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Bis(alkyl) scandium and yttrium complexes coordinated by an amidopyridinate ligand: synthesis, characterization and catalytic performance in isoprene polymerization, hydroelementation and carbon dioxide hydrosilylation
Ist Teil von
Dalton transactions : an international journal of inorganic chemistry, 2020-01, Vol.49 (3), p.638-65
Ort / Verlag
England: Royal Society of Chemistry
Erscheinungsjahr
2020
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
New neutral bis(alkyl) Sc and Y complexes [N,N
py
,N
−
]Ln(CH
2
SiMe
3
)
2
(THF)
n
[
n
= 0, Ln = Sc (
1
Sc
), Y (
1
Y
);
n
= 1, Ln = Y (
1
Y
THF
)] stabilized by a tridentate monoanionic amidopyridinate ligand were straightforwardly prepared by alkane elimination, upon mixing ligand [N,N
py
,N
−
]H and metal precursor Ln(CH
2
SiMe
3
)
3
(THF)
2
in toluene at 0 °C. Depending on the work-up conditions, yttrium bis(alkyl)s were isolated as either a pentacoordinate Lewis base free complex [N,N
py
,N
−
]Y(CH
2
SiMe
3
)
2
(
1
Y
) or as a hexacoordinate THF adduct [N,N
py
,N
−
]Y(CH
2
SiMe
3
)
2
THF (
1
Y
THF
). For the smaller Sc ion the only solvent-free complex [N,N
py
,N
−
]Y(CH
2
SiMe
3
)
2
(
1
Sc
) was isolated as a pentacoordinate species irrespective of the reaction/work-up/crystallization conditions applied. Complexes
1
Ln
(Ln = Y, Sc) and
1
Y
THF
were scrutinized as pre-catalysts in ternary catalytic systems Ln/borate/Al
i
Bu
3
(borate = [HNMe
2
Ph][B(C
6
F
5
)
4
] or [Ph
3
C][B(C
6
F
5
)
4
]), applied to isoprene (IP) polymerization, providing moderate activity albeit high selectivity with predominant formation of 1,4-
cis
polyisoprene (up to 99%). The same complexes proved to be effcient catalysts also for the intermolecular hydrolelementation of styrene with various EH sustrates (pyrrolidine, morpholine, Ph
2
PH, PhPH
2
, PhSH) affording linear anti-Markovnikov addition products exclusively. After a preliminary activation by B(C
6
F
5
)
3
, selected bis(alkyl) complexes from this series have been finally used as valuable pre-catalysts for the CO
2
hydrosylilation to CH
4
in the presence of organosilanes as reducing agents (PhMe
2
SiH, PhSiH
3
, Et
2
MeSiH).
Highly versatile and robust organolanthanides as catalysts or catalyst precursors for a variety of challenging transformations.