Two-electron reductive reactivity of trivalent uranium tetraphenylborate complexes of (C5Me5)1- and (C5Me4H)1-

Article abstract of DOI:10.1016/j.jorganchem.2007.04.046

The reductive reactivity of the (BPh₄)^1- ligand in pentamethylcyclopentadienyl [(C₅Me₅)₂U][(μ-η²:η¹-Ph)₂BPh₂] (1) was compared with that of the tetramethyl analog, [(C₅Me₄H)₂U][(μ-η⁶:η¹-Ph)(μ-η¹:η¹-Ph)BPh₂] (2) using PhSSPh as a probe to determine if the mode of (BPh₄)^1- bonding affected the reduction. Both complexes act as two-electron reductants to form (C₅Me₄R)₂U(SPh)₂ [R = Me, 3; H, 4], but only in the R = H case could the product be crystallographically characterized. An improved synthesis of 1 from [(C₅Me₅)₂UH]₂ (5) and [Et₃NH][BPh₄] is also reported as well as its reaction with MeCN that provides another route to the unusual, parallel-ring, uranium metallocene [(C₅Me₅)₂U(NCMe)₅][BPh₄]₂ (6).

Full text of DOI:10.1016/j.jorganchem.2007.04.046

Journal of Organometallic Chemistry 692 (2007) 3649–3654
www.elsevier.com/locate/jorganchem
Two-electron reductive reactivity of trivalent uranium
tetraphenylborate complexes of (C5Me5)1ꢀ and (C5Me4H)1ꢀ
*
William J. Evans , Kevin A. Miller, Wes R. Hillman, Joseph W. Ziller
Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
Received 15 March 2007; received in revised form 26 April 2007; accepted 28 April 2007
Available online 8 May 2007
Abstract
The reductive reactivity of the (BPh4)1ꢀ ligand in pentamethylcyclopentadienyl [(C5Me5)2U][(l-g2:g1-Ph)2BPh2] (1) was compared
with that of the tetramethyl analog, [(C5Me4H)2U][(l-g6:g1-Ph)(l-g1:g1-Ph)BPh2] (2) using PhSSPh as a probe to determine if the mode
of (BPh4)1ꢀ bonding affected the reduction. Both complexes act as two-electron reductants to form (C5Me4R)2U(SPh)2 [R = Me, 3; H, 4],
but only in the R = H case could the product be crystallographically characterized. An improved synthesis of 1 from [(C5Me5)2UH]2 (5)
and [Et3NH][BPh4] is also reported as well as its reaction with MeCN that provides another route to the unusual, parallel-ring, uranium
metallocene [(C5Me5)2U(NCMe)5][BPh4]2 (6).
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Organouranium; Chalcogens; Organouranium tetraphenylborate
1. Introduction
participates in the half reaction shown at the bottom of
Scheme 2 [3,8], the reactivity has not been combined with
conventional metal based reducing agent to effect multi-
electron reduction of this type.
Recent studies of f element reduction chemistry have
shown that steric crowding can induce reductive reactivity
in normally inert ligands [1–4]. Specifically, (C5Me5)1ꢀ can
become a one-electron reductant in sterically crowded com-
plexes such as (C5Me5)3U [5] and [(C5Me5)2U]2(C6H6) [2]
in which the U–C(C5Me5) distances are unusually long
[6]. By combining this ligand-based reduction with the
reducing U3+ ion, these complexes become capable of
multi-electron reduction as shown in the four-electron
reduction in Scheme 1 [3].
It was of interest to determine if this (BPh4)1ꢀ redox activ-
ity was specific to (C5Me5)1ꢀ complexes and if it had any
dependence on its mode of attachment to U3+. Accordingly,
the reductive reactivity of the tetramethylcyclopentadienyl
complex [(C5Me4H)2U][(l-g6:g1-Ph)(l-g1:g1-Ph)BPh2] (2)
[9] was examined. Complex 2 differs from 1 in that one phenyl
group is oriented g6 to U3+ and the other is g1, whereas 1 has
two g2-phenyl groups. We report here a comparison of
(BPh4)1ꢀ reduction chemistry with 1 and 2. PhSSPh was used
as the substrate since it allows a direct comparison, it
expands the range of substrates involved in (BPh4)1ꢀ reduc-
tion chemistry [3], and one of the possible products,
(C5Me5)U(SPh)2 had previously been identified by Ephri-
tikhine et al. [10].
To compare the reactivity of these sterically crowded
complexes with
a sterically ‘‘normal’’ complex, the
reactivity of [(C5Me5)2U][(l-g2:g1-Ph)2BPh2] (1) [7] was
investigated [3]. Surprisingly, 1 can accomplish the same
four-electron reduction shown in Scheme 1 by combining
a U3+ to U6+ conversion with a (BPh4)1ꢀ reduction.
Although it has been known for decades that (BPh4)1ꢀ
Since 1 has proven to be a crucial starting material for
recent developments in reduction chemistry [2,3,7], new
methods to synthesize this complex were sought. Previously,
the synthesis of 1 required multiple steps and alkali metal
reduction of U4+ to U3+ [7]. We also report here an improved
*
Corresponding author. Fax: +1 949 824 2210.
E-mail address: wevans@uci.edu (W.J. Evans).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.04.046

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W.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 3649–3654
slurry of [Et3NH][BPh4] (1.12 g, 2.66 mmol) in C6H6
(15 mL) in a 100 mL round bottom flask. A translucent
brown solution immediately formed. The round bottom
flask was vented periodically over a period of 8 h. After
the mixture was stirred for 12 h, the brown solution was
evaporated to dryness yielding 1 as a brown powder
(1.89 g, 86%) that was identified by 1H NMR spectroscopy
[7].
N
N
U
U
+
PhN NPh
-1/2(C5Me5)2
4e1-
PhN NPh
2(PhN)2-
+
[(C5Me5)2U]4+ + 3e1-
[(C5Me5)2U]1+
(C5Me5)1-
1/2 (C5Me5)2 + 1e1-
2.3. Synthesis of (C5Me5)2U(SPh)2 (3) from
[(C5Me5)2U][(l-g2:g1-Ph)2BPh2] (1)
Scheme 1.
PhSSPh (13 mg, 0.060 mmol) in C6H6 (2 mL) was added
to 1 (50 mg, 0.060 mmol) in C6H6 (5 mL) and stirred for
12 h. The resulting red solution was evaporated to dryness
N
U
U
B
+
PhN NPh
- BPh3
- 1/2Ph2
N
1
to yield a dark red oil that contained 3 [10] by H NMR
spectroscopy and another product that displayed a single
C5Me5 resonance at 9.4 ppm of intensity equal to that of
the C5Me5 resonance of 3.
1
+
4e1-
2(PhN)2-
PhN NPh
[(C5Me5)2U]1+
[(C5Me5)2U]4+ + 3e1-
1-
1
BPh3
+
/
2 Ph2 + 1e1-
BPh4
The 9.4 ppm resonance was consistent with the
1H NMR resonance of the product obtained by reacting
1 with 1 equiv. of KSPh as follows. Compound 1 (95 mg,
0.13 mmol) in toluene (5 mL) was added to a white slurry
of KSPh (19 mg, 0.13 mmol) in toluene (5 mL) and stirred
for 24 h. Brown insoluble materials were removed by cen-
trifugation and the solvent was removed under vacuum
to yield a dark red oil that displayed a single resonance
Scheme 2.
synthesis of 1 from [Et3NH][BPh4] and [(C5Me5)2UH]2
[11,12] that is more efficient in both time and reagents. Due
to the recent synthesis of an unprecedented type of linear
metallocene, [(C5Me5)2U(NCMe)5][BPh4]2 (6) [13], complex
1 was reacted with MeCN in an attempt to synthesize a U3+
analog. This resulted in a new synthetic route to the U4+
complex.
1
at 9.4 ppm in the H NMR spectrum. Repeated attempts
to crystallize this product for X-ray analysis and to make
solid derivatives suitable for elemental analysis were not
successful.
2. Experimental
2.4. Synthesis of (C5Me4H)2U(SPh)2 (4) from
(C5Me4H)2UCl2
2.1. General procedures
The manipulations described below were performed
under argon (unless otherwise noted) with the rigorous
exclusion of air and water using Schlenk, vacuum line,
and glovebox techniques. Solvents were dried over Q-5
and molecular sieves and saturated with argon using Glass-
Contour [14] columns. Benzene-d6 was dried over NaK
alloy and vacuum transferred before use. (C5Me4H)2UCl2
[11], [(C5Me5)2UH]2 [11,12] [Et3NH][BPh4] [15] and KSPh
[16] were prepared as previously described. PhSSPh was
purchased from Aldrich and sublimed before use. MeCN
was purchased from Aldrich and distilled over CaH2 onto
molecular sieves and degassed by three freeze–pump–thaw
cycles. NMR spectra were recorded with a Bruker DRX
500 MHz system. Infrared spectra were recorded as thin
films on an ASI ReactIR 1000 instrument [17]. Elemental
analysis was performed by Analytische Laboratorien,
Lindlar, Germany.
A dark red solution of (C5Me4H)2UCl2 (150 mg,
0.27 mmol) in toluene (10 mL) was added to a white
slurry of KSPh (81 mg, 0.54 mmol) in toluene (10 mL)
and stirred for 12 h. Brown insoluble materials were
removed by centrifugation, and the solvent was removed
under vacuum to form a dark orange oil. This was dis-
solved in hexane and cooled to ꢀ35 ꢁC. After 2 days, 4
was obtained as red crystals (124 mg, 65%). Crystals of
4 suitable for X-ray diffraction were grown at ꢀ35 ꢁC
from a concentrated solution in hexane. 1H NMR
(C6D6): d 26.5 (s, 12H, C5Me4H, Dm1/2 = 17 Hz), ꢀ4.8
3
(s, 12H, C5Me4H, Dm1/2 = 13 Hz), 2.9 (t, 2H, JHH
=
8 Hz, p-H), 2.5 (br t, 4H, m-H), ꢀ24.6 (s with broad
shoulder, 6H, o-H, C5Me4H). 13C NMR (C6D6): d 7.6
(C5Me4H), 183.3 (C5Me4H), 106.0 (m-phenyl), 132.9 (p-
phenyl), 142.3 (o-phenyl), 129.7 (C5Me4H), 128.9
(C5Me4H), 126.0 (C5Me4H). IR: 2961m, 2910s, 2856s,
1720w, 1579m, 1476s, 1444s, 1382m, 1320m, 1258vs,
1085vs, 1011vs, 957m, 865m, 784vs, 741s, 695vs, 676vs
cmꢀ1. Anal. Calc. for C30H36S2U: C, 51.57; H, 5.19; S,
9.18; U, 34.06. Found: C, 51.32; H, 5.02; S, 9.00; U,
33.80%.
2.2. Synthesis of [(C5Me5)2U][(l-g2:g1-Ph)2BPh2] (1)
A brown-green solution of [(C5Me5)2UH]2 (1.35 g,
1.32 mmol) in C6H6 (30 mL) was added to a stirred white

W.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 3649–3654
3651
2.5. Synthesis of (C5Me4H)2U(SPh)2 (4) from
[(C5Me4H)2U][(l-g6:g1-Ph)(l-g1:g1-Ph)BPh2] (2)
squares techniques. The analytical scattering factors [22]
for neutral atoms were used throughout the analysis.
Hydrogen atoms were located from a difference-Fourier
map and refined (x, y, z and Uiso). At convergence,
wR2 = 0.0456 and GOF = 1.075 for 442 variables refined
against 6674 data. As a comparison for refinement on F,
R1 = 0.0192 for those 5874 data with I > 2.0r(I). Details
are given in Table 1.
PhSSPh (10 mg, 0.046 mmol) in C6D6 was added to an
NMR tube containing 2 (37 mg, 0.046 mmol) in C6D6.
The color immediately changed from brown to red. After
12 h, the 1H, 13C, 11B NMR spectra showed complete con-
version of starting materials to 4 and BPh3.
2.6. Synthesis [(C5Me5)2U(NCMe)5][BPh4]2 (6)
3. Results
In a nitrogen filled glovebox, 1 (100 mg, 0.12 mmol) was
dissolved in 10 mL of MeCN and allowed to stir for 12 h.
The resulting brown-green solution was reduced to 5 mL
under vacuum and cooled to ꢀ35 ꢁC. After 5 days, 6 was
obtained as black crystals (21 mg, 26%) that were identified
3.1. Reduction of PhSSPh
[(C5Me5)2U][(l-g2:g1-Ph)2BPh2] (1) reacts within 12 h
with PhSSPh to form (C5Me5)2U(SPh)2 (3) a complex pre-
viously reported by Ephritikhine et al. from the reaction of
(C5Me5)2UCl2 and NaSPh [10]. No crystallographic data
were obtained in that study although numerous sulfur
donor atom complexes of uranium have been crystallo-
graphically characterized [10,23,24] and, in our hands,
1
by X-ray crystallography and H NMR spectroscopy [13].
2.7. X-ray data collection and refinement for
(C5Me4H)2U(SPh)2 (4)
1
crystals of 3 were also elusive. The H NMR spectrum of
A
red crystal of approximate dimensions 0.13 ·
the product of the reaction of 1 and PhSSPh also revealed
another product with a (C5Me5)1ꢀ resonance at 9.4 ppm.
This complex also did not crystallize, but could be obtained
as a single product from the reaction of 1 and KSPh. On
the basis of this reaction chemistry, the 9.4 ppm complex
was expected to be the trivalent phenylsulfide, [(C5Me5)2-
U(SPh)]n, but it could only be isolated as a tacky oil.
Attempts to make crystalline base adducts or derivatives
by CO2 insertion, a reaction useful with the lanthanide ana-
0.17 · 0.25 mm was mounted on a glass fiber and trans-
ferred to a Bruker CCD platform diffractometer. The
SMART [18] program package was used to determine the
unit-cell parameters and for data collection (30 s/frame
scan time for a sphere of diffraction data). The raw frame
data were processed using SAINT [19] and SADABS [20] to
yield the reflection data file. Subsequent calculations were
carried out using the SHELXTL [21] program. The diffrac-
tion symmetry was 2/m and the systematic absences were
consistent with the monoclinic space groups Cc and C2/c.
It was later determined that the centrosymmetric space
group C2/c was correct. The structure was solved by
direct methods and refined on F2 by full-matrix least-
1
logs, [(C5Me5)2Ln(SPh)]2 [25], were not successful. The H
and 13C NMR spectrums of the reaction of 1 and PhSSPh
also displayed resonances consistent with BPh3, however,
resonances of the other expected byproduct Ph2, were not
observed. Although biphenyl has been observed in other
reductions involving uranium complexes of (BPh4)1ꢀ [3],
it was not observed in this case. The fate of the phenyl rad-
icals required by the stoichiometry is unknown.
Table 1
X-ray data collection parameters for (C5Me4H)2U(SPh)2 (4)
In contrast to the pentamethylcyclopentadienyl chemis-
try, the tetramethylcyclopentadienyl analog, [(C5Me4H)2U]-
[(l-g6:g1-Ph)(l-g1:g1-Ph)BPh2] (2) reacts with PhSSPh to
form only one uranium metallocene complex (C5Me4H)2-
U(SPh)2 (4), Eq. (1) and BPh3. Again, biphenyl was not
observed in the 1H and 13C NMR spectra. To aid in the iden-
tification of 4, this complex was made independently from
(C5Me4H)2UCl2 and KSPh, Eq. (2). In contrast to 3, com-
plex 4 readily crystallizes to give the structure shown in
Fig. 1.
Compound
4
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C
698.74
163(2)
Monoclinic
C2/c
16.2886(12)
14.0086(10)
24.7932(18)
90
106.0030(10)
90
5438.1(7)
8
1.707
30H36S2U
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
qcalc (Mg/m3)
S
+ BPh3 + "1/2Ph2 "
l (mmꢀ1
)
6.139
0.0192
0.0456
U
U
+
PhSSPh
B
S
Ra1 [I > 2.0r(I)]
wRb2 (all data)
P
P
4
2
a
R1 = iFoj ꢀ jFci/ jFoj.
P
P
b
2
wR2 = [ [w(Fo ꢀ Fc2)2]/ [w(Fo2)2]]1/2
.
ð1Þ

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W.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 3649–3654
Table 2
Selected bond distances (A) and angles (ꢁ) for (C5Me4H)2U(SPh)2 (4)
˚
˚
Bond distance (A)
U(1)–S(1)
U(1)–S(2)
U(1)–Cnt1
U(1)–Cnt2
S(1)–C(19)
S(2)–C(25)
2.6845(7)
2.6967(7)
2.448
2.437
1.776(3)
1.775(3)
Bond angle (ꢁ)
Cnt1–U(1)–S(1)
Cnt1–U(1)–S(2)
Cnt2–U(1)–S(1)
Cnt2–U(1)–S(2)
Cnt1–U(1)–Cnt2
C(19)–S(1)–U(1)
C(25)–S(2)–U(1)
S(1)–U(1)–S(2)
97.7
112.4
110.3
98.0
128.9
104.44(9)
108.57(9)
109.12(2)
Fig. 1. Molecular structure of (C5Me4H)2U(SPh)2 (4) with thermal
ellipsoids drawn at the 50% probability level.
Cl
Cl
Me
Me
U
U
+
2MeLi
U
-2LiCl
Cl
Cl
Me
Me
S
S
Me
Me
+ 2KSPh
U
U
+
K
U
K
ð2Þ
-2KCl
4
Complex 4 has a typical uranium bent metallocene struc-
ture in which the two (C5Me4H)1ꢀ rings and the two
(PhS)1ꢀ ligands define a distorted tetrahedron around the
U4+ center. The bonding parameters are normal for
eight-coordinate tetravalent uranium complexes. For exam-
Me
Me
+
2[Et3NH][BPh4]
U
K
U
B
-KBPh4
-2Et3N
-2CH4
1
˚
Scheme 3.
ple, the 2.443 A average U-(C5Me4H ring centroid) distance
˚
is similar to the 2.444, 2.429, and 2.42 A distances in
(C5Me4H)2UMe2 [9], (C5Me4H)2UMeCl [9], and
(C5Me4H)2UCl2 [9], respectively.
four days to form (C5Me5)2UMe2K [7]. This compound
was subsequently treated with [Et3NH][BPh4] to form 1
in 82% overall yield. Although this process produces 1 in
high yield, it is limited in that, in our hands, only small
quantities, ca. 500 mg, can be successfully synthesized at
one time. When the synthesis of larger quantities of
(C5Me5)2UMe2K is attempted, we find that the reaction
of (C5Me5)2UMe2 and K is not complete.
˚
The 2.691(6) A average U–S distance in 4 is equivalent
˚
to the 2.687(2)–2.700(2) A U–S distances in the bis(dithio-
lene) complex [Na(18-crown-6)][U(C8H8)(C4H4S4)2] [23]
crystallographically characterized by Ephritikhine et al.
˚
The U–S average in 4 is also 0.056 A shorter than the ana-
˚
logue in (C5Me5)2Th(SPh)2 [12] consistent with the 0.05 A
difference in the Shannon ionic radii of eight-coordinate
U4+ and Th4+ [26]. It is also shorter than the 2.7997(7)
An alternative route to 1 was envisioned using the U3+
hydride [(C5Me5)2UH]2 [11,12] (5) and 2 equiv. of
[Et3NH][BPh4]. Complex 5 is made from the same
(C5Me5)2UMe2 precursor as 1. The hydride route to 1 ini-
tially seemed problematic since 5 is made in a mixture con-
taining [(C5Me5)2UH2]2 [11] (7), Eq. (3). This mixture of
hydrides could give both U3+ and U4+ (BPh4)1ꢀ products.
˚
and 2.8011(7) A U–Se distances in (C5Me5)2U(SePh)2 [12]
˚
consistent with the 0.14 A difference in Shannon ionic radii
of S2ꢀ and Se2ꢀ [26]. The U–S–C(Ph) angles are close to
tetrahedral: 104.4(1)ꢁ and 108.6(1)ꢁ (see Table 2).
3.2. Improved synthesis of [(C5Me5)2U][(l-g2:g1-
Ph)2BPh2] (1)
-H2
H2 1 atm
-4CH4
Me
Me
H
H
U
U
7
U
5
H
Complex 1 was previously made by the sequence of reac-
tions shown in Scheme 3. (C5Me5)2UMe2, formed from
(C5Me5)2UCl2 and MeLi, reacts with potassium sand over
ð3Þ
+H2
2
2

W.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 3649–3654
3653
2(PhS)1-
PhSSPh + 2e1-
[(C5Me4R)2U]1+
(BPh4)1-
Recently, however, it was found that 5 could be isolated in
[(C5Me4R)2U]2+ + 1e1-
nearly pure form. Removal of solvent from a toluene solu-
tion of 7 followed by dissolution in hexane, removal of sol-
vent, and finally dissolution in toluene and removal of
1
BPh3
Scheme 4.
+
/
2 Ph2 + 1e1-
1
solvent generates a brown-green solid that analyzes by H
NMR spectroscopy in C6D6 as 5 [12].
(C5Me4H)1ꢀ complexes. Apparently, this two-electron
reduction reactivity for the (BPh4)1ꢀ/U3+ combination is
not connected with some special aspect of the (C5Me5)1ꢀ
complexes. This contrasts with the sterically induced reduc-
tion chemistry of (C5Me5)3M compounds [6] which does not
occur with the less sterically crowded (C5Me4H)3M analogs
[9,28,29].
To test these ideas, 5 was treated with 2 equiv. of
[Et3NH][BPh4]. Complex 1 was formed in high yield (94%)
1
and purity on the basis of H NMR spectroscopy, Eq. (4).
Samples of 1 prepared by this route have also proven to be
good precursors to (C5Me5)3U [5], [(C5Me5)2U]2(C6H6) [2],
[(C5Me5)2U(l-N)U(l-N3)(C5Me5)2]4 [27], and (C5Me5)2-
U(C4Ph4) [3]. Complex 1 can now be prepared in three days
starting from (C5Me5)2UCl2 instead of six days and it can be
done on a 2 g scale.
The (C5Me5)1ꢀ and (C5Me4H)1ꢀ complexes do differ in
the crystallinity of the products: the (C5Me4H)1ꢀ products
crystallize more readily in this system. In addition, the
(C5Me4H)1ꢀ system provides as single product, 4, rather
than the mixture obtained with the (C5Me5)1ꢀ reaction.
The special aspects of (C5Me4H)1ꢀ in f element chemistry
have been noted before [30].
C6H6
2
U
+
2[Et3NH][BPh4]
U
H
B
-2Et3N
-2H2
2
The synthesis of 1 from [(C5Me5)2UH]2 (5) is much
improved over the multi-step route previously used to
make this useful precursor. The synthesis of the parallel-
ring metallocene [(C5Me5)2U(NCMe)5][BPh4]2 (6) from 1
does not represent an improved synthesis since 6 can also
be obtained from (C5Me5)2UMe2 [13], a precursor to 1.
However, the formation of 6 from 1 may indicate that it
is a thermodynamically favorable end product of bis(pen-
tamethylcyclopentadienyl) uranium U4+ chemistry in ace-
tonitrile despite its unusual structure.
5
1
ð4Þ
3.3. New synthesis of [(C5Me5)2U(NCMe)5][BPh4]2 (6)
Complex 1 was treated with MeCN to determine if a
trivalent analog of [(C5Me5)2U(NCMe)5][BPh4]2 [13] (6)
could be isolated. Complex 6 is unusual because it is
the first actinide metallocene to be found to have parallel
pentamethylcyclopentadienyl rings, i.e. a 180ꢁ (C5Me5
ring centroid)–An–(C5Me5 ring centroid) angle. Crystal-
line material was obtained from 1 in neat MeCN, but
X-ray crystallographic analysis revealed that it was the
tetravalent metallocene 6, Eq. (5). The byproduct of the
oxidation of the trivalent precursor was not readily
identified.
5. Conclusion
Both [(C5Me5)2U][(l-g2:g1-Ph)2BPh2] and [(C5Me5)2U]
[(l-g6:g1-Ph)(l-g1:g1-Ph)BPh2] function as two-electron
reductants with PhSSPh to form (C5Me4R)2U(SPh)2 prod-
ucts. The reductive chemistry of the (BPh4)1ꢀ ligand is not
affected by either its solid state mode of coordination or the
ancillary ligands in this case.
MeCN
MeCN
MeCN
NCMe
NCMe
MeCN
[BPh4]2
2
U
U
B
Acknowledgment
1
6
We thank the National Science Foundation for support
of this research.
ð5Þ
4. Discussion
Appendix A. Supplementary material
Both 1 and 2 function as two-electron reductants with
PhSSPh to generate the corresponding phenylsulfide com-
plexes, (C5Me4R)2U(SPh)2 (R = Me, H), by combining
CCDC 633748 contains the supplementary crystallo-
graphic data for 3. These data can be obtained free of
charge
via
http://www.ccdc.cam.ac.uk/conts/retriev-
(BPh4)1ꢀ reduction chemistry with reduction by U3+
.
ing.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2007.04.046.
Scheme 4 shows the half reactions involved. Hence, the
(BPh4)1ꢀ ligand can function as a reductant along with
U3+ when it arises from a [(l-g6:g1-Ph)(l-g1:g1-Ph)-
BPh2]1ꢀ complex as well as a [(l-g2:g1-Ph)2BPh2]1ꢀ com-
pound. This reactivity also occurs in both (C5Me5)1ꢀ and

3654
W.J. Evans et al. / Journal of Organometallic Chemistry 692 (2007) 3649–3654
[16] W.J. Evans, K.A. Miller, D.S. Lee, J.W. Ziller, Inorg. Chem. 44
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