Formation of new halogenothiocarbonylsulfenyl halides, XC(S)SY, through photochemical matrix reactions starting from CS2 and a dihalogen molecule XY (XY = Cl2, Br2, or BrCl)

Article abstract of DOI:10.1021/ic070119+

Isolation of a dihalogen molecule XY (XY = Cl₂, Br₂, or BrCl) with CS₂ in a solid Ar matrix at about 15 K leads, by broad-band UV-vis photolysis (200 ≤ λ ≤ 800 nm), to a variety of products depending on the natures of X and Y. These products have been identified on the basis of the IR spectra of the matrices. In addition to the familiar species SCCl₂;, ClCS^?, Cl ^?...SCS, CCl₄, ?CCl₃, :CCl ₂, SCl₂, SCBr₂, CBr₄, ?CBr ₃, BrC(S)Cl, BrCCl₃, and :CBrCl, the following new molecules have also been identified as products of the various photoreactions: syn-CIC(S)SCI, anti-CIC(S)SCI, syn-BrC(S)SBr, anti-BrC(S)SBr, syn-ClC(S)SBr, anti-ClC(S)SBr, syn-BrC(S)SCl, anti-BrC(S)SCl, ClC(S)S^?, BrCS^?, and Br^?...SCS. The IR spectra of these hitherto unknown species have been interpreted with reference to the predictions of ab initio (HF and MP2) and density functional theory (DFT) calculations. The results are analyzed in relation to the reaction pathways accessed by matrix photolysis.

Full text of DOI:10.1021/ic070119+

Inorg. Chem. 2007, 46, 4692−4703
Formation of New Halogenothiocarbonylsulfenyl Halides, XC(S)SY,
through Photochemical Matrix Reactions Starting from CS and a
2
Dihalogen Molecule XY (XY
) Cl , Br , or BrCl)
2
2
Yeny A. Tob o´ n,† Rosana M. Romano,*,† Carlos O. Della V e´ dova,†,‡ and Anthony J. Downs§
CEQUINOR (UNLP-CONICET) and Laboratorio de SerVicios a la Industria y al Sistema
Cient ´ı fico (UNLP-CIC-CONICET), Departamento de Qu ´ı mica, Facultad de Ciencias Exactas,
UniVersidad Nacional de La Plata, 47 esq. 115, (1900) La Plata, Argentina, and Inorganic
Chemistry Laboratory, UniVersity of Oxford, South Parks Road, Oxford, OX1 3QR, U.K.
Received January 23, 2007
Isolation of a dihalogen molecule XY (XY
2 2 2
) Cl , Br , or BrCl) with CS in a solid Ar matrix at about 15 K leads,
by broad-band UV vis photolysis (200 e λ e 800 nm), to a variety of products depending on the natures of X and
−
Y. These products have been identified on the basis of the IR spectra of the matrices. In addition to the familiar
, ClCS , Cl•‚‚‚SCS, CCl
•
•
•
species SCCl
2
4
,
3 2
CCl , :CCl , SCl
2
, SCBr
2
, CBr
4
,
3
CBr , BrC(S)Cl, BrCCl
3
, and :CBrCl, the
following new molecules have also been identified as products of the various photoreactions: syn-ClC(S)SCl,
anti-ClC(S)SCl, syn-BrC(S)SBr, anti-BrC(S)SBr, syn-ClC(S)SBr, anti-ClC(S)SBr, syn-BrC(S)SCl, anti-BrC(S)SCl,
ClC(S)S , BrCS , and Br•‚‚‚SCS. The IR spectra of these hitherto unknown species have been interpreted with
reference to the predictions of ab initio (HF and MP2) and density functional theory (DFT) calculations. The results
are analyzed in relation to the reaction pathways accessed by matrix photolysis.
•
•
2
Introduction
reports of how the new molecules BrC(O)SBr and IC(O)-
3
SBr come to be formed upon photolysis of Ar matrixes
containing, respectively, OCS/Br and OCS/IBr mixtures. In
2
these photolytically activated reactions between OCS and a
dihalogen molecule, only the syn conformer of the carbon-
ylsulfenyl product was detected. The corresponding anti form
can be identified only upon irradiation of a matrix initially
Our research group in La Plata has been interested for
some time in the matrix photochemistry of relatively small
molecules. For example, carbonylsulfenyl compounds of the
type XC(O)SY (X, Y ) H, halogen, or an organic group)
have been shown to possess a rich photochemistry involving
a variety of reaction pathways which we have sought to
elucidate. An earlier study of the matrix photochemistry of
4
containing the more stable syn form (as with ClC(O)SCl
1
1
and ClC(O)SBr ).
chlorocarbonylsulfenyl bromide, ClC(O)SBr, has served in
Studies of the spectroscopic and conformational properties
of thiocarbonylsulfenyl compounds have been motivated
partly by the discovery that molecules containing the
dithioester group afford an ideal resonance Raman probe for
particular as a prototype for subsequent research. Broad-band
UV-vis irradiation of ClC(O)SBr trapped in a solid Ar
matrix was shown to result not only in partial transformation
of the more stable syn conformer into the anti conformer of
the parent molecule, but also in the formation of its isomer
BrC(O)SCl, as well as the fragments BrCl, BrSCl, CO, and
OCS. The photoreversibility of some of the changes sug-
gested new synthetic options, exemplified by our recent
monitoring catalytic events within the active site of an
5
enzyme. Compounds of the type RC(S)SR
1
(R ) CH
3 1
; R
)
CH
3
or CH
2
CH
3
-8
) have been found to assume only the
syn conformation. Microwave spectra of dithioformic acid,
6
*
To whom correspondence should be addressed. E-mail: romano@
(2) Romano, R. M.; Della V e´ dova, C. O.; Downs, A. J. Chem. Commun.
2001, 2638-2639.
quimica.unlp.edu.ar.
†
CEQUINOR (UNLP-CONICET).
Laboratorio de Servicios a la Industria y al Sistema Cient ´ı fico (UNLP-
(3) Tob o´ n, Y. A.; Nieto, L. I.; Romano, R. M.; Della V e´ dova, C. O.;
Downs, A. J. J. Phys. Chem. A 2006, 110, 2674-2681.
(4) Romano, R. M.; Della V e´ dova, C. O.; Downs, A. J. J. Phys. Chem. A
2004, 108, 7179-7187.
‡
CIC-CONICET).
§
Inorganic Chemistry Laboratory.
(
1) Romano, R. M.; Della V e´ dova, C. O.; Downs, A. J.; Greene, T. M. J.
(5) Lee, H.; Storer, H. C.; Carey, P. R. Biochemistry 1983, 22, 4781-
4789.
Am. Chem. Soc. 2001, 123, 5794-5801.
4692 Inorganic Chemistry, Vol. 46, No. 11, 2007
10.1021/ic070119+ CCC: $37.00
© 2007 American Chemical Society
Published on Web 04/06/2007

Halogenothiocarbonylsulfenyl Halides
HC(S)SH, have been interpreted, however, in terms of a
0.5:1:200, were prepared by standard manometric methods. Each
such mixture was deposited on a CsI window cooled to ∼15 K by
a Displex closed-cycle refrigerator (Air Products, model CS202)
using the pulsed-deposition technique.1
conformational equilibrium between syn and anti forms, with
the syn form predominating.9
2,13
To the best of our knowledge, no thiocarbonylsulfenyl
halides of the type XC(S)SY (X, Y ) the same or different
halogen atoms) have hitherto been characterized experimen-
tally. The chloride ClC(S)SCl has been proposed as an
The IR spectrum of each matrix sample was recorded at a
-1
resolution of 0.5 cm , with 256 scans and a wavenumber accuracy
-
1
of ( 0.1 cm , using a Nicolet Magna-IR 560 FT-IR instrument
equipped with either an MCTB or a DTGS detector (for the ranges
1
0
intermediate in the chemical reaction represented by eq 1.
-1
of 4000-400 or 600-250 cm , respectively). After deposition and
However plausible this may be, direct evidence has yet to
be advanced.
IR analysis of the resulting matrix, the sample was exposed to
broad-band UV-vis radiation (200 e λ e 800 nm) from a Spectral
Energy Hg-Xe arc lamp operating at 800 W. The output from the
lamp was limited by a water filter to absorb infrared radiation to
minimize any heating effects. The IR spectrum of the matrix was
then recorded at different times of irradiation, with close attention
to the decay of absorptions due to the reactants and to the
appearance and subsequent behavior of any new absorptions.
All of the quantum chemical calculations were performed using
the Gaussian 98 program system14 under the Linda parallel
execution environment with two coupled PCs. HF, density func-
tional theory (DFT), and MP2 methods were used in combination
with a 6-31+G* basis set for C, S, and Cl atoms, and a LANL2DZ
basis set,15 including an effective core potential (ECP), for Br atoms.
Here we report studies of some photochemical reactions
2 2
involving a dihalogen molecule XY (Cl , Br , or BrCl) and
CS isolated together in an Ar matrix at about 15 K. Analysis
2
of the FT-IR spectrum of such a matrix shows that broad-
band UV-vis irradiation gives access to three primary
reaction channels, as represented by eqs 2-4. Hence, in
16
The ECP chosen is that proposed by Hay and Wadt which
incorporates the mass velocity and Darwin relativistic effects.
Representative levels of approximation are cited throughout this
paper. Geometry optimizations were sought using standard gradient
techniques by simultaneous relaxation of all the geometric param-
eters. The calculated vibrational properties corresponded in all cases
to potential energy minima for which no imaginary vibrational
frequencies were found.
SdCdS + XY f XC(S)SY
SdCdS + XY f XC(S)Y + S
SdCdS + XY f :CXY + 2S
(2)
(3)
(4)
addition to the known thiocarbonyl dihalide XC(S)Y and the
carbene :CXY, we have gained the first evidence for the
halogenothiocarbonylsulfenyl halide XC(S)SY. Both the syn
and anti rotamers of XC(S)SY are formed simultaneously.
Various radicals are observed as intermediates. These include
Results and Discussion
(i) Cl + CS . A mixture of Cl , CS , and Ar, typically in
2
2
2
2
the proportions 0.5:1:200 or 2:1:200, was deposited on the
cooled CsI window. The IR spectrum of the resulting matrix,
•
•
•
ClC(S)S , Br ‚‚‚SCS, and BrCS , each identified for the first
•
•
time, as well as the known species ClCS , Cl ‚‚‚SCS, and
CX . Among the final products detected in these experi-
ments are the tetrahalomethanes CCl , CBr , and CBrCl and
the sulfur dihalide SCl . Characterization of the new products
measured immediately after deposition, displayed only the
IR absorptions characteristic of either free CS21
7,18
or the
•
3
4
4
3
weakly bound van der Waals complex CS ‚‚‚Cl described
2
2
1
9
2
only very recently.
by their IR spectra has been underpinned by the isotopic
effects observed and by comparison with the results of
appropriate quantum chemical calculations.
(12) (a) Almond, M. J.; Downs, A. J. AdV. Spectrosc. 1989, 17, 1-511.
b) Dunkin, I. R. Matrix-Isolation Techniques: A Practical Approach;
(
Oxford University Press: New York, 1998.
(
13) Perutz, R. N.; Turner, J. J. J. Chem. Soc., Faraday Trans. 2 1973, 69,
452-461.
Experimental and Theoretical Methods
(
14) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Baboul, A. G.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts,
R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C.
Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.;
Johnson, B.; Chen, W.; Wong, M. W.; Andres, J. L.; Head-Gordon,
M.; Replogle, E. S.; Pople, J. A. Gaussian 98, revision A.7; Gaussian
Inc.: Pittsburgh, PA, 1998.
Commercial samples of Cl
used without further purification. CS
2
and Br
2
(both from Aldrich) were
(again from Aldrich) was
2
purified by repeated trap-to-trap condensation in vacuo. BrCl was
produced by mixing equimolar amounts of Cl and Br , leading to
an equilibrium mixture of BrCl, Cl , and Br
.11 Gas mixtures of
the dihalogen XY (Cl , Br , or BrCl), CS , and Ar, typically with
the composition of XY/CS /Ar being between 2:1:200 and
2
2
2
2
2
2
2
2
(
(
(
(
6) Herzog, K.; Steger, E.; Rosmus, P.; Scheithauer, S.; Mayer, R. J. Mol.
Struct. 1969, 3, 339-350.
7) Fausto, R.; Martins, A. G.; Teixeira-Dias, J. J. C.; Tonge, P. J.; Carey,
P. R. J. Mol. Struct. 1994, 323, 59-69.
(15) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284-298.
(16) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270-283.
(17) Bahou, M.; Lee, Y. C.; Lee, Y. P. J. Am. Chem. Soc. 2000, 122, 661-
667.
(18) Givan, A.; Loewenschuss, A.; Bier, K. D.; Jodl, H. J. Chem. Phys.
1986, 106, 151-159.
(19) Romano, R. M.; Picone, A. L.; Downs, A. J. J. Phys. Chem. A 2006,
110, 12129-12135.
8) Teixeira-Dias, J. J. C.; Fausto, R.; Batista de Carvalho, L. A. E. J.
Mol. Struct. (THEOCHEM) 1992, 262, 87-103.
9) Bak, B.; Nielsen, O. J.; Svanholt, H. J. Mol. Spectrosc. 1978, 69, 401-
408.
(
10) Senning, A. Angew. Chem., Int. Ed. Engl. 1979, 18, 941-942.
(11) Mattraw, H. C.; Pachucki, C. F.; Hawkins, N. J. J. Chem. Phys. 1954,
22, 1117-1119.
Inorganic Chemistry, Vol. 46, No. 11, 2007 4693

Tob o´ n et al.
Table 1. Wavenumbers and Assignments of the IR Absorptions
Appearing after Broad-Band UV-vis Photolysis of an Ar Matrix
Containing a Mixture of CS2 and Cl2 at ∼15 K
solutions of CS
theoretical studies were then performed, revealing that the
most stable structure is one with the Cl atom linked to an S
in CCl
at 1 M concentration. Several
2
4
•
Ar
matrix
wavenumbers
reported previously
o 20
atom to give a Cl‚‚‚SdC bond angle of ∼107 . The other
assignment
vibrational mode
two features appearing in the ν(CdS) region, near 1145
ν (cm-1)
molecule
ν [cm-1
]
-
1
and 1088 cm , will be shown (quode vide) to be the most
intense absorptions of the new chlorothiocarbonylsulfenyl
chloride molecules syn-ClC(S)SCl and anti-ClC(S)SCl,
respectively.
•
1468a
1
1
1
1
1
1
1
1
1
1
9
8
8
8
8
8
7
7
7
481.5 Cl ‚‚‚SCS
νas(SdCdS)
ν(CdS)
•
1189.3b
189.1 ClCS
145.5 syn-ClC(S)SCl ν(CdS)
this work
145.0
144.3
143.4
Continued broad-band UV-vis photolysis resulted in the
development of yet more new bands. Among these, features
centered near 1130/1124, 812, 785/784/778, and 498/493
129.7 SCCl2
ν(CdS) (ν1)
1130.0
123.9
1123.8c
this work
088.5 anti-ClC(S)SCl ν(CdS)
-
1
cm could be recognized as the ν
1
, (ν
2
+ ν
5 4
), ν , and ν
2
084.7
ClC(S)S•
•CCl3
anti-ClC(S)SCl νas(Cl-C-S)
ν(CdS)
νas(CCl3) (ν3)
this work
898.4d
this work
22
14.6
98.1
89.4
84.9
12.0
08.8
88.6
87.4
86.4
vibrational transitions of the SCCl molecule. A set of bands
near 789/787/786 cm could also be identified with the ν
fundamental of CCl
could be identified with the (ν
2
-1
3
-1
23
4
; a multiplet at 767/765/764/762 cm
SCCl2
(ν2 + ν5)
810.0c
this work
789.1
787.9
786.7
1
+ ν ) combination mode of
4
syn-ClC(S)SCl νas(Cl-C-S)
CCl4
this molecule. Other familiar products were SCl
2
, the carbene
νas(C-Cl) (n3)
•
:
CCl
2
, and the radicals ClCS and •CCl
3
recognizable by
2
4
25
26
-1 27
bands at 513-521, 746.5, 1189.1, and 898.1 cm ,
respectively.
7
7
85.8
84.6e
3
5
35
c
Furthermore, the spectrum showed the growth of some
new bands that could not be attributed to any known species.
For example, a family of bands arising from a single product,
based on the evidence of a common growth pattern, was
observed near 1145/1144/1143, 809, 540, 503, and 414/411
7
7
7
7
7
7
7
85.4
83.7
78.2
67.0
64.8
63.9
61.6
SCCl2
SCCl2
SCCl2
CCl4
νas( Cl-C- Cl) (ν4)
785.0
3
7
35
782.6c
776.8c
767.4
765.9
764.5
762.1
νas( Cl-C- Cl) (ν4)
3
7
37
νas( Cl-C- Cl) (ν4)
(ν1 + ν4)
-1
cm . The wavenumbers give strong circumstantial evidence
7
7
7
61.1
59.5
58.0
of a molecule incorporating the Cl-CdS and S-Cl frag-
e
f
22,24,26
ments.
In addition, quantum chemical calculations pre-
746.5
540.0
520.6
517.1
516.2
511.9
514.7
513.3
503.4
498.1
493.2
449.3
445.6
414.3
411.5
:CCl2
νas(Cl-C-Cl)
745.7
dict vibrational properties for the hitherto unknown molecule
syn-ClC(S)SCl in persuasive agreement with the observed
pattern of IR absorptions (see Table 2). Another family com-
posed of bands centered near 1088/1085, 889/885, 516/512,
449, and 446 cm could then be assigned to the rotational
isomer anti-ClC(S)SCl, a conclusion again supported by the
results of theoretical calculations (see Table 2).
After 15 min of irradiation, an absorption at 914.6 cm-1
became discernible. This differed in its growth from the
bands attributed to the ClC(S)SCl molecules, and its likely
origin invited further quantum chemical calculations. There
is no wholly satisfactory consensus between the predictions
of the HF, DFT (B3LYP), and MP2 methods (see Supporting
Information), but the B3LYP method, in combination with
syn-ClC(S)SCl ν(S-Cl)
SCl2
SCl2
this work
3
5
35
g
νs( Cl-S- Cl)
520.2
3
5
35
517.5g
νas( Cl-S- Cl)
anti-ClC(S)SCl ν(S-Cl)
this work
-
1
3
5
37
515.2 g
SCl2
SCl2
νs( Cl-S- Cl)
35 37
νas( Cl-S- Cl)
512.8 g
syn-ClC(S)SCl νs(Cl-C-S)
SCCl2
SCCl2
this work
3
5
35
c
νs( Cl-C- Cl) (ν2)
499.5
3
7
35
495.25c
νs( Cl-C- Cl) (ν2)
anti-ClC(S)SCl νs(Cl-C-S)
this work
this work
this work
h
anti-ClC(S)SCl δoop
h
syn-ClC(S)SCl δoop
a
Ref 20 (Raman spectrum of CCl4 solution). Ref 26. c Ref 22. d Ref
b
2
7. e Ref 23. Ref 25. Ref 24. δoop ) out-of-plane deformation.
f
g
h
Subsequent irradiation of the matrix with broad-band UV-
vis light (200 e λ e 800 nm) led, however, to drastic
changes in the spectrum. Decay of the bands from the
a 6-31+G* basis set, gives grounds for believing that the
band could be carried by the hitherto unknown ClC(S)S•
radical.
2 2
complex CS ‚‚‚Cl was accompanied by the appearance and
growth of new bands from a variety of products, as listed in
Table 1. The first of these bands to appear after 1 min of
irradiation occurred near 1481, 1145, and 1088 cm , that
(20) Wang, D.; Li, Y.-L.; Ho, W. S.; Leung, K. H.; Phillips, D. L. J. Org.
Chem. 2002, 67, 747-752.
(
21) Sumiyoshi, T.; Nakayama, M.; Fujiyoshi, R.; Sawamura, S. Rad. Phys.
-
1
Chem. 2006, 75, 20-25.
is, in a region generally characteristic of ν(CdS) vibrations.
(22) Hauswirth, W.; Willner, H. Spectrochim. Acta, Part A 1979, 35, 263-
-
1
269.
The development of a new band at 1481.5 cm with a shift
(
23) King, S. T. J. Chem. Phys. 1968, 49, 1321-1330.
(24) Bielefeldt, D.; Willner, H. Spectrochim. Acta, Part A 1980, 36, 989-
95.
-
1
2
of -46.6 cm with respect to free CS suggests the
9
formation of a molecular complex by the interaction of CS
2
(
25) (a) Andrews, L. J. Chem. Phys. 1968, 48, 979-982. (b) Jacox, M. E.;
•
with a Cl atom released through photodissociation of Cl
2
.
Milligan, D. E. J. Chem. Phys. 1970, 53, 2688-2701.
•
Such a complex, Cl ‚‚‚SCS, has already been studied
(26) Schallmoser, G.; Wurfel, B. E.; Thoma, A.; Caspary, N.; Bondybey,
V. E. Chem. Phys. Lett. 1993, 201, 528-534.
27) Rogers, E. E.; Abramowitz, S.; Jacox, M. E.; Milligan, D. E. J. Chem.
extensively,2
0,21
but the vibrational wavenumbers reported
(
were derived not from the IR but from Raman spectra of
Phys. 1970, 52, 2198-2204.
4694 Inorganic Chemistry, Vol. 46, No. 11, 2007

Halogenothiocarbonylsulfenyl Halides
Table 2. Experimental and Calculated IR Spectra of syn-Chlorothiocarbonylsulfenyl Chloride, syn-ClC(S)SCl, and anti-Chlorothiocarbonylsulfenyl
a
Chloride, anti-ClC(S)SCl
syn-ClC(S)SCl
theoretical calculations
HF/6-31+G* B3LYP/6-31+G* MP2/6-31+G*
anti-ClC(S)SCl
Ar matrix
ν (cm-1)
Ar matrix
ν (cm-1
theoretical calculations
vibrational
mode
)
HF/6-31+G* B3LYP/6-31+G* MP2/6-31+G*
1
1
1
1
8
145.5
1117.4 (100)
1145.1 (100)
1188.9 (100) 1088.5
1084.7
1078.0 (100)
1079.3 (100)
1148.8 (100) ν(CdS)
} (100)
58)
145.0
144.3
143.4
(100)
}
08.8 (48)
801.5 (37)
547.0
723.1 (46)
802.5 (67)
561.0
555.5
521.3 (4)
435.9 (2)
889.4
873.0 (42)
869.5 (74)
900.5 (93)
524.7
519.8
495.1 (14)
432.2 (1)
νas(Cl-C-S)
} (
}
884.9
3
5
5
40.0 (25)
520.4
(20)
}
516.2
511.9
449.3 (13)
445.6 (17)
528.0
(11)
}
458.9
(19)
}
ν(S- Cl)
(
11)
(18)
(9)
(25)
}
}
}
35
5
42.1
515.7
523.3
454.5
ν(S- Cl)
5
4
4
03.4 (7)
497.8 (5)
500.5 (2)
458.9 (1)
472.3 (6)
477.0 (8)
νs(Cl-C-S)
b
14.3
455.0 (<1)
458.5 (<1)
458.8 (23)
δoop
} (5)
11.5
320.7 (<1)
315.5 (1)
334.0 (1)
311.3 (1)
313.5 (2)
326.8 (1)
δ(Cl-CdS)
a
Wavenumbers in cm-1; relative intensities given in parentheses. b δoop ) out-of-plane deformation
Figure 2. FT-IR spectra of an Ar matrix containing Cl2 and CS2
-
1
(
Cl2/CS2/Ar ) 0.5:1:200) in the region of 850-650 cm immediately after
deposition (bottom), after 15 min of photolysis (middle), and after 240 min
of photolysis (top).
Figure 1. FT-IR spectra of an Ar matrix containing Cl2 and CS2
(
Cl2/CS2/Ar ) 0.5:1:200) in the region of 1180-1050 cm-1 immediately
after deposition (bottom), after 15 min of photolysis (middle), and after
Scheme 1. Possible Mechanism for the Formation of the syn and anti
Forms of ClC(S)SCl in an Ar Matrix at ∼15 K
2
40 min of photolysis (top).
Table 1 lists the wavenumbers of all the new absorptions
observed to develop in the photochemical reaction occurring
between CS
2
and Cl
2
when isolated together in an Ar matrix.
•
20
Literature data is also included for the Cl ‚‚‚SCS complex,
•26
27
25
22
,23
the ClCS and •CCl
and SCl
3
radicals, and :CCl
2
, SCCl
2
, CCl
4
;24 with the exception of the Cl ‚‚‚SCS complex
•
2
CS
isolated together with Cl
gave any hint of an absorption
2
2
(
quode vide), these data relate to species similarly isolated
in Ar matrixes. Figures 1 and 2 show two different regions
of the IR spectra of an Ar matrix doped with CS and Cl
-1
in the neighborhood of 1280 cm that could be attributed
to the CS molecule. Hence, although the photoproducts
included numerous species that could be formed only with
the rupture of one or both CdS bonds of the CS
29
2
2
,
with traces recorded immediately after deposition and again
after broad-band UV-vis irradiation.
2
parent,
•
that is, ClCS , SCCl
2
, :CCl
2
, •CCl , and CCl , there is no
3 4
2
Photolysis of matrix-isolated CS to bring about either
photodissociation to CS and S atoms or ionization to give
(
28) (a) Fournier, J.; Lalo, C.; Deson, J.; Vermeil, C. J. Chem. Phys. 1977,
+
28
the CS
2
radical cation, reported previously, occurs only
66, 2656-2659. (b) Bondybey, V. E.; English, J. H.; Miller, T. A. J.
Chem. Phys. 1979, 70, 1621-1625.
under the action of vacuum-UV radiation. None of the IR
spectra recorded for photolyzed matrixes initially containing
(29) Taylor, G. W.; Setser, D. W.; Coxon, J. A. J. Mol. Spectrosc. 1972,
44, 108-117 and references cited therein.
Inorganic Chemistry, Vol. 46, No. 11, 2007 4695

Tob o´ n et al.
•
•
Figure 3. Plots as a function of irradiation time of the intensities of the bands assigned to (a) Cl ‚‚‚SCS, SCCl2, and ClCS , (b) syn-ClC(S)SCl, (c)
•
ClC(S)S , and (d) anti-ClC(S)SCl in the IR spectrum of an Ar matrix initially containing Cl2, CS2, and Ar in the proportion of 0.5:1:200.
reason to believe that photodissociation of CS
a significant part in the photochemistry displayed by matrix-
2
alone plays
depicted in Figure 3. This brings to light significant aspects
of the growth or decay of the species in question. Thus, the
syn and anti forms of ClC(S)SCl start to decay after 15 min
of broad-band UV-vis irradiation, whereas the radicals
isolated mixtures of CS
2
and Cl
2
. Instead, it would appear
•
that Cl
2
or Cl atoms act through coordination or, at the very
•
•
least, close proximity to photosensitize the CS
2
. Therefore,
ClC(S)S and ClCS start to grow. As indicated above, the
•
•
almost certainly, species such as ClCS and SCCl
2
evolve
ClCS radical is unlikely to be formed directly from CS
2
•
; a
•
•
primarily from the complexes Cl
Cl and S atoms being formed simultaneously. It is likely,
2
‚‚‚SCS and Cl ‚‚‚SCS, with
more plausible precursor is ClC(S)S , making ClCS a
•
photoevolution product from syn- and anti-ClC(S)SCl. It was
too, that the chlorocarbon products are formed in a similar
found that the relative yields of SCCl
ClC(S)SCl increased as the concentration of Cl
By contrast, an excess of Cl relative to CS
increased yield of CCl
an excess of CS favors reaction network 1, whereas an
excess of Cl favors network 2 outlined in Scheme 2.
The geometric and vibrational properties of the species
syn-ClC(S)SCl and anti-ClC(S)SCl have been simulated
by ab initio (HF, MP2) and DFT (B3LYP) methods in
combination with a 6-31+G* basis set, with the results
presented in Table 2. The most intense IR absorptions
predicted by the calculations are in good agreement with the
features observed for the new products. In view of the
calculated wavenumbers and IR intensities, there was
significantly less chance of locating any of the other
fundamental bands under the conditions prevailing in our
experiments. The calculated geometric parameters are pre-
sented as Supporting Information.
2
and syn- and anti-
•
•
•
way from complexes such as ClCS ‚‚‚Cl or Cl ‚‚‚SCCl
2
,
2
decreased.
2
led to an
although no positive evidence of these intermediates was
2
•
apparent. Both the Cl and S atoms are relatively immobile
4
. The inference to be drawn is that
30
in a solid Ar matrix at ∼15 K, even if the extra energy
supplied by the photolyzing radiation may be sufficient to
mobilize them to some extent. The photochemistry observed
is therefore likely to be dominated by the interactions
between molecules or between molecules and atoms that are
already held close together within a common matrix cage.
The formation of both syn and anti forms of the chlo-
rothiocarbonylsulfenyl chloride, ClC(S)SCl, is apparent from
the earliest stages of irradiation. There is no evidence to
suggest that one rotamer is formed first and converted into
the other upon continued photolysis (cf., the behavior of
2
2
4
chlorocarbonylsulfenyl chloride, ClC(O)SCl ). The highly
•
reactive complex Cl ‚‚‚SCS is most likely to be the precursor
to the syn and anti forms of ClC(S)SCl (as suggested in
Scheme 1).
(ii) Br
2
+ CS
2
. Similar studies were carried out with
, CS , and Ar, typically
matrixes formed by mixtures of Br
2
2
To help determine the sequence of the changes, the
integrated intensities of some of the new bands have been
monitored as a function of irradiation time, with the results
(
30) Himmel, H.-J.; Downs, A. J.; Greene, T. M. Chem. ReV. 2002, 102,
4191-4241 and references cited therein.
4696 Inorganic Chemistry, Vol. 46, No. 11, 2007

Halogenothiocarbonylsulfenyl Halides
Scheme 2. Possible Mechanisms of the Photochemical Reactions Occurring in an Ar Matrix Doped with Cl2 and CS2 at ∼15 K
in the proportions 2:1:200 or 1:1:200. The IR spectrum of
the matrix recorded immediately after deposition was
veloped in these conditions, together with literature data for
2
2
31
the singlet molecules SCBr
radical.
2
and CBr
4
and the •CBr
3
17,18
27,31
dominated by the absorptions of CS
complicated by the presence of both the free CS
2
,
made more
molecule
The expo-
2
As in the experiments with Cl , the reactions are presum-
2
1
9
and the van der Waals complex Br
2
‚‚‚CS
2
.
ably initiated primarily by the photodisociation of Br
2
to give
•
sure of such a matrix to broad-band UV-vis light pro-
duced significant changes in the spectrum, as illustrated
in Figures 4-6. Table 3 lists the wavenumbers, as well as
the proposed assignments, of the absorptions that de-
Br atoms. Two new bands in the νas(CS
2
) region at 1499.4
-
1
and 1493.7 cm were observed to develop after irradiation
-1
with shifts of -28.7 and -30.8 cm , respectively, compared
with free CS
2
. In the light of the precedent set by the complex
•
formed between Cl and CS
2
, an analogous complex between
•
Br and CS
2
would be the obvious carrier of these bands.
Because we found no prior information about such a
complex, we have performed calculations to determine the
optimized geometry and vibrational properties of the complex
Figure 4. FT-IR spectra of an Ar matrix containing Br2 and CS2
(
deposition (bottom) and after 240 min of photolysis (top).
Figure 5. FT-IR spectra of an Ar matrix containing Br2 and CS2
(Br2/CS2/Ar ) 2:1:200) in the region of 850-400 cm immediately after
deposition (bottom) and after 240 min of photolysis (top).
Br2/CS2/Ar ) 2:1:200) in the region of 1230-900 cm-1 immediately after
-1
Inorganic Chemistry, Vol. 46, No. 11, 2007 4697

Tob o´ n et al.
relevant portion of the spectrum is illustrated in Figure 6.
The continuation of photolysis resulted in the appearance
of more new bands. Two of these, centered near 1109/1108
-
1
and 691/687 cm , are recognizable as the fundamentals ν
1
2
2
and ν
4 2
, respectively, of the SCBr molecule. A third band
occurring near 675 cm can be identified as the ν
fundamental of CBr
attributed to the •CBr
-
1
3
3
1
-1
4
, while a fourth close to 767 cm is
2
7,31
3
radical.
In addition, the spectrum showed the growth of new bands
that could not be attributed to any known species. One group
of such bands, with centers near 1140/1139, 713, 466, and
-
1
4
36/435 cm , with a common growth/decay pattern, can
be plausibly assigned to the hitherto unknown molecule syn-
Figure 6. FT-IR spectra of an Ar matrix containing Br2 and CS2
Br2/CS2/Ar ) 2:1:200) in the region of 1550-1450 cm-1 immediately
after deposition (bottom), after 60 min of photolysis (middle), and after
40 min of photolysis (top).
BrC(S)SBr on the basis of the wavenumbers and pattern of
(
79
81
the Br/ Br isotopic splitting. Similarly, another group, with
-
1
band centers at ∼1087/1084, 823, and 417/416 cm can be
2
identified with the corresponding anti isomer. As in the
Table 3. Wavenumbers and Assignments of the IR Absorptions
Appearing after Broad-Band UV-vis Photolysis of an Ar Matrix
Containing a Mixture of CS2 and Br2 at ∼15 K
2
experiments with Cl , both the syn and anti rotamers appear
to be formed simultaneously in the matrix.
Yet another band also appeared weakly on photolysis.
wavenumbers
reported previously
-
1
Ar matrix
ν (cm-1)
assignment
vibrational mode
This, occurring at 1190.6 cm , was distinguished by a
growth pattern quite unlike that of any other band. The
wavenumber value implies that it arises from a species
containing a CdS group. After careful analysis of the
different species that might be formed in primary or
secondary photochemical processes, including some com-
putational tests, this band seems most likely to belong to
molecule
ν (cm-1
)
•
32
32
1
1
1
1
1
1
1
1
1
8
7
7
6
6
6
6
4
4
4
4
4
499.4
493.7
190.6
140.4
138.9
108.8
107.6
086.8
084.1
23.2
67.0
13.4
91.3
86.8
74.7
63.1
66.1
36.2
34.7
16.8
15.9
Br ‚‚‚SdCdS
νas( SdCd S)
this work
this work
this work
this work
•
34
32
Br ‚‚‚SdCdS
νas( SdCd S)
ν(CdS)
•
BrCS
syn-BrC(S)SBr ν(CdS)
SCBr2
ν(CdS) (ν1)
1109.0a
•
the hitherto unknown radical BrCS . There was no sign that
anti-BrC(S)SBr ν(CdS)
anti-BrC(S)SBr νas(Br-C-S)
this work
•
•
the BrC(S)S radical, a likely precursor to BrCS , is produced
(
this work
773b
•
cf. ClC(S)S ).
•CBr3
νas(CBr3) (ν3)
3
1
syn-BrC(S)SBr νas(Br-C-S)
this work
Failure to detect this last species, the carbene :CBr
or
2
SCBr2
νas(Br-C-Br) (ν4)
688.5a
32
either SBr or SBr
2
marks points of departure from the
, although the relevant features could
675b
experiments with Cl
CBr4
SCBr2
νas(C-Br) (ν3)
νas(Br- C-Br) (ν4)
2
1
3
664.2a
well be masked by more intense absorptions from other
products. A further difference emerges with the discovery
that the relative yields of the various photoproducts in the
syn-BrC(S)SBr νs(Br-C-S)
syn-BrC(S)SBr ν(S- Br)
81
this work
this work
7
9
ν(S- Br)
79
anti-BrC(S)SBr ν(S- Br)
this work
Br
primary reagents. Enhanced yields of all the products were
observed as the concentration of Br was increased. It may
be that the greater bulk of Br limits to one the number of
dihalogen molecules that can be accommodated within the
2
experiments are not affected by the proportions of the
8
1
ν(S- Br)
a
Ref 22. b Ref 31.
2
2
Table 4. Experimental and Calculated Wavenumbers and Wavenumber
-
1
Shifts (in cm ) for the νas(SdCdS) Fundamental of the Complex
•
Br ‚‚‚SdCdS
same immediate reaction sphere as the CS
energetic Br atoms having the power to add to the primary
reactions. By contrast, more than one dihalogen molecule
2
, with only
•
B3LYP/6-31+G*
Ar matrix
species
νas(SdCdS) ∆ν(SdCdS) νas(SdCdS) ∆ν(SdCdS)
•
may be admitted to this sphere in the case of Cl
2
, with a
Br ‚‚‚SdCdS
1521.0
1517.7
1516.7
1513.7
-28.2
-27.9
-28.9
-28.3
1499.4
1493.7
-28.7
-30.8
•
34
Br ‚‚‚ SdCdS
probability that increases as the square of the Cl concentra-
2
•
34
Br ‚‚‚SdCd S
34
tion. Taking account of the species observed and their
behavior with increasing irradiation time (as revealed in
Figure 7), we are led to propose the reaction paths for the
•
34
Br ‚‚‚ SdCd S
•
Br ‚‚‚SCS. The results of these calculations give wavenumber
shifts for the νas(SdCdS) fundamental in satisfactory
agreement with the experimental shifts. The more intense
band then corresponds to the predominant isotopomer
system Br
2 2
/CS set out in Scheme 3.
The syn and anti forms of BrC(S)SBr are generated
•
•
presumably by the addition of a Br atom to the Br ‚‚‚SCS
•
32
32
Br ‚‚‚ SdCd S, while the weaker one, toward lower
complex but are themselves photolabile and decompose upon
•
energy, corresponds to the less abundant isotopomer
continued irradiation to furnish the BrCS radical, as depicted
•
32
34
Br ‚‚‚ SdCd S. The results are listed in Table 4, and the
(32) Sulphur; Gmelin Handbook of Inorganic Chemistry Suppl. Vol. 2;
(31) Andrews, L.; Carver, T. G. J. Chem. Phys. 1968, 49, 896-902.
Springer-Verlag: Heidelberg, Germany, 1978.
4698 Inorganic Chemistry, Vol. 46, No. 11, 2007

Halogenothiocarbonylsulfenyl Halides
•
•
Figure 7. Plots as a function of irradiation time of the intensities of the bands assigned to (a) Br ‚‚‚SCS and BrCS , (b) syn-BrC(S)SBr, (c) SCBr2, and (d)
anti-BrC(S)SBr in the IR spectrum of an Ar matrix initially containing Br2, CS2, and Ar in the proportion of 2:1:200.
Scheme 3. Possible Mechanisms of the Photochemical Reactions Occurring in an Ar Matrix Doped with Br2 and CS2 at ∼15 K
Table 5. Experimental and Calculated IR Spectra of syn-Bromothiocarbonylsulfenyl Bromide, syn-BrC(S)SBr, and anti-Bromothiocarbonylsulfenyl
a
Bromide, anti-BrC(S)SBr
syn-BrC(S)SBr
theoretical calculations
HF/6-31+G* B3LYP/6-31+G* MP2/6-31+G*
anti-BrC(S)SBr
Ar matrix
ν (cm-1)
Ar matrix
ν (cm-1
theoretical calculations
vibrational
mode
)
HF/6-31+G* B3LYP/6-31+G* MP2/6-31+G*
1
1
7
4
140.4
138.9
13.4 (44)
66.1 (4)
1104.0 (100)
1148.5 (100)
1192.7 (100) 1086.8
1084.1
1057.0 (100)
1061.0 (100)
1122.0 (91)
ν(CdS)
(100)
(100)
}
}
732.6 (32)
665.5 (34)
461.2 (4)
456.7 (1)
703.7 (35)
462.2 (6)
433.5 (2)
396.1
823.2 (41)
822.9 (39)
373.7 (4)
467.6 (<1)
833.0 (76)
374.1 (9)
471.6 (1)
843.0 (100)
345.8 (11)
426.4 (2)
νas(Br-C-S)
νs(Br-C-S)
456.7 (<1)
b
456.8 (<1)
δoop
7
9
4
36.2
449.5
448.5
430.7
(18)
}
416.8
459.5
458.7
259.5 (<1)
414.5
(27)
}
400.0
(20)
}
ν(S- Br)
} (15)
}
(9)
}
(9)
} (11)
}
(6)
81
4
34.7
429.1
394.7
415.9
413.7
399.3
ν(S- Br)
250.5 (<1)
237.6 (1)
237.2 (2)
259.8 (1)
262.1 (3)
δ(Br-CdS)
a
Wavenumbers in cm-1; relative intensities given in parentheses. b δoop ) out-of-plane deformation.
in Scheme 3. This change opens the way to several secondary
radical may then recombine with these atoms, still held in
•
channels. Thus, BrC(S)SBr dissociates first to give BrCS ,
the same matrix cage, to regenerate BrC(S)SBr, or it may
•
•
•
together with the S and Br atoms. The highly reactive BrCS
add only a Br atom to form SCBr
2
.
Inorganic Chemistry, Vol. 46, No. 11, 2007 4699

Tob o´ n et al.
Table 6. Experimental and Calculated IR Spectra of the
The geometric and vibrational properties of the new
Bromothiocarbonyl Radical, BrCS•a
•
species syn-BrC(S)SBr, anti-BrC(S)SBr, BrCS , and the
•
Ar matrix
ν [cm-1]
theoretical calculations
B3LYP MP2
Br ‚‚‚SCS complex have been simulated by ab initio and DFT
vibrational
mode
HF
methods using a 6-31+G* basis set for the C and S atoms
1
5
1190.6
1019.8 (100) 1195.4 (100) 1683.4 (100) ν(CdS)
and a LANL2DZ basis set, including an effective core
potential (ECP), for the Br atoms, with the results set out in
Tables 4-6. The most intense IR absorptions predicted by
the calculations tally well with the features observed for the
new products in the matrix spectra. The geometric parameters
are presented as Supporting Information.
4
91.3 (84)
491.1 (24)
416.0 (7)
241.7 (2)
ν(C-Br)
δ(Br-CdS)
254.4 (<1)
262.0 (<1)
a
Wavenumbers in cm-1; relative intensities given in parentheses.
Table 7. Wavenumbers (in cm-1) and Assignments of the IR
Absorptions Appearing after Broad-Band UV-vis Photolysis of an Ar
Matrix Containing a Mixture of CS2, Cl2, Br2, and BrCl at ∼15 K
2 2 2
(iii) BrCl + CS . Gaseous mixtures of Cl and Br give
wavenumbers
rise to an equilibrium mixture including these two species
Ar matrix
assignment
vibrational mode
reported previously
11
and the interhalogen BrCl, the components of which cannot
ν (cm-1)
molecule
ν (cm-1
)
2 2 2
be separated. When a gaseous mixture of Cl , Br , CS , and
•
32
32
1499.4
1493.8
1481.7
1188.8
1190.0
1144.8
1143.4
1139.9
1129.9
Br ‚‚‚SdCdS
νas( SdCd S)
this work
this work
Ar, typically in the initial proportions 2:2:1:200, was
deposited on a CsI window at ∼15 K, the IR spectrum of
the resulting matrix showed only the absorptions character-
•
34
32
Br ‚‚‚SdCdS
νas( SdCd S)
νas(SdCdS)
ν(CdS)
•
a
Cl ‚‚‚SdCdS
1468
•
•
1189.3b
ClCS
BrCS
17,18
-1 33
ν(CdS)
ν(CdS)
this work
this work
this work
this work
1130.0
istic of free CS
,
BrCl (near 420 cm ), and the van
2
syn-ClC(S)SCl
der Waals complex ClBr‚‚‚SCS, which was reported only
syn-BrC(S)SCl ν(CdS)
syn-BrC(S)SBr ν(CdS)
SCCl2
1
9
very recently.
ν(CdS) (ν1)
Subsequent irradiation of the matrix with broad-band UV-
vis light led to significant changes in the spectrum; new
bands appeared and grew, notably at the expense of the bands
from the complex ClBr‚‚‚SCS. The first to appear were bands
1
123.8c
1
1
1
1
1
1
9
8
8
8
7
7
7
7
7
7
128.6
120.0
108.7
104.2
088.7
054.7
14.5
83.6
08.7
01.2
85.4
syn-ClC(S)SBr ν(CdS)
this work
BrC(S)Cl
SCBr2
ν(CdS)
1106d
ν(CdS) (ν1)
1109.0c
anti-ClC(S)SBr ν(CdS)
this work
this work
this work
this work
this work
this work
this work
785.0c
-1
around 1499 and 1482 cm , which were recognized readily
from the experiments with Br and Cl as separately arising
from the molecular complexes formed by the interaction of
anti-ClC(S)SCl ν(CdS)
anti-BrC(S)SCl ν(CdS)
2
2
•
ClC(S)S
ν(CdS)
anti-ClC(S)SBr νas(Cl-C-S)
•
•
a Br or Cl atom with a CS
2
molecule. As in the experiments
syn-ClC(S)SCl
syn-ClC(S)SBr
SCCl2
νas(Cl-C-S)
νas(Cl-C-S)
νas(Cl-C-Cl) (ν4)
νas(CCl3)
previously described, therefore, the first step involves pho-
•
•
todissociation of the dihalogen to give Cl and Br atoms
77.7
51.6
38.6
37.6
BrCCl3
777.8e
which bind loosely to CS
Waals complexes Cl ‚‚‚SCS and Br ‚‚‚SCS, respectively.
2
in the formatio of the van der
syn-BrC(S)SCl
:CBrCl
BrC(S)Cl
BrCCl3
νas(Br-C-S)
νas(Br-C-Cl)
νas(Br-C-Cl)
νs(CCl3)
this work
f
•
•
739
742d
Continued photolysis gave rise to new bands in other
24.7
725.7
7
23.9e
regions of the spectrum. Two of these bands, occurring at
713.8
691.3
556.0
528.2
518.9
472.3
466.9
453.4
451.9
436.2
434.7
syn-BrC(S)SBr νas(Br-C-S)
this work
-1
∼
1120 and 738 cm , can be identified as the ν(CdS) and
SCBr2
νas(Br-C-Br) (ν4)
νs(Cl-C-S)
688.5c
ν
as(Br-C-Cl) modes of the thiocarbonyl dihalide BrC(S)-
syn-ClC(S)SBr
this work
this work
this work
this work
syn-BrC(S)SCl ν(S-Cl)
Cl, a compound first synthesized by Diderrich and Haas in
anti-BrC(S)SCl ν(S-Cl)
34
1
976. The spectrum of the liquid was then reported,
syn-BrC(S)SCl
νs(Br-C-S)
although no assignment of the bands was proposed. Theo-
retical calculations support, and offer an interpretation of the
earlier, as well as the present, results with the assignments
given in Tables 7 and 10. The spectrum of the photolyzed
7
9
syn-ClC(S)SBr ν(S- Br)
this work
this work
8
1
ν(S- Br)
7
9
syn-BrC(S)SBr ν(S- Br)
8
1
ν(S- Br)
3
1
matrix also revealed the presence of the carbene :CBrCl
a
Ref 20. b Ref 26. c Ref 22. d Ref 34 (IR spectrum of the liquid). e Ref
2
3
3. f Ref 31.
and the tetrahalomethane BrCCl
3
.
The first was recogniz-
able by a band at 738.6 cm and the second by the bands
2
-
1
Table 8. Experimental and Calculated IR Spectra of syn-Chlorothiocarbonylsulfenyl Bromide, syn-ClC(S)SBr, and anti-Chlorothiocarbonylsulfenyl
a
Bromide, anti-ClC(S)SBr
syn-ClC(S)SBr
theoretical calculations
HF/6-31+G* B3LYP/6-31+G* MP2/6-31+G*
anti-ClC(S)SBr
theoretical calculations
HF/6-31+G* B3LYP/6-31+G* MP2/6-31+G*
Ar matrix
ν (cm-1)
Ar matrix
ν (cm-1
1104.2 (100) 1074.5 (100)
vibrational
mode
)
1
8
5
128.6 (100) 1113.8 (100)
1142.2 (100)
717.7 (50)
500.2 (7)
1188.1 (100)
786.8 (68)
520.6 (7)
1077.2 (100)
863.9 (80)
476.8 (7)
1141.9 (80)
903.9 (100)
497.1 (6)
ν(CdS)
01.2 (80)
56.0 (1)
794.6 (43)
501.2 (3)
883.6 (90)
869.9 (45)
486.0 (1)
νas(Cl-C-S)
νs(Cl-C-S)
b
466.4 (<1)
467.3 (1)
443.6 (1)
468.0 (<1)
469.2 (1)
436.4 (1)
δoop
7
9
4
4
53.4
51.9
462.2
461.3
453.9
452.6
304.1 (1)
420.6
419.8
315.0 (<1)
439.3
409.2
(26)
}
485.3
(14)
}
ν(S- Br)
} (5)
}
(4)
}
(9)
}
(5)
}
(9)
81
438.5
408.4
384.6
ν(S- Br)
309.5 (<1)
301.8 (<1)
303.0 (2)
307.9 (4)
δ(Cl-CdS)
a
Wavenumbers in cm-1; relative intensities given in parentheses. b δoop ) out-of-plane deformation.
4700 Inorganic Chemistry, Vol. 46, No. 11, 2007

Halogenothiocarbonylsulfenyl Halides
Table 9. Experimental and Calculated IR Spectra of syn-Bromothiocarbonylsulfenyl Chloride, syn-BrC(S)SCl, and anti-Bromothiocarbonylsulfenyl
Chloride, anti-BrC(S)SCl
syn-BrC(S)SCl
theoretical calculations
HF/6-31+G* B3LYP/6-31+G* MP2/6-31+G*
anti-BrC(S)SCl
theoretical calculations
HF/6-31+G* B3LYP/6-31+G* MP2/6-31+G*
Ar matrix
ν (cm-1)
Ar matrix
ν (cm-1
vibrational
mode
)
1
7
5
143.4 (100) 1108.8 (100)
1153.0 (100)
675.5 (33)
1191.9 (100)
716.7 (37)
1054.7 (100) 1058.5 (100)
822.2 (35)
1065.4 (100)
833.6 (70)
1130.2 (100)
835.6 (77)
ν(CdS)
51.6 (50)
28.2 (10)
741.9 (27)
νas(Br-C-S)
3
5
534.7
497.4
(20)
}
542.4
(17)
}
518.9 (50)
525.2
520.1
386.1 (4)
457.4
(42)
}
521.2
(32)
}
ν (S- Cl)
(13)
(14)
}
}
37
529.6
491.3
536.0
452.8
514.7
ν(S- Cl)
4
4
4
72.3 (3)
462.7 (2)
468.9 (9)
464.5 (1)
472.4 (8)
430.5 (2)
384.4 (9)
464.3 (1)
373.3 (10)
427.2 (2)
νs(Br-C-S)
b
72.3
463.4 (<1)
459.6 (<1)
δoop
}
66.9
255.6 (<1)
242.7 (2)
243.3 (2)
275.8 (1)
275.9 (2)
288.1 (2)
δ(Br-CdS)
a
Wavenumbers in cm-1; relative intensities given in parentheses. b δoop ) out-of-plane deformation.
Table 10. Experimental and Calculated IR Spectra of Thiocarbonyl Chloride Bromide, BrC(S)Cl
Ar matrix
ν (cm-1)
reported valuesb
theoretical calculations
ν (cm-1
)
HF/6-31+G*
B3LYP/6-31+G*
MP2/6-31+G*
vibrational mode
1
7
120.0 (100)
37.6 (90)
1106
742
1117.9 (100)
785.7 (53)
1124.0 (100)
724.7 (80)
498.7 (1)
433.5 (6)
263.2 (<1)
243.6 (<1)
1167.8 (100)
769.8 (91)
454.5 (1)
433.5 (9)
262.8 (1)
ν(CdS)
νas(Br-C-Cl)
4
4
2
2
87.2 (<1)
δoopc
νs(Br-C-Cl)
δ(Cl-CdS)
δ(Br-C-Cl)
34.9 (3)
61.8 (<1)
37.6 (<1)
250.3 (<1)
a
Wavenumbers in cm-1; relative intensities given in parentheses. b Ref 34 (liquid phase). c δoop ) out-of-plane deformation.
-
1
at 777.7 and 724.7 cm . Table 7 lists not only the
wavenumbers and suggested origins of all the new absorp-
tions observed to develop under these conditions but also
•
20
• 26
relevant literature data for the species Cl ‚‚‚SCS, ClCS ,
31
23
22
22
:CBrCl, BrCCl
3 2 2
, SCCl , and SCBr , similarly isolated
3
4
in Ar matrixes, as well as for liquid BrC(S)Cl.
The spectrum confirmed that BrC(S)Cl is not the only
thiocarbonyl dihalide to be formed because the absorp-
2
2
22
tions characteristic of SCCl
2
and SCBr
2
also appear
upon photolysis. In addition, bands corresponding to the syn
forms of both ClC(S)SCl and BrC(S)SBr could be dis-
cerned, although the yields were low. The presence of the
anti form of each species could be inferred only by the
perception of weak shoulders on the bands from the syn form.
Very weak bands which appeared only after irradiation for
•
26
•
2
h were identifiable as the radicals ClCS , BrCS , and
•
ClC(S)S .
Moreover, the spectrum included new bands not attribut-
able to any known species. One group of such bands with
-
1
centers near 1129, 801, 556, and 453/452 cm can be
ascribed to the hitherto unknown molecule syn-ClC(S)SBr,
while another group with centers near 1143, 752, 528, and
Figure 8. FT-IR spectra of an Ar matrix containing Cl2, Br2, and CS2
-
1
4
72/467 cm can be attributed to syn-BrC(S)SCl. These
-1
(Br2/Cl2/CS2/Ar ) 2:2:1:200) in the region of 1150-1050 cm immediately
identities were endorsed by the evidence of splitting at-
after deposition (bottom), after 15 min of photolysis (middle), and after
120 min of photolysis (top).
tributed to the isotopic pairs 7 Br and
9/81
35/37
Cl displayed by
certain bands and also by the results of quantum chemical
calculations (see Table 8). Four weak bands centered near
at 1104.2 and 883.6 cm-1 can be linked to anti-ClC(S)SBr,
and those at 1054.7 and 518.9 cm can be linked to anti-
-1
-
1
1104, 1055, 884, and 519 cm were seen as candidates for
BrC(S)SCl. The antisymmetric Br-C-S stretching funda-
mental of anti-BrC(S)SCl was masked presumably by intense
absorptions of the anti forms of ClC(S)SBr and BrC(S)SCl.
With the aid of further theoretical calculations, it was possible
satisfactorily to assign all four absorptions. Thus, the bands
-1
absorptions in the region of 840-700 cm resulting from
other molecules; the theoretical calculations predict a wave-
-
1
number of about 830 cm for this mode. Figures 8 and 9
illustrate two different regions of the IR spectrum of such a
matrix.
(
33) Wight, C. A.; Ault, B. S.; Andrews, L. J. Mol. Spectrosc. 1975, 56,
39-250.
34) Diderrich, G.; Haas, A. Chem. Ber. 1976, 109, 3432-3440.
2
(
Inorganic Chemistry, Vol. 46, No. 11, 2007 4701

Tob o´ n et al.
continued irradiation leads us to propose the reaction scheme
summarized in Scheme 4.
The optimized geometries and vibrational properties of all
the new species have been calculated by ab initio and DFT
methods using a 6-31+G* basis set for Cl, C, and S atoms
1
5
and a LANL2DZ basis set, including an effective core
potential (ECP), for Br atoms, with the results set out in
Tables 8 and 9. The most intense IR absorptions predicted
by the calculations anticipate the matrix features observed
for the new products well. On the evidence of the calculated
wavenumbers and IR intensities, there was significantly less
chance of locating any of the other fundamentals under the
experimental conditions described. The geometry and vi-
brational properties of the known molecule BrC(S)Cl have
also been calculated in the absence of any previous attempt
to determine its structure or to interpret its IR spectrum. The
vibrational results are given in Table 10. The calculated
geometric parameters of all these molecules are presented
as Supporting Information.
Figure 9. FT-IR spectra of an Ar matrix containing Cl2, Br2, and CS2
(
after deposition (bottom) and after 120 min of photolysis (top).
Conclusions
Br2/Cl2/CS2/Ar ) 2:2:1:200) in the region of 850-600 cm-1 immediately
Photoinduced reactions carried out in a solid Ar matrix at
∼
15 K doped with CS
Br , or BrCl) have been shown to give rise to one or more
2
2 2
and a dihalogen molecule XY (Cl ,
The behavior of certain bands as a function of irradiation
time, as shown in Figure 10, suggests that, as with the
halothiocarbonylsulfenyl halide molecules, XC(S)SY. Thus,
syn-ClC(S)SCl, anti-ClC(S)SCl, syn-BrC(S)SBr, anti-BrC-
(S)SBr, syn-ClC(S)SBr, anti-ClC(S)SBr, syn-BrC(S)SCl, and
anti-BrC(S)SCl have each been identified and characterized
2 2 2 2
systems Cl /CS and Br /CS , the photolytic processes are
•
•
mediated by the complexes Cl ‚‚‚SCS and Br ‚‚‚SCS. The
evidence of the species observed and of their response to
•
•
Figure 10. Plots as a function of irradiation time of the intensities of the bands assigned to (a) Br ‚‚‚SCS and Cl ‚‚‚SCS, (b) syn-BrC(S)SCl, (c) syn-ClC-
S)SBr, and (d) anti-ClC(S)SBr in the IR spectrum of an Ar matrix initially containing CS2, Cl2, Br2, and BrCl.
(
4702 Inorganic Chemistry, Vol. 46, No. 11, 2007

Halogenothiocarbonylsulfenyl Halides
Scheme 4. Possible Scheme for the Photochemical Reactions Occurring in an Ar Matrix Doped with CS2 and BrCl at ∼15 K
Table 11. Comparison of the Energy Difference and Energy Barrier
between syn and anti Forms of Carbonylsulfenyl and
that the energy barrier for interconversion of the syn and
anti rotamers is quite high and not very different for the
carbonylsulfenyl and thiocarbonylsulfenyl derivatives
Thiocarbonylsulfenyl Compounds of the Type XC(E)SY (X, Y ) Cl or
a
Br; E ) O or S) Calculated with the B3LYP Method
-1
(
10-14 kcal mol ), although the energy difference between
∆
E anti-syn
energy barrier
(kcal mol )
-
1
-1
the minima is smaller in the thiocarbonylsulfenyl case
molecule
(kcal mol
)
-1
(
0.2-1.4 vs 2.6-3.8 kcal mol ). If a matrix containing syn-
ClC(O)SCl
ClC(S)SCl
BrC(O)SBr
BrC(S)SBr
ClC(O)SBr
ClC(S)SBr
BrC(O)SCl
BrC(S)SCl
2.6
0.4
3.6
0.3
2.9
0.2
3.8
1.4
12.5
12.4
12.1
11.2
11.3
10.9
13.8
13.7
XC(O)SY is irradiated with broad-band UV-vis light,
1,4
however, partial isomerization to the anti form occurs.
Table 11 compares the energy differences and energy barriers
calculated for carbonylsulfenyl and thiocarbonylsulfenyl
compounds by the B3LYP/6-31+G* method.
a
Using a 6-31+G* basis set for C, S, and Cl atoms and a LANL2DZ
Acknowledgment. The authors acknowledge with thanks
a British Council- Fundaci o´ n Antorchas award for British-
Argentine cooperation. C.O.D.V. and R.M.R. thank Jesus
College, Oxford, the Consejo Nacional de Investigaciones
Cient ´ı ficas y T e´ cnicas (CONICET) (PIP 4695), the Comisi o´ n
de Investigaciones Cient ´ı ficas de la Provincia de Buenos
Aires (CIC), and the Facultad de Ciencias Exactas, Univer-
sidad Nacional de La Plata, for financial support. R.M.R. is
also grateful to the Fundaci o´ n Antorchas and to the Royal
Society of Chemistry for a grant for international authors.
In addition, A.J.D. is indebted to the EPSRC for support
allowing the purchase of equipment, while Y.A.T. acknowl-
edges a Deutscher Akademischer Austausch Dienst (DAAD)
award. C.O.D.V. thanks the DAAD, which generously
sponsors the DAAD Regional Program of Chemistry of the
Republic Argentina supporting Latin-American students to
obtain their PhD in La Plata.
1
5
basis set, including an effective core potential (ECP), for Br atoms.
at least partially by their IR spectra, with findings endorsed
by the results of appropriate quantum chemical calculations.
Some radicals, namely, ClC(S)S , Br ‚‚‚SCS, and BrCS , have
also been detected and characterized for the first time as
reactive intermediates of the reactions starting from Cl
•
•
•
2 2
, Br ,
or BrCl.
The yields of the different photoproducts are liable to vary
significantly with the proportions dihalogen/CS present in
the matrix. In the case of Cl , the amounts of SCCl and
syn- and anti-ClC(S)SCl formed were found to increase as
the proportion of Cl decreased, while an excess of Cl
relative to CS led to an increased yield of CCl . In the
reactions starting from Br , however, all of the products were
formed in higher concentrations as the proportion of Br to
CS increased.
Whereas the photochemical reactions involving CS
a dihalogen molecule XY (Cl , Br , or BrCl) led to the
2
2
2
2
2
2
4
2
2
2
2
and
Supporting Information Available: Calculated optimized
geometric parameters (i) of the syn and anti conformers of each of
ClC(S)SCl, BrC(S)SBr, ClC(S)SBr, and BrC(S)SCl and (ii) of the
2
2
simultaneous formation of the syn and anti forms of the
respective halogenothiocarbonylsulfenyl halide molecule,
XC(S)SY, the analogous reactions involving OCS yielded
only the syn forms of the corresponding halogenocarbonyl-
sulfenyl halide, XC(O)SY.2 Theoretical calculations predict
•
•
•
radicals ClC(S)S , BrCS , and Br ‚‚‚SCS. This material is available
free of charge via the Internet at http://pubs.acs.org.
,3
IC070119+
Inorganic Chemistry, Vol. 46, No. 11, 2007 4703