Chemistry Reference
In-Depth Information
-OBu
t
2
OBu
t
6
] were reported.
98
Both molecules are modelled on the familiar
M
3
O
11
structure involving three ZrO
6
octahedra. It is noteworthy that in the
tert
-
butoxide the OH-group occupied a
-position rather than the
3
-position that might
have been expected.
Some zirconium lead heterometallic oxo-alkoxides have been characterized. In
the tetranuclear mixed ligand compound [Zr
3
Pb
4
-O
3
-OPr
i
2
-OPr
i
4
-
OAc
2
OPr
i
4
] the central oxo ligand is in a distorted (squashed tetrahedral) configura-
tion whilst the zirconiums are distorted octahedral and the lead atom is five-coordinated
(tetragonal pyramid with lone electron pair in the vacant octahedral site).
121
The acetato
ligands are bidentate bridging. In the hexanuclear complex [Zr
4
Pb
2
4
-O
-OEt
8
-
OAc
2
OEt
4
OAc
2
] two acetates are bidentate bridging and two are chelating. Two
of the zirconiums are six-coordinated and two are seven-coordinated.
126
The oxo-
tert
-butoxide [ZrPb
3
4
-O
3
-OBu
t
-OBu
t
5
OBu
t
2
]hasa
4
-oxo ligand in a
distorted tetrahedral coordination. The zirconium in six-coordinated, 2 lead atoms are
five-coordinated but the third is only three-coordinated (pyramidal).
22
Seven-coordinated Zr is also found in the mixed ligand compound [Zr
3
Fe
4
-O
-
OPr
n
6
OPr
n
4
acac
3
]. The
4
-oxo ligand is tetrahedrally coordinated and the Fe(
III
)
atom is five-coordinated (distorted TBP).
127
However, with Co(
II
) the hexanuclear
[Zr
2
Co
4
6
-O
-OPr
n
8
OPr
n
2
acac
4
] was obtained. This has a
6
-oxo ligand
encapsulated in an octahedron (
trans
-Zr
2
) of metal atoms in the familiar cubic M
6
O
19
core framework with all metals octahedrally coordinated.
128
Some interesting zirconium copper(
I
) and zirconium copper(
II
) oxo-isopropoxides
have been characterized.
129
In [Zr
4
Cu
4
4
-O
-OPr
i
10
OPr
i
8
] the central
4
-oxo
ligand is in a distorted tetrahedral Cu
4
O system linked to two confacial bioctahedral
Zr
2
OPr
i
9
moieties by bridging isopropoxo ligands. The copper(
I
)atomsaretwo-
coordinated (linear) and the zirconiums octahedral. The centrosymmetric Cu(
II
) complex
[Zr
4
Cu
4
4
-O
3
-OPr
i
10
OPr
i
8
] has a central
4
-oxo ligand exhibiting a novel
square planar configuration in the planar Cu
4
O
OPr
i
2
fragment which is capped by
two confacial bioctahedral Zr
2
O
OPr
i
8
moieties.
5.5 Vanadium Sub-group Metal-containing Oxo-alkoxides (Including
Heterometallic Compounds) (Table 5.5)
5.5.1
Vanadium
The chemistry of vanadium is replete with oxo vanadium complexes including a large
number of vanadium oxo-alkoxides.
The first structural determination revealed that vanadyl(
V
) trimethoxide had a poly-
meric structure built up from weakly bound dimer units [VO
-OMe
OMe
2
]
2
giving
the vanadium a distorted octahedral configuration.
130
The 2-chloroethoxo-derivative
gave a weakly bound dimer with distorted TBP coordination
46
as did the cyclopentyloxo-
derivative.
134
The distorted TBP configuration was also found in several mononuclear
oxovanadatrane molecules [OV
OC
2
H
4
3
N],
83
,
131
[OV
OCHMeCH
2
3
N],
83
[OVf
OC
2
H
4
2
CHEtCH
2
O
g],
132
and [OV
OCHBu
t
CH
2
3
N].
133
By contrast the binu-
clear complex [V
2
O
2
Cl
2
OC
2
H
4
O
2
] had a cyclic structure with distorted tetrahedral
vanadium atoms,
135
whilst the complex [V
2
O
2
f
OCH
2
2
CMe
CH
2
OH
g
2
Cl
2
]had
edge-sharing octahedral V(
V
)atoms.
136
