Polyhedron 20 (2001) 2711 – 2720
Scandium, yttrium and lanthanum nitrate complexes of tertiary
arsine oxides: synthesis and multinuclear spectroscopic studies.
X-ray structures of [M(Me
3
AsO)
6
](NO
3
)
3
(M = Sc or Y),
[Sc(Ph
3
AsO)
3
(NO
3
)
2
]NO
3
, [M(Ph
3
AsO)
4
(NO
3
)
2
]NO
3
(M = Y or
La) and [La(Ph
3
AsO)
2
(EtOH)(NO
3
)
3
]
William Levason *, Bhavesh Patel, Michael C. Popham, Gillian Reid, Michael Webster
Department of Chemistry, Uniersity of Southampton, Southampton, SO17 1BJ, UK
Received 30 May 2001; accepted 29 June 2001
Abstract
The reaction of Ph
3
AsO with Sc(NO
3
)
3
·5H
2
O, Y(NO
3
)
3
·6H
2
O or La(NO
3
)
3
·6H
2
O in acetone gave [Sc(Ph
3
AsO)
2
(NO
3
)
3
],
[Y(Ph
3
AsO)
4
(NO
3
)
2
]NO
3
, [La(Ph
3
AsO)
4
(NO
3
)
2
]NO
3
, and [La(Ph
3
AsO)
3
(NO
3
)
3
], whilst from ethanol solution
[Sc(Ph
3
AsO)
3
(NO
3
)
2
]NO
3
, [Y(Ph
3
AsO)
2
(EtOH)(NO
3
)
3
] and [La(Ph
3
AsO)
2
(EtOH)(NO
3
)
3
] were produced. Similar reactions using
Me
3
AsO produced [M(Me
3
AsO)
6
](NO
3
)
3
(M=Sc, Y or La) and [La(Me
3
AsO)
2
(H
2
O)(NO
3
)
3
]. All complexes were characterised by
analysis, IR and
1
H,
45
Sc or
89
Y NMR spectroscopy, and conductance measurements. The solution speciation and interconver-
sions of the Sc and Y complexes have been probed by
45
Sc and
89
Y NMR spectroscopy. X-Ray crystal structures are reported for
the 6-coordinate [M(Me
3
AsO)
6
](NO
3
)
3
(M=Sc or Y), seven-coordinate [Sc(Ph
3
AsO)
3
(NO
3
)
2
]NO
3
, eight-coordinate
[M(Ph
3
AsO)
4
(NO
3
)
2
]NO
3
(M =Y or La), and nine-coordinate [La(Ph
3
AsO)
2
(EtOH)(NO
3
)
3
]. © 2001 Elsevier Science Ltd. All
rights reserved.
Keywords: Scandium; Yttrium; Lanthanum; NMR spectroscopy; X-ray structures
www.elsevier.com/locate/poly
1. Introduction
Compared to other d-block metals, the coordination
chemistries of scandium and yttrium remain little ex-
plored. The only accessible oxidation state in solution,
the d
0
M(III), form labile complexes and lack both
magnetic and d–d UV–Vis spectroscopic probes. How-
ever, both metals are suitable for NMR studies, being
monoisotopic (
45
Sc and
89
Y) and diamagnetic in the
M(III) oxidation state. Scandium-45 is quadrupolar
(I =7/2) but with only a moderate quadrupole moment
-0.22 ×10
-28
m
2
, and is one of the most sensitive
nuclei in the periodic table (D
c
(receptivity relative to
13
C) =1700), whilst
89
Y has I =1/2 and moderate sensi-
tivity (D
c
=0.67), but has a low absolute frequency
( =4.92 MHz) and very long relaxation times. We
have recently described the characterisation of scand-
ium(III) and yttrium(III) nitrate complexes of a range
of phosphine oxides, [1] using a combination of multin-
uclear NMR (
1
H,
31
P{
1
H},
45
Sc or
89
Y) and X-ray
crystallography. In a related work, the synthesis and
structures of Ln(Ph
3
PO)
4
(NO
3
)
3
for the lanthanides
have been examined [2]. Here, we extend the work to
tertiary arsine oxide (Me
3
AsO and Ph
3
AsO) complexes
and demonstrate that
45
Sc or
89
Y NMR spectroscopy
can be used to probe the solution behaviour of these
two elements, even without the support of
31
P NMR as
used for the phosphine oxide analogues. Apart from
some early exploratory synthesis of lanthanide nitrate
complexes of Ph
3
AsO [3], nothing is known about these
compounds, and no examples with Sc, Y or La have
been structurally characterised.
* Corresponding author. Tel.: +44-2380-595-000; fax: +44-2380-
593-782.
E-mail address: wxl@soton.ac.uk (W. Levason).
0277-5387/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII:S0277-5387(01)00889-0