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Stoichiometric Dependence of the Long-Established Reaction of Butyllithium with Pyridine A Hidden Secondary Reaction That Produces a Pyridine Adduct of a Lithiodihydropyridine.

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Table 1. Lattice constants
[A] and transition temperatures
[K] of sodium yttrium carbide bromide
[a] Brph
benrophenone, Naph
r, [cl
T, lbl
Reagents [a]
7.009(1 )
7.020( 1)
3.748( 1)
naphthalene. [b] As prepared. [c] Annealed.
Table 2. Lattice constants [A] and transition temperatures T, [K] of thorium yttrium carbide bromide and Y,Br,C,
Tho ,Y,&,C,
Th,,,Y, RBr2C2
Th,, ,Y, .Br,C,
Th,, ,Y, hBrLCl
This result appears to contradict the intercalation experiment
and must be interpreted in terms of an overcompensation effect.
The T, increase due to increased carrier concentration is outweighed by the T, decrease due to the introduced disorder.
The corresponding substitution of Y by Ca has not yet been
Received: November 29, 1995 [Z 8604IEl
German version: Angeiv. Chern. 1996. 108, 837--839
Keywords: intercalation compounds superconductivity yttrium compounds
[I] A. Simon. Afi,qtw C%en?.1987. 99, 602; Angew. Chem. / f i t . Ed. EngI. 1986, 26,
[2] A. Simon, H . J. Mattausch. R. Eger, R. K. Kremer. A q e i v . Cliem. 1991, 103,
1209. Anfieii Chmi. I n f . Ed. Engl. 1991, 30. 1188.
[ 3 ] A. Simon, A. Yoshiasa. M. Bicker, R. Henn, C . Felser. R. K. Kremer, H. J.
Mattausch. is. Anoyq. A&. Chcm. 1996, 622, 123.
[4] R. W. Henn. R. K. Kremer. W. Schnelle, A. Simon, P h w . Rev. Lett., submitted.
[ 5 ] U. Schwanitr-Schiiller. A. Simon, 2. Nutn[fimch. B, 1985, 40, 710.
[h] H. J . Mattausch. H . Borrmann. A. Simon. Z. Kristollogr. 1994. 209, 281.
171 M. Backer. Diplom thesis. Universitit Diisseldorf, 1994.
[XI R. Schollhorn. .Injieii.. Cheni. 1980, 92, 1015; Angeiv. Cheni. h i . Ed. Engi.
1980. 19. 983
[9] J. D. Corbett. in /ntrr.caldiow ChmiiJ/rj, (Eds.: M. Whittingham. A. Jacobson). Academic Press. New York. 1980. Chap. 11.
[lo] J. E. Ford, .I. D. Corbett, S. J. Hwu, Inorg. Cheni.1983. 22, 2789.
[l I ] J. R . Kennedy, A. Simon. fnorg. Chern. 1991, 30. 2564.
[12] D. W. Murphy. P. A. Christian, Science 1979. 205. 651.
1131 Lattice constants were obtained from Guinier-~Simonfilms [14] and subsequent least-squares refinement (for Na, ,,Y,C,Br, from Rietveld refinement).
Onset transition temperatures were taken from magnetic susceptibility measurcments (MPMS magnetometer: Fa. Quantum Design).
3. 11.
[14] A. Simon. J. .4ppl. C r , w f a l / u ~ r1970.
(1 51 J. Rouxel. J Chnn. P / i ~ s1986,
83. 841.
[16] For intercalation reactions in the presence of benzophenone o r naphthalene,
bentoplienone (130 mg. 0.71 mmol) and freshly cut sodium (50 mg, 2.2 mmol)
oi- nap1ith;ilcne (90 mg, 0.71) and sodium (30 mg. 1.3 mmol) were added to
Y,C,Br, (200 mg. 0.55 mmol) in a 100 mL Schlenk flask. After introducing
40 inL freshly distilled THF. the mixture was stirred for 5 days a t room temperature. The reaction mixture w'as filtered and washed several times with T H F
before the excess of agplomerated Na was removed. All operations were carried
out under an inert atmosphere (argon). The color of the intercalated crystals
iiitcnsifies lr~:iiiibronze (Y,C,Br,) to deep copper red.
[17] X-ray poadcr diagrams were measured at room temperature with an INEL
powder diffnictometer (0.2 inm capillary: Cu,,, radiation: 6.72 2 2 8 8
113.70 :step rate 0.03 ). Rietveld refinement wascarried out with the program
DBW 9006 (181 for two phases with YOBr as minority phase. The profile
matching of the 3567 data points was performed with a pseudo-Voigt function
and 19 parameters. of which 7 global ( 1 instrumental parameter. 5 profile
parameter. I asymmetry parameter) and 1 1 + 1 local parameters ( I overall scale
parameter. 1 parameter for preferred orientation, 4 for the lattice constants, 4
positional psrameters. 1 site occupation parameter for Na, 2 3 Y L C Z B r1I over;
all scale parameter for YOBr). Thermal vibrations were neglected. The C
positions were calculated for d ( C - C ) = 1.3 A and fixed. The residual values are
R , = 0.076. R,, = 0.105 and R,,,,,(I) = 0.057 for Na, ,,Y,C,Br, and RHragg(f)
= 0.076 for YOBr, the goodness of tit GUF = 2.97.
(181 D. W. Wiles, R. A. Young, J. Appl. CrystuNogr. 1981, 14, 148.
[19] The obtained positions (lattice constants in Table 2) for Na, ,,Y,C,Br, in the
space group C2jm (No. 12) are Na in Zu with site occupancy factor SUF of
O.l16(6):Yin4iwithr = 0.3540(6),= = 0.3680(3); B r i n 4 i w i t h s = 0.6861(6),
:= 0.1780(3), and C in 4i (not refined) with .x = 0.081. z = 0.470. The sample
contained 92.8(9)% Na, ,,Y,C,Br,. The lattice and positional parameters for
YOBr were taken from Ref. [20] and were not refined.
(201 I. Mayer, S. Zolotov, F. Kassierer, fnorg. Chem. 1965. If. 1637.
Stoichiometric Dependence of the LongEstablished Reaction of Butyllithium with Pyridine:
A Hidden Secondary Reaction That Produces
a Pyridine Adduct of a Lithiodihydropyridine**
William Clegg, Lorraine Dunbar, Lynne Horsburgh,
and Robert E. Mulvey*
Over 60 years ago Ziegler first recognized the value of alkyllithium compounds in converting pyridine to 2-alkyl-substituted derivatives."] However, only recently has the reactive intermediate in such processes, a solvated nitrogen-lithium adduct
1, been isolated and studied directly.[21. Examination of the
adduct 1['] revealed that addition is accompanied by bis(pyridine) solvation of the nitrogen-attached metal center,
which requires a n-butyllithium: pyridine ratio of 1:3. As reported here, by using more than a threefold molar excess of the
heterocycle, we have uncovered a remarkable secondary reaction which, despite the age of and considerable attention given
to this chemistry, had previously gone unnoticed. Formally the
new reaction involves reduction of pyridine by lithium hydride,
though it is certain that the conventional ionic solid does not
form during the process. The isolated product 2, characterized
both in the crystal and in solution, is a novel bis(pyridine)dihydropyridyllithium dimer.
Earlier work[21established that the solid adduct 1 was susceptible to LiH elimination even at ambient temperature. Here, by
preparing it in situ in hexane solution warmed to near boiling
[*] Prof. R. E. Mulvey, L. Dunbar
Department of Pure and Applied Chemistry
University of Strathclyde
GB-Gkasgow. G1 IXL (UK)
Fax: Int. code f(141) 552 0876
Angrii . < ' / z t n . lni. Ed. Eiifil. 1996. 35. N o . 7
(3 VCH
Prof. W. Clegg, L. Horsburgh
Department of Chemistry
University of Newcastle
GB-Newcastle upon Tyne, NE1 7RU (UK)
This work was supported by the UK Engineering and Physical Science Research Council and by the Caruegie Trust (sponsors of an undergraduate vacation scholarship to L. D.). We express our sincere gratitude to a very thorough
referee for assistance in the interpretation of the X-ray structural results.
Vtr/ugsgese//schufrm h H , 0-69451 we in he in^, 1996
0570-0833,'96/3507-0753 S 15.00f .?>/(I
positions. while the neutral ligands bind terminally, as is the
norm in complexed lithium dimers. While other neutral ligands
such as T H F have occasionally been reported in bridging roles
to lithium,[’] it is significant that to date no such cases have been
found for pyridine. Two of the terminal pyridine ligands exhibit
twofold disorder, but this could be resolved and refined with the
assistance of restraints. The geometries of the terminal pyridine
ligands compare favorably with those of the forty-four neutral
pyridine ligands bonded to lithium (covering seventeen crystal
structures) presently contained in
the Cambridge Structural Data1.321
base: the mean geometry in the
database is shown in Figure 2.
Though the two central N
for three minutes, this process would presumably accelerate.
124.0 I18.0
atoms (N(I), N(2)) bridge the Li
Critically, however, the dark wine red solution still maintained
Fig. 2. Mean bond lengths [A]
centers they form slightly shorter
its homogeneity (i.e., with no visible signs of LiH precipitation).
and angles [‘I in Li-bound pyribonds to lithium (mean length,
The introduction of further pyridine at this stage (making seven
dine ligands. The data were tak2.069 A) than their terminal counequivalents overall per equivalent of n-BuLi) followed by allowen from the Cambridge Structerparts (mean length, 2.098 A),
ing the solution to slowly cool from this elevated temperature,
tural Database,
reflecting the anionic nature of the
produced yellow-orange crystals of 2.[31This adduct is noticecentral pyridine ligands. These bridging ligands have geometries
ably more robust than I , which begins to degrade immediately
consistent with 1,4-dihydropyridyl anions, as evidenced by a
following isolation; 2 is stable indefinitely in the absence of air
comparison with the structure of bis(l,4-dihydro-l -pyridyl)and moisture. The byproduct of this reaction is 2-n-butylwhich also contains neutral, terminally
bis(pyridine)zinc(rr) ,IR1
pyridine. Significantly, no reaction was observed when a susbound pyridine ligands: in particular, the positions of the C = C
pension of lithium hydride in pyridine (more than 15 molar
double bonds [C24-C25, C21 -C22 and C11 -C12, C14-C15]
equivalents in a small amount of hexane) was heated vigorously
are clearly indicated by the pattern in bond lengths (see legend
for five hours, reflecting the formidable barrier presented by the
to Fig. 1). Presumably, in view of the mixture of 1,2-dihydrohigh lattice energy of the ionic solid.
and 1,4-dihydropyridyl anions found in solution, the latter must
The molecular constitution of 2 gives it the distinct advantage
crystallize preferentially in 2.
of being soluble in arenes, a property denied conventional lithiOne possible explanation for the formation of 2 is the inum hydride because of its extended face-centred cubic lattice
structure. ‘H NMR spectroscopic studies of 2 in [D,]ben~ene[~] tramolecular mechanism depicted in Scheme 1 . The incoming
revealed a 1 :1 mixture of 1,2-dihydro- and 1.4-dihydropyridyl
anions as well as four normal pyridine molecules. Lithium tetrakis(N-dihydropyridyl)al~minate.[~~
a reducing agent which
exhibits novel selectivity towards certain ketones, is known to
contain a similar mixture of dihydropyridyl anions, though they
are reported to be bound to aluminum and not to lithium. Each
distinct type of proton in 2 gives rise to an individual resonance
signal in the ‘H NMR spectrum, generally well-separated from
each other, thus making assignments straightfor~ard.[~I
Consistent with this solution data, a dinuclear arrangement is
found for crystalline 2 by an X-ray diffraction
structure (Fig. 1) shows that the anions occupy the bridging
\ NH
c 2 4 C23
Scheme 1. Part of the postulated mechanism of the synthesis of the bis(pyridine)dihydropyridyllithium dimer. py = pyridine.
Fig. 1. Molecubdr structure of 2 with important atoms labeled (thermal ellipsoid
plot (30 % probability)). Hydrogen atoms and minor disorder components are
omitted for clarity. Selected bond lengths [A] and angles [’I: Lit-N1 2.070(10),
Lil-N2 2.047(9). LIZ-N1 2.088(10). Li2-NZ 2.069(10). Li1-N3 2.104(9). Lil-N4
2.081(8), Li2-N5 2.106(10), Li2-N6 2.102(9): Lit-N1-Li2 74.8(3), Lil-N2-L12
75.7(4), N1-Lil-NZ 105.4(4), Nl-Li2-NZ 104.1(4). N3-Lil-N4 100.7(4). N5-Li2-N6
1 0 2 4 4 ) ; within bridging ligands: N-C 1.373(7)-1.412(7). C=C 1.288(8)-1.338(8),
C-C 1.387(9)- 1.453(10).
((? VCH Ver.iugsfi~,.sPllschuflmbH, 0-69451 Weinhein?, 1996
“excess” pyridine molecule in solvating (or attempting to solvate) the Li’ center sets up a six-membered cyclic intermediate.
Hydride transfer then occurs driven by the electron-poor, 6 +
nature of the pyridine C atoms and aided by the electron-donating character of the 2-butyl substituent in 1. Thus LiH never
actually forms in this formal LiH reduction process. Complex 2
could undergo a similar elimination process but the absence of
an electron-donating group in the 2-position---where two
H atoms reside---makes it less favorable, hence the reason why
2 is more stable than 1.
$ 7/5.00+
Angr2iv. C k m . Int. ELi. EngI. 1996, 35, N o . 7
2 The prcp;ii-au(in
performed i i i a Schlenk tube under z dry arson blanket.
ir-But).llithiuni (10 inniol in hexane) was added to a chilled volume of pyridine
(30 inniol) The iiiixiurc w:is allowed to warm to ambient temperature. leading to an
m m g e pi-ccipita~cDissolution occurred ongently rewarming the mixtureand additional pyridiiic (40 mmol) was then d d e d Immersing rhe solution in a water bath
tnniiit:iincd ;it 50 <' led t o the growth of transparent orange crystals of 2 [3]
Decoiiip fi-oni 90 c' Satidactory C. H. Li. N analyses Single crystals suitable for
X-KI) ci)at;ill<)gr:ipliy were examined and mounted under an inert oil.
ReceiLed: October 12. 1995
Reviaed vcrson: December 27. 1995 [Z 8467 IE]
German veraion: Aiigcii.. Chriii. 1996. /ti#. 81 5 816
Keywords: dihydropyridine * heterocycles
lithium compounds . structure elucidation
hydride transfer
[ I ] K. Zizglei-. t l . Lciscr, Chivii Be,-. 1930. 63. 1847: B. 1. Waketieid. 0,xoii"/ i r / i i i r i r i L I i , ! / i d ~4cadtmic Press. London. 1988. pp. 58 - 62.
121 a ) I> Barr. R Sniiith. R. E. Mulvey. D. Reed. P o / i . / i i 4 w i i 1988. 7. 665: b) D R
Aimstrong. I~ F Mul\ey. D Barr. R Snaith. D. Reed. J. Ovgfiiioiiwi Cheiii.
1988. 350. I'll
[3] Yield 01lirst crop. obtoined without recourse to subambient cooling (based on
i i i i t i r i l . i i i i ~ u i i t oC .ilkyllithiuin). 8 5 % . decomp. from 90 C . Elemental " ~ a l y s i s
for C. H. Li. N gxve the formula C,,,H,,Li,N,.
H NMR \pcctruin (400MHz. [D,]benzene, 300 K. TMS) 1.2-dihydro ligand.
d = 4 2X (111. I l l ' . 2 H . d ) . 4.77 ( H 2 . 1 H. m). 6 76 ( H 3 . 1 H. mi. 5.56 ( H 4 . 1 H.
i d ) . 7.36 (//J. I H. dm). 1.4-dihydro Iigand- 0 = 6.68 ( H I . HJ, 2H. dm). 4.61
( H ~ . I / 4 . 2 H . i n ) . l16iH3. ~ 1 3 . 2 H . i n ) . n e i i t r a l p y r i d i n ~ l i g d n d s :=S 6 6 3 ( / I H .
XH. 111). 6 x 9 l ; , H . 4 H . 111). 8.77 ( I f f . XH. in).
151 1'. T L:in.;hiir). .I 0 . Peterson. J. ,4171. C/iiwi. S o ( . 1963. X5. 2236.
161 C'i-!\ti dnia 1oi- 2 - c',,,H31Li2N,9. .LI = 490.5. orthorhombic. Piio2,. [ I =
17 XOX(4). h = I0 849(2). <' = 14.579(3) A. b'= 2816.6(10) A'. Z = 4. piriid =
I 157 g c i n ,'. /.(Cii,,) = 1.54184
11 = 0.535 mm-'. F!000) = 1040 Measurem e n t \ u e r c ni'ide a t 160 K o n ii Stoe-Siemens diffractometei- with a n Oxford
c r \ o ~ t r e . ~ COi>li.i
Cionl a
tiii of si7e 0 8 x 0.6 x 0.5mm3 Structure solution
w i t bq dii-ect incthods and refinement by full-matrix least squares on f' 2693
.ui-ed. 2611 unique (R,,, = 0 0147). 435 refined parameters.
- F:)21 x[i~.(F:)~]i
' = 0.195X.conventional R = 0 0598 for
rcllecrions ha\ing 6; > k ( F ; ) . goodness of fit S = 1.052 on F'.
large\t peal. hole II 2 9 -0.168 c k ' Twofold disorder oTorientation was re\ol\cd and reliiied for two terminal pyridine Iigands, with occupancy factors
0 771 0 129fX) .md relatnel! high displacement parameters for
man! (11the carhon a t o i i i s indicates possible further unresolved disorder i n the
hgaiidr R c \ ~ i a i i i i *for
. similarit) of geometry and on displacement parameters
were .ipplied t o the terminal ligands to aid the disorder refinement. but the
hi-idging Iigand, Mere relined freely. Hkdrogen iitoins were geometrically positioned .ind coii\traincd u ith a riding model. other tiionis were refined anisotropicnll! The ahwlutc mucture (poldr axis direction) could not be reliably determined c ' r ~ \ t ; i I l o aphic
darn (excluding structure factors) for the structure(s)
reported i i i lhh paper ha! e been depoiited with the Cambridge Crystallographic
Data C'cntrc iib \upplemcntary publication no. CCDC-I 79-4. Copies of the data
caii he ohtiiincd Tree ofcharge o i i application toThe Director. CCDC. 17 Union
UK (fiix Int. code + ( 1 1 2 3 ) 336-033: e-inail.
L Hoinhurgh. F %I. Mackenrie. R . E. ,Muive). J
C/im S w C/rwi.
101 I
A L. Speh. C ' r i \i Sifuci. Co~tim.1982. I I . 1621. For a related structure o f a
l i t l i i o h e i ~ ~ o q u i n ~dei-ivative
~ l ~ i ~ e see: W. N . Setzei-. P. von R. Schkyer. W Mahdi.
1-1 Ihctinch 7 < , / ii i / w d r f i i l 1988. 44. 3339
171 U ('leg:.
( ' o i i i i i i ~ ~ i r1995.
Diazodi(6pyridyl)methane and Diazophenyl(4-pyridy1)methane as Photoresponsive Ligands
for Metal-Carbene Hetero-Spin Systems
Noboru Kogd,* Yoichiro Ishimaru, and Hiizu Iwarnura*
Diphenylcarbene with a triplet ground state has served as an
important building block in the construction of molecules and
molecular assemblies with high spin multiplicities."' Thus the
connection of n cdrbene units through nwra-phenylene, 1,3.5benzenetriyl, and other ferromagnetic coupling units gives rise
to various polycarbenes with S = 17 ground states: in the series
the highest spin state reported so far is S = 9.I3l Efforts to increase the number of aligned spins have. however, been hampered by the development of antiferromagnetic intra- and/or
interchain interactions between the carbene centers assembled
in high local concentration; chemical bonds appear to be
formed in the extreme case.[41Our last recourse is a strategy of
assembling carbene centers in a rigid polymeric metal complex.
We report here on the
ligation of the pyridyl
nitrogens of diazodi(4-pyridy1)methane (1)
with coordinatively doubly unsaturated paramagnetic metal ions and
on the photolysis of the
resulting complex.
The 1:1 complex
[Mn(hfac),(l)] was obtained as orange rectanF4
gular prisms from a
solution of anhydrous
manganese(i1) bis(hexafluoroacetylacetonate)
[Mn(hfac),] and 1 in
n-heptane/CH,C12 containing a small amount
of methanol. The 1:2
complex [Mn(hfac),(2),]
analogously as a reference complex by using
two mole equivalents of Fig. 1. ORTEP dr'iwing (11 the X-ray crybtal
diazophenyl(4-pyridy1)- structure of [Mn(hfac),(2),] (ellipsoids ;II 30%
methane (2). X-ray crys- probabtltry)
tal structure analysis of
[Mn(hfac),(2),] shows that the two pyridyl nitrogens are ligated in tr'tms form to a manganese ion (Fig. 1). The Mn-N and
M n - 0 bond lengths are 2.28 and 2.1 5 A, respectively; the coordination geometry is an elongated octahedron. Considering that
1 is a bismonodentate ligand and forms a 1 : 1 complex with
[Mn(hfac),] in contrast with the monodentate ligand 2, we may
assume that the two pyridyl nitrogens of I are coordinated to two
different manganese ions to produce a one-dimensional chain.[']
[*] Prof Dr. N Kogi. Y. lshiinaru
Faculry of Pharmnceutical Science. Kyushu University
Mnidashi. Higashi-ku. Fukuoka 812-82 (Japan)
Prof. Dr. H. [wamui-a
Institute for Fundainental Rescarch in Organic Chemistr)
Kyushu Univeiait)
H a k o z i k i . Higashi-ku. Fukuoka 812-81 (Japiin)
Fax: lnt. code +(92)641-0915
This work was supported by a Grant-in-Aid o n Priority-Are.1-Research "Photot-eaction Dynamics-' from the Ministry of Education. Science and Culture.
J'ipan ( N o . 07228104)
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adduct, pyridin, established, reaction, lithiodihydropyridine, stoichiometry, long, secondary, dependence, producer, butyllithium, hidden
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