Synthesis and characterization of a tetranuclear hydride cluster of yttrium [{(η5-C5Me4SiMe3)Y} 4(μ-H)4(μ3-H)4(THF) 2]

Article abstract of DOI:10.1002/zaac.200300063

Hydrogenolysis of the dialkyl complexes [Y(η⁵-C ₅Me₄SiMe₂R)(CH₂SiMe ₃)₂(THF)] (1a, R = Me; 1b, R = Ph) results in the formation of the tetranuclear dihydrido complexes [{(η⁵

Full text of DOI:10.1002/zaac.200300063

Synthesis and Characterization of a Tetranuclear Hydride Cluster of Yttrium
[{(η5-C5Me4SiMe3)Y}4(µ-H)4(µ3-H)4(THF)2]
Kai C. Hultzscha,1), Peter Vothb, Thomas P. Spaniolb, and Jun Okudab,2),
*
a Erlangen, Institut für Organische Chemie, Friedrich Alexander-Universität Erlangen-Nürnberg
b Mainz, Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität
Received February 27th, 2003.
Dedicated to Professor Heinrich Nöth on the Occasion of his 75th Birthday
Abstract:
Hydrogenolysis
of
the
dialkyl
complexes
[Y(η5-C5Me4SiMe3)] units is observed, two of which contain each
one molecule of THF. Each yttrium atom is bonded to two µ2-
as well as three µ3-bridging hydrido ligands.
[Y(η5-C5Me4SiMe2R)(CH2SiMe3)2(THF)] (1a, R ϭ Me; 1b, R ϭ
Ph) results in the formation of the tetranuclear dihydrido com-
plexes [{(η5-C5Me4SiMe2R)Y}4(µ-H)4(µ3-H)4(THF)2] (2a, R ϭ
Me; 2b, R ϭ Ph), characterized by NMR spectroscopy. 2a
was studied by single crystal X-ray diffraction. In the solid
state, an unsymmetrical tetrahedral configuration of four
Keywords: Dihydrides; Hydrogenolysis; Half-sandwich hydrido
complexes
Synthese und Charakterisierung eines vierkernigen Hydrid-Clusters von Yttrium
[{η5-(C5Me4SiMe3)Y}4(µ-H)4(µ3-H)4(THF)2]
Inhaltsübersicht. Die Hydrogenolyse von Dialkyl-Komplexen
[Y(η5-C5Me4SiMe2R)(CH2SiMe3)2(THF)] (1a,
Me; 1b,
Komplex 2a wurde mit einer Einkristallstrukturanalyse untersucht.
Im Festkörper wurde eine unsymmetrische tetraedrische Anord-
nung der vier [Y(η5-C5Me4SiMe3)]-Einheiten gefunden, von denen
zwei je ein Molekül THF koordinieren. Jedes Yttriumatom ist an
zwei µ2- und an drei µ3-verbrückende Hydridoliganden gebunden.
R
ϭ
R
ϭ
Ph) führt zu vierkernigen Dihydrido-Komplexen
[{(η5-C5Me4SiMe2R)Y}4(µ-H)4(µ3-H)4(THF)2] (2a, R ϭ Me; 2b,
R ϭ Ph), die mit NMR Spektroskopie untersucht wurden. Der
Introduction
complexes that contain a dianionic linked amido-cyclopen-
tadienyl ligand [6]. We report here the structural charac-
terization of hydrido yttrium complexes of the general com-
position [Y(η5-C5R5)H2Ln] with tetranuclear structure [7].
Since the discovery of metallocene hydrido complexes by
Evans et al. as the first examples of molecular hydrides of
the rare earth metals [1], this class of complexes has gained
enormous importance in the context of homogeneous ca-
talysis [2]. Although scattered examples of hydrido com-
plexes of the non-metallocene class are known, half-sand-
wich hydrido complexes remain relatively unexplored [3].
Moreover, despite the rich chemistry of transition metal po-
lyhydrides [4], only a few reports on commonly poorly
characterized dihydrido complexes have emerged [5]. We
have recently systematically studied the synthesis, charac-
terization, and reactivity of rare-earth metal mono(hydrido)
Results and Discussion
When the dialkyl complexes [Y(η5-C5Me4SiMe2R)-
(CH2SiMe3)2(THF)] (1a, R ϭ Me; 1b, R ϭ Ph), prepared
by the C-H activation method using the trialkyl yttrium
complex [Y(CH2SiMe3)3(THF)2] and the corresponding
cyclopentadiene (C5Me4H)SiMe2R as previously described
[6a], are hydrogenated under 4 bar of dihydrogen at 25 °C
in pentane, good yields of the colorless dihydrido complexes
2a and 2b are obtained (Scheme 1). The dihydrido com-
plexes 2a and 2b can be also prepared without isolating the
dialkyl complexes 1a and 1b. Recrystallization of 2a from
pentane afforded single crystals suitable for X-ray diffrac-
tion study. Figure 1 shows an ORTEP diagram and Table 1
gives selected bond parameters.
1) Dr. K. C. Hultzsch
Institut für Organische Chemie
Friedrich Alexander-Universität Erlangen-Nürnberg
D-91054 Erlangen
Email: hultzsch@chemie.uni-erlangen.de
*
2) Prof. Dr. J. Okuda
The crystal structure analysis confirms the presence of a
tetranuclear cluster consisting of four LYH2 units of which
two contain a THF ligand, as postulated previously [6a].
The structure can be thought of derived from a Y4-tetra-
hedron with four triply bridging and four doubly
Institut für Anorganische Chemie und Analytische Chemie
Johannes Gutenberg-Universität Mainz
Duesbergweg 10-14
D-55099 Mainz
Email: okuda@mail.uni-mainz.de
1272
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DOI: 10.1002/zaac.200300063
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A Tetranuclear Hydride Cluster of Yttrium
Scheme 1
Fig. 1 ORTEP diagram of [{η5-C5Me4SiMe3)Y}4(µ-H)4(µ3-H)4-
(THF)2] (2a). Thermal ellipsoids are drawn at the 50 % probability
level. All hydrogen atoms, except the hydrido ligands, are omitted
for clarity.
Fig. 2 Structure of the Y4H8 core in 2a. The THF ligands are
only denoted by their oxygen atoms. Thermal ellipsoids are drawn
at the 50 % probability level.
˚
bridging hydrido ligands, somewhat resembling to
[(η5-C5Me4Et)4Cr4(µ2-H)5(µ3-H)2] [8]. The Y4-tetrahedron
is considerably distorted by the trans-influence of the coor-
dinated THF molecules to Y1 and Y2 resulting in a signifi-
3.3299(5) to 3.4084(5) A found for the remaining Y···Y dis-
tances. While the latter Y···Y distances are the shortest ones
observed so far [9,10], the former represent among the long-
˚
est ones, only surpassed by the distance of 4.10(1) A found
in the trimeric [(η5-C5H3Me2)2Y(µ-H)]3 [9b]. The positions
˚
˚
cant elongation by 0.5 A of the Y1···Y4 (3.9097(5) A) and
˚
Y2···Y3 (3.9144(5) A) distance compared to the range of
of all eight hydrido ligands could be determined and in-
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K. C. Hultzsch, P. Voth, Th. P. Spaniol, J. Okuda
˚
behavior of 2a contrasts the non-fluxionality observed in
the ate-complex [Li(THF)4][{(η5-C5H5)2Y(µ2-H)}3(µ3-H)]
[1b], which displays distinctive signals for the µ2- and the
µ3-hydrido ligands at room temperature.
Table 1 Selected Bond lengths/A and angles/° of
[Y(η5-C5Me4SiMe3)(µ-H)2]4(THF)2 (2a).
Y1···Y2
Y1···Y4
Y1···Y3
Y2···Y3
Y2···Y4
Y3···Y4
3.4084(5)
3.9097(5)
3.3940(5)
3.9144(5)
3.3864(5)
3.3299(5)
2.411(3)
2.411(3)
2.46(3)
Y4 Ϫ H1
Y4 Ϫ H3
Y4 Ϫ H4
Y4 Ϫ H7
2.12(3)
2.13(5)
2.28(4)
2.30(4)
2.08(4)
Y4 Ϫ H8
Y1 Ϫ Y2 Ϫ Y3
Y1 Ϫ Y3 Ϫ Y2
Y2 Ϫ Y1 Ϫ Y3
Y2 Ϫ Y1 Ϫ Y4
Y2 Ϫ Y4 Ϫ Y1
Y3 Ϫ Y1 Ϫ Y4
Y3 Ϫ Y4 Ϫ Y1
Y3 Ϫ Y4 Ϫ Y2
Y4 Ϫ Y2 Ϫ Y1
Y4 Ϫ Y2 Ϫ Y3
Y4 Ϫ Y3 Ϫ Y1
Y4 Ϫ Y3 Ϫ Y2
O1 Ϫ Y1 Ϫ Y2
O1 Ϫ Y1 Ϫ Y3
O1 Ϫ Y1 Ϫ Y4
O2 Ϫ Y2 Ϫ Y1
O2 Ϫ Y2 Ϫ Y3
O2 Ϫ Y2 Ϫ Y4
54.696(10)
55.042(9)
70.262(11)
54.609(10)
55.137(10)
53.686(9)
55.213(10)
71.293(11)
70.254(11)
53.682(9)
71.100(11)
55.025(9)
99.67(7)
Y1 Ϫ O1
Y2 Ϫ O2
Y1 Ϫ H1
Y1 Ϫ H2
Y1 Ϫ H3
Y1 Ϫ H5
Y1 Ϫ H6
Y2 Ϫ H1
Y2 Ϫ H2
Y2 Ϫ H4
Y2 Ϫ H5
Y2 Ϫ H7
Y3 Ϫ H2
Y3 Ϫ H3
Y3 Ϫ H4
Y3 Ϫ H6
Y3 Ϫ H8
2.27(4)
2.39(3)
2.19(3)
2.14(4)
2.22(3)
2.19(4)
2.26(4)
2.10(3)
2.14(4)
2.27(4)
2.08(5)
2.19(4)
100.35(7)
146.53(7)
103.11(7)
148.65(7)
100.45(7)
1.97(4)
2.23(4)
Fig. 3 1H NMR spectrum of 2a in C6D6 at 25 °C. The insert
O1 Ϫ Y1 Ϫ Y2 Ϫ O2 106.95(10)
shows the Y-H region.
cluded in the refinement. Thus each yttrium atom is bonded
to five hydrido ligands, two in a µ2- and three in a µ3-bridg-
ing mode. As a result of the elongated Y1···Y4 and Y2···Y3
distances the µ2-hydrido bridges span over the shorter edges
of the distorted Y4-tetrahedron. The YϪH bond lengths of
˚
the µ2-hydrido ligands range from 1.97(4) A (Y3ϪH6) to
˚
2.30(4) A (Y4ϪH7), which is the typical range found in di-
meric yttrium hydrido complexes [9]. The YϪH bond dis-
tances for triply bridging hydrido ligands are longer and
˚
range from 2.08(5) (Y3ϪH3) to 2.46(3) A (Y1ϪH1). The
THF ligands are coordinated in a transoidal fashion related
to Y1ϪY2 edge of the tetrahedron (torsion angle
O1ϪY1ϪY2ϪO2 107(1)°). The YϪO(THF) bond lengths
˚
are equal (2.411(3) A) and fall within the usual range
˚
(2.35Ϫ2.45 A) found in other THF-containing yttrium
complexes [11]. Similarly, the YϪC(Cp) bond lengths
˚
(2.614(3)Ϫ2.720(3) A) are similar to those found in yttro-
cene complexes [12].
Not unexpectedly, the complexes 2a and 2b exhibit high
1
fluxionality. In the H NMR spectrum of 2a in C6D6 at
room temperature (Figure 3) a quintet at 4.29 ppm
1
(4.45 ppm for 2b) with JYH ϭ 15.3 Hz is recorded for all
eight hydrido ligands, suggesting that all eight hydrido li-
gands are equivalent on the NMR timescale. The two THF
ligands appear to be dissociatively labile. The YH coupling
constant is similar to the typical range of 17 Ϫ 18 Hz for
µ3-hydrido ligands found in [{(η5-C5H5)2Y(µ2-H)x-
(OMe)1-x}3(µ3-H)] (x
ϭ 0, 1/3, 2/3, 1) [1b,10] as
well as 16.25 Hz found in the supposedly trimeric
[TpMeYH2(THF)x] [5c] (TpMe ϭ tris(3,5-dimethyl-1-pyrazo-
lyl)borohydride). These coupling constants are significantly
smaller than the values of 27 Ϫ 35 Hz , usually found for
m2-hydrido ligands [6c]. The 89Y NMR spectrum shows a
quintet at 338.9 ppm with 1JYH ϭ 15 Hz, the same coupling
Fig. 4 1H NMR spectrum (Y-H region) of 2a in THF-d8 a) at
25 °C and b) at Ϫ80 °C.
Variable-temperature studies in THF-d8 suggest a rather
complicated decoalescence pattern for the hydride quintet.
At Ϫ80 °C, four signals in the intensity ratio of 4 : 1 : 2 : 1
1
constant as found in the H NMR spectrum. The fluxional
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A Tetranuclear Hydride Cluster of Yttrium
[Y(η5-C5Me4SiMe2Ph)(CH2SiMe3)2(THF)] (1b)
1
are observed at 2.99 (br m), 4.07 (t, JYH ϭ 30 Hz), 4.36
1
1
(t, JYH ϭ 30 Hz), and 4.53 (t, JYH ϭ 32 Hz) ppm (Fig-
ure 4). The broad signal of intensity 4 is assigned to the
four triply bridging hydrides which remain fluxional at tem-
peratures at which the doubly bridging ones are frozen out.
The three different triplets in the ratio of 1 : 2 : 1 can be
assigned to three sets of inequivalent hydrides bridging the
edge Y1ϪY2, Y1ϪY3/Y2ϪY4, and Y3ϪY4, respectively.
The inequivalence of the four ring ligands is also indicated
at lower temperatures. For the SiMe3 groups one singlet is
found at room temperature, but at Ϫ 40 °C, decoalescence
occurs and at Ϫ80 °C two separated singlets are recorded
at 0.30 and 0.25 ppm. For the ring methyl groups two sing-
lets at 2.01 and 2.12 ppm are detected at room temperature
in THF-d8. Upon lowering the temperature the signal at the
lower field decoalesces at Ϫ30 °C and at Ϫ80 °C three
slightly broadened signals for the C5Me4 groups are de-
tected.
This compound was prepared analogously to the synthesis of 1a
and isolated as an colorless oil in 97 % yield.
2
1H NMR (C6D6): δ ϭ Ϫ0.58 (d, JYH ϭ 3.1 Hz, 4 H, YCH2), 0.30 (s, 18 H,
CH2SiMe3), 0.69 (s, 6 H, SiMe2Ph), 1.20 (m, 4 H, β-THF), 1.97, 2.15
(s, 2 ϫ 6 H, ring CH3), 3.47 (m, 4 H, α-THF), 7.17 (m, 3 H, C6H5), 7.53 (m,
2 H, C6H5). 13C{1H} NMR (C6D6): δ ϭ 1.8 (SiCH3Ph), 4.6 (CH2SiMe3),
1
11.6, 14.8 (ring CH3), 24.9 (β-THF), 34.9 (d, JYC ϭ 43.7 Hz, YCH2), 70.0
(α-THF), 112.6 (ring C attached to Si), 123.6, 127.1 (ring C), 128.0, 128.8,
134.3 (C6H5), 141.6 (ipso-C6H5). 29Si{1H} NMR (C6D6):
(SiMe2Ph), Ϫ3.2 (d, JYSi ϭ 2 Hz, CH2SiMe3).
δ ϭ Ϫ13.8
2
[{(η5-C5Me4SiMe3)Y}4(µ-H)4(µ3-H)4(THF)2] (2a)
In a thick-walled glass reactor [Y(CH2SiMe3)3(THF)2] (1.15 g,
2.3 mmol) was dissolved in pentane (30 mL) and (C5Me4H)SiMe3
(0.45 g, 2.3 mmol) was added at room temperature. Hydrogen gas
(5 bar) was charged and the mixture was stirred vigorously 12 h.
After filtration the solution was reduced in vacuo and cooled to
Ϫ30 °C. The product was isolated as colorless crystals in 43 %
(290 mg) yield.
C56H108O2Si4Y4 (1281.4): C 51.93 (calc. 52.49), H 8.59 (8.49), Y
26.42 (27.75) %.
1H NMR (C6D6): δ ϭ 0.53 (s, 9 H, SiMe3), 1.41 (m, 2 H, β-THF), 2.25, 2.36
1
(s, 2 ϫ 6 H, C5Me4), 3.59 (br s, 2 H, α-THF), 4.29 (quint, JYH ϭ 15.3 Hz,
2 H, YH). 13C{1H} NMR (C6D6): δ ϭ 3.0 (ring SiMe3), 12.5, 15.3 (C5Me4),
25.5 (β-THF), 69.2 (α-THF), 114.6 (ring C attached to Si), 124.4, 127.0 (ring
C). 1H NMR ([D8]-THF): δ ϭ 0.24 (s, 9 H, SiMe3), 1.69 (m, 2 H, β-THF),
Experimental Part
2.01, 2.12 (s, 2 ϫ 6 H, C5Me4), 3.53 (br s, 2 H, α-THF), 3.71 (quint, 1JYH
ϭ
All operations were performed under an inert atmosphere of argon
using standard Schlenk-line or glovebox techniques. All solvents
were purified by distillation from sodium/triglyme benzophenone
ketyl under argon. (C5Me4H)SiMe3 [13a], (C5Me4H)SiMe2Ph
[13b], and [Y(CH2SiMe3)3(THF)2] [6c,14] were prepared according
to published procedures. NMR spectra were recorded on a Bruker
DRX 400 spectrometer (1H, 400 MHz; 13C, 101 MHz; 29Si,
79.5 MHz, 89Y, 19.6 MHz) at 25 °C, unless otherwise stated.
15.3 Hz, 2 H, YH). 1H NMR ([D8]-THF, Ϫ80 °C): δ ϭ 0.25, 0.30 (s, 18 H,
SiMe3), 1.74 (m, 8 H, β-THF),1.93 (s, 3 H, C5Me4), 2.01 (s, 15 H, C5Me4),
2.34 (br s, 6 H, C5Me4), 2.99 (m, 4 H, YH), 3.59 (br s, 2 H, α-THF), 4.07
1
1
(t, JYH ϭ 29.4 Hz, 1 H, YH), 4.36 (t, JYH ϭ 30.6 Hz, 2 H, YH), 4.53
1
(t, JYH ϭ 33.4 Hz, 1 H, YH). 89Y NMR ([D8]-toluene): δϭ 338.9 (quin,
1JYH ϭ 15 Hz).
[{(η5-C5Me4SiMe2Ph)Y}4(µ-H)4(µ3-H)4(THF)2] (2b)
1
Chemical shifts for H and 13C spectra were referenced internally
A
solution of 1.10 g
(1.87 mmol) [Y(η5-C5Me4SiMe2Ph)-
using the residual solvent resonances and reported relative to tetra-
methylsilane. 89Y spectra were referenced externally to a 1 M solu-
tion of YCl3 in D2O. Elemental analyses were performed by the
Microanalytical Laboratory of this department. In many cases the
results were not satisfactory and the best values from repeated runs
were given. Moreover the results were inconsistent from run to run
and therefore not reproducible. We ascribe this difficulty observed
also by other workers [9e] to the extreme sensitivity of the material.
Metal analysis was performed by complexometric titration [15].
The sample (10 to 20 mg) was dissolved in acetonitrile (1 mL) and
titrated with a 0.005 M solution of EDTA using xylenol orange as
indicator and 1 M ammonium acetate as buffer solution (20 mL).
(CH2SiMe3)2(THF)] (1b) in pentane (20 mL) was loaded in a thick-
walled glass vessel. At room temperature, H2 (4 bar) was charged
and the solution was stirred vigorously. After 24 h, the solution
was transferred to a Schlenk tube in the glovebox. The solvent was
removed in vacuo and the colorless residue was recrystallized from
pentane at Ϫ30 °C. The product was obtained in 91 % yield
(650 mg) as colorless powder.
C76H116O2Si4Y4 (1529.7): C 56.80 (calc. 59.67); H 6.90 (7.46).
1H-NMR (C6D6): δ ϭ 0.83 (s, 6 H, SiMe2Ph), 1.36 (br s, 2 H, β-THF), 2.26,
1
2.28 (s, 2 ϫ 6 H, C5Me4), 3.61 (br s, 2 H, α-THF), 4.45 (quint, 1 H, JY, H
ϭ
3
15.3 Hz, YH), 7.21 (m, 3 H, C6H5), 7.62 (d, JH,H ϭ 7.8 Hz, 2 H, 2-C6H5).
13C{1H}NMR (C6D6):
δ
ϭ
12.5 (SiCH3Ph), 12.6, 15.4 (C5Me4), 25.1
(β-THF), 70.4 (α-THF), 112.4 (ring C at SiMe2Ph), 124.9 (ring C), 128.1,
128.8, 134.3 (C6H5), 141.8 (ipso-C6H5). 29Si NMR (C6D6): δ ϭ Ϫ13.6.
89Y NMR (C6D6): δ ϭ 344 (m).
[Y(η5-C5Me4SiMe3)(CH2SiMe3)2(THF)] (1a)
[Y(CH2SiMe3)3(THF)2] (1.03 g, 2.1 mmol) was dissolved in pen-
tane (30 mL) and cooled to Ϫ78 °C. The cyclopentadiene
(C5Me4H)SiMe3 (0.40 g, 2.1 mmol) was added and the mixture was
stirred for 3 h in which the mixture was warmed up to 0 °C. The
solvent was reduced in vacuo and after cooling 12 h at Ϫ30 °C the
product was obtained as colorless crystals in 43 % (480 mg) yield.
C24H51OSi3Y (528.83): C 52.72 (calc. 54.51), H 10.20 (9.72), Y
16.59 (16.81) %.
Crystal structure determination of 2a. Colorless crystals of
[{(η5-C5Me4SiMe3)Y}4(µ-H)4(µ3-H)4(THF)2] (2a), C56H108O2Si4Y4,
1281.45 g·molϪ1, were obtained from pentane solution at Ϫ30 °C.
¯
For a prism of dimensions 0.68 ϫ 0.46 ϫ 0.33 mm, triclinic, P1,
˚
˚
˚
˚
a ϭ 12.4061(4) A, b ϭ 13.4975(4) A, c ϭ 22.1238(7) A, α ϭ
3
99.014(2), β ϭ 92.874(2)°, γ ϭ 114.320(2), V ϭ 3307.1(2) A , Z ϭ
2, ρcalcd ϭ 1.287 g cmϪ3, µ ϭ 3.581 mmϪ1, F(000) ϭ 1344, the data
set was obtained with a Bruker AXS diffractometer at Ϫ70 °C in
the ω-scan mode up to 2θmax ϭ 56.6° (Mo-Kα radiation). 30744
reflections were collected, 16258 were unique [R(int) ϭ 0.0551] of
which 10271 were observed [I > 2σ(I)]. The data correction was
carried out using the program system SAINT [16]. The structure
was solved by Patterson and Fourier methods using the program
2
1H NMR (C6D6): δ ϭ Ϫ0.60 (d, JYH ϭ 2.6 Hz, 4 H, YCH2), 0.30 (s, 18 H,
CH2SiMe3), 0.42 (s, 9 H, ring SiMe3), 1.13 (m, 4 H, β-THF), 1.96, 2.24
(s, 2 ϫ 6 H, C5Me4), 3.50 (br s, 4 H, α-THF). 13C{1H} NMR (C6D6): δ ϭ
2.6 (ring SiMe3), 4.6 (CH2SiMe3), 11.5, 14.7 (C5Me4), 24.8 (β-THF), 34.7
1
(d, JYC ϭ 43.2 Hz, YCH2), 70.4 (α-THF), 115.0 (ring C attached to Si),
123.3, 126.4 (ring C).
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K. C. Hultzsch, P. Voth, Th. P. Spaniol, J. Okuda
SHELXS-86 [17], the refinement was carried out using the program
SHELXL-97 based on F2 [18]. Anisotropic thermal parameters
were refined for the non-hydrogen atoms. Hydrogen atoms of the
methyl groups were included into calculated positions; the torsional
angle was allowed to refine. All hydrogen atoms that are attached
to the Y4-fragment were located in a Fourier difference map and
were refined in their positions with isotropic thermal parameters.
R1 ϭ 0.0456, wR2 ϭ 0.1040 (obsd. data), goodness-of-fit on F2 ϭ
[8] R. A. Heintz, T. F. Koetzle, R. L. Ostrander, A. L. Rheingold,
K. H. Theopold, P. Wu, Nature 1995, 378, 359.
˚
[9] a) [(C5H4Me)2Y(THF)(µ-H)]2: Y-H ϭ 2.17(8), 2.19(8) A,
˚
Y···Y ϭ 3.664(1) A, see: W. J. Evans, J. H. Meadows, A. L.
Wayda, W. E. Hunter, J. L. Atwood, J. Am. Chem. Soc. 1982,
104, 2008. b) [(C5H3Me2)2Y(THF)(µ-H)]2: Y-H ϭ 2.03(7),
˚
2.27(6) A, see: W. J. Evans, D. K. Drummond, T. P. Hanusa,
R. J. Doedens, Organometallics 1987, 6, 2279. c)
0.959; residual electron density (max/min) 1.211/Ϫ0.786 e AϪ3. For
˚
˚
[(MeOCH2CH2C5H4)2Y)(µ-H)]2: Y-H ϭ 2.02(6) Ϫ 2.15(6) A,
˚
Y···Y ϭ 3.611(2), 3.622(2) A, see: D. Deng, Y. Jiang, C. Qian,
the graphical representation, ORTEP-III for Windows was used as
implemented in the program system WINGX [19].
G. Wu, P. Zheng, J. Organomet. Chem. 1994, 470, 99. d)
˚
[{PhC(NSiMe3)2}2Y(µ-H)]2: Y-H ϭ 2.11(3)Ϫ2.19(3) A, see: R.
Crystallographic data for the structure have been deposited with
the Cambridge Data Centre. Copies of the data can be obtained
free of charge on application The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: int.codeϩ(1223)336-033; email:
teched@chemcrys.cam.ac.uk).
Duchateau, C. T. van Wee, A. Meetsma, P. T. van Duijnen,
J. H. Teuben, Organometallics 1996, 15, 2279. e) (rac)-[(R,S)-
(C20H12O2)Si{C5H2(CMe3)(SiMe3)}2)Y(µ-H)]2: Y-H ϭ 2.0(1),
˚
˚
2.4(1) A, Y···Y ϭ 3.668(3) A, see: J. P. Mitchell, S. Hajela, S. K.
Brookhart, K. I. Hardcastle, L. M. Henling, J. E. Bercaw, J. Am.
Chem. Soc. 1996, 118, 1045. f) [(2,4,7-Me3C9H4)2Y(µ-H)]2:
Acknowledgement. We thank the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie for generous financial
support.
˚
Y-H ϭ 2.09(4)Ϫ2.14(7) A, see: W. P. Kretschmer, S. I. Troy-
anov, A. Meetsma, B. Hessen, J. H. Teuben, Organometallics
1998, 17, 284. g) [{2,2Ј-bis-((tert-butyl-dimethylsilyl)amido)-
˚
Note added in proof: 2a was mentioned in: O. Tardif, M. Nishiura,
Z. Hou, Organometallics 2003, 22, 1171.
6,6Ј-dimethylbiphenyl}Y(THF)(µ-H)]2: Y-H ϭ 2.22(4), 2.27(4) A,
˚
Y···Y ϭ3.6652(8) A, see: T. I. Gountchev, T. D. Tilley, Organomet-
allics 1999, 18, 2896. h) [Y(η5:η1-C5Me4SiMe2NCMe3)-
˚
˚
(THF)(µ-H)]2: Y-H ϭ 1.98(6)Ϫ2.48(4) A, Y···Y ϭ 3.672(1) A, see
ref [6a]. i) [Y(η5:η1-C5Me4SiMe2NCMe3)(PMe3)(µ-H)]2: Y-H ϭ
References
˚
˚
3.703(1) A, see ref [6d].
2.25(6)Ϫ2.28(6) A, Y···Y
ϭ
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ϭ
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