金属有机课件Chapter 2【荐】.pdf

Chapter 2 Complexes with metal-carbon σ bonds Metal alkyls, aryl, hydride and related σ-bonded ligands Outline 1. The stability of transition metal-carbon σ bonds 2. Preparation of complexes with metal-carbon σ bonds 3. Chemical properties of complexes with metal- carbon σ bonds 4. Related σ-bonded ligands complexes [M-SiR , M-X (X = OR, NR , F, Cl, etc.) ] 3 2 5. Metal hydrides 1. The stability of transition metal-carbon σ bonds 1). Thermal stability of transition metal-carbon bonds 2). Factors affecting M-C bond strength 3). Origin of earlier failure in obtaining TM alkyls: Kinetic consideration. 1). Thermal stability of transition metal- carbon bonds The thermal stability can be related to bond dissociation energy. M-X (g) M (g) + X (g) ∆Hº = BDE (M-X) If BDE (M-X) is large, M-X is thermally more stable. Range of M-C bond dissociation energy (BDE). (See next two pages) BDE (M-C) values in MRn complexes (KJ/mol) Non-transition metals Transition metals M-C bond BDE Compound M-C bond BDE Li-Et 209 Ti(CH C(CH ) Ti-CH R 170 2 3 4 2 Li-Bu 248 Ti(CH2Ph)4 Ti-CH2R 240 Zn-Me 176 Ti(CH2Si(CH ) Ti-CH R 250 3 4 2 Zn-Et 145 Cp2Ti(CH ) Ti-CH 250 3 2 3 Cd-Me 139 Cp TiPh Ti-Ph 350 2 2 Hg-Me 122 (CO)5MnCH3 Mn-CH3 150 Hg-Et 101 (CO) ReCH