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C₂-Symmetric Bis(phosphines) and Their Metal Complexes : Synthesis, Materials Application, and Screening Racemic Catalysts / Sanderson, Matthew David

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Author	Sanderson, Matthew David
Title	C₂-Symmetric Bis(phosphines) and Their Metal Complexes : Synthesis, Materials Application, and Screening Racemic Catalysts / Sanderson, Matthew David
Date	2015
Abstract	Chapter 1: The dimethylation of the C2-symmetric Pt-phosphido complex Pt((R,R)-Me-DuPhos)(IsPCH2PIs) (Is = 2,4,6-(iPr)3C6H2) to yield rac- and meso- [Pt((R,R)-Me-DuPhos)(IsMePCH2PMeIs)][OTf]2 represents an interesting case of the Horeau principle as applied to chiral bifunctional substrates. Tim Chapp initially synthesized these complexes, but a rational synthesis of meso-IsMePCH2PMeIs, which was needed for independent synthesis of the metal complexes, could not be found. The synthesis and isolation of rac-IsMePCH2PMeIs is reproducible on a large scale. While meso-IsMePCH2PMeIs could be prepared in a highly enriched form (dr = meso/rac = 11:1), we were unable to fully separate it from its rac diastereomer using column chromatography or fractional crystallization. Attempted inversion of a single phosphorus center of pure rac-IsMePCH2PMeIs also failed to produce meso-IsMePCH2PMeIs in a pure form. Chapter 2: Reaction of the bis(phosphine) rac-IsMePCH2PMeIs (Is = 2,4,6-(i-Pr)3C6H2) with two equiv of CuI gave the complex Cu4I4(rac-IsMePCH2PMeIs)2 as a mixture of two diastereomers. The crystal structure of Cu4I4(rac-IsMePCH2PMeIs)2•4CHCl3 showed it adopted a distorted “octahedral” geometry with a rectangular Cu4 plane, two asymmetrically bridging μ4-iodides, two μ2-iodides and two bis(phosphines) bridging two copper atoms. On UV excitation in the solid state, the cluster Cu4I4(rac-IsMePCH2PMeIs)2 showed temperature-dependent emission from 3XLCT (halide-to-ligand charge transfer) and 3CC (Cu4I4 cluster-centered) excited states. Chapter 3: Kagan’s method for obtaining selectivity information from racemic catalysts was applied to the Pt-catalyzed asymmetric benzylation of secondary bis(phosphines) and also expanded to account for cases of substrate control and substrate dissociation. The catalysts Pt((±)-BenzP)(Ph)(Cl) and Pt((R,R)-BenzP)(Ph)(Cl) were synthesized and screened in a set of reactions with the substrate PhHP(CH2)3PHPh, a variety of benzyl halides (YnC6H5-n)CH2X (Y = alkyl, -OMe, -Br, -CF3, -F, -CN, -Ph; X = -Cl, -Br), and NaOSiMe3 as a base. C6H5CH2Br was found to be the most selective alkylating agent for this reaction, and the results were compared to those obtained by Brian Anderson using Pt((R,R)-Me-DuPhos)(Ph)(Cl) as catalyst. Pt((R,R)-BenzP)(Ph)(Cl) (dr = 5.5 ± 0.5, er = 27 ± 13 ) was predicted to be a more selective catalyst than Pt((R,R)-Me-DuPhos)(Ph)(Cl), but some substrate dissociation was observed (positive half-alkylation test) due to ligand steric effects, and substrate control with negative cooperativity was detected by comparison with the same reaction utilizing Pt((±)-BenzP)(Ph)(Cl) (dr 4.4 ± 0.4, predicted x = 0.92, er = 120). Lithium-mediated P-phenyl bond cleavage of Ph2PCH2C(CH3)2CH2PPh2 gave the gem-dimethyl secondary bis(phosphine) substrate PhHPCH2C(CH3)2CH2PHPh. Asymmetric alkylation of PhHPCH2C(CH3)2CH2PHPh using the catalysts Pt((±)-BenzP)(Ph)(Cl) (dr = 2.0, predicted x = 0.80, er = 16) and Pt((R,R)-BenzP)(Ph)(Cl) (dr = 2.0, er = 2) confirmed that the Thorpe-Ingold effect was successful in preventing substrate dissociation (negative half alkylation test). However, the added steric demand of the two methyl groups exacerbated the negative cooperativity observed previously.
Description	1 online resource (xiii, 148 leaves) : illustrations (some color)
Format	application/pdf
College	Dartmouth College -- Department of Chemistry.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Copyright	All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means without permission in writing from the author.
DOI	http://dx.doi.org/10.1349/ddlp.1621

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C₂-Symmetric Bis(phosphines) and Their Metal Complexes : Synthesis, Materials Application, and Screening Racemic Catalysts / Sanderson, Matthew David

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