Synthesis, characterization, and reactivity of The thermally stable lutetium tris(alkyl) complex (tBu2bpy)Lu(CH 2SiMe3)3

Article abstract of DOI:10.1021/om701159d

4,4′-Di-tert-butyl-2,2′-bipyridyl (^tBu ₂bpy) stabihzes the thermally sensitive [Lu(CH₂SiMe ₃)₃] unit, giving the isolable lutetium(III) (trimethylsilyl)methyl complex (^tBu₂bpy)Lu(CH ₂SiMe₃)₃ (4). This tris(alkyl) complex does not undergo alkane elimination, and it readily reacts with Ph₃COH, H₂N-2,6-ⁱPr₂-C₆H₃, H ₂N-2,4,6-^tBu₃-C₆H₂, and N,N′-dicyclohexylcarbodiimide (DCHCDI) to afford a variety of Lu(III) tris(alkoxide), tris(amide), mono(amide) bis(alkyl), and amidinate bis(alkyl) compounds. Reaction of the amide bis(alkyl) complex (^tBu ₂bpy)Lu(NH-2,4,6-^tBu₂-C₆H ₂)(CH₂SiMe₃)₂ (7) with triphenylphosphine oxide gives (Ph₂PO)₂Lu(NH-2,4,6- ^tBu₃-C₆H₂)(CH₂SiMe ₃)₂ (9), showing that the bidentate ^tBu ₂bpy ligand can be displaced.

Full text of DOI:10.1021/om701159d

Organometallics 2008, 27, 1299–1304
1299
Synthesis, Characterization, and Reactivity of the Thermally Stable
Lutetium Tris(alkyl) Complex (tBu2bpy)Lu(CH2SiMe3)3
Jason D. Masuda, Kimberly C. Jantunen, Brian L. Scott, and Jaqueline L. Kiplinger*
Los Alamos National Laboratory, Mail Stop J514, Los Alamos, New Mexico 87545
ReceiVed NoVember 17, 2007
4,4′-Di-tert-butyl-2,2′-bipyridyl (tBu2bpy) stabilizes the thermally sensitive [Lu(CH2SiMe3)3] unit, giving
the isolable lutetium(III) (trimethylsilyl)methyl complex (tBu2bpy)Lu(CH2SiMe3)3 (4). This tris(alkyl)
complex does not undergo alkane elimination, and it readily reacts with Ph3COH, H2N-2,6-iPr2-C6H3,
H2N-2,4,6-tBu3-C6H2, and N,N′-dicyclohexylcarbodiimide (DCHCDI) to afford a variety of Lu(III)
tris(alkoxide), tris(amide), mono(amide) bis(alkyl), and amidinate bis(alkyl) compounds. Reaction of the
amide bis(alkyl) complex (tBu2bpy)Lu(NH-2,4,6-tBu3-C6H2)(CH2SiMe3)2 (7) with triphenylphosphine oxide
gives (Ph3PdO)2Lu(NH-2,4,6-tBu3-C6H2)(CH2SiMe3)2 (9), showing that the bidentate tBu2bpy ligand can
be displaced.
numerous examples of complexes containing AndN, AndP,
and AndO linkages.1,7
Introduction
In our recent efforts to prepare robust lanthanide tris(alkyl)
complexes as precursors to alkylidene complexes,8 we discov-
ered that lutetium(III) alkyl fragments supported by terpyridines
are not stable and undergo facile 1,3-alkyl migration, resulting
in dearomatization and functionalization of the terpyridine
ligand, as illustrated in eq 1.
Terminal alkylidene (MdCR2), imido (MdNR), phosphin-
idene (MdPR), and oxo (MdO) complexes are pervasive in
transition-metal chemistry.1 Although there have been reports
of lanthanide systems containing bridging or capping imido2
and oxo3 ligands, as well as numerous lanthanide carbene
complexes,4 terminal oxo, phosphinidene, and alkylidene func-
tional groups are noticeably absent for the lanthanide elements.5
Recently, however, the lutetium imido complexes LuCl2-
(ImNDipp)(THF)3 and (C8H8)Lu(ImNDipp)(THF)2 (where ImNDipp
) 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imide), were re-
ported by Tamm and co-workers.6 The overall lack of these
species is curious, since the related actinide series displays
(1)
* To whom correspondence should be addressed. Tel: 505-665-9553.
Fax: 505-667-9905. E-mail: kiplinger@lanl.gov.
Although this observation clearly demonstrated that the
terpyridine ligand is not an ideal platform for this chemistry,
density functional theory calculations suggested that the forma-
tion of a lutetium alkylidene functional group is energetically
viable from a thermodynamic standpoint.8 Toward this goal,
we now report that 4,4′-di-tert-butyl-2,2′-bipyridyl (tBu2bpy)
(1) (a) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds;
Wiley-Interscience: New York, 1988. (b) Wigley, D. E. Prog. Inorg. Chem.
1994, 42, 239–482. (c) Schrock, R. R. J. Chem. Soc., Dalton Trans. 2001,
2541–2550. (d) Schrock, R. R. Chem. ReV. 2002, 102, 145–179, and
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1999, 18, 1578–1579. (b) Gordon, J. C.; Giesbrecht, G. R.; Clark, D. L.;
Hay, P. J.; Keogh, D. W.; Poli, R.; Scott, B. L.; Watkin, J. G. Organome-
tallics 2002, 21, 4726–4734. (c) Chan, H. S.; Li, H. W.; Xie, Z. Chem.
Commun. 2002, 652–653. (d) Cui, D.; Nishiura, M.; Hou, Z. Angew. Chem.,
Int. Ed. 2005, 44, 959–962.
(7) For recent AndN examples, see: (a) Arney, D. S. J.; Burns, C. J.
J. Am. Chem. Soc. 1995, 117, 9448–9460, and references therein. (b) Evans,
W. J.; Kozimor, S. A.; Ziller, J. W. Science 2005, 309, 1835–1838. (c)
Hayton, T. W.; Boncella, J. M.; Scott, B. L.; Batista, E. R.; Hay, P. J.
J. Am. Chem. Soc. 2006, 128, 10549–10559. (d) Ephritikhine, M. Dalton
Trans. 2006, 2501–2516, and references therein. (e) Graves, C. R.; Scott,
B. L.; Morris, D. E.; Kiplinger, J. L. J. Am. Chem. Soc. 2007, 129, 11914–
11915. For AndP examples, see: (f) Duttera, M. R.; Day, V. W.; Marks,
T. J. J. Am. Chem. Soc. 1984, 106, 2907–2912. (g) Arney, D. S. J.; Schnabel,
R. C.; Scott, B. L.; Burns, C. J. J. Am. Chem. Soc. 1996, 118, 6780–6781.
For recent AndO examples, see: (h) Andrews, L.; Zhou, M.; Liang, B.;
Li, J.; Bursten, B. E. J. Am. Chem. Soc. 2000, 122, 11440–11449. (i)
Vaughn, A. E.; Bassil, D. B.; Barnes, C. L.; Tucker, S. A.; Duval, P. B.
J. Am. Chem. Soc. 2006, 128, 10656–10657, and references therein. (j)
Berthet, J. C.; Siffredi, G.; Thuery, P.; Ephritikhine, M. Chem. Commun.
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(4) (a) Arduengo, A. J.; Tamm, M.; McLain, S. J.; Calabrese, J. C.;
Davidson, F.; Marshall, W. J. J. Am. Chem. Soc. 1994, 116, 7927–7928.
(b) Schumann, H.; Glanz, M.; Winterfeld, J.; Hemling, H.; Kuhn, N.; Kratz,
T. Angew. Chem., Int. Ed. 1994, 33, 1733–1734. (c) Herrmann, W. A.;
Munck, F. C.; Artus, G. R. J.; Runte, O.; Anwander, R. Organometallics
1997, 16, 682–688. (d) Aparna, K.; Ferguson, M.; Cavell, R. G. J. Am.
Chem. Soc. 2000, 122, 726–727. (e) Cantat, T.; Jaroschik, F.; Nief, F.;
Mézailles, N.; Le Floch, P. Chem. Commun. 2005, 5178–5180. (f) Cantat,
T.; Jaroschik, F.; Ricard, L.; Le Floch, P.; Nief, F.; Mézailles, N.
Organometallics 2006, 25, 1329–1332. (g) Dietrich, H. M.; Törnroos; K,
W.; Anwander, R. J. Am. Chem. Soc. 2006, 128, 9298–9299. (h) Arnold,
P. L.; Liddle, S. T. Organometallics 2006, 25, 1485–1491, and references
therein.
(5) (a) Giesbrecht, G. R.; Gordon, J. C. Dalton Trans. 2004, 2387–
2393. (b) Clark, D. L.; Gordon, J. C.; Hay, P. J.; Poli, R. Organometallics
2005, 24, 5747–5787.
(6) Panda, T. K.; Randoll, S.; Hrib, C. G.; Jones, P. G.; Bannenberg,
T.; Tamm, M. Chem. Commun. 2007, 5007–5009.
(8) Jantunen, K. C.; Scott, B. L.; Hay, P. J.; Gordon, J. C.; Kiplinger,
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10.1021/om701159d CCC: $40.75
2008 American Chemical Society
Publication on Web 02/22/2008

1300 Organometallics, Vol. 27, No. 6, 2008
Masuda et al.
enables the stabilization of the thermally sensitive
[Lu(CH2SiMe3)3] unit, giving the isolable lutetium(III) tris(alkyl)
complex (tBu2bpy)Lu(CH2SiMe3)3 (4). Herein, we describe the
preparation, characterization, and chemistry of this new lutetium
tris(alkyl) system and its ability to stabilize multiply bonded
functional groups.
Results and Discussion
Reaction of [Lu(CH2SiMe3)3(THF)2] (1) with 1 equiv of 4,4′-
di-tert-butyl-2,2′-bipyridyl (tBu2bpy) at ambient temperature
affords the neutral lutetium tris(alkyl) complex (tBu2bpy)-
Lu(CH2SiMe3)3 (4) as an orange powder in 83% isolated yield
(eq 2).
(2)
Figure 1. Molecular structure of 4 (left) with thermal ellipsoids
projected at the 50% probability level. Selected bond distances (Å)
and angles (deg): Lu(1)-N(1) ) 2.437(7), Lu(1)-N(2) ) 2.427(7),
Lu(1)-C(19) ) 2.369(8), Lu(1)-C(20) ) 2.358(9), Lu(1)-C(21)
) 2.318(9); N(1)-Lu(1)-N(2) ) 65.7(2), Lu(1)-C(19)-Si(2) )
139.5(5), Lu(1)-C(20)-Si(3) ) 120.8(4), Lu(1)-C(21)-Si(1) )
126.1(5).
Diagnostic 1H NMR spectroscopic data (benzene-d6, 23 °C)
demonstrate the formation of 4 with resonances centered at δ
9.06, 7.67, and 6.86 ppm for the three pyridyl protons, a singlet
t
at δ 0.96 ppm for the two Bu groups on the bipyridyl ligand,
and signals at δ 0.31 and -0.08 ppm corresponding to the
methyl and methylene protons, respectively, on the three
equivalent -CH2SiMe3 groups. Whereas the THF complex 1
is thermally sensitive, decomposing if not stored below -35
°C,9 (tBu2bpy)Lu(CH2SiMe3)3 (4) is stable as a solid at room
temperature for at least 3 months and for 2 weeks in solution
(benzene-d6). However, the complex does decompose over a
24 h period when heated at 60 °C in benzene-d6. For comparison
purposes, even the recently reported (iPr-trisox)Lu(CH2SiMe3)3
was observed to decompose over a few days at ambient
temperature.10 The neutral lutetium tris(alkyl) system [(12-
crown-4)Lu(CH2SiMe3)3] has also been noted to have enhanced
thermal stability relative to the THF complex 1.11 Thus, complex
4 may serve as a complement to the crown ether derivative.
Single crystals of complex 4 suitable for X-ray diffraction
analysis were obtained from a concentrated pentane solution at
-35 °C. Similar to [Lu(CH2SiMe3)3(THF)2] (1),12 the molecular
structure of 4 reveals a five-coordinate geometry about the
lutetium(III) center, which is best described as distorted trigonal
bipyramidal with the equatorial plane being defined by two
metal-bound (trimethylsilyl)methyl groups and one of the
bipyridyl nitrogens (Figure 1). The two Lu-Nbpy dative bonds
have distances of 2.437(7) and 2.427(7) Å, which are compa-
rable to those reported for other structurally characterized
lutetium bipyridyl complexes. For example, [(C5Me5)Lu(NH-
2,6-iPr2-C6H3)(CH2SiMe3)(bpy)], [(C5Me5)Lu(NH-2,6-iPr2-C6-
H3)2(bpy)], [(C5Me5)Lu(Ct CPh)2(bpy)(NC5H5)], [{(C5Me5)Lu-
(Ct CPh)(bpy)}2(µ-η2:η2-PhC4Ph)], [(C5Me5)Lu(NH-2,6-iPr2-
C6H3){OCH(CH2SiMe3)(C10H7N2)}], and [(C5Me5)Lu{OC-
(SiMe3)dCH2}{OCH(CH2SiMe3)(C10H7N2)}] have Lu-Nbpy
bond distances ranging between 2.360(3) and 2.500(7) Å.13 The
Lu-CH2 distances (Lu(1)-C(19) ) 2.369(8) Å, Lu(1)-C(20)
) 2.358(9) Å, Lu(1)-C(21) ) 2.318(9) Å) and Lu-CH2-Si
angles (Lu(1)-C(19)-Si(2) ) 139.5(5)°, Lu(1)-C(21)-Si(1)
) 126.1(5)°, Lu(1)-C(20)-Si(3) ) 120.8(4)°) are within
previously reported ranges of 2.30–2.40 Å and 115–149°
typically observed for Lu-CH2SiMe3 complexes.8–12,13a,14
The reactivity of the lutetium tris(alkyl) system 4 was probed,
and a summary of its behavior is presented in Scheme 1. As
evidenced by 1H NMR spectroscopy, thermolysis of 4 (benzene-
d6, 60 °C, 24 h) results in the formation of SiMe4 and
decomposition to intractable materials even in the presence of
pyridine, 2,2′-bipyridine, and 2-(diphenylphosphino)-2′-(dim-
ethylamino)biphenyl (to capture any potential (tBu2bpy)-
Lu(dCHR) species).
The alkyl groups in 4 are susceptible to protonation by
amines, as demonstrated by the reaction of 4 with 3 equiv of
H2N-2,6-iPr2-C6H3 in toluene to give the tris(amide) complex
5 in 76% isolated yield. No evidence was seen for the formation
of any imido-containing lutetium complexes, even at elevated
temperatures (toluene-d8, 90 °C, 24 h). Attempts were made to
prepare the corresponding mono- and bis(amide) species
(tBu2bpy)Lu(NHAr)(CH2SiMe3)2 and (tBu2bpy)Lu(NHAr)2-
1
(CH2SiMe3) (Ar ) 2,6-iPr2-C6H3); however, H NMR spec-
troscopy showed that the tris(amide) 5 was produced irrespective
of the amount of aniline reacted with complex 4. Similar
chemistry was observed between 4 and alcohols, with reaction
(9) (a) Schumann, H.; Müller, J. J. Organomet. Chem. 1979, 169, C1–
C4. (b) Arndt, S.; Voth, P.; Spaniol, T. P.; Okuda, J. Organometallics 2000,
19, 4690–4700. (c) Rufanov, K. A.; Freckmann, D. M. M.; Kroth, H. J.;
Schutte, S.; Schumann, H. Z. Naturforsch. 2005, 60b, 533–537.
(10) Lukešová, L.; Ward, B. D.; Bellemin-Laponnaz, S.; Wadepohl, H.;
Gade, L. H. Organometallics 2007, 26, 4652–4657.
(14) For examples, see: (a) Schumann, H.; Genthe, W.; Bruncks, N.;
Pickardt, J. Organometallics 1982, 1, 1194–1200. (b) Cameron, T. M.;
Gordon, J. C.; Michalczyk, R.; Scott, B. L. Chem. Commun. 2003, 2282–
2283. (c) Tardif, O.; Nishiura, M.; Hou, Z. Tetrahedron 2003, 59, 10525–
10539. (d) Zhang, L.; Suzuki, T.; Luo, Y.; Nishiura, M.; Hou, Z. Angew.
Chem., Int. Ed. 2007, 46, 1909–1913. (e) Yang, Yi.; Liu, B.; Lv, K.; Gao,
W.; Cui, D.; Chen, X.; Jing, X. Organometallics 2007, 26, 4575–4584. (f)
Konkol, M.; Spaniol, T. P.; Kondracka, M.; Okuda, J. Dalton Trans. 2007,
4095–4102. (g) Liu, B.; Yang, Y.; Cui, D.; Tang, T.; Chen, X.; Jing, X.
Dalton Trans. 2007, 4252–4254. (h) Wang, D.; Cui, D.; Miao, W.; Li, S.;
Huang, B. Dalton Trans. 2007, 4576–4581.
(11) Arndt, S.; Zeimentz, P. M.; Spaniol, T. P.; Okuda, J.; Honda, M.;
Tatsumi, K. Dalton Trans. 2003, 3622–3627.
(12) Schumann, H.; Freckmann, D. M. M.; Dechert, S. Z. Anorg. Allg.
Chem. 2002, 628, 2422–2426.
(13) (a) Cameron, T. M.; Gordon, J. C.; Scott, B. L. Organometallics
2004, 23, 2995–3002. (b) Cameron, T. M.; Gordon, J. C.; Scott, B. L.;
Tumas, W. Chem. Commun. 2004, 1398–1399.

A Thermally Stable Lutetium Tris(alkyl) Complex
Organometallics, Vol. 27, No. 6, 2008 1301
Scheme 1. Reactivity Displayed by the Lu(III) Tris(alkyl)
Complex (tBu2bpy)Lu(CH2SiMe3)3 (4)
stabilized by multidentate ancillary ligands such as cyclopenta-
dienyls,13,14c,19 amidinates,20 bis(oxazolinates),21 ꢀ-diketimi-
nates,22 amido-phosphines,14d,g,23 anilido-pyridine-imines,11
amido-pyridines,8 and imino-pyrrolides.14e As such, complex
7 represents a rare example of a lanthanide bis(alkyl) complex
supported by a monodentate anionic ancillary ligand and, to
the best of our knowledge, the first example of a lutetium metal
center supported by the sterically demanding 2,4,6-tri-tert-
butylamide ligand. Other examples are limited to the aryloxide-
supported lutetium bis(alkyl) ate complex [(Me3SiCH2)2Lu(O-
2,6-tBu2-C6H3)2][Li(THF)4](THF)2 mentioned above,17 the
silanolate-supported bis(alkyl) complexes [(Me3SiCH2)2Ln-
{µ,η2-OSi(OtBu)3}]2 (Ln ) Tb, Lu),24 and the anilide-sup-
ported bis(alkyl) complexes [2,6-iPr2-C6H3N(SiMe3)]Ln(CH2Si-
Me3)2(THF) (Ln ) Ho, Lu).25
Single crystals of 7 suitable for X-ray diffraction analysis
were obtained from a concentrated pentane/toluene solution at
-35 °C. The molecular structure of compound 7 is available in
Figure 3 and shows that the lutetium metal center is coordinated
in a distorted-trigonal-bipyramidal fashion by the bidentate
tBu2bpy, two alkyl groups, and the bulky amide ligand. Clearly,
this geometry seems to be common to all the (tBu2bpy)LuX3
systems presented in this work and the Lu-Nbpy dative bond
distances (2.467(3) and 2.453(3) Å) are in agreement with those
observed in the other (tBu2bpy)LuX3 systems discussed above.
The most interesting aspect of the structure is the Lu-Nanilide
interaction, with a bond distance of 2.144(3) Å and the nearly
linear Lu-N-CAr angle of 157.7(2)°, which compare well with
those reported for other structurally characterized lutetium aryl
amide complexes, including complex 5.13 Finally, the metrics
associated with the two Lu-CH2SiMe3 fragments (2.345(4),
2.363(4) Å and 116.25(17), 128.68(18)°) are similar to those
found in other lutetium bis(alkyl) complexes.8,14c,d,17,19–25
Efforts to promote alkane elimination from 7 were unsuc-
cessful. Whereas no reaction was observed upon heating 7
(benzene-d6, 60 °C) for 24 h, thermolysis for 72 h resulted in
the formation of SiMe4 and decomposition, as monitored by
1H NMR spectroscopy. Interestingly, in the presence of
Ph3PdO, alkane elimination is also not observed but rather
of 4 and 3 equiv of Ph3COH affording the tris(alkoxide)
derivative 6.
Figure 2 displays the molecular structures for both the
tris(amide) and tris(alkoxide) complexes 5 and 6, respectively,
which both feature a lutetium(III) metal center coordinated in
a distorted-trigonal-bipyramidal fashion by a bidentate tBu2bpy
and three amide or alkoxide ligands, respectively. In both
complexes, the Lu-Nbpy dative bond distances (5, 2.423(4) and
2.444(4) Å; 6, 2.456(3) and 2.432(3) Å) compare favorably with
those observed in the tris(alkyl) complex 4. The Lu-Nanilide bond
distances (2.167(4), 2.207(4), 2.167(4) Å) and Lu-N-CAr
angles (142.5(4), 145.6(4), 153.5(4)°) in complex 5 are com-
parable to the Lu-Nanilide interactions reported for the structur-
ally related [(C5Me5)Lu(NH-2,6-iPr2-C6H3)(CH2SiMe3)(bpy)]
(2.22(1) Å, 145.8(9)°), [(C5Me5)Lu(NH-2,6-iPr2-C6H3)2(bpy)]
(2.208(7) Å, 150.9(6)°; 2.209(7) Å, 143.2(5)°), and [(C5Me5)Lu-
(NH-2,6-iPr2-C6H3){OCH(CH2SiMe3)(C10H7N2)}] (2.238(4) Å,
135.8(3)°).13
Similarly, the metrical parameters for the Lu-O interactions
in 6 (2.030(2), 2.032(2), 2.059(2) Å) are also in agreement with
those found in other crystallographically characterized lutetium
alkoxide complexes and can be compared to the average Lu-O
distances of 2.044(4), 2.052(5), and 2.077(9) Å found in Lu(O-
2,6-iPr2-C6H3)3(THF)2,15Lu(O-2,6-Ph2-C6H3)3,16and[(Me3SiCH2)2-
Lu(O-2,6-tBu2-C6H3)2][Li(THF)4](THF)2,17 respectively. The
Lu-O-CAr angles are almost linear (164.7(3), 161.1(2),
155.8(2)°) and are typical of those seen in other early-transition-
metal, lanthanide, and actinide complexes bearing bulky alkox-
ide or aryloxide ligands.18
t
displacement of the bidentate Bu2bpy ligand to give complex
9 (eq 3).
(3)
The aminolysis chemistry can be controlled by using sterically
demanding amide ligands such as H2N-2,4,6-tBu3-C6H2. Reac-
tion of complex 4 with excess H2N-2,4,6-tBu3-C6H2 resulted in
loss of SiMe4 with concomitant formation of the mono(amide)
bis(alkyl) lutetium complex 7 in 84% isolated yield. Most of
the lanthanide bis(alkyl) complexes reported to date have been
Clearly, this reaction sequence demonstrates the limitations
of the tBu2bpy as a supporting ligand on lutetium in competition
with stronger donor ligands such as Ph3PdO. Although the yield
(19) Ce: (a) Heeres, H. J.; Meetsma, A.; Teuben, J. H.; Rogers, R. D.
Organometallics 1989, 8, 2637–2646. Lu: (b) Arndt, S.; Spaniol, T. P.;
Okuda, J. Organometallics 2003, 22, 775–781. Lu: (c) Tardif, O.; Nishiura,
M.; Hou, Z. Organometallics 2003, 22, 1171–1173. Dy: (d) Cui, D.;
Nishiura, M.; Hou, Z. Macromolecules 2005, 38, 4089–4095.
(20) Bambirra, S.; Bouwkamp, M. W.; Meetsma, A.; Hessen, B. J. Am.
Chem. Soc. 2004, 126, 9182–9183.
(15) Barnhart, D. M.; Clark, D. L.; Gordon, J. G.; Huffman, J. C.;
Vincent, R. L.; Watkin, J. G.; Zwick, B. D. Inorg. Chem. 1994, 33, 3487–
3497.
(16) Deacon, G. B.; Feng, T.; Forsyth, C. M.; Gitlits, A.; Hockless,
D. C. R.; Shen, Q.; Skelton, B. W.; White, A. H. Dalton Trans. 2000, 961–
966.
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2003, 125, 14768–14783.
(17) Evans, W. J.; Broomhall-Dillard, R. N. R.; Ziller, J. W. J.
Organomet. Chem. 1998, 569, 89–97.
(22) Ce: (a) Hitchcock, P. B.; Lappert, M. F.; Tian, S. J. Chem. Soc.,
Dalton Trans. 1997, 194, 5–1952. Tb: (b) Neculai, D.; Roesky, H. W.;
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and Aryloxo DeriVatiVes of Metals; Academic Press: London, 2001.

1302 Organometallics, Vol. 27, No. 6, 2008
Masuda et al.
Figure 2. Molecular structures of 5 (left) and 6 (right) with ellipsoids projected at the 50% probability level. Selected bond distances (Å)
and angles (deg) for 5: Lu(1)-N(1) ) 2.423(4), Lu(1)-N(2) ) 2.444(4), Lu(1)-N(3) ) 2.167(4), Lu(1)-N(4) ) 2.207(4), Lu(1)-N(5)
) 2.167(4); N(1)-Lu(1)-N(2) ) 65.16(14), Lu(1)-N(3)-C(19) ) 142.5(4), Lu(1)-N(4)-C(31) ) 145.6(4), Lu(1)-N(5)-C(43) ) 153.5(4).
Selected bond distances (Å) and angles (deg) for 6: Lu(1)-N(1) ) 2.456(3), Lu(1)-N(2) ) 2.432(3), Lu(1)-O(1) ) 2.030(2), Lu(1)-O(2)
) 2.059(2), Lu(1)-O(3) ) 2.030(2); N(1)-Lu(1)-N(2) ) 65.60(10), Lu(1)-O(1)-C(19) ) 164.7(3), Lu(1)-O(2)-C(38) ) 161.1(2),
Lu(1)-O(3)-C(57) ) 155.8(2).
Figure 3. Molecular structures of 7 (left) and 9 (right) with ellipsoids projected at the 50% probability level. Selected bond distances (Å)
and angles (deg) for 7: Lu(1)-N(1) ) 2.467(3), Lu(1)-N(2) ) 2.453(3), Lu(1)-N(3) ) 2.144(3), Lu(1)-C(19) ) 2.345(4), Lu(1)-C(23)
) 2.363(4); N(1)-Lu(1)-N(2) ) 65.12(10), Lu(1)-N(3)-C(27) ) 157.7(2), Lu(1)-C(19)-Si(1) ) 116.25(17), Lu(1)-C(23)-Si(2) )
128.68(18). Selected bond distances (Å) and angles (deg) for 9: Lu(1)-O(1) ) 2.217(6), Lu(1)-O(2) ) 2.239(6), Lu(1)-N(1) ) 2.224(7),
Lu(1)-C(37) ) 2.401(8), Lu(1)-C(41) ) 2.346(9), P(1)-O(1) ) 1.499(6), P(2)-O(2) ) 1.506(6); O(1)-Lu(1)-O(2) ) 177.7-
(2), Lu(1)-O(1)-P(1) ) 176.0(4), Lu(1)-O(2)-P(2) ) 167.5(4), Lu(1)-N(1)-C(45) ) 156.6(6), Lu(1)-C(37)-Si(2) ) 125.6(4),
Lu(1)-C(41)-Si(1) ) 138.4(5).
was not optimized, the formation of 9 was easily apparent from
1H NMR spectroscopy (benzene-d6, 23 °C), which showed the
release of free Bu2bpy (δ 9.05, 8.63, 6.93, 1.14 ppm) and the
appearance of diagnostic signals centered at δ 7.50 ppm for
the two aromatic anilide protons and at δ 4.15 ppm for the N-H
(upfield from δ 5.52 ppm for 7), singlets at δ 1.64 and 1.56
ppm for the tBu groups on the anilide ligand, and resonances at
δ 0.24 and -0.46 ppm corresponding to the methyl and
methylene protons, respectively, on the two -CH2SiMe3 groups.
The 31P NMR spectrum for 9 shows a peak at δ 33.14 ppm for
the two coordinated Ph3PdO ligands. Formation of 9 was
confirmed by a single-crystal X-ray diffraction study, and the
molecular structure is presented in Figure 3. The metrical
parameters for the ligands in the compound are all within
expected ranges.
Finally, as Scheme 1 illustrates, complex 4 also participates
in insertion chemistry and reacts smoothly with 1 equiv of N,N′-
dicyclohexylcarbodiimide (DCHCDI) in toluene at room tem-
perature to form the monoinsertion product 8, which is a rare
example of a lutetium amidinate complex.14g,23 Although a
crystal suitable for X-ray diffraction studies could not be
obtained, the 1H and 13C{1H} NMR spectra confirm the
formation of the amidinate fragment. In addition, similar
t
(23) Liu, B.; Cui, D.; Ma, J.; Chen, X.; Jing, X. Chem. Eur. J. 2007,
13, 834–845.
(24) Elvidge, B. R.; Arndt, S.; Spaniol, T. P.; Okuda, J. Dalton Trans.
2006, 890–901.
(25) Luo, Y.; Nishiura, M.; Hou, Z. J. Organomet. Chem. 2007, 692,
536–544.

A Thermally Stable Lutetium Tris(alkyl) Complex
Organometallics, Vol. 27, No. 6, 2008 1303
powder (0.470 g, 0.67 mmol, 83%). 1H NMR (benzene-d6, 298
K): δ 9.06 (d, 2H, 5.5 Hz, CAr H), 7.67 (s, 2H, CAr H), 6.86 (d,
2H, 5.5 Hz, CAr H), 0.96 (s, 18H, CMe3), 0.31 (s, 27H, SiMe3),
-0.08 (s, 6H, Lu-CH2). 13C{1H} NMR (benzene-d6, 298 K): δ
165.84 (s, CAr), 154.47 (s, CAr), 152.04 (s, CAr), 123.75 (s, CAr),
118.15 (s, CAr), 46.15 (s, Lu-CH2), 35.59 (s, CMe3), 30.34 (s,
CMe3), 5.03 (s, SiMe3). Anal. Calcd for C30H57N2LuSi3 (mol wt
705.01): C, 51.11; H, 8.15; N, 3.97. Found: C, 51.18; H, 8.26; N,
4.08. Mp ) 99–100 °C.
insertion chemistry was recently reported for (amido-
phosphine)Lu(CH2SiMe3)2 complexes and (N,N′)-diisopro-
pylcarbodiimide.14g
Conclusion
The 4,4′-di-tert-butyl-2,2′-bipyridyl (tBu2bpy) ligand stabilizes
the thermally sensitive [Lu(CH2SiMe3)3] unit, giving the isolable
lutetium(III) (trimethylsilyl)methyl complex (tBu2bpy)Lu(CH2-
SiMe3)3 (4), though it is not able to support lutetium complexes
containing multiply bonded functional groups. Nevertheless,
complex 4 does participate in a variety of protonolysis and
insertion reactions, affording Lu(III) tris(alkoxide), tris(amide),
mono(amide) bis(alkyl), and amidinate bis(alkyl) compounds.
This work forms the basis for exploring complex 4 and the
bis(alkyl) derivatives 7 and 8 as starting materials for the
synthesis of new organolanthanide derivatives such as cationic
alkyl complexes. As such, we intend to extend this chemistry
to other lanthanide derivatives and examine their potential as
polymerization and hydroamination catalysts.
Synthesis of (tBu2bpy)Lu(NH-2,6-iPr2-C6H3)3 (5). A 20-mL
scintillation vial was charged with (tBu2bpy)Lu(CH2SiMe3)3 (4;
0.208 g, 0.29 mmol) and hexanes (18 mL). To the resulting orange
solution was added dropwise 2,6-diisopropylaniline (0.17 mL, 0.157
g, 0.88 mmol) with stirring. An orange solid immediately precipi-
tated from the reaction solution. The reaction mixture was filtered
through a Celite-padded coarse frit to remove the filtrate. The
collected orange solid was washed with pentane (3 × 1 mL). Using
a clean 125-mL side-arm flask, the frit was placed on top of the
empty side-arm flask and THF was used (until washings were
colorless) to pass the product through the Celite. The filtrate was
collected, and the volatiles were removed under reduced pressure.
The resulting oily product was triturated with pentane, and the
pentane was removed under reduced pressure to give complex 5
as an analytically pure bright orange powder (0.216 g, 0.22 mmol,
Experimental Section
1
General Procedures. All reactions and manipulations were
carried out using either a MBraun 150 B-G or a Vacuum
Atmospheres (MO 40-2 Dri-train) recirculating nitrogen atmosphere
drybox or using standard Schlenk techniques. Glassware was dried
at 150 °C before use. 1H, 13C{1H}, DEPT-135, and 2-D
13C{1H}-1H NMR spectra were collected in benzene-d6 using a
Bruker Avance 300 MHz spectrometer. Chemical shifts were
referenced to the protio solvent impurity in benzene-d6 at δ 7.16
ppm (1H NMR) and δ 128.39 ppm (13C{1H} NMR) or external
H3PO4 (31P NMR). 1H and 13C{1H} NMR assignments were
confirmed through the use of DEPT-135 and HMQC NMR
experiments.
76%). H NMR (benzene-d6, 298 K): δ 8.89 (d, 2H, 5.8 Hz, CAr
H), 7.82 (s, 2H, CAr H), 7.16 (s, 3H, CAr H), 7.14 (s, 3H, CAr H),
6.83 (t, 3H, 7.41 Hz, CAr H), 6.60 (dd, 2H, 5.8 and 1.7 Hz, CAr H),
5.07 (s, 3H, NH), 3.36 (sep, 6H, 6.6 Hz, CHMe2), 1.24 (d, 36H,
6.6 Hz, CHMe2), 0.85 (s, 18H, CMe3). 13C{1H} NMR (benzene-
d6, 298 K): δ 166.16 (s, quat CAr), 154.07 (s, quat CAr), 153.90 (s,
quat CAr), 152.79 (s, CAr), 134.15 (s, quat CAr), 124.09 (s, CAr),
123.45 (s, CAr), 117.79 (s, CAr), 115.73 (s, CAr), 35.55 (s, CMe3),
30.73 (s, CHMe2), 30.10 (s, CMe3), 23.99 (s, CHMe2). Anal. Calcd
for C54H78N5Lu (mol wt 972.20): C, 66.71; H, 8.09; N, 7.20. Found:
C, 66.68; H, 8.19; N, 6.97. MS (EI, 70 eV): m/z 795 (M+ - NH-
2,6-iPr2C6H3). Mp ) 183–184 °C.
Melting points were determined with a Mel-Temp II capillary
melting point apparatus equipped with a Fluke 51 II K/J thermo-
couple using capillary tubes flame-sealed under nitrogen; values
are uncorrected. Mass spectrometric (MS) analyses were obtained
at the University of California-Berkeley Mass Spectrometry Facility,
using a VG ProSpec mass spectrometer. Elemental analyses were
performed at the University of California-Berkeley Microanalytical
Facility on a Perkin-Elmer Series II 2400 CHNS analyzer.
Unless otherwise noted, reagents were purchased from com-
mercial suppliers and used without further purification. Celite
(Aldrich), 4 Å molecular sieves (Aldrich), and alumina (Brockman
I, Aldrich) were dried under dynamic vacuum at 250 °C for 48 h
prior to use. Anhydrous toluene (Aldrich), pentane (Aldrich), and
hexanes (Aldrich) were dried over KH for 24 h, passed through a
column of activated alumina, and stored over activated 4 Å
molecular sieves prior to use. Benzene-d6 (Aldrich) was dried over
activated 4 Å molecular sieves prior to use. 2,6-Diisopropylaniline
(Aldrich) was passed through a column of activated alumina and
stored over activated 4 Å molecular sieves prior to use. 4,4′-Di-
tert-butyl-2,2′-bipyridyl (Aldrich), 2,4,6-tri-tert-butylaniline (Ald-
rich), triphenylmethanol (Aldrich), and triphenylphosphine oxide
(Aldrich) were purified by recrystallization from toluene at -35
°C. [Lu(CH2SiMe3)3(THF)2] (1) was prepared according to the
literature procedure.9b
Synthesis of (tBu2bpy)Lu[OC(C6H5)3] (6). A 50-mL side-arm
flask equipped with a stir bar was charged with (tBu2bpy)Lu-
(CH2SiMe3)3 (4; 0.172 g, 0.244 mmol) and hexanes (15 mL). To
the resulting orange solution was added dropwise a solution (10
mL of toluene and 10 mL of hexanes) of Ph3COH (0.190 g, 0.244
mmol) with stirring. The resultant reaction solution turned yellow,
and a yellow precipitate was deposited upon stirring overnight. The
volatiles were removed under reduced pressure, and the resulting
product was triturated with pentane (6 mL). Upon removal of the
pentane solution by decantation and drying under reduced pressure,
complex 6 was isolated as an analytically pure yellow powder
(0.274 g, 0.224 mmol, 92%). 1H NMR (benzene-d6, 298 K): δ 8.40
(d, 2H, 5.7 Hz, CAr H), 7.63 (br s, 9H, CAr H), 7.44 (s, 1H, CAr H),
7.43 (s, 1H, CAr H), 6.98 (m, 36H, CAr H), 6.52 (dd, 2H, 5.7 and
1.7 Hz, CAr H), 0.89 (s, 18H, CMe3). 13C{1H} NMR (benzene-d6,
298 K): δ 163.95 (s, quat CAr), 153.69 (s, quat CAr), 153.10 (s,
CAr), 152.90 (s, quat CAr), 129.41 (s, CAr), 128.00 (s, CAr), 126.22
(s, CAr), 122.55 (s, CAr), 117.09 (s, CAr), 35.17 (s, CMe3), 30.26 (s,
CMe3). Anal. Calcd for C81H83LuN2O3 (mol wt 1307.50): C, 74.41;
H, 6.40; N, 2.14. Found: C, 74.48; H, 6.83; N, 1.94. Mp ) 197–198
°C.
Synthesis of (tBu2bpy)Lu(NH-2,4,6-tBu3-C6H2)(CH2SiMe3)2
(7). A 50-mL side-arm flask equipped with a stir bar was charged
with (tBu2bpy)Lu(CH2SiMe3)3 (4; 0.207 g, 0.293 mmol) and toluene
(15 mL). To the resulting clear orange solution was added dropwise
a 5 mL toluene solution of H2N-2,4,6-tBu3-C6H2 (0.069 g, 0.293
mmol) with stirring. The resultant reaction solution gradually turned
red overnight. The volatiles were removed under reduced pressure,
and the resulting product was triturated with 10 mL of pentane.
The pentane solution was removed, and the remaining solids were
dried under reduced pressure to give 7 as an analytically pure red
Synthesis of (tBu2bpy)Lu(CH2SiMe3)3 (4). A 125-mL side-arm
flask equipped with a stir bar was charged with Lu(CH2-
SiMe3)3(THF)2 (1; 0.469 g, 0.81 mmol) and toluene (30 mL). To
the resulting clear, colorless solution was added dropwise a 10 mL
toluene solution of tBu2bpy (0.217 g, 0.81 mmol) with stirring. The
reaction mixture immediately turned orange and was stirred for 1 h
at ambient temperature. The volatiles were then removed under
reduced pressure to give complex 4 as an analytically pure orange

1304 Organometallics, Vol. 27, No. 6, 2008
Masuda et al.
1
powder (0.215 g, 0.245 mmol, 84%). H NMR (benzene-d6, 298
using direct methods and difference Fourier techniques. One of the
SiMe3 groups (Si(1), C(22)-C(24)) and one of the Bu groups
(C(11)-C(14)) were disordered, and the methyl groups were refined
in two positions at half-occupancy. The C-C and Si-C bond
distances were restrained to chemically reasonable values. All
hydrogen atom positions were idealized and rode on the atom to
which they were attached.
t
K): δ 9.07 (d, 2H, 5.7 Hz, CAr H), 7.74 (s, 1H, CAr H), 7.73 (s, 1H,
Ar H), 7.47 (s, 2H, CAr H), 6.75 (dd, 2H, 5.6 and 1.7 Hz, CAr H),
C
5.52 (s, 1H, NH), 2.10 (s, 18H, CMe3), 1.76 (s, 9H, CMe3), 0.91
(s, 18H, CMe3), 0.27 (s, 18H, CH2SiMe3), -0.07 (s, 4H, CH2SiMe3).
13C{1H} NMR (benzene-d6, 298 K): δ 165.67 (s, quat CAr), 154.49
(s, quat CAr), 153.86 (s, quat CAr), 152.67 (s, CAr), 135.01 (s, CAr),
134.54 (s, quat CAr), 123.85 (s, CAr), 122.23 (s, CAr), 118.12 (s,
CAr), 41.47 (s, CH2SiMe3), 35.80 (s, CMe3), 35.52 (s, CMe3), 34.86
(s, CMe3), 32.73 (s, CMe3), 32.19 (s, CMe3), 30.18 (s, CMe3), 4.91
(s, CH2SiMe3). Anal. Calcd for C44H76N3LuSi2 (mol wt 878.23):
C, 60.17; H, 8.72; N, 4.78. Found: C, 60.23; H, 8.52; N, 4.36. Mp
) 161–162 °C.
Crystals of 5-7 and 9 were mounted in a nylon cryoloop from
Paratone-N oil under argon gas flow. The data were collected on a
Bruker D8 APEX II charge-coupled-device (CCD) diffractometer,
with a KRYO-FLEX liquid nitrogen vapor cooling device. The
instrument was equipped with graphite-monochromated Mo KR
X-ray source (λ) 0.710 73 Å), with MonoCap X-ray source optics.
A hemisphere of data was collected using ω scans, with 5 s frame
exposures and 0.3° frame widths. Data collection and initial
indexing and cell refinement were handled using APEX II soft-
ware.29 Frame integration, including Lorentz-polarization correc-
tions, and final cell parameter calculations were carried out using
SAINT+ software.30 The data were corrected for absorption using
the SADABS program.31 Decay of reflection intensity was moni-
tored by analysis of redundant frames. The structure was solved
using direct methods and difference Fourier techniques. In 6, one
of the -CPh3 groups was disordered and was refined in two half-
occupancy positions. Also, in 6, four disordered toluene molecules
per unit cell were removed using PLATON/SQUEEZE:32 1266 Å3
and 1227 electrons/cell. All hydrogen atom positions were idealized
and rode on the atom to which they were attached. Hydrogen atom
positions were not included on disordered atoms. The final
refinement included anisotropic temperature factors on all non-
hydrogen atoms.
Synthesis of (tBu2bpy)Lu[CyNC(CH2SiMe3)NCy](CH2SiMe3)2
(8). A 125-mL side-arm flask equipped with a stir bar was charged
with (tBu2bpy)Lu(CH2SiMe3)3 (4; 0.302 g, 0.428 mmol) and toluene
(30 mL). To the resulting clear orange solution was added dropwise
a 10 mL toluene solution of CyNdCdNCy (0.088 g, 0.428 mmol)
with stirring. The resultant reaction solution gradually turned dark
red overnight. The volatiles were removed under reduced pressure,
the resulting oily product was redissolved in pentane, and the solvent
was removed under reduced pressure to give 8 as an analytically
pure orange powder (0.202 g, 0.221 mmol, 52%). 1H NMR
(benzene-d6, 298 K): δ 9.34 (d, 2H, 5.4 Hz, CAr H), 7.94 (s, 1H,
C
Ar H), 7.93 (s, 1H, CAr H), 6.97 (dd, 2H, 5.7 and 1.7 Hz, CAr H),
3.06 (br s, 2H, Cy CH), 1.93 (s, 2H, CH2SiMe3), 1.77 (br s, 4H,
Cy CH2), 1.64 (br s, 4H, Cy CH2), 1.52 (br s, 1H, Cy CH2), 1.48
(br s, 1H, Cy CH2), 1.14–1.36 (m, 10H, Cy CH2), 0.99 (s, 18H,
CMe3), 0.27 (s, 18H, CH2SiMe3), 0.13 (s, 9H, CH2SiMe3), -0.31
(s, 4H, CH2SiMe3). 13C{1H} NMR (benzene-d6, 298 K): δ 173.85
(s, quat CAr), 164.77 (s, quat CAr), 155.11 (s, quat CAr), 151.59 (s,
CAr), 123.07 (s, CAr), 117.97 (s, CAr), 57.31 (s, CH), 37.61 (s, CH2),
37.48 (s, CH2), 35.50 (s, CMe3), 30.40 (s, CMe3), 26.97 (s, CH2),
26.75 (s, CH2), 17.07 (s, CH2), 5.42 (s, CH2SiMe3), 0.38 (s,
CH2SiMe3). Anal. Calcd for C48H91N4LuSi3 (mol wt 983.49): C,
58.62; H, 9.33; N, 5.70. Found: C, 58.42; H, 9.06; N, 5.99. Mp )
111–113 °C.
Crystallographic Details for Complexes 4–7 and 9. A crystal
of 4 was mounted in a nylon cryoloop from Paratone-N oil under
argon gas flow. The crystal was placed on a Bruker P4 diffracto-
meter with 1k CCD and cooled to 203 K using a Bruker LT-2 liquid
nitrogen vapor low-temperature device. The instrument was equipped
with a sealed, graphite-monochromated Mo KR X-ray source (λ )
0.710 73 Å). A hemisphere of data was collected using ꢁ scans,
with 30 s frame exposures and 0.3° frame widths. Data collection
and initial indexing and cell refinement were handled using SMART
software.26 Frame integration, including Lorentz-polarization
corrections, and final cell parameter calculations were carried out
using SAINT software.27 The data were corrected for absorption
using the SADABS program.28 Decay of reflection intensity was
monitored by analysis of redundant frames. The structure was solved
Structure solution, refinement, and creation of publication
materials were performed using SHELXTL.33 All figures were made
using ORTEP-3 for Windows.34 Additional details of the data
collection and structure refinement and tables of bond lengths and
angles are given in the Supporting Information.
Acknowledgment. For financial support, we acknowledge
the LANL (Director’s Postdoctoral Fellowship to J.D.M.),
the LANL Glenn T. Seaborg Institute for Transactinium
Science (Postdoctoral fellowship to J.D.M.; summer student
fellowship to K.C.J.), the Division of Chemical Sciences,
Office of Basic Energy Sciences, Heavy Element Chemistry
program, and the LANL Laboratory Directed Research &
Development program.
Supporting Information Available: Tables and CIF files giving
X-ray crystallographic data for complexes 4–7 and 9. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM701159D
(29) APEX II 1.08; Bruker AXS, Inc., Madison, WI 53719, 2004.
(30) SAINT+ 7.06; Bruker AXS, Inc., Madison, WI 53719, 2003.
(31) Sheldrick, G. SADABS 2.03; University of Göttingen, Göttingen,
Germany, 2001.
(26) SMART-NT Version 4; Bruker AXS, Inc., Madison, WI 53719,
1996.
(27) SAINT-NT Version 5.050; Bruker AXS, Inc., Madison, WI 53719,
1998.
(28) Sheldrick, G. SADABS 1.0; University of Göttingen, Göttingen,
Germany, 1996.
(32) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.
(33) SHELXTL Version 6.10; Bruker AXS, Inc., Madison, WI 53719,
2000.
(34) Farrugia, J. J. Appl. Crystallogr. 1997, 30, 565.