4,4,6,6-Tetrachloro-2,2-(2,2-dimethylpropane-1,3-diyldioxy)-1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphorine

The title spiro­cyclic compound (alternative name: 2,2,4,4-tetra­chloro-9,9-di­methyl-7,11-dioxa-1,3,5-tri­aza-2λ⁵,4λ⁵,6λ⁵-triphospha­spiro­[5.5]­undeca-1,3,5-triene), C₅H₁₀Cl₄N₃O₂P₃, does not contain alternating long–short P—N bond lengths in the phosphazene ring [P—N 1.559 (2)–1.596 (2) Å], as are observed in other analogous spiro­cyclic compounds. The six-membered phosphazene ring has a chair conformation in the solid state, but a conformational equilibrium in solution is indicated by NMR spectroscopy.

S1. Comment

We are interested in utilizing substituted cyclotriphosphazenes as bases in our synthetic research. Since the most readily accessible among these, N₃P₃Cl₆, (I), has six reactive Cl atoms that can affect its utility, we wished to reduce the number of functionalities. One of the easiest ways to do this is to treat (I) with a suitable difunctional reagent and obtain `spiro' or `ansa' types of products (Contractor et al., 1984; Kumaraswamy et al., 1999; Chandrasekhar & Thomas, 1993). Since tetracoordinate P^V compounds with six-membered rings at the P are more stable to hydrolysis than those with five-membered rings, the diol 2,2-dimethyl-1,3-propanediol, which is cheaper than 1,3-propanediol, was used as the starting material. Differences in the reactivity patterns of these two diols were also studied, as observed in the reaction of the cyclodiphosphazane, (III), [ClPN-^tBu]₂ (Kumaravel et al., 1987; Kommana & Kumara Swamy, 2000). We found that the reaction of (I) with 2,2-dimethyl-1,3-propanediol gave the title spirocyclic compound, (II), as the only product. Herein we report the X-ray structure of (II). \sch

An ORTEX drawing of (II) is shown in Fig. 1. The bond distances and angles are in the normal range expected for compounds of this type (Chandrasekhar & Thomas, 1993). The P1—N1 distance is the longest, but P1—N3 is close in length to N2—P3 and N2—P2. This pattern is slightly different from those observed in analogous monospirocyclic cyclotriphosphazenes (Contractor et al., 1985; Kumaraswamy et al., 1999), wherein a long-short-long pattern for the ring P—N bond lengths was noted. The P—Cl bond lengths are within the normal range observed for analogous compounds (Contractor et al., 1984; Kumaraswamy et al., 1999).

The phosphazene ring can be considered to be planar, the maximum deviation from planarity of 0.135 Å being observed for N3. The 1,3,2-dioxaphosphorinane ring has the usual chair form, with atoms C2 and P1 above and below the mean plane containing O1, O3, C1 and C3. Since this feature would make the two methyl groups and the two H atoms of each OCH₂ group inequivalent (for examples giving NMR in solution and solid-state X-ray structures see Muthiah et al., 2000), the observed ¹H NMR spectrum in solution (i.e. equivalence of the methyl and OCH₂ H atoms) suggests a conformational equilibrium in solution.

Regarding intermolecular contacts, we note that atom C3 is close to O3 of a related molecule [C3···O3ⁱ 3.352 (3) Å; symmetry code: 2 - x, -y, 1 - z] and vice versa. The corresponding H3B···O3 distance is 2.88 Å. Although this is a minor point, it could be important in connection with our understanding of crystal packing and it has not been considered in the cyclophosphazene structures reported to date.

Related literature

For related literature, see: Chandrasekhar & Thomas (1993); Contractor et al. (1984, 1985); Kommana & Kumara Swamy (2000); Kumaraswamy et al. (1999); Kumaravel et al. (1987); Muthiah et al. (2000); Sheldrick (1997).

S2. Experimental

To a solution of N₃P₃Cl₆ (3.48 g, 10 mmol) in toluene (10 ml) was added a solution of 2,2-dimethyl-1,3-propanediol (1.04 g, 10 mmol) and triethylamine (2.02 g, 20 mmol) in toluene (10 ml) dropwise over 10 min with continuous stirring. The reaction mixture was then heated under reflux for 8 h, followed by filtration and removal of the solvent. The solid obtained was crystallized from dichloromethane-hexane (1:4) (yield 3.23 g, 85%; m.p. 427–428 K). Crystals were used for X-ray examination as obtained. ¹H NMR (CDCl₃, δ, p.p.m.): 1.10 [s, 6H, C(CH₃)₂], 4.12 (d, ³J_P—H = 14.0 Hz, 4H, OCH₂); ³¹P NMR: 1.3 (t, ²J_PP = 69.6 Hz, P_spiro), 22.6 (d, ²J_PP = 69.6 Hz, PCl₂).

S3. Refinement

H atoms were placed geometrically and refined using a riding model with the SHELXL97 (Sheldrick, 1997) defaults.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: SDP (Frenz, 1985); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEX (McArdle, 1995); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The molecular structure of (II) showing the atom-numbering scheme. Displacement ellipsoids are shown at the 25% probability level and H atoms have been omitted for clarity.

4,4,6,6-Tetrachloro-2,2-(2,2-dimethylpropane-1,3-diyldioxy)- 1,3,5,2λ⁵,4λ⁵,6λ⁵-triazatriphosphorine

Crystal data

C5H10Cl4N3O2P3	F(000) = 760
Mr = 378.87	Dx = 1.714 Mg m^−3
Monoclinic, P21/n	Melting point: 427-428K K
Hall symbol: -p_2yn	Mo Kα radiation, λ = 0.71073 Å
a = 12.106 (2) Å	Cell parameters from 25 reflections
b = 7.708 (2) Å	θ = 9.5–12.0°
c = 15.776 (2) Å	µ = 1.13 mm^−1
β = 93.997 (10)°	T = 293 K
V = 1468.5 (5) Å^3	Rectangular block, colourless
Z = 4	0.4 × 0.3 × 0.2 mm

Data collection

Enraf-Nonius MACH3 diffractometer	2135 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.014
Graphite monochromator	θmax = 25.0°, θmin = 2.1°
profile data from ω scans	h = 0→14
Absorption correction: ψ-scan (DATCOR; Reibenspies, 1989)	k = 0→9
Tmin = 0.662, Tmax = 0.806	l = −18→18
2693 measured reflections	3 standard reflections every 90 min
2571 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.029	H-atom parameters constrained
wR(F^2) = 0.083	w = 1/[σ^2(Fo^2) + (0.046P)^2 + 0.6318P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max = 0.001
2571 reflections	Δρmax = 0.29 e Å^−3
157 parameters	Δρmin = −0.28 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0198 (11)

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.

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

	x	y	z	Uiso*/Ueq
P1	0.79618 (5)	0.16178 (8)	0.55887 (4)	0.03942 (18)
P2	0.68778 (5)	0.13328 (7)	0.39980 (4)	0.03753 (17)
P3	0.74190 (6)	0.45278 (8)	0.46501 (4)	0.04539 (19)
Cl1	0.52712 (5)	0.06854 (9)	0.39184 (5)	0.0573 (2)
Cl2	0.73638 (6)	0.01798 (11)	0.29600 (4)	0.0622 (2)
Cl3	0.86624 (7)	0.59767 (11)	0.42789 (5)	0.0714 (2)
Cl4	0.62883 (7)	0.63274 (10)	0.48496 (6)	0.0769 (3)
O1	0.74559 (13)	0.0968 (2)	0.64185 (11)	0.0492 (4)
O2	0.92300 (13)	0.1267 (2)	0.57436 (10)	0.0475 (4)
N1	0.74802 (19)	0.0486 (3)	0.48000 (13)	0.0511 (6)
N2	0.6983 (2)	0.3359 (3)	0.38729 (13)	0.0527 (6)
N3	0.7768 (2)	0.3643 (3)	0.55212 (14)	0.0570 (6)
C1	0.7805 (2)	−0.0748 (4)	0.67355 (17)	0.0507 (6)
H1A	0.7556	−0.1625	0.6324	0.061*
H1B	0.7462	−0.0986	0.7261	0.061*
C2	0.9052 (2)	−0.0853 (4)	0.68916 (15)	0.0469 (6)
C3	0.9570 (2)	−0.0442 (4)	0.60650 (16)	0.0487 (6)
H3A	1.0370	−0.0477	0.6158	0.058*
H3B	0.9349	−0.1316	0.5645	0.058*
C21	0.9358 (3)	−0.2740 (5)	0.7121 (2)	0.0852 (11)
H21A	0.9031	−0.3057	0.7637	0.128*
H21B	1.0148	−0.2846	0.7201	0.128*
H21C	0.9085	−0.3495	0.6670	0.128*
C22	0.9459 (3)	0.0399 (6)	0.75896 (18)	0.0792 (11)
H22A	0.9297	0.1567	0.7411	0.119*
H22B	1.0244	0.0266	0.7702	0.119*
H22C	0.9093	0.0153	0.8097	0.119*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P1	0.0459 (3)	0.0396 (3)	0.0316 (3)	−0.0032 (3)	−0.0051 (2)	0.0009 (2)
P2	0.0441 (3)	0.0323 (3)	0.0347 (3)	−0.0015 (2)	−0.0077 (2)	−0.0027 (2)
P3	0.0581 (4)	0.0301 (3)	0.0465 (4)	−0.0052 (3)	−0.0063 (3)	−0.0007 (3)
Cl1	0.0431 (3)	0.0604 (4)	0.0675 (4)	−0.0038 (3)	−0.0018 (3)	−0.0015 (3)
Cl2	0.0612 (4)	0.0769 (5)	0.0482 (4)	0.0046 (4)	0.0008 (3)	−0.0202 (3)
Cl3	0.0746 (5)	0.0652 (5)	0.0741 (5)	−0.0272 (4)	0.0028 (4)	−0.0003 (4)
Cl4	0.0763 (5)	0.0458 (4)	0.1080 (7)	0.0106 (4)	0.0023 (5)	−0.0067 (4)
O1	0.0418 (9)	0.0616 (11)	0.0445 (9)	0.0093 (8)	0.0049 (7)	0.0103 (8)
O2	0.0439 (9)	0.0594 (11)	0.0391 (9)	−0.0084 (8)	0.0014 (7)	0.0092 (8)
N1	0.0729 (15)	0.0315 (10)	0.0454 (12)	−0.0003 (10)	−0.0206 (11)	0.0010 (9)
N2	0.0752 (15)	0.0357 (11)	0.0442 (11)	−0.0087 (10)	−0.0173 (10)	0.0061 (9)
N3	0.0878 (17)	0.0393 (12)	0.0414 (11)	−0.0024 (11)	−0.0130 (11)	−0.0071 (9)
C1	0.0458 (14)	0.0583 (16)	0.0484 (14)	0.0012 (12)	0.0073 (11)	0.0165 (12)
C2	0.0437 (13)	0.0618 (16)	0.0349 (12)	0.0065 (12)	0.0008 (10)	0.0092 (11)
C3	0.0389 (12)	0.0640 (17)	0.0432 (13)	0.0060 (12)	0.0031 (10)	0.0035 (12)
C21	0.080 (2)	0.089 (3)	0.088 (2)	0.030 (2)	0.0160 (19)	0.042 (2)
C22	0.070 (2)	0.128 (3)	0.0375 (15)	0.007 (2)	−0.0124 (13)	−0.0102 (17)

Geometric parameters (Å, º)

P1—N1	1.596 (2)	C1—C2	1.515 (3)
P1—N3	1.581 (2)	C1—H1A	0.9700
P1—O1	1.5656 (18)	C1—H1B	0.9700
P1—O2	1.5613 (18)	C2—C21	1.538 (4)
P2—Cl1	2.0034 (9)	C2—C22	1.520 (4)
P2—Cl2	1.9880 (9)	C2—C3	1.519 (3)
P2—N1	1.559 (2)	C3—H3A	0.9700
P2—N2	1.581 (2)	C3—H3B	0.9700
P3—Cl3	1.9946 (10)	C21—H21A	0.9600
P3—Cl4	1.9892 (11)	C21—H21B	0.9600
P3—N2	1.582 (2)	C21—H21C	0.9600
P3—N3	1.565 (2)	C22—H22A	0.9600
O1—C1	1.466 (3)	C22—H22B	0.9600
O2—C3	1.461 (3)	C22—H22C	0.9600
N1—P1—N3	116.26 (11)	C2—C1—H1B	109.4
O1—P1—O2	104.57 (9)	H1A—C1—H1B	108.0
O1—P1—N1	109.52 (11)	C1—C2—C3	108.4 (2)
O1—P1—N3	107.88 (12)	C1—C2—C22	110.7 (2)
O2—P1—N1	109.22 (11)	C3—C2—C22	110.9 (2)
O2—P1—N3	108.75 (12)	C1—C2—C21	108.0 (2)
Cl1—P2—Cl2	100.29 (4)	C3—C2—C21	107.0 (2)
N1—P2—Cl1	110.11 (9)	C22—C2—C21	111.6 (3)
N1—P2—Cl2	109.45 (9)	O2—C3—C2	111.3 (2)
N1—P2—N2	118.54 (11)	O2—C3—H3A	109.4
N2—P2—Cl1	108.95 (9)	C2—C3—H3A	109.4
N2—P2—Cl2	107.93 (9)	O2—C3—H3B	109.4
Cl3—P3—Cl4	101.40 (5)	C2—C3—H3B	109.4
N2—P3—Cl3	107.99 (10)	H3A—C3—H3B	108.0
N2—P3—Cl4	108.88 (10)	C2—C21—H21A	109.5
N3—P3—Cl3	109.81 (10)	C2—C21—H21B	109.5
N3—P3—Cl4	108.14 (10)	H21A—C21—H21B	109.5
N2—P3—N3	119.16 (11)	C2—C21—H21C	109.5
P1—N1—P2	121.92 (13)	H21A—C21—H21C	109.5
P1—N3—P3	121.27 (13)	H21B—C21—H21C	109.5
P2—N2—P3	119.42 (13)	C2—C22—H22A	109.5
C1—O1—P1	116.97 (15)	C2—C22—H22B	109.5
C3—O2—P1	117.42 (15)	H22A—C22—H22B	109.5
O1—C1—C2	111.3 (2)	C2—C22—H22C	109.5
O1—C1—H1A	109.4	H22A—C22—H22C	109.5
C2—C1—H1A	109.4	H22B—C22—H22C	109.5
O1—C1—H1B	109.4