Examples of different reactions of benzylsulfanyl-substituted alkynes with selected complexes of TiII and CoI

Article abstract of DOI:10.1002/ejic.201300312

Reactions of the group 4 metallocene alkyne complexes [Cp ₂M(L)(btmsa)] (Cp = η⁵-cyclopentadienyl = η⁵-C₅H₅, btmsa = η²-Me ₃SiC₂SiMe₃; 1: M = Ti, L = none; 2: M = Zr, L = pyridine) and of the [(triphos)Co^I] moiety [triphos = 1,1,1-tris(diphenylphosphanylmethyl)ethane] with the benzylsulfanyl-substituted acetylenes PhCH₂S-C₂-SCH₂Ph (3) and PhCH ₂S-C₂-SFmoc (4) (Fmoc = fluorenylmethoxycarbonyl) have been investigated. Complex 1 reacted with 3 to give a mixture of a violet solid and [Cp₂Ti(SCH₂Ph)₂] (5). Subsequently, the violet solid transformed in toluene at 70 °C into the dinuclear complex [(Cp₂Ti)₂(μ-κ²-κ²- BnSC₄SBn)] (6) displaying two [Cp₂Ti] moieties bridged by a 1,4-bis(benzylsulfanyl)-1,3-butadiyne in the trans configuration. Complex 6 was further degraded in toluene at 100°C to the tetranuclear cluster [CpTiS]₄ (7). Similar reactivity was deduced indirectly for the reaction partners 1/4 and 2/3. For Co^I, the side-on alkyne complexes [(triphos)Co(3)](PF₆) (9-PF₆) and [(triphos)Co(4)](PF ₆) (10-PF₆) were obtained. Reductive removal of the benzyl groups in 9-PF₆ and subsequent coordination of the [Cp(PPh ₃)Ru^II]⁺ moiety led to the dinuclear complex [(triphos)Co(μ-η²-κ²-C₂S ₂)RuCp(PPh₃)] (13) displaying acetylene dithiolate (acdt^2-) in a side-on carbon-sulfur chelate coordination mode. In contrast, the reaction of 10-PF₆ with piperidine under very mild conditions resulted in the thio-alkyne complex [(triphos)Co(PhCH ₂SC₂S)] (11) bearing a terminal sulfur substituent at the coordinated alkyne. However, a subsequent rearrangement reaction led to the Co^III dithiolene complex [(triphos)Co{S₂C ₂(NC₅H₁₀)(CH₂Ph)}](PF₆) (14-PF₆). The intricate rearrangement very likely involves a dinuclear Co species with a η²-κ² coordination of the C₂S₂ moiety. Sulfur-substituted alkynes show contrasting behaviour in their reactions with Ti^II and Co ^I. Whereas the Ti^II centre in the titanocene η²-alkyne complex effects a cleavage of the alkyne C _sp-S bond concomitant with C-C coupling, Co^I in the [Co(triphos)] η²-alkyne complex leads to loss of the benzyl groups to give either a heterobimetallic Co/Ru acetylene dithiolate complex or a dithiolene complex.

Full text of DOI:10.1002/ejic.201300312

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DOI:10.1002/ejic.201300312
Examples of Different Reactions of Benzylsulfanyl-
Substituted Alkynes with Selected Complexes of TiII and
CoI
Kai Altenburger,[a] Julia Semmler,[b] Perdita Arndt,[a]
Anke Spannenberg,[a] Matthias J. Meel,[b] Alexander Villinger,[b]
Wolfram W. Seidel,*[b] and Uwe Rosenthal*[a]
Keywords: Metallacycles / Alkynes / Metallocenes / Sulfur / Reaction mechanisms
Reactions of the group 4 metallocene alkyne complexes
[Cp2M(L)(btmsa)] (Cp
η5-cyclopentadienyl η5-C5H5,
alkyne complexes [(triphos)Co(3)](PF6) (9-PF6) and [(triphos)-
Co(4)](PF6) (10-PF6) were obtained. Reductive removal of the
=
=
btmsa = η2-Me3SiC2SiMe3; 1: M = Ti, L = none; 2: M = Zr, L benzyl groups in 9-PF6 and subsequent coordination of the
= pyridine) and of the [(triphos)CoI] moiety [triphos = 1,1,1-
tris(diphenylphosphanylmethyl)ethane] with the benzylsul-
fanyl-substituted acetylenes PhCH2S–C2–SCH2Ph (3) and
PhCH2S–C2–SFmoc (4) (Fmoc = fluorenylmethoxycarbonyl)
have been investigated. Complex 1 reacted with 3 to give a
mixture of a violet solid and [Cp2Ti(SCH2Ph)2] (5). Sub-
sequently, the violet solid transformed in toluene at 70 °C
into the dinuclear complex [(Cp2Ti)2(μ-κ2-κ2-BnSC4SBn)] (6)
displaying two [Cp2Ti] moieties bridged by a 1,4-bis(benzyl-
sulfanyl)-1,3-butadiyne in the trans configuration. Complex 6
was further degraded in toluene at 100 °C to the tetranuclear
cluster [CpTiS]4 (7). Similar reactivity was deduced indirectly
for the reaction partners 1/4 and 2/3. For CoI, the side-on
[Cp(PPh3)RuII]+ moiety led to the dinuclear complex
[(triphos)Co(μ-η2-κ2-C2S2)RuCp(PPh3)]
(13) displaying
acetylene dithiolate (acdt2–) in a side-on carbon–sulfur che-
late coordination mode. In contrast, the reaction of 10-PF6
with piperidine under very mild conditions resulted in the
thio-alkyne complex [(triphos)Co(PhCH2SC2S)] (11) bearing
a terminal sulfur substituent at the coordinated alkyne. How-
ever, a subsequent rearrangement reaction led to the CoIII
dithiolene complex [(triphos)Co{S2C2(NC5H10)(CH2Ph)}]-
(PF6) (14-PF6). The intricate rearrangement very likely in-
volves a dinuclear Co species with a η2-κ2 coordination of the
C2S2 moiety.
far only been isolated as dinuclear complexes, which were
formed by coordination of a second metal at the distal side
of the metallaheterocyclopent-3-yne (Scheme 1, E and F).
Complexes of this type show a remarkable versatility of
bonding modes and canonical forms. According to Lentz et
al., the dinuclear Mo complex E is best described as a cis-
diazabutatriene complex formed by the C–C coupling of
CF3NC.[9] The corresponding sulfur congeners F are related
to acetylene dithiolate, but the precise description is de-
pendent on the oxidation state of the metals.[10]
In addition, Hessen et al. observed an interesting alterna-
tive trans-diazabutatriene complex D (Scheme 1).[11] The
obvious structural flexibility of the heterometallacycles mir-
rors that of the prototype all-carbon metallacyclocumulenes
and -cyclopentynes (Scheme 2). Although the trans configu-
ration was observed for group 4 metallocenes and diazamet-
allacycles, dinuclear complexes with acdt2– (acetylenedithi-
olato) and group 6/group 8 transition metals show predomi-
nantly a cis configuration.
Introduction
In general, the isolation of small unsaturated all-carbon
metallacycles (Scheme 1, A–C, X = CH2, CMe2) is challeng-
ing due to their high ring strain,[1–5] although an essential
stabilisation effect has been attributed to interactions of
metal d orbitals with remote π bonds. The formal substitu-
tion of ring CR2 moieties by heteroatom groups leads to a
variety of new species, the synthesis of which are motivated
by their prospective preparative potential as well as an
interest in investigating their stability. The first examples of
stable type B metallapent-3-ynes with X = SiMe2 and type
C metallacycloallenes with X = NR appeared recently.[6–8]
However, examples of type B with X = NR or S have so
[a] Leibniz-Institut für Katalyse e.V. an der Universität Rostock,
Albert-Einstein-Straße 29a, 18059 Rostock, Germany
Fax: +49-381-1281-51176
E-mail: uwe.rosenthal@catalysis.de
[b] Institut für Chemie, Universität Rostock,
Albert-Einstein-Straße 3a, 18059 Rostock, Germany
Fax: +49-381-4986382
To gain a deeper insight into the existence and stability
of such five-membered, unsaturated ring systems with dif-
ferent heteroatoms, the coordination chemistry of neutral
donor-substituted acetylenes like R2N–C2–NR2, R2P–C2–
E-mail: wolfram.seidel@uni-rostock.de
Homepage: http://www.chemie1.uni-rostock.de/seidel
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201300312.
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[triphos
=
1,1,1-tris(diphenylphosphanylmethyl)ethane]
with the alkynes PhCH2S–C2–SCH2Ph (3) and FmocS–C2–
SBn (4). Different reaction patterns and coordination
modes of the stable final products were uncovered. As a
result we present the full characterisation and X-ray crystal
structure analyses of a dinuclear titanocene complex with a
bridging C–C-coupled butadiyne derivative, a dinuclear Co/
Ru complex with a bridging acdt2– and an intricate re-
arrangement reaction of a Co thioalkyne complex resulting
in a CoIII dithiolene complex.
Results and Discussion
Scheme 1. Strained five-membered metallacycles and examples of
dinuclear complexes of metallaheterocyclopent-3-ynes.
The reactions of group 4 metallocene alkyne complexes
[CpЈ2M(L)(btmsa)] (1: M = Ti, CpЈ = Cp = η5-cyclopen-
tadienyl, L = none; 2: M = Zr, CpЈ = Cp, L = pyridine)
and more sterically hindered complexes [M = Ti, Zr; L =
none; CpЈ2 = rac-(ebthi) = rac-ethylenebis(tetrahydroind-
enyl), Cp*2 = (η5-pentamethylcyclopentadienyl)2] with the
alkynes PhCH2S–C2–SCH2Ph (3) and FmocS–C2–SBn (4)
were investigated. The alkyne 4, which is furnished with a
potential S-protecting group, was synthesised by a standard
procedure.[12] However, with the metallocenes 1 and 2, only
the symmetrically substituted alkyne 3 led to isolable com-
pounds.
Complex 1 reacted with 3 in diethyl ether at room tem-
perature to give
a mixture of a violet solid and
[Cp2Ti(SCH2Ph)2] (5), which is already known[16]
(Scheme 3). The violet solid, which is insoluble in diethyl
ether, thf, n-hexane and toluene, was separated by filtration.
Scheme 2. Observed cis and trans dinuclear complexes of all-carbon
metallacyclocumulenes or metallacyclopentynes.
PR2 and RS–C2–SR as well as the corresponding anionic Complex 5 was obtained from the filtrate by fractionated
ligands like [S–C2–S]2– (acdt2–) is of high interest. We were crystallisation using n-hexane. These crystals of 5 were suit-
particularly interested in whether the cis and trans configu- able for X-ray crystallography. The violet solid was sus-
ration is forced either by a particular type of transition pended in toluene and stirred at 70 °C for several hours,
metal or the nature of the donor heteroatom. Therefore we yielding [(Cp2Ti)2(μ-κ2-κ2-BnSC4SBn)] (6) as a dark-green
have investigated the behaviour of exclusively sulfur-substi- solid, which is poorly soluble in thf and toluene and insolu-
tuted alkynes with group 4 metallocenes on the one hand ble in diethyl ether and n-hexane. When 6 was suspended in
and electron-rich late-transition-metal complexes on the toluene and stirred at 100 °C for several hours, the solution
other. Because acetylenedithiol is intrinsically unstable, the turned dark brown and contained brown solids, which were
bis(sulfanyl)alkynes were furnished with potential thiol pro- recrystallised from toluene to yield 7 as dark-brown crys-
tecting groups like benzyl and fluorenylmethoxycarbonyl tals. This multistep reaction is summarised in Scheme 3.
(Fmoc). With respect to the electron/hole formalism, the d2
Furthermore, 2 was treated with 3 in diethyl ether under
metallocenes are the inverse of the CoI d8 system. There- the same conditions as described above for 1. This pro-
fore, in this contribution we compare the diverse reactivity cedure yielded a brown complex reaction mixture from
of selected TiII metallocenes and the [(triphos)CoI]+ moiety which only a few crystals of [Cp2Zr(SBn)2] (8) could be iso-
Scheme 3. Pathway for the reaction of 1 with 3.
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lated by crystallisation from n-hexane. The reactions of the fragment [Cp2Ti], which reacts with 3 to give the metallacy-
more sterically hindered titano- and zirconocenes under the clopropene [Cp2Ti(η2-BnSC2SBn)]. From this presumed in-
same conditions led to black, very complex reaction mix- termediate both a dinuclear and mononuclear reaction
tures from which no defined product could be isolated.
pathway are possible (Scheme 4, left and right side, respec-
When one benzyl residue in the starting alkyne was sub- tively). The latter would involve the oxidative addition of
stituted by an Fmoc protecting group (alkyne 4) and the the Csp–S bond to yield a σ-bonded acetylide and benzyl-
reaction with 1 was carried out under the same conditions thiolate directly attached to Ti in [Cp2Ti(SBn)(C2SBn)].
as described above, a very complex reaction mixture was Similar reactions have been reported for other acetylenes
obtained from which a small amount of a red solid was like PhC2Ph and Me3SiC2SiMe3 with the formation of the
isolated and identified as 5. This led us to conclude that a acetylide moieties [M(Ph)(C2Ph)] or [M(SiMe3)(C2SiMe3)],
similar Csp–S bond activation occurred. Unfortunately, a respectively.[13] The rearrangement of [Cp2Ti(SBn)(C2SBn)]
complex related to 6 was not isolated.
to 5 and the tweezer compound [Cp2Ti(C2SBn)2], and the
Based on the isolated complexes and reaction steps, a subsequent reaction of the latter TiIV complex with [Cp2Ti]
reaction mechanism is proposed for the synthesis of com- should give a σ,π-acetylide-bridged TiIII complex. Related
plex 6 (Scheme 4). First, the starting material 1 generates dinuclear complexes have been extensively investigated for
in a typical dissociation of Me3SiC2SiMe3 the titanocene the combination of titanocene and late transition metals by
Scheme 4. Suggested pathways for the formation of complexes 5 and 6.
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Lang and co-workers.[14] C–C coupling of the acetylides in Table 1. Selected bond lengths [Å] and angles [°] of compound 6
and 6-tBu.
such compounds is very typical and gives the product 6.
The alternative dinuclear mechanism (Scheme 4, left
side) includes the coordination of both sulfur atoms in the
metallacyclopropene [Cp2Ti(η2-BnSC2SBn)] by [Cp2Ti],
which results in a dinuclear structure derived from B (X = Ti1–C2
SBn, Scheme 1). This compound could dissociate to give
6
6-tBu[a]
C1–C2
C1–C1A
1.325(3)
1.468(3)
2.078(2)
2.117(2)
127.3(2)
123.3(2)
C1–C2
C2–C2A
Ti–C1
1.325(5)
1.494(6)
2.093(4)
2.142(3)
128.2(4)
132.0(3)
Ti1–C1A
C1A–C1–C2
C1–C2–S1
Ti–C2A
C2A–C2–C1
C2–C1–C3
[Cp2Ti(SBn)] and [Cp2Ti(C2SBn)], both as TiIII complexes
with the typical tendency of such compounds to dimerise.
The acetylide gives the σ,π-acetylide-bridged TiIII complex
and, after C–C coupling of the acetylides, the product 6.
The TiIV–dithiolate complex 5 is formed after rearrange-
ment and dissociation of [Cp2Ti] from the dinuclear TiIII
species [Cp2Ti(SBn)]2.
The molecular structure of 6 is depicted in Figure 1 and
selected bond lengths and angles are given in Table 1. The
central bond between C1–C1A has a length of 1.468(3) Å,
consistent with a Csp2–Csp2 single bond. The C1–C2 (C1A–
C2A) bond has a length of 1.325(3) Å, in the typical range
of a double bond. Therefore the Lewis representation of 6
in Scheme 4 can be regarded as appropriate. The Ti–C dis-
tances [2.078(2) and 2.117(2) Å] are not equal, resulting in
an asymmetric coordination with respect to the Ti1–C1
axis. The central C4 moiety lies in one plane with the tita-
nium atoms. Angles C2–C1–C1A of 127.3(2)° and C1–C2–
S1 of 123.3(2)° were observed.
[a] See ref.[15]. The corresponding bond lengths and angles are dis-
played on the same line. The original labelling scheme was retained.
ates by about 9° from the corresponding angle in 6-tBu
[132.0(3)°]. Significant differences within the Ti2C4 core are
solely observed for the bond lengths Ti1–C1A (correspond-
ing to Ti–C2A in 6-tBu), being somewhat shorter in the
sulfide derivative 6. In summary, the terminal substituents
at the coordinated butadiyne chain exert a marginal influ-
ence on the structural parameters.
The side-product 5 has already been described in the lit-
erature,[16] but its molecular structure has not been pub-
lished until now. Red crystals of 5 suitable for X-ray crystal-
lography were obtained from n-hexane solution. The molec-
ular structure and selected parameters of 5 are depicted in
Figure 2. It shows a tetrahedral geometry, with two SBn
and two Cp moieties occupying the coordination sites. The
heavier congener [Cp2Zr(SBn)2] (8) shows a significantly
larger S1–M–S2 angle of 99.52(2)°.[17]
Figure 2. Molecular structure of 5 in the crystal form with thermal
ellipsoids set at the 50% probability level. Hydrogen atoms have
been omitted for clarity. Selected bond lenghts [Å] and angles [°]:
Ti1–S1 2.4085(5), Ti1–S2 2.3822(5), S1–Ti1–S2 95.42(2).
The cubic compound 7, which was obtained after ther-
molysis of 6, was recrystallised from toluene to yield crys-
tals suitable for X-ray analysis (Figure 3). The molecular
structure shows a distorted cube composed of four [CpTi]
units and four sulfur atoms with obtuse angles at titanium
and acute ones at sulfur. Furthermore, the bond lengths
and angles around the titanium atom are not equal: the Ti–
S distances vary from 2.3508(8) to 2.4199(8) Å, the S–Ti–S
Figure 1. Molecular structure of 6 in the crystal form with thermal
ellipsoids set at the 50% probability level. Hydrogen atoms have
been omitted for clarity.
The structural parameters of 6 are very similar to those angles are in the range of 97.84(3) to 105.42(3)° and the
of the related complex [(Cp2Ti)2{μ-κ2(1,3),κ2(2,4)-tBu-C4- Ti–S–Ti angles range from 74.38(2) to 79.40(3)°. A similar
tBu}] (6-tBu) bearing two terminal tert-butyl groups structure with comparable bond lengths and angles was
(Table 1).[15] Only the angle C1–C2–S1 [123.3(2)°] in 6 devi- published for [Cp*TiS]4 by Mach and co-workers.[18] Re-
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lated uncharged metal–sulfur cubane structures [CpMS]4
have also been reported for other transition metals like va-
nadium,[19] iron,[20] chromium[21] and cobalt.[22]
Figure 3. Molecular structure of 7 in the crystal fom with thermal
ellipsoids set at the 50% probability level. Cp rings are displayed
as grey spheres for clarity. Selected bond lenghts [Å] and angles
[°]: Ti1–S2 2.3508(8), Ti1–S1 2.3839(8), Ti1–S2A 2.4091(8), Ti2–S1
2.3537(8), Ti2–S2 2.3828(8), Ti2–S1A 2.4199(8), S2–Ti1–S1
97.89(3), S2–Ti1–S2A 100.63(3), S1–Ti1–S2A 105.42(3), S1–Ti2–
S2 97.84(3), S1–Ti2–S1A 100.74(3), S2–Ti2–S1A 105.12(3), Ti2–
S1–Ti1 79.32(2), Ti2–S1–Ti2A 77.70(2), Ti1–S1–Ti2A 74.38(2),
Ti1–S2–Ti2 79.40(3), Ti1–S2–Ti1A 77.79(3), Ti2–S2–Ti1A
74.60(2).
Figure 4. Molecular structure of the cation [10]+ in the crystal of
10-PF6·1.25CH2Cl2 with thermal ellipsoids set at the 40% prob-
ability level. Hydrogen atoms are omitted for clarity. Selected bond
lengths [Å] and angles [°]: Co1–C1 1.846(5), Co1–C2 1.872(5),
Co1–P2 2.149(1), Co1–P3 2.203(2), Co1–P4 2.163(2), C1–C2
1.288(7), C1–C2–S2 146.7(5), C2–C1–S1 144.4(5).
CoC2(S)(SBn)] (11), which was obtained (by a different pro-
cedure) and characterised previously,[10c] must be isolated
between the two reduction steps. Complex K-12 is difficult
to characterise due to its limited stability. However, trap-
ping experiments with K-12 and [CpRu(PPh3)2Cl] gave the
neutral dinuclear complex 13 in moderate yields. Complex
13 shows a large low-field shift of the 13C NMR resonance
for the Co-bound C atoms to 267.4 ppm.
The cleavage of Csp–S bonds is in fact a frequent con-
comitant reaction in alkynyl thiolato and alkynyl sulfide co-
ordination chemistry.[23] However, the facile cleavage in
bis(benzylsulfanyl)acetylene is surprising as the benzyl
group usually serves as a protecting group in the prepara-
tion of alkyne complexes with acetylene dithiolate (acdt2–)
still bearing two terminal sulfur atoms.[24] This strategy led
successfully to a variety of heterobimetallic complexes with
acdt2– bridges, the side-on carbon-bound metals being
either WII (d4) or CoI (d8).[10] With respect to the targeted
metalladithiacyclopentynes (B, X = S, Figure 1), we chose
at first the latter transition metal Co, which is thiophilic on
the one hand and forms stable side-on carbon π complexes
on the other. In addition, we decided to test the fluorenyl-
methoxycarbonyl (Fmoc) group as an S-protecting group,
which can be removed by solvolysis under milder conditions
compared with the benzyl group. Following the procedure
of Dartiguenave and co-workers,[25] the reaction of the sym-
metrical alkyne 3 as well as FmocS–C2–SBn (4) with
[(triphos)CoBr] in the presence of KPF6 in CH3CN led to
the alkyne complexes [(triphos)Co(3)](PF6) (9-PF6) and
[(triphos)Co(4)](PF6) (10-PF6). The dark-green complexes
Scheme 5. Synthesis of K-12 and trapping as dinuclear complex 13.
Reagents and conditions: (i) C8K, thf; (ii) [CpRu(PPh3)2Cl], thf.
The molecular structure of 13, which was determined by
were characterised as four-electron donor alkyne complexes X-ray diffraction analysis, is depicted in Figure 5 and se-
by the 13C NMR resonances of the Co-bound C atoms lected parameters are given in the caption. Complex 13 dis-
(195.0 and 190.8 ppm for 10-PF6). In addition, the identity plays a side-on carbon–sulfur chelate coordination of acdt2–
of 10-PF6 was proven by X-ray crystal structure analysis. bridging Ru and Co and representing a type F alkyne com-
The molecular structure of the cation [10]+ is depicted in plex (Scheme 1) of a cycloruthenadithiapentyne. The μ-η2-
Figure 4 and selected parameters are given in the caption. κ2-coordination mode of acdt2– is caused by a substantial
The complex cation [10]+ forms a distorted tetrahedral co- decrease in the alkyne bend back angles. Although the Csp–
ordination sphere with the alkyne considered as occupying Csp–S angles in 10-PF6 of 146.7(5) and 144.4(5)° are typical
one coordination site. The bonding parameters are in the of 4e-donor alkyne complexes, these angles are 124.7(4) and
expected range and match those of related CoI alkyne com- 123.8(4)° in 13. Interestingly, this change is not reflected in
plexes.[10c,26]
the Co–C1/C2 bond lengths, which are very similar in 10-
A two-step reductive removal of the benzyl groups in 9- PF6 and 13. Another striking feature of the structure of 13
PF6 using C8K led to the anionic target complex K-12 is the folding about the S–S axis. The plane angles SRuS
(Scheme 5). The intermediate complex [(triphos)- and SCCS of the crystallographically independent mole-
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cules in the X-ray structure solution of 13 range from 14.78
to 20.28°, which indicates the flat energy profile of the fold-
ing.
Figure 5. Molecular structure of a selected crystal of 13 in
13·0.5C4H8O2 with thermal ellipsoids set at the 50% probability
level. Hydrogen atoms have been omitted for clarity. Selected bond
lengths [Å] and angles [°]: Co1–C1A 1.850(5), Co1–C2 1.859(4),
Co1–P1 2.169(1), Co1–P2 2.165(1), Co1–P3 2.165(1), C1A–C2
1.362(6), Ru1A–S1A 2.404(1), Ru1A–S2A 2.394(1), Ru1A–P4
2.257(1), C1A–C2–S2A 124.7(4), C2–C1A–S1A 123.8(4), S1A–
Ru1A–S2A 85.71(4).
Scheme 6. Reaction of 10-PF6 with piperidine to give 14-PF6 in-
cluding a proposed mechanism via intermediate I.
The reaction of 10-PF6 with an excess of piperidine in
thf solution led to the fast removal of the Fmoc group and
formation of neutral [(triphos)CoC2(S)(SBn)] (11), which is
indicated by a distinct colour change from intense green to
dark blue (Scheme 6). The identity of compound 11 dis-
playing one terminal sulfur atom could be proven by 31P
NMR and UV/Vis absorption spectroscopy (see Figures S1
and S2 in the Supporting Information). Surprisingly, pure
11 could not be isolated by the Fmoc method; the solutions
turned green while evaporating the excess piperidine. Ac-
cording to 31P NMR spectroscopy, the crude product con-
sisted of different species with partially free CH2PPh2 arms
of triphos. Finally, from a solution of the mixture in either
thf or toluene we were able to crystallise in up to 27% yield
a new complex showing an unexpected connectivity. The
result of the X-ray crystal structure analysis is depicted in
Figure 6 and selected parameters are given in the caption.
The isolated complex cation [14]+ is a dithiolene com-
plex. The alkyne ligand has formally flipped over and two
thiolato groups are coordinated to the Co centre. The free
valences at the former triple bond are now substituted by a
piperidinyl and a benzyl group. Owing to the positive over-
all charge, cobalt is reasonably regarded as CoIII. Hence, an
oxidation has occurred on going from 10-PF6 to 14-PF6
Figure 6. Molecular structure of the cation [14]+ in the crystal of
14-PF6·2.25toluene with thermal ellipsoids set at the 40% prob-
ability level. Hydrogen atoms have been omitted for clarity. Selected
bond lengths [Å] and angles [°]: Co1–S1 2.159(2), Co1–S2 2.146(2),
Co1–P1 2.188(2), Co1–P2 2.236(2), Co1–P3 2.242(2), C1–C2
1.348(8), C1–C2–S2 119.7(5), C2–C1–S1 117.9(5), S1–Co1–S2
88.13(7).
with the oxidation equivalents coming from protons of due to the constraint of the triphos ligand. All bonding
piperidine (now attached to carbon) and piperidinium parameters are in the expected range. On average, the Co1–
(formed in the essential deprotonation of the Fmoc group). P bond lengths are clearly longer in [14]+ than those in [10]+
The overall coordination polyhedron is best described as and 13, which reflects the different physical oxidation states
square pyramidal with a τ value of 0.11. However, the (CoIII vs. CoI). The Co–S bond lengths are similar to those
bonding of the donor atom P1 is rather restricted apical found in related dithiolato complexes. The values of
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2.159(2) and 2.146(2) Å for Co1–S1 and Co1–S2 deter- cies from the alkyne bond must involve a concerted reac-
mined for [14]+ are somewhat shorter than the values of tion, or at least a preceding nucleophilic attack, because
2.174(2) and 2.164(2) Å found in [(triphos)Co- DFT calculations ruled out a minimum for the hypothetical
(S2C6H4)]+,[27] which can be attributed to the more pro- cobaltadithiacyclopentyne complex [(triphos)CoS(SBn)C2].
nounced dithiolene character in the ethylene derivative. Geometry optimizations led always to a standard κ1-alk-
Interestingly, the related alkyldithiolato complexes show τ ynethiolato complex with a terminal BnS group. The obser-
values between 0.29 and 0.42, leading to two distinctively vation of free arms of the triphos ligand by 31P NMR might
different Co–S bond lengths (2.155 and 2.197 Å, the latter indicate that piperidine is already coordinated to the cobalt
being close to a trans phosphorus position),[27a] whereas the in the position of the dangling triphos arm ready to move
dithiolene complexes are characterised by small τ values to the carbon if the [(triphos)Co]+ moiety binds to the sulf-
(avoiding a trans phosphorus position) and, accordingly, ur atoms. An alternative mechanism based on a mononu-
have comparable Co–S bond lengths.
clear transformation is discussed in the Supporting Infor-
The formation of the dithiolene complex 14-PF6 from mation (Figure S5). Unfortunately, further kinetic studies
the side-on alkyne complex 10-PF6 raises the question as to prove the different mechanisms were seriously hampered
to whether the formal flipping of the alkyne ligand indeed by side-reactions.
involves only the mononuclear complex species or whether,
in contrast, the dinuclear complex I shown in Scheme 6 is
Conclusion
an essential intermediate. Insights into the mechanism were
sought by reactivity studies, 31P NMR investigations and
DFT calculations. The thio-alkyne complex 11, formed
from [(triphos)Co(η2-BnS–C2–SC2H4TMS)]PF6 (15-PF6)
by reaction with [NBu4]F is indefinitely stable in solution
with hydrocarbons and ethers in an inert atmosphere. Com-
plex 11 had been fully characterised and its molecular struc-
ture was elucidated by X-ray diffraction.[10c] The reaction
of pure 11 with an excess of piperidine in thf did not lead
to [14]+ according to NMR spectroscopic evidence. How-
ever, 31P NMR studies indicated the existence of different
species in solution including the starting material 11. Fi-
nally, the addition of a small amount of trifluoroacetic acid
led to the formation of 14-CO2CF3. It is instructive that
none of the NMR spectroscopic investigations gave any evi-
dence for any paramagnetic species. In addition, the 31P
NMR spectra display resonances of the CH2PPh2 arms of
free triphos (see Figure S1). DFT calculations with 11Me
(methyl instead of the benzyl substituent) using the B3lYP
functional and a 6-311G(d,p) standard basis set revealed
the in-plane lone pair at the terminal sulfur atom to be the
HOMO (Figure S4). According to a natural bond order
(NBO) analysis, the negative charges are located in the thio-
alkyne (–0.234 e– at the terminal sulfur atom), which sup-
ports coordination of a second metal ion. In turn, positive
charges are found on the CoP3 moiety. However, the central
Co atom is sterically protected by six phenyl groups. Any
nucleophilic attack at Co requires the dissociation of one
(diphenylphosphanyl)methyl arm, which is indeed observed
in the NMR spectra.
Complexes of transoid butadiynes coordinated by two
titanium atoms are usually obtained either from butadiynes
and TiII precursors[29–31] or from acetylides and TiIII hal-
ides.[32] In the latter case, C–C coupling of two phenylacet-
ylide moieties in a titanocene complex was observed.
The facile synthesis of 6 from the Cp2TiII complex 1 and
BnSC2SBn (3) is unprecedented in so far as the cleavage of
an alkyne carbon–heteroatom bond, with SBn as the leav-
ing group, and the subsequent C–C coupling of the formed
acetylide moieties leading to the zig-zag butadiyne complex
6 proceed consecutively.
In contrast, CoI in the [Co(triphos)] η2-alkyne moiety
allows the removal of thiol protective groups in order to
derive coordinated alkynes with terminal sulfur atoms.
However, the 1,3-shift of a Bn group in an alkyne complex
with a distal BnS substituent and the subsequent rearrange-
ment of the C2S2 moiety in the formation of 14-PF6 is ex-
ceptional. Interestingly, for both transformations a change
in the (metal) oxidation state is involved. For the early tran-
sition metals Ti and Zr the high d-orbital energies and the
corresponding strong bias to oxidative addition may be cru-
cial for the initial reaction step. For cobalt, the balance be-
tween π-donor ability to stabilise the alkyne complex and
the thiophilicity of the final CoIII centre might be the de-
termining factor. Nevertheless, the contrasting behaviour of
alkynyl sulfides with TiII and CoI sheds light on the versa-
tile reactivity of sulfur-substituted alkynes.
In summary, a plausible reaction mechanism is suggested
in Scheme 6 for the synthesis of 14-PF6. First, the concerted
mechanism with a dinuclear intermediate I could explain
why no paramagnetic species was observed. Secondly, the
dinuclear complex [(triphos)Co(C2S2)Co(triphos)], which is
closely related to the cationic intermediate suggested, had
recently been isolated and structurally characterised.[28] The
formation of the necessary [(triphos)Co]+ species even in
catalytic amounts by dissociation of the alkyne BnS–C2–SH
from 11 could be provoked by protonation by the piperidin-
Experimental Section
General: All experiments were conducted with exclusion of oxygen
and moisture. All operations were carried out under argon using
standard Schlenk techniques. Prior to use, n-hexane and toluene
were distilled from sodium tetraethylaluminate and stored under
argon. thf and diethyl ether were dried with sodium, then distilled
from sodium tetraethylaluminate and stored under argon.
[Cp2Ti(btmsa)] (1), [Cp2Zr(py)(btmsa)] (2) and the bis(benzylsulf-
anyl)acetylene (3) were prepared according to literature pro-
cedures.[12,33] The following spectrometers were used: Mass spectra:
ium cation. The final dissociation of the [(triphos)Co]+ spe- MAT 95-XP (Thermo Electron); NMR spectra: Bruker AV250 and
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AV300. 1H and 13C chemical shifts are referenced to the solvent
signals: [D6]toluene (δCH3 = 2.09 ppm, δCH3 = 20.4 ppm), [D8]thf
Reaction of [Cp2Zr(btmsa)(pyridine)] (2) with Alkyne 3: A solution
of 3 (270 mg, 0.5 mmol, 1 equiv.) in toluene (30 mL) was added at
–78 °C to a stirred solution of 2 (471 mg, 0.5 mmol, 1 equiv.) in
toluene (30 mL). The solution was warmed to room temperature
and stirred for 2 h. After removal of the solvent and all volatiles in
vacuo the resulting yellow-brownish solid was extracted with n-hex-
ane (5ϫ20 mL). The solvent of the extracts was removed in vacuo
and the resulting yellow solid was recrystallised from toluene to
yield a few yellow crystals. X-ray analysis of these crystals iden-
tified the product as the previously reported complex [Cp2Zr-
(δO-CH2 = 3.58 ppm, δO-CH2 = 67.57 ppm) and CDCl3 (δH
=
7.26 ppm, δC = 77.16 ppm). IR: Nicolet 6700 FT-IR spectrometer
with a smart endurance attenuated total reflection (ATR) device.
Melting points: MP70, Mettler Toledo. Melting points were mea-
sured in sealed capillaries.
S-(4-Phenyl-3-thiabut-1-ynyl) O-Fluorenylmethyl Thiocarbonate (4):
At –78 °C a solution of benzylethynyl sulfide (0.5 g, 3.38 mmol) in
diethyl ether (80 mL) was treated with n-butyllithium (1.6 m solu-
tion in n-hexane, 2.1 mL). After 15 min of stirring, sulfur
(108.3 mg, 3.38 mmol, dried in vacuo overnight) was added. After
stirring at –78 °C for a further 15 min, the mixture was warmed to
room temperature and stirred until the sulfur was consumed. The
light-orange solution was cooled again to –20 °C and solid fluoren-
ylmethoxycarbonyl chloride (874 mg, 3.38 mmol) was added in
small portions. After stirring at –20 °C for a further 15 min, the
solution was warmed to room temperature and stirred overnight.
The orange suspension was filtered and the clear filtrate concen-
trated in vacuo. Finally, the crude product was purified by column
chromatography (silica, n-hexane/ethyl acetate, 20:1) to obtain 4 as
an orange oil, yield 1.02 g (75%). 1H NMR (300 MHz, CDCl3,
297 K): δ = 7.72–7.18 (m, 13 H, Ph), 4.45 (d, JH,H = 7.55 Hz, 2 H,
OCH2), 4.18 (t, JH,H = 7.55 Hz, 1 H, Fmoc-CH), 3.95 (s, 2 H,
SCH2) ppm. 13C NMR (75 MHz, CDCl3, 297 K): δ = 142.7 (CO),
142.9, 141.3 (Fmoc-Cipso), 135.9 (Ph-Cipso), 129.1, 128.7, 128.1,
128.0, 127.3, 125.2, 120.2 (Ph-CH), 95.7 (BnSC-C-SCO), 78.3
(BnSC-CSCO), 71.1 (OCH2), 46.6 (CH), 41.3 (BnSCH2) ppm.
C24H18O2S2 (402.53): calcd. C 71.61, H 4.51, S 15.93; found C
70.99, H 4.55, S 15.79.
(SBn)2] (8). All the obtained data are in agreement with ref.[17]
.
Reaction of [Cp2Ti(btmsa)] (1) with Alkyne 4: A solution of 4
(201 mg, 0.5 mmol, 1 equiv.) in diethyl ether was added at –20 °C
to a stirred solution of 1 (178 mg, 0.5 mmol, 1 equiv.) in diethyl
ether. The solution instantly turned dark brown. Removal of the
volatiles at room temp. in vacuo resulted in a brown solid. This
solid was extracted with n-hexane (20 mL), the extract reduced in
vacuo to 10 mL and then filtered again. The filtrate was stored at
–78 °C to yield a small amount of a red solid, which was identified
by NMR spectroscopy as [Cp2Ti(SBn)2] (5).[16]
[(Triphos)Co(η2-BnSC2SBn)](PF6) (9-PF6): A mixture of 3 (2.0 g,
7.4 mmol) and 1,1,1-tris(diphenylphosphanylmethyl)ethaneco-
balt(I) bromide (2.1 g, 2.75 mmol) was dissolved in CH3CN
(30 mL). A solution of KPF6 (0.5 g, 2.75 mmol) in CH3OH
(10 mL) was added. The dark-green solution obtained was stirred
overnight and subsequently concentrated to dryness in vacuo. Col-
umn chromatography (silica, thf) yielded an oily product, which
was crystallised by gas-phase diffusion of Et2O into a thf solution
1
of 9-PF6, yield 1.09 g (41%). H NMR (300 MHz, CDCl3, 297 K):
δ = 7.40–6.90 (m, 40 H, Ph), 4.20 (s, 2 H, CH2), 2.50 (br. s, 6 H,
PCH2), 1.80 (br. s, 3 H, CH3) ppm. 31P NMR (121 MHz, CDCl3,
297 K): δ = 35.90 (PCH2), –144.50 (PF6) ppm. MS (MALDI-
TOF): m/z = 953 [M]+, 683 [M – 3]+. C57H53CoF6P4S2 (1098.98):
calcd. C 62.30, H 4.86, S 5.84; found C 62.17, H 4.76, S 5. 62.
[(Cp2Ti)2(BnSC4SBn)] (6): A solution of 3 (135 mg, 0.5 mmol,
1 equiv.) in diethyl ether (20 mL) was added at room temp. to a
stirred solution of 1 (267 mg, 0.75 mmol, 1.5 equiv.) in diethyl ether
(20 mL). After stirring for 2.5 d at room temp., a black solution
and a black-violet solid were formed. The solid was filtered off and
washed once with thf (25 mL) and diethyl ether (2ϫ20 mL). The
resulting violet solid [m.p. 189–193 °C (dec.)] was too insoluble for
NMR studies or recrystallisation. It was suspended in toluene and
heated at 70 °C for 4 d to give a light-green solution and dark-
green (almost black) rhombic crystals of 6. After filtration, washing
with toluene and drying in vacuo, pure 6 was obtained. In addition,
the byproduct [Cp2Ti(SBn)2] (5) was isolated from the filtrate and
the washing solutions as red crystals by recrystallisation from tolu-
ene/n-hexane (ca. 1:2). 6: Yield 71 mg (44%), m.p. 122–124 °C
(dec.). 1H NMR (300 MHz, [D8]thf, 297 K): δ = 4.38 (s, 4 H, CH2),
5.53 (s, 20 H, Cp), 7.21–7.28 (m, 2 H, Ph), 7.31–7.39 (m, 4 H, Ph),
7.47–7.56 (m, 4 H, Ph) ppm. 13C NMR (300 MHz, [D8]thf, 297 K):
δ = 107.8 (Cp) ppm. Further signals were not observed due to low
solubility. MS spectra showed only the thermolysis product 7,
which could originate from the sample being heated in a steel cruci-
ble after introducing it into the spectrometer. C38H34S2Ti2 (650.57):
calcd. C 70.16, H 5.27; found C 66.63, H 5.48. The data obtained
[(Triphos)Co(η2-BnSC2SFmoc)](PF6) (10-PF6): A solution of 4
(369 mg, 0.92 mmol) in acetonitrile (15 mL) was added to a suspen-
sion of 1,1,1-tris(diphenylphosphanylmethyl)ethanecobalt(I) brom-
ide (350 mg, 0.46 mmol) in acetonitrile (15 mL). After stirring for
15 min, solid KPF6 (84.4 mg, 0.46 mmol) was added. The mixture
was stirred overnight at room temperature. Subsequently, the green
solution was concentrated in vacuo and finally purified by column
chromatography (silica, dichloromethane/methanol, 30:1). Crystals
were obtained by slow evaporation of a solution of 10-PF6 in
dichloromethane (5 mL) and toluene (0.5 mL), yield 485 mg (86%).
1H NMR (300 MHz, CDCl3, 297 K): δ = 7.73–6.88 (m, 43 H, Ph),
4.61 (d, JH,H = 7.36 Hz, 2 H, OCH2), 4.30 (s, 2 H, CH2), 4.26 (t,
JH,H = 7.55 Hz, 1 H, CH), 2.44 (br. s, 6 H, PCH2), 1.78 (br. s, 3
H, CH3) ppm. 13C NMR (75 MHz, CDCl3, 297 K): δ = 195.0,
190.8 (CϵC), 142.7, 141.3 (Fmoc-Cipso), 136.9 (Ph-Cipso), 131.7,
131.6, 131.5, 130.1, 129.1, 128.8, 128.5, 128.2, 127.6, 127.3, 124.89
(Ph-CH), 70.5 (OCH2), 46.7 (CH), 41.9 (BnSCH2), 39.3 (triphos-
Cquart), 36.3 (CH3), 33.3 (PCH2) ppm. 31P NMR (121 MHz,
CDCl3, 297 K): δ = 39.03 (PCH2), –144.14 (PF6) ppm. C65H57Co-
F6O2P4S2 (1231.10): calcd. C 63.41, H 4.67, S 5.21; found C 63.10,
H 4.66, S 5.03.
for 5 were in accordance with ref.[16]
.
Thermolysis of Complex 6: Complex 6 (20 mg, 0.03 mmol) was sus-
pended in [D8]toluene (0.7 mL) and transferred into a Young’s
tube. After heating to 100 °C for 1 d, the colour changed from
green to brown. Small dark-brown crystals were also observed. X-
ray analysis of these crystals identified the product as compound 7,
[(Triphos)(η2-C,CЈ-acetylenedithiolato)cobaltate-κ2-S,SЈ-ruthenium-
(cyclopentadienyl)(triphenylphosphane)] (13): At –78 °C, C8K
m.p. 172–174 °C (dec.). 1H NMR (300 MHz, [D8]toluene, 297 K): δ (44 mg, 0.325 mmol) was added to a green solution of 9-PF6
= 5.87 (s, Cp) ppm. 13C NMR (300 MHz, [D8]toluene, 297 K): δ =
109.7 (Cp) ppm. MS (EI, 70 eV): m/z (%) = 580 (92) [M]+, 515 (15),
450 (14), 385 (7). Further analytical data were unobtainable due to
very poor yields and therefore insufficient amounts of substance.
(275 mg, 0.25 mmol) in thf (50 mL). The mixture was stirred over-
night and subsequently evaporated to dryness under reduced pres-
sure. Extraction with toluene (3ϫ 20 mL) resulted in a blue solu-
tion, which was filtered to remove graphite and KPF6. Finally, the
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toluene was evaporated to yield 11, which was sufficiently pure to
be used in the next step. Again at –78 °C, C8K (31 mg, 0.23 mmol)
was added to a solution of crude 11 (110 mg, 0.127 mmol) in thf
(20 mL). After 2 h of stirring at ambient temperature, [(C5H5)-
Ru(PPh3)2Cl] (93 mg, 0.128 mmol) was added. Subsequently the
mixture was heated at reflux for 2 h to give an intense green solu-
tion. After evaporation of the solvent, the residue was washed with
CH3CN to remove PPh3. Finally, the crude product 13 was sub-
jected to chromatographic purification (SiO2, ethyl acetate/n-hex-
ane, 4:1). Crystals of 13 were obtained by vapour diffusion of n-
pentane into an ethyl acetate solution, yield 35 mg (23%). 1H
NMR (400 MHz, C6D6): δ = 7.95, 7.61, 7.12–6.77 (m, 45 H, Ph-
H), 4.50 (s, 5 H, C5H5), 1.96 (br. s, 6 H, PCH2), 1.13 (br. s, 3 H,
CH3) ppm. 13C NMR (100 MHz, C6D6): δ = 267.4 (CoC2), 141–
128 (8 signals, Ph-C), 78.1 (C5H5), 37.5 (q, CH3), 36.7 (q, CCH3),
34.3 (m, PCH2) ppm. 31P NMR (161.9 MHz, C6D6): δ = 54.18
(PPh3), 36.44 (PCH2) ppm. MS (ESI-TOF, CH3OH): m/z =
125.653(1)°, V = 3074.11(11) Å3, T = 150(2) K, Z = 4, 29652 mea-
sured reflections, 3548 unique reflections (Rint = 0.0342), final R
values [IϾ2σ(I)]: R1 = 0.0360, wR2 = 0.0869, final R values (all
data): R1 = 0.0454, wR2 = 0.0931, 178 parameters.
Crystal Data for 7: C20H20S4Ti4, M = 580.20, monoclinic, space
group C2/c, a = 18.1469(5), b = 8.2013(2), c = 15.9455(4) Å, β =
115.287(1)°, V = 2145.74(10) Å3, Z = 4, 27784 measured reflec-
tions, 2656 unique reflections (Rint = 0.0230), final R values
[IϾ2σ(I)]: R1 = 0.0345, wR2 = 0.0787, final R values (all data): R1
= 0.0366, wR2 = 0.0795, 119 parameters.
Crystal Data for 10-PF6: C65H57CoF6O2P4S2·1.25CH2Cl2, M =
1337.19, green plates, monoclinic, space group C2/c, a = 40.370(3),
b
= 13.6487(8), c = 25.1746(14) Å, β = 116.215(5)°, V =
12444.6(13) Å3, ρ = 1.427 gcm–3, μ = 0.616 mm–1, Z = 8, 74925
measured reflections, 11059 unique reflections (Rint = 0.1121), 5875
observed reflections, 722 parameters, final R values [IϾ2σ(I)]: R1
= 0.0790, wR2 = 0.1829, largest peak/hole 1.417/–0.862 e– Å–3.
1200.1383 [M]+, 938.0473 [M
–
PPh3]+. C66H59CoP4RuS2·
0.5C4H8O2 (1244.25): calcd. C 65.64, H 5.10, S 5.15; found C 65.93,
H 5.03, S 5.12.
Crystal Data for 13: C66H59CoP4RuS2·0.5C4H8O2, M = 1244.18,
green plates, triclinic, space group P1, a = 11.4343(6), b =
13.4639(7), c = 20.1101(10) Å, α = 101.7250(10), β = 100.1630(10),
γ = 102.0140(10)°, V = 2886.6(3) Å3, ρ = 1.431 gcm–3, μ =
0.777 mm–1, Z = 2, 33830 measured reflections, 29916 unique re-
flections (Rint = 0.0205), 23024 observed reflections, 1424 param-
eters, final R values [IϾ2σ(I)]: R1 = 0.0517, wR2 = 0.1076, largest
peak/hole 0.587/–0.751 e– Å–3.
[(Triphos)(1-piperidinyl-2-benzylethene-1,2-dithiolato)cobaltate(lll)]-
(PF6) (14-PF6): At –78 °C, piperidine (2 mL) was added to a green
solution of 9-PF6 (30 mg, 0.024 mmol) in thf (20 mL). An immedi-
ate colour change to deep blue was observed. The solution was
warmed to room temperature and stirred for further 2 h. Sub-
sequently, the solvent was evaporated in vacuo and the black resi-
due was dissolved in toluene (5 mL). The resulting black-green sus-
pension was filtered through Celite and the filtrate was concen-
trated in vacuo. Finally, crystals were obtained by evaporation of
a solution of 14-PF6 in toluene (5 mL) under argon, yield 7.2 mg
Crystal Data for 14-PF6: C55H56CoF6NP4S2·2.25C7H8,
M =
1299.24, blue blocks, monoclinic, space group P21/n, a = 23.319(3),
b
= 11.6992(11), c = 23.504(3) Å, β = 104.423(3)°, V =
6210.3(12) Å3, ρ = 1.390 gcm–3, μ = 0.509 mm–1, Z = 4, 42571
measured reflections, 10897 unique reflections (Rint = 0.1445), 4685
1
(27%). H NMR (500 MHz, [D8]thf, 297 K): δ = 7.28–6.85 (m, 35
H, Ph), 4.08 (s, 2 H, Ph-CH2), 2.98 [t, J(H,H) = 5.23 Hz, 4 H, observed reflections, 687 parameters, final R values [IϾ2σ(I)]: R1
NCH2], 2.72 (br. s, 6 H, PCH2), 1.80 (s, 3 H, CH3), 1.67 (m, 6 H, = 0.0736, wR2 = 0.1393, largest peak/hole 0.562/–0.470 e– Å–3.
piperidine-CH2) ppm. 13C NMR (125 MHz, [D8]thf, 297 K): δ =
Supporting Information (see footnote on the first page of this arti-
133.6 (Ph-Cipso), 132.5, 129.9, 128.8, 128.2, 126.06 (Ph-CH), 55.0
cle): Mechanism studies, reaction control for the formation of 14-
(NCH2), 42.9 (CH2-Ph), 35.3 (CH3), 29.6 (PCH2), 26.3 (piperidine-
PF6 by 31P NMR and UV/Vis spectroscopy, additional structure
data for 3 and 13, computational details, Kohn-Sham molecular
CH2), 23.8 (piperidine-p-CH2) ppm. 31P NMR (121 MHz, [D8]thf,
297 K): δ = 32.66 (PCH2), –144.11 (PF6) ppm. C55H56CoF6NP4S2
orbitals of 11.
(1091.99): calcd. C 60.49, H 5.17, N 1.28, S 5.87; found C 61.02,
H 5.22, N 1.26, S 5.73.
Acknowledgments
Crystal Structure Determination: Diffraction data were collected
with a Bruker–Nonius Apex X8 CCD and a Bruker Kappa Apex
II Duo diffractometer using graphite-monochromated Mo-Kα radi-
The authors thank the staff at LIKAT for their technical and ana-
lytical support. Financial support by the Deutsche Forschungsge-
meinschaft (DFG) (RO 1269/8-1 and SE 890/3-1) is acknowledged.
ation. Structure solutions were found by direct methods (SHELXS-
97) and refined by full-matrix least-squares procedures on F2
(SHELXL-97).[34] All non-hydrogen atoms were refined anisotropi-
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cally, and hydrogen atoms were included at calculated positions
with fixed thermal parameters.
CCDC-912589 (for 3), -911894 (for 5), -911895 (for 6), -911896 (for
7), -912590 (for 10-PF6), -927145 (for 13) and -912591 (for 14-PF6)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_requ-
est/cif.
Crystal Data for 5: C24H24S2Ti, M = 424.45, monoclinic, space
group P21/n, a = 12.8348(2), b = 9.7228(2), c = 16.4166(3) Å, β =
91.030(1)°, V = 2048.30(6) Å3, T = 150(2) K, Z = 4, 30727 mea-
sured reflections, 5077 unique reflections (Rint = 0.0354), final R
values [IϾ2σ(I)]: R1 = 0.0290, wR2 = 0.0670, final R values (all
data): R1 = 0.0432, wR2 = 0.0742, 244 parameters.
Crystal Data for 6: C38H34S2Ti2, M = 650.57, monoclinic, space
group C2/c, a = 26.6277(6), b = 8.9374(2), c = 15.8971(3) Å, β =
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Received: March 7, 2013
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