A conspicuous deprotonation in complexes of diphenyllead(IV) with ligands containing both semicarbazone and thiosemicarbazone chains

Article abstract of DOI:10.1002/ejic.201001030

In the search for new chelating agents for organolead(IV) ions, 2,6-diacetylpyridine was sequentially condensed with semicarbazide and 4-methylthiosemicarbazide to give H₂L¹. According to an X-ray study, this molecule is nearly planar with the semicarbazone (SC) and the thiosemicarbazone (TSC) chains in "open-arm" and "closed- arm" orientations, respectively. Similar condensation of 2,3-butanedione with semicarbazide and 4-methylthiosemicarbazide or with 4-phenylsemicarbazide and 4-phenylthiosemicarbazide afforded H₂L² and H ₂L³, respectively. The reactions of H₂L ^x with diphenyllead(IV) diacetate in methanol gave the complexes [PbPh₂(HL¹)](OAc)_0.75Cl _0.25·2.375H₂O, [PbPh₂(OAc)(HL ²)]·MeOH and [PbPh₂(H_0.5L ³)(MeOH)](OAc)_0.5. When the latter was recrystallised from dmso, the new derivative [PbPh₂(L³)(dmso)]·2dmso was isolated. The X-ray study of the H₂L¹ complex showed that the ligand, with the TSC chain deprotonated and the SC chain not deprotonated, binds the organometallic moiety through the N3, N4, N5, O1 and S atoms to afford a previously unknown [PbC₂N₃OS] kernel. In the H₂L² and H₂L³ complexes the coordination for the diphenyllead(IV) moiety is the same, with the ligand N,N,S,O-bound, but these complexes differ in the protonation status of the SC chain. In [PbPh₂(OAc)(HL²)]·MeOH the chain is not deprotonated, and in [PbPh₂(L³)(dmso)]·2dmso it is deprotonated. Conspicuously, in [PbPh₂(H_0.5L ³)(MeOH)](OAc)_0.5 the SC "arm" is formally only "half" deprotonated according to the X-ray study and analysis of the occupation factors in the lattice. From a more "chemical" point of view, this complex can be depicted as containing both (HL³) ^- and (L³)^2- ligands in a 1:1 ratio. This partial deprotonation of the SC chain is supported both by a bond length analysis and by ¹H NMR spectroscopy.

Full text of DOI:10.1002/ejic.201001030

FULL PAPER
DOI: 10.1002/ejic.201001030
A Conspicuous Deprotonation in Complexes of Diphenyllead(IV) with Ligands
Containing Both Semicarbazone and Thiosemicarbazone Chains
José S. Casas,*[a] Estefanía Castro-Vidal,[a] María S. García-Tasende,*[a] Agustín Sánchez,[a]
José Sordo,[a] Ángeles Touceda,[a] and Ezequiel M. Vázquez-López[b]
Keywords: Lead / Diphenyllead(IV) / O ligands / S ligands / Partial deprotonation
In the search for new chelating agents for organolead(IV)
ions, 2,6-diacetylpyridine was sequentially condensed with
semicarbazide and 4-methylthiosemicarbazide to give H2L1.
According to an X-ray study, this molecule is nearly planar
with the semicarbazone (SC) and the thiosemicarbazone
(TSC) chains in “open-arm” and “closed-arm” orientations,
respectively. Similar condensation of 2,3-butanedione with
semicarbazide and 4-methylthiosemicarbazide or with 4-
phenylsemicarbazide and 4-phenylthiosemicarbazide af-
forded H2L2 and H2L3, respectively. The reactions of H2Lx
with diphenyllead(IV) diacetate in methanol gave the com-
plexes [PbPh2(HL1)](OAc)0.75Cl0.25·2.375H2O, [PbPh2(OAc)-
(HL2)]·MeOH and [PbPh2(H0.5L3)(MeOH)](OAc)0.5. When the
latter was recrystallised from dmso, the new derivative
[PbPh2(L3)(dmso)]·2dmso was isolated. The X-ray study of
the H2L1 complex showed that the ligand, with the TSC
chain deprotonated and the SC chain not deprotonated,
binds the organometallic moiety through the N3, N4, N5, O1
and S atoms to afford a previously unknown [PbC2N3OS]
kernel. In the H2L2 and H2L3 complexes the coordination for
the diphenyllead(IV) moiety is the same, with the ligand
N,N,S,O-bound, but these complexes differ in the proton-
ation status of the SC chain. In [PbPh2(OAc)(HL2)]·MeOH the
chain is not deprotonated, and in [PbPh2(L3)(dmso)]·2dmso it
is deprotonated. Conspicuously, in [PbPh2(H0.5L3)(MeOH)]-
(OAc)0.5 the SC “arm” is formally only “half” deprotonated
according to the X-ray study and analysis of the occupation
factors in the lattice. From a more “chemical” point of view,
this complex can be depicted as containing both (HL3)– and
(L3)2– ligands in a 1:1 ratio. This partial deprotonation of the
SC chain is supported both by a bond length analysis and by
1H NMR spectroscopy.
tered, move to the tissue, displace the endogenous ligands
to which the metal is bound and form a complex with the
metal ion that can be excreted in the urine or faeces. Intra-
venous calcium sodium edentate (calcium disodium ethyl-
enediaminetetraacetic acid, CaNa2edta) is the most com-
monly used chelating agent for “inorganic lead” poisoning.
This compound binds the PbII ion through the amino and
carboxylic acid groups to form stable chelates[4] but it is
mainly distributed extracellularly and appears to cause the
redistribution of lead to the brain.[5] An emerging alterna-
tive is the water-soluble derivative meso-2,3-dimercaptosuc-
cinic acid (dmsa), which has been approved by the US FDA
for the treatment of lead intoxication in children.[5] Accord-
ing to a recent review,[6] dmsa in humans is a good chelator
for renal lead(II) but occasionally causes significant adverse
effects. Thus, even though some chelators are effective for
“inorganic lead” poisoning, they all have some drawbacks
and are, at present, far from being considered as “ideal”
chelating drugs. With respect to organolead(IV) com-
pounds (“organic lead”, PbRn(4–n)+), a specific therapy for
their toxic effects has yet to be developed.[7]
Introduction
Lead is one of the seven metals of antiquity and has
played a very important role in the progress of mankind. It
also, however, constitutes one of the oldest known toxicants
for living beings. In humans, lead at blood concentrations
Ն30 μg/dL affects all major body systems but is particularly
damaging for the developing central nervous system of chil-
dren.[1] Despite the accumulated evidence of the adverse
health effects of this metal, lead and its compounds are still
widely used, and this makes lead poisoning a recurrent
problem in society.[2]
The present approved clinical procedure to deal with lea-
d(II) (“inorganic lead”) poisoning is the use of chelating
agents that are able to remove the metal from lead-bur-
dened tissue.[3] Theoretically, these agents, once adminis-
[a] Departamento de Química Inorgánica, Facultade de Farmacia,
Universidade de Santiago de Compostela,
15782 Santiago de Compostela, Galicia, Spain
Fax: +34-981-547102
E-mail: sergio.casas@usc.es
soledad.garcia@usc.es
As part of a programme aimed at preparing new chela-
[b] Departamento de Química Inorgánica, Facultade de Química,
Universidade de Vigo,
(4–n)+
tors for the treatment of PbRn
poisoning, we describe
36310 Vigo, Galicia, Spain
here the synthesis of some mixed semicarbazone/thiosemi-
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201001030.
carbazone ligands (H2L1–3) and their interaction with di-
868
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 868–878

A Conspicuous Deprotonation in Complexes of Diphenyllead(IV)
phenyllead(IV), which was used as a coordination model far as we know, this is the first ligand of this type to be
for the very poisonous dimethyl- and diethyllead(IV) cat- characterized by X-ray diffraction.
ions. These ligands can bind to the metal ions through the
O and S atoms and also through N atoms (Scheme 1). As
far as we know, only one mixed ligand similar to H2L1 has
been used before to prepare a complex – in this case with
SmIII [8]
.
Figure 1. Molecular structure of H2L1.
Table 1. Selected bond lengths [Å] and angles [°] for H2L1.
S–C(11)
O–C(1)
N(1)–C(1)
N(2)–N(3)
N(2)–C(1)
N(3)–C(2)
N(4)–C(3)
N(4)–C(7)
1.692(3) N(7)–C(11)
1.236(3) N(7)–C(12)
1.332(3) C(2)–C(3)
1.365(3) C(2)–C(9)
1.394(3) C(3)–C(4)
1.291(3) C(4)–C(5)
1.345(3) C(5)–C(6)
1.352(3) C(6)–C(7)
1.293(3) C(7)–C(8)
1.368(3) C(8)–C(10)
1.358(3)
1.324(3)
1.453(3)
1.488(3)
1.501(3)
1.396(3)
1.377(4)
1.383(3)
1.395(3)
1.486(3)
1.503(3)
Scheme 1. Semicarbazone/thiosemicarbazone mixed ligands.
N(5)–C(8)
N(5)–N(6)
N(6)–C(11)
Results and Discussion
N(3)–N(2)–C(1)
C(2)–N(3)–N(2)
C(3)–N(4)–C(7)
C(8)–N(5)–N(6)
C(11)–N(6)–N(5)
C(11)–N(7)–C(12)
O–C(1)–N(1)
O–C(1)–N(2)
N(1)–C(1)–N(2)
N(3)–C(2)–C(3)
N(3)–C(2)–C(9)
C(3)–C(2)–C(9)
N(4)–C(3)–C(4)
N(4)–C(3)–C(2)
119.6(2) C(4)–C(3)–C(2)
117.8(2) C(5)–C(4)–C(3)
118.9(2) C(4)–C(5)–C(6)
119.4(2) C(5)–C(6)–C(7)
119.5(2) N(4)–C(7)–C(6)
124.2(2) N(4)–C(7)–C(8)
124.7(2) C(6)–C(7)–C(8)
118.6(2) N(5)–C(8)–C(7)
116.6(2) N(5)–C(8)–C(10)
114.4(2) C(7)–C(8)–C(10)
124.5(2) N(7)–C(11)–N(6)
121.2(2) N(7)–C(11)–S
122.1(2) N(6)–C(11)–S
117.2(2)
120.7(2)
118.9(2)
119.2(2)
119.5(2)
121.3(2)
118.8(2)
119.9(2)
127.9(2)
114.1(2)
118.0(2)
117.1(2)
124.07(19)
118.84(18)
Synthesis
The semicarbazone/thiosemicarbazone mixed ligands de-
rived from 2,6-diacetylpyridine and 2,3-butanedione diket-
ones were prepared by two consecutive condensation reac-
tions. The first reaction, between the diketone and semi-
carbazide or 4-phenylsemicarbazide, formed the corre-
sponding semicarbazone (SC1, SC2, SC3); the second reac-
tion, between SCx and 4-methyl-3-thiosemicarbazide or 4-
phenyl-3-thiosemicarbazide, afforded the corresponding
mixed ligand H2Lx (Scheme 1).
Reaction of these ligands with diphenyllead(IV) diacetate
gave the complexes [PbPh2(HL1)](OAc)0.75Cl0.25·2.375H2O,
The values for the bond lengths and angles in the semi-
[PbPh2(OAc)(HL2)]·MeOH,
[PbPh2(H0.5L3)(MeOH)]- carbazone and thiosemicarbazone moieties are in the ex-
(OAc)0.5 and [PbPh2(L3)(dmso)]·2dmso. These compounds pected range.[9] The orientation of the SC and TSC chains
were studied by X-ray diffraction. The presence of Cl– in with respect to the pyridine ring (as “open-arm” and
the first complex is plausibly due to the incomplete dis- “closed-arm”, respectively, Figure 1) is similar to that de-
placement of this anion from PbPh2Cl2 during the synthesis scribed for the ligand 2,6-diacetylpyridine bis(thiosemi-
of PbPh2(OAc)2 (see below).
carbazone) methanol solvate[10] and 2,6-diacetylpyridine
bis(N-ethyl-thiosemicarbazone).[11] The “closed-arm” ori-
entation of the TSC chain enables the formation of a strong
intramolecular hydrogen bond between N(6)–H(6A) and
the pyridine nitrogen atom [N(4)] (Figure 1 and Table 2).
Apparently, the ligand prefers to “close” the TSC “arm”
X-ray Studies
Crystal Structure of H2L1
The molecular structure of H2L1 is shown in Figure 1, instead of the SC “arm”, suggesting that the partial positive
and selected structural parameters are listed in Table 1. As charge on H(6A) is greater than that on H(2A). This situa-
Eur. J. Inorg. Chem. 2011, 868–878
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J. S. Casas, M. S. García-Tasende et al.
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tion is consistent with the easier deprotonation of the TSC C(2)=N(3) and C(8)=N(5) bonds, and the O and S atoms
chain with respect to the SC chain (see below). Addition- are cis to N(3) and N(5). This arrangement permits the for-
ally, both chains exhibit the usual intramolecular hydrogen mation of four five-membered chelate rings.
bonds between one hydrogen atom of the amino group and
the nitrogen atom of the carbohydrazide group [N(1)–
H(1A)···N(3) and N(7)–H(7A)···N(5)], a situation that
places N(3) and N(5) trans to O and S, respectively. The
molecule is nearly planar (rms = 0.0970 for all non-hydro-
gen atoms) and the S and C(10) atoms show the highest
deviation from this plane.
Table 2. Hydrogen-bond lengths [Å] and angles [°] in H2L1.
D–H···A[a]
d(D–H) d(H···A) d(D···A) Ͻ(DHA)
N(1)–H(1A)···N(3)
N(6)–H(6A)···N(4)
N(7)–H(7A)···N(5)
N(1)–H(1A)···Oi
N(1)–H(1B)···Sii
N(2)–H(2A)···Siii
0.80(3)
0.84(3)
0.84(3)
0.80(3)
0.98(3)
0.79(3)
2.35(3)
1.97(3)
2.21(3)
2.22(3)
2.56(3)
2.99(3)
2.665(3)
2.642(3)
2.635(3)
2.881(3)
3.531(2)
3.653(2)
104(2)
136(3)
111(2)
140(3)
172(2)
143(3)
Figure 2. Molecular structure of [PbPh2(HL1)]·(OAc)0.75
Cl0.25·2.375H2O.
-
[a] Symmetry operators: i = x + 1/2, –y – 1/2, z + 1/2; ii = –x –
1/2, y – 1/2, –z + 1/2; iii = –x, –y, –z.
The N–H protons not involved in the intramolecular hy-
drogen bonds, along with the O and S atoms, form several
intermolecular hydrogen bonds (Table 2) that lead to the
arrangement of the molecules in a supramolecular network.
Table 3. Selected bond lengths [Å] and angles [°] for
[PbPh2(HL1)](OAc)0.75Cl0.25·2.375H2O.
Pb–C(20)
2.193(6)
2.196(6)
2.440(5)
2.457(5)
2.521(5)
2.558(6)
2.7226(16)
1.762(7)
1.239(8)
1.342(8)
1.374(9)
1.375(8)
1.296(9)
1.345(9)
1.365(9)
1.295(8)
171.6(2)
67.30(18)
63.68(18)
62.73(16)
N(5)–N(6)
N(6)–C(11)
N(7)–C(11)
N(7)–C(12)
C(2)–C(9)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
C(8)–C(10)
O(2)–C(40)
O(3)–C(40)
C(40)–C(41)
1.371(7)
1.311(9)
1.345(9)
1.454(9)
1.473(11)
1.492(10)
1.383(10)
1.389(11)
1.360(11)
1.376(10)
1.464(10)
1.511(9)
1.263(13)
1.184(15)
1.539(17)
One of these interactions, N(1)–H(1A)···O(1)i, the influence Pb–C(30)
Pb–N(5)
of which on the opening of the chain can not be discarded,
Pb–N(4)
associates the molecules in chains (Figure S1), whereas ad-
Pb–O(1)
jacent chains are connected by weak N–H···S hydrogen
Pb–N(3)
Pb–S
S–C(11)
bonds (Figure S2).
O(1)–C(1)
N(1)–C(1)
N(2)–C(1)
N(2)–N(3)
N(3)–C(2)
N(4)–C(3)
N(4)–C(7)
N(5)–C(8)
C(20)–Pb–C(30)
N(5)–Pb–N(4)
N(4)–Pb–N(3)
O(1)–Pb–N(3)
Crystal Structure of [PbPh2(HL1)](OAc)0.75Cl0.25·2.375H2O
The molecular structure of [PbPh2(HL1)](OAc)0.75
-
Cl0.25·2.375H2O is shown in Figure 2 along with the num-
bering scheme. Selected bond lengths and angles are listed
in Table 3. The asymmetric unit consists of the cationic
complex [PbPh2(HL1)]+, a disordered acetate or chloride
anion with occupation factors of 0.75 and 0.25, respectively,
and 2.375 molecules of water disordered over four positions
with occupation factors of 1 (for O3w), 0.75 (for O1w), 0.25
N(5)–Pb–S
O(1)–Pb–S
O(2)–C(40)–O(3)
72.56(13)
93.77(11)
125.3(12)
Deprotonation of the N(6)H group in the TSC chain in-
(for O4w) and 0.375 (for O2w). In the cationic complex the stead of the N(2)H group in the SC chain is supported by
(HL1)– ligand has a deprotonated TSC chain and binds the the structural changes experienced by the ligand upon me-
metal atom through the N(3), N(4), N(5), O(1) and S atoms tallation. The TSC moiety partially evolves to the thiol
to afford a [PbC2N3OS] kernel, which has previously been form [d(C–S) = 1.692(3) Å in the free ligand and 1.762(7) Å
unknown according to a search of the Cambridge Struc- in the complex], and the Pb–N bond lengths suggest
tural Database.[12] The coordination geometry around the stronger interactions with this chain than with the SC
metal atom can be described as a slightly distorted pentago- chain.
nal bipyramid with the phenyl groups in axial positions and
In the crystal, two [PbPh2(HL1)]+ cations with the HL1–
(HL1)– on the equatorial plane. The main distortions with ligands in the same plane are linked through N(1)–H(1A)···
regard to the ideal geometry correspond to the C–Pb–C O(1)i hydrogen bonds to form dimers (Figure S3, Table 4).
[171.6(2)°] and O–Pb–S [93.77(11)°] bond angles. To achieve These dimers are in turn connected into chains through
their coordination, the TSC and SC chains of the ligand N(7)–H(7)···S(1)iii bonds. The packing and the relative loca-
both adopt an (E) configuration with respect to the tion of these chains are shown in Figure S4. A weak π···π
870
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Eur. J. Inorg. Chem. 2011, 868–878

A Conspicuous Deprotonation in Complexes of Diphenyllead(IV)
interaction between the pyridine ring and the C(20)–C(25)
phenyl ring (centroid–centroid distance 3.927 Å) and a
weak C–H···π interaction between the C(23)–H and the
C(30)–C(25) phenyl ring (C23–centroid distance 3.465 Å)
connect adjacent chains.
Table 4. Hydrogen-bond lengths [Å] and angles [°] in [PbPh2-
(HL1)](OAc)0.75Cl0.25·2.375H2O.[a]
D–H···A[b]
d(D–H) d(H···A) d(D···A)
Ͻ(DHA)
N(1)–H(1A)···O(1)i
0.86
2.09
1.98
2.39
1.95
2.55
2.86
2.44
2.902(7)
156.8
N(1)–H(1B)···O(3)ii 0.86
2.842(10) 176.1
3.193(12) 156.5
2.645(10) 136.5
3.317(12) 148.2
3.502(6)
2.974(11) 120.9
N(1)–H(1B)···Clii
N(2)–H(2)···O(2)ii
N(2)–H(2)···Clii
N(7)–H(7)···Siii
0.86
0.86
0.86
0.86
0.86
132.6
N(7)–H(7)···O(3)iv
[a] Those involving the water molecules are not included. [b] Sym-
metry operators: i = –x + 3/2, –y + 1/2, –z + 2; ii = x + 1, y, z +
1; iii = –x + 1, y, –z + 3/2; iv = x + 1/2, –y + 1/2, z + 1/2.
Figure 4. Molecular structure of [PbPh2(OAc)(HL2)]·MeOH.
Table 5. Selected bond lengths [Å] and angles [°] for [PbPh2-
The acetate and chloride anions interact (Table 4, Fig-
ure 3) with the chains without increasing the association.
Although the hydrogen atoms of the water molecules were
not located, the position of their oxygen atom suggests that
they form hydrogen bonds with [PbPh2(HL1)]+, AcO– and
Cl–, giving rise to an extended network.
(OAc)(HL2)]·MeOH.
Pb–C(20)
Pb–C(30)
Pb–N(4)
2.182(6)
2.183(6)
2.467(5)
2.496(5)
2.579(5)
2.603(4)
2.7010(17)
1.749(7)
1.239(7)
1.320(8)
1.359(7)
1.378(8)
1.295(8)
165.5(2)
86.57(15)
77.06(12)
N(4)–C(3)
N(4)–N(5)
N(5)–C(4)
N(6)–C(4)
N(6)–C(7)
C(2)–C(3)
C(2)–C(5)
C(3)–C(6)
O(2)–C(8)
O(3)–C(8)
C(8)–C(9)
O(1S)–C(1S)
1.304(8)
1.380(7)
1.318(8)
1.342(8)
1.452(8)
1.481(9)
1.512(8)
1.498(9)
1.152(8)
1.260(7)
1.555(10)
1.383(10)
Pb–O(2)
Pb–N(3)
Pb–O(1)
Pb–S
S–C(4)
O(1)–C(1)
N(1)–C(1)
N(2)–N(3)
N(2)–C(1)
N(3)–C(2)
C(20)–Pb–C(30)
O(1)–Pb–O(2)
O(2)–Pb–S
S–Pb–N(4)
N(4)–Pb–N(3) 63.90(18)
N(3)–Pb–O(1) 61.69(16)
70.91(13)
The partially deprotonated H2L2 ligand coordinates to
the organometallic moiety through the S, N(4), N(3) and O
atoms to form three five-membered chelate rings, which are
almost coplanar (Pb, C1, N2, N3, C2, C3, N4, N5, C4, S;
rms = 0.1173). The interactions of the metal atom with the
TSC “arm” are comparable with those previously discussed
for the complex of H2L1, but the Pb–O(1) bond with the
SC “arm” is slightly weaker in the present derivative. Both
the SC and TSC chains adopt an (E) configuration to che-
late the metal atom, and the C(4)–S bond length in the TSC
chain indicates a thione-to-thiol evolution upon deproton-
ation and metallation. The C=O bond length, however, re-
mains within the range found in free semicarbazones that
are not deprotonated.[11]
Figure 3. Hydrogen bonds between acetate (a) or chloride (b)
anions and the complex cation in [PbPh2(HL1)](OAc)0.75
-
Cl0.25·2.375H2O.
The reduction in the number of donor atoms in H2L2
with respect to H2L1 allowed the incorporation of an ad-
ditional monodentate acetate group on the equatorial plane
of the complex (Pb, O1, N3, N4, S, O2; rms = 0.0638) and
again leads to a distorted pentagonal-bipyramidal arrange-
Crystal Structure of [PbPh2(OAc)(HL2)]·MeOH
The molecular structure and the numbering scheme for ment around the metal atom with the phenyl groups in the
this complex are shown in Figure 4, and selected bond apical positions. The coordination mode of the acetate dif-
lengths and angles are given in Table 5.
fers from that previously observed in some heteroleptic
Eur. J. Inorg. Chem. 2011, 868–878
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J. S. Casas, M. S. García-Tasende et al.
FULL PAPER
(monothiosemicarbazone)diphenyllead(IV) complexes[13–15] the SC chain not being deprotonated. The MeOH mole-
in which the acetate moiety is anisobidentate and binds to cules, which behave both as hydrogen-bond donors and as
the metal atom with a bite angle of around 50°.
double-acceptors, connect the chains and extend the associ-
The molecules of the complex associate through intermo- ation into a 2D network (Figure S6).
lecular hydrogen bonds (Table 6) that involve the N(1)H
and N(2)H groups from the SC “arm” and the oxygen
atoms from the acetate ligand [O(2) and O(3)] to give a
chain along the b axis (Figure S5). The fact that the N(2)–
H group is involved in a hydrogen bond clearly supports
Crystal Structures of [PbPh2(H0.5L3)(MeOH)](OAc)0.5 and
[PbPh2(L3)(dmso)]·2dmso
The molecular structures of complexes obtained from the
H2L3 ligand are shown in Figures 5 and 6. Selected bond
lengths and angles are listed in Tables 7 and 8.
Table 6. Hydrogen-bond lengths [Å] and angles [°] in [PbPh2-
(OAc)(HL2)]·MeOH.
According to the X-ray study, the reaction of H2L3 with
diphenyllead(IV) diacetate under conditions similar to
those described for H2L2 afforded the complex
[PbPh2(H0.5L3)(MeOH)](OAc)0.5, in which the TSC “arm”
of H2L3 is deprotonated but the SC “arm” is formally only
“half” deprotonated. This rather unusual deprotonation be
haviour of H2L3 was concluded from an analysis of the oc-
cupation factors in the lattice. These factors are 1 for all
D–H···A[a]
d(D–H) d(H···A) d(D···A) Ͻ(DHA)
N(1)–H(1A)···O(1S)i 0.86
2.18
2.08
2.42
1.99
2.08
3.029(8) 167.8
2.935(7) 170.3
3.225(5) 166.4
2.815(7) 160.6
2.879(7) 154.1
N(1)–H(1B)···O(2)ii
O(1S)–H(1S)···Siii
N(2)–H(2)···O(3)ii
N(6)–H(6)···O(1S)
0.86
0.82
0.86
0.86
[a] Symmetry operators: i = x + 1/2, –y + 1/2, z – 1/2; ii = –x +
3/2, y – 1/2, –z + 3/2; iii = –x + 1, –y + 1, –z + 2.
Figure 5. Asymmetric unit of [PbPh2(H0.5L3)(MeOH)](OAc)0.5. The acetate group and the proton on N2 have occupation factors of 0.5.
Figure 6. Molecular structure of [PbPh2(L3)(dmso)]·2dmso.
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A Conspicuous Deprotonation in Complexes of Diphenyllead(IV)
Table 7. Selected bond lengths [Å] and angles [°] for distances, which decrease as deprotonation of the semi-
[PbPh2(H0.5L3)(MeOH)](OAc)0.5
.
carbazone chain increases. Note that the distances in the
SC chain (see Tables 7 and 8) also appear to be sensitive to
the different degree of H2L3 deprotonation [the O(1)–C(1)
and N(2)–C(1) bond lengths increase and decrease, respec-
tively, when the degree of deprotonation increases, as one
would expect if the ligand evolved to the enol form
(Scheme 2)], although these changes are within the esds
values.
Pb–C(20)
Pb–C(30)
Pb–N(4)
Pb–N(3)
Pb–O(1)
Pb–O(1S)
Pb–S
2.175(4)
2.182(4)
2.466(3)
2.482(3)
2.492(3)
2.574(3)
2.7475(11)
1.738(4)
1.253(5)
1.361(5)
1.407(5)
1.350(5)
N(2)–C(1)
N(3)–C(2)
N(4)–C(3)
N(4)–N(5)
N(5)–C(4)
N(6)–C(4)
N(6)–C(13)
C(2)–C(3)
O(1S)–C(1S)
O(2)–C(40)
O(21)–C(40)
C(40)–C(41)
O(1)–Pb–O(1S)
N(4)–Pb–S
O(1S)–Pb–S
1.366 (5)
1.300(5)
1.305(5)
1.380(4)
1.311(5)
1.361(5)
1.409(5)
1.461(5)
1.408(5)
1.277(9)
1.258(9)
1.603(9)
77.39(11)
70.28(8)
83.39(10)
S–C(4)
O(1)–C(1)
N(1)–C(1)
N(1)–C(7)
N(2)–N(3)
C(20)–Pb–C(30) 169.21(14)
N(4)–Pb–N(3)
N(3)–Pb–O(1)
65.49(11)
63.47(10)
Scheme 2. Deprotonation of the SC chain and tautomeric evolu-
tion.
Table 8. Selected bond lengths [Å] and angles [°] for
[PbPh2(L3)(dmso)]·2dmso.
The hydrogen bonds in the two complexes of H2L3 are
listed in Tables 9 and 10 and are represented in Figures S7
and S8. In [PbPh2(H0.5L3)(MeOH)](OAc)0.5 these interac-
tions involve all of the N–H groups and the O atoms from
the acetate group and the methanol molecule. It is worth
noting the presence of the N(2)–H(2)···O(2) bond, which
links the partially deprotonated hydrazinic group of the SC
chain to the AcO– anion. This hydrogen bond is the strong-
est of all the N–H···O bonds according to the bond lengths,
and it fixes the H(2) atom well enough to be located in the
difference maps – even though its occupation factor is only
0.5. It is tempting to hypothesize that this hydrogen bond
provides us with a glimpse of the proton transfer from the
donor [N(2)–H] to the acceptor (AcO–) when the process is
“under way”.
Pb–C(30)
Pb–C(20)
Pb–N(3)
Pb–N(4)
Pb–O(1)
Pb–O(1s)
Pb–S(1)
S(1)–C(4)
O(1)–C(1)
N(1)–C(1)
C(1)–N(2)
N(2)–N(3)
2.182(10)
2.209(10)
2.427(7)
2.428(8)
2.434(6)
2.506(8)
2.696(3)
1.755(11)
1.277(12)
1.372(13)
1.346(13)
1.373(10)
C(2)–N(3)
C(2)–C(3)
C(3)–N(4)
C(3)–C(6)
N(4)–N(5)
C(4)–N(5)
C(4)–N(6)
S(1s)–O(1s)
S(2s)–O(2s2)
S(2s)–O(2s1)
S(3s)–O(3s)
1.300(12)
1.484(14)
1.310(13)
1.479(14)
1.383(10)
1.294(13)
1.380(13)
1.456(9)
1.50(4)
1.505(12)
1.493(8)
C(30)–Pb–C(20) 172.9(4)
O(1)–Pb–O(1s)
N(4)–Pb–S(1)
O(1s)–Pb–S(1)
82.5(2)
71.3(2)
73.9(2)
N(3)–Pb–N(4)
N(3)–Pb–O(1)
67.4(2)
65.0(2)
atoms except for the hydrogen atom on N(2) and the acetate
atoms, which are 0.5. Although from a crystallographic
point of view this compound contains the (H0.5L3)1.5– li-
gand, from a more “chemical” point of view it can be de-
picted as containing both (HL3)– and (L3)2– ligands in a 1:1
ratio.
Table 9. Hydrogen-bond lengths [Å] and angles [°] in
[PbPh2(H0.5L3)(MeOH)](OAc)0.5
.
D–H···A[a]
d(D–H) d(H···A) d(D···A) Ͻ(DHA)
N(1)–H(1)···O(2)
N(1)–H(1)···O(21)
O(1s)–H(1s)···O(2)i
0.86
0.86
2.56
2.15
2.09(5)
2.56(6)
3.276(6) 141.3
2.985(7) 163.3
2.613(6) 158(9)
2.897(7) 122(8)
This partial deprotonation of the SC chain is also sup-
0.56(5)
1
O(1s)–H(1s)···O(21)ii 0.56(5)
ported by H NMR spectroscopy (see below) and by the
structural parameters of the complex [PbPh2(L3)(dmso)]·
2dmso obtained when [PbPh2(H0.5L3)(MeOH)](OAc)0.5 was
recrystallised from dmso.
N(2)–H(2)···O(2)
0.68(10) 2.17(10) 2.821(7) 159(12)
0.86 2.77 3.370(4) 128.3
N(6)–H(6)···Siii
[a] Symmetry operators: i = x – 1/2, y – 1/2, z; ii = –x + 1/2, y –
1/2, –z + 1/2; iii = –x, –y, –z + 1.
In both H2L3 complexes, the coordination environment
for the diphenyllead(IV) unit is similar to that previously
described for [PbPh2(OAc)(HL2)]·MeOH, with the equato-
rial plane occupied by the N,N,O,S-tetradentate semicarb-
azone/thiosemisemicarbazone ligand plus another O-bound
(MeOH or dmso) ligand. The (H0.5L3)1.5– and (L3)2– li-
gands have an identical conformation in both complexes,
with the O(1) and S atoms cis to N(3) and N(4), respec-
tively. As usual, the deprotonated TSC chain evolves from
thione (the C=S bond length in free TSCs has an average
value of 1.685 Å[9]) to thiol and binds the metal atom
through the S and N(4) atoms slightly more strongly in
Table 10. Hydrogen-bond lengths [Å] and angles [°] in
[PbPh2(L3)(dmso)]·2dmso.
D–H···A[a]
d(D–H) d(H···A) d(D···A)
Ͻ(DHA)
2.865(13) 169.6
2.925(12) 167.0
N(1)–H(1)···O(2s1)
N(6)–H(6)···O(3s)i
0.86
0.86
2.015
2.080
[a] Symmetry operators: i = x, y + 1, z.
In [PbPh2(L3)(dmso)]·2dmso, two N–H···O interactions
[PbPh2(L3)(dmso)]·2dmso than in [PbPh2(H0.5L3)(MeOH)]- link the uncoordinated dmso molecules to the complex
(OAc)0.5. More significant are the Pb–O(1) and Pb–N(3) (Figure S8).
Eur. J. Inorg. Chem. 2011, 868–878
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873

J. S. Casas, M. S. García-Tasende et al.
FULL PAPER
1H and 13C NMR Spectroscopy
of the ligand to a second form [responsible for spectrum (c),
Figure 7] in which the N(6)–H···N(4) bond is weakened or
even disappears, thus increasing the shielding of the N(6)H
proton and bringing the C(4)H and C(6)H doublets in the
spectrum closer together. In this second form the TSC arm
may adopt an “open” orientation[10] similar to that shown
by the SC arm in the solid-state structure. This conforma-
tion with both arms in the “open-orientation” has been de-
scribed for other related molecules.[19,20]
1
The H and 13C NMR spectroscopic data for SCx and
H2Lx (see Scheme 1 for numbering) are listed in the Experi-
mental Section. The assignment of the signals was initially
based on those of related semicarbazones and thiosemi-
carbazones[8,16,17] and then confirmed by HMBC and
HMQC experiments.
1
In the H NMR spectra of SCx, the integration of the
signals associated with the N(2)H and N(1)H2 [or N(1)
HPh] groups indicates the presence of only one semicarb-
azone chain for each molecule (Scheme 3). The signal at δ
= 197–199 ppm in the 13C NMR spectra confirms that one
of the carbonyl groups from the starting diketone remains
unchanged.
Figure 7. Evolution over time of the 1H NMR spectrum of H2L1
in dmso solution: (a) t = 0, (b) t = 1 h, (c) t = 24 h. See the Experi-
mental Section.
In the 1H NMR spectrum of [PbPh2(HL1)](OAc)0.75
-
Cl0.25·2.375H2O, the presence of a very broad signal at δ =
11.82 ppm indicates that the N(2)H group remains intact.
Scheme 3. Synthesis of semicarbazone/thiosemicarbazone ligands.
Condensation of the SCx derivatives with the thiosemi- The integration of the acetate group for fewer than three
carbazides and the formation of H2Lx led to the appearance protons is consistent with the presence of the chloride
of additional signals in the 1H NMR spectra, and these anion. Although there is no signal at low field that is di-
1
correspond to the NH and NH2 (or NHR) groups of the rectly attributable to N(2)H in the H NMR spectrum of
new TSC chains. Furthermore, in the 13C NMR spectra, [PbPh2(OAc)(HL2)]·MeOH, the presence of a very broad
the signal due to the remaining diketone carbonyl group signal for HDO suggests that this proton possibly ex-
vanished, and the appearance of two new signals at δ = changes with water in the solvent.
148 (C=N group) and 178 (C=S group) ppm confirmed the
The 1H NMR spectra of the H2L3 complexes also reflect
the protonation status of the ligand and are consistent with
condensation of the thiosemicarbazide molecule.
1
The H NMR spectrum of H2L1 in dmso shows some the solid-state study. Thus, in the spectrum of
concentration-independent evolution of this compound [PbPh2(L3)(dmso)]·2dmso, signals are not observed for N(2)
(Figure 7). In a freshly prepared sample [spectrum (a)], the H and N(6)H groups, as expected if the ligand is fully de-
N(6)H proton from the TSC chain is highly deshielded (δ protonated. In the spectrum of [PbPh2(H0.5L3)(MeOH)]-
= 14.17 ppm), and only one set of signals is observed for (OAc)0.5, however, there is a broad signal at δ = 11.94 ppm
each proton in the molecule. After 1 h [spectrum (b)], in and another narrow one at δ = 1.90 ppm, which integrate
addition to the signals in spectrum (a), a new set of signals to 0.5 and 1.5 protons per mol of complex, respectively.
appears, suggesting the presence of two different forms of Once again this is consistent with the previous formula in
the ligand in solution. After 24 h [spectrum (c)], only the which half of the N(2)–H groups remain protonated, and
signals corresponding to the second set remain, with the there is 0.5 mol of acetate. Although this is the most obvi-
signal of the N(6)H proton at δ = 10.51 ppm. The spectrum ous explanation for the NMR spectroscopic data, it is
of the freshly prepared sample probably corresponds to the worth noting that another plausible interpretation for the
ligand conformation found in the solid state, which has the results exists that is also coherent with the half-protonation
strong N(6)–H···N(4) intramolecular hydrogen bond men- of the SC chain in solid [PbPh2(H0.5L3)(MeOH)](OAc)0.5
.
tioned above (see discussion on X-ray data). This bond is The positions of the signals at δ = 11.94 and 1.90 ppm are
probably responsible for the strong deshielding of the N(6) rather similar to those observed for acetic acid in dmso
H proton[18] and also influences the mutual positions of the solution (δ = 11.91 and 1.91 ppm[21]). Thus, under the influ-
doublets associated with the pyridine C(4)H and C(6)H ence of the solvent, the evolution to the fully deprotonated
protons, which are 0.75 ppm apart in spectrum (a). The in- (L3)2– ligand and HOAc cannot be ruled out. This alterna-
teraction with the solvent seemingly induces the evolution tive interpretation is supported by the isolation of only
874
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Eur. J. Inorg. Chem. 2011, 868–878

A Conspicuous Deprotonation in Complexes of Diphenyllead(IV)
[PbPh2(L3)(dmso)]·2dmso when
a dmso solution of
Bruker IFS66V FT-IR spectrophotometer and are reported in
cm–1. FAB+ mass spectra were recorded with a VG AUTOSPEC
spectrometer equipped with an OPUS system by using m-ni-
trobenzyl alcohol as matrix. NMR spectra were recorded in [D6]-
dmso with a Bruker AMX 300 spectrometer at 300.14 MHz for 1H
NMR spectra and at 75.4 MHz for 13C NMR spectra (referenced
to TMS by using the solvent signal; 1H: δ = 2.50 ppm, 13C: δ =
39.50 ppm). Elemental analysis and spectroscopic measurements
were carried out by the RIAIDT services of the University of Santi-
ago de Compostela.
[PbPh2(H0.5L3)(MeOH)](OAc)0.5 is concentrated to dryness
(see the Experimental Section).
3
The values of J(1H-207Pb) coupling constants in these
compounds range from 208.6 to 226 Hz, that is, the ex-
pected values for a lead coordination number of six or
above.[10,22] This suggests that the metal–ligand interactions
described in the solid state probably remain in dmso solu-
tion.
Synthesis
Ligands: The synthesis of the asymmetric semicarbazone–thiosemi-
carbazone ligands was carried out according to a previously de-
scribed procedure.[8] Briefly, the corresponding diketone was con-
densed with the semicarbazide hydrochloride in a 1:1 molar ratio,
and the resulting monosemicarbazone (SCx) was then condensed
with the thiosemicarbazide in the same molar ratio (see Scheme 3).
Conclusion
We have described the synthesis of new H2Lx multiden-
tate ligands containing both SC and TSC arms and their
complexation behaviour towards the PbPh2
2+
ion in a
methanol solution. All of the ligands readily form com-
plexes with the organometallic cation, and these are stable
at room temperature in air. The pentadentate character of
the (HL1)– anion derived from 2,6-diacetylpyridine permit-
ted the isolation of a homoleptic complex, [PbPh2-
(HL1)](OAc)0.75Cl0.25·2.375H2O. In this compound the do-
nor atoms of the anion occupy all the equatorial positions
of a pentagonal-bipyramidal coordination sphere in which
the phenyl groups are in the apical positions. The H2L2 and
H2L3 ligands derived from 2,3-butadione coordinate
through only four donor atoms. This situation allows an
additional donor atom from an acetate group or a molecule
of solvent to enter the equatorial coordination plane, and
this gives rise to heteroleptic complexes such as
[PbPh2(OAc)(HL2)]·MeOH.
In all the complexes, the TSC chain deprotonates easily,
but the SC chain is clearly less acidic and remains proton-
ated in the complexes of H2L1 and H2L2. The direct reac-
tion of diphenyllead(IV) diacetate with H2L3 afforded a so-
lid with the stoichiometry [PbPh2(H0.5L3)(MeOH)](OAc)0.5
in which, besides TSC deprotonation, an unusual partial
deprotonation of the SC occurs with only half of the ligand
molecules SC-deprotonated. When this complex was dis-
solved in dmso, the medium facilitated complete proton
transfer, and the heteroleptic [PbPh2(L3)(dmso)]·2dmso
complex was formed.
H2L1: 2,6-Diacetylpyridine (1.60 g, 9.8 mmol) and distilled water
(150 mL) were mixed in a 250 mL round-bottomed flask. A solu-
tion of semicarbazide hydrochloride (1.09 g, 9.8 mmol) in distilled
water (30 mL) was slowly added to the suspension. The mixture
was stirred and heated under reflux for 30 min, and the resulting
cream coloured solid was isolated and characterized. Yield 84%;
m.p. 219 °C. C10H12N4O2 (SC1, diacetylpyridine semicarbazone)
(220.23): calcd. C 54.54, H 5.49, N 25.44; found C 54.49, H 5.50,
N 25.37. IR (KBr): ν = 3494 (m), 3361 (m), 3208 (m, N–H), 1730
˜
(s), 1704 (s, C=O), 1575 (s, C=N), 1435 (s, ring) cm–1. 1H NMR
([D6]dmso): δ = 9.89 [s, 1 H, N(2)H], 8.58 [d, 1 H, C(4)H], 7.94 [t,
1 H, C(5)H], 7.86 [d, 1 H, C(6)H], 6.69 [s, 2 H, N(1)H2], 2.66, 2.33
[s, 6 H, C(9,10)H3] ppm. 13C NMR ([D6]dmso): δ = 199.4 (C8),
156.9 (C2), 154.9 (C7), 151.8 (C3), 144.0 (C2), 137.5 (C5), 124.0
(C6), 120.5 (C4), 11.3, 25.4 (C9,C10) ppm. SC1 (0.50 g, 2.27 mmol)
and ethanol (50 mL) were mixed in a 250 mL round-bottomed
flask. The suspension was heated and then mixed with a solution
of 4-methyl-3-thiosemicarbazide (0.24 g, 2.27 mmol) in ethanol
(55 mL). The pale yellow solution was heated under reflux for 4 h
and stirred overnight. The resulting yellow precipitate was filtered
off and characterized as H2L1. Yield 80%; m.p. 247–248 °C.
C12H17N7OS (H2L1) (307.39): calcd. C 46.89, H 5.57, N 31.90, S
10.43; found C 46.80, H 5.67, N 31.76, S 10.50. FAB+: m/z = 308
[H L1 + H]+, 293 [H L1 – Me + H]+. IR (KBr): ν = 3430 (m), 3363
˜
2
2
(m) and 3110 (m, N–H), 1680 (s, C=O), 1579 (s), 1548 (s, C=N),
1
1433 (s, ring), 849 (m), 819 (m, C=S) cm–1. H NMR ([D6]dmso);
spectrum (a) (Figure 7): δ = 14.17 [s, 1 H, N(6)H], 9.76 [s, 1 H,
N(2)H], 8.68 [q, 1 H, N(7)H], 8.46 [d, 1 H, C(6)H], 8.00 [t, 1 H,
C(5)H], 7.70 [d, 1 H, C(4)H], 6.71 [s, 2 H N(1)H2], 3.38, 2.37 [s, 6
1
H, C(9,10)H3], 3.01 [d, 3 H, C(12)H3] ppm. H NMR ([D6]dmso);
Experimental Section
spectrum (c) (Figure 7): δ = 10.31 [s, 1 H, N(6)H], 9.49 [s, 1 H N(2)
H], 8.63 [q, 1 H, N(7)H], 8.35 [d, 1 H, C(6)H], 8.28 [d, 1 H, C(4)
H], 7.72 [t, 1 H, C(5)H], 6.62 [s, 2 H, N(1)H2], 3.05 [d, 3 H, C(12)
H3], 2.42, 2.31 [s, 6 H, C(9,10)H3] ppm. 13C NMR ([D6]dmso);
spectrum (c) (Figure 7): δ = 178.5 (C11), 156.8 (C1), 154.1 (C7),
153.3 (C3), 147.8 (C8), 144.5 (C2), 136.4 (C5), 120.0 (C4), 119.9
(C6), 31.1 (C12), 11.9 (C10), 11.3 (C9) ppm. Crystals suitable for
X-ray analysis were grown from a solution of H2L1 in dmso at
room temperature.
Reagents and Instruments: Commercially available chemicals, 2,6-
diacetylpyridine (Aldrich), 2,3-butanedione (Aldrich), semicarb-
azide hydrochloride (Alfa), 4-phenyl-3-semicarbazide (Alfa), 4-
methyl-3-thiosemicarbazide (Aldrich), 4-phenyl-3-thiosemicarbaz-
ide (Aldrich), diphenyllead(IV) dichloride (ABCR) and silver(I)
acetate (Fluka) were reagent grade and were used as received. Di-
phenyllead(IV) diacetate was prepared[10] by the reaction of di-
phenyllead(IV) dichloride with silver(I) acetate in a 1:2 molar ratio
in methanol. The silver(I) chloride formed was filtered off, and the
solution containing the diphenyllead(IV) diacetate was used imme-
diately in the preparation of the complexes. Elemental analyses for
C, H, N and S were performed with a Fisons 1108 microanalyzer.
Melting points were determined with an electrically heated Gallen-
kamp apparatus. IR spectra were recorded from KBr discs with a
H2L2: 2,3-Butanedione (0.5 mL, 5.69 mmol) in water (10 mL) was
added to semicarbazide hydrochloride (0.635 g, 5.69 mmol) in
water (12 mL). The mixture was stirred for 30 min, and the re-
sulting white solid was filtered off and identified. Yield 86%; m.p.
226 °C. C5H9N3O2 (SC2, butanedione semicarbazone) (143.15):
calcd. C 41.95, H 6.35, N 29.35; found C 41.89, H 6.38, N 29.09.
Eur. J. Inorg. Chem. 2011, 868–878
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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875

J. S. Casas, M. S. García-Tasende et al.
20% (first batch); m.p. 198 °C. 25.5H33Cl0.25N7O4.88SPb
FULL PAPER
FAB+: m/z = 144 [SC2 + H]+. IR (KBr): ν = 3493 (s), 3352 (s),
C
˜
3106 (m, N–H), 1686 (s), 1603 (s, C=O), 1579 (s, C=N) cm–1. H {[PbPh2(HL1)](OAc)0.75Cl0.25·2.375H2O} (763.79): calcd. C 40.10,
1
NMR ([D6]dmso): δ = 9.85 [s, 1 H, N(2)H], 6.71 [s, 2 H, N(1)H2], H 4.35, N 12.84, S 4.20; found C 39.85, H 4.20, N 12.38, S 3.98.
2.33, 1.84 [s, 6 H, C(3,5)H3] ppm. 13C NMR ([D6]dmso): δ = 197.2
FAB+: m/z = 668 [(PbPh2)(HL1)]+, 590 [(PbPh)(HL1)]+, 307 [HL1
(C4), 156.2 (C1), 143.9 (C2), 24.39 (C5), 9.40 (C3) ppm. A solution + H]+. IR (KBr): ν = 3375 (m), 3051 (m, N–H), 1671 (m, C=O),
˜
of 4-methyl-3-thiosemicarbazide (0.36 g, 3.42 mmol) in ethanol
(55 mL) was added to a suspension of SC2 (0.49 g, 3.42 mmol) in
ethanol (50 mL) along with a few drops of acetic acid. The suspen-
sion was heated under reflux for 4 h and stirred overnight. The
small amount of white solid in suspension was removed by fil-
tration and discarded. The clear solution was then stored for 24 h
to afford a new white precipitate, which was filtered off and charac-
terized as H2L2. Yield 33%; m.p. 252 °C. C7H14N6OS (H2L2)
(230.29): calcd. C 36.51, H 6.13, N 36.49, S 13.90; found C 36.38,
H 6.28, N 36.78, S 13.70. FAB+: m/z = 231 [H2L2 + H]+. IR (KBr):
1566 (m), 1433 m (m, OAc, Δν = 133), 1503 (m), 1474 (m, C=N),
˜
1
1382 (s, ring), 805 (w, C=S) cm–1. H NMR ([D6]dmso): δ = 11.82
[br. s, 1 H, N(2)H], 8.06 [t, 1 H, C(5)H], 7.72 [d, 1 H, C(6)H], 7.70
3
[d, 1 H C(4)H], 7.46 [d, J(1H-207Pb) = 226 Hz, 4 H, Ho-(PbPh)],
7.28 [t, 4 H, Hm-(PbPh)], 7.19 [t, 2 H, Hp-(PbPh)], 7.15 [br. s, 1 H,
N(7)H], 6.45 [br. s, 2 H, N(1)H2], 2.91 [d, 3 H, C(12)H3], 2.57,
2.38 [s, 6 H, C(9,10)H3], 1.90 (s, 2.25 H, –OAc) ppm. Crystals of
[PbPh2(HL1)](OAc)0.75Cl0.25·2.375H2O suitable for X-ray studies
were obtained from the mother liquors.
[PbPh2(OAc)(HL2)]·MeOH: A freshly prepared methanolic solu-
tion of diphenyllead(IV) diacetate (0.208 g, 0.43 mmol in 25 mL)
was added to a suspension of H2L2 (0.10 g, 0.43 mmol) in methanol
(30 mL). The resulting yellow solution was stirred and heated un-
der reflux for 7 h and then concentrated under vacuum until a fine
grey suspension appeared. This solid was removed by filtration,
and the clear solution was slowly concentrated at room temperature
for a few days until a precipitate formed. This solid comprised two
types of crystals; white needles of diphenyllead(IV) diacetate and
yellow prisms of the title complex; m.p. 201 °C. C22H30N6O4PbS
{[PbPh2(OAc)(HL2)]·MeOH} (681.77): calcd. C 38.76, H 4.44, N
12.33, S 4.47; found C 38.48, H 4.60, N 12.55, S 4.67. FAB+: m/z
ν = 3468 (m) 3346 (m), 3265 (m), 3202 (m, N–H), 1683 (s, C=O),
˜
1594 (m), 1554 (s, C=N), 955 (w, C=S) cm–1. 1H NMR ([D6]dmso):
δ = 10.09 [s, 1 H, N(5)H], 9.37 [s, 1 H, N(2)H], 8.27 [q, 1 H, N(6)
H], 6.45 [s, 2 H, N(1)H2], 2.99 [d, 3 H, C(7)H3], 2.06, 2.12 [s, 6 H,
C(3,5)H3] ppm. 13C NMR ([D6]dmso): δ = 178.4 (C6), 156.5 (C1),
148.4 (C4), 144.9 (C2), 31.1 (C7), 11.4 (C5), 11.0 (C3) ppm.
H2L3: 4-Phenyl-3-semicarbazide (0.86 g, 5.69 mmol) in water
(70 mL) was added to an aqueous solution of 2,3-butanedione
(0.50 mL, 5.69 mmol) in water (10 mL). The mixture was stirred
for 1.5 h, and the resulting solid was isolated. Yield 84%; m.p. 229–
230 °C. C11H13N3O2, (SC3, butanedione phenylsemicarbazone)
(219.10): calcd. C 60.25, H 5.98, N 19.17; found C 60.01, H 6.09,
= 591 [PbPh (HL2)]+, 437 [Pb(HL2)]+. IR (KBr): ν = 3332 (m),
˜
2
N 19.38. FAB+: m/z = 220 [SC3 + H]+. IR (KBr): ν = 3379 (m),
3127 (m), 3051 (m, N–H), 1675 (s, C=O), 1565 (s), 1334 (s, OAc,
˜
1
Δν = 231), 1553 (s), 1529 (s, C=N), 734 (m, C=S) cm–1. H NMR
˜
3367 (m), 3199 (m, NH), 1698 (s), 1686 (s, C=O), 1595 (s, C=N)
cm–1. 1H NMR ([D6]dmso): δ = 10.25 [s, 1 H, N(2)H], 8.96 [s, 1 H,
N(1)H], 7.57 (d, 2 H, Ho-Ph), 7.31 (t, 2 H, Hm-Ph), 7.04 (t, 1 H,
Hp-Ph), 1.91, 2.44 [s, 6 H, C(3,5)H3] ppm. 13C NMR ([D6]dmso):
δ = 197.2 (C4), 154.3 (C2), 152.4 (C1), 138.5 (Ci), 128.6 (Cm), 123.0
(Cp), 120.0 (Co), 24.6 (C5), 9.6 (C3) ppm. SC3 (0.24 g, 1.10 mmol),
4-phenyl-3-thiosemicarbazide (0.17 g, 1.12 mmol) and ethanol
(25 mL) were introduced into a 50 mL flask. The yellow suspension
was stirred for 17 h and then filtered. This first solid isolated was
identified as a small amount of SC3. The mother liquor, when
slowly concentrated at room temperature for 24 h, afforded H2L3.
Yield 30%; m.p. 239 °C. C18H20N6OS (H2L3) (368.46): calcd. C
58.68, H 5.47, N 22.81, S 8.70; found C 58.50, H 5.35, N 22.58, S
([D6]dmso): δ = 7.83 [d, 3J(1H-207Pb) = 208.6 Hz, 4 H, Ho-(PbPh)],
7.40 [t, 4 H, Hm-(PbPh)], 7.29 [t, 2 H, Hp-(PbPh)], 6.94 [br. s, 1 H,
N(6)H], 6.03 [s, 2 H, N(1)H2], 4.11 [m, 1 H, OH(MeOH)], 3.16 [d,
3 H, CH3(MeOH)], 2.77 [d, 3 H, C(7)H3], 2.28, 2.14 [s, 6 H, C(3,5)
–
H3], 1.83 (s, 3 H, OAc) ppm. A very broad signal is observed for
HDO.
[PbPh2(H0.5L3)(MeOH)](OAc)0.5: A solution of diphenyllead(IV)
diacetate (0.13 g, 0.27 mmol) in methanol (25 mL) was slowly
added to a suspension of H2L3 (0.10 g, 27.1 mmol) in methanol
(22 mL). The resulting orange mixture was heated under reflux and
stirred for 5 h. The mixture was cooled to room temperature, and
a small amount of a dark solid was filtered off and discarded. The
mother liquor afforded an orange crystalline solid after 2 d of slow
concentration. Yield 50%; m.p. 189 °C. C32H34N6O3PbS,
{[PbPh2(H0.5L3)(MeOH)](OAc)0.5} (789.91): calcd. C 48.66, H
4.34, N 10.64, S 4.06; found C 48.52, H 4.20, N 10.66, S 3.95.
8.51. FAB+: m/z = 369 [H L3 + H]+. IR (KBr): ν = 3373 (w), 3312
˜
2
(w), 3188 (w, N–H), 1681 (s, C=O), 1595 (m), 1546 (s, C=N), 1032
(w, C=S) cm–1. 1H NMR ([D6]dmso): δ = 10.58 [s, 1 H, N(5)H],
9.92 [s, 1 H, N(2)H], 9.92 [s, 1 H, N(6)H], 8.79 [s, 1 H, N(1)H],
7.58 (d), 7.29 (t), 7.02 (t, 5 H, Ph(SC)], 7.58 (d), 7.36 (t), 7.20 (t, 5
H Ph(TSC)], 2.30, 2.20 [s, 6 H, C(3,5)H3] ppm. 13C NMR ([D6]-
dmso): δ = 176.8 (C6), 152.9 (C1), 149.4 (C4), 146.5 (C2), 139.0,
128.1, 125.5, 125.4 [Ph(TSC)], 138.7, 128.5, 122.6, 119.7 [Ph(SC)],
12.0 (C5), 11.5 (C3) ppm.
FAB+: m/z = 729 [PbPh (HL3)]+. IR (KBr): ν = 3197 (w), 3052
˜
2
(w), 2987 (w, N–H), 1667 (m, C=O), 1602 (s), 1313 (s, OAc, Δν =
˜
1
289), 1518 (s), 1493 (s, C=N), 692 (m, C=S) cm–1. H NMR ([D6]-
dmso): δ = 11.92 [br. s, 0.5 H, N(2)H], 9.16 [s, 1 H, N(6)H], 9.01
[s, 1 H, N(1)H], 7.90 [d, 3J(1H-207Pb) = 210.1 Hz, 4 H, Ho-(PbPh)],
7.70, 7.63 (d, 4 H, Ho), 7.43 [t, 4 H, Hm-(PbPh)], 7.30, 7.19 (m, 4
H, Hm), 7.23 [t, 2 H, Hp-(PbPh)], 6.89, 6.83 (t, 2 H, Hp), 4.09 [q, 1
H, OH(MeOH)], 3.17 [d, 3 H, CH3(MeOH)], 2.30, 2.38 [s, 6 H,
C(3,5)H3], 1.91 (s, 1.5 H, –OAc) ppm. The same results were ob-
tained when the reaction mixture was refluxed and stirred for 2 d.
From the crystalline orange solid, a single crystal of composition
[PbPh2(H0.5L3)(MeOH)](OAc)0.5 was selected and studied by X-ray
diffraction. A portion of this solid was recrystallised from dmso
to afford single crystals of composition [PbPh2(L3)(dmso)]·2dmso:
C36H46N6O4PbS4 (962.24): calcd. C 44.94, H 4.82, N 8.73, S 13.32;
Complexes: Diphenyllead(IV) complexes of the semicarbazone/
thiosemicarbazone ligands H2L1–H2L3 were obtained by treating
the corresponding ligand with a freshly prepared methanolic solu-
tion of diphenyllead(IV) diacetate in a 1:1 molar ratio.
Caution! Lead is a highly toxic cumulative poison. Lead com-
pounds should be handled carefully.[5]
[PbPh2(HL1)](OAc)0.75Cl0.25·2.375H2O: A recently prepared solu-
tion of diphenyllead(IV) diacetate (0.15 g, 0.31 mmol) in methanol
(25 mL) was added to a suspension of H2L1 (0.10 g, 0.32 mmol) in
methanol (30 mL). The resulting solution was stirred for 20 h and
then stored at room temperature for a few days. A small amount
of yellow crystalline solid had formed and was filtered off. Yield
1
found C 44.89, H 4.61, N 8.75, S 13.01. H NMR ([D6]dmso): δ =
3
9.15 [s, 1 H, N(6)H], 9.01 [s, 1 H, N(1)H], 7.91 [d, J(1H-207Pb) =
208.0 Hz, 4 H, Ho-(PbPh)], 7.70, 7.63 (d, 4 H, Ho), 7.43 [t, 4 H,
876
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 868–878

A Conspicuous Deprotonation in Complexes of Diphenyllead(IV)
Table 11. Crystal data, data collection and refinement for the ligand and complexes.
H2L1
[PbPh2(HL1)](OAc)0.75Cl0.25
·
[PbPh2(OAc)(HL2)]· [PbPh2(H0.5L3)(MeOH)](AcO)0.5 [PbPh2(L3)(dmso)]·
2.375H2O
MeOH
2dmso
Empirical formula C12H17N7OS
C25.5H33Cl0.25N7O4.88PbS
763.7
100.0(1)
monoclinic
C2/c
23.0384(17)
16.6605(13)
17.1170(14)
90
105.479(4)
90
6331.7(9)
8
C22H30N6O4PbS
681.77
110.0(2)
monoclinic
P21/n
9.9325(7)
15.1109(10)
17.3815(13)
90
103.313(4)
90
C64H68N12O6Pb2S2
1579.80
100.0(1)
monoclinic
C2/c
13.0041(8)
13.8846(8)
33.6220(19)
90
91.169(3)
90
6069.4(6)
4
C36H46N6O4PbS4
962.22
110.0(2)
Formula mass
T [K]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
307.39
100.0(1)
monoclinic
P21/n
8.2319(3)
20.5305(7) A
9.1091(4)
90
triclinic
¯
P1
9.6563(3)
14.4927(5)
15.4194(5)
100.312(2)
95.718(2)
108.599(2)
1983.52(11)
2
β [°]
113.414(2)
90
1412.72(9)
4
γ [°]
V [Å3]
Z
2538.7(3)
4
6.768
μ [mm]–1
0.241
5.460
5.673
4.509
Crystal size [mm] 0.24ϫ0.11ϫ0.03
0.20ϫ0.10ϫ0.09
2.44–26.02
0.21ϫ0.10ϫ0.09
1.81–26.39
0.60ϫ0.13ϫ0.11
2.15–26.02
0.15ϫ0.08ϫ0.02
1.52–22.87
θ range [°]
Reflections
collected
2.63–26.44
9643
29477
6212
0.0350
1.075
21023
5196
0.0564
1.007
40538
5946
0.0554
1.053
77234
5299
0.0506
1.074
Unique data
Rint
GOF
2996
0.0399
1.030
R1 [IϾ2σ(I)]
(all data)
wR2 [IϾ2σ(I)]
(all data)
0.0470
0.0732
0.1000
0.1105
0.0362
0.0641
0.0873
0.1010
0.0361
0.0726
0.0608
0.0722
0.0285
0.0398
0.0533
0.0558
0.0500
0.0580
0.1176
0.1255
Residual electron
density [eÅ–3]
0.847/–0.410
1.463/–1.804
2.043/–1.525
1.903/–0.796
3.153/–2.287
Hm-(PbPh)], 7.30, 7.19 (t, 4 H, Hm), 7.25 [t, 2 H, Hp-(PbPh)], 6.89,
6.83 (t, 2 H, Hp), 2.54 [s, 18 H, CH3(dmso)], 2.39, 2.30 [s, 6 H, –794202 {for [PbPh2(H0.5L3)(MeOH)](OAc)0.5} and -794203 {for
Cl0.25·2.375H2O}, -794201 {for [PbPh2(OAc)(HL2)]·MeOH},
C(3,5)H3] ppm. Removal of the solvent to dryness, after a few
weeks of slow concentration, showed the complete evolution of
[PbPh2(H0.5L3)(MeOH)](OAc)0.5 to [PbPh2(L3)(dmso)]·2dmso.
[PbPh2(L3)(dmso)]·2dmso} contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
X-ray Crystallography: Crystal data were collected at low tempera-
ture with a Bruker Kappa-APEX II diffractometer using Mo-Kα
radiation (RIAIDT, University of Santiago de Compostela). Data
were corrected for absorption by multi-scans (SADABS).[23] Struc-
tures were solved by direct methods in the case of the ligand H2L1
and the Patterson method for all the complexes, followed by nor-
mal difference Fourier techniques. The program used was
SHELX97.[24] Although the diffraction data for [PbPh2(L3)(dmso)]·
2dmso were not of very good quality (probably due to the small
size of the crystal), the successive refinements allowed atomic posi-
tions and structural information to be obtained with reasonable
accuracy. Hydrogen atoms were included in idealized positions and
refined by using a riding model, except those of H2L1 and H(2)
and H(1s) of [PbPh2(H0.5L3)(MeOH)](OAc)0.5, which were located
from the difference maps. Some disorder was found not only in the
solvent molecules in [PbPh2(HL1)](OAc)0.75Cl0.25·2.375H2O, but
also in the acetate ligand in [PbPh2(OAc)(HL2)]·MeOH and in the
dmso molecules in [PbPh2(L3)(dmso)]·2dmso. In the latter, this dis-
order affects the dmso molecules 1 and 2. In molecule 1, the aniso-
tropic displacement parameters and the bond lengths were re-
strained to be similar by using SIMU. Molecule 2, in which the
disorder mainly affects the oxygen atom, was modelled over two
positions whose s.o.f. were 0.8 and 0.2. Atomic displacement pa-
rameters for all the atoms in this molecule, except S(2S), were con-
strained to be identical by using free variables. Molecular graphics
were obtained with ORTEP[25] and MERCURY.[26] Crystal data,
experimental details and refinement results are listed in Table 11.
Supporting Information (see footnote on the first page of this arti-
cle): Figures S1–S3 and S5–S8 showing the hydrogen bonding inter-
actions in the lattices of H2L1 and complexes; Figure S4 showing
the packing of chains in the network of [PbPh2(HL1)](OAc)0.75
-
Cl0.25·2.375H2O.
Acknowledgments
We thank the Spanish Ministry of Education and Science (Project
CTQ2006-11805) and the Spanish Ministry of Science and Innova-
tion (Project CTQ2009-10738) for financial support.
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Received: September 28, 2010
Published Online: January 13, 2011
878
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Eur. J. Inorg. Chem. 2011, 868–878