Cobalt tris(mercaptoimidazolyl)borate complexes: Synthetic studies and the structure of the first cobaltaboratrane

Article abstract of DOI:10.1039/b401056f

The paramagnetic complexes (Tm^tBu)CoX (X = Cl, Br, I) have been readily prepared and structurally characterized and provide a convenient entry into cobalt(II) tris(mercaptoimidazolyl)borate chemistry. A number of derivatives, including mononuclear triphenylphosphine adducts [(Tm ^tBu)Co(PPh₃)]X and dinuclear compounds [Co ₂(Tm^tBu)₂X]Y, have been prepared in order to ascertain whether cobalt is a reliable surrogate for zinc in biological systems, particularly in sulfur-rich coordination environments. The structure of the first cobaltaboratrane is also reported.

Full text of DOI:10.1039/b401056f

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Cobalt tris(mercaptoimidazolyl)borate complexes:
synthetic studies and the structure of the first cobaltaboratrane
a
a
b
c
David J. Mihalcik, Jennifer L. White, Joseph M. Tanski,† Lev N. Zakharov,‡
c
c
c
a
Glenn P. A. Yap, Christopher D. Incarvito,§ Arnold L. Rheingold‡ and Daniel Rabinovich*
Department of Chemistry, The University of North Carolina at Charlotte,
a
9
201 University City Boulevard, Charlotte, North Carolina 28223, USA.
E-mail: drabinov@email.uncc.edu
b
c
Department of Chemistry, Columbia University, New York, New York 10027, USA
Department of Chemistry and Biochemistry, University of Delaware, Newark,
Delaware 19716, USA
Received 22nd January 2004, Accepted 23rd March 2004
First published as an Advance Article on the web 7th April 2004
tBu
The paramagnetic complexes (Tm )CoX (X = Cl, Br, I) have been readily prepared and structurally characterized
and provide a convenient entry into cobalt() tris(mercaptoimidazolyl)borate chemistry. A number of derivatives,
tBu
tBu
including mononuclear triphenylphosphine adducts [(Tm )Co(PPh )]X and dinuclear compounds [Co (Tm )2X]Y,
3
2
have been prepared in order to ascertain whether cobalt is a reliable surrogate for zinc in biological systems,
particularly in sulfur-rich coordination environments. The structure of the first cobaltaboratrane is also reported.
Introduction
substituents may exert on its complexes, and the enhanced
solubility of its compounds relative to that of those containing
The coordination chemistry of the poly(mercaptoimidazolyl)-
borate ligands (Fig. 1), usually regarded as soft analogues of
Trofimenko’s versatile poly(pyrazolyl)borates, continues to
grow at an accelerated pace. For example, the preparation of
the first manganese Tm complex, the syntheses of tungsten
alkylidyne derivatives, and the structure of the unusual nick-
el() compound [Ni(Tm ) ]Br have all been reported within
the last few months. Although many tris- and bis(mercaptoimi-
Me Ϫ
the original methyl-substituted analogue [Tm ] .
1
2
Results and discussion
R
3
tBu
4
Synthesis and molecular structures of (Tm )CoX (X ؍ Cl, Br, I)
Me
5
tBu
The cobalt() complexes (Tm )CoX (X = Cl, Br, I) were read-
2
ily prepared by mixing equimolar amounts of the corre-
1,6
dazolyl)borate complexes of zinc are now known, related
compounds of cadmium or cobalt, the two divalent metal ions
most frequently used as zinc surrogates in spectroscopic and
sponding anhydrous cobalt dihalides CoX and the thallium()
2
tBu
reagent Tl(Tm ) in dichloromethane (Scheme 1), and isolated
in 55–85% yield after the appropriate work-up. Unlike the syn-
7
tBu
structural studies of zinc enzymes, are clearly less common. In
theses of the closely related group 12 complexes (Tm )MBr
6g
tBu
tBu
this regard, while a number of simple LCdX and CdL (L =
(M = Zn, Cd, Hg), the use of Na(Tm ) instead of Tl(Tm )
2
R
R
8
Tm or Bm ) complexes have recently been synthesized,
in the above reactions typically resulted in the formation of
Ph
9
tBu
Co(Tm ) appears to be the only reported example for cobalt.
intractable mixtures of products, including Co(Tm )2 (vide
2
Interested in contrasting the coordination preferences of zinc,
cadmium, and cobalt in a sulfur-rich environment, we describe
in this paper our initial steps towards a systematic investigation
of the syntheses and structures of cobalt complexes supported
infra). The new cobalt compounds are all air-stable para-
magnetic green solids, soluble in acetone, acetonitrile, chloro-
form, dichloromethane, tetrahydrofuran (THF), and dimethyl
sulfoxide (DMSO) but insoluble in benzene, diethyl ether, or
water. Satisfactory analytical data have been obtained for the
three complexes, which have also been characterized by stand-
by the sterically demanding tris(mercaptoimidazolyl)borate
tBu Ϫ 10
[
Tm ] . In addition to its ease of preparation in high yield,
1
this ligand was selected because of its simple spectroscopic (e.g.,
NMR) features, the protecting effect that the bulky tert-butyl
ard spectroscopic methods, including H NMR, IR, and UV/
Vis spectroscopies. Their paramagnetism (µ = 4.5–4.9 µ ) is
eff
B
7
typical of high spin Co() (d , S = 3/2) and is evident from their
H NMR spectra, all of which are qualitatively similar and
1
exhibit three broad contact-shifted signals in a 9 : 1 : 1 ratio,
corresponding to the tert-butyl and the two imidazolyl protons,
respectively. The complexes were further characterized in solu-
tion by using electrospray ionization mass spectrometry (ESI-
MS). Dilute acetonitrile solutions of the three complexes show
tBu
ϩ
the same two strong peaks that correspond to the [(Tm )Co]
tBu
ϩ
(
m/z = 536) and [(Tm )Co(NCMe)] (m/z = 577) fragments,
both matching the theoretical isotopic distributions (Fig. 2).
This observation is consistent with the fact that loss of a
halide is the most common ionization pathway for metal com-
R
Fig. 1 The tris(mercaptoimidazolyl)borate (Tm ) and bis(mercapto-
R
imidazolyl)borate (Bm ) ligand systems.
11
plexes containing such ligands. Interestingly, a more careful
examination of the ESI mass spectra revealed the presence of
†
Current address: Department of Chemistry, Vassar College, 124
Raymond Avenue, Box 601, Poughkeepsie, New York, 12604, USA.
Current address: Department of Chemistry and Biochemistry,
University of California – San Diego, 9500 Gilman Drive, La Jolla,
California 92093, USA.
tBu
ϩ
additional heavier ions of stoichiometry [Co (Tm ) X] (m/z =
2
2
‡
1
107, 1153 and 1199 for X = Cl, Br, and I, respectively), a
situation that argues for the potential existence in solution
of a fast equilibrium (in the NMR time scale) between mono-
§
Current address: Department of Chemistry, Yale University, New
tBu
tBu
Haven, Connecticut 06520, USA.
nuclear (Tm )CoX or [(Tm )Co(NCMe)]X and dinuclear
1
626
D a l t o n T r a n s . , 2 0 0 4 , 1 6 2 6 – 1 6 3 4
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4

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Scheme 1
tBu
Table 1 Selected bond lengths (Å) and angles (Њ) for (Tm )CoX
(
X = Cl, Br, I)
X = Cl
X = Br
X = I
Co–X
2.2329(9)
2.3122(9)
2.3058(9)
2.3124(9)
1.718(3)
1.726(3)
1.735(3)
2.3817(8)
2.3142(11)
2.3360(12)
2.3261(12)
1.737(4)
1.727(4)
1.720(4)
2.5769(7)
2.3319(12)
2.3089(14)
2.3130(13)
1.734(4)
1.724(5)
1.733(4)
Co–S(1)
Co–S(2)
Co–S(3)
S(1)–C
S(2)–C
S(3)–C
X–Co–S(1)
X–Co–S(2)
X–Co–S(3)
S(1)–Co–S(2)
S(1)–Co–S(3)
S(2)–Co–S(3)
Co–S(1)–C
Co–S(2)–C
Co–S(3)–C
107.12(3)
114.67(3)
111.23(3)
107.38(3)
109.87(3)
106.47(3)
96.00(11)
98.14(11)
97.64(11)
110.38(3)
118.03(4)
106.81(4)
105.74(4)
107.36(4)
108.08(4)
97.86(13)
96.24(13)
95.33(12)
116.70(4)
107.42(4)
112.11(4)
108.71(5)
105.13(5)
106.29(5)
95.90(14)
98.65(15)
97.99(15)
Fig. 2 Positive ion ESI mass spectrum (cone voltage = 90 V) of an
tBu
acetonitrile solution of (Tm )CoBr.
tBu
tBu
Co (Tm ) X or [Co (Tm ) X]X complexes (Scheme 2). In
2
2
2
2
2
tBu
order to better understand the behavior of the (Tm )CoX
compounds in solution, the syntheses of complexes of general
formulas [(Tm )Co(L)]X and [Co (Tm )2X]Y were therefore
tBu
tBu
(X = halide) are exceedingly rare and Riordan’s tris(thioether)-
borate complex (PhTt )CoCl appears to be the only structur-
ally characterized example reported prior to this work. It is
also worth highlighting that, in general, the less constrained
geometry imposed by Tm vs. tris(pyrazolyl)borate (Tp
2
tBu
pursued independently (vide infra).
13
R
RRЈ
)
ligands in their metal complexes (i.e., formation of eight- vs
six-membered chelating rings) is reflected in average S–Co–S
tBu
and X–Co–S angles in (Tm )CoX (ca. 107.2 and 111.6Њ,
respectively) that clearly deviate less from the ideal tetrahedral
value than the typical N–Co–N and X–Co–N angles observed
RRЈ
in related halo complexes (Tp )CoX (ca. 94.7 and 121.9Њ,
Scheme 2
14
respectively). However, the related “soft” but sterically more
demanding tris(diphenylphosphino)borate ligand [PhB(CH
tBu
-
2
The molecular structures of the complete series (Tm )CoX
X = Cl, Br, I) were established by X-ray crystallography, with
that of the bromo derivative illustrated in Fig. 3 and selected
bond lengths and angles for all three given in Table 1. The
isostructural four-coordinate complexes exhibit only slightly
distorted tetrahedral geometries in the solid state and display
Ϫ
PPh ) ] (PhBP ) does not always enforce pseudotetrahedral
2
3
3
(
coordination in cobalt() complexes, as verified for (PhBP )-
3
CoI, since the chloro and bromo analogues (PhBP )CoX
3
(
X = Cl, Br) are dimeric in the solid state and present approx-
15
imate square pyramidal geometries at their metal centers.
tBu
tBu Ϫ
The Co–X bond lengths in (Tm )CoX (2.233, 2.382 and
.577 Å for X = Cl, Br, and I, respectively) are very close to the
the three mercaptoimidazolyl groups of the [Tm ] ligand in a
propeller-like arrangement around the approximate C axis that
2
3
corresponding mean values (2.257, 2.387 and 2.564 Å) found in
contains the Co and B atoms, thereby resembling other com-
R
12
the Cambridge Structural Database (CSD) for such terminal
pounds of general formula (Tm )MX (M = Zn, Cd, Hg).
16
groups bound to tetracoordinate cobalt. Similarly, the Co–S
Significantly, mononuclear cobalt species having [CoS X] cores
3
tBu
bond distances in (Tm )CoX, all within the relatively narrow
range of 2.306 to 2.336 Å, are only slightly shorter than those in
Ph
9
Co(Tm ) (2.370 and 2.372 Å) and are also comparable to
2
those in the related bis(mercaptoimidazolyl)(pyrazolyl)borate
Me
17
complex Co(pzBm )2 (2.303–2.320 Å) and other four-
coordinate thione complexes of cobalt present in the CSD
16
(
mean = 2.308 Å).
tBu
Synthesis and molecular structure of Co(Tm )2
tBu
In contrast to the syntheses of (Tm )CoX (X = Cl, Br, I), the
tBu
dark green homoleptic cobalt() complex Co(Tm )2 was easily
prepared by reacting CoBr with a slight excess of the sodium
2
tBu
reagent Na(Tm ) in methanol, and isolated in analytically
tBu
pure form as the disolvate Co(Tm )2ؒ2MeOH in ca. 80% yield.
tBu
Alternatively, base-free Co(Tm )2 could be obtained in
tBu
Fig. 3 Molecular structure of (Tm )CoBr.
ca. 40–60% yield by reacting CoBr with two molar equivalents
2
D a l t o n T r a n s . , 2 0 0 4 , 1 6 2 6 – 1 6 3 4
1627

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tBu
of Tl(Tm ) in dichloromethane. Like the halo complexes
(Y = BF , BPh , PF ) and the tetraphenylborate salts of the
4 4 6
tBu
tBu
described above, Co(Tm )2 is an air-stable paramagnetic com-
pound and exhibits similar physical and spectroscopic properties.
The molecular structure of Co(Tm )2 was determined by
chloro and iodo derivatives [Co (Tm ) X]BPh (X = Cl, I) were
2 2 4
tBu
isolated in 45–75% yield from the reactions of (Tm )CoX with
tBu
the appropriate NH Y salts in a 2 : 1 molar ratio (Scheme 3).
4
single-crystal X-ray diffraction (Fig. 4). The C -symmetric com-
The dark green (X = Br) or brown (X = Cl, I) paramagnetic
2
plex presents a central distorted tetrahedral [CoS ] core sup-
solids are soluble in chlorinated hydrocarbons (e.g., CH Cl ,
4
2
2
plemented by two relatively weak, adjacent Co ؒ ؒ ؒ H–B
CHCl ) or polar solvents such as acetone, acetonitrile, or
3
Ph
9
interactions and is thereby isostructural with Co(Tm ) . As
DMSO, and were characterized analytically and spectro-
scopically. Interestingly, ESI mass spectra of acetonitrile solu-
2
tBu
such, the Co–S bond length averages in both Co(Tm )2 and
Ph
tBu
Co(Tm ) are identical (2.371 Å) and the range of S–Co–S
tions of [Co (Tm ) Br]Y (Y = BF , BPh , PF ) were almost
2
2
2
4
4
6
tBu
bond angles in the former (90.9–127.9Њ) is also very similar to
that in the latter (92.7–134.9Њ). The Co ؒ ؒ ؒ H distances in
identical to that of (Tm )CoBr in the same solvent and exhibit
tBu ϩ
prominent peaks corresponding to the [(Tm )Co] (m/z =
R
t
tBu
ϩ
tBu
ϩ
Co(Tm ) (2.20 Å for R = Bu , 2.11 Å for R = Ph), while signifi-
536), [(Tm )Co(NCMe)] (m/z = 577), and [Co (Tm )2Br]
2
2
cantly longer than those in terminal hydride complexes of
cobalt (which are typically 1.35–1.65 Å), are within the range
(m/z = 1153) molecular ions. Although we are uncertain
16
whether an equilibrium between the mononuclear and di-
tBu
of values observed for such bonds in cobalt poly(pyrazolyl)-
nuclear species is quickly established in solution or [(Tm )-
18
ϩ
borate (Bp or Tp) derivatives. It is also worth mentioning that
Co(NCMe)] is being generated by fragmentation of the latter,
3
although the κ -S,S,H coordination mode is not common in
even at low cone voltages, we note that solution NMR data for
R
tBu
tBu
Tm chemistry, and structurally characterized examples thereof
(Tm )CoX and [Co (Tm )2X]Y are rather different (vide
2
1
9
R
are rare, such bonding scheme is the norm in Bm com-
infra). With regards to the nature of the dinuclear complexes,
20
plexes and has also been found for one of the two mixed-
donor ligands present in Co(pzBm ) . Furthermore, the
structure of Co(Tm )2, together with those of its zinc and
cadmium analogues, also allows for a direct comparison of a
series of isosteric complexes having sulfur-rich metal centers.
we initially considered that they could be the halide-bridged
Me
17
tBu
tBu
ϩ
species [(Tm )Co(µ-X)Co(Tm )] , plausibly generated from
tBu tBu ϩ
2
tBu
6e
either the reaction of (Tm )CoX with [(Tm )Co(NCMe)] or
halide loss from a putative doubly-bridged neutral derivative
(Tm )Co(µ-X) Co(Tm ). However, the observation of six
2
1
tBu
tBu
2
tBu
1
tBu
For example, while the Zn–S bond lengths in Zn(Tm )2 (in the
main peaks in the H NMR spectra of [Co (Tm )2X]Y, which
2
range 2.356–2.413 Å) are virtually identical to the corre-
sponding values in the cobalt complex, the Cd–S bond dis-
we have tentatively assigned to six magnetically inequivalent
tert-butyl groups, implied the existence in solution of a more
asymmetric species, which was not fluxional in the NMR time
scale.
tBu
tances in Cd(Tm )2 (2.559 and 2.564 Å) are predictably
22
longer. More interestingly, it appears that the cadmium com-
plex is the one whose geometry deviates less from tetrahedral
tBu
since the span of S–Cd–S bond angles in Cd(Tm ) (100.7–
2
tBu
1
19.2Њ) is clearly more limited than those in either Zn(Tm )2
tBu
(
85.6–118.6Њ) or Co(Tm )2 (90.9–127.9Њ).
Scheme 3
Elucidation of the structure of the dinuclear complexes
was finally achieved by an X-ray diffraction study of the
tBu
hexafluorophosphate derivative [Co (Tm )2Br]PF6 (Fig. 5).
2
Selected bond lengths and angles are listed in Table 2. The two
cobalt atoms in the dinuclear complex are held together by the
tBu Ϫ
two [Tm
]
ligands, both of which exhibit unprecedented
bridging tetradentate coordination modes. More specifically,
tBu Ϫ
whereas the [Tm
] ligand centered on B(1) coordinates in a
2 3
bidentate:tridentate (µ-κ -S,S:κ -S,S,H ) fashion, with one of
tBu
Fig. 4 Molecular structure of Co(Tm )2 showing the Co atom in a
crystallographically imposed two-fold rotation axis. The shortest
intermolecular contact for the sulfur atom not involved in coordination
to the cobalt center [i.e., S(3)], at 2.89(1) Å, is with a methyl H atom of a
neighbouring molecule. The additional “A” letters in the atom labels
correspond with atoms at equivalent position (1 Ϫ x, 1/2 Ϫ y, z).
Selected bond lengths (Å) and angles (Њ): Co(1)–S(1) 2.3804(5), Co(1)–
S(2) 2.3607(5), Co(1) ؒ ؒ ؒ H 2.201; S(1)–Co(1)–S(1A) 90.88(3), S(1)–
Co(1)–S(2) 106.54(2), S(1)–Co(1)–S(2A) 109.39(2), S(2)–Co(1)–S(2A)
1
8
27.86(3), S(1)–Co ؒ ؒ ؒ H 171.3, S(2)–Co ؒ ؒ ؒ H 73.5, S(1A)–Co ؒ ؒ ؒ H
1.0, S(2A)–Co ؒ ؒ ؒ H 76.2.
tBu
Synthesis and characterization of [Co (Tm )2X]Y
2
We found that several weakly nucleophilic (“non-coordin-
ating”) anions could be used to isolate salts of the dinuclear
tBu
ϩ
cationic complexes [Co (Tm )2X] (X = Cl, Br, I), first
2
detected in the ESI mass spectra of acetonitrile solutions of
tBu
tBu
tBu
(
Tm )CoX. Thus, the bromo compounds [Co (Tm )2Br]Y
Fig. 5 Molecular structure of the cation in [Co (Tm ) Br]PF .
2
2
2
6
1
628
D a l t o n T r a n s . , 2 0 0 4 , 1 6 2 6 – 1 6 3 4

View Article Online
Scheme 4
tBu
Table 2 Selected bond lengths (Å) and angles (Њ) for [Co (Tm ) -
resolved resonances between Ϫ8 and 17 ppm (Fig. 6). ESI mass
2
2
Br]PF6
tBu
spectra of acetonitrile solutions of [(Tm )Co(PPh )]X present
3
tBu
ϩ
the expected peak corresponding to the [(Tm )Co(PPh )]
3
Co(1)–S(12)
Co(1)–S(22)
Co(1) ؒ ؒ ؒ H(1)
Co(2)–Br
2.4405(15)
2.3505(15)
2.26(5)
2.3701(9)
2.3393(15)
Co(1)–S(13)
Co(1)–S(23)
Co(1) ؒ ؒ ؒ H(2)
Co(2)–S(11)
Co(2)–S(21)
2.3789(16)
2.3296(17)
2.02(5)
2.3127(17)
2.3278(16)
molecular ion (m/z = 798) in addition to those assigned to the
tBu
ϩ
tBu
ϩ
[
(Tm )Co] (m/z = 536) and [(Tm )Co(NCMe)] (m/z = 577)
fragments.
Co(2)–S(12)
S(12)–Co(1)–S(13) 103.53(6)
S(12)–Co(1)–S(22) 97.69(6)
S(12)–Co(1)–S(23) 145.00(6)
S(23)–Co(1)–H(1)
S(23)–Co(1)–H(2)
H(1)–Co(1)–H(2)
83.3(13)
79.6(13)
97.4(18)
S(12)–Co(1)–H(1)
S(12)–Co(1)–H(2)
S(13)–Co(1)–S(22)
S(13)–Co(1)–S(23)
S(13)–Co(1)–H(1)
S(13)–Co(1)–H(2) 176.3(13)
S(22)–Co(1)–S(23) 107.57(6)
S(22)–Co(1)–H(1) 168.9(12)
71.4(12)
80.0(13)
97.77(5)
96.75(6)
82.8(12)
S(11)–Co(2)–Br
S(12)–Co(2)–Br
S(21)–Co(2)–Br
S(11)–Co(2)–S(12)
S(11)–Co(2)–S(21)
S(12)–Co(2)–S(21)
116.46(5)
107.41(5)
105.77(5)
116.54(5)
108.14(6)
100.87(6)
S(22)–Co(1)–H(2)
82.7(13)
Co(1)–S(12)–Co(2) 104.52(6)
the thione moieties directly linked to both metal centers, the
other exhibits a unidentate:tridentate (µ-κ -S:κ -S,S,H ) co-
1
tBu
1
3
Fig. 6 H NMR spectrum of [(Tm )Co(PPh )]PF in CDCl .
3 6 3
ordination mode. It is worth noting that while dinuclear or
R
Several attempts to obtain the molecular structure of a
tBu ϩ
higher nuclearity Tm complexes are not common, a related
2
2
[(Tm )Co(PPh )] complex were thwarted by the poor quality
3
bridging bidentate:bidentate (µ-κ -S,S:κ -S,S) binding has
Me
23
of the crystals or severely disordered counterions. The best data
been observed in dimeric [Ag(Tm )] . The structure of
2
tBu
set and refinement (R = 9.9%) was obtained for the hexa-
[
Co (Tm ) Br]PF is also remarkable because of the two dis-
2 2 6
tBu
fluorophosphate derivative [(Tm )Co(PPh )]PF6 co-crystal-
3
tinctive coordination environments observed for the cobalt
centers: (i) distorted octahedral six-coordinate [CoS H ] for
lized with 0.5 equiv of NH PF . As illustrated in Fig. 7,
4
6
4
2
tBu
ϩ
[
(Tm )Co(PPh )] displays in the solid state a slightly dis-
3
Co(1), with two thione groups and one B–H bond from each
tBu Ϫ
torted tetrahedral geometry with a crystallographically
imposed three-fold rotation axis containing the Co and P
[Tm
]
ligand interacting with the metal, thereby resembling
R
t
the Co(Tm ) (R = Bu , Ph) complexes described above, and (ii)
2
atoms. Surprisingly, there is only one mononuclear four-co-
distorted tetrahedral four-coordinate [CoS Br] for Co(2), with
3
16
tBu Ϫ
ordinate cobalt compound having a [CoS P] core in the CSD,
3
two thione groups from one [Tm ] ligand, one from the other,
and a terminal bromide surrounding the cobalt atom. Accord-
ingly, whereas the bond angles around Co(1) span the substan-
tial range of 71.4 to 176.3Њ, those subtended at Co(2) vary only
between 100.9 and 116.5Њ. The Co–S bond distances are in the
narrow range 2.313–2.379 Å, with the exception of one of the
two bond lengths to the bridging thione group, which is moder-
ately longer (2.441 Å). The Co ؒ ؒ ؒ H distances (2.02 and 2.26
Å) are comparable to those observed in the homoleptic
R
t
Co(Tm ) (R = Bu , Ph) complexes mentioned above.
2
tBu
Synthesis and structure of [(Tm )Co(PPh )]X
3
tBu
All attempts to isolate the adducts [(Tm )Co(NCMe)]X,
tBu
including the reactions of (Tm )CoBr with one molar
equiv. of AgX (X = BF , PF ) in acetonitrile, invariably yielded
4
6
tBu
the dinuclear species [Co (Tm ) Br]X as the only cobalt-
containing products. Seeking to access related [(Tm )Co(L)]X
complexes with stronger donor ligands (L), we found that the
2
2
tBu
tBu
reaction of equimolar amounts of (Tm )CoBr and triphenyl-
phosphine in the presence of NH X (X = BPh , PF ) or NaSbF
tBu
4
4
6
6
Fig. 7 Molecular structure of the cation in [(Tm )Co(PPh )]PF ,
3 6
tBu
cleanly produced the bright green [(Tm )Co(PPh )]X com-
with thermal ellipsoids at the 30% probability level and carbon atoms
depicted with arbitrary radii due to high anisotropic displacements. The
cation has C symmetry, with the Co, P1 and B1 atoms on a three-fold
axis; the additional “A” and “B” letters in the atom labels correspond
with atoms at equivalent positions (2 Ϫ y, 1 ϩ x Ϫ y, z) and (1 Ϫ x ϩ y,
Ϫ x, z), respectively. Selected bond lengths (Å) and angles (Њ): Co–S
.266(3), Co–P 2.327(5), S–C 1.711(11); S–Co–S 110.40(8), S–Co–P
3
plexes in 60–70% yield (Scheme 4).
The air-stable paramagnetic (µeff = 4.8 µ ) solids are only
3
B
slightly soluble in diethyl ether and methanol but more so
in acetone, acetonitrile, chloroform, dichloromethane, and
DMSO. They were characterized analytically and spectro-
2
2
1
scopically and their H NMR spectra show six broad but well-
108.52(9), Co–S–C 97.2(4), Co–P–C 111.7(4).
D a l t o n T r a n s . , 2 0 0 4 , 1 6 2 6 – 1 6 3 4
1629

View Article Online
namely the tris(phenylthiolate) complex (Et N)[Co(SPh) -
Experimental
4
3
24
(
PPh )]. Although the S–Co–S and S–Co–P angles in
3
tBu
1
General considerations
[(Tm )Co(PPh )]PF6 (110.4 and 108.5Њ, respectively) are
3
tBu
within the range of those in (Tm )CoX, the Co–S bond dis-
tances (2.266 Å) are slightly shorter (ca. 0.04–0.07 Å) than the
All reactions were performed under aerobic conditions unless
otherwise noted, solvents were purified and degassed by stand-
ard procedures, and all commercially available reagents were
used as received. 2-Mercapto-1-tert-butylimidazole was pre-
pared as published. H and C NMR spectra were obtained
on General Electric QE 300 or Varian Gemini (300 MHz) FT
spectrometers. Chemical shifts are reported in ppm relative to
corresponding values in the latter. Similarly, the Co–P bond
tBu
length in [(Tm )Co(PPh )]PF6 (2.327 Å) does not deviate
3
significantly from either the corresponding value in (Et N)-
29
1
13
4
[
Co(SPh) (PPh )] (2.366 Å) or the mean value for such distances
3 3
in four-coordinate triphenylphosphine complexes of Co()
16
found in the CSD (2.379 Å).
SiMe (δ = 0 ppm) and were referenced internally with respect to
4
1
the solvent resonances [ H: δ 5.32 for CHDCl , 7.24 for CHCl ;
2
3
Structure of the first cobaltaboratrane
13
C: δ 53.8 for CH Cl ]; coupling constants are given in Hz. IR
2
2
spectra were recorded as KBr pellets on a Thermo Mattson
Satellite 3000 FT-IR spectrophotometer and are reported in
cm ; relative intensities of the absorptions are indicated in par-
While trying to crystallize the tetraphenylborate derivative
tBu
[
(Tm )Co(PPh )]BPh by slow diffusion of diethyl ether into
3 4
Ϫ1
an acetonitrile solution of the compound, single crystals of a
remarkably different complex were obtained (Fig. 8). Indeed,
activation of the B–H bond accompanied by formal reduction
of the metal center to Co() resulted in the formation of a five-
coordinate complex having a direct cobalt to boron dative
bond. Although a number of complexes exhibiting such inter-
entheses (vs = very strong, s = strong, m = medium, w = weak).
UV-Vis spectra were obtained using a Varian Cary 300 Bio
spectrophotometer. Electrospray ionization mass spectra were
obtained on a PerSeptive Biosystems Mariner ESI-TOF mass
spectrometer by direct infusion using dilute acetonitrile solu-
Ϫ1
25,26
tions and a flow rate of 10 µL min . Magnetic susceptibility
actions have been isolated in the last 40 years,
the first struc-
measurements were done at room temperature using a Johnson
turally authenticated transition metal borane complex, Hill’s
3
0
Me
Matthey magnetic susceptibility balance for solid samples
closely related ruthenaboratrane {B(mim ) }Ru(PPh )(CO),
3
3
31
27
or the Evans NMR method for solutions, with standard
diamagnetic correction factors applied to the data in each case.
Elemental analyses were determined by Atlantic Microlab, Inc.
has only recently been reported. The geometry of our cobalt-
tBu
aboratrane complex [{B(mim ) }Co(PPh )]BPh , having a
3
3
4
28
trigonality index (τ) of 0.94, can be aptly described as being
(
Norcross, GA).
trigonal bipyramidal and warrants a close comparison of its
metrical parameters with those of the phosphine derivative
tBu
tBu
2
Synthesis of Tl(Tm
)
[
(Tm )Co(PPh )]PF described above. For example, whereas
3 6
tBu
the S–Co–S angles in [(Tm )Co(PPh )]PF (110.4Њ) deviate
3
6
A suspension of NaBH (0.323 g, 8.53 mmol) and 2-mercapto-
4
only slightly from the ideal tetrahedral value, the correspond-
ing values in the cobaltaboratrane increase to an average of
1
-tert-butylimidazole (4.00 g, 25.6 mmol) in toluene (60 mL)
was heated to reflux for 3 days under an atmosphere of argon.
The reaction mixture was allowed to cool to room temperature
and the solvent was removed under reduced pressure to give
1
19.8Њ (with a concomitant increase in the sums of S–Co–S
angles from 331.2 to 359.3Њ, respectively). Conversely, the
S–Co–P angles in the former (108.5Њ) decrease to an average
of 92.8Њ in the latter. Interestingly, with the exception of the
tBu
crude Na(Tm ) as a white powder. The solid was dissolved in
methanol (140 mL) and the slightly cloudy solution was filtered
to separate a small amount of insoluble material. The clear
filtrate was treated with a solution of thallium() acetate (2.246
g, 8.53 mmol) in water (50 mL), resulting in the immediate
formation of a white solid suspended in a pale yellow solution.
The milky white suspension was stirred for an additional 30 min
and the product was isolated by filtration and dried in vacuo for
conspicuous shortening of the Co ؒ ؒ ؒ B separation, from 3.414
tBu
Å in [(Tm )Co(PPh )]PF to 2.132 Å in the cobaltaboratrane,
3
6
the remaining bond lengths do not change by more than ca.
.03 Å. We are now actively pursuing the rational synthesis of
0
tBu
[{B(mim ) }Co(PPh )]BPh and related metallaboratranes.
3 3 4
1
4 h (5.324 g, 92%). Mp = 220 ЊC (decomp.). NMR data (in
1
3
CD Cl ): H δ 1.79 [s, 27 H, C(CH ) ], 6.00 (d, J = 2.0, 3 H,
imidazole H ), 6.92 (d, J
observed; C δ 28.8 [q, J
C(CH ) ], 116.2 (dd, J
2
2
3
3
H–H
3
= 2.0, 3 H, imidazole H ), BH not
= 128, 9 C, C(CH ) ], 58.8 [s, 3 C,
= 196, J
H–H
13
1
C–H
3 3
1
2
= 12, 3 C, imidazole C),
3
3
C–H
2
C–H
1
1
18.7 (dd, J
= 190, J
= 10, 3 C, imidazole C), 160.9 (s, 3
C–H
C–H
C, C᎐S). IR data: 3146 (w), 2963 (m), 2922 (m), 2451 (w), 1560
᎐
(
w), 1481 (w), 1407 (s), 1397 (m), 1357 (vs), 1270 (m), 1223 (m),
1
7
5
200 (s), 1164 (s), 1101 (m), 1057 (w), 981 (w), 927 (w), 820 (w),
16 (m), 684 (m). Anal. Calc. for C H BN S Tl: C, 37.0; H,
.0; N, 12.3. Found: C, 36.5; H, 5.2; N, 11.9%.
21
34
6 3
tBu
3
Synthesis of (Tm )CoCl
tBu
A solution of Tl(Tm ) (0.200 g, 0.293 mmol) in dichloro-
methane (8 mL) was added dropwise to a stirred blue suspen-
sion of CoCl (0.038 g, 0.29 mmol) in the same solvent (5 mL),
2
resulting in the immediate formation of a white precipitate
(TlCl) and a green solution. The suspension was stirred for 1 h
and filtered. Concentration of the filtrate under reduced pres-
sure to ca. 3 mL and addition of diethyl ether (15 mL) resulted
in the separation of a green solid, which was isolated by fil-
tBu
Fig. 8 Molecular structure of the cation in [{B(mim ) }Co(PPh )]-
3
3
BPh . Selected bond lengths (Å) and angles (Њ): Co–S(1) 2.2372(10),
Co–S(2) 2.2269(11), Co–S(3) 2.2400(9), Co–P 2.3581(10), Co–B(1)
4
2
1
.132(4), S(1)–C(11) 1.731(3), S(2)–C(18) 1.728(3), S(3)–C(115)
.725(3); S(1)–Co–S(2) 121.56(4), S(1)–Co–S(3) 120.18(4), S(2)–Co–
S(3) 117.56(4), P–Co–B(1) 177.88(11), S(1)–Co–P 94.30(4), S(1)–Co–
B(1) 86.79(10), S(2)–Co–P 90.36(3), S(2)–Co–B(1) 87.52(11), S(3)–Co–
P 93.68(3), S(3)–Co–B(1) 87.33(10), Co–S(1)–C(11) 101.12(12), Co–
S(2)–C(18) 101.03(12), Co–S(3)–C(115) 100.89(10), Co–P–C(21)
tration and dried in vacuo for 4 h (0.120 g, 72%). Mp = 220 ЊC
1
(
decomp.). H NMR data (in CDCl ): δ 0.2 (br s, 3 H, imidazole
3
H ), 0.4 (br s, 3 H, imidazole H ), 0.9 [br s, 27 H, C(CH ) ], BH
3
3
not observed. IR data: 3162 (w), 3134 (m), 3109 (w), 2976 (s),
2965 (s), 2926 (m), 2887 (w), 2662 (w), 2420 (w), 2305 (w), 2239
1
12.77(11), Co–P–C(27) 115.92(11), Co–P–C(213) 115.57(11).
1
630
D a l t o n T r a n s . , 2 0 0 4 , 1 6 2 6 – 1 6 3 4

View Article Online
(
w), 1567 (w), 1481 (w), 1457 (w), 1416 (s), 1398 (s), 1361 (vs),
C H B CoN O S : C, 49.0; H, 7.1; N, 15.6. Found: C, 48.7;
44 76 2 12 2 6
1
1
7
307 (m), 1297 (m), 1261 (m), 1196 (vs), 1175 (s), 1090 (m),
373 (m), 1029 (w), 929 (w), 822 (m), 782 (w), 760 (w), 744 (m),
31 (m), 684 (m), 589 (w), 549 (w), 494 (w), 470 (w). UV/Vis
H, 6.9; N, 15.6%.
tBu
7
Synthesis of [Co (Tm )2Cl]BPh4
2
Ϫ3
Ϫ1
Ϫ1
[MeCN, λmax/nm (10 ε/M cm )]: 226 (15.6), 245 (16.1), 377
tBu
A solution of (Tm )CoCl (0.045 g, 0.079 mmol) and NH BPh4
4
(
1.7), 661 (0.5), 700 (0.7), 746 (0.5). µeff = 4.9 µ . Anal. Calc. for
B
(
0.013 g, 0.039 mmol) in methanol (5 mL) was stirred for 1 h,
C H BClCoN S : C, 44.1; H, 6.0; N, 14.7. Found: C, 43.4; H,
5
2
1
34
6 3
resulting in a slow change in color from green to brown and the
formation of a brown solid. The product was separated by
decantation, washed with diethyl ether (5 × 1 mL) and dried in
.9; N, 14.2%.
tBu
4
Synthesis of (Tm )CoBr
1
vacuo for 18 h (0.034 g, 62%). Mp = 244 ЊC (decomp.). H NMR
tBu
data (in CDCl ): δ 1.1 [br s, 9H, C(CH ) ], 1.6 [br s, 9H,
A solution of Tl(Tm ) (0.306 g, 0.449 mmol) in dichloro-
methane (8 mL) was added dropwise to a stirred green suspen-
sion of CoBr (0.098 g, 0.45 mmol) in the same solvent (10 mL),
3
3 3
C(CH ) ], 5.8 [br s, 9H, C(CH ) ], 6.4–6.8 (m, 20 H, BPh ), 9.6
3
3
3
3
4
[
br s, 9H, C(CH ) ], 26.5 [br s, 9H, C(CH ) ], other peaks not
3
3
3
3
2
observed or unassigned due to the paramagnetic nature of the
complex. IR data: 3176 (w), 3055 (w), 2980 (m), 2930 (w), 1579
resulting in the immediate formation of a white precipitate
(
TlBr) and a green solution. The suspension was stirred for 1 h
(
w), 1561 (w), 1478 (w), 1416 (s), 1400 (w), 1368 (vs), 1292 (m),
and filtered. Concentration of the filtrate under reduced pres-
sure to ca. 3 mL and addition of diethyl ether (15 mL) resulted
in the separation of a light green solid, which was isolated by
1
6
202 (s), 1165 (s), 1120 (m), 1060 (m), 730 (m), 706 (m), 689 (w),
12 (w). Anal. Calc. for C H B ClCo N S : C, 55.5; H, 6.2;
66 88
3
2
12 6
N, 11.8. Found: C, 55.3; H, 6.0; N, 11.1%.
filtration and dried in vacuo for 3.5 h (0.208 g, 75%). Mp =
1
2
35 ЊC (decomp.). H NMR data (in CDCl ): δ Ϫ0.4 (br s, 3 H,
3
tBu
8
Synthesis of [Co (Tm )2Br]BF
imidazole H ), 0.7 (br s, 3 H, imidazole H ), 1.2 [br s, 27 H,
C(CH ) ], BH not observed. IR data: 3181 (w), 3143 (w), 3097
2
4
tBu
3
3
A solution of (Tm )CoBr (0.120 g, 0.195 mmol) and NH BF4
4
(
1
w), 2978 (m), 2927 (m), 2886 (w), 2410 (w), 2296 (w), 2236 (w),
565 (w), 1481 (w), 1418 (s), 1398 (m), 1362 (vs), 1306 (m), 1260
(
0.010 g, 0.097 mmol) in methanol (5 mL) was stirred for 1 h,
resulting in the formation of a dark green solid suspended in a
brownish solution. The product was separated by decantation,
washed with diethyl ether (5 × 1 mL) and dried in vacuo for 18 h
(
(
(
w), 1229 (m), 1195 (vs), 1174 (vs), 1131 (m), 1070 (m), 1030
w), 930 (w), 820 (w), 758 (m), 731 (m), 688 (m), 589 (w), 552
w), 494 (w), 455 (w). UV/Vis [MeCN, λmax/nm (10 ε/M
Ϫ3
Ϫ1
1
(
0.053 g, 44%). Mp = 249 ЊC (decomp.). H NMR data (in
Ϫ1
cm )]: 242 (16.4), 379 (1.8), 716 (0.7). µ = 4.8 µ . Anal. Calc.
for C H BBrCoN S : C, 40.9; H, 5.6; N, 13.6. Found: C, 40.9;
H, 5.6; N, 13.5%.
eff
B
CDCl ): δ 1.6 [br s, 9H, C(CH ) ], 1.8 [br s, 9H, C(CH ) ], 2.4 [br
3
3
3
3 3
21
34
6
3
s, 9H, C(CH ) ], 5.5 [br s, 9H, C(CH ) ], 9.3 [br s, 9H, C(CH ) ],
3
3
3
3
3 3
2
7.9 [br s, 9H, C(CH ) ], other peaks not observed or
3 3
unassigned due to the paramagnetic nature of the complex. IR
data: 3145 (w), 2976 (m), 2932 (w), 1561 (w), 1479 (w), 1417 (s),
1401 (w), 1368 (vs), 1297 (m), 1263 (w), 1203 (s), 1165 (s), 1122
tBu
5
Synthesis of (Tm )CoI
tBu
A solution of Tl(Tm ) (0.203 g, 0.298 mmol) in dichloro-
methane (6 mL) was added dropwise to a stirred green suspen-
(
m), 1060 (s), 820 (w), 730 (m), 689 (m). Anal. Calc. for
C H B BrCo F N S : C, 40.7; H, 5.5; N, 13.6. Found: C,
42
68
3
2
4
12 6
sion of CoI (0.093 g, 0.30 mmol) in the same solvent (4 mL),
2
3
9.5; H, 5.8; N, 12.9%.
resulting in the immediate formation of a white precipitate (TlI)
and a green solution. The suspension was stirred for 30 min and
filtered. Concentration of the filtrate under reduced pressure to
ca. 3 mL and addition of pentane (10 mL) resulted in the separ-
ation of a forest green solid, which was isolated by filtration and
tBu
9
Synthesis of [Co (Tm )2Br]BPh4
2
tBu
A solution of (Tm )CoBr (0.090 g, 0.146 mmol) and
NH BPh (0.025 g, 0.073 mmol) in methanol (8 mL) was stirred
4
4
1
dried in vacuo for 2 h (0.104 g, 53%). Mp = 205 ЊC (decomp.). H
for 1 h, resulting in the formation of a dark green solid sus-
pended in a brownish solution. The product was separated by
decantation, washed with diethyl ether (5 × 1 mL) and dried in
NMR data (in CDCl ): δ Ϫ0.2 (br s, 3 H, imidazole H ), 0.8 [br
3
s, 27 H, C(CH ) ], 1.0 (br s, 3 H, imidazole H ), BH not
3
3
1
observed. IR data: 3175 (w), 3147 (w), 3102 (w), 2978 (s), 2925
m), 2884 (w), 2665 (w), 2466 (w), 2440 (w), 2344 (w), 2254 (w),
685 (w), 1566 (m), 1482 (m), 1458 (w), 1420 (s), 1397 (s), 1362
vs), 1308 (s), 1259 (m), 1228 (m), 1196 (vs), 1176 (vs), 1138 (m),
vacuo for 18 h (0.082 g, 77%). Mp = 256 ЊC (decomp.). H NMR
(
1
(
1
7
[
(
1
data (in CDCl ): δ 1.4 [br s, 9H, C(CH ) ], 1.7 [br s, 9H,
3
3 3
C(CH ) ], 2.9 [br s, 9H, C(CH ) ], 5.7 [br s, 9H, C(CH ) ], 6.5–
3
3
3
3
3 3
6
.8 (m, 20 H, BPh ), 9.3 [br s, 9H, C(CH ) ], 28.1 [br s, 9H,
4
3
3
071 (m), 1028 (w), 981 (w), 929 (w), 820 (m), 759 (m), 735 (s),
26 (s), 687 (s), 589 (w), 551 (w), 494 (w), 454 (w). UV/Vis
C(CH ) ], other peaks not observed or unassigned due to the
3
3
paramagnetic nature of the complex. IR data: 3175 (w), 3055
(m), 2980 (m), 2931 (w), 1579 (w), 1561 (w), 1479 (w), 1416 (m),
1400 (w), 1368 (vs), 1292 (m), 1263 (w), 1231 (w), 1202 (s), 1165
Ϫ3
Ϫ1
Ϫ1
MeCN, λmax/nm (10 ε/M cm )]: 245 (25.5), 396 (2.3), 713
0.5). µeff = 4.5 µ . Anal. Calc. for C H BCoIN S : C, 38.0; H,
B 21 34 6 3
2.7; N, 5.2. Found: C, 39.1; H, 12.8; N, 5.4%.
(
(
s), 1119 (m), 1060 (m), 820 (w), 730 (m), 706 (m), 687 (w), 613
w). Anal. Calc. for C H B BrCo N S : C, 53.9; H, 6.0; N,
66
88
3
2
12 6
tBu
.
2
6
Synthesis of Co(Tm ) 2MeOH
11.4. Found: C, 53.5; H, 6.0; N, 11.5%.
Methanol (5 mL) was added to a mixture of CoBr (0.040 g,
2
tBu
1
0
Synthesis of [Co (Tm )2Br]PF
tBu
2
6
0
.18 mmol) and Na(Tm ) (0.200 g, 0.40 mmol), resulting in
tBu
the immediate formation of a dark green precipitate and a dark
green solution. After stirring for 1 h, the product was separated
by decantation, washed with diethyl ether (3 × 2 mL) and dried
A solution of (Tm )CoBr (0.090 g, 0.146 mmol) and NH PF6
4
(0.012 g, 0.0973 mmol) in methanol (3 mL) was stirred for 1 h,
resulting in the formation of a dark green solid suspended in a
brownish solution. The product was separated by decantation,
washed with diethyl ether (5 × 1 mL) and dried in vacuo for 18 h
1
in vacuo for 18 h (0.180 g, 79%). Mp = 242 ЊC (decomp.). H
NMR data (in CDCl ): δ Ϫ1.6 (br s), 0.8 (br s), 2.1 (br s), 3.47
3
1
(
s, 6H, CH OH), 4.6 (br s), 7.9 (br s), other peaks not observed
(0.063 g, 66%). Mp = 245 ЊC (decomp.). H NMR data (in
3
or unassigned due to the paramagnetic nature of the complex.
IR data: 3144 (w), 2976 (w), 2925 (w), 2428 (w), 2365 (w), 2344
CDCl ): δ 1.4 [br s, 9H, C(CH ) ], 1.8 [br s, 9H, C(CH ) ], 2.8 [br
3
3
3
3 3
s, 9H, C(CH ) ], 5.6 [br s, 9H, C(CH ) ], 9.3 [br s, 9H, C(CH ) ],
3
3
3
3
3 3
(
(
(
(
w), 1562 (w), 1410 (m), 1400 (m), 1363 (vs), 1295 (m), 1264
28.2 [br s, 9H, C(CH ) ], other peaks not observed or
3 3
m), 1200 (s), 1157 (m), 1096 (m), 823 (w), 778 (w), 717 (m), 680
unassigned due to the paramagnetic nature of the complex. IR
data: 2975 (w), 1655 (w), 1647 (w), 1637 (m), 1628 (m), 1561
(w), 1419 (m), 1400 (w), 1366 (vs), 1202 (s), 1165 (s), 1101 (s),
Ϫ3
Ϫ1
Ϫ1
m), 469 (w). UV/Vis [MeCN, λmax/nm (10 ε/M cm )]: 222
43.4), 273 (49.4), 412 (3.2). µeff = 4.5 µ . Anal. Calc. for
B
D a l t o n T r a n s . , 2 0 0 4 , 1 6 2 6 – 1 6 3 4
1631

D
a
l
t
o
n
T
r
a
n
s
.
Table 3 Crystal, intensity collection, and refinement data
tBu
tBu
tBu
tBu
tBu
tBu
(
0
Tm )CoClؒ
(Tm )CoBrؒ
CH Cl (2)
Co(Tm ) ؒ
[Co (Tm )2Br]-
[(Tm )Co(PPh )]PF ؒ
[{B(mim ) }Co(PPh )]-
2
2
3
6
3
3
tBu
.5C H (1)
(Tm )CoI (3)
C H (4)
PF (5)
0.5NH PF (6)
BPh ؒCH CN (7)
5
12
2
2
6
6
6
4
6
4
3
Formula
Formula weight
C23.5H BCoClN S
607.98
C H BBrCl CoN S
701.30
C H BCoIN S
663.36
C H B CoN S
1092.10
C H B BrCo F N PS
1297.80
C H BCoF N6.5P2.5S3
1025.21
C H B CoN PS
65 71 2 7 3
1157.99
40
6
3
22 36
2
6
3
21 34
6
3
48 74
2
12
6
42 68
2
2
6
12
6
39 51
9
Crystal system
Space group
a/Å
b/Å
c/Å
α/Њ
Orthorhombic
Fdd2 (no. 43)
35.234(2)
35.516(2)
9.4836(5)
90
Monoclinic
Monoclinic
Tetragonal
Orthorhombic
Fdd2 (no. 43)
34.694(2)
40.456(2)
19.3445(13)
90
90
90
27152(3)
16
Trigonal
Triclinic
¯
¯
P2 /c (no. 14)
P2 /n (no. 14)
I4 /a (no. 88)
P3 1c (no. 163)
11.460(2)
11.460(2)
44.773(9)
90
90
120
P1 (no. 2)
10.7637(18)
17.534(3)
18.649(3)
62.397(3)
82.260(3)
83.717(3)
3086.2(9)
2
1
1
1
9.5500(19)
32.730(7)
10.410(2)
90
111.11(3)
90
10.4384(12)
16.788(2)
16.2395(19)
90
90.499(2)
90
19.4434(12)
19.4434(12)
29.922(4)
90
90
90
β/Њ
90
90
γ/Њ
V/Å
3
11867.3(12)
16
3035.5(11)
4
2845.7(6)
4
11312.0(17)
8
5092.2(16)
4
Z
T /K
Radiation (λ/Å)
100(2)
0.71073
1.361
0.900
18911
100(2)
0.71073
1.535
2.288
34253
150(2)
0.71073
1.548
1.929
17307
150(2)
0.71073
1.283
0.569
35520
243(2)
0.71073
1.270
1.338
46620
150(2)
0.71073
1.337
0.609
14167
243(2)
0.71073
1.246
0.451
21220
Ϫ3
D /g cm
c
Ϫ1
µ(Mo-Kα)/mm
Reflections collected
Independent
6304 (0.0409)
7205 (0.0551)
6567 (0.0479)
6798 (0.0454)
15065 (0.0466)
1597 (0.0538)
13531 (0.0325)
reflections (Rint
Reflections
with I > 2σ(I )
)
5866
5845
4483
298
5279
289
9575
1377
7937
No. of parameters
302
325
676
155
722
R ; wR [I > 2σ(I )]
0.0397; 0.0944
0.0433; 0.0964
0.0547; 0.1689
0.0695; 0.1777
0.0513; 0.1349
0.0835; 0.1586
0.0407; 0.0992
0.0579; 0.1059
0.0502; 0.1279
0.0983; 0.1485
0.0992; 0.2691
0.1071; 0.2735
0.0550; 0.1291
0.1093; 0.1466
1
2
R ; wR (all data)
1
2

View Article Online
1
062 (s), 845 (s), 732 (w), 687 (w), 600 (w). Anal. Calc. for
H in Ph), 5.3 (br s, 3H, imidazole H ), 6.0 [br s, 27H, C(CH ) ],
m 3 3
C H B BrCo F N PS : C, 38.9; H, 5.3; N, 13.0. Found: C,
16.3 (br s, 6H, H or H in Ph), BH not observed. IR data: 3164
4
2
68
2
2
6
12
6
o
m
3
9.0; H, 5.4; N, 12.8%.
(w), 3137 (w), 2995 (w), 1637 (w), 1561 (w), 1479 (w), 1434 (m),
421 (m), 1399 (w), 1375 (w), 1362 (vs), 1310 (w), 1232 (w),
1191 (vs), 1096 (w), 1073 (w), 1030 (w), 748 (s), 696 (m), 656
1
tBu
1
1
Synthesis of [Co (Tm )2I]BPh4
2
(
4
vs), 522 (m), 496 (w). Anal. Calc. for C H BCoF N PS Sb: C,
5.3; H, 4.8; N, 8.1. Found: C, 45.3; H, 4.8; N, 8.2%.
tBu
39 49 6 6 3
A mixture of (Tm )CoI (0.040 g, 0.060 mmol) and NH BPh4
(
4
0.010 g, 0.030 mmol) was dissolved in methanol (5 mL), result-
ing in the formation, within a few minutes, of a light brown
suspension. After stirring for 2 h, the product was separated by
decantation, washed with diethyl ether (5 × 1 mL) and dried
1
5 X-Ray structure determinations
A summary of crystal data collection and refinement param-
eters for (Tm )CoClؒ0.5C H (1), (Tm )CoBrؒCH Cl (2),
(Tm )CoI (3), Co(Tm ) ؒC H (4), [Co (Tm ) Br]PF (5),
[(Tm )Co(PPh )]PF ؒ0.5NH PF (6), and [{B(mim )3}-
1
tBu
tBu
in vacuo for 18 h (0.018 g, 40%). Mp = 246 ЊC (decomp.). H
5
12
2
2
tBu
tBu
tBu
NMR data (in CDCl ): δ 1.2 [br s, 9H, C(CH ) ], 2.2 [br s,
3
3
3
2
6
6
2
2
6
tBu
tBu
9
6
9
H, C(CH ) ], 2.5 [br s, 9H, C(CH ) ], 5.4 [br s, 9H, C(CH ) ],
3
3
3
3
3
3
3 6 4 6
.6–6.9 (m, 20 H, BPh ), 9.0 [br s, 9H, C(CH ) ], 28.9 [br s,
Co(PPh )]BPh ؒCH CN (7) are given in Table 3. X-Ray diffrac-
3 4 3
4
3
3
H, C(CH ) ], other peaks not observed or unassigned due to
tion data were collected on Bruker APEX (1–4, 6) or Bruker P4
(5, 7) diffractometers equipped with SMART CCD detectors
[Mo-Kα (λ = 0.71073 Å)] at 100 (1, 2), 150 (3, 4, 6) or 243 K
(5, 7). Space groups for 1–6 were determined based on system-
atic absences. All data sets were treated with SADABS absorp-
tion corrections based on redundant multiscan data. Despite
repeated attempts of crystallization, compound 6 consistently
deposited as multiple, weakly diffracting crystalline masses. The
results presented here represent the best of several trials.
3
3
the paramagnetic nature of the complex. IR data: 3177 (w),
055 (w), 2981 (m), 2931 (w), 1579 (w), 1561 (w), 1479 (w), 1416
m), 1399 (w), 1367 (vs), 1293 (m), 1202 (s), 1165 (s), 1119 (w),
060 (w), 731 (m), 706 (m), 687 (w), 612 (w). Anal. Calc. for
C H B ICo N S : C, 52.2; H, 5.8; N, 11.1. Found: C, 52.4; H,
3
(
1
32
6
6
88
3
2
12 6
5
.9; N, 11.1%.
tBu
1
2
Synthesis of [(Tm )Co(PPh )]BPh4
3
tBu
The structures were solved using direct methods and differ-
ence map techniques, and were refined by full-matrix least
squares procedures on F . All non-hydrogen atoms were refined
A mixture of (Tm )CoBr (0.045 g, 0.073 mmol), PPh (0.019
3
g, 0.072 mmol), and NH BPh (0.025 g, 0.073 mmol) in meth-
4
4
2
anol (3 mL) led to the formation, within 5 min, of a bright
green solid suspended in a dark green solution. After stirring
for 1 h, the product was separated by decantation, washed with
diethyl ether (3 × 1 mL) and dried in vacuo for 14 h (0.057 g,
0%). Mp = 237 ЊC (decomp.). H NMR data (in CDCl ):
with anisotropic displacement parameters. Hydrogen atoms
were treated as idealized contributions. The Flack parameters
for the non-centrosymmetrical structures of 1 and 5 are 0.05(2)
and 0.000(9), respectively. Highly disordered pentane, benzene,
1
7
3
Ϫ
6
and NH PF molecules (in 1, 4 and 6, respectively) and the PF
4
6
δ Ϫ7.0 (br s, 3H, H in Ph), Ϫ6.5 (br s, 3H, imidazole H ), Ϫ4.5
p
counterion (in 6) were treated with the SQUEEZE bypass filter
(
2
br s, 6H, H or H in Ph), 5.1 (br s, 3H, imidazole H ), 5.9 [br s,
o m
33
of PLATON. Whereas the correction of 307 electron/cell for 1
7H, C(CH ) ], 6.7–7.2 (m, 20H, BPh ), 16.3 (br s, 6H, H or H
3 3 4 o m
and 4 are close to the required value (336 electron/cell), the
experimental correction of 121 electron/cell for 6 is low and is
attributed to less-than-ideal crystal quality. All software and
sources of scattering factors are contained in the SHELXTL
in Ph), BH not observed. IR data: 3173 (w), 3142 (w), 3055 (w),
981 (m), 2932 (w), 1655 (w), 1578 (w), 1561 (w), 1478 (m), 1420
m), 1399 (w), 1364 (vs), 1312 (w), 1262 (w), 1230 (w), 1194 (s),
096 (m), 1071 (w), 1031 (w), 820 (w), 733 (s), 706 (s), 692 (s),
12 (m), 521 (w). µeff = 4.8 µ . Anal. Calc. for C H B -
2
(
1
6
32
(
5.10) program package.
B
63 69
2
CCDC reference numbers 229395–229401.
See http://www.rsc.org/suppdata/dt/b4/b401056f/ for crystal-
lographic data in CIF format.
CoN PS : C, 67.7; H, 6.2; N, 7.5. Found: C, 67.6; H, 6.3; N,
6
3
7
.5%.
tBu
1
3
Synthesis of [(Tm )Co(PPh )]PF6
3
tBu
Acknowledgements
A mixture of (Tm )CoBr (0.090 g, 0.146 mmol), PPh3
(
0.038 g, 0.145 mmol), and NH PF (0.024 g, 0.147 mmol) in
4 6
We thank the Camille and Henry Dreyfus Foundation, Inc. for
a Henry Dreyfus Teacher-Scholar Award to D. R., Research
Corporation for a Cottrell College Science Award, the donors
of the Petroleum Research Fund, administered by the Ameri-
can Chemical Society, the National Science Foundation (Award
No. CHE-0316723) and The University of North Carolina at
Charlotte for support of this research. D. J. M. and J. L. W. are
particularly grateful to the Thomas D. Walsh Tuition Fellow-
ship Fund for financial assistance.
methanol (5 mL) led to the formation, within 5 min, of a bright
green solid suspended in a dark green solution. After stirring
for 1 h, the product was separated by decantation, washed with
diethyl ether (2 × 2 mL) and dried in vacuo for 18 h (0.080 g,
5
Ϫ6.9 (br s, 3H, H in Ph), Ϫ6.3 (br s, 3H, imidazole H ), Ϫ4.4
(
2
1
8%). Mp = 229 ЊC (decomp.). H NMR data (in CDCl ): δ
3
p
br s, 6H, H or H in Ph), 5.3 (br s, 3H, imidazole H ), 6.0 [br s,
o m
7H, C(CH ) ], 16.3 (br s, 6H, H or Hm in Ph), BH not
3 3 o
observed. IR data: 3163 (w), 3136 (w), 2996 (w), 1560 (w), 1480
w), 1434 (w), 1421 (w), 1400 (w), 1362 (s), 1311 (w), 1232 (w),
(
1
5
2
192 (s), 1096 (w), 1073 (w), 838 (vs), 748 (s), 696 (m), 556 (m),
References and notes
Ϫ3
Ϫ1
Ϫ1
21 (w), 497 (w). UV/Vis [MeCN, λmax/nm (10 ε/M cm )]:
58 (24.9), 390 (2.5), 701 (0.6). Anal. Calc. for C H BCoF -
1
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39
49
6
N P S : C, 49.6; H, 5.2; N, 8.9. Found: C, 49.7; H, 5.2; N, 9.0%.
6
2 3
2
3
S. Trofimenko, Scorpionates: The Coordination Chemistry of
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tBu
1
4
Synthesis of [(Tm )Co(PPh )]SbF6
3
tBu
A mixture of (Tm )CoBr (0.045 g, 0.073 mmol), PPh (0.019
g, 0.072 mmol), and NaSbF (0.019 g, 0.073 mmol) in methanol
5 mL) led to the formation, within 5 min, of a bright green
solid suspended in a dark green solution. After stirring for 2 h,
the product was separated by decantation, washed with diethyl
ether (3 mL) and dried in vacuo for 18 h (0.050 g, 66%). Mp =
21 ЊC (decomp.). H NMR data (in CDCl ): δ Ϫ6.8 (br s, 3H,
H in Ph), Ϫ6.3 (br s, 3H, imidazole H ), Ϫ4.4 (br s, 6H, H or
3
4 M. R. St.-J. Foreman, A. F. Hill, A. J. P. White and D. J. Williams,
6
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(
5
1
181.
6
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T. Hascall and G. Parkin, J. Chem. Soc., Dalton Trans., 2000, 891;
1
2
3
p
o
D a l t o n T r a n s . , 2 0 0 4 , 1 6 2 6 – 1 6 3 4
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(
4
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9
(
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1
1
1
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6 CSD Version 5.25 (November 2003 ϩ January 2004 update). 3D
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1
634
D a l t o n T r a n s . , 2 0 0 4 , 1 6 2 6 – 1 6 3 4