Activation reactions of 1,1-dialkoxoalkanes and unsaturated O-donors by titanium tetrafluoride

Article abstract of DOI:10.1016/j.ica.2012.01.051

The reactivity of TiF₄ with a variety of non cyclic 1,1-dialkoxoalkanes [CH₂(OR)₂, R = Me, Et, Me ₂C(OMe)₂, MeCH(OEt)_2, ClCH₂CH(OEt) ₂, CH(OMe)₃, PhCCCH(OEt)₂], 1,3-dioxolane, N₂CHCO₂Et and 1,2-epoxybutane has been investigated. Activation, including fragmentation and/or rearrangement of the organic moiety, has been observed at room temperature in some cases; it generally occurs unselectively via C-O bond fission and the formation of new C-O, C-H and C-C bonds. Small differences in the structure of the organic substrate may determine significant differences in the reactivity with TiF₄.

Full text of DOI:10.1016/j.ica.2012.01.051

Inorganica Chimica Acta 385 (2012) 135–139
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Activation reactions of 1,1-dialkoxoalkanes and unsaturated O-donors
by titanium tetrafluoride
⇑
Fabio Marchetti, Guido Pampaloni , Lorenzo Biancalana
Università di Pisa, Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, I-56126 Pisa, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactivity of TiF4 with a variety of non cyclic 1,1-dialkoxoalkanes [CH (OR) , R = Me, Et, Me C(OMe) ,
2
2
2
2
Received 8 November 2011
Received in revised form 20 January 2012
Accepted 23 January 2012
Available online 6 February 2012
MeCH(OEt)2, ClCH
2
CH(OEt)
2
, CH(OMe)
3
, PhC„CCH(OEt)
2
], 1,3-dioxolane, N
2
2
CHCO Et and 1,2-epoxybu-
tane has been investigated. Activation, including fragmentation and/or rearrangement of the organic moi-
ety, has been observed at room temperature in some cases; it generally occurs unselectively via CÀO
bond fission and the formation of new CÀO, CÀH and CÀC bonds. Small differences in the structure of
4
the organic substrate may determine significant differences in the reactivity with TiF .
Keywords:
Titanium
Fluoride
Ó 2012 Elsevier B.V. All rights reserved.
Activation
O-Donor
Coordination
1
. Introduction
normally exhibited by other early transition metal halides in high
oxidation state, which rapidly hydrolyze to give oxide derivatives
The reactivity of titanium tetrafluoride has been much less
[14]. Moreover HF is not produced in the reaction of TiF
salenH in boiling thf, Scheme 1, which affords the 1:1 adduct
TiF (salenH (sa-
): cleavage of the TiÀF bond and formation of TiF
len) is achieved in the presence of the SiMe fragment [15].
Recently we reported on the reactions of MX (M = Nb, Ta; X = F,
Cl, Br, I), MoCl and WCl with O-donor species, showing that the
formation of the strong MÀO bond favors the CÀO cleavage within
the organic unit, possibly resulting in fragmentation and rearrange-
ment reactions even at room temperature [16]. In particular the
reactions involving diethers showed the formation of new CÀC
and CÀO bonds, and higher reactivity was observed with 1,1-dial-
koxyalkanes rather than 1,2-dialkoxyalkanes [17,18]. These reac-
tions are strongly influenced by the nature of the halide, the
4
with
developed with respect to that of the heavier congeners, especially
the tetrachloride TiCl [1]. One of the reasons is probably related to
the particular inertness of TiF , due to the polymeric structure in the
solid state [2] and the strength of the TiÀF bond (D = 584 kJ/mol, to
be compared with TiÀCl, D = 429.3 kJ/mol, TiÀBr, D = 366.9 kJ/
mol, and TiÀI, D = 296.2 kJ/mol) [3].
Titanium tetrafluoride and O-donors L generally form 1:2 ad-
ducts of formula TiF , L = thf [4], Ph PO [5], disso [6], dimethyl-
2
4
4
2
2
4
3
0
5
0
0
5
6
0
L
4 2
3
formamide [6c] dimethylacetamide [6c,7], tetramethylurea [6c],
substituted pyridine- and quinoline-N-oxide [8]. Complex TiF
4
(dme) is obtained by straightforward 1:1 reaction of TiF
,2-dimethoxyethane (dme) [9]. Polymeric fluorine-bridged com-
plexes may be obtained with weak Lewis bases such as pyridine
4
with
1
5
fluorides MF (M = Nb, Ta) usually activating the diether at high
[
6c] and benzonitrile [10].
Compounds of formula TiF
temperatures only [16a].
L
4 2
show generally the cis-configura-
At variance to niobium and tantalum derivatives, the group 4 tet-
tion although cis–trans equilibria in solution have been observed
when strongly donating, sterically hindered ligands are involved
rahalides MX
anes are less prone to undergo activation of the coordinated organic
fragments [9]. On the other hand, it was reported that TiCl may
4
(M = Ti, Zr, X = Cl, Br, I) adducts with 1,2-dialkoxoalk-
[
8a,11].
4
The strong TiÀF bond is not cleaved by alcohols, which react
show the ‘‘deprotecting’’ behavior typical of Lewis acids with re-
spect to 1,1-dialkoxylkanes (acetal and ketals), thus determining
the generation of the relevant carbonylic compounds [19]. Con-
i
with TiF
[
4
affording TiF
4
(ROH)
2
adducts, R = Me [12], Et [6c,12], Pr
forms a stable coordination adduct
upon reaction with water [13], in contrast with the behavior
12]. It is remarkable that TiF
4
4
versely, it was found that TiCl was able to activate substituted diox-
olanes to give chlorinated organic compounds [20].
In this context, we decided to explore the chemistry of the rel-
4
atively inert TiF with 1,1-dialkoxoalkanes or unsaturated oxygen
compounds. The results of this investigation are reported in the
present paper.
⇑
Corresponding author. Tel.: +39 050 2219 219; fax: +39 050 2219 246.
E-mail addresses: fabmar@dcci.unipi.it (F. Marchetti), pampa@dcci.unipi.it
(
G. Pampaloni).
0
020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2012.01.051

1
36
F. Marchetti et al. / Inorganica Chimica Acta 385 (2012) 135–139
F
run 2). It is interesting to note that the analogous reaction involv-
ing MF (M = Nb, Ta) gave the mixed ether OMeEt, as a conse-
quence of the concerted activation of CÀO and CÀH bonds [17].
In the case of TiF and CH (OEt) , ethers do not form thus suggest-
ing that pathways b and c (Scheme 2) are almost non viable (see
Scheme 3) and that a small variation in the structure of the sub-
strate can determine strong difference in the nature of the reaction
products.
F
5
N
N
Ti
F
OH
F
HO
F
4
2
2
TiF4
TiF4
N
OH
N
The hydrolysis of the mixture obtained by reaction of TiF
4
with
HO
MeCH(OEt) gave only EtOH and Et O as identifiable materials (Ta-
2
2
ble 1, run 3). Although a similar process to that reported in Scheme
2 may be invoked, it has not been possible to identify the other
products necessary for the full justification of the fragmentation
scheme.
A substantially different reactivity was observed by formal sub-
stitution of a methyl hydrogen with chlorine. In fact the reaction
N
O
N
O
Et N, SiMe Cl
Ti
F
3
3
2 4
Scheme 1. The reactions of salenH with TiF .
between TiF
4
2 2 2
and ClCH CH(OEt) gave ClCH CHO (Table 1, run
4
): in this case, TiF
4
seems to behave as a traditional Lewis acid,
2
. Results and discussion
‘‘deprotecting’’ the carbonyl functionality (see Section 1) [19,21].
Hydrolysis of the reaction mixture did not change the relative com-
position of the organic compounds. A similar result was obtained
on increasing the reaction temperature or the substrate/Ti molar
ratio (Table 2, run 6).
Titanium tetrafluoride reacted slowly with CH
2 2
(OR) , R = Me, Et,
Me
2
C(OMe) , MeCH(OEt)2, ClCH CH(OEt) , either at room temper-
2
2
2
ature or at ca. 80 °C, affording mixtures of products which pre-
vented the identification of any coordination compound.
However, it was possible to identify the products of the activation
of the organic substrate after exhaustive hydrolysis of the reaction
mixture, Table 1, runs 1–5.
The data of Table 1 suggest that the reactions are not selective,
similarly to what observed in the analogous reactivity of Group 5
metal pentahalides [17]. The reaction of TiF
The reaction of Me
temperature and gave, after hydrolysis, MeOH plus minor amounts
of MeCO Me, Me O and Me CO (Table 1, run 5). A possible scheme
of formation is given (Scheme 4). It is interesting to note that the
same reaction performed with NbF afforded mesityloxide [17],
i.e. the product of acetone dehydration, thus confirming the higher
affinity for water of NbF with respect to TiF [1,14].
Trimethoxymethane reacted with TiF at room temperature
affording Me O and HCO Me in comparable amounts (molar ratio
ca. 14:10; Table 1, run 6). Analogous activation process was ob-
served previously in the case of NbF [17]. The presence of dimeth-
2 2 4
C(OMe) with TiF was fast even at room
2
2
2
5
4
with CH
2
(OMe)
2
(Ta-
5
4
ble 1, run 1) produced methyl formate and dimethylether. These
compounds were identified together with a significative amount
4
2
2
of unreacted CH
tion mixture after hydrolysis. An increase of the reaction tempera-
ture and/or the CH (OMe) /Ti molar ratio caused a substantial
increase of dimethylether (Table 2, run 2). The presence of HCO Me
and Me O suggests that the activation reaction proceeds with
cleavage of CÀO and CÀH bonds followed by formation of new
CÀO and CÀH bonds, see Scheme 2a and b. The presence of meth-
anol might be the consequence of the formation of the [TiÀOMe]
unit, see Scheme 2c.
2 2
(OMe) . In addition MeOH was found in the reac-
5
ylether suggests that the coupling between different fragments,
including the formation of a new CÀO bond, is operative in the sys-
tem, see Scheme 5. Methanol was observed in the reaction mixture
after hydrolysis.
2
2
2
2
An interesting case of CÀC bond formation was observed when
4
a dichloromethane suspension of TiF was treated with 1,3-dioxo-
2
lane. After heating and hydrolysis steps, HCO Me, 1,4-dioxane,
2
According to the Me O/MeOH molar ratio detected (16:1, Table
MeO(CH OMe, and Me O were identified in 8:20:10:10 molar ra-
2
)
2
2
1
, run 1), process b should occur more easily than process c
tios (Table 1, run 7). With a conversion of ca. 20%, 1,4-dioxane rep-
resents the product formed in higher amount in this reaction. A
tentative suggestion concerning the formation of 1,4-dioxane from
1,3-dioxolane is sketched in Scheme 6 and implies the formation of
(Scheme 2).
The reaction of TiF
4
with CH
2
2
(OEt) proceeds similarly to what
discussed for CH
2
(OMe)
2
. Thus HCO
2
Et and EtOH (ratio 1:3) have
been identified after hydrolysis of the reaction mixture (Table 1,
a new CÀC bond with intermolecular transfer of a [CH
2
] fragment.
Table 1
Summary of the organic compounds obtained from TiF
mixtures.
4 3 2 2 2
and 1,1-dialkoxoalkanes, CH(OMe) , PhC„CCH(OEt) , 1,2-epoxybutane, N CHCO Et, after hydrolysis of the reaction
Run
Reagent (L)
Products (molar ratios) d
HCO Me + CH (OMe) + MeOH + Me
Et + CH (OEt) + EtOH (10:1:5:3)
+ MeCH(OEt) + EtOH + Et O (4:1:4:1)
+ ClCH CHO + ClCH CH(OEt) + ClCH CO
+ MeCO Me + MeOH + Me O + Me CO (10:0.4:4:0.3:0.4)
Me + MeOH + Me O (10:7:1:5)
Me + 1,3-dioxolane + 1,4-dioxane + MeO(CH
+ EtOH (5:3:3)
(OH)CH(OH)Et (10:8)
FCO Et (3:1)
a
1
2
3
4
5
6
7
8
9
CH
CH
2
(OMe)
2
a
2
2
2
2
O (10:5:1:16)
2
(OEt)
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
2
2
2
2
2
2
2
2
2
+ HCO
2
2
2
a
MeCH(OEt)
ClCH CH(OEt)
Me C(OMe)
HC(OMe)
1,3-dioxolane
PhC„CCH(OEt)
2
2
2
b,c
2
2
2
2
2
2
2
Et (10:14:1:0.5)
a
2
2
2
2
2
a
3
+ HCO
+ HCO
2
2
2
a
2 2 2
) OMe + Me O (100:8:14:20:10:10)
a
2
+ PhCC„CH(OEt)
2
b
1,2-epoxybutane
+ CH
+ CH
2
a
1
0
2
N CHCO
2
Et
2
2
a
b
c
At 298 K.
After heating.
L/Ti molar ratio = 2.
d
2 2 2 2
CH Cl used as internal standard (CH Cl /Ti molar ratio = 1).

F. Marchetti et al. / Inorganica Chimica Acta 385 (2012) 135–139
137
Table 2
4
Experimental details of the reactions between TiF and O-donors.
Run TiF
mmol)
4
L
L/M
molar
ratio
Reaction
time (h)
NMR spectra
1H NMR: HCO
(
1
0.44
CH
2
(OMe)
2
1
48
2
Me [8.11 (s, CH), 3.79 ppm (s, Me)]; CH
Me:CH (OMe) :Me
After hydrolysis (12 h): H NMR: HCO Me [8.08 (s, CH), 3.76 ppm (s, Me)]; CH
.37 ppm (s, Me)]; MeOH [3.48 ppm (s, Me)]; Me O [3.33 ppm (s, Me)].
O = 10:5:1:16. 13C NMR: CH
(OMe) [97.4 (CH
Me [161.9 ppm (CH); 50.8 ppm (Me)]; Me O [60.4 ppm]
Me [8.05 (s, CH), 3.73 ppm (s, Me)]; CH
O [3.36 ppm (s, Me)]. HCO Me:CH (OMe) :Me O = 4:1:7
[5.31 ppm]; HCO Et [8.06 (s, CH), 4.24 (q, CH ), 1.31 ppm (t, CH
), 3.61 ppm (q, CH (OCH )]; 3.38 ppm (s); 1.38 ppm (t).
:HCO Et:CH (OEt) = 10:1:5
After hydrolysis: H NMR: CH Cl
CH (OEt) [4.67 (s, CH (OEt) ), 3.61 (m, CH
.02 (br, OH), 1.22 (m, CH )]; 3.37 ppm. CH
After hydrolysis: H NMR: CH Cl [5.29 ppm]; MeCH(OEt)
.29 ppm (d, CH CH), 1.21 (t, OCH CH )]; EtOH [3.66 (q, CH
q, CH ), 1.18 ppm (t, Me)]. CH Cl :MeCH(OEt) :EtOH:Et O = 4:1:4:1. C NMR: CH
67.5 (CH ), 15.2 ppm (Me)]; EtOH [58.0 (CH ), 18.1 ppm (Me)]
CHO [9.62 (s, CH), 4.07 ppm (s, CH )]; ClCH
), 1.24 ppm (t, Me]. ClCH CHO:ClCH CH(OEt) = 1:5. C NMR: ClCH
CH), 62.5 ppm (OCH ), 43.8 (ClCH ), 15.1 ppm (CH )]
After heating (18 h): H NMR: ClCH CHO [9.62 (s, CH), 4.07 ppm (s, CH
CH), 3.51 ppm (d, ClCH ), 3.66 (m, OCH ), 1.24 (t, Me)]. ClCH CHO:ClCH
CHO [9.41 ppm (s, CH), 4.01 ppm (s, br, CH
), 1.21 ppm (m, Me)]. CH Cl :ClCH
[101.6 (CH), 62.5 (OCH ), 43.8 (ClCH
Cl [5.29 ppm]; ClCH CHO [9.40 ppm (s, CH), 4.04 ppm (s,
[4.60 (m, CH), 3.62 (m, OCH ), 3.47 (m, ClCH ), 1.20 (m, Me)].
= 10:1:15
2
(OMe)
2
[4.61 (s, CH
2
), 3.39 ppm (s, Me)]; 3.48 ppm
(OMe) [4.58 (s, CH ),
), 55.0 ppm (CH )];
(OMe) [4.56 (s, CH
)]; CH (OEt) [4.69 (s,
(
br); Me
2
O [3.39 ppm (s, Me)]. HCO
2
2
2
2
O = 10:6:3
1
2
2
2
2
3
HCO
HCO
2
2
Me:CH
2
(OMe)
2
:MeOH:Me
2
2
2
2
3
2
2
1
2
3
0.45
0.69
CH
2
2
(OMe)
2
2
1
48
96
After heating, no hydrolysis: H NMR: HCO
.34 ppm (s, Me)]; Me
2
2
2
2
),
3
2
2
2
2
2
1
CH
(OEt)
2
H NMR: CH
CH (OEt)
CH Cl
2
Cl
2
2
2
3
2
2
2
2
2
2
CH
3
)
2
) 1.22 ppm (t, CH
3
2
2
2
2
2
1
2
2
[5.30 ppm]; HCO
(OCH CH
Cl :HCO
2
Et [8.05 (s, CH), 4.23 (m, CH
2
), 1.31 ppm (t, CH
)]; EtOH [3.70 (quint, CH
3
)];
),
2
2
2
2
2
2
3
)
2
), 1.22 ppm (m, CH
Et:CH (OEt) :EtOH = 10:1:5:3
[4.67 ppm (q, CH), 3.57 ppm (m, CH
), 2.66 (s, OH), 1.20 ppm (t, Me)]; Et
3
2
2
3
2
2
2
2
2
1
4
5
0.71
0.48
MeCH(OEt)
2
1
1
96
96
2
2
2
2
),
O [3.47
1
(
[
3
2
3
2
2
13
2
2
2
2
2
2 2 2
Cl [53.4 ppm]; Et O
2
2
1
ClCH
ClCH
2
CH(OEt)
CH(OEt)
2
2
At 298 K: H NMR: ClCH
OCH ), 3.52 (d, ClCH
2
2
2
CH(OEt)
2
[4.64 (t, CH), 3.61 ppm (m,
CH(OEt) [101.6
1
3
2
2
2
2
2
2
2
(
2
2
3
1
2
2
)]; ClCH
2 2
CH(OEt) [4.64 ppm (t,
2
2
2
2
CH(OEt)
2
= 1:5
1
6
0.70
2
2
96
H NMR: CH
CH), 3.48 (d, ClCH
NMR: CH Cl [53.4 ppm]; ClCH
After heating (18 h): H NMR d(ppm): CH
2
Cl
2
[5.29 ppm]; ClCH
), 3.63 (m, OCH
2
2
)]; ClCH
2
CH(OEt)
2
[4.60 (t,
= 10:2:10. 1
3
C
2
2
2
2
2
CHO:ClCH
2
CH(OEt)
2
2
2
2
CH(OEt)
2
2
2
), 15.1 ppm (Me)]
1
2
2
2
CH
CH
2
)]; 5.90 ppm; ClCH
Cl :ClCH CHO:ClCH
2
CH(OEt)
CH(OEt)
2
2
2
2
2
2
2
2
1
After heating (18 h) and hydrolysis: H NMR: CH
CH )]; ClCH CH(OEt) [4.58 (t, CH), 3.61 (m, OCH
q, OCH ), 4.02 (s, ClCH ), 1.29 ppm (br, Me)].
CH Cl :ClCH CHO:ClCH CH(OEt) :ClCH CO Et = 10:14:1:0.5
H NMR: CH Cl
[5.31 ppm]; 3.72 (br) ppm. After hydrolysis: 1H NMR: CH
3.67 (s, CO Me), 2.06 ppm (s, MeCO )]; MeOH [3.48 (s, Me), 1.85 ppm (br, OH)]; Me
Me)]; Me CO [2.17 ppm (s, Me)]. CH Cl : MeCO Me: MeOH: Me O: Me CO = 10:0.4:4:0.3:0.4. C NMR:
CH Cl [53.4 ppm]; MeOH [50.6 ppm].
H NMR: CH Cl [5.30 ppm]; HCO Me [8.06 (s, CH), 3.74 ppm (s, Me)]; Me
CH Cl :HCO Me:Me Cl [53.4 ppm]; HCO Me [161.3 (CH), 50.8 ppm (Me)];
O = 10:7:5. 13C NMR: CH
Me O [60.5 ppm (Me)]
After hydrolysis: 1H NMR: CH
Me O [3.30 (s, Me)]. CH Cl :HCO
O [60.3 ppm]; MeOH [50.8 ppm]
[5.31 ppm]; HCO Me [8.09 (s, CH), 3.74 ppm (s, Me)]; 1,3-dioxolane [4.92 (s,
O), 3.89 ppm (s, OCH CH )]. CH Cl :HCO Me:1,3-dioxolane = 5:1:2
Cl [5.31 ppm]; HCO Me [8.08 (s, CH), 3.76 ppm (s, Me)]; 1,3-dioxolane
O), 3.89 ppm (s, OCH CH )]. CH Cl :HCO Me:1,3-dioxolane = 100:13:8
After heating (18 h) and hydrolysis: H NMR: CH Cl [5.30 ppm]; HCO Me [8.07 (s, CH), 3.74 ppm (s,
Me)]; 1,3-dioxolane [4.89 ppm (s, OCH O), 3.87 ppm (s, OCH CH ]; 1,4-dioxane [3.69 (s, CH )];
MeO(CH OMe [3.53 (s, CH ), 3.37 ppm (s, CH )]; Me O [3.30 ppm (s, Me)]. CH Cl :HCO Me:1,3-
dioxolane:1,4-dioxane:MeO(CH OMe:Me O = 100:8:14:20:10:10
After hydrolysis: 1H NMR: CH
Cl [5.30 ppm]; 9.44 ppm; PhCC„CH(OEt)
.85, 3.71 (m, CH ), 1.30 ppm (t, Me)]; EtOH [3.68 (q, CH ), 1.25 ppm (t, CH
CH Cl :PhCC„CH(OEt) Cl [53.4 ppm]; PhC„CCH(OEt)
:EtOH = 5:3:3. 13C NMR: CH
28.8, 128.2 (CH), 121.9 (m, Ph), 91.8, 85.2 (C„C), 60.9 (CH ), 15.1 ppm (CH )]; EtOH [58.3 (CH
8.3 ppm (CH )].
Cl
2
Cl
2
[5.27 ppm]; ClCH
2
CHO [9.39 (s, CH), 4.02 ppm (s,
2
2
2
2
), 3.46 (d, ClCH
2
), 1.18 ppm (t, Me)]; ClCH
2
CO Et [4.20
2
(
2
2
2
2
2
2
2
2
2
1
7
8
0.75
0.65
Me
2
C(OMe)
2
1
1
96
96
2
2
Cl
2 2
[5.31 ppm]; MeCO
2
Me
[
2
2
2
O [3.32 ppm (s,
13
2
2
2
2
2
2
2
2
1
HC(OMe)
3
2
2
2
2
O [3.31 (s, Me)].
2
2
2
2
2
2
2
2
2
Cl
2
[5.30 ppm]; HCO
2
Me [8.05 (s, CH), 3.74 (s, Me)]; MeOH [3.45 (s, Me)];
13
2
2
2
2
Me: MeOH:Me O = 10:7:1:5. C NMR: CH Cl [53.4 ppm]; HCO Me
2
2
2
2
[
161.9 (CH), 50.8 (Me)]; Me
H NMR d(ppm): CH
OCH
After heating (12 h): H NMR: CH
4.91 (s, OCH
2
1
9
0.84
1,3-dioxolane
1
96
2
Cl
2
2
2
2
2
2
2
2
1
2
2
2
[
2
2
2
2
2
2
1
2
2
2
2
2
2
2
2
)
2
2
3
2
2
2
2
)
2 2
2
10
11
12
0.43
0.75
0.73
PhC„CCH(OEt)
2
1
1
1
72
96
96
2
2
2
[7.50, 7.34 (m, Ph), 5.51 (s, CH),
)].
3
2
2
3
2
2
2
2
2
2
[133.3, 131.9,
),
1
2
3
2
1
3
1
1,2-
epoxybutane
H NMR: CH
2
2
[5.32 ppm]; 3.52 (br), 1.57 (br), 0.96 ppm (m)
1
After hydrolysis: H NMR: CH
CH Cl :CH (OH)CH(OH)Et = 1:1
After heating (5 h) and hydrolysis: 1H NMR: CH
.96 ppm (m)]. CH Cl :CH (OH)CH(OH)Et = 10:8
[5.33 ppm]; CH FCO
Et [4.85 (d, 1
Et = 2:1. 13C NMR: CH
Cl [53.4 ppm]; CH
O), 14.2 ppm (CH )]
After hydrolysis: H NMR: CH
.33 ppm (t, CH )]. CH Cl :CH
Cl
2 2
2
[5.31 ppm]; CH (OH)CH(OH)Et [3.53 (m), 1.47 (m), 0.97 ppm (m)].
2
2
2
2
Cl
2
[5.31 ppm]; CH (OH)CH(OH)Et [3.52 (br), 1.57 (br),
2
0
2
2
2
1
2
N CHCO
2
Et
H NMR: CH
CH Cl : CH FCO
CH
2
Cl
2
2
2
J
HF = 47 Hz, CH
2
F), 4.30 (q, CH
FCO Et [168.1 (d, CO
2
O), 1.33 ppm (t, CH
3
)].
2
2
2
2
2
2
2
2
2
), 77.8 (d, CH F), 61.5
2
(
2
3
1
2 2 2 2
FCO JHF = 47 Hz, CH F), 4.30 (q, CH O),
Et [4.85 (d, 1
2
Cl
FCO
2
[5.33 ppm]; CH
Et = 3:1
1
3
2
2
2
2
In agreement with the relatively weak TiÀCl bond (see Section
), the reaction between TiCl and substituted dioxolanes proceeds
with ring opening and chlorination of the organic fragment [20].
1,3-Dioxolane and CH
adduct TiF (CH CN) , which was considered more reactive than
TiF in view of its mononuclear structure [10]. We observed that
2 2
(OEt) were reacted with the acetonitrile
1
4
4
3
2
4

1
38
F. Marchetti et al. / Inorganica Chimica Acta 385 (2012) 135–139
O
H
H
O
Me
H
H
O
Me
(a)
(b) [H]
Me O
2
OMe
HOMe
OMe
Me]
[
H
H
O
Me
(c) [H]
Me2O + [Ti-OMe]
OMe
Ti]
H O
2
MeOH
[
2
Scheme 2. Activation of CH (OMe)
2
by TiF
4
.
[Ti]
O
H
H
O
Et
[H]
H
H
OEt
(a)
(b)
[Ti-OEt] +........
[Et]
OEt
H
OEt
OEt
H O
2
[Ti]
EtOH
Scheme 3. Activation of CH
2
(OEt)
2
4
by TiF .
O
Me
a)
O
Me
Me
O
Me
(
(b)
Me O + Me CO
2
2
Me
OMe
MeOMe
Me
OMe
Me]
[
[
Me]
[Ti]
Me
OMe
Me
Me O (d)
O
Me
(
c)
[Ti-OMe]
2
Me
OMe
Me]
Me
OMe
Ti]
H O
2
MeOH
[
[
2 2 4
Scheme 4. Activation of CMe (OMe) by TiF .
a low amount of acetonitrile (8% and 20%, respectively) was re-
leased after 20 days at room temperature or some hours at ca.
2
and the diethylacetal of phenylpropynal, PhC„CCH(OEt) (Table
1, run 8). No activation was observed in the first case while small
amounts of EtOH were formed under drastic conditions in the lat-
ter reaction.
Even the three-membered ring of 1,2-epoxybutane was not
4
activated by means of TiF , and the probable formation of a coordi-
7
0 °C. No activation of the organic molecule was observed under
the same experimental conditions used for the reactions with TiF
In order to investigate in more detail the possibility of fluorine-
transfer reactions, we allowed TiF to react with compounds con-
4
.
4
taining unsaturated functionalities such as propargylic alcohol
nation adduct could not be demonstrated (Table 1, run 9). The
treatment of the reaction mixture with water caused the presum-
able metal-assisted quantitative conversion to 1,2-diol [22]. It has
to be remarked that epoxides easily undergo ring-opening reac-
tions in the presence of metal halides of Group 5, affording either
halo-alkoxo or ketone complexes depending on the halide [23].
Titanium tetrafluoride reacted with ethyldiazoacetate at room
O
MeO
Me
O
Me
+
Me O
2
OMe
MeOMe
2
temperature affording CH FCOOEt as prevalent product, although
in low yield (ca. 35%) (Table 1, run 10, Scheme 7).
Scheme 5. Activation of CMe(OMe)
3
4
by TiF .
O
O
O
H
O
F
CH2
C
O
N2
CH
TiF4
+
HCO CH3
2
C
OEt
OEt
H
O
-
N2
O
O
Scheme 6. Formation of 1,4-dioxane from 1,3-dioxolane and TiF
4
.
4
Scheme 7. Fluorine transfer to ethyldiazoacetate mediated by TiF .

F. Marchetti et al. / Inorganica Chimica Acta 385 (2012) 135–139
139
The formation of ethylfluoroacetate is the result of the formal
addition of HF to the fragment obtained by dinitrogen loss. It is
noteworthy that, under comparable experimental conditions, the
In the case of the reactions of TiF
4
(CH
3
CN)
2
with CH
2
(OEt)
2
and
1,3-dioxolane, respectively 20% and 8% of acetonitrile was released
into the solution after 20 days stirring at room temperature. In
both cases, the organic reactant was the only product which could
be detected after prolonged heating of the reaction mixture fol-
lowed by hydrolysis.
reaction of NbF
tion adduct NbF
5
with N
[O@C(OEt)CHN
2
CHCO
2
Et generated the stable coordina-
2
] [24].
5
3
. Conclusions
Suspensions of TiF
Acknowledgments
4
in chlorinated solvents promote room tem-
The authors wish to thank the Ministero dell’Istruzione,
dell’Università e della Ricerca (MIUR, Roma), for financial support.
perature fragmentation and rearrangement of O-containing spe-
cies, mainly 1,1-dialkoxyalkanes. The reactions are generally slow
4
due to the polynuclear structure of TiF . The organic compounds
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The possible formation of Ti-OR species, evidenced on the basis
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[
[
[
À2
argon. TiF
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4
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(
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(
3
referenced to the non-deuterated aliquot of the solvent.
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4.1. Reactions between TiF and TiF (CH CN) with O-donors: general
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4
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4
, CDCl
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(
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2
2
2
2
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recorded. Then the mixture was heated at temperature as high as
(
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8
0 °C. Thus the tube was cooled to ca. À30 °C and opened: the mix-
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