Neutral binuclear rare-earth metal complexes with four μ2-bridging hydrides

Article abstract of DOI:10.1039/c4cc07262f

The first neutral rare-earth metal dinuclear dihydrido complexes [(NPNPN)LnH₂]₂ (2-Ln; Ln = Y, Lu; NPNPN: N[Ph₂PNC₆H₃(ⁱPr)₂]₂) bearing μ₂-bridging hydride l

Full text of DOI:10.1039/c4cc07262f

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Neutral binuclear rareꢀearth metal complexes with four µ2ꢀbridging
hydrides†
Weifeng Rong,a,b Dongliang He,a,d Meiyan Wang,c Zehuai Mou,a,b Jianhua Cheng,a Changguang Yao,a,b
Shihui Li,a Alexander A. Trifonov*,e,f Dmitrii M. Lyubov,e,f and Dongmei Cui*a
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
collapse to give complicated intermediates.6j Therefore, to
The first neutral rareꢀearth metal dinuclear dihydrido
synthesize the simple dinuclear and the finally targeted
monomeric terminal rareꢀearth metal hydrides, is a challenging
55 and promising project, as the simple structural hydride complexes
are crucial factors to realize the cyclic catalysis. To date, the
dinuclear rareꢀearth metal dihydrides are rather unstable and very
scarce.7,8 There is only one cationic rareꢀearth metal dihydrido
complex bearing quadruply bridged hydrido ligands.9 Herein we
60 report the first neutral dimeric rareꢀearth metal hydride
complexes containing quadruply bridged hydrido ligands and its
reaction triggered by a THF molecule.
complexes [(NPNPN)LnH2]2 (2ꢀLn; Ln = Y, Lu; NPNPN:
N[Ph2PNC6H3(iPr)2]2) bearing µ2ꢀbridging hydride ligands
10 have been synthesized. In the presence of THF, 2ꢀY
undergoes intramolecular activation of sp2 C–H bond to form
dinuclear arylꢀhydride complex 3ꢀY containing three µ2ꢀ
bridging hydride ligands.
Metal hydride complexes occupy an important and unique
15 position in organometallic chemistry1 because of their peculiar
and versatile applications, such as molecular models for
hydrogenꢀstorage material,2 catalytic reduced reagent3 and
activation of small melecules.4 Rareꢀearth metal hydrides have
also witnessed a spectacular growth in the last three decades,5
20 among which dihydride complexes bearing “LMH2” moiety have
Treatment of the phosphazeneꢀligated rareꢀearth dialkyl
complexes 1ꢀLn [(NPNPN)Ln(CH2SiMe3)2] (Ln = Y, Lu)10 with
o
65 dihydrogen or phenylsilane in toluene or benzene at 25 C (for Y
complex) or at 60 oC (for Lu complex) afforded the dinuclear
tetrahydride complexes 2ꢀLn in moderate yields (Scheme 1). 2ꢀ
Ln were sparingly soluble in toluene and benzene but insoluble in
hexane. In the 1H NMR spectrum of complex 2ꢀY, the YꢀH signal
70 was overlapped with the aromatic H signals;11 but the hydride
resonance in 2ꢀLu was recorded at δ 10.26 ppm as a distinct
singlet, which is consistent with the previous reports that the
hydride ligands usually give downfield resonances such as [(Meꢀ
PNPiPr)LuH2]3 at δ 9.70 ppm,6c [(NCN)LuH2]2(THF)3 at δ 8.72
attracted
a particular interest because of their fascinating
structures and versatile reactivity.6 However, most of the rareꢀ
earth dihydride species reported so far tend to assemble to
polynuclear structures such as [LMH2]n (n
≥ 3) through
25 ‘intermolecular’ metalꢀhydride interactions, especially for the
nonꢀCpꢀtype hydrido complexes, which may be ascribed to the
steric unsaturation of the large fꢀelement ions and their strong
Lewis basic nature, as well as the small steric bulkiness of the
hydride ligand.7 The stoichiometric reactions of these
30 polyhydrides show that different coordinate hydride ligands
display different reactivity and the polynuclear skeletons usually
75 ppm,7a [(NCN)LuH(THF)3][BPh4] at
δ
12.28 ppm,7b and
[(Ap*Lu)3(ꢁ2ꢀH)3(ꢁ3ꢀH)2(CH2SiMe3)(THF)2] at δ 9.08, 12.25, and
12.37 ppm).11b Colorless single crystals of 2ꢀY and 2ꢀLu were
a
State Key Laboratory of Polymer Physics and Chemistry, Changchun
Ph
Ph
Ph
Ph
Ph
Ph
N
P
P
N
Institute of Applied Chemistry, Chinese Academy of Sciences, 5625
35 Renmin street, Changchun 130022, China. Fax: +86 431 85262774; Tel:
+86 431 85262773; Eꢀmail: dmcui@ciac.ac.cn
Ph
N
H
P
P
P
Ph
2.5 PhSiH3 or H2 (1 bar)
toluene
H
H
N
N
N
Ln
Ln
Ln
N
Ph
Ph
P
Y: 25 o
Lu: 60 oC
C
Ph
Ph
b
N
Si
Si
N
H
University of Chinese Academy of Sciences, Changchun Branch,
Changchun 130022, China.
College of Material Science and Engineering, Jilin University,
c
1-Ln
2-Ln
Ln = Y, Lu
40 Changchun 130022, China.
d
Scheme 1. Synthesis of neutral tetrahydrido complexes 2ꢀLn.
Medicinal Materials Synthesis & Design Lab
，College of Medicine,
Changchun University of Chinese Medicine, Changchun 130022, China.
e
G. A. Razuvaev Institute of Organometallic Chemistry of Russian
Ph
Ph
N
Academy of Sciences Tropinina 49, GSPꢀ445, 603950 Nizhny Novgorod
Ph
N
N
O
H
N
N
Ph
Ph
P
P
P
Ph
Ph
N
Ph
Ph
H
P
P
THF / 25 o
-H2
C
P
45 Russia
H
H
N
N
Y
Y
H
Y
Y
f
N
N
P
Nizhny Novgorod State University, 23 Gagarin av., 603950, Nizhny
Novgorod, Russia
Electronic Supplementary Information (ESI) available: Experimental
Ph
H
Ph
O
Ph
Ph
P
H
N
Ph
N
Ph
†
2-Y
3-Y
section, NMR, and crystallographic data. CCDC 1020089 (2ꢀY) 1020088
50 (2ꢀLu), 1020087 (3ꢀY). For ESI and crystallographic data in CIF See
DOI: 10.1039/b000000x/
80
Scheme 2. Synthesis of neutral trihydrido complex 3ꢀY.
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Fig. 2 ORTEP plot of 3ꢀY with thermal ellipsoids at the 35% probability
level. Hydrogen atoms except bridging hydrides and iPr groups have been
omitted for clarity. Selected bond distances (Å): Y1···Y2 3.3681(8), Y1–
10 C1 2.513(7), Y1–H1 2.12(6), Y1–H2 2.19(7), Y1–H3 2.30(6), Y2–H1
2.22(6), Y2–H2 2.18(7), Y2–H3 2.06(6).
Fig. 1 ORTEP plot of 2ꢀLu with thermal ellipsoids at the 35% probability
level. Hydrogen atoms except bridging hydrides and iPr groups have been
omitted for clarity. Selected bond distances (Å): Lu1–N2 2.276(12), Lu1–
N1 2.507(15), Lu1···P1 2.982(4), Lu1···Lu1A 3.104(3), Lu1–H1 2.0622.
5
obtained by slow evaporation of a mixture of toluene and benzene
at room temperature. The Xꢀray diffraction study revealed that
their lattice parameters were almost identical and their structures
bridging hydrides in rareꢀearth metal chemistry, although the
similar structures [LMꢀ(ꢁ2ꢀH)4ꢀML] have been reported in Zr, Re,
Ta and Hf complexes.14
15 were refined in the uncommon space group I222.12 Hence the
final molecular structures were solved from one quarter initially
after 222 symmetry operator.13 The molecular structure of
complex 2ꢀLu is shown in Fig. 1 (Fig.S2 for 2ꢀY), in which the
two Lu3+ are bridged by the unprecedented four ꢁ2ꢀH ligands,
35
The poor solubility of 2ꢀLn in aromatic solvents arouse great
difficulty in NMR characterization, so we could not provide the
convincing 13C NMR data. However 2ꢀY turned out to be highly
soluble in THF. Removal of the THF solvent and drying in vacuo
1
gave a residue that was reꢀdissolved by THFꢀd8. The obtained H
20 additionally, each Lu3+ is coordinated by the anionic 40 NMR spectrum presented, surprisingly, a set of resonances
{N[Ph2PNC6H3(iPr)2]2}− ligand in a κ3ꢀNNN mode. No THF was
found to coordinate to the metal centers owing to the steric bulky
NPNPN ligand. It is noteworthy that two NPNPN planes are
almost perpendicular, as the thus staggered conformation is low
different from that of 2ꢀY, suggesting the formation of a new
compound 3ꢀY (Scheme 2). Similar to its congener 2ꢀY, the Y−H
signals of 3ꢀY could not be distinguished from the aromatic H
signals. Fortunately we successfully isolated high quality single
25 energy and more stable. The Lu−H bond lengths are 2.062 Å and 45 crystals of 3ꢀY suitable for the Xꢀray study, which allowed us to
2.112 Å, which are comparable with those found in [Cp’LuH2]4
(1.85(3)−2.44(6) Å),6h and [(NCN)LuH(THF)2]2[BPh4]2 (2.01(5),
2.15(5) Å).7b The Lu···Lu distance (3.104(3) Å) is the shortest
among the values reported for neutral hydride complexes, but
determine the structure of 3ꢀY with defined hydride localization.
Complex 3ꢀY remains the dimeric structure like its congener but
contains two THF molecules, where one Y3+ ion is bonded to the
monoanionic κ3ꢀNPNPN ligand while the other Y3+ ion is
30 longer than that in the cationic example (2.9270(6) Å).9 So far, 2ꢀ 50 coordinated by the dianionic κ3ꢀCPNPN ligand arising from the
Lu represents the first binuclear neutral complex with four ꢁ2ꢀ
Ph−H (sp2) activation of the NPNPN ligand. The two Y3+ ions are
Ph
Ph
Ph
N
Ph
P
N
H
N
P
Ph
H
Ph
H
H
Y
P
Y
N
P
Ph
N
Ph
Ph
Ph
Ο
H
N
Ph
Ph
Ph
Ph
N
Ph
TS'
P
Ph
H
N
P
N
P
Ph
Ph
N
Ph
N
H
H
Y
Y
Ph
Ph
N
Ph
Ph
P
H
N
Ph
Ph
Ph
Ph
Ph
N
P
Ph
Ph
H
H
H
N
P
N
Y
P
P
Y
N
Ph
H
H
N
Ph
Ph
Ph
6.8
1.9
2-Y
Y
Ph
Y
P
Ph
N
P
N
P
H2
H
P
Ph
Ph
Ο
N
N
N
Ph
Ph
Ο
Ph
H
0.0
N
Ph
Ph
Ph
Ph
b'
Ph
c'
-9.7
-9.9
Ph
Ph
Ph
Ο
-13.7
Ph
N
N
H2
P
H
-18.9
Ο
H
-21.6
N
N
P
Ph
H
H
Ph
Ph
Y
P
Y
Ph
N
P
Ph
Ph
N
Ph
Ph
N
N
Ph
Ph
Ph
Ph
Ph
P
N
Ο
H
Ο
H
Ο
Ο
N
Ph
P
N
P
Ph
P
N
H
H
H
H
Ph
P
Ph
Ph
Ph
Ph
Y
Y
Y
Y
P
N
Ph
Ph
N
TS
N
Ph
Ph
Ph
N
Ph
Ph
P
N
H
Ο
P
H
N
Ο
N
Ο
Ph
H
Ph
Ph
Ph
Ph
Ph
a
Ph
3-Y
H
H
P
Ph
N
Y
P
Y
N
Ph
N
P
H
P
Ph
Ph
Ο
N
N
Ph
Ph
b
Ph
Ph
Fig.3 Calculated energy profile from 2ꢀY to 3ꢀY.
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Jochmann and D. W. Stephan, Angew. Chem., Int. Ed., 2013, 52,
9831.
55 4. (a) T. Shima, S. Hu, G. Luo, X. Kang, Y. Luo and Z. Hou, Science,
2013, 340, 1549. (b) S. Hu, T. Shima and Z. Hou, Nature, 2014, 512,
413; (c) W. Sattler and G. Parkin, J. Am. Chem. Soc., 2011, 133,
9708.
connected by three ꢁ2ꢀbridged hydride ligands, generating a Y2H3
core (Fig. 2), which is similar to those found in the cationic
8b
complexes [(Me5TRENCH2)Luꢀ(ꢁ2ꢀH)3Lu(Me6TREN)][X]2 and
[(Me3TACDꢀCH2)Luꢀ(ꢁ2ꢀH)3Lu(Me4TACD)][A]2.9 The Y···Y
5
distance is 3.368 Å, significantly shorter than those in the
polynuclear hydrides ([Y(Me3TACD)H2]3, 3.516(1) Å;6f
5. (a) M. Konkol and J. Okuda, Coord. Chem. Rev. 2008, 252, 1577; (b)
60
P. M. Zeimentz, S. Arndt, B. R. Elvidge and J. Okuda, Chem. Rev.,
2006, 106, 2404; (c) Z. Hou and Y. Wakatsuki, Coord. Chem. Rev.,
2002, 231, 1. (d) F. T. Edelmann, D. M. M. Freckmann and H.
Schumann, Chem. Rev., 2002, 102, 1851; (e) S. Arndt and J. Okuda,
Chem. Rev., 2002, 102, 1953.
[TpMe Y(ꢁꢀH)2]4,
3.5329(5)−3.7114(6)
Å;6g
[(η5ꢀ
2
C5Me4SiMe3)Y(ꢁꢀH)2]4, 3.460−3.621 Å6i). Obviously, THF
triggered the intramolecular phenyl C–H bond activation by the
10 hydride ligand, leading to hydrogen extrusion and the formation
of 3ꢀY.
65 6. For examples of rareꢀearth dihydride complexes, see: (a) T. Shima,
M. Nishiura and Z. Hou, Organometallics, 2011, 30, 2513; (b) M.
Nishiura, J. Baldamus, T. Shima, K. Mori and Z. Hou, Chem. Eur. J.,
2011, 17, 5033; (c) J. Cheng, T. Shima and Z. Hou, Angew. Chem.,
Int. Ed., 2011, 50, 1857; (d) D. M. Lyubov, C. Doring, S. Y. Ketkov,
To gain more insight into the reaction pathways for 2ꢀY
transferring to 3ꢀY, a DFT calculation was carried out using the
B3PW91 functional (Fig. 3), where the isopropyl groups were
15 neglected. The coordination of a THF molecule to the Y3+ ion of
complex 2ꢀY breaks one bridging H to give complex a bearing a
terminal hydride ligand. Adopting a second THF generates
complex b. The activation of the ortho C−H bond of phenyl
substituent on P by the terminal hydride ligand via transition state
20 TS releases H2 to afford complex 3ꢀY. Alternatively, the rotation
around P−N bond makes one phenyl group on P adjacent to Y−H
bond (complex b′), which arouses dehydrogenation to give the
final product via transition state TS′ and the intermediate c′. The
free energy of the transition state TS is 4.9 kcal/mol lower than
25 that of TS′, indicating that the first reaction pathway is preferred.
In summary, we have demonstrated that the bulky
N[Ph2PNC6H3(iPr)2]2 moiety can serve as an excellent supporting
ligand to stabilize the rareꢀearth hydride species, resulting in the
first neutral binuclear fꢀelement metal based dihydride complexes
30 bearing four ꢁ2ꢀbridging hydride ligands. In addition, THF can
behave as a trigger to initiate the intramolecular activation of the
very stable phenyl group sp2 C−H bond by releasing H2, giving
an unprecedented dinuclear arylꢀhydride complex with three ꢁ2ꢀ
bridging hydride ligands.
70
75
80
R. Kempe and A. A. Trifonov, Chem. Eur. J., 2011, 17, 3824; (e) J.
Cheng, M. J. Ferguson and J. Takats, J. Am. Chem. Soc., 2010, 132, 2;
(f) M. Ohashi, M. Konkol, I. Del Rosal, R. Poteau, L. Maron and J.
Okuda, J. Am. Chem. Soc., 2008, 130, 6920; (g) J. Cheng, K. Saliu, G.
Y. Kiel, M. J. Ferguson, R. McDonald and J. Takats, Angew. Chem.,
Int. Ed., 2008, 47, 4910; (h) O. Tardif, M. Nishiura and Z. Hou,
Organometallics, 2003, 22, 1171; (i) Y. Luo, J. Baldamus, O. Tardif
and Z. Hou, Organometallics, 2005, 24, 4362; (j) D. Cui, O. Tardif
and Z. Hou, J. Am. Chem. Soc., 2004, 126, 1312.
7. (a) J. Cheng, H. Wang, M. Nishiura and Z. Hou, Chem. Sci., 2012, 3,
2230; (b) J. Cheng and Z. Hou, Chem. Commun., 2012, 48, 814.
8. (a) J. Zhou, J. Chu, Y. Zhang, G. Yang, X. Leng and Y. Chen,
Angew. Chem., Int. Ed., 2013, 52, 4243; (b) A. Venugopal, W. Fegler,
T. P. Spaniol, L. Maron and J. Okuda, J. Am. Chem. Soc., 2011, 133,
17574.
85 9. W. Fegler, A. Venugopal, T. P. Spaniol, L. Maron and J. Okuda,
Angew. Chem., Int. Ed., 2013, 52, 7976.
10. W. Rong, D. Liu, H. Zuo, Y. Pan, Z. Jian, S. Li and D. Cui,
Organometallics, 2013, 32, 1166.
11. (a) E. Lu, Y. Chen and X. Leng, Organometallics, 2011, 30, 5433;
90
95
(b) D. M. Lyubov, C. Döring, G. K. Fukin, A. V. Cherkasov, A. S.
Shavyrin, R. Kempe and A. A. Trifonov, Organometallics, 2008, 27,
2905.
12. We did not deeply discuss the structure of 2ꢀY here because the
checkcif report of 2ꢀY has a mistake in level A (Supporting
Information).
13. Point group 222 has three mutuallyꢀperpendicular twoꢀfold rotation
axes.
14. (a) H. Kulinna, T. P. Spaniol, L. Maron and J. Okuda, Inorg. Chem.,
2012, 51, 12462; (b) S. C. Mayo, M. Bown and V. K. Lloyd, Acta
Crystallogr. Sect. C 1994, 50, 367; (c) J. Ballmann, F. Pick, L. Castro,
M. D. Fryzuk and L. Maron, Organometallics, 2012, 31, 8516; (d) M.
D. Fryzuk, S. A. Johnson and S. J. Rettig, Organometallics, 2000, 19,
3931; (e) J. G. Hinman, K. AbdurꢀRashid, A. J. Lough and R. H.
Morris, Inorg. Chem., 2001, 40, 2480; (f) F. A. Cotton and R. L. Luck,
Inorg. Chem., 1989, 28, 4522.
35
This work was partially supported by The National Natural
Science Foundation of China for project Nos. 51321062,
21374112 and 21361140371 and the Ministry of education and
science of the Russian Federation (the agreement of August 27,
2013 № 02.В.49.21.0003 between The Ministry of education and
100
105
40 science of the Russian Federation and Lobachevsky State
University of Nizhny Novgorod).
Notes and references
1. R. H. Crabtree. The Organometallic Chemistry of The Transition
Metals, Ed. 6th. Wiley. 2014.
45 2. (a) S. Harder, Chem Commun., 2012, 48, 11165; (b) S. Harder, J.
Spielmann, J. Intemann and H. Bandmann, Angew. Chem., Int. Ed.,
2011, 50, 4156.
3. (a) S. J. Bonyhady, S. P. Green, C. Jones, S. Nembenna and A.
Stasch, Angew. Chem., Int. Ed., 2009, 48, 2973; (b) C. Boone, I.
50
Korobkov and G. I. Nikonov, ACS Catal., 2013, 3, 2336; (c) V. K.
Chidara and G. Du, Organometallics, 2013, 32, 5034; (d) B.
Chatterjee and C. Gunanathan, Chem. Commun., 2014, 50, 888; (e) P.
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Table of contents entry:
Neutral binuclear rare-earth metal complexes with four µ2-bridging
hydrides
Weifeng Rong, Dongliang He, Meiyan Wang, Zehuai Mou, Jianhua Cheng, Changguang Yao, Shihui Li, Alexander A. Trifonov*,
Dmitrii M. Lyubov and Dongmei Cui*
Ph
Ph
Ph
Ph
N
Ph
Ph
N
N
Ph
Ph
N
H
N
N
P
N
P
N
O
H
H
H
THF, 25 o
-H2
C
P
N
P
H
H
Y
Y
Y
Y
N
Ph
P
P
Ph
Ph
Ph
Ph
Ph
Ph
P
O
P
H
N
N
The first neutral dimeric rareꢀearth metal hydride complexes containing quadruply bridged hydrido ligands were
prepared, in which the intramolecular activation of the stable phenyl group sp2 C−H bond triggered by a THF molecule
has been observed.