Silver(I) and copper(I) complexes supported by fully fluorinated 1,3,5-triazapentadienyl ligands

Article abstract of DOI:10.1039/c1dt10524h

Synthesis of the perfluorinated 1,3,5-triazapentadiene [N{(CF ₃)C(C₆F₅)N}₂]H and the use of its conjugate base as a supporting ligand for the isolation of silver(i) and copper(i) complexes are reported. Some of

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PAPER
Silver(I) and copper(I) complexes supported by fully fluorinated
1,3,5-triazapentadienyl ligands†
H. V. Rasika Dias,*a Jaime A. Flores,a Maura Pellei,b Barbara Morresi,b Giancarlo Gioia Lobbia,b
Shreeyukta Singh,a Yoshihiro Kobayashi,a Muhammed Yousufuddinc and Carlo Santini*b
Received 28th March 2011, Accepted 9th June 2011
DOI: 10.1039/c1dt10524h
Synthesis of the perfluorinated 1,3,5-triazapentadiene [N{(CF3)C(C6F5)N}2]H and the use of its
conjugate base as a supporting ligand for the isolation of silver(I) and copper(I) complexes are reported.
Some of the related chemistry involving [N{(C3F7)C(C6F5)N}2]- (that has bulkier –C3F7 groups on the
1,3,5-triazapentadienyl ligand backbone) is also presented. X-ray crystallographic data show a wide
variety of structures ranging from intermolecular, hydrogen-bonded chain structure for
[N{(CF3)C(C6F5)N}2]H with a twisted W-shaped N3C2 core, monomeric [N{(CF3)C(C6F5)N}2]Ag-
1
(CNtBu)2 and [N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 where the k -bonded triazapentadienyl ligand
bonding to the metal fragment via the central nitrogen atom, monomeric [N{(CF3)C(C6F5)N}2]Ag-
1
(PPh3)2 and [N{(C3F7)C(C6F5)N}2]Ag(PPh3)2 that feature k -bonded triazapentadienyl ligand bonding
to the metal fragment via one of the terminal nitrogen atoms, to that of the monomeric
2
[N{(CF3)C(C6F5)N}2]Cu(CNtBu)2 containing a k -bonded triazapentadienyl ligand and a U-shaped
NCNCN ligand backbone. The isocyanide adducts show relatively high nCN values in the IR spectra.
backbone C atoms (e.g. fluoroalkyls).35–41 The anionic form of
1,3,5-triazapentadienes also offers an additional coordination site
Introduction
Chelating systems such as b-diketones1,2 and their ni-
(compared to 1,5-diazapentadienyl systems) at the central nitrogen
atom.30,37,39,42–48 Moreover, the central nitrogen atom is also known
to take part in facile acid–base equilibria,46,49 thus providing pH
sensing properties to their complexes.50
trogen analogues, b-iminoketones and b-diketimines (1,5-
diazapentadienes),3–16 are some of the most ubiquitous ligands
in chemistry. They have been utilized widely in coordination
chemistry17–20 and to prepare homogeneous catalysts21–24 as well
as for modeling active sites of metalloenzymes.25–27 In con-
trast, the 1,3,5-triazapentadienes as trinitrogen analogues of 1,5-
diazapentadienes have received relatively less attention.28 This is
probably because facile and general synthetic methods for their
generation have been rather poorly developed. Reactions between
the 1,3,5-triazapentadiene bearing electron-donor substituents
and metal ions are also rare because free ligands are reactive
and many of them are elusive in the free state.29 Nevertheless,
several neutral non-fluorinated triazapentadiene ligands and their
mononuclear metal complexes, homo- or hetero-trinuclear clusters
are known.30–34 Direct metal–ligand reactions have been realized
(thus far) only with thermally stable 1,3,5-triazapentadienes
which usually bear strong electron withdrawing groups on the
An area of research activity in our laboratories concerns
the chemistry of fluorinated ligands including those of 1,3,5-
triazapentadienes. Fluorinated ligands are of significant interest
in metal coordination chemistry because they commonly
improve the thermal stability, oxidative resistance, volatility,
and fluorocarbon solubility of metal adducts.51 We and others
have reported the synthesis and use of several fluorinated
1,3,5-triazapentadienes including [N{(CF3)C(H)N}2]H,43,52,53
[N{(C3F7)C(Ph)N}2]H,39 [N{(C3F7)C(Dipp)N}2]H,35,37 (Dipp =
2,6-iPr2C6H3), [N{(C3F7)C(Mes)N}2]H36 (Mes
=
2,4,6-
Me3C6H2),
[N{(C3F7)C(C6F5)N}2]H,54
[N{(C3F7)C(2-F,6-
(CF3)C6H3)N}2]H54 and [N{(C3F7)C(2,6-Cl2C6H3)N}2]H55 (Fig. 1
a–g show the N-deprotonated form). These studies also show
that metal adducts of 1,3,5-triazapentadienyl ligands display
interesting solid-state structures and solution behavior and
diverse coordination modes. For example, [N{(C3F7)C(Dipp)-
aDepartment of Chemistry and Biochemistry, Box 19065, The University
of Texas at Arlington, Arlington, Texas, 76019-0065, USA. E-mail: dias@
uta.edu
1
N}2]Ag(CNtBu) features a k -bonded [N{(C3F7)C(Dipp)N}2]-
bSchool of Science and Technology - Chemistry Division, Universita` di
Camerino, via S. Agostino 1, 62032, Camerino, Macerata, Italy. E-mail:
carlo.santini@unicam.it
ligand with the silver(I) ion on the central nitrogen atom ligand
with a W-shaped backbone (Fig. 2).35 On the other hand, the
35
silver and copper complexes [N{(C3F7)C(Dipp)N}2]AgPPh3
cCenter for Nanostructured Materials, Box 19065, The University of Texas
at Arlington, Arlington, Texas, 76019-0065, USA
and [N{(C3F7)C(Dipp)N}2]Cu(CH3CN)37 have k -bonded U-
2
shaped ligand backbones. The [N{(C3F7)C(Ph)N}2]HgCH3
† CCDC reference numbers 818790–818795. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt10524h
1
is believed to exist as two slowly inter-converting k -bonded
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Fig. 1 A few examples of 1,3,5-triazapentadineyl ligands.
Here we describe details of
a
new fluorinated 1,3,5-
triazapentadienyl auxiliary ligand [N{(CF3)C(C6F5)N}2]-
(Fig. 1h), and its copper(I) and silver(I) isocyanide and phosphine
chemistry. For comparison, several copper and silver adducts
of [N{(C3F7)C(C6F5)N}2]- (Fig. 1g, which features a longer
fluoro-alkyl substituent on the backbone) are also reported.
Fig. 2 Several coordination modes of 1,3,5-triazapentadineyl ligands.
Results and discussion
isomers in solution.38 The solid state structure features a
k -bonded triazapentadienyl ligand with the mercury atom
[N{(CF3)C(C6F5)N}2]H (1) was synthesized in good yield by
the reaction of C6F5NH2, perfluoro-3-aza-2-pentene (prepared
using N(C2F5)3 and SbF5 and used directly), and triethylamine
(Scheme 1).56,57
It is a colorless crystalline solid. The most challenging aspect
is the synthesis and handling of perfluoro-3-aza-2-pentene due
to its high volatility. The room temperature 19F NMR spec-
trum of [N{(CF3)C(C6F5)N}2]H is somewhat complex which is
normal for fluorinated 1,3,5-triazapentadienenes. For example, it
displays three resonances corresponding to –CF3 groups. This is
1
coordinating to the central nitrogen atom. Polyfluorinated
1,3,5-triazapentadienyls are good ligands for the stabilization
of carbon monoxide and ethylene adducts of copper.37,54
A
rare gold(I) ethylene complex has also been isolated using
[N{(C3F7)C(2,6-Cl2C6H3)N} ]- as the supporting ligand.
[N{(C3F7)C(2,6-Cl2C6H3)N}22]Au(C2H4) features
a U-shaped
a three-coordinate,
triazapentadienyl ligand backbone and
trigonal gold center.55
Scheme 1 Synthesis of the ligand [N{(CF3)C(C6F5)N}2]H (1).
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Fig. 3 Two views showing the molecular structure and atom numbering scheme of [N{(CF3)C(C6F5)N}2]H (1) and extended structure formation via
◦
˚
inter-molecular H-bonding. Thermal ellipsoids drawn at the 50% level. Selected bond lengths (A) and angles ( ): N(1)–C(1) 1.338(3), N(2)–C(1) 1.269(3),
N(2)–C(2) 1.361(3), N(3)–C(2) 1.273(3), N(1)–C(1)–N(2) 122.7(2), C(1)–N(2)–C(2) 133.1(2), N(2)–C(2)–N(3) 128.7(2).
presumably due to the presence of relatively rigid conformational
isomers and tautomers in solution.
the addition of CNtBu to the resulting product. The stoi-
chiometry of the compound was not affected by reducing (to
1 equivalent) or increasing (>2 equivalents) the amount of
the relevant isocyanide. [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 and
[N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 are air stable solids. They
show good solubility in chloroform and CH2Cl2. Crystals of
[N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 (3) were obtained by slow
diffusion of hexane into a solution of the compound in CH2Cl2
while [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 (2) was recrystallized
from CHCl3–diethyl ether at room temperature. The 19F NMR
spectrum of [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 shows one singlet
assignable to CF3 in contrast to the complex 19F NMR spectrum
observed for the free ligand. [N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2
also displays a relatively less complex 19F NMR spectrum com-
pared to that of the free ligand [N{(C3F7)C(C6F5)N}2]H.
X-ray crystal structure of [N{(CF3)C(C6F5)N}2]H (1) is de-
picted in Fig. 3. It has a twisted, non-planar, W-shaped
(which is approaching an S-shape with two F3C-CN(central)
planes at 88.1◦) NCNCN triazapentadiene backbone. The pro-
ton is located on one of the terminal nitrogen atoms and
the HNCNCN backbone displays long-short-long-short C–N
bonds consistent with this observation. The crystal packing
diagram shows the existence of NH ◊ ◊ ◊ N hydrogen bonds
(Fig. 3b) between neighboring molecules leading to a polymeric
chain structure. X-ray structures of [N{(C3F7)C(Dipp)N}2]H,
[N{(C3F7)C(Mes)N}2]H (shows polymorphs), [N{(C3F7)C(2,6-
Cl2C6H3)N}2]H and [N{(C3F7)C(C6F5)N}2]H have been reported
previously.36,37,55,58 All these fluorinated 1,3,5-triazapentadienes
feature non-planar, distorted W-shaped triazapentadienyl ligand
backbones. [N{(C3F7)C(2,6-Cl2C6H3)N}2]H, and one of the poly-
morphs of [N{(C3F7)C(Mes)N}2]H, and [N{(C3F7)C(C6F5)N}2]H
show aggregation via inter-molecular NH ◊ ◊ ◊ N hydrogen bonding.
The tert-butyl isocyanide complexes of silver [N{(CF3)C(C6F5)-
N}2]Ag(CNtBu)2 (2) and [N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 (3)
were synthesized by first treating the corresponding triazapen-
tadiene with Ag2O at an elevated temperature followed by
Strong signals in the IR spectra of (2) and (3) at 2214 cm-1
and 2211 cm-1, respectively, indicate the presence of the CNtBu
moiety in the product. The nCN bands show a significant increase
in frequency as a result of coordination to the silver(I) centers.
[N{(C3F7)C(Dipp)N}2]Ag(CNtBu) is known and it also displays
a nCN band at a fairly high wave number 2219 cm-1 (see Table 1).
The nCN bands in (2) and (3) show a shift of about 75 cm-1
as a result of coordination to the silver(I) center (nCN of free
Table 1 Selected Ag(I)–CNtBu complexes of tris(pyrazolyl)borates and 1,3,5-triazapentadienyl ligands and some of their structural and spectroscopic
parameters
CN/cm-1
Ag–C/A
Ag–N/A
Ref.
˚
˚
Complex
n
[N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 (2)
[N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 (3)
2214
2211
2.088(3)
2.095(3)
2.113(4)
2.109(4)
2.046(5)
2.059(4)
2.445(2)
2.415(3)
This work
This work
[N{(C3F7)C(Dipp)N}2]Ag(CNtBu)
2219
2214
2.179(3)
2.349(3)
2.390(3)
2.387(3)
2.271(9)
2.36(1)
35
59
[HB(3,5-(CF3)2pz)3]Ag(CNtBu)
[HB(3,5-(CH3)2pz)3]Ag(CNtBu)
[HB(3,5-(Ph)2pz)3]Ag(CNtBu)
2178
2185
2.05(1)
2.08(1)
60
60
2.38(1)
2.319(7)
2.363(7)
2.321(7)
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Fig. 4 Molecular structure of [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 (2) ([N{(CF3)C(C6F5)N}2] moiety is disordered over two positions and only the
major component is shown fo◦r clarity) and a view showing the triazapentadienyl ligand backbone. Thermal ellipsoids drawn at the 50% level. Selected
˚
bond lengths (A) and angles ( ): Ag–N(2) 2.445(2), Ag–C(17) 2.088(3), Ag–C(22) 2.095(3), N(5)–C(22) 1.125(4), N(4)–C(17) 1.144(4), C(17)–Ag–C(22)
154.56(13), N(2)–Ag–C(17) 102.42(11), N(2)–Ag–C(22) 102.78(11), Ag–C(17)–N(4) 173.7(3), Ag–C(22)–N(5) 174.3(3).
CNtBu = 2138 cm-1).61 For comparison, the nCN bands of highly
electron deficient tris(pyrazolyl)borates or 1,3,5-triazapentadienyl
ligands show a shift of the same order of magnitude. Complexes
with more electron rich metal sites display the nCN bands at a
relatively low frequency (see Table 1).
relevant isocyanide. Compound (4) displays a strong IR band at
2175 cm-1 (and a shoulder at 2193 cm-1) that can be assigned
to the C N stretch. This is similar to the nCN value observed
for [N{(C3F7)C(Dipp)N}2]Cu(CNtBu) (see Table 2). The related
copper(I) complexes (see above) have relatively high CN stretching
frequencies.
The IR stretching bands corresponding to the of tert-butyl
isocyanide derivatives of 1,3,5-triazapentadienyl ligands appear
as strong peaks at about 2175 cm-1 at frequencies significantly
higher than the nCN value observed for the free tert-butyl iso-
cyanide, in accordance with the occurrence of a primarily s-
bond between the metal and the isocyanide.65 They are also
higher than the corresponding values for [B(pz)4]Cu(CNtBu) and
[HB(pz)3]Cu(CNtBu) as a direct result of the increased Lewis
acidity of the copper center due to the presence of the weakly
donating ligands while they are of the same order of magnitude
of complexes containing poly(pyrazolyl)borate ligands bearing
electron withdrawing substituents (Table 2). A number of other
Cu(I) complexes containing the bis(isocyanide)copper(I) fragment
are also known in the literature.66–69
X-ray data show that [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2
(2) crystallizes in the P21/c space group and features a
distorted W-shaped N3C2 core of the [N{(CF3)C(C6F5)N}2]-
ligand (which is disordered over two positions at a 56 : 44
occupancy ratio) that coordinates to a Ag(CNtBu)2 moiety
1
in
a
k -fashion via the central N-atom (Fig. 4). The
three-coordinate silver center adopts
a distorted trigonal
planar (almost T-like) geometry with a large C22–Ag–C17
angle of 154.56(13)◦. [N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 (3)
crystallizes in P21/c space group with three independent
[N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2
molecules
in
the
asymmetric unit (Fig. 5). Except for the disorder, the basic
structural features are similar to those observed for [N{(CF3)-
C(C6F5)N}2]Ag(CNtBu)2.
[N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2
features relatively smaller C–Ag–C angles (141.01(17)◦,
142.36(16)◦ and 147.94(15)◦ for the three independent
molecules). As observed in [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2
and [N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2, previously reported
X-ray crystal structure of [N{(CF3)C(C6F5)N}2]Cu(CNtBu)2
(4) is illustrated in Fig. 6. In contrast to [N{(CF3)C(C6F5)-
N}2]Ag(CNtBu)2, [N{(CF3)C(C6F5)N}2]Cu(CNtBu)2 features a
U-shaped [N{(CF3)C(C6F5)N}2]- ligand backbone that coordi-
[N{(C3F7)C(Dipp)N}2]Ag(CNtBu) also displays a k -bonded
1
2
(via central N) 1,3,5-triazapentadienyl moiety. [N{(C3F7)C-
(Dipp)N}2]Ag(CNtBu) is however a mono-isocyanide complex
and has a two-coordinate, linear silver center.35 It has a
significantly shorter Ag–N bond perhaps due to the lower
coordination number at silver (Table 1).
nates to copper(I) in a k -fashion via the two terminal N-atoms.
The copper atom ◦adopts a tetrahedral geometry with a C–Cu–C
angle of 125.01(7) . Although [N{(C3F7)C(Dipp)N}2]Cu(CNtBu)
2
is known and believed to contain a k -bonded triazapentadienyl
moiety based on spectroscopic data, the structural data are not-
1,3,5-Triazapentadienyl ligands also allow us to stabilize
di(tert-butyl isocyanide) adducts of copper(I). For example,
[N{(CF3)C(C6F5)N}2]Cu(CNtBu)2 (4) can be obtained quite
easily using [N{(CF3)C(C6F5)N}2]H, Cu2O and CNtBu. The
stoichiometry of the compound was not affected by reducing (to
1 equivalent) or increasing (>2 equivalents) the amount of the
available for comparison.
The
silver(I)
phosphine complex [N{(CF3)C(C6F5)-
N}2]Ag(PPh3)2 (5) was synthesized by the reaction of
[N{(CF3)C(C6F5)N}2]H and Ag2O in acetonitrile at reflux
temperature for 16 h. Removal of solvent yielded a yellow
solid,
presumably
[N{(CF3)C(C6F5)N}2]Ag(CH3CN)2.
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Fig. 5 Molecular structure of [N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 (3) and a view showing the triazapentadienyl ligand backbone. Thermal ellipsoids
◦
˚
drawn at the 50% level. Selected bond lengths (A) and angles ( ): Ag(1)–N(1) 2.415(3), Ag(1)–C(21) 2.113(4), Ag(1)–C(26) 2.109(4), N(4)–C(21)
1.142(5), N(5)–C(26) 1.135(5), N(1)–Ag(1)–C(21) 104.37(12), N(1)–Ag(1)–C(26) 107.68(13), C(21)–Ag(1)–C(26) 147.94(15), Ag(1)–C(21)–N(4) 179.0(3),
Ag(1)–C(26)–N(5) 176.8(3).
Table 2 Selected Cu(I)—CNtBu complexes of poly(pyrazolyl)borates and 1,3,5-triazapentadienyl ligands and some of their structural and spectroscopic
parameters
CN/cm-1
Cu–C/A
Cu–N/A
Ref.
˚
˚
Complex
n
[N{(CF3)C(C6F5)N}2]Cu(CNtBu)2 (4)
2175, 2193sh
1.9162(18)
1.9078(18)
—
2.0653(14)
2.0712(14)
—
2.072(5)
2.093(4)
2.093(4)
—
This work
[N{(C3F7)C(Dipp)N}2]Cu(CNtBu)
2176
2196
37
62
[HB(3,5-(CF3)2pz)3]Cu(CNtBu)
1.827(6)
[H3B(5-(CF3)pz)]Cu(CNtBu)2
[H3B(3-(NO2)pz)]Cu(CNtBu)2
[H2B(3-(NO2)pz)2]Cu(CNtBu)2
2179
2178
2166, 2190sh
—
—
63
61
61
—
1.926(2)
1.903(2)
—
1.914(2)
1.9308(19)
1.855(3)
2.121(2)
2.129(2)
—
2.0606(16)
2.0840(17)
2.018(3)
2.014(3)
—
[HB(3-(NO2)pz)3]Cu(CNtBu)
[H2B(3-(CF3)pz)2]Cu(CNtBu)2
2162
2161, 2182sh
61
63
{[H2B(3,5-(CF3)2pz)2]Cu(CNtBu)}2
2196
62
[HB(pz)3]Cu(CNtBu)
2155
2140
—
—
64
64
[B(pz)4]Cu(CNtBu)
—
The product was dissolved in diethyl ether and
of triphenylphosphine were added to the solution. After
solvent removal, pale yellow solid was obtained. The
2
eq.
constants are in the range of the Ag–P couplings (from 300 to 500
Hz) typical of various silver diphosphine complexes (see Table 3).
The ratio of J(109Ag–31P)/J(107Ag–31P) is in good agreement with
the 109Ag/107Ag gyromagnetic ratio of 1.15.
a
compound showed good solubility in chloroform and CH2Cl2.
Similar to [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 or [N{(C3F7)C-
(C6F5)N}2]Ag(CNtBu)2, [N{(CF3)C(C6F5)N}2]Ag(PPh3)2 did not
show signs of decomposition after prolonged exposure to light.
It was stable in air for at least 60 days. Crystals of compound
(5) were obtained by slow diffusion of hexane into a solution of
the compound in CH2Cl2 after 16 h as colorless plates. 31P NMR
spectrum of (5) in CDCl3 at 293 K displayed a broad singlet at d
10.79 but gave rise to an overlapping doublet of doublets at 218 K
revealing the coupling to the two silver isotopes (1J(107Ag–31P) =
The
X-ray
molecular
structure
of
crystalline
[N{(CF3)C(C6F5)N}2]Ag(PPh3)2 (5) is illustrated in Fig. 7.
The NCNCN core adopts a twisted W-shaped conformation,
as previously found for [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2.
1
[N{(CF3)C(C6F5)N}2]Ag(PPh3)2 also has
a
k -bonded
triazapentadienyl moiety. However, in contrast to [N{(CF3)C-
(C6F5)N}2]Ag(CNtBu)2 (2), the [N{(CF3)C(C6F5)N}2]- ligand in
[N{(CF3)C(C6F5)N}2]Ag(PPh3)2 (5) coordinates to silver(I) via
one of the terminal N-atoms. Existence of such a coordination
mode was proposed for [N{(C3F7)C(Ph)N}2]AuPPh3 but no
1
425 Hz, J(109Ag–31P) = 486 Hz). The observed Ag–P coupling
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Table 3 Selected Ag(I)–PPh3 complexes of poly(pyrazolyl)borates and 1,3,5-triazapentadienyl ligands and some of their structural and spectroscopic
parameters
˚
˚
Complex
31P NMR/d (ppm)
Ag–P/A
Ag–N/A
Ref.
35
[N{(C3F7)C(Dipp)N}2]AgPPh3
17.3 dd (298 K)
2.3487(10)
2.250(3)
2.252(3)
1J(107Ag–31P) = 616 Hz
1J(109Ag–31P) = 709 Hz
10.31 dd (218 K)
[N{(CF3)C(C6F5)N}2]Ag(PPh3)2 (5)
2.4308(7)
2.4406(7)
2.321(2)
This work
1J(107Ag–31P) = 425 Hz
1J(109Ag–31P) = 486 Hz
6.39 d (218 K)
[N{(CF3)C(C6F5)N}2]Ag(PPh3)3 (6)
[N{(C3F7)C(C6F5)N}2]Ag(PPh3)2 (7)
—
—
This work
This work
71
1J(Ag–31P) = 232 Hz
10.8 d (298 K)
2.4464(6)
2.4514(6)
2.4256(9),
2.461(1)
2.5049(9),
2.484(1)
2.3849(19)
1J(Ag–31P) = 365 Hz
5.4 dd (183 K)
a
[H2B(pz)2]Ag(PPh3)2
2.326(3),
2.295(2)
2.360(3),
2.323(2)
1J(107Ag–31P) = 361 Hz
1J(109Ag–31P) = 414 Hz
3.37 d (223 K)
[H2B(3,5-Me2pz)2]Ag(PPh3)2
[H2B(tz)2]Ag(PPh3)2
—
—
71
72
1J(Ag–31P) = 301 Hz
7.44 dd (223 K)
2.4329(8)
2.4344(8)
2.297(3)
2.425(3)
1J(107Ag–31P) = 383 Hz
1J(109Ag–31P) = 439 Hz
7.40 dd (223 K)
[H2B(btz)2]Ag(PPh3)2
—
—
73
1J(107Ag–31P) = 300 Hz
1J(109Ag–31P) = 332 Hz
6.1 br (223 K)
[B(pz)4]Ag(PPh3)2
2.4265(6)
2.5342(7)
2.4138(6)
2.4641(6)
—
2.319(2)
2.364(2)
2.3970(17)
2.5661(19)
—
74
75
75
[H2B(3-(NO2)pz)2]Ag(PPh3)2
11.53 d (223 K)
1J(Ag–31P) = 455 Hz
4.16 dd (193 K)
b
[H2B(3-(CF3)pz)2]Ag(PPh3)2
1J(107Ag–31P) = 281 Hz
1J(109Ag–31P) = 323 Hz
8.57 dd (193 K)
1J(107Ag–31P) = 404 Hz
1J(109Ag–31P) = 465 Hz
16.66 dd (193 K)
1J(107Ag–31P) = 638 Hz
1J(109Ag–31P) = 733 Hz
9.31 d (223 K)
[H3B(5-(CF3)pz)]Ag(PPh3)2
2.4285(10)
2.4736(10)
2.5458(4)
2.5592(6)
2.5256(6)
2.335(3)
2.403(1)
76
73
1J(Ag–31P) = 417 Hz
6.36 d (218 K)
c
[HB(btz)3]Ag(PPh3)3
1J(Ag–31P) = 405 Hz
16.04 d (218 K)
1J(Ag–31P) = 701 Hz
a Dinuclear complex. b In the 31P NMR spectrum double doublets are observed at 223 K with coupling constants typical of tri-, di- and mono-phosphine
species, suggesting the occurrence of dissociative equilibria. c In the 31P NMR spectrum doublets are observed at 223 K with coupling constants, 1J(Ag–31P),
of 405 and 701 Hz, typical of di- and mono-phosphine species, respectively, suggesting the occurrence of dissociative equilibria.
structural data were reported.38 The silver atom in (5) is three
coordinate and adopts an essentially trigonal planar geometry
(sum of the angles at Ag = 356.8◦) with P–Ag–P angle of
129.11(2)◦.
spectroscopic data. The 31P NMR spectrum of (6) in CDCl3
at 293 K displayed a broad singlet at d 6.71 but gave rise to a
doublet at 218 K with a coupling constant 1J(Ag–31P) of 232 Hz,
in accordance with a AgNP3 coordination core. The observed
Ag–P coupling constant is at the lower end of the Ag–P couplings
of various other silver phosphine complexes (see Table 3).
For comparison to compound (5) we have also
synthesized and investigated the structural features of
[N{(C3F7)C(C6F5)N}2]Ag(PPh3)2 (7). This was also the product
we isolated from a reaction containing 1 : 1 molar ratio of
Ag:PPh3 (rather than 1 : 2). [N{(C3F7)C(C6F5)N}2]Ag(PPh3)2 (7)
features a twisted, S-shaped triazapentadienyl NCNCN core.
It also coordinates to silver(I) via one of the terminal nitrogen
atoms (Fig. 8). The three-coordinate silver center in (7) adopts
a trigonal planar geometry (sum of the angles at Ag = 358.4◦)
with P–Ag–P angle of 128.81(2)◦. The X-ray crystal structure
Recently
a
gold(I) diketiminato complex, [HC{(CF3)-
C(R)N}2]Au(PPh3) (R = 3,5-C6H3(CF3)2) was reported, adopting
1
a k -bonded 1,5-diazapentadienyl moiety; by contrast, the analo-
gous complex [HC{(CF3)C(R)N}2]Cu(PPh3)2 adopts the expected
chelate structure with a k -bonded 1,5-diazapentadienyl moiety.70
2
Interestingly,
during
the
repeated
synthesis
of
[N{(CF3)C(C6F5)N}2]Ag(PPh3)2 (5), we observed that it is
possible to obtain [N{(CF3)C(C6F5)N}2]Ag(PPh3)3 (6) by varying
the phosphine to silver ratio. Although we have managed
to isolate and characterize [N{(CF3)C(C6F5)N}2]Ag(PPh3)3
(6) using spectroscopic methods, it is difficult to propose the
triazapentadienyl ligand coordination mode solely based on
8574 | Dalton Trans., 2011, 40, 8569–8580
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conformers). We have reported that the two lowest energy confor-
mations found for the [N{(C3F7)C(Dipp)N}2]- at the PM3 level of
theory are U-shaped and W-shaped.77 The U-shaped conformer is
only 0.1 kcal mol-1 lower in energy than the W-shaped conformer
pointing to essentially degenerate structures. Furthermore, the
HOMO is more or less evenly distributed among the three N
atoms of either the W- or U-conformer of the anionic ligand.
Calculated Mulliken charges of the U and W conformers are -0.2
for the terminal nitrogens and -0.4 for the central nitrogen. Thus,
fluorinated [N{(R2)C(R1)N}2]- systems are an interesting class of
highly flexible supporting ligands and they seem to adapt easily
by changing the coordination mode to satisfy the steric-electronic
demands of the coordinating fragment. More detailed studies are
presently underway to understand the ligands coordination modes
and to see whether we can predict the observed structures using
computational methods.
In summary, we report the synthesis of [N{(CF3)C(C6F5)N}2]H
(1) and the use of its conjugate base as a supporting ligand for
the isolation of silver(I) and copper(I) complexes. Some of the
related chemistry involving the [N{(C3F7)C(C6F5)N}2]- is also
presented. X-ray crystallographic data show an interesting array
of coordination modes and triazapentadienyl ligand backbone
conformations, and demonstrate the ability of triazapentadienyl
supporting ligands to adopt their mode of coordination based on
the requirements of the metal fragment.
Fig. 6 Molecular structure of [N{(CF3)C(C6F5)N}2]Cu(CNtBu)2 (4).
˚
Thermal ellipsoids drawn at the 50% level. Selected bond lengths (A) and
angles (◦): Cu–N(1) 2.0653(14), Cu–N(3) 2.0712(14), Cu–C(17) 1.9162(18),
Cu–C(22) 1.9078(18), N(1)–Cu–N(3) 87.66(6), N(1)–Cu–C(22) 112.91(6),
N(1)–Cu–C(17) 106.22(6), N(3)–Cu–C(22) 110.36(6), N(3)–Cu–C(17)
108.28(7), C(17)–Cu–C(22) 125.01(7).
of [N{(C3F7)C(Dipp)N}2]AgPPh3 was reported earlier.35 It
also has a three-coordinate, trigonal planar silver center. The
triazapentadienyl ligand in [N{(C3F7)C(Dipp)N}2]AgPPh3
2
however acts as k -donor.
Experimental
Coordination properties of fluorinated [N{(R2)C(R1)N}2]- also
merit some comments. This work and prior reports show that
Materials and general methods
1
they bind to metal ions in several different fashions (e.g., k -
1
2
N(central), k -N(terminal), or k -N(terminal) with W- or U-
All syntheses and handling were carried out under an atmosphere
of dry dinitrogen, using standard Schlenk techniques or in a glove
shaped (sometimes with significant twisting or S-shaped) ligand
Fig. 7 Molecular structure of [N{(CF3)C(C6F5)N}2]Ag(PPh3)2 (5) and a view showing the triazapentadienyl ligand backbone. Thermal ellipsoids drawn
◦
˚
at the 50% level. Selected bond lengths (A) and angles ( ): Ag(1)–N(1) 2.321(2), Ag(1)–P(1) 2.4308(7), Ag(1)–P(2) 2.4406(7), N(1)–C(37) 1.316(3),
N(2)–C(38) 1.354(3), N(3)–C(38) 1.283(3), Ag(1)–N(1)–C(37) 127.53(17), N(1)–Ag(1)–P(1) 121.80(6), N(1)–Ag(1)–P(2) 105.94(5), P(1)–Ag(1)–P(2)
129.11(2), N(2)–C(38)–N(3) 127.6(2).
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Fig. 8 Molecular structure of [N{(C3F7)C(C6F5)N}2]Ag(PPh3)2 (7) and a view showing the triazapentadienyl ligand backbone. Thermal ellipsoids drawn
◦
˚
at the 50% level. Selected bond lengths (A) and angles ( ): Ag–N(1) 2.3849(19), Ag–P(1) 2.4464(6), Ag–P(2) 2.4514(6), N(1)–C(1) 1.322(3), N(2)–C(1)
1.305(3), N(2)–C(2) 1.341(3), N(3)–C(2) 1.287(3), N(1)–Ag–P(1) 122.53(5), N(1)–Ag–P(2)107.02(5), P(1)–Ag–P(2) 128.81(2), Ag–N(1)–C(1) 129.27(15),
N(1)–C(1)–N(2) 134.5(2), C(1)–N(2)–C(2) 132.1(2), N(2)–C(2)–N(3) 127.9(2).
box. All solvents were dried, degassed and distilled prior to use.
Elemental analyses (C, H, N) were performed in-house with a
Synthesis of [N{(CF3)C(C6F5)N}2]H (1)
Perfluoro-3-aza-2-pentene was prepared under a nitrogen atmo-
sphere by dropwise addition of N(C2F5)3 (15.0 g, 40.4 mmol) to
SbF5 (10.0 g, 46.1 mol) which was pre-heated at 55 ◦C in a 50 mL
three-neck flask while stirring vigorously.56 The temperature was
raised to 60 ◦C to distill off the product as quickly as it was
formed (this is important because, based on our experience, the
product yield suffers significantly if it is left in the crude mixture)
through a short pass condenser cooled at -10 ◦C and collected
in a 50 mL pear shape flask cooled at -78 ◦C. Yield: 5.01 g,
(53%). This volatile compound was used immediately in the next
step (or stored at -20 ◦C). Perfluoro-3-aza-2-pentene (5.4 g, 23.0
mmol) was added dropwise (which is also a challenging task due
to the high volatility of perfluoro-3-aza-2-pentene) to a mixture
of triethylamine (3.5 mL, 34.5 mmol) and perfluoroaniline (4.2 g,
Fisons Instruments 1108 CHNS-O Elemental Analyser. Melting
points were taken on an SMP3 Stuart Scientific Instrument. IR
spectra were recorded from 4000 to 100 cm-1 with a Perkin–Elmer
SPECTRUM ONE System. FT-IR instrument accessorised with a
single reflection ATR unit (universal diamond ATR top-plate). IR
annotations used: br = broad, m = medium, s = strong, sbr = strong
broad, sh = shoulder, w = weak. 1H, 13C, 19F and 31P NMR spectra
were recorded on an Oxford-400 Varian spectrometer (400.4 MHz
1
for H, 376.8 MHz for 19F and 162.1 MHz for 31P). Chemical
shifts, in ppm, for 1H NMR spectra are relative to internal Me4Si.
19F NMR chemical shifts were referenced relative to external
CFCl3. 31P NMR chemical shifts were referenced to a 85% H3PO4
standard. The 31P NMR spectroscopic data were accumulated with
1H decoupling. NMR annotations used: br = broad, d = doublet,
dd = double doublet, m = multiplet, s = singlet, sbr = broad
singlet, t = triplet, tt = triple triplet. Electrospray mass spectra (ESI
MS) were obtained in positive- or negative-ion mode on a Series
1100 MSD detector HP spectrometer, using a methanol mobile
phase. The compounds were added to reagent grade methanol
to give solutions of approximate concentration 0.1 mM. These
solutions were injected (1 mL) into the spectrometer via a HPLC
HP 1090 Series II fitted with an autosampler. The pump delivered
the solutions to the mass spectrometer source at a flow rate of
300 mL min-1, and nitrogen was employed both as a drying and
nebulizing gas. Capillary voltages were typically 4000 V and 3500 V
for the positive- and negative-ion mode, respectively. Confirmation
of all major species in this ESI MS study was aided by comparison
of the observed and predicted isotope distribution patterns, the
latter calculated using the IsoPro 3.0 computer program. All
reagents were purchased from Aldrich and used without further
purification. [N{(C3F7)C(C6F5)N}2]H was synthesized using the
method reported in the literature.54
◦
23 mmol) in ether 100 mL at -5 C (salt–ice–water bath). After
addition the solution was stirred overnight at room temperature.
A nitrogen atmosphere was not necessary after this point during
this ligand synthesis. The mixture was then filtered, and the filtrate
was collected and washed at 5 ◦C, first with 5% HCl and then twice
with deionized water. The ether layer was separated and dried over
anhydrous CaCl2 or Na2SO4. The solvent was removed at reduced
pressure to obtain [N{(CF3)C(C6F5)N}2]H as a colorless solid.
Yield: 8.06 g (65%). Mp: 130–140 ◦C. IR (cm-1): 3142 w, 2992 w,
2914 w (CH); 1716 s, 1639 m, 1500 s, 1463 m, 1443 w, 1369 w, 1327
m, 1312 m, 1202 s, 1171 m, 1133 m, 1196 s, 993 s, 979 sh, 932 m,
812 m, 789 w, 755 m, 740 w, 719 m, 702 m. 1H NMR (CDCl3, 293
K): d 7.67 (s, 1H, NH). 1H NMR (DMSO-d6, 293 K): d 11.97 (s,
1H, NH).19F NMR (CDCl3, 293 K): d -69.44, -71.24 and -74.81
(s, 6F, CF3), -143.51 (d, J = 15.2 Hz, CF), -144.67, -148.23 and
-150.67 (sbr, CF), -152.58 (t, J = 21.7 Hz, CF), -159.44 and
-159.96 (sbr, CF), -160.36 (t, J = 21.7 Hz, CF), -162.67 (sbr, CF).
19F NMR (DMSO-d6, 293 K): d -69.51, -73.64 and -75.10 (s, 6F,
8576 | Dalton Trans., 2011, 40, 8569–8580
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CF3), -145.17 (d, J = 19.5 Hz, CF), -148.28 (sbr, CF), -154.49
(t, J = 23.8 Hz, CF), -161.93 (t, J = 23.8 Hz, CF), -164.32 (sbr,
CF). ESI MS (major negative-ions, CH3OH), m/z (%): 538 (100)
[N{(CF3)C(C6F5)N}2]-. Anal. Calcd. for C16HF16N3: C, 35.64; H,
0.19; N, 7.79%. Found: C, 35.30; H, 0.23; N, 7.62%.
16 h. The solution was filtered over a bed of Celite and tert-butyl
isocyanide (0.10 mL, 0.88 mmol) was added to the filtrate. The
solvent was removed under vacuum to leave light yellow solid.
The solid was dissolved in minimum amount of dichloromethane
and layered with hexane to obtain colorless prismatic crystals
(the mixture first formed a yellow oil at the bottom of the flask,
but eventually formed crystals.) Yield: 0.240 g (88%). M.p. 60–
65 ◦C. IR (cm-1): 3000 w, 2947 w (CH); 2211 s (C N); 1558 sbr,
1513 sbr, 1437 s, 1399 s, 1378 m, 1344 s, 1306 m, 1235 sbr, 1123 s,
1072 m, 1002 s, 982 s, 910 w, 838 s, 747 m, 709 w, 657 m. 1H NMR
(CDCl3, 293 K): d 1.49 (s, CCH3). 19F NMR (CDCl3, 293 K):
d -83.6 (t, J = 11.0 Hz, CF3), -111.2 and -117.8 (AB multiplet,
Synthesis of [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 (2)
[N{(CF3)C(C6F5)N}2]H (1) (0.270 g, 0.50 mmol) was added to a
suspension of Ag2O (0.058 g, 0.25 mmol) in acetonitrile (25 mL);
the mixture was refluxed for 12 h. The solvent was removed
under vacuum, the resulting residue was dissolved in chloroform
(25 mL) and tert-butyl isocyanide (0.083 g, 1.00 mmol) was
added at room temperature. The mixture stirred overnight and the
solvent was removed under vacuum to afford a grey solid in 52%
yield. The crude complex [N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 (2)
was dissolved in CHCl3–diethyl ether (1 : 4) solution and crystals
suitable for X-ray dif◦fraction analysis were obtained at room
temperature. M.p. 116 C. IR (cm-1): 2996 w (CH); 2214 s (C N);
1747 w, 1650 w, 1626 w; 1558 s, 1498 sbr, 1440 m, 1377 m, 1309 w,
1190 s, 1160 s, 1140 s, 1131 s, 1123 s, 1104 s, 994 s, 980 s, 913 m,
845 w, 725 s, 712 m. 1H NMR (CDCl3, 293 K): d 1.51 (s, CCH3).
19F NMR (CDCl3, 293 K): d -69.56 (s, CF3), -146.85 (sbr, CF),
-163.92 (t, J = 21.5 Hz, CF), -164.6 (t, J = 20.5 Hz, CF). ESI MS
(major posive-ions, CH3OH), m/z (%): 274 (100) [Ag(CNtBu)2]+,
920 (50) [[N{(CF3)C(C6F5)N}2]AgCNtBu + AgCNtBu]+. ESI
MS (major negative-ions, CH3OH), m/z (%): 538 (100)
[N{(CF3)C(C6F5)N}2]-, 1184 (30) [[N{(CF3)C(C6F5)N}2]2Ag]-.
Anal. Calcd. for C26H18AgF16N5: C, 38.44; H, 2.23; N, 8.62%.
Found: C, 38.03; H, 1.98; N, 8.43%.
JAB = 271.5 Hz, a-CF2), -125.9 and -128.3 (AB multiplet, JAB
=
286.1 Hz, b-CF2), -149.7 (s, CF), -167.2 (t, J = 22 Hz, CF), -167.6
(t, J = 22 Hz, CF). Anal. Calcd. for C30H18AgF24N5: C, 35.59; H,
1.79; N, 6.92%. Found: C, 35.39; H, 1.40; N, 6.85%.
Synthesis of [N{(CF3)C(C6F5)N}2]Cu(CNtBu)2 (4)
[N{(CF3)C(C6F5)N}2]H (1) (0.270 g, 0.50 mmol) was added to a
suspension of Cu2O (0.036 g, 0.25 mmol) in acetonitrile (25 mL);
the mixture was refluxed for 12 h. The solvent was removed under
vacuum, the resulting residue was dissolved in dichloromethane
(25 mL) and tert-butyl isocyanide (0.083 g, 1.00 mmol) was added
at room temperature. The mixture stirred overnight and the solvent
was removed under vacuum to afford a green–brown solid in 55%
yield. The crude complex [N{(CF3)C(C6F5)N}2]Cu(CNtBu)2 (4)
was dissolved in CHCl3–diethyl ether (1 : 4) solution and a single
crystal suitable for X-ray diffraction analysis was obtained at room
temperature. M.p. 136–137 ◦C. IR (cm-1): 2993 w (CH); 2193 sh,
2175 s (C N); 1599 m, 1506 s, 1498 m, 1469 m, 1416 w, 1374 w,
1339 w, 1306 w, 1222 sh, 1193 s, 1153 m, 1112 m, 1025 w, 987 s, 906
w, 842 m, 809 w, 768 w, 753 w, 730 w, 706 w. 1H NMR (CDCl3, 293
K): d 1.43 (s, CCH3). 19F NMR (CDCl3, 293 K): d -68.42 (s, CF3),
-150.26 (sbr, CF), -162.92 (br, CF), -164.48 (sbr, CF). ESI MS
Synthesis of [N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 (3)
[N{(C3F7)C(C6F5)N}2]H(0.200g, 0.271mmol)and Ag2O (0.047 g,
0.203 mmol, 50% excess) were mixed in THF and refluxed for
Table 4 Crystal data and summary of data collection and refinement
[N{(CF3)C(C6F5)- [N{(CF3)C(C6F5)-
[N{(C3F7)C(C6F5)- [N{(CF3)C(C6F5)-
[N{(CF3)C(C6F5)- [N{(C3F7)C(C6F5)-
Formula
N}2]H (1)
N}2]Ag(CNtBu)2 (2 N}2]Ag(CNtBu)2 (3) N}2]Cu(CNtBu)2 (4) N}2]Ag(PPh3)2 (5) N}2]Ag(PPh3)2 (7)
FW
539.20
100(2)
Monoclinic
P21/n
812.32
100(2)
Monoclinic
P21/c
3037.09
100(2)
Monoclinic
767.99
100(2)
Monoclinic
C2/c
1170.60
100(2)
Monoclinic
1370.64
100(2)
Temperature (K)
Crystal system
Space group
Cell dimensions
Triclinic
¯
P21/c
P21/n
P1
˚
˚
˚
˚
˚
˚
˚
˚
˚
˚
˚
˚
˚
a = 7.660(2) A
a = 19.9480(8) A
a = 15.6234(19) A
a = 20.3464(14) A
a = 11.3585(9) A
a = 11.3132(4) A
˚
˚
˚
b = 7.236(2) A
b = 11.4960(5) A
b = 19.773(2) A
b = 16.8298(12) A
b = 16.9513(14) A b = 13.4430(5) A
˚
˚
c = 31.921(9) A
c = 13.2404(5) A
c = 35.489(4) A
c = 19.7746(14) A
c = 24.725(2) A
c = 18.4935(7) A
a = 90◦
a = 90◦
a = 90◦
a = 90◦
a = 90◦
a = 75.796(1)◦
b = 77.788(1)◦
g = 86.892(1)◦
2664.86(17)
2
b = 90.188(3)◦
g = 90◦
b = 90.466(1)◦
b = 96.133(2)◦
b = 115.546(1)◦
b = 93.422(1)◦
g = 90◦
g = 90◦
g = 90◦
g = 90◦
3
˚
V (A )
1769.2(2)
4
2.024
0.241
1048
3036.2(2)
4
10900(2)
4
6109.4(7)
8
4752.1(7)
4
Z
dc (g cm-3)
m (mm-1)
1.777
0.789
1600
2.04 to 26.00
24 060
0.0375(5963)
5963/23/676
1.138
0.0374/0.0402
0.0951/0.0971
1.851
0.710
5952
1.18 to 28.37
107 229
0.0452 (27199)
27199/30/1639
1.047
0.0571/0.0765
0.1455/0.1612
1.670
0.840
3056
1.64 to 26.50
24 961
0.0263(6320)
6320/0/439
1.049
0.0320/0.0367
0.0810/0.0845
1.636
0.596
2336
1.46 to 28.29
46 428
0.0544(11784)
11784/0/667
1.025
0.0420/0.0648
0.0903/0.1006
1.708
0.566
1360
1.71 to 26.00
21 671
0.0213(10405)
10405/0/775
1.041
0.0342/0.0393
0.0869/0.0901
F(000)
q range (◦)
Reflns collected
Rint (ind reflns)
Data/restr/params
GOF on F2
1.28 to 26.50
15 226
0.0263(3666)
3666/0/321
1.033
R1 [I > 2s(I)]/all data 0.0455/0.0475
wR2 [I > 2s(I)]/all
0.1185/0.1202
data
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(major positive-ions, CH3OH), m/z (%): 230 (100) [Cu(CNtBu)2]+,
831 (30) [[N{(CF3)C(C6F5)N}2]CuCNtBu + CuCNtBu]+. ESI
MS (major negative-ions, CH3OH), m/z (%): 538 (100)
[N{(CF3)C(C6F5)N}2]-, 1140 (50) [[N{(CF3)C(C6F5)N}2]2Cu]-.
Anal. Calcd. for C26H18CuF16N5: C, 40.66; H, 2.36; N, 9.12%.
Found: C, 40.50; H, 2.22; N, 8.97%.
a bed of Celite and the filtrate added dropwise over a solution
of triphenylphosphine (0.73 g, 2.8 mmol) in n-hexane (30 mL)
at room temperature. It was left to stir for 12 h. The solution
was then filtered and concentrated up to 2 mL. Transparent
square rods of [N{(C3F7)C(C6F5)N}2]Ag(PPh3)2 crystallized at
room temperature after 16 h. Yield: 1.40 g (73%). M.p. 153–154 ◦C.
3
1H NMR (C6D6): d 7.13 (d, J = 7.1 Hz, 6H, o-Ar), 6.96 (tt, J =
4
3
7.3 Hz, J = 2.2 Hz, 3H, p-Ar), 6.9 (t, J = 7.5 Hz, 6H, m-Ar).
19F NMR (C6D6): d -80.07 (t, J = 8.3 Hz, 6F, CF3), -114.17 and
-113.11 (AB multiplet, J = 264.1 Hz, 4F, a-CF3), -124.61 (s, 2F,
b-CF2), -124.71 (s, 2F, b-CF2), -147.92 (d, J = 15.1 Hz, 4F, CF),
-163.73 (t, J = 19.3 Hz, 2F, CF), -164.44 (t, J = 21.2 Hz, 4F, CF).
31P NMR (C6D6): d 10.8 (d, 1J(Ag–31P) = 365 Hz). Anal. Calcd for
C56H30F24N3P2Ag: C, 49.07; H, 2.21; N, 3.07%. Found: C, 48.40;
H, 2.15; N, 3.12%.
Synthesis of [N{(CF3)C(C6F5)N}2]Ag(PPh3)2 (5)
[N{(CF3)C(C6F5)N}2]H (1) (0.270 g, 0.50 mmol) was added to a
suspension of Ag2O (0.058 g, 0.25 mmol) in acetonitrile (25 mL);
the mixture was refluxed for 12 h. The solvent was removed
under vacuum, the resulting residue was dissolved in diethyl ether
(25 mL) and triphenylphosphine (0.262 g, 1.0 mmol) was added
at room temperature. The mixture was stirred overnight and the
solvent was removed under vacuum to obtain a solid that was
recrystallized with n-hexane to afford a pale yellow solid in 90%
yield. Crystals suitable for X-ray diffraction analysis were obtained
after 16 h as colorless plates by slow diffusion of hexane into a
solution of the compound in CH2Cl2. M.p. 139–141 ◦C. IR (cm-1):
3057 w (CH); 1594 br; 1499 s, 1488 sh (C C + C N); 1436
m, 1332 w, 1307 w, 1234 m, 1194 m, 1141 m, 1094 m, 1026 w,
X-ray data collection and structure determinations
Suitable crystals covered with a layer of paratone-N oil, were
selected and mounted within 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-Ka fine-focus
1
978 s, 917 m, 847 w, 785 w, 742 s, 690 s. H NMR (CDCl3, 293
K): 7.17–7.43 (m, PPh3). 19F NMR (CDCl3, 293 K): d -70.05 (s,
CF3), -148.58 (sbr, CF), -164.76 (sbr, CF), -165.39 (sbr, CF).31P
NMR (CDCl3, 293 K): d 10.79 (sbr). 31P NMR (CDCl3, 218 K): d
10.31 (dd, 1J(107Ag–31P) = 425 Hz, 1J(109Ag–31P) = 486 Hz). ESI MS
(major positive-ions, CH3OH), m/z (%): 632 (100) [Ag(PPh3)2]+.
ESI MS (major negative-ions, CH3OH), m/z (%): 538 (100)
[N{(CF3)C(C6F5)N}2]-. Anal. Calcd. for C52H30AgF16N3P2: C,
53.35; H, 2.58; N, 3.59%. Found: C, 53.76; H, 2.38; N, 3.41%.
78
˚
sealed tube (l = 0.71073 A). The data frames were integrated
with the Bruker SAINT-Plus software package.79 Data were
corrected for absorption effects using the multi-scan technique
(SADABS). Structures were solved and refined using Bruker
SHELXTL (Version 6.14) software package.80 Crystallographic
data are summarized in Table 4.
[N{(CF3)C(C6F5)N}2]H (1). Crystallized in space group
P21/n. All the non-hydrogen atoms were refined anisotropically.
The N-hydrogen atom was located from the difference map,
included and refined. All other hydrogen atoms were placed
at calculated positions and refined riding on the corresponding
carbons. The structure was refined using the TWIN command
with a twin ratio of 76 : 24.
Synthesis of [N{(CF3)C(C6F5)N}2]Ag(PPh3)3 (6)
[N{(CF3)C(C6F5)N}2]H (1) (0.270 g, 0.50 mmol) was added to a
suspension of Ag2O (0.058 g, 0.25 mmol) in acetonitrile (25 mL);
the mixture was refluxed for 12 h. The solvent was removed
under vacuum, the resulting residue was dissolved in diethyl ether
(25 mL) and triphenylphosphine (0.393 g, 1.5 mmol) was added
at room temperature. The mixture was stirred overnight and the
solvent was removed under vacuum to obtain a gray solid that
was recrystallized with n-hexane to afford a light gray solid in 85%
yield. M.p. 149–150 ◦C. IR (cm-1): 3064 w (CH); 1768 w, 1655 w,
1580 m; 1509 sh, 1497 s, 1479 m, 1435 s, 1348 m, 1305 m, 1245
m, 1198 m, 1161 w, 1136 m, 1081 m, 1026 m, 992 s, 867 m, 840
[N{(CF3)C(C6F5)N}2]Ag(CNtBu)2 (2). Crystallized in space
group P21/c. All the non-hydrogen atoms were refined anisotropi-
cally except for C5 (carbon atom from C6F6). The ISOR command
was used to refine C26 anisotropically. Hydrogen atoms were
placed at calculated positions and refined riding on the corre-
sponding carbons. The molecule demonstrated positional disorder
in the “[N{(CF3)C(C6F5)N}2]” fragment over two positions which
was modeled successfully and the occupancies were refined to a
ratio of 56 : 44.
1
m, 783 m, 743 s, 691 s. H NMR (CDCl3, 293 K): 7.00–7.37 (m,
PPh3). 19F NMR (CDCl3, 293 K): d -70.77 (s, CF3), -149.02 (sbr,
CF), -166.60 (t, J = 21.5 Hz, CF), -167.27 (sbr, CF).31P NMR
(CDCl3, 293 K): d 6.71 (sbr). 31P NMR (CDCl3, 218 K): d 6.39
(d, 1J(Ag–31P) = 232 Hz). ESI MS (major positive-ions, CH3OH),
m/z (%): 632 (100) [Ag(PPh3)2]+. ESI MS (major negative-ions,
CH3OH), m/z (%): 538 (100) [N{(CF3)C(C6F5)N}2]-. Anal. Calcd.
for C70H45AgF16N3P3: C, 58.68; H, 3.17; N, 2.93%. Found: C,
58.86; H, 3.09; N, 2.73%.
[N{(C3F7)C(C6F5)N}2]Ag(CNtBu)2 (3). Crystallized in space
group P21/c. Three independent molecules are present in the
asymmetric unit. All the non-hydrogen atoms were refined
anisotropically. The ISOR command was used to refine atoms
C67, C68, F56, F58, and F62.
[N{(CF3)C(C6F5)N}2]Cu(CNtBu)2 (4). Crystallized in space
group C2/c. All the non-hydrogen atoms were refined anisotrop-
ically. Hydrogen atoms were placed at calculated positions and
refined riding on the corresponding carbons.
Synthesis of [N{(C3F7)C(C6F5)N}2]Ag(PPh3)2 (7)
[N{(C3F7)C(C6F5)N}2]H (1.0 g, 1.4 mmol), Ag2O (0.16 g, 0.7
mmol), triethylamine (0.2 mL, 1.4 mmol) and THF (20 mL)
were stirred at 75 ◦C for 16 h. The mixture was filtered over
[N{(CF3)C(C6F5)N}2]Ag(PPh3)2 (5). Crystallized in space
group P21/n. All the non-hydrogen atoms were refined
8578 | Dalton Trans., 2011, 40, 8569–8580
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The Royal Society of Chemistry 2011
©

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anisotropically. Hydrogen atoms were placed at calculated po-
sitions and refined riding on the corresponding carbons.
25 C. Shimokawa, J. Teraoka, Y. Tachi and S. Itoh, J. Inorg. Biochem.,
2006, 100, 1118.
26 B. A. Jazdzewski, P. L. Holland, M. Pink, V. G. Young Jr., D. J. E.
Spencer and W. B. Tolman, Inorg. Chem., 2001, 40, 6097.
27 S. Hong, L. M. R. Hill, A. K. Gupta, B. D. Naab, J. B. Gilroy, R. G.
Hicks, C. J. Cramer and W. B. Tolman, Inorg. Chem., 2009, 48, 4514.
28 M. N. Kopylovich and A. J. L. Pombeiro, Coord. Chem. Rev., 2011,
255, 339.
29 P. V. Gushchin, M. R. Tyan, N. A. Bokach, M. D. Revenco, M. Haukka,
M.-J. Wang, C.-H. Lai, P.-T. Chou and V. Y. Kukushkin, Inorg. Chem.,
2008, 47, 11487.
[N{(C3F7)C(C6F5)N}2]Ag(PPh3)2 (7). Crystallized in space
¯
group P1. All the non-hydrogen atoms were refined anisotrop-
ically. Hydrogen atoms were placed at calculated positions and
refined riding on the corresponding carbons. Individual C3F7
groups were not disordered and refined well without further
restraints.
30 J. Guo, W.-K. Wong and W.-Y. Wong, Eur. J. Inorg. Chem., 2004, 267.
31 J.-P. Guo, W.-K. Wong and W.-Y. Wong, Eur. J. Inorg. Chem., 2006,
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Acknowledgements
This work was financially supported by MIUR (PRIN
20078EWK9B). We are grateful to CIRCMSB (Consorzio In-
teruniversitario di Ricerca in Chimica dei Metalli nei Sistemi
Biologici). Support by the National Science Foundation (CHE-
0845321 to H.V.R.D) and the Robert A. Welch Foundation (Grant
Y-1289 to H.V.R.D) are also gratefully acknowledged. The NSF
(CHE-0840509) is thanked for providing funds to upgrade the
NMR spectrometer at UT Arlington used in this work. The X-ray
crystallography was performed in the Center for Nanostructured
Materials (CNM) at the University of Texas at Arlington.
33 M. Zhou, Y. Song, T. Gong, H. Tong, J. Guo, L. Weng and D. Liu,
Inorg. Chem., 2008, 47, 6692.
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