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Exhaustive Oxidative Decarbonylation of Metal Carbonyls by Light and Oxygen The Example of (5-C5Me5)ReO3.

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S
[Mo(N2R')(H2NNR')L21
1
R ' = C(
SEt
i
(*'
[ L ( O ) M O ( ~ - N N R ' ) ~ M O L2]
S
L = Me2N-C,:?
S
,
I
lybdenum atoms of 2 has no terminal oxygen or sulfur ligands; this coordination site is occupied rather by the two
sulfur atoms of a Me2NCSp ion, without essentially changing the structure. The molybdenum atom concerned (Mol)
is surrounded by a trigonal-prismatic arrangement of four
S atoms and two N atoms. To a good approximation 2 has
C, symmetry; the mirror plane is defined by the atoms 01,
Mol, and Mo2.
Received: January 24, 1984;
supplemented: March 1, 1984 [Z 688 IE]
German version: Angew. Chem. 96 (1984) 375
CAS Registry numbers:
1, 84849-46-7; 2, 89922-67-8; Mo, 7439-98-7.
I
I1
someric formulations I ++ 11. The coordination of the sulfur
atoms lead to a preference for 11. Therefore, in comparison to the previously known p-diazenido N-complexes, the
NN bond in 2 is elongated by more than 10pm from
123k 1 pm to 135.0(8) pm. The novel complex 2 is thus to
be designated as a hydrazido(3 -)- and not as a diazenidocomplex.
[I] Cf. H. Weber, R. Mattes, Chem. Ber. 113 (1980) 2833, and references cited
therein.
[21 R. Mattes, H. Scholand, Angew. Cbem. 95 (1983) 246: Angew. Chem. Int.
Ed. Engl. 22 (1983) 245.
[3] C. F. Barrientos-Penna, F. W. 8. Einstein, T. Jones, D. Sutton, Inorg.
Chem. 22 (1983) 2614, and references cited therein.
[4] a) Experimental procedure: A suspension of 0.6 g (approx. 1 mmol)
1 Cin
[MO(N~C(S)SE~)(NH,NC(S)E~J(M~~N
S ~ }40
~ ] mL methanol is
treated with 1 mL conc. hydrochlorid acid and heated under reflux for
30 min. The color changes from reddish brown to deep red. The product
2 is filtered off and recrystallized l'rom CH,0H/C2H4CIz (yield 53%),
m.p. 97"C, correct elemental analysis: b) IR (KBr, cm-I): 1572 sh, 1545
vs (vCN, L'), 1400 vs (vCN, L'), 1263 s, 1245 s (v,,NCZ, L'), 1160 s (vCS,
L2), 1000 vs, 990 vs (v,,CS2, L' and vNN, L'), 945 vs (vMoO), 760 m, 730
m (v..Mo2N2) [L'= MezNCSz,L2= NNC(S)SEt].
[5] 2 crystallizes in the space group Pi, a=916.1(6), b=1033.0(7),
c=1504.7(9) pm, a=90.39(5), 8=93.96(5), y=115.20(5)", Z = 2 ; Syntex
P2' diffractometer, 2946 independent reflections with Fo > 3.92u(F0),
28,.. = 48 262 parameters, R = 0.050, R, = 0.056, H atoms not located,
all atoms refined anisotropically.
[a] E. I. Stiefel, h o g . Inorg. Cbem. 22 (1976) 1; R. A. D. Wentworth, Coord.
Chem. Rev. 18 (1976) 1.
O,
5
53
Exhaustive Oxidative Decarbonylation of Metal
Carbonyls by Light and Oxygen: The Example of
(q5-C5Me5)Re03**
C8
LIL
Fig. I. Molecular structure of the binuclear molybdenum complex 2 in the
crystal. Selected bond lengths [pm]: Mol-Mo2 267.2(1), Mol-Nl 192.9(7),
MOl-N3 194.1(7), MOl-S4 241.7(3), Mol-S6 242.2(3), Mo2-NI 199.0(7),
Mo2-N3 197.7(7), Nl-N2 1.361(11), N2-C1 126.9(13), C1-S4 173.3(10),
N3-N4 1.339(11), N4-C2 128.7(13), C2-S6 170.8(10); selected bond angles,
mean values ["I: MoNMo 85.97(2), NNMol 134.31(4), NNMo2 135.1(9),
NMoN 91.0(3), dihedral angle NMolN/NMo2N 152.5". Further details of
the crystal structure investigation are available on request from the Fachinformationszentrum Energie Physik Mathematik, D-7514 Eggenstein-Leopoldshafen 2, on quoting the depository number CSD 50792, the names of
the authors, and the journal citation.
Further structure parameters support this hypothesis:
The NO atoms (N1 and N3) are not spz hybridized. The
sum of the bond angles to them is 353.9(5) and 357.0(5)",
respectively. The Nu atoms (N2 and N4) lie 30 and 40 pm,
respectively, outside the Mo, NB, Mo planes. The mean
values of the N-C and C-S distances in the hydrazido ligands are 127.8(9) and 172.0(7) pm, and thus correspond to
the values of C N double and CS single bonds, respectively.
For hydrazido(3 -) ligands the formal oxidation state of
the central atoms of 2 is 5. Actually, the structural array
with the Mo-Mo distance of 267.2(1) pm corresponds to
that of numerous binuclear Mo" complexes with metalmetal bonding and central Mo202(p-02)groupsL6'.However, as observed here for the first time, one of the two mo-
+
Angew. Chem. Int. Ed. Engl. 23 (1984) No. 5
By Wolfgang A . Herrmann*, Ricardo Serrano, and
Hans Bock
The photosensitivity of carbonylmetal compounds has
been exploited for some considerable time to synthesize
substituted derivatives"]. To this end, one frequently selects the indirect route via photochemical generation of
solvent-stabilized intermediates which are open for introduction of the desired ligands in subsequent dark reactions. A typical example of general preparative importance
is the photochemistry of cymantrene, (T$-C~H~)M~(CO)~,
which via this method affords complexes of type ($C5H5)Mn(C0)2L (L = two-electron ligand) that are frequently not accessible along other routes[',21.Whereas in
the intermediate complex (q5-C5H5)Mn(C0)2(THF)the
cyclic ether ligand can readily be exchanged for better nacceptors, in the analogous rhenium complex the considerably greater stability of the metal-oxygen bond renders further substitution reactions more d i f f i ~ u l t ~The
~ ] . much
[*I Prof. Dr. W. A. Herrmann, Dr. R. Serrano, Prof. Dr. H. Bock
Institut fur Anorganische Chemie der Universitat
Niederurseler Hang, D-6000 Frankfurt am Main 50 (FRG)
[**I Multiple Bonds between Main Group Elements and Transition Metals,
Part 6. This work was supported by the Fonds der Chemischen Industrie, by the Deutsche Forschungsgerneinschaft, and by the Spanish Ministry of Education (post-doctoral fellowship to R. S., 1 9 8 2 4 4 ) . We
thank Prof. Dr. D. Breilinger (Universitat Erlangen-Nurnberg) for the
Raman spectrum. - Part 5 : W. A. Herrmann, C. Hecht, M. L. Ziegler, B.
Balbach, J . Chem. SOC.Chem. Comrnun., in press.
0 Verlag Chemie GmbH, 0-6940 Weinheim, 1984
0570-0833/84/0505-0383 $ 02.50/0
383
higher oxophilicity of rhenium relative to that of manganese accounts for the remarkable formation tendency of
the novel title compound 3, too.
-+?Re
hv (<300nm)
+
crystal[’]. Among the reactions of 3 investigated to date is
its partial deoxygenation by triphenylphosphane. This is of
co/co,
+O,/THF
0
0
(-rCH3)
1
3
I
I
Irradiation of a solution of the half-sandwich complex 1
in tetrahydrofuran (THF) under rigorous exclusion of oxygen (argon atmosphere or vacuum, quartz glass, Hg highpressure lamp) effects CO-elimination with formation of
the THF complex 2 ; the latter species has not yet been isolated in substance but its identity has been established
from subsequent reactions with phosphanes. Whereas
analogous manganese complexes decompose in the presence of atmospheric oxygen, 2 eliminates CO and C 0 2
(GC) to form the carbonyl-free product 3, which after
work-up by means of column chromatography is obtained
as air-stable, lemon yellow, sublimable crystals in up to ca.
40% yield[‘]. 3 has the unexpected constitution of a mononuclear trioxo complex (MS, IR, Raman, NMR); elemental analysis and determination of M , by vapor osmometry
indicate the formula CI0Hl5O3Rewith only one Re atom[4].
3 is derived from the educt 1 by oxidative substitution of
the entire set of carbonyl groups by 0x0 ligands. The latter
can be identified by their intense v(Re=O) stretching
bands (IR, Raman); the n-coordination of the pentamethylcyclopentadienyl ligands follows from the ‘H- and
I3C-NMR spectra, which even at - 120°C (CHFC12) only
exhibit simple signal patterns[‘’. In terms of bonding theory, it is significant that the metal center in 1 is present in
the oxidation state 1 (d6-Re1),but in 3, for the first time
in a half-sandwich complex, as ReV1’having a do configuration. This enormous difference in the d-electron bookkeeping is reflected in the spectra. Thus, replacement of
the CO by the 0x0 groups leads to a drastic deshielding
(A6 > 20 ppm) of the C atoms of the ring ligands bonded to
the metal in the I3C-NMRspectrum, indicating a markedly
reduced charge density. More impressive is that the PE
spectra convincingly show the change in oxidation state:
In the d6 complex 1 (Fig. lb) the first group of bands centered around 8 eV is assigned to the ionizations of metal d
electrons, and the second at 9.2 eV to the almost degenerate n ionizations of the ring ligandc5].As expected, for the
trioxo complex 3 no further ionizations bands which could
be assigned to metal d electrons are found in the low energy region of the PE spectrum (Fig. la)[61.
The results of a preliminary X-ray structure analysis indicate that the ring ligand is symmetrically n-bonded in the
563,
ncp
[a
Fig. 1. He([) PE spectra of a) trioxo- and of b) tricarbonyl(q’-pentamethylcyc1opentadienyl)rhenium recorded using a Leybold-Heraeus UPG 200 spectrometer at lo-’ mbar and 500 K (a) and 410 K (b). Calibrated with the
AI(~P,,~)
peak at 15.76 eV; for assignment cf. [S,61.
particular importance in that the binuclear derivative 4 is
formed quantitatively and that this cleaves thermally into
(q5-C5Me5)Re02fragments and hence makes secondary
reactions accessible. Even in the solid state 4 rapidly rearranges in air to form the educt 3 (quantitative yield); this
process corresponds to the formal change in oxidation
state ReV-+ReV1l[sl.
Compound 4 reacts smoothly with
bromine at -78°C in CH2C12 to give the mononuclear
green complex (q5-C5Me,)ReOBr2(air-sensitive), whereas
reaction with CO (20 bar, toluene, 70 h) affords the title
compound 3 as well as the carbonyl complex 1 and ($-
+
384
0 Verlag Chemie GmbH, 0-6940 Weinheim. 1984
C5Me5)2Re2(p-C0)3.Compound 3 also undergoes reductive carbonylation if it is allowed to react with ($C5H5)2Ti(C0)2;in this case the rhenium-containing product is the crystalline, red 0x0-complex (p-O)[($C5Me5)Re(C0)2]2(X-ray structure). The novel complex 3
is certainly comparable stoichiometrically with the tetrahedrally configurated derivatives CH3Re03[9a1and XRe03
(X = F, CI, BT)[’~]but represents the first half-sandwich
OS70-0833/84/0SOS-O384 $02.50/0
Angew. Chem. Inl. Ed. Engl. 23 (1984) No. S
complex of the type (qs-CsR5)M0, and, therefore, is the
first representative of a novel class of compounds.
Received: January 26, 1984 [Z 692 IE]
German version: Angew. Chem. 96 (1984) 364
[ I ] Review: G. L. Geoffroy, M. S. Wrighton: OrganometaNic Photochemistry,
Academic Press, New York 1980.
[2] a) E. 0. Fischer, M. Herherhold, "Photochemische Substitutionsreaktionen
an Cyclopentadienylmangan-tricarbonyl",in W. Schneider, G. Anderegg,
R. Gut: Essays in Coordination Chemistry, Exper. Suppl. IX, Birkhauser,
Basel. 1964, p. 259-305; b) cf. P. M. Treichel in G. Wilkinson, F. G. A.
Stone, E. W. Ahel: Comprehensive Organometallic Chemistry, Vol. 4, ch.
29, Pergamon Press, Oxford 1982.
[3] D. Sellmann, E. Kleinschmidt, Z . Naturforsch. B32 (1977) 795; cf. K. G.
Caulton, Coord. Chem. Rev. 38 (1981) I, and N. M. Boag, H. D. Kaesz in
[2b], ch. 30.
[4] Procedure; 1 (1.01 g, 2.5 mmol) is dissolved in 100 mL THF in a quartz
glass Schlenk tube (1=25 cm, 0 = 3.4 cm). The reaction vessel is sealed
and evacuated until the solution foams up. Subsequently, the vessel is
placed at ca. 4 cm distance from a water-cooled lamp housing (quartz
glass) in which an Hg high-pressure lamp (TQ 150, Original Hanau) is located. The solution is stirred and irradiated for 8 h (solution temperature
30-40°C). At 2 h intervals the mixture is filtered in air and the clear, yellow-brown filtrate is stored in an open flask for 15 h, subsequently concentrated in vacuo, and the residue chromatographed on a silica gel column (Merck 7734, Act. 11-111; /=40 cm, 0 = 1.2 cm). Small amounts of
unreacted 1 as well as unidentified side products are eluted with benzene. 3 is then eluted in a bright yellow zone using toluene/diethyl ether
(1 :2 v/v). The crude product is washed with 20 mL n-hexane and recrystallized from diethyl ether/dichloromethane (2 :1 v/v; 25.. . -35°C);
by this means, 3 forms as refractive, lemon-yellow needles, which are
both stable in air and up to temperatures above 140°C (slow decomposition with brown coloration upon prolonged heating in the temperature
range 150-200°C; no definite melting point). Yield 296-379 mg (3241%); insoluble in aliphatic hydrocarbons, very soluble in CH2Cl2,toluene, and THF. 'H-NMR (270 MHz, C6Da, 26°C): GCH, 1.63 (s); 'HNMR (270 MHz, CD2C12,-80°C): SCH, 2.08 (s); no signal broadening
at this temperature.- "C('H]-NMR (CDCI,, 28°C): GCH3 10.24, SC,MeS
120.35.-1R (KBr): 909 s-vs, 878 vs, [va.(Re=O)]; further hands 334 w,
393 m, 797 w-m, 960 w, 1024 m, 1073 w, 1362 m, 1373 m, 1381 m, 1440 m
(br), 1472 w (br), 1504 m; 2920-3000 w-m [v(CH)].--IR [CSZ;
v,,(Re=O)]: 922 s-vs, 892 vs.-Raman [solid: v(Re=O)]: 907 vs, 889 m,
874 w-m (C,-symmetry).-MS (Varian MAT CH7; 12 eV T'= IOO"C,
TE=120"C, Ia7Re): M"' (m/z 370, rel. int. loo%), [M-01"' (354, 32),
[M-20Im0 (338, 40), CloH7s' (135, 96; with decomposition spectrum,
m/z< 135).-FD-MS: 370 (parent ion, 187Re).-Correct elemental analysis (C, H, Re, 0).
[5] D. C. Calabro, J. L. Hubbard, C. H. Blevins 11, A. C. Campbell, D. L.
Lichtenberger, J . A m . Chem. SOC.103 (1981) 6839, and literature cited
therein. The PE spectrum of 1 was assigned by comparison of the radical
cation state with those of the similar complexes CpRe(CO),, CpMn(CO),,
and Me5CpMn(CO)3on the basis of the observed vibrational fine structure and with parameter-free Fenske/Hall model calculations: Accordingly, the group of bands around 8 eV contains the metal d-states X('E,,,)
and B('E,,,) split by spin/orbit coupling to ;\('A,) under the local C,,
symmetry, and the second group of bands at ca. 9.2 eV the states C('E).
which are almost degenerated under the local DSh symmetry, with predominant I[ Cp contribution.
[6] Because of the unexpectedly large relaxation and correlation effects, the
PE spectra of organometallic compounds cannot usually be assigned on
the basis of MO calculations and Koopman's theorem (cf. e.g. M. C.
Bohm, Inorg. Chem. 22 (1983) 83, and literature cited therein). For the
novel title compound, comparison of the radical cation state with similar
complexes is also not possible. Qualitative considerations-starting from
the intensity ratio 2 : 1 :2 : 1 of the four PE bands of lowest energy and the
CsHS n-system as well as the oxygen lone-pairs no, which are the most
electron-rich sites in the Re(do) compound 3, and which can each be subdivided into three parallel (11) and three horizontal ( I )componentslead to the proposed assignment nc,(e) < n,f (a2)< nb'(e) < n;(a,). The
missing degenerate combination &(e) should he stabilized by overlap
with d,,(Re) and d,,(Re). An EHMO-approximation calculation for the
(still) fictitious CpMnO, with program-specific standard parameters reproduces this qualitative MO sequence.-Cf. J. C. Green, S . E. Jackson,
B. Higginson, J . Chem. Sac. Dalton Trans. 1975, 403.
171 H. Noth, Universitat Miinchen, personal communication.
[8] Spectroscopic data for 4 (brown crystals): IR (vReO, cm-', KBr): 930 s
(terminal); 634 s, 614 m (bridging). 'H-NMR (CDzCIz, 28°C):
6CH1=2.03 (s). Correct elemental analysis (C, H, Re, 0). W.A. Herrmann, R. Serrano, A. Schafer, M. L. Ziegler, E. Guggolz, J . Organometal.
Chem., in press.
[9] a) I. R. Beattie, P. J. Jones, Inorg. Chem. 18 (1976) 2318, and literature
cited therein; b) cf. K. Dehnicke, W. Liese, Chem. Ber. 110 (1977) 3959.
+
Angew. Chem. Int. Ed. Engl. 23 (1984) No. 5
Dextran-Linked N6-(2-1sopentenyl)adenosineA Polymer-Bound Antimetabolite with a
Predetermined Cleavage Position**
By Helmut Rosemeyer and Frank Seela*
N6-(2-1sopentenyl)adenosine [6-(3-methyl-2-butenylamino)-9-ribosylpurine, PA], 1, is a modified nucleoside
which exhibits cytokinine activity and stimulates cell division and cell differentiation. It is found in the tRNA's of
many organisms and, furthermore, shows strong antitumor
activity in transformed cells, animals, and man"].
The covalent attachment of 1 to biopolymers (e.g. dextrans) is expected to increase the circulatory lifetime
(plasma half-life) of 1 and would alter the uncontrolled
distribution of the pharmacon over the compartments of
the organism. Furthermore, polymer-linked anticancer
drugs should show an enhanced tumor cell selectivity since
the latter possess an increased pinocytic uptake activity
compared to normal cells['].
Dextrans which contain linear chains of 1+6--linked aD-glucopyranose residues as the dominant structural feature have proven valuable as biopolymeric carriers for biologically active compounds since they can be slowly hydrolyzed by dextranases in vivo. Dextran is used as a
blood-volume expander in the molecular-weight range
4 x lo4-8 x lO4C3l.
We report here on the covalent attachment of 1 via a
cyclic acetal side chain to activated dextran T 80 bearing a
spacer with a disulfide bridge as a predetermined cleavage
position. Furthermore, we describe the chemically controlled release of the derivative 3b of 1 from the polymer 5
by reduction of the disulfide bridge of the spacer using dithiothreitol. This can serve as a model reaction for a drug
delivery by reducing enzymes like glutathione reductase.
HN
Hor2
HO
A
0 0
Et0-X
OH
1
0
2
A
H
A'
[*I Prof. Dr. F. Seela, Dr. H. Rosemeyer
Fachbereich Organische Chemie der Universitat-Gesamthochschule
Warburger Strasse 100, D-4790 Paderborn (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
die Regierung des Landes Nordrhein-Westfalen.
0 Verlag Chemie GmbH, 0-6940 Weinheim, 1984
0570-0833/84/0505-0385 $02.50/0
385
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