Synthesis and crystal structure of 1,3-di-tert-butyl-2-chloro-4,4-diphenyl-1,3,2λ3,4-di­aza­phospha­siletidine

Mo, D.; Frank, W.

doi:10.1107/S2056989019002627

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Volume 75| Part 3| March 2019| Pages 405-409

https://doi.org/10.1107/S2056989019002627

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Synthesis and crystal structure of 1,3-di-tert-butyl-2-chloro-4,4-diphenyl-1,3,2λ³,4-diazaphosphasiletidine

Dennis Mo ^a and Walter Frank ^a ^*

^aInstitut für Anorganische Chemie und Strukturchemie, Lehrstuhl II: Material- und Strukturforschung, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany
^*Correspondence e-mail: wfrank@hhu.de

Edited by S. Parkin, University of Kentucky, USA (Received 8 February 2019; accepted 20 February 2019; online 28 February 2019)

The chemical reaction of dilithium N,N′-di(^tbutyl)-Si,Si-diphenylsilanediamide and PCl₃ yielded an off-white solid. Sublimation of the crude product under reduced pressure at elevated temperature gave colourless prismatic crystals of the title compound, C₂₀H₂₈ClN₂PSi, which crystallizes in the non-centrosymmetric monoclinic space group Cc. The asymmetric unit of the crystal structure contains one molecule and it is dominated by the central SiN₂P four-membered ring, which is almost planar with a mean deviation of the atoms from the best plane of 0.014 Å. The angles between the plane defined by the silicon atom and the two nitrogen atoms and the best planes of the Si-phenyl groups are 85.1 (2) and 77.4 (2)°, with the tilt of the phenyl rings in the opposite direction. Both tert-butyl groups suffer from a two-position rotational disorder with site occupancies of 0.752 (6)/0.248 (6) and 0.878 (9)/0.122 (9). The P—Cl bond [2.2078 (17) Å] is remarkably elongated compared to the P—Cl distance in PCl₃ [2.034 Å; Galy & Enjalbert (1982). J. Solid State Chem. 44, 1–23].

Keywords: diazaphosphasiletidine; four-membered heterocycle; crystal structure; long P—Cl bond.

CCDC reference: 1898427

1. Chemical context

Diazaphosphasiletidines are heterocyclic compounds that contain an SiN₂P four-membered ring as the central building block. The first synthesis was described in the year 1963 (Fink, 1963 ) and compounds of the class have attracted considerable attention in phosphorus chemistry (e.g. Scherer et al., 1982 ; Veith et al., 1988 ; Frank et al., 1996 ; Mo et al., 2018 ). The P-chlorosubstituted diazaphosphasiletidines are well known members of this class and syntheses of such compounds have been described in the literature over a couple of decades (Klingebiel et al., 1976 ; Veith et al., 1988; Eichhorn & Nöth, 2000 ). They have found widespread use as reagents for reactions based on the P-chlorofunctionalization. Our research group, for instance, has shown that they play a crucial role in the preparation of dispirocyclic tetraphosphetes (Frank et al., 1996; Breuers et al., 2015 ) and diazaphosphasiletidine adducts with P-coordination (Veith et al., 1988; Gün et al., 2017 ). However, due to their high moisture sensitivity, the structural characterization of such P-chloroderivatives by X-ray diffraction remains a challenge. There are only two reports on the crystal structure of P-chlorosubstituted diazaphosphasiletidines of type Me₂Si(NR)₂PCl, namely 2-chloro-1,3-bis(2,4,6-trimethylphenyl)-4,4-dimethyl-1,3,2λ³,4-diazaphosphasiletidine (A; Breuers & Frank, 2016 ) and 1,3-di-tert-butyl-2-chloro-4,4-dimethyl-1,3,2λ³,4-diazaphosphasiletidine (B; Gün et al., 2017), and there is only one report on a structure of type Ph₂Si(NR)₂PCl, namely 2-chloro-1,3-di-tert-pentyl-4,4-diphenyl-1,3,2λ³,4-diazaphosphasiletidine (C; Mo et al., 2018). Crystals of the first structurally characterized chloro-substituted diazaphosphasiletidine A contained approximately 12% of a second compound, namely 2-chloro-1,3-bis(2,4,6-trimethylphenyl)-4-chloro-4-methyl-1,3,2λ³,4-diazaphosphasiletidine. With respect to this impurity, an Si,Si-diphenyl-substituted diazaphosphasiletidine (C) has successfully been introduced to preparative chemistry to avoid problems related to the content of Si,P-bis(chloro)functionalized species present in samples of the Si,Si-dimethyl derivative. However, the crystal-structure determination of C suffered from severe disorder. All the aspects mentioned before persuaded us to focus on preparation of single crystals of the title compound suitable for structure determination. After extensive attempts, we were finally able to grow single crystals by slow sublimation in vacuo and confirmed its composition and its structure via X-ray diffraction.

2. Structural commentary

The asymmetric unit of the title compound contains one molecule (Fig. 1). The central feature of this diazaphosphasiletidine molecule, the SiN₂P four-membered ring, is almost planar. The nitrogen atoms exhibit a trigonal–planar coordination sphere [sums of bond angles 359.9° (N1) and 359.4° (N2)]. The phosphorus and silicon atoms bear the main ring strain [N1—Si1—N2 = 82.08 (19)° and N1—P1—N2 = 85.4 (2)°]. The Si–N bond lengths [Si1—N1 = 1.736 (4) Å and Si1—N2 =1.749 (4) Å] exceed the expected length of an Si—N single bond [1.724 (4) Å; Brown et al., 1985 ] but correspond to those in directly related cyclosilazanes (Breuers et al., 2016; Gün et al., 2017; Clegg et al., 1981 , 1984 ; Shah et al., 1996 ; Anagho et al., 2005 ). In contrast, the P—N distances are shorter [P1—N1 = 1.689 (4) Å and P1—N2 = 1.684 (4) Å] than reported for a typical single bond [1.704 (9) Å; Brown et al., 1985], but they also correspond to those in A–C. The P—Cl bond of the title compound is remarkably elongated [P1—Cl1 = 2.2078 (17) Å] compared to the P—Cl distance in PCl₃ (2.034 Å; Galy et al., 1982 ) and exceeds the sum of the covalence radii (Hollemann et al., 2007 ). A comparison of the average Si—N, P—N and P—Cl distances in the title compound and the analogous distances of in the previously published P-chloro-substituted diazaphosphasiletidines A–C gives no evidence of substitution effects except for the P—Cl distance in B [2.2498 (6) Å, due to dimerization]: Si—N = 1.743 (4) Å average (in the title compound) vs 1.7441 (17) Å in A, 1.7474 (14) Å in B and 1.7406 (15) Å in C (average values); P—N = 1.687 (4) Å vs 1.6856 (17) Å (A), 1.6815 (14) Å (B), 1.6910 (16) Å (C); P—Cl 2.2078 (17) Å vs 2.1813 (7) Å (A), 2.2498 (6) Å (B) (dimerization), 2.1965 (17) Å (C). The tert-butyl groups in the title compound are rotationally disordered (see Refinement).

Figure 1
The molecular structure of the title compound, with atom labels and 50% probability displacement ellipsoids for non-H atoms.

3. Supramolecular features

Fig. 2 shows the arrangement of molecules in the non-centrosymmetric solid of the title compound. Taking into account its absolute structure, in the crystal under investigation the P—Cl bond vectors are oriented approximately parallel to the c axis, but point in the opposite direction. The nearest intermolecular contact is between the Cl atom and the meta-H atom of one of the Si-bonded phenyl groups of a neighbouring molecule (symmetry code: x, y, –z). In the figure, this contact is indicated by dashed lines. However, the geometric features of this contact [C⋯Cl 3.677 (6); C—H 0.95; H⋯Cl 2.90 Å; C—H⋯Cl 139°] indicate that if at all, it is a borderline case of a directed bonding interaction.

Figure 2
Packing of the molecules of the title compound in the solid state. The closest contact of the Cl atom to neighbouring molecules is indicated by dashed lines.

4. Database survey

A search in the Cambridge Structural Database (Version 5.40, November 2018; Groom et al., 2016 ) for diazaphosphasiletidines in general yielded 143 hits. However, only three of these structures contain an Si,Si-diphenyl fragment instead of the common Si,Si-dimethyl fragment. On the other hand, only seven of the aforementioned 143 structures exhibit P-chlorofunctionalization. Of these, BADLUO (Nieger et al., 2002 ) is a λ⁵P-chloro(imino)phosphorane, VUHTOJ (Holthausen & Weigand, 2016 ) contains a complex N,N′-trimethylsilyl-Si-dispirocyclic cation incorporating a tricylic P₅ fragment. ILEKER is the N,N′-dimesityl derivative A, mentioned above (Breuers & Frank, 2016). DEXTOS is the Si,Si-dimethyl derivative B, mentioned above, accompanied in Gün et al. (2017) by its BCl₃ adduct DEXTUY and its W(CO)₅ complex DEXVAG. The structure of the only Si,Si-diphenyl-P-chloro derivative (C), 2-chloro-1,3-bis(2-methylbutan-2-yl)-4,4-diphenyl-1,3,2λ³,4-diazaphosphasiletidine (YETCAE; Mo et al., 2018) suffers heavily from a combination of several types of disorder of the N,N′-alkyl substituents.

In compound B, molecules are connected via very weak P—Cl bridging bonds, which leads to a weak state of dimerization. Generally, the strength of association of molecules via E—Cl bridging bonds increases from P to Bi in related diazasileditines of type Me₂Si(NR)₂ECl. Me₂Si(N^tBu)₂AsCl contains dimers and in the antimony and the bismuth analogues the molecules are connected into chains via bridging Cl atoms (Veith & Bertsch, 1988 ; Veith et al., 1988). In contrast, the solid-state structures of the title compound, A, C, Ph₂Si(N^tBu)₂AsCl (Belter, 2016 ) and Me₂Si(NDipp)₂SbCl (Ma et al., 2013 ) do not exhibit intermolecular E⋯Cl interactions and consist of isolated molecules.

5. Synthesis and crystallization

The title compound was prepared (Fig. 3) according to generally known procedures under an argon atmosphere in oven-dried glassware using Schlenk techniques, modifying a published protocol (Eichhorn & Nöth, 2000). 5.5 g (16.8 mmol) of N,N′-di(^tbutyl)-Si,Si-diphenylsilanediamine were dissolved in 60 ml n-pentane. 13.6 ml of a n-butyllithium solution (c = 2.5 mol/l in n-hexane, 16.8 mmol) were added at 263 K. The reaction mixture was stirred for 24 h at room temperature. Cooling to 178 K and addition of 1.5 ml (16.8 mmol) PCl₃ yielded an off-white suspension. This was stirred for 3 h. After filtration and removal of the solvent under reduced pressure, the crude product was obtained as an off-white solid. Sublimation at 333 K under reduced pressure yielded colourless crystals within a couple of hours (77% yield based on PCl₃). ¹H NMR (300 MHz, CDCl₃, 298 K): δ (p.p.m.) 1.17 (d, ⁴J (P,H) = 0.9 Hz, 18H,C(CH₃)₃), 7.48 (m, 6H, m-, p-CH), 7.86 (m, 2H,o-CH), 8.08 (m, 2H, o-CH). ¹³C{¹H} NMR (75 MHz, CDCl₃, 298 K): δ(p.p.m.) 32.9 [d, ³J(P,C) = 7.1 Hz, 6 C, C(CH₃)₃], 52.6 [d, ²J(P,C) = 7.9 Hz, 2 C, C(CH₃)₃], 128.3–136.3 (12 C, Ar-C). ³¹P{¹H} NMR (121 MHz, CDCl₃, 298 K): δ (p.p.m.) 214.4 (s) EI–MS spectra were obtained using a Finnigan TSQ 7000 instrument. EI–MS: m/z (%) 390 (11) [M⁺], 375 (100) [M⁺—C(CH₃)₃]. IR spectra were measured using a Bio-Rad Excalibur FTS 3500 FT–IR spectrometer with ATR-unit, 4000–560 cm⁻¹: 3070(w), 3050(w), 3026(sh), 3014(sh), 2956(vs), 2927(s), 2903(sh), 2868(m), 1964(vw), 1903(vw), 1827(vw), 1774(vw), 1588(w), 1429(s), 1305(vw), 1207(s), 1113(s), 1102(sh), 1055(s), 1042(sh), 889(vs), 820(w), 755(sh), 739(s), 696(s). Analysis calculated for C₂₀H₂₈ClN₂PSi (326.56 g mol⁻¹): C 61.44, H 7.22, N 7.17; found C 61.10, H 7.56, N 7.08, m.p.: 393.5 K.

Figure 3
Reaction scheme for the preparation of the title compound.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. Positions of the majority of the hydrogen atoms were identified via subsequent Fourier syntheses. In the refinement, a riding model was applied using idealized C—H bond lengths (0.95–0.98 Å) as well as H—C—H and C—C—H angles. In addition, the H atoms of the CH₃ groups were allowed to rotate around the neighboring C—C bonds. The U_iso values were set to 1.5U_eq(C_methyl) and 1.2U_eq(C_ar). To account for residual electron density in the regions of the two tert-butyl groups and for elongated anisotropic displacement ellipsoids of several carbon atoms that did not appear to be physically meaningful, a two-position disorder for each tert-butyl group was introduced with partial occupation sites for all carbon atoms but the tertiary ones C1 and C5 [occupancy ratio 0.752 (6):0.248 (6) ratio (group containing C1) and 0.878 (9):0.122 (9) ratio (C5); in Figs. 1 and 2 disorder is omitted for clarity]. Appropriate same distance and anisotropic displacement restraints and some equivalent anisotropic displacement parameters had to be applied to stabilize the geometry of the minor occupancy parts of the partial occupation site models. The correct absolute structure of the non-centrosymmetric structural model is confirmed by the Flack parameter (Table 1).

Table 1
Experimental details

Crystal data
Chemical formula	C₂₀H₂₈ClN₂PSi
M_r	390.95
Crystal system, space group	Monoclinic, Cc
Temperature (K)	173
a, b, c (Å)	13.4004 (7), 15.6272 (6), 10.3817 (5)
β (°)	95.739 (4)
V (Å³)	2163.14 (18)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.31
Crystal size (mm)	0.44 × 0.38 × 0.21

Data collection
Diffractometer	Stoe IPDS
Absorption correction	Multi-scan (SHELXTL; Sheldrick, 2008 )
T_min, T_max	0.688, 0.875
No. of measured, independent and observed [I > 2σ(I)] reflections	11994, 5765, 4920
R_int	0.064
(sin θ/λ)_max (Å⁻¹)	0.684

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.063, 0.104, 1.50
No. of reflections	5765
No. of parameters	255
No. of restraints	32
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.26, −0.27
Absolute structure	Flack x determined using 1837 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
Absolute structure parameter	0.08 (8)
Computer programs: X-AREA (Stoe & Cie, 2009 ), SHELXT (Sheldrick, 2015a ), DIAMOND (Brandenburg, 2016 ), SHELXL2014/7 (Sheldrick, 2015b ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1898427

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2056989019002627/pk2614sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019002627/pk2614Isup2.hkl

checkCIF report

Computing details top

Data collection: X-AREA (Stoe & Cie, 2009); cell refinement: X-AREA (Stoe & Cie, 2009); data reduction: X-AREA (Stoe & Cie, 2009); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg, 2016); software used to prepare material for publication: SHELXL2014/7 (Sheldrick, 2015b) and publCIF (Westrip, 2010).

1,3-Di-tert-butyl-2-chloro-4,4-diphenyl-1,3,2λ³,4-\ diazaphosphasiletidine top

Crystal data top

C₂₀H₂₈ClN₂PSi	D_x = 1.201 Mg m⁻³
M_r = 390.95	Melting point: 393.5 K
Monoclinic, Cc	Mo Kα radiation, λ = 0.71073 Å
a = 13.4004 (7) Å	Cell parameters from 12536 reflections
b = 15.6272 (6) Å	θ = 2.6–29.7°
c = 10.3817 (5) Å	µ = 0.31 mm⁻¹
β = 95.739 (4)°	T = 173 K
V = 2163.14 (18) Å³	Prismatic, colourless
Z = 4	0.44 × 0.38 × 0.21 mm
F(000) = 832

Data collection top

Stoe IPDS diffractometer	5765 independent reflections
Radiation source: sealed tube	4920 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.064
ω scans	θ_max = 29.1°, θ_min = 2.6°
Absorption correction: multi-scan (SHELXTL; Sheldrick, 2008)	h = −18→18
T_min = 0.688, T_max = 0.875	k = −20→21
11994 measured reflections	l = −14→14

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.063	H-atom parameters constrained
wR(F²) = 0.104	w = 1/[σ²(F_o²) + (0.008P)² + 1.4244P] where P = (F_o² + 2F_c²)/3
S = 1.50	(Δ/σ)_max = 0.001
5765 reflections	Δρ_max = 0.26 e Å⁻³
255 parameters	Δρ_min = −0.27 e Å⁻³
32 restraints	Absolute structure: Flack x determined using 1837 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.08 (8)

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Cl1	0.72280 (12)	0.34044 (10)	0.44721 (13)	0.0555 (4)
P1	0.75140 (9)	0.32990 (8)	0.65977 (11)	0.0340 (3)
Si1	0.63594 (9)	0.21721 (8)	0.74331 (11)	0.0292 (3)
N1	0.6359 (3)	0.3262 (2)	0.7115 (4)	0.0327 (9)
N2	0.7534 (3)	0.2234 (3)	0.6842 (4)	0.0347 (9)
C1	0.5626 (4)	0.3962 (3)	0.7149 (5)	0.0403 (11)
C2	0.4879 (6)	0.3880 (5)	0.5905 (9)	0.059 (2)	0.752 (6)
H21	0.4348	0.4309	0.5925	0.089*	0.752 (6)
H22	0.4582	0.3306	0.5867	0.089*	0.752 (6)
H23	0.5238	0.3972	0.5139	0.089*	0.752 (6)
C3	0.5049 (7)	0.3845 (6)	0.8317 (10)	0.073 (3)	0.752 (6)
H31	0.4508	0.4268	0.8292	0.110*	0.752 (6)
H32	0.5503	0.3924	0.9109	0.110*	0.752 (6)
H33	0.4763	0.3268	0.8307	0.110*	0.752 (6)
C4	0.6140 (6)	0.4825 (4)	0.7091 (9)	0.0531 (19)	0.752 (6)
H41	0.5638	0.5282	0.7083	0.080*	0.752 (6)
H42	0.6484	0.4858	0.6303	0.080*	0.752 (6)
H43	0.6630	0.4892	0.7851	0.080*	0.752 (6)
C2A	0.5825 (18)	0.4340 (15)	0.8546 (19)	0.059 (2)	0.248 (6)
H24	0.5403	0.4847	0.8622	0.089*	0.248 (6)
H25	0.6533	0.4502	0.8713	0.089*	0.248 (6)
H26	0.5664	0.3909	0.9179	0.089*	0.248 (6)
C3A	0.579 (2)	0.4643 (16)	0.619 (3)	0.073 (3)	0.248 (6)
H34	0.5288	0.5095	0.6240	0.110*	0.248 (6)
H35	0.5728	0.4397	0.5319	0.110*	0.248 (6)
H36	0.6463	0.4885	0.6386	0.110*	0.248 (6)
C4A	0.4558 (13)	0.3610 (13)	0.712 (3)	0.0531 (19)	0.248 (6)
H44	0.4086	0.4085	0.7168	0.080*	0.248 (6)
H45	0.4514	0.3224	0.7853	0.080*	0.248 (6)
H46	0.4391	0.3295	0.6307	0.080*	0.248 (6)
C5	0.8384 (4)	0.1638 (4)	0.6749 (5)	0.0464 (12)
C6	0.9360 (5)	0.2115 (6)	0.6854 (13)	0.084 (3)	0.878 (9)
H61	0.9906	0.1718	0.6721	0.126*	0.878 (9)
H62	0.9480	0.2374	0.7716	0.126*	0.878 (9)
H63	0.9332	0.2566	0.6194	0.126*	0.878 (9)
C7	0.8229 (6)	0.1177 (5)	0.5448 (8)	0.071 (2)	0.878 (9)
H71	0.8780	0.0773	0.5377	0.106*	0.878 (9)
H72	0.8215	0.1597	0.4745	0.106*	0.878 (9)
H73	0.7591	0.0865	0.5386	0.106*	0.878 (9)
C8	0.8350 (6)	0.0952 (6)	0.7785 (8)	0.075 (3)	0.878 (9)
H81	0.8821	0.0493	0.7628	0.112*	0.878 (9)
H82	0.7670	0.0718	0.7755	0.112*	0.878 (9)
H83	0.8539	0.1204	0.8639	0.112*	0.878 (9)
C6A	0.799 (4)	0.075 (2)	0.647 (9)	0.084 (3)	0.122 (9)
H64	0.8552	0.0353	0.6409	0.126*	0.122 (9)
H65	0.7599	0.0560	0.7170	0.126*	0.122 (9)
H66	0.7558	0.0744	0.5649	0.126*	0.122 (9)
C7A	0.890 (4)	0.160 (4)	0.814 (3)	0.071 (2)	0.122 (9)
H74	0.9482	0.1210	0.8164	0.106*	0.122 (9)
H75	0.9131	0.2169	0.8416	0.106*	0.122 (9)
H76	0.8430	0.1381	0.8722	0.106*	0.122 (9)
C8A	0.915 (4)	0.216 (4)	0.608 (7)	0.075 (3)	0.122 (9)
H84	0.9742	0.1814	0.5984	0.112*	0.122 (9)
H85	0.8848	0.2350	0.5230	0.112*	0.122 (9)
H86	0.9345	0.2668	0.6612	0.112*	0.122 (9)
C9	0.6452 (4)	0.1891 (3)	0.9186 (4)	0.0350 (10)
C10	0.6963 (4)	0.2448 (4)	1.0070 (5)	0.0455 (12)
H101	0.7210	0.2975	0.9776	0.055*
C11	0.7117 (4)	0.2239 (4)	1.1385 (5)	0.0547 (14)
H111	0.7460	0.2627	1.1979	0.066*
C12	0.6774 (5)	0.1475 (5)	1.1817 (5)	0.0598 (16)
H121	0.6877	0.1338	1.2712	0.072*
C13	0.6286 (5)	0.0909 (4)	1.0973 (5)	0.0596 (16)
H131	0.6052	0.0379	1.1276	0.072*
C14	0.6134 (4)	0.1115 (3)	0.9657 (5)	0.0451 (12)
H141	0.5805	0.0715	0.9070	0.054*
C15	0.5370 (3)	0.1539 (3)	0.6457 (4)	0.0350 (10)
C16	0.4537 (4)	0.1194 (4)	0.6972 (6)	0.0493 (13)
H161	0.4452	0.1282	0.7860	0.059*
C17	0.3831 (4)	0.0724 (4)	0.6203 (7)	0.0622 (17)
H171	0.3274	0.0483	0.6571	0.075*
C18	0.3932 (5)	0.0604 (4)	0.4901 (7)	0.0632 (18)
H181	0.3452	0.0274	0.4380	0.076*
C19	0.4732 (5)	0.0966 (4)	0.4362 (6)	0.0534 (14)
H191	0.4796	0.0899	0.3464	0.064*
C20	0.5442 (4)	0.1429 (3)	0.5136 (5)	0.0417 (11)
H201	0.5990	0.1677	0.4758	0.050*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0735 (10)	0.0566 (9)	0.0376 (6)	0.0008 (8)	0.0126 (6)	0.0061 (6)
P1	0.0318 (6)	0.0347 (6)	0.0360 (6)	−0.0002 (6)	0.0057 (5)	−0.0022 (5)
Si1	0.0298 (6)	0.0277 (6)	0.0301 (6)	0.0026 (5)	0.0030 (4)	−0.0025 (5)
N1	0.032 (2)	0.0295 (19)	0.038 (2)	0.0074 (17)	0.0075 (17)	−0.0009 (15)
N2	0.031 (2)	0.039 (2)	0.034 (2)	0.0092 (18)	0.0066 (17)	0.0012 (17)
C1	0.035 (3)	0.032 (2)	0.055 (3)	0.008 (2)	0.007 (2)	−0.005 (2)
C2	0.041 (4)	0.045 (4)	0.088 (6)	0.015 (3)	−0.013 (4)	−0.005 (4)
C3	0.067 (6)	0.063 (5)	0.098 (7)	0.026 (5)	0.041 (5)	0.004 (5)
C4	0.046 (4)	0.035 (3)	0.076 (5)	0.008 (3)	−0.001 (4)	−0.007 (3)
C2A	0.041 (4)	0.045 (4)	0.088 (6)	0.015 (3)	−0.013 (4)	−0.005 (4)
C3A	0.067 (6)	0.063 (5)	0.098 (7)	0.026 (5)	0.041 (5)	0.004 (5)
C4A	0.046 (4)	0.035 (3)	0.076 (5)	0.008 (3)	−0.001 (4)	−0.007 (3)
C5	0.036 (3)	0.046 (3)	0.058 (3)	0.016 (2)	0.008 (2)	−0.003 (3)
C6	0.030 (3)	0.070 (5)	0.151 (9)	0.010 (4)	0.002 (4)	−0.032 (6)
C7	0.061 (5)	0.067 (5)	0.087 (6)	0.024 (4)	0.020 (4)	−0.025 (4)
C8	0.062 (5)	0.072 (5)	0.094 (6)	0.043 (4)	0.024 (4)	0.026 (5)
C6A	0.030 (3)	0.070 (5)	0.151 (9)	0.010 (4)	0.002 (4)	−0.032 (6)
C7A	0.061 (5)	0.067 (5)	0.087 (6)	0.024 (4)	0.020 (4)	−0.025 (4)
C8A	0.062 (5)	0.072 (5)	0.094 (6)	0.043 (4)	0.024 (4)	0.026 (5)
C9	0.036 (2)	0.038 (2)	0.031 (2)	0.0016 (19)	0.0042 (18)	−0.0014 (19)
C10	0.046 (3)	0.050 (3)	0.040 (3)	−0.003 (2)	0.006 (2)	−0.004 (2)
C11	0.055 (3)	0.074 (4)	0.034 (3)	−0.007 (3)	−0.003 (2)	−0.008 (3)
C12	0.061 (4)	0.090 (5)	0.028 (2)	−0.002 (4)	0.002 (2)	0.008 (3)
C13	0.071 (4)	0.063 (4)	0.045 (3)	0.004 (3)	0.009 (3)	0.016 (3)
C14	0.053 (3)	0.041 (3)	0.041 (3)	−0.005 (2)	0.003 (2)	0.004 (2)
C15	0.036 (2)	0.029 (2)	0.038 (2)	0.0033 (19)	−0.0021 (18)	0.0018 (19)
C16	0.038 (3)	0.055 (3)	0.054 (3)	−0.007 (3)	0.002 (2)	0.003 (3)
C17	0.042 (3)	0.064 (4)	0.077 (4)	−0.012 (3)	−0.007 (3)	0.016 (3)
C18	0.054 (4)	0.051 (3)	0.078 (4)	−0.010 (3)	−0.028 (3)	0.002 (3)
C19	0.064 (4)	0.049 (3)	0.043 (3)	0.005 (3)	−0.014 (3)	−0.009 (2)
C20	0.046 (3)	0.038 (3)	0.040 (2)	0.003 (2)	−0.001 (2)	−0.003 (2)

Geometric parameters (Å, º) top

Cl1—P1	2.2078 (17)	C6—H62	0.9800
P1—N2	1.684 (4)	C6—H63	0.9800
P1—N1	1.689 (4)	C7—H71	0.9800
Si1—N1	1.736 (4)	C7—H72	0.9800
Si1—N2	1.749 (4)	C7—H73	0.9800
Si1—C9	1.864 (5)	C8—H81	0.9800
Si1—C15	1.869 (5)	C8—H82	0.9800
N1—C1	1.473 (6)	C8—H83	0.9800
N2—C5	1.481 (6)	C6A—H64	0.9800
C1—C3A	1.487 (18)	C6A—H65	0.9800
C1—C3	1.512 (9)	C6A—H66	0.9800
C1—C4	1.518 (8)	C7A—H74	0.9800
C1—C4A	1.530 (17)	C7A—H75	0.9800
C1—C2	1.559 (8)	C7A—H76	0.9800
C1—C2A	1.564 (17)	C8A—H84	0.9800
C2—H21	0.9800	C8A—H85	0.9800
C2—H22	0.9800	C8A—H86	0.9800
C2—H23	0.9800	C9—C14	1.390 (7)
C3—H31	0.9800	C9—C10	1.394 (7)
C3—H32	0.9800	C10—C11	1.398 (7)
C3—H33	0.9800	C10—H101	0.9500
C4—H41	0.9800	C11—C12	1.372 (9)
C4—H42	0.9800	C11—H111	0.9500
C4—H43	0.9800	C12—C13	1.365 (9)
C2A—H24	0.9800	C12—H121	0.9500
C2A—H25	0.9800	C13—C14	1.399 (7)
C2A—H26	0.9800	C13—H131	0.9500
C3A—H34	0.9800	C14—H141	0.9500
C3A—H35	0.9800	C15—C16	1.394 (7)
C3A—H36	0.9800	C15—C20	1.395 (6)
C4A—H44	0.9800	C16—C17	1.386 (8)
C4A—H45	0.9800	C16—H161	0.9500
C4A—H46	0.9800	C17—C18	1.385 (9)
C5—C6	1.500 (9)	C17—H171	0.9500
C5—C6A	1.51 (2)	C18—C19	1.379 (9)
C5—C8	1.523 (9)	C18—H181	0.9500
C5—C7	1.526 (8)	C19—C20	1.386 (7)
C5—C8A	1.53 (2)	C19—H191	0.9500
C5—C7A	1.54 (2)	C20—H201	0.9500
C6—H61	0.9800

N2—P1—N1	85.4 (2)	C8A—C5—C7A	101 (4)
N2—P1—Cl1	102.87 (15)	C5—C6—H61	109.5
N1—P1—Cl1	104.31 (15)	C5—C6—H62	109.5
N1—Si1—N2	82.08 (19)	H61—C6—H62	109.5
N1—Si1—C9	114.6 (2)	C5—C6—H63	109.5
N2—Si1—C9	112.4 (2)	H61—C6—H63	109.5
N1—Si1—C15	115.4 (2)	H62—C6—H63	109.5
N2—Si1—C15	117.0 (2)	C5—C7—H71	109.5
C9—Si1—C15	112.3 (2)	C5—C7—H72	109.5
C1—N1—P1	128.1 (3)	H71—C7—H72	109.5
C1—N1—Si1	135.4 (3)	C5—C7—H73	109.5
P1—N1—Si1	96.37 (19)	H71—C7—H73	109.5
C5—N2—P1	127.8 (4)	H72—C7—H73	109.5
C5—N2—Si1	135.5 (3)	C5—C8—H81	109.5
P1—N2—Si1	96.1 (2)	C5—C8—H82	109.5
N1—C1—C3A	111.8 (10)	H81—C8—H82	109.5
N1—C1—C3	109.0 (5)	C5—C8—H83	109.5
N1—C1—C4	110.6 (4)	H81—C8—H83	109.5
C3—C1—C4	114.2 (6)	H82—C8—H83	109.5
N1—C1—C4A	110.9 (9)	C5—C6A—H64	109.5
C3A—C1—C4A	116.3 (17)	C5—C6A—H65	109.5
N1—C1—C2	107.0 (4)	H64—C6A—H65	109.5
C3—C1—C2	108.5 (6)	C5—C6A—H66	109.5
C4—C1—C2	107.3 (6)	H64—C6A—H66	109.5
N1—C1—C2A	104.5 (9)	H65—C6A—H66	109.5
C3A—C1—C2A	109.1 (17)	C5—C7A—H74	109.5
C4A—C1—C2A	103.2 (15)	C5—C7A—H75	109.5
C1—C2—H21	109.5	H74—C7A—H75	109.5
C1—C2—H22	109.5	C5—C7A—H76	109.5
H21—C2—H22	109.5	H74—C7A—H76	109.5
C1—C2—H23	109.5	H75—C7A—H76	109.5
H21—C2—H23	109.5	C5—C8A—H84	109.5
H22—C2—H23	109.5	C5—C8A—H85	109.5
C1—C3—H31	109.5	H84—C8A—H85	109.5
C1—C3—H32	109.5	C5—C8A—H86	109.5
H31—C3—H32	109.5	H84—C8A—H86	109.5
C1—C3—H33	109.5	H85—C8A—H86	109.5
H31—C3—H33	109.5	C14—C9—C10	117.4 (4)
H32—C3—H33	109.5	C14—C9—Si1	123.8 (4)
C1—C4—H41	109.5	C10—C9—Si1	118.5 (4)
C1—C4—H42	109.5	C9—C10—C11	120.8 (5)
H41—C4—H42	109.5	C9—C10—H101	119.6
C1—C4—H43	109.5	C11—C10—H101	119.6
H41—C4—H43	109.5	C12—C11—C10	120.1 (5)
H42—C4—H43	109.5	C12—C11—H111	120.0
C1—C2A—H24	109.5	C10—C11—H111	120.0
C1—C2A—H25	109.5	C13—C12—C11	120.6 (5)
H24—C2A—H25	109.5	C13—C12—H121	119.7
C1—C2A—H26	109.5	C11—C12—H121	119.7
H24—C2A—H26	109.5	C12—C13—C14	119.4 (6)
H25—C2A—H26	109.5	C12—C13—H131	120.3
C1—C3A—H34	109.5	C14—C13—H131	120.3
C1—C3A—H35	109.5	C9—C14—C13	121.7 (5)
H34—C3A—H35	109.5	C9—C14—H141	119.2
C1—C3A—H36	109.5	C13—C14—H141	119.2
H34—C3A—H36	109.5	C16—C15—C20	117.7 (5)
H35—C3A—H36	109.5	C16—C15—Si1	123.3 (4)
C1—C4A—H44	109.5	C20—C15—Si1	118.9 (4)
C1—C4A—H45	109.5	C17—C16—C15	120.7 (6)
H44—C4A—H45	109.5	C17—C16—H161	119.6
C1—C4A—H46	109.5	C15—C16—H161	119.6
H44—C4A—H46	109.5	C18—C17—C16	120.4 (6)
H45—C4A—H46	109.5	C18—C17—H171	119.8
N2—C5—C6	110.7 (5)	C16—C17—H171	119.8
N2—C5—C6A	109.6 (19)	C19—C18—C17	119.8 (5)
N2—C5—C8	108.6 (4)	C19—C18—H181	120.1
C6—C5—C8	112.7 (7)	C17—C18—H181	120.1
N2—C5—C7	108.4 (4)	C18—C19—C20	119.6 (5)
C6—C5—C7	109.8 (6)	C18—C19—H191	120.2
C8—C5—C7	106.4 (6)	C20—C19—H191	120.2
N2—C5—C8A	104 (2)	C19—C20—C15	121.6 (5)
C6A—C5—C8A	130 (4)	C19—C20—H201	119.2
N2—C5—C7A	104.2 (19)	C15—C20—H201	119.2
C6A—C5—C7A	105 (4)

N2—P1—N1—C1	−174.3 (4)	P1—N2—C5—C8	144.0 (5)
Cl1—P1—N1—C1	−72.2 (4)	Si1—N2—C5—C8	−24.2 (8)
N2—P1—N1—Si1	1.9 (2)	P1—N2—C5—C7	−100.8 (6)
Cl1—P1—N1—Si1	104.00 (16)	Si1—N2—C5—C7	91.0 (6)
N2—Si1—N1—C1	173.9 (4)	P1—N2—C5—C8A	−13 (3)
C9—Si1—N1—C1	−75.0 (5)	Si1—N2—C5—C8A	179 (3)
C15—Si1—N1—C1	57.8 (5)	P1—N2—C5—C7A	92 (3)
N2—Si1—N1—P1	−1.8 (2)	Si1—N2—C5—C7A	−76 (3)
C9—Si1—N1—P1	109.3 (2)	N1—Si1—C9—C14	157.3 (4)
C15—Si1—N1—P1	−118.0 (2)	N2—Si1—C9—C14	−111.2 (4)
N1—P1—N2—C5	−173.6 (4)	C15—Si1—C9—C14	23.1 (5)
Cl1—P1—N2—C5	82.8 (4)	N1—Si1—C9—C10	−29.7 (5)
N1—P1—N2—Si1	−1.9 (2)	N2—Si1—C9—C10	61.8 (4)
Cl1—P1—N2—Si1	−105.51 (15)	C15—Si1—C9—C10	−163.9 (4)
N1—Si1—N2—C5	172.4 (5)	C14—C9—C10—C11	−2.0 (8)
C9—Si1—N2—C5	59.0 (5)	Si1—C9—C10—C11	−175.4 (4)
C15—Si1—N2—C5	−73.0 (5)	C9—C10—C11—C12	0.7 (9)
N1—Si1—N2—P1	1.8 (2)	C10—C11—C12—C13	0.4 (10)
C9—Si1—N2—P1	−111.6 (2)	C11—C12—C13—C14	−0.2 (10)
C15—Si1—N2—P1	116.4 (2)	C10—C9—C14—C13	2.2 (8)
P1—N1—C1—C3A	24.1 (17)	Si1—C9—C14—C13	175.3 (4)
Si1—N1—C1—C3A	−150.6 (16)	C12—C13—C14—C9	−1.1 (9)
P1—N1—C1—C3	−145.9 (6)	N1—Si1—C15—C16	−107.9 (4)
Si1—N1—C1—C3	39.5 (8)	N2—Si1—C15—C16	158.0 (4)
P1—N1—C1—C4	−19.6 (7)	C9—Si1—C15—C16	25.9 (5)
Si1—N1—C1—C4	165.8 (5)	N1—Si1—C15—C20	69.6 (4)
P1—N1—C1—C4A	155.6 (12)	N2—Si1—C15—C20	−24.4 (4)
Si1—N1—C1—C4A	−19.0 (13)	C9—Si1—C15—C20	−156.5 (4)
P1—N1—C1—C2	97.0 (5)	C20—C15—C16—C17	2.9 (8)
Si1—N1—C1—C2	−77.7 (6)	Si1—C15—C16—C17	−179.5 (5)
P1—N1—C1—C2A	−93.8 (12)	C15—C16—C17—C18	−1.3 (9)
Si1—N1—C1—C2A	91.6 (12)	C16—C17—C18—C19	−1.0 (10)
P1—N2—C5—C6	19.7 (8)	C17—C18—C19—C20	1.6 (9)
Si1—N2—C5—C6	−148.5 (7)	C18—C19—C20—C15	0.0 (9)
P1—N2—C5—C6A	−156 (4)	C16—C15—C20—C19	−2.3 (7)
Si1—N2—C5—C6A	36 (4)	Si1—C15—C20—C19	−180.0 (4)

Acknowledgements

We thank E. Hammes and P. Roloff for technical support.

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