Infrared spectra and quantum chemical calculations of the bridge-bonded HC(F)LnF2 (Ln = La-Lu) complexes

Article abstract of DOI:10.1021/om200533q

Lanthanide metal atoms, produced by laser ablation, were condensed with CHF₃ (CDF₃) in excess argon or neon at 4 K, and new infrared absorptions are assigned to the oxidative addition product fluoromethylene lanthanide difluoride complex on the basis of deuterium substitution and density functional theory frequency calculations. Two dominant bands in the 500 cm^-1 region are identified as metal-fluorine stretching modes. A band in the mid-600 cm^-1 region is diagnostic for the unusual fluorine bridge bond C-(F)-Ln. Our calculations show that most of the bridged HC(F)LnF₂ structures are 3-6 kcal/mol lower in energy than the open CHF-LnF₂ structures, which is in contrast to the open structures observed for the corresponding CH₂-LnF₂ methylene lanthanide difluorides. Argon-to-neon matrix shifts are 15-16 cm ^-1 to the blue for stretching of the almost purely ionic Ln-F bonds, as expected, but 10 cm^-1 to the red for the bridge C-(F)-Ln stretching mode, which arises because Ar binds more strongly to the electropositive Ln center, decreasing the bridge bonding, and thus allowing a higher C-F stretching frequency.

Full text of DOI:10.1021/om200533q

ARTICLE
pubs.acs.org/Organometallics
Infrared Spectra and Quantum Chemical Calculations of the
Bridge-Bonded HC(F)LnF2 (Ln = LaÀLu) Complexes
Yu Gong,† Xuefeng Wang,†,‡ Lester Andrews,*,† Mingyang Chen,§ and David A. Dixon*,§
†Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, United States
‡Department of Chemistry, Tongji University, Shanghai, 200092 China
§Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama, United States
S Supporting Information
b
ABSTRACT: Lanthanide metal atoms, produced by laser ablation, were condensed with
CHF3 (CDF3) in excess argon or neon at 4 K, and new infrared absorptions are assigned to the
oxidative addition product fluoromethylene lanthanide difluoride complex on the basis of
deuterium substitution and density functional theory frequency calculations. Two dominant
bands in the 500 cmÀ1 region are identified as metalÀfluorine stretching modes. A band in the
mid-600 cmÀ1 region is diagnostic for the unusual fluorine bridge bond CÀ(F)ÀLn. Our
calculations show that most of the bridged HC(F)LnF2 structures are 3À6 kcal/mol lower in
energy than the open CHF-LnF2 structures, which is in contrast to the open structures
observed for the corresponding CH2-LnF2 methylene lanthanide difluorides. Argon-to-neon
matrix shifts are 15À16 cmÀ1 to the blue for stretching of the almost purely ionic LnÀF bonds,
as expected, but 10 cmÀ1 to the red for the bridge CÀ(F)ÀLn stretching mode, which arises
because Ar binds more strongly to the electropositive Ln center, decreasing the bridge bonding, and thus allowing a higher CÀF
stretching frequency.
’ INTRODUCTION
In the current work, we present new experimental and theoretical
results on the reactions of lanthanide atoms with CHF3. Although
the methylene complexes (CHFLnF2) are still the major reaction
products, all are found to have bridged CÀF bonds, which differ
from the open products observed in the reactions with CH2F2.
Transition metal alkylidene complexes are important inter-
mediates involved in a wide range of reactions. A large number of
studies on the synthesis, characterization, and reactivity of these
important species have been performed.1À4 However, the alky-
lidene complexes of the group 3 transition metals, and especially
the lanthanide metals, have attracted less attention compared with
the wide range of studies on other transition metal systems.5 Due
to the limited number of valence electrons for the group 3 transition
metals, typical alkylidene complexes with strong metalÀcarbon
bonds such as those of group 4 metals6 are not expected to be
formed, so investigations on the structure and bonding of group 3
alkylidene complexes are of interest. Synthetic methods have
contributed to this topic in recent years,7À10 as have studies of
the simplest versions of such molecules using matrix isolation
infrared spectroscopy.11À13 The insertion products and methy-
lidene complexes of scandium, yttrium, and lanthanum generated
by the reaction with methane and methyl halides have been pre-
pared and characterized in noble gas matrixes.11À13 Our electro-
nic structure calculations benchmarked by the infrared data show
that the group 3 methylidene complexes basically have CÀM
single bonds in contrast to the CdM double bonds found for the
group 4, 5, and 6 and Th and U methylidene complexes.14À18
Recently the reactions of methyl fluoride and methylene fluoride
with lanthanide atoms have been studied in our laboratories.19,20
The insertion and methylene products dominate the reactions of
lanthanide atoms and CH3F,19 whereasonlymethylene complexes
with an LnÀC single bond were found in the CH2F2 reactions.20
’ EXPERIMENTAL AND COMPUTATIONAL METHODS
The experimental apparatus and procedure for investigating laser-
ablated lanthanide metal atom reactions with CHF3 during condensa-
tion in excess argon and neon at 4 K have been described previously.21
The Nd:YAG laser fundamental (1064 nm, 10 Hz repetition rate with
10 ns pulse width) was focused onto a freshly cleaned lanthanide metal
target (Johnson-Matthey) mounted on a rotating rod. Laser-ablated
lanthanide metal atoms were co-deposited with 3À4mmolof Ar (Matheson,
research) containing 1% CHF3 or 1À1.5% CDF3 (prepared by reaction
of CDCl3 with HgF2 at 150 ꢀC for 18 h) onto a CsI cryogenic window
for 60 min. Complementary Ne matrix experiments were done with
most metals. FTIR spectra were recorded at 0.5 cmÀ1 resolution on a
Nicolet 750 FTIR instrument with 0.1 cmÀ1 accuracy using a HgCdTe
range B detector. Matrix samples were annealed at different tempera-
tures, and selected samples were subjected to broadband photolysis by a
medium-pressure mercury arc street lamp (Philips, 175 W) with the
outer globe removed.
Density functional theory (DFT)22 calculations were performed
using the Gaussian 03/09 program systems.23 The geometries of the
Received: June 21, 2011
Published: July 18, 2011
r
2011 American Chemical Society
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ARTICLE
products of the Ln + CH3F reactions were optimized, and second
derivatives were calculated to predict the vibrational frequencies for all
lanthanide metals. The energies for the reaction CHF3 + Ln f CHFLnF2
for multiple spin states of CHFLnF2 were calculated to predict the ground
spin state for each lanthanide reaction product molecule. The DFT cal-
culations were performed with the B3LYP hybrid functional24 with the
DZVP225 basis set onH, C, andF andthesegmentedsmallcorerelativistic
effective corepotential(ECP)26 from the Stuttgart group (ECP28MWB)27
with the corresponding segmented basis set (ECP28MWB_SEG)27 on
the lanthanide elements.28 There are 28 electrons subsumed in the ECP
leaving the 4s, 4p, 4d, 5s, 5p, 6s, and 4f (or 5d) electrons in the valence
space for the Ln. The basis set is of the form (14s,13p,10d,8f,6 g/10s,
8p,5d,4f,2 g), and we denote this as the Stutt basis set. This combination
of basis sets and exchangeÀcorrelation functional has been found to
work well for our analysis of similar reactions of Ln with CH2F2 and
CH3F.19,20
Figure 1. Infrared spectra of laser-ablated Yb atoms and fluoroform
reaction products in solid argon at 4 K: (a) Yb + 1% CHF3 deposition for
60 min; (b) after λ >220 nm irradiation; (c) after annealing to 30 K;
(d) Yb + 1% CDF3 deposition for 60 min; (e) after λ >220 nm irradiation;
(f) after annealing to 30 K. The label m denotes fluoromethylene
lanthanide difluoride complex. The asterisk denotes the CO2 absorption.
’ RESULTS AND DISCUSSION
Reactions of all of the lanthanide metal atoms (including La
but not the radioactive Pm) and CHF3 were performed in an Ar
matrix, and 11 of these were also studied in a Ne matrix. Absorp-
tions due to CF3, CHF2, CF2, and other common bands produced
from the photodecomposition of the CHF3 precursor were
present in all of the experiments.29À32 Lanthanide trifluoride mole-
cule products were observed in most of the matrix samples,33
while weak lanthanide difluoride absorptions were also found in
the Yb, Sm, and Eu experiments.34 The infrared spectra from the
reactions of different lanthanide atoms and CHF3 and CDF3 in
Ar or Ne matrixes are illustrated in Figures 1À5, and the product
absorptions are listed in Table 1. We consider several examples below.
Infrared Spectra. Figure 1 compares the infrared spectra from
the co-deposition of laser-ablated Yb atoms and CHF3 and CDF3
in solid Ar. The major product absorptions are 672.6, 562.6, and
549.5 cmÀ1 (labeled m for fluoromethylene lanthanide difluoride
complex in Figure 1), which are barely observed upon sample
deposition. Broadband irradiation increased these bands mark-
edly, and they sharpened when the sample was further annealed.
Complementary infrared spectra in a Ne matrix are shown in
Figure 2, and these spectra exhibited a similar pattern for the
product absorptions. New bands at 662.6, 578.0, and 564.9 cmÀ1
(labeled m in Figure 2) correspond to the above absorptions
observed in the argon matrix. The 562.6 and 549.5 cmÀ1 absorp-
tions lie in the region of LnÀF vibrations. Experiments with CDF3
revealed very small red shifts of less than 0.5 cmÀ1, suggesting the
hydrogen (deuterium) atom is involved very little in these two
vibrational modes. We assign these two bands to the symmetric
and antisymmetric FÀYbÀF stretching vibrations; the results of
the electronic structure calculations discussed below provide
further support for this assignment. This identification of the
YbÀF vibrations is also supported by the large Ar-to-Ne blue
shift (about 15 cmÀ1) due to the high ionic character of the
YbÀF bond.
Figure 2. Infrared spectra of laser-ablated Yb atoms and fluoroform
reaction products in solid neon at 4 K: (a) Yb + 0.5% CHF3 deposition
for 40 min; (b) after λ >220 nm irradiation; (c) after annealing to 10 K;
(d) Yb + 0.5% CDF3 deposition for 40 min; (e) after λ >220 nm
irradiation; (f) after annealing to 10 K. The label m denotes fluoro-
methylene lanthanide difluoride complex. The asterisk denotes the CO2
absorption.
frequencies in Table 2 and Supporting Information). We note
that the Ne matrix shifts for this band are 10 cmÀ1 to the red, in
contrast to the above blue shifts for the ionic YbÀF stretching
modes. The deuterium shift remains the same 2.7 cmÀ1 lower for
this C-(F)-Yb stretching mode in solid Ne. The observation of
these three vibrational modes coupled with the computational
results leads us to propose a CH(F)YbF2 molecule with a bridged
C-(F)-Yb bond as the product of the reaction of Yb and CHF3.
We observed the new band in the bridge CÀ(F)ÀLn stretch-
ing mode region for six metals (Table 1). In the Lu case,
following Yb, three new bands were observed at 648.0, 580.2,
and 570.3 cmÀ1 in solid Ne and at 657.0, 565.4, and 554.5 cmÀ1
in solid Ar with 2.5À2.9 cmÀ1 deuterium shifts for the higher
band and smaller deuterium shifts for the lower two bands
(Figures S1, S2). In the Er case, like Yb, three bands were
observed at 659.6, 570.6, and 558.1 cmÀ1 in solid Ne and
The 672.6 cmÀ1 absorption in solid Ar is diagnostic for the
structural description of the product. This band exhibited a small
deuterium shift of 2.7 cmÀ1, which is larger than that for the LnF2
vibrations mentioned above. As a result, a CÀF stretching vibra-
tion is proposed as the assignment for this band, although the
band is significantly lower than the typical CÀF stretch in the
1000 to 1050 cmÀ1 range.35 Our DFT calculations (see below for
details) show that the 672.6 cmÀ1 band position is indicative of a
bridge C-(F)-Yb stretching vibration instead of a terminal CÀF
stretch, which should be around 1000 cmÀ1 (compare the computed
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Figure 3. Infrared spectra of laser-ablated Ce atoms and fluoroform
reaction products in solid argon at 4 K: (a) Ce + 1% CHF3 deposition for
60 min; (b) after λ >220 nm irradiation; (c) after annealing to 30 K;
(d) Ce + 1% CDF3 deposition for 60 min; (e) after λ >220 nm irradiation;
(f) after annealing to 30 K. The label mdenotes fluoromethylene lanthanide
difluoride complex.
Figure 5. Infrared spectra of laser-ablated La atoms and CHF3 reaction
products in solid neon at 4 K: (a) La + 0.5% CHF3 deposition for 40 min;
(b) after λ >220 nm irradiation; (c) after annealing to 10 K; (d) La + 0.5%
CDF3 deposition for 40 min; (e) after λ >220 nm irradiation; (f) after
annealing to 10 K. The label m denotes fluoromethylene lanthanide
difluoride complex.
position of this band is expected to be about the same as the
CHF3 precursor absorption, which results in it being masked by
precursor in the CHF3 experiment. Thus, we assign the 512.4 cmÀ1
absorption observed in the CDF3 experiment to the symmetric
FÀCeÀF stretching vibrational mode, and the absorption at
492.1 cmÀ1 to the antisymmetric FÀCeÀF vibration. No other
band is found to track with the 492.1 cmÀ1 absorption in the
terminal CÀF stretching region, which again suggests the pre-
sence of a bridge CÀ(F) bond in the product structure. The
absorption for a bridged CÀF stretching vibration is probably
overlapped with the strong precursor absorption near 700 cmÀ1
.
Hence a fluorine bridge HC(F)CeF2 structure is proposed as the
product from the reactions of Ce and CHF3.
Figure 4 shows the infrared spectra in the region of LnÀF
stretching vibration from the reactions of all of the lanthanide
atoms (except Pm) and CHF3 insolid Ar. The symmetric and anti-
symmetric FÀLnÀF stretching vibrations were observed in this
region for most metal products with the band positions blue-
shiftedstepwisefromLatoLu, whichreflects the effect of lanthanide
contraction.37 A similar blue shift has been found in the CH2LnF2
complexes as well.20 Pr is the only exception, with unusually
higher frequencies than its neighbors. Both the symmetric and
antisymmetric FÀPrÀF stretching vibrational modes were blue-
shifted in the Ne matrix, while no new absorption was observed,
which strongly supports the identification of these two bands for
the Pr reaction product. The unusual frequencies in the Pr case
are probably related to a vibronic perturbation with a low-lying
electronic state. Such an explanation has been used to account for
the difference in vibrational frequencies of PrF3 from those of the
other lanthanide metal trifluorides.38 A similar anomaly was also
observed in the Pr and CH2F2 reaction product frequencies.20
Only a single product absorption peak is observed in the
spectra of La, Ce, and Nd, respectively (Figure 4). Following the
trend for the symmetric and antisymmetric FÀLnÀF vibrations,
it is reasonable to assume that the missing bands for these three
metals are overlapped by the CHF3 precursor absorption. In some
cases, changing the matrix moves the precursor band and allows
the observation of an additional product absorption. As shown in
Figure 5, the infrared spectra from the reactions of laser-ablated
La atoms and CHF3 in a Ne matrix clearly demonstrate the
Figure 4. Infrared spectra of laser-ablated lanthanide atoms and (1%)
CHF3 reaction products in solid argon at 4 K. The arrows denote the
fluoromethylene lanthanide difluoride complex absorptions. The asterisks
denote absorptions of LnF3. All the infrared spectra were recorded after
10 min of λ >220 nm irradiation or after subsequent sample annealing.
Broad bands common to fluoroform experiments labeled c (ref 32).
at 670.0, 555.7, and 542.4 cmÀ1 in solid Ar. In the Ho case, three
analogous absorptions were observed in each matrix. Again the
LnÀF modes are blue-shifted by about 15 cmÀ1 higher in Ne, as
is the case for the LnF3 molecules.33 The bridged CÀ(F)ÀLn
mode is red-shifted by about 10 cmÀ1 in Ne, with the same 2.4 to
2.1 cmÀ1 deuterium shift, and the latter mode behaves opposite
the matrix shift expected for an ionic bond.36
The infrared spectra from co-deposition of laser-ablated Ce
atoms and CHF3 are shown in Figure 3. A band centered around
492.1 cmÀ1 (labeled m in Figure 3) was observed upon deposi-
tion. This band increased on broadband photolysis and sharp-
ened on annealing together with an increase in the intensity of
the nearby CeF3 absorptions.33 The experiment with CDF3
revealed a 0.3 cmÀ1 red-shift for the 492.1 cmÀ1 absorption,
suggesting a CeÀF vibration for this band. Another weak band at
512.4 cmÀ1 was also observed in the CDF3 experiment. The
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Table 1. Infrared Absorptions of HC(F)LnF2 Molecules from the Reactions of Lanthanide Atoms and CHF3 in Solid Ar and Ne
(frequencies in bold are for DC(F)LnF2)
metal
La
bridging CÀF str. Ar
sym. FLnF str. Ar
asym. FLnF str. Ar
bridging CÀF str. Ne
sym. FLnF str. Ne
asym. FLnF str. Ne
a
483.8
483.6
492.1
491.8
518.7
521.0
520.4
527.7
526.8
560.4
499.9
499.5
a
a
Ce
Pr
512.4
543.3
543.2
523.9
523.3
533.1
532.8
534.9b
534.4
541.1b
541.0
546.4
546.3
549.6
549.1
552.0
551.9
555.7
555.4
561.2
560.9
562.6
562.4
565.4
564.8b
505.5
532.9
518.5
a
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
707.5
a
538.0
521.2
512.4
512.1
516.3b
515.9
523.0
522.9
531.4
531.3
539.4
539.0
539.7
539.7
542.4
542.3
547.8
547.7
549.5
549.1
554.5
554.4
546.6
546.6
550.1
527.7
527.3
532.3
547.6
561.2
547.3
560.9
674.8
671.7
671.4
669.0
661.3
659.2
659.6
657.0
567.0
566.9
570.6
570.2
555.6
555.6
558.1
558.0
670.0
a
Tm
Yb
Lu
672.6
669.9
657.0
654.5
662.6
659.9
648.0
645.1
578.0
577.4
580.2
580.2
564.9
564.4
570.3
570.3
a Absorptions unresolved due to band overlap. b Major site at 20 K.
existence of two different FÀLaÀF vibrations at 521.1 and
499.9 cmÀ1 (labeled m in Figure 5) with the CHF3 precursor
absorption between these two bands. In the CDF3 reaction the
precursor absorption moves 5.2 cmÀ1, but the product absorp-
cases, except for Eu (∼5 kcal/mol lower, see below) and Sm and
Gd (∼10 kcal/mol higher), this structure is much higher in energy
than the single F-bridge HC(F)LnF2 or open HFCLnF2 struc-
tures. If one of the bridged fluorine atoms transfers to C in the
HC(FF)LnF structure, it forms HFC(F)LnF. All of the HFC-
(F)LnF have similar energies to the dibridged HC(FF)LnF. The
energies for the reactions of CHF3 with Ln become less exothermic
from La to Eu as the f orbitals on the Ln metal are occupied up to
7 f electrons. The reaction energy becomes more exothermic for
Gd, with 7 f and 1 d electrons, and then increases substantially to
Tb with an f9 configuration. As predicted for the early part of the
series, as more f electrons are added, the reaction exothermicity decreases
until Lu, with a filled f14 shell, where it increases substantially.
F-Bridged Structures. The geometry of the bridge structure
for HC(F)CeF2 is shown in Figure 6. The HC(F)LnF2 molecule
with a bridging F center is an intermediate structure along the F
migration pathway, which does not proceed to complete F
transfer owing to the trivalence of the Ln metal. All of the
methylene lanthanide fluoride complexes observed in the reac-
tions of lanthanide metal atoms with CH3F and CH2F2 possess
structures without bridge-bonded atoms,19,20 whereas structures
with a bridged F were predicted in the CHF3 reactions for all Ln
except Gd; for Eu, the structure HC(FF)LnF is lower in energy.
In the HC(F)LnF2 molecules, one hydrogen and one fluorine
atom are left on the carbon after the transfer of two fluorine
tions shift only 0.4À0.6 cmÀ1
.
The CÀF vibration assigned to the bridge fluorine was
observed for most of the late HC(F)LnF2 complexes (Table 1),
which strongly supports the assignment of the bridge fluorine
structure. Although this mode was observed only for Nd among
the early lanthanide products (Table 1), the bridge fluorine
structure is still the most probable due to the lack of strong
terminal CÀF vibrations in the 1000À1050 cmÀ1 region and the
results of our electronic structure calculations (Tables 2 and 3).
Electronic Structure Calculations. Our calculations show
that the bridged structure HC(F)LnF2 (containing a C(F)Ln
triangle) is the lowest energy structure for all Ln except for Gd,
where the bridge structure was not predicted to form, and for Eu,
where HC(F)EuF2 is ∼4 kcal/mol higher than the lowest energy
double-bridged structure. In addition, it was not possible to
optimize an open structure (no bridge bonds) for the molecules
with La and Ce. The open structures are about 5 kcal/mol higher
in energy for most of the molecules except for Ln = Pm and Eu,
where the energy difference is close to 0 kcal/mol and for Tb
with a 20 kcal/mol more stable bridged structure. We also
optimized a double F-bridged structure for HC(FF)LnF. In all
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Table 2. Calculated Reaction and Isomerization Energies (kcal/mol) and Frequencies (cmÀ1) for Bridge HC(F)LnF2 and
DC(F)LnF2 (in bold) Except Gd
a
Ln
spin
2
ΔErxn
ΔEiso opena
ΔEiso CH(FF)LnFa
LnÀC str
LnF2 asym
LnF2 sym
CÀF strb
FÀCÀH bend
c
La
Ce
Pr
À156.5
53.2
441 (107)
417 (99)
450 (105)
425 (97)
453 (101)
428 (92)
465 (101)
439 (92)
463 (97)
438 (89)
447 (28)
420 (27)
381 (26)
357 (21)
363 (1)
504 (243)
504 (238)
514 (225)
514 (222)
508 (237)
509 (243)
523 (233)
522 (230)
534 (238)
534 (236)
522 (221)
522 (220)
513 (234)
512 (214)
529 (167)
529 (167)
532 (164)
532 (169)
529 (169)
529 (170)
553 (193)
553 (191)
556 (186)
555 (184)
557 (186)
557 (184)
559 (175)
559 (173)
561 (174)
561 (172)
566 (166)
566 (164)
568 (161)
568 (159)
520 (104)
520 (109)
536 (113)
536 (118)
532 (107)
533 (113)
539 (102)
538 (108)
542 (96)
542 (101)
529 (178)
529 (178)
521 (201)
520 (204)
551 (123)
550 (96)
549 (140)
548 (130)
548 (90)
548 (85)
564 (90)
564 (93)
569 (89)
568 (92)
568 (81)
568 (83)
570 (88)
570 (89)
574 (89)
574 (89)
577 (86)
576 (164)
577 (79)
577 (79)
705 (114)
701 (113)
726 (115)
721 (114)
721 (118)
718 (117)
718 (121)
713 (119)
712 (118)
707 (117)
744 (147)
738 (144)
906 (257)
895 (226)
1097 (328)
1108 (307)
1082 (390)
1094 (359)
1118 (214)
1124 (238)
685 (118)
680 (117)
700 (120)
695 (118)
661 (123)
656 (121)
649 (121)
644 (120)
647 (120)
642 (118)
638 (122)
633 (121)
636 (124)
630 (122)
1210 (24)
911 (6)
c
3
4
5
6
7
8
7
9
9
8
7
6
5
4
3
2
À154.0
À119.9
À127.1
À98.6
À78.0
À56.9
À90.1
À89.5
À89.1
À208.5
À157.9
À126.3
À104.3
À83.9
À64.4
À140.8
51.6
42.7
38.8
29.3
11.6
À4.2
7.6
1213 (24)
915 (7)
4.3
4.7
0.3
2.2
1212 (21)
915 (6)
Nd
1207 (20)
911 (5)
Pm
1204 (20)
909 (5)
Sm
1229 (7)
930 (4)
Eu
0.3
1309 (7)
997 (34)
1305 (14)
972 (29)
1307 (13)
973 (39)
1249 (64)
935 (16)
1194 (21)
901 (5)
c
Gd open
Gd open
Gd open
Tb
337 (2)
c
c
359 (1)
336 (0)
402 (22)
378 (24)
470 (77)
444 (73)
483 (74)
455 (70)
480 (65)
454 (63)
476 (58)
451 (57)
477 (56)
452 (56)
479 (58)
453 (57)
484 (52)
457 (52)
19.6
3.1
5.1
5.6
6.2
5.4
4.5
48.2
32.0
79.1
56.6
29.9
11.8
50.3
Dy
1193 (24)
903 (7)
Ho
1183 (21)
894 (6)
Er
1180 (19)
890 (6)
Tm
1179 (21)
889 (6)
Yb
1176 (20)
887 (6)
Lu
1171 (18)
884 (5)
a ΔErxn is the reaction energy of the CHF3 + Ln f HC(F)LnF2 reaction; ΔEiso is the isomerization energy for converting the single bridging
HC(F)LnF2 to the open HFC-LnF2 and the double bridging HC(FF)-LnF. b CÀF (bridge) stretches for the HC(F)LnF2, and CÀF (open) stretches
for HFC-LnF2. c No bridging structure found for Gd. No open structure found for La and Ce.
atoms to the metal center. For the reactions of CHF3 with Ln to
form the +3 oxidation state, one F has to be bonded to the C, and
these structures are not present when more hydrogen is present
in the starting fluoromethane. In the current case, the CHF group
can be considered as :CHFÀ. Another way to write the structure
would be as the Ln in the +2 oxidation state which forms a σ bond
with the :CHF fluoromethylene species. In either case, the excess
spin on the Ln is the same.
The r(LnÀC) bond distances are between 2.3 and 2.5 Å for
most of the HC(F)LnF2 compounds, and the r(LnÀF) bond
distances are in the range 1.9 to 2.1 Å for the terminal F and
2.2À2.6 Å for the bridged F. The r(LnÀC) and r(LnÀF) bond
distances generally decrease with increasing atomic number due
to the lanthanide contraction.37 The values of r(CÀFbridge) are
approximately 1.5 Å and increase with increasing atomic number
of the lanthanide as the F atom becomes more strongly bonded
to the Ln (Table 3). The r(CÀFbridge) is substantially longer than
the calculated CÀF bond length of 1.403 Å in CH3F and of 1.352
Å in CHF3. The r(LnÀC) in HC(F)LnF2 are slightly shorter
than the r(LnÀC) in CH2LnF2 by up to 0.02 Å and slightly
longer than those in CH2LnHF by up to 0.02 Å; so, there is very
little change in r(LnÀC) in all three compounds.19,20
The geometry of HC(F)LnF2 has the CH(F) group approxi-
mately orthogonal to the LnF2 plane. This is in contrast to the
structures of CH2LnF2 and CH2LnHF, where the plane defining
the CH2 groups is approximately parallel to the LnF2 plane. The
structures with the CH2 groups have a low rotation barrier about
the LnÀC bond consistent with an electron distribution with an
unpaired electron on the C. The electron distribution is essen-
tially the same in HC(F)LnF2 for most of the lanthanides. As
shown in Table 3 and Figure 6 (except for Gd, where no single
bridge structure is predicted and Eu with only 0.6 e on the C), the
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Table 3. Geometry Parameters and Mulliken Charges for Bridged Speciesa
metal r(LnÀC) r(CÀF) r(LnÀF) bridge r(LnÀF) —CFLn bridge Ln charge F bridge charge F(Ln) charge CH group charge spin on C spin on Ln
La
2.479
2.440
2.420
2.394
2.386
2.388
2.460
2.344
2.317
2.311
2.308
2.299
2.287
2.272
1.514
1.503
1.505
1.507
1.511
1.487
1.419
1.527
1.519
1.543
1.552
1.553
1.560
1.564
2.507
2.512
2.479
2.460
2.430
2.456
2.652
2.353
2.364
2.300
2.266
2.249
2.246
2.223
2.117
2.092
2.081
2.072
2.066
2.063
2.076
2.015
2.005
2.006
1.997
1.990
1.976
1.970
71.3
69.7
69.9
69.6
70.1
69.7
66.6
70.7
69.4
70.8
71.6
71.8
71.3
71.3
1.416
1.398
1.415
1.429
1.452
1.440
1.377
1.450
1.435
1.474
1.474
1.471
1.477
1.528
À0.308
À0.306
À0.307
À0.309
À0.311
À0.293
À0.231
À0.316
À0.314
À0.294
À0.323
À0.320
À0.296
À0.338
À0.485
À0.481
À0.487
À0.496
À0.505
À0.519
À0.552
À0.502
À0.495
À0.513
À0.513
À0.514
À0.512
À0.534
À0.137
À0.130
À0.134
À0.128
À0.131
À0.108
À0.041
À0.130
À0.131
À0.122
À0.125
À0.122
À0.122
À0.122
0.98
0.96
0.95
0.94
0.95
0.85
0.58
0.98
1.00
0.99
1.00
1.00
1.00
1.01
0.02
1.04
2.07
3.07
4.07
5.17
6.45
6.01
4.97
4.00
3.00
1.99
0.99
À0.01
Ce
Pr
Nd
Pm
Sm
Eu
Tb
Dy
Ho
Er
Tm
Yb
Lu
a No bridged Gd species could be optimized.
Figure 6. Molecular orbital diagrams (isovalue = 0.06 e auÀ3) of (a) unpaired C 2p, (b) unpaired Ce 4f, (c) CeÀC bond (ionic), and (dÀg) CÀF,
CÀH, and F lone pairs and (h) spin density diagram (isovalue = 0.005 e auÀ3for HC(F)CeF2).
C in HC(F)LnF2 has essentially a single electron in a p orbital
perpendicular to the LnÀC bond and the remaining unpaired
spin density on the Ln (see the spin density for HC(F)CeF2,
Figure 6h). The rotation of the p orbital by 90ꢀ enables the F to
bridge to the Ln and minimizes any steric interactions with the F
atoms on the Ln. Similar total spin densities are obtained for the
open CHFLnF2, CH2LnF2, and CH2LnHF molecules. These
results suggest that the electronic structures of the bridge-
bonded HC(F)LnF2 molecules are similar to those of the open
structure for CHFLnF2, especially for the LnÀC bonding.
The CÀFbridge bond has substantial p character (Figure 6).
The orbitals in Figure 6d and f show the “bent-sigma”-like
interactions between the F 2p and C 2p lone pairs. Figure 6e
depicts delocalization of a lone pair on F to from a partial π bond
with the C. The orbitals clearly show that the interaction of the
bridge F with the Ln is mostly ionic in nature. The bridge CÀ(F)
bond interaction with a metal center is unusual, as numerous
examples of transition metal compounds X2C(Cl)MX with a
bridging chlorine atom have been observed, but only one with a
bridging fluorine, H2C(F)NiCl.39,40 For this latter molecule,
involving a first-row transition metal atom, the CÀF bond is
shorter and the frequency for the bridge fluorine is higher
(845 cmÀ1), showing a smaller bridging interaction than found
in the lanthanide molecules under study. Although the single
CÀLn bond is longer than that in the Ni case, the bonding
interaction between the bridge F and the C is larger in the Ni
compound (and weaker with the Ni) than in the lanthanides,
consistent with the lower CÀ(F) stretching vibrational fre-
quency as well as the smaller (F)ÀCÀLn bond angle in the
lanthanides. This stronger interaction of the F with the lantha-
nide could arise due to the larger radius of the Ln. The HC-
(F)LnF2 bridge bond arises from interactions of the negative
bridge-F atom with the positive charge on the Ln; so the
LnÀFbridge bonding will be dominated by the electrophilicity
(charge) of the metal center. If the metal is more electron-
deficient (positive charge), then there will be more transfer of the
F toward the metal and less interaction with the carbon. It is not
easy to form an H-bridged species, as the hydrogen has an
electron affinity of only 0.75 eV and hence will be much less
negative as well as much smaller. Chlorine has a higher electron
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Organometallics
ARTICLE
affinity than F, is larger, and its electron density is more easily
polarized; so we would expect compounds with Cl bridges to be
more common than compounds with F bridges.
stable than the dibridged structure. It is predicted to have a strong
LnÀF stretching mode near 480 cmÀ1 and a strong CÀFbridge
stretching mode near 600 cmÀ1, which are also not observed.
The CÀFterminal stretching mode in HFC(F)EuF is calculated
to be at 1044 cmÀ1 with a strong intensity and HÀCÀF bend
ing mode at 1188 cmÀ1 with a moderate intensity. Although
bridged HC(F)EuF2 is predicted to be ∼4 kcal/mol less stable
than HC(FF)EuF, the calculated vibrational frequencies for
HC(F)EuF2 are in good agreement with the experimental IR
results. The prediction for the antisymmetric EuF stretching
mode is within 5 cmÀ1 of experiment and within 10 cmÀ1 of
experiment for the predicted symmetric EuF stretching mode.
We thus assign HC(F)EuF2 as the major product for the Eu +
CHF3 reaction. As the calculations are done at the DFT level,
errors in the relative energies of several kcal/mol are possible. Eu
in the +2 oxidation state has an f7 configuration and in the +3 has
an f6 configuration. The complete f7 shell is stable so the Ln tries
to reach this configuration by borrowing spin from the C. Thus,
the best way to consider the structure of HFC(F)EuF may be as a
sum of the following structures {[C(p1) + Ln (f6)] + [C(p0) + Ln
(f7)]}. The Mulliken charge analysis shows that HC(F)EuF2 has
the lowest positive charge on the Ln for all of the HC(F)LnF2,
consistent with this argument. The spin distribution of 0.58e on
C and 6.45e on Eu is also consistent.
The LnÀF bonds in HC(F)LnF2 are highly ionic (Figure 6),
just as found for CH2LnF2. The orbitals show that the CÀLn
bond is highly ionic as well (Figure 6). In CH2LnF2, there is no π
bond between the Ln and C. Instead, there is a lone electron on
the C in a p orbital approximately perpendicular to the CÀLn
axis,20 so that CH2LnF2 is best described as a metal-substituted
methyl radical. The LnÀC bond in CH2LnF2 can be described as
arising from the electron distribution of the triplet ground state of
the carbene CH2 with one electron in the CH2 plane and one
electron perpendicular to the plane. The in-plane electron forms
the LnÀC bond. However, the ground state of CHF is a singlet
with both electrons nominally in the CHF plane, and the excited
state is the triplet calculated to be 11.0 kcal/mol higher in energy.
Thus, the Ln reaction energies for addition of CHF3 to form
CH(F)LnF2 should be less negative than the reaction energies
for CH2F2 and CH3F with Ln, as found. The first CÀF bond
energy in CHF3 is stronger than that in CF2H2 or CH3F, again
consistent with the lower reaction energies for the former.41 The
difference in the ability of the ground state of CH2 and CHF to
bind to the Ln may also influence the formation of the bridged
CÀ(F)ÀLn bond. The fact that CHF has to be excited to the
triplet state to generate a better LnÀC bond means that the bond
is inherently less stable. The F in the triplet state is slightly more
negative by 0.03 e than is the F in the singlet state. In addition, the
HCF bond angle opens up from 101.5ꢀ in the singlet to 121.1ꢀ in
the triplet. In order to further stabilize the LnÀC interaction, the
negative F can bond with the cationic Ln. This is enabled by the
increase in the HCF bond angle and the enhancement of the
negative charge on the F bonded to C.
For Ln = La and Ce, we attempted to optimize the open HFC-
LnF2 structures, but the optimization always resulted in the
bridged HC(F)LnF2. The energy difference between the open
and the bridged structures is ∼5 kcal/mol for Ln = Pr and Nd and
decreases to less than 2 kcal/mol for Ln = Pm, Sm, and Eu for the
early lanthanides. Gd is the only Ln for which we could not
optimize a bridged HC(F)LnF2 structure, which is consistent
with the decrease in the isomerization energy with increasing
atomic number for the early lanthanides. We predict the septet
state to be the lowest energy for HFC-GdF2, with two nonet
states less than 1 kcal/mol higher in energy. These three molecules
have similar geometries and have similar predicted spectra especial-
ly for the GdÀF antisymmetric and symmetric stretching modes
in the GdF2 moiety. The open/bridge energy differences increases
to 20 kcal/mol for Ln = Tb, which is the largest energy difference
excluding La and Ce. The energy differences then decrease to
3 kcal/mol for Ln = Dy and are ∼5 kcal/mol for the remaining
lanthanides.
Matrix Effects. The unusual 10 cmÀ1 red shift in the bridged
CÀ(F)ÀLn stretching mode from the solid Ar to the Ne
environment requires an explanation, as the usual effect of
medium polarizability is a blue matrix shift like that found for
the strong polar LnÀF bond stretching vibrations.33,34 The
strongest matrix interaction for the HC(F)LnF2 molecules will
be at the electropositive metal center; for example, the Mulliken
charge on Yb is +1.48e (Table 3). In order to estimate the effect
of the rare gas, we predicted the structures and vibrational spectra
for simple model complexes with one or two Ar or Ne atoms
interacting with the Yb center. The resulting frequencies for six
model complexes are given in Table 4, and the structures are
illustrated in Figure 7. The effect of binding Ar and Ne atoms to
the Yb center on the bridge CÀF stretching mode is to weaken
the interaction of the Ln with bridging F and strengthen [less red
shift in the CÀF mode] the CÀF bonding interaction, resulting
in a blue shift in the bridge CÀF stretching mode. The syn
interaction of the rare gas on the side where the CÀFÀYb bridge
is present is larger than if the rare gas is anti to the bridged F.
Argon is a more polarizable rare gas than neon and has a stronger
interaction with Yb, so Ar has a larger effect on the CÀF bridge
bond. This leads to a larger blue shift in the CÀF frequency
relative to the isolated molecule. The Ne atom, as expected, has a
smaller interaction with the Yb center than does Ar, and hence its
blue shift relative to the isolated molecule is smaller than that for
Ar. This leads to the experimental observation of a red shift in the
CÀFÀYb bridge stretching mode when the matrix is changed
from Ar to Ne. The rare gases are effectively removing positive
charge from the metal, which weakens the interaction with the
bridging F atom.
The energy differences between the dibridged HC(FF)LnF
and the monobridge HC(F)LnF2 decrease from 52 kcal/mol for
Ce to 12 kcal/mol for Sm and then become negative for Eu. Our
calculations show for Ln = Eu that the open insertion product
converges to the dibridged product. Although there is a small
imaginary frequency of ∼40i cmÀ1, the dibridged structure is the
lowest energy structure, 61 kcal/mol more stable than the reactants.
However the predicted vibrational frequencies of the weak
EuÀC stretching mode at 460 cmÀ1, the strong EuÀFterminal
stretching mode at ∼470 cmÀ1, and two strong symmetric and
antisymmetric CÀF stretching mode at ∼700 and ∼830 cmÀ1
are not observed. The HFC(F)EuF complex is 1 kcal/mol less
Reaction Pathways in the Matrix. On the basis of consider-
able experience with laser-ablated metal atom reactions,6,11À18,40
the first reaction is insertion into a CÀF bond to form the pro-
duct HF2CLnF followed by F-transfer rearrangement to form the
observed HC(F)LnF2 species. As an example, consider Ln = Lu
with all reaction energies given with respect to the separated
reactants, Lu + CHF3. The direct insertion step to form HC-
(FF)LuF similar in structure to HF2CLuF but with two F atoms
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ARTICLE
Table 4. Calculated Reaction Energies (kcal/mol), Bond Lengths (Å), and Frequencies (cmÀ1) for Bridged HC(F)YbF2 and
Model Ar and Ne Complexesa
e
property
HC(F)YbF2
A(Ar)
B(Ar)
C(Ar2)
D(Ne)
E(Ne)
F(Ne2)
E B3LYPb
À1.4
À1.2
À1.6
À0.8
À0.7
1.2
E CCSD(T)c
À2.8
À2.7
À5.9
À1.4
À1.4
À3.2
1.557
ꢀ
r(CÀF) A
1.560 [1.387]
2.246 [3.232]
2.287 [2.312]
479 (58)
1.550
1.559
1.550
1.555
1.561
ꢀ
r(F–Yb) Aꢀ
2.269
2.228
2.262
2.257
2.227
2.245
r(CÀYb) A
2.287
2.304
2.294
2.287
2.301
2.293
YbÀC str cmÀ1 (km/mol)
YbF2 asym str cmÀ1 (km/mol)
YbF2 sym str cmÀ1 (km/mol)
CÀF bridge strd cmÀ1 (km/mol)
FÀCÀH bend cmÀ1 (km/mol)
Mulliken on Yb
480 (63)
563 (157)
574 (81)
654 (122)
1183 (19)
1.438
467 (47)
561 (157)
574 (80)
641 (124)
1179 (19)
1.429
473 (57)
559 (152)
568 (77)
652 (125)
1185 (18)
1.411
480 (59)
564 (162)
577 (86)
645 (122)
1180 (19)
1.440
470 (49)
565 (164)
576 (83)
639 (121)
1178 (20)
1.431
475 (56)
545 (187)
575 (67)
646 (124)
1181 (17)
1.403
566 (166)
577 (86)
638 (122)
1176 (20)
1.477 [1.410]
a E = E(complex) À E(HC(F)YbF2) À nE(Ar/Ne), n = 1, 2. b Noble (Ar and Ne) gas binding energies in kcal/mol using B3LYP/DZVP2+Stuttgart
+aug-cc-pVDZ. Negative energy means binding. c Noble (Ar and Ne) gas binding energies in kcal/mol using U/UCCSD(T)/DZVP2+Stuttgart+aug-cc-
pVDZ with zero-point energies from the previous DFT calculations. Negative energy means binding. d Observed C-F str 672.6 cmÀ1 in solid argon and
662.6 cmÀ1 in solid neon. e Values for open HFC-YbF2 structure bond distance and Mulliken charge in brackets.
Figure 7. Calculated structures of the HC(F)YbF2(Ng)x (Ng = Ar, Ne, x = 1, 2) complexes.
on C leaning toward Lu is 90 kcal/mol exothermic, the reaction
to form the bridge HFC(F)LuF complex is 93 kcal/mol exother-
mic, the reaction to produce the open HFCLuF2 complex is 136
kcal/mol exothermic, and the reaction to form the final observed
bridge structure HC(F)LuF2 is 141 kcal/mol exothermic. The
high exothermicity for the final product suggests that the HC-
(FF)LuF insertion intermediate and the F transfer HFC(F)LuF
intermediate are not expected to be trapped in solid matrixes.
HC(FF)EuF is the exception. Unlike the group 4, 5, and 6
transition metal cases,6,14À16 the three-F-transfer product with a
CÀLn triple bond is not produced for the lanthanide metals due
in part to the inability of the Ln metal to form π bonds with the
available electrons on the C, as already shown for CH2LnF2.20
Although the +4 oxidation state is expected to be stable for some
lanthanide atoms such as Ce, our previous studies revealed that
Ce behaved similarly with other lanthanide metal atoms when
reacted with CH2F2.20 The single electron on the Ce center
remained unpaired in the H2C-CeF2 complex, resulting in a
single CÀCe bond. In our current experiments with CHF3, no
absorption can be assigned to the HC-CeF3 molecule, which
suggests that all of the lanthanide atoms have the same reaction
mechanism toward CHF3 and that the +3 oxidation state
dominates in all of the reaction products. Note that the decom-
position products of CHF3 are also present in the matrix, indicat-
ing the production of fluorine atoms during sample deposition.
These fluorine atoms can diffuse and react with lanthanide atoms
on sample annealing, which accounts for the observation of LnF3
and some LnF2 molecules in our experiments. If a transient
HC-CeF3 intermediate were formed, it decomposes straightaway
to the HC and CeF3 species.
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Organometallics
ARTICLE
’ CONCLUSIONS
(4) de Frꢀemonta, P.; Marionb, N.; Nolanb, S. P. Coord. Chem. Rev.
2009, 253, 862.
The reactions of lanthanide atoms and CHF3 were studied
using matrix isolation infrared spectroscopy and theoretical
calculations. The major product for all of the lanthanide atoms
is the fluoromethylene lanthanide difluoride complex, HC-
(F)LnF2, with an unusual bridged fluorine. The reaction product
is proposed to be formed via insertion of the Ln into a CÀF bond
followed by the transfer of a second fluorine. In most cases, the
DFT calculations predict that the bridged HC(F)LnF2 structures
are slightly more stable than the open HFCLnF2 isomers. The
unusual blue shift of the bridged CÀ(F) stretching frequency
from neon to argon arises from the stronger interaction between
argon atom(s) and the metal center of the lanthanide difluoride
complex, which weakens the LnÀ(F) bridge-bonding interaction
and allows the CÀ(F) stretching frequency to increase. The
formation of the bridge bonded F atom is consistent with the
need for the CHF fragment to be in the triplet state to bind to the
Ln. An energy on the order of 11 kcal/mol (calculated) is
required to excite CHF from the ground-state singlet. The
formation of the triplet CHF increases the HCF bond angle
and the negative charge on the F so that the F can interact with
the Ln to further stabilize the LnÀC interaction. The participa-
tion of the triplet CHF fragment is consistent with the presence
of an unpaired electron on the C.
(5) Giesbrecht, G. R.; Gordon, J. C. Dalton Trans. 2004, 33, 2387.
(6) Andrews, L.; Cho, H.-G. Organometallics 2006, 25, 4040.
(7) (a) Mills, D. P.; Soutar, L.; Lewis, W.; Blake, A. J.; Liddle, S. T.
J. Am. Chem. Soc. 2010, 132, 14379. (b) Mills, D. P.; Cooper, O. J.;
McMaster, J.; Lewis, W.; Liddle, S. T. Dalton Trans. 2009, 4547.
(c) Liddle, S. T.; McMaster, J.; Green, J. C.; Arnold, P. L. Chem.
Commun. 2008, 1747.
(8) Zimmermann, M.; Rauschmaier, D.; Eichele, K.; Toernroos,
K. W.; Anwander, R. Chem. Commun. 2010, 46, 5346.
(9) Scott, J.; Fan, H.; Wicker, B. F.; Fout, A. R.; Baik, M. H.;
Mindiola, D. J. J. Am. Chem. Soc. 2008, 130, 14438.
(10) (a) Fustier, M.; Le Goff, X. F.; Le Floch, P.; Mezailles, N. J. Am.
Chem. Soc. 2010, 132, 13108. (b) Cantat, T.; Mezailles, N.; Auffrant, A.;
Le Floch, P. Dalton Trans. 2008, 37, 1957. (c) Cantat, T.; Jaroschik, F.;
Nief, F.; Ricard, L.; Mezailles, N.; Le Floch, P. Chem. Commun.
2005, 5178. (d) Cantat, T.; Jaroschik, F.; Ricard, L.; Le Floch, P.; Nief,
F.; Mezailles, N. Organometallics 2006, 25, 1329. (e) Buchard, A.;
Auffrant, A.; Ricard, L.; Le Goff, X. F.; Platel, R. H.; Williams, C. K.;
Le Floch, P. Dalton Trans. 2009, 10219. (f) Dietrich, H. M.; Toernroos,
K. W.; Anwander, R. J. Am. Chem. Soc. 2006, 128, 9298.
(11) Cho, H. G.; Andrews, L. Organometallics 2007, 26, 633.
(12) Cho, H. G.; Andrews, L. J. Phys. Chem. A 2007, 111, 2480.
(13) Cho, H. G.; Andrews, L. Inorg. Chim. Acta 2008, 361, 551.
(14) (a) Lyon, J. T.; Andrews, L. Inorg. Chem. 2007, 46, 4799.
(b) Lyon, J. T.; Andrews, L. Organometallics 2006, 25, 1341. (c) Cho,
H. G.; Andrews, L. Inorg. Chem. 2005, 44, 979. (d) Cho, H. G.; Andrews,
L. Organometallics 2004, 23, 4357. (e) Cho, H. G.; Andrews, L. J. Am.
Chem. Soc. 2004, 126, 10485. (f) Cho, H. G.; Andrews, L. Inorg. Chem.
2004, 43, 5253. (g) Cho, H. G.; Andrews, L. J. Phys. Chem. A 2004,
108, 6294.
(15) (a) Cho, H. G.; Andrews, L. J. Phys. Chem. A 2006, 110, 10063.
(b) Cho, H. G.; Andrews, L. Organometallics 2006, 25, 477.
(16) (a) Lyon, J. T.; Cho, H. G.; Andrews, L. Organometallics 2007,
26, 6373. (b) Cho, H. G.; Andrews, L. J. Phys. Chem. A 2006, 110, 13151.
(c) Cho, H. G.; Andrews, L. Organometallics 2005, 24, 5678. (d) Cho,
H. G.; Andrews, L. Chem.—Eur. J. 2005, 11, 5017.
(17) (a) Lyon, J. T.; Andrews, L. Eur. J. Inorg. Chem. 2008, 1047.
(b) Andrews, L.; Cho, H.-G. J. Phys. Chem. A 2005, 109, 6796. (c) Lyon,
J. T.; Andrews, L. Inorg. Chem. 2005, 44, 8610.
’ ASSOCIATED CONTENT
S
Supporting Information. Figure S1: infrared spectra of
b
laser-ablated Lu atoms and CHF3 reaction products in solid
argon at 4 K; Figure S2: infrared spectra of laser-ablated Lu atoms
and CHF3 reaction products in solid neon at 4 K; Table S1:
calculated reaction and isomerization energies and frequencies
for open HFCLnF2 and DFCLnF2 except for Ln = La and Ce;
Table S2: calculated reaction and isomerization energies and
frequencies for the dibridged HC(FF)-LnF; Table S3: optimized
Cartesian x, y, z coordinates. This material is available free of
charge via the Internet at http://pubs.acs.org.
(18) (a) Lyon, J. T.; Andrews, L.; Hu, H.-S.; Li, J. Inorg. Chem. 2008,
47, 1435. (b) Lyon, J. T.; Andrews, L.; Malmqvist, P. A.; Roos, B. O.;
Wang, T.; Bursten, B. E. Inorg. Chem. 2007, 46, 4917. (c) Lyon, J. T.;
Andrews, L. Inorg. Chem. 2006, 45, 1847.
(19) Chen, M. Y.; Dixon, D. A.; Wang, X. F.; Cho, H. G.; Andrews, L.
J. Phys. Chem. A 2011, 115, 5609 (Ln+CH3F).
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: lsa@virginia.edu, dadixon@as.ua.edu.
(20) Wang, X. F.; Cho, H. G.; Andrews, L.; Chen, M. Y.; Dixon,
D. A.; Hu, H. S.; Li, J. J. Phys. Chem. A 2011, 115, 1913 (Ln+CH2F2).
(21) (a) Andrews, L.; Citra, A. Chem. Rev. 2002, 102, 885. (b) Andrews,
L. Chem. Soc. Rev. 2004, 33, 123.
(22) (a) Hohenberg, P.; Kohn, W. Phys. Rev. 1964, 136, B864.
(b) Kohn, W.; Sham, L. J. Phys. Rev. 1965, 140, A1133. (c) Parr, R. G.;
Yang, W. Density-Functional Theory of Atoms and Molecules; Oxford Univ.
Press: Oxford, 1989. (d) Salahub, E. D. R.; Zerner, M. C. The Challenge
of d and f Electrons; ACS: Washington, D.C., 1989.
(23) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.;
Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.;
Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.;
Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.;
’ ACKNOWLEDGMENT
We gratefully acknowledge financial support from DOE Office
of Science, Basic Energy Sciences Grant No. DE-SC0001034 and
NCSA computing Grant No. CHE07-0004N (University of Virginia)
and Grant No. DE-FG02-03ER15481 (University of Alabama).
D.A.D. thanks the Robert Ramsay Fund at the University of
Alabama for partial support. J. Thrasher (University of Alabama)
kindly provided the CDF3 sample.
’ REFERENCES
(1) (a) Schrock, R. R. Chem. Rev. 2002, 102, 145. (b) Schrock, R. R.;
Hoveyda, A. H. Angew. Chem., Int. Ed. 2003, 42, 4592. (c) Schrock, R. R.
Chem. Commun. 2005, 2773.
(2) (a) Scott, J.; Mindiola, D. J. Dalton Trans. 2009, 38, 2387.
(b) Mindiola, D. J.; Scott, J. Nat. Chem. 2011, 3, 15.
(3) (a) Herndon, J. W. Coord. Chem. Rev. 2006, 250, 1889. (b) Harder,
S. Coord. Chem. Rev. 2011, 255, 1252.
4451
dx.doi.org/10.1021/om200533q |Organometallics 2011, 30, 4443–4452

Organometallics
ARTICLE
Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich,
€
S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.;
Fox, D. J. Gaussian 09, Revision B.01; Gaussian, Inc.: Wallingford, CT,
2010. Frisch, M. J.; et al. Gaussian 09, Revision A.2; Gaussian, Inc.:
Wallingford, CT, 2009.
(24) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.;
Yang, Y.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
(25) Godbout, N.; Salahub, D. R.; Andzelm, J.; Wimmer, E. Can.
J. Chem. 1992, 70, 560.
(26) (a) Dolg, M.; Stoll, H.; Preuss, H. J. Chem. Phys. 1989, 90, 1730.
(b) Cao, X.; Dolg, M. J. Chem. Phys. 2001, 115, 7348.
(27) http://www.theochem.uni-stuttgart.de/pseudopotentials/index.
en.html.
(28) Cao, X.; Dolg, M. J. Molec. Struct. (THEOCHEM) 2002,
581, 139.
(29) Milligan, D. E.; Jacox, M. E. J. Chem. Phys. 1968, 48, 2265.
(30) Forney, D.; Jacox, M. E.; Irikura, K. K. J. Chem. Phys. 1994,
101, 8290.
(31) (a) Carver, T. G.; Andrews, L. J. Chem. Phys. 1969, 50, 5100.
(b) Jacox, M. E. J. Mol. Spectrosc. 1980, 81, 349.
(32) Andrews, L.; Prochaska, F. T. J. Phys. Chem. 1979, 83, 824.
(33) Kovꢀacsa, A.; Konings, R. J. M. J. Phys. Chem. Ref. Data 2004, 33,
337, and references therein.
(34) DeKock, C. W.; Wesley, R. D.; Radtke, D. D. High Temp. Sci.
1972, 4, 41.
(35) Shimanouchi, T. Tables of Molecular Vibrational Frequencies
Consolidated; National Bureau of Standards: Washington, D.C., 1972;
Vol. I.
(36) Jacox, M. E. Chem. Phys. 1994, 189, 149.
(37) Greenwood, N, N,; Earnshaw, A. Chemistry of the Elemenets;
Pergamon Press: Oxford, 1984; pp 1429À1432.
(38) Lesiecki, M.; Nibler, J. W.; DeKock, C. W. J. Chem. Phys. 1972,
57, 13852.
(39) (a) Cho, H.-G.; Andrews, L.; Vlaisavljevich, B; Gagliardi, L.
Organometallics 2009, 28, 6871. (b) Cho, H.-G.; Lyon, J. T.; Andrews, L.
Organometallics 2008, 27, 5241.
(40) Cho, H.-G.; Andrews, L. Organometallics 2009, 28, 5623.
(41) Luo, Y.-R. Comprehensive Handbook of Chemical Bond Energies;
CRC Press, Taylor and Francis Group: Boca Raton, FL, USA, 2007.
4452
dx.doi.org/10.1021/om200533q |Organometallics 2011, 30, 4443–4452