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Novel Bonding Mode for a Cyanometalate Ligand Synthesis and Crystal Structure of the Mn4Pd4 Cluster [(OC)Pd(-NC)Mn(-C5H4Me)(CO)2]4 Containing an Orthogonal Arrangement of Helical Units.

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lectivity appears to be restricted to the C-terminal amino
acid: the substrate H-Gly-D-Phe-Tyr-NH, is deamidated,
whereas H-Gly-Phe-D-Phe-NH, and H-Arg-Pro-D-Ala-NH,
do not react.
Amino acid amides with free a-amino groups are not hydrolyzed, whereas N-protected amino acid amides are accepted as substrates (see the first three entries in Table 1).
Substituted amides, such as peptide anilides, which are frequently used in analysis of proteases, are not cleaved.
The enzyme can be readily used in enzymatic peptide syntheses, since it does not cleave the amino acid amides preferentially used as nucleophiles.['. 3*41 Therefore, these are always available for reaction, whereas the resulting peptide
amide is deamidated. Thus, a peptide synthesis with simultaneous deamidation of the product is possible."]
When amino acid amides are used instead of esters as
nucleophiIes in enzymatic peptide syntheses, a much lower
excess of nucleophile is required,"] thereby facilitating
workup of the peptide. For some carboxypeptidases, amides
are obligatory substrates as nucleophiles for peptide synthesis.[61
Because of the poor solubility of many peptide substrates
in water, the effect of water-miscible organic solvents on the
stability of the peptide amidase was investigated. The results
are shown in Figure 2. The least loss of activity was observed
f [dl
Fig. 2. Effect of organic solvents on the stability of the peptide amidase. Reaction conditions: 40 pg mL- ' enzyme was preincubated at 30°C in 50 mM Tris
buffer (pH 7.5) containing 30% organic solvent. The reaction was started at
t = 0 by addition of substrate (2-Gly-Tyr-NH,). In the corresponding control
(enzyme in 50 mM Tris/HCI, pH 7.5, without organic solvent), the activity
remained unchanged. rn = DMF,
= acetone, * = ethanol, T = acetonitrile.
with dimethylformamide (DMF) : after three days of incubation in DMF/HzO (30/70) at 30"C, 30% of the original
activity was still present.
reference sample (if available). The following reference substances, obtained
from Bachem, Heidelberg, were used for product identification: Ac-Trp-OH,
Bz-Arg-OH, 2-Gly-Tyr-OH, H-Asp-Phe-OH, H-Ala-Phe-OH, H-Arg-MetOH, H-Val-Phe-OH, 2-Pro-Leu-Gly-OH, 2-Gly-Gly-Leu-OH, and H-GlyPhe-Phe-OH.
Received: July 17, 1990 [ Z 4071 IE]
German version. Angew. Chem. 102 (1990) 1204
[l] V. Kasche, Enzyme Microb. Technol. 8 (1986) 4- 15.
[2] A Schwarz, D. Steinke, M.-R. Kula, C. Wandrey, Biotechnol. Appl.
Biochem. 12 (1990) 188-195.
[3] H. D. Jakubke in S. Udenfriend, J. Meienhofer(Eds.): The Peptides, Analysis, Synthesis, Biology, Academic Press, London 1987, pp. 103-165.
[4] T. Oka, K. Morihard, J. Biochem. 82 (1977) 1055-1062.
[5] D. Steinke, M.-R. Kula, A. Schwarz, C. Wdndrey: Pepridamidase undderen
Verwendung, Patentanmeldung P 4014 564.6-41
[6] D. Steinke, M.-R. Kula, Enzyme Microb. Technol., in press.
Novel Bonding Mode for a Cyanometalate Ligand:
Synthesis and Crystal Structure of the Mn,Pd,
Cluster [(OC)Pd(p-NC)Mn(q-C,H,Me)(CO),],
Containing an Orthogonal Arrangement of Helical
Units **
By Pierre Braunstein,* Benoit Oswald, Antonio Tiripicchio,
and Marisa Tiripicchio Camellini
Cyanide complexes attract increasing interest in synthetic
and physical chemistry owing to the ability of the cyanide
ligand to link different organometallic units, to stabilize unusual electron counts and mixed-valence systems, to act as a
charge-transfer mediator,"] and to form catalytically active
transition-metal complexes.[21The fact that the cyanide ligand is isosteric with CO has also made it a model for CO
chemistry,[31though it is a poorer n acceptor and better 0
donor than CO. Although the donor strength of the cyanide
ion is the dominant property of this ligand in [Cp'Mn(CN)(C0),le (le, Cp' = q-C,H,Me), the title complex represents the first example of a polynuclear complex displaying
both direct metal-metal bonding and M-CN-M' bridge formation, which result in a novel molecular architecture.
Here we compare the reactivity of le['] with that of the
isostericr6] anion [CpMo(CO),le (2@)towards palladium
complexes. The reaction of trans-[PdCI,(PPh,),] with two
equivalents of Na . 1 (THF, 0.5 h, 25 "C) led to chloride substitution and formation of the red-violet complex trans[Pd{(p-NC)Mn(CO),Cp'),(PPh,),](3) in 89% yield.
Experimental Procedure
The enzyme preparation was obtained from the flavedo of oranges, that is, from
the outermost colored layer of the peel, by a two-step purification involving
fractionating salt precipitation and ion exchange chromatography. The peptide
amidase had an activity of 2 to 100 U mg-', depending on the substrate, whereby an activity of 1 U corresponds to the formation of 1 pmol of product per
minute at 30°C and pH 7.5. Unless otherwise stated, 10-50 mM peptide amide
in 50 mM TrisiHCl buffer at pH 7.5 was treated with 20-40 pg mL-' of the
peptide amidase. The determination and quantification of the peptide was
accomplished by HPLC on an RP-18 column, which was eluted isocratically
with various compositions of TBAiacetonitrile at a rate of 1.0 mL min-'. The
UV detector was set to the absorption maximum of the respective substrate.
The eluent compositions are given in Table 1. In all experiments, only one new
peak was observed in the chromatogram; its area remained unchanged even
after 24-48 h of incubation and its retention time was identical with that of a
Verlagsgeselischafi mbH, 0-6940 Weinheim, 1990
[*] Dr. P. Braunstein, B. Oswald
Laboratoire de Chimie de Coordination, URA 416 CNRS
Universite Louis Pasteur
4 rue Blaise Pascal, F-67070 Strasbourg Cedex (France)
Prof. A. Tiripicchio. Prof. M. Tiripicchio Camellini
Istituto di Chimica Generale ed Inorganica
Universita di P a m a
Centro di Studio per la Strutturistica Diffrattometrica del CNR
Viale delle Scienze, 1-43100 Parma (Italy)
[**I Financial support from the CNRS (Paris) and the Commission of the
European Communities (Contract No. ST2J-0347-C) is gratefully acknowledged.
0570-0833190jfOfO-1140S 3.50f.2510
Angew. Chem. Int. Ed. Engl 29 (1990) No. 10
I t
- 2 NaCl
+ NaCl
P -P
I t
I t
Scheme 1.
Under similar conditions, Na . 2 afforded the planar cluster [Pd,Mo,Cp,(CO),(PPh,),] (4), in which the metal atoms
form two edge-sharing triangles and Pd" has been reduced to
Pd'.f6] This difference is steric in origin, since the trans-MoPd-Mo chain structure is not stable when two PR, ligands
are bonded to Pd.l6]
The reaction of the Pd'-Pd' dinuclear complex [Pd,Cl,(pCO)(PPh,), J with le (toluene, 5 h, 0 to 25 "C) led to disproportionation to 3 (44% yield) and Pd metal, but reaction
with 2 O gave 4."' The reasons for the instability of the primary reaction product resulting from simple substitution of
the chloride ligand by le or 2@must be electronic in the first
case and again steric in the second since one Pd-Mo bond
would be cis with respect to the two PPh, ligands.
The dppm-stabilized dinuclear complex [Pd,(pdppm),CI,] (dppm = Ph,PCH,PPh,) reacted with two
equivalents of l o (THF, 1 h, 25 "C) to form the stable eightatom chain complex [Pd,(p-dppm),((p-NC)Mn(CO),Cp'},]
(5) in 91 YOyield (Scheme 1). The spectroscopic data for 5 are
consistent with the symmetrical structure shown: the singlet
observed in the 31P(1H)NMR spectrum has a chemical shift
of 6 = - 5.33, similar to that of other [Pd2(p-dppm),X,]
complexes,['] and the IR F(CN) and F(C0) absorptions are,
as in 3, similar to those observed when this or analogous
fragments are bonded through nitrogen to a metal cenIn a formal sense, 3 and 5 may also be viewed as
isocyano" Pd complexes[91 stabilized by the 16-electron
fragment Cp'Mn(CO),. In contrast, 2 O reacted with
to give the triangulo cluster
[Pd,MoClCp(CO),(p-dppm),] (6), formed by phosphorus
migration from Pd to an adjacent Mo atom in the sterically
crowded and therefore unstable Mo-Pd-Pd-Mo
intermediate chain complex [Pd,(p-dppm),(Mo(CO),Cp),l"O1
(Scheme 1).
The tetranuclear Pd' complex [Pd,(CO),(OAc),](AcOH),
reacted quantitatively with four equivalents of Na . 1
(toluene, 3 h, - 40 to 25 "C) to form a deep violet solution of
the new, air-stable cluster 7 ("Mn,Pd,"). The structure of
the ethanol solvate 7 . C,H,OH has been fully elucidated by
a n X-ray study." Neglecting the Cp' ligands, this cluster
has approximate S, symmetry. It consists of two nearly orthogonal, bent Mn-Pd-Pd-Mn metal chains, s-trans connected by four Mn-(p-CN)-Pd bridges (Figs. 1 and 2). A
terminal CO completes the approximately square-planar coordination of each Pd atom. One of the Mn-bound CO ligands is semibridging, as indicated by the rather short contact
Angew. Chem Inr. Ed. Engl. 29 (1990) No. 10
with the Pd atom (Pd-C distances in the range 2.35(3)2.41(3) A) and by the slightly bent Mn-C-0 angle (in the
range 162(3)-165(3)"). Of note is that each p-CN ligand also
makes short contacts with a Pd atom in the neighboring
Mn-Pd-Pd-Mn chain: the Pd-C distances are in the range
2.49(2)-2.56(3) A, while the corresponding Pd-N distances
(3.09(2)-3.14(2) A) are in a range consistent with the weak
interactions between the filled 71 orbitals of the nitrile functions and the empty 5p orbitals of the palladium atoms." 31
Fig. 1. View of the molecular structure of 7. Selected bond distances [A] and
angles I"]: Pd(l)-Pd(2) 2.591(3), Pd(3)-Pd(4) 2.612(3), Pd(1)-Mn(1) 2.791(4),
Pd(2)-Mn(2) 2.810(4), Pd(3)-Mn(3) 2.788(5), Pd(4)-Mn(4) 2.800(5), Pd(1)- C(l)
1.78(4). Pd(l)-C(6) 2.39(2), Pd(l)-C(13) 2.49(2), Pd(l)-N(4) 2.05(3), Pd(2)-C(2)
1.82(3), Pd(2)-C(8) 2.35(3), Pd(2)-C(l4) 2.50(3), Pd(2)-N(3) 2.01(2), Pd(3)-C(3)
1.81(3), Pd(3)-C(lO) 2.38(2), Pd(3)-C(15) 2.56($), Pd(3)-N(l) 2.06(2), Pd(4)-'
C(4) 1.87(2), Pd(4)-C(12) 2.41(3), Pd(4)-C(16) 2.52(3), Pd(4)-N(2) 2.05(2),
Mn(l)-C(13) 1.90(3), Mn(2)-C(14) 1.93(3), Mn(3)-C(15) 1.97(2), Mn(4)-C(16)
1.97(3),C(l3)-N(1) 1.18(3),C(14)-N(2) 1.16(3), C(15)-N(3) 1.15(3), C(16)-N(4)
1.12(4); Mn(l)-Pd(l)-Pd(2) 161.6(2), Pd(l)-Pd(2)-Mn(2) 161.1(2). Mn(3)PW)-Pd(4) 153.3(2), Pd(3)-Pd(4)-Mn(4) 154.9(2), Pd(l)-Mn(l)-C(13) 60.5(7),
Pd(2)-Mn(2)-C(14) 60.3(7), Pd(3)-Mn(3)-C(15) 62.3(8), Pd(4)-Mn(4)- C(16)
61.0(8), Mn(l)-C(13)-N(l) 173(2), C(13)-N( l)-Pd(3) 160(2), Mn(2)-C(14)-N(2)
173(2), C(14)-N(2)-Pd(4) 161(2), Mn(3)-C(IS)-N(3) 175(2), C(15)-N(3)-Pd(2)
164(2), Mn(4)-C(16)-N(4) 173(2), C(16)-N(4)-Pd(l) 162(2).
mbH, 0-6940 Weinheim, 1990
0570-0833190jl010-1141 i? 3.50+ .25!0
Fig. 2. Stereoview of the structure of 7.
No redox reaction has occurred in the course of the synthesis, and it could be considered that le has formally replaced an acetate ligand of the precursor complex, thus acting as an overaIl four-electron donor ligand. Of note is that
the Pd, core of 7 contains two short metal-metal bonds
(2.591(3) and 2.612(3) A), as in the rectangular, 60-electroq
Pd' clusters [Pd,(CO),(OAc), J (2.663(1) A) and [Pd,(pCl),(p-dppm),](PF,)2 (2.594(2) A).1141The topology of the
Pd,Mn,(CN), core is that of a tetrahedron, which is colored
(the Pd-Pd edges are different from the Pd-Mn-CN-Pd
ones) and oriented (through the Mn-CN-Pd vector)
(Fig. 3).1'51 The structure may be viewed as formed by two
helices of opposite chirality whose axes are orthogonal, thus
resulting in an overall mesu structure.[161The shape is largely
controlled by the coordination geometry about the metals, in
particular with Pd-Mn-C,,,,,
angles ranging from 60.3(7)
to 62.3(8)". Cluster 7 remained the only product observed
when the stoichiometry of the reaction was changed, thus
providing an interesting example of molecular self-assembly.
The Pd-bound CO ligands of 7 (Pd') are readily displaced
by, for example, PPh,, resulting in quantitative disproportionation to 3 (Pd") and Pd'. The reaction of
[Pd,(CO),(OAc),] .(AcOH), with 2e was recently sh0wn['~1
to afford the anionic cluster [ P ~ , ( M O C ~ ( C O ) , } , ] ~in~ ,
which each MoCp(CO), fragment bridges a Pd-Pd edge of
the central Pd, square in a manner similar to that encountered in 4.16'The latter reaction occurs with formal reduction
of Pd' to Pd"'. Whereas the ability of [CpMo(CO),le to act
as a bridging metallo ligand is now well documented,[lsl the
first examples of le acting as a bridging ligand via the N
atom have only recently been reported.14"]
Reactions with lo afford di-, tri-, and tetranuclear mixedmetal complexes, in which the metals are only linked by
M-(p-NC)-Mn bridges (CN-centered donor ability), and
the octanuclear title cluster, the first cyanometalate complex
with additional metal-metal interactions. Whereas most of
the electron density in le is localized on the nitrogen atom,
sufficient electron density must remain at the metal for further metal-metal bonding. These results provide an interesting contrast with the bonding behavior of 2@,where metalmetal bond formation is usual (metal-centered donor ability)
and M-(p-0C)-Mo
bridge formation much less comm ~ n . ~It' ~
is ]noteworthy that the metal-centered basicity of
CpCo(CO), was recently found to account for the formation
of the Lewis acid-base complexes [Cp(OC),Co --t HgX,],
whereas, with the stronger base [CpCo(CN)(CO)Je, the corresponding complex is unstable with respect to further electron transfer and elemental mercury is formed.[201
Experimental Procedure
Reactions were performed under purified nitrogen, using standard Schlenktype techniques. All compounds have been fully characterized by elemental
analysis and spectroscopy. Unless otherwise noted, IR spectra were measured
(Bruker IFS 66 spectrometer) in CH,CI, and 'Hand "P{'H) NMR spectra in
C,D, (6 values in ppm relative to TMS) and THF/C,D, (6 values in ppm
relative to external H,PO,), respectively.Selected data: 3: deep red crystals. IR:
G(CN) = 2074 s, f(C0) = 1918 vs, 1865 vs cm-'. IR(Nujo1): F(CN) = 2070 vs,
F(C0) = 1918vs, 1909vs,1849vs,brcm-'.'HNMR:6=7.83-7.11 (m,30H,
C,H,), 3.71-3.66 (m. 8H, CH,-C,H,), 1.54 Is, 6H, CH,-C,H,). "P{'H)
NMR:6 = 19.17 (s). 5 : IR: G(CN) = 2067 S, f(C0) = 1913 VS,1846 V S C X I - .
IR (Nujol): <(CN) = 2075 vs, $CO) = 1916 vs, 1905 vs, 1834vscm-'. 'H
NMR:6 =7.43-7.07(m,40H,C6H,),4.26-3.66(m,8H,CH,-C,H,),3.68(m,
4H, 2+4J(P,H)= 5 Hz, PCH,), 1.71 (s, 6H, CH,-C,H,). "P{'H} NMR:
(THF/C,H,): 6 = - 5.33 (s). 7: Deep violet crystals. IR: G = 2055 w, 2018 s,
1932 vs, 1876 wcm-'. IR (Nujol): G(C0) = 2061 m, 2048 m, 2023 w, 1938 vs,
1925 vs, 1870 m, 1855 m, brcm-'. 'H NMR: S = 4.37-4.14 (m.16H. CH,C,H,), 1.65 (s, 12H, CH,-C,H,).
Received: May 25, 1990 [Z 3979 IE]
German Version: Angew. Chem. f02 (1990) 1206
Fig. 3. Top: Core structure of7 showing the Pd(l)N(4)C(16)Mn(4)Pd(4)Pd(3)Mn(3)C(15)N(3)Pd(2) and Pd(3)N(l)C(I 3)Mn(l)Pd(l)Pd(2)Mn(2)C(l4)N(Z)
Pd(4) M and P whorls of helices whose axes are orthogonal to each other,
resulting in a meso arrangement [21]. Bottom: Schematic drawing of the structure.
Verlagsgeselkchaft mbH. 0-6940 Weinheim, 1990
[l] a) A. Christofides, N. G. Connelly, H. J. Lawson, A. C. Loyns, J. Chem.
SOC.Chem. Commun. 1990, 597; b)C. Carini, C. Pelizzi, G. Pelizzi, G.
Predieri, P. Tarasconi, F. Vitali, ibid. f990, 613; c) G. A. Camedo, N. G.
Connelly, M. C. Crespo, I. C. Quarmby, V. Riera, ibid. f987, 1806; d) M.
Adam, A. K.Brimah, R. D. Fischer, L. Xing-Fu, Inorg. Chem. 29 (1990)
1595; e) A. Burewicz, A. Haim, ibid. 27 (1988) 1611; f) A. J. Deeming,
G. P. Proud, H. M. Dawes, M. B. Hursthouse, J: Chem. SOC.Dalion 7iuns.
1988,2475; Polyhedron 7 (1988) 651 ;g) F. Calderazzo, U. Mazzi, G. Pampaloni, R. Poli, F. Tisato, P. F. Zanazzi, Guzz. Chim. Ital. 1f 9 (1989) 241 ;
h) W. F. McNamara, E. N. Duesler, R. T. Paine, Organometallics 7 (1988)
384; i) E. Bar, W. P. Fehlhammer, J. Organomet. Chem. 353 (1988) 197;
j) H. Behrens, G. Landgraf, P. Merbach, M. Moll, K.-H. Trummer, ibid.
253(1983) 217; k) J. A. Davies, F. R. Hartley, S. G. Murray, M. A. PierceButler, J. Chem. SOC.Dalion Trans. 1983, 1305; 1) D. M. Duggan, R. G.
Jungst, K.R. Mann, G. D. Stucky, D. N. Hendrickson, 1 Am. Chem. SOC.
96 (1974) 3443, and references cited therein.
0570-0833/90/1010-1142 $3.50+.25/0
Angew. Chem. h i . Ed. Engl. 29 (f990) No. 10
[2] See, for example: a) I. Hashimoto, N. Tsuruta, M. Ryang, S. Tsutsumi, J.
Org. Chem. 35 (1970) 3748; b) M. Iguchi, Nippon Kagaku Kaishi (192147) 63 (1942) 1752; c) T. Funabiki, S. Yoshida, K. Tarama, J. Chem. SOC.
Chem. Commun. 1978, 1059.
[3] G. J. Baird, S. G. Davies, S. D. Moon, S. J. Simpson, R. H. Jones, J. Chem.
Sor. Dalton Trans. 1985, 1479.
[4] a) E. 0. Fischer, R. J. J. Schneider, J. Organomet. Chem. I2 (1968) P27;
b) B. Oswald, A. K. Powell, F. Rashwan, J. Heinze, H. Vahrenkamp,
Chem. Ber. 123 (1990) 243.
[5] F. A. Holleman, N. Wiberg: Lehrbuch der Anorganischen Chemie, W de
Gruyter, Berlin 1985, p. 130. In the narrow sense, le is isosteric with
[CpCr(CO),le, but the latter anion was shown to afford compounds
isostructural with their Mo analogues[6].
161 R. Bender, P. Braunstein, J.-M. Jud, Y. Dusausoy, Inorg. Chem. 22 (1983)
[7] R. Bender, P. Braunstein, A. Tinpicchio, M. Tiripicchio Camellini, J.
Chem. SOC.Chem. Commun. 1984,42.
[8] C. T Hunt, A. L. Balch, Inorg. Chem. 20(1981) 2267; ibid. 21 (1982) 1242.
[9] Md. N. I. Khan, C. King, J.-C. Wang, S. Wang, J. P. Fackler, Jr., Inorg.
Chem. 28 (1989) 4656.
[lo] a) P. Braunstein, M. Ries, C. de Meric de Bellefon, Y. Dusausoy, J.-P.
Mangeot, J. Organomet. Chem. 355 (1988) 533; b) P. Braunstein, C. de
Meric de Bellefon, M. Ries, J. Fischer, Organometallics 7 (1988) 332.
[I I] Crystal structure determination of 7 . C,H,OH:C,,H,,Mn,N,O,,Pd,
C,H,OH, M = 1448.10, triclinic, space group P i , a = 13.324(6), b =
18.377(8), c = 10.954(6) A, CL = 101.90(2), p = 109.90(2), y = 90.98(2)",
V = 2457(2)
2 = 2, ecSlsa
= 1.958 g ~ m - graphite-monochromated,
~ ,
Mo,. radiation, 1 = 0.71073 A, I, = 24.28 cm-'. The intensity data were
collected on a Philips PW 1100 diffractometer, using the w-28 scan technique at room temperature. A decay of about 30% of the initial intensity
of a standard reflection, measured after 50 reflections, was observed during the data collection and corrected. 7135 unique reflections, 3 < 8 < 25",
2635 with I > 2a(l) used in the refinement. The structure was solved by
Patterson and Fourier methods and refined by full-matrix least-squares fit
procedures, with anisotropic thermal parameters in the last cycles of refinement for all the non-hydrogen atoms except the carbon atoms of the
methylcyclopentadienyl rings and the atoms of the molecule of solvation.
The hydrogen atoms were introduced in calculated positions, but their
parameters were not refined. The SHELX-76 and SHELXS-86 system of
computer programs was used[l2]. The R and R, values were 0.0578 and
0 0852, respectively. Further details of thecrystal structure analysis may be
obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur
wissenschaftlich-technische Information mbH, D-7514 EggensteinLeopoldshafen 2 (FRG), on quoting the depository number CSD-54 697,
the names of the authors, and the journal citation.
[12] G. M. Sheldrick, ..SHELX-76 ", Program for Crystal Structure Determinalion, University of Cambridge (UK) 1976. ,.SHELXS-86". Program for
Crystal Structure Solution, Universitit Gottingen 1986.
[13] For related interactions with Cu': M. J. Begley, P. Hubberstey, P. H. Walton, J. Chem. SOC.Chem. Commun. 1989, 502; with I?: P. A. Chetcuti,
C. B. Knobler, M. F. Hawthorne, Organomelallics 7 (1988) 650; and with
Mo": T. C. Wright, G. Wilkinson, M. Motevalli, M. B. Hursthouse, J.
Chem. Soc. Dalton Trans. 1986, 2017.
[I41 P. Braunstein, M. A. Luke, A. Tiripicchio, M. Tiripicchio Camellini,
Angew. Chem. 99 (1987) 802; Angew. Chem. Int. Ed. Engl. 26 (1987) 768.
1151 D. M. Walba, Terrahedron 41 (1985) 3161.
1161 There is an obvious and aesthetically pleasing topological relationship
between the core structure of 7 and that of tricyclo[']octane
(bisnoradamantane). For bisnoradamantane, see: P. K. Freeman,
V. N. M. Rao. G . E. Bigam, Chem. Commun. 1965,511 ; B. R. Vogt, S. R.
Suter, J. R. E. Hoover, Tetrahedron Lett. 1968, 1609.
An Azacyclopentadienyl Ligand in a Novel
Bridging Function **
By Norbert Kuhn,* Gerald Henkel, and Jorg Kreutzberg
Dedicated to Professor Max Schmidt
on the occasion of his 65th birthday
The structure and reactivity of pyrrolides (1) exhibit features of cyclopentadienides as well as of pyridines and
amides. These similarities are reflected in the coordination of
structure 2 and 3, which have been identified in dimeric
carbazolides of the alkali metals (4 and 5)"- (Scheme 1).
[17] T. A. Stromnova, I. N. Busygina, S . B. Katser, A. S. Antsyshkina, M. A.
Porai-Koshits, I. I. Moiseev, J. Chem. SOC.Chem. Commun. /988, 114.
[IS] R. Bender, P. Braunstein, C. de Meric de Bellefon, Polyhedron 7 (1988)
2271, and references cited therein.
[19] C. P. Honvitz, D. F. Shriver, Adv. Organomet. Chem. 23 (1984) 219.
[20] S. J. Carter, L. S. Stuhl, Organometallics 7 (1988) 1909.
[21] The authors are grateful to I - P . Mage and P . Verley ( G r o u p IAO, Centre
de calcul du CNRS, Strasbourg) for the computer-generated color drawing
of 7 in Figure 3, which was obtained by using the actual atomic coordinates of the Pd, Mn, C, and N atoms and the CATIA software.
Angew. Chem. Int. Ed. Engl. 29 (1990) No. 10
-VnIC, Me,NNa),
C, Me, N H NaH
- HZ
Scheme 1
The structure of 2,3,4,5-tetramethyl-l-sodiopyrrole
combines the characteristic features of amide bridges[41with
the x coordination of dienyl ligands.I5I In Figure 1, the double chain structure, consisting of alternating sodium and
nitrogen atoms, shows that each pyrrolyl ligand@]bridges
three sodium atoms; the unusual coordination numbers 7
and 5 are thereby attained for sodium and nitrogen, respectively. As observed for 1ithiocarbazole,'la1 the two Na-N
bonds involving q bonding are of different lengths (Na-Nj
2.411(2), Na-Nk 2.351(1) A); however, since the two q'bonded sodium atoms in 6 lie outside the plane of the linking
pyrrolyl ligand to the same extent (the angle Na'-N-Na' is
roughly bisected by the ring plane), a differentiation between
G and 7[: bonding makes no sense in this case. On the other
hand, the Na-N bond involving q5 bonding (2.694(1) A) is
clearly longer and lies in the range observed for x bonding.171
A comparison of the Na-C bonds (Na-C1 2.660(2), Na-C2
2.631(2), Na-C3 2.635(2), Na-C4 2.666(2) A), also lying in
the expected range,15] shows that the sodium atom is displaced toward the carbon atoms in p position; this finding is
in agreement with the structure calculated for lithiopyrrole.['"] The bond lengths in the pyrrole ring (N-C1 1.387(2),
N-C4 1.384(2), Cl-C2 1.386(2), C2-C3 1.432(2), C3-C4
1.387(2) A) are markedly longer than those of noncoordinat[*] Prof. Dr. N. Kuhn, Prof. Dr. G. Henkel, Dip1.-Chem. J. Kreutzberg
Fachbereich 6 (Chemie) der Universitat-Gesamthochschule
Lotharstrasse 1, D-4100 Duisburg 1 (FRG)
Heterocycles as Ligands, Part 6. This work was supported by the Fonds
der Chemischen Industrie. We thank Prof. Dr. P . Sartori for his support.
Part 8: N. Kuhn, E.-M. L a m p , J. Organomet. Chem. 385 (1990) C9-Cl2.
VPrlagsgesellschaft mbH, D-6940 Weinheim. 1990
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crystals, bonding, mode, helical, arrangement, orthogonal, mn4pd4, c5h4me, ligand, unit, structure, synthesis, containing, clusters, cyanometalate, novem
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