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Chelate Complexes of Tripodal Aliphatic Triisocyanide Ligands.

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Experimental Procedure
Fig. 3 Arrhenius plot of the rate constants k [s-'1 for the proton exchange in
the H,O; ion.
Crystalline sodium hydroxosodalite hydrate [Na,(H,O,)],[SiAIO,],
was prepared according to the procedure given in [I 31 from sintered Kaolin and carbonate-free, 16M sodium hydroxide solution by hydrothermal synthesis at
623 K and 110 MPa. The crystals (0.5-1 mm) were ground into fine powders
prior to NMR study. A microcrystalline powder of sodium hydroxoalumogermanate sodalite hydrate ~a,(H,O,)],[GeAIO,], was obtained from GeO,,
y-Al,O,, and carbonate-free, 1 6 sodium
hydroxide solution at 473 K and a
reaction time of 14 days in teflon-coated steel autoclaves. The 'H MAS NMR
spectra were recorded at 400.13 MHz with a Bruker MSL-400 NMR spectrometer utilizing a double bearing MAS probe and ZrO, rotors with 4 mm diameter. Dry nitrogen was used as bearing and drive gas for the sample rotation, the
rotation rate was kept constant at 8 kHz. For each spectrum 16 FIDs were
accumulated, the length of pulse was 3 ps (corresponding to a flip angle of 65 "),
the pulse separation 3 s. The samples were thermostated with the bearing gas
and the temperatures were corrected with a calibration curve, which was obtained by the 13C NMR spectra of samarium acetate recorded at identical
thermostated conditions and rotation rates [17].
Received: March 21, 1992 [Z5252IE]
German version: Angew. Chem. 1992, f04. 1248
hydroxosodalite hydrate recorded between 365 and 250 K
for ten temperatures were included in the evaluation. Average life times z,between 7.5 x
s at 365 K and 3 x
at 250 K as well as an activation energy E, for the exchange
process of 39 5 kJmol- (estimation of the error according
to [14]) were calculated this way. The activation energy lies
significantly below the energy required for the dissociation
of H,O; into H,O and OH- (100 kJmol-'), determined
experimentally14]as well as by ab initio calculations.[31Accordingly, the proton exchange in hy'droxosodalite hydrate
cannot occur via a complete splitting of the hydrogen bond
and subsequent reorientation of the H,O molecule
(Scheme 1 top). Energetically more favorable and in better
agreement with the estimated activation energy is the formation of a short-lived intermediate with bifurcated hydrogen
bonds. According to ab initio calculations the energy of this
intermediate is only 20-40 kJmol-' above the one of the
structure of the H,O; ion with a linear hydrogen bond.['.31
The exchange between terminal and central H atoms could
thus occur as shown in Scheme 1 (bottom). Analogous 'H
MAS NMR investigations on the hydroxo alumogermanate
sodalite hydrate [Na,(H,O,)],[GeAlO,],
showed that here a
dynamic proton exchange within the H30; ion also occurs,
for which an activation energy of 50+ 10 kJmol-' was determined.
Our results show that even without the application of
complicated multipulse techniques such as CRAMPS the 'H
MAS NMR spectroscopy of solids can produce highly resolved spectra, from whose temperature dependence detailed
and selective information about the kinetics and mechanism
of dynamic proton exchange and reorientation processes on
the time scale of between approximately
be derived. Recent investigations using inelastic and the
quasi-elastic neutron scattering" showed that faster dynamic reorientation in the ps range, such as those proven for
the OH group in the dehydrated hydroxosodalite
[Na,(OH)],[SiAI0,],,['5~do not occur in the H,O; ion of
the hydroxosodalite hydrate.
0 H 0,
0 H 0/H
CAS Registry numbers:
H,O;, 12501-19-8 ; ~a,(H,O,)],[SiAIO,].
. 142810-07-9.
[I] M. D. Newton, S. Ehrenson, 1 Am. Chem. SOC.1971, 93,4971.
[2] C. McMichael Rohlfing, L. C. Allen, C. M. Cook, J. Chem. Phys. 1983. 78,
[3] J. Gao, D. S. Garner, W. L. Jorgensen, J Am. Chem. SOC.1986,108,4784.
[4] P. Kebarle. Annu. Rev. Phys. Chem. 1977, 28, 445.
[S] K. Abu-Dari, K. N. Raymond, D. P. Freyberg, J Am. Chem. Soc. 1979,
101, 3688.
[6] G. Giester, J. Zemann, Z . Krista/logr. 1987, 179, 431.
[7] G. Chevrier, G. Giester, D. Jarosch, J. Zemann. Acla CrysraNogr Sect. C
1990, 46, 175.
[8] M . Ardon, A. Bino, Struct. Bonding (Berlin) 1987, 65, 1.
191 M. Wiebcke, G. Engelhardt, J. Felsche, P. B. Kempa, P. Sieger, J. Schefer,
P. Fischer, .l Phvs. Chem. 1992, 96, 392.
[lo] K. C . Ramey, J. F. OBrien, 1. Hasegawa, A. E. Borchert. J. Phys. Chem.
1965, 69, 3418.
[Ill C. McMichael Rohlfing, L. C. Allen, R. Ditchfield, Chem. Phys. Lett.
1982, 86, 380.
[12] J. P. Yesinowski, H. Eckert, .
Am. Chem. Soc. 1987, 109. 6274.
[13] G . Engelhardt, J. Felsche, P. Sieger, J. Am. Chem. Soc. 1992, 114, 1173.
[14] G. Binsch in Dynamic Nuclear Magnetic Resonance Spectroscopy (Eds.:
L. M. Jackman, F. A. Cotton), Academic Press, New York, 1975, S. 45.
[15] 0 . Elsenhans, W. Biihrer. I. Anderson, J. Nicol, T. Udovic, F. Rieutord, J.
Felsche, P. Sieger, G. Engelhardt, unpublished.
[16] W. Biihrer, J. Felscbe, S. Luger, J. Chem. Phys. 1987, 87, 2316.
[17] G . C. Campbell, R. C. Crosby. J. F. Haw, J Magn. Reson. 1986, 69, 191.
Chelate Complexes of Tripodal, Aliphatic
Triisocyanide Ligands""
By E Ekkehardt Hahn* and Matthias Tamm
For some time we have been occupied with the coordination chemistry of multidentate isocyanides with regard to the
preparation of stable hexaisocyanide complexes of 99mTcas
myocardium perfusion agents.''. 21 Recently we were able to
prove that aromatic, tripodal triisocyanides form chelate
complexes of the form fac-[(triisocyanide)W(CO),] in spite
of the linear M-CNR unit in the metal complex.[31Depending on the ligand three 18- or 20-membered chelate rings
were formed, which rank with the largest ring systems in
organometallic compounds. We have now prepared the
aliphatic triisocyanide Ctalc 1 and studied its coordination
Scheme 1. Improbable (top) and probable (bottom) mechanism of the exchange process in the H,O; ion.
Verlagsgesellschafi mbH, W-6940 Weinheim, 1992
Prof. Dr. F. E. Hahn. Dipl.-Chem. M. Tamm
Institut fur Anorganische Chemie der Freien Universitdt
Fabeckstrasse 34-36, D-W-1000 Berlin 33 (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie. We thank the BASF Aktiengesellschaft for a predoctoral grant for M.T.
0570-0833192jO909-1212B 3 . 5 0 i ,2510
Angew. Chem. Inl. Ed. Engl. 1992, 31, No. 9
chemistry. Attempts to obtain chelate complexes with the
similar ligand Ntalc 2, led only to insoluble products. This
behavior can be explained by the protonation of the central
nitrogen atom[31or by the formation of polymers as a result
of the small number of framework atoms (rings with a maximum size of 12 atoms can be formed). Ctalc 1 can no longer
be protonated at the central methine unit, so that the coordination chemistry of aliphatic triisocyanides with a small
number of framework atoms can be studied with the preclusion of the protonation of the ligand.
Fig. 1. 'H NMR spectrum
(270 MHz, CD,CI,) of 4.
Compound 1 was synthesized according to Scheme 1 and
isolated as a colorless oil. It was completely characterized by
elemental analyses and IR, 'H, and I3C NMR spect r o ~ c o p y .The
~ ~ ]'H NMR spectrum (400 MHz, in CDCl,) of
1 shows three groups of signals.141The protons of the
H,O, dioxane
CH3N02 i- wCN
3.0 2.5
the proton at the central methine group is the most obvious.
It experiences a low-field shift of more than A6 = 1 and appears as a septet at 6 = 2.48. To our knowledge the 'H NMR
signal of a methine group substituted with three propyl
groups has so far never been observed at such low field.
From the low-field shift of the signal for the methine group
the structure of the presumably isostructural chelate complexes 3 and 4 can be deduced. From previous studies of
metal complexes of tripodal ligands with a nitrogen atom as
the central framework atom it is known that this atom can
Similar isomers
adopt the inL3,'I or the out c~nfiguration.~~]
are possible for the coordinated ligand 1. with a central methine unit (Scheme 2).
1 . HC(0)OEt
Scheme 1. Synthesis of 1
methylene groups next to the isocyanide functions appear as
a triplet of triplets at 6 = 3.41 by 14N 'H coupling. The
signal for the proton of the central methine group and for the
protons of the neighboring methylene group form a multiplet at 6 = 1.45. The remaining methylene protons appear as
a broad multiplet at 6 = 1.69. The observed 'J(I4N 'H) coupling in aliphatic isocyanides has already been described.I3.61
The reaction of 1 with [(C,H,)M(CO),] (C,H, =
cycloheptatriene, M = Cr, W) in CH,Cl, leads to the colorless complexes 3 and 4.
3, M = Cr; 4, M = W
The new compounds were completely characterized by
elemental analyses, mass spectrometry, and IR, 'H, and 13C
NMR s p e c t r o ~ c o p yThe
. ~ ~ ~'H NMR spectra for complexes
3 and 4 are very similar to each other but differ appreciably
from the spectrum of the free ligand 1 (Fig. 1). In 4 the
multiplicity of the signal for the methylene group D was
reduced by the coordination of the isocyanide functions to
the metal atom from a triplet of triplets in the free ligand to
a triplet at 6 = 3.65. As expected, the I4N 'H coupling is
removed by the coordination of the isocyanide function to
the metal center. Hence, also for the signals of the methylene
groups C (quint) and B (dt) only the expected 3J('H 'H)
coupling patterns are observed. The change of the signal for
Angew. Chem. Int. Ed. Engl. 1992, 31, No. 9
Scheme2. The in and 0111 isomers for complexes of the type fac[HC(CH2CH2CHz-NC),M(CO)J.
The low-field shift of the signal of the methine protons in
3 and 4151can only be explained by the formation of in
isomers since here the proton of the methine group would
penetrate the deshielding region of the anisotropy cone of
the NC triple bonds, which leads to the observed low-field
shift. In the out configuration this proton should not be
deshielded and thus its chemical shift approximates that of
the free ligand. To gain support for this hypothesis and to
show that also aliphatic triisocyanides with a low number of
framework atoms can form chelate complexes a structural
analysis of 4 was carried out.[81
Single crystals of 4 were obtained from dichloromethane/
hexane (1 :1) by slow evaporation of the solvents at room
temperature. The X-ray structural analysis shows that the
conclusions drawn from the 'H NMR spectrum are correct
(Fig. 2 left). The ligand coordinates through three isocyanide
groups to the tungsten atom forming three 12-membered
chelate rings. Complex 4 and the probably isostructural3 are
the first chelate complexes with aliphatic tripodal triisocyanide ligands.
The quality of the X-ray diffraction data (28,,, 55" at
lOO(5) "C) allowed for the determination and refinement
Verlagsgesellschaft mbH, W-6940 Weinheim, f992
3 3.50+.25/0
of the positional parameters of H 1. Thus, the postulated in
configuration of the central methine group in 4 was proven
unequivocally. The C 1-H 1 vector points towards the W
atom [angle C 1-H 1-W 177(3)"I. The distances of H 1 to the
nitrogen atoms lie between 2.69(4) and 2.78(5) A, the H 1-W
distance is 3.56(5) A. These data clearly explain the observed
low-field shift of the signal for the methine proton by penetration of this proton into the deshielding region of the anisotropy cone of the NC triple bonds.
Fig. 2. Crystal structures of 4 (left) and 5 (right) (ORTEP) without hydrogen
atoms (with the exception of H 1 in 4). Selected distances [A] and angles ["I for
4 [5]: W-C5 2.138(3) [2.130(4)], W-C9 2.131(3) [2.125(4)], W-C13 2.119(3)
[2.114(4)], W-C14 2.005(3) [1.999(4)], W-C15 1.994(3) [1.996(4)], W-C16
1.989(3) [1.983(4)], 01-C14 1.153(4) [1.157(5)], 02-C15 1.158(4) [1.157(5)], 0 3 C16 1.152(4) [1.160(5)], N1-C5 1.159(4) [1.158(5)], N2-C9 2.151(4) [1.165(5)],
N3-Cl3 1.152(4) [1.157(5)], Cl-H1 l.ll(5); W-C5-Nl 170.3(3) [170.1(3)], WC9-N2 171.6(2) [171.3(3)], W-C13-N3 174.5(3) [173.6(3)], CS-Nl-C4 174.7(3)
[174.8(4)], C9-N2-C8 173.4(3) [174.6(4)], C13-N3-C12 174.1(3) [171.6(4)].
The influence on the chemical shift of protons by their
interaction with aromatic ring systems have often been described, for example, the marked high-field shift of methine
protons in certain cycl~phanes.[~~
In contrast, we report
herein about the induction of a low-field shift, caused by the
coordination of the ligand to a metal center and the resulting
change of configuration of the ligand.
After we were able to show that also aliphatic tripodal
triisocyanides such as 1 can form chelate complexes with
only eleven framework atoms, the experiments with the
Ntalc 2 ligand were repeated. If a very dilute solution of 2 is
allowed to react with [(C,H,)W(CO),], the p ~ l y m e r s [orig~l
inally postulated by us are not formed but a soluble monomeric complex, which was completely characterized. Microanalytical data and 'H NMR and IR spectra"] indicate the
~ ~ c - [ N ( C H ~ C H ~ C H , - N C ) ~ W ( C5O ) ~ ]
formation of complex 5. This assumption is confirmed by the
structural analysis of 5 (Fig. 2 right). This is also a chelate
complex with three 12-membered rings. The central nitrogen
atom is not protonated, and the ligand adopts the in configuration.
The bond parameters for 4 and 5 lie in the expected range.
Corresponding parameters in these complexes are identical
within the margins of error. The aliphatic triisocyanides are
weaker 71: acceptors than the previously described aromatic
Hence, the W-CN distances are longer
than in compounds of the type fac[(aromatic triisocyanide)W(CO),]. The W-C-N angles deviate from linearity
by up to 10" whereas the W-C-0 angles are almost linear.
0 VCH Verlagsgeselischaft mbH,
Received: April 8, 1992 [Z52931E]
German version: Angew. Chem. 1992, 104,1218
With the compounds 3-5 it could be shown that also
aliphatic triisocyanides with a small number of framework
atoms are able to form chelate complexes with low-valent
transition metals. In comparison to the aromatic triisocyanidesr3I it is noticeable that the marked reduction in the
number of framework atoms (from 17 and 19) to 11 does not
influence the ability to form chelates.
W-6940 Weinheim, 1992
(11 M. J. Abrams, A. Davison, A. G. Jones, C. E. Costello, H. Pang. Inorg.
Chem. 1983, 22, 2798-2800.
[2] Q . 4 . Li, T. L. Frank, D. Franceschi, H. N . Wagner, Jr., L. C. Becker, J.
Nucl. Med. 1988,29, 1539-1548.
[3] F. E. Hahn, M. Tamm, Angew. Chem. 1991. 103,213-215; Angew. Chem.
Inr. Ed. Engl. 1991,30,203-205; J. Organomet. Chem. 1990,398, C19-C21;
F. E. Hahn. M. Tamm, A. Dittler-Klingemann, R. Neumeier. Chem. Ber.
1991, 124, 1683-1686; F. E. Hahn, M. Tamm, Orgunumerollics 1992, If,
[4] Correct elemental analysis. Selected physical data of 1: Total yield 31 %
(based on nitromethane); colorless oil; I R (KBr): v'[cm-'] = 2148 (NC);
'H NMR (400 MHz, CDCI,): 6 = 3.41 [tt, 2J(14N,'H) =1.6 Hz,
'J('H,'Hj = 6.5 Hz, 6 H ; CH,NC], 1.69 (m, br, 6 H ; CH,CH,CH,), 1.491.43 (m. br, 7 H ; HC-CH, and HC-CH,); I3C{'H} NMR (20.15 MHz,
CDCI,): 6 =156.07(t,'J('4N,'3C) = S.~HZ;NC),~~.S~(~.'J('~N,'~C)
6.7 Hz; CH,-NC), 35.35 (HC-CH,), 29.60 (CH,-CH,-CH,), 25.82 (HCCHJ.
[5] Correct elemental analyses for 3-5. Analytical data: 3: Yield 23%; colorless crystals; 1R (KBr): JIcm-'] = 2162, 2120 (NC), 1933, 1859 (CO); 'HN M R (270 MHz, CD,CI,): 6 = 3.60 (t, 6 H ; CH,NC), 2.43 (septet, 1 H ;
HC-CH,), 1.82 (quint, 6 H ; CH,CH,CH,), 1.44 (dt, 6 H ; HC-CH,);
I3C{'H} N M R (67.89 MHz. CD,CI,): 6 = 206.57 (CO), 151.00 (br, NC),
46.09 (CH2-NC), 35.49 (HC-CHI), 34.88 (CHz-CH,-CH,), 25.61 (HCC H , ) . 4 : yield 1 3 % colorless crystals; IR (KBr): g[cm-'] = 2167, 2122
(NC), 1930, 1849 (CO); ' H NMR (270 MHz. CD,CI,): S = 3.65 (t. 6 H ;
CH,NC), 2.48 (septet, 1 H ; HC-CH,), 1.86 (quint, 6 H ; CH,CH,CH,). 1.50
(dt, 6 H ; HC-CHI); 13C{'H] N M R (67.89 MHz, CD,CI,): 6 = 206.57
(CO), 150.78 (br, NC), 46.09 (CH,-NC), 35.49 (HC-CH,). 34.87 (CH,CH,-CH,), 25.60 (HC-CH,); MS (70eV): m / z 485 ( M e , 27.3%), 457
( M e - CO, 17.0), 429 ( M O - 2 C 0 , loo), 401 (Me- 3 C 0 , 95.5).-5:
yield 15%;colorlesscrystals; lR(KBr): t[cm-'] = 2160, 2115(NC), 1932.
1854 (CO); 'H NMR (270 MHz, CD,CI,): 6 = 3.65 (t, 6 H ; CH,NC), 2.47
(t. 6 H ; NCH,CH,). 1.94 (quint, 6 H ; CH,CH,CH,); ''C{'H} N M R
(67.89 MHz, CD,CI,j: 6 = 207.40 (CO), 151.78 (br, NC), 56.77 (N-CH,),
45.18 (CH,-NC), 28.33 (CH,-CH,-CH,); MS (70eV): m/; 486 ( M e ,
73.6%), 458 (Me- CO, 51.0), 430 (M" - 2 C 0 , 55.9). 402 ( M O- 3 C 0 ,
[6] 1. D. Kuntz, P. von R. Schleyer, A. Allerhand, J. Chmr. Phyx 1961, 35,
1533 1534.
[7] F. E. Hahn, S. Rupprecht, K. H. Mook, J Chem. Sue. Chem. Cummun.
1991,224-225; A. R. Bulls, C. G. Pippin, F. E. Hahn. K. N. Raymond. J.
Am. Chem. Soc. 1990, 112, 2627-2632; T. M. Garrett, T. J. McMurry,
M. W. Hossaini, Z. E. Reyes, F. E. Hahn, K. N. Raymond, ibrd. 1991, f IS,
[XI Structure determinations: 4 [5]: C,,H,,N,O,~W [C,,H,,N,O,W],
a =7.974(2)
[7.8685(12)], b =13.588(2) [13.468(3)]. c = 8.104(2)
[8.1525(11)] A, fi = 99.52(3) [98.501(12)]", V = 866.0(6) [854.4(5)] .&,,
monoclinic space group P2,[P2,], p,,, = 1.88 [1.90], pEnlCd
= 1.861
radiation (A = 0.71073 A), p(Mo,) = 68.29
[1.890] gem-', Mo,,
[69.23] cm-I. 3981 [3015] symmetry-independent reflections (h, +k. *I,
polar axis), measured at - lOO(5) 'C in the 28 range 2"-55" [2 "-SO"]. Solution of the structure in both cases with Patterson methods, refinement of all
non-hydrogen atoms with anisotropic thermal parameters. The positional
parameters of H 1 in 4 were taken from a difference Fourier analysis and
refined. All other hydrogen atoms were in calculated positions (d(CH) = 0.95 A) with B.,,,, =1.3 Beq0,. R = 0.0149 [0.0151]. R, = 0.0216
[0.0199] for 3882 [2930] reflections with Fi t 3u (Fez). The crystallographically correct enantiomer in the chiral space group P2, was in both cases
determined by the refinement of the inverted structrural model; the structural model with the better R value was taken as correct one (difference in
the R values 1.8 [1.9]%). Further details of the crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe,
Gesellschaft fur wissenschaftlich-technische Information mbH, D-W-7514
Eggenstein-Leopoldshafen 2 (FRG) on quoting the depository number
CSD-56469, the names of the authors, and the journal citation.
[9] R. A. Pascal. Jr., C. G. Winans, D. Van Engen, J Am. Ckem. SOC.1989, J / J ,
3007-3010; R. P. LEsperance, A. P. West, Jr., D. Van Engen, R. A. Pascal.
Jr.. ibid. 1991, 113, 2672-2676.
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tripodal, aliphatic, complexes, triisocyanide, ligand, chelate
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