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Novel Synthesis of -Methylene Complexes.

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151 W Rotherme/, Diplomarheit, Universitat Marburg 1976: W Siebert. part
of a lecture at the 111. Int. Meet. Boron Chem., Ettal, July 1976.
C6l W Siehwt, R. Fui!, J . Edwi!!, K . Kinhcvycv. C. K~iilqer,J. Organomet.
Chem.. in press.
171 W S i d w t , K . Kirihergrr, Angew. Chem. 88, 451 (1976); Angew. Chem.
Int. Ed. Engl. 15. 434 (1976).
181 J . W LULI/W,M . Eliari, R . H . Summercille. R. Ho//munn. J. Am. Chem.
Soc. 98. 3219 (1976).
c91 K . Wade, Chem. Brit. 11, 177 (1975): literature cited therein.
Novel Synthesis of p-Methylene
Complexes[**]
By Wolfgang A . Nerrmann, Carl Kriiger, Richard Goddard,
and Ivan Bernal[*l
As recently reported['], N-alkyl-N-nitrosourea derivatives
are suitable for use as especially mild nitrosylation reagents
in organometallic chemistry. We have now found that this
class of compounds also provides a facile and productive
entry to p-methylene-transition metal complexes.
The rhodium complex ( I ) reacts with N-methyl-N-nitrosourea in boiling benzene to give a red coordination compound
( 2 0 ) which is stable in the solid state and in solution. On
the basis of total elemental analysis, osmometric molecularweight determination, and 'H-NMR, IR, and mass spectra
the compound has been characterized as p-methylenebis(carbonyl-q-cyclopentadienylrhodium)(Rh-Rh) (Table I). The
homologous p-ethylidene derivative (2 b ) can be obtained
in similar manner with N-ethyl-N-nitrosourea. Deuteriumlabeling experiments confirm that the carbene bridge ligand
originates from the alkyl groups of the organic reagent. The
surprising formation of ( 2 a ) and ( 2 b ) requires ring opening
of the metallacyclic system of ( 1 ) ; mechanistic details are
still unknown.
Table 1. Properties and spectroscopic data of (Zu) and ( Z h ) .
~i-CH2[rl-C5H5Rh(C0)]),1 2 ~ ) pale
:
red needles, m.p. 94"C.--'H-NMR
([D,];acetone; T [ppm], TMS int.): '4.50 (C5H5),"2.88 (CH2): int. 5 : I . -1R
[cm- 1 : 1984 vs (vCO) [ti-pentane]; 1950 vs (vCO), 2963 vw and 2903
w (vCH,) [KBr].-MS
(70eV: T, 50, TS 80°C): M t ( m / e 406, rel. int. 34%,
isotopically corrected), [M -CO]
(378. 44), iCsHs),Rh2Ct (348. 59),
(C5H5),RhT (233, 100); ions < 8 ' k not considered: m* 351.9 (406-378).
p-CH3CH[q-C5HjRh(CO)]2 ( 2 h ) : red-brown needles, dec. I 1 1-1 12°C.'H-NMR ([D,]-acetone: I [ppm], TMS int.): '4.57 (C5H5), 27.47 (CH,).
"1.32 (CH): int. 10:3:1.-IR [cm-'1: 1970 vs ( v C 0 ) [ri-pentane]: 1948
vs IvCO), 2965 vw. 2900 w, 2837 vw IvCH. vCH3) [KBr].-MS
(70eV:
7; 100, '& 60°C): M ? 1410. 1 1 ) . (CjH5),Rh: (336, 7), ( C s H j ) > R h ? (233,
100); C,H,Rht i21X. 71. C 5 H i R h t (168, 6): ions <3"/, not considered.
orientation of the centrically bonded, almost parallel cyclopentadienyl rings leads to identical configurations at the chiral
metal centers.
Fig. 1. ORTEP plot of p C H 2 [ q - C 5 H j R h ( C 0 ) l 2 .
Bond lengths [pm]
n
Rhl-Rh2
Rhl-CI
Rh2-CZ
Rhl-C3
Rhl-CjHj
Rh2-CsHs
o
(2aJ, R = H
(2b). R = CH,
The new procedure obviates use of diazoalkanes for methylene transferI2]. A further advantage is the ready accessibility
of numerous alkyl-substituted nitrosoureas.
We performed the first crystal structure determination[31
of an organometallic compound with bridging CH2 by analyzing ( 2 a ) (Fig. 1): the carbene C atom, like the two Rh atoms,
is located in a distorted tetrahedral environment. The trans
-~
[*I
Dr. W. A. Herrmann
Chemisches lnstitut der Universitat
Universitatsstrasse 3 1, D-8400 Regenshurg 1 (Germany)
Dr. C. Kriiger, Dr. R. Goddard
Max-Planck-lnstitut fur Kohlenforschung
Kaiser-Wilhelm-Platz 1, D-4330 Miilheim-Ruhr 1 (Germany)
Prof. Dr. I . Bernal
Chemistry Department, University of Houston
Houston, Texas 77004 (USA)
[**I Transition Metal Methylene Complexes. Part 2.-Part I : Ref. [3].-This
work was supported by the Deutsche Forschungsgemeinschaft. the Alexandervon-Humholdt-Stiftung, and Degussa Hanau.
334
Angles
266.5(1)
183.1(4)
183.3(4)
202.9(4)
225.9130)
225.6(22)
["I
Rh 1 -C3-Rh2
Rh I -Cl-0
1
Rh2-C2-02
Torsional angle ["I
C1, Rhl, Rh2, C2
81 .7(1)
178.2(4)
176.0(4)
-176.90
p-CO[q-C5H5Rh(CO)]2[51( I j (420mg, 1.0mmol) and N methyl-N-nitrosourea (1.03g, 1O mmol) are refluxed in benzene
(50ml) for 25 h. On column chromatography of the crude
product on Kieselgel 60 (Merck 7734, Act. 11-111; 20 x 3 cm;
15°C) ( 2 a ) is eluted as an orange-yellow zone with n-pentane/benzene (2: I); it is recrystallized from n-pentane at
- 78 "C. Yield 349 mg (86 %). A small amount of ( I ) is developed as a deep red zone with benzene. Analogous reaction
with N-ethyl-N-nitrosourea affords 240 mg (5770) of (2b).
+
Received: March 2, 1977 [Z 691 IE]
German version: Angew. Chem. 89. 342 (1977)
W A . Herrmurin, 1. Ber.nol. Angew. Chem. 89, 186 (1977): Angew. Chem.
Chem. Int. Ed. Engl. 16. 172 (1977).
W A . Herrmumi. B. Reirer, H . Biersack, J. Organomet. Chem. 97. 245
(1975).
Crystal data: triclinic, space group P i . a = 803.42(5). b=909.98(6),
c = 938.81( 2 )pm, x = 74.402(3), [I = 81.923(3), 7 = 82.685(6)"; 27 I8 observed
reflections (20,,, = 55"). MoKl-radiation (0.71069 A). Computer-controlled diffractometer Enraf-Nonius CAD-4. R = 0.0379 ( R , =0.0546).
All operations performed under N2 and with use of dry solvents.
We synthesized this compound, which was first prepared by E. 0.Fischer.
et a / . [Z. Naturforsch. 1 6 8 , 835 (1961)] [6], by 80 hours' refluxing
of q-C5H5Rh(CO), ( 1 . 0 ~in
) benzene (40ml)--yield 630mg (67 %). -In
place of ( I ) its precursor q-C5HsRb(CO)2can also he used directly
for preparation of ( ? a ) and ( 2 h ) (yield <50u/,).
Structure: 0.S. Mills, J. P. Nice, J. Organomet. Chem. 10, 337 (1967);
cf. F . A . Cottori, D. L. Hunter., Inorg. Chem. 13, 2044 (1974).
Anyrw. Chem. I n [ . Ed. O q l . 16 ( 1 9 7 7 ) N o . 5
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