Silver(I) complexes of a sterically demanding fluorinated triazapentadienyl ligand [N{(C3F7)C(Dipp)N}2]- (Dipp = 2,6-diisopropylphenyl)

Article abstract of DOI:10.1021/ic0491231

Sterically demanding triazapentadiene [N{(C₃F ₇)C(Dipp)N}₂]H affords the isolation of thermally stable, two- and three-coordinate silver complexes. The free ligand [N{(C ₃F₇)C(Dipp)N}₂]H ha

Full text of DOI:10.1021/ic0491231

Inorg. Chem. 2004, 43, 7396−7402
Silver(I) Complexes of a Sterically Demanding Fluorinated
-
Triazapentadienyl Ligand [N
2,6-Diisopropylphenyl)
{
(C3F7)C(Dipp)N
}
]
2
(Dipp )
H. V. Rasika Dias* and Shreeyukta Singh
Department of Chemistry and Biochemistry, The UniVersity of Texas at Arlington,
Arlington, Texas 76019
Received July 5, 2004
Sterically demanding triazapentadiene [N
three-coordinate silver complexes. The free ligand [N
solid state. [N (C3F7)C(Dipp)N 2]H reacts with silver(I) oxide in acetonitrile leading to CH3CNAg[N
It features a two-coordinate silver center and a
1-coordinated triazapentadienyl ligand. This silver acetonitrile
complex serves as an excellent precursor to obtain thermally stable, silver isocyanide t-BuNCAg[N (C3F7)C(Dipp)N
and silver phosphine [N (C3F7)C(Dipp)N 2]AgPPh3 adducts. IR spectroscopic data for the silver(I) isocyanide
t-BuNCAg[N (C3F7)C(Dipp)N
2] shows νCN at 2219 cm-1. The silver ion coordinates to the triazapentadienyl ligand
via the central nitrogen atom. The silver PPh3 adduct, [N (C3F7)C(Dipp)N 2]AgPPh3, was synthesized by treating
CH3CNAg[N (C3F7)C(Dipp)N 2] with PPh3. It displays relatively large Ag
P coupling in the 31P NMR spectrum.
2]AgPPh3 acts as a chelating P bond is
2-donor. The Ag
{
(C3F7)C(Dipp)N
}
2]H affords the isolation of thermally stable, two- and
2]H has a W-shaped ligand backbone in the
(C3F7)C(Dipp)N 2].
{
(C3F7)C(Dipp)N
}
{
}
{
}
κ
{
} ]
2
{
}
{
}
{
}
{
}
−
The triazapentadienyl ligand in [N
{
(C3F7)C(Dipp)N
}
κ
−
relatively short (2.3487(10) Å).
Introduction
example of a metal carbonyl where the bonding between the
metal and the CO is essentially of σ-type (with little to no
π-back-bonding).10-12 Compounds such as [HB(3,5-(CF3)2-
Pz)3]Ag(THF) show useful catalytic properties as well. For
example, it facilitates the carbene insertion to C-H and
C-Cl bonds under mild conditions.13,14
Although silver(I) complexes of the related bis(pyrazolyl)-
borate ligands such as [H2B(3,5-(CF3)2Pz)2]- (2) are also of
interest, they are generally less stable.15-17 This is partly due
to the relative ease of reducing silver(I) to metallic silver by
The chemistry of metal complexes containing fluorinated
ligands such as [HB(3,5-(CF3)2Pz)3]- (1) is of significant
interest.1-6 Polyfluorinated ligands commonly improve the
thermal stability, oxidative resistance, volatility, and fluoro-
carbon solubility of metal adducts. Some of the interesting
complexes of silver(I) that have been isolated using fluori-
nated tris(pyrazolyl)borates include [HB(3,5-(CF3)2Pz)3]AgL,
where L ) CO, CH2dCH2, HCtCH, NNNAd, and
NNC(CO2Me)2.7-9 The [HB(3,5-(CF3)2Pz)3]AgCO is an
* Author to whom correspondence should be addressed. E-mail: dias@
uta.edu.
(1) Thrasher, J. S.; Strauss, S. H. Inorganic Fluorine Chemistry: Toward
the 21st Century; ACS Symposium Series 555; American Chemical
Society: Washington, DC, 1994.
(8) Dias, H. V. R.; Polach, S. A. Inorg. Chem. 2000, 39, 4676-4677.
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D. S. Inorg. Chem. 2000, 39, 3894-3901.
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(12) Lupinetti, A. J.; Strauss, S. H.; Frenking, G. Prog. Inorg. Chem. 2001,
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K.; Lovely, C. J. J. Am. Chem. Soc. 2003, 125, 9270-9271.
(14) Dias, H. V. R.; Browning, R. G.; Richey, S. A.; Lovely, C. J.
Organometallics 2004, 23, 1200-1202.
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pyrazolylborate Ligands; Imperial College: London, 1999.
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II; Elsevier Pergamon: New York, 2004; Vol. 1.
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R.; Derecskei-Kovacs, A.; Marynick, D. S. Organometallics 1996, 15,
2994-3003 and the references therein.
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(4) Fekl, U.; van Eldik, R.; Lovell, S.; Goldberg, K. I. Organometallics
2000, 19, 3535-3542 and the references therein.
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V. G., Jr.; Gorun, S. M. Chem. Commun. 2003, 1576-1577.
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6215.
7396 Inorganic Chemistry, Vol. 43, No. 23, 2004
10.1021/ic0491231 CCC: $27.50
© 2004 American Chemical Society
Published on Web 10/14/2004

Ag(I) Complexes of [N{(C3F7)C(Dipp)N}2]-
(Dipp)N}2]CuCO suggest that [N{(C3F7)C(Dipp)N}2]- is a
fairly weak donor.
Herein, we report the use of [N{(C3F7)C(Dipp)N}2]- (4)
in silver chemistry. In particular, the synthesis, spectroscopic
data, and the X-ray crystal structures of CH3CNAg[N-
{(C3F7)C(Dipp)N}2], t-BuNCAg[N{(C3F7)C(Dipp)N}2], and
[N{(C3F7)C(Dipp)N}2]AgPPh3 are reported. These molecules
display two interesting modes of triazapentadienyl ligand co-
ordination. Previous work on silver triazapentadienyl adducts
has been limited to [N{(C3F7)C(Ph)N}2]Ag and [(diphos)-
Ag][N{(C3F7)C(Ph)N}2].20 None of these silver complexes
have been characterized structurally using X-ray diffraction.
Experimental Details
General Procedures. All manipulations were carried out under
an atmosphere of purified nitrogen using standard Schlenk tech-
niques. Solvents were purchased from commercial sources, distilled
from conventional drying agents, and degassed by the freeze-
pump-thaw method twice prior to use. Glassware was oven-dried
at 150 °C overnight. NMR spectra were recorded at 25 °C on a
JEOL Eclipse 500 spectrometer (1H, 500.16 MHz; 13C, 125.78
MHz; 19F, 470.62 MHz; 31P, 202.47 MHz). Proton and carbon
chemical shifts are reported in ppm versus Me4Si. 19F NMR
the B-H moieties present in these ligands. As an alternative
ligand without the problematic B-H moieties, we decided
to examine the chemistry of the fluorinated triazapentadienyl
systems.18,19 They are both monoanionic, nitrogen-based
donors capable of forming six-membered metallacycles upon
coordination to metal ions. Very little is known about the
coordination chemistry of triazapentadienyl ligands.18-27 One
reason may be the lack of versatile methods for the ligand
synthesis.18,28 Recently, a convenient route to fluoroalkylated
triazapentadienes starting with (C4F9)3N appeared in the
literature.18 This method permits the synthesis of N-substi-
tuted molecules such as [N{(C3F7)C(Ph)N}2]H. Several metal
adducts of [N{(C3F7)C(Ph)N}2]- are also known including
the solid-state structures of CH3Hg[N{(C3F7)C(Ph)N}2] and
[N{(C3F7)C(Ph)N}2]2Co.18-20 Early work involving fluori-
nated triazapentadienyl ligands concerns the use of [N{(CF3)C-
(H)N}2]- (3) as a ligand for few group 8-12 metal ions
and for gallium.21-25 Recently, we described the synthesis
of a sterically demanding triazapentadienyl ligand [N{(C3F7)C-
(Dipp)N}2]- (Dipp ) 2,6-diisopropylphenyl) and its copper-
(I) complexes in a communication.29 IR data for [N{(C3F7)C-
chemical shifts were referenced relative to external CFCl3, and 31
P
NMR was referenced to external 85% H3PO4. Infrared spectra were
recorded on a JASCO FT-IR 410 spectrometer. Melting points were
obtained on a Mel-Temp II apparatus and were not corrected. Ag2O,
PPh3, tert-butyl isocyanide, and 2,6-diisopropylaniline were pur-
chased from commercial sources. Perfluoro-5-aza-4-nonene was
synthesized using the published procedure.30 Elemental analyses
were performed using a Perkin-Elmer model 2400 instrument.
[N{C3F7)C(Dipp)N}2]H. Perfluoro-5-aza-4-nonene (10 g, 0.023
mol) was added dropwise to a solution of 2,6-diisopropylaniline
(20.4 g, 0.115 mol) in ether (100 mL) at 0 °C. After addition, the
solution was allowed to stir overnight at room temperature. The
resulting mixture was filtered, and the filtrate was collected and
washed first with 10% HCl and then twice with distilled water.
The ether layer was separated and dried over CaCl2. The solvent
was removed under reduced pressure, and the resulting residue was
recrystallized from hexane at room temperature to obtain colorless
crystal of [N{C3F7)C(Dipp)N}2]H in 76% yield. Although we haVe
not attempted to confirm, spectroscopic data seem to indicate both
the amino-imino and diimino forms of the ligand present in
solution. Mp: 88-90 °C. 19F NMR (CDCl3): δ -124.5 and -124.0
(AB multiplet, JAB = 294 Hz, â-CF2), -123.4 (s, â-CF2), -123.1
(s, â-CF2), -113.6 and -111.9 (AB multiplet, JAB ) 288 Hz,
R-CF2), -111.9 and -111.2 (AB multiplet, JAB ) 293 Hz, R-CF2),
-109.8 (d, JFF ) 9 Hz, R-CF2), -80.2 (apparent triplet, JFF ) 12
Hz, 9 Hz, CF3), -80.0 (apparent triplet, JFF ) 12 Hz, 9 Hz, CF3).
(18) 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., Jr. Inorg. Chem. 2003, 42, 932-934.
(19) Siedle, A. R.; Webb, R. J.; Brostrom, M.; Newmark, R. A.; Behr, F.
E.; Young, V. G., Jr. Organometallics 2004, 23, 2281-2286.
(20) Siedle, A. R.; Webb, R. J.; Brostrom, M.; Chou, S.-H.; Weil, D. A.;
Newmark, R. A.; Behr, F. E.; Young, V. G., Jr. Inorg. Chem. 2003,
42, 2596-2601.
(21) Brown, H. C.; Schuman, P. D. J. Org. Chem. 1963, 28, 1122-1127.
(22) Bottrill, M.; Goddard, R.; Green, M.; Hughes, R. P.; Lloyd, M. K.;
Taylor, S. H.; Woodward, P. J. Chem. Soc., Dalton Trans. 1975,
1150-1155.
(23) Hursthouse, M. B.; Mazid, M. A.; Robinson, S. D.; Sahajpal, A. J.
Chem. Soc., Dalton Trans. 1994, 3615-3620.
(24) Robinson, V.; Taylor, G. E.; Woodward, P.; Bruce, M. I.; Wallis, R.
C. J. Chem. Soc., Dalton Trans. 1981, 1169-1173.
(25) Aris, D. R.; Barker, J.; Phillips, P. R.; Alcock, N. W.; Wallbridge, M.
G. H. J. Chem. Soc., Dalton Trans. 1997, 909-910.
(26) Guo, J.; Wong, W.-K.; Wong, W.-Y. Eur. J. Inorg. Chem. 2004, 267-
275.
3
1H NMR (CDCl3): δ 0.29-1.26 (nine separate d, JHH ) 8.0 Hz,
3
24H, CH3), 2.37-3.01 (four separate heptets, JHH ) 8.0 Hz, 4H,
CH), 6.29 (br s, 0.69H, NH), 6.81-7.28 (several multiplets, m-
1
and p-Ar), 12.92 (br s, 0.19H, NH). H NMR (C6D6): δ 0.49-
1.32 (multiplet, 24H, CH3), 2.31-3.10 (four separate heptets, 3JHH
) 8.0 Hz, 4H, CH), 6.06 (br s, 0.88H, NH), 6.89-7.09 (several
multiplets, m- and p-Ar), 13.27 (br s, 0.12H, NH); see Supporting
Information for hard copies of the spectra. Anal. Calcd for
C32H35F14N3: C, 52.82; H, 4.85; N, 5.78. Found: C, 52.70; H, 4.62;
N, 5.61.
(27) Barker, J.; Kilner, M.; Mahmoud, M. M.; Wallwork, S. C. J. Chem.
Soc., Dalton Trans. 1989, 837-841.
(28) Paciorek, K. J. L.; Nakahara, J. H.; Kratzer, R. H. J. Fluorine Chem.
1985, 30, 241-250.
(30) Siedle, A. R.; Webb, R. J.; Newmark, R. A.; Brostrom, M.; Weil, D.
A.; Erickson, K.; Behr, F. E.; Young, V. G. J. Fluorine Chem. 2003,
122, 175-182.
(29) Dias, H. V. R.; Singh, S. Inorg. Chem. 2004, 43, 5786-5788.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7397

Dias and Singh
Table 1. X-ray Crystallographic Data for LAgNCCH3, LAgCNBut, and
LAgPPh3 (L ) [N{(C3F7)C(Dipp)N}2])
CH3CNAg[N{(C3F7)C(Dipp)N}2]. [N{C3F7)C(Dipp)N}2]H (0.63
g, 0.87 mmol) and Ag2O (0.10 g, 0.43 mmol) were mixed in
acetonitrile (50 mL) and refluxed for 12 h. The resulting mixture
was filtered, and the filtrate was concentrated and cooled to -15
°C to obtain white crystals of CH3CNAg[N{(C3F7)C(Dipp)N}2].
Yield: 87%. Mp: ∼130 °C (dec). 19F NMR (CDCl3): δ -122.4
and -121.6 (AB multiplet, JAB ) 278 Hz, â-CF2), -107.5 and
param
formula
fw
space group
a, Å
b, Å
LAgNCCH3
LAgCNBut
LAgPPh3
C34H37AgF14N4 C37H43AgF14N4 C50H49AgF14N3P
875.55
Pna21
18.4525(8)
12.0836(5)
16.6622(7)
90
90
90
3715.2(3)
4
1.565
917.62
Pca21
23.111(3)
19.512(2)
18.112(2)
90
1096.76
I41/a
38.717(4)
38.717(4)
13.053(3)
90
1
-106.9 (AB multiplet, JAB ) 304 Hz, R-CF2), -80.4 (s, CF3). H
c, Å
3
NMR (CDCl3): δ 0.90 (d, JHH ) 7.0 Hz, 6H, CH(CH3)2), 0.98
R, deg
â, deg
γ, deg
V, Å3
Z
3
3
(d, JHH ) 7.0 Hz, 6H, CH(CH3)2), 1.08 (d, JHH ) 6.5 Hz, 6H,
90
90
90
90
3
CH(CH3)2), 1.14 (d, JHH ) 6.5 Hz, 6H, CH(CH3)2), 2.02 (s, 3H,
CH3CN), 2.83 (heptet, 3JHH ) 7.0 Hz, 2H, CH(CH3)2), 2.89 (heptet,
3JHH ) 6.5 Hz, 2H, CH(CH3)2), 6.90 (nonfirst-order t, 2H, p-Ar),
8167.9(15)
8
1.492
19567(5)
16
1.489
F
calc, g/cm3
3
3
6.96 (d, JHH ) 7.0 Hz, 2H, m-Ar), 7.03 (d, JHH ) 7.5 Hz, 2H,
m-Ar). Selected 13C{1H} NMR (CDCl3): δ 1.9 (CH3CN), 21.5 (CH-
(CH3)2), 22.8 (CH(CH3)2), 23.6 (CH(CH3)2). 25.4 (CH(CH3)2), 27.8
(CH(CH3)2), 28.0 (CH(CH3)2), 116.6 (p-CAr), 123.3 (m-CAr), 138.0
(o-CAr), 140.5 (Cipso), 149.9 (t, 2JCF ) 23.0 Hz, NCN). Anal. Calcd
for C34H37F14N4Ag: C, 46.64; H, 4.26; N, 6.40. Found: C, 47.22;
H, 4.70; N, 6.21.
µ, mm-1
λ, deg
T, K
0.643
0.710 73
100(2)
0.589
0.536
0.710 73
100(2)
R1 ) 0.0540
0.710 73
100(2)
R1 ) 0.0385
final R indices R1 ) 0.0221
(I > 2σ(I))
R indices
(all data)
wR2 ) 0.0550 wR2 ) 0.1237 wR2 ) 0.0904
R1 ) 0.0231 R1 ) 0.0514 R1 ) 0.0568
wR2 ) 0.0556 wR2 ) 0.1210 wR2 ) 0.1016
t-BuNCAg[N{(C3F7)C(Dipp)N}2]. CH3CNAg[N{(C3F7)C(Dipp)-
N}2] (0.10 g, 0.12 mmol) was dissolved in hexane and treated with
tert-butyl isocyanide (0.014 g, 0.11 mmol) at room temperature.
The mixture stirred overnight, and the solution was concentrated
and cooled to -15 °C to obtain colorless crystals. Yield: 85%.
Mp: 89 °C. 19F NMR (CDCl3): δ -122.3 and -121.6 (AB
multiplet, JAB ) 291 Hz, â-CF2), -107.4 and -106.6 (AB multiplet,
JAB ) 288 Hz, R-CF2), -80.4 (s, CF3). 1H NMR (CDCl3): δ 0.96
Structures were solved and refined using Bruker SHELXTL (version
6.14) software package. Some details of the data collection and
refinement of CH3CNAg[N{(C3F7)C(Dipp)N}2], t-BuNCAg[N-
{(C3F7)C(Dipp)N}2], and [N{(C3F7)C(Dipp)N}2]AgPPh3 are given
in Table 1. Selected bond distances and angles of these adducts as
well as that of the free ligand are presented in Tables 2-5.
Results and Discussion
3
3
(d, JHH ) 7.0 Hz, 6H, CH(CH3)2), 1.02 (d, JHH ) 7.0 Hz, 6H,
CH(CH3)2), 1.11 (d, 3JHH ) 7.0 Hz, 6H, CH(CH3)2), 1.18 (d, 3JHH
) 7.0 Hz, 6H, CH(CH3)2), 1.44 (s, 9H, C(CH3)3), 2.86 (heptet,
Synthesis of the triazapentadiene ligand [N{(C3F7)C-
(Dipp)N}2]H was described in a communication.29 It can be
obtained in good yield from the reaction of 2,6-diisopropyl-
aniline with the perfluoro-5-aza-4-nonene (C3F7CFdNC4F9)30
in ether. Colorless crystals of this molecule could be obtained
from hexane at room temperature. Various solutions of pure
[N{(C3F7)C(Dipp)N}2]H (e.g., in benzene, toluene, hexane,
Et2O, CHCl3) are yellow-orange in color. Solid [N{(C3F7)C-
(Dipp)N}2]H prior to recrystallization also has a yellow color.
3
3JHH ) 7.0 Hz, 2H, CH(CH3)2), 2.90 (heptet, JHH ) 7.0 Hz, 2H,
3
CH(CH3)2), 6.92 (nonfirst-order t, 2H, p-Ar), 6.96 (d, JHH ) 6.5
3
Hz, m-Ar), 7.06 (d, JHH ) 7.0 Hz, m-Ar). IR (Nujol, cm-1):
2219(CN). Anal. Calcd for C37H43F14N4Ag: C, 48.43; H, 4.72; N,
6.11. Found: C, 48.02; H, 4.36; N, 6.45.
[N{(C3F7)C(Dipp)N}2]AgPPh3. CH3CNAg[N{(C3F7)C(Dipp)N}2]
(0.10 g, 0.12 mmol) was dissolved in hexane and treated with
triphenylphosphine (0.03 g, 0.11 mmol) at room temperature. The
mixture stirred overnight, and the solution was concentrated and
cooled to -15 °C to obtain yellow crystals. Yield: 89%. Mp: 154-
155 °C. 31P NMR (CDCl3): δ 17.3 (1J(107Ag-31P) ) 616 Hz) and
(1J(109Ag-31P) ) 709 Hz). 19F NMR (CDCl3): δ -121.7 (s, â-CF2),
-104.4 (Apparent quartet, JFF ) 12, 8 Hz, R-CF2), -80.4 (t, JFF
) 12 Hz, CF3). 1H NMR (CDCl3): δ 0.75 (d, 3JHH ) 7.0 Hz, 12H,
CH(CH3)2), 1.19 (d, 3JHH ) 7.0 Hz, 12H, CH(CH3)2), 3.23 (heptet,
3JHH ) 7.0 Hz, 4H, CH(CH3)2), 6.56-6.60 (m, 6H, m- and p-Ar),
7.02-7.29 (m, 15H, PPh). Selected 13C{1H} NMR (CDCl3): δ 23.2
(CH(CH3)2), 24.6 (CH(CH3)2), 28.1 (CH(CH3)2), 113.5 (p-CAr),
125.4 (m-CAr), 137.9 (o-CAr), 145.3 (Cipso), 151.1 (t, 2JCF ) 23.0
Hz, NCN). Anal. Calcd for C50H49F14N3AgP: C, 54.76; H, 4.50;
N, 3.83. Found: C, 55.01; H, 4.22; N, 4.11.
1
The room-temperature H and 19F NMR spectra of [N{-
(C3F7)C(Dipp)N}2]H are fairly complex. For example, the
1H NMR spectrum (in CDCl3 at room temperature) shows
that signals due to the isopropyl CH(CH3)2 and CH(CH3)2
protons appear as nine sets of doublets and four sets of
multiplets, respectively. This is likely a result of hindered
rotation of the aryl groups at room temperature, as well as
due to the presence of relatively rigid conformational isomers
and tautomers. Fluorinated triazapentadiene molecules with
U- or W-shaped backbones are known in the solid state (vide
infra).19 The 1H NMR spectrum [N{(C3F7)C(Dipp)N}2]H also
shows two broad signals at δ 12.92 and 6.26 (in a 0.3:0.7
((0.1) ratio). In C6D6, these two peaks are observed at δ
13.28 and 6.01 (0.2:0.8 ((0.1) ratio), respectively. These
signals disappear upon the addition of a few drops of D2O
to the solution. Although we have not investigated NMR
spectroscopic properties in detail, these two broad peaks may
correspond to the NH protons of the two tautomers where
the acidic proton is attached to the terminal nitrogen or to
the central nitrogen atom. Rather complex NMR spectro-
scopic properties of [N{(C3F7)C(Ph)N}2]H as well as iso-
meric forms of CH3Hg[N{(C3F7)C(Ph)N}2] in solution have
been noted previously.18-20 Interestingly, the related diaza-
X-ray Structure Determinations. A suitable crystal covered
with a layer of hydrocarbon oil was selected and mounted with
paratone-N oil on a cryo-loop and immediately placed in the low-
temperature nitrogen stream. The X-ray intensity data were
measured at 100(2) K on a Bruker SMART APEX CCD area
detector system equipped with a Oxford Cryosystems 700 Series
cooler, a graphite monochromator, and a Mo KR fine-focus sealed
tube (λ ) 0.710 73 Å). The detector was placed at a distance of
5.995 cm from the crystal. The data frames were integrated with
the Bruker SAINT-Plus software package. Data were corrected for
absorption effects using the multiscan technique (SADABS).
7398 Inorganic Chemistry, Vol. 43, No. 23, 2004

Ag(I) Complexes of [N{(C3F7)C(Dipp)N}2]-
Table 2. Selected Bond Distances (Å) and Angles (deg) for Triazapentadienes [N{(C3F7)C(Dipp)N}2]H, [N{(C3F7)C(Mes)N}2]H, and
[N{(C3F7)C(Ph)N}2]H, Triazapantadienyl Anion [N{(C3F7)C(Ph)N}2]-, and Diazapentadiene [HC{(CF3)C(Dipp)N}2]H a
param
[N{(C3F7)C(Dipp)N}2]H
[N{(C3F7)C(Mes)N}2]H
[N{(C3F7)C(Ph)N}2]H
[N{(C3F7)C(Ph)N}2]-
[HC{(CF3)C(Dipp)N}2]H
ref
this work
W
32
W
20
U
20
W
31
U
conformatn
N1-C1
1.3523(14)
1.2714(15)
1.3868(14)
1.2651(15)
122.54(10)
129.08(10)
128.20(11)
1.357(5)
1.269(4)
1.370(5)
1.281(5)
119.0(4)
132.3(4)
127.0(4)
1.345(11)
1.258(10)
1.377(9)
1.259(9)
132.7(7)
131.8(6)
131.6(7)
1.297(6)
1.337(6)
1.336(5)
1.288(5)
130.0(4)
129.4(4)
129.6(4)
N1-C1
1.357(3)
1.363(4)
1.429(4)
1.289(3)
124.2(2)
118.1(1)
121.3(2)
C1-N2
C1-CH
N2-C2
CH-C2
C2-N3
C2-N3
N1-C1-N2
C1-N2-C2
N2-C2-N3
N1-C1-CH
C1-CH-C2
CH-C2-N3
a Note that N2 ) CH for [HC{(CF3)C(Dipp)N}2]H).
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
CH3CNAg[N{(C3F7)C(Dipp)N}2]
Ag-N(4)
2.1070(15)
2.1605(13)
1.2761(19)
1.424(2)
1.3607(19)
1.3740(19)
N(3)-C(2)
N(3)-C(21)
N(4)-C(33)
C(1)-C(3)
C(2)-C(6)
C(33)-C(34)
1.2792(19)
1.4251(19)
1.136(2)
1.544(2)
1.544(2)
1.460(2)
Ag-N(2)
N(1)-C(1)
N(1)-C(9)
N(2)-C(2)
N(2)-C(1)
N(4)-Ag-N(2)
C(2)-N(2)-C(1)
C(2)-N(2)-Ag
C(1)-N(2)-Ag
177.33(6)
126.76(13)
116.94(10)
116.29(10)
C(1)-N(1)-C(9)
N(1)-C(1)-C(3)
N(2)-C(1)-C(3)
N(3)-C(2)-N(2)
N(3)-C(2)-C(6)
N(2)-C(2)-C(6)
121.56(13)
111.01(13)
119.98(13)
128.18(14)
110.32(12)
120.94(12)
C(2)-N(3)-C(21) 122.26(13)
C(33)-N(4)-Ag
N(1)-C(1)-N(2)
171.05(14)
127.98(14)
N(4)-C(33)-C(34) 179.6(2)
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
t-BuNCAg[N{(C3F7)C(Dipp)N}2]
Ag(1)-C(33)
Ag(1)-N(2)
Ag(2)-C(70)
Ag(2)-N(6)
N(1)-C(1)
N(1)-C(9)
N(2)-C(2)
N(2)-C(1)
N(3)-C(2)
N(3)-C(21)
2.046(5)
2.179(3)
2.026(5)
2.156(3)
1.289(5)
1.440(5)
1.366(5)
1.380(5)
1.273(5)
1.434(5)
N(4)-C(33)
N(4)-C(34)
N(5)-C(38)
N(5)-C(46)
N(6)-C(38)
N(6)-C(39)
N(7)-C(39)
N(7)-C(58)
N(8)-C(70)
1.164(6)
1.455(6)
1.278(5)
1.421(5)
1.368(5)
1.370(5)
1.272(5)
1.434(5)
1.155(7)
Figure 1. Crystal structure of [N{(C3F7)C(Dipp)N}2]H illustrating the
W-shaped conformation. (All hydrogen atoms except the one on nitrogen
have been omitted for clarity.)
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
[N{(C3F7)C(Dipp)N}2]AgPPh3
Ag-N(3)
Ag-N(1)
Ag-P
P-C(33)
P-C(39)
P-C(45)
N(1)-C(1)
2.250(3)
2.252(3)
2.3487(10)
1.824(3)
1.827(4)
1.832(4)
1.299(4)
N(1)-C(9)
N(2)-C(2)
N(2)-C(1)
N(3)-C(2)
N(3)-C(21)
C(1)-C(3)
C(2)-C(6)
1.446(4)
1.345(4)
1.350(4)
1.301(4)
1.445(4)
1.550(5)
1.558(5)
C(33)-Ag(1)-N(2) 175.31(15)
C(70)-Ag(2)-N(6) 175.31(17)
C(33)-N(4)-C(34) 176.9(5)
C(38)-N(5)-C(46) 122.1(3)
C(38)-N(6)-C(39) 127.3(3)
C(38)-N(6)-Ag(2) 117.8(2)
C(39)-N(6)-Ag(2) 114.9(2)
C(39)-N(7)-C(58) 121.4(3)
C(1)-N(1)-C(9)
C(2)-N(2)-C(1)
C(2)-N(2)-Ag(1)
C(1)-N(2)-Ag(1)
C(2)-N(3)-C(21)
N(1)-C(1)-C(3)
N(2)-C(1)-C(3)
N(3)-C(2)-N(2)
N(3)-C(2)-C(6)
N(2)-C(2)-C(6)
C(10)-C(9)-N(1)
C(14)-C(9)-N(1)
121.1(3)
127.2(3)
117.6(2)
115.0(3)
121.3(3)
111.0(3)
121.0(3)
127.7(3)
110.3(3)
121.2(3)
116.8(3)
121.5(4)
N(1)-C(1)-N(2)
N(4)-C(34)-C(36) 106.5(4)
127.3(3)
127.2(4)
N(3)-Ag-N(1)
N(3)-Ag-P
N(1)-Ag-P
C(33)-P-C(39)
C(45)-P-Ag
85.81(10)
C(33)-P-C(45)
C(39)-P-C(45)
C(33)-P-Ag
104.59(16)
103.37(16)
113.06(11)
116.41(12)
119.3(3)
130.0(3)
124.4(3)
105.6(3)
130.1(3)
N(5)-C(38)-N(6)
141.61(7)
132.55(7)
105.23(16)
112.99(12)
125.2(3)
122.1(2)
112.1(2)
127.7(3)
N(5)-C(38)-C(40) 110.4(3)
N(6)-C(38)-C(40) 121.7(3)
C(39)-P-Ag
N(7)-C(39)-N(6)
128.0(3)
C(14)-C(9)-N(1)
N(1)-C(1)-N(2)
N(1)-C(1)-C(3)
N(2)-C(1)-C(3)
N(3)-C(2)-N(2)
N(3)-C(2)-C(6)
N(2)-C(2)-C(6)
N(7)-C(39)-C(43) 110.5(3)
N(6)-C(39)-C(43) 120.4(3)
C(51)-C(46)-N(5) 121.7(4)
N(5)-C(46)-C(47) 117.1(3)
C(59)-C(58)-N(7) 122.5(4)
C(63)-C(58)-N(7) 116.0(3)
N(8)-C(70)-Ag(2) 177.5(4)
C(1)-N(1)-C(9)
C(1)-N(1)-Ag
C(9)-N(1)-Ag
C(2)-N(2)-C(1)
C(26)-C(21)-N(3) 122.0(3)
C(22)-C(21)-N(3) 116.6(3)
N(4)-C(33)-Ag(1) 175.7(4)
N(4)-C(34)-C(35) 107.6(4)
N(4)-C(34)-C(37) 107.0(4)
C(2)-N(3)-C(21) 123.7(3)
123.7(3)
106.2(3)
C(2)-N(3)-Ag
C(21)-N(3)-Ag
121.9(2)
114.3(2)
C(26)-C(21)-N(3) 119.8(3)
C(22)-C(21)-N(3) 118.4(3)
C(10)-C(9)-N(1) 118.4(3)
pentadiene [HC{(CF3)C(Dipp)N}2]H shows a fairly simple
1H NMR spectrum with just two sets of doublets for CH-
(CH3)2 and a septet for CH(CH3)2.31
The X-ray crystal structure of [N{(C3F7)C(Dipp)N}2]H is
illustrated in Figure 1. It crystallizes in the form where acidic
proton is bonded to one of the terminal nitrogen atoms. This
proton (H1 on N1) was located from the difference map and
refined freely. There are no inter- or intramolecular close
contacts between H1 and the other nitrogen atoms. The
closest contact is with one of the fluorines of the â-CF2
moiety (H1‚‚‚F3 distance ) 2.43 Å). The backbone of [N{-
(C3F7)C(Dipp)N}2]H adopts a W-shaped configuration.
(31) Carey, D. T.; Cope-Eatough, E. K.; Vilaplana-Mafe, E.; Mair, F. S.;
Pritchard, R. G.; Warren, J. E.; Woods, R. J. Dalton Trans. 2003,
1083-1093.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7399

Dias and Singh
The NCNCN moiety, however, is not planar. [N{(C3F7)C-
(Dipp)N}2]H shows a long-short-long-short C-N bond
length pattern in the backbone (see Table 2) consistent with
the localized proton on one of the terminal nitrogens (N1).
A similar trend is observed for [N{(C3F7)C(Mes)N}2]H
(where Mes ) 2,4,6-trimethylphenyl)32 and [N{(C3F7)C-
(Ph)N}2]H.20 One of these (i.e., [N{(C3F7)C(Ph)N}2]H),
however, features a U-shaped backbone. The closely related
diazapentadine [HC{(CF3)C(Dipp)N}2]H also shows bond
distances consistent with amine and imine type nitrogen sites.
In contrast to the triazapentadiene [N{(C3F7)C(Dipp)N}2]H,
the diazapentadiene [HC{(CF3)C(Dipp)N}2]H crystallizes in
the U-shaped conformation and features an intramolecular
NH‚‚‚N hydrogen bond.31
Figure 2. Crystal structure of CH3CNAg[N{(C3F7)C(Dipp)N}2]. (Hydro-
gen atoms have been omitted for clarity.)
scopic data for [N{(C3F7)C(Ph)N}2]Ag have not been
reported. It is known to behave as a 1:1 electrolyte in
acetonitrile.20
The X-ray crystal structure of CH3CNAg[N{(C3F7)C-
(Dipp)N}2] shows that [N{(C3F7)C(Dipp)N}2]- acts as a κ1-
donor (Figure 2). Silver coordinates to the triazapentadienyl
ligand via the central nitrogen atom and adopts a linear
geometry. Ligand backbone features a W-shaped configu-
ration with the two Dipp moieties flanking the silver ion.
The closest Ag‚‚‚C(aryl) distances are 2.892 Å (Ag‚‚‚C9)
and 2.844 Å (Ag‚‚‚C21). These values are within the sum
of van der Waals radii of silver and carbon atoms (rvW(Ag)
+ rvW(C) ) 3.42 Å). The Ag-N(CCH3) distance of
2.1070(15) Å is not much different from the corresponding
distances of two-coordinate species (CF3)2FCAgNCCH3
(2.083(7) Å)33 and four-coordinate silver adduct [HB(3,5-
(CF3)2Pz)3]AgNCBut (2.120(4) Å).7 Compounds with much
longer Ag-N distances are also known, e.g., (PPh3)2-
AgNCCH3 (2.321(2) Å)34 and [Ag(NCCH3)4]BF4 (2.266 Å).35
The closely related copper analogue [N{(C3F7)C(Dipp)N}2]-
CuNCCH3 has been reported.29 It features a κ2-bonded
triazapentadienyl ligand and a three-coordinate copper center.
The Cu-N(CCH3) bond length of 1.867(3) Å is, as expected,
shorter than the Ag-N(CCH3) distance observed for the
silver analogue CH3CNAg[N{(C3F7)C(Dipp)N}2].
The silver(I) acetonitrile complex CH3CNAg[N{(C3F7)C-
(Dipp)N}2] was prepared by refluxing a mixture of silver
oxide and [N{(C3F7)C(Dipp)N}2]H in acetonitrile for 12 h.
It is a colorless solid with somewhat limited stability in most
organic solvents at room temperature. CH3CNAg[N{(C3F7)C-
(Dipp)N}2] is stable in acetonitrile but decomposes in hexane
or benzene over a period of several hours. In solvents such
as CH2Cl2 or CHCl3, a slow formation of a black solid could
be observed within minutes. However, CH3CNAg[N{(C3F7)C-
(Dipp)N}2] survives even in chlorinated solvents long enough
to obtain good NMR spectra or to perform reactions with
other reagents (vide infra). The related [N{(C3F7)C(Ph)N}2]-
Ag has been obtained as an acetonitrile free solid following
a similar route.20 It is reported to be stable only in acetonitrile
solutions or as a solid.
The 19F NMR spectrum of CH3CNAg[N{(C3F7)C(Dipp)N}2]
shows a singlet assignable to CF3 and two AB multiplets
corresponding to the R-CF2 and â-CF2 fluorines. This is in
sharp contrast to the complex 19F NMR spectrum observed
for the free ligand. The 1H NMR spectrum in CDCl3 is also
relatively simple. It displays four sets of doublets for CH-
(CH3)2 and two septets for CH(CH3)2. The NMR spectro-
Silver adducts such as CH3CNAg[N{(C3F7)C(Dipp)N}2]
containing weakly coordinating fluorinated ligands are of
significant interest because they serve as useful ligand
transfer agents.36 However, not many silver(I) complexes of
monoanionic, nitrogen-based ligands are known in the
literature. We have reported a number of such adducts
involving the fluorinated, tridentate tris(pyrazolyl)borates and
(33) Burch, R. R.; Calabrese, J. C. J. Am. Chem. Soc. 1986, 108, 5359-
5360.
(34) Bachman, R. E.; Andretta, D. F. Inorg. Chem. 1998, 37, 5657-5663.
(35) Jones, P. G.; Bembenek, E. Z. Kristallogr. 1993, 208, 213-218.
(36) Strauss, S. H. Chem. ReV. 1993, 93, 927-942.
(32) Dias, H. V. R.; Singh, S. Unpublished results.
7400 Inorganic Chemistry, Vol. 43, No. 23, 2004

Ag(I) Complexes of [N{(C3F7)C(Dipp)N}2]-
one example containing the bidentate, bis(pyrazolyl)-
borate.7-10,13,14,37-42 [N{(C3F7)C(Ph)N}2]Ag and [(diphos)-
Ag][N{(C3F7)C(Ph)N}2] are the only silver complexes
reported for the triazapentadienyl family.20
CH3CNAg[N{(C3F7)C(Dipp)N}2] may be used as a con-
venient starting material for other silver derivatives of
[N{(C3F7)C(Dipp)N}2]-. For example, CH3CNAg[N{(C3F7)C-
(Dipp)N}2] reacts with tert-butyl isocyanide in hexane to
yield t-BuNCAg[N{(C3F7)C(Dipp)N}2] in 85% yield. A
strong signal in the IR spectrum at 2219 cm-1 indicates the
presence of the CNBut moiety in the product. The νCN band
shows a shift of about 78 cm-1 as a result of coordination to
the silver(I) center (νCN of free CNBut ) 2138 cm-1). The
ν
CN value is similar to that observed for [HB(3,5-(CF3)2Pz)3]-
AgCNBut, which appears at 2214 cm-1.7 There are no
isocyanide complexes of silver(I) bis(pyrazolyl)borates to our
knowledge.15 The related copper(I) triazapentadienyl com-
plex, [N{(C3F7)C(Dipp)N}2]CuCNBut, displays the νCN at a
much lower value (2176 cm-1).29
Figure 3. Crystal structure of t-BuNCAg[N{(C3F7)C(Dipp)N}2]. (One of
the two molecules in the asymmetric unit is shown. Hydrogen atoms have
been omitted for clarity.)
those observed for the corresponding acetonitrile adduct. The
X-ray crystal structure of t-BuNCAg[N{(C3F7)C(Dipp)N}2]
(Figure 3) indeed reveals closely related structures. The
isocyanide adduct crystallizes in the Pca21 space group with
two molecules in the asymmetric unit. One of these shows
minor rotational disorder of the tert-butyl moiety. As in the
acetonitrile adduct, the triazapentadienyl ligand coordinates
to silver atom in an κ1-fashion via the central nitrogen atom.
The Ag1-N2 distance is 2.179(3) Å (Ag2-N6 2.156(3) Å).
The Ag-C distances (2.046(5), 2.026(5) Å) are in the typical
range. For example, the related Ag-C distances of [HB-
(3,5-(CF3)2Pz)3]AgCNBut and [HB(3,5-(Ph)2Pz)3]AgCNBut
are 2.059(4) and 2.063(5) Å, respectively.7,43 The two aryl
groups (Dipp groups) of the triazapentadienyl ligand sand-
wich the silver center. The closest Ag‚‚‚C(aryl) separation
is about 2.80 Å (e.g., Ag1‚‚‚C21 ) 2.802 Å, Ag2‚‚‚C46 )
2.801 Å). The Ag-C-N moieties are essentially linear
(175.7(4) and 177.5(4)°).
The Ag(I)-PPh3 analogue could be obtained by treating
CH3CNAg[N{(C3F7)C(Dipp)N}2] with 1 equiv of PPh3.
Interestingly, [N{(C3F7)C(Dipp)N}2]AgPPh3 has an κ2-
coordinated triazapentadienyl ligand (vide infra). The 19F
NMR data indicate that this compound has equivalent C3F7
1
groups. The H NMR spectrum displays just two sets of
doublets for CH(CH3)2 and a septet for CH(CH3)2. This
pattern is similar to those observed for [N{(C3F7)C(Dipp)N}2]-
CuL (L ) CO, NCCH3, and CNBut) featuring a κ2-bonded
[N{(C3F7)C(Dipp)N}2]- ligand.29 Note however that the κ1-
coordinted silver(I) adducts described above display four sets
of doublets for CH(CH3)2 and two septets for CH(CH3)2.
The 31P NMR spectrum of [N{(C3F7)C(Dipp)N}2]AgPPh3
shows a superposition of two doublets arising from the
The 1H NMR peaks corresponding to the triazapentadienyl
moiety of t-BuNCAg[N{(C3F7)C(Dipp)N}2] are similar to
(37) Dias, H. V. R.; Wang, Z. Inorg. Chem. 2000, 39, 3890-3893.
(38) Dias, H. V. R.; Wang, Z. Inorg. Chem. 2000, 39, 3724-3727.
(39) Ayers, A. E.; Dias, H. V. R. Inorg. Chem. 2002, 41, 3259-3268 and
the references therein.
(40) Omary, M. A.; Rawashdeh-Omary, M. A.; Diyabalanage, H. V. K.;
Dias, H. V. R. Inorg. Chem. 2003, 42, 8612-8614.
(41) Dias, H. V. R.; Jin, W. Inorg. Chem. 1996, 35, 267-268.
(42) Dias, H. V. R.; Jin, W.; Kim, H.-J.; Lu, H.-L. Inorg. Chem. 1996, 35,
2317-2328.
(43) Gioia Lobbia, G.; Pettinari, C.; Santini, C.; Skelton, B. W.; White, A.
H. Inorg. Chim. Acta 2000, 298, 146-153.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7401

Dias and Singh
tadienyl plane (the aryls are twisted by about 83 and 84°
from the NCNCN plane). The Ag-P distance of [N{(C3F7)C-
(Dipp)N}2]AgPPh3 is 2.3487(10) Å. This is at the shorter
end of the typical Ag-PPh3 distances (average Ag-P value
of 27 silver triphenylphosphine complexes ) 2.419 Å).47 This
suggests a strong Ag-P bonding interaction. The three-
coordinate Ag(I) pyrazolate adduct PPh3Ag[3,5-(CF3)2-
Pz]2AgPPh3 (2.350(1), 2.374(1) Å)48 and the four-coordinate
tris(pyrazolyl)borate complex [HB(3,5-(CF3)2Pz)3]AgPPh3
(2.376(1) Å)42 also have relatively short Ag-P bonds. A few
bis(pyrazolyl)borato complexes of silver(I) containing phos-
phine ligands are known.15
Overall, we described the use of a bulky, fluoroalkyl-
substituted, triazapentadieneyl ligand in silver(I) coordination
chemistry. Compounds such as CH3CNAg[N{(C3F7)C-
(Dipp)N}2] may serve as good [N{(C3F7)C(Dipp)N}2]-
transfer agents or as precursors for silver triazapentadienyl
complexes. Silver adducts CH3CNAg[N{(C3F7)C(Dipp)N}2]
and t-BuNCAg[N{(C3F7)C(Dipp)N}2] feature κ1-bonded tri-
azapentadienyl ligands, whereas [N{(C3F7)C(Dipp)N}2]-
AgPPh3 has a chelating, κ2-bonded ligand. The NCNCN
backbone adopts either W- or U-shaped conformation. These
adducts represent the first structurally characterized silver
complexes of the triazapentadienyl family. We also note that,
to the best of our knowledge, thermally stable silver(I)
complexes of closely related diazapentadienyl (â-diketimi-
nate) ligands have not been reported.49 We are presently
investigating the use of these triazapentadienyl silver adducts
in various catalytic and ligand transfer applications.
Figure 4. Crystal structure of [N{(C3F7)C(Dipp)N}2]AgPPh3. (Hydrogen
atoms have been omitted for clarity.)
107Ag-31P and 109Ag-31P coupling. The observed Ag-P
coupling constants (J(107Ag-31P) ) 616 Hz) and (J(109Ag-
31P) ) 709 Hz) are at the higher end of the Ag-P coupling
of various other silver phosphine complexes (typical 1J(Ag-
P) constants range from 200 to 800 Hz).44-46 The ratio of
J(109Ag-31P)/J(107Ag-31P) is in good agreement with the
109Ag/107Ag gyromagnetic ratio of 1.15. We have observed
similar large 1J(Ag-P) coupling in the tris(pyrazolyl)borate
adduct, [HB(3,5-(CF3)2Pz)3]AgPPh3 (657.5 and 758.8 Hz).42
The 31P NMR spectrum of [(diphos)Ag][N{(C3F7)C(Ph)N}2]
in CDCl3 shows a broad doublet with much smaller 1J(Ag-
P) coupling (201 Hz). It primarily exists as a 1:1 electrolyte
in acetonitrile.20
Acknowledgment. This work has been supported by the
Robert A. Welch Foundation (Grant Y-1289) and the
National Science Foundation (Grant CHE-0314666).
Supporting Information Available: X-ray crystallographic data
for CH3CNAg[N{(C3F7)C(Dipp)N}2], t-BuNCAg[N{(C3F7)C(Dipp)-
N}2], and [N{(C3F7)C(Dipp)N}2]AgPPh3 (CIF) and 1H NMR
spectra of [N{(C3F7)C(Dipp)N}2]H and selected regions showing
the characteristic (CH3)2CH resonances of the free ligand and silver
complexes. This material is available free of charge via the Internet
at http://pubs.acs.org.
The X-ray crystal structure of [N{(C3F7)C(Dipp)N}2]-
AgPPh3 reveals the presence of a three-coordinate, trigonal
planar silver center (Figure 4). The triazapentadienyl ligand
acts as an κ2-donor. The Ag-N bond distances are equiva-
lent, and the U-shaped ligand backbone is essentially planar.
The Dipp groups lie almost perpendicular to the triazapen-
IC0491231
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