Tetrahydropentalenyl-phosphazene constrained geometry complexes of rare-earth metal alkyls

Article abstract of DOI:10.1039/c3dt53596g

Reactions of CpHPPh₂ (1, diphenyl(4,4,6,6-tetramethyl-1, 4,5,6-tetrahydropentalen-2-yl)phosphane) with the organic azides AdN₃ and DipN₃ (Ad = 1-adamantyl; Dip = 2,6-di-iso-propylphenyl) led to the formation of two novel CpPN ligands: P-amino-cyclopentadienylidene- phosphorane (CpPPh₂NHAd; L_AdH) and P-cyclopentadienyl-iminophosphorane (CpHPPh₂NDip; L _DipH). Both were characterized by NMR spectroscopy and X-ray structure analysis. For both compounds only one isomer was observed. Neither possesses any detectable prototropic or elementotropic isomers. Reactions of these ligands with [Lu(CH₂SiMe₃)₃(thf) ₂] or with rare-earth metal halides and three equivalents of LiCH₂SiMe₃ produced the desired bis(alkyl) CpPN complexes: [{CpPN}M(CH₂SiMe₃)₂] (M = Sc (1_Ad, 1_Dip), Lu (2_Ad, 2_Dip), Y (3_Ad, 3_Dip), Sm (4_Ad), Nd (5_Ad), Pr (6_Ad), Yb (7_Ad)). These complexes were characterized by extensive NMR studies for the diamagnetic and the paramagnetic complexes with full signal assignment. An almost mirror inverted order of the paramagnetic shifts has been observed for ytterbium complex 7_Ad compared to 4 _Ad, 5_Ad and 6_Ad. For the assignment of the NMR signals [{η¹:η⁵-C₅Me ₄PMe₂NAd}Yb(CH₂SiMe₃)₂] 7 was synthesized, characterized and the ¹H NMR signals were compared to 7_Ad and to other paramagnetic lanthanide complexes with the same ligand. 1_Ad, 2_Ad, 2_Dip, 3_Ad and 3_Dip were characterized by X-ray structure analysis revealing a sterically congested constrained geometry structure.

Full text of DOI:10.1039/c3dt53596g

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PAPER
Tetrahydropentalenyl-phosphazene constrained
geometry complexes of rare-earth metal alkyls†
Cite this: Dalton Trans., 2014, 43,
7109
Noa K. Hangaly, Alexander R. Petrov, Michael Elfferding, Klaus Harms and
Jörg Sundermeyer*
Reactions of Cp™HPPh2 (1, diphenyl(4,4,6,6-tetramethyl-1,4,5,6-tetrahydropentalen-2-yl)phosphane)
with the organic azides AdN3 and DipN3 (Ad = 1-adamantyl; Dip = 2,6-di-iso-propylphenyl) led to the for-
mation of two novel CpPN ligands: P-amino-cyclopentadienylidene-phosphorane (Cp™PPh2NHAd;
L
AdH) and P-cyclopentadienyl-iminophosphorane (Cp™HPPh2NDip; LDipH). Both were characterized by
NMR spectroscopy and X-ray structure analysis. For both compounds only one isomer was observed.
Neither possesses any detectable prototropic or elementotropic isomers. Reactions of these ligands with
[Lu(CH2SiMe3)3(thf)2] or with rare-earth metal halides and three equivalents of LiCH2SiMe3 produced the
desired bis(alkyl) Cp™PN complexes: [{Cp™PN}M(CH2SiMe3)2] (M = Sc (1Ad, 1Dip), Lu (2Ad, 2Dip), Y (3Ad
Dip), Sm (4Ad), Nd (5Ad), Pr (6Ad), Yb (7Ad)). These complexes were characterized by extensive NMR studies
for the diamagnetic and the paramagnetic complexes with full signal assignment. An almost mirror
inverted order of the paramagnetic shifts has been observed for ytterbium complex 7Ad compared to 4Ad
,
3
,
5Ad and 6Ad. For the assignment of the NMR signals [{η1 : η5-C5Me4PMe2NAd}Yb(CH2SiMe3)2] 7 was syn-
thesized, characterized and the 1H NMR signals were compared to 7Ad and to other paramagnetic lantha-
nide complexes with the same ligand. 1Ad, 2Ad, 2Dip, 3Ad and 3Dip were characterized by X-ray structure
analysis revealing a sterically congested constrained geometry structure.
Received 21st December 2013,
Accepted 20th February 2014
DOI: 10.1039/c3dt53596g
www.rsc.org/dalton
cyclopentadienyl framework have been described in the litera-
ture.4,5 These variations include for example totally or partly
Introduction
The organometallic chemistry of the rare-earth metals began substituted Cp rings and ancillary linked donor atoms like
in the middle of the last century with the synthesis of their tris- O, N, P or S. The latter are used to form constrained geometry
(cyclopentadienyl) derivatives by Wilkinson and Birmingham.1 complexes (CGCs).6
Since then the cyclopentadienyl (Cp) ligand has remained one
of the most ubiquitous ligands of this chemistry. For a long molecular structures of two novel cyclopentadienyl-phospha-
time, rare-earth organometallic chemistry has been dominated zene (CpPN) ligands with tetrahydropentalene unit:
In this work we describe the synthesis, NMR studies and
a
by metallocenes,2 especially when these complexes are used as Cp™PPh2NHAd (LAdH) and Cp™HPPh2NDip (LDipH). This
precursors in various stoichiometric and catalytic processes.3 tetrahydropentalene unit is very attractive as it is easily syn-
More recently, however, considerable attention has been thesized by condensation of NaCp with Ph2PCl and two
directed towards rare-earth mono-cyclopentadienyl complexes.4 equivalents of acetone. Compared to other sterically demand-
But the selective synthesis of monomeric rare-earth metal ing cyclopentadienyls such as C5Me4R, it is cheap and can
mono-Cp complexes is generally difficult. A great steric bulk of easily be synthesized on a large scale. The new ligands bear a
the Cp ligand is advantageous for a successful synthesis. In sterically very demanding, well crystallizing, electron rich and
search of better ligand systems, wide variations of the aromatic rigid cyclopentadienyl ring. Therefore we are confident that
these and related tetrahydropentalenyl ligands are good
alternatives for the commonly used but expensive C5Me4R
building blocks in organometallic chemistry.
Fachbereich Chemie der Philipps-Universität Marburg, Hans-Meerwein-Straße,
Constrained geometry complexes with the cyclopentadienyl-
silylamido (CpSiN) type ligands, initially developed by
Bercaw7–9 and Okuda,10 became one of the best developed
classes of CGCs (Scheme 1; A). In contrast, however, con-
strained geometry rare-earth metal(III) complexes with different
single-atom bridging units in the ligand system have received
35032 Marburg, Germany. E-mail: jsu@staff.uni-marburg.de;
Fax: +49 6421 2825711; Tel: +49 6421 2825693
†Electronic supplementary information (ESI) available: Experimental details for
X-ray crystallographic studies, detailed NMR experiments (1H, 31P, 13C and 2D
NMR experiments) with signal assignment and crystallographic information
files (CIF). CCDC 817338–817344. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c3dt53596g
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7109–7120 | 7109

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Cp™PPh2NHAd (LAdH) and Cp™HPPh2NDip (LDipH) ligands
with the tetrahydropentalene unit. Assignment of ligand group
shifts of paramagnetic organometallic lanthanide complexes is
not routinely reported in literature, but it might become a very
valuable tool for following catalytic steps.
Results and discussion
Synthesis and characterization of the Cp™PN-ligands
The ligands were prepared by a Staudinger reaction (Scheme 2)
of the novel phosphane Cp™HPPh2 (1, diphenyl(4,4,6,6-tetra-
methyl-1,4,5,6-tetrahydropentalen-2-yl)phosphane)24
with
Scheme 1 Examples of known constrained geometry rare-earth metal
organic azides (AdN3 and DipN3; Dip = 2,6-di-iso-propylphe-
nyl). It should be mentioned that compared to our previously
published synthesis of 1 we could exchange the highly toxic
TlCp by NaCp, which can easily be synthesized on a large scale
out of Na and (CpH)2.25 The improved ligand synthesis is fol-
lowing the condensation of NaCp with one Ph2PCl and two
acetone molecules, which are cheap starting materials making
the final Cp™PN ligand very attractive as an alternative for
commonly used but expensive ligands with a C5Me4R moiety.
The Staudinger reaction of the highly crowded Cp™HPPh2
1 with AdN3 proceeds very slowly. Therefore, under classical
Staudinger conditions a reaction time of 10 d is needed in
refluxing THF, yielding LAdH (Cp™PPh2NHAd) in only 46%
yield. Higher reaction temperatures accelerate the reaction and
it was completed after only 2 d in refluxing toluene. The yellow
crystalline compound LAdH was isolated from n-hexane in 75%
yield. In contrast, the oxidation with the more electron-poor
DipN3 was completed within 14 h in THF at room temperature.
complexes.
much less attention and have remained almost unexplored to
date. Some examples are CpSiP complexes (B)11 and CpSiC
complexes (C)12 which have dianionic ligands. There are also
some complexes bearing monoanionic ligands which are iso-
electronically related to the classical dianionic CpSiN ligand
system such as CpSiNP (D),13 CpSiNIm (E)14 and the cyclopenta-
dienyl-phosphazenes (CpPN) (F) that is the focus of our
current investigation.15–19
Previously we reported a general and convenient synthetic
protocol for a large variety of CpPN type ligands,20 and their
use in the stabilization of highly reactive alkyls of rare-earth
and group 4 metals has been claimed.21 Independently,
related fluorenyl- and indenyl-phosphazene ligands (FluPN
and IndPN) and their rhodium22 and zirconium23 complexes
were presented by Bourissou and co-workers. The synthesis
and characterization of a series of rare-earth metal constrained
The
desired,
sterically
demanding
ligand
LDipH
(Cp™HPPh2NDip) was obtained in 78% yield after crystalliza-
tion from cold acetonitrile.
geometry
CpPN
complexes
[{η5,η1-C5Me4PMe2NAd}-
M(CH2SiMe3)2] (M = Sc, Lu, Y, Sm, Nd, Pr, Ce) and their high
catalytic activities in the intramolecular hydroamination/cycli-
zation have been reported by us.15,17 Recently, the organo-
metallic chemistry and catalysis in ethylene polymerization of
rare-earth metal CpPN, IndPN and FluPN complexes was
studied. CpPN ligands, with less steric bulkiness of the
Cp-ring, lead to the coordination of THF, while IndPN adopt a
η3-bonding fashion and the more bulky FluPN-type ligands
display a η1-bonding mode.18 Moreover, the reactivity toward
various substrates was recently studied and, among others,
CpPN amidinate, hydride and terminal imido complexes were
synthesized, characterized and their reactivity was probed.19
These current developments reveal that CpPN type com-
plexes appear to be a promising class of catalysts. Therefore it
is of general and fundamental interest to develop novel, steri-
cally most demanding and rigid CpPN type ligands as useful
building blocks and to study their stabilizing properties for
dialkyls of the smallest and larger rare-earth metal cations (Sc,
Lu, Y, Yb, Sm, Nd and Pr). Besides synthetic and XRD struc-
tural aspects, the focus of this study will be on the beautiful
1H and 13C NMR spectra obtained from paramagnetic
organometallic compounds carrying the chelating rigid
Compared to LDipH, which is a highly air-sensitive sub-
stance with a melting point of 142.4–143.0 °C and a high solu-
bility in n-hexane, compound LAdH is only moderately air-
sensitive, has a higher melting point (176.5–177.0 °C) and is
only marginally soluble in n-hexane. Further investigations by
means of NMR spectroscopy and X-ray structure analysis show
significant dissimilarities in their molecular compositions:
compound LAdH occurs in the form of P-amino-cyclopentadie-
nyl-phosphorane, whereas LDipH exists in the tautomeric form
of a P-cyclopentadienyl-imino-phosphorane.
Scheme 2 Synthesis of the ligands
LAdH and LDipH by Staudinger
reaction.
7110 | Dalton Trans., 2014, 43, 7109–7120
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NMR spectroscopy
Table 1 Selected bond lengths (Å) and angles (°) for LAdH and LDipH
LAd LDip
The 31P NMR signal of LAdH (15.6 ppm) is essentially identical
to those of compound C5Me4PR2NHAd (17.6 for R = Me15 and
12.3 ppm for the main isomer in R = Ph16 resp.). In contrast,
compound LDipH shows a 31P NMR resonance at −15.8 ppm.
This chemical shift is in good agreement with the iminophos-
phorane tautomer IndPPh2vNR (Ind = indenyl-1; δP = −8.3
and −16.5 ppm for R = Ph and Dip resp.).23 However, in con-
trast to C5Me4PPh2NHAd,16 C5Me4HPMe2NR (R = SiMe3, Dip)20
and IndPPh2vNR (R = Ph and Dip),23 LAdH and LDipH show
only one sharp resonance in the 31P NMR spectra, indicating
the absence of isomers. Recently, we also observed only one
H
H
P1–N1
P1–C1
P1–C13
P1–C19
N1–C25
1.652(2)
1.704(2)
1.799(2)
1.801(2)
1.494(3)
1.556(2)
1.788(2)
1.819(2)
1.806(2)
1.408(2)
C1–P1–N1
115.6(1)
102.6(1)
110.0(1)
112.5(1)
106.4(1)
109.3(1)
115.2(1)
113.2(1)
110.1(1)
106.6(1)
103.0(1)
108.0(1)
C13–P1–N1
C19–P1–N1
C1–P1–C13
C13–P1–C19
C19–P1–C1
tautomer in C5Me4HPR2NC6H3R′ (R = Me, R′ = iPr; R = Ph,
2
C1–P1–N1–C25
37.5(2)
17.5(2)
R′ = Me, iPr) at thermodynamic equilibrium.18
The resonance of the NH-proton in LAdH at δH = 2.05 ppm
appears as a doublet (2JHP = 5.0 Hz). It does not correlate with
any carbon atom in the molecule according to the HMQC cor-
relation spectrum. This confirms the presence of an amino-
phosphorane. Unlike LAdH, compound LDipH shows four reso-
nances in the aliphatic region (besides resonances of iso-
propyl (Dip) protons) which resemble the pattern of the parent
phosphane 1. Especially the allylic CH2 group at δH = 3.08 ppm
confirms that the ligand is in the imino-phosphorane form in
solution (for spectra see ESI†). No tautomerization or isomeri-
zation could be observed for LAdH and LDipH by multinuclear
NMR spectroscopy in C6D6.
The cyclopentadienyl rings of both ligands are essentially
planar; the largest deviations from the ideal C5 plane are
Δmax = 0.004(2) for LAdH and 0.006(2) Å for LDipH resp.
As anticipated the P–CCp bond length in P-ylide LAdH is
quite short, P1–C1 1.704(2) Å, and can be compared with
26
d(P–CCp) 1.718(2) Å in Ph3PvC5H4
while the P–N bond
length 1.652(2) Å is rather long. This can be better compared
with the values found in phosphonium salts [Ph3P–NH(iso-Pr)]-
Br (P–N = 1.621(3) Å).27 The C–C bonds of the Cp ring of LAd
H
are conjugated (average bond length d(C–C)
= 1.41 Å,
maximum C–C bond difference d = 0.07 Å). The parameters
resemble the expected values for a cyclopentadienylidene-
aminophosphorane structure.
The structure of LDipH is unexceptional with a short P–N
bond length of 1.556(2) Å, typical for imino-phosphoranes
(compare: Ph3PvN(2,6-C6H3) (1.553(2) Å)28 and Ph3PvN(tert-
Bu) (1.543(2) Å)).26 The alternating bond order and the bond
lengths in the Cp™-moiety are similar to those found in the
parent phosphine Cp™HPPh2 124 and lie in ranges typical for
cyclopentadiene compounds.29 The P1–C1 1.788(2) Å is signifi-
cantly larger than that in LAdH. Moreover, this value is much
closer to P–CPh bond lengths where a C(sp2)–P bond is
present.
X-Ray structure analysis
The compound LAdH crystallizes from benzene at room temp-
erature with two disordered solvent molecules per unit cell.
Compound LDipH crystallizes without incorporated solvent
molecules. Both compounds crystallize in monoclinic crystal
systems (space groups P21/n and P21/c resp.) with 4 units in
the unit cell (Fig. 1). Selected bond lengths (Å) and angles (°)
for LAdH and LDipH are presented in Table 1. In the structure
of compound LDipH one of the iso-propyl groups is disordered
and treated with an occupancy factor of 63 : 37.
Preparation and characterization of Cp™PN rare-earth metal
alkyls
For the syntheses of the lutetium complexes, [Lu(CH2SiMe3)3-
(thf)2] was used and the complexes were isolated in high yields
as microcrystalline, colourless solids [{LAd}Lu(CH2SiMe3)2]
(2Ad) and [{LDip}Lu(CH2SiMe3)2] (2Dip) (Scheme 3). For the
Fig. 1 Molecular structures of LAdH × 2C6H6 and LDipH. All hydrogen
atoms, except N–H for LAdH and protons of the C5-ring for LDipH, have
been omitted for clarity. Incorporated benzene molecules and dis-
ordered iso-Pr group with lower occupancies have also been omitted
for clarity.
Scheme 3 Synthesis of complexes [{Cp™PN}M(CH2SiMe3)2].
Dalton Trans., 2014, 43, 7109–7120 | 7111
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other rare-earth metals (Sc, Y, Sm, Nd, Pr and Yb), the com- Nd) are isolated with a coordinated THF molecule.18 1H NMR
plexes were synthesized under essentially the same reaction spectra of the diamagnetic 1Ad–3Ad and 1Dip–3Dip complexes
conditions reported for [{C5Me4PMe2NAd}M(CH2SiMe3)2] com- are very similar (for spectra see ESI†); therefore only some
plexes.15,17 Following this in situ protocol three equivalents of main aspects should be discussed here. Because of the
LiCH2SiMe3 were added to a stirred suspension of an equi- η5-coordination of the Cp ring, Cp protons appear as one
3
molar mixture of the respective {Cp™PN}H ligand (LAdH, doublet at about 6.2 ppm with a JHP of about 3 Hz. The
LDipH) and a rare-earth metal halide source in ether–toluene signals of the methyl and methylene group in the annulated
or ether–n-hexane at 0 °C. Filtration, solvent removal, extrac- five membered ring are, because of their fixed exo- and endo-
tion with n-hexane and crystallization afforded the Cp™PN positions, chemically inequivalent. Consequently, the methyl
complexes [{LAd}M(CH2SiMe3)2] (M = Sc (1Ad), Y (3Ad), Sm (4Ad), group resonances appear as two singlets and the resonances of
Nd (5Ad), Pr (6Ad), Yb (7Ad)) and [{LDip}M(CH2SiMe3)2] (M = the methylene group appear as two doublets (2JHH about
Sc (1Dip), Y (3Dip)) (Scheme 3).
12 Hz). Silylmethylene protons are, like in [{C5Me4PMe2NAd}-
The complexes 1Ad–7Ad, and 1Dip–3Dip are fairly air- and M(CH2SiMe3)2],17 diastereotopic and for that magnetically
moisture-sensitive solids and show good solubility in saturated non-equivalent. They appear as two doublets in all spectra. For
hydrocarbons and high solubility in ethers and aromatic sol- yttrium complexes the protons appear as two doublet of doub-
vents. All complexes were fully characterized by NMR spec- lets due to Y–H-coupling (2JHH = 11.2 Hz, JHY = 2.7 Hz). Fur-
2
troscopy and elemental analysis, and complexes 1Ad, 2Ad, 3Ad
2Dip and 3Dip were also characterized by X-ray structure with a 1JCY coupling of 40.9 Hz in the 13C NMR spectrum. Both
analysis. are in the same range as shown in the literature, for example
The complexes with ligand LDip reveal a different thermo- for classic [{η5:η1-CpSiN}Y(CH2SiMe3)(thf)] CGC.30
stability in comparison with those bearing ligand LAd. Com- Lanthanides have a short relaxation time for the unpaired
,
thermore, in this case the methylene carbons show a doublet
pounds 1Dip–3Dip appear to be less stable than the analogue electron so that little line broadening occurs. The mechanism
complexes 1Ad–3Ad. Complexes 1Dip and 2Dip are still stable at of action within the lanthanides is principally the pseudocon-
room temperature in solution but decompose fast at elevated tact mechanism, which falls off in a predictable manner with
temperatures. Yttrium complex 3Dip is not stable at room distance (1/R3).31 The direction of shift depends on the an-
temperature both in solution and in the solid state. Thus, for isotropy in the susceptibility, but it also depends on the angle
larger metals such as samarium, no stable complex could be between the principal axis of susceptibility and the vector R to
isolated with this ligand.
the nucleus. Despite this principal insight, systematic NMR
studies on paramagnetic organolanthanide compounds are
not a routine characterization method.32 NMR studies are
typically restricted to the diamagnetic derivatives (Lu(III), Sc, Y,
and La(III)),2,4 whereas some of the best catalysts are obtained
with the paramagnetic metal cations like neodymium or
samarium.3,4 Here we report 1H NMR spectra recorded in C6D6
at 27 °C of paramagnetic complexes 4Ad–7Ad that show
defined, relatively sharp signals with distinctive paramagnetic
shifts, indicating a rigid constrained-geometry structure in
solution. The assignment of the NMR signals for complexes
Multinuclear NMR spectroscopy of CpPN complexes
All complexes were established by NMR spectroscopy. The 31P
NMR spectra of diamagnetic 1Ad–3Ad and 1Dip–3Dip complexes
appear in the region 6.4–7.3 and 8.9–9.3 ppm, respectively.
The 31P resonances of the paramagnetic complexes 4Ad–7Ad are
broadened signals at δ = 24.4 (4Ad, M = Sm), −92.00 (5Ad, M =
Nd), −66.0 (6Ad, M = Pr) and −117.2 (7Ad, M = Yb).
According to the 1H and 13C NMR spectroscopy, 1Ad–7Ad
and 1Dip–3Dip crystallize without coordinated solvent mole-
cules, whereas complexes with less steric bulkiness of the Cp-
ring in [{C5H4PPh2NDip}M(CH2SiMe3)2(thf)] (M = Lu, Y, Sm,
4
Ad–6Ad requires 2D NMR experiments due to the paramag-
netic shift. The signals are summarized in Table 2. The width
Table 2 1H NMR resonances (δ/ppm) and coupling constants (J/Hz) of the paramagnetic complexes 4Ad–7Ad in C6D6 at 27 °C
4Ad (f5Sm3+ 5Ad (f3Nd3+ 6Ad (f2Pr3+
)
)
)
7Ad (f13Yb3+
)
Ln-HCH
CpH
12.65, 12.52
10.87
10.34
7.94 (7.5)
7.74 (7.4)
1.70
33.48, 30.19
12.03
15.40
9.92
9.13
99.51, 93.03
30.03
20.73
12.08 (6.8)
10.65 (6.8)
6.08
−239.26, −225.45
−117.29
−28.92
−7.77
o-PhH
m-PhH (3JHH
)
)
p-PhH (3JHH
SiMe3
−3.77
4.30
−29.57
38.85
51.24
49.65
41.74
65.27
81.49
148.51
162.74
exo-δ-AdH (2JHH
γ—AdH
)
−0.56
−0.73
−4.93 (10.2)
−10.72 (10.5)
−6.47
−14.21
endo-δ-AdH (2JHH
exo-MeCMe
)
−1.12 (11.6)
−1.29
−7.52 (11.9)
−5.48
−14.90 (10.5)
−11.93
endo-MeCMe
−1.58
−13.41
−21.50
exo-HCH(CMe2)2 (2JHH
)
−2.15 (12.7)
−4.80 (12.7)
−7.18
−12.29 (8.5)
−24.05 (10.2)
−27.26
−23.81 (10.0)
−45.27 (10.0)
−52.96
endo-HCH(CMe2)2 (2JHH
β–AdH
)
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Fig. 2 Two sections out of the 1H NMR spectrum (300.1 MHz) of complex [(LAd)Pr(CH2SiMe3)2] (6Ad) in C6D6 at 27 °C. The resonances denoted with
(#), (+) and (*) are assigned to SiMe4, silicon grease and the residual protons of C6D6.
1
of the resonances at half-height (ν1/2) is shown in the Experi- corresponding H NMR signals of 7Ad and 7 of the same para-
mental section.
magnetic shift region allowed the assignment of all signals.
In Fig. 2, the NMR spectrum of f2Pr3+ complex 6Ad which Both spectra show an almost mirror inverted order of shifts
ranges from +100 to −53 ppm is shown as a representative compared to all other paramagnetic complexes [{Cp™PN}-
example (for other spectra see ESI†).
M(CH2SiMe3)2] (M = Sm (4Ad), Nd (5Ad), Pr (6Ad)) or with
All resonances of the adamantyl and annulated five-ring [{C5Me4PMe2NAd}M(CH2SiMe3)2].17 In Fig. 3, the NMR spec-
moiety protons are shifted upfield while the CH2SiMe3 alkyl trum of 7Ad is shown as an example (for 7 see ESI†). The
groups, the phenyl substituents on the phosphorus and the analogue praseodymium complex (6Ad) displays a downfield
cyclopentadienyl protons are shifted downfield.
shift of the diastereotopic protons Pr–CH2–SiMe3 to 93.03 and
Because of the paramagnetic shifting, the signals of the 99.51 ppm and an upfield shift of the adamantyl and annulated
phenyl protons are distributed over a wide range. The o-PhH five-ring moiety protons to the range between −10 and −53 ppm
are furthest downfield shifted due to the relatively small dis- (Fig. 2), whereas for 7Ad both are shifted to the contrary way:
tance to the paramagnetic metal centre. The m-PhH and p-PhH the diastereotopic proton signals are shifted strongly upfield
resonances are less shifted as they are located further away to −225.45 and −239.26 ppm and the adamantyl and annu-
from the metal centre. Using the dependence of the paramag- lated five-ring moiety signals are shifted strongly downfield to
netic shift on the distance to the metal centre, one can specify the range between 38 and 163 ppm. This trend can also be
the methylene and methyl group resonances of the annulated assigned for the other proton signals. It is a consequence of
five ring moiety. The methylene and methyl group resonances the sign variation of spin densities and therefore of the chemi-
that are more upfield shifted are the ones closer to the para- cal shift within the lanthanide series.31
magnetic centre (exo-proton/group) leaving the other to be the
Molecular structures of Cp™PN complexes
endo-proton/group.
For the Sm(III) complex the 13C NMR spectrum was showing
The molecular structures of 1Ad–3Ad, 2Dip and 3Dip were estab-
similar but only slightly paramagnetically shifted signals com-
pared to those of the diamagnetic homologues.
lished by X-ray structure analyses. Single crystals were obtained
by cooling saturated n-hexane (2Dip and 3Dip) or n-pentane
(1Ad) solution to −30 °C. One pentane molecule is incorporated
in the unit cell of structure 1Ad. Single crystals of 2Ad were
obtained from benzene at room temperature with one solvent
molecule per unit cell. Single crystals of 3Ad were obtained by
slowly evaporating a toluene solution, while one toluene mole-
cule is incorporated in the unit cell. Complexes 1Ad–3Ad crystal-
CpPN complexes of ytterbium(III) have never been described
1
before. The H NMR spectrum of f13Yb3+ complex 7Ad reaches
from −240 to +163 ppm but still shows all the expected
defined signals. For unambiguous assignment of all the NMR
signals we also synthesized the new complex [{C5Me4PMe2-
NAd}Yb(CH2SiMe3)2] (7). Similar to 7Ad the related complex
7 reveals a 31P NMR signal at δ = −133.1 ppm. Integration of
ˉ
lize in the triclinic space group P1 with the two formal units in
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Fig. 3 1H NMR spectrum (500.2 MHz) of ytterbium complex 7Ad in C6D6 at 27 °C. Signals denoted with (*), (+) and (#) are assigned to SiMe4, silicon
grease and the residual protons of C6D6.
Fig. 4 Molecular structures of complexes [(LAd)M(CH2SiMe3)2] (Sc = 1Ad; Lu = 2Ad; Y = 3Ad). All hydrogen atoms and incorporated solvent molecules
have been omitted for clarity.
the unit cell (Fig. 4). In contrast to 1Ad the different incorpor- the nitrogen atom of the CpPN-ligand together with two σ-
ated solvent molecules in structures 2Ad and 3Ad have little bonded alkyl groups. The pseudo-tetrahedral environment
effect on the unit cell and for that they are isostructural. Struc- around the metal centre can be shown by comparison of the
tures 2Dip and 3Dip are also isostructural and crystallize in the
CCH2SiMe3–M–N1,
CCH2SiMe3–M–N1,
CCH2SiMe3–M–CCH2SiMe3
orthorhombic space group Pbca with 8 formal units in the unit bond angles, which are all very close to 109°.
cell. Selected bond lengths (Å) and angles (°) for 1Ad–3Ad, 2Dip
The average M–CH2 bond lengths are comparable to those
and 3Dip are presented in Table 3. In the structure of the com- reported for [M(CH2SiMe3)3(L)x] complexes (for M = Sc;33 Lu;34 Y).35
plexes 2Dip and 3Dip one of the CH2SiMe3 groups is disordered
and treated with an occupancy factor of 56 : 44 and 62 : 38, 1.776(2) Å) are longer than in the free ligand (1.703(2) Å), while
respectively (Fig. 5). the P–N bonds are essentially shorter (1.603(2), 1.596(2) and
The P–C1 bond lengths in 1Ad–3Ad (1.775(2), 1.775(2) and
Despite the sterically demanding Cp-moiety 1Ad–3Ad, 2Dip 1.605(2) Å versus 1.653(2) Å for LAd). However, for 2Dip and 3Dip
and 3Dip reveal that the Cp ring coordinates to the metal P–C1 bonds (1.767(4) and 1.758(4) Å) are shorter (1.788(2) Å)
centre in a typical η5 mode, while IndPN adopt an η3-bonding and P–N bonds (1.626(4) and 1.609(3) Å) longer (1.556(2) Å).
fashion and the more bulky FluPN-type ligands have a rare The reason for this different behaviour is the different tauto-
η1-bonding mode.18 In the solid state, all complexes adopt meric forms of the free ligand.
mononuclear structures, in which the metal atoms reveal a
The Cpcentr.–M–N-angles (M = 1Ad: 97.5; 2Ad: 93.9; 3Ad: 92.4;
pseudo-tetrahedral coordination by the η5-bonded C5-ring and 2Dip: 92.2; 3Dip: 90.2°) are similar to those of [{C5Me4PMe2-
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Table 3 Selected bond lengths (Å) and angles (°) for 1Ad, 2Ad, 3Ad, 2Dip and 3Dip
1Ad
2Ad
3Ad
2Dip
3Dip
P1–N1
P1–C1
M–N
M–CCH2SiMe3
M–CCH2SiMe3
M–Z
1.603(2)
1.775(2)
2.210(2)
2.236(2)
2.215(2)
2.288
1.596(2)
1.775(2)
2.288(2)
2.348(3)
2.349(2)
2.371
1.605(2)
1.776(2)
2.339(2)
2.407(2)
2.409(2)
2.419
1.623(3)
1.767(4)
2.293(3)
2.347(4)
2.317(4)
2.409
1.610(3)
1.758(3)
2.342(3)
2.40(2)
2.400(3)
2.455
C1–P1–N1
Z–M–N1
101.0(1)
97.5
115.7(1)
102.6(1)
104.1(1)
102.4(1)
93.9
103.4(1)
112.8(1)
107.7(1)
102.6(1)
92.4
103.4(1)
115.2(1)
108.6(1)
100.7(2)
92.2
101.7(2)
115.4(1)
100.5(1)
101.3(1)
90.2
100.2(6)
117.3(1)
100.5(6)
C
C
C
CH2SiMe3–M–N1
CH2SiMe3–M–N1
CH2SiMe3–M–CCH2SiMe3
C1–P1–N1–C25
−172.2(2)
174.5(2)
−173.3(2)
155.5(3)
156.0(3)
1,4,5,6-tetrahydropentalen-2-yl)phosphane)
with
organic
azides (AdN3 and DipN3; Ad = 1-adamantyl; Dip = 2,6-di-iso-
propylphenyl), the two novel chelate ligands Cp™PPh2NHAd
(LAdH) and Cp™HPPh2NDip (LDipH) were obtained in high
selectivity and yields. Depending on the substituent at the
nitrogen atom, they occur either in the P-amino-cyclopentadie-
nylidene-phosphorane (R = Ad) or in the P-cyclopentadienyl-
iminophosphorane (R = Dip) tautomeric form. Neither pos-
sesses any NMR detectable prototropic or elementotropic
isomers. The rare-earth metal complexes were synthesized fol-
lowing a one-pot protocol, which combines deprotonation and
salt elimination methods by addition of 3 equivalents of
LiCH2SiMe3 as a base/ligand to a stirred mixture of the corres-
ponding THF or DME solvated rare-earth metal trihalide and
the appropriate {Cp™PN}H ligand. The very short synthetic
protocol allows the successful isolation of the highly reactive
and labile alkyl complexes of early lanthanides, which are
usually prone to decompose in solution at ambient tempera-
Fig. 5 Molecular structures of complexes [(LDip)M(CH2SiMe3)2] (Lu =
Dip; Y = 3Dip). All hydrogen atoms and disordered Me3SiCH2-groups
with lower occupancies have been omitted for clarity.
2
NAd}M(CH2SiMe3)2]15,17 and are clearly smaller than the
Cpcentr.–M–N-angles in analogue [(η5:η1-CpSiN)M(R)] CGC (M =
Sc: 102.5;8 Lu: 98.3;36 Y: 96.8° 33). Moreover, the real con-
strained geometry character of the complexes can be seen as
they are significantly smaller than 109°.
ture. All complexes [{Cp™PN}M(CH2SiMe3)2] (M = Sc (1Ad
,
In contrast to the long M–N bond found in
[{C5H4PPh2NDip}M(CH2SiMe3)2(thf)] the M–N bond lengths
1Dip), Lu (2Ad, 2Dip), Y (3Ad, 3Dip), Sm (4Ad), Nd (5Ad), Pr (6Ad),
Yb (7Ad)) were isolated as microcrystalline solids and were com-
pletely characterized by microanalysis and partially by X-ray
crystal structure determination. As a non-routine characteriz-
ation method for organolanthanide complexes an extensive
NMR study of a series of paramagnetic complexes with assign-
ment of all signals is presented. Paramagnetic complexes Sm
(4Ad), Nd (5Ad), Pr (6Ad) reveal an almost mirror inverted signal
order compared to previously unknown ytterbium(III) CpPN
complexes 7Ad or its counterpart [{η1:η5-C5Me4PMe2NAd}Yb-
(CH2SiMe3)2] 7.
(1Ad: 2.210(2); 2Ad: 2.288(2); 3Ad: 2.339(2); 2Dip: 2.293(4); 3Dip
:
2.342(3) Å) are short and approach the length of an amide
bond like in complexes [{C5Me4PMe2NAd}M(CH2SiMe3)2].15,17
They are closer to the covalent bonds represented by [(CpSiN)-
M(R)] (M = Sc: 2.083(5);7–9 Lu: 2.296(7);33 Y: 2.327(5) Å)33 and
by [M{N(SiMe3)2}3] (M = Sc: av. 2.05;37 Lu: av. 2.19;38 Y: av.
2.22 Å)39 than those in donor–acceptor complexes which can
be demonstrated by an average value of M = Sc: 2.46 and
Y: 2.60 Å40 determined in [(Me3TACN)M(CH2SiMe3)3].
Conclusions
Experimental section
General procedures
A new sterically most demanding CpPN chelate ligand system,
cheaper than all tetramethyl-based building blocks and there-
fore more privileged to provide constrained-geometry com- All manipulations were performed under purified argon or
plexes and catalysts of many more metals, has been developed. nitrogen using standard high vacuum or Schlenk- or Glovebox-
By condensation of NaCp with Ph2PCl and with two molecules techniques. Solvents were dried and distilled under argon
of acetone, followed by carbolithiation and Staudinger reaction employing standard drying agents. All organic reagents were
of the phosphane Cp™HPPh2 (1, diphenyl(4,4,6,6-tetramethyl- purified by conventional methods. NMR spectra were recorded
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at 300 K (27 °C) on a Bruker ARX200, Bruker AMX300, and 176.5–177.0 °C. 1H NMR (300.1 MHz, C6D6): δ = 1.44 (s, 6H,
Bruker AVANCE 500. Elemental analyses were performed at δ-AdH), 1.53 (s, 6H, β-AdH), 1.68 (s, 12H, CMe2), 1.80 (br s, 3H,
2
the Analytical Laboratory of the Chemistry Department/ γ-AdH), 2.05 (d, JHP = 5.0 Hz, 1H, NH), 2.46 (s, 2H,
3
Philipps-Universität Marburg. EI mass spectra were taken on a CH2(CMe2)2), 6.17 (d, JHP = 3.1 Hz, 2H, CpH), 7.00–7.03 (m,
Finnigan MAT CH7 spectrometer. The following starting 6H, m-/p-PhH), 7.90–8.01 (m, 4H, o-PhH) ppm. 13C{1H} NMR
materials were prepared according to the literature procedures: (75.5 MHz, C6D6): δ = 30.4 (s, γ-AdC), 33.4 (s, CMe2), 36.2 (s,
4
3
NaCp,25
AdN3,41
DipN3,42
[Lu(CH2SiMe3)3(thf)2],43 δ-AdC), 39.3 (d, JCP = 1.3 Hz, CMe2), 44.5 (d, JCP = 4.0 Hz,
2
[ScCl3(thf)3],9 [MCl3(dme)n] (M = Lu, Y, Sm (n = 2); Nd, Pr, Ce β-AdC), 54.0 (d, JCP = 2.0 Hz, α-AdC), 65.0 (s, CH2(CMe2)2),
(n = 1)),44 LiCH2SiMe3 45 and C5Me4PMe2NHAd.15
80.8 (d, JCP = 116.1 Hz, α-CpC), 106.6 (d, JCP = 16.0 Hz,
1
2
β-CpC), 128.5 (d, 3JCP = 12.3 Hz, m-PhC), 131.7 (d, 4JCP = 2.7 Hz,
X-ray crystallographic studies
1
2
p-PhC), 131.9 (d, JCP = 105.3 Hz, ipso-PhC), 132.9 (d, JCP
=
Suitable crystals were obtained from a concentrated benzene 10.5 Hz, o-PhC), 146.8 (d, JPC = 18.5 Hz, γ-CpC) ppm. 31P{1H}
solution at room temperature (LAdH, 2Ad), by cooling concen- NMR (121.5 MHz, C6D6): δ = 15.6 (s) ppm. EI-MS: m/z (%) =
trated n-hexane (2Dip and 3Dip) or n-pentane (1Ad) solution to 495 (70.1) [M+], 480 (100) [M+ − Me], 466 (5.2) [M+H − 2 Me],
−30 °C and by slow evaporation of toluene solution (3Ad). 135 (22.1) [Ad+]. Anal. calcd for C34H42PN (495.68): C 82.38, H
Crystal data were collected with a Stoe-IPDS area-detector diffr- 8.54, N 2.83; found C 81.40, H 8.45, N 2.59.
3
actometer using graphite-monochromatised Mo-Kα-radiation
Synthesis of ligand LDipH. To a solution of Cp™HPPh2
(λ = 71.073 pm) at 193 K (LAdH, 3Ad, 2Dip) or with a Stoe IPDS2 (6.59 g, 19.0 mmol, 1.00 eq.) in 75 mL of THF, DipN3 (4.46 g,
diffractometer at 100 K. Data reduction was carried out using 21.9 mmol, 1.15 eq.) was added and stirred overnight at room
the IPDSI software or X-Area (Stoe).46 The data were empirically temperature, whereupon N2-evolution occurs. Removal of the
corrected for absorption and other effects by using multi- solvent in a vacuum yielded a foamy residue. The compound
scans,47 except for compound LAdH, where no improvement in was crystallized from acetonitrile at ambient temperature. A
the refinement was achieved through its application. The pale rose, crystalline solid was obtained. Yield: 7.51
g
structures were solved by direct methods (Sir-92,48 Sir-2004,49 (14.4 mmol, 76%). M.p. = 142.5–143.0 °C. 1H NMR (300.1,
and SHELXS-9750) and refined by full-matrix least-squares MHz, C6D6): δ = 1.00 (s, 6H, CMe2), 1.03 (s, 6H, CMe2), 1.18 (d,
techniques against Fo (SHELXL-97).47 C bonded hydrogen 3JHH = 7.0 Hz, 12H, Me2CH), 1.91 (s, 2H, CH2(CMe2)2), 3.08 (s,
2
3
atoms were included in idealized positions and refined with 2H, CpCH2), 3.66 (sept, JHH = 6.8 Hz, 2H, Me2CH), 6.77 (d,
fixed isotropic displacement factors. The N-bonded hydrogen 3JHP = 8.5 Hz, 1H, CpH), 7.03–7.06 (m, 6H, m-/p-PhH),
atom of LAdH was located and refined isotropically. The 7.07–7.12 (m, 1H, p-DipH), 7.25 (d, 3JHH = 7.4 Hz, 2H, m-DipH),
program PLATON51 was used to check the results of the X-ray 7.79–7.87 (m, 4H, o-PhH) ppm. 13C{1H} NMR (75.5 MHz,
analyses. Diamond was used for 30% thermal ellipsoid rep- C6D6): δ = 24.1 (s, Me2CH), 29.1 (s, Me2CH), 29.9 (s, CMe2),
2
resentations.52 CCDC no. 817338 (LAdH), 817339 (LDipH), 30.3 (s, CMe2), 37.1 (d, JCP = 10.4 Hz, β-CpCH2), 40.0 (s,
817340 (1Ad), 817341 (2Ad), 817342 (3Ad), 817343 (2Dip), and CMe2), 41.8 (s, CMe2), 61.6 (s, CH2(CMe2)2), 119.9 (d, 5JCP = 3.3
4
817344 (3Dip) contain the supplementary crystallographic data Hz, p-DipC), 123.2 (d, JCP = 2.2 Hz, m-DipC), 128.6 (d, super-
3
for this paper.
impose with residual protons of C6D6, p-PhC), 131.1 (d, JCP
=
=
2
1
Synthesis of Cp™HPPh2 (1). To 9.43 g Na(C5H5) (108 mmol, 2.5 Hz, m-PhC), 132.3 (d, JCP = 9.6 Hz, o-PhC), 134.6 (d, JCP
2
1.03 eq.) in 200 mL of n-pentane at 0 °C, 23.16 mL of PPh2Cl 106.4 Hz, ipso-PhC), 140.7 (d, JCP = 10.5 Hz, β-CpC), 142.6 (d,
(105 mmol, 1.00 eq.) was added. The mixture was stirred for 1JCP = 100.0 Hz, α-CpC), 143.1 (d, JCP = 6.9 Hz, ipso-DipC),
2
3
3
16 h at ambient temperature, and then 10 mL of ethane-1,2- 145.5 (s, o-DipC), 155.3 (d, JCP = 14.5 Hz, γ-CpC), 163.2 (d, JCP
diol was added under vigorous stirring. The solution was dec- = 6.2 Hz, γ′-CpC) ppm. 31P{1H} NMR (121.5 MHz, C6D6): δ =
anted from the precipitate, the precipitate was washed twice −15.8 (s) ppm. EI-MS m/z (%): 521 (47.0) [M+], 506 (31.6)
with 20 mL of n-pentane, and the solvent of the transferred [M+ − Me], 185 (56.2) [Ph2P+]. Anal. calcd for C36H44NP (521.73):
solution was evaporated in a vacuum. The following steps were C 82.88, H 8.50, N 2.68; found C 82.53, H 8.57, N 2.88.
carried out according to the literature, while spectroscopic fea-
tures match perfectly with the reported ones.24
Synthesis of [(LAd)Lu(CH2SiMe3)2] (2Ad). To a stirred solu-
tion of [Lu(CH2SiMe3)2(thf)2] (580 mg, 1.00 mmol, 1.00 eq.) in
Synthesis of ligand LAdH. To a solution of phosphane 1 10 mL of toluene, a solution of ligand LAdH (500 mg,
Cp™HPPh2 (2.40 g, 6.93 mmol, 1.00 eq.) in 30 mL of toluene, 1.01 mmol, 1.01 eq.) in the same amount of solvent was added
AdN3 (1.35 g, 7.62 mmol, 1.10 eq.) was added and stirred at dropwise at ambient temperature. After 0.5 h the solvent was
120 °C for 17 h. The colour of the reaction mixture progress- completely removed in a vacuum and the foamy residue was
ively turns brown. The reaction proceeding was monitored by triturated with 10 mL of n-hexane, which results in dissolution
31P NMR spectroscopy. The solvent was completely removed in and immediate deposition of a colourless crystalline solid. It
a vacuum and the oily residue was dissolved in 10 mL of was filtered off and dried in a vacuum. An additional amount
n-hexane yielding a clear dark brown solution. Upon sonifi- of the compound can be obtained by storing the mother liquor
cation of the n-hexane solution a yellow powder precipitated. It at −30 °C. Yield: combined 660 mg (0.78 mmol, 78%).
2
was filtered off, washed with 3 mL of n-hexane and dried in 1H NMR (300.1 MHz, C6D6): δ = −0.58 (d, JHH = 11.5 Hz, 2H,
2
a
vacuum. Yield: 2.33
g
(4.70 mmol, 68%). M.p.
=
Lu-HCH), −0.19 (d, JHH = 11.5 Hz, 2H, Lu-HCH), 0.48 (s, 18H,
7116 | Dalton Trans., 2014, 43, 7109–7120
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2
SiMe3), 1.19 (s, 6H, MeCMe), 1.45 (d, JHH = 12.3 Hz, 3H, stripped off, whereupon a colourless foamy solid forms, which
2
δ-AdH), 1.56 (d, JHH = 12.4 Hz, 3H, δ-AdH), 1.64 (s, 6H, was crystallized from n-hexane. Storage at −30 °C followed by
MeCMe), 1.92–1.97 (m, 3H, γ-AdH, superimpose with 1H, filtration and drying in a vacuum resulted in isolation of a
2
HCH(CMe2)2), 2.08 (s, 6H, β-AdH), 2.24 (d, JHH = 13.1 Hz, 1H, microcrystalline solid.
3
HCH(CMe2)2), 5.96 (d, JHP = 2.8 Hz, 2H, CpH), 6.99–7.08 (m,
Analytical data for [(LAd)Sc(CH2SiMe3)2] (1Ad). Yield: 251 mg
6H, p-/m-PhH), 7.82–7.89 (m, 4H, o-PhH) ppm. 13C{1H} NMR (0.35 mmol, 70%) of a colourless, microcrystalline solid. 1H
(62.9 MHz, C6D6): δ = 5.1 (s, SiMe3), 30.5 (d, JCP = 1.1 Hz, NMR (300.1 MHz, C6D6): δ = −0.08 (d, JHH = 11.4 Hz, 2H,
4
2
2
γ-AdC), 32.3 (s, MeCMe), 32.9 (s, MeCMe), 36.3 (s, δ-AdC), 40.1 Sc-HCH), 0.46 (s, 18H, SiMe3), 0.56 (d, JHH = 11.4 Hz, 2H,
(d, 4JCP = 0.6 Hz, CMe2), 40.6 (s, Lu-CH2), 47.3 (d, 3JCP = 8.4 Hz, Sc-HCH), 1.22 (s, 6H, MeCMe), 1.49 (d, JHH = 12.3 Hz, 3H,
2
2
2
β-AdC), 55.7 (d, JCP = 7.2 Hz, α-AdC), 63.0 (s, CH2(CMe2)2), δ-AdH), 1.60 (d, JHH = 11.7 Hz, 3H, δ-AdH), 1.68 (s, 6H,
93.7 (d, JCP = 115.4 Hz, α-CpC), 106.7 (d, JCP = 12.9 Hz, MeCMe), 1.97–2.01 (m, 4H, γ-AdH superimpose with
1
2
4
1
4
β-CpC), 128.6 (d, JCP = 11.6 Hz, p-PhC), 131.2 (d, JCP
=
HCH(CMe2)2), 2.17 (d, JHP = 2.0 Hz, 6H, β-AdH), 2.33 (d,
87.0 Hz, ipso-PhC), 132.5 (d, JCP = 2.9 Hz, m-PhC), 133.5 (d, 2JHH = 13.0 Hz, 1H, HCH(CMe2)2), 5.94 (d, JHP = 2.8 Hz, 2H,
3
3
2JCP = 10.6 Hz, o-PhC), 149.0 (d, JCP = 13.9 Hz, γ-CpC) ppm. CpH), 7.00–7.07 (m, 6H, m-/p-PhH), 7.83–7.88 (m, 4H, o-PhH)
3
31P{1H} NMR (121.5 MHz, C6D6): δ = 6.4 (s) ppm. Anal. calcd ppm. 13C{1H} NMR (75.5 MHz, C6D6): δ = 4.6 (s, SiMe3), 30.7 (s,
for C42H63LuNPSi2 (844.09): C 59.76, H 7.53, N 1.66; found: γ-AdC), 32.3 (s, MeCMe), 32.5 (s, MeCMe), 36.4 (s, δ-AdC), 40.4
3
C 59.51, H 7.34, N 1.75.
(s, CMe2), 40.4 (s, Sc-CH2), 47.3 (d, JCP = 8.3 Hz, β-AdC), 56.1
2
1
Synthesis of [(LDip)Lu(CH2SiMe3)2] (2Dip). 2Dip was prepared (d, JCP = 7.1 Hz, α-AdC), 62.9 (s, CH2(CMe2)2), 94.5 (d, JCP
=
2
using the same synthetic protocol as for 2Ad starting from 114.4 Hz, α-CpC), 107.1 (d, JCP = 12.9 Hz, β-CpC), 128.5
4
1
[Lu(CH2SiMe3)3(thf)2] (580 mg, 1.00 mmol, 1.00 eq.) and (d, JCP = 11.9 Hz, p-PhC), 130.9 (d, JCP = 86.9 Hz, ipso-PhC),
ligand LDipH (520 mg, 1.00 mmol, 1.00 eq.). The reaction was 132.5 (d, 3JCP = 2.8 Hz, m-PhC), 133.5 (d, 2JCP = 10.5 Hz, o-PhC),
3
performed at 0 °C. A colourless, microcrystalline solid was 150.3 (d, JCP
=
13.7 Hz, γ-CpC) ppm. 31P{1H} NMR
obtained by storing the n-hexane solution at −30 °C in a yield (121.5 MHz, C6D6):
of 480 mg (0.55 mmol, 55%). H NMR (300.1 MHz, C6D6): δ = C42H63NPScSi2 (714.06): C: 70.65, H: 8.89, N: 1.96. Found:
δ = 7.3 (s) ppm. Anal. calcd for
1
−0.56 (br s, 2H, Lu-HCH), −0.30 (br s, 2H, Lu-HCH), 0.37 (s, C: 67.79, H: 8.84, N: 2.03.
18H, SiMe3), 0.38 (d, 6H, Me2CH superimpose with SiMe3),
Analytical data for [(LAd)Y(CH2SiMe3)2] (3Ad). Yield: 190 mg
1.29 (s, 6H, MeCMe), 1.35 (br s, 6H, Me2CH), 1.68 (s, 6H, (0.25 mmol, 50%) of a colourless, microcrystalline solid. 1H
2
2
2
MeCMe), 2.01 (d, JHH = 13.0 Hz, 1H, HCH(CMe2)2), 2.36 (d, NMR (300.1 MHz, C6D6): δ = −0.39 (dd, JHH = 11.2 Hz, JHY
=
2JHH = 13.0 Hz, 1H, HCH(CMe2)2), 3.51 (sep, 3JHH = 9.0 Hz, 2H, 2.7 Hz, 2H, Y-HCH), −0.04 (dd, JHH = 11.2 Hz, JHY = 2.7 Hz,
2
2
3
Me2CH), 6.47 (d, JHP = 2.6 Hz, 2H, CpH), 6.92–7.04 (m, 9H, 2H, Y-HCH), 0.47 (s, 18H, SiMe3), 1.18 (s, 6H, MeCMe), 1.45 (d,
p-/m-PhH, p-/m-DipH), 7.48–7.54 (m, 4H, o-PhH) ppm. 13C{1H} 2JHH = 12.0 Hz, 3H, δ-AdH), 1.56 (d, 2JHH = 12.0 Hz, 3H, δ-AdH),
2
NMR (62.9 MHz, C6D6): δ = 4.6 (s, SiMe3), 22.7 (br s, Me2CH), 1.62 (s, 6H, MeCMe), 1.94 (s, 3H, γ-AdH), 1.96 (d, JHH
24.1 (br s, Me2CH), 29.0 (s, Me2CH), 32.3 (s, MeCMe), 32.5 (s, 13.1 Hz, 1H, HCH(CMe2)2), 2.12 (s, 6H, β-AdH), 2.23 (d, JHH
MeCMe), 40.2 (s, CMe2), 43.0 (s, Lu-CH2), 62.6 (s, CH2(CMe2)2), 13.1 Hz, 1H, HCH(CMe2)2), 6.05 (d, JHP = 2.5 Hz, 2H, CpH),
=
=
2
3
1
2
93.3 (d, JCP = 113.3 Hz, α-CpC), 107.0 (d, JCP = 12.8 Hz, 7.05–7.21 (m, 6H, p-/m-PhH), 7.85–7.92 (m, 4H, o-PhH) ppm.
β-CpC), 124.8 (d, 4JCP = 3.6 Hz, m-DipC), 125.3 (d, 5JCP = 3.7 Hz, 13C{1H} NMR (75.5 MHz, C6D6): δ = 4.9 (s, SiMe3), 30.5 (s,
1
4
1
p-DipC), 128.6 (d, JCP = 90.0 Hz, ipso-PhC), 128.8 (d, JCP
=
=
γ-AdC), 32.2 (s, MeCMe), 33.1 (s, MeCMe), 33.8 (d, JCY = 40.9
12.1 Hz, p-PhC), 132.7 (d, 3JCP = 2.7 Hz, m-PhC), 132.9 (d, 2JCP
Hz, Y-CH2), 36.3 (s, δ-AdC), 40.1 (s, CMe2), 47.4 (d, JCP
=
3
2
2
9.1 Hz, o-PhC), 133.4 (d, JCP = 9.8 Hz, ipso-DipC), 145.7 (d, 8.7 Hz, β-AdC), 55.8 (d, JCP = 6.9 Hz, α-AdC), 63.1 (s,
3JCP = 6.1 Hz, o-DipC), 150.1 (d, JCP = 13.7 Hz, γ-CpC) ppm. CH2(CMe2)2), 94.5 (d, JCP = 117.0 Hz, α-CpC), 106.8 (d, JCP
=
3
1
2
31P{1H} NMR (121.5 MHz, C6D6): δ = 9.3 (s) ppm. Anal. calcd 13.3 Hz, β-CpC), 128.6 (d, 4JCP = 9.7 Hz, p-PhC), 131.4 (d, 1JCP
=
3
for C44H65LuNPSi2 (870.13): C 68.27, H 7.53, N 1.61; found: C 86.5 Hz, ipso-PhC), 132.4 (d, JCP = 2.8 Hz, m-PhC), 133.4 (d,
67.76, H 7.39, N 1.80.
3
2JCP = 10.6 Hz, o-PhC), 149.2 (d, JCP = 13.8 Hz, γ-CpC) ppm.
31P{1H} NMR (121.5 MHz, C6D6): δ = 6.5 (s) ppm. Anal. calcd
for C42H63NPSi2Y (758.01): C: 66.55, H: 8.38, N: 1.85. Found:
C: 66.57, H: 7.98, N: 1.94.
General procedure for the preparation of complexes
[{Cp™PPh2NR}M(CH2SiMe3)2] (M = Sc (R = Ad: 1Ad
;
R = Dip: 1Dip), Y (R = Ad: 3Ad; R = Dip: 3Dip), Sm (R = Ad: 4Ad),
Nd (R = Ad: 5Ad), Pr (R = Ad: 6Ad), Yb (R = Ad: 7Ad)) and
[{C5Me4PMe2NAd}Yb(CH2SiMe3)2] 7
To a stirred suspension of [ScCl3(thf)3] or [MCl3(dme)x] β-AdH), −4.80 (d, 2JHH = 12.7 Hz, 1H, endo-HCH(CMe2)2), −2.15
Analytical data for [(LAd)Sm(CH2SiMe3)2] (4Ad). Yield:
170 mg (0.21 mmol, 41%) of a yellow, microcrystalline solid.
1H NMR (300.1 MHz, C6D6): δ = −7.18 (s, 6H, ν1/2 = 10 Hz,
2
(0.50 mmol, 1.00 eq.) and the protonated ligand (0.50 mmol, (d, JHH = 12.7 Hz, 1H, exo-HCH(CMe2)2), −1.58 (s, 6H, ν1/2
=
1.00 eq.) in 15 mL of ether, a solution of LiCH2SiMe3 4 Hz, endo-MeCMe), −1.29 (s, 6H, ν1/2 = 3 Hz, exo-MeCMe),
2
(1.50 mmol, 3.00 eq.) in 10 mL of toluene was added dropwise −1.12 (d, JHH = 11.6 Hz, 3H, endo-δ-AdH), −0.73 (s, 3H, ν1/2
=
2
at 0 °C. The reaction mixture was stirred at 0 °C for another 10 Hz, γ-AdH), −0.56 (d, JHH = 11.6 Hz, 3H, exo-δ-AdH), 1.70
0.5 h and concentrated in a vacuum to half of the original (s, 18H, ν1/2 = 2 Hz, SiMe3), 7.74 (t, JHH = 7.4 Hz, 2H, p-PhH),
volume. LiCl was filtered off over Celite®. The solvent was 7.94 (t, JHH = 7.5 Hz, 4H, m-PhH), 10.34 (s, 4H, ν1/2 = 17 Hz,
3
3
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o-PhH), 10.87 (s, 2H, ν1/2 = 9 Hz, CpH), 12.52 (br s, 2H, ν1/2
=
Analytical data for [(LDip)Sc(CH2SiMe3)2] (1Dip). Yield:
25 Hz, Sm-HCH), 12.65 (br s, 2H, ν1/2 = 22 Hz, Sm-HCH) ppm. 132 mg (0.18 mmol, 36%) of a colourless solid. 1H NMR
13C{1H} NMR (125.8 MHz, C6D6): δ = 4.3 (s, SiMe3), 26.3 (s, (300.1 MHz, C6D6): δ = −0.07 (d, JHH = 11.3 Hz, 2H, Sc-HCH),
2
MeCMe), 26.4 (s, γ-AdC), 28.5 (s, MeCMe), 32.1 (s, CMe2), 33.2 0.38 (s, 18H, SiMe3), 0.40 (d, 3JHH = 6.6 Hz, 6H, MeCHMe), 0.50
2
(s, δ-AdC), 38.0 (s, β-AdC), 49.8 (s, α-AdC), 55.1 (s, CH2(CMe2)2), (d, JHH = 11.3 Hz, 2H, Sc-HCH), 1.34 (s, 6H, MeCMe), 1.38 (d,
102.0 (s, β-CpC), 125.7 (s, γ-CpC), 129.6 (s, m-PhC), 133.4 (s, 3JHH = 6.7 Hz, 6H, MeCHMe), 1.73 (s, 6H, MeCMe), 2.05 (d,
p-PhC), 135.7 (s, o-PhC) ppm. The signals of the Sm-CH2, 2JHH = 13.0 Hz, 1H, H(H)C(CMe2)2), 2.45 (d, 2JHH = 13.0 Hz, 1H,
3
α-CpC and the ipso-PhC atoms could not be found in the H(H)C(CMe2)2), 3.58 (sept, JHH = 6.7 Hz, 2H, MeCHMe), 6.52
13C-NMR-Spectrum. 31P{1H} NMR (121.5 MHz, C6D6): δ = 24.4 (d, JHP = 2.4 Hz, 2H, HCp), 6.92–7.00 (m, 6H, p-/m-PhH),
3
(br s) ppm. Anal. calcd for C42H63NPSi2Sm (819.46): C: 61.56, 7.01–7.07 (m, 3H, p-/m-DipH), 7.48–7.55 (m, 4H, o-PhH) ppm.
H: 7.75, N: 1.71. Found: C: 60.61, H: 7.61, N: 2.02.
13C{1H} NMR (75.5 MHz, C6D6): δ = 4.1 (s, SiMe3), 23.7 (br s,
Analytical data for [(LAd)Nd(CH2SiMe3)2] (5Ad). Yield: Me2CH), 26.3 (br s, Me2CH), 28.9 (s, Me2CH), 31.9 (s, MeCMe),
1
164 mg (0.20 mmol, 40%) of a blue, microcrystalline solid. H 32.6 (s, MeCMe), 40.4 (s, CMe2), 45.2 (br s, Sc-CH2), 62.6 (s,
1
2
NMR (300.1 MHz, C6D6): δ = −27.26 (s, 6H, ν1/2 = 31 Hz, CH2(CMe2)2), 94.2 (d, JCP = 112.6 Hz, α-CpC), 107.4 (d, JCP
=
2
4
5
β−AdH), −24.05 (d, JHH = 10.2 Hz, 1H, endo-HCH(CMe2)2), 12.6 Hz, β-CpC), 124.9 (d, JCP = 3.5 Hz, m-DipC), 125.3 (d, JCP
2
1
−13.41 (s, 6H, ν1/2 = 16 Hz, endo-MeCMe), −12.29 (d, JHH
=
= 3.7 Hz, p-DipC), 128.5 (d, JCP = 82.6 Hz, ipso-PhC), 128.8 (d,
8.5 Hz, 1H, exo-HCH(CMe2)2), −7.52 (d, JHH = 11.9 Hz, 3H, 4JCP = 12.0 Hz, p-PhC), 132.7 (d, 3JCP = 2.8 Hz, m-PhC), 133.6 (d,
2
endo-δ-AdH), −6.47 (s, 3H, ν1/2 = 11 Hz, γ-AdH), −5.48 (s, 6H, 2JCP = 9.9 Hz, o-PhC), 140.9 (d, JCP = 9.9 Hz, ipso-DipC), 145.7
2
ν1/2 = 8 Hz, exo-MeCMe), −4.93 (d, JHH = 10.2 Hz, 3H, (d, 3JCP = 6.2 Hz, o-DipC), 151.0 (d, 3JCP = 13.5 Hz, γ-CpC) ppm.
2
exo-δ-AdH), 4.30 (s, 18H, ν1/2 = 10 Hz, SiMe3), 9.13 (s, 2H, ν1/2
=
31P{1H} NMR (121.5 MHz, C6D6): δ = 8.9 (s) ppm. Anal. calcd
16 Hz, p-PhH), 9.92 (s, 4H, ν1/2 = 16 Hz, m-PhH), 12.03 (br s, for C44H65NPScSi2 (740.09): C: 71.41, H: 8.85, N: 1.89. Found:
2H, ν1/2 = 58 Hz, CpH), 15.40 (s, 4H, ν1/2 = 23 Hz, o-PhH), C: 70.33, H: 8.56, N: 2.07.
30.19 (br s, 2H, ν1/2 = 116 Hz, Nd-HCH), 33.48 (br s, 2H, ν1/2
=
Analytical data for [(LDip)Y(CH2SiMe3)2] (3Dip). Yield:
132 Hz, Nd-HCH) ppm. 31P{1H} NMR (121.5 MHz, C6D6): δ = 125 mg (0.16 mmol, 32%) of a colourless, microcrystalline
1
2
−92.0 (br s) ppm. Anal. calcd for C42H63NPSi2Nd (813.34): solid. H NMR (300.1 MHz, C6D6): δ = −0.31 (br d, JHH = 8.9
C: 62.02, H: 7.81, N: 1.72. Found: C: 60.70, H: 7.86, N: 1.88.
2
Hz, 2H, Y-HCH), −0.09 (br d, JHH = 9.0 Hz, 2H, Y-HCH), 0.39
Analytical data for [(LAd)Pr(CH2SiMe3)2] (6Ad). Yield: 223 mg (s, 18H, SiMe3), 0.45 (s, 6H, MeCHMe), 1.29 (s, 6H, MeCMe),
1
2
(0.28 mmol, 55%) of a light brown, microcrystalline solid. H 1.35 (s, 6H, MeCHMe), 1.68 (s, 6H, MeCMe), 2.03 (d, JHH
=
2
NMR (300.1 MHz, C6D6): δ = −52.96 (s, 6H, ν1/2 = 24 Hz, 12.4 Hz, 1H, H(H)C(CMe2)2), 2.36 (d, JHH = 13.3 Hz, 1H, H(H)
3
β-AdH), −45.27 (br d, 1H, ν1/2 = 26 Hz, endo-HCH(CMe2)2), C(CMe2)2), 3.47 (sept, JHH = 6.8 Hz, 2H, MeCHMe), 6.49 (d,
−23.81 (d, 2JHH = 10.0 Hz, 1H, exo-HCH(CMe2)2), −21.50 (s, 6H, 3JHP = 2.6 Hz, 2H, CpH), 6.96–7.02 (br m, 9H, p-/m-PhH, p-/m-
ν1/2 = 11 Hz, endo-MeCMe), −14.90 (d, JHH = 10.5 Hz, 3H, DipH), 7.50–7.57 (br m, 4H, o-PhH) ppm. 13C{1H}
2
endo-δ-AdH), −14.21 (s, 3H, ν1/2 = 12 Hz, γ-AdH), −11.93 (s, 6H, NMR (75.5 MHz, C6D6): δ = 4.4 (s, SiMe3), 22.7 (br s, Me2CH),
2
ν1/2 = 7 Hz, exo-MeCMe), −10.72 (d, JHH = 10.5 Hz, 3H, exo- 26.9 (br s, Me2CH), 29.0 (s, Me2CH), 31.9 (s, MeCMe), 32.2
δ-AdH), 6.08 (s, 18H, ν1/2 = 6 Hz, SiMe3), 10.65 (t, 3JHH = 6.8 Hz, (s, MeCMe), 37.1 (d, 1JCY = 42.3 Hz, Y-CH2), 40.1 (s, CMe2), 62.6
3
1
2H, p-PhH), 12.08 (t, JHH = 6.8 Hz, 4H, m-PhH), 20.73 (br s, (s, CH2(CMe2)2), 94.2 (d, JCP = 114.1 Hz, α-CpC), 107.0 (d,
4H, ν1/2 = 24 Hz, o-PhH), 30.03 (s, 2H, ν1/2 = 26 Hz, CpH), 93.03 2JCP = 12.9 Hz, β-CpC), 124.7 (d, JCP = 3.5 Hz, m-DipC), 125.1
4
5
4
(br s, 2H, ν1/2 = 57 Hz, Pr-HCH), 99.51 (br s, 2H, ν1/2 = 60 Hz, (d, JCP = 3.9 Hz, p-DipC), 128.7 (d, JCP = 12.0 Hz, p-PhC),
Pr-HCH) ppm. 31P{1H} NMR (121.5 MHz, C6D6): δ = −66.0 (br 130.8 (d, JCP = 97.5 Hz, ipso-PhC), 132.6 (d, JCP = 2.7 Hz,
1
3
s) ppm. Anal. calcd for C42H63NPSi2Pr (810.01): C: 62.28, H: m-PhC), 133.3 (d, 2JCP = 9.8 Hz, o-PhC), 140.4 (d, 2JCP = 10.5 Hz,
3
3
7.84, N: 1.73. Found: C: 60.95, H: 7.89, N: 1.88.
ipso-DipC), 145.4 (d, JCP = 6.0 Hz, o-DipC), 150.2 (d, JCP =
Analytical data for [(LAd)Yb(CH2SiMe3)2] (7Ad). Yield: 318 mg 13.8 Hz, γ-CpC) ppm. 31P{1H} NMR (121.5 MHz, C6D6): δ =
(0.38 mmol, 76%) of a dark red, microcrystalline solid. 1H 9.1 (s) ppm.
NMR (500.2 MHz, C6D6): δ = −239.26 (br s, 2H, ν1/2 = ca.
Analytical data for [{C5Me4PMe2NAd}Yb(CH2SiMe3)2]
700 Hz, Yb-HCH), −225.45 (br s, 2H, ν1/2 = ca. 770 Hz, (7). Yield: 126 mg (0.19 mmol, 37%) of a dark red, micro-
Yb-HCH), −117.29 (s, 2H, ν1/2 = ca. 309 Hz, CpH), −29.57 (s, crystalline solid. 1H NMR (500.2 MHz, C6D6): δ = −243.89 (br s,
18H, ν1/2 = 40 Hz, SiMe3), −28.92 (s, 4H, ν1/2 = 64 Hz, o-PhH), 2H, ν1/2 = ca. 480 Hz, Yb-HCH), −215.83 (br s, 2H, ν1/2 = ca.
−7.77 (s, 4H, ν1/2 = 22 Hz, m-PhH), −3.77 (s, 2H, ν1/2 = 22 Hz, 530 Hz, Yb-HCH), −71.44 (s, 6H, ν1/2 = 71 Hz, β-C5Me4),
p-PhH), 38.85 (s, 3H, ν1/2 = 34 Hz, exo-δ-AdH), 41.74 (s, 6H, ν1/2 −38.71 (s, 6H, ν1/2 = 28 Hz, Me2P), −18.37 (s, 18H, ν1/2 = 27 Hz,
= 36 Hz, exo-MeCMe), 49.65 (s, 3H, ν1/2 = 34 Hz, endo-δ-AdH), SiMe3), 35.33 (s, 3H, ν1/2 = 32 Hz, exo-δ-AdH), 45.92 (s, 3H,
51.24 (s, 3H, ν1/2 = 48 Hz, γ-AdH), 65.27 (s, 6H, ν1/2 = 146 Hz, ν1/2 = 26 Hz, endo-δ-AdH), 46.40 (s, 3H, ν1/2 = 42 Hz, γ-AdH),
endo-MeCMe), 81.49 (s, 1H, ν1/2 = 49 Hz, exo-HCH(CMe2)2), 104.27 (s, 6H, ν1/2 = 117 Hz, γ-C5Me4), 148.54 (s, 6H, ν1/2
=
148.51 (s, 1H, ν1/2 = 178 Hz, endo-HCH(CMe2)2), 162.74 (s, 6H, ca. 320 Hz, β-AdH) ppm. 31P{1H} NMR (121.5 MHz, C6D6):
ν1/2 = ca. 410 Hz, β-AdH) ppm. 31P{1H} NMR (202.5 MHz, C6D6): δ = −133.1 (br s) ppm. Anal. calcd for C29H55NPSi2Yb
δ = −117.2 (br s) ppm. Anal. calcd for C42H63NPSi2Yb (842.16): C: (677.90): C: 51.38, H: 8.18, N: 2.07. Found: C: 50.06, H: 8.44,
59.90, H: 7.54, N: 1.66. Found: C: 58.94, H: 7.45, N: 1.71.
N: 2.12.
7118 | Dalton Trans., 2014, 43, 7109–7120
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14 T. K. Panda, C. G. Hrib, P. G. Jones, J. Jenter, P. W. Roesky
Acknowledgements
and M. Tamm, Eur. J. Inorg. Chem., 2008, 4270–4279.
Financial support by DFG (Priority Program Lanthanide- 15 K. A. Rufanov, A. R. Petrov, V. V. Kotov, F. Laquai and
Specific Functionality SPP-1166), by Chemetall GmbH, Frank- J. Sundermeyer, Eur. J. Inorg. Chem., 2005, 3805–3807.
furt and by Studienstiftung des Deutschen Volkes is gratefully 16 A. R. Petrov, K. A. Rufanov, N. K. Hangaly, M. Elfferding,
acknowledged. The authors thank Dr Thomas Linder for his
contribution to the X-ray analysis of LAdH.
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20, 197–199.
17 N. K. Hangaly, A. R. Petrov, K. A. Rufanov, K. Harms,
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18 Z. Jian, A. R. Petrov, N. K. Hangaly, S. Li, W. Rong, Z. Mou,
K. A. Rufanov, K. Harms, J. Sundermeyer and D. Cui,
Organometallics, 2012, 31, 4267–4282.
19 Z. Jian, N. K. Hangaly, W. Rong, Z. Mou, D. Liu, S. Li,
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2012, 31, 4579–4587; Z. Jian, W. Rong, Z. Mou, Y. Pan,
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