Crystallographic characterization of (C₅H₄SiMe₃)₃U(BH₄)

New syntheses have been developed for the synthesis of (borohydrido-κ³H)tris­[η⁵-(tri­methyl­sil­yl)cyclo­penta­dien­yl]uranium(IV), [U(BH₄)(C₈H₁₃Si)₃] or Cp′₃U(BH₄) (Cp′ = C₅H₄SiMe₃) and its structure has been determined by single-crystal X-ray crystallography. This compound crystallized in the space group P and the structure features three η⁵-coordinated Cp′ rings and a κ³-coordinated (BH₄)⁻ ligand.

1. Chemical context

Actinide borohydrides have been of inter­est since the 1940s, owing to their potential volatility and applied use in vapor deposition technologies for the production of thin films (Hoekstra & Katz, 1949; Daly & Girolami, 2010). Uranium borohydride compounds are structurally inter­esting because the (BH₄)⁻ ligand can coordinate large electropositive cations (such as uranium) in several modes. For example, κ¹, κ², and κ³ U–(BH₄) binding has previously been reported (Ephritikhine, 1997). Borohydrides can also achieve high coordination numbers with uranium, e.g. the oligomeric 14-coordinate U(BH₄)₄ (Bernstein et al., 1972). Although several cyclo­penta­dienyl uranium borohydrides have been crystallographically characterized (Ephritikhine, 1997), the structure of Cp′₃U(BH₄) (Cp′ = C₅H₄SiMe₃), made in 1992 (Berthet & Ephritikhine, 1992), has not been reported. Our inter­est in Cp′ uranium chemistry (MacDonald et al., 2013; Windorff et al., 2017) prompted us to determine the coordination mode of (BH₄)⁻ within the tris-cyclo­penta­dienyl uranium platform using single-crystal X-ray diffraction. Toward this end, we developed new synthetic routes to the Cp′₃U(BH₄) compound.

The Cp′₃U(BH₄) compound was originally synthesized by reacting Cp′₃UH with H₃B-PPh₃ (Berthet & Ephritikhine, 1992). Our attempts to repeat this procedure in toluene and diethyl ether solvents were unsuccessful, potentially because we were uncertain about the details of the reaction. However, we were successful in synthesizing Cp′₃U(BH₄) from Cp′₃UH with H₃B-PPh₃ in hot THF solvent. We also observed Cp′₃U(BH₄) could be prepared in high yield (96%) by reacting Cp′₃UI with NaBH₄ in the presence of 15-crown-5. When this reaction was carried out in toluene at room temperature, the I⁻ ligand was substituted by the (BH₄)⁻ anion. Another method we developed for synthesizing Cp′₃U(BH₄) involved reacting U(BH₄)₄ with KCp′ (3 equiv.) in diethyl ether. This reaction, where (BH₄)⁻ was substituted by (Cp′)⁻, also proceeded in high yield (89%). X-ray quality crystals of Cp′₃U(BH₄) formed at 253 K overnight from diethyl ether solutions.

Of our two synthetic routes, we preferred making Cp′₃U(BH₄) from Cp′₃UI over U(BH₄)₄ because the U(BH₄)₄ starting material was more challenging to isolate in a chem­ic­ally pure form. Another inter­esting comparison between the two synthetic methods involved the substitution chemistry. The (Cp′)⁻ anion displaced (BH₄)⁻ from U(BH₄)₄ and (BH₄)⁻ displaced I⁻ in Cp′₃UI. Hence, we qualitatively concluded that the stability of the U—X bond for mol­ecular compounds dissolved in organic solvents was largest for (Cp′)⁻, inter­mediate for (BH₄)⁻, and lowest for I⁻. The generality of this conclusion is limited, and we acknowledge the solubility of the other reaction products (such as NaI) might significantly influence the substitution chemistry on uranium.

2. Structural commentary

Single crystal X-ray data from Cp′₃U(BH₄) were refined in the triclinic P space group with one crystallographically unique mol­ecule in the unit cell, see Fig. 1. The data are of high quality, and electron-density difference peaks consistent with the location and geometry of bridging hydrides were located from a difference-Fourier map with U—H distances of 2.35 (5), 2.35 (5), and 2.36 (5) Å. Although the uncertainty associated with the U—H bonds is relatively high, they are consistent with previously reported bond lengths for actin­ide(IV) hydride inter­actions (Ephritikhine, 1997; Daly et al., 2010). Significantly lower uncertainty is associated with the U—B distance at 2.568 (4) Å, which is similar to two of the three U—B distances in [U(BH₄)₃(DME)]₂(μ-O) (DME = 1,2-di­meth­oxy­ethane), 2.574 (6), 2.584 (6), and 2.635 (7) Å (Daly et al., 2012). The U—B distance in (C₅H₅)₃U(BH₄) was reported to be 2.48 Å (Zanella et al., 1988), although disorder in that structure prevented a full solution from being obtained. Theoretical calculations on (C₅H₅)₃U(BH₄) in the gas phase and in solution predicted U—B distances of 2.533 and 2.557 Å (Elkechai et al., 2009), which are also consistent with our data. Other (C₅R₅)₂U(BH₄)₂ structures showed similar U—B distances of 2.56 (1) Å for [C₅H₃(SiMe₃)₂]₂U(BH₄)₂ (Blake et al., 1995), 2.58 (3) Å in (C₅Me₅)₂U(BH₄)₂ (Gradoz et al., 1994, Marsh et al., 2002), and 2.553 (1) Å in (PC₄Me₄)₂U(BH₄)₂ (Baudry et al., 1990).

Figure 1 Structure of Cp′3U(BH4) with atomic displacement parameters drawn at the 50% probability level. Boron-bound hydrogen atoms are represented as isotropic circles. All carbon-bound hydrogen atoms are omitted. Selected structural metrics, U—(Cp′ centroid) average 2.48 (2) Å, U—H average 2.35 (1) Å, (Cp′ centroid)—U—(Cp′ centroid) average 113.9 (6)°, (Cp′ centroid)—U—B average 104.4 (4)°, and terminal B—H distance of 1.11 (5) Å.

The uranium–(Cp′ centroid) distances in Cp′₃U(BH₄) range from 2.458–2.500 Å and average 2.48 (2) Å (uncertainty reported as the standard deviation from the mean at 1σ). These uranium–(Cp′ centroid) distances compare well with the 2.473 Å analogous metric in Cp′₃UCl (Windorff et al., 2017) and other Cp′₃UX structures (see Table 1) with average U–(Cp′ centroid) distances of 2.478 (3) Å in Cp′₃UI (Windorff et al., 2017), 2.484 (4) Å in Cp′₃U(η¹-CH=CH₂) (Schock et al., 1988) and 2.478 (7) Å in Cp′₃U[Si(SiMe₃)₃] (Réant et al., 2020). The 113.9 (6)° average of (Cp′ centroid)—U—(Cp′ centroid) angles in Cp′₃U(BH₄) is more acute than the 117.0° angle in Cp′₃UCl and other Cp′₃UX structures, where the average (Cp′ centroid)—U—(Cp′ centroid) angles were reported as 117 (1)° in Cp′₃UI, 112 (2)° in Cp′₃U(η¹-CH=CH₂), and 118.7 (4)° in Cp′₃U[Si(SiMe₃)₃]. The more acute (Cp′ centroid)—U—(Cp′ centroid) angles are complemented by a more obtuse average (Cp′ centroid)—U—B angle of 104.4 (4)° in Cp′₃U(BH₄), likely due to the close proximity of the (BH₄)¹⁻ ligand compared with (Cp′ centroid)—U—X angles of 100.0° in Cp′₃UCl, 100 (2)° in Cp′₃UI, 98 (3)° in Cp′₃U(η¹-CH=CH₂), and 96.7 (9)° in Cp′₃U[Si(SiMe₃)₃], see Table 1.

Table 1
A comparison of structural parameters (Å, °) in Cp′₃U(BH₄) and other Cp′₃UX {X = Cl⁻, I⁻, [Si(SiMe₃)₃]⁻} complexes

cent = C₅H₄SiMe₃ centroid.

	Cp′3U(BH4)	Cp′3UCl^a (Windorff et al., 2017)	Cp′3UI (Windorff et al., 2017)	Cp′3U(η^1-CH=CH2) (Schock et al., 1988)	Cp′3U[Si(SiMe3)3] (Réant et al., 2020)
U—(cent)	2.458, 2.490, 2.500	2.473	2.475, 2.478, 2.480	2.481, 2.483, 2.489	2.472, 2.478, 2.485
(cent)—U—X	104.13, 104.14, 104.83	100.00	97.9, 101.2, 101.6	95.1 100.0 100.2	96.04, 96.30, 97.65
(cent)—U—(cent)	113.28, 114.26, 114.26	117.00	116.1, 116.4, 118.3	116.4, 117.2, 120.0	118.28, 118.88, 119.08
Note: (a) The asymmetric unit contains one Cp′ ring, one-third of a chloride atom, and one-third of a uranium atom.

An unusual feature of the Cp′₃U(BH₄) structure is that all three of the tri­methyl­silyl groups are oriented in a single direction towards the (BH₄)⁻ unit. This orientation has not been observed in other Cp′₃U(anion) and Cp′₃U(μ-dianion)UCp′₃ structures, which are shown in Figs. 2–12. The closest comparison is with the Cp′₃UCl structure (Windorff et al., 2017), where all three tri­methyl­silyl groups are oriented towards the Cl⁻ unit, but twisted down and away from the chloride towards the meridian. The Cp′₃UI (Windorff et al., 2017) and Cp′₃U(η¹-CH=CH₂) (Schock et al., 1988) complexes have one tri­methyl­silyl group pointed away from the anionic ligand. The Cp′₃U[Si(SiMe₃)₃] complex (Réant et al., 2020) represents the opposite extreme where all of the tri­methyl­silyl groups are oriented away from the [Si(SiMe₃)₃]¹⁻ unit. Since Cp′₃U(BH₄) has the smallest mono-anion of the Cp′₃U(anion) complexes and the correspondingly smallest (Cp′ centroid)—U—(Cp′ centroid), and the largest (Cp′ centroid)—U—X angles, the orientation of the silyl groups could occur due to steric factors. However, it is also possible that some dispersion forces between the (BH₄)⁻ and the tri­methyl­silyl groups could contribute to the orientation (Liptrot et al., 2016). It is inter­esting to note that in the Cp′₃ThX series where X = Cl (Réant et al., 2020), Br (Windorff et al., 2017), and CH₃ (Wedal et al., 2019), all three tri­methyl­silyl groups are oriented towards the anion, but twisted down and away from the anion towards the meridian as in Cp′₃UCl.

Figure 2 Structure of Cp′3UCl with atomic displacement parameters drawn at the 50% probability level, as reproduced from the published CIF (Windorff et al., 2017); the isomorphous thorium complex, Cp′3ThCl, is also known (Réant et al., 2020). Hydrogen atoms are omitted for clarity.

Figure 3 Structure of Cp′3UCH3/Cl with only the (CH3)^− ligand shown, with atomic displacement parameters drawn at the 50% probability level, except the –CH3 unit, which has been plotted as an isotropic sphere, as reproduced from the published CIF (Windorff et al., 2017), see the manuscript for further details. Hydrogen atoms are omitted for clarity.

Figure 4 Structure of Cp′3UI with atomic displacement parameters drawn at the 50% probability level, as reproduced from the published CIF (Windorff et al., 2017). Hydrogen atoms are omitted for clarity.

Figure 5 Structure of Cp′3U(η^1-CH=CH2) with atomic displacement parameters drawn as isotropic spheres, as reproduced from the CIF (Schock et al., 1988). Hydrogen atoms are omitted for clarity.

Figure 6 Structure of Cp′3U[Si(SiMe3)3] with atomic displacement parameters drawn at the 50% probability level, as reproduced from the published CIF (Réant et al., 2020); the isomorphous thorium complex, Cp′3Th[Si(SiMe3)3], is also known (Réant et al., 2020). Hydrogen atoms are omitted for clarity.

Figure 7 Structure of Cp′3ThCH3 with atomic displacement parameters drawn at the 50% probability level, as reproduced from the published CIF (Wedal et al., 2019). Hydrogen atoms are omitted for clarity.

Figure 8 Structure of Cp′3ThBr with atomic displacement parameters drawn at the 50% probability level, as reproduced from the published CIF in the P space group (Windorff et al., 2017); there is a second report of the same mol­ecule in the P21/c space group, featuring the same ligand orientation (Wedal et al., 2019). Hydrogen atoms are omitted for clarity.

Figure 9 Structure of (Cp′3U)2(μ-O) with atomic displacement parameters drawn as isotropic spheres, as reproduced from the CIF (Berthet et al., 1991); the isomorphous thorium complex, (Cp′3Th)2(μ-O), is also known (Wedal et al., 2019). Hydrogen atoms are omitted for clarity.

Figure 10 Structure of (Cp′3U)2[μ-(N2C4H4)] with atomic displacement parameters drawn at the 50% probability level, as reproduced from the published CIF (Mehdoui et al., 2004). Hydrogen atoms are omitted for clarity.

Figure 11 Structure of (Cp′3U)2(μ-CCO) with atomic displacement parameters drawn at the 50% probability level and disorder in the (μ-CCO)^2− unit displayed in one configuration, as reproduced from the published CIF (Tsoureas & Cloke, 2018). The mol­ecule contains a plane of symmetry, and the unit cell contains two half mol­ecules with the same orientation. For clarity, only one full mol­ecular unit is depicted and hydrogen atoms are omitted for clarity.

Figure 12 Structure of (Cp′3U)4(μ-L) where L = a complex organic structure containing a central cyclo­butene-1,3-dione ring, with atomic displacement parameters drawn at the 50% probability level, as reproduced from the published CIF (Tsoureas & Cloke, 2018). Hydrogen atoms and disorder in the –SiMe3 groups are omitted for clarity.

3. Supra­molecular features

There are no major supra­molecular features to report. The mol­ecules pack in an alternating 180° rotation from one another within the unit cell and stack `head to tail' between the unit cells.

4. Database survey

A search using the Cambridge Structural Database (Version 5.41, March 2020; Groom et al., 2016) for borohydride structures containing η⁵-aromatic five-membered rings bound to uranium showed two classes of complexes. There were the uranium(IV) piano-stool complexes: (C₅H₅)U(BH₄)₃ (DEKVEU and DEKVEU10; Baudry et al., 1985, 1989); (C₅Me₅)U(BH₄)(SPS^Me) (JOJTIM; Arliguie et al., 2008), where SPS^Me = PC₅H-3,5-Ph,-2,6-(P(S)Ph₂)-1-Me, a λ⁴-phosphinine with two lateral phosphino­sulfide groups, and the tetra­methyl­phosphol (PC₄Me₄) compound (PC₄Me₄)(C₈H₈)U(BH₄)(THF) (MOBVEE; Cendrowski-Guillaume et al., 2002). There were also uranium(IV) metallocene structures, (Ring)₂U(BH₄)₂, where Ring = C₅H₅ (CPURBH; Zanella et al., 1977), C₅H₃(SiMe₃)₂ (ZEYZOS; Blake et al., 1995), C₅Me₅ (WIFFOG and WIFFOG01; Gradoz et al., 1994; Marsh et al., 2002), C₉H₇ (VASVUG, C₉H₇ = indenide; Rebizant et al., 1989) and PC₄Me₄ (KIJBEK, PC₄Me₄ = tetra­methyl­phosphol; Baudry et al., 1990). The macrocyclic trans-calix[2]benzene­[2]pyrrolide (L) complex [LU(BH₄)][B(C₆F₅)₄] was also in the database (CUJMEB; Arnold et al., 2015). This last compound features two η⁵-bound NC₄H₂R₂ ligands. Also in the database were a few examples of uran­ium(III) borohydrides, such as the mono borohydride [(PC₄Me₄)₂U(BH₄)]₂ (YEZJES; Gradoz et al., 1994) and the mixed oxidation state piano stool [Na(THF)₆][(C₅Me₅)U(BH₄)₃]₂ (VAXMUC; Ryan et al., 1989)] complexes.

There are also three dimeric uranium(IV) complexes with Cp′⁻ ligands, all of the form (Cp′₃U)₂(μ-X) where X = O²⁻ (SOSXON; Berthet et al., 1991), (pyrazine)²⁻, (N₂C₄H₄)²⁻ (EYERIJ; Mehdoui et al., 2004), and CCO²⁻ (PIKFAT; Tsoureas & Cloke, 2018). There is also the tetra­metallic (Cp′₃U)₄(μ-L) (PIKDUL; Tsoureas & Cloke, 2018) where L is a complex organic structure containing a central cyclo­butene-1,3-dione ring.

5. Spectroscopic Features

The fully defined Cp′₃U(BH₄) compound was also characterized by ¹H, ¹¹B{¹H}, ¹³C{¹H}, and ²⁹Si{¹H} multi-nuclear NMR spectroscopy. It was of particular inter­est to examine the ²⁹Si{¹H} spectrum for comparison with previous studies of silicon-containing paramagnetic uranium complexes (Windorff & Evans, 2014). The ¹H NMR spectrum in C₇D₈ was in good agreement with the literature (Berthet & Ephritikhine, 1992). ¹¹B{¹H}, ¹³C{¹H}, and ²⁹Si{¹H} spectra were also obtained in both C₇D₈ and C₆D₆, as well as different field strengths, 500 vs 600 MHz for ¹H, to see if any significant solvent or field effects were present. Since the spectra were not dependent on solvent or field strength, only the spectra obtained in C₆D₆ in a 600 MHz field will be discussed here. See Section 6 for full details.

In general, the resonances attributable to the Cp′⁻ ligands are sharp (ν_1/2 < 50 Hz) and paramagnetically shifted over a range of δ 9.6 to −22.6 ppm, in the ¹H NMR spectrum, and a ²⁹Si{¹H} resonance at δ −57.4 ppm was observed, typical of other tetra­valent uranium complexes (Windorff & Evans, 2014). The resonances attributable to the (BH₄)⁻ unit showed considerably more shifting and broadening, resonating at δ −59.5 (ν_1/2 = 300 Hz) and 79.6 (ν_1/2 = 240 Hz) in the ¹H and ¹¹B{¹H} spectra, respectively. Since the (BH₄)⁻ ligand exhibited a single ¹H NMR resonance whereas two distinct hydride environments are present in the solid state, it appears that the complex is fluxional in solution. This is in line with previous studies (Ephritikhine, 1997).

6. Synthesis and crystallization

6.1. General considerations

All manipulations and syntheses described below were conducted with the rigorous exclusion of air and water using glovebox techniques under an argon atmosphere. Solvents (THF, Et₂O, toluene, hexane, and penta­ne) were sparged with UHP argon (Praxair) and dried by passage through columns containing a copper(II) oxide oxygen scavenger (Q-5) and mol­ecular sieves prior to use or stirred over sodium benzo­phenone ketyl, briefly exposed to vacuum several times to degas and distilled under vacuum. All ethereal solvents were stored over activated 4 Å mol­ecular sieves. Deuterated solvents (Cambridge Isotopes) used for nuclear magnetic resonance (NMR) spectroscopy were dried over sodium benzo­phenone ketyl, degassed by three freeze-pump-thaw cycles, and distilled under vacuum before use. The ¹H, ¹¹B{¹H}, ¹³C{¹H} and ²⁹Si{¹H} NMR spectra were recorded on a GN 500, Cryo 500 or Bruker Avance 600 spectrometer operating at 500.2 MHz, 160.1 MHz, 125.8 MHz, and 99.1 MHz for the 500 MHz spectrometers, respectively, and 600.1 MHz, 192.6 MHz, 150.9 MHz and 119.2 MHz for the 600 MHz spectrometer, respectively, at 298 K unless otherwise stated. The ¹H and ¹³C{¹H} NMR spectra were referenced inter­nally to solvent resonances, ¹¹B and ²⁹Si{¹H} NMR spectra were referenced externally to BF₃(Et₂O) and SiMe₄, respectively, the ²⁹Si{¹H} spectra were acquired using the INEPT pulse sequence. The 15-crown-5 (Aldrich) reagent was dried over activated mol­ecular sieves and degassed by three freeze–pump–thaw cycles before use. The NaBH₄ (Aldrich) reagent was placed under vacuum (10 ⁻³ Torr) for 12 h before use. The following compounds were prepared following literature procedures: KCp′ (Peterson et al., 2013), U(BH₄)₄ (Schles­inger & Brown, 1953), Cp′₃UI (Windorff et al., 2017).

6.2. Cp′₃U(BH₄) from Cp′₃UI, NaBH₄ and 15-crown-5

Solid NaBH₄ (15 mg, 0.40 mmol) was added to a C₇D₈ (toluene-d₈, 0.6 mL) solution of Cp′₃UI (37 mg, 0.048 mmol) in a J-Young NMR tube, an excess of 15-crown-5 (1 drop) was added and the tube was sealed and removed from the glovebox and vortexed (30 s). The NaBH₄ was not fully soluble in C₇D₈ even in the presence of 15-crown-5. After 18 h, NMR spectroscopy showed complete conversion to Cp′₃U(BH₄). The sample was brought back into the glovebox and the volatiles were removed under reduced pressure. The product was then extracted into Et₂O, filtered away from white insoluble solids [presumably Na(15-crown-5)I and excess NaBH₄] and the volatiles were removed under reduced pressure to give Cp′₃U(BH₄) (30 mg, 96%) as a wine-red solid. ¹H NMR (C₇D₈, 500.2 MHz): δ 9.7 (s, C₅H₄SiMe₃, 6H), −2.1 (s, C₅H₄SiMe₃, 27H), −23.1 (s, C₅H₄SiMe₃, 6H), −59.8 (s, br, ν_1/2 = 325 Hz, U—(BH₄), 4H); ¹¹B{¹H} NMR (C₇D₈, 160.1 MHz): δ 79.1 [s, br, ν_1/2 = 230 Hz, U—(BH₄)]; ¹³C{¹H} NMR (C₇D₈, 125.8 MHz): δ 233.1 (C₅H₄SiMe₃), 214.0 (C₅H₄SiMe₃), 185.6 (C₅H₄SiMe₃), 0.4 (C₅H₄SiMe₃); ²⁹Si{¹H} NMR (C₇D₈, 99.1 MHz, INEPT): δ −57.7 (s, C₅H₄SiMe₃); ¹H NMR (C₆D₆, 600.1 MHz): δ 9.6 (s, C₅H₄SiMe₃, 6H), −2.0 (s, C₅H₄SiMe₃, 27H), −22.6 (s, C₅H₄SiMe₃, 6H), −59.3 (s, br, ν_1/2 = 300 Hz, U—(BH₄), 4H); ¹¹B{¹H} NMR (C₆D₆, 192.6 MHz): δ 79.6 [s, br, ν_1/2 = 240 Hz, U-(BH₄)]; ¹³C{¹H} NMR (C₆D₆, 150.9 MHz): δ 232.0 (C₅H₄SiMe₃), 214.2 (C₅H₄SiMe₃), 186.5 (C₅H₄SiMe₃), 0.6 (C₅H₄SiMe₃); ²⁹Si{¹H} NMR (C₆D₆, 119.2 MHz, INEPT): δ −57.4 (s, C₅H₄SiMe₃).

6.3. Cp′₃U(BH₄) from U(BH₄)₄ and KCp′

An Et₂O (5 mL) solution of KCp′ (460 mg, 2.61 mmol) was added to a pale-green solution of U(BH₄)₄ (250 mg, 0.841 mmol), also dissolved in Et₂O (5 mL). White solids precipitated (presumably KBH₄) as the solution quickly turned orange and then slowly changed to dark red (30 min). After stirring the mixture for an additional 12 h, volatiles were removed under reduced pressure, and the product was extracted into hexane leaving white solids behind (presumably KBH₄). Removal of the volatiles under reduced pressure gave Cp′₃U(BH₄) (496 mg, 89%) as a dark wine-red solid. X-ray quality crystals were grown from a concentrated ether solution at 253 K.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. Analytical scattering factors neutral atoms were used throughout the analysis. A 3-D rendering of the mol­ecule can be found at the following web address: https://submission.iucr.org/jtkt/serve/z/Utgd9EjfTrqJVoXA/zz0000/0/.

Table 2
Experimental details

Crystal data
Chemical formula	[U(BH4)(C8H13Si)3]
Mr	664.69
Crystal system, space group	Triclinic, P
Temperature (K)	112
a, b, c (Å)	8.7530 (15), 12.217 (2), 13.657 (2)
α, β, γ (°)	94.159 (3), 96.016 (3), 103.256 (3)
V (Å^3)	1406.6 (4)
Z	2
Radiation type	Mo Kα
μ (mm^−1)	5.91
Crystal size (mm)	0.88 × 0.62 × 0.17
Data collection
Diffractometer	Bruker D8 Quest with Photon II detector
Absorption correction	Multi-scan (SADABS; Krause et al., 2015)
Tmin, Tmax	0.413, 0.747
No. of measured, independent and observed [I > 2σ(I)] reflections	30231, 10686, 9355
Rint	0.055
(sin θ/λ)max (Å^−1)	0.769
Refinement
R[F^2 > 2σ(F^2)], wR(F^2), S	0.037, 0.102, 1.07
No. of reflections	10686
No. of parameters	274
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å^−3)	3.87, −2.72
Computer programs: APEX3 and SAINT (Bruker, 2018), SHELXS97 (Sheldrick, 2008), SHELXL2018/3 (Sheldrick, 2015), and SHELXTL2018/3 (Sheldrick, 2008).

C—H bond distances were constrained to 0.95 Å for cyclo­penta­dienyl C—H moieties, and to 0.98 Å for aliphatic CH₃ moieties, respectively. Methyl torsion angles were not refined but constrained to be staggered. The borohydride H atoms were located from a difference-Fourier map and their positions were freely refined. U_iso(H) values were set to a multiple of U_eq(C/B) with 1.5 for CH₃ and BH₄ and 1.2 for C—H units, respectively.

Supporting information

Computing details

Data collection: APEX3 (Bruker, 2018); cell refinement: APEX3 (Bruker, 2018); data reduction: SAINT (Bruker, 2018); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: SHELXTL2018/3 (Sheldrick, 2008); software used to prepare material for publication: SHELXTL2018/3 (Sheldrick, 2008).

(Borohydrido-κ³H)tris[η⁵-(trimethylsilyl)cyclopentadienyl]uranium(IV)

Crystal data

[U(BH4)(C8H13Si)3]	Z = 2
Mr = 664.69	F(000) = 652
Triclinic, P1	Dx = 1.569 Mg m^−3
a = 8.7530 (15) Å	Mo Kα radiation, λ = 0.71073 Å
b = 12.217 (2) Å	Cell parameters from 30231 reflections
c = 13.657 (2) Å	θ = 2.4–33.1°
α = 94.159 (3)°	µ = 5.91 mm^−1
β = 96.016 (3)°	T = 112 K
γ = 103.256 (3)°	Plate, red
V = 1406.6 (4) Å^3	0.88 × 0.62 × 0.17 mm

Data collection

Bruker D8 Quest with Photon II detector diffractometer	9355 reflections with I > 2σ(I)
Radiation source: IµS 3.0 microfocus	Rint = 0.055
ω scans	θmax = 33.1°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −13→13
Tmin = 0.413, Tmax = 0.747	k = −18→18
30231 measured reflections	l = −20→20
10686 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.037	Hydrogen site location: mixed
wR(F^2) = 0.102	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0549P)^2] where P = (Fo^2 + 2Fc^2)/3
10686 reflections	(Δ/σ)max = 0.002
274 parameters	Δρmax = 3.87 e Å^−3
0 restraints	Δρmin = −2.72 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
U1	0.51249 (2)	0.16808 (2)	0.26353 (2)	0.00963 (4)
B1	0.8150 (5)	0.2329 (4)	0.3009 (4)	0.0177 (8)
H1A	0.761 (6)	0.294 (5)	0.308 (4)	0.027*
H1B	0.771 (6)	0.205 (5)	0.219 (4)	0.027*
H1C	0.762 (6)	0.166 (5)	0.348 (4)	0.027*
H1D	0.944 (6)	0.271 (5)	0.317 (4)	0.027*
Si1	0.76504 (13)	0.39347 (9)	0.07862 (8)	0.0156 (2)
Si2	0.71528 (13)	0.35432 (9)	0.54090 (9)	0.0161 (2)
Si3	0.79753 (13)	−0.07373 (10)	0.23562 (8)	0.0161 (2)
C1	0.5747 (4)	0.3269 (3)	0.1255 (3)	0.0134 (6)
C2	0.4548 (4)	0.2353 (3)	0.0762 (3)	0.0142 (7)
H2	0.467664	0.185642	0.022485	0.017*
C3	0.3126 (4)	0.2291 (3)	0.1192 (3)	0.0168 (7)
H3A	0.205686	0.182752	0.090235	0.020*
C4	0.3423 (5)	0.3169 (3)	0.1952 (3)	0.0194 (8)
H4A	0.259820	0.343109	0.229549	0.023*
C5	0.5036 (5)	0.3754 (3)	0.2021 (3)	0.0170 (7)
H5A	0.551554	0.449334	0.242324	0.020*
C6	0.8516 (6)	0.2832 (4)	0.0182 (4)	0.0258 (9)
H6A	0.773894	0.237713	−0.034755	0.039*
H6B	0.946750	0.320007	−0.009698	0.039*
H6C	0.879493	0.234315	0.067481	0.039*
C7	0.9080 (5)	0.4833 (4)	0.1805 (4)	0.0259 (9)
H7A	0.935861	0.435704	0.231009	0.039*
H7B	1.003659	0.521095	0.153741	0.039*
H7C	0.859331	0.540147	0.210342	0.039*
C8	0.7126 (6)	0.4851 (4)	−0.0173 (4)	0.0284 (10)
H8A	0.637627	0.438442	−0.070950	0.043*
H8B	0.664218	0.541988	0.012768	0.043*
H8C	0.808545	0.522937	−0.043833	0.043*
C9	0.5445 (4)	0.2558 (3)	0.4617 (3)	0.0139 (6)
C10	0.5031 (4)	0.1358 (3)	0.4589 (3)	0.0129 (6)
H10A	0.566960	0.090586	0.496241	0.016*
C11	0.3457 (4)	0.0938 (3)	0.4159 (3)	0.0148 (7)
H11A	0.280490	0.015468	0.418243	0.018*
C12	0.2877 (4)	0.1864 (3)	0.3859 (3)	0.0159 (7)
H12A	0.174487	0.184244	0.363546	0.019*
C13	0.4089 (5)	0.2856 (3)	0.4155 (3)	0.0156 (7)
H13	0.400650	0.360371	0.406008	0.019*
C14	0.7834 (5)	0.4881 (3)	0.4818 (4)	0.0236 (9)
H14A	0.694252	0.523095	0.467930	0.035*
H14B	0.867433	0.540488	0.526781	0.035*
H14C	0.823995	0.470669	0.419794	0.035*
C15	0.6386 (6)	0.3890 (4)	0.6594 (3)	0.0269 (9)
H15A	0.553651	0.428013	0.645944	0.040*
H15B	0.597529	0.319142	0.688904	0.040*
H15C	0.724665	0.438154	0.705407	0.040*
C16	0.8764 (5)	0.2804 (4)	0.5706 (3)	0.0226 (8)
H16A	0.965381	0.332556	0.612059	0.034*
H16B	0.836522	0.215057	0.606193	0.034*
H16C	0.911947	0.254911	0.509097	0.034*
C17	0.6012 (4)	−0.0360 (3)	0.2171 (3)	0.0128 (6)
C18	0.4764 (5)	−0.0648 (3)	0.2755 (3)	0.0140 (6)
H18	0.485999	−0.088223	0.340226	0.017*
C19	0.3343 (4)	−0.0530 (3)	0.2215 (3)	0.0153 (7)
H19	0.232617	−0.068713	0.243279	0.018*
C20	0.3699 (4)	−0.0141 (3)	0.1306 (3)	0.0145 (7)
H20A	0.290811	−0.013775	0.072251	0.017*
C21	0.5350 (4)	−0.0017 (3)	0.1283 (3)	0.0130 (6)
H21A	0.589324	0.009939	0.067662	0.016*
C22	0.8854 (5)	−0.0487 (4)	0.3683 (3)	0.0238 (9)
H22A	0.904791	0.031903	0.390761	0.036*
H22B	0.811913	−0.092648	0.408388	0.036*
H22C	0.985486	−0.072076	0.375288	0.036*
C23	0.7622 (7)	−0.2283 (4)	0.1955 (4)	0.0334 (11)
H23A	0.716059	−0.243268	0.125928	0.050*
H23B	0.862889	−0.250933	0.203265	0.050*
H23C	0.689316	−0.271505	0.236365	0.050*
C24	0.9339 (5)	0.0070 (4)	0.1537 (4)	0.0277 (10)
H24A	0.883975	−0.008159	0.084891	0.042*
H24B	0.954902	0.088142	0.174393	0.042*
H24C	1.033665	−0.016878	0.159288	0.042*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
U1	0.00980 (6)	0.01025 (6)	0.00983 (7)	0.00336 (4)	0.00194 (4)	0.00341 (4)
B1	0.0131 (18)	0.019 (2)	0.021 (2)	0.0041 (15)	0.0016 (16)	0.0059 (16)
Si1	0.0167 (5)	0.0131 (4)	0.0176 (5)	0.0025 (4)	0.0052 (4)	0.0052 (4)
Si2	0.0188 (5)	0.0123 (4)	0.0163 (5)	0.0030 (4)	0.0004 (4)	0.0002 (4)
Si3	0.0160 (5)	0.0195 (5)	0.0161 (5)	0.0099 (4)	0.0025 (4)	0.0049 (4)
C1	0.0143 (15)	0.0126 (15)	0.0135 (16)	0.0032 (12)	0.0010 (12)	0.0050 (12)
C2	0.0163 (16)	0.0158 (16)	0.0109 (16)	0.0038 (13)	0.0015 (13)	0.0037 (12)
C3	0.0140 (16)	0.0207 (18)	0.0172 (18)	0.0051 (13)	0.0010 (13)	0.0098 (14)
C4	0.0163 (17)	0.0192 (18)	0.028 (2)	0.0106 (14)	0.0061 (15)	0.0141 (16)
C5	0.0186 (17)	0.0148 (16)	0.0210 (19)	0.0079 (13)	0.0051 (14)	0.0091 (14)
C6	0.030 (2)	0.020 (2)	0.029 (2)	0.0048 (17)	0.0154 (19)	0.0026 (17)
C7	0.024 (2)	0.021 (2)	0.030 (2)	−0.0006 (16)	0.0056 (18)	0.0030 (17)
C8	0.028 (2)	0.029 (2)	0.032 (3)	0.0063 (18)	0.0100 (19)	0.021 (2)
C9	0.0145 (15)	0.0117 (15)	0.0165 (17)	0.0045 (12)	0.0024 (13)	0.0022 (12)
C10	0.0168 (16)	0.0122 (15)	0.0102 (15)	0.0033 (12)	0.0028 (12)	0.0028 (12)
C11	0.0148 (15)	0.0169 (16)	0.0132 (16)	0.0016 (13)	0.0061 (13)	0.0057 (13)
C12	0.0119 (15)	0.0236 (18)	0.0143 (17)	0.0067 (13)	0.0046 (13)	0.0026 (14)
C13	0.0167 (16)	0.0175 (17)	0.0145 (17)	0.0076 (13)	0.0025 (13)	0.0023 (13)
C14	0.026 (2)	0.0122 (17)	0.032 (2)	0.0031 (15)	0.0054 (18)	0.0032 (16)
C15	0.037 (2)	0.023 (2)	0.018 (2)	0.0031 (18)	0.0037 (18)	−0.0048 (16)
C16	0.0228 (19)	0.0204 (19)	0.025 (2)	0.0080 (15)	−0.0036 (16)	0.0027 (16)
C17	0.0141 (15)	0.0125 (15)	0.0126 (16)	0.0041 (12)	0.0025 (12)	0.0029 (12)
C18	0.0190 (17)	0.0126 (15)	0.0104 (16)	0.0033 (13)	0.0025 (13)	0.0024 (12)
C19	0.0137 (15)	0.0127 (15)	0.0182 (18)	−0.0003 (12)	0.0032 (13)	0.0031 (13)
C20	0.0140 (15)	0.0176 (16)	0.0097 (16)	0.0018 (13)	−0.0030 (12)	−0.0001 (12)
C21	0.0149 (16)	0.0140 (15)	0.0111 (16)	0.0063 (12)	0.0007 (12)	−0.0007 (12)
C22	0.0220 (19)	0.033 (2)	0.020 (2)	0.0142 (17)	0.0007 (16)	0.0059 (17)
C23	0.040 (3)	0.025 (2)	0.041 (3)	0.022 (2)	0.001 (2)	−0.001 (2)
C24	0.023 (2)	0.038 (3)	0.030 (2)	0.0164 (19)	0.0102 (18)	0.014 (2)

Geometric parameters (Å, º)

U1—B1	2.568 (4)	C7—H7B	0.9800
U1—C21	2.731 (4)	C7—H7C	0.9800
U1—C10	2.732 (4)	C8—H8A	0.9800
U1—C20	2.733 (4)	C8—H8B	0.9800
U1—C5	2.740 (4)	C8—H8C	0.9800
U1—C12	2.748 (4)	C9—C13	1.419 (5)
U1—C11	2.754 (3)	C9—C10	1.424 (5)
U1—C4	2.755 (4)	C10—C11	1.403 (5)
U1—C3	2.755 (4)	C10—H10A	1.0000
U1—H1A	2.35 (5)	C11—C12	1.411 (5)
U1—H1B	2.35 (5)	C11—H11A	1.0000
U1—H1C	2.36 (5)	C12—C13	1.417 (5)
B1—H1A	0.98 (6)	C12—H12A	1.0000
B1—H1B	1.15 (6)	C13—H13	0.9500
B1—H1C	1.12 (5)	C14—H14A	0.9800
B1—H1D	1.11 (5)	C14—H14B	0.9800
Si1—C7	1.868 (5)	C14—H14C	0.9800
Si1—C8	1.871 (4)	C15—H15A	0.9800
Si1—C6	1.872 (5)	C15—H15B	0.9800
Si1—C1	1.877 (4)	C15—H15C	0.9800
Si2—C16	1.867 (4)	C16—H16A	0.9800
Si2—C9	1.871 (4)	C16—H16B	0.9800
Si2—C15	1.873 (5)	C16—H16C	0.9800
Si2—C14	1.877 (4)	C17—C18	1.415 (5)
Si3—C22	1.867 (5)	C17—C21	1.421 (5)
Si3—C23	1.873 (5)	C18—C19	1.420 (5)
Si3—C17	1.876 (4)	C18—H18	0.9500
Si3—C24	1.884 (5)	C19—C20	1.402 (5)
C1—C2	1.418 (5)	C19—H19	0.9500
C1—C5	1.432 (6)	C20—C21	1.421 (5)
C2—C3	1.420 (5)	C20—H20A	1.0000
C2—H2	0.9500	C21—H21A	1.0000
C3—C4	1.396 (6)	C22—H22A	0.9800
C3—H3A	1.0000	C22—H22B	0.9800
C4—C5	1.418 (5)	C22—H22C	0.9800
C4—H4A	1.0000	C23—H23A	0.9800
C5—H5A	1.0000	C23—H23B	0.9800
C6—H6A	0.9800	C23—H23C	0.9800
C6—H6B	0.9800	C24—H24A	0.9800
C6—H6C	0.9800	C24—H24B	0.9800
C7—H7A	0.9800	C24—H24C	0.9800
B1—U1—C21	91.29 (14)	C3—C4—H4A	125.3
B1—U1—C10	88.27 (13)	C5—C4—H4A	125.3
C21—U1—C10	121.25 (11)	U1—C4—H4A	125.3
B1—U1—C20	121.42 (14)	C4—C5—C1	108.8 (4)
C21—U1—C20	30.15 (11)	C4—C5—U1	75.7 (2)
C10—U1—C20	116.28 (11)	C1—C5—U1	77.6 (2)
B1—U1—C5	89.68 (13)	C4—C5—H5A	124.8
C21—U1—C5	119.23 (12)	C1—C5—H5A	124.8
C10—U1—C5	119.52 (12)	U1—C5—H5A	124.8
C20—U1—C5	115.78 (12)	Si1—C6—H6A	109.5
B1—U1—C12	128.78 (14)	Si1—C6—H6B	109.5
C21—U1—C12	131.96 (12)	H6A—C6—H6B	109.5
C10—U1—C12	48.97 (11)	Si1—C6—H6C	109.5
C20—U1—C12	104.45 (12)	H6A—C6—H6C	109.5
C5—U1—C12	89.90 (12)	H6B—C6—H6C	109.5
B1—U1—C11	117.73 (13)	Si1—C7—H7A	109.5
C21—U1—C11	113.80 (11)	Si1—C7—H7B	109.5
C10—U1—C11	29.63 (11)	H7A—C7—H7B	109.5
C20—U1—C11	95.57 (11)	Si1—C7—H7C	109.5
C5—U1—C11	118.89 (12)	H7A—C7—H7C	109.5
C12—U1—C11	29.73 (11)	H7B—C7—H7C	109.5
B1—U1—C4	119.54 (13)	Si1—C8—H8A	109.5
C21—U1—C4	115.96 (13)	Si1—C8—H8B	109.5
C10—U1—C4	114.79 (12)	H8A—C8—H8B	109.5
C20—U1—C4	98.00 (13)	Si1—C8—H8C	109.5
C5—U1—C4	29.91 (11)	H8A—C8—H8C	109.5
C12—U1—C4	70.43 (12)	H8B—C8—H8C	109.5
C11—U1—C4	99.66 (12)	C13—C9—C10	105.6 (3)
B1—U1—C3	129.05 (13)	C13—C9—Si2	125.9 (3)
C21—U1—C3	87.02 (12)	C10—C9—Si2	126.4 (3)
C10—U1—C3	134.56 (12)	C11—C10—C9	109.8 (3)
C20—U1—C3	69.70 (12)	C11—C10—U1	76.0 (2)
C5—U1—C3	49.08 (12)	C9—C10—U1	77.7 (2)
C12—U1—C3	85.59 (12)	C11—C10—H10A	124.4
C11—U1—C3	109.24 (11)	C9—C10—H10A	124.4
C4—U1—C3	29.34 (13)	U1—C10—H10A	124.4
B1—U1—H1A	22.4 (14)	C10—C11—C12	107.6 (3)
C21—U1—H1A	110.3 (14)	C10—C11—U1	74.3 (2)
C10—U1—H1A	88.4 (14)	C12—C11—U1	74.9 (2)
C20—U1—H1A	139.8 (14)	C10—C11—H11A	125.7
C5—U1—H1A	70.3 (13)	C12—C11—H11A	125.7
C12—U1—H1A	115.5 (14)	U1—C11—H11A	125.7
C11—U1—H1A	116.7 (14)	C11—C12—C13	107.6 (3)
C4—U1—H1A	99.3 (13)	C11—C12—U1	75.4 (2)
C3—U1—H1A	116.2 (13)	C13—C12—U1	76.6 (2)
B1—U1—H1B	26.5 (14)	C11—C12—H12A	125.4
C21—U1—H1B	70.8 (14)	C13—C12—H12A	125.4
C10—U1—H1B	113.0 (14)	U1—C12—H12A	125.4
C20—U1—H1B	100.0 (14)	C12—C13—C9	109.4 (3)
C5—U1—H1B	85.6 (13)	C12—C13—H13	125.3
C12—U1—H1B	154.6 (14)	C9—C13—H13	125.3
C11—U1—H1B	141.1 (13)	Si2—C14—H14A	109.5
C4—U1—H1B	113.1 (13)	Si2—C14—H14B	109.5
C3—U1—H1B	109.6 (13)	H14A—C14—H14B	109.5
H1A—U1—H1B	39.9 (19)	Si2—C14—H14C	109.5
B1—U1—H1C	25.8 (13)	H14A—C14—H14C	109.5
C21—U1—H1C	90.4 (14)	H14B—C14—H14C	109.5
C10—U1—H1C	66.9 (14)	Si2—C15—H15A	109.5
C20—U1—H1C	116.7 (13)	Si2—C15—H15B	109.5
C5—U1—H1C	112.4 (13)	H15A—C15—H15B	109.5
C12—U1—H1C	114.2 (14)	Si2—C15—H15C	109.5
C11—U1—H1C	94.8 (13)	H15A—C15—H15C	109.5
C4—U1—H1C	140.7 (13)	H15B—C15—H15C	109.5
C3—U1—H1C	154.7 (13)	Si2—C16—H16A	109.5
H1A—U1—H1C	42.1 (18)	Si2—C16—H16B	109.5
H1B—U1—H1C	46.4 (18)	H16A—C16—H16B	109.5
U1—B1—H1A	66 (3)	Si2—C16—H16C	109.5
U1—B1—H1B	66 (3)	H16A—C16—H16C	109.5
H1A—B1—H1B	97 (4)	H16B—C16—H16C	109.5
U1—B1—H1C	67 (3)	C18—C17—C21	106.5 (3)
H1A—B1—H1C	107 (4)	C18—C17—Si3	126.3 (3)
H1B—B1—H1C	110 (4)	C21—C17—Si3	125.2 (3)
U1—B1—H1D	174 (3)	C17—C18—C19	108.8 (3)
H1A—B1—H1D	108 (4)	C17—C18—H18	125.6
H1B—B1—H1D	115 (4)	C19—C18—H18	125.6
H1C—B1—H1D	118 (4)	C20—C19—C18	108.2 (3)
C7—Si1—C8	109.1 (2)	C20—C19—H19	125.9
C7—Si1—C6	111.5 (2)	C18—C19—H19	125.9
C8—Si1—C6	108.4 (2)	C19—C20—C21	107.5 (3)
C7—Si1—C1	110.74 (19)	C19—C20—U1	77.0 (2)
C8—Si1—C1	106.02 (19)	C21—C20—U1	74.8 (2)
C6—Si1—C1	110.83 (18)	C19—C20—H20A	125.5
C16—Si2—C9	109.96 (19)	C21—C20—H20A	125.5
C16—Si2—C15	107.7 (2)	U1—C20—H20A	125.5
C9—Si2—C15	105.7 (2)	C20—C21—C17	109.0 (3)
C16—Si2—C14	113.1 (2)	C20—C21—U1	75.0 (2)
C9—Si2—C14	111.05 (19)	C17—C21—U1	78.9 (2)
C15—Si2—C14	109.0 (2)	C20—C21—H21A	124.6
C22—Si3—C23	108.2 (2)	C17—C21—H21A	124.6
C22—Si3—C17	111.93 (19)	U1—C21—H21A	124.6
C23—Si3—C17	107.1 (2)	Si3—C22—H22A	109.5
C22—Si3—C24	111.8 (2)	Si3—C22—H22B	109.5
C23—Si3—C24	108.4 (3)	H22A—C22—H22B	109.5
C17—Si3—C24	109.23 (18)	Si3—C22—H22C	109.5
C2—C1—C5	105.6 (3)	H22A—C22—H22C	109.5
C2—C1—Si1	126.1 (3)	H22B—C22—H22C	109.5
C5—C1—Si1	126.4 (3)	Si3—C23—H23A	109.5
C1—C2—C3	109.7 (4)	Si3—C23—H23B	109.5
C1—C2—H2	125.2	H23A—C23—H23B	109.5
C3—C2—H2	125.2	Si3—C23—H23C	109.5
C4—C3—C2	107.5 (3)	H23A—C23—H23C	109.5
C4—C3—U1	75.3 (2)	H23B—C23—H23C	109.5
C2—C3—U1	75.9 (2)	Si3—C24—H24A	109.5
C4—C3—H3A	125.5	Si3—C24—H24B	109.5
C2—C3—H3A	125.5	H24A—C24—H24B	109.5
U1—C3—H3A	125.5	Si3—C24—H24C	109.5
C3—C4—C5	108.4 (4)	H24A—C24—H24C	109.5
C3—C4—U1	75.3 (2)	H24B—C24—H24C	109.5
C5—C4—U1	74.4 (2)
C7—Si1—C1—C2	−164.8 (3)	Si2—C9—C10—U1	−128.1 (3)
C8—Si1—C1—C2	76.9 (4)	C9—C10—C11—C12	3.1 (4)
C6—Si1—C1—C2	−40.5 (4)	U1—C10—C11—C12	−68.1 (3)
C7—Si1—C1—C5	33.1 (4)	C9—C10—C11—U1	71.2 (3)
C8—Si1—C1—C5	−85.2 (4)	C10—C11—C12—C13	−2.8 (4)
C6—Si1—C1—C5	157.4 (3)	U1—C11—C12—C13	−70.5 (3)
C5—C1—C2—C3	1.5 (4)	C10—C11—C12—U1	67.7 (3)
Si1—C1—C2—C3	−163.6 (3)	C11—C12—C13—C9	1.6 (4)
C1—C2—C3—C4	0.3 (4)	U1—C12—C13—C9	−68.1 (3)
C1—C2—C3—U1	−69.1 (3)	C10—C9—C13—C12	0.3 (4)
C2—C3—C4—C5	−2.0 (4)	Si2—C9—C13—C12	−163.7 (3)
U1—C3—C4—C5	67.7 (3)	C22—Si3—C17—C18	−45.2 (4)
C2—C3—C4—U1	−69.7 (3)	C23—Si3—C17—C18	73.3 (4)
C3—C4—C5—C1	3.0 (4)	C24—Si3—C17—C18	−169.5 (4)
U1—C4—C5—C1	71.3 (3)	C22—Si3—C17—C21	153.2 (3)
C3—C4—C5—U1	−68.3 (3)	C23—Si3—C17—C21	−88.3 (4)
C2—C1—C5—C4	−2.8 (4)	C24—Si3—C17—C21	28.9 (4)
Si1—C1—C5—C4	162.3 (3)	C21—C17—C18—C19	2.5 (4)
C2—C1—C5—U1	67.2 (2)	Si3—C17—C18—C19	−161.9 (3)
Si1—C1—C5—U1	−127.7 (3)	C17—C18—C19—C20	−1.5 (4)
C16—Si2—C9—C13	−172.4 (3)	C18—C19—C20—C21	0.0 (4)
C15—Si2—C9—C13	71.6 (4)	C18—C19—C20—U1	−69.3 (3)
C14—Si2—C9—C13	−46.5 (4)	C19—C20—C21—C17	1.6 (4)
C16—Si2—C9—C10	26.8 (4)	U1—C20—C21—C17	72.3 (3)
C15—Si2—C9—C10	−89.2 (4)	C19—C20—C21—U1	−70.8 (3)
C14—Si2—C9—C10	152.7 (3)	C18—C17—C21—C20	−2.5 (4)
C13—C9—C10—C11	−2.1 (4)	Si3—C17—C21—C20	162.1 (3)
Si2—C9—C10—C11	161.8 (3)	C18—C17—C21—U1	67.2 (3)
C13—C9—C10—U1	68.0 (3)	Si3—C17—C21—U1	−128.1 (3)

 

Footnotes

‡Present address: New Mexico State University, Department of Chemistry and Biochemistry, Las Cruces, NM 88003, USA.