Synthesis and Reactivity of Organosamarium Diarylpnictide Complexes: Cleavage Reactions of Group 15 E-E and E-C Bonds by Samarium(II)

Article abstract of DOI:10.1021/ic951627z

(C₅Me₅)₂Sm (2 equiv) reacts with Ph₂EEPh₂ to give (C₅Me₅)₂SmEPh2 (E: P, 1; As, 2), while (C₅Me₅)₂Sm(THF)₂ (2 equiv) reacts with Ph₂EEPh₂ to give (C₅Me₅)₂Sm(EPh₂)(THF) (E: P, 3; As, 4). 3 and 4 are also available from the reactions of 1 and 2 with THF. 3 and 4 undergo further reaction to produce the THF ring-opened products (C₅Me₅)₂Sm[O(CH₂) ₄EPh₂](THF) (E: P, 5; As, 6). (C₅Me₅)2Sm (4 equiv) reacts with Ph₂EEPh₂ to give the mixed-valent (C₅Me₅)₂Sm(μ-EPh2)Sm(C₅Me ₅)2 (E: P, 7; As, 8). These compounds are also available from the reaction of 1 and 2 with (C₅Me₅)₂Sm. The X-ray crystal structure of 2, crystallized from hexanes (P2_1/n; a = 26.188(24) A?, b = 9.911(10) A?, c = 23.280(23) A?, β = 97.150(12)°, V= 5995(2) A?³, D_calcd = 1.488 Mg/m₃; Z = 8; T = 156 K), revealed, in addition to a conventional seven-coordinate bent metallocene geometry with 2.698 A? Sm-C(C₅Me₅) and 2.970 A? Sm-As average distances, two very different Sm-As-C(Ph) angles, 74.2 and 118.7°. As a result, one phenyl group is closer to the metal (2.901 A? minimum Sm-C distance). 4, crystallized from toluene (P2_1/n; a = 10.713(9) A?, b = 14.143(11) A?, c = 21.620(16) A?, β= 101.08(6)°, V = 3215(4) A?3, D_calcd = 1.492 Mg/m³; Z = 4; 7= 163 K), and 6, crystallized from hexanes (P2_1/n; a = 9.3958(16) A?, b = 22.245(3) A?, c = 17.931(3) A?, β = 96.497(11)°, V= 3724(1) A?³, D_calcd = 1.416 Mg/m³; Z = 4; T= 163 K), have conventional eight-coordinate, bent metallocene structures.

Full text of DOI:10.1021/ic951627z

Inorg. Chem. 1996, 35, 4283-4291
4283
Synthesis and Reactivity of Organosamarium Diarylpnictide Complexes: Cleavage
Reactions of Group 15 E-E and E-C Bonds by Samarium(II)
William J. Evans,* John T. Leman, and Joseph W. Ziller
Department of Chemistry, University of California, Irvine, California 92717
Saeed I. Khan
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024
ReceiVed December 20, 1995X
(C5Me5)2Sm (2 equiv) reacts with Ph2EEPh2 to give (C5Me5)2SmEPh2 (E: P, 1; As, 2), while (C5Me5)2Sm(THF)2
(2 equiv) reacts with Ph2EEPh2 to give (C5Me5)2Sm(EPh2)(THF) (E: P, 3; As, 4). 3 and 4 are also available
from the reactions of 1 and 2 with THF. 3 and 4 undergo further reaction to produce the THF ring-opened
products (C5Me5)2Sm[O(CH2)4EPh2](THF) (E: P, 5; As, 6). (C5Me5)2Sm (4 equiv) reacts with Ph2EEPh2 to
give the mixed-valent (C5Me5)2Sm(µ-EPh2)Sm(C5Me5)2 (E: P, 7; As, 8). These compounds are also available
from the reaction of 1 and 2 with (C5Me5)2Sm. The X-ray crystal structure of 2, crystallized from hexanes
(P21/n; a ) 26.188(24) Å, b ) 9.911(10) Å, c ) 23.280(23) Å, â ) 97.150(12)°, V ) 5995(2) Å3, Dcalcd ) 1.488
Mg/m3; Z ) 8; T ) 156 K), revealed, in addition to a conventional seven-coordinate bent metallocene geometry
with 2.698 Å Sm-C(C5Me5) and 2.970 Å Sm-As average distances, two very different Sm-As-C(Ph) angles,
74.2 and 118.7°. As a result, one phenyl group is closer to the metal (2.901 Å minimum Sm-C distance). 4,
crystallized from toluene (P21/n; a ) 10.713(9) Å, b ) 14.143(11) Å, c ) 21.620(16) Å, â ) 101.08(6)°, V )
3215(4) Å3, Dcalcd ) 1.492 Mg/m3; Z ) 4; T ) 163 K), and 6, crystallized from hexanes (P21/n; a ) 9.3958(16)
Å, b ) 22.245(3) Å, c ) 17.931(3) Å, â ) 96.497(11)°, V ) 3724(1) Å3, Dcalcd ) 1.416 Mg/m3; Z ) 4; T ) 163
K), have conventional eight-coordinate, bent metallocene structures.
Introduction
phorus and arsenic analogs is described as well as reactions of
a series of alternative phenylbismuth precursors which were
studied to learn more about reaction 1. These studies have
revealed an unusual mixed-valent phosphorus compound and a
system in which the stepwise coordination and ring opening of
THF by an AsPh2 unit can be documented.
Recent studies of the chemistry of the bent metallocene
(C5Me5)2Sm1 with inorganic substrates including N2,2 BiPh3,3
SbnBu3,4 and elemental S, Se, and Te5,6 have revealed that this
organometallic reagent offers opportunities to isolate and
crystallographically characterize new and rare types of main
group element compositions and structures. Hence, planar M2N2
and M2Bi2 units have been discovered in [(C5Me5)2Sm]2(µ-η2:
η2-N2)2 and [(C5Me5)2Sm]2(µ-η2:η2-Bi2),3 the (Sb3)2- 4 and
(Se3)4- 6 ions have been structurally characterized for the first
Experimental Section
All manipulations described below employing (C5Me5)2Sm and
workup of subsequent reaction products were carried out under argon
in an inert-atmosphere glovebox free of coordinating solvents. All other
chemistry was performed under nitrogen with rigorous exclusion of
air and water by using Schlenk, vacuum-line, and glovebox techniques.
Physical measurements were obtained, solvents were purified, and
time, and facile routes to the relatively rare group 16 ions (S3)2-
(Se3)2-, and (Te3)2- have been found.5
,
In this study, we examine the generality of the reactions which
formed the (Bi2)2- and (Sb3)3- ions in eqs 1 and 2. The
7
(C5Me5)2Sm1 and (C5Me5)2Sm(THF)2 were prepared as previously
described.8 Ph2PPPh2,9 Ph2AsAsPh2,10 Ph2SbSbPh2,11 and Ph2BiBiPh2,12
were prepared by literature procedures. Ph2BiCl was prepared by ligand
redistribution between Ph3Bi and BiCl3 in a 2:1 molar ratio in refluxing
toluene. Ph2PH and Ph2PCl (Aldrich) employed in the synthesis of
Ph2PPPh2 were distilled under vacuum before use. BiCl3 was used as
received. Ph3P, Ph3As, Ph3Sb, and Ph3Bi were recrystallized from
absolute ethanol and dried under high vacuum.
(C5Me5)2Sm(THF)x/Ph3E Reactions (x ) 0, 2; E ) P, As, Sb,
Bi). The following general procedure was used to screen (C5Me5)2Sm
and (C5Me5)2Sm(THF)2 for reactivity toward the triphenylpnictides. A
2(C5Me5)2Sm + Ph3Bi f [(C5Me5)2Sm]2(µ-η2:η2-Bi2) (1)
3(C5Me5)2Sm + 3nBu3Sb f
[(C5Me5)2Sm]3(µ-η2:η2:η1-Sb3)(THF) (2)
chemistry of (C5Me5)2Sm and (C5Me5)2Sm(THF)2 with phos-
X Abstract published in AdVance ACS Abstracts, May 15, 1996.
(1) (a) Evans, W. J.; Hughes, L. A.; Hanusa, T. P. J. Am. Chem. Soc.
1984, 106, 4270. (b) Evans, W. J.; Hughes, L. A.; Hanusa, T. P.
Organometallics 1986, 5, 1285.
(2) Evans, W. J.; Ulibarri, T. A.; Ziller, J. W. J. Am. Chem. Soc. 1988,
110, 6877.
(3) Evans, W. J.; Gonzales, S. L.; Ziller, J. W. J. Am. Chem. Soc. 1991,
113, 9880.
(4) Evans, W. J.; Gonzales, S. L.; Ziller, J. W. J. Chem. Soc., Chem.
Commun. 1992, 1138.
(7) Evans, W. J.; Grate, J. W.; Choi, H. W.; Bloom, I.; Hunter, W. E.;
Atwood, J. L. J. Am. Chem. Soc. 1985, 107, 941.
(8) Evans, W. J.; Chamberlain, L. R.; Ulibarri, T. A.; Ziller, J. W. J. Am.
Chem. Soc. 1988, 110, 6423.
(9) Kuchen, W.; Buchwald, H. Chem. Ber. 1958, 91, 2871.
(10) Busse, P. J.; Irgolic, K. J.; Dominguez, R. J. G. J. Organomet. Chem.
1974, 81, 45.
(5) Evans, W. J.; Rabe, G. W.; Ziller, J. W. Inorg. Chem. 1994, 33, 2719.
(6) Evans, W. J.; Rabe, G. W.; Ziller, J. W.; Ansari, M. A. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 210.
(11) Hewertson, W.; Watson, H. R. J. Chem. Soc. 1962, 1490.
(12) Calderazzo, F.; Morvillo, A.; Pelizzi, G.; Poli, R. J. Chem. Soc., Chem.
Commun. 1983, 507.
S0020-1669(95)01627-2 CCC: $12.00 © 1996 American Chemical Society

4284 Inorganic Chemistry, Vol. 35, No. 15, 1996
Evans et al.
small quantity (5-10 mg) of Ph3E dissolved in 0.5 mL of C6D6 was
treated dropwise with a solution of 2 equiv of the metallocene in an
equal volume of the same solvent. The reaction mixtures were
homogeneous in all cases. Aliquots were withdrawn and flame-sealed
at atmospheric pressure in 5 mm NMR tubes.
cycles on a high-vacuum line, left under vacuum, and placed in an oil
bath at 65 °C. After 60 h, the solution had changed from its initial
dark brown color to yellow. The THF was removed under vacuum,
and the resultant yellow oil was taken up in hexane (1 mL), centrifuged
to remove a small amount of insolubles, and then cooled to -40° C.
Yellow crystals of 5 (178 mg, 70%) were isolated by decantation from
the mother liquor followed by vacuum-drying. Anal. Calcd for
C40H56SmPO2: C, 64.04; H, 7.52; Sm, 20.04. Found: C, 55.77; H,
6.73; Sm, 21.28. 1H NMR (C6D6, 300 MHz, 25 °C): δ 7.61 (“t”, J )
6.9 Hz, 4H, Ph o-H), 7.10 (mult, 4H, Ph m-H), 7.04 (mult, 2H, Ph
(C5Me5)2Sm(PPh2), 1. A solution of (C5Me5)2Sm (100.5 mg, 0.239
mmol) in toluene (3 mL) was added dropwise to a stirred solution of
Ph2PPPh2 (44.1 mg, 0.119 mmol) in toluene (3 mL). The deep-green
color of the (C5Me5)2Sm solution was quenched immediately to a pale
brown color which increased in intensity as the addition progressed.
After 15 min of stirring, the solvent was removed in vacuo to give a
dark brown oil, which was triturated with hexanes (1 mL). The resultant
brown solid was dried under vacuum to give pure 1 (132 mg, 90%).
Anal. Calcd for C32H40SmP: C, 63.42; H, 6.65; Sm, 24.81; P, 5.11.
Found: C, 63.20; H, 6.77; Sm, 25.10; P, 5.22. Isopiestic molecular
weight (0.057 M in C6H6): calcd for C32H40SmP, 606; found, 560. 1H
NMR (C6D6, 300 MHz, 25 °C): δ 5.82 (t, J ) 7.3 Hz, 2H, Ph p-H),
4.54 (br “t”, ∆ν1/2 ) 10 Hz, 4H, Ph m-H), 3.43 (br d, ∆ν1/2 ) 20 Hz,
4H, Ph o-H), 0.54 (s, 30H, C5Me5). 13C NMR (C6D6, 25 °C): δ 155.5,
p-H), 5.50 (br mult, ∆ν1/2 ) 17 Hz, 2H, CH2), 4.05 (br mult, ∆ν1/2
)
22 Hz, 2H, CH2), 2.77 (br mult, ∆ν1/2 ) 14 Hz, 4H, CH2), 1.40 (s,
30H, C5Me5), -2.29 (br s, ∆ν1/2 ) 60 Hz, 4H, THF), -3.59 (br s,
∆ν1/2 ) 140 Hz, 4H, THF). 13C NMR (C6D6, 25 °C): δ 140.2 (d,
JP-C ) 15 Hz, C6H5), 133.5 (C6H5), 133.3 (d, JP-C ) 18 Hz, C6H5),
128.6 (mult, C6H5), 113.5 (C5Me5), 74.0 [O(CH2)4PPh2], 60.8 (br, R-C,
THF), 37.8 (d, JP-C ) 12 Hz, [O(CH2)4PPh2]), 29.6 (d, JP-C ) 12 Hz,
[O(CH2)4PPh2]), 24.8 (d, JP-C ) 16 Hz, [O(CH2)4PPh2]), 19.4 (br, â-C,
293K
THF), 17.9 (C5Me5). Magnetic susceptibility: øM
cgsu; µeff ) 1.1 µB.
) 537 × 10-6
120.5, 118.1 (C6H5), 118.7 (C5Me5), 19.6 (C5Me5). Magnetic
293K
susceptibility: øM
) 425 × 10-6 cgsu; µeff ) 1.0 µB.
(C5Me5)2Sm[O(CH2)4AsPh2](THF), 6. A solution of 4, prepared
as above from (C5Me5)2Sm(THF)2 (75.4 mg, 0.133 mmol) and
Ph2AsAsPh2 (30.5 mg, 0.067 mmol) in THF (5 mL) was placed in a
50 mL, thick-walled glass reaction tube equipped with a Teflon high-
vacuum stopcock. The solution was degassed by three freeze-pump-
thaw cycles on a high-vacuum line, left under vacuum, and placed in
an oil bath at 65 °C. After 20 h, the solution had undergone a change
from its initial dark brown color to yellow, which was similar to that
seen for the conversion of 3 to 5 above. The THF was removed under
vacuum, and the resultant yellow oil was taken up in hexane (1 mL),
centrifuged to remove a small amount of insolubles, and then cooled
to -40 °C. Yellow crystals of 6 (83 mg, 79%) were isolated by
decantation from the mother liquor, followed by vacuum-drying.
Crystals for the X-ray diffraction study were grown from a dilute
solution of 4 in hexane over an extended period of time. Anal. Calcd
for C40H56SmAsO2: C, 60.50; H, 7.11; Sm, 18.93. Found: C, 58.63;
H, 7.10; Sm, 18.88. 1H NMR (C6D6, 300 MHz, 25 °C): δ 7.61 (d, J
) 7.0 Hz, 4H, Ph o-H), 7.11 (“t”, J ) 7.8 Hz, 4H, Ph m-H), 7.04 (t,
J ) 7.1 Hz, 2H, Ph p-H), 5.51 (br mult, ∆ν1/2 ) 15 Hz, 2H, CH2),
4.05 (br mult, ∆ν1/2 ) 15 Hz, 2H, CH2), 2.77 (br mult, ∆ν1/2 ) 15 Hz,
2H, CH2), 2.75 (broad mult, ∆ν1/2 ) 15 Hz, 2H, CH2), 1.40 (s, 30H,
(C5Me5)2Sm(AsPh2), 2. As described above for 1, (C5Me5)2Sm (96.5
mg, 0.229 mmol) and Ph2AsAsPh2 (52.5 mg, 0.114 mmol) were
combined in toluene (5 mL). Removal of the solvent under vacuum
gave a brown powder which was pure by 1H NMR spectroscopy.
Cooling a warm saturated hexane solution to -36 °C gave dark brown
plates of 2 (92 mg, 65%) suitable for X-ray crystallography. Anal.
Calcd for C32H40SmAs: C, 59.14; H, 6.20; Sm, 23.13; As, 11.53.
Found: C, 58.91; H, 6.17; Sm, 23.40; As, 11.35. Isopiestic molecular
weight (0.038 M in C6H6): calcd for C32H40SmAs, 650; found, 624.
1H NMR (C6D6, 300 MHz, 25 °C): δ 5.84 (t, J ) 7.3 Hz, 2H, Ph
p-H), 4.68 (br “t”, ∆ν1/2 ) 18 Hz, 4H, Ph m-H), 3.75 (br d, ∆ν1/2 ) 18
Hz, 4H, Ph o-H), 0.53 (s, 30H, C5Me5). 13C NMR (C6D6, 25 °C): δ
157.1, 134.8, 122.1, 121.8 (C6H5), 118.7 (C5Me5), 19.4 (C5Me5).
293K
Magnetic susceptibility: øM
) 437 × 10-6 cgsu; µeff ) 1.0 µB.
(C5Me5)2Sm(PPh2)(THF), 3. As described above for 1, (C5Me5)2-
Sm(THF)2 (173.6 mg, 0.307 mmol) and Ph2PPPh2 (56.8 mg, 0.153
mmol) were combined in toluene (5 mL). A dark brown color
developed immediately, and after 15 min the solvent was removed under
vacuum to give a brown oil. Trituration with hexanes (2 mL), removal
of the solvent via pipet, and vacuum-drying gave a green-brown solid,
3 (218 mg, 95%). Anal. Calcd for C36H48SmOP: Sm, 22.17. Found:
Sm, 21.7. 1H NMR (C6D6 + 1 equiv of THF,13 300 MHz, 25 °C): δ
6.94 (t, J ) 7.4 Hz, 2H, Ph p-H), 6.59 (“t”, J ) 7.2 Hz, 4H, Ph m-H),
5.82 (d, J ) 7.2 Hz, 4H, Ph o-H), 1.20 (s, 30H, C5Me5). 13C NMR
(C6D6, 25 °C): δ 148.4, 133.2 (d, JP-C ) 22 Hz), 128.2, 121.8 (C6H5),
C5Me5), -2.38 (br s, ∆ν1/2 ) 40 Hz, 4H, THF), -3.66 (br s, ∆ν1/2
)
75 Hz, 4H, THF). 13C NMR (C6D6, 25 °C): δ 141.8, 133.5, 131.6,
128.8 (C6H5), 113.5 (C5Me5), 74.0 [O(CH2)4AsPh2], 61.3 (br, R-C,
THF), 38.3, 29.5, 25.2 [O(CH2)4AsPh2], 19.8 (br, â-C, THF), 17.9
293K
(C5Me5). Magnetic susceptibility: øM
0.95 µB.
) 379 × 10-6 cgsu; µeff
)
117.1 (C5Me5), 65.7 (br, R-C, THF), 21.4 (br, â-C, THF), 18.5 (C5Me5).
293K
) 419 × 10-6 cgsu; µeff ) 1.0 µB.
(C5Me5)2Sm(µ-PPh2)Sm(C5Me5)2, 7. A solution of Ph2PPPh2 (23.7
mg, 0.064 mmol) in toluene (3 mL) was treated with a solution of
(C5Me5)2Sm (107.9 mg, 0.256 mmol) in toluene (3 mL) and isolated
as for 1 above. Anal. Calcd for C52H70Sm2P: C, 60.82; H, 6.87; Sm,
29.29; P, 3.02. Found: C, 60.45; H, 6.72; Sm, 29.65; P, 3.24. 1H
NMR (C6D6, 300 MHz, 25 °C, concentration dependent, 5.6 mM): δ
6.13 (t, J ) 7.1 Hz, 1H, Ph p-H), 5.20 (br mult, ∆ν1/2 ) 20 Hz, 2H, Ph
m-H), 3.73 (br mult, ∆ν1/2 ) 20 Hz, 2H, Ph o-H), 0.80 (s, 30H, C5Me5).
13C NMR (C6D6, 25 °C): δ 180.6, 133.3, 128.5, 121.0 (C6H5), 57.8
(C5Me5), 17.3 (C5Me5). Magnetic susceptibility: øM293K ) 2560 × 10-6
cgsu; µeff ) 2.45 µB.
Magnetic susceptibility: øM
(C5Me5)2Sm(AsPh2)(THF), 4. (C5Me5)2Sm(THF)2 (143.5 mg, 0.254
mmol) and Ph2AsAsPh2 (58.2 mg, 0.127 mmol) were combined in
toluene (5 mL) as described for 3. Trituration with hexanes (2 mL),
removal of the solvent, and vacuum-drying gave a green-brown solid,
4 (140 mg, 77%). Anal. Calcd for C36H48SmAsO: Sm, 20.82.
Found: Sm, 20.20. 1H NMR (C6D6 + 1 equiv THF,14 300 MHz, 25
°C): δ 6.92 (t, J ) 7.2 Hz, 2H, Ph p-H), 6.57 (“t”, J ) 7.4 Hz, 4H, Ph
m-H), 5.64 (d, J ) 7.4 Hz, 4H, Ph o-H), 1.22 (s, 30H, C5Me5). 13C
NMR (C6D6, 25 °C): δ 149.4, 131.2, 127.8, 122.7 (C6H5), 117.2
(C5Me5), 65.4 (br, R-C, THF), 21.3 (br, â-C, THF), 18.3 (C5Me5).
293K
Magnetic susceptibility: øM
) 354 × 10-6 cgsu; µeff ) 0.9 µB.
Isolated 1 (39.0 mg, 0.065 mmol) was reacted in a similar fashion
1
with (C5Me5)2Sm (28.7 mg, 0.068 mmol) in toluene (3 mL). The H
(C5Me5)2Sm[O(CH2)4PPh2](THF), 5. A solution of 3, prepared as
above from (C5Me5)2Sm(THF)2 (190 mg, 0.34 mmol) and Ph2PPPh2
(62.1 mg, 0.17 mmol) in THF (5 mL) was placed in a 50 mL, thick-
walled glass reaction tube equipped with a Teflon high-vacuum
stopcock. The solution was degassed by three freeze-pump-thaw
NMR spectrum of the resulting brown solid corresponded closely to
that for (C5Me5)2Sm(µ-PPh2)Sm(C5Me5)2 above. 1H NMR (C6D6, 300
MHz, 25 °C, concentration dependent, 5.6 mM): δ 6.11 (t, 1H, Ph
p-H), 5.15 (br “t”, 2H, Ph m-H), 3.70 (br d, 2H, Ph o-H), 0.79 (s, 30H,
C5Me5).
(C5Me5)2Sm(µ-AsPh2)Sm(C5Me5)2, 8. Ph2AsAsPh2 (5.0 mg, 0.011
mmol) and (C5Me5)2Sm (18.4 mg, 0.044 mmol) were combined in C6D6
(1.20 mL), and the NMR spectrum was measured immediately. 1H
NMR (C6D6, 300 MHz, 25 °C, concentration dependent, 18 mM): δ
8.40 (br s, ∆ν1/2 ) 30 Hz, 2H, C6H5), 7.68 (s, ∆ν1/2 ) 20 Hz, 1H, Ph
p-H), 5.49 (br s, ∆ν1/2 ) 30 Hz, 2H, C6H5), 1.00 (s, 30H, C5Me5).
Isolated 2 (13.5 mg, 0.021 mmol) and (C5Me5)2Sm (8.9 mg, 0.021
(13) In the absence of additional THF, the NMR spectrum of 3 is highly
dependent on the extent of drying of the compound and the amount
of THF present. Chemical shifts are observed in the following
ranges: 6.71-6.94 (Ph p-H), 6.16-6.59 (Ph m-H), 5.33-5.82 (Ph
o-H), and 1.08-1.20 (C5Me5) ppm.
(14) Compound 4 is like 3.13 Chemical shifts are observed in the following
ranges: 6.81-6.92 (Ph p-H), 6.37-6.57 (Ph m-H), 5.44-5.64 (Ph
o-H), and 1.15-1.22 (C5Me5) ppm.

Organosamarium Diarylpnictide Complexes
Inorganic Chemistry, Vol. 35, No. 15, 1996 4285
Table 1. Crystal Data and Experimental Details for the X-ray Diffraction Studies of 2, 4, and 6
(C5Me5)2SmAsPh2‚1/4C6H14 (2‚1/4C6H14)
(C5Me5)2SmAsPh2(THF) (4)
(C5Me5)2SmO(CH2)4AsPh2(THF) (6)
empirical formula
fw
temp (K)
crystal system
space group
a (Å)
b (Å)
c (Å)
â (deg)
V (Å3)
C32H40SmAs‚1/4C6H14
C36H48SmAsO
722.0
163
monoclinic
P21/n
10.713(9)
14.143(11)
21.620(16)
101.08(6)
3215(4)
4
C40H56SmAsO2
794.1
163
monoclinic
P21/n
9.3958(16)
22.245(3)
17.931(3)
671.45
156
monoclinic
P21/n
26.188(24)
9.911(10)
23.280(23)
97.150(12)
5995(2)
96.497(11)
3724(1)
4
Z
D
8
calcd (Mg/m3)
1.488
1.429
1.416
diffractometer
radiation (λ (Å))
scan type
Picker (Crystal Logic)
Siemens P3
Mo KR (0.710 730)
ω
Siemens P3
Mo KR (0.710 730)
Mo KR (0.710 730)
θ-2θ
θ-2θ
2θ range (deg)
µ(Mo KR) (mm-1
abs cor
1.0-45.0
4.0-40.0
4.0-45.0
)
3.080
2.874
none
0.080
0.103
2.490
semiempirical (ψ-scan method)
0.068
0.076
semiempirical (ψ-scan method)
0.045
0.047
a
RF
a
RwF
2
a RF ) ∑||Fo| - |Fc||/∑|Fo|; RwF ) ∑w(|Fo| - |Fc|)2/∑w|Fo| .
mmol) were combined in C6D6 (1.13 mL) and analyzed immediately.
The 1H NMR spectrum of the resulting brown solution was nearly
identical to that of (C5Me5)2Sm(µ-AsPh2)Sm(C5Me5)2 above. 1H NMR
(C6D6, 300 MHz, 25 °C, concentration dependent, 19 mM): δ 8.47
(br s, ∆ν1/2 ) 30 Hz, 2H, C6H5), 7.71 (br s, ∆ν1/2 ) 20 Hz, 1H, Ph
p-H), 5.53 (br s, ∆ν1/2 ) 30 Hz, 2H, C6H5), 0.99 (s, 30H, C5Me5).
Reaction of (C5Me5)2Sm(µ-PPh2)Sm(C5Me5)2, 7, with Ph2PPPh2.
Ph2PPPh2 (0.8 mg, 0.002 mmol) and (C5Me5)2Sm(µ-PPh2)Sm(C5Me5)2
(3.9 mg, 0.004 mmol) were combined in C6D6 (≈0.5 mL) and allowed
to react for 5 min, producing a dark brown solution. The solution was
examined by 1H NMR spectroscopy, which showed complete reaction
to form (C5Me5)2SmPPh2, 1.
X-ray Data Collection, Structure Determination, and Refinement
for 2. A deep red, irregularly-shaped crystal of 2 of approximate
dimensions 0.30 × 0.26 × 0.20 mm was coated with Paratone oil,
mounted on the tip of a glass fiber, and transferred to the 156 K nitrogen
cold stream of a modified four-circle Picker diffractometer equipped
with a monochromatized Mo X-ray source. Accurate cell dimensions
and the crystal orientation matrix were determined by a least-squares
fit of the setting angles of 20 reflections in the range 12 < 2θ < 20°.
Intensity data were collected by the θ-2θ method using a scan speed
of 3.0°/min up to a maximum 2θ ) 45°. Three intense reflections
were monitored after every 97 reflections collected and showed no
significant variation. The intensities of 7856 reflections were measured,
of which 4109 had |Fo| > 6.0σ(|Fo|) and were considered observed.
Data were corrected for Lorentz and polarization effects, and an
X-ray Data Collection, Structure Determination, and Refinement
for 4 and 6. A dark orange crystal of 4 of approximate dimensions
0.17 × 0.20 × 0.38 mm was oil-mounted17 on a glass fiber and
transferred to a Siemens P3 diffractometer. The determinations of Laue
symmetry, crystal class, unit cell parameters, and the crystal’s orienta-
tion matrix were carried out by previously described methods similar
to those of Churchill.18 Intensity data were collected at 163 K using
an ω-scan technique with Mo KR radiation under the conditions
described in Table 1. All 3393 data were corrected for Lorentz and
polarization effects and were placed on an approximately absolute scale.
Any reflection with I(net) < 0 was assigned the value |Fo| ) 0. The
diffraction symmetry was 2/m with systematic absences 0k0 for k )
2n + 1 and h0l for h + l ) 2n + 1. The centrosymmetric monoclinic
space group P21/n [C5 ; No. 14] is therefore uniquely defined.
2h
All crystallographic calculations were carried out using either our
locally modified version of the UCLA Crystallographic Computing
Package15 or the SHELXTL PLUS program set.19 The analytical
scattering factors for neutral atoms were used throughout the analysis20
both the real (∆f ′) and imaginary (i∆f ′′) components of anomalous
dispersion were included. The quantity minimized during least-squares
analysis was ∑w(|Fo| - |Fc|)2 where w-1 ) σ2(|Fo|) + 0.0020(|Fo|)2.
The structure was solved by direct methods and refined by full-
matrix least-squares techniques. Hydrogen atoms were included using
a riding model with d(C-H) ) 0.96 Å and U(iso) ) 0.08 Å2.
Refinement of positional and thermal parameters led to convergence
with RF ) 8.0%, RwF ) 10.3%, and GOF ) 1.61 for 167 variables
refined against those 2232 data with |Fo| > 4.0σ(|Fo|). A final
difference-Fourier map was devoid of significant features; F(max) )
2.10 e Å-3. The crystal decomposed after data were collected to a
2θ(max) of 40.0°. It was therefore not possible to apply an absorption
correction since our standard practice is to measure ψ scans at the
conclusion of data collection.
empirical absorption correction based on ψ-scans was applied.
A
summary of crystallographic data is included in Table 1.
The structure was solved by Patterson methods and expanded by
Fourier techniques in the monoclinic space group P21/n.15 Hydrogen
atoms were included in calculated positions and were constrained to
ride upon the appropriate carbon atoms. For methyl groups, at least
one of the hydrogen atoms was located from the difference-Fourier
map. A disordered solvent molecule, presumably n-hexane, was located
close to the inversion center, but could not be refined satisfactorily.
The three strongest peaks from the difference map were arbitrarily
assigned as carbon atoms and were not refined. A total of 293
parameters with Sm and As anisotropic and all other non-hydrogens
atoms isotropic were refined using full-matrix least-squares techniques.
Refinement converged at RF ) 6.8%, RwF ) 7.6%. An anomalous
dispersion correction was applied to all non-hydrogen atoms.16 The
final difference electron density map showed some residual electron
density (F(max) ) 2.45 e Å-3) close to the disordered solvent molecule;
the rest of the map was featureless.
A pale yellow crystal of 6 of approximate dimensions 0.13 × 0.33
× 0.36 mm was handled as described above for 4. Intensity data were
collected at 163 K. Details appear in Table 1. All 5410 data were
(17) The crystal was immersed in a lube-oil additive, which allowed for
manipulation on the bench top and prevented decomposition due to
air or moisture. The crystal was secured to a glass fiber (the oil acts
as the adhesive) which was attached to an elongated brass mounting
pin. Further details appear in: Hope, H. Experimental Organometallic
Chemistry: A Practicum in Synthesis and Characterization; Wayda,
A. L., Darensbourg, M. Y., Eds.; ACS Symposium Series 357;
American Chemical Society: Washington, DC, 1987.
(18) Churchill, M. R.; Lashewycz, R. A.; Rotella, F. J. Inorg. Chem. 1977,
16, 265.
(15) UCLA Crystallographic Computing Package, University of California,
Los Angeles, 1981; C. Strouse, personal communication.
(16) International Tables for X-Ray Crystallography; Kynoch: Birming-
ham, England, 1974; Vol. IV.
(19) Sheldrick, G. SHELXTL PLUS program set; Siemens Analytical X-Ray
Instruments, Inc.: Madison, WI, 1990.
(20) International Tables for X-Ray Crystallography; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1992; Vol. C.

4286 Inorganic Chemistry, Vol. 35, No. 15, 1996
Evans et al.
corrected for absorption and for Lorentz and polarization effects and
placed on an approximately absolute scale. The diffraction symmetry
was 2/m with systematic absences 0k0 for k ) 2n + 1 and h0l for h +
l ) 2n + 1. The centrosymmetric monoclinic space group P21/n
[C52h; No. 14] is therefore uniquely defined. All crystallographic
calculations were carried out as described above for 4. The quantity
minimized during least-squares analysis was Σw(|Fo| - |Fc|)2 where
w-1 ) σ2(|Fo|) + 0.0004(|Fo|)2.
No evidence for a stable 1:1 acid base adduct, (C5Me5)2Sm-
(EPh3), was found in reactions of (C5Me5)2Sm with Ph3Sb and
Ph3Bi, however. Instead, E-C cleavage reactions occur. In
the bismuth case, the reaction is immediate and [(C5Me5)2Sm]2-
(µ-η2:η2-Bi2) and (C5Me5)2SmPh are formed. For Sb, the
reaction is slower. The C5Me5 resonance of the starting material
disappears over a 1-2 day period, and (C5Me5)2SmPh can be
1
identified by H NMR in the product mixture obtained. No
The structure was solved by direct methods and refined by full-
matrix least-squares techniques. Hydrogen atoms were included using
a riding model with d(C-H) ) 0.96 Å and U(iso) ) 0.08 Å2.
Refinement of positional and thermal parameters led to convergence
with RF ) 4.5%, RwF ) 4.7%, and GOF ) 1.42 for 397 variables refined
against those 4053 data with |Fo| > 3.0σ(|Fo|). A final difference-
clear evidence for products such as [(C5Me5)2Sm]3(µ-η2:η2:η1-
Sb3)(THF) or [(C5Me5)2Sm]2(µ-η2:η2-Sb2) was found. Ph3Bi
also reacts with (C5Me5)2Sm(THF)2 to give (C5Me5)2SmPh-
(THF), but no other organosamarium products were identifiable.
As previously reported,3 the reaction of 2 equiv of (C5Me5)2-
Sm with 1 equiv of Ph3Bi forms [(C5Me5)2Sm]2(µ-η2:η2-Bi2)
and (C5Me5)2SmPh. Further investigation of this reaction shows
that not all of the Ph3Bi is consumed with this stoichiometry
and the complicated mixture of products formed in the 2:1
reaction can be avoided if a 4:1 Sm:Bi ratio is used. As shown
in eq 3, a 4:1 ratio leads to complete consumption of both
Fourier map yielded F(max) ) 0.81 e Å-3
.
Results and Discussion
Reactions of (C5Me5)2Sm(THF)x with Ph3E (x ) 0, 2; E
) P, As, Sb, Bi). The reactivity of (C5Me5)2Sm and (C5Me5)2-
Sm(THF)2 with the group 15 triphenyl compounds, Ph3E, was
surveyed as shown in Table 2. Each system was periodically
monitored by NMR until no further changes in the spectrum
occurred. As expected, (C5Me5)2Sm is more reactive than
(C5Me5)2Sm(THF)2 and cleavage of the E-C bonds is more
facile for the heavier congeners in group 15.
8(C5Me5)2Sm + 2 Ph3Bi f
[(C5Me5)2Sm]2(µ-η2:η2-Bi2) + 6(C5Me5)2SmPh (3)
reactants and clean formation of only [(C5Me5)2Sm]2(µ-η2:η2-
Bi2) and (C5Me5)2SmPh.
Table 2. Summary of Reactivity of (C5Me5)2Sm(THF)x with
Cleavage of E-C bonds has previously been observed with
group 15 compounds in reactions with alkali metals. For
example, Gilman et al.28 established that alkali metals in liquid
ammonia or THF easily cleave the E-C bond in Ph3E
compounds as shown in eq 4. When reactions with excess alkali
Triphenylpnictides
compd
Ph3P
Ph3As
Ph3Sb
Ph3Bi
(C5Me5)2Sm adduct formn no reacn E-C cleavage E-C cleavage
(C5Me5)2Sm- no reacn
(THF)2
no reacn no reacn
E-C cleavage
2M + Ph3E NH (l)8 MPh + MEPh2
(4)
3
In the experiments with (C5Me5)2Sm(THF)2 and Ph3P, Ph3As,
and Ph3Sb, no significant perturbation of the Ph3E resonances
from their positions in the free ligands was observed and the
low-field resonance characteristic for coordinated THF re-
mained.21 Apparently, none of these group 15 triphenyl
complexes are sufficiently Lewis basic to displace the THF. In
contrast, addition of base-free (C5Me5)2Sm to Ph3P causes the
multiplets in free Ph3P at 7.38 and 7.03 ppm (2:3 ratio) to change
to a series of triplet-like peaks at 7.80, 7.20, and 7.07 ppm in
a ratio of 2:2:1. Selective homonuclear spin-decoupling experi-
ments confirmed these peaks as arising from the o-, m-, and
p-protons, respectively. Coordination of the phosphine perturbs
the o-H resonances the most and removes the near-degeneracy
in chemical shift of the m-and p-protons in the free ligand.
In order to probe the stoichiometry of this system, portions
of (C5Me5)2Sm were added to a solution of Ph3P up to the 2:1
ratio employed above. No further change in the NMR spectrum
of the system occurred after the Sm:P ratio exceeded unity,
which indicates formation of a 1:1 metal-ligand complex.
Similar shifts were not observed between (C5Me5)2Sm and
Ph3As. Formation of a phosphine complex of the very elec-
trophilic (C5Me5)2Sm2,22 is not unexpected, given the crystal-
lographically established structures of both divalent and trivalent
lanthanide phosphine complexes such as Yb[N(SiMe3)2]2(Me2-
PCH2CH2PMe2),23 (C5Me5)2YbCl(Me2PCH2PMe2),24 La[TeSi-
(SiMe3)3]3(Me2PCH2CH2PMe2)2,25 (MeC5H4)3Ce(PMe3),26 and
Nd[OCH(PMe2)CH(t-C4H9)2]3.27
M ) Li, Na, K; E ) P, As, Sb
metal in liquid ammonia were quenched with NH4Cl, the
products were Ph2EH and benzene for P, As, and Sb.29 The
corresponding reduction of Ph3Bi was different, however, in
that only benzene (3 equiv) was observed.
E-C cleavage in reactions of (C5Me5)2Sm(THF)2 and
(C5Me5)2Sm with Ph3E is therefore reasonable, since parallels
between the reactions of alkali metals and these bent metallo-
cenes have been previously noted in reactions with substrates
as diverse as CO30 and anthracene.31 The (C5Me5)2Sm(THF)x
reagents differ from alkali metals, however, because they are
more soluble and the presence of (C5Me5)2Sm units allows for
the assembly and isolation of reduced products either not
accessible or unstable with alkali metals. Hence, [(C5Me5)2-
Sm]2(µ-η2:η2-Bi2), rather than metallic bismuth or insoluble,
uncharacterized alkali metal bismuthides, is isolated in reaction
1. Since Bi-C bonds are the weakest in the EPh3 series,32 it is
reasonable that Ph3Bi is the most likely to undergo E-C
cleavage and form polyelement anions (Zintl ions).
Reactions of (C5Me5)2Sm with Ph2PPPh2 and
Ph2AsAsPh2: Formation of (C5Me5)2Sm(EPh2) (E ) P, As).
Since the Ph3E compounds of the lighter congeners in group
15 did not undergo E-C cleavage to form homopolyatomic
anions, other precursors to these anions were sought. The
(21) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. Organometallics
1985, 4, 112.
(22) Evans, W. J. Polyhedron 1987, 6, 803.
(23) Tilley, T. D.; Andersen, R. A.; Zalkin, A. J. Am. Chem. Soc. 1982,
104, 3725.
(24) Tilley, T. D.; Andersen, R. A.; Zalkin, A. Inorg. Chem. 1983, 22,
856.
(25) Cary, D. R.; Arnold, J. J. Am. Chem. Soc. 1993, 115, 2520.
(26) Stults, S.; Zalkin, A. Acta Crystallogr., Sect. C 1987, 43, 430.
(27) Hitchcock, P. B.; Lappert, M. F.; MacKinnon, I. A. J. Chem. Soc.,
Chem. Commun. 1988, 1557.
(28) Gilman, H.; Wittenberg, D. J. Org. Chem. 1958, 23, 1063.
(29) Rossi, R. A.; Bunnett, J. F. J. Am. Chem. Soc. 1974, 96, 112.
(30) Evans, W. J.; Grate, J. W.; Hughes, L. A.; Zhang, H.; Atwood, J. L.
J. Am. Chem. Soc. 1985, 107, 3728.
(31) Evans, W. J.; Gonzales, S. L.; Ziller, J. W. J. Am. Chem. Soc. 1994,
116, 2600.
(32) Steele, W. V. J. Chem. Thermodyn. 1979, 11, 187.

Organosamarium Diarylpnictide Complexes
Inorganic Chemistry, Vol. 35, No. 15, 1996 4287
Ph2EEPh2 compounds were attractive, since they contained one
less E-C(phenyl) bond compared to Ph3E. The availability of
Ph2EEPh2 for E ) P, As, Sb, and Bi also allows for a
comparison of reactivity in a homologous series, as was done
for Ph3E.
(E ) P, As). Both 1 and 2 react immediately with THF to
form donor-acceptor adducts which are spectroscopically
identical to the products obtained when reaction 5 is repeated
using (C5Me5)2Sm(THF)2 as shown in eq 6. This reaction can
(C5Me5)2Sm (2 equiv) reacts quickly and quantitatively with
Ph2PPPh2 and Ph2AsAsPh2 to give the Sm(III) phosphide and
arsenide compounds 1 and 2, respectively, as shown in eq 5.
2(C5Me5)2Sm(THF)2 + Ph2EEPh2 f
2(C5Me5)2Sm(EPh2)(THF)
(6)
E: P, 3; As, 4
2(C Me ) Sm(EPh )
2(C5Me5)2Sm + Ph2EEPh2 f
(5)
5
5 2
2
be conducted equally well in either THF or nonpolar solvents
such as hexane, benzene, and toluene. However, in light of
the further reactivity of 3 and 4 with THF (see below), the
nonpolar solvents are preferred. Both 3 and 4 are obtained as
dark green-brown powders which have lower solubility in
common organic solvents than their THF-free analogs. The
THF in 3 and 4 can be partially removed under vacuum, so
EP P, 1; As, 2
Both compounds are dark brown crystalline solids which are
soluble in hexane and stable in both the solid state and solution
at room temperature under an inert atmosphere. These com-
pounds are hydrolytically sensitive and decompose to [(C5Me5)2-
Sm]2(µ-O)33 and Ph2EH when exposed to moisture. The H
1
NMR spectra of 1 and 2 show a single sharp resonance for the
C5Me5 ligand and a single A2B2C monosubstituted phenyl ring
pattern, arising from the Ph2E- group. The equivalence of the
two phenyl rings dictates either that the Ph2E- ligand is in a
highly symmetrical environment or that there is free rotation
about the E-Ph bonds in solution. For the former case, a
symmetrical bridging µ-EPh2 mode of coordination, such as that
seen in (C5H5)2Lu(µ-EPh2)2Li(TMED) (E ) P,34 As35 ), is
consistent with the NMR data. However, previous studies have
shown that [(C5Me5)2Sm(µ-Z)]2 complexes where Z is a large
anionic ligand are likely to be too sterically crowded to form
simple bridged dimers.36 Consistent with this supposition,
solution molecular weight measurements show 1 and 2 to be
monomeric in benzene, which implies a terminal mode of
coordination and formally seven-coordinate structures. This is
consistent with the spectroscopic and analytical data reported
for the related species (MeC5H4)2Sm(PPh2)37 and (C5Me5)2Sm-
(PEt2).38
1
samples of both compounds exhibit H NMR spectra that are
dependent on the amount of coordinated solvent removed during
workup.40 Resonances for the aromatic rings and the C5Me5
ligands move consistently downfield with increasing amounts
of THF, reaching limiting values in the presence of an additional
1 equiv of THF. Attempts to completely remove the THF from
3 and 4 to form the unsolvated compounds 1 and 2, respectively,
were only partly successful. Heating 3 at 65 °C for 12 h under
high vacuum produced a mixture of the solvent-free compound
1 and a decomposition product 5 (see below). Similar treatment
of 4 gave a mixture of partially desolvated 4, (C5Me5)2Sm-
(AsPh2)(THF)x (x < 1), and an analogous decomposition
product, 6.
Structures of (C5Me5)2Sm(AsPh2), 2, and (C5Me5)2Sm-
(AsPh2)(THF), 4. Since there are currently no structural data
available for Sm-As bonds and only one example of a Ln-As
bonded compound in the literature,35 an X-ray structural
determination on 2 was performed. Structural data were also
obtained on 4 for comparison with the unusual features in 2.
Selected interatomic distances and angles are given in Tables 3
and 4, and the structures of 2 and 4 are shown in Figures 1 and
2. 2 crystallizes with two independent, but chemically equiva-
lent, molecules in the asymmetric unit, along with one hexane
solvent molecule for every four molecules of 2. The structure
consists of discrete monomeric units with no unusual intermo-
lecular contacts, which is consistent with the monomeric solution
molecular weight data. 4 also crystallizes as a monomer as
expected.
Since all phenyl resonances appear at unusually high field
for aromatic protons (3-6 ppm range) and only the lowest field
triplets in the H NMR spectra, assigned to the p-H are well-
1
resolved, additional weak Sm‚‚‚H-C interactions may exist in
solution which serve to increase the effective coordination
number. The other resonances for the o- and m-protons are
broadened and may be indicative of further metal-ligand
interaction. This is supported by the solid state structure
described below for 2 and by the fact that upon addition of
THF to these complexes all the resonances become well resolved
and move downfield to a more normal range for aromatic
protons. A similar situation is observed for the benzyl and
phenyl complexes (C5Me5)2SmCH2Ph39 and (C5Me5)2SmPh.21
For the unsolvated complexes the aryl o-H and m-H resonances
are at high field and are poorly resolved or otherwise unobserv-
able. Addition of THF also sharpens these resonances and
causes them to move to the normal aromatic region.
While there is no indication in the solid state of aggregation
through bridging arsenido groups for 2, several aspects of the
data suggest an increase in coordination number through
intramolecular interactions as shown in Figure 1. Both arsenic
atoms in the independent molecules of 2 are located asym-
metrically between the C5Me5 rings, as shown by the difference
in (ring centroid)-Sm-As angles (117.3 vs 100.5° and 119.1
vs 100.2° for molecule 1 and molecule 2, respectively). The
arsenic is also asymmetrically located with respect to the plane
determined by the two ring centroids and Sm as illustrated in
Figure 3. As(1) is 1.45 Å out of this plane, As(2) is displaced
by 1.38 Å, and the angles between the Sm-As vectors and these
planes are 29.2° [Sm(1)-As(1)] and 27.6° [Sm(2)-As(2)].
Alternatively, this asymmetry can be described in terms of the
deviation of the Sm atoms from the plane formed by arsenic
and the ring centroids [Sm(1) 0.35 Å, Sm(2) 0.34 Å]. The
arsenic atom in 4 is also located off center (1.76 Å) from the
(ring centroid)-Sm-(ring centroid) plane, but this is not unusual
Reactions of (C5Me5)2Sm(THF)2 with Ph2PPPh2 and
Ph2AsAsPh2: Formation of (C5Me5)2Sm(EPh2)(THF) Species
(33) Evans, W. J.; Grate, J. W.; Bloom, I.; Hunter, W. E.; Atwood, J. L.
J. Am. Chem. Soc. 1985, 107, 405.
(34) Schumann, H.; Palamidis, E.; Schmid, G.; Boese, R. Angew. Chem.,
Int. Ed. Engl. 1986, 25, 718.
(35) Schumann, H.; Palamidis, E.; Loebel, J.; Pickhardt, J. Organometallics
1988, 7, 1008.
(36) (a) Evans, W. J.; Peterson, T. T.; Rausch, M. D.; Hunter, W. E.; Zhang,
H.; Atwood, J. L. Organometallics 1985, 4, 554. (b) Evans, W. J.;
Keyer, R. A.; Ziller, J. W. Organometallics 1993, 12, 2618.
(37) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. Organometallics
1983, 2, 709-714.
(38) Nolan, S. P.; Stern, D.; Marks, T. J. J. Am. Chem. Soc. 1989, 111,
7844-7853.
(39) Evans, W. J.; Ulibarri, T. A.; Ziller, J. W. Organometallics 1991, 10,
134-142.
(40) For a related example, see: Evans, W. J.; Drummond, D. K.; Grate,
J. W.; Zhang, H.; Atwood, J. L. J. Am. Chem. Soc. 1987, 109, 3928.

4288 Inorganic Chemistry, Vol. 35, No. 15, 1996
Table 3. Selected Interatomic Distances (Å) and Interatomic
Evans et al.
a
Angles (deg) in 2‚1/4C6H14, (C5Me5)2Sm(AsPh2)‚1/4C6H14
molecule 1
molecule 2
Sm(1)-As(1)
2.973(3) Sm(2)-As(2)
2.966(3)
2.423
2.407
1.965(18)
1.990(18)
2.967
Sm(1)-Cnt(1)
Sm(1)-Cnt(2)
As(1)-C(26)
As(1)-C(32)
Sm(1)-C(31)
Sm(1)-C(32)
2.413
2.423
Sm(2)-Cnt(3)
Sm(2)-Cnt(4)
1.911(19) As(2)-C(64)
1.919(20) As(2)-C(58)
2.901
3.031
Sm(2)-C(59)
Sm(2)-C(64)
3.117
Sm(1)-C(1)
Sm(1)-C(3)
Sm(1)-C(5)
Sm(1)-C(7)
Sm(1)-C(9)
2.702(19) Sm(2)-C(33)
2.694(19) Sm(2)-C(35)
2.689(21) Sm(2)-C(37)
2.687(17) Sm(2)-C(39)
2.736(20) Sm(2)-C(41)
2.698(19)
2.677(21)
2.693(19)
2.778(19)
2.674(19)
Figure 1. Thermal ellipsoid plot of (C5Me5)2Sm(AsPh2), 2, with
ellipsoids drawn at the 50% probability level.
Sm(1)-C(11)
Sm(1)-C(13)
Sm(1)-C(15)
Sm(1)-C(17)
Sm(1)-C(19)
2.668(20) Sm(2)-C(43)
2.682(19) Sm(2)-C(45)
2.751(18) Sm(2)-C(47)
2.720(20) Sm(2)-C(49)
2.665(19) Sm(2)-C(51)
2.663(21)
2.655(22)
2.722(22)
2.680(20)
2.719(21)
Cnt(1)-Sm(1)-Cnt(2) 136.3
Cnt(1)-Sm(1)-As(1) 117.3
Cnt(2)-Sm(1)-As(1) 100.5
Cnt(3)-Sm(2)-Cnt(4) 135.1
Cnt(3)-Sm(2)-As(2) 119.1
Cnt(4)-Sm(2)-As(2) 100.2
Sm(1)-As(1)-C(26) 118.8(5) Sm(2)-As(2)-C(58) 118.5(6)
Sm(1)-As(1)-C(32) 73.0(6)
Sm(2)-As(2)-C(64) 75.4(5)
C(26)-As(1)-C(32) 104.3(8) C(58)-As(2)-C(64) 104.9(8)
C(31)-C(32)-As(1) 115.0(15) C(59)-C(64)-As(2) 113.1(13)
C(27)-C(32)-As(1) 129.0(16) C(63)-C(64)-As(2) 128.8(15)
C(21)-C(26)-As(1) 119.8(14) C(57)-C(58)-As(2) 117.3(15)
C(25)-C(26)-As(1) 125.9(14) C(53)-C(58)-As(2) 120.5(14)
a Cnt(1) is the centroid of the C(1)-C(3)-C(5)-C(7)-C(9) ring.
Cnt(2) is the centroid of the C(11)-C(13)-C(15)-C(17)-C(19) ring.
Cnt(3) is the centroid of the C(33)-C(35)-C(37)-C(39)-C(41) ring.
Cnt(4) is the centroid of the C(43)-C(45)-C(47)-C(49)-C(51) ring.
Figure 2. Thermal ellipsoid plot of (C5Me5)2Sm(AsPh2)(THF), 4. with
ellipsoids drawn at the 50% probability level.
Table 4. Selected Interatomic Distances (Å) and Interatomic
Angles (deg) in 4, (C5Me5)2Sm(AsPh2)(THF)a
Sm(1)-As(1)
Sm(1)-O(1)
3.049(3)
2.471(15)
Sm(1)-Cnt(1) 2.464
Sm(1)-Cnt(2) 2.425
Cnt(1)-Sm(1)-Cnt(2) 136.4
Cnt(1)-Sm(1)-As(1)
Cnt(1)-Sm(1)-O(1)
Cnt(2)-Sm(1)-As(1)
100.5
103.3
114.7
102.4
88.8(3)
Sm(1)-C(1)
Sm(1)-C(2)
Sm(1)-C(3)
Sm(1)-C(4)
Sm(1)-C(5)
2.711(24) Cnt(2)-Sm(1)-O(1)
2.697(24) As(1)-Sm(1)-O(1)
2.788(22)
2.772(22) Sm(1)-As(1)-C(25)
2.737(23) Sm(1)-As(1)-C(31)
C(25)-As(1)-C(31)
120.8(6)
109.1(6)
96.9(9)
Sm(1)-C(11)
Sm(1)-C(12)
Sm(1)-C(13)
Sm(1)-C(14)
Sm(1)-C(15)
2.728(23)
2.687(20) C(32)-C(31)-As(1)
2.650(21) C(36)-C(31)-As(1)
2.694(21) C(30)-C(25)-As(1)
2.738(21) C(32)-C(31)-As(1)
122.6(16)
117.2(16)
115.9(16)
126.4(18)
Figure 3. Top view of (C5Me5)2Sm(AsPh2), 2.
tipped toward the metal in each of the molecules in the unit
cell. In each of these tilted phenyl rings, one C(ortho)-
C(ipso)-As angle [C(31)-C(32)-As(1) 115.0(15)°, C(59)-
C(64)-As(2) 113.1(13)°] is considerably smaller than that on
the opposite side of the ring [C(27)-C(32)-As(1) 129.0(16)°,
C(63)-C(64)-As(2) 128.8(15)°]. In contrast, the difference
between proximal and distal C(ortho)-C(ipso)-As angles
observed in the adjacent phenyl rings [C(21)-C(26)-As(1)
119.8(14)°, C(57)-C(58)-As(2) 117.3(15)° vs C(25)-C(26)-
As(1) 125.9(14)°, C(53)-C(58)-As(2) 120.5(14)°] is much less
dramatic.
In comparison, the geometry around arsenic in (C5Me5)2Sm-
(AsPh2)(THF) is distinctly pyramidal (sum of angles ) 326.8°)
and there is no overt bending of the As-C(ipso) bond toward
the samarium. The Sm(1)-As(1)-C(31) angle of 109.1(6)° is
perfectly regular, and the more obtuse Sm(1)-As(1)-C(31)
angle to the aromatic ring nearer the THF ligand is correspond-
a Cnt(1) is the centroid of the C(1)-C(5) ring. Cnt(2) is the centroid
of the C(11)-C(15) ring.
considering the presence of the additional THF ligand in the
coordination sphere.
Examination of the geometry about the arsenic in 2 shows
considerable deviation from either an ideal pyramidal or planar
arrangement. The sum of the angles averages 297.4° and the
C(ipso)-As-C(ipso) angles are 104.3(8)°-104.9(8). The Sm-
As-C(ipso) angles are divided into two distinctly different
sets: one group has values close to a planar arrangement
[Sm(1)-As(1)-C(26) 118.8(5)° and Sm(2)-As(2)-C(58)
118.5(6)°], and the remaining set is far more acute [Sm(1)-
As(1)-C(32) 73.0(6)° and Sm(2)-As(2)-C(64) 75.4(6)°]. Both
narrow angles are associated with an o-carbon on the side of
the ring closer to the samarium, which results in one ring being

Organosamarium Diarylpnictide Complexes
Inorganic Chemistry, Vol. 35, No. 15, 1996 4289
ingly opened to 120.8(6)°. Unlike 2, there is no trend apparent
in the C(ortho)-C(ipso)-As angles [C(32)-C(31)-As(1)
122.6(16)°, C(36)-C(31)-As(1) 117.2(16)°, C(30)-C(25)-
As(1) 115.9(16)°, C(32)-C(31)-As(1) 126.4(18)°] based on
the proximity of the o-carbon to the samarium, nor is the
difference between the proximal and distal sides of the phenyl
ring as pronounced as in 2.
distances. This elongation may be due to the increased steric
demand of the C5Me5 ligand as compared to C5H5 in the Lu
compound.
THF Ring Opening by (C5Me5)2Sm(EPh2)(THF) Com-
pounds. In contrast to 1 and 2, compounds 3 and 4 are not
stable and undergo a further reaction involving the ring opening
of the coordinated THF. As shown in eq 7, EPh2-substituted
The result of the distortions in geometry about arsenic in 2
is that one phenyl ring is oriented toward the samarium center,
with the possibility of an η2-interaction involving the ipso- and
o-carbons. The shortest interatomic distances are to the
o-carbons [Sm(1)-C(31) 2.901 Å, Sm(2)-C(59) 2.967 Å]. The
samarium-ipso-carbon distances are longer [Sm(1)-C(32)
3.031 Å, Sm(2)-C(64) 3.117 Å]. In contrast, in 4 the shortest
Sm‚‚‚C(phenyl) distance is 4.13 Å.
In the past, when interactions of this type have been observed
in organolanthanide complexes,41 a measure of their strength
has been estimated by comparing the distance of the metal to
the carbon in question with the metal-cyclopentadienyl carbon
distance. For example, in the styrene complex, [(C5Me5)2Sm]2-
(µ-PhCHCH2),41 a 2.772(17) Å Sm-C(ortho phenyl) distance
is observed, which is equivalent to the 2.792(36) Å Sm-
C(cyclopentadienyl) average. Since the Sm-C(cyclopentadi-
enyl) distances in 2 are 2.665(19)-2.778(19) Å, the above
secondary Sm-C(phenyl) interactions are outside the range
consistent with a strong bonding interaction. However, the Sm-
C(ortho phenyl) distances are comparable to the long-range
interactions clearly extant in molecules like (C5Me5)2Yb-
(MeCtCMe),42 (C5Me5)2Yb(µ-H2CdCH2)Pt(PPh3)2,43 and
(C5Me5)2Sm(µ-C5H5)Sm(C5Me5)2.44 All of these structural
observations, together with the features from the 1H NMR
spectrum (see above), support the existence of a weak interaction
between the samarium and one phenyl ring in each diphenyl-
arsenido ligand, in accordance with the expected electrophilicity
of the formally seven-coordinate samarium center.
(C5Me5)2Sm(EPh2)(THF) f
(C5Me5)2Sm[O(CH2)4EPh2](THF)
(7)
E: P, 5; As, 6
butoxide complexes 5 and 6 result. This ring opening occurs
over a period of days at room temperature in benzene, toluene,
hexane, or THF. (C5Me5)2Sm[O(CH2)4AsPh2](THF) can be
produced on a preparative scale by heating 4 in refluxing THF
for 16 h. These reactions go to completion in the presence of
just 2 equiv of THF, although the reaction is slower than in
neat THF. 5 and 6 also form over a period of several weeks in
the solid state when stored at ambient temperature in an inert-
atmosphere glovebox containing THF. Ring opening to form
a substituted butoxide ligand is further observed when samples
of 3 and 4 are heated under vacuum (see above). The presence
of both desolvated species as well as 3 and 4 shows that loss of
THF from the complexes is accompanied by nucleophilic attack
on THF, which must, of necessity, be intramolecular under these
conditions. This transformation is remarkable in that the ring
opening reaction, which requires THF, is competitive with the
loss of THF from the inner coordination sphere, even under
vacuum where such loss is irreversible.
Structure of (C5Me5)2Sm[O(CH2)4AsPh2](THF), 6. Com-
pounds 5 and 6 were first identified by the distinctive appearance
of the butoxide ligand in the 1H NMR spectrum and by
comparison with spectral data for the related compounds
(C5Me5)2Sm[O(CH2)3CH3](THF),39(C5Me5)2Ln[O(CH2)4C5Me5]-
(THF) (Ln ) Sm, La, Nd, Tm, Lu),46,47 and {(C5H5)2Lu[µ-
O(CH2)4PPh2]}2.48 Where structural information is available
for these compounds, the alkoxide ligands function as simple
terminal or dinuclear bridging ligands with no further metal-
ligand interactions. In the case of compounds 5 and 6, however,
the possibility exists for secondary ligation from the EPh2
terminus to form a seven-membered Sm-O(CH2)4E cycle. To
explore this possibility, an X-ray structural determination was
carried out on 6, which confirmed the presence of the THF-
derived ligand suggested by the spectral data (Figure 4).
Selected bond lengths and angles are given in Table 5.
The extent of this interaction can also be evaluated by
examining the structural parameters of the (C5Me5)2Sm units
in 2 and 4, since a formally seven-coordinate 2 would be
expected to have smaller Sm-C(C5Me5) distances than those
in formally eight-coordinate 4.45 The fact that the 2.665(19)-
2.778(19) Å Sm-C(C5Me5) distances in unsolvated 2 are
indistinguishable from the analogous 2.650(21)-2.788(22) Å
values in solvated 4 is consistent with 2 having an effective
coordination number greater than 7. The 135.7° average (ring
centroid)-Sm-(ring centroid) angle in 2 is also equivalent to
the 136.4° angle in 4.
The molecular structure of (C5Me5)2Sm[O(CH2)4AsPh2](THF)
shows an eight-coordinate geometry about the samarium with
an approximately tetrahedral arrangement of cyclopentadienyl
ring centroids and oxygen atoms. The angle between the (ring
centroid)-Sm-(ring centroid) and O-Sm-O planes is 89.9°.
The butoxide ligand coordinates in a terminal fashion, and there
is no interaction between the diphenylarsenido ligand and the
samarium. Overall, the (C5Me5)2SmO2 geometry for the
complex is quite similar to that of (C5Me5)2Sm[O(CH2)4C5Me5]-
(THF), with the corresponding Sm-O(butoxide), Sm-O(THF),
and average Sm-C(ring carbon) distances in both compounds
within experimental error of each other. The distinct trend
toward linearity in the 165.2(7)° Sm-O-C bond angle in
(C5Me5)2Sm[O(CH2)4C5Me5](THF)46 (and other lanthanide
However, the 3.049(3) Å Sm-As bond in eight-coordinate
(C5Me5)2Sm(AsPh2)(THF) is about 0.08 Å longer than the
2.966(3) and 2.973(3) Å distances in 2, which suggests that the
extra phenyl coordination in 2 is not fully equivalent to another
ligand such as THF. In 4, THF approaches Sm with a Sm-
O(THF) distance of 2.471(15) Å, which is typical.45
The Sm-As bonds in both 2 and 4 are significantly longer
(0.031-0.077 Å) than the 2.870(2) and 2.895(2) Å Lu-As
bonds of (C5H5)2Lu(µ-AsPh2)2Li(Me2NCH2CH2NMe2),35 the
only other structurally characterized lanthanide arsenic complex,
even when the difference in ionic radius is taken into account.
The difference between the extremes of the error limits is only
0.013 Å, but terminal lengths are typically shorter than bridging
(41) Evans, W. J.; Ulibarri, T. A.; Ziller, J. W. J. Am. Chem. Soc. 1990,
112, 219.
(42) Burns, C. J.; Andersen, R. A. J. Am. Chem. Soc. 1987, 109, 941.
(43) Burns, C. J.; Andersen, R. A. J. Am. Chem. Soc. 1987, 109, 915.
(44) Evans, W. J.; Ulibarri, T. A. J. Am. Chem. Soc. 1987, 109, 4292.
(45) Evans, W. J.; Foster, S. E. J. Organomet. Chem. 1992, 433, 79.
(46) Evans, W. J.; Ulibarri, T. A.; Chamberlain, L. R.; Ziller, J. W.; Alvarez,
D. Organometallics 1990, 9, 2124-2130.
(47) Schumann, H.; Glanz, M.; Hemling, H.; Gorlitz, F. H. J. Organomet.
Chem. 1993, 462, 155.
(48) Schumann, H.; Palamidis, E.; Loebel, J. J. Organomet. Chem. 1990,
384, C49.

4290 Inorganic Chemistry, Vol. 35, No. 15, 1996
Evans et al.
Figure 5. Structure of (C5Me5)2Sm(µ-PPh2)Sm(C5Me5)2, 7.
definitively characterized by X-ray crystallography50 (Figure 5).
The corresponding arsenic product, 8 (E ) As), is unstable,
showing signs of decomposition within 15 min of synthesis,
Figure 4. Thermal ellipsoid plot of (C5Me5)2Sm[O(CH2)4AsPh2](THF),
6, with ellipsoids drawn at the 50% probability level.
1
and was characterized only in solution by H NMR spectros-
copy. Neither product results from E-C cleavage; each results
instead from coordination of (C5Me5)2Sm to the lone pair of
electrons of the respective pnictide. It is noteworthy that these
“(C5Me5)2Sm” complexation reactions do not occur when
(C5Me5)2Sm(THF)2 is substituted for (C5Me5)2Sm. In other
words, (C5Me5)2SmEPh2(THF) compounds 3 and 4 do not
undergo any further reaction in the presence of additional
equivalents of (C5Me5)2Sm(THF)2. The H NMR spectra of
the reaction mixtures are a simple superposition of the two
components.
The 13C NMR and magnetic data for 7 give an indication of
the electronic structure of this formally mixed-oxidation-state
Sm(II,III) compound. Resonances for the C5Me5 ring and
methyl carbons in the 13C NMR spectra of compounds 1-6
fall in the ranges 113-118 and 18-20 ppm, respectively, as is
common for trivalent (pentamethylcyclopentadienyl)samarium
complexes. In contrast, the methyl carbons in 7 are observed
at 57.3 ppm and the ring carbon resonance appears at 17.8 ppm.
These unusual positions do not resemble those found in typical
divalent pentamethylcyclopentadienyl compounds but rather lie
between the values observed for strictly divalent and trivalent
complexes,1b,51 as is observed for a related mixed-valent
complex (C5Me5)2Sm(µ-C5H5)Sm(C5Me5)2.49
Table 5. Selected Interatomic Distances (Å) and Interatomic
Angles (deg) in 6, (C5Me5)2Sm[O(CH2)4AsPh2](THF)a
Sm(1)-O(1)
Sm(1)-O(2)
Sm(1)-Cnt(1)
Sm(1)-Cnt(2)
2.085(5)
2.475(5)
2.478
Cnt(1)-Sm(1)-Cnt(2)
136.0
Sm(1)-O(1)-C(21)
O(1)-Sm(1)-O(2)
Cnt(1)-Sm(1)-O(1)
Cnt(1)-Sm(1)-O(2)
Cnt(2)-Sm(1)-O(1)
Cnt(2)-Sm(1)-O(2)
175.4(4)
85.3(2)
107.1
107.2
104.8
2.479
1
Sm(1)-C(1)
Sm(1)-C(2)
Sm(1)-C(3)
Sm(1)-C(4)
Sm(1)-C(5)
2.754(9)
2.699(9)
2.729(8)
2.760(7)
2.790(9)
104.7
C(24)-As(1)-C(25)
C(24)-As(1)-C(31)
C(25)-As(1)-C(31)
98.3(3)
97.9(3)
101.7(3)
Sm(1)-C(11)
Sm(1)-C(12)
Sm(1)-C(13)
Sm(1)-C(14)
Sm(1)-C(15)
2.749(10)
2.752(9)
2.731(8)
2.742(7)
2.767(8)
a Cnt(1) is the centroid of the C(1)-C(5) ring. Cnt(2) is the centroid
of the C(11)-C(15) ring.
alkoxides)49 is also followed in 6, where the Sm(1)-O(1)-
C(21) angle reaches an even larger value of 175.4(4)°.
Reaction of (C5Me5)2Sm with (C5Me5)2Sm(EPh2) (E ) P,
As) To Form Mixed-Valent Products. Formation of Sm-
EPh2 complexes from Ph2EEPh2 precursors is consistent with
the relative E-E and E-C bond strengths in these compounds.
In efforts to cleave the E-C bonds in these compounds, 1 and
2 were treated with additional (C5Me5)2Sm; i.e., reaction 5 was
run with a 4:1 stoichiometry as shown in eq 8. Alternatively,
Similarly, the room-temperature molar magnetic susceptibility
of (C5Me5)2Sm(µ2-PPh2)Sm(C5Me5)2 measured in benzene
solution52 is 2560 × 10-6 cgsu, giving an effective magnetic
moment per samarium of 2.45 µB. The former value is close
to the average of the susceptibilities per metal center for the
individual components (C5Me5)2Sm, 5050 × 10-6 cgsu,21 and
(C5Me5)2Sm(PPh2), 425 × 10-6 cgsu. The magnetic data alone
indicate that 7 is a class I mixed-valence system53 where the
two metals exist in distinct oxidation states. However, the single
4(C5Me5)2Sm + Ph2EEPh2 f
2(C5Me5)2Sm(µ2-EPh2)Sm(C5Me5)2
(8)
1
resonance in the H NMR spectrum and the unusual shifts for
E: P, 7; As, 8
the cyclopentadienyl ligands in the 13C NMR spectrum are
indicative of a single, or perhaps averaged, environment.
Together, these data suggest that in solution there is some degree
of delocalization mediated through the bridging diphenylphos-
phido unit, allowing for a change between the Sm(II) and
Sm(III) oxidation states that is rapid on the NMR time scale.
Irrespective of the actual valence description, the availability
of the divalent (C5Me5)2Sm moiety in 7 for further reactivity is
isolated (C5Me5)2Sm(EPh2) can be reacted with (C5Me5)2Sm
in a 1:1 ratio as shown in eq 9 to form products that are
(C5Me5)2Sm(EPh2) + (C5Me5)2Sm f
(C5Me5)2Sm(µ2-EPh2)Sm(C5Me5)2
E: P, 7; As, 8
(9)
spectroscopically the same as those formed in eq 8. On the
basis of 1H NMR data, a new compound is formed in both cases,
but only for E ) P has a new product, 7, been isolated and
(50) Several attempts were made to obtain precise metrical data for crystals
of 7, but the data were not of sufficient quality to yield any information
other than atom connectivity.
(51) Evans, W. J.; Ulibarri, T. A. J. Am. Chem. Soc. 1987, 109, 4292.
(52) Evans, D. F. J. Chem. Soc. 1959, 2003. Becconsall, J. K. Mol. Phys.
1968, 15, 129.
(49) (a) Evans, W. J.; Sollberger, M. S.; Hanusa, T. P. J. Am. Chem. Soc.
1988, 110, 1841. (b) Evans, W. J.; Hanusa, T. P.; Levan, K. R. Inorg.
Chim. Acta 1985, 110, 191 and references therein.
(53) Robin, M. B.; Day, P. AdV. Inorg. Chem. Radiochem. 1967, 10, 247.

Organosamarium Diarylpnictide Complexes
Inorganic Chemistry, Vol. 35, No. 15, 1996 4291
evidenced by the P-P bond cleavage of Ph2PPPh2 and its
conversion back to (C5Me5)2Sm(PPh2), eq 10.
2(C5Me5)2Sm(THF)2 + 2Ph2BiCl f
2(C5Me5)2SmCl(THF) + Ph2BiBiPh2 (16)
2(C5Me5)2Sm(µ2-PPh2)Sm(C5Me5)2 + Ph2PPPh2 f
3Ph2BiBiPh2 f 4Ph3Bi + 2 Bi (17)
4(C5Me5)2Sm(PPh2) (10)
quantitatively recovered according to the net overall reaction
shown in eq 18. Reactions conducted with (C5Me5)2Sm in place
Reactions of (C5Me5)2Sm and (C5Me5)2Sm(THF)2 with
Ph2SbSbPh2 and Ph2BiBiPh2. In contrast to the phosphorus
and arsenic systems described above, eqs 5 and 6, the analogous
reactions with antimony and bismuth do not simply lead to
cleavage of the element-element bond. In each case, E-C
bond cleavage occurs with (C5Me5)2Sm, as evidenced by the
appearance of (C5Me5)2SmPh, eqs 11 and 12. The reactions
3(C5Me5)2Sm(THF)2 + 3Ph2BiCl f
3(C5Me5)2SmCl(THF) + 2 Ph3Bi + Bi(0) (18)
of (C5Me5)2Sm(THF)2 proceed analogously to eqs 15 and 16,
except that the THF-free compounds (C5Me5)2SmCl and
(C5Me5)2SmPh are formed. This chemistry is reminiscent of
that with alkali metals and Ph2BiCl. A 1:1 ratio of Na:Ph2BiCl
in liquid ammonia leads to reductive coupling and the formation
of Ph2BiBiPh2.55 Excess alkali metal effects cleavage of the
Bi-Bi bond and affords Bi(0) and Ph3Bi.56
2(C5Me5)2Sm + Ph2SbSbPh2 f
(C5Me5)2SmPh + unreacted Ph2SbSbPh2 (11)
2(C5Me5)2Sm + Ph2BiBiPh2 f
(C5Me5)2SmPh + Bi(0) + unreacted Ph2BiBiPh2 (12)
Conclusion
with (C5Me5)2Sm(THF)2 mirror those of the THF-free reactions,
except that (C5Me5)2SmPh(THF) is produced, eqs 13 and 14.
(C5Me5)2Sm and (C5Me5)2Sm(THF)2 react with aryl-substi-
tuted group 15 compounds by three modes: coordination, E-C
cleavage, and E-E cleavage. E-C cleavage is most common
for the heavier congeners, which have weaker E-C bonds.
Hence, (C5Me5)2SmPh products are found in reactions with Sb
and Bi but not with P and As. E-E cleavage occurs with all
of the systems studied: P, As, Sb, and Bi. For the lighter
congeners with stronger E-C bonds, the E-E cleavage products
are isolated as the EPh2 complexes (C5Me5)2Sm(PPh2) and
(C5Me5)2Sm(AsPh2). The THF adducts display further chem-
istry and provide a system in which THF coordination and ring
opening can be separately defined. The base-free complexes
interact with additional (C5Me5)2Sm to form mixed-valent
compounds. Reaction of (C5Me5)2Sm with Ph3Bi appears to
be a rather special case, since it is the only one in which the
(E2)2- ion is isolated. Hence, the dibismuth complex
[(C5Me5)2Sm]2(µ-η2:η2-Bi2) is accessible from neither Ph2BiBiPh2
nor Ph2BiCl and the only organosamarium products of reactions
with other Ph3E complexes are E-C(phenyl) cleavage products.
The complexes (C5Me5)2Sm(AsPh2), 2, and (C5Me5)2Sm-
(AsPh2)(THF), 4, constitute an interesting pair of compounds
which show the flexibility of the (C5Me5)2Sm unit to stabilize
different ligand systems. The isolation and structural charac-
terization of the lower coordinate 2 are possible, although there
is clearly room for the addition of THF to form 4. The isolation
of 4 indicates that this typical eight-coordinate structure is
possible even with ligands as large as AsPh2. However, 4 can
be desolvated under vacuum and can engage in THF ring-
opening reactivity. Studies directed toward exploiting this
unusual balance of steric saturation are in progress.
2(C5Me5)2Sm(THF)2 + Ph2SbSbPh2 f
(C5Me5)2SmPh(THF) + unreacted Ph2SbSbPh2 (13)
2(C5Me5)2Sm(THF)2 + Ph2BiBiPh2 f
(C5Me5)2SmPh(THF) + Bi(0) (14)
With these Ph2EEPh2 substrates, no (E2)2- or (E3)3- products
are observed. Only elemental bismuth and antimony are
obtained. The bismuth reactions readily deposit elemental
bismuth, but the antimony reactions are curious in that elemental
antimony does not appear until the reactions have run for 1-3
days. Intermediate products have been neither isolable nor
identifiable by 1H NMR spectroscopy. Neither variation in the
solvent from hexane to arenes to THF nor low temperature
reactions have yielded any other compounds.
Reactions of (C5Me5)2Sm and (C5Me5)2Sm(THF)2 with
Ph2BiX. Since the reactivity of Ph3Bi to form [(C5Me5)2Sm]2-
(µ-η2:η2-Bi2) was found to be unique in the group 15 Ph3E and
Ph2EEPh2 compounds investigated, the reactions of Ph2BiCl
with (C5Me5)2Sm and (C5Me5)2Sm(THF)2 were examined to
see if they would parallel that of Ph3Bi or Ph2BiBiPh2. Halide
abstraction was expected to form (C5Me5)2SmCl40 and (C5Me5)2-
SmCl(THF),54 respectively. This would leave a Ph2Bi moiety
which could couple to Ph2BiBiPh2 or react with (C5Me5)2Sm-
(THF)x to form (C5Me5)2Sm(BiPh2)(THF)x. Either pathway
would lead to the formation of Sm-Bi or Bi-Bi bonds
necessary for the assembly of [(C5Me5)2Sm]2(µ-η2:η2-Bi2).
Reaction of (C5Me5)2Sm(THF)2 with a 2:1 Sm/Bi ratio as
shown in eq 15 gives a variety of products resulting from both
Acknowledgment. We thank the National Science Founda-
tion for support for this research.
2(C5Me5)2Sm(THF)2 + Ph2BiCl f (C5Me5)2SmCl(THF) +
(C5Me5)2SmPh(THF) + Bi(0) + Ph3Bi (15)
Supporting Information Available: Tables of crystal data, posi-
tional parameters, bond distances and angles, and thermal parameters
(35 pages). Ordering information is given on any current masthead
page.
Bi-Cl and Bi-Ph cleavage, as well as small amounts of
products consistent with limited reductive coupling of Ph2BiCl
(see below). The 1:1 reaction is more selective and leads only
to Bi-Cl cleavage, eq 16. Coupling of Ph2BiCl to form
Ph2BiBiPh2 is implied by the presence of Bi(0) and Ph3Bi as
products of dibismuthine disproportionation, eq 17. Bi(0) is
IC951627Z
(55) (a) Calderazzo, F.; Morvillo, A.; Pelizzi, G.; Poli, R. J. Chem. Soc.,
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J. Chem. Soc., Dalton Trans. 1984, 2365. (c) Ashe, A. J.; Ludwig, E.
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