Substitution reactions of labile rhenium(V) precursors
with
o-(diphenylphosphino)-N,N′
-dimethylaniline, L, gave a series of monooxorhenium(V)
complexes of general formula [ReOX
2
Y(L)]
(X = Y = Cl 1;
X = Cl, Y = OMe 2) and
[ReOX
2
(OEt)L] (X = Cl 3, Br 4
or I 5). These complexes, which contain only one aminophosphine
chelate, have a distorted-octahedral geometry, as evidenced by a crystal
structure determination of 2. Reactions conducted in basic
media, or treatment of 2 in the presence of the weakly
co-ordinating trifluoromethanesulfonic acid, gave the bis(chelate)
cationic complexes [ReO
2
L
2
]
+
6
and [ReCl
2
L
2
]
+
7,
respectively. Similar ligand-exchange reactions between the
lower-oxidation-state precursor
[Re
III
Cl
3
(MeCN)(PPh
3
)
2
] and
L or L′ [o-(diphenylphosphino)aniline] still produced
mono-substituted aminophosphine complexes, i.e.
[Re
III
Cl
3
L(PPh
3
)] 8 or
[Re
III
Cl
3
L′(PPh
3
)] 9 in
which there is a meridional arrangement of chloride ligands along with a
cis-phosphorus co-ordination. The crystal structure of
8 was determined. On the contrary, treatment of
[Re
III
X
3
(MeCN)(PPh
3
)
2
]
(X = Cl or Br) with L′ in the presence of
co-ordinating hydrohalogenic acid gave bis-substituted cationic
complexes [ReX
2
L′
2
]
+
(X = Cl 10 or Br 11). In spite of the
paramagnetism of the low-spin d
4
ion, all of the
rhenium(III) complexes can be conveniently characterised in
solution by proton NMR spectroscopy.
