Crystal structure of catena-poly[[potassium-tri-μ-di-methyl-acetamide-κ(6) O:O] iodide].

The structure of catena-poly[[potassium-tri-μ-di-methyl-acetamide-κ(6) O:O] iodide], {[K(C4H9NO)3]I} n , at 120 K has trigonal (P-3) symmetry. The structure adopts a linear chain motif parallel to the crystallographic c axis. Two crystallographically independent K(+) cations are present in the asymmetric unit located on threefold rotoinversion axes at [0, 0, 0] and [0, 0, 1/2] and are bridged by the O atoms of the acetamide moiety. This is an example of a rare μ2-bridging mode for di-methyl-acetamide O atoms. The iodide counter-ion resides on a threefold rotation axis in the channel formed by the [K(C4H9NO)](+) chains.

Chemical context

Coordination of di­methyl­acetamide (DMA) to metal centers has been observed previously in a number of metal complexes, but μ2-coordination of the O atom has only been reported in two crystallographically confirmed structures. Tikhonova et al. (2001 ▶) crystallized a bis­(μ3-N,N-di­methyl­acetamide)­tris­(μ2-perfluoro-o-phenyl­ene)trimercury(II) complex and found Hg—O(DMA) bond lengths in the range 2.776 (2)–2.989 (2) Å. Dias et al. (1995 ▶) synthesized bis­{(μ2-di­methyl­acetamido-O,O){μ2-hydrogen tris­[3,5-bis­(tri­fluoro­meth­yl)pyra­zol­yl]borate}potassium}, in which the O atom is μ2-bridging between two K+ cations and the K—O bond length is 2.703 (2) Å. In the KI·3DMA structure reported here, the K—O bond lengths are in the range 2.763 (2)–2.774 (3) Å, slightly longer than in the closely related potassium complex synthesized by Dias et al. (1995 ▶).

Structural commentary

The cation of title compound consists of two crystallographically independent potassium cations. Each K+ cation is octa­hedrally coordinated by six O atoms from the DMA moieties, with each oxygen adopting a μ2-bridging mode (Fig. 1 ▶ and Table 1 ▶). The C=O distance is comparable with that in free di­methyl­acetamide (see Database survey ). The iodide anion is independent of the one-dimensional chain and does not form any covalent contacts to the cation.

Figure 1

The atom-labeling scheme for KI·3DMA, with displacement ellipsoids depicted at the 50% probability level. [Symmetry codes: (i) −x, −y, −z; (ii) y, −x + y, −z; (iii) −y, x − y, z; (iv) x − y, x, −z; (v) −x + y, −x, z; (vi) x, y, z − 1.]

Table 1

Selected geometric parameters (Å, °)

K1—O1	2.7438 (16)	O1—C2	1.254 (3)
K1—K2	3.6728 (4)	O1—K2	2.7627 (16)
O1i—K1—O1	180.0	O1iii—K1—O1	80.70 (5)
O1ii—K1—O1	99.30 (5)

Symmetry codes: (i) ; (ii) ; (iii) .

The extended structure forms a chain of K+ cations, bridged by μ2-O-di­methyl­acetamide moieties. The two independent K+ cations are located at [0, 0, 0] and [0, 0, ½] (Wyckoff positions a and b, respectively) and the iodine is located at [, , z] (Wyckoff position d). In the primary structure, each K+ cation adopts a slightly distorted octa­hedral coordination sphere (key bond lengths and angles are given in Table 1 ▶).

Supra­molecular features

The μ2-O-di­methyl­acetamide bridging the two K+ cations forms a linear [K(DMA)3]+ chain parallel to the c axis. The application of the symmetry results in an aesthetic­ally pleasing ‘snowflake’ configuration when viewed along the c axis (Fig. 2 ▶). The iodide counter-ion resides in the channels formed by the [K(DMA)3]+ chains. With regards to the extended structure, there are very weak C—H⋯I inter­actions within the lattice (Table 2 ▶). These serve to locate the iodine in a pocket within the structure.

Figure 2

(A) Packing diagram viewed along the b axis. (B) View along the c axis. Legend: black = carbon, dark blue = nitro­gen, light blue = potassium, magenta = iodine, and red = oxygen. H atoms have been omitted for clarity.

Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1A⋯I1iv	0.98	3.20	4.178 (3)	177
C3—H3A⋯I1iv	0.98	3.20	4.178 (3)	174
C4—H4C⋯I1	0.98	3.00	3.967 (3)	170

Symmetry code: (iv) .

Database survey

A search in the Cambridge Structure Database (CSD, Version 5.35, November 2013 plus three updates; Allen, 2002 ▶) for structures in which K+ is triple bridged in a μ2-fashion by three O atoms returns 17 results, but only 3 of them are relevant to the structure reported herein. Gonzalez-Rodriguez et al. (2009 ▶) have shown a complex guanosine-derived nucleoside to crystallize as an acetone solvate monohydrate in which the six bridging K+ cations are each coordinated to eight O atoms from eight guanosine ligands, and the two terminal K+ cations are coordinated to eight O atoms from four guanosine ligands and either four acetone mol­ecules or four water mol­ecules. Cunningham et al. (2000 ▶) crystallized catena-[tetra­kis­[N,N′-bis­(3-meth­oxy­salicyl­idene)propane-1,3-di­amino­ato]iodido­nickel(II)potassium], where K+ is bridged by four μ2-O, one μ2-N, and one μ2-I. In fact, both of these structures contain four μ2-O atoms bridging K+ cations. No close K⋯K contacts were observed: the K⋯K distances are in the range 3.451 (2)–3.567 (2) Å. Most closely related is the structure of catena-[tris­(μ2-di­methyl­formamide-O,O)potassium iodide], reported by Batsanov & Struchkov (1994 ▶), with a K⋯K distance of 3.4170 (10) Å and a K—O distance of 2.6570 (13) Å. In the KI·3DMA structure reported herein, the K1⋯K2 distance is 3.6728 (4) Å, which is longer by approximately 0.106 Å. In the Gonzalez-Rodriguez and Cunningham structures, iodine is found to form bonds to the K+ cations, while it is located in a channel within the Batsanov structure and not covalently bound. In the title compound, the iodine is not covalently bonded to the cation chain.

A search in the Cambridge Structure Database for free acetamide returned 180 results, featuring C=O bond lengths between 1.123 Å (Patra & Goldberg, 2013 ▶) and 1.67 Å (Gole et al., 2011 ▶), with a mean of 1.259 Å (std. dev. 0.059), which is very close to the C=O bond length reported herein [1.254 (3) Å]

Synthesis and crystallization

A carbon–carbon Heck coupling reaction catalyzed by a PdII diphosphane precatalyst was performed using conditions established previously by Brase & de Meijere (1998 ▶). In a typical synthesis, 1-iodo-4-nitro­benzene (IC6H4NO2; 102.1 mg, 0.41 mmol) was mixed with 2 equivalents of n-butyl acrylate [CH2=CHCOO(CH2)3CH3; 105.6 mg, 0.82 mmol] in the presence of K2CO3 (63.6 mg, 0.46 mmol) and n-Bu4NBr (13 mg, 0.041 mmol) in di­methyl­acetamide (DMA) over a period of 4 h at 413 K. The title compound formed and was recrystallized from the filtered reaction mixture at room temperature. The target PdII complex of the reaction has been reported (Comanescu & Iluc, 2014 ▶).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3 ▶. H atoms were included in a riding model and allowed to rotate to minimize electron-density contribution. C—H distances were set at 0.98 Å, with U iso(H) = 1.5U eq(C).

Table 3

Experimental details

Crystal data
Chemical formula	[K(C4H9NO)3]I
M r	427.37
Crystal system, space group	Trigonal, P
Temperature (K)	120
a, c (Å)	11.9776 (8), 7.3455 (7)
V (Å3)	912.62 (15)
Z	2
Radiation type	Mo Kα
μ (mm−1)	1.99
Crystal size (mm)	0.20 × 0.09 × 0.06
Data collection
Diffractometer	Bruker APEX
Absorption correction	Multi-scan (SADABS; Bruker, 2012 ▶)
T min, T max	0.615, 0.745
No. of measured, independent and observed [I > 2σ(I)] reflections	11940, 1248, 1194
R int	0.026
(sin θ/λ)max (Å−1)	0.623
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.024, 0.059, 1.07
No. of reflections	1248
No. of parameters	65
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	1.14, −0.43

Computer programs: APEX2 and SAINT (Bruker, 2012 ▶), SHELXS97, SHELXL2013 and XP in SHELXTL (Sheldrick, 2013 ▶) and publCIF (Westrip, 2010 ▶).

Crystal structure: contains datablock(s) I. DOI: 10.1107/S1600536814020005/zl2601sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536814020005/zl2601Isup2.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S1600536814020005/zl2601Isup3.cml

CCDC reference: 1022963

Additional supporting information: crystallographic information; 3D view; checkCIF report

[K(C4H9NO)3]I	Dx = 1.555 Mg m−3
Mr = 427.37	Mo Kα radiation, λ = 0.71073 Å
Trigonal, P3	Cell parameters from 7529 reflections
a = 11.9776 (8) Å	θ = 2.7–26.3°
c = 7.3455 (7) Å	µ = 1.99 mm−1
V = 912.62 (15) Å3	T = 120 K
Z = 2	Block, colorless
F(000) = 432	0.20 × 0.09 × 0.06 mm

Bruker APEX diffractometer	1248 independent reflections
Radiation source: fine-focus sealed tube	1194 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.026
Detector resolution: 8.33 pixels mm-1	θmax = 26.3°, θmin = 2.0°
combination of ω and φ–scans	h = −14→14
Absorption correction: multi-scan (SADABS; Bruker, 2012)	k = −14→14
Tmin = 0.615, Tmax = 0.745	l = −9→9
11940 measured reflections

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)] = 0.024	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.059	H-atom parameters constrained
S = 1.07	w = 1/[σ2(Fo2) + (0.0227P)2 + 1.7319P] where P = (Fo2 + 2Fc2)/3
1248 reflections	(Δ/σ)max = 0.001
65 parameters	Δρmax = 1.14 e Å−3
0 restraints	Δρmin = −0.43 e Å−3

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.

	x	y	z	Uiso*/Ueq
I1	0.6667	0.3333	0.83886 (4)	0.02490 (11)
K1	0.0000	0.0000	0.0000	0.0172 (2)
O1	0.18933 (16)	0.14411 (16)	0.2481 (2)	0.0229 (4)
N1	0.3896 (2)	0.2882 (2)	0.3421 (3)	0.0262 (5)
C1	0.3288 (3)	0.3114 (3)	0.0349 (3)	0.0281 (5)
H1A	0.4093	0.3202	−0.0125	0.042*
H1B	0.3388	0.3971	0.0517	0.042*
H1C	0.2588	0.2620	−0.0516	0.042*
K2	0.0000	0.0000	0.5000	0.0227 (3)
C2	0.2970 (2)	0.2414 (2)	0.2163 (3)	0.0249 (5)
C3	0.5155 (3)	0.4036 (3)	0.3094 (4)	0.0320 (6)
H3A	0.5574	0.3884	0.2054	0.048*
H3B	0.5697	0.4223	0.4178	0.048*
H3C	0.5033	0.4770	0.2830	0.048*
C4	0.3621 (3)	0.2247 (3)	0.5200 (4)	0.0315 (6)
H4A	0.3164	0.1310	0.5031	0.047*
H4B	0.3083	0.2488	0.5913	0.047*
H4C	0.4432	0.2516	0.5848	0.047*

	U11	U22	U33	U12	U13	U23
I1	0.02578 (13)	0.02578 (13)	0.02315 (16)	0.01289 (6)	0.000	0.000
K1	0.0195 (4)	0.0195 (4)	0.0126 (5)	0.00975 (18)	0.000	0.000
O1	0.0183 (8)	0.0237 (9)	0.0202 (8)	0.0057 (7)	−0.0003 (6)	−0.0034 (7)
N1	0.0242 (11)	0.0271 (11)	0.0237 (10)	0.0100 (9)	0.0003 (8)	−0.0003 (8)
C1	0.0284 (13)	0.0352 (14)	0.0196 (12)	0.0152 (11)	0.0012 (10)	0.0047 (10)
K2	0.0278 (4)	0.0278 (4)	0.0123 (5)	0.0139 (2)	0.000	0.000
C2	0.0291 (13)	0.0286 (13)	0.0223 (12)	0.0185 (11)	0.0013 (10)	−0.0037 (10)
C3	0.0212 (12)	0.0280 (13)	0.0336 (14)	0.0025 (11)	0.0023 (10)	−0.0045 (11)
C4	0.0325 (14)	0.0321 (14)	0.0218 (12)	0.0100 (12)	−0.0043 (11)	0.0038 (10)

K1—O1i	2.7437 (16)	C1—H1B	0.9800
K1—O1ii	2.7437 (16)	C1—H1C	0.9800
K1—O1iii	2.7437 (16)	K2—O1vii	2.7627 (16)
K1—O1iv	2.7437 (16)	K2—O1v	2.7627 (16)
K1—O1v	2.7437 (16)	K2—O1viii	2.7627 (16)
K1—O1	2.7438 (16)	K2—O1iii	2.7627 (16)
K1—K2vi	3.6728 (4)	K2—O1ix	2.7627 (17)
K1—K2	3.6728 (4)	K2—K1x	3.6728 (4)
O1—C2	1.254 (3)	C3—H3A	0.9800
O1—K2	2.7627 (16)	C3—H3B	0.9800
N1—C2	1.333 (3)	C3—H3C	0.9800
N1—C4	1.465 (3)	C4—H4A	0.9800
N1—C3	1.468 (3)	C4—H4B	0.9800
C1—C2	1.517 (3)	C4—H4C	0.9800
C1—H1A	0.9800
O1i—K1—O1ii	80.70 (5)	O1v—K2—O1viii	99.97 (5)
O1i—K1—O1iii	99.30 (5)	O1vii—K2—O1iii	99.97 (5)
O1ii—K1—O1iii	180.00 (7)	O1v—K2—O1iii	80.03 (5)
O1i—K1—O1iv	80.70 (5)	O1viii—K2—O1iii	180.0
O1ii—K1—O1iv	80.70 (5)	O1vii—K2—O1ix	80.03 (5)
O1iii—K1—O1iv	99.30 (5)	O1v—K2—O1ix	99.97 (5)
O1i—K1—O1v	99.30 (5)	O1viii—K2—O1ix	80.03 (5)
O1ii—K1—O1v	99.30 (5)	O1iii—K2—O1ix	99.97 (5)
O1iii—K1—O1v	80.70 (5)	O1vii—K2—O1	99.97 (5)
O1iv—K1—O1v	180.00 (7)	O1v—K2—O1	80.03 (5)
O1i—K1—O1	180.0	O1viii—K2—O1	99.96 (5)
O1ii—K1—O1	99.30 (5)	O1iii—K2—O1	80.04 (5)
O1iii—K1—O1	80.70 (5)	O1ix—K2—O1	180.0
O1iv—K1—O1	99.30 (5)	O1vii—K2—K1	132.06 (3)
O1v—K1—O1	80.70 (5)	O1v—K2—K1	47.94 (3)
O1i—K1—K2vi	48.39 (3)	O1viii—K2—K1	132.06 (3)
O1ii—K1—K2vi	48.39 (3)	O1iii—K2—K1	47.94 (3)
O1iii—K1—K2vi	131.61 (3)	O1ix—K2—K1	132.06 (3)
O1iv—K1—K2vi	48.39 (3)	O1—K2—K1	47.94 (3)
O1v—K1—K2vi	131.61 (3)	O1vii—K2—K1x	47.94 (3)
O1—K1—K2vi	131.61 (3)	O1v—K2—K1x	132.06 (3)
O1i—K1—K2	131.61 (3)	O1viii—K2—K1x	47.94 (3)
O1ii—K1—K2	131.61 (3)	O1iii—K2—K1x	132.06 (3)
O1iii—K1—K2	48.39 (3)	O1ix—K2—K1x	47.94 (3)
O1iv—K1—K2	131.61 (3)	O1—K2—K1x	132.06 (3)
O1v—K1—K2	48.39 (3)	K1—K2—K1x	180.0
O1—K1—K2	48.39 (3)	O1—C2—N1	121.0 (2)
K2vi—K1—K2	180.0	O1—C2—C1	122.3 (2)
C2—O1—K1	127.11 (15)	N1—C2—C1	116.8 (2)
C2—O1—K2	147.87 (15)	N1—C3—H3A	109.5
K1—O1—K2	83.67 (5)	N1—C3—H3B	109.5
C2—N1—C4	118.5 (2)	H3A—C3—H3B	109.5
C2—N1—C3	121.9 (2)	N1—C3—H3C	109.5
C4—N1—C3	119.6 (2)	H3A—C3—H3C	109.5
C2—C1—H1A	109.5	H3B—C3—H3C	109.5
C2—C1—H1B	109.5	N1—C4—H4A	109.5
H1A—C1—H1B	109.5	N1—C4—H4B	109.5
C2—C1—H1C	109.5	H4A—C4—H4B	109.5
H1A—C1—H1C	109.5	N1—C4—H4C	109.5
H1B—C1—H1C	109.5	H4A—C4—H4C	109.5
O1vii—K2—O1v	180.0	H4B—C4—H4C	109.5
O1vii—K2—O1viii	80.03 (5)
K1—O1—C2—N1	−167.19 (17)	C4—N1—C2—O1	−1.0 (4)
K2—O1—C2—N1	32.0 (4)	C3—N1—C2—O1	−178.7 (2)
K1—O1—C2—C1	12.8 (3)	C4—N1—C2—C1	179.0 (2)
K2—O1—C2—C1	−148.1 (2)	C3—N1—C2—C1	1.4 (4)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1A···I1vi	0.98	3.20	4.178 (3)	177
C3—H3A···I1vi	0.98	3.20	4.178 (3)	174
C4—H4C···I1	0.98	3.00	3.967 (3)	170