An N-bridged tritungsten compound for the chemical vapor deposition of WN_x thin films

In the title compound, octa­chlorido-1κ⁴Cl,3κ⁴Cl-di-μ₂-nitrido-1:2κ²N:N;2:3κ²N:N-tetra­pyridine-1κN,2κ²N,3κN-bis­(trimeth­yl­silylimido-2κN)tritungsten(V) dichloro­methane disolvate, [W₃(C₃H₉NSi)₂Cl₈N₂(C₅H₅N)₄]·2CH₂Cl₂, the central W metal atom is located on a twofold rotation axis and is coordinated in a distorted octa­hedral environment by two trimethyl­silylimido groups, two pyridine mol­ecules and two μ-N atoms which bridge it to the two other W atoms. These terminal W centers also show a distorted octa­hedral coordination, the bridging N atom and the pyridine ligand being trans with respect to each other. Additionally, four Cl atoms are bound to each terminal W atom, in a square-planar geometry, completing the octa­hedral coordination.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.008 Å
• R factor = 0.029
• wR factor = 0.054
• Data-to-parameter ratio = 23.7

checkCIF/PLATON results

No syntax errors found



Alert level C
GOODF01_ALERT_2_C  The least squares goodness of fit parameter lies
            outside the range 0.80 <> 2.00
            Goodness of fit given =      0.758
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.51 Ratio
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.09 Ratio
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        Si1
PLAT244_ALERT_4_C Low   'Solvent' Ueq as Compared to Neighbors for        C14

Alert level G
PLAT794_ALERT_5_G Check Predicted Bond Valency for W1          (9)       7.09

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   6 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

---

S1. Comment

The title compound is a C₂-symmetric trimetallic tungsten complex incorporating two µ-N moieties which are fairly rare in organometallic chemistry with only a few reported occurrences (Ergezinger et al., 1989). The W1—N2 bond distance of 2.090 (4) Å is in the range of W—N single bonds seen in tungsten amido compounds (Wu et al., 2006), whereas the W2—N2 bond (1.707 (4) Å) more closely resembles a tungsten imido triple bond (Bradley et al., 1987). Both bond lengths are comparable to the bond lengths seen in [WNCl₃(PhCN)]₄.3CH₂Cl₂, a compound which also incorporates a µ-N moiety (Ergezinger et al., 1989). This observation is further corroborated by a W2—N2—W1 bond angle of 169.2° which is typical for tungsten imido complexes (Bradley et al., 1983). The trimethylsilyl-imido functionality with a W1—N1 bond distance of 1.773 (4) Å and a W1—N1—Si1 bond angle of 169.3° are similar to reported values (Rische et al., 2006). The W—Cl bonds averaging 2.33 Å are within the expected range for chlorine rich tungsten imido complexes (Orpen et al., 1989). The W1—N3(py) bond length of 2.326 (4) Å is consistent with reported values whereas the W2—N4(py) bond (2.424 (4) Å) seems to be elongated due to the decreased trans-effect of the trimethylsilyl imido ligand compared to the bridging µ-N atom (Rische et al., 2006). Although the complex is C₂-symmetric in the solid state, two resonances (δ 0.77 and 0.76 p.p.m.) can be observed in the ¹H NMR spectrum.

Related literature

Closely related structures were reported by Dehnicke & Strähle (1992) and Ergezinger et al. (1989). For related literature concerning the properties of tungsten nitrides, see: Dehnicke & Strähle (1965). For properties of tungsten–imido complexes and their application in chemical vapor deposition, see: Bradley et al., (1983, 1987) Bchir et al.(2005), Orpen et al., (1989) and Rische et al. (2006). For related literature, see: Wu et al. (2006).

S2. Experimental

In a 250 ml Schlenk flask WCl₆ (3.75 g, 9.46 mmol) was suspended in 100 ml of toluene. 1,1,1,3,3,3-Hexamethyldisilazane (2.76 ml, 13.2 mmol) and of pyridine (4.08 ml, 50.4 mmol) were added via syringe at room temperature. The reaction mixture was stirred for an additional 24 h. The resulting red solution was filtered and the solvent removed in vacuo. The remaining solid was extracted with 2 x 10 ml of methylene chloride. The extracts were combined and filtered. The solution was layered with an equal volume of pentane and cooled to 248 K (-25 °C) to yield the pure title compound as a red crystalline solid. Yield 411 mg (10%, 3.15 mmol). ¹H NMR (Benzene-d₆, 298 K): δ 9.70 (br s, 4H, aromatic), 9.42 (d, 4H, aromatic), 6.95 (br s, 6H, aromatic), 6.73 (t, 2H, aromatic), 6.48 (t, 4H, aromatic), 0.77 (s, 9H, (SiCH₃)₃), 0.76 (s, 9H, (SiCH₃)₃). ¹³C NMR (Benzene-d₆, 298 K): δ 3.59 (Si(CH₃)₃), 124.36 (aromatic), 125.07 (aromatic), 138.10 (aromatic), 139.35 (aromatic), 152.11 (aromatic), 153.26 (aromatic).

S3. Refinement

The H atoms were placed in idealized positions and were refined riding on their parent atoms. C—H distances of 0.98 and 0.95 Å were used for aromatic and methyl atoms respectively. The H atoms thermal parameters were 1.2U_eq of the parent C; 1.5U~eq~ for the methyl atoms.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker 1998); data reduction: SHELXTL (Sheldrick, 2000); program(s) used to solve structure: SHELXTL (Sheldrick, 2000); program(s) used to refine structure: SHELXTL (Sheldrick, 2000); molecular graphics: SHELXTL (Sheldrick, 2000); software used to prepare material for publication: SHELXTL (Sheldrick, 2000).

Figures

Fig. 1. : The molecular structure with 50% probability ellipsoids, showing the atom labeling scheme. Subscript "A" in the atomic labels denotes atoms created by the symmetry operation i = (x + 1, y, z + 1/2).

octachlorido-1κ⁴Cl,3κ⁴Cl-di-µ₂-nitrido-1:2κ²N:N;2:3κ²N:N-tetrapyridine-1κN,2κ²N,3κN-bis(trimethylsilylimido-2κN)tritungsten(V) dichloromethane disolvate

Crystal data

[W3(C3H9NSi)2Cl8N2(C5H5N)4]·2CH2Cl2	F(000) = 2880
Mr = 1523.83	Dx = 2.036 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.0546 (8) Å	Cell parameters from 4105 reflections
b = 19.5493 (15) Å	θ = 2.0–28.0°
c = 25.359 (2) Å	µ = 7.65 mm^−1
β = 94.329 (2)°	T = 173 K
V = 4970.3 (7) Å^3	Plate, red
Z = 4	0.34 × 0.29 × 0.04 mm

Data collection

Bruker SMART CCD area-detector diffractometer	5688 independent reflections
Radiation source: fine-focus sealed tube	3802 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.074
ω scans	θmax = 27.5°, θmin = 1.6°
Absorption correction: integration [based on measured indexed crystal faces (SHELXTL; Sheldrick, 2000)]	h = −12→12
Tmin = 0.107, Tmax = 0.736	k = −23→25
15825 measured reflections	l = −30→32

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)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.054	H-atom parameters constrained
S = 0.76	w = 1/[σ^2(Fo^2) + (0.0063P)^2] where P = (Fo^2 + 2Fc^2)/3
5688 reflections	(Δ/σ)max = 0.002
240 parameters	Δρmax = 1.54 e Å^−3
0 restraints	Δρmin = −1.24 e Å^−3

Special details

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

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

The asymmetric unit consists of a half complex and a dichloromethane molecule.

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

	x	y	z	Uiso*/Ueq
W1	0.5000	0.579772 (14)	0.2500	0.02631 (8)
W2	0.700778 (18)	0.558005 (11)	0.130958 (9)	0.02924 (6)
Cl1	0.75725 (13)	0.44150 (7)	0.13040 (6)	0.0456 (4)
Cl2	0.91447 (12)	0.57892 (8)	0.17020 (6)	0.0528 (4)
Cl3	0.67204 (14)	0.67298 (7)	0.11095 (6)	0.0488 (4)
Cl4	0.51146 (11)	0.53051 (7)	0.07504 (5)	0.0388 (3)
Cl5	0.14238 (18)	0.81650 (10)	0.01595 (9)	0.0922 (7)
Cl6	−0.12476 (16)	0.79117 (9)	0.04710 (7)	0.0704 (5)
Si1	0.29608 (13)	0.70110 (8)	0.18333 (7)	0.0444 (4)
N1	0.3864 (3)	0.6351 (2)	0.21422 (16)	0.0335 (11)
N2	0.6182 (3)	0.5604 (2)	0.18735 (16)	0.0310 (10)
N3	0.3784 (3)	0.4851 (2)	0.21409 (16)	0.0295 (10)
N4	0.8088 (4)	0.5616 (2)	0.04871 (17)	0.0350 (11)
C1	0.1684 (5)	0.7262 (3)	0.2266 (3)	0.075 (2)
H1A	0.2109	0.7445	0.2597	0.112*
H1B	0.1142	0.6863	0.2343	0.112*
H1C	0.1113	0.7614	0.2092	0.112*
C2	0.2213 (6)	0.6674 (4)	0.1205 (2)	0.086 (3)
H2A	0.1617	0.6293	0.1275	0.129*
H2B	0.2919	0.6512	0.0990	0.129*
H2C	0.1703	0.7037	0.1015	0.129*
C3	0.4096 (6)	0.7721 (3)	0.1717 (3)	0.091 (3)
H3A	0.4485	0.7895	0.2057	0.136*
H3B	0.3601	0.8088	0.1526	0.136*
H3C	0.4810	0.7559	0.1506	0.136*
C4	0.2439 (5)	0.4848 (3)	0.2134 (2)	0.0410 (15)
H4A	0.2010	0.5232	0.2276	0.049*
C5	0.1662 (6)	0.4319 (3)	0.1934 (2)	0.0494 (16)
H5A	0.0720	0.4338	0.1941	0.059*
C6	0.2253 (6)	0.3769 (3)	0.1726 (2)	0.0560 (18)
H6A	0.1729	0.3395	0.1592	0.067*
C7	0.3623 (6)	0.3757 (3)	0.1709 (2)	0.0441 (15)
H7A	0.4060	0.3384	0.1555	0.053*
C8	0.4322 (5)	0.4299 (2)	0.1920 (2)	0.0363 (13)
H8A	0.5264	0.4288	0.1911	0.044*
C9	0.7786 (5)	0.5171 (3)	0.0082 (2)	0.0414 (15)
H9A	0.7151	0.4820	0.0128	0.050*
C10	0.8371 (5)	0.5209 (3)	−0.0397 (2)	0.0456 (15)
H10A	0.8128	0.4895	−0.0673	0.055*
C11	0.9305 (5)	0.5707 (3)	−0.0464 (2)	0.0495 (16)
H11A	0.9723	0.5737	−0.0787	0.059*
C12	0.9635 (5)	0.6164 (3)	−0.0061 (2)	0.0450 (15)
H12A	1.0274	0.6514	−0.0103	0.054*
C13	0.9011 (5)	0.6101 (3)	0.0410 (2)	0.0425 (15)
H13A	0.9245	0.6413	0.0688	0.051*
C14	−0.0070 (6)	0.8512 (3)	0.0316 (3)	0.0626 (19)
H14A	−0.0442	0.8788	0.0013	0.075*
H14B	0.0100	0.8824	0.0621	0.075*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
W1	0.02293 (14)	0.02997 (17)	0.02613 (19)	0.000	0.00256 (12)	0.000
W2	0.02455 (10)	0.03619 (13)	0.02732 (13)	−0.00144 (9)	0.00412 (8)	0.00063 (10)
Cl1	0.0468 (7)	0.0413 (8)	0.0502 (10)	0.0111 (6)	0.0139 (7)	0.0082 (7)
Cl2	0.0292 (7)	0.0874 (12)	0.0414 (10)	−0.0116 (7)	−0.0003 (6)	0.0000 (8)
Cl3	0.0599 (9)	0.0359 (8)	0.0531 (11)	−0.0014 (7)	0.0215 (7)	0.0034 (7)
Cl4	0.0298 (6)	0.0512 (8)	0.0349 (9)	−0.0032 (6)	−0.0007 (6)	−0.0006 (7)
Cl5	0.0739 (12)	0.0853 (15)	0.120 (2)	0.0036 (11)	0.0277 (12)	0.0040 (13)
Cl6	0.0784 (11)	0.0629 (11)	0.0714 (14)	−0.0211 (9)	0.0153 (9)	−0.0163 (9)
Si1	0.0259 (7)	0.0428 (10)	0.0640 (13)	0.0041 (7)	0.0001 (7)	0.0170 (9)
N1	0.032 (2)	0.037 (3)	0.031 (3)	0.0010 (19)	0.005 (2)	0.005 (2)
N2	0.0173 (19)	0.048 (3)	0.027 (3)	−0.0022 (18)	−0.0010 (17)	−0.006 (2)
N3	0.024 (2)	0.036 (3)	0.027 (3)	−0.0002 (18)	0.0007 (18)	0.003 (2)
N4	0.029 (2)	0.047 (3)	0.029 (3)	0.001 (2)	0.0058 (19)	0.002 (2)
C1	0.052 (4)	0.064 (5)	0.109 (7)	0.021 (3)	0.018 (4)	0.000 (4)
C2	0.063 (4)	0.146 (7)	0.047 (5)	−0.004 (5)	−0.017 (4)	0.027 (5)
C3	0.051 (4)	0.047 (4)	0.176 (9)	0.005 (3)	0.021 (5)	0.033 (5)
C4	0.030 (3)	0.057 (4)	0.035 (4)	−0.008 (3)	−0.005 (2)	0.006 (3)
C5	0.040 (3)	0.064 (4)	0.043 (4)	−0.014 (3)	−0.003 (3)	−0.001 (3)
C6	0.064 (4)	0.049 (4)	0.053 (5)	−0.024 (3)	−0.009 (3)	0.004 (3)
C7	0.062 (4)	0.034 (3)	0.037 (4)	−0.008 (3)	0.006 (3)	−0.004 (3)
C8	0.039 (3)	0.038 (3)	0.032 (3)	−0.003 (2)	0.006 (3)	0.003 (3)
C9	0.033 (3)	0.045 (4)	0.045 (4)	−0.004 (2)	−0.004 (3)	−0.004 (3)
C10	0.039 (3)	0.068 (4)	0.029 (4)	0.008 (3)	0.002 (3)	−0.009 (3)
C11	0.036 (3)	0.084 (5)	0.030 (4)	0.010 (3)	0.013 (3)	0.016 (3)
C12	0.037 (3)	0.062 (4)	0.038 (4)	0.000 (3)	0.010 (3)	0.006 (3)
C13	0.031 (3)	0.053 (4)	0.043 (4)	−0.003 (3)	0.006 (3)	0.001 (3)
C14	0.081 (4)	0.042 (4)	0.067 (5)	−0.002 (3)	0.024 (4)	0.009 (3)

Geometric parameters (Å, º)

W1—N1^i	1.773 (4)	C2—H2B	0.9800
W1—N1	1.773 (4)	C2—H2C	0.9800
W1—N2	2.090 (4)	C3—H3A	0.9800
W1—N2^i	2.090 (4)	C3—H3B	0.9800
W1—N3^i	2.362 (4)	C3—H3C	0.9800
W1—N3	2.362 (4)	C4—C5	1.370 (7)
W2—N2	1.707 (4)	C4—H4A	0.9500
W2—Cl3	2.3174 (14)	C5—C6	1.356 (8)
W2—Cl2	2.3347 (12)	C5—H5A	0.9500
W2—Cl1	2.3475 (13)	C6—C7	1.382 (7)
W2—Cl4	2.3486 (12)	C6—H6A	0.9500
W2—N4	2.424 (4)	C7—C8	1.358 (6)
Cl5—C14	1.721 (6)	C7—H7A	0.9500
Cl6—C14	1.733 (6)	C8—H8A	0.9500
Si1—N1	1.730 (4)	C9—C10	1.390 (7)
Si1—C1	1.819 (6)	C9—H9A	0.9500
Si1—C2	1.831 (6)	C10—C11	1.373 (7)
Si1—C3	1.835 (6)	C10—H10A	0.9500
N3—C8	1.349 (6)	C11—C12	1.379 (8)
N3—C4	1.351 (6)	C11—H11A	0.9500
N4—C13	1.351 (6)	C12—C13	1.396 (7)
N4—C9	1.364 (6)	C12—H12A	0.9500
C1—H1A	0.9800	C13—H13A	0.9500
C1—H1B	0.9800	C14—H14A	0.9900
C1—H1C	0.9800	C14—H14B	0.9900
C2—H2A	0.9800
N1^i—W1—N1	104.8 (2)	H1B—C1—H1C	109.5
N1^i—W1—N2	96.79 (16)	Si1—C2—H2A	109.5
N1—W1—N2	95.93 (16)	Si1—C2—H2B	109.5
N1^i—W1—N2^i	95.93 (17)	H2A—C2—H2B	109.5
N1—W1—N2^i	96.79 (16)	Si1—C2—H2C	109.5
N2—W1—N2^i	159.1 (2)	H2A—C2—H2C	109.5
N1^i—W1—N3^i	89.20 (15)	H2B—C2—H2C	109.5
N1—W1—N3^i	165.99 (15)	Si1—C3—H3A	109.5
N2—W1—N3^i	80.98 (14)	Si1—C3—H3B	109.5
N2^i—W1—N3^i	82.67 (14)	H3A—C3—H3B	109.5
N1^i—W1—N3	165.99 (15)	Si1—C3—H3C	109.5
N1—W1—N3	89.20 (15)	H3A—C3—H3C	109.5
N2—W1—N3	82.67 (14)	H3B—C3—H3C	109.5
N2^i—W1—N3	80.98 (14)	N3—C4—C5	123.4 (5)
N3^i—W1—N3	76.87 (18)	N3—C4—H4A	118.3
N2—W2—Cl3	95.54 (14)	C5—C4—H4A	118.3
N2—W2—Cl2	97.36 (11)	C6—C5—C4	119.3 (5)
Cl3—W2—Cl2	91.09 (5)	C6—C5—H5A	120.4
N2—W2—Cl1	99.47 (14)	C4—C5—H5A	120.4
Cl3—W2—Cl1	164.98 (5)	C5—C6—C7	119.6 (5)
Cl2—W2—Cl1	87.55 (5)	C5—C6—H6A	120.2
N2—W2—Cl4	95.10 (11)	C7—C6—H6A	120.2
Cl3—W2—Cl4	90.45 (5)	C8—C7—C6	117.5 (6)
Cl2—W2—Cl4	167.24 (5)	C8—C7—H7A	121.3
Cl1—W2—Cl4	87.69 (5)	C6—C7—H7A	121.3
N2—W2—N4	175.95 (16)	N3—C8—C7	125.2 (5)
Cl3—W2—N4	80.80 (10)	N3—C8—H8A	117.4
Cl2—W2—N4	84.49 (10)	C7—C8—H8A	117.4
Cl1—W2—N4	84.18 (10)	N4—C9—C10	122.6 (5)
Cl4—W2—N4	83.25 (10)	N4—C9—H9A	118.7
N1—Si1—C1	107.3 (3)	C10—C9—H9A	118.7
N1—Si1—C2	107.0 (3)	C11—C10—C9	119.1 (5)
C1—Si1—C2	111.1 (3)	C11—C10—H10A	120.5
N1—Si1—C3	109.0 (2)	C9—C10—H10A	120.5
C1—Si1—C3	111.6 (3)	C10—C11—C12	119.7 (6)
C2—Si1—C3	110.6 (3)	C10—C11—H11A	120.2
Si1—N1—W1	169.3 (3)	C12—C11—H11A	120.2
W2—N2—W1	169.2 (2)	C11—C12—C13	118.6 (6)
C8—N3—C4	115.1 (4)	C11—C12—H12A	120.7
C8—N3—W1	125.1 (3)	C13—C12—H12A	120.7
C4—N3—W1	119.8 (3)	N4—C13—C12	122.9 (5)
C13—N4—C9	117.1 (5)	N4—C13—H13A	118.5
C13—N4—W2	120.1 (4)	C12—C13—H13A	118.5
C9—N4—W2	122.8 (4)	Cl5—C14—Cl6	114.1 (3)
Si1—C1—H1A	109.5	Cl5—C14—H14A	108.7
Si1—C1—H1B	109.5	Cl6—C14—H14A	108.7
H1A—C1—H1B	109.5	Cl5—C14—H14B	108.7
Si1—C1—H1C	109.5	Cl6—C14—H14B	108.7
H1A—C1—H1C	109.5	H14A—C14—H14B	107.6

Symmetry code: (i) −x+1, y, −z+1/2.