Synthesis and characterisation of complexes of the 2,6-diphenoxyphenyl ligand

Article abstract of DOI:10.1016/j.jorganchem.2010.12.023

The use of the 2,6-diphenoxyphenyl ligand has facilitated the stabilisation of lithium, silane and stannane complexes. The ortho-metallation reaction between 1,3-(PhO)₂C₆H₄ and ⁿBuLi yields 2,6-(PhO)₂

Full text of DOI:10.1016/j.jorganchem.2010.12.023

Journal of Organometallic Chemistry 696 (2011) 1787e1791
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterisation of complexes of the 2,6-diphenoxyphenyl ligand
Alexander J. Blake, Alexandra L. Gower, William Lewis, Graeme J. Moxey, Thomas J. Reade,
*
Deborah L. Kays
School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The use of the 2,6-diphenoxyphenyl ligand has facilitated the stabilisation of lithium, silane and stannane
complexes. The ortho-metallation reaction between 1,3-(PhO)2C6H4 and nBuLi yields 2,6-(PhO)2C6H3Li
(1); the crystallographically characterised dimer [2,6-(PhO)2C6H3Li(OEt2)]2 ([1.Et2O]2) can be obtained by
the crystallisation of 1 from diethyl ether. The reaction between 1 and Me3ECl gives rise to the struc-
turally authenticated complexes 2,6-(PhO)2C6H3EMe3 [E ¼ Si, 2; E ¼ Sn, 3].
Received 4 June 2010
Received in revised form
1 December 2010
Accepted 20 December 2010
Ó 2011 Elsevier B.V. All rights reserved.
Keywords:
Silane
Stannane
Lithium
Aryl
1. Introduction
2. Experimental
The utilisation of ligands featuring intramolecular donors is an
area of intense research interest [1]. In particular, aryl ligands
featuring alkoxysubstituents in the 2 and 6 positions havebeen used
to great effect in the stabilisation of main group and transition metal
compounds [2e6]. The rigid structure conferred by these ligands has
given rise to unusual planar tetracoordinate carbon atoms in the
tetrameric aggregate [2,6-(MeO)2C6H3Li]4 [2] and T-shaped oxygen
coordination within the trimer [2,6-(tBuO)2C6H3Li]3 [3]. The use of
the lithium complexes of 2,6-dialkyloxyphenyl ligands has been
instrumental in opening up newareas of transition metal chemistry,
forexamplewith the stabilisation of veryshort metal-metal bonding
interactions in [2,6-(MeO)2C6H3M]2 (M ¼ V, Cr, Mo) [4]. Moreover,
2,6-dialkyloxyphenyl ligands have been used to stabilise highly
reactive main group centres, such as compounds containing CaeC
2.1. General
All manipulations were carried out under a nitrogen or argon
atmosphere using standard Schlenk line or glove box techniques.
Hexane, diethyl ether, THF and toluene were pre-dried over Na wire
prior to passing through a column of alumina. Benzene-d6 (Goss)
was dried over potassium, while d8-THF was dried over CaH2; these
NMR solvents were degassed with three freezeepumpethaw cycles
prior to use. CDCl3 was used as received. 1H, 13C, 7Li, 29Si and 119Sn
NMR spectra for these complexes were collected on a Bruker DPX
400 spectrometer. Chemical shifts are quoted in ppm relative toTMS
(1H, 13C and 29Si), LiCl/D2O solution (7Li) or SnMe4 (119Sn). The NMR
spectra were assigned according to the ligand numbering scheme
(Fig. 1). Mass spectra were measured by the EPSRC National Mass
Spectrometry Service Centre, University of Wales, Swansea, and by
the departmental service at the School of Chemistry, University of
Nottingham. Perfluorotributylamine was used as the standard for
high-resolution EI mass spectra. Elemental analyses were per-
formed by Stephen Boyer, London Metropolitan University.
bonds [(THF)2Ca{m-C6H3-2,6-(OMe)2}3Ca(THF)I] [5] and the first
germanium radical to exhibit near-planarity at the metal centre, ꢀGe
[3,5-tBu2-2,6-(EtO)2C6H] [6].
The chemistry of the 2,6-substituted aryls of this type is domi-
nated by these 2,6-dialkoxy species; as part of our ongoing inves-
tigations into the use of bulky ligands in the stabilisation of unusual
coordination modes [7e9] we are investigating the synthesis of
complexes of 2,6-diaryloxy substituted aryl ligands, in order to
probe the effect of changing the electronic and steric features of 2,6-
substituted aryl ligand systems on their coordination chemistry.
2.2. Syntheses
2.2.1. Synthesis of 2,6-(PhO)2C6H3Li (1) and [2,6-(PhO)2C6H3Li
(OEt2)]2 ([1.Et2O]2)
To a solution of 1,3-(PhO)2C6H4 (1.0 g, 3.81 mmol) in hexane
(30 cm3) was added nBuLi (1.51 cm3, 3.81 mmol, 2.5 M in hexanes)
and the resulting mixture heated to reflux with stirring for 16 h.
* Corresponding author. Tel.: þ44 115 9513461; fax: þ44 115 9513555.
E-mail address: Deborah.Kays@nottingham.ac.uk (D.L. Kays).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.12.023

1788
A.J. Blake et al. / Journal of Organometallic Chemistry 696 (2011) 1787e1791
w, 889 w, 843 md, 826 w, 753 w, 744 md, 691 md. Mass spec. (EI): m/
z 334 ([M]þ, 85%), 319 ([M ꢁ Me]þ, 100%), 303 ([M ꢁ 2Me]þ, 15%),
261 ([M ꢁ SiMe3]þ, 10%), 226 ([M ꢁ OPh ꢁ Me]þ, 15%), 211
([M ꢁ OPh ꢁ 2Me]þ, 50%). Accurate mass: Calcd for C21H22O2Si:
334.1389, measd 334.1389; Calcd for C20H19O2Si (i.e. M ꢁ Me):
319.1145, measd 319.1137.
2.2.3. Synthesis of 2,6-(PhO)2C6H3SnMe3 (3)
To a suspension of 1 (0.20 g, 0.75 mmol) in toluene (20 cm3) was
added a solution of Me3SnCl (0.15 g, 0.75 mmol) in toluene (10 cm3)
and the resulting mixture was allowed to react with stirring
overnight. Volatiles were removed in vacuo and the precipitate was
extracted with hexane (30 cm3). Cooling of the saturated hexane
solution yielded 2,6-(PhO)2C6H3SnMe3 (3) as colourless crystals
suitable for X-ray diffraction studies. Yield: 0.14 g, 45%. 1H NMR
Fig. 1. Numbering scheme for the NMR spectra for the compounds in this
investigation.
The reaction mixture was cooled to room temperature and a white
precipitate of 2,6-(PhO)2C6H3Li (1) was collected by filtration. Yield:
0.78 g; 76%.
(C6D6, 298 K, 300.13 MHz):
d
0.52 (s, 9H, SnMe3, 2J117SnH ¼ 54.9 Hz,
2J119SnH ¼ 57.6 Hz), 6.66 (d, 2H, H3 þ H5, J ¼ 7.8 Hz), 6.98 (m, 3H,
H4 þ H24 þ H64), 7.06 (m, 4H, H22 þ H26 þ H62 þ H66), 7.17
(m, 4H, H23 þ H25 þ H63 þ H65). 13C{1H} NMR (C6D6, 298 K,
2.2.1.1. Data for 1. 1H NMR (d8-THF, 298 K, 400.20 MHz):
d 6.43
(d, 2H, H3 þ H5, J ¼ 7.6 Hz), 6.74e6.79 (m, 2H, H24 þ H64), 6.83
(t, 1H, H4, J ¼ 7.6 Hz), 6.86e6.90 (m, 4H, H22 þ H26 þ H62 þ H66),
7.10e7.15 (m, 4H, H23 þ H25 þ H63 þ H65). 13C{1H} NMR (d8-THF,
100.64 MHz):
d
ꢁ7.44 (SnMe3, 1J117SnC ¼ 352.4 Hz, 1J119SnC ¼ 369.1 Hz),
113.3 (C3 þ C5), 118.8 (C22 þ C26 þ C62 þ C66), 123.0 (C24 þ C64),
129.6 (C23 þ C25 þ C63 þ C65), 131.3 (C4), 158.9 (C21 þ C61), 163.5
(C2 þ C6), (C1 not observed). 119Sn{1H} NMR (C6D6, 298 K,
298 K, 100.64 MHz):
d
113.3 (C3 þ C5), 117.4 (C24 þ C64), 119.7 (C4),
125.6 (C22 þ C26 þ C62 þ C66), 128.9 (C23 þ C25 þ C63 þ C65),
161.8 (C21 þ C61), 164.4 (C1), 168.0 (C2 þ C6). 7Li NMR (d8-THF,
149.21 MHz):
d
ꢁ37.9. Elemental analysis: calcd for C21H22O2Sn: C
298 K, 155.53 MHz):
d
ꢁ0.79. Elemental analysis: calcd for
59.33, H 5.22; found: C 59.25, H 5.26%. IR (nujol mull) n
/cmꢁ1 2869 st,
C18H13LiO2: C 80.56, H 4.89; found C 80.59, H 4.89%. IR (nujol mull)
n/
1957 w,1739 w br,1598 w,1569 md,1490 md,1436 st,1261 md,1218 st,
1173 w, 1098 w, 1076 w, 1024 md, 976 w, 799 w, 771 w, 750 w, 691 md.
Mass spec. (EI): m/z 411 ([M ꢁ Me]þ, 100%), 396 ([M ꢁ 2Me]þ, 10%),
380 ([M ꢁ 3Me]þ, 20%), 302 ([M ꢁ OPh ꢁ 2Me]þ, 5%), 287
([M ꢁ OPh ꢁ 3Me]þ, 20%), 261 ([M ꢁ SnMe3]þ, 20%). Accurate mass:
Calcd for C20H19O1212Sn, i.e. (M ꢁ Me): 403.0428, measd 403.0426.
cmꢁ11592 md,1565 md,1490 st,1412 st,1262 w,1213 st,1162 st,1086
md,1023 md, 994 w, 948 st, 791 md, 761 md, 693 md, 585 w, 491 w.
Recrystallisation of 1 from diethyl ether solution at room
temperature yielded [2,6-(PhO)2C6H3Li(OEt2)]2 ([1.Et2O]2) as colour-
less crystals suitable for X-ray diffraction studies. Yield: 0.65 g; 66%.
2.2.1.2. Data for [1.Et2O]2. 1H NMR (d8-THF, 298 K, 400.20 MHz):
2.3. Crystallography
d
1.17 (t, 12H, OEt2, J ¼ 7.0 Hz), 3.43 (q, 8H, OEt2, J ¼ 7.0 Hz), 6.47
(d, 4H, H3 þ H5, J ¼ 7.6 Hz), 6.79e6.83 (m, 4H, H24 þ H64), 6.87
(t, 2H, H4, J ¼ 7.6 Hz), 6.90e6.94 (m, 8H, H22 þ H26 þ H62 þ H66),
7.14e7.19 (m, 8H, H23 þ H25 þ H63 þ H65). 13C{1H} NMR (d8-THF,
Crystals of [1.Et2O]2, 2 and 3 were mounted on dual-stage glass
fibres using YR-1800 perfluoropolyether oil (Lancaster) and cooled
rapidly to 150 K in a stream of cold nitrogen using an Oxford Cry-
osystems low-temperature device [10]. Diffraction data were
collected on a Bruker SMART APEX diffractometer equipped with
298 K, 100.64 MHz):
d
15.4 (OEt2), 66.0 (OEt2), 113.2 (C3 þ C5), 117.7
(C24 þ C64), 119.6 (C4), 125.4 (C22 þ C26 þ C62 þ C66), 129.1
(C23 þ C25 þ C63 þ C65), 161.8 (C21 þ C61), 164.4 (C1), 167.8
a graphite-monochromated Mo-Ka radiation source (
l
¼ 0.71073 Å).
(C2 þ C6). 7Li NMR (d8-THF, 298 K, 155.53 MHz):
d 1.04. Elemental
Absorption corrections were applied using a multi-scan method
(SADABS) [11]. All non-H atoms were located using direct methods
[12] and difference Fourier syntheses. All non-H atoms were refined
with anisotropic displacement parameters. Hydrogen atoms were
constrained in calculated positions and refined with a riding model.
For [1.Et2O]2, atoms C(19), C(20), C(21) and C(22) of the diethyl ether
ligand exhibited disorder over two positions. The disorder was
successfully modelled with 22:78 occupancy levels, in conjunction
with distance restraints and anisotropic displacement parameter
restraints and constraints. Crystal data for [1.Et2O]2, 2 and 3 can be
found in Table 1.
analysis: calcd for C44H46Li2O6: C 77.15, H 6.77; found: C 77.23,
H 6.65%. IR (nujol mull) n
/cmꢁ1: 1593 md, 1565 md, 1490 st, 1412 st,
1262 w,1214 st,1164 st,1071 md,1023 md, 994 w, 947 st, 911 w, 848
w, 815 w, 790 md, 762 md, 693 md, 585 w, 491 w.
2.2.2. Synthesis of 2,6-(PhO)2C6H3SiMe3 (2)
To a suspension of 1 (0.21 g, 0.78 mmol) in toluene (20 cm3) and
THF (1 cm3) was added Me3SiCl (0.15 cm3,1.18 mmol) viasyringe and
the resulting mixture was allowed to react with stirring for 72 h.
Volatiles were removed in vacuo and the precipitate was extracted
with hexane (30 cm3). Cooling of the saturated hexane solution to
ꢁ30 ꢂC yielded 2,6-(PhO)2C6H3SiMe3 (2) as colourless crystals suit-
able for X-ray diffraction studies. Yield: 0.19 g, 73%. 1H NMR (CDCl3,
3. Results and discussion
298 K, 400.20 MHz):
d
0.40 (s, 9H, SiMe3), 6.66 (d, 2H, H3 þ H5,
3.1. Syntheses
J ¼ 8.2 Hz), 7.05e7.09 (m, 4H, H22 þ H26 þ H62 þ H66), 7.14e7.18
(m, 2H, H24 þ H64), 7.26 (t, 1H, H4, J ¼ 8.0 Hz), 7.39e7.44 (m, 4H,
H23 þ H25 þ H63 þ H65). 13C{1H} NMR (CDCl3, 298 K, 100.64 MHz):
The ortho-metallation of 1,3-(PhO)2C6H4 with nBuLi proceeds
smoothly in hexane under reflux conditions over a period of 16 h to
yield 2,6-(PhO)2C6H3Li (1) as a colourless powder (Eq. (1)):
d
1.2 (SiMe3), 113.5 (C3 þ C5), 118.7 (C22 þ C26 þ C62 þ C66), 123.0
(C24 þ C64), 129.8 (C23 þ C25 þ C63 þ C65), 131.3 (C4), 157.6
(C21 þ C61),162.9 (C2 þ C6), (C1 notobserved). 29Si{1H} NMR (CDCl3,
n
n
1,3-(PhO)2C6H4 þ BuLi / 2,6-(PhO)2C6H3Li þ BuH
(1)
298 K, 79.51 MHz):
d
ꢁ5.27. Elemental analysis: calcd for C21H22O2Si:
C 75.41, H 6.63; found: C 75.57, H 6.38%. IR (nujol mull)
n
/cmꢁ1 2868
Recrystallisation of from Et2O affords [2,6-(PhO)2C6H3Li
1
st, 1959 w, 1595 md, 1588 md, 1561 md, 1489 md, 1435 st, 1290 w,
1260 w,1246 md,1218 st,1159 w,1109 w,1075 w,1055 w,1024 w, 984
(OEt2)]2 [1.Et2O]2 as colourless crystals suitable for X-ray diffraction
studies. Reaction of 1 with one equivalent of Me3ECl yields

A.J. Blake et al. / Journal of Organometallic Chemistry 696 (2011) 1787e1791
1789
Table 1
Table 2
Crystal data for [1.Et2O]2, 2 and 3.
Selected distances (Å) and angles (ꢂ) for [1.Et2O]2.
[1.Et2O]2
2
3
Li(1)eC(1)
Li(1_2)eC(1)
Li(1)eC(2_2)
Li(1)eO(1_2)
Li(1)eO(3)
C(2)eO(1)
C(6)eO(2)
C(7)eO(1)
C(13)eO(2)
C(1)eC(2)
2.159(4)
2.374(3)
2.530(3)
2.055(3)
1.948(3)
1.434(2)
1.418(2)
1.392(2)
1.378(2)
1.388(2)
1.393(2)
Li(1)/Li(1_2)
C(1)eC(2)eO(1)
C(1)eC(6)eO(2)
Li(1)eC(1)eLi(1_2)
C(1)eLi(1)eC(1_2)
C(2)eC(1)eC(6)
C(2)eO(1)eC(7)
C(6)eO(2)eC(13)
2.585(6)
116.00(15)
114.97(15)
69.36(14)
110.64(14)
111.29(15)
117.46(13)
120.35(14)
76.97(6)
Formula
Mw
Crystal system
Space group
a (Å)
C44H46Li2O6
C21H22O2Si
334.48
Monoclinic
P21/n
11.5391(8)
8.0884(5)
19.4009(13)
90
99.667(1)
90
C21H22O2Sn
425.8
Monoclinic
P21/n
19.8792(11)
8.1532(4)
11.5190(6)
90
99.350(2)
90
684.69
Triclinic
P1
9.2412(10)
9.7208(10)
11.7094(12)
98.000(2)
110.240(2)
98.723(2)
954.45(17)
150(2)
b (Å)
c (Å)
:C(7) ring and central phenyl ring
:C(13) ring and central phenyl ring
:C(7) and C(13) rings
a
b
g
(ꢂ)
(ꢂ)
(ꢂ)
64.43(5)
51.96(8)
38.25(11)
C(1)eC(6)
Li(1)/O(2)
V (Å3)
1785.0(2)
150(2)
1842.2(3)
150(2)
2.8976(35) :Li(1)eC(1)eLi(1_2)eC(1_2) and
central phenyl ring
T (K)
Dcalc (g cmꢁ3
F000
)
1.191
364
1.245
712
1.533
856
Symmetry operation _2 ¼ ꢁx, ꢁy þ 1, ꢁz þ 1.
Crystal size (mm)
0.47 ꢃ 0.21 ꢃ 0.14 0.52 ꢃ 0.48 ꢃ 0.17 0.84 ꢃ 0.16 ꢃ 0.06
aryllithium complexes [2,3,13,14]. The 7Li NMR spectra of 1 and
[1.Et2O]2 display only one resonance each: at ꢁ0.79 and
ꢁ1.04 ppm, respectively.
m
(mmꢁ1
)
0.077
1
0.141
4
1.396
4
Z
Reflections
measured
Independent
reflections
Rint
8391
11256
10308
The 29Si{1H} NMR chemical shift for 2 (
d
ꢁ5.27) is in good
4294
4084
4146
agreement with those values reported for related compounds;
¼ ꢁ5.10 for 2,6-(MeO)2C6H3SiMe3 and ¼ ꢁ6.6 for 2,4,6-
(MeO)3C6H2SiMe3 [15,16]. The 119Sn{1H} NMR resonance for 3
ꢁ37.9) is similar to those for related organostannanes 2,6-
(MeO)2C6H3SnMe3 (
d
d
0.059
0.0178
0.0384
Final GooF
R1, wR2
1.058
1.071
1.079
0.0584, 0.0784
ꢁ0.37, 0.64
0.0416, 0.107
ꢁ0.21, 0.42
0.0461, 0.107
ꢁ1.80, 1.55
(d
Min. and max.
electron
d
ꢁ43.7) and 2,4,6-(MeO)3C6H2SnMe3 ( ꢁ43.8)
d
[17]. The 29Si{1H} chemical shift for 2 is very similar to that for the
correspondingunsubstitutedphenylderivativePhSiMe3 (d29Si ¼ ꢁ4.1
in CDCl3) [18]; and indicates that there is likely no coordination of the
phenoxy units to the silicon atom in solution. Similarly, the slight
highfieldshiftof 3 compared to PhSnMe3 (d119Sn ¼ ꢁ24.1 in C6D6) [19]
indicates that there is likely no coordination of the phenoxy moieties
to the tin atom in solution. These findings are in contrast to the
highfield chemical shifts observed for the Si and Sn atoms in the
hypercoordinate complexes 2,6-(Me2NCH2)2C6H3EMe3 (E ¼ Si,
d29Si ¼ ꢁ7.7; E ¼ Sn, d119Sn ¼ ꢁ86.9) [20].
densities (e Åꢁ3
)
2,6-(PhO)2C6H3EMe3 (E ¼ Si, 2; E ¼ Sn, 3) in good yields (Eq. (2)).
Complexes 1, [1.Et2O]2, 2 and 3 have been characterised by multi-
nuclear NMR spectroscopy, elemental analysis and IR spectroscopy,
and additionally in the case of 2 and 3, mass spectrometry.
2,6-(PhO)2C6H3Li þ Me3ECl / 2,6-(PhO)2C6H3EMe3 þ LiCl
(2)
The NMR spectroscopy for 1 and [1.Et2O]2 has been performed
in d8-THF solution, allowing the unambiguous assignment of ligand
protons and carbons in the 1H and 13C{1H} NMR spectra. In the case
of both 1 and [1.Et2O]2 one ligand environment is observed in
solution; it is conceivable that the dissolution of these complexes in
a coordinating solvent such as d8-THF leads to the formation of
monomers, or that the existence of oligomers in solution combined
with fluxionality of the coordinated ligand oxygen (the coordina-
tion of one of the flanking phenoxy substituents to the lithium
centres is observed in the solid state for [1.Et2O]2) leads to the
observation of one ligand environment in the NMR spectra of these
complexes. Due to the poor solubility of 1 and [1.Et2O]2 it was not
possible to obtain low-temperature NMR measurements on solu-
tions of these compounds as has been performed for other
3.2. Crystal structure analyses
Although it has not been possible to isolate single crystals of 1, its
diethyl ether adduct [1.Et2O]2 forms single crystals suitable for X-ray
diffraction from saturated solutions at ambient temperature. The
crystal structure of [1.Et2O]2 is shown in Fig. 2 and relevant bond
lengths andangles can be found inTable 2. The solid state structure of
[1.Et2O]2 reveals a dimeric structure with the molecule lying across
a crystallographic inversion centre, which requires the lithium-
bonded aryl rings to be parallel. The lithium atoms bridge the phenyl
groups and the primary interactions are with the ipso carbons of the
central aryl rings. Additional coordination comes from diethyl ether
and one of the ether linkages in the 2,6-(PhO)2C6Hꢁ3 ligand. The
Fig. 2. Crystal structure of [2,6-(PhO)2C6H3Li(OEt2)]2 ([1.Et2O]2) (right) and side view
(left) with displacement ellipsoids set at 50% probability. Hydrogen atoms are omitted
for clarity. Symmetry operation _2 ¼ ꢁx, ꢁy þ 1, ꢁz þ 1.
Fig. 3. Crystal structure of 2,6-(PhO)2C6H3SiMe3 (2) with displacement ellipsoids set at
50% probability. Hydrogen atoms are omitted for clarity.

1790
A.J. Blake et al. / Journal of Organometallic Chemistry 696 (2011) 1787e1791
Table 3
Selected distances (Å) and angles (ꢂ) for 2.
Si(1)eC(1)
Si(1)eC(7)
Si(1)eC(8)
Si(1)eC(9)
C(2)eO(1)
C(6)eO(2)
C(1)eC(2)
C(1)eC(6)
1.9019(14) C(2)eC(1)eC(6)
1.8636(15) C(1)eC(2)eO(1)
1.8617(15) C(1)eC(6)eO(2)
1.8682(15) C(2)eO(1)eC(10)
1.3969(16) C(6)eO(2)eC(16)
1.4028(16) :C(10) ring and central phenyl ring
1.4015(18) :C(16) ring and central phenyl ring
1.4009(18) :C(10) and C(16) rings
114.27(12)
116.75(11)
119.11(12)
117.89(10)
117.56(10)
76.69(4)
86.96(4)
27.34(6)
Si(1)/O(1) 2.9764(11)
Si(1)/O(2) 3.2419(10)
twofold aggregation observed for [1.Et2O]2 differs from that of the
tetrameric aggregate [2,6-(MeO)2C6H3Li]4 [2] and the trimer [2,6-
(tBuO)2C6H3Li]3 [3].
Fig. 4. Crystal structure of 2,6-(PhO)2C6H3SnMe3 (3) with displacement ellipsoids set
at 50% probability. Hydrogen atoms are omitted for clarity.
The solid state structure of [1.Et2O]2 features a planar Li(1)eC
(1)eLi(1_2)eC(1_2) unit [S internal angles ¼ 360ꢂ by symmetry;
symmetry operation _2 ¼ (ex, ey þ 1, ez þ 1)], akin to related m-
terphenyl dimers [2,6-(2,6-Me2C6H3)2C6H3Li]2 and [2,6-(2,3,4,5,6-
Me5C6)2C6H3Li]2 [21]. The distance between the lithium centres in
[1.Et2O]2 [Li(1)/Li(1_2) ¼ 2.585(6) Å] is similar to that found in
vary significantly [76.97(6)ꢂ and 64.43(5)ꢂ]; this difference is
presumably in part due to the coordination of the phenoxy ring to
the Li centre affecting the former angle.
Single crystals of 2 and 3 of quality suitable for X-ray diffraction
were obtained by the storage of saturated hexane solutions at
ꢁ30 ꢂC. The crystal structure of 2 is shown in Fig. 3 and relevant
bond lengths and angles can be found in Table 3. The comparison of
selected crystallographic parameters of 2 and 3 with literature
values can be found in Table 4. In 2, the SieC(aryl) distance [Si(1)eC
dimeric complexes [2,4,6-(CF3)3C6H2Li]2 and [2,6-(Me2PCH2)2
-
C6H3Li]2 [13,14]. Unlike these more symmetrical aryl bridged
dimers, the Li(1)eC(1) and Li(1_2)eC(1) distances in [1.Et2O]2 are
very different [2.159(4) and 2.374(3) Å, respectively], which may be
a reflection of the asymmetrical coordination of the flanking phe-
noxy groups (vide infra) in these complexes. The difference
between the two LieC distances in [1.Et2O]2 is greater than that in
[2,6-(2,3,4,5,6-Me5C6)2C6H3Li]2 [2.176(2) and 2.230(2) Å] [21]. The
Li(1)eC(1)eLi(1_2) angle of 69.36(14)ꢂ is in the range of that
reported for other dimeric lithium aryls [61.74(10)e73.82(18)ꢂ] [21-
23]. Overall, the coordination environment around C(1) in the solid
state structure of [1.Et2O]2 is distorted tetrahedral.
(1) ¼ 1.9019(14) Å] is similar to that found in 2,4,6-(MeO)3C6H2
-
SiMe3 [ave. ¼1.904(3) Å] [16]. This distance is longer than the SieC
(alkyl) distances in 2; ave. SieC(alkyl) distance ¼ 1.8645(26) Å. The
two Si/O distances for 2 differ significantly [Si(1)/O(1) ¼ 2.9764
(11) Å, Si(1)/O(2) ¼ 3.2419(10) Å], this difference in distances has
also been seen in 2,4,6-(MeO)3C6H2Si(CH2Cl)3 [Si/O ¼ 2.8708(15)
and 3.069(14) Å] [26] and 2,4,6-trimethoxysilanes [27]. These Si/O
distances are smaller than the sum of the van der Waals radii
for these elements [3.65 Å] [25], but are significantly longer
than a typical SieO bond for a four-coordinate Si atom [ave. 1.63 Å]
[28].
A comparitively short Li(1)eO(1_2) distance [2.055(3) Å] indi-
cates relatively strong coordination of one phenoxy unit to each
lithium centre. The coordination environment around O(1_2) is
pyramidal [S(angles) ¼ 335.56(13)ꢂ], concomitant with this the Li
(1)eO(1_2) distance in [1.Et2O]2 is in the range of LieO(pyramidal)
In the case of 3, the SneC(aryl) distance [Sn(1)eC(1) ¼ 2.157(4)
Å] is longer than that found in 2,5-(C8H17O)2C6H2(SnMe3)2-1,4
[SneC(aryl) ¼ 2.146(2) Å], presumably due to the greater degree of
crowding around the Sn centre in 3 [29]. The crystal structure of 3 is
shown in Fig. 4 and relevant bond lengths and angles can be found
in Table 5. This distance in 3 is similar to those SneC(aryl) bond
lengths found in the sterically crowded crown ether complex
dimethylbis[(1,3-phenylene-16-crown-5)-2-yl]stannane [2.148(3),
2.152(2) Å] [30]. Analogous to the short Si/O distances in 2, short
Sn/O distances are observed in 3 [Sn(1)/O(1) ¼ 3.101(3) Å, Sn
(1)$$$O(2) ¼ 3.395(3) Å], the shorter of these being similar to that
found in 2,5-(C8H17O)2C6H2(SnMe3)2-1,4 [Sn/O ¼ 3.094 Å]. The
Sn/O distances in 3 are smaller than the sum of the van der Waals
radii for these elements [3.80 Å] [25], but are significantly longer
than that of a typical SneO bond for a four-coordinate Sn atom [ave.
2.14 Å] [28].
distances reported by Brandsma and co-workers for [2,6-(tBuO)2
-
C6H3Li]3 [2.043(6)e2.111(5) Å] [3]. The central ligand aryl rings sit
at an angle of 38.25(11)ꢂ out of the best mean plane of the Li(1)eC
(1)eLi(1_2)eC(1_2) moiety; this is in the range of that reported for
dimeric m-terphenyl lithium complexes (32.4e43.5ꢂ) [21,24], but
smaller than that for other pincer-type lithium dimers such as [2,6-
(Me2PCH2)2C6H3Li]2 [14]. In [1.Et2O]2 the Li(1)/O(2) distance
[2.8976(35) Å] is significantly longer than that for Li(1)eO(1_2), but
still significantly shorter than the sum of the van der Waals radii for
these elements [3.75 Å] [25], indicating the possibility of a weak
interaction between this oxygen and the lithium atom in the solid
state. The formation of dimers and the intramolecular coordination
of only one phenoxy moiety in [1.Et2O]2 may be indicative of
greater steric demands of the 2,6-(PhO)2C6Hꢁ3 ligand compared
with 2,6-(MeO)2C6H3ꢁ and 2,6-(tBuO)2C6Hꢁ3 . In [1.Et2O]2 the two
flanking phenyl rings form a dihedral angle of 51.96(8)ꢂ; the
dihedral angles between these phenyls and the central aryl ring
The torsion angles between the two flanking phenyl rings in 2
and 3 [27.34(6)ꢂ and 29.09(19)ꢂ, respectively] are comparable to
Table 4
The comparison of selected crystallographic parameters (Å) of 2 and 3 with literature values.
EeC(aryl)
EeC(alkyl)
E/O(1)
E/O(2)
Ref.
2
1.9019(14)
1.904(3)
1.854(2)
2.157(4)
2.146(2)
2.150(4)
1.8645(3)
1.870(6)
1.869(3)
2.135(7)
2.143(5)
2.134(4)
2.9764(11)
2.926
2.8768(15)
3.101(3)
3.094
3.2419(10)
3.129
3.069(14)
3.395(3)
e
This work
[16]
[26]
This work
[29]
[30]
2,4,6-(MeO)3C6H2SiMe3
2,4,6-(MeO)3C6H2Si(CH2Cl)3
3
2,5-(C8H17O)2C6H2(SnMe3)2-1,4
Dimethylbis[(1,3-phenylene-16-crown-5)-2-yl]stannane
3.075(3)
2.233(3)

A.J. Blake et al. / Journal of Organometallic Chemistry 696 (2011) 1787e1791
1791
Table 5
(b) M. Rubio, A. Suarez, D. del Rio, A. Galindo, E. Alvarez, A. Pizzano, Organ-
ometallics 28 (2009) 547;
Selected distances (Å) and angles (ꢂ) for 3.
(c) A. Soran, H.J. Breunig, V. Lippolis, M. Arca, C. Silvestru, Dalton Trans. (2009)
77;
(d) J. Cho, T.K. Hollis, T.R. Helgert, E.J. Valente, Chem. Commun. (2008) 5001;
(e) M.M. Al-Ktaifani, P.B. Hitchcock, M.F. Lappert, J.F. Nixon, P. Uiterweerd,
Dalton Trans. (2008) 2825;
Sn(1)eC(1)
Sn(1)eC(19)
Sn(1)eC(20)
Sn(1)eC(21)
C(2)eO(1)
C(6)eO(2)
C(1)eC(2)
C(1)eC(6)
Sn(1)/O(1)
Sn(1)/O(2)
2.157(4)
2.135(4)
2.128(4)
2.143(4)
1.403(5)
1.398(5)
1.389(6)
1.392(5)
3.101(3)
3.395(3)
C(2)eC(1)eC(6)
C(1)eC(2)eO(1)
C(1)eC(6)eO(2)
C(2)eO(1)eC(7)
115.4(4)
117.0(4)
118.7(4)
118.1(3)
117.5(3)
76.54(13)
86.38(12)
29.09(19)
(f) R. Jambor, B. Kasna, K.N. Kirschner, M. Schurmann, K. Jurkschat, Angew.
Chem. Int. Ed. 47 (2008) 1650;
C(6)eO(2)eC(13)
:C(7) ring and central phenyl ring
:C(13) ring and central phenyl ring
:C(7) and C(13) rings
(g) J.L. Bollinger, O. Blacque, C.M. Frech, Angew. Chem. Int. Ed. 46 (2007) 6514;
ꢀꢁ ꢁ
ꢁ
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(h) L. Dostál, R. Jambor, A. Ruzicka, I. Císarová, J. Holecek, M. Biesemans,
R. Willem, F. De Proft, P. Geerlings, Organometallics 26 (2007) 6312;
(i) V. Pandarus, D. Zargarian, Chem. Commun. (2007) 978.
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that found in 2,6-(PhO)2C6H3P(O)FH (29.41ꢂ) [31]. These differ
significantly from the corresponding value in [1.Et2O]2 [51.96(8)ꢂ]
due to the differing coordination environments in these complexes.
The torsion angles between the least-square mean planes of the
flanking phenyl rings and the central aryl are similar for 2 and 3
[76.69(4)ꢂ and 86.96(4)ꢂ for 2, 76.54(13)ꢂ and 86.38(12)ꢂ for 3].
4. Conclusions
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The ortho-metallation reaction between 1,3-(PhO)2C6H4 and
nBuLi forms 2,6-(PhO)2C6H3Li (1) in good yields. We have shown
that 1 can be used as a precursor towards the formation of new
aryl-element bonds (e.g. in compounds 2 and 3) via methathesis
chemistry. Long Si/O and Sn/O distances indicate that any
interactions between these atoms in 2 and 3 are certainly very
weak. Reactivity studies of these compounds are underway.
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Acknowledgements
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We acknowledge the Nuffield Foundation (Undergraduate
Research Bursary for A. L. G.), EPSRC and the University of Not-
tingham for financial support of this research. We also thank the
EPSRC National Mass Spectrometry Service Centre for mass spec-
trometry measurements on some of the compounds and Mr. Ste-
phen Boyer (Microanalysis Service, London Metropolitan
University) for elemental analyses.
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Appendix A. Supplementary material
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[28] F.H. Allen, Acta Cryst. B58 (2002) 380.
CCDC-778702, CCDC-778703, and CCDC-778704 (for [1.Et2O]2, 2
and 3) contain the supplementary data for these compounds. These
data can be obtained free of charge from The Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
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