Cyclopentadienyl nitrosyl compounds of chromium: aqueous solution
chemistry, π bonding and nitric oxide loss
Abstract
The complex
[Cr(η-C
5
H
5
)(NO)
2
(CF
3
SO
3
)] 1 was synthesised in order to explore the relationship
between π-donor ligands and nitrosyl lability and to investigate the
aqueous chemistry of the
[Cr(η-C
5
H
5
)(NO)
2
]
+
fragment. Treatment of 1 with σ-donor ligands gave
[Cr(η-C
5
H
5
)(NO)
2
(L)][CF
3
SO
3
] salts. Potentiometric titrations and
1
H
NMR spectroscopic studies of 1 provided evidence for the existence of
[Cr(η-C
5
H
5
)(NO)
2
(H
2
O)]
+
and
[Cr(η-C
5
H
5
)(NO)
2
(OH)] in aqueous
solution. When generated in situ,
[Cr(η-C
5
H
5
)(NO)
2
(OH)] reacted with
acetylacetone, pyridinecarboxylic acid, or salicylaldehyde to form
paramagnetic, mononitrosyl complexes, which were independently
synthesised from the mononitrosyl precursor
[Cr(η-C
5
H
5
)(NO)(µ-I)]
2
.
The solid-state molecular structures of
[Cr(η-C
5
Me
5
)(NO)
2
(CF
3
SO
3
)] 2,
[Cr(η-C
5
H
5
)(NO)
2
(N
2
C
5
H
7
)] 9 and
[Cr(η-C
5
H
5
)(NO)(O
2
C
5
H
7
)] 10 were determined by X-ray crystallography. Crystals of
2 are monoclinic, a = 8.575(1),
b = 8.642(1),
c = 21.8626(9) Å,
β = 91.760(7)°, Z = 4,
space group P2
1
/n; crystals of 9 are
monoclinic, a = 18.3382(4),
b = 11.1774(3),
c = 12.9102(1) Å,
β = 121.386(1)°, Z = 8,
space group C2/c; and those of 10 are orthorhombic,
a = 17.373(2),
b = 8.833(1), c = 6.926(2)
Å, Z = 4, space group Pnma.
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