in 3 is adopted as a reference plane 3N. For the Zn²⁺ complex, the pyrrole nitrogen bonded to the benzamido (BA) ligand lies in a plane with a dihedral angle of 33.8° with respect to the 3N plane, but for the Cd²⁺ complex, this dihedral angle is found to be 31.4°. In the former complex, Zn²⁺ and N(5) are located on the different side at -0.08 and 1.39 A from its 3N plane, and in the latter one, Cd²⁺ and N(5) are also located on the different side at 1.08 and -1.51 A? from its 3N plane. VT NMR (¹H and ¹³C) studies of 3 show that the acetate acts as a bidentate ligand and the OAc^- exchange does not occur in CD₂Cl₂. Moreover, the NH proton [i.e., H(5)] of 3 in CD₂Cl₂ is observed as a sharp singlet at δ = -1.13 ppm with Δν1/2 = 4 Hz at 20 °C indicating that the intermolecular proton exchange between water and NH proton is rapid.

Full text of DOI:10.1021/ic0207202

Inorg. Chem. 2003, 42, 4603−4609
Metal Complexes of N-Benzamidoporphyrin:
(N-Benzimido-meso-tetraphenylporphyrinato)(methanol)zinc(II)
Methanol Solvate and
(Acetato)(N-benzamido-meso-tetraphenylporphyrinato)cadmium(II)
Benzene Solvate
,†
Fuh-An Yang,† Jyh-Horung Chen,* Hsi-Ying Hsieh,‡ Shanmugam Elango,§ and Lian-Pin Hwang|,∧
Department of Chemistry, National Chung-Hsing UniVersity, Taichung 40227, Taiwan,
Chung Hwa College of Medical Technology, Tainan 717, Taiwan, Department of Chemistry,
National Taiwan UniVersity, Taipei, Taiwan, and Institute of Atomic and Molecular Sciences,
Academia Sinica, Taipei 10764, Taiwan
Received December 17, 2002
The crystal structures of N-benzamido-meso-tetraphenylporphyrin (NHCOC H -Htpp; 1), (N-benzimido-meso-
6
5
tetraphenylporphyrinato)(methanol)zinc(II) [Zn(N-NCOC H -tpp)(MeOH); 2(MeOH)], and (acetato)(N-benzamido-meso-
6
5
tetraphenylporphyrinato)cadmium(II) [Cd(N-NHCOC H -tpp)(OAc); 3] were established. The coordination sphere around
6
5
Zn2+ ion in 2(MeOH) is a distorted trigonal bipyramid with N(2), N(5), and O(2) lying in the equatorial plane,
whereas, for Cd2+ ion in 3, it is a sitting-atop derivative with a distorted trigonal bipyramidal geometry in which the
apical site is occupied by atoms N(2) and O(2). Cd in 3 acquires five-coordination with five strong bonds [Cd(1)−
N(1) ) 2.319(5) Å, Cd(1)−N(2) ) 2.252(5) Å, Cd(1)−N(3) ) 2.332(5) Å, Cd(1)−O(2) ) 2.292(5) Å, and Cd(1)−
O(3) ) 2.317(5) Å] and with one secondary intramolecular interaction [Cd(1)‚‚‚N(4)]. The porphyrin ring in these
two complexes is distorted to a large extent. The plane of the three pyrrole nitrogen atoms [i.e., N(1)−N(3)] strongly
bonded to Zn2+ in 2(MeOH) and to Cd2+ in 3 is adopted as a reference plane 3N. For the Zn2+ complex, the pyrrole
nitrogen bonded to the benzamido (BA) ligand lies in a plane with a dihedral angle of 33.8° with respect to the 3N
plane, but for the Cd2+ complex, this dihedral angle is found to be 31.4°. In the former complex, Zn2+ and N(5) are
located on the different side at −0.08 and 1.39 Å from its 3N plane, and in the latter one, Cd2+ and N(5) are also
located on the different side at 1.08 and −1.51 Å from its 3N plane. VT NMR (1H and 13C) studies of 3 show that
the acetate acts as a bidentate ligand and the OAc- exchange does not occur in CD Cl2. Moreover, the NH proton
2
[i.e., H(5)] of 3 in CD Cl2 is observed as a sharp singlet at δ ) −1.13 ppm with ∆ν1/2 ) 4 Hz at 20 °C indicating
2
that the intermolecular proton exchange between water and NH proton is rapid.
Introduction
aminated porphyrins led to a series of bridged porphyrins
bearing a nitrene moiety inserted between the metal and a
pyrrole nitrogen. Many bridged metalloporphyrins with
M-NTs-N [M ) Zn(II),5 Ni(II),3 Fe(III),6 Ga(III),7 Tl(III);7
Ts ) tosyl] and with M-NNB-N linkages [M ) Zn(II),8
The preparation of N-substituted-N-aminoporphyrins has
been described by two groups.1-4 Metalation of these
* To whom correspondence should be addressed. E-mail: jyhhchen@
dragon.nchu.edu.tw.
† National Chung-Hsing University.
(3) Callot, H. J.; Chevrier, B.; Weiss, R. J. Am. Chem. Soc. 1978, 100,
4733.
(4) Ichimura, K. Bull. Chem. Soc. Jpn. 1978, 51, 1444.
(5) Li, Y. I.; Chang, C. S.; Tung, J. Y.; Tsai, C. H.; Chen, J. H.; Liao, F.
L.; Wang, S. L. Polyhedron 2000, 19, 413.
(6) Mahy, J. P.; Battioni, P.; Bedi, G.; Mansuy, D.; Fishcher, J.; Weiss,
R.; Morgenstern-Badarau, I. Inorg. Chem. 1988, 27, 353.
(7) Tung. J. Y.; Jang, J. I.; Lin, C. C.; Chen, J. H.; Hwang. L. P. Inorg.
Chem. 2000, 39, 1106.
‡ Chung Hwa College of Medical Technology.
§ Present address: Institute of Chemical and Engineering Science Ltd.,
Singapore 139959.
| National Taiwan University.
∧ Academia Sinica.
(1) Callot, H. J. Tetrahedron 1979, 35, 1455.
(2) Callot, H. J.; Fischer, J.; Weiss, R. J. Am. Chem. Soc. 1982, 104,
1272.
10.1021/ic0207202 CCC: $25.00 © 2003 American Chemical Society
Published on Web 07/03/2003
Inorganic Chemistry, Vol. 42, No. 15, 2003 4603

Yang et al.
Ni(II),9 Fe(III),8 Tl(III);9 NNB ) N-p-nitrobenzoylimido]
have so far been reported. However, in certain cases the metal
may be coordinated with only three porphyrinic N atoms as
previously reported for bis(chloromercury(II)) complex of
(N-tosylamino)octaethylporphyrin, C43H51N5O2SCl2Hg2.10 In
related areas, N-monoalkylated porphyrins form metal com-
plexes in which the metal is coordinated to the four (or three)
porphyrinic N atoms.11-14 Moreover, we have found no
example of the metal complexes in which the metal is
coordinated to the four (or three) porphyrinic N atoms in
the aminated porphyrin. This result prompted us to synthesize
a new N-benzamido-meso-tetraphenylporphyrin (NHCOC6H5-
Htpp) (1) [tpp ) dianion of meso-tetraphenylporphyrin] and
to study its metalation which might lead to mononuclear
metal complexes where the metal is four-coordinate either
to four porphyrinic N atoms or to three porphyrinic N atoms
plus one side-chain N atom. However, in certain cases the
metal in this new monometallic complexes might be fixed
to the porphyrin with three M-N bonds and form a Tsutsui’s
“sitting-atop” (SAT) complex.15
The d10 configuration permits a wide variety of geometries
and coordination numbers. In this paper, we described the
X-ray structural investigation on the metalation of 1 leading
to mononuclear complexes of (N-benzimido-meso-tetraphe-
nylporphyrinato)(methanol)zinc(II) [Zn(N-NCOC6H5-tpp)-
(MeOH); 2(MeOH)] and (acetato)(N-benzamido-meso-
tetraphenylporphyrinato)cadmium(II) [Cd(N-NHCOC6H5-
tpp)(OAc); 3]. The structural analysis of complexes 2(MeOH)
and 3 was undertaken to discover the effects of incorporating
the d10 metal ions (i.e., Zn2+ and Cd2+) into the highly
distorted and relatively rigid coordination environment
provided by the N-substituted-N-aminoporphyrin ligand
system.
mesh). The desired compound was eluted with CHCl3 either as dark
green band on aluminum oxide or as dark brown band on silica
gel. Removal of the solvent and recrystallization from CH2Cl2-
MeOH [1:5 (v/v)] gave the purple solid of 1 (130 mg, 0.18 mmol,
54%). Compound 1 was dissolved again in CHCl3 and layered with
MeOH to give purple crystals for single-crystal X-ray analysis. 1H
3
NMR (499.85 MHz, CDCl3, 20 °C): δ 9.10 [d, Hâ(4,13), J(H-
H) ) 5 Hz], where Hâ(a,b) represents the two equivalent â-pyrrole
protons attached to carbons a and b, respectively; 8.89 [s, Hâ(8,9)];
3
8.80 [d, Hâ(3,14), J(H-H) ) 5 Hz]; 8.10 [s, Hâ(18,19)]; 7.75-
8.21 (m) for phenyl protons; 6.22 [t, HBA(49) or BA-H4, 3J(H-H)
) 9 Hz], where BA ) benzamido ligand; 5.63 [t, HBA(48,50) or
BA-H3,5, 3J(H-H) ) 8 Hz]; 3.41 [d, HBA(47,51) or BA-H2,6, 3J(H-
H) ) 8 Hz]. MS [m/z (assignment, rel intensity)]: 734 ([NHCOC6H5-
Htpp]+, 100); 733 ([NHCOC6H5-tpp]+, 61.32); 614 ([Htpp]+,
82.68); 613 ([tpp]+, 27.24) UV/visible spectrum [λ, nm (10-3ꢀ, M-1
cm-1)] in CH2Cl2: 324 (16.7), 430 (246), 557 (9.6), 639 (6.3).
Preparation of Zn(N-NCOC6H5-tpp)(MeOH)‚MeOH [2(MeO-
H).MeOH]. Compound 2 in 74% yield was prepared in the same
way as described for Zn(N-p-NCOC6H4NO2-tpp) using NHCOC6H5-
Htpp.8 Compound 2 was dissolved in CH2Cl2 and layered with
MeOH to obtain purple crystals for single-crystal X-ray analysis.
1H NMR (499.85 MHz, CDCl3, 20 °C): δ 9.09 [d, Hâ(4,13), 3J(H-
3
H) ) 5 Hz]; 8.88 [d, Hâ(3,14), J(H-H) ) 5 Hz]; 8.86 [s, Hâ-
(8,9)]; 7.76 [s, Hâ(18,19)]; 7.79-8.41 (m) for phenyl protons; 6.26
3
[t, HBA(49) or BA-H4, J(H-H) ) 7 Hz]; 5.82 [t, HBA(48,50) or
BA-H3,5, 3J(H-H) ) 8 Hz]; 3.95 [d, HBA(47,51) or BA-H2,6, 3J(H-
3
H) ) 9 Hz]; 3.36 [d, MeOH-CH3, J(H-H) ) 5 Hz]; 1.16 [q,
3
MeOH-OH, J(H-H) ) 5 Hz]; 1.71(s, H2O). MS [m/z (assign-
ment, rel intensity)]: 797 ([M+, 9.64]); 796 ([M - 1]+, 11.05); 692
([M - C6H5CO]+, 12.43); 678 ([Zn(tpp)]+, 74.44); 676 ([Zntpp -
2H]+, 100) UV/visible spectrum [λ, nm (10-3ꢀ, M-1 cm-1)] in CH2-
Cl2: 325 (18.6), 440 (214.3), 565 (17.8), 612 (18.2), 664 (10.5).
Cd(N-NHCOC6H5-tpp)(OAc).C6H6 (3‚C6H6). A mixture of 1
(73.3 mg, 0.1 mmol) in CH2Cl2 (50 cm3) and Cd(OAc)2‚2H2O (69
mg, 0.3 mmol) in MeOH (50 cm3) was refluxed in CH3CN (100
cm3) for 8 h. After concentration, the residue was dissolved in CH2-
Cl2 and extracted with distilled water to remove the excess Cd-
(OAc)2‚2H2O. The CH2Cl2 layer was concentrated to dryness
affording a bluish-green precipitate, which was recrystallized from
toluene-hexane [1:3 (v/v)] yielding a blue solid of 3 (47 mg, 0.052
mmol, 52%). Compound 3 was redissolved in CH2Cl2, with a few
drops of benzene added, and layered with toluene to afford blue
Experimental Section
Preparation of NHCOC6H5-Htpp (1).3 A solution of Zn(tpp)
(206 mg, 0.33 mmol) and benzoyl azide (0.5 g, 3.3 mmol) in CH2-
Cl2 (200 cm3) in a stoppered 250 mL Erlenmeyer flask was left for
ca. 8 h in the sunlight. To this solution was added 0.5 N HCl (250
cm3) with vigorous shaking for 0.5 h. After the organic layer was
separated, solid ammonium carbonate was added to it and then dried
with anhydrous Na2SO4. The excess (NH4)2CO3 and Na2SO4 were
removed by filtration. After concentration, the residue was dissolved
in a minimum of CHCl3 and chromatographed either on aluminum
oxide 90 (50 g, neutral, activity V) or on silica gel (100 g, 70-230
1
crystals for single-crystal X-ray analysis. H NMR (599.95 MHz,
4
CD2Cl2, 20 °C): δ 8.91 [s, Hâ (4,5), | J(Cd-H)| ) 4.2 Hz]; 8.80
[d, Hâ(10,19), 3J(H-H) ) 5 Hz]; 8.76 [d, Hâ(9,20), 3J(H-H) ) 5
Hz]; 8.60 [s, Hâ(14,15)]; 8.57 (s) for ortho protons O-H(38,40)
and O-H(34,44); 8.39 [s, ortho protons O′-H(22,32)]; 8.16 [bs, ortho
protons O′-H(26,28)]; 7.79-7.89 (m, meta and para protons); 6.44
3
(8) Chen, C. H.; Lee. Y. Y.; Liau, B. C.; Elango, S.; Chen, J. H.; Hsieh,
H. Y.; Liao, F. L.; Wang, S. L.; Hwang, L. P. J. Chem. Soc., Dalton
Trans. 2002, 3001.
(9) Chang, C. S.; Chen, J. H.; Li, Y. I.; Liau, B. C.; Ko, B. T.; Elango,
S.; Chen, J. H. Inorg. Chem. 2001, 40, 2905.
(10) Callot, H. J.; Chevrier, B.; Weiss, R. J. Am. Chem. Soc. 1979, 101,
7729.
(11) Lavallee, D. K.; Kopelove, A. B.; Anderson, O. P. J. Am. Chem. Soc.
1978, 100, 3025.
(12) Balch, A. L.; Cornman, C. R.; Latos-Grazynski, L.; Olmstead, M. M.
J. Am. Chem. Soc. 1990, 112, 7552.
(13) Schauer, C. K.; Anderson, O. P.; Lavallee, D. K.; Battioni, J. P.;
Mansuy, D. J. Am. Chem. Soc. 1987, 109, 3922.
(14) Wang, M. C.; Sue, L. S.; Liau, B. C.; Ko, B. T.; Elango, S.; Chen, J.
H. Inorg. Chem. 2001, 40, 6064.
[t, HBA(49) or BA-H4, J(H-H) ) 7 Hz]; 5.93 [t, HBA(48,50) or
BA-H3,5, 3J(H-H) ) 8 Hz]; 3.82 [d, HBA(47,51) or BA-H2,6, 3J(H-
H) ) 8 Hz]; 0.08 (s, OAc-Me); -1.13 (s, NH). 1H NMR (599.95
MHz, CD2Cl2, -90 °C): δ 8.96 [s, Hâ(4,5)] 8.77 [s, Hâ(10,19)];
8.72 [bs, Hâ(9,20)]; 8.65 [s, Hâ(14,15)]; 8.51 [d, ortho protons
3
O-H(38,40), J(H-H) ) 7 Hz]; 8.42 [d, ortho protons O-H(34,-
44), 3J(H-H) ) 7 Hz]; 8.35 [d, ortho protons O′-H(22,32), 3J(H-
3
H) ) 6 Hz]; 8.16 [d, ortho protons O′-H(26,28), J(H-H) ) 6
Hz]; 7.89(m) for meta H(37,41) and meta H(35,43); 7.82 [m, para
H(36,42)]; 7.79 [m, meta H(23,31)]; 7.78 [m, para H(24,30)]; 7.74
[m, meta H(25,29)]; 6.41 [t, HBA(49) or BA-H4, 3J(H-H) ) 7 Hz];
3
5.92 [t, HBA(48,50) or BA-H3,5, J(H-H) ) 7 Hz]; 3.72 [d, HBA
-
(15) Macquet, J. P.; Millard, M. M.; Theophanides, T. J. Am. Chem. Soc.
1978, 100, 4741.
3
(47,51) or BA-H2,6, J(H-H) ) 7 Hz]; 0.01 (s, OAc-Me); -1.42
4604 Inorganic Chemistry, Vol. 42, No. 15, 2003

Metal Complexes of N-Benzamidoporphyrin
Table 1. Crystal Data for NHCOC6H5-Htpp (1), 2(MeOH)‚MeOH, and 3‚C6H6
param
1
2(MeOH)‚MeOH
3‚C6H6
empirical formula
fw
C51H35N5O
733.84
C53H41N5O3Zn
861.28
C59H43CdN5O3
982.38
space group
cryst syst
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
P1h
P21/n
C2/c
triclinic
10.881(2)
13.003(2)
14.094(2)
95.976(4)
95.902(4)
90.611(3)
1972.3(6)
2
monoclinic
14.790(1)
17.160(1)
17.425(1)
90
98.369(1)
90
4375.1(5)
4
monoclinic
26.345(1)
11.4355(6)
32.317(2)
90
91.548(1)
90
9732.4(8)
8
F000
D
768
1.236
0.075
0.893
1792
1.308
0.612
0.981
4032
1.341
0.50
1.105
calcd, g cm-3
µ(Μï ΚR), mm-1
S
cryst size, mm3
θ, deg
0.11 × 0.29 × 0.51
0.08 × 0.13 × 0.56
0.21 × 0.16 × 0.10
25.06
26.04
28.28
T, K
293(2)
293(2)
294(2)
no. of reflcns measd
no. of reflcns obsd
R,a %
10 427
6910 (I > 2σ(I))
6.71
24 533
8590 (I > 2σ(I))
5.36
30 708
11 695 (I > 2σ(I))
9.79
Rw,b %
15.19
14.88
17.51
2
2
2
2
a R ) [Σ||Fo| - |Fc||/Σ|Fo|]. b Rw ) {Σ[w(Fo - Fc )2]/Σ[w(Fo )2]}1/2; w ) A/(σ2Fo + BFo ).
Table 2. Selected Bond Distances (Å) and Angles (deg) for
Compounds 2(MeOH)‚MeOH and 3.C6H6
(s, NH). UV/visible spectrum [λ, nm (10-3ꢀ, M-1 cm-1)] in CH2-
Cl2: 332 (37.1), 442 (375.3), 563 (14.2), 617 (23.9), 664 (11.7).
Spectroscopy. Proton and 13C NMR spectra were recorded at
599.95 and 150.87 MHz, respectively, on Varian Unity Inova-600
spectrometers locked on deuterated solvent and referenced to the
solvent peak. Proton NMR is relative to CD2Cl2 or CDCl3 at δ )
5.30 or 7.24, and 13C NMR, to the center line of CD2Cl2 or CDCl3
at δ ) 53.6 or 77.0. HMQC (heteronuclear multiple quantum
coherence) 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 Over-
hauser effect (NOE) difference spectroscopy was employed to
2(MeOH)‚MeOH
Distances
Zn-N(1)
Zn-N(2)
Zn-N(3)
2.057(3)
1.945(3)
2.067(3)
Zn-N(5)
Zn-O(2)
2.036(3)
2.142(3)
Angles
N(5)-Zn-N(1)
N(5)-Zn-N(2)
N(5)-Zn-N(3)
N(5)-Zn-O(2)
N(1)-Zn-N(2)
N(1)-Zn-N(3)
86.1(1)
131.6(1)
84.8(1)
116.8(1)
94.6(1)
N(2)-Zn-N(3)
O(2)-Zn-N(1)
O(2)-Zn-N(2)
O(2)-Zn-N(3)
N(4)-N(5)-Zn
94.0(1)
94.8(1)
111.3(1)
86.3(1)
94.8(2)
170.3(1)
1
determine the H-1H proximity through space over a distance of
3‚C6H6
Distances
up to about 4 Å.
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 spectrometer. UV/visible spectra
were recorded at 25 °C on a Hitachi U-3210 spectrophotometer.
Crystallography. Table 1 presents the crystal data as well as
other information for 1, 2(MeOH)‚MeOH, and 3‚C6H6. Measure-
ments were taken on a Bruker AXS SMART-1000 diffractometer
using monochromatized Mo KR radiation (λ ) 0.710 73 Å). The
SADABS absorption corrections were made for 1 and 2(MeOH)‚
MeOH. Empirical absorption corrections were made for 3‚C6H6.
The structures were solved by direct methods (SHELXTL PLUS)
and refined by the full-matrix least-squares method. All non-
hydrogen atoms were refined with anisotropic thermal parameters,
whereas all hydrogen atom positions were calculated using a riding
model and were included in the structure factor calculation. Table
2 lists selected bond distances and angles for complexes 2(MeOH)‚
MeOH and 3‚C6H6.
Cd(1)-N(1)
Cd(1)-N(2)
Cd(1)-N(3)
2.319(5)
2.252(5)
2.332(5)
Cd(1)-N(4)
Cd(1)-O(2)
Cd(1)-O(3)
2.612(5)
2.292(5)
2.317(5)
Angles
O(2)-Cd(1)-O(3)
O(2)-Cd(1)-N(1)
O(2)-Cd(1)-N(2)
O(2)-Cd(1)-N(3)
O(2)-Cd(1)-N(4)
55.9(2)
112.2(2)
156.6(2)
106.4(2)
81.7(2)
O(3)-Cd(1)-N(1)
O(3)-Cd(1)-N(2)
O(3)-Cd(1)-N(3)
O(3)-Cd(1)-N(4)
117.1(2)
101.1(2)
117.7(2)
137.5(2)
define the 3N reference plane. The BA-substituted pyrrole
N(4) is most highly canted from the 3N plane (30.4°). The
N-protonated pyrrole N(2) is tilted by 11.7°, while the other
two pyrroles are tilted by 2.4 [N(3)] and 8.5° [N(1)]. The
N-H protons are attached to N(2) and N(5) atoms in 1. The
deviations from the 3N plane of the BA atoms N(5) and
H(5A) are 1.20 and 1.10 Å, respectively. Moreover, H(2A)
is located on different side at -0.17 Å from the 3N plane
(Figure 2a).
Results and Discussion
Structure of 1. The X-ray structure of 1 with the
numbering is displayed in Figure 1a. The atoms of the
porphyrin core are nonplanar, while the pyrrole rings [N(1)],
[N(2)], [N(3)], and [N(4)] are individually planar. The three
pyrrolic nitrogens N(1), N(2), and N(3) are coplanar, which
Molecular Structures of 2(MeOH)‚MeOH and 3‚C6H6.
Using the d10 metals zinc(II) and cadmium(II), new zinc
[2(MeOH)‚MeOH] and new cadmium (3‚C6H6) complexes
were synthesized. The synthetic strategy is outlined in
Scheme 1.
Inorganic Chemistry, Vol. 42, No. 15, 2003 4605

Yang et al.
Figure 1. Molecular configuration and atom-labeling scheme for (a)
NHCOC6H5-Htpp (1), (b) 2(MeOH)‚MeOH, and (c) 3‚C6H6, with ellipsoids
drawn at 30% probability. Hydrogen atoms for all compounds and solvent
C6H6 for 3‚C6H6 are omitted for clarity.
The absolute values of hardness η for Zn2+ and Cd2+ are
10.88 and 10.29 eV, respectively.16 The softness of acidity
increases from Zn2+ to Cd2+. During the metalation of Cd-
(OAc)2 with free base 1 (Scheme 1), the soft acid Cd2+
prefers to retain one OAc- ligand and coordinates to the
N-H proton [i.e., H(2A)] of 1 to form a five-coordinate
complex 3. Complex 3 is the first example of an N-substituted-
N-aminoporphyrin-metal (cadmium) complex with retention
of the N-benzamido substituent. Moreover, the borderline
(or intermediate)17 acid Zn2+ prefers to attack the two N-H
protons [i.e., H(2A) and H(5A)] of 1 and leads to a five-
coordinate distorted trigonal bipyramidal zinc(II) derivative
2(MeOH) possessing a nitrene moiety inserted between the
zinc and one nitrogen atom [N(4)] (Scheme 1). The molecular
frameworks are depicted in Figure 1b for 2(MeOH)‚MeOH
and in Figure 1c for 3‚C6H6. The geometry around Cd in 3
is a distorted square-based pyramid in which the apical site
is occupied by atoms N(2) and O(2), whereas, for Zn2+ in
2, it is also described as a distorted trigonal bipyramid with
N(2), N(5), and O(2) lying in the equatorial plane. Compound
3 is a five-coordinate N-benzamidoporphyrin complex of the
porphyrin N3 [i.e., N(1), N(2), and N(3)] with two oxygen
atoms of the chelating bidentate OAc- ligand. The zinc is
also pentacoordinated with three nitrogen atoms of the
porphyrins, one methanol oxygen, and one extra nitrogen
atom of the nitrene fragment in 2. The metal-ligand bond
Figure 2. Diagram of the porphyrinato core (C20N4, M, BA, and OAc-)
of (a) 1, (b) 2(MeOH)‚MeOH, and (c) 3‚C6H6 . The values represent the
displacements (in Å) of the atoms from the mean 3N plane [i.e., N(1)-
N(3)].
(16) Pearson, R. G. Inorg. Chem. 1988, 27, 734.
(17) Hancock, R. D.; Martell, A. E. J. Chem. Educ. 1996, 73, 654.
4606 Inorganic Chemistry, Vol. 42, No. 15, 2003

Metal Complexes of N-Benzamidoporphyrin
Scheme 1
interaction. This kind of secondary interaction was previously
observed for [Cd(H3daps)Cl]‚CH3CN‚0.25H2O [H4daps )
2,6-bis(1-salicyloylhydrazonoethyl)pyridine] with Cd‚‚‚N(6)
) 2.74(1) Å.21
The distortion in five-coordinate complexes can be quanti-
fied by the “degree of trigonality” which is defined as τ )
(â - R)/60, where “â” is the largest and “R” the second
largest of the Lbasal-M-Lbasal angles.22 The limiting values
are τ ) 0 for an ideal tetragonal geometry and τ ) 1 for an
ideal trigonal bipyramid. In the present case, we find â )
170.3(1)° [N(1)-Zn-N(3)] and R ) 131.6(1)° [N(2)-Zn-
N(5)] for 2(MeOH)‚MeOH, and â ) 156.2(2)° [N(2)-Cd-
(1)-O(2)] and R ) 124.1(2)° [N(1)-Cd(1)-N(3)] for 3.
Thus, the values τ ) 0.65 and 0.54 are obtained for
2(MeOH)‚MeOH and 3, respectively. Hence, the geometries
around Zn(II) in 2(MeOH)‚MeOH and Cd(II) in 3 are best
described as a distorted trigonal bipyramid (or a square-based
pyramidal distorted trigonal bipyramid, SBPDTBP)23 with
N(2), N(5), and O(2) [or N(1), N(3), and O(3)] lying in the
equatorial plane for 2(MeOH)‚MeOH (or 3). In 2(MeOH)
(Figure 1b), the observed H(3B)‚‚‚O(1) and O(3)‚‚‚O(1)
distances were 1.90 and 2.62 Å, respectively, which fall
below those values expected for van der Waals distances
(2.60 and 2.80 Å, respectively). The O(3)-H(3B)-O(1)
angle was 163.4°, and its deviation from linearity was not
too severe. Therefore, a hydrogen bond exists between H(3B)
and O(1). The intramolecular hydrogen bonds cause the
downfield shifts of +6.2 and +8.4 ppm for salicyaldehyde
and O-hydroxyacetophenone relative to the parent com-
pounds. In a similar fashion this intermolecular hydrogen
bonding causes an increased polarization of the carbonyl
bond in 2(MeOH). Consequently, the carbonyl carbon C(45)
in 2(MeOH) becomes more positive, thereby accounting for
why the downfield shift of +3.5 ppm is observed at 20 °C,
i.e., from 160.7 ppm for C(45) in 3 to 164.2 ppm for the
same carbonyl carbon in 2(MeOH).
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 2(MeOH)‚MeOH and 3. The benzamide
nitrogen N(5) in 2 is located considerably far from the 3N
plane. In 2, Zn2+ and N(5) are located on different sides at
-0.08 and 1.39 Å from its 3N plane (Figure 2). Apparently,
chelating bidentate acetate in 3 is trans to the BA group with
O(2) and O(3) being located separately at 2.88 and 3.29 Å
out of the 3N plane (Figure 2). The N(4) pyrrole rings bearing
the BA group in 2 and 3 would deviate mostly from the 3N
plane, thus orienting separately in a dihedral angle of 33.8
and of 31.4°, whereas small angles of 16.9, 8.2, and 14.5°
occur with N(1), N(2), and N(3) pyrrole for 2 and the
corresponding angles are 22.4, 3.3, and 20.4° for 3. In 2,
such a large deviation from planarity for the N(4) pyrrole is
also reflected by observing a 14-16 ppm upfield shift in
distances and the angles are summarized in Table 2. In 2, it
appears that the benzamido (BA) moiety is inserted into the
Zn-N bond of (meso-tetraphenylporphyrinato)zinc(II) [Zn-
(tpp)] resulting in the elongation of the N(2)‚‚‚N(4) distance
from 4.245 Å in 3 to 4.475 Å in 2. But the N(1)‚‚‚N(3)
distance of 4.108 Å remains the same for 2 and 3.
The bond distance (Å) of Zn-O(2) is 2.142(3), and the
mean Zn-N(p) ) 2.026(3) for 2(MeOH)‚MeOH; for 3‚C6H6
the values are Cd(1)-O(2) ) 2.292(5) and Cd(1)-O(3) )
2.317(5) and the mean Cd(1)-N(p) ) 2.301(5). The Zn-
O(2)(MeOH) distance of 2.142(3) Å is slightly longer than
the sum of the covalent radii of Zn and O (1.93 Å) but is
significantly shorter than the sum of the van der Waals radii
of Zn and O (2.90 Å).18 This Zn-O(2) contact may be
described as a weak covalent bond. This type of Zn‚‚‚
O(MeOH) contact was also previously observed for Zn(N-
PNCOC6H5NO2-tpp) with Zn(1)-O(4) ) 2.106(3) Å.8 The
pyrrole nitrogen N(4) and BA nitrogen N(5) are no longer
bonded to zinc and cadmium as indicated by their longer
internuclear distances, 2.570(3) Å for Zn‚‚‚N(4) and 3.094-
(5) Å for Cd(1)‚‚‚N(5). The cadmium-nitrogen bond
distances [Cd(1)-N(1) ) 2.319(5), Cd(1)-N(2) ) 2.252-
(5), and Cd(1)-N(3) ) 2.332(5)] are comparable to those
of Cd-N(3) ) 2.387(3) Å in bis[tetrakis(1-pyrazolyl)borato]-
cadmium(II), [B(pz)4]2Cd,19 and are also smaller than the
upper limit 2.54(1) Å for the typical covalent bond distance
of Cd-N13 in Cd(C32H34N5)(C7H6N2)NO3‚CHCl3.20 Hence
N(1), N(2), and N(3) are bonded strongly as well as
covalently to Cd atom in 3. Cadmium(II) is bonded to fewer
than four nitrogen atoms, and so 3 may be considered as a
Tsutsui’s sitting-atop (SAT) complex.15 The similar kind of
SAT complex was previously reported for bis(chloromercury-
(II)) complex of (N-tosylamino)octaethylporphyrin.10 The Cd-
(1)‚‚‚N(4) distance of 2.612(5) Å is longer than 2.54(1) Å
but is signficantly shorter than the sum of the van der Waals
radii of Cd and N (3.15 Å).18 This longer Cd(1)‚‚‚N(4)
contact is too long to be considered as a true coordinated
bond and may be viewed as a secondary intramolecular
(21) Fondo, M.; Sousa, A.; Bermejo, M. R.; Garcia-Deibe, A.; Sousa-
Pedrares, A.; Hoyos, O. L.; Helliwell, M. Eur. J. Inorg. Chem. 2002,
703.
(22) Addison, A. W.; Rao, T. N.; Reedijk, J.; Rijn, J. V.; Verschoor, G. C.
J. Chem. Soc., Dalton Trans. 1984, 1349.
(23) Murphy, G.; Nogle, P.; Murphy, B.; Hathaway, B. J. Chem. Soc.,
Dalton Trans. 1997, 2645.
(18) Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry, 4th
ed.; Harper Collins College: New York, 1993; pp 114, 292.
(19) Reger, D. L.; Mason, S. S.; Rheingold, A. L.; Ostrander, R. L. Inorg.
Chem. 1993, 32, 5216.
(20) Sessler, J. L.; Murai, T.; Lynch, V. Inorg. Chem. 1989, 28, 1333.
Inorganic Chemistry, Vol. 42, No. 15, 2003 4607

Yang et al.
the 13C NMR spectrum of the Câ(18,19) at 118.5 ppm
compared to 134.1 ppm for Câ(4,13), 132.5 ppm for Câ(3,-
14), and 132.2 ppm for Câ(8,9). In 3, a similar deviation is
also found for the N(4) pyrrole by observing a 7-10 ppm
upfield shift of the Câ(14,15) at 123.9 ppm compared to 134.2
ppm for Câ(4,5), 131.8 ppm for Câ(9,20), and 131.2 ppm
for Câ(10,19).
The ionic radius is found to increase from 0.82 Å for Zn2+
(with CN ) 5) to 1.01 Å for Cd2+ (with CN ) 5).18 Because
of the large size of Cd2+, Cd(1) lies 1.08 Å above the 3N
plane toward the acetate oxygen in 3, compared to ∼0.08 Å
for Zn in 2. The Cd ion in 3 is displaced from the plane of
the four individual pyrrole groups, suggesting that the pyrrole
nitrogen lone pairs are not optimally situated for covalent
bonding to the metal. The displacements of Cd ion from the
plane of each pyrrole ring are 0.20 Å for pyrrole N(1) ring,
1.20 Å for pyrrole N(2) ring, 0.28 Å for pyrrole N(3), and
2.32 Å for pyrrole N(4) ring. The angles between the Cd-N
vector and the corresponding pyrrole rings are 7.5° for
pyrrole N(1) ring, 31.6° for pyrrole N(2), 8.8° for pyrrole
N(3), and 60.2° for pyrrole N(4) ring.
The dihedral angles between the mean plane of the
skeleton (3N) and the plane of the phenyl group are 37.9°
[C(24)], 50.9° [C(30)], 54.6° [C(36)], and 40.6° [C(42)] for
2(MeOH) and the corresponding angles are 58.1, 49.3, 34.9,
and 36.5° for 3.
1H and 13C of 2(MeOH) and 3 in CD2Cl2. The signal
arising from the NH protons of 1 was not observed at 20
°C. At -90 °C, traces of water were frozen from solution
of 1 in CD2Cl2. Thus, the frozen water inhibits intermolecular
proton exchange between water and NH proton of 1 and
allows the observation of a broad singlet for NH proton at
-0.74 ppm.24 The cadmium(II) complex of 3 is diamagnetic
1
and hence readily becomes susceptible for studies by H
(Figure 3) and 13C NMR techniques. Figure 3 reveals that
broadening due to intermolecular proton exchange for NH
proton is eliminated upon metalation. The 1H NMR spectrum
of 3 in CD2Cl2 (Figure 3) showed a sharp singlet at δ )
-1.13 ppm (∆ν1/2 ) 4 Hz) for the NH proton at 20 °C. These
NMR data for 3 suggest that the NH proton [i.e., H(5)] bound
to N(5) undergoes rapid intermolecular proton exchange with
water at 20 °C.
In solution, the molecule has effective Cs symmetry with
a mirror plane running through the N(5)-N(4)-Cd(1)-
N(2)-O(2)-O(3) unit for 3, the N(2)-Zn-N(5)-N(4) unit
for 2(MeOH), or the N(4)-N(5)-C(45)-N(2) unit for 1.
There are four â-pyrrole protons Hâ, four â-pyrrole carbons
Câ, four R-pyrrole carbons CR, two different meso carbons
Cmeso, and two phenyl-C1 carbons for these three complexes.
On the basis of NOE difference spectrum (1-D) studies, the
Hâ(4,5) of 3 in CD2Cl2 at 20 °C was observed at δ ) 8.91
4
ppm with | J(Cd-Hâ)| ) 4.2 Hz and the singlet at 8.60 ppm
is assigned to Hâ(14,15) (Figure 3b). This coupling satellites
of Hâ(4,5) in 3 is comparable to the | J(113Cd-Hâ)| value of
4
4.8 Hz for the Hâ protons in Cd(N-Me-tpp)Cl[chloro(N-
methyl-meso-tetraphenylporphyrinato)cadmium(II)].25 In a
Figure 3. 1H NMR spectra for 3 at 599.95 MHz in CD2Cl2: (a) 20 °C,
entire spectrum; (b) expansion of the region of 7.6-9.2 ppm of (a) showing
four different â-pyrrole protons Hâ and phenyl protons (O-H, m, p-H); (c)
-90 °C.
(24) Henold, K. J. Chem. Soc., Chem Commun. 1970, 1340.
4608 Inorganic Chemistry, Vol. 42, No. 15, 2003

Metal Complexes of N-Benzamidoporphyrin
3
similar case, the sign and magnitude of the coupling constant
O-H(38,40) with J(H-H) ) 7 Hz (Figure 3c). The other
4
with J(113Cd-Hâ) ) -5 Hz was obtained for Cd(tpp)(py)
doublet at 8.42 ppm is due to ortho protons O-H(34,44) with
3J(H-H) ) 7 Hz.29 Likewise, the doublet at 8.35 ppm is
due to the ortho protons O′-H(22,32) with J(H-H) ) 6
Hz. The corresponding doublet at 8.16 ppm is due to the
(py ) pyridine) by using the 13C{H} off-resonance/selective
decoupling technique.26 In 3, the doublet at 8.80 ppm is
assigned to Hâ(10,19) with 3J(H-H) ) 5 Hz, and the other
3
3
3
doublet at 8.76 ppm is due to Hâ(9,20) with J(H-H) ) 5
ortho protons O′-H(26,28) with J(H-H) ) 6 Hz (Figure
1
Hz. The H NMR spectrum (Figure 3a) reveals that the
3c). In a similar way, the meta and para protons appearing
as multiplet (7.79-7.89 ppm) at 20 °C (Figure 3b) changed
to 7.89 [m, m-H(37,41) and m-H(35,43)], 7.79 [m, m-H(23,-
31)], 7.74 [m, m-H(25,29)], 7.82 [m, p-H(36,42)], and 7.78
ppm [m, p-H(24,30)] at -90 °C (Figure 3c). The analysis
of these data was confirmed by the NOE difference
spectroscopy for 3 in CD2Cl2 at -90 °C.
aromatic protons of the BA group appear as two triplets,
one at 6.44 ppm (BA-H4) and the other at 5.93 ppm (BA-
H3,5) and as one doublet at 3.82 ppm (BA-H2,6) for 3 and at
1
6.26 (t), 5.82 (t), and 3.95 (d) ppm for 2(MeOH). The H
NMR spectrum (Figure 3a) for OAc- of 3 in CD2Cl2 displays
a sharp singlet for CH3 at δ ) 0.08 ppm with ∆ν1/2 ) 6 Hz
at 20 °C and remains a sharp singlet for the same methyl
protons at δ ) 0.01 ppm with ∆ν1/2 ) 7 Hz at -90 °C. This
minimum deviation in the value of line width (∆ν1/2) upon
cooling indicates that OAc- exchange does not occur in
compound 3. All BA and acetato protons are shifted upfield
compared to their counterparts in free BA and OAc-. Such
a shift is presumably attributed to the porphyrin ring current
effect. The ring current effect indicates that the acetate ligand
is bonded to Cd in 3. This bonding argument is further
supported by the result that in 13C NMR the OAc-CO [i.e.,
C(52)] and the OAc-Me [i.e., C(53)] in 3 were observed at
In previous work,8 we reported the electronic and magnetic
properties of paramagnetic complex Fe(N-p-NCOC6H4NO2-
tpp)Cl (4) and diamagnetic species Zn(N-p-NCOC6H4NO2-
tpp)(MeOH) [5(MeOH)] by magnetic susceptibility mea-
surements and EPR spectroscopic studies. In this work we
investigated the metal-binding ability of porphyrin N-
substituted pyrroles, leading to formation of a diamagnetic
metal complex 3, with substituted groups on the nitrogen.
Meanwhile, we also reported the insertion of Zn2+ into the
rigid environment to form a diamagnetic complex 2. The
three bridged metalloporphyrins 2(MeOH), 4, and 5(MeOH)
are five-coordinate, and the value τ ) 0.65 is obtained for
these compounds. Hence the geometry around Zn(II) in
2(MeOH) and 5(MeOH) and Fe(III) in 4 is described as a
distorted trigonal bipyramid (or SBPDTBP). The sitting-atop
structure of 3 is definitely different from those structures of
compounds 2(MeOH), 4, and 5(MeOH) but is quite similar
to that of N-monoalkylated porphyrins, i.e., Hg(N-Me-tpp)-
Cl [chloro(N-methyl-meso-tetraphenylporphyrinato)mercury-
(II)].14
2
176.3 ppm with J(Cd-C) ) 32 Hz and at 18.5 ppm with
3
| J(Cd-C)| ) 48 Hz, respectively, at -90 °C. In a series of
tetraarylporphyrins with Ga, In, Tl, Ge, or Sn as the central
metal atom, 13C NMR chemical shifts were shown to be
useful tools for diagnosing whether acetato ligands were
monodentate or bidentate.27 Monodentate acetato ligands
were located at 20.5 ( 0.2 and 168.2 ( 1.7 ppm, and the
bidentate acetato ligands at 18.0 ( 0.7 and 175.2 ( 1.6
ppm.27,28 The methyl and carboyl chemical shifts of the
acetate group in 3 at 20 °C are separately located at 18.6
and 176.5 ppm confirming that the acetate is chelating
bidentately and coordinated to the cadmium atom.27
Conclusion
We have investigated the new free base 1 and two
diamagnetic and mononuclear zinc(II) and cadmium(II)
porphyrin complexes 2(MeOH) and 3 and their X-ray
structures are established. NOE difference spectroscopies,
HMQC (Figures S4 and S5 in the Supporting Information)
and HMBC (Figures S1-S3 in the Supporting Information),
were employed to unambiguous assignment of the H and
13C NMR resonances of 3 in CD2Cl2 at -90 °C and in CDCl3
at 20 °C.
Figure 3 depicts the representative 1H spectra for 3 in CD2-
Cl2 at 20 and -90 °C. At 20 °C, the rotation of phenyl group
along the C1-Cmeso [C(12)-C(33) or C(17)-C(39)] bond is
near fast.29 This near-fast rotation is supported by assigning
the singlet at 8.57 ppm to ortho protons O-H(38,40) and
O-H(34,44) (Figure 3b). Moreover, the rotation of phenyl
group along the C(2)-C(21) [or C(7)-C(27)] bond is
intermediately slow. This intermediately slow rotation is also
supported by assigning the two broad singlets at 8.39 and
8.16 ppm to ortho protons O′-H(22,32) and O′-H(26,28),
respectively (Figure 3b). At -90 °C, this rotation is
extremely slow. Hence, the rate of intramolecular exchange
of the ortho protons for 3 in CD2Cl2 is also extremely slow.
The doublet at 8.51 ppm is assigned to ortho protons
1
Acknowledgment. The financial support from the Na-
tional Science Council of the ROC under Grant NSC 91-
2113-M-005-015 is gratefully acknowledged.
Supporting Information Available: Tables and figures pre-
senting crystal structure information for Cd(N-Me-tpp)Cl and 13C
NMR data for complexes 1, 2(MeOH), and 3, Figure S1-S3,
showing the HMBC spectra of 3 in CDCl3 at 20 °C, Figure S4 and
S5, showing the HMQC spectra of 3 in CDCl3 at 20 °C, and X-ray
crystallographic files in CIF format for compounds 1, 2(MeOH),
and 3. This material is available free of charge via the Internet at
http://pubs.acs.org.
(25) The crystal structure of Cd(N-Me-tpp)Cl is shown in the Supporting
Information.
(26) Jakobsen, H. J.; Ellis, P. D.; Inners, R. R.; Jensen, C. F. J. Am. Chem.
Soc. 1982, 104, 7442.
(27) Lin, S. J.; Hong, T. N.; Yung, J. Y.; Chen, J. H. Inorg. Chem. 1997,
36, 3886.
(28) Ye, B. H.; Li, X. Y.; Williams, I. D.; Chen, X. M. Inorg. Chem. 2002,
41, 6426.
(29) Drago, R. S. Physical Methods for Chemists, 2nd ed.; Saunders College
Publishing: New York, 1992; pp 290-295.
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