353
A copper complex with 1,3,5-benzenetricarboxylic acid (BTC) of the formula
Cu 3 (BTC) 2 and N-heterocyclic carbenes (NHC) also catalyzes the dehydrocondensation of hydrosilanes with alcohols (Gao and Cui 2013; Dhakshinamoorthy et al.
2016). In the presence of 0.1 mol.% of NHC in acetonitrile aryl-substituted dihydrosilanes gives almost quantitatively cyclosiloxanes (free of silanols) and H 2 , for several minutes. Appropriate silanols and disiloxanes were obtained by Qing and Cui
(2017) from tertiary H-silanes. The coupling of hydrosilanes with alcohols have
also been catalyzed by [RuCl 2 (p-cym)(NHC)] complex, which can be applied for
hydrogen storage in the form of chemical bonds. Primary, secondary and tertiary
silanes reacted with different alcohols with good yields at low concentration of this
Ru catalyst. Its immobilization onto the graphene surface increases the catalytic
activity and allows the easy separation of this catalyst, which can be reused for ten
times without any decrease in activity (Ventura-Espinosa et al. 2017).
The decarboxylation of silyl formates and their dehydrocoupling with alcohols
was also catalyzed by Chauvier et al. (2017) by using the (acetoxy)tris(diphenylphosphinomethyl)ethane) ruthenium(II) complex. Dehydrocondensation of alcohols
with hydrosilanes have also been catalyzed by sodium trialkylborohydrides: sodium
triethylborohydride (NaHBEt 3 ) or sodium tri(s-butyl)borohydride (NaHB(s-Bu) 3 )
without solvent, yielding almost quantitatively (monoalkoxy)silane derivatives
(Scheme 14.4) (Skrodzki et al. 2018a).
Superhydrophobic (s-h) polymethylhydroxysiloxane (PMHOS) powders have
also been prepared in one-pot method using PMHS and NaOH in ethanol-water
medium (within 2–8 h at 2 days) or in the presence of K 2 HPO 4 ·3H 2 O (within
4–5 days). The PMHS gelation did not occur after the addition of aqueous ammonia
or HCl into ethanol and water. The mesoporous PMHOS powder showed excellent
hydrophobic surface properties on a coated glass substrate. A specific surface area
(BET 300–460 m
2
/g) and a pore volume (0.33–0.81 cm
3
/g) were determined. The
static contact angle (~160–170°) confirmed its superhydrophobic (s-h) properties.
The surface properties and particle size of s-h PMHOS powder has been dependent
on the NaOH concentration (Nagappan and Ha 2014).
Ph-Si-H +
H
H
OH
O
NaHBEt 3
+ H 2
Ph-Si-O
H
H
100 o C, 24h
O
Scheme 14.4 The reaction of phenylsilane (PhSiH 3 ) with 2-allyloxyethanol in the presence of
NaHBEt 3 . Reprinted with permission from Skrodzki et al. (2018a)
14 Hydrosilyl-Functional Polysiloxanes: Synthesis Reactions and Applications
A copper complex with 1,3,5-benzenetricarboxylic acid (BTC) of the formula
Cu 3 (BTC) 2 and N-heterocyclic carbenes (NHC) also catalyzes the dehydrocondensation of hydrosilanes with alcohols (Gao and Cui 2013; Dhakshinamoorthy et al.
2016). In the presence of 0.1 mol.% of NHC in acetonitrile aryl-substituted dihydrosilanes gives almost quantitatively cyclosiloxanes (free of silanols) and H 2 , for several minutes. Appropriate silanols and disiloxanes were obtained by Qing and Cui
(2017) from tertiary H-silanes. The coupling of hydrosilanes with alcohols have
also been catalyzed by [RuCl 2 (p-cym)(NHC)] complex, which can be applied for
hydrogen storage in the form of chemical bonds. Primary, secondary and tertiary
silanes reacted with different alcohols with good yields at low concentration of this
Ru catalyst. Its immobilization onto the graphene surface increases the catalytic
activity and allows the easy separation of this catalyst, which can be reused for ten
times without any decrease in activity (Ventura-Espinosa et al. 2017).
The decarboxylation of silyl formates and their dehydrocoupling with alcohols
was also catalyzed by Chauvier et al. (2017) by using the (acetoxy)tris(diphenylphosphinomethyl)ethane) ruthenium(II) complex. Dehydrocondensation of alcohols
with hydrosilanes have also been catalyzed by sodium trialkylborohydrides: sodium
triethylborohydride (NaHBEt 3 ) or sodium tri(s-butyl)borohydride (NaHB(s-Bu) 3 )
without solvent, yielding almost quantitatively (monoalkoxy)silane derivatives
(Scheme 14.4) (Skrodzki et al. 2018a).
Superhydrophobic (s-h) polymethylhydroxysiloxane (PMHOS) powders have
also been prepared in one-pot method using PMHS and NaOH in ethanol-water
medium (within 2–8 h at 2 days) or in the presence of K 2 HPO 4 ·3H 2 O (within
4–5 days). The PMHS gelation did not occur after the addition of aqueous ammonia
or HCl into ethanol and water. The mesoporous PMHOS powder showed excellent
hydrophobic surface properties on a coated glass substrate. A specific surface area
(BET 300–460 m
2
/g) and a pore volume (0.33–0.81 cm
3
/g) were determined. The
static contact angle (~160–170°) confirmed its superhydrophobic (s-h) properties.
The surface properties and particle size of s-h PMHOS powder has been dependent
on the NaOH concentration (Nagappan and Ha 2014).
Ph-Si-H +
H
H
OH
O
NaHBEt 3
+ H 2
Ph-Si-O
H
H
100 o C, 24h
O
Scheme 14.4 The reaction of phenylsilane (PhSiH 3 ) with 2-allyloxyethanol in the presence of
NaHBEt 3 . Reprinted with permission from Skrodzki et al. (2018a)
14 Hydrosilyl-Functional Polysiloxanes: Synthesis Reactions and Applications