M Ű EGYETEM 1782 THEORETICAL STUDY ON THE STRUCTURE, REACTIVITY AND STABILITY OF SILYLENES AND SILENES Ph. D. dissertation Julianna Oláh Supervisor: Dr. Tamás Veszprémi Budapest University of Technology and Economics Department of Inorganic Chemistry 2005 Köszönetnyilvánítás Szeretnék köszönetet mondani témavezetőmnek, Veszprémi Tamásnak, az együtt töltött hét év során nyújtott folyamatos támogatásáért, és a lehetőségért, hogy összesen másfél évet belgiumi kutatócsoportokkal tölthettem. Hálás vagyok Nyulászi Lászlónak, a Szervetlen Kémia tanszék tanszékvezetőjének. Köszönöm a tanszék minden dolgozójának és hallgatójának a jó hangulatot. Külön köszönet illeti Höltzl Tibit a számítógépek karbantartásáért és Olasz Andrást a számomra írt programért. Nagyon sokat tanultam Dínótól (Szieberth Dénes), Okitól (Hajgató Balázs) és Tomától (Kárpáti Tamás). Hálás vagyok Dínónak a tanszéki számítógépek karbantartásáért, Okinak a kimerítő válaszaiért. Tomának külön köszönöm, hogy elviselt az utóbbi két évben, mialatt közös szobában dolgoztunk, a sok csokit és üdítőt☺. Köszönetet szeretnék mondani segítőkészségéért és kedvességéért Lengyel L. Tibornénak. Hálás vagyok Paul Geerlings-nek és Christian Van Alsenoy-nak a lehetőségért, hogy csoportjukban dolgozhattam, valamint Frank Blockhuys-nek és Frank de Proftnak az együttműködésért. Bár sokat köszönhetek a tanáraimnak, munkatársaimnak, legnagyobb köszönet mégis a családomat illeti. Édesanyám mindig, mindenben segített. Hálás vagyok Gergőnek, édesapámnak és testvéreimnek, hogy mindig mellettem álltak, s támogattak. Table of Contents Table of Contents _____________________________________________________1 List of Figures, Schemes and Tables______________________________________2 Notations used in conceptual DFT _______________________________________4 1 Introduction________________________________________________________5 2 Low coordinated silicon compounds ____________________________________9 2.1 Silylenes and carbenoids________________________________________________ 9 2.2 Alcohol addition reactions of silenes _____________________________________ 18 3 Computational chemistry ____________________________________________27 3.1 Overview of quantum chemistry ________________________________________ 27 3.1.1 Wave function based methods ______________________________________________ 27 3.1.2 Density Functional Theory (DFT) ___________________________________________ 35 3.1.3 DFT-derived chemical concepts (Conceptual Density Functional Theory) __________ 37 3.2 Computational methods applied ________________________________________ 45 4 Silylenes __________________________________________________________47 4.1 Conceptual DFT studies on hypovalent Group 14 and 15 compounds (Publications 1, 2, 3 and 4)____________________________________________________________ 48 4.1.1 Spin-related DFT indices __________________________________________________ 49 4.1.2 Similarity of molecular groups _____________________________________________ 54 4.1.3 Lewis acid and Lewis base character of silylenes and germylenes _________________ 57 4.1.4 Relationship between spin-philicity / spin-donicity and electrophilicity / nucleophilicity indices ______________________________________________________________________ 68 4.2 Relationship between the stability and dimerization ability of silylenes (Publication 5) _____________________________________________________________________ 72 4.3 Design of a new silylene with a novel structure ____________________________ 77 5 Water addition reaction of Si=C double bonds attached to ring substituents____85 6 Summary ________________________________________________________103 List of Publications__________________________________________________105 References_________________________________________________________106 Appendix _________________________________________________________A-1 Publication 1______________________________________________________A-20 Publication 2 _____________________________________________________A-31 Publication 3 _____________________________________________________A-37 Publication 4 _____________________________________________________A-46 Publication 5 _____________________________________________________A-67 1 List of Figures, Schemes and Tables List of Figures Figure 1 Free energy diagram at the CBS-Q level of theory of water addition reaction to disilene taken from Ref. [74]......................................................................................................................................... 21 Figure 2 Derivatives of the energy.......................................................................................................... 38 Figure 3 Qualitative representation of the formulas of the spin potentials ............................................. 44 + Figure 4 Linear relationship between the maximal spin acceptance ∆N s,max (in spins) and the ∆Ev1 (in kcal/mol) for singlet silylenes (molecules 1-24, 26-27 from Table A1 in the Appendix) and between the − maximal spin release ∆N s,max (in spins) plotted against ∆Ev2 (in kcal/mol) for triplet phosphinidenes (molecules 114-123 from Table A1 in the Appendix)............................................................................ 50 Figure 5 Spin-philicities (in eV) plotted against the vertical singlet-triplet gap ∆Ev1 (in kcal/mol) for singlet silylenes (molecules 1,4-7, 10-24,26-27 from Table A1 in the Appendix)................................. 51 Figure 6 Spin-donicity index (in eV) vs. the vertical singlet-triplet gap, ∆Ev2 (in kcal/mol) phosphinidenes (molecules 114-123 from Table A1 in the Appendix) .................................................. 52 Figure 7 Comparison of the definitions, defining equations, properties of electrophilicity, spin-philicity and spin-donicity indices ........................................................................................................................ 53 Figure 8 Spin hardness of nitrenes (molecules 104-113 from Table A1 in the Appendix) plotted against the spin hardness of phosphinidenes(molecules 114-123 from Table A1 in the Appendix)................... 56 Figure 9 Spin hardness of phosphinidenes (molecules 114-119,121-123 from Table A1) plotted against the spin hardness of triplet carbenes (molecules 28-29,31-34,39-41 from Table A1) ............................ 56 Figure 10 Electrostatic potential calculated at Point A (VA) vs. the reaction energy ∆E (in kcal/mol) of silylenes with NH3 (molecules 1,3-7,9-22,26-27 from Table A1) SiF2 (18)and SiCl2 (19) are shown but excluded from the fit). ............................................................................................................................ 62 Figure 11 Global (ω) and local (ωSi) electrophilicity of silylenes vs. the reaction energy (∆E in kcal/mol) of the complexation reaction with NH3 (molecules 1,3-7,9-22,26-27 from Table A1)......... 64 Figure 12 Reaction energies (∆E) and Gibbs free energies (∆G) (in kcal/mol) of the complexation of silylenes with BH3 plotted against the minimum of the electrostatic potential (Vmin, in au) (molecules 5,3-7,15-17,20-24,26-27 from Table A1 and HSiH+NH3, HSiH+2NH3) The disubstituted species are shown, but not included in the fit............................................................................................................ 67 Figure 13 Electrophilicity, ω vs. the adiabatic singlet-triplet ∆Es-t gap for silylenes (molecules 1,3-7,9- 22,26-27) germylenes (molecules 54,56-60,62-70,73-75) and nitrenes (molecules 104,105,107-109,111- 113), phosphinidenes (molecules 114-119,21-123 from Table A1). ...................................................... 69 + − Figure 14 Spin-philicity ωS and spin-donicity ωS vs. the adiabatic singlet-triplet gap ∆Es-t for carbenes (+, molecules 28-37,39-53 from Table A1), silylenes (♦, molecules 1-24,26-27 from Table A1), germylenes (-, molecules 54-63, 65-79 from Table A1), nitrenes (▲, molecules 104-113 from Table A1), phosphinidenes (*,molecules 114-123 from Table A1) and molecules by Pérez in [Ref. 116] (, Table A8). ......................................................................................................................................... 70 + Figure 15 Spin-philicity ωS vs. electrophilicity ω for silylenes (molecules 1,3-7,9-22,26-27 from Table A1) and germylenes (molecules 54,56-60,62-70,73-75 from Table A1)................................................ 71 Figure 16 Isodesmic reaction energy (kcal/mol) (▲) and Gibbs free energy (kcal/mol) (♦) vs. the dimerization energy (kcal/mol) at the B3LYP/6-31G(D) level (Path 1) (molecules 1-27 in Table A1). 75 Figure 17 Singlet-triplet energy separation (kcal/mol) vs. the dimerization energy (kcal/mol) at the MP2/6-311+G(2D) level (Path 1) (molecules 1-27 in Table A1) ........................................................... 75 Figure 18 Optimized geometrical parameters of the investigated silylenes........................................... 79 Figure 19 Changes of the NICS(1) values for the different derivatives of the investigated silylenes: silylenes, complex with BH3, the silane, complex with NH3, and the triplet silylene............................. 82 Figure 20 Molecular orbitals of compounds 1 and 11 ............................................................................ 83 Figure 21 Structure of 12 in the singlet and triplet state and its dimer ................................................... 84 Figure 22 Comparison of the free energy diagram at the CBS-QB3 level for the reaction channels