Formation of intramolecular rings in ferramonocarbollide complexes

Article abstract of DOI:10.1021/ic800780w

Addition of PPh₂Cl and Tl[PF₆] to CH ₂Cl₂ solutions of [N(PPh₃)₂][6,6,6- (CO)₃-closo-6,1-FeCB₈H₉] (1) affords the isomeric B-substituted species [6,6,6-(CO)₃-n-(PHPh ₂)-closo-6,1-FeCB₈H₈] [n = 7 (2a) or 10 (2b)]. Deprotonation (NaH) of the phosphine ligand in 2a, with subsequent addition of [IrCl(CO)(PPh₃)₂] and TI[PF₆], yields the neutral, zwitterionic complex [6,6,6-(CO)₃-4,7-μ-{Ir(H)(CO) (PPh₃)₂PPh₂}-closo-6,1-FeCB₈H ₇] (3), which contains a B-P-Ir-B ring. Alternatively, deprotonation using NEt₃, followed by addition of HC≡CCH₂Br, affords [6,6,6-(CO)₃-7-(PPh₂C≡CMe)-closo-6,1- FeCB₈H₈] (4). Addition of [Co₂(CO)₈] to CH₂Cl₂ solutions of the latter gives [6,6,6-(CO) ₃-7-(PPh₂-{(μ-η²:η²- C≡CMe)Co₂(CO)₆})-closo-6,1-FeCB₈H ₈] (5), which contains a {C₂Co₂} tetrahedron. In the absence of added substrates, deprotonation of the PHPh₂ group in compounds 2, followed by reaction of the resulting anions with CH ₂Cl₂ solvent, affords [6,6,6-(CO)₃-n-(PPh ₂CH₂Cl)-closo-6,1-FeCB₈H₈] [n = 7 (6a) or 10 (6b)] plus [6,6-(CO)₂-6,7-μ-{PPh₂CH ₂PPh₂}-closo-6,1-FeCB₈H₈] (7, formed from 2a), of which the latter species possesses an intramolecular B-P-C-P-Fe ring. Addition of Me₃NO to CH₂Cl₂ solutions of 2a causes loss of an Fe-bound CO ligand and formation of [6,6-(CO) ₂-6,7-μ-{NMe₂CH₂PPh₂}-closo-6,1- FeCB₈H₈] (8), which incorporates a B-P-C-N-Fe ring. A similar reaction in the presence of ligands L yields [6,6-(CO) ₂-6-L-7-(PPh₂CH₂Cl)-closo-6,1-FeCB ₈H₈] [L = PEt₃ (9) or CNBu^t (10)], in addition to 8.

Full text of DOI:10.1021/ic800780w

Inorg. Chem. 2008, 47, 8788-8797
Formation of Intramolecular Rings in Ferramonocarbollide Complexes
Andreas Franken, Bruce E. Hodson, Thomas D. McGrath, and F. Gordon A. Stone*
Department of Chemistry & Biochemistry, Baylor UniVersity, Waco, Texas 76798-7348
Received April 29, 2008
Addition of PPh2Cl and Tl[PF6] to CH2Cl2 solutions of [N(PPh3)2][6,6,6-(CO)3-closo-6,1-FeCB8H9] (1) affords the
isomeric B-substituted species [6,6,6-(CO)3-n-(PHPh2)-closo-6,1-FeCB8H8] [n ) 7 (2a) or 10 (2b)]. Deprotonation
(NaH) of the phosphine ligand in 2a, with subsequent addition of [IrCl(CO)(PPh3)2] and Tl[PF6], yields the neutral,
zwitterionic complex [6,6,6-(CO)3-4,7-µ-{Ir(H)(CO)(PPh3)2PPh2}-closo-6,1-FeCB8H7] (3), which contains a B-P-Ir-B
ring. Alternatively, deprotonation using NEt3, followed by addition of HCt CCH2Br, affords [6,6,6-(CO)3-7-
(PPh2Ct CMe)-closo-6,1-FeCB8H8] (4). Addition of [Co2(CO)8] to CH2Cl2 solutions of the latter gives [6,6,6-(CO)3-
2
2
7-(PPh2-{(µ-η :η -Ct CMe)Co2(CO)6})-closo-6,1-FeCB8H8] (5), which contains a {C2Co2} tetrahedron. In the absence
of added substrates, deprotonation of the PHPh2 group in compounds 2, followed by reaction of the resulting
anions with CH2Cl2 solvent, affords [6,6,6-(CO)3-n-(PPh2CH2Cl)-closo-6,1-FeCB8H8] [n ) 7 (6a) or 10 (6b)] plus
[6,6-(CO)2-6,7-µ-{PPh2CH2PPh2}-closo-6,1-FeCB8H8] (7, formed from 2a), of which the latter species possesses an
intramolecular B-P-C-P-Fe ring. Addition of Me3NO to CH2Cl2 solutions of 2a causes loss of an Fe-bound CO
ligand and formation of [6,6-(CO)2-6,7-µ-{NMe2CH2PPh2}-closo-6,1-FeCB8H8] (8), which incorporates a B-P-C-N-Fe
ring. A similar reaction in the presence of ligands L yields [6,6-(CO)2-6-L-7-(PPh2CH2Cl)-closo-6,1-FeCB8H8] [L )
PEt3 (9) or CNBut (10)], in addition to 8.
Introduction
[closo-1-CB7H8]-) have appeared,4 we have been able to
extend very considerably the scope of our studies of reactions
of metallamonocarbollide compounds, generally obtaining
products with unusual molecular structures.
In recent times numerous transition metal half-sandwich
metallamonocarbollide compounds have been described with
a metal atom incorporated in a cage framework containing
12 or fewer vertices. Our initial studies focused on those
species with 12-atom, icosahedral frameworks.1 These
complexes were usually obtained by treating salts of the long
known2 monoanion [nido-7-CB10H13]- with suitable transi-
tion element reagents. Thus reaction of this carborane anion
with [Fe3(CO)12] affords [2,2,2-(CO)3-closo-2,1-FeCB10-
H11]-,3 a species isolobal with [Mn(CO)3(η-C5H5)]. As
reports of straightforward syntheses of monocarbon carbo-
ranes with fewer than 10 boron atoms (e.g., salts of [arachno-
9-CB9H14]-, [6-Ph-nido-6-CB9H11]-, [closo-1-CB8H9]-, and
Not unexpectedly the chemical reactivity of these new
metal complexes varies according to the transition element
they contain, for example, iron versus manganese, and with
the metal’s oxidation state. However, an especially interesting
feature of the chemistry is the discovery that in several of
the new compounds initially formed the terminal {B-H}
groups can react further, affording molecules with functional
organic groups attached to the peripheral boron atoms.1,5
These products may in turn be converted into other new
molecules in which the closo-cage may or may not play a
role. The functionalization of (hetero)borane cages has been
of interest for many years, particularly with a view to medical
* To whom correspondence should be addressed. E-mail: gordon_stone@
baylor.edu.
(1) McGrath, T. D.; Stone, F. G. A. AdV. Organomet. Chem. 2005, 53, 1.
(2) Noth, W. H.; Little, J. L.; Lawrence, J. R.; Scholer, F. R.; Todd, L. J.
Inorg. Synth. 1968, 11, 33.
(3) Ellis, D. D.; Franken, A.; Jelliss, P. A.; Stone, F. G. A.; Yu, P.-Y.
Organometallics 2000, 19, 1993.
(4) (a) Brellochs, B. In Contemporary Boron Chemistry; Davidson, M. G.,
Hughes, A. K., Marder, T. B., Wade, K.; Royal Society of Chemistry:
Cambridge, U.K., 2000, p 212. (b) Brellochs, B.; Backovsky, J.; Stibr,
B.; Jelinek, T.; Holub, J.; Bakardjiev, M.; Hnyk, D.; Hofmann, M.;
Cisarova, I.; Wrackmeyer, B. Eur. J. Inorg. Chem. 2004, 3605.
(5) See also Jelliss, P. A.; Stone, F. G. A. J. Organomet. Chem. 1995,
500, 307.
8788 Inorganic Chemistry, Vol. 47, No. 19, 2008
10.1021/ic800780w CCC: $40.75  2008 American Chemical Society
Published on Web 09/04/2008

Intramolecular Rings in Ferramonocarbollide Complexes
Chart 1
yields a neutral, zwitterionic species containing a {B-
PHPh2} vertex. Few examples of clusters involving this unit
have been reported,10 and derivatization of this compound
affords several novel and surprising products.
Results and Discussion
Addition of PPh2Cl and Tl[PF6] to CH2Cl2 solutions of
the ferramonocarbollide complex [N(PPh3)2][6,6,6-(CO)3-
closo-6,1-FeCB8H9] (1)8 affords two neutral, zwitterionic,
isomeric species [6,6,6-(CO)3-n-(PHPh2)-closo-6,1-FeCB8H8]
[n ) 7 (2a) or 10 (2b)] in the approximate ratio 49:1 (Chart
1). Attempts to separate completely these compounds by
column chromatography proved unsuccessful, small quanti-
ties of 2b appearing in all samples of 2a. However, full
characterization of the latter was achieved. Physical and
spectroscopic data for 2a and 2b (where possible) are
presented in Tables 1-3. The IR spectrum of 2a contains
strong CO stretching bands at 2056 and 1995 cm-1, values
higher than those for the precursor 1 (2033 and 1964 cm-1),
as is to be expected following formation of a neutral species
from an anionic complex. An 11B{1H} NMR study revealed
six signals for 2a in intensity ratio 1:1:2(1+1 coincidence):
1:2(1+1 coincidence):1 (low to high field), indicating a lack
of symmetry in the cluster. The highest field, doublet
resonance (δ -31.9) retained this multiplicity in the corre-
sponding 11B spectrum and as such was assigned to the
{B-PHPh2} vertex. The phosphorus atom of this unit gave
rise to a quartet resonance in the 31P{1H} NMR spectrum at
δ 1.5 [J(BP) ) 128 Hz] and to a doublet-of-quartets peak
[J(HP) ) 433 Hz] in the 31P NMR spectrum. Additionally,
1
the phosphorus-bound hydrogen atom appeared in the H
NMR spectrum as a doublet peak [J(PH) ) 426 Hz] centered
on δ 6.32, which collapsed into a singlet upon 31P decoupling.
1
The H NMR spectrum also contained a broad resonance
due to the cage {CH} unit at δ 5.21 with complex multiplet
resonances in the range δ 7.77-7.31 due to the Ph groups
in the molecule. The 13C{1H} spectrum of 2a revealed
resonances due to the Fe-bound CO ligands at δ 210.2 and
to the cage carbon atom at δ 60.5.
Attempts to isolate significant quantities of 2b proved
unsuccessful as a consequence of its low yield and physical
properties similar to those of its isomer 2a. In the reactions
involving 2a discussed below, small quantities of 2b are
assumed to be present. The paucity of data for 2b prevents
any complete, even tentative characterization. However,
examination of 11B{1H} and 31P{1H} NMR data of 2a/2b
mixtures, in addition to the crystal structure of 6b obtained
fortuitously and discussed below, fully justifies the formula-
tion for 2b. Thus, an 11B{1H} NMR study of a 2a/2b mixture
reveals a low intensity doublet resonance at δ 48.6, sug-
gesting the presence of a {B-P} unit other than that in 2a.
This δ value is significantly lower field in comparison with
applications; thus the in ViVo solubility of boron-containing
clusters is one of the essential factors for effective Boron
Neutron Capture Therapy (BNCT).6
Complexes obtained from iron carbonyls and {CB7} or
{CB8} precursors7,8 appear readily to yield molecules that
display interesting derivative chemistry.9 In this paper we
focus on compounds derived from the anion [6,6,6-(CO)3-
closo-6,1-FeCB8H9]-,8 here used as the [N(PPh3)2]+ salt (1;
see Chart 1), in which the introduction of cage substituents
is readily accomplished. Thus, a {B-H} substitution reaction
(6) For a recent review, see Bregadze, V. I.; Sivaev, I. B.; Glazun, S. A.
Anti-Cancer Agents Med. Chem. 2006, 6, 75.
(7) Franken, A.; McGrath, T. D.; Stone, F. G. A. Organometallics 2005,
24, 5157.
(8) Franken, A.; McGrath, T. D.; Stone, F. G. A. Inorg. Chem. 2006, 45,
2669.
(9) (a) Franken, A.; McGrath, T. D.; Stone, F. G. A. J. Am. Chem. Soc.
2006, 128, 16169. (b) Franken, A.; Hodson, B. E.; McGrath, T. D.;
Stone, F. G. A. Dalton Trans. 2007, 2254.
(10) (a) Fontaine, X. L. R.; Greenwood, N. N.; Kennedy, J. D.; MacKinnon,
P.; Thornton-Pett, M. J. Chem. Soc., Dalton Trans. 1988, 2059. (b)
Zakharkin, L. I.; Ol’shevskaya, V. A.; Zhigareva, G. G.; Antonovich,
V. A.; Petrovskii, P. V.; Yanovskii, A. I.; Polyakov, A. V.; Struchkov,
Yu. T. Metalloorg. Khimi. 1989, 2, 1274. (c) Shea, S. L.; Jelinek, T.;
Perera, S. D.; Stibr, B.; Thornton-Pett, M.; Kennedy, J. D. Inorg. Chim.
Acta 2004, 357, 3119.
Inorganic Chemistry, Vol. 47, No. 19, 2008 8789

Franken et al.
Table 1. Analytical and Physical Data
anal/%b
C H
compd
color
ν
max(COa/cm-1
[6,6,6-(CO)3-7-(PHPh2)-closo-6,1-FeCB8H8] (2a)c
yellow
yellow
yellow
red
yellow
yellow
orange
yellow
yellow
2056 s, 1995 s
2041 s, 1981 s
2054 s, 1995 s
2099 s, 2068 s, 2054 s, 2038 s, 1994 s
2056 s, 1999 s
1994 s, 1948 s
1983 s, 1927 s
1974 s, 1924 s
2004 s, 1960 s
(44.4) 44.2
(54.1) 53.8
(48.5) 48.3
(39.7) 40.1
(42.4) 42.2
(55.8) 55.6e
(46.8) 46.4
(46.3) 46.1
(47.0) 47.3
(4.4) 4.1
(4.1) 4.3
(4.5) 4.7
(2.8) 2.9
(4.2) 4.4
(5.0) 5.1
(5.7) 6.1
(6.2) 6.4
(5.5) 5.7
[6,6,6-(CO)3-4,7-µ-{Ir(H)(CO)(PPh3)2PPh2}-closo-6,1-FeCB8H7] (3)
[6,6,6-(CO)3-7-(PPh2Ct CMe)-closo-6,1-FeCB8H8] (4)
[6,6,6-(CO)3-7-(PPh2{(µ-η2:η2-Ct CMe)Co2(CO)6})-closo-6,1-FeCB8H8] (5)
[6,6,6-(CO)3-7-(PPh2CH2Cl)-closo-6,1-FeCB8H8] (6a)d
[6,6-(CO)2-6,7-µ-{PPh2CH2PPh2}-closo-6,1-FeCB8H8] (7)
[6,6-(CO)2-6,7-µ-{NMe2CH2PPh2}-closo-6,1-FeCB8H8] (8)
[6,6-(CO)2-6-PEt3-7-(PPh2CH2Cl)-closo-6,1-FeCB8H8] (9)
[6,6-(CO)2-6-CNBut-7-(PPh2CH2Cl)-closo-6,1-FeCB8H8] (10)
a Measured in CH2Cl2; a broad, medium-intensity band observed at ca. 2500-2550 cm-1 in the spectra of all compounds is due to B-H absorptions. In
addition: for 4, νmax(C≡C) 2211 w cm-1; for 10, νmax(C≡N) 2158 s cm-1
.
b Calculated values are given in parentheses. In addition, % N: for 8, (3.0) 2.9;
for 10, (2.6) 2.8. c Samples contained approximately 2% [6,6,6-(CO)3-10-(PHPh2)-closo-6,1-FeCB8H8] (2b). d Samples contained approximately 2% [6,6,6-
(CO)3-10-(PPh2CH2Cl)-closo-6,1-FeCB8H8] (6b). e Co-crystallizes with one mol. equiv. of CH2Cl2.
a
1
Table 2. H and 13C NMR Data
compd
1H/δb
13C/δc
2a 7.77-7.31 (m, 10H, Ph), 6.32 [d, J(PH), 1H, PH ) 426], 5.21 (br s,
210.2 (CO), 135.1-128.5 (Ph), 60.5 (br, cage C)
1H, cage CH)
3
4
7.50-6.98 (m, 40H, Ph), 4.11 (br, 1H, cage CH), -8.68 (br, 1H, Ir-H) 211.8 (Fe-CO), 180.9 (br, Ir-CO), 134.2-128.5 (Ph), 60.5 (br, cage C)
7.93-7.53 (m, 10H, Ph), 5.23 (br, 1H, cage CH), 2.11 (s, 3H, Me)
210.4 (CO), 132.0-122.4 (Ph), 114.6 [d, J(PC) ) 29, PCt C], 66.5
(Ct CMe), 59.9 (br, cage C), 5.5 (Me)
5
8.18-7.50 (m, 10H, Ph), 5.12 (br, 1H, cage CH), 3.17 (s, 3H, Me)
209.8 (Fe-CO), 197.5 (Co-CO), 133.8-127.3 (Ph), 106.0 (CMe), 72.2
[d, J(PC) ) 30, PC], 60.9 (br, cage C), 23.5 (Me)
6a 8.14-7.38 (m, 10H, Ph), 5.38 (br, 1H, cage CH), 4.23 [dd, J(HaHb) ) 210.1 (CO), 133.4-128.5 (Ph), 60.8 (br, cage C), 35.8 [d, J(PC) ) 40,
32, J(PH) ) 144, 1H, PCHaHb], 4.13 [dd, J(HbHa) ) 32, J(PH) )
144, 1H, PCHaHb]
CH2]
7
8
7.88-7.21 (m, 20H, Ph), 5.29 (br, 1H, cage CH), 3.66 (m, 1H, CH2), 215.5 [d, J(PC) ) 21, CO], 212.8 [d, J(PC) ) 19, CO], 133.7-128.4
3.20 (m, 1H, CH2) (Ph), 60.7 (br, cage C), 36.7 [dd, J(PC) ) 18 and 54, CH2]
7.77-7.48 (m, 10H, Ph), 5.05 (br s, 1H, cage CH), 3.78 [dd, J(PH) ) 218.2 (CO), 216.4 (CO), 134.0-128.5 (Ph), 68.3 [d, J(PC) ) 45,
42, J(HH) ) 13, 1H, CH2], 3.15 [dd, J(PH) ) 15, J(HH) ) 5, 1H,
CH2], 3.08, 2.22 (s × 2, 3H × 2, Me × 2)
NCH2P], 62.6, 60.3 (NMe × 2), 57.9 (br, cage C)
9
7.59-7.45 (m, 10H, Ph), 5.13 (br s, 1H, cage CH), 4.29 (br, 2H,
BPCH2), 1.68 (m, 6H, FePCH2), 1.07 (m, 9H, Me)
219.5 [d, J(PC) ) 27, CO], 215.1 [d, J(PC) ) 27, CO], 133.7-128.4
(Ph), 59.1 (br, cage C), 36.0 [d, J(PC) ) 35, BPCH2], 19.3 [d, J(PC)
) 29, FePCH2], 7.6 (Me)
10 7.75-7.43 (m, 10H, Ph), 5.18 (br s, 1H, cage CH), 4.17 (m, 2H, CH2), 215.2 (CO), 213.7 (CO), 156.3 (N≡C), 133.7-121.4 (Ph), 58.5 (br,
1.32 (s, 9H, Me)
cage C), 57.6 (CMe3), 36.1 [d, J(PC) ) 39, PCH2], 30.0 (CMe3)
a Chemical shifts (δ) in ppm, coupling constants (J) in hertz, measurements at ambient temperatures in CD2Cl2. b Resonances for terminal BH protons
c
occur as broad unresolved signals in the range δ ca. -1 to +3. 1H-decoupled chemical shifts are positive to high frequency of SiMe4.
Table 3. 11B and 11P NMR Dataa
compd
11B/δb
31P/δc
2a
3
4
5
6a
7
8
9
10
55.9, -3.4, -3.0 (2B), -23.0, -24.4 (2B), -31.9 [d, J(PB) ) 127]
53.6, 1.3, -6.5 (2B), -17.5, -23.8 (2B), -34.1
54.8, -2.0, -3.2, -5.2, -22.7, -24.2, -25.3, -28.3 [d, J(PB) ) 120]
54.6, -2.8, -5.2, -23.3 (2B), -25.0 (2B), -27.5 [d, J(PB) ) 132]
54.2, -3.6, -5.6 (2B), -22.8, -24.0, -25.0, -30.5 [d, J(PB) ) 127]
57.5, -0.3, -1.6, -4.2, -22.8, -23.9, -24.5, -26.1 [d, J(PB) ) 131]
58.8, -0.4, -2.1, -7.1, -23.3 (2B), -24.6, -29.9
1.5 [q, J(BP) ) 128]
2.3 [d, J(PP) ) 260, Ir-P], -3.4 (d, Ir-P), -48.3 (br, B-P)
1.3 [q, J(BP) ) 122]
22.4 [q, J(BP) ) 126]
17.5 [q, J(BP) ) 127]
77.4 [d, J(PP) ) 95], 18.5 [br dq, J(BP) ) ca. 132]
23.7 [q, J(BP) ) 130]
59.9 (Fe-P), 19.5 [q, J(BP) ) 120, B-P]
18.7 [q, J(BP) ) 122]
52.6, -3.7, -5.6, -6.8, -23.0, -23.9, -24.5, -32.3 [d, J(PB) ) 122]
52.5, -5.9 (3B), -22.9, -24.4, -24.6, -32.3 [d, J(PB) ) 125]
a Chemical shifts (δ) in ppm, coupling constants (J) in hertz, measurements at ambient temperatures in CD2Cl2. 1H-decoupled chemical shifts are
b
positive to high frequency of BF3 ·Et2O (external); resonances are of unit integral except where indicated. In addition, for 2b δ 48.6 [d, J(PB) ) 127]; for
c
6b δ 49.8 [d, J(PB) ) 155]. 1H-decoupled chemical shifts are positive to high frequency of 85% H3PO4 (external). In addition, for 2b δ -4.5 [q, J(BP)
) 74]; for 6b δ 14.1 [q, J(BP) ) 155].
the corresponding value for the {B-P} unit in 2a (δ -31.9),
as expected for such a group occupying the four-connectivity
position [B(10)], rather than a five-connectivity position as
seen in 2a [B(7)]. The presence of a phosphorus substitutent
at B(10) in 6b (see below) fully corroborates this suggestion.
In 2b, the P atom of the {B-PHPh2} unit appears as a low
intensity quartet resonance in the corresponding 31P{1H}
NMR spectrum at δ -4.5. Unfortunately, further definitive
assignment of any NMR data for 2b was not possible.
The mechanism of formation of 2a (and 2b) is believed
to involve initial reaction between PPh2Cl and Tl[PF6] to
generate {PPh2}+. This species then abstracts a hydride from
a {B-H} unit in 1, forming PHPh2 and a “denuded”,
formally positively charged boron vertex. Attack at this
“naked” site by the diphenylphosphine molecule is then
reasonable. The preferential formation of the B(7)- (2a) rather
than B(10)-substituted product (2b) is intuitively associated
with the hydrogen atom of the {B(7)H} vertex in 1 being
more hydridic.
Deprotonation of the {B-PHPh2} fragment in 2a is facile
using a variety of bases; the resulting species, which contains
an electron rich phosphorus atom, readily reacts with
electrophiles. Thus, reaction of 2a with excess NaH, followed
by filtration and addition to the filtrate of [IrCl(CO)(PPh3)2]
8790 Inorganic Chemistry, Vol. 47, No. 19, 2008

Intramolecular Rings in Ferramonocarbollide Complexes
Chart 2
and Tl[PF6] (a source of the {Ir(CO)(PPh3)2}+ fragment)
affords the zwitterionic compound [6,6,6-(CO)3-4,7-µ-
{Ir(H)(CO)(PPh3)2PPh2}-closo-6,1-FeCB8H7] (3) (Chart 2).
An 11B{1H} NMR study of 3 revealed the asymmetric nature
of the cluster with six peaks in the intensity ratios 1:1:2:1:
2:1. The signals were broad, and as a result the expected
doublet resonance corresponding to the {B-P} vertex was
not identified. Similarly, the 11B NMR spectrum failed to
provide any information regarding coupling to exopolyhedral
atoms at each vertex, even under variable temperature
conditions (233 to 313 K). The resonance due to the {B-Ir}
unit, which would be expected to have singlet multiplicity
in this spectrum, was therefore not identified. Strong CO
stretching bands appeared in the IR spectrum of 3 at 2041
and 1981 cm-1, with corresponding resonances in the
13C{1H} NMR spectrum at δ 211.8 (Fe-CO) and 180.9
(Ir-CO), respectively. The latter signal suffered from
significant broadening because of unresolved coupling with
the Ir-bound phosphorus ligands. A 1H NMR spectrum of 3
contained complex multiplet peaks in the range δ 7.50-6.98
due to the phenyl groups, as well as two broad peaks at δ
4.11 and δ -8.68 assigned to the cage {CH} and {Ir-H}
units, respectively. The 31P{1H} NMR spectrum contained
a very broad resonance at δ -48.3 for the {B-P} unit, in
addition to broad doublet peaks assigned to PPh3 groups at
Figure 1. Structure of 3 showing the crystallographic labeling scheme. In
this and subsequent figures, thermal ellipsoids are draw with 40%
probability. For clarity, only the ipso carbon atoms of phenyl rings, and
only chemically significant H atoms, are shown. Selected distances (Å) and
angles (deg) are as follows: Ir(1)-B(4) 2.198(6), B(4)-B(7) 1.818(9),
P(1)-B(7) 1.920(7), Ir(1)-P(1) 2.3985(13), Ir(1)-H(11) 1.67(2), Ir(1)-C(5)
1.928(6), Ir(1)-P(2) 2.3513(14), Ir(1)-P(3) 2.4213(15), Fe(6)-B(2) 2.210(7),
Fe(3)-B(3)2.218(7),Fe(6)-B(7)2.222(7),Fe(6)-B(9)2.208(7),Fe(6)-B(10)
2.028(8);B(4)-Ir(1)-P(1)71.88(16),B(7)-P(1)-Ir(1)92.69(19),B(7)-B(4)-
Ir(1) 102.5(4), B(4)-B(7)-P(1) 92.6(4).
groups. The iridium center has acquired a hydride ligand,
presumably sourced from the {B(4)-H} vertex in 2a.
Formation of the ring moiety in 3 presumably proceeds via
initial coordination of the {Ir(CO)(PPh3)2}+ fragment at the
phosphorus atom of the {B-PPh2}- unit, followed by
oxidative insertion of the iridium atom into the adjacent
exopolyhedral B(4)-H bond.
Deprotonation of 2a using NEt3, followed by addition of
HCt CCH2Br, affords [6,6,6-(CO)3-7-(PPh2Ct CMe)-closo-
6,1-FeCB8H8] (4) (Chart 1). Inseparable minor impurities
present in samples of 4 are attributed to the intuitive initial
product containing a {PPh2CH2Ct CH} unit and to small
quantities of the corresponding B(10)-substituted isomers
formed from 2b. Unfortunately, none of these other species
could be isolated in sufficient quantity to allow full identi-
fication. The observed redistribution of hydrogen atoms in
the {PPh2Ct CMe} group in the final product 4 may depend
upon the presence of the nearby, formally positively charged
phosphorus atom. In any event, such terminal-to-internal
rearrangements for alkynes are well-known and in the present
case might be catalyzed by the weak base NEt3.11
1
δ 2.3 and -3.4. Both the 31P{1H} and H NMR spectra
indicated the presence of small quantities of as yet unidenti-
fied impurities.
The molecular structure of compound 3 determined by
X-ray diffraction is displayed in Figure 1. Its iridium atom
[Ir(1)] coordinates to B(4) and to the phosphorus atom of
1
The H NMR spectrum of 4 contains peaks assigned to
the phosphine-bound Ph groups and to the cage {CH} units
at δ 7.93-7.53 and δ 5.23, respectively, and the {PCt CMe}
methyl protons gave rise to a singlet resonance at δ 2.11. In
the 13C{1H} NMR study, corresponding peaks due to the
{PCt CMe} fragment were observed at δ 114.6 [d, J(PC)
) 29 Hz], 66.5, and 5.5, corresponding to the PCt , CMe,
and Me groups, respectively. Also contained therein were
peaks due to the Fe-bound CO ligands (δ 210.4), cage {CH}
unit (δ 59.9), and Ph groups (δ 132.0-122.4). The carbonyl
ligands were observed in the IR spectrum of 4 as strong
the {B(7)-P(1)} unit, forming a four-membered B-P-Ir-B
ring. The bridged B(4)-B(7) connectivity [1.814(7) Å] is
comparable with the remaining B-B distances within the
cluster (average 1.820 Å). The B(7)-B(4)-Ir(1)-P(1) ring
is distorted into a shallow butterfly configuration, the triangles
defined by B(4)B(7)P(1) and P(1)Ir(1)B(4) being tilted by
5.8° relative to one another. Internal angles at each corner
are 102.0(3) [B(4)], 71.91(13) [Ir(1)], 92.66(16) [P(1)], and
93.1(3)° [B(7)]. This deviation from planarity is assumed to
be due both to the differing atomic radii of the ring
constituents, particularly the large iridium atom, and to steric
interactions between phenyl rings on the peripheral phosphine
(11) Smith, M. B.; March, J. In AdVanced Organic Chemistry; John Wiley
and Sons: Hoboken, NY, 2007; pp 768-769.
Inorganic Chemistry, Vol. 47, No. 19, 2008 8791

Franken et al.
Å] in comparison with average B-B distances (1.800 Å) in
the remainder of the cluster. Average C-B and Fe-B
distances are 1.594 and 2.183 Å, respectively. The {C2Co2}
unit, typically, describes a closed tetrahedron and the
{PPh2C{µ-Co2(CO)6}CMe} fragment as a whole is oriented
to provide the least possible steric interaction with the Fe-
bound CO ligands. This structure is in agreement with the
formulation of 4 as also containing a pendant {PCt CMe}
fragment.
Addition of NEt3 to CH2Cl2 solutions of 2a (containing
small amounts of its isomer 2b as noted above) afforded
three identifiable species: the two isomeric molecules [6,6,6-
(CO)3-n-(PPh2CH2Cl)-closo-6,1-FeCB8H8] [n ) 7 (6a) or 10
(6b)] (Chart 1), with the latter produced in very small
quantities, in addition to the “ring”-containing compound
[6,6-(CO)2-6,7-µ-{PPh2CH2PPh2}-closo-6,1-FeCB8H8] (7)
(Scheme 1). As with 2b above, bulk compound 6b was not
itself isolated but fortuitously was characterized by a
crystallographic determination (discussed below), along with
limited supporting NMR data. The formation of 6a and 6b
is assumed to proceed via initial deprotonation of the
{PHPh2} group in 2a or 2b, respectively. In the absence of
other suitable substrates, the intermediates formed react
directly with CH2Cl2 solvent molecules by simple nucleo-
philic Cl displacement.
Figure 2. Structure of 5 showing the crystallographic labeling scheme.
Selected distances (Å) are as follows: B(7)-P(7) 1.935(4), P(7)-C(71)
1.781(3), C(71)-C(72) 1.347(3), C(72)-C(73) 1.490(3), C(71)-Co(1)
1.951(3), C(71)-Co(2) 1.994(3), C(72)-Co(1) 1.971(3), C(72)-Co(2)
1.960(3), Fe(6)-B(2) 2.228(4), Fe(6)-B(3) 2.217(3), Fe(6)-B(7) 2.223(3),
Fe(6)-B(9) 2.205(3), Fe(6)-B(10) 2.043(3).
absorptions at 2054 and 1995 cm-1, as was a weak Ct C
stretch at 2211 cm-1. The asymmetric nature of the carborane
cage fragment was revealed by the presence of eight peaks
of unit intensity in the 11B{1H} NMR study. The lowest field
resonance in the latter spectrum (δ -28.3) appeared as a
doublet and hence was assigned to the {B-P} vertex; this
unit also gave rise to a quartet peak at δ 1.3 [J(BP) ) 122
Hz] in the 31P{1H} NMR spectrum.
An IR spectrum of 6a displayed strong CO group
absorptions at 2056 and 1999 cm-1, almost identical to those
for 2a (2056 and 1995 cm-1). The 11B{1H} NMR spectrum
for 6a likewise indicates its carborane moiety to be electroni-
cally similar to that for 2a, with the lowest field peak (δ
-30.5) appearing as a doublet [J(PB) ) 127 Hz], because
of the exopolyhedral {PPh2CH2Cl} group; the corresponding
signal for the {PHPh2} group in 2a appears at δ -31.9. A
resonance assigned to the carbonyl ligands in 6a appeared
in its 13C{1H} NMR spectrum at δ 210.1, as were peaks due
to the cage carbon atom (δ 60.8) and to the {PPh2CH2Cl}
group methylene carbon [δ 35.8, d, J(PC) ) 40 Hz]. The
Addition of [Co2(CO)8] to CH2Cl2 solutions of 4 gives
[6,6,6-(CO)3-7-(PPh2-{(µ-η2:η2-Ct CMe)Co2(CO)6})-closo-
6,1-FeCB8H8] (5) (Chart 1), in which a {Co2(CO)6} fragment
orthogonallybridgesthetriplebondofthependant{PCt CMe}
group in 4, forming a {C2Co2} tetrahedron. Similar reactivity
of pendant acetylene groups has been observed in other
subicosahedral dicarborane species.12 An IR spectrum of 5
revealed strong CO stretching frequencies at 2099, 2068,
2054, 2038, and 1994 cm-1. Peaks due to these groups were
observed at δ 209.8 and 197.5 (Fe-CO and Co-CO,
respectively) in the 13C{1H} NMR spectrum of 5, as were
resonances assigned to the {PCt CMe} fragment [δ 106.0
(CMe), 72.2 [d, J(PC) ) 30 Hz, PC], and 23.5 (Me)], and
1
two protons of the latter group appeared in the H NMR
spectrum as separate doublet-of-doublet resonances at δ 4.13
and 4.23 [J(HaHb) ) 32 Hz; J(PH) ) 144 Hz in each case].
The phosphorus atom of the {B-P} vertex was observed as
a quartet resonance in the 31P{1H} NMR spectrum at δ 17.5
[J(BP) ) 127 Hz].
1
to the cage carbon atom (δ 60.9). A H NMR spectrum
revealed resonances due to the cage {CH} unit and the
methyl group at δ 5.12 and δ 3.17, respectively. As in 2a,
3, and 4, the presence of the pendant {PCt CMe} moiety in
5 renders the cluster asymmetric, and hence the 11B{1H}
NMR spectrum contained six peaks with relative intensity
1:1:1:2:2:1 (low to high field), of which the highest field
peak (δ -27.5) appeared as a doublet [J(PB) ) 132 Hz],
and hence was assigned to the {B-P} vertex.
The structure of 5 was fully established by an X-ray
diffraction study (Figure 2). The atomic arrangement in the
{FeCB8} unit remains unchanged in comparison with 4, and
the B(2)-B(3) connectivity is slightly elongated [1.968(5)
Evidence for [6,6,6-(CO)3-10-(PPh2CH2Cl)-closo-6,1-
FeCB8H8] (6b) was provided in the form of a low-field
doublet resonance in the 11B{1H} NMR spectrum at δ 49.8,
analogous to that for 2b, and a quartet resonance at δ 14.1
in the 31P{1H} NMR spectrum. A comparison of relative peak
integrals indicates an approximate 49:1 ratio (6a:6b) in the
product mixture. Single crystal X-ray diffraction quality
crystals were grown by slow diffusion of petroleum ether
and a CH2Cl2 solution of a 6a/6b mixture and led to the
structural analysis of both 6a (included as Supporting
Information) and 6b (see Figure 3). Within the molecule
shown, the central {FeCB8} cluster core carries an exopoly-
hedral {PPh2CH2Cl} unit at the four connected B(10) vertex.
As a result, a mirror plane is present within the molecule,
inconsistent with the 11B{1H} NMR data obtained for 6a.
(12) (a) Nie, Y.; Goswami, A.; Siebert, W. Z. Naturforsch., B 2005, 60,
597. (b) Franken, A.; McGrath, T. D.; Stone, F. G. A. Organometallics
2008, 27, 908.
8792 Inorganic Chemistry, Vol. 47, No. 19, 2008

Intramolecular Rings in Ferramonocarbollide Complexes
Scheme 1. Formation and Interconversion of Compounds 6a and 7-10 from 2aa
a
Reagents and conditions: (i) NEt3 in CH2Cl2; (ii) PHPh2 and Me3NO in CH2Cl2; (iii) Me3NO in CH2Cl2; (iv) L and Me3NO in CH2Cl2.
Moreover, the low frequency of the {P-B} resonance in the
11B{1H} NMR of 6a would not be expected for a {B-P}
vertex occupying a four-connected position. Logically,
therefore, the structure shown in Figure 3 is that of 6b, and
supports the formulation for 2b described previously.
Compound 7 (Scheme 1), which forms as a co-product
with 6a and 6b, contains a rare example of a B-P-C-P-Fe
intramolecular ring. Previous examples of this arrangement
are restricted to adducts of the smaller boranes.13 Although
an analogous species derived from 2b was not observed, its
formation cannot be discounted and it may be simply that
yields are too low to permit its detection. Spectroscopic data
for 7 are listed in Tables 1-3. Two strong CO absorptions
are evident at 1994 and 1948 cm-1 in the IR spectrum; the
13C{1H} NMR spectrum contained two doublet resonances
at δ 215.5 [J(PC) ) 21 Hz] and δ 212.8 [J(PC) ) 19 Hz],
indicating as expected unique electronic environments for
(13) (a) Alcock, N. W.; Colquhoun, H. M.; Haran, G.; Sawyer, J. F.;
Figure 3. Structure of 6b showing the crystallographic labeling scheme.
Selected distances (Å) are as follows: Fe(6)-B(2) 2.214(5), Fe(6)-B(3)
2.193(5), Fe(6)-B(7) 2.227(5), Fe(6)-B(9) 2.261(5), Fe(6)-B(10) 2.037(4),
C(2)-Cl(1) 1.775(4), P(1)-B(10) 1.906(4), P(1)-C(2) 1.825(4).
Wallbridge, M. G. H. J. Chem. Soc., Chem. Commun. 1977, 368. (b)
Alcock, N. W.; Colquhoun, H. M.; Haran, G.; Sawyer, J. F.;
Wallbridge, M. G. H. J. Chem. Soc., Dalton Trans. 1982, 2243. (c)
Hata, M.; Kawano, Y.; Shimoi, M. Inorg. Chem. 1998, 37, 4482.
Inorganic Chemistry, Vol. 47, No. 19, 2008 8793

Franken et al.
Figure 4. Structure of one of the crystallographically independent molecules
of 7 showing the labeling scheme. Selected distances (Å) and angles (deg)
are as follows: P(1A)–C(2A) 1.812(3), P(1A)–B(7A) 1.920(4), P(2A)–C(2A)
1.852(3),P(2A)–Fe(6A)2.2151(8),Fe(6A)–B(7A)2.189(3);C(2A)–P(1A)–B(7A)
102.76(13),C(2A)–P(2A)–Fe(6A)110.86(10),P(1A)–C(2A)–P(2A)107.74(14),
B(7A)–Fe(6A)–P(2A) 86.91(9), P(1A)–B(7A)–Fe(6A) 116.20(15).
Figure 5. Structure of 8 showing the crystallographic labeling scheme.
Selected distances (Å) and angles (deg) are as follows: P(1)-B(7) 1.895(5),
P(1)-C(27) 1.814(4), C(27)-N(63) 1.499(5), Fe(6)-N(63) 2.147(3),
Fe(6)-B(7) 2.160(5); C(27)-P(1)-B(7) 100.7(2), N(63)-Fe(6)-B(7)
86.91(16), P(1)-B(7)-Fe(6) 110.8(2), N(63)-C(27)-P(1) 111.6(3),
C(27)-N(63)-Fe(6) 113.0(2).
Reaction of 2a with Me3NO in the absence of a suitable
donor ligand yields the complex [6,6-(CO)2-6,7-µ-{NMe2-
CH2PPh2}-closo-6,1-FeCB8H8] (8; Scheme 1), which con-
the two carbonyl ligands. Resonances due to the cage carbon
vertex and to the bridging {PCH2P} unit were also present
at δ 60.7 and 36.7 [dd, J(PC) ) 18 and 54 Hz], respectively.
The latter moiety gave rise to separate multiplet resonances
tains an unprecedented intramolecular B-P-C-N-Fe ring.
The molecular structure of 8 is presented in Figure 5. In
comparison with 2a, the {closo-6,1-FeCB8} unit remains
unchanged, but with the five-atom B(7)-P(1)-C(27)-N(63)-
Fe(6) ring clearly evident. The latter is puckered, so that the
{NCP} triangle makes an angle of 40.8 ° with the {BPNFe}
plane.
1
for each of the two protons in the H NMR spectrum. In
each case, coupling to the two adjacent phosphorus atoms
and the other unique methylene proton resulted in apparent
quartet multiplicity. A 31P{1H} NMR spectrum revealed a
broad multiplet signal centered on δ 18.5 assigned to the
{B-P} vertex, in addition to a doublet resonance (δ 77.4)
assigned to the {Fe-P} unit [J(PP) ) 95 Hz].
One of the crystallographically independent molecules of
compound 7 is shown in Figure 4. It is immediately obvious
that a carbonyl ligand has been lost from the Fe center and
that this has been replaced by the donor phosphorus atom
P(2A). With the additional loss of the Cl atom from 6a, an
The IR spectrum of 8 contains strong CO stretching bands
at 1983 and 1927 cm-1. In the 13C{1H} NMR spectrum two
resonances due to these groups were seen at δ 218.2 and
216.4. Peaks due to the cage {CH} (δ 57.9) and NMe2 groups
(δ 62.6 and 60.3) were also present therein, the hydrogen
1
atoms of which gave rise to corresponding peaks in the H
NMR spectrum at 5.05 (br), and 3.08 and 2.22, respectively.
The methylene linkage of the exopolyhedral ring moiety
appeared as a doublet resonance [J(PC) ) 45 Hz] at δ 68.3
in the 13C{1H} spectrum while in the 1H NMR spectrum its
two hydrogen atoms gave rise to individual doublet-of-
doublet resonances at δ 3.78 [J(PH) ) 42 Hz; J(HH) ) 13
Hz] and δ 3.15 [J(PH) ) 15 Hz; J(HH) ) 5 Hz]. The
presence of the heteronuclear ring in 8 renders the ferracar-
borane cluster asymmetric, with eight inequivalent boron
atoms, and as such the 11B{1H} NMR spectrum contained
eight resonances for the boron vertices. Of these, the doublet
expected for the {B-P} unit was not clear as that signal
coincides with another centered at δ -23.3. However, this
moiety is evident in the corresponding 31P{1H} NMR
spectrum as a quartet at δ 23.7 [J(BP) ) 130 Hz].
intermolecular B-P-C-P-Fe ring has been formed. This
moiety is puckered, giving an “envelope” conformation, with
the {P(1A)C(2A)P(2A)} triangle making an angle of 39.6°
with the {P(1A)B(7A)Fe(6A)P(2A)} plane.
The mechanism of formation of 7 is not entirely clear.
Perhaps surprisingly, the yield of 7 was not noticeably improved
on addition of excess PPh2Cl to the reaction mixture, suggesting
that its formation is associated with decomposition of the
precursor 2a rather than its contamination with traces of this
phosphine. Indeed, it seems reasonable that incorporation of
PHPh2 by CO substitution of 6a would be a likely precursor to
compound 7. Thereafter, deprotonation of this Fe-bound PHPh2
ligand, followed by its nucleophilic attack upon the methylene
C atom of the PCH2Cl unit from 6a would eliminate chloride
and form the observed B-PPh2-CH2-PPh2-Fe linkage seen
in 7. In practice, treatment of 6a in CH2Cl2 with PHPh2 and
Me3NO does form small quantities (ca. 10%) of 7. However,
the reaction is complicated by side reactions and the formation
of (multiple) other products, including compound 8 described
below.
Compound 8 was also observed as a side-product in
reactions intended to produce simple, Fe-substituted deriva-
tives of 2a. In practice, however, the primary species obtained
from such reactions instead were relatives of compound 6a.
Thus, addition of Me3NO to solutions of 2a in the presence
of ligands L affords [6,6-(CO)2-6-L-7-(PPh2CH2Cl)-closo-
8794 Inorganic Chemistry, Vol. 47, No. 19, 2008

Intramolecular Rings in Ferramonocarbollide Complexes
Conclusions
We have demonstrated a protocol whereby reaction
between PPh2Cl and Tl[PF6] generates (at least formally)
the species {PPh2}+ in situ; the latter then acts as a hydride
abstractor toward a {B-H} vertex, forming a molecule of
PHPh2 that then binds to the denuded boron atom. Thus,
substitution by this phosphine at the B(7) position of the
ferracarborane anion in 1 resulted in a metallacarborane
containing a {B-PHPh2} vertex (compound 2a). The acidic
nature of the phosphorus-bound hydrogen atom of this group
allowed for its removal using a variety of bases, and
subsequent derivatization of the phosphine unit. When a
pendant propynyl group is introduced at this site, its reaction
with [Co2(CO)8] afforded a compound containing both a
{C2Co2} tetrahedron and an {FeCB8} cluster linked by a
{PPh2} group. Alternatively, deprotonation of the phosphine
ligand and addition of a source of {Ir(CO)(PPh3)2}+ afforded
Figure 6. Structure of 9 showing the crystallographic labeling scheme.
Selected distances (Å) are as follows: Fe(6)-P(6) 2.2301(5), B(7)-P(7)
1.9178(19), P(7)-C(71) 1.8262(16), C(71)-Cl(1) 1.7824(16), Fe(6)-B(2)
2.2001(18), Fe(6)-B(3) 2.1906(18), Fe(6)-B(7) 2.2131(18), Fe(6)-B(9)
2.2494(19), Fe(6)-B(10), 2.0488(18).
an intramolecular B-P-Ir-B ring. When the deprotonation
of the B-PHPh2 ligand in 2a is performed in the absence
of another suitable substrate, reaction with a CH2Cl2 solvent
molecule instead occurs, affording a {B-PPh2CH2Cl} vertex.
Removal of the chlorine atom of the latter unit is evidently
facile and allowed for the preparation of species containing
unprecedented 5-membered heteroatomic intramolecular
rings.
We believe that the protocol that yielded the parent
compounds 2 can likely be extended to substrates other than
PPh2Cl, thus allowing for the introduction of other boron-
bound functionalities. Likewise, the possibility (demonstrated
herein) of exploiting the acidity of the P-H unit to attach
other groups to the cage can be extended in a variety of
directions. We are actively exploring all of these avenues.
6,1-FeCB8H8] [L ) PEt3 (9) or CNBut (10)]. In each case,
compound 8 is also obtained in significant quantities (Scheme
1). The close similarity of all three species, 6a, 9, and 10, is
evident in their near-identical NMR data, save for the
additional resonances due to the added ligands L being
present in characteristic positions. In particular, the presence
1
of the BPCH2Cl moiety was immediately noted in the H
and 13C{1H} NMR spectra of 9 and 10, and the integrity of
the B-P linkage was also clear from 11B{1H} and 31P{1H}
NMR spectra. All of this was further substantiated by the
molecular structure of 9 established by X-ray diffraction,
which is shown in Figure 6. The Fe-bound PEt3 ligand and
the B(7)-bound {PPh2CH2Cl} unit are clearly evident therein.
These data otherwise merit little further comment.
Experimental Section
It seems likely the formation of all three of compounds
8-10 from 2a involves compound 6a as an intermediate.
[Indeed, treatment of 6a with ligands L does indeed form
compounds 9 (L ) PEt3) and 10 (L ) CNBut).] We surmise
that initial reaction of 2a with Me3NO removes a metal-
bound CO ligand as CO2 and liberates Me3N and that the
latter can then convert another molecule of 2a to 6a in the
same manner as treatment of 2a with Et3N discussed above.
A straightforward CO f L substitution process then converts
6a to 9 or 10, as appropriate. Formation of 8 from 6a is less
well understood. Most probably, 6a is converted to an Fe-
substituted analogue (similar to compounds 9 and 10) with
L ) NMe3, the latter being available in solution as noted
above. From there, formal CH3Cl elimination (from
B-PPh2CH2-Cl and CH3-NMe2-Fe) would afford 8, a
suggestion supported by the fact that compound 8 can be
synthesized by direct reaction of 6a with Me3NO. Alterna-
tively, an Fe-NMe3 substituted derivative of 2a might be
invoked, from where formal H2 elimination (from
B-PPh2-H and H-CH2NMe2-Fe) could also form 8. Our
efforts continue as we seek fully to understand these and
related systems.
General Considerations. All reactions were carried out under
an atmosphere of dry, oxygen-free nitrogen using Schlenk-line
techniques. Solvents were stored over and freshly distilled from
appropriate drying agents prior to use. Petroleum ether refers to
that fraction of boiling point 40-60 °C. Chromatography columns
(typically ca. 20 cm in length and ca. 2 cm in diameter) were packed
with silica gel (Acros, 60-200 mesh). NMR spectra were recorded
1
at the following frequencies: H, 360.13; 13C, 90.56; 11B, 115.5;
and 31P, 145.78 MHz. Compound 18 and [IrCl(CO)(PPh3)2]14 were
synthesized as previously described; all other materials were used
as received.
Synthesis of [6,6,6-(CO)3-n-(PHPh2)-closo-6,1-FeCB8H8] [n
) 7 (2a), 10 (2b)]. Compound 1 (0.20 g, 0.25 mmol) was dissolved
in CH2Cl2 (10 mL), and PPh2Cl (0.1 mL, 0.5 mmol) and Tl[PF6]
(0.18 g, 0.50 mmol) were added. The resulting mixture was stirred
for 18 h, volatile material was removed in vacuo and the residue
dissolved in CH2Cl2/petroleum ether (1:1, 3 mL) before being
transferred to the top of a chromatography column. Elution with
the same solvent mixture gave a yellow fraction from which
removal of solvents yielded yellow microcrystals of 2a (0.08 g,
72%) that were contaminated with a small amount (<0.005 g) of
the isomeric species 2b.
(14) Vrieze, K.; Collman, J. P.; Sears, C. T.; Kubota, M. Inorg. Synth.
1968, 11, 101.
Inorganic Chemistry, Vol. 47, No. 19, 2008 8795

Franken et al.
Table 4. Crystallographic Data for Compounds 3, 5, 6b, 7, 8, and 9
3·2CH2Cl2
5
6b
7·CH2Cl2
8·CH2Cl2
9
formula
fw
crystal system
space group
a, Å
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
C54H52B8Cl4FeIrO4P3 C25H21B8Co2FeO9P C17H20B8ClFeO3P C29H32B8Cl2FeO2P2 C19H28B8Cl2FeNO2P C22H35B8ClFeO2P2
1346.21
triclinic
P1
756.58
monoclinic
P21/c
481.08
monoclinic
P21/n
687.72
monoclinic
P21/n
546.62
orthorhombic
Pbca
571.22
monoclinic
P21/n
j
12.8499(3)
15.1213(4)
16.2676(4)
68.664(1)
77.017(1)
69.987(1)
2748.31(12)
2
10.9431(10)
25.772(3)
12.2708(13)
90
116.374(5)
90
10.0669(15)
22.458(3)
10.9514(17)
90
115.722(2)
90
14.9044(7)
21.1435(9)
21.6197(10)
90
103.225(2)
90
15.2504(17)
14.8275(17)
23.126(3)
90
90
90
14.6201(5)
11.3672(3)
17.1562(6)
90
103.500(2)
90
3100.5(5)
4
2230.5(6)
4
6632.4(5)
8
5229.5(10)
8
2772.40(15)
4
Z
wR2, R1 (all data)a 0.1488, 0.0782
wR2, R1 (obsb data) 0.1340, 0.0554
0.1369, 0.1006
0.1106, 0.0568
1.017
0.1514, 0.1071
0.1258, 0.0647
1.025
0.1077, 0.0640
0.0963, 0.0433
0.990
0.1272, 0.1201
0.1083, 0.0610
0.987
0.0862, 0.0403
0.0803, 0.0320
1.043
GOFc
1.033
a wR2 ) [∑{w(Fo - Fc )2}/∑w(Fo )2]1/2; R1 ) ∑||Fo| - | Fc||/∑|Fo|. b Fo > 4σ(Fo). c GOF ) [∑{w (Fo - Fc )2}/(n - p)]1/2 where n ) number of
2
2
2
2
2
reflections and p ) number of refined parameters.
Synthesis of [6,6,6-(CO)3-4,7-µ-{Ir(H)(CO)(PPh3)2PPh2}-closo-
6,1-FeCB8H7] (3). A THF solution (20 mL) of 2a (0.22 g, 0.50
mmol) was treated with NaH (0.16 g, 60% dispersion in mineral
oil) and stirred at ambient temperature for 0.25 h. The suspension
was then filtered and the filtrate evaporated to dryness in vacuo.
The compounds [IrCl(CO)(PPh3)2] (0.39 g, 0.50 mmol), Tl[PF6]
(0.17 g, 0.50 mmol), and CH2Cl2 (20 mL) were added to the residue
and the resulting suspension stirred at room temperature for 18 h.
After filtration and evaporation of the resulting filtrate in vacuo,
the residue was dissolved in CH2Cl2/petroleum ether (1:1, 3 mL),
and transferred to the top of a chromatography column. Elution
with the same solvent mixture gave a yellow fraction, removal of
solvents from which afforded yellow microcrystals of 3 (0.39 g,
61%).
Synthesis of [6,6-(CO)2-6,7-µ-{NMe2CH2PPh2}-closo-6,1-Fe-
CB8H8] (8). Compound 2a (0.22 g, 0.50 mmol) was dissolved
in CH2Cl2 (10 mL), Me3NO (0.08 g, 1 mmol) was added, and
the resulting solution stirred for 60 h at ambient temperature.
Solvent was removed under reduced pressure, and the residue
dissolved in CH2Cl2/petroleum ether (4:1, 3 mL) and applied to
a chromatography column. Elution with the same solvent mixture
gave an orange fraction, which afforded orange microcrystals
of 8 (0.06 g, 26%).
Synthesisof[6,6-(CO)2-6-L-7-(PPh2CH2Cl)-closo-6,1-FeCB8-
H8] [L ) PEt3 (9), CNBut (10)]. (i) Compound 2a (0.22 g, 0.50
mmol) was dissolved in CH2Cl2 (10 mL), and PEt3 (0.15 mL, 1.0
mmol) and Me3NO (0.08 g, 1.0 mmol) were added. The mixture
was stirred for 60 h at ambient temperature. Solvent was removed
under reduced pressure, and the residue dissolved in CH2Cl2/
petroleum ether (3:2, 3 mL) and applied to a chromatography
column. Elution with the same solvent mixture gave a yellow
fraction which, upon removal of solvents, gave yellow microcrystals
of 9 (0.15 g, 52%). Further elution with CH2Cl2/petroleum ether
(4:1) gave an orange fraction, removal of solvents from which
yielded orange microcrystals of 8 (0.05 g, 22%).
(ii) Similarly, compound 2a (0.22 g, 0.50 mmol), CNBut (0.11
mL, 1.0 mmol), and Me3NO (0.08 g, 1.0 mmol) were stirred for
18 h at ambient temperature, with the same workup procedure,
yielded yellow microcrystals of 10 (0.15 g, 57%) and orange
microcrystals of 8 (ca. 0.04 g, 19%), respectively.
X-ray Diffraction Experiments. Experimental data for com-
pounds 3, 5, 6b, and 7-9 are presented in Table 4; those for
compound 6a are included as Supporting Information (see
below). Diffraction data were acquired at 110(2) K using a
Bruker-Nonius X8 Apex area-detector diffractometer (graphite
monochromated Mo KR radiation, λ ) 0.71073 Å). Several sets
of data frames were collected at different θ values for various
initial values of φ and ω, each frame covering a 0.5° increment
of φ or ω. The data frames were integrated using SAINT.15 The
substantial redundancy in data allowed empirical absorption
corrections (SADABS)15 to be applied on the basis of multiple
measurements of equivalent reflections.
Synthesis of [6,6,6-(CO)3-7-(PPh2Ct CMe)-closo-6,1-FeCB8-
H8] (4). Compound 2a (0.22 g, 0.50 mmol) was dissolved in CH2Cl2
(20 mL). Propargyl bromide (80% solution in toluene, 0.5 mL, 4.5
mmol) and NEt3 (0.5 mL, 3.6 mmol) were added, and the resulting
mixture stirred for 60 h at ambient temperatures. Solvent was
removed in vacuo, and the residue dissolved in CH2Cl2/petroleum
ether (1:1, 3 mL) before being transferred to the top of a
chromatography column. Elution with the same solvent mixture
gave a yellow fraction, removal of solvents from which afforded
yellow microcrystals of 4 (0.17 g, 71%).
Synthesisof[6,6,6-(CO)3-7-(PPh2-{(µ-η2:η2-Ct CMe)Co2(CO)6})-
closo-6,1-FeCB8H8] (5). To a CH2Cl2 (20 mL) solution of 4 (0.24
g, 0.5 mmol) was added [Co2(CO)8] (0.18 g, 0.51 mmol), and the
mixture stirred for 18 h at ambient temperature. Solvents were then
removed in vacuo, and the residue dissolved in CH2Cl2/petroleum
ether (1:1, 3 mL) and subjected to column chromatography. Elution
with the same solvent mixture gave a red fraction, which after
evaporation yielded red microcrystals of 5 (0.31 g, 82%).
Synthesis of [6,6,6-(CO)3-7-(PPh2CH2Cl)-closo-6,1-FeCB8H8]
(6a) and [6,6-(CO)2-6,7-µ-{PPh2CH2PPh2}-closo-6,1-FeCB8H8]
(7). Compound 2a (0.22 g, 0.50 mmol) was dissolved in CH2Cl2
(20 mL), NEt3 (0.5 mL, 3.6 mmol) was added, and the mixture
stirred for 60 h at ambient temperature. Solvent was removed in
vacuo, and the residue redissolved in CH2Cl2/petroleum ether
(1:1, 3 mL) and applied to a chromatography column. Elution with
the same solvent mixture gave a yellow fraction, removal of solvents
from which yielded yellow microcrystals of 6a (0.17 g, 72%).
Further elution with CH2Cl2/petroleum ether (3:2) gave a second
yellow fraction, which afforded yellow microcrystals of 7 (0.04 g,
12%).
The structures were solved (SHELXS-97)15 via conventional
direct methods and were refined (SHELXL-97) by full-matrix least-
squares on all F2 data using SHELXTL.15,16 All non-H atoms were
assigned anisotropic displacement parameters. The locations of the
cage C atoms were verified by examination of the appropriate
(15) APEX 2, version 2.1-0; Bruker AXS: Madison, WI, 2003-2004.
(16) SHELXTL, version 6.12; Bruker AXS: Madison, WI, 2001.
8796 Inorganic Chemistry, Vol. 47, No. 19, 2008

Intramolecular Rings in Ferramonocarbollide Complexes
internuclear distances and the magnitudes of their isotropic thermal
displacement parameters. All hydrogen atoms were set riding on
their parent atoms in calculated positions and with fixed isotropic
thermal parameters [calculated as Uiso(H) ) 1.2 × Uiso(parent) or
Uiso(H) ) 1.5 × Uiso(parent) for methyl groups], with the exception
of the Ir-H which was freely refined.
Acknowledgment. We thank the Robert A. Welch Foun-
dation for support (Grant AA-0006). The Bruker-Nonius X8
APEX diffractometer was purchased with funds received
from the National Science Foundation Major Instrumentation
Program (Grant CHE-0321214).
Compound 3 co-crystallizes with two CH2Cl2 solvate molecules
in the asymmetric unit. Compound 7 crystallizes with two inde-
pendent molecules in the unit cell, differing in the relative
orientation of a CH2Cl2 solvate molecule associated with each.
Compound 8 co-crystallizes with one molecule of CH2Cl2 in the
asymmetric unit.
Supporting Information Available: Full details of the crystal
structure analyses in CIF format, including data for compound 6a.
This material is available free of charge via the Internet at
http://pubs.acs.org.
IC800780W
Inorganic Chemistry, Vol. 47, No. 19, 2008 8797