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Binuclear Iron Complexes Containing Unsymmetrically Substituted Silanediyl Bridges.

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to prevent undesired hydrosilylation of the aldehyde. Analogously, reaction of n-butanal and cyclohexanecarboxaldehydegave(1 b ) and (1 c) in 67 % and 37 % yields, respectively.
In the case of cyclohexanecarboxaldehyde, the yield of ( 1 c )
was low because of the formation of diethyl(methy1)siloxymethylenecyclohexane (61 %) by dehydrogenative silylation. Interestingly, a similar reaction (using a fivefold excess of the
hydrosilane, but in this case without Ph3P) of tetrahydrofuran
was found to give the same type of compound ( I d ) in 89 %
yield-probably via the intermediate 5-diethyl(methyl)siloxyn-pentanal, which was the product when the reaction was
carried out using a fivefold excess of tetrahydrofuran over
the silane and without Ph3PL3J.
It has been reported that formates can be produced from
aldehydes (via 0 - C bond formation) under hydroformylation (0x0 synthesis) conditions[41.In contrast, by using a hydrosilane instead of hydrogen, bis-siloxyalkenes (1) instead of
esters were obtained (via C-C bond formation).
Binuclear Iron Complexes Containing Unsymmetrically
Substituted Silanediyl Bridges"]
By Wolfgang Malisch and Wovgang Ries"]
The ability of 4B elements germanium, tin, and lead to
function as bridges between transition metal atoms has been
demonstrated by numerous examples['], whereas only few
corresponding examples of complexes with silicon bridges
have so far been described[31.We have now found that nucleophilic metalation of chlorosilyliron complexes of type ( 1 )I4]
with the extremely reactive anion [Cp(CO),Fe]"['] affords
easy access to binuclear complexes containing a silicon bridge
if the chlorosilyl group still bears at least one hydrogen atom
and the reaction is carried out heterogeneously in methylcyclohexane.
+ Na[Fe(CO)zCp]
Synthesis of ( 1 a ) : A solution of 1.14g (10mmol) of n-heptanal, 4.4 ml (30 mmol) of diethyl(methyl)silane, 0.068 g
(0.2 mmol) of Co2(CO)*, and 0.052 g (0.2 mmol) of triphenylphosphane in 20 ml of benzene was placed in a 100 ml stainless
steel autoclave. The autoclave was flushed with N2 (50kp/cm2)
and C O (50kp/cm2), then charged with C O (50kp/cm2) and
heated at 140°C with stirring. After 20h, the autoclave was
cooled and depressurized. Analysis of the reaction mixture
by GLC [Silicon OV-I, 5 % , on Uniport KS, 3m, 170°C,
internal standard n-hexadecane] showed it to contain ( 1 a )
in 66% yield; at longer retention times there were at least two
further unidentified products (total ca. 14 %). An analytical
sample of (1 a ) was obtained by fractional distillation (b.p.
Diferriosilane ( 2 ) , which is isolable as orange-yellow crystals, m. p. 89-9OoC, exhibits increasing solubility in the series
pentane cyclohexane, benzene, toluene, and, according to the
IR spectrum, has C1 symmetry[61in the dissolved state (cyclohexane). The prochiral character of the Cp(C0)'Fe group is
demonstrated by 3C-NMR spectroscopy[']. The unusual
position of the vSiH vibrational band at 2025 cm- characterizes the metal group as a strong donor. This "transition
cis (CH,)
(3a). m - p . 163-165 "C
120-1 23 "C/0.5 torr) and preparative gas chromatography
Received: November 7, 1977 [Z 880 IE]
German version: Angew. Chem. 90, 139 (1978)
CAS Registry numbers:
C O ~ ( C O10210-68-1
;diethyl(methyl)silane, 760-32-7; carbon monoxide, 63080-0
[l] Transition Metal Reactions of Silanes. Part 5.-Part 4: see Ref. [2c].
[2] a) Y Seki, A. Hidaka, S. Murai, N . Sonoda, Angew. Chem. 89, 196
(1977); Angew. Chem. Int. Ed. Engl. 16, 174 (1977); b) Y Seki, A . Hidaka,
S. Makino, S . Murai, N . Sonoda, J . Organomet. Chem. J40, 361 (1977);
c) Y Seki, S. Murai, A. Hidaka, N . Sonoda, Angew. Chem. 89, 919
(1977); Angew. Chem. Int. Ed. Engl. 16, 881 (1977).
[3] Y Seki, S. Murai, I . Yamamoto, N . Sonoda, Angew. Chem. 89, 818 (1977);
Angew. Chem. Int. Ed. Engl. 16, 789 (1977).
[4] R . F . Heck: Organotransition Metal Chemistry, A Mechanistic Approach.
Academic Press, New York 1974, p. 218; F. Piacenri, M . Bianchi in
I. Wender, P . Pinot Organic Syntheses via Metal Carbonyls, Vol. 2.
Wiley, New York 1977, pp. 12. 37.
metal effect" also gives rise to the pronounced tendency of
the strongly hydridic Si-H function to undergo exchange
reactions, as exemplified by the halogenation of the latter
on reaction with CC14 or PhC'BF:
under very mild conditions
(in benzene, 25 'C)['].
When ( 2 ) , either in the solid state or in solution, is exposed
to daylight it is slowly transformed with loss of C O into
the bicyclic species ( 3 a ) , in which the two iron atoms are
now coupled both directly and by a CO bridge. This conversion can be considerably accelerated photo~hemically['~.
The 'H-NMR spectrum of (3 a ) in benzene contains, besides
four signals for the cyclopentadienyl groups, three signals
each for the HSi and the CH3 groups (as quartet and doublet,
respectively) and thus proves that the ring system is present
[*] Priv.-Doz. Dr. W. Malisch, Dip].-Chem. W. Ries
lnstitut f i r Anorganische Chemie der Universitat
Am Hubland, D-8700 Wiirzburg (Germany)
Angew. Chem. Int. Ed. Engl. 17 (1978) No. 2
in solution as a mixture of all three theoretically conceivable
stereoisomerslS1.An unequivocal assignment of signals (cf.
Table 1) is possible only in the case of the trans form (two
CsHS signals of equal intensity). Assuming steric preference
for the cis(H) form an isomeric ratio of 56/cis(H): 26/cis(CH3):
18/trans would result. Spectra recorded immediately after dissolution of crystalline (3a) show only the two cis isomers
[86/cis(H): 14/cis(CH3)], while the equilibrium concentration
of the trans form is reached only after 20 minutes. Hence,
a cisltrans isomerization already takes place at room temperature, and, in principle, is possible both from the cis(H) as
well as from the cis(CH3) form['].
(3 a): A solution of (2) (492mg, 1.24 mmol) in 60 ml benzene
is irradiated for ca. 6 h with UV light (quartz lamp Ql50
Hanau), the carbon monoxide that is formed being removed
from the reaction vessel with a stream of Nz. The filtered
solution is concentrated to 7ml and ( 3 a ) precipitated with
5 ml pentane at room temperature. The deep-red crystals are
washed twice with 5ml cold pentane and dried in uacuo;
yield 271 mg (59 %).
(3b): A suspension of (3a) (270mg, 0.73mmol) in 5ml
CCll is allowed to stand for 30 min at 25 "C. After removal
of volatile components, multiple extraction of the solid residue
with lOml toluene/methvlcvclohexane (1
. : 1). and freezing out
- 78°C affords 242 mg (82 %) (3 b).
Table 1. Spectroscopic data of the p-silanediyliron complexes (2), ( 3 a )
and ( 3 b ) [a].
Received: November 3, 1977 [Z 881 IE]
revised: November 10. 1977
German version: Angew. Chem. 90, 140 (1978)
'H-NMR (C6H6): 6C5H534.37 (s, IOH); 6CH3=1.14 (d, 3H),
(9. 1 H).-13C-NMR (C6D6): 6CsHs=84.3;
3 J ~ c s L ~ = 3GHSi=5.46
6CH3=12.0; 61C0=216.52; 62CO=216.65.-29Si-NMR (C6Dh):
6Si =62.8.-1R
(cyclohexane): v C 0 = 1990 (vs), 1952 ( s ) , 1943 (s),
1935 (m) cm-'.
( 3 a ) : 'H-NMR (C6D6):
(s, 5 H bzw. IOH)
(d, 3H)
(9. 1 H)
62=4.29 1.38
IR (cyclohexane): vCO=1999 (w). 1976 (vs), 1958 (s), 1939 (s), 1794
(sh) cm-l.
( 3 b ) : 'H-NMR (CeD6): trans: 6CsHs=4.42, 4.28 (s, 5H); 6CH3=1.62 (s,
3H) / Cis(CI): GCsHs=4.23 (s, 10H); 6CH3=1.71 (s, 3H)) / cis(CH3):
6CsHs =4.03 (s, 10H); 6CH3 = 1.59 (s, 3H).--IR (cyclohexane):
vC0=2000 (w). 1980 (vs), 1968 (sh), 1946 (s), 1791 (vs) cm-'.
[a] Chemical shifts downfield rel. to TMS int.; coupling constants in Hz.
Analytical data consistent with the given formulas.
In accord with the even smaller magnitude of the Si-H
valence vibration (vSiH = 2015 cm- '), hydrogen exchange at
the silanediyl bridge of (3a) proceeds more rapidly than
in the open-chain species (2).
- CHCll
Hindered "Benzoxetes"
Synthesis and Reactivity of Silicon-Transition Metal Complexes, Part
13. This work was supported by the Deutsche F0rschungsgemeinschaft.Part 12: W Molisch, W Ries, Chem. Ber., in press.
R. D. Adams, M . D. Brice, F . A . Cotton, Inorg. Chem. 13, 1080 (1974).
B. J . Aylett, H . M . Colquhoun, J. Chem. Res. (S) 1 , 148 (1977); C .
S . Cundy, B . M. Kingston, M. F . Lappert, Adv. Organomet. Chem.
I f , 253 (1973).
W Malisch, M. Kuhn, Chem. Ber. 107, 979 (1974).
R. E. Dessy, R. L. Pohl, R. B. King, J. Am. Chem. SOC.88, 5121 (1966).
The intensities of the v C 0 bands (Table 1) decrease monotonically
with decreasing wave number. Cf. N . Flitcroft, D. A. Harbourne, I . Paul,
P . M . Tucker, F. G . A . Stone, J. Chem. SOC.AI966, 1130.
An analogous cyclization reaction has already been observed with
(CH3)2Ge-bridged complexes: R. C. Job, M . D. Curtis, Inorg. Chem.
12, 2514 (1973).
This finding is confirmed by the "C('H}-NMR spectrum (in C6D6).
6CsHs=83.83, 84.27, 84.86, 85.30; 6CH3=7.89, 8.97, 10.09;
6CO,,,, =212.57.
Investigations presently being carried out on the activation parameters
of this process should clarify whether the cis/cis and cisltrans isomerizations are independent processes.
- co \
Reaction of (3 a) with CC14 smoothly affords the chloro-substituted cyclic compound (3b), m.p. 183--185"C, which is
distinctlymorestable than thehydrosilane(3 a) (both thermally
and solvolytically), and in which the isomeric equilibrium
is shifted further in favor of the cis(X) form [83/cis(Cl): 5/
cis(CH3):12/trans]. The derivative (3 b) can also be generated
photolytically from (4)['].
True Nature of Sterically
By Herbert Meier, Hans-Peter Schneider, Anton Rieker, and
Peter B. Hitchcock"]
In 1961 E. Miiller et al. observed that dehydrogenation
of 2,4-di-tert-butylphenol, 2,4-di-tert-butyl-6-iodophenol,
biphenol (1 a) in benzene yields a deep violet solution suspected to contain the corresponding o,o'-diphenoquinone (2 a)
( Z - and/or E-configuration). A pale yellow compound, assigned
the structure of a benzoxete (3a), could be isolated in good
Structural proof was based on the formal analogy to the
formation of homologous spiroquinol ethers, reduction to
the biphenol (1 a), and the 'H-NMR spectrum[']. Later on,
compound (4a) first isolated by Baltes and Volbert in 1955,
which exists in equilibrium with the diphenoquinone (2 b)['"],
was ascribed the same kind of structure (3b)[2b,cl.The oxidation products of the biphenols (1 c-g) were also regarded
[*] Prof. Dr. H. Meier, Dipl.-Chem. H.-P. Schneider,
Prof. Dr. A. Rieker [ '1
(2): A solution of Cp(C0)3FeSiHCH3Clr41(1.57g,
6.12 mmol) in 50 ml methylcyclohexane is treated with 1.58g
(7.88 mmol) of dry Na[Fe(CO),Cp][']. The mixture is stirred
in the absence of light for 6d at 25"C, filtered, the filtrate
evaporated in uacuo, and the resulting residue extracted several
times with pentane. Freezing out at -78°C affords 1.43g
(59 %) (2).
Institut fur Organische Chemie der Universitat
Auf der Morgenstelle 18, D-7400 Tiibingen I (Germany)
Dr. P. B. Hitchcock
The School of Molecular Sciences, University of Sussex
Falmer Brighton BNl 9QJ (England)
['I To whom correspondence should be addressed.
[**I This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie.
Angew. Chem. Int. Ed. Engl. 17 ( 1 9 7 8 ) N o . 2
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binucleata, containing, bridge, iron, unsymmetrical, complexes, substituted, silanediyl
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