Organometallic chemistry on a metallathiaborane cluster: Reactions of [8,8-(PPh3)2-nido-8,7-RhSB9H10] with bidentate phosphine ligands

Article abstract of DOI:10.1021/om9901168

Reactions of the unsaturated cluster [8,8-(PPh₃)₂-nido-8,7-RhSB₉H₁₀] (1) with the bidentate 1,n-bis(diphenylphosphino)alkanes (CH₂)_n(PPh₂)₂, where n = 1-3 (abbreviated as dppm, dppe, and dppp, respectively), have been studied. When a 1:1 molar ratio of phosphine to rhodathiaborane is used, for dppe and dppp, simple substitution to form [8,8-(η²-dppe)-nido-8,7-RhSB₉H₁₀] (2) or [8,8-(η²-dppp)-nido-8,7-RhSB₉H₁₀] (3) is observed. However, in the presence of an excess of dppe or dppp, mixtures of the species 2 and [8,8-(η²-dppe)-9-(η¹-dppe)-nido-8,7-RhSB ₉H₁₀] (4) or of 3 and [8,8-(η²-dppp)-9-(η¹-dppp)-nido-8,7-RhSB ₉H₁₀] (5) are formed, respectively. Under both sets of conditions, when dppm is used, only one product, [8,8-(η²-dppm)-8-(η¹-dppm)-nido-8,7-RhSB ₉H₁₀] (6), is observed. This latter species has two dppm ligands coordinating to the metal, one in a unidentate mode and the other bidentate. Species 2 and 3 are formally unsaturated, two electrons short of the number required for the observed 11-vertex nido structure. In contrast, 4 and 5 are saturated with the cage-bonded unidentate ligand providing an additional skeletal electron pair to the cluster. The species 4 and 5 are unstable in solution; depending on the conditions, they dissociate to give free phosphine and the chelate 2 or 3 or they undergo nido to closo transformation with loss of dihydrogen, affording the corresponding 11-vertex closo compounds [1,1-(η²-dppe)-3-(η¹-dppe)-closo-1,2-RhSB ₉H₈] (17) and the dppp analogue [1,1-(η²-dppp)-3-(η¹-dppp)-closo-1,2-RhSB ₉H₈] (18). Further reaction in the case of 5 allows isolation of the linked cluster system [{1,1-(η²-dppp)-closo-1,2-RhSB₉H₈} ₂-3,3′-(μ-dppp)] (19). The species have been characterized by NMR and mass spectrometry, and crystal structure determinations are described for 3, the OEt derivative of 3, [8,8-(η²-dppp)-9-(OEt)-nido-RhSB₉H₉] (14), 6, and the phosphine oxide of 17, [1,1-(η²-dppe)-3-(η¹-dppeO)-closo-1,2-RhSB ₉H₈] (20).

Full text of DOI:10.1021/om9901168

Organometallics 1999, 18, 3637-3648
3637
Or ga n om eta llic Ch em istr y on a Meta lla th ia bor a n e
Clu ster : Rea ction s of [8,8-(P P h 3)2-n id o-8,7-Rh SB9H10]
w ith Bid en ta te P h osp h in e Liga n d s
Ramo´n Mac´ıas, Nigam P. Rath, and Lawrence Barton*
Department of Chemistry, University of MissourisSt. Louis, St. Louis, Missouri 63121
Received February 22, 1999
Reactions of the unsaturated cluster [8,8-(PPh3)2-nido-8,7-RhSB9H10] (1) with the bidentate
1,n-bis(diphenylphosphino)alkanes (CH2)n(PPh2)2, where n ) 1-3 (abbreviated as dppm,
dppe, and dppp, respectively), have been studied. When a 1:1 molar ratio of phosphine to
rhodathiaborane is used, for dppe and dppp, simple substitution to form [8,8-(η2-dppe)-nido-
8,7-RhSB9H10] (2) or [8,8-(η2-dppp)-nido-8,7-RhSB9H10] (3) is observed. However, in the
presence of an excess of dppe or dppp, mixtures of the species 2 and [8,8-(η2-dppe)-9-(η1-
dppe)-nido-8,7-RhSB9H10] (4) or of 3 and [8,8-(η2-dppp)-9-(η1-dppp)-nido-8,7-RhSB9H10] (5)
are formed, respectively. Under both sets of conditions, when dppm is used, only one product,
[8,8-(η2-dppm)-8-(η1-dppm)-nido-8,7-RhSB9H10] (6), is observed. This latter species has two
dppm ligands coordinating to the metal, one in a unidentate mode and the other bidentate.
Species 2 and 3 are formally unsaturated, two electrons short of the number required for
the observed 11-vertex nido structure. In contrast, 4 and 5 are saturated with the cage-
bonded unidentate ligand providing an additional skeletal electron pair to the cluster. The
species 4 and 5 are unstable in solution; depending on the conditions, they dissociate to
give free phosphine and the chelate 2 or 3 or they undergo nido to closo transformation
with loss of dihydrogen, affording the corresponding 11-vertex closo compounds [1,1-(η2-
dppe)-3-(η1-dppe)-closo-1,2-RhSB9H8] (17) and the dppp analogue [1,1-(η2-dppp)-3-(η1-dppp)-
closo-1,2-RhSB9H8] (18). Further reaction in the case of 5 allows isolation of the linked cluster
system [{1,1-(η2-dppp)-closo-1,2-RhSB9H8}2-3,3′-(µ-dppp)] (19). The species have been char-
acterized by NMR and mass spectrometry, and crystal structure determinations are described
for 3, the OEt derivative of 3, [8,8-(η2-dppp)-9-(OEt)-nido-RhSB9H9] (14), 6, and the phosphine
oxide of 17, [1,1-(η2-dppe)-3-(η1-dppeO)-closo-1,2-RhSB9H8] (20).
In tr od u ction
nido to closo; in the latter, two acetylene groups have
been coupled to form an iridacyclopenta-2,4-dienyl
moiety and the cluster transformed from nido to closo.2b
Other reactions of alkynes and alkenes with metallabo-
ranes in which reaction appears to take place at the
metal center have been reported. These include aroma-
tization of norbornadiene at a Rh center3 and reactions
involving metal-promoted alkyne4a and norbornadiene4b
insertion into B-H bonds, although incorporation of
carbon into the cluster was not observed in either case.
In our laboratory, we have observed that reactions of
arachno-[(PMe3)2(CO)IrB8H11] with acetylenic sub-
strates afford new metallacarboranes as the result of
carbon incorporation into the cluster framework.5,6
Related to these results are reactions of metallaboranes
with unsaturated bases such as nitriles, which can form
The organometallic chemistry of metallacarboranes
has been reasonably well-studied during the last 30
years.1 In contrast, the reactivity of polyhedral metalla-
boranes and metallaheteroboranes (containing p-block
elements other than carbon in the cluster framework)
has been less developed. There is great potential for
novel chemistry in this latter area, as evidenced by some
of the remarkable studies heretofore conducted. For
example, the reaction of the iridaborane [6,6-(PPh3)H-
6,5-µ-(Ph2P-o-C6H4)-nido-6-IrB9H12] with acetylene af-
fords [10-(PPh3)-2,2-(PH3)2-1,2-µ-(Ph2P-o-C6H4)-closo-2-
IrB9H7] and [1,1,1-(C4H4)(Ph2P-o-C6H4)-isocloso-1-IrB9H7-
5-(PPh3)-2].2 In the former, the PPh3 ligands have been
converted to PH3 ligands2a and the cluster oxidized from
(1) (a) Grimes, R. N. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Abel, E. W., Stone, F. G. A., Eds.; Pergamon: Oxford,
U.K., 1982; Part 1, Chapter 5.5, pp 459-543. (b) Geiger, W. E., J r. In
Metal Interactions with Boron Clusters; Grimes, R. N., Ed.; Plenum:
New York, 1982; p 239. (c) Hawthorne, M. F. Mol. Struct. Energ. 1986,
5, 225. (d) Grimes, R. N. Chem. Rev. 1992, 92, 251. (e) Saxena, A. K.;
Hosmane, N. S. Chem. Rev. 1993, 93, 1081. (f) Grimes, R. N. In
Comprehensive Organometallic Chemistry II; Wilkinson, G., Abel, E.
W., Stone, F. G. A., Eds.; Pergamon: Oxford, U.K., 1995; Vol. 1,
Chapter 9, pp 374-430. (g) Saxena, A. K.; Maguire, J . J .; Hosmane,
N. S. Chem. Rev. 1997, 97, 2421. (h) Hawthorne, M. F. Advances in
Boron Chemistry; Siebert, W., Ed.; The Royal Society of Chemistry:
London, 1997; p 261.
(2) (a) Bould, J .; Brint, P.; Fontaine, X. L. R.; Kennedy, J . D.;
Thornton-Pett, M. J . Chem. Soc., Chem. Commun. 1989, 1763. (b)
Bould, J .; Brint, P.; Fontaine, X. L. R.; Kennedy, J . D.; Thornton-Pett,
M. J . Chem. Soc., Dalton Trans. 1993, 2335.
(3) Speckman, D. M.; Knobler, C. B.; Hawthorne, M. F. Organome-
tallics 1985, 4, 1692.
(4) (a) Brauers, G.; Dossett, S. J .; Green, M.; Mahon, M. F. J . Chem.
Soc., Chem. Commun. 1995, 985. (b) Green, M.; Howard, J . A. K.;
J ames, A. P.; Nunn, C. M.; Stone, F. G. A. J . Chem. Soc., Dalton Trans.
1987, 61.
(5) Bould, J .; Rath, N. P.; Barton, L. Organometallics 1996, 15, 4916.
(6) Bould, J .; Rath, N. P.; Barton, L.; Kennedy, J . D. Organometallics
1998, 17, 902.
10.1021/om9901168 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 08/08/1999

3638 Organometallics, Vol. 18, No. 18, 1999
Mac´ıas et al.
simple metal7,8 or cage8,9 adducts, become incorporated
into the cage,10 or in some cases cause cage contrac-
tion.11 Examples of adduct formation include [6-Cp*-
6,9-(MeNC)2-arachno-6-(RhB9H11)] and [4-(Cp*)-4-(endo-
the presence of two unusual o-CH‚‚‚Rh agostic interac-
tions,16 and the molecule undergoes interesting fluxional
behavior in solution.14a Compound 1 is reactive toward
both electrophiles and nucleophiles. In particular, the
reactions of 1 with Lewis bases L (where L ) CO, PMe2-
Ph, or CH3CN) result in either addition of the ligand L
to the metal center or addition and substitution, giving
rise to species such as [8-L-8,8-(PPh3)2-nido-8,7-Rh-
SB9H10] (where L ) CO14b or CH3CN16) and [8,8,8-
(PMe2Ph)3-nido-8,7-RhSB9H10].17 Interestingly, [8-(CO)-
8,8-(PPh3)2-nido-8,7-RhSB9H10] in refluxing benzene
leads to the formation of [1-(CO)-1,3-(PPh3)2-closo-1,2-
RhSB9H8], which when treated with an excess of PMe2-
Ph at reflux temperature in benzene affords [1-(CO)-1-
(PMe2Ph)-3-L-closo-1,2-RhSB9H10] (where L ) PMe2Ph
or PPh3).14b Other reaction patterns such as terminal
hydrogen substitution at the 9-position by an OEt
group18 or metal incorporation to form 12-vertex bime-
tallic species have also been reported.14b Herein we
report the results of a study of the reactions of 1 with
the bidentate 1,n-bis(diphenylphosphino)alkanes (CH2)n-
(PPh2)2, where n ) 1-3 (abbreviated as dppm, dppe,
and dppp, respectively). A minor aspect of this work has
appeared in a preliminary communication.20
MeNC)-arachno-4-IrB8H12], obtained in the reactions
8
between MeNC and the nido species [6-(Cp*Rh)B9H13
]
and [6-(Cp*Ir)B9H13],7 respectively. On the other hand,
the reaction between the related species [6,6,6-(PMe2-
Ph)3-nido-6-OsB9H13] and BuNC affords the 10-vertex
t
isocloso-osmaborane [1,1,1-H(PMe2Ph)2-1-OsB9H8-5-
(PMe2Ph)]11 in a cluster contraction process. Hetero-
atom insertion has been observed in the reaction of a
RCN moiety with ruthena- and rhodadecaboranes,
although it is not clear whether initial interaction
between the base and the metallaborane involves the
borane cage or the metal center.10 Finally, an example
of stepwise reduction of MeNC to Me2NH on a ruthena-
decaborane cluster has been reported.8
In this context of the organometallic chemistry of
metallaboranes and metallaheteroboranes, we decided
to extend our work on the reactions of small molecules
with metallaboranes5,6 by exploring the reactivity of
unsaturated clusters with bidentate phosphine ligands.
The motivation for this project was based on our
previous success in the interaction of small metallabo-
ranes with bidentate bases wherein pendant phosphine
ligands, which exhibit the potential to form linked
Resu lts a n d Discu ssion
Reactions of [8,8-(PPh3)2-nido-8,7-RhSB9H10] (1) with
the respective bidentate phosphines dppe and dppp in
a 1:1 molar ratio in CH2Cl2 solvent at ambient temper-
ature afford good yields of the corresponding 11-vertex
nido-rhodathiaboranes [8,8-(η2-dppe)-nido-8,7-RhSB9H10]
(2) and [8,8-(η2-dppp)-nido-8,7-RhSB9H10] (3) as orange
and yellow air-stable solids, respectively (eqs 1 and 2).
These compounds are formed by substitution reactions,
in which the two PPh3 ligands in 1 are replaced by the
bis(diphenylphosphino)alkanes acting as bidentate chelat-
ing ligands.
clusters, were observed.12 Two substrates came to mind
13
for such a study: [9,9-(PPh3)2-nido-9,7,8-RhC2B8H11
]
and [8,8-(PPh3)2-nido-8,7-RhSB9H10] (1),14 compounds
which are formally isoelectronic and are two electrons
short of the number notionally required to satisfy the
polyhedral skeletal electron pair theory.15 Since our goal
was not to focus on metallacarboranes, we selected the
latter species. Unlike the rhodacarborane, which is
unstable, easily rearranging to a more closed configu-
ration,13 the rhodathiaborane 1 is stable, is easily
prepared, and has been more extensively studied.14,16-19
There are novel features associated with compound 1.
The unsaturation has been put into question, invoking
CH2Cl2
[(PPh3)2RhSB9H10] + dppe room temp8
[dppeRhSB H ]
+ 2PPh3 (1)
9
10
(7) Nestor, K.; Fontaine, X. L. R.; Greenwood, N. N.; Kennedy, J .
D.; Thornton-Pett, M. J . Chem. Soc., Dalton Trans. 1989, 1465.
(8) Fontaine, X. L. R.; Greenwood, N. N.; Kennedy, J . D.; MacKin-
non, P.; Thornton-Pett, M. J . Chem. Soc., Dalton Trans. 1988, 2809.
(9) Ditzel, E. J .; Fontaine, X. L. R.; Greenwood, N. N.; Kennedy, J .
D.; Sisan, Z.; Thornton-Pett, M. J . Chem. Soc., Chem. Commun. 1989,
1762.
(10) Ditzel, E. J .; Fontaine, X. L. R.; Greenwood, N. N.; Kennedy,
J . D.; Sisan, Z.; Stibr, B.; Thornton-Pett, M. J . Chem. Soc., Chem.
Commun. 1990, 1741.
2
CH2Cl2
[(PPh3)2RhSB9H10] + dppp room temp8
[dpppRhSB H ]
+ 2PPh3 (2)
9
10
3
When the reactions of compound 1 with dppe and
dppp are carried out in 1:3 metallathiaborane to phos-
phine molar ratios, compounds 2 and 3 are formed
together with the yellow nido-rhodathiaboranes [8,8-
(η2-dppe)-9-(η1-dppe)-nido-8,7-RhSB9H10] (4) and [8,8-
(η2-dppp)-9-(η1-dppp)-nido-8,7-RhSB9H10] (5). The new
species, 4 and 5, are formed by substitution reactions
at the metal center and the addition of a second ligand
at the 9-position in the cluster. Surprisingly, the reac-
tion of 1 with dppm, in either a 1:1 or 1:3 molar ratio,
affords the yellow compound [8,8-(η2-dppm)-8-(η1-dppm)-
nido-8,7-RhSB9H10] (6).20 Compound 6 is formed by
substitution of the PPh3 ligands by dppm and the
addition of a second dppm molecule at the rhodium
atom. The dppm analogues of 2-5 are not observed (eqs
(11) Coldicott, R. S. In Current Topics in the Chemistry of Boron;
Kabalka, G. W., Ed.; Special Publication 143; Royal Society of
Chemistry: London, 1994; p 297.
(12) Barton, L.; Bould, J .; Fang, H.; Hupp, K.; Rath, N. P.; Gloechk-
ner, C. J . Am. Chem. Soc. 1997, 119, 631.
(13) J ung, C. W.; Hawthorne, M. F. J . Am. Chem. Soc. 1980, 102,
3024.
(14) (a) Ferguson, G.; J ennings, M. C.; Lough, A. J .; Coughlan, S.;
Spalding, T. R.; Kennedy, J . D.; Fontaine, X. L. R.; Sˇt´ıbr, B. J . Chem.
Soc., Chem. Commun. 1990, 891. (b) Coughlan, S.; Spalding, T. R.;
Ferguson, G.; Gallagher, J . F.; Lough, A. J .; Fontaine, X. L. R.;
Kennedy, J . D.; Sˇt´ıbr, B. J . Chem. Soc., Dalton Trans. 1992, 2865.
(15) (a) Williams, R. E. Adv. Inorg. Chem. Radiochem. 1976, 18, 67.
(b) Wade, K. Adv. Inorg. Chem. Radiochem. 1976, 18, 60. (c) Rudolph,
R. W. Acc. Chem. Res. 1976, 9, 446.
(16) Adams, K. J .; McGrath, T. D.; Rosair, G. M.; Weller, A. S.;
Welch, A. J . J . Organomet. Chem. 1998, 550, 315.
(17) Ferguson, G.; Lough, A. L.; Coughlan, S.; Spalding, T. R. Acta
Crystallogr., Sect. C: Cryst. Struct. Commun. 1992, C48, 440.
(18) Murphy, M.; Spalding, T. R.; Ferguson, G.; Gallagher, J . F. Acta
Crystallogr., Sect. C: Cryst. Struct. Commun. 1992, C48, 638.
(19) Adams, K. J .; McGrath, T. D.; Thomas, R. Ll.; G. M.; Weller,
A. S.; Welch, A. J . J . Organomet. Chem. 1997, 527, 283.
(20) Mac´ıas, R.; Rath, N. P.; Barton, L. Angew. Chem., Int. Ed. 1999,
38, 162.

Organometallic Chemistry on a Metallathiaborane
Organometallics, Vol. 18, No. 18, 1999 3639
Sch em e 1. P r op osed “Sw itch in g” a n d
Ha lf-Rota tion of th e Meta l Cen ter a bove th e Op en
F a ce of th e Heter obor a n e F r a gm en t in
Com p ou n d s 1-3, 7, a n d 8
3-5 are not stoichiometric, they just illustrate the
outcome of the reactions). The species 2 is not a new
CH2Cl2
[(PPh3)2RhSB9H10] + 3dppe room temp8
[dppeRhSB H ] [(dppe) RhSB H ]
+
(3)
(4)
(5)
9
10
2
9
10
2
4
CH2Cl2
[(PPh3)2RhSB9H10] + 3dppp room temp8
[dpppRhSB H ] [(dppp) RhSB H ]
+
9
10
2
9
10
3
5
CH2Cl2
[(PPh3)2RhSB9H10] + 3dppm room temp8
mechanism that may account for the chemical dynamics
of this family of isoelectronic 11-vertex metallahetero-
boranes has been proposed,14,21 and it is easily extended
to the new species. It involves a shift and rotation of
the metal center {MLn} (where M ) Rh, L ) PPh3 (1
and 8), dppe (2), or dppp (3); M ) Pt, L ) PMe2Ph (7))
above the six-membered face {E(7)B(3)B(4)B(9)B(10)B-
(11)} of the heteroborane fragment {EB9H10} (where E
) S (for compounds 1-3), C (for compound 7), and N
(for compound 8)). In the case of compound 7, the
prochiral nature of the PMe2Ph phosphine allowed the
authors to conclude that the metal center {MLn}, rather
than a full rotation, undergoes half-rotation (Scheme
1).
The intimate nature of the transition state of this
fluxional process is unknown; however, as suggested
elsewhere,21 it is likely to consist of an 11-vertex
intermediate of Cs symmetry, with the bridging hydro-
gen bonded to the metal atom in either a terminal (M-
H) or a bridging (M-H-B) fashion. The equilibrium
observed in solution between the nido-metallacarborane
[9,9-(PEt3)2-9,7,8-RhC2B8H11] (9) and its isonido iso-
mer13 [1,1,1-H(PEt3)2-1,2,4-RhC2B8H10] (10) and the
formation of the isonido species [1,1,1-H(PMe3)2-1,2,4-
IrC2B8H10] (11), obtained from the thermolysis of [9,9,9-
CO(PMe3)2-9,7,8-IrC2B8H11] (12),5a,23 provide chemical
support for the proposal of a closed or pseudo-closed
species of Cs symmetry as the transition state in the
fluxional process described above. This is further sug-
gested by the nido to closo structural change that
compound 2 undergoes upon deprotonation to give the
closo anion [1,1-(η2-dppe)-1,2-RhSB9H9]- (13), which,
upon addition of proton, is reversibly transformed to the
parent neutral nido compound, 2.16,19
[(dppm)2RhSB9H10]
6
compound, having been obtained previously in a differ-
ent, lower yield, route. Our spectroscopic data for 2
conform with the values reported previously.16 The new
species 3-6 were characterized by multinuclear NMR
spectroscopy and mass spectrometry, and the structures
of compounds 3 and 6 were confirmed by single-crystal
X-ray diffraction methods. The NMR spectra for 3 were
entirely consistent with the crystallographically deter-
mined molecular structure, indicating that the crystal
selected represented the bulk material. Unfortunately,
we were unable to definitively establish purity for 3.
Isolated as a single species by TLC, with NMR spectra
exhibiting only peaks attributable to 3, it gave unsat-
isfactory elemental analysis results and the mass
spectra, although providing a parent cluster in the
correct mass region, were noisy and precluded accurate
comparisons with the calculated spectra.
The boron-11 NMR spectrum of 3 at 331 K exhibits
four different peaks of relative intensity 3:1:4:1. The
overlap of the signals precludes complete assignment
of the spectrum; however, 1H{11B(selective)} experi-
1
ments, which relate the cluster H resonances to their
directly bonded boron atoms, demonstrate that the 11B
and 1H spectra consist of an overlapped 2:1:1:2:2:1
intensity pattern. The 31P NMR spectrum at 331 K
shows a broad signal. In contrast, the 11B and H NMR
1
spectra at 231 K reveal nine different BH resonances,
whereas the 31P NMR spectrum gives two doublets of
doublets, suggesting an asymmetric structure. The
presence of a bridging hydrogen atom in the boron
framework is revealed at both high and low tempera-
tures in the proton NMR spectra; the resonance appears
in the negative region of the spectra (-2.02 ppm at 231
K and -1.80 ppm at 331 K).
The NMR data for 3 at different temperatures are
suggestive of an intramolecular dynamic process, which
resembles the fluxional behavior of the analogous rho-
dathiaboranes 1 and 2, the isoelectronic platinacarbo-
rane [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11] (7),21 and the
rhodaazaborane [8,8-(PPh3)2-nido-8,7-RhNB9H11] (8).22
The activation energy, ∆Gq, calculated for 3 at the
coalescence temperature of 310 K in the 31P NMR
spectrum, is 53 kJ mol-1, between the values of 62 and
46 kJ mol-1 reported for 7 and 8, respectively. A
Another perspective of this fluxional process is that
there is a continuously reversing internal redox reac-
tion, involving the insertion and extrusion of the metal
atom from the B(9)-H-B(10) bond of the heteroborane
subcluster {EB9H10} (where E ) S (1-3), C (7), and N
(8)). This would imply a two-electron-oxidation trans-
formation of the metal center {M(L2)}+ upon insertion
in the cluster framework to form the oxidized fragment
{M(L2)H}2+ and two-electron reduction when the metal
is extruded. Alternatively, the fluxional behavior of this
family of 11-vertex metallaheteroboranes may be simply
viewed as a hindered closo-nido isomerization in solu-
tion.
The reaction of 3 with EtOH in CH2Cl2-EtOH, in a
1:1 molar ratio, affords the ethoxy derivative [8,8-(η2-
(21) Sˇt´ıbr, B.; J el´ınek, T.; Kennedy, J . D.; Fontaine, X. L. R.;
Thornton-Pett, M. J . Chem. Soc., Dalton Trans. 1993, 1261.
(22) Mac´ıas, R. Ph.D. Thesis, University of Leeds, 1996.
(23) Bould, J .; Rath, N.; Barton. L. Acta Crystallogr., Sect. C: Cryst.
Struct. Commun. 1997, C53, 416.

3640 Organometallics, Vol. 18, No. 18, 1999
Mac´ıas et al.
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t P a r a m eter s for [8,8-(η2-d p p p )-8,7-Rh SB9H10] (3),
[8,8-(η2-d p p p )-9-(OEt)-8,7-Rh SB9H9] (14), [8,8-(η2-d p p m )-8-(d p p m )-8,7-Rh SB9H10] (6), a n d
[1,1-(η2-d p p e)-3-(η1-d p p eO)-1,2-Rh SB9H8] (20)
3
14
6
20
empirical formula
fw
C
28H37B9Cl3P2RhS
C29H40B9OP2RhS
698.81
223(2)
0.71073
triclinic
P1h
10.0168(1)
11.2339(1)
16.2335(2)
75.879(1)
74.070(1)
74.435(1)
1663.30(3)
2
C102H114B18Cl4P8Rh2S2
2210.01
223(2)
0.71073
triclinic
C55H62B9OP4RhS
1095.19
293(2)
0.71073
monoclinic
P21/n
12.6671(1)
21.1004(2)
19.9250(1)
90
94.241(1)
90
774.13
218(2) K
0.71073
monoclinic
P21/n
10.8921(1)
16.4904(2)
19.9240(2)
10.8921(1)
16.4904(2)
19.9240(2)
3568.76(7)
4
temp (K)
wavelength
cryst syst
space group
a (Å)
P1h
13.6177(1)
18.8835(2)
22.6213(2)
102.61(1)
92.675(1)
103.587(1)
5488.30(9)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
5310.99(7)
4
1.370
Z
D(calcd) (g/cm3)
1.441
0.872
1.395
0.697
1.337
0.599
abs coeff (mm-1
cryst size (mm)
F(000)
)
0.522
0.40 × 0.33 × 0.16
0.40 × 0.20 × 0.10
0.33 × 0.26 × 0.18
0.33 × 0.22 × 0.20
1568
716
2268
2264
2θ range for data (deg)
no. of rflns collected
no. of indep rflns
1.60-28.30
69 334
8440
2.66-55.22
31 204
7340
2.24-50
60 636
19 166
2.82-54
100 986
11 495
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
1.027
1.063
1.022
1.027
R1 ) 0.0340
wR2 ) 0.0925
-1.008
R1 ) 0.0409
wR2 ) 0.0750
-0.385
R1 ) 0.0812
wR2 ) 0.2576
-1.256
R1 ) 0.0553
wR2 ) 0.1565
-0.529
(∆/σ)min (e Å-3
(∆/σ)max (e Å-3
)
)
1.035
0.390
2.029
1.439
dppp)-9-(OEt)-nido-RhSB9H9] (14). The same reactivity
is observed for the starting material 1 and for the
isoelectronic platinacarborane 7, which in alcoholic
media give the corresponding ethoxy and methoxy
species [8,8-(PPh3)2-9-(OEt)-nido-RhSB9H9] (15)18 and
[8,8-(PMe2Ph)2-9-(OMe)-nido-8,7-PtCB9H10] (16),21 re-
spectively. These results indicate that the boron vertex
at the 9-position in this series of unsaturated 11-vertex
metallaheteroboranes, 1-3 and 7, is prone to undergo
nucleophilic substitution reactions of the terminal hy-
drogen atom.
The difference in the activation energy of the substi-
tuted versus the unsubstituted species is large, and it
may arise from the inductive electron-withdrawing
effect (-I, electron acceptance)24 of the alkoxy substitu-
ent at the 9-position, which causes a polarization of the
B(9)-H-B(10) bond, suggested by the shift of 1 ppm to
low field of the resonance of the bridging hydrogen in
14 with respect that found in 3. Since this bond
participates significantly in the fluxionality described
above, it is expected that any change in its electronic
character will result in a substantial variation of the
energy of the transition state. The differences in the
structures of 3 and 14 are minimal except for the B(9)-
B(10) distances which differ by 0.083 Å, the OEt
derivative distance is 1.944(4) compared to 1.861(5) Å
in 3. This tends to suggest a role for this bond in the
fluxional process, although a purely steric influence of
the substituent in 14 cannot be ruled out.
The 11B and 1H NMR spectra for 6 indicate the
presence of nine BH groups and a B-H-B bridging
hydrogen atom. The resonance of the latter is shifted
ca. 2 ppm upfield with respect to the values found for 2
and 3. The 31P NMR spectra, however, suggest two
dppm ligands bonded to the rhodium atom, one chelat-
ing the Rh atom and the other coordinating in a
unidentate mode. The molecular structures of com-
pounds 3, 14, and 6 have been confirmed by X-ray
analysis and are consistent with their NMR data
reported herein. Crystallographic data for the three
species are summarized in Table 1, and selected inter-
atomic distances and angles appear in Tables 2-4,
respectively. These rhodathiaboranes have an 11-vertex
nido cluster geometry that can be derived from an
icosahedron by removing 1 vertex (Figures 1-3). The
sulfur atom is positioned on the open face adjacent to
the rhodium center, and in all the species, there is a
bridging hydrogen at the open-face B(9)B(10) site. In
Compound 14 was characterized by NMR spectros-
copy, mass spectrometry, and X-ray diffraction, but we
were unable to unambiguously demonstrate purity for
this species since the mass spectra were quite noisy, and
elemental analysis gave unsatisfactory results. The
NMR spectra for 14 were entirely consistent with the
crystallographically determined molecular structure,
indicating that the crystal selected represented the bulk
material. The 11B NMR spectrum consists of nine
different resonances; 1H{11B(sel)} experiments indicated
the existence of eight terminal hydrogen atoms directly
bonded to the corresponding boron atoms of the cluster.
The proton NMR spectrum exhibits also the signals of
the OEt substituent and the exo-polyhedral chelating
ligand dppp. In addition, the 31P NMR spectrum at room
temperature exhibits two doublets of doublets. In con-
trast to the parent rhodathiaborane 3, compound 14
does not feature fluxional behavior even at 373 K,
implying, perhaps, ∆Gq values greater than 64 kJ mol-1
for the hypothetical dynamic process in 14, versus the
value of 53 kJ mol-1, found for 3. An increase in the
activation energy upon substitution of the terminal
hydrogen atom at the 9-position in the metallahetero-
borane cage is also observed in the case of [8,8-(PMe2-
Ph)2-9-(OMe)-nido-8,7-PtCB9H10] (16), for which the
activation energy, ∆Gq, is found to be 12 kJ mol-1
greater than that of the unsubstituted parent platina-
carborane 7.22
(24) Herma´nek, S. Chem. Rev. 1992, 92, 325.

Organometallic Chemistry on a Metallathiaborane
Organometallics, Vol. 18, No. 18, 1999 3641
Ta ble 2. Selected In ter a tom ic Dista n ces (Å) a n d An gles (d eg) for [8,8-(η2-d p p p )-8,7-Rh SB9H10] (3)
Rh(8)-B(9)
Rh(8)-P(2)
S(7)-B(11)
P(2)-C(3)
C(1)-C(2)
2.138(3)
2.2645(6)
1.908(4)
1.829(3)
1.520(4)
Rh(8)-B(4)
Rh(8)-P(1)
S(7)-B(2)
B(9)-B(10)
C(2)-C(3)
2.236(3)
2.3324(7)
1.984(4)
1.861(5))
1.532(4)
Rh(8)-B(3)
Rh(8)-S(7)
S(7)-B(3)
B(10)-B(11)
P(1)-C(1)
2.238(3)
2.3644(7)
2.053(4)
1.859(5)
1.827(3)
B(9)-Rh(8)-B(4)
B(9)-Rh(8)-S(7)
B(11)-S(7)-B(2)
B(3)-S(7)-Rh(8)
B(1)-B(2)-B(3)
B(4)-B(3)-Rh(8)
B(9)-B(4)-Rh(8)
B(11)-B(6)-B(10)
B(2)-B(6)-B(1)
B(10)-B(9)-Rh(8)
B(11)-B(10)-B(9)
B(10)-B(11)-S(7)
P(2)-Rh(8)-S(7)
C(1)-C(2)-C(3)
49.41(14)
B(4)-Rh(8)-B(3)
B(3)-Rh(8)-S(7)
B(2)-S(7)-B(3)
C(1)-P(1)-Rh(8)
B(11)-B(2)-S(7)
B(3)-B(4)-B(1)
B(9)-B(5)-B(10)
B(6)-B(5)-B(1)
B(5)-B(9)-B(10)
B(6)-B(10)-B(5)
B(6)-B(11)-B(2)
B(3)-B(2)-S(7)
C(2)-C(1)-P(1)
B(6)-B(1)-B(5)
46.63(14)
52.91(10)
55.71(16)
116.29(9)
60.10(16)
59.0(2)
63.3(2)
59.6(2)
58.6(2)
60.1(2)
P(2)-Rh(8)-P(1)
P(1)-Rh(8)-S(7)
B(11)-S(7)-Rh(8)
C(3)-P(2)-Rh(8)
B(2)-B(3)-S(7)
B(3)-B(4)-Rh(8)
B(6)-B(5)-B(10)
B(3)-B(1)-B(4)
B(4)-B(9)-Rh(8)
B(5)-B(10)-B(9)
B(6)-B(11)-B(10)
S(7)-B(3)-Rh(8)
C(2)-C(3)-P(2)
B(1)-B(6)-B(5)
91.43(2)
90.41(2)
106.72(11)
116.85(9)
60.28(16)
66.73(16)
59.4(2)
93.42(8)
55.61(19)
60.38(9)
57.2(2)
66.64(15)
62.51(14)
64.7(2)
60.2(2)
60.1(3)
68.08(16)
58.09(19)
58.9(2)
66.71(11)
116.4(2)
60.4(2)
114.17(19)
111.1(2)
113.0(2)
173.27(3)
114.1(2)
59.2(3)
64.02(16)
112.8(2)
60.0(2)
Ta ble 3. Selected In ter a tom ic Dista n ces (Å) a n d An gles (d eg) for [8-(η2-d p p p )-9-(OEt)-n id o-8,7-Rh SB9H9]
(14)
Rh(8)-B(9)
Rh(8)-P(2)
S(7)-B(11)
B(9)-B(10)
B(6)-B(11)
P(1)-C(1)
2.122(3)
2.2680(7)
1.921(3)
1.944(4)
1.710(5)
1.820(3)
Rh(8)-B(4)
Rh(8)-P(1)
S(7)-B(2)
B(9)-O(1)
B(10)-B(11)
P(2)-C(3)
2.218(3)
2.3337(8)
1.994(4)
1.386(3)
1.853(5)
1.830(3)
Rh(8)-B(3)
Rh(8)-S(7)
S(7)-B(3)
O(1)-C(28)
C(1)-C(2)
C(2)-C(3)
2.264(3)
2.3693(7)
2.064(3)
1.436(3)
1.533(4)
1.531(4)
P(2)-Rh(8)-P(1)
P(1)-Rh(8)-S(7)
B(9)-Rh(8)-B(4)
B(2)-S(7)-B(3)
B(10)-B(11)-S(7)
B(5)-B(10)-B(9)
B(2)-B(6)-B(1)
B(9)-B(5)-B(10)
B(9)-B(4)-Rh(8)
S(7)-B(3)-Rh(8)
B(1)-B(2)-B(3)
C(1)-P(1)-Rh(8)
C(3)-C(2)-C(1)
C(2)-C(3)-P(2)
90.08(3)
93.60(3)
B(9)-Rh(8)-S(7)
B(3)-Rh(8)-S(7)
B(11)-S(7)-Rh(8)
B(11)-S(7)-B(2)
B(6)-B(11)-B(2)
B(11)-B(10)-(9)
B(5)-B(9)-(10)
B(5)-B(6)-B(1)
B(6)-B(5)-B(1)
B(3)-B(4)-Rh(8)
B(2)-B(3)-S(7)
B(3)-B(2)-S(7)
B(3)-B(1)-B(4)
C(3)-P(2)-Rh(8)
95.98(8)
52.85(8)
106.02(10)
57.01(15)
58.8(2)
P(2)-Rh(8)-S(7)
B(4)-Rh(8)-B(3)
B(3)-S(7)-Rh(8)
B(6)-B(11)-(10)
B(6)-B(10)-B(5)
B(10)-B(9)-Rh(8)
B(4)-B(9)-Rh(8)
B(11)-B(6)-(10)
B(6)-B(5)-B(10)
B(3)-B(4)-B(1)
B(4)-B(3)-Rh(8)
B(11)-B(2)-S(7)
B(5)-B(1)-B(6)
C(2)-C(1)-P(1)
168.43(3)
46.47(12)
60.95(9)
580.86(19)
60.29(18)
111.06(18)
67.21(14)
64.6(2)
58.64(18)
58.73(19)
65.40(15)
59.54(15)
59.55(17)
112.25(19)
50.91(12)
55.51(14)
113.14(19)
56.03(16)
58.36(19)
66.15(19)
61.88(14)
66.19(10)
57.05(18)
111.46(10)
115.6(2)
111.9(2)
57.81(17)
59.88(18)
60.57(18)
68.13(16)
60.36(15)
64.13(15)
60.39(18)
117.66(9)
117.9(2)
Ta ble 4. Selected In ter a tom ic Dista n ces (Å) a n d An gles (d eg) for
[8,8-(η2-d p p m )-8-(η1-d p p m )-n id o-8,7-Rh SB9H10] (6)
Rh(8)-P(1)
Rh(8)-S(7)
Rh(8)-B(9)
S(7)-B(11)
B(2)-B(3)
2.393(2)
2.370(2)
2.280(9)
1.908(11)
1.893(15)
Rh(8)-P(2)
Rh(8)-B(3)
S(7)-B(2)
B(9)-B(10)
B(1)-B(2)
2.295(2)
Rh(8)-P(3)
Rh(8)-B(4)
S(7)-B(3)
2.411(2)
2.251(10)
2.013(11)
1.886(14)
1.741(16)
2.235(10)
2.072(10)
1.804(17)
B(11)-B(10)
P(1)-Rh(8)-P(2)
P(2)-Rh(8)-S(7)
S(7)-Rh(8)-B(9)
B(10)-B(9)-Rh(8)
B(4)-Rh(8)-B(9)
B(2)-S(7)-B(3)
B(2)-B(11)-B(6)
B(6)-B(10)-(11)
B(4)-B(9)-B(5)
B(1)-B(6)-B(2)
B(1)-B(5)-B(4)
B(3)-B(4)-Rh(8)
S(7)-B(3)-B(2)
B(1)-B(2)-B(3)
71.30(7)
P(1)-Rh(8)-P(3)
P(1)-Rh(8)-B(9)
S(7)-Rh(8)-P(3)
B(11)-B(10)-(9)
P(3)-Rh(8)-B(9)
Rh(8)-S(7)-B(3)
B(6)-B(11)-(10)
B(5)-B(10)-B(9)
B(4)-B(9)-Rh(8)
B(1)-B(6)-B(5)
B(9)-B(5)-B(4)
B(3)-B(4)-B(1)
B(1)-B(3)-B(2)
B(6)-B(2)-B(1)
99.12(7)
P(3)-Rh(8)-P(2)
P(3)-Rh(8)-B(9)
B(11)-S(7)-Rh(8)
S(7)-Rh(8)-B(3)
B(11)-S(7)-B(2)
S(7)-B(11)-B(2)
B(5)-B(10)-B(6)
B(4)-B(9)-Rh(8)
B(2)-B(6)-B(11)
B(9)-B(5)-B(10)
B(9)-B(4)-Rh(8)
S(7)-B(3)-Rh(8)
S(7)-B(2)-B(3)
B(2)-B(1)-B(3)
103.44(7)
83.5(2)
112.0(4)
53.2(3)
57.3(5)
64.2(5)
58.6(6)
65.3(4)
64.7(6)
63.6(6)
68.0(4)
66.3(3)
64.0(5)
65.7
157.25(8)
88.2(2)
117.7(6)
46.7(3)
55.2(2)
57.7(6)
59.1(6)
59.8(6)
58.9(6)
59.9(6)
66.9(5)
60.8(5)
57.4(6)
174.4(2)
97.24(7)
112.1(7)
83.5(2)
60.5(3)
59.3(7)
58.4(5)
65.3(4)
61.7(6)
59.9(5)
58.3(6)
56.9(6)
61.2(7)
contrast with compounds 1-3 and 14, the structure
determination confirms that the rhodium atom in the
dppm derivative 6 bears two exo-polyhedral ligands,
featuring two coordination modes, chelating bidentate
and unidentate. The structural parameters for the three
clusters are very similar and are within the range found
for compounds 1 and 2. The longest interboron distances
are the B(9)-B(10) edge, bridged by a hydrogen atom
for compounds 1, 3, and 14, and the B(2)-B(3) edge,
flanked by the sulfur atom, for 6. In all of the compounds
1-3, 6, and 14 the P-Rh bond distance of the phos-
phorus atom trans to the sulfur vertex of the cluster is
substantially shorter than the other P-Rh bond, trans
to the boron side of the cage. The P(1)-Rh(8)-P(2)
angles vary from the value of 98.50(2)° in 1, through
84.22(6), 91.43(2), and 90.08(3)° found in 2, 3, and 14,

3642 Organometallics, Vol. 18, No. 18, 1999
Mac´ıas et al.
F igu r e 3. Molecular structure of [8,8-(η2-dppm)-8-(η1-
dppm)-nido-8,7-RhSB9H10] (6). Displacement ellipsoids are
drawn at the 50% level. The phenyl rings, ipso-carbon
atoms excepted, are omitted.
F igu r e 1. Molecular structure of [8,8-(η2-dppp)-nido-8,7-
RhSB9H10] (3). Displacement ellipsoids are drawn at the
50% level. The phenyl rings, ipso-carbon atoms excepted,
are omitted.
Although compounds 1-3, 6, and 14 have the same
basic 11-vertex nido structure, their electronic struc-
tures, in principle, are different. Compounds 1-3 and
14 (and also the isoelectronic 7 and 8) do not conform
to the skeletal electron counting rules, being two
electrons short for the observed nido structure.15 This
cluster unsaturation can be related to the unsaturated
character of the metal vertex,25 which contributes two
orbitals and one electron to the metal-to-thiaborane
bonding. In contrast, in compound 6 the rhodium atom
is saturated, and the cluster has the predicted number
of skeletal electron pairs. Therefore, in terms of a metal-
to-ligand description, the unsaturated species can be
regarded as “square-planar” 16-electron rhodium com-
plexes, in which 2 coordination positions are occupied
by the exo-polyhedral groups and the other 2 by the
thiaborane fragment, acting as a bidentate ligand in a
η4 fashion. On the other hand, compound 6 resembles
an “octahedral” 18-electron complex with 3 coordination
positions filled by the two dppm ligands and the other
3 by the thiaborane fragment, acting as a tridentate
ligand in a η4 manner. There is an alternative proposal
for the electronic structure of the metal center in
compounds related to 1, 3, and 14. Welch and co-
workers, in a discussion of compound 2 in another
context, have suggested that the Rh atom gains the two
electrons via unique agostic interactions between pairs
of ortho hydrogen atoms on the P-phenyl groups, as we
described in the Introduction.16 We prefer to regard
these systems as unsaturated. Although the closest
C-H‚‚‚Rh distances in 3 and 14 are all about 3.00 Å,
within the ranges described by Welch et al., some
B-H‚‚‚Rh distances are shorter than those for what
would be the agostic C-H moieties. We believe that the
many examples of square-planar 16-electron metal
centers with short electron counts in the literature
mitigate against requiring such agostic interactions in
3 and 14, although we cannot rule them out.
F igu r e 2. Molecular structure of [8,8-(η2-dppp)-9-(OEt)-
nido-8,7-RhSB9H9] (14). Displacement ellipsoids are drawn
at the 50% level. The phenyl rings, ipso-carbon atoms
excepted, are omitted.
respectively, to the value of 71.30(7)° in 6. A common
structural feature of these species is that they exhibit
a significant twist of the plane formed by the P(1)Rh-
(8)P(2) atoms with respect to the plane formed by S(7)-
Rh(8)B(9). These angles range from the value of 77°
found in 2 and 14, through 59° in 1 and 3, to 19° in 6.
The large twist angles found for 2 and 14 could be due
to exigencies of the chelating ligands and/or packing
forces. In the context of the fluxionalty discussed herein,
the observed solid-state conformations could also rep-
resent rotamers of minimum energy. Compound 6, in
contrast, has a rigid metal-to-thiaborane interaction, in
which the chelating dppm ligand is forced to stay almost
parallel to the S(7)Rh(8)B(9) plane and the second,
monodentate, dppm group completes the coordination
sphere around the rhodium atom.
The species 4 and 5, isolated from the reactions of 1
with excesses of dppe and dppp, respectively (eqs 3 and
(25) (a) Kennedy, J . D. Main Group Metal Chem. 1989, 12, 149. (b)
Barton, L.; Bould, J .; Rath, N. P.; Fang, H. Inorg. Chem. 1996, 35,
2062. (c) Bould, J .; Cooke, P. A.; Do¨rfler, U.; Kennedy, J . D.; Barton,
L.; Rath, N. P.; Thornton-Pett, M. Inorg. Chim. Acta, in press.

Organometallic Chemistry on a Metallathiaborane
Organometallics, Vol. 18, No. 18, 1999 3643
The formation of 4 and 5 from the starting material
1 implies (a) substitution of the PPh3 groups by a
chelating bis(diphenylphosphino)alkane ligand at the
rhodium atom and (b) nucleophilic attack of a second
phosphine at the boron atom at the 9-position, with the
concomitant migration of the terminal 9-hydrogen atom
to either the B(9)-B(10) bridging position or to the
rhodium atom. However, we cannot rule out a mecha-
nism with an initial step similar to the formation of 6,
in which two ligands first coordinate to the metal
followed by transfer of the unidentate one to the
electrophilic site at B(9). There is no experimental
evidence for this process, but it is clear that for the more
nucleophilic pendant PPh2 group on dppp or dppe, it
would be sterically more favorable for a concerted
transfer of a ligand from Rh to the B(9) position than
for dppm. We have no explanation for the absence of
the formation of a species involving a bidentate dppm,
only, coordinating to the Rh atom, as we observe for 2
and 3. For descriptive purposes, compounds 4 and 5 can
be regarded as phosphine adducts of the unsaturated
parent rhodathiaboranes 2 and 3, respectively. The new
adducts have two skeletal electrons more than the
parent, conforming therefore to the electron-counting
rules.15
F igu r e 4. Proposed molecular structure for [8,8-(η2-dppe)-
9-(η1-dppe)-nido-8,7-RhSB9H10] (4) and [8,8-(η2-dppp)-9-(η1-
dppp)-nido-8,7-RhSB9H10] (5).
4), were characterized by NMR spectroscopy and mass
spectrometry. The 11B NMR spectra consist of five broad
peaks of relative intensity 1:1:4:2:1 for compound 4 and
seven peaks of relative intensity 2:1:1:1:1:2:1 for com-
1
pound 5. H{11B(sel)} experiments assigned eight dif-
ferent terminal hydrogen atoms to their directly bound
boron atoms, indirectly resolving the boron-11 spectra.
One of the boron atoms has no terminal hydrogen atom,
since it bears a PPh2 terminus of the 1,n-bis(diphen-
1
ylphosphino)alkane substituent. The H NMR spectra
include peaks at -1.39 and -11.97 ppm for 4 and at
-2.39 and -11.96 ppm for 5. The signals at the highest
frequencies in the negative region of the spectra, which
are broad singlets, are assigned to B-B bridging
hydrogen atoms on the cluster, whereas the peaks at
the lowest frequencies, observed as multiplets, are
assigned to the rhodium-bonded hydrides. The 103Rh-
1H coupling is clearly visible. The proton NMR spectra
also confirm the presence of two exo-polyhedral phos-
phine ligands in both 4 and 5. Additionally, the 31P
NMR spectrum of 4 shows (a) doublets at 59.1 and 54.7
ppm, assigned to the phosphorus atoms of the chelating
dppe ligand bound to the rhodium atom, (b) a very broad
signal at 5.9 ppm, due to the phosphorus atom directly
bonded to a cage boron atom, and (c) a sharp doublet at
-12.4 ppm, arising from the pendant PPh2 group.
Similarly, the 31P NMR spectra for 5 exhibit (a) doublets
at 13.9 and 9.3 ppm, arising from the chelating dppp
ligand, (b) a very broad signal at 7.4 ppm, due to the
phosphorus linked to a boron atom, and (c) a sharp
singlet at -18.8 ppm, assigned to the pendant phos-
phine. The observed spectroscopic data suggest that the
molecular structures of 4 and 5 are based on 11-vertex
nido clusters with the rhodium and sulfur atoms
adjacent on the pentagonal open face, on which the
B(9)-B(10) edge is bridged by a hydrogen atom and a
terminal hydride ligand is bonded to the rhodium. The
structure is completed by two exo-polyhedral bis(diphen-
ylphosphino)alkane groups, one bound in a unidentate
manner to the boron atom at the 9-position and the
other acting as a chelating ligand at the rhodium center
(Figure 4). Mass spectrometry shows the isotopic enve-
lope of the protonated species [(MO - H2) + H]+ ion at
1054.2 amu for 4 and the [M]+ and [M + O]+ ions at
1067.2 and 1082.4 amu, respectively, for 5. The mass
envelopes for the measured masses for 4 and 5 match
those calculated from the known isotopic abundances
of the constituent elements. These spectrometric results
are consistent with the proposed chemical formulations
of 4 and 5 and demonstrate the facile oxygenation of
the pendant PPh2 group present in both species.
Interestingly, compounds 4 and 5 are unstable in
solution. If a dilute solution of 4 is heated at reflux
temperature in CH2Cl2 for 1 day, the resultant solution
contains a mixture of the parent rhodathiaborane 2 and
free phosphine dppe as major components, together with
a new species, 17, as minor component. Under the same
conditions, compound 5 affords a mixture of only the
parent 3 and free phosphine dppp. In contrast, when a
concentrated solution of 4 in CDCl3 is heated at 40 °C
in an NMR tube, the new species 17 is obtained almost
quantitatively. Under the same conditions, 5 gives a
mixture of 3 and free dppp, this time as minor products,
and two new compounds, 18 and 19.
The new compounds were characterized as [1,1-(η2-
dppe)-3-(η1-dppe)-closo-1,2-RhSB9H8] (17), [1,1-(η2-dppp)-
3-(η1-dpppO)-closo-1,2-RhSB9H8] (18), and [{1,1-(η2-
dppp)-closo-1,2-RhSB9H8}2-3,3′-(µ-dppp)] (19). The 11B
NMR spectra of the three species are almost identical,
consisting of five resonances of relative intensity 1:1:3:
2:2. 1H{11B(sel)} experiments indicate eight terminal
hydrogen atoms in a 1:1:2:1:2:2 relative intensity pat-
tern, which indirectly also resolves the 11B spectra. The
31P NMR spectra are diagnostic of the molecular struc-
tures of these compounds. For compounds 17 and 18,
the following signals are found: (a) a sharp doublet in
the region corresponding to the chelating phosphine
ligands, (b) a doublet and a singlet due to the dangling
PPh2 groups, for 17 and 18, respectively, and (c) a broad
signal for the phosphorus atom bound to a boron atom
of the cage. The 31P NMR spectrum of 19 exhibits a
doublet, assigned to a dppp chelating ligand, and a very
broad signal typical of a phosphorus atom directly
bonded to boron; the two signals appear in a 2:1 relative
intensity ratio, respectively. In contrast to the 31P NMR
spectra of 17 and 18, compound 19 does not exhibit
signals corresponding to either dangling PPh2 or PPh2O
groups. These spectroscopic results, together with the
X-ray analysis of 20, discussed below, lead us to
proposed the molecular structure of 19 as two 11-vertex

3644 Organometallics, Vol. 18, No. 18, 1999
Mac´ıas et al.
Ta ble 5. Selected In ter a tom ic Dista n ces (Å) a n d An gles (d eg) for
[1,1-(η2-d p p e)-3-(η1-d p p eO)-closo-1,2-Rh SB9H8] (20)
Rh(1)-P(1)
Rh(1)-B(3)
Rh(1)-B(7)
S(2)-B(8)
B(3)-P(3)
P(4)-C(28)
2.2805(12)
2.106(4)
2.437(5)
1.999(6)
1.920(5)
1.822(4)
Rh(1)-P(2)
Rh(1)-B(4)
S(2)-B(4)
C(1)-C(2)
P(4)-O(1)
B(3)-B(6)
2.2638(11)
2.526(5)
1.916(5)
1.502(6)
1.513(3)
1.712(8)
Rh(1)-S(2)
Rh(1)-B(6)
S(2)-B(5)
C(27)-C(28)
P(3)-C(27)
B(4)-B(7)
2.3689(11)
2.337(5)
1.957(6)
1.524(5)
1.822(4)
1.843(7)
P(1)-Rh(1)-P(2)
P(2)-Rh(1)-B(3)
S(2)-Rh(1)-B(5)
Rh(1)-S(2)-B(4)
Rh(1)-B(3)-B(7)
B(6)-B(3)-B(9)
Rh(1)-B(4)-B(7)
B(6)-B(5)-Rh(1)
B(5)-B(6)-Rh(1)
B(3)-B(7)-Rh(1)
S(2)-B(8)-B(4)
P(2)-C(2)-C(1)
84.77(4)
114.09(13)
48.8(2)
71.4(2)
78.9(2)
62.8(3)
65.7(2)
65.9(2)
67.8(2)
58.0(2)
58.6(2)
112.4(3)
P(1)-Rh(1)-S(2)
P(2)-Rh(1)-S(2)
B(3)-Rh(1)-B(7)
Rh(1)-S(2)-B(5)
Rh(1)-B(3)-B(6)
P(3)-B(3)-Rh(1)
B(8)-B(4)-S(2)
S(2)-B(5)-B(8)
B(3)-B(6)-Rh(1)
B(4)-B(7)-Rh(1)
Rh(1)-P(1)-C(1)
Rh(1)-P(2)-C(2)
110.20(5)
111.79(4)
43.1(2)
65.6(2)
74.7(2)
129.9(2)
63.0(3)
62.3(3)
60.3(2)
70.8(2)
P(1)-Rh(1)-B(3)
S(2)-Rh(1)-B(4)
B(3)-Rh(1)-B(6)
B(4)-S(2)-B(8)
B(7)-B(3)-B(9)
Rh(1)-B(4)-S(2)
S(2)-B(5)-Rh(1)
B(6)-B(5)-B(11)
B(3)-B(6)-B(9)
B(4)-B(7)-B(10)
C(2)-C(1)-P(1)
B(3)-P(3)-C(27)
111.09(14)
45.94(12)
45.0(2)
58.4(3)
63.8(3)
62.7(2)
65.6(2)
59.2(3)
59.3(4)
58.4(3)
108.7(3)
111.0(2)
108.8(2)
109.8(2)
F igu r e 5. Proposed molecular structure for [{1,1-(η2-
dppp)-closo-1,2-RhSB9H8}2-3,3′-(µ-dppp)] (19).
closo clusters linked by an inter-cage bridging dppp
ligand (Figure 5). This hypothesis is supported by mass
spectrometry, which shows a molecular ion, [M]+,
centered at 1718.9 amu, with an isotopic distribution
that conforms to the calculated values for the proposed
formulation of 19.
The proposed molecular structures of 17 and 18 are
supported by the X-ray diffraction analysis of a crystal
of [1,1-(η2-dppe)-3-(η1-dppeO)-closo-1,2-RhSB9H8] (20).
This structure determination also supports the proposed
linked-dicage structure of 19. Crystallographic data for
20 are summarized in Table 1, and selected interatomic
distances and angles appear in Table 5. The molecule
can be described as an 11-vertex closo-rhodathiaborane
with the metal center at position 1, which has a
connectivity of 6, and the sulfur atoms at the adjacent
2-position (Figure 6). The coordination sphere of the
rhodium atom is completed by a bidentate dppe ligand,
while a second dppe is linked to B(3); the pendant PPh2
group bears an oxygen atom, demonstrating that in
these species the pendant phosphine group is easily
oxidized in the presence of air. The cluster dimensions
of 20 are comparable to those of the analogue [1-(CO)-
1,3-(PMe2Ph)2-closo-1,2-RhSB9H8] (21),15 although the
latter is reported to exhibit positional disorder of the
rhodium atoms. In both closo-species the Rh(1)-B(3)
distance is ca. 0.2 Å shorter than the distances of Rh(8)
with B(4), B(5), B(6) and B(7). The P(3)-B(3) bond
length of 1.920(5) Å is within the range 1.87-1.93 Å,
usually found for that type of interaction.26 The confor-
mations of the chelating dppe and dangling and dppeO
F igu r e 6. Molecular structure of [1,1-(η2-dppe)-3-(η1-
dppeO)-closo-1,2-RhSB9H8] (20). Displacement ellipsoids
are drawn at the 50% level. The phenyl rings, ipso-carbon
atoms excepted, are omitted.
ligands break the symmetry of the molecule in the solid
state; however, fast conformational changes result in
an effective Cs point group symmetry in solution.
Con clu sion s
The reactions of [(CH2)nPPh2] (where n ) 1, dppm; n
) 2, dppe; n ) 3, dppp) with 1 have demonstrated that
this rhodathiaborane contains two main centers of
reactivity: (a) the rhodium atom and (b) the boron atom
at the 9-position. The rhodium center behaves as a
typical 16-electron complex, undergoing facile substitu-
tion of the PPh3 groups by the chelating bis(diphen-
ylphosphino)alkane ligands. In the case of dppm, a
second phosphine molecule is added at the metal center,
even if the reaction is carried out in a 1:1 molar ratio.
In contrast, an excess of dppe or dppp appears to give
rise to nucleophilic attack at the boron atom in the
9-position, although as we point out above, we cannot
rule out alternative mechanisms. The resulting P-B
bond is labile, and in dilute solutions it dissociates to
give a mixture of the corresponding free phosphines and
(26) Kennedy, J . D. Prog. Inorg. Chem. 1984, 32, 519; 1986, 34, 211
and references therein.

Organometallic Chemistry on a Metallathiaborane
Organometallics, Vol. 18, No. 18, 1999 3645
Sch em e 2. Rea ctivity of 1 w ith d p p m , d p p e, a n d d p p p
for handling air-sensitive compounds.27 Products were isolated
in air using thin-layer chromatography (TLC) on 20 × 20 cm
glass plates coated with 0.1 cm of silica gel (Aldrich standard
grade with gypsum binder and fluorescent indicator), made
from aqueous slurries followed by drying in air at 80 °C. [8,8-
unsaturated rhodathiaborane chelates. At higher con-
centration, in competition with the dissociation, the
adducts 4 and 5 also experience a nido to closo trans-
formation, with loss of H2, presumably the bridging H
and Rh-H hydride atoms. The chemistry described
herein is summarized in Scheme 2. Reactions of 1 with
1,n-bis(diphenylphosphino)alkanes have provided a route
to the formation of new rhodathiaboranes containing
pendant phosphine groups, PPh2. These groups are
reactive centers available for further chemistry. Facile
oxidation with oxygen in solution has been observed at
the pendant PPh2 group for all the species. The unsat-
urated Rh center for compounds 3 and 14, and the
presence of the reactive PPh2 group in 4-6, 17, and 18
perhaps account for our inability to obtain satisfactory
elemental analyses for these compounds. The formation
of the dicage derivative 19 demonstrates that an en-
trance to linked cages and thence possibly supramo-
lecular chemistry are also available in this system.
These and other aspects of the chemistry of compound
1 remain to be further developed. Some chemistry of
the species 6 has been described in a preliminary
communication.20
(PPh3)2-nido-8,7-RhSB9H10] (1) was prepared according to the
28
literature method14b from the reaction between Cs[SB9H12
]
and [RhCl(PPh3)3].29 PPh3 and [(PPh2)2(CH2)2] were obtained
from Aldrich, and [(PPh2)2(CH2)] and [(PPh2)2(CH2)3] were
obtained from Strem. Solvents used were reagent grade and
were dried before use. NMR spectroscopy was carried out on
a Bruker ARX 500 spectrometer operating at 500.1 MHz for
proton, 160.5 MHz for boron-11, and at 202.5 MHz for
phosphorus-31 and on a Varian Unity Plus 300 spectrometer
operating at 96.2 MHz for 11B, 299.9 MHz for 1H, and 121.4
MHz for 31P. Chemical shifts are reported in ppm for CDCl3
solutions, unless otherwise stated, to low field (high frequency)
1
of Et2O‚BF3 for 11B, of SiMe4 for H, and of 85% H3PO4 for 31P.
Elemental analyses were attempted by Atlantic Microlabs Inc.,
Norcross, GA, but they were unable to obtain satisfactory data;
however, NMR spectra were run on all samples sent for mass
spectra and crystal growth was generated from NMR samples,
after spectral analysis. The mass spectra were measured in
the FAB mode on a VG ZAB-E using 3-nitrobenzyl alcohol (3-
NBA) and also on a Kratos MS-50 using 3-NBA/Ar gas, at the
Washington University Mass Spectrometry Resource, an NIH
Research Resource (Grant No. P41RR0954).
Exp er im en ta l Section
(27) Shriver, D. F.; Drezdon, M. A. The Manipulation of Air-Sensitive
Compounds; Wiley: New York, 1986.
(28) Rudolph, R. W.; Pretzer, W. R. Inorg. Synth. 1983, 22, 226.
(29) Osborn, J . A.; Wilkinson, G. Inorg. Synth. 1990, 28, 77.
Gen er a l Con sid er a tion s. Solvents used were reagent
grade and were dried before use. Some reactions were carried
out using a Schlenk line, a glovebox, and standard techniques

3646 Organometallics, Vol. 18, No. 18, 1999
Mac´ıas et al.
P r ep a r a tion of [8,8-(η2-d p p e)-n id o-8,7-Rh SB9H10] (2). A
route different from that reported16 is described herein. A 50
mg (0.07 mmol) portion of [8,8-(PPh3)2-nido-8,7-RhSB9H10] was
dissolved in 30 mL of CH2Cl2 in a 50 mL round-bottom flask;
the resulting bright red solution was degassed and the system
filled with nitrogen gas. Then dppe (28 mg, 0.07 mmol) was
added to the reaction vessel at ambient temperature. Upon
addition, the initially red solution turned immediately to
orange. The reaction mixture was stirred at room temperature
under N2 for 16 h. After this time, the solvent was reduced in
volume and the resulting orange solution applied to TLC plates
using CH2Cl2-pentane (70:30) as mobile phase. The chromato-
gram resulted in the isolation of 32 mg of an orange air-stable
solid with Rf 0.3, which was characterized as the previously
reported 11-vertex rhodathiborane [8,8-(η2-dppe)-nido-8,7-
RhSB9H10] (2: 32 mg, 0.05 mmol; 71%). The NMR data
conform to the values published in ref 16. 11B NMR (160.5
MHz, CDCl3, 300 K; ordered as relative intensity δ(11B)
(relative to BF3‚OEt2) [δ(1H)]): 3BH 10.8 [3.26, 2H; 2.34, 1H],
1BH -7.4 [1.92, 1H], 4BH -12.2 [2.88, 2H; 1.64, 2H], 1BH
-27.0 [1.65] (1J (B,H) coupling constants could not be resolved
due to broadness of the peaks). Additional 1H NMR (500 MHz,
CDCl3, 300 K): δ 7.69-7.25 (m, 20H; C6H5), 2.77 (br m, 2H;
CH2), 2.32 (br m, 2H; CH2), -2.25 (br s, 1H; µ-H-BB). 31P-
{1H} NMR (202.5 MHz, CDCl3, 228 K): δ 66.1 (dd, 1J (Rh,P) )
[B-PPh3], 1BH(9) 27.6 [4.02, d, J ) 14 Hz], 3BH(4,5; 8) 2.0
[2.94, 1H; 2.12, 2H], 2BH(6,7) -15.8 [0.57], 2BH(10,11) -27.4
[0.16] (1J (B,H) coupling constants could not be resolved due
to broadness of the peaks). Additional 1H NMR (500 MHz,
CDCl3, 300 K): δ 7.47-7.06 (m, 40H; C6H5), 2.47-2.42 (br m,
2H; CH2), 2.30-2.27 (m, 2H; CH2), 2.20-2.16 (m, 2H; CH2),
1.84-1.80 (m, 2H; CH2). 31P{1H} NMR (202.5 MHz, CDCl3,
1
300 K): δ 61.3 (d, J (Rh,P) ) 148 Hz, 2P), 4.9 (v br; PPh2B),
3
-12.8 (d, J (P,P) ) 39 Hz; dangling PPh2).
[1,1-(η2-d p p e)-3-(η1-d p p eO)-closo-1,2-Rh SB9H8] (20). 11
B
NMR (96.2 MHz, CDCl3, 300 K; ordered as relative intensity
1
δ(11B) (relative to BF3‚OEt2) [δ(1H)]): 1B(3) 33.6 (d, J (P,B) )
114 Hz), 1BH(9) 27.2 [4.08, d, J ) 17 Hz], 3BH(4,5; 8) 1.23
[2.97, 1H; 2.13, 2H], 2BH(6,7) -15.8 [0.68], 2BH(10,11) -27.3
[0.23] (1J (B,H) coupling constants could not be resolved due
to broadness of the peaks; assignments were made by com-
parison with closo analogues previously reported).14b Ad-
1
ditional H NMR (500 MHz, CDCl3, 300 K): δ 7.63-6.86 (m,
40H; C6H5), 2.57 (m. 4H; CH2), 2.26-2.19 (m, 4H; CH2). 31P-
1
{1H} NMR (202.5 MHz, CDCl3, 300 K): δ 61.2 (d, J (Rh,P) )
3
149 Hz, 2P), 31.9 (d, J (P,P) ) 45 Hz, 1P; PPh2O), 2.3 (v br,
1P; PPh2-B). LRMS (VG ZAB-E, FAB with 3-NBA/Gly/TFA;
amu): calcd maximum for C52H56B9OP4RhS [MO]+, 1053.3;
obsd 1053.7. The mass envelope for the measured masses for
17 matches that calculated from the known isotopic abun-
dances of the constituent elements. The data are available as
Supporting Information.
1
1
142 Hz, J (P,P) ) 25 Hz), 49.9 (dd, J (Rh,P) ) 133 Hz).
R ea ct ion of [8,8-(P P h 3)2-n id o-8,7-R h SB9H 10 w it h
]
{(CH2)2(P P h 2)2] (d p p e). A 50 mL two-neck round-bottom
flask was loaded with 168 mg (0.22 mmol) of [8,8-(PPh3)2-nido-
8,7-RhSB9H10] and 30 mL of CH2Cl2; the system was filled with
nitrogen and evacuated several times. Then dppe 263 mg (0.66
mmol) was added via a tip tube previously attached to the
reaction vessel. The initial bright red solution of the rhoda-
thiaborane turned orange upon the addition of the phosphine.
The reaction mixture was stirred for 25 h. After this time, the
solvent was evaporated to dryness, the orange residue dis-
solved in CH2Cl2-pentane, and this solution applied to TLC
plates. The chromatogram was developed using CH2Cl2-
pentane (70:30) as eluent. Two yellow components were
separated from the plates with Rf values of 0.1 and 0.3, which
were characterized as [8,8-(η2-dppe)-9-(η1-dppe)-nido-8,7-
RhSB9H10] (4: 38 mg, 0.04 mmol; 18%) and [8,8-(η2-dppe)-nido-
8,7-RhSB9H10] (2: 52 mg; 0.08 mmol; 36%), respectively. The
new rhodathiaborane [8,8-(η2-dppe)-9-(η1-dppe)-nido-8,7-RhSB9-
P r ep a r a tion of [8,8-(η2-d p p p )-n id o-8,7-Rh SB9H10] (3).
A 62 mg (0.08 mmol) portion of [8,8-(PPh3)2-nido-8,7-RhSB9H10
]
(1) was dissolved in 25 mL of CH2Cl2. The reaction system was
evacuated and filled with nitrogen; then 34 mg (0.08 mmol) of
dppp was added to the reaction flask. The resulting orange
solution was stirred at room temperature under N2 for 25 h.
The final reaction mixture was reduced in volume and applied
to TLC plates using CH2Cl2-pentane (3:2). A yellow band with
Rf 0.7 was removed from the TLC plates, and the component
was extracted from the silica gel using CH2Cl2 solvent.
Recrystallization in CH2Cl2-pentane gave rise to the isolation
of 46 mg of a yellow product, which was characterized as [8,8-
(η2-dppp)-nido-8,7-RHSB9H10] (3; 0.07 mmol, 88%). 11B NMR
(160.5 MHz, CDCl3, 231 K; ordered as relative intensity δ-
(11B) (relative to BF3‚OEt2) [δ(1H)]): 1BH 15.0 [3.64], 1BH 7.9
[3.20], 3BH 1.7 [3.02, 2.36, 1.82], 1BH -8.5 [1.97], 3BH -24.1
[1.43, 1.24, 0.76] (1J (B,H) coupling constants could not be
H
10] (4) is unstable in solution, and it reacts further, giving
1
rise to the closo derivative [1,1-(η2-dppe)-3-(η1-ddpe)-1,2-
RhSB9H8] (17). The dangling phosphine group, present in these
species, reacts with oxygen in solution, giving rise to the Pd
O derivative [1,1-(η2-dppe)-3-(η1-ddpeO)- closo-1,2-RhSB9H8]
(20), studied by X-ray diffraction analysis.
resolved due to broadness of the peaks). Additional H NMR
(500 MHz, CDCl3, 231 K): δ 7.42-7.16 (m, 20H; C6H5), 2.71-
2.64 (br m, 2H; Ph2PCH2), 2.64-2.56 (br m, 3H; Ph2-
PCH2CHH), 1.85-1.73 (m, 1H; Ph2PCH2CHH), -2.02 (s, 1H;
µ-H-BB). 31P{1H} NMR (202.5 MHz, CDCl3, 231 K): δ 22.5
1
2
1
(dd, J (Rh,P) ) 140 Hz, J (P,P) ) 55 Hz), 6.9 (dd, J (Rh,P) )
130 Hz); the two doublet of doublets coalesce at 310 K (∆Gq )
53 kJ mol-1). 11B NMR (160.5 MHz, CDCl3, 331 K; ordered as
relative intensity δ(11B) (relative to BF3‚OEt2) [δ(1H)]): 3BH
[8,8-(η2-d p p e)-9-(η1-d p p e)-n id o-8,7-Rh SB9H10] (4). 11B
NMR (160.5 MHz, CDCl3, 300 K; ordered as relative intensity
δ(11B) (relative to BF3‚OEt2) [δ(1H)]): 1BH 2.2 [3.40], 1BH -1.4
[2.92], 4B -5.8 [2.52, 1H; 2.34, 2H], 2BH -20.2 [1.63, 1.37],
1BH -25.5 [1.53] (1J (B,H) coupling constants could not be
1
10.1 [3.37, 1H; 2.9, 2H], 1BH -7.9, J (B,H) ) 140 Hz, [2.07],
1
4BH -10.6 [2.25, 2H; 1.70, 2H], 1BH -26.7 [1.52]. Additional
1H NMR (500 MHz, CDCl3, 331 K): δ 7.50-7.18 (m, 20H;
C6H5), 2.66 (m, 2H; Ph2PCH2), 2.53 (m, 2H; Ph2PCH2), 1.67
(m, 1H; Ph2PCH2CH2), -1.80 (s, 1H; µ-H-BB). 31P{1H} NMR
(202.5 MHz, CDCl3, 331 K): δ 14.8 (v br, coupling no resolved).
LRMS (VG ZAB-E (in FAB mode with 3-NBA; amu): calcd
for [C27H36B9P2RhS]+, 654.8; obsd, cluster at 641-657 over-
lapped with spectral noise, precluding a detailed comparison.
resolved due to broadness of the peaks). Additional H NMR
(500 MHz, CDCl3, 300 K): δ 7.85-6.78 (m, 40H; C6H5), 2.65
(apparent d, J ) ca. 44 Hz, 2H; CH2), 2.29-2.07 (br m, 4H;
CH2), 1.80 (br m, 2H; CH2), -1.39 (s, 1H; µ-H-BB), -11.97
(m, 1H; RhH). 31P{1H} NMR (202.5 MHz, CDCl3, 300 K): δ
1
1
58.1 (br d, J (Rh,P) not well resolved; 1P), 54.7 (d, J (Rh,P) )
3
123 Hz, 1P), 5.9 (v br, 1P; Ph2PB), -12.4 (d, J (P,P) ) 34 Hz,
1P; dangling PPh2). Mass spectral data for 4 (LRMS, VG ZAB-
SE, FAB+ with 3-NBA; amu): calcd maximum for [(MO - H2)
+ H]+ C52H57B9OP4RhS, 1054.3; obsd, 1054.2. The mass
envelope for the measured masses for 4 matches that calcu-
lated from the known isotopic abundances of the constituent
elements. The data are available as Supporting Information.
[1,1-(η2-d p p e)-3-(η1-d d p e)-closo-1,2-Rh SB9H8] (17). 11B
NMR (160.5 MHz, CDCl3, 300 K; ordered as relative intensity
δ(11B) (assignments) (relative to BF3‚OEt2) [δ(1H)]): 1B(3) 34.9
R ea ct ion of [8,8-(P P h 3)2-n id o-8,7-R H SB9H 10
]
w it h
[(CH2)3P P h 2)2] (d p p p ). A 50 mg (0.065 mmol) portion of [8,8-
(PPh3)2-nido-8,7-RhSB9H10] (1) was placed in a two-neck 50
mL round-bottom flask and dissolved in 20 mL of CH2Cl2. The
system was evacuated and filled with nitrogen. To the result-
ing bright red solution of the rhodathiaborane was added 82
mg (0.20 mmol) of dppp via a sidearm of the reaction vessel.
The initial bright red solution immediately turned yellow on

Organometallic Chemistry on a Metallathiaborane
Organometallics, Vol. 18, No. 18, 1999 3647
the addition of phosphine. The reaction mixture was stirred
at ambient temperature under N2 for 16 h. After this time,
the final yellow solution was reduced in volume and applied
to TLC plates, using CH2Cl2-pentane (3:2) as eluent. The
chromatogram resulted in the isolation of two compounds,
which were characterized as the yellow [8-(η2-dppp)-nido-8,7-
RhSB9H10] (3: Rf 0.41; 20 mg, 0.03 mmol; 47%) and the yellow
[8-(η2-dppp)-9-(η1-dppp)-nido-8,7-RhSB9H10] (5: Rf 0.18; 30 mg,
0.03 mmol; 46%).
applied to TLC plates. The plates were developed using CH2-
Cl2-pentane (7:3) as the mobile phase. Two compounds were
separated and identified as unreacted [8-(η2-dppp)-nido-8,7-
RhSB9H10] (3: Rf 0.63) and [8-(η2-dppp)-9-(OEt)-nido-8,7-
RhSB9H10] (14: Rf 0.75; 8 mg, 55%).
[8,8-(η2-d p p p )-9-(OEt)-n id o-8,7-Rh SB9H9] (14). 11B NMR
(160.5 MHz, CDCl3, 300 K; ordered as relative intensity δ-
1
(11B) (relative to BF3‚OEt2); J (B,H) [δ(1H)]): 1B 26.6 [OEt],
1BH 14.2 [3.58], 1BH 4.5 [2.18], 1BH -5.1, br d, 123 Hz, [2.22,
d, J ) 20 Hz], 1BH -9.8 [2.33], 1BH -10.3, br d, ca. 116 Hz
[2.32], 1BH -24.9, d, 144 Hz [1.24], 1BH -30.4 [1.20], 1BH
-31.7, d, 122 Hz [0.40] (not all 1J (B,H) coupling constants
could be resolved due to broadness of the peaks). Additional
1H NMR (500 MHz, CDCl3, 300 K): δ 7.69-7.12 (m, 20H;
C6H5), 4.11-4.05 (m, 1H; OCHHCH3), 4.02-3.96 (m, 1H;
OCHHCH3), 2.81-2.74 (br m, 1H; Ph2PCHH), 2.63-2.54 (br
m, 3H; Ph2PCHHCH2CH2PPh2), 2.49-2.36 (v br m, 1H; Ph2-
PCH2CHHCH2PPh2), 1.83-1.72 (br m, 1H; Ph2PCH2CHHCH2-
[8,8-(η2-d p p p )-9-(η1-d p p p )-n id o-8,7-Rh SB9H10] (5). 11B
NMR (160.5 MHz, CDCl3, 300 K; ordered as relative intensity
δ(11B) (relative to BF3‚OEt2) [δ(1H)]): 2BH 4.6 [3.54; 3.08, d,
J ) 15 Hz], 1BH -0.1 [2.25], 1BH -2.9 [2.72], 1BH -6.4
[B-PPh2], 1BH -8.6 [2.12], 2BH -16.7 [1.44], 1BH -23.9
[1.50] (1J (B,H) coupling constants could not be resolved due
to broadness of the peaks). Additional 1H NMR (500 MHz,
CDCl3, 300 K): δ 7.50-6.93 (m, 40H; C6H5), 2.68 (br m, 2H;
CH2), 2.53 (br m, 2H; CH2), 2.16 (br m, 2H; CH2), 2.04 (br m,
2H; CH2), 1.92 (br m, 2H; CH2), 1.83 (m, 2H; CH2), -2.39 (s,
3
PPh2), 1.50 (t, J (H,H) ) 7 Hz, 3H; OCH2CH3), -0.82 (s, 1H;
1
1H; µ-H-BB), -11.96 (m, J ) ca. 10 Hz; {31P}, d, J (H,Rh) )
µ-HBB). 31P{1H} NMR (121.4 MHz, CDCl3, 300 K): δ 25.8 (dd,
18 Hz). 31P{1H} NMR (203 MHz, CDCl3, 300 K): δ 13.6 (br
dd, 1J (P,Rh) ) ca. 108 Hz), 9.3 (dd, 1J (P,Rh) ) 119 Hz, 1J (P,P)
) 44 Hz), 7.4 (v br; PPh2P-B), -18.8 (s, dangling PPh2P).
LRMS (VG ZAB-E (in FAB+ mode with Gly/thioglycerol-Na;
amu): calcd for C54H62P4B9RhS, 1067.35; obsd, 1067.2; calcd
maximum for C54H62P4B9RhSO [M + O]+, 1083.35; obsd,
1082.2. The mass spectral envelopes for the measured masses
for both 5 and 5′ [M + O]+ match those calculated from the
known isotopic abundances of the constituent elements. The
data are available as Supporting Information.
1J (Rh,P) ) 151 Hz, J (P,P) ) 55 Hz), 7.7 (dd, J (Rh,P) ) 130
Hz). These two peaks do not coalesce at 373 K in C6D5CD3,
implying a ∆Gq value higher than 64 kJ mol-1 for the fluxional
process. LRMS (VG ZAB-E in FAB+ ONPOE; amu): calcd for
[C29H40B9P2ORhS]+, 698.84; obsd, 699.1. The mass envelopes
for the measured masses for 14 match quite well with those
calculated from the known isotopic abundances of the constitu-
ent elements, although the spectra were quite noisy and
overlapped features from the [M + Li]+ cluster and other
unidentifiable features. The mass spectral data are all included
as Supporting Information.
2
1
P r ep a r a t ion of [8,8-(η2-d p p m )(η1-d p p m )-n id o-8,7-R h -
SB9H10] (6). (a) dppm (30 mg, 0.078 mmol) was added slowly
to a solution of [8,8-(PPh2)2-nido-7,8-RhSB9H10] (1; 60 mg,
0.078 mmol) in CH2Cl2 under N2. The reaction mixture was
stirred at room temperature for 1 h. After this time, the solvent
was reduced in volume and the solution applied to a TLC plate,
with CH2Cl2-pentane (3:2) as the mobile phase. A compound
with Rf 0.4 was isolated and characterized as [8-(η2-dppm)-8-
(η1-dppm)-nido-7,8-RhB9H10] (25 mg, 0.025 mmol, 32%).
(b) To a solution of [8,8-(PPh2)2-nido-7,8-RhSB9H10] (32 mg,
0.042 mmol) in CH2Cl2 was added dppm (51 mg, 0.133 mmol).
The initial bright red solution turned immediately to bright
yellow; this reaction mixture was stirred at room temperature
under nitrogen. After 40 min, the solvent was evaporated
under vacuum and the yellow residue applied to TLC using a
CH2Cl2-pentane (3:2) mixture as the mobile phase. The
chromatogram allowed separation of a yellow component with
Rf 0.4, which was characterized as [8-(η2-dppm)-8-(η1-dppm)-
nido-7,8-RhB9H10] (6: 20 mg, 0.02 mmol; 47%). 11B NMR (160.5
MHz, CDCl3, 300 K; ordered as relative intensity δ(11B)
(relative to BF3‚OEt2) [δ(1H)]): 1BH 14.7 [3.85], 3BH 8.1 [2.83,
d, J ) 12 Hz; 3.27, d, J ) 23 Hz; 3.74], 1.2 [2.11], 1BH -13.5
[1.68], 1BH -14.9 [1.68], 1BH -19.0 [1.71], 1BH -29.2 [1.10].
Additional 1H NMR (500 MHz, CDCl3, 300 K): δ 7.80-6.52
[8,8-(η2-d p p p )-8-(CH3CN)-n id o-8,7-Rh SB9H10] (21) was
formed in quantitative yield on refluxing [8,8-(η2-dppp)-nido-
8,7-RhSB9H10] (3) in CH3CN. Compound 3 is insoluble in CH3-
CN, but the yellow solid dissolved on reflux to afford a bright
yellow solution from which yellow crystals were obtained. The
species was amenable to X-ray diffraction analysis, which
afforded data comparable to those for the related species [8,8-
(η2-dppe)-8-(CH3CN)-nido-8,7-RhSB9H10] reported by Welch et
al.16 The data have been deposited with the Cambridge
Crystallographic Data Center as supplementary publication
No. 133103.
Th er m olysis of [8,8-(η2-d p p e)-9-(η1-d p p e)-n id o-8,7-Rh -
SB9H10] (4) a n d [8,8-(η2-d p p p )-9-(η1-d p p p )-n id o-8,7-Rh SB9-
H
10] (5). (a) In a 50 mL round-bottom flask, 7 mg of [8-(η2-
dppp)-9-(η1-dppp)-nido-8,7-RhSB9H10] (5) was dissolved in 30
mL of CH2Cl2. The solution was degassed and, then, heated
at reflux temperature under N2 for 6 days. After this time,
NMR spectroscopy showed that the nido-rhodathiaborane had
transformed quantitatively into [8-(η2-dppp)-nido-8,7-RhSB9H10
]
(3) and free dppp. Under the same conditions, thermolysis of
[8-(η2-dppe)-9-(η1-dppe)-nido-8,7-RhSB9H10] (4) afforded a mix-
ture of [1-(η2-dppe)-3-(η1-dppe)-closo-1,2-RhSB9H8] (17), [8-(η2-
dppe)-nido-8,7-RhSB9H10] (2), and free dppe. In this mixture,
the nido-rhodathiaborane and free phosphine were the major
components.
1
(m, 40H; C6H5), -4.38 (s, 1H; µ-H). H{31P} NMR (500 MHz,
CD2Cl2, 25 °C): δ 4.29, 4.18 (both AB q, 2J (H,H) ) 14 Hz, 2H;
CH2), 3.58, 2.83 (each d, 2J (H,H) ) 16 Hz, 2H; CH2). 31P NMR
(202.5 MHz, CD2Cl2, 25 °C): δ 15.2 (dt, 1J (P,Rh) ) 126 Hz,
(b) In a 5 mm NMR tube, 7 mg of [8-(η2-dppp)-9-(η1-dppp)-
nido-8,7-RhSB9H10] (5) was dissolved in CDCl3 (ca. 0.8 mL)
and, then, heated to 40 °C under air atmosphere for 1 day.
31P NMR spectra of the crude reaction mixture indicated a
mixture of species, which were separated by TLC, using CH2-
Cl2-pentane (3:1). The chromatogram resulted in the isolation
of [8-(η2-dppp)-nido-8,7-RhSB9H10] (3: Rf 0.7; 46%), [{1,1-(η2-
dppp)-closo-1,2-RhSB9H8}2-3,3′-µ-(dppp)] (19: Rf 0.3; 36%), and
[1,1-(η2-dppp)-3-(η1-ddppO)-closo-1,2-RhSB9H8] (18: Rf 0.0;
14%), together with free dppp. Under the same conditions,
thermolysis of 7 mg of [8,8-(η2-dppe)-9-(η1-dppe)-nido-8,7-
RhSB9H10] (4) gives rise to a mixture of [8,8-(η2-dppe)-nido-
8,7-RhSB9H10] (2), [1,1-(η2-dppe)-3-(η1-ddpeO)-closo-1,2-RhSB9H8]
(20), and free dppe, the closo-rhodathiaborane being the major
component of the resulting mixture.
1
2
2J (P,P) ) 26 Hz), -7.7 (ddd, J (P,Rh) ) 122 Hz, J (P,P) ) 13
2
1
and 63 Hz), -26.9 (d, J (P,P) ) 31 Hz), -42.9 (br td, J (P,Rh)
+
2J (P,P) ) ca. 68 Hz, 2J (P,P) ) ca. 26 Hz). HRMS (FAB
Kratos MS-50, 3-NBA/Ar gas; amu): calcd for C50H52B9P4RhS,
1010.2633, [M+ - H2]; found, 1010.2632.
Rea ction of [8,8-(η2-d p p p )-n id o-8,7-Rh SB9H10] (3) w ith
EtOH. A 14 mg (0.021 mmol) portion of [8-(η2-dppp)-nido-8,7-
RhSB9H10] (1) was dissolved in 20 mL of CH2Cl2-EtOH (1:1).
The resulting yellow-orange solution was degassed, the system
filled with nitrogen, and the reaction mixture stirred at room
temperature under nitrogen for 2 days. After this time, the
solution was evaporated to dryness, the orange residue dis-
solved in the minimum amount of CH2Cl2, and the solution

3648 Organometallics, Vol. 18, No. 18, 1999
Mac´ıas et al.
[{1,1-(η2-d p p p )- closo-1,2-Rh SB9H8}2-3,3′-µ-(d p p p )] (19).
11B NMR (160.5 MHz, CDCl3, 300 K; ordered as relative
intensity δ(11B) (relative to BF3‚OEt2) [δ(1H)]): 1BH 32.1 [Ph2-
PB], 1BH 25.7 [4.03], 3BH 1.6 [2.24, 2H; 2.98, 1H], 2BH -17.6
[-0.04], 2BH -27.9 [0.29] (1J (B,H) coupling constants could not
be resolved due to broadness of the peaks). Additional 1H NMR
(500 MHz, CDCl3, 300 K): δ 7.70-6.90 (m, 60H; C6H5), 2.16-
2.00 (br m, 18; H; CH2). 31P{1H} NMR (202.5 MHz, CDCl3, 300
Crystal data and intensity data collection parameters are
listed in Table 1. Structure solution and refinement were
carried out using the SHELXTL-PLUS software package.32 The
structures were solved by direct methods and refined success-
fully in the space groups P21/n, P1h, P1h, and P21/n for 3, 14, 6,
and 20, respectively. Full-matrix least-squares refinement was
carried out by minimizing ∑w(Fo - Fc2)2. The non-hydrogen
2
atoms were refined anisotropically to convergence. The hy-
drogen atoms were treated using an appropriate riding model
(AFIX m3). The cage hydrogens were located from the differ-
ence Fourier and were refined. The final residual values R(F)
and Rw(F2) and the structure refinement parameters are listed
in Table 1. The geometrical parameters are listed in Tables
2-5, and projection views of the molecules with non-hydrogen
atoms represented by 50% probability ellipsoids, showing the
atom labeling, are presented in Figures 1-3 and 6, respec-
tively, for 3, 14, 6, and 20.
Complete listings of the atomic coordinates for the non-
hydrogen atoms, the positional and isotropic displacement
coefficients for hydrogen atoms, anisotropic displacement
coefficients for the non-hydrogen atoms, and calculated and
observed structure factors have been submitted as Supporting
Information.
1
K): δ 14.7 (d, J (Rh,P) ) 140 Hz; 4P), 1.81 (v br, 2P; Ph2PB).
LR-MS for 19 (ZAB-E, FAB+ with 3-NBA; amu): calcd
maximum for C81H94B18P6Rh2S2, [M+], 1718.5; obsd, 1718.3.
The mass envelopes for the measured masses for 19 match
quite well with those calculated from the known isotopic
abundances of the constituent elements. The data are available
as Supporting Information.
[1,1-(η2-d p p p )-3-(η1-d d p p O)-closo-1,2-Rh SB9H8] (18). 11
B
NMR (160.5 MHz, CDCl3, 300 K; ordered as relative intensity
δ(11B) (relative to BF3‚OEt2) [δ(1H)]): 1BH 32.5 [Ph2PB], 1BH
25.8 [3.88], 3BH 1.6 [2.18, 2H; 2.79, 1H], 2BH -17.8 [-0.16],
2BH -32.9 [0.07] (1J (B,H) coupling constants could not be
1
resolved due to broadness of the peaks). Additional H NMR
(500 MHz, CDCl3, 300 K): δ 7.77-6.97 (m, 40H; C6H5), 2.77
(m, 2H; CH2), 2.49 (m, 2H; CH2), 2.01 (m, 2H; CH2), 1.66 (m,
2H; CH2). 31P{1H} NMR (202.5 MHz, CDCl3, 300 K): δ 32.7
(s; Ph2PdO), 14.0 (d, 1J (Rh,P) ) 141 Hz; 2P), 2.2 (v br, 1P;
Ph2PB). LRMS (VG ZAB-E, FAB+ with 3-NBA; amu): calcd
for C54H60B9OP4RhS, i.e., [M + O]+, 1081.4; obsd, 1081.3. The
mass envelopes for the measured masses for 18 match quite
well with those calculated from the known isotopic abundances
of the constituent elements. The data are available as Sup-
porting Information.
X-r a y Diffr a ct ion An a lysis for 3, 14, 6, 20, a n d 21.
Crystals of appropriate dimensions were mounted on glass
fibers in random orientations. Preliminary examinations and
data collections were performed using a Bruker SMART charge
coupled device (CCD) detector system single-crystal X-ray
diffractometer using graphite-monochromated Mo KR radia-
tion (λ ) 0.710 73 A) equipped with a sealed-tube X-ray source
at -50 °C. Preliminary unit cell constants were determined
with a set of 45 narrow frames (0.3° in $) scans. A typical
data set collected consists of 4028 frames of intensity data
collected with a frame width of 0.3° in $ and counting time of
15 s/frame at a crystal to detector distance of 4.930 cm. The
double-pass method of scanning was used to exclude any noise.
The collected frames were integrated using an orientation
matrix determined from the narrow frame scans. SMART and
SAINT software packages30 were used for data collection and
data integration. Analysis of the integrated data did not show
any decay. Final cell constants were determined by a global
refinement of xyz centroids of 8192 reflections. Collected data
were corrected for systematic errors using SADABS31 based
upon the Laue symmetry using equivalent reflections.
Ack n ow led gm en t. We acknowledge support from
the Missouri Research Board, the donors of the Petro-
leum Research Fund, administered by the American
Chemical Society, and the National Science Foundation.
We also acknowledge the NSF (Grant No. CHE-
9318696), the DOE (Grant No. DE-FG02-92CH10499),
and the UM-St. Louis Center for Molecular Electronics
for grants which allowed purchase of the Varian Unity
Plus NMR spectrometer and the last two along with the
NSF (Grant No. CHE-9309690) for funds to purchase
the X-ray diffractometer. We thank the Washington
University Mass Spectrometry NIH Research Resource
(Grant No. P41RR094) for the mass spectra.
Su p p or tin g In for m a tion Ava ila ble: Tables giving X-ray
structural data for 3, 6, 14, and 20, including a summary of
crystallographic parameters, atomic coordinates, bond dis-
tances and angles, and anisotropic thermal parameters, and
tables giving detailed mass spectral data, including compari-
sons of the observed and calculated intensities of the parent
peak envelope, for 3, 4, 5, 5′, 14, 17, 18, 19, and 20. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM9901168
(31) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(32) Sheldrick, G. M. Bruker Analytical X-ray Division, Madison,
WI, 1997.
(30) Bruker Analytical X-ray Division, Madison, WI, 1997.