DOI: 10.1002/chem.201504725
Communication
&
Organometallic Chemistry
Non-Pincer-Type Mononuclear Scandium Alkylidene Complexes:
Synthesis, Bonding, and Reactivity
[
a]
[a]
[b]
[b]
[a]
Chen Wang, Jiliang Zhou, Xuefei Zhao, Laurent Maron,* Xuebing Leng, and
[a]
Yaofeng Chen*
Dedicated to Professor Xuelong Hou on the occasion of his 60th birthday
2À
phosphinoyl) methandiide dianion [C(PPh NSiMe ) ] into the
2
3 2
rare-earth metal chemistry and synthesized a pincer-type sa-
Abstract: The first non-pincer-type mononuclear scandi-
um alkylidene complexes were synthesized and structural-
ly characterized. These complexes exhibited short ScÀC
bond lengths and even one of the shortest reported to
date (2.1134(18) ). The multiple character of the ScÀC
bond was highlighted by a DFT calculation. This was con-
firmed by experimental reactivity study where the com-
plex underwent [2+1] cycloaddition with elemental seleni-
um and [2+2] cycloaddition with imine. DFT calculation
also revealed a strong nucleophilic behavior of the alkyli-
dene complex that was experimentally demonstrated by
the CÀH bond activation of phenylacetylene.
[
5]
marium carbene complex [Sc{C(PPh NSiMe ) }(NCy )(THF)].
2
3 2
2
Later, Liddle, Le Floch, MØzailles, and Nief made important con-
[
6–8]
tributions to this field:
Liddle and Le Floch synthesized
other pincer-type rare-earth metal carbene complexes with the
[
7]
bis(iminophosphinoyl) methandiide dianion and Le Floch,
MØzailles, and Nief developed the di-lithium bis(thiophosphi-
noyl) methandiide Li [C(PPh S) ] and synthesized pincer-type
2
2
2
[
8]
rare-earth metal carbene complexes based on this dianion.
Introducing the pincer-type structure with two hypervalent
phosphorous substituents stabilizes the mononuclear rare-
earth metal alkylidene (or carbene) complexes, but simultane-
[
9]
ously reduces their reactivity. Reactivity studies of these com-
plexes were mainly focused on ketones and the highly reactive
heteroallenes, such as isocyanide, isothiocyanide, and carbodi-
[
10]
Mononuclear transition metal alkylidene (or carbene) com-
plexes have attracted intense attention and been extensively
imide. How to balance stabilization and reactivity of mono-
nuclear rare-earth metal alkylidene (or carbene) complexes re-
mains a big challenge. Herein, we report the synthesis, bond-
ing analysis (DFT), and reactivity (cycloaddition and CÀH bond
activation) of the first non-pincer-type mononuclear scandium
alkylidene complexes.
[1]
studied in past decades. Such transition metal complexes are
not only of fundamental interest for coordination chemistry,
but are also known to have important applications, especially
in the area of synthetic chemistry. Therefore, a great number
of mononuclear transition metal alkylidene (or carbene) com-
plexes have been synthesized. One exception is those with
rare-earth metal ions. Due to HOMO/LUMO orbital energies
Scandium
methyl
chlorides
[L1Sc(Me)Cl]
(L1=
À
[MeC(NDIPP)CHC(Me)(NCH CH N(iPr) )] , DIPP=2,6-(iPr) C H )
2
2
2
2
6
3
À
and [L2Sc(Me)Cl] (L2=[MeC(NDIPP)CHC(Me)(NCH CH N(Me) )] )
2
2
2
0
[11a]
mismatch between the d rare-earth metal ions and the alkyli-
were
treated
with
11b] 1
Li[CH(SiMe )PPh S]
or
3
2
[
dene (or carbene) groups, the formation of mononuclear rare-
Li[CH(SiPh )PPh S](THF).
H NMR spectral monitoring of the
reactions in C D showed the formation of new complexes 1–4
3
2
[
2]
earth metal alkylidene (or carbene) complexes is unfavorable.
6
6
The alkylidene (or carbene) groups have a strong tendency to
bind more than one rare-earth metal ion or one rare-earth
with concomitant appearance of CH (d=0.15 ppm) at room
4
temperature. The scaled-up reactions in toluene provided the
complexes 1–4 in 58–87% yields. The complexes 1–4 were
characterized by NMR spectroscopy and elemental analysis;
the solid-state structures of 1–3 were determined by crystallo-
graphic methods. The complexes 1–4 are mononuclear scandi-
um alkylidene complexes [LSc{C(SiR’ )PPh S}] (1: L=L1, R’=
[3,4]
metal ion and two other metal ions.
For the purpose of sta-
bilization of mononuclear rare-earth metal alkylidene (or car-
bene) complexes, Cavell and co-workers introduced a bis(imino-
[
a] C. Wang, Dr. J. Zhou, Dr. X. Leng, Prof. Dr. Y. Chen
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences
3
2
Me; 2: L=L1, R’=Ph; 3: L=L2, R’=Me; 4: L=L2, R’=Ph) as
shown in Scheme 1.
The molecular structure of 1 is shown in Figure 1, while
those of 2 and 3 are given in the Supporting Information (Fig-
3
45 Lingling Road, Shanghai 200032 (P. R. China)
E-mail: yaofchen@mail.sioc.ac.cn
À
À
[
b] X. Zhao, Prof. Dr. L. Maron
LPCNO, CNRS & INSA
ures S1 and S2). In 1, 2, and 3, the [L1] or [L2] ligand coordi-
nates to the scandium center through three nitrogen atoms;
UniversitØ Paul Sabatier
2À
2À
the [C(SiMe )PPh S] or [C(SiPh )PPh S] dianion coordinates
3
2
3
2
1
35 Avenue de Rangueil, 31077 Toulouse (France)
to the scandium center through carbon and S atoms. The ScÀ
C bond lengths are 2.125(2), 2.159(4), and 2.1134(18) , respec-
tively. It is noteworthy that the ScÀC bond lengths in the less
E-mail: laurent.maron@irsamc.ups-tlse.fr
Chem. Eur. J. 2016, 22, 1258 – 1261
1258
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim