Reactions of [Cp2Ti(η2-Me3SiC2SiMe3)] with 1,4-Bis(diphenylphosphanyl)but-2-yne: Coupling and Isomerization versus Phosphorylation

Article abstract of DOI:10.1002/ejic.201500032

The reactions of [Cp₂Ti(η²-Me₃SiC₂SiMe₃)] (1; Cp = η⁵-cyclopentadienyl) with 1,4-bis(diphenylphosphanyl)but-2-yne (2) have been investigated and found to yield a mixture of products. From these, through the coupling of 2, the tetrasubstituted titanacyclopentadiene [Cp₂Ti(CCH₂PPh₂)₄] (3) was isolated. In addition, small amounts of very unusual complexes were obtained and characterized. In one case, the substrate 2 isomerized to the allene Ph₂PC(H)=C=C(H)CH₂PPh₂, which formed the complex [Cp₂Ti{η³-Ph₂PC(H)=C=C(H)CH₂PPh₂}] (4) through the coordination of a double bond and one of the phosphorus atoms. Another complex, [Cp₂Ti{-C(CH₂PPh₂)=C(CH₂PPh₂)P(Ph₂)H-}] (5), was identified to be the result of a formal hydrophosphorylation of the substrate 2 by HPPh₂, and features a Ti-H-P bridge. It is not clear how HPPh₂ was formed. One possible explanation is the dehydrophosphorylation of the substrate with the formation of HPPh₂ and the butatriene H₂C=C=C=C(H)PPh₂ [tautomer of the but-2-en-3-yne HC≡C-CH=C(H)PPh₂]. The molecular structures of complexes 4 and 5 were determined by X-ray analysis.

Full text of DOI:10.1002/ejic.201500032

FULL PAPER
DOI:10.1002/ejic.201500032
2
Reactions of [Cp Ti(η -Me SiC SiMe )] with
2
3
2
3
1
,4-Bis(diphenylphosphanyl)but-2-yne: Coupling and
Isomerization versus Phosphorylation
[
a]
[a]
[a]
Kai Altenburger, Fabian Reiß, Kathleen Schubert,
[a]
[a]
[a]
Wolfgang Baumann, Anke Spannenberg, Perdita Arndt, and
Uwe Rosenthal*[
a]
Dedicated to Dr. Sc. Vladimir V. Burlakov on the occasion of his 60th birthday
Keywords: Metallacycles / Allenes / Phosphorylation / Isomerization / Titanium
2
5
The reactions of [Cp
2
Ti(η -Me
3
SiC
2
SiMe
3
)] (1; Cp = η -cyclo- of the phosphorus atoms. Another complex, [Cp
2
Ti{-C-
)H-}] (5), was identified to be
the result of a formal hydrophosphorylation of the substrate
2 by HPPh , and features a Ti–H–P bridge. It is not clear how
HPPh was formed. One possible explanation is the dehy-
drophosphorylation of the substrate with the formation of
HPPh and the butatriene H C=C=C=C(H)PPh [tautomer of
the but-2-en-3-yne HCϵC-CH=C(H)PPh ]. The molecular
pentadienyl) with 1,4-bis(diphenylphosphanyl)but-2-yne (2)
have been investigated and found to yield a mixture of prod-
ucts. From these, through the coupling of 2, the tetrasubsti-
tuted titanacyclopentadiene [Cp
lated. In addition, small amounts of very unusual complexes
2 2 2 2 2
(CH PPh )=C(CH PPh )P(Ph
2
2
Ti(CCH
2
PPh
2
)
4
] (3) was iso-
2
were obtained and characterized. In one case, the substrate 2
2
2
2
isomerized to the allene Ph
2
PC(H)=C=C(H)CH
2
PPh
PC(H)=C=C(H)CH
4) through the coordination of a double bond and one
2
, which
2
3
formed the complex [Cp
(
2
Ti{η -Ph
2
2
PPh }]
2
structures of complexes 4 and 5 were determined by X-ray
analysis.
Introduction
with the metals binding to the alkyne moiety as well as to
[
6]
one of the heteroatoms. For the bis-phosphorus-substi-
Recently, we investigated the reactions of symmetrically
[3]
tuted alkyne Ph PCϵCPPh , such an interaction was pro-
2
2
[1]
[2]
dihetero-substituted alkynes YCϵCY (Y = BR , NR2,
2
posed to be dynamic in nature with a rapid exchange in
the coordination of both phosphorus atoms in a flip-flop
[
3]
[4]
OR, PR2, SR ) with group 4 metallocenes. It became evi-
dent that heteroatoms have a significant influence on the
structural parameters and reactivities of the obtained com-
plexes as the heteroatoms of α-hetero-substituted alkynes
interact directly with the alkyne triple bond and increase its
electron density for donor heteroatoms (NR , OR, PR ,
[3]
mechanism. It seemed particularly interesting to investi-
gate how the chemistry would change if the P atoms were
located not in the α, but in the β positions with respect to
the triple bond, for example, in Ph PCH CϵCCH PPh
2
2
2
2
2
2
(2). This ligand is typically coordinated through its phos-
SR) or decrease its electron density for acceptor hetero-
phorus atoms in singly bridged molybdenum, iron, and co-
atoms (BR ). More recently, we extended these investi-
[7]
2
balt complexes, as well as in doubly bridged molybd-
gations to unsymmetrically dihetero-substituted alkynes
[8]
[7]
[7]
enum, nickel, and platinum complexes. In one case,
the molecule contains three molybdenum tetracarbonyl
units coordinated by 2 as a bidentate ligand, these ligands
linked side-on through the triple bond to a further molybd-
YCϵCSiMe , for example, the α-donor-substituted tri-
3
methylsilylalkynes R NCϵCSiMe , EtOCϵCSiMe , and
2
3
3
[
5]
Me PCϵCSiMe .
2
3
In these investigations we aimed to use donor hetero-
atoms to supply an additional coordination site directly at-
tached to the alkyne moiety, which could promote the for-
[8]
enum carbonyl fragment.
mation of highly strained, four-membered metallacycles Results and Discussion
2
In the reaction of [Cp Ti(η -Me SiC SiMe )] (1, Cp =
2
3
2
3
[
a] Leibniz Institut für Katalyse e.V. an der Universität Rostock,
Albert-Einstein-Straße 29a, 18059 Rostock, Germany
E-mail: uwe.rosenthal@catalysis.de
5
[9]
η -cyclopentadienyl)
with 1,4-bis(diphenylphosphanyl)-
[7]
but-2-yne (2), the metallacyclopentadiene 3 was obtained
at room temperature as a result of an oxidative alkyne cou-
pling reaction (Scheme 1).
http://www.catalysis.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201500032.
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the hydrogen atoms and thus alter its electronic environ-
ment. This would explain the greater difference in the chem-
ical shifts of the α-CH protons at –66 °C and the broader
2
signal at 24 °C in comparison with the β-CH protons. This
2
observation is supported by the larger signal splitting of the
ortho-phenyl protons at the α positions (Δδ = 0.64 ppm)
compared with those at the β positions of the titanacyclo-
pentadiene (Δδ = 0.2 ppm; see Figure S3 in the Supporting
Information).
The metallacyclopentadiene 3 is not very stable and de-
composes slowly (about 8 d) at room temperature and
quickly at 60 °C in a toluene solution, in which the reaction
is completed after 3 h.
2
Scheme 1. Reaction of [Cp
2
Ti(η -Me
3
SiC
2
SiMe
3
)] (1) with
The decomposition product 4 was identified to be the
Ph PCH CϵCCH PPh (2) to yield complex 3.
2
2
2
2
result of an isomerization of
2
to the allene
Ph PC(H)=C=C(H)CH PPh followed by the coordination
2
2
2
of a double bond and one of the phosphorus atoms. It is
In this reaction, 1 equivalent of the metallocene precur- formed most likely via the intermediary metallacycloprop-
sor 1 always reacted with 2 equivalents of the alkyne, re- ene A by a 1,3-hydrogen atom shift from one of the CH2
gardless of whether a 1:2 or a 1:1 stoichiometry was ap- groups to the remote alkynic carbon atom. This fast
plied. Metallacyclopentadienes usually form via the corre- hydrogen shift might explain why no metallacyclopropene
1
13
sponding metallacyclopropene A (Scheme 1) by insertion of A could be detected during the H and C NMR analyses
a second alkyne. This reaction is sometimes reversible and of 3. The same product 4 was obtained from the reaction
causes an equilibrium to form between the metallacyclopro- of the metallocene precursor 1 and the alkyne 2 in a 1:1
pene and -pentadiene. In the formation of 3, no metallacy- ratio at elevated temperatures (Scheme 2). The isomeriza-
clopropene A could be detected, which reveals that the equi- tion by 1,3-H shift seems to be irreversible because solu-
librium lies far to the side of the five-membered ring in 3. tions of pure samples of the allene complex 4 did not show
Its structure was established by 2D NMR spectroscopy. any traces of the metallacyclopentadiene 3, even with a
These investigations revealed that the CH groups at the α slight excess of the free alkyne 2. It should be noted that
2
positions of the ring show a much broader signal than those we were able to isolate a small amount of trans-1,4-bis(di-
at the β positions (Figure 1, bottom).
phenylphosphanyl)-1,3-butadiene during the thermal treat-
ment of a toluene solution of 4. The butadiene was iden-
tified by X-ray crystallography and NMR spectroscopy (for
re-determined structural data see the Supporting Infor-
[
10]
mation).
The formation of this butadiene fits well with
the isomerization theory and can be explained by an ad-
ditional 1,3-H shift from the remaining CH group to the
2
quaternary carbon of the allene unit. Although the isomer-
ization of alkynes to allenes in the presence of strong bases
[
11a]
is well known,
tion is very rare.
the transition-metal-mediated isomeriza-
[
11b]
1
Figure 1. H NMR spectra of 3 in [D
8
]toluene showing the CH
2
resonances at selected temperatures (#: 2, *: toluene).
When the solution was cooled stepwise to –66 °C, both
signals split into two. Although the signals of the β-CH2
groups are only about 0.2 ppm apart, those of the α-CH2
groups differ by about 1.8 ppm. The splitting of the β-CH2
signals could be caused by hindered rotation of the
CH PPh substituents on the sterically crowded five-mem-
Scheme 2. Formation of 4 directly or from 3 by a 1,3-H shift in the
intermediary metallacyclopropene A.
2
2
bered ring. The far greater splitting of the α-CH signals
The molecular structure of complex 4 is depicted in Fig-
2
may not only be a consequence of hindered rotation, be- ure 2. The titanium center is surrounded by two Cp ligands
cause the neighboring metal atom may interact with one of and the allene, which forms a titanacyclopropane by coordi-
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nation of two of the allenic carbon atoms (C1, C2) as well
as a five-membered metallacycle with three carbon atoms
C2, C3, C4) and one of the phosphorus atoms (P2). To the
(
best of our knowledge, there is only one structurally exam-
2
ined example of a phosphorus-stabilized η -bound allene–
titanium complex, which was described by Binger et al. in
[
12]
2
1
(
(
994.
In contrast to the complex 4, the Binger complex
1,2-η -3,3-diphenylallene)(trimethylphosphane)titanocene
[Cp Ti(PMe ){η -CH =C=CPh }], B) is stabilized by the lighted in bold.
Scheme 3. Allene complexes 4 and B. The allene units are high-
2
2
3
2
2
PMe ligand, which is located next to the less sterically de-
3
manding side of the allenic unit in the solid state
Table 1. Comparison of selected structural features of 4 and B.
(Scheme 3). The major structural differences between 4 and
C1–C2[a]
Å]
C2–C3[b]
[Å]
Ti–C1
[Å]
Ti–C2
[Å]
C1–C2–C3[c]
[°]
B can be attributed to the intramolecular coordination of
phosphorus in 4 (Table 1).
[
4
B
1.410(2)
1.423(5)
1.326(2) 2.364(1) 2.149(1)
1.344(4) 2.241(3) 2.188(3)
139.31(12)
132.8(2)
[d]
[
a] C1 and C2 form the titanacyclopropane ring. [b] C2 quaternary
carbon atom. [c] Angle of the allene unit. [d] Data taken from
ref.[
12]
bonds [1.503(2) Å]. Comparison of the Ti–C bonds in 4 and
B reveals that the bonds to the quaternary carbon atom C2
are shorter than those to the secondary (B) and tertiary (4)
carbon atoms (C1). The C1–C2–C3 bond angle in 4 is
about 6.5° greater than in B. This might be a consequence
of the P2 atom connecting both the titanium center and the
allene unit. Interestingly, the structures of 4 and B show
1
13
smaller deviations than expected, and even the H and
C
NMR analyses of 4 indicate the similarity of the two com-
plexes. For example, the 13C resonances of the quaternary
carbon atoms (C2) can be found, as expected, in the low-
field region at δ = 197.0 ppm for 4 and δ = 194.9 ppm for
[
12]
B.
In the reaction of 1 with 2, alongside 3 and 4, a few
Figure 2. Molecular structure of complex 4. Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms have been
omitted for clarity. Selected bond lengths [Å] and angles [°]: C1–
P1 1.801(1), C1–C2 1.410(2), C2–C3 1.326(2), C3–C4 1.503(2), C4–
P2 1.843(1), Ti1–C1 2.364(1), Ti1–C2 2.149(1), Ti1–P2 2.5808(4),
crystals of the complex 5 were isolated as an additional
product (Scheme 4). In this complex, the coordination of a
phosphorylated ligand was identified, which is the result of
a formal insertion of H–PPh into the Ti–C bond of the
2
P1–C1–C2 116.8(1), C1–C2–C3 139.3(1), C2–C3–C4 118.0(1), C3– metallacyclopropene A to yield [Cp Ti{-C(CH PPh )=
2
2
2
C4–P2 102.39(8).
C(CH PPh )P(Ph )H-}] (5). The alkenyl complex 5 shows
2
2
2
an interaction of the hydrogen atom with titanium and the
The C1–C2 bond lengths of the titanacyclopropane rings phosphorus atom of the inserted PPh group (Scheme 5).
2
in 4 and B are nearly equal and lie between a Csp
2
–Csp
2
The molecular structure of complex 5 is depicted in Fig-
double and a single bond due to coordination to the tita- ure 3. The titanium center is surrounded by two Cp ligands
nium center. The C2–C3 bond length in 4 is in the same and the phosphorylated substrate, which forms a five-mem-
range as the corresponding bond in B and can be described bered metallacycle containing the titanium atom, the for-
as a double bond [cf. Σrcov(C=C) = 1.34 Å].[ The bond mer acetylenic carbon atoms (C1, C2), and the inserted P–
13]
length C3–C4 in 4 is in the range of typical Csp
2
–Csp single H unit (P1, H1). To the best of our knowledge, compound
3
Scheme 4. Synthesis of 5 as well as 4.
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NMR silent species such as 5 in addition to Ph PPPh and
2
2
other unknown products. The formation of the diphosphine
can potentially be explained via a species C (Scheme 6 and
Scheme 7), as expected on the basis of the report of Harrod,
[
14]
Samuel and co-workers.
Scheme 5. Possible resonance structures of 5.
5
is the first example of this unusual structural motif. The
C1–C2 bond is typical Csp –Csp double bond
1.352(2) Å]. All the other bonds in the central unit (C1–
a
2
2
[
C3, C2–C4, C1–P1, C4–P3, C3–P2) are single bonds. The
distance between C1 and Ti1 is larger than the sum of the
covalent radii [2.9 Å, cf. Σrcov(Ti–C) = 2.11 Å],[ which Scheme 6. Possible generation of H
13]
2
2 2
and Ph PPPh from C.
confirms the absence of a direct C1–Ti1 interaction. This
C1 atom is planar and the sum of the angles is 360.0(1)°.
The huge deviation of the C2–C1–P1 angle [105.1(1)°] from
120° indicates the ring strain of the metallacycle. The P1–
C1–C2–Ti1 torsion angle of 11.4(1)° shows the five-mem-
bered ring to have a disturbed planarity. Unfortunately, the
very low yield of complex 5 did not allow further investi-
gations of the bonding in this intriguing molecule. Never-
theless, the results of the elemental analysis (calcd. C 76.34,
H 5.77; found C 76.50, H 5.77) and the mass spectra (m/z
+
+
=
785 [5] , 607 [5 – Cp Ti] ) correspond very well to the
2
description of complex 5. On the basis of this data, 5 can
be described either as a hydrido alkenyl species 5a or an
inner phosphonium ate complex 5b (Scheme 5).
Scheme 7. Possible mechanism for the formation of complex 5.
Additional experiments underlined the observation that
the PP coupling reaction proceeded irrespective of the pres-
ence of alkynes (see Figure S8 in the Supporting Infor-
mation). Furthermore, the thermal treatment of 4 dissolved
in toluene without the addition of HPPh also resulted in
2
the formation of a complex reaction mixture containing
Ph PPPh , Ph PC(H)=C(H)–C(H)=C(H)PPh , and com-
2
2
2
2
pound 5 as identified products. Although we were not able
to isolate compound 5 during these reactions, we unambig-
uously determined its presence by mass spectroscopy (see
the Supporting Information). These experiments supported
the idea of a stepwise dehydrophosphorylation of 4 to the
presumed compounds C and D, followed by a formal phos-
phorylation of 2 or A to yield 5 (Scheme 7). It should be
noted that we observed a 31P NMR resonance at δ =
Figure 3. Molecular structure of complex 5. Thermal ellipsoids are
drawn at the 30% probability level. Hydrogen atoms have been
omitted for clarity, exept for H1. Selected bond lengths [Å] and 178 ppm during these experiments, which could be evidence
angles [°]: C1–P1 1.798(1), C1–C2 1.352(2), C1–C3 1.511(2), C2–
C4 1.511(2), C3–P2 1.862(1), C4–P3 1.858(2), Ti1–C2 2.214(1),
for the formation of compound C (see the Supporting In-
formation).
Ti1–P1 2.6598(5), Ti1–H1 1.93(2), H1–P1 1.28(2), C2–C1–P1
Nevertheless, no further information can be presented on
1
05.1(1), C1–C2–Ti1 111.0(1), P1–C1–C2–Ti1 11.4(1), C2–C1–C3–
how HPPh and the resulting complex 5 were formed and
P2 97.8(2), C1–C2–C4–P3 94.9(1).
2
what byproducts were generated. Complex 5 formally con-
To rationalize the formation of 5, we investigated the re- tains a molecule of 2 as ligand together with an additional
actions of 1 as well as of 3 in the presence of HPPh . Al- HPPh group. Because no other phosphine was added, a
2
2
though the reaction of 1 with HPPh led to hydrogen and second molecule of 2 must be the source of HPPh . One
2
2
the diphosphine Ph PPPh , the reaction of 3 with HPPh
possible explanation for its formation could be the dehy-
2
2
2
gave a more complex mixture of compounds, including drophosphorylation of the substrate with the formation of
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HPPh2 [and eventually the butatriene H C=C=C=C(H)- ation step. Therefore we must conclude that the alkyne
2
PPh (D) or the but-2-en-3-yne HCϵC–CH=C(H)PPh as complex 1 acts as a titanocene source that is stabilized by
2
2
its tautomer]. Both compounds should be very reactive by- alkyne coordination (A and its follow-up products) and
products that reduce the yield of 4 and disturb the synthesis simultaneously as an agent that cleaves phosphorus–ele-
of 5. It is worth mentioning that such butatrienes and but- ment bonds.
2-en-3-ynes are coordinated by group 4 metallocenes to give
strained metallacycles such as 1-metallacyclopenta-3-ynes
and metallacycloallenes.[ Like compound 2 used herein, Experimental Section
15]
the very similar 1,4-disubstituted but-2-yne substrate 1,4-
dichlorobut-2-yne also forms 1-metallacyclopentynes.
[
16]
General: All manipulations were carried out in oxygen- and moist-
ure-free argon using standard Schlenk and drybox techniques. The
solvents were purified by using the Grubbs-type column system
Also, ClMe SiCϵCSiMe Cl yields 1-metalla-2,5-disilacy-
2
2
clopentynes after Cl abstraction.[ All the postulated un-
17]
“Pure Solv MD-5” and dispensed into thick-walled glass Schlenk
2
saturated byproducts, the butatriene H C=C=C=C(H)PPh2
bombs equipped with Young-type Teflon valve stopcocks. Di-
and the but-2-en-3-yne HCϵC–CH=C(H)PPh (or the di-
2
phenylphosphine (99%, Strem Chemicals) was used as received.
2
5
acetylene HCϵC–CϵCH as a product from its subsequent [Cp Ti(η -Me SiC SiMe )] (1, Cp = η -cyclopentadienyl) and
dehydrophosphorylation with the formation of HPPh2) Ph
should be very reactive without any chance of their isola-
2
3
2
3
2
PCH
procedures.
2
CϵCCH
2
PPh
2
(2) were prepared according to literature
[7,9a]
NMR spectra: Bruker AV300 and AV400 spec-
1
13
trometers. H and C chemical shifts were referenced to the solvent
signal: [D ]benzene: δ = 7.16 ppm, δ = 128.0 ppm; [D ]toluene:
= 2.09 ppm, δ = 20.4 ppm. IR: Bruker Alpha FT-IR spectrom-
tion as products. In addition, by alkyne exchange of
2
6
H
C
8
[
Cp Ti(η -Me SiC SiMe )] (1) with 2, an intermediary
2
3
2
3
2
δ
H
C
titanacyclopropene
[Cp Ti(η -Ph PCH CϵCCH PPh )]
2
2
2
2
2
eter. MS: Finnigan MAT 95-XP (Thermo-Electron). Elemental
analysis: Leco Tru Spec elemental analyzer. Melting points:
Mettler-Toledo MP 70. The melting points were measured in sealed
capillaries.
(
A) is proposed, into which is inserted HPPh , leading to
2
complex 5. In principle, this reaction is very similar to the
reactions of group 4 metallocene alkyne complexes
2
[
Cp M(L)(η -Me SiC R)]
with
diisobutylaluminium
2
3
2
Diffraction data for 4 and 5 were collected with Bruker APEX-II
CCD and STOE-IPDS II diffractometers, respectively, using graph-
hydride HAl(iBu) . The resulting complexes of the type
2
1
2
[
(Cp M)(μ-η :η -RCCSiMe )(μ-H){Al(iBu) }] (Cp Ti: R =
2 3 2 2
ite-monochromated Mo-K
α
radiation. The structures were solved
[18]
Ph, SiMe ; Cp Zr: R = SiMe ) show a similar structural
3
2
3
by direct methods and refined by full-matrix least-squares pro-
motif as found in 5. In contrast to complex 5, an additional
interaction between the metal center and the planar β-C was used for the graphical representation.[25]
2
[24]
cedures on F with the SHELXTL software package. Diamond
atom was observed in these complexes. Similar compounds
have been described previously for zirconium by Erker and
–
1
Crystal Data for 4: C38
H
34
P
2
Ti, M = 600.49 gmol , triclinic, space
¯
group P1, a = 9.7272(2), b = 12.7932(3), c = 13.8751(3) Å, α =
5.6182(7), β = 80.8831(7), γ = 76.9664(7)°, V = 1527.98(6) Å , T
150(2) K, Z = 2, 31461 reflections measured, 7380 independent
[
19]
co-workers
workers.
and for titanium by Binger and co-
Compounds like these as well as 5 provide the
basics for understanding hydroheterofunctionalization reac- reflections (Rint = 0.0228), final R values [IϾ2σ(I)]: R = 0.0294,
3
6
=
[
20]
1
tions such as hydroalumination,[ hydroamination, and wR
21]
[22]
= 0.0716, final R values (all data): R
2
1 2
= 0.0356, wR = 0.0756,
378 parameters.
hydrophosphorylation. Westerhausen and co-workers re-
ported such a calcium-catalyzed hydrophosphorylation of a
–1
45 3
Crystal Data for 5: C50H P Ti, M = 786.67 gmol , monoclinic,
space group P2 /n, a = 10.1847(5), b = 36.955(2), c = 11.0612(6) Å,
β = 101.967(1)°, V = 4072.7(4) Å , T = 150(2) K, Z = 4, 61953
[
23]
1,3-butadiyne.
1
3
reflections measured, 9845 independent reflections (Rint = 0.0303),
final R values [IϾ2σ(I)]: R = 0.0352, wR
1
2
= 0.0832, final R values
Conclusions
(
all data): R = 0.0430, wR = 0.0876, 491 parameters.
1
2
2
The reaction of [Cp Ti(η -Me SiCϵCSiMe )] (1) and CCDC-1043501 (for 4) and -1043502 (for 5) contain the supple-
2
3
3
Ph PCH CϵCCH PPh (2) has been investigated. Initially, mentary crystallographic data for this paper. These data can be
the coupling of two alkynes 2 led to metallacyclopentadiene
, the structure of which was determined by 2D NMR spec-
2
2
2
2
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
3
troscopy. This compound was found to undergo elimination Synthesis of [Cp Ti(CCH PPh ) ] (3): 1,4-Bis(diphenylphosphan-
2
2
2 4
of one alkyne and a 1,3-H shift in the remaining alkyne unit yl)but-2-yne (2; 0.211 g, 1.0 mmol) in toluene (5 mL) was added
2
to form the allene complex 4. In addition, the compound dropwise to a stirred solution of [Cp
2 3 2 3
Ti(η -Me SiC SiMe )] (1;
0
.175 g, 0.5 mmol) in toluene (10 mL) at ambient temperature. The
[
Cp Ti{-C(CH PPh )=C(CH PPh )P(Ph )H-}] (5) was iso-
2 2 2 2 2 2
resulting brownish solution was stirred at this temperature for 12 h.
The solvent was then removed in vacuo and the resulting residue
was dried for 1 h. The reaction mixture was treated with n-hexane
15 mL) and filtered. The resulting brownish solution was stored at
78 °C over a period of 12 h, which resulted in the deposition of a
lated alongside 4, showing an unusual Ti–H–P bridge. Its
formation most likely proceeds by phosphorylation of an
intermediary titanacyclopropene. Because no source of
phosphorus other than alkyne 2 is present in the reaction
mixture, a dehydrophosphorylation of this alkyne is as-
sumed. Prolonged heating of the reaction mixture resulted
(
–
yellow solid. Removal of supernatant by syringe and drying in
vacuo at ambient temperature for 1 h yielded 3 as a yellow solid.
in the formation of molecular hydrogen and the diphos- It should be mentioned that 3 was always contaminated with 4,
phine Ph PPPh , thus validating the dehydrophosphoryl- yield 110 mg, 0.11 mmol, 21%; M(3) = 1023.0 gmol ; m.p. 61 °C.
–
1
2
2
Eur. J. Inorg. Chem. 2015, 1709–1715
1713
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
1H NMR (25 °C, [D
H, α-CH ), 2.89 (s, 4 H, β-CH
H, α/β-p-C ), 7.15–7.23 (m, 16 H, α/β-m-C
H, α-o-C ), 7.55–7.61 (m, 8 H, β-o-C
]toluene, 400.13 MHz): δ = 2.3–2.5 (m, 4 H, α-CH
.76 (s, 4 H, β-CH ), 7.43 (m, 8 H, α-o-C ), 7.51 (m, 8 H, β-o-
) ppm. H NMR (–66 °C, [D ]toluene, 400.13 MHz): δ = 1.40
m, 2 H, α-CH ), 2.60 (s, 2 H, β-CH ), 2.81 (s, 2 H, β-CH ), 3.20
m, 2 H, α-CH ), 7.17 (m, 4 H, α-o-C ), 7.53 (m, 4 H, β-o-C ),
.73 (m, 4 H, β-o-C ), 7.81 (m, 4 H, α-o-C ). C NMR
25 °C, [D ]benzene, 100.62 MHz): δ = 30.9 (m, β-CH ), 37.4 (m,
), 113.7 (m, Cp), 128.6 (m, m-C ), 128.6 (s, p-C ), 128.8
), 133.0–134.3 (m, α-o-C ), 133.8 (d, β-o-C
41.0 (d, J = 18.4 Hz, ipso-C ), 141.2 (d, J = 17.3 Hz, β-C
P{ H} NMR (25 °C, [D
61.98 MHz): δ = –15.9 (AAЈBB’ pattern) ppm. IR (ATR, 32
]benzene, 400.13 MHz): δ = 2.30–2.70 (m, 4
), 5.94 (s, 10 H, Cp), 7.02–7.13 (m, 692 (s), 622 (m), 606 (m), 515 (s), 505 (s), 474 (m), 443 (m) cm .
(w), 841 (w), 804 (s), 789 (m), 775 (m), 749 (m), 736 (s), 715 (m),
6
–
1
2
2
+
+
8
8
(
2
C
(
(
7
6
H
5
6
H
H
6 5
5
), 7.45–7.54 (m, MS (CI): m/z = 602 [M] , 417 [M – PPh
) ppm. 1H NMR calcd. C 76.01, H 5.71, P 10.32; found C 75.91, H 5.88, P 10.20.
),
2 34 2
] . C38H P Ti (600.5):
6
H
5
25 °C, [D
8
2
5:
MS (CI): m/z
=
785 [M]+, 607 [C(CH
2
PPh
2
)=C(PPh
)] , 239 [C{CH
Ti (786.7): calcd. C 76.34, H 5.77;
2
)-
2
6 5
H
+
+
(
CH
2
PPh
2
)] , 423 [C(CH
2
PPh
2
)=CH(CH
2
PPh
2
2
P-
1
6
H
5
8
+
(
H)Ph
2
}=CCH
3
] . C50
H
45
P
3
2
2
2
found C 76.50, H 5.77.
2
6
H
5
6 5
H
13
6
H
5
6 5
H
(
6
2
Acknowledgments
α-CH
2
6
H
5
6 5
H
(m, m-C
6
H
5
6
H
5
6
H
5
),
),
The authors would like to thank our technical and analytical staff
for their assistance. Financial support by the Deutsche Forschungs-
gemeinschaft (DFG) (RO 1269/9-1) is gratefully acknowledged.
1
1
1
6
1
H
5
q
31
95.1 (m, α-C
q
) ppm.
6
]benzene,
scans): ν˜ = 3066 (w), 3048 (w), 3012 (w), 2997 (w), 1583 (w), 1570
(
w), 1560 (w), 1478 (w), 1430 (m), 1370 (w), 1359 (w), 1304 (w), [1] K. Altenburger, P. Arndt, A. Spannenberg, W. Baumann, U.
Rosenthal, Eur. J. Inorg. Chem. 2013, 3200–3205.
1
271 (w), 1181 (w), 1155 (w), 1092 (w), 1067 (w), 1013 (m), 933
[
[
[
2] Ò. Àrias, A. R. Petrov, T. Bannenberg, K. Altenburger, P.
(w), 910 (w), 879 (w), 843 (w), 807 (m), 732 (s), 692 (s), 590 (w),
–1
+
Arndt, P. G. Jones, U. Rosenthal, M. Tamm, Organometallics
500 (m), 474 (m), 440 (w) cm . MS (CI): m/z = 835 [M – HPPh
2
] ;
2014, 33, 1774–1786.
+
M
5
could not be detected. C66H P Ti (1023.0): calcd. C 77.45, H
58 4
3] M. Haehnel, S. Hansen, K. Schubert, P. Arndt, A. Spannen-
berg, H. Jiao, U. Rosenthal, J. Am. Chem. Soc. 2013, 135,
17556–17565.
.72, P 12.11; found C 77.46, H 5.81, P 12.07.
3
Synthesis of [Cp
2
Ti(η -Ph
2
PCH=C=CHCH
2
PPh
2
)] (4): 1,4-Bis(di-
4] K. Altenburger, J. Semmler, P. Arndt, A. Spannenberg, M. J.
Meel, A. Villinger, W. W. Seidel, U. Rosenthal, Eur. J. Inorg.
Chem. 2013, 4258–4267.
phenylphosphanyl)but-2-yne (2; 0.138 g, 0.33 mmol) in toluene
2
(
5 mL) was added dropwise to a stirred solution of [Cp
Me SiC SiMe )] (1; 0.114 g, 0.33 mmol) in toluene (10 mL) at am-
bient temperature. The resulting brownish solution was heated at
0 °C for 4 h. All the volatiles were removed in vacuo and the resi-
2
Ti(η -
3
2
3
[
[
5] K. Altenburger, W. Baumann, A. Spannenberg, P. Arndt, U.
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2007, 36, 719–728; c) N. Suzuki, D. Hashizume, Coord. Chem.
Rev. 2010, 254, 1307–1326.
6
due dissolved in diethyl ether (10 mL) and filtered through a can-
nula. The filtrate was stored at –40 °C over a period of 12 h, which
resulted in the deposition of a brownish solid. The supernatant was
decanted and the residue dissolved in diethyl ether (8 mL). This
solution was then concentrated to a volume of 5 mL in vacuo and
stored for 3 d at ambient temperature, which resulted in the deposi-
tion of a red microcrystalline solid. Removal of the supernatant by
syringe and drying in vacuo at ambient temperature for 1 h yielded
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4
as a red solid. In addition, a few crystals of 5 suitable for X-ray
crystallography were isolated.
–
1
4: Yield: 130 mg, 0.1653 mmol, 50%; M(4) = 600.5 gmol ; m.p.
[
[
10] A. A. Barney, P. E. Fanwick, C. P. Kubiak, Phosphorus Sulfur
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1
40 °C. For the NMR assignment scheme, see the Supporting In-
1
31
formation. H{ P} NMR (25 °C, [D
.16 (m, 1 H), 3.00 (m, 1 H), 3.41 (m, 1 H), 5.03 (s, 5 H, Cp
s, 5 H, Cp
6
]benzene, 400.13 MHz): δ =
2
1
) 5.20
(
2
), 6.81 (m, 2 H, m-Ph), 6.87 (m, 1 H, p-Ph), 6.92 (m, 1 [12] P. Binger, F. Langhauser, P. Wedemann, B. Gabor, R. Mynott,
H), 7.14 (m, 1 H, p-Ph), 7.15 (m, 1 H, p-Ph), 7.16 (m, 3 H, m,p-
Ph), 7.25 (m, 2 H, m-Ph), 7.28 (m, 2 H, m-Ph), 7.30 (m, 2 H, o-
Ph), 7.35 (m, 2 H, o-Ph), 7.89 (m, 2 H, o-Ph), 7.94 (m, 2 H, o-
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14] S. Xin, H. G. Woo, J. F. Harrod, E. Samuel, A.-M. Lebuis, J.
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Ph) ppm. 1 C NMR (25 °C, [D
q, J = 40.0, 8.2 Hz, C
01.7 (d, J = 6.6 Hz, Cp), 118.8 (q, J = 18.0, 8.2 Hz, α-C), 127.6
m, m-Ph), 127.7 (m, m-Ph), 128.1 (d, J = 7.0 Hz, m-Ph), 128.4 (d,
3
6
]benzene, 100.62 MHz): δ = 27.9
), 43.6 (d, J = 37.1 Hz, C ), 100.2 (s, Cp),
[
(
A
B
2
013, 3, 18–28; b) T. Beweries, U. Rosenthal, Nat. Chem. 2013,
1
(
5
, 649–650.
[
16] V. V. Burlakov, P. Arndt, W. Baumann, A. Spannenberg, U.
Rosenthal, P. Parameswaran, E. D. Jemmis, Chem. Commun.
2004, 2074–2075.
J = 5.7 Hz, m-Ph), 128.5 (d, J = 5.7 Hz, p-Ph), 128.9 (d, J = 6.6 Hz,
p-Ph), 128.9 (d, J = 1.7 Hz, p-Ph), 129.9 (d, J = 1.7 Hz, p-Ph),
130.8 (d, J = 6.4 Hz, o-Ph), 133.2 (d, J = 16.8 Hz, o-Ph), 133.4 (d,
[17] M. Lama cˇ , A. Spannenberg, H. Jiao, S. Hansen, W. Baumann,
J = 18.8 Hz, o-Ph), 133.7 (d, J = 8.7 Hz, o-Ph), 138.4 (m, J = 4.2,
P. Arndt, U. Rosenthal, Angew. Chem. Int. Ed. 2010, 49, 2937–
2
940; Angew. Chem. 2010, 122, 2999–3002.
1
1
1
1
.3 Hz, ipso-Ph), 141.4 (d, J = 20.4 Hz, ipso-Ph), 144.9 (d, J =
[
18] a) P. Arndt, A. Spannenberg, W. Baumann, S. Becke, U. Rosen-
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3
1
1
8.1 Hz,
C
V
) ppm.
6
P{ H} NMR (25 °C, [D ]benzene,
3
31 31
3
31
61.98 MHz): δ = 7.1 [d, J( P- P) = 13 Hz, P1], 89.7 [d, J( P-
P) = 13 Hz, P2] ppm. IR (ATR, 32 scans): ν˜ = 3060 (w), 2969
3
1
[
(
1
(
w), 2893 (w), 2800 (w), 1648 (w), 1583 (w), 1569 (w), 1477 (w),
433 (m), 1364 (w), 1307 (w), 1235 (m), 1179 (w), 1157 (w), 1119
w), 1100 (m), 1068 (m), 1008 (w), 983 (w), 939 (w), 923 (w), 866
Eur. J. Inorg. Chem. 2015, 1709–1715
1714
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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FULL PAPER
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Published Online: February 27, 2015
Beller, Chem. Eur. J. 2004, 10, 2409–2420; c) A. Tillack, I. G.
Eur. J. Inorg. Chem. 2015, 1709–1715
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim