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Dative ligands with more than one donor atom s Metal complexes

Dative ligands with more than one donor atom s Metal complexes. Metal dihydrogen complexes. Discovered in 1984 by Kubas: M(CO) 3 (PR 3 ) 2 (H 2 ) (M = Mo, W; R = Cy, i -Pr) Bonding. d H-H = 0.84 Å ( 0.74 Å in free H 2 ); d W-H = 1.75 Å n HH = 2690 cm -1 ; n HD = 2360 cm -1

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Dative ligands with more than one donor atom s Metal complexes

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  1. Dative ligands with more than one donor atoms Metal complexes

  2. Metal dihydrogen complexes • Discovered in 1984 by Kubas: M(CO)3(PR3)2(H2) (M = Mo, W; R = Cy, i-Pr) • Bonding dH-H = 0.84 Å (0.74 Å in free H2); dW-H = 1.75 Å nHH = 2690 cm-1; nHD = 2360 cm-1 dHH = -4.21 (24 Hz wide), dHD = -4.21 (8 Hz wide, 1:1:1 triplet, JHD = 33 Hz, JHD (HD gas) = 43 Hz) Good p acceptors (CO, NO) are effective in stabilizing the H2 ligand. Reference: Kubas, G. J. et al. J. Am. Chem. Soc. 1984, 106, 451

  3. Complexes of Anionic, Multiple-Carbon Ligands

  4. Discovery of ferrocene • 1948: Miller, Tebboth, Tremain report that olefins in the presence of Fe salts form FeC10H10 • 1951: Keally, Pauson, and Miller oxidized C5H5MgBr with FeCl3: • Wilkinson/Woodward (Harvard) and Fischer (Munich) report the correct structure: Fe(h5-C5H5)2 • 1973 Nobel prizeGeoffrey Wilkinson and Ernst Otto Fischer on sandwich compounds

  5. Sandwich complexes • They usually follow the 18 e rule • 1st row TMs: electron counts from 15 to 20 are known because of the favorable metallocene structure • 18 e rule does not apply to lanthanides and actinides

  6. Synthesis of metallocenes

  7. Cyclopentadienyl (Cp) complexes: orbitals in Cp- Bonding is covalent, there is very little charge separation.

  8. Cp: orbital combinations for two ligands

  9. Metallocenes, MCp2 HOMO of FeCp2, dz2 (nonbonding) Most important interaction: e1g C-C bond in Cp is 1.44 Ǻ (C6H6, 1.35 Ǻ); H atoms of Cp are bent downwards.

  10. Reactivity Electrophilic aromatic substitution: faster than for benzene Reactions of paramagnetic metallocenes

  11. Uranocene: Streitwieser, 1968 U-C: 2.647(10); C-C: 1.392(13) Å K. N. Raymond et al. Inorg. Chem. 1972, 11, 1083

  12. COT2- vs. benzene COT2-HOMO Benzene LUMO

  13. dbonding in uranocene • UV-PES studies show that bonding in uranocene has 5f and 6d contributions. • e2u interaction shown can only occur via f orbitals. • C. Elschenbroich; A. Salzer Organometallics, 2nd ed., VCH, Weinheim, 1992, p. 363

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