A Rare-Earth-Metal Ensemble of the Tebbe Reagent: Scope of Coligands and Carbonyl Olefination

Article abstract of DOI:10.1021/acs.organomet.0c00447

Treatment of the half-sandwich complexes CpRLn(AlMe4)2 (CpR = C5Me5, C5Me4SiMe3; Ln = Y, La, Lu) with the mild halogenido transfer reagents SiMe3X (X = Cl, Br, I) resulted in efficient and selective halogenido/tetramethylaluminato exchange. Depending on the size of the rare-earth metal, dimeric [CpRLn(AlMe4)(μ-X)]2 (Ln = Y, Lu) and decametallic [CpR3La3(AlMe4)2(μ-X)4]2 could be obtained. Donor (THF)-induced tetramethylaluminato cleavage gave access to methyl-free mixed methylidene/halogenido complexes CpR3Ln3(μ-X)3(μ3-X)(μ3-CH2)(THF)3 for yttrium (X = Cl, Br) and lanthanum (X = Cl, Br, I) in good yields. Additionally, mixed methylidene/halogenido Y(III) complexes could be obtained via methyl/halogenido exchange employing (C5Me5)3Y3(μ-Me)3(μ3-Me)(μ3-CH2)(THF)2 and SiMe3X via tetramethylsilane elimination. All methylidene complexes were probed in olefination reactions and found to act as efficient Schrock-type nucleophilic carbenes converting ketones and aldehydes into the respective terminal alkenes. Such reactivity is as high as that of the prominent Tebbe reagent but is less tolerant toward sterically demanding and functionalized substrates (such as esters). In contrast to the Tebbe reagent, complexes CpR3Ln3(μ-X)3(μ3-X)(μ3-CH2)(THF)3 polymerize δ-valerolactone in an efficient manner, generating polylactones with molecular weight distributions Mw/Mn as low as 1.13. Moreover, the bromido variant of the Tebbe reagent, Cp2Ti(μ-CH2)(μ-Br)AlMe2, is described, underlying similar synthesis limitations: that is, the coformation (and hence cocrystallization) of the trivalent species Cp2Ti(μ-Br)2AlMe2.

Full text of DOI:10.1021/acs.organomet.0c00447

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Article
A Rare-Earth-Metal Ensemble of the Tebbe Reagent: Scope of
Coligands and Carbonyl Olefination
̈
̈
Verena M. Birkelbach, Felix Kracht, H. Martin Dietrich, Christoph Stuhl, Cacilia Maichle-Mossmer,
and Reiner Anwander*
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ABSTRACT: Treatment of the half-sandwich complexes CpRLn-
(AlMe4)2 (CpR = C5Me5, C5Me4SiMe3; Ln = Y, La, Lu) with the mild
halogenido transfer reagents SiMe3X (X = Cl, Br, I) resulted in
efficient and selective halogenido/tetramethylaluminato exchange.
Depending on the size of the rare-earth metal, dimeric [CpRLn-
(AlMe4)(μ-X)]2 (Ln = Y, Lu) and decametallic [CpR La3(AlMe4)2(μ-
3
X)4]2 could be obtained. Donor (THF)-induced tetramethylaluminato
cleavage gave access to “methyl-free” mixed methylidene/halogenido
complexes CpR Ln3(μ-X)3(μ3-X)(μ3-CH2)(THF)3 for yttrium (X =
3
Cl, Br) and lanthanum (X = Cl, Br, I) in good yields. Additionally,
mixed methylidene/halogenido Y(III) complexes could be obtained via methyl/halogenido exchange employing (C5Me5)3Y3(μ-
Me)3(μ3-Me)(μ3-CH2)(THF)2 and SiMe3X via tetramethylsilane elimination. All methylidene complexes were probed in olefination
reactions and found to act as efficient Schrock-type nucleophilic carbenes converting ketones and aldehydes into the respective
terminal alkenes. Such reactivity is as high as that of the prominent Tebbe reagent but is less tolerant toward sterically demanding
and functionalized substrates (such as esters). In contrast to the Tebbe reagent, complexes CpR Ln3(μ-X)3(μ3-X)(μ3-CH2)(THF)3
3
polymerize δ-valerolactone in an efficient manner, generating polylactones with molecular weight distributions Mw/Mn as low as
1.13. Moreover, the bromido variant of the Tebbe reagent, Cp2Ti(μ-CH2)(μ-Br)AlMe2, is described, underlying similar synthesis
limitations: that is, the coformation (and hence cocrystallization) of the trivalent species Cp2Ti(μ-Br)2AlMe2.
the other hand, reduced titanium species such as those
obtained from the ternary systems CH2Br2/TiCl4/Zn and
CH2Br2/TiCl4/Mg have been employed according to the
Takai−Lombardo reaction for the mild methylenation of
ketones counteracting enolization (thus counteracting any
epimerization of α-chiral centers; also displaying high func-
tional group tolerance).23,24 Moreover, an excess of divalent
Cp2Ti[P(OEt)3]2 (via Cp2TiCl2/Mg/P(OEt)3) has been
successfully used in the olefination of thioacetals with carbonyl
compounds (Takeda reaction, also characterized by a wide
substrate scope).25 Switching to group 6 reagents, the iodo-
methylidene Cr(III) complex Cr2Cl4(CHI)(THF)4 (Takai
olefination reagent) has been employed successfully to convert
aldehydes to E-iodido-functionalized olefins accessible to
further derivatization.26−29
INTRODUCTION
■
The seminal discoveries by Schrock and Tebbe of discrete
Cp2Ta(CH2)(CH3)1,2 and Cp2Ti(μ-CH2)(μ-Cl)Al(CH3)2,3
respectively, in the mid 1970s marked a true breakthrough in
molecular transition-metal alkylidene chemistry. The feasibility
of such “Schrock”-type nucleophilic carbenes and their
applicability/superb performance in fundamental organic
transformations such as olefin metathesis4−6 and carbonyl
methylenation (Wittig-type reactivity)4,7 have triggered
immense research activities.5,8,9 Tebbe’s compound Cp2Ti(μ-
CH2)(μ-Cl)Al(CH3)2, also termed the Tebbe reagent,
involving a Lewis acid (LA = AlMe2Cl) stabilized [Ti
CH2] moiety,3,10 has featured a most efficient (rapid CO to
CCH2 conversion at ambient temperatures) and hence
prominent carbonyl methylenation reagent in organic synthesis
ever since.11−14 Crucially, in natural product synthesis the
Tebbe reagent often outperforms the Wittig reagent CH2PPh3
due to its enhanced functional group tolerance (e.g., ester or
acetal) and also the Petasis reagent Cp2Ti(CH3)2, which
requires elevated temperatures (65 °C) to form the [Ti
CH2] moiety via methane elimination.15−20 Drawbacks of the
Tebbe reagent are its moisture sensitivity, the coformation of
Ti(III) species when Cp2TiCl2 is reacted with the “reducing”
reagent AlMe3, and the viability of only methylenation.21,22 On
Despite this eminent performance of early-transition-metal-
based methylidene complexes in olefination reactions, rare-
Received: July 1, 2020
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earth-metal (Ln) variants showing this extraordinary reactivity
came into focus only recently.30 As with the Tebbe reagent,
Lewis acids (mainly AlMe3) were shown to exert a stabilizing
effect on increasingly ionic rare-earth-metal methylidene
compounds.31−36 Most of such LA-stabilized Ln(III) com-
plexes with [Ln(μ-CH2)(μ-CH3)Al] moieties have revealed
promising reactivity in methylidene transfer reactions;
however, Ln−CH3−Al and Ln−CH3−Ln bridging methyl
groups can further engage in Ln(III)-size-dependent carbonyl
alkylation reactions, forming alkoxy compounds as well.32,37−39
To obtain and ensure the unique and clean Wittig-type
reactivity, homometallic compounds devoid of alkylating LAs
seem necessary. So far, two structural motifs of rare-earth-
metal methylidene complexes have been utilized in methyl-
idene transfer reactions, comprising cubane-like tetrametallic
[(L)Ln(CH2)]4 (I; Ln = smaller-sized expensive rare-earth
metals only)40 and trimetallic complexes L3Ln3(μ-X)3(μ3-
X)(μ3-CH2)(THF)n (II−VI) with L being a monoanionic
ligand and X being either a methyl or halogenido moiety
(Figure 1).37−47
A key step for the synthesis of these rare-earth-metal
methylidene complexes is the intermediate formation of very
reactive Ln−Me moieties. For example, the generation of the
cubane-like lutetium complex stabilized by the trimethylsilyl-
substituted cyclopentadienyl ligand C5Me4SiMe3 (Cp′) was
achieved by C−H-bond activation of the dimethyl precursor
[Cp′Lu(CH3)2]3 via release of CH4.40 Such reactive Ln−Me
moieties are also easily generated via alkyl exchange in
[(L)Ln(R)2] (II, R = CH2C6H4NMe2, L = PhC(NC6H3iPr2-
2,6)2 for Ln = Sc, Y, Er, Lu; III, L = (C6H4NMe2)CH2C-
(NC6H3iPr2-2,6)2 for Ln = Lu; IV, R = CH2SiMe3, L =
C5Me4SiMe3, Ln = Tm)38,40,42 with AlMe3 or through donor-
induced cleavage of tetramethyl-aluminate in (L)Ln(AlMe4)2
(VY, L = C5Me5, Ln = Y;44 VI, L = N(C6H3iPr2-2,6)(SiMe3),
Ln = Y, Nd, Ho, Lu; II, L = PhC(NC6H3iPr2-2,6)2, Ln = Sc,
Lu) for bridging methyl groups37,38,45,46 or [(L)Ln-
(AlMe4)x(Cl)y]z (V, L = C5Me5, Ln = Y with x = y, z = 2,
La with 2x = y, z = 6) for bridging chlorido units.47 In all cases
inter- or intramolecular C−H-bond activation will afford the
desired dianionic methylidene moiety.
To selectively achieve clean conversion of carbonylic
substrates into terminal alkenes, the additional bridging
positions need to carry unreactive ligands such as halogenidos,
as in (C5Me5)3Ln3(μ-Cl)3(μ3-Cl)(μ3-CH2)(THF)3 (V, Ln = Y,
La, Sm).47 Herein, we present a full account of the synthesis of
complexes of the type CpR Ln3(μ-X)3(μ3-X)(μ3-CH2)(THF)3,
3
giving consideration to effective synthesis protocols, the scope
of the bridging ligand X, implications of the Ln(III) size, and
application of the complexes in methylidene transfer reactions.
For the last olefination reactions, comparison is drawn to the
illustrious Tebbe reagent.48 Along the lines “all for one and one
for all”, three Ln(III) centers are shown to team up to stabilize
the methylidene moiety, while the last center engages in
olefination to a full extent, “rewarding” the rare-earth metals
with the much sought after oxy environment.
RESULTS AND DISCUSSION
■
Figure 1. Different types of tetra- and trimetallic rare-earth-metal
methylidene complexes shown to be active in methylidene transfer
reactions.
Mixed-Ligand AlMe4/X Ln(III) Half-Sandwich Precur-
sor Synthesis: Scope and Molecular Composition.
Recently, we reported the synthesis of mixed chlorido/
tetramethylaluminato heterobimetallic rare-earth-metal com-
plexes of different nuclearities depending on the size of the
Scheme 1. Synthesis Pathway toward Heterobimetallic Complexes [CpRLn(AlMe4)(μ-X)]2 and [CpR La3(AlMe4)2(μ-X)4]2 of
3
Distinct Nuclearity
B
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Ln(III) center.49 This procedure required the treatment of the
half-sandwich complexes (C5Me5)Ln(AlMe4)2 with the chlor-
ido transfer reagent Me2AlCl at low temperatures.
half-sandwich complexes, a doublet for the AlMe4 signal with a
2J(YH) coupling constant of around 2.3 Hz was observed,
except for 1*-YCl, indicating a highly fluxional nature. The
respective Lu complexes display very broad signals for the Lu-
Me moiety, indicating a less pronounced dynamic behavior of
the bridging and terminal Me groups in solution as expected
for the smaller-sized Lu(III) center. The 13C{1H} NMR
spectra clearly show the same trend of the halogenido ligands
on the 13C{1H} chemical shift and, as expected, two signals for
C5Me5 and six signals for C5Me4SiMe3, respectively. For most
of the complexes, the Al-CH3 carbon signals could not be
detected, due to their low solubility as well as the relatively fast
ligand redistribution processes, which is consistent with results
In search of milder and adjustable halogenido transfer
reagents, we opted for trimethylsilyl halide reagents,50 inspired
by the work of Orpen et al. on SiMe3I (TMSI)-promoted
alkyl/iodido exchange reactions.51 We envisaged that these
increasingly versatile reagents SiMe3X could reveal the effect of
less electronegative halogens (X) not only on the hetero-
bimetallic cluster synthesis but also (if the latter succeeds) on
the olefination reactions. To probe any Ln(III)-size and
“cyclopentadienyl” effects, we chose CpRLn(AlMe4)2 (CpR =
C5Me5, C5Me4SiMe3; Ln = Y, La, Lu) as representative
precursors. As found earlier for the chlorido derivative
[(C5Me5)Y(AlMe4)(μ-Cl)]2, treatment of the bis-
(alkylaluminato) half-sandwich complexes containing the
smaller-sized rare-earth metals yttrium and lutetium with 0.9
equiv or less of the halogenido transfer reagent led to a
successful single AlMe4/X anion exchange and the formation
of the dimeric complexes [CpRLn(AlMe4)(μ-X)]2 in moderate
to good crystalline yields (1-LnX; Scheme 1, left).49,52
Elemental and crystal structure analyses confirmed the
general composition of dimeric yttrium and lutetium
complexes 1-LnX; however, the NMR data showed two
different sets of signals, one belonging to unreacted CpRLn-
(AlMe4)2. A closer look at this apparent discrepancy between
solid-state analytics and NMR solution measurements
indicated the occurrence of ligand redistribution in aromatic
solvents over time (Scheme 1). Such intermolecular ligand
exchange would involve the coformation of putative
[CpRLnX2],50,53 but the hardly soluble byproducts were not
further characterized. Furthermore, the true nature of the
composition of the complexes 1-LnX was validated with
elemental analysis as well as various unit-cell checks confirming
that the products 1-LnX crystallized from the mother liquor in
n-hexane as the exclusive product when they were not
redissolved in aromatic solvents. The ambient-temperature
1H NMR spectra of all complexes [(C5Me5)Ln(AlMe4)(μ-X)]2
clearly display one signal for the Cp-CH3 groups as well as one
for the AlMe4 moieties as expected from the Ci symmetry of
the complexes, and further one set of signals of (C5Me5)Ln-
(AlMe4)2 due to the aforementioned behavior in solution
(spectra shown in the Supporting Information). For all
compounds 1*-LnX, a clear trend was found for the Cp-CH3
signals with a shift downfield for each respective metal from Cl
to I (1*-YCl 1.89 ppm, 1*-YBr 1.92 ppm, 1*-YI 1.98 ppm; 1*-
LuCl 1.93 ppm, 1*-LuBr 1.96 ppm, 1*-LuI 2.00 ppm) as well as
for the Ln-Me signals (1*-YCl −0.20 ppm, 1*-YBr −0.18 ppm,
1*-YI −0.15 ppm; 1*-LuCl −0.05 ppm, 1*-LuBr 0.00 ppm, 1*-
LuI 0.04 ppm). Furthermore, the signals compare well with
those of the starting compounds (C5Me5)Ln(AlMe4)2 (Y, 1.72
ppm, −0.33 ppm; Lu, 1.75 ppm, −0.18 ppm). Exactly the same
Cl to I trend was observed for all [(C5Me4SiMe3)Ln(AlMe4)-
(μ-X)]2 (1′-LnX) complexes. The proton NMR spectra show
four different signals, two for the Cp-Me moieties (1′-YCl 2.15/
1.85 ppm, 1′-YBr 2.17/1.86 ppm, 1′-YI 2.22/1.93 ppm; 1′-LuCl
2.17/1.87 ppm, 1′-LuBr 2.19/1.88 ppm, 1′-LuI 2.23/1.86
ppm), one for the SiMe3 groups, and one for the Al-Me
moieties (1′-YCl −0.18 ppm, 1′-YBr −0.15 ppm, 1′-YI −0.13
ppm; 1′-LuCl −0.05 ppm, 1′-LuBr 0.01 ppm, 1′-LuI 0.01 ppm).
Again, the signals compare well with those of the starting
compounds (C5Me4SiMe3)Ln(AlMe4)2 (Y, 2.00/1.75 ppm,
−0.31 ppm; Lu, 1.99/1.75 ppm, −0.14 ppm). For the yttrium
in the literature.49 The 89Y NMR resonances from H−89Y
1
HSQC measurements also revealed high-field-shifted signals in
the presence of the more electron-withdrawing halogenido
ligand (e.g., 1*-YCl 208 ppm versus 1*-YBr 246 ppm) but only
a marginal effect of the cyclopentadienyl ligand (e.g., 1*-YCl
208 ppm versus 1′-YCl 206 ppm). For comparison, the starting
compounds CpRY(AlMe4)2 display 89Y NMR resonances at
175 ppm (CpR = C5Me5) and 170 ppm (CpR = C5Me4SiMe3).
Due to solubility issues, long measurement periods, and rapid
1
ligand redistribution, H−89Y HSQC spectra could not be
obtained for 1*-YI and 1′-YI (detection of precursors only).
X-ray diffraction (XRD) analyses were performed on 1*-YBr,
1*-YI, and 1*-LuBr (Figure 2 and Figures S65 and S66). The
Figure 2. Crystal structure of 1*-YBr with atomic displacement
parameters set at the 50% level. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg) for 1*-YBr: Y1−
Br1 2.8493(8), Y1−Br1′ 2.8687(10), Y1−C1 2.531(2), Y1−C2
2.566(2), Y1···Al1 3.0970(10), Y1···Ct1 2.310, Al1−C1 2.073(2),
Al1−C2 2.079(2), Al1−C3 1.981(2), Al1−C4 1.969(2); Br1−Y−
Br1′ 79.54(3), Y1−Br1−Y1′ 100.46(3), C1−Y1−C2 83.26(8), Y1−
C1−Al1 83.90(8), Y1−C2−Al1 82.92(8).
aforementioned [(C5Me5)Ln(AlMe4)(μ-X)]2 complexes re-
vealed the dimeric solid-state structure with seven-coordinate
Ln centers: the monoanionic Cp ligand occupies three
coordination sites, and the methyl groups as well as the
bridging halogenido ligands each occupy two. The crystal
structures are isostructural with 1*-YCl.49 The Y−C(Me)
distance appears slightly decreased for the heavier halide
complexes 1*-YBr and 1*-YI as a result of the changed halogen
electronegativity (1*-YCl, av 2.573 Å;49 1*-YBr, 2.531(2)/
2.566(2) Å; 1*-YI, 2.529(4)/2.563(4) Å) but compare well
with those of the reactant (C5Me5)Y(AlMe4)2 (2.549(3)−
2.655(3) Å).54 As expected, the Lu−C(Me) bond lengths in
1*-LuBr are shortened (2.486(3)/2.529(3) Å) in comparison
C
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to 1*-YBr, reflecting the smaller Ln(III) size. This is further
supported by the differences in the Ln−Br distances (1*-YBr,
2.8493(8)/2.8687(10) Å; 1*-LuBr, 2.7961(7)/2.8257(8) Å) as
well as the Ln···Al interatomic distances (1*-YCl, 3.0584(12)
Å;46 1*-YBr, 3.0970(10) Å; 1*-LuBr, 3.0434(10) Å). Only a
few complexes with bromido ligands bridging two rare-earth-
metal centers are known including, dimeric 3-(2,6-iPr2C6H3)-
1-[2-(1-(4,7-Me2)indenyl)propyl]imidazol-2-ylidene-
(trimethylsilylmethyl)bromido yttrium (Y−Br bond lengths:
2.8645(7) and 2.8747(7) Å),55 [Y(η5-Me2C5H3)2Br]2
(2.857(1) and 2.868(1) Å),56 and [(η5:η5-C5H4-CMe2-
fluorenyl)Y(μ-Br)]2 (2.8055(13)/2.8065(12) Å),57 the last
showing shorter Y−Br distances in comparison to 1*-YBr.
The tetramethylaluminato/halogenido exchange was also
probed for the lanthanum complexes CpRLa(AlMe4)2. Treat-
ment of the respective bis(tetramethylaluminato) half-
sandwich complexes with 1.3 equiv of TMSX resulted in the
formation of hexalanthanum clusters of the general composi-
(2*-LaX: X = Cl, I)49,50 and (C5H4SiMe3)6La6(AlMe4)4(I)8.50
Two La3Al2 subunits, related by C2 symmetry, feature distinctly
coordinating halogenido ligands (μ2, μ3) and a strand of (μ,η2-
Me2)Al(Me)(μ,η1-Me)-interconnecting aluminato ligands. The
Ln:X ratio of 1:1.3 is striking, being distinct from that of the
dimeric yttrium and lutetium complexes in this work (1:1).
Overall, the CpR ligand seems to have only a small effect on the
molecular structure; however, the bond lengths are signifi-
cantly affected. The La−X bond lengths of 2′-LaCl
(2.8087(7)−3.0787(6) Å) are slightly elongated in comparison
to 2*-LaCl (La−Cl: 2.8049(9)−3.0708(9) Å),49 while the La−
C(Me) bond lengths and the La···Al distances appear slightly
shortened (2*-LaCl La−C(Me) 2.742(3)−2.970(3) Å, La···Al
3.3150(11)−3.3534(11) Å;49 2′-LaCl La−C(Me) 2.771(4)−
2.777(4) Å, La···Al 3.2849(9)−3.3371(9) Å). For further
comparison, the precursor (C5Me5)La(AlMe4)258 displays La−
C(Me) bond lengths (2.694(3)−2.802(4) Å) as well as La···Al
distances (3.0141(9)−3.2687(9) Å) which are shorter than in
2*-LaCl and 2′-LaCl.
tion CpR La6(AlMe4)4(X)8. All reactions yielded colorless
6
The introduction of electron-withdrawing pseudohalogenido
ligands such as triflato (OTf) proved more difficult but was
successful for the system (C5Me5)La(AlMe4)2/SiMe3OTf,
yielding the crystalline heterobimetallic complex
crystals from resting n-hexane solutions at ambient temper-
atures, and an XRD analysis was carried out exemplarily for 2′-
LaCl (Figure 3). Due to the insolubility of all complexes 2-La
in nonpolar and aromatic NMR solvents, solution NMR
spectroscopic analysis was not accessible. The crystal structure
of 2′-LaCl with formally eight-coordinate La(III) centers has
the molecular connectivity (C5Me4SiMe3)6La6{(μ-
Me)3AlMe}4(μ3-Cl)2(μ-Cl)6, being isostructural with the
previously reported complexes (C5Me5)6La6(AlMe4)4(X)8
(C5Me5)3La3(AlMe4)(μ-OTf)3(μ3-OTf)2(THF)2 (3*-LaOTf
)
(Scheme 2). The solubility of this complex in nonpolar and
Scheme 2. Reactivity of (C5Me5)La(AlMe4)2 toward
Pseudohalogenido-Transfer Reagent SiMe3OTf
aromatic solvents is limited, while decomposition to several
C−F-bond cleavage products occurred in THF over time
1
(monitored by H NMR spectroscopy), if not prevented by
lower temperatures.
An XRD analysis of 3*-LaOTf (crystallized from THF)
revealed a tetrametallic complex with three μ2- and two μ3-
bridging triflato ligands (Figure 4). The core structure can be
best described as a 12-membered ring consisting of three [La−
O−S−O] units with two μ3-coordinating triflato caps. An 8-
fold coordination of the lanthanum centers is accomplished by
the peripheral cyclopentadienyl rings, two THF molecules, and
Figure 3. Crystal structure of 2′-LaCl with atomic displacement
parameters set at the 50% level. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg) for 2′-LaCl: La1−
Cl1 3.0787(6), La1−Cl2 2.8382(7), La1−Cl3 2.8298(7), La2−Cl1
3.0725(7), La2−Cl2 2.8421(7), La2−Cl4 2.8395(7), La3−Cl1
3.0111(6), La3−Cl3 2.8101(7), La3−Cl4 2.8087(7), La1−C1
2.809(3), La1−C2 2.774(3), La2−C5 2.742(3), La2−C6 2.764(3),
La3−C3′ 2.947(3), La3−C7′ 2.970(3), La1···Ct1 2.507, La2···Ct2
2.507, La3···Ct3 2.501, La1···Al2 3.3371(9), La2···Al1 3.2849(9);
La1−Cl1−La2 100.878(19), La1−Cl1−La3 100.870(18), La1−Cl2−
La2 113.20(2), La1−Cl3−La3 112.70(2), La2−Cl1−La3
100.579(19), La2−Cl4−La3 111.91(2), La1−C1−Al2 85.28(10),
La1−C2−Al2 86.40(10), La2−C5−Al1 85.40(10), La2−C6−Al1
84.78(10), C1−La1−C2 75.19(9), C5−La2−C6 76.58(9), C3′−
La3−C7′ 77.39(9).
−
one remaining AlMe4 ligand, which coordinates one
lanthanum center in a η1 fashion. The La···Ct distances
(2.463−2.564 Å) match those detected in the other 2-LaX
complexes. Furthermore, the La−O distances range between
2.436(5) and 2.591(5) Å for μ2-bridging triflato ligands and
between 2.496(5) and 2.575(4) Å for μ3-bridging triflato
moieties. The La−C(Me) distance of 2.942(7) Å is located in
the upper range of 2-LaX complexes.
Donor-Induced Methylidene Formation from Mixed-
Ligand AlMe4/X Ln(III) Complexes. We communicated
previously that mixed-ligand complexes [(C5Me5)Ln-
(AlMe4)x(Cl)y]z (Ln = Y with x = y, z = 2; La with 2x = y,
D
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achieved, most likely because of another Ln(III)/halogenido
1
size mismatch (Y(III) medium sized, I− too large). H NMR
spectroscopic studies revealed the formation of methyl/iodido
species [CpRYMeI(THF)x]n and diiodido complexes
[CpRYI2(THF)x]n upon addition of THF to 1*-YI and 1′-YI,
but any cluster formation was not observed. For all probed
methylidene clusters, their formation is strongly dependent on
the chosen reaction conditions. More precisely, if the synthesis
was carried out below ambient temperatures, Cp-stabilized
dihalogenido Ln(III) complexes CpRLnX2(THF)3 could be
isolated, which was verified by elemental analyses and unit cell
checks. In addition, while the formation of the lanthanum
methylidene derivatives follows a stoichiometrically correct
pathway (8X− + 4AlMe4 → 2[4X− + CH2 + 2AlMe3 +
−
2−
CH4]), there is an obvious stoichiometric mismatch for the
yttrium reactions (1.5[2X− + 2AlMe4 ] → 3X− + CH2
+
−
2−
[3AlMe3 + CH4]), clearly indicating a shortage of halogenido
ligands. Although the formation of the targeted methyl-free
complexes 4-YX seems to be favored under the chosen
crystallization conditions, halogenido-deficient mixed methyl/
halogenido/methylidene Ln(III) complexes of the type
Figure 4. Crystal structure of 3*-LaOTf with atomic displacement
parameters set at the 50% level. Hydrogen atoms and the disorder in
the Cp rings as well as the CF3 groups are omitted for clarity. Selected
bond lengths (Å) for 3*-LaOTf: La1···Ct1 2.564, La2···Ct2 2.463,
La3···Ct3 2.498, La3−C31 2.942(7), La1−O1 2.477(5), La1−O4
2.441(6), La1−O7 2.520(5), La1−O10 2.496(5), La2−O2 2.490(5),
La2−O8 2.529(5), La2−O11 2.553(5), La2−O13 2.436(5), La3−O5
2.591(5), La3−O9 2.601(4), La2−O12 2.575(4), La2−O14
2.584(5), La3−C31 2.942(7), La3···Al1 4.971.
CpR Y3(μ2-CH3)x(μ2-X)y(μ3-X)(μ3-CH2)(THF)3 (x + y = 3)
3
can be identified and crystallized/isolated as well (Figure S58
in the Supporting Information). Spurred by these obvious
drawbacks, we devised an alternative synthesis protocol.
Methyl/Methylidene to X/Methylidene Transforma-
tion. Having in mind the very rigid methylidene cluster
entities (as evidenced by NMR spectroscopy, vide infra), we
envisaged the mixed methyl/methylidene cluster complex
(C5Me5)3Y3(μ-Me)3(μ3-Me)(μ3-CH2)(THF)2 (VY, cf. Figure
1) as a potential precursor for 4-type complexes. Compound
VY could be readily obtained from [(C5Me5)Y(μ-Me)2]3 via
addition of THF.46 Much to our delight, treatment of VY with
4 equiv of the halogenido transfer reagent SiMe3X in THF gave
the desired complexes 4*-YCl and 4*-YBr via tetramethylsilane
elimination (Scheme 3, path B). However, once again, the
yttrium methylidene complex with bridging iodido moieties,
that is the putative 4*-YI, was not feasible, and only
degradation of the inner core and an ill-defined product
mixture were found. It is noteworthy that protonolyses of
complex VY are more difficult to control. For example, the
reaction of VY with 4 equiv of neopentyl alcohol was rather
unselective and afforded the bis(alkoxy) yttrium half-sandwich
z = 6) can selectively undergo donor (THF)-promoted
alkylaluminato cleavage (separation of AlMe3(THF)) and
engage in subsequent C−H-bond activation of the emerging
terminal Ln-CH3 moiety. Accordingly, complexes 1 and 2 were
suspended in toluene and treated with an excess of THF at
ambient temperature (Scheme 3, path A). As found earlier for
the pentamethylcyclopentadienyl ancillary ligand and the
chlorido coligand, the yttrium and lanthanum reactions gave
the trimetallic rare-earth-metal methylidene complexes
CpR Ln3(μ-X)3(μ3-X)(μ3-CH2)(THF)3 (3*-LnX and 3′-LnX;
3
Ln = Y, La).
Despite major efforts, the respective lutetium methylidene
complexes could not be synthesized via this protocol
(presumably due to Lu(III)-imparted size restrictions).
Furthermore, the Y/I/CH2 combination could not be
Scheme 3. Different Synthesis Pathways for the Generation of Mixed Halogenido/Methylidene Rare-Earth-Metal Complexes
E
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Figure 5. Crystal structures of 4*-YBr (left), 4*-LaBr (middle), and 4′-LaCl (right) with atomic displacement parameters set at the 50% level.
Hydrogen atoms except for the CH2 group and lattice toluene are omitted for clarity. Selected bond lengths and angles for 4*-YBr, 4*-LaBr, and 4′-
LaCl are given in Table 1.
Table 1. Selected Structural Parameters (Å, deg) for Methylidene Complexes 4*-YBr, 4*-LaBr, and 4′-LaCl
Ln−CH2
Ln1−μ2(X)
Ln2−μ2(X)
Ln3−μ2(X)
Ln−μ3(X)
Ln−O
Ln···Ct
Ln−CH2−Ln
4*-YBr 2.431(3), 2.484(3), 2.8538(5),
2.8781(5),
2.8853(5),
2.8699(5),
2.8870(5),
3.0578(5), 3.0609(5), 2.406(3), 2.420(3), 2.387, 2.388, 97.44(12), 98.12(12),
2.532(3) 2.8757(5)
2.553(3), 2.572(3), 3.0279(4),
2.646(4) 3.0307(5),
2.572(3), 2.576(3), 2.8782(8),
2.580(3) 2.8796(7),
3.0807(5) 2.460(3) 2.400 100.45(13),
3.1670(4), 3.1849(4), 2.573(3), 2.573(3), 2.538, 2.541, 98.37(12), 98.51(12),
3.2074(4) 2.599(3) 2.544 99.98(12)
3.0226(7), 3.0314(8), 2.53(1), 2.593(3), 2.449, 2.543, 98.03(10), 98.60(10),
3.0325(8), 2.611(2) 2.572 98.63(10)
4*-
LaBr
4′-
LaCl
3.0047(5),
3.0274(4)
3.0307(4),
3.0385(5)
2.8828(8),
2.8906(7),
2.8783(8),
2.8834(9),
complex [(C5Me5)Y(OCH2tBu)(μ-OCH2tBu)]2 (5*-Y,
Scheme 3; the crystal structure is depicted in Figure S67),
involving the alcoholysis of both the methyl and methylidene
ligands. Compound 5*-Y was previously obtained via amine
elimination by utilizing (C5Me5)Y(NiPr2)2(THF).59
YBr 183 ppm) and clearly display a high-field shift in
comparison to the respective dimeric starting compounds 1-
YX.
Crystallization of the obtained methylidene complexes could
be achieved from saturated solutions in a mixture of toluene
and THF at −40 °C. XRD analyses were carried out for 4*-
YBr, 4*-LaBr, and 4′-LaCl, and the obtained crystal structures
are depicted in Figure 5 (see also Table 1). As detected
previously for 4*-LnCl (Ln = Y, La), the three Ln(III) centers
adopt a distorted-pseudo-octahedral geometry involving one
shielding C5Me5 site, one μ3-bridging and three μ2-halogenido
ligands, and THF donor ligands, as well as the μ3-bridging
methylidene moiety, protruding from the Ln3X3 plane. A
comparison of 4*-YCl with 4*-YBr revealed elongated bond
lengths for both Y−X (4*-YCl, μ2 2.7028(6)−2.72787(6) Å, μ3
2.8522(5)−2.8897(5) Å;47 4*-YBr, μ2 2.8538(5)−2.8870(5)
Å, μ3 3.0578(5)−3.0807(5) Å) and Y−C(CH2) (4*-YCl,
2.424(2)−2.450(2) Å;47 4*-YBr, 2.431(3)−2.532(3) Å) of the
bromido derivative. The same trend can be found for the La−
X distances of 4*-LaX (4*-LaCl, μ2 2.8614(8)−2.8929(8) Å, μ3
3.0014(7)−3.0334(7) Å;47 4*-LaBr, μ2 3.0047(5)−3.0385(5)
Å; μ3 3.1670(4)−3.2074(4) Å). Similarly, the La−C(CH2)
distances appear significantly elongated for the bromide
derivative (4*-LaCl, 2.537(3)−2.635(3) Å;47 4*-LaBr,
2.553(3)−2.646(4) Å; 4′-LaCl, 2.572(3)−2.580(3) Å), while
those of the C5Me4SiMe3-supported complex 4′-LaCl tend to
be longer, with similar La−Cl bond lengths (4′-LaCl, μ2
2.8782(8)−2.8906(7) Å, μ3 3.0226(7)−3.0325(8) Å). Further
comparison can be drawn to the tris(pyrazolyl)borato-
supported rare-earth-metal variant of the Tebbe reagent
TptBu,MeLa(CH2)(AlMe3)2, featuring a La−C(CH2) bond
length of 2.519(2) Å.32 The Y−C(CH2) distances in
complexes 4-YX can be compared to those of complex VIY
(see Figure 1, 2.345(5)−2.424(4) Å),37 VY (2.283(4)−
2.477(3) Å),46 and (NCNdipp)3Y3(μ-Me)3(μ3-CH2)(μ3-
Characterization of Methylidene Complexes 4-LnX.
1
The ambient-temperature H NMR spectra of all crystalline
compounds CpR Ln3(μ-X)3(μ3-X)(μ3-CH2)(THF)3 recorded
3
in [D8]THF show one set of signals for the ancillary Cp
ligands, in accordance with their symmetrical arrangement in
the solid state (spectral data pictured in the Supporting
Information). As detected for the precursors 1*-YX and 1′-YX,
the shift of the CH2 group is significant for each introduced
halogenido ligand and shows a clear trend from Cl− to I− for
the respective ligand set. The methylidene signal of all yttrium
complexes features a quartet due to the coupling with the three
89Y nuclei (4*-YCl, −0.35 ppm; 4*-YBr, −0.33 ppm; 4′-YCl,
−0.42 ppm; 4′-YBr, −0.42 ppm), which is shifted slightly to
higher field in comparison to that in VY (−0.31 ppm).44 For
further comparison the methylidene signal of the Tebbe
reagent is found far downfield at δ 8.28 ppm (Figure S59).22 It
is noteworthy that the complex 4′-YBr showed decomposition
in THF after 30 min. For all lanthanum compounds, the
methylidene signal exhibits a singlet markedly shifted to higher
field in comparison to the yttrium congeners. As indicated by
the same shift range (4*-LaCl −0.93 ppm, 4*-LaBr −0.93 ppm,
4*-LaI −0.97 ppm; 4′-LaCl −0.96 ppm, 4′-LaBr −0.97 ppm, 4′-
LaI −0.96 ppm), the halogenido ligand exerts only a minor
2−
influence on lanthanum-bound CH2 groups.
As expected, the 13C{1H} NMR spectra show one set of
signals for the respective Cp ligand; however, the 13C{1H}
signal for the CH2 group could not be detected even after 18 h
1
of measuring time. Moreover, H−89Y HSQC NMR spectra
reinforce the dependence of the 89Y shift on the halogenido
ligand (4*-YCl 163 ppm, 4*-YBr 196 ppm; 4′-YCl 150 ppm, 4′-
F
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Table 2. Methylidene-Transfer Reactivity of Rare-Earth-Metal Complexes 4*-Ln and 4′-Ln in [D8]THF, Probed for 9-
a
Fluorenone (A), Benzaldehyde (B), Cyclohexanone (C), Dihydrocoumarin (D), and δ-Valerolactone (E)
yield (%)
b
b
entry
4*-YCl
4*-YBr
4′-YCl
4′-YBr
4*-LaCl
4*-LaBr
4*-LaI
4′-LaCl
4′-LaBr
4′-LaI
TebbeCl
TebbeBr
c
A
B
C
D
E
>99
>99
>99
0
>99
>99
>99
0
>99
>99
>99
0
>99
>99
>99
0
59
52
59
0
65
45
63
0
0
48
43
0
60
58
>99
0
39
59
>99
0
0
64
>99
0
>99
>99
>99
59
77 (>99)
>99
c
86 (>99)
c
7 (90)
35 (44)
d
d
d
d
d
d
d
d
d
d
c
76%
86%
60%
51%
67%
87%
23%
88%
85%
70%
>99%
a
b
c
d
In THF, after 15 min. In C6D6, after 15 min. The yield after 18 h is given in parentheses. Polymerization.
CCTMS) (2.382(6)−2.418(6) Å),43 which tend to be shorter.
Overall, trimetallic rare-earth-metal methylidene complexes as
depicted in Figure 1 show similar average Ln−C(CH2) bond
lengths considering the different ionic radii of the rare-earth-
metal centers: e.g., IISc 2.367 Å,38 IIEr 2.388 Å,43 IILu 2.376
Å,38 IVTm 2.346 Å,40 VINd 2.475 Å,45 VIHo 2.391 Å,45 and VILu
2.347 Å.42
Tebbe reagent. Additionally, the reactivities of complexes 3-
LaX were tested for their capability for in situ methylidene
transfer in THF; however, no Tebbe-like olefination was
observed.
Interestingly, the reaction of cyclic esters as δ-valerolactone
with the mixed halogenido/methylidene complexes afforded
ring-opening polymerization in moderate to good yields, in
contrast to the methylidene transfer performed by the Tebbe
reagent (Table 2, entry E, and Table S1; the exact procedure
for the polymerization is given in the Supporting Information).
For better comparison to the methylidene transfer reactivity of
the Tebbe reagent, the general polymerization reactions were
conducted within 15 min. In rare-earth-metal chemistry,
mainly hydrido, triflato, alkyl, amido, and alkoxy groups were
shown to perform in the ring-opening polymerization of
lactones.60−66 Similar to results found in the literature, all
polymerizations carried out in this work show a relatively
narrow molecular weight distribution Mw/Mn ranging from
1.13 to 1.47. The reaction of 4*-YCl with 1 equiv of lactone
Methylidene-Transfer Reactions: Carbonyl Methyle-
nation and Lactone Polymerization. Naturally, we were
interested in the reactivity of these new methylidene complexes
to determine any Ln(III) size effect and the effect of the
halogenido ligand. With addition of the carbonylic substrates,
it was demonstrated previously that the methylidene
complexes under study act as Schrock-type nucleophilic
carbenes.37,47 Accordingly, reactivity studies were carried out
by monitoring the transformations of 2 equiv of cyclo-
hexanone, benzaldehyde, 9-fluorenone, and dihydrocoumarin
with methylidene complexes 4-LnX in [D8]THF at ambient
temperature. The yields were determined after 15 min (see
also the Supporting Information). For comparison, the
established Tebbe reagent was probed under the same
conditions in [D6]benzene (the Tebbe reagent decomposes
in THF). The sole formation of the respective olefinic product
in decent to excellent yields revealed the intended suppression
of undesired methylated side products (Table 2). Strikingly,
complexes bearing bridging iodides (4*-LaI and 4′-LaI) are
not capable of converting the sterically demanding 9-
fluorenone (entry A) even after a prolonged reaction time
(>12 h), likely attributable to the decreased accessibility of the
CH2 moiety, which is less protruding and efficiently shielded
by the bulky iodido ligands. Despite this, the yttrium
complexes convert all tested ketones and aldehydes in very
good yields, equaling the performance of the Tebbe reagent
Cp2Ti(μ-CH2)(μ-Cl)AlMe2. The lanthanum-based methyli-
dene complexes also convert the carbonyl functionalities in
good yields, and the reactivity increases from the chlorido to
bromido derivatives; however, the conversion decreases again
with the introduction of iodido ligands in the bridging
positions. The conversion of cyclohexanone (entry C)
proceeds in good yields for all complexes. Furthermore, the
presence of the silyl-substituted Cp ancillary ligand not only
increased the solubility of these complexes but even increased
the yields, except for 4′-LaBr with 9-fluorenone (entry A),
possibly due to the increased steric bulk implied by SiMe3
substituents. Unfortunately, no reaction was observed for
dihydrocoumarin (entry D), in contrast to that shown for the
1
monitored by H NMR spectroscopy revealed the disappear-
ance of the reactive methylidene moiety as the initiating group
of the polymerization (Figure S63).
Revisiting the Tebbe Reagent. It was only recently that
Mindiola and co-workers reported on the successful structural
elucidation of the prominent Tebbe reagent Cp2Ti(μ-CH2)(μ-
Cl)AlMe2.21 They could show that it favorably cocrystallizes
from n-pentane solution with the trivalent decomposition
product Cp2Ti(μ-Cl)2AlMe2 (site occupancy 0.38). Similarly
to their results, we obtained crystals from a saturated solution
of a mixture of n-pentane and toluene (as originally performed
by Tebbe) but the crystal structure analysis revealed only a
minor amount (site occupancy 0.08) of the side product
Cp2Ti(μ-Cl)2AlMe2 (Figure 6, top). Not surprisingly, the Ti−
C(CH2) bond lengths of Mindiola’s and our studies differ
significantly (this work, 2.058(3) Å; Mindiola’s work, 2.095(5)
Å),21 as do the Ti−Cl distances (this work, 2.5367(6) Å;
Mindiola’s work, 2.5585(7) Å),21 which can only be attributed
to the different quantities of side product present in the crystal.
Given the similar performances of complexes 3-LaCl and 3-
LaBr, and for reasons of further comparability, we envisaged a
bromido variant of the Tebbe reagent, TebbeBr. Surprisingly,
the putative complex Cp2Ti(μ-CH2)(μ-Br)AlMe2 has not been
described in the literature so far. We found that TebbeBr can
67
be accessed via treatment of Cp2TiBr2 with AlMe3, similarly
to TebbeCl. However, the generation of TebbeBr is even slower
than that of TebbeCl and also suffers from the concomitant
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CONCLUSION
■
Treatment of readily available rare-earth-metal half-sandwich
complexes CpRLn(AlMe4)2 with the mild halogenido transfer
reagents SiMe3X gives efficient access to mixed-ligand
tetramethylaluminato/halogenido derviatives [CpRLn-
(AlMe4)x(X)y]z (Ln = Y, La, Lu; X = Cl, Br, I; CpR = Cp*,
Cp′). Crucially, this reaction protocol seems widely applicable,
as shown for larger- and smaller-sized rare-earth-metal centers,
differently substituted cyclopentadienyl ligands, and different
halogenido anions. Interestingly, the nuclearity z is strongly
dependent on the rare-earth-metal size, while the effect of the
varying cyclopentadienyl and halogenido ligands on the solid-
state structure was found to be minor. The transformation of
complexes [CpRLn(AlMe4)x(Cl)y]z into methylidene deriva-
tives CpR Ln3(μ-X)3(μ3-X)(μ3-CH2)(THF)3 is (a) temper-
3
ature dependent (lower temperatures mainly gave bis-
(halogenido) Ln(III) complexes CpRLnX2(THF)3), (b) Ln-
(III) size dependent (respective Lu(III) methylidene
complexes could not be obtained), and (c) halogenido size
dependent (feasible combinations: Y/Cl, Y/Br, La/Cl, La/Br,
La/I). Furthermore, a silane elimination reaction employing
(C5Me5)3Y3(μ-Me)3(μ3-Me)(μ3-CH2)(THF)2 and SiMe3X
was implemented as an alternative protocol for the synthesis
of the respective halogenido/methylidene complex. Such rare-
earth-metal methylidene complexes can be fine-tuned (via
Ln(III), the cyclopentadienyl ligand, and the halogenido ligand
X) to match the performance of the Tebbe reagent in
methylenation reactions of ketones and aldehydes (“[CpRLn-
(CH2)](CpRLnX2)2” vs “[Cp2Ti(CH2)](ClAlMe2)”). How-
ever, the CpR-shielded “Ln3(CH2)” moieties are less tolerant
toward bulky and functionalized substrates, as evidenced for
the polymerization of δ-valerolactone. Finally, in addition to
the preferable Ln(III) redox stability (limitation of undesired
side products during synthesis), the “Ln3(CH2)” moieties can
better cope with distinct halogenido coligands, as evidenced
Figure 6. Crystal structures of the Tebbe reagent Cp2Ti(μ-CH2)(μ-
Cl)AlMe2 (TebbeCl, 92%; Cp2Ti(μ-Cl)2AlMe2, 8%; top) and the
bromide variant Cp2Ti(μ-CH2)(μ-Br)AlMe2 (TebbeBr, 82%; Cp2Ti-
(μ-Br)2AlMe2, 18%; bottom) with atomic displacement parameters
set at the 50% level. Hydrogen atoms except for the CH2 group and
lattice toluene are omitted for clarity. Selected bond lengths (Å): for
TebbeCl, Ti1−C1 2.058(3), Ti1−Cl1 2.5367(6), Ti1−Cl2 2.456(7),
Ti1···Ct1 2.049, Ti1···Ct2 2.047, Al1−C1 2.067(2), Al1−Cl1
2.3090(5), Al1−Cl2 2.074(8); for TebbeBr, Ti1−C1 2.049(8),
Ti1−Br1 2.684(2), Ti1−Br2 2.602(4), Ti1···Ct1 2.049, Ti1···Ct2
2.088, Al1−CH2 2.050(6), Al1−Br1 2.474(2), Al1−Br2 2.154(4).
formation of the respective Ti(III) reduction product Cp2Ti-
(μ-Br)2AlMe2 (presence of a paramagnetic species confirmed
by X-band EPR spectroscopy, Figure S68).68 The methylidene
proton resonance of TebbeBr appeared slightly shifted to
higher field in comparison to TebbeCl (δ 8.17 versus 8.28 ppm;
Figure S60). Notwithstanding, crystals of TebbeBr suitable for
an X-ray structure analysis could be obtained by repeated
recrystallization from an n-pentane/toluene solvent mixture
(Figure 6, bottom).
Although the crystal data are not as good as those for
TebbeCl, a comparison of the metrical parameters suggests a
significant shortening of the Ti−CH2 distance (2.058(3)
versus 2.049(8) Å) upon Cl/Br exchange. Other structurally
characterized titanocene methylidene complexes comprise the
closely related complex Cp2Ti(μ-CH2)(μ-Cl)Al(CH2tBu)2 (in
the solid state, the bridging Cl and CH2 groups are partially
disordered with average distances to the titanium center of
2.494(1) and 2.380(2) Å)69 and the heterobimetallic
complexes Cp2Ti(μ-CH2)(μ-Cl)Rh(COD) (2.018 Å)70 and
Cp2Ti(μ-CH2)(μ-CH3)Rh(COD) (2.147(5) Å).71 Treatment
of the carbonylic substrates under study with TebbeBr revealed
the envisaged methylenation reaction but at a conversion rate
much slower than that detected for TebbeCl (Table 2). This
can be attributed to a more rapid formation of the desired
transient methylidene species “Cp2TiCH2”, as a result of the
enhanced Lewis acidity of ClAlMe2 in comparison to BrAlMe2.
Interestingly, all yttrium methylidene complexes 4*/′-YX (X =
Cl, Br) outperform TebbeBr in the methylenation of ketones A
and C as well as that of aldehyde B.
for the respective bromido derivatives CpR Ln3(μ-Br)3(μ3-
3
Br)(μ3-CH2)(THF)3 versus Cp2Ti(μ-CH2)(μ-Br)AlMe2.
EXPERIMENTAL SECTION
■
All operations were performed with rigorous exclusion of air and
moisture by using standard Schlenk, high-vacuum, and glovebox
techniques (MBraun 200B; <0.1 ppm of O2, <0.1 ppm of H2O).
Solvents were purified by using Grubbs-type columns (MBraun SPS,
solvent purification system) and stored inside a glovebox. [D6]-
benzene, [D8]toluene, and [D8]THF were obtained from Sigma-
Aldrich and degassed; [D6]benzene and [D8]THF were dried over
NaK alloy for 2 days, and [D8]toluene was stored over Na.
[D6]benzene and [D8]toluene were filtered prior to use. [D8]THF
was distilled prior to use. SiMe3Cl, SiMe3Br, and SiMe3OTf were
purchased from Sigma-Aldrich and used as received. SiMe3I was
purchased from ABCR and filtered prior to use. Neopentyl alcohol
was purchased from Alfa Aesar and sublimed prior to use.
Trimethylaluminum was purchased from ABCR and used as received.
Cp2TiCl2 was purchased from Sigma-Aldrich and sublimed prior to
use. 9-Fluorenone was purchased from Sigma-Aldrich and sublimed,
benzaldehyde and cyclohexanone were purchased from Acros
Organics and distilled, and dihydrocoumarin was purchased from
TCI and distilled. δ-Valerolactone was purchased from Sigma-Aldrich
and distilled prior to use. (C5Me5)Ln(AlMe4)2,58 (C5Me4SiMe3)Ln-
46
(AlMe4)2,50 (C5Me5)3Y3(μ-Me)3(μ3-Me)(μ3-CH2)(THF)2 and
67
Cp2TiBr2 were synthesized according to literature procedures.
The NMR spectra of air- and moisture-sensitive compounds were
recorded by using J. Young valve NMR tubes on a Bruker AVII+400
spectrometer (1H, 400.13 MHz; 13C, 100.61 MHz) and on a Bruker
AVII+500 spectrometer (1H, 500.13 MHz; 13C, 125.76 MHz; 89Y,
H
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24.51 MHz). IR spectra were recorded on a Thermo Fisher Scientific
NICOLET 6700 FTIR spectrometer using a DRIFT chamber with a
dry KBr/sample mixture and KBr windows; IR (DRIFT) data were
converted by using the Kubelka−Munk refinement. Elemental
analyses were performed on an Elementar Vario MICRO Cube
instrument. EPR spectra were measured on a continuous wave X-band
Bruker ESP 300E instrument using 5 mm O.D. Wilmad quartz (CFQ)
EPR tubes. Spectra are referenced to the Bruker strong pitched
standard giso = 2.0088. Size exclusion chromatography (SEC) was
performed on a Viscotek GPCmax apparatus and a Model TDA 305
triple detector array. Sample solutions (1.0 mg of polymer/mL of
THF) were filtered through a 0.45 μm syringe filter prior to injection.
The flow rate was 1 mL min−1. dn/dc and dA/dc data were
determined by means of integrated OmniSec software.
13C{1H} NMR (101 MHz, [D8]toluene, 26 °C): δ 121.4 (C5Me5),
12.1 (Cp-CH3) ppm. 13C resonances for the AlMe4 groups could not
̃
be detected. IR (KBr): ν 3013 (vw), 2975 (w), 2916 (m), 2888 (m),
2840 (w), 2823 (w), 2736 (vw), 1558 (vw), 1539 (vw), 1520 (vw),
1506 (w), 1488 (vw), 1455 (w), 1435 (w), 1418 (w), 1379 (vw),
1374 (vw), 1219 (w), 1192 (m), 1021 (vw), 800 (vw), 715 (vs), 700
(vs), 693 (vs), 668 (m), 582 (s), 471 (m), 457 (m), 419 (vw) cm−1.
Anal. Calcd (%) for C28H54Al2Cl2Lu2: C, 38.86; H, 6.29. Found: C,
38.91; H, 6.27.
[(C5Me5)Lu(AlMe4)(μ-Br)]2 (1*-LuBr). Following the procedure
described above, SiMe3Br (29.2 mg, 191 μmol) and (C5Me5)Lu-
(AlMe4)2 (100 mg, 212 μmol) yielded 1*-LuBr as a white powder
1
(67.0 mg, 70.2 μmol, 66%). H NMR (400 MHz, [D8]toluene, 26
°C): δ 1.96 (s, 30H, Cp-CH3), 0.00 (br s, 24H, Al-CH3) ppm.
13C{1H} NMR (101 MHz, [D8]toluene, 26 °C): δ 121.8 (C5Me5),
12.3 (Cp-CH3) ppm. 13C resonances for the AlMe4 groups could not
General Procedure for the Synthesis of [CpRLn(AlMe4)(μ-
X)]2 (1-LnX: Ln = Y, Lu; X= Cl, Br, I; CpR = C5Me5, C5Me4SiMe3).
A solution of 0.9 equiv of SiMe3X in n-hexane (2 mL) was added to a
solution of CpRLn(AlMe4)2 in n-hexane (2 mL). The reaction mixture
was heated to 70 °C for 1 h and cooled to ambient temperature.
Crystals suitable for XRD analysis were grown within 2−4 days at
ambient temperature. Washing the crystals several times with n-
hexane could remove potential impurities of the starting compound.
[(C5Me5)Y(AlMe4)(μ-Cl)]2 (1*-YCl). Following the procedure
described above, SiMe3Cl (49.1 mg, 452 μmol) and (C5Me5)Y-
(AlMe4)2 (200 mg, 502 μmol) yielded 1*-YCl as a white powder (148
be detected. IR (KBr): ν 3014 (w), 2976 (w), 2917 (s), 2887 (m),
̃
2841 (m), 2824 (w), 2734 (vw), 1556 (vw), 1486 (vw), 1435 (w),
1418 (w), 1391 (vw), 1379 (vw), 1219 (m), 1192 (m), 1022 (w), 800
(vw), 713 (vs), 697 (vs), 613 (m), 578 (s), 473 (m), 459 (m), 413
(vw) cm−1. Anal. Calcd (%) for C28H54Al2Br2Lu2: C, 35.24; H, 5.70.
Found: C, 35.22; H, 5.51.
[(C5Me5)Lu(AlMe4)(μ-I)]2 (1*-LuI). Following the procedure de-
scribed above, SiMe3I (38.1 mg, 190 μmol) and (C5Me5)Lu(AlMe4)2
(100 mg, 212 μmol) yielded 1*-LuI as white powder (74.0 mg, 70.6
1
mg, 213 μmol, 85%). H NMR (500 MHz, [D8]toluene, 26 °C): δ
1
μmol, 67%). H NMR (400 MHz, [D8]toluene, 26 °C): δ 2.00 (s,
2
1.89 (s, 30H, Cp-CH3), −0.20 (d, J(YH) = 2.3 Hz, 24H, Al-CH3)
30H, Cp-CH3), 0.04 (br s, 24H, Al-CH3) ppm. 13C{1H} NMR (101
MHz, [D8]toluene, 26 °C): δ 122.6 (C5Me5), 13.1 (Cp-CH3) ppm.
13C resonances for the AlMe4 groups could not be detected. IR (KBr):
ppm. 13C{1H} NMR (101 MHz, [D8]toluene, 26 °C): δ 123.0 (d,
1J(YC) = 1.7 Hz, C5Me5), 12.0 (Cp-CH3) ppm. 13C resonances for
1
the AlMe4 groups could not be detected. 89Y NMR (from H−89Y
ν 2969 (w), 2915 (m), 2886 (m), 2862 (w), 1444 (w), 1433 (w),
̃
HSQC, 25 MHz, [D8]toluene, 26 °C): δ 208 ppm. IR (KBr): ν 2948
̃
1419 (w), 1379 (w), 1226 (w), 1190 (w), 1022 (vw), 712 (vs), 696
(vs), 580 (s), 480 (w), 473 (w), 459 (w), 402 (w) cm−1. Anal. Calcd
(%) for C28H54Al2I2Lu2: C, 32.08; H, 5.19. Found: C, 31.94; H, 5.01.
[(C5Me4SiMe3)Y(AlMe4)(μ-Cl)]2 (1′-YCl). Following the procedure
described above, SiMe3Cl (21.4 mg, 197 μmol) and (C5Me4SiMe3)-
Y(AlMe4)2 (100 mg, 219 μmol) yielded 1′-YCl as a white powder
(s), 2907 (s), 2859 (m), 1488 (w), 1454 (m), 1433 (m), 1387 (w),
1379 (m), 1194 (w), 1065 (vw), 1024 (w), 803 (vw), 705 (vs), 690
(s), 592 (vw), 576 (w), 401 (m) cm−1. Anal. Calcd (%) for
C28H54Al2Cl2Y2: C, 48.50; H, 7.85. Found: C, 48.32; H, 7.30. The
analytical data were consistent with those previously published.49
[(C5Me5)Y(AlMe4)(μ-Br)]2 (1*-YBr). Following the procedure
described above, SiMe3Br (69.2 mg, 452 μmol) and (C5Me5)Y-
(AlMe4)2 (200 mg, 502 μmol) yielded 1*-YBr as a white powder (104
1
(40.0 mg, 49.4 μmol, 45%). H NMR (400 MHz, [D8]toluene, 26
°C): δ 2.15 (s, 12H, Cp-CH32-2,5), 1.85 (s, 12H, Cp-CH3-3,4), 0.32
(s, 18H, Si-CH3), −0.18 (d, J(YH) = 2.4 Hz, 24H, Al-CH3) ppm.
13C{1H} NMR (101 MHz, [D8]toluene, 26 °C): δ 132.3 (2,5-
C5Me4SiMe3), 128.4 (3,4-C5Me4SiMe3), 120.3 (1-C5Me4SiMe3), 15.7
(Cp-CH3), 11.9 (Cp-CH3), 2.1 (Si-Me), 0.3 (br, Al-Me) ppm. 89Y
1
mg, 150 μmol, 60%). H NMR (400 MHz, [D8]toluene, 26 °C): δ
2
1.92 (s, 30H, Cp-CH3), −0.18 (d, J(YH) = 2.3 Hz, 24H, Al-CH3)
ppm. 13C{1H} NMR (101 MHz, [D8]toluene, 26 °C): δ 123.5 (d,
1J(YC) = 1.5 Hz, C5Me5), 12.3 (Cp-CH3) ppm. 13C resonances for
1
NMR (from H−89Y HSQC, 25 MHz, [D8]toluene, 26 °C): δ 206
1
the AlMe4 groups could not be detected. 89Y NMR (from H−89Y
ppm. IR (KBr): ν 2948 (m), 2918 (m), 2892 (m), 2826 (w), 2794
̃
HSQC, 25 MHz, [D8]toluene, 26 °C): δ 246 ppm. IR (KBr): ν 2929
̃
(vw), 1456 (w), 1448 (w), 1436 (vw), 1429 (vw), 1419 (vw), 1406
(vw), 1322 (w), 1248 (m), 1219 (w), 1187 (w), 1019 (vw), 846 (vs),
838 (vs), 756 (m), 715 (vs), 697 (vs), 633 (w), 608 (w), 583 (s), 481
(w), 459 (vw), 425 (w) cm−1. Anal. Calcd (%) for C32H66Al2Cl2Si2Y2:
C, 47.47; H, 8.22. Found: C, 47.58; H, 7.94. The analytical data were
consistent with those previously published.52
(m), 2914 (m), 2888 (w), 2863 (w), 2823 (w), 2789 (vw), 1487
(vw), 1446 (w), 1234 (w), 1419 (w), 1434 (vw), 1380 (w), 1219
(m), 1188 (w), 1022 (vw), 801 (vw), 715 (vs), 697 (vs), 608 (w),
587 (s), 482 (w), 457 (w), 422 (w) cm−1. Anal. Calcd (%) for
C28H54Al2Br2Y2: C, 42.99; H, 6.96. Found: C, 42.66; H, 7.30.
[(C5Me5)Y(AlMe4)(μ-I)]2 (1*-YI). Following the procedure described
above, SiMe3I (90.4 mg, 452 μmol) and (C5Me5)Y(AlMe4)2 (200 mg,
502 μmol) yielded 1*-YI as a white powder (165 mg, 188 μmol,
75%). 1H NMR (400 MHz, [D8]toluene, 26 °C): δ 1.98 (s, 30H, Cp-
CH3), −0.15 (br s, 24H, Al-CH3) ppm. 13C{1H} NMR (101 MHz,
[D8]toluene, 26 °C): δ 124.1 (C5Me5), 11.4 (Cp-CH3) ppm. 13C
[(C5Me4SiMe3)Y(AlMe4)a(μ-Br)]2 (1′-YBr). Following the procedure
described above, SiMe3Br (30.2 mg, 197 μmol) and (C5Me4SiMe3)-
Y(AlMe4)2 (100 mg, 219 μmol) yielded 1′-YBr as a white powder
1
(60.0 mg, 66.8 μmol, 61%). H NMR (400 MHz, [D8]toluene, 26
°C): δ 2.17 (s, 12H, Cp-CH32-2,5), 1.86 (s, 12H, Cp-CH3-3,4), 0.33
(s, 18H, Si-CH3), −0.15 (d, J(YH) = 2.4 Hz, 24H, Al-CH3) ppm.
13C{1H} NMR (101 MHz, [D8]toluene, 26 °C): δ 132.8 (2,5-
C5Me4SiMe3), 128.3 (3,4-C5Me4SiMe3), 120.5 (1-C5Me4SiMe3), 15.8
(Cp-CH3), 12.3 (Cp-CH3), 2.8 (br, Al-Me), 2.2 (Si-Me) ppm. 89Y
resonances for the AlMe4 groups could not be detected. IR (KBr): ν
2968 (w), 2917 (m), 2885 (m), 2862 (w), 2823 (w), 2731 (vw),
̃
1683 (vw), 1669 (vw), 1575 (w), 1568 (w), 1532 (vw), 1520 (w),
1506 (vw), 1472 (w), 1455 (w), 1446 (w), 1435 (w), 1418 (w), 1394
(vw), 1379 (w), 1218 (w), 1188 (m), 1063 (vw), 1022 (w), 800
(vw), 714 (vs), 697 (vs), 691 (vs), 604 (w), 580 (s), 536 (vw), 527
1
NMR (from H−89Y HSQC, 25 MHz, [D8]toluene, 26 °C): δ 240
ppm. IR (KBr): ν 2955 (w), 2918 (m), 2892 (w), 2824 (w), 2790
̃
(vw), 518 (vw), 482 (w), 479 (w), 458 (w), 419 (vw), 401 (w) cm−1
.
(vw), 1482 (vw), 1448 (vw), 1408 (vw), 1388 (vw), 1377 (vw), 1344
(vw), 1321 (w), 1248 (m), 1219 (w), 1190 (w), 1128 (vw), 1019
(vw), 846 (vs), 838 (vs), 756 (m), 716 (vs), 697 (vs), 633 (w), 611
(w), 582 (w), 482 (w), 460 (w), 426 (m) cm−1. Anal. Calcd (%) for
C32H66Al2Br2Si2Y2: C, 42.77; H, 7.40. Found: C, 42.81; H, 7.34.
[(C5Me4SiMe3)Y(AlMe4)(μ-I)]2 (1′-YI). Following the procedure
described above, SiMe3I (39.4 mg, 197 μmol) and (C5Me4SiMe3)-
Y(AlMe4)2 (100 mg, 219 μmol) yielded 1′-YI as a white powder (70.0
Anal. Calcd (%) for C28H54Al2I2Y2: C, 38.38; H, 6.21. Found: C,
38.19; H, 6.07.
[(C5Me5)Lu(AlMe4)(μ-Cl)]2 (1*-LuCl). Following the procedure
described above, SiMe3Cl (21.0 mg, 193 μmol) and (C5Me5)Lu-
(AlMe4)2 (100 mg, 212 μmol) yielded 1*-LuCl as a white powder
1
(52.0 mg, 60.1 μmol, 57%). H NMR (400 MHz, [D8]toluene, 26
°C): δ 1.93 (s, 30H, Cp-CH3), −0.05 (br s, 24H, Al-CH3) ppm.
I
https://dx.doi.org/10.1021/acs.organomet.0c00447
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
1
mg, 70.5 μmol, 64%). H NMR (400 MHz, [D8]toluene, 26 °C): δ
2.22 (s, 12H, Cp-CH3-2,5), 1.93 (s, 12H, Cp-CH3-3,4), 0.37 (s, 18H,
Si-CH3), −0.13 (s, 24H, Al-CH3)ppm. 13C{1H} NMR (101 MHz,
[D8]toluene, 26 °C): δ 133.3 (2,5-C5Me4SiMe3), 129.4 (3,4-
C5Me4SiMe3), 121.4 (1-C5Me4SiMe3), 16.3 (Cp-CH3), 13.2 (Cp-
[(C5Me5)3La3(AlMe4)2(μ-Cl)4]2 (2*-LaCl). Following the procedure
described above, SiMe3Cl (63.0 mg, 580 μmol) and (C5Me5)La-
(AlMe4)2 (200 mg, 446 μmol) yielded 2*-LaCl as a white powder
(119 mg, 50.4 μmol, 68%). IR (KBr): ν 2911 (s), 2858 (m), 1488
̃
(vw), 1439 (w), 1379 (vw), 1190 (m), 1043 (w), 1027 (w), 763 (w),
696 (vs), 623 (m), 587 (m), 531 (w) cm−1. Anal. Calcd for
C76H138Al4Cl8La6 x C6H14: C, 41.68 H 6.48. Found: C, 41.46; H,
6.50. The analytical data were consistent with those previously
published.49
CH3), 3.7 (br, Al-Me), 2.1 (Si-Me) ppm. IR (KBr): ν 2948 (m), 2898
̃
(m), 2870 (w), 2736 (vw), 1504 (vw), 1481 (vw), 1454 (w), 1447
(w), 1417 (w), 1404 (vw), 1388 (vw), 1374 (vw), 1345 (vw), 1321
(w), 1263 (w), 1253 (m), 1246 (m), 1216 (w), 1194 (w), 1127 (vw),
1020 (w), 987 (vw), 848 (s), 836 (vs), 755 (m), 736 (w), 707 (vs),
698 (vs), 693 (s), 687 (s), 638 (w), 630 (w), 601 (w), 579 (w), 559
(w), 526 (vw), 515 (w), 508 (vw), 496 (vw), 472 (vw), 457 (vw),
421 (m), 405 (vw) cm−1. Anal. Calcd (%) for C32H66Al2I2Si2Y2: C,
38.72; H, 6.70. Found: C, 38.58; H, 6.64.
[(C5Me5)3La3(AlMe4)2(μ-Br)4]2 (2*-LaBr). Following the procedure
described above, SiMe3Br (88.8 mg, 580 μmol) and (C5Me5)La-
(AlMe4)2 (200 mg, 446 μmol) yielded 2*-LaBr as a white powder
(139 mg, 51.1 μmol, 69%). IR (KBr): ν 2954 (m), 2912 (s), 2858
̃
(m), 1449 (w), 1436 (w), 1420 (w), 1379 (w), 1193 (w), 1039 (m),
1026 (m), 768 (w), 700 (vs), 621 (s), 585 (m), 558 (w), 530 (w)
cm−1. Anal. Calcd for C76H138Al4Br8La6 x C6H14: C, 36.23; H, 5.64.
Found: C, 36.60; H, 5.54.
[(C5Me4SiMe3)Lu(AlMe4)(μ-Cl)]2 (1′-LuCl). Following the procedure
described above, SiMe3Cl (18.0 mg, 166 μmol) and (C5Me4SiMe3)-
Lu(AlMe4)2 (100 mg, 184 μmol) yielded 1′-LuCl as a white powder
[(C5Me5)3La3(AlMe4)2(μ-I)4]2 (2*-LaI). Following the procedure
described above, SiMe3I (116 mg, 580 μmol) and (C5Me5)La-
(AlMe4)2 (200 mg, 446 μmol) yielded 2*-LaI as a white powder (200
1
(36.1 mg, 36.7 μmol, 40%). H NMR (400 MHz, [D8]toluene, 26
°C): δ 2.17 (s, 12H, Cp-CH3-2,5), 1.87 (s, 12H, Cp-CH3-3,4), 0.32
(s, 18H, Si-CH3), −0.05 (br s, 24H, Al-CH3) ppm. 13C{1H} NMR
(101 MHz, [D8]toluene, 26 °C): δ 130.9 (2,5-C5Me4SiMe3), 126.8
(3,4-C5Me4SiMe3), 118.4 (1-C5Me4SiMe3), 15.8 (Cp-CH3), 11.8
(Cp-CH3), 2.1 (Si-CH3) ppm. 13C resonances for the AlMe4 groups
mg, 64.6 μmol, 87%). IR (KBr): ν 2954 (s), 2915 (s), 2857 (m), 1487
̃
(w), 1454 (m), 1436 (m), 1419 (w), 1388 (vw), 1378 (w), 1195 (m),
1037 (m), 1026 (m), 768 (w), 698 (vs), 616 (s), 583 (m), 555 (w),
523 (w) cm−1. Anal. Calcd for C76H138Al4I8La6 x C6H14: 31.83; H,
4.95. Found: C, 32.26; H, 4.76.
could not be detected. IR (KBr): ν 2949 (vw), 2887 (w), 2771 (w),
̃
2730 (vw), 1485 (vw), 1448 (w), 1327 (vw), 1243 (w), 1185 (m),
1131 (w), 1107 (vw), 845 (w), 758 (m), 687 (s), 630 (m), 505 (s),
459 (m), 445 (m), 418 (vw) cm−1. Anal. Calcd (%) for
C32H66Al2Cl2Lu2Si2: C, 39.15; H, 6.78. Found: C, 39.22; H, 6.86.
[(C5Me4SiMe3)Lu(AlMe4)(μ-Br)]2 (1′-LuBr). Following the procedure
described above, SiMe3Br (25.4 mg, 166 μmol) and (C5Me4SiMe3)-
Lu(AlMe4)2 (100 mg, 184 μmol) yielded 1′-LuBr as a white powder
[(C5Me4SiMe3)3La3(AlMe4)2(μ-Cl)4]2 (2′-LaCl). Following the proce-
dure described above, SiMe3Cl (55.8 mg, 514 μmol) and
(C5Me4SiMe3)La(AlMe4)2 (200 mg, 395 μmol) yielded 2′-LaCl as a
white powder (80.0 mg, 34.7 μmol, 46%). IR (KBr): ν 2950 (w),
̃
2906 (w), 2861 (w), 1482 (vw), 1452 (w), 1431 (vw), 1386 (vw),
1375 (vw), 1344 (vw), 1325 (w), 1261 (w), 1247 (m), 1195 (w),
1124 (vw), 1043 (w), 1029 (w), 1019 (w), 847 (vs), 836 (vs), 755
(m), 704 (m), 627 (m), 584 (w), 532 (w), 418 (m) cm−1. Anal. Calcd
for C88H174Si6Al4Cl8La6: C, 40.25; H, 6.68. Found: C, 40.40; H, 6.64.
[(C5Me4SiMe3)3La3(AlMe4)2(μ-Br)4]2 (2′-LaBr). Following the pro-
cedure described above, SiMe3Br (78.6 mg, 513 μmol) and
(C5Me4SiMe3)La(AlMe4)2 (200 mg, 395 μmol) yielded 2′-LaBr as a
1
(44.0 mg, 41.1 μmol, 45%). H NMR (400 MHz, [D8]toluene, 26
°C): δ 2.19 (s, 12H, Cp-CH3-2,5), 1.88 (s, 12H, Cp-CH3-3,4), 0.34
(s, 18H, Si-CH3), 0.01 (br s, 24H, Al-CH3) ppm. 13C{1H} NMR (101
MHz, [D8]toluene, 26 °C): δ 131.4 (2,5-C5Me4SiMe3), 127.1 (3,4-
C5Me4SiMe3), 120.4 (1-C5Me4SiMe3), 15.9 (Cp-CH3), 12.2 (Cp-
CH3), 2.2 (Si-CH3) ppm. 13C resonances for the AlMe4 groups could
white powder (160 mg, 52.2 μmol, 79%). IR (KBr): ν 2951 (w), 2906
̃
not be detected. IR (KBr): ν 3014 (w), 2970 (m), 2947 (m), 2920
̃
(w), 1482 (vw), 1451 (w), 1430 (vw), 1406 (vw), 1387 (vw), 1375
(vw), 1344 (vw), 1324 (w), 1260 (w), 1247 (m), 1195 (w), 1123
(vw), 1039 (w), 1022 (w), 844 (vs), 836 (vs), 755 (m), 701 (m), 626
(m), 585 (w), 533 (vw), 418 (w) cm−1. Anal. Calcd for
C88H174Si6Al4Br8La6 x C6H14: C, 36.80; H, 6.18. Found: C, 36.46;
H, 6.09.
(m), 2892 (m), 2825 (w), 2740 (vw), 1484 (vw), 1447 (w), 1433
(w), 1408 (w), 1388 (vw), 1377 (vw), 1371 (vw), 1344 (w), 1321
(m), 1248 (s), 1227 (w), 1188 (w), 1129 (vw), 1020 (vw), 846 (vs),
837 (vs), 756 (s), 715 (vs), 701 (vs), 633 (m), 613 (m), 582 (s), 530
(w), 476 (w), 463 (w), 425 (w), 405 (vw) cm−1. Anal. Calcd (%) for
C32H66Al2Br2Lu2Si2: C, 35.90; H, 6.21; found C 35.68; H, 5.95.
[(C5Me4SiMe3)Lu(AlMe4)(μ-I)]2 (1′-LuI). Following the procedure
described above, SiMe3I (33.2 mg, 166 μmol) and (C5Me4SiMe3)-
Lu(AlMe4)2 (100 mg, 184 μmol) yielded 1′-LuI as a white powder
[(C5Me4SiMe3)3La3(AlMe4)2(μ-I)4]2 (2′-LaI). Following the proce-
dure described above, SiMe3I (103 mg, 515 μmol) and
(C5Me4SiMe3)La(AlMe4)2 (200 mg, 395 μmol) yielded 2′-LaI as a
white powder (100 mg, 28.3 μmol, 43%). IR (KBr): ν 2954 (m),
̃
1
(48.0 mg, 41.2 μmol, 45%). H NMR (400 MHz, [D8]toluene, 26
2904 (m), 2861 (w), 1485 (w), 1454 (w), 1387 (vw), 1375 (w), 1344
(w), 1323 (m), 1249 (m), 1196 (w), 1123 (vw), 1037 (w), 1018 (w),
847 (vs), 836 (vs), 754 (s), 697 (s), 618 (m), 585 (w), 554 (w), 519
(w), 420 (w) cm−1. Anal. Calcd for C88H174Si6Al4I8La6·2C6H14: C,
34.03; H, 5.77. Found: C, 33.92; H, 5.84.
°C): δ 2.23 (br s, 12H, Cp-CH3-2,5), 1.86 (s, 12H, Cp-CH3-3,4), 0.33
(s, 18H, Si-CH3), 0.01 (br s, 24H, Al-CH3) ppm. 13C{1H} NMR (101
MHz, [D8]toluene, 26 °C): δ 132.1 (2,5-C5Me4SiMe3), 127.6 (3,4-
C5Me4SiMe3), 123.0 (1-C5Me4SiMe3), 16.2 (Cp-CH3), 12.6 (Cp-
CH3), 1.7 (Si-CH3) ppm. 13C resonances for the AlMe4 groups could
(C5Me5)3La3(AlMe4)(μ-OTf)3(μ3-OTf)2(THF) (3*-LaOTf). Following
the procedure described for 2-LaX, SiMe3OTf (64.4 mg, 290 μmol)
and (C5Me5)La(AlMe4)2 (100 mg, 223 μmol) yielded 3*-LaOTf as a
not be detected. IR (KBr): ν 2973 (w), 2948 (w), 2905 (w), 2860
̃
(w), 2731 (vw), 1575 (w), 1485 (vw), 1455 (w), 1436 (w), 1436 (w),
1428 (w), 1418 (w), 1405 (w), 1386 (vw), 1374 (vw), 1345 (vw),
1321 (m), 1249 (m), 1129 (vw), 1085 (vw), 1021 (w), 989 (vw), 952
(vw), 847 (vs), 839 (vs), 756 (m), 688 (w), 668 (vw), 630 (w), 570
(vw), 424 (m), 404 (w) cm−1. Anal. Calcd (%) for C32H66Al2I2Lu2Si2:
C, 33.00; H, 5.71. Found: C, 33.64; H, 5.67.
white powder (105 mg, 58.9 μmol, 79%). IR (KBr): ν 2919 (w), 2872
̃
(w), 1505 (vw), 1455 (w), 1446 (w), 1436 (w), 1380 (w), 1325 (w),
1312 (vs), 1287 (vs), 1260 (s), 1245 (s), 1227 (s), 1209 (s), 1195
(s), 1104 (vw) 1043 (vs), 941 (vw), 771 (w), 763 (w), 719 (m), 694
(m), 687 (m), 668 (w), 636 (s), 631 (s), 588 (w), 582 (w), 559 (w),
518 (m), 509 (m), 490 (vw) cm−1. Anal. Calcd (%) for
C47H58AlF15La3O17S5 C 31.64; H, 3.28. Found: C, 32.71; H, 4.49.
Due to the high F and S content no better elemental analysis could be
obtained. The yield was determined in relation to the metal.
General Procedure for the Synthesis of [CpR La3(AlMe4)2(μ-
3
X)4]2 (2-LaX: X = Cl, Br, I; CpR = C5Me5, C5Me4SiMe3). A solution
of 1.3 equiv of SiMe3X in n-hexane (2 mL) was added to a solution of
CpRLa(AlMe4)2 in n-hexane (2 mL). The reaction mixture was stirred
overnight at ambient temperature. The precipitate was allowed to
settle, washed with n-hexane (3 × 1 mL), and dried in vacuo. Crystals
could be obtained by performing the reaction under the same
conditions without stirring. Due to poor solubility no meaningful
NMR spectra could be obtained.
General Procedure for the Synthesis of CpR Y3(μ-X)3(μ3-
3
X)(μ3-CH2)(THF)3 (4-YX: X = Cl, Br, I; CpR = C5Me5, C5Me4SiMe3).
Route A. [CpRY(AlMe4)(μ-X)]2 (1-YX) was suspended in toluene (1
mL) and THF (2 mL) was added. The reaction mixture was shaken
several times, filtered, and allowed to stand at ambient temperatures
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Article
for 3−4 days. A color change to yellow-orange occurred, and the
mixture was concentrated and stored at −40 °C to yield crystalline
material. The yield was determined in relation to the metal content.
Route B. A solution of 4 equiv of SiMe3X in THF (1 mL) was
added to a solution of (C5Me5)3Y3(μ-Me)3(μ3-Me)(μ3-CH2)(THF)2
(VY) in THF (4 mL). The solution was stirred for 46 h at ambient
temperature. Removal of the solvent and washing with n-hexane gave
the product as a white powder. Crystals were obtained from a
saturated solution in THF at −40 °C.
NMR (101 MHz, [D8]THF, 26 °C): δ 128.3 (2,5-C5Me4SiMe3),
124.5 (3,4-C5Me4SiMe3), 115.1 (1-C5Me4SiMe3), 67.6 (THF), 25.4
(THF), 15.7 (Cp-CH3), 13.7 (Cp-CH3), 2.9 (Si-Me) ppm. 13C
resonances for the CH2 group could not be detected. 89Y NMR (from
1H−89Y HSQC, 25 MHz, [D8]THF, 26 °C): δ 183 ppm. IR (KBr): ν
2980 (m), 2949 (m), 2894 (m), 2727 (vw), 1494 (vw), 1454 (w),
1405 (vw), 1384 (vw), 1372 (vw), 1344 (w), 1324 (m), 1243 (m),
1183 (vw), 1130 (vw), 1081 (vw), 1019 (m), 916 (w), 875 (m), 845
(vs), 834 (vs), 754 (s), 729 (m), 694 (w), 684 (w), 640 (w), 628
(m), 573 (vw), 511 (w), 499 (vw), 491 (vw), 476 (w), 466 (w), 451
(m), 422 (m), 410 (w) cm−1. Anal. Calcd (%) for C49H77Br4O3Si3Y3 x
OC4H8: C, 43.70; H, 5.88. Found: C, 43.59; H, 5.86.
̃
(C5Me5)3Y3(μ-Cl)3(μ3-Cl)(μ3-CH2)(THF)3 (4*-YCl). Following route A
described above, 1*-YCl (100 mg, 144 μmol) yielded 4*-YCl as
colorless crystals (68.0 mg, 65.2 μmol, 68%).
General Procedure for the Synthesis of CpR La3(μ-X)3(μ3-
X)(μ3-CH2)(THF)3 (4-LaX: X = Cl, Br, I; Cp3R = C5Me5,
Following route B described above, SiMe3Cl (48.8 mg, 449 μmol),
and VY (100 mg, 112 μmol) yielded 4*-YCl as a white powder (70.0
mg, 67.0 μmol, 64%). 1H NMR (400 MHz, [D8]THF, 26 °C): δ 3.61
(m, 12H, THF), 1.98 (s, 45H, Cp-CH3), 1.77 (m, 12H, THF), −0.35
C5Me4SiMe3). [CpR La3(AlMe4)2(μ-X)4]2 2-LaX was suspended in
3
toluene (1 mL) and THF (2 mL) was added. The reaction mixture
was shaken several times, filtered, and allowed to stand at ambient
temperature for 3−4 days. A color change to yellow-orange occurred,
and the mixture was concentrated and stored at −40 °C to yield
crystalline material.
2
(q, J(YH) = 4.4 Hz, 2H, Y-CH2) ppm. 13C{1H} NMR (101 MHz,
[D8]THF, 26 °C): δ 118.0 (C5Me5), 67.4 (THF), 25.3 (THF), 12.2
(Cp-CH3) ppm. 13C resonances for the CH2 group could not be
1
detected. 89Y NMR (from H−89Y HSQC, 25 MHz, [D8]THF, 26
(C5Me5)3La3(μ-Cl)3(μ3-Cl)(μ3-CH2)(THF)3 (4*-LaCl). Following the
procedure described above, 2*-LaCl (200 mg, 84.6 μmol) yielded 4*-
°C): δ 163 ppm. IR (KBr): ν 2967 (s), 2930 (vs), 2896 (vs), 2856
̃
(vs), 2751 (w), 2719 (w), 1484 (w), 1450 (s), 1374 (m), 1344 (w),
1313 (w), 1295 (w), 1248 (w), 1176 (w), 1065 (m), 1024 (vs), 920
(m), 878 (s), 804 (w), 661 (m), 635 (m), 594 (m), 505 (s), 438 (s),
428 (s), 415 (s), 407 (s) cm−1. Anal. Calcd (%) for C43H71Cl4Y3O3:
C, 49.44; H, 6.85. Found: C, 49.19; H, 6.81. The analytical data are
similar to those previously published.47
1
LaCl as light yellow crystals (27.8 mg, 23.3 μmol, 55%). H NMR
(400 MHz, [D8]THF, 26 °C): δ 3.65 (m, 12H, THF), 2.09 (s, 45H,
Cp-CH3), 1.81 (m, 12H, THF), −0.93 (s 2H, La-CH2) ppm. 13C{1H}
NMR (101 MHz, [D8]THF, 26 °C): δ 117.2 (C5Me5), 67.3 (THF),
25.3 (THF), 10.8 (Cp-CH3) ppm. 13C resonances for the CH2 group
(C5Me5)3Y3(μ-Br)3(μ3-Br)(μ3-CH2)(THF)3 (4*-YBr). Following route A
described above, 1*-YBr (100 mg, 128 μmol) yielded 4*-YBr as
colorless crystals (60.0 mg, 49.1 μmol, 58%).
could not be detected. IR (KBr): ν 2981 (s), 2890 (vs), 2803 (m),
̃
2729 (vw), 1488 (w), 1437 (m), 1420 (w), 1376 (w), 1172 (m),
1023 (s), 992 (s), 920 (w), 870 (m), 840 (w), 717 (vs), 671 (s), 595
(m), 565 (s), 544 (s), 462 (vw), 451 (vw), 434 (vw), 419 (vw), 405
(vw) cm−1. Anal. Calcd (%) for C43H71Cl4La3O3: C, 43.23; H, 5.99.
Found: C, 43.77; H, 6.10. The analytical data were consistent with
those previously published.47
Following route B described above, SiMe3Br (68.7 mg, 44.9 μmol),
and VY (100 mg, 112 μmol) yielded 4*-YBr as a white powder (80.0
mg, 65.4 μmol, 63%). 1H NMR (400 MHz, [D8]THF, 26 °C): δ 3.62
(m, 12H, THF), 2.01 (s, 45H, Cp-CH3), 1.77 (m, 12H, THF), −0.33
(q, J(YH) = 4.4 Hz, 2H, Y-CH2) ppm. 13C{1H} NMR (101 MHz,
(C5Me5)3La3(μ-Br)3(μ3-Br)(μ3-CH2)(THF)3 (4*-LaBr). Following the
procedure described above, 2*-LaBr (200 mg, 73.6 μmol) yielded 4*-
2
[D8]THF, 26 °C): δ 118.7 (C5Me5), 67.4 (THF), 25.2 (THF), 12.7
1
(Cp-CH3) ppm. 13C resonances for the CH2 group could not be
LaBr as light yellow crystals (36.4 mg, 26.5 μmol, 72%). H NMR
1
detected. 89Y NMR (from H−89Y HSQC, 25 MHz, [D8]THF, 26
(400 MHz, [D8]THF, 26 °C): δ 3.66 (m, 12H, THF), 2.10 (s, 45H,
Cp-CH3), 1.81 (m, 12H, THF), −0.93 (s 2H, La-CH2) ppm. 13C{1H}
NMR (101 MHz, [D8]THF, 26 °C): δ 120.8 (C5Me5), 67.3 (THF),
25.2 (THF), 12.0 (Cp-CH3) ppm. 13C resonances for the CH2 group
°C): δ 196 ppm. IR (KBr): ν 2968 (s), 2937 (s), 2892 (s), 2853 (s),
̃
2719 (vw), 1568 (vw), 1557 (vw), 1539 (vw), 1506 (w), 1520 (w),
1471 (w), 1455 (m), 1436 (m), 1374 (w), 1343 (vw), 1314 (vw),
1295 (vw), 1246 (vw), 1185 (vw), 1063 (w), 1020 (vs), 921 (m), 874
(vs), 667 (m), 594 (w), 499 (m), 484 (m), 471 (m), 458 (m), 437
(m), 419 (vs), 412 (s) cm−1. Anal. Calcd (%) for C43H71Br4Y3O3: C,
42.25; H, 5.85. Found: C, 42.74; H, 5.89.
could not be detected. IR (KBr): ν 2961 (s), 2891 (vs), 2856 (vs),
̃
2752 (w), 2723 (w), 1558 (w), 1532 (vw), 1506 (w), 1495 (w), 1488
(w), 1471 (w), 1456 (m), 1447 (m), 1436 (m), 1375 (w), 1344 (vw),
1247 (vw), 1185 (vw), 1061 (vw), 1021 (vs), 916 (w), 875 (s), 729
(vw), 694 (w), 667 (w), 633 (w), 623 (w), 590 (w), 550 (vw), 517
(vw), 501 (vw), 457 (w), 423 (w), 418 (m), 405 (s) cm−1. Anal.
Calcd (%) for C43H71Br4La3O3: C, 37.63; H, 5.21. Found: C, 37.70;
H, 5.68.
(C5Me4SiMe3)3Y3(μ-Cl)3(μ3-Cl)(μ3-CH2)(THF)3 (4′-YCl). Following
route A described above, 1′-YCl (100 mg, 123 μmol) yielded 4′-YCl
as colorless crystals (64.0 mg, 53.0 μmol, 65%). 1H NMR (400 MHz,
[D8]THF, 26 °C): δ 3.61 (m, 12H, THF), 2.11 (s, 18H, Cp-CH3-
2,5), 2.06 (s, 18H, Cp-CH3-3,4), 1.77 (m, 12H, THF), 0.24 (s, 27H,
(C5Me5)3La3(μ-I)3(μ3-I)(μ3-CH2)(THF)3 (4*-LaI). Following the
procedure described above, 2*-LaI (200 mg, 64.6 μmol) yielded
2
Si-Me), −0.42 (q, J(YH) = 4.4 Hz, 2H, Y−CH2) ppm. 13C{1H}
1
4*-LaI as light yellow crystals (39.7 mg, 25.5 μmol, 79%). H NMR
NMR (101 MHz, [D8]THF, 26 °C): δ 127.6 (2,5-C5Me4SiMe3),
123.8 (3,4-C5Me4SiMe3), 113.9 (1-C5Me4SiMe3), 67.5 (THF), 25.2
(THF), 15.2 (Cp-CH3), 13.0 (Cp-CH3), 2.8 (Si-Me) ppm. 13C
resonances for the CH2 group could not be detected. 89Y NMR (from
(400 MHz, [D8]THF, 26 °C): δ 3.62 (m, 12H, THF), 2.14 (s, 45H,
Cp-CH3), 1.77 (m, 12H, THF), −0.97 (s 2H, La-CH2) ppm. 13C{1H}
NMR (101 MHz, [D8]THF, 26 °C): δ 123.2 (C5Me5), 67.3 (THF),
25.2 (THF), 13.2 (Cp-CH3) ppm. 13C resonances for the CH2 group
1H−89Y HSQC, 25 MHz, [D8]THF, 26 °C): δ 150 ppm. IR (KBr): ν
2979 (m), 2948 (s), 2894 (s), 2861 (m), 2360 (vw), 1558 (w), 1539
(w), 1520 (w), 1506 (w), 1496 (w), 1488 (w), 1472 (w), 1456 (m),
1447 (m), 1436 (m), 1418 (w), 1404 (w), 1386 (vw), 1373 (vw),
1326 (m), 1245 (m), 1186 (vw), 1130 (w), 1106 (vw), 1020 (m),
917 (w), 847 (vs), 834 (vs), 752 (s), 684 (s), 668 (s), 641 (m), 628
(m), 571 (w), 559 (w), 518 (w), 502 (w), 489 (w), 473 (w), 457
(m), 435 (w), 419 (m) cm−1. Anal. Calcd (%) for C49H77Cl4O3Si3Y3:
C, 48.76; H, 6.43. Found: C, 48.90; H, 7.22.
̃
could not be detected. IR (KBr): ν 2975 (m), 2934 (m), 2890 (s),
̃
1487 (w), 1455 (m), 1432 (w), 1377 (vw), 1367 (vw), 1343 (vw),
1294 (vw), 1243 (w), 1176 (w), 1062 (vw), 1035 (s), 1012 (vs), 949
(w), 920 (m), 912 (m), 854 (vs), 839 (s), 834 (s), 665 (w) cm−1.
Anal. Calcd (%) for C43H71I4La3O3: C, 33.10; H, 4.59. Found: C,
33.69; H, 4.75.
(C5Me4SiMe3)3La3(μ-Cl)3(μ3-Cl)(μ3-CH2)(THF)3 (4′-LaCl). Following
the procedure described above, 2′-LaCl (200 mg, 73.7 μmol) yielded
1
4′-LaCl as light yellow crystals (40.0 mg, 29.2 μmol, 79%). H NMR
(C5Me4SiMe3)3Y3(μ-Br)3(μ3-Br)(μ3-CH2)(THF)3 (4′-YBr). Following
route A described above, 1′-YBr (100 mg, 111 μmol) yielded 4′-YBr
as colorless crystals (56.9 mg, 41.1 μmol, 56%).1H NMR (400 MHz,
[D8]THF, 26 °C): δ 3.62 (m, 12H, THF), 2.14 (s, 18H, Cp-CH3-
2,5), 2.10 (s, 18H, Cp-CH3-3,4), 1.78 (m, 12H, THF), 0.25 (s, 27H,
(400 MHz, [D8]THF, 26 °C): δ 3.62 (m, 12H, THF), 2.19 (s, 18H,
Cp-CH3-2,5), 2.14 (s, 18H, Cp-CH3-3,4), 1.77 (m, 12H, THF), 0.25
(s, 27H, Si-Me), −0.96 (s, 2H, La-CH2) ppm. 13C{1H} NMR (101
MHz, [D8]THF, 26 °C): δ 129.5 (2,5-C5Me4SiMe3), 126.0 (3,4-
C5Me4SiMe3), 117.2 (1-C5Me4SiMe3), 67.4 (THF), 25.3 (THF), 14.5
2
Si-Me), −0.42 (q, J(YH) = 4.4 Hz, 2H, Y−CH2) ppm. 13C{1H}
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(Cp-CH3-2,5), 12.5 (Cp-CH3-3,4), 2.7 (Si-Me) ppm. 13C resonances
for the CH2 group could not be detected. IR (KBr): ν 2969 (m), 2949
Cp2Ti(μ-CH2)(μ-Br)AlMe2 (TebbeBr). Cp2TiBr2 (100 mg, 0.295
mmol) was dissolved in toluene (10 mL) and a solution of AlMe3
(41.5 mg, 0.592 mmol) in n-hexane (5 mL) was added. The solution
was stirred at 40 °C for 360 h. The solvent was removed in vacuo. The
remaining oily solid was extracted with n-pentane (3 × 10 mL). The
solution was concentrated and toluene (1 mL) was added for better
crystallization. Crystals suitable for XRD analysis grew from a
saturated solution at −40 °C and were recrystallized three times to
obtain the desired product as dark red crystals (39.0 mg, approximate
̃
(m), 2889 (m), 2858 (m), 2757 (vw), 1558 (w), 1539 (vw), 1520
(w), 1506 (vw), 1489 (w), 1472 (w), 1456 (m), 1447 (w),1435 (w),
1418 (w), 1404 (w), 1385 (vw), 1373 (vw), 1326 (m), 1243 (m),
1128 (vw), 1025 (m), 916 (w), 871 (m), 835 (vs), 754 (m), 730 (w),
685 (m), 668 (w), 629 (w), 417 (s), 403 (m) cm−1. Anal. Calcd (%)
for C49H89Cl4La3O3Si3 x C4H8O: C, 44.63; H, 6.73. Found: C, 44.66;
H, 6.76.
(C5Me4SiMe3)3La3(μ-Br)3(μ3-Br)(μ3-CH2)(THF)3 (4′-LaBr). Following
the procedure described above, 2′-LaBr (200 mg, 65.2 μmol) yielded
4′-LaBr as light yellow crystals (40.0 mg, 25.9 μmol, 79%).1H NMR
(400 MHz, [D8]THF, 26 °C): δ 3.61 (m, 12H, THF), 2.22 (s, 18H,
Cp-CH3-2,5), 2.18 (s, 18H, Cp-CH3-3,4), 1.77 (m, 12H, THF), 0.26
(s, 27H, Si-Me), −0.97 (s, 2H, La-CH2) ppm. 13C{1H} NMR (101
MHz, [D8]THF, 26 °C): δ 130.1 (2,5-C5Me4SiMe3), 126.6 (3,4-
C5Me4SiMe3), 118.0 (1-C5Me4SiMe3), 67.3 (THF), 25.2 (THF), 15.0
(Cp-CH3-2,5), 13.1 (Cp-CH3-3,4), 2.8 (Si-Me) ppm. 13C resonances
1
yield corrected for trivalent coproduct 35%). H NMR (400 MHz,
[D6]benzene, 26 °C): δ 8.17 (s, 2H, CH2), 5.62 (s, 10H, Cp-H),
−0.19 (s, 6H, Al-CH3) ppm. 13C{1H} NMR (101 MHz, [D6]benzene,
26 °C): δ 185.6 (CH2), 112.1 (C5H5) ppm. 13C resonances for the
Al(CH3)2 group could not be detected.
General Procedure for the Methylidene Transfer. All
1
reactions were monitored via H NMR spectroscopy and performed
according to the following protocol. The respective methylidene
complex (5 mg except for TebbeBr (3 mg)) was dissolved in 0.3 mL
of [D8]thf in a J. Young valved NMR tube. Two equivalents of the
carbonylic reagent dissolved in 0.2 mL of [D8]thf was added. The
for the CH2 group could not be detected. IR (KBr): ν 2976 (w), 2971
̃
(w), 2951 (w), 2890 (w), 2860 (w), 1456 (w), 1447 (w), 1436 (w),
1343 (vw), 1326 (w), 1242 (m), 1021 (m), 914 (vw), 870 (m), 848
(vs), 835 (vs), 754 (m), 684 (w), 668 (vw), 638 (vw), 628 (w), 442
(vw), 420 (w), 408 (w), 403 (w) cm−1. Anal. Calcd (%) for
C49H89Br4La3O3Si3: C, 38.05; H, 5.80. Found: C, 38.09; H, 5.72.
(C5Me4SiMe3)3La3(μ-I)3(μ3-I)(μ3-CH2)(THF)3 (4′-LaI). Following the
procedure described above, 2′-LaI (200 mg, 56.7 μmol) yielded 4′-LaI
1
NMR tube was shaken several times within 15 min, and then a H
NMR spectrum was recorded immediately. The yields of all reactions
were calculated from the integral ratio olefinic functionality/CpR
(CH2/Cp-Me or CH2/SiMe3) or from the integral ratio olefinic
functionality/Y-CH2 depending on the accessibility of the respective
signals. The reactivity studies with the Tebbe reagent were performed
under the same conditions except for the solvent. For the Tebbe
reagent (TebbeCl) and TebbeBr [D6]benzene was chosen, due to their
decomposition in THF.
X-ray Crystallography and Crystal Structure Determina-
tions. Single crystals of 1*-LnBr, 1*-YI, 2′-LaCl, 3*-LaOTf, 4*-LnBr,
4′-LaCl, 5*-Y, Cp2Ti(μ-CH2)(μ-Cl)AlMe2, and TebbeBr were grown
by standard techniques from saturated solutions in n-hexane, toluene,
or THF at −40 °C as stated earlier in the Experimental Section.
Suitable crystals were collected in a glovebox and coated with Parabar
10312 (previously known as Paratone N, Hampton Research) and
fixed on a nylon loop/glass fiber.
1
as light yellow crystals (47.9 mg, 27.7 μmol, 85%). H NMR (400
MHz, [D8]THF, 26 °C): δ 3.62 (m, 12H, THF), 2.19 (s, 18H, Cp-
CH3-2,5), 2.19 (s, 18H, Cp-CH3-3,4), 1.77 (m, 12H, THF), 0.36 (s,
27H, Si-Me), −0.96 (s, 2H, La-CH2) ppm. 13C{1H} NMR (101 MHz,
[D8]THF, 26 °C): δ 131.3 (2,5-C5Me4SiMe3), 128.7 (3,4-
C5Me4SiMe3), 120.7 (1-C5Me4SiMe3), 67.3 (THF), 25.2 (THF),
15.3 (Cp-CH3-2,5), 13.8 (Cp-CH3-3,4), 3.3 (Si-Me) ppm. 13C
resonances for the CH2 group could not be detected. IR (KBr): ν
2973 (w), 2950 (w), 2893 (w), 1481 (vw),1471 (w), 1454 (vw), 1447
(w), 1405 (vw), 1386 (vw), 1375 (vw), 1324 (w), 1246 (m), 1124
(vw), 1013 (w), 948 (vw), 914 (vw), 847 (vs), 837 (vs), 754 (w), 686
(w), 636 (vw), 627 (w), 422 (w) cm−1. Anal. Calcd (%) for
C49H89I4La3O3Si3: C, 33.92; H, 5.17. Found: C, 34.20; H, 5.67.
[(C5Me5)Y(OCH2tBu)(μ-OCH2tBu)]2 (5*-Y). Following route B
̃
X-ray data for compounds of 1*-LnBr, 1*-YI, 2′-LaCl, 3*-LaOTf, 4*-
LnBr, 4′-LaCl, 5*-Y, Cp2Ti(μ-CH2)(μ-Cl)AlMe2, and TebbeBr were
collected on a Bruker APEX II DUO instrument equipped with an IμS
microfocus sealed tube and QUAZAR optics for Mo Kα (λ = 0.71073
Å) and Cu Kα (λ = 1.54184 Å) radiation. For 1*-YI data were
collected on a Bruker SMART APEX II instrument equipped with a
fine-focus sealed tube and TRIUMPH monochromator using Mo Kα
radiation (λ = 0.71073 Å). The data collection strategy was
determined using COSMO72 employing ω scans. Raw data were
processed using APEX73 and SAINT,74 and corrections for absorption
effects were applied using SADABS.75 The structures were solved by
direct methods and refined against all data by full-matrix least-squares
methods on F2 using SHELXTL76 and ShelXle.77 Disorder models
were calculated using DSR,78 a program for refining structures in
ShelXl. All graphics were produced by employing ORTEP-379 and
POV-Ray.80 Further details of the refinement and crystallographic
data are given in Table S1 in the Supporting Information and in the
CIF files. CCDC deposition numbers 2008158−2008167 and
2010151 contain 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/structures/.
described for 4-YX, HOCH2tBu (36.6 mg, 41.5 μmol) and
[(C5Me5)3Y3(μ-Me)3(μ3-Me)(μ3-CH2)(THF)2] (100 mg, 112
μmol) yielded 5*-Y as white crystals (49.0 mg, 61.5 μmol, 30%).
1
The yield was determined in relation to HOCH2tBu. H NMR (400
MHz, [D6]benzene, 26 °C): δ 3.69 (s, 4H, CH2), 3.49 (s, 4H, CH2),
2.15 (s, 30H, Cp-CH3), 0.99 (s, 18H, CH3), 0.91 (s, 18H, CH3) ppm.
13C{1H} NMR (101 MHz, [D6]benzene, 26 °C): δ 117.7 (C5Me5),
78.6 (CH2), 76.6 (CH2), 33.7 (C(CH3)3), 33.1 (C(CH3)3), 27.1
(C(CH3)3), 26.6 (C(CH3)3), 11.4 (Cp-CH3) ppm. 89Y NMR (from
1H−89Y HSQC, 25 MHz, [D6]benzene, 26 °C): δ 20 ppm. IR (KBr):
ν 2948 (vs), 2906 (s), 2862 (s), 2812 (m), 2726 (vw), 2695 (w),
̃
1506 (vw), 1478 (m), 1457 (m), 1437 (w), 1418 (vw), 1392 (w),
1361 (w), 1256 (vw), 1132 (vs), 1047 (s), 1017 (s), 933 (w), 898
(w), 752 (vw), 615 (s), 559 (m), 440 (m), 420 (s), 411 (m) cm−1
.
Anal. Calcd (%) for C40H74O4Y2: C, 60.29; H, 9.36. Found: C, 59.63;
H, 8.63. The analytical data were consistent with those previously
published.59
Cp2Ti(μ-CH2)(μ-Cl)AlMe2 (TebbeCl). Cp2TiCl2 (500 mg, 2.01
mmol) was dissolved in toluene (15 mL), and a solution of AlMe3
(290 mg, 4.02 mmol) in n-hexane (5 mL) was added. The solution
turned dark red within 5 min. The solution was allowed to rest at
ambient temperatures for 60 h. The solvent was removed in vacuo.
The remaining oily solid was extracted with n-pentane (3 × 5 mL).
The solution was concentrated and toluene (1 mL) was added for
better crystallization. Red crystals grew from a saturated solution at
−40 °C (413 mg, approximate yield corrected for trivalent coproduct
ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.0c00447.
Supporting figures, detailed crystallographic data,
spectroscopic data (NMR), and analytical details
(PDF)
1
71%). H NMR (400 MHz, [D6]benzene, 26 °C): δ 8.28 (s, 2H,
CH2), 5.60 (s, 10H, Cp-H), −0.26 (s, 6H, Al-CH3) ppm. The
analytical data were consistent with those previously published.22
L
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Article
classification, structures, and chemistry. Chem. Rev. 1983, 83, 135−
201.
Accession Codes
CCDC 2008158−2008167 and 2010151 contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/data_request/
cif, or by emailing data_request@ccdc.cam.ac.uk, or by
contacting The Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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AUTHOR INFORMATION
Corresponding Author
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Reiner Anwander − Institut fur Anorganische Chemie, Eberhard
Karls Universitat Tubingen, 72076 Tubingen, Germany;
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Felix Kracht − Institut fur Anorganische Chemie, Eberhard Karls
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Universitat Tubingen, 72076 Tubingen, Germany
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̈
̈
̈
Eberhard Karls Universitat Tubingen, 72076 Tubingen,
Germany
Christoph Stuhl − Institut fur Anorganische Chemie, Eberhard
̈
Karls Universitat Tubingen, 72076 Tubingen, Germany
̈
̈
̈
̈
̈
̈
Cacilia Maichle-Mossmer − Institut fur Anorganische Chemie,
̈
̈
̈
Eberhard Karls Universitat Tubingen, 72076 Tubingen,
Germany; orcid.org/0000-0001-7638-1610
Complete contact information is available at:
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful to the German Science Foundation for support
(grant: AN 238/15-2) and to A. Mortis for assistance with
recording NMR spectra. We also thank the NMR section of
the Institute of Organic Chemistry at EKUT for the EPR
measurements and Dr. A. Berkefeld for discussions.
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