Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes

Article abstract of DOI:10.1016/j.tet.2019.04.062

The ligand-redistribution reactions of aryl- and alkoxy-hydrosilanes can potentially cause the formation of gaseous hydrosilanes, which are flammable and pyrophoric. The ability of generic nucleophiles to initiate the ligand-redistribution reaction of commonly used hydrosilane reagents was investigated, alongside methods to hinder and halt the formation of hazardous hydrosilanes. Our results show that the ligand-redistribution reaction can be completely inhibited by common electrophiles and first-row transition metal pre-catalysts.

Full text of DOI:10.1016/j.tet.2019.04.062

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Nucleophile induced ligand rearrangement reactions of alkoxy- and
arylsilanes
,
, *
Jamie H. Docherty a **, Andrew P. Dominey b, Stephen P. Thomas a
a EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, UK
b GSK Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire SG1 2NY, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The ligand-redistribution reactions of aryl- and alkoxy-hydrosilanes can potentially cause the formation
of gaseous hydrosilanes, which are flammable and pyrophoric. The ability of generic nucleophiles to
initiate the ligand-redistribution reaction of commonly used hydrosilane reagents was investigated,
alongside methods to hinder and halt the formation of hazardous hydrosilanes. Our results show that the
ligand-redistribution reaction can be completely inhibited by common electrophiles and first-row
transition metal pre-catalysts.
Received 16 February 2019
Received in revised form
23 April 2019
Accepted 24 April 2019
Available online xxx
© 2019 Elsevier Ltd. All rights reserved.
Keywords:
Catalysis
Silane
Reduction
Redistribution
Phenylsilane
1. Introduction
[10], Sm [11], Mo [12], Co [13], Ti [14], Yb [15] and Ru [16]. Similarly,
a number of hydride sources, including LiAlH4, KH and NaH, have
Hydrosilanes are a highly important class of reagent used in
widespread applications from organic synthesis to polymer pro-
duction [1,2]. The formation of carbon-silicon bonds by olefin
hydrosilylation constitutes one of the largest applications of ho-
mogeneous catalysis with the silicones industry forecast to be
worth $18 billion per annum by 2021 (Scheme 1, a) [3]. Predomi-
nantly these reactions have been achieved using platinum-based
catalysts, however Earth-abundant alternatives have emerged [4].
The utility of hydrosilane reagents has been further exemplified by
their use in other reductive transformations; such as the hydrogen-
atom transfer mediated reductive functionalisation of alkenes
(Scheme 1, b) [5], carbonyl reduction [6] and nitro-group reduction
[7].
proven effective towards ligand-redistribution [17]. The common
feature in all ligand-redistribution reactions of phenylsilane is the
formation of a mixture of products containing: diphenylsilane,
silane (SiH4) and triphenylsilane.
Hu has shown that stable alkoxy-hydrosilane reagents can be
used as surrogates to access volatile and challenging to handle
alkyl-hydrosilanes (Scheme 1, d) [18]. Using this method, olefin
hydrosilylation could be used to access primary hydrosilane prod-
ucts that would have normally required the use of gaseous
hydrosilane reactants.
Given that silane (SiH4, b.p. /112 ꢀC) [19], methylsilane
(MeSiH3, b.p /57 ꢀC) [20] and dimethylsilane (Me2SiH2, /20 ꢀC)
[21] are hazardous, flammable and pyrophoric gases, the use and
generation of these reagents presents a safety concern [22].
Importantly Hu has shown that while ligand-redistribution occurs
when using alkoxy-hydrosilanes in the presence of NaOtBu, there
was no build-up of hazardous gaseous alkyl-hydrosilanes in the
presence of the nickel-catalyst [18]. Similarly, Thomas, and others,
have made use of alkoxide salts to enable pre-catalyst activation for
a range of reductive functionalisation reactions using Earth-
abundant metals with no build-up or formation of hazardous
gases under the catalytic reaction conditions [23].
While hydrosilane reagents show a wide breadth of reactivity in
reductive transformations, they have often been observed to un-
dergo ligand-redistribution reactions (Scheme 1, c) [8]. Most
commonly ligand-redistribution reactions of arylsilanes have been
observed using metal complexes as catalysts; including: Ir [9], Pd
* Corresponding author.
** Corresponding author.
E-mail addresses: jdocher5@ed.ac.uk (J.H. Docherty), stephen.thomas@ed.ac.uk
(S.P. Thomas).
https://doi.org/10.1016/j.tet.2019.04.062
0040-4020/© 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: J.H. Docherty et al., Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.04.062

2
J.H. Docherty et al. / Tetrahedron xxx (xxxx) xxx
Scheme 1. Utility of silane reagents in modern synthetic chemistry. a Metal-catalysed hydrosilylation of alkene or alkynes. b Reductive functionalisation of alkenes by hydrogen
atom transfer. c Ligand-redistribution reaction of phenylsilane to diphenylsilane, silane and triphenylsilane. d Use of ligand-redistribution as masked hazardous silanes.
2. Results and discussion
catalysed hydrosilylation suggested that the presence of an elec-
trophile, or electrophilic metal complex, may hinder, or retard, the
formation of these hazardous species. We therefore investigated
whether common electrophiles could inhibit the ligand-
redistribution reaction (Fig. 2). By adding the electrophile after
the nucleophile, the initiator of hydrosilane redistribution, any
subsequent reactivity could be monitored to assess whether ligand-
redistribution had stalled. In separate reactions, the ligand-
redistribution of phenylsilane initiated by NaOtBu was monitored
by 1H NMR to which an electrophile was added after 10 min. The
standard reaction, without any added electrophile, displayed ca.
40% conversion after 10 min and continued to a plateau at ca. 84%
conversion after 7 h. However, when benzaldehyde was added,
10 min after initiation, the ligand-redistribution reaction was
completely retarded and the conversion of phenylsilane at each
subsequent time point was equivalent to that observed at 10 min
(Fig. 2, ).
The addition of ethyl benzoate produced the same observation,
with complete cessation of ligand-redistribution (Fig. 2, ). The
addition of either a cobalt(II) dichloride complex (EtBIPCoCl2) or
iron(II) dichloride complex (EtBIPFeCl2) proved similarly effective at
inhibiting the ligand-redistribution reaction (Fig. 2, , ) [24]. Addi-
tion of acetonitrile showed some retardation activity, with a
significantly lower observed rate of reaction when compared to the
control reaction with no added acceptor (Fig. 2, ).
To gain insight into these processes we opted to assess the effect
of the nucleophile on the rate of the reaction. Specifically we
questioned if a variation of the nucleophile loading showed any rate
change in the ligand-redistribution reaction of phenylsilane. Using
sodium tert-butoxide as the nucleophile we monitored the reaction
progress using different loadings (2.5, 3.75 and 5 mol%, Fig. 3, a).
The kinetic data obtained showed similar patterns of reactivity to
that obtained when using other nucleophiles (Fig. 1). On changing
the loading, or concentration, of sodium tert-butoxide there was a
slight but noticeable change in the rate of reactions whereby
increased loading of sodium tert-butoxide led to increased rates of
ligand-redistribution. Taking these results we could use the
These precedents prompted us to consider the factors important
to hydrosilane ligand-redistribution reactions. One important
question was whether any generic nucleophile could be used to
initiate ligand-redistribution. In answering this possibility we
selected phenylsilane as a test substrate in combination with
various nucleophiles (Fig. 1). Using 1H NMR, the reaction progress
of the ligand-redistribution reaction could be directly monitored.
Lithium tert-butoxide proved to be a slow initiator for the reaction,
only achieving 10% conversion after 13 h. Lithium aluminium hy-
dride displayed significantly better reactivity, and steadily con-
verted phenylsilane to a mixture of diphenylsilane, silane and
triphenylsilane over the course of ca. 17 h to 80% total conversion.
Hexamethyldisilazide (HMDS) anions of both sodium and potas-
sium reacted faster than both previous reagents, but achieved less
overall conversion, plateauing at ca. 70%. Sodium- and potassium
tert-butoxide demonstrated the best reactivity towards the ligand-
redistribution reaction, both showing the fastest rate of reaction
and highest conversion. Reaction profiling of all components of the
reaction mixture containing phenylsilane and sodium tert-butoxide
(5 mol%) showed concomitant consumption of phenylsilane and
formation of silane and diphenylsilane. The latter is subsequently
consumed as triphenylsilane is formed (Fig. 1, bottom).
Additionally we tested a range of alkoxy-hydrosilane reagents
in combination with sodium tert-butoxide to both assess the rate
of ligand-redistribution and identify the products of these
reactions (Scheme 2). Methyldiethoxysilane underwent ligand-
redistribution to quickly generate methylsilane and methyl-
triethoxysilane. The analogous dimethylethoxysilane reacted to
form dimethylsilane and dimethyldiethoxysilane. Triethoxysilane
rapidly underwent redistribution to form silane and tetraethox-
ysilane. Tetramethyldisiloxane (TMDS) reacted significantly slower
to give a complex mixture of products, as observed by 1H and 29Si
NMR, with dimethylsilane being one component of the mixture.
1,1,1,3,5,5,5-Heptamethyltrisiloxane (MD’M) slowly decomposed
to an unidentifiable mixture of silicon containing products.
The prevailing reactivity across all alkoxy-hydrosilanes examined
is suggestive of a general pathway towards the entropically
favoured gaseous alkyl-hydrosilanes (or silane). The general reac-
tivity trend observed was: (EtO)3SiH > Me(EtO)2SiH > Me2(EtO)
SiH > PhSiH3 > Me2SiHOSiHMe2 > (Me3SiO)2MeSiH.
graphical variable time normalisation analysis method (VTNA) re-
t
ꢀ
ported by Bures to determine the reaction order in [NaO Bu] [25].
The normalized time scale directly uses reaction profile kinetics
adjusted for t[NaOtBu]n on the x-axis, where t represents time and n
is the order in sodium tert-butoxide. When n ¼ 0.5, overlay be-
tween all reaction profiles was found suggesting that the order with
The absence of a build-up of alkyl-hydrosilane gases in metal-
Please cite this article as: J.H. Docherty et al., Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.04.062

J.H. Docherty et al. / Tetrahedron xxx (xxxx) xxx
3
Scheme 2. Redistribution of various alkoxysilanes with NaOtBu. General reaction
conditions: alkoxysilane (0.4 mmol), NaOtBu (1e5 mol%) in d8-THF (0.8 M). Products
identified by 1H and 29Si NMR. Observed ratios of products in solution, not accounting
for gas dissolution.
Fig. 1. Ligand-redistribution reaction of phenylsilane with various nucleophiles,
monitoring consumption of PhSiH3 (top). Reaction conditions: PhSiH3 (0.4 mmol),
additive (2.5 mol%) in d8-THF (0.8 M). Monitoring formation of distribution products
over time (bottom). Reaction conditions: PhSiH3 (0.4 mmol), NaOtBu (5 mol%) in d8-
THF (0.8 M). Mass balance <100% due to gas loss. Conversions are relative to PhSiH3.
Fig. 2. Ligand-redistribution reaction of phenylsilane with NaOtBu retarded by added
hydride acceptors. Reaction conditions: PhSiH3 (0.4 mmol), NaOtBu (2.5 mol%) in d8-
THF (0.8 M) and hydride acceptor added at 10 min, denoted by dashed black line.
respect to sodium tert-butoxide is 0.5 (Fig. 3, b). The same process
suggested an order with respect to the concentration of phenyl-
silane of 2 (Fig. 3, c, d).
reactions resulted in the cessation of ligand-redistribution. These
strategies may hold promise for use in the safe application and
handling of hazardous hydrosilane reagents from more stable sur-
rogate hydrosilanes.
3. Conclusions
4. Experimental section
In summary, nucleophiles such as alkoxides, hydrides and
nitrogen-based anions serve as good initiators of the ligand-
redistribution reaction of hydrosilane reagents. Phenylsilane
readily underwent ligand-redistribution to form silane, diphe-
nylsilane and triphenylsilane, with the latter formed at a signifi-
cantly slower rate. Alkoxy-hydrosilanes favoured ligand-
redistribution to the corresponding alkyl-hydrosilanes. Signifi-
cantly, the addition of electrophiles or metal pre-catalysts to these
4.1. General
Reaction setup: All reactions were performed in oven (185 ꢀC)
and/or flame dried J-Youngs NMR tubes under an atmosphere of
anhydrous argon. All glassware was cleaned using base (KOH,
iPrOH) and acid (HClaq) baths. All reported reaction temperatures
correspond to ambient room temperature, which was
Please cite this article as: J.H. Docherty et al., Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.04.062

4
J.H. Docherty et al. / Tetrahedron xxx (xxxx) xxx
approximately 20 ꢀC.
NMR spectroscopy: 1H, 13C and 29Si NMR spectra were recorded
on Bruker Avance III 400 and 500 MHz; Bruker AVI 400 MHz; and
Bruker Avance I 600 MHz spectrometers. Chemical shifts are re-
ported in parts per million (ppm). 1H and 13C NMR spectra were
referenced to the residual deuterated solvent peak (d8-THF:
1.73 ppm). Multiplicities are indicated by s (singlet), t (triplet), q
(quartet), sept. (septet). Coupling constants, J, are reported in Hertz
and rounded to the nearest 0.1 Hz. Integration is provided and as-
signments are indicated.
The spin-lattice relaxation value (T1) for PhSiH3 (Si-H) in d8-THF
was measured by the standard inversion recovery method with a
variable delay (d1) and found to be 5 s at room temperature [26]. A
50 s delay between acquisitions was used to allow for reliable in-
tegrations when monitoring consumption of PhSiH3.
Chemicals: All reagents were purchased from Sigma Aldrich,
Alfa Aesar, Acros organics, Tokyo Chemical Industries UK, Fluo-
rochem and Apollo Scientific or synthesised within the laboratory.
Sodium tert-butoxide (97%) was purchased from Sigma Aldrich
(UK).
4.2. Procedures for ligand-redistribution reactions
Reaction monitoring: Ligand-redistribution reactions of phe-
nylsilane were monitored by combination of 1H and 29Si NMR
spectroscopy. Relative conversions of phenylsilane were deter-
mined by comparison of the overall integration of aromatic protons
(7.73e7.27 ppm) to that of phenylsilane (PhSiH3, 4.21 ppm, s, 3H),
diphenylsilane (Ph2SiH2, 4.95 ppm, s, 2H) and silane (SiH4,
3.23 ppm, s, 4H).
General procedure: Hydrosilane (0.4 mmol) was added to d8-
THF (0.5 mL) in a dried J-Youngs NMR tube. Following a vigorous
shake, nucleophile (2.5 mol%, 0.01 mmol) was added and the tube
sealed, shaken and the NMR spectra quickly recorded. The NMR
spectra were subsequently recorded at further time points to obtain
overall reaction progress plots.
Safety note: Given the hazardous nature of the gaseous products
often formed in these reactions, precautions should be taken when
using any hydrosilane reagent, particularly in the absence of elec-
trophile or metal-catalyst or if conducted on a large scale. J-Youngs
NMR tubes containing hazardous product hydrosilanes were care-
i
fully opened and diluted with PrOH (0.5 mL), then NaOH (2 M,
0.5 mL) to destroy remaining hydrosilanes. See also reference [18].
Characterisation: Ligand-redistribution reaction of phenyl-
silane by NaOtBu.1H NMR (500 MHz, d8-THF): 7.73e7.27 (m, 5H, Ar-
H), 4.95 (s, 2H, Ph2SiH2), 4.21 (s, 3H, PhSiH3), 3.23 (s, 4H, SiH4). 29Si
NMR (99 MHz, d8-THF): /33.9 (Ph2SiH2), /60.6 (PhSiH3), /96.2
(SiH4).
MeSiH3 1H NMR (500 MHz, d8-THF): 3.54 (q, J ¼ 4.6 Hz, 3H), 0.21
(q, J ¼ 4.7 Hz, 3H). 29Si NMR (99 MHz, d8-THF): /65.7.
Me2SiH2 1H NMR (500 MHz, d8-THF): 3.80 (sept., J ¼ 4.0 Hz, 2H),
0.17 (t, J ¼ 4.0 Hz, 6H). 29Si NMR (99 MHz, d8-THF): /38.5.
SiH4 1H NMR (500 MHz, d8-THF): 3.23 (s, 4H). 29Si NMR (99 MHz,
d8-THF): /96.2.
Values are in good agreement with those previously reported
[27].
Fig. 3. Ligand-redistribution reaction of phenylsilane with NaOtBu.
a Monitoring
Acknowledgements
consumption of PhSiH3 over time with varied loadings of NaOtBu. Reaction conditions:
PhSiH3 (0.4 mmol), NaOtBu (n mol%) in d8-THF (0.8 M). b VTNA x-axis normalisation for
[NaOtBu]. c Monitoring the formation of Ph2SiH2 over time at varied concentration of
PhSiH3. Reaction conditions: PhSiH3 (0.4 mmol), NaOtBu (2.5 mol%) in d8-THF (n M)
d VTNA x-axis normalisation for [PhSiH3]. Conversions and %Ph2SiH2 observed are
relative to PhSiH3.
S.P.T. acknowledges the University of Edinburgh for a Chancel-
lor's Fellowship and the Royal Society for a University Research
Fellowship. J.H.D. and S.P.T. acknowledge GlaxoSmithKline and the
EPSRC (EP/M506515/1) for post-doctoral funding.
Please cite this article as: J.H. Docherty et al., Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.04.062

J.H. Docherty et al. / Tetrahedron xxx (xxxx) xxx
5
g) X. Yang, C. Wang, Manganese-catalyzed hydrosilylation reactions, Chem.
Asian J. 13 (17) (2018) 2307e2315;
References
h) T.K. Mukhopadhyay, M. Flores, T.L. Groy, R.J. Trovitch, A highly active
manganese precatalyst for the hydrosilylation of ketones and esters, J. Am.
Chem. Soc. 136 (3) (2014) 882e885;
ꢀ
[1] a) F.J. Fernandez-Alvarez, A.M. Aitani, L.A. Oro, Homogeneous catalytic
reduction of CO2 with hydrosilanes, Catal. Sci. Technol. 4 (3) (2014) 611e624;
b) G.L. Witucki, Back to Basics A Silane Primer : Chemistry and Applications of
AIkoxy Silanes, vol. 65, 1993;
i) J.R. Carney, B.R. Dillon, S.P. Thomas, Recent advances of manganese catalysis
for organic synthesis, Eur. J. Org. Chem. 2016 (23) (2016) 3912e3929.
[7] a) R.G. de Noronha, C.C. Romaeo, A.C. Fernandes, Highly chemo- and regiose-
lective reduction of aromatic nitro compounds using the system silane/oxo-
rhenium complexes, J. Org. Chem. 74 (18) (2009) 6960e6964;
b) K. Zhu, M.P. Shaver, S.P. Thomas, Chemoselective nitro reduction and
c) J. Pesti, G.L. Larson, Tetramethyldisiloxane:
a practical organosilane
reducing agent, Org. Process Res. Dev. 20 (2016) 1164e1181;
d) J.Y. Corey, Reactions of hydrosilanes with transition metal complexes,
Chem. Rev. 116 (19) (2016) 11291e11435;
e) J.J. Chrusciel, E. Lesniak, Modification of epoxy resins with functional si-
lanes, polysiloxanes, silsesquioxanes, silica and silicates, Prog. Polym. Sci. 41
(2015) 67e121;
ꢀ
ꢀ
hydroamination using
a single iron catalyst, Chem. Sci. 7 (5) (2016)
3031e3035.
[8] a) T. Yoshida, L. Ilies, E. Nakamura, Silylation of aryl halides with mono-
organosilanes activated by lithium alkoxide, Org. Lett. 20 (10) (2018)
2844e2847;
€
€
f) E. Yilgor, I. Yilgor, Silicone containing copolymers: synthesis, properties and
applications, Prog. Polym. Sci. 39 (2014) 1165e1195.
[2] a) J.D. Citron, Reductions with organosilicon hydrides. II., reduction of acyl
fluorides to esters, J. Org. Chem. 36 (1971) 2547e2548;
b) A. Volkov, F. Tinnis, H. Adolfsson, Catalytic reductive dehydration of tertiary
amides to enamines under hydrosilylation conditions, Org. Lett. 16 (2014)
680e683;
c) X. Ren, C. Han, X. Feng, H. Du, A borane-catalyzed metal-free hydrosilylation
of chromones and flavones, Synlett 28 (18) (2017) 2421e2424.
[3] Global Silicones Market by Market, Product and Country, fourth ed., Summary,
vol. 1.
b) R.A. Benkeser, D.J. Foster, The reaction of sodium with organosilanes at
elevated temperatures, J. Am. Chem. Soc. 74 (21) (1952) 5314e5317;
c) M. Itoh, K. Inoue, J. Ishikawa, K. Iwata, Disproportionation reactions of
organohydrosilanes in the presence of base catalysts, J. Organomet. Chem. 629
(1e2) (2001) 1e6;
d) T. Bleith, L.H. Gade, Mechanism of the iron(II)-Catalyzed hydrosilylation of
ketones: activation of iron carboxylate precatalysts and reaction pathways of
the active catalyst, J. Am. Chem. Soc. 138 (14) (2016) 4972e4983.
[9] a) E. Calimano, T.D. Tilley, Alkene hydrosilation by a cationic hydrogen-
substituted iridium silylene complex, J. Am. Chem. Soc. 130 (29) (2008)
9226e9227;
[4] a) X. Du, Z. Huang, Advances in base-metal-catalyzed alkene hydrosilylation,
ACS Catal. 7 (2) (2017) 1227e1243;
b) Y. Nakajima, S. Shimada, Hydrosilylation reaction of olefins: recent ad-
vances and perspectives, RSC Adv. 5 (26) (2015) 20603e20616;
c) T. Hayashi, Hydrosilylation of carbon-carbon double bonds, Compr. Asym-
metric Catal. 1 (1999) 319e333;
d) Clarson, S.J. Bogdan Marciniec, Hydrosilylation: a comprehensive review on
recent advances, Silicon 1 (1) (2009) 57e58;
e) K. Junge, K. Schroder, M. Beller, Homogeneous catalysis using iron com-
plexes: recent developments in selective reductions, Chem. Commun. 47 (17)
(2011) 4849;
b) N.T. Mucha, R. Waterman, Iridium pincer catalysts for silane dehydrocou-
pling: ligand effects on selectivity and activity, Organometallics 34 (15) (2015)
3865e3872;
c) P. Sangtrirutnugul, T.D. Tilley, Silyl derivatives of [Bis(8-Quinolyl)Methyl-
silyl]Iridium(III) complexes: catalytic redistribution of arylsilanes and dehy-
drogenative arene silylation, Organometallics 26 (23) (2007) 5557e5568.
[10] A. Purkayastha, J.B. Baruah, Palladium(II) catalysed silicon-oxygen bond for-
mation versus rearrangement reactions, Phosphorus sulfur Silicon relat. Elem.
168e169 (2001) 333e338.
[11] a) N.S. Radu, F.J. Hollander, T.D. Tilley, A.L. Rheingold, Samarium-mediated
redistribution of silanes and formation of trinuclear samariumesilicon clus-
ters, Chem. Commun. 21 (1996) 2459e2460;
€
f) J.V. Obligacion, P.J. Chirik, Earth-abundant transition metal catalysts for
alkene hydrosilylation and hydroboration, Nat. Rev. Chem.
2 (5) (2018)
15e34;
g) A.K. Roy, A review of recent progress in catalyzed homogeneous hydro-
silation (hydrosilylation), in: Advances in Organometallic Chemistry, 2007,
pp. 1e59;
h) S. Banerjee, Y.-F. Yang, I.D. Jenkins, Y. Liang, A.A. Toutov, W.-B. Liu,
D.P. Schuman, R.H. Grubbs, B.M. Stoltz, E.H. Krenske, K.N. Houk, R.N. Zare,
J. Am. Chem. Soc. 139 (2017) 6880e6887.
b) I. Castillo, T.D. Tilley, Mechanistic aspects of samarium-mediated
s-bond
activations of arene CꢁH and arylsilane SiꢁC bonds, J. Am. Chem. Soc. 123 (43)
(2001) 10526e10534.
[12] a) M. Minato, T. Matsumoto, M. Ichikawa, T. Ito, Dehydropolymerization of
arylsilanes catalyzed by a novel silylmolybdenum complex, Chem. Commun.
24 (2003) 2968;
[5] a) C. Obradors, R.M. Martinez, R.A. Shenvi, Ph(i-PrO)SiH2: an exceptional
reductant for metal-catalyzed hydrogen atom transfers, J. Am. Chem. Soc. 138
(14) (2016) 4962e4971;
b) A.Y. Khalimon, R. Simionescu, G.I. Nikonov, Catalytic and stoichiometric
reactivity of b-silylamido agostic complex of Mo: intermediacy of a silanimine
complex and applications to multicomponent coupling, J. Am. Chem. Soc. 133
(18) (2011) 7033e7053.
b) S.W.M. Crossley, C. Obradors, R.M. Martinez, R.A. Shenvi, Mn-, Fe-, and Co-
catalyzed radical hydrofunctionalizations of olefins, Chem. Rev. 116 (15)
(2016) 8912e9000;
c) K. Iwasaki, K.K. Wan, A. Oppedisano, S.W.M. Crossley, R.A. Shenvi, Simple,
chemoselective hydrogenation with thermodynamic stereocontrol, J. Am.
Chem. Soc. 136 (4) (2014) 1300e1303;
d) J.C. Lo, Y. Yabe, P.S. Baran, A practical and catalytic reductive olefin coupling,
J. Am. Chem. Soc. 136 (4) (2014) 1304e1307;
e) J.C. Lo, J. Gui, Y. Yabe, C.-M. Pan, P.S. Baran, Functionalized olefin cross-
coupling to construct carbonecarbon bonds, Nature 516 (7531) (2014)
343e348;
f) J. Zheng, D. Wang, S. Cui, Fe-catalyzed reductive coupling of unactivated
alkenes with b-nitroalkenes, Org. Lett. 17 (18) (2015) 4572e4575;
g) M. Saladrigas, G. Loren, J. Bonjoch, B. Bradshaw, Hydrogen atom transfer
(HAT)-Triggered iron-catalyzed intra- and intermolecular coupling of alkenes
with hydrazones: access to complex amines, ACS Catal.
[13] X. Du, Y. Zhang, D. Peng, Z. Huang, Base-metal-catalyzed regiodivergent
alkene hydrosilylations, Angew. Chem. Int. Ed. 55 (23) (2016) 6671e6675.
[14] S. Xin, C. Aitken, J.F. Harrod, Y. Mu, E. Samuel, Redistribution reactions of
alkoxy- and siloxysilanes, catalyzed by dimethyltitanocene, Can. J. Chem. 68
(3) (1990) 471e476.
[15] X. Liu, L. Xiang, E. Louyriac, L. Maron, X. Leng, Y. Chen, Divalent ytterbium
complex-catalyzed homo- and cross-coupling of primary arylsilanes, J. Am.
Chem. Soc. 141 (1) (2019) 138e142.
[16] a) T. Sakakura, O. Kumberger, R.P. Tan, M.-P. Arthur, M. Tanaka, Ruthenium
complex-catalysed selective redistribution reaction of aryltrihydrosilanes and
desilanative polymerization of bis(Trihydrosilyl)Benzenes, J. Chem. Soc.,
Chem. Commun. 2 (1995) 193;
b) M.E. Fasulo, M.C. Lipke, T.D. Tilley, Structural and mechanistic investigation
of a cationic hydrogen-substituted ruthenium silylene catalyst for alkene
hydrosilation, Chem. Sci. 4 (10) (2013) 3882.
8 (12) (2018)
11699e11703;
ꢀ
[17] B. Becker, R.J.P. Corriu, C. Guerin, B.J.L. Henner, Hypervalent silicon hydrides:
ꢀ
ꢀ
h) S.A. Green, S.W.M. Crossley, J.L.M. Matos, S. Vasquez-Cespedes, S.L. Shevick,
R.A. Shenvi, The high chemofidelity of metal-catalyzed hydrogen atom
transfer, Acc. Chem. Res. 51 (11) (2018) 2628e2640.
evidence for their intermediacy in the exchange reactions of di- and tri-
hydrogenosilanes catalysed by hydrides (NaH, KH and LiAlH4),
J. Organomet. Chem. 369 (1989) 147e154.
ꢀ
[6] a) S. Díez-Gonzalez, S.P. Nolan, Transition metal-catalyzed hydrosilylation of
[18] I. Buslov, S.C. Keller, X. Hu, Alkoxy hydrosilanes as surrogates of gaseous si-
lanes for hydrosilylation of alkenes, Org. Lett. 18 (8) (2016) 1928e1931.
[19] R.N. Lewis, A.E. Newkirk, A method of calculating the boiling points of silicon
compounds, J. Am. Chem. Soc. 69 (3) (1947) 701e703.
carbonyl compounds and imines. A review, Org. Prep. Proced. Int. 39 (6)
(2007) 523e559;
b) Y. Li, J.A. Molina de La Torre, K. Grabow, U. Bentrup, K. Junge, S. Zhou,
A. Brückner, M. Beller, Selective reduction of amides to amines by boronic acid
catalyzed hydrosilylation, Angew. Chem. Int. Ed. 52 (44) (2013)
11577e11580;
c) K. Zhu, M.P. Shaver, S.P. Thomas, Stable and easily handled Fe(III) catalysts
for hydrosilylation of ketones and aldehydes, Eur. J. Org. Chem. 2015 (10)
(2015) 2119e2123;
d) A.M. Tondreau, E. Lobkovsky, P.J. Chirik, Bis(Imino)Pyridine iron complexes
for aldehyde and ketone hydrosilylation, Org. Lett. 10 (13) (2008) 2789e2792;
e) J. Yang, T.D. Tilley, Efficient hydrosilylation of carbonyl compounds with the
simple amide catalyst [Fe{N(SiMe3)2}2], Angew. Chem. Int. Ed. 49 (52) (2010)
10186e10188;
[20] M. Minato, T. Nanami, K. Kogoma, T. Ito, formation of metal-coordinated
doubly
chelating
pentadentate
ligands
by
the
reactions
of
[MoH4(ph2PCH2CH2PPh2)2] with organohydrodisilanes, Chem. Lett. 47 (9)
(2018) 1105e1107.
[21] Y. Ma, L. Zhang, Y. Luo, M. Nishiura, Z. Hou, B(C6F5)3 -catalyzed CeSi/SieH
cross-metathesis of hydrosilanes, J. Am. Chem. Soc. 139 (36) (2017)
12434e12437.
[22] S.L. Buchwald, Chem. Eng. News 71 (13) (29 Mar 1993) 2.
[23] a) J.H. Docherty, J. Peng, A.P. Dominey, S.P. Thomas, Activation and discovery
of earth-abundant metal catalysts using sodium tert-butoxide, Nat. Chem. 9
(6) (2017) 595e600;
f) B.A.F. Le Bailly, S.P. Thomas, Iron-catalysed reduction of carbonyls and
olefins, RSC Adv. 1 (8) (2011) 1435;
b) P. Asgari, Y. Hua, A. Bokka, C. Thiamsiri, W. Prasitwatcharakorn,
A. Karedath, X. Chen, S. Sardar, K. Yum, G. Leem, et al., Catalytic hydrogen
Please cite this article as: J.H. Docherty et al., Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.04.062

6
J.H. Docherty et al. / Tetrahedron xxx (xxxx) xxx
atom transfer from hydrosilanes to vinylarenes for hydrosilylation and
polymerization, Nat. Catal. 2 (2) (2019) 164e173;
S.A. Nye, J.L. Boyer, J.G.P. Delis, P.J. Chirik, High-selectivity bis(Imino)Pyridine
iron catalysts for the hydrosilylation of 1,2,4-trivinylcyclohexane, ACS Catal. 2
(10) (2012) 2169e2172, c);
c) B. Cheng, W. Liu, Z. Lu, Iron-catalyzed highly enantioselective hydro-
silylation of unactivated terminal alkenes, J. Am. Chem. Soc. 140 (15) (2018)
5014e5017;
d) H. Wen, X. Wan, Z. Huang, Asymmetric synthesis of silicon-stereogenic
vinylhydrosilanes by cobalt-catalyzed regio- and enantioselective alkyne
hydrosilylation with dihydrosilanes, Angew. Chem. 130 (21) (2018)
6427e6431;
e) B. Cheng, P. Lu, H. Zhang, X. Cheng, Z. Lu, Highly enantioselective cobalt-
catalyzed hydrosilylation of alkenes, J. Am. Chem. Soc. 139 (28) (2017)
9439e9442.
d) C.C.H. Atienza, T. Diao, K.J. Weller, S.A. Nye, K.M. Lewis, J.G.P. Delis,
J.L. Boyer, A.K. Roy, P.J. Chirik, Bis(Imino)Pyridine cobalt-catalyzed dehydro-
genative silylation of alkenes: scope, mechanism, and origins of selective
allylsilane formation, J. Am. Chem. Soc. 136 (34) (2014) 12108e12118.
ꢀ
[25] a) J.A. Bures, Simple graphical method to determine the order in catalyst,
Angew. Chem. Int. Ed. 55 (6) (2016) 2028e2031;
ꢀ
b) J. Bures, Variable time normalization analysis: general graphical elucidation
of reaction orders from concentration profiles, Angew. Chem. Int. Ed. 55 (52)
(2016) 16084e16087;
ꢀ
[24] These classes of complex have previously been used for hydrosilylation re-
actions: a) M.D. Greenhalgh, D.J. Frank, S.P. Thomas, Iron-catalysed chemo-,
regio-, and stereoselective hydrosilylation of alkenes and alkynes using a
bench-stable iron(II) pre-catalyst, Adv. Synth. Catal. 356 (2e3) (2014)
584e590;
c) C.D.-T. Nielsen, J. Bures, Visual kinetic analysis, Chem. Sci. 10 (2) (2019)
348e353.
[26] R.R. Ernst, G. Bodenhausen, A. Wokaun, Principles of Nuclear Magnetic
Resonance in One and Two Dimensions, Oxford University Press, Oxford, U.K.,
1987.
b) A.M. Tondreau, C.C.H. Atienza, K.J. Weller, S.A. Nye, K.M. Lewis, J.G.P. Delis,
P.J. Chirik, Iron catalysts for selective anti-markovnikov alkene hydrosilylation
using tertiary silanes, Science (80) 335 (6068) (2012) 567e570;
C.C. Hojilla Atienza, A.M. Tondreau, K.J. Weller, K.M. Lewis, R.W. Cruse,
[27] A.G. Sturm, J.I. Schweizer, L. Meyer, T. Santowski, N. Auner, M.C. Holthausen,
Lewis base catalyzed selective chlorination of monosilanes, Chem. Eur J. 24
(67) (2018) 17796e17801.
Please cite this article as: J.H. Docherty et al., Nucleophile induced ligand rearrangement reactions of alkoxy- and arylsilanes, Tetrahedron,
https://doi.org/10.1016/j.tet.2019.04.062