Synthesis of the first hyper-closo-type monocarbon ruthenacarboranes by polyhedral contraction of [nido-B10H12CH]- and molecular structure of 2-Cl-2,5-(Ph3P)2-2-H-3,9-(MeO)2-2,1-RuCB 8H6

Article abstract of DOI:10.1021/om970690o

Treatment of [nido-B₁₀H₁₂CH]^-Cs⁺ with RuCl₂(PPh₃)₃ in methanol under gentle reflux afforded the two novel 10-vertex monocarbon ruthenacarboranes 2-Cl-2,5-(Ph₃P)₂-2-H-3,9-(MeO)₂-2,1-RuCB ₈H₆ (3) and 2,2-(Ph₃P)₂-2-H-3,9-(MeO)₂-2,1-RuCB ₈H₇ (4) along with a small amount of the 8-vertex complex (PPh₃)₂-HRuCB₆H₄(OMe)₃ (6). The 10-vertex clusters 3 and 4 on the basis of their capped-tricapped-trigonal-prismatic geometry, established for 3 by a single-crystal X-ray diffraction study, and the formal Wadian electroncounting arguments can be regarded as hyper-closo species having n rather than n + 1 skeletal electron pairs.

Full text of DOI:10.1021/om970690o

5598
Organometallics 1997, 16, 5598-5600
Syn th esis of th e F ir st h yper -closo-Typ e Mon oca r bon
Ru th en a ca r bor a n es by P olyh ed r a l Con tr a ction of
[n id o-B10H12CH]- a n d Molecu la r Str u ctu r e of
2-Cl-2,5-(P h 3P )2-2-H-3,9-(MeO)2-2,1-Ru CB8H6
Irina V. Pisareva, Igor T. Chizhevsky,* Pavel V. Petrovskii,
Vladimir I. Bregadze, Fedor M. Dolgushin, and Aleksandr I. Yanovsky
A. N. Nesmeyanov Institute of Organoelement Compounds, 28 Vavilov Street,
117813 Moscow, Russian Federation
Received August 7, 1997X
Summary: Treatment of [nido-B10H12CH]-Cs+ with
RuCl2(PPh3)3 in methanol under gentle reflux afforded
the two novel 10-vertex monocarbon ruthenacarboranes
2-Cl-2,5-(Ph3P)2-2-H-3,9-(MeO)2-2,1-RuCB8H6 (3) and
2,2-(Ph3P)2-2-H-3,9-(MeO)2-2,1-RuCB8H7 (4) along with
ally related monocarbon metallacarborane species ap-
pears to be iso-nido-[{IrC(OH)B8H6(OMe)}(C6H4PPh2)-
(PPh3)] (5),4 isolated quite unexpectedly as one of the
products of the reaction between trans-[Ir(CO)Cl(PPh3)2]
and closo-[B10H10]
2-. The iridium atom in 5 is coordi-
a
small amount of the 8-vertex complex (PPh3)2-
nated by five rather than six atoms of the six-membered
open face. Herein we present a single-crystal X-ray
diffraction study of cluster 3 which, in contrast to 5,
proved to have a completely closed deltahedral geometry
and, therefore, may be regarded as the first example of
a crystallographically characterized 10-vertex monocar-
bon metallacarborane of hyper-closo type.
HRuCB6H4(OMe)3 (6). The 10-vertex clusters 3 and 4
on the basis of their capped-tricapped-trigonal-prismatic
geometry, established for 3 by a single-crystal X-ray
diffraction study, and the formal Wadian electron-
counting arguments can be regarded as hyper-closo
species having n rather than n + 1 skeletal electron
pairs.
Treatment of the Cs+ salt of 1 with 1 equiv of 2 in
deoxygenated methanol at reflux temperature for 4 h,
followed by column chromatographic separation and
fractional crystallization of the reaction products, af-
forded the two air-stable metallacarborane complexes
3 and 4 as predominant products in isolable moderate
yields5,6 (Scheme 1). In addition, several minor products
were formed in the reaction, and one of them was
isolated as a colorless crystalline solid (6) whose NMR
and mass spectrum data were consistent with the
formula (PPh3)2HRuCB6H4(OMe)3 based on the RuCB6
rather than the RuCB8 framework.7
The [nido-B10H12CH]- anion (1) is normally used as
a convenient source for the π-monocarbollide ligand,
which, in turn, is most widely employed for the prepa-
ration of 12-vertex monocarbon closo-metallacarboranes
via treatment with transition-metal reagents.1 In this
paper we demonstrate an unprecedented use of 1 as a
precursor to smaller cage monocarbon carborane ligands,
and, in particular, we report the first example of a
polyhedral contraction reaction of 1 where the elimina-
tion of 2 and even 4 boron-containing fragments is
effected by the action of 16-electron RuCl2(PPh3)3 (2).
Such deep transformations upon treatment with transi-
tion-metal reagents have never before been observed for
either mono- or dicarbon nido-carboranes and may thus
be considered as new and efficient synthetic routes at
least to the MCB8 derivatives. The main products of
the reaction are found to be the novel 10-vertex mono-
carbon ruthenacarborane clusters 2-Cl-2,5-(Ph3P)2-2-H-
3,9-(MeO)2-2,1-RuCB8H6 (3) and 2,2-(Ph3P)2-2-H-3,9-
(MeO)2-2,1-RuCB8H7 (4), which may be viewed as rare
types of monocarbon hyper-closo-metallacarboranes.
According to an X-ray diffraction study,8 cluster 3
adopts the 10-vertex closo geometry and involves the
CB8-cage ligand substituted by two MeO and one PPh3
groups at the boron atoms and coordinated by its
6-membered (CB5) open face to the Ru atom of the 12-
electron RuHCl(PPh3) moiety (Figure 1). The molecular
geometry of 3 seems to be best described as a tricapped
trigonal prism with one additional vertex C(1) wherein
two axial bonds, B(3)-B(5) (2.746(7) Å) and B(6)-B(9)
(3) (a) Bould, J .; Greenwood, N. N.; Kennedy, J . D.; McDonald, W.
S. J . Chem. Soc., Chem. Commun. 1982, 465. (b) Crook, J . E.; Elrington,
M.; Greenwood, N. N.; Kennedy, J . D.; Thornton-Pett, M.; Woollins, J .
D. J . Chem. Soc., Dalton Trans. 1985, 2407.
(4) Crook, J . E.; Greenwood, N. N.; Kennedy, J . D.; McDonald, W.
S. J . Chem. Soc., Chem. Commun. 1981, 933.
Although now a number of super-electron-deficient
10-vertex hyper-closo-metallacarborane clusters2 as well
as closely related iso-closo-metallaboranes3 are known,
analogous monocarbon metallacarboranes with the closo
geometry have never been reported. The only structur-
(5) To a suspension of 2 (100 mg, 0.38 mmol) in 30 mL of deoxy-
genated absolute MeOH was added a stoichiometric amount of 1 (360
mg, 0.38 mmol); the mixture was stirred at ambient temperature for
1 h and thereafter refluxed for 4 h under argon. The resulting claret-
colored mixture was filtered through a coarse frit and the filtrate
concentrated in vacuo. The remaining dark residue was separated by
column chromatography on silica gel using CH2Cl2 as eluent into two
yellow fractions which were reduced in vacuo and subjected separately
to the same chromatographic procedure by using 5-40 mesh silica gel.
The resulting separation yielded three principal products, 3 and 6 (as
a mixture, Rf 0.42) and the pure solid form of 4 (52 mg, 17% yield, Rf
0.88). In addition, at least three minor products of unidentified
structures could be also isolated as crude solids in 2-5% yields. Finally,
recrystallization of the mixture of 3 and 6 two times from CH2Cl2/n-
hexane (2:1 mixture) afforded 3 as a yellow solid (140 mg, 45% yield).
A small amount of 6 (16 mg, 5.3% yield) was obtained as colorless
crystals from the first mother liquor diluted with n-hexane.
X Abstract published in Advance ACS Abstracts, November 15, 1997.
(1) (a) Hyatt, D. E.; Little, J . L.; Moran, J . T.; Scholer, F. R.; Todd,
L. J . J . Am. Chem. Soc. 1967, 89, 3342. (b) Knoth, W. H. J . Am. Chem.
Soc. 1967, 89, 3342. (c) Knoth, W. H. Inorg. Chem. 1971, 10, 599. (c)
Reitz, R. R.; Dustin, D. F.; Hawthorne, M. F. Inorg. Chem. 1974, 13,
1580. (d) Carroll, W. E.; Green, M.; Stone, F. G. A.; Welch, A. J . J .
Chem. Soc., Dalton Trans. 1975, 2263. (e) Schultz, R. V.; Sato, F.; Todd,
L. J . J . Organomet. Chem. 1977, 125, 115.
(2) (a) Gallahan, K. P.; Evans, W. J .; Lo, F. Y.; Strouse, C. E.;
Hawthorne, M. F. J . Am. Chem. Soc. 1975, 97, 296. (b) J ung, C. W.;
Baker, R. T.; Knobler, C. B.; Hawthorne, M. F. J . Am. Chem. Soc. 1980,
102, 5782. (c) J ung, C. W.; Baker, R. T.; Hawthorne, M. F. J . Am. Chem.
Soc. 1981, 103, 810.
S0276-7333(97)00690-0 CCC: $14.00 © 1997 American Chemical Society

Communications
Organometallics, Vol. 16, No. 26, 1997 5599
Sch em e 1
It can be seen from Figure 1 that an alternative
description of the polyhedron as a bicapped Archimedian
square antiprism, which is normally found for electron-
precise 10-vertex monocarbon metallacarboranes of the
closo type,9 seems much less appropriate in this case.
In particular, the B(6)‚‚‚B(9) distance within the basal
prism face B(6)B(7)B(8)B(9) is too long to be considered
as bonding and, in contrast, one extra bond, B(10)-Ru-
(2), which does not comply to the bicapped antiprismatic
geometry is formed. One of the basal fragments of the
antiprism, B(3)B(4)B(5)Ru(2), shows quite significant
deviations from planarity, the folding angle along the
B(5)‚‚‚B(3) line being equal to 20.2°. Moreover, the
mean plane of this cycle is not quite parallel to another
basal plane of the antiprism, B(6)B(7)B(8)B(9), forming
with the latter the dihedral angle of 9.5°.
The structure of 3 has revealed several specific
geometrical features typical of the 10-vertex hyper-closo
polyhedra. The 6-membered open face coordinating by
the Ru atom has an almost ideal chair conformation.
Thus, the signs of the torsion angles about the bonds of
the six-membered cycle are alternating with their
absolute values in the range of 48.7-57.2°. The Ru(2)
atom is located in the vicinity of the approximate 3-fold
axis of the 6-membered ring, so that the atoms with low
cluster connectivity of 4, C(1), B(6), and B(9), turned
out to be much closer to the ruthenium center (2.157-
(3), 2.095(4), and 2.083(4) Å, respectively) as compared
F igu r e 1. Molecular structure of 3 (thermal ellipsoids are
drawn at the 50% probability level); the phenyl group
carbon atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): Ru(2)-Cl(1), 2.4212(13); Ru(2)-P(1),
2.3243(13); Ru(2)-H(2), 1.63(4); Ru(2)-C(1), 2.157(3); Ru-
(2)-B(3), 2.502(5); Ru(2)-B(5), 2.436(4); Ru(2)-B(6), 2.095-
(4); Ru(2)-B(9), 2.083(4); Ru(2)-B(10), 2.346(4); Cl(1)-
Ru(2)-P(1), 89.16(4); P(1)-Ru(2)-H(2), 68(2); Cl(1)-Ru(2)-
H(2), 94(2).
(2.944(6) Å) are disrupted and one extra bond, Ru(2)-
B(10) (2.346(4) Å), is formed. The C(1) vertex bridges
one of the broken axial bonds, B(3)-B(5), and is
simultaneously bonded to two capping atoms, Ru(2) and
B(4) (the C(1)-Ru(2) and C(1)-B(4) distances are equal
to 2.157(3) and 1.664(6) Å, respectively).
(7) Although complex 6 was not isolated in sufficient quantities to
allow complete characterization, the NMR and mass spectral data
available are consistent with the formulation of this species as having
an eight-vertex monocarbon metallacarborane structure, (PPh3)2-
HRuCB6H4(OMe)3: 1H NMR (400.13 MHz, C6D6, J (Hz)) 7.51, 6.97,
(m + m 12H + 18H, Ru(PPh3)2), 4.17 (s, 3H, MeO), 3.05 (s, 6H, 2 MeO),
2.99 (s br, 1H, CHCb), -9.02 (t, 1H, HRu, J H-P ) 20.7); 31P{1H} NMR
(161.98 MHz, C6D6) 49.4 (s, PRu); 11B NMR (128.33 MHz, CD2Cl2, J B-H
(6) Characterization data for 3 and 4 are as follows. 3: IR (KBr)
νBH 2527 cm-1 νRuH 1955 cm-1; 1H NMR (400.13 MHz, CD2Cl2, J (Hz))
7.81-7.40, 7.06 (m + d br, 29H + 1H, Ph, J d ) 12), 3.60 (s br, 1H,
*CHCb), 3.46 (s, 3H, MeO), 3.13 (s, 3H, MeO), -4.68 (d, 1H, HRu, J H-P
) 57) (the asterisk indicates that the resonance was assigned by 13C-
{1H}-1H correlation); 31P{1H} NMR (161.98 MHz, C6D6, J P-B (Hz)) 52.1
(s, 1P, PRu), 3.9 (q-like, 1P, PB, 152 (av)); 13C{1H} NMR (100.51 MHz,
CD2Cl2, J d ) J C-P (Hz)) 134.8, 133.0, 130.3 (s v br + d br, s br,
(Hz)) 68.9 (s br, 1B), 33.7 (s, 2B), 12.8 (d, 1B, 140), -31.8 (d, 2B, 150);
12
FAB MS (positive ion, m/e): calcd for
C
1H4411B616O331P2101Ru 801.2,
40
found 801.6 [M]+, 724.4 [M - Ph]+, 647.3 [M - 2Ph]+, 570.2 [M -
3Ph]+, 539.4 [M - PPh3]+, 462.4 [M - PPh3 - Ph]+. Since this species
seems to have a hyper-closo structure (there is the characteristic low-
field resonance at 68.9 ppm in the 11B NMR spectra which could be
ascribed to the low-coordinate boron atom), a detailed investigation of
its formation and structure as well as those of other minor products
of the above reaction is planned.
CPh-o,m,p(k?)(B-PPh3), J d ≈ 4), 134.7, 129.3, 127.9, 122.8 (d, CPh-o,m,p,k
-
(Ru-PPh3),1J d ) 7, 2J d ) 12, 3J d ) 12, 4J d ) 65 (Ck)), 57.5 (s, MeO),
56.2 (s, MeO), 48.9 (q-like br, CCb); 11B NMR (128.33 MHz, CD2Cl2,
J B-H (Hz)) 77.0 (d br, 1B, B6, 122), 70.2 (s, 1B, B9), 15.1 (d, 1B, B7(8),
160), 13.8 (d, 1B, B8(7), 160), 11.7 (s, 1B, B3), -4.1 (d, 1B, B4, 145),
-25.8 (d, 1B, B5, J B-P ) 150), -29.0 (d, 1B, B10, 145). Anal. Calcd for
C39H43B8ClO2P2Ru‚CH2Cl2: C, 52.58; H, 4.71; P, 6.79. Found: C, 52.99;
(8) Crystal data for 3: RuC39H43B8ClO2P2‚CH2Cl2, Mr ) 913.60,
triclinic, space group P1h, a ) 9.968(2) Å, b ) 12.269(3) Å, c ) 19.455-
(4) Å, R ) 94.83(3)°, â ) 90.39(3)°, γ ) 111.68(3)°, V ) 2201.1(8) Å3 for
Z ) 2, d(calcd) ) 1.378 g/cm3, F(000) ) 932, µ ) 6.45 cm-1. Data
collection was carried out with an Enraf-Nonius CAD-4 diffractome-
ter: λ(Mo KR) ) 0.710 73 Å, T ) 293 K; 10 585 independent reflections
with 2.0° < 2θ < 56.0° collected and used in refinement; R1 ) 0.0397
(on F for 6513 observed reflections with I > 2.0σ(I)), wR2 ) 0.1281
(on F2 for all data); 677 variables refined. Hydrogen atoms were refined
isotropically, except for the solvent molecule.
(9) (a) Crook, J . E.; Greenwood, N. N.; Kennedy, J . D.; McDonald,
W. S. J . Chem. Soc., Chem. Commun. 1983, 83. (b) Alcock, N. W.;
Taylor, J . G.; Wallbridge, M. G. H. J . Chem. Soc., Chem. Commun.
1983, 1168. (c) Sˇtibr, B.; J anousˇek, Z.; Basˇe, K.; Plesˇek, J .; Solntsev,
K. A.; Butman, L. A.; Kuznetsov, I. I.; Kuznetzov, N. T. Collect. Czech.
Chem. Commun. 1984, 49, 1660. (d) Baker, G. K.; Garcia, M. P.; Green,
M.; Pain, G. N.; Stone, F. G. A.; J ones, S. K. R.; Welch, A. J . J . Chem.
Soc., Chem. Commun. 1981, 652.
H, 4.52; P, 6.54. 4: IR (KBr) νBH 2530 cm-1, νRuH 1950 cm-1 1H NMR
;
(400.13 MHz, CD2Cl2, J (Hz)) 7.37, 7.35-7.10 (t-like + m, 31H, Ph +
CHCb(?), J t ) 8), 4.07 (s, 3H, MeO), 3.70 (s, 3H, MeO), -5.36 (d d, 1H,
J H-P1 ) 22.1, J H-P2 ) 45.3); 31P{1H} NMR (161.98 MHz, CD2Cl2, J P-P
(Hz)) 50.7 (d, 1P, P1, 16), 38.7 (d, 1P, P2, 16); 13C{1H} NMR (100.51
MHz, CD2Cl2, J d ) J C-P (Hz)) 135.2, 134.5, 133.3, 130.8, 130.0, 128.4,
127.5 (s br + 6 d (partly overlapped), CPh-o,m,p,k(Ru-PPh3), J d) 48.2
(Ck), 32.0 (Ck), J d ≈ 8), 132.1 (s v br, CCb?), 59.5 (s br, MeO), 57.7 (s,
MeO); 11B NMR (128.33 MHz, CD2Cl2, J B-H (Hz)) 82.4 (s, 1B, B9), 78.8
(s br, 1B, B6), 19.8 (d, 1B, B4(7 or 8), 124), 12.7 (s br + s, 3B, B7,8(4,7
or 4,8), B3), -23.7 (d br, 1B, B5(10), 120), -28.7 (d br, 1B, B10(5),
120). Anal. Calcd for C39H44B8O2P2Ru: C, 58.94; H, 5.54, Found:
C, 59.30; H, 5.59. FAB MS (positive ion, m/e): calcd for
12
C
1H4411B816O231P2101Ru 794.3, found 794.6 [M]+, 717.3 [M - Ph]+,
39
530.3 [M - PPh3 - H2]+, 456.2 [M - PPh3 - Ph]+.

5600 Organometallics, Vol. 16, No. 26, 1997
Communications
with the remaining three atoms of the coordinating face,
each of them having a cluster connectivity of 5, Ru(2)-
B(3) ) 2.502(5) Å, Ru(2)-B(5) ) 2.436(4) Å, and Ru-
(2)-B(10) ) 2.346(4) Å. The RuHCl(PPh3) moiety in
molecule 3 has an almost ideally eclipsed conformation
with respect to the three short Ru-C(1), Ru-B(6), and
Ru-B(9) bonds which are formed by the cage atoms
occupying low-coordinate apical vertices (the torsion
angles H(1)C(1)Ru(2)Cl(1), O(9)B(9)Ru(2)H(2), and H(6)B-
(6)Ru(2)P(1) are equal to 1.9, 14.7, and 15.0°, respec-
tively). Quite identical orientation of the same metal-
containing moiety relative to the six-membered cage
open face was found in iso-closo-1,1,1-(PPh3)HCl-3,5-
(PPh3)2-1-RuB9H7.3b
phosphorus signals the hydride resonance in the 1H
NMR spectrum of 4 has collapsed into two doublets with
J H-P(1) ) 22.1 Hz and J H-P(2) ) 45.3 Hz, respectively.
According to the skeletal electron-counting formal-
ism,11 clusters 3 and 4 cannot be regarded as usual 10-
vertex 2n + 2 electron closo-metallacarboranes which
normally possess a D4d symmetry.9 Considering an Ru-
(PPh3)HCl unit as contributing zero electrons and three
orbitals to the CB8 cage for bonding, and then taking
into account the presence of the pendant phosphine
ligand on B(5) which contributes one extra electron to
the cluster, 3 would have only 20 framework electrons
available for bonding and would, therefore, be consid-
ered as a hyper-closo cluster. However, earlier discus-
sion12 concerning the structure and type of bonding in
such 10-vertex and other related metallacarborane and
metallaborane clusters of “hyper-closo” or “iso-closo” type
based on the geometry of a capped tricapped trigonal
prism showed that more experimental evidence will be
required to entirely resolve this problem, and any new
examples of 2n skeletal electron systems such as those
presented above would seem to be an important contri-
bution to the area.
The 11B NMR spectra of 3 and 4 both display a set of
doublets and singlets in the range -28 to +82 ppm
grouped into three distinct groups of signals, with one
of these groups of two signals shifted to the extreme low
field of about 70-80 ppm. These low-field boron reso-
nances are indicative of a low-coordinate boron atom
adjacent to a metal center3b,10 and may be, therefore,
assigned to the B(6) and B(9) atoms. On the basis of
the known substituent positions at the cage ligand in
cluster 3 and taking into account the obvious similarity
in the 11B NMR spectra parameters observed for clus-
ters 3 and 4, a partial assignment of their boron
resonances has been made.6 In spite of the presence of
the two different metal- and boron-bound triphenylphos-
phine ligands in the molecule of 3, the terminal metal
Ack n ow led gm en t. This research has been sup-
ported in part by INTAS Grant No. 94-541. We also
gratefully acknowledge the financial support of the
Russian Foundation for Basic Research (Grants Nos. 97-
03-33783 and 95-03-08831). We are indebted to Dr. L.
Wesemann and his colleagues from the Institut fu¨r
Anorganische Chemie der Technischen Hochschule
(Aachen, Germany) for their help in the FAB mass
spectra measurements of complexes 3 and 6.
1
hydride resonances found in the H NMR spectrum at
-4.68 ppm splits into a doublet (J H-P ) 57 Hz), and no
indication of the long-range coupling of hydride to the
unique phosphine on B(5) was revealed. The metal-
hydride resonance in the 1H NMR spectrum of 4, by
contrast, is observed as a doublet of doublets at -5.36
ppm due to coupling of hydride to phosphorus nuclei of
the two nonequivalent metal-coordinated triphenylphos-
phine ligands. This is confirmed by the observation of
two separated 1:1 doublets at 50.7 and 38.7 ppm with
2J P-P ) 16 Hz. After selective 31P decoupling of the
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data collection parameters, atomic coordinates and
U values, bond lengths and angles, and anisotropic parameters
1
for 3 and figures giving H and 11B NMR spectra of 6 in CD2-
Cl2 (11 pages). Ordering information is given on any current
masthead page.
OM970690O
(10) (a) Salentine, C. G.; Hawthorne, M. F. J . Am. Chem. Soc. 1975,
97, 6382 and references therein. (b) Micciche, R. P.; Briguglio, J . J .;
Sneddon, L. G. Inorg. Chem. 1984, 23, 3992. (c) Kennedy, J . D. In
Multinuclear NMR (NMR in Inorganic and Organometallic Chemistry);
Mason, J ., Ed.; Plenum: London and New York, 1987; Chapter 8, p
221.
(11) Wade, K. Adv. Inorg. Chem. Radiochem. 1979, 18, 1.
(12) (a) Nishimura, E. K. J . Chem. Soc., Chem. Commun. 1978, 858.
(b) Baker, R. T. Inorg. Chem. 1986, 25, 109. (c) Kennedy, J . D. Inorg.
Chem. 1986, 25, 111. (d) J ohnston, R. L.; Mingos, D. M. P. Inorg. Chem.
1986, 25, 3321.