Reactivity of tuck-in and tuck-over uranium metallocene complexes

Article abstract of DOI:10.1021/om1007538

The reactivity of the uranium tuck-in and tuck-over cyclopentadienyl moieties {[ν⁵:ν¹-C₅Me₄CH ₂]U}²⁺ and {U[μ- ν⁵:ν¹- C₅Me₄CH₂]U}⁶⁺, respectively, has been investigated by examining the reactivity of (C₅Me ₅)U[μ- ν⁵:ν¹:ν¹-C ₅Me₃(CH₂)₂](μ-H) ₂U(C₅Me₅)₂, 1, and (C ₅Me₅)(ν⁵:ν¹-C ₅Me₄CH₂)(hpp)U [(hpp)^- = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato], 2, with hydrogen, silyl halide, sulfide, amine, and hydrocarbon reagents. The reactivity of 2, which has a single tuck-in reactive site, provides valuable comparisons with that of 1, where the presence of two hydride ligands as well as both tuck-in and tuck-over moieties leads to products in which multiple transformations have occurred. Both 1 and 2 react with H₂ to form hydrides, namely, the [(C ₅Me₅)₂UH₂]₂/[(C ₅Me₅)₂UH]₂ equilibrium mixture and (C₅Me₅)₂(hpp)UH, 3, respectively. Attempts to make a simple chloride derivative of 1 with Me₃SiCl yielded a new tethered metallocene, (C₅Me₅)ClU(ν⁵-C ₅Me₄CH₂SiMe₂CH₂-κC) , 4, which formally results from a silylmethyl C-H bond activation as well as insertion of the silyl group into the U-CH₂ tuck-in linkage. The trivalent chloride [(C₅Me₅)₂UCl]₃, 5, is the byproduct of this reaction. This sequence of reactions is probably not initiated by the tuck-in functionality, since 2 does not react with Me ₃SiCl under comparable conditions. Hydride complex 3 reacts readily with Me₃SiCl to form (C₅Me₅) ₂(hpp)UCl, but (C₅Me₅)₂(hpp)UMe, 6, requires 100 °C to form the chloride. Complex 1 also displays complicated reactivity with HC=CPh, whereas 2 and 3 react with this substrate to form (C₅Me₅)₂(hpp)U(C=CPh), 7, in high yield. Complex 1 converts PhSSPh cleanly to (C₅Me₅) ₂U(SPh)₂, 8, in a reaction that involves S-S cleavage and C-H bond formation. Complex 1 reacts with a 1:1 mixture of PhSSPh and p-tolylSS-p-tolyl to form a 1:2:1 mixture of (C₅Me₅) ₂U(SPh)₂, 8, (C₅Me₅) ₂U(SPh)(S-p-tolyl), 9, and (C₅Me₅) ₂U(S-p-tolyl)₂, 10, but the mechanistic implications are compromised by exchange of 8 with 10 to make 9. PhSH, a possible intermediate in a δ-bond metathesis reaction pathway for the 1/PhSSPh reaction, reacts with 1 to form 8. Complex 2 forms a δ-bond metathesis product, (C ₅Me₄CH₂SPh)(C₅Me₅)(hpp) U(SPh), 11, from PhSSPh that contains a new peralkylated cyclopentadienyl ligand. The reaction of 2 and PhSH forms (C₅Me₅) ₂(hpp)U(SPh), 12. Complexes 1 and 2 react similarly with PhNH ₂ to generate amide products (C₅Me₅) ₂U(NHPh)₂, 13, and (C₅Me₅) ₂(hpp)U(NHPh), 14, respectively. No reactions were observed between complex 1 or 2 and methane, benzene, or toluene, but 1 and 2 react with CuI to form (C₅Me₅)₂UI₂, 15, and (C ₅Me₅)₂(hpp)UI, 16, respectively, in which the CH₂ tuck components have been converted to methyl groups.

Full text of DOI:10.1021/om1007538

Organometallics 2010, 29, 4159–4170 4159
DOI: 10.1021/om1007538
Reactivity of Tuck-in and Tuck-over Uranium Metallocene Complexes
Elizabeth Montalvo, Kevin A. Miller, Joseph W. Ziller, and William J. Evans*
Department of Chemistry, University of California, Irvine, California 92697-2025
Received August 2, 2010
The reactivity of the uranium tuck-in and tuck-over cyclopentadienyl moieties {[η5:η1-C5Me4-
CH2]U}2þ and {U[μ-η5:η1-C5Me4CH2]U}6þ, respectively, has been investigated by examining the
reactivity of (C5Me5)U[μ-η5:η1:η1-C5Me3(CH2)2](μ-H)2U(C5Me5)2, 1, and (C5Me5)(η5:η1-C5Me4-
CH2)(hpp)U [(hpp)- = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato], 2, with hydrogen,
silyl halide, sulfide, amine, and hydrocarbon reagents. The reactivity of 2, which has a single tuck-in
reactive site, provides valuable comparisons with that of 1, where the presence of two hydride ligands
as well as both tuck-in and tuck-over moieties leads to products in which multiple transforma-
tions have occurred. Both 1 and 2 react with H2 to form hydrides, namely, the [(C5Me5)2UH2]2/
[(C5Me5)2UH]2 equilibrium mixture and (C5Me5)2(hpp)UH, 3, respectively. Attempts to make a
simple chloride derivative of 1 with Me3SiCl yielded a new tethered metallocene, (C5Me5)ClU-
(η5-C5Me4CH2SiMe2CH2-κC), 4, which formally results from a silylmethyl C-H bond activation as
well as insertion of the silyl group into the U-CH2 tuck-in linkage. The trivalent chloride
[(C5Me5)2UCl]3, 5, is the byproduct of this reaction. This sequence of reactions is probably not
initiated by the tuck-in functionality, since 2 does not react with Me3SiCl under comparable
conditions. Hydride complex 3 reacts readily with Me3SiCl to form (C5Me5)2(hpp)UCl, but
(C5Me5)2(hpp)UMe, 6, requires 100 °C to form the chloride. Complex 1 also displays complicated
reactivity with HCtCPh, whereas 2 and 3 react with this substrate to form (C5Me5)2(hpp)-
U(CtCPh), 7, in high yield. Complex 1 converts PhSSPh cleanly to (C5Me5)2U(SPh)2, 8, in a
reaction that involves S-S cleavage and C-H bond formation. Complex 1 reacts with a 1:1 mixture
of PhSSPh and p-tolylSS-p-tolyl to form a 1:2:1 mixture of (C5Me5)2U(SPh)2, 8, (C5Me5)2U(SPh)-
(S-p-tolyl), 9, and (C5Me5)2U(S-p-tolyl)2, 10, but the mechanistic implications are compromised by
exchange of 8 with 10 to make 9. PhSH, a possible intermediate in a σ-bond metathesis reaction pathway
for the 1/PhSSPh reaction, reacts with 1 to form 8. Complex 2 forms a σ-bond metathesis product,
(C5Me4CH2SPh)(C5Me5)(hpp)U(SPh), 11, from PhSSPh that contains a new peralkylated cyclopenta-
dienyl ligand. The reaction of 2 and PhSH forms (C5Me5)2(hpp)U(SPh), 12. Complexes 1 and 2 react
similarly with PhNH2 to generate amide products (C5Me5)2U(NHPh)2, 13, and (C5Me5)2(hpp)-
U(NHPh), 14, respectively. No reactions were observed between complex 1 or 2 and methane, benzene,
or toluene, but 1 and 2 react with CuI to form (C5Me5)2UI2, 15, and (C5Me5)2(hpp)UI, 16, respectively,
in which the CH2 tuck components have been converted to methyl groups.
Introduction
ligand, [μ-η5:η1:η1-C5Me3(CH2)2]3-. This complex also provided
the first crystallographic evidence on f element tuck-in complexes
25 years after they were first invoked as intermediates in
Recent studies of uranium metallocene hydride chemistry1
generated the bimetallic uranium dihydride complex, 1,
shown in eq 1, which contains pentamethylcyclopentadienyl
(2) Thompson, M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J.;
Nolan, M. C.; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. J. Am.
Chem. Soc. 1987, 109, 203.
(3) Evans, W. J.; Ulibarri, T. A.; Ziller, J. W. Organometallics 1991,
10, 134.
(4) Booij, M.; Deelman, B. J.; Duchateau, R.; Postma, D. S.;
Meetsma, A.; Teuben, J. H. Organometallics 1993, 12, 3531.
(5) Evans, W. J.; Perotti, J. M.; Ziller, J. W. Inorg. Chem. 2005, 44,
5820.
(6) Evans, W. J.; Champagne, T. M.; Ziller, J. W. J. Am. Chem. Soc.
2006, 128, 14270.
(7) Watson, P. L. J. Am. Chem. Soc. 1983, 105, 6491.
(8) Watson, P. L.; Parshall, G. W. Acc. Chem. Res. 1985, 18, 51.
(9) Bercaw, J. E. J. Am. Chem. Soc. 1974, 96, 5087.
(10) Schock, L. E.; Brock, C. P.; Marks, T. J. Organometallics 1987, 6,
232.
ring that has undergone two C-H bond activation reactions to
form the first example of a trianionic “tuck-in”2 “tuck-over”3-6
*Fax: 949-824-2210 Email: wevans@uci.edu.
(1) Evans, W. J.; Miller, K. A.; DiPasquale, A. G.; Rheingold, A. L.;
Stewart, T. J.; Bau, R. Angew. Chem., Int. Ed. 2008, 47, 5075.
r
2010 American Chemical Society
Published on Web 08/31/2010
pubs.acs.org/Organometallics

4160 Organometallics, Vol. 29, No. 18, 2010
Montalvo et al.
Scheme 1
C-H bond activation of alkanes, eq 2.7,8 Although tuck-in
structures were previously identified by X-ray crystallography
complexes in which the hydride and alkyl ligands are highly
polarized anions: R- and H- f 2e- þ RH would not be
expected to be favorable on electrostatic grounds. In fact,
Scheme 1 and eq 3 provide the first examples of this type of
reactivity with the f elements.
The type of reaction shown in eq 3 would not be con-
sidered out of the ordinary for transition metals where
less polar bonds and two-electron metal-based redox
couples are available. This would be a double reductive
elimination reaction in which two C-H bonds are for-
med and four electrons are transferred to the two metals,
Scheme 2a.
with transition metals9-16 and several lanthanide tuck-over
structures were found,3-6 f element tuck-in complexes were
elusive until 1 was identified.
However, in the uranium case, this would generate an
organometallic U2þ complex, a species that has not yet been
isolated and definitively characterized.17-24 As an alterna-
tive, this type of reductive elimination could occur stepwise,
Scheme 2b, but this would still involve the unusual coupling
of two anions. Obtaining detailed mechanistic data on these
aspects of the reactivity of 1 has been challenging due to the
presence of four reactive functionalities: the two uranium
hydride bonds and the tuck-in and tuck-over alkyl uranium
moieties.
Not only was the structure of complex 1 unique, it also had
unusual reactivity. As shown in Scheme 1, it can function as a
multielectron reductant in which the bimetallic compound
provides four, six, or eight electrons depending on the
substrate. The formal half-reaction for the tuck-in, tuck-
over, and hydride-based components of these reductions is
shown in eq 3. This is an unusual reaction since it requires the
hydride ligands to come together with the alkyl anions of the
3 -
-
½C5Me3ðCH2Þ2ꢀ þ 2H- f ðC5Me5Þ þ 4e- ð3Þ
(17) Diaconescu, P. L.; Arnold, P. L.; Baker, T. A.; Mindiola, D. J.;
Cummins, C. C. J. Am. Chem. Soc. 2000, 122, 6108.
(18) Fagan, P. J.; Manriquez, J. M.; Maatta, E. A.; Seyam, A. M.;
Marks, T. J. J. Am. Chem. Soc. 1981, 103, 6650.
(19) Warner, B. P.; Scott, B. L.; Burns, C. J. Angew. Chem., Int. Ed.
1998, 37, 959.
(20) Arunachalampillai, A.; Crewdson, P.; Korobkov, I.; Gambarotta,
S. Organometallics 2006, 25, 3856.
(21) Fagan, P. J.; Manriquez, J. M.; Marks, T. J.; Day, C. S.; Vollmer,
S. H.; Day, V. W. Organometallics 1982, 1, 170.
(22) Manriquez, J. M.; Fagan, P. J.; Marks, T. J.; Vollmer,
S. H.; Day, C. S.; Day, V. W. J. Am. Chem. Soc. 1979, 101,
5075.
tuck-in tuck-over species and then give up electrons and
form C-H bonds. This is unusual reactivity for f element
(11) Bulls, A. R.; Schaefer, W. P.; Serfas, M.; Bercaw, J. E. Organo-
metallics 1987, 6, 1219.
(12) Luinstra, G. A.; Teuben, J. H. J. Am. Chem. Soc. 1992, 114, 3361.
(13) Fischer, J. M.; Piers, W. E.; Young, V. G., Jr. Organometallics
1996, 15, 2410.
(14) Kreindlin, A. Z.; Dolgushin, F. M.; Yanovsky, A. I.; Kerzina,
Z. A.; Petrovskii, P. V.; Rybinskaya, M. I. J. Organomet. Chem. 2000,
616, 106.
(15) Beweries, T.; Burlakov, V. V.; Bach, M. A.; Peitz, S.; Arndt, P.;
Baumann, W.; Spannenberg, A.; Rosenthal, U.; Pathak, B.; Jemmis,
E. D. Angew. Chem., Int. Ed. 2007, 46, 6907.
(23) Korobkov, I.; Gambarotta, S.; Yap, G. P. A. Angew. Chem., Int.
Ed. 2002, 41, 3433.
(16) Rybinskaya, M. I.; Kreindlin, A. Z.; Struchkov, Y. T.; Yanovskii,
A. I. J. Organomet. Chem. 1989, 359, 233.
(24) Gambarotta, S.; Scott, J. Angew. Chem., Int. Ed. 2004, 43,
5298.

Article
Organometallics, Vol. 29, No. 18, 2010 4161
Scheme 2
Recently, a second uranium tuck-in complex, (C5Me5)-
(η5:η1-C5Me4CH2)(hpp)U25 [(hpp)-=1,3,4,6,7,8-hexahydro-
2H-pyrimido[1,2-a]pyrimidinato], 2, was isolated, eq 4, that
of p-tolylSH with 1 equiv of potassium bis(trimethylsilyl)amide
in hexane. Potassium bis(trimethylsilyl)amide (Sigma-Aldrich)
was extracted with toluene before use. Hydrogen gas (Praxair),
Me3SiCl (Sigma-Aldrich), and CuI (Sigma-Aldrich) were used as
1
received. H and 13C NMR spectra were recorded on a Bruker
DRX500 spectrometer at 25 °C. Due to the paramagnetism of
uranium, only resonances that could be unambiguously identified
are reported. Infrared spectra were recorded as KBr pellets on a
Varian 1000 FTIR spectrophotometer at 25 °C. Elemental analy-
ses were performed on a Perkin-Elmer 2400 Series II CHNS ana-
lyzer. GC-MS analyses were performed on a Thermo Trace MSþ.
[(C5Me5)2UHx]2 from 1. On a high-vacuum line (10-5 Torr),
H2 (1 atm) was introduced to a J-Young NMR tube containing a
degassed, dark green solution of 1 (14 mg, 0.014 mmol) in C6D6.
After 2 h, H2 (1 atm) was reintroduced to the J-Young NMR
provides an opportunity to investigate the reactivity of a
single U4þ tuck-in moiety in the absence of additional tuck-
over and hydride reactive sites as in 1. This report describes
the reactivity of the single tuck-in moiety in 2 as well as a
comparison of the reactivity of 1 and 2. A rare example of a
monometallic uranium hydride, (C5Me5)2(hpp)UH, 3, was
synthesized in the course of these studies, and its reactivity is
also described in comparison to that of 1 and 2. The overall
study gives the first data on the reactivity of isolated, fully
characterized, f element tuck-in complexes and has led to a
new tethered uranium metallocene system.
1
tube to ensure all of the uranium reagent reacted. H NMR
spectroscopy showed quantitative conversion of 1 to the pre-
viously characterized [(C5Me5)2UHx]2 (x = 1, 2; 4.7:1 ratio
observed).18
(C5Me5)2(hpp)UH, 3, from (C5Me5)2(hpp)UEt. On a high-
vacuum line (10-5 Torr), H2 (1 atm) was introduced to a Schlenk
flask containing a degassed, dark red solution of (C5Me5)2-
(hpp)UEt (220 mg, 0.325 mmol) in toluene (20 mL). After 2 h
and again after 4 h, H2 (1 atm) was subsequently reintroduced
to the Schlenk flask to ensure all of the uranium reagent
reacted. After the Schlenk flask was brought into a glovebox,
Experimental Section
solvent was removed under vacuum to yield 3 as a dark yellow
=
The manipulations described below were conducted under
argon with rigorous exclusion of air and water using Schlenk,
vacuum line, and glovebox techniques. Solvents were spar-
ged with UHP argon and dried over columns containing
Q-5 and molecular sieves. NMR solvents (Cambridge Isotope
Laboratories) were dried over sodium-potassium alloy, de-
gassed by three freeze-pump-thaw cycles, and vacuum-trans-
ferred before use. (C5Me5)U[μ-η5:η1:η1-C5Me3(CH2)2](μ-H)2U-
(C5Me5)2, 1,1 (C5Me5)(η5:η1-C5Me4CH2)(hpp)U, 2,25 (C5Me5)2-
(hpp)UR25 (R = Me, 6; Et), (C5Me5)2U(SPh)2, 8,26 [(C5Me5)2-
UMe(OTf)]2,27 and (C5Me5)2UCl218 were prepared according to
literature methods. PhSSPh and p-tolylSS-p-tolyl (Sigma-
Aldrich) were sublimed before use. PhSH, p-tolylSH, PhNH2,
aniline-d7, and HCtCPh (Sigma-Aldrich) were dried over acti-
1
solid (190 mg, 90%). H NMR (C6D6): δ 18.34 (s, Δν1/2
21 Hz, 2H, C7H12N3), 5.60 (s, Δν1/2 = 21 Hz, 2H, C7H12N3),
-0.67 (s, Δν1/2 = 14 Hz, 30H, C5Me5), -8.00 (s, Δν1/2
=
21 Hz, 2H, C7H12N3), -13.08 (s, Δν1/2 = 35 Hz, 2H, C7H12N3),
-18.00 (s, Δν1/2 = 30 Hz, 2H, C7H12N3), -34.91 (s, Δν1/2 = 31
Hz, C7H12N3). 13C NMR (C6D6): δ 59.2 (C7H12N3), 53.3
(C7H12N3), 50.2 (C5Me5), 28.9 (C7H12N3), 9.7 (C7H12N3),
-99.9 (C7H12N3). IR: 2923s, 2899s, 2851s, 2720w, 1548s, 1502s,
1472w, 1452s, 1439m, 1379m, 1358w, 1319m, 1292m, 1260w,
1200s, 1146m, 1111w, 1064m, 1024m, 979w, 898w, 878w, 803w,
727m, 693w, 606w cm-1. Anal. Calcd for C27H43N3U: C, 50.07;
N, 6.49; H, 6.69. Found: C, 50.15; N, 6.70; H, 6.43.
(C5Me5)2(hpp)UD, 3D, from (C5Me5)2(hpp)UEt. On a high-
vacuum line (10-5 Torr), D2 (1 atm) was introduced to a
J-Young NMR tube containing a degassed, dark red solution
of (C5Me5)2(hpp)UEt (18 mg, 0.027 mmol) in C6D6. 1H NMR
spectroscopy showed quantitative conversion of starting ma-
terial to 3D and deuterium incorporation into the (C5Me5)- and
(hpp)- ligands. Only a broad resonance at -0.64 ppm was
observed in the 2H NMR spectrum, consistent with deuterium
in the (C5Me5)-. IR: 2925s, 2897s, 2850s, 2725w, 1546s, 1501s,
1471w, 1452s, 1439m, 1380m, 1359w, 1319m, 1291m, 1260w,
˚
vated 4 A molecular sieves and degassed by three freeze-pump-
thaw cycles before use. KS-p-tolyl was prepared by deprotonation
(25) Evans, W. J.; Montalvo, E.; Ziller, J. W.; DiPasquale, A. G.;
Rheingold, A. L. Organometallics 2010, 29, 2104.
(26) Lescop, C.; Arliguie, T.; Lance, M.; Nierlich, M.; Ephritikhine,
M. J. Organomet. Chem. 1999, 580, 137.
(27) Evans, W. J.; Walensky, J. R.; Furche, F.;Ziller, J. W.;DiPasquale,
A. G.; Rheingold, A. L. Inorg. Chem. 2008, 47, 10169.

4162 Organometallics, Vol. 29, No. 18, 2010
Montalvo et al.
1201s, 1146m, 1111w, 1064m, 1025m, 979w, 879w, 808w, 727m,
change from dark green to dark red was observed immediately.
1H NMR spectroscopy showed the quantitative conversion
of starting material to previously characterized (C5Me5)2-
U(SPh)2.26
693w, 605w cm-1
.
(C5Me5)2(hpp)UH, 3, from 2. On a high-vacuum line (10-5
Torr), H2 (1 atm) was introduced to a J-Young NMR tube
containing a degassed, brown solution of 2 (16 mg, 0.025 mmol)
in C6D6. After 2 h and again after 4 h, H2 (1 atm) was
subsequently reintroduced to the Schlenk flask to ensure all of
(C5Me5)2U(SPh)(S-p-tolyl), 9. PhSH (67 μL, 0.65 mmol) was
added to a stirred, dark red solution of [(C5Me5)2UMe(OTf)]2
27
(399 mg, 0.594 mmol) in toluene (15 mL). After the reaction
mixture was stirred for 12 h, solvent was removed under
vacuum, leaving (C5Me5)2U(SPh)(OTf) as a dark red solid
1
the uranium reagent reacted. H NMR spectroscopy showed
quantitative conversion of starting material to 3.
1
(420 mg, 92%). H NMR (C6D6): δ 12.96 (s, Δν1/2 = 22 Hz,
(C5Me5)2(hpp)UCl from 3. Me3SiCl (3 μL, 0.02 mmol) was
added to a J-Young NMR tube containing 3 (15 mg, 0.023
mmol) in C6D6. The J-Young NMR tube was immediately
30H, C5Me5), 0.88 (s, Δν1/2 = 15 Hz, 2H, Ph), 0.44 (s, Δν1/2
=
19 Hz, 2H, Ph), -6.83 (s, Δν1/2 = 18 Hz, 1H, Ph). 13C NMR
(C6D6): δ 134.2 (Ph), 100.7 (Ph), 84.7 (Ph), -23.9 (C5Me5). IR:
3050w, 2986m, 2952m, 2906m, 2860m, 2728w, 1579w, 1471w,
1448w, 1437w, 1355s, 1238s, 1192s, 1162m, 1085w, 1067w,
1024w, 1011m, 983s, 959m, 804w, 766w, 742m, 698m, 632s,
587w, 521w, 504w, 479w, 430w cm-1. Subsequently, KS-p-tolyl
(38 mg, 0.23 mmol) was added to a stirred solution of (C5Me5)2-
U(SPh)(OTf) (150 mg, 0.19 mmol) in toluene (15 mL). After the
reaction mixture was stirred for 12 h, an insoluble material was
removed from the mixture via centrifugation and filtration.
Solvent was removed under vacuum, leaving a dark red solid
that had a 1H NMR spectrum consistent with the formation of 8,
9 [1H NMR (C6D6) δ 12.82 (s, C5Me5); other resonances could
not be definitively differentiated from those of 8 and 10], and
(C5Me5)2U(S-p-tolyl)2, 10, in a 1:2.4:1.7 ratio.
1
capped. H NMR spectroscopy showed quantitative conver-
sion of starting material to the previously characterized (C5-
Me5)2(hpp)UCl.28 Me3SiH was identified by GC-MS.
(C5Me5)2(hpp)UCl from (C5Me5)2(hpp)UMe, 6. Me3SiCl
(2 μL, 0.02 mmol) was added to a J-Young NMR tube contain-
ing 6 (7 mg, 0.01 mmol) in C6D6. The J-Young NMR tube was
1
immediately capped. H NMR spectroscopy showed the pre-
sence of starting material and resonances consistent with the
formation of (C5Me5)2(hpp)UCl28 and Me4Si. Upon heating the
reaction mixture to 100 °C for 12 h, complete conversion of 6 to
(C5Me5)2(hpp)UCl28 was observed.
(C5Me5)ClU(η5-C5Me4CH2SiMe2CH2-KC), 4. Me3SiCl (76 μL,
0.60 mmol) was added via syringe to a stirred, dark green solution
of 1 (307 mg, 0.302 mmol) in toluene (15 mL). After stirring for
24 h, the dark red solution was centrifuged, separated from a green
insoluble powder, and evaporated to dryness, yielding a dark red
oil, which was subsequently extracted with pentane to yield 4 as
a dark red solid (120 mg, 49%). Dark red crystals of 4 suitable
for X-ray diffraction were grown from a concentrated hexane
solution at -35 °C. 1H NMR (C6D6): δ 9.99 (s, Δν1/2 = 47 Hz,
(C5Me5)2U(S-p-tolyl)2, 10. KS-p-tolyl (154 mg, 0.949 mmol)
was added to a stirred, dark red solution of (C5Me5)2UCl2
(262 mg, 0.452 mmol) in toluene (15 mL). After the reaction
mixture was stirred for 12 h, an insoluble material was removed
from the mixture via centrifugation and filtration. Solvent was
removed under vacuum to yield 10 as a dark red solid (288 mg,
84%). 1H NMR (C6D6): δ 12.70 (s, Δν1/2 = 22 Hz, 30H,
C5Me5), 2.42 (s, Δν1/2 = 5 Hz, 6H, Me), 0.27 (s, Δν1/2 = 10 Hz,
4H, Ph), -32.32 (s, Δν1/2 = 27 Hz, 4H, Ph). 13C NMR (C6D6):
δ 146.0 (Ph), 102.0 (Ph), 12.9 (Me), -23.9 (C5Me5). IR: 2972s,
2904s, 2861s, 2728w, 1596w, 1559w, 1488s, 1448m, 1378m,
1243w, 1210w, 1181w, 1120w, 1086s, 1016m, 980w, 842w, 807s,
732s, 696m, 628m, 491w cm-1. Anal. Calcd for C34H44S2U: C,
54.10; H, 5.88. Found: C, 53.51; H, 5.86.
15H, C5Me5), -4.38 (s, Δν1/2 = 23 Hz, 2H), -8.91 (s, Δν1/2
21 Hz, 3H), -16.92 (s, Δν1/2 = 160 Hz, 3H), -17.68 (s, Δν1/2
=
=
96 Hz, 3H), -19.57 (s, Δν1/2 = 106 Hz, 3H). 13C NMR (C6D6):
δ -21.4 (C5Me5). IR: 2947s, 2902s, 2859s, 2726w, 1487m,
1438m, 1380m, 1246m, 1164m, 1062w, 1021m, 980w, 856s,
803m, 765w, 722w, 693w cm-1. Anal. Calcd for C23H37ClSiU:
C, 44.98; H, 6.07. Found: C, 45.08; H, 6.26. The green insoluble
byproduct was transferred to a vial using small portions of
toluene. The solvent was evaporated to dryness to yield a green
powder (90 mg, 14%). The green powder was identified as
[(C5Me5)2UCl]3,22 5, on the basis of its 1H NMR spectrum
in THF-d8, which matched that of (C5Me5)2UCl(THF). In a
separate experiment in a NMR tube capped with a rubber
septum, the volatiles were removed with a syringe, analyzed by
GC-MS, and found to contain Me3SiH. A J & W Scientific DB-
5 column (30 m ꢁ 0.32 mm i.d. ꢁ 0.25 μm film thickness) was
used with a temperature ramp of 35 °C for 1 min and then 10 °C
per min to 290 °C.
(C5Me4CH2SPh)(C5Me5)(hpp)U(SPh), 11. PhSSPh (71 mg,
0.32 mmol) was added to a stirred, brown solution of 2 (209 mg,
0.324 mmol) in toluene (10 mL). After the reaction mixture was
stirred for 12 h, solvent was removed under vacuum and a tacky
orange solid was obtained, which was triturated with hexane to
yield 11 as an orange solid (210 mg, 76%). Orange crystals of 11
suitable for X-ray diffraction were grown from a concentrated
ether solution at -35 °C. 1H NMR (C6D6): δ 10.42 (s, Δν1/2
36 Hz, 1H, Ph), 9.27 (s, Δν1/2 = 27 Hz, 1H, Ph), 8.57 (s, Δν1/2
=
=
30 Hz, 1H, Ph), 8.27 (s, Δν1/2 = 15 Hz, 2H, C7H12N3), 7.41 (s,
Δν1/2 = 14 Hz, 2H, C7H12N3), 6.32 (s, Δν1/2 = 10 Hz, 3H,
C5Me4CH2SPh), 6.04 (s, Δν1/2 = 9 Hz, 3H, C5Me4CH2SPh),
4.89 (s, Δν1/2 = 8 Hz, 15H, C5Me5), 3.98 (s, Δν1/2 = 11 Hz,
3H, C5Me4CH2SPh), 3.54 (s, Δν1/2 = 28 Hz, 1H, Ph), 2.59 (s,
Δν1/2 = 14 Hz, 2H, C7H12N3), 0.86 (s, Δν1/2 = 11 Hz, 3H,
C5Me4CH2SPh), 0.26 (s, Δν1/2 = 30 Hz, 1H, Ph), -0.21 (s,
Δν1/2 = 18 Hz, 1H, Ph), -1.12 (s, Δν1/2 = 30 Hz, 1H, Ph), -1.36
(s, Δν1/2 = 38 Hz, 1H, Ph), -1.62 (s, Δν1/2 = 18 Hz, 2H,
(C5Me5)2(hpp)U(CtCPh), 7, from 2. HCtCPh (2 μL, 0.02
mmol) was added to a J-Young NMR tube containing 2 (14 mg,
0.022 mmol) in C6D6. The J-Young tube was capped, and a color
change from brown to dark yellow was observed immediately.
1H NMR spectroscopy showed quantitative conversion of start-
ing material to the previously characterized (C5Me5)2(hpp)-
U(CtCPh), 7.25
(C5Me5)2(hpp)U(CtCPh), 7, from 3. HCtCPh (1 μL, 0.01
mmol) was added to a J-Young NMR tube containing 3 (7 mg,
0.01 mmol) in C6D6. The J-Young NMR tube was immediately
capped. 1H NMR spectroscopy showed quantitative conversion
of starting material to (C5Me5)2(hpp)U(CtCPh),25 7, and a
resonance consistent with the formation of H2 at 4.46 ppm was
also observed.
C7H12N3), -2.12 (s, Δν1/2 = 36 Hz, 1H, Ph), -3.85 (s, Δν1/2
=
21 Hz, 2H, C7H12N3), -4.17 (s, Δν1/2 = 16 Hz, 1H, Ph), -26.24
(s, Δν1/2 = 23 Hz, 2H, C7H12N3). 13C NMR (C6D6): δ 149.8
(C7H12N3), 130.8 (C7H12N3), 129.7 (C7H12N3), 125.8 (Ph),
107.2 (C7H12N3), 55.9 (Ph), 54.9 (Ph), 47.2 (Ph), 39.1 (Ph), 4.7
(Ph), -15.2 (Ph), -18.6 (C7H12N3), -31.8 (C5Me4SPh), -34.8
(C5Me4SPh), -38.4 (C5Me4SPh), -36.6 (Ph), -41.3 (C5Me5),
-46.4 (C5Me4SPh), -59.2 (Ph), -62.6 (C7H12N3). IR: 3048w,
2928s, 2900s, 2851s, 2721w, 1623m, 1574m, 1550s, 1491m,
1472m, 1438s, 1377m, 1317s, 1298m, 1257m, 1208s, 1143m,
1110w, 1081m, 1053w, 1024s, 997w, 997w, 979w, 900w, 880w,
842w, 816w, 738s, 650s, 614w, 534w, 475m, 425w cm-1. Anal.
(C5Me5)2U(SPh)2, 8, from 1. PhSH (3 μL, 0.03 mmol) was
added to a J-Young NMR tube containing 1 (7 mg, 0.007 mmol)
in C6D6. The J-Young NMR tube was capped, and a color
(28) Evans, W. J.; Montalvo, E.; Ziller, J. W.; DiPasquale, A. G.;
Rheingold, A. L. Inorg. Chem. 2010, 49, 222.

Article
Organometallics, Vol. 29, No. 18, 2010 4163
Calcd for C38H49N3S2U: C, 53.70; N, 4.94; H, 5.81. Found: C,
53.26; N, 5.43; H, 5.95.
(C6D6): δ 135.2 (C7H12N3), 84.9 (C7H12N3), 52.2 (Ph), 47.9
(C7H12N3), 40.4 (C7H12N3), 27.6 (C7H12N3), -24.7 (C7H12N3),
-49.8 (C5Me5), -62.6 (Ph), -70.8 (Ph). IR: 3331w, 2942s, 2924s,
2897s, 2850s, 2722w, 1618m, 1591s, 1570w, 1544s, 1498m, 1486m,
1540m, 1438m, 1379m, 1357w, 1319m, 1290m, 1274s, 1207m,
1172w, 1144m, 1112w, 1059m, 1026m, 992w, 902w, 837m, 804w,
754m, 725m, 697m, 622w, 580m, 495w, 460w cm-1. Anal. Calcd
for C33H48N4U: C, 53.65; N, 7.58; H, 6.55. Found: C, 53.59; N,
7.47; H, 6.26.
(C5Me5)2(hpp)U(NHPh), 14, from 3. PhNH2 (2μL, 0.02 mmol)
was added to a J-Young NMR tube containing 3 (10 mg, 0.02
mmol) in C6D6. The J-Young NMR tube was capped, and a color
change from dark yellow to orange was observed immediately. 1H
NMR spectroscopy showed quantitative conversion of starting
material to 14 and a resonance consistent with the formation of H2
was also observed.
(C5Me5)2(hpp)U(SPh), 12, from (C5Me5)2(hpp)UMe, 6. PhSH
(46 μL, 0.45 mmol) was added to a stirred, dark yellow solution
of 628 (296 mg, 0.447 mmol) in toluene (15 mL). After the
reaction mixture was stirred for 12 h, solvent was removed
under vacuum, leaving 12 as an orange solid (303 mg, 90%).
Yellow crystals of 12 suitable for X-ray diffraction were grown
from a concentrated toluene solution at -35 °C. 1H NMR (C6D6):
δ 31.50 (s, Δν1/2 = 22 Hz, 2H, C7H12N3), 9.31 (s, Δν1/2 = 18 Hz,
2H, C7H12N3), 7.58 (s, Δν1/2 = 12 Hz, 2H, C7H12N3), 5.64 (s,
Δν1/2 = 9 Hz, 30H, C5Me5), 3.83 (s, Δν1/2 = 8 Hz, 2H, Ph), -0.47
(s, Δν1/2 = 15 Hz, 1H, Ph), -1.29 (s, Δν1/2 = 18 Hz, 2H, C7-
H12N3), -1.98 (s, Δν1/2 = 17 Hz, 2H, Ph), -4.25 (s, Δν1/2 = 16
Hz, 2H, C7H12N3), -27.80 (s, Δν1/2 = 26 Hz, C7H12N3). 13C
NMR (C6D6): δ 147.3 (C7H12N3), 123.5 (Ph), 105.9 (Ph), 55.2
(C7H12N3), 54.3 (C7H12N3), 46.1 (Ph), 37.1 (C7H12N3), 32.3
(C7H12N3), 0.90 (C7H12N3), -39.1 (C5Me5). IR: 3058w, 2949s,
2898s, 2850s, 2719w, 1637m, 1574m, 1549s, 1494s, 1472s, 1451s,
1379s, 1319s, 1291m, 1269m, 1201s, 1144m, 1111w, 1082m,
(C5Me5)2UI2, 15. CuI (43 mg, 0.22 mmol) was added to a
stirred, dark green solution of 1 (58 mg, 0.057 mmol) in toluene
(10 mL). After the reaction mixture was stirred for 12 h, an
insoluble material was removed from the mixture via centrifuga-
tion and filtration. Solvent was removed under vacuum, leaving
15 as a dark red solid (64 mg, 74%). The identity of 15 was
confirmed by comparison of its 1H NMR spectrum with that of
the previously characterized (C5Me5)2UI2.30 Anal. Calcd for
C20H30I2U: C, 31.51; H, 3.97. Found: C, 31.80; H, 3.52.
(C5Me5)2(hpp)UI, 16, from 2. CuI (7 mg, 0.04 mmol) was
added to a J-Young NMR tube containing 2 (12 mg, 0.018
mmol) in C6D6. The J-Young NMR tube was immediately
1056m, 1025m, 901w, 898w, 876w, 806w, 739s, 696s, 549w cm-1
.
Anal. Calcd for C33H47N3SU: C, 52.44; N, 5.56; H, 6.27. Found:
C, 52.50; N, 5.86; H, 5.91. Crystal system: tetragonal; space group:
˚
˚
P43; unit cell dimensions a = 11.2897(12) A, b = 11.2897(12) A,
3
˚
˚
c = 47.192(5) A, R = 90°, β = 90°, γ = 90°; V = 6015.0(11) A .
(C5Me5)2(hpp)U(SPh), 12, from 2. PhSH (3 μL, 0.03 mmol)
was added to a J-Young NMR tube containing 2 (18 mg, 0.028
mmol) in C6D6. The J-Young tube was capped, and a color
change from brown to orange was observed. 1H NMR spectros-
copy showed quantitative conversion of starting material to 12.
(C5Me5)2(hpp)U(SPh), 12, from 3 and PhSH. PhSH (2 μL,
0.02 mmol) was added to a J-Young NMR tube containing 3
(10 mg, 0.02 mmol) in C6D6. The J-Young NMR tube was
capped, and a color change from dark yellow to orange was
1
capped. H NMR spectroscopy showed the formation of the
previously characterized (C5Me5)2(hpp)UI25 (23% when Me4Si
was used as an internal standard) along with other products.
(C5Me5)2(hpp)UI, 16, from 3. CuI (8 mg, 0.01 mmol) was
added to a J-Young NMR tube containing 3 (2 mg, 0.01 mmol) in
1
C6D6. The J-Young NMR tube was immediately capped. H
1
NMR spectroscopy showed the quantitative conversion of start-
ing material to previously characterized (C5Me5)2(hpp)UI.25
X-ray Data Collection, Structure Determination, and Refine-
ment. Crystallographic information on complexes 4, 11, 12, and
14 is summarized in the Supporting Information and Table 1.
observed immediately. H NMR spectroscopy showed quanti-
tative conversion of starting material to 12, and a resonance
consistent with the formation of H2 was also observed.
(C5Me5)2(hpp)U(SPh), 12, from 3 and PhSSPh. PhSSPh
(3 mg, 0.02 mmol) was added to a J-Young NMR tube contain-
ing 3 (9 mg, 0.01 mmol) in C6D6. The J-Young NMR tube was
capped, and a color change from dark yellow to orange was
Results
1
observed immediately. H NMR spectroscopy showed quanti-
Reactions with H2. Since hydrogenolysis of M-C bonds is a
characteristic reaction of alkyl complexes of lanthanides and
actinides,18,31-33 the reactivity of 1 and 2 with H2 was exam-
ined. Hydrogen (1 atm) reacts with 1 within 10 min to generate
tative conversion of starting material to 12, and resonances
consistent with the formation of PhSH were also observed.
(C5Me5)2U(NHPh)2, 13. PhNH2 (20 μL, 0.2 mmol) was added
to a stirred, dark green solution of 1 (57 mg, 0.056 mmol) in
toluene (10 mL). After the reaction mixture was stirred for 12 h,
solvent was removed under vacuum, affording a dark orange oil,
which was extractedwith hexane to yield13 as a darkorange solid
(28 mg, 36%). The identity of 13 was confirmed by comparison of
its 1H NMR spectrum with that of the previously characterized
(C5Me5)2U(NHPh)2.29 A resonance consistent with the forma-
tion of H2 was observed in the 1H NMR spectrum when a similar
reaction was carried out in a sealed J-Young NMR tube.
1
a solution with a complicated H NMR spectrum. However,
over the course of 72 h, the spectrum simplifies and only the
equilibrium mixture of [(C5Me5)2UH2]2 and [(C5Me5)2UH]2 is
observed,18 eq 5. This is the reverse of the reaction that forms 1.
(C5Me5)2(hpp)U(NHPh), 14. PhNH2 (26 μL, 0.28 mmol) was
added to a stirred, brown solution of 2 (183 mg, 0.0283 mmol) in
toluene (10 mL). After the reaction mixture was stirred for 12 h,
solvent was removed under vacuum, and a tacky light orange
solid was obtained, which was triturated with hexane to yield 14
as a light orange solid (159 mg, 75%). Gold crystals of 14
suitable for X-ray diffraction were grown from a concentrated
Reaction of 1 with D2 gives products with a 1H NMR
spectrum that is consistent with deuterium incorporation
toluene solution at -35 °C. 1H NMR (C6D6): δ 30.15 (s, Δν1/2
=
37 Hz, 2H, C7H12N3), 28.92 (s, Δν1/2 = 24 Hz, 1H, Ph), 22.38
(s, Δν1/2 = 25 Hz, 2H, C7H12N3), 5.13 (s, Δν1/2 = 15 Hz,
2H, C7H12N3), 0.22 (s, Δν1/2 = 7 Hz, 30H, C5Me5), -2.37 (s,
Δν1/2 = 9 Hz, 2H, Ph), -3.24 (s, Δν1/2 = 11 Hz, 2H, Ph), -3.54
(s, Δν1/2 = 13 Hz, 2H, C7H12N3), -7.27 (s, Δν1/2 = 20 Hz, 2H,
C7H12N3), -9.06 (s, Δν1/2 = 18 Hz, 2H, C7H12N3). 13C NMR
(30) Maynadie, J.; Berthet, J.-C.; Thuery, P.; Ephritikhine, M. Orga-
nometallics 2006, 25, 5603.
(31) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J. Am.
Chem. Soc. 1983, 105, 1401.
(32) Evans, W. J.; Seibel, C. A.; Ziller, J. W. J. Am. Chem. Soc. 1998,
120, 6745.
(33) Evans, W. J.; Meadows, J. H.; Wayda, A. L.; Hunter, W. E.;
(29) Arney, D. S. J.; Burns, C. J. J. Am. Chem. Soc. 1995, 117, 9448.
Atwood, J. L. J. Am. Chem. Soc. 1982, 104, 2008.

4164 Organometallics, Vol. 29, No. 18, 2010
Montalvo et al.
Table 1. X-ray Data Collection Parameters for (C5Me5)ClU(η5-C5Me4CH2SiMe2CH2-KC), 4, (C5Me4CH2SPh)(C5Me5)(hpp)U(SPh),
11, (C5Me5)2(hpp)U(SPh), 12, and (C5Me5)2(hpp)U(NHPh), 14
empirical formula
C23H37ClSiU, 4
C39H51N3S2U, 11
C33H47N3SU, 12
C33H48N4U, 14
fw
615.10
153(2)
monoclinic
P21/c
9.7385(10)
15.5793(16)
16.2137(16)
90
104.249(2)
90
2384.2(4)
4
1.714
863.98
93(2)
monoclinic
P21/c
10.0722(4)
17.4433(7)
20.8522(9)
90
102.2811(5)
90
3579.7(3)
4
1.603
4.682
0.0248
0.0516
755.83
93(2)
tetragonal
P43
11.2897(12)
11.2897(12)
47.192(5)
90
90
90
6015.0(11)
8
1.669
5.493
0.0722
0.1776
738.78
93(2)
monoclinic
P21/c
17.855(2)
10.7301(14)
17.385(2)
90
112.6683(16)
90
3073.4(7)
4
1.597
5.309
0.0297
0.0818
temperature (K)
cryst syst
space group
˚
a (A)
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
volume (A )
Z
3
˚
F
calcd (Mg/m3)
μ (mm-1
)
6.975
R1a (I > 2.0σ(I))
wR2b (all data)
P
0.0203
0.0486
P
P
P
aR1 =
Fo| - |Fc
/
|Fo|. bwR2 = [ [w(Fo2 - Fc2)2/ [w(Fo2)2 ]]1/2
.
into the (C5Me5)- ligands, as was previously observed with
mixtures of [(C5Me5)2UH2]2 and [(C5Me5)2UH]2.18
Tuck-in complex 2 also reacts with H2 and generates the
terminal hydride (C5Me5)2(hpp)UH, 3, eq 6. Complex 3
reverts back to 2 upon heating to 110 °C.
into the (C5Me5)- and (hpp)- ligands was observed by H
NMR spectroscopy. The infrared spectrum of 3D was similar
to that of 3.1
Reactions with Me3SiCl. The presence of the hydride
ligand in 3 was supported by the reaction of 3 with Me3SiCl.
As shown in eq 8, (C5Me5)2(hpp)UCl28 was formed and the
byproduct Me3SiH was detected by GC-MS.
1
Complex 3 can also be generated by hydrogenolysis of the
ethyl complex (C5Me5)2(hpp)UEt, eq 7. Since the ethyl com-
plex is the precursor to 2, complex 3 is more directly made
from (C5Me5)2(hpp)UEt.
The reaction of 1 with Me3SiCl was attempted to obtain a
simple derivative with chloride in place of hydride,39 as was
done in eq 8. Alternatively, if 1 reacted as shown in Scheme 2a,
products such as (C5Me5)2UClx(SiMe3)y (x þ y = 2) could re-
sult. Uranium chloride bonds do form in this reaction, but the
reaction was much more complicated than the two possibilities
just presented. The complexity of the reaction demonstrated
the potential of the multiple reactive sites in 1to work in concert
to generate unusual results. Specifically, this reaction generates
a new type of tethered metallocene, (C5Me5)ClU(η5-C5Me4-
CH2SiMe2CH2-κC), 4, as a major product in which a “Me2-
SiCH2” unit has been inserted into a uranium-methylene
bond of the original tuck-in structure, eq 9.
Complex 3 had an elemental analysis and spectroscopic
characteristics consistent with its formulation as (C5Me5)2-
(hpp)UH, but single crystals suitable for X-ray crystallogra-
phy were not obtained. Terminal U4þ hydrides are rare,34-38
and the only crystallographically characterized examples
t
are (C5H4 Bu)3UH34 and [(Me3Si)2N]3UH.35 Complex 3, as
well as the other new (hpp)- complexes described below, 11,
12, and 14, have six (hpp)- 1H NMR resonances with wide-
spread chemical shifts as well as one (C5Me5)- resonance.
The hydride resonance of 3 could not be located in this para-
magnetic system. When the reaction of (C5Me5)2(hpp)UEt
with D2 was carried out to make 3D, deuterium incorporation
(34) Berthet, J. C.; Le Marechal, J. F.; Lance, M.; Nierlich, M.;
Vigner, J.; Ephritikhine, M. J. Chem. Soc., Dalton Trans. 1992, 1573.
(35) Andersen, R. A.; Zalkin, A.; Templeton, D. H. Inorg. Chem.
1981, 20, 622.
(36) Berthet, J. C.; Le Marechal, J. F.; Ephritikhine, M. J. Chem.
Soc., Chem. Commun. 1991, 360.
Complex 4 was characterized by spectroscopic and analy-
tical means, and the structure of the tethered cyclopentadienyl
(37) Turner, H. W.; Simpson, S. J.; Andersen, R. A. J. Am. Chem.
Soc. 1979, 101, 2782.
(38) Baudry, D.; Ephritikhine, M. J. Organomet. Chem. 1988, 349,
123.
(39) Reddy, N. D.; Kumar, S. S.; Roesky, H. W.; Vidovic, D.;
Magull, J.; Noltemeyer, M.; Schmidt, H.-G. Eur. J. Inorg. Chem.
2003, 442.

Article
Organometallics, Vol. 29, No. 18, 2010 4165
form (C5Me5)2(hpp)UCl28 and Me4Si, but the reaction needs
to be heated to 100 °C for 12 h to go to completion, eq 10.
Reactions with HCtCPh. Complex 1 reacts with phenyl-
acetylene to form multiple products, whereas 2 reacts with
this substrate to form (C5Me5)2(hpp)U(CtCPh), 7, in quanti-
tative yield, eq 11. The phenylalkynide 7 has previously
been made from (C5Me5)2(hpp)UCl and LiCtCPh25 and its
Figure 1. Thermal ellipsoid plot of (C5Me5)ClU(η5-C5Me4-
CH2SiMe2CH2-κC), 4, drawn at the 50% probability level with
hydrogen atoms omitted for clarity.
alkyl ligand (η5-C5Me4CH2SiMe2CH2-κC)2- was established
by X-ray crystallography, Figure 1. The closest related cyclo-
pentadienyl uranium complex, (η5-C5Me4SiMe2CH2-κC)2U,40
contains (η5-C5Me4SiMe2CH2-κC)2- ligands that differ by a
CH2 unit and were formed by metalation of the silyl group in a
(C5Me4SiMe3)- precursor. An additional product isolated
from the reaction of 1 with Me3SiCl is the previously reported
trivalent uranium chloride complex [(C5Me5)2UCl]3, 5.22 Crys-
tallographic data on 4 and the other new complexes reported in
this paper fall in the normal ranges and are described in detail
only in the Supporting Information.
The reaction observed between 1 and Me3SiCl was not
simply a “(C5Me5)2U” to (C5Me5)2UClx(SiMe3)y conver-
sion, and it appeared that multiple reaction pathways are
accessible with this polyfunctional compound. The product
composition indicates that C-H bond activation reactivity
involving the Me3Si group as well as insertion chemistry with
the silyl group occurred. C-H bond formation is also
indicated since only one of the CH2 groups in 1 remains in
the products. This indicates that one of the tuck-in or tuck-
over methylene moieties was converted back to a methyl
group in the reaction. This methylene to methyl conversion is
observed in all of the reactions in Scheme 1. If this C-H bond
formation occurred with reduction as shown in Scheme 2b, this
could provide a route to the trivalent byproduct [(C5Me5)2-
UCl]3,22 5. To date, we have not been able to separate out these
reactions to determine their exact sequence. Several scenarios
are reasonable.
preparation via eq 11 was confirmed by 1H NMR spectros-
copy.
Complex 7 can also be synthesized from hydride 3 and
HCtCPh, eq 11, whereas the methyl complex 6 does not
react with HCtCPh under the same reaction conditions. No
reactions were observed between complex 1 or 2 and other
hydrocarbon reagents such as methane, benzene, or toluene.
Reactions with PhSSPh. The reaction of 1 with PhSSPh that
forms (C5Me5)2U(SPh)2, 8,42 Scheme 1, was examined in more
detail since it could occur not only by the reductive pathways
shown in Scheme 2 but also by a series of σ-bond metathesis
reactions as shown in Scheme 3. To form the observed products,
the initial reaction of PhSSPh with 1 would have to involve the
U-H bonds and have sulfur in the position diagonal to the
metal. This would generate PhSH as a byproduct that could
subsequently react with the U-C(CH2 tuck) bonds to form
methyl groups and the U-SPh linkages in the product.
Initially, the reaction of 1 with a 1:1 mixture of PhSSPh and
p-tolylSS-p-tolyl was pursued to evaluate the possible presence
of an intermediate of formal composition “(C5Me5)2U”. If this
reaction proceeded through a “(C5Me5)2U” intermediate, a 1:1
mixture of (C5Me5)2U(SPh)2, 8, and (C5Me5)2U(S-p-tolyl)2,
10, would be expected with no mixed ligand byproduct,
(C5Me5)2U(SPh)(S-p-tolyl), 9. However, as described below,
exchange reactions interfered with the analysis.
The reaction of 1 with Me3SiCl was compared with the
reactivity of the tuck-in moiety in 2. Lanthanide and yttrium
alkyl complexes are known to react with Me3SiCl to form the
corresponding chloride complexes,41 and a similar reaction
could occur with 2. However, no reaction was observed
between 2 and Me3SiCl at 25 °C. Reactivity is observed after
12 h at 55 °C, but a mixture of products forms and the
individual components have not yet been definitively identi-
fiable by X-ray crystallography.
For this study, (C5Me5)2U(S-p-tolyl)2, 10, was synthe-
sized, eq 12, in a reaction analogous to that of (C5Me5)2-
U(SPh)2, 8.26 The synthesis of 9 was attempted by
The reactivity of the U4þ methyl complex (C5Me5)2(hpp)-
UMe, 6,28 was also examined for comparison with the reac-
tions of 1 and 2. Complex 6 reacts with Me3SiCl at 25 °C to
(40) Evans, W. J.; Siladke, N. A.; Ziller, J. W. Chem. Eur. J. 2010,
16, 796.
(41) Voskoboynikov, A. Z.; Parshina, I. N.; Shestakova, A. K.;
Butin, K. P.; Beletskaya, I. P.; Kuz’mina, L. G.; Howard, J. A. K.
Organometallics 1997, 16, 4041.
(42) Evans, W. J.; Montalvo, E.; Kozimor, S. A.; Miller, K. A. J. Am.
Chem. Soc. 2008, 130, 12258.

4166 Organometallics, Vol. 29, No. 18, 2010
Montalvo et al.
Scheme 3
generating (C5Me5)2U(SPh)(OTf) from [(C5Me5)2UMe(OTf)]2
and PhSH and then reacting the triflate thiolate with KS-p-
tolyl. Unfortunately, this gives a 1:2.4:1.7 mixture of 8, 9, and
10 due to ligand exchange, eq 13. Consistent with this result, the
2ðC Me Þ UðSPhÞðOTfÞ þ 2KS-p-tolyl
þ 2PhSH
½ðC5Me5Þ2UMeðOTfÞꢀ2
f
f
5
5
2
- 2CH4
- 2KOTf
8 þ 9 þ 10
ð13Þ
combination of 8 with 10 affords 9, by exchange, eq 14.
Hence, although 1 reacts with a 1:1 mixture of PhSSPh and
Figure 2. Thermal ellipsoid plot of (C5Me4CH2SPh)(C5Me5)-
(hpp)U(SPh), 11, drawn at the 50% probability level. Hydrogen
atoms have been omitted for clarity.
in this paper, 3, 12, and 14, have analogous C-N stretches at
1549, 1544, and 1548 cm-1, respectively.43
In contrast to the reaction of 2 in eq 16, (C5Me5)2-
(hpp)UMe, 6, does not react with PhSSPh at 25 °C.28
However, the hydride complex 3 reacts with PhSSPh to form
(C5Me5)2(hpp)U(SPh), 12, and PhSH, eq 17.
p-tolylSS-p-tolyl to form a 1:2:1 mixture of (C5Me5)2U(SPh)2,
8, (C5Me5)2U(SPh)(S-p-tolyl), 9, and (C5Me5)2U(S-p-tolyl)2,
10, eq 15, this result cannot be used to exclude U2þ inter-
mediates.
The reaction of 2 with PhSSPh was examined to determine
how an isolated tuck-in moiety would react with this sub-
strate. Complex 2 reacts with PhSSPh to form the σ-bond
metathesis product (C5Me4CH2SPh)(C5Me5)(hpp)U(SPh),
11, eq 16.
Reactions with PhSH. The observation of σ-bond meta-
thesis reactivity with the single tuck-in moiety in 2 and the
hydridein 3 suggested thatthe reactionsinScheme3 shouldbe
examined further. The necessary intermediate in that scheme,
PhSH, was the next substrate studied. With a pKa of 10.3
(DMSO),44 PhSH is on the protonolysis end of the continuum
of reactions that can be formally viewed as σ-bond metath-
eses. It has previously been shown that 1 reacts with PhOH
(pKa = 18, DMSO)44 to form (C5Me5)2U(OPh)2.1 As shown
in eq 18, 1 reacts cleanly with PhSH to generate an analogous
product, (C5Me5)2U(SPh)2, 8. Complex 8 was also obtained
from 1 and PhSSPh, Scheme 1.
The structure of 11 was determined by X-ray crystallo-
graphy and is shown in Figure 2. The 1H NMR spectrum of
11 contained one (C5Me5)- resonance along with four
resonances, each of which integrated to three protons corre-
sponding to the methyl groups in the (C5Me4CH2SPh)-
ligand. In addition, ten (C6H5)- resonances were observed
as well as six (hpp)- resonances typical for (C5Me5)2(hpp)-
UX (X = Cl, Me, N3, CtCPh, Et, Ph, I).25,28 The IR spec-
trum of 11 contains a C-N stretch arising from the (hpp)-
ligand at 1550 cm-1. The other new (hpp)- complexes presented
(43) Wilkins, J. D. J. Organomet. Chem. 1974, 80, 349.
(44) Bordwell, F. G.; McCallum, R. J.; Olmstead, W. N. J. Org.
Chem. 1984, 49, 1424.

Article
Organometallics, Vol. 29, No. 18, 2010 4167
Figure 4. Thermal ellipsoid plot of (C5Me5)2(hpp)U(NHPh),
14, drawn at the 50% probability level. Hydrogen atoms have
been omitted for clarity.
Figure 3. Thermal ellipsoid plot of (C5Me5)2(hpp)U(SPh), 12,
drawn at the 50% probability level. Hydrogen atoms have been
omitted for clarity.
Complex 2 also reacts cleanly with PhSH to form the pro-
tonolysis product (C5Me5)2(hpp)U(SPh), 12, eq 19. Complex
12 can be more conveniently synthesized from the reaction of
PhSH with (C5Me5)2(hpp)UH, 3, or (C5Me5)2(hpp)UMe, 6,
eq 19. The connectivity of 12 was determined by X-ray crys-
tallography, Figure 3.
Reactions with CuI. Reactions of 1 and 2 with CuI were
examined since CuI has recently been shown to be an
excellent reagent to convert U4þ alkyls to iodides in quanti-
tative yields with elimination of the corresponding alkane,
e.g., eq 22.25,45 Kiplinger andco-workershave also shown that
copper salts can oxidize U4þ metallocenes, e.g., eq 23.46-49
Reactions with PhNH2. Reactions with PhNH2 (pKa = 30.6,
DMSO) were examined since polyfunctional 1had the potential
to make (dNPh)2- imide products as well as (NHPh)- analo-
gues of the PhSH and PhOH reactions. As shown in eq 20,
the bis(amide) complex (C5Me5)2U(NHPh)2,29 13, was isola-
ted rather than the imide. When complex 1 was reacted with
aniline-d7, incorporation of deuterium into the (C5Me5)- ligand
was observed by 1H NMR spectroscopy.
The main products isolated from reactions of 1 and 2 with
CuI are not oxidation products, but are instead the iodide
complexes (C5Me5)2UI2, 15, eq 24, and (C5Me5)2(hpp)UI,25
(45) Evans, W. J.; Walensky, J. R.; Ziller, J. W. Organometallics 2010,
29, 101.
(46) Graves, C. R.; Scott, B. L.; Morris, D. E.; Kiplinger, J. L. J. Am.
Chem. Soc. 2007, 129, 11914.
(47) Graves, C. R.; Scott, B. L.; Morris, D. E.; Kiplinger, J. L.
Organometallics 2008, 27, 3335.
(48) Graves, C. R.; Vaughn, A. E.; Schelter, E. J.; Scott, B. L.;
Thompson, J. D.; Morris, D. E.; Kiplinger, J. L. Inorg. Chem. 2008,
47, 11879.
(49) Graves, C. R.; Yang, P.; Kozimor, S. A.; Vaughn, A. E.; Clark,
D. L.; Conradson, S. D.; Schelter, E. J.; Scott, B. L.; Thompson, J. D.;
Hay, P. J.; Morris, D. E.; Kiplinger, J. L. J. Am. Chem. Soc. 2008, 130,
5272.
Complex 2 similarly reacts with PhNH2 to make the amide
complex (C5Me5)2(hpp)U(NHPh), 14, eq 21. Complex 14
can also be made from (C5Me5)2(hpp)UH, 3, and PhNH2,
eq 21, but it was not accessible from (C5Me5)2(hpp)UMe, 6,
and PhNH2. The X-ray crystal structure of 14 is shown in
Figure 4.

4168 Organometallics, Vol. 29, No. 18, 2010
Montalvo et al.
16, eq 25, respectively. The generation of a mixture of
products differs from the reactivity observed for the mono-
alkyl (C5Me5)2(hpp)UR (R = Me, 6; CtCPh, Ph, Et) comp-
lexes with CuI, where the (C5Me5)2(hpp)UI complex is
formed in quantitative yields. However, the hydride complex
3 reacts with CuI to form 16 in quantitative yield, eq 26.
substrate examined. This discussion will be structured starting
with the most similar observed reactivity going to the least
similar.
The reactions with H2 appear to be directly analogous.
Hydrogenolyses of U-C tuck-in and tuck-over bonds in 1,
eq 5, and U-C tuck-in bonds in 2, eq 6, are observed and
form the expected hydride products. This is typical U-
C(alkyl) reactivity and can be explained as a σ-bond meta-
thesis, eq 27 (X = H). The reactivity of these U-C
linkages seems to be similar regardless of tuck-in or tuck-
over structure, and the hydrogenolyses occur in the presence
of other reactive ligands. Since this is a hydride-forming
reaction and the other reactive ligands are hydrides, it makes
sense that this should be the most analogous set of reactions.
Although these hydrogenolyses are superficially straightfor-
ward, the reactions with deuterium that show exchange into
(C5Me5)- and (hpp)- ligands indicate that considerable
dynamic behavior is occurring with hydrogen in these sys-
tems. Exchange of deuterium into the rings in 1 has precedent
in the chemistry of the uranium hydrides, [(C5Me5)2UHx]2,18
but the deuterium exchange into (hpp)- hydrogen sites has
not been previously reported. This facile hydrogen transfer
makes it difficult to pinpoint the reactivity of the hydride
ligands in 1.
The reactions of increasingly polar element-H bonds will
be considered next. The reaction of HCtCPh with 2 to form
the alkynide (C5Me5)2(hpp)U(CtCPh), 7, eq 11, is another
example of a straightforward σ-bond metathesis reaction of
the type typical for f element-C bonds. As is common in
σ-bond metathesis, hydrogen is in the position diagonal to
the metal and only U-alkynide and CH2-H bonds result
in the product. The alternative would form U-H and
CH2-CtCPh bonds and generate a (C5Me2CH2CtCPh)-
ligand.
The observation that the hydride (C5Me5)2(hpp)UH, 3,
can also react with HCtCPh to make 7, eq 11, is consistent
with the result that the analogous reaction with 1 gives
multiple products. Both hydride and tuck-in moieties in 1
can react with HCtCPh, and when several of these reactive
sites are present, multiple products can form. The fact that
the methyl complex (C5Me5)2(hpp)UMe, 6, does not react
with HCtCPh suggests that the U-C(tuck-in) bond is more
reactive than a simple U-C alkyl linkage. This would be
expected on the basis of ring strain and the steric availability
and longer bond distance of the U-C(tuck-in) bond versus
the U-C(Me) bond in 6, a complex that has been shown to
have low reactivity.28
The reaction of 2 with PhNH2 also appears to be a
straightforward σ-bond metathesis, eq 27 (X = NHPh),
with hydrogen in the position diagonal to the metal. Since
2 has only one reactive U-element bond for σ-bond metath-
esis, a (NHPh)- product, 14, is cleanly formed, eq 21. The
hydride complex, 3, also reacts with PhNH2 to form the
amide complex 14, eq 21. Since 1 has four U-element bonds
that can participate in σ-bond metathesis, i.e., tuck-in U-C,
tuck-over U-C, and two U-H linkages, it was conceivable
Competition Experiments. In attempts to examine the
relative rates of tuck-in versus hydride reactivity, competition
experiments between 2 and 3 with PhSH and PhNH2 were
conducted. Since HX substrates can react with the U-H bond
in 3 to form U-X and H2 and the H2 can in turn convert the
U-C tuck-in bond in 2 to U-H by hydrogenolysis as
described in the first part of the Results section, this reaction
can be complicated. However, if the rate of reaction of the
tuck-in moiety is much faster than that of the hydride, this is
not a problem. When a 1:1 mixture of 2 and 3 was reacted with
1 equiv of PhSH in an open scintillation vial (to avoid building
1
up a concentration of H2), the H NMR spectrum of this
reaction showed the presence of 2 and 3 in a 1:3 ratio and
resonances consistent with the formation of 12. When a 1:1
mixture of 2 and 3 was reacted with 1 equiv of PhNH2 under
similar conditions, 1H NMR spectroscopy showed only 3 and
resonances consistent with the formation of 14. Hence, in both
of these reactions, the tuck-in complex disappears faster than
the hydride complex. Since reaction of the hydride complex 3
with PhSH or PhNH2 can generate hydrogen as a byproduct
that can also lead to the disappearance of 2, it cannot unequi-
vocally be stated that the tuck-in reacts faster. However, the
data indicate that the tuck-in reacts at least at rates compar-
able to that of the hydride since all of the hydride would have
to react first to generate enough hydrogen to eliminate the
tuck-in complex by the competing hydrogenolysis reaction.
Discussion
Correlations between the reactivities of the tuck-in tuck-
over dihydride (C5Me5)U[μ-η5:η1:η1-C5Me3(CH2)2](μ-H)2-
U(C5Me5)2, 1, and the tuck-in complex (C5Me5)(η5:η1-C5-
Me4CH2)(hpp)U, 2, are highly dependent upon the particular

Article
Organometallics, Vol. 29, No. 18, 2010 4169
Scheme 4
that (dNPh)2- products could result. However, the net
result is analogous to that of 2 with only an (NHPh)-
product being formed, eq 20. This result could arise in several
ways that, at present, are indistinguishable. σ-Bond meta-
thesis could occur with all four reactive sites to make the
observed four U-NHPh bonds, two C-H bonds, and 2
equiv of H2. Alternatively, hydride-alkyl anion elimination
could occur according to Scheme 2 to re-form the (C5Me5)-
methyl groups and U2þ or U3þ intermediates, and these
could reduce PhNH2 to form (PhNH)- and H2.
The reactivity of PhSH with 1 and 2 is similar to that for
PhNH2. Both complexes give the products expected from
σ-bond metathesis, eqs 18, 19, and 27 (X = SPh). The reac-
tion of 2 and 3 with PhSH shows that tuck-in and hydride
functionalities can effect this reaction cleanly. With 1 there
again is ambiguity in terms of σ-bond metathesis or reductive
elimination pathways involving lower oxidation states.
PhSSPh is not a common σ-bond metathesis sub-
strate since it does not have a hydrogen or silicon to put in
the diagonal position of a four-centered intermediate.50-53
However, σ-bond metathesis-like reactivity of PhEEPh
(E = S, Se, Te) has been reported with (C5Me5)2UMe2,
e.g., eq 28.54 The reaction of 2 with PhSSPh, eq 19,
cleanly generates a σ-bond metathesis product, (C5Me4-
CH2SPh)(C5Me5)(hpp)U(SPh), 11. Again, this indicates that
U-C(tuck-in) bonds can participate in σ-bond metathesis
reactions like U-Me bonds, eq 28. In contrast to the
reactions described so far in this section, complex 1 does
not make a product directly analogous to that of 2, as
(C5Me4CH2SPh)- products are not observed. Since 1 reacts
with PhSSPh to give (C5Me5)2U(SPh)2, 8, with SPh only
attached to U and no (C5Me4CH2SPh)- ligands, the hy-
drides must react faster with PhSSPh than the tuck-in and
tuck-over units if σ-bond metathesis is occurring. However,
the PhSSPh reaction with 1 could proceed by reductive
elimination, Scheme 2, an option not available to 2.
Evidence supporting higher reactivity for U-H bonds
versus tuck-in U-C bonds is also found in the reactions of
2 and 3 with Me3SiCl. The tuck-in complex 2 does not react
(50) Perrin, L.; Eisenstein, O.; Maron, L. New J. Chem. 2007, 31, 549.
(51) Perrin, L.; Maron, L.; Eisenstein, O. Inorg. Chem. 2002, 41, 4355.
(52) Perrin, L.; Maron, L.; Eisenstein, O.; Tilley, T. D. Organome-
tallics 2009, 28, 3767.
(53) Werkema, E. L.; Andersen, R. A.; Yahia, A.; Maron, L.;
Eisenstein, O. Organometallics 2009, 28, 3173.
(54) Evans, W. J.; Miller, K. A.; Ziller, J. W.; DiPasquale, A. G.;
Heroux, K. J.; Rheingold, A. L. Organometallics 2007, 26, 4287.

4170 Organometallics, Vol. 29, No. 18, 2010
Montalvo et al.
with Me3SiCl at 25 °C, but the hydride, 3, cleanly converts
to (C5Me5)2(hpp)UCl, eq 8. The analogous reaction of 1
with Me3SiCl shows how complicated the reactivity of this
multifunctional complex can be. The chloride ligands in the
reaction products, (C5Me5)ClU(η5-C5Me4CH2SiMe2CH2-
κC), 4, and [(C5Me5)2UCl]3, 5, are consistent with the re-
placement of hydride by chloride in eq 9. However, the
formation of a U3þ product clearly shows that reductive
reaction pathways are accessible from 1. In addition, the for-
mation of the (η5-C5Me4CH2SiMe2CH2-κC)2- ligand indi-
cates that C-H activation is also accessible in this system.
σ-Bond metathesis of Me3SiCl with a tuck-in or tuck-over
U-C bond could make a (η5-C5Me4CH2SiMe3)- intermedi-
ate that is subsequently converted to the observed (η5-C5-
Me4CH2SiMe2CH2-κC)2- ligand by σ-bond metathesis with
either the remaining U-C tuck-in or tuck-over bond or the
hydride ligands. Metalation of silylmethyl groups in (η5-C5-
Me4SiMe3)- by U-Me bonds has recently been reported.40
Scheme 4 shows one route to the products, but many path-
ways are possible.
The reaction of 1 with CuI, eq 24, gives analogous U-I bonds
in the product, but in this case the hydrogen that combines
with the U-CH2 linkages to form U-Me units could be the
hydride ligands in 1. These reactions can involve reductive
elimination reactions in which CuI is reduced by lower oxi-
dation state uranium intermediates.
Conclusion
Comparison of the reactivity of tuck-in tuck-over dihy-
dride 1, tuck-in 2, hydride 3, and methyl 6 shows that the
reactions of these functionalities can be quite substrate
dependent. Both σ-bond metathesis/protonolysis and reduc-
tive elimination pathways are possible. Hydride ligands
appear to be more reactive with Me3SiCl and PhSSPh than
tuck functionalities, but PhSH and PhNH2 appear to react at
least as fast with tuck moieties as with hydride ligands.
Interestingly, none of these isolable tuck functional groups
show reactivity with alkanes or arenes, substrates that
originally led to the identification of tuck-in moieties.
In contrast to the reactions discussed above, where the
hydride ligands appear to be more reactive than the tuck
U-C bond, competition reactions between tuck-in 2 and
hydride 3 with PhSH and PhNH2 suggest that the tuck-in
reacts as fast as, if not faster than, the hydride complex.
Hence, as stated in the first paragraph of the Discussion
section, the reactivity is substrate dependent.
The final reactions to be discussed involve CuI. The
reaction of 2 with CuI to make (C5Me5)2(hpp)UI, 16,
eq 25, is quite unusual in that the hydrogen source is
unknown. Reactions of CuI with (C5Me5)2[iPrNC(Me)-
NiPr-κ2N,N0]UMe45 and (C5Me5)2(hpp)UR25 (R = Me, Ct
CPh, Ph, Et) in deuterated solvents have also been observed
to form an RH byproduct without a clear source of hydrogen.
Acknowledgment. We thank the Chemical Sciences,
Geosciences, and Biosciences Division of the Office of
Basic Energy Sciences of the Department of Energy for
support. This research was facilitated in part by a Na-
tional Physical Science Consortium Fellowship and by
stipend support from Los Alamos National Laboratory
(to E.M.). We thank Dr. John Greaves for assistance with
the GC-MS studies.
Supporting Information Available: X-ray diffraction data,
atomic coordinates, thermal parameters, and complete bond
distances and angles. This material is available free of charge via
the Internet at http://pubs.acs.org.