The Complementary Competitors: Palladium and Copper in C-N Cross-Coupling Reactions

Organometallic Fluorides: Compounds Containing Carbon−Metal−Fluorine Fragments of d-Block Metals†

Transmetalation of Unsaturated Carbon Nucleophiles from Boron-Containing Species to the Mid to Late d-Block Metals of Relevance to Catalytic C−X Coupling Reactions (X = C, F, N, O, Pb, S, Se, Te)

Marriage of heavy main group elements with π-conjugated materials for optoelectronic applications

Because of the role that metal-mediated carbon -hydrogen bond activation could play in the conversion of saturated hydrocarbons to more useful, functionalized organic compounds, much effort has gone into developing mild methods for carrying out this transformation in solution. 1 Most of the classical methods for activating C-H bonds involve oxidative addition reactions with uncharged, electron-rich, coordinatively unsaturated metal centers (eq 1). Recently, however, several new C -H activation reactions have been discovered that take place at cationic “electrophilic” late transition metal centers, creating a resurgence of interest in this class of C-H activating reactions (eq 2). 2-8 Most of the

Exceptionally low-temperature carbon--hydrogen/carbon--deuterium exchange reactions of organic and organometallic compounds catalyzed by the Cp*(PMe(3))IrH(ClCH(2)Cl)(+) cation.

The reaction between B(C
 6
F
 5
)
 3
 and
[Fe(η-C
 5
H
 5
)(CO)
 2
Me] gave the
unexpected product
[Fe{C
 6
F
 4
C(O)Me-2}(η-C
 5
H

 5
)(CO)] 1 which reacts with the donor molecules
L = PMe
 3
, PPh
 3
 or Bu
 t
NC
giving
[Fe{C
 6
F
 4
C(O)Me-2}(η-C
 5
H

 5
)L].* Likewise
[{Fe[C
 6
F
 4
C(O)Me-2](η-C
 5
H
 
5
)}
 2
(µ-dppe)]* was formed from 1 and
Ph
 2
P(CH
 2
)
 2
PPh
 2
 (dppe). The
formation of the compound where L = PMe
 3
 is
shown to proceed via initial formation of
[Fe{C
 6
F
 4
C(O)Me-2}(η-C
 5
H

 5
)(CO)(PMe
 3
)]*. The reaction between
B(C
 6
F
 5
)
 3
 and
[M(η-C
 5
H
 5
)(CO)
 3
Me]
(M = Mo or W) gave the compounds
[M{C
 6
F
 4
C(O)Me-2}(η-C
 5
H

 5
)(CO)
 2
]. The compounds
[M{C
 6
F
 3
X-5-C(O)Me-2}(η-C
 5

H
 5
)(CO)
 2
]* (M = Mo or W) where
X = H were prepared from the compounds where
X = F via unusual C–F bond-activation
reactions. The compound
[Fe{C
 6
F
 3
H-5-C(O)Me-2}(η-C
 5

H
 5
)(PMe
 3
)] was prepared by photolysis of a
mixture of
[Fe{C
 6
F
 3
H-5-C(O)Me-2}(η-C
 5

H
 5
)(CO)] and PMe
 3
. The asterisk indicates
the crystal structure has been determined.

Synthesis of fluorophenyl derivatives of iron, molybdenum and tungstenvia B(C6F5)3 and unusualcarbon–fluorine bond reactions

Gas-phase electronic absorption spectra of
(η
 6
-C
 6
H
 6
)
 2
Cr 1
and (η
 6
-C
 6
D
 6
)
 2
Cr
2 have been measured with 30 cm
 -1
 resolution. Both
spectra show 3d(a
 1g
)→Rnp(e
 1u
)
(n=4–12) and
3d(a
 1g
)→Rnp(a
 2u
)
(n=5–8) series. The first ionization potentials,
determined as a convergence limit of the Rnp(e
 1u
)
series, are 5.459±0.004 and 5.446±0.004 eV for 1
and 2, respectively. The Rydberg np
0
 0

 0
 bands display a ca. 100
cm
 -1
 shift on going from 1 to 2. The
decreases in ionization potential and Rydberg frequencies have
vibrational nature and indicate lower zero-level vibrational energy
for bis(η
 6
-benzene)chromium in the ground electronic
state in comparison with that of the molecule in the Rydberg
np states and the ground-state cation. A complete assignment
of the vibronic components of the Rydberg transitions in 1
and 2 has been made on the basis of comparison of the
spectra. In addition to vibrational progressions on the totally
symmetric metal–ring stretching mode, the R4p(e
 1u
)
and R5p(e
 1u
) transitions show components arising from
excitation of CH vibrations. The corresponding absorption features are
shifted towards the 0
 0

 0
 bands on going from
1 to 2.

Christian P. Mehnert

Papers

Synthesis of fluorophenyl derivatives of iron, molybdenum and tungstenvia B(C6F5)3 and unusualcarbon–fluorine bond reactions

Rydberg transitions inbis(η6-benzene)chromium; a study of isotopic effectsand vibronic structures

Synthesis and structure of the first η6-pyrazine complex [V(η6-Me4pyrazine)2] and related studies

Synthesis and reactions of [Mo(2,6-lutidine)(η-allyl)] derivatives

Electronic excited states of bis(η6-arene) tungsten: an investigation by ultraviolet photoabsorption spectroscopy in the vapour and solution phases