Matrix-isolation infrared spectroscopic and density functional theory studies on reactions of laser-ablated lead and tin atoms with water molecules

Article abstract of DOI:10.1246/bcsj.80.2149

Reactions of laser-ablated lead and tin atoms with water molecules in excess argon were studied by infrared spectroscopy. Insertion products HMOH and HMO (M = Pb and Sn) formed in the present experiments and characterized using infrared spectroscopy on the basis of the results of isotopic shifts, mixed isotopic splitting patterns, stepwise annealing, changes in reagent concentration and laser energy, and a comparison with theoretical predictions. Density functional theory calculations were performed on these molecules and the corresponding transition states. Agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these molecules from the matrix infrared spectra. Plausible reaction mechanisms have been proposed to account for the formation of these molecules.

Full text of DOI:10.1246/bcsj.80.2149

Ó 2007 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 80, No. 11, 2149–2156 (2007) 2149
Matrix-Isolation Infrared Spectroscopic and Density Functional
Theory Studies on Reactions of Laser-Ablated Lead
and Tin Atoms with Water Molecules
ꢀ1;2
Yun-Lei Teng,1;2 Ling Jiang,1;2 Song Han,1 and Qiang Xu
1National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 563-8577
2Graduate School of Engineering, Kobe University, Nada-ku, Kobe 657-8501
Received May 31, 2007; E-mail: q.xu@aist.go.jp
Reactions of laser-ablated lead and tin atoms with water molecules in excess argon were studied by infrared spec-
troscopy. Insertion products HMOH and HMO (M ¼ Pb and Sn) formed in the present experiments and characterized
using infrared spectroscopy on the basis of the results of isotopic shifts, mixed isotopic splitting patterns, stepwise
annealing, changes in reagent concentration and laser energy, and a comparison with theoretical predictions. Density
functional theory calculations were performed on these molecules and the corresponding transition states. Agreement
between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts sup-
ports the identification of these molecules from the matrix infrared spectra. Plausible reaction mechanisms have been
proposed to account for the formation of these molecules.
The interactions of metals with water molecules are of con-
siderable interest from academic and industrial viewpoints and
have attracted experimental and theoretical attention, because
of their important roles in a wide variety of areas, such as
catalytic synthesis, surface chemistry, and biochemical sys-
tems.1–11 Many efforts have been made to explore the interac-
tion of H2O with clean and preadsorbed single crystal metal
surfaces and real catalyst surfaces.1,2 Previous matrix-isolation
infrared spectroscopic studies have shown that early transition
metal atoms react with water molecules to form initially inser-
tion products spontaneously on annealing, whereas late transi-
tion metal atoms react with water molecules to form metal–
water adducts.5–9 Recently, it has been found that Nd, Sm,
and Eu atoms react with water molecules to form metal–water
adduct complexes and HMOH insertion molecules in solid
argon,10 whereas for U and Th, the insertion H2UO and H2ThO
molecules, respectively, are generated.11
Many efforts have been made to investigate group 14 metal–
water complexes and group 14 metal hydroxides. For instance,
argon matrix investigations of the reactions of thermally
evaporated Si, Ge, Sn, and Pb atoms with water molecules
have suggested the formation of M(H2O) (M ¼ Si, Ge, Sn, and
Pb), HMOH (M ¼ Si, Ge, and Sn), HMOH(H2O) (M ¼ Si and
Ge), and HM2OH (M ¼ Ge and Sn) complexes.5a However,
there are no isotopic substitution experiments and theoretical
calculations to support the assignments, and it seems that some
assignments for the previously reported IR bands require con-
firmation. The electronic absorption spectra of M(H2O) (M ¼
Si, Ge, Sn, and Pb) and HMOH (M ¼ Si, Ge, and Sn) com-
plexes have also been observed in the electronic matrix-iso-
lation spectroscopic studies.5b In addition, lead and tin hydrox-
ides M(OH), M(OH)2, and M(OH)4 (M ¼ Pb and Sn) have
been found in the reaction of laser-ablated Pb and Sn atoms
with H2O2 in excess argon.12 Recently, we have reported
the reaction of laser-ablated Ge atoms with water molecules
and the characterization of the adduct and insertion products,
such as Ge(H2O), HGeOH, HGeO, H2GeO, GeOH, Ge(OH)2,
HGeOGeH, and HGeGeO.5d
Recent studies have shown that, with the aid of isotopic sub-
stitution techniques, matrix isolation infrared spectroscopy
combined with quantum chemical calculation is very powerful
for investigating structure and bonding of novel species.13,14
Here, we report our results for the reactions of water molecules
with lead and tin atoms in a solid-argon matrix. IR spectros-
copy and theoretical calculations provide evidence for the
formation of insertion molecules HMOH and HMO (M ¼ Pb
and Sn).
Experimental and Theoretical Methods
The experiment for laser ablation and matrix-isolation infrared
spectroscopy was similar to those previously reported.14 Briefly, a
Nd:YAG laser fundamental (1064 nm, 10 Hz repetition rate with
10 ns pulse width) was focused on rotating Pb and Sn targets.
The laser-ablated Pb and Sn atoms were co-deposited with H2O
in excess argon onto a CsI window cooled normally to 4 K by
means of a closed-cycle helium refrigerator. Typically, a 1–10
mJ pulseꢁ1 laser power was used. H2O, H218O (96% 18O), and
D2O were subjected to several freeze–pump–thaw cycles before
use. In general, matrix samples were deposited for 30–60 min with
a typical rate of 2–4 mmol per hour. After sample deposition, IR
spectra were recorded on a BIO-RAD FTS-6000e spectrometer
at 0.5 cmꢁ1 resolution using a liquid-nitrogen-cooled HgCdTe
(MCT) detector for the spectral range of 5000–400 cmꢁ1. Samples
were annealed at different temperatures and subjected to broad-
band irradiation (ꢀ > 250 nm) using a high-pressure mercury arc
lamp (Ushio, 100 W).
Quantum chemical calculations were performed to predict the
structures and vibrational frequencies of the observed reaction
products using the Gaussian 03 program.15 The B3LYP density
Published on the web November 13, 2007; doi:10.1246/bcsj.80.2149

2150 Bull. Chem. Soc. Jpn. Vol. 80, No. 11 (2007)
Reactions of Lead and Tin with Water
0.5
HPbOH
HPbO
Pb(OH)
HPbOH
PbOH
2
0.06
0.04
0.02
0.00
0.06
0.04
0.02
0.00
0.4
0.3
0.2
0.1
0.0
Pb(H O)
2
(d)
(c)
(b)
(a)
1520
1510
1500
1490
540
520
500
480
460
1660 1640 1620 1600 1580 1560 1540
Wavenumber / cm-1
Fig. 1. Infrared spectra in the 1520–1480 and 540–460 cmꢁ1 regions from co-deposition of laser-ablated Pb atoms with 1.0% H2O
in argon: (a) 1 h sample deposition at 4 K; (b) after annealing to 25 K; (c) after 20 min of broad-band irradiation; (d) after annealing
to 30 K.
0.08
functional method was utilized.16 The 6-311++G(d, p) basis set
was used for H and O atoms, and Los Alamos ECP Plus DZ
(LANL2DZ) for Pb and Sn.8,12,17 Previous investigations have
shown that such computational methods can provide reliable in-
formation for the Pb and Sn containing molecules, such as infrared
frequencies, relative absorption intensities, and isotopic shifts.18
Geometries were fully optimized and vibrational frequencies were
calculated with analytical second derivatives. Transition-state op-
timizations were done with the synchronous transit-guided quasi-
Newton (STQN) method, followed by the vibtrational calculations
showing the obtained structures to be true saddle points. The in-
trinsic reaction coordinate (IRC) method was used to track mini-
mum energy paths from transition structures to the corresponding
local minima.
2
Pb(OH)
HPbOH
0.06
0.04
0.02
0.00
(d)
(c)
(b)
(a)
520
510
500
490
480
470
Wavenumber / cm-1
Results and Discussion
Fig. 2. Infrared spectra in the 520–470 cmꢁ1 region from
co-deposition of laser-ablated Pb atoms with 1.0% H218O
in argon: (a) 1 h sample deposition at 4 K; (b) after anneal-
ing to 25 K; (c) after 20 min of broad-band irradiation;
(d) after annealing to 30 K.
Experiments were done with H2O concentrations ranging
from 0.1% to 2.0% in excess argon. Typical infrared spectra
for the reactions of laser-ablated Pb and Sn atoms with H2O
molecules in excess argon in the selected regions are illustrat-
ed in Figs. 1–6, and the absorption bands are listed in Table 1.
The stepwise annealing and irradiation behaviors of these
product absorptions are also shown in the figures and will be
discussed below.
Quantum chemical calculations were carried out for the pos-
sible isomers and electronic states of the potential product
molecules. Figure 7 shows the optimized structures and elec-
tronic ground states. Table 2 reports a comparison of the ob-
served and calculated IR frequencies and isotopic frequency
ratios of the reaction products. Calculated vibrational frequen-
cies and intensities of the potential products are listed in
Table 3.
M(H2O). In the Pb þ H2O experiment, an absorption at
1585.8 cmꢁ1 appeared during sample deposition and changed
little on annealing and after broad-band irradiation. Although
this band has been observed previously,5a here, we present a
more detailed discussion. It shifted to 1171.7 cmꢁ1 with D2O
and to 1579.3 cmꢁ1 with H218O, giving an isotopic H/D ratio
of 1.3534 and 16O/18O ratio of 1.0041. The band position and
isotopic shifts are characteristic of the H2O bending vibration
of a H2O complex perturbed by a metal atom. No intermediate
absorptions were observed in the mixed H216O þ H218O ex-
periments, indicating that only one H2O subunit is involved
in this complex. This band was assigned to the H2O bending
vibration of the Pb(H2O) complex, which is in agreement with
the previous thermal matrix isolation study in solid argon
(1583.3 cmꢁ1).5a
Density functional theory (DFT) calculations predict the
Pb(H2O) complex to have an 3A00 electronic ground state with
a Cs structure, as shown in Fig. 7. The H2O bending vibra-
tional frequency was calculated to be 1613.3 cmꢁ1 (Table 3),
which should be scaled by 0.9830 (observed frequency divided
by calculated frequency) to fit the experimental frequency. The
calculated isotopic frequency ratios are also in agreement with
the experimental values (Table 2).
In the Sn þ H2O experiment, the 1577.4 cmꢁ1 band ap-
peared during sample deposition, markedly increased on sam-
ple annealing to 25 and 30 K, disappeared after broad-band
irradiation, while the absorption at 810.6 cmꢁ1 due to SnO5a
markedly increased, and did not recover on further annealing

Y.-L. Teng et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 11 (2007) 2151
0.05
0.04
0.03
0.02
0.01
0.00
HPbO
HPbOH
DPbO
DPbOD
0.04
0.02
0.00
(d)
(c)
(b)
(a)
1530 1520 1510 1500 1490 1480 1100
1090
1080
1070
1060
Wavenumber / cm-1
Fig. 3. Infrared spectra in the 1530–1480 and 1100–1155 cmꢁ1 regions from co-deposition of laser-ablated Pb atoms with 0.3%
H2O + 0.6% HDO + 0.3% D2O in argon: (a) 1 h sample deposition at 4 K; (b) after annealing to 25 K; (c) after 20 min of
broad-band irradiation; (d) after annealing to 30 K.
0.20
Sn(OH)
2
0.6
HSnO
0.5
0.15
(e)
HSnOH
Sn(OH)
HSnOH
2
0.4
0.3
0.2
0.1
0.0
(d)
(c)
(b)
0.10
0.05
0.00
Sn(H O)
2
(a)
1640
1620
1600
1580
620
600
580
560
540
520
Wavenumber / cm-1
Fig. 4. Infrared spectra in the 1645–1570 and 630–510 cmꢁ1 regions from co-deposition of laser-ablated Sn atoms with 0.2% H2O
in argon: (a) 1 h sample deposition at 4 K; (b) after annealing to 25 K; (c) after annealing to 30 K; (d) after 20 min of broad-band
irradiation; (e) after annealing to 35 K.
(Fig. 4). Although this band was observed previously,5a here,
we present a more detailed discussion. It shifted to 1169.0
cmꢁ1 with D2O and to 1570.6 cmꢁ1 with H218O, giving an
isotopic H/D ratio of 1.3494 and 16O/18O ratio of 1.0043. No
intermediate absorptions were observed in the mixed H216O þ
H218O experiments, indicating that only one H2O subunit is in-
volved in this complex. This band was assigned to the H2O
bending vibration of the Sn(H2O) complex, which is accord
to the previous thermal matrix isolation study in solid argon
(1578.0 cmꢁ1).5a
As shown in Fig. 7, DFT calculations predicted the
Sn(H2O) complex to have an 3A00 electronic ground state with
a Cs structure, which lies 79.5 kJ molꢁ1 lower in energy than
the singlet one. The H2O bending vibrational frequency was
calculated to be 1613.9 cmꢁ1 (Table 3), which should be
scaled by 0.9774 (observed frequency divided by calculated
frequency) to fit the experimental frequency. As shown in
Table 2, the calculated isotopic frequency ratios are also in
agreement with the experimental values.
HMOH. In the Pb þ H2O experiment, a new absorption at
1511.0 cmꢁ1 appeared on annealing to 25 K, changed little on
broad-band irradiation, and markedly increased on annealing
to 30 K (Fig. 1). This band barely shifted with H218O but shift-
ed to 1085.4 cmꢁ1 with D2O. The H/D isotopic ratio of 1.3921
indicates a Pb–H stretching vibrational mode. The doublet
feature in the experiment with the H2O/HDO/D2O mixture
indicates that only one Pb–H subunit is involved (Fig. 3). This
band was assigned to the Pb–H stretching vibration of the
HPbOH molecule. Two bands at 506.5 and 495.5 cmꢁ1 exhib-
ited the same annealing and irradiation behavior with the
1511.0 cmꢁ1 band, suggesting that these absorptions are due
to the different modes of the same molecule. The 506.5
cmꢁ1 band shifted to 480.9 cmꢁ1 with H218O (Fig. 2) and to
502.4 cmꢁ1 with D2O. The 16O/18O isotopic ratio of 1.0532

2152 Bull. Chem. Soc. Jpn. Vol. 80, No. 11 (2007)
Reactions of Lead and Tin with Water
0.15
0.15
0.12
0.09
0.06
0.03
0.00
HSnOH
HSnOH
0.12
(c)
(c)
Sn(OH)
Sn(OH)
2
2
0.09
0.06
0.03
0.00
Sn(OH)
Sn(OH)
2
2
(b)
(a)
(b)
(a)
HSnOH
HSnOH
620
600
580
560
540
520
500
620
600
580
560
540
520
500
Wavenumber / cm-1
Wavenumber / cm-1
Fig. 5. Infrared spectra in the 630–500 cmꢁ1 regions from
co-deposition of laser-ablated Sn atoms with isotopic H2O
in argon: (a) 0.2% H2O; (b) 0.2% H2O + 0.2% H218O;
(c) 0.2% H218O.
Fig. 6. Infrared spectra in the 1645–1570 and 1173–1140
cmꢁ1 regions from co-deposition of laser-ablated Sn
atoms with 0.1% H2O + 0.2% HDO + 0.1% D2O in
argon: (a) 1 h sample deposition at 4 K; (b) after annealing
to 25 K; (c) after annealing to 30 K; (d) after 20 min of
broad-band irradiation; (e) after annealing to 35 K.
Table 1. Infrared Absorptions (cmꢁ1) from Codeposition of Laser-Ablated Pb and Sn Atoms
with H2O in Excess Argon at 4 K
H2O
D2O
H218O
H/D
16O/18O
Assignment
1585.8
1511.0
1493.8
506.5
495.5
481.2
1605.5
1597.2
1577.4
569.0
1171.7
1085.4
1070.7
502.4
1579.3
1511.0
1493.6
480.9
1.3534
1.3921
1.3952
1.0082
1.0041
1.0000
1.0001
1.0532
1.0043
Pb(H2O) (H2O bend)
HPbOH (Pb–H stretch)
HPbO (Pb–H stretch)
HPbOH (Pb–OH stretch)
HPbOH (Pb–O–H deform)
PbOH (Pb–OH stretch)
HSnOH (Sn–H stretch)
HSnO (Sn–H stretch)
Sn(H2O) (H2O bend)
HSnOH (Sn–OH stretch)
493.4
472.4
1157.1
1147.4
1169.0
567.6
1.0186
1.3875
1.3920
1.3494
1.0025
1604.7
1596.9
1570.6
549.0
1.0005
1.0002
1.0043
1.0364
and H/D isotopic ratio of 1.0082 suggest that a Pb–OH stretch-
ing mode is involved. The mixed H216O þ H218O isotopic
spectra indicated that only one O atom is involved. On the
experiment with the H2O/HDO/D2O mixture, the doublet
feature indicates that only one Sn–H subunit is involved
(Fig. 6). The lower band shifted to 549.0 cmꢁ1 with H218O
(Fig. 5) and to 567.6 cmꢁ1 with D2O. The 16O/18O isotopic
ratio of 1.0364 and H/D isotopic ratio of 1.0025 imply a Sn–
OH stretching mode is involved. The doublet feature in the
mixed H216O þ H218O experiment indicates that only one O
atom is involved (Fig. 5).
other hand, the band at 495.5 cmꢁ1 slightly shifted (2.1 cmꢁ1
)
with H218O and is mainly due to a Pb–O–H deforming mode.
Present DFT calculations predicted HPbOH to have an A0
1
electronic ground state with Cs symmetry (Fig. 7) and to be the
most stable structural isomer of Pb–H2O. The corresponding
triplet one was found to have an imaginary frequency. The
Pb–H, Pb–OH stretching vibrations and the Pb–O–H deform-
ing vibration were calculated to be 1541.4, 492.1, and 519.5
cmꢁ1 (Tables 2 and 3), respectively, which supports for the
above assignment. Furthermore, as shown in Table 2, the cal-
culated isotopic frequency ratios are also consistent with the
experimental values.
In the Sn þ H2O experiment, a new band at 1605.5 cmꢁ1
and a band at 569.0 cmꢁ1 appeared after broad-band irradia-
tion, and disappeared on further annealing (Fig. 4). The upper
band scarcely shifted with H218O but shifted to 1157.1 cmꢁ1
with D2O, giving a H/D isotopic ratio of 1.3875. This indi-
cates that it is a Sn–H stretching vibrational mode. In the
1
The HSnOH molecule was predicted to have an A0 elec-
tronic ground state with a Cs symmetry (Fig. 7) and to be the
most stable structural isomer of Sn–H2O. The corresponding
triplet one was found to have an imaginary frequency. The
Sn–H and Sn–OH stretching vibrations were calculated to
be at 1631.5 and 536.6 cmꢁ1 (Tables 2 and 3), respectively,
which supports for the above assignment. Furthermore, as
shown in Table 2, the calculated isotopic frequency ratios
are also consistent with the experimental values.
HMO. In the Pb þ H2O experiment, a new 1493.8 cmꢁ1
band appeared during sample deposition, visibly increased
on sample annealing to 25 K, slightly decreased on broad-band
irradiation, and markedly increased on further annealing

Y.-L. Teng et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 11 (2007) 2153
H
H
O
0.963
O
2.629
H
1.846
2.011
Pb
106.8°
90.3°
94.6°
118.9°
0.962
H
Pb
Pb
O
1.832
H
2.053
Pb(H2O), 3A''
HPbOH, 1A'
HPbO, 2A'
H
H
0.964
H
2.534
O
H
1.792
Sn
107.0°
94.5°
121.7°
0.961
120.7°
0.962
Pb
Sn
O
O
2.057
H
1.972
Sn(H2O), 3A''
HSnOH, 1A'
PbOH, 2A'
Sn
1.926
35.0°
O
H
128.8°
1.287
1.874
O
102.4°
H
0.969
H
Sn
1.773
TS, 1A
HSnO, 2A'
Fig. 7. Optimized structures (bond length in angstroms, bond angle in degrees) of the possible products and the transition states
calculated at the B3LYP level.
Table 2. Comparison of Observed and Calculated IR Frequencies and Isotopic Frequency Ratios of
the Reaction Products
Freq/cmꢁ1
H/D
16O/18O
Molecule
Mode
obsd
calcd
obsd
calcd
obsd
calcd
Pb(H2O)
HPbOH
H2O bend
1585.8
1511.0
506.5
495.5
1493.8
481.2
1577.4
1605.5
569.0
1613.3
1541.4
492.1
519.5
1530.3
489.3
1613.9
1631.5
536.6
1.3534
1.3921
1.0082
1.3640
1.4100
1.0117
1.3621
1.4100
1.0066
1.3638
1.4074
0.9902
1.4079
1.0041
1.0000
1.0532
1.0043
1.0001
1.0044
1.0000
1.0540
1.0043
1.0000
1.0552
1.0044
1.0000
1.0443
1.0000
Pb–H stretch
Pb–OH stretch
Pb–O–H deform
Pb–H stretch
Pb–OH stretch
H2O bend
Sn–H stretch
Sn–OH stretch
Sn–H stretch
HPbO
PbOH
Sn(H2O)
HSnOH
1.3952
1.0186
1.3494
1.3875
1.0025
1.3920
1.0043
1.0005
1.0364
1.0002
HSnO
1597.2
1615.6
(Fig. 1). This band barely shifted with H218O but shifted to
1070.7 cmꢁ1 with D2O. The band position and isotopic fre-
quency ratios (H/D, 1.3952, 16O/18O, 1.0001) suggest that
this band is due to a Pb–H stretching vibrational mode. The
mixed H2O þ HDO þ D2O experiments indicate that only
one H atom is involved in this mode (Fig. 3). Accordingly,
the 1493.8 cmꢁ1 band was assigned to the Pb–H stretching
vibration of the HPbO molecule.
H2O2.12 The Pb–O stretching vibration of the PbO molecule
was observed at 711.2 cmꢁ1 in solid argon,19 and the Pb–O
stretching vibration of the HPbO molecule is expected to shift
to a lower frequency than that of the PbO molecule. The
calculated intensity of the Pb–O stretching vibration was too
small to be observed, which is consistent with the present
experiments.
In the Sn þ H2O experiment, an absorption at 1597.2 cmꢁ1
appeared during sample deposition, slightly increased on an-
nealing to 25 and 30 K, visibly increased on broad-band irradi-
ation and markedly increased on annealing to 35 K (Fig. 4).
This band barely shifted with H218O, but shifted to 1147.4
cmꢁ1, giving a H/D isotopic ratio of 1.3920, which implies
2
The HPbO molecule was predicted to have an A0 ground
state with Cs symmetry (Fig. 7). The Pb–H and Pb–O stretch-
ing vibrations were predicted to be at 1530.3 (381 km molꢁ1
)
and 471.4 (3 km molꢁ1) cmꢁ1, respectively, which is similar
to the results recently reported for the reaction of Pb with

2154 Bull. Chem. Soc. Jpn. Vol. 80, No. 11 (2007)
Reactions of Lead and Tin with Water
2
have an A0 ground state with a nonlinear structure (Fig. 7).
The calculated Pb–OH stretching vibrational frequency was
489.3 cmꢁ1 (Table 3), which is in accord with the experimen-
tal observations (481.2 cmꢁ1).
Table 3. Calculated Vibrational Frequencies and Intensities
(km molꢁ1) of Possible Species Involved in the Pb and
Sn þ H2O Reactions (Only the Frequencies Above 400
cmꢁ1 are Listed)
Reaction Mechanism. On the basis of the behavior of
sample annealing and irradiation together with the observed
species and calculated stable isomers, plausible reaction mech-
anisms are proposed as follows. Under the present experimen-
tal conditions, laser-ablated Pb atoms co-deposit with water
molecules to form the Pb(H2O) complex during sample depo-
sition, which slightly increased on annealing and changed little
after broadband irradiation. This suggests that the ground state
3P Pb atoms can react with water to form the Pb(H2O) com-
plex spontaneously and the Pb(H2O) molecule is more stable
than M(H2O) (M ¼ Si,5c Ge,5d and Sn), which rearranges after
broadband irradiation. This addition reaction is predicted to
be exothermic by about 37.7 kJ molꢁ1 (reaction 1). The IR
absorptions of HPbOH markedly increased on annealing to
30 K after broadband irradiation, whereas the IR absorption
of Pb(H2O) barely changed, implying that the HPbOH mole-
cule is not generated from the isomerization of Pb(H2O).
The HPbOH molecule may be formed from the reaction of
Frequency/cmꢁ1
Elec
Species
Point group
state
Pb(H2O) 3A00
(intensity, mode)
3914.3 (138, A00), 3811.3 (62, A0),
1613.3 (83, A0)
Cs
HPbOH 1A0
Cs
3865.6 (54, A0), 1541.4 (708, A0),
742.6 (27, A0), 525.8 (50, A0),
519.5 (207, A00), 492.1 (149, A0)
1530.3 (381, A0), 471.4 (3, A0)
3857.9 (72, A0), 629.6 (61, A0),
489.3 (131, A0)
HPbO
PbOH
2A0
2A0
Cs
Cs
Sn(H2O) 3A00
HSnOH 1A0
Cs
Cs
3907.3 (145, A00), 3803.4 (64, A0),
1613.9 (85, A0)
3872.7 (57, A0), 1631.5 (603, A0),
761.1 (53, A0), 578.0 (9, A0),
540.7 (200, A00), 536.6 (194, A0)
1615.6 (199, A0), 621.6 (7, A0)
3720.2 (9, A), 1519.9 (111, A),
624.2 (69, A), 475.1 (46, A),
311.5 (182, A), 1546.0i (2218, A)
HSnO
TS
2A0
1A
Cs
C1
ꢀ
the excited Pb atom generated by the broad-band irradiation
with water molecule during further annealing (reaction 2). IR
absorptions for HPbO appeared during sample deposition, sug-
gesting that part of the Pb(H2O) complexes formed during
the co-deposition of H2O with the Pb atoms generated by pulse
laser ablation are dissociated to HPbO and H during deposi-
tion. The formation of HPbO molecule may be also due to
the reactions of excited atoms. Similar features have also been
observed in the reactions of group 4 metal atoms with H2O in
solid argon.8b Pb(OH)2 appeared during sample deposition and
increased upon annealing, which form by the reaction of Pb
with two water molecules (reaction 3), suggesting that the for-
mation of Pb(OH)2 does not require activation energy.
that this band is due to a Sn–H stretching vibrational mode.
The doublet feature in the mixed H2O þ HDO þ D2O experi-
ments indicates that only one H atom is involved in this mode
(Fig. 6). Accordingly, the 1597.2 cmꢁ1 band was assigned to
the Sn–H stretching vibration of the HSnO molecule; different
from the previous report in which a band at 1597.7 cmꢁ1 has
been assigned to the HSnOH molecule.5a
The present DFT calculations lend support for the assign-
ment of HSnO. The HSnO molecule was predicted to have
an 2A0 ground state with Cs symmetry (Fig. 7). The Sn–H and
Sn–O stretching vibrations were predicted to be at 1615.6
(199 km molꢁ1) and 621.6 (7 km molꢁ1) cmꢁ1, respectively.
The calculated intensity of the Sn–O stretching vibration was
too small to be observed, which is consistent with the present
experimental observation.
Pb (3P) þ H2O (1A1) ! Pb(H2O) (3A00)
ꢀE ¼ ꢁ37:7 kJ molꢁ1
;
ð1Þ
ð2Þ
ð3Þ
ꢀ
Pb (5P) þ H2O (1A1) ! HPbOH (1A0)
M(OH)2.
In the Pb þ H2O experiment, absorptions at
ꢀE ¼ ꢁ109:6 kJ molꢁ1
Pb (3P) þ 2H2O (1A1) ! Pb(OH)2 (1A0) þ H2
ꢀE ¼ ꢁ174:9 kJ molꢁ1
;
:
707.1, 533.5, and 502.7 cmꢁ1 appeared during sample deposi-
tion, changed little on annealing to 25 K, visibly increased
after broad-band irradiation, and markedly increased upon
further annealing (Fig. 1). These bands were assigned to the
Pb(OH)2 molecule on the basis of a recent report (706.8,
533.5, and 502.7 cmꢁ1) on the reaction of Pb and H2O2.12
In the Sn þ H2O experiment, the absorptions at 728.0,
599.9, and 567.8 cmꢁ1 markedly increased after broad-band
irradiation and were assigned to the Sn(OH)2 molecule, based
on a recent report (727.4, 598.8, and 565.7 cmꢁ1) on the reac-
tion of Sn and H2O2.12
Laser-ablated Sn atoms co-deposited with water molecules
to form the Sn(H2O) complex during sample deposition
(Fig. 4), which slightly increased on annealing, suggesting that
3
the ground state P Sn atoms can react with water to form the
Sn(H2O) complex spontaneously. This addition reaction is pre-
dicted to be exothermic by about 39.7 kJ molꢁ1 (reaction 4). IR
absorptions for HSnOH appeared after broadband irradiation,
while the IR absorption for Sn(H2O) disappeared, implying
that the HSnOH molecule may be generated from the isomer-
ization of Sn(H2O) (reaction 5) via broad-band irradiation.
From the 3A00 Sn(H2O) molecule, there is spin crossing leading
to the 1A0 HSnOH molecule. Although this reaction is predict-
ed to be exothermic by 104.6 kJ molꢁ1, it has a 149.8 kJ molꢁ1
energy barrier. HSnOH absorptions appeared after broad-band
irradiation, suggesting that reaction 5 requires activation
Other Absorption. In the Pb þ H2O experiment, a new
weak absorption at 481.2 cmꢁ1 appeared after broad-band irra-
diation and changed little on further annealing (Fig. 1). This
band shifted to 472.4 cmꢁ1 with D2O. The H/D isotopic fre-
quency ratio was 1.0186, implying a Pb–OH stretching vibra-
tional mode. Accordingly, the 481.2 cmꢁ1 band was tentatively
assigned to the Pb–OH stretching vibration of the PbOH mole-
cule. B3LYP calculations predicted the PbOH molecule to

Y.-L. Teng et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 11 (2007) 2155
200
150
100
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.
Sn (3P) þ H2O (1A1) ! Sn(H2O) (3A00)
ꢀE ¼ ꢁ39:7 kJ molꢁ1
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Conclusion
Reactions of laser-ablated lead and tin atoms with water
molecules in argon were studied using matrix-isolation infra-
red spectroscopy. Adduct and insertion products (M(H2O),
HMOH, and HMO, M ¼ Pb and Sn) were observed in the
present experiments. The products were identified on the basis
of the results of the isotopic substitution, step-wise annealing,
changes in water concentration and laser energy, and compar-
ison with theoretical predictions. Pb(H2O) is more stable than
M(H2O) (M ¼ Si, Ge, and Sn), and its isomerization is more
difficult than that of M(H2O) (M ¼ Si, Ge, and Sn). In contrast
with the HPbOH molecule, the HSnOH molecule may form
from the isomerization of Sn(H2O).
The authors thank the reviewers for valuable suggestions
and comments. This work was supported by a Grant-in-Aid
for Scientific Research (B) (Grant No. 17350012) from the
Ministry of Education, Culture, Sports, Science and Technolo-
gy (MEXT) of Japan. Y.-L.T. thanks JASSO and Kobe Univer-
sity for Honors Scholarship.

2156 Bull. Chem. Soc. Jpn. Vol. 80, No. 11 (2007)
Reactions of Lead and Tin with Water
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