Reactions of the perfluoroalkyltriazapentadiene Ph2N3C2(C3F7) 2H with acids, bases, and water

Article abstract of DOI:10.1021/ic020716q

Treatment of the bis(perfluoroalkyl)triazapentadiene PhN=C(C₃F₇)-N=C(C₃F₇)-NHPh, 2, with bases affords salts of the conjugate base. Alkylation of the Na⁺ salt with CH₃l yields PhN=C(C₃F₇)-N=C(C₃F₇)-NMePh. The crystal structure of [Bu₄N][Ph₂N₃C₂ (C₃F₇)₂] demonstrates a twisted, zigzag geometry for the anion in the solid state, but in solution, it is conformationally unstable. Both compounds are stable in aqueous methanol, but hydrolysis occurs under acidic conditions. Protonation with CF₃SO₃H acid occurs at the sp² nitrogen to give [PhN_H^..HC(C₃F₇) ^..N^..-C-(C₃F₇)- ^..NHPh][CF₃SO₃]. Heating 2 in CF₃SO₃H produces 2,4-bis(heptafluoropropyl)-1,3-quinazoline.

Full text of DOI:10.1021/ic020716q

Inorg. Chem. 2003, 42, 2596−2601
Reactions of the Perfluoroalkyltriazapentadiene Ph2N3C2(C F ) H with
3 7 2
Acids, Bases, and Water
,†
A. R. Siedle,* Robert J. Webb,† Myles Brostrom,† Shih-Hung Chou,† David A. Weil,†
Richard A. Newmark,† Fred E. Behr,‡ and Victor G. Young, Jr.§
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 December 13, 2002
Treatment of the bis(perfluoroalkyl)triazapentadiene PhNdC(C F )sNdC(C F )sNHPh, 2, with bases affords salts
3
7
3 7
of the conjugate base. Alkylation of the Na+ salt with CH I yields PhNdC(C F )sNdC(C F )sNMePh. The crystal
3
3
7
3 7
structure of [Bu4N][Ph2N C (C F ) ] demonstrates a twisted, zigzag geometry for the anion in the solid state, but in
3
2
3 7 2
solution, it is conformationally unstable. Both compounds are stable in aqueous methanol, but hydrolysis occurs
under acidic conditions. Protonation with CF SO H acid occurs at the sp2 nitrogen to give [PhN-HC(C F )-N-C-
3
3
H
3
7
(C F )-NHPh][CF SO ]. Heating 2 in CF SO H produces 2,4-bis(heptafluoropropyl)-1,3-quinazoline.
3
7
3
3
3
3
Introduction
and conjugate acid of 2. The alkali metal and silver salts of
2 reported here are useful in preparing inorganic and
organometallic coordination complexes through metathetic
reactions.
-
Pentadienyl anions, the acyclic analogues of C5H5 , that
contain heteroatoms as part of the five-atom conjugated π
system have attracted attention because of their synthetic
utility and theoretical interest.1 The reaction of perfluoro-5-
aza-4-nonene, C3F7sCFdNsC4F9, 1, with primary amines
yields triazapentadienes, RN(3)dC(2)(C3F7)sN(1)dC(1)-
(C3F7)sN(2)HR (the skeletal atom numbering scheme is
designed for easy reference to that in the crystal structure of
the derived anion, vide infra), whose chemistry has recently
been outlined.2 This paper reports some fundamental chem-
istry of 2 (R ) Ph), an exemplary member of this broad
class of compounds, which is obtained from 1 and aniline.
Triazapentadienes are amphoteric because they contain an
ionizable NH hydrogen atom and two potentially basic sp2
nitrogen atoms. We describe here the synthesis, structure,
and reactivity (including hydrolysis) of the conjugate base
Results and Discussion
Triazapentadiene 2 is a weak monoprotic acid. Its pKa in
dimethyl sulfoxide is 14.3. Salts of the conjugate base of 2,
[C3F7sC(dNPh)sNsC(dNPh)sC3F7]-, were obtained from
onium (e.g., Bu4N+, Bu4P+, Me3S+) or metal (e.g., K+, Cs+)
hydroxides in aqueous methanol, from metal hydrides (NaH,
KH) in tetrahydrofuran, or from alkyllithium reagents in
hydrocarbon solvents. Thus, for example, Li[Ph2N3C2-
(C3F7)2], 3, was obtained from 2 and n-butyllithium in
hexane; [Bu4N][Ph2N3C2(C3F7)2], 4, using [Bu4N]OH in
methanol-water; and K[Ph2N3C2(C3F7)2], 5, from 2 and KH
in THF.
A survey of reactions of 2 with various metal oxides and
carbonates (e.g., HgO, CoCO3) uncovered only one example
of a salt (or complex) that could be prepared in organic sol-
vents. Refluxing 2 with a suspension of Ag2O in acetonitrile
gave, after evaporation of the solvent, Ag[Ph2N3C2(C3F7)2],
6. This compound behaved as a 1:1 electrolyte in CH3CN,
the only solvent found in which it did not decompose.
Reaction with Ph2PC2H4PPh2 afforded [(diphos)Ag][Ph2N3C2-
(C3F7)2], 7. This compound also behaved as a 1:1 electrolyte
in CH3CN although NMR experiments with more concen-
trated solutions were suggestive of cation-anion interaction.
* To whom correspondence should be addressed. E-mail: arsiedle@
mmm.com.
† 3M Corporate Research Laboratories.
‡ 3M Specialty Materials Division.
§ University of Minnesota.
(1) (a) A panoply of leading references is cited in: Konemann, M.; Erker,
G.; Frohlich, R.; Wurthwein, E.-U. J. Am. Chem. Soc. 1997, 119,
11155. (b) Krol, A.; Frohlich, R.; Wurthwein. E.-U. Chem. Commun.
1998, 485. (c) Ernst, R. D. Chem. ReV. 1988, 88, 1255. (d) Powell, P.
AdV. Organomet. Chem. 1986, 26, 125. (e) Overby, J. S.; Hanusa, T.
P. Angew. Chem., Int. Ed. Engl. 1994, 33, 2191.
(2) Siedle, A. R.; Webb, R. J.; Behr, F. E.; Newmark, R. A.; Weil, D. A.;
Erickson, K. A.; Naujok, R.; Brostrom, M.; Mueller, M.; Chou, S.-
H.; Young, V. G., Jr. Inorg. Chem. 2003, 42, 932.
2596 Inorganic Chemistry, Vol. 42, No. 8, 2003
10.1021/ic020716q CCC: $25.00 © 2003 American Chemical Society
Published on Web 03/20/2003

Perfluoroalkyltriazapentadiene Ph2N3C2(C3F7)2H
Figure 1. ORTEP drawing of the cation and anion components of 4 showing the numbering scheme.
Table 1. Bond Distances (Å) and Angles (deg) in 4
Thus, in CDCl3, the 19F spectrum comprises three broad res-
onances at -81, -115, and -126 ppm; the 31P NMR spec-
trum is a doublet δ ) 0.77 with J(107,109AgP) ) 201 Hz,
whereas, in CD3CN, the 19F resonances are sharper but the
31P signal is a broad hump. The infrared spectra of both silver
complexes as Nujol mulls show C-N bands in the same
positions as the alkali metal and quaternary ammonium salts
of 2, substantiating their formulation as ionic materials.
For the tetrabutylammonium salt 4, the CdN stretching
bands in the infrared [Raman] spectrum occur at 1606 (m)
[1615 (s)] and 1551 (s) [1587 (m)] cm-1. Corresponding
bands in the Li+ salt are at 1616 (s) and 1579 (s) cm-1. The
higher frequency band is attributed to the symmetric
combination mode, and the lower frequency band to the
asymmetric combination. This accounts for the interchange
of intensities in these two bands in the infrared and Raman
spectra. The lower C-N stretching frequencies (vs 1682 (s)
[1691] and 1633 (m) [1625] cm-1) in 2 indicate a reduction
in C-N bond order upon deprotonation of 2. The small
separation between ν(CN)sym,asym, 55 and 49 cm-1 in 4 and
2, respectively, indicates little stretch-stretch interaction
between the intervening N atom.3 A similar conclusion
follows from the 15N NMR chemical shifts of the terminal
nitrogen atoms. In 2, δ15N for NPh and N(Ph)H are 288.4
and 113.7 ppm (NH3 reference), and for 3 in acetone, δ15N
N3-C5
1.288(5)
1.336(5)
1.337(6)
1.297(6)
1.415(6)
1.411(6)
C5-N3-C15
N3-C5-N1
C5-N1-C4
N2-C4-N1
C4-N2-C9
N2-C4-C3
N3-C5-C6
N1-C5-C6
119.3(4)
129.6(4)
129.4(4)
130.0(4)
119.7(4)
110.9(4)
110.9(4)
118.5(4)
N1-C5
N1-C4
N2-C4
N2-C9
N3-C15
suggest that this process corresponds to generation of
different conformations of the Ph2N3C2(C3F7)2 ion by
-
rotation about one of the C-N bonds (vide infra). It could,
for example, involve conversion of the W-shaped anion into
an energetically similar S-shaped conformer. Solvent and
cation effects for the rearrangement are small. 19F DNMR
spectra of the lithium salt 3 in acetone disclose a rearrange-
ment process analogous to that just described for the Bu4N+
salt. The activation energy, 14.7 kcal mol-1 at 295 K, is the
same within experimental error. The close similarity in
7
activation energies and the narrow Li resonance (w/2 16
Hz, δ -3.66) indicate the absence of a chemically significant
cation-anion interaction in 3 in solution.
The conjugate base of 2 behaves as a nucleophile and can
readily be alkylated. For example, Na[Ph2N3C2(C3F7)2],
prepared from 2 and NaH in THF, reacted with methyl iodide
to give C3F7sC(dNPh)sNdC(NMePh)sC3F7, 8, the N-
methyl analogue of 2. Electrophilic substitution occurs
exclusively at the terminal nitrogen atom(s), suggesting (but
not proving) that these are the sites of highest charge density
in the anion.
for these (now equivalent) nitrogen atoms is 234.5 ppm and
13
J15 C is 7 Hz.2 Thus, deprotonation causes the sp nitrogen
N
to shift to higher field, and the sp2 nitrogen moves to lower
field reflecting the changes in hybridization at these atoms.
There is little concomitant change in δ13C, 147.3 ppm,
compared with 145.2 (C(2)) and 139.9 ppm (C(1)) in 2.
In chloroform solution, 4 exhibits interesting dynamic
behavior. The fluorine nuclei in both CF2 groups are
geminally inequivalent and show exchange broadened pairs
of AB doublet 19F resonances in which the weaker, outer
lines are significantly broader than the inner ones. Further
analysis of the spectra showed that the free energy of
activation for the process that averages the pairs of geminally
inequivalent fluorine atoms is 14.8 kcal mol-1 at 296 K. We
Structure of [Bu4N][Ph2N3C2(C3F7)2]. The crystal struc-
ture of 4 consists of well separated cations and anions. An
ORTEP view of the complete ion pair is shown in Figure 1,
and important bond distances and angles are collected in
Table 1. If the N,C skeleton of the anion in 4 is represented
as N(2)-C(4)-N(1)-C(5)-N(3) (the numbering is that used
in Figure 1), a short-long-long-short pattern of C-N bond
lengths can be seen: d(N(2)-C(4)) and d(C(5)-N(3)) are
1.297(6) and 1.288(5) Å, respectively, while d(C(4)-N(1))
and d(C(5)-N(1)) are 1.337(6) and 1.336(5) Å, respectively.
The short bonds correspond, formally, to CdN fragments,
and the long bonds to CsN moieties with a bond order
(3) Cf. 33 cm-1 in ZrH2D2: Chertihin, G. V.; Andrews, L. J. Am. Chem.
Soc. 1995, 117, 5402.
Inorganic Chemistry, Vol. 42, No. 8, 2003 2597

Siedle et al.
The geometrical structure of Ph2N3C2(C3F7)2- in the crystal
lattice is grossly different from that of its conjugate acid
Ph2N3C2(C3F7)2H, and it is evident that substantial rearrange-
ment attends seemingly simple detachment of a proton. Using
the same HN(2)-C(4)-N(1)-C(5)-N(3) representation of
the N3C2 skeleton in 2, the pattern of CsN bond lengths is
instead long-short-long-short, implying conjugation of the
CdN units. The N(2)-C(4), C(4)-N(1), N(1)-C(5), and
C(5)-N3 distances are 1.345(11), 1.258(10), 1,377(9), and
1.259(9) Å, respectively. The angles centered at N(1), C(4),
and C(5) are similar, 131.8(6)°, 132.7(7)°, and 131.6(7)°,
respectively. However, relative to Ph2N3C2(C3F7)2H, the N3C2
skeleton in the anion is rotated 180° about C(4)-N(1) so
that the former is U-shaped whereas the latter is W-shaped.
It is possible that both conformers are present in solution,
and that their interconversion leads to permutation of
geminally inequivalent CF2 fluorine atoms as already
described. There is abundant precedent for such rotational
processes in homoatomic pentadienyl anions (and also
enamines, for which the barrier to torsional isomerization is
ca. 10 kcal mol-1) that interconvert U- and W-shaped anions.7
In pentadienyllithium itself, the carbon framework in the
ground state structure is thought to be W-shaped, an
arrangement that minimizes steric strain and permits electron
delocalization over the greater distance than U- or S-shaped
structures. However, NMR studies have shown that this
compound is conformationally dynamic in solution8 as is the
case for its triaza congener 4 already described.
Hydrolysis of Ph2N3C2(C3F7)2H. Solutions of 2 in neutral
methanol-water showed no change by 19F NMR after
heating for 4 h at 65°. Similar solutions of Na[Ph2N3C2-
(C3F7)], produced by adding 1 equiv of NaOH, were stable
under the same conditions. In contrast, heating solutions of
2 in aqueous methanol containing g1 equiv of HCl produced
a complex mixture of products. Analysis by GC/MS and
infrared and NMR spectroscopy showed that it contained
[PhNH3]Cl, (C3F7CO)2NH, C3F7CONH2, C3F7CO2H, and a
bis(perfluoropropyl)quinazoline that will be described in
detail. Thus, 2 and its conjugate base exhibit substantial
hydrolytic stability, but gross degradation occurs under acidic
conditions. Because it seemed likely that acid-catalyzed
hydrolysis might involve protonation, reactions of 2 with
acids under anhydrous conditions were studied.
Figure 2. View of the Ph2N3C2(C3F7)2(-) anion looking down the C(4)-
C(5) vector.
between 1 and 2. This pattern indicates that the CdN units
-
in Ph2N3C2(C3F7)2 are weakly interacting (conjugated), in
contrast with those in 2 (vide infra). The N3C2 framework
is not planar (even though the largest displacement from its
least-squares plane is 0.23 Å at C(5)). It has instead a distinct
helical twist such that the dihedral angle between the N(3)-
C(5)-N(1) and N(1)-C(4)-N(2) planes is 55.8°. This
framework describes a twisted zigzag trace or a W-shaped
anion. This description is supported by noting that the N(2)-
C(4)-N(1), C(4)-N(1)-C(5), and N(1)-C(5)-N(3) bond
angles are 130.0(4), 129.4(4), and 129.6(6)°, respectively.
Figure 2 shows a view of the Ph2N3C2(C3F7)2 anion looking
down the C(4)-C(5) vector. N(1,2,3) and the two N-terminal
phenyl groups are clustered to one side. N(1,2,3) atoms are
seen not to be collinear in this projection because of the twist
already noted. The two C3F7 groups are on the other side,
and the anion has an endo structure. The terminal C-N
bonds, N(2)-C(9) (phenyl) and N(3)-C(15)(phenyl), are
1.411(6) and 1.415(6) Å, comparable to the 1.402 Å C-N
distance in aniline.4 The dihedral angle between the two C6H5
planes is 73.65°.
Protonation of Ph2N3C2(C3F7)2H. Dissolution of 2 in
trifluoromethanesulfonic (triflic) acid was mildly exothermic.
Conversion to the triflate salt of its conjugate acid, [Ph2N3C2-
(C3F7)2H2][CF3SO3], 9, was quantitative. Quenching with
water at this point regenerated 2, and so, the structure of 9
was deduced from solution-phase experiments. The conclu-
sion from many NMR experiments is that the cation in 9
has a static C2V structure and may be represented as PhN-
(1)1H-C(C3F7)-N(2)-C(C3F7)-N(3)HPh+ for which nu-
merous resonance structures can be written. Importantly, the
15N NMR spectrum of the analogue of 9 in which N(1,3)
The compounds 1,7-bis(trimethylsilyl)-1,3,5,7-tetraaza-
heptatrienylsodium5 and -lithium6 provide useful structural
paradigms for 4 despite the complex interactions of the
electropositive alkali metals with the several nitrogen atoms
in the anion. In the former, C-N distances of 1.25 Å were
considered to correspond to double bonds between carbon
and nitrogen, 1.38 Å to short single bonds, and 1.33 Å to
distances characteristic of a delocalized system.
(4) Lister, D. G.; Tyler, J. K.; Hog, J. H.; Larsen, N. W. J. Mol. Struct.
1974, 23, 253.
(5) Boesveld, W. M.; Hitchcock, P. B.; Lappert, M. F.; Noth, H. Angew.
Chem., Int. Ed. 2000, 39, 222.
(6) Boesveld, W. M.; Hitchcock, P. B.; Lappert, M. F. J. Chem. Soc.,
Dalton Trans. 1999, 4041.
(7) Schlosser, M.; Desponds, O.; Lehmann, R.; Moret, E.; Rauschwalbe,
G. Tetrahedron 1993, 49, 10175.
(8) Bates, R. B.; Gosslink, D. W.; Kaczynski, J. A. Tetrahedron Lett.
1967, 205.
2598 Inorganic Chemistry, Vol. 42, No. 8, 2003

Perfluoroalkyltriazapentadiene Ph2N3C2(C3F7)2H
Scheme 1
atoms were labeled with 15N, shows a doublet at 151 ppm
with JNH being 95 Hz. This indicates that 9 has a static
structure on the NMR time scale and that it is not undergoing
2-D gCOSY, DEPT, and HMQC NMR spectra (cf. Experi-
mental Section). The H NMR spectrum shows a typical
o-disubstituted ring pattern, but in addition, H5, δ 8.42, is
broadened due to a 1.5 Hz five bond coupling to the
R-fluorine in the nearby CF2CF2CF3 group that is clearly
resolved in the 19F spectrum.
We suggest that the quinazoline ring is formed by
nucleophilic attack by a formal carbocationic center in
PhNHsC+(C3F7)sNdC(C3F7)sNHPh at the ortho carbon
atom in one of the phenyl rings to form a new CsC bond.
Protonation at the exocyclic nitrogen and loss of aniline and
then of H+ generates 10.
1
1
rapid loss and reaccession of its proton. H and 13C NMR
indicated that both phenyl rings were equivalent; the C3F7
groups are equivalent as well by 19F NMR, but as is often
the case in 2 and its derivatives, the R- and â-CF2 fluorine
nuclei are geminally inequivalent. A detailed assignment of
the NMR spectra is given in the Experimental Section. In 9,
δ13C, 150.6 ppm, is only 3.3 ppm deshielded relative to the
skeletal carbon atoms in the anion in 4. The Raman spectrum
of 9 in CF3SO3H in the C-N stretching region shows bands
at 1633(m) and 1586(s) cm-1 compared with 1625(s) and
1591(m) cm-1 in 2. This suggests that the C-N bond order
is not greatly affected by protonation notwithstanding that
these frequencies may not represent pure modes.
Experimental Section
Reactions with metal alkyls and hydrides were conduced under
dry nitrogen. Hexane and THF were distilled from NaK alloy and
sodium-benzophenone, respectively. Reactions in triflic acid were
also conducted under nitrogen with the intent of excluding water
from this very hygroscopic liquid. NMR spectra were obtained on
Varian instruments having 1H operating frequencies of 500 or 600
MHz. Chemical shifts are expressed in ppm (coupling constants in
Hz) relative to internal (CH3)4Si (1H and 13C), and CFCl3 (19F).
15N spectra were referenced to external CH3NO2 and the chemical
shifts converted to the NH3 scale to obtain the reported values.
Raman spectra were recorded with 782 nm laser excitation. Infrared
spectra were obtained on Nujol mulls unless otherwise noted.
Experimental details for synthesis of 2 are given in ref 2.
Atomic charges at N(1,2,3) in PhN(3)dC(C3F7)sN(1)d
C(C3F7)sN(2)HPh were calculated by DFT methods to be
-0.17, -0.18, and -0.49 e, respectively. The sp2 nitrogen
atom, N(2), is thus expected to be the most basic of the three
and to be the site of protonation. It is clear, however, that
the observed product, 9, results from protonation at N(3).
We believe that although PhNdC(C3F7)sNdC(C3F7)sNH2-
Ph+ may be the kinetically preferred product, PhNHd
C(C3F7)sNdC(C3F7)sNHPh+ is the thermodynamically
preferred product. This is because the latter has multiple
resonance forms that, collectively, lead to charge delocal-
ization over both the two carbon atoms and the two terminal
nitrogen atoms in the N3C2 fragment. Extensive charge
delocalization is consistent with the NMR and vibrational
spectroscopic data, and some positive charge at carbon is
consistent with the chemical reactivity now to be related.
Li[Ph2N2C2(C3F7)2], 3. n-Buyllithium, 0.4 mL of a 2.5 M
solution in hexane, was added under nitrogen with stirring to 0.56
g (1 mmol) of 2 in 5 mL of hexane. The product separated as a
white solid that was collected on a Schlenk filter washed with
toluene and then vacuum-dried. The yield was 0.38 g (67%). Anal.
Calcd (Found) for C20H10LiF14N3: C, 42.5 (42.7); H, 1.8 (1.8); Li,
1.2 (1.3); N, 7.4 (7.3). NMR (acetone-d6): 1H: δ 6.99 (t, 8, Hmeta),
Solutions of 9 in triflic acid were stable for several hours
at room temperature, but then, NMR signals arising from a
reaction product slowly grew in. When such solutions were
heated at 80° and quenched with ice, 2,4-bis(heptafluoro-
propyl)-1,3-quinazoline, 10, was isolated in 82% yield. The
numbering scheme for this compound and a proposed
mechanism for its formation are shown in Scheme 1. The
structure of 10 was deduced from 1-D NMR spectra and
7
6.7 (overlapping triplet and doublet, Hpara, ortho). Li: δ -3.66 (s,
w/2 16 Hz) wrt LiCl in D2O. 13C: δ 150.0 (Cipso), 146.9 (t, 23,
CCF2), 127.3 (Cmeta), 123.3 (Cortho), 120.9 (Cpara). 19F: δ -80.92
4
(t, JFF ) 9, CF3), -115.37 and -113.51 (AB, JAB 260, CF2CN),
-125.87 and -125.67 (AB, JAB 286, CF2CF3). IR: 1680, 1617,
1579, 1351, 1234, 1210, 1180, 1117, 1104, 909, 865 and 694 cm-1
.
[Bu4N][Ph2N3C2(C3F7)2], 4. Compound 2, 1.12 g (2 mmol), was
dissolved in 4 mL of 1 M [Bu4N]OH in methanol. Water was added
Inorganic Chemistry, Vol. 42, No. 8, 2003 2599

Siedle et al.
to the cloud point. Slow rotary evaporation gave 1.35 g (87%) of
product. Recrystallization from diethyl ether gave colorless rods,
mp 102-103°, suitable for X-ray crystallography. Anal. Calcd
(Found) for C36H39F14N3: C, 54.5 (54.2); H, 4.9 (4.9), N, 7.1 (7.0).
911, 874, 748, and 693 cm-1. Molar conductance: 85 Ω-1 cm2
mol-1 (8.6 × 10-4 M in CH3CN).
[(diphos)Ag][Ph2N3C2(C3F7)2], 7. Diphos (1,2-bis(diphenylphos-
phino)ethane), 0.24 g (0.6 mmol), and compound 6, 0.4 g (0.6
mmol), in 5 mL of CH3CN were stirred for 30 min. The solution
was centrifuged to remove a small amount of dark solid and then
evaporated under vacuum. The residue was recrystallized by slow
evaporation of a CH2Cl2-hexane solution to give 0.58 g (90%) of
7 as a light yellow powder that decomposed on heating. Anal. Calcd
(Found) for C46H34AgF14N3P2: C, 51.9 (52.6); H, 3.2 (3.3); N, 4.0
(3.9). In the laser desorption mass spectrum, no molecular ion was
observed. Instead, clusters of peaks due to isotopomers of Agn+ (n
) 3,5,7,9) and m/z 558 due to the triazapentadiene ligand were
observed. IR: 1610, 1570, 1523, 1371, 1344, 1229, 1199, 1113,
743, 694, and 510 cm-1. Molar conductance: 61 and 27 Ω-1 cm2
mol-1 (1.6 × 10-3 M in CH3CN and 1.3 × 10-3 M in CH3NO2,
respectively). NMR. 19F: δ -78.7, -112.5, and -123.2; -80.8,
-115, and -126; -83.0, -116, and -128 in CD3CN, CDCl3, and
toluene-d8, respectively. 31P: δ 4.8 (hump), 0.77 (d, 201 Hz), and
-0.1 (broad doublet, ca. 200 Hz) in CD3CN, CDCl3, and toluene-
d8, respectively. The 31P and 19F line widths appear, approximately,
to be inversely related. The 201 Hz 31P-107,109Ag coupling is
suggestive of 4-coordinate silver.17 In the final analysis, none of
the characterization data obtained in fluid solution are adequate to
differentiate between free (or paired) ions, structures with different
silver coordination numbers, or equilibria between all of these.
1
NMR (CDCl3). H: δ 7.05 (dd, 8,7, Hmeta), 6.78 (tt, 7, 2, Hpara),
6.75 (dd, 8, 1, Hortho), 2.69 (m, CH2N), 1.23-1.15 (m, CH2CH2),
0.88 (t, 7, CH3). 13C: δ 149.7 (Cipso), 147.3 (t, 23, CCF2), 127.5
(Cmeta), 123.3 (Cortho), 121.1 (Cpara), 58.1 (CH2N), 23.5 (CH2CH2N),
19.3 (CH2CH3), 13.3 (CH3). 15N: δ 235.5 (N1). 19F: δ -80.9 (t,
4JFF ) 9, CF3), -114.04 and -115.23 (AB, JAB ) 261 Hz, CF2-
CN), -126.05 and -125.48 (AB, JAB 284, CF2CF3). UV λmax (CH3-
CN, log ꢀ): 203 (4.40), 327 (3.97) nm. IR: 1605, 1551, 1225,
1200, 1117, and 843 cm-1. Raman: 1691, 1625, 1590, 1350, 1372,
1225, 1006, 756, 726, 623, and 303 cm-1. Molar conductance: 96
Ω-1 cm2 mol-1 (9.2 × 10-4 M in CH3NO2).
19F spectra of 4 were calculated using the equations of Kaplan9
1
for dynamic NMR analysis of a pair of coupled spin /2 nuclei.
The center CF2 group (i.e., CF2CF2CF3) displays inner and outer
resonances for the AB quartet having line widths of 7.7 and 41.4
Hz, respectively, determined from a resolution enhanced spectrum
in which the line width of the CFCl3 reference was 1.0 Hz.
Activation energies were 14.72 and 14.81 kcal mol-1 for the inner
and outer resonances, respectively. The CF2N resonances also show
exchange broadening, but accurate measurements of line widths
would have required simultaneous decoupling of the 9 Hz FF
interaction with CF3.
K[Ph2N3C2(C3F7)2], 5. Solid 2, 0.84 g (1.5 mmol), was added
to a stirred suspension of (excess) KH in THF. After gas evolution
had ceased, the reaction mixture was allowed to settle. The
supernatant was withdrawn and clarified by centrifugation. Solvent
was removed under vacuum. After 16 h of pumping, the solid was
washed with hexane and dried. The yield of 5, a pale yellow powder,
was 0.75 g (83%). Anal. Calcd (Found) for C20H10F14KN3: C, 40.2
(40.0); H, 1.7 (1.8); N, 7.0 (7.1). IR: 1607, 1584, 1379, 1344, 1231,
C3F7-C(dNPh)-NdC(NMePh)-C3F7, 8. A solution of 1.2
g (2 mmol) of 2 in 20 mL of THF was stirred with excess NaH
until gas evolution ceased. The unreacted NaH was allowed to settle
and the supernatant solution of Na[Ph2N3C2(C3F7)2] removed by
cannula and treated with 0.43 gm (3 mmol) methyl iodide. After
16 h, the THF was stripped and the oily residue sublimed under
vacuum. The sublimate was recrystallized from hexane to give 0.81
g (71%) of colorless product, mp 60-61°. Anal. Calcd (Found)
for C21H13F14N3: C, 44.0 (44.1); H, 2.3 (2.3); N, 7.3 (7.3). Mass
1113, 910, 853, 758, and 701 cm-1
.
Ag[Ph2N3C2(C3F7)2], 6. Compound 2, 0.56 g (1 mmol), and a
suspension of 0.13 g (1 mmol, 50% excess) of Ag2O were refluxed
and stirred for 12 h. A silver mirror lined the reaction vessel. The
cooled reaction mixture was filtered through Celite. Evaporation
of the solvent under vacuum left 0.56 g (84%) of 6 as a yellow
powder. It was stored in an amber bottle. The compound decom-
posed without melting on heating. DSC analysis (under N2) revealed
three exothermic events at 210°, 240°, and 275° with that at 240°
being the most highly exothermic. The residue after heating
consisted of Ag metal (XRD). In the mass spectrum, the positive-
ion thermal desorption electron impact spectrum showed no silver-
containing species. However, the laser desorption positive-ion
spectrum was more informative: m/z 666, 668 (6‚H+); 772, 774,
spectrum: m/z 573.0877 (M+, calcd 573.0886), 404.0927 (M+
-
-
-
C3F7). NMR (CDCl3). 1H: δ 7.38 (dd, 8, 8, Hmeta[B]), 7.25 m, Hpara
[A]), ∼7.23 (m, Hpara[B]), 7.20 (m, Hmeta[A]), 7.04 (dd, 9, 1, Hortho
[B]), 6.39 (d, ∼6, Hortho[A]), 3.14 (CH3). A and B refer to the C6H5
rings that are respectively proximal and distal to the NCH3 group.
13C: δ 147.16 (dd, 3JCF 31, 24, CdNPh), 145.96 (Cipso[B]), 144.78
(t, 3JCF 27, C-NMePh), 141.86 (Cipso[A]), 129.37 (Cmeta[B]), 129.22
(Cmeta[A]), 128.31 (Cpara[A]), 126.22 (Cortho[A]), 125.10 (Cpara[B]),
121.51 (Cortho[B]), 42.71 (CH3). 19F: δ -127.30 and -126.97 (AB,
JAB 287, CF2CF3 [B]), -124.95 and -123.96 (AB, JAB 288, CF2-
CF3 [A]), -117.6 and -116.37 (AB, JAB 268, NCCF2 [B]),
-108.30 and -104.31 (AB, JAB 289, NCCF2 [A]), -81.3 (t, 8,
CF3 [B]), -81.6 (t, 10, CF3 [A]). IR (KBr): 1651 (br), 1590, 1492,
+
and 776 (6‚Ag+). In addition, Agn clusters were seen up to n )
1353, 1222 (br), 1123, 826, 752, and 699 cm-1
.
17 and, at longer trapping times, up to n ) 25.16 Anal. Calcd
(Found) for C20H10AgN3F14: C, 36.1 (36.2); H, 1.5 (1.5); Ag, 16.2
(16.0); N, 6.3 (6.5). IR: 1693, 1612, 1566, 1377, 1231 (br), 1122,
[Ph2N3C2(C3F7)2H2][CF3SO3], 9. This compound was character-
ized in situ using ca. 0.1 M solutions of 2 in CF3SO3H or CF3-
SO3D that were prepared in a drybox using freshly opened ampules
of the acids (Aldrich). Samples were contained in 5 mm NMR tubes
sealed with J. Young Teflon in-line valves. After NMR spectra
had been collected, they were reacquired in rapid survey scans after
adding small amounts of CFCl3 and (CH3)4Si to serve as internal
19F, 1H, and 13C references, thus defining the chemical shift scale.
Only a short time was available for this purpose because (CH3)4Si
(9) Kaplan, J. I. J. Chem. Phys. 1958, 28, 278.
(10) (a) Kohn, W.; Sham, L. J. Phys. ReV. 1965, 140, A1133. (b) Parr, R.
G.; Yang, W. Density-Functional Theory of Atoms and Molecules;
Oxford University Press: Oxford, 1989.
(11) http://cachesoftware.com./
(12) Becke, A. D. Phys. ReV. A. 1988, 38, 3098.
(13) Lee, C.; Parr, R. G.; Yang, W. Phys. ReV. 1988, B37, 785.
(14) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284.
(15) Mulliken, R. S. J. Chem. Phys. 1955, 23, 1833, 1841, 2338, 2342.
(16) Perfluorocarbon-stabilized silver nanoparticles have been obtained by
pyrolysis of silver perfluorocarboxylates: Lee, S. J.; Han, S. W.; Kim,
(17) In triarylphosphine-silver complexes, JPAg (averaged for 107,109Ag)
values are approximately 242 Hz for 4-coordinate L4Ag+, 316 Hz for
L3Ag+, and 390 Hz for linear L2Ag+: Muetterties, E. L.; Peet, W.
G.; Wegner, P. A.; Alegranti, C. W. Inorg. Chem. 1970, 9, 2447.
+
K. Chem. Commun. 2002, 442. Apparently, Agn cluster formation
occurs under mass spectrometric conditions.
2600 Inorganic Chemistry, Vol. 42, No. 8, 2003

Perfluoroalkyltriazapentadiene Ph2N3C2(C3F7)2H
reacts with triflic acid to form CH4 and silicon triflates. [15NH4]Cl
in triflic acid was used as an external 15N chemical shift reference.
NMR. 1H: δ 9.64 (d, JNH 94), 7.89 (t, 7, Hpara), 7.85 (t, 8, Hmeta),
7.50 (d, 8, Hortho). 13C: δ 152.0 (NC, 2JCF 31), 133.61 (Cpara), 133.46
(Cipso), 132.56 (Cmeta), 126.15 (Cortho). 15N: δ 151.1 (d, JNH 95,
N1). 19F: δ -80.2 (t, 10, CF3), -122.6 and -122.0 (AB pattern,
JAB 275, NCCF2), -129.7 and -129.5 (AB pattern, JAB 296,
Table 2. Crystallographic Data for 4
C36H46N4F14
0.4 × 0.2 × 0.08 mm3
orthorhombic
Pna2l
16.8541(6) Å
14.2085(6) Å
17.0180(6) Å
4075.3(3) Å3
4
cryst size
cryst syst
space group
a
b
c
V
Z
CF3CF2). J C, determined from the 13C spectrum of a terminally
15N13
15N labeled sample, was 9 Hz. UV λmax (CF3SO3H, log ꢀ): 231
(4.19), 315 (3.94) nm.
λ
fw
0.71073 Å
800.77 g mol-1
1.305 g cm-1
0.122 mm-1
173(2) K
1664
2,4-Bis(heptafluoropropyl)-1,3-quinazoline, 10. A solution of
0.8 g (1.4 mmol) of 2 in 1 mL of triflic acid was heated at 80° in
a Schlenk tube for 16 h. The cooled reaction mixture was poured
onto ice. The solid phase was collected on a filter, washed with
ice water, and purified by vacuum sublimation onto a probe cooled
to 0°. The yield of clear, colorless prisms was 0.55 g (82%), mp
30.5-31.5°. Anal. Calcd (Found) for C14H4F14N2: C, 36.1 (36.1);
H, 0.9 (0.9); N, 6.0 (6.2). Mass spectrum: m/z 466.0145 (M+, calcd
Dcalcd
µ
T
F(000)
θ range for data collection
reflns collected
indep reflns
1.87-25.06°
21184
7077 (Rint ) 0.0747)
R1 ) 0.0622; wR2 ) 0.0951
R1 ) 0.133; wR2 ) 0.1135
1.050
R indicesa (I > 2σ(I) ) 4084)
R indices (all data)
GOF on F2
1
466.0170). NMR (CDCl3). H: δ 8.42 (br d, 9, H5), 8.30 (d, 9,
largest diff peak and hole
0.176 and -0.223 e Å-3
H8), 8.18 (dt, 8, 1, H7), 7.96 (dt, 8, 1, H6). 13C: δ 156.3 (t, 3JCF 26,
2
2
2
a Rint ) ∑|Fo
-
Fo |/∑|Fo |, R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 )
3
C4), 152.0 (t, JCF 26, C2), 151.5 (s, C8a), 136.0 (C7), 131.5 (C6),
[∑[w(Fo - Fc )2]/∑w(Fo )2]1/2 where w ) q/σ2(Fo ) + (ap)2 + bp. GOF
2
2
2
2
4
130.4 (C8), 124.8 (t, JCF 7, C5), 122.0 (s, C4a). 19F: δ -80.27,
) S ) [∑[w(Fo - Fc )2]/(n - p)1/2
.
2
2
5
-80.92 (t, 9, CF3), -109.14 (qd, 9, JH(5)F 1.5, C4CF2), -115.65
(q, 9, C2CF2), -125.8 (s, C4CF2CF2), -126.42 (s, C2CF2CF2). IR:
with anisotropic displacement parameters. All hydrogen atoms were
placed in ideal positions and refined as riding atoms with individual
displacement parameters. Crystallographic data are summarized in
Table 2.
1615, 1563, 1497, 1466, 1004, 952, 899, 844, 825, 799, 749, 725,
675, 660, 596, and 510 cm-1
.
Crystal Structure Determination. A crystal of 4 was attached
to a glass fiber and mounted on the Siemens SMART system. An
initial set of cell constants was calculated from reflections harvested
from three sets of 20 frames. The initial sets of frames were oriented
so that orthogonal wedges of reciprocal space were surveyed. Final
cell constants were calculated from a set of 6846 strong reflections.
Hemisphere data collection was used. A randomly oriented region
of reciprocal space was surveyed to 1.3 hemispheres and a resolution
of 0.84 Å. Three major swaths of frames were collected with 0.30°
steps in ω. The space group Pna21was determined on the basis of
systematic absences and intensity statistics. A successful direct-
methods solution provided most non-hydrogen atoms from the
E-map. Several full-matrix least-squares difference Fourier cycles
located the remainder of them. All non-hydrogen atoms were refined
Computational Studies. The structure of 2 was determined by
a geometry optimization calculation using density functional theory
(DFT)10 code Dgauss 4.1 (CAChe/Fujitsu)11 using the B88-LYP12,13
GGA functional with polarized double ú split valence DZVP14 basis
sets. The charge distributions correspond to Mulliken net atomic
charges.15
Supporting Information Available: X-ray file in CIF format.
This material is available free of charge via the Internet at
http://pubs.acs.org.
IC020716Q
Inorganic Chemistry, Vol. 42, No. 8, 2003 2601