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Cyclohexenyl(1 5-cyclooctadiene)iridiumЧ-Diene Hydride or Enyl Structure.

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meters (atom/x:a/y:b/z:c): As / 0.1470(1) / 0.2149(2) / 0.0310(1)P / 0.1331(4) / 0.6164(4) / -0.0271(2)--CI / 0.3782(4) / 0.1713(5) /
0.1438(2)-N(I) / 0.202(1) / 0.396(1) / -0.0338(6)-N(2)
/ 0.1313(9) j
0.591(1)/ 0.0766(5)-N(3)/ 0.070(1) /0.406(1)/ 0.0SS2(5)-C(l)/0.242(1)/
0.332(2) ,' -0.11 17(7)-C(11) / 0.088(2) /0.269(3) -0.1896(9)-C(12) ;
0.354(2)/ 0.172(2) / -0.0811(9)-C(13) /0.308(2)/ 0.500(3)/ -0.1421(9)C(2) / 0.272(1) / 0.645(2) / 0.1559(8).
[5] J . Weiss and W Eisenhurh, Z. Natui-lorsch. 22b, 454 (1967); R. Ullmumi
and H . Niirh, Chem. Ber. IOY, 2581 (1976); literature cited therein.
,'
pear into the background. Accordingly, there must be rapid
interchange between the forms ( 3 a ) and ( 3 b ) ; collapse of
the proton signal of the cyclohexadiene ligands comes about
because hydride addition and abstraction, respectively, can
take place at both sides of the n-system, so that this "rotates"
over all six ring positions.
Cyclohexenyl(1,5-cyclooctadiene)iridiumq-Diene Hydride or Enyl Structure[**]
By Jiirn Miiller, Walter Holzinger, and Helmut Menig[*]
The transfer of a hydrogen atom from an q-enyl- or q-dienyl
ligand to the central metal atom should play an important
role in numerous reactions of n-complexes with olefins, e. g.
ligand-exchange processes which are partial steps of catalytic
isomerizations and oligomerizations of alkenes and dienes.
Thus the ligand exchange"] in the reaction of cyclohexenyl( 1,5cyc1ooctadiene)rhodium (1 )['I with butadiene may perhaps
be most simply explained in terms of the formation of hydride
intermediates [ ( l a ) , ( I b)].
13n)
(361
On lowering the temperature the equilibrium shifts in favor
of (3 a). This is confirmed by the temperature-dependence
of the 13C-NMR spectrum[51. Cycloheptenyl(1,S-cyclooctadiene)iridium (S), obtained by reaction of ( 4 ) with 1,3-cycloheptadiene in the presence of i-C3H7MgBr,behaves in exactly
the same way as (3). O n the other hand, the 1,5-cyclooctadiene(penteny1)iridium ( 6 ) , synthesized in a similar way, has
so far yielded no evidence of a hydride form.
Experimental :
Similarly the reactive behavior of 1,5-cyclooctadiene(4-5q-cycloocteny1)cobalt ( 2 ) suggests that this complex i s in equilibrium with a hydride form ( 2 ~ ) ' ~ ~ .
12)
[*] Prof. Dr. J. Miiller, Dipl.-Chem. W. Holzinger, and Dipl.-Chem. H.
Menig
Institut fur Anorganische und Analytische Chemie der Technischen Universitat
Strasse des 17. Juni 135, D-1000 Berlin 12 (Germany)
[**] This work was supported by the Deutsche Forschungsgemeinschaft
702
Received: August 20. 1976 [Z 543 IE]
German version: Angew. Chem. 88, 768 (1976)
(la)
So far, however, there has been no direct spectroscopic
evidence for an equilibrium of the type ( l ) + ( l a ) or
(2)* ( 2 a ) .
We have now synthesized and investigated the analog of
( 1 ), the iridium compound (3). Reaction under UV radiation
of di-p-chlorobis[( 1,S-cyclooctadiene)iridium] (4)14' with 1,3cyclohexadiene in the presence of i-C3H7MgBr furnished (3)
in the form of yellow-brown crystals. Spectroscopic findings
prove that (3) is in equilibrium with a hydride form at room
temperature, and that the six-membered ring ligand has a
fluxional structure.
Evidence for the existence of an Ir-H bond is provided
by the occurrence of a medium-strength absorption at
2010cm-' in the IR spectrum (KBr) and a broad singlet
at T = 12.6 in the 'H-NMR spectrum ([D8]toluene). The protons of the cyclohexadiene ligand likewise give rise to only one
singlet at r=6.76. Both singlets become sharper on warming
the solution; on cooling they broaden and at ca. 280K disap-
and the Fonds der Chemischen Industrie.
All work must be carried out under nitrogen or argon.
1,3-Cyclohexadiene (2mI) is added to a suspension of (4)
(1.62g, 2.41 mmol) in ether (20ml) at -78°C; a Grignard
solution prepared from Mg (182 mg, 7.49mmol) and i-C3H7Br
(0.7ml) in ether (30ml) is then added with vigorous stirring.
The mixture is allowed to warm slowly to 20°C and irradiated
for 5 h with UV light (Hg high-pressure lamp Q81, Heraeus,
Hanau). Solvent and excess diene are then removed by evaporation, the residue eluted with hexane (1 SO ml), and the resulting
solution concentrated and chromatographed on an A1203
(S % H20)column(Iength50cm,diameter 1.5 cm) with hexane.
Analytically pure (3) crystallizes from the yellow-brown eluate
at -78°C. Yield 1.09g (2.86mmol; 59%), m.p. 68-69°C.
CAS Registry numbers:
( 3 u ) , 60410-67-5; ( 3 h ) , 60140-68-6; (4)- 12112-67-3: ( 5 1 , 60410-69-7;
(6). 60410-70-0
[I] H.-0. Stiihlev, Dissertation, Technische Universitat Miinchen 1976.
[2] J . Miiller, H . - 0 . Stiihler, and W Goll, Chem. Ber. 108, 1074 (1975).
[3] H . Bonnemann, Angew. Chem. 85, 1024 (1973); Angew. Chem. Int. Ed.
Engl. 12, 964 (1973).
[4] G. Winkhaus and H . Singer, Chem. Ber. 99, 3602 (1966).
[ 5 ] J . Miiller, H.-0. Sriihfer, G. Hurmrr, and K . Seherzrr, Chem. Ber. 109,
1211 (1976).
Simplified Synthesis of Bis(triphenylphosphorany1idene)methane
By Rolf Appel, Fritz Knoll, Heinfried Scholer, and Horst-Dieter
Wihler PI
Hexaorganylcarbodiphosphoranes of type R3P=C=PR3
are extremely reactive compounds[' - 3 1 which on account of
their pronounced ylide character avidly abstract protons and
halogen[4! Their wide-spread use, however, has hitherto been
.~
-
[*] Prof. Dr. R. Appel, Dr. F. Knoll, Dipl.-Chem. H. F. Scholer, and Dipl.Chem. H.-D. Wihler
Anorganisch-chemisches lnstitut der Unlversitat
Max-Planck-Strasse I , D-5300 Bonn (Germany)
Angew. Chem. Int. Ed. Engl.
1 Vol. 15
( 1 9 7 6 ) No. 1 I
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