Sterically demanding aryloxides as supporting ligands in organoactinide chemistry. Synthesis, structural characterization, and reactivity of Th(O-2,6-t-Bu2C6H3)2(CH 2SiMe3)2 and

Article abstract of DOI:10.1021/om950654u

Reaction of ThBr₄(THF)₄ with 2 equiv of KOAr (Ar = 2,6-t-Bu₂C₆H₃) produces the bis-(aryloxide) complex ThBr₂(OAr)₂(THF)₂ (1) in 67percent yield. Alkylation of 1 with 2

Full text of DOI:10.1021/om950654u

Organometallics 1996, 15, 949-957
949
Ster ica lly Dem a n d in g Ar yloxid es a s Su p p or tin g Liga n d s
in Or ga n oa ctin id e Ch em istr y. Syn th esis, Str u ctu r a l
Ch a r a cter iza tion , a n d Rea ctivity of
Th (O-2,6-t-Bu 2C6H3)2(CH2SiMe3)2 a n d F or m a tion of th e
Tr im er ic Th or iu m Hyd r id e Th 3H6(O-2,6-t-Bu 2C6H3)6
David L. Clark,*,1a Steven K. Grumbine,1b Brian L. Scott,1b and
J ohn G. Watkin*,1b
Chemical Science and Technology (CST) Division, Los Alamos National Laboratory,
Los Alamos, New Mexico 87545
Received August 22, 1995X
Reaction of ThBr4(THF)4 with 2 equiv of KOAr (Ar ) 2,6-t-Bu2C6H3) produces the bis-
(aryloxide) complex ThBr2(OAr)2(THF)2 (1) in 67% yield. Alkylation of 1 with 2 equiv of
Me3SiCH2MgCl allows the isolation of Th(OAr)2(CH2SiMe3)2 (2) in 61% yield. Thermolysis
of 2 (benzene, 60 °C, 36 h) in the presence of NEt3 results in the formation of the
cyclometalated ligand redistribution product Th(OC6H3-t-BuCMe2CH2)(OAr)2 (3). Reaction
of 2 with 1 equiv of 2,6-dimethylphenyl isocyanate leads to insertion into the Th-C bond to
yield (ArO)2Th[OC(dNR)CH2SiMe3](CH2SiMe3) (4; R ) 2,6-Me2C6H3). Aminolysis of 2 with
2 equiv of 2,6-diisopropylaniline allows the isolation of the bis(amido) species Th(OAr)2(NH-
2,6-i-Pr2C6H3)2 (5) in 92% yield. 2 reacts with dihydrogen (1.5 atm) over a period of 7 days
to form the trimeric dihydride complex Th3(µ3-H)2(µ2-H)4(OAr)6 (6). In the presence of 1
equiv of [HNMe2Ph][B(C6F5)4], 2 catalyzes the hydrogenation of 1-hexene (Nt ) 1 h-1), while
6 is found to be a single-component catalyst for the analogous process (Nt ) 3 h-1). Complexes
1
1-6 have been characterized by H NMR and IR spectroscopy, microanalysis, and, in the
case of 2 and 6, by single-crystal X-ray diffraction studies. 2 comprises a pseudotetrahedral
thorium metal center bearing two aryloxide and two alkyl ligands. The O-Th-O angle
between the aryloxide ligands (119.2(4)°) is significantly larger than the C-Th-C angle
(101.4(6)°). Th-O and Th-C distances average 2.137(11) and 2.462(18) Å, respectively, while
Th-C-Si angles are 125.9(8) and 122.8(8)°. The alkyl groups of 2 also display a reduced
C-H coupling constant (J CH ) 98 Hz), suggestive of R-agostic interaction between the
methylene group and the Th metal center. 6 exhibits a triangular arrangement of three
thorium metal centers, each bearing two terminal aryloxide ligands. Two sides of the
trimetallic core (Th-Th distances 3.781(1) and 3.818(1) Å) are bridged by single µ2-hydride
ligands, while the third side is bridged by two µ2-hydride ligands (Th-Th distance 3.588(1)
Å). Each face of the trimer is capped by a µ3-hydride ligand to produce a structurally unique
M3(µ3-X)2(µ2-X)4X6 geometry. Th-(µ2-H) and Th-(µ3-H) distances lie in the ranges 2.0(1)-
2.3(1) and 2.3(1)-2.6(1) Å, respectively, while Th-O distances range from 2.126(7) to 2.164-
(7) Å.
In tr od u ction
of mixtures of thermally unstable products which proved
difficult to characterize.3,4 Numerous methodologies
have subsequently been employed to overcome the
problem of stabilizing homoleptic actinide σ-alkyl de-
rivatives, including the preparation of anionic alkyl
complexes which possess high coordination numbers at
the metal center,5 the use of phosphine ligands to
prepare base-stabilized alkyl complexes ThR4(Me2PCH2-
The synthesis of σ-alkyl derivatives of the early
actinide elements has long represented a synthetic
challenge,2 due to the fact that the large size of the
actinide metal center often imparts a degree of steric
unsaturation to the isolated complex and can provide
facile decomposition pathways, such as â-elimination,
for alkyl-containing complexes. Therefore, it is not
surprising that the earliest attempts to prepare homo-
leptic actinide alkyl complexes often led to the isolation
(3) (a) Marks, T. J .; Seyam, A. M. J . Organomet. Chem. 1974, 67,
61. (b) Evans, W. J .; Wink, D. J .; Stanley, D. R. Inorg. Chem. 1982,
21, 2565. (c) Seyam, A. M. Inorg. Chim. Acta 1983, 77, L123.
(4) (a) Wilke, G.; Bogdanovic, B.; Hardt, P.; Heimbach, P.; Keim,
W.; Kro¨ner, M.; Oberkirch, W.; Tanaka, K.; Streinru¨cke, E.; Walter,
D.; Zimmerman, H. Angew. Chem., Int. Ed. Engl. 1966, 5, 151. (b)
Lugli, G.; Marconi, W.; Mazzei, A.; Paladino, N.; Pedretti, U. Inorg.
Chim. Acta 1969, 3, 253.
X Abstract published in Advance ACS Abstracts, J anuary 1, 1996.
(1) (a) LANL, Mail Stop G739. (b) LANL, Mail Stop C346.
(2) (a) Marks, T. J . In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
Oxford, England, 1982; Vol. 3, pp 211-223. (b) Ephritikhine, M. New
J . Chem. 1992, 16, 451. (c) Clark, D. L.; Sattelberger, A. P. In
Encyclopedia of Inorganic Chemistry; King, R. B., Ed.; Wiley: New
York, 1994; Vol. 1, pp 19-34. (d) Marks, T. J . Acc. Chem. Res. 1992,
25, 57.
(5) (a) Sigurdson, E. R.; Wilkinson, G. J . Chem. Soc., Dalton Trans.
1977, 815. (b) Lauke, H.; Swepston, P. N.; Marks, T. J . J . Am. Chem.
Soc. 1984, 106, 6841.
0276-7333/96/2315-0949$12.00/0 © 1996 American Chemical Society

950 Organometallics, Vol. 15, No. 3, 1996
Clark et al.
CH2PMe2) (R ) Me, CH2Ph),6 and the use of the
sterically demanding bis(trimethylsilyl)methyl ligand to
prepare the homoleptic uranium(III) alkyl derivative
U[CH(SiMe3)2]3.7 Many alkyl derivatives of the actinide
elements have also been isolated by using carbocyclic
supporting ligands such as cyclopentadienyl8 and cy-
clooctatetraenyl9 to produce steric saturation at the
metal center and thus inhibit potential decomposition
reactions. As an alternative to the ubiquitous cyclo-
pentadienyl moiety, other workers have successfully
employed sterically encumbered pyrazolylborate,10 bis-
(trimethylsilyl)amide,11 and bis(trimethylsilyl)benza-
midinato12 ligands for the stabilization of actinide alkyl
complexes.
The pioneering investigations of Marks and co-work-
ers into the use of the pentamethylcyclopentadienyl
moiety as a sterically demanding supporting ligand in
organoactinide chemistry have led to a recent resur-
gence of interest in actinide σ-alkyl derivatives, follow-
ing the discovery of extremely high catalytic activity of
many of these species in hydrogenation and polymeri-
zation processes.13 Our interest in the alkoxide and
aryloxide chemistry of the f-elements has recently been
directed toward investigation of the sterically encum-
bered 2,6-di-tert-butylphenoxide ligand as a surrogate
for the pentamethylcyclopentadienyl moiety, and we
have recently reported the synthesis of the mono-
(pentamethylcyclopentadienyl) complex (η-C5Me5)Th-
(OAr)(CH2SiMe3)2 (Ar ) 2,6-t-Bu2C6H3) and compared
its catalytic activity with that of analogous bis(pentam-
ethylcyclopentadienyl) alkyl species.14 Having noted the
extensive series of investigations by Rothwell and co-
workers in which aryloxide-supported alkyl complexes
of groups 4 and 5 have been found to mediate a number
of catalytic and stoichiometric reactions,15 we wished
to investigate whether thorium complexes of the type
Th(OAr)2R2 (Ar ) 2,6-t-Bu2C6H3) would exhibit similar
reactivity. There have been a limited number of reports
in the literature of alkoxide and aryloxide moieties being
utilized as supporting ligands for actinide σ-alkyl com-
plexes,16 but reactivity studies of these species have not
been undertaken. This paper describes the synthesis
and structural characterization of the bis(alkyl) complex
Th(OAr)2(CH2SiMe3)2 (Ar ) 2,6-t-Bu2C6H3) and com-
pares its reactivity with that of both cyclopentadienyl-
supported actinide alkyls as well as alkyl-aryloxide
derivatives of the group 4 transition metals. A portion
of this work has been the subject of a previous com-
munication.17
Resu lts a n d Discu ssion
Syn th esis a n d Rea ctivity. Addition of 2 equiv of
KOAr (Ar ) 2,6-t-Bu2C6H3) to a THF solution of ThBr4-
(THF)4,18 followed by crystallization from toluene, leads
to isolation of the bis(aryloxide) complex ThBr2(OAr)2-
(THF)2 (1) as colorless crystals in 67% yield (eq 1).
ThBr4(THF)4 + 2KOAr THF, 18 h8
ThBr2(OAr)2(THF)2 + 2KBr (1)
1
Ar ) 2,6-t-Bu2C6H3
Microanalytical and 1H NMR spectral data for 1 support
the proposed formulation. We note the isolation by
Burns et al. of the related uranium aryloxide derivative
UI2(OAr)2(THF)‚THF,19 in which one THF ligand is
bound to the metal center while a second THF molecule
is contained within the lattice. We formulate 1 as
ThBr2(OAr)2(THF)2 rather than ThBr2(OAr)2(THF)‚-
THF, since the slightly larger ionic radius of thorium
compared to uranium and the smaller steric require-
ment of bromide compared to iodide ligands would
appear to facilitate the coordination of a second molecule
of THF at the metal center. In addition, analysis
samples of 1 were recrystallized from toluene solution,
which would mitigate against the inclusion of THF into
their lattice structures. 1H NMR spectra of the crude
reaction mixture from eq 1 contained minor resonances
which may tentatively be assigned to the mono- and tris-
(aryloxide) complexes ThBrx(OAr)4-x (x ) 1, 3).
(6) Edwards, P. G.; Andersen, R. A.; Zalkin, A. Organometallics
1984, 3, 293.
(7) Van der Sluys, W. G.; Burns, C. J .; Sattelberger, A. P. Organo-
metallics 1989, 8, 855.
(8) For the earliest examples of complexes of the type (η-C5H5)3AnR,
see: (a) Marks, T. J .; Seyam, A. M. J . Am. Chem. Soc. 1972, 94, 6545.
(b) Gabala, A. E.; Tsutsui, M. J . Am. Chem. Soc. 1973, 95, 91. (c) Marks,
T. J .; Seyam, A. M.; Kolb, J . R. J . Am. Chem. Soc. 1973, 95, 5529. (d)
Brandi, G.; Brunelli, M.; Lugli, G.; Mazzei, A. Inorg. Chim. Acta 1973,
7, 319.
(9) (a) Berthet, J .-C.; Le Marechal, J .-F.; Ephritikhine, M. J .
Organomet. Chem. 1994, 480, 155. (b) Arliguie, T.; Baudry, D.; Berthet,
J .-C.; Ephritikhine, M.; Le Marechal, J .-F. New J . Chem. 1991, 15,
569.
(10) (a) Silva, M.; Marques, N.; Pires de Matos, A. J . Organomet.
Chem. 1995, 493, 129. (b) Domingos, A.; Marc¸alo, J .; Pires de Matos,
A. Polyhedron 1992, 11, 909. (c) Santos, I.; Marques, N. New J . Chem.
1995, 19, 551 and references therein. (d) Domingos, A.; Leal, J . P.;
Marc¸alo, J .; Marques, N.; Pires de Matos, A.; Santos, I.; Silva, M.;
Kanellakopulos, B.; Maier, R.; Apostolidis, C.; Martinho Simo˜es, J . A.
Eur. J . Solid State Inorg. Chem. 1991, 28(Suppl.), 413.
(11) Turner, H. W.; Andersen, R. A.; Zalkin, A.; Templeton, D. H.
Inorg. Chem. 1979, 18, 1221.
Compound 1 may be smoothly alkylated with 2 equiv
of a diethyl ether solution of Me3SiCH2MgCl, followed
by addition of dioxane. Subsequent crystallization from
(15) (a) Chamberlain, L. R.; Durfee, L. D.; Fanwick, P. E.; Kobriger,
L.; Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Folting, K.;
Huffman, J . C.; Streib, W. E.; Wang, R. J . Am. Chem. Soc. 1987, 109,
390. (b) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell, I.
P.; Huffman, J . C. Organometallics 1985, 4, 902. (c) Zambrano, C. H.;
Fanwick, P. E.; Rothwell, I. P. Organometallics 1994, 13, 1174. (d) Yu,
J . S.; Ankianiec, B. C.; Rothwell, I. P.; Nguyen, M. T. J . Am. Chem.
Soc. 1992, 114, 1927. (e) Profilet, R. D.; Zambrano, C. H.; Fanwick, P.
E.; Nash, J . J .; Rothwell, I. P. Inorg. Chem. 1990, 29, 4362. (f)
Zambrano, C. H.; McMullen, A. K.; Kobriger, L.; Fanwick, P. E.;
Rothwell, I. P. J . Am. Chem. Soc. 1990, 112, 6565. (g) Chesnut, R. W.;
Durfee, L. D.; Fanwick, P. E.; Rothwell, I. P.; Folting, K.; Huffman, J .
C. Polyhedron 1987, 6, 2019. (h) Zambrano, C. H.; Profilet, R. D.; Hill,
J . E.; Fanwick, P. E.; Rothwell, I. P. Polyhedron 1993, 12, 689. (i)
Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Huffman, J . C. J . Am.
Chem. Soc. 1985, 107, 5981.
(12) Wedler, M.; Knosel, F.; Edelmann, F. T.; Behrens, U. Chem.
Ber. 1992, 125, 1313.
(13) (a) Maatta, E. A.; Marks, T. J . J . Am. Chem. Soc. 1981, 103,
3576. (b) Bowman, R. G.; Nakamura, R.; Fagan, P. J .; Burwell, R. L.,
J r.; Marks, T. J . J . Chem. Soc., Chem. Commun. 1981, 257. (c) He,
M.-Y.; Xiong, G.; Toscano, P. J .; Burwell, R. L., J r.; Marks, T. J . J .
Am. Chem. Soc. 1985, 107, 641. (d) Toscano, P. J .; Marks, T. J .
Langmuir 1986, 2, 820. (e) He, M.-Y.; Burwell, R. L., J r.; Marks, T. J .
Organometallics 1983, 2, 566. (f) Hedden, D.; Marks, T. J . J . Am. Chem.
Soc. 1988, 110, 1647.
(16) (a) Stewart, J . L.; Andersen, R. A. J . Chem. Soc., Chem.
Commun. 1987, 1846. (b) Beshouri, S. M.; Fanwick, P. E.; Rothwell, I.
P. Organometallics 1987, 6, 2498. (c) Brunelli, M.; Perego, C.; Lugli,
G.; Mazzei, A. J . Chem. Soc., Dalton Trans. 1979, 861.
(17) Clark, D. L.; Grumbine, S. K.; Scott, B. L.; Watkin, J . G. J .
Am. Chem. Soc. 1995, 117, 9089.
(18) Clark, D. L.; Frankcom, T. M.; Miller, M. M.; Watkin, J . G.
Inorg. Chem. 1992, 31, 1628.
(19) Avens, L. R.; Barnhart, D. M.; Burns, C. J .; McKee, S. D.; Smith,
W. H. Inorg. Chem. 1994, 33, 4245.
(14) Butcher, R. J .; Clark, D. L.; Grumbine, S. K.; Scott, B. L.;
Watkin, J . G. Submitted for publication in Organometallics.

Aryloxides as Ligands in Organoactinide Chemistry
Organometallics, Vol. 15, No. 3, 1996 951
Sch em e 1
in the presence of OdPPh3, which results in isolation
of the cyclometalated ligand redistribution product
Cp*Th(OC6H3-t-BuCMe2CH2)(OAr)(OdPPh3).14 The ti-
tanium and zirconium analogs of 3 have been described
previously, following reaction of the metallacyclic spe-
cies M(OC6H3-t-BuCMe2CH2)(OAr)(CH2Ph) (M ) Ti, Zr)
with a further 1 equiv of 2,6-di-tert-butylphenol.15i
Complex 2 reacts with 1 equiv of 2,6-dimethylphenyl
isocyanate in hexane at room temperature to form the
monoinsertion product (ArO)2Th[OC(dNR)CH2SiMe3]-
(CH2SiMe3) (4; R ) 2,6-Me2C6H3) in 67% isolated yield
(eq 4). 4 does not react with a second equivalent of
isocyanate over a period of 18 h at room temperature
in benzene-d6.
toluene allows the isolation of the bis(alkyl) complex Th-
(OAr)2(CH2SiMe3)2 (2) as colorless crystals in 61% yield
(eq 2).
ThBr2(OAr)2(THF)2 + 2Me3SiCH2MgCl toluene, 3 h8
dioxane
Th(OAr)2(CH2SiMe3)2 (2)
The alkyl groups in 2 are susceptible to protonation
by amines, as demonstrated by the reaction of 2 with 1
equiv of H2N-2,6-i-Pr2C6H3 in cold (-78 °C) hexane. A
1H NMR spectrum of the crude reaction mixture showed
resonances due to unreacted 2 in addition to signals
consistent with the presence of the mono- and bis(amide)
species Th(OAr)2(NHR)(CH2SiMe3) and Th(OAr)2(NHR)2
(R ) 2,6-i-Pr2C6H3). Addition of a second equivalent of
amine to the crude reaction mixture, followed by stirring
at room temperature for 24 h and low-temperature
crystallization, led to isolation of the bis(amide) Th-
(OAr)2(NH-2,6-i-Pr2C6H3)2 (5) as a white powder in 92%
yield (eq 5). No evidence was seen for the formation of
any imido-containing thorium complexes.
2
Ar ) 2,6-t-Bu2C6H3
The reactivity of complex 2 has been investigated, and
a summary of its behavior is presented in Scheme 1.
Thermolysis of 2 (benzene-d6, 60 °C, 36 h) in the
presence of NEt3 (to capture any potential Th(OAr)2-
(dCHR) species) leads to the formation of a complex
which is formulated on the basis of 1H NMR and
microanalytical data as the cyclometalated species Th-
(OC6H3-t-BuCMe2CH2)(OAr)2 (3) (eq 3). 1H NMR stud-
Th(OAr)2(CH2SiMe3)2 + 2RNH2 hexane8
24 h
2
Th(OAr)2(NHR)2 + 2SiMe4 (5)
5
Ar ) 2,6-t-Bu2C6H3; R ) 2,6-i-Pr2C6H3
The closely related bis(arylamido) species M(OAr)2-
(NHPh)2 (M ) Zr, Hf) have been prepared by reaction
of Zr(OAr)2Me2 with 2 equiv of aniline or of Hf(CH2Ph)4
with 2 equiv of aniline followed by 2 equiv of phenol,
respectively.15e,h
A benzene solution of 2 reacts with dihydrogen (1.5
atm) over a period of 7 days to produce a thorium
hydride complex with the empirical formula ThH2(OAr)2
in 33% yield after crystallization from hexane (eq 6).
ies showed the formation of SiMe4 as the reaction
progressed, but no other thorium-containing species
could be conclusively identified in the reaction mixture.
Compound 3 may be isolated in 24% yield following
crystallization from hexane. The cyclometalation20 and
aryloxide ligand redistribution15i,19 reactions necessary
for the formation of 3 both have precedent in the litera-
ture, and we also note that the overall reactivity depic-
ted in eq 3 closely parallels that observed upon ther-
molysis of the related complex Cp*Th(OAr)(CH2SiMe3)2
H2
Th(OAr)2(CH2SiMe3)2 benzene, 7 days8
2
1/3[ThH2(OAr)2]3 + 2SiMe4 (6)
6
(20) (a) Chamberlain, L.; Keddington, J .; Rothwell, I. P.; Huffman,
J . C. Organometallics 1982, 1, 1538. (b) Rothwell, I. P. Acc. Chem. Res.
1988, 21, 153.
Ar ) 2,6-t-Bu2C6H3

952 Organometallics, Vol. 15, No. 3, 1996
Clark et al.
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta
An X-ray diffraction study (vide infra) shows 6 to be
trimeric in the solid state, and the trimeric structure
remains intact in solution, as demonstrated by a mo-
lecular weight determination in benzene (isopiestic
method, calcd for trimer 1934, found 2061). The deu-
terated complex [ThD2(OAr)2]3 (6-d6) can be prepared
in an analogous procedure using deuterium gas.
The hydride ligands in 6 undergo slow exchange with
deuterium gas (1 atm, benzene-d6, half-life ∼36 h) to
produce the perdeuterio complex 6-d6 (eq 7). The slow
rate of H-D exchange in 6 is in marked contrast to the
fast exchange observed in the dimeric hydride complex
[(η5-C5Me5)2Th(µ-H)(H)]2.21
2
6
empirical formula
C39H64O2Si2Th
C26H32O2Th
space group
P21/c
P21/c
cell dimens
a, Å
b, Å
c, Å
11.779(2)
18.276(4)
20.276(4)
103.55(3)
4243.4
4
13.571(1)
26.610(3)
27.510(2)
96.716(3)
9866
â, deg
V, Å3
Z (molecules/cell)
4
fw
D
853.1
1.335
35.98
0.710 69
-70
2.0-45.0
6217
2106.4
1.418
45.6
0.710 69
-100
5.0-45.0
15402
calc, g cm-3
abs coeff, cm-1
λ(Mo KR)
temp, °C
2θ range, deg
no. of measd rflns
D2
[ThH2(OAr)2]3 benzene8 [ThD2(OAr)2]3
(7)
no. of unique intensities 5523
12789
no. of obsd rflns
3883 (F > 4.0σ(F)) 8144 (F > 4.0σ(F))
half-life ∼36 h
R(F)b
0.0694
0.0945c
1.08
0.0460
0.0812d
1.01
Rw(F) or wR2
goodness of fit
The catalytic hydrogenation and polymerization ac-
tivity of 2 toward R-olefins was also investigated. The
ammonium salt [HNMe2Ph][B(C6F5)4] was employed as
a proton source to remove one alkyl ligand and form a
cationic thorium complex with the noncoordinating
tetrakis(perfluorophenyl)borate anion. Since attempts
to characterize fully the presumed ionic species [Th-
(OAr)2(CH2SiMe3)][B(C6F5)4] were unsuccessful, a mix-
ture of 2 and [HNMe2Ph][B(C6F5)4] was used in situ as
the active catalyst. The addition of 1-hexene to an
equimolar toluene solution of 2 and [HNMe2Ph][B-
(C6F5)4], followed by admission of 1 atm of dihydrogen,
led to the catalytic hydrogenation of the olefin. Analysis
of the volatile components from the reaction mixture by
GC-MS, and quantification of the hexane present,
allowed calculation of the turnover rate of 1 h-1. The
activity of 2/[HNMe2Ph][B(C6F5)4] is thus substantially
lower than that of the bis(pentamethylcyclopentadienyl)
methyl derivative [(η-C5Me5)2ThMe][B(C6F5)4], for which
a turnover rate of 16 450 h-1 has been reported,22 but
is only slightly lower than that of (η-C5Me5)Th(OAr)(CH2-
SiMe3)2 (3 h-1).14
a
2 ) Th(O-2,6-t-Bu2C6H3)2(CH2SiMe3)2; 6 ) Th3(µ3-H)2(µ2-
H)4(O-2,6-t-Bu2C6H3)6. R(F) ) ∑||Fo| - |Fc||/∑|Fo|. c Rw(F) )
b
[∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2; w ) 1/σ2(|Fo|). wR2 ) [∑[w(Fo
-
2
d
2
Fc2)2]/∑[w(Fo2)2]]1/2, where w ) 1/[σ2(Fo2) + (0.0325P)2, with P )
2
(Fo + 2Fc2)/3.
Ta ble 2. Selected Atom ic Coor d in a tes a n d
Equ iva len t Isotr op ic Disp la cem en t Coefficien ts for
Th (O-2,6-t-Bu 2C6H3)2(CH2SiMe3)2‚C7H8 (2)
104x
104y
104z
104U(eq),a Å2
Th(1)
Si(1)
C(1)
Si(2)
C(11)
O(1)
2325.5(5)
-751(4)
649(14)
3695(4)
3156(16)
3570(9)
4312(13)
3975(13)
4717(14)
5743(17)
6088(17)
5366(14)
2845(14)
5812(15)
1715(8)
1350(13)
931(13)
490(15)
494(14)
946(13)
1392(12)
945(13)
1954(16)
1502.6(3)
1607(3)
2075(9)
1190(3)
775(9)
2341(5)
2798(9)
3530(9)
3967(9)
3730(10)
2999(10)
2520(9)
3832(9)
1741(10)
799(6)
2049.2(3)
874(2)
1289(9)
554(2)
110(2)
182(15)
272(63)
180(16)
242(64)
172(37)
146(36)
178(37)
187(38)
300(68)
295(67)
161(54)
182(38)
277(64)
127(23)
124(35)
139(36)
308(46)
242(40)
186(38)
132(35)
171(36)
279(67)
1240(8)
2456(5)
2906(7)
2935(8)
3405(8)
3794(9)
3725(8)
3268(7)
2477(8)
3182(9)
2727(5)
3199(7)
3709(7)
4143(9)
4077(8)
3589(8)
3135(7)
3812(8)
2610(9)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(31)
O(2)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(50)
An equimolar toluene solution of 2 and [HNMe2Ph]-
[B(C6F5)4] was found to be inactive as an ethylene
polymerization catalyst, in contrast to the related pen-
tamethylcyclopentadienyl complex (η-C5Me5)Th(OAr)-
(CH2SiMe3)2, which, in the presence of 1 equiv of
[HNMe2Ph][B(C6F5)4], showed an activity of 34 600 g
h-1 atm-1 (mol catalyst)-1 (Nt ) 0.35 s-1).14
362(8)
702(9)
244(10)
-482(10)
-822(9)
-417(9)
1543(9)
-794(10)
The dihydride species [ThH2(OAr)2]3 (6) was found to
be a single-component catalyst for the hydrogenation
of olefins. Thus, a toluene solution of 6 was found to
catalyze the hydrogenation of 1-hexene under 1 atm of
dihydrogen at a modest turnover rate of 3 h-1. The
activity of 6 is thus somewhat greater than that of the
bis(pentamethylcyclopentadienyl) analog [(η-C5Me5)2Th-
a
Equivalent isotropic U, defined as one-third of the trace of the
orthogonalized Uij tensor.
2 were grown by cooling a concentrated toluene solution
to -40 °C. A summary of data collection and crystal-
lographic parameters is given in Table 1. Selected
fractional coordinates are given in Table 2, while
selected bond lengths and angles are presented in Table
3. An ORTEP drawing giving the atom-numbering
scheme used in the tables is shown in Figure 1. The
overall molecular structure of 2 features a thorium
metal center coordinated in a pseudotetrahedral fashion
by two aryloxide and two alkyl ligands. The sterically
demanding aryloxide ligands have a significantly larger
angle between them (O(1)-Th(1)-O(2) ) 119.2(4)°) than
the somewhat smaller alkyl ligands (C(1)-Th(1)-C(11)
) 101.4(6)°). Th-O bond distances in 2 are statistically
indistinguishable (2.147(10) and 2.127(11) Å) and are
(µ-H)(H)]2 (0.5 h-1 21
of the “tied-back” derivative [Me2Si(η-C5Me4)2Th(µ-H)2]2
)
but considerably lower than that
(610 h-1 23
) and the mono(pentamethylcyclopentadienyl)
complex [(η-C5Me5)ThH2(OAr)]3 (10 h-1).14
Solid -Sta te a n d Molecu la r Str u ctu r es. Th (O-2,6-
t-Bu 2C6H3)2(CH2SiMe3)2 (2). X-ray-quality crystals of
(21) Fagan, P. J .; Manriquez, J . M.; Maatta, E. A.; Seyam, A. M.;
Marks, T. J . J . Am. Chem. Soc. 1981, 103, 6650.
(22) Yang, X.; Stern, C. L.; Marks, T. J . Organometallics 1991, 10,
840.
(23) Fendrick, C. M.; Schertz, L. D.; Day, V. W.; Marks, T. J .
Organometallics 1988, 7, 1828.

Aryloxides as Ligands in Organoactinide Chemistry
Organometallics, Vol. 15, No. 3, 1996 953
Ta ble 4. Selected Atom ic Coor d in a tes a n d
Equ iva len t Isotr op ic Disp la cem en t Coefficien ts for
[Th H2(O-2,6-t-Bu 2C6H3)2]3 (6)
104x
104y
104z
104U(eq),a Å2
Th(1)
Th(2)
Th(3)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
H(a)
H(b)
H(c)
H(d)
H(e)
H(f)
2930(1)
2143(1)
2348(1)
2122(5)
4371(5)
3004(5)
747(5)
1013(5)
3630(5)
1939(74)
2819(73)
3363(73)
1833(73)
1757(75)
3179(74)
1858(1)
3146(1)
2482(1)
1171(3)
1720(2)
3827(3)
3269(2)
2377(3)
2574(3)
3211(38)
1844(38)
2598(38)
2359(39)
2385(39)
2666(39)
3056(1)
3036(1)
1822(1)
3141(2)
3441(2)
3170(2)
3295(2)
1337(2)
1453(2)
2232(36)
2310(36)
3402(36)
3357(35)
2551(35)
2561(36)
32(1)
31(1)
38(1)
36(2)
33(2)
38(2)
30(2)
40(2)
40(2)
80
80
80
80
80
80
a
F igu r e 1. ORTEP representation (50% probability el-
lipsoids) of the molecular structure of Th(O-2,6-t-
Bu2C6H3)2(CH2SiMe3)2 (2), giving the atom-numbering
scheme used in the tables.
Equivalent isotropic U, defined as one-third of the trace of the
orthogonalized Uij tensor.
Ta ble 5. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Th H2(O-2,6-t-Bu 2C6H3)2]3 (6)
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Th (O-2,6-t-Bu 2C6H3)2(CH2SiMe3)2‚C7H8 (2)
Th(1)-O(1)
Th(2)-O(3)
Th(3)-O(5)
Th(1)-H(b)
Th(1)-H(e)
Th(2)-H(a)
Th(2)-H(d)
Th(2)-H(f)
Th(3)-H(b)
Th(3)-H(f)
Th(1)-Th(2)
2.159(7)
2.164(7)
2.139(7)
2.04(10)
2.43(10)
2.20(10)
2.33(10)
2.40(10)
2.21(10)
2.26(10)
3.5884(6)
Th(1)-O(2)
Th(2)-O(4)
Th(3)-O(6)
Th(1)-H(d)
Th(1)-H(f)
Th(2)-H(c)
Th(2)-H(e)
Th(3)-H(a)
Th(3)-H(e)
Th(2)-Th(3)
Th(1)-Th(3)
2.143(7)
2.126(7)
2.127(7)
2.23(10)
2.58(10)
2.34(10)
2.45(10)
2.34(10)
2.26(10)
3.8176(6)
3.7806(6)
Th(1)-O(1)
Th(1)-C(1)
2.147(10)
2.438(16)
Th(1)-O(2)
Th(1)-C(11)
2.127(11)
2.485(18)
O(1)-Th(1)-C(1)
O(2)-Th(1)-C(1)
O(1)-Th(1)-O(2)
Th(1)-C(1)-Si(1)
108.4(5)
108.8(5)
119.2(4)
125.9(8)
O(1)-Th(2)-C(11)
O(2)-Th(2)-C(11)
C(1)-Th(2)-C(11)
Th(1)-C(11)-Si(2)
107.2(5)
110.4(5)
101.4(6)
122.8(8)
comparable to those found in Th(O-2,6-t-Bu2C6H3)2(CH2-
py-6-Me)2 (2.190(9) Å)16b and Th(O-2,6-t-Bu2C6H3)4 (2.189-
(6) Å).24 Th-C distances of 2.438(16) and 2.485(18) Å
are similar to those found in other crystallographically
characterized thorium alkyl complexes and can be
compared to the average Th-C distances of 2.55(1),
2.47(1), 2.54(1), 2.49(2), and 2.58(1) Å found in Th(O-
O(2)-Th(1)-O(1)
O(6)-Th(3)-O(5)
Th(1)-Th(2)-Th(3)
104.4(2)
113.5(2)
61.30(1) Th(1)-Th(3)-Th(2)
O(4)-Th(2)-O(3)
Th(2)-Th(1)-Th(3)
107.4(2)
62.34(1)
56.36(1)
constant for the methylene carbon atom have been
interpreted as evidence for R-agostic interactions, al-
though mechanistic studies of alkane elimination from
these complexes provide no evidence for R-hydrogen
abstraction.29
2,6-t-Bu2C6H3)2(CH2-py-6-Me)2,16b (η-C5Me5)2Th(CH2-
SiMe2CH2),25 (η-C8H8)(η-C5Me5)Th[CH(SiMe3)2],26 (η-
27a
C5Me5)2Th(CH2SiMe3)2 and (η-C5Me5)Th(CH2C6H5)3,27b
Th 3(µ3-H)2(µ2-H)4(O-2,6-t-Bu 2C6H3)6 (6). Crystals
of 6 suitable for an X-ray diffraction study were grown
by cooling a concentrated hexane solution to -40 °C.
Selected fractional coordinates are given in Table 4,
while selected bond lengths and angles are presented
in Table 5. An ORTEP drawing giving the atom-
numbering scheme used in the tables is shown in Figure
2. The basic structure of 6 consists of a triangular core
of three thorium atoms with each thorium bonded to
two terminal aryloxide ligands. Two of the located and
refined hydride ligands cap the two faces of the trimer
(µ3-H), while the remaining four hydrides bridge the
edges of the trimetallic core (µ2-H). Two sides of the
trimer are bridged by single µ2-H ligands and display
nonbonding Th-Th distances of 3.781(1) and 3.818(1)
Å, while the third side has two µ2-H ligands and a very
short nonbonding Th-Th distance of 3.588(1) Å (cf. Th-
Th distance in thorium metal, 3.59 Å).30 The Th(1)-
Th(2) separation appears to be the shortest yet docu-
mented in a molecular complex but is attributable
primarily to the four bridging hydride interactions,
which draw the metals into close proximity. The related
respectively. Th-O-C angles are almost linear (162.1-
(10) and 176.9(8)°) and are typical of those seen in other
transition-metal complexes bearing bulky aryloxide
ligands.28 The Th-C-Si angles of 125.9(8) and 122.8-
(8)° in 2 are larger than those typically found for sp3-
hybridized carbon atoms. Comparable Th-C-Si angles
have precedence in the literature in the cyclopentadienyl
complexes (η-C5Me5)2Th(CH2SiMe3)2 (Th-C-Si
)
132.0(6) and 148.0(7)°),27a [Me2Si(η-C5Me4)2]Th(CH2-
SiMe3)2 (123.7(14) and 149.5(12)°),23 and (η-C5Me5)Th-
(OAr)(CH2SiMe3)2 (120.0(4) and 139.8(6)°).14 These
large angles and the corresponding reduced coupling
(24) Berg, J . M.; Clark, D. L.; Huffman, J . C.; Morris, D. E.;
Sattelberger, A. P.; Streib, W. E.; Van der Sluys, W. G.; Watkin, J . G.
J . Am Chem. Soc. 1992, 114, 10811.
(25) Bruno, J . W.; Marks, T. J .; Day, V. W. J . Am. Chem. Soc. 1982,
104, 7357.
(26) Gilbert, T. M.; Ryan, R. R.; Sattelberger, A. P. Organometallics
1989, 8, 857.
(27) (a) Bruno, J . W.; Marks, T. J .; Day, V. W. J . Organomet. Chem.
1983, 250, 237. (b) Mintz, E. A.; Moloy, K. G.; Marks, T. J . J . Am.
Chem. Soc. 1982, 104, 4692.
(28) (a) Zozulin, A. J .; Moody, D. C.; Ryan, R. R. Inorg. Chem. 1982,
21, 3083. (b) Edwards, P. G.; Andersen, R. A.; Zalkin, A. J . Am. Chem.
Soc. 1981, 103, 7792. (c) Hitchcock, P. B.; Lappert, M. F.; Singh, A.;
Taylor, R. G.; Brown, D. J . Chem. Soc., Chem. Commun. 1983, 561.
(d) Evans, W. J .; Hanusa, T. P.; Levan, K. R. Inorg. Chim. Acta 1985,
110, 191. (e) Stecher, H. A.; Sen, A.; Rheingold, A. L. Inorg. Chem.
1988, 27, 1130.
(29) Bruno, J . W.; Smith, G. M.; Marks, T. J .; Fair, C. K.; Schultz,
A. J .; Williams, J . M. J . Am. Chem. Soc. 1986, 108, 40.
(30) Hampel, C. A. The Encyclopedia of the Chemical Elements;
Reinhold: New York, 1968; p 715.

954 Organometallics, Vol. 15, No. 3, 1996
Clark et al.
1
Sp ectr oscop ic Stu d ies. The H NMR spectra of 1
and 2 showed resonances which were straightforwardly
assignable to aryloxide and alkyl ligands in the expected
ratios. In the proton-coupled 13C NMR spectrum of 2,
the methylene carbon resonance appears as a triplet at
δ 93.96 (J CH ) 98 Hz) with a C-H coupling constant
which is significantly reduced from that of a typical sp3-
hybridized carbon atom. In the analogous cyclopenta-
dienyl complexes [Me2Si(η-C5Me4)2]Th(CH2SiMe3)2 and
(η-C5Me5)Th(OAr)(CH2SiMe3)2, similarly reduced cou-
pling was observed and was attributed to R-agostic
interactions with the metal.14,23 Additional evidence for
this interaction has also been observed in the solid-state
structure of 2 (vide supra).
The 1H NMR spectrum of 3 displays resonances
assignable to two terminal aryloxide ligands in addition
to a distinctive set of resonances in a 9:6:2 ratio which
are characteristic of a cyclometalated di-tert-butylphe-
noxide ligand. The 1H NMR spectrum of 4 exhibits two
sets of resonances due to the metal-bound and carbon-
bound CH2SiMe3 groups, together with resonances for
the di-tert-butylphenoxide and (dimethylphenyl)imido
groups. A resonance at 182.7 ppm in the 13C NMR
spectrum of 4 is consistent with insertion of the isocy-
anate OdC bond into the ThsC bond, as would be
expected for an oxophilic actinide complex. The infrared
spectrum of 4 contains a strong absorption at 1520 cm-1
assigned to the CdN stretching mode. This relatively
low CdN stretching frequency is consistent with sig-
nificant NfTh interaction, as shown schematically in
resonance structure C. In contrast, a CdN stretching
F igu r e 2. ORTEP representation (40% probability el-
lipsoids) of the molecular structure of Th3(µ3-H)2(µ2-H)4(O-
2,6-t-Bu2C6H3)6 (6), giving the atom-numbering scheme
used in the tables. tert-Butyl carbon atoms have been
omitted for clarity.
bis(cyclopentadienyl) complex {[Me2Si(η-C5Me4)2]Th(µ-
H)2}2, which also features four bridging hydride ligands,
exhibits a Th-Th distance of 3.632(2) Å.23 Th-(µ2-H)
distances (2.0(1)-2.3(1) Å) are found to be slightly
shorter than the Th-(µ3-H) distances (2.3(1)-2.6(1) Å)
and are in the range expected for bridging thorium-
hydride interactions, as demonstrated by the neutron
diffraction study of [(η-C5Me5)2Th(µ-H)(H)]2 with Th-
(µ2-H) distances of 2.29(3) Å.31 Th-O distances of 2.126-
(7)-2.164(7) Å are directly comparable to those observed
in 2 and related complexes (vide supra). The Th-O-C
angles are also similar to those observed in 2, ranging
from 166.6(6) to 179.1(7)°.
The molecular geometry of 6 is highly unusual and
is worthy of special note. The central M3(µ3-H)2(µ2-H)4
core appears to be structurally unprecedented among
metal hydride complexes, and we are aware of only
three structurally characterized complexes among the
later transition metals which feature triply bridging
hydride ligands capping both faces of a trimetallic core.32
The overall M3X12 moiety may be considered as a
derivative of the well-known M3X11 structural type33
formed by the addition of a single µ2 ligand along one
edge. The resulting M3(µ3-X)2(µ2-X)4X6 geometry ap-
pears to be a new structural type of triangular cluster.
frequency of 1610 cm-1 was observed in the isocyanate
insertion product (η-C5Me5)2Zr[C4H6(dN-t-Bu)O], which
was shown to have no NfZr interaction by means of
an X-ray diffraction study.34 Insertion of PhNdCdO
into a ZrsC bond of Cp2ZrMe2 has been previously
reported, and the bonding mode as determined by X-ray
crystallography was best described by a delocalized
structure analogous to that depicted in B.35
(33) (a) Cotton, F. A.; Marler, D. O.; Schwotzer, W. Inorg. Chim.
Acta 1984, 95, 207. (b) Cotton, F. A.; Marler, D. O.; Schwotzer, W.
Inorg. Chim. Acta 1984, 95, L23. (c) Evans, W. J .; Sollberger, M. S.
Inorg. Chem. 1988, 27, 4417. (d) Evans, W. J .; Sollberger, M. S.;
Hanusa, T. P. J . Am. Chem. Soc. 1988, 110, 1841. (e) Bradley, D. C.;
Chudzynska, H.; Hursthouse, M. B.; Motevalli, M. Polyhedron 1991,
10, 1049. (f) Chisholm, M. H.; Folting, K.; Huffman, J . C.; Kirkpatrick,
C. C. J . Am. Chem. Soc. 1981, 103, 5967. (g) Leverd, P. C.; Arliguie,
T.; Ephritikhine, M.; Nierlich, M.; Lance, M.; Vigner, J . New J . Chem.
1993, 17, 769. (h) Clark, D. L.; Gordon, J . C.; Huffman, J . C.; Watkin,
J . G.; Zwick, B. D. New J . Chem. 1995, 19, 495.
(31) Broach, R. W.; Schultz, A. J .; Williams, J . M.; Brown, G. M.;
Manriquez, J . M.; Fagan, P. J .; Marks, T. J . Science (Washington, D.C.)
1979, 203, 172.
(32) (a) Haupt, H.-J .; Florke, U.; Balsaa, P. Acta Crystallogr., Sect.
C 1988, 44, 61. (b) Schneider, J . J .; Goddard, R.; Kru¨ger, C.; Werner,
S.; Metz, B. Chem. Ber. 1991, 124, 301. (c) Haupt, H.-J .; Florke, U.;
Schneider, H. Acta Crystallogr., Sect. C 1991, 47, 2531.
(34) Yasuda, H.; Okamoto, T.; Matsuoka, Y.; Nakamura, A.; Kai,
Y.; Kanehisa, N.; Kasai, N. Organometallics 1989, 8, 1139.
(35) Gambarotta, S.; Strologo, S.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. Inorg. Chem. 1985, 24, 654.

Aryloxides as Ligands in Organoactinide Chemistry
Organometallics, Vol. 15, No. 3, 1996 955
1
The H NMR spectrum of complex 6 has a resonance
M ) Th, R ) 2,6-i-Pr2C6H3 (5)). Complex 2 thus differs
considerably in its reactivity from that of the cyclopen-
tadienyl-supported bis(alkyl) complex (η-C5Me5)2UMe2,
which reacts with 2,6-diisopropylaniline to produce the
imido species (η-C5Me5)2U(N-2,6-i-Pr2C6H3).38 The zir-
conium complex Zr(OAr)2(NHPh)2 is also observed to
undergo facile conversion to the imido derivative Zr-
(OAr)2(NPh)(py′) upon treatment with 1 equiv of 4-pyr-
rolidinopyridine (py′).15h All attempts to isolate a
thorium imido species using similar methodologies were
unsuccessful.
at 20.54 ppm, indicative of a thorium hydride spe-
cies,21,23 and this resonance shows only slight broaden-
ing at -90 °C in toluene-d8. The IR spectrum of 6 (Nujol
mull, KBr plates) displays ν(Th-H) stretches at 1336,
975, and 795 cm-1 which are shifted to 954, 705, and
560 cm-1, respectively, upon deuteration. In the tho-
rium hydrido complexes {[Me2Si(η-C5Me4)2]Th(µ-H)2}2
and [(η-C5Me5)2Th(µ-H)(H)]2, the bridging thorium hy-
drides show ν(Th-H) stretches in the region 1285-481
cm-1, while terminal Th-H stretching frequencies were
observed at 1404 and 1370 cm-1 21,23
.
The overwhelming majority of transition-metal hy-
dride complexes are supported by soft π-acceptor ligands
such as carbon monoxide or phosphine, or π-bound
carbocyclic ligands such as cyclopentadienyl, and the
number of hydride complexes supported exclusively by
π-donating alkoxides or aryloxide ligands is very small,
with most of the known examples being based upon Mo,
W, or Re metal centers.39 Early-transition-metal alkox-
ide/hydride complexes are limited to the group 5 species
Ta(OSi-t-Bu3)3H2,40a [M(OSi-t-Bu3)2H2]2 (M ) Nb,40b
Ta40a), Nb(O-2,6-(C6H11)2C6H3)4H,40c and Ta(O-2,6-i-
Pr2C6H3)3H2L (L ) phosphine ligand)40d and the tita-
nium derivatives Ti4(OEt)13(H)41 and Ti3(OPh)6(H),42
which have been proposed only upon the basis of
reactivity data. Complex 6 thus represents a rare
example of an early-metal hydrido complex supported
exclusively by aryloxide ligation. However, while Roth-
well and co-workers have found aryloxide-supported
hydrido derivatives of group 5 to be effective arene
hydrogenation catalysts,40d,43 the trimeric dihydride
complex [ThH2(OAr)2]3 (6) was found to exhibit only
modest activity in the catalytic hydrogenation of 1-hex-
ene (3 turnovers h-1 at 1 atm).
Con clu d in g Rem a r k s
We have shown that the sterically demanding 2,6-di-
tert-butylphenoxide moiety serves as a useful ancillary
ligand for thorium alkyl complexes. The aryloxide
ligand may be readily introduced into the coordination
sphere of the thorium metal center by selective metath-
esis reaction of ThBr4(THF)4 with KOAr to form ThBr2-
(OAr)2(THF)2 (1). Straightforward alkylation of 1 with
a Grignard reagent subsequently allows access to the
aryloxide-supported alkyl complex Th(OAr)2(CH2SiMe3)2
(2).
The reactivity of 2 provides some interesting com-
parisons both with cyclopentadienyl-supported thorium
alkyls and also with analogous group 4 aryloxide-alkyl
derivatives. Thus, the thermolysis of 2 in benzene at
60 °C leads to ligand redistribution and the isolation of
the cyclometalated tris(aryloxide) complex Th(OC6H3-
t-BuCMe2CH2)(OAr)2 (3). In contrast, thermolysis of
M(OAr)2(CH2Ph)2 (M ) Ti, Zr) in toluene at 120 °C leads
to elimination of toluene and the formation of the
A most interesting reactivity comparison is provided
by the ethylene polymerization activities of the bis(alkyl)
complexes (η-C5Me5)2ThMe2, (η-C5Me5)Th(OAr)(CH2-
SiMe3)2, and Th(OAr)2(CH2SiMe3)2 (2) in the presence
of 1 equiv of [HNMe2Ph][B(C6F5)4]. While the bis(pen-
tamethylcyclopentadienyl) derivative [(η-C5Me5)2ThMe]-
[B(C6F5)4] showed an extremely high activity of 3.6 ×
106 g h-1 atm-1 (mol of catalyst)-1 (Nt ) 36 s-1),22 the
mono(aryloxide) complex [(η-C5Me5)Th(OAr)(CH2SiMe3)]-
[B(C6F5)4] displayed a substantially lower activity of
3.46 × 104 g h-1 atm-1 (mol of catalyst)-1 (Nt ) 0.35
cyclometalated aryloxide-alkyl species M(OC6H3-t-
BuCMe2CH2)(OAr)(CH2Ph), but ligand redistribution is
not observed.15i However, heating the homoleptic alkyl
Ti(CH2SiMe3)4 to 80 °C with 2 equiv of HOAr is reported
to produce a mixture of products, including the titanium
analog of 3, namely Ti(OC6H3-t-BuCMe2CH2)(OAr)2.15i
Reaction of 2 with 2,6-dimethylphenyl isocyanate
presented the possibility of an insertion reaction into
either the Th-C bond of a (trimethylsilyl)methyl group
or the Th-O bond of an aryloxide ligand, both reactions
having ample literature precedence.36 Although pref-
erential insertion into a M-O bond rather than an M-C
bond has been observed in an alkylzinc alkoxide,37 it
was expected in the case of 2 that the highly oxophilic
thorium metal center would direct reactivity toward the
Th-C bond. This was confirmed by a 1H NMR study
of the monoinsertion product 4, which revealed that both
aryloxide ligands remained equivalent while two sets
of resonances due to metal-bound and carbon-bound
alkyl groups were observed.
s-1 14
and the bis(aryloxide) complex Th(OAr)2(CH2-
)
SiMe3)2 (2) was found to be inactive. This trend in
reactivity may be rationalized by the presence of the
aryloxide ligands, which are capable of substantial
π-donation to the metal center. It has been reported
previously that the presence of alkoxide ligands in Cp*2-
Th(X)(Y) systems can significantly lower the rate of
alkyl ligand hydrogenolysis by decreasing the electro-
(38) Arney, D. S. J .; Burns, C. J . J . Am. Chem. Soc. 1993, 115, 9840.
(39) Barry, J . T.; Chacon, S. T.; Chisholm, M. H.; Huffman, J . C.;
Streib, W. E. J . Am. Chem. Soc. 1995, 117, 1974 and references therein.
(40) (a) Miller, R. L.; Toreki, R.; LaPointe, R. E.; Wolczanski, P. T.;
Van Duyne, G. D.; Roe, D. C. J . Am. Chem. Soc. 1993, 115, 5570. (b)
LaPointe, R. E.; Wolczanski, P. T. J . Am. Chem. Soc. 1986, 108, 3535.
(c) Chesnut, R. W.; Steffey, B. D.; Rothwell, I. P. Polyhedron 1989, 8,
1607. (d) Visciglio, V. M.; Fanwick, P. E.; Rothwell, I. P. J . Chem. Soc.,
Chem. Commun. 1992, 1505.
The reactivity of 2 toward 2 equiv of substituted
aniline parallels that of the related zirconium complex
Zr(OAr)2Me2, in that both alkyl ligands undergo facile
aminolysis in hydrocarbon solvent to produce the bis-
(arylamido) species M(OAr)2(NHR)2 (M ) Zr, R ) Ph;15h
(41) Sabo, S.; Gervais, D. C.R. Seances Acad. Sci., Ser. C 1980, 291,
207.
(36) Braunstein, P.; Nobel, D. Chem. Rev. 1989, 89, 1927.
(37) (a) Boersma, J .; Noltes, J . G. In Organozinc Coordination
Chemistry; International Lead Zinc Research Organization: New York,
1968; p 61. (b) Noltes, J . G. Recl. Trav. Chim. Pays-Bas 1965, 84, 126.
(42) Flamini, A.; Cole-Hamilton, D. J .; Wilkinson, G. J . Chem. Soc.,
Dalton Trans. 1978, 454.
(43) Ankianiec, B. C.; Fanwick, P. E.; Rothwell, I. P. J . Am. Chem.
Soc. 1991, 113, 4710.

956 Organometallics, Vol. 15, No. 3, 1996
Clark et al.
philicity of the metal center.44 The presence of alkoxide
reaction mixture showed one main product with a number of
minor products. The solvent was allowed to evaporate from
the NMR tube in the glovebox, resulting in an oil which formed
crystals upon addition of 0.2 mL of hexane. The crystals were
isolated by decantation of the solvent and were washed with
a small amount of hexane, resulting in 0.025 g of product.
ligands can also result in an increase in Th-R bond
disruption enthalpies by 2-4 kcal mol-1 44
.
Exp er im en ta l Section
3
Yield: 24%. 1H NMR (300 MHz, benzene-d6): δ 7.45 (d, J HH
Gen er a l P r oced u r es a n d Tech n iqu es. All manipula-
tions were carried out under an inert atmosphere of oxygen-
free UHP grade argon using standard Schlenk techniques, or
under oxygen-free helium in a Vacuum Atmospheres glovebox.
ThBr4(THF)4 was prepared as described previously.18 2,6-
Dimethylphenyl isocyanate and 2,6-diisopropylaniline were
obtained from Aldrich and degassed prior to use. 2,6-Di-tert-
butylphenol (Aldrich) was used as received. KO-2,6-t-Bu2C6H3
was prepared from the reaction of 2,6-di-tert-butylphenol with
potassium hydride in THF. [HNMe2Ph][B(C6F5)4] was ob-
tained from Quantum Design and used as received. Solvents
were degassed and distilled from Na or Na/benzophenone ketyl
under nitrogen. Benzene-d6 was dried with Na/benzophenone
ketyl and then trap-to-trap-distilled before use.
) 8 Hz, 1 H, meta OAr), 7.31 (d, 3J HH ) 8 Hz, 1 H, meta OAr),
3
3
7.18 (d, J HH ) 8 Hz, 4 H, meta OAr), 6.94 (t, J HH ) 8 Hz, 1
3
H, para OAr), 6.79 (t, J HH ) 8 Hz, 2 H, para OAr), 1.76 (s, 6
H, ThCH2CMe2), 1.57 (s, 9 H, Th-t-BuC6H3), 1.50 (s, 36 H,
t-Bu2C6H3), 1.39 (s, 2 H, ThCH2CMe2). IR (cm-1): 1407 (s),
1265 (m), 1221 (s), 1196 (m), 1123 (m), 1101 (w), 860 (s), 820
(m), 796 (w), 749 (s), 722 (m), 657 (m). Anal. Calcd for
C
42H62O3Th: C, 59.56; H, 7.38. Found: C, 59.22; H, 7.03.
Th (O-2,6-t-Bu 2C6H3)2{OC[dN(2,6-Me2C6H3)]CH2SiMe3}-
(CH2SiMe3) (4). 2,6-Dimethylphenyl isocyanate (0.038 g,
0.257 mmol) in hexane (1 mL) was added to a hexane (8 mL)
solution of 2 (0.200 g, 0.245 mmol), and the mixture was stirred
at room temperature for 18 h. All solvent was removed under
vacuum, 1 mL of hexane was added, and the resulting solution
was cooled to -40 °C, resulting in colorless crystals. The
crystals were isolated by filtration and washed with 0.5 mL
of cold hexane. Yield: 0.167 g (67%). 1H NMR (300 MHz,
NMR spectra were recorded at 22 °C on a Bru¨ker WM 300
1
spectrometer in benzene-d6. All H NMR chemical shifts are
1
reported in ppm relative to the H impurity in benzene-d6 at
δ 7.15. Infrared spectra were recorded on a BioRad FTS-40
spectrophotometer as Nujol mulls between KBr plates. El-
emental analyses were performed on a Perkin-Elmer 2400
CHN analyzer. Elemental analysis samples were prepared
and sealed in tin capsules in the glovebox prior to combustion.
Th Br 2(O-2,6-t-Bu 2C6H3)2(THF )2 (1). THF (70 mL) was
added to a mixture of ThBr4(THF)4 (8.57 g, 10.2 mmol) and
KO-2,6-t-Bu2C6H3 (5.00 g, 20.4 mmol), and the mixture was
stirred for 18 h at room temperature with much precipitate
being formed. All solvent was removed under vacuum; the
solid was extracted with toluene (3 × 25 mL) and filtered
through a Celite pad. The filtrate was cooled to -40 °C,
resulting in a solid mass of colorless crystals which were
isolated by filtration and washed with hexane. Yield: 6.5 g
3
benzene-d6): δ 7.25 (d, J HH ) 8 Hz, 4 H, meta OAr), 6.82 (m,
5 H, Ar), 2.14 (s, 6 H, NC6H3Me2), 1.58 (s, 36 H, t-Bu), 1.38 (s,
2 H, ThOCCH2), 0.46 (s, 2 H, ThCH2), 0.32 (s, 9 H, SiMe3),
0.00 (s, 9 H, SiMe3). 13C NMR (75.5 MHz, benzene-d6): δ
-0.43 (SiMe3), 4.07 (SiMe3), 19.84 (NC6H3Me2), 25.64 (CCH2-
SiMe3), 32.21(CMe3), 34.97 (CMe3), 88.83 (ThCH2), 120.12,
125.21, 125.66, 128.60, 131.46, 137.67, 144..06, 162.94 (aro-
matic carbons), 182.68 (ThOC). IR (cm-1): 1520 (m), 1411 (s),
1378 (m), 1244 (m), 1220 (s), 1200 (m), 1165 (w), 1125 (w),
1117 (w), 1107 (w), 869 (br s), 828 (m), 780 (w), 759 (m), 732
(w) 625 (m), 562 (w). Anal. Calcd for C44H73NO3Si2Th: C,
56.05; H, 7.63; N, 1.45. Found: C, 55.45; H, 7.70; N, 1.22.
Th (O-2,6-t-Bu 2C6H3)2(NH-2,6-i-P r 2C6H3)2 (5). A hexane
solution (4 mL) of H2N-2,6-i-Pr2C6H3 (0.095 g, 0.490 mmol) was
added to a cold (-78 °C) hexane solution (50 mL) of 1 (0.400
g, 0.490 mmol), and the reaction mixture was stirred for 1 h
at -78 °C. The solution was warmed to room temperature
and stirred for 2 h, after which all solvent was removed in
vacuo. An NMR spectrum of the crude reaction mixture
showed resonances assigned to the starting material in addi-
tion to signals consistent with mono- and bis(amide) products.
A further 1 equiv of H2N-2,6-i-Pr2C6H3 (0.095 g, 0.490 mmol)
in hexane (30 mL) was added to the crude reaction mixture,
and the resulting solution was stirred for 24 h. The solution
was concentrated to 1 mL and cooled to -40 °C, resulting in
a white powder. Yield: 0.44 g (92%). 1H NMR (300 MHz,
3
(67%). 1H NMR (300 MHz, benzene-d6): δ 7.49 (d, J HH ) 8
Hz, 4 H, meta OAr), 6.85 (t, 3J HH ) 8 Hz, 2 H, para OAr), 3.11
(m, 8 H, R-THF), 1.69 (s, 36 H, t-Bu), 0.97 (m, 8 H, â-THF). IR
(cm-1): 1408 (s), 1314 (w), 1266 (m), 1231 (m), 1212 (s), 1193
(s), 1122 (m), 1003 (m), 882 (m), 845 (s), 820 (m), 799 (w), 754
(m), 724 (m), 663 (m). Anal. Calcd for C36H58Br2O4Th: C,
45.67; H, 6.18. Found: C, 45.89; H, 6.37.
Th (O-2,6-t-Bu 2C6H3)2(CH2SiMe3)2 (2). A diethyl ether
solution of Me3SiCH2MgCl (1 M, 6.4 mL, 6.4 mmol) was added
to a toluene (30 mL) solution of ThBr2(O-2,6-t-Bu2C6H3)2(THF)2
(2.54 g, 2.68 mmol), and this mixture was stirred for 3 min.
Dioxane (2 mL) was added, resulting in much precipitation
and the mixture was stirred for 2 h before the mixture was
taken to dryness in vacuo. The solid was extracted with
toluene (2 × 25 mL); the extracts were filtered through a Celite
pad, concentrated to 10 mL, and cooled to -40 °C, resulting
in colorless crystals. The crystals were isolated by filtration
and washed with 2 × 3 mL of cold hexane. Yield: 1.34 g (61%).
3
benzene-d6): δ 7.22 (d, J HH ) 7 Hz, 4 H, meta Ar), 7.03 (d,
3J HH ) 8 Hz, 4 H, meta Ar), 7.25 (m, 4 H, para Ar), 5.90 (s, 2
H, HN), 3.39 (septet, 3J HH ) 7 Hz, 4 H, CHMe2), 1.60 (s, 36 H,
3
t-Bu), 1.25 (d, J HH ) 7 Hz, 24 H, CHMe2). IR (cm-1): 1407
(s), 1326 (m), 1306 (w), 1263 (w), 1246 (w), 1268 (s), 1195 (s),
1117 (m), 1103 (w), 873 (m), 861 (s), 848 (s), 820 (m), 796 (w),
749 (s), 722 (m), 689 (w), 658 (m), 568 (w), 547 (w). Anal. Calcd
for C52H78N2O2Th: C, 62.76; H, 7.90; N, 2.81. Found: C, 62.71;
H, 7.77; N, 2.89.
3
1H NMR (300 MHz, benzene-d6): δ 7.21 (d, J HH ) 8 Hz, 4 H,
meta OAr), 6.81 (t, 3J HH ) 8 Hz, 2 H, para OAr), 1.50 (s, 36 H,
t-Bu), 0.50 (s, 4 H, ThCH2), 0.30 (s, 18 H, SiMe3). 13C NMR
(75.5 MHz, benzene-d6): 162.73, 137.44, 125.60, 120.31 (aro-
matic carbons), 93.96 (t, J CH ) 98 Hz, ThCH2), 34.83 (CMe3),
32.14 (CMe3), 4.12 (SiMe3). IR (cm-1): 1411 (s), 1242 (m), 1219
(s), 1195 (w), 1124 (w), 1099 (w), 866 (s), 849 (s), 822 (m), 750
(m), 727 (m), 662 (m), 605 (w), 551 (w). Anal. Calcd for
[Th H2(O-2,6-t-Bu 2C6H3)2]3 (6). Benzene (10 mL) was
added to a 50 mL Kontes flask containing 2 (0.325 g, 0.40
mmol), and a hydrogen atmosphere (1.5 atm) was placed over
the solution. The mixture was stirred for 3 days, and then all
solvent was removed in vacuo. 1H NMR spectra of the crude
reaction mixture showed the presence of unreacted 2 and two
products. Benzene (8 mL) and hydrogen (1.5 atm) were again
added to the flask, and the solution was stirred an additional
4 days. All solvent was removed in vacuo, and upon addition
of 1 mL of hexane, crystals were deposited. Yield: 0.085 g
(33%). 1H NMR (300 MHz, benzene-d6): δ 20.54 (s, 2 H, ThH),
C
36H64O2Si2Th: C, 52.92; H, 7.89. Found: C, 53.17; H, 7.38.
Th (OC6H3-t-Bu CMe2CH2)(O-2,6-t-Bu 2C6H3)2 (3). Th(O-
2,6-t-Bu2C6H3)2(CH2SiMe3)2 (2; 0.100 g, 0.122 mmol) and NEt3
(0.020 g, 0.20 mmol) were dissolved in benzene-d6 in an NMR
tube and heated to 60 °C for 36 h. A 1H NMR spectrum of the
(44) Cp*2ThMe2 is found to undergo hydrogenolysis 4 × 103 times
faster than Cp*2Th(OR)(R): Lin, Z.; Marks, T. J . J . Am. Chem. Soc.
1987, 109, 7979.
3
3
7.21 (d, J HH ) 8 Hz, 4 H, meta OAr), 6.79 (t, J HH ) 8 Hz, 2
H, para OAr), 1.59 (s, 36 H, t-Bu). IR (cm-1): 1476 (m), 1437

Aryloxides as Ligands in Organoactinide Chemistry
Organometallics, Vol. 15, No. 3, 1996 957
(w), 1409 (s), 1390 (m), 1356 (m), 1336 (w), 1263 (m), 1222 (s),
1195 (w), 1120 (s), 1101 (w), 975 (w), 866 (s), 922 (m), 795 (m),
748 (s), 662 (s). Anal. Calcd for C28H44O2Th: C, 52.17; H, 6.88.
Found: C, 52.27; H, 6.75.
Th 3(µ3-H)2(µ2-H)4(O-2,6-t-Bu 2C6H3)6 (6). A light yellow
block was attached to a thin glass fiber using silicone grease
and placed under a nitrogen cold stream on a Siemens P4/PC
diffractometer (graphite-monochromated Mo KR radiation, λ
) 0.710 69 Å). The lattice parameters were optimized from a
least-squares calculation on 32 carefully centered reflections
of high Bragg angle. Three check reflections monitored every
97 reflections showed no systematic variation of intensities.
Lattice determination and data collection were carried out
using XSCANS Version 2.10b software. All data reduction,
including Lorentz and polarization corrections, and structure
solution and graphics were performed using SHELXTL PC
Version 4.2/360 software.45 The structure refinement was
performed using SHELX 93 software. All data were corrected
for absorption using the ellipsoid routine in the XEMP facility
of SHELXTL PC.
The space group, P21/c, was uniquely determined by the
systematic absences. The structure was solved by Patterson
and Fourier techniques and refined by full-matrix least
squares. Non-hydrogen atoms were treated anisotropically,
except for two severely disordered hexane molecules in the
lattice, which were modeled using isotropic carbon atoms of
partial occupancy. The carbon atom hydrogens were placed
in fixed, idealized positions with their isotropic temperature
factors set at 1.5 (methyl) or 1.2 (aromatic) times the equiva-
lent isotropic U of the carbon atom they were bonded to. A
high-angle refinement was used (the weighting function w was
multiplied by 1 - exp[-5((sin θ)/λ)2] for all data) to locate the
hydrogen atoms associated with the thorium cluster. (All
subsequent refinements were performed using the standard
weighting scheme.) All six hydrogen atoms associated with
the thorium core appeared in the high-angle difference map
as peaks with an average height of 0.80 e/Å3 and were refined
with isotropic temperature factors fixed at 0.08 Å2. These
hydrogen atom positions were refined without difficulty to
their final positions. Analysis of the final difference map
showed the residual peaks to be evenly distributed throughout
the unit cell at constant height (0.53 e/Å3). Moreover, none of
these peaks were at chemically meaningful positions for a
thorium-hydride bond. The large majority of the peaks were
either within 1.0 Å of a thorium atom or at nonbonding
positions in the unit cell. Two peaks were within 1.0 Å of H(a),
but their Th-H distances did not correspond to a thorium-
hydride bond. The final refinement converged to R1 ) 0.0460
and wR2 ) 0.0812.
Hyd r ogen a tion of 1-Hexen e by 2. Toluene (5.6 mL) was
added to a 100 mL flask containing 2 (0.019 g, 0.023 mmol)
and [HNMe2Ph][B(C6F5)4] (0.019 g, 0.023 mmol), and the
resulting solution was stirred for 20 min. Hexene (0.62 g, 7.2
mmol) was syringed into the flask, and after 5 min a dihy-
drogen atmosphere was introduced over the solution. The
reaction mixture was stirred for 1 h and then quenched with
1-propanol. All volatile components were vacuum transferred
to a second flask and analyzed by GC-mass spectroscopy. The
mass of hexane produced corresponded to a catalytic rate of 1
turnover h-1 (Th atom)-1
.
Hyd r ogen a tion of 1-Hexen e by 6. Toluene (4.84 mL) was
added to a 100 mL flask containing 6 (0.013 g, 0.023 mmol of
Th). Hexene (0.62 g, 7.2 mmol) was syringed into the flask,
and after 5 min a dihydrogen atmosphere was introduced over
the solution. The reaction mixture was stirred for 3 h and
then quenched with 1-propanol. All volatile components were
vacuum-transferred to a second flask, and the solution was
analyzed by GC-mass spectroscopy. The mass of hexane
produced corresponded to a catalytic rate of 3 turnover h-1
(Th atom)-1
.
H-D Exch a n ge in 6. A benzene-d6 solution of 6 was frozen
in an NMR tube and that was then sealed under an atmo-
sphere of deuterium. The hydride region was monitored
1
periodically by H NMR spectroscopy, and the hydride signal
was found to decrease with a half-life of ca. 36 h.
Cr ysta llogr a p h ic Stu d ies. Th (O-2,6-t-Bu 2C6H3)2(CH2-
SiMe3)2‚C7H8 (2). The clear, well-formed crystals were ex-
amined in mineral oil under an argon stream. The chosen
crystal was affixed to the goniometer head of a CAD4 diffrac-
tometer (employing graphite monochromated Mo KR radiation)
using Apiezon grease and cooled to -70 °C in a cold nitrogen
stream. Unit cell parameters were determined from the least-
squares refinement of ((sin θ)/λ)2 values for 25 accurately
centered reflections with a 2θ range between 16 and 32°.
Three reflections were chosen as intensity standards and were
measured every 3600 s of X-ray exposure time.
The data were reduced using the Structure Determination
Package provided by Enraf-Nonius and corrected for absorp-
tion empirically using high chi ψ-scans. The structure was
solved by routine Patterson and Fourier techniques and refined
by full-matrix least squares. After inclusion of anisotropic
thermal parameters for all non-hydrogen atoms, except for part
of the aryloxide ligands and the toluene of crystallization
(C21-C23, C27, O2, C40-C46, C60-C61), and geometrical
generation of hydrogen atoms, which were constrained to “ride”
upon the appropriate carbon atoms, final refinement using
3883 unique observed (F > 4σ(F)) reflections converged at R
) 0.069 and Rw ) 0.095 (where w ) [σ2(F) + 0.006(F)2]-1). A
final difference Fourier contained some residual electron
density around the thorium atom, the largest peak being 2.42
e/Å3. All calculations were performed using the Siemens
SHELXTL PLUS computing package.45
Ack n ow led gm en t. This work was performed under
the auspices of the Laboratory Directed Research and
Development Program. Los Alamos National Labora-
tory is operated by the University of California for the
U.S. Department of Energy under Contract W-7405-
ENG-36.
Su p p or tin g In for m a tion Ava ila ble: Tables of fractional
atomic coordinates, bond lengths and angles, anisotropic
thermal parameters, and hydrogen atom coordinates for 2 and
6 (22 pages). Ordering information is given on any current
masthead page.
(45) Siemens Analytical X-ray Instruments, Inc., 6300 Enterprise
Lane, Madison, WI 53719.
OM950654U