Structural diversity in a family of copper(I) thioether complexes

Article abstract of DOI:10.1021/ic010273a

Copper(I) complexes of the tridentate thioether ligands [PhB(CH₂SCH₃)₃] (abbreviated PhTt), [PhB(CH₂SPh)₃] (PhTt^Ph), [PhB(CH₂S^tBu)₃] (PhTt^tBu), and [PhB(CH₂S^PTol)₃] (PhTt^pTol) and bidentate thioether ligands [Ph₂B(CH₂SCH₃)₂] (Ph₂Bt), [Et₂B(CH₂SCH₃)₂] (Et₂Bt), and [Ph₂B(CH₂SPh)₂] (Ph₂Bt^Ph) have been prepared and characterized. The solution and solid state structures are highly sensitive to the identity of the borato ligand employed. Ligands possessing the smaller (methylthio)methyl donors, [PhTt] and [Ph₂Bt], yielded tetrameric species, [(PhTt)Cu]₄ and [(Ph₂Bt)Cu]₄, containing both terminal and bridging thioether ligation. The ligands containing the larger (arylthio)methyl groups, [PhTt^Ph] and [PhTt^pTol], form monomeric [PhTt^Ar]Cu(NCCH₃) in solution and one-dimensional extended structures in the solid state. Each complex type reacted cleanly with acetonitrile, pyridine, or triphenylphosphine generating the corresponding four-coordinate monomer, of which [PhTt^Ph]Cu(PPh₃), [PhTt^pTol]Cu(PPh₃), and [Et₂Bt]Cu(PPh₃)₂ have been structurally characterized.

Full text of DOI:10.1021/ic010273a

4276
Inorg. Chem. 2001, 40, 4276-4283
Structural Diversity in a Family of Copper(I) Thioether Complexes
Carl Ohrenberg, Louise M. Liable-Sands, Arnold L. Rheingold, and Charles G. Riordan*
Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
ReceiVed March 12, 2001
Copper(I) complexes of the tridentate thioether ligands [PhB(CH2SCH3)3] (abbreviated PhTt), [PhB(CH2SPh)3]
(PhTtPh), [PhB(CH2StBu)3] (PhTttBu), and [PhB(CH2SpTol)3] (PhTtpTol) and bidentate thioether ligands [Ph2B(CH2-
SCH3)2] (Ph2Bt), [Et2B(CH2SCH3)2] (Et2Bt), and [Ph2B(CH2SPh)2] (Ph2BtPh) have been prepared and characterized.
The solution and solid state structures are highly sensitive to the identity of the borato ligand employed. Ligands
possessing the smaller (methylthio)methyl donors, [PhTt] and [Ph2Bt], yielded tetrameric species, [(PhTt)Cu]4
and [(Ph2Bt)Cu]4, containing both terminal and bridging thioether ligation. The ligands containing the larger
(arylthio)methyl groups, [PhTtPh] and [PhTtpTol], form monomeric [PhTtAr]Cu(NCCH3) in solution and one-
dimensional extended structures in the solid state. Each complex type reacted cleanly with acetonitrile, pyridine,
or triphenylphosphine generating the corresponding four-coordinate monomer, of which [PhTtPh]Cu(PPh3),
[PhTtpTol]Cu(PPh3), and [Et2Bt]Cu(PPh3)2 have been structurally characterized.
Introduction
Results and Discussion
Ligand Syntheses. The newly reported ligands, [PhTtpTol],
[Ph2BtPh], and [Et2Bt], were prepared following procedures
developed in these laboratories for [PhTt], [PhTttBu], [PhTtPh],
and [Ph2Bt].1,2 Briefly, the appropriate methyl sulfide was
quantitatively deprotonated by BuLi in the presence of TMEDA.
To this solution was added either PhBCl2, for preparation of
the tridentate ligands, or Ph2BBr or Et2B(OTs), for preparation
of the bidentate ligands. Isolation entailed precipitation of the
[Bu4N] salt. In some instances, e.g., [PhTttBu], greater yields
were achieved using cesium or thallium counterions. In general,
the yields of the bidentate ligands were significantly higher than
those for the corresponding tridentate ligand. Nonetheless, each
ligand may be prepared in multigram quantities. All ligands are
stable to air and moisture and freely soluble in THF, acetone,
acetonitrile, and chlorinated hydrocarbons. Spectroscopic data
and elemental analysis are contained in the Experimental
Section.
[(PhTt)Cu]4 and [(PhTtPh)Cu]∞. The syntheses and struc-
tures of [(PhTt)Cu]4 and [(PhTtPh)Cu]∞, reported previously,
highlight the structural diversity of this class of copper(I)
complexes, Scheme 1.6,7 In [(PhTt)Cu]4 each copper ion is
ligated by four thioethers in a roughly tetrahedral arrangement.
Two sulfurs are ligated terminally while the other two are
bridging between two adjacent metal ions. The solid state
structure persists in noncoordinating solvents. In chlorinated
hydrocarbons, the proton NMR spectrum of [(PhTt)Cu]4 clearly
supports the solid state structure. The terminal and bridging
thioethers are present as distinct sets of resonances. Coordinating
solvents or strong donor ligands such as phosphines or thiolates
disrupt the tetramer, yielding monomers of the composition
[PhTt]Cu(L).6 [(PhTtPh)Cu]∞ forms a one-dimensional infinite
chain structure in the solid state. Each copper ion is approxi-
mately four coordinate. Two sulfur donors are provided by a
single borato ligand while the third sulfur donor arises from a
second, adjacent borato unit. The copper ion coordination sphere
is completed by an η2-phenyl interaction from the latter ligand;
the η2-phenyl group coordinated through the ipso and one of
the ortho carbon atoms. Again, in coordinating solvents or in
In our continued exploration of the coordination and bio-
inorganic chemistry of the borato ligand class PhB(CH2SR)3
-
(abbreviated [PhTtR]),1-3 we report the preparation, character-
ization, and reactivity of a family of copper(I) complexes.
Significant features of the [PhTtR] ligands include the anionic
charge provided by the borate, the high polarizability of the
thioether donors, which contrasts the hard nitrogen donors of
the ubiquitous [Tp] ligands, and, most importantly, the synthetic
versatility that permits incorporation of a range of boron and
sulfur substituents.4 Indeed, there is now ready preparative
access to tridentate, [PhTtR], and bidentate, [Ph2BtR],5 derivatives
complemented with a range of alkyl and aryl thioether groups.
The resulting [S3] and [S2] donor sets impart unique electronic
and molecular structural properties to the attendant metal
complexes. Herein are reported the solution and solid state
structures for copper(I) complexes of the following ligands:
[PhTt], [PhTtPh], [PhTtpTol], [PhTttBu], [Ph2Bt], [Et2Bt], and [Ph2-
BtPh], Chart 1.6,7 For each ligand a complex of 1:1 empirical
stoichiometry was isolated. Solid state structures are highly
ligand dependent ranging from monomers, [(Ph2BtPh)Cu(CH3-
CN)2], to cyclic tetramers, [(PhTt)Cu]4 and [(Ph2Bt)Cu]4, to
extended chain structures, [(PhTtPh)Cu]∞, [(PhTtpTol)Cu]∞, and
[(PhTttBu)Cu]x. Nonetheless, each complex serves as a source
of monomeric [PhTtR]Cu or [Ph2BtR]Cu for binding the donors
acetonitrile, pyridine, and triphenylphosphine.
(1) Ohrenberg, C.; Ge, P.; Schebler, P.; Riordan, C. G.; Yap, G. P. A.;
Rheingold, A. L. Inorg. Chem. 1996, 35, 749-754.
(2) Schebler, P. J.; Riordan, C. G.; Guzei, I.; Rheingold, A. L. Inorg.
Chem. 1998, 37, 4754-4755.
(3) Chiou, S.-J.; Innocent, J.; Lam, K.-C.; Riordan, C. G.; Liable-Sands,
L.; Rheingold, A. L. Inorg. Chem. 2000, 39, 4347-4353.
(4) Chiou, S.-J.; Ge, P.; Riordan, C. G.; Liable-Sands, L.; Rheingold, A.
L. Chem. Commun. 1999, 159-160.
(5) Ge, P.; Riordan, C. G.; Yap, G. P. A.; Rheingold, A. L. Inorg. Chem.
1996, 35, 5408-5409.
(6) Ohrenberg, C.; Saleem, M. M.; Riordan, C. G.; Yap, G. P. A.;
Rheingold, A. L. Chem. Commun. 1996, 1081-1082.
(7) Ohrenberg, C.; Riordan, C. G.; Liable-Sands, L.; Rheingold, A. L.
Coord. Chem. ReV. 1998, 174, 301-311.
10.1021/ic010273a CCC: $20.00 © 2001 American Chemical Society
Published on Web 07/06/2001

Structural Diversity in Cu(I) Thioether Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4277
Chart 1
Scheme 1
the presence of donor ligands, the monomers, [PhTtPh]Cu(L),
predominate.
formation of a tetrameric structure containing a central Cu4S4
ring, similar to [(PhTt)Cu]4. The S-Cu-S bond angles range
from 93.13(8)° to 124.03(8)° with an average angle of 110.3°.
The smaller angles involve sulfur atoms from the same ligand.
Unlike [(PhTt)Cu]4, there is little difference between the average
Cu-Sbridge distance, 2.301 Å, and the average Cu-Sterminal
distance, 2.304 Å, in [(Ph2Bt)Cu]4. The average Cu-Cipso and
Cu-Cortho distances are 2.633 and 2.420 Å. Slightly different
from those distances seen in [(PhTtPh)Cu]∞ (2.68(1), 2.32(1) Å),
these lengths are in accord with η2-phenyl coordination.8
In contrast to [(PhTt)Cu]4, where the Cu4 unit is planar, the
Cu4 unit of [(Ph2Bt)Cu]4 is distorted toward a “butterfly”
[(Ph2Bt)Cu]4. The solid state structure of [(Ph2Bt)Cu]4
displays features present in both [(PhTt)Cu]4 and [(PhTtPh)Cu]∞,
Figure 1A, Table 1. Selected metric parameters are contained
in Table 2. The Cu coordination sphere is roughly tetrahedral
and contains a mixture of bridging and terminal thioether
ligands, as in [(PhTt)Cu]4, and the η2-phenyl ligation, as
observed in [(PhTtPh)Cu]∞. Here, the absence of a third thioether
arm requires the ligation of the phenyl rings to fulfill the
tetrahedron of the Cu(I) ions. Furthermore, the small methyl
substituents on sulfur permit for bridging thioethers and the

4278 Inorganic Chemistry, Vol. 40, No. 17, 2001
Ohrenberg et al.
Figure 1. Thermal ellipsoid plots of [(Ph2Bt)Cu]4 (A) and [(Ph2BtPh)Cu(CH3CN)2] (B) at the 30% probability level; hydrogen atoms are not
shown.
Table 1. Crystallographic Data for [(Ph2Bt)Cu]4‚Et2O‚CHCl3, [(Ph2BtPh)Cu(CH3CN)2], [(PhTtPh)Cu(PPh3)], [(PhTtpTol)Cu(PPh3)], and
[(Et2Bt)Cu(PPh3)2]
[(Ph2Bt)Cu]4‚Et2O‚CHCl3
[(Ph2BtPh)Cu(CH3CN)2]
[(PhTtPh)Cu(PPh3)]
[(PhTtpTol)Cu(PPh3)]
[(Et2Bt)Cu(PPh3)2]
formula
fw
color habit
cryst size, mm
cryst syst
space group
a, Å
C69H91B4Cl3Cu4OS8
1596.7
pale yellow rod
0.3 × 0.3 × 0.2
monoclinic
P21/n
12.1588(2)
31.0044(3)
19.9278(3)
94.023(1)
7493.8(2)
4
C30H30BCuN2S2
557.0
colorless plate
0.3 × 0.2 × 0.1
monoclinic
P21/c
11.1694(2)
11.8052(2)
21.8502(2)
101.548(1)
2822.8(1)
4
C45H31BCuPS3
783.3
colorless block
0.4 × 0.3 × 0.2
monoclinic
P21/c
12.060(6)
19.69(2)
16.98(2)
94.4(1)
4019(6)
4
C48H47BCuPS3
825.4
colorless block
0.5 × 0.4 × 0.4
monoclinic
C2/c
26.990(4)
13.864(3)
24.05(1)
109.54(3)
8482(5)
C44H50BCuP2S2
779.3
colorless rod
0.4 × 0.35 × 0.2
orthorhombic
P212121
12.9902(2)
14.8748(3)
21.4937(4)
90
4153.2(1)
4
b, Å
c, Å
â, deg
V, Å3
Z
8
T, K
203(2)
0.71073
1.415
14.90
173(2)
0.71073
1.311
9.43
293(2)
0.71073
1.294
7.70
5.32, 12.85
250(2)
0.71073
1.293
7.33
4.61, 11.32
198(2)
0.71073
1.246
7.33
λ, Å (Mo KR)
F(calc), g cm-3
µ(Mo KR), cm-1
R(F), Rw(F)a
6.07, 12.84
5.31, 8.66
4.96, 9.96
a Quantity minimized ) R(wF2) ) ∑[w(Fo - Fc2)2]/∑[(wFo )2]1/2; R ) ∑|Fo - Fc|/(Fo) × 100%.
2
2
1
arrangement of metal ions. As a consequence of this conforma-
tion, the Cu-Cu distances, 3.947, 3.948, 3.950, and 3.932 Å,
are shorter (on average, 0.27 Å shorter) than in [(PhTt)Cu]4.
The deviations of the copper atoms from the least squares plane
are as follows: Cu1, -0.522 Å; Cu2, 0.524 Å; Cu3, -0.524
Å; Cu4, 0.521 Å.
to result in upfield shifts of the H NMR signals for protons
attached to the carbons involved in the interaction.9 Notably,
the ortho protons of the η2-bound phenyl ring appear as a
doublet, inconsistent with the solid state structure. This result
implies that on the NMR time scale the ligated phenyl ring is
rapidly moving between two “static” structures in which the
metal is coordinated to the two different Cipso-Cortho bonds. The
diastereotopic methylene protons result from the rigidity of the
six-membered chelate ring. The singlets at δ 2.24 and 2.10
correspond to protons of the distinct bridging and terminal
thioether methyl groups, respectively, assigned by comparison
to the proton NMR spectrum of [(PhTt)Cu]4.6
The solution structure of [(Ph2Bt)Cu]4 is highly solvent
dependent. Proton NMR spectra of [(Ph2Bt)Cu]4 in CD3CN and
CDCl3 are shown in Figure 2. The spectrum in CD3CN displays
two peaks in the aliphatic region and a single set of aromatic
resonances which is consistent with the formation of a C2
symmetric monomer with two molecules of CD3CN coordinated
to the copper ion. However, the spectrum in CDCl3 is consider-
ably more complex and is consistent with the persistence of
the tetrameric solid state structure in solution. In the aromatic
region of the latter spectrum, two distinct sets of phenyl
resonances are present, arising from bonded and nonbonded
phenyl rings. The η2-coordination to the copper ion alters the
electronics of the bonded phenyl ring such that the ortho protons
are shifted considerably upfield, δ 6.72, while the meta and
para protons are shifted downfield, appearing as part of a
multiplet at δ 7.60. The binding of olefins to copper(I) is known
[(Ph2BtPh)Cu(CH3CN)2] and [(Ph2BtPh)Cu]x. As with
[PhTtPh], the reaction of Cu(I) with [Ph2BtPh] was expected to
result in the formation of an extended linear structure in the
solid state, [(Ph2BtPh)Cu]∞. Alternatively, the reaction could lead
to a monomer with ligation of two solvent molecules completing
the coordination sphere. Both products were formed depending
upon the reaction conditions. In acetonitrile, the monomer, [(Ph2-
BtPh)Cu(CH3CN)2], was formed, Scheme 1. This is the first
example in this series of complexes in which acetonitrile remains
(8) Pasquali, M.; Floriani, C.; Gaetani-Manfredotti, A. Inorg. Chem. 1980,
19, 1191-1197.
(9) Håkansson, M.; Lopes, C.; Jagner, S. Organometallics 1998, 17, 210-
215.

Structural Diversity in Cu(I) Thioether Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4279
Table 2. Selected Bond Distances (Å) and Angles (deg) for
[(Ph2Bt)Cu]4‚Et2O‚CHCl3, [(Ph2BtPh)Cu(CH3CN)2],
[(PhTtPh)Cu(PPh3)], [(PhTtpTol)Cu(PPh3)], and [(Et2Bt)Cu(PPh3)2]
[(Ph2Bt)Cu]4
Cu1-S2
Cu1-S7
Cu1-S1
Cu1-C75
Cu1-C76
Cu2-S1
Cu2-S4
Cu2-S3
Cu2-C11
Cu3-S3
Cu3-S6
Cu3-S5
Cu3-C31
Cu4-S7
Cu4-S5
2.306(2)
2.316(2)
2.324(2)
2.365(7)
2.528(8)
2.296(2)
2.301(2)
2.303(2)
2.433(7)
2.286(2)
2.300(2)
2.304(2)
2.511(8)
2.292(2)
2.292(2)
Cu4-S8
2.307(2)
2.374(7)
111.36(8)
93.13(8)
122.01(7)
114.84(8)
124.03(8)
94.57(7)
114.13(8)
122.51(7)
94.26(8)
Cu4-C55
S2-Cu1-S7
S2-Cu1-S1
S7-Cu1-S1
S1-Cu2-S4
S1-Cu2-S3
S4-Cu2-S3
S3-Cu3-S6
S3-Cu3-S5
S6-Cu3-S5
S7-Cu4-S5
S7-Cu4-S8
S5-Cu4-S8
122.29(8)
95.51(7)
114.89(8)
Cu1-N51
Cu1-N41
Cu1-S1
122.3(1)
112.9(1)
106.8(1)
108.4(1)
97.00(4)
Cu1-S2
N41-C41
N51-C51
1
Figure 2. (A) H NMR spectrum of [(Ph2Bt)Cu(CD3CN)2] in CD3-
[PhTtPh]Cu(PPh3)
CN, indicating the formation of a monomer in solution with single
1
Cu-P
2.201(2)
2.329(2)
2.331(2)
2.354(3)
119.92(8)
P-Cu-S1
S3-Cu-S1
P-Cu-S2
S3-Cu-S2
S1-Cu-S2
126.07(8)
96.81(9)
119.61(7)
93.81(8)
93.11(8)
BCH2 (#) and SCH3 (*) resonances. (B) H NMR spectrum of [(Ph2-
Cu-S3
Cu-S1
Cu-S2
P-Cu-S3
Bt)Cu]4 in CDCl3 showing diastereotopic methylene protons ()), a shift
in the η2-bound ortho protons (¥), and both terminal (‡) and bridging
(†) thioether methyl substituents.
[PhTtpTol]Cu(PPh3)
Cu-P
2.195(1)
2.309(2)
2.339(1)
2.355(1)
127.35(5)
P-Cu-S1
S3-Cu-S1
P-Cu-S2
S3-Cu-S2
S1-Cu-S2
121.41(4)
93.89(4)
116.19(4)
94.12(5)
96.84(4)
Cu-S3
Cu-S1
Cu-S2
P-Cu-S3
[Et2Bt]Cu(PPh3)2
Cu-P1
2.294(1)
2.318(1)
2.351(1)
2.371(1)
113.50(5)
P1-Cu-S1
P2-Cu-S1
P1-Cu-S2
P2-Cu-S2
S1-Cu-S2
116.21(5)
110.17(5)
117.19(4)
102.63(4)
95.04(4)
Cu-P2
Figure 3. Proposed solid state structure of [(Ph2BtPh)Cu]x.
Cu-S1
Cu-S2
Cu(CH3CN)2] are essentially superimposable, with the exception
of the two νCN stretches present for [(Ph2BtPh)Cu(CH3CN)2].
[(PhTttBu)Cu]n. Similar to [(Ph2Bt)Cu]4, [(PhTttBu)Cu] is
monomeric in coordinating solvents and oligomeric in non-
coordinating solvents. The 1H NMR spectrum of [(PhTttBu)Cu-
(CD3CN)] in acetonitrile displays two aliphatic resonances
corresponding to the tert-butyl and methylene protons consistent
P1-Cu-P2
coordinated. The coordinated acetonitrile ligands give rise to
two weak νCN vibrations at 2302 and 2277 cm-1 10
.
The molecular structure of [(Ph2BtPh)Cu(CH3CN)2], deter-
mined by X-ray diffraction, is contained in Figure 1B with
selected bond distances and angles in Table 2. The coordination
geometry about copper is roughly tetrahedral. The Cu-S bond
lengths are 2.394(1) and 2.311(1) Å. The S-Cu-S bond angle
of 97.00(4)° is similar to the borato bite angle observed for other
ligands of this class.5 In [(PhTtPh)Cu]∞ the angle is 98.42(7)°,
and in [(Ph2Bt)Cu]4 the angles range from 93.13(8)° to
95.51(7)°.7
1
with a C3 symmetric monomer. The H spectrum of the same
material in CDCl3 is consistent with a significantly lower
symmetry structure. Multiple resonances are present for the
methylene and aromatic protons. There are four distinct, equal
intensity signals for the tert-butyl substituents. Given the low
symmetry and the good solubility of the material, a low
nuclearity oligomeric structure is likely. Unfortunately, repeated
attempts to elucidate the nuclearity of this material by X-ray
structural analysis, ESI-MS analysis, and solution molecular
weight determination by osmometry proved unsuccessful.
Monomeric Pyridine Adducts. Each of the homoleptic
complexes, [(PhTt)Cu]4, [(PhTtPh)Cu]∞, [(PhTtpTol)Cu]∞, [(Ph-
TttBu)Cu]n, [(Ph2Bt)Cu]4, and [(Ph2BtPh)Cu]∞, reacts reversibly
with pyridine to form the appropriate four-coordinate monomer,
as determined by 1H NMR spectroscopy.6,7 For example,
dissolution of [(PhTttBu)Cu]n in d5-pyridine resulted in a high-
symmetry spectrum exhibiting single methylene and tert-butyl
signals in accord with C3 symmetric ligation of the borato ligand.
The spectrum is very similar to that recorded in CD3CN and
The reaction of [Cu(CH3CN)4][BF4] with [Ph2BtPh] in acetone
yielded a complex with the empirical formula [(Ph2BtPh)Cu].
By analogy to the crystallographically characterized [(PhTtPh)Cu‚
CH3CN]∞, a structure is proposed in which the copper coordina-
tion sphere contains two terminal thioether sulfurs and two η2-
ligation to phenyl borato substituents, Figure 3. The proton NMR
spectrum of [(Ph2BtPh)Cu]∞ in CD3CN is identical to the
spectrum of [(Ph2BtPh)Cu(CD3CN)2] in the same solvent.
Additionally, the FT-IR spectra of [(Ph2BtPh)Cu]∞ and [(Ph2BtPh)-
(10) Kubas, G. J. In Inorganic Synthesis; Shriver, D., Ed.; Wiley-
Interscience: New York, 1979; Vol. 19, pp 90-92.

4280 Inorganic Chemistry, Vol. 40, No. 17, 2001
Ohrenberg et al.
Table 3. 1H NMR Chemical Shifts of Borato Ligand Methylene
Protons in the PPh3 Complexes and the Corresponding Free Ligands
1
derivatives, and this distinction in the H NMR spectrum is
diagnostic for the formation of a monomeric complex.6
Furthermore, examination of the 1H NMR spectra of the Cu-
(I)-PPh3 complexes allows for assessment of the effects of
binding on the chemical shift of the thioether protons. This is
not possible in the case of the [(PhTtR)Cu]x complexes where
their oligomeric nature gives rise to complex spectra. One easily
observable trend is that the thioether methylene protons shift
downfield upon binding to copper.
PPh3
complex
δ SCH2,
free ligand
(L)
δ SCH2,
ppma
ppma
[(PhTt)Cu(PPh3)]
2.23
2.78
2.83
2.18
2.37
2.73
1.83
[Bu4N][PhTt]
[Bu4N][PhTtPh]
[Bu4N][PhTtpTol
1.97
2.40
2.34
1.81b
2.23
2.58
1.55
[(PhTtPh)Cu(PPh3)]
[(PhTtpTol)Cu(PPh3)]
[(PhTttBu)Cu(PPh3)]
[(Ph2Bt)Cu(PPh3)2]
[(Ph2BtPh)Cu(PPh3)2]
[(Et2Bt)Cu(PPh3)2]
]
Cs[PhTttBu
]
[Bu4N][Ph2Bt]
[Bu4N][Ph2BtPh]
[Bu4N][Et2Bt]
The 31P chemical shift data and full width at half peak
maximum for each of the PPh3 complexes is listed in Table 4
along with the chemical shifts for some related poly(pyrazolyl)-
borate Cu(I) complexes, including two bis(phosphine) com-
plexes, [pzTpCu(PPh3)2] and [BpCu(PPh3)2] (pzTp ) tetrakis-
(pyrazolyl)borate, Bp ) dihydridobis(pyrazolyl)borate).11 In all
cases the 31P{1H} NMR spectra of the PPh3 complexes exhibit
a single broad resonance at room temperature. Addition of 1
equiv of PPh3 to a solution of [(PhTt)Cu(PPh3)] in CDCl3 causes
the 31P resonance to move upfield toward free PPh3, shifting
from δ 7.39 to 0.39. The observation of a single broad peak in
the presence of excess PPh3 is consistent with fast exchange
between bound and free PPh3. This phenomenon has been
documented for related [Tp] complexes.12 In all cases, the 31P
resonances occur upfield of free PPh3 (-6.0 ppm).13 The
chemical shift differences between [(Ph2BtR)Cu(PPh3)2] and free
PPh3 are considerably smaller than the differences between
[(PhTtR)Cu(PPh3)] and free PPh3 due to a greater shielding of
the phosphorus atom. This observation is likely a result of a
weaker interaction between the phosphorus and copper caused
by steric crowding around the metal atom, preventing closer
access to the Cu(I) ion. This is supported by the longer Cu-P
bond lengths in [(Et2Bt)Cu(PPh3)2] and is suggested to occur
in [Tp*Cu(PCy3)] (Tp* ) hydridotris(3,5-dimethylpyrazolyl)-
borate) where there are steric interactions between the bulky
cyclohexyl groups and the methyl substituents of the borato
ligand preventing the phosphine from coming closer to the
copper ion.14 It is interesting to note that in the poly(pyrazolyl)-
borate complexes the 31P chemical shifts of the bis triphen-
ylphosphine complexes are displaced upfield relative to the
mono triphenylphosphine derivatives.
(c) Molecular Structures of PPh3 Adducts. The structures
of [(PhTtPh)Cu(PPh3)],7 [(PhTtpTol)Cu(PPh3)], and [(Et2Bt)Cu-
(PPh3)2] have been determined by X-ray crystallography, Table
1. The thermal ellipsoid plots of [(PhTtpTol)Cu(PPh3)] and [(Et2-
Bt)Cu(PPh3)2] are contained in Figure 4. Table 2 lists pertinent
structural parameters for the three molecules. In each complex,
the Cu(I) ion is in a roughly tetrahedral environment. The
tetrahedral coordination sphere is completed by PPh3 ligation,
the number of which is dictated by the denticity of the borate
ligand. All of the S-Cu-S bond angles are smaller than that
for a perfect tetrahedron, ranging from 91.34(4)° to 98.37(4)°.
As seen before in the [(PhTtR)Cu(PPh3)] and [(Ph2BtR)Cu-
(PPh3)2] complexes, this is a consequence of the inherent bite
of the ligand. This results in correspondingly wide P-Cu-S
angles, with an average of 118.5°. The Cu-S distances in the
[(PhTtR)Cu(PPh3)] complexes are in the same range as those
seen for the [(PhTtR)Cu]n complexes. The Cu-P bond distances
lie within the range reported for other known Cu(I) phosphine
b
a CDCl3. As the Cs(I) salt in (CD3)2SO; δ 2.38 as the Tl(I) salt in
CDCl3.
Table 4. 31P{1H} NMR Spectral Data for PPh3 Complexes and
Selected [TpRR′Cu(PPh3)n] Complexes
δ,
fwhm,
Hz
δ,
ppma
ppmb
[(PhTt)Cu(PPh3)]
7.39 595 [TpCu(PPh3)]15
-6.12c
[(PhTtPh)Cu(PPh3)]
[(PhTtpTol)Cu(PPh3)]
[(PhTttBu)Cu(PPh3)]
[(Ph2Bt)Cu(PPh3)2]
[(Ph2BtPh)Cu(PPh3)2]
[(Et2Bt)Cu(PPh3)2]
6.16 340 [TpMeCu(PPh3)]d15 -4.92
6.28 284 [Tp*Cu(PPh3)]d15
-4.99
5.49 567 [Tp*ClCu(PPh3)]d15 -5.00
0.89 181 [pzTpCu(PPh3)2]11
0.07 255 [BpCu(PPh3)2]11
-3.20 124
0.41
-1.92
a CDCl3, referenced vs 85% H3PO4 as external standard. bCDCl3, δ
in ppm from TMS, calibrated against internal deuterium solvent peak.
cMeasured at -40 °C. TpMe ) hydridotris(3-methylpyrazolyl)borate,
d
Tp* ) hydridotris(3,5-dimethylpyrazolyl)borate, Tp*Cl ) hydridotris-
(4-chloro-3,5-dimethylpyrazolyl)borate.
assigned as [(PhTttBu)Cu(CD3CN)]. Therefore, the structure of
the species in pyridine is monomeric [(PhTttBu)Cu(py)]. Further
support for this assignment comes from spectral and structural
characterization of the PPh3 adducts, described below. Pyridine
is competitive with acetonitrile binding as evidenced by NMR
spectral titrations of [(PhTtPh)Cu(CD3CN)] in CD3CN. At 25
°C, Keq for pyridine binding is 300 M-1. The tetramer, [(PhTt)-
Cu]4, binds pyridine much less avidly, even in noncoordinating
solvents. At 25 °C, Keq for pyridine in CDCl3 is 1 × 10-2 M-1
.
The dramatic 105 difference in Keq for pyridine binding to
[(PhTtPh)Cu(CD3CN)] versus [(PhTt)Cu]4 is likely a conse-
quence of the nature of the initial Cu(I) complexes in solution.
[(PhTt)Cu]4 is tetrameric in CDCl3, and the disassembly of this
structure is required in order for the formation of the pyridine
complex to occur, while the latter is already a monomer in CD3-
CN and only requires the displacement of a solvent molecule
for the formation of the pyridine adduct.
Phosphine Complexes. (a) Synthesis. Two routes were
employed in the synthesis of [(PhTtR)Cu(PPh3)] and [(Ph2BtR)-
Cu(PPh3)2] derivatives. In the first approach, the complexes were
prepared by reacting PPh3 with the appropriate [(PhTtR)Cu] or
[(Ph2BtR)Cu] precursor in either acetonitrile or THF. The second
method entailed reaction of the appropriate ligand with equimo-
lar [Cu(CH3CN)4][BF4] and an excess of PPh3. The latter
reactions were conducted in THF. The PPh3 complexes have
excellent solubility in chlorinated hydrocarbons and good
solubility in aromatic hydrocarbons. In addition, they are stable
to air and moisture both in the solid state and in solution for
several days.
(b) NMR Spectroscopy. The H and 31P NMR spectra of
the PPh3 complexes have been obtained, and the chemical shift
data are reported in Tables 3 and 4. In all cases, the H NMR
spectra support monomeric structures. Specifically, there is a
single methylene resonance indicative of symmetric borato
ligation. Similar results are seen for the other [PhTtR]Cu(L)
1
(11) Cechi, P.; Bovio, B.; Lobbia, G. G.; Pettinari, C.; Leonesi, D.
Polyhedron 1995, 14, 2441-2449.
1
(12) Santini, C.; Lobbia, G. G.; Pettinari, C.; Pellei, M.; Valle, G.; Calogero,
S. Inorg. Chem. 1998, 37, 890-900.
(13) Grim, S. O.; Yankowsky, A. W. J. Org. Chem. 1977, 42, 1236.
(14) Lobbia, G. G.; Pettinari, C.; Santini, C.; Calapietoro, M.; Cecchi, P.
Polyhedron 1997, 16, 207-215.

Structural Diversity in Cu(I) Thioether Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4281
Figure 4. Thermal ellipsoid plots of [PhTtpTol]Cu(PPh3) (A) and [Et2Bt]Cu(PPh3)2 (B) at the 30% probability level; hydrogen atoms are not shown.
in the literature. [Bu4N]PhTtPh was prepared as described previously.7
All ligands and metal complexes were dried under vacuum at refluxing
acetone temperatures unless otherwise stated. Elemental analyses were
performed by Desert Analytics, Inc., Tuscon, AZ. Electronic spectra
complexes, 2.15-2.30 Å, and are less than the sum of the
covalent radii.15 The Cu-S distances, 2.351(1) and 2.371(1)
Å, and the Cu-P distances, 2.294(1) and 2.318(1) Å, in [(Et2-
Bt)Cu(PPh3)2] are longer on average than the metrics of
were recorded with SLM-Aminco 3000 or Hewlett-Packard 8453 diode
[(PhTtPh)Cu(PPh3)] and [(PhTtpTol)Cu(PPh3)]. Similarly, longer
array spectrophotometers. NMR spectra were recorded on a 400 MHz
Cu-P bonds are seen in the complex [(k2-pzTp)Cu(PPh3)2],
Bru¨ker spectrometer equipped with a Sun workstation, a Bru¨ker AM-
250, or a Bru¨ker AC-250 spectrometer. Samples were referenced to
2.273(1) and 2.359(1) Å,11 compared to [TpCu(PPh3)]. This
could arise from the steric crowding of the PPh3 ligands.
the solvent signal. Cyclic voltammetry was performed on a BAS 50W
system. All experiments were performed in an Ar-filled glovebox in a
cell consisting of a glassy carbon or platinum disk working electrode
(r ) 1 mm), Pt wire counter electrode, and Ag/AgCl reference electrode.
Solutions contained 0.1 M electrolyte ([Bu4N][PF6], dried prior to use)
and 10 mM sample. Potentials were referenced to internal Fc/Fc+ (+410
mV vs Ag/AgCl).
CAUTION! The sulfides employed in the following syntheses are
flammable liquids and possess a hazardous stench. The deprotonation
reactions should be vented through aqueous NaOCl.
[Bu4N]Ph2Bt, Tetrabutylammonium Diphenylbis((methylthio)-
methyl)borate.5 Methyl sulfide (3.5 mL, 48 mmol) and TMEDA (0.1
mL, 0.65 mmol) were charged into a round-bottom flask. To the mixture
was added n-BuLi (10.0 mL 2.5 M in hexanes) dropwise with vigorous
stirring. The viscous yellow solution was stirred for 1 h at room
temperature (RT) before heating to 45 °C for an additional hour to
remove excess methyl sulfide. THF (20 mL) was added and the solution
cooled to -78 °C followed by dropwise addition of a benzene solution
(20 mL) of Ph2BBr (3.1 g, 12.5 mmol). The reaction mixture was
warmed to RT and stirred for 12 h. H2O (30 mL) was added to quench,
and the organic volatiles were removed under vacuum. The remaining
aqueous solution was filtered through Celite. To the filtrate was added
[Bu4N]Br (4.0 g, 12.5 mmol), resulting in precipitation was a white
solid, which was collected by filtration and washed with H2O (2 × 25
mL). Yield: 5.3 g (80%). [Bu4N]Ph2Bt is soluble in acetone, THF,
acetonitrile and chlorinated hydrocarbons. Mp: 117-118 °C. 1H NMR
(CDCl3): δ 7.46 (br, m-C6H5, 4 H), 7.04 (d, o-C6H5, 4 H), 6.86 (t,
p-C6H5, 2 H), 2.80 (t, NCH2, 8 H), 2.27 (br, BCH2, 4 H), 2.04 (s, SCH3,
6H), 1.35 (m, NCH2CH2, 8 H), 1.06 (m, N(CH2)2CH2, 8 H), 0.99 (t,
N(CH2)3CH3, 12 H). Anal. Calcd for C32H56BNS2: C, 72.6; H, 10.7;
N, 2.64. Found: C, 72.3; H, 10.34; N, 2.84.
Summary
Reaction of a series of poly(thioether)borate ligands with
[Cu(CH3CN)4][BF4] led to a set of structurally diverse 1:1
complexes. These results show that the structural chemistry of
Cu(I) thioether complexes of this type can be rationally
controlled by the proper substitution at the thioether sulfur and
the central boron atom, as well as by judicious choice of the
number of chelate arms incorporated in the ligand. Ligands
possessing the smaller (methylthio)methyl donors, [PhTt] and
[Ph2Bt], yield tetrameric species, [(PhTt)Cu]4 and [(Ph2Bt)-
Cu]4, containing both terminal and bridging thioether ligation.
However, ligands possessing the larger (arylthio)methyl groups,
[PhTtPh] and [PhTtpTol], form copper(I) one-dimensional ex-
tended structures in the solid state. Clearly, in cases where there
are an insufficient number of thioether donors to satisfy a Td
coordination environment, η2 ligation via the phenyl substituent
on boron permits for completion of the coordination sphere.
The η2-phenyl interaction represents a significant driving force
for these structures. Although three-coordinate Cu(I) structures
are well precedented, in the present studies this structure type
was not observed.
Experimental Section
General Procedures. Unless otherwise stated, all reagents were
obtained from commercial sources and used without further purification.
When dry solvents were required, they were distilled under N2 and
dried as indicated. Hexanes, Et2O, THF, toluene, benzene, and pentane
were freshly distilled over Na/benzophenone. Acetonitrile, CH2Cl2,
pyridine, and TMEDA were distilled over CaH2, the latter two under
reduced pressure. HPLC grade acetone (e0.05% H2O) and benzonitrile
(e0.005% H2O) were purchased from Acros Organics, Fisher Scientific.
HPLC grade acetonitrile (e0.001% H2O) was purchased from Burdick
and Jackson, Inc. [Cu(CH3CN)4][BF4],10 Et2B(OTs),16 Ph2BBr,17 and
ButSCH318 were prepared according to procedures previously outlined
[Bu4N]Ph2BtPh, Tetrabutylammonium Diphenylbis((phenylthio)-
methyl)borate. [Bu4N]Ph2BtPh was prepared according to the procedure
above for [Bu4N]Ph2Bt using thioanisole in place of methyl sulfide.
Thioanisole (3.1 g, 25 mmol) and TMEDA (0.1 mL, 0.65 mmol) were
charged into a round-bottom flask. To the mixture was added n-BuLi
(10.0 mL 2.5 M in hexanes) dropwise with vigorous stirring. The
viscous yellow solution was stirred for 2 h at RT. THF (20 mL) was
(15) Lobbia, G. G.; Pettinari, C.; Marchetti, F.; Bovio, B.; Cecchi, P.
Polyhedron 1996, 15, 881-890.
(16) Trofimenko, S. J. Am. Chem. Soc. 1969, 91, 2139-2140.
(17) Eisch, J.; King, R. B. In Organometallic Syntheses; Academic Press:
New York, 1981; pp 126-127.
(18) Vogel, A. I.; Cowan, D. M. J. Chem. Soc. 1943, 16.

4282 Inorganic Chemistry, Vol. 40, No. 17, 2001
Ohrenberg et al.
added and the solution cooled to -78 °C followed by dropwise addition
of a benzene solution (20 mL) of Ph2BBr (3.1 g, 12.5 mmol). The
reaction mixture was warmed to RT and stirred for 24 h. H2O (30 mL)
was added to quench, and the organic volatiles were removed under
vacuum. The remaining aqueous solution was filtered through Celite.
To the filtrate was added [Bu4N]Br (4.0 g, 12.5 mmol), resulting in
precipitation was a white solid, which was collected by filtration and
washed with H2O (2 × 25 mL). Yield: 3.5 g (50%). [Bu4N]Ph2BtPh is
soluble in acetone, THF, acetonitrile, and chlorinated hydrocarbons.
Mp: 152-153 °C. 1H NMR (CDCl3): δ 7.49 (d, C6H5, 4 H), 7.28 (d,
C6H5, 4 H), 7.11 (m, C6H5, 8 H), 6.91 (m, C6H5, 4 H), 2.59 (br, BCH2,
4 H), 2.40 (br, NCH2, 8 H), 1.14 (m, NCH2CH2, 8 H), 1.06 (m,
N(CH2)2CH2, 8 H), 0.90 (t, N(CH2)3CH3, 12 H).
[Bu4N]PhTtpTol, Tetrabutylammonium Phenyltris((p-tolylthio)-
methyl)borate. [Bu4N]PhTtpTol was prepared according to the procedure
for [Bu4N]PhTtPh replacing thioanisole with methyl p-tolyl sulfide.7 The
following reagent quantities were employed in the reaction: methyl
p-tolyl sulfide (9.3 mL, 69 mmol), TMEDA (13.0 mL, 86 mmol), BuLi
(27.6 mL, 2.5 M in hexanes), and PhBCl2 (3.0 mL, 23 mmol). Isolation
was carried out as follows. The reaction was quenched with 30 mL of
H2O, and 100 mL of THF was added before filtering through Celite.
The filtrate was concentrated by rotary evaporation, and [Bu4N]Cl (6.3
g, 23 mmol), in a minimum of acetone, was added. The product was
precipitated from this solution with ethyl acetate and collected by
filtration. The crude product was washed with H2O (3 × 20 mL) and
recrystallized from acetone/H2O to produce a fine white powder.
Yield: 6.7 g (39%). [Bu4N]PhTtpTol is soluble in acetone, THF,
acetonitrile, and chlorinated hydrocarbons. Mp: 175 °C. 1H NMR
(CDCl3): δ 7.59 (d, (o-C6H5)B, 2 H), 7.14 (d, (o- C6H4(CH3))S, 6 H),
7.09 (t, (m-C6H5)B, 2 H), 6.92 (m, (p-C6H5)B and (m-C6H4(CH3))S, 7
H), 2.51 (m, NCH2, 8 H), 2.34 (br, BCH2, 6 H), 2.21 (s, (C6H4(CH3))S,
9H), 1.16 (m, NCH2CH2, 8 H), 1.06 (m, N(CH2)2CH2, 8 H), 0.86 (t,
N(CH2)3CH3, 12 H). Anal. Calcd. for C46H68BNS3: C, 74.5; H, 9.24;
N, 1.88. Found: C, 74.6; H, 9.34; N, 1.82.
7.05 (t, (m-C6H5)B, 4 H), 6.90 (t, (p-C6H5)B, 2 H), 2.32 (m, BCH2, 4
H) 2.26 (s, SCH3, 6 H). Anal. Calcd for C64H80B4Cu4S8: C, 54.8; H,
5.75. Found: C, 53.9; H, 5.79.
[(PhTtpTol)Cu]∞. [Cu(CH3CN)4][BF4] (125 mg, 0.40 mmol) in 20
mL of acetonitrile was added to [Bu4N]PhTtpTol (290 mg, 0.39 mmol)
in 20 mL of acetonitrile under a N2 atmosphere, yielding a cloudy white
solution within 1 h. The reaction was stirred for 6 h. The fine white
powder was collected under N2 by filtration, washed with acetonitrile
(2 × 15 mL) and Et2O (2 × 15 mL), and dried under vacuum at 65
°C. Yield: 162 mg (74%). [(PhTtpTol)Cu]∞ is soluble in benzonitrile
and pyridine. Mp: 135-138 °C dec. 1H NMR (pyridine-d5): see
[(PhTtpTol)Cu(py)] below. Anal. Calcd for C30H32BS3Cu: C, 64.0; H,
5.73. Found: C, 64.0; H, 5.82.
[(PhTttBu)Cu]n. [Cu(CH3CN)4][BF4] (223 mg, 0.71 mmol) in 20 mL
of acetone was added to Cs[PhTttBu] (372 mg, 0.70 mmol) in 20 mL of
acetone with gentle stirring under a N2 atmosphere. A fine white powder
formed immediately upon mixing, and the reaction was terminated after
30 min. The powder was collected via vacuum filtration and washed
with H2O (4 × 15 mL) and pentane (3 × 15 mL). Yield: 220 mg
(68%). [(PhTttBu)Cu]n is soluble in acetonitrile (as [(PhTttBu)Cu(CH3-
CN)]), THF, and chlorinated hydrocarbons. Solid samples of [(PhTttBu)-
Cu]n are stable to air and water, but solutions turn blue over several
1
hours when exposed to O2. Mp: 104-106 °C dec. H NMR (CD3-
CN): δ 7.31 (br, (o-C6H5)B, 2 H), 7.08 (t, (m-C6H5)B, 2 H), 6.93 (t,
(p-C6H5)B, 1 H), 1.93 (BCH2, br, 6 H), 1.31 (s, C(CH3)3 27 H). Anal.
Calcd for [(PhTttBu)Cu]n C21H38BCuS3: C, 54.7; H, 8.31. Found: C,
54.1; H, 7.99.
[(Ph2BtPh)Cu(CH3CN)2]. [Cu(CH3CN)4][BF4] (300 mg, 0.46 mmol)
in 10 mL of acetonitrile was added to [Bu4N]Ph2BtPh (290 mg, 0.39
mmol) in 20 mL of acetonitrile under a N2 atmosphere, yielding a
homogeneous pale yellow solution. The solution was stirred for 2 h
and then concentrated in vacuo to produce white crystalline material.
Yield: 175 mg (80%). 1H NMR ((CD3)2SO): δ 7.17 (m, C6H5, 14 H),
7.04 (d, C6H5, 4 H), 6.91 (t, C6H5, 2 H) 2.50 (br, BCH2, coincident
with residual dmso) 2.06 (s, NCCH3, 6 H). 1H NMR (CD3CN): δ 7.30
(m, C6H5, 12 H), 7.17 (d, C6H5, 2 H) 7.08 (t, C6H5, 4 H), 6.94 (t, C6H5,
2H), 2.60 (b, BCH2, 4 H). Anal. Calcd for C30H30BCuN2S2: C, 64.7;
H, 5.43; N, 5.03. Found: C, 64.5; H, 5.38; N, 4.77
Cs[PhTttBu], Cesium Phenyltris((tert-butylthio)methyl)borate. The
synthetic procedure for Cs[PhTttBu] was analogous to that reported for
Tl[PhTttBu].2 Isolation was achieved by extracting the reaction mixture
with H2O (4 × 50 mL), filtering the combined aqueous portions through
Celite, and adding aqueous CsCl. The resulting white powder was
collected by filtration and washed with Et2O. Cs[PhTttBu] is soluble in
acetone, acetonitrile, and THF but is insoluble in chlorinated hydro-
[(PhTtPh)Cu(PPh3)].7 The synthesis and isolation of [(PhTtPh)Cu-
(PPh3)] were performed using the procedure reported for [(PhTt)Cu-
(PPh3)].6 PPh3 (200 mg, 0.76 mmol) in 20 mL of acetonitrile was added
to [(PhTtPh)Cu]∞ (300 mg, 0.58 mmol) in 50 mL of acetonitrile. Yield:
375 mg (83%). Mp: 86 °C. 1H NMR ((CD3)2CO): δ 7.45 (t, (o-C6H5)B
and (p-C6H5)P, 5 H), 7.29 (t, (m-C6H5)S, 6 H), 7.15 (m, (m-C6H5)B,
(o-C6H5)S, (p-C6H5)S and (m-C6H5)P, 16 H), 6.98 (t, (o-C6H5)P and
1
carbons. Mp: 206 °C dec. H NMR (CDCl3): δ 7.53 (br, (o-C6H5)B,
2 H), 6.96 (t, (m-C6H5)B, 2 H), 6.80 (t, (p-C6H5)B, 1 H), 1.81 (br,
BCH2, 6 H), 1.18 (s, C(CH3)3, 18 H).
[Bu4N]Et2Bt, Tetrabutylammonium Diethylbis((methylthio)meth-
yl)borate. [Bu4N]Et2Bt was prepared according to the procedure
reported for [Bu4N]PhTt1 replacing PhBCl2 with Et2B(OTs). In a typical
reaction the following reagent quantities were used: methyl sulfide
(8.1 mL, 110 mmol), TMEDA (9.1 mL, 60 mmol), BuLi (22 mL, 2.5
M in hexanes), Et2B(OTs) (25 mL, 1.1 M in toluene), and [Bu4N]Br
(4.6 g, 14 mmol). The reaction required 72 h of stirring after the addition
of the Et2B(OTs). Yield: 2.7 g (23%). [Bu4N]Et2Bt has good solubility
in acetone, acetonitrile, aromatic and chlorinated hydrocarbons, THF,
and alcohols. Mp: 58-66 °C. 1H NMR (CDCl3): δ 3.15 (m, NCH2, 8
H), 1.96 (s, SCH3, 6 H), 1.55 (m, BCH2, and NCH2CH2, 12 H), 1.40
(h, N(CH2)2CH2, 8 H), 0.95 (t, CH3, 12 H), 0.72 (t, BCH2CH3, 6 H),
0.07 (q, BCH2CH3, 4 H). Anal. Calcd for C24H56BNS2: C, 66.5; H,
13.0; N, 3.23. Found: C, 66.2; H, 13.1; N, 3.48. Alternatively, the
product was isolated as the [Ph4P] salt by the addition [Ph4P]Br (6.0 g,
15 mmol). The solubility properties of [Ph4P]Et2Bt are similar to those
of the [Bu4N]Et2Bt.
1
(p-C6H5)B, 7 H), 2.78 (s, BCH2, 6 H). H NMR (C6H6): δ 7.83 (d,
(o-C6H5)B, 2 H), 7.49 (t, (m-C6H5)B, 2 H), 7.31 (t, (p-C6H5)B, 1 H),
7.15 ((o-C6H5)S, coincident with C6D6), 7.01 (t, (m-C6H5)S, 6 H), 6.93
(t, (p-C6H5)S, 3 H), 6.85 (m, (C6H5)P, 15 H), 3.17 (br, SCH2, 6 H).
31P{1H} NMR (CDCl3): δ 6.2. Anal. Calcd for C45H41BCuPS3: C, 69.0;
H, 5.28. Found: C, 69.0; H, 5.54.
[(PhTtpTol)Cu(PPh3)]. A slurry of [Cu(CH3CN)4][BF4] (210 mg, 0.67
mmol) in 20 mL of THF was added to PPh3 (260 mg, 0.99 mmol) and
[Bu4N]PhTtpTol (500 mg, 0.67 mmol) in 20 mL of THF under a N2
atmosphere. Upon addition, the Cu(I) salt was immediately brought
into solution. The reaction was stirred overnight before the solvent was
removed by rotary evaporation. The resulting white solid was extracted
with 100 mL of dry Et2O and filtered. The solvent was removed under
vacuum, and the resulting product was collected and washed with
pentane (3 × 25 mL). Yield: 530 mg (96%). Mp: 135-138 °C dec.
1H NMR (C6H6): δ 7.79 (d, (o-C6H5)B, 2 H), 7.43 (t, (m-C6H5)B, 2
H), 7.40 (t, (p-C6H5)B, 1 H), 7.09 (C6H5, m, 21 H, coincident with
C6H6), 6.95-6.78 (m, C6H5, 10 H), 6.63 (d, C6H5, 6 H), 3.17 (br, SCH2,
6 H) 1.93 (s, CH3, 9 H). 31P{1H} NMR (CDCl3): δ 6.3. Anal. Calcd
for C48H47BCuPS3: C, 69.8; H, 5.74. Found: C, 69.9; H, 5.85.
[(PhTttBu)Cu(PPh3)]. [(PhTttBu)Cu]n (100 mg, 0.27 mmol) in 20 mL
of acetonitrile was combined with PPh3 (108 mg, 0.41 mmol) in 5 mL
of acetonitrile and stirred overnight. The resulting white precipitate
was collected by filtration and washed with pentane (4 × 15 mL).
[(Ph2Bt)Cu]4. [(Ph2Bt)Cu]4 was prepared from [Cu(CH3CN)4][BF4]
(0.91 g, 2.89 mmol) and [Bu4N]Ph2Bt (1.53 g, 2.89 mmol) using the
procedure for [(PhTt)Cu]4.6 Reaction time was 10 min. [(Ph2Bt)Cu]4
was dried under vacuum at RT. Yield: 0.60 g (60%). [(Ph2Bt)Cu]4 is
soluble in THF and chlorinated hydrocarbons and reacts with acetonitrile
1
and pyridine. Mp: 68 °C dec. H NMR (CDCl3): δ 7.60 (m, η2-(p-
C6H5)B, (o-C6H5)B and η2-(m-C6H5)B, 5 H), 7.09 (t, (m-C6H5)B, 2 H),
6.97 (t, (p-C6H5)B, 1 H), 6.72 (d, η2-(o-C6H5)B, 2 H), 2.62 (d, SCH2,
1 H), 2.42 (d, SCH2, 1 H), 2.24 (s, SbCH3, 3 H), 2.20 (m, SCH2, 2 H),
2.10 (s, StCH3, 3 H). 1H NMR (CD3CN): δ 7.28 (br, (o-C6H5)B, 4 H),
1
Yield: 85 mg (54%). Mp: 148 °C dec. H NMR (C6H6): δ 7.99 (br,
(o-C6H5)B, 2 H), 7.56 (m, (m-C6H5)B and (C6H5)3P, 8 H), 7.30 (t, (p-

Structural Diversity in Cu(I) Thioether Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4283
C6H5)B, 1 H), 7.03 (m, (C6H5)3P, 9 H), 2.68 (br, BCH2, 6 H), 1.17 (s,
C(CH3)3, 28 H). 31P{1H} NMR (CDCl3): δ 5.49. Anal. Calcd for C39H53-
BCuPS3: C, 64.8; H, 7.38. Found: C, 65.1; H, 7.19.
Equilibrium Constant Determination for Pyridine Binding to
[(PhTt)Cu]4 and [(PhTtPh)Cu(NCCH3)]. Copper complex (10 mg)
was dissolved in 0.7 mL of CD3CN (for [(PhTtPh)Cu]∞) or CDCl3 (for
[(PhTt)Cu]4) along with 9 mg of ferrocene as an internal standard. To
this solution were added neat aliquots of pyridine (1.5 µL per addition).
Equilibrium ratios were calculated by integration of the SCH2 reso-
nances for the individual complexes.
[(Ph2Bt)Cu(PPh3)2]. The synthesis and isolation of [(Ph2Bt)Cu-
(PPh3)2] were performed using the procedure reported for [(PhTt)Cu-
(PPh3)].6 [(Ph2Bt)Cu]4 (254 mg, 0.18 mmol) and PPh3 (370 mg, 1.41
mmol) were combined in THF. Yield, 400 mg (65%). Mp: 142 °C
dec. 1H NMR (C6H6): δ 7.95 (d, (o-C6H5)B, 4 H), 7.49 (t, (m-C6H5)B,
4 H), 7.29 (t, (p-C6H5)B, 2 H), 7.22 (t, (C6H5)3P, 11 H), 6.93 (m,
(C6H5)3P, 18 H), 2.80 (b, BCH2, 4 H), 1.72 (s, SCH3, 6 H). 31P{1H}
NMR (CDCl3): δ 0.9. Anal. Calcd for C52H50BCuP2S2: C, 71.4; H,
5.76. Found: C, 71.4; H, 5.70.
Crystallographic Structure Determinations. Suitable crystals for
X-ray analysis were obtained by slow diffusion of Et2O into concen-
trated chloroform solutions of [(Ph2Bt)Cu]4, slow evaporation of
concentrated acetonitrile solutions of [(Ph2BtPh)Cu(CH3CN)2], slow
diffusion of pentanes into concentrated toluene solutions of [(PhTtPh)-
Cu(PPh3)] and [(PhTtpTol)Cu(PPh3)], and slow diffusion of pentanes
into concentrated benzene solutions of [(Et2Bt)Cu(PPh3)2]. Suitable
crystals were chosen and mounted on glass fibers with epoxy cement.
Crystal data, collection, and refinement parameters are given in Table
1. The systematic absences in the diffraction data are uniquely consistent
for the reported space groups for [(Ph2Bt)Cu]4, [(Ph2BtPh)Cu(CH3CN)2],
[(PhTtPh)Cu(PPh3)], and [(Et2Bt)Cu(PPh3)2]. The systematic absences
in the diffraction data are consistent for the C-centered monoclinic space
groups, Cc and C2/c for [(PhTtpTol)Cu(PPh3)]. The E-statistics suggested
the centrosymmetric space group for [(PhTtpTol)Cu(PPh3)], and solution
in the corresponding space groups yielded chemically reasonable and
computationally stable results of refinement. The structures were solved
using direct methods, completed by subsequent difference Fourier
syntheses and refined by full-matrix, least-squares procedures. There
is one molecule each of chloroform and diethyl ether in the asymmetric
unit of [(Ph2Bt)Cu]4. Two of the carbon atoms of the diethyl ether
molecule of [(Ph2Bt)Cu]4 are disordered over two positions, 80/20 and
55/45, respectively. The carbon atoms of the diethyl ether molecule of
[(Ph2Bt)Cu]4 were refined isotropically. All other non-hydrogen atoms
on the diethyl ether molecule of [(Ph2Bt)Cu]4 were ignored, and all
other hydrogen atoms were treated as idealized contributions. The sulfur
atoms S(1), S(2), and S(3) of [(PhTtPh)Cu(PPh3)] and one of the methyl
carbon atoms, C(6), of [(Et2Bt)Cu(PPh3)2] are disordered over two
positions, 90/10 and 65/35, respectively. The hydrogen atoms on the
methylene carbon atom in [(Et2Bt)Cu(PPh3)2] bound to the disordered
methyl carbon atoms, C(6), were ignored in the refinement because of
the disorder, and all other hydrogen atoms were treated as idealized
contributions. All software and sources of the scattering factors are
contained in the SHELXTL (5.1) program library (G. Sheldrick,
Siemens XRD, Madison, WI).
[(Ph2BtPh)Cu(PPh3)2]. [Bu4N]Ph2BtPh (310 mg, 0.47 mmol), [Cu-
(CH3CN)4][BF4] (155 mg, 0.49 mmol), and PPh3 (250 mg, 0.95 mmol)
were combined as above for [(PhTtpTol)Cu(PPh3)]. The reaction was
stirred for 1 h, resulting in the precipitation of the product as a white
solid. The solid was collected by filtration. Yield: 270 mg (58%). [(Ph2-
BtPh)Cu(PPh3)2] is soluble in aromatic and chlorinated hydrocarbons.
1
Mp: 157 °C. H NMR (C6H6): δ 7.99 (d, o-C6H5, 4 H), 7.43 (t, (m-
C6H5), 4 H), 7.27 (t, (p-C6H5), 2 H), 6.99 (m, (p-C6H5) and (C6H5)3P,
19 H), 6.87 (t, (C6H5)3P, 15 H), 6.75 (t, (m-C6H5), 4 H), 6.57 (d, (o-
C6H5), 4H), 3.20 (br, SCH2, 4H). 31P{1H} NMR (CDCl3): δ -0.1.
Anal. Calcd for C26H54BCuP2S2: C, 74.5; H, 5.45. Found: C, 74.4; H,
5.51.
[(Et2Bt)Cu(PPh3)2]. The synthesis and isolation of [(Et2Bt)Cu-
(PPh3)2] were combined as above for [(PhTtpTol)Cu(PPh3)] employing
[Cu(CH3CN)4][BF4] (169 mg, 0.54 mmol), PPh3 (282 mg, 1.08 mmol),
and [Bu4N]Et2Bt (225 mg, 0.52 mmol). Yield: 300 mg (74%). Mp:
1
126 °C dec. H NMR (C6H6): δ 7.35 (m, (C6H5)3P, 12 H), 6.97 (m,
(C6H5)3P, 18 H), 2.36 (br, BCH2, 4 H), 1.74 (s, SCH3, 6 H), 1.62 (t,
CH3, 6 H), 1.10 (m, BCH2, 4 H). 31P{1H} NMR (CDCl3): δ -3.2.
Anal. Calcd for C44H50BCuP2S2: C, 67.8; H, 6.47. Found: C, 68.0; H,
6.62.
In Situ Preparation of Monomeric Copper Pyridine Complexes.
The pyridine complexes [PhTtR]Cu(py) and [Ph2BtR]Cu(py)2 were
formed by dissolution of 10 mg of the appropriate parent complex in
1
pyridine-d5 and detected in situ by H NMR spectroscopy. [(PhTtPh)-
Cu(py)]: δ 8.20 (d, (o-C6H5)B, 2 H), 7.49 (m, (m-C6H5)B and (o-
C6H5)S, 8H), 7.18 (m, (p-C6H5)B and (m-C6H5)S, ∼7 H, coincident
with py), 7.00 (t, (p-C6H5)S, 3 H), 3.06 (br, SCH2, 6 H). [(PhTtpTol)-
Cu(py)]: δ 8.21 (d, (o-C6H5)B, 2 H), 7.49, 7.44 (t, (m-C6H5)B, and
(d, (o-C6H4(CH3))S, 8H), 7.25 (t, (p-C6H5)B, 1 H), 7.02 (d, (m-C6H4-
(CH3))S, 6 H), 3.05 (br, BCH2, 6 H), 2.12 (s, (C6H4(CH3))S, 9 H).
[(Ph2Bt)Cu(py)2]: δ 7.91 (d, (o-C6H5)B, 4 H), 7.37 (t, (m-C6H5)B, 4
H), 7.20 (m, (p-C6H5)B, coincident with py), 2.78 (br, BCH2, 4 H),
2.08 (s, SCH3, 6 H). [(Ph2BtPh)Cu(py)2]: δ 8.11 (d, (o-C6H5)B, 4 H),
7.48 (d and t (m-C6H5)B and (o-C6H5)S, 8H), 7.18 (m, (p-C6H5)B and
(m, m-C6H5)S, 8 H), 7.00 (t, (p-C6H5)S, 3 H), 3.23 (br, SCH2, 4 H).
[(PhTttBu)Cu(py)]: δ 8.10 (d, (o-C6H5)B, 2H), 7.45 (t, (m-C6H5)B, 2
H), 7.20 ((p-C6H5)B, coincident with py), 2.50 (br, BCH2, 6 H), 1.22
(s, C(CH3)3, 28 H).
Acknowledgment. We gratefully acknowledge the financial
support provided by the National Science Foundation (NYI and
CHE-9974628 to C.G.R.).
Supporting Information Available: Crystallographic data in CIF
format. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC010273A