Alkali metal reduction of 1,3,2-diazaborol and 1,3,2-diazagermol derivatives based on 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene

Article abstract of DOI:10.1039/c9dt04652f

The reduction of [(dpp-bian)BBr] (1, dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with dilithium naphthalenide in Et₂O gives [{(dpp-bian)BBr}Li₂(Et₂O)₂]₂ (3). The treatment of [(dpp-b

Full text of DOI:10.1039/c9dt04652f

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Alkali metal reduction of 1,3,2-diazaborol and
1,3,2-diazagermol derivatives based on 1,2-bis
Cite this: DOI: 10.1039/c9dt04652f
[(2,6-diisopropylphenyl)imino]acenaphthene†
Daria A. Lukina,
Alexandra A. Skatova, Anton N. Lukoyanov,
Ekaterina A. Kozlova and Igor L. Fedushkin
*
The reduction of [(dpp-bian)BBr] (1, dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with
dilithium naphthalenide in Et2O gives [{(dpp-bian)BBr}Li2(Et2O)2]2 (3). The treatment of [(dpp-bian)BONa]
(5) and [(dpp-bian)Ge:] (7) with sodium is accompanied by protonation of the acenaphthylene fragment
and affords [{(H-dpp-bian)BONa(dme)2}Na(dme)3] (6) and [(H-dpp-bian)Ge:][Na(dme)3] (8), respectively.
Received 5th December 2019,
Accepted 29th January 2020
1
DOI: 10.1039/c9dt04652f
Compounds 3, 6 and 8 have been characterized by H NMR and IR spectroscopy. The molecular struc-
rsc.li/dalton
tures of 3, [(dpp-bian)BOK] (4) and 8 have been established by single crystal X-ray analysis.
tives reveal specific reactivities due to the presence of the
redox-active ligand.17–21 Among the poly-anionic metal com-
Introduction
Hydrocarbons with extended π-electron conjugated systems plexes there are only a few compounds containing tri- or tetra-
have attracted considerable attention owing to their unique anion of the redox-active ligand. Thus, in 2002 Gambarotta
structures and electronic properties. For example, sp2-hybri- and Budzelaar reported the lithium salt of the tri-anion of the
dized carbon networks, such as graphite1,2 and nanotubes,3,4 redox-active diiminopyridine (Chart 1d).22
serve as key anode components in rechargeable Li-ion bat-
In 2015 Bart and co-workers obtained the uranium complex
teries. Meanwhile, the electronic saturation of such systems [(MesPDIMe)UI3(thf)] containing the radical-anion of the pyridi-
allows fine-tuning their redox potentials and changing their nediimine ligand. A subsequent reduction of the prepared
chemical and physical properties. For instance, tetra-reduced complex with potassium graphite led to structurally character-
nanotubes are more soluble than common nanotubes.5 ized derivatives with the di-, tri- and tetra-anionic MesPDIMe
However, to date only a few examples of poly-anionic organic ligands.23 The abovementioned supercharged anions were
systems, in which a high negative charge is delocalized over characterized spectroscopically, and only a few of them were
many atoms, are known. Mainly these are alkali metal salts of isolated in an individual state and characterized structurally.
the tri-, tetra- or hexa-anions of carbocyclic or heterocyclic
In 2003 the formation of four anionic ligands derived from
hydrocarbons. Among the carbocyclic poly-anions are deriva- 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian)
tives of corannulene (Chart 1a), octalene, cycloheptaace- has been documented through isolation and structural charac-
naphthylene, pyracyclene, anthracene, rubrene, fullerene C60 terization of their sodium salts, [(dpp-bian)n−Na+nLm] (n = 1, 2,
and nanotubes.6–10 Representatives of heterocyclic poly-anions
are the tetra-anions of carboranes (Chart 1b), silacyclopenta-
diene, phthalocyanines and octasilyltrimethylenecyclopentene
(Chart 1c).11–13
Metal complexes based on redox-active ligands have
attracted increasing attention in the last few years. Transition
metal complexes with redox-active ligands are promising cata-
lysts for organic synthesis.14–16 Also, main group metal deriva-
G. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of
Sciences, Tropinina Str. 49, Nizhny Novgorod, 603137, Russian Federation.
E-mail: igorfed@iomc.ras.ru
†Electronic supplementary information (ESI) available: Crystallographic data
and 1H, 13C, 7Li and 11B NMR spectra. See DOI: 10.1039/C9DT04652F
Chart 1 Organic molecules for which poly-anions are known.
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7
3 or 4; L = diethyl ether or tetrahydrofuran).24 Stabilization of tioned in the range of 7.55–6.50 ppm.27 The 11B and Li NMR
(dpp-bian)n− with di- and trivalent cations, e.g. group II metals spectra of compound 3 exhibit the 11B and 7Li signals at δ =
and the lanthanides have been demonstrated just recently.25,26 16.5 and 1.0 ppm respectively. The crystal structure of com-
In this paper we report on the alkali metal reduction of 1,3,2- pound 3 has been determined by single crystal X-ray analysis.
diazaborol and 1,3,2-diazagermol derivatives derived from 1,2-
bis[(2,6-diisopropylphenyl)imino]-acenaphthene.
The reaction of 1,3,2-diazaborol 2 with KOH afforded the
potassium salt of 1,3,2-diazaboronic acid [(dpp-bian)BOK]27
(4). The reduction of compound 4 with potassium in thf
resulted in a highly soluble product that could not be isolated.
Like compound 4, complex [(dpp-bian)BONa] (5) can be pre-
pared by reacting 2 with an excess of NaOH in thf. The
reduction of complex 5 with an excess of sodium caused a
change in color from blue to red-brown. The replacement of
thf with 1,2-dimethoxyethane (dme) and a concentration of the
dme solution afforded red-brown crystals of [{(H-dpp-bian)
BONa(dme)2}Na(dme)3] (6, 86%) (Scheme 2). As for compound
3 the 1H NMR spectrum of complex 6 (Fig. 2) proves the
reduction of the acenaphthylene part of the dpp-bian ligand in
complex 5. However, from the spectrum of 6 it turns out that,
in contrast to 3, the negative charge in 6 is not delocalized
over six-membered rings but is located at the C-5 atom
(Scheme 2).
Results and discussion
Synthesis and spectroscopic characterization of alkali metal
salts of 1,3,2-diazaborol and 1,3,2-diazagermol derivatives
derived from dpp-bian
1,3,2-diazaborols [(dpp-bian)BX] (X = Br, 1; and Cl, 2) have
been prepared by the exchange reaction of [(dpp-bian)Na2]
with BX3 (1 : 1 molar ratio).27 The treatment of a suspension of
1 in Et2O with an excess of lithium in the presence of one
molar equivalent of naphthalene resulted in a brown solution.
The complex [{(dpp-bian)BBr}Li2(Et2O)2]2 (3, 54%) has been
isolated from the concentrated solution as green crystals
(Scheme 1).
1
The H NMR spectrum of 6 also indicates hydrogenation of
1
Complex 3 has been characterized by H NMR and IR spec-
the atom C-6. The protons of the non-hydrogenated ring give
rise to three signals at δ 5.76 (t, 1H), 5.59 (d, 1H), and 5.27 (d,
1H) ppm. The protons H2C-6 appear as a slightly broadened
signal at δ 3.75 (br s, 2H) ppm, while the HC-4 proton results
in a signal at δ 5.45 (d, 1H) ppm. Due to the negative charge
the HC-5 signal of the naphthalene fragment is high-field
troscopy. The reduction of 1 with lithium results in a formal
negative charge of −2 for the acenaphthylene fragment of the
dpp-bian ligands in 3. As a consequence the signals of the ace-
1
naphthylene protons in the H NMR spectrum of 3 (Fig. 1) are
high-field shifted (δ 4.51, pst, 2H; 3.93, d, 2H; and 2.88, d, 2H)
ppm, while those signals of the starting complex 1 are posi-
Scheme 2 Synthesis of compound 6.
Scheme 1 Synthesis of compound 3.
Fig. 1 A section of the 1H NMR spectrum of 3 (200 MHz, 300 K, thf-d8).
The signals ranging from δ 3.70 to 3.35 ppm correspond to thf and
diethyl ether. For a full spectrum see the ESI.†
Fig. 2 A section of the 1H NMR spectrum of 6 (200 MHz, 298 K, thf-d8).
The signals ranging from δ 3.70 to 3.20 ppm correspond to thf and dme.
For a full spectrum see the ESI.†
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shifted, δ 4.03 (dt, 1H) in comparison with all the other signals BONa] (5) and [(dpp-bian)Ge:] (7), but not for [(dpp-bian)BBr]
of the naphthalene part. The signals of the methyl protons of (1), [(dpp-bian)Ca(thf)4],25 and [(dpp-bian)LaI(thf)2]2.26 This
isopropyl substituents lie in the range of 1.28–0.90 ppm. Thus, regularity is not well understood. One can suggest that in the
the reduction of complex 5 with sodium in thf proceeds with a intermediates formed in the course of the reduction of 5 and 7
transfer of two electrons and one proton to dpp-bian. One can the negative charge is not well delocalized over two six-mem-
suggest that the initially formed dianionic 1,3,2-diazaborol bered rings but concentrated at the C-6 atom thus making it
[(dpp-bian)BO]2− cleaves the C–H bond in the solvent to form nucleophilic enough to split the C–H bond of ethereal
complex 6 as the final product.
solvents.
Upon the reduction of germylene [(dpp-bian)Ge:] (7) (in situ
from GeCl4 and [(dpp-bian)Na4])28 with two equivalents of
sodium in thf, the color of the reaction mixture changed from
red-brown to green, and finally to brown. The replacement of
thf with dme and concentration of the dme solution afforded
brown crystals of complex [H(dpp-bian)Ge:][Na(dme)3] (8, 47%)
(Scheme 3).
In contrast to the starting complex 7 product 8 does not
possess a mirror plane which bisects the N–Ge–N angle.
Therefore, the methine protons of the isopropyl groups
become non-equivalent in pairs. In the 1H NMR spectrum of 8
(Fig. 3) these protons afford two septets at δ 3.58 and
3.53 ppm. Four overlapping doublets of methyl protons range
from δ 1.42 to 1.21 ppm. The protons of the acenaphthylene
moiety in complex 8 produce the NMR signal set (δ = 6.29 (d,
1H), 6.19 (pst, 1H), 6.01 (d, 1H), 5.97 (d, 1H), 4.57 (dt, 1H),
and 4.07 (br s, 2H) ppm), which is very similar to that in the
spectrum of compound 6. This leads to the conclusion that
the ligand structures of 6 and 8 are identical.
The molecular structures of compounds 3, 4 and 8
The molecular structures of compounds 3, 4 and 8 have been
determined by single crystal X-ray analysis and are shown in
Fig. 4, 5 and 6, respectively. X-ray quality crystals of 3, 4 and 8
have been obtained from diethyl ether, toluene and dme,
respectively. For the crystal data and structure refinement
details see the ESI.†
The unit cell of compound 3 consists of two crystallographi-
cally independent molecules whose geometrical parameters
are very close. Each of them represents the centrosymmetric
Thus, protonation of dpp-bian under alkali metal reduction
of its metal complexes has been observed for [(dpp-bian)
Scheme 3 Synthesis of compound 8.
Fig. 4 The molecular structure of 3. Thermal ellipsoids are of 30%
probability. Hydrogen atoms are omitted.
Fig. 3 A section of the 1H NMR spectrum of 8 (400 MHz, 296 K, C6D6).
The signals at δ 3.12 and 2.98 ppm correspond to dme. For the full spec-
trum see the ESI.†
Fig. 5 The molecular structure of 4. Thermal ellipsoids are of 30%
probability. Hydrogen atoms are omitted.
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aryl substituents at the nitrogen atoms of the diimine frag-
ment are normal to this plane. Dearomatization of one of the
six-membered rings does not lead to the alteration of the N–Ge
and N–C bonds within the diazagermole cycle (Ge–N(1) 1.880
(3), Ge–N(2) 1.889(3), C(1)–C(2) 1.417(6), N(1)–C(1) 1.390(5),
and N(2)–C(2) 1.392(5) Å). Moreover these bond lengths almost
coincide with the bond lengths in the starting complex 7 (Ge–
N(1) 1.896(3), Ge–N(2) 1.885(3), C(1)–C(2) 1.381(5), N(1)–C(1)
1.374(4), and N(2)–C(2) 1.370(4) Å).28
Fig. 6 The molecular structure of anion 8. Thermal ellipsoids are of
30% probability. Hydrogen atoms are omitted except H(6) and H(6’).
Conclusions
We have shown that compound 1, in which 1,3,2-diazaborole
is fused with the naphthalene system, undergoes two-electron
reduction with lithium to afford di-anionic 1,3,2-diazaborole
derivative 3. The reduction of complex 5 with sodium in thf
proceeds with a transfer of two electrons and one proton to the
di-anionic dpp-bian ligand and results in diamagnetic mono-
anionic sodium 1,3,2-diazaborolate 6. The difference in the
structures of 3 and 6 could also be related to the stronger
Lewis acidity of Li+ vs. Na+. Dearomatization of one of the six-
membered rings also takes place when germylene 7 is reduced
with sodium to afford product 8. Compounds 6 and 8 rep-
resent a new class of metal complexes derived from non-inno-
cent 1,2-bis(arylimino)acenaphthenes. The study of their reac-
tivity towards organic substrates is in progress and will be pub-
lished elsewhere.
dimer. The inversion center is located in the middle between
two dpp-bian ligands that are disposed in parallel planes and
connected by two lithium atoms, resulting in a sandwich-like
structure. The structural motif of 3 is similar to those in
the lithium salt of the acenaphthylene di-anion
[Li(Et2O)2]2{µ2:η3[Li(η3:η3-C12H8)]2}29 and the sodium salt of
the dpp-bian tetra-anion [{(dpp-bian)Na4(thf)4}2].24 Further,
the structure of 3 can be compared with the sandwich-like
structure of the lithium salt of the corannulene tetra-anion
4− 7,8
C20H10
.
The coordination of lithium cations to six-mem-
bered rings in 3 confirms the two-electron reduction of the
naphthalene part in complex 3. The sandwiched lithium
atoms do not coordinate solvent molecules, while both the
outer sphere lithium cations coordinate two diethyl ether
molecules. The distance between the planes of the ligands in 3
is 3.88 Å. The distances from the internal lithium atoms to the
normal planes defined by the naphthalene fragments are
1.913 and 1.963 Å. The N(1)–C(1), N(2)–C(2) and C(1)–C(2)
bond lengths in compound 3 are close to those in boron com-
plexes of the dpp-bian di-anion, as for instance in [(dpp-bian)
BBr]30 (1) (N(1)–C(1) 1.395(2), N(2)–C(2) 1.399(2) and C(1)–C(2)
1.364(2) Å); [(dpp-bian)BCl]27 (2) (N(1)–C(1) 1.385(3), N(2)–C(2)
1.395(3) and C(1)–C(2) 1.362(4) Å); [(dpp-bian)BH]27 (N(1)–C(1)
1.398(2), N(2)–C(2) 1.391(2) and C(1)–C(2) 1.357(3) Å); and ger-
mylene 8 (N(1)–C(1) 1.390(5), N(2)–C(2) 1.392(5) and C(1)–C(2)
1.417(6) Å).
Experimental
General remarks
Compounds 3, 6 and 8 as well as some of their precursors are
sensitive towards oxygen and moisture. Therefore, all manipu-
lations were carried out under vacuum using Schlenk
ampoules. Toluene, diethyl ether, 1,2-dimethoxyethane and
thf as well as thf-d8 and C6D6 were dried over sodium/benzo-
phenone and condensed under vacuum in a reaction vessel or
an NMR tube just prior to use. IR spectra were recorded on an
FSM-1201 spectrometer in Nujol and 1H NMR spectra on
Bruker DPX-200 (200 MHz) and Bruker Avance III (400 MHz)
NMR spectrometers. The melting points were measured in
sealed capillaries. The dpp-bian was prepared by the conden-
sation of acenaphthenequinone with 2,6-diisopropylaniline in
acetonitrile under reflux.31 The yields of the products were cal-
culated from the amount of the dpp-bian used (0.5 g,
1.0 mmol) in the syntheses. Boron halides (1 M solutions in
hexane) and germanium chloride(IV) were purchased from
Aldrich and used as received.
ˉ
Complex 4 crystallizes in the tetragonal space group I4
with eight dimeric molecules in the unit cell. The dimers are
built from two chemically equivalent fragments (dpp-bian)
BOK that are connected through bridging potassium
atoms. The latter interacts with the π systems of the Ar substi-
tuents of the neighboring fragment. The central K2O2 core is
nearly flat with the K–O distances lying in the range of 2.533
(4)–2.619(4) Å. Interestingly, the B–N bond lengths in com-
plexes 2 and 4 are notably different (2: av. 1.435 Å; and 4: av.
1.490 Å).
[{(dpp-bian)BBr}Li2(Et2O)2]2 (3)
Complex 8 crystallizes in the orthorhombic space group
P212121. The chemical entity is composed of the germylene To a solution of [(dpp-bian)Na2] [in situ from dpp-bian (0.50 g,
anion (Fig. 6) protonated at the C(6) atom and the solvent sep- 1.0 mmol) and sodium (0.10 g, 4.34 mmol)] in toluene
arated cation [Na(dme)3]. The metallacycle GeN2C2 is flat and (30 mL), 1 M solution of BBr3 in hexane (1 mL, 1.0 mmol) was
well coplanar with two six-membered rings. The planes of the added. The color of the solution changed from green to red
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indicating the formation of [(dpp-bian)BBr]. After the separ- The reaction mixture was stirred at ambient temperature for
ation of precipitated sodium bromide the solvent was removed 2 h. After the separation of sodium chloride from the red-
under vacuum and diethyl ether (30 mL) was added. The brown solution of [(dpp-bian)Ge:] sodium metal (0.09 g,
resulting suspension was added to the mixture of lithium 4.0 mmol) was added. After stirring for 6 h at room tempera-
metal (0.05 g, 7.14 mmol) and naphthalene (1.28 g, 1.0 mmol). ture the color of the solution changed from red-brown to green
After vigorous stirring for 4 h the initial precipitate was dis- and finally to brown. The solvent was removed under vacuum
solved to form a brown solution, which was decanted from the and the residue was dissolved in dme (15 mL). The solution
metal. After concentration of the ether solution (15 mL) the formed was filtered off. Concentration of the solution under
green crystals of compound 3 (0.44 g, 54%) were isolated. M.p. vacuum caused the precipitation of brown crystals of complex
> 240 °C (decomp.). Anal. calcd for C96.75H127B2Br2Li4N4O4 8 (0.81 g, 47%). M.p. 168 °C. Anal. calcd for C48H71GeN2NaO6
1
1
(1619.22): C, 74.58; H, 7.47. Found: C, 74.27; H, 7.24. H NMR (867.64): C, 66.45; H, 8.24. Found: C, 65.87; H, 8.03. H NMR
spectrum (200 MHz, thf-d8, 300 K): δ = 7.27–6.95 (m, 6H, (400 MHz, C6D6, 296 K): δ = 7.38 (m, 6H, C6H3(Pri)2), 6.29 (d,
C6H3 Pr2), 4.51 (pst, 2H, J = 7.7 Hz, CH naphthalene part), 3.93 1H, J = 7.5 Hz, CH naphthalene part), 6.19 (pst, 1H, J = 6.8 Hz,
i
(d, 2H, J = 7.9 Hz, CH naphthalene part), 3.40 (q, 24H, J = 7.0 CH naphthalene part), 6.01 (d, 1H, J = 9.5 Hz, CH naphthalene
Hz, Et2O), 3.30–3.10 (m, 4H, CH(CH3)2), 2.88 (d, 2H, J = 6.2 Hz, part), 5.97 (d, 1H, J = 6.5 Hz, CH naphthalene part), 4.57 (dt,
CH naphthalene part), 1.25–1.05 (m, 48H, Et2O + CH(CH3)2). 1H, J = 9.5, J = 3.8 Hz, CH naphthalene part), 4.07 (br s, 2H, J =
11B NMR spectrum (64.21 MHz, thf-d8, 300 K): δ = 16.5 (s, 1B). 1.3 Hz, CH2 naphthalene part), 3.58 (sept, 2H, J = 7.0 Hz,
7Li NMR spectrum (77.78 MHz, thf-d8, 300 K): δ = 1.0 (s, 2Li). CH(CH3)2), 3.53 (sept, 2H, J = 7.0 Hz, CH(CH3)2), 3.12 (s, 12H,
IR (Nujol) ν/cm−1: 1587 s, 1540 s, 1253 m, 1175 m, 1153 w, DME), 2.98 (s, 18H, DME), 1.42 (pst, 18H, J = 7.0 Hz, CH
1104 w, 1057 m, 1043 w, 1001 w, 977 w, 935 m, 807 s, 764 m, (CH3)2), 1.21 (d, 6H, J = 7.0 Hz, CH(CH3)2). 13C NMR (100 MHz,
750 m, 695 w, 678 w, 654 m, 615 w, 579 w, 560 w, 527 w.
C6D6, 296 K): δ = 146.2, 145.9, 145.5, 141.9, 141.5, 140.8, 133.3,
126.0, 125.9, 124.9, 124.8, 122.9, 122.8, 111.8, 31.7, 28.1, 27.9,
27.2, 26.3, 24.0, 23.5. IR (Nujol) ν/cm−1: 1932 w, 1860 w, 1811
[{(H-dpp-bian)BONa(dme)2}Na(dme)3] (6)
To a solution of 227 (1.0 mmol) in thf (30 mL) NaOH (0.20 g, w, 1670 w, 1645 m, 1612 w, 1587 m, 1562 s, 1540 s, 1517 w,
5 mmol) was added. The reaction mixture was sonicated at 1405 w, 1363 w, 1349 w, 1325 m, 1298 m, 1253 m, 1192 m,
90 °C for 24 h. The color of the solution changed from red to 1167 m, 1112 s, 1084 s, 1029 m, 1010 w, 982 w, 957 w, 938 m,
blue. Precipitated NaCl was separated by filtration. The result- 902 m, 855 s, 803 s, 792 m, 775 w, 761 s, 695 m, 673 w, 665 m,
ing solution of [(dpp-bian)BONa] was poured to an excess of 651 w, 618 w, 596 w, 582 w, 568 w, 543 w, 532 m, 516 w, 493 w,
sodium metal (1 g, 4.3 mmol). After stirring for 8 h at ambient 460 m.
temperature the color of the solution changed from blue to
red-brown. After evaporation of the solvent under vacuum 1,2-
dimethoxyethane (20 mL) was added. Concentration of the
resulting solution (10 mL) led to the formation of 7 as red-
Conflicts of interest
brown crystals (0.85 g, 83%). M.p. 136 °C (decomp.). Anal.
There are no conflicts to declare.
calcd for C56H91BNa2N2O11 (1023.98): C, 65.63; H, 8.97. Found:
1
C, 65.23; H, 8.44. H NMR (200 MHz, thf-d8, 298 K): δ = 7.09
i
(d, 6H, J = 3.9 Hz, C6H3 Pr2), 5.76 (t, 1H, J = 7.3 Hz, CH
naphthalene part), 5.59 (d, 1H, J = 7.7 Hz, CH naphthalene Acknowledgements
part), 5.45 (d, 1H, J = 9.5 Hz, CH naphthalene part), 5.27 (d,
This study has been carried out within the State Assignment of
1H, J = 6.3 Hz, CH naphthalene part), 4.03 (dt, 1H, J = 9.4, J =
the Ministry of Science and Education of Russian Federation.
3.4 Hz, CH naphthalene part), 3.75 (br s, 2H, CH2 naphthalene
This work was performed using the facilities of the Analytical
Center of the G.A. Razuvaev Institute of Organometallic
Chemistry of Russian Academy of Sciences.
part), 3.68–3.54 (m, 12H, CH(CH3)2 + THF), 3.43 (s, 20H,
DME), 3.28 (s, 30H, DME), 1.74 (br s, THF), 1.28–0.90 (m, 24H,
CH(CH3)2). 13C NMR (100 MHz, thf-d8, 295 K): δ = 147.7, 147.1,
126.8, 126.3, 126.2, 124.6, 122.1, 111.4, 109.1, 105.7, 104.9,
104.5, 103.9, 87.3, 82.0, 67.2, 41.5, 38.2, 31.7, 30.1, 28.1, 27.7,
23.08, 22.8, 22.6, 22.5. IR (Nujol) ν/cm−1: 2725 w, 1642 w, 1606
w, 1584 m, 1537 m, 1305 w, 1250 m, 1192 m, 1115 m, 1087 m,
Notes and references
1059 w, 1032 w, 974 m, 935 w, 894 w, 858 m, 819 w, 802 s, 747
s, 736 s, 703 w, 670 m, 615 w, 562 w, 504 w, 474 w.
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