Ζ. Kristallogr. NCS 217 (2002) 35-37
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35
Crystal structure of (18-crown-6)bis(tetrahydrofuran)potassium
bis(2,3,4,5-tetramethylphospholyl)bis(borohydride)neodymium(III),
[K(Ci2H2406)(C4H
8
0)2]{[C4(CH3)4P]2Nd(BH4)
2
}
S. Cendrowski-Guillaume, G. Le Gland, M. Ephritikhine and M. Nierlich*
CEA Saclay. DSM/DRECAM/SCM. Bβt. 125. F-91191 Gif-sur-Yvette Cedex. France
Received September 9. 2001. accepted December 18, 2001: CCDC-No. 1267/722
Abstract _
C36H72B
2
KNd0
8
P2, triclinio,wmkfdcaSRPKIF PI (No. 2), a = 10.489(2) Β,
Ώ>= 11.784(2) k,c= 19.103(4) Β, a = 98.29(3)°, β = 94.07(3)°,
γ = 104.26(3)°, V= 2250.5 Β
3
, Z = 2, R ^ F ) = 0.069,
wR
Kf
(F
2
) = 0.194,7= 123 K.
Source of material
Addition of 18-crown-6 (1.7 equivalents, 143 //mol) to a THF
(20 mL) solution of [K(THF)][Nd(PC4Me
4
)2(BH4)2] (47.3 mg,
84 //mol) quantitatively gave the title compound. The product
was recrystallized from a THF-pentane mixture to afford light
blue crystals within 7 days. The sample was also characterized by
NMR and IR spectroscopy. Spectroscopic data are included in the
deposited CIF-file.
Experimental details
Hydrogen atoms (except H atoms of BH4) were introduced at cal-
culated positions as riding atoms, with an isotropic displacement
parameter equal to 1.2 (CH, CH2) or 1.5 (CH
3
) times that of the
parent atom. The hydrogen atoms of BH4 were not found.
Discussion
Organometallic borohydrides complexes of neodymium are quite
rare [1,5]. Bisborohydride derivatives include the cyclopenta-
dienyl substituted species (C5H'Pr
4
)Nd(BH
4
)2 [1] and
[K(18-crown-6){(Ci3H
8
)CPh
2
(C5H4)Nd(BH4)2}]2 [3] while the
monoborohydride compounds, in addition to
(C5H
4
CH2CH20Me)
2
Nd(BH4) [4], are essentially limited to the
cyclooctatetraenyl derivatives (J7-CgH8)Nd(BH4)(THF)2 and
(j7-C
5
Me
5
)Nd(BH4)2(THF)2 [2,5]. Such borohydrides of neo-
dymium(III) revealed themselves as versatile precursors for the
synthesis of previously inaccessible compounds such as the
cationic derivatives [(i7-C
8
H
8
)Nd(L)
x
][BPh
4
] (L = THF4,
HMPA3) [5,6]. Although a few bis(phospholyl)lanthanide(III)
examples are known [7,8], the complex we isolated,
[K(THF)][(PC
4
Me4)2Nd(BH
4
)2] [2], is the first mixed
borohydride-phospholyl derivative of a 4/element. Addition of a
crown ether to that product allowed the synthesis of the parent
complex [K( 18-crown-6)(THF)2] [(PC^tethNdiBH^], the crys-
tal structure of which has been determined and that is reported in
this paper.
The structure of [K(18-crown-6)(THF)
2
][(PC
4
Me
4
)
2
Nd(BH4)2]
reveals molecular cation and anion pairs. The figure shows the mo-
lecular anion. The potassium ion, which is encapsulated into the
crown ether and surrounded by two coordinated THF, displays
the expected coordination. The molecular anion adopts a dis-
torted tetrahedral configuration with the following relevant an-
gles ΏBl-Nd-B2 = 98.7(3)°, ZLP1*-Nd-P2* = 128.7(7)° and
the mean value for ΏB-Nd-P* = 106.3(7)°, ranging from
105.6(2) to 107.3(2)° (P* = phospholyl centroid). The phospholyl
ligands are bound to the metal in an η
5
mode. Both phospholyl
rings are planar (within 0.031 Β and 0.021 Β for phospholyls
"PI" and "P2" respectively) with average Nd—C bond distance
of 2.87(2) Β, Nd—PI and Nd—P2 bond distances of 2.982(3) Β
and 2.995(3) Β and Nd-phospholyl centroid of 2.579(3) Β and
2.595(3) Β for " PI " and " P2 ", respectively. These distances are
comparable to those observed in the only other crystallographi-
cally characterized bisphospholyl lanthanide(III) complex,
([V
5
-CtMe
4
P)Sm(u
3
-a)
2
(M:>7
5
^
1
-C4Me
4
P)KCEt20)]oo), (</(Sm—C)
= 2.78(2) Β, d(Sm—P) = 2.916(11) Β) [9]. The Nd-borohydride
ligands distances ranging from 2.588(7) ΐ to 2.670(5) Β and av-
eraging to 2.63(5) Β agree well with the short distances observed
for a tridentate binding mode of the BH
4
ligand in
(C5H'Pr
4
)Nd(BH
4
)2 (mean Ώ(Nd—B) = 2.600(8) Β) [1],
(C
5
H
4
CH
2
CH20Me)2Nd(BH
4
) (2.664(25) ΐ) [4] or in
[K(18-crown-6){(Ci3H
8
)CPh
2
(C5H
4
)Nd(BH
4
)
2
}]2 · C
4
H
8
0
2
(mean d(Nd—B) = 2.632(9) ΐ) [3], This value is however
much shorter than that measured in the dimeric complex
[(?7-C
8
H8)NdO«3-H)2BCu
2
-H)2(THF)]2 (2.875(6) Β and
2.941(6) Β) [5]. The infrared data of our complex confirm the
tridentate binding mode observed crystallographically [10,11].
* Correspondence author (e-mail: nierlich@drecam.cea.fr)