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Coordinative unsaturation in chiral ...
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Northwestern University.
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Coordinative unsaturation in chiral organolanthanides: A synthetic and asymmetric catalytic mechanistic study of yttrium and lutetium Ansa-metallocene complexes having pseudo-meso ancillary ligation.
紀錄類型:
書目-電子資源 : Monograph/item
正題名/作者:
Coordinative unsaturation in chiral organolanthanides: A synthetic and asymmetric catalytic mechanistic study of yttrium and lutetium Ansa-metallocene complexes having pseudo-meso ancillary ligation./
作者:
Haar, Christopher Michael.
面頁冊數:
97 p.
附註:
Source: Dissertation Abstracts International, Volume: 57-01, Section: B, page: 0324.
Contained By:
Dissertation Abstracts International57-01B.
標題:
Chemistry, Inorganic. -
電子資源:
http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9614746
Coordinative unsaturation in chiral organolanthanides: A synthetic and asymmetric catalytic mechanistic study of yttrium and lutetium Ansa-metallocene complexes having pseudo-meso ancillary ligation.
Haar, Christopher Michael.
Coordinative unsaturation in chiral organolanthanides: A synthetic and asymmetric catalytic mechanistic study of yttrium and lutetium Ansa-metallocene complexes having pseudo-meso ancillary ligation.
- 97 p.
Source: Dissertation Abstracts International, Volume: 57-01, Section: B, page: 0324.
Thesis (Ph.D.)--Northwestern University, 1995.
As established by NMR, circular dichroism, and x-ray diffraction, organolanthanide complexes of the new chelating cyclopentadienyl-based ligand MeSubjects--Topical Terms:
517253
Chemistry, Inorganic.
Coordinative unsaturation in chiral organolanthanides: A synthetic and asymmetric catalytic mechanistic study of yttrium and lutetium Ansa-metallocene complexes having pseudo-meso ancillary ligation.
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Haar, Christopher Michael.
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Coordinative unsaturation in chiral organolanthanides: A synthetic and asymmetric catalytic mechanistic study of yttrium and lutetium Ansa-metallocene complexes having pseudo-meso ancillary ligation.
300
$a
97 p.
500
$a
Source: Dissertation Abstracts International, Volume: 57-01, Section: B, page: 0324.
500
$a
Adviser: Tobin J. Marks.
502
$a
Thesis (Ph.D.)--Northwestern University, 1995.
520
$a
As established by NMR, circular dichroism, and x-ray diffraction, organolanthanide complexes of the new chelating cyclopentadienyl-based ligand Me
$\
sb2
$\
sb3
$-
$)
-menthylCp
$\
rbrack \sp{2-}
$
(Cp =
$\
eta\sp5
$-
$\
rm C\sb5H\sb3)
$
(1) preferentially adopt a single planar chiral configuration of the asymmetric metal-ligand template. The chloro complexes (S,R)-Me
$\
sb2
$\
sb3
$-
$)
-menthylCp) Ln(
$\
mu
$-
Cl)
$\
sb2
$\
sb2)\sb2
$
(Ln = Y, Lu) (2) were isolated diastereomerically pure by crystallization from diethyl ether solution. For (S,R)-Me
$\
sb2
$\
sb3
$-
$)
-menthylCp) Lu(
$\
mu
$-
Cl)
$\
sb2
$\
sb2)\sb2
$:
space group P
$\
sb1;
$
$a
=11.580(4),\ b=11.756(2),
$
and
$c
=16.678(4)
$
A;
$\
alpha=108.93(2)\sp\circ,\ \beta=94.52(2)\sp\circ,\ \gamma=110.50(2)\sp\circ;\ Z=2;\ R\sb{\rm w}=0.051.
$
The unusual pseudo-meso configuration of the complex leads to a gross distortion of the ideal C
$\
sb{2v}
$
symmetry, evidenced by a significant deviation of
$\
angle\rm Si\sb{bridge}
$-
Lu-Li from linearity
$(
158\sp\circ).
$
At least two additional epimers are observed in THF solution. Alkylation of the (S,R) epimers with LiCH(SiMe
$\
sb3)\sb2
$
proceeds with retention of configuration as determined by NMR and circular dichroism, affording chiral hydrocarbyl complexes (3) in quantitative yield. In solution, the hydrocarbyls exhibit temperature-dependent conformational exchange processes in the NMR ascribable to restricted rotation about the Ln-CH(SiMe
$\
sb3)\sb2
$
bond. These alkyl complexes are effective precatalysts for asymmetric hydrogenation of unfunctionalized olefins and for the reductive cyclization of unfunctionalized 1,5-diolefins. The highest enantioselectivities are obtained when the lutetium complex is used for hydrogenation of 2-phenyl-1-butene (45% ee) and deuteration of 1-pentene (30% ee) and styrene (10% ee). The hydrogenation of 2-phenyl-1-butene with the yttrium catalyst (yielding exclusively 2-phenylbutane-1,2-d
$\
sb2
$
under D
$\
sb2)
$
obeys a rate law of the approximate form
$v
=(k\lbrack\rm olefin\rbrack\sp1\lbrack lanthanide\rbrack\sp{1/2}\lbrack H\sb2\rbrack\sp1)/({\it K\/} + \lbrack olefin\rbrack),
$
suggesting rapid, operationally irreversible olefin insertion at a putative hydride (4), a rapid preequilibrium involving an alkyl or alkyl/hydride dimer, and turnover-limiting hydrogenolysis of an intermediate yttrium alkyl with
$v
\rm\sb{H\sb2}/v\sb{D\sb2}=2.2\pm0.1.
$
The apparent rate constant for 2-phenyl-1-butene hydrogenation in the present case
$(
12(1)\times10\sp{-3}
$
M
$\
sp{1/2}
$
atm
$\
sp{-1}
$
s
$\
sp{-1})
$
is ca. one order of magnitude lower than those found for chiral Me
$\
sb2
$\
sb4
$\
sb5
$)
(3-R*Cp)Ln-based systems (R* = (
$-
$)
-menthyl, (+)-neomenthyl; Ln = Y, La, Nd, Sm, Lu), reflecting diminished Ln-C bond hydrogenolytic reactivity, which is apparently a result of decreased ligand electron-donating ability.
590
$a
School code: 0163.
650
4
$a
Chemistry, Inorganic.
$3
517253
690
$a
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2 0
$a
Northwestern University.
$3
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773
0
$t
Dissertation Abstracts International
$g
57-01B.
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$a
Marks, Tobin J.,
$e
advisor
790
$a
0163
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$a
Ph.D.
792
$a
1995
856
4 0
$u
http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9614746
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