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Kinetic Study and Linear Free Energy Relationship Analysis of Some Metal Carbonyl Complexes

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Kinetic Study and Linear Free Energy Relationship Analysis of Some Metal Carbonyl Complexes KINETIC STUDY AND LINEAR FREE ENERGY RELATIONSHIP ANALYSIS OF SOME METAL CARBONYL COMPLEXES Jianbin Hao A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Graduate Department of Chemistry University of Toronto @ Copyright by Jianbin Hao 1997 National Library Bibliothèqus nationale du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. nie Wellington OttawaON KtAON4 Ottawa ON K1A ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microfom, vendre des copies de cette thèse sous paper or electronic formats. la fome de microficiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fkom it Ni la thèse ni des extraits substantiels may be printed or othemise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. KINETIC STUDY AND LINEAR FREE ENERGY RELATIONSEIIP ANALYSIS OF SOME METAL CARBOlYYL COMPLEXES Jianbin Bao, Doctor of Philosophy thesis 1997 Depmmtent of Chemistry, University of Toronto The kinetics of CO-substitution reactions with various P- and As-donor nucleophiles of RU~(CO)~~L(L = P(OPh)3, P(O-i-Pr)3, PCy3, P(II-BU)~and PPhEt2) and Ru~C(CO)~~L(L = P(OPh), and PCy3) have been studied. It has been found that RU~(CO)~~Lundergo monosubstitution reactions via both associative and dissociative pathways and Ru~C(CO)~&reaa via sole associative path.. The rate data have been successfully analyzed using the newly developed methodology of quantitative separation of electronic and stenc eEects represented by: Substituent effect s for Ru,(CO) L show that higher standard reactivity(SR) values are favored by ligands with stronger electronic donicity for associative reactions and larger size for both dissociative and associative reactions. Ru3(CO)1 with higher SR values show less assistance from metal-nucleophile bond making during their associative reactions. RU~C(CO)~~Lshow lower SR (-2.0-0.5 vs. 2.9), smailer amount of bond making (P = 0.1 vs. 0.21 f 0.04) in the transition state(TS), a little more "flexible" (y = - 0.05 vs. -0.07) TS and earlier onset of stenc effect (& 5 10 1O vs. 6L, = 1 17O) compared with those of the unsubstituted clusters. AH2* and A&* values show excellent linear correlations and suggest entropy dominated reactions. Another analysis of quantitative separation of electronic and stenc effects has been successfÙIly carried out for Mnz(C0)8b and CO~(CO)&~containing non-z-acid phosphine substituents. The measured -8 transition energies in these complexes show clear aryl effect. The equation h<mcP) = a + ppK2 + y0 + aE, gives an excellent description of the data (100( 1-R2) 5 2.6%). Increasing o-basicity increases h im@) and increasing ligand size and increasing numbers of aryl groups decrease it. The magnitudes of the effkcts are discussed and suggestions regarding their physical origins are offered. The activation effect of a zeolitic environment on the substitution reactions with chemisorbed(Pc) and physisorbed(Pp) PMe3 of Mo(CO)~encapsulated in the a-cages of Na56-Y zeolite has also been studied and precise activation parameters measured: M(Pc)* = 44.8 2 1.0 k.J mol-', AS(Pc)* = -194 + 3 J R' mol*'; AH(Pp)* = 122.6 5 3.5 kJ mol-', A.S(Pp)* = -29.9 9-8 J K-' mol-'. The encapsulated Mo(C0)6 is very strongly activated, in enthalpic terms, towards associative substitution by Pc molecuIes but this effect is almost exactly canceled out at ca. 66 OC by accompanying unfavorable entropic factors. Associative substitution by Pp molecules is believed to be stencally hindered by the unavoidable presence of Pc molecules in the nanoreactor(nr) to the extent that advantage cannot be taken of the high intrinsic susceptibility of the Mo(CO)~ to associative substitution. Activation parameters (AH2= 72 + 3 kl mol-'; ASdf = -106 5 8 J K-' mol-') for the CO dissociative reaction in the presence of 2 Pc rnolecules/nr have also been determined and are close to those for the dissociative displacement of 12c0by "CO. Isokinetic relationship analysis has been done on a number of inorganic and organometallic reaction systems and most of them have been found to obey isokinetic relationship. Variations in the relationship have been related to the changes in reaction mechanisms. For the associative CO-substitution reaction of Ru5C(CO)l~(OPh)3with L' in particular it has been discovered as the vetyfirst example that an isokinetic Tolrnan's cone angle(& = 1 53 O) exists. dedicated to my parents, my wife, Shuhui, and my love& daughter-Mimi wifh love ACKNOWLEDGMENTS 1 would Iike to thank rny supervisor, Professor A. J. Poë, for his constant encouragement, supe~sionand support throughout my study, aiso for his understanding and the fieedom allowed to pursue the projects. I would also Iike to thank: Professors D. H. Farrar, R. H. Moms, G. A. Ozin, 1. Manners and J. Powell for giving me helpfbl lectures; Lezhan for his help in the early stage of my work; Bob for comments especially on stmcture and cornputer; Ravi for good suggestions on synthesis; and Professors Eduardo J. S. Vichi and Sergey Tunik for helpfùl discussions. TABLE OF CONTENTS Chapter 1 Introduction 1.1 Catdysis by Metal Cahonyls and Carbonyl Clusters .................................................. 1 1-2 Metal Carbonyls Chemistq ........................................................................................... 2 1.3 Mechanisms ................................................................................................................... 3 1 3.1 Substitution Reactions ......................................................................................... 3 1 -3-2 Meta] Carbonyls ................................................................................................... 3 1-3 -3 Metal Carbonyl Clusters ...................................................................................... 4 1-4 Modification of Reactivity ............................................................................................ 6 1.4.1 Substituent Effects ............................................................................................... 7 1.4.2 Solid Support Effects ........................................................................................... 9 1-5 Quantitative SeParation of Electronic & Stenc Eflects ............................................ 12 1 .5 . 1 Electronic and Stenc Eflects .......................................................................... 12 1-5 -2 Quantitative SeParation .................................................................................. 13 1 .5.3 The ~mplicationsof the Denved Parameten ................................................. 15 1S.4 The Protocol of Steroelectronic Analysis Using Eqn 1.4 ............................a 18 References .................................................................................................................... 20 Chapter 2 Experimental 2.1 General ......................................................................................................................... 27 2.2 Instruments .................................................................................................................. 27 2.3 Chernicals ..................................................................................................................... 29 2.4 Synthesis of RU3(CO)]IL complexe^ ......................................................................... 30 2.4.1 Preparation of Sodium Diphenylketyl Solution ............................................. 30 2.4.2 Reactions of Ru3(C0)12................................................................................. 30 2-4-3 purification of Ru,(CO), IL ............................................................................ 31 2.4.4 Characterization of' RU3(CO)l L .................................................................... 31 2.5 Synthesis of Ru5C(CO),, L (L = PCy3 and P(OPh)3) .................................................. 32 2.5.1 Synthesis ofRU6C(C0)17............................................................................... 32 2.5.2 SynthesisofRu5C(CO)l ............................................................................... 32 2.5.3 Synthesis of Ru~C(CO)~,L (L = PCy3 and P(OPh)3) ..................................... 33 Chapter 3 Kinetics of Reactions of Ru3(CO). IL (L = P(OPh).. PCyJ. P(O=i.Pr):, and PPhEt2) with Some P-and As-donor Nucleophiles Chapter 4 Kinetics of Associative Substitution Reactions of RU~C(CO)~~L(L = P(OPh)3 and PCy3) with Some P-donor Nucleophiles Chapter 5 The Aryl Effect in Disubstituted Dimanganese and Dicobalt Carbonyls 5 -3 Discussion ...................................................................................................................... 133 5.3.1 Dependence of h ia-+oC)on the Electronic and Stenc Propenies of Phosphine Ligands ........................................................... 133 5.3.2 The Contributions of ~Donicity,Ligand Size, and the ml Effect to h v ........................................................................................
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