Journal of Organometallic Chemistry 647 (2002) 71 – 83
www.elsevier.com/locate/jorganchem
Mini review
Aspects of non-classical organolanthanide chemistry
M. Cristina Cassani, Yurii K. Gun’ko, Peter B. Hitchcock, Alexander G. Hulkes,
Alexei V. Khvostov, Michael F. Lappert *, Andrey V. Protchenko
The Chemistry Laboratory, School of Chemistry, Physics and Enironmental Science, Uniersity of Sussex, Brighton, East Sussex BN19QJ, UK
Received 29 October 2001; accepted 25 November 2001
Abstract
This paper provides a survey of our studies on: (i) subvalent compounds of lanthanum and early 4f elements; (ii) cationic
mononuclear samarium(II) and ytterbium(II) organic complexes; (iii) low valent samarium and ytterbium -diketiminates; and (iv)
mononuclear cerium(IV) amides and a mixed valence trinuclear Ce(IV)/Ce(III) cluster. A brief introductory section points to our
earlier (1973 – 1995) studies on organo-4f-element chemistry. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Lanthanide complexes; Cyclopentadienyls; Amides; -Diketiminates; tert -Butoxides
1. Introduction
This survey will focus on four areas of organolan-
thanide chemistry which we regard as ‘non-classical’
(the ‘classical’ organo-Ln(II) compounds are neutral or
anionic Sm, Eu or Yb derivatives). These are: (i) subva-
lent compounds of lanthanum and the early 4f ele-
ments; (ii) cationic mononuclear samarium(II) and
ytterbium(II) organic complexes; (iii) low valent samar-
ium and ytterbium -diketiminates; and (iv) mononu-
clear cerium(IV) amides and a mixed valence trinuclear
Ce(IV)/Ce(III) cluster. These studies date from 1995.
Our earlier work on organolanthanide chemistry
(which we take to encompass Sc, Y, La, as well as the
4f elements, collectively abbreviated as Ln) began in the
early 1970s (for the first publication, see Ref. [1]) and
was carried out by (in chronological order): (a) post-
doctoral fellows R. Pearce, G.K. Barker, A. Singh,
G.A. Lawless and X. Cai; and (b) graduate students J.
Holton (1976), P.I.W. Yarrow (1979), R.G. Smith
(1987), S. Prashar (1991), S.R. Holmes (1992), S. Tian
(1994) and J.R. van den Hende (1995); the dates in
parentheses refer to their DPhil (Sussex) Theses. Some
highlights of their contributions relate to a number of
‘firsts’ (R =SiMe
3
): (a) Ln (III ) alkyls : the neutral
[Ln(CH
2
R)
3
(thf)
2
] (Ln =Sc, Y) [1], [Ln(CHR
2
)
3
] (Ln =
La, Sm) [2], and the heterobinuclear [Li(thf)
4
][Ln-
(CHR
2
)
3
Cl] and [Li(thf)
4
][Ln(CH
2
R)
4
] (Ln =Er, Yb) [3]
and [Ln(CHR
2
)
3
(-X)Li(pmdeta)] (Ln =La, Sm; X =
Cl, Me) [4]; (b) Ln (III ) bridging alkyls : [LnCp
2
(-
Me)
2
AlMe
2
] and [{LnCp
2
(-Me)}
2
] [5]; (c) Ln (II ) alkyls
and cyclopentadienyls : [{Yb(CR
3
)(-OEt)(OEt
2
)}
2
] [6a]
(see also Ref. [7]), [Yb(CHR
2
)
2
(OEt
2
)
2
] [6b] and
[YbCp
2
(thf)
2
] [8] (see also Ref. [9]); (d) Ln (III ) 1,3 -
bis (trimethylsilyl )cyclopentadienyls : [{PrCp
2
(-Cl)}
2
]
[10], [NdCp
2
(-Cl)
2
Li(thf)
2
] [11], and [AsPh
4
][NdCp
2
-
Cl
2
] [12]; (e) Ln(III) mononuclear aryloxides and thio -
lates : [Ln(OArMe)
3
] (Ln =Sc, Y) [13] and [Sm(SAr
t
-
Bu)
3
] [14] (OArMeOC
6
H
2
t
Bu
2
-2,6-Me-4; SAr
t
Bu
C
6
H
2
t
Bu
3
-2,4,6); (f) Ln (II ) alkoxides and aryloxides :
[Yb(OC
t
Bu
3
)
2
(thf)
2
] [15] and [Yb(OArMe)
2
(thf)
2
] [16];
(g) homoleptic Ln (II ) cyclopentadienyls : [(LnCp
2
)
]
(Ln =Eu, Yb) [17]; (h) mononuclear Ln (III ) -diketimi -
nates (LL) and 1 -azaallyls (LL): [Ce(LL)(CHR
2
)
2
] and
[Nd(LL)
2
Cl] [18] (see also Ref. [19]) and [Sm(LL)
2
-
I(thf)] [20]; (i) observation of
171
Yb-NMR spectra [21];
and (j) silylene complexes [LnCp
3
{Si(NCH
2
t
Bu)
2
C
6
H
4
-
1,2}] (Ln =Y, Yb) [22].
* Corresponding author. Tel.: +44-1273-678316; fax: +44-1273-
677196.
E-mail address: m.f.lappert@sussex.ac.uk (M.F. Lappert).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
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