Chemistry Reference
In-Depth Information
andHidai (
Chatt, 1978
;
Hidai
, 1999) demonstrated that dinitrogen could be bound and reduced to ammonia at a single
metal centre by Mo and W complexes. However, although examples of virtually all of the proposed intermediates in
a “Chatt” cyclewere isolated, no catalytic reduction of N
2
toNH
3
was ever achieved. Catalytic reduction of dinitrogen
to ammonia at a single molybdenum centre has now been achieved by the group of Richard R. Schrock
5
using the
HITP [3,5-(2,4,6-i-Pr
3
C
6
H
2
)
2
C
6
H
3
] ligand (
Yandulov and Schrock, 2003; Schrock, 2005
)
. The essential intermedi-
ates in the Chatt mechanism for N
2
reduction on a mononuclear Mo metal complex as elaborated with the recent
observation of catalytic reduction by Mo complexes by the Schrock group are shown in
Figure 17.14
(left). N
2
N
Dinitrogen
N
2
N
M
Diazenido
NH
N
Distal
Alternating
M
NH
NH
2
NH
NH
Diazene
Diazene
NH
N
NH
NH
M
M
NH
3
NH
2
N
NH
Nitrido
Hydrazido
M
M
NH
2
NH
2
Hydrazine
NH
NH
2
NH
2
Imido
M
M
NH
2
Amido
M
NH
3
NH
3
Amine
M
NH
3
FIGURE 17.14
Possible reaction mechanisms for nitrogenase. Shown are two possible reaction mechanisms for nitrogenase. On the left is
shown the distal mechanism and on the right the alternating mechanism. FeMo-cofactor is abbreviated as M and the names of different bound
states are shown. Possible points of entry for diazene and hydrazine are shown.
(Adapted from
Seefeldt et al., 2009
.)
5. Who shared the 2005 Nobel prize in chemistry with R.H. Grubbs and Y. Chauvin.
