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Towards Transition Metal-Catalyzed Hydration of Olefins; Aquo Ions, And

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Towards Transition Metal-Catalyzed Hydration of Olefins; Aquo Ions, And Towards Transition Metal-Catalyzed Hydration of Olefins; Aquo Ions, and Pyridylphosphine-Platinurn and Palladium Complexes By YUNXIE B.Sc. Peking University, 1983 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Chemistry) We accept this thesis as confirming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA July, 1990 © YUN XIE, 1990 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT This thesis work resulted from an on-going project in this laboratory focusing on the hydration of olefins, using transition metal complexes as catalysts, with the ultimate aim of achieving catalytic asymmetric hydration, for example: (H02C)CH=CH(C02H) (H02C)CH2-CH(OH)(C02H) * (C = chiral carbon atom). 3+ Initially, the hydration of maleic to malic acid, catalyzed by Cr(H20)6 at 100°C in aqueous solution was studied, including the kinetic dependences on Cr3+, maleic acid and pH. A proposed mechanism involving 1:1 complexes of Cr3+ with the maleato and malato monoanions is consistent qualitatively with the kinetic data. This Cr system was, however, ineffective for hydration of prochiral olefins, and the work became a minor component of the thesis and is described in the last chapter. Emphasis was switched to the study of water-soluble phosphine systems based on Pd and Pt. The major part of this thesis describes the synthesis and characterization, principally by lK, 31P{1H} and l95Pt{1H} NMR spectroscopies, of: square-planar complexes of the type MX2(PPh.3.npyn)2 (M = Pd, Pt; X = halides; n = 1, 2, 3); the binuclear species M2X2(u- PPh3.npyn)2 (head-to-tail, HT) and Pt2I2(u-PPh3_„pyn)2 (head-to-head, HH; n = 1,10a, n = 2, 10b and n = 3, 10c); and the Pt(PPh2py>3,27a, and Pt(Ppy3)3, 26c, complexes. The reactivities of the binuclear complexes toward acetylenes, and the Pt(0) species toward 02, olefins, HC1 and Mel, are also described. With use of PPhpy2 within the binuclear phosphine-bridged species, the P atom incidentally becomes chiral. The diastereomers of 10b were isolated and characterized by 3lp{ lH} NMR spectral data. All the isolated binuclear complexes react in CH2C12 with dimethylacetylene- dicarboxylate, DMAD, to form an A-frame insertion product. The HH or HT configuration of the precursor is maintained in every case except for 10b and 10c which form initially an HH- DMAD adduct that slowly isomerizes to the corresponding HT-DMAD adduct. Detailed ii 3IP{1H} NMR spectroscopic studies show that the presence of a properly positioned pyridyl group promotes the isomerization by forming a detectable chelated P-N intermediate, and that insertion of DMAD precedes chelation. The reactions of Pt2l2(u-PPh3_npyn)2 (HH) (n = 1, 2, 3) with DMAD in CH2CI2 are kinetically first-order in both [Pt.2] and [DMAD] for the insertion step, and first-order in [Pt2] and zero-order in [DMAD] for the isomerization step. The activation parameters for the insertion step are consistent with oxidative addition to a binuclear system. A proposed mechanism is fully supported by 31P{ lU) and 195Pt{ lH] NMR spectral data. Complex 26c, reacts in CH2CI2 or CDCI3 with limited oxygen to give Pt(Ppy3)3(C>2), which may contain an end-on superoxo structure as judged by an IR band at 1114 cm-1. Complex 26c, under 1 arm O2, forms the 'expected' peroxo species Pt(Ppy3>202. Complexes 26c and 27a, react with the olefins (maleic anhydride, acrylonitrile, 2 methacrylonitrile and crotonitrile) to give the square-planar species Pt(PPh3-npyn)2Cn -olefin). The square-planar geometry infers strong rc-back donation from metal to olefin, a state which is probably undesirable for the purpose of olefin activation toward hydration. Indeed, complex Pt(PPh2py)2Cn2-maleic anhydride), 47a, shows no olefin hydration product when heated at 80°C in aqueous NaOH solution. Trans-Pt(H)Cl(PPh2py)2, 50a, was prepared from 27a and gaseous HCl in THF; 50a -d6, in acetone reacts with acrylonitrile to give cis-PtCl(CH2CH2CN)(PPh2py)2» but in the presence of aqueous NaOH at 80°C, 50a was inactive for hydration of acrylonitrile to either (3- cyanoethanol or acrylamide. ui Table of Contents Page Abstract ii Table of contents iv List of tables x List of figures . xii List of schemes xvi Abbreviations and symbols xvii Acknowledgements xxii CHAPTER ONE: INTRODUCTION 1.1 Overview of homogeneous catalysis 1 1.2 Objective of this thesis 2 1.3 Alcohol manufacture and synthesis of asymmetric alcohols 3 1.4 Feasibility of catalytic hydration by transition metal complexes 9 1.4.1 Activation of water 9 1.4.2 Activation of olefins toward nucleophilic attack by hydroxide, and migratory insertion of olefin into an M-OH bond 12 1.4.3 Reductive elimination of alkyl-hydride and alkyl hydroxy moieties 15 1.4.4 Olefin hydration catalyzed by metal phosphine complexes 15 1.4.5 Olefin hydration catalyzed by metal non-phosphine complexes.... 18 1.4.6 A comparison of catalytic hydrocyanation and hydration of olefins; olefin oxidation via hydration 19 1.5 Chemistry of pyridylphosphines 21 1.5.1 Developments in syntheses of pyridylphosphines 21 1.5.2 Coordination chemistry of pyridylphosphines 22 1.5.3 Reactivity of the coordinated pyridylphosphines and catalytic activities of their metal complexes 25 iv 1.6 The scope of this thesis 26 References 28 CHAPTER TWO: GENERAL EXPERIMENTAL PROCEDURES 2.1 Materials 37 2.2 General instrumentation 40 2.3 Preparation of Pd and Pt starring materials 40 2.3.1 Dichlorobis(benzonitrile)-palladium(II) and -platinumCJf) 41 2.3.2 Cis-dichloro(l,5-cyclooctadiene)platinum(II) 41 2.3.3 Tris(dibenzyMeneacetone)dipalladium(0) 41 2.3.4 Bis(dibenzylideneacetone)platinum(0) 42 2.4 Preparation of 2-pyridylphosphines 42 2.4.1 2-(Diphenylphosphino)pyridine 43 2.4.2 Bis(2-pyridyl)phenylphosphine 43 2.4.3 Tris(2-pyridyl)phosphine 44 2.5 Preparation of Pt(D) and Pd(H) complexes of 2-pyridylphosphines 44 2.5.1 Cis-dihalobis(2-pyridylphosphine)platinum(II) 44 2.5.2 Dmalobis(2-pyridylphosphine)palladium(II) 45 2.6 Preparation of homo- and hetero- dinuclear palladium(I) and platinum© complexes of pyridylphosphines 47 2.6.1 Dihalobis(2-pyridylphosphine)diplatinum(T) (head-to-tail, HT)... 47 2.6.2 Duodobis(2-pyridylphospnine)diplatinum(I) (head-to-head, HH) 48 2.6.3 Dihalobis(2-pyridylphosphine)dlpalladium(I) (HT) 50 2.6.4 Diahalobis[tri(2-pvridyl)phospr^ (HT) 52 2.7 Preparation of DMAD A-frame adducts 52 2.8 Preparation of Pt(0) complexes of pyridylphosphines and their derivatives from reactions with olefin, hydrogen chloride and methyl iodide 53 2.8.1 Terrakis[tri(2-pyridyl)phosphine]plarinum(0) 54 2.8.2 Tris[2-(diphenylphosphino)pyridine]platinum(0) 55 v 2.8.3 Olefin derivatives from Pt(0) complexes of pyrdylphosphines.... 55 2.8.3.1 Acrylonitrile, methacrylonitrile and crotonitrile complexes 55 2.8.3.2 Maleic anhydride and diethyl maleate complexes 56 2.8.4 Hydridochloro derivatives from Pt(0) complexes of pyridylphosphines 57 2.8.4.1 Tr^s-cWorohyd^dobis[(2-aUphenylphosphmo)pyridine]- platinum(II) 57 2.8.4.2 Attempted preparation of hydridochlorobis[rri(2-pyridyl)- phosphine]platinum(n) 58 2.8.5 Iodo(methyl) derivatives from Pt(0) complexes of pyridylphosphines 59 2.9 Preparation of bis(maleato) and bis(malato) chromium(JJI) species 59 2.9.1 Cis-potassium (haquobis(maleato)chromate(in) trihydrate 60 2.9.2 Cis-potassium (h^uobis(n^ato)chrormte(IJJ) monohydrate 60 References 61 CHAPTER THREE: STRUCTURES OF M(TJ) AND M(I) (M = Pd, Pt) PYRIDYL- PHOSPHJNE COMPLEXES AND THEIR SOLUTION CHEMISTRY 3.1 Introduction 63 3.2 Structural characterization of pyridylphosphine complexes 66 3.2.1 Pt(II) pyridylphosphine complexes 66 3.2.2 Pd(II) pyridylphosphine complexes 69 3.2.3 Pt(I) dinuclear pyridylphosphine complexes 81 3.2.4 Pd(I) dinuclear pyridylphosphine complexes 83 3.3 Solution equilibrium of the cis-Ptl2(PN2)2 complex in CDCI3 96 3.4 Aqueous solution studies 102 3.4.1 Dichlorobis[tri(2-pyridyl)phospWne]dipalladium(I) 102 3.4.2 Cis-dichlorobis[tri(2-pyridyl)phosphine]paUadium(n) 105 References 112 vi CHAPTER FOUR: REACTIVITIES OF THE HEAD-TO-HEAD ISOMERS OF Pt2l2(H-PN3)2 COMPLEXES TOWARD DIMETHYLACETYLENEDICARBOXYLATE AND TOWARD PHOSPHINE 4.1 Introduction , 116 4.2 Experimental 118 4.3 Results and discussion 120 4.3.1 Reactions of Pt2l2(H-PN3)2 (HT) with acetylenes 120 4.3.2 Reaction of Pt2l2(H-PN3>2 (HH) with DMAD 122 4.3.3 Reaction of Pt2l2(^-PNi)2 (HH) with DMAD 132 4.3.4 Reactions of Pt2l2(u-PN2)2 (HH) with DMAD 137 4.3.4.1 Reaction of Pt2l2(u-PN2)2 (HH) (IS, 2R) with DMAD 137 4.3.4.2 Reaction of Pt2l2(^-PN2)2 (HH) (IS, 2S)/(1R, 2R) mixture with DMAD 140 4.3.4.3 Kinetic studies on the reactions of the diastereomers of Pt2l2(^-PN2)2 (HH) with DMAD 141 4.3.5 Mechanism of the reaction of Pt2l2(u-pNn)2 (HH) with DMAD.
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