Singlet Halophenylcarbenes as Strong Hydrogen-Bond Acceptors

Article abstract of DOI:10.1021/acs.jpca.6b02550

Chlorophenylcarbene and fluorophenylcarbene were generated in water-doped argon matrices at cryogenic temperatures by photolysis of the corresponding matrix-isolated diazirines. When diffusion of H₂O in solid argon was induced by annealing of the matrices at temperatures above 20 K, hydrogen-bonded complexes between the carbenes and water were formed. UV photolysis of these complexes resulted in the formation of benzaldehyde and hydrogen halides HX. The same products were obtained after photolysis of the diazirines in amorphous water ice. Obviously, the primary insertion product of the carbenes into H-OH is unstable under these conditions, and benzaldehyde is formed via secondary photolysis. The stable primary photochemical insertion product of chlorophenylcarbene into an O-H bond was observed in the reaction of the carbene with methanol.

Full text of DOI:10.1021/acs.jpca.6b02550

Subscriber access provided by BALL STATE UNIV
Article
Singlet Halophenylcarbenes as Strong Hydrogen Bond Acceptors
Genevieve Richter, Enrique Mendez Vega, and Wolfram Sander
J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.6b02550 • Publication Date (Web): 27 Apr 2016
Downloaded from http://pubs.acs.org on April 28, 2016
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
The Journal of Physical Chemistry A is published by the American Chemical Society.
1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
Singlet Halophenylcarbenes as Strong Hydrogen Bond Acceptors
*
Geneviève Richter, Enrique MendezꢀVega, and Wolfram Sander
Lehrstuhl für Organische Chemie II, RuhrꢀUniversität Bochum, Dꢀ44780 Bochum, Germany
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Abstract
Chlorophenylcarbene and fluorophenylcarbene were generated in waterꢀdoped argon matrices at
cryogenic temperatures by photolysis of the corresponding matrixꢀisolated diazirines. When
diffusion of H O in solid argon was induced by annealing of the matrices at temperatures above
2
20 K, hydrogenꢀbonded complexes between the carbenes and water were formed. UV photolysis
of these complexes resulted in the formation of benzaldehyde and hydrogen halides HX. The
same products were obtained after photolysis of the diazirines in amorphous water ice.
Obviously, the primary insertion product of the carbenes into HꢀOH is unstable under these
conditions, and benzaldehyde is formed via secondary photolysis. The stable primary
photochemical insertion product of chlorophenylcarbene into an OꢀH bond was observed in the
reaction of the carbene with methanol.
Introduction
The properties of closedꢀshell singlet carbenes are governed by the presence of a lone pair in the
σꢀplane and an empty π orbital, rendering them both nucleophilic and electrophilic. Substituents
strongly influence the philicity of singlet carbenes, and the spectrum of carbene reactivity ranges
1
, 2
from the extremely electrophilic difluorovinylidene that even with CO reacts as electrophile
2
3
4
by abstracting an oxygen atom, to the highly nucleophilic Nꢀheterocyclic carbenes (NHCs) that
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 2 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
are more or less stable under ambient conditions. Typical electrophilic reactions of singlet
carbenes are the formation of complexes and ylides with N and O containing aprotic compounds
5
6
such as ethers. Singlet carbenes are strong neutral bases, and for the parent singlet CH a proton
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
affinity (PA) of 207 kcal/mol, similar to that of NH (204 kcal/mol) was determined. Typical
3
7
NHCs are even more basic and show PAs between 250 and 260 kcal/mol. The lowestꢀlying
(closedꢀshell) singlet states of fluorenylidene (FL) and diphenylcarbene (DPC, Chart 1) are
8, 9
among the most basic neutral compounds with PAs of 272 and 275 kcal/mol, respectively.
Reaction heats and rate constants of the protonation of carbenes to yield carbocations have been
1
0, 11
determined by timeꢀresolved photoacoustic calorimetry
and by stoppedꢀflow laserꢀflash
1
2
photolysis. Therefore, singlet carbenes should be able to act as powerful hydrogen bond
acceptors. An interesting example for a hydrogenꢀbonded carbene complex is the complex
13
between two NHCs bridged by a single proton resulting in a strong C···H···C hydrogen bond.
In contrast to the (closedꢀshell) singlet states of carbenes, the triplet states do not form hydrogen
bonds, and therefore hydrogen bonding stabilizes the singlet state of a carbene with respect to the
triplet state. This results in a decrease of the singletꢀtriplet splitting or even in a reversal of the
ground state of triplet carbenes. This has been recently used by us to switch the spin state of
1
4ꢀ16
diphenylcarbene and fluorenylidene, respectively, from triplet to singlet.
Chart 1. Structures of arylcarbenes.
Chlorophenylcarbene 1a and fluorophenylcarbene 1b are prototypical reactive singlet ground
state carbenes of low nucleophilicity. The chemistry of 1a in solution was studied in great detail
ACS Paragon Plus Environment

Page 3 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
17, 18
19ꢀ21
by trapping experiments,
matrix isolation spectroscopy,
and by timeꢀresolved
2
2ꢀ25
spectroscopy (Scheme 1).
As a singlet carbene, 1a reacts only very slowly (compared to
1
9
triplet carbenes) with molecular oxygen to form the corresponding carbonyl Oꢀoxide. UVꢀ
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
photolysis of matrixꢀisolated 1a results in ring opening to form cycloheptatetraene 4 in high
2
0
yields. The chemistry of fluorophenylcarbene 1b has also been studied by time resolved
2
6ꢀ28
29ꢀ31
spectroscopy
of 1a.
and low temperature spectroscopy,
and, as expected, is rather similar to that
Scheme 1. Photochemistry of diazirines 2a and b under the conditions of matrix isolation.
Here, we describe the formation of hydrogenꢀbonded complexes between carbenes 1a and b as
hydrogen bond acceptor and water and methanol, respectively, as hydrogen bond donors. An
interesting aspect is that hydrogen bonding changes the photochemistry of the carbenes, which
has to be considered when generating these carbenes by photolysis of precursors in solution.
Results and Discussion
Chlorophenylcarbene Water Complex. Chlorophenylcarbene 1a was generated in solid argon
doped with 0.1–1% water by visible light photolysis (405 nm) of chlorophenyldiazirine 2a at 3 K.
Under these conditions, matrices are very rigid and diffusion, even of small molecules such as
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 4 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
H O, is efficiently inhibited. After the photolysis the IR spectra show the presence of carbene 1a,
2
isolated water molecules, and water clusters (dimers and higher, depending on the water
concentration). Annealing of these matrices at temperatures between 25 and 35 K allows water
molecules to diffuse and to undergo aggregation and bimolecular reactions with 1a. Several new
IR bands that appear during warming the matrices are assigned to a complex 1a···HꢀOH between
the carbene and water (Chart 2, Figure 1aꢀd, Table 1). These bands are observed only if both 1a
and water are present in the matrix.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Chart 2. Interaction of carbene 1a with water to form the hydrogenꢀbonded complex 1a···H O
2
As expected, the formation of the complex 1a···HꢀOH results in only moderate or small shifts of
ꢀ1
IR bands compared to the constituents 1a and H O. The strongest band of 1a at 1226.4 cm
2
ꢀ1
assigned to the CꢀC stretching vibration at the carbene center is blueꢀshifted to 1237.0 cm
ꢀ1
(
Table 1). The bands at 847.1 and 739.5 cm assigned to the antisymmetric and symmetric CꢀCꢀ
ꢀ1
Cl stretching vibrations, respectively, are blueꢀshifted to 855.6 and 766.7 cm , and the band at
ꢀ1
ꢀ1
5
68.4 cm , assigned to an inꢀplane CꢀH deformation mode, is shifted to 575.5 cm . The large
shifts of the stretching vibrations involving the carbene center indicates a C···HꢀOH hydrogen
bond between the central carbon atom of 1a and H O. The dependency of the intensity of the
2
bands of 1a···HꢀOH from the concentration of H O in argon suggests that a 1:1 complex between
2
H O and 1a is formed. With 1% H O, about 55% yield of the complex was obtained after 10 min
2
2
annealing at 35 K, and prolonged annealing did not result in a further increase of the yield. With
1
8
18
D O and H O, the corresponding isotopologues 1a···DꢀOD and 1a···Hꢀ OH with very similar
2
2
IR absorptions in the midꢀIR region are observed (see SI).
ACS Paragon Plus Environment

Page 5 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. IR spectra showing the formation of the complex between carbene 1a and H O. a) 1a in
2
argon doped with 0.1% H O at 3 K. b) After annealing the matrix to 35 K for 10 min. c) 1a in
2
argon doped with 1% H O at 3 K. d) After annealing the matrix to 35 K for 10 min. The
2
vibrational absorption bands of the 1a···H O complex are highlighted in grey.
2
3
2ꢀ34
Since annealing of waterꢀdoped argon matrices results in the formation of the water dimer,
35
36
trimer, and higher oligomers that all exhibit strong absorptions in the OH stretching region, it
ꢀ1
is difficult to identify IR bands of 1a···HꢀOH in this region. A new band at 3199.6 cm is formed
only during annealing of matrices containing both 1a and H O, and is thus tentatively assigned to
2
an OH stretching vibration of the complex. This band is redꢀshifted from the symmetric OꢀH
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 6 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
ꢀ1
ꢀ1
stretching vibration of H O at 3638.0 cm by 438.4 cm (Figure 2, Table 2). With D O, the
2
2
ꢀ1
ꢀ1
corresponding OꢀD stretching vibration is found at 2286.4 cm , redꢀshifted by 371.4 cm from
ꢀ1
the symmetrical D O stretching vibration at 2657.8 cm . The large red shift of the OH stretching
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
vibration provides strong evidence for a hydrogen bonded complex, where water acts as
hydrogen bond donor and carbene 1a as hydrogen bond acceptor.
Figure 2. IR spectra showing the formation of the complex between 1a and H O. a) 1a in argon
2
at 3 K. b) 1% H O in argon at 3 K. c) After annealing the matrix to 35 K for 10 min and cooling
2
down to 3 K. d) 1 in argon doped with 1% H O at 3 K. e) After annealing the matrix to 35 K for
2
1
0 min and cooling down to 3 K. D: water dimer, T: water trimer, P: water oligomer. The OꢀH
stretching vibration of the 1a···H O complex is highlighted in grey.
2
ACS Paragon Plus Environment

Page 7 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
Several possible structures for complexes between carbene 1a and H O were considered, and their
2
geometries, energies, and IR spectra were calculated at the B3LYPꢀD3/6ꢀ311++G(2d,2p) level of
theory (Figure 3). Only complex A shows the strong C···HꢀO hydrogen bond expected from the
spectroscopic data. This complex is computed to be stabilized by 7.53 kcal/mol (including BSSE
and ZPE corrections), whereas the other complexes are only weakly stabilized by Cl···HO
(complex B), CH···OH (complex C), and π···HO (complex D) interactions. For complex A, a
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ꢀ1
very large red shift of the OH stretching vibration of water is predicted (ꢀ447 cm ), in excellent
ꢀ1
agreement with the experiment (ꢀ438.4 cm ). Complexes B–D are described best as weakly
bound van der Waals complexes with predicted red shifts of the OH stretching vibrations of less
ꢀ1
than 35 cm .The small shifts of the IR bands of carbene 1a observed after annealing of waterꢀ
doped argon matrices are in good agreement with predictions from DFT calculations, further
providing evidence for the formation of complex A (Table 1).
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 8 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 3. Four weakly bound complexes A ꢀ C between 1a and water calculated at the B3LYPꢀ
D3/6ꢀ311++G(2d,2p) level of theory are shown, including selected bond lengths (in Å) and bond
angles (in degree); the complex energies are relative to nonꢀinteracting monomers.
Fluorophenylcarbene Water Complex. The interaction of 1b with water is analogous to that of
1a, and therefore only briefly described here (see SI for details). The carbene is formed in high
yields by 365 nm photolysis of matrixꢀisolated fluorophenyldiazirine 2b at 3 K. If the matrix is
doped with 1% H O, annealing at 35 K results in the formation of complex 1b···HꢀOH in up to
2
40% yield. The complex shows some characteristic shifts in the IR spectrum, similar to that of
ꢀ1
1
a···HꢀOH (Table 3). Most notably is the strong red shift of 455.6 cm of the OH stretching
ACS Paragon Plus Environment

Page 9 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
vibration of the water molecule in the complex 1b···HꢀOH, which is slightly larger than in
1a···HꢀOH. The assignment of the IR spectra of 1b···HꢀOH was confirmed by isotopic labelling
1
8
(D O, H O) and by comparison with results from DFT calculations at the B3LYPꢀD3/6ꢀ
2
2
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3
11++G(2d,2p) level of theory. The large red shift of the OH stretching vibration is only
compatible with a C···OꢀH hydrogen bond involving the carbene center (Figure 3, complex A).
The other calculated structures are of lower energy (Figure 4) and predicted to show much
smaller red shifts of the OH stretching modes.
Figure 4. Four weakly bound complexes between 1b and water calculated at the B3LYPꢀD3/6ꢀ
311++G(2d,2p) level of theory are shown, including selected bond lengths (in Å) and bond
angles (in degree); the complex energies are relative to nonꢀinteracting monomers.
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 10 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Photochemistry of the Halophenylcarbene Water Complexes. The halophenylcarbenes 1a and
1b are stable towards visible light irradiation, but upon short wavelength UV irradiation (254 nm)
rearrange to the corresponding cycloheptatetraenes 4a and 4b, respectively (Scheme 1). Visible
light irradiation of the complexes (1a···HꢀOH: 630, 450 nm, 1b···HꢀOH: 450 nm) at 3 K results
in their dissociation and formation of the “free” carbenes 1. Annealing of the matrices at 30–35 K
again produces the complexes, and this photolysis/annealing process can be repeated several
times without formation of other products. The UV photochemistry of the complexes 1···HꢀOH
is markedly different not only from their visible light photochemistry, but also from that of the
carbenes 1a and 1b that are not bound to water. Several hours of 254 nm irradiation of matrices
containing a mixture of the carbenes 1 and their water complexes 1···HꢀOH results in the
expected rearrangement of “free” carbenes 1 to cycloheptatetraenes 4a and 4b, respectively. In
contrast, photolysis of 1···HꢀOH produces hydrogenꢀbonded complexes between benzaldehyde 6
and HCl or HF, respectively (Scheme 2, Figure 5). The complex 6···HꢀCl was synthesized
independently by annealing matrices containing both benzaldehyde 6 and HCl. In complex 6···Hꢀ
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
ꢀ1
ꢀ1
Cl the C=O stretching vibration of 6 is redꢀshifted from 1718.0 cm to 1703.2 cm .
Photolysis of the complexes of 1a or 1b with D O results in the formation of the corresponding
2
deuterated complexes d ꢀ6···DꢀCl or d ꢀ6···DꢀF, respectively, with the aldehyde group of 6
1
1
1
8
18
deuterated. If H O is used in these experiments, the O isotopologue of 6 is formed, as
2
expected. The isotopic shifts in the IR spectra of these isotopologues are in excellent agreement
with the shifts predicted from DFT calculations (for details see SI).
ACS Paragon Plus Environment

Page 11 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
H
O
H
+ H O, 35 K
2
X
X
2
54 nm
450 nm, 3 K
3 K
1 a: X = Cl
b: X = F
- H O
1...H-OH
2
H
O H
X
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2
54 nm, 3 K
O
H Cl
5
X
H
.
..
4
6 HX
Scheme 2. Reaction of 1a and 1b with H O and subsequent photochemistry.
2
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 12 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Figure 5. IR spectra showing the secondary photochemistry of the 1a···H O complex. a) The
2
1
a···H O complex produced in H Oꢀdoped argon matrix at 3 K. b) Difference IR spectrum
2 2
obtained after 254 nm irradiation for 15 h. Bands pointing downwards are disappearing during
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
irradiation and belong to the 1a···H O complex and carbene 1a. Bands pointing upwards are
2
appearing concomitantly and are assigned to 4 (bands marked by asterisks) and the 6···H O
2
complex. c) Benzaldehyde 6 in 1% HClꢀdoped argon at 9 K. The bands marked by ° are due to
HCl and H O complexes.
2
A reasonable mechanism for the formation of benzaldehyde and HX involves the unstable αꢀ
halobenzylalcohol 5, the formal product of the insertion of carbenes 1 into the OH bond of water.
This step obviously needs photochemical excitation; however, it is not clear from our
experiments if this is a true photochemical or a “hot ground state” reaction. Calculations at the
B3LYPꢀD3/6ꢀ311++G(d,p) level of theory predict activation barriers of 11.1 kcal/mol for the
insertion of 1a (Figure 6), and 12.2 kcal/mol for the insertion of 1b into the OH bond of water to
form the corresponding halobenzylalcohols 5. These barriers are too large to be overcome in
thermal reactions at temperatures below 20 K, and therefore photochemical excitation is
necessary.
ACS Paragon Plus Environment

Page 13 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Chart 3. Activation barriers E for the OH insertion reactions of carbeneꢀwater complexes
a
calculated at the B3LYPꢀD3/6ꢀ311++G(d,p) level of theory.
This is in marked contrast to the thermal behavior of the water complexes of singlet
15
14, 16
fluorenylidene FL and singlet diphenylcarbene DPC
which are only metastable, and even
at temperatures as low as 3 K slowly react to the corresponding OH insertion products. In the
temperature range between 3 and 20 K the rates for these insertion reactions are independent of
temperature, and thus the Arrhenius activation barriers for these reactions are zero, indicating a
tunneling reaction. The activation barriers for the OH insertion reaction of the water complexes
of FL and DPC are calculated to 5.1 kcal/mol and 6.6 kcal/mol, respectively, and thus
considerably lower than that of 1a and 1b (Chart 3). The larger activation barriers, and
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 14 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
presumably also larger tunneling distances, effectively inhibit tunneling rearrangements of
1a···HꢀOH and 1b···HꢀOH.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 6. Intrinsic reaction coordinate (IRC) for the OꢀH insertion of carbene 1a into H O and
2
CH OH calculated at the B3LYPꢀD3/6ꢀ311++G(d,p) level of theory. Energies are given in
3
ACS Paragon Plus Environment

Page 15 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
kcal/mol. Some structures along the reaction coordinate are shown in the diagram. OꢀH and CꢀH
bond distances involving the hydroxyl H atom in Å.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Halophenylcarbenes 1 in Amorphous Water Matrices. Visible light (λ = 405 nm) irradiation
of the diazirines 2a or 2b in amorphous water ice at 9 K resulted in the rapid photolysis of the
precursors, similar to the experiments in argon matrices. The photolysis was followed by IR and
UVꢀvis spectroscopy, which revealed the formation of the corresponding carbenes 1a and 1b in
addition to the halophenyldiazomethanes 3a and 3b (Scheme 1). A comparison of the IR spectra
shows that, as expected, the water complexes of the carbenes 1 are formed rather than the free
carbenes. In the ice matrix carbene 1a shows a strong UVꢀabsorption at 308 nm and 1b at 279
nm. These absorptions are slightly redꢀshifted compared to the bands in argon at 302 and 269 nm,
respectively. Annealing at temperatures up to 50 K did not result in any reaction of the 1···HꢀOH
1
5
complexes. This is in contrast to the chemistry of fluorenylidene FL and diphenylcarbene DPC
1
6
in amorphous water, which are readily protonated at cryogenic temperatures under formation of
the corresponding carbenium ions. Prolonged 405 nm irradiation leads to the formation of the
HCl or HF complexes, respectively, of benzaldehyde 6, again in analogy to the photochemistry of
the 1···HꢀOH complexes in solid argon. In amorphous D O ice, the DX complexes of d ꢀ6 are
2
1
formed, as expected (Figure 7).
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 16 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 7. IR spectra in solid D O showing the formation of the 1a···D O complex, a small
2
2
amount of 3a and the d ꢀ6···DCl complex at 9 K. a) IRꢀspectrum of 2a in amorphous D O ice at
1
2
9 K. b) Difference IR spectrum after 405 nm photolysis of 2a in D O at 9 K for 10 min. Bands
2
pointing downwards are disappearing during irradiation and are assigned to 2a. Bands pointing
upwards are appearing concomitantly and are assigned to the 1a···D O complex, a small amount
2
of 3a and the d ꢀ6···DCl complex (bands marked by *). c) 1a···D O complex formed in an argon
1
2
matrix doped with 1% D O upon annealing from 9 to 35 K. d) Difference IR spectrum after
2
prolonged irradiation of the matrix a with 405 nm for a total of 20 min in D O matrix at 9 K.
2
Bands pointing downwards are disappearing and are assigned to the 1a···D O complex and 2a
2
(
bands marked by °). Bands pointing upwards are appearing and are assigned to the d ꢀ6···DCl
1
3
7
complex (bands marked by *). e) IR spectrum of d ꢀ6 simulated with data from ref.
1
ACS Paragon Plus Environment

Page 17 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
Chlorophenylcarbene 1a Methanol Complex. Carbene 1a was also generated in 0.1–2%
methanolꢀdoped argon matrices at 3 K. Annealing of these matrices at 25–35 K resulted in
characteristic shifts of some bands of 1a, indicating the formation of the hydrogenꢀbonded
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
complex 1a···HꢀOCH (Scheme 3, Figure 8). The band shifts are very similar than those
3
observed for the water complex 1a···HꢀOH. Complex 1a···HꢀOCH proved to be photolabile,
3
and UV light (λ > 305 nm) irradiation resulted in the formation of the primary OH insertion
product 7. In contrast to the water adduct 5, the methanol adduct 7 is stable and can be identified
by comparison of the IR spectra with that of the authentic matrixꢀisolated compound. Prolonged
irradiation did not result in the formation of further photoproducts. As expected, with CH OD the
3
corresponding deuterated d ꢀ7 is formed.
1
Scheme 3. Reaction of 1a with CH OH and subsequent photochemistry.
3
The activation barrier for the insertion of carbene 1a into the OH bond of methanol and the
intrinsic reaction coordinate (IRC) for this reaction was calculated at the B3LYPꢀD3/6ꢀ
311++G(d,p) level of theory (Figure 6). With 7 kcal/mol the barrier is considerably lower than
that of the insertion of 1a into HꢀOH (11.1 kcal/mol), and only slighter larger than that of the
insertion of DPC into HꢀOH (6.6 kcal/mol). Nevertheless, a tunneling reaction as in the insertion
reactions of both DPC and FL into water and methanol was not observed.
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 18 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 8. Difference IR spectra showing the formation of the 1a···HꢀOH and 1a···HꢀOCH3
complexes. a) Difference spectrum after annealing an argon matrix containing 1a and 1% H O. b)
2
Difference spectrum calculated at the B3LYPꢀD3/6ꢀ311++G(2d,2p) level of theory. c) Difference
spectrum after annealing an argon matrix containing 1a and 1% CH OH. d) Difference spectrum
3
calculated at the B3LYPꢀD3/6ꢀ311++G(2d,2p) level of theory.
Conclusion
The halophenylcarbenes 1a and 1b are very strong bases and excellent hydrogen bond acceptors,
and thus form strongly hydrogenꢀbonded complexes 1···HꢀOH with water. For 1a the complex
with methanol 1a···HꢀOCH was also investigated. All hydrogenꢀbonded complexes of 1 are
3
ACS Paragon Plus Environment

Page 19 of 31
The Journal of Physical Chemistry
1
2
3
4
5
stable under the conditions of matrix isolation, OH insertions via quantum mechanical tunneling
(QMT) are not observed. This is in contrast to the hydrogenꢀbonded complexes of (singlet)
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
1
4, 16
15
diphenylcarbene DPC
and fluorenylidene FL, which undergo OH insertions via tunneling
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
even at temperatures as low as 3 K. DPC and FL are even stronger basic and form stronger
hydrogen bonds than halophenylcarbenes 1, which results in lower activation barriers for the OH
insertions. DFT calculations predict a considerably larger activation barrier for the insertion of 1a
and 1b into water than for DPC and FL (Chart 3), in agreement with the experimental findings.
Photochemical excitation of 1···HꢀOR results in OH insertion, however, our experiments do not
allow to discriminate between true photochemical and “hot ground state” reactions.
The behavior of 1a and 1b in amorphous water ice also differs from that of DPC and FL. While
the latter two carbenes are rapidly protonated to form the corresponding carbenium ions, 1a and
1b only form water complexes, and proton transfer does not occur.
It is noticeable that none of these carbenes formed ylides with HOR via interaction of the lone
pairs at oxygen with the vacant pꢀorbital at the carbene center. Obviously, hydrogen bonding is
preferred, at least under the conditions of matrix isolation.
Experimental section
Matrix isolation experiments at 3ꢀ50 K were performed by standard techniques using a closedꢀ
cycle helium cryostat. Matrix infrared spectra were recorded with a FTIR spectrometer using a
ꢀ1
ꢀ1
standard resolution of 0.5 cm in the range of 400ꢀ4000 cm . Matrix UVꢀvis spectra were
recorded with a UVꢀvis NIR spectrophotometer in the range of 200ꢀ800 nm with a resolution of
18
2
0
.1 nm. Water, D O, H O, methanol and methanolꢀD were degassed several times prior to use
2
in the matrix isolation experiments. The matrices were generated by coꢀdeposition of the
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 20 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
18
substance of interest (2a, 2b or 6,) and water, D O, H O, methanol or methanolꢀD with a large
2
2
excess of argon on top of different substrates (CsI and sapphire windows for IR and UVꢀvis
spectroscopy, respectively) at 3ꢀ50 K. A flow rate of approximately 1 mbar/min was used for the
deposition of the matrix. Matrixꢀisolated chlorophenylcarbene 1a or fluorophenylcarbene 1b
were generated by photolysis of chlorophenyldiazirine 2a or fluorophenyldiazirine 2b in argon
matrices at 3 K using 405 nm or 365 nm LED source. After annealing at 35 K for several minutes
the matrices were cooled back to 3 K to record spectra. The experiments in low density
amorphous ice (LDA ice, H O or D O) were performed in a similar manner by replacing argon
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
2
with H O or D O. For the preparation of LDA ice, purified H O or D O was degassed in several
2
2
2
2
freezeꢀthaw cycles. The deposition rate of the water or D O vapors was controlled by a fine
2
metering valve. Water or D O was coꢀdeposited with the substance of interest (2a, 2b or 6) in a
2
high vacuum system on top of different spectral windows (CsI (for IR spectroscopy) or sapphire
window (for UVꢀvis spectroscopy)) at 50 K. After deposition the matrices were cooled back to 3ꢀ
10 K. For irradiations of matrixꢀisolated species, LEDs (530, 470, 450, 405 and 365 nm), a lowꢀ
pressure mercury lamp (254 nm) and a 500 W highꢀpressure mercury lamp and cutꢀoff filter with
18
5
0% transmission at 305 nm were used. Solvents (D O (99% D), H O (97% isotopic purity),
2 2
Methanol (99.9% anhydrous) and methanolꢀD (99.5% isotopic purity)) were purchased and used
as received without further purification. Benzaldehyde 6 was purified by distillation prior to use.
HCl gas (99.8%) was also used without further purification.
3
8
Chlorophenyldiazirine 2a was synthesized according to a published procedure. For additional
purification, 3a was chromatographed (silica gel 60, 230ꢀ400 mesh) using pentane as eluent. (Ar,
ꢀ1
3
K): ꢀȬ (cm ) (%) = 3075.1 (5), 1573.7 (53), 1498.0 (17), 1450.9 (13), 1260.3 (7), 1109.0 (1),
ꢀ1
1040.2 (14), 1015.0 (27) 912.7 (100), 757.1 (31), 692.3 (40), 666.7 (22), 544.5 (10) cm .
ACS Paragon Plus Environment

Page 21 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
Fluorophenyldiazirine 2b was synthesized by a ClꢀtoꢀF exchange reaction with the use of tetraꢀnꢀ
3
9
butylammonium fluoride according to a published procedure. 2a was further purified by HPLC
ꢀ1
(pentane). IR (Ar, 3 K): ꢀȬ (cm ) (%) = 3075 (4), 1559 (8), 1451 (13), 1306 (83), 1077 (34), 1010
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ꢀl
(
58), 759 (96), 693 (93), 559.6 (56), 553 (50) cm .
40
1
ꢀchloroꢀ1ꢀmethoxytoluene 7 was synthesized according to a literature procedure. IR (Ar, 3 K):
ꢀ1
ꢀ
Ȭ (cm ) (%) = 1369.3 (24), 1251.6 (71), 1195.1 (67), 1121.7 (92), 987.0 (25), 851.0 (24), 695.5
(100), 628.4 (12), 616.3 (8).
Computational Methods. The geometries and vibrational frequencies of all species were
4
1
calculated using the B3LYPꢀD3 density functional with the 6ꢀ311++G(2d,2p) basis set. 7 and
4
2
d1ꢀ7 were calculated at the MP2/6ꢀ311++G(2d,2p) level of theory. All calculations were
4
3
performed using the Gaussian 09 suite of programs. The multiple minima hypersurface
44
(
MMH) approach was used to localize the minima of the 1aꢀwater and methanol, 1bꢀwater, 6ꢀ
HCl and 6ꢀHF systems. 100 randomly arranged complexes of each of those systems described
above were generated as starting points and preoptimized at the B3LYP/6ꢀ31G(d,p) level of
theory. The most stable structures were taken for further optimizations at different methods
4
5
46
41
(
M06ꢀ2X , B3LYP and B3LYPꢀD3 ) with the 6ꢀ311++G(2d,2p) basis set. All interaction
4
7
energies were corrected by the Boys and Bernardi counterpoise correction. The stabilization
energies were calculated by subtracting the energies of the monomers from those of the dimeric
complexes including ZPE corrections.
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 22 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Associated Content
Supporting Information. Additional IR and UV/vis spectroscopic data of the experiments in LDA
ice, H Oꢀ and CH OHꢀdoped argon matrices, isotopic labelling IR spectra, experimental and
2
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
calculated vibrational frequencies, calculated energies and geometries of Hꢀbonded complexes
and Cartesian coordinates of all optimized structures. The Supporting Information is available
free of charge on the ACS Publications website.
Author Information
Corresponding Author
*W.G.: eꢀmail: wolfram.sander@rub.de. Tel.: +49 234 32 24593
Notes
The authors declare no competing financial interest.
Acknowledgment
This work was supported by the Cluster of Excellence RESOLV (EXC 1069) funded by the
Deutsche Forschungsgemeinschaft (DFG).
ACS Paragon Plus Environment

Page 23 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
References
1.
Sander, W.; Kötting, C., Reactions of Difluorovinylidene ꢀ a SuperꢀElectrophilic Carbene.
Chem. Eur. J. 1999, 5, 24ꢀ28.
Breidung, J.; Bürger, H.; Kötting, C.; Kopitzky, R.; Sander, W.; Senzlober, M.; Thiel, W.;
Willner, H., Difluorovinylidene. Angew. Chem. Int. Ed. 1997, 36, 1983ꢀ1985.
3. Kotting, C.; Sander, W.; Senzlober, M.; Burger, H., Oxidation of Difluorovinylidene.
Chem-Eur J 1998, 4, 1611ꢀ1615.
Arduengo, A. J., Looking for Stable Carbenes: The Difficulty in Starting Anew. Acc.
Chem. Res. 1999, 32, 913ꢀ921.
Moss, R. A., Solvation and Complexation of Carbenes ꢀ a Perspective. J. Phys. Org.
Chem. 2011, 24, 866ꢀ875.
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
4.
5.
6.
Kirmse, W., Carbene Protonation. In Advances in Carbene Chemistry, Brinker, U. H., Ed.
Elsevier Science B.V.: 2001; Vol. 3, pp 1ꢀ51.
7.
Chen, H.; Justes, D. R.; Cooks, R. G., Proton Affinities of NꢀHeterocyclic Carbene Super
Bases. Org. Lett. 2005, 7, 3949ꢀ3952.
Pliego, J. R.; DeAlmeida, W. B., Absolute Proton Affinity and Basicity of the Carbenes
Ch2, Cf2, Ccl2, C(Oh)(2), Fcoh, Cph2 and Fluorenylidene. J. Chem. Soc. Faraday Trans. 1997,
8.
93, 1881ꢀ1883.
9. Keeffe, J. R.; O'Ferrall, R. A. M., The Protonation of Carbenes and Structural Effects on
the ΑꢀProton Acidity of Carbocations. ARKIVOC (Gainesville, FL, U. S.) 2008, 183ꢀ204.
0. Lavilla, J. A.; Goodman, J. L., The Experimental Heats of Formation and Reaction of
1
Singlet Carbenes Via TimeꢀResolved Photoacoustic Calorimetry. J. Am. Chem. Soc. 1989, 111,
712ꢀ714.
11.
Du, X. M.; Fan, H.; Goodman, J. L.; Kesselmayer, M. A.; KroghꢀJespersen, K.; LaVilla,
J. A.; Moss, R. A.; Shen, S.; Sheridan, R. S., Reactions of Dimethoxycarbene and
Fluoromethoxycarbene with Hydroxyl Compounds. Absolute Rate Constants and the Heat of
Formation of Dimethoxycarbene. J. Am. Chem. Soc. 1990, 112, 1920ꢀ1926.
12.
Belt, S. T.; Bohne, C.; Charette, G.; Sugamori, S. E.; Scaiano, J. C., Carbocation
Formation Via Carbene Protonation Studied by the Technique of StoppedꢀFlow LaserꢀFlash
Photolysis. J. Am. Chem. Soc. 1993, 115, 2200ꢀ2205.
13.
Arduengo, A. J., III; Gamper, S. F.; Tamm, M.; Calabrese, J. C.; Davidson, F.; Craig, H.
A., A Bis(Carbene)ꢀProton Complex: Structure of a CꢀHꢀC Hydrogen Bond. J. Am. Chem. Soc.
1995, 117, 572ꢀ573.
14.
from Triplet to Singlet. Angew. Chem., Int. Ed. 2014, 53, 5122ꢀ5125.
5. Costa, P.; Trosien, I.; FernandezꢀOliva, M.; SanchezꢀGarcia, E.; Sander, W., The
Fluorenyl Cation. Angew. Chem. Int. Ed. 2015, 54, 2656ꢀ2660.
6. Costa, P.; FernandezꢀOliva, M.; SanchezꢀGarcia, E.; Sander, W., The Highly Reactive
Benzhydryl Cation Isolated and Stabilized in Water Ice. J. Am. Chem. Soc. 2014, 136, 15625ꢀ
Costa, P.; Sander, W., Hydrogen Bonding Switches the Spin State of Diphenylcarbene
1
1
1
1
2
1
5630.
7.
Moss, R. A., Improved Production of Phenylchlorocarbene. J. Org. Chem. 1962, 27,
683ꢀ&.
8. Moss, R. A.; Whittle, J. R.; Freidenreich, P., Stereoselectivity of Carbene Intermediates.
Vi. Selectivity of Phenylchlorocarbene. J. Org. Chem. 1969, 34, 2220ꢀ2224.
19. Ganzer, G. A.; Sheridan, R. S.; Liu, M. T. H., Reaction of Phenylchlorocarbene in
OxygenꢀDoped Matrices. J. Am. Chem. Soc. 1986, 108, 1517ꢀ1520.
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 24 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
0.
Sander, W. W., Chemiluminescence from Arylcarbene Oxidation: Phenylchlorocarbene
and (2ꢀChlorophenyl)Carbene. Spectrochim. Acta A 1987, 43A, 637ꢀ646.
1. Pliego, J. R., Jr.; De, A. W. B.; Celebi, S.; Zhu, Z.; Platz, M. S., SingletꢀTriplet Gap, and
2
the Electronic and Vibrational Spectra of Chlorophenylcarbene: A Combined Theoretical and
Experimental Study. J. Phys. Chem. A 1999, 103, 7481ꢀ7486.
2
Absolute Rate Constants for Additions of Phenylchlorocarbene to Alkenes. J. Am. Chem. Soc.
1
2
by Capture of Phenylchlorocarbene and TertꢀButylchlorocarbene ꢀ ReactionꢀRates of an
Alkylchlorocarbene by Laser FlashꢀPhotolysis. J. Am. Chem. Soc. 1988, 110, 5595ꢀ5596.
2
Bonds of Alkanes: Measurement of the Rate Constants by Laser Flash Photolysis. J. Photochem.
Photobiol., A 1992, 68, 97ꢀ106.
2.
Turro, N. J.; Butcher, J. A., Jr.; Moss, R. A.; Guo, W.; Munjal, R. C.; Fedorynski, M.,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
980, 102, 7576ꢀ7578.
3. Jackson, J. E.; Soundararajan, N.; Platz, M. S.; Liu, M. T. H., Pyridine Ylide Formation
4.
Bonneau, R.; Liu, M. T. H., Insertion of Phenylchlorocarbenes in the CarbonꢀHydrogen
25.
Reactions. Tetrahedron Lett. 1998, 39, 9381ꢀ9384.
6. Moss, R. A.; Jang, E. G.; Ho, G. J., Absolute Rate Constants for the Reactions of
Phenylhalocarbenes with Alkynes. J. Phys. Org. Chem. 1990, 3, 760ꢀ763.
7. Sun, Y.; Tippmann, E. M.; Platz, M. S., A Search for CarbeneꢀSolvent Interactions Using
TimeꢀResolved Infrared Spectroscopy. Org. Lett. 2003, 5, 1305ꢀ1307.
28. Wang, J.; Burdzinski, G.; Kubicki, J.; Platz, M. S.; Moss, R. A.; Fu, X.; Piotrowiak, P.;
Moss, R. A.; Yan, S. Q., Absolute Kinetics of Phenylchlorocarbene CꢀH Insertion
2
2
Myahkostupov, M., Ultrafast Spectroscopic Study of the Photochemistry and Photophysics of
Arylhalodiazirines: Direct Observation of Carbene and Zwitterion Formation. J. Am. Chem. Soc.
2
2
006, 128, 16446ꢀ16447.
9. Sander, W.; Bucher, G.; Wierlacher, S., Carbenes in Matrices ꢀ Spectroscopy, Structure,
and Reactivity. Chem. Rev. 1993, 93, 1583ꢀ1621.
30. Sheridan, R. S., Exploring Matrix Isolated Carbenes and BisꢀCarbenes with Electronic
Spectroscopy as a Guide. J. Phys. Org. Chem. 2010, 23, 326ꢀ332.
1. McMahon, R. J.; Abelt, C. J.; Chapman, O. L.; Johnson, J. W.; Kreil, C. L.; LeRoux, J.
3
P.; Mooring, A. M.; West, P. R., 1,2,4,6ꢀCycloheptatetraene: The Key Intermediate in
Arylcarbene Interconversions and Related C7h6 Rearrangements. J. Am. Chem. Soc. 1987, 109,
2456ꢀ2469.
3
2.
and Water Dimer Isolated in Solid Neon. J. Mol. Spectrosc. 1993, 157, 479ꢀ493.
3. Ayers, G. P.; Pullin, A. D. E., IrꢀSpectra of MatrixꢀIsolated Water Species .4.
Configuration of Water Dimer in Argon Matrices. Spectrochim Acta A 1976, 32, 1695ꢀ1704.
34. Ayers, G. P.; Pullin, A. D. E., IrꢀSpectra of MatrixꢀIsolated Water Species .1. Assignment
of Bands to (H2o)2, (D2o)2 and Hdo Dimer Species in Argon Matrices. Spectrochim Acta A
Forney, D.; Jacox, M. E.; Thompson, W. E., The Midꢀ and nearꢀInfrared Spectra of Water
3
1
3
976, 32, 1629ꢀ1639.
5. Engdahl, A.; Nelander, B., On the Structure of the Water Trimer. A Matrix Isolation
Study. J. Chem. Phys. 1987, 86, 4831.
6. Ceponkus, J.; Uvdal, P.; Nelander, B., Water Tetramer, Pentamer, and Hexamer in Inert
Matrices. J. Phys. Chem. A 2012, 116, 4842ꢀ4850.
7. Gerbig, D.; Reisenauer, H. P.; Wu, C.ꢀH.; Ley, D.; Allen, W. D.; Schreiner, P. R.,
Phenylhydroxycarbene. J. Am. Chem. Soc. 2010, 132, 7273ꢀ7275.
8. Graham, W. H., The Halogenation of Amidines. I. Synthesis of 3ꢀHaloꢀ and Other
3
3
3
Negatively Substituted Diazirines1. J. Am. Chem. Soc. 1965, 87, 4396ꢀ4397.
ACS Paragon Plus Environment

Page 25 of 31
The Journal of Physical Chemistry
1
2
3
39.
Moss, R. A.; Terpinski, J.; Cox, D. P.; Denny, D. Z.; KroghꢀJespersen, K., Azide and
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Fluoride Exchange Reactions of Halodiazirines. J. Am. Chem. Soc. 1985, 107, 2743ꢀ2748.
0. Berliner, M. A.; Belecki, K., Simple, Rapid Procedure for the Synthesis of Chloromethyl
Methyl Ether and Other Chloro Alkyl Ethers1. J. Org. Chem. 2005, 70, 9618ꢀ9621.
41. Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H., A Consistent and Accurate Ab Initio
Parametrization of Density Functional Dispersion Correction (DftꢀD) for the 94 Elements HꢀPu.
J. Chem. Phys. 2010, 132, 154104.
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
4
2.
Chem. Phys. Lett. 1988, 153, 503ꢀ506.
43. Frisch, M.; Trucks, G.; Schlegel, H. B.; Scuseria, G.; Robb, M.; Cheeseman, J.; Scalmani,
HeadꢀGordon, M.; Pople, J. A.; Frisch, M. J., Mp2 Energy Evaluation by Direct Methods.
G.; Barone, V.; Mennucci, B.; Petersson, G., Gaussian 09, Revision A. 02; Gaussian, Inc.
Wallingford, CT 2009, 19, 227ꢀ238.
44.
Montero, L. A.; Esteva, A. M.; Molina, J.; Zapardiel, A.; Hernandez, L.; Marquez, H.;
Acosta, A., A Theoretical Approach to Analytical Properties of 2,4ꢀDiaminoꢀ5ꢀPhenylthiazole in
Water Solution. Tautomerism and Dependence on Ph. J. Am. Chem. Soc. 1998, 120, 12023ꢀ
12033.
45.
Zhao, Y.; Truhlar, D. G., The M06 Suite of Density Functionals for Main Group
Thermochemistry, Thermochemical Kinetics, Noncovalent Interactions, Excited States, and
Transition Elements: Two New Functionals and Systematic Testing of Four M06ꢀClass
Functionals and 12 Other Functionals. Theoret. Chem. Acc. 2008, 120, 215ꢀ241.
46.
Energy Formula into a Functional of the ElectronꢀDensity. Phys Rev B 1988, 37, 785ꢀ789.
7. Boys, S. F.; Bernardi, F., The Calculation of Small Molecular Interactions by the
Differences of Separate Total Energies. Some Procedures with Reduced Errors. Mol. Phys. 1970,
9, 553ꢀ566.
Lee, C. T.; Yang, W. T.; Parr, R. G., Development of the ColleꢀSalvetti Correlationꢀ
4
1
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 26 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
Tables
Table 1. Experimental and calculated vibrational frequencies of 1a and its complexes with H O and CH OH.
2
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
a
f
b
f
c
f
d
f
e
h
Ar , (Irel.
)
Ar/H
2
O , (Irel.
)
LDA , (Irel.
)
Ar/CH
3
OH , (Irel.
)
DFT , (Iabs.)
ꢀ1
ꢀ1
g
ꢀ1
g
ꢀ1
g
ꢀ1
g
ν (cm )
68.4 (10)
675.4 (15)
ν (cm )
shift
ν (cm )
shift
ν (cm )
shift
ν (cm )
shift
assignment
5
575.5 (6)
+7.1
ꢀ2.4
567.5 (3)
676.1 (6)
ꢀ0.9
578.9 (8)
+10.5 588.2 (29)
ꢀ3.2 687.3 (33)
+8.5
ꢀ4.7
CꢀH. i.p. def.
CꢀH o.o.p. def.
673.0 (8)
+0.7
672.2 (10)
7
7
8
39.5 (51)
64.1 (20)
47.1(24)
766.7 (25)
772.7 (10)
855.6 (14)
1174.8 (16)
1237.0 (28)
1309.2 (6)
1326.3 (4)
+27.2 768.2 (30)
+28.7 767.7 (20)
+15.9 777.9 (12)
+13.8 857.5 (13)
+28.2 762.2 (129)
+13.8 794.9 (68)
+10.4 865.8 (61)
+30.4 CꢀCꢀCl str. sym.
+8.6
+8.5
+2.6
780.0 (15)
860.9 (18)
+6.5
+3.4
+5.6
CꢀH o.o.p. def.
CꢀCꢀCl str. asym.
CꢀH i.p. def.
1172.2 (40)
1171.4 (39) ꢀ0.8
1174.4 (16)
1236.9 (31)
1309.2 (3)
1329.1 (5)
+2.2
1199.4 (7)
1
1
1
226.4 (100)
305.3 (7)
320.7 (3)
+10.6 1230.5 (50) +4.1
+10.5 1268.5 (266)
+21.4 CꢀC str. carbene center
+4.2 C=C str. ring
+13.3 CꢀH i.p. def.
+3.9
+5.6
1312.0 (5)
1330.4 (2)
+6.7
+2.7
+3.9
+8.4
1332.7 (20)
1368.5 (12)
ACS Paragon Plus Environment

Page 27 of 31
The Journal of Physical Chemistry
1
2
3
4
5
1
1
445.7 (10)
1443.2 (4)
ꢀ2.5
1458.3 (12) +12.6 1442.2 (3)
ꢀ3.5
+1.8
/
1475.3 (26)
1626.7 (95)
ꢀ0.7
C=C str. ring
C=C str. ring
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
588.8 (28)
1588.6 (20)
3199.6 (100)
+0.2
1596.5 (35) +7.7
1590.6 (25)
+1.5
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
/
/
ꢀ438.4
ꢀ41.6
/
/
/
/
/
/
3372.8 (1036) ꢀ447.1 OꢀH str. sym.
3692.7 (15)
/
3884.5 (57)
ꢀ33.1 OꢀH str. asym.
a
b
c
d
e
In argon matrix at 3 K. In argon matrix doped with 1% H O at 3 K. In LDA ice matrix at 9 K. In argon matrix doped with 1% CH OH at 3 K. Calculated at
2
3
f
g
the B3LYPꢀD3/6ꢀ311++G(2d,2p) level of theory. Relative intensities based on the strongest observed absorption band. Frequency shift relative to the monomers
ꢀ1
h
(
cm ). Absolute intensities in km/mol.
ACS Paragon Plus Environment

The Journal of Physical Chemistry
Page 28 of 31
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
1
8
Table 2. Comparison of the OꢀH and OꢀD shifts of 1a···H
2
2 2
O, 1a···D O and 1a···H O.
…
…
18
…
18
Mode H O
1a H O
D O
2
1a D O
H O
1a H O
2
2
2
2
2
a
ν
1
3638.0 3199.6 (ꢀ 438.4) 2657.8 2286.4 (ꢀ 371.4) 3630.8 3190.2 (ꢀ 440.6)
3734.3 3692.7 (ꢀ 41.6) 2766.0 2726.2 (ꢀ 39.8) 3723.5 3680.9 (ꢀ 42.6)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
b
ν3
a
18
b
18
sym. str. OꢀH, OꢀD, OꢀH. asym. str. OꢀH, OꢀD, OꢀH. Frequency shifts are given in
ꢀ1
parenthesis. Frequencies in cm .
ACS Paragon Plus Environment

Page 29 of 31
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
Table 3. Vibrational frequencies and shifts of the 1b···H
2
O complex.
a
b
c
d
Ar
Ar/H
2
O
LDA ice
DFT
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
ꢀ1
e
rel
e
rel
e
rel
f
ꢀ1
e
rel
f
ꢀ1
g
f
ν (cm )
I
I
I
shift
ν (cm )
I
shift
ν (cm )
I
abs
shift assignment
6
6
26.8
80.0
21
27
15
47
94
10
100
17
/
631.4
678.3
6
+4.2
ꢀ2.5
636.0
678.4
860.9
1057.9
1122.5
1188.5
1266.4
1317.5
/
5
+9.2
ꢀ1.6
644.7
688.7
863.6
15
29
3
+5.8 skel. vibr.
ꢀ3.6 CꢀH o.o.p. def.
+13.5 CꢀCꢀF def.
10
2
6
2
2
838.0
847.7
+.7
+22.9
ꢀ6.3
1064.2
1070.0
1127.1
1176.3
1243.3
1318.9
3182.4
1
+5.8
+16.9
+8.0
+16.5
+4.1
1097.2 144 +21.8 CꢀH i.p. def.
1
1
110.2
168.3
36
5
10
6
+12.3 1141.3 131 +20.6 CꢀF str.
+20.2 1215.3 45 +15.4 CꢀH bend
+39.6 1274.2 274 +26.0 CꢀC str. carbene center
1226.8
13
3
15
3
1
314.8
/
+2.7
/
1346.0
11
+4.7 CꢀH i.p. def.
h
100 ꢀ455.6
/
3420.0 844 ꢀ399.9 OꢀH str. sym.
a
b
c
d
In argon at 3 K. In argon matrix doped with 1% H
2
O at 3 K. In LDA ice matrix at 9 K. Calculated at the B3LYPꢀD3/6ꢀ311++G(2d,2p) level of
e
f
ꢀ1
g
theory. Relative intensities based on the strongest observed absorption band. Frequency shift relative to the monomers (cm ). Absolute intensities
ACS Paragon Plus Environment