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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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
Bonding is covalent, there is very little charge separation.
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.
Electrophilic aromatic substitution: faster than for benzene
Reactions of paramagnetic metallocenes
U-C: 2.647(10); C-C: 1.392(13) Å
K. N. Raymond et al. Inorg. Chem. 1972, 11, 1083