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Free Radical Additions to Dicyclopentadienylcobalt.

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spectrum (film): 1690 cm-1 (vc=o amide), 1730 cm-1
( v c - 0 ester), 1520 cm-1 (VNH),
and 3300 cm-1 (VNH).
N M R spectrum (CC14, T): 1 . 8 2 (HC=O).
Received: September 3, 1970
[Z 275 IE]
German version: Angew. Chem. 82, 932 (1970)
__[*I Prof. Dr. U. Schollkopf and K. Hantke
Organisch-Chemisches Institut der Universitat
34 Gottingen, Windausweg 2 (Germany)
[ l ] Syntheses with a-Metalated Isocyanides, Part 8. - Part 7:
U. Schollkopf and D . Hoppe, Angew. Chem. 82, 483 (1970);
Angew. Chem. internat. Edit. 9, 459 (1970).
121 I. Wgi, U. Fetzer, U.Eholzer, H . Knupfer, and K . Ofermann,
Angew. Chem. 77, 492 (1965); Angew. Chem. internat. Edit. 4,
472 (1965).
Free Radical Additions to Dicyclopentadienylcobalt 111 [**I
By Gerhard E. Herberich and Johann Schwarzer [*I
A two-step radical mechanism has been proposed [31 for the
reaction of dicyclopentadienylcobalt ( I ) with organic
halides C2-41, in which ( I ) acts both as one-electron donor
[eq. (a)] and as radical trap [eq. (b)]:
We have found direct proof of the addition of a radical to
( I ) . Thermal decomposition of a n excess of azoisobutyronitrile (AIBN) in boiling toluene containing ( I ) affords
cyclopentadienyl-[5-exo-(1-cyano-1 - methylethy1)cyclopentadienelcobalt ( 3 ) almost quantitatively. This product
forms red prisms, stable in air and melting at 93-94OC;
~ C N
= 2230cm-1; 1H-NMR spectrum in C6D6: T = 5.02
[HQ), H(3); “triplet”], T = 5.54 (C5Hs; singlet), T = 7.32
[H(endo); triplet], T = 7.46 [H(1), H(4); “quartet”], T = 9.39
(2 CH3; singlet); cf. [2,41. As shown by the IH-NMR data
for ( 3 ) , the addition occurs stereospecifically:
The mechanistic alternative of a n initial one-electron
transfer from ( I ) t o (2) with subsequent nucleophilic
addition of [C(CH3)2CN]- to [Co(C5H5>21fcan be excluded
because ( 3 ) is also obtained in very good yieId using
1-butanol as solvent a t 100 ‘C.
O n thermolysis of AIBN in styrene, only 50% of the radicals (2) formed are incorporated into the polymer chain[5l;
the extensive dimerization is ascribed to a cage effect.
However, decomposition of AIBN in presence of a small
excess of ( I ) in dilute benzene solution affords more than
80% of the adduct ( 3 ) . These findings support the mechanism cited above and make it probable that ( I ) could add a
variety of C-radicals in accord with eq. (b).
Experimental:
A solution of AIBN (148 mg, 0 . 9 0 mmole) and Co(CgH5)2
(249 mg, 1.32 mmoles) in anhydrous toluene (5 ml) is refluxed (oil-bath temperature 130°C) for 15 min with
rigorous exclusion of 0 2 (ca. 9 7 % decomposition of
Angew. Chern. internat. Edit. J Vol. 9 (1970)
No. I 1
AIBNIsl). The mixture is then cooled rapidly, filtered
through a G4 frit, and freed from solvent and organic impurities a t 2OoC in a high vacuum. Sublimation of the
residue in a high vacuum then gives analytically pure ( 3 )
[330 mg, 9 7 % based on (I)].
A solution of AIBN (117 mg, 0.71 mmole) and CO(CgH5)2
(327 mg, 1.73 mmoles) in benzene (20 ml) is heated for
15 h under reflux (>99 % decomposition of the AIBN [61).
The excess of C O ( C ~ H Sis) ~
extracted with aqueous NH4Cl
solution, and the benzene phase is dried over CaC12.
Further working up as above affords ( 3 ) (297 mg, 81 %
based o n AIBN).
Received: September 3, 1970
[Z 276 IEl
German version: Angew. Chem. 82, 883 (1970)
[“I Doz. Dr. G. E. Herberich and Dip1.-Chem. J. Schwarzer
Anorganisch-Chemisches Laboratorium
Technische Universitat Miinchen
8 Miinchen 2, Arcisstrasse 21 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft.
[I] Investigations of the Reactivity of Organometallic Complexes, Part I. - Part 6: G. E . Herberich and R. Michelbrink,
Chem. Ber., in press.
[2] M . L . H . Green, L. Pratr, and G . Wilkinson, J. chem. SOC.
(London) 1959, 3753.
[3] G. E. Herberich and E. Bauer, J. organometallic Chem. 16,
301 (1969).
[4] G. E. Herberich, E . Bauer, and .
I
Schwarrer,
.
J. organometallic Chem. 17, 445 (1969).
[5] G. Henrici-Olivd and S. O f i v i , Makromolekulare Chemie
58, 188 (1962).
[6] Calculation based on data given in G. Henrici-Olive and
S . Olivd: Polymerisation. Verlag Chemie, Weinheim 1969.
Hexathio-digermanates and -distannates :
A New Type of Dimeric Tetrahedral Ion
By Bernt Krebs, Siegfried Pohl, and Willy Schiwy[*I
The only statements so far made about the nature of the
thiogermanates(1v) that are formed from aqueous solution
have been mutually contradictory 111. Characterization of
definite phases has been made difficult by formation of
various hydration stages. The formal analogs of the anhydrous thiogermanates and ternary sulfides 121 that can be
obtained by high-temperature methods are hydrated salts
of probable fundamental composition MiGeS4, M:GeS3,
and MfGe2Ss (each .xHzO; MI = alkali metal) 111; nothing
is known about the structure of thiogermanate ions except
for tetrahedral G e S - (e.g. [3,61).
We have now obtained definite alkali metal salts containing
the ion Ge&
by dissolving GeSz in a. concentrated
aqueous solution of the alkali sulfide and precipitating the
extremely water-soluble salts by a large excess of acetone
(cf. [la]) at constant p H (7-8). Higher members (GenS2n+Z)4can also be prepared by altering the ratio MIS : GeS2 and
the pH.
NadGe& . 14 H 2 0 (1) was characterized by analysis,
vibration spectra, and a complete X-ray structure analysis.
These showed that “trithiogermanates” (“metathiogermanates”) contain dimeric isolated Ge&- anions with the
structure shown in Fig. 1. This unexpected structure, which
is novel for thio- and 0x0-anions and consists of edgesharing tetrahedra, corresponds to the structure of, e.g.,
A l ~ C l 6(in the gas phase), AlzBr6, and the thiohalides
(SCX2)z and (SSiX2)2 (X = halogen). Of the sulfides, only
the chain-polymeric SiS2 has this edge junction; GeS2 does
not [21.
( I ) crystallizes in the triclinic system (Pi) with a = 9.978(6)
A, b = 7.020(5) A, c = 9.601(6) A, a = 108.41(4)’, =
92.39(4)’, y = 91.69(4)”, dabs. = 1.80, dX-ray = 1.778
gcm-3, Z = 1. The Ge2S:- ion in ( I ) has exact Ci sym-
897
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