Structures of the reaction products of lithium metal with N,N-di­methyl­acetamide and tetra­methyl­urea

Purdy, A.; Butcher, R.J.

doi:10.1107/S2056989026009989

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ISSN: 2056-9890

Volume 82| Part 11| November 2026| Pages 1362-1366

https://doi.org/10.1107/S2056989026009989

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Structures of the reaction products of lithium metal with N,N-dimethylacetamide and tetramethylurea

Andrew Purdy ^a and Raymond J. Butcher ^b ^*

^aNaval Research Laboratory, Chemistry Division, Code 6100, 4555 Overlook Av, SW, Washington DC 20375, USA, and ^bDepartment of Chemistry, Howard University, 525 College Street NW, Washington DC 20059, USA
^*Correspondence e-mail: [email protected]

Edited by F. Di Salvo, University of Buenos Aires, Argentina (Received 3 June 2026; accepted 24 September 2026; online 30 October 2026)

The reaction of lithium metal with dry N,N-dimethylacetamide produced crystals of catena-poly[(μ₃-N,N-dimethylacetoacetamidato)lithium(I)], [Li(C₆H₁₀NO₂)]_n, (I), which crystallizes as a coordination polymer with a chain of fused Li₂O₂ rings. A similar reaction of lithium metal with N,N-tetramethylurea produces crystals of hexakis[μ₃-1,2-bis(dimethylamino)-2-oxoethan-1-olato]hexalithium(I), [Li₆(C₆H₁₃N₂O₂)₆], (II), which crystallizes as a hexamer, with the alkoxide O atoms in a Li₆O₆ barrel-shaped cluster with threefold symmetry, and the keto O atoms bonded to the lithium atoms outside the cage.

Keywords: crystal structure; β-diketonate; Li reactivity; alkoxide.

CCDC references: 2590805; 2590806

1. Chemical context

Even though highly polar solvents containing carbonyl groups like propylene carbonate are generally believed to be unreactive with alkali metals, they actually do react, albeit slowly. To search for less reactive solvents, Li foil was immersed in a vial containing a number of dry solvents of this type in an argon-filled drybox. The reactions took many days to months to proceed to completion, with the non-cyclic amide solvents reacting the quickest, and the cyclic CHO solvents reacting the slowest. Years later, crystals were isolated from reactions with N,N-dimethylacetamide [DMAC, Me₂NC(=O)Me] and tetramethyl urea [TMU, Me₂N(C=O)NMe₂]. The DMAC formed a Li salt of N,N-dimethylacetoacetamide (I), possibly from deprotonation of a methyl group on one DMAC molecule, which then undergoes a nucleophilic attack on a second DMAC molecule. However, formation of the N,N-dimethylacetoacetamide ligand has been reported during solution of cellulose in DMAC containing LiCl (Potthast, et al., 2003 ). The reaction with TMU appears to have cleaved a Me₂N group, followed by coupling of two Me₂N(C=O) radicals, and protonation, producing the hexameric Li salt of Me₂NCH(OH)C(=O)NMe₂. Such a coupling has been observed before from a reaction between potassium t-butoxide and dimethylformamide (DMF) (Barham et al., 2016 ), and from a reduction using rubidium amalgam in DMF (Boeddinghaus et al., 2012 ). While N,N-dimethylacetoacetamide is commercially available and has been used as a standard β-diketonate ligand, for which the V, Ti and Pd complexes have been structurally characterized (Crans et al., 2001 , CSD refcode ICITUJ; Gornshtein et al., 2007 , XEVNOC; Kiers et al., 1992 , JUFJID), and its Li salt has been prepared before and characterized by infrared spectroscopy (Coll, 1985 ), assembly of this ligand from coupling two DMAC moieties is relatively unusual, with very few references in the literature.

2. Structural commentary

Compound I crystallizes in the space group P2₁/n. Its N,N-dimethylacetoacetamidate ligand coordinates as a typical β-diketonate, which is chelated to the Li⁺ ion. Selected geometrical parameters are given in Table 1. Both C=O distances of 1.2731 (10) and 1.2882 (10) Å are ordinary for molecules of this type. The molecules assemble into a chain of fused four-membered Li₂O₂ rings that zigzag along the a-axis direction, and the rings are slightly offset. The basic dimeric unit is shown in Fig. 1, and the assemblage in a chain is shown in Fig. 2. A plane drawn through Li1/O1/Li1ⁱ/O1ⁱ makes an angle of 66.71 (8)° with a plane drawn through Li1/O2/Li1ⁱⁱ/O2ⁱⁱ [symmetry codes: (i) 1 − x,−y, −z; (ii) 2 − x,−y, −z] on the adjacent Li₂O₂ ring along this zigzagging chain. Bond distances in the Li chelate are normal, as expected for an unstrained chelate of this type, and the Li-O rings with bond lengths of 1.9045 (17)–1.9626 (18) Å are normal as well.

Table 1
Selected geometric parameters (Å, °) for I

O1—Li1	1.9071 (17)	O2—Li1ⁱⁱ	1.9626 (18)
O1—Li1ⁱ	1.9376 (18)	Li1—Li1ⁱ	2.594 (3)
O2—Li1	1.9045 (17)	Li1—Li1ⁱⁱ	2.690 (3)

O2—Li1—O1	95.19 (8)	O2—Li1—O2ⁱⁱ	91.86 (7)
O2—Li1—O1ⁱ	139.00 (10)	O1—Li1—O2ⁱⁱ	124.75 (9)
O1—Li1—O1ⁱ	95.13 (7)	O1ⁱ—Li1—O2ⁱⁱ	113.88 (8)
Symmetry codes: (i) ; (ii) .

Figure 1
The dimer of the molecular unit of I, showing the Li₂O₂ ring. Unlabeled atoms are generated by the symmetry operation 1 − x, −y, −z. Atomic displacement parameters are at the 30% probability level.

Figure 2
A view of I showing the fused Li₂O₂ ring chain, overlaid with the unit cell, along with the weak C—H⋯O interactions that support the chain.

In 2015 the parameter τ4′ was developed to distinguish whether the geometry of the coordination center tends towards square planar or tetrahedral (Okuniewski et al., 2015 ). When τ4′ is close to 0 the geometry is similar to square planar, while if τ4′ is close to 1 then the geometry is similar to tetrahedral. In this structure, the value τ4′ was found to be 0.714, which indicates a distorted tetrahedral geometry. A search of the Cambridge Structural Database (version 6.00, update August 2025; Groom et al., 2016 ) for similar compounds containing a five-membered chelate ring with an O–C–C–O backbone with at least one C—O bond yielded seven hits (FAQFEK, Chen et al., 2009 ; IDOXIL, Al-Khafaji et al., 2017 ; KIJZUZ01, Budanow et al., 2010 ; NEFNAQ, Kingsbury et al., 2017 ; OZUCUI, Sazama & Betley, 2011 ; UCUSUK, Vuković et al., 2021 ; and VAYCUV, Wan et al., 2012 .). In these structures the τ4′ value was found to be 0.930, 0.760–0.826 (four different Li sites), 0.675 and 0.784 (two different Li sites),

Compound II crystallizes in the trigonal space group R $[\overline{3}]$ . Selected geometrical parameters are given in Table 2. The core of II is a barrel-shaped hexamer consisting of two Li₃O₃ rings in a slightly puckered chair conformation, facially bonded together around a threefold rotation axis, (Fig. 3), which is a fairly common structural motif for Li alkoxides. For example, lithium-t-butoxide (Nekola et al., 2002 , ZZZJZU01) has a similar motif without the high crystal symmetry, and a lithium siloxide (Jones et al., 1992 , JOTROZ) has the threefold symmetry as well. However, this particular ligand is unusual and has been structurally characterized only once previously (Boeddinghaus et al., 2012, TEXHUB), where it is coordinated to rubidium. The C1—O1 distance of 1.379 (3) Å, and the C2—O2 distance of 1.242 (3) Å are consistent with a C—O single bond and double bond, respectively, and are very similar to the corresponding distances in TEXHUB [1.346 (6) Å and 1.221 (7) Å]. Also similar are the C—N bond distances between the C=O carbon atom and its attached NMe₂ group [C2—N2 = 1.348 (4) Å versus 1.345 (8) Å in TEXHUB], and the C—O (alkoxide) carbon atom and its attached NMe₂ group [C1—N1 = 1.466 (4) Å, versus 1.520 (7) Å in TEXHUB], which shows some double-bond character exists between the NMe₂ group and the carbonyl group. This results in different conformations for the two NMe₂ groups with the environment of N1 being pyramidal while the environment for N2 being trigonal planar [C1, C2 O2, N2, C5 and C6 are almost coplanar with an r.m.s. deviation of only 0.030 (2) Å]. The O—C—C bond angles in both compounds are also almost identical [O1—C1—C2 = 110.6 (2)° and O2—C2—C1 =120.0 (3)° versus 110.3 (4) and 118.2 (5) ° in TEXHUB].

Table 2
Selected geometric parameters (Å, °) for II

O1—Li1	1.923 (5)	O1—Li1ⁱⁱ	1.974 (5)
O1—Li1ⁱ	1.940 (5)	O2—Li1ⁱⁱ	1.944 (5)

O1—Li1—O1ⁱⁱ	99.6 (2)	O1—Li1—O1ⁱ	98.4 (2)
O1—Li1—O2ⁱ	141.2 (3)	O1ⁱⁱ—Li1—O1ⁱ	120.4 (3)
O1ⁱⁱ—Li1—O2ⁱ	111.4 (2)	O2ⁱ—Li1—O1ⁱ	85.8 (2)
Symmetry codes: (i) $[y-{\script{1\over 3}}, -x+y+{\script{1\over 3}}, -z+{\script{1\over 3}}]$ ; (ii) $[x-y+{\script{2\over 3}}, x+{\script{1\over 3}}, -z+{\script{1\over 3}}]$ .

Figure 3
A structural diagram of II showing a side view of the Li₆O₆ cage and the bonding of the keto O atoms O2 to the cage. Unlabeled atoms are generated by the symmetry operations: − $[{1\over 3}]$ + y, $[{1\over 3}]$ − x + y, $[{1\over 3}]$ − z; $[{2\over 3}]$ + x − y, $[{1\over 3}]$ + x, $[{1\over 3}]$ − z. Atomic displacement parameters are at the 30% probability level.

The τ4′ value for the coordination environment of Li in II is 0.760, indicating a distorted tetrahedral conformation. A search of the Cambridge Structural Database for related Li structures containing a β-diketone ligand with both C and N substituents gave zero hits. However there are 46 structures where both substituents are carbon atoms. A typical example is BOWMAE (Petrus et al., 2020 ) where the τ4′ value was found to be 0.772, a value similar to that in II.

3. Supramolecular features

In the extended structure of I, as indicated above, the molecules assemble into a chain of fused four-membered Li₂O₂ rings that zigzag along the a-axis direction. These chains are supported on both sides by interactions involving C5. This is a remarkable case of methyl group involved into the two types of common interactions simultaneously: C5 is donor of a weak C—H⋯O bond to O1 [H5C⋯O1( $[{3\over 2}]$ − x, $[{1\over 2}]$ + y, $[{1\over 2}]$ − z) = 2.81 Å], with a C—O distance of 3.5908 (12) Å as well as being involved in a typical tetrel bond (Varadwaj et al., 2023 ) [C3—H3⋯O2( $[{1\over 2}]$ + x, $[{1\over 2}]$ − y, $[{1\over 2}]$ + z)] with a very short C—O distance of 3.0815 (12) Å as shown in Fig. 2

There is weak hydrogen bonding in II between C—H groups and O and N donors. Both C5—H5B⋯N1 and C1—H1⋯O2 are notable, and help to consolidate overall structure (Table 3, Fig. 4). In the structure, the orientation of the CH₃ methyl group involving C5 is such that there is a weak intramolecular C5—H5B⋯N1 hydrogen bond.

Table 3
Hydrogen-bond geometry (Å, °) for II

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1⋯O2ⁱⁱⁱ	1.00	2.59	3.322 (4)	130
C5—H5B⋯N1	0.98	2.34	3.059 (4)	130
Symmetry code: (iii) .

Figure 4
A packing diagram of II down the c axis showing the threefold symmetry.

4. Database survey

A search of the CSD database (version 6.00, update August 2025; Groom et al., 2016) found 35 instances of a barrel-shaped Li₆O₆ cluster similar to that in II, mostly in lithium alkoxides and siloxides, with additional structures where that motif is a subunit of a larger cluster. The great structural flexibility of Li–O clusters results in many other structural patterns, for example, stacked cubes (Goldfuss et al., 1997 , NOXWEC) or prism structures (Dell'Aera et al. 2024 , UHUWUT01). While the polymeric fused Li₂O₂ chains of I are less common, there are still plenty of examples of this general motif, particularly with β-diketonate salts such as the lithium salt of 1-ethoxy-3-difluoromethyl-1,3-dipropanone, and its trifluoromethyl analog (Slepukhin et al., 2009 EJUZIT, EJUZOZ), and the phenyl difluoromethyl analog as well (Karpenko et al., 2005 , REGQAW).

5. Synthesis and crystallization

A piece of Li foil of about 0.1 g was added to scintillation vials containing ∼10 mL of dry tetramethyl urea (TMU), N,N-dimethylacetamide (DMAC), γ-valerolactone, and N,N-dimethylimidazolidinone (DMIZ) inside an argon-filled drybox. Within three days, the Li in the TMU dissolved to an orange solution, and the piece in DMAC reacted to form a yellow solution and a white precipitate, but the ones in DMIZ and γ-valerolactone did not fully react until three months had passed. Suitable crystals were isolated several years later from the DMAC and TMU mixtures. The solids isolated from the other two vials were not suitable for x-ray diffraction.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 4. For both I and II, all H atoms were located in difference maps and treated as riding in geometrically idealized positions with C—H distances of 0.98 Å for the methyl groups. For II there was unresolved solvent peaks along the threefold axis. This was treated by using the SQUEEZE routine in PLATON (Spek, 2015 )

Table 4
Experimental details

	I	II
Crystal data
Chemical formula	[Li(C₆H₁₀NO₂)]	[Li₆(C₆H₁₃N₂O₂)₆]
M_r	135.09	912.74
Crystal system, space group	Monoclinic, P2₁/n	Trigonal, R $[\overline{3}]$
Temperature (K)	100	116
a, b, c (Å)	5.2478 (2), 12.3868 (5), 10.9921 (5)	18.156 (4), 18.156 (4), 13.698 (4)
α, β, γ (°)	90, 103.461 (2), 90	90, 90, 120
V (Å³)	694.90 (5)	3911 (2)
Z	4	3
Radiation type	Mo Kα	Mo Kα
μ (mm⁻¹)	0.09	0.09
Crystal size (mm)	0.26 × 0.18 × 0.12	0.15 × 0.12 × 0.05

Data collection
Diffractometer	Bruker APEXII CCD	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )	Multi-scan (SADABS; Krause et al., 2015)
T_min, T_max	0.635, 0.743	0.393, 0.745
No. of measured, independent and observed [I > 2σ(I)] reflections	17985, 3219, 2619	5186, 1589, 915
R_int	0.050	0.094
(sin θ/λ)_max (Å⁻¹)	0.844	0.602

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.048, 0.126, 1.06	0.064, 0.163, 1.01
No. of reflections	3219	1589
No. of parameters	96	104
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.57, −0.23	0.43, −0.22
Computer programs: APEX2 (Bruker, 2005 ), SAINT (Bruker, 2002 ), SHELXT (Sheldrick 2015a ), SHELXL2019/2 (Sheldrick, 2015b ) and SHELXTL (Sheldrick, 2008 ).

Supporting information

CCDC references: 2590805; 2590806

Crystal structure: contains datablocks I, II. DOI: https://doi.org/10.1107/S2056989026009989/vu2021sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989026009989/vu2021Isup2.hkl

Structure factors: contains datablock II. DOI: https://doi.org/10.1107/S2056989026009989/vu2021IIsup3.hkl

checkCIF report

Computing details top

catena-Poly[(µ₃-N,N-dimethylacetoacetamidato)lithium(I)] (I) top

Crystal data top

[Li(C₆H₁₀NO₂)]	F(000) = 288
M_r = 135.09	D_x = 1.291 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 5.2478 (2) Å	Cell parameters from 6211 reflections
b = 12.3868 (5) Å	θ = 3.3–30.6°
c = 10.9921 (5) Å	µ = 0.09 mm⁻¹
β = 103.461 (2)°	T = 100 K
V = 694.90 (5) Å³	Prism, colourless
Z = 4	0.26 × 0.18 × 0.12 mm

Data collection top

Bruker APEXII CCD diffractometer	2619 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.050
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	θ_max = 36.8°, θ_min = 3.3°
T_min = 0.635, T_max = 0.743	h = −8→8
17985 measured reflections	k = −19→19
3219 independent reflections	l = −18→17

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.126	H-atom parameters constrained
S = 1.06	w = 1/[σ²(F_o²) + (0.0607P)² + 0.1969P] where P = (F_o² + 2F_c²)/3
3219 reflections	(Δ/σ)_max < 0.001
96 parameters	Δρ_max = 0.57 e Å⁻³
0 restraints	Δρ_min = −0.23 e Å⁻³

Special details top

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

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

	x	y	z	U_iso*/U_eq
O1	0.59962 (12)	−0.01383 (5)	0.13056 (6)	0.01357 (13)
O2	1.01783 (12)	0.09654 (5)	0.06579 (6)	0.01264 (12)
N1	1.23735 (15)	0.21292 (6)	0.21082 (7)	0.01497 (14)
C1	0.61051 (18)	−0.02321 (8)	0.34787 (8)	0.01594 (16)
H1A	0.712848	0.006620	0.426777	0.024*
H1B	0.622423	−0.102169	0.350360	0.024*
H1C	0.426848	−0.001393	0.335987	0.024*
C2	0.71778 (16)	0.01900 (7)	0.24042 (7)	0.01192 (14)
C3	0.92905 (16)	0.08955 (7)	0.26828 (7)	0.01299 (14)
H3	0.991510	0.110908	0.353001	0.016*
C4	1.05980 (15)	0.13250 (6)	0.17718 (7)	0.01154 (14)
C5	1.3038 (2)	0.25888 (8)	0.33664 (9)	0.02047 (18)
H5A	1.428371	0.318298	0.339481	0.031*
H5B	1.383134	0.203015	0.396732	0.031*
H5C	1.144541	0.286157	0.358115	0.031*
C6	1.38164 (17)	0.25529 (7)	0.12269 (9)	0.01694 (16)
H6A	1.361515	0.333922	0.117195	0.025*
H6B	1.312649	0.223310	0.040036	0.025*
H6C	1.567660	0.237110	0.151656	0.025*
Li1	0.7387 (3)	0.00402 (14)	−0.01375 (15)	0.0151 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0121 (3)	0.0182 (3)	0.0102 (2)	−0.0017 (2)	0.00199 (19)	−0.0012 (2)
O2	0.0130 (3)	0.0150 (3)	0.0101 (2)	−0.0012 (2)	0.00284 (18)	−0.00230 (19)
N1	0.0155 (3)	0.0144 (3)	0.0145 (3)	−0.0036 (2)	0.0025 (2)	−0.0038 (2)
C1	0.0161 (4)	0.0207 (4)	0.0118 (3)	0.0009 (3)	0.0049 (3)	0.0025 (3)
C2	0.0114 (3)	0.0142 (3)	0.0102 (3)	0.0023 (2)	0.0026 (2)	0.0006 (2)
C3	0.0133 (3)	0.0160 (3)	0.0094 (3)	−0.0003 (2)	0.0022 (2)	−0.0018 (2)
C4	0.0109 (3)	0.0116 (3)	0.0116 (3)	0.0009 (2)	0.0013 (2)	−0.0010 (2)
C5	0.0234 (4)	0.0185 (4)	0.0175 (4)	−0.0040 (3)	0.0006 (3)	−0.0072 (3)
C6	0.0151 (4)	0.0152 (4)	0.0203 (4)	−0.0023 (3)	0.0038 (3)	0.0011 (3)
Li1	0.0140 (7)	0.0192 (7)	0.0122 (6)	−0.0015 (5)	0.0031 (5)	−0.0023 (5)

Geometric parameters (Å, º) top

O1—C2	1.2882 (10)	C1—H1C	0.9800
O1—Li1	1.9071 (17)	C2—C3	1.3888 (12)
O1—Li1ⁱ	1.9376 (18)	C3—C4	1.4410 (11)
O2—C4	1.2731 (10)	C3—H3	0.9500
O2—Li1	1.9045 (17)	C5—H5A	0.9800
O2—Li1ⁱⁱ	1.9626 (18)	C5—H5B	0.9800
N1—C4	1.3553 (11)	C5—H5C	0.9800
N1—C6	1.4590 (12)	C6—H6A	0.9800
N1—C5	1.4608 (12)	C6—H6B	0.9800
C1—C2	1.5149 (11)	C6—H6C	0.9800
C1—H1A	0.9800	Li1—Li1ⁱ	2.594 (3)
C1—H1B	0.9800	Li1—Li1ⁱⁱ	2.690 (3)

C2—O1—Li1	123.31 (7)	H5A—C5—H5B	109.5
C2—O1—Li1ⁱ	140.20 (7)	N1—C5—H5C	109.5
Li1—O1—Li1ⁱ	84.87 (7)	H5A—C5—H5C	109.5
C4—O2—Li1	126.47 (7)	H5B—C5—H5C	109.5
C4—O2—Li1ⁱⁱ	121.59 (7)	N1—C6—H6A	109.5
Li1—O2—Li1ⁱⁱ	88.14 (7)	N1—C6—H6B	109.5
C4—N1—C6	120.89 (7)	H6A—C6—H6B	109.5
C4—N1—C5	122.83 (8)	N1—C6—H6C	109.5
C6—N1—C5	116.23 (7)	H6A—C6—H6C	109.5
C2—C1—H1A	109.5	H6B—C6—H6C	109.5
C2—C1—H1B	109.5	O2—Li1—O1	95.19 (8)
H1A—C1—H1B	109.5	O2—Li1—O1ⁱ	139.00 (10)
C2—C1—H1C	109.5	O1—Li1—O1ⁱ	95.13 (7)
H1A—C1—H1C	109.5	O2—Li1—O2ⁱⁱ	91.86 (7)
H1B—C1—H1C	109.5	O1—Li1—O2ⁱⁱ	124.75 (9)
O1—C2—C3	126.21 (7)	O1ⁱ—Li1—O2ⁱⁱ	113.88 (8)
O1—C2—C1	115.90 (7)	O2—Li1—Li1ⁱ	129.06 (11)
C3—C2—C1	117.89 (7)	O1—Li1—Li1ⁱ	48.06 (6)
C2—C3—C4	124.33 (7)	O1ⁱ—Li1—Li1ⁱ	47.07 (6)
C2—C3—H3	117.8	O2ⁱⁱ—Li1—Li1ⁱ	136.17 (11)
C4—C3—H3	117.8	O2—Li1—Li1ⁱⁱ	46.82 (5)
O2—C4—N1	118.27 (7)	O1—Li1—Li1ⁱⁱ	118.67 (10)
O2—C4—C3	122.38 (7)	O1ⁱ—Li1—Li1ⁱⁱ	146.07 (11)
N1—C4—C3	119.35 (7)	O2ⁱⁱ—Li1—Li1ⁱⁱ	45.04 (5)
N1—C5—H5A	109.5	Li1ⁱ—Li1—Li1ⁱⁱ	166.50 (14)
N1—C5—H5B	109.5

Li1—O1—C2—C3	13.93 (13)	Li1—O2—C4—C3	13.19 (13)
Li1ⁱ—O1—C2—C3	−114.50 (12)	Li1ⁱⁱ—O2—C4—C3	−100.84 (10)
Li1—O1—C2—C1	−166.94 (8)	C6—N1—C4—O2	−1.56 (12)
Li1ⁱ—O1—C2—C1	64.63 (14)	C5—N1—C4—O2	−178.94 (8)
O1—C2—C3—C4	−3.85 (14)	C6—N1—C4—C3	177.40 (8)
C1—C2—C3—C4	177.04 (8)	C5—N1—C4—C3	0.02 (12)
Li1—O2—C4—N1	−167.88 (8)	C2—C3—C4—O2	−10.97 (13)
Li1ⁱⁱ—O2—C4—N1	78.09 (11)	C2—C3—C4—N1	170.12 (8)

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

Hexakis[µ₃-1,2-bis(dimethylamino)-2-oxoethan-1-olato]hexalithium(I) (II) top

Crystal data top

[Li₆(C₆H₁₃N₂O₂)₆]	D_x = 1.163 Mg m⁻³
M_r = 912.74	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3	Cell parameters from 894 reflections
a = 18.156 (4) Å	θ = 3.0–24.8°
c = 13.698 (4) Å	µ = 0.09 mm⁻¹
V = 3911 (2) Å³	T = 116 K
Z = 3	Prism, colorless
F(000) = 1476	0.15 × 0.12 × 0.05 mm

Data collection top

Bruker APEXII CCD diffractometer	915 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.094
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	θ_max = 25.3°, θ_min = 3.0°
T_min = 0.393, T_max = 0.745	h = −21→18
5186 measured reflections	k = −19→21
1589 independent reflections	l = −13→16

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.064	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.163	H-atom parameters constrained
S = 1.01	w = 1/[σ²(F_o²) + (0.0741P)²] where P = (F_o² + 2F_c²)/3
1589 reflections	(Δ/σ)_max < 0.001
104 parameters	Δρ_max = 0.43 e Å⁻³
0 restraints	Δρ_min = −0.22 e Å⁻³

Special details top

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

	x	y	z	U_iso*/U_eq
O1	0.35939 (12)	0.57409 (12)	0.24712 (13)	0.0223 (5)
O2	0.50447 (13)	0.67719 (13)	0.33958 (15)	0.0282 (6)
N1	0.38352 (16)	0.46658 (15)	0.32016 (17)	0.0276 (7)
N2	0.46926 (16)	0.59789 (17)	0.47645 (17)	0.0333 (7)
C1	0.37433 (18)	0.54192 (18)	0.3312 (2)	0.0232 (7)
H1	0.325206	0.526187	0.376097	0.028*
C2	0.45485 (18)	0.61048 (19)	0.3831 (2)	0.0227 (7)
C3	0.3028 (2)	0.3907 (2)	0.2969 (3)	0.0533 (11)
H3A	0.309407	0.340456	0.301229	0.080*
H3B	0.285549	0.395578	0.230512	0.080*
H3C	0.259255	0.385195	0.343320	0.080*
C4	0.4479 (2)	0.4799 (2)	0.2475 (2)	0.0403 (9)
H4A	0.459547	0.432748	0.250370	0.061*
H4B	0.500227	0.533471	0.261159	0.061*
H4C	0.427018	0.482353	0.182310	0.061*
C5	0.4119 (2)	0.5224 (2)	0.5341 (2)	0.0505 (11)
H5A	0.445502	0.506740	0.576227	0.076*
H5B	0.376906	0.475082	0.489987	0.076*
H5C	0.374993	0.535034	0.574409	0.076*
C6	0.5401 (2)	0.6652 (2)	0.5305 (2)	0.0484 (10)
H6A	0.573690	0.642522	0.560430	0.073*
H6B	0.518138	0.686848	0.581628	0.073*
H6C	0.576184	0.711568	0.485828	0.073*
Li1	0.3600 (3)	0.5773 (3)	0.1068 (3)	0.0268 (12)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0223 (12)	0.0237 (11)	0.0194 (11)	0.0106 (9)	−0.0005 (9)	0.0045 (9)
O2	0.0244 (12)	0.0263 (12)	0.0294 (12)	0.0092 (10)	−0.0032 (10)	0.0013 (10)
N1	0.0329 (15)	0.0223 (14)	0.0266 (14)	0.0130 (13)	−0.0032 (12)	0.0040 (11)
N2	0.0299 (16)	0.0381 (17)	0.0180 (13)	0.0065 (13)	−0.0027 (12)	0.0008 (12)
C1	0.0236 (17)	0.0286 (18)	0.0189 (15)	0.0142 (14)	−0.0007 (13)	0.0020 (13)
C2	0.0198 (16)	0.0278 (17)	0.0207 (16)	0.0121 (15)	0.0024 (13)	0.0012 (14)
C3	0.054 (2)	0.0229 (19)	0.066 (3)	0.0070 (18)	−0.025 (2)	−0.0015 (18)
C4	0.064 (3)	0.039 (2)	0.0335 (19)	0.037 (2)	−0.0022 (18)	−0.0027 (16)
C5	0.050 (2)	0.060 (3)	0.0223 (17)	0.013 (2)	0.0010 (17)	0.0122 (18)
C6	0.047 (2)	0.057 (3)	0.0276 (19)	0.016 (2)	−0.0081 (17)	−0.0070 (18)
Li1	0.021 (3)	0.036 (3)	0.024 (3)	0.014 (2)	−0.001 (2)	−0.001 (2)

Geometric parameters (Å, º) top

O1—C1	1.379 (3)	C3—H3A	0.9800
O1—Li1	1.923 (5)	C3—H3B	0.9800
O1—Li1ⁱ	1.940 (5)	C3—H3C	0.9800
O1—Li1ⁱⁱ	1.974 (5)	C4—H4A	0.9800
O2—C2	1.242 (3)	C4—H4B	0.9800
O2—Li1ⁱⁱ	1.944 (5)	C4—H4C	0.9800
N1—C3	1.459 (4)	C5—H5A	0.9800
N1—C4	1.460 (4)	C5—H5B	0.9800
N1—C1	1.466 (4)	C5—H5C	0.9800
N2—C2	1.348 (4)	C6—H6A	0.9800
N2—C6	1.458 (4)	C6—H6B	0.9800
N2—C5	1.469 (4)	C6—H6C	0.9800
C1—C2	1.540 (4)	Li1—Li1ⁱⁱ	2.518 (7)
C1—Li1ⁱⁱ	2.779 (5)	Li1—Li1ⁱ	2.519 (7)
C1—H1	1.0000	Li1—Li1ⁱⁱⁱ	3.310 (9)
C2—Li1ⁱⁱ	2.649 (6)	Li1—Li1^iv	3.310 (9)

C1—O1—Li1	148.1 (2)	H6A—C6—H6B	109.5
C1—O1—Li1ⁱ	116.6 (2)	N2—C6—H6C	109.5
Li1—O1—Li1ⁱ	81.4 (2)	H6A—C6—H6C	109.5
C1—O1—Li1ⁱⁱ	110.7 (2)	H6B—C6—H6C	109.5
Li1—O1—Li1ⁱⁱ	80.5 (2)	O1—Li1—O1ⁱⁱ	99.6 (2)
Li1ⁱ—O1—Li1ⁱⁱ	115.5 (3)	O1—Li1—O2ⁱ	141.2 (3)
C2—O2—Li1ⁱⁱ	110.6 (2)	O1ⁱⁱ—Li1—O2ⁱ	111.4 (2)
C3—N1—C4	110.5 (3)	O1—Li1—O1ⁱ	98.4 (2)
C3—N1—C1	112.0 (2)	O1ⁱⁱ—Li1—O1ⁱ	120.4 (3)
C4—N1—C1	111.8 (2)	O2ⁱ—Li1—O1ⁱ	85.8 (2)
C2—N2—C6	120.3 (3)	O1—Li1—Li1ⁱⁱ	50.6 (2)
C2—N2—C5	124.1 (3)	O1ⁱⁱ—Li1—Li1ⁱⁱ	49.02 (11)
C6—N2—C5	115.2 (3)	O2ⁱ—Li1—Li1ⁱⁱ	153.5 (3)
O1—C1—N1	116.6 (2)	O1ⁱ—Li1—Li1ⁱⁱ	118.64 (17)
O1—C1—C2	110.6 (2)	O1—Li1—Li1ⁱ	49.6 (2)
N1—C1—C2	107.3 (2)	O1ⁱⁱ—Li1—Li1ⁱ	119.20 (18)
O1—C1—Li1ⁱⁱ	41.64 (16)	O2ⁱ—Li1—Li1ⁱ	123.9 (2)
N1—C1—Li1ⁱⁱ	129.9 (2)	O1ⁱ—Li1—Li1ⁱ	48.86 (11)
C2—C1—Li1ⁱⁱ	68.94 (18)	Li1ⁱⁱ—Li1—Li1ⁱ	82.2 (3)
O1—C1—H1	107.4	O1—Li1—C2ⁱ	142.9 (3)
N1—C1—H1	107.4	O1ⁱⁱ—Li1—C2ⁱ	117.3 (2)
C2—C1—H1	107.4	O2ⁱ—Li1—C2ⁱ	26.03 (11)
Li1ⁱⁱ—C1—H1	121.7	O1ⁱ—Li1—C2ⁱ	60.49 (15)
O2—C2—N2	120.9 (3)	Li1ⁱⁱ—Li1—C2ⁱ	165.2 (3)
O2—C2—C1	120.0 (3)	Li1ⁱ—Li1—C2ⁱ	104.1 (2)
N2—C2—C1	119.1 (3)	O1—Li1—C1ⁱ	120.8 (2)
O2—C2—Li1ⁱⁱ	43.38 (17)	O1ⁱⁱ—Li1—C1ⁱ	124.5 (2)
N2—C2—Li1ⁱⁱ	158.4 (2)	O2ⁱ—Li1—C1ⁱ	58.31 (15)
C1—C2—Li1ⁱⁱ	78.21 (18)	O1ⁱ—Li1—C1ⁱ	27.65 (10)
N1—C3—H3A	109.5	Li1ⁱⁱ—Li1—C1ⁱ	144.72 (16)
N1—C3—H3B	109.5	Li1ⁱ—Li1—C1ⁱ	73.54 (16)
H3A—C3—H3B	109.5	C2ⁱ—Li1—C1ⁱ	32.85 (10)
N1—C3—H3C	109.5	O1—Li1—Li1ⁱⁱⁱ	91.59 (16)
H3A—C3—H3C	109.5	O1ⁱⁱ—Li1—Li1ⁱⁱⁱ	32.56 (17)
H3B—C3—H3C	109.5	O2ⁱ—Li1—Li1ⁱⁱⁱ	127.03 (16)
N1—C4—H4A	109.5	O1ⁱ—Li1—Li1ⁱⁱⁱ	90.95 (15)
N1—C4—H4B	109.5	Li1ⁱⁱ—Li1—Li1ⁱⁱⁱ	48.92 (13)
H4A—C4—H4B	109.5	Li1ⁱ—Li1—Li1ⁱⁱⁱ	90.0
N1—C4—H4C	109.5	C2ⁱ—Li1—Li1ⁱⁱⁱ	116.97 (12)
H4A—C4—H4C	109.5	C1ⁱ—Li1—Li1ⁱⁱⁱ	105.04 (14)
H4B—C4—H4C	109.5	O1—Li1—Li1^iv	90.98 (16)
N2—C5—H5A	109.5	O1ⁱⁱ—Li1—Li1^iv	91.57 (16)
N2—C5—H5B	109.5	O2ⁱ—Li1—Li1^iv	110.2 (2)
H5A—C5—H5B	109.5	O1ⁱ—Li1—Li1^iv	31.93 (16)
N2—C5—H5C	109.5	Li1ⁱⁱ—Li1—Li1^iv	90.0
H5A—C5—H5C	109.5	Li1ⁱ—Li1—Li1^iv	48.92 (13)
H5B—C5—H5C	109.5	C2ⁱ—Li1—Li1^iv	84.46 (17)
N2—C6—H6A	109.5	C1ⁱ—Li1—Li1^iv	54.75 (16)
N2—C6—H6B	109.5	Li1ⁱⁱⁱ—Li1—Li1^iv	60.0

Li1—O1—C1—N1	−15.2 (6)	Li1ⁱⁱ—O2—C2—C1	17.4 (3)
Li1ⁱ—O1—C1—N1	104.1 (3)	C6—N2—C2—O2	4.6 (4)
Li1ⁱⁱ—O1—C1—N1	−121.1 (3)	C5—N2—C2—O2	177.4 (3)
Li1—O1—C1—C2	107.6 (4)	C6—N2—C2—C1	−173.7 (3)
Li1ⁱ—O1—C1—C2	−133.1 (2)	C5—N2—C2—C1	−0.9 (4)
Li1ⁱⁱ—O1—C1—C2	1.7 (3)	C6—N2—C2—Li1ⁱⁱ	−33.1 (8)
Li1—O1—C1—Li1ⁱⁱ	105.9 (4)	C5—N2—C2—Li1ⁱⁱ	139.7 (6)
Li1ⁱ—O1—C1—Li1ⁱⁱ	−134.8 (3)	O1—C1—C2—O2	−13.3 (4)
C3—N1—C1—O1	−71.2 (3)	N1—C1—C2—O2	114.8 (3)
C4—N1—C1—O1	53.4 (3)	Li1ⁱⁱ—C1—C2—O2	−12.1 (2)
C3—N1—C1—C2	164.3 (2)	O1—C1—C2—N2	165.0 (2)
C4—N1—C1—C2	−71.1 (3)	N1—C1—C2—N2	−66.9 (3)
C3—N1—C1—Li1ⁱⁱ	−119.0 (3)	Li1ⁱⁱ—C1—C2—N2	166.2 (3)
C4—N1—C1—Li1ⁱⁱ	5.6 (4)	O1—C1—C2—Li1ⁱⁱ	−1.2 (2)
Li1ⁱⁱ—O2—C2—N2	−160.9 (3)	N1—C1—C2—Li1ⁱⁱ	126.9 (2)

Symmetry codes: (i) y−1/3, −x+y+1/3, −z+1/3; (ii) x−y+2/3, x+1/3, −z+1/3; (iii) −y+1, x−y+1, z; (iv) −x+y, −x+1, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···O2^iv	1.00	2.59	3.322 (4)	130
C5—H5B···N1	0.98	2.34	3.059 (4)	130

Symmetry code: (iv) −x+y, −x+1, z.

Funding information

Funding for this research was provided by: The Office of Naval Research through the NRL Base Program.

References

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Volume 82| Part 11| November 2026| Pages 1362-1366

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research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Structures of the reaction products of lithium metal with N,N-di­methyl­acetamide and tetra­methyl­urea

1. Chemical context

2. Structural commentary

3. Supra­molecular features

4. Database survey

5. Synthesis and crystallization

6. Refinement

Supporting information

Funding information

References

research communications

Structures of the reaction products of lithium metal with N,N-dimethylacetamide and tetramethylurea

3. Supramolecular features