A new method of synthesis of monomeric aryloxide complexes of manganese (II): Structures of manganese phenoxides

Article abstract of DOI:10.1002/zaac.201000021

Monomeric manganese(II) complexes of bulky alkyl/arylsubstituted phenoxides, [Mn,{C₆H_nR_mO}₂(DME)] [1: R = C₆H₅, n = 3, m = 2 (2,6); 1: R = Me₃C, n = 3, m = 2 (2,6); 3: R = Me₃C, n = 2, m = 3 (2,4,6)] were prepared in yields of 37,44 and. 72 %, respectively, from the reaction of manganese powder, Hg(C₆F₅)₂ and the corre- sponding phenol in the presence of a little mercury in dimethoxyethane (DME). The compounds were characterized spectroscopically and by magnetic measurements. The single crystal, structures of 1 and 3 and also of the mixed phenoxide complex [Mn ((C₆H₃(C₆H₅)₂OO} {C ₆H,(Me₃C)₂-2,6-O}(DME)] 4 are reported.

Full text of DOI:10.1002/zaac.201000021

ARTICLE
DOI: 10.1002/zaac.201000021
A New Method of Synthesis of Monomeric Aryloxide Complexes of
Manganese(II): Structures of Manganese Phenoxides
Glen B. Deacon,*[a] Lai Yoong Goh,*[b] W. Roy Jackson,[a] Brian W. Skelton,[c]
Wei Chen,[d] and Allan H. White[c]
Keywords: Manganese; Phenoxides; Crystal structure; Alkoxides; Mercury
Abstract. Monomeric manganese(II) complexes of bulky alkyl/aryl- sponding phenol in the presence of a little mercury in dimethoxyethane
substituted phenoxides, [Mn{C6HnRmO}2(DME)] [1: R = C6H5, n = 3, (DME). The compounds were characterized spectroscopically and by
m = 2 (2,6); 2: R = Me3C, n = 3, m = 2 (2,6); 3: R = Me3C, n = 2, magnetic measurements. The single crystal structures of 1 and 3 and
m = 3 (2,4,6)] were prepared in yields of 37, 44 and 72 %, respectively, also of the mixed phenoxide complex [Mn{(C6H3(C6H5)2-2,6-
from the reaction of manganese powder, Hg(C6F5)2 and the corre- O}{C6H3(Me3C)2-2,6-O}(DME)] 4 are reported.
obviated by using sterically bulky aryloxide ligands, first de-
Introduction
veloped by Horvath [8]. To date, synthetic approaches for or-
Metal alkoxides have enjoyed almost a century of interest
gano-oxo derivatives of the transition metals mainly involve
[1], initially intermittent, beginning with the first report of alu-
the reaction of alcohols, phenols or phenoxides with the fol-
minium alkoxides in 1899 by Tishchenko [2], and then of bi-
lowing classes of compounds: (i) arylalkyl metal complexes,
metallic alkoxides by Meerwein and co-workers in the 1920s
e.g. [Mn(CH2CMe2Ph)2]2 [9] and Zr(CH2Ph)4 or
[3]. The further development of the modern chemistry of metal
Zr(CH2C6H4F)4 [10]; (ii) metal halides, e.g. [MnCl2(MeCN)]
alkoxides began in the laboratory of Bradley in the 1950s [4],
or [CrCl3(THF)3] [11]; (iii) metal amides [M{N(SiMe3)2}2]2
and has burgeoned therefrom. In the 1980s, interest in soluble
(M = Mn, Fe), giving homoleptic aryloxides [M{OAr}2]n (n =
monomeric transition metal alkoxides and aryloxides was ad-
1 [8], n = 2 [12]. Other specific methods involve the reaction
vanced by their observed intermediary role in processes such
of Group 4–6 metal halides with 2,6-dimethylphenoxy(tri-
as the carboxylation of olefins [5] and the hydrogenation of
methyl)silane [13], and the unusual utilization of simple binary
aldehydes and ketones [6]. In the same period the onset of sol-
carbonyls, e.g. [M2(CO)10] (M = Mn, Re) in the presence of
gel technology and the development of the MOCVD process
1,2-bis(diphenylphosphanyl)ethane (dppe) to yield fac-
for the deposition of metal oxides paved the way for the exten-
[(CO)3(dppe)MOR] (R = Me, Et, Ph) [14]. However, despite
sive use of these compounds as precursors for metal oxides in
these various methods, soluble monomeric alkoxides or phe-
the manufacture of electronic, ceramics and other high-tech
noxides of the d-block elements remain scarce, though slightly
materials [4d, 7], spurring a search for new efficient methods
more numerous for manganese [1, 4d], for which a higher in-
of synthesis and isolation, which are often impeded by their
terest has arisen because of the conversion of acylmanganese
extreme sensitivity to air and moisture, as well as their procliv-
complexes to alkoxy carbonyl derivatives upon treatment with
ity to polymerization. The latter tendency has been somewhat
syn-gas [15]. Alternative methods are therefore highly desira-
ble.
* Prof. Dr. G. B. Deacon
We have developed a simple and useful route for the synthe-
sis of phenoxides of the lanthanoid(II) and (III) elements [4d,
16] through redox transmetallation/ligand exchange, which in-
volves the direct reaction of the metal, bis(pentafluoro-
phenyl)mercury (and other diaryl mercurials) and phenol
HOAr [Equation (1)].
Fax: + 613-9905-4597
E-Mail: Glen.Deacon@sci.monash.edu.au
* Dr. L. Y. Goh
E-Mail: LaiYoongGoh@ntu.edu.sg
[a] School of Chemistry
Monash University
Melbourne, Vic 3800, Australia
[b] Division of Chemistry and Biological Chemistry
School of Physical and Mathematical Sciences
Nanyang Technological University
Singapore 637371, Singapore
M + Hg(C6F5)2 + 2HOAr → M(OAr)2 + 2C6F5H + Hg
(1a)
2Ln + 3Hg(C6F5)2 + 6HOAr → 2Ln(OAr)3 + 6C6F5H + 3Hg
(1b)
[c] School of Biomedical, Biomolecular and Chemical Sciences
Chemistry M313
Having successfully carried out the redox transmetallation
reaction between Hg(C6F5)2 and Mn powder [Equation (2)]
[17], even though manganese is much less electropositive than
the lanthanoid elements, the application of the more generally
The University of Western Australia
Crawley, WA 6009, Australia
[d] Department of Chemistry
University of Malaya
59100 Kuala Lumpur, Malaysia
1478
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 636, 1478–1483

Monomeric Aryloxide Complexes of Manganese(II)
di-tert-butylphenol (0.84 g, 4.08 mmol) and bis(pentafluorophenyl)-
mercury(II) (2.18 g, 4.08 mmol) in DME (25 mL) was ultrasonicated
in a stoppered flask at 50–60 °C. The reaction, monitored by the IR
spectra of sample aliquots, took 4 days to reach completion. The result-
ant mixture was filtered through Celite, and the pale yellow filtrate
concentrated to ca. 5 mL, mixed with a little n-hexane and left to crys-
tallise overnight at –28 °C. Three crops of fine colourless crystals of
2 were collected (total weight 0.49 g, 0.89 mmol, 44 % yield). Found:
C, 72.29; H, 9.05; Mn, 11.92. C32H52MnO4 (555.7) requires C, 69.16;
H, 9.43; Mn, 9.89 %. {With loss of DME, C28H42MnO2 (465.6) re-
useful one-pot reaction (1a) to manganese appears possible.
This paper describes the results of the investigation, including
the structures of three bulky aryloxides of manganese(II). Four
related reported structures are those of dinuclear manganese
2,4,6-tri-tert-butylphenoxide [12], the monomeric acetonitrile
complex [11], [Mn(C6H2(CF3)3-2,4,6)2(THF)3] [18], and
[Mn(OCPh3)2(py)2] [12].
Mn + Hg(C6F5)2 → Mn(C6F5)2 + Hg
(2)
quires C, 72.23; H, 9.09; Mn, 11.80 %.} IR (Nujol): ν = 2855vs,
˜
1581m, 1409vs, 1291ssh, 1277s, 1198m, 1150vw, 1100m, 1048s,
1025m, 863s, 869s, 822m, 751s, 738s, 657m, 547w cm–1. MS (m/z):
464 ([(Mn{C6H3(Me3C)2O}2) – H]+), 410 ([(Mn{C6H3(Me3C)O}2] –
C 4 H 7 ] + , 4 0 8 ( [ ( M n { C 6 H 3 ( M e 3 C ) O } 2 ) – C 4 H 9 ] + , 3 5 1
[(Mn{C6H3(Me3C)O}2) – 2(C4H9)]+, 206 ([Mn{C6H3(Me3C)O} +
3H]+), 191([Mn{C6H3(Me2C)O) + 3H]+), 175 ([Mn{C6H3(MeC)O}
+ 2H]+). μeff = 5.90 B.M.
Experimental Section
General Procedures and Physical Measurements
Manipulations were carried out using Schlenk techniques or in a dry-
box under an argon atmosphere, as all the compounds were extremely
sensitive to oxygen/water. Tetrahydrofuran (THF), 1,2-dimethoxye-
thane (DME), and hexane were distilled from sodium/benzophenone
prior to use. Manganese powder was obtained from Merck, and dried at
140 °C before use. 2,6-diphenylphenol (Aldrich) were used as supplied
while 2,6-di-tert-butylphenol (Merck) and 2,4,6-tri-tert-butylphenol
(Aldrich) were recrystallised from ethanol and evacuated dry before
use. Bis(pentafluorophenyl)mercury(II) was prepared according to re-
ported methods [19]. Elemental analyses (of evacuated samples) were
carried out by microanalytical laboratories at the University of Otago,
New Zealand, University Sains Malaysia, Malaysia or the Research
School of Chemistry, Australian National University, Canberra. IR
spectra were recorded as Nujol mulls on a Perkin–Elmer 1600 Series
FTIR spectrometer. Mass spectra were recorded on a VG Micromass
7070F mass spectrometer, using a sample holder which could be
loaded in the drybox. Magnetic moments were determined using a
Johnson–Matthey magnetic susceptibility balance calibrated with
Ni(en)3S2O3.
Single crystals of 2 could be obtained from DME/hexane at –28 °C
but these rapidly lost solvent of crystallisation, even when submerged
in oil, precluding a structure determination.
On exposure to a trace amount of air, a solution of 2 turned orange-
brown. Subjection of the solid residue to sublimation at ca. 80 °C/
10–6 Torr, gave some orange crystals, the crystal structure of which
confirmed the quinonoid compound 5 [8a].
[Mn{C6H2(Me3C)3-2,4,6-O}2 (DME)] (3): A suspension of manga-
nese powder (1.0 g, 18.2 mmol) and mercury (3 drops) in a solution
2,4,6-tri-tert-butylphenol (0.66 g, 2.51 mmol) and bis(pentafluoro-
phenyl)mercury(II) (1.34 g, 2.50 mmol) in DME (25 mL) was ultra-
sonicated at 50–60 °C. The reaction monitored by the IR spectra of
sample aliquots, took 6 days for completion. The resultant mixture was
filtered through Kieselguhr (5 × 1.2 cm), giving a pale brown solution,
which was concentrated in vacuo to ca. 2 mL. Addition of n-hexane
(ca. 2 mL), followed by cooling for several h at –28 °C, gave fine
colourless crystals of 3 (0.60 g, 0.90 mmol, 72 % yield). Found: C,
73.28, 76.31; H, 11.17, 10.96; Mn, 9.23. C40H68MnO4 (667.9) requires
C, 71.93; H, 10.26; Mn, 8.23 %. {With loss of DME, C36H58MnO2
Syntheses
[Mn{C6H3(C6H5)2-2,6-O}2(DME)] (1): A suspension of manganese
powder (0.50 g, 9.1 mmol) and mercury (3 drops) in a DME solution
(25 mL) of bis(pentafluorophenyl)mercury(II) (1.09 g, 2.04 mmol)
and 2,6-diphenylphenol (0.50 g, 2.03 mmol) in a stoppered flask, was
ultrasonicated at 50–60 °C. The reaction, monitored by IR spectra of
sample aliquots, took 4 days for completion. The resultant mixture
was filtered through a disk of Celite. The filtrate was concentrated to
saturation point and left to crystallise at –30 °C. Three successive
crops of colourless needles of 1 were collected (total 0.24 g,
0.38 mmol, 37 % yield). Found: C, 72.79, 72.92, 81.53; H, 6.20, 6.11,
6.28; Mn, 9.06, 10.27. C40H36MnO4 (635.6) requires C, 75.58; H, 5.71;
Mn, 8.64 %. {With loss of DME, C36H26MnO2 (545.5) requires C,
(577.8) requires C, 74.84; H, 10.12; Mn, 9.51 %.} IR (Nujol): ν =
˜
2855vs, 1424vs, 1359m, 1296s, 1273vs, 1244m, 1218w, 1194m,
1156vw, 1120w, 1096w, 1051s, 1019w, 974w, 920w, 890wsh, 878m,
862m, 839s, 820wsh, 785m, 746m, 723wsh, 668vw, 644w, 546m,
469m cm–1. MS (m/z): 998 [Mn2(C6H2(Me3C)3O)3(C6H2(Me)O) – H]+,
262 ([(C6H2(Me3C)3OH)]+), 248 ([(C6H2(Me3C)3OH) – CH2]+), 247
[(C6H2(Me3C)3OH) – Me]+ and 245 [(C6H2(Me3C)3OH) – Me – 2H]+.
μeff = 6.03 B.M.
Diffraction-quality single crystals were deposited from DME/hexane
solution after prolonged standing at –28 °C.
79.26; H, 4.80; Mn, 10.07 %.} IR (Nujol): ν = 2855vs, 1590m, 1583m,
˜
1560w, 1411s, 1318wsh, 1293s, 1249m, 1169w, 1104w, 1086vw,
1062m, 1026w, 871wsh, 856m, 804w, 768msh, 754s, 748s, 723wsh,
[Mn{C6H3(C6H5)2-2,6-O}{C6H3(Me3C)2-2,6-O}(DME)] (4): The
compound was fortuitously similarly deposited from DME/hexane in
low yield. Found: C, 72.89; H, 10.11. C36H44MnO4 (595.7) requires C
72.59, H, 7.45 %. {With loss of DME, C32H34MnO2 (505.6) requires
C, 76.03; H, 6.78 %.}
713m, 693m, 605m, 588m, 478w cm–1. MS (m/z)
:
545
246
([Mn{C6H3(C6H5)2O}2]+),
300
([Mn{C6H3(C6H5)2O}]+),
([C6H3(C6H5)2OH]+), together with lower intensity molecular mass
fragments:
845
([Mn2{C6H3(C6H5)2O}3]+)
and
599
([(Mn2{C6H3(C6H5)2O}2) – H]+). μeff = 5.82 B.M.
Diffraction-quality colourless crystals were deposited from DME solu-
tion after standing several days at ambient temperature.
Structure Determinations
For 1 and 4, unique data sets were measured using a single counter
[Mn{C6H3(Me3C)2-2,6-O}2(DME)] (2): A suspension of manganese instrument at ca. 295 K (monochromatic Mo-Kα radiation, λ =
powder (1.0 g, 18.2 mmol) and mercury (3 drops) in a solution of 2,6- 0.71073 Å; 2θ/θ scan mode) Gaussian absorption corrections were ap-
Z. Anorg. Allg. Chem. 2010, 1478–1483
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1479

G. B. Deacon, L. Y. Goh, W. R. Jackson, B. W. Skelton, W. Chen, A. H. White
ARTICLE
plied. For 3, a full sphere of CCD area detector diffractometer data was
measured at ca. 130 K (ω-scans), an “empirical”/multiscan absorption
correction being applied. In all structures, all unique data were used in
the full-matrix least-squares refinements on F2, refining anisotropic
displacement parameters for the non-hydrogen atoms, hydrogen atom
treatment following a riding model (reflection weights: (σ2(Fo)2 + (aP)2
Previous work [17] has demonstrated that redox transmetal-
lation occurs between Hg(C6F5)2 and manganese [Equation
(2)]. It is therefore likely that the compounds 1–3 are formed
by a subsequent protolytic ligand exchange [Equation (3)], as
has been established for LnII and LnIII compounds [22].
2
2
(+ bP))–1 (P = (Fo + 2Fc )/3)). No reflections with F > 4σ(F) were
considered “observed”. Neutral atom complex scattering factors were
employed within the SHELXL 97 program [20]. Pertinent results are
given below and in the Tables and Figures the latter showing non-
hydrogen atoms with 50 % displacement amplitude envelopes, hydro-
gen atoms having arbitrary radii of 0.1 Å. Full.cif depositions (exclud-
ing structure factor amplitudes) reside with the Cambridge Crystallo-
graphic Data Centre, CCDC-733616, -733617, -733618. These data
can be obtained free of charge from the Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data request/cif.
Mn(C6F5)2 + 2HOAr → Mn(OAr)2 + 2C6F5H
(3)
This methodology lends itself to a convenient one-pot syn-
thesis, with attractive mild reaction conditions for metal alkox-
ides or aryloxides, which are often thermally unstable.
These compounds are extremely air- and moisture-sensitive;
this feature together with facile loss of lattice solvent led to
generally unsatisfactory microanalytical data. Compound 1 at
different stages after isolation gave manganese analyses corre-
sponding to either retention or loss of DME, whilst those for
2 and 3 indicated loss of DME. The C, H analysis of 2 was
consistent with loss of DME, as was the average of two carbon
analyses for 3, whilst the C analysis of 4 was consistent with
DME retention, but both this and 3 gave high % H values.
Easy loss of THF from [Mn(C6H2(Me3C)3-2,4,6-O]2(THF)2]
has been reported [8a]. Electron impact mass spectra of 1–3
showed no evidence for DME, indicative of easy loss. 1 and 3
gave Mn2-containing ions, as would be expected for unsolv-
ated species, since the structure of [Mn(C6H2(Me3C)3-2,4,6-
O)2]2] is an aryloxo-bridged dimer [12]. Additionally intense
mononuclear manganese-containing ions were observed for 1
and 2, but not 3, and 2, for which an X-ray structure could not
be obtained, gave no dinuclear ions. Their pale yellow solu-
tions rapidly turned orange-brown to brown, in the presence of
traces of air. The IR spectroscopic data indicate the absence
of free phenol from adventitious hydrolysis. Their magnetic
moments (5.82–6.03 B.M.) correspond to five unpaired elec-
trons, consistent with the presence of high-spin MnII com-
pounds.
Crystal/Refinement Data
1. [Mn{C6H3(C6H5)2-2,6-O}2(DME)] ≡ C40H36MnO4, M = 635.6.
Monoclinic, space group C2/c (C62h, No.15), a = 11.050(13), b =
12.455(14), c = 23.992(8) Å, β = 99.02(6)°, V = 3261 Å3. Dc (Z = 4) =
1.295 g·cm–3. μMo = 0.45 mm–1; specimen: = 0.32 × 0.25 × 0.12 mm;
Tmin/max = 0.97. 2θmax = 50°; N = 2849, No = 905; R1 = 0.060, wR2 =
0.21 (a = 0.087), S = 1.13. |Δρmax| = 0.54 e·Å–3.
3. [Mn{C6H2(Me3C)3-2,4,6-O}2(DME)] ≡ C40H68MnO4, M = 667.9.
Monoclinic, space group P21/c (C52h, No.14), a = 14.828(3), b =
14.505(2), c = 36.988(5) Å, β = 95.34(2)°, V = 7921 Å3. Dc (Z = 8) =
1.120 g·cm–3. μMo = 0.37 mm–1; specimen: not recorded; Tmin/max
=
0.95. 2θmax = 45°; N = 9817, No = 4946; R1 = 0.12, wR2 = 0.31 (a =
0.13, b = 43), S = 1.05. |Δρmax| = 0.87 e·Å–3.
Variata. The data were weak and limited in scope and would support
meaningful anisotropic displacement parameter refinement for Mn
only.
From an air-contaminated solution of 2, orange crystals were
isolated, the crystal structure of which confirmed the quinoxide
compound 5, previously obtained in high yield from the oxida-
tion of unsolvated [Mn{C6H3(Me3C)2-2,6-O}2] (2-DME) with
excess O2 [8a], and in low yield by the oxidation of 2,6-di-
tbutylphenol with CoII complexes of Schiff bases [21].
4.
[Mn{C6H3(C6H5)2-2,6-O}{C6H3(Me3C)2-2,6-O}(DME)]
≡
C36H44MnO4, M = 595.7. Monoclinic, space group P21/c, a =
13.125(3), b = 15.682(10)), c = 17.15(2) Å, β = 111.41(7)°, V =
3286 Å3. Dc (Z = 4) = 1.204 g·cm–3. μMo = 0.44 mm–1; specimen: =
0.50 × 0.42 × 0.28 mm; Tmin/max = 0.93. 2θmax = 50°; N = 5308, No =
3118; R1 = 0.049, wR2 = 0.13 (a = 0.038, b = 3.9), S = 1.08. |Δρmax| =
0.28 e·Å–3.
Results and Discussion
Synthesis of Manganese Phenoxides
The reaction between manganese powder, bis(pentafluoro-
phenyl)mercury, Hg(C6F5)2 and substituted phenols, HOAr, in
the presence of a little mercury, has been investigated. A typi-
cal reaction was carried out by ultrasonication at 50–60 °C, of
a suspension of four equivalents of manganese to one equiva-
lent of Hg(C6F5)2 and HOAr, together with a few drops of
mercury, in 1,2-dimethoxyethane (DME). The reactions with
Molecular Structures
The results of the single-crystal X-ray studies in all three
2,6-diphenylphenol and 2,6-di-tert-butylphenol took four days cases are consistent with the presence of mononuclear
to reach completion, while that with 2,4,6-tri-tert-butylphenol [Mn(C6HnRmO)2(DME)] species, the manganese atom being
required six days. From the product solutions, colourless crys- coordinated by a pair of O-phenoxide donors and an O,O'-
tals of DME solvates of bis(phenoxo)manganese (1–3) were DME chelate. In 4, one molecule, devoid of crystallographic
obtained in yields of 37, 44 and 72 %, respectively.
symmetry, comprises the asymmetric unit of the structure, in
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Z. Anorg. Allg. Chem. 2010, 1478–1483

Monomeric Aryloxide Complexes of Manganese(II)
3, two, and in 1, one half of a molecule, the manganese atom
being disposed on a crystallographic twofold axis, which re-
lates the two phenoxide ligands and passes through the centre
of the (disordered) central C–C bond of the DME ligand.
Throughout the array Mn–O(DME) (ca. 2.2 Å) are appreciably
longer than Mn–O(phenoxide) (ca. 1.9 Å), consistent with the
loss of DME; O(DME)–Mn–O(DME) angles are similar (ca.
74°). The chelate array conforms to (quasi-) twofold symmetry
with C–O–C–C torsions trans and O–C–C–O ca. 53° (Table 1)
(Exception: the ligand of molecule 2 of compound 3, where
one of the C–O–C–C torsions is 83(1)°.) Mn–O distances are
rather erratic [e.g. in 4: 2.171(3), 2.225(3) Å], presumably a
consequence of hindrances consequent on the sprawling of the
bulky phenoxide substituents (Figure 1).
Table 1. Manganese atom environments for compounds 1, 3 and 4.
1
3 (mols. 1,2)
4
Distances /Å
Mn–O(Ph)
1.958(4) 1.905(7), 1.916(7) 1.895(2)
1.931(7), 1.932(7) 1.906(2)
2.221(5) 2.189(7), 2.178(8) 2.171(3)
2.218(8), 2.255(8) 2.225(3)
Mn–O(DME)
Angles/degrees
O(Ph)–Mn–O(Ph)
O(Ph1)–Mn–O(DME)
109.2(2) 137.4(3), 141.0(3) 125.6(1)
91.6(2) 98.8(3), 98.3(3)
94.3(1)
155.1(2) 104.0(3), 117.4(3) 122.3(1)
117.4(3), 108.6(3) 124.0(1)
107.3(3), 97.0(3)
105.5(1)
74.9(1)
O(DME)–Mn–O(DME)
Mn–O(Ph)–C(Ph)
72.3(2) 73.3(3), 74.6(3)
133.4(4) 127.9(6), 135.5(6) 149.9(2)
177.3(7), 143.2(7) 172.0(3)
Figure 1. Molecular projections of [Mn{C6H3(C6H5)2-2,6-O}2(DME)]
(1). (The (CH2)2 bridge of the DME is disordered (see text)) (a) down
and (b) normal to the twofold axis.
Mn–O(DME)–C(DME)
Mn–O(DME)–C(Me)
115.3(8) 106.2(7), 108.9(7) 109.3(2)
117.8(6) 116.9(6), 113.4(7) 114.3(2)
126.9(5) 127.8(8), 119.4(7) 121.4(2)
125.7(6), 133.0(7) 124.3(2)
DME torsion angles/degrees
C–O–C–C
atom and one of the ortho carbon atoms of the ring is
2.838(6) Å; the C–Mn–C angle is 149.4(2)°. Distances be-
tween the manganese atom and adjacent pendant and meta-
ring atoms are 3.080(7) and 3.464(7) Å. Despite their long dis-
tances, the pair of Mn–C(ortho) interactions may be regarded
as incipient occupants of a pair of trans sites in a six-coordi-
159(1) –157(1), 83(1)
–160(1) –177(1), 166(1)
–175.0(4)
–176.0(4)
–53.7(6)
48.2(4)
O–C–C–O
Mn–O–C–C
50(2)
25(2)
–55(1), 53(1)
58(1), –54(1)
–39(2) 26(1), –26(1)
33.0(5)
Similarly erratic are parameters associated with the bonding nate array – the Mn(O-DME)2(O-OPh)2 array is remarkably
of the phenoxide ligands. Again, within 4, where the Mn–O ‘flat’ and quasi-planar four-coordinate. In 4, the phenyl substit-
distances are essentially identical [1.895(2), 1.906(2) Å], asso- uents are similarly twisted with respect to the central ring (in-
ciated Mn–O–C angles differ by 20° (Table 1), and across all terplanar C6/C6 dihedral angles: 41.6(2), 51.6(2)°), but the
compounds the range of Mn–O–C is 127.9(6)–177.3(7)° (both closest approach to the manganese atom of any ring atom here
within the one compound, 3, Figure 2). The O–Mn–O angles is 3.412(5) Å (again from an ortho atom) (Figure 3).
between the phenoxide donors also vary widely from 109.2(2)
The existence of metal alkoxides or aryloxides in the mono-
(1) through 125.6(1) (4) to 137.4(3)/141.0(3)° in 3. The coordi- meric state requires the presence of bulky ligands to hinder
nation environments in 3 and 4 may be viewed as highly dis- or prevent intermolecular association. For manganese(II), few
torted four-coordinate tetrahedral, with O(DME)–Mn–O(Ph) examples have been structurally characterized [11, 12, 18], to
ranging between 94.3(1)–124.0(1)° (both extremes in 4). More the best of our knowledge, viz. the four-coordinate complexes
remarkable is the environment found in 1. Here the phenyl [Mn{C6H2(Me3C)3-2,4,6-O}2(MeCN)2].2MeCN [11], (Mn–O
substituents on the ligand have a role to play; the dihedral 1.910(6) Å, O–Mn–O 121.2(3)°, Mn–O–C 179.1(5)°) and
angles between their C6 planes (χ2 3.9, 8.0) and the central C6 [Mn(OCPh3)2(py)2] [12], (Mn–O 1.956(4) Å (×2), O–Mn–O
ring plane (χ2 9.5) are 49.6(2), 43.6(3)°, with one of the rings 140.4(2), Mn–O–C 131.2(4), 131.3(4)°) and the lithium salts
(and its twofold image) approaching the manganese atom in a of the anionic three- and four-coordinate complexes of the tri-
quasi(-offset)-η6 mode. The distance between the manganese tert-butylmethoxide ligand [23]. In the five coordinate com-
Z. Anorg. Allg. Chem. 2010, 1478–1483
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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G. B. Deacon, L. Y. Goh, W. R. Jackson, B. W. Skelton, W. Chen, A. H. White
ARTICLE
doubt that their monomeric nature is stabilized by the presence
of bulky ortho substituents on the phenoxides.
Acknowledgement
The authors thank the Australian Department of Industry, Technology
and Regional Development for a Bilateral Science and Technology
Program Grant (G.B.D., W.R.J. and L.Y.G.).
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Received: January 10, 2010
Published Online: April 26, 2010
Z. Anorg. Allg. Chem. 2010, 1478–1483
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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