Structure and dynamics in a bis(perfluoroalkyl)triazapentadiene methylmercury compound

Article abstract of DOI:10.1021/om030408f

The compound [Ph₂N₃C₂(C₃F ₇)₂]HgCH₃ was synthesized from Na[Ph ₂N₃C₂(C₃F₇)₂] and CH_3- HgCl. In solution, it exists as a mixture of two isomers that interconvert slowly on the NMR time scale. Both isomers feature a η¹-Ph₂N₃C₂(C₃F ₇₎₂ ligand. In the asymmetrical one, the CH₃Hg group is bonded to one of the two terminal nitrogen atoms. In the more stable symmetrical isomer, [PhN=C(C₃F₇)]₂NHgCH₃, mercury is attached to the central nitrogen atom. It is this isomer that crystallizes and that was characterized by X-ray diffraction. Thermodynamic parameters for the CH₃Hg shift reaction were obtained by DNMR spectroscopy. ¹⁹F NMR spectra were analyzed. A metallotropic rearrangement was not observed in [Ph₂N₃C ₂(C₃F₇)₂]AuPPh₃.

Full text of DOI:10.1021/om030408f

Organometallics 2004, 23, 2281-2286
2281
Str u ctu r e a n d Dyn a m ics in a
Bis(p er flu or oa lk yl)tr ia za p en ta d ien e Meth ylm er cu r y
Com p ou n d
A. R. Siedle,*,† Robert J . Webb,† Myles Brostrom,† Richard A. Newmark,†
Fred E. Behr,‡ and Victor G. Young, J r.§
3M Corporate Research Laboratories, St. Paul, Minnesota 55144, 3M Specialty Materials
Division, St. Paul, Minnesota 55144, and Chemistry Department, University of Minnesota,
Minneapolis, Minnesota 55455
Received May 30, 2003
The compound [Ph2N3C2(C3F7)2]HgCH3 was synthesized from Na[Ph2N3C2(C3F7)2] and CH3-
HgCl. In solution, it exists as a mixture of two isomers that interconvert slowly on the NMR
time scale. Both isomers feature a η1-Ph2N3C2(C3F7)2 ligand. In the asymmetrical one, the
CH3Hg group is bonded to one of the two terminal nitrogen atoms. In the more stable
symmetrical isomer, [PhNdC(C3F7)]2NHgCH3, mercury is attached to the central nitrogen
atom. It is this isomer that crystallizes and that was characterized by X-ray diffraction.
Thermodynamic parameters for the CH3Hg shift reaction were obtained by DNMR
spectroscopy. 19F NMR spectra were analyzed. A metallotropic rearrangement was not
observed in [Ph2N3C2(C3F7)2]AuPPh3.
In tr od u ction
1.0 (w/2 20 Hz) and -0.13 (w/2 14 Hz). These two peaks
persisted unchanged after repeated recrystallizations
from hexane, casting doubt on the initial hypothesis that
the product was merely impure.
Reaction of perfluoro-5-aza-4-nonene, C3F7-CFdN-
C4F9, with primary amines, exemplified by aniline,
proceeds by a series of addition-HF elimination pro-
cesses and yields the triazapentadiene Ph2N3C2(C3F7)2H,
1, a triaza analogue of the much studied diimines. This
compound is a weak acid that can be readily deproto-
nated to form Ph2N3C2(C3F7)2(-), 2, which has a rich and
diverse coordination chemistry.1,2 Alkylation of 2 with
CH3I affords Ph2N3C2(C3F7)2CH3, 3, in which the methyl
group is attached to a terminal nitrogen atom. A similar
reaction with CH3HgCl was carried out to obtain the
N-HgCH3 analogue. The reaction was successful, but the
product has an unanticipated structure with mercury
being bonded to the central rather than the terminal
nitrogen atom. This diimine complex exists in solution
in equilibrium with another isomer in which mercury
is bonded to the terminal nitrogen atom.
On cooling, both 1H signals sharpen; the lower field
one decreases in intensity, while that at δ -0.13
increases. Conversely, upon heating, both resonances
broaden and then coalesce. Exemplary variable-tem-
perature 1H NMR spectra (1,2-C2D2Cl4 solvent) are
shown in Figure 1. They indicate that 4 is actually a
mixture of two slowly interconverting isomers, 4a and
4b, with the latter being more stable. Analysis of the
DNMR data indicates that ∆Ho and ∆So are 10.5 kJ
mol-1 and 35 J K-1 mol-1, respectively, and that the
barrier connecting the two isomers is 69 kJ mol-1. The
4a :4b ratio is little affected by solvent, being 1:1.1 in
c-C6D12 at 30°. The structures of the two isomers were
inferred from 19F NMR spectra at -25 °C. At this
temperature, 4b is more abundant, and so assignments
to the two species present can be made on the basis of
relative peak intensities. The minor isomer 4a (at this
temperature) has inequivalent C3F7 groups. By analogy
to 3, it is considered to be [η1-1-Ph2N3C2(C3F7)2]HgCH3,
in which the HgCH3 group is attached to one of the
terminal nitrogen atoms. In contrast, isomer 4b has
equivalent C3F7 groups. Although several structures
having this feature can be imagined, we believe that
the correct one is [η1-2-Ph2N3C2(C3F7)2]HgCH3, in which
the CH3Hg group is attached to the central nitrogen
atom. Although such a bonding mode has not been
observed before in triazapentadienide chemistry, it is
the one that occurs in the crystalline state (vide infra).
NMR Sp ectr a . Data for 4a and 4b are collected in
Table 1. The CH3 protons in both are in a normal
position for alkylmercury compounds.3 The CH3 shifts
Resu lts
Syn th etic Ch em istr y a n d Dyn a m ic P r op er ties.
Reaction of 1 with NaH in THF produced Na[Ph2N3C2-
(C3F7)2], treatment of which with 1 equiv of CH3HgCl
yielded [Ph2N3C2(C3F7)2]HgCH3, 4. Analytical and mass
spectral data were wholly consistent with a single
1
species of this composition. The H NMR spectrum of 4
revealed two broad HgCH3 signals in a 1:1 ratio at δ
* Corresponding author. E-mail: arsiedle@mmm.com.
† 3M Corporate Research Laboratories.
‡ 3M Specialty Materials Division.
§ University of Minnesota.
(1) Siedle, A. R.; Webb, R. J .; Behr, F. E.; Newmark, R. A.; Weil, D.
A.; Erickson, K.; Naujok, R.;Brostrom, M.; Mueller, M.; Chou, S.-H.;
Young, V. G., J r. Inorg. Chem. 2003, 42, 932.
(2) Siedle, A. R.; Webb, R. J .; Brostrom, M.; Chou, S.-H.; Weil, D.
A.; Newmark, R. A.; Behr, F.; Young, V. G., J r. Inorg. Chem. 2003, 42,
2596.
(3) Nugent, W. A.; Kochi, J . K. J . Am. Chem. Soc. 1976, 98, 5979.
10.1021/om030408f CCC: $27.50 © 2004 American Chemical Society
Publication on Web 03/25/2004

2282 Organometallics, Vol. 23, No. 10, 2004
Siedle et al.
1
F igu r e 1. Variable-temperature H NMR spectra of 4a and 4b in 1,2-C2D4Cl2. The δ 1.7 peak at -25 °C is attributed to
adventitious water. Temperatures (top to bottom, °C) are 100, 75, 50, 30, 0, and -25.
Ta ble 1. NMR Da ta for 4a a n d 4ba
4a
4b
1H
1.0 (w/2 ) 20, J HCHg ) 191) CH3
1H
-0.13 (w/2 ) 14, J HCHg ) 202), CH3
2
2
13C
147.6, 147.4 (t, J CF ∼ 25) CCF2
13C
151.8 (dd, J CF ) 32, 21), CCF2
2
2
145.7, 142.7 (Ph Cipso
)
)
145.9 (Ph Cipso
129.9 (Ph Cmeta
126.2 (Ph Cpara
121.3 (Ph Cortho
)
129.6, 128.3 (Ph Cmeta
126.3, 124.69 (Ph Cpara
124.75, 122.6 (Ph
)
)
)
)
)
ortho
1.87 (w/2 ) 34), CH3
1.64 (w/2 ) 16, J CHg ) 754), CH3
19F
-80.42 (t,4J FF ) 11), CF3
19F
-80.21 (dd, J FF ) 12, 7), CF3
4
-81.11 (t,4J FF ) 9), CF3
-108.25 (d of heptets, 269, 8), CF2(a)C
-117.21 (d, 270), CF2(b)C
-124.17 (dt, 290, 12), CF3CF2(a)
-126.83 (dd, 290, 5), CF3CF2(b)
-770 (w/2 ) 103)
AB quartet, δA ) -112.3, δB ) -113.8, J AB ) 270, CF2C
AB quartet, δA ) -115.7, δB ) -121.5, J AB ) 262, CF2C
AB quartet, δA ) -125.0, δB ) -125.8, J AB ) 289, CF3CF2
AB quartet, δA ) -127.8, δB ) -128.0, J AB ) 286, CF3CF2
-926 (w/2 ) 429)
199Hg
199Hg
a
In 1,2-C2D2Cl4 at -25 °C. Coupling constants and line widths at half-height are in Hz.
Sch em e 1
it is difficult to make correlations with structure. The
problem is compounded by the dominant effect of the
paramagnetic shielding term.5 Nevertheless, shifts for
4a ,b, -926 and -770 ppm, are in the range found for
two-coordinate mercury in CH3HgX (X ) Cl, Br, I: -811,
-910, -1085 ppm, respectively).6 Changes in metal
coordination number from 2 to 3 or 4 are associated with
substantially decreased 199Hg shielding.7 Given that δ
-770 represents two-coordinate mercury in 4b, the
upfield shift of only 156 ppm in 4a appears to be small
and inconsistent with three-coordinate mercury, as
would occur in a η3-NCN diaza-allyl structure.
Some additional aspects of the NMR data warrant
1
comment. First, the H, 13C, 19F, and 199Hg resonances
for 4a are broader than for 4b. This effect is presumably
due to migration of the HgCH3 moiety from central to
terminal positions, a process, which, at this tempera-
ture, is intermediate on the NMR time scale. Second,
in 4a , the geminally inequivalent CF3CF2 geminal AB
doublets (J ≈ 280 Hz) show very different line widths.
Further, the two relatively sharp CF3CF2 resonances
(5) Goodfellow, R. J . In Multinuclear NMR; Mason, J ., Ed.; Ple-
num: New York, 1987; p 583.
(6) Kennedy, J . D.; McFarlane, W. J . Chem. Soc., Faraday Trans. 2
1976, 1653.
(7) (a) Wrackmeyer, B.; Contreras, R. Ann. Rept. NMR Spectrosc.
1992, 24, 267. (b) Bebout, D. C.; Garland, M. M.; Murphy, G. S.;
Bowers, E. V.; Abelt, C. J .; Butcher, R. J . J . Chem. Soc., Dalton Trans.
2003, 2578. (c) Goodfellow, R. J . In Multinuclear NMR; Mason, J ., Ed.;
Plenum: New York, 1987; p 580.
are substantially upfield of the model compound CH3-
2
HgCl, δ 6.03, but the J H-C-Hg values are unremark-
able.4 199Hg chemical shifts cover such a large range that
(4) Wilson, N. K.; Zehr, R. D.; Ellis, P. D. J . Magn. Reson. 1976, 21,
437.

Bis(perfluoroalkyl)triazapentadiene Methylmercury
Organometallics, Vol. 23, No. 10, 2004 2283
F igu r e 2. 19F NMR spectrum of 4a and 4b in 1,2-C2D4Cl2 at -25 °C. Insets of the resonances showing FF coupling are
resolution enhanced. Other resonances of 4b are exchange broadened.
Ta ble 2. 19F -19F NMR COSY Cor r ela tion s in 4b
in 4b). The broader δ -117.21 resonance will exhibit
attenuated COSY intensity, and so the larger coupling,
12.4 Hz, must be due to this fluorine. The COSY
spectrum also indicates strong correlations between the
12.4 Hz triplet at δ -124.17 and both the δ -108.25
and -117.21 multiplets. The former correlation is 3-fold
stronger, although both correlations must be from
identical 12 Hz coupling constants, thus confirming the
attenuation due to the greater line width of the latter.
There is also a strong correlation between the δ
-108.25 resonance and the poorly resolved 5 Hz mul-
tiplets in the AB pattern centered at δ -126.83. We
conclude that, to a first approximation, the multiplets
for the fluorine at δ -108.25 should be a 270 Hz doublet
of 12.4 doublets of 6.2 Hz quartets of 5 Hz doublets.
Each half of the 270 Hz doublet is then approximately
12 Hz doublets of 6 Hz quintets, which gives an
apparent 6 Hz heptet with calculated intensities of
1:4:7:8:7:4:1, in good agreement with experiment.
fluorine
δ (ppm)
J ’s (Hz)
COSY correlations
CF3
-80.21 dd, 12.2, 6.9
-108.25 d of heptets,
270, 8
-108.25, -117.21
CFAFBN
CFAFBN
-80.21, -117.21, -124.17,
-126.83
-117.21 d, 271a
-80.21, -108.25, -124.17
CFAFBCF3 -124.17 dt, 289.4, 12.4 -126.83, -108.25, -117.21
CFAFBCF3 -126.83 dd, 289, 5b
-108.25, -124.17
a
Broad resonances due to exchange; coupling under 10 Hz
would not be resolved. b5 Hz splitting is barely resolved.
in 4b also show different line widths with resolved
couplings in the downfield doublets but broader reso-
nances without resolved coupling in the upfield dou-
blets. We conclude that, at -25 °C, both 4a and 4b are
each involved in dynamic processes in addition to the
equilibrium between the two. Similar effects have also
been seen in 2, and on the basis of DNMR studies of
[Bu4N][Ph2N3C2(C3F7)2],8 we think that the process
involves restricted rotation about the C-N bonds in the
triazapentadiene ligand.
3
Vicinal J FF coupling constants in perfluoroalkyl
A
19F NMR spectrum of 4a ,b at -25 °C is shown in
groups are typically undetectable (<2 Hz). Larger values
of 3J FF occur in XCF2-CF2Y if X and Y have electrone-
gativities different from that of carbon. They range from
+3.5 Hz in CF3-CF3 to -23 Hz in CF2Cl-CFClI.9,10 The
3J FF coupling constants are also a function of dihedral
angle: they are -16.1 and -21.5 Hz in the asym-
metrical and symmetrical isomers of CF2Br-CFBr2.11
It is unclear how to assess the effect of the MeHgN
Figure 2; resolution-enhanced expansions of selected
regions of the spectrum are displayed as insets and 19F
COSY correlations are listed in Table 2. A COSY
spectrum is included in the Supporting Information.
Scrutiny of the data in this figure for the η1-N(2) isomer
4b reveals some unusual features. The CF3 fluorines, δ
-80.21, appear as a double doublet, J ) 12 and 7 Hz,
due to four-bond coupling to the two inequivalent CF2
substituent on the electron distribution in the C
3F7
4
fluorines, δ -108.25 and -117.21. The J FF values are
groups. It appears, however, that the conformations of
the CF3-CF2Y moieties are impacted because the two
4J FF couplings differ by 5.3 Hz in 4b but are identical
in 4a .
Evidence for a second isomer of 4 in solution was also
obtained using infrared spectroscopy. The solid in a
Nujol mull shows two bands in the C-N stretching
region at 1606 and 1588 cm-1 that are attributable to
4b. In 1,2-C2D2Cl4 solution, the same two bands (at 1610
and 1587 cm-1) are seen, but, in addition, there is an
additional C-N stretching band appearing as a shoulder
within normal limits for such a spin-spin interaction,
but it is remarkable that they are different. The 19F
resonance at δ -108.25 is a symmetrical 270 Hz doublet
of 8 Hz heptets. Large couplings to the δ -126.83
fluorines are indicated by a COSY experiment, but only
3
the δ -124.17 resonance shows resolved J FF coupling
(as a 12.4 Hz triplet). The COSY intensities for the
correlations from the δ -80.21 CF3 to the geminally
inequivalent fluorines at δ -108.25 and -117.21 are
identical despite the broadening present in the latter
resonance (possibly due to additional dynamic processes
(9) Graves, R. E.; Newmark, R. A. J . Chem. Phys. 1967, 47, 3681.
(10) Cavalli, L. J . Magn. Reson. 1972, 6, 298.
(11) Newmark, R. A.; Sederholm, C. H. J . Chem. Phys. 1965, 43,
602.
(8) Siedle, A. R.; Webb, R. J .; Brostrom, M.; Chou, S.-H.; Weil, D.
A.; Newmark, R. A.; Behr, F. E.; Young, V. G., J r., submitted for
publication.

2284 Organometallics, Vol. 23, No. 10, 2004
Siedle et al.
F igu r e 3. ORTEP drawing of η1-[PhNdC(C3F7)]2NHgMe,
4b. The Hg atom (arrow) lies between N1 and the CH3
group behind it.
Ta ble 3. Selected Bon d Dista n ces (Å) An gles (d eg)
in 4b
F igu r e 4. ORTEP drawing of η1-[PhNdC(C3F7)]2NHgMe,
4b; packing diagram along the c-axis.
C(1)-Hg(1)
Hg(1)-N(1)
N(1)-C(2)
C(2)-N(2)
N(2)-C(6)
2.029(17)
2.168(14)
1.368(9)
1.272(8)
1.414(8)
rather long in comparison with, for example, [(7-
methylguanine)HgCH3]‚2H2O, 2.101(5) Å, and [(7-
methylguanine‚H)HgCH3][NO3], 2.111(4) Å.13 The in-
termolecular and intramolecular distances between the
center of the phenyl rings to Hg are 4.78 and 3.20 Å,
respectively.
C(1)-Hg(1)-N(1)
C(2)-N(2)-C(6)
N(1)-C(2)-N(2)
C(2)-N(1)-C(2)#1
180.000(2)
119.1(5)
129.6(7)
127.3(12)
Each molecule contains four equivalent 2.50 Å inter-
molecular contacts between H(10A), a meta hydrogen
atom in a phenyl ring, and F4, located in the â-CF2
group in the adjacent PhNdC(C3F7) group. The C(4)-
F(4)-H(10A) and C(10)-H(10A)-F(4) angles, 127.5°
and 164.9°, respectively, indicate a relatively strong
interaction between F(4) and H(10A). The molecule
contains two equivalent 2.74 Å intramolecular contacts
between H(7A), an ortho hydrogen atom in a phenyl
ring, and F(3), located in the â-CF2 group in the adjacent
PhNdC(C3F7) group. The C(4)-F(3)-H(7A) and C(7A)-
H(7A)-F(3) angles, 115.3° and 124.8°, respectively, are
so acute as to imply that this interaction is primarily
electrostatic in nature.13 There are four layers of
molecules in the unit cell, and the orientation of the
molecules in a single layer is identical. Adjacent layers
are related by a translation along the c axis by c/4 and
molecules within a layer are rotated 90° about the c axis
with respect to adjacent layers. Intramolecular contacts
are between layers separated by c/2 and which have the
same molecular orientation.
at 1640 cm-1 that is attributed to 4a (cf. 1645 and 1588
cm-1 for 3 in Nujol).
Molecu la r Str u ctu r e of [P h 2N3C2(C3F 7)2]HgCH3.
An ORTEP view of the structure and numbering scheme
are shown in Figure 3. Intramolecular bond distances
and angles are summarized in Table 3.2 The N3C2
skeleton approximates a helix. The CH3Hg moiety is
bonded to the center nitrogen atom [N(1) in Figure 3]
in it. C(1), Hg, and N(1) lie on a crystallographic 2-fold
axis, and the N(1)-Hg-C(1) axis coincides with the
crystallographic c axis. The CH3 group is 2-fold rota-
tionally disordered with equal populations of the two
conformations. A packing diagram viewed along the
crystallographic c axis is shown in Figure 4.
There is a short-long-short-long pattern in the
C-N bond lengths: the C(2)-N(2) and N(1)-C(2)
distances are 1.272(8) and 1.368(9) Å, respectively. This
is consistent with localized CdN and C-N bonding, and
in valence bond formalism, the structure can be written
as PhNdC(C3F7)-N(HgCH3)-C(C3F7)dNPh. For com-
parison, in a series of tri- and tetraaza-heptadienyl-
lithium compounds, C(sp2)dN(sp2) and C(sp2)-N(sp2)
bond distances of 1.28 and 1.37 Å, respectively, were
reported.12 The coordination geometry of mercury is
precisely linear because of crystallographic constraints,
in accord with the tendency for linear geometry in
organomercury compounds. D(Hg-N), 2.168(14) Å, is
Discu ssion
Nucleophilic displacement of chloride from CH3HgCl
by the triazapentadienide anion Ph2N3C2(C3F7)2- affords
(13) Sheldrick, W. S.; Gross, P. Inorg. Chim. Acta 1988, 153, 247.
Similar Hg-N distances have been reported for CH3Hg derivatives of
1-methyladenine [Sheldrick, W. S.; Heeb, G. Inorg. Chim. Acta 1992,
194, 67] and 7-azaindole [Dufour, P.; Dartiguenave, Y.; Dartiguenave,
M.; Dufour, N.; Lebuis, A.-M.; Belanger-Gariepy, F.; Beauchamp, A.
L. Can. J . Chem. 1990, 68, 193].
(12) Boesveld, W. M.; Hitchcock, P. B.; Lappert, M. F. J . Chem. Soc.,
Dalton Trans. 1999, 4014.

Bis(perfluoroalkyl)triazapentadiene Methylmercury
Organometallics, Vol. 23, No. 10, 2004 2285
1
[Ph2N3C2(C3F7)2]HgCH3. Variable-temperature H and
Na[Ph2N3C2(C3F7)2] and Ph3PAuCl. This compound has
nonequivalent C3F7 groups, and so it is believed to
contain a η1-Ph2N3C2(C3F7)2 ligand as in 3 and 4a . The
19F NMR spectra of this compound are both subtle and
complex and have not been completely analyzed. The
CF2C fluorine resonances are broad. The broadening is
not symmetric within either CF2 group, suggestive of
three dynamic processes: two averaging the inequiva-
lent CF2 fluorine nuclei in different CF2 groups and
another averaging the two different C3F7 groups. The
latter process is somewhat slower on the NMR time
scale because there is no line broadening evident in the
resolution-enhanced 13C NMR of the N-C6H5 groups. We
believe that the first two processes reflect restricted
rotation about C-N bonds in the N3C2 skeleton. How-
ever, in the context of the isomeric pair of HgMe
compounds 4a ,b, 19F spectra between +50 and -50 °C
show no evidence of an additional, stable, symmetrical
isomer corresponding to 4b.
19F NMR spectra showed that, in 1,2-C2D2Cl4 or CDCl3
solution, this compound exists as two slowly intercon-
verting (at room temperature) isomers. The minor, less
stable, and asymmetrical one, 4a , is formulated as
having the CH3Hg group attached to a terminal nitrogen
atom. The more abundant, more stable symmetrical
isomer, 4b, is considered to have the CH3Hg moiety
attached to the central nitrogen atom, and it is this
bonding mode that was revealed by an X-ray diffraction
study of crystals obtained from hexane.
As the temperature is increased, the CH3Hg group
moves increasingly rapidly among the two terminal and
central nitrogen sites. Metallotropic rearrangements, in
which a metal atom moves from one ligating site to
another, are well known in organometallic and coordi-
nation chemistry. Pertinent examples are the 1,3-shifts
of HgR groups in ArN(HgR)-NdNAr′ and ArN(HgR)d
CH-NAr′.15 Often, only one of several equilibrating
structures is observed in solution, the other(s) being
intermediates lying in shallow wells on the potential
energy surface. It is therefore interesting that, in the
case of 4, the concentrations of the two isomers at 25
°C are instead approximately equal. The long Hg-N
distance in 4b, as well as the similarity of its 199Hg
Exp er im en ta l Section
Gen er a l P r oced u r es. NMR spectra were obtained on a
Varian XL-600 instrument with a 1H operating frequency of
600 MHz. Chemical shifts are expressed in ppm relative to
internal (CH3)4Si (1H and 13C) or CFCl3 (19F); coupling con-
stants and line widths at half-height are in Hz. {1H}199Hg
spectra were referenced to external saturated aqueous Hg-
(NO3)2 (δ -2340 ppm) but are expressed relative to (CH3)2Hg
(0.0 ppm).
2
chemical shift and J HCHg coupling constant to the
methylmercury halides, suggests that the [PhNd
C(C3F7)]2N group is electron-withdrawing, cf. (CF3-
SO2)2N.16
[P h 2N3C2(C3F 7)2]HgCH3, 4. A suspension of (excess) NaH
in THF and 0.56 g of 1 (1 mmol) were stirred under N2 until
gas evolution ceased. The reaction mixture was allowed to
settle and decanted by cannula into a clean Schlenk tube
containing 0.25 g (1 mmol) of MeHgCl. After stirring for 16 h,
the solvent was evaporated. The residue was sublimed at 100-
120 °C onto a water-cooled probe to give 0.66 g of product. This
was crystallized from hexane to give 0.51 g (66%) of colorless
blocks, mp 88-89 °C. The compound developed a light pink
color on standing in daylight and so was stored in a dark bottle.
Anal. Calcd (found) for C21H13F14HgN3: C, 32.6 (32.5); H, 1.7
(1.7); Hg, 26.0 (25.8); N, 5.4 (5.5). MS: m/z 771.038 with Hg
isotopomers; 606.057 (M+ - C3F7); 558.052 (M+ - HgCH3). IR
(Nujol): 1606, 1588, 1351, 1325, 1220, 1160, 1116, 847, 758,
743, 706, 698, 651 cm-1. Raman (neat, λex 782 nm): 1635, 1585,
1227, 1002 cm-1. UV [isooctane, λmax (log ꢀ)]: 202 (3.97), 285
(sh) nm. Molar conductance (1.4 × 10-3 M in CH3CN): 14 Ω-1
cm2 mol-1. Crystals for the X-ray study were grown from
hexane solution.
The triazapentadienide ligand 2 bears comparison
with â-diketonates, which most often occur as η2-O,O
structures.17 However, heavy metallic elements such as
Pt and Hg give rise to η1-C structures in which the metal
is attached to the central carbon atom of the ligand. Bis-
(dipivaloylmethyl)mercury crystallizes as an isomer in
which both ligands are C-bonded to the metal, but in
solution, additional isomers in which one or both dike-
tonates are in a η1-enol form were detected by NMR.18
This is analogous to the 4a -4b rearrangement. How-
ever, with â-diketone ligands, the ligating atom changes
from carbon to oxygen, whereas in the triazapentadi-
enide complex, the ligating atom in both forms is
nitrogen. Thus, at this point, it is not understood why
4b is more stable than 4a .
Similarly, it is not clear why only 4b crystallizes from
a solution containing both 4a and 4b except to note that,
in solution, the latter is more stable. When 4b is melted
then cooled and allowed to crystallize, the melting point
is unchanged. This indicates that only 4b crystallizes
from the melt.
To see if metallotropic rearrangements analogous to
that seen for mercury would occur with other heavy
metals, [Ph2N3C2(C3F7)2]AuPPh3, 5, was prepared from
[P h 2N3C2(C3F 7)2]Au P P h 3, 5. To a solution of 1 mmol of Na-
[Ph2N3C2(C3F7)2] in 15 mL of THF was added 0.495 g (1 mmol)
of Ph3PAuCl. After stirring for 16 h, solvent was evaporated.
The residue was extracted with boiling heptane. Concentration
and cooling of the filtered extract gave 0.60 g (54%) of a yellow
solid that crystallized upon standing, mp 91-93 °C after
vacuum-drying. Anal. Calcd (found) for C38H25AuF14N3P: C,
44.8 (44.8); H, 2.5 (2.6); N, 4.4 (4.1). MS: m/z 1017.1155 (M+,
calcd 1017.1222), 848 (M+ - C3F7). IR (Nujol): 1606, 1569,
1236, 1207, 1121, 1104, 748, 594, 547, and 506 cm-1. NMR
(14) Steiner, T. Angew Chem., Int. Ed. 2002, 41, 48.
(15) (a) Kuz’mina, L. G.; Struchkov, Y. T.; Krautsov, D. N. J . Struct.
Chem. (Engl. Transl.) 1979, 20, 470. (b) Kuz’mina, L. G.; Bokii, N. G.;
Struchkov, Y. Y.; Minkin, V. I.; Olekhnovich, L.ikhailov, I. E. J . Struct.
Chem. (Engl. Trans.) 1977, 18, 96. Cited by Wardell, J . L. In
Comprehensive Organometallic Chemistry; Pergamon: New York,
1982; Vol. 2, p 918.
4
4
(CDCl3, 30 °C) 19F: -80.2 (t, J FF ) 7) and -81.1 (t, J FF ) 9)
(CF3), -111.3 and -111.8 (AB quartet, J AB ) 265, CF2C),
-116.1 and -122.0 (AB quartet, J AB ) 259, CF2C), -126.6 and
-125.7 (AB quartet, J AB ) 281, CF3CF2), -127.9 and -128.2
(AB quartet, J AB ) 283, CF3CF2). 31P: 26.8 (s). UV [CH3CN,
λmax (log ꢀ)] 204 (4.90), 240 (sh), and 320 (sh) nm. Molar
2
(16) The J HCHg coupling constant in CH3HgX compounds has been
correlated with numerous physical and chemical properties of the X
group: (a) Scheffold, R. Helv. Chim. Acta 1967, 50, 1419 (b) Scheffold,
R. Helv. Chim. Acta 1969, 52, 56.
conductance (1.8 × 10-3 M in CH3CN): 11 Ω-1 cm2 mol-1
.
(17) Siedle, A. R. In Comprehensive Coordination Chemistry; Wilkin-
son, G. W., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: New York,
1987; Vol. 2, p 365.
(18) Allman, R.; Flateau, K.; Musso, H. Chem. Ber. 1972, 105, 3067.
Dynamics of a similar rearrangement in (C3F7-CO-CH-CO-tC4H9)2-
Hg have been reported: Fish, R. H. J . Am. Chem. Soc. 1974, 96, 6664.

2286 Organometallics, Vol. 23, No. 10, 2004
Siedle et al.
Ta ble 4. Cr ysta l Da ta a n d Refin em en t for 4b
tions. Data collection was carried out with a frame time of 30
s and a detector distance of 4.9 cm. A randomly oriented region
of reciprocal space was surveyed to the extent of 1.5 hemi-
spheres and to a resolution of 0.77 Å. Three major sections of
frames were collected with 0.50° steps in ω at three different
φ settings and a detector position of -28° in 2θ. Intensity data
were corrected for absorption and decay with SADABS.19 Final
cell constants were calculated from 3800 strong reflections
from the actual data collection after integration (SAINT
6.01).20
formula
C21H13F14HgN3
773.93
fw
temp, K
173(2)
cryst habit, color
cryst size, mm
cryst syst
space group
unit cell dimens
block, colorless
0.40 × 0.37 × 0.21
orthorhombic
Fdd2
a ) 17.814(4) Å, R ) 90°
b ) 20.590(4) Å, â ) 90°
c ) 13.184(3) Å, γ ) 90°
4835.7(17)
The structure was solved using SHELXS-8621 and refined
using SHELXL-97. The space group was determined on the
basis of systematic absences and intensity statistics. A direct-
methods solution was calculated that provided most non-
hydrogen atoms from the E-map. Full-matrix least-squares/
difference Fourier cycles were performed that located the
remaining non-hydrogen atoms. All non-hydrogen atoms were
refined with anisotropic displacement parameters unless
otherwise noted. All hydrogen atoms were placed in ideal
positions and refined as riding atoms with relative isotropic
displacement parameters. No disorder or twinning was found
in the structure. Crystallographic data are summarized in
Table 4.
V, Å3
Z
F
8
calcd, g cm-3
2.126
λ, Å
0.71073
6.490
abs coeff, mm-1
θ range for data collection, deg
no. of reflns collected
no. of indep reflns
max., min. transmn
no. of data/restraints/params
GOF on F2
2.16 to 27.57
10 691
2426 [R(int) ) 0.0345]
1.000000 and 0.599670
2774/1/179
1.061
final R indices [I>2σ(I)]
R indices (all data)
abs struct param
R1 ) 0.0282, wR2 ) 0.0694
R1 ) 0.0356, wR2 ) 0.0729
-0.025(11)
largest diff peak and hole, e Å-3
1.103 and -0.653
Su p p or tin g In for m a tion Ava ila ble: 19F COSY spectrum
of 4a ,b and X-ray file in CIF format. This information is
available free of charge via the Internet at http://pubs.acs.org.
A similar reaction with Et3PAuCl produced metallic gold.
X-r a y Cr ysta llogr a p h ic An a lysis. A crystal was secured
to a 0.1 mm glass fiber and mounted on a Bruker SMART
system for data collection. A preliminary set of cell constants
was calculated from reflections harvested from 3 sets of 20
frames. The initial sets of frames were oriented so that
orthogonal wedges of reciprocal space were surveyed. This
produced orientation matrixes determined from 180 reflec-
OM030408F
(19) An empirical correction for absorption anisotropy: Blessing, R.
Acta Crystallogr. 1995, A51, 33.
(20) SAINT V6.1; Bruker Analytical X-Ray Systems: Madison, WI.
(21) SHELXTL-Plus V5.10; Bruker Analytical X-Ray Systems: Madi-
son, WI.