ADC-metal complexes as effective catalysts for hydrosilylation of alkynes

Article abstract of DOI:10.1016/j.jcat.2013.09.003

Aminocarbene complexes cis-[PtCl₂{C(N(H)N = CR²R ³)=N(H)R¹}(CNR¹)] (7-15) prepared via the nucleophilic addition of hydrazones H₂N-N=CR²R³ [R², R³

Full text of DOI:10.1016/j.jcat.2013.09.003

Journal of Catalysis 309 (2014) 79–86
Contents lists available at ScienceDirect
Journal of Catalysis
journal homepage: www.elsevier.com/locate/jcat
ADC-metal complexes as effective catalysts for hydrosilylation
of alkynes
Bruno G.M. Rocha a, Elena A. Valishina a,b, Rogério S. Chay a, M. Fátima C. Guedes da Silva a,c
,
Tatyana M. Buslaeva b, Armando J.L. Pombeiro a, , Vadim Yu. Kukushkin d,e, Konstantin V. Luzyanin d,f,
⇑
⇑
a Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
b Lomonosov Moscow State University of Fine Chemical Technologies, 119571 Moscow, Russian Federation
c Universidade Lusófona de Humanidades e Tecnologias, ULHT Lisbon, 1749-024 Lisbon, Portugal
d Department of Chemistry, Saint Petersburg State University, 198504 Stary Petergof, Russian Federation
e Institute of Macromolecular Compounds of Russian Academy of Sciences, Bolshoii Pr. 31, 199004 Saint Petersburg, Russian Federation
f Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Aminocarbene complexes cis-[PtCl2{C(N(H)N = CR2R3)=N(H)R1}(CNR1)] (7–15) prepared via the nucleo-
philic addition of hydrazones H2N–N=CR2R3 [R2, R3 = Ph 4; R2/R3 = 9H-fluorenyl 5; R2 = H, R3 = 2-(OH)C6-
H
Article history:
Received 9 July 2013
Revised 19 August 2013
Accepted 2 September 2013
4 6] to cis-[PtCl2(CNR1)2] [R1 = cyclohexyl (Cy) 1, 2,6-Me2C6H3 (Xyl) 2, 2-Cl-6-MeC6H3 3] were evaluated
as catalysts for the hydrosilylation of terminal alkynes with trisubstituted silanes giving vinyl silanes. The
optimized catalytic system runs at 80–100 °C in dry toluene for 3–6 h with a typical catalyst loading of
i
0.1 mol%. A range of substrates with different steric hindrance and activity (Et3SiH, Pr3SiH, Pr3SiH, and
Keywords:
PhMe2SiH as silanes; PhC„CH, tBuC„CH, and 4-(tBu)C6H4C„CH as alkynes) were successfully trans-
formed into the target silylated products in 83–99% yields attesting the versatility of our catalytic system.
Decreasing the catalysts loading to 10ꢀ3 mol% guaranteed the maximum TONs of 4.0 ꢁ 104 and TOFs of
1.7 ꢁ 103 (hꢀ1) that were accomplished within 24 h of the reaction.
Acyclic diaminocarbenes
Platinum-(acyclic diminocarbene) catalysts
Metal-mediated coupling
Isocyanides
Ó 2013 Elsevier Inc. All rights reserved.
Hydrazones
Hydrosilylation
Terminal alkynes
1. Introduction
Refs. [1,24–26]). Among them, one that is based on a metal-medi-
ated nucleophilic addition to isocyanides (Scheme 1B) permits a
Acyclic diaminocarbene ligands (ADCs, Scheme 1A) have re-
cently gained prominence in catalysis of organic transformations
as potential alternatives to the widely used N-heterocyclic species
(NHCs) [1–8]. ADCs are structurally related to the NHCs and pos-
sess similar electronic stabilization and comparable donor proper-
ties [9–15]. The combination of the greater steric control (due to
the wider N–C–N bond angles in the ADCs with respect to the
NHCs) [16–18] with their rotational freedom (NHCs are rigid due
to their cyclic structures) [19–23], on the one hand, leads poten-
tially to an easier catalyst adaptation to inconsistent steric require-
ments of various stages of the catalytic process, while, on the other
hand, it guarantees the high stability of the ADC-based catalysts.
Metal complexes with the ADC ligands can be easily accessed
via several synthetic strategies (for the surveys in the field, see
straightforward assembly of a wide range of well-defined metal-
ADC species [24–26]. In addition, this approach is modular and
facilitates an optimization of steric and electronic properties and,
consequently, the catalytic efficiency of the target [M]-ADCs.
Up-to-date metal-ADC species have been successfully employed
as catalysts for several organic transformations, i.e., Suzuki–Miya-
ura, Sonogashira, Heck, Kumada, and Buchwald–Hartwig cross-
coupling, as well as for various cyclizations/additions to substrates
having the C„C and C = C bonds [1,2,8]. Surprisingly, metal-ADCs
have never been employed in hydrosilylation and, in particular, in
the hydrosilylation of alkynes—one of the fundamental approaches
for the laboratory and industrial synthesis of organosilicon and sil-
icon-related compounds [27,28]—and even the use of metal-NHCs
species for this purpose [29–34] is limited to scarce examples.
Recently, we [35–44] and others [45] reported the preparation
of several new types of aminocarbene ligands via the integration
of palladium- and platinum-bound isocyanides with sp2-N (imines
[35,36,40,41]) or mixed sp2-N/sp3-N (amidines [39,46] or hydra-
zones [37]) type nucleophiles. Among the thus-generated species,
palladium complexes demonstrated elevated efficiency as catalysts
⇑
Corresponding authors. Addresses: Centro de Química Estrutural, Complexo I,
Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon,
Portugal (A.J.L. Pombeiro); Saint Petersburg State University, 198504 Stary Petergof,
Russian Federation (K.V. Luzyanin).
E-mail addresses: pombeiro@ist.utl.pt (A.J.L. Pombeiro), konstantin.luzyanin@
liv.ac.uk (K.V. Luzyanin).
0021-9517/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/j.jcat.2013.09.003

80
B.G.M. Rocha et al. / Journal of Catalysis 309 (2014) 79–86
undertaken (Table 1). When the reactions were completed, the
subsequent workup afforded the carbene species cis-[PtCl2{-
C(N(H)N=CR2R3)=N(H)R1}(CNR1)] (7–15) in good (75–85%) isolated
yields. The reaction between cis-[PtCl2(CNtBu)2] (16) and any of 4–
6 in CHCl3 even under prolonged reflux furnished no isolable car-
bene species. Only a mixture of the starting materials along with
small amounts of yet unidentified decomposition products was
identified after reflux for 2d.
The prepared aminocarbene complexes 7–15 were character-
ized by elemental analyses (C, H, N), ESI+–MS, IR, 1D (1H, 13C{1H})
and 2D (1H,1H-COSY, 1H,13C-HMQC/1H,13C-HSQC, 1H,13C-HMBC)
NMR spectroscopies. In addition, the structures of three species
(11, 13, and 14) were elucidated by single-crystal X-ray diffraction.
For detailed characterization of aminocarbene species 7–15, see
Supplementary information.
The crystallographic data and processing parameters for 11, 13,
and 14 are summarized in Table 1S (see Supplementary Informa-
tion), while the corresponding molecular structure plots can be
found in Figs. 1 and 1S, and bond lengths and angles are given in
Table 2. As far as the most significant structural features are con-
cerned, it is worth mentioning that in all three structures, the me-
tal centers adopt square-planar geometries (s4 in the 0.061–0.077
range), and the carbene ligands {C(N(H)N=CR2R3)=N(H)R1} are in
the cis position with respect to the unreacted isocyanide. Further-
more, the carbene moiety is roughly planar and the angles includ-
ing the C-carbene atoms (i.e., N–N–Ccarbene, N–Ccarbene–N and
Scheme 1. Acyclic diaminocarbenes (ADCs) versus N-heterocyclic carbenes (NHCs)
and generation of the [M]-ADC from the corresponding [M]-CNR species.
in Suzuki–Miyaura [37,40–42] and Sonogashira [39] couplings,
while the corresponding platinum species were not active. Addi-
tionally, inspection of literature data led to the conclusion that
the reported ADC-based catalytic systems contain palladium (in
case of cross-coupling) [1,2] or gold (in case of cyclization reac-
tions) [1,2] in the core of the catalyst, and only rare examples of
other metals, e.g. nickel [47], copper [48], ruthenium [22], or rho-
dium [15], are known. To the best of our knowledge, no use of plat-
inum-ADCs in catalysis has been demonstrated beforehand.
In order to verify whether metal-ADC species and, in particular,
platinum-ADCs can be employed as catalysts for the hydrosilyla-
tion of terminal alkynes, we prepared several new aminocarbene
derivatives (via the addition of hydrazones to platinum-bound iso-
cyanides) and evaluated their catalytic properties. Consequently,
we report herein on the first metal–ADCs catalysts for the hydrosi-
lylation of alkynes and, also, on the first application of platinum-
ADCs in catalysis. The results of our study are disclosed in the sec-
tions that follow.
C
carbene–N–C) range from 111.5(19) to 132.1(16), therefore sustain-
ing their sp2 hybridization. The two C–N bonds of the carbene frag-
ments are equal (in 13) or differ insignificantly (ca. 0.04–0.06 Å in
11 and 14).
2. Results and discussions
2.2. Application of platinum-aminocarbene complexes as catalysts for
hydrosilylation of terminal alkynes
2.1. Synthesis and characterization of the platinum-aminocarbene
complexes
In the last decade, metal complexes featuring ADC ligands have
been successfully employed as catalysts for several cross-coupling
(e.g. Suzuki–Miayura, Heck, and Sonogashira reactions) and some
cyclization reactions. Recent comprehensive reviews written by
two of us [1] and by Slaughter [2] survey the accumulated experi-
mental data indicating that M-ADCs species have never been pre-
viously employed as catalysts for hydrosilylation and, in
particular, in the hydrosilylation of terminal alkynes with organo-
silanes. In pursuit of our on-going research on novel efficient cata-
lytic systems [37,39–41], we decided to evaluate the catalytic
properties of the aminocarbene complexes from this study in the
hydrosilylation of terminal alkynes.
As a model system, we have chosen the reaction of phenylacet-
ylene with triethylsilane furnishing a mixture of vinyl silanes
(Scheme 3) employed previously for catalytic studies on hydrosily-
lation of terminal alkynes [33]. As it was previously reported [33]
for the hydrosilylation reaction catalyzed by platinum compounds,
no formation of (Z)-triethyl(styryl)silane (b-(Z) product) was ob-
served [33]. Accordingly, in all our trials, the hydrosilylation reac-
The reaction between the platinum(II)-isocyanide cis-[PtCl2(-
CNR1)2] [R1 = cyclohexyl (Cy) 1, 2,6-Me2C6H3 (Xyl) 2] complexes
and H2N–N=CPh2 (4) furnishing aminocarbene species 7 and 10,
correspondingly, was previously reported by some of us [37]. In
the current study, we extended the scope of this coupling to the
new platinum-isocyanide compound cis-[PtCl2(CNR1)2] (R1 = 2-Cl-
6-MeC6H3 3) and also to the hydrazones H2N–N=CR2R3 [R2/
R3 = 9H-fluorenyl 5; R2 = H, R3 = 2-(OH)C6H4 6] that were not previ-
ously explored in this reaction.
We observed that the coupling between the equimolar amounts
of 1–3 and 4–6 (in all possible combinations) proceeded smoothly
under reflux in chloroform (Scheme 2). The reaction rate varied
with the type of the starting materials used (in the previously re-
ported coupling of 1 and 2 with 4 [37], all additions proceeded
with a similar rate), i.e., bulky hydrazones and sterically hindered
isocyanides, required longer reaction time. Therefore, the optimi-
zation of the time for each of isocyanide ligand/hydrazone pair,
upon monitoring of the reaction mixture by IR spectroscopy, was
tion furnished
a mixture of triethyl(1-phenylvinyl)silane (a
Scheme 2. Coupling between cis-[PtCl2(CNR1)2] (1–3) and H2N–N = CR2R3 (4–6) affording aminocarbene complexes 7–15.

B.G.M. Rocha et al. / Journal of Catalysis 309 (2014) 79–86
81
Table 1
Reaction times and numbering of the prepared aminocarbene species.
R1 in cis-[PtCl2(CNR1)2]
Cy 1
R2 and R3 in H2N–N = CR2R3
Reaction time, h
Product
R2, R3 = Ph 4
8
15
17
8
26
26
18
9
7 [37]
8
9
10 [37]
11
12
13
14
15
R2/R3 = 9H-fluorenyl 5
R2 = H, R3 = 2-(OH)C6H4
R2, R3 = Ph 4
6
6
6
Xyl 2
R2/R3 = 9H-fluorenyl 5
R2 = H, R3 = 2-(OH)C6H4
R2, R3 = Ph 4
2-Cl-6-MeC6H3
3
R2/R3 = 9H-fluorenyl 5
R2 = H, R3 = 2-(OH)C6H4
18
product) and (E)-triethyl(styryl)silane (b-(E) product), and no (Z)-
triethyl(styryl)silane (b-(Z) product) was isolated.
of benzophenone hydrazone 4 (R2, R3 = Ph) to any of the cis-[PtCl2(-
CNR1)2] (1–3) complexes.
In the preliminary optimization of the conditions, we found tol-
uene be the most appropriate solvent for the hydrosilylation of al-
kynes. In dry toluene, the reaction afforded high yields of the
products at 80–100 °C for 3–6 h with catalyst loading of
0.1 mol%. When non-dried toluene was taken as a solvent, no sig-
nificant difference in yields and composition of the reaction mix-
ture was observed at temperatures below 90 °C suggesting that
the water traces present in solvents do not affect our system. How-
ever, at 100 °C, a significant drop (more than 20%) in product yields
was observed justifying the use of dry solvent for further studies.
Comparison of the catalytic activity of 7–15 in the model sys-
tem was performed at two temperatures (80, 100 °C) and the dura-
tion of each trial was 3 or 6 h. The obtained results are summarized
in Table 3. Among all the studied catalysts, complexes 14 and 15
were the most active under all examined conditions. Moreover,
compounds 11 and 12 exhibited slightly lower efficiencies, and
7–10 and 13 were less active. With respect to the structure of
the complexes, we noted that 11, 12, 14, and 15 that are derived
from the addition of sterically hindered hydrazones H2N–
N=CR2R3 5 (R2/R3 = 9H-fluorenyl) and 6 (R2 = H, R3 = 2-(OH)C6H4)
to aryl isocyanide in cis-[PtCl2(CNR1)2] [R1 = Xyl 2, 2-Cl-6-MeC6H3
3] were generally more active than those derived from the addition
For further screening of the functional group tolerance and
scope of our system (Table 4), the most promising catalysts 14
and 15 were used. A range of substrates of different steric hin-
drance was successfully transformed employing our catalytic sys-
tem, thus showing its versatility. The best results for each pair of
the reactants are given in bold in Table 4. It is noteworthy that, ex-
cept for the reactions of iPr3SiH and tBuC„CH (entry 18, 87%), and
Pr3SiH with 4-(tBu)C6H4C„CH (entry 32, 83%), all the yields were
higher than 90%.
Finally, we also examined the effect of catalyst loading in the
model hydrosilylation system (Table 5). We found that performing
the process with lower catalyst loadings (10ꢀ2–10ꢀ3 mol%) re-
quires longer times guaranteeing higher TONs and TOFs. Thus,
the maximum TONs of 4.0 ꢁ 104 and TOFs 1.7 ꢁ 103 (hꢀ1) for cat-
alyst 14, and TONs of 3.3 ꢁ 104 and TOFs 1.4 ꢁ 103 (hꢀ1) for cata-
lyst 15, were accomplished within 24 h of the reaction although
with low product yields (40% and 33%, correspondingly).
3. Final remarks
In pursuit of our studies, we have revealed that complexes
with acyclic diaminocarbenes can be suitable catalysts for alkyne
Fig. 1. View of 11 (left) and 14 (right) with the atomic numbering schemes. Thermal ellipsoids are drawn with the 30% probability. Hydrogen labels and chloroform molecules
are omitted for simplicity. In 14, only one component of the substitutional disorder (C16A and Cl1A) is shown.

82
B.G.M. Rocha et al. / Journal of Catalysis 309 (2014) 79–86
Table 2
with trisubstituted silanes giving vinyl silanes. Our optimized cat-
Selected bond lengths [Å] and angles [°] for 11, 13, and 14.
alytic system runs at 80–100 °C in dry toluene for 3–6 h with a typ-
ical catalyst loading of 0.1 mol% and allows the successful
transformation of a range of substrates with different steric hin-
drances (Et3SiH, Pr3SiH, iPr3SiH, and PhMe2SiH as silanes; PhC„CH,
tBuC„CH, and 4-(tBu)C6H4C„CH as alkynes). Under the described
conditions, the target silylated products were obtained in 83–99%
yields.
11
13a
14
Bond lengths
Pt–C1
Pt–C2
Pt–C11
Pt–Cl1
Pt–Cl2
Pt–Cl3
Pt–Cl4
C1–N1
C1–N3
C1–N12
C2–N2
C11–N11
N3–N4
N12–N13
1.995(3)
1.902(4)
–
2.3125(10)
2.3591(8)
–
–
1.312(5)
1.350(4)
–
1.143(5)
–
1.374(4)
–
1.96(2)
–
1.88(2)
2.312(5)
2.361(6)
–
2.000(15)
1.862(14)
–
–
–
It is important to mention that despite the fact that platinum
complexes with ADC ligands have never been previously employed
in catalysis [1,2], the current study clearly validates their potential.
In addition, the comparison of our results for the hydrosilylation of
terminal alkynes with platinum-ADCs as catalysts with those re-
ported for the structurally related platinum-NHCs [33,34,49] re-
veals a higher catalytic activity of the former species. In fact, the
majority of platinum-NHC systems demand higher catalyst loading
(0.5–1 mol%) [33,34,49], while with the lower (0.01–0.1 mol%) cat-
alyst amount, the process required much longer time (up to 48 h)
[33]. Among abovementioned systems that reported by de Jesús
et al. [34] and based on platinum(0)-NHCs (0.1–0.5 mol%) worked
in an aqueous medium at lower temperature of 30 °C and that
should be recognized as one of its benefits. In our system running
at 80–100 °C, reduced catalyst loading (0.001 mol%) assured the
maximum TONs of up to 4.0 ꢁ 104 and TOFs of 1.7 ꢁ 103 (hꢀ1) that
were achieved within 24 h, thus showing one of the best ever re-
ported efficiencies for platinum-catalyzed hydrosilylation of termi-
nal alkynes [33,34,49].
2.358(4)
2.302(4)
1.358(17)
1.300(15)
–
1.181(16)
–
1.364(15)
–
–
1.35(3)
–
1.35(3)
–
1.15(2)
–
1.36(2)
Bond angles
Cl1–Pt1–Cl2
Cl3–Pt1–Cl4
C1–Pt1–C2
C1–Pt1–C11
Pt1–C1–N1
Pt1–C1–N3
Pt1–C1–N12
N1–C1–N3
N1–C1–N12
C1–N3–N4
C1–N12–N13
88.81(3)
–
95.45(15)
–
128.8(3)
115.6(3)
–
115.6(3)
–
120.8(3)
–
89.5(2)
–
–
–
88.43(13)
95.7(6)
–
127.6(9)
116.7(11)
–
115.6(13)
–
122.3(13)
–
96.8(9)
129.3(16)
–
119.4(15)
–
111.3(19)
–
121.8(17)
a
Only the Pt1 containing molecule is presented.
4. Experimental section
hydrosilylation; these species have never been employed for this
purpose [1,2]. Thus, we have prepared several new platinum-
(ADC) derivatives via the metal-mediated integration of isocya-
nides and hydrazones, fully characterized them, and evaluated
their catalytic properties in the hydrosilylation of terminal alkynes
4.1. Materials and instrumentation
Solvents, K2[PtCl4], all isocyanides, and hydrazones were ob-
tained from commercial sources and used as received, apart from
chloroform that was purified by conventional distillation over
Scheme 3. Model system for the hydrosilylation of alkynes.
Table 3
Comparison of the catalytic activity of 7–15 [yields and (a/b ratio)].
Catalyst
Yieldsa and (
Time = 3 h
a
/b ratio) at T = 80 °C
Yieldsa and (
Time = 3 h
a/b ratio) at T = 100 °C
Time = 6 h
Time = 6 h
7
8
9
10
11
12
13
14
15
63 (22/78)
34 (18/82)
20 (18/82)
51 (34/66)
55 (22/78)
64 (20/80)
55 (48/52)
93 (22/78)
78 (20/80)
85 (21/79)
66 (19/81)
56 (23/77)
63 (41/59)
92 (21/79)
95 (21/79)
72 (50/50)
99 (19/81)
92 (20/80)
73 (26/74)
76 (22/78)
80 (23/77)
70 (27/73)
71 (18/82)
84 (19/81)
79 (25/75)
99 (25/75)
84 (23/77)
89 (29/71)
92 (22/78)
97 (22/78)
91 (30/70)
98 (29/71)
93 (15/85)
56 (23/77)
99 (24/76)
98 (21/79)
PhC„CH (5.0 ꢁ 10ꢀ4 mol, 1 equiv), Et3SiH (5.0 ꢁ 10ꢀ4 mol, 1 equiv), any of catalysts 7–15 (5.0 ꢁ 10ꢀ7 mol); toluene (0.5 mL).
a
Yields are based on 1H NMR measurements.

B.G.M. Rocha et al. / Journal of Catalysis 309 (2014) 79–86
83
Table 4
Scope of the hydrosilylation system employing catalysts 14 and 15 [yields and (
a
/b ratio)].a,b
Entry
Catalyst
Substrates
Et3SiH
PhC„CH
4-(tBu)C6H4C„CH
tBuC„CH
1–3
4–6
7–9
10–12
13–15
16–18
19–21
22–24
14
93 (22/78)
99 (25/75)
43 (17/83)
85 (31/69)
12 (83/17)
99 (83/17)
90 (28/72)
99 (25/75)
80 (17/83)
86 (27/75)
36 (17/83)
77 (34/66)
9 (87/13)
94 (85/15)
97 (24/76)
95 (26/74)
97 (6/94)
90 (12/88)
87 (5/95)
99 (11/89)
10 (41/59)
87 (52/48)
97 (3/97)
99 (9/91)
Pr3SiH
iPr3SiH
PhMe2SiH
25–27
28–30
31–33
34–36
37–39
40–42
43–45
48–48
15
Et3SiH
92 (20/80)
97 (21/79)
59 (18/82)
91 (20/80)
18 (99/1)
90 (81/19)
71 (29/71)
91 (30/70)
89 (17/83)
97 (19/81)
83 (16/84)
73 (21/79)
26 (99/1)
94 (85/15)
91 (25/75)
95 (26/74)
97 (6/94)
92 (9/91)
72 (4/96)
75 (8/92)
55 (51/49)
84 (52/48)
97 (4/96)
85 (6/94)
Pr3SiH
iPr3SiH
PhMe2SiH
Selected alkyne (5.0 ꢁ 10ꢀ4 mol, 1 equiv), selected sylane (5.0 ꢁ 10ꢀ4 mol, 1 equiv), selected catalyst (5.0 ꢁ 10ꢀ7 mol); toluene (0.5 mL).
a
For each cell, data were obtained at 80 (first line) and 100 (second line) °C; yields are based on 1H NMR measurements.
Reaction time was 3 h for catalyst 14 and 6 h for 15.
b
calcium chloride. The starting cis-[PtCl2(CNR)2] (R = Cy 1, Xyl 2,
2-Cl-6-MeC6H3 3, and tBu 16) [50–54], and known aminocarbene
complexes 7 and 10 [37] were prepared as previously reported.
C, H, and N elemental analyses were carried out by Microanalytical
Service of Instituto Superior Técnico. ESI+ mass-spectra were ob-
tained on a VARIAN 500-MS LC ion trap mass-spectrometer in
MeOH (ion spray voltage: +5 kV, capillary voltage: 30 V, RF load-
ing: 100%). Infrared spectra (4000–400 cmꢀ1) were measured on
14 (Table 1S) as a result of the poor quality of crystals (disorder,
weak diffraction), bond distances and angles were within a chem-
ically reasonable range. CCDC 938950–938952 contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
4.3. Synthetic work
a
BIO-RAD FTS 3000MX instrument in KBr pellets. 1D (1H,
13C{1H}) and 2D (1H,1H-COSY, 1H,13C-HMQC/1H,13C-HSQC and
1H,13C-HMBC) NMR spectra were recorded on Bruker Avance
II + 400 MHz (UltraShield™ Magnet) and Bruker Avance
II + 500 MHz (UltraShield™ Plus Magnet) spectrometers at ambi-
ent temperature using solvent resonances as a reference.
Reactions of 1–3 and 4–6.
A
solution of H2N–N=CR2R3
(0.50 mmol) in CHCl3 (5 mL) was added to a solution of cis-[PtCl2(-
CNR1)2] (0.50 mmol) in CHCl3 (10 mL), and the reaction mixture
was refluxed for 8–26 h (see Table 1). During this period, the color
of the mixture gradually turned from light orange to bright yellow.
When the reaction was complete, the resulting mixture was evap-
orated to dryness at 20–25 °C under a stream of dinitrogen, and the
product was extracted with two 5-mL portions of CHCl3. The bright
yellow solution was filtered to remove some insoluble material;
the filtrate was evaporated to dryness at RT under a stream of N2
4.2. X-ray structure determinations
The X-ray quality single crystals of complexes 11, 13, and 14
were immersed in cryo-oil, mounted in a Nylon loop and measured
at a temperature of 150 K (Table 1S). Intensity data were collected
using a Bruker AXS-KAPPA APEX II diffractometer with graphite
i
and washed with five 5-mL portions of Pr2O, one 1-mL portion
i
of cold (5 °C) Et2O, and again with five 5-mL portions of Pr2O,
monochromated Mo K
a (k 0.71073) radiation. Data were collected
whereupon dried in vacuo at RT. Yields of 7–15 were 75–85%, based
on Pt. The authenticity of known species 7 and 10 was established
upon comparison of their 1H and 13C{1H} NMR and IR spectra with
those reported previously [37].
using scans of 0.5° per frame and full sphere of data were ob-
x
tained. Cell parameters were retrieved using Bruker SMART soft-
ware and refined using Bruker SAINT [55] on all the observed
reflections. Absorption corrections were applied using SADABS
[56]. Structures were solved by direct methods by using the SHEL-
XS-97 package and refined with SHELXL-97 [57]. Calculations were
performed using the WinGX System–Version 1.80.03 [58]. All
hydrogen atoms were inserted in calculated positions. Least square
refinements with anisotropic thermal motion parameters for all
the non-hydrogen atoms (C8, C18, C48, C58 in 13 and C16A,
C16B, Cl1B in 14 were exceptions) and isotropic for the remaining
atoms were employed. There was a substitutional disorder in the
structure of 14 in the phenyl ring of the aminocarbene ligand;
the occupancies of its methyl carbon and the chlorine atoms were
determined by using the ‘‘free variable’’ (FVAR) option in SHELXL
software [59]. A value of 0.57 as an average for FVAR was obtained.
Although R-values are relatively high for the resulting structure of
(8, 75%). Anal. Calcd for C27H32N4Cl2Pt: C, 47.79; H, 4.75; N,
8.26. Found: C, 48.10; H, 4.93; N, 8.25%. ESI+–MS, m/z: 642 [M–
Cl]+, 606 [M–2Cl–H]+. IR (KBr, selected bands, cmꢀ1): 3354 mw,

84
B.G.M. Rocha et al. / Journal of Catalysis 309 (2014) 79–86
Table 5
Effect of catalyst loading and reaction time for 14 and 15.
Catalyst
Catalyst loading, mol% and (time, h)
T = 80 °C
T = 100 °C
Yields (%)a
a
/b ratio
TON
TOF (hꢀ1
)
Yields (%)a
a
/b ratio
TON
TOF (hꢀ1
)
14
0.1 (3)
0.1 (6)
0.01 (12)
0.001 (24)
93
99
98
28
22/78
19/81
72/28
83/17
9.3 ꢁ 102
9.9 ꢁ 102
9.8 ꢁ 103
2.8 ꢁ 104
3.1 ꢁ 102
1.7 ꢁ 102
8.2 ꢁ 102
1.2 ꢁ 103
99
99
94
40
25/75
24/76
69/31
78/22
9.9 ꢁ 102
9.9 ꢁ 102
9.4 ꢁ 103
4.0 ꢁ 104
3.3 ꢁ 102
1.7 ꢁ 102
7.8 ꢁ 102
1.7 ꢁ 103
15
0.1 (3)
0.1 (6)
0.01 (12)
0.001 (24)
78
92
72
19
20/80
20/80
63/37
77/23
7.8 ꢁ 102
9.2 ꢁ 102
7.2 ꢁ 103
1.9 ꢁ 104
2.6 ꢁ 102
1.5 ꢁ 102
6.0 ꢁ 102
7.9 ꢁ 102
84
98
99
33
23/77
21/79
71/29
72/28
8.4 ꢁ 102
9.8 ꢁ 102
9.9 ꢁ 103
3.3 ꢁ 104
2.8 ꢁ 102
1.6 ꢁ 102
8.3 ꢁ 102
1.4 ꢁ 103
PhC„CH (5.0 ꢁ 10ꢀ4 mol, 1 equiv), Et3SiH (5.0 ꢁ 10ꢀ4 mol, 1 equiv); toluene (0.5 mL).
a
Yields are based on 1H NMR measurements.
3276 mw
1608 m
1H NMR (CDCl3, d): 9.92 (s, 1H, Ccarbene–NH), 8.81 (s, 1H, Ccarbene
NHN), 8.42–7.12 (m, 8H, aryls), 4.51 (s) and 4.02 (s, 2H, CH-Cy),
2.42–1.28 (m, 20H, CH2-Cy). 13C{1H} NMR (CDCl3, d): 165.1 and
153.6 (Ccarbene–NH and C=N), 142.3–127.3 (aryls), 59.1 and 52.2
(CH), 34.2–22.1 (CH2).
m
(N–H); 2933 s, 2857 m
m
(C–H from Cy); 2223 s
m
(C„N);
1608 s
m
(N=C); 1532 s m(N–Ccarbene); 730 m d(C–H from Ar).
m(N=C); 1579 s (N–Ccarbene); 734 m d(C–H from Ar).
m
1H NMR (CDCl3, d): 10.94 (s, 1H, Ccarbene–NH), 9.64 (s, 1H, Ccarbene
–
–
NHN), 8.35–6.93 (m, 18H, aryls), 2.49 (s), 2.44 (s), 2.29 (s), and 2.16
(s, 12H, Me). 13C{1H} NMR (CDCl3, d): 167.0 and 151.6 (Ccarbene–NH
and C=N), 151.6–120.3 (aryls), 19.5, 19.4, 18.7, and 18.6 (Me).
(12, 78%). Anal. Calcd for C25H26N4Cl2OPt: C, 45.19; H, 3.94; N,
8.43. Found: C, 45.42; H, 3.87; N, 8.27%. ESI+–MS, m/z: 665
[M + H]+, 629 [M–Cl]+. ESI––MS, m/z: 663 [M–H]ꢀ. IR (KBr, selected
(9, 81%). Anal. Calcd for C21H30N4Cl2OPt: C, 40.65; H, 4.87; N,
9.03. Found: C, 40.62; H, 4.77; N, 9.07%. ESI+–MS, m/z: 584 [M–
Cl]+, 548 [M–2Cl–H]+. IR (KBr, selected bands, cmꢀ1): 3352 mw,
bands, cmꢀ1): 3254 mw, 3181 mw
(N=C); 1562 s
m
(N–H); 2196 s
m(C„N); 1622 s
m
m
(N–Ccarbene); 764 m d(C–H from Ar). 1H NMR
3232 mw
(C„N); 1621 s
Ar). 1H NMR (CDCl3, d): 11.56 (s, 1H, OH), 9.98 (s, 1H, Ccarbene
NH), 9.42 (s, 1H, Ccarbene–NHN), 8.44 (s, 1H, CH=N), 7.18–6.74 (m,
4H, aryls), 4.58 (s) and 4.12 (s, 2H, CH-Cy), 2.40–1.32 (m, 20H,
CH2-Cy). 13C{1H} NMR (CDCl3, d): 168.6 and 155.7 (Ccarbene–NH
and C=N), 152.8 (C–O), 131.6–128.1 (aryls), 58.7 and 53.2 (CH),
33.6–21.5 (CH2).
m
(N–H); 2962 m, 2932 s
m
(C–H from Cy); 2226 s
(CDCl3, d): 11.72 (s, 1H, OH), 10.12 (s, 1H, Ccarbene–NH), 9.72 (s,
1H, Ccarbene–NHN), 8.44 (s, 1H, CH=N), 7.16–6.71 (m, 10H, aryls),
2.38 (s), 2.29 (s), 2.09 (s), and 2.03 (s, 12H, Me). 13C{1H} NMR
(CDCl3:DMSO-d6, 9:1 v/v, d): 166.2 and 153.7 (Ccarbene–NH and
C=N), 151.9 (C–O), 131.6–128.1 (aryls), 19.2, 19.0, 18.8, and 18.3
(Me).
m
m
(N=C); 1578 s (N–Ccarbene); 803 m d(C–H from
m
–
(13, 76%). Anal. Calcd for C29H24N4Cl4Pt: C, 45.51; H, 3.16; N,
7.32. Found: C, 45.42; H, 3.05; N, 7.27%. ESI+–MS, m/z: 729 [M–
Cl]+. ESIꢀ–MS, m/z: 763 [M–H]ꢀ. IR (KBr, selected bands, cmꢀ1):
(11, 76%). Anal. Calcd for C31H27N4Cl2Pt: C, 51.60; H, 3.77; N,
7.75. Found: C, 51.53; H, 3.91; N, 7.67%. ESI+–MS, m/z: 723
[M + H]+, 686 [M–Cl]+. IR (KBr, selected bands, cmꢀ1): 3309 mw,
3254 mw, 3187 mw
1536 s
(N–Ccarbene); 777 m d(C–H from Ar). 1H NMR (CDCl3, d):
9.74 (s, 1H, Ccarbene–NH), 9.52 (s, 1H, Ccarbene–NHN), 7.65–6.92
m(N–H); 2189 s m(C„N); 1618 m m(N=C);
m
3220 mw m(N–H); 2919–2851 m m(C–H from Cy); 2196 s m(C„N);

B.G.M. Rocha et al. / Journal of Catalysis 309 (2014) 79–86
85
(m, 16H, aryls), 2.70 (s) and 2.17 (s, 6H, Me). 13C{1H} NMR (CDCl3,
d): 167.1 and 158.2 (Ccarbene–NH and C=N), 138.9–125.5 (aryls),
20.6 and 19.2 (Me).
mixture
of
triethyl(1-phenylvinyl)silane
(
a
product,
J2HH ¼ ca:3 Hz) and (E)-triethyl(styryl)silane (b-(E) isomer,
J3HH ¼ ca:19 Hz) [33,34]. Quantifications were performed upon
integration of the selected peaks of the product with those of the
standard. In some cases, the products were isolated by extraction
of the residue after evaporation of the reaction mixture with CH2-
Cl2, followed by column chromatography on silica gel (Fluka 40/60;
hexane/ethyl acetate).
Acknowledgments
This work has been partially supported by the Fundação para a
Ciência e a Tecnologia (FCT), Portugal, its PPCDT program (FEDER
funded) and through the research projects PTDC/QUI-QUI/
098760/2008, PTDC/QUI-QUI/109846/2009 and PEst-OE/QUI/
UI0100/2013 and PhD fellowship for RSC (SFRH/BD/90280/2012).
The authors thank Saint Petersburg State University for a research
Grant (2011–2013), the Federal Targeted Program ‘‘Scientific and
Scientific-Pedagogical Personnel of the Innovative Russia in
2009–2013’’ (contract P676 from 20/05/2010 and Agreement No.
14.B37.21.0794), Russian Fund for Basic Research (Grants 12-03-
00076-a, 12-03-33071, and 13-03-12411-ofim). V.Y.K. gratefully
acknowledges a travel grant (Meropriyatie 6; 2013) from Saint
Petersburg State University.
(14, 85%). Anal. Calcd for C29H22N4Cl4Pt: C, 45.63; H, 2.90; N,
7.34. Found: C, 45.42; H, 3.04; N, 7.27%. ESI+–MS, m/z: 764
[M + H]+, 726 [M–Cl]+. IR (KBr, selected bands, cmꢀ1): 3220 w,
3187 mw
C
m(N–H); 2194 s m(C„N); 1607 s m(N=C); 1534 s m(N–
carbene); 781 m d(C–H from Ar). 1H NMR (CDCl3, d): 10.93 (s,
1H, Ccarbene–NH), 9.72 (s, 1H, Ccarbene–NHN), 8.33–6.93 (m, 14H,
aryls), 2.74 (s) and 2.21 (s, 6H, Me). 13C{1H} NMR (CDCl3, d):
167.9 and 152.5 (Ccarbene–NH and C=N), 133.1–120.2 (aryls),
20.7 and 19.2 (Me).
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.jcat.2013.09.003.
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