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Coordinative unsaturation in chiral ...

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.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Coordinative unsaturation in chiral organolanthanides: A synthetic and asymmetric catalytic mechanistic study of yttrium and lutetium Ansa-metallocene complexes having pseudo-meso ancillary ligation./
Author:	Haar, Christopher Michael.
Description:	97 p.
Notes:	Source: Dissertation Abstracts International, Volume: 57-01, Section: B, page: 0324.
Contained By:	Dissertation Abstracts International57-01B.
Subject:	Chemistry, Inorganic. -
Online resource:	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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035 $a AAI9614746
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100 1 $a Haar, Christopher Michael. $3 1903227
245 1 0 $a 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 0488
710 2 0 $a Northwestern University. $3 1018161
773 0 $t Dissertation Abstracts International $g 57-01B.
790 1 0 $a Marks, Tobin J., $e advisor
790 $a 0163
791 $a Ph.D.
792 $a 1995
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9614746