{2,6-Bis[(dimethylamino-κN)methyl]phenyl-κC}iodopalladium(II) bis(diiodine)

The distorted square-planar coordination environment of the palladium(II) centre in [Pd(NCN)I]·2I₂ {NCN is 2,6-bis­[(di­methyl­amino)­methyl]­phenyl, C₁₂H₁₉N₂} is defined by the monoanionic terdentate NCN ligand and one iodide anion. Two neutral I₂ mol­ecules interact with the coordinated iodide anion at distances of ∼3.3 Å, suggesting an alternative description of the title compound as a palladium pentaiodide complex, i.e. [Pd(NCN)I₅]. Weaker interactions of ∼3.6 Å between the I₅⁻ anions link the complexes into a two-dimensional network.

S1. Comment

In its terdentate coordination mode, the monoanionic aryldiamine ligand 2,6-bis((dimethylamino)methyl)phenyl (NCN) acts as a rigid backbone with strong electron-donating ability (Albrecht & van Koten, 2001; Rietveld et al., 1997). The unique properties of this pincer ligand allowed the preparation of the first complex containing an end-on coordinated I₂ molecule, [Pt(NCN)I(η¹-I₂)] (van Beek et al., 1986; Gossage et al., 1999). A number of similar five-coordinate η¹-I₂—Pt complexes with aryldiamine pincer ligands have subsequently been reported (van Beek et al., 1990; Gossage et al., 1999). More recently, the unusual octahedral complex trans-[Pt(dmpe)₂I(η¹-I₂)]I₃ [dmpe is 1,2-bis(dimethylphosphino)ethane] has been synthesized (Makiura et al., 2001). These compounds have been proposed as models for the initial stage of the oxidative addition of dihalides to d⁸ transition metal complexes. An attempt to prepare an analogous palladium complex, [Pd(NCN)I(η¹-I₂)], by reaction of [Pd(NCN)I] with I₂ led to the isolation of purple crystals with the stoichiometry [Pd(NCN)I₅] (Gossage et al., 1999). In the title compound, [Pd(NCN)I]·2I₂, (I), two neutral I₂ molecules per [Pd(NCN)I] complex have been incorporated, but neither interacts strongly with the metal. Selected geometric parameters for (I) are presented in Table 1.

As shown in Fig. 1, the coordination environment of the palladium(II) centre in (I) is defined by the monoanionic NCN pincer ligand and one iodide anion. The terdentate NCN ligand is coordinated to the metal via the anionic C1 [Pd—C 1.920 (8) Å] and the two amine N atoms [Pd—N 2.111 (7)—2.126 (7) Å] at distances comparable to those in other NCN–Pd complexes, such as [(NCN)Pd(µ-Cl)Pd(NCN)]BF₄ [Terheijden et al., 1987; Pd—C 1.929 (4) Å and Pd—N 2.100 (4)–2.105 (3) Å]. The iodide anion is coordinated trans to C1, an sp² donor with a large trans influence, at a Pd—I distance of 2.7731 (10) Å that is somewhat longer than that observed in trans-[Pd{η¹-κC-(3,5-NCN)}(PPh₃)₂I] {3,5-NCN is 3,5-bis[(dimethylamino)methyl]phenyl; Spee et al., 2000; Pd—I 2.6968 (4)Å}. The small 80.2 (3)–81.3 (3)° range of C—Pd—N bite angles of the NCN ligand result in a distorted square-planar geometry at the metal; although the cis angles sum to 360.0 (5)°, they deviate by up to 13° from the ideal 90° values. The two five-membered PdC₃N chelate rings both adopt envelope conformations, but are puckered in opposite directions, with the N-donors mutually trans. Thus, the PdCN₂I coordination plane is tilted by 13.7 (4)° with respect to the plane of the aryl ring. The meridional coordination mode of the NCN ligand observed in (I) is typical of most square planar NCN–metal complexes, including [Pt(NCN)I] (Smeets et al., 1987), and results in approximate (non-crystallographic) C2 symmetry for [Pd(NCN)I].

Two neutral I₂ molecules are positioned 3.2720 (11) and 3.2886 (11) Å, respectively, from the coordinated iodide anion. These contacts are somewhat shorter than the weakly bonding 3.496 (6) Å intermolecular distance in the crystal structure of iodine. The bond lengths within the perturbed I₂ molecules [I—I 2.7477 (11)–2.7729 (11) Å], on the other hand, are slightly elongated compared to the 2.715 (6) Å intramolecular distance in elemental iodine (van Bolhuis et al., 1967). These considerations suggest an alternative description of the title compound as a palladium pentaiodide complex, [Pd(NCN)I₅], in which the I₅^- anion is an adduct of the type [I^-·2I₂]. The coordinated I₅^- anion is L-shaped, with inner and outer angles of 90.37 (2) and 172.42 (3)–175.53 (3)°, respectively, and is oriented such that one I₂ component is nearly perpendicular to the NCN aryl ring plane [83.5 (4)°]. The observed values of both the I—I—I angles and I—I distances in the coordinated ion fall within the range reported for free I₅^- anions (Cambridge Structural Database, Version 5.22 of October 2001; Allen & Kennard, 1993).

The [Pd(NCN)I₅] complexes are linked by weaker I···I interactions, listed in Table 2, that are nevertheless considerably shorter than the sum of the van der Waals radii (Bondi, 1964; 3.96 Å). The central I1 of one I₅^- anion interacts with the terminal I3 atom of the next [I1—I3ⁱ 3.5851 (13) Å; symmetry code: (i) 1 + x, y, z], forming infinite one-dimensional chains that run along the a direction. Head-to-tail I₅^-···I₅^- contacts [I3—I5ⁱⁱ 3.6495 (13) Å; symmetry code: (ii) x - 1, 1/2 - y, z - 1/2] link the chains into a two-dimensional network. In the anionic [I₅^-] substructure, kinked polyiodide nets composed of fused 12-membered rings, presented in Fig. 2, are stacked perpendicular to the b direction.

S2. Experimental

The title compound was prepared by adding I₂ to a solution of [Pd(NCN)I] in CH₂Cl₂. Purple crystals suitable for X-ray analysis were obtained after recrystallization of the crude product from a CH₂Cl₂/hexanes mixture (Gossage et al., 1999).

S3. Refinement

X-ray data were collected using Zr-filtered Mo Kα radiation with a collimator broad enough to accommodate the larger than usual maximum crystal dimension of 1.45 mm (Alexander & Smith, 1962). The aromatic and methylene H atoms were placed in idealized positions and allowed to ride on their C atoms, with C—H = 0.93 or 0.97 Å, respectively, and U_iso(H) = 1.2U_eq(C). The methyl H atoms were constrained to ideal geometries and allowed to rotate freely about their C—C bonds, with C—H = 0.96 Å and U_iso(H) = 1.5U_eq(C).

Computing details

Data collection: locally modified CAD-4 Software (de Boer & Duisenberg, 1984); cell refinement: SET4 (de Boer & Duisenberg, 1984); data reduction: HELENA (Spek, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2002); software used to prepare material for publication: PLATON.

Figures

	Fig. 1. PLATON/ORTEP representation (Spek, 2002) of (I) with displacement ellipsoids at the 50% probability level. The dashed lines indicate intermediate ~3.3 Å I—I bonds between the coordinated iodide anion and the neutral I2 molecules.
	Fig. 2. View down the b axis of the kinked two-dimensional [I5^-] net in (I). The I5^- anions are connected by weak ~3.6 Å I···I contacts, which are represented by the dashed lines [symmetry codes: (i) 1 + x, y, z; (ii) x - 1, 1/2 - y, z - 1/2; (iii) x - 1, y, z; (iv) 1 + x, 1/2 - y, 1/2 + z].

[2,6–Bis((dimethylamino–κN)methyl)phenyl–κC]iodopalladium(II) bis(diiodine)

Crystal data

[PdI(C12H19N2)]·2I2	F(000) = 1664
Mr = 932.19	Dx = 2.878 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 9.585 (2) Å	θ = 11.3–14.2°
b = 15.510 (2) Å	µ = 8.03 mm^−1
c = 15.865 (2) Å	T = 294 K
β = 114.198 (11)°	Needle, purple
V = 2151.3 (6) Å^3	1.45 × 0.38 × 0.30 mm
Z = 4

Data collection

Enraf-Nonius CAD-4F diffractometer	3296 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.038
Graphite monochromator	θmax = 25.0°, θmin = 1.9°
ω/2θ scans	h = −11→0
Absorption correction: analytical (ABSTOMPA in PLATON; Spek, 2002)	k = −18→0
Tmin = 0.063, Tmax = 0.140	l = −17→18
4036 measured reflections	2 standard reflections every 60 min
3796 independent reflections	intensity decay: 25%

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)] = 0.040	H-atom parameters constrained
wR(F^2) = 0.104	w = 1/[σ^2(Fo^2) + (0.0422P)^2 + 15.2774P] where P = (Fo^2 + 2Fc^2)/3
S = 1.16	(Δ/σ)max < 0.001
3796 reflections	Δρmax = 1.45 e Å^−3
186 parameters	Δρmin = −0.93 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00323 (15)

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
I1	0.96703 (7)	0.06200 (5)	0.35171 (4)	0.0532 (2)
I2	0.64297 (7)	0.04592 (4)	0.37342 (4)	0.0520 (2)
I3	0.35374 (8)	0.04854 (5)	0.37347 (5)	0.0618 (2)
I4	1.09363 (8)	0.20068 (5)	0.52348 (5)	0.0587 (2)
I5	1.18956 (8)	0.30849 (5)	0.67409 (5)	0.0575 (2)
Pd1	0.80241 (7)	0.08624 (4)	0.16342 (4)	0.03467 (19)
N1	0.7226 (8)	0.2141 (5)	0.1555 (5)	0.0404 (17)
N2	0.8403 (7)	−0.0398 (4)	0.1245 (5)	0.0355 (15)
C1	0.7047 (9)	0.0998 (6)	0.0316 (6)	0.0370 (18)
C2	0.6672 (10)	0.1808 (6)	−0.0046 (6)	0.042 (2)
C3	0.5996 (12)	0.1904 (7)	−0.1002 (7)	0.054 (2)
H3	0.5717	0.2447	−0.1266	0.065*
C4	0.5748 (12)	0.1189 (7)	−0.1551 (7)	0.055 (3)
H4	0.5311	0.1255	−0.2190	0.067*
C5	0.6134 (10)	0.0364 (6)	−0.1176 (6)	0.044 (2)
H5	0.5953	−0.0114	−0.1560	0.053*
C6	0.6786 (9)	0.0266 (6)	−0.0230 (6)	0.0384 (19)
C7	0.7107 (11)	0.2516 (6)	0.0657 (7)	0.046 (2)
H7A	0.6338	0.2967	0.0457	0.055*
H7B	0.8079	0.2765	0.0732	0.055*
C8	0.8183 (12)	0.2712 (7)	0.2325 (8)	0.061 (3)
H8A	0.7798	0.3291	0.2201	0.091*
H8B	0.9220	0.2701	0.2382	0.091*
H8C	0.8153	0.2514	0.2891	0.091*
C9	0.5674 (10)	0.2106 (6)	0.1544 (7)	0.046 (2)
H9A	0.5711	0.1800	0.2078	0.068*
H9B	0.4994	0.1814	0.0995	0.068*
H9C	0.5309	0.2682	0.1550	0.068*
C10	0.7183 (10)	−0.0566 (5)	0.0297 (6)	0.041 (2)
H10A	0.7548	−0.0980	−0.0024	0.049*
H10B	0.6282	−0.0804	0.0345	0.049*
C11	0.8305 (12)	−0.1102 (6)	0.1844 (7)	0.051 (2)
H11A	0.7328	−0.1083	0.1877	0.077*
H11B	0.9102	−0.1035	0.2453	0.077*
H11C	0.8423	−0.1646	0.1592	0.077*
C12	0.9940 (10)	−0.0410 (6)	0.1216 (7)	0.051 (2)
H12A	1.0113	−0.0965	0.1009	0.077*
H12B	1.0714	−0.0299	0.1822	0.077*
H12C	0.9980	0.0026	0.0797	0.077*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.0439 (3)	0.0746 (5)	0.0402 (3)	0.0008 (3)	0.0166 (3)	−0.0084 (3)
I2	0.0510 (4)	0.0567 (4)	0.0457 (4)	0.0038 (3)	0.0171 (3)	0.0014 (3)
I3	0.0511 (4)	0.0828 (5)	0.0517 (4)	0.0022 (4)	0.0211 (3)	0.0152 (4)
I4	0.0584 (4)	0.0566 (4)	0.0712 (5)	0.0034 (3)	0.0367 (4)	0.0055 (3)
I5	0.0611 (4)	0.0524 (4)	0.0725 (5)	−0.0007 (3)	0.0410 (4)	0.0026 (3)
Pd1	0.0313 (3)	0.0360 (4)	0.0373 (3)	−0.0007 (3)	0.0146 (3)	−0.0064 (3)
N1	0.033 (4)	0.035 (4)	0.056 (4)	−0.006 (3)	0.021 (3)	−0.019 (3)
N2	0.034 (4)	0.033 (4)	0.043 (4)	0.006 (3)	0.019 (3)	0.003 (3)
C1	0.033 (4)	0.044 (5)	0.033 (4)	0.004 (4)	0.013 (3)	0.005 (4)
C2	0.046 (5)	0.037 (5)	0.046 (5)	−0.009 (4)	0.024 (4)	−0.005 (4)
C3	0.068 (6)	0.049 (6)	0.053 (6)	0.006 (5)	0.031 (5)	0.015 (5)
C4	0.059 (6)	0.069 (7)	0.043 (5)	−0.006 (5)	0.027 (5)	0.006 (5)
C5	0.049 (5)	0.042 (5)	0.041 (5)	0.003 (4)	0.019 (4)	−0.005 (4)
C6	0.029 (4)	0.046 (5)	0.038 (4)	0.005 (4)	0.012 (3)	−0.006 (4)
C7	0.052 (5)	0.032 (5)	0.065 (6)	−0.005 (4)	0.035 (5)	−0.002 (4)
C8	0.055 (6)	0.044 (6)	0.069 (7)	−0.008 (5)	0.013 (5)	−0.027 (5)
C9	0.039 (5)	0.049 (5)	0.055 (5)	−0.002 (4)	0.025 (4)	−0.008 (4)
C10	0.039 (5)	0.036 (5)	0.043 (5)	−0.005 (4)	0.011 (4)	−0.011 (4)
C11	0.055 (6)	0.036 (5)	0.062 (6)	0.005 (4)	0.023 (5)	0.008 (4)
C12	0.042 (5)	0.047 (5)	0.064 (6)	0.005 (4)	0.021 (5)	−0.010 (5)

Geometric parameters (Å, º)

I1—Pd1	2.7731 (10)	C4—H4	0.9300
I1—I2	3.2720 (11)	C5—C6	1.378 (12)
I1—I4	3.2886 (11)	C5—H5	0.9300
I2—I3	2.7729 (11)	C6—C10	1.499 (12)
I4—I5	2.7477 (11)	C7—H7A	0.9700
Pd1—C1	1.920 (8)	C7—H7B	0.9700
Pd1—N1	2.111 (7)	C8—H8A	0.9600
Pd1—N2	2.126 (7)	C8—H8B	0.9600
N1—C9	1.481 (10)	C8—H8C	0.9600
N1—C8	1.483 (11)	C9—H9A	0.9600
N1—C7	1.500 (12)	C9—H9B	0.9600
N2—C11	1.475 (11)	C9—H9C	0.9600
N2—C12	1.493 (11)	C10—H10A	0.9700
N2—C10	1.502 (11)	C10—H10B	0.9700
C1—C2	1.367 (12)	C11—H11A	0.9600
C1—C6	1.387 (12)	C11—H11B	0.9600
C2—C3	1.393 (13)	C11—H11C	0.9600
C2—C7	1.498 (12)	C12—H12A	0.9600
C3—C4	1.368 (15)	C12—H12B	0.9600
C3—H3	0.9300	C12—H12C	0.9600
C4—C5	1.397 (14)
I1···I3^i	3.5851 (13)	I3···I5^ii	3.6495 (13)
Pd1—I1—I2	88.75 (3)	C5—C6—C10	127.0 (8)
Pd1—I1—I4	131.13 (3)	C1—C6—C10	114.6 (7)
I2—I1—I4	90.37 (2)	C2—C7—N1	108.2 (7)
I3—I2—I1	172.42 (3)	C2—C7—H7A	110.1
I5—I4—I1	175.53 (3)	N1—C7—H7A	110.1
C1—Pd1—N1	80.2 (3)	C2—C7—H7B	110.1
C1—Pd1—N2	81.3 (3)	N1—C7—H7B	110.1
N1—Pd1—N2	161.4 (3)	H7A—C7—H7B	108.4
C1—Pd1—I1	174.8 (2)	N1—C8—H8A	109.5
N1—Pd1—I1	102.9 (2)	N1—C8—H8B	109.5
N2—Pd1—I1	95.65 (19)	H8A—C8—H8B	109.5
C9—N1—C8	108.2 (7)	N1—C8—H8C	109.5
C9—N1—C7	108.5 (7)	H8A—C8—H8C	109.5
C8—N1—C7	109.4 (7)	H8B—C8—H8C	109.5
C9—N1—Pd1	107.7 (5)	N1—C9—H9A	109.5
C8—N1—Pd1	115.2 (6)	N1—C9—H9B	109.5
C7—N1—Pd1	107.8 (5)	H9A—C9—H9B	109.5
C11—N2—C12	109.6 (7)	N1—C9—H9C	109.5
C11—N2—C10	106.7 (7)	H9A—C9—H9C	109.5
C12—N2—C10	109.9 (7)	H9B—C9—H9C	109.5
C11—N2—Pd1	115.5 (5)	C6—C10—N2	109.0 (7)
C12—N2—Pd1	108.0 (5)	C6—C10—H10A	109.9
C10—N2—Pd1	107.1 (5)	N2—C10—H10A	109.9
C2—C1—C6	122.7 (8)	C6—C10—H10B	109.9
C2—C1—Pd1	119.0 (6)	N2—C10—H10B	109.9
C6—C1—Pd1	118.3 (6)	H10A—C10—H10B	108.3
C1—C2—C3	118.7 (8)	N2—C11—H11A	109.5
C1—C2—C7	114.6 (8)	N2—C11—H11B	109.5
C3—C2—C7	126.6 (9)	H11A—C11—H11B	109.5
C4—C3—C2	119.3 (9)	N2—C11—H11C	109.5
C4—C3—H3	120.4	H11A—C11—H11C	109.5
C2—C3—H3	120.4	H11B—C11—H11C	109.5
C3—C4—C5	121.7 (9)	N2—C12—H12A	109.5
C3—C4—H4	119.2	N2—C12—H12B	109.5
C5—C4—H4	119.2	H12A—C12—H12B	109.5
C6—C5—C4	119.2 (9)	N2—C12—H12C	109.5
C6—C5—H5	120.4	H12A—C12—H12C	109.5
C4—C5—H5	120.4	H12B—C12—H12C	109.5
C5—C6—C1	118.4 (8)
I2—I1—Pd1—N1	74.90 (19)	N2—Pd1—C1—C6	11.2 (6)
I4—I1—Pd1—N1	−14.49 (19)	C6—C1—C2—C3	0.1 (13)
I2—I1—Pd1—N2	−104.26 (18)	Pd1—C1—C2—C3	178.5 (7)
I4—I1—Pd1—N2	166.35 (18)	C6—C1—C2—C7	−177.5 (8)
C1—Pd1—N1—C9	90.2 (6)	Pd1—C1—C2—C7	0.9 (10)
N2—Pd1—N1—C9	83.3 (10)	C1—C2—C3—C4	−0.9 (14)
I1—Pd1—N1—C9	−94.1 (5)	C7—C2—C3—C4	176.4 (9)
C1—Pd1—N1—C8	−149.1 (7)	C2—C3—C4—C5	1.0 (15)
N2—Pd1—N1—C8	−155.9 (8)	C3—C4—C5—C6	−0.2 (15)
I1—Pd1—N1—C8	26.7 (7)	C4—C5—C6—C1	−0.6 (13)
C1—Pd1—N1—C7	−26.7 (5)	C4—C5—C6—C10	175.8 (9)
N2—Pd1—N1—C7	−33.5 (11)	C2—C1—C6—C5	0.7 (13)
I1—Pd1—N1—C7	149.1 (5)	Pd1—C1—C6—C5	−177.7 (6)
C1—Pd1—N2—C11	−143.3 (6)	C2—C1—C6—C10	−176.2 (8)
N1—Pd1—N2—C11	−136.5 (8)	Pd1—C1—C6—C10	5.4 (10)
I1—Pd1—N2—C11	41.0 (6)	C1—C2—C7—N1	−23.8 (10)
C1—Pd1—N2—C12	93.7 (6)	C3—C2—C7—N1	158.8 (9)
N1—Pd1—N2—C12	100.5 (9)	C9—N1—C7—C2	−83.2 (8)
I1—Pd1—N2—C12	−82.0 (5)	C8—N1—C7—C2	159.1 (7)
C1—Pd1—N2—C10	−24.6 (5)	Pd1—N1—C7—C2	33.2 (8)
N1—Pd1—N2—C10	−17.7 (11)	C5—C6—C10—N2	157.0 (8)
I1—Pd1—N2—C10	159.7 (5)	C1—C6—C10—N2	−26.5 (10)
N1—Pd1—C1—C2	15.0 (7)	C11—N2—C10—C6	157.0 (7)
N2—Pd1—C1—C2	−167.2 (7)	C12—N2—C10—C6	−84.2 (8)
N1—Pd1—C1—C6	−166.5 (7)	Pd1—N2—C10—C6	32.8 (8)

Symmetry codes: (i) x+1, y, z; (ii) x−1, −y+1/2, z−1/2.