Dative ligands with more than one donor atom s metal complexes
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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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Dative ligands with more than one donor atom s metal complexes

Dative ligands with more than one donor atoms Metal complexes


Metal dihydrogen complexes

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


Complexes of anionic multiple carbon ligands

Complexes of Anionic, Multiple-Carbon Ligands


Discovery of ferrocene

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


Sandwich complexes

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


Synthesis of metallocenes

Synthesis of metallocenes


Cyclopentadienyl cp complexes orbitals in cp

Cyclopentadienyl (Cp) complexes: orbitals in Cp-

Bonding is covalent, there is very little charge separation.


Cp orbital combinations for two ligands

Cp: orbital combinations for two ligands


Metallocenes mcp 2

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.


Reactivity

Reactivity

Electrophilic aromatic substitution: faster than for benzene

Reactions of paramagnetic metallocenes


Uranocene streitwieser 1968

Uranocene: Streitwieser, 1968

U-C: 2.647(10); C-C: 1.392(13) Å

K. N. Raymond et al. Inorg. Chem. 1972, 11, 1083


Cot 2 vs benzene

COT2- vs. benzene

COT2-HOMO

Benzene LUMO


D bonding in uranocene

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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