Thorium(IV) and uranium(IV) ketimide complexes prepared by nitrile insertion into actinide-alkyl and -aryl bonds

Article abstract of DOI:10.1021/om0343824

Migratory insertion of benzonitrile into both An-C bonds of the bis(alkyl) and bis(aryl) complexes (C₅Me₅)₂AnR₂ yields the actinide ketimido complexes (C₅Me₅) ₂An[-N=C(Ph)(R)]₂ (where An = Th, R = Ph, CH ₂Ph, CH₃; An = U, R = CH₂Ph, CH₃) and provides a versatile method for the construction of electronically and sterically diverse ketimide ligands. The Th(IV) compounds represent the first examples of thorium ketimide complexes. The uranium complexes are surprisingly unreactive, and both the uranium and thorium bis(ketimido) complexes display unusual electronic structure properties. The combined chemical and physical properties of these complexes suggest a higher An-N bond order due to significant ligand-to-metal π-bonding in the actinide ketimido interactions and indicate that the f-electrons in mid-valent organouranium complexes might be far more involved in chemical bonding and reactivity than previously thought. We also report herein the structures of the known thorium and uranium complexes (C₅Me₅)₂Th(CH₂Ph)₂, (C₅Me₅)₂ThMe₂, (C₅Me ₅)₂U(CH₂Ph)₂, and (C ₅Me₅)₂UMe₂.

Full text of DOI:10.1021/om0343824

4682
Organometallics 2004, 23, 4682-4692
Th or iu m (IV) a n d Ur a n iu m (IV) Ketim id e Com p lexes
P r ep a r ed by Nitr ile In ser tion in to Actin id e-Alk yl a n d
-Ar yl Bon d s
Kimberly C. J antunen, Carol J . Burns, Ingrid Castro-Rodriguez, Ryan E. Da Re,
J effery T. Golden, David E. Morris, Brian L. Scott, Felicia L. Taw, and
J aqueline L. Kiplinger*
Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
Received December 17, 2003
Migratory insertion of benzonitrile into both An-C bonds of the bis(alkyl) and bis(aryl)
complexes (C5Me5)2AnR2 yields the actinide ketimido complexes (C5Me5)2An[-NdC(Ph)(R)]2
(where An ) Th, R ) Ph, CH2Ph, CH3; An ) U, R ) CH2Ph, CH3) and provides a versatile
method for the construction of electronically and sterically diverse ketimide ligands. The
Th(IV) compounds represent the first examples of thorium ketimide complexes. The uranium
complexes are surprisingly unreactive, and both the uranium and thorium bis(ketimido)
complexes display unusual electronic structure properties. The combined chemical and
physical properties of these complexes suggest a higher An-N bond order due to significant
ligand-to-metal π-bonding in the actinide ketimido interactions and indicate that the
f-electrons in mid-valent organouranium complexes might be far more involved in chemical
bonding and reactivity than previously thought. We also report herein the structures of the
known thorium and uranium complexes (C5Me5)2Th(CH2Ph)2, (C5Me5)2ThMe2, (C5Me5)2U-
(CH2Ph)2, and (C5Me5)2UMe2.
In tr od u ction
have shown that bulky ketimide ligands are instrumen-
tal for the preparation of novel diuranium inverted
naphthalene and cyclooctatetraene sandwich complexes
(1)1 and organouranium complexes that exhibit oxida-
tion state ambiguity (2).2
A variety of methods have proven useful in the
synthesis of transition-metal and lanthanide ketimide
complexes including, but not limited to, nucleophilic
addition to coordinated nitrile ligands,3 nitrile insertion
into M-H, M-C, and M-Si bonds,4 metathesis reac-
tions between metal halides and alkali metal ketimide
or 1-azallyl compounds,1,5 addition of oximes and oxi-
The ketimide, or azavinylidene, functionality (-Nd
CR2) has recently found increasing utility as an ancil-
liary ligand due to its steric and electronic flexibility
(can serve as both a σ- and π-donor) and its ability to
support a broad range of oxidation states for both
d-block and f-block metals.1-13 In fact, recent reports
* To whom correspondence should be addressed. Phone: 505-665-
9553. Fax: 505-667-9905. E-mail: kiplinger@lanl.gov.
(1) Diaconescu, P. L.; Cummins, C. C. J . Am. Chem. Soc. 2002, 124,
7660-7661.
(2) Kiplinger, J . L.; Morris, D. E.; Scott, B. L.; Burns, C. J .
Organometallics 2002, 21, 3073-3075.
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1994, 116, 8613-8620. (b) Kukushkin, V. Y.; Pombeiro, A. J . L. Chem.
Rev. 2002, 102, 1771-1802, and references therein.
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Engl. 1987, 26, 248-250. (b) Werner, H.; Daniel, T.; Mu¨ller, M.; Mahr,
M. J . Organomet. Chem. 1996, 512, 197-205. (c) Ferreira, C. M. P.;
Guedes da Silva, M. F.; Kukushkin, V. Y.; Frau´sto da Silva, J . J . R.;
Pombeiro, A. J . L. J . Chem. Soc., Dalton Trans. 1998, 325-326.
(7) (a) Zippel, T.; Arndt, P.; Ohff, A.; Spannenberg, A.; Kempe, R.;
Rosenthal, U. Organometallics 1998, 17, 4429-4437.
(8) (a) Lefeber, C.; Arndt, P.; Tillack, A.; Baumann, W.; Kempe, R.;
Burlakov, V. V.; Rosenthal, U. Organometallics 1995, 14, 3090-3093.
(b) Hou, Z.; Yoda, C.; Koizumi, T.; Nishiura, M.; Wakatsuki, Y.;
Fukuzawa, S.; Takats, J . Organometallics 2003, 22, 3586-3592, and
references therein.
(4) (a) Evans, W. J .; Meadows, J . H.; Hunter, W. E.; Atwood, J . L.
J . Am. Chem. Soc. 1984, 106, 1291-1300. (b) Erker, G.; Fro¨mberg,
W.; Atwood, J . L.; Hunter, W. E. Angew. Chem., Int. Ed. Engl. 1984,
23, 68-69. (c) Bercaw, J . E.; Davies, D. L.; Wolczanski, P. T.
Organometallics 1986, 5, 443-450. (d) J ordan, R. F.; Bajgur, C. S.;
Dasher, W. E.; Rheingold, A. L. Organometallics 1987, 6, 1041-1051.
(e) Bochmann, M.; Wilson, L. M.; Hursthouse, M. B.; Motevalli, M.
Organometallics 1988, 7, 1148-1154. (f) Woo, W. G.; Tilley, T. D. J .
Organomet. Chem. 1990, 393, C6-C9. (g) Debad, J . D.; Legzdins, P.;
Lumb, S. A.; Batchelor, R. J .; Einstein, F. W. B. Organometallics 1992,
11, 6-8. (h) Erker, G.; Pfaff, R.; Kowalski, D.; Wu¨rthwein, E. U.;
Kru¨ger, C.; Goddard, R. J . Org. Chem. 1993, 58, 6771-6778. (i) Temme,
B.; Erker, G.; Fro¨lich, R.; Grehl, M. J . Chem. Soc., Chem. Commun.
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Erker, G.; Ahlers, W.; Fro¨hlich, R. J . Am. Chem. Soc. 1995, 117, 5853-
5854. (l) Armstrong, D. R.; Henderson, K. W.; Little, I.; J enny, C.;
Kennedy, A. R.; McKeown, A. E.; Mulvey, R. E. Organometallics 2000,
19, 4369-4375. (m) For a photochemically induced nitrile insertion
into a Ta-CH3 bond, see: Boring, E.; Sabat, M.; Finn, M. G.; Grimes,
R. Organometallics 1997, 16, 3993-4000.
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M. D.; Cummins, C. C. Organometallics 2003, 22, 2902-2913.
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1003-1006. (c) Redshaw, C.; Wilkinson, G.; Hussain-Bates, B.; Hurst-
house, M. B. J . Chem. Soc., Dalton Trans. 1992, 555-562. (d)
Mommertz, A.; Leo, R.; Massa, W.; Dehnicke, K. Z. Naturforsch. 1998,
53b, 887-892. (e) Tanabe, Y.; Seino, H.; Ishii, Y.; Hidai, M. J . Am.
Chem. Soc. 2000, 122, 1690-1699.
(11) Cramer, R. E.; Panchanatheswaran, K.; Gilje, J . W. J . Am
Chem. Soc. 1984, 106, 1853-1854.
(5) (a) Collier, M. R.; Lappert, M. F.; McMeeking, J . Inorg. Nucl.
Chem. Lett. 1971, 7, 689-694. (b) Erker, G.; Fro¨mberg, W.; Kru¨ger,
C.; Raabe, E. J . Am. Chem. Soc. 1988, 110, 2400-2405. (c) Zhang; S.;
Piers, W. E. Organometallics 2001, 20, 2088-2092.
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Acta 1987, 139, 171-176.
10.1021/om0343824 CCC: $27.50 © 2004 American Chemical Society
Publication on Web 08/24/2004

Thorium(IV) and Uranium(IV) Ketimide Complexes
Organometallics, Vol. 23, No. 20, 2004 4683
mate salts to electron-rich metal centers,6 reductive
cleavage of azines,2,7 and reductive coupling of both
Schiff bases8 and nitriles.9,10 Compared to the transition-
metal ketimides, actinide ketimide complexes are rare;
only a handful of examples possessing a uranium metal
center have been reported. The ketimide ligands in
complex 1 were introduced using metathesis chemistry
and in complex 2 by the reductive cleavage of benzophe-
none azine. The remaining examples consist of the
uranium mono(ketimide) complexes 4,11 6,12 and 812,13
prepared by nitrile insertion into UdC, U-CH2, and
U-CH3 bonds, respectively.
F igu r e 1. Molecular structure of 10a with thermal el-
lipsoids at the 25% probability level. Selected bond dis-
tances (Å) and angles (deg): Th(1)-N(1) 2.259(4), Th(1)-
N(2) 2.265(5), N(1)-C(21) 1.259(7), N(2)-C(34) 1.272(7),
C(21)-N(1)-Th(1) 174.0(4), C(34)-N(2)-Th(1) 179.4(5),
N(1)-Th(1)-N(2) 108.95(17).
ThMe2, (C5Me5)2U(CH2Ph)2, and (C5Me5)2UMe2, as these
complexes are useful starting materials for the prepara-
tion of many organometallic actinide complexes, yet
their molecular structures have not been reported.
Resu lts a n d Discu ssion
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of
Th or iu m a n d Ur a n iu m Ketim id e Com p lexes. As
depicted in eq 4, treatment of a colorless toluene solution
of (C5Me5)2ThPh2 (9a ) with excess benzonitrile instantly
generates the highly iridescent orange-colored thorium-
(IV) bis(ketimido) complex 10a , which was isolated as
an orange crystalline solid in 82% yield.
The above examples represent the body of work
currently known for ketimide chemistry of the actinide
metals. To the best of our knowledge, there are no
previous reports of thorium ketimide complexes.
Reaction of 9b and 9c with benzonitrile similarly
affords the bright yellow colored thorium(IV) bis-
(ketimido) complexes 10b (72% isolated yield) and 10c
(75% isolated yield), respectively. It is important to note
that reaction of 9a with acetonitrile (NtC-CH3) also
gives the bis(ketimido) complex 10c, further illustrating
the generality of this synthetic method for the construc-
tion of ketimide ligands. The modest isolated yields
reflect the high solubility of the ketimide complexes
rather than the formation of any byproducts. When the
reactions are monitored by 1H NMR spectroscopy,
compounds 10a -c are the only observable thorium-
containing products and are formed in yields greater
than 95%. All compounds display sharp NMR reso-
nances consistent with a diamagnetic 6d05f0 Th(IV)
metal center being present.
A single-crystal X-ray diffraction study of complex 10a
(Figure 1) revealed that benzonitrile inserted into both
Th-C bonds of (C5Me5)2ThPh2 (9a ) in a 1,2-fashion to
form two new nitrogen bonds to the thorium metal
center. The Th-N-C angles are nearly linear (174.0(4)°,
179.4(5)°) and the Th-N distances (2.259(4) Å, 2.265(5)
Å) are shorter on average by ca. 0.1 Å than those
observed for other thorium amide complexes (e.g., (η3-
In our effort to explore valence ambiguity in organo-
metallic actinide chemistry2 and develop synthetic
entries into actinide complexes containing multiply
bonded functional groups,14 we devised a general high-
yield method for preparation of actinide bis(ketimide)
compounds. We now report that benzonitrile inserts into
thorium-alkyl and -aryl bonds in complexes of the type
(C5Me5)2ThR2 to afford the first examples of thorium
ketimido complexes (C5Me5)2Th[-NdC(Ph)(R)]2 (where
R ) Ph, CH2Ph, CH3). This chemistry can be readily
extended to the preparation of uranium bis(ketimide)
complexes, (C5Me5)2U[-NdC(Ph)(R)]2 (where R )
CH2Ph, CH3), and constitutes a generalized method for
the construction of electronically and sterically diverse
ketimide ligands. Herein, we describe the syntheses,
structures, and properties of these thorium(IV) and
uranium(IV) bis(ketimido) complexes. In addition, we
also present the structures for the known thorium and
uranium complexes, (C5Me5)2Th(CH2Ph)2, (C5Me5)2-
(14) (a) Arney, D. S. J .; Burns, C. J . J . Am. Chem. Soc. 1995, 117,
9448-9460, and references therein. (b) Warner, B. P.; Scott, B. L.;
Burns, C. J . Angew. Chem., Int. Ed. 1998, 37, 959-960.

4684 Organometallics, Vol. 23, No. 20, 2004
J antunen et al.
are monitored by 1H NMR spectroscopy, compounds
12b,c are the only observable uranium-containing prod-
ucts and are formed in yields greater than 95%. Fur-
thermore, the NMR spectra for 12b,c are sharp and
paramagnetically shifted, suggesting that the complexes
retain the U(IV) oxidation state.18
In contrast to the thorium chemistry, the reaction
between (C5Me5)2UPh2 (11a ) and benzonitrile does not
give the bis(ketimide) complex (C5Me5)2U(-NdCPh2)2
(2), and instead leads to an intractable mixture of
products. This marked difference in reactivity may be
explained by analogy to previous observations that
solutions of the uranium diphenyl derivative 11a elimi-
nate benzene at room temperature.19 The formation of
benzyne intermediates in this system has been postu-
lated in the preparation of a uranindene complex (14),
prepared from the insertion of diphenylacetylene into
one of the two U-C bonds of the transient (C5Me5)2U-
(benzyne) (13) species (eq 6).
F igu r e 2. Molecular structure of 10b with thermal
ellipsoids at the 25% probability level. Selected bond
distances (Å) and angles (deg): Th(1)-N(1) 2.256(8), N(1)-
C(11) 1.264(13), C(11)-N(1)-Th(1) 161.2(8), N(1)-Th(1)-
N(1A) 102.9(4).
BH4)Th[N(SiMe3)2]3, Th-Nav ) 2.32(2) Å;15a (C5Me5)2-
Th(Cl)(C6H8N3), Th-Nav ) 2.46(1) Å;15b (η8-C8H8)Th-
[N(SiMe3)2]2, Th-Nav ) 2.34(1) Å;15c Th[N(SiMe3)2]2-
(NMePh)2, Th-Nav ) 2.308(7) Å15d). An interesting
comparison is provided by the structurally related
Th(IV) imido complex (C5Me5)2Th(dN-2,6-Me2C6H3)-
(THF), which possesses a ThdN bond distance of
2.045(8) Å and a Th-N-C bond angle of 171.5(7)°.16 In
complex 10a , the planes defined by N(1)dC(21)(Cipso 2
)
and N(2)dC(34)(Cipso)2 are nearly orthogonal (110.6° and
84.9°, respectively) to the Cp(centroid)-Th-Cp(centroid) (Cp
) C5Me5) plane. The NdC bond lengths (1.259(7) Å;
1.272(7) Å) are consistent with sp2-hybridization17 and
compare well with those found in other structurally
characterized ketimido complexes.1-10 In total, all of the
structural features suggest that there is ligand-to-metal
π-bonding in both thorium ketimido interactions.
The molecular structure of complex 10b (Figure 2) is
nearly identical to that for 10a except that it displays
a bent geometry at the ketimide nitrogens (Th-N-C
161.2(8)°). This bending may simply be a manifestation
of unfavorable steric interactions. Similar to 10a , the
Th-N distances (2.256(8) Å) in complex 10b are sig-
nificantly shorter compared to other structurally char-
acterized thorium amide complexes.15 As such, short-
ening of the Th-N bond distances due to sp-hybridization
cannot be ruled out.
The nitrile insertion chemistry was successfully ap-
plied to the synthesis of uranium bis(ketimide) com-
plexes. Reaction of the bis(alkyl) uranium complexes
11b and 11c with excess benzonitrile affords the dark
red uranium(IV) bis(ketimido) complexes 12b (88%
isolated yield) and 12c (71% isolated yield), respectively
(eq 5).
As with the thorium systems, the modest isolated
yields observed for the uranium compounds reflect the
high solubility of the ketimide complexes rather than
the formation of any byproducts. When the reactions
The thorium analogue 9a undergoes the same trans-
formation as in eq 6; however, temperatures of 100 °C
are required to achieve rates comparable to the uranium
system at room temperature.19
As mentioned above, earlier reports demonstrated
that under the appropriate conditions, organonitriles
insert into uranium-carbon bonds to give uranium
ketimide functional groups (eqs 1-3).11-13 In all three
examples, only a single uranium-carbon bond was
elaborated to give a ketimide functional group. For
complex 5, ring strain is clearly a factor in promoting
the nitrile insertion chemistry to give the six-membered
metallacycles 6a -c.12 Whereas nitrile insertion into the
U-CH3 bond in 7 could be achieved under mild condi-
tions,13 insertion of acetonitrile into the UdC bond of 3
required elevated temperatures to give the unusual
uranium ketimide complex 4.11 Thus, the chemistry in
this report is distinctive in that it demonstrates that
nitrile insertion chemistry (1) is not limited to uranium
alkyl complexes and (2) can take place at more than one
uranium-carbon or thorium-carbon bond using readily
accessible actinide alkyl derivatives to furnish a broad
range of actinide bis(ketimide) complexes.
(15) Turner, H. W.; Andersen, R. A.; Zalkin, A.; Templeton, D. H.
Inorg. Chem. 1979, 18, 1221-1224. (b) Sternal, R. S.; Sabat, M.; Marks,
T. J . J . Am. Chem. Soc. 1987, 109, 7920-7921. (c) Gilbert, T. M.; Ryan,
R. R.; Sattelberger, A. P. Organometallics 1988, 7, 2514-2518. (d)
Barnhart, D. M.; Clark, D. L.; Grumbine, S. K.; Watkin, J . G. Inorg.
Chem. 1995, 34, 1695-1699.
(16) Haskel, A.; Straub, T.; Eisen, M. Organometallics 1996, 15,
3773-3775.
(17) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2 1987, S1-S19.
The X-ray structure of the uranium bis(ketimide)
complex 2 was previously reported.2 This complex was
(18) (a) Marks, T. J .; Kolb, J . R. J . Am. Chem. Soc. 1975, 97, 27-
33. (b) Marks, T. J . Prog. Inorg. Chem. 1979, 25, 223-333.
(19) Fagan, P. J .; Manriquez, J . M.; Maatta, E. A.; Seyam, A. M.;
Marks, T. J . J . Am. Chem. Soc. 1981, 103, 6650-6667.

Thorium(IV) and Uranium(IV) Ketimide Complexes
Organometallics, Vol. 23, No. 20, 2004 4685
which have been described as containing significant
π-bonding between the uranium and nitrogen. For
comparison purposes, it is useful to note that complexes
2 and 12b are reminiscent of high-valent uranium(VI)
bis(imido) complexes, which have significant uranium-
imido multiple-bond character as illustrated by the
complex (C5Me5)2U(dN-Ph)2, which exhibits a U-N-C
bond angle of 177.8(6)° and U-N ) 1.952(7) Å.23
However, the metal center in complexes 2 and 12b is
not U(VI), but is clearly U(IV) on the basis of comparison
of the U-N bond distances in the two systems as well
as the NMR and UV-visible-near-IR spectra (vide
infra).
Further evidence for a higher U-N bond order in the
U(IV) ketimido interactions is provided by their chem-
istry, which is distinct from known U(IV) amide com-
plexes. For example, we previously noted that complex
2 displays no reaction chemistry with substrates such
as benzophenone, phenylacetylene, diphenylacetylene,
carbon monoxide, pyridine N-oxide, or dihydrogen.2 This
lack of reactivity is in marked contrast to observations
by Marks and Eisen, who have shown that uranium(IV)
amide complexes of the type (C5Me5)2U(NR′R)2 readily
insert carbon monoxide to form bis(carbamoyl) com-
plexes (C5Me5)2U(η2-CONR′R)2,24 as well as undergo
amine elimination upon reaction with phenylacetylene
to generate the bis(acetylide) complex (C5Me5)2U(-Ct
C-Ph)2.21b
The thorium and uranium ketimide complexes pos-
sess markedly different chemical properties. A survey
of the reactivity of 10a indicates that the Th-N linkage
is reactive toward Ph-CtC-H and pyridine-N-oxide as
evidenced by the formation of benzophenone imine. This
is clearly distinct from the analogous uranium ketimido
system (2), which displays no reaction chemistry toward
identical substrates as noted above. Furthermore, the
mass spectrometry for the uranium and thorium ketim-
ide systems may provide some insight into the nature
of the bonding in the U-N and Th-N linkages. Whereas
the thorium ketimide complexes are unstable and do
not produce a discernible mass spectrum, the uranium
ketimide mass spectrometry fragmentation pattern
reveals loss of C5Me5 rather than loss of NdCPh2,
providing further evidence for the robust character of
the U(-NdCPh2)2 core. These observations suggest that
there are important differences in the ketimido ligand
N(2p) lone-pair π-bonding interactions with U(IV) ver-
sus Th(IV), and therefore in the degree of multiple
bonding between the ketimide ligand and U(IV) and
Th(IV) metal centers.25
F igu r e 3. Molecular structure of 12b with thermal
ellipsoids at the 25% probability level. Selected bond
distances (Å) and angles (deg): U(1)-N(1) 2.184(3), N(1)-
C(11) 1.274(4), C(11)-N(1)-U(1) 162.4(3), N(1)-U(1)-
N(1A) 102.40(15).
prepared by the reaction of (C5Me5)2UCl2 with two
reducing equivalents (provided by KC8), followed by
addition of 1 equiv of benzophenone azine, Ph2CdN-
NdCPh2. Complex 2 is isostructural to the thorium
derivative 10a ; any significant deviation in the M-N
bond distances between the two complexes is readily
attributable to the smaller ionic radius of U(IV) versus
Th(IV).20 Important structural parameters are the U-N
distances of 2.179(6) and 2.185(5) Å, the NdC distances
of 1.293(8) and 1.281(8) Å, and the U-N-C bond angles
of 173.4(6)° and 176.5(5)°. These are consistent with the
formulation of the ligands as ketimide groups with the
uranium metal center accepting density from the ni-
trogen 2p lone-pairs.
As noted for the thorium bis(ketimide) derivatives,
the molecular structure of complex 12b (Figure 3) is
nearly identical to that of 2 except that it displays a
significantly more bent geometry at the ketimide nitro-
gens (U-N-C 162.4(3)°). Similar to 2, the U-N dis-
tances (2.184(3) Å) in complex 12b are significantly
shorter compared to other structurally characterized
uranium(IV) amide complexes (e.g., Cp3U[N(C6H5)2],
U-N ) 2.29(1) Å;21a (C5Me5)2U[NH(2,6-Me2C6H3)]2,
U-N ) 2.267(6) Å;21b (C5Me5)(η5-C5Me4CH2NAd)U[NH-
(Ad)], U-N ) 2.231(6), 2.155(7) Å;21c (C5Me5)2U{η3-
(N,N′,N′′)-[N(H)(2,4-tBu2C6H2-6-CH2-N-NdCPh2)]},
U-N ) 2.315(9), 2.228(10) Å;14c [Me2Si(η5-C5Me4)(tBuN)]-
U(NMe2)2, U-N ) 2.278(4), 2.207(4), 2.212(4) Å21d). The
short U-N bond distances and nearly linear U-N-C
bond angles in complexes 2 and 12b are consistent with
significant uranium-nitrogen multiple-bond character
and compare favorably with other uranium(IV) ketimide
(e.g., (DME)(I)U[-NdC(tBu)(2,4,6-Me3C6H2)]3,1 U-N )
2.176(12), 2.196(12), 2.196(13) Å, U-N-C ) 171.4(17)°,
160.4(13)°, 172.8(14)°, and Cp3U-NdC(Me)CH-
(PMePh2),11 U-N ) 2.06(1) Å, U-N-C ) 163(1)°) and
uranium(IV) sulfilimine (e.g., (C5Me5)2U(-N-SPh2)2,22
U-N ) 2.143(3) Å, U-N-S ) 152.2(2)°) complexes
Electr on ic Str u ctu r a l Ch a r a cter iza tion of th e
Th or iu m a n d Ur a n iu m Ketim id e Com p lexes. The
structural data described above demonstrate that the
interaction between the tetravalent actinide metals and
the ketimide ligands involves some degree of π-bonding
to account for the relative shortening of the metal-
(22) Ariyaratne, K. A. N. S.; Cramer, R. E.; Gilje, J . W. Organome-
tallics 2002, 21, 5799-5802.
(23) Arney, D. S. J .; Burns, C. J .; Smith, D. C. J . Am. Chem. Soc.
1992, 114, 10068-10069.
(24) Fagan, P. J .; Manriquez, J . M.; Vollmer, S. H.; Day, C. S.; Day,
V. W.; Marks, T. J . J . Am. Chem. Soc. 1981, 103, 2206-2220.
(25) Further studies employing techniques such as PES will be of
interest for probing the degree of multiple bonding between the
ketimide ligand and U(IV)/Th(IV). For example, see: Brennan, J . G.;
Green. J . C.; Redfern, C. M. Inorg. Chim. Acta 1987, 139, 331-333.
(20) Shannon, R. D. Acta Crystallogr., Sect. A 1976, A32, 751-767.
(21) (a) Cramer, R. E.; Engelhardt, U.; Higa, K. T.; Gilje, J . W.
Organometallics 1987, 6, 41-45. (b) Straub, T.; Frank, W.; Reiss, G.
J .; Eisen, M. S. J . Chem. Soc., Dalton Trans. 1996, 2541-2546. (c)
Peters, R. G.; Warner, B. P.; Scott, B. L.; Burns, C. J . Organometallics
1999, 18, 2587-2589. (d) Stubbert, B. D.; Stern, C. L.; Marks, T. J .
Organometallics 2003, 22, 4836-4838.

4686 Organometallics, Vol. 23, No. 20, 2004
J antunen et al.
F igu r e 4. Electronic absorption spectra of ∼1 × 10-4
M
toluene solutions of (C5Me5)2Th[-NdC(Ph)(R)]2 (10a , R )
Ph, blue; 10b, R ) CH2Ph, green; 10c, R ) CH3, red) and
(C5Me5)2U[-NdC(Ph)(CH2Ph)]2 (12b, pink).
F igu r e 5. Cylic voltammograms of ∼5 × 10-3 M solutions
of (C5Me5)2Th[-NdC(Ph)(R)]2 (10a , R ) Ph, blue; 10b, R
) CH2Ph, green) and (C5Me5)2U(-NdCPh2)2 (2, pink) in
0.1 M [(n-Bu4N][B(C6F5)4]/THF at a Pt electrode. Scan rate
is 200 mV/s.
nitrogen bonds. The resulting enhanced electronic in-
teraction between the metal and ligands should also be
reflected in probes of electronic structure, namely,
electronic absorption spectroscopy and cyclic voltam-
metry. The vivid colors exhibited by the Th(IV) ketimido
complexes (10a -c) are clearly reflected in the UV-
visible electronic absorption spectra (Figure 4). These
complexes all possess broad, intense electronic absorp-
tion bands that extend from the UV into the visible
wavelength range, with an additional weak feature
between 450 and 500 nm (Figure 4). The spectrum of
(C5Me5)2U[-NdC(Ph)(CH2Ph)]2 (12b) is included in
Figure 4 for comparison. This complex has similarly
intense, broad absorption bands throughout the UV-
visible region, but in addition possesses weaker and
somewhat more structured broad bands that tail to
lower energy. These additional lower-energy transitions
render the U(IV) complex a dark red color. (This
complex also has numerous f-f bands in the near-
infrared (not shown in Figure 4) derived from the 5f 2
electronic configuration.)26
Most Th(IV) complexes are colorless, reflecting the
absence of valence electrons on the metal center
(6d05f0 electronic configuration). There have been a few
reports of colored Th(IV) organometallic species, and the
color in these complexes has been attributed to visible
ligand-to-metal charge-transfer (LMCT) transitions.27
Thorium(III) complexes, while relatively rare, are in-
tensely colored because the 6d15f 0 or 6d05f 1 electronic
configurations engender ligand field (d-d or f-f) or
electric dipole-allowed metal-localized (f-d) transi-
tions.28 Interestingly, the structurally related d0 early
transition metal ketimido complexes (C5H5)2M(-Nd
CPh2)2 (M ) Ti, Zr) are also highly colored (red in both
cases); however, no electronic spectral data have been
reported for these and the origin of the color has not
been ascribed to any specific electronic transition.4b,7
The high molar absorptivity values found for these
Th(IV) and U(IV) ketimido complexes in the UV-visible
region are consistent with ligand-localized π-π* and/
or charge-transfer transitions. In fact, the molar ab-
sorptivity in this spectral region for other (C5Me5)2An-
(R)(R′) complexes where R, R′ ) alkyl or aryl seldom
exceeds about 5000 M-1 cm-1 at the short wavelength
limit of the solvent.26 Thus, the more intense bands seen
for the ketimido complexes must be attributable to new
electronic states derived from transitions into or out of
high-lying ligand-based orbitals. We have also observed
visible luminescence from these Th(IV) ketimido com-
plexes and resonance-enhanced Raman vibrational spec-
tra from both the Th(IV) and U(IV) ketimido systems.
The existence of these more molecular-type spectral
properties is quite unusual, even for the early actinide
metals and their complexes other than the actinyl
(AnO2n+) species that possess metal-oxygen multiple
bonds. However, such properties are consistent with
enhanced electronic interactions between the actinide
and the ketimido ligands. Complete details of this novel
molecular-spectroscopic behavior will be provided in a
forthcoming paper.29
The cyclic voltammetric data for the ketimido com-
plexes (Figure 5) reflect the novel electronic structure
in two important ways. First, although the Th(IV)
complexes do not possess voltammetric waves attribut-
able to metal-based redox processes, they do possess
ketimido ligand-based reduction waves. This demon-
strates the existence of empty low-lying ligand-based
acceptor orbitals that are available to participate as the
terminal orbitals in an optical excitation process as seen
in the absorption spectral data. Second, the U(IV)
ketimido complexes (such as 2 shown in Figure 5)
(26) Morris, D. E.; Da Re, R. E.; J antunen, K. C.; Castro-Rodriguez,
I.; Kiplinger, J . L. Organometallics, in press.
(27) Cloke, F. G. N.; Hitchcock, P. B. J . Am. Chem. Soc. 1997, 119,
7899-7900.
(28) (a) Kaltsoyannis, N.; Bursten, B. E. J . Organomet. Chem. 1997,
528, 19-33. (b) Parry, J . S.; Cloke, F. G. N.; Coles, S. J .; Hursthouse,
M. B. J . Am. Chem. Soc. 1999, 121, 6867-6871. (c) Blake, P. C.;
Edelstein, N. M.; Hitchcock, P. B.; Kot, W. K.; Lappert, M. F.;
Shalimoff, G. V.; Tian, S. J . Organomet. Chem. 2001, 636, 124-129.
(29) Da Re, R. E.; J antunen, K. C.; Golden, J . T.; Kiplinger, J . L.;
Morris, D. E., manuscript in preparation.

Thorium(IV) and Uranium(IV) Ketimide Complexes
Organometallics, Vol. 23, No. 20, 2004 4687
complexes are as expected; the Th-CH3 and U-CH3
bond distances compare favorably with those found in
other structurally characterized thorium(IV) and ura-
nium(IV) methyl complexes (e.g., Cp2Th(dmpe)(CH3)2,
Th-C ) 2.583(7), 2.562(8) Å;32a (C5Me5)2Th[P(SiMe3)2]-
(CH3), Th-C ) 2.510(13) Å;32b (C11H11)3Th(CH3), Th-C
) 2.48(3), 2.50(3) Å;32c (C9Me7)2Th(CH3)2, Th-C )
2.48(2), 2.47(2) Å;32d (dmpe)U(CH2Ph)3(CH3), U-C )
2.41(1) Å;33a [PhC(NSiMe3)2]3U(CH3), U-C ) 2.498(5)
Å;33b [1,3-(Me3Si)2C5H3]2U(CH3)2, U-C ) 2.42(2) Å;33c
[(3,5-Me2C6H3)(tBu)N]3U(CH3), U-C ) 2.446(7) Å;33d
[(C5Me5)2U(OSO2CF3)(CH3)]2, U-Cav ) 2.416(7) Å33e).
Figure 7 illustrates the molecular structures of com-
plexes 9b and 11b. As with the methyl derivatives,
these complexes are isostructural; any significant devia-
tion between the M-C bond distances exhibited by the
two complexes is readily attributable to the smaller ionic
radius of U(IV) versus Th(IV).20 If one ignores the short
U(1)-C(22) and Th(1)-C(22) contacts, the geometry of
the complexes is pseudotetrahedral about the actinide
metal centers. In both 9b and 11b, the actinide(IV)
metal center is bound to the pentamethylcyclopentadi-
enyl ligands in an η5-manner and the two benzyl ligands
are positioned in the equatorial girdle of the (C5Me5)2-
An (An ) Th, U) bent metallocene framework. One of
the benzyl ligands is bound to the metal center in an
η1-fashion (complex 11b, benzyl ligand #1: U(1)-C(28)
) 2.467(5) Å, U(1)-C(29) ) 3.656(5) Å, U(1)-C(28)-
C(29) ) 134.2(4)°; complex 9b, benzyl ligand #1: Th(1)-
C(28) ) 2.551(7) Å, Th(1)-C(29) ) 3.709(6) Å, Th(1)-
C(28)-C(29) ) 133.0(6)°) and displays no secondary
interactions between the arene ring and the actinide
metal center. The second benzyl ligand is bound to the
actinide metal center in a multihapto fashion as clearly
demonstrated by the metrical parameters associated
with the uranium- and thorium-benzyl linkages (com-
plex 11b, benzyl ligand #2: U(1)-C(21) ) 2.489(5) Å,
U(1)-C(22) ) 2.970(5) Å, U(1)-C(21)-C(22) ) 93.6(3)°,
U(1)-C(23) ) 3.605(6) Å, U(1)-C(27) ) 3.581(6) Å;
complex 9b, benzyl ligand #2: Th(1)-C(21) ) 2.552(7)
Å, Th(1)-C(22) ) 2.979(6) Å, Th(1)-C(21)-C(22) )
91.7(4)°, Th(1)-C(23) ) 3.622(7) Å, Th(1)-C(27) )
3.556(6) Å). These benzyl groups are best described as
η4 with the strongest secondary interaction occurring
between the actinide metal center and the ipso carbon
of the coordinated benzyl ligand, in addition to weaker
unsymmetrical secondary interactions taking place
between the actinide metal and the ortho carbons of the
benzyl ligand.
F igu r e 6. Molecular structures of complexes 9c (left) and
11c (right) with thermal ellipsoids at the 25% probability
level. Selected bond distances (Å) and angles (deg) for 9c:
Th(1)-C(1) 2.471(8); Th(1)-C(2) 2.478(9); C(1)-Th(1)-C(2)
98.6(4); Th-Ccent 2.518; Th-Cring(av) 2.792(6); C5Me5(cent)
-
Th-C5Me5(cent) 133.9. Selected bond distances (Å) and
angles (deg) for 11c: U(1)-C(21) 2.424(7); U(1)-C(22)
2.414(7); C(21)-U(1)-C(22) 94.5(3); U-Ccent 2.456, 2.461;
U-Cring(av) 2.732(7), 2.739(6); C5Me5(cent)-U-C5Me5(cent) 140.5.
exhibit reversible redox waves associated with metal-
based reduction [U(IV)/U(III)] and oxidation [U(V)/
U(IV)]. While the reduction process is quite common for
U(IV) organometallic complexes, the presence of an
electrochemically reversible oxidation wave to generate
a U(V) species is rare.30 The stabilization of the U(V)
oxidation state appears to be a direct consequence of
the additional π-bonding interaction between the ac-
tinide metal and the ketimido ligands.26
Str u ctu r a l Ch a r a cter iza tion of th e Th or iu m a n d
Ur a n iu m Com p lexes (C5Me5)2Th Me2 (9c), (C5Me5)2-
UMe2 (11c), (C5Me5)2Th (CH2P h )2 (9b), a n d (C5Me5)2-
U(CH2P h )2 (11b). In the course of our studies on
thorium(IV) and uranium(IV) bis(ketimide) complexes,
we obtained single crystals of the known complexes 9b,c
and 11b,c suitable for X-ray diffraction.31 The molecular
structures of these widely used actinide starting materi-
als have not been reported. As illustrated in Figure 6,
the molecular structures of 9c and 11c reveal a typical
bent metallocene framework with a pseudotetrahedral
coordination environment about the thorium and ura-
nium atoms, respectively. The complexes are isostruc-
tural; any significant deviation between the M-C bond
distances exhibited by the two complexes is readily
attributable to the smaller ionic radius of U(IV) versus
Th(IV).20 Within the metallocene wedge lie the two
methyl ligands (Th(1)-C(1) 2.471(8) Å, Th(1)-C(2)
2.478(9) Å, C(1)-Th(1)-C(2) 98.6(4)° for 9c and U(1)-
C(21) 2.424(7) Å, U(1)-C(22) 2.414(7) Å, C(21)-U(1)-
C(22) 94.5(3)° for 11c). The metrical parameters in these
(32) (a) Zalkin, A.; Brennan, J . G.; Andersen, R. A. Acta Crystallogr.
1987, C43, 418-420. (b) Hall, S. W.; Huffman, J . C.; Miller, M. M.;
Avens, L. R.; Burns, C. J .; Arney, D. S. J .; England, A. F.; Sattelberger,
A. P. Organometallics 1993, 12, 752-758. (c) Spirlet, M. R.; Rebizant,
J .; Bettonville, S.; Goffart, J . Acta Crystallogr. 1993, C49, 1138-1140.
(d) Trnka, T. M.; Bonanno, J . B.; Bridgewater, B. M.; Parkin, G.
Organometallics 2001, 20, 3255-3264.
(33) (a) Edwards, P. G.; Andersen, R. A.; Zalkin, A. Organometallics
1984, 3, 293-298. (b) Wedler, M.; Kno¨sel, F.; Edelmann, F. T.; Behrens,
U. Chem. Ber. 1992, 125, 1313-1318. (c) Lukens, W. W., J r.; Beshouri,
S. M.; Blosch, L. L.; Stuart, A. L.; Andersen, R. A. Organometallics
1999, 18, 1235-1246. (d) Diaconescu, P. L.; Odom, A. L.; Agapie, T.;
Cummins, C. C. Organometallics 2001, 20, 4993-4995. (e) Kiplinger,
J . L.; J ohn, K. D.; Morris, D. E.; Scott, B. L.; Burns, C. J . Organome-
tallics 2002, 21, 4306-4308.
(30) (a) Clappe, C.; Leveugle, D.; Hauchard, D.; Durand, G. J .
Electroanal. Chem. 1998, 448, 95-103. (b) Hauchard, D.; Cassir, M.;
Chivot, J .; Ephritikhine, M. J . Electroanal. Chem. 1991, 313, 227-
241. (c) Hauchard, D.; Cassir, M.; Chivot, J .; Baudry, D.; Ephritikhine,
M. J . Electroanal. Chem. 1993, 347, 399-407. (d) Schnabel, R.; Scott,
B.; Smith, W.; Burns, C. J . Organomet. Chem. 1999, 591, 14-23. (e)
Sonnenberger, D. C.; Gaudiello, J . G. Inorg. Chem. 1988, 27, 2747-
2748. (f) Ossola, F.; Zanella, P.; Ugo, P.; Seeber, R. Inorg. Chim. Acta
1988, 147, 123-126. (g) Finke, R. G.; Gaughan, G.; Voegeli, R. J .
Organomet. Chem. 1982, 229, 179-184.
(31) Fagan, P. J .; Manriquez, J . M.; Maatta, E. A.; Seyam, A. M.;
Marks, T. J . J . Am. Chem. Soc. 1981, 103, 6650-6667.

4688 Organometallics, Vol. 23, No. 20, 2004
J antunen et al.
F igu r e 7. Molecular structures of complexes 9b (left) and 11b (right) with thermal ellipsoids at the 25% probability
level. Selected bond distances (Å) and angles (deg) for complex 9b: Th(1)-C(21) 2.552(7); Th(1)-C(28) 2.551(7); Th(1)-
C(22) 2.979(6); Th(1)-C(29) 3.709(6); Th(1)-C(23) 3.622(7); Th(1)-C(27) 3.556(6); Th(1)-C(30) 4.700(6); Th(1)-C(34)
4.341(6); Th-Ccent 2.564, 2.577; Th-Cring 2.836(8), 2.843(8); Th(1)-C(21)-C(22) 91.7(4); Th(1)-C(28)-C(29) 133.0(6); C(21)-
Th(1)-C(28) 108.4(3); C5Me5(cent)-Th-C5Me5(cent) 131.4. Selected bond distances (Å) and angles (deg) for complex 11b: U(1)-
C(21) 2.489(5); U(1)-C(28) 2.467(5); U(1)-C(22) 2.970(5); U(1)-C(29) 3.656(5); U(1)-C(23) 3.605(6); U(1)-C(27) 3.581(6);
U(1)-C(30) 4.675(5); U(1)-C(34) 4.292(5); U-Ccent 2.492, 2.514; U-Cring 2.768(5), 2.787(6); U(1)-C(21)-C(22) 93.6(3);
U(1)-C(28)-C(29) 134.2(4); C(21)-U(1)-C(28) 107.55(18); C5Me5(cent)-U-C5Me5(cent) 131.5.
Ta ble 1. Bon d Len gth s (Å) in Actin id e Ben zyl Com p lexes
a
b
c
d
compound
(dmpe)U(CH2Ph)3(Me)f
MCipso-MCH2
MCo-MCH2
MCo′-MCH2
∆
∆′e
ref
0.22
0.55
0.91
0.33
0.43
0.56
0.48
0.63
0.58
0.64
0.61
0.69
33a
33a
34b
34a
(shortest contacts)
(dmpe)Th(CH2Ph)4
(shortest contacts)
(C5Me5)U(CH2Ph)3
(shortest contacts)
f
0.35
0.34
0.29
1.16
0.43
1.19
0.48
0.78
0.89
0.77
1.79
1.00
1.83
1.09
0.39
0.94
1.00
2.15
1.11
2.21
1.12
0.58
0.61
0.71
0.99
0.68
1.02
0.64
(C5Me5)Th(CH2Ph)3
(shortest contacts)
(C5Me5)2Th(CH2Ph)2 (9b)
(benzyl ligand #1, Th-CH2 ) Th(1)-C(28))
(C5Me5)2Th(CH2Ph)2 (9b)
(benzyl ligand #2, Th-CH2 ) Th(1)-C(21))
(C5Me5)2U(CH2Ph)2 (11b)
this work
this work
this work
this work
(benzyl ligand #1, U-CH2 ) U(1)-C(28))
(C5Me5)2U(CH2Ph)2 (11b)
(benzyl ligand #2, U-CH2 ) U(1)-C(21))
a
b
Metal-to-ipso carbon bond length minus metal-to-methylene carbon bond length. Metal-to-shorter ortho carbon bond length minus
metal-to-methylene carbon bond length. c Metal-to-longer ortho carbon bond length minus metal-to-methylene carbon bond length. [MCo
d
- MCH2] - [MCipso - MCH2]. e [MCo′ - MCH2]. f dmpe ) 1,2-bis(dimethyldiphosphino)ethane.
The propensity for benzyl ligands to bond in an η4-
mode with actinide metals has been previously noted.33a,34
These interactions are relatively weak and are a mani-
festation of the requirement of large electropositive
actinide metals to maximize their coordination numbers
and to minimize the intramolecular ligand-ligand
repulsions; the resulting molecular structure is a com-
promise between these two conflicting tendencies. Two
parameters have been defined by Marks33a and Ander-
sen34a to quantify the benzyl ligand-to-metal interaction,
∆ and ∆′, where ∆ ) [MCo - MCH2] - [MCipso - MCH2]
and ∆′ ) [MCo′ - MCH2] - [MCipso - MCH2] and where
MCo is the shorter metal-to-ortho carbon contact, MCo′
is the longer metal-to-ortho contact, MCH2 is the metal-
to-methylene carbon bond length, and MCipso is the
metal-to-ipso carbon bond length. For the f-block metals,
∆ and ∆′ have been shown to have comparable values,
as would be expected for an η4-benzyl-to-metal bonding
interaction. Table 1 compares and contrasts the ∆ and
∆′ values determined for complexes 9b and 11b with
the other structurally characterized actinide benzyl
complexes that exhibit η4-benzyl-to-metal bonding in-
teractions. The metrical parameters exhibited by com-
plexes 9b and 11b support the assignment of η1 and η4
hapticity for the benzyl ligands in these complexes.
Con clu d in g Rem a r k s
In conclusion, we have reported a convenient method
for the construction of electronically and sterically
diverse ketimide ligands and demonstrated its efficacy
through the preparation of a variety of novel thori-
um(IV) and uranium(IV) bis(ketimido) complexes. The
thorium compounds represent the first examples of
thorium ketimide complexes. The uranium complexes
are surprisingly unreactive, and both the uranium and
thorium bis(ketimido) complexes display unusual elec-
tronic structure properties. The combined chemical and
physical properties of these complexes suggest an An-N
bond order greater than 1 due to significant ligand-to-
metal π-bonding in the actinide ketimido interactions.
For the uranium complexes, these data are suggestive
of electronic delocalization throughout the N-U-N core
in the uranium(IV) bis(ketimide) systems and indicate
that the f-electrons in mid-valent organouranium com-
(34) (a) Mintz, E. A.; Moloy, K. G.; Marks, T. J .; Day, V. W. J . Am.
Chem. Soc. 1982, 104, 4692-4695. (b) Kiplinger, J . L.; Morris, D. E.;
Scott, B. L.; Burns, C. J . Organometallics 2002, 21, 5978-5982.

Thorium(IV) and Uranium(IV) Ketimide Complexes
Organometallics, Vol. 23, No. 20, 2004 4689
rich) were dried in vacuo at 250 °C for 48 h prior to use.
Anhydrous toluene (Aldrich), hexanes (Aldrich), diethyl ether
(Aldrich), and tetrahydrofuran (Aldrich) were passed through
a column of activated alumina (A2, 12 × 32, Purifry) under
nitrogen and stored over activated 4 Å molecular sieves prior
to use.
Benzonitrile (Aldrich) and acetonitrile (Aldrich) were dis-
tilled from CaH2 and stored over activated 4 Å molecular sieves
under N2 prior to use. (C5Me5)2Th(Ph)2 (9a ),35 (C5Me5)2Th(CH2-
Ph)2 (9b),31 (C5Me5)2Th(CH3)2 (9c),31 (C5Me5)2U(CH2Ph)2 (11b),31
and (C5Me5)2U(CH3)2 (11c)31 were prepared according to
literature procedures. Deuterated solvents were purified by
storage over activated 4 Å molecular sieves or sodium metal
prior to use.
plexes might be far more involved in chemical bonding
and reactivity than previously thought.
Exp er im en ta l Section
Gen er a l P r oced u r es. Unless otherwise noted, reactions
and manipulations were performed at 20 °C in a recirculating
Vacuum Atmospheres Model HE-553-2 inert atmosphere (N2
or He) drybox with a MO-40-2 Dri-Train, or using standard
Schlenk and high vacuum line techniques. Glassware was
dried overnight at 150 °C before use. All NMR spectra were
obtained using a Bruker Avance 300 MHz spectrometer.
Except when noted, NMR spectra were acquired at room
temperature (25 °C). Benzene-d6 and toluene-d8 were obtained
from Cambridge Isotope Laboratories (CIL). Chemical shifts
were referenced to protio solvent impurities (δ 7.14 for
benzene-d6 and δ 2.05 for toluene-d8), which are referenced to
internal Si(CH3)4 at δ 0.00 ppm.
Melting points were determined with a Mel-Temp capillary
melting point apparatus equipped with a Fluke 51 II K/J
thermocouple using capillary tubes flame-sealed under nitro-
gen; values are uncorrected. Mass spectrometric (MS) analyses
were obtained at the University of California, Berkeley Mass
Spectrometry Facility, using either VG ProSpec (EI) or VG70-
SE (FAB) mass spectrometers. Elemental analyses were
performed at the University of California, Berkeley Microana-
lytical Facility, on a Perkin-Elmer Series II 2400 CHNS
analyzer.
Electronic absorption spectral data were obtained for tolu-
ene solutions of all complexes over the wavelength range from
300 to 1600 nm on a Perkin-Elmer Model Lambda 19 UV-
visible-near-infrared spectrophotometer. All data were col-
lected in 1 cm path length cuvettes loaded in an inert
atmosphere glovebox and run versus a toluene reference.
Strong absorption bands from overtone vibrations of the
toluene solvent precluded the collection of data at wavelengths
longer than 1600 nm, but samples were run separately versus
air references to ensure that the observed absorption bands
were attributable to the complexes and not the solvent.
Samples were run at two dilutions, 0.1 and 0.5 mM, to optimize
absorbance in the UV-visible and near-infrared, respectively.
Spectral resolution was typically 2 nm in the visible region
and 4-6 nm in the near-infrared.
Cyclic voltammetric data were obtained in the Vacuum
Atmospheres drybox system described above. All data were
collected using a Perkin-Elmer Princeton Applied Research
Corporation (PARC) Model 263 potentiostat under computer
control with PARC Model 270 software. All sample solutions
were ∼5 mM in complex with 0.1 M [(n-C4H9)4N][B(C6F5)4]
supporting electrolyte in THF solvent. This electrolyte has
been shown previously to greatly diminish the solution resis-
tance in low-dielectric solvents such as THF. All data were
collected with the positive-feedback IR compensation feature
of the software/potentiostat activated to ensure minimal
contribution to the voltammetric waves from uncompensated
solution resistance (typically ∼1 kΩ under the conditions
employed). Solutions were contained in PARC Model K0264
microcells consisting of an ∼3 mm diameter Pt disk working
electrode, a Pt wire counter electrode, and a silver wire quasi-
reference electrode. Scan rates from 20 to 5000 mV/s were
employed to assess the chemical and electrochemical revers-
ibility of the observed redox transformations. Potential cali-
brations were performed at the end of each data collection cycle
using the ferrocenium/ferrocene couple as an internal stan-
dard.
Syn th esis of (C5Me5)2Th (-NdCP h 2)2 (10a ). A 125 mL
Erlenmeyer flask equipped with a stir bar was charged with
(C5Me5)2Th(C6H5)2 (0.38 g, 0.57 mmol) and toluene (50 mL).
To the resulting colorless solution was added 0.13 mL of
benzonitrile (0.131 g, 1.26 mmol) with stirring. The reaction
mixture changed color to a bright orange solution and was
stirred at room temperature for 15 h. The resultant mixture
was filtered through a Celite-padded coarse frit. The filtrate
was collected, and the volatiles were removed under reduced
pressure to give an orange crystalline solid. The solid was
collected by filtration, washed with hexanes (2 × 10 mL), and
dried in vacuo to afford crude 10a as an orange crystalline
solid. Analytically pure samples of 10a were obtained by
recrystallization from hot hexanes (0.453 g, 0.419 mmol, 82%).
1H NMR (C6D6, 298 K): δ 7.64 (dd, 8H, meta H), 7.17 (d, J )
2.2 Hz, 8H, ortho H), 1.96 (s, 30H, C5(CH3)5). The para proton
on the phenyl ring is unobserved in the 1H NMR (this was
also evident in a {C, H} 2D-COSY experiment). 13C{1H} NMR
(C6D6, 298 K): δ 173.72 (s, (-NdCPh2)2), 144.21 (s, quat aryl
C), 129.21, 129.10, 128.44 (aryl C’s), 123.73 (s, C5(CH3)5), 11.67
(s, C5(CH3)5). UV-vis/NIR (ꢀ, M-1 cm-1, toluene): 300 (10 900),
333 (4800), 480 (480). Mp ) 187-189 °C. Anal. Calcd for
C
46H50N2Th (862.96 g/mol): C, 64.02; H, 5.84; N, 3.25. Found:
C, 63.91; H, 5.88; N, 3.31.
Syn th esis of (C5Me5)2Th [-NdC(P h )(CH2P h )]2 (10b). A
125 mL Erlenmeyer flask equipped with a stir bar was charged
with (C5Me5)2Th(CH2Ph)2 (0.50 g, 0.73 mmol) and toluene (50
mL). To the resulting pale yellow solution was added 0.149
mL of benzonitrile (0.150 g, 1.46 mmol) with stirring. The
resultant reaction mixture changed color to a bright yellow
and was stirred at room temperature for 12 h. The resultant
mixture was filtered through a Celite-padded coarse frit. The
filtrate was collected, and the volatiles were removed under
reduced pressure to give a yellow solid. The solid was collected
by filtration, washed with hexanes (3 × 10 mL), and dried in
vacuo to afford crude 10b as a yellow solid. Analytically pure
samples of 10b were obtained by recrystallization from a
concentrated hexanes solution at -30 °C (0.468 g, 0.525 mmol,
72%). 1H NMR (C6D6, 298 K): δ 7.79 (d, 4H, ortho H (phenyl),
7.31 (d, 4H, ortho H (benzyl)), 7.02 (m, 12 H, meta/para H),
4.14 (br s, 4H, CH2Ph), 2.03 (s, 30H, C5(CH3)5). UV-vis/NIR
(ꢀ, M-1 cm-1, toluene): 300 (13,150), 463 (155). Mp ) 178-
182 °C. Anal. Calcd for C55H59N3Th (994.13 g/mol): C, 66.45;
H, 5.98; N, 4.23. Found: C, 66.10; H, 6.09; N, 4.18.
Syn t h esis of (C5Me5)2Th [-NdC(P h )(CH3)]2 (10c).
Meth od A. A 125 mL Erlenmeyer flask equipped with a stir
bar was charged with (C5Me5)2Th(CH3)2 (1.42 g, 2.66 mmol)
and toluene (50 mL). To the resulting colorless solution was
added 0.656 mL of benzonitrile (0.663 g, 6.43 mmol) with
stirring. The resultant reaction mixture changed color to bright
yellow and was stirred at room temperature for 48 h. The
resultant mixture was filtered through a Celite-padded coarse
frit. The filtrate was collected, and the volatiles were removed
under reduced pressure to give a yellow oil. The oil was
Both electronic absorption data and cyclic voltammetric data
were analyzed using Wavemetrics IGOR Pro (Version 4.0)
software on a Macintosh platform.
Ma ter ia ls. Unless otherwise noted, reagents were pur-
chased from commercial suppliers and used without further
purification. Celite (Aldrich) and alumina (Brockman I, Ald-
(35) England, A. F.; Burns, C. J .; Buchwald, S. L. Organometallics
1994, 13, 3491-3495.

4690 Organometallics, Vol. 23, No. 20, 2004
J antunen et al.
triturated sequentially with pentanes (3 × 10 mL) and hexanes
(3 × 10 mL) to give a bright yellow powder, which was dried
in vacuo to afford analytically pure 10c as a yellow solid (1.46
g, 1.99 mmol, 75%). 1H NMR (C6D6, 298 K): δ 7.85 (m, 4H,
ortho H), 7.24 (m, 6H, meta/para H), 2.41 (s, 6H, CH3), 1.99
(s, 30H, C5(CH3)5). UV-vis/NIR (ꢀ, M-1 cm-1, toluene): 300
(7,500), 345 (1,770), 452 (165). Mp ) 178-182 °C. Anal. Calcd
for C36H46N2Th‚1/2C6H14 (781.89 g/mol): C, 59.91; H, 6.83; N,
3.58. Found: C, 60.01; H, 6.69; N, 3.27.
Syn t h esis of (C5Me5)2Th [-NdC(P h )(CH3)]2 (10c).
Meth od B. A 5 mm Teflon NMR tube insert seated inside a 5
mm glass NMR tube was charged with (C5Me5)2Th(C6H5)2
(0.024 g, 3.65 × 10-5 mol) and 0.5 mL of C6D6. A syringe was
used to introduce 4 µL of acetonitrile. Immediately upon
addition of the acetonitrile, the solution surface region was
noted to turn bright yellow. The Teflon NMR liner was sealed
with a Teflon plug and the glass NMR tube capped with a
plastic cap. The resulting apparatus was shaken vigorously
to ensure thorough mixing of the solution. Over a period of 5
min the solution slowly changed color from nearly colorless to
a bright yellow clear solution. 1H NMR experiments show the
product is identical to 10c (apparent quant. yield). 1H NMR
(C6D6, 298 K): δ 7.85 (m, 4H, ortho H), 7.24 (m, 6H, meta/
para H), 2.41 (s, 6H, CH3), 1.99 (s, 30H, C5(CH3)5).
(796.36 g/mol): C, 59.58; H, 6.14; N, 4.49. Found: C, 59.51;
H, 6.18; N, 4.16.
Cr ysta llogr a p h ic Deta ils for (C5Me5)2Th (CH2P h )2 (9b).
A pale yellow crystal (0.28 × 0.10 × 0.10 mm) grown from a
concentrated hexanes solution of 9b at -30 °C was mounted
from Paratone N oil onto a glass fiber under argon gas flow
and placed on a Bruker P4/CCD diffractometer, equipped with
a Bruker LT-2 temperature device. A hemisphere of data was
collected using æ scans, with 30 s frame exposures and 0.3°
frame widths. A total of 18 073 reflections (-11 e h e 11, -14
e k e 13, -28 e l e 29) were collected at T ) 203(2) K in the
θ range 1.72-25.43° of which 5312 were unique (Rint ) 0.0328);
Mo KR radiation (λ ) 0.71073 Å). Data collection and initial
indexing and cell refinement were handled using SMART36
software. Frame integration and final cell parameter calcula-
tions were carried out using SAINT37 software. The data were
corrected for absorption using the SADABS program.38 Decay
of reflection data was monitored by analysis of redundant
frames. The structure was solved using direct methods,
completed by subsequent difference Fourier techniques, and
refined by full-matrix least-squares procedures. All non-
hydrogen atoms were refined anisotropically, and hydrogen
atoms were treated as idealized contributions. The absorption
coefficient was 5.156 mm-1. The least-squares refinement
converged normally with residuals of R1 ) 0.0404 (I > 2σ(I)),
wR2 ) 0.1286, and GOF ) 1.058 (F2); C34H44Th (684.73 g/mol),
space group P21/n, monclinic a ) 9.886(3) Å, b ) 12.410(4) Å,
c ) 24.078(7) Å, R ) 90°, â ) 100.639(5)°, γ ) 90°, V )
Syn th esis of (C5Me5)2U[-NdC(P h )(CH2P h )]2 (12b). A
125 mL Erlenmeyer flask equipped with a stir bar was charged
with (C5Me5)2U(CH2Ph)2 (0.50 g, 0.73 mmol) and toluene (50
mL). To the resulting green-black solution was added 0.195
mL of benzonitrile (0.197 g, 1.91 mmol) with stirring. The
resultant mixture changed color to a red-brown and was stirred
at room temperature for 12 h. The reaction mixture was
filtered through a Celite-padded coarse frit. The filtrate was
collected, and the volatiles were removed under reduced
pressure to give crude 12b as a red-brown crystalline solid.
Analytically pure samples of 12b were obtained by recrystal-
lization from a concentrated toluene solution at -30 °C (0.58
2903.1(14) Å3, Z ) 4, F(000) ) 1352, Fcalcd ) 1.567 g cm-3
.
Structure solution, refinement, graphics, and creation of
publication materials were performed using SHELXTL.39
Cr ysta llogr a p h ic Deta ils for (C5Me5)2Th (CH3)2 (9c). A
colorless crystal (0.24 × 0.10 × 0.08 mm) grown from a
concentrated hexanes solution of 9c at -30 °C was mounted
from Paratone N oil onto a glass fiber under argon gas flow
and placed on a Bruker P4/CCD diffractometer, equipped with
a Bruker LT-2 temperature device. A hemisphere of data was
collected using æ scans, with 30 s frame exposures and 0.3°
frame widths. A total of 7884 reflections (-9 e h e 10, -22 e
k e 22, -11 e l e 11) were collected at T ) 203(2) K in the θ
range 2.70-28.10° of which 2497 were unique (Rint ) 0.0226);
Mo KR radiation (λ ) 0.71073 Å). Data collection and initial
indexing and cell refinement were handled using SMART36
software. Frame integration and final cell parameter calcula-
tions were carried out using SAINT37 software. The data were
corrected for absorption using the SADABS program.38 Decay
of reflection data was monitored by analysis of redundant
frames. The structure was solved using direct methods,
completed by subsequent difference Fourier techniques, and
refined by full-matrix least-squares procedures. All non-
hydrogen atoms were refined anisotropically, and hydrogen
atoms were treated as idealized contributions. The disordered
pentamethylcyclopentadienyl ligand was refined as two one-
half occupancy positions (C3 through C12 and C3′ through
C12′). The absorption coefficient was 6.852 mm-1. The least-
squares refinement converged normally with residuals of R1
) 0.0326 (I > 2σ(I)), wR2 ) 0.0930, and GOF ) 1.576 (F2);
1
g, 0.64 mmol, 88%). H NMR (toluene-d8, 90 °C): δ 29.94 (br
s, 4H, ortho H), 13.64 (t, J ) 6.5 Hz, 2H, para H), 9.84 (br s,
4H, meta H), 8.46 (d, 4H, ortho H), 6.79 (t, J ) 7.1 Hz, 2H,
para H), 2.12 (br s, 4H, meta H), -1.54 (s, 30H, C5(CH3)5),
-2.94 (br s, 4H, CH2Ph). UV-vis/NIR (ꢀ, M-1 cm-1, toluene):
312 (14 000), 380 (3700), 540 (600), 594 (480), 680 (240), 770
(160), 845 (35), 940 (35), 1022 (65), 1108 (25), 1178 (300), 1220
(390), 1369 (115). Mp ) 204-205 °C. MS (EI, 70 eV): m/z 896
(M+), 702 (M+ - NdC(Ph)(Bz)). Anal. Calcd for C48H54N2U
(896.99 g/mol): C, 64.27; H, 6.07; N, 3.12. Found: C, 64.60;
H, 6.19; N, 2.93.
Syn th esis of (C5Me5)2U[-NdC(P h )(CH3)]2 (12c). A 125
mL Erlenmeyer flask equipped with a stir bar was charged
with (C5Me5)2U(CH3)2 (0.50 g, 0.93 mmol) and toluene (50 mL).
To the resulting orange solution was added 0.245 mL of
benzonitrile (0.247 g, 2.39 mmol) with stirring. The resultant
reaction mixture changed color to a dark ruby red and was
stirred at room temperature for 16 h. The volatiles were
removed from the reaction mixture under reduced pressure
to afford a foamy brown solid. This solid was taken up in
hexanes (20 mL) and filtered through a Celite-padded coarse
frit. The filtrate was collected, and the volatiles were removed
under reduced pressure to give a red-brown solid. This solid
was taken up in hexamethyldisiloxane (20 mL) and filtered
through a Celite-padded coarse frit. Concentration of this
hexamethyldisiloxane solution to ∼10 mL and storage at -30
°C affords analytically pure 12c as a red-brown micro-
crystalline solid (0.495 g, 6.65 mmol, 71%). 1H NMR (toluene-
d8, 91.7 °C): δ 17.15 (br s, 4H, ortho H), 12.44 (t, J ) 7.1 Hz,
2H, para H), 6.40 (t, J ) 7.1 Hz, 4H, meta H), -2.04 (s, 30H,
C
22H36Th (532.55 g/mol), space group C2/c, monoclinic a )
8.3232(14) Å, b ) 17.302(3) Å, c ) 8.4939(15) Å, â )
117.185(3)°, V ) 1088.1(3) Å3, Z ) 2, F(000) ) 516, Fcalcd
)
1.625 g cm-3. Structure solution, refinement, graphics, and
creation of publication materials were performed using SHELX-
TL.39
Cr yst a llogr a p h ic Det a ils for (C5Me5)2Th (-NdCP h 2)2
(10a ). An orange crystal (0.40 × 0.28 × 0.26 mm) grown from
C5(CH3)5), -2.54 (br s, 6H, CH3). UV-vis/NIR (ꢀ, M-1 cm-1
,
(36) SMART-NT 4; Bruker AXS, Inc.: Madison, WI 53719, 1996.
(37) SAINT-NT 5.050; Bruker AXS, Inc.: Madison, WI 53719, 1998.
(38) Sheldrick, G. SADABS, first release; University of Go¨ttingen:
Germany.
(39) SHELXTL Version 5.10; Bruker AXS, Inc.: Madison, WI 53719,
1997.
toluene): 306 (2200), 380 (1400), 540 (400), 640 (250), 840 (50),
934 (50), 982 (75), 1097 (220), 1175 (270), 1229 (335), 1350
(100). Mp ) 116-117 °C. MS (EI, 70 eV): m/z 744 (M+), 626
(M+ - NdC(Ph)(Me)). Anal. Calcd for C48H54N2Th‚1/2NCC6H5

Thorium(IV) and Uranium(IV) Ketimide Complexes
Organometallics, Vol. 23, No. 20, 2004 4691
a concentrated hexanes solution of 10a was mounted from
Paratone N oil onto a glass fiber under argon gas flow and
placed on a Bruker P4/CCD diffractometer, equipped with a
Bruker LT-2 temperature device. A hemisphere of data was
collected using æ scans, with 30 s frame exposures and 0.3°
frame widths. A total of 20 868 reflections (-11 e h e 11, -22
e k e 22, -22 e l e 22) were collected at T ) 203(2) K in the
θ range 1.1-23.3° of which 10 444 were unique (Rint ) 0.0184);
Mo KR radiation (λ ) 0.71073 Å). Data collection and initial
indexing and cell refinement were handled using SMART36
software. Frame integration and final cell parameter calcula-
tions were carried out using SAINT37 software. The data were
corrected for absorption using the SADABS program.38 Decay
of reflection data was monitored by analysis of redundant
frames. The structure was solved using direct methods,
completed by subsequent difference Fourier techniques, and
refined by full-matrix least-squares procedures. All non-
hydrogen atoms were refined anisotropically, and hydrogen
atoms were treated as idealized contributions. The absorption
coefficient was 3.791 mm-1. The least-squares refinement
converged normally with residuals of R1 ) 0.0337 (I > 2σ(I)),
wR2 ) 0.0601, and GOF ) 2.092 (F2); C46H50N2Th (862.92
g/mol), space group P1h, triclinic a ) 10.640(4) Å, b ) 20.378(7)
Å, c ) 20.555(7) Å, R ) 64.241(5)°, â ) 82.931(6)°, γ )
82.307(7)°, V ) 3967(2) Å3, Z ) 4, F(000) ) 1720, Fcalcd ) 1.445
g cm-3. Structure solution, refinement, graphics, and creation
of publication materials were performed using SHELXTL.39
frames. The structure was solved using direct methods,
completed by subsequent difference Fourier techniques, and
refined by full-matrix least-squares procedures. All non-
hydrogen atoms were refined anisotropically, and hydrogen
atoms were treated as idealized contributions. The absorption
coefficient was 5.720 mm-1. The least-squares refinement
converged normally with residuals of R1 ) 0.0280 (I > 2σ(I)),
wR2 ) 0.0786, and GOF ) 2.181 (F2); C34H44U (690.72 g/mol),
space group P21/n, monclinic a ) 9.772(3) Å, b ) 12.328(4) Å,
c ) 24.037(7) Å, R ) 90°, â ) 100.514(5)°, γ ) 90°, V )
2847.2(15) Å3, Z ) 4, F(000) ) 1360, Fcalcd ) 1.611 g cm-3
.
Structure solution, refinement, graphics, and creation of
publication materials were performed using SHELXTL.39
Cr ysta llogr a p h ic Deta ils for (C5Me5)2U(CH3)2 (11c). An
orange crystal (0.24 × 0.16 × 0.16 mm) grown from
a
concentrated hexanes solution of 11c at -30 °C was mounted
from Paratone N oil onto a glass fiber under argon gas flow
and placed on a Bruker P4/CCD diffractometer, equipped with
a Bruker LT-2 temperature device. A hemisphere of data was
collected using æ scans, with 30 s frame exposures and 0.3°
frame widths. A total of 29 886 reflections (-38 e h e 40, -31
e k e 41, -10 e l e 10) were collected at T ) 203(2) K in the
θ range 1.28-28.45° of which 5026 were unique (Rint ) 0.0320);
Mo KR radiation (λ ) 0.71073 Å). Data collection and initial
indexing and cell refinement were handled using SMART36
software. Frame integration and final cell parameter calcula-
tions were carried out using SAINT37 software. The data were
corrected for absorption using the SADABS program.38 Decay
of reflection data was monitored by analysis of redundant
frames. The structure was solved using direct methods,
completed by subsequent difference Fourier techniques, and
refined by full-matrix least-squares procedures. All non-
hydrogen atoms were refined anisotropically, and hydrogen
atoms were treated as idealized contributions. The absorption
coefficient was 7.609 mm-1. The least-squares refinement
converged normally with residuals of R1 ) 0.0456 (I > 2σ(I)),
wR2 ) 0.0922, and GOF ) 1.953 (F2); C22H36U (538.54 g/mol),
space group I1/a, tetragonal, a ) 31.797(5) Å, c ) 8.438(3) Å,
Cr yst a llogr a p h ic Det a ils for (C5Me5)2Th [-NdC(P h )-
(Bz)]2 (10b). A yellow-orange crystal (0.10 × 0.08 × 0.08 mm)
grown from a concentrated hexanes solution of 10b was
mounted from Paratone N oil onto a glass fiber under argon
gas flow and placed on a Bruker P4/CCD diffractometer,
equipped with a Bruker LT-2 temperature device. A hemi-
sphere of data was collected using æ scans, with 30 s frame
exposures and 0.3° frame widths. A total of 9973 reflections
(-16 e h e 16, -14 e k e 14, -17 e l e 20) were collected at
T ) 203(2) K in the θ range 2.01-22.46° of which 2597 were
unique (Rint ) 0.0948); Mo KR radiation (λ ) 0.71073 Å). Data
collection and initial indexing and cell refinement were
handled using SMART36 software. Frame integration and final
cell parameter calculations were carried out using SAINT37
software. The data were corrected for absorption using the
SADABS program.38 The structure was solved using direct
methods, completed by subsequent difference Fourier tech-
niques, and refined by full-matrix least-squares procedures.
All non-hydrogen atoms were refined anisotropically, and
hydrogen atoms were treated as idealized contributions. The
absorption coefficient was 3.761 mm-1. The least-squares
refinement converged normally with residuals of R1 ) 0.0615
(I > 2σ(I)), wR2 ) 0.1135, and GOF ) 1.273 (F2); C48H54N2Th
(890.97 g/mol), space group C2/c, monoclinic a ) 15.416(5) Å,
b ) 13.461(5) Å, c ) 19.347(6) Å, R ) 90°, â ) 94.673(6)°, γ )
90°, V ) 4001(2) Å3, Z ) 4, F(000) ) 1784, Fcalcd ) 1.479 g
cm-3. Structure solution, refinement, graphics, and creation
of publication materials were performed using SHELXTL.39
V ) 8532(3) Å3, Z ) 16, F(000) ) 4160, Fcalcd ) 1.677 g cm-3
.
Structure solution, refinement, graphics, and creation of
publication materials were performed using SHELXTL.39
Cr ysta llogr a p h ic Deta ils for (C5Me5)2U[-NdC(P h )-
(Bz)]2 (12b). A dark red crystal (0.14 × 0.10 × 0.04 mm) grown
from evaporation of a concentrated toluene solution of 12b was
mounted from Paratone N oil onto a glass fiber under argon
gas flow and placed on a Bruker P4/CCD diffractometer,
equipped with a Bruker LT-2 temperature device. A hemi-
sphere of data was collected using æ scans, with 30 s frame
exposures and 0.3° frame widths. A total of 12 464 reflections
(-18 e h e 18, -16 e k e 16, -21 e l e 22) were collected at
T ) 203(2) K in the θ range 2.02-25.35° of which 3507 were
unique (Rint ) 0.0256); Mo KR radiation (λ ) 0.71073 Å). Data
collection and initial indexing and cell refinement were
handled using SMART36 software. Frame integration and final
cell parameter calculations were carried out using SAINT37
software. The data were corrected for absorption using the
SADABS program.38 The structure was solved using direct
methods, completed by subsequent difference Fourier tech-
niques, and refined by full-matrix least-squares procedures.
All non-hydrogen atoms were refined anisotropically, and
hydrogen atoms were treated as idealized contributions. The
absorption coefficient was 4.138 mm-1. The least-squares
refinement converged normally with residuals of R1 ) 0.0236
(I > 2σ(I)), wR2 ) 0.0550, and GOF ) 1.208 (F2); C48H54N2U
(896.96 g/mol), space group C2/c, monoclinic a ) 15.272(3) Å,
b ) 13.469(3) Å, c ) 19.301(4) Å, R ) 90°, â ) 94.784(4)°, γ )
90°, V ) 3956.3(14) Å3, Z ) 4, F(000) ) 1792, Fcalcd ) 1.506 g
cm-3. Structure solution, refinement, graphics, and creation
of publication materials were performed using SHELXTL.39
Cr ysta llogr a p h ic Deta ils for (C5Me5)2U(CH2P h )2 (11b).
A green-black crystal (0.14 × 0.10 × 0.06 mm) grown from a
concentrated hexanes solution of 11b at -30 °C was mounted
from Paratone N oil onto a glass fiber under argon gas flow
and placed on a Bruker P4/CCD diffractometer, equipped with
a Bruker LT-2 temperature device. A hemisphere of data was
collected using æ scans, with 30 s frame exposures and 0.3°
frame widths. A total of 14 577 reflections (-11 e h e 11, -14
e k e 12, -28 e l e 28) were collected at T ) 203(2) K in the
θ range 1.72-25.45° of which 4871 were unique (Rint ) 0.0190);
Mo KR radiation (λ ) 0.71073 Å). Data collection and initial
indexing and cell refinement were handled using SMART36
software. Frame integration and final cell parameter calcula-
tions were carried out using SAINT37 software. The data were
corrected for absorption using the SADABS program.38 Decay
of reflection data was monitored by analysis of redundant

4692 Organometallics, Vol. 23, No. 20, 2004
J antunen et al.
Ack n ow led gm en t. For financial support of this
work, we acknowledge the LANL G.T. Seaborg Institute
for Transactinium Science (fellowships to K.C.J . and
I.C.R.), the LANL Laboratory Directed Research and
Development Program, and the Division of Chemical
Sciences, Office of Basic Energy Sciences, U.S. Depart-
ment of Energy. J .L.K. acknowledges support as a
Fredrick Reines Postdoctoral Fellow at Los Alamos
National Laboratory during the initial stages of this
work.
Su p p or tin g In for m a tion Ava ila ble: Tables with bond
lengths, bond angles, atomic coordinates, and anisotropic
displacement parameters for the structures of 9b, 9c, 10a , 10b,
11b, 11c, and 12b. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM0343824