Alkali-Metal-Catalyzed Cross-Dehydrogenative Couplings of Hydrosilanes with Amines

Article abstract of DOI:10.1002/cctc.201501356

We report the N-H/H-Si cross-dehydrogenative coupling (CDC) of hydrosilanes and amines with high conversion (>90 %) and chemoselectivity for the production of silazanes, using group 1 metal hexamethyldisilazides [MN(SiMe₃)₂] (M=Li, Na, K) as precatalysts under mild conditions. [KN(SiMe₃)₂] showed higher activity than the congeneric lithium and sodium salts. The catalyzed CDC reaction displays a broad substrate scope. Phenylsilane and diphenylsilane react with a number of amines under ambient conditions; more elevated temperature is required for triphenylsilane to undergo CDC reactions. The intermediate lithium complex [(THF)₂Li-{N(SiHPh₂)(Dipp)}] (1) has been isolated and characterized in an attempt to identify the operative reaction mechanism.

Full text of DOI:10.1002/cctc.201501356

DOI: 10.1002/cctc.201501356
Full Papers
Alkali-Metal-Catalyzed Cross-Dehydrogenative Couplings
of Hydrosilanes with Amines
Srinivas Anga,[a] Yann Sarazin,[b] Jean-FranÅois Carpentier,*[b] and Tarun K. Panda*[a]
We report the NÀH/HÀSi cross-dehydrogenative coupling
(CDC) of hydrosilanes and amines with high conversion
(>90%) and chemoselectivity for the production of silazanes,
using group 1 metal hexamethyldisilazides [MN(SiMe3)2] (M=
Li, Na, K) as precatalysts under mild conditions. [KN(SiMe3)2]
showed higher activity than the congeneric lithium and
sodium salts. The catalyzed CDC reaction displays a broad sub-
strate scope. Phenylsilane and diphenylsilane react with
a number of amines under ambient conditions; more elevated
temperature is required for triphenylsilane to undergo CDC re-
actions. The intermediate lithium complex [(THF)2Li-
{N(SiHPh2)(Dipp)}] (1) has been isolated and characterized in an
attempt to identify the operative reaction mechanism.
Introduction
Sustainable production of chemicals in modern industrial pro-
cesses requires high efficiency in any organic reactions, by
minimizing by-products and wastes. Well-defined organometal-
lic complexes have played a key role in homogeneous catalysis
and the development of environmentally benign processes. In
particular, metal-catalyzed cross-couplings constitute a power-
ful methodology to connect two molecular entities.[1] The
cross-dehydrocoupling (CDC) of NÀH and SiÀH fragments has
been advocated as an attractive, efficient, and atom-economi-
cal route to silazanes, which are in turn used as silylating
agents,[2] ligands for organometallic compounds,[3] bases,[4] pro-
tecting groups,[5] and precursors for Si/N polymeric materials.[6]
Previously, silazanes have been synthesized through ammonol-
ysis and aminolysis reactions;[7] however, the drawback of this
process lies in the formation of ammonium chlorides as side-
products. As a result, significant efforts have been devoted to
provide an alternative protocol to create SiÀN bonds using
NÀH/HÀSi CDC reactions. Catalyzed reactions have largely in-
volved catalysts based on TiIV,[8] AlIII,[9] CuI,[10] RhI,[5b,11] Ru0,[12]
YbII,[13a,b] YIII,[13c] ZnII,[14] and UIV,[15] or also metal-free frustrated
Lewis pairs (FLPs).[16,5c] SiÀN coupling catalyzed by main-group
metal reagents, chiefly group 2, is particularly effective. Harder
and co-workers first reported that the calcium complex [Ca(h3-
Ph2CNPh)(HMPA)3] (HMPA=hexamethylphosphoramide) cata-
lyzes the CDC formation of SiÀN bonds,[17a] in a way similar to
that of a YbII congener previously reported.[17b] Other alkaline-
earth complexes were later shown to be active CDC precata-
lysts, in particular {TOM}MgMe [TOM=tris-(4,4-dimethyl-2-oxa-
zolinyl)phenyl-borate)] disclosed by Sadow and co-workers,[18a]
and M{N(SiMe3)2}2 (M=Mg, Ca, Sr) as reported by Hill et al.[18b]
Very recently, some of us showed that Ba{E(SiMe3)2}2(THF)x (E=
N, x=2; E=CH, x=3) and related heteroleptic alkaline-earth
complexes are very active, productive, and chemoselective pre-
catalysts for CDC reactions.[18c–e] Elsewhere, Mulvey and Robert-
son have recently reviewed the broad utility of various alkali
metal amides.[19] The CDC of the amine–borane adduct
Me2NH·BH3 catalyzed by alkali hexamethyldisilazides was re-
ported by Hill et al.[20] The KH-mediated formation of oligo-
and polysilazanes, which constitute Si3N4 preceramic polymers,
was reported by Seyferth and co-workers.[6a,c] On the other
hand, the use of alkali amides for the CDC of amines and hy-
drosilanes has not been reported to date. As they are easily
available, nontoxic, and economically viable, we were keen on
assessing their use as precatalysts in this catalyzed reaction.
We report here the CDC of hydrosilanes with a wide range of
amines using [MN(SiMe3)2] (M=Li–K) precatalysts.
Results and Discussion
Alkali hexamethyldisilazides [MN(SiMe3)2] (M=Li, Na, K) were
first used as precatalysts for the benchmark CDC of triphenylsi-
lane with pyrrolidine at room temperature under neat condi-
tions (Scheme 1). Illustrative results for this preliminary screen-
ing, using 5 mol% of the complex, are collated in Table 1.
The potassium derivative proved the most active precatalyst
among the three metallic compounds, achieving complete
conversion of the amine to return the silazane Ph3SiN(CH2)4
(Table 1, entry 3), while congeneric lithium and sodium com-
plexes showed slightly less activity (Table 1, entries 1 and 2).[21]
Similarly to what was seen in alkaline-earth mediated CDC cat-
[a] S. Anga, Dr. T. K. Panda
Department of Chemistry
Indian Institute of Technology Hyderabad
Kandi – 502 285, Sangareddy, Telangana (India)
E-mail: tpanda@iith.ac.in
[b] Dr. Y. Sarazin, Prof. J.-F. Carpentier
UniversitØ de Rennes 1
UMR 6226 - Catalyse et OrganomØtalliques
Bât 10C, Campus de Beaulieu – 35042 Rennes (France)
E-mail: jean-francois.carpentier@univ-rennes1.fr
Supporting Information and the ORCID identification number(s) for the
author(s) of this article can be found under http://dx.doi.org/10.1002/
cctc.201501356.
ChemCatChem 2016, 8, 1373 – 1378
1373
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Papers
Scheme 1. Cross-dehydrogenative coupling (CDC) of Ph3SiH and pyrrolidine
catalyzed by alkali hexamethyldisilazide [MN(SiMe3)2].
Table 1. Comparison of the catalytic activity of [MN(SiMe3)2] (M=Li, Na,
K) for the CDC of Ph3SiH with pyrrolidine.[a]
Entry
Catalyst
precursor
t
[h]
Conversion of
silane [%]
1
2
3
[LiN(SiMe3)2]
[NaN(SiMe3)2]
[KN(SiMe3)2]
12
12
12
74
95
100
[a] Reaction conditions: Pyrrolidine (1.0 mmol), triphenylsilane (1.0 mmol),
catalyst precursor (5.0 mol%), neat substrates, 258C. Conversions were
obtained on the basis of the consumption of silane as calculated by
1H NMR spectroscopy.
alysis (Ca<Sr<Ba),[18c–d] the catalytic activity therefore in-
creased with the size, polarisability, and electropositivity of the
metal center.
The CDC reactions of primary and secondary amines with
various hydrosilanes, catalyzed by [KN(SiMe3)2] (5 mol%) were
next investigated. The reactions displayed a broad substrate
scope and the results for the NÀH/HÀSi CDC are displayed in
Table 2. In most cases, complete substrate conversion was ach-
ieved to afford the corresponding silazanes with excellent che-
moselectivity, and in particular without formation of oligosila-
zanes. The reaction of phenylsilane with pyrrolidine proceeded
rapidly at room temperature with vigorous evolution of H2 to
selectively produce either the bis- or tris-dehydrocoupling pro-
ducts A and B, depending on the initial [PhSiH3]0/[pyrrolidine]0
ratio (entries 1 and 2 in Table 2). However, in the case of Et2NH,
only the monocoupled product C was obtained, even in the
presence of excess amine at elevated temperature (608C)
(entry 3). The sterically bulky primary tert-butylamine smoothly
formed the corresponding cyclodisilazane D (entry 4), leading
to the formation of a four-membered Si2N2 core (confirmed by
X-ray diffraction analysis although the data were of poor quali-
ty and hence are not discussed here; it was also characterized
Figure 1. ORTEP drawing of the molecular structures of products H (top)
and K (bottom), showing the atom-labeling scheme; ellipsoids drawn to at
the 50% probability level. H atoms are omitted for clarity.
(entries 7 and 8). The molecular solid-state structure of H was
established by single crystal X-ray analysis (Figure 1, top; see
the Supporting Information for details). The geometry of the Si
atom, with all angles very close to 109.58, is best described as
tetrahedral. The coupling of HNEt2 with Ph2SiH2 to give the
monocoupled I was very facile (entry 9), irrespectively of the
[Ph2SiH2]0/[HNEt2]0 feed ratio. The reaction of tert-butylamine
with Ph2SiH2 yielded selectively the mono- and dicoupled
products J and K (entries 10 and 11) when the number of
equivalents of silane per tBuNH2 was increased from 1 to 2.
The formation of K indicated that the monocoupled product J
undergoes further rapid CDC reaction with a second molecule
of Ph2SiH2.
1
by H and 13C NMR, see the Supporting information). Benzyl-
Compound K was also characterized by single-crystal X-ray
diffraction analysis (Figure 1, bottom). The geometry around
the central N atom can be described as distorted trigonal
planar, with C1ÀN1ÀSi1, Si1ÀN1ÀSi2, and C1ÀN1ÀSi2 angles
equal to 120.2(6), 116.9(4) and 122.8(6)8, respectively. The devi-
ation from pyramidal to planar arrangement is characteristically
owed to the delocalization of the nitrogen electrons lone pair
to the vacant d-orbital on both the Si atoms (pp-dp). However,
the SiÀN bond length [1.732(7) Š] in K is slightly elongated
with respect to those in H [1.707(3) Š], likely due to the pres-
ence of two N atoms attached to the quaternary Si atom in H,
while the Si is tertiary in K.
amine reacted with PhSiH3 to provide a mixture of compounds
which contained predominantly (>60%) the monocoupled
product
E (entry 5); similar observations were reported
before.[18b] The cumbersome aromatic 2,6-diisopropylaniline
(DippH) could also be smoothly converted (90%) to the mono-
coupled silazane F but only at slightly higher temperature
(608C, entry 6), presumably because of the enhanced steric
crowding about the nitrogen atom and the low nucleophilicity
of anilines. We next extended our investigation to CDC reac-
tions of the moderately bulky Ph2SiH2. Pyrrolidine reacted with
this silane at room temperature to afford quantitatively and se-
lectively the mono- and dicoupled silazanes G and H with ini-
tial ratios [Ph2SiH2]0/[pyrrolidine]0 of 1:1 and 1:2, respectively
The coupling of benzylamine with Ph2SiH2 in 1:1 molar ratio
afforded cyclodisilazane L having a four-membered Si2N2 core
ChemCatChem 2016, 8, 1373 – 1378
www.chemcatchem.org
1374
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Papers
(Table 2, entry 12).[18c] The bulky DippH reacted with
Ph2SiH2 (1:1 molar ratio) to form the monocoupled
product M with 82% conversion even at elevated
temperature (608C, entry 13).
Table 2. CDC reactions of various amines and silanes catalyzed by [KN(SiMe3)2].[a]
Entry Silane
Amine
Molar ratio Product
Conversion
[%][c]
The substrate scope was finally extended to the
more sterically challenging triphenylsilane. The CDC
of this silane with pyrrolidine (Table 2, entry 14) and
with benzylamine (entry 17) gave the corresponding
silazanes N and Q in 99% each at room temperature.
The analogous reactions with Et2NH (entry 15) and
with tBuNH2 (entry 16) proceeded to afford the re-
spective monocoupled products, but required heat-
ing at 608C. With DippH, the reaction was sluggish
and only 29% conversion was observed (entry 18).
The reaction of 1,2-ethylenediamine with Ph3SiH
([Ph3SiH]0/[H2NCH2CH2NH2]0 =2:1) yielded a mixture
of the mono- and dicoupled products S and T in a ap-
proximately 1:3 ratio (entry 19).
1
2
3
PhSiH3
PhSiH3
PhSiH3
pyrrolidine
pyrrolidine
HNEt2
1:2
1:3
1:2
99
99[b]
99
4
5
6
7
PhSiH3
PhSiH3
PhSiH3
tBuNH2
1:1
1:1
1:1
1:1
99
Thus, from this survey of the reactivity of the dif-
ferent coupling partners, it emerges that a clear influ-
ence of steric and electronic factors in both the react-
ing hydrosilanes and amines exists. In the case of
PhSiH3, the reactions proceeded very smoothly under
mild conditions, whereas higher temperature was re-
quired to promote CDC reactions with the more hin-
dered hydrosilanes Ph2SiH2 and even more so for
Ph3SiH. Importantly, it must be noted that under the
chosen conditions, the formation of oligosilazanes
was never observed, by contrast with similar reac-
tions mediated by alkali–hydride bases.[6]
Bn-NH2
99 (60)[d]
90[b]
99
Dipp-NH2
Ph2SiH2 pyrrolidine
Ph2SiH2 pyrrolidine
8
1:2
99
In Scheme 2, two possible mechanistic pathways
are depicted for the CDC reaction between organosi-
lanes and amines mediated by group 1 hexamethyl-
disilazido precatalysts. The first mechanism
(Scheme 2, top) is based on that recently proposed
for the alkaline-earth-promoted catalysis of NÀH/HÀSi
CDC reactions.[18c–d] In the initial step of this stepwise
process, the alkali amide precatalyst reacts with pyr-
rolidine (the archetype of a reactive amine) upon
elimination of HN(SiMe3)2 to generate a metal pyrro-
lide I as the catalytically competent species. Next, nu-
cleophilic attack of the Npyrrolide atom onto the elec-
trophilic Si center of the incoming hydrosilane (illus-
trated with PhSiH3 in Scheme 2) furnishes the inter-
mediate II, featuring an hypervalent silicate atom,
which then undergoes b-hydrogen transfer to the
metal ion to give the transient metal hydride [MH]
(III) upon release of the coupled silazane. The metal
hydride next reacts with another molecule of pyrroli-
dine to regenerate the active metal–pyrrolido species
with elimination of H2. The rival pathway (Scheme 2,
bottom) is a more traditional s-bond metathesis. In
this case, the reaction proceeds via a four-membered
cyclic transition state; it also entails the key participa-
tion of a metal hydride (III). Mechanisms different
from these two scenarios are also possible, as evoked
by Hill et al. for the alkaline-earth-metal catalyst.[18a]
9
Ph2SiH2 Et2NH
1:1
1:1
99
99
10
Ph2SiH2 tBuNH2
11
12
13
Ph2SiH2 tBuNH2
Ph2SiH2 Bn-NH2
Ph2SiH2 Dipp-NH2
2:1
1:1
1:1
99
99
82[b]
14
15
Ph3SiH
Ph3SiH
pyrrolidine
Et2NH
1:1
1:1
99
99[b]
ChemCatChem 2016, 8, 1373 – 1378
www.chemcatchem.org
1375
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Papers
The data at our disposal at this moment do not allow
us to discriminate which mechanism prevails.
Table 2. (Continued)
Entry Silane Amine
Molar ratio Product
Conversion
[%][c]
To check whether metal hydrides can potentially
intervene in the catalytic cycle, the CDC of PhSiH3
and pyrrolidine in 1:1 molar ratio catalyzed by KH
(5 mol%) was performed at room temperature. The
reaction indeed proceeded as to afford the corre-
sponding silazane, however, the observed conversion
during triplicate experiments was only 25%. At 608C,
it only reached 63% after 12 h. Such low to moderate
levels of conversion are most probably the outcome
of the very poor solubility and partial passivation of
commercial KH.[22] In addition, during a controlled
equimolar reaction between DippH with Ph2SiH2 in
the presence of one equivalent of [LiN(SiMe3)2] in
THF, the complex [(THF)2Li{N(SiHPh2)(Dipp)}] (1) was
isolated in 87% yield. As depicted in Scheme 3, this
lithium complex is presumably formed upon reaction
of the monocoupled product M with a putative lithi-
um hydride [LiH] species such as that (III) proposed
as an intermediate in the mechanisms suggested in
Scheme 2. Complex 1 was characterized in solution
16
17
Ph3SiH
Ph3SiH
tBuNH2
1:1
1:1
99[b]
99
Bn-NH2
18
19
Ph3SiH
Ph3SiH
Dipp-NH2
1:1
29[b]
mono:bis
23:77
H2N(CH2)2NH2 2:1
[a] Reaction conditions: [KN(SiMe3)2] (5 mol%), neat reagents, room temperature, 12 h
(unoptimized reaction time). [b] Reaction performed at 608C. [c] Conversions were cal-
culated on the basis of the consumption of the silane, from integration of signals in
the 1H NMR spectra. [d] Full conversion (99%) of reagents was observed, to yield
a mixture of compounds that contained predominantly (60%) the monocoupled
product.
1
by H and 13C{1H} NMR, and its molecular solid-state
Scheme 3. Stoichiometric reaction of DippH with diphenylsilane (1:1 molar
ratio) in the presence of [LiN(SiMe3)2] to give complex 1.
structure was established by X-ray diffraction analysis
(Figure 2). It crystallizes in the monoclinic space group P21,
containing two independent molecules in the unit cell. The Li
ion is coordinated by the nitrogen atom of the disilazide and
by two THF molecules. The LiÀN distance is 1.929(9) Š, and
two LiÀO distances amount to 1.895(9) and 1.911(9) Š. The
geometry around Li can be described as distorted trigonal
planar, with the ion resting 0.12 Š above the mean plane de-
fined by the N1, O1 and O2 atoms. As [LiN(SiMe3)2] is itself in-
sufficiently basic to deprotonate M, it is very tempting to
regard 1 as the product formed by reaction of “LiH” and M,
thereby indirectly supporting the likely existence of metal hy-
drides in the mechanistic scenario evoked in Scheme 2.
Conclusions
Alkali hexamethyldisilazides [MN(SiMe3)2] act as competent pre-
catalysts for the cross-dehydrogenative coupling of SiÀH and
NÀH fragments. The potassium derivative is the best precata-
Scheme 2. Possible mechanisms for the cross-dehydrogenative coupling of
phenylsilane with pyrrolidine catalyzed by [MN(SiMe3)2] (M=Li, Na, K). Top,
via stepwise silicate intermediate; bottom, via s-bond metathesis.
ChemCatChem 2016, 8, 1373 – 1378
www.chemcatchem.org
1376
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Papers
tensities of resonances characteristic of the substrates and prod-
ucts.
[(THF)2Li{N(SiHPh2)(Dipp)}] (1)
In a glovebox, to a stirred solution of Li[N(SiMe3)2] (1.0 mmol,
167 mg) in THF (10 mL) were added 2,6-di-isopropylaniline
(1.0 mmol, 177 mg) and then diphenylsilane (1.0 mmol, 184 mg).
Foaming was rapidly observed, and the mixture was left to stir
overnight. After this time, the THF was removed in vacuo to give
a white solid that was recrystallized from hexane at À208C over-
night. Suitable colorless single crystals suitable for XRD studies
1
characterization were isolated in 87% (443 mg). H NMR (400 MHz,
C6D6, 258C): d=7.71–7.69 (4H, m, ArH), 7.02–7.68 (6H, m, ArH),
7.02–6.98 (2H, m, ArH), 6.96–6.73 (1H, m, ArH), 6.23 (1H, s, SiH),
4.12 (2H, sept, iPrCH), 2.90–2.86 (8H, m, O-CH2), 1.11 (12H, d, J=
6.8 CH3), 0.94–0.92 ppm (8H, m, O-CH2-CH2). 13C{1H} NMR (100 MHz,
C6D6, 258C): d=154.2 (CAr), 143.9 (CAr), 142.5 (CAr), 135.1 (CAr),
135.0 (CAr), 127.6 (CAr), 122.7 (CAr), 116.0 (CAr), 67.9 (O-CH2), 27.7
(iPrCH), 25.1 (O-CH2-CH2), 24.7 ppm (CH3). Elemental Analysis:
C32H44LiNO2Si (509.72): Calcd. C 75.40, H 8.70, N 2.75. Found C
75.19, H 8.57, N 2.64.
Figure 2. ORTEP drawing of intermediate lithium complex 1 showing the
atom labeling scheme; ellipsoids drawn at the 50% probability. H atoms are
omitted for clarity. Selected bond lengths [Š] and angles [8] are given. Li1À
N1 1.929(9) Li1ÀO1 1.895(9) Li1ÀO2 1.911(9) N1ÀSi1 1.656(4) N1ÀC1 1.396(6)
O1-Li1-O2 104.2(4) O2-Li1-N1 120.9(5) Li1-N1-C1 109.6(4) Li1-N1-Si1 115.1(3)
C1-N1-Si1 135.3(3).
lyst, achieving high conversion and chemoselectivity with
a large variety of hydrosilanes and amines. Phenylsilane and di-
phenylsilane are reactive substrates at room temperature;
higher temperature is required for triphenylsilane. The mecha-
nism of this catalyzed reaction is unclear at this stage, but it
almost certainly entails the participation of metal hydrido spe-
cies.
Characterization of the products
The data for PhSi(N(CH2)4)3 (A), PhSiH(N(CH2)4)2 (B), PhSiH2NEt2 (C),
PhSiH2CH2Ph
(E),PhSiH2(NHDipp)
(F),
PhSi2H(N(CH2)4)
(G),
Ph2Si(N(CH2)4)2 (H), Ph2SiHNEt2 (I), Ph2SiHNHtBu (J), (Ph2SiNBn)2 (L),
Ph2SiH(NHDipp) (M), Ph3SiN(CH2)4 (N), Ph2SiHNEt2 (O), Ph3Si(NHtBu)
(P), Ph3Si(NHBn) (Q), Ph3Si(NHDipp) (R), NH2(CH2)2NHSiPh3 (S), and
Ph3SiNH2(CH2)2NHSiPh3 (T) are already described in the literature.[18]
1H and 13C NMR spectra of silylamines D, K and the lithium com-
plex 1 are given in the Supporting Information.
Experimental Section
General
All manipulations of air-sensitive materials were performed under
inert atmosphere in flame dried Schlenk-type glassware, either on
a dual manifold Schlenk line interfaced with a high vacuum
(10À4 Torr) line, or in an argon-filled M. Braun glovebox. THF was
predried over Na wire and distilled under nitrogen from sodium
and benzophenone ketyl prior to use. Hydrocarbon solvents (tolu-
ene, hexane and n-pentane) were distilled under nitrogen from
Acknowledgements
This work was supported by the Science and Engineering Re-
search Board (SERB), Department of Science and Technology
(DST), India, under project no. (SB/S1/IC/045/2013) and S.A.
thanks CSIR for his PhD fellowship. S.A. thanks the Science and
Technology Department, Embassy of France in India, Bangalore,
for travel grants to visit France.
1
LiAlH4 and stored in the glovebox. H NMR (400 MHz) and 13C{1H}
(100 MHz) spectra were recorded on a BRUKER AVANCE III-400
spectrometer. All amines and silanes were purchased from either
Sigma Aldrich or Alfa Aesar. Amines were distilled over CaH2 prior
to use. LiN(SiMe3)2, NaN(SiMe3)2 and KN(SiMe3)2 were purchased
from Sigma Aldrich and used as received. NMR solvent (C6D6) was
purchased from Sigma Aldrich and dried over Na/K alloy.
Keywords: alkali metals
dehydrogenation · hydrosilanes and silazanes
·
amines
·
cross-coupling
·
[1] a) C. S. Yeung, V. M. Dong, Chem. Rev. 2011, 111, 1215; b) C. J. Scheuer-
mann, Chem. Asian J. 2010, 5, 436; c) G. E. Dobereiner, R. H. Crabtree,
Chem. Rev. 2010, 110, 681; d) C. J. Li, Acc. Chem. Res. 2009, 42, 335;
e) X. M. Jie, Y. P. Shang, P. Hu, W. P. Su, Angew. Chem. Int. Ed. 2013, 52,
3630; Angew. Chem. 2013, 125, 3718; f) N. Kuhl, M. N. Hopkinson, F. Glo-
rius, Angew. Chem. Int. Ed. 2012, 51, 8230; Angew. Chem. 2012, 124,
8354.
[2] Y. Tanabe, T. Misaki, M. Kurihara, A. Iida, Y. Nishii, Chem. Commun. 2002,
1628.
[3] M. Lappert, P. P. Power, A. Protchenko, A. Seeber, Metal Amide Chemistry,
Wiley, Chichester, 2009.
Typical procedure for CDC reactions
Catalyzed cross-dehydrocoupling (CDC) reactions were performed
by using the following standard protocol. In the glovebox, the
chosen precatalyst (0.05 mmol) was loaded into a Schlenk tube
and subsequently the amine (n”0.05 mmol, n equiv.) followed by
silane (n’”0.05 mmol, n’ equiv.) were added to the Schlenk tube.
The reaction was stirred in an oil bath at the desired temperature
(25 or 608C). After the required period of time, the reaction was
quenched by adding commercial (not dried) C6D6 to the mixture.
Substrate conversion was monitored by examination of the
1H NMR spectrum of the reaction mixture, comparing relative in-
[4] L. F. Fieser, M. Fieser, Reagents in Organic Chemistry, John Wiley & Sons,
Inc., Hoboken, 1967.
[5] a) D. W. Robbins, T. A. Boebel, J. F. Hartwig, J. Am. Chem. Soc. 2010, 132,
4068; b) S. Itagaki, K. Kamata, K. Yamaguchi, N. Mizuno, Chem. Commun.
ChemCatChem 2016, 8, 1373 – 1378
www.chemcatchem.org
1377
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Papers
2012, 48, 9269; c) L. Greb, S. Tamke, J. Paradies, Chem. Commun. 2014,
50, 2318.
M. F. Mahon, T. P. Robinson, Chem. Sci. 2013, 4, 4212; c) C. Bellini, J.-F.
Carpentier, S. Tobisch, Y. Sarazin, Angew. Chem. Int. Ed. 2015, 54, 7679;
Angew. Chem. 2015, 127, 7789; d) C. Bellini, J.-F. Carpentier, S. Tobisch, Y.
Sarazin, Chem. Eur. J. 2016, DOI: 10.1002/chem.201504316; e) C. Bellini,
C. Orione, J.-F. Carpentier, Y. Sarazin, Angew. Chem. Int. Ed. 2016, DOI:
10.1002/anie.201511342; Angew. Chem. 2016, DOI: 10.1002/
ange.201511342.
[6] a) D. Seyferth, G. H. Wiseman, J. Am. Ceram. Soc. 1984, 67, C132; b) Y. D.
Blum, K. B. Schwartz, R. M. Laine, J. Mater. Sci. 1989, 24, 1707; c) N. R.
Dando, A. J. Perrotta, C. Strohmann, R. M. Stewart, D. Seyferth, Chem.
Mater. 1993, 5, 1624; d) M. Birot, J.-P. Pilot, J. Dunogu›s, Chem. Rev.
1995, 95, 1443.
[7] R. Fessenden, J. S. Fessenden, Chem. Rev. 1961, 61, 361.
[8] H. Q. Liu, J. F. Harrod, Organometallics 1992, 11, 822.
[9] L. K. Allen, R. Garcia-Rodriquez, D. S. Wright, Dalton Trans. 2015, 44,
12112.
[10] H. Q. Liu, J. F. Harrod, Can. J. Chem. 1992, 70, 107.
[11] H. Kono, I. Ojima, M. Matsumoto, Y. Nagai, Org. Prep. Proced. Int. 1973,
5, 135.
[19] P. Bellham, M. S. Hill, G. Kociok-Kçhn, Dalton Trans. 2015, 44, 12078.
[20] R. E. Mulvey, S. D. Robertson, Angew. Chem. Int. Ed. 2013, 52, 11470;
Angew. Chem. 2013, 125, 11682.
[21] In the coupling of triphenylsilane and pyrrolidine catalyzed by
ꢀ5 mol% n-butyl lithium, complete (99%) conversion was observed
after 12 h at RT. A very vigorous reaction occurred while adding n-butyl
lithium into the reaction mixture. This is attributed to the higher reac-
tivity and basicity of alkyl lithium reagents relative with LiN(SiMe3)2. Be-
sides, the accurate knowledge of the contents of nBuLi is hampered by
the recurring variations of the concentration of commercially available
solutions, whereas solid nBuLi cannot be stored and handled safely.
Moreover, common alkyl sodium and potassium compounds are not
available. For these reasons, alkali amides constitute much more con-
venient precursors of CDC catalytic systems.
[12] C. D. F. Kçnigs, M. F. Müller, N. Aiguabella, H. F. T. Klare, M. Oestreich,
Chem. Commun. 2013, 49, 1506.
[13] a) K. Takaki, T. Kamata, Y. Miura, T. Shishido, K. Takehira, J. Org. Chem.
1999, 64, 3891; b) W. Xie, H. Hu, C. Cui, Angew. Chem. Int. Ed. 2012, 51,
11141; Angew. Chem. 2012, 124, 11303; c) A. E. Nako, W. Chen, A. J. P.
White, M. R. Crimmin, Organometallics 2015, 34, 4369.
[14] T. Tsuchimoto, Y. Iketani, M. Sekine, Chem. Eur. J. 2012, 18, 9500.
[15] J. X. Wang, A. K. Dash, J.-C. Berthet, M. Ephritikhine, M. S. Eisen, J. Orga-
nomet. Chem. 2000, 610, 49.
[22] For soluble alkali hydrides, see: a) A. Stasch, Angew. Chem. Int. Ed. 2012,
51, 1930; Angew. Chem. 2012, 124, 1966; b) A. Stasch, Dalton Trans.
2014, 43, 7078; c) A. Stasch, Chem. Commun. 2015, 51, 5056.
[16] a) M. PØrez, C. B. Caputo, R. Dobrovetsky, D. W. Stephan, Proc. Natl.
Acad. Sci. USA 2014, 111, 10917.
[17] a) F. Buch, S. Harder, Organometallics 2007, 26, 5132; b) Y. Makioka, Y.
Tangiguchi, Y. Fugiwara, K. Takaki, Z. Hou, Y. Wakatsuki, Organometallics
1996, 15, 5476.
[18] a) J. F. Dunne, S. R. Neal, J. Engelkemier, A. Ellern, A. D. Sadow, J. Am.
Chem. Soc. 2011, 133, 16782; b) M. S. Hill, D. J. Liptrot, D. J. MacDougall,
Received: December 11, 2015
Revised: January 22, 2016
Published online on February 22, 2016
ChemCatChem 2016, 8, 1373 – 1378
www.chemcatchem.org
1378
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim