Small heteroborane cluster systems. 8. Preparation of phosphaborane clusters from the reaction of polyhedral boranes with low-coordinate phosphorus compounds: Reaction chemistry of phosphaalkynes with decaborane(14)

Article abstract of DOI:10.1021/om960197x

The room-temperature reaction of equimolar quantities of phosphaalkyne RC≡P (2a; R = ^tBu; 2b, R = adamantyl) with the decaborane(12)-Lewis base adduct B₁₀H₁₂·2CH₃CN (3) resulted in the formation of new phosphaborane compounds (phosphine-methylene ylides), nido-RC(H)PB₁₀H₁₃ (4a, R = ^tBu; 4b, R = adamantyl), in good yield (approximately 50% each). These slightly air-sensitive compounds were fully characterized by ¹H, ¹¹B, ¹³C, and ³¹P NMR, 2D ¹¹B-¹¹B COSY NMR, FT-IR, and mass spectroscopic analyses. The structures of 4a and 4b are proposed to consist of a nido-PB₁₀ framework formally based upon a 26-skeletal-electron nido-[B₁₁H₁₁]^- parent compound. Only the phosphorus atom was observed to be incorporated into the polyhedral framework with an exopolyhedral C(H)R group doubly bound to the cage phosphorus atom. Two related mechanisms are proposed to account for the observed products from these reactions.

Full text of DOI:10.1021/om960197x

+
+
Organometallics 1996, 15, 4293-4300
4293
Sm a ll Heter obor a n e Clu ster System s. 8. P r ep a r a tion of
P h osp h a bor a n e Clu ster s fr om th e Rea ction of
P olyh ed r a l Bor a n es w ith Low -Coor d in a te P h osp h or u s
Com p ou n d s: Rea ction Ch em istr y of P h osp h a a lk yn es
w ith Deca bor a n e(14)1
Robert W. Miller and J ames T. Spencer*
Department of Chemistry and the W. M. Keck Center for Molecular Electronics, Center for
Science and Technology, Syracuse University, Syracuse, New York 13244-4100
Received March 14, 1996X
The room-temperature reaction of equimolar quantities of phosphaalkyne RCtP (2a ; R )
tBu; 2b, R ) adamantyl) with the decaborane(12)-Lewis base adduct B10H12‚2CH3CN (3)
resulted in the formation of new phosphaborane compounds (phosphine-methylene ylides),
t
nido-RC(H)PB10H13 (4a , R ) Bu; 4b, R ) adamantyl), in good yield (approximately 50%
1
each). These slightly air-sensitive compounds were fully characterized by H, 11B, 13C, and
31P NMR, 2D 11B-11B COSY NMR, FT-IR, and mass spectroscopic analyses. The structures
of 4a and 4b are proposed to consist of a nido-PB10 framework formally based upon a 26-
skeletal-electron nido-[B11H11]- parent compound. Only the phosphorus atom was observed
to be incorporated into the polyhedral framework with an exopolyhedral C(H)R group doubly
bound to the cage phosphorus atom. Two related mechanisms are proposed to account for
the observed products from these reactions.
In tr od u ction
significant development of the chemistry of these low-
coordinate species. Recently, however, numerous mul-
tiply bonded phosphorus compounds, including several
phosphaalkynes, have been reported which are rather
stable, primarily due to the presence of bulky substit-
uents on the carbon atom (kinetic stabilization).3,5,7 For
The chemistry of multiply bonded main-group com-
pounds has been an area of intense recent interest.2,3
For many years such compounds were believed not to
be stable enough for isolation, due to the proposed
weakness of the pπ-pπ bonding interactions between
the elements beyond the second period. These observa-
tions gave rise to the well-known “classical double bond
rule”.4 In the past decade, however, numerous doubly
and triply bonded main-group species have been pre-
pared as stable compounds by either kinetic stabiliza-
tion (steric blocking) or thermodynamic stabilization
(mesomeric π-electron delocalization) techniques.5 In
the former technique, the main-group multiple bond has
been found to remain sufficiently reactive to display a
wide variety of chemical reactions directed to the
unsaturated site, despite the requisite steric blockage.
t
example, the sterically protected BuCtP, AdCtP, and
MesCtP compounds (where Bu ) butyl, Ad ) adaman-
tyl, and Mes ) mesityl) are all air-stable at room
temperature and are even stable at elevated tempera-
tures under an inert atmosphere.8-10 Advances in the
understanding of the chemical reactivities of these
species have been greatly enhanced by the recent
development of several straightforward synthetic pro-
cedures for the preparation of relatively large quantities
of both phosphaalkenes and phosphaalkynes.11-13 Thus,
the chemistry of the CtP bond is currently being
vigorously investigated, and numerous reviews have
been written in the last decade in an attempt to keep
pace with this intense activity.7,11,12,14,15 It is clear from
much of this detailed work, however, that phos-
phaalkynes often react rather similarly to the related
organic alkynes in a variety of reactions, despite the
presence of the sterically demanding groups.3-5
Phosphaalkenes (R2CdPR) and phosphaalkynes
(RCtP) constitute two important types of main-group
multiply bonded compounds. Phosphaalkynes have
been known since the first report of the formation of
HCtP by Gier in 1961.6 In this work, HCtP was
prepared by passing phosphine gas (PH3) through a
rotating electric arc discharge and trapping the volatile
products under vacuum at low temperature.6 This
phosphaalkyne, however, was stable only under vacuum
and at very low temperatures (below -124 °C). The
synthetic difficulty and extreme instability of the ini-
tially reported phosphaalkynes effectively precluded any
(7) Ishmaeva, E. A.; Patsanovskii, I. I. Russ. Chem. Rev. (Engl.
Transl.) 1985, 54, 43.
(8) Becker, G.; Gresser, G.; Uhl, W. Z. Naturforsch., B 1981, 36, 16.
(9) Allspach, T.; Regitz, M.; Becker, G.; Becker, W. Synthesis 1986,
171.
(10) Markl, P. G.; Sejpka, H. Tetrahedron Lett. 1986, 27, 171.
(11) Appel, R.; Knoll, F.; Ruppert, I. Angew. Chem., Int. Ed. Engl.
1981, 20, 731.
(12) Becker, G.; Becker, W.; Knebl, R.; Schmidt, H.; Hildenbrand,
U.; Westerhausen, M. Phosphorus Sulfur Relat. Elem. 1987, 30, 349.
(13) Regitz, M.; Binger, P. Angew. Chem., Int. Ed. Engl. 1988, 27,
1484.
X Abstract published in Advance ACS Abstracts, September 1, 1996.
(1) Part 7: Miller, R. W.; Spencer, J . T. Polyhedron 1996, 15, 3151.
(2) Barron, A. R.; Cowley, A. H.; Hall, S. W. J . Chem. Soc., Chem.
Commun. 1987, 980.
(3) Cowley, A. H. Polyhedron 1984, 4, 389.
(14) Regitz, M.; Binger, P. Angew. Chem., Int. Ed. Engl. 1988, 27,
1484.
(15) Regitz, M. In Heteroatom Chemistry; Block, E., Ed.; VHS: New
York, 1990; Chapter 17.
(4) Gusel’nikov, L. E.; Nametkin, N. S. Chem. Rev. 1979, 79, 529.
(5) Appel, R.; Knoll, F. Adv. Inorg. Chem. 1989, 33, 259.
(6) Gier, T. E. J . Am. Chem. Soc. 1961, 83, 1769.
S0276-7333(96)00197-5 CCC: $12 00 © 1996 American Chemical Society

+
+
4294 Organometallics, Vol. 15, No. 20, 1996
Miller and Spencer
The reaction of substituted alkynes with polyhedral
borane clusters has been shown to readily insert the sp
carbons of the alkyne directly into the borane cage
framework in good yields, as summarized in Scheme
1.16-19 This synthetic technique has been employed in
the larger polyhedral phosphaboranes are usually quite
stable and are, therefore, often easier to purify and
characterize relative to the smaller cage systems.24-34
Exp er im en ta l Section
P h ysica l Mea su r em en ts. Routine boron (11B) NMR spec-
tra were recorded on either a Bruker WM-360 or a Cryomag-
netics CM-250 spectrometer operating at 115.52 and 80.26
MHz, respectively. Spectra were recorded in either 5 or 10
mm (o.d.) tubes in both the coupled and decoupled modes and
were externally referenced to BBr3 at +40.0 ppm (positive
chemical shifts indicate downfield resonances). Typical 11B
NMR acquisition parameters employed were a relaxation delay
of 0.1 s and a 90° pulse of 20 ms for the 80.26 MHz spectra.
The 2D 11B-11B {1H} COSY NMR spectra, both the absolute
value and pure phase versions, were obtained on either the
CM-250 or a GN-500 spectrometer (operating at 160.45 MHz).
Typically, a 90° pulse width of 15-25 ms was required on the
CM-250, while the GN-500 required approximately twice this
value. In most cases, the previously described absolute value
mode COSY pulse sequence35 was used to generate the t1, t2
data matrix (relaxation delay (π/2)-t1-(π/2)-t2), in which t1
was incremented by the inverse of the sweep width in the F1
dimension and t2 was the usual acquisition time in a 1D
experiment. Typically, the t1, t2 matrix was collected as 128
× 256 data points, unless otherwise indicated. Data process-
ing involved the application of a dc offset and first point
correction, shifted sine bell apodization, zero filling (twice in
t1 and once in t2), Fourier transformation, and a magnitude
calculation to give the 512 × 512 2D 11B-11B COSY NMR
spectrum.36 Carbon (13C) NMR spectra were obtained on a
General Electric QE-300 spectrometer operating at 75.48 MHz.
The spectrometer was operated in the FT mode while locked
on the deuterium resonance of the solvent in 5 mm (o.d.)
sample tubes. The reference was set relative to tetramethyl-
silane from the known chemical shifts of the solvent carbon
atoms (either CDCl3 at δ 77.0 ppm or d8-THF at δ 67.4 ppm).
Phosphorus (31P) NMR spectra were obtained in either 5 or
10 mm (o.d.) tubes on either a Bruker WM-360 or a Cryomag-
netics CM-250 spectrometer operating at 145.81 and 101.27
MHz, respectively. Chemical shifts were referenced to an
external standard of 85% phosphoric acid sealed in a 1 mm
capillary tube and held coaxially in the sample tube by a Teflon
vortex plug. Both proton broad-band decoupled and coupled
Sch em e 1. Syn th esis of Su bstitu ted Ca r bor a n es
fr om th e Rea ction of Alk yn es w ith Bor a n e Clu ster sa
RCtCR′ + nido-B10H12L2 f closo-B10H10C2RR′
RCtCR′ + nido-B5H9 f nido-B4H6C2RR′
a
For nido-RR′C2B4H6:16-19 R ) R′ ) H, alkyl, phenyl, benzyl,
indenyl, fluorenyl, adamantyl, naphthyl, etc.; R ) H, R′ ) phen-
yl, indenyl, fluorenyl, phenethyl, norbornadienyl, etc. For closo-
RR′C2B10:
16c R ) H, alkyl, phenyl, bromomethyl, etc.; R ) H, al-
kyl, phenyl, bromomethyl, etc.
the formation of a large variety of exopolyhedrally
substituted carborane species. Motivated by some of the
striking similarities and apparent differences between
unsaturated organic compounds and the related unsat-
urated phosphorus main-group compounds, two inves-
tigations have been reported in which borane cages have
been reacted with phosphaalkenes. In the work of
Gaines, an inserted nido-R2CdPB5H8 compound was
reported from the reaction of [B5H8]- and R2CdPCl
(where R ) phenyl, SiMe3).20 In the second report, we
described the formation of both bridged B5H8P(H)(CH-
(OSiMe3)R) and phosphorus-inserted B5H7PdC(OSiMe3)R
phosphaborane compounds from the reaction of neutral
pentaborane(9) with (Me3Si)dCR(OSiMe3) (where R )
tBu, Ad).21,22
Phosphaalkynes have been found to react more like
alkynes than nitriles in a variety of reactions.11-13,23a
Since organic alkynes readily participate in insertion
reactions with a variety of boranes as described above,17,18
similar reactions might be expected to occur between
phosphaalkynes and boranes. The extension of this
synthetic pathway to the formation of heteroborane
clusters using triply bound phosphorus species, how-
ever, has not been previously explored. In the work
reported here, we describe the reactions of several
phosphaalkynes with nido-decaborane(14) in the prepa-
ration of inserted phosphaborane clusters in good yield.
The reaction of a phosphaalkyne with the large nido-
decarborane(14) cluster was initially investigated, since
(24) Friedman, L. B.; Perry, S. L. Inorg. Chem. 1973, 12, 288.
(25) Thornton-Pett, M.; Beckett, M. A.; Kennedy, J . D. J . Chem. Soc.,
Dalton Trans. 1986, 303.
(26) Mastryukov, V. S.; Atavin, E. G.; Vilkov, L. V.; Golubinskii, A.
V.; Kalinin, V. N.; Zhigareva, G. G.; Zakharkin, L. I. J . Mol. Struct.
1979, 56, 139.
(27) Wong, H. S.; Lipscomb, W. N. Inorg. Chem. 1975, 14, 1350.
(28) Beer, D. C.; Todd, L. J . J . Organomet. Chem. 1973, 55, 363.
(29) Geiger, W. E.; Brenien, D. E.; Little, J . L. Inorg. Chem. 1982,
21, 2529.
(30) Smith, H. D., J r. J . Am. Chem. Soc. 1965, 87, 1817.
(31) Little, J . L.; Kester, J . G.; Huffman, J . C.; Todd, L. J . Inorg.
Chem. 1989, 28, 1087.
(16) (a) Cendrowski-Guillaume, S. M.; Spencer, J . T. Organometal-
lics 1992, 11, 969. (b) Grimes, R. N. In Comprehensive Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E., Eds.; Pergamon:
Oxford, U.K., 1982; Chapter 5.5, p. 474. (c) Mellor, J . W. A Compre-
hensive Treatise on Inorganic and Theoretical Chemistry; Longman:
London, 1981; Vol. 5, Suppl. 1. (d) Onak, T. In Comprehensive
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E.,
Eds.; Pergamon: Oxford, U.K., 1982; Chapter 5.4, p 423.
(17) Hosmane, N. S.; Grimes, R. N. Inorg. Chem. 1979, 18, 3294.
(18) Fessler, M. E.; Spencer, J . T.; Lomax, J . F.; Grimes, R. N. Inorg.
Chem. 1988, 27, 3069.
(19) Muetterties, E. L. Boron Hydride Chemistry; Academic Press:
New York, 1975.
(20) Coons, D. E.; Gaines, D. F. Inorg. Chem. 1987, 26, 1985.
(21) Miller, R. W.; Donaghy, K. J .; Spencer, J . T. Phosphorus, Sulfur
Silicon Relat. Elem. 1991, 57, 287.
(32) Getman, T. D.; Deng, H.-B.; Hsu, L.-Y.; Shore, S. G. Inorg.
Chem. 1989, 28, 3612.
(33) Yamamoto, T.; Todd, L. J . J . Organomet. Chem. 1974, 67, 75.
(34) (a) Todd, L. J .; Paul, I. C.; Little, J . L.; Welcker, P. S.; Peterson,
C. R. J . Am. Chem. Soc. 1968, 90, 4489. (b) Beer, D. C.; Todd, L. J . J .
Organomet. Chem. 1972, 36, 77. (c) Todd, L. J .; Little, J . L.; Silverstein,
H. T. Inorg. Chem. 1969, 8, 1698. (d) Little, J . L. Inorg. Chem. 1976,
15, 114. (e) Little, J . L.; Wong, A. C. J . Am. Chem. Soc. 1971, 93, 522.
(f) Little, J . L.; Moran, J . T.; Todd, L. J . J . Am. Chem. Soc. 1967, 89,
5495. (g) Wright, W. F.; Garber, A. R.; Todd, L. J . J . Magn. Reson.
1978, 30, 595. (h) Silverstein, H. T.; Beer, D. C.; Todd, L. J . J .
Organomet. Chem. 1970, 21, 139. (i) Welcker, P. S.; Todd, L. J . Inorg.
Chem. 1970, 2, 286. (j) Little, J . L.; Welcker, P. S.; Loy, N. J .; Todd,
L. J . Inorg. Chem. 1970, 9, 63. (k) Storhoff, B. N.; Infante, A. J . J .
Organomet. Chem. 1975, 84, 291. (l) Kameda, M.; Kodama, G. Inorg.
Chem. 1987, 26, 2011.
(22) Miller, R. W.; Donaghy, K. J .; Spencer, J . T. Organometallics
1991, 10, 1161.
(23) (a) Mathey, F. Chem. Rev. 1990, 90, 997. (b) Baudler, M.;
Sayowski, F. Z. Naturforsch., B 1978, 33, 1208. (c) Marienetti, A.;
Mathey, F.; Fischer, J .; Mitschler, A. J . Am. Chem. Soc. 1982, 104,
4484. (d) Wagner, O.; Maas, G.; Regitz, M. Angew. Chem., Int. Ed.
Engl. 1987, 26, 1257. (e) Niecke, E.; Streubel, R.; Nieger, M.; Strahlke,
D. Angew. Chem., Int. Ed. Engl. 1989, 28, 1673.
(35) Goodreau, B. H.; Spencer, J . T. Inorg. Chem. 1992, 31, 2612.
(36) (a) J ames, T. L.; McDonald, G. G. J . Magn. Reson. 1973, 11,
58. (b) Levy, G. C.; Peat, I. R. J . Magn. Reson. 1975, 18, 500.

+
+
Small Heteroborane Cluster Systems
Organometallics, Vol. 15, No. 20, 1996 4295
spectra were routinely observed for each sample with a
decoupling power of about 5 W. Proton (1H) NMR spectra were
obtained on a General Electric QE-300 spectrometer operating
at 300.15 MHz. Spectra were recorded on samples dissolved
in CDCl3 in 5 mm (o.d.) tubes with chemical shifts referenced
to internal tetramethylsilane, with a positive shift indicating
a resonance at an applied field lower than that of the standard.
Mass spectra were obtained on a Finnigan 4021 mass spec-
trometer using an ionization potential of between 11 and 70
eV. Chemical ionization spectra were obtained using methane
as the bulk reactant gas. FT-IR spectra in the range of 400-
4000 cm-1 were measured on either a Mattson Galaxy 2020
spectrometer or an IBM IR/32 spectrometer and were refer-
enced to the 1601.8 cm-1 band of polystyrene. All compounds
were recorded sandwiched between NaCl plates. HPLC
purifications were accomplished on a Waters DeltaPrep-3000
system equipped with both tunable UV-vis absorbance (rou-
tinely monitored at 275 nm) and differential refraction detec-
tors. All separations were performed using a 2.5 × 10 cm RCM
15 µm Porasil column and eluting with reagent grade solvents
degassed by continuous He sparging.
(tBu )CtP (2a ). Phosphaalkyne 2a was prepared by using
a literature synthesis44 modified according to a private com-
munication from Prof. J . F. Nixon and summarized here. In
a typical preparation employed in our work, the phosphaalkene
(Me3Si)PdC(tBu)(OSiMe3) (1a ; 5.0 g, 19 mmol) was syringed
into a dry nitrogen-filled dropping funnel which was attached
to a flask containing approximately 0.5 g of dry NaOH ground
into small pieces. This flask was then connected to a vacuum
line equipped with cold traps which were maintained at 0, -78,
and -196 °C (10-3 mmHg vacuum). The NaOH in the flask
was then heated to 150-160 °C under vacuum, at which point
the phosphaalkene was added slowly dropwise to the hot
NaOH. The (MeSi)2O and (tBu)CtP products were formed
immediately and were collected together in the -78 °C trap.
The 0 °C trap contained small amounts of phosphaalkene that
distilled over along with small amounts of other impurities.
From this reaction, 1.5 g of (tBu)CtP (75% yield) was collected
with (Me3Si)2O and used without further purification. The
product gave spectroscopic data consistent with those previ-
ously reported.44
(Ad )CtP (2b). Phosphaalkyne 2b was prepared in a
fashion similar to that employed for the synthesis of compound
2a described above. In a typical preparation, the starting
phosphaalkene (Me3Si)PdC(Ad)(OSiMe3) (1b; 5.0 g, 15 mmol)
was added to a dry nitrogen-filled dropping funnel and slowly
dropped in 1 mL portions onto approximately 0.5 g of ground
pieces of NaOH which had been previously heated to 180 °C
under vacuum. The (Me3Si)2O and (Ad)CtP (2b) that formed
were collected in the -196 and 0 °C cold traps, respectively.
(Ad)CtP was then dissolved in pentane, and this solution was
passed down a 7.5 cm × 2.5 cm column of silica gel which was
eluted with pentane; the eluate was resublimed under vacuum
to give pure (Ad)CtP. Typically, 1.3 g of pure product was
obtained (50% yield) which gave spectroscopic data consistent
with those previously reported.44 Compound 2a was then used
without further purification.
Ma ter ia ls. All solvents used were reagent grade or better
and were distilled from the appropriate drying agents under
a dry nitrogen atmosphere prior to use [THF (Na), pentane
(Na), acetonitrile (CaH), diethyl ether (Na)]. All solvents, after
drying, were first degassed with a stream of dry nitrogen
followed by repeated freeze-evacuate-thaw cycles and finally
stored in vacuo prior to use. Deuterated solvents were used
as received and, after degassing cycles, were stored over 4 Å
molecular sieves prior to use. Decarborane(14) was purchased
from the Callery Chemical Co. and freshly sublimed prior to
use. (Me3Si)PdC(tBu)(OSiMe3)13,37 (1a ) and (Me3Si)PdC(Ad)-
(OSiMe3)38 (1b) were prepared and purified according to
literature methods. The starting material tris(trimethylsilyl)-
phosphine (P(SiMe3)3) was prepared by a modification of the
procedure previously reported in the literature.39 The modi-
fication employed 10% less than the stoichiometric amount of
HMPA, and the product was distilled directly from the reaction
precipitate. The following commercially available (Aldrich)
anhydrous chemicals were either used as received or purified
by the method indicated and, where possible, were stored over
4 Å molecular sieves prior to use: sodium hydroxide (dried at
150 °C under vacuum), hexamethylphosophoric triamide
(HMPA), phosphorus trichloride, chlorotrimethylsilane, mag-
nesium metal, bromine, methanol, hexafluoroboric acid, and
sodium hydride (the 80% mineral oil dispersion of NaH was
washed several times with dry pentane, and the washes were
decanted off to remove the mineral oil). Analytical thin-layer
chromatography was conducted on 2.5 × 7.5 cm silica gel strips
(1B-F, Baker), and conventional column chromatography was
conducted using 2.5 × 30 cm columns packed with 230-400
mesh (ASTM) silica gel (EM Science).
n id o-B10H12(CH3CN)2 (3). Compound 3 was prepared
according to a literature procedure by refluxing freshly sub-
limed nido-B10H14 in dry, degassed CH3CN.45 After 5 h, the
refluxing solution was found to contain a white precipitate.
The reaction mixture was then cooled to room temperature
and the solvent removed under vacuum. The resultant off-
white compound gave spectroscopic data which were consistent
with those previously reported and was used without further
purification.
n id o-(tBu )C(H)P B10H13 (4a ). In a typical reaction, 0.81 g
(4.0 mmol) of B10H12(CH3CN)2 (3) was added to 15 mL of dry,
degassed THF in a 50 mL round-bottom flask under dry
nitrogen. One equivalent (0.40 g, 4.0 mmol) of (tBu)CtP (2a ),
in about 1 mL of (Me3Si)2O, was added to the reaction flask,
and the mixture was stirred under nitrogen. The solution
slowly turned bright orange, and the solvent was removed
under vacuum after 12 h, leaving an orange-yellow solid
residue. The residue was then dissolved in a small quantity
of ethyl acetate and this solution passed down a 15 cm × 2.5
cm silica gel column to give the product as a slightly air-
sensitive, off-white oil in 50.4% yield. The product was found
to contain a small amount of THF which could not be removed
from the oily product. The difficulty in removing all traces of
THF presumably stems from the oily and very viscous nature
Th eor etica l Ca lcu la tion s. The MNDO (Modified Neglect
of Differential Overlap) calculations employed in this work
were performed with either version 4.01 or 5.02 of MOPAC40
on either a Hewlett-Packard Series 800 computer system in
the Center for Molecular Electronics at Syracuse University
or a VAX 8820 system of the Syracuse University Academic
Computing Services, respectively. Parameterizations used for
the atoms were those reported in the literature.41 All calcula-
tions were freely varied and were run with the PRECISE42
option employed. The procedure used to find the MNDO-
optimized minimum energy geometries on the potential energy
surface for the phosphaborane clusters followed the procedure
previously reported.43
(41) Parametrizations used for the MNDO calculations were as
follows. (a) Boron: Dewar, M. J . S.; McKee, M. L. J . Am. Chem. Soc.
1977, 99, 5231. (b) Hydrogen, carbon, and oxygen: Dewar, M. J . S.;
Theil, W. J . Am. Chem. Soc. 1977, 99, 4899. (c) Phosphorus: Dewar,
M. J . S.; McKee, M. L.; Rzepa, H. S. J . Am. Chem. Soc. 1978, 100,
3607. (d) Silicon: Dewar, M. J . S.; Friedheim, J .; Grady, G.; Healy,
E. F.; Stewart, J . J . P. Organometallics 1986, 5, 375.
(42) Boyd, D. B.; Smith, D. W.; Stewart, J . J . P.; Wimmer, E. J . J .
Comput. Chem. 1988, 9, 387.
(37) Becker, G. Z. Anorg. Allg. Chem. 1977, 430, 66.
(38) Allspach, T.; Regitz, M.; Becker, G.; Becker, W. Synthesis 1986,
31.
(39) Schumann, H.; Rosch, L. J . Organomet. Chem. 1973, 55, 257.
(40) Stewart, J . J . P.; Seiler, F. J . Quantum Chemistry Program
Exchange; Program No. 549.
(43) Glass, J . A., J r.; Whelan, T. A.; Spencer, J . T. Organometallics
1991, 10, 1148.
(44) Regitz, M. J . Organomet. Chem. 1986, 306, 39.
(45) Schaeffer, R. J . Am. Chem. Soc. 1957, 79, 1006.

+
+
4296 Organometallics, Vol. 15, No. 20, 1996
Miller and Spencer
t
Ta ble 1. NMR Da ta (p p m ) for RCP a n d RC(H)P B10H13 Com p ou n d s (Wh er e R ) Bu , Ad )
compd
11Ba
1Hb
13C{1H}c,d
31Pe
-71.8 this workf
ref
2a
1.08 (d, 9H, J PH ) 1.2 Hz)
31.36 (d, C(CH3)3, J CP ) 6.0 Hz), 36.39
(d, C(CH3)3, J C3P ) 18.0 Hz), 184.64
(d, PC, J CP ) 37.6 Hz)
2b
4a
1.6-2.1 (m, 15H, C10H15
)
27.8 (s, CB), 35.7 (s, CC), 38.5 (d, CD,
-66.8 this workg
-45.0 this work
J CP ) 18.0 Hz), 42.9 (d, CA, J CP
)
6.0 Hz), 184.7 (d, PC, J CP ) 39.0 Hz)
4.3 (d, B(5), J BH ) 172 Hz), -18.0
(d, B(8,9,10,11), J BH ) 163 Hz),
-19.3 (d, B(2,3), J BH ) 163 Hz),
-39.3 (d, B(1,4,6), J BH ) 176 Hz)
4.4 (d, B(5), J BH ) 168 Hz), -17.8
(d, B(8,9,10,11), J BH ) 160 Hz),
-19.2 (d, B(2,3), J BH ) 163 Hz),
-39.4 (d, B(1,4,6), J BH ) 168 Hz)
-3.54 (br, 3H, bridging H), 1.64 30.31 (s, C(CH3)3), 37.21 (d, C(CH3)3,
(s, 9H, C(CH3)3), 2.66 (d, 1H,
PCH, J HP ) 1.5 Hz)
J CP ) 13.0 Hz), 125.51 (s, PC)
4b
-3.63 (br, 3H, bridging H), 1.5- 25.15 (s, C10H15), 27.86 (s, C10H15), 36.07
2.1 (m, 15H, C10H15), 2.36 (d,
1H, PCH, J HP ) 1.8 Hz)
-71.0 this work
(s, C10H15), 43.17 (d, C10H15, J CP ) 6.0 Hz),
80.38 (s, PC)
a
b
d
In CDCl3 relative to BBr3 (40.0 ppm). In CDCl3 relative to TMS (0.0 ppm). c In CDCl3 relative to TMS. Adamantyl numbering
scheme:
e In CDCl3 relative to 85% H3PO4. f 13C, 1H, and 31P data for this compound were originally reported in ref 37. The data shown here for
comparison are our data, which are comparable with those reported earlier. g 13C, 1H, and 31P data for this compound were originally
reported in ref 38. The data shown here for comparison are our data, which are comparable with those reported earlier.
t
Ta ble 2. In fr a r ed Da ta for RCP a n d RC(H)P B10H13 Com p ou n d s (Wh er e R ) Bu , Ad )
a
compd
IR (cm-1
)
ref
2a
2968 (vs), 2922 (vs), 2898 (sh), 2862 (vs), 2363 (vw), 2858 (vw), 1533 (vs), 1462 (sh), 1451 (s), 1361 (vs), 1252 (vw), 1198 (vs), this workb
1175 (sh), 1049 (sh), 1022 (m), 925 (vw), 845 (sh), 835 (m), 531 (vs), 463 (w), 355 (w)
2b
4a
1528 (vs, νCP
)
33c
2990 (m, νCH), 2955 (m, νCH), 2896 (w, νCH), 2555 (s, br, νBH), 2420 (sh, νBH), 1660 (w), 1613 (sh), 1594 (w), 1578 (w), 1539 (sh), this work
1520 (sh), 1502 (sh), 1488 (m), 1467 (m), 1425 (m), 1389 (w), 1278 (m), 1212 (m), 1171 (w),
1114 (m), 1026 (m), 995 (sh), 970 (w), 850 (w), 808 (m), 686 (w)
4b
2955 (m, νCH), 2892 (s, νCH), 2840 (s, νCH), 2522 (m, br, νBH), 2418 (sh, νBH), 1521 (m), 1446 (m), 1400 (w), 1337 (w), 1296 (w), this work
1255 (m), 1094 (m), 1065 (m), 1006 (s), 909 (w), 793 (s), 680 (w)
a
b
NaCl or CsI plates. Abbreviations: vs ) very strong; s ) strong; m ) medium; w ) weak, sh ) shoulder; br ) broad. IR data for
this compound were originally reported in ref 38. The data shown here for comparison are our data, which are comparable with those
reported earlier. c IR/Raman data for solid film.
of the product compound, and no evidence has been found
supporting the formation of a complex between 4a and THF.
Negative ion mass spectroscopy for 4a (the reported percent
relative intensity values are normalized to the largest peak
in the spectrum (at m/e 147 from the PB10H10 envelope)): m/e
224 (0.31%; P+ envelope), 223 (1.51%; P+ - 1H envelope), 175
(7.93%, C2PB10H10 envelope), 174 (12.75%; C2PB10H10 enve-
lope), 173 (12.35%; C2PB10H10 envelope), 172 (7.93%; C2PB10H10
envelope), 171 (5.22%; C2PB10H10 envelope), 151 (32.93%;
PB10H10 envelope), 150 (44.08%; PB10H10 envelope), 149 (76.20%;
PB10H10 envelope), 148 (96.59%; PB10H10 envelope), 147 (100%;
PB10H10 envelope), 146 (83.84%; PB10H10 envelope), 145 (64.76%;
PB10H10 envelope), 144 (39.66%; PB10H10 envelope), 143 (23.29%;
PB10H10 envelope), 142 (15.46%; PB10H10 envelope), 141 (9.34%;
PB10H10 envelope), 69 (21.39%; C5H9), 57 (70.68%; 12C4H9). The
1H, 11B, 13C, and 31P NMR data are given in Table 1, and FT-
IR data are given in Table 2.
295-302 (C11H29B10P+ parent envelope, observable but rela-
tively low in intensity), 151 (4.4%; PB10H10 envelope), 150
(4.4%; PB10H10 envelope), 149 (22.2%; PB10H10 envelope), 148
(7.4%; PB10H10 envelope), 147 (7.5%; PB10H10 envelope), 146
(4.8%; PB10H10 envelope), 145 (4.7%; PB10H10 envelope), 144
(2.3%; PB10H10 envelope), 136 (11.3%; 12C913C1H15), 135 (61.0%;
12
C
H15). The 1H, 11B, 13C, and 31P NMR data are given in
10
Table 1, and FT-IR data are given in Table 2.
Resu lts a n d Discu ssion
The reaction of several phosphaalkynes with a de-
caborane bis-adduct compound under relatively mild
experimental conditions has been explored. In the
room-temperature reaction of equimolar quantities of
phosphaalkyne RCtP (2a , R ) tBu; 2b, R ) adamantyl)
with the decarborane(12)-Lewis base adduct B10-
H12‚2CH3CN (3), two new phosphaborane compounds
(compounds 4a and 4b) were isolated in rather good
yield (each obtained in approximately 50% yield). These
slightly air-sensitive phosphine-methylene ylide com-
n id o-(Ad )C(H)dP B10H13 (4b). In a typical reaction, 1.0 g
(5.6 mmol) of (Ad)CtP (2b) and 1.1 g (5.6 mmol) of nido-
B
10H12(CH3CN)2 (3) were added under inert conditions to a 100
mL round-bottom flask containing 40 mL of dry, degassed
THF. The initially cloudy, colorless solution was stirred for
2.5 h at room temperature to give a clear, light orange solution.
1
pounds have been fully characterized by H, 11B, 13C,
and 31P NMR, 2D 11B-11B COSY NMR, FT-IR, and
mass spectroscopic analyses. The synthetic pathways
employed in the preparation of 4a and 4b are sum-
marized in Scheme 2. The structure of these closely
related compounds is proposed to be based on an nido
11-vertex, phosphorus cage inserted compound on the
basis of the data presented below.
The solution was concentrated in vacuo, dissolved in
a
minimum of dry ethyl acetate, and chromatographed on a 15
cm × 2.5 cm silica gel column eluted with ethyl acetate. The
product was obtained as a slightly air-sensitive, off-white oil
in 50% yield (based on 11B NMR). As with compound 4a , the
4b product was found to contain a small amount of THF which
could not be removed from the oily product. Negative ion mass
spectroscopy for 4b (the reported percent relative intensity
values are normalized to the base peak in the spectrum): m/e
From precedent established in previous reactions of
unsaturated compounds, including organic alkynes and

+
+
Small Heteroborane Cluster Systems
Organometallics, Vol. 15, No. 20, 1996 4297
F igu r e 1. Possible structural types for compound 4 (all cage hydrogens have been omitted for clarity).
t
Sch em e 2. Syn th etic P a th w a ys for th e F or m a tion of n id o-RC(H)P B10H13 Com p ou n d s (4a , R ) Bu ; 4b, R )
Ad ) fr om th e Rea ction of P h osp h a a lk yn es 2a a n d 2b w ith B10H12‚2CH3CN (3)
phosphaalkenes, with borane clusters and from a more
general consideration of other potential structural modi-
fications, four types of structures are possible for
compounds 4a and 4b which incorporate both a B10
framework and the components of the phosphaalkyne
reactant (on the basis of the molecular formula estab-
lished from mass spectral data). These structural types
include phosphorus-bridged structures, phosphorus ter-
minally substituted compounds, structures in which
both the carbon and the phosphorus atoms are inserted
into the cage framework, and the compound which
results from the insertion of only the phosphorus atom
into the cluster. These possible structural modifications
are shown in Figure 1. Literature examples for each of
these structural types are known in boron cluster
chemistry, albeit with different cage sizes and phospho-
rus substituents.
Figure 2 shows both the proton-coupled and -decoupled
11B NMR spectra of compound 4a . The spectrum for
compound 4b was essentially identical with that ob-
served for 4a . Both spectra consist of four resonances
in a 1:4:2:3 relative intensity pattern. In the spectra,
each resonance was observed to be split into B-H-
coupled doublets and no phosphorus-boron couplings
1
were observed for any of the resonances. The H NMR
data show, besides peaks clearly assignable to the R
t
substituents on carbon (either the Bu or adamantyl
group), resonances arising from bridging B-H-B pro-
tons (at -3.54 and -3.63 ppm for compounds 4a and
4b, respectively). In addition, the spectra show a peak
for a proton on carbon which is clearly coupled to
2
phosphorus (2.66 ppm with J PH ) 1.5 and 1.8 ppm for
compounds 4a and 4b, respectively).
In consideration of the observed 11B and 1H NMR
data, most of the structures shown in Figure 1 may be
readily eliminated from consideration. Structures A
11B and 1H NMR data provide a great deal of
information on the structure of compounds 4a and 4b.

+
+
4298 Organometallics, Vol. 15, No. 20, 1996
Miller and Spencer
F igu r e 3. Structures of nido-RPB10H12 (7; R ) CH3,
C2H5),32 nido-(Fe(η5-C5H5)(CO)2)PB10H12 (8),33 and nido-(Fe-
(η5-C5H5)(CO)2)AsB10H12 (9)33 (terminal cage hydrogen
atoms have been omitted for clarity).
F igu r e 2. Proton coupled (upper plot) and decoupled
(lower plot) 11B NMR spectra for compound 4a .
and D (Figure 1) display a terminal phosphorus cage
substitution pattern. Structure A contains seven sets
of inequivalent boron atoms, while in structure D all
the boron atoms are chemically inequivalent. Fortu-
itous overlap of peaks, however, could simplify the
spectra of A and D considerably. The 11B NMR data,
however, unambiguously eliminate the terminally sub-
stituted phosphorus structures, since all the boron
resonances clearly display B-H terminal coupling. It
is possible to obtain a phosphorus terminal substitution
pattern in which a cage boron atom has both a proton
and a terminal phosphino linkage. This substitution
pattern can also be eliminated, however, since P-B
coupling would be expected for this pattern and such
coupling was not observed for any of the 11B NMR
resonances. From precdent well established in the
literature for terminal B-P systems, terminal P-B-H
substitution patterns should result in large P-B cou-
plings (ca. 100 Hz), which were clearly not observed.34l
The bridging structures B and E can be similarly
eliminated due to the absence of any observed P-B
coupling in the 11B NMR spectra. In the 5,6-bridged
structure B, all the boron atoms are chemically in-
F igu r e 4. Numbering scheme for compounds 4a and 4b.
(CO)2)AsB10H12 (9),33 as shown in Figure 3. As de-
scribed previously, compounds 4a and 4b show four 11B
NMR resonances in a 1:4:2:3 ratio. The 11B NMR data
for the previously reported nido-EB10 heteroboranes
7-9 often show a single resonance for boron atoms B(1),
B(4), and B(6) (numbering scheme shown in Figure 4).
In addition, boron atoms B(8), B(9), B(10), and B(11)
may also be observed as a single 11B resonance, as has
been reported for compound 9.33 The 11B NMR for
compounds 4a and 4b would, therefore, be expected to
exhibit the observed four resonances in a 1:4:2:3 ratio,
as reported for the closely related cluster 9. The
chemical shifts and distributions of peak intensities
observed for the resonances of 4a and 4b are also very
similar to those found for the other known nido-EB10
heteroboranes, with the resonance of intensity 1 at
lowest field strength and the resonance of intensity 3
at highest field strength.
equivalent. The known 5,6-bridged compound [B10H13
-
The 11B-11B COSY NMR spectrum of compound 4
provides support for the structural assignment pre-
sented above. In the 2D spectrum, cross-peaks were
only observed between adjacent equivalent sets of cage
boron atoms, as expected on the basis of previous 2D
experiments.47,48 Recently, the 2D 11B-11B COSY NMR
and X-ray crystal structure of compound 7, nido-(CH3
or C2H5)PB10H12, was reported by Shore.32 The spec-
troscopic assignments reported for 7, on the basis of the
crystallographic structure, are fully consistent with our
spectral and structural assignments. All attempts to
prepare a crystalline sample of either compound 4a and
4b for X-ray analysis, however, have been unsuccessful.
Further support for the proposed structures of com-
pounds 4a and 4b may be obtained from other spectro-
5,6-µ-(PPh2)] (5) shows all 10 resonances in the 11B NMR
spectrum.10 The 6,9-bridged structure E contains four
types of boron atoms in a 1:2:1:1 ratio. The 11B NMR
spectrum of the closely related deprotonated 6,9-bridged
compound [B10H13-6,9-µ-(PPh2)]- (6) clearly shows this
four-peak pattern with phosphorus coupling observed.10
Finally, the closo structure C can also be eliminated,
since resonances due to B-H-B bridging protons were
1
clearly observed in the H NMR spectra of 4a and 4b.
The remaining structure in Figure 1, F , consists of a
nido-PB10 framework. This structure is formally based
upon a 26-skeletal-electron nido-[B11H11]- parent com-
pound.46 The PB10 cage contains boron atoms in six
different chemical environments in a 2:2:2:1:2:1 ratio.
A number of heteroborane clusters are known which
display structures similarly based upon the nido-EB10
framework. These closely related compounds include
nido-RPB10H12 (7, where R ) CH3, C2H5),32 nido-(Fe-
(η5-C5H5)(CO)2)PB10H12 (8),33 and nido-(Fe(η5-C5H5)-
(47) Venable, J . L.; Hutton, W. C.; Grimes, R. N. J . Am. Chem. Soc.
1984, 100, 29.
(48) (a) Venable, T. L.; Hutton, W. C.; Grimes, R. N. J . Am. Chem.
Soc. 1982, 104, 4716. (b) Venable, T. L.; Hutton, W. C.; Grimes, R. N.
J . Am. Chem. Soc. 1984, 106, 29. (c) Gaines, D. F.; Edvenson, G. M.;
Hill, T. G.; Adams, B. R. Inorg. Chem. 1987, 26, 1813. (d) Edvendon,
G. M.; Gaines, D. F.; Harris, H. A.; Campana, C. F. Organometallics
1990, 9, 401.
(46) Fritchie, C. J ., J r. Inorg. Chem. 1967, 6, 1199.

+
+
Small Heteroborane Cluster Systems
Organometallics, Vol. 15, No. 20, 1996 4299
Sch em e 3. P ossible Mech a n istic Step s in th e F or m a tion of n id o-RC(H)P B10H13 fr om th e Rea ction of
B10H12L2 w ith P h osp h a a lk yn esa
a
Terminal hydrogen atoms of the cage have been omitted for clarity.
scopic data. Both compounds clearly show phosphorus-
nitrogen has a much larger and negative partial
coupled doublets (4a , 2J PH ) 1.5 Hz; 4b, 2J PH ) 1.8 Hz)
at 2.66 ppm in the 1H NMR data which arise from a
single proton on the doubly bound, exopolyhedral carbon
attached to the cage phosphorus. The 31P NMR data
show a single resonance for compounds 4a and 4b at
-45 and -71 ppm, respectively. These chemical shifts
are comparable to the 31P NMR data for the other
previously reported nido-EB10 heteroborane compounds.
The 13C{1H} NMR data show the resonances expected
charge.13,50 A directly analogous reaction for the phos-
phaalkynes to alkynes would have resulted in the
insertion of both the phosphorus and the carbon into
the cluster framework, forming a closo-cage system. The
mechanism for the formation of compound 4 from a
phosphaalkyne and B10H12L2 may be considered to be
similar to that proposed for the reaction of phosphaalk-
enes with pentaborane(9). Several mechanisms, of
which only two are summarized in Scheme 3, may be
proposed to account for the observed reactivity patterns.
In the first mechanism (A in Scheme 3), the lone pair
of electrons on the phosphorus center is proposed to
initially attack at a boron position of the decaborane
cage system. This nucleophilic attack presumably oc-
curs at the open face of the cage at one of the B(5,7,8,-
10) atoms, since these are among the most electropos-
itive and sterically free sites in the cage.51 This results
in the formation of a phosphorus-boron bond and a
hydride shift from an adjacent bridging position to a
terminal position on the neighboring boron. This shift
may then be followed by the transfer of a terminal
proton from this boron unit to the carbon center of the
phosphaalkyne, resulting in the hydroboration of the
phosphaalkyne bond. As a result of this rearrangement,
a basic boron center is generated adjacent to the
phosphorus-boron linkage. The close proximity of the
relatively electropositive phosphorus center to this basic
site allows the cage insertion reaction to occur. A very
similar mechanism, shown in Scheme 4, from the work
of Gaines20 is believed to occur, which results in the
insertion of only a phosphorus atom into a pentaborane
cage to form the observed inserted nido-B5H8PdCR2
compound.
t
for the exopolyhedral R group (either Bu or Ad) along
with a resonance at lower field. This 13C resonance was
assigned to the PdC unit and occurs, for example, in
4a (125.5 ppm) approximately equidistantly between the
13C resonance for the phosphaalkyne starting material
1 (184.8 ppm)8 and that observed for PsC single-bonded
13C resonances in phosphinopentaborane compounds
(near 80 ppm).22 This PdC resonance is also quite
similar to the 13C resonances reported for exopolyhedral
PdC units in other phosphaborane cluster systems
(148.5 ppm for [µ-((tBu)(Me3SiO)CdP)B5H8]).22 Finally,
as presented above, the mass spectra for compounds 4a
and 4b displayed parent envelopes for R(H)CdPB10H13
as the highest mass peaks.49 Also observed in the mass
spectra were components from cage and exopolyhedral
organic unit fragmentation along with the PB10 frag-
ment envelope, which contained the largest intensity
peaks (the base peak for 4a ).
The insertion of only the phosphorus atom and not
the carbon atom of the phosphaalkyne unit into the cage
framework was initially somewhat surprising. Phos-
phaalkynes have been found to react more similarly to
alkynes than to nitriles in a variety of reactions.15,32,33,49,50
The lower electronegativity of phosphorus most likely
significantly contributes to this reactivity by inducing
a reversal of the polarity in phosphaalkynes relative to
nitriles. Thus, in phosphaalkynes, the phosphorus has
a small partial positive charge, while in nitriles the
In a second mechanistic pathway, the first step may
involve a proton shift from the cage to the carbon center
of the incoming phosphaalkyne concurrent with the
formation of a phosphorus-boron bond. The lone pair
of electrons on the phosphorus may then attack at an
(49) Ditter, J . F.; Gerhart, F. J .; Williams, R. E. Mass Spectroscopy
of Inorganic Compounds; ACS Monograph 71; American Chemical
Society: Washington, DC, 1968; p 191.
(50) Beckett, M. A.; Kennedy, J . D. J . Chem. Soc., Chem. Commun.
1983, 575.
(51) (a) Lipscomb, W. N. Boron Hydrides; Benjamin: New York,
1963. (b) Laws, E. A.; Stevens, R. M.; Lipscomb, W. N. J . Am. Chem.
Soc. 1972, 94, 4467.

+
+
4300 Organometallics, Vol. 15, No. 20, 1996
Miller and Spencer
Sch em e 4. P ossible Mech a n istic Step s in th e
F or m a tion of n id o-R2CdP B5H8 fr om th e Rea ction
of P en ta bor a n e(8) w ith a Ch lor op h osp h a a lk en ea
The final step in each of the mechanisms presented
above in the formation of the final product, however,
raises significant concern. In these steps, the two Lewis
base ligands are lost from the cage and a net of two
hydrogens are added. The loss of the Lewis base ligands
from B10H12L2 has, however, been observed to readily
occur in the formation of carboranes, such as R2C2B10H10,
from the reaction of B10H12L2 with alkynes.16-19 The
final net addition of two hydrogens to the cage is much
less straightforward. It may be that, since no starting
decaborane complex was isolated from the reaction
mixture and the maximum yield observed for the
reaction was near 50%, that some of the B10H12L2 itself
may have served as the hydrogen source through an
intermolecular process. These two questions have not
been adequately resolved, and further detailed mecha-
nistic studies are required to elucidate the reaction
pathway in greater depth.
a
Terminal hydrogen atoms of the pentaborane cage have
been omitted for clarity.
Ack n ow led gm en t. We wish to thank the National
Science Foundation (Grant Nos. MSS-89-09793 and
CHE-9521572), the donors of the Petroleum Research
Fund, administered by the American Chemical Society,
the General Electric Co., the Rome Air Development
Center (Award No. F30602-89-C-0113), IBM, and the
Industrial Affiliates Program of the Center for Molec-
ular Electronics for support of this work. We also wish
to thank Prof. Alan H. Cowley and Prof. J ohn F. Nixon
for their generous assistance and enormously helpful
conversations. Finally, we also wish to thank Mr. J ohn
A. Glass, J r., for assistance with the MNDO calculations
included in this work.
adjacent borane cage site to accomplish the insertion
reaction to produce the observed product. This mecha-
nistic pathway can be related to that reported previously
by Sneddon52 for the incorporation of a cyanide unit into
-
a borane cluster from the reaction of arachno-S2B7H8
-
anion with nitriles. In the arachno-S2B7H8 mecha-
nism, the first step was proposed to involve the nucleo-
philic attack of a thiaborane anion on the relatively
electropositive carbon atom of the polarized nitrile,
followed by a hydroboration of the nitrile bond. As a
consequence of this interaction, the lone pair of electrons
on the pendant imino group becomes strongly nucleo-
philic and attacks at the most electropositive center of
the thiaborane cage. This lone-pair interaction forces
a cage rearrangement and closes the cage ring system
to produce the observed cluster.
Su p p or tin g In for m a tion Ava ila ble: A table of MNDO
calculated bond indices for [tBuC(H)PB10H13] (4a ) and figures
1
giving H, 11B, and 2D 11B-11B COSY NMR spectra for 4a ,b
and 13C NMR and FT-IR spectra for 4b (9 pages). Ordering
information is given on any current masthead page.
(52) Sang, O. K.; Furst, G. T.; Sneddon, L. G. Inorg. Chem. 1989,
28, 2339.
OM960197X