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Complexes of Iridium with Terminal PF2-Ligands.

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2893 (1963); E. Vogel, R. Feldmann, H . Duwel. Tetrahedron Lett. 1970,
1941 ; E. Vogei, W. Wiedemann. H. D. Rofh. Justus Liebigs Ann. Chem.
759. l(1972).
[21 a) G. Moier, Angew. Chem. 79,446 (1967); Angew. Chem. Int. Ed. Engl.
6. 402 (1967); T.Toda, Yuki Gosei Kagaku Kyokaishi 30, 412 (1972); b)
M . Schafer-Ridder, A. Wagner, M . Schwamborn, H. Schreiner, E. Devroui, E. Vogel, Angew. Chem. YO, 894 (1978); Angew. Chem. Int. Ed.
Engl. 17. 853 (1978).
[31 a) B. Halron, Chem. Rev. 73,113 (1973); W. E. Billups, Acc. Chem. Res.
11. 245 (1978); b) W. E. Biliups. A . J. Blakeney, W. Y. Chow, Org. Synth.
55. 12 (1976).
[41 R. G. Guy, J . J . 7hompson. Tetrahedron 34, 541 (1978).
[51 a) Earlier Vogel ef a / . , synthesized 1,6-diiodocycloheptatriene
(2b)from
(1)and IZ in CCL; the yield was, however, small and (3c) was the major
product: E. Vogel, W . Grimme, S. Korfe, Tetrahedron Lett. 1965, 3625;
b) when the reaction was conducted in normal sunlight, never more than
2% (26) was obtained.
[61 a) K. Tamao, K. Sumitani, Y. Kiso. M.Zenbayashi, A . Fujioka. S . Kodama, I . Nakajima, A. Minafo, M. Kumada, Bull. Chem. SOC.Jpn. 49,
1958 (1976); b) M. Yamamura, I . Morifani, S.Murahashi, J. Organomet.
Chem. 91, C39 (1975).
[7] H . Giinther. H . Schmickler, U. H. Brinker, K . Nachikamp, J . Wassen, E.
Vogel, Angew. Chem. 85. 762 (1973); Angew. Chem. Int. Ed. Engl. 12.
760 (1973).
[81 J.-F. Normanf.A. CommerGon, G . Cahier. J . Villiiras. C. R. Acad. Sci.,
Ser. C 278. 967 (1974).
191 F. D. King, D. R. M . Walron. J. Chem. SOC.Chem. Commun. 1974,
256.
[lo] J . R. Campbell, J. Org. Chem. 29. 1830 (1964).
[I I1 R. N . Cosile. J . L. Riebsomer, J. Org. Chem. 21, 142 (1956).
cant alteration in the environment of the PF,-group. Moreover, the magnitude of 'J(PP) becomes smaller and
J(HPF,) drops from 415 Hz to 7.5 Hz. In the 'H-NMR
spectrum, the resonance at 6 = 8 . 4 disappears and is replaced by a complex multiplet at 6 = - 16 that must be
due to H bound to Ir. It follows that the pentacoordinated
iridium complex (1) (type A) formed initially has rearranged to give a new complex (5) of hexacoordinated iridium(rr1) (type B in Scheme 1) by oxidative addition of PH,
leaving H and a terminal PF,-group bound to the metal.
-
trans-Ir(CO)(PEt3)zX+ PFzQ
PEt,
PEt,
I ,co
-+
I
FO
X-Ir-PF,
X-lF
PEt,
PFzQ
QI'
A
PEt3
B
Scheme I.
Complexes of Iridium with Terminal PF,-Ligands[**]
By E. A . V. Ebsworth. Neil T. McManus,
Dacid W . H. Rankin, and John D. Whitelock[']
Attempts to prepare complexes containing a metal
bound to tricoordinated phosphorus have usually produced bridged species. Some derivatives of chromium and
tungsten are known in which terminal PC1,-groups are
bound to the metal"], but attempts to prepare PF2-complexes of platinum have led to the production of dinuclear
diplatinum complexes1z1.Here we report the synthesis and
characterization of some complexes of iridium(Ir1) containing terminal PFJigands; these compounds should be
suitable for use in the controlled synthesis of mixed-metal
bridged complexes.
Reaction of a solution of PF2H and trans-Ir(CO)I(PEt3),
at 233 K in toluene leads to the formation of a PF2H-complex of pentacoordinated iridium (type A in Scheme 1).
Two signals are observed in the 31P(H)-NMRspectrum
(Table I); a doublet at 6 = - 7 ('J(PP)=38 Hz) arising
from PEt,, and a wide triplet from the PF,-group at
6 = 142 ('J(PF)= 1103 Hz) each line of which is further
split into a narrow triplet because of coupling with the P
atoms of the two Et3P-groups. In the non-decoupled spectrum, each line of the PF,-signal shows an additional
doublet splitting of 415 Hz, a typical value for 'J(PH) in tetracoordinated phosphorus compounds. The 'H-NMR
spectrum shows a resonance at 6 = 8 . 4 with a doublet splitting of 415 Hz; each line is further split into a triplet [due
to 'J(FH)] of triplets [due to 3J(PH)].
When the solution was allowed to warm to room temperature, the spectra changed. The P resonance of the PFZgroup shifts from 6= 142 to 6 = 378; this implies a signifi[*I
['*I
Prof. Dr. E. A. V. Ebsworth, N. T. McManus, Dr. D. W. H. Rankin, Dr.
J. D. Whitelock,
Department of Chemistry, University of Edinburgh,
Edinburgh EH9 3JJ (Scotland)
This work was supported by Messrs Johnson Matthey and the Science
Research Council
Angew. Chem. In1 Ed Engl. 20 (1981) No. 9
Similar reactions occur between PFzX and transIr(CO)X(PEt,),, X = C1, Br or I. When X = C1, the I9F- and
31P-NMRspectra show peaks with the multiplet structures
expected for a complex of type A; the PF2-chemical shift
(6=97) is in the same region as that of PF,CI-complexes. When the solution is allowed to warm to room temperature, the PFz-resonance shifts to 6= 364.8 i. e. the
signal for (6) is similar to that for (5). When X=Br, the
concentration of the complex (3) (type A) at 193 K is small,
and the assignment of the PF,-resonance is doubtful;
when X = I, we were unable to identify any of the signals
expected for complex (4). In each case, however, there are
resonances due to complexes (7) or (8) (type B); in keeping
with the assigned structure, all the PF,-chemical shifts are
very similar (Table 1).
Table I. NMR data for the complexes of types A and B recorded in [Ds]toluene at 233 K [(l)- (5)l and at 298 K [(6)- (811; precision. It 1 to the last figure quoted (J in Hz).
Complex
Type G(PEt,)
- 6.9
142
97
6(F)
-60.8
4.9
110
0.3
6.2
resonances not observed
-10.8
376.7
-61.5
- 9.3
364.8
-68.3
-18.1
363.1
-64.8
-31.9
364.8
-61.0
-
7.2
6(PF2)
'J(PF)
'J(PP)
3J(PF)
1103
1333
1341
38
42
45
[c]
9
Icl
1111
1106
1108
1112
25.9
9.2
8.5
8.3
17.1
11.6
11.1
10.6
[a]6(H)=8.72. [b]6(H)= -16.0; zJIHp(Et)]=lO, *JIHP(F)1=7.5, 'J(HF)= 11.5
Hz. [c] Not resolved.
Complex (5) decomposes slowly in solution at room
temperature, but complexes (6)-(8) are stable at room
temperature and have been isolated and characterized by
elemental analysis, IR-, and NMR-spectroscopy. Addition
of B,H6 to a solution of (8) in C7Hs leads to a shift in the
PF,-resonance in the 31P(1H)-NMRspectrum to 6=250,
0 Verlag Chemie GmbH, 6940 Weinheim, 1981
0570-0833/81/0909-080I $02.50/0
801
together with a marked broadening of the lines. We interpret these observations as evidence that a bridged complex
containing the grouping Ir-PF2-BH3
has been formed;
in confirmation of this view, the I9F-NMR spectrum consists of a broad doublet, due to ‘J(PF), each line of which
is split into a I :3 :3 : 1 quartet by F-H coupling.
3. The ligands in (2), all of which were either previously
unknown - (2a-d) - o r incompletely characterized (2e,
f j I V - may be liberated as colorless oils in high yield by oxidative demetalationr6] (Table 1). Decomplexation of the
mixtures (2d) and (28 gave only one product, corroborating the structural assignment of the minor component.
~
Received: August 18, 1980 [Z 825 IE]
German version: Angew. Chem. 93. 785 (1981)
(11 W. MaLsch, R. Alsmann, Angew. Chem. 88, 809 (1976); Angew. Chem.
Int. Ed. Engl. IS, 769 (1976).
121 E. A. V. Ebsworth. D. W. H . Rankin. J. D. Whitebck. unpublished results.
cocp
+ +
Cobalt Mediated I2 2 21-Cycloadditions:
Stereospecific Intramolecular Reactions
of Enediynes
to Tricyclic Dienes Bearing Angular Methyl Croups[’*]
/
F
/
By Thomas R . Gadek and K . Peter C. Vollhardt[’l
We recently reported on the inter- and intramolecular
[2 2 2]cycloaddition of linear achiral enediynes containing terminal double bonds, using C ~ C O ( C O )to~ ,give polycyclic diene complexes (cp = cyclopentadienyl)rll. We
now describe similar stereospecific reactions of enediynes
which may even be used to incorporate trisubstituted double bonds, producing tricyclic dienes with angular methyl
groups. The molecules synthesized constitute good model
systems for a variety of polycyclic natural products, particularly vitamin D precursors.
The educts (1) were prepared by Wittig reaction of the
terminal acetylenic aldehydes or ketones with the appropriate acetylenic ylides[’l. The aldehydes o r ketones generally originated from internal propargyl alcohols via the
“acetylene-zipper’’ reactionr3’, followed by standard structural manipulations. Cis- and trans-(1) were interconvertible by irradiation in the presence of sensitizer[41 and, if
necessary, separated by preparative gas chromatography.
In a typical experiment, a solution of (I) and
C ~ C O ( C Oin
) ~boiling m-xylene was irradiated to give the
red-brown complexes (2) (Table 1) in fairly good yield,
after chromatography on alumina. Stereochemical and
spectral assignments were carried out by comparison with
model compounds, utilizing the effect of the anisotropy of
cobalt on the N M R spectra”], symmetry considerations [cf.
(2a) with (2b)], and off-center resonance proton decoupled
I3C-NMR spectroscopy.
Three points of particular interest are:
1. The [2 + 2 + 2]-cycloaddition proceeds with retention
of stereochemistry at the original double bond and also
with remarkable stereoselectivity with respect to cobalt [cf.
(2a), (2b), (2c). (2e)I; this might be valuable in asymmetric
syntheses with an optically active metal compound.
2. The cyclopentadienylcobalt not only fulfills the function of the mediator of the cyclization but also serves to
protect the diene unit from rearrangement and polymerization.
+ +
[*] Professor Dr. K. P. C. Vollhardt, T. R. Gadek
Department of Chemistry. University of California, Berkeley
Materials and Molecular Research Division,
Lawrence Berkeley Laboratory
Berkeley, California 94720 (USA)
[**I
0 Verlag Chemie GmbH, 6940 Weinheim. 1981
(2ri c o c p
(2d) 3 : 2 mixture
COCP
The origin of the stereoselectivity observed in the above
reactions is not clear at present. It should be noted that trimethylsilylation of the alkyne moieties is detrimental to
the successful outcome of the reaction.
Hydrogenated benz[e]indanes and phenanthrenes of the
type synthesized here are frequent structural features in
natural products. The ligands in (2e) and (2fj are of particular interest since they may be regarded as constituting
the ABC-portion of steroids, which function as precursors
to vitamin D and valuable steroid hormones. The cobalt
mediated [2 + 2 + 21-cycloaddition approach should provide a simple and effective route to these classes of compounds.
Procedure
This work was supported by the National Science Foundation (CHE 7903954) and the National Institutes of Health (GM 22479). K P.C. V. is a
Camille and Henry Dreyfus Teacher Scholar (1978- 1983).
802
i
A degassed solution of ( 1 ) ( 1 mmol) and C ~ C O ( C O( 1) .~1
mmol) in m-xylene (50 mL) was refluxed and irradiated
(visible light, GE-ENH, 250 W). After 1 h, the solvent was
removed in uacuo (0.05 torr) and the residue chromato-
0570-0833/81/0909-0802
$02.50/0
Angew Chem. Int. Ed. Engl. 20 (1981) No. 9
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