Synthesis and reactivity of monocarbollide carbonyl complexes of iron and molybdenum with icosahedral frameworks

Article abstract of DOI:10.1021/om000033n

The [NEt₄]⁺ (1a), [NHMe₃]⁺ (1b), and [N(PPh₃)₂]⁺ (1c) salts of the monoanion [Fe(CO)₃-(η⁵-7-CB₁₀H₁₁)] ^- have been prepared via the reaction between [Fe₃(CO)₁₂] and [NHMe₃][nido-7-CB₁₀H₁₃] in THF (tetrahydrofuran). The complexes [N(PPh₃)₂][Fe(CO)₂(L)(η ⁵-7-CB₁₀H₁₁)] (L = PPh₃ (2), CNBu^t (3)) were obtained by treating 1c in THF with PPh₃ and CNBu^t, respectively, in the presence of Me₃NO. The compound [N(PPh₃)₂][Mo(CO)₄(η⁵-7-CB ₁₀H₁₁)] (4) has been synthesized from [Na]₃[nido-7-CB₁₀H₁₁] and [Mo(CO)₃(NCMe)₃] in the presence of CO and with addition of HBF₄·Et₂O and [N(PPh₃)₂]Cl. An X-ray diffraction study established that in the anion of 4 the Mo atom is coordinated on one side by the four CO molecules and on the other by a nido-7-CB₁₀H₁₁ carborane in a η⁵ manner. In reactions with PPh₃ and CNBu^t, the salt 4 gives the species [N(PPh₃)₂][Mo(CO)₃(L)(η ⁵-7-CB₁₀H₁₁)] (L = PPh₃ (5a), CNBu^t (6)). Salts of the anions [Fe(CO)₃(η⁵-7-CB₁₀H₁₁)] ^- and [Mo(CO)₃(PPh₃)(η⁵-7-CB₁₀H ₁₁)]^- react with donor molecules (THF, OEt₂, SMe₂) in the presence of acids and other hydride abstracting reagents to give zwitterionic complexes: [Fe(CO)₃(η⁵-9-L-7-CB₁₀H₁₀)] (L = O(CH₂)₄ (7), OEt₂ (8), SMe₂ (9)) and [Mo(CO)₃(PPh₃)(η⁵-9-L-7-CB ₁₀H₁₀)] (L = O(CH₂)₄ (10), OEt₂ (11)), formed as single isomers. That the donor molecules L are bonded to a boron atom which lies in a β-site with respect to the carbon in the CBBBB ring ligating the metal was established by X-ray diffraction studies on 7 and 10. In the latter the PPh₃ molecule is transoid to the BO(CH₂)₄ group, presumably for steric reasons. Alkyne-molybdenum complexes [N(PPh₃)₂][Mo(CO)₂(Bu ^tC≡CH)(η⁵-7-CB₁₀H₁₁)] (13) and [N(PPh₃)₂]-[Mo(CO)₂(PhC≡CR)(η ⁵-7-CB₁₀H₁₁)] (R = H (14), Ph (15)) have also been prepared.

Full text of DOI:10.1021/om000033n

Organometallics 2000, 19, 1993-2001
1993
Syn th esis a n d Rea ctivity of Mon oca r bollid e Ca r bon yl
Com p lexes of Ir on a n d Molybd en u m w ith Icosa h ed r a l
F r a m ew or k s†
Dianne D. Ellis, Andreas Franken, Paul A. J elliss, F. Gordon A. Stone,* and
Pui-Yin Yu
Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798-7348
Received J anuary 18, 2000
The [NEt4]+ (1a ), [NHMe3]+ (1b), and [N(PPh3)2]+ (1c) salts of the monoanion [Fe(CO)3-
(η5-7-CB10H11)]- have been prepared via the reaction between [Fe3(CO)12] and [NHMe3][nido-
7-CB10H13] in THF (tetrahydrofuran). The complexes [N(PPh3)2][Fe(CO)2(L)(η5-7-CB10H11)]
(L ) PPh3 (2), CNBut (3)) were obtained by treating 1c in THF with PPh3 and CNBut,
respectively, in the presence of Me3NO. The compound [N(PPh3)2][Mo(CO)4(η5-7-CB10H11)]
(4) has been synthesized from [Na]3[nido-7-CB10H11] and [Mo(CO)3(NCMe)3] in the presence
of CO and with addition of HBF4‚Et2O and [N(PPh3)2]Cl. An X-ray diffraction study
established that in the anion of 4 the Mo atom is coordinated on one side by the four CO
molecules and on the other by a nido-7-CB10H11 carborane in a η5 manner. In reactions with
PPh3 and CNBut, the salt 4 gives the species [N(PPh3)2][Mo(CO)3(L)(η5-7-CB10H11)] (L )
PPh3 (5a ), CNBut (6)). Salts of the anions [Fe(CO)3(η5-7-CB10H11)]- and [Mo(CO)3(PPh3)(η5-
7-CB10H11)]- react with donor molecules (THF, OEt2, SMe2) in the presence of acids and
other hydride abstracting reagents to give zwitterionic complexes: [Fe(CO)3(η5-9-L-7-
CB10H10)] (L ) O(CH2)4 (7), OEt2 (8), SMe2 (9)) and [Mo(CO)3(PPh3)(η5-9-L-7-CB10H10)] (L )
O(CH2)4 (10), OEt2 (11)), formed as single isomers. That the donor molecules L are bonded
to a boron atom which lies in a â-site with respect to the carbon in the CBBBB ring ligating
the metal was established by X-ray diffraction studies on 7 and 10. In the latter the PPh3
molecule is transoid to the BO(CH2)4 group, presumably for steric reasons. Alkyne-
molybdenum complexes [N(PPh3)2][Mo(CO)2(ButCtCH)(η5-7-CB10H11)] (13) and [N(PPh3)2]-
[Mo(CO)2(PhCtCR)(η5-7-CB10H11)] (R ) H (14), Ph (15)) have also been prepared.
In tr od u ction
[Ru(CO)3(η5-7,8-R2-7,8-C2B9H9)] (R ) H, Me),5 and [Cs]-
[Re(CO)3(η5-7,8-C2B9H11)]6 amply support these consid-
erations. Indeed, the ruthenium complex [Ru(CO)3(η5-
7,8-C2B9H11)], isolobal with [Ru(CO)3(η5-C5H5)]+ or
[M(CO)3(η5-C5H5)] (M ) Mn, Re), is the precursor to
numerous mono- and polynuclear metal compounds very
different from those found in cyclopentadienide metal
chemistry.7
Cyclopentadienide metal carbonyl complexes continue
to be of great importance in the development of organo-
transition-metal chemistry. The isolobal mapping of the
[C5H5]- ligand with the icosahedral cage fragments
2-
3-
[nido-7,8-C2B9H11
]
and [nido-7-CB10H11
]
suggests
that studies on the reactions of carbonyl metallacar-
boranes should also contribute to the development of
organometallic chemistry. However, differences between
the donor and steric requirements of the two classes of
ligands are likely to result in different patterns of
behavior in their complexes.1 Moreover, the tendency
of carbollide groups to adopt nonspectator roles, a
property associated with activation of BH vertexes in
Reports of compounds in which the monocarbon [nido-
3-
7-CB10H11
]
group, or a derivative thereof, and CO
ligands simultaneously ligate a metal center have as
yet been very limited. Several years ago the anionic
molybdenum complex [Mo(CO)4(η5-7-OH-7-CB10H10)]-
was the unexpected product of the reaction between
the closo-3,1,2-MC2B9H112a,b and closo-2,1-MCB10H11
frameworks, also leads to many species with unusual
molecular structures. Studies with the reagents [Pt-
(CO)2(η5-7,8-C2B9H11)],3 [Co2(CO)2(η5-7,8-C2B9H11)2],4
2c,d
(2) (a) J elliss, P. A.; Stone, F. G. A. J . Organomet. Chem. 1995, 500,
307. (b) Brew, S. A.; Stone, F. G. A. Adv. Organomet. Chem. 1993, 35,
135. (c) Blandford, I.; J effery, J . C.; J elliss, P. A.; Stone, F. G. A.
Organometallics 1998, 17, 1402. (d) J effery, J . C.; J elliss, P. A.; Rees,
L. H.; Stone, F. G. A. Organometallics 1998, 17, 2258.
(3) Carr, N.; Mullica, D. F.; Sappenfield, E. L.; Stone, F. G. A. Inorg.
Chem. 1994, 33, 1666.
(4) Hendershot, S. L.; J effery, J . C.; J elliss, P. A.; Mullica, D. F.;
Sappenfield, E. L.; Stone, F. G. A. Inorg. Chem. 1996, 35, 6561.
(5) (a) Anderson, S.; Mullica, D. F.; Sappenfield, E. L.; Stone, F. G.
A. Organometallics 1995, 14, 3516. (b) Liao, Y.-H.; Mullica, D. F.;
Sappenfield, E. L.; Stone, F. G. A. Organometallics 1996, 15, 5102. (c)
J effery, J . C.; J elliss, P. A.; Liao, Y.-H.; Stone, F. G. A. J . Organomet.
Chem. 1998, 551, 27.
† The compounds described in this paper have iron or molybdenum
atoms incorporated into closo-1-carba-2-metalladodecaborane frame-
works. However, to avoid a complicated nomenclature for the complexes
reported, and to relate them to the many known iron and molybdenum
species with η5-coordinated cyclopentadienyl ligands, we treat the cages
as nido-11-vertex ligands with numbering as for an icosahedron from
which the 12th vertex has been removed.
(1) Grimes, R. N. in Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press:
Oxford, U.K., 1995; Vol. 1 (Housecroft, C. E., Ed.), Chapter 9.
(6) Ellis, D. D.; J elliss, P. A.; Stone, F. G. A. Organometallics 1999,
18, 4982.
10.1021/om000033n CCC: $19.00 © 2000 American Chemical Society
Publication on Web 04/19/2000

1994 Organometallics, Vol. 19, No. 10, 2000
Ta ble 1. An a lytica l a n d P h ysica l Da ta
Ellis et al.
anal./%b
H
compd
color
yield/%
ν
max(CO)a/cm-1
C
N
[NEt4][Fe(CO)3(η5-7-CB10H11)] (1a )
colorless
yellow
yellow
yellow
80
41
35
40
93
70
40
36
53
45
82
50
60
50
53
50
2065 s, 1999 s
35.9 (35.6)
65.4 (65.6)
61.2 (61.1)
56.4 (56.1)
54.8 (54.9)
58.8 (57.9)
7.7 (7.8)
5.4 (5.4)
5.9 (5.8)
4.7 (4.7) 1.6 (1.6)
6.4 (6.3) 1.9 (1.8)
5.5 (5.4) 2.6 (3.0)
5.4 (5.3)
5.9 (5.9)
4.9 (4.9)
5.1 (5.1)
5.5 (5.4)
[N(PPh3)2][Fe(CO)2(PPh3)(η5-7-CB10H11)] (2)
[N(PPh3)2][Fe(CO)2(CNBut)(η5-7-CB10H11)] (3)
[N(PPh3)2][Mo(CO)4(η5-7-CB10H11)] (4)
1993 s,1940 s
2005 s,c 1964 s
2070 s, 1994 s, 1956 s
2009 s, 1932 s, 1908 s
2020 s,e 1950 s, 1926 s
2076 s, 2029 m, 2011 m 27.9 (28.1)
2076 s, 2029 m, 2011 m 27.9 (27.9)
2082 s, 2029 m, 2017 m 21.9 (21.7)
2024 s, 1954 s, 1922 s
2024 s, 1954 s, 1924 s
2037 s,f 1977 s, 1937 s
2018 s, 1952 s
[NEt3(CH2Ph)][Mo(CO)3(PPh3)(η5-7-CB10H11)] (5b)d yellow
[N(PPh3)2][Mo(CO)3(CNBut)(η5-7-CB10H11)] (6)
[Fe(CO)3{η5-9-O(CH2)4-7-CB10H10}] (7)
[Fe(CO)3(η5-9-OEt2-7-CB10H10)] (8)
yellow
colorless
colorless
yellow
yellow
yellow
yellow
[Fe(CO)3(η5-9-SMe2-7-CB10H10)] (9)
[Mo(CO)3(PPh3){η5-9-O(CH2)4-7-CB10H10}] (10)
[Mo(CO)3(PPh3)(η5-9-OEt2-7-CB10H10)] (11)
[Mo(CO)3(CNBut)(η5-9-OEt2-7-CB10H10)] (12)
48.3 (48.4)
48.3 (48.3)
32.2g (31.8) 5.9 (5.9) 2.8 (2.8)
[N(PPh3)2][Mo(CO)2(ButCtCH)(η5-7-CB10H11)] (13) purple
58.9 (59.8)
60.3 (61.1)
64.0 (63.7)
5.7 (5.7) 1.6 (1.6)
5.3 (5.1) 1.7 (1.5)
5.2 (5.1) 1.5 (1.4)
[N(PPh3)2][Mo(CO)2(PhCtCH)(η5-7-CB10H11)] (14)
purple
2023 s, 1958 s
2020 s, 1960 s
1918 m, 1826 s
[N(PPh3)2][Mo(CO)2(PhCtCPh)(η5-7-CB10H11)] (15) purple
[PPh4][Mo(CO)2(PPh3)2(η5-7-CB10H11)] (16)
yellow
63.1g (64.1) 5.2 (5.2)
a
Measured in CH2Cl2; broad medium-intensity bands observed at ca. 2550 cm-1 in the spectra of all compounds are due to B-H
adsorptions. Calculated values are given in parentheses. c νmax(NC) 2154 m cm-1
.
Complex prepared and used as its [N(PPh3)2]+ salt
b
d
5a ; see Experimental Section. e νmax(NC) 2158 m cm-1
.
f νmax(NC) 2169 m cm-1
.
Crystallizes with 0.5 mol equiv of CH2Cl2.
g
Ch a r t 1
[Mo(CO)6] and [Na][nido-B10H13].8a Its triphenylphos-
phine derivative [Mo(CO)3(PPh3)(η5-7-OH-7-CB10H10)]-
was subsequently obtained by treating [Mo(CO)3(NCMe)2-
(PPh3)] with [NEt4]2[arachno-B10H14].8b Formation of
these complexes is interesting, since it involved incor-
poration of a carbon atom from a CO group into the cage
framework. Clearly neither reaction was designed to
prepare a monocarbollide carbonyl molybdenum species.
However, by using the rational process of treating
[ReBr(CO)3(THF)2] with [Na]3[nido-7-CB10H11] followed
by addition of [N(PPh3)2]Cl, we recently obtained the
complex [N(PPh3)2]2[Re(CO)3(η5-7-CB10H11)].2c The an-
ion [Re(CO)3(η5-7-CB10H11)]2- reacts readily with elec-
trophilic metal-ligand fragments containing Pd, Pt, Rh,
or Ir to afford binuclear metal compounds in which these
metals and their associated ligands are attached to the
closo-2,1-ReCB10H11 cage system by a metal-metal bond
and by at least one exopolyhedral B-HFMLn three-
center-two-electron linkage.2c,d In another study9 the
reaction between [Ru3(CO)12] and [NHMe3][nido-7-
CB10H13] afforded the triruthenium compound [NHMe3]-
[Ru3(CO)8(η5-7-CB10H11)], and the latter was then used
as a precursor to mixed-metal clusters containing
ruthenium bonded to copper, silver, and gold.
Resu lts a n d Discu ssion
These results strongly suggest that monocarbollide
metal carbonyls are likely to be sources of much new
chemistry, and to exploit this area we report herein the
synthesis of salts of the anionic complexes [M(CO)n(η5-
7-CB10H11)]- (M ) Fe, n ) 3; M ) Mo, n ) 4) and
describe some reactions of these compounds.
When [Fe3(CO)12] and [NHMe3][nido-7-CB10H13] are
refluxed in THF, the anionic complex [Fe(CO)3(η5-7-
CB10H11)]- is formed and may be isolated pure as its
[NEt4]+ salt 1a (Chart 1). The [NHMe3]+ (1b) and
[N(PPh3)2]+ (1c) salts may be prepared in essentially
quantitative yields and used in situ since when formed
they are sufficiently pure for further reactions. In the
IR spectrum of the anion strong CO stretching bands
are observed at 2065 and 1999 cm-1 (Table 1). In the
spectra of the neutral isolobal species [Fe(CO)3(η5-7,8-
C2B9H11)] the CO absorptions occur, as expected, at
higher frequency (2103 and 2042 cm-1).10 In the IR
spectrum of the isoelectronic cation [Fe(CO)3(η5-C5H5)]+
the corresponding bands are seen at 2121 and 2074
(7) (a) Anderson, S.; Mullica, D. F.; Sappenfield, E. L.; Stone, F. G.
A. Organometallics 1996, 15, 1676. (b) Anderson, S.; J effery, J . C.; Liao,
Y.-H.; Mullica, D. F.; Sappenfield, E. L.; Stone, F. G. A. Organometallics
1997, 16, 958. (c) J effery, J . C.; J elliss, P. A.; Psillakis, E.; Rudd, G. E.
A.; Stone, F. G. A. J . Organomet. Chem. 1998, 562, 17. (d) Ellis, D. D.;
Farmer, J . M.; Malget, J . M.; Mullica, D. F.; Stone, F. G. A. Organo-
metallics 1998, 17, 5540. (e) J effery, J . C.; J elliss, P. A.; Rudd, G. E.
A.; Sakanishi, S.; Stone, F. G. A.; Whitehead, J . J . Organomet. Chem.
1999, 582, 90.
(8) (a) Wegner, P. A.; Guggenberger, L. J .; Muetterties, E. L. J . Am.
Chem. Soc. 1970, 92, 3473. (b) Fontaine, X. L. R.; Greenwood, N. N.;
Kennedy, J . D.; MacKinnon, P. I.; Macpherson, I. J . Chem. Soc., Dalton
Trans. 1987, 2385.
(9) Ellis, D. D.; Franken, A.; Stone, F. G. A. Organometallics 1999,
18, 2362.
(10) Lee, S. S.; Knobler, C. B.; Hawthorne, M. F. Organometallics
1991, 10, 670, 1054.

Monocarbollide CO Complexes of Fe and Mo
Organometallics, Vol. 19, No. 10, 2000 1995
11B{1H}/δd
Ta ble 2. 1H, 13C, a n d 11B NMR Da ta a
1H/δb
13C/δc
1b
2
6.90 (br s, 1 H, NH), 3.00 (s, 9 H,
Me), 1.80 (s, 1 H, cage CH)
7.65-7.37 (m, 45 H, Ph), 1.54 (s, 1
H, cage CH)
208.5 (CO), 49.8 (cage C), 46.8 (Me)
9.9 (1 B), -2.5 (2 B), -5.7 (2 B), -8.6 (1 B),
-11.1 (2 B), -16.0 (2 B)
215.8 (d, CO, J (PC) ) 23),
134.0-126.7 (Ph), 48.9 (cage C)
213.7 (CO), 158.5 (CN), 134.0-126.7
(Ph), 57.6 (CMe3), 48.2 (cage C),
30.5 (CMe3)
7.1 (1 B), -2.8 (2 B), -5.7 (2 B), -8.2 (1 B),
-12.5 (2 B), -17.6 (2 B)
3
7.66-7.46 (m, 30 H, Ph), 1.61 (s, 1
6.9 (1 B), -3.3 (2 B), -6.7 (2 B), -8.1 (1 B),
-12.2 (2 B), -17.3 (2 B)
H, cage CH), 1.45 (s, 9 H, But)
4
7.69-7.46 (m, 30 H, Ph), 1.81 (s, 1
H, cage CH)
7.66-7.37 (m, 45 H, Ph), 1.52 (s, 1
H, cage CH)
227.8 (CO), 134.0-126.7 (Ph),
6.7 (1 B), -3.0 (2 B), -5.5 (1 B), -8.8 (2 B),
-11.0 (2 B), -15.8 (2 B)
3.0 (1 B), -3.1 (2 B), -5.3 (1 B),
-10.3 (4 B), -16.7 (2 B)
51.2 (cage CH)
5a
239.6 (d, CO, J (PC) ) 7), 236.4 (d,
CO × 2, J (PC) ) 28), 134.0-126.7
(Ph), 54.1 (cage CH)
6
7.68-7.47 (m, 30 H, Ph), 1.60 (s, 1
238.6 (CO), 233.9 (CO × 2), 159.0
(br, CN), 134.0-126.7 (Ph), 58.9
(CMe3), 50.6 (cage CH), 30.3 (CMe3)
207.0 (CO), 81.8 (OCH2),
2.8 (1 B), -3.7 (2 B), -6.4 (1 B),
-11.7 (4 B), -16.7 (2 B)
H, cage CH), 1.50 (s, 9 H, But)
7
4.36 (br m, 4 H, OCH2), 2.19 (br
m, 4 H, CH2), 1.83 (s, 1 H, cage
CH)
20.4* (1 B), 9.6 (1 B), -2.9 (1 B),
-6.6 (1 B), -8.3 (2 B), -11.3 (2 B),
-17.2 (1 B), -19.1 (1 B)
22.8* (1 B), 9.8 (1 B), -2.8 (1 B),
-6.6 (1 B), -8.2 (2 B), -11.1 (2 B),
-17.3 (1 B), -19.0 (1 B)
11.9 (1 B), 1.7* (1 B), 0.4 (1 B),
-5.2 (1 B), -5.9 (1 B), -9.1 (2 B),
-12.6 (1 B), -14.4 (1 B), -16.1 (1 B)
22.9* (1 B), -0.9 (1 B), -6.4 (2 B),
-10.2 (1 B), -11.3 (1 B), -12.7 (1 B),
-14.6 (1 B), -17.4 (1 B), -21.0 (1 B)
46.0 (cage C), 25.3 (CH2)
8
4.46 (br m, 4 H, OCH2), 1.69 (s, 1
H, cage CH), 1.47 (t, 6 H, Me,
J (HH) ) 7)
207.0 (CO), 78.0 (OCH2),
45.7 (cage C), 12.8 (Me)
9
2.53, 2.42 (s × 2, 6H, Me), 1.92 (s,
206.3 (CO), 50.0 (cage C),
26.2, 25.8 (Me × 2)
1 H, cage CH)
10
7.52-7.28 (m, 15 H, Ph), 4.21 (br
m, 4 H, OCH2), 2.07 (br m, 4 H,
CH2), 1.33 (s, 1 H, cage CH)
238.3 (d, CO, J (PC) ) 6), 233.9 (d,
CO, J (PC) ) 30), 231.3 (d, CO, J (PC) )
28), 133.7-129.0 (Ph), 79.8 (OCH2),
52.6 (cage CH), 24.9 (CH2)
11
7.52-7.27 (m, 15 H, Ph), 4.23 (AB
q, 4 H, OCH2, J (AB) ) 16, J (HH)
) 7), 1.56 (s, 1 H, cage CH), 1.34
(t, 6 H, Me, J (HH) ) 7)
238.0 (d, CO, J (PC) ) 6), 233.7 (d, CO,
J (PC) ) 30), 231.2 (d, CO, J (PC) )
29), 133.7-129.0 (Ph), 74.2 (OCH2),
52.5 (cage CH), 12.2 (Me)
25.9* (1 B), -0.6 (1 B), -6.2 (2 B),
-10.1 (1 B), -11.1 (1 B), -12.9 (1 B),
-14.9 (1 B), -17.5 (1 B), -20.8 (1 B)
12
13
14
4.21 (br m, 4 H, OCH2), 1.72 (s, 1
H, cage CH), 1.55 (s, 9 H, But),
1.36 (t, 6 H, Me, J (HH) ) 7)
9.86 (s, 1 H, CCH), 7.69-7.47 (m,
30 H, Ph), 4.02 (s, 1 H, cage CH),
1.45 (s, 9 H, But)
10.66 (s, 1 H, CCH), 7.66-7.44
(m, 35 H, Ph), 3.75 (s, 1 H, cage
CH)
234.8,e 229.3, 228.3 (CO × 3), 75.0
(OCH2), 60.0 (CMe3), 48.4 (cage
CH), 30.2 (CMe3), 12.6 (CH2Me)
230.8 (CO), 196.4 (CCH), 164.4
(CCBut), 134.0-126.0 (Ph), 47.9 (cage
CH), 39.8 (CMe3), 31.3 (CMe3)
229.2 (CO), 185.5 (CCPh), 170.3
(CCH), 134.0-126.7 (Ph), 51.3
(cage CH)
24.8* (1 B), -0.5 (1 B), -7.2 (2 B),
-10.8 (1 B), -12.0 (1 B), -13.0 (1 B),
-15.0 (1 B), -17.0 (1 B), -21.3 (1 B)
1.6 (1 B), -2.0 (4 B), -12.7 (2 B),
-14.7 (2 B), -15.2 (1 B)
1.8 (1 B), -0.6 (2 B), -2.2 (2 B),
-12.4 (2 B), -14.6 (2 B), -15.2 (1 B)
15
16
7.65-7.45 (m, 40 H, Ph), 3.49 (s, 1
229.4 (CO), 181.5 (CPh),
2.0 (1 B), -0.7 (2 B), -1.9 (2 B),
-11.9 (3 B), -14.4 (2 B)
0.9 (1 B), -2.8 (2 B), -9.5 (3 B),
-12.5 (2 B), -17.6 (2 B)
H, cage CH)
137.9-126.7 (Ph), 54.1 (CH)
7.74-7.71 (m, 50 H, Ph), 0.96 (s, 1
H, cage CH)
245.8 (t, CO, J (PC) ) 30),
136.0-117.2 (Ph), 56.0 (cage CH)
a
b
Chemical shifts (δ) in ppm, coupling constants (J ) in hertz, measurements at ambient temperatures in CD2Cl2. Resonances for
terminal BH protons occur as broad unresolved signals in the range δ ca. -1 to +3. c 1H-decoupled chemical shifts are positive to high
frequency of SiMe4. Chemical shifts (δ) are positive to high frequency of BF3‚Et2O (external). Signals ascribed to more than one boron
d
nucleus may result from overlapping peaks and do not necessarily indicate symmetry equivalence. Peaks marked with an asterisk are
assigned to cage-boron nuclei carrying L substituents (see text), since they occur as singlets in fully coupled 11B spectra. e Peak due to
CNBut nucleus not observed.
cm-1 11
.
That the absorptions for these neutral and
this did give the complex anion [Mo(CO)4(η5-7-CB10H11)]-.
This complex was also obtained from the reaction
between [Na]3[nido-7-CB10H11] and [Mo(CO)3(NCMe)3],
presumably via the intermediate species [Mo(CO)3(η5-
7-CB10H11)]3-, which is isolobal with the long-known12
dianion [Mo(CO)3(η5-7,8-C2B9H11)]2-. Evidently any salt
of [Mo(CO)3(η5-7-CB10H11)]3- is readily oxidized, ab-
stracting a CO molecule to afford the final product. We
were, however, able to prepare the salt [N(PPh3)2]-
[Mo(CO)4(η5-7-CB10H11)] (4) in moderate yield by bub-
bling CO through a mixture containing [Na]3[nido-7-
CB10H11], suspended in THF, and [Mo(CO)3(NCMe)3] in
MeCN followed by successive addition of HBF4‚Et2O and
[N(PPh3)2]Cl at -78 °C. We propose that 4 is formed
via a pathway involving the intermediacy of unstable
hydrido species [MoH(CO)3(η5-7-CB10H11)]2- and [Mo-
cationic species are at significantly higher frequencies
than those observed for the anionic monocarbollide iron
complex 1 is in accordance with its anionic nature,
leading to a more electron rich metal center.
It was difficult to replace the CO groups in 1 with
other donor molecules. Thus, no reactions occurred on
heating 1c with PPh3 or CNBut in THF, but upon
addition of Me3NO to the reaction mixtures, the com-
plexes [N(PPh3)2][Fe(CO)2(L)(η5-7-CB10H11)] (L ) PPh3
(2), CNBut (3)) were formed at room temperature. Data
characterizing these compounds are given in Tables 1
and 2.
In an attempt to form a molybdenum species related
to compound 1, [Mo(CO)3(NCMe)3] was treated with
[NHMe3][nido-7-CB10H13] and, albeit in very poor yield,
(12) Hawthorne, M. F.; Young, D. C.; Andrews, D. C.; Howe, D. V.;
Pilling, R. L.; Pitts, D.; Reintjes, M.; Warren, L. F.; Wegner, P. A. J .
Am. Chem. Soc. 1968, 90, 879.
(11) (a) Busetto, L.; Angelici, R. J . Inorg. Chim. Acta 1968, 2, 391.
(b) J etz, W.; Graham, W. A. G. Inorg. Chem. 1971, 10, 1159.

1996 Organometallics, Vol. 19, No. 10, 2000
Ellis et al.
Ta ble 3. Selected In ter n u clea r Dista n ces (Å) a n d An gles (d eg) for th e An ion of
[N(P P h 3)2][Mo(CO)4(η5-7-CB10H11)] (4) w ith Estim a ted Sta n d a r d Devia tion s in P a r en th eses
Mo-C(2)
Mo-B(2)
Mo-C(1)
C(5)-O(5)
1.998(9)
2.368(7)
2.388(6)
1.202(10)
Mo-C(5)
Mo-B(4)
C(2)-O(2)
1.998(9)
2.374(7)
1.116(9)
Mo-C(3)
Mo-B(3)
C(3)-O(3)
2.015(9)
2.381(6)
1.113(9)
Mo-C(4)
Mo-B(5)
C(4)-O(4)
2.019(11)
2.386(7)
1.172(10)
C(2)-Mo-C(5)
C(2)-Mo-C(4)
O(2)-C(2)-Mo
78.7(6)
114.0(6)
178(2)
O(5)-C(5)-Mo
C(2)-Mo-C(3)
C(5)-Mo-C(4)
174.1(13)
82.6(7)
71.6(6)
O(3)-C(3)-Mo
C(5)-Mo-C(3)
176.0(11)
130.8(4)
C(3)-Mo-C(4)
O(4)-C(4)-Mo
75.5(5)
176.8(11)
Ch a r t 2
F igu r e 1. Structure of the anion [Mo(CO)4(η5-7-CB10H11)]-
of 4, showing the crystallographic labeling scheme. Hydro-
gen atoms are omitted for clarity, and thermal ellipsoids
are shown at the 40% probability level.
(H)2(CO)3(η5-7-CB10H11)]-, with the latter releasing
hydrogen in the presence of CO to produce the anion of
4. In the IR spectrum of 4 there are three CO bands at
2070, 1994, and 1956 cm-1. These frequencies may
usefully be compared with those in the spectra of the
isoelectronic cation [Mo(CO)4(η5-C5H5)]+ (2128, 2041,
and 1980 cm-1 13 and the neutral species [Mo(CO)4(η5-
)
7,8-Me2-7,8-C2B9H9)] (2097, 2034, and 2013 cm-1).14
Because the salts 1 and 4 are precursors to other
compounds, an X-ray structural study on one species
seemed merited to place the work on a firm structural
basis. The anion [Mo(CO)4(η5-7-CB10H11)]- of 4 is shown
in Figure 1, and selected structural parameters are
listed in Table 3. As anticipated, the molybdenum atom
is ligated on one side by the nido-7-CB10H11 group in
an η5 manner and on the other by the four CO molecules
adopting essentially linear bonding modes. If the cage
ligand is formally regarded as a three-orbital ligand, the
MoII center adopts a “3:4 piano-stool configuration”. The
cage-metal distances are Mo-C(1) ) 2.388(6) Å, Mo-
B(2) ) 2.368(7) Å, Mo-B(3) ) 2.381(6) Å, Mo-B(4) )
2.374(7) Å, and Mo-B(5) ) 2.386(7) Å. An X-ray
diffraction study on the closely related monoanion
[Mo(CO)3(PPh3)(η5-7-OH-7-CB10H10)]- revealed a simi-
lar structure with cage-metal distances of Mo-C )
2.409(7) Å and Mo-B ) 2.354(9), 2.353(8), 2.403(8), and
2.401(8) Å.8b
Lewis bases than does 1. Thus, the complexes [N(PPh3)2]-
[Mo(CO)3(L)(η5-7-CB10H11)] (L ) PPh3 (5a ), or CNBut
(6)), data for which are given in Tables 1 and 2, are
readily formed by heating solutions of 4 in THF with
PPh3 and CNBut, respectively.
We have recently reported the synthesis of [Re(CO)2-
(NO)(η5-7,8-C2B9H11)] by treating the anion [Re(CO)3-
(η5-7,8-C2B9H11)]- with [NO][BF4].15 In the expectation
that a similar reaction between [NO][BF4] and one or
other of the salts 1 would yield [Fe(CO)2(NO)(η5-7-
CB10H11)], complex 1b was treated in THF with the
nitrosyl reagent. Surprisingly the product was the
charge-compensated complex [Fe(CO)3{η5-9-O(CH2)4-7-
CB10H10}] (7; Chart 2), the structure of which was only
established after an X-ray crystallographic study. The
complex crystallizes with three independent molecules
in the asymmetric unit, selected structural parameters
for which are listed in Table 4. It was immediately
apparent (Figure 2) that the THF molecule is bonded
to a boron atom which is in a â-site with respect to the
Since compound 4 has four ligated CO molecules
rather than three, it reacts much more readily with
carbon in the CBBBB ring ligating the iron atom. All
three molecules are structurally akin with B(3)-O(5)
(13) Fischer, E. O.; Fichtl, K.; O¨ fele, K. Chem. Ber. 1962, 95, 249.
(14) Dossett, S. J .; Li, S.; Stone, F. G. A. J . Chem. Soc., Dalton Trans.
1993, 1585.
(15) Ellis, D. D.; J elliss, P. A.; Stone, F. G. A. Chem. Commun. 1999,
2385.

Monocarbollide CO Complexes of Fe and Mo
Organometallics, Vol. 19, No. 10, 2000 1997
Ta ble 4. Selected In ter n u clea r Dista n ces (Å) a n d An gles (d eg) for [F e(CO)3{η5-9-O(CH2)4-7-CB10H10}] (7)
w ith Estim a ted Sta n d a r d Devia tion s in P a r en th eses
Molecule 1
Fe(1)-C(4)
Fe(1)-B(5)
C(2)-O(2)
1.782(4)
2.148(3)
1.132(4)
Fe(1)-C(3)
Fe(1)-B(2)
C(3)-O(3)
1.803(3)
2.157(3)
1.138(4)
Fe(1)-C(2)
Fe(1)-B(3)
C(4)-O(4)
1.813(4)
2.161(3)
1.139(4)
Fe(1)-C(1)
Fe(1)-B(4)
B(3)-O(5)
2.129(3)
2.190(4)
1.519(4)
C(4)-Fe(1)-C(3)
O(2)-C(2)-Fe(1)
93.60(14)
180.0(4)
C(4)-Fe(1)-C(2)
O(3)-C(3)-Fe(1)
94.9(2)
178.7(3)
C(3)-Fe(1)-C(2)
91.61(14)
O(4)-C(4)-Fe(1)
176.6(3)
Molecule 2
Fe(2)-C(23)
Fe(2)-B(25)
C(22)-O(22)
1.778(4)
2.137(4)
1.134(4)
Fe(2)-C(24)
Fe(2)-B(22)
C(23)-O(23)
1.804(3)
2.150(4)
1.142(4)
Fe(2)-C(22)
Fe(2)-B(23)
C(24)-O(24)
1.812(4)
2.164(3)
1.141(3)
Fe(2)-C(21)
Fe(2)-B(24)
B(23)-O(25)
2.124(3)
2.191(3)
1.520(4)
C(23)-Fe(2)-C(24)
94.99(14) C(23)-Fe(2)-C(22)
93.2(2) C(24)-Fe(2)-C(22) 89.98(13) O(24)-C(24)-Fe(2) 178.6(3)
O(22)-C(22)-Fe(2) 177.3(3)
O(23)-C(23)-Fe(2) 178.1(3)
Molecule 3
1.804(4)
2.157(4)
1.143(4)
Fe(3)-C(43)
Fe(3)-B(45)
C(42)-O(42)
1.777(4)
2.138(4)
1.132(4)
Fe(3)-C(44)
Fe(3)-B(42)
C(43)-O(43)
Fe(3)-C(42)
Fe(3)-B(43)
C(44)-O(44)
1.810(4)
2.176(3)
1.136(4)
Fe(3)-C(41)
Fe(3)-B(44)
B(43)-O(45)
2.123(3)
2.186(3)
1.509(4)
C(43)-Fe(3)-C(44)
95.21(14) C(43)-Fe(3)-C(42)
92.6(2) C(44)-Fe(3)-C(42) 91.18(14) O(44)-C(44)-Fe(3) 178.6(3)
O(42)-C(42)-Fe(3) 178.2(3)
O(43)-C(43)-Fe(3) 177.9(3)
the cage-substitution product [Fe(CO)3(η5-9-OEt2-7-
CB10H10)] (8) (Tables 2 and 3). The NMR data leave no
doubt about the nature of this product. The resonance
observed in the 11B{1H} NMR spectrum at δ 22.8 is
diagnostic of the BOEt2 nucleus.16a Again, only one
isomer is formed, and that is most likely to be the
â-system as observed for 7.
During the course of the study it was observed that 7
also formed, but in low yield, when HBF4‚OEt2 was
added to THF solutions of the salts 1 in the absence of
[NO][BF4]. There was no evidence for the existence of
the hydrido species [FeH(CO)3(η5-7-CB10H11)], reflecting
an absence of nucleophilicity at the iron center in the
monoanion. The salts 1 are thus similar to those of
[Re(CO)3(η5-7-CB10H11)]2- and [Re(CO)3(η5-7,8-C2B9H11)]-
in this respect.2c,6
Charge-compensated metallacarborane complexes with
12-vertex closo-3,1,2-MC2B9 core structures are well-
established.17 More recently several zwitterionic met-
allacarboranes based on closo-2,1-MCB10 (M ) Rh,18,19
Ru,20a Os20b) icosahedral frameworks have also been
reported. These monocarbon metallacarboranes were
prepared from reactions between metal complexes and
a carborane precursor which carried a substituent other
than H on a cage-carbon vertex. In contrast, compounds
7 and 8 are formed by formal hydride removal from a
boron vertex on a preformed metallacarborane in the
presence of a donor molecule, leading to nucleophilic
substitution on boron by the latter. Hawthorne and co-
workers17a were the first to use this methodology to form
B-substituted derivatives of carbollide ligands. Species
F igu r e 2. Structure of [Fe(CO)3{η5-9-O(CH2)4-7-CB10H10}]
(7), showing the crystallographic labeling scheme. Hydro-
gen atoms are omitted for clarity, and thermal ellipsoids
are shown at the 40% probability level.
) 1.519(4) Å, B(23)-O(25) ) 1.520(4) Å, and B(43)-
O(45) ) 1.509(4) Å.
The NMR data (Table 2) for 7 are in accord with the
X-ray diffraction results. The presence of the boron-
bound exopolyhedral THF group is apparent from the
1H and 13C{1H} NMR spectra. The 11B{1H} NMR data
are especially informative. There are seven peaks in the
range δ +9.6 to -19.1 corresponding in intensity to nine
boron nuclei, with an eighth resonance due to one boron
at δ 20.4. The latter peak remained a singlet in a fully
coupled 11B spectrum, while the others became doublets
(J (BH) ) ca. 130 Hz). This pattern and the chemical
shift are diagnostic for a BH cage substitution of the
type observed,16 although only from the result of the
X-ray structure determination could a confident dis-
crimination be made between the R- and â-isomers, both
of which would give rise to asymmetrical structures. In
Et2O solutions 1b also reacts with [NO][BF4], yielding
(17) (a) Hawthorne, M. F.; Warren, L. F.; Callahan, K. P.; Travers,
N. F. J . Am. Chem. Soc. 1971, 93, 2407. (b) King, R. E.; Miller, S. B.;
Knobler, C. B.; Hawthorne, M. F. Inorg. Chem. 1983, 22, 3548. (c)
Kang, H. C.; Lee, S. S.; Knobler, C. B.; Hawthorne, M. F. Inorg. Chem.
1991, 30, 2024.
(18) (a) J effery, J . C.; Lebedev, V. N.; Stone, F. G. A. Inorg. Chem.
1996, 35, 2967. (b) J effery, J . C.; J elliss, P. A.; Lebedev, V. N.; Stone,
F. G. A. Inorg. Chem. 1996, 35, 5399. (c) J effery, J . C.; J elliss, P. A.;
Lebedev, V. N.; Stone, F. G. A. Organometallics 1996, 15, 4737.
(19) Chizhevsky, I. T.; Pisareva, I. V.; Petrovskii, P. V.; Bregadze,
V. I.; Yanovsky, A. I.; Struchkov, Y. T.; Knobler, C. B.; Hawthorne, M.
F. Inorg. Chem. 1993, 32, 3393.
(20) (a) Lebedev, V. N.; Mullica, D. F.; Sappenfield, E. L.; Stone, F.
G. A. Organometallics 1996, 15, 1669. (b) Lebedev, V. N.; Mullica, D.
F.; Sappenfield, E. L.; Stone, F. G. A. J . Organomet. Chem. 1997, 536-
537, 537.
(16) (a) Mullica, D. F.; Sappenfield, E. L.; Stone, F. G. A.; Woollam,
S. F. Organometallics 1994, 13, 157. (b) Go´mez-Saso, M,; Mullica, D.
F.; Sappenfield, E. L.; Stone, F. G. A. Polyhedron 1996, 15, 793.

1998 Organometallics, Vol. 19, No. 10, 2000
Ellis et al.
Ta ble 5. Selected In ter n u clea r Dista n ces (Å) a n d An gles (d eg) for [Mo(CO)3(P P h 3){η5-9-O(CH2)4-7-CB10H10}]
(10) w ith Estim a ted Sta n d a r d Devia tion s in P a r en th eses
Mo-C(4)
Mo-B(5)
Mo-P
1.981(2)
2.378(2)
2.5542(7)
1.532(2)
Mo-C(5)
Mo-B(4)
C(3)-O(3)
2.020(2)
2.381(2)
1.149(2)
Mo-C(3)
Mo-B(2)
C(4)-O(4)
2.023(2)
2.394(2)
1.148(2)
Mo-B(3)
Mo-C(1)
C(5)-O(5)
2.370(2)
2.396(2)
1.145(2)
B(3)-O(6)
C(4)-Mo-C(5)
C(4)-Mo-P
C(1)-Mo-P
B(4)-Mo-P
73.95(7)
120.45(5)
85.90(4)
O(4)-C(4)-Mo
C(4)-Mo-C(3)
C(5)-Mo-P
176.44(14)
78.50(7)
79.01(5)
B(5)-Mo-P
O(5)-C(5)-Mo
C(5)-Mo-C(3)
100.66(5)
173.9(2)
124.40(7)
C(3)-Mo-P
B(3)-Mo-P
O(3)-C(3)-Mo
74.93(5)
151.49(5)
177.96(14)
144.34(4)
B(2)-Mo-P
107.07(5)
with Fe(η5-7,8-C2B9H11) groups were converted to those
having Fe(η5-10-SR2-7,8-C2B9H10) (R ) Me, Et) moieties
by adding alkyl sulfides to the former, employing
strongly acid media for the deprotonation step.
Following on Quintana and Sneddon’s21 discovery that
-
the monocarbon carborane anion [nido-7-CB10H13
]
reacts with SMe2 in the presence of concentrated
sulfuric acid to give zwitterionic [nido-8-SMe2-7-CB10H12],
we have found that the compound [Fe(CO)3(η5-9-SMe2-
7-CB10H10)] (9) can be prepared by treating 1b under
the same conditions. Data characterizing 9 are listed
in Tables 1 and 2. The 11B{1H} NMR spectrum of the
compound displayed a resonance at δ 1.7 which re-
mained a singlet in a fully coupled 11B spectrum and
thus may be assigned to the BSMe2 nucleus.
Interestingly, the charge-compensated complexes 7-9
are also formed in reactions with the respective donor
molecules when [CPh3][BF4] is used for hydride abstrac-
tion at the BH vertex. This correlates with our earlier
results16a when the complexes [NEt4][Mo(CO)2(η3-C3H5)-
(η5-7,8-R2-C2B9H9)] (R ) H, Me) underwent formal
hydride abstraction with [CPh3][BF4] in the presence
of donors generating the charge-compensated com-
pounds [Mo(CO)2(η3-C3H5)(η5-10-L-7,8-R2-C2B9H8)] (L )
OEt2, THF, SMe2).
Following studies leading to the isolation of the iron
complexes 7-9, similar reactions were carried out with
the molybdenum complex 5a . This compound was
chosen for study rather than the tetracarbonyl 4 because
solutions of the latter in organic solvents decomposed,
albeit slowly. Addition of tris(4-bromophenyl)aminium
hexachloroantimonate to THF solutions of 5a resulted
in the immediate discharge of the blue color of the
oxidant and formation of [Mo(CO)3(PPh3){η5-9-O(CH2)4-
7-CB10H10}] (10). There was no evidence for the conver-
sion of 5a into a dimolybdenum species as in the
oxidation of [Mo(CO)3(η5-C5H5)]- to give [Mo2(CO)6(η5-
C5H5)2]. Data for 10 are given in Tables 1 and 2. The
resonance for the BO(CH2)4 nucleus is observed as a
singlet at δ 22.9 in the fully coupled 11B NMR spectrum.
The corresponding peak in the spectrum of [Mo(CO)2-
(η3-C3H5)(η5-7,8-Me2-10-O(CH2)4-7,8-C2B9H8)] is seen at
δ 23.8.16a Complex 10 could also be prepared by reacting
5a in THF with CF3SO3Me, a â-B site in the precursor
undergoing hydride removal by Me+ instead of the metal
center in the anion being alkylated to generate a Mo-
Me linkage. An X-ray diffraction study was made on 10
because the NMR data did not unambiguously establish
whether the THF molecule was coordinated to an R- or
F igu r e 3. Structure of [Mo(CO)3(PPh3){η5-9-O(CH2)4-7-
CB10H10}] (10), showing the crystallographic labeling
scheme. Hydrogen atoms are omitted for clarity, and
thermal ellipsoids are shown at the 40% probability level.
5. As in compound 7 the THF molecule is attached to a
boron in the â-site (B(3)-O(6) ) 1.532(2) Å) in the
CBBBB ring. The PPh3 molecule lies transoid to B(3)
and B(4) and cisoid to C(1) (P-Mo-B(3) ) 151.49(5)°,
P-Mo-B(4) ) 144.34(4)°, P-Mo-C(1) ) 85.90(4)°),
probably in order to reduce steric interactions between
this ligand and the THF group. The Mo-P bond length
(2.5542(7) Å) is typical of such distances.22 Neither with
10 nor with 7 was formation of more than one isomer
observed. Hence, the reactions leading to their synthesis
are remarkably regiospecific.
Addition of HBF4‚Et2O to 5a in a 1:1 CH2Cl2-Et2O
mixture at -78 °C afforded the complex [Mo(CO)3-
(PPh3)(η5-9-OEt2-7-CB10H10)] (11). Similarly 6 with
HBF4‚Et2O gave [Mo(CO)3(CNBut)(η5-9-OEt2-7-CB10H10)]
(12). Data characterizing these two compounds are
given in Tables 1 and 2. The pattern of chemical shifts
displayed in the 11B{1H} NMR spectra of these com-
plexes is very similar to that in the same spectrum of
10, leaving no doubt as to their structures. Again, there
was no evidence for formation of a second isomer of
either of these species having R-BOEt2 groups.
During the course of our studies the alkyne-molyb-
denum complexes [N(PPh3)2][Mo(CO)2(ButCtCH)(η5-7-
CB10H11)] (13) and [N(PPh3)2][Mo(CO)2(PhCtCR)(η5-7-
CB10H11)] (R ) H (14), Ph (15)) were prepared by
treating 4 in THF with the alkyne and warming to ca.
60 °C. Examination of the 13C{1H} NMR spectra of these
compounds (Table 2) revealed that the contact carbons
a â-boron with respect to the carbon in the CBBBB ring
ligating the Mo atom. The molecule is shown in Figure
3, and some structural parameters are listed in Table
(22) Allen, F. H.; Brammer, L.; Kennard, O.; Orpen, A. G.; Taylor,
R.; Watson, D. G. J . Chem. Soc., Dalton Trans. 1989, S1.
(21) Quintana, W.; Sneddon, L. G. Inorg. Chem. 1990, 29, 3242.

Monocarbollide CO Complexes of Fe and Mo
Organometallics, Vol. 19, No. 10, 2000 1999
Syn th esis of [N(P P h 3)2][F e(CO)2(L)(η5-7-CB10H11)] (L )
P P h 3, CNBu t). (i) The compounds 1c (0.41 g, 0.50 mmol) and
PPh3 (0.26 g, 1.00 mmol) were dissolved in THF (10 mL), and
Me3NO (0.08 g, 1.00 mmol) was added. After the mixture was
stirred at room temperature for 12 h, solvent was removed in
vacuo, and the residue was treated with CH2Cl2 (20 mL).
Following filtration through a Celite plug, and addition of silica
gel (ca. 2 g) to the filtrate, solvent was removed in vacuo,
affording a yellow powder. The latter was transferred to the
top of a chromatography column. Elution with neat CH2Cl2
gave a pale yellow fraction. Removal of solvent in vacuo yielded
pale yellow microcrystals of [N(PPh3)2][Fe(CO)2(PPh3)(η5-7-
CB10H11)] (2; 0.21 g). 31P{1H} NMR: δ 67.4 (s, PPh3).
(ii) Compound 1c (0.41 g, 0.50 mmol) was dissolved in THF
(10 mL), and CNBut (0.11 mL, 1.00 mmol) and Me3NO (0.08
g, 1.00 mmol) were added. After the mixture was stirred at
room temperature for 12 h, solvent was removed in vacuo, and
the residue was treated with CH2Cl2 (20 mL). Following
filtration through a Celite plug, and addition of silica gel (ca.
2 g), solvent was removed in vacuo, affording a yellow powder.
The latter was transferred to the top of a chromatography
column. Elution with neat CH2Cl2 gave a pale yellow fraction.
Removal of solvent in vacuo yielded a pale yellow powder of
[N(PPh3)2][Fe(CO)2(CNBut)(η5-7-CB10H11)] (3; 0.15 g).
Syn th esis of [N(P P h 3)2][Mo(CO)4(η5-7-CB10H11)]. The
reagent nido-7-NMe3-7-CB10H12 (0.96 g, 5.00 mmol) was dis-
solved in dry THF (15 mL), and three small pieces of freshly
cut sodium metal (ca. 0.30 g) were added. The mixture was
refluxed for ca. 3 days, yielding a white precipitate of [Na]3-
[nido-7-CB10H11]. Approximately 6 h before the [Na]3[nido-7-
CB10H11] was required, the compound [Mo(CO)3(NCMe)3] was
prepared by heating [Mo(CO)6] (1.32 g, 5.00 mmol) in MeCN
(15 mL) to reflux temperatures in a Schlenk tube fitted with
a condenser. When ready, heating was simultaneously dis-
continued from the two refluxing reagents. Any residual
resonated between δ 196.4 and 164.4 in the range
associated with alkynes functioning as four-electron
donors.23 It was anticipated that the complexes could
be used in further syntheses, but protonation in CH2Cl2
at -78 °C resulted in decomposition. The alkyne was
displaced with PPh3 from the [PPh4]+ salt of 13 to yield
[PPh4][Mo(CO)2(PPh3)2(η5-7-CB10H11)] (16).
Con clu sion s
The complexes 1 and 4 are evidently useful starting
reagents for preparing organoiron and -molybdenum
species involving the monocarbon carbollide ligand
[nido-7-CB10H11]
3- and are thus well worthy of further
study. Although protonation of the monoanions did not
yield neutral hydrido complexes, the charge-compen-
sated molecules 7-12 are themselves potential precur-
sors to other metallacarboranes, especially through
reduction in the charge by one unit in passing from the
anions [M(CO)n(η5-7-CB10H11)]- (M ) Fe, n ) 3; M )
Mo, n ) 4) to the neutral species [M(CO)n(η5-9-L-7-
CB10H10)] (L ) donor molecule). Clearly replacement of
the CO ligands in the latter by other groups will be of
interest and other reactions are under investigation.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. Solvents were distilled from
appropriate drying agents under nitrogen prior to use. Petro-
leum ether refers to that fraction of boiling point 40-60 °C.
All reactions were carried out under an atmosphere of dry
nitrogen using Schlenk line techniques. Chromatography
columns (ca. 15 cm in length and ca. 2 cm in diameter) were
packed with silica gel (Acros, 60-200 mesh). Celite pads used
for filtration were ca. 3 cm in length and 2 cm in diameter.
NMR spectra were recorded at the following frequencies: 1H,
360.1 MHz; 13C, 90.6 MHz; 31P, 145.7 MHz;, 11B, 115.5 MHz.
The 31P{1H} chemical shifts listed below are positive to high
frequency of H3PO4 (external). Species with the cation [N(P-
Ph3)2]+ show a 31P{1H} resonance at δ 21.7, except for 16 (δ
23.8, [PPh4]+). The salts [Na]3[nido-7-CB10H11] and [NHMe3]-
[nido-7-CB10H13] were synthesized from nido-7-NMe3-7-CB10H12
according to the method of Knoth and co-workers.24 The acid
HBF4‚Et2O as a 54% solution in Et2O was used as purchased
from Aldrich Chemical Co.
Syn th esis of Salts of th e An ion [Fe(CO)3(η5-7-CB10H11)]-.
The compounds [Fe3(CO)12] (0.25 g, 0.50 mmol) and [NHMe3]-
[nido-7-CB10H13] (0.10 g, 0.50 mmol) were refluxed in THF (10
mL) for 24 h. The mixture containing [NHMe3][Fe(CO)3(η5-7-
CB10H11)] was then cooled to room temperature, and [NEt4]I
(0.26 g, 1.00 mmol) was added. Solvent was removed in vacuo,
and the residue was treated with CH2Cl2 (20 mL). After
filtration through a Celite plug and addition of silica gel (ca.
2 g) to the filtrate, solvent was removed in vacuo, affording a
yellow brownish powder. The latter was transferred to the top
of a chromatography column. Elution with CH2Cl2-MeCN (4:
1) gave a yellow brownish fraction. Removal of solvent in vacuo
followed by crystallization from CH2Cl2 layered with petroleum
ether yielded pale yellow microcrystals of [NEt4][Fe(CO)3(η5-
7-CB10H11)] (1a ; 0.16 g). Reactions of the ferracarborane anion
described below were studied using the [NHMe3]+ (1b) and
[N(PPh3)2]+ (1c) salts. The former was obtained by omitting
addition of [NEt4]I and the latter by adding [N(PPh3)2]Cl
instead of [NEt4]I.
sodium was carefully removed from the [Na]3[nido-7-CB10H11
]
suspension. Then the [Mo(CO)3(NCMe)3] solution was trans-
ferred into the [Na]3[nido-7-CB10H11] suspension via a cannula.
The resulting mixture was stirred at room temperature for
ca. 1 h. Following this, CO was bubbled through the solution
at -78 °C and HBF4‚Et2O (1.38 mL, 10 mmol) was added. The
resulting mixture was then warmed to room temperature and
stirred for ca. 2 h. The salt [N(PPh3)2]Cl (2.87 g, 5.00 mmol)
was added and the mixture stirred overnight. After filtration
through a Celite plug, the solvent was removed in vacuo. The
residue was taken up in CH2Cl2 (2 mL) and the solution
chromatographed. A yellow fraction was eluted with CH2Cl2-
petroleum ether (4:1). The salt [N(PPh3)2][Mo(CO)4(η5-7-
CB10H11)] (4; 1.76 g) was isolated after removal of solvent in
vacuo.
Syn th esis of [N(P P h 3)2][Mo(CO)3(L)(η5-7-CB10H11)] (L
) P P h 3, CNBu t). (i) The reagents 4 (1.00 g, 1.15 mmol) and
PPh3 (0.32 g, 1.27 mmol) were dissolved in THF (15 mL), and
the mixture was stirred for 2 h at 60 °C. Solvent was removed
in vacuo, the residue was dissolved in CH2Cl2 (1 mL), and this
solution was chromatographed. A yellow fraction was eluted
with CH2Cl2-petroleum ether (4:1), affording [N(PPh3)2]-
[Mo(CO)3(PPh3)(η5-7-CB10H11)] (5a ; 1.20 g) after removal of
solvent. The product was obtained analytically pure as its
[NEt3(CH2Ph)]+ salt 5b (Table 1). 31P{1H} NMR: 5a , δ 53.4
(s, PPh3).
(ii) Compound 4 (0.22 g, 0.25 mmol) was dissolved in THF
(15 mL), CNBut (29 µL, 0.28 mmol) was added, and the
mixture was stirred for 2 h at 60 °C. Solvent was removed in
vacuo, the residue was taken up in CH2Cl2 (1 mL), and this
solution was chromatographed. A yellow fraction was eluted
with CH2Cl2-petroleum ether (4:1), from which [N(PPh3)2]-
[Mo(CO)3(CNBut)(η5-7-CB10H11)] (6; 0.16 g) was obtained after
removal of solvent in vacuo.
(23) Templeton, J . L. Adv. Organomet. Chem. 1989, 29, 1.
(24) Knoth, W. H.; Little, J . L.; Lawrence, J . R.; Scholer, F. R.; Todd,
L. J . Inorg. Synth. 1968, 11, 33.

2000 Organometallics, Vol. 19, No. 10, 2000
Ellis et al.
Ca ge Su bstitu tion Rea ction s of [NHMe3][F e(CO)3(η5-
7-CB10H11)]. (i) The compounds [Fe3(CO)12] (0.25 g, 0.50 mmol)
and [NHMe3][nido-7-CB10H13] (0.10 g, 0.50 mmol) were heated
at reflux in THF (10 mL) for 24 h to generate the salt 1b in
situ. The mixture was cooled to room temperature and
[NO][BF4] (0.12 g, 1.00 mmol) added. After this mixture was
stirred at room temperature for ca. 24 h, solvent was removed
in vacuo and the dark brown residue was taken up in CH2Cl2
(20 mL). After filtration through a Celite plug, ca. 2 g of silica
gel was added to the filtrate, and solvent was removed in
vacuo, affording a yellow brownish powder which was trans-
ferred to the top of a chromatography column. Elution with
neat CH2Cl2 gave a pale yellow fraction. Removal of solvent
in vacuo followed by crystallization from CH2Cl2 layered with
petroleum ether yielded pale yellow microcrystals of [Fe(CO)3-
{η5-9-O(CH2)4-7-CB10H10}] (7; 0.07 g).
CH2Cl2 (1 mL), and this solution was chromatographed. A
yellow fraction was eluted with CH2Cl2-petroleum ether (2:
1), which gave [Mo(CO)3(PPh3)(η5-9-OEt2-7-CB10H10)] (11; 0.12
g) after removal of solvent. 31P{1H} NMR: δ 49.3 (s, PPh3).
(iii) Similarly 6 (0.21 g, 0.23 mmol) in CH2Cl2-Et2O (20 mL,
1:1) at -78 °C with HBF4‚Et2O (340 µL, 2.30 mmol) gave
[Mo(CO)3(CNBut)(η5-9-OEt2-7-CB10H10)] (12; 0.05 g).
Syn th esis of Alk yn e-Molybd en u m Com p lexes. (i) Com-
pound 4 (0.22 g, 0.25 mmol) was dissolved in THF (15 mL),
ButCtCH (34 µL, 0.28 mmol) was added, and the mixture was
stirred for 2 h at 60 °C. Solvent was removed in vacuo, the
residue was taken up in CH2Cl2 (1 mL), and this solution was
chromatographed. A violet fraction was eluted with CH2Cl2-
petroleum ether (4:1). The compound [N(PPh3)2][Mo(CO)2-
(ButCtCH)(η5-7-CB10H11)] (13; 0.14 g) was obtained after
removal of solvent in vacuo.
(ii) The salt 1b (0.50 mmol) was formed in THF (10 mL) as
described above. After the mixture was cooled to room tem-
perature, solvent was removed in vacuo. The residue was
dissolved in diethyl ether (10 mL), and [NO][BF4] (0.12 g, 1.00
mmol) was added. After this mixture was stirred at room
temperature for ca. 24 h, solvent was removed in vacuo and
the dark brown residue taken up in CH2Cl2 (20 mL). Following
filtration through a Celite plug, silica gel (ca. 2 g) was added
to the filtrate, the solvent was removed in vacuo, and the
yellow brownish powder was transferred to the top of a
chromatography column. Elution with CH2Cl2, removal of
solvent in vacuo, and crystallization of the product from CH2Cl2
layered with petroleum ether yielded pale yellow microcrystals
of [Fe(CO)3{η5-9-OEt2-7-CB10H10}] (8; 0.06 g).
(iii) After formation of the salt 1b (0.50 mmol) as a solid as
in (ii), the residue was treated with dimethyl sulfide (12 mL),
followed by concentrated sulfuric acid (2 mL). The resulting
two-phase solution was stirred for 24 h. The dimethyl sulfide
layer was then extracted with CH2Cl2. After removal of solvent
in vacuo, the brown residue was taken up in CH2Cl2 (20 mL)
and this solution filtered through a Celite plug. Silica gel (ca.
2 g) was added to the filtrate, solvent was removed in vacuo,
and the yellow brownish powder was transferred to the top of
a chromatography column. Elution with neat CH2Cl2 gave a
pale yellow fraction. Removal of solvent in vacuo followed by
crystallization from CH2Cl2-petroleum ether yielded pale
yellow microcrystals of [Fe(CO)3(η5-9-SMe2-7-CB10H10)] (9; 0.09
g).
(ii) The compounds [N(PPh3)2][Mo(CO)2(PhCtCH)(η5-7-
CB10H11)] (14; 0.12 g) and [N(PPh3)2][Mo(CO)2(PhCtCPh)(η5-
7-CB10H11)] (15; 0.13 g) were similarly obtained from 4 (0.22
g, 0.25 mmol) using 0.28 mmol of PhCtCH (31 µL) and PhCt
CPh (0.05 g), respectively.
(iii) The [PPh4]+ salt of 13 (0.18 g, 0.25 mmol) was dissolved
in THF (20 mL), and PPh3 (0.14 g, 0.55 mmol) was added. The
mixture was stirred at 60 °C, affording a yellow precipitate,
which was removed by filtration after 2 h. Yellow microcrystals
of [PPh4][Mo(CO)2(PPh3)2(η5-7-CB10H11)] (16; 0.14 g) were
obtained after recrystallization from CH2Cl2-petroleum ether
using the layering method. 31P{1H} NMR: δ 68.5 (s, PPh3).
Cr ysta l Str u ctu r e Deter m in a tion s a n d Refin em en ts.
Crystals of 7 were grown from CH2Cl2-pentane, while those
of 4 and 10 were grown from CH2Cl2-petroleum ether. The
asymmetric unit of 7 contained three crystallographically
independent molecules of the complex in general positions.
Diffracted intensities for 4 were collected on an Enraf-Nonius
CAD-4 diffractometer operating in the ω-2θ scan mode, using
graphite-monochromated Mo KR X-radiation. The final unit
cell dimensions were determined from the setting angle values
of 25 accurately centered reflections. The stability of the crystal
during the period of the data collection was monitored by
measuring the intensities of three standard reflections every
2 h. Data were collected at a constant scan speed of 5.17° m-1
in ω with a scan range of 1.15° + 0.35 tan θ. The data were
corrected for Lorentz, polarization, and X-ray absorption
effects, the last by a semiempirical method based on azimuthal
scans of ψ data of several Euclerian angles (ø) near 90°.
Single crystals of 7 and 10 were mounted on glass fibers,
and low-temperature data (173 K for 7 and 163 K for 10) were
collected on a Bruker SMART CCD area-detector three-circle
diffractometer (Mo KR X-radiation, graphite monochromator,
λh ) 0.710 73 Å). For three or four settings of æ, narrow data
“frames” were collected for 0.3° increments in ω. For complex
7 just over a hemisphere of data was collected, while for 10 a
full sphere of data was collected. It was confirmed that crystal
decay had not taken place during the course of the data
collection. The substantial redundancy in data allows empirical
absorption corrections (SADABS)25 to be applied using multiple
measurements of equivalent reflections. The data frames were
integrated using SAINT25 and refined by full-matrix least
squares on all F2 data using SHELXTL version 5.0325 or
SHELXL-97.26
Ca ge Su bstitu tion Rea ction s of [N(P P h 3)2][Mo(CO)3-
(P P h 3)(η5-7-CB10H11)]. (i) (a) A THF solution of tris(4-bromo-
phenyl)aminium hexachloroantimonate (0.20 g, 0.25 mmol)
was added to a THF (20 mL) solution of 5a (0.25 g, 0.23 mmol)
via a cannula. The deep blue color of tris(4-bromophenyl)-
aminium hexachloroantimonate immediately disappeared. The
mixture was stirred for 30 min, and then the solvent was
removed in vacuo. The residue was dissolved in CH2Cl2 (1 mL)
and chromatographed, with CH2Cl2-petroleum ether (2:1) as
eluent. A yellow fraction was collected, which gave [Mo(CO)3-
(PPh3){η5-9-O(CH2)4-7-CB10H10}] (10; 0.02 g) after removal of
solvent in vacuo. 31P{1H} NMR: δ 49.4 (s, PPh3).
(b) Compound 5a (0.25 g, 0.23 mmol) was dissolved in THF
(20 mL), methyl trifluoromethanesulfonate (29 µL, 0.25 mmol)
was added, and the mixture was stirred for 30 min. Solvent
was removed in vacuo, the residue was taken up in CH2Cl2 (1
mL), and this solution was chromatographed. A yellow fraction
was eluted with CH2Cl2-petroleum ether (2:1), affording
[Mo(CO)3(PPh3){η5-9-O(CH2)4-7-CB10H10}] (10; 0.07 g) after
removal of solvent in vacuo.
The structures were solved by conventional direct meth-
ods, and the non-hydrogen atoms, except for those described
below, were refined with anisotropic thermal parameters. The
cage carbon atom in each complex was identified from the
magnitude of its anisotropic thermal parameters and from a
(ii) Compound 5a (0.25 g, 0.23 mmol) was dissolved in
CH2Cl2-Et2O (20 mL, 1:1) and the solution cooled to -78 °C.
After addition of HBF4‚Et2O (340 µL, 2.30 mmol) the mixture
was gradually warmed to room temperature and stirred for 2
h. Solvent was removed in vacuo, the residue was taken up in
(25) SHELXTL-PC; Bruker AXS, Madison, WI, 1995.
(26) Sheldrick, G. M. University of Go¨ttingen, Go¨ttingen, Germany,
1997.

Monocarbollide CO Complexes of Fe and Mo
Organometallics, Vol. 19, No. 10, 2000 2001
Ta ble 6. Da ta for X-r a y Cr ysta l Str u ctu r e An a lyses
4
7
10
cryst dimens (mm)
formula
Mr
0.30 × 0.20 × 0.20
0.20 × 0.18 × 0.10
C8H18B10O4Fe
342.17
0.50 × 0.45 × 0.10
C26H33B10O4PMo
644.53
C
41H41B10NO4P2Mo
877.73
cryst color, shape
cryst syst
space group
a (Å)
b (Å)
c (Å)
yellow prisms
monoclinic
P21/c
16.577(2)
15.845(5)
18.448(4)
pale yellow plates
monoclinic
P21/c
17.5961(14)
16.6039(13)
16.8279(13)
yellow blocks
triclinic
P1h
10.7962(19)
10.943(3)
13.959(3)
107.392(15)
95.60(2)
100.476(19)
1527.1(6)
2
R (deg)
â (deg)
113.22(2)
102.73(2)
γ (deg)
V (Å3)
4452.9(18)
4
1.309
4.07
4795.7(7)
12
1.422
9.48
Z
dcalcd (g cm-3
)
1.402
5.14
656
µ(Mo KR) (cm-1
F(000) (e)
)
1792
2088
T (K)
293
173
163
2θ range (deg)
4.4-45.0
3.4-50.0
3.8-55.0
no. of rflns coll (excld stds)
no. of unique rflns
no. of obsd rflns
6025
13 199
15 477
5789
3621
7279
4924
6884
5963
rfln limits: h, k, l
0-17, 0-17,
-19 to +18
566
0.1120 (0.0527)
a ) 0.0340, b ) 4.1318
1.051
-20 to +19, -19 to +10,
-18 to +20
622
0.0997 (0.0389)
a ) 0.0554, b ) 0.000
0.948
-14 to +14, -13 to +14,
-17 to +18
379
0.0576 (0.0221)
a ) 0.0335, b ) 0.000
0.962
no. of params refined
final residuals wR2 (R1), all dataa
weighting factorsa
goodness of fit on F2
final electron density diff
0.362, -0.438
0.688, -0.399
0.409, -0.273
features (max/min) (e Å-3
)
Refinement was block full-matrix least squares on all F2 data: wR2 ) [∑{w(Fo - Fc2)2}/∑w(Fo2)2]1/2 where w-1 ) [σ2(Fo2) + (aP)2
a
2
+bP] and P ) [max(Fo2,0) + 2Fc2]/3. The value in parentheses is given for comparison with refinements based on Fo with a typical threshold
2
of Fo > 4σ(Fo) and R1 ) ∑||Fo | - |Fc||/∑|Fo| and w-1 ) [σ2(Fo) + g(Fo2)].
comparison of the bond lengths to adjacent boron atoms. All
the carbonyl groups of 4 were disordered across two sites (78:
22): their bond distances were restrained and all the minor
component atoms refined with isotropic thermal parameters.
The final residuals for complex 4 were high, presumably due
to the poorly diffracting crystals obtained and the disorder of
the carbonyl groups. All hydrogen atoms were included in
calculated positions and allowed to ride on the parent boron
Ack n ow led gm en t. We thank the Robert A. Welch
Foundation for support (Grant AA-1201) and Dr. J . C.
J effery for use of X-ray facilities by D.D.E. at the
University of Bristol, Bristol, U.K., and for collecting
the data for 10.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and U values, bond lengths and angles, and
anisotropic thermal parameters and ORTEP diagrams for 4,
7, and 10 in CIF format. This material is available free of
charge via the Internet at http://pubs.acs.org.
or carbon atoms with isotropic thermal parameters (Uiso
)
1.2Uiso of the parent atom). All calculations were carried out
on Dell or Viglen PC computers, and the experimental data
are summarized in Table 6.
OM000033N