Structural diversity in lanthanide phosphido complexes. Formation and X-ray crystal structure determination of an unusual dinuclear phosphido complex of divalent samarium: [(Me3Si)2P]Sm[μ-P(SiMe3)2] 3

Article abstract of DOI:10.1021/om950624r

The dinuclear phosphido complex of divalent samarium [(Me₃Si)₂P]Sm[μ-P(SiMe₃)₂] ₃Sm(thf)₃ (1) can be readily made from SmI₂(thf)₂ and 2 equiv of KP-(SiMe₃)<

Full text of DOI:10.1021/om950624r

Organometallics 1996, 15, 439-441
439
Str u ctu r a l Diver sity in La n th a n id e P h osp h id o
Com p lexes. F or m a tion a n d X-r a y Cr ysta l Str u ctu r e
Deter m in a tion of a n Un u su a l Din u clea r P h osp h id o
Com p lex of Diva len t Sa m a r iu m :
1
[(Me3Si)2P ]Sm [µ-P (SiMe3)2]3Sm (th f)3‚C7H8
Gerd W. Rabe,* J u¨rgen Riede, and Annette Schier
Anorganisch-chemisches Institut, der Technischen Universita¨t Mu¨nchen, Lichtenbergstrasse 4,
85747 Garching, Germany
Received August 8, 1995X
Summary: The dinuclear phosphido complex of divalent
samarium [(Me3Si)2P]Sm[µ-P(SiMe3)2]3Sm(thf)3 (1) can
be readily made from SmI2(thf)2 and 2 equiv of KP-
(SiMe3)2 in tetrahydrofuran solution. The unusual
molecular structure of complex 1 in the solid state is
discussed.
Amido species of both divalent2 and trivalent3-6
lanthanide elements have been intensively studied
during the past two decades. We were interested in a
comparison of homologous binary amido and phosphido
complexes of the lanthanides.
Recently, we reported on the synthesis and structural
characterization of two novel trivalent homoleptic lan-
thanide phosphido complexes of the general formula Ln-
[P(SiMe3)2]3(thf)2 (Ln ) Tm, Nd).7 These results show
clearly that the coordination sphere around the lan-
thanide center is not as sterically saturated as in the
case of the corrresponding tris[bis(trimethylsilyl)amido]
species, thus allowing for the coordination of two solvent
molecules in axial positions. Efforts have been under-
taken now to extend this comparative study to divalent
lanthanide species.
F igu r e 1. Molecular structure of [(Me3Si)2P]Sm[µ-
P(SiMe3)2]3Sm(thf)3 (1) (SCHAKAL, H atoms omitted for
clarity). Selected bond distances (Å) and angles (deg): Sm-
(1)-P(1) 3.178 (3), Sm(1)-P(2) 3.165 (3), Sm(1)-P(3) 3.100
(3), Sm(1)-O(1) 2.597 (8), Sm(1)-O(2) 2.571 (7), Sm(1)-
O(3) 2.610 (8), Sm(2)-P(1) 3.019 (3), Sm(2)-P(2) 3.033 (3),
Sm(2)-P(3) 3.066 (3), Sm(2)-P(4) 3.027 (3); P(2)-Sm(1)-
P(1) 81.6 (1), P(3)-Sm(1)-P(1) 79.4 (1), P(3)-Sm(1)-P(2)
81.1 (1), O(1)-Sm(1)-P(1) 151.0 (2), O(1)-Sm(1)-P(2)
121.0 (2), O(1)-Sm(1)-P(3) 86.1 (2), O(2)-Sm(1)-P(1)
126.1 (2), O(2)-Sm(1)-P(2) 84.3 (2), O(2)-Sm(1)-P(3)
148.2 (2), O(2)-Sm(1)-O(1) 77.5 (2), O(3)-Sm(1)-P(1) 87.5
(2), O(3)-Sm(1)-P(2) 145.9 (2), O(3)-Sm(1)-P(3) 128.5 (2),
O(3)-Sm(1)-O(1) 82.1 (2), O(3)-Sm(1)-O(2) 76.3 (2),
P(2)-Sm(2)-P(1) 86.4 (1), P(3)-Sm(2)-P(1) 82.5 (1), P(3)-
Sm(2)-P(2) 83.8 (1), P(4)-Sm(2)-P(1) 129.0 (1), P(4)-Sm-
(2)-P(2) 120.8 (1), P(4)-Sm(2)-P(3) 137.6 (1), Sm(2)-
P(1)-Sm(1) 80.7 (1), Sm(2)-P(2)-Sm(1) 80.7 (1), Sm(2)-
P(3)-Sm(1) 81.2 (1).
Evans and co-workers reported earlier on the syn-
thesis and X-ray crystal structure determination of
divalent monometallic Sm[N(SiMe3)2]2(thf)2.2 Here we
describe the preparation and crystal structure deter-
mination of [(Me3Si)2P]Sm[µ-P(SiMe3)2]3Sm(thf)3 (1)
(Figure 1), which is obtained from the reaction of SmI2-
8
9
(thf)2 and 2 equiv of KP(SiMe3)2 in tetrahydrofuran
solution at room temperature. A comparison of these
two analogous amido and phosphido complexes with
respect to their solid state structures shows that in the
case of the phosphido species 1 a bimetallic species is
being formed versus a monometallic system in the case
of the bis(amido) complex. This new disilylphosphido
complex has also been examined in solution by variable-
X Abstract published in Advance ACS Abstracts, November 15, 1995.
(1) Reported in part at the 209th National Meeting of The American
Chemical Society, Anaheim, CA, April 1995; INOR 137.
(2) Evans, W. J .; Drummond, D. K.; Zhang, H.; Atwood, J . L. Inorg.
Chem. 1988, 27, 575, and references cited therein.
(3) Bradley, D. C.; Gothra, J . S.; Hart, F. A.; Hursthouse, M. B.;
Raithby, P. R. J . Chem. Soc., Dalton Trans. 1977, 1166.
(4) Eller, P. G.; Bradley, D. C.; Hursthouse, M. B.; Meek, D. W.
Coord. Chem. Rev. 1977, 24, 1, and references cited therein.
(5) Andersen, R. A.; Templeton, D. H.; Zalkin, A. Inorg. Chem. 1978,
17, 2317.
(6) Herrmann, W. A.; Anwander, R.; Munck, F. C.; Scherer, W.;
Dufaud, V.; Huber, N. W.; Artus, G. R. J . Z. Naturforsch. 1994, 49B,
1789.
(7) (a) Rabe, G. W.; Riede, J .; Schier, A. J . Chem. Soc., Chem.
Commun. 1995, 577. (b) Rabe, G. W.; Ziller, J . W. Inorg. Chem. 1995,
34, 5378.
1
temperature H NMR spectroscopy.
Buhro and co-workers reported earlier that P(SiMe3)2
complexes are found to exhibit higher molecularities and
higher coordination numbers than the homologous
N(SiMe3)2 complexes.10 The differing behaviors of these
two classes of ligands were ascribed to normal periodic
trends that distinguish the properties of N and P, e.g.,
lower electronegativity, larger size, and lower hybrid-
ization tendency of P.
The molecular structure of 1 is unique in lanthanide
chemistry and differs significantly from the solid state
(8) Girard, P.; Namy, J . L.; Kagan, H. B. J . Am. Chem. Soc. 1980,
102, 2693.
(9) Hall, S. W.; Huffman, J . C.; Miller, M. M.; Avens, L. R.; Burns,
C. J .; Arney, D. S. J .; England, A. F.; Sattelberger, A. P. Organome-
tallics 1993, 12, 752.
(10) Matchett, M. A.; Chiang, M. Y.; Buhro, W. E. Inorg. Chem. 1994,
33, 1109, and references cited therein.
0276-7333/96/2315-0439$12.00/0 © 1996 American Chemical Society

440 Organometallics, Vol. 15, No. 1, 1996
Notes
structures reported for divalent lanthanide bis(diphe-
nylphosphido) complexes of the general formula Ln-
[PPh2]2(L)4 (Ln ) Sm, Yb; L ) thf, N-methylimidazole).11
These species were found to be hexacoordinated lan-
thanide complexes in slightly distorted octahedral en-
vironments with the phosphido ligands in trans posi-
tions. Additionally, the crystal structure of the title
compound is clearly different from other structural types
we reported earlier in the area of lanthanide phosphido
chemistry, namely, trivalent (tBu2P)2La[(µ-PtBu2)2Li-
(thf)] and divalent Yb[(µ-PtBu2)2Li(thf)]2.12
3.689 (11) [Sm(1)‚‚‚C(53)]; 3.257 (11) [Sm(2)‚‚‚C(11)];
3.454 (13) Å [Sm(2)‚‚‚C(32)], and 3.747 (13) Å [Sm(2)‚‚‚C-
(62)]. These numbers can be compared with reports
from Evans and co-workers on agostic interactions in
the two monometallic complexes of divalent samarium,
Sm[N(SiMe3)2]2(thf)2 [3.32 (1)-3.46 (1) Å]2 and (C5Me5)2-
Sm [3.22 (1) Å].16
The nonbonding Sm‚‚‚Sm distance in complex 1 is
4.014 (2) Å. Sm(1) deviates 2.09 (2) Å from the plane
described by the three bridging phosphorus atoms P(1),
P(2), and P(3). The corresponding distance for Sm(2)
is 1.92 (2) Å. The arrangement of Sm(1), Sm(2), and
P(4) is almost linear with a Sm(1)‚‚‚Sm(2)‚‚‚P(4) angle
of 171.0°.
The P-Si distances in 1 are 2.195 (4)-2.218 (4) Å
[average 2.206 (7) Å] with Si-P-Si angles ranging from
102.6 (1) to 104.1 (1)° [average 103.4 (3)°]. The dihedral
angles between the PSi2 planes and the P3 plane are
33.2° [P(1)], 25.6° [P(2)], and 30.2° [P(3)]. The sum of
angles around P(4) is 326.7°, thus showing a distinctly
pyramidal environment around P(4). The geometry
around the P(4) ligand in 1 can be compared with the
gas phase structure17 of tris(trimethylsilyl)phosphine
[sum of angles around phosphorus 315.6°, average P-Si
distances of 2.259 (1) Å, and average Si-P-Si angles
of 105.1 (2)°] and the solid state structure18 of tris-
(trimethylsilyl)phosphine [sum of angles around phos-
phorus 318.1°, average P-Si distances of 2.245 (3) Å,
and average Si-P-Si angles of 106.0 (3)°], both of which
exhibit a distinctly pyramidal environment around
phosphorus.
Since complex 1 has a rather peculiar structure in
the solid state, we were interested in investigating its
solution structure in different solvent media. Due to
the strong paramagnetism of samarium(II) as well as
fluxional behavior of complex 1 in solution, we were
unable to detect any signals in the 13C or 31P NMR
spectra at room temperature.
The molecular structure of 113 features the two
samarium centers in different coordination environ-
ments. The asymmetry of the title complex is unusual
but is somewhat reminiscent of the europium amide
[(Me3Si)2N]Eu[µ-N(SiMe3)2]2Na.14 Sm(1) is surrounded
by three thf ligands as well as three bridging phosphido
ligands. The arrangement of ligands around Sm(1) can
best be described as slightly distorted trigonal prismatic
with an average twist angle of 16° between the two
triangles. Contrary to Sm(1), Sm(2) is surrounded by
four only-phosphorus containing substituents, three
bridging and one terminal phosphido ligand. Two of the
three bridging Sm(1)-P distances are significantly
longer [Sm(1)-P(1) 3.178 (3) Å; Sm(1)-P(2) 3.165 (3)
Å] than the third one [Sm(1)-P(3) 3.100 (3) Å]. The
opposite observation is made in the case of tetracoor-
dinated Sm(2): the bond distances for Sm(2)-P(1)
[3.019 (3) Å] as well as for Sm(2)-P(2) [3.033 (3) Å] are
clearly shorter than Sm(2)-P(3) [3.066 (3) Å]. One
would expect the terminal Sm(2)-P(4) distance to be
shorter than the bridging Sm(2)-P(1) to Sm(2)-P(3)
distances. However, the terminal Sm(2)-P(4) bond
distance of 3.027 (3) Å was found to match the Sm(2)-
P(1) as well as the Sm(2)-P(2) bond distances within
the error limits. These Sm-P distances are also
significantly shorter than the Sm-P distance of 3.1908
(6) Å reported for hexacoordinated (η1-C12H8P)2Sm-
(thf)4,15 the Sm-P distance of 3.139 (3) Å in hexacoor-
A VT 1H NMR study of 1‚C7H8 in both deuterated
toluene and deuterated tetrahydrofuran revealed that
the solution structure of complex 1 must be different
from the molecular structure observed in the solid state.
Details are given in the Experimental Section. How-
ever, it needs to be pointed out that the nature of the
molecular structure of complex 1 in toluene or tetrahy-
drofuran solution is not clear.
11a
dinated Sm[PPh2]2(N-MeIm)4
(N-MeIm ) N-meth-
ylimidazole), and the corresponding distance of 3.0775
(1) Å in (η5-2,3-(CH3)2(C9H6P)2Sm(thf)2.15
Agostic interactions are present in complex 1, for both
Sm(1) and Sm(2). Therefore, an accurate determination
of the coordination numbers for both metal centers is
difficult. The closest nonbonding Sm‚‚‚C distances are
The synthesis and structural characterization of the
title compound provides easy access to a novel phos-
phido species of divalent samarium. The utility of 1
remains to be determined by its chemistry in a variety
of systems.
(11) (a) Rabe, G. W.; Yap, G. P. A.; Rheingold, A. L. Inorg. Chem.
1995, 34, 4521. (b) Rabe, G. W.; Riede, J .; Schier, A. Main Group Chem.,
in press.
(12) Rabe, G. W.; Riede, J .; Schier, A. Inorg. Chem. in press.
(13) Crystal data for 1‚C7H8 (C43H104O3P4Si8Sm2): Mr ) 1318.59;
orthorhombic, space group P212121 with a ) 12.561 (2) Å, b ) 22.122
(3) Å, c ) 24.595 (3) Å, V ) 6834.3 Å3, F ) 1.281 g cm-3, Z ) 4, F(000)
) 2728; Enraf Nonius CAD4 diffractometer. The structure was solved
by direct methods. Data collected at 211K with Mo KR (λ ) 0.710 69
Å). Data were corrected for Lorentz and polarization effects as well as
for decay (-16.7%) and absorption [empirical, Tmin ) 0.83, Tmax ) 0.99,
µ(Mo KR) ) 19.67 cm-1]. From 12 608 measured [(sin Θ/λ)max ) 0.59
Å-1] and 11 796 unique reflections, 10 490 were considered “observed”
[Fo > 4σ(Fo)] and used for refinement. All non-H atoms were refined
with anisotropic displacement parameters except for the C atoms of
the solvent toluene, which was treated as a rigid group. All H atoms
were calculated and allowed to ride on their corresponding carbon atom
with fixed isotropic contributions (Uiso(fix) ) 0.08 and 0.15 Å2, respec-
tively). The structure converged for 506 refined parameters to an R(Rw)
Exp er im en ta l Section
The compounds described below were handled under nitro-
gen using Schlenk double-manifold, high-vacuum, and glove-
box (M. Braun, Labmaster 130) techniques. Solvents were
dried and physical measurements were obtained following
typical laboratory procedures. SmI2(thf)2 was prepared from
samarium metal (Strem) and 1,2-diiodoethane (Aldrich).8 KP-
(SiMe3)2 was prepared according to the literature.9
value of 0.0472 (0.0525). The function minimized was [∑w(|Fo| - |Fc|)2/
2
∑wFo
]
1/2, w ) 1/σ2(Fo). Residual electron densities: +1.67/-1.60 eÅ-3
,
located at Sm(1) and Sm(2). Refinement of the inverse model gave
R(Rw) values of 0.058 (0.062).
(16) Evans, W. J .; Hughes, L. A.; Hanusa, T. P. J . Am. Chem. Soc.
1984, 106, 4270.
(14) Tilley, T. D.; Andersen, R. A.; Zalkin, A. Inorg. Chem. 1984,
23, 2271.
(15) Nief, F.; Ricard, L. J . Organomet. Chem. 1994, 464, 149.
(17) Forsyth, G. A.; Rankin, D. W. H., Robertson, H. E. J . Mol.
Struct. 1990, 239, 209.
(18) Bruckmann, J .; Kru¨ger, C. Acta Crystallogr. 1995, C51, 1152.

Notes
[(Me3Si)2P ]Sm [µ-P (SiMe3)2]3Sm (th f)3 (1). In the glove-
Organometallics, Vol. 15, No. 1, 1996 441
) 11 Hz). 1H NMR (C4D8O, 400 MHz, -100 °C) δ 3.94 (s, ν1/2
) 16 Hz), -0.01 (s, ν1/2 ) 8 Hz). IR (Nujol) 1494 w, 1294 w,
1238 s, 1028 s, 823 vs, 728 s, 694 w, 676 m, 624 s, 520 w, 464
s, 425 m cm-1. Anal. Calcd for C43H104O3P4Si8Sm2: C, 39.17;
box, KP(SiMe3)2 (157 mg, 0.72 mmol) dissolved in 5 mL of
tetrahydrofuran was added to a solution of SmI2(thf)2 (200 mg,
0.36 mmol) in 7 mL of tetrahydrofuran to give a purple
suspension. After 20 min, the reaction mixture was centri-
fuged. Removal of solvent and subsequent crystallization from
toluene at -30 °C gave 1‚C7H8 as dark purple crystals (119
mg, 50%): 1H NMR (C6D6, 270 MHz, 20 °C) δ 1.10 (s, ν1/2 ) 20
Hz). 1H NMR (C7D8, 270 MHz, 20 °C) δ 0.99 (s, ν1/2 ) 20 Hz).
1H NMR (C7D8, 270 MHz, -20 °C) δ 5.9 (vbr), 4.1 (vbr), 3.8
(vbr), 2.6 (vbr), 1.60 (s, ν1/2 ) 10 Hz), -0.4 (vbr), -2.5 (vbr).
1H NMR (C7D8, 270 MHz, -80 °C) δ 13.6 (vbr), 8.5 (vbr), 6.1
(vbr), 3.8 (vbr), 3.09 (s, ν1/2 ) 10 Hz), -0.54 (br), -2.93 (br).
H, 7.95; P, 9.40. Found: C, 38.83; H, 7.80; P, 9.13. Magnetic
293K
susceptibility: XM
) 4.33 × 10-3 cgs; µeff ) 3.2 BM.
Ack n ow led gm en t . We thank the Deutsche For-
schungsgemeinschaft and the Stiftung Stipendien-
Fonds des Verbandes der Chemischen Industrie for
support of this research and the award of a DFG
fellowship to G.W.R. We also wish to thank Prof. H.
Schmidbaur for generous support of this project.
1
1H NMR (C4D8O, 400 MHz, 20 °C) δ 0.42 (s, ν1/2 ) 10 Hz). H
NMR (C4D8O, 400 MHz, 0 °C) δ 0.52 (s, ν1/2 ) 117 Hz). 1H
NMR (C4D8O, 400 MHz, -20 °C) δ 0.85 (br, ν1/2 ) 170 Hz),
0.28 (vbr). 1H NMR (C4D8O, 400 MHz, -40 °C) δ 1.18 (s, ν1/2
) 67 Hz), 0.06 (s, ν1/2 ) 84 Hz). 1H NMR (C4D8O, 400 MHz,
-60 °C) δ 1.60 (s, ν1/2 ) 25 Hz), 0.03 (s, ν1/2 ) 23 Hz). 1H NMR
(C4D8O, 400 MHz, -80 °C) δ 2.38 (s, ν1/2 ) 18 Hz), 0.03 (s, ν1/2
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, positional parameters, bond distances and angles, and
thermal parameters (11 pages). Ordering information is given
on any current masthead page.
OM950624R