复旦大学 无机化学IC15.pptVIP

Other binary compounds Sulfides MS nonstoichiometric TiS2 VS2 layer structure Later trans. el. MS2 S22- FeS2 FeⅡ no FeⅣ CuS CuⅠ CuⅡ S2- S22- Cu2ⅠCuⅡ(S2)(S) Hydrides Nitride TiN, TiC stoichiometric Carbides nonstoichiometric with metallic prop. Interstitial comp. C, N insert 4.1.4 metal-to-metal bonds and metal atom clusters 4.1.4.1 introduction-the two general types of metal cluster compounds 4.1.4.2 the lower halide type of clusters 4.1.4.3 the metal carbonyl clusters 4.1.4.4 Preparation of clusters 4.1.4.1 introduction a metal atom cluster may be defined as a group of two or more metal atoms in which there are substantial and direct bonds between the metal atoms (F.Albert Cotton) ordinary classical werner polynuclear complexes there is no significant amount of direct M-M bonding Two broad generalizations to M-M bonding M-M bond formation is most likely to occur when the metal atoms are in their lower oxidation states. high positive charge causes contraction of the valence orbitals to the extent that overlap with another set of similarly contracted metal atom orbitals is too small to allow effective bond formation. For any given group in the periodic table,the tendency to form M-M bonds is usually greater for the heavier elements. Note: attached ligands number of d electrons Two general types of metal clusters V Cr Mn Fe Co Ni Nb Mo Tc Ru Rh Pd Ta W Re Os Ir Pt 4.1.4.2 the lower halide type of clusters M-M multiple bonds Quadruple bonds Re(III) d bonding M-M quadruple bonds σπδ σπδ 2×7+8×1+2=24e 2 [ReCl4] 16e M/M bonding 8e Re-Re 224pm, B.E.=481-544 KJ/mol in metallic Re