Exploring the Transphobia Effect on Heteroleptic NHC Cycloplatinated Complexes

Article abstract of DOI:10.1021/acs.inorgchem.5b01655

The synthesis of 1-(4-cyanophenyl)-1H-imidazol (1) has been carried out by an improved method. Then its corresponding imidazolium iodide salt, 2, has been used to prepare the N-heterocyclic carbene (NHC) cycloplatinated compound [{Pt(μ-Cl)(CC?)}₂] (4) (HCC?-κC? = 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-ylidene) following a step-by-step protocol. The intermediate complex [PtCl(η³-2-Me-C₃H₄) (HCC?-κC?)] (3) has also been isolated and characterized. Using 4 as precursor, several heteroleptic complexes of stoicheometry [PtCl(CC?)L] (L = PPh₃ (5), pyridine (py, 6), 2,6-dimethylphenyl isocyanide (CNXyl, 7), and 2-mercapto-1-methylimidazole (MMI, 8)) and [Pt(CC?)LL′]PF₆ (L = PPh₃, L′ = py (9), CNXyl (10), and MMI (11)) have been synthesized. Complexes 6-8 were obtained as a mixture of cis- and trans-(C?,L) isomers, while trans-(C?,L) isomer was the only one observed for complexes 5 and 9-11. Their geometries have been discussed in terms of the degree of transphobia (T) of pairs of trans ligands and supported by theoretical calculations. The trans influence of the two σ Pt-C bonds present in these molecules, Pt-C_Ar and Pt-C?_(NHC), has been compared from the J_Pt-P values observed in the new complex [Pt(CC?)(dppe)]PF₆ (dppe = 1, 2-bis(diphenylphosphino)ethane, 12).

Full text of DOI:10.1021/acs.inorgchem.5b01655

Article
pubs.acs.org/IC
Exploring the Transphobia Effect on Heteroleptic NHC
Cycloplatinated Complexes
Sara Fuertes,† Andres J. Chueca,† and Violeta Sicilia*,‡
́
†Departamento de Química Inorgan
́
ica, Facultad de Ciencias, Instituto de Síntesis Química y Catal
CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain
‡Departamento de Química Inorgan
ica, Escuela de Ingeniería y Arquitectura de Zaragoza, Instituto de Síntesis Química y Catal
Homogenea (ISQCH), CSIC-Universidad de Zaragoza, Campus Río Ebro, Edificio Torres Quevedo, 50018 Zaragoza, Spain
́ ́
isis Homogenea (ISQCH),
́
́
isis
́
S
* Supporting Information
ABSTRACT: The synthesis of 1-(4-cyanophenyl)-1H-imidazol (1) has been
carried out by an improved method. Then its corresponding imidazolium
iodide salt, 2, has been used to prepare the N-heterocyclic carbene (NHC)
cycloplatinated compound [{Pt(μ-Cl)(C∧C*)}2] (4) (HC∧C*-κC* = 1-(4-
cyanophenyl)-3-methyl-1H-imidazol-2-ylidene) following a step-by-step pro-
tocol. The intermediate complex [PtCl(η3-2-Me-C3H4) (HC∧C*-κC*)] (3)
has also been isolated and characterized. Using 4 as precursor, several
heteroleptic complexes of stoicheometry [PtCl(C∧C*)L] (L = PPh3 (5),
pyridine (py, 6), 2,6-dimethylphenyl isocyanide (CNXyl, 7), and 2-mercapto-
1-methylimidazole (MMI, 8)) and [Pt(C∧C*)LL′]PF6 (L = PPh3, L′ = py (9),
CNXyl (10), and MMI (11)) have been synthesized. Complexes 6−8 were
obtained as a mixture of cis- and trans-(C*,L) isomers, while trans-(C*,L)
isomer was the only one observed for complexes 5 and 9−11. Their
geometries have been discussed in terms of the degree of transphobia (T) of pairs of trans ligands and supported by theoretical
calculations. The trans influence of the two σ Pt−C bonds present in these molecules, Pt−CAr and Pt−C*(NHC), has been
compared from the JPt−P values observed in the new complex [Pt(C∧C*)(dppe)]PF6 (dppe = 1, 2-bis(diphenylphosphino)-
ethane, 12).
regarding the size of the π system have been studied to tune
their photophysical properties.10a−l However, these preparative
methods are slightly limited in terms of reactivity and ligand
exchange reactions. Normally, ancillary ligands account for
secondary roles within the molecular complex, but they could
be determinant when modulating their emissive properties11 or
tuning their catalytic activity and selectivity.10m,n,12
In this context, as part of our previous work, we prepared and
studied the photophysical properties of many heteroleptic
complexes of Pt(II) with the 7,8-benzoquinolinate and different
monodentate auxiliary ligands.11 Now, we have conducted our
ongoing research to new platinum(II) complexes with C∧C*-
cyclometalated NHCs. Generic compounds, such as [{Pt(μ-
Cl)(C∧C*)}2], are expected to be useful starting materials for
complexes containing the “Pt(C∧C*)” moiety, because different
kinds of ancillary ligands can be coordinated in the vacant sites
resulting from chlorine-bridge cleavage or chlorine-atoms
elimination. We recently reported the synthesis of [{Pt(μ-
Cl)(C∧C*)}2] (HC∧C* = 3-methyl-1-(naphthalen-2-yl)-1H-
imidazol-2-ylidene).13 Thus, the first goal of this work, the
synthesis of the generic precursor [{Pt(μ-Cl)(C∧C*)}2] (4)
(HC∧C*-κC* = 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-
INTRODUCTION
■
The chemistry of platinum(II) complexes has attracted much
interest in the past decade due to their phosphorescence
properties and potential use as dopants in LEDS,1 chemical
sensors,2 or biolabeling agents,2b,3 with particular consideration
given to C∧N-cyclometalated derivatives.1b,4 The C∧C*-cyclo-
metalated N-heterocyclic carbenes (NHC) may surpass the
high ligand field splitting capacity of the conventional C∧N-
cyclometalated ligands, since they present two C−σ bonds.
This implies an even greater heightening of the d−d energy
levels on the metal center, enlarging the energy gap with the
emissive excited states, avoiding the thermal quenching and
improving the quantum yields.5 Furthermore, as a consequence
of the strong metal−ligand binding, metal complexes of C∧C*-
cyclometalated NHCs are very robust and stable which may
provide long-term functional materials.
NHCs have been widely used in organometallic chemistry
and particularly in the targeted fields of transition-metal
catalysis,6 liquid crystals,7 biomedicine,8 and luminescent
materials.5,8d,9 In particular, platinum(II) compounds contain-
ing C∧C*-cyclometalated NHCs ligands have received much
attention in the past decade.9k,10 Most of them are photo-
luminescent β-diketonates or β-ketoiminates derivatives pre-
pared straightforward in one-pot reactions. Variations regarding
substituents in the NHC or the β-diketonate groups and also
Received: July 23, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
react for 3 h to give a yellow precipitate (AgI), which was separated by
filtration through Celite under Ar. The resulting solution was
evaporated to dryness and treated with n-hexane (3 × 15 mL) to
afford 3 as a pale-yellow solid. Yield: 1.1222 g, 83%. Anal. Calcd for
C15H16ClN3Pt: C, 38.42; H, 3.43; N, 8.96. Found: C, 38.23; H, 3.35;
ylidene) following the same strategy, was achieved. Therefore,
the use of [{Pt(μ-Cl)(η3-2-Me-C3H4)}2] to accomplish the
cyclometalation of the NHCs through the intermediate carbene
complex [PtCl(η3-2-Me-C3H4) (HC∧C*-κC*)] (3) endorses
the generality and viability of this step-by-step synthetic
protocol for [{Pt(μ-Cl)(C∧C*)}2]
Then we explored the use of 4 as a precursor for the
preparation of new heteroleptic complexes such as [PtCl-
(C∧C*)L] (L = PPh3 (5), py (6), CNXyl (7), and 2-mercapto-
1-methylimidazole (MMI, 8)) and [Pt(C∧C*)LL′]+ (L = PPh3;
L′ = py (9), CNXyl (10), and MMI (11)). Some of them were
obtained as a mixture of two isomers, cis- and trans-(C*,L),
while others were obtained selectively as the trans-(C*,L) one.
The geometries observed for them have been discussed in
terms of the degree of transphobia (T) of pairs of trans
ligands,14 which has been related with the trans influence of the
two σ Pt−C bonds present in the molecule, Pt−CAr and Pt−
C*(NHC). The trans influence of σ CAr and σ C* has been
evaluated from the JPt,P values observed in the new complex
[Pt(C∧C*) (dppe)]+ (12).
1
N, 8.52. H NMR (400 MHz, methylene chloride-d2): δ = 7.95 (d,
3
3
3JH,H = 8.8, 2H, H7), 7.74 (d, JH,H = 8.8, 2H, H6), 7.26 (d, JH2,H3
=
2.1, 4JH,Pt = 13.4, 1H, H2), 7.15 (d, 4JH,Pt = 10.6, 1H, H3), 3.91 (s, 3H,
Me (NHC)), 3.64 (m, 1Hsyn, η3-2-Me-C3H4), 2.63 (m, JH,Pt = 28.3,
2
1Hsyn, η3-2-Me-C3H4), 2.37 (m, JH,Pt = 34.1, 1Hanti, η3-2-Me-C3H4),
2
1.74 (s, JH,Pt = 64.7, 3H, Me, η3-2-Me-C3H4), 1.44 (m, 1Hanti, η3-2-
3
Me-C3H4). 13C{1H} NMR plus HMBC and HSQC (101 MHz,
methylene chloride-d2): δ = 177.4 (s, C1), 144.1 (s, C5), 133.2 (s, 2C,
3
3
C6), 126.2 (s, 2C, C7), 123.6 (s, JC,Pt = 41.3, C3), 120.7 (s, JC,Pt
=
42.4, C2), 118.6 (s, CN), 118.4 (s, C2′, η3-2-Me-C3H4), 112.1 (s, C8),
58.1 (s, JC,Pt = 77.6, C1′, η3-2-Me-C3H4), 38.3 (s, C4 (Me), NHC)),
1
37.1 (s, C3′, η3-2-Me-C3H4), 23.4 (s, 2JC,Pt = 40.1, C4′ (Me), η3-2-Me-
C3H4). 195Pt{1H} NMR (85.6 MHz, methylene chloride-d2): δ =
−4460. IR (ATR, cm−1): ν = 285 (s, Pt−Cl), 2228 (w, CN).
[{Pt(μ-Cl)(C∧C*)}2] (4). Compound 3 (500.0 mg, 1.07 mmol) was
refluxed in 2-methoxyethanol (15 mL) for 3 h, and then it was cooled
down to rt. The resulting solid was filtered and washed with
dichloromethane (10 mL) and diethyl ether (15 mL). Then it was
treated with activated carbon in hot acetonitrile (3 × 40 mL), and the
suspension was filtered through Celite. The resulting solution was
evaporated to dryness, and the residue was washed with hexane to give
a yellow solid, 4. Yield: 357.6 mg, 81%. Anal. Calcd for
C22H16Cl2N6Pt2: C, 32.01; H, 1.95; N, 10.18. Found: C, 31.63; H,
2.33; N, 10.16. 1H NMR (400 MHz, DMSO-d6): δ = 8.72 (s, br, 3JH7,Pt
= 60, 1H, H7), 8.14 (d, 3JH2,H3 = 1.7, 1H, H2), 7.63 (dd, 3JH9,H10 = 8.0,
4JH9,H7 = 1.5, 1H, H9), 7.57 (d, 1H, H10), 7.53 (d, 1H, H3), 4.14 (s, 3H,
H4). 13C{1H} NMR plus HMBC and HSQC (101 MHz, DMSO-d6): δ
= 156.0 (s, C1), 149.8 (s, C5), 137.0 (s, C7), 129.3 (s, C9), 127.9 (s,
C6), 125.5 (s, C3), 119.6 (s, CN), 115.7 (s, C2), 112.3 (s, C10), 106.9
(s, C8), 37.6 (s, C4). IR (ATR, cm−1): ν = 266 (s, Pt−Cl), 2250 (w,
CN), 2215 (w, CN).
EXPERIMENTAL SECTION
■
General Comments. Information describing materials, instrumen-
tal methods used for characterization and spectroscopic studies, DFT
computational details, and X-ray structures together with the
characterization data of 1−12 are contained in the Supporting
Information. All chemicals were used as supplied, and [{Pt(μ-Cl)(η3-2-
Me-C3H4)}2]15 was prepared following the literature procedure.
1-(4-Cyanophenyl)-1H-imidazole (1). Slight modifications of
previous synthetic methods were employed.16 To a solution of 4-
bromobenzonitrile (800.0 mg, 4.35 mmol) in degassed dimethyl
sulfoxide (12 mL), imidazole (592.5 mg, 8.70 mmol), K2CO3 (1202.9
mg, 8.70 mmol), and CuI (165.8 mg, 8.70 mmol) were added in the
presence of 4 Å molecular sieves (500.0 mg). After 70 h at 110 °C
under an argon atmosphere the crude was cooled down to rt, washed
with 100 mL of ethyl acetate, and then filtered through Celite. The
solution was treated with H2O (2 × 20 mL) and brine (2 × 20 mL).
The organic layer was dried using anhydrous MgSO4. Evaporation
under reduced pressure yielded a white solid which was washed with
trans-(C*,P)[Pt(Cl)(C∧C*)(PPh3)] (5). PPh3 (128.1 mg, 0.48 mmol)
was added to a suspension of 4 (177.8 mg, 0.22 mmol) in
dichloromethane (30 mL) at −8 °C (ice/brine bath). After 1 h of
reaction, the solvent was removed under reduced pressure. The
residue was treated with MeOH (5 mL), filtered, and washed with
MeOH (3 mL) to give 5 as a pale yellow solid. Yield: 193.5 mg, 67%.
Anal. Calcd for C29H23ClN3PPt: C, 51.60; H, 3.43; N, 6.22. Found: C,
51.26; H, 3.49; N, 6.18. 1H NMR (400 MHz, methylene chloride-d2):
δ = 7.72 (m, 6H, Ho (PPh3)), 7.52−7.35 (m, 10H, Hm, Hp (PPh3)
and H2), 7.24 (dd, 3JH9,H10 = 8.0, 4JH9,H7 = 1.6, 1H, H9), 7.05 (d, 4JH10,Pt
1
hexane to give 1 as a white-off powder. Yield: 609.5 mg, 83%. H
3
3
NMR (400 MHz, DMSO-d6): δ = 8.46 (dd, JH,H = 1.3, JH,H = 0.9,
1H, H1), 8.09 (d, 3JH6,H7 = 8.8, 2H, H7), 7.99 (d, 3JH6,H7 = 8.8, 2H, H6),
7.98 (m, 1H, Im), 7.16 (dd, 3JH,H = 1.3, 3JH,H = 0.9, 1H, Im). 13C{1H}
NMR (101 MHz, DMSO-d6): δ = 140.1 (s, C5), 135.7 (s, C1), 134.1
(s, 2C, C7), 130.5 (s, 1C, Im), 120.4 (s, 2C, C6), 118.3 (s, CN), 117.6
(s, 1C, Im), 109.0 (s, C8). IR (ATR, cm−1): ν = 2224 (m, CN).
1-(4-Cyanophenyl)-3-methyl-1H-imidazolium Iodide (2). Methyl
iodide (0.3 mL, 4.83 mmol) was added to a solution of 1 (544.5 mg,
3.22 mmol) in dried THF (10 mL) under Ar atmosphere. The mixture
was refluxed for 48 h, and after cooling, the white precipitate was
filtered and washed with THF (5 mL) and diethyl ether (5 mL) and
dried under vacuum to give 2 as a pure solid. Yield: 967.9 mg, 97%.
Anal. Calcd for C11H10IN3: C, 42.46; H, 3.24; N, 13.51. Found: C,
42.03; H, 3.33; N, 13.48. 1H NMR (400 MHz, DMSO-d6): δ = 9.91 (s,
3
= 14.2, 1H, H10), 6.99 (m, 1H, H3), 6.88 (m, JH7,Pt = 64.0, 1H, H7),
4.29 (s, 3H, H4). 13C{1H} NMR plus HMBC and HSQC (101 MHz,
methylene chloride-d2): δ = 170.1 (s, C1), 150.5 (s, C5), 141.0 (d,
3JC7,P = 8.7, 2JC7,Pt = 57.0, C7), 135.5 (d, 2JC,P = 11.3, 3JC,Pt = 20.7, 6C,
1
Co (PPh3)), 130.7 (s, 3C, Cp (PPh3)), 130.1 (d, JC,P = 53.6, 3C, Ci
3
(PPh3)), 128.5 (s, C6), 128.1 (d, JC,P = 10.6, 6C, Cm (PPh3)), 127.8
(s, C9), 124.3 (d, 4JC,P = 6.1, 4JC3,Pt = 26.0, C3), 118.8 (s, CN), 113.9 (s,
4JC2,Pt = 40.1, C2), 111.0 (s, 3JC10,Pt = 32.5, C10), 108.0 (s, C8), 38.6 (s,
C4). 31P{1H} NMR (162 MHz, methylene chloride-d2): δ = 28.6 (s,
1JP,Pt = 2868.0). 195Pt{1H} NMR (85.6 MHz, methylene chloride-d2): δ
= −4227.0 (d). IR (ATR, cm−1): ν = 279 (m, Pt−Cl), 2218 (w, CN).
MS (MALDI+): m/z 639.1 [Pt(C∧C*) (PPh3)]+.
3
3
br, 1H, H1), 8.39 (dd, JH2,H3 = 1.9, JH2,H1 = 1.8, 1H, H2), 8.21 (d,
3JH6,H7 = 8.8, 2H, H7), 8.02 (d, 2H, H6), 8.00 (m, 1H, H3), 3.96 (s, 3H,
cis/trans-(C*,N) [Pt(Cl)(C∧C*)(py)] (6). Pyridine (Py) (24.8 μL, 0.30
mmol) was added to a suspension of 4 (115.2 mg, 0.14 mmol) in
dichloromethane (30 mL) at −8 °C (ice/brine bath). After 2 h of
stirring, the solvent was removed under reduced pressure. The residue
was treated with MeOH (5 mL), filtered, and washed with MeOH (3
mL) to give 6-t (92%)/6-c (8%) as a yellow solid. Yield: 99.9 mg, 73%.
Anal. Calcd for C16H13ClN4Pt: C, 39.07; H, 2.66; N, 11.39. Found: C,
38.67; H, 2.73; N, 11.22. 1H NMR data for 6-t (400 MHz, methylene
chloride-d2): δ = 8.81 (dd, 3JH,H = 6.4, 4JH,H = 1.6, 3JH,Pt = 28.0, 2H, Ho
(py)), 7.97 (tt, 3JH,H = 7.7, 4JH,H = 1.6, 1H, Hp (py)), 7.56 (m, 2H, Hm
H4). 13C{1H} NMR plus HMBC and HSQC (101 MHz, DMSO-d6): δ
= 137.9 (s, C5), 136.5 (s, C1), 134.4 (s, 2C, C7), 124.6 (s, C3), 122.5
(s, 2C, C6), 120.7 (s, C2), 117.7 (s, CN), 112.2 (s, C8), 36.3 (s, C4). IR
(ATR, cm−1): ν = 2235 (m, CN). MS (MALDI+): m/z 184.1
(HC∧C*H)+.
[PtCl(η3-2-Me-C3H4)(HC∧C*-κC*)] (3) (HC∧C* = 1-(4-Cyanophen-
yl)-3-methyl-1H-imidazol-2-ylidene). To a suspension of 2 (893.7
mg, 2.87 mmol) in anhydrous dichloromethane (30 mL), Ag2O (332.8
mg, 1.44 mmol) was added in the absence of light under an argon
atmosphere. After 3 h of stirring at rt, [{Pt(η3-2-Me-C3H4)(μ-Cl)}2]
(779.1 mg, 1.36 mmol) was added and the mixture was allowed to
(py)), 7.38 (dd, 3JH9,H10 = 8.0, 4JH9,H7 = 1.7, 1H, H9), 7.33 (d, 3JH2,H3
=
B
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
4
4
2.1, 1H, H2), 7.06 (d, JH10,Pt = 16.8, 1H, H10), 6.94 (d, JH31,Pt = 9.1,
through Celite. Then the solvent was removed under reduced
pressure, and the residue was treated with diethyl ether (10 mL),
filtered, and washed with diethyl ether (5 mL). The solid was
recrystallized from acetone (0 °C)/Et2O to give 9 as a pale yellow
solid. Yield: 88.3 mg, 49%. Anal. Calcd for C34H28F6N41P2Pt: C, 47.28;
H, 3.27; N, 6.49. Found: C, 46.86; H, 3.05; N, 6.47. H NMR (400
3
1H, H3), 6.69 (d, JH7,Pt = 61.8, 1H, H7), 4.24 (s, 3H, H4). H NMR
data for 6-c: δ = 8.91 (dd, 3JH,3H = 6.3, 4JH,H = 1.6, 3JH,Pt = 20.7, 2H, Ho
3
3
(py)), 8.41 (d, JH7,H9 = 1.6, JH7,Pt = 55.1, 1H, H7), 7.91 (tt, JH,H
=
7.8, JH,H = 1.6, 1H, Hp (py)), 3.06 (s, 3H, H4). 13C{1H} NMR plus
HMBC and HSQC for 6-t (101 MHz, methylene chloride-d2): δ =
152.7 (s, C1), 152.0 (s, 2JC,Pt = 12.2, 2C, Co (py)), 150.3 (s, C5), 138.5
4
3
4
MHz, methylene chloride-d2): δ = 8.40 (dd, JH,H = 6.2, JH,H = 1.1,
2
3
4
3JH,Pt = 23.0, 2H, Ho (py)), 7.69 (tt, JH,H = 7.7, JH,H = 1.4, 1H, Hp
(s, Cp (py)), 135.2 (s, JC7,Pt = 37.8, C7), 131.3 (s, C6), 128.3 (s, C9),
126.1 (s, 3JC,Pt = 31.2, 2C, Cm (py)), 123.1 (s, 3JC3,Pt = 38.4, C3), 119.4
(py)), 7.59 (m, 6H, Ho (PPh3)), 7.53−7.45 (m, 4H, H2, Hp (PPh3)),
3
3
3
4
(s, CN), 114.4 (s, JC2,Pt = 47.2, C2), 110.7 (s, JC10,Pt = 36.1, C10),
108.1 (s, C8), 37.6 (s, C4). 195Pt{1H} NMR (85.6 MHz, methylene
chloride-d2): δ = −3731.9 (s, br, 6-t); − 3775.4 (s, 6-c). IR (ATR,
cm−1): ν = 271 (m, Pt−Cl), 2220 (w, CN). MS (MALDI+): m/z
456.0 [Pt(C∧C*) (py)]+.
7.36 (m, 6H, Hm (PPh3)), 7.31 (dd, JH9,H10 = 8.1, JH9,H7 = 1.7, 1H,
H9), 7.19 (m, 3H, H10, Hm (py)), 7.03 (m, 1H, H3), 6.85 (m, 3JH7,Pt
=
58.8, 1H, H7), 2.87 (s, 3H, H4). 13C{1H} NMR plus HMBC and
HSQC (101 MHz, methylene chloride-d2): δ = 171.2 (d, 2JC,P = 136.2,
C1), 151.9 (s, 2JC,Pt = 10.0, 2C, Co (py)), 150.8 (s, C5), 142.9 (d, 3JC7,P
cis/trans-(C*,C) [Pt(Cl)(C∧C*)(CNXyl)] (7). 2,6-Dimethylphenyl
isocyanide (CNXyl) (35.7 mg, 0.27 mmol) was added to a suspension
of 4 (100.0 mg, 0.12 mmol) in dichloromethane (30 mL) at −8 °C
(ice/brine bath). After 2.5 h of stirring, the solvent was removed under
reduced pressure. The residue was treated with MeOH (0 °C, 5 mL),
filtered, and washed with MeOH (3 mL) to give 7-t (86%)/7-c (14%)
as a yellow solid. Yield: 61.8 mg, 47%. Anal. Calcd for C20H17ClN4Pt:
= 9.6, 2JC7,Pt = 55.4, C7), 139.3 (s, Cp (py)), 134.7 (d, 2JC,P = 11.7, 6C,
3
Co (PPh3)), 131.7 (s, 3C, Cp (PPh3)), 129.9 (s, C9), 129.0 (d, JC,P
=
4
10.0, 6C, Cm (PPh3)), 127.5 (s, 2C, Cp (py)), 124.6 (d, JC3,P = 4.8,
3JC3,Pt = 31.3, C3), 118.4 (s, CN), 115.1 (s, br, 3JC2,Pt = 40.2, C2), 111.7
(s, 3JC10,Pt = 29.2, C10), 108.3 (s, C8), 35.3 (s, C4). 31P{1H} NMR (162
MHz, methylene chloride-d2): δ = 28.2 (s, JP,Pt = 2881.6). 195Pt{1H}
1
NMR (85.6 MHz, methylene chloride-d2): δ = −4274.6 (d). ΛM (5 ×
10−4 M acetone solution) = 76.87 Ω−1 cm2 mol−1. IR (ATR, cm−1): ν
= 2226 (w, CN). MS (MALDI+): m/z 639.1 [Pt(C∧C*)(PPh3)]+.
trans-(C*,P) [Pt(C∧C*)(CNXyl)(PPh3)]PF6 (10). Method a. 2,6-
Dimethylphenyl isocyanide (CNXyl) (20.6 mg, 0.15 mmol) and
KPF6 (28.9 mg, 0.15 mmol) were added to a pale yellow suspension of
5 (103.8 mg, 0.15 mmol) in acetone (30 mL). After 1 h of stirring at
room temperature, the solvent was evaporated to dryness and the
residue treated with dichloromethane (20 mL) and filtered through
Celite. Then the solvent was removed under reduced pressure, and the
residue was treated with diethyl ether (5 mL), filtered, and washed
with diethyl ether (3 mL) to give 10 as a pale yellow solid. Yield: 124.9
mg, 89%.
1
C, 44.16; H, 3.15; N, 10.30. Found: C, 44.09; H, 3.02; N, 9.92. H
NMR data for 7-t (400 MHz, methylene chloride-d2): δ = 7.97 (d,
4JH9,H7 = 1.7, 3JH7,Pt = 77.3, 1H, H7), 7.47 (dd, JH9,H10 = 8.0, 1H, H9),
3
7.36 (d, 3JH2,H3 = 2.0, 4JH2,Pt = 5.3, 1H, H2), 7.33 (t, 3JHp,Hm = 7.7, 1H,
4
Hp (Xyl)), 7.21 (d, 2H, Hm (Xyl)), 7.14 (d, JH10,Pt = 15.4, 1H, H10),
4
6.97 (d, JH3,Pt = 7.9, 1H, H3), 4.28 (s, 3H, H4), 2.51 (s, 6H, Me
(Xyl)). 1H NMR data for 7-c: δ = 8.45 (d, 4JH7,H10 = 1.7, 3JH,Pt = 47.2,
1H, H7), 7.43 (dd, 3JH9,H10 = 8.0, 1H, H9), 7.09 (d, 1H, H10), 7.00 (d,
4JH3,Pt = 12.3, 1H, H3), 3.92 (s, 3H, H4), 2.45 (s, 6H, Me (Xyl)).
13C{1H} NMR plus HMBC and HSQC for 7-t (101 MHz, methylene
2
chloride-d2): δ = 167.7 (s, C1), 149.5 (s, C5), 140.8 (s, JC7,Pt = 72.4,
C7), 135.8 (s, 2C, Co (Xyl)), 129.7 (s, Cp (Xyl)), 128.7 (s, C9), 128.1
(s, 2C, Cm (Xyl)), 123.9 (s, 3JC3,Pt = 30.9, C3), 119.0 (s, CN), 114.8 (s,
Method b. PPh3 (34 mg, 0.129 mmol) and KPF6 (23 mg, 0.125
mmol) were added to a yellow suspension of 7-c/7-t (14/86%) (70
mg, 0.128 mmol) in acetone (10 mL). After 1 h of stirring at room
temperature, the solvent was evaporated to dryness and the residue
treated with dichloromethane (20 mL) and filtered through Celite.
Then the solvent was removed under reduced pressure, treated with
diethyl ether (5 mL), filtered, and washed with diethyl ether (3 mL) to
give 10 as a pale yellow solid. Yield: 91.1 mg, 77%. Anal. Calcd for
C38H32F61N4P2Pt: C, 49.84; H, 3.52; N, 6.12. Found: C, 49.59; H, 3.34;
N, 6.05. H NMR (400 MHz, methylene chloride-d2): δ = 7.67 (m,
3
C2), 111.6 (s, JC10,Pt = 32.9, C10), 109.5 (s, C8), 37.3 (s, C4), 18.7 (s,
2C, Me (Xyl)). 195Pt{1H} NMR (85.6 MHz, methylene chloride-d2): δ
2
= −4042.7 (t, JPt,N = 89.7 Hz, 7-t); − 4160.2 (m, 7-c). IR (ATR,
cm−1): ν = 285 (m, Pt−Cl), 2161 (s, CN, CNXyl), 2217 (w, CN,
NHC). MS (MALDI+): m/z 508.1 [Pt(C∧C*) (CNXyl)]+.
cis/trans-(C*,S) [Pt(Cl)(C∧C*)(MMI)] (8). 2-Mercapto-1-methylimi-
dazole (MMI) (37 mg, 0.32 mmol) was added to a suspension of 4
(120.0 mg, 0.15 mmol) in acetone (30 mL) at −8 °C (ice/brine bath).
After 1 h of stirring, the mixture was filtered through Celite, and the
filtrated was evaporated to dryness. The residue was treated with
diethyl ether (5 mL), filtered, and washed with diethyl ether (3 mL).
The resulting orange solid was recrystallized from CH2Cl2/Et2O to
give 8-t (86%)/8-c (14%). Yield: 78.6 mg, 51%. Anal. Calcd for
C15H14ClN5PtS: C, 34.19; H, 2.68; N, 13.29; S, 6.09. Found: C, 34.57;
H, 2.97; N, 13.13; S, 6.75. 1H NMR data for 8-t (400 MHz, methylene
chloride-d2): δ = 12.72 (s, 1H, NH, MMI), 8.27 (s, 3JH7,Pt = 65.9, 1H,
3
6H, Ho (PPh3)), 7.56 (d, JH2,H3 = 2.1, 1H, H2), 7.46−7.35 (m, 10H,
3
Hm, Hp (PPh3)) and H9), 7.30 (d, JH10,H9 = 8.8, 1H, H10), 7.28 (d,
3JH2,H3 = 2.1, 1H, H3), 7.26 (t, 3JH,H = 7.7, 1H, Hp (Xyl)), 7.08 (d, 3JH,H
= 7.7, 2H, Hm (Xyl)), 7.02 (s, br, 3JH7,Pt = 50.7, 1H, H7), 3.91 (s, 3H,
H4), 2.12 (s, 6H, Me (Xyl)). 13C{1H} NMR plus HMBC and HSQC
2
(101 MHz, methylene chloride-d2): δ = 169.3 (d, JC,P = 127.7, C1),
3
2
151.6 (s, C5), 143.5 (d, JC7,P = 9.2, JC7,Pt = 51.0, C7), 138.6 (s, C6),
3
3
2
H7), 7.41 (d, JH9,H10 = 7.6, 1H, H9), 7.30 (d, JH2,H3 = 2.1, 1H, H2),
7.04 (d, JH10,Pt = 14.3, 1H, H10), 6.92 (d, JH3,Pt = 8.9, 1H, H3), 6.87
(m, 1H, H4′, MMI), 6.84 (m, 1H, H5′, MMI), 4.19 (s, 3H, H4), 3.75 (s,
134.8 (s, 2C, Co (Xyl)), 134.5 (d, JC,P = 11.7, 6C, Co (PPh3)), 132.4
4
4
(s, 3C, Cp (PPh3)), 131.4 (s, C9), 130.8 (s, Cp (Xyl)), 129.5 (d, 3JC,P
=
11.0, 6C, Cm (PPh3)), 128.7 (d, 1JC,P = 57.2, 3C, Ci (PPh3)), 128.6 (s,
2C, Cm (Xyl)), 125.3 (s, br, C3), 118.7 (s, CN), 116.1 (s, C2), 112.4 (s,
3JC10,Pt = 25.8, C10), 109.7 (s, C8), 39.2 (s, C4), 18.2 (s, Me (Xyl)).
1
4
3H, NMe, MMI). H NMR data for 8-c: δ = 8.47 (d, JH7,H9 = 1.1,
3JH7,Pt = 57.5, 1H, H7), 4.04 (s, 3H, H4), 3.68 (s, 3H, NMe, MMI).
13C{1H} NMR plus HMBC and HSQC (101 MHz, methylene
chloride-d2) for 8-t: δ = 159.3 (s, C1), 156.1 (s, CS, MMI), 149.9 (s,
C5), 135.4 (s, 2JC7,Pt = 37.1, C7), 126.7 (s, C6), 128.4 (s, C9), 123.6 (s,
3JC3,Pt = 37.3, C3), 120.4 (s, C5′, MMI), 119.8 (s, CN), 115.1 (s, C4′,
MMI), 113.6 (s, 3JC2,Pt = 45.2, C2), 110.7 (s, 3JC10,Pt = 35.8, C10), 107.5
(s, C8), 37.9 (s, C4), 34.5 (s, NMe, MMI). 195Pt{1H} NMR (85.6
MHz, methylene chloride-d2): δ = −3856.5 (s, 8-t); −3884.2 (s, 8-c).
IR (ATR, cm−1): ν = 268 (m, Pt−Cl), 2216 (w, CN), 3100 (w, NH).
MS (MALDI+): m/z 491.0 [Pt(C∧C*) (MMI)]+.
31P{1H} NMR (162 MHz, methylene chloride-d2): δ = 19.3 (s, 1JP,Pt
=
2585.2). 195Pt{1H} NMR (85.6 MHz, methylene chloride-d2): δ =
−4697 (dt, JPt,N = 61.7 Hz,). ΛM (5 × 10−4 M acetone solution) =
2
70.63 Ω−1 cm2 mol−1. IR (ATR, cm−1): ν = 2231 (m, CN), 2187 (s,
CNXyl). MS (MALDI+): m/z 770.1 [Pt(C∧C*) (CNXyl)
(PPh3)]+.
trans-(C*,P) [Pt(C∧C*)(PPh3)(MMI)]PF6 (11). 2-Mercapto-1-methyl-
imidazole (MMI) (22.0 mg, 0.19 mmol) and KPF6 (34.8 mg, 0.19
mmol) were added to a pale yellow suspension of 5 (125.0 mg, 0.19
mmol) in acetone (30 mL). After 1.5 h of stirring at room
temperature, the solvent was evaporated to dryness and the residue
was treated with dichloromethane (7 × 10 mL) and filtered through
Celite. Then the solvent was removed under reduced pressure, and the
residue was treated with diethyl ether (10 mL), filtered, and washed
trans-(C*,P) [Pt(C∧C*)(py)(PPh3)]PF6 (9). Pyridine (15.8 μL, 0.20
mmol) and KPF6 (36.9 mg, 0.20 mmol) were added to a pale yellow
suspension of 5 (132.6 mg, 0.20 mmol) in acetone (30 mL). After 1 h
of stirring at room temperature, the solvent was evaporated to dryness
and the residue treated with dichloromethane (35 mL) and filtered
C
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
a
Scheme 1. Synthesis of Compounds 1−4
a
Numerical scheme for NMR purporses.
1
1
with 5 mL more. The orange solid was washed with dichloromethane
(3 × 4 mL) to give 11 as a pale yellow solid. Yield: 59.2 mg, 36%. Anal.
Calcd for C33H29F6N5P2PtS: C, 44.10; H, 3.25; N, 7.79; S, 3.57.
7.0, JP,Pt = 2673.8, trans C*), 43.1 (d, JP,Pt = 2014.6, trans Cph).
195Pt{1H} NMR (85.6 MHz, methylene chloride-d2): δ = −4996 (dd).
Λ
M (5 × 10−4 M acetone solution) = 69.01 Ω−1 cm2 mol−1. IR (ATR,
1
cm−1): ν = 2223 (m, CN). MS (MALDI+): m/z 775.2 [Pt(C∧C*)
Found: C, 43.72; H, 3.27; N, 7.69; S, 3.85. H NMR (400 MHz,
acetone-d6) δ = 11.70 (s, 1H, NH (MMI)), 8.06 (d, 3JH2,H3 = 1.7, 1H,
H2), 7.77 (m, 6H, Ho (PPh3)), 7.61−7.54 (m, 4H, H10 and Hp
(dppe)]+
3
(PPh3)), 7.49 (m, 7H, H3 and Hm (PPh3)), 7.43 (dd, JH9,H10 = 8.2,
RESULTS
4JH9,H7 = 1.6, 1H, H9), 7.18 (m, 1H, H5′, MMI), 7.05 (m, 1H, H4′,
■
MMI), 6.97 (m, 3JH7,Pt = 59.4, 1H, H7), 4.08 (s, 3H, H4), 3.32 (s, 3H,
Improved Method of Preparation of a NHC Ligand
and Its Use in the Stepwise Synthesis of [{Pt(μ-
Cl)(C∧C*)}2] (HC∧C*-κC*= 1-(4-Cyanophenyl)-3-methyl-
1H-imidazol-2-ylidene). The synthesis of the N-heterocyclic
carbene (NHC) 1-(4-cyanophenyl)-1H-imidazol (1) has been
previously reported.16a,b However, we prepared it by a slightly
modified method (Scheme 1, path a, Experimental Section) to
avoid the use of coligands (pyrrolidinylmethylimidazole) and
the purification step by column chromatography. 4-Bromo-
benzonitrile was coupled with imidazole in DMSO at 110 °C
using copper(I) iodide and potassium carbonate in the
presence of 4 Å molecular sieves. After workup, 1 was obtained
by precipitation with n-hexane in good yield (83%). Then the
addition of methyl iodide to a refluxing THF solution of 1
rendered the corresponding imidazolium salt: 1-(4-cyanophen-
yl)-3-methyl-1H-imidazolium iodide (2) (Scheme 1, path b,
and Experimental Section).
2
NMe, MMI). 13C NMR (101 MHz, acetone-d6) δ 170.7 (d, JC1,P
=
=
3
144.4, C1), 153.7 (s, CS (MMI)), 151.8 (s, C5), 142.6 (d, JC7,Pt
56.1, 3JC7,P = 8.9, C7), 136.1 (d, 2JC,P = 11.2, 6C, Co (PPh3)), 132.3 (d,
4JC,P = 11.2, 3C, Cp (PPh3)), 130.5 (d, JC,P = 54.38, 3C, Ci (PPh3)),
1
3
4
130.4 (s, C9) 129.2 (d, JC,P = 10.7, 6C, Cm (PPh3)), 126.7 (d, JC,P
=
5.1, C3), 123.2 (s, C5′, MMI), 119.2 (s, CN), 116.7 (s, C4′, MMI),
3
116.5 (s, br, C2), 113.1 (s, JC10,Pt = 29.2, C10), 109.2 (s, C8), 38.3 (s,
C4), 34.7 (s, NMe, MMI). 31P{1H} NMR (162 MHz, acetone-d6): δ =
26.1 (s, 1JP,Pt = 2786.3). 195Pt{1H} NMR (85.6 MHz, acetone-d6): δ =
−4533.7 (d). ΛM (5 × 10−4 M acetone solution) = 84.26 Ω−1 cm2
mol−1. IR (ATR, cm−1): ν = 2224 (m, CN). MS (MALDI+): m/z
753.2 [Pt(C∧C*)(MMI) (PPh3)]+, 639.1 [Pt(C∧C*)(PPh3)]+.
[Pt(C∧C*)(dppe)]PF6 (12). 1,2-Bis(diphenylphosphino)ethane
(dppe) (118.3 mg, 0.30 mmol) and KPF6 (55.8 mg, 0.30 mmol)
were added to a suspension of 4 (122.6 mg, 0.15 mmol) in acetone
(30 mL). After 2.5 h of stirring at rt the solvent was removed in vacuo.
Dichloromethane (50 mL) was then added, and the resulting
suspension was filtered through Celite. The solvent was removed
under reduced pressure, and Et2O (20 mL) was added to the residue
to obtain 12 as a white solid. Yield: 245.3 mg, 90%. Anal. Calcd for
C37H32F6N3P3Pt: C, 48.27; H, 3.50; N, 4.56. Found: C, 47.93; H, 3.35;
N, 4.49. 1H NMR (400 MHz, methylene chloride-d2): δ = [7.96−7.80]
(m, 8H, Ho (dppe)), [7.69−7.54] (m, 13H, H2 and Hm, Hp (dppe)),
7.43 (dd, 3JH9,10 = 8.4, 4JH9,7 = 1.7, 1H, H9), 7.34 (m, 3JH7,Pt = 50.6, 1H,
Compound 2 was reacted with silver(I) oxide for 3 h and
subsequently with [{Pt(μ-Cl)(η3-2-Me-C3H4)}2] (η3-2-Me-
C3H4 = η3-2-methylallyl) to yield the neutral complex
[PtCl(η3-2-Me-C3H4) (HC∧C*-κC*)] (3), which was isolated
as a pale yellow and air-stable solid in very good yield (83%, see
Experimental Section and Scheme 1, path c). Spectroscopic IR
and NMR data support the proposed structure for complex 3.
Its IR spectrum shows an absorption band at 285 cm−1, which
is consistent with the presence of a terminal Pt−Cl bond in
3
5
4
H7), 7.31 (dd, JH10,9 = 8.4, JH10,P = 2.3, 1H, H10), 7.05 (m, JH3,Pt
=
9.1, 1H, H3), 3.04 (s, 3H, H4), 2.37 (m, 4H, CH2 (dppe)). 13C{1H}
NMR plus HMBC and HSQC (101 MHz, methylene chloride-d2): δ =
2
2
172.7 (dd, JC1,Ptrans = 126.9; JC1,Pcis = 8.8, C1), 151.0 (s, C5), 143.9
trans disposition to a ligand with a large trans influence such as
2
2
3
(dd, JC6,Ptrans = 103.5, JC1,Pcis = 6.0, C6), 142.5 (dd, JC7,Ptrans = 9.9;
13,14c
η3-2-Me-C3H4
and another one at 2228 cm−1 due to the
3JC7,Pcis = 2.8, JC7,Pt = 54, C7), 134.1 (d, JC,P = 12.1, 4C, Co (dppe)),
2
2
cyano group of the HC∧C* ligand.
133.6 (d, 2JC,P = 12.3, 4C, Co (dppe)), 132.8 (s, 4C, Cp (dppe)), 131.1
The disappearance of the signal attributed to H1 in the free
ligand 2 (9.91 ppm) and the presence of Pt satellites in the
signals corresponding to the H2 and H3 protons of the
imidazolyl moiety (see Figure S1 in the SI) indicate that the
imidazolium salt has been successfully anchored to the Pt
center through the C1 of the N-heterocyclic carbene (HC∧C*-
3
3
(s, C9), 130.0 (d, JC,P = 11.0, 4C, Cm (dppe)), 129.7 (d, JC,P = 11.0,
4
3
4C, Cm (dppe)), 124.9 (d, JC3,P = 4.0, JC3,Pt = 29.0, C3), 118.5 (s,
CN), 116.4 (d, 4JC2,P = 2.0, 3JC3,Pt = 33.0, C2), 112.04 (s, 3JC10,Pt = 21.7,
1
2
C10), 110.7 (m, C8), 38.9 (s, C4), 31.7 (dd, JC,P = 37.6, JC,P = 10.0,
1
2
CH2 (dppe)), 30.6 (dd, JC,P = 39.8, JC,P = 12.4, CH2 (dppe)).
31P{1H} NMR (162 MHz, methylene chloride-d2): δ = 50.2 (d, 2JP,P
=
D
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
κC*). This statement was confirmed by the similarities of the
195Pt{1H} resonance (δ = −4460 ppm) and the 1H and
13C{1H} ones corresponding to the imidazolyl moiety and the
methyl allyl group (η3-2-Me-C3H4) with those of [PtCl(η3-
C4H7)(HC∧C*-κC*)] (HC∧C* = 3-methyl-1-(naphthalen-2-
yl)-1H-imidazol-2-ylidene).13
spectroscopic data of compounds 5−8 are consistent with the
proposed stoichiometry for them (see Experimental Section in
the SI). Relevant structural information was provided by
multinuclear NMR spectra (see Experimental Section in the SI
1
and Table 1). It deserves to be noted that the H NMR
resonances corresponding to both cyanophenyl and imidazole
fragments of C∧C* are clearly altered by the coordination of
the ancillary ligands (L). Especially sensitive to both the nature
of L and the geometric disposition of the ligands around the Pt
center are the H7 and H4 resonances. In all cases, as depicted
in Figure 1, the H7 resonances of the trans-(C*,L) isomers
appear more shielded than those of the cis derivatives.
A refluxing suspension of 3 in 2-methoxyethanol yielded the
precipitation of a dark-colored solid which was recrystallized in
hot acetonitrile solution (see Scheme 1, path d, and
Experimental Section) to render 4 as a pure yellow solid in
very good yield (81%). Compound 4 was not soluble in the
common organic solvents, only in DMSO. The NMR data of 4
in DMSO-d6 show the absence of the allyl group and the
metalation of the 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-
ylidene) (HC∧C*-κC*) through the C6 (see Experimental
Section and Figure S2 in the SI). This is evident by the lack of
the H6 resonance and by the presence of a broad singlet
corresponding to H7 at 8.72 ppm with a Pt−H coupling
constant of ca. 60 Hz. The observed C1 resonance (δ = 156.0
ppm) is in good agreement with the literature value-
s10a−c,e,h,13,17 for related cyclometalated platinum(II) com-
pounds.
These results embrace the feasibility of this stepwise
synthetic pathway for [{Pt(μ-Cl)(C∧C*)}2] systems; since in
this work, we have been able to reproduce the same strategy
described by ourselves to prepare C∧N14b,c and more recently
C∧C*13-cyclometalated complexes of platinum(II).
Reactivity of 4. Synthesis and Characterization of
[PtCl(C∧C*)L] (L = PPh3 (5), py (6-t/6-c), CNXyl (7-t/7-c),
MMI (8-t/8-c)). The dinuclear complex [{Pt(μ-Cl)(C∧C*)}2]
(4) reacts with several neutral P, N, C, and S donor ligands,
such as PPh3, py, CNXyl, and MMI in a 1:2 molar ratio at low
temperature (−8 °C) (Scheme 2 and Experimental Section) to
Within the trans isomer complexes, in particular, when L =
PPh3 (5) and py (6-t), the H7 resonance undergoes an
important upfield shift comparing with that in complexes with
L = CNXyl (7-t) and MMI (8-t) (Table 1). This effect has
been associated with the anisotropic shielding effect caused by
the proximity in space of the aromatic ring current of the
phenyl (5) and pyridine (6-t) groups to the H7.14b,c,18 This C−
H7···π interaction was also observed in the X-ray structure of 5,
as discussed below. Likewise, in the cis-(C*,L) isomers of
complexes 6−8, the H4 resonance is the one that suffers from
the anisotropic effect since it moves upfield in relation to the
trans isomers, the effect being more intense when L is pyridine
(3.06 6-c; 4.24 6-t). In both geometric isomers, the H7 signal
appears accompanied by platinum satellites. The Pt−H7
coupling constants of the trans isomers are larger than those
of the cis derivatives, which is in agreement with the higher
trans influence of the L ligands comparing to the Cl.11c,14a,19
It is worth noting that the cis/trans isomer ratios of 6−8
from the worked up solids match with those from the crude
reaction mixtures, as proven by NMR experiments. We also
confirmed that these ratios do not change over the time.
As expected, the 195Pt{1H} spectrum of 5 exhibits only a
doublet at −4227 ppm with a 195Pt−31P coupling constant of
2868 Hz, while two 195Pt resonances were observed for each
one of the complexes 6−8, due to the existence of both isomers
(Figure 2). The main one, which corresponds to the trans
isomer, appears less shielded than the cis one in all three cases.
In agreement with its formulation, the 31P{1H} NMR
spectrum of 5 shows only one sharp signal at 28.6 ppm
flanked by platinum satellites. The 195Pt−31P coupling constant
value is typical of a P−Pt−C trans arrangement,19,20 making
evident the strong trans influence of the carbene atom (C*).
The molecular structure of 5 (see Figure 3), obtained by X-
ray diffraction analysis of a single crystal of it, confirmed the
complex to be the isomer trans-(C*,P)[PtCl(C∧C*)(PPh3)].
Data analysis is discussed below.
Scheme 2. Synthetic Pathway to Compounds 5−8
Synthesis and Characterization of the new Cationic
“Pt(C∧C*)” Complexes: trans-(C*,P)-[Pt(C∧C*)(PPh3)L′]PF6
(L′ = py (9), CNXyl (10), MMI (11)) and [Pt(C∧C*)
(dppe)]PF6 (12). With the aim of preparing new heteroleptic
compounds with the N-heterocyclic carbene {Pt(C∧C*)LL′},
various strategies were followed (see Scheme 3). Using
different starting materials 4, 5, or 7, we have been able to
prepare the first cationic complexes with the “Pt(C∧C*)”
moiety. Hence, the addition of equimolecular amounts of KPF6
and L′ to a solution of 5 in acetone rendered compounds 9−11
as pure solids (Scheme 3, path a). The formulation and
geometry proposed are in agreement with the spectroscopic
and crystallographic data discussed below. As inferred from
these data, the PPh3 remains coordinated trans to the C*.
Interestingly, compound 10 can also be prepared by adding
give the mononuclear complexes [PtCl(C∧C*)L] (L = PPh3
(5); py (6-t/6-c), CNXyl (7-t/7-c), MMI (8-t/8-c)). X-ray and
spectroscopic data discussed below indicate that compound 5
was obtained as a solid with trans-(C*,L) being the only isomer
observed, while in all other cases (6−8), cleavage of the
bridging system rendered both isomers cis- and trans-(C*,L)
with the trans isomer being the main one, especially when L is
py (6).
For compound 7, several reaction conditions were tested at
room temperature and also in refluxing chloroform. End results
were cis/trans mixtures with the same ratios. Analytical and
E
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
a
Table 1. Significant NMR Data for Compound Characterization
δH (JPt,H
)
δC (JPt,C)
compd
H7
H4
C1
C7
C3
δP (JPt,P
)
δPt
b
5
6.88 (64.0)
6.69 (61.8)
8.41 (55.1)
7.97 (77.3)
8.45 (47.2)
8.27 (65.9)
8.47 (57.5)
6.85 (58.8)
7.02 (50.7)
6.97 (59,4)
7.34 (50.6)
4.29
4.24
3.06
4.28
3.92
4.19
4.04
2.87
3.91
4.08
3.04
170.1
152.7
141.0 (57.0)
135.2 (37.8)
124.3 (26.0)
123.1 (38.4)
28.6 (2868.0)
−4227.0
−3731.9
−3775.4
−4042.7
−4160.2
−3856.5
6-t
6-c
7-t
7-c
8-t
8-c
167.7
159.3
140.8 (72.4)
135.4 (37.1)
123.9 (30.9)
123.6 (37.3)
−3884.2
b
9
171.2
169.3
170.7
172.7
142.9 (55.4)
143.5 (51.0)
142.6 (56.1)
142.5 (54.0)
124.6 (31.3)
125.3
28.2 (2881.6)
19.3 (2585.2)
26.1 (2786.3)
−4274.6
−4697.0
−4533.7
−4996.0
b
10
b
11
126.7
12
124.9 (29.0)
(t-C*): 50.2 (2673.8)
(c-C*): 43.1 (2014.6)
a
b
δ (ppm), J (Hz). trans-(C*,P) isomer is the only one observed.
1
Figure 1. H NMR spectra of 5−8 in CD2Cl2.
KPF6 and PPh3 to the mixture of cis/trans isomers of complex
7 (see Scheme 3, path b). Therefore, in this case, the main
fraction of this reaction does not proceed with stereoretention,
since the CNXyl ligand, which is located trans to C* in 7-t,
migrates to the cis position by the coordination of the PPh3.
When a suspension of 4 in acetone was treated with KPF6 and
dppe (1:2 molar ratio) compound 12 was formed, a
mononuclear species with the dppe acting as a chelate ligand.
Relevant structural information arises from the multinuclear
NMR spectra (see Experimental Section, Table 1, and Figures
S4 in the SI). The 31P{1H} NMR spectra of 9−11 show a
singlet flanked by platinum satellites. The δP and 195Pt−31P
coupling constants are quite similar to those found in complex
5, indicating a trans-(C*,PPh3) arrangement in these
complexes. In the 31P NMR spectrum of 12, the two different
P atoms appear as two doublet signals accompanied by Pt
satellites. The chemical shifts and the observed P−P coupling
of 7 Hz confirm the chelating arrangement of the dppe around
the platinum center.21
Figure 2. 195Pt{1H} spectra of 5−8 in CD2Cl2.
F
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 4. 195Pt{1H} spectra of 5 and 9−12 in CD2Cl2.
of doublets for 12 due to the coupling with the 31P nuclei; these
chemical shifts are ranging from −4274 to −4996 ppm.
The structural information obtained from the NMR spectra
was confirmed by X-ray diffraction studies on compounds 9−
12, as can be seen in Figures 5 and 6 (for complexes 10 and 12)
and Figures S6 and S8 for complexes 9 and 11).
Figure 3. Molecular structure of complex 5·MeOH. Thermal ellipsoids
are drawn at the 50% probability level. Solvent molecules and
hydrogen atoms have been omitted for clarity.
Scheme 3. Synthethic Pathway to Cationic Complexes 9−12
Figure 5. Molecular structure of the complex 10·0.5 OEt2. Thermal
ellipsoids are drawn at the 50% probability level. Hydrogen atoms,
PF6, and solvent molecules have been omitted for clarity.
Crystal Structure Determination. Single-crystal X-ray
diffraction studies were performed on compounds 5 and 9−12
to confirm their molecular structures. Crystallographic data are
given in Table S1, and a selection of bond lengths and angles is
shown in Table 2. As shown in Figures 3, 5, 6, and S5−S9 (in
the SI), the Pt center lies in a distorted square planar
coordination environment as a consequence of the small bite
angle of the NHC-cyclometalated (C∧C*) ligand [79.83(11)−
78.54(13)°]. This angle together with the Pt−C6 and Pt−
C1(C*) distances are similar to those found in other five-
membered metalacycles of Pt(II) with N-heterocyclic carbene-
s.10a−h,13 PPh3 and L (L = Cl 5, py 9, CNXyl 10 and MMI 11)
complete the coordination sphere of platinum(II), whereas in
12, a chelate dppe ligand does.
According to the geometry proposed (see Scheme 3), H7
resonances appear in the range of 6.80−7.30 ppm due to the
anisotropic shielding effect caused by the proximity in space of
the phenyl groups of the PPh3. When L′ is pyridine and dppe,
the H4 resonance also suffers from the anisotropic shielding
effect, since it moves upfield (2.87 9, 3.04 12) comparing with
that in complexes 10 and 11 (3.91 10, 4.08 11).
Significant are also the 195Pt{1H} spectra (see Figure 4 and
Table 1) which confirm the presence of a single isomer in each
case. They exhibit doublets for compounds 9−11 and a doublet
G
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(5), 10.9(8)° (9), 8.83(8)° (10), 10.39(3)° (11), and 10.27(5)
(12).27 The rings of the ancillary ligands are almost
perpendicular to the platinum coordination plane with dihedral
angles of 78.94(9)° (N4, C12−C16, 9), 82.48(12)° (N4, C50−
C56, 10), and 89.18(4)° (N4, N5, C50−C53, 11).
Further inspection of the molecule packing within the crystal
structures revealed the presence of weak intra- and
intermolecular interactions (see the SI); however, no Pt···Pt
contacts were observed. In all crystal structures (Figures 3, 5, 6,
and S5−S9) we find an edge-to-face, also known as T-shaped,
C−H···π interaction: the H7 hydrogen atom is pointing to the
phenyl ring of the PPh3 ligand, showing moderately short
distances (C−H···π; C7···Cph (PPh3) = 3.22 (5), 3.28 (9), 3.35
(10), 3.15 (11) and 3.23 Å (12)). Only in 9 and 12, there is a
C−H···π interaction between the Me group (C4) and the
pyridine or phenyl rings (C4···Cpy = 3.42 Å (9), C4···Cph
=
3.23 Å (12)). Also in 9−11, the phenyl group of the PPh3
displays short intramolecular π···π interactions (3.11−3.58 Å)
with the rings of the ancillary ligands (py, CNXyl, MMI), which
are placed almost parallel to each other [15.30(11)° (9),
5.42(16)° (10), 9.47(9)° (11)]. Additionally, compound 9
crystallizes with one water molecule, which is holding a
hydrogen bond with the CN group of the cyclometalated NHC
fragment (see Figure S6). Finally, in 9 and 12, the molecules
arrange themselves in pairs in a head-to-tail fashion supported
by π···π intermolecular contacts between the NHC fragments
(3.70 (9) and 3.32 Å (12)), see Figures S6 and S9).
Figure 6. Molecular structure of complex 12·CH2Cl2. Thermal
ellipsoids are drawn at the 50% probability level. Hydrogen atoms,
PF6, and solvent molecules have been omitted for clarity.
The Pt−Cl,14b,c,22 Pt−N,23 Pt−C,11c,f Pt−S,24 and Pt−P19,25
distances are within the typical range for platinum(II)
compounds with these trans to σ-bonded carbon atoms. The
Pt−C6 bond lengths are clearly altered by the ancillary ligand
coordinated at the trans position [from 2.015(3) (Cl, 5) to
2.080(4) Å (P, 12)], while the Pt−C1 ones are practically the
same regardless of the neutral (5) or cationic (9−12) nature of
the complexes. These are the first examples of [Pt(C∧C*)-
L′L]0,+ heteroleptic complexes studied by X-ray diffraction.
Thus far, all crystal structures of NHC-cycloplatinated
compounds have been reported with diketonate derivative-
s.10a−h
The chelating dppe ligand adopts the gauche conformation
with a P−CH2−CH2−P torsion angle of 46.7°. The Pt−P2
bond length is slightly longer than the Pt−P1 one, due to the
higher trans influence of the CAr. Nevertheless, both distances
and the small bite angle (83.15°) are similar to those of related
compounds.21c,26
DISCUSSION
■
As shown above, cleavage of the chlorine-bridge system in
[{Pt(μ-Cl)(C∧C*)}2] (4) by different ancillary ligands (L) led
to the clean formation of trans-(C*,L)-[PtCl (C∧C*)L] when L
is PPh3 (5). If L is py, CNXy, and MMI, the bridge-splitting
reaction gave mixtures of cis/trans isomers (6−8).
In an attempt to explain this behavior we used the term
transphobia degree (T) of pairs of trans ligands, which has been
accepted by many authors to explain the geometries of stable
square-planar complexes of d8 transition metals. The degree of
T has been assumed to be related to the trans influence in such
a way that the greater the trans influence of two ligands the
greater the transphobia and the cis disposition of them will be
the favored geometry. In this sense the heteroleptic complexes
[PtCl(C∧N)L] (HC∧N = 3,8-dinitro-6-phenylphenanthridine,
2-(4-bromophenyl)imidazol [1,2-a]pyridine; L= PPh3, tht, C
NR (R = tBu, 2,6-dimethylphenyl)), and [Pt(C∧P)(C
CPh)L] (C∧P = CH2C6H4P(o-tolyl)2-κC,P; L = CO, py, tht)
exist as the trans-(C,Cl) isomer as expected on the basis of the
transphobia degree (T) of pairs of trans ligands.14a,b However,
the steric requirements of the ligands involved can also play an
important role in determining the geometries of these
The cyclometalated NHC carbene ligand itself is not
completely planar; it exhibits a small interplanar angle between
the cyanophenyl and the imidazole fragments of 2.45(10)° (5),
6.42(9)° (9), 12.35(13)° (10), 5.79(8)° (11), and 5.81(14)°
(12). As well as the molecular complexes that show dihedral
angles between the platinum coordination plane (Pt01, C1, C6,
P1, X) and the NHC ligand (N1−N3, C1−C11) of 10.7(2)°
Table 2. Selected Bond Lengths (Angstroms) and Angles (degrees) for 5 and 9−12
5·MeOH (X = Cl(1))
9·H2O (X = N(4))
10·0.5 Et2O (X = C(50))
11 (X = S(1))
12·CH2Cl2 (X = P(2))
Pt(1)−C(1)
Pt(1)−C(6)
Pt(1)−P(1)
Pt(1)−X
C(1)−Pt(1)−C(6)
C(6)−Pt(1)−P(1)
C(1)−Pt(1)−X
P(1)−Pt(1)−X
2.030(3)
2.015(3)
2.3024(7)
2.3860(7)
79.83(11)
96.60(8)
95.85(8)
88.92(2)
2.033(3)
2.035(3)
2.3075(9)
2.099(3)
78.54(13)
95.90(10)
94.94(12)
89.45(8)
2.035(4)
2.065(4)
2.037(3)
2.047(3)
2.3046(8)
2.3781(13)
79.54(10)
94.67(7)
97.45(8)
89.28(3)
2.055(4)
2.080(4)
2.3171(11)
1.974(4)
2.2787(13)
2.3218(13)
79.05(17)
96.00(12)
101.91(13)
83.15(5)
78.58(17)
93.35(12)
98.74(17)
89.39(13)
H
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
complexes. In this sense, complex [Pt(C∧P)(CCPh)PPh3],
exhibits the trans-(C,CCPh) geometry instead of the
expected one considering electronic preferences (trans-
C,PPh3), which was attributed to the crowding associated
with the cis disposition of the P(o-tolyl)2 and PPh3 groups.14a
Therefore, we tried to explain the preferred geometry for
complexes [PtCl(C∧C*)L] (5−8) and [Pt(C∧C*) (PPh3)L]+
(9−11) on the basis of the transphobia effect (T). With this
purpose we studied the relative trans influences of the two σ
Pt−C bonds present in the Pt(C∧C*) unit, both expected to
have a great trans influence, and those of the auxiliary ligands
to indicate that the difference between T[CAr/PPh3)] and
T[C*/PPh3] is big enough to direct clean formation of trans-
(C*,PPh3) complexes 5 and 9−11.
However, the difference between T[CAr/L)] and T[C*/L]
(L = py, CNXyl, MMI, Cl) is, in each case, not big enough to
avoid the formation of mixtures of isomers. On the basis of the
order of T[CAr/L] named above, the cleavage of the chlorine-
bridge system in [{Pt(μ-Cl)(C∧C*)}2] (4) by py to give
complex 6 was expected to be no more stereoselective than that
with CNXyl or MMI, but it is. Other factors to promote the
greater stability of 6-t, such as the steric hindrance between py
and the imidazol fragment of C∧C* in the cis isomer, can be
excluded. Given that the H7 and H4 resonances in 6-t and 6-c
suffer a great anisotropic shielding effect, which was discussed
in the NMR section, we considered the C−H···π (py)
interactions to be involved in it. C−H···π interactions have
been known to play a key role in the stereoselectivity of
coordination compounds among other fields in chemistry.28 It
has been widely reported that intramolecular C−H···π
hydrogen bonds can induce the formation of single linkage
isomers.29 In both isomers of 6, a C−H···π interaction could be
possible: Csp3−H4 (Me)···π (py) in 6-c and a T-shaped Csp2−
H7 (Ar)···π (py) in 6-t. As reported before, the interaction
energy involving a T-shaped aromatic C−H is somewhat
stronger than that of the aliphatic ones.28a,30 Thus, we would
expect 6-t to be more stable than 6-c. DFT calculations for
models of 6-c/-t in a solution of CH2Cl2 were carried out (see
Figure 7). In effect, isomer 6-t with the C−H7 pointing at the
1
2
(Cl, PPh3, py, CNXyl, MMI), comparing the JPt,P, JPt,C, and
3JPt,H values affected by the ligands located at their trans
positions.
1
The JPt,P values observed for complexes trans-(C*,P)
[PtCl(C∧C*) (PPh3)] (5) and [Pt(C∧C*) (PPh3)L′]PF6 (L′
= py (9), CNXyl (10), MMI (11)) range from 2585.2 to
2881.6 Hz, which are typical of a P−Pt−C trans arrange-
ment.19,20 These values are also very similar to those observed
in Q[Pt(CH2−C6H4−P(o-tolyl)2)(CCPh)2] (Q = Li+ (2746
+
Hz), NBu4 (2603 Hz)) with the Pt−P bond trans to a Pt−
Cacetylide one.14a In addition, the JPt,P corresponding to the P
trans to C* (2673.8 Hz) in [Pt(C∧C*) (dppe)]PF6 (12) was
found to be similar to that observed in complexes with
phosphine ligands located in the trans position, such as
[Pt(C∧P)(dppe)]+ [C∧P = {(R)-1-[1-diphenylphosphino]-
ethyl}naphthyl-C,P; JPt,P(transP) = 2770 Hz,21c or [Pt(dppe)
(PAn-H)]+ [PAn = 9-diphenylphosphinoanthracene; JPt,P(transP)
= 2796],26d indicating that the C* displays a great trans
influence, similar to alkynyl or phosphine ligands.
Then we focused again on complex [Pt(C∧C*) (dppe)]PF6
1
(12), and we observed the JPt,P values for the P trans to CAr
and C* are 2014.6 and 2673.8 Hz, respectively. These values
indicate that the trans influence of CAr is slightly greater than
that of C*. The same assessment was inferred from the
3JPt,Ho(py) in complex 6 which exhibits different values when
pyridine is facing CAr (6-c, 20.7 Hz) or C* (6-t, 28.0 Hz).
Moreover, an evaluation of the electronic effects of the different
L ligands can be undertaken by comparison of the
spectroscopic and crystallographic data of complexes with the
same stoichiometry and configuration, such as trans-(C*,P)-
[Pt(C∧C*) (PPh3)L]0,+ (L = Cl (5), py (9), CNXyl (10), MMI
(11)) or cis-(C*,L)-[PtCl(C∧C*)L] (L = py (6-c), CNXyl (7-
Figure 7. DFT-computed energies for the 6-c/-t isomers (ΔE, kcal
3
c), MMI (8-c)) (Table 1). On the basis of the observed JPt,H7
mol−1).
2
(64.0 (5), 58.8 (9), 50.7 (10), and 59.4 Hz (11)) and JPt,C7
(57.0 (5), 55.4 (9), 51.0 (10), and 56.1 Hz (11)) in the trans-
(C*,P) named complexes, the trans influence order seems to be
CNXyl > py ≈ MMI > Cl. An additional comparison of the
values of δC1 (170.1 ppm (5), 152.7 (6-t), 167.7 (7-t), 159.3
pyridine ring is 1.01 kcal mol−1 more stable than 6-c. This
subtle difference in energy added to the bigger T[CAr/py)] vs
T[C*/py] results to be reasonably determining for the high
stereoselectivity of isomers in 6.
3
(8-t)) and JPt,C3 (26.0 Hz (5), 38.4 (6-t), 30.9 (7-t), 37.3 (8-
t)) in complexes trans-(C*,L)-[PtCl(C∧C*)L] (L = PPh3 (5),
py (6-t), CNXyl (7-t), MMI (8-t)) indicates that the trans
influence of PPh3 is even greater than that of CNXyl. Finally, X-
ray data analysis of 5 and 9−12 (Table 2) indicates that the
longest Pt−C6 distances correspond to those of 12 and 10,
with the dppe and CNXyl located at the trans position.
Therefore, the trans influence of all the used ancillary ligands
seems to follow the order PPh3/dppe > CNXyl > py ≈ MMI >
Cl.
Taking into account all these assumptions T[CAr/L)] >
T[C*/L] and T[CAr/PPh3)] > T[CAr/CNXyl)] > T[CAr/py)]
≈ T[CAr/MMI)] > T[CAr/Cl)]. Therefore, the T[CAr/PPh3)]
should be the greatest one, and the experimental results seem
In complexes 5 and 9−11, their X-ray structures and NMR
data also show the presence of Csp2−H7(Ar)···π interactions,
which will contribute together with the difference of T[CAr/L)]
vs T[C*/L] to the selective formation of the trans-(C*,PPh3)
isomer, as experimentally observed.
CONCLUSIONS
■
The synthetic method for 1 has been greatly improved, and the
corresponding imidazolium salt, 2, has been successfully
anchored and subsequently cyclometalated to the Pt center,
which endorse the generality and viability of this step-by-step
synthetic pathway for cyclometalated NHCs complexes,
[{Pt(μ-Cl)(C∧C*)}2]. The chlorine-bridge complex 4 has
I
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(b) Wang, P.; Leung, C. H.; Ma, D. L.; Lu, W.; Che, C. M. Chem. -
Asian J. 2010, 5, 2271−2280. (c) Koo, C. K.; Wong, K. L.; Man, C. W.
Y.; Lam, Y. W.; So, K. Y.; Tam, H. L.; Tsao, S. W.; Cheah, K. W.; Lau,
K. C.; Yang, Y. Y.; Chen, J. C.; Lam, M. H. W. Inorg. Chem. 2009, 48,
872−878.
(4) (a) Williams, J. A. G.; Develay, S.; Rochester, D. L.; Murphy, L.
Coord. Chem. Rev. 2008, 252, 2596−2611. (b) Williams, J. A. G. In
Topics in Organometallic Chemistry; Bozec, H., Guerchais, V., Eds.;
Springer: New York, 2009; Vol. 28.
been revealed as a useful starting material for neutral and
cationic heteroleptic complexes containing the “Pt(C∧C*)”
moiety, 5−12.
The transphobia degree (T) of pairs of trans ligands, as
inferred from spectroscopic data, resulted was T[CAr/L)] >
T[C*/L] and T[CAr/PPh3)] > T[CAr/CNXyl)] > T[CAr/py)]
≈ T[CAr/MMI)] > T[CAr/Cl)]. The difference between
T[CAr/L)] and T[C*/L] (L = py, CNXyl, MMI) is not
enough to avoid the formation of mixtures of cis/trans isomers
during the splitting of the chlorine bridge in 4 by L, but in all
cases, the trans-(C*,L)-[PtCl(C∧C*)L] isomer is the major
species, especially when L is py. In this case, the intramolecular
T-shaped CAr−H···π (py) interaction seems to contribute to
the stabilization of this isomer, as proven by DFT calculations.
Otherwise, the greatest T[CAr/PPh3)] together with the
intramolecular T-shaped CAr−H···π (Ph) interactions present
in the trans-(C*,PPh3)-[Pt(C∧C*)(PPh3)L] complexes (L = Cl
(5), py (9), CNXyl (10), MMI (11)) would account for the
stereoselective formation of this isomer in each case, as
experimentally observed.
(5) Sajoto, T.; Djurovich, P. I.; Tamayo, A.; Yousufuddin, M.; Bau,
R.; Thompson, M. E.; Holmes, R. J.; Forrest, S. R. Inorg. Chem. 2005,
44, 7992−8003.
(6) (a) Bugaut, X.; Glorius, F. Chem. Soc. Rev. 2012, 41, 3511−3522.
(b) Fortman, G. C.; Nolan, S. P. Chem. Soc. Rev. 2011, 40, 5151−5169.
(c) Liddle, S. T.; Edworthy, I. S.; Arnold, P. L. Chem. Soc. Rev. 2007,
36, 1732−1744. (d) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41,
1290−1309. (e) Kuhl, O. Chem. Soc. Rev. 2007, 36, 592−607.
̈
(f) Wang, F. J.; Liu, L. J.; Wang, W. F.; Li, S. K.; Shi, M. Coord. Chem.
Rev. 2012, 256, 804−853. (g) Nelson, D. J. Eur. J. Inorg. Chem. 2015,
2015, 2012−2027. (h) Levin, E.; Ivry, E.; Diesendruck, C. E.; Lemcoff,
N. G. Chem. Rev. 2015, 115, 4607−4692. (i) Diez-Gonzalez, S.;
Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109, 3612−3676.
(7) (a) Lin, I. J. B.; Vasam, C. S. J. Organomet. Chem. 2005, 690,
3498−3512. (b) Huang, R. T. W.; Wang, W. C.; Yang, R. Y.; Lu, J. T.;
Lin, I. J. B. Dalton Trans. 2009, 7121−7131. (c) Lee, C. K.; Vasam, C.
S.; Huang, T. W.; Wang, H. M. J.; Yang, R. Y.; Lee, C. S.; Lin, I. J. B.
Organometallics 2006, 25, 3768−3775.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.5b01655.
■
S
(8) (a) Melaiye, A.; Sun, Z. H.; Hindi, K.; Milsted, A.; Ely, D.;
Reneker, D. H.; Tessier, C. A.; Youngs, W. J. J. Am. Chem. Soc. 2005,
127, 2285−2291. (b) Hindi, K. M.; Panzner, M. J.; Tessier, C. A.;
Cannon, C. L.; Youngs, W. J. Chem. Rev. 2009, 109, 3859−3884.
(c) Raubenheimer, H. G.; Cronje, S. Chem. Soc. Rev. 2008, 37, 1998−
2011. (d) Mercs, L.; Albrecht, M. Chem. Soc. Rev. 2010, 39, 1903−
1912.
General procedures and materials, computational, and
crystallographic details; full NMR spectra of 3 and 4; full
NMR spectra of 6 and 10 (selected as examples of the
neutral and cationic derivatives; X-ray structures; tables
of atomic coordinates of compounds (PDF)
(9) (a) Yam, V. W. W.; Cheng, E. C. C. In Photochemistry and
Photophysics of Coordination Compounds II; Balzani, V., Campagna, S.,
Eds.; Springer-Verlag: Berlin, 2007; Vol. 281, pp 269−309. (b) Hock,
S. J.; Schaper, L.-A.; Herrmann, W. A.; Kuhn, F. E. Chem. Soc. Rev.
2013, 42, 5073−5089. (c) Son, S. U.; Park, K. H.; Lee, Y. S.; Kim, B.
Y.; Choi, C. H.; Lah, M. S.; Jang, Y. H.; Jang, D. J.; Chung, Y. K. Inorg.
Chem. 2004, 43, 6896−6898. (d) Unger, Y.; Zeller, A.; Ahrens, S.;
Strassner, T. Chem. Commun. 2008, 3263−3265. (e) Holmes, R. J.;
Forrest, S. R.; Sajoto, T.; Tamayo, A.; Djurovich, P. I.; Thompson, M.
E.; Brooks, J.; Tung, Y. J.; D’Andrade, B. W.; Weaver, M. S.; Kwong, R.
C.; Brown, J. J. Appl. Phys. Lett. 2005, 87, 243507. (f) Chang, C. F.;
Cheng, Y. M.; Chi, Y.; Chiu, Y. C.; Lin, C. C.; Lee, G. H.; Chou, P. T.;
Chen, C. C.; Chang, C. H.; Wu, C. C. Angew. Chem., Int. Ed. 2008, 47,
4542−4545. (g) Hsieh, C. H.; Wu, F. I.; Fan, C. H.; Huang, M. J.; Lu,
K. Y.; Chou, P. Y.; Yang, Y. H. O.; Wu, S. H.; Chen, I. C.; Chou, S. H.;
Wong, K. T.; Cheng, C. H. Chem. - Eur. J. 2011, 17, 9180−9187.
(h) Sasabe, H.; Takamatsu, J.; Motoyama, T.; Watanabe, S.;
Wagenblast, G.; Langer, N.; Molt, O.; Fuchs, E.; Lennartz, C.; Kido,
J. Adv. Mater. 2010, 22, 5003. (i) Lu, K. Y.; Chou, H. H.; Hsieh, C. H.;
Yang, Y. H. O.; Tsai, H. R.; Tsai, H. Y.; Hsu, L. C.; Chen, C. Y.; Chen,
I. C.; Cheng, C. H. Adv. Mater. 2011, 23, 4933−4937. (j) Visbal, R.;
Ospino, I.; Lopez-de-Luzuriaga, J. M.; Laguna, A.; Gimeno, M. C. J.
Am. Chem. Soc. 2013, 135, 4712−4715. (k) Haneder, S.; Da Como, E.;
Feldmann, J.; Lupton, J. M.; Lennartz, C.; Erk, P.; Fuchs, E.; Molt, O.;
Munster, I.; Schildknecht, C.; Wagenblast, G. Adv. Mater. 2008, 20,
3325−3330.
Crystallographic data (CIF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: sicilia@unizar.es.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Spanish Ministerio de
́
Economia y Competitividad (MINECO)/FEDER (Project
CTQ2012-35251 led by Dr. Babil Menjo
Departamento de Industria e Innovacion del Gobierno de
Aragon and Fondo Social Europeo (Grupo Consolidado E21:
Quimica Inorganica y de los Compuestos Organometalicos led
by Dr. Jose M. Casas). The authors thank the Centro de
Supercomputacion de Galicia (CESGA) for generous allocation
́
n) and the
́
́
́
́
́
́
́
́
of computational resources and Dr. Antonio Martin for his
valuable help with some of the X-ray structure determinations.
REFERENCES
■
(1) (a) Murphy, L.; Williams, J. A. G. Top. Organomet. Chem. 2010,
28, 75−111. (b) Williams, J. A. G. Top. Curr. Chem. 2007, 281, 205−
268. (c) Zhou, G.; Wang, Q.; Wang, X.; Ho, C.-L.; Wong, W.-Y.; Ma,
D.; Wang, L.; Lin, Z. J. Mater. Chem. 2010, 20, 7472−7484.
(2) (a) Zhao, Q.; Li, F.; Huang, C. Chem. Soc. Rev. 2010, 39, 3007−
3030. (b) Wong, K. M.-C.; Chan, M. M.-Y.; Yam, V. W.-W. Adv.
Mater. 2014, 26, 5558−5568. (c) Taylor, S. D.; Howard, W.; Kaval, N.;
Hart, R.; Krause, J. A.; Connick, W. B. Chem. Commun. 2010, 46,
1070−1072.
(10) (a) Tronnier, A.; Nischan, N.; Metz, S.; Wagenblast, G.;
Munster, I.; Strassner, T. Eur. J. Inorg. Chem. 2014, 2014, 256−264.
̈
(b) Tronnier, A.; Pothig, A.; Herdtweck, E.; Strassner, T. Organo-
̈
metallics 2014, 33, 898−908. (c) Tronnier, A.; Metz, S.; Wagenblast,
G.; Munster, I.; Strassner, T. Dalton Trans. 2014, 43, 3297−3305.
̈
(d) Tronnier, A.; Nischan, N.; Strassner, T. J. Organomet. Chem. 2013,
730, 37−43. (e) Tronnier, A.; Risler, A.; Langer, N.; Wagenblast, G.;
(3) (a) Wang, P.; Leung, C. H.; Ma, D. L.; Sun, R. W. Y.; Yan, S. C.;
Chen, Q. S.; Che, C. M. Angew. Chem., Int. Ed. 2011, 50, 2554−2558.
Munster, I.; Strassner, T. Organometallics 2012, 31, 7447−7452.
̈
(f) Hudson, Z. M.; Sun, C.; Helander, M. G.; Chang, Y. L.; Lu, Z. H.;
J
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Wang, S. N. J. Am. Chem. Soc. 2012, 134, 13930−13933. (g) Hudson,
Z. M.; Blight, B. A.; Wang, S. N. Org. Lett. 2012, 14, 1700−1703.
(22) (a) Meijer, M. D.; Kleij, A. W.; Williams, B. S.; Ellis, D.; Lutz,
M.; Spek, A. L.; van Klink, G. P. M.; van Koten, G. Organometallics
2002, 21, 264−271. (b) Zucca, A.; Cinellu, M. A.; Minghetti, G.;
Stoccoro, S.; Manassero, M. Eur. J. Inorg. Chem. 2004, 2004, 4484−
4490. (c) Zucca, A.; Petretto, G. L.; Stoccoro, S.; Cinellu, M. A.;
Manassero, M.; Manassero, C.; Minghetti, G. Organometallics 2009,
28, 2150−2159. (d) Martin, R.; Crespo, M.; Font-Bardia, M.; Calvet,
T. Organometallics 2009, 28, 587−597.
(23) (a) Rao, Y.-L.; Wang, S. N. Inorg. Chem. 2009, 48, 7698−7713.
(b) Harris, C. F.; Vezzu, D. A. K.; Bartolotti, L.; Boyle, P. D.; Huo, S.
Q. Inorg. Chem. 2013, 52, 11711−11722. (c) Karakostas, N.; Mavridis,
I. M.; Seintis, K.; Fakis, M.; Koini, E. N.; Petsalakis, I. D.; Pistolis, G.
Chem. Commun. 2014, 50, 1362−1365. (d) Jude, H.; Krause Bauer, J.
A.; Connick, W. B. Inorg. Chem. 2004, 43, 725−733.
(24) (a) Fornies, J.; Sicilia, V.; Casas, J. M.; Martin, A.; Lopez, J. A.;
Larraz, C.; Borja, P.; Ovejero, C. Dalton Trans. 2011, 40, 2898−2912.
(b) Jacquot-Rousseau, S.; Khatyr, A.; Schmitt, G.; Knorr, M.; Kubicki,
M. M.; Blacque, O. Inorg. Chem. Commun. 2005, 8, 610−613.
(c) Hudson, Z. M.; Zhao, S.-B.; Wang, R.-Y.; Wang, S. N. Chem. - Eur.
J. 2009, 15, 6131−6137. (d) Chuchuryukin, A. V.; Chase, P. A.; Mills,
A. M.; Lutz, M.; Spek, A. L.; van Klink, G. P. M.; van Koten, G. Inorg.
Chem. 2006, 45, 2045−2054.
(25) (a) Crespo, M.; Anderson, C. M.; Kfoury, N.; Font-Bardia, M.;
Calvet, T. Organometallics 2012, 31, 4401−4404. (b) Alcarazo, M.;
Radkowski, K.; Goddard, R.; Furstner, A. Chem. Commun. 2011, 47,
776−778. (c) Anderson, C.; Crespo, M.; Rochon, F. D. J. Organomet.
Chem. 2001, 631, 164−174. (d) Rodríguez, J.; Zafrilla, J.; Albert, J.;
Crespo, M.; Granell, J.; Calvet, T.; Font-Bardia, M. J. Organomet.
Chem. 2009, 694, 2467−2475.
(h) Unger, Y.; Meyer, D.; Molt, O.; Schildknecht, C.; Munster, I.;
̈
Wagenblast, G.; Strassner, T. Angew. Chem., Int. Ed. 2010, 49, 10214−
10216. (i) Tronnier, A.; Schleicher, D.; Strassner, T. J. Organomet.
Chem. 2015, 775, 155−163. (j) Tronnier, A.; Pothig, A.; Metz, S.;
̈
Wagenblast, G.; Munster, I.; Strassner, T. Inorg. Chem. 2014, 53,
̈
6346−6356. (k) Tronnier, A.; Heinemeyer, U.; Metz, S.; Wagenblast,
G.; Muenster, I.; Strassner, T. J. Mater. Chem. C 2015, 3, 1680−1693.
(l) Ko, S.-B.; Park, H.-J.; Gong, S.; Wang, X. N.; Lu, Z.-H.; Wang, S. N.
Dalton Trans. 2015, 44, 8433−8443. (m) Zhang, Y. X.; Jullien, H.;
Brissy, D.; Retailleau, P.; Voituriez, A.; Marinetti, A. ChemCatChem
2013, 5, 2051−2057. (n) Jullien, H.; Brissy, D.; Sylvain, R.; Retailleau,
P.; Naubron, J.-V.; Gladiali, S.; Marinetti, A. Adv. Synth. Catal. 2011,
353, 1109−1124. (o) Brissy, D.; Skander, M.; Jullien, H.; Retailleau,
P.; Marinetti, A. Org. Lett. 2009, 11, 2137−2139.
́ ́ ́
(11) (a) Fernandez, S.; Fornies, J.; Gil, B.; Gomez, J.; Lalinde, E.
Dalton Trans. 2003, 822−830. (b) Fornies, J.; Fuertes, S.; Lopez, J. A.;
Martin, A.; Sicilia, V. Inorg. Chem. 2008, 47, 7166−7176. (c) Diez, A.;
Fornies, J.; Fuertes, S.; Lalinde, E.; Larraz, C.; Lopez, J. A.; Martin, A.;
Moreno, M. T.; Sicilia, V. Organometallics 2009, 28, 1705−1718.
(d) Fornies
Dalton Trans. 2009, 2224−2234. (e) Díez, A.; Fornies, J.; Larraz, C.;
Lalinde, E.; Lopez, J. A.; Martin, A.; Moreno, M. T.; Sicilia, V. Inorg.
́
, J.; Fuertes, S.; Martin, A.; Sicilia, V.; Gil, B.; Lalinde, E.
́
Chem. 2010, 49, 3239−3259. (f) Fornies, J.; Sicilia, V.; Borja, P.; Casas,
J. M.; Diez, A.; Lalinde, E.; Larraz, C.; Martin, A.; Moreno, M. T.
Chem. - Asian J. 2012, 7, 2813−2823.
(12) Palacios, L.; Di Giuseppe, A.; Castarlenas, R.; Lahoz, F. J.; Perez-
Torrente, J. J.; Oro, L. A. Dalton Trans. 2015, 44, 5777−5789 and
references therein..
(13) Fuertes, S.; Garcia, H.; Peralvarez, M.; Hertog, W.; Carreras, J.;
Sicilia, V. Chem. - Eur. J. 2015, 21, 1620−1631.
(14) (a) Casas, J. M.; Fornies, J.; Fuertes, S.; Martin, A.; Sicilia, V.
Organometallics 2007, 26, 1674−1685. (b) Sicilia, V.; Fuertes, S.;
Martin, A.; Palacios, A. Organometallics 2013, 32, 4092−4102.
(c) Fornies, J.; Sicilia, V.; Larraz, C.; Camerano, J. A.; Martin, A.;
Casas, J. M.; Tsipis, A. C. Organometallics 2010, 29, 1396−1405.
(d) Slater, J. W.; Lydon, D. P.; Alcock, N. W.; Rourke, J. P.
Organometallics 2001, 20, 4418−4423. (e) Vicente, J.; Abad, J. A.;
Martinez-Viviente, E.; Jones, P. G. Organometallics 2002, 21, 4454−
4467.
(26) (a) DePriest, J.; Zheng, G. Y.; Woods, C.; Rillema, D. P.;
Mikirova, N. A.; Zandler, M. E. Inorg. Chim. Acta 1997, 264, 287−296.
(b) Haghighi, M. G.; Nabavizadeh, S. M.; Rashidi, M.; Kubicki, M.
Dalton Trans. 2013, 42, 13369−13380. (c) Saha, R.; Abdul Qaium, M.;
Debnath, D.; Younus, M.; Chawdhury, N.; Sultana, N.; Kociok-Kohn,
̈
G.; Ooi, L.; Raithby, P. R.; Kijima, M. Dalton Trans. 2005, 2760−2765.
(d) Hu, J.; Lin, R.; Yip, J. H. K.; Wong, K.-Y.; Ma, D.-L.; Vittal, J. J.
Organometallics 2007, 26, 6533−6543.
(27) Nardelli, M. J. Appl. Crystallogr. 1995, 28, 659−659.
(28) (a) Nishio, M.; Umezawa, Y.; Honda, K.; Tsuboyama, S.;
Suezawa, H. CrystEngComm 2009, 11, 1757−1788. (b) Saigo, K.;
Kobayashi, Y. Chem. Rec. 2007, 7, 47−56. (c) Nishio, M.; Umezawa, Y.
Topics in Stereochemistry 2006, 25, 255−302.
(29) (a) Yamanari, K.; Nozaki, T.; Fuyuhiro, A.; Kushi, Y.; Kaizaki, S.
J. Chem. Soc., Dalton Trans. 1996, 2851−2856. (b) Yamanari, K.;
Nozaki, T.; Fuyuhiro, A.; Kaizaki, S. Chem. Lett. 1996, 35−36.
(c) Nakamura, M.; Okawa, H.; Kida, S. Bull. Chem. Soc. Jpn. 1985, 58,
3377−3378. (d) Onaka, S.; Furuta, H.; Takagi, S. Angew. Chem., Int.
Ed. Engl. 1993, 32, 87−88. (e) Chowdhury, S. K.; Joshi, V. S.; Samuel,
A. G.; Puranik, V. G.; Tavale, S. S.; Sarkar, A. Organometallics 1994, 13,
4092−4096.
(15) Mabbott, D. J.; Mann, B. E.; Maitlis, P. M. J. Chem. Soc., Dalton
Trans. 1977, 294−299.
(16) (a) Huang, Y. Z.; Miao, H.; Zhang, Q. H.; Chen, C.; Xu, J. Catal.
Lett. 2008, 122, 344−348. (b) Zhu, L. B.; Cheng, L.; Zhang, Y. X.; Xie,
R. G.; You, J. S. J. Org. Chem. 2007, 72, 2737−2743. (c) Wang, H. F.;
Li, Y. M.; Sun, F. F.; Feng, Y.; Jin, K.; Wang, X. N. J. Org. Chem. 2008,
73, 8639−8642.
(17) Bernhammer, J. C.; Huynh, H. V. Organometallics 2014, 33,
172−180.
(30) Tsuzuki, S.; Honda, K.; Uchimaru, T.; Mikami, M.; Tanabe, K. J.
Am. Chem. Soc. 2002, 124, 104−112.
(18) (a) Edwards, G. L.; Black, D. S. C.; Deacon, G. B.; Wakelin, L.
P. G. Can. J. Chem. 2005, 83, 980−989. (b) Newman, C. P.; Casey-
Green, K.; Clarkson, G. J.; Cave, G. W. V.; Errington, W.; Rourke, J. P.
Dalton Trans. 2007, 3170−3182. (c) Perez, S.; Lopez, C.; Caubet, A.;
Solans, X.; Font-Bardia, M. J. Organomet. Chem. 2004, 689, 3184−
3196.
NOTE ADDED AFTER ASAP PUBLICATION
■
This paper was published on the Web on October 8, 2015, with
errors in Table 1. The corrected version was reposted on
October 8, 2015.
(19) Zucca, A.; Maidich, L.; Carta, V.; Petretto, G. L.; Stoccoro, S.;
Agostina Cinellu, M.; Pilo, M. I.; Clarkson, G. J. Eur. J. Inorg. Chem.
2014, 2014, 2278−2287.
(20) (a) Maidich, L.; Zuri, G.; Stoccoro, S.; Cinellu, M. A.; Zucca, A.
Dalton Trans. 2014, 43, 14806−14815. (b) Minghetti, G.; Zucca, A.;
Stoccoro, S.; Cinellu, M. A.; Manassero, M.; Sansoni, M. J. Organomet.
Chem. 1994, 481, 195−204.
(21) (a) Haghighi, M. G.; Rashidi, M.; Nabavizadeh, S. M.; Jamali, S.;
Puddephatt, R. J. Dalton Trans. 2010, 39, 11396−11402. (b) Garrou,
P. E. Chem. Rev. 1981, 81, 229−266. (c) Jia, Y.-X.; Li, B.-B.; Li, Y.;
Pullarkat, S. A.; Xu, K.; Hirao, H.; Leung, P.-H. Organometallics 2014,
33, 6053−6058.
K
DOI: 10.1021/acs.inorgchem.5b01655
Inorg. Chem. XXXX, XXX, XXX−XXX