To Coordinate or not to Coordinate: The Special Role of Chalcogen Ether Functionalities in the Design of Twofold Functionalized Cyclopentadienyl Ligands [Cp,O,Ch (Ch = S, Se)]

Article abstract of DOI:10.1002/zaac.201900012

The solvent- and catalyst free synthesis of two β-thio ketones L1a and L1b is reported. L1a, L1b, and a β-seleno ketone L1c were successfully employed as ligand precursors in the synthesis of a novel series of cationic titanium complexes 4a–4c via a well-

Full text of DOI:10.1002/zaac.201900012

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201900012
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
To Coordinate or not to Coordinate: The Special Role of
Chalcogen Ether Functionalities in the Design of Twofold
Functionalized Cyclopentadienyl Ligands [Cp,O,Ch (Ch = S, Se)]
Malte Fischer,[a] Marc Schmidtmann,[a] and Ruediger Beckhaus*[a]
Abstract. The solvent- and catalyst free synthesis of two β-thio ionic titanium complexes 4a–4c bear twofold functionalized cyclopen-
ketones L1a and L1b is reported. L1a, L1b, and a β-seleno ketone
L1c were successfully employed as ligand precursors in the synthesis
of a novel series of cationic titanium complexes 4a–4c via a well-
tadienyl [Cp,O,Ch (Ch = S, Se)] ligand frameworks built directly in
the coordination sphere of the metal, in which the chalcogen ether
functionalities do not coordinate to the central metal atoms as demon-
established reaction sequence: insertion of the carbonyl functional strated by NMR experiments. Consequently, Cp,O σ,π chelating ligand
group into the polarized Ti–Cq,exo bond of the monopentafulvene com-
plex Cp*Ti(Cl)(π-η5:σ–η1-C5H4=CR2) (1) (CR2 = adamantylidene),
subsequent methylation, and final activation with B(C6F5)3. The cat-
systems are formed with free coordination sites at the central titanium
atoms and pendant chalcogen ether moieties.
hemilability,[6] noninnocence,[7] variations of bite angles, and
ring size effects.
Introduction
Ligand design is the key to organometallic chemistry and
requires intensive studies because even small variations in
designing appropriate ligands can have a tremendous effect on
enabling subsequent reactions, especially when taking the
main field of application, the homogeneous (asymmetric) ca-
talysis, into account.[1]
Another interesting and important, but less developed tri-
dentate ligand platform is based on η5-cyclopentadienyls,
which are usually synthesized by multistep syntheses followed
by subsequent coordination to the metal fragments.[8]
We have recently addressed the synthesis of such ligands
and established a convenient, flexible, and high-yielding syn-
thesis of novel types of tridentate ligands with a cyclopen-
tadienyl basis by directly building such ligands in the coordi-
nation spheres of the central metal atoms, thus distinguished
from the classic approach. Starting with monopentafulvene
complexes of group 4 metals, the umpolung of the exocyclic
quaternary carbon atom (Cq,exo) of the ligated pentafulvene li-
gand enabled the insertion of various bidentate ligand precur-
sors. Subsequent methylation and final activation with the
strong Lewis acid B(C6F5)3 yielded cationic d0 complexes of
group 4 metals bearing Cp,X,Y ligand frameworks (Scheme 1,
top).
Complexes with a Cp,O,P ligand set were synthesized, and
their possible modifications and limitations with regard to this
special ligand set were pointed out.[9,10] Further studies dealt
with the corresponding Cp,N,P and Cp,O,N ligand systems and
their respective titanium complexes. They proved to be rare
examples of titanium based frustrated Lewis pairs, hence they
were able to activate acetone, phenylacetylene, dihydrogen, or,
in the case of the Cp,O,N congeners they were even capable
of activating carbon–halogen bonds (Scheme 1, middle).[11,12]
These recent examples have already shown the high versatility
of this approach, which might offer tuning potentials compar-
able to those of the ubiquitous and comprehensively analyzed
class of pincer ligands (Scheme 1, middle). To further address
and verify the influence of the hemilabile donor site and its
donor strength, we herein present a series of cationic titanium
complexes with twofold functionalized cyclopentadienyl li-
Tridentate ligands have risen in popularity mostly due to
their versatility, and so called pincer ligands have become the
most employed representatives.[2a–2f] Although the definition
of pincer ligands has broadened after the first description by
van Koten in 1989,[3] the term now generally refers to triden-
tate ligands, that occupy adjacent binding sites in a metal com-
plex with a strong preference of adopting a meridional arrange-
ment.[2a–2f] In this context, the seminar studies of Shaw et al.
reported one of the first Pincer complexes (PCP)NiCl via or-
thometalation of NiCl2(H2O)6 with 1,3-(CH2PtBu2)2C6H4.[28]
Since van Koten, a multitude of different pincer ligands have
been studied, synthesized, and reviewed in several books[4,5]
and articles,[2a–2f] demonstrating their high impact as platforms
for homogeneous catalysis. The key factors for the success of
pincer ligands to be mentioned are their ability of effectively
controlling and tuning steric and electronic properties by intro-
ducing hard or soft donor sites in conjunction with aspects of
* Prof. Dr. R. Beckhaus
Fax: (+49) 441-798-3581
E-Mail: ruediger.beckhaus@uni-oldenburg.de
https://www.uni-oldenburg.de/ac-beckhaus/
[a] Institut für Chemie
Fakultät für Mathematik und Naturwissenschaften
Carl von Ossietzky Universität Oldenburg
Postfach 2503
26111 Oldenburg, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201900012 or from the au-
thor.
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Scheme 2. Solvent- and catalyst-free synthesis of the β-thio ketones
L1a,b, and synthesis of the β-seleno ketone L1c.[14]
Removal of slight excess of the starting materials under re-
duced pressure yielded L1a and L1b as yellow (L1a) and col-
orless (L1b) oils respectively in very good isolated yields and
adequate purity without the requirement of further purification
steps. Previous efforts to synthesize β-thio ketones by 1,4-ad-
dition mention the employment of strong bases[15] or the use
of Lewis acids[16a–16c] in organic solvents. These strong acidic
or basic conditions are often accompanied by the formation of
undesired byproducts. More recent improvements describe the
synthesis of β-thio ketones catalyst-free in water with the em-
ployment of micellar solutions[17] or ionic liquids.[18] Our ap-
proach appears far more efficient.
In addition to the β-thio ketones L1a and L1b, the β-seleno
ketone L1c was synthesized following a procedure reported
by Tatar et al.,[14] and NMR spectroscopic data of L1c was
recollected in C6D6 for reasons of comparison (Scheme 2). The
introduction of selenium provides further derivatization pros-
pects and an additional NMR active nucleus for characteriza-
tion.
L1a–c feature carbonyl functional groups, which are suit-
able for the targeted insertion reaction into the polarized bond
between the titanium atom and the quaternary exocyclic carbon
atom (Cq,exo) of the pentafulvene ligand of 1, and chalcogen
ether units connected and spaced from the carbonyl group by
two methylene groups.
Scheme 1. Overview of tridentate Cp,X,Y ligands built directly in the
coordination sphere of the metal; synthesis, tuning potential, previous
examples, and attempted synthesis of Cp,O,Ch ligands (Ch = S, Se).
gands [Cp,O,Ch (Ch = S, Se)]. These complexes are bearing
bidentate π,σ Cp,O chelating ligands with unoccupied chalco-
gen ether functionalities, showing no interaction to the central
titanium atom in the final cationic complexes.
Synthesis of Cationic Titanium Complexes with Tridentate
Cp,O,Ch (Ch = S, Se) Ligands
Results and Discussion
The reactions of the titanium monopentafulvene complex 1
with the bidentate O,Ch-ligand precursors L1a–c in n-hexane
at room temperature were accompanied by color changes from
yellow-brown to yellow-orange and yielded the titanium com-
Synthesis of the O,Ch-Ligand Precursor Compounds L1a–c
(Ch = S, Se)
Inspired by pioneering work concerning the solvent- and plexes 2a–2c in good isolated yields of 86% (2a), 88% (2b),
catalyst free synthesis of various β-substituted diphenylphos- and 81% (2c). All complexes show good (2a, 2b) or moderate
phino ketones[10,13] and β-amino ketones,[12] which are access- (2c) solubilities in n-hexane, benzene, toluene, and tetra-
ible without any further purification steps starting from methyl hydrofuran. The insertion reactions lead to the formation of
vinyl ketone and appropriate secondary amines and phos- Cp,O π,σ-chelating ligands due to the formation of new C–C
phines, the analogous synthesis of β-thio ketones was targeted. bonds (Scheme 3).
The reactions of methyl vinyl ketone with propane-2-thiol and
The subsequent exchange of the chlorido ligand by a methyl
1
benzylthiol resulted in clean conversions (shown by H NMR group was performed with methyllithium in tetrahydrofuran at
analysis) to the corresponding 1,4-addition products L1a and room temperature to give complexes 3a–3c in good yields of
L1b within 16 h of vigorous stirring at room temperature up to 81% after removal of lithium chloride and all volatiles.
(Scheme 2).
3a–3c show the same solubility properties as 2a–2c.
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Figure 2. Molecular structure of 2c in the crystal. Thermal ellipsoids
are drawn at the 50% probability level (hydrogen atoms are omitted
for clarity). Selected bond lengths /Å and angles /°: Ti1–Cl1 2.3759(5),
Ti1–O1 1.8584(9), O1–C26 1.4310(16), Se1–C28 1.9620(15), C11–
C16 1.5178(18), C16–C26 1.6229(19), C26–C27 1.5439(19), C26–
C29 1.5325(18), Cl1–Ti1–O1 98.51(3), Ct1–Ti1–Ct2 134.0, ΣЄC11
359.5, Σangles C26 320.9 (O1–C26–C27 + O1–C26–C29 + C27–C26–
Scheme 3. Three-/two-step synthesis of cationic titanium complexes
4a–4c with twofold functionalized cyclopentadienyl ligands.
Compounds 2a–2c and 3a–3c were fully characterized by C29) (Ct1 = centroid of C1–C5; Ct2 = centroid of C11–C15).
NMR analyses, and, in the case of 2a, 2c, and 3c crystals for
single-crystal X-ray diffraction were obtained either from satu-
rated solution in n-hexane at –26 °C (2a, 3c) or by recrystalli-
zation in n-hexane at room temperature (2c). The molecular
structures of 2a, 2c, and 3c are shown in Figure 1, Figure 2,
and Figure 3.
Figure 1. Molecular structures of 2a in the crystal. Thermal ellipsoids
are drawn at the 50% probability level (hydrogen atoms are omitted
for clarity). Selected bond lengths /Å and angles /°: Ti1–Cl1 2.3734(8),
Ti1–O1 1.854(2), O1–C26 1.430(3), S1–C28 1.819(3), C11–C16
1.523(4), C16–C26 1.630(4), C26–C27 1.543(4), C26–C29 1.529(4),
C27–C28 1.536(4), Cl1–Ti1–O1 99.32(6), Ct1–Ti1–Ct2 134.0,
Σangles C26 321.2 (O1–C26–C27 + O1–C26–C29 + C27–C26–C29)
(Ct1 = centroid of C1–C5; Ct2 = centroid of C11–C15).
Figure 3. Molecular structure of 3c in the crystal. Thermal ellipsoids
are drawn at the 50% probability level (hydrogen atoms are omitted
for clarity). Selected bond lengths /Å and angles /°: Ti1–C36
2.1794(17), Ti1–O1 1.8653(10), O1–C26 1.4275(17), Se1–C28
1.9690(16), C11–C16 1.527(2), C16–C26 1.6236(19), C26–C27
1.551(2), C26–C29 1.536(2), C36–Ti1–O1 98.62(6), Ct1–Ti1–Ct2
134.9, Σangles C11 359.5, Σangles C26 320.7 (O1–C26–C27 + O1–
Complex 2a crystallizes in the monoclinic space group
C2/c and displays the expected pseudotetrahedral coordination
environment at the central titanium atom as represented by the
Cl1–Ti1–O1 and Ct1–Ti1–Ct2 angles of 99.32(6) and 134.0°, of C11–C15).
C26–C29 + C27–C26–C29) (Ct1 = centroid of C1–C5; Ct2 = centroid
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respectively. Whereas the newly formed bond Ti1–O1 with a NMR spectra and lie between 4:1 and 15:1. The formations of
bond length of 1.854(2) Å constitutes a typical single diastereoisomers in similar ratios was also observed previously
bond,[19,20] the second newly formed bond C16–C26 with a by our group for cationic group 4 complexes with tridentate
bond length of 1.630(4) Å is significantly elongated compared Cp,O,P or Cp,O,N-ligand systems.[9,10,12] The most character-
to typical C(sp3)–C(sp3) single bonds.[21] This elongation of istic NMR spectroscopic data of 2a–2c and 3a–3c are summa-
the Cp,O σ,π-chelating ligand framework is comparable to ste- rized in Table 1 and compared with the NMR spectroscopic
rically crowded alkanes,[22] and also characteristic for com- data of Ia, Ib and IIa, IIb, which feature amine or phosphine
plexes derived from insertion reactions of carbonyl compounds moieties instead of the chalcogen ether functional groups.
into the polarized M–Cq,exo bond of monopentafulvene com-
As can be gathered from Table 1, the chemical shifts of 2a–
plexes.[9,10,12,23] The former carbonyl carbon atom C26 is sp3- 2c and 3a–3c are in excellent agreement with the previously
hybridizied as shown by the sum of angles around C26 (e.g. reported complexes Ia, Ib and IIa, IIb, which were synthe-
O1–C26–C27 + O1–C26–C29 + C27–C26–C29 = 321.2°). The sized by the same reaction sequence, thus being highly charac-
C11–C16 bond length of 1.523(4) Å constitutes now a C(sp2)– teristic for the whole compound class bearing bidentate Cp,O
C(sp3) single bond.[21] This elongation compared to 1[24] con- chelating ligands with a donor functional group in the ligand
firms the transition from the pentafulvene ligand in 1 to a sub- backbone.[9,10,12]
stituted cyclopentadienyl ligand in 2a. The sulfur–carbon bond
According to the established reaction pathway, 3a–3c were
lengths [e.g. S1–C28 1.819(3) Å], and the Ti1–Cl1 bond length finally reacted with the strong Lewis acid B(C6F5)3 in toluene
of 2.3734(8) Å are also typical of single bonds.[19–21] Com- at room temperature. After a few minutes of vigorous stirring
plexes 2c and 3c are isostructural and crystallize in the mono- these reactions were accompanied by the development of two
clinic space group P21/c. The structural parameters are com- phases as soon as the stirring processes were stopped, which
parable to those of 2a. The selenium–carbon bonds in 2c and is already indicative for the formation of the envisaged ionic
3c are typical of Se–C(sp3) single bonds [e.g. Se1–C28 species. After purification the corresponding cationic d0 tita-
1.9620(15) Å (2c), 1.9690(16) Å (3c)], and the Ti1–C36 bond nium complexes 4a–4c, now diastereomerically pure, were ob-
length of 2.1794(17) Å is typical of Ti–C(sp3) single bonds.[21] tained in good isolated yields (Scheme 3).
The NMR spectroscopic data of 2a–2c and 3a–3c show a
The fact that they are diastereomerically pure is clearly veri-
double set of signals in some cases. This is caused by the fied by single set of signals in the NMR spectroscopic data. In
insertion of the carbonyl functional group of the prochiral addition, high-resolution ESI mass spectrometry provides
O,Ch-ligand precursors L1a–c into the polarized Ti–Cq,exo clean detection of the M+ signals of the cationic moieties of
bond, which lead, in addition to the titanium atoms, to the 4a–4c.[25] Compounds 4a–4c are insoluble in aliphatic and aro-
generation of second stereogenic centers at the former carbonyl matic hydrocarbons such as n-hexane, benzene, and toluene,
carbon atoms. Thus, 2a–2c and 3a–3c are obtained as mixtures which proved ideal for purification purposes. Noteworthy, 4a–
of diastereoisomers. The ratios of the diastereoisomers were 4c are consistently stable and excellently soluble in deuterated
determined by integration of appropriate signals in the 1H dichloromethane, which was therefore chosen for measuring
a)
Table 1. Selected NMR parameters of complexes 2a–2c, 3a–3c, Ia, Ib, and IIa, IIb
.
δ1H / δ13C{1H}
MCH3
δ13C{1H}
OCq
δ1H / δ13C{1H}
OCqCH3
δ13C{1H}
Cq,exo/Cq,ipso
δ = 77Se
b)
b)
2a
2b
2c
3a
3b
3c
–
–
–
111.7
111.5
111.7
107.3
107.1
107.5
111.7
107.4
112.1
107.6
1.35/31.1
1.24/31.0
1.32/30.9
1.28/30.9
1.18/30.8
1.23/30.7
1.39/31.0
1.32/30.8
1.29/31.2
1.24/31.1
54.6/156.8
54.6/156.7
54.6/156.5
54.9/151.4
54.8/151.3
54.9/151.3
54.7/156.7
54.9/151.4
54.8/156.9
55.0/151.5
–
–
307.8
–
–
b)
b)
0.22/34.4
0.13/34.5
0.17/34.6
–
0.26/35.3
–
301.9
Ia [10]
Ib [10]
IIa [12]
IIb [12]
–
–
–
–
b)
0.10/34.8
a) The δ values are given in ppm. Measurements were carried out in C6D6 at room temperature. b) Product is a mixture of diastereoisomers;
therefore, only clearly assignable signals of the main diastereoisomer are given.
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the 1D and 2D NMR spectra. The stability towards dichloro- –165.4 (p-FArB), –133.0 (o-FArB) ppm. The Horton parameter
methane is in stark contrast to the analogous cationic titanium
complexes with amine moieties obtained after methyl group
abstraction. For instance IIb reacts readily and cleanly with
CD2Cl2 to give R3NCD2Cl+ and Ti–Cl functional groups
(Scheme 4, bottom).[12]
Δδ(m,p-F) of Δδ(m,p-F) = 2.5 ppm for 4c shows, that the
MeB(C6F5)3– anion is noncoordinating.[26a–26c] This is in good
agreement with other cationic group 4 complexes with this
specific borate anion.[9–11]
Of high diagnostic value, and particularly useful for de-
termining the connectivity of 4c is the 77Se NMR spec-
troscopy. In comparison to the precursor complexes 2c, 3c, and
the free ligand precursor L1c with 77Se NMR chemical shifts
of δ77Se = 309.4 ppm (L1c), 307.8 ppm (2c), and 301.9 ppm
(3c) respectively, the chemical shift in 4c remains nearly un-
changed (δ77Se = 316.1 ppm).[27] This parameter is not only
indicative for same chemical environments at the selenium
atom in this series, but shows that the selenium atom also has
no interaction with the titanium atom in 4c after abstraction of
the methyl group with B(C6F5)3 (Scheme 4, top). Conse-
quently, 4c features a free coordination site at the central tita-
nium atom. This is further supported by the analytical data of
the cationic titanium complexes bearing phosphine functional
groups, reported recently.[9,10] Here, the phosphorus shows a
persistent titanium–phosphorus bond after activation of Ib with
B(C6F5)3 as verified by a significant shift toward lower field
by comparison of the 31P{1H} NMR chemical shifts of Ib and
Ic, respectively [Δδ31P{1H}
= =
41.3 ppm (δ31P{1H}
–12.7 ppm for Ib, and 28.6 ppm for Ic)] (Scheme 4, middle).
All other chemical shifts are in the expected ranges and fit well
into the series of cationic titanium complexes derived from
monopentafulvene complexes and bidentate ligand precursors
with a carbonyl unit and an additional donor functional group
(Table 2).
Scheme 4. Unique features of cationic titanium complexes with dif-
ferent Cp,O,X ligand frameworks and their reactivity toward CD2Cl2
(top: X = S, Se, middle: representative example for X = PR2[10], bot-
tom: representative example for X = NR2[12]).
Based on the results from the 77Se NMR in the series 2c,
3c, 4c, it is very likely, that complexes 4a and 4b with the
thioether functional groups also show no interactions between
the central titanium atoms and the sulfur, which we attribute
to thioether and selenoethers generally being weaker Lewis
bases than phosphine or amine functionalities. Although clear
evidence is missing due to poor crystallization properties of
The NMR spectroscopic data are exemplary discussed for
the selenium congener 4c and summarized for all in Table 2.
They are compared with the previously reported phosphine
substituted cationic complex Ic.[10] The methyl borate anion
–
MeB(C6F5)3 shows the typical chemical shifts in the NMR
spectra, e.g. δ1H/δ13C{1H}(BCH3) = 0.49 s(br) / 9.9 ppm,
δ11B{1H} = –14.8 ppm, and δ19F{1H} = –167.9 (m-FArB), 4a–4c[29] and nearly identical NMR spectroscopic data in com-
a)
Table 2. Selected NMR parameters of complexes 4a–4c, and Ic
.
δ1H / δ13C{1H}
BCH3
δ1H / δ13C{1H}
OCqCH3
δ13C{1H}
OCq
δ13C{1H}
Cq,exo/Cq,ipso
δ11B{1H}
4a
4b
4c
Ic [10]
0.49/10.0
0.50/10.3
0.50/9.9
1.51/32.5
1.51/35.1
1.58/32.8
1.70/34.3
111.2
112.4
112.2
113.9
55.4/157.3
55.4/156.1
55.6/157.8
55.0/155.6
–14.9
–14.9
–14.8
–15.5
0.48/12.8
a) The δ values are given in ppm. Measurements were carried out in CD2Cl2 at room temperature.
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and weighed in a glovebox or dried under high vacuum before use.
parison to the cationic titanium complex Ic with a persistent
The methyllithium was used as a 1.6 m solution in diethyl ether. The
pentafulvene complex 1 was synthesized according to a literature pro-
cedure.[24] Methyl vinyl ketone, propane-2-thiol, and benzylthiol were
purchased from commercial sources, freshly distilled over CaCl2,
freeze-pump-thaw degassed three times prior to use, and stored under
nitrogen. Diphenyl diselenide, ruthenium(III)chloride hydrate, and zinc
dust were purchased from commercial sources and used as received.
Thin-layer chromatography was performed using commercially avail-
able Alugram SIL/G UV254 sheets with fluorescent indicator (254 nm)
Ti/P interaction, a further reason might be the overall high
similarity of thioethers and selenoethers.
In summary, the implementation of chalcogen ether func-
tional groups into the design of twofold functionalized Cp,O,X
based ligand frameworks leads to the maintenance of a biden-
tate Cp,O ligand system after activation with B(C6F5)3. Hence
a free coordination site at the central titanium atom, and also
a pendant and unoccupied chalcogen ether moiety are present
in 4a–4c, clearly emphasizing the unique characteristics of this from Macherey–Nagel. Silica gel from Grace (particle size 40–63 μm)
was used for column chromatography. High-resolution mass spectra of
4a–4c were measured with a Finnigan-MAT95 spectrometer using ESI
(solvent: dichloromethane). Infrared spectra were performed with a
Bruker Tensor 27 spectrometer with a MKII Reflection Golden Gate
Single Diamond ATR system. NMR spectra were recorded with Bruker
Avance 300, Bruker Avance 500, and Bruker Avance III 500 spectrom-
eters. 1H NMR spectra were referenced to the residual solvent reso-
nance as internal standard ([D6]benzene (C6D6): δ1H(C6D5 H) =
7.16 ppm, [D2]dichloromethane (CD2Cl2): δ1H(CDHCl2) = 5.32 ppm)
and 13C{1H} spectra were referenced by using the central line of the
solvent signal ([D6]benzene (C6D6): δ13C{1H}(C6D6) = 128.06 ppm,
[D2]dichloromethane (CD2Cl2): δ13C{1H}(CD2Cl2) = 53.84 ppm).
11B{1H} NMR, 19F{1H} NMR, and 77Se NMR spectra were referenced
explicit substitution pattern, especially when compared to the
Cp,O,P and Cp,O,N congeners.
Conclusions
A high-yielding, solvent- and catalyst free synthesis of the
β-thio ketones L1a and L1b is described, starting from the
commercially available methyl vinyl ketone and selected thi-
ols. The synthesized β-thio ketones L1a, L1b, and the β-seleno
ketone L1c were successfully employed as ligand precursors
in the established three-step synthesis of the cationic titanium
complexes 4a–4c by insertion, subsequent methylation and ac-
tivation with the strong Lewis acid B(C6F5)3. 4a–4c were ob-
tained in good isolated yields under mild reaction conditions.
The analytical data show that the corresponding methyl borate
anion MeB(C6F5)3– is noncoordinating in all cases. 77Se NMR
spectroscopy of derivative 4c showed, that in contrast to the
previously reported cationic titanium complexes with triden-
tate Cp,O,P ligands,[9,10] the respective chalcogen atoms of the
chalcogen ether functionalities do not coordinate to the central
titanium atoms in 4a–4c. Thus 4a–4c are bearing bidentate
Cp,O chelating ligands with unoccupied chalcogen ether func-
tionalities in the ligands backbone, and free coordinate sites at
the central titanium atoms, clearly distinguishing this series of
cationic d0 titanium complexes from the previously reported
ones. These findings underline the flexibility in tuning elec-
tronic and steric properties of tridentate and bidentate ligands,
which are built directly in the coordination sphere of the cen-
tral metal atom. Due to the missing interaction between the
central Lewis acidic titanium atom and the pendant chalcogen
ether functionalities, it might be challenging to find metal-li-
gand cooperative activations of substrates, which has been key
to success in the previous reported systems with Ti···N and
Ti–N functionalities.[11,12] Nevertheless, the free coordination
site might open up novel subsequent reactions and applica-
tions, which are currently subject to investigation in our group.
against external standards [BF3·OEt2 (δ11B{1H}(BF3·OEt2)
=
0.0 ppm); CFCl3 (δ19F{1H}(CFCl3) = 0.0 ppm); Me2Se (δ77Se(Me2Se)
= 0.0 ppm)]. Elemental analyses were carried out with a EuroEA 3000
Elemental Analyzer. The carbon and hydrogen values in the elemental
analysis are found in some times higher, which we attribute to residue
of solvents. Melting points were determined with a “Mel-Temp” appa-
ratus by Laboratory Devices, Cambridge, U·K. Single crystal X-ray
data were measured with a Bruker AXS diffractometer with Apex II
CCD detector and graphite monochromated Mo-Kα1 radiation with
λ = 0.71073 Å.
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1886225, CCDC-1886226, and CCDC-1886227.
(Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk, http://
www.ccdc.cam.ac.uk)
Synthesis of L1a: Propane-2-thiol (2.2 mL, 23.68 mmol) was slowly
added to freshly condensed methyl vinyl ketone (2.0 mL, 23.68 mmol)
at room temperature. The solution was stirred for 16 h at room tem-
perature to yield L1a as slightly yellow oil in quantitative yield and
was used without further purification steps. Yield: 3.256 g
1
(22.26 mmol; 94%). H NMR (500 MHz, C6D6, 300 K): δ = 1.10 [d,
3J(H,H) = 6.7 Hz, 6 H, CH(CH3)2], 1.57 (s, 3 H, O = CqCH3), 2.17 (t,
3
3JH,H = 7.4 Hz, SCH2CH2), 2.60 (t, JH,H = 7.4 Hz, SCH2CH2), 2.64
3
[hept, JH,H = 6.8 Hz, CH(CH3)2] ppm. 13C{1H} NMR [126 MHz,
C6D6, 300 K):
δ = 23.5 [CH(CH3)2], 24.7 (SCH2CH2), 29.4
(O=CqCH3), 35.3 [CH(CH3)2], 43.6 (SCH2CH2), 204.7 (O=CqCH3)
ppm.
Experimental Section
General: All air- and moisture-sensitive reactions were carried out in Synthesis of L1b: Benzylthiol (2.8 mL, 23.68 mmol) was slowly
an inert atmosphere of argon or nitrogen with rigorous exclusion of added to freshly condensed methyl vinyl ketone (2.0 mL, 23.68 mmol)
oxygen and moisture using standard glovebox and Schlenk techniques.
The glass equipment was stored in an oven at 120 °C and evacuated
prior to use. Solvents and liquid starting materials were dried accord-
ing to standard procedures and/or freeze-pump-thaw degassed three
at room temperature. The solution was stirred for 16 h at room tem-
perature to yield L1b as colorless oil in quantitative yield and was
used without further purification steps. Yield: 4.223 g (21.74 mmol;
92%). 1H NMR (500 MHz, C6D6, 305 K): δ = 1.51 (s, 3 H,
3
3
times prior to use. Solvents were distilled over Na/K alloy and benzo- O=CqCH3), 2.05 (t, JH,H = 7.3 Hz, 2 H, SCH2CH2), 2.48 (t, JH,H
=
phenone or CaH2 in a nitrogen atmosphere. Solid materials were stored 7.3 Hz, 2 H, SCH2CH2), 3.41 (s, 2 H, SCH2Ph), 7.00–7.05 (m, 1 H,
Z. Anorg. Allg. Chem. 0000, 0–0
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
p-CHPhCH2S), 7.08–7.11 (m, 2 H, 2ϫm-CHPhCH2S), 7.16–7.18 (m,
7.50–7.51 (m, 2 H, 2ϫo-CHPhCH2S) ppm. 13C{1H} NMR (126 MHz,
2 H, 2ϫo-CHPhCH2S)* ppm. 13C{1H} NMR (126 MHz, C6D6, C6D6, 305 K): δ = 12.5 (C5Me5), 27.5 (CHAd), 28.0 (CHAd), 31.0
305 K): δ = 25.6 (SCH2CH2), 29.3 (O=CqCH3), 36.9 (SCH2Ph), 43.2 (OCqCH3), 32.7 (CHAd), 32.9 (CHAd), 33.7 (CH2,Ad), 34.8 (CH2,Ad),
(SCH2CH2), 127.2 (p-CHPhCH2S), 128.7 (2ϫm-CHPhCH2S), 129.2 37.2 (CH2,Ad), 37.3 (CH2,Ad), 37.6 (CH2,Ad), 37.7 (SCH2Ph), 39.4
(2ϫo-CHPhCH2S), 139.1 (Cq,Ph), 204.5 (O=CqCH3) ppm. * = overlap
with C6D6 signals.
(SCH2CH2), 40.3 (SCH2CH2), 54.6 (Cq,exo), 104.5 (C5H4), 111.5
(OCqCH3), 111.7 (C5H4), 112.8 (C5H4), 120.0 (C5H4), 123.8 (C5Me5),
126.7 (p-CHPhCH2S), 128.5 (2ϫm-CHPhCH2S), 129.5 (2ϫo-
CHPhCH2S), 140.8 (Cq,Ph), 156.7 (Cq,ipso) ppm. C36H47ClOSTi: calcd.
C 70.75; H 7.75%; found: C 71.51; H 7.88%.
Synthesis of L1c: L1c was synthesized according to a literature pro-
cedure.[14] Diphenyl diselenide (0.400 g, 1.282 mmol), zinc dust
(0.450 g, 6.883 mmol), and ruthenium(III)chloride hydrate (30 mg,
0.133 mmol) were suspended in 12 mL of acetonitrile and 2 mL of
water. The reaction mixture was stirred for 1 h at 80 °C, followed by
the addition of methyl vinyl ketone (0.22 mL, 2.563 mmol) and further
stirring at 80 °C for 1 h. The solution was filtered, all volatile compo-
nents were removed under vacuum, and the crude product was purified
by column chromatography (SiO2; hexane:EE = 4:1). L1c was ob-
tained as slightly yellow oil. Rf = 0.30 (SiO2; hexane:EE = 4:1). Yield:
Synthesis of 2c: In a glove box compound L1c (0.250 g, 1.101 mmol)
in n-hexane (3ϫ2 mL) was added to a solution of complex 1 (0.459 g,
1.101 mmol) in 12 mL of n-hexane. The reaction mixture was stirred
for 16 h at room temperature. All volatile components were removed
under vacuum, and the residue was recrystallized from n-hexane to
give 2c as an orange solid as a mixture of both diastereoisomers (ratio
approximately 10:1). Yield: 0.576 g (0.894 mmol, 81%). Melting
point: 154–156 °C (dec.). IR (ATR): ν˜ = 2950, 2912, 2850, 1717,
1577, 1476, 1449, 1435, 1375, 1329, 1300, 1208, 1197, 1173, 1144,
1099, 1060, 1021, 981, 947, 914, 875, 847, 817, 744, 691, 670, 644,
1
0.312 g (1.373 mmol; 54%). H NMR (500 MHz, C6D6, 305 K): δ =
3
1.48 (s, 3 H, OCqCH3), 2.25 (t, JH,H = 7.3 Hz, SeCH2CH2), 2.86 (t,
3JH,H = 7.2 Hz, SeCH2CH2), 6.96–7.00 (m, 3 H, 3ϫCHPh), 7.37–7.39
(m, 2 H, 2ϫCHPh) ppm. 13C{1H} NMR (126 MHz, C6D6, 305 K): δ
= 20.8 (SeCH2CH2), 29.2 (OCqCH3), 43.8 (SeCH2CH2), 127.1 (CHPh),
129.4 (2ϫCHPh), 130.9 (Cq,Ph), 132.9 (2ϫCHPh), 204.7 (OCqCH3)
ppm. 77Se NMR (95 MHz, C6D6, 305 K): δ = 309.4 ppm.
1
631, 616 cm–1. H NMR (500 MHz, C6D6, 305 K): δ = 1.32 (s, 3 H,
OCqCH3), 1.39–1.43 (m, 1 H, CHAd/CH2,Ad), 1.52–1.73 (m, 8 H,
CHAd/CH2,Ad), 1.77 (s, 15 H, C5Me5), 2.06–2.16 (m, 3 H, CHAd
/
CH2,Ad, OCqCH2CH2Se), 2.28–2.28 (m, 1 H, CHAd/CH2,Ad), 2.36–2.45
(m, 2 H, CHAd/CH2,Ad), 2.98–3.04 (m, 2 H, OCqCH2CH2Se), 3.19–
3.23 (m, 1 H, OCqCH2CH2Se), 5.02–5.03 (m, 1 H, C5H4), 5.36–5.37
(m, 1 H, C5H4), 5.46–5.48 (m, 1 H, C5H4), 6.39–6.40 (m, 1 H, C5H4),
6.99–7.02 (m, 1 H, p-CHPh), 7.08–7.11 (m, 2 H, 2ϫm-CHPh), 7.69–
7.71 (m, 2 H, 2ϫo-CHPh) ppm. 13C{1H} NMR (126 MHz, C6D6,
305 K): δ = 12.6 (C5Me5), 23.4 (OCqCH2CH2Se), 27.5 (CHAd), 28.0
(CHAd), 30.9 (OCqCH3), 32.7 (CHAd), 32.9 (CHAd), 33.5 (CH2,Ad),
34.8 (CH2,Ad), 37.2 (CH2,Ad), 37.3 (CH2,Ad), 39.4 (CH2,Ad), 40.3
(OCqCH2CH2Se), 54.6 (Cq,exo), 104.6 (C5H4), 111.4 (C5H4), 111.7
(OCqCH3), 113.0 (C5H4), 120.3 (C5H4), 123.9 (C5Me5), 126.3 (p-
CHPh), 129.2 (2ϫCHPh), 132.7 (2ϫCHPh), 132.9 (Cq,Ph), 156.5
(Cq,ipso) ppm. 77Se NMR (95 MHz, C6D6, 305 K): δ = 307.8 ppm.
C35H45ClOSeTi: calcd. C 65.28; H 7.04%; found: C 64.94; H 7.00%.
Synthesis of 2a: In a glove box compound L1 (0.211 g, 1.439 mmol)
in toluene (3ϫ2 mL) was added to a solution of complex 1 (0.600 g,
1.439 mmol) in 8 mL of toluene. The reaction mixture was stirred for
16 h at room temperature. All volatile components were removed un-
der vacuum to give 2a as a yellow-orange solid as a mixture of both
diastereoisomers (ratio: approximately 5:1). NMR spectroscopic data
is given for the clearly assignable signals of the main diastereoisomer.
Yield: 0.696 g (1.236 mmol, 86%). Melting point: 71–73 °C (dec.). IR
(ATR): ν˜ = 2902, 2855, 1714, 1481, 1450, 1374, 1245, 1186, 1167,
1148, 1098, 1073, 1063, 1022, 998, 982, 969, 954, 874, 849, 812, 790,
771, 692, 683, 658, 634 cm–1. 1H NMR (500 MHz, C6D6, 299 K):
3
δ = 1.35 (s, 3 H, OCqCH3), 1.37 [d, JH,H = 6.8 Hz, 3 H, CH(CH3)2],
3
1.42 [d, JH,H = 6.6 Hz, 3 H, CH(CH3)2], 1.77 (s, 15 H, C5Me5), 3.20
Synthesis of 3a: To a solution of complex 2a (0.600 g, 1.066 mmol)
in 10 mL of tetrahydrofurane was added a methyllithium solution
(0.7 mL, 1.066 mmol; 1.6 m in diethyl ether). The reaction mixture
was stirred for 16 h at room temperature. The solvent was completely
removed, and the residue was dissolved in 12 mL of toluene. The solu-
tion was filtered, and the residue was washed with toluene
(2ϫ12 mL). All volatile components were removed under vacuum to
give complex 3a as a pale yellow solid as a mixture of both diastereo-
isomers (ratio: approximately 7:1). NMR spectroscopic data is given
for the clearly assignable signals of the main diastereoisomer. Yield:
0.471 g (0.868 mmol, 81%). Melting point: 74–76 °C (dec.). IR
(ATR): ν˜ = 2901, 2855, 1638, 1480, 1450, 1374, 1329, 1244, 1205,
1182, 1167, 1148, 1117, 1097, 1072, 1062, 1022, 969, 961, 874, 849,
809, 684, 659, 634 cm–1. 1H NMR (500 MHz, C6D6, 305 K): δ = 0.22
3
[hept, JH,H = 6.7 Hz, 1 H, CH(CH3)2], 5.03–5.04 (m, 1 H, C5H4),
5.38–5.40 (m, 1 H, C5H4), 5.44–5.46 (m, 1 H, C5H4), 6.41–6.43 (m,
1 H, C5H4) ppm. 13C{1H} NMR (126 MHz, C6D6, 299 K): δ = 12.6
(C5Me5), 24.1 [CH(CH3)2], 24.6 [CH(CH3)2], 25.9 (CH2), 27.5
(CHAd), 28.0 (CHAd), 31.1 (OCqCH3), 32.7 (CHAd), 32.9 (CHAd), 33.6
(CH2), 34.8 (CH2), 35.8 [CH(CH3)2], 37.2 (CH2), 37.3 (CH2), 39.4
(CH2), 40.4 (CH2), 54.6 (Cq,exo), 104.5 (C5H4), 111.66 (OCqCH3),
111.7 (C5H4), 112.7 (C5H4), 120.0 (C5H4), 123.7 (C5Me5), 156.8
(Cq,ipso) ppm. C32H47ClOSTi: calcd. C 68.26; H 8.41%; found: C
68.19; H 8.59%.
Synthesis of 2b: In a glove box compound L1 (0.248 g, 1.276 mmol)
in toluene (3ϫ2 mL) was added to a solution of complex 1 (0.532 g,
1.439 mmol) in 8 mL of toluene. The reaction mixture was stirred for
16 h at room temperature. All volatile components were removed un-
der vacuum to give 2b as a yellow-brown solid as a mixture of both CH(CH3)2], 1.31 [d, JH,H = 6.7 Hz, 3 H, CH(CH3)2], 1.70 (s, 15 H,
diastereoisomers (ratio: approximately 4:1). NMR spectroscopic data
3
(s, 3 H, TiCH3), 1.28 (s, 3 H, OCqCH3), 1.30 [d, JH,H = 6.7 Hz, 3 H,
3
3
C5Me5), 2.92 [hept, JH,H = 6.8 Hz, 1 H, CH(CH3)2], 4.85–4.86 (m, 1
is given for the clearly assignable signals of the main diastereoisomer. H, C5H4), 5.07–5.09 (m, 1 H, C5H4), 5.28–5.29 (m, 1 H, C5H4), 6.15–
Yield: 0.687 g (1.124 mmol, 88%). Melting point: 64–68 °C (dec.). IR 6.16 (m, 1 H, C5H4) ppm. 13C{1H} NMR (126 MHz, C6D6, 305 K): δ
(ATR): ν˜ = 2901, 2852, 1711, 1493, 1481, 1451, 1374, 1223, 1186,
= 11.9 (C5Me5), 23.9 [CH(CH3)2], 24.1 [CH(CH3)2], 25.8 (CH2), 27.8
(CHAd), 28.2 (CHAd), 30.9 (OCqCH3), 32.9 (CHAd), 33.0 (CHAd), 33.9
(CH2), 34.4 (TiCH3), 35.0 (CH2), 35.7 [CH(CH3)2], 37.38 (CH2), 37.4
(CH2), 39.6 (CH2), 40.5 (CH2), 54.9 (Cq,exo), 103.5 (C5H4), 107.3
(OCqCH3), 108.1 (C5H4), 108.7 (C5H4), 116.3 (C5H4), 118.6 (C5Me5),
1167, 1148, 1098, 1064, 1023, 970, 955, 875, 849, 812, 791, 770, 701,
1
658, 634 cm–1. H NMR (500 MHz, C6D6, 305 K): δ = 1.24 (s, 3 H,
OCqCH3), 1.74 (s, 15 H, C5Me5), 2.77–2.85 (m, 2 H, SCH2CH2), 3.89
(s, 2 H, SCH2Ph), 5.01–5.02 (m, 1 H, C5H4), 5.38–5.40 (m, 1 H,
C5H4), 5.44–5.46 (m, 1 H, C5H4), 6.39–6.41 (m, 1 H, C5H4), 7.06– 151.4 (Cq,ipso) ppm. C33H50OSTi: calcd. C 73.06; H 9.29%; found: C
7.10 (m, 1 H, p-CHPhCH2S), 7.18–7.21 (m, 2 H, 2ϫm-CHPhCH2S), 71.97; H 8.49%.
Z. Anorg. Allg. Chem. 0000, 0–0
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Synthesis of 3b: To a solution of complex 2b (0.370 g, 0.605 mmol)
(0.4 mL, 0.605 mmol; 1.6 m in diethyl ether). The reaction mixture
in 10 mL of tetrahydrofurane was added a methyllithium solution was stirred for 16 h at room temperature. The solvent was completely
(0.4 mL, 0.605 mmol; 1.6 m in diethyl ether). The reaction mixture
was stirred for 16 h at room temperature. The solvent was completely
removed, and the residue was dissolved in 8 mL of toluene. The solu-
removed, and the residue was dissolved in 8 mL of toluene. The solu-
tion was filtered, and the residue was washed with toluene
(2ϫ10 mL). All volatile components were removed under vacuum to
tion was filtered, and the residue was washed with toluene give complex 3b as an orange solid as a mixture of both diastereoiso-
(2ϫ10 mL). All volatile components were removed under vacuum to mers (ratio: approximately 10:1). NMR spectroscopic data is given for
give complex 3b as an orange solid as a mixture of both diastereoiso-
the clearly assignable signals of the main diastereoisomer. Yield:
mers (ratio: approximately 10:1). NMR spectroscopic data is given for 0.253 g (0.428 mmol, 71%). Melting point: 81–83 °C. IR (ATR): ν˜ =
the clearly assignable signals of the main diastereoisomer. Yield:
0.253 g (0.428 mmol, 71%). Melting point: 81–83 °C. IR (ATR): ν˜ =
2901, 2852, 1493, 1480, 1451, 1373, 1331, 1261, 1235, 1206, 1182,
1168, 1147, 1098, 1063, 1023, 971, 961, 876, 849, 808, 697, 658,
634 cm–1. 1H NMR (500 MHz, C6D6, 305 K): δ = 0.13 (s, 3 H,
TiCH3), 1.18 (s, 3 H, OCqCH3), 1.65 (s, 15 H, C5Me5), 3.66–3.67 (m,
2 H, SCH2Ph), 4.83–4.85 (m, 1 H, C5H4), 5.07–5.08 (m, 1 H, C5H4),
5.24–5.26 (m, 1 H, C5H4), 6.12–6.13 (m, 1 H, C5H4), 7.06–7.09 (m,
1 H, p-CHPhCH2S), 7.16–7.19 (m, 2 H, 2ϫm-CHPhCH2S)*, 7.34–7.36
(m, 2 H, 2ϫo-CHPhCH2S) ppm. 13C{1H} NMR (126 MHz, C6D6,
2901, 2852, 1493, 1480, 1451, 1373, 1331, 1261, 1235, 1206, 1182,
1168, 1147, 1098, 1063, 1023, 971, 961, 876, 849, 808, 697, 658,
634 cm–1. 1H NMR (500 MHz, C6D6, 305 K): δ = 0.13 (s, 3 H,
TiCH3), 1.18 (s, 3 H, OCqCH3), 1.65 (s, 15 H, C5Me5), 3.66–3.67 (m,
2 H, SCH2Ph), 4.83–4.85 (m, 1 H, C5H4), 5.07–5.08 (m, 1 H, C5H4),
5.24–5.26 (m, 1 H, C5H4), 6.12–6.13 (m, 1 H, C5H4), 7.06–7.09 (m,
1 H, p-CHPhCH2S), 7.16–7.19 (m, 2 H, 2ϫm-CHPhCH2S)*, 7.34–7.36
(m, 2 H, 2ϫo-CHPhCH2S) ppm. 13C{1H} NMR (126 MHz, C6D6,
305 K): δ = 11.9 (C5Me5), 27.2 (CH2), 27.8 (CHAd), 28.2 (CHAd), 30.8
(OCqCH3), 32.7 (CH2), 32.8 (CHAd), 33.0 (CHAd), 33.9 (CH2), 34.5
305 K): δ = 11.9 (C5Me5), 27.2 (CH2), 27.8 (CHAd), 28.2 (CHAd), 30.8 (TiCH3), 35.0 (CH2), 37.4 (SCH2Ph), 37.7 (CH2), 39.6 (CH2), 40.3
(OCqCH3), 32.7 (CH2), 32.8 (CHAd), 33.0 (CHAd), 33.9 (CH2), 34.5 (CH2), 54.8 (Cq,exo), 103.4 (C5H4), 107.1 (OCqCH3), 108.0 (C5H4),
(TiCH3), 35.0 (CH2), 37.4 (SCH2Ph), 37.7 (CH2), 39.6 (CH2), 40.3 108.7 (C5H4), 116.2 (C5H4), 118.6 (C5Me5), 126.9 (p-CHPhCH2S),
(CH2), 54.8 (Cq,exo), 103.4 (C5H4), 107.1 (OCqCH3), 108.0 (C5H4), 128.6 (2ϫm-CHPhCH2S), 129.3 (2ϫo-CHPhCH2S), 140.0 (Cq,Ph),
108.7 (C5H4), 116.2 (C5H4), 118.6 (C5Me5), 126.9 (p-CHPhCH2S), 151.3 (Cq,ipso) ppm. C37H50OSTi: calcd. C 75.23; H, 8.53%; found: C
128.6 (2ϫm-CHPhCH2S), 129.3 (2ϫo-CHPhCH2S), 140.0 (Cq,Ph),
151.3 (Cq,ipso) ppm. C37H50OSTi: calcd. C 75.23; H 8.53%; found: C
74.02; H 8.16%.
74.02; H, 8.16%.
Synthesis of 4a: A mixture of complex 3a (0.150 g, 0.276 mmol) and
B(C6F5)3 (0.142 g, 0.276 mmol) was stirred in 8 mL of toluene. By
stopping the stirring process after a few minutes, the development of
two phases can be observed due to the formation of 4a. The solvent
was decanted, the residue was washed with n-hexane (3ϫ5 mL), and
dried under vacuum to give complex 4a as an orange solid. Yield:
0.243 g (0.230 mmol, 83%). Melting point: 58–60 °C (dec.). IR
(ATR): ν˜ = 2913, 2861, 1638, 1509, 1455, 1380, 1267, 1081, 979, 965,
950, 934, 891, 824, 757, 705, 659, 603, 565 cm–1. 1H NMR (500 MHz,
CD2Cl2, 305 K): δ = 0.49 (s(br), 3 H, BCH3), 1.01 [d, JH,H = 6.8 Hz,
3 H, CH(CH3)2], 1.51–1.52 [m, 6 H, OCqCH3, CH(CH3)2], 1.64–1.79
(m, 9 H, CHAd/CH2,Ad), 1.89–1.97 (m, 3 H, CHAd/CH2,Ad), 2.02 (s, 15
H, C5Me5), 2.23–2.26 (m, 1 H, NCH2CH2), 2.33–2.38 (m, 1 H, CHAd
CH2,Ad)*, 2.54–2.55 (m, 1 H, CHAd/CH2,Ad), 2.63–2.66 (m, 1 H,
NCH2CH2), 2.79–2.85 (m, 1 H, NCH2CH2), 2.95–2.99 (m, 1 H,
NCH2CH2), 3.09 [hept, JH,H = 6.5 Hz, 1 H, CH(CH3)2], 5.12–5.13
(m, 1 H, C5H4), 5.34–5.35 (m, 1 H, C5H4), 6.34–6.35 (m, 1 H, C5H4),
6.65–6.66 (m, 1 H, C5H4) ppm. 13C{1H} NMR (126 MHz, CD2Cl2,
305 K): δ = 10.0 (BCH3)**, 12.9 (C5Me5), 22.2 [CH(CH3)2], 22.7
[CH(CH3)2], 27.4 (CHAd), 28.0 (CHAd), 32.5 (OCqCH3), 32.9 (CH2),
33.0 (CH2), 33.8 (CHAd), 34.1 (CHAd), 34.3 (CH2), 36.4 (CH2), 36.9
(CH2), 37.5 (CH2), 39.2 (CH2), 39.8 [CH(CH3)2], 55.4 (Cq,exo), 107.3
(C5H4), 111.2 (OCqCH3), 113.5 (C5H4), 113.6 (C5H4), 119.1 (C5H4),
Synthesis of 3c: To a solution of complex 1 (0.200 g, 0.311 mmol) in
8 mL of tetrahydrofurane was added a methyllithium solution (0.2 mL,
0.311 mmol; 1.6 m in diethyl ether). The reaction mixture was stirred
for 16 h at room temperature. The solvent was completely removed,
and the residue was dissolved in 8 mL of toluene. The solution was
filtered, and the residue was washed with toluene (2ϫ8 mL). All vola-
tile components were removed under vacuum to give complex 3c as a
pale yellow solid as a mixture of both diastereosiomers (ratio: approxi-
mately 15:1). NMR spectroscopic data is given for the clearly assign-
able signals of the main diastereoisomer. Yield: 0.136 g (0.218 mmol,
70%). Melting point: 58–60 °C (dec.). IR (ATR): ν˜ = 2900, 2853,
1579, 1477, 1450, 1436, 1373, 1324, 1301, 1207, 1166, 1146, 1119,
1097, 1061, 1022, 998, 982, 957, 912, 872, 849, 809, 732, 690, 670,
3
/
1
631, 618 cm–1. H NMR (500 MHz, C6D6, 305 K): δ = 0.18 (s, 3 H,
3
TiCH3), 1.23 (s, 3 H, OCqCH3), 1.42–1.49 (m, 2 H, CHAd/CH2,Ad),
1.55–1.60 (m, 3 H, CHAd/CH2,Ad), 1.66–1.68 (m, 3 H, CHAd/CH2,Ad),
1.68 (s, 15 H, C5Me5), 1.77–1.78 (m, 1 H, CHAd/CH2,Ad), 1.92–1.95
(m, 1 H, CHAd/CH2,Ad), 2.06–2.12 (m, 1 H, SeCH2CH2), 2.18–2.19
(m, 1 H, CHAd/CH2,Ad), 2.28–2.29 (m, 1 H, CHAd/CH2,Ad), 2.45–2.54
(m, 2 H, SeCH2CH2, CHAd/CH2,Ad), 2.68–2.71 (m, 1 H, CHAd
/
CH2,Ad), 2.75–2.81 (m, 1 H, SeCH2CH2), 2.92–2.97 (m, 1 H,
SeCH2CH2), 4.85–4.86 (m, 1 H, C5H4), 5.05–5.07 (m, 1 H, C5H4),
5.26–5.27 (m, 1 H, C5H4), 6.13–6.14 (m, 1 H, C5H4), 6.98–7.01 (m,
1 H, p-CHArylSe), 7.05–7.08 (m, 2 H, 2ϫm-CHArylSe), 7.60–7.62 (m,
2 H, 2ϫo-CHArylSe) ppm. 13C{1H} NMR (126 MHz, C6D6, 305 K):
δ = 11.9 (C5Me5), 23.4 (SeCH2CH2), 27.7 (CHAd), 28.2 (CHAd), 30.7
(OCqCH3), 32.8 (CHAd), 33.0 (CHAd), 33.7 (CH2), 34.6 (TiCH3), 35.0
(CH2), 37.35 (CH2), 37.38 (CH2), 39.6 (CH2), 41.0 (SeCH2CH2), 54.9
(Cq,exo), 103.5 (C5H4), 107.5 (OCqCH3), 107.9 (C5H4), 108.8 (C5H4),
116.3 (C5H4), 118.7 (C5Me5), 126.6 (p-CHArySe), 129.2 (2ϫm-
CHArylSe), 132.4 (Cq,Ph), 132.8 (2ϫo-CHArylSe), 151.3 (Cq,ipso) ppm.
77Se NMR (95 MHz, C6D6, 305 K): δ = 301.9 ppm. C36H48OSeTi:
calcd. C 69.34; H 7.76%; found: C 69.40; H 8.02%.
1
128.2 (C5Me5), 128.7 (Cq,ArB)**, 136.8 (dm, JC,F = 237.2 Hz,
Cq,ArF), 137.9 (dm, JC,F = 243.5 Hz, Cq,ArF), 148.7 (dm, JC,F
1
1
=
236.0 Hz, Cq,ArF), 157.3 (Cq,ipso) ppm. * = overlay with the signals of
residue of toluene. ** = assignment by 1H/13C-HMQC/HMBC spectra.
11B{1H} NMR (160 MHz, CD2Cl2, 305 K): δ = –14.9 ppm. 19F{1H}
NMR (470 MHz, CD2Cl2, 305 K): δ = –167.9 (m, 6F, m-FArB), –165.3
(t, 3JF,F = 20.3 Hz, 3F, p-FArB), –133.1 (m, 6F, o-FArB) ppm; Δδ19Fm,p
= 2.6 ppm. HR/MS: calculated: m/z = 527.2827 [M+]; measured (ESI):
m/z = 527.2831. C51H50BF15OSTi: calcd. C 58.08; H, 4.78%; found:
C 57.06; H, 4.87%.
Synthesis of 4b: A mixture of complex 3b (0.105 g, 0.178 mmol) and
Synthesis of 3b: To a solution of complex 2b (0.370 g, 0.605 mmol)
B(C6F5)3 (0.091 g, 0.178 mmol) was stirred in 8 mL of toluene. By
in 10 mL of tetrahydrofurane was added a methyllithium solution stopping the stirring process after a few minutes, the development of
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two phases can be observed due to the formation of 4b. The solvent C54H48BF15OSeTi: calcd. C 57.12; H, 4.26%; found: C 57.55; H,
was decanted, the residue was washed with n-hexane (3ϫ5 mL), and 3.73%.
dried under vacuum to give complex 4b as an orange solid. Yield:
0.160 g (0.146 mmol, 82%). Melting point: 77–79 °C (dec.). IR
(ATR): ν˜ = 2914, 1640, 1509, 1450, 1379, 1267, 1081, 951, 934, 900,
826, 765, 732, 701, 659, 643, 603 cm–1. 1H NMR (500 MHz, CD2Cl2,
305 K): δ = 0.50 [s(br), 3 H, BCH3], 1.51 (s, 3 H, OCqCH3), 1.74–
1.96 (m, 10 H, CHAd/CH2,Ad/SCH2CH2), 2.03 (s, 15 H, C5Me5), 2.06–
2.19 (m, 3 H, CHAd/CH2,Ad), 2.57–2.58 (m, 2 H, CHAd/CH2,Ad), 2.68–
2.72 (m, 1 H, SCH2CH2), 2.78–2.89 (m, 2 H, SCH2CH2), 3.63–3.71
(m, 2 H, SCH2Ph), 5.06–5.07 (m, 1 H, C5H4), 5.39–5.40 (m, 1 H,
C5H4), 6.43–6.44 (m, 1 H, C5H4), 6.65–6.66 (m, 1 H, C5H4), 7.31–
7.33 (m, 2 H, 2ϫCHPh), 7.43–7.44 (m, 3 H, 3ϫCHPh) ppm. 13C{1H}
NMR (126 MHz, CD2Cl2, 305 K): δ = 10.3 (BCH3)*, 12.7 (C5Me5),
27.2 (CHAd), 27.9 (CHAd), 33.3 (CHAd), 33.46 (CHAd), 33.51 (CH2),
34.4 (CH2), 34.9 (CH2), 35.1 (OCqCH3), 36.6 (CH2), 37.3 (CH2), 37.6
(CH2), 39.0 (CH2), 41.7 (SCH2Ph), 55.4 (Cq,exo), 106.2 (C5H4), 112.4
(OCqCH3), 113.4 (C5H4), 115.8 (C5H4), 119.5 (C5H4), 127.7 (C5Me5),
128.9 (Cq,ArB)*, 129.7 (3ϫCHPh), 130.0 (2ϫCHPh), 133.0 (Cq,Ph),
Supporting Information (see footnote on the first page of this article):
The general considerations, the synthesis and characterization of the
compounds L1a, L1b, L1c, 2a, 2b, 2c, 3a, 3b, 3c, 4a, 4b, 4c, the
Crystallographic Data of 2a, 2c, 3c, and the 1H-, 13C{1H}-, 77Se-,
11B{1H}-, 19F{1H}-NMR-Spectra can be found in the electronic
supporting information (ESI).
Acknowledgements
Financial Support by the DFG Research Training Group 2226 is kindly
acknowledged.
Keywords: Pentafulvene; Titanium; Cationic complex;
Ligand design; NMR spectroscopy
1
1
136.8 (dm, JC,F = 243.5 Hz, Cq,ArF), 137.9 (dm, JC,F = 243.1 Hz,
Cq,ArF), 148.8 (dm, 1JC,F = 243.1 Hz, Cq,ArF), 156.1 (Cq,ipso) ppm. * =
assignment by 1H/13C-HMQC/HMBC spectra. 11B{1H} NMR
References
(160 MHz, CD2Cl2, 305 K): δ = –14.9 ppm. 19F{1H} NMR (470 MHz,
3
CD2Cl2, 305 K): δ = –167.9 (m, 6F, m-FArB), –165.3 (t, JF,F
=
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HR/MS: calculated: m/z = 575.2827 [M+]; measured (ESI): m/z =
575.2821. C55H50BF15OSTi: calcd. C 59.91; H, 4.57%; found: C
58.76; H, 4.43%.
Synthesis of 4c: A mixture of complex 1 (0.100 g, 0.160 mmol) and
B(C6F5)3 (0.082 g, 0.160 mmol) was stirred in 5 mL of toluene. By
stopping the stirring process after a few minutes, the development of
two phases can be observed due to the formation of 4c. The solvent
was decanted, the residue was washed with n-hexane (2ϫ5 mL), and
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0.146 g (0.129 mmol, 81%). Melting point: 46–48 °C (dec.). IR
(ATR): ν˜ = 2915, 2861, 1640, 1509, 1451, 1380, 1267, 1212, 1081,
1022, 980, 964, 948, 934, 887, 834, 805, 786, 765, 734, 690, 659,
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642 cm–1. H NMR (500 MHz, CD2Cl2, 305 K): δ = 0.50 (s(br), 3 H,
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BCH3), 1,49–1.52 (m, 1 H, CHAd/CH2,Ad), 1.58 (s, 3 H, OCqCH3),
1.64–1.80 (m, 7 H, CHAd/CH2,Ad), 1.92–1.95 (m, 2 H, CHAd/CH2,Ad),
2.06–2.07 (m, 2 H, CHAd/CH2,Ad), 2.12 (s, 15 H, C5Me5), 2.19–2.22
(m, 1 H, SeCH2CH2), 2.41–2.42 (m, 1 H, CHAd/CH2,Ad), 2.60–2.63
(m, 1 H, CHAd/CH2,Ad), 2.90–2.97 (m, 1 H, SeCH2CH2), 3.04–3.09
(m, 1 H, SeCH2CH2), 3.51–3.55 (m, 1 H, SeCH2CH2), 4.84–4.86 (m,
1 H, C5H4), 5.39–5.40 (m, 1 H, C5H4), 5.70–5.71 (m, 1 H, C5H4),
6.59–6.61 (m, 1 H, C5H4), 7.07–7.09 (m, 2 H, 2ϫCHPh), 7.49–7.52
(m, 3 H, 3ϫCHPh) ppm. 13C{1H} NMR (126 MHz, CD2Cl2, 305 K):
δ = 9.9 (BCH3)*, 13.0 (C5Me5), 27.3 (CHAd), 27.9 (CHAd), 31.2
(SeCH2CH2), 32.8 (OCqCH3), 33.3 (CH2,Ad), 33.8 (CHAd), 34.3
(CHAd), 34.4 (CH2,Ad), 36.4 (CH2,Ad), 36.9 (SeCH2CH2), 37.5
(CH2,Ad), 39.0 (CH2,Ad), 55.6 (Cq,exo), 108.2 (C5H4), 112.2 (OCqCH3),
113.6 (C5H4), 116.4 (C5H4), 119.1 (C5H4), 126.9 (Cq,Ph), 127.7
(C5Me5), 128.6 (2ϫCHPh), 129.0 (Cq,ArB)*, 130.4 (CHPh), 131.4
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1
1
(2ϫCHPh), 136.9 (dm, JC,F = 246.7 Hz, Cq,ArF), 137.9 (dm, JC,F
=
)
237.0 Hz, Cq,ArF), 148.8 (dm, 1JC,F = 233.5 Hz, Cq,ArF), 157.8 (Cq,ipso
ppm. * = assignment by 1H/13C-HMQC/HMBC spectra. 11B{1H}
NMR (160 MHz, CD2Cl2, 305 K): δ = –14.8 ppm. 19F{1H} NMR
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calculated: m/z = 609.2115 [M+]; measured (ESI): m/z = 609.2113.
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[29] Note: Multiple attempts to obtain crystals suitable for single-crys-
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pounds: (1) storage of saturated and unsaturated solutions of 4a–
4c in dichloromethane, chloro/bromobenzene, or dichlorobenzene
at –4 °C, –26 °C, and –80 °C (adjusted to the relative melting
points of the chosen solvents). (2) Slow diffusion of n-pentane
or n-hexane into saturated or unsaturated solutions of 4a–4c in
dichloromethane, chloro/bromobenzene, or dichlorobenzene. (3)
Two-layer procedures including dichloromethane, chloro/bromo-
benzene, dichlorobenzene, n-pentane, n-hexane, and toluene. (4)
Organizing the synthesis as slow diffusion of the cationic precur-
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increase the coordination number at the selenium from two to
three and a significant high-field shift would be observed in the
Received: January 16, 2019
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M. Fischer, M. Schmidtmann, R. Beckhaus* ................. 1–11
To Coordinate or not to Coordinate: The Special Role of
Chalcogen Ether Functionalities in the Design of Twofold
Functionalized Cyclopentadienyl Ligands [Cp,O,Ch (Ch = S,
Se)]
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