Di-μ-hydro­xo-bis­(diiso­propyl­gallium)–1,4,8,11-tetra­methyl-1,4,8,11-tetra­aza­cyclo­tetra­decane (1/1)

The hydro­lysis product [Ga₂(C₃H₇)₄(OH)₂]·C₁₄H₃₂N₄, derived from the tetrakis­(triiso­propyl­gallium)–1,4,8,11-tetra­methyl-1,4,8,11-tetra­aza­cyclo­tetra­decane (1/1) adduct, consists of a centrosymmetric [ⁱPr₂Ga(μ-OH)]₂ unit hydrogen bonded through the hydroxyl group to a nitro­gen on an adjacent centrosymmetric 1,4,8,11-tetra­methyl-1,4,8,11-tetra­aza­cyclo­tetra­decane molecule, resulting in the generation of a molecular chain through the crystal.

S1. Comment

The product of controlled hydrolysis of gallium trialkyls depends on the steric bulk of the alkyl group and may result in tetramers, [Me₂Ga(µ₂–OH)]₄ (Smith & Hoard, 1959), trimers, [^tBu₂Ga(µ₂–OH)]₃ (Naiini et al., 1993; Atwood et al., 1993), or dimers [R₂Ga(µ–OH)]₂ [R = CH(SiMe₃)₂, mesityl, C₆H₄–2–CH₂NMe₂] (Uhl et al., 1996; Storre et al., 1996; Coggin et al., 1993). Increasing the steric congestion by substitution of the OH group by an alkoxide also results in a decrease in the degree of oligomerization, e.g. [^tBu₂Ga(µ–O^tBu)]₂ (Cleaver et al., 1994). This latter effect may apparently be mimicked by hydrogen bonding of the bridging hydroxyl species to an appropriate base e.g. [{Me₃Ga(µ–OH)}₃·3H₂O]₂.18-crown-6 (Croucher et al., 1999). This feature has allowed us to determine the molecular structure of [ⁱPr₂Ga(µ–OH)]₂ as a hydrogen-bonded adduct of 1,4,8,11–tetramethyl–1,4,8,11–tetraazacyclotetradecane, (I). \sch

The molecule contains a centrosymmetric Ga₂(µ–OH)₂ four-membered ring with gallium-bonded isopropyl groups above and below the ring plane. The hydroxyl protons are located 0.38 (2) Å above/below this plane, which subtends an angle of ~152° to the O–H vector.

The structure is analogous to other [R₂Ga(µ–OH)]₂ species and also to the chloride-substituted compounds [R(Cl)Ga(µ–OH)]₂ [R = 2,4,6–ⁱPr₃Ph, 2,4,6–(CF₃)₃Ph, (Me₃Si)₃Si] (Twamley & Power, 1999; Schluter et al., 1994; Linti et al., 1996).

The intra-annular Ga—Ga vector, 2.9425 (7) Å, is the shortest of the reported dialkyl derivatives, [R₂Ga(µ–OH)]₂, (2.970–3.064 Å) presumably due to reduced steric hindrance. Accordingly, the internal angle subtended at gallium, 81.04 (6)°, is larger than that found in the other six examples of this structural type (78.8–80.6°) and the corresponding angle at oxygen, 98.96 (6)°, is the smallest (99.1–102.1°). The length of Ga–O bonds, 1.9339 (12) and 1.9368 (12) Å, is compatible with the range of Ga—O bonds found in the other four-membered-ring species, 1.893–1.969 Å. However, the Ga—O bonds in the chloride-substituted derivatives, [R(Cl)Ga(µ–OH)]₂, are generally shorter, which leads to shorter intra-annular Ga—Ga vectors (2.887–2.939 Å). The Ga—C bonds are some 0.03 Å shorter than the average found for adducts of ⁱPr₃Ga (Coward et al., 2000), where the bond length sequence Ga—Me < Ga—Et < Ga—ⁱPr was demonstrated. However, they are comparable to those in other µ₂–OH gallium species such as [Me₂Ga(µ₂–OH)]₄ (Smith & Hoard, 1959) and [^tBu₂Ga(µ₂–OH)]₃ (Atwood et al., 1993), although there are insufficient accurately determined data to confirm a similar sequence.

The four N atoms of the tetraazacyclotetradecane ring are crystallographically constrained to be coplanar. This plane subtends an angle of 82.71 (5)° to the plane of the Ga₂O₂ ring. Two independent ring configurations were found in the crystal stucture of free 1,4,8,11-tetramethyl-1,4,8–11-tetraazacyclotetradecane, RSSR trans-IV and RRSS trans-III (Willey et al., 1993; Kelly et al., 1996). The tetraazacyclotetradecane ring in the gallium adduct adopts the higher energy RRSS trans-III configuration, which facilitates strong hydrogen bonding between N2 and the hydroxyl hydrogen, 2.03 (2) Å. The hydrogen bonds are approximately parallel to the c axis, resulting in a molecular chain running throughout the crystal. Apart from a possible intra-annular interaction between N1 and H3a (2.40 Å), there are no non-classical hydrogen bonds present.

S2. Experimental

The 4:1 adduct of triisopropylgallium and 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (Coward et al., 2000) was dissolved in dry toluene and left to crystallize at 243 K. After one week there was evident decomposition, presumably due to hydrolysis. A few well shaped crystals present in the mixture were isolated and dried in a stream of dinitrogen.

S3. Refinement

The H atoms were placed in calculated positions and allowed to ride except for the hydroxyl hydrogen which was identified from a difference map and allowed to refine freely.

Computing details

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-Plus (Siemens, 1995); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The molecular structure of (I) with the displacement ellipsoids drawn at the 50% probability level.

bis(µ ₂-hydroxo)bis(diipropylgallium). 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane

Crystal data

[Ga2(C3H7)4(OH)2]·C14H32N4	Z = 1
Mr = 602.24	F(000) = 323
Triclinic, P1	Dx = 1.209 Mg m^−3
a = 8.5877 (7) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.7161 (17) Å	Cell parameters from 32 reflections
c = 11.1425 (10) Å	θ = 5.4–15.0°
α = 113.138 (8)°	µ = 1.65 mm^−1
β = 97.516 (4)°	T = 223 K
γ = 98.551 (7)°	Block, colourless
V = 826.92 (18) Å^3	0.45 × 0.30 × 0.25 mm

Data collection

Siemens P4 diffractometer	3277 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.018
Graphite monochromator	θmax = 27.5°, θmin = 2.0°
profile fitting of θ/2θ scans	h = −1→11
Absorption correction: ψ scan (XPREP in SHELXTL-Plus; Siemens 1995)	k = −11→11
Tmin = 0.568, Tmax = 0.661	l = −14→14
4385 measured reflections	3 standard reflections every 97 reflections
3645 independent reflections	intensity decay: 5%

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.026
wR(F^2) = 0.065	(Δ/σ)max = 0.001
S = 1.04	Δρmax = 0.34 e Å^−3
3645 reflections	Δρmin = −0.22 e Å^−3
164 parameters

Special details

Experimental. %T The crystal was mounted on a glass pin using Fomblin YR-1800 oil (Lancaster Synthesis).

The crystal was coated with Fomblin YR–1800 oil [Lancaster Synthesis, Ref. 17548 (CAS 69991–67–9)], mounted on a glass fibre and cooled to 223 K. Counting statistics indicated a non-centrosymmetric cell [mean $|$E*E$-1$$|$ = 0.714] and the structure could only be solved in P1 (Patterson and direct methods). However, following identification of all non-hydrogen atoms from difference maps and inspection of the Flack (1983) parameter, which suggested a racemic twin, it was clear that the correct space group was $Pοverline 1$. The positions of the Ga and O were calculated for this space group and and a successful solution was subsequently obtained.

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 (Ų)

	x	y	z	Uiso*/Ueq
Ga	0.53668 (2)	0.66406 (2)	0.528901 (17)	0.03091 (7)
O	0.40399 (15)	0.52378 (13)	0.57831 (12)	0.0354 (3)
H1	0.383 (3)	0.541 (3)	0.650 (2)	0.049 (6)*
C6	0.7236 (2)	0.8007 (2)	0.67372 (17)	0.0388 (4)
H6	0.7462	0.7502	0.7339	0.047*
C61	0.6890 (3)	0.9559 (2)	0.7565 (2)	0.0561 (5)
H61A	0.7801	1.0159	0.8297	0.084*
H61B	0.5937	0.9405	0.7917	0.084*
H61C	0.6713	1.0099	0.7007	0.084*
C62	0.8728 (3)	0.8212 (3)	0.6163 (2)	0.0571 (5)
H62A	0.8548	0.8728	0.5586	0.086*
H62B	0.8939	0.7214	0.5653	0.086*
H62C	0.9646	0.8822	0.6886	0.086*
C7	0.3975 (2)	0.7377 (2)	0.42098 (18)	0.0386 (4)
H7	0.4677	0.8158	0.4041	0.046*
C71	0.2771 (3)	0.8157 (3)	0.4988 (2)	0.0582 (6)
H71A	0.2115	0.8527	0.4454	0.087*
H71B	0.3350	0.9014	0.5813	0.087*
H71C	0.2084	0.7424	0.5190	0.087*
C72	0.3091 (3)	0.6111 (3)	0.2862 (2)	0.0522 (5)
H72A	0.2371	0.5340	0.2996	0.078*
H72B	0.3866	0.5644	0.2368	0.078*
H72C	0.2473	0.6543	0.2362	0.078*
N1	0.27516 (19)	0.30534 (17)	0.90116 (15)	0.0407 (3)
C11	0.1385 (3)	0.2823 (3)	0.9623 (2)	0.0639 (6)
H11A	0.0618	0.1886	0.9015	0.096*
H11B	0.0868	0.3686	0.9811	0.096*
H11C	0.1763	0.2743	1.0447	0.096*
C1	0.2215 (2)	0.3106 (2)	0.77267 (18)	0.0486 (5)
H1A	0.1370	0.2188	0.7173	0.058*
H1B	0.3122	0.3059	0.7273	0.058*
C2	0.1576 (2)	0.4503 (3)	0.7804 (2)	0.0530 (5)
H2A	0.0867	0.4245	0.6947	0.064*
H2B	0.0920	0.4741	0.8486	0.064*
N2	0.2813 (2)	0.5889 (2)	0.81193 (15)	0.0431 (4)
C21	0.2001 (3)	0.7068 (3)	0.7979 (3)	0.0716 (8)
H21A	0.1292	0.6643	0.7107	0.107*
H21B	0.2801	0.7941	0.8072	0.107*
H21C	0.1377	0.7395	0.8665	0.107*
C3	0.3790 (3)	0.6456 (2)	0.94756 (18)	0.0431 (4)
H3A	0.4208	0.5610	0.9571	0.052*
H3B	0.3094	0.6777	1.0119	0.052*
C4	0.5192 (3)	0.7786 (2)	0.9817 (2)	0.0494 (5)
H4A	0.4783	0.8701	0.9896	0.059*
H4B	0.5793	0.7542	0.9098	0.059*
C5	0.6313 (3)	0.8118 (2)	1.1126 (2)	0.0510 (5)
H5A	0.7051	0.9118	1.1434	0.061*
H5B	0.5673	0.8176	1.1804	0.061*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ga	0.03262 (10)	0.02896 (10)	0.03068 (10)	0.00787 (7)	0.00861 (7)	0.01104 (7)
O	0.0417 (7)	0.0324 (6)	0.0343 (6)	0.0103 (5)	0.0180 (5)	0.0125 (5)
C6	0.0414 (9)	0.0361 (9)	0.0343 (8)	0.0058 (7)	0.0026 (7)	0.0127 (7)
C61	0.0582 (13)	0.0394 (10)	0.0545 (12)	0.0035 (9)	0.0124 (10)	0.0055 (9)
C62	0.0382 (10)	0.0646 (14)	0.0547 (12)	0.0066 (9)	0.0059 (9)	0.0137 (10)
C7	0.0387 (9)	0.0412 (9)	0.0417 (9)	0.0104 (7)	0.0113 (7)	0.0220 (8)
C71	0.0604 (13)	0.0681 (14)	0.0605 (13)	0.0349 (12)	0.0214 (11)	0.0317 (11)
C72	0.0441 (11)	0.0632 (13)	0.0442 (11)	0.0096 (9)	−0.0004 (9)	0.0211 (10)
N1	0.0431 (8)	0.0392 (8)	0.0324 (7)	0.0000 (6)	0.0125 (6)	0.0093 (6)
C11	0.0566 (13)	0.0780 (16)	0.0523 (12)	−0.0026 (12)	0.0221 (11)	0.0251 (12)
C1	0.0431 (10)	0.0565 (12)	0.0323 (9)	−0.0018 (9)	0.0079 (8)	0.0087 (8)
C2	0.0353 (10)	0.0857 (16)	0.0410 (10)	0.0173 (10)	0.0101 (8)	0.0276 (10)
N2	0.0459 (9)	0.0610 (10)	0.0370 (8)	0.0286 (8)	0.0171 (7)	0.0270 (7)
C21	0.0844 (18)	0.103 (2)	0.0690 (15)	0.0680 (17)	0.0364 (14)	0.0561 (15)
C3	0.0579 (12)	0.0447 (10)	0.0354 (9)	0.0187 (9)	0.0161 (8)	0.0213 (8)
C4	0.0743 (14)	0.0342 (9)	0.0484 (11)	0.0167 (9)	0.0227 (10)	0.0218 (8)
C5	0.0728 (14)	0.0288 (9)	0.0421 (10)	0.0023 (9)	0.0160 (10)	0.0074 (7)

Geometric parameters (Å, º)

Ga—O^i	1.9339 (12)	N1—C11	1.463 (2)
Ga—O	1.9368 (12)	N1—C1	1.468 (2)
Ga—C7	1.9853 (18)	C11—H11A	0.9700
Ga—C6	1.9872 (18)	C11—H11B	0.9700
Ga—Ga^i	2.9425 (7)	C11—H11C	0.9700
O—Ga^i	1.9339 (12)	C1—C2	1.514 (3)
O—H1	0.80 (2)	C1—H1A	0.9800
C6—C61	1.524 (3)	C1—H1B	0.9800
C6—C62	1.526 (3)	C2—N2	1.473 (3)
C6—H6	0.9900	C2—H2A	0.9800
C61—H61A	0.9700	C2—H2B	0.9800
C61—H61B	0.9700	N2—C3	1.472 (2)
C61—H61C	0.9700	N2—C21	1.474 (2)
C62—H62A	0.9700	C21—H21A	0.9700
C62—H62B	0.9700	C21—H21B	0.9700
C62—H62C	0.9700	C21—H21C	0.9700
C7—C72	1.522 (3)	C3—C4	1.515 (3)
C7—C71	1.532 (3)	C3—H3A	0.9800
C7—H7	0.9900	C3—H3B	0.9800
C71—H71A	0.9700	C4—C5	1.526 (3)
C71—H71B	0.9700	C4—H4A	0.9800
C71—H71C	0.9700	C4—H4B	0.9800
C72—H72A	0.9700	C5—N1^ii	1.460 (3)
C72—H72B	0.9700	C5—H5A	0.9800
C72—H72C	0.9700	C5—H5B	0.9800
N1—C5^ii	1.460 (3)
O^i—Ga—O	81.04 (6)	C5^ii—N1—C11	111.04 (18)
O^i—Ga—C7	112.84 (7)	C5^ii—N1—C1	111.59 (15)
O—Ga—C7	109.58 (7)	C11—N1—C1	111.02 (17)
O^i—Ga—C6	109.36 (7)	N1—C11—H11A	109.5
O—Ga—C6	112.91 (7)	N1—C11—H11B	109.5
C7—Ga—C6	123.30 (8)	H11A—C11—H11B	109.5
O^i—Ga—Ga^i	40.56 (4)	N1—C11—H11C	109.5
O—Ga—Ga^i	40.48 (4)	H11A—C11—H11C	109.5
C7—Ga—Ga^i	118.40 (6)	H11B—C11—H11C	109.5
C6—Ga—Ga^i	118.30 (5)	N1—C1—C2	115.56 (16)
Ga^i—O—Ga	98.96 (6)	N1—C1—H1A	108.4
Ga^i—O—H1	122.8 (16)	C2—C1—H1A	108.4
Ga—O—H1	127.0 (16)	N1—C1—H1B	108.4
C61—C6—C62	110.70 (17)	C2—C1—H1B	108.4
C61—C6—Ga	112.18 (13)	H1A—C1—H1B	107.5
C62—C6—Ga	110.46 (13)	N2—C2—C1	115.24 (16)
C61—C6—H6	107.8	N2—C2—H2A	108.5
C62—C6—H6	107.8	C1—C2—H2A	108.5
Ga—C6—H6	107.8	N2—C2—H2B	108.5
C6—C61—H61A	109.5	C1—C2—H2B	108.5
C6—C61—H61B	109.5	H2A—C2—H2B	107.5
H61A—C61—H61B	109.5	C3—N2—C2	111.18 (15)
C6—C61—H61C	109.5	C3—N2—C21	110.71 (17)
H61A—C61—H61C	109.5	C2—N2—C21	108.36 (18)
H61B—C61—H61C	109.5	N2—C21—H21A	109.5
C6—C62—H62A	109.5	N2—C21—H21B	109.5
C6—C62—H62B	109.5	H21A—C21—H21B	109.5
H62A—C62—H62B	109.5	N2—C21—H21C	109.5
C6—C62—H62C	109.5	H21A—C21—H21C	109.5
H62A—C62—H62C	109.5	H21B—C21—H21C	109.5
H62B—C62—H62C	109.5	N2—C3—C4	114.00 (16)
C72—C7—C71	110.16 (17)	N2—C3—H3A	108.8
C72—C7—Ga	113.03 (13)	C4—C3—H3A	108.8
C71—C7—Ga	110.56 (13)	N2—C3—H3B	108.8
C72—C7—H7	107.6	C4—C3—H3B	108.8
C71—C7—H7	107.6	H3A—C3—H3B	107.6
Ga—C7—H7	107.6	C3—C4—C5	110.82 (16)
C7—C71—H71A	109.5	C3—C4—H4A	109.5
C7—C71—H71B	109.5	C5—C4—H4A	109.5
H71A—C71—H71B	109.5	C3—C4—H4B	109.5
C7—C71—H71C	109.5	C5—C4—H4B	109.5
H71A—C71—H71C	109.5	H4A—C4—H4B	108.1
H71B—C71—H71C	109.5	N1^ii—C5—C4	112.31 (15)
C7—C72—H72A	109.5	N1^ii—C5—H5A	109.1
C7—C72—H72B	109.5	C4—C5—H5A	109.1
H72A—C72—H72B	109.5	N1^ii—C5—H5B	109.1
C7—C72—H72C	109.5	C4—C5—H5B	109.1
H72A—C72—H72C	109.5	H5A—C5—H5B	107.9
H72B—C72—H72C	109.5
O^i—Ga—O—Ga^i	0.0	Ga^i—Ga—C7—C72	−22.72 (16)
C7—Ga—O—Ga^i	111.16 (7)	O^i—Ga—C7—C71	146.10 (14)
C6—Ga—O—Ga^i	−107.32 (7)	O—Ga—C7—C71	57.80 (16)
O^i—Ga—C6—C61	176.02 (13)	C6—Ga—C7—C71	−78.92 (16)
O—Ga—C6—C61	−95.75 (14)	Ga^i—Ga—C7—C71	101.29 (14)
C7—Ga—C6—C61	39.72 (17)	C5^ii—N1—C1—C2	−166.47 (17)
Ga^i—Ga—C6—C61	−140.49 (12)	C11—N1—C1—C2	69.1 (2)
O^i—Ga—C6—C62	51.99 (15)	N1—C1—C2—N2	81.3 (2)
O—Ga—C6—C62	140.23 (13)	C1—C2—N2—C3	−65.7 (2)
C7—Ga—C6—C62	−84.31 (16)	C1—C2—N2—C21	172.46 (16)
Ga^i—Ga—C6—C62	95.48 (14)	C2—N2—C3—C4	174.27 (16)
O^i—Ga—C7—C72	22.09 (16)	C21—N2—C3—C4	−65.2 (2)
O—Ga—C7—C72	−66.21 (15)	N2—C3—C4—C5	−169.74 (16)
C6—Ga—C7—C72	157.07 (13)	C3—C4—C5—N1^ii	72.3 (2)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O—H1···N2	0.80 (2)	2.03 (2)	2.8119 (19)	167 (2)