вход по аккаунту


Bis[trimethylphosphorio(-onio)]methanide A УSemi-YlidicФ Ligand in Transition Metal Complexes.

код для вставкиСкачать
[4] D. CI! Jones, .I.Chem. SOC.Perkin Trans. I 1973, 1951, has described
isomeric dih ydrotetraphenylinden-1 -ones.
[5] F . Arndt, P . Nachtwey, J . Pusch, Ber. Dtsch. Chem. Ges. 58, 1633 (1925).
161 Y. Guoni, Tetrahedron Lett. 1976, 2167.
(71 L. A . Puquerte, L. D. Wise, J. Am. Chem. SOC. 90, 807 (1968).
A "Semi-Ylidic" Ligand in Transition Metal
Complexes[* "1
By Fritz R. Kreissl, Karl Eberl, and Peter Stiickler[*]
Transition metal complexes of type (3) ought to be accessible, either by addition of an organyl to the ylide carbon
atom in bis-ylide complexes (I), or by addition of a phosphane
to the sp' carbon atom in metal-substituted phosphorus ylides
208.01, CGH5 139.07 (2.4), 134.33 (7.3), 128.07, 127.64, C5H5
85.24, CHzClz 54.38, PCH3 16.79 (N=61.0), RcC
(22.0Hz). In contrast to the CO ligands, two aryl signals
and the ylide carbon show triplet splitting, which rules out
an attack by the phosphane on rhenium and clearly evidences
formation of a semi-ylidic ligand. This finding also confirms
the AXX' system with N=61.0Hz expected for the PCH3
carbon atom[']]. The 31P{'H}-NMR spectrum (CD3COCD3)
shows only one singlet at 6=36.61, which once again underlines the equivalency and the ylidic character of the two phosphorus atoms.
All operations must be carried out in anhydrous (Na, P4OL0)
solvents saturated with NZ. A solution of ( 2 ~ ) ~(1.23g,
2.0 mmol) in dichloromethane (20ml) is treated with trimethylphosphane (0.25 g, 3.30mmol) at -78°C. A colorless precipitate is formed. After treatment with 20ml ether and 20ml
pentane the supernatant liquor is decanted off and the residue
washed with 5 x 10ml pentane and 5 x 10ml ether. Removal
of solvent in a high vacuum (-78"C, 48 h) furnishes colorless
crystals; yield ca. 1.2 g (86 %).
Received: June 27, 1977 [ Z 772 IE]
German version: Angew. Chem. 89,657 (1977)
CAS Registry numbers:
(2a), 63428-44-4; (3a), 63428-42-2; P(CH&, 594-09-2; 13C, 14762-74-4
Occurrence of a comparable complex [(CO)5WCH(PPh3)2]CI['l as intermediate in the reaction of
(C0)5WC(PPh3)2with HCI has been postulated but not isolated. We now report the first isolation and characterization of the phenylbis[trimethylphosphorio(-onio)]methanide
complex (3 a), formed in the reaction of dicarbonyl(q-cyclopentadienyl)[~-(trimethy1phosphoranediyl)benzyl]rhenium
tetrachloroborate (2 a)['] with trimethylphosphane in dichloromethane.
[I] W C. Kaska, D . K . Mitchell, R . F. Reichelderfrr, J. Organomet. Chem.
47, 391 (1973).
[2] F . R . Kreissl, P . Stuckler, E. W Meinecke. Chem. Ber., in press;
F. R. Kreissl, P . Friedrich, Angew. Chem. 8Y, 553 (1977): Angew. Chem.
Int. Ed. Engl. 16. 543 ( I 977).
[3] The corresponding manganese compound was prepared in the same
[4] R. K . Harris, Can. J. Chem. 42, 2275 (1964).
[5] D. A . Redfield, J . H . Nelson, L. W Cnry, Inorg. Nucl. Chem. Lett.
10, 727 (1974).
Steric Enhancement of Chemical Reactivity.
The Molecular Structure of Tris(tert-buty1)methyl
The thermolabile compound (3 a)[31,which crystallizes with
one molecule of CH2CI2, is readily soluble in acetone but
practically insoluble in ether or pentane. At room temperature
it rapidly loses phosphane with regeneration of (2a). The
position of the two v C 0 bands of (3a) [KBr: 1885 and
1805 cm- '1 indicates a large a-donor/n-acceptor ratio for
the "semi-ylidic ligand". The 'H-NMR spectrum shows four
signals of relative intensity 5 :2 :5 : 18, which are assigned to
the phenyl(6 = 8.03 and 7.53), methylene chloride (5.83), cyclopentadienyl(5.20), and P-methyl(2.38) protons; due to 31P-1H
coupling the latter signal appears as an A9XX'A9 system
with N = 12.0 HzC4]and proves the magnetic equivalence of
all PCH3 groups. The constitution of (3a) follows from the
I3C{'H)-NMR spectrum (CD3COCD3, -4O"C, 6 rel.
CD3COCD3= 206.5 ppm, coupling constants in Hz): CO
By Pei-Tak Cheng, S . C. Nyburg, Chacko Thankachan, and
Thomas Tidwellpl
Significant steric accelerations have been observed both
in reactions leading to formation of carbenium ions and in
fragmentations to free radicals. Examples include carbenium
ion formation by the solvolysis of p-nitrobenzoate esters or
chlorides, and free radical formation from peresters, diazenes,
and hexasubstituted ethaned' - 31. Bulky substituents on these
reactants lead to rate accelerations that are sometimes quite
large and the origin of these accelerations has been the subject
of considerable discussion.
Dr. F. R. Kreissl [+I, Dip].-Chem. K. Eherl, Dr. P. Stiickler
Anorganisch-chemisches Institut der Technischen Universitat
Arcisstrasse 21, D-8000 Miinchen 2 (Germany)
['I Author to whom correspondence should be addressed.
[**I This work was supported by the Deutsche Forschungsgemeinschaft.
p] Prof.
Dr. T. T. Tidwell, Dr. P.-T. Cheng, Prof. Dr. S. C. Nyhurg,
C. Thankachan
Department of Chemistry, University of Toronto
Toronto, Ontario MSS 1Al (Canada)
Aiiyew. Chem. I n t . Ed. Engl. 16 (1977) No. Y
Без категории
Размер файла
122 Кб
уsemi, methanide, trimethylphosphorio, ylidicф, metali, transitional, bis, complexes, onion, ligand
Пожаловаться на содержимое документа