Bis­(tetra-n-butyl­ammonium) (μ-N,N′-diselenium dinitride)­bis­[tri­bromo­palladate(II)]

Aucott, S.M.; Dale, S.H.; Elsegood, M.R.J.; Holmes, K.E.; James, S.L.M.; Kelly, P.F.

doi:10.1107/S0108270104027040

metal-organic compounds

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 60| Part 12| December 2004| Pages m643-m644

doi:10.1107/S0108270104027040

Bis(tetra-n-butylammonium) (μ-N,N′-diselenium dinitride)bis[tribromopalladate(II)]

Stephen M. Aucott,^a Sophie H. Dale,^a Mark R. J. Elsegood,^a Kathryn E. Holmes,^a Sarah L. M. James ^a and Paul F. Kelly ^a ^*

^aChemistry Department, Loughborough University, Loughborough, Leicestershire LE11 3TU, England
^*Correspondence e-mail: p.f.kelly@lboro.ac.uk

(Received 12 October 2004; accepted 25 October 2004; online 11 November 2004)

The reaction of Se₄N₄ with (Bu₄N)₂[Pd₂Br₆] gives the title compound, (C₁₆H₃₆N)₂[Pd₂Br₆(N₂Se₂)], in good yield. The [Pd₂(Se₂N₂)Br₆]²⁻ anion lies on an inversion centre, and therefore the asymmetric unit contains half a formula unit. The crystal structure confirms the coordination of the Se₂N₂ unit to Pd through the N atoms, as previously assigned by IR spectroscopic analysis [Kelly, Slawin & Soriano-Rama (1997 ). J. Chem. Soc. Dalton Trans. pp. 559–562]. The title compound contains the longest Pd—N bond so far observed for such systems.

Comment

During the course of our work on the reactivity of Se₄N₄ towards metal centres, we have successfully demonstrated that, under the right circumstances, adducts of diselenium dinitride, Se₂N₂, can be generated. Examples so far fully characterized by X-ray crystallography are (AlBr₃)₂(Se₂N₂) (Kelly & Slawin, 1996 ), (PPh₄)₂[Pd₂(Se₂N₂)Br₆] (Kelly et al., 1997) and (PPh₄)₂[Pd₂(Se₂N₂)Cl₆] (Kelly & Slawin, 1995 ). All are of great interest due to the fact that, unlike its sulfur analogue (the four-membered ring S₂N₂), Se₂N₂ is unknown in the free state. Thus, these compounds have the potential to act as sources of the free material via appropriate substitution reactions.

In terms of performing such reactions, however, the aluminium compound is hampered by its extreme air-sensitivity, while the tetraphenylphosphonium salts of the air-stable palladium adducts form in rather poor yield. By far the best yield thus far obtained for one of these palladium adducts occurs when Se₄N₄ is reacted with (Bu₄N)₂[Pd₂Br₆] to give (Bu₄N)₂[Pd₂(Se₂N₂)Br₆], (I) [typically ca 67% yield, compared with ca 20% for the tetraphenylphosphonium salts]. However, in our previous report on this compound, we used only IR spectroscopy and microanalysis as characterization techniques (Kelly et al., 1997). Given that, thanks to its high yield, this compound is the obvious starting point for investigations into the ability of such adducts to act as sources of the free nitride, and in the light of the general lack of structural data on complexes of Se₂N₂, confirmation of the structure of (I) by X-ray crystallography becomes desirable.

The X-ray crystal structure of (I) confirms the presence of the four-membered Se₂N₂ ring, N-bound to the Pd centres, with the [Pd₂(Se₂N₂)Br₆]²⁻ anion situated on an inversion centre. The asymmetric unit therefore contains half a formula unit. The Se—N bond lengths are almost equivalent, in direct contrast with the other examples shown in Table 2. Co-crystallization of the anion with tetraphenylphosphonium cations results in a greater asymmetry in the Se—N bond lengths than seen in (I). In comparison with (PPh₄)₂[Pd₂(Se₂N₂)Br₆] (Kelly et al., 1997), the presence of the tetrabutylammonium cations in (I) appears to result in a lengthening of the Pd—N bond, in addition to an increase in the symmetry of the Se₂N₂ unit.

Analysis of the salts (PPh₄)₂[Pd₂(Se₂N₂)Br₆] (Kelly et al., 1997) and (PPh₄)₂[Pd₂(Se₂N₂)Cl₆] (Kelly & Slawin, 1995) shows that there are interactions between the cations and anions which are absent from compound (I). In the case of (PPh₄)₂[Pd₂(Se₂N₂)Br₆], there are C—H⋯Se interactions having C⋯Se distances of the order of 4.5 Å and C—H⋯Br interactions having C⋯Br distances in the range 3.8–3.95 Å. In addition, there is weak π–π stacking, with the Se₂N₂ unit held between two benzene rings, at a distance of 4.3 Å from each benzene ring. This weak π–π stacking is not observed in (PPh₄)₂[Pd₂(Se₂N₂)Cl₆]; instead, there are C—H⋯Se interactions having C⋯Se distances of the order of 4.3 Å and C—H⋯Cl interactions having C⋯Cl distances of the order of 3.6 Å. It is possible that the absence from (I) of relatively acidic C—H donors, such as the aromatic C—H groups of the tetraphenylphosphonium cations, may thus lead to a greater symmetry in the Se₂N₂ unit in the former.

A potentially important feature of (I) is the fact that the Pd—N bond is the longest so far observed for such systems (Tables 1 and 2). This fact, along with the high yield of the compound, suggests that it is likely to be the most effective starting material for studies into the liberation of the Se₂N₂ unit.

Figure 1
A view of (I

), showing the atom-labelling scheme and with displacement ellipsoids drawn at the 50% probability level. H atoms have been omitted for clarity. [Symmetry code: (i) 1 − x, 1 − y, 2 − z.]

Experimental

The title compound was prepared according to the literature method of Kelly et al. (1997) and single crystals were grown by slow diffusion of diethyl ether into a CH₂Cl₂ solution.

Crystal data

(C₁₆H₃₆N)₂[Pd₂Br₆(N₂Se₂)]
M_r = 1363.12
Triclinic, $[P\overline 1]$
a = 9.081 (2) Å
b = 10.671 (3) Å
c = 12.415 (3) Å
α = 95.131 (4)°
β = 98.598 (4)°
γ = 98.689 (4)°
V = 1168.1 (5) Å³
Z = 1
D_x = 1.938 Mg m⁻³
Mo Kα radiation
Cell parameters from 2921 reflections
θ = 2.4–27.2°
μ = 7.49 mm⁻¹
T = 150 (2) K
Lath, orange
0.30 × 0.20 × 0.09 mm

Data collection

Bruker SMART 1000 CCD area-detector diffractometer
ω rotation scans with narrow frames
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ) T_min = 0.195, T_max = 0.508
8065 measured reflections
4049 independent reflections
3002 reflections with I > 2σ(I)
R_int = 0.037
θ_max = 25.0°
h = −10 → 10
k = −12 → 12
l = −14 → 14

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.050
wR(F²) = 0.131
S = 1.04
4049 reflections
212 parameters
H-atom parameters constrained
w = 1/[σ²(F_o²) + (0.046P)² + 10.845P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max = 0.001
Δρ_max = 0.85 e Å⁻³
Δρ_min = −1.50 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

Pd1—N1	1.978 (7)
Pd1—Br1	2.4299 (12)
Pd1—Br2	2.4066 (13)
Pd1—Br3	2.4316 (12)
Se1—N1ⁱ	1.806 (7)
Se1—N1	1.809 (7)

N1—Pd1—Br2	176.6 (2)
N1—Pd1—Br1	85.4 (2)
Br2—Pd1—Br1	94.39 (4)
N1—Pd1—Br3	85.7 (2)
Br2—Pd1—Br3	94.61 (4)
Br1—Pd1—Br3	170.88 (5)
Se1ⁱ—N1—Se1	97.9 (3)
Se1ⁱ—N1—Pd1	130.5 (4)
Se1—N1—Pd1	130.2 (4)
N1ⁱ—Se1—N1	82.1 (3)
Symmetry code: (i) 1-x,1-y,2-z.

Table 2
Selected bond lengths (Å) in (I) and related compounds

Compound	Metal—N	Se—N	Reference
(I)	1.978 (7)	1.806 (7), 1.809 (7)	a
(AlBr₃)₂(Se₂N₂)	1.92 (2)	1.77 (1), 1.81 (1)	b
(PPh₄)₂[Pd₂(Se₂N₂)Br₆]	1.875 (9)	1.809 (10), 1.920 (9)	c
(PPh₄)₂[Pd₂(Se₂N₂)Cl₆]	1.946 (4)	1.804 (5), 1.779 (4)	d
(a) This work; (b) Kelly & Slawin (1996); (c) Kelly et al. (1997); (d) Kelly & Slawin (1995).

Methylene (C—H = 0.99 Å) and methyl (C—H = 0.98 Å) H atoms were placed in geometric positions and refined using a riding model. U_iso(H) values were set at 1.2U_eq(C) for methylene and 1.5U_eq(C) for methyl H atoms. The data set was truncated at 2θ = 50°, as only statistically insignificant data were present above this limit.

Data collection: SMART (Bruker, 2001 ); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2000 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and local programs.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S0108270104027040/bm1591sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S0108270104027040/bm1591Isup2.hkl

Comment top

During the course of work on the reactivity of Se₄N₄ towards metal centres, we have successfully demonstrated that, in the right circumstances, adducts of diselenium dinitride, Se₂N₂, can be generated. Examples so far fully characterized by X-ray crystallography are (AlBr₃)₂(Se₂N₂) (Kelly & Slawin, 1996), [PPh₄]₂[Pd₂(Se₂N₂)Br₆] (Kelly et al., 1997) and [PPh₄]₂[Pd₂(Se₂N₂)Cl₆] (Kelly & Slawin, 1995). All are of great interest due to the fact that, unlike the sulfur analogue, the four-membered rings S₂N₂ or Se₂N₂ are unknown in the free state. Text altered by Coeditor - please confirm. Thus, these compounds have the potential to act as sources of the free material via appropriate substitution reactions.

In terms of performing such reactions, however, the aluminium compound is hampered by its extreme air-sensitivity, while the tetraphenylphosphonium salts of the air-stable palladium adducts form in rather poor yield. By far the best yield thus far obtained for one of these palladium adducts occurs when Se₄N₄ is reacted with (Bu₄N)₂[Pd₂Br₆] to give (Bu₄N)₂[Pd₂(Se₂N₂)Br₆], (I) [typically ca 67% yield, compared with ca 20% for the (PPh₄)⁺ salts]. However, in our previous report on this compound, we only used IR spectroscopy and microanalysis as characterization techniques (Kelly et al., 1997). Given that, thanks to its high yield, this compound is the obvious starting point for investigations into the ability of such adducts to act as sources of the free nitride, and in the light of the general lack of structural data on complexes of Se₂N₂, confirmation of the structure of (I) by X-ray crystallography becomes desirable. \sch

The X-ray crystal structure of (I) confirms the presence of the four-membered Se₂N₂ ring, N-bound to the Pd centres, with the [Pd₂(Se₂N₂)Br₆]²⁻ anion situated on an inversion centre. The asymmetric unit therefore contains half of a formula unit. The Se—N bond lengths are almost equivalent, in direct contrast with the examples shown in Table 2. Co-crystallization of the anion with tetraphenylphosphonium cations results in a greater asymmetry in the Se—N bond lengths than seen in (I). In comparison with (PPh₄)₂[Pd₂(Se₂N₂)Br₆] (Kelly et al., 1997), the presence of the tetrabutylammonium cations in (I) appears to result in a lengthening of the Pd—N bond, in addition to an increase in the symmetry of the Se₂N₂ unit.

Analysis of the salts (PPh₄)₂[Pd₂(Se₂N₂)Br₆] (Kelly et al., 1997) and (PPh₄)₂[Pd₂(Se₂N₂)Cl₆] (Kelly & Slawin, 1995) shows that there are interactions between the cations and anions which are absent from compound (I). In the case of (PPh₄)₂[Pd₂(Se₂N₂)Br₆], there are C—H···Se interactions having C···Se distances of the order of 4.5 Å and C—H···Br interactions having C···Br distances in the range 3.8–3.95 Å. In addition, there is weak π–π stacking, with the Se₂N₂ unit held between two Ph rings, at a distance of 4.3 Å from each Se₂N₂ unit. This weak π–π stacking is not observed in (PPh₄)₂[Pd₂(Se₂N₂)Cl₆]. Instead, there are C—H···Se interactions having C···Se distances of the order of 4.3 Å and C—H···Cl interactions having C···Cl distances of the order of 3.6 Å. It is possible that the absence from (I) of relatively acidic C—H donors, such as the aromatic C—H groups of the tetraphenylphosphonium cations, may thus lead to a greater symmetry in the Se₂N₂ unit in the former. From the Coeditor: Minor changes in last sentence OK?

A potentially important feature of (I) is the fact that the Pd—N bond length is the longest so far measured for such systems (Tables 1 and 2). This fact, alongside the high yield of the material, suggests that this is likely to be the most effective starting material for studies into the liberation of the Se₂N₂ unit.

Experimental top

The title compound was prepared using the literature method of Kelly et al. (1997) and single crystals were grown by slow diffusion of diethyl ether into a CH₂Cl₂ solution.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and local programs.

Figures top

Fig. 1. A view of (I), showing the atom-labelling scheme and with displacement ellipsoids drawn at the 50% probability level. H atoms have been omitted for clarity. [Symmetry code: (i) 1 − x, 1 − y, 2 − z.] From the Coeditor: Original caption was contradictory - please check this.

Bis(tetra-n-butylammonium) (µ-N,N'-diselenium dinitride)bis[tribromopalladate(II)] top

Crystal data top

(C₁₆H₃₆N)₂[Pd₂Br₆(N₂Se₂)]	Z = 1
M_r = 1363.12	F(000) = 662
Triclinic, P1	D_x = 1.938 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 9.081 (2) Å	Cell parameters from 2921 reflections
b = 10.671 (3) Å	θ = 2.4–27.2°
c = 12.415 (3) Å	µ = 7.49 mm⁻¹
α = 95.131 (4)°	T = 150 K
β = 98.598 (4)°	Lath, orange
γ = 98.689 (4)°	0.30 × 0.20 × 0.09 mm
V = 1168.1 (5) Å³

Data collection top

Bruker SMART 1000 CCD area-detector diffractometer	4049 independent reflections
Radiation source: sealed tube	3002 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.037
ω rotation with narrow frames scans	θ_max = 25.0°, θ_min = 1.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	h = −10→10
T_min = 0.195, T_max = 0.508	k = −12→12
8065 measured reflections	l = −14→14

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.050	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.131	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.046P)² + 10.845P] where P = (F_o² + 2F_c²)/3
4049 reflections	(Δ/σ)_max = 0.001
212 parameters	Δρ_max = 0.85 e Å⁻³
0 restraints	Δρ_min = −1.50 e Å⁻³

Crystal data top

(C₁₆H₃₆N)₂[Pd₂Br₆(N₂Se₂)]	γ = 98.689 (4)°
M_r = 1363.12	V = 1168.1 (5) Å³
Triclinic, P1	Z = 1
a = 9.081 (2) Å	Mo Kα radiation
b = 10.671 (3) Å	µ = 7.49 mm⁻¹
c = 12.415 (3) Å	T = 150 K
α = 95.131 (4)°	0.30 × 0.20 × 0.09 mm
β = 98.598 (4)°

Data collection top

Bruker SMART 1000 CCD area-detector diffractometer	4049 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	3002 reflections with I > 2σ(I)
T_min = 0.195, T_max = 0.508	R_int = 0.037
8065 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.050	0 restraints
wR(F²) = 0.131	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.046P)² + 10.845P] where P = (F_o² + 2F_c²)/3
4049 reflections	Δρ_max = 0.85 e Å⁻³
212 parameters	Δρ_min = −1.50 e Å⁻³

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Pd1	0.38454 (7)	0.27271 (7)	0.81142 (5)	0.0250 (2)
Br1	0.60510 (11)	0.35536 (10)	0.73407 (8)	0.0389 (3)
Br2	0.31511 (11)	0.08397 (11)	0.68135 (9)	0.0453 (3)
Br3	0.17092 (11)	0.22292 (10)	0.90619 (8)	0.0355 (3)
N1	0.4496 (8)	0.4223 (7)	0.9237 (6)	0.0273 (17)
Se1	0.37705 (10)	0.46360 (9)	1.04779 (7)	0.0267 (2)
N2	0.7449 (7)	0.8942 (7)	0.7313 (6)	0.0203 (15)
C1	0.5911 (9)	0.8135 (8)	0.7296 (7)	0.0214 (18)
H1A	0.5967	0.7689	0.7963	0.026*
H1B	0.5170	0.8720	0.7349	0.026*
C2	0.5298 (9)	0.7150 (9)	0.6320 (7)	0.027 (2)
H2A	0.5990	0.6522	0.6265	0.032*
H2B	0.5212	0.7568	0.5638	0.032*
C3	0.3748 (10)	0.6478 (9)	0.6468 (7)	0.029 (2)
H3A	0.3040	0.7100	0.6451	0.035*
H3B	0.3826	0.6156	0.7195	0.035*
C4	0.3115 (10)	0.5358 (10)	0.5569 (8)	0.036 (2)
H4A	0.2969	0.5682	0.4853	0.053*
H4B	0.2145	0.4925	0.5712	0.053*
H4C	0.3828	0.4755	0.5569	0.053*
C5	0.7997 (9)	0.9643 (9)	0.8442 (7)	0.0229 (19)
H5A	0.9027	1.0117	0.8458	0.027*
H5B	0.8079	0.9004	0.8969	0.027*
C6	0.7015 (9)	1.0590 (9)	0.8844 (7)	0.0242 (19)
H6A	0.7015	1.1291	0.8373	0.029*
H6B	0.5961	1.0146	0.8779	0.029*
C7	0.7581 (12)	1.1130 (12)	0.9996 (8)	0.047 (3)
H7A	0.8588	1.1655	1.0034	0.056*
H7B	0.7716	1.0417	1.0440	0.056*
C8	0.6588 (11)	1.1934 (11)	1.0505 (9)	0.045 (3)
H8A	0.6814	1.2810	1.0323	0.067*
H8B	0.6777	1.1934	1.1303	0.067*
H8C	0.5526	1.1583	1.0220	0.067*
C9	0.8593 (10)	0.8099 (9)	0.7057 (7)	0.027 (2)
H9A	0.8295	0.7710	0.6286	0.032*
H9B	0.9589	0.8650	0.7116	0.032*
C10	0.8776 (10)	0.7057 (9)	0.7764 (8)	0.029 (2)
H10A	0.7794	0.6483	0.7698	0.035*
H10B	0.9077	0.7432	0.8539	0.035*
C11	0.9946 (10)	0.6288 (10)	0.7454 (8)	0.034 (2)
H11A	1.0883	0.6880	0.7418	0.041*
H11B	0.9575	0.5826	0.6712	0.041*
C12	1.0323 (11)	0.5326 (10)	0.8245 (9)	0.042 (3)
H12A	1.0741	0.5777	0.8975	0.063*
H12B	1.1067	0.4849	0.7984	0.063*
H12C	0.9403	0.4732	0.8286	0.063*
C13	0.7294 (9)	0.9863 (9)	0.6456 (7)	0.025 (2)
H13A	0.6426	1.0297	0.6554	0.030*
H13B	0.7053	0.9363	0.5722	0.030*
C14	0.8670 (10)	1.0875 (9)	0.6474 (8)	0.031 (2)
H14A	0.9558	1.0455	0.6411	0.037*
H14B	0.8879	1.1423	0.7185	0.037*
C15	0.8441 (11)	1.1703 (9)	0.5546 (8)	0.033 (2)
H15A	0.8322	1.1169	0.4834	0.040*
H15B	0.7504	1.2066	0.5571	0.040*
C16	0.9753 (10)	1.2765 (9)	0.5632 (8)	0.032 (2)
H16A	0.9837	1.3320	0.6319	0.047*
H16B	0.9596	1.3262	0.5011	0.047*
H16C	1.0684	1.2406	0.5624	0.047*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Pd1	0.0231 (4)	0.0280 (4)	0.0221 (4)	0.0029 (3)	0.0017 (3)	−0.0002 (3)
Br1	0.0377 (6)	0.0458 (6)	0.0350 (5)	0.0040 (5)	0.0167 (4)	0.0014 (5)
Br2	0.0327 (6)	0.0482 (7)	0.0475 (6)	0.0093 (5)	−0.0050 (5)	−0.0194 (5)
Br3	0.0291 (5)	0.0411 (6)	0.0322 (5)	−0.0064 (4)	0.0053 (4)	0.0025 (4)
N1	0.028 (4)	0.031 (4)	0.021 (4)	−0.003 (3)	0.007 (3)	0.002 (3)
Se1	0.0243 (5)	0.0294 (5)	0.0255 (5)	−0.0028 (4)	0.0093 (4)	0.0007 (4)
N2	0.013 (3)	0.025 (4)	0.025 (4)	0.004 (3)	0.007 (3)	0.005 (3)
C1	0.014 (4)	0.029 (5)	0.022 (4)	−0.001 (4)	0.008 (3)	0.001 (4)
C2	0.015 (4)	0.036 (5)	0.028 (5)	−0.003 (4)	0.008 (4)	−0.002 (4)
C3	0.021 (5)	0.038 (6)	0.027 (5)	0.001 (4)	0.007 (4)	0.003 (4)
C4	0.021 (5)	0.040 (6)	0.040 (6)	−0.002 (4)	0.001 (4)	−0.006 (5)
C5	0.019 (4)	0.032 (5)	0.018 (4)	0.004 (4)	0.005 (3)	0.004 (4)
C6	0.017 (4)	0.032 (5)	0.022 (4)	0.012 (4)	−0.005 (3)	−0.002 (4)
C7	0.044 (6)	0.061 (8)	0.035 (6)	0.028 (6)	−0.001 (5)	−0.012 (5)
C8	0.035 (6)	0.056 (7)	0.041 (6)	0.010 (5)	0.010 (5)	−0.015 (5)
C9	0.022 (4)	0.035 (5)	0.027 (5)	0.011 (4)	0.009 (4)	0.001 (4)
C10	0.027 (5)	0.029 (5)	0.032 (5)	0.000 (4)	0.015 (4)	0.004 (4)
C11	0.025 (5)	0.046 (6)	0.035 (5)	0.012 (4)	0.007 (4)	0.006 (5)
C12	0.030 (5)	0.048 (7)	0.049 (6)	0.018 (5)	−0.001 (5)	0.009 (5)
C13	0.016 (4)	0.035 (5)	0.024 (5)	0.003 (4)	0.007 (4)	0.000 (4)
C14	0.017 (4)	0.033 (5)	0.040 (5)	−0.005 (4)	−0.002 (4)	0.016 (4)
C15	0.040 (6)	0.023 (5)	0.033 (5)	−0.005 (4)	0.005 (4)	0.007 (4)
C16	0.029 (5)	0.031 (5)	0.032 (5)	0.002 (4)	−0.002 (4)	0.005 (4)

Geometric parameters (Å, º) top

Pd1—N1	1.978 (7)	C7—H7A	0.9900
Pd1—Br1	2.4299 (12)	C7—H7B	0.9900
Pd1—Br2	2.4066 (13)	C8—H8A	0.9800
Pd1—Br3	2.4316 (12)	C8—H8B	0.9800
Se1—N1ⁱ	1.806 (7)	C8—H8C	0.9800
Se1—N1	1.809 (7)	C9—C10	1.491 (13)
N2—C5	1.504 (10)	C9—H9A	0.9900
N2—C13	1.517 (11)	C9—H9B	0.9900
N2—C1	1.522 (10)	C10—C11	1.510 (12)
N2—C9	1.522 (10)	C10—H10A	0.9900
C1—C2	1.508 (12)	C10—H10B	0.9900
C1—H1A	0.9900	C11—C12	1.524 (13)
C1—H1B	0.9900	C11—H11A	0.9900
C2—C3	1.525 (11)	C11—H11B	0.9900
C2—H2A	0.9900	C12—H12A	0.9800
C2—H2B	0.9900	C12—H12B	0.9800
C3—C4	1.539 (12)	C12—H12C	0.9800
C3—H3A	0.9900	C13—C14	1.519 (11)
C3—H3B	0.9900	C13—H13A	0.9900
C4—H4A	0.9800	C13—H13B	0.9900
C4—H4B	0.9800	C14—C15	1.522 (12)
C4—H4C	0.9800	C14—H14A	0.9900
C5—C6	1.544 (11)	C14—H14B	0.9900
C5—H5A	0.9900	C15—C16	1.500 (12)
C5—H5B	0.9900	C15—H15A	0.9900
C6—C7	1.478 (12)	C15—H15B	0.9900
C6—H6A	0.9900	C16—H16A	0.9800
C6—H6B	0.9900	C16—H16B	0.9800
C7—C8	1.502 (14)	C16—H16C	0.9800

N1—Pd1—Br2	176.6 (2)	C8—C7—H7B	108.5
N1—Pd1—Br1	85.4 (2)	H7A—C7—H7B	107.5
Br2—Pd1—Br1	94.39 (4)	C7—C8—H8A	109.5
N1—Pd1—Br3	85.7 (2)	C7—C8—H8B	109.5
Br2—Pd1—Br3	94.61 (4)	H8A—C8—H8B	109.5
Br1—Pd1—Br3	170.88 (5)	C7—C8—H8C	109.5
Se1ⁱ—N1—Se1	97.9 (3)	H8A—C8—H8C	109.5
Se1ⁱ—N1—Pd1	130.5 (4)	H8B—C8—H8C	109.5
Se1—N1—Pd1	130.2 (4)	C10—C9—N2	116.2 (7)
N1ⁱ—Se1—N1	82.1 (3)	C10—C9—H9A	108.2
C5—N2—C13	111.3 (7)	N2—C9—H9A	108.2
C5—N2—C1	108.9 (6)	C10—C9—H9B	108.2
C13—N2—C1	108.7 (6)	N2—C9—H9B	108.2
C5—N2—C9	108.1 (6)	H9A—C9—H9B	107.4
C13—N2—C9	109.3 (6)	C9—C10—C11	112.1 (7)
C1—N2—C9	110.6 (6)	C9—C10—H10A	109.2
C2—C1—N2	117.6 (6)	C11—C10—H10A	109.2
C2—C1—H1A	107.9	C9—C10—H10B	109.2
N2—C1—H1A	107.9	C11—C10—H10B	109.2
C2—C1—H1B	107.9	H10A—C10—H10B	107.9
N2—C1—H1B	107.9	C10—C11—C12	114.0 (8)
H1A—C1—H1B	107.2	C10—C11—H11A	108.8
C1—C2—C3	108.5 (7)	C12—C11—H11A	108.8
C1—C2—H2A	110.0	C10—C11—H11B	108.8
C3—C2—H2A	110.0	C12—C11—H11B	108.8
C1—C2—H2B	110.0	H11A—C11—H11B	107.7
C3—C2—H2B	110.0	C11—C12—H12A	109.5
H2A—C2—H2B	108.4	C11—C12—H12B	109.5
C2—C3—C4	111.8 (7)	H12A—C12—H12B	109.5
C2—C3—H3A	109.2	C11—C12—H12C	109.5
C4—C3—H3A	109.2	H12A—C12—H12C	109.5
C2—C3—H3B	109.2	H12B—C12—H12C	109.5
C4—C3—H3B	109.2	N2—C13—C14	115.7 (7)
H3A—C3—H3B	107.9	N2—C13—H13A	108.4
C3—C4—H4A	109.5	C14—C13—H13A	108.4
C3—C4—H4B	109.5	N2—C13—H13B	108.4
H4A—C4—H4B	109.5	C14—C13—H13B	108.4
C3—C4—H4C	109.5	H13A—C13—H13B	107.4
H4A—C4—H4C	109.5	C13—C14—C15	111.8 (7)
H4B—C4—H4C	109.5	C13—C14—H14A	109.3
N2—C5—C6	116.2 (7)	C15—C14—H14A	109.3
N2—C5—H5A	108.2	C13—C14—H14B	109.3
C6—C5—H5A	108.2	C15—C14—H14B	109.3
N2—C5—H5B	108.2	H14A—C14—H14B	107.9
C6—C5—H5B	108.2	C16—C15—C14	111.1 (8)
H5A—C5—H5B	107.4	C16—C15—H15A	109.4
C7—C6—C5	111.4 (7)	C14—C15—H15A	109.4
C7—C6—H6A	109.3	C16—C15—H15B	109.4
C5—C6—H6A	109.3	C14—C15—H15B	109.4
C7—C6—H6B	109.3	H15A—C15—H15B	108.0
C5—C6—H6B	109.3	C15—C16—H16A	109.5
H6A—C6—H6B	108.0	C15—C16—H16B	109.5
C6—C7—C8	115.3 (8)	H16A—C16—H16B	109.5
C6—C7—H7A	108.5	C15—C16—H16C	109.5
C8—C7—H7A	108.5	H16A—C16—H16C	109.5
C6—C7—H7B	108.5	H16B—C16—H16C	109.5

Br1—Pd1—N1—Se1ⁱ	−10.2 (5)	C9—N2—C5—C6	178.0 (7)
Br3—Pd1—N1—Se1ⁱ	171.8 (5)	N2—C5—C6—C7	174.7 (8)
Br1—Pd1—N1—Se1	−173.1 (5)	C5—C6—C7—C8	−172.6 (10)
Br3—Pd1—N1—Se1	9.0 (5)	C5—N2—C9—C10	64.2 (9)
Se1ⁱ—N1—Se1—N1ⁱ	0.0	C13—N2—C9—C10	−174.6 (7)
Pd1—N1—Se1—N1ⁱ	166.9 (8)	C1—N2—C9—C10	−54.9 (10)
Pd1—N1—Se1—Se1ⁱ	166.9 (8)	N2—C9—C10—C11	−179.3 (8)
C5—N2—C1—C2	−167.7 (8)	C9—C10—C11—C12	172.4 (8)
C13—N2—C1—C2	71.0 (9)	C5—N2—C13—C14	51.4 (9)
C9—N2—C1—C2	−49.1 (10)	C1—N2—C13—C14	171.3 (7)
N2—C1—C2—C3	−179.0 (7)	C9—N2—C13—C14	−67.9 (9)
C1—C2—C3—C4	−173.8 (8)	N2—C13—C14—C15	176.7 (7)
C13—N2—C5—C6	58.0 (9)	C13—C14—C15—C16	175.2 (8)
C1—N2—C5—C6	−61.8 (9)

Symmetry code: (i) −x+1, −y+1, −z+2.

Experimental details

Crystal data
Chemical formula	(C₁₆H₃₆N)₂[Pd₂Br₆(N₂Se₂)]
M_r	1363.12
Crystal system, space group	Triclinic, P1
Temperature (K)	150
a, b, c (Å)	9.081 (2), 10.671 (3), 12.415 (3)
α, β, γ (°)	95.131 (4), 98.598 (4), 98.689 (4)
V (Å³)	1168.1 (5)
Z	1
Radiation type	Mo Kα
µ (mm⁻¹)	7.49
Crystal size (mm)	0.30 × 0.20 × 0.09

Data collection
Diffractometer	Bruker SMART 1000 CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2003)
T_min, T_max	0.195, 0.508
No. of measured, independent and observed [I > 2σ(I)] reflections	8065, 4049, 3002
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.050, 0.131, 1.04
No. of reflections	4049
No. of parameters	212
H-atom treatment	H-atom parameters constrained
	w = 1/[σ²(F_o²) + (0.046P)² + 10.845P] where P = (F_o² + 2F_c²)/3
Δρ_max, Δρ_min (e Å⁻³)	0.85, −1.50

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SAINT, SHELXTL (Sheldrick, 2000), SHELXTL and local programs.

Selected geometric parameters (Å, º) top

Pd1—N1	1.978 (7)	Pd1—Br3	2.4316 (12)
Pd1—Br1	2.4299 (12)	Se1—N1ⁱ	1.806 (7)
Pd1—Br2	2.4066 (13)	Se1—N1	1.809 (7)

N1—Pd1—Br2	176.6 (2)	Br1—Pd1—Br3	170.88 (5)
N1—Pd1—Br1	85.4 (2)	Se1ⁱ—N1—Se1	97.9 (3)
Br2—Pd1—Br1	94.39 (4)	Se1ⁱ—N1—Pd1	130.5 (4)
N1—Pd1—Br3	85.7 (2)	Se1—N1—Pd1	130.2 (4)
Br2—Pd1—Br3	94.61 (4)	N1ⁱ—Se1—N1	82.1 (3)

Symmetry code: (i) −x+1, −y+1, −z+2.

Selected bond lengths from structures related to (I) (Å) top

Compound	Metal-N	Se-N	Reference
(I)	1.978 (7)	1.806 (7), 1.809 (7)	a
(AlBr₃)₂(Se₂N₂)	1.92 (2)	1.77 (1), 1.81 (1)	b
(PPh₄)₂[Pd₂(Se₂N₂)Br₆]	1.875 (9)	1.809 (10), 1.920 (9)	c
(PPh₄)₂[Pd₂(Se₂N₂)Cl₆]	1.946 (4)	1.804 (5), 1.779 (4)	d

(a) this work; (b) Kelly & Slawin (1996); (c) Kelly et al. (1997); (d) Kelly & Slawin (1995).

Acknowledgements

The authors would like to acknowledge the EPSRC (UK) for the provision of a studentship (to KEH) and a Postdoctoral Research Assistantship (to SMA).

References

Bruker (2001). SMART (Version 5.611) and SAINT (Version 6.02a). Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Kelly, P. F. & Slawin, A. M. Z. (1995). Angew. Chem. Int. Ed. Engl. 34, 1758–1759. CSD CrossRef CAS Web of Science Google Scholar
Kelly, P. F. & Slawin, A. M. Z. (1996). J. Chem. Soc. Dalton Trans. pp. 4029–4030. CSD CrossRef Web of Science Google Scholar
Kelly, P. F., Slawin, A. M. Z. & Soriano-Rama, A. (1997). J. Chem. Soc. Dalton Trans. pp. 559–562. CSD CrossRef Web of Science Google Scholar
Sheldrick, G. M. (2000). SHELXTL. Version 6.10. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Sheldrick, G. M. (2003). SADABS. Version 2.08. University of Göttingen, Germany. Google Scholar

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