Rhenium complexes with weakly coordinating solvent ligands, cis-[Re(PR3)(CO)4-(L)][BArF], L = CH2Cl2, Et2O, NC5F5: Decomposition to chloride-bridged dimers in CH2Cl2 solution

Article abstract of DOI:10.1021/ic980912q

The solvent-coordinated complexes [cis-Re(CO)₄(PR₃)(S)][BAr_F] (R = Ph, ⁱPr, Cy, BAr_F = [B(3,5-(CF₃)₂C₆H₃)₄] ^-) for S = Et₂O, CH₂Cl₂, and NC₅F₅ have been prepared from reaction of the neutral methyl precursors, cis-Re-(CO)₄(PR₃)(Me), with either [H(OEt₂)₂][BAr_F] or [Ph₃C][BAr_F] in the appropriate solvent. A crystal structure of the complex [cis-Re(CO)₄(PⁱPr₃)(ClCH ₂Cl)][BAr_F] shows that the dichloromethane ligand is coordinated through one chlorine, with an Re-Cl distance of 2.554(2) ?. The first example of a structurally characterized pentafluoropyridine complex of rhenium was also determined, [cis-Re(CO)₄(PⁱPr₃)(NC₅F ₅)][BAr_F], with an Re-N distance of 2.319(5) ?. Activation of C-Cl bonds in the dichloromethane complexes result in the formation of the chloride-bridged dimers, {[cis-Re(CO)₄(PR₃)]₂(μ-Cl)}{BAr _F}, and the X-ray structures of the Ph and Cy derivatives were determined.

Full text of DOI:10.1021/ic980912q

Inorg. Chem. 1999, 38, 115-124
115
Rhenium Complexes with Weakly Coordinating Solvent Ligands, cis-[Re(PR3)(CO)4-
(L)][BArF], L ) CH2Cl2, Et2O, NC5F5: Decomposition to Chloride-Bridged Dimers in
CH2Cl2 Solution
Jean Huhmann-Vincent, Brian L. Scott, and Gregory J. Kubas*
Chemical Science and Technology Division, MS J514, Los Alamos National Laboratory,
Los Alamos, New Mexico 87545
ReceiVed July 31, 1998
The solvent-coordinated complexes [cis-Re(CO)4(PR3)(S)][BArF] (R ) Ph, iPr, Cy, BArF ) [B(3,5-(CF3)2C6H3)4]-)
for S ) Et2O, CH2Cl2, and NC5F5 have been prepared from reaction of the neutral methyl precursors, cis-Re-
(CO)4(PR3)(Me), with either [H(OEt2)2][BArF] or [Ph3C][BArF] in the appropriate solvent. A crystal structure of
the complex [cis-Re(CO)4(PiPr3)(ClCH2Cl)][BArF] shows that the dichloromethane ligand is coordinated through
one chlorine, with an Re-Cl distance of 2.554(2) Å. The first example of a structurally characterized
pentafluoropyridine complex of rhenium was also determined, [cis-Re(CO)4(PiPr3)(NC5F5)][BArF], with an Re-N
distance of 2.319(5) Å. Activation of C-Cl bonds in the dichloromethane complexes result in the formation of
the chloride-bridged dimers, {[cis-Re(CO)4(PR3)]2(µ-Cl)}{BArF}, and the X-ray structures of the Ph and Cy
derivatives were determined.
Introduction
Part of the success of these systems stems from the ability to
have the appropriate solvent (S): one which is polar enough to
There has recently been a great deal of interest in cationic
transition metal complexes [LnM(S)][A] which possess a
provide adequate solubility of the ionic complex, but does not
itself react or bind irreversibly with the metal center. An
illustration of this balance is evident in Bercaw’s Pt(NC5F5)
system, where if either Et2O or CH2Cl2 are used as the solvent
instead of NC5F5, products resulting from C-H activation (Et2O)
or C-Cl activation (CH2Cl2) are isolated.5 Keeping these points
in mind, we have generated a simple organometallic Lewis acid
system with a noncoordinating anion [cis-Re(CO)4(PR3)]+ and
examined its reactivity toward the solvents commonly present
in [LnM(S)][A] systems: Et2O, CH2Cl2, and NC5F5. The
preparation of the anion coordinated complexes [cis-Re(CO)4-
(PPh3)(A)] have previously been reported by Hope6 (A )
OTeF5-) and Beck7 (A ) FBF3-). However, we are interested
in systems with noncoordinating anions, such as BArF-, which
are much more likely to show reactivity toward substrates since
there are no interactions with the anion to stabilize the
electrophilic metal center.
This paper describes the preparation of solvent coordinated
complexes [cis-Re(CO)4(PR3)(S)][BArF] (R ) Ph, iPr, Cy) for
diethyl ether, dichloromethane, and pentafluoropyridine, and the
first crystal structure of a Re complex with a bound NC5F5 is
presented. We also observe the irreversible C-Cl bond activa-
tion of coordinated CH2Cl2, which is proposed to be formed
from nucleophilic attack of the weak base Et2O on the methylene
carbon. A brief report of the isolation of [cis-Re(CO)4(PR3)-
(S)][BArF] (R ) Ph, Cy; S ) OEt2, ClCH2Cl) and their
activation of H2 has been recently communicated.8
-
-
noncoordinating anion (A), such as PF6 or BArF (BArF )
[B(3,5-(CF3)2C6H3)4]), and a weakly coordinated solvent mol-
ecule (S). Due to the lability of the solvent ligand, these
complexes act as a source of the corresponding 16e organo-
metallic Lewis acid [LnM][A] and are therefore highly reactive
toward σ donors (eq 1).1
[LnM(S)][A] y-Sz [LnM][A] +L′8 [LnM(L′)][A]
(1)
+S
For example, Gladysz’s chiral Re complex [Cp*Re(PPh3)(NO)-
(ClCH2Cl)][BF4] binds ligands by loss of methylene chloride;2
we have previously demonstrated that the weak solvent ligand
in trans-[PtH(PiPr3)2(S)][BArf] (S ) Et2O, CH2Cl2) can be easily
substituted by PhI or H2,3 and Bergman’s [Cp*Ir(PMe3)(Me)-
(ClCH2Cl)][BArF]4 system and Bercaw’s [Pt(Me)(tmeda)-
(NC5F5)][BArF]5 complexes activate C-H bonds of alkanes and
other functionalized organic compounds.
(1) For a recent review of organometallic Lewis acids, see: Beck, W.;
Su¨nkel, K. Chem. ReV. 1988, 88, 1405-1421.
(2) (a) Peng, T. S.; Winter, C. H.; Gladysz, J. A. Inorg. Chem. 1994, 33,
2534-2542. (b) Zhou, Y.; Dewey, M. A.; Gladysz, J. A. Organome-
tallics 1993 12, 3918-3923. (c) Agbossou, S. K.; Roger, C.; Igau,
A.; Gladysz, J. A. Inorg. Chem. 1992, 31, 419-424. (d) Agbossou,
S. K.; Ferna´ndez, J. M.; Gladysz, J. A. Inorg. Chem. 1990, 29, 476-
480. (e) Ferna´ndez, J. M.; Gladysz, J. A. Organometallics 1989, 8,
207-219. (f) Winter, C. H.; Arif, A. M.; Gladysz, J. A. Organome-
tallics 1989, 8, 219-225. (g) Winter, C. H.; Gladysz, J. A. J.
Organomet. Chem. 1988, 354, C33-C36.
(3) Butts, M. D.; Scott, B. L.; Kubas, G. J. J. Am. Chem. Soc. 1996, 118,
11831-11843.
(4) (a) Alaimo, P. J.; Arndtsen, B. A.; Bergman, R. G. J. Am. Chem. Soc.
1997, 119, 5269-5270. (b) Arndtsen, B. A.; Bergman, R. G. Science
1995, 270, 1970-1973.
(5) (a) Holtcamp, M. W.; Henling, L M.; Day, M. W.; Labinger, J. A.;
Bercaw, J. E. Inorg. Chim. Acta 1998, 270, 467-478. (b) Holtcamp,
M. W.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 1997, 119,
848-849.
(6) Brewer, S. A.; Buggey, L. A.; Holloway, J. H.; Hope, E. G. J. Chem.
Soc., Dalton Trans. 1995, 2941-2945.
(7) Beck, W.; Schweiger, M. Z. Anorg. Allg. Chem. 1991, 595, 203-210.
(8) Huhmann-Vincent, J.; Scott, B. L.; Kubas, G. J. J. Am. Chem. Soc.
1998, 120, 6808-6809.
(9) Abel, E. W.; Hargreaves, G. B.; Wilkinson, G. J. Chem. Soc. 1958,
3149-3152.
(10) Zingales, F.; Sartorelli, U.; Canziani, F.; Raveglia, M. Inorg. Chem.
1966, 6, 154-157.
10.1021/ic980912q CCC: $18.00 © 1999 American Chemical Society
Published on Web 12/17/1998

116 Inorganic Chemistry, Vol. 38, No. 1, 1999
Table 1. IR and 31P Spectral Data for Complexes 1-6
Huhmann-Vincent et al.
complex
IR (Nujol, νCO, cm-1
)
31P (CD2Cl2, RT)
1a
1b
1c
2a
2b
2c
3a
3b
3c
4a
2106(m), 2018(s), 2002(vs), 1945(s)a
2101(m), 2010(s), 1995(vs), 1934(s)
2098(m), 2008(s), 1992(vs), 1932(s)
2077(m), 1992(s), 1973(vs), 1935(s)b
2072(m), 1980(s), 1964(vs), 1927(s)
2070(m), 1976(s), 1969(vs), 1924(s)
2118(m), 2035(s), 2010(s), 1988(s)
2118(m), 2034(s), 2015(s), 1979(s)
2111(m), 2032(s), 1999(s), 1974(s)
2122(m), 2051(s), 2041(s), 2033(s),
2019(vs), 2008(vs), 1987 (s)
4.8
27.5
18.5
10.1
22.4
13.1
15.5c
36.3
27.9
11.1
4b
4c
5a
2124(m), 2044(s), 2026(s), 1996(s)
2119(m), 2040(s), 2017(s), 1990(s)
2122(m), 2116(m), 2034(s), 2011(vs),
1982(s), 1973(s)
33.6
25.5
10.0
5b
5c
6
2118(m), 2110(w), 2025(s),
2015(s), 1965(s)
2113(m), 2104(m), 2025(s), 2003(s),
1992(s), 1984(s), 1967(s)
2124(m), 2042(s), 2030(s), 1988(s)
31.7
23.3
30.4d
Figure 1. ORTEP diagram for cis-Re(CO)4(PiPr3)Cl, 1b (50% prob-
ability ellipsoids).
a Solvent was CCl4, ref 10. b Reference 12. c 31P{1H} NMR (CD2Cl2,
-73 °C) 16.2. d Solvent was NC5F5.
Results and Discussion
Preparation of cis-Re(CO)4(PR3)Cl (1a-c) and Reaction
with NaBArF. Neutral metal halide complexes MX are often a
convenient precursor to solvent or anion coordinated cationic
systems, i.e., organometallic Lewis acid sources. For instance,
our [trans-PtH(PiPr3)2(S)][BArf] (S ) Et2O, CH2Cl2) solvent
complexes were prepared from metathesis of the PtCl precursor
with NaBArF.3 A similar route has been used by Beck to prepare
the anion coordinated [cis-Re(CO)4(PPh3)(A)] (A ) FBF3,
OSO2CF3) from the neutral ReBr precursor and Ag(A).7
Reaction of 1 equiv of phosphine (PPh3, PiPr3, PCy3) with
Re(CO)5Cl in refluxing chloroform proceeded with the elimina-
tion of CO and cleanly provided the monophosphine complexes
1a-c in high yields after 12 h. Similarly, 1a could be obtained
at shorter reaction times under photolytic conditions in a 1/1
mixture of dichloromethane/cyclohexane (eq 2). In both routes,
Figure 2. ORTEP diagram for cis-Re(CO)4(PCy3)Cl, 1c (50% prob-
ability ellipsoids).
a singlet for each complex, and the 13C{1H} NMR spectrum of
the carbonyl region shows three doublets from coupling to the
phosphine, consistent with a cis arrangement of the phosphine
and chloride ligands. The carbonyl region in the IR spectra each
show one weak band around 2100 cm-1, and three strong bands
between 1930 and 2010 cm-1, also consistent with a cis
configuration. Table 1 lists the IR and 31P spectral data for all
compounds described in this paper.
The reaction of 1 with an excess (up to 5 equiv) of NaBArF
in CH2Cl2 was very slow and did not lead to the isolation of
the cationic chloride-free complex. Instead, the chloride-bridged
Re dimers {[cis-Re(CO)4(PR3)]2(µ-Cl)}{BArF} (5) were present
after 12 h in solution and were identified as the major products
after 1 week in solution. The dimers were not isolated but were
assigned on the basis of their 31P chemical shift that was identical
to that found for authentic samples of 5 as described later in
this paper. The formation of the dimers must occur from the
incomplete metathesis of 1 with NaBArF to generate [cis-Re-
(CO)4(PR3)(ClCH2Cl)][BArF] (4, not observed), followed by
quick reaction with remaining chloride complex 1 to form the
dimer.
a slight excess of Re(CO)5Cl (5%) was used to ensure that none
of the bis-phosphine complex trans-Re(CO)3(PR3)2Cl would be
generated. The progress of the reaction was monitored by
measuring an IR spectrum of the reaction mixture periodically,
and was judged complete when bands attributed to the carbonyl
groups of Re(CO)5Cl (2056, 1987 cm-1)9 were approximately
less than 10% of the total intensity. Evaporation of solvents
gave a crude product, which was dissolved in hot cyclohexane,
and unreacted Re(CO)5Cl was removed by filtration. The
monophosphine complexes were isolated as air stable white
solids by crystallization from cyclohexane/hexane solutions.
Complex 1a has been prepared previously from [Re(CO)4Cl]2
and PPh3 in CCl4,10 and the thermal route shown in eq 2 is
similar to that used to prepare cis-Re(CO)4(PPh)3Br from Re-
(CO)5Br and PPh3.11 The 31P{1H} NMR spectra for 1a-c show
Structure of cis-Re(CO)4(PR3)Cl (1b, 1c). The structures
of 1b and 1c were solved by X-ray diffraction for the purpose
of comparing neutral Re-Cl complexes with the cationic solvent
(11) Jolly, P. W.; Stone, F. G. A. J. Chem. Soc. 1965, 5259-5261.

Re Complexes with Weakly Coordinating Solvent Ligands
Inorganic Chemistry, Vol. 38, No. 1, 1999 117
Table 2. Crystal Data and Structure Refinementa
complex
1bb
1cc
4bd
5ae
5cf
6g
empirical
formula
fw
space group
λ, Å
temp (°C)
a (Å)
C13H21ClO4PRe C22H30ClO4PRe C46H35BCl2F24O4PRe C76H46BClF24O10P2Re2 C76H72BClF24O8P2Re2 C50H33BF29NO4PRe
493.92
C2/c
0.710 73
-80
611.01
P21/c
0.710 73
-80
1406.62
P21/c
0.710 73
-70
2055.73
P1
0.710 73
-75
2049.94
P1h
0.710 73
-70
1490.75
P1h
0.710 73
-70
25.803(2)
8.6720(10)
15.578(2)
90
92.254(7)
90
9.1150(10)
11.2030(10)
23.195(2)
90
93.589(6)
90
11.4222(5)
16.7303(8)
27.772(1)
90
97.325(1)
90
13.048(2)
16.348(2)
19.496(4)
92.52(1)
96.58(1)
100.24(1)
4056.7(12)
2
13.4105(2)
18.0091(3)
18.9398(3)
91.776(1)
108.642(1)
103.470(1)
4187.27(11)
2
14.1056(8)
14.2860(8)
14.7448(7)
94.555(1)
109.249(1)
100.458(1)
2727.3(3)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
volume (Å3)
Z
3483.1(7)
8
2363.9(4)
4
5263.7(4)
4
F
calc (g cm-1
)
1.884
0.7230
1.717
0.5345
1.775
0.2568
1.683
0.3164
1.626
0.3063
1.815
0.2402
µ (cm-1
)
final R indices R1 ) 0.0429
R1 ) 0.0348
R2w ) 0.0829
R1 ) 0.0441
R2w ) 0.1105
R1 ) 0.0665
R2w ) 0.1483
R1 ) 0.0525
R2w ) 0.1441
R1 ) 0.0476
R2w ) 0.1199
R2w ) 0.1045
a R1 ) Σ||Fo| - |Fc||/Σ|Fo| and R2w ) [Σ[w(Fo - Fc2)2]/Σ[w(Fo )2]]1/2
.
b The parameter w ) 1/[σ2(Fo ) + (0.0744P)2]. c The parameter w )
2
2
2
1/[σ2(Fo ) + (0.0468P)2 + 14.9032P]. d The parameter w ) 1/[σ2(Fo ) + (0.0575P)2]. e The parameter w ) 1/[σ2(Fo ) + (0.0758P)2]. f The parameter
2
2
2
w ) 1/[σ2(Fo ) + (0.0622P)2]. g The parameter w ) 1/[σ2(Fo ) + (0.0759P)2].
2
2
and the 31P{1H} NMR spectra show a single phosphorus signal
for each complex. The 13C{1H} NMR spectra exhibit three
carbonyl resonances which are all doublets (confirming the cis
geometry), and an upfield doublet for the rhenium methyl ligand.
A carbonyl band pattern similar to that observed in the IR
spectra for the chloride complexes 1 was obtained for the methyl
complexes 2. However, the CO bands are shifted to slightly
lower frequencies due to the increased electron donation of
methyl versus chloride to the Re and therefore increased back-
donation from the Re to the CO antibonding orbitals.
Table 3. Selected Bond Distances (Å) and Angles (deg) for
Complexes 1b and 1c
distances
1b 1c
angles
1b
1c
Re(1)-P(1) 2.507(2) 2.521(2) P(1)-Re(1)-Cl(1) 88.38(7) 86.39(14)
Re(1)-Cl(1) 2.483(2) 2.489(7) P(1)-Re(1)-C(1) 90.9(2) 175.2(2)
Re(1)-C(1) 1.986(9) 1.959(6) P(1)-Re(1)-C(4) 176.6(2) 91.6(12)
Re(1)-C(2) 1.879(9) 1.955(7) Cl(1)-Re(1)-C(2) 177.2(2) 92.7(2)
Re(1)-C(3) 1.993(9) 1.961(8) Cl(1)-Re(1)-C(3) 86.1(3) 176.9(2)
Re(1)-C(4) 1.956(8) 2.10(5)
Reaction of cis-Re(Me)(CO)4(PR3) with [H(OEt2)2][BArF].
Protonation of the methyl complexes 2 with 1 equiv of
[H(OEt2)2][BArF] in diethyl ether provided the solvent-
coordinated complexes [cis-Re(CO)4(PR3)(OEt2)][BArF] (3a-
c) (eq 4). The complexes were isolated by addition of hexanes
analogues [Re-(S)]+. Table 2 lists a summary of crystal-
lographic data for all of the structures presented in this paper.
ORTEP diagrams of 1b and 1c are shown in Figures 1 and 2,
respectively, and selected bond lengths and angles can be found
in Table 3. The ORTEP diagrams show the expected octahedral
cis arrangement of the ligands about the metal, with Re-Cl
distances of 2.483(2) Å (1b) and 2.489(7) Å (1c).
Preparation of cis-Re(Me)(CO)4(PR3) (2a-c). Neutral
methyl or hydride species are often useful precursors to
coordinately unsaturated cationic transition metal complexes.
The chloride complexes 1a-c are converted to the methyl
complexes 2a-c by treatment with one equiv of MeLi at low
temperature in ether solution (eq 3). Removal of the solvent
to the reaction mixture and were obtained in excellent yields
as colorless crystals. These cationic complexes are insoluble in
aromatic and aliphatic hydrocarbon solvents but soluble in Et2O
and CH2Cl2. The presence of 1 equiv of Et2O in 3 was confirmed
by elemental analysis. The coordinated Et2O could not be
removed by exposing the crystals to a vacuum for 12 h but
was easily replaced by more basic ligands such as water and
THF. Complexes 3a-c are air stable for hours in crystalline
form but slowly form water complexes in Et2O solutions in air.
The IR spectra for these complexes show four bands in the
carbonyl region similar to those for 1 and 2, but at slightly higher
frequencies due to the decreased electron donation of Et2O
under vacuum provided a mixture of LiCl and the crude product
as a yellow paste or foam. The product was purified by eluting
the crude product through an SiO2 column with hexanes or
benzene/hexanes, which removed the yellow color and LiCl.
Complexes 2a-c were isolated as air stable white solids in
moderate yields. Similar preparation of 2a from MeLi and cis-
Re(CO)4(PPh3)Br has been previously reported.12
-
versus CH3 or Cl- and the positive charge on the complex.
The X-ray crystal structure of 3a was determined to confirm
coordination of the ether to the metal center (Re-O ) 2.254-
(11) Å) and has been recently communicated.8 The 13C and 1H
NMR spectra for 3a were measured at -73 °C and confirmed
the coordination of one Et2O molecule in CD2Cl2 solution. The
resonances assigned to the bound Et2O appear in the 1H NMR
The 1H NMR spectra for 2 each show an upfield doublet for
the rhenium methyl ligand due to coupling to the phosphine,
(12) McKinney, R. J.; Kaesz, H. D. J. Am. Chem. Soc. 1975, 97, 3066-
3072.

118 Inorganic Chemistry, Vol. 38, No. 1, 1999
Huhmann-Vincent et al.
spectrum at δ 3.54 (q) and 0.98 (t), and at 77.13 (br) and 12.82
(br) in 13C{1H} NMR spectrum. These are shifted from those
of free Et2O at this temperature in CD2Cl2 solution at δ 3.34
(q) and 1.02 (t), and at δ 65.79 (s) and 14.98 (s) in the 1H and
13C{1H} NMR spectra, respectively. The 31P NMR spectrum
for 3a at -73 °C showed one phosphorus environment. The
room temperature 1H NMR spectra of 3a-c after 5 min in CD2-
Cl2 solution confirmed the persistence of coordinated Et2O,
identified by resonances shifted downfield from that of free
Et2O, as well as peaks due to reaction of 3 with dichloromethane
(discussed below).
The strong coordination of diethyl ether to the Re center is
quite surprising when considering that Heinekey’s analogous
bis-phosphine complexes [mer-Re(CO)3(PR3)2][BArF] are iso-
lated as the agostic compounds from protonation of [mer-(PR3)2-
Re(CO)3Me] with [H(OEt2)2][BArF].13 An agostic complex is
one in which the sixth coordination site is taken up by interaction
between the metal center and a C-H bond of one of the
phosphine ligands. These complexes are usually deeply colored,
and the agostic interaction is readily displaced by other
substrates. This preference for the [cis-Re(CO)4(PR3)]+ fragment
to form solvent complexes instead of an agostic compound is
due to the high electrophilicity of the metal center and the lack
of steric hindrance at the open coordination site. There are a
number of examples of isolated diethyl ether complexes reported
in the literature,3,14 including one other complex of rhenium,
[CpRe(NO)(PPh3)(OEt2)][BF4].2d
Figure 3. 13C NMR spectra for [cis-Re(CO)4(PiPr3)(ClCH2Cl)][BArF],
4b, in CH2Cl2 solution. (a) 13C, -80 °C; (b) 13C{1H}, -80 °C; (c)
13C{1H}, 20 °C.
Preparation of [cis-Re(CO)4(PR3)(ClCH2Cl)][BArF] (4a-
c). Reaction of the methyl complexes 2 with 1 equiv of [Ph3C]-
[BArF] in methylene chloride provided the solvent-coordinated
complexes [cis-Re(CO)4(PR3)(ClCH2Cl)][BArF] (4a-c) (eq 5).
rapidly on the NMR time scale in CH2Cl2 solution at room
temperature, and is not distinguishable from free CH2Cl2 in the
1H or 13C NMR spectra. However, when CH2Cl2 solutions of 4
are cooled to -80 °C, signals assigned to bound CH2Cl2 at 66.36
(4a), 68.05 (4b), and 67.62 (4c) ppm are observed in the 13C-
{1H} NMR spectra. The peak assigned to bound CH2Cl2 in 4b
is a doublet (JCP ) 2.1 Hz), while those for 4a and 4c are slightly
broadened singlets. These peaks are split into triplets JCH
)
1
184.3 (4a), 184.8 (4b), and 186.5 (4c) Hz in the H-coupled
experiment, as shown in Figure 3. The signals are shifted
downfield from that of free CH2Cl2 at -80 °C (54.00 ppm, JCH
) 179.9 Hz), and are not present in the analogous NMR
experiments performed in CD2Cl2 due to peak broadening from
deuterium coupling. These observations in the low temperature
13C spectra are very similar to those observed by Gladysz with
[Cp′Re(NO)(PPh3)(ClCH2Cl)][BF4] in CH2Cl2 at -85 °C (78.3
ppm, JCH ) 185.5 Hz, JCP ) 3.8 Hz).
There have recently been a number of examples of isolated
complexes with coordinated dichloromethane, most of which
are derived from extremely electron deficient cationic metal
centers with low-interacting anions.2a,3,4b,15 In the complexes
characterized by X-ray crystallography, dichloromethane has
The complexes were isolated from the Ph3CCH3 by addition of
hexanes to the reaction mixture and were obtained in good yields
as pale yellow or colorless crystals. The presence of 1 equiv of
CH2Cl2 in 4 was confirmed by elemental analysis. Complexes
4a-c are stable in methylene chloride solution for 1 day;
however, they will form the chloride-bridged dimers 5a-c after
days in CD2Cl2 solution or in the presence of water or other
bases. These dichloromethane complexes are much more stable
than Gladysz’s [Cp′Re(NO)(PPh3)(ClCH2Cl)][BF4] (Cp′ )
C5H5, C5Me5), which decomposes to a chloride-bridged dimer
in CH2Cl2 solution above -20 °C.2a,e,g
The IR spectra for 4b and 4c in Nujol mulls each show one
weak band around 2120 cm-1 and three strong bands between
1980 and 2050 cm-1. The spectrum for 4a is a bit more
complicated with one weak band at 2122 cm-1 and six
overlapping bands between 1980 and 2050 cm-1, presumably
because of band splitting. The bound CH2Cl2 in 4 exchanges
(15) For example: (a) Huang, D.; Huffman, J. C.; Bollinger, J. C.;
Eisenstein, O.; Caulton, K. G. J. Am. Chem. Soc. 1997, 119, 7398-
7399. (b) Fornie´s, J.; Mart´ınez, F.; Navarro, R.; Urriolabeitia, E. P.
Organometallics 1996, 15, 1813-1819. (c) Colsman, M. R.; New-
bound, T. D.; Marshall, L. J.; Noirot, M. D.; Miller, M. M.; Wulfsberg,
G. P.; Frye, J. S.; Anderson, O. P.; Strauss, S. H. J. Am. Chem. Soc.
1990, 112, 2349-2362. (d) Newbound, T. D.; Colsman, M. R.; Miller,
M. M.; Wulfsberg, G. P.; Anderson, O. P.; Strauss, S. H. J. Am. Chem.
Soc. 1989, 111, 3762-3764. (e) Su¨nkel, K.; Urban, G.; Beck, W. J.
Organomet. Chem. 1983, 187-194. (f) Beck, W.; Schloter, K. Z.
Naturforsch., B: Anorg. Chem., Org. Chem. 1978, 33, 1214-1222.
(g) For a review on the coordination chemistry of halocarbons, see:
Kulawiec, R. J.; Crabtree, R. H. Coord. Chem. ReV. 1990, 99, 89-
115.
(13) Heinekey, D. M.; Radzewich, C. E.; Voges, M. H.; Schomber, B. M.
J. Am. Chem. Soc. 1997, 119, 4172-4181.
(14) For example: (a) Yi, C. S.; Wodka, D.; Rhingold, A. L.; Yap, G. P.
A. Organometallics 1996, 15, 2-4. (b) Rix, R. C.; Brookhart, M.;
White, P. S. J. Am. Chem. Soc. 1996, 118, 2436-21448. (c) Solari,
E.; Musso, F.; Gallo, E.; Floriani, C.; Re, N.; Chiesi-Villa, A.; Rizzoli,
C. Organometallics 1995, 14, 2265-2276. (d) Kolodziej, R. M.;
Schrock, R. R.; Dewan, J. C. Inorg. Chem. 1989, 28, 1243-1248.

Re Complexes with Weakly Coordinating Solvent Ligands
Inorganic Chemistry, Vol. 38, No. 1, 1999 119
Figure 5. Decomposition of 3a in CD2Cl2 solution, 20 °C, monitored
by integration of 31P{1H} signals.
These distances are similar to those found for 4a (1.817(6) Å),
the Ir complex (1.820(15) Å), and the Pt complex (1.79(2), 1.80-
(4) Å). The C-Cl(unbound) distances were refined as 1.78(2)
and 1.55(2) Å for 4b, 1.716(6) Å for 4a, 1.730(15) Å for Ir,
and 1.70(2) and 1.69(4) Å for Pt. Finally, the Cl-C-Cl angles
for 4b are 109.8(9) and 116.6(11)°, compared to 112.0(3)° for
4a, 110.7(8)° for the Ir complex, and 111.6(13) and 103(2)°
for the Pt complex. The orientation of the dichlromethane ligand
in 4a and 4b differs somewhat. In 4a, the two chlorine atoms
of the CH2Cl2 molecule are essentially in the plane defined by
the Re and three equatorial CO carbon atoms, with the
methylene C atom pointed down away from the phosphine: Cl-
(bound) +0.19 Å, C(methylene) -0.82 Å, and Cl(unbound)
-0.11 Å out of the equatorial plane. In contrast to this, the
whole dichloromethane ligand in 4b is pointed down away from
the phosphine, with Cl(1) 0.0 Å, C(5) -1.57 Å, C(5)′ -1.15
Å, Cl(2) -2.31 Å, and Cl(2)′ -2.63 Å out of the equatorial
plane.
Figure 4. ORTEP diagram for [cis-Re(CO)4(PiPr3)(ClCH2Cl)][BArF],
4b; BArF not shown (50% probability ellipsoids).
Table 4. Selected Bond Distances (Å) and Angles (deg) for
Methylene Chloride Complex 4b
distances (Å)
angles (deg)
Re(1)-Cl(1)
2.554(2)
1.765(13)
1.86(2)
1.78(2)
1.55(2)
2.5354(13)
2.006(6)
1.914(6)
1.998(6)
1.973(6)
P(1)-Re(1)-Cl(1)
86.59(5)
177.2(2)
174.9(9)
178.3(2)
117.8(6)
112.6(6)
109.8(9)
116.6(11)
Cl(1)-C(5)
Cl(1)-C(5)′
C(5)-Cl(2)
C(5)′-Cl(2)′
Re(1)-P(1)
Re(1)-C(1)
Re(1)-C(2)
Re(1)-C(3)
Re(1)-C(4)
P(1)-Re(1)-C(4)
C(1)-Re(1)-C(3)
Cl(1)-Re(1)-C(2)
Re(1)-Cl(1)-C(5)
Re(1)-Cl(1)-C(5)′
Cl(1)-C(5)-Cl(2)
Cl(1)-C(5)′-Cl(2)′
Decomposition of [cis-Re(CO)4(PR3)(S)][BArF]. The ether
complexes 3 are not stable in methylene chloride solution at
room temperature, and after 24 h 3a-c convert entirely to the
chloride-bridged dimers {[cis-Re(CO)4(PR3)]2(µ-Cl)}{BArF}
(5a-c). The decomposition of the 3 in CD2Cl2 solution was
monitored by 31P{1H} NMR spectroscopy. The rate of formation
of the chloride-bridged dimers was found to vary with the nature
of the phosphine, with the PiPr3 and PCy3 derivatives completely
converting to the dimers within 7 h, while the PPh3 analogue
required 24 h to completely convert to the dimer. The dichlo-
romethane complexes [cis-Re(CO)4(PR3)(ClCD2Cl)][BArF], iden-
tified by comparison of 31P shift to authentic samples of 4, were
observed as intermediates in the decomposition of 3 to 5. A
graph illustrating the conversion of 3a to 5a over 24 h is shown
in Figure 5. Similar plots were obtained for 3b and 3c, and are
provided in the supplementary data.
been found to coordinate bidentate through the chloride atoms
in Ag2(CH2Cl2)4Pd(OTeF5)15d and [RuH(CO)(CH2Cl2)(PtBu2-
Me)2][BArF],15a and monodentate through one of the chloride
atoms in [PtAg(CH2Cl2)(C6F5)2(acac)]2,15b [Cp*Ir(Me)(PMe3)-
(ClCH2Cl)][BArF],4b and [trans-PtH(PiPr3)2(ClCH2Cl)][BArF].3
The coordinated dichloromethane in [CpMo(CO)3(ClCH2Cl)]-
[PF6]15f and [Cp′Re(NO)(PPh3)(ClCH2Cl)][BF4]2a has been
assigned on the basis of IR spectral data and low-temperature
13C NMR spectral data, respectively.
Structure of [cis-Re(CO)4(PiPr3)(CH2Cl2)][BArF] (4b). The
X-ray crystal structure of 4a was recently communicated and
confirmed the retention of cis geometry and η1-coordination of
the CH2Cl2 ligand through one chloride.8 In the current study,
i
we determined the structure of the Pr complex 4b for the
purpose of comparison to that of the Ph analogue. An ORTEP
diagram of 4b is shown in Figure 4, and selected bond lengths
and angles are listed in Table 4. As in the case of 4a, the
coordinated CH2Cl2 is η1-bound to the Re through one chloride.
The CH2Cl2 ligand is disordered at the methylene carbon C(5)
and the unbound chloride Cl(2), and these were refined as two
one-half occupancy atom positions.
The Re-Cl distance in 4b is 2.554(2) Å, which is comparable
to that found for the PPh3 derivative 4a, 2.546(2) Å,8 and those
reported for the related η1-coordinated dichloromethane com-
plexes [Cp*Ir(Me)(PMe3)(ClCH2Cl)][BArF] (2.462(3) Å)4b and
[trans-PtH(PiPr3)2(ClCH2Cl)][BArF] (2.489(4), 2.60(1) Å), which
was disordered at the bound chloride and methylene carbon.3
As expected, the Re-Cl distance in 4b is longer than the Re-
Cl distance (2.554(3) Å) in the corresponding neutral chloride
compound 1b (2.483(2) Å). The C-Cl(bound) distances in 4b
are 1.765(13) and 1.86(2) Å for C(5) and C(5)′, respectively.
Changes were also apparent in the ether and BArF regions of
1
the H NMR spectra as 3 converted to 5 in CD2Cl2 solution.
The resonances due to coordinated Et2O in 3 decreased in
intensity as two sets of peaks at δ 4.63 (q, JHH ) 7.1 Hz) and
1.63 (t, JHH ) 7.1 Hz), and 3.5 (br) and 1.2 (br t) grew in, and
no peaks due to coordinated Et2O in 3 were observed in the 1H
NMR spectra after 24 h in CD2Cl2 solution. These two new
sets of ethyl resonances were at virtually identical chemical
shifts for all three phosphine derivatives, whereas the original
resonances due to bound Re-OEt2 varried slightly for each
derivative of 3. This observation suggests that the two new sets
of resonances are due to ether which is not associated with a
Re center. When the reaction mixture was placed under a
vacuum after 24 h in CD2Cl2 solution, free ether was observed
in the trapped volatiles. Subsequent dissolution of the residue
in CD2Cl2 resulted in the same two sets of ether resonances in
the 1H NMR spectra (δ 4.63, 1.63 and 3.5, 1.2), with an overall

120 Inorganic Chemistry, Vol. 38, No. 1, 1999
Huhmann-Vincent et al.
Scheme 1. Proposed Mechanism for Conversion of 3 to 5
of halide ions X- upon the methylene carbon in [Cp′Re(NO)-
(PPh3)(ClCH2Cl)][BF4] to provide the neutral ReCl complex
and CH2ClX.2g The decomposition of the corresponding diethyl
ether and tetrahydrofuran coordinated complexes [Cp′Re(NO)-
(PPh3)(OR2)][BF4] were also observed when warmed above -20
°C in CD2Cl2 solution, although the decomposition products
and pathway were not reported.2d It is possible that the
conversion of 3 to 5 is catalyzed by trace amounts of adventi-
tious water in solution, even though water was rigorously
excluded from these systems. This would require nucleophilic
attack of H2O on the methylene carbon of 4 to generate [H2-
OCH2Cl]+, which would then have to react further with Et2O
to produce an ethyloxoinium ion.
Preparation of {[cis-Re(CO)4(PR3)]2(µ-Cl)}{BArF} (5a-
c). To unambiguously assign the decomposition products of the
ether complexes 3 in methylene chloride solution, the chloride-
bridged Re dimers {[cis-Re(CO)4(PR3)]2(µ-Cl)}{BArF} (5) were
prepared. Reaction of the chloride complexes 1 with 1 equiv of
the corresponding methyl compound 2 in the presence of 1 equiv
of [H(Et2O)2][BArf] in diethyl ether solution cleanly provided
5 as colorless crystals (eq 6). The dimers gave satisfactory
integration of phosphine protons versus ethyl protons consistent
with 1 equiv of Et2O per Re dimer.
The chemical shifts in the 1H NMR spectra of the downfield
set of Et2O resonances at δ 4.63 (q, JHH ) 7.1 Hz) and 1.63 (t,
JHH ) 7.1 Hz) are consistent with the existence of an
ethyloxonium ion. For comparison, [Et3O][BF4] (Acros Organ-
ics) in CD2Cl2 solution exhibits resonances at δ 4.78 (q, JHH
)
7.1 Hz) and 1.63 (t, JHH ) 7.1 Hz). The second set of resonances
at δ 3.5 and 1.2 ppm increase in intensity when free ether is
added and thus have been assigned as a solvate of the oxonium
ion. To support this assignment, similar broad resonances at δ
1
3.6 and 1.2 ppm in the H NMR spectrum of [Et3O][BF4] in
CD2Cl2 increased in intensity upon addition of free ether.
Formation of an oxonium ion in this system could result from
nucleophilic attack of the weak base Et2O on the methylene
carbon of [Re-ClCH2Cl]+ (4), generating the neutral chloride,
1, and [Et2OCH2Cl]+. The dichloromethane complex 4 would
be formed by dissociation of the Et2O from the Re center in
solution, and should be faster for the PiPr and PCy3 complexes
3b and 3c than for the PPh3 complex 3a since the more electron
donating and bulkier phosphines should not bind Et2O as
strongly. This is consistent with the observed slower rate for
conversion of 3 to 5 for the PPh3 derivative versus the PiPr3
and PCy3 analogues. In a separate experiment, 1 µL of Et2O
was added to a CD2Cl2 solution of 4a (10 mg/0.5 mL) and
conversion to 5a was complete within 24 h. The proposed
mechanism for conversion of 3 to 5 is shown in Scheme 1.
In an attempt to determine the fate of the methylene chloride
molecule which must give up a Cl- to form the chloride-bridged
Re dimer 5, a CH2Cl2 solution of 3a was allowed to stand for
24 h, the volatiles removed under vacuum, and the residue
elemental analysis. The IR spectra for each derivative of 5
showed two weak or medium bands in the region 2100-2122
cm-1 and multiple strong overlapping bands between 1965 and
2030 cm-1. The 1H and 31P NMR spectra corresponded to one
phosphine environment, and one BArF anion per two phosphine
ligands. The complexes were quite stable and did not decompose
when exposed to air for 1 day. No reaction was observed from
combination of the dimer 5a with approximately 10 equiv of
NaBArF in CD2Cl2 solution after one week.
The stability of the dimers and ease of formation from [Re-
(S)]+ and chloride sources is not surprising when considering
the high electrophilicity of the rhenium center and the lack of
steric restraint from the ligands. This is not the case in the more
sterically demanding bis-phosphine complexes which react
completely with NaBArF in CH2Cl2 solution to remove all of
the halide: mer-ReCl(CO)3(PR3)2 forms the Re(H2) complex
under H2 atmosphere,13 mer-MnBr(CO)3(PCy3)2 forms the
agostic complex,16 and trans-PtH(Cl)(PiPr3)2 forms the Pt-
(ClCH2Cl) solvent complex.3
1
redissolved in CD2Cl2. The resulting H NMR spectrum was
identical to that obtained from the reaction in CD2Cl2, as
described in the previous paragraph. Unfortunately, no new
1
peaks were observed in the H NMR spectrum that could be
assigned to [ClCH2OEt2][BArF] products that would result from
loss of Cl- from CH2Cl2. GC/MS analysis of the trapped
volatiles showed the presence of CH2Cl2, Et2O, CHCl3, and 1,3-
(CF3)2C6H4. This would seem to suggest that if [ClCH2OEt2]-
[BArF] were formed, it is unstable under the reaction conditions
and reacts further with the BArF to form a new ethyloxonium
ion, [Et2OX]+. Furthermore, small additional peaks appeared
in the BArF region of the 1H NMR spectra as 3 converted to 5,
providing more evidence that decomposition of BArF occurs.
Finally, there was no indication of [H(OEt2)2][BArF] formation
in the 1H NMR spectra, and no observation of a carbene in the
13C NMR spectra.
Structures of {[cis-Re(CO)4(PR3)]2(µ-Cl)}{BArF} (5a, 5c).
Addition of bulk hexanes (not dried) to a CH2Cl2 solution of
4a and storage for 1 week at room temperature provided
approximately a 20% yield of 5a as colorless crystals with two
water molecules in the lattice. Similar conditions produced 5c
as large crystals in approximately 40% yield. The structures of
each were determined by X-ray crystallography and ORTEP
The reaction of a base with coordinated methylene chloride
has precedence in Gladysz’s observation of nucleophilic attack
(16) Toupadakis, A.; Kubas, G. J.; King, W. A.; Scott, B. L.; Huhmann-
Vincent, J. Organometallics 1998, 17, 5315-5323.

Re Complexes with Weakly Coordinating Solvent Ligands
Inorganic Chemistry, Vol. 38, No. 1, 1999 121
chemical shift observed for 6 in NC5F5 solutions (see Experi-
mental Section). This peak in CD2Cl2 solution is therefore
assigned to the pentafluoropyridine-coordinated complex 6.
Subsequent addition of 25 µL of Et2O resulted in complete
conversion to the diethyl ether complex 3b (36.3 ppm). These
results give the binding order of Et2O > NC5F5 . CH2Cl2.
Finally, conversion of 6 to the chloride-bridged dimer 5b in
CD2Cl2 solution is slow, and only 50% conversion was obtained
after one week (31P NMR).
Structure of [cis-Re(CO)4(PiPr3)(NC5F5)][BArF] (6). The
X-ray crystal structure of 6 was determined in order to confirm
the coordination of pentafluoropyridine to the Re center, instead
of just being in the lattice. An ORTEP diagram of 6 is shown
in Figure 8, and selected bond lengths and angles are listed in
Table 6. The Re-N distance is 2.319(5) Å, which is intermediate
in length between the corresponding Re-Cl distances in the
methylene chloride complexes 4a (2.546(2) Å) and 4b (2.554-
(2) Å), and the Re-O distance in the ether complex 3a (2.254-
(11) Å). The pentafluoropyridine is tilted 27.9° about the Re-N
axis from the plane defined by the Re and three equatorial
carbonyl C atoms (C(1)-C(3)). There are no short contacts
between the Re-NC5F5 cation and the BArF anion. Bercaw has
recently reported the crystal structure of a Pt-NC5F5 complex,
[Pt(Me)(tmede)(NC5F5)][BArF], with a much shorter Pt-N
distance of 2.043(6) Å.5a
Figure 6. ORTEP diagram for {[cis-Re(CO)4(PPh3)]2(µ-Cl)}{BArF},
5a; BArF not shown (50% probability ellipsoids).
Conclusions
The solvent coordinated complexes [cis-Re(PR3)(CO)4(S)]-
[BArF] are conveniently prepared from the corresponding neutral
ReMe precursors and either [H(OEt2)2][BArF] (S ) Et2O) or
[Ph3C][BArF] (S ) CH2Cl2, NC5F5) in the appropriate solvent.
The low-temperature 13C NMR data and X-ray structures of
the dichloromethane complexes confirm that CH2Cl2 coordina-
tion persists in both solution and the solid state. Of the
structurally characterized complexes (3a, 4a, 4b, 6) for this [cis-
Re(PR3)(CO)4(S)]+ system, the Re-S distance increases in the
order Et2O < NC5F5 < CH2Cl2, and the binding affinities of S
to Re+ in methylene chloride solution decreases in the order
Et2O > NC5F5 . CH2Cl2. The dichloromethane complexes are
not stable in CH2Cl2 solution in the presence of the weak base
diethyl ether, and decompose to chloride-bridged Re dimers.
Figure 7. ORTEP diagram for {[cis-Re(CO)4(PCy3)]2(µ-Cl)}{BArF},
5c; BArF not shown (50% probability ellipsoids).
diagrams of 5a and 5c are shown in Figures 6 and 7, and selected
interatomic distances and angles can be found in Table 5.
The structures are similar, both retaining the cis orientation
of phosphines and chloride, with approximately octahedral
geometry about each Re. The Re-Re interatomic distances are
4.333 Å for the Ph derivative 5a and 4.460 Å for the Cy
derivative 5c. There is no center of symmetry about the bridging
chloride thus complex has two inequiv Re-Cl distances, 2.421-
(4) and 2.397(5) Å for 5a, and 2.5264(5) and 2.5285(7) Å for
5c. As expected, the bulkier PCy3 complex has a longer Re-
Re distance and longer Re-Cl distances than the PPh3 complex.
The Re-Cl distances for 5a are slightly shorter than the Re-
Cl distances found in the dichloromethane complex 4a (2.546-
(2) Å), and the Re-Cl bond lengths of 5c are slightly longer
than that of the neutral chloride complex 1c (2.489(7) Å). The
Re-Cl-Re angle is larger for the PPh3 complex 5a (128.2-
(2)°) than for the PCy3 complex 5c (123.85(2)°), due to the
shorter Re-Re distance in 5a versus 5c.
Experimental Section
General Considerations. NMR spectra were measured on a Varian
UNITY series 300 MHz spectrometer. FT-IR spectra were obtained
either on a Bio-Rad FTS-40 or Nicolet Magna 750 spectrometer.
Solvents were dried either by distillation from P2O5 (CH2Cl2, NC5F5),
Na/benzophenone (Et2O, hexanes), or by elution from columns of
activated alumina and BTS catalyst according to the procedure describe
by Grubbs.17 NMR solvents were dried over either CaH2 or P2O5 and
Preparation of [cis-Re(CO)4(PiPr3)(NC5F5)][BArF] (6).
i
Reaction of the Pr complex 2b with 1 equiv of [Ph3C][BArF]
1
vacuum transferred before use. H NMR spectra were referenced to
in NC5F5 provided the pentafluoropyridine-coordinated complex
[cis-Re(CO)4(PiPr3)(NC5F5)][BArF] (6). Complex 6 is isolated
from hexanes/NC5F5 as colorless crystals and is stable in NC5F5
solution. The presence of one NC5F5 molecule in the complex
was determined by elemental analysis. The IR spectrum for 6
is very similar to that obtained for the methylene chloride
complex 4b, and the 1H and 31P NMR spectra in NC5F5 solution
are consistent with one phosphine environment.
Solutions of 6 in CD2Cl2 (5-7 mg/0.5 mL) immediately
convert to the ClCD2Cl-coordinated complex 4b as determined
by the 31P NMR chemical shift of 33.6 ppm. However, when
an aliquot of 50 µL of NC5F5 was injected to a CD2Cl2 solution
of 6 (10 mg/0.5 mL) and the 31P{1H} NMR spectrum measured,
one sharp peak was observed at 30.4 ppm, which is at the same
either CHDCl2 or TMS, 31P NMR spectra were referenced to H3PO3,
and 13C spectra were referenced to CD2Cl2. The BArF peaks are not
reported in the 13C NMR data and are virtually identical to those
previously reported, regardless of the cationic fragment.3 All manipula-
tions and reactions with air-sensitive compounds were carried out either
in a Vacuum Atmospheres He Drybox or under Ar using standard
Schlenk techniques. All reactions were carried out at atmospheric
pressure, which is 600 milliTorr at Los Alamos (elevation ) 7000 ft)
unless otherwise noted. The reagents [H(OEt2)2][BArF]18 and [Ph3C]-
(17) Pangborn, A. B.; Giardellow, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518-1520.
(18) Brookhart, M.; Grant, B.; Volpe, A. F., Jr. Organometallics 1992,
11, 3920-3921.
(19) Bahr, S. T.; Boudjouk, P. J. Org. Chem. 1992, 57, 5545-5547.

122 Inorganic Chemistry, Vol. 38, No. 1, 1999
Huhmann-Vincent et al.
Table 5. Selected Interatomic Distances (Å) and Angles (deg) for Chloride-Bridged Complexes 5a and 5c
distances
angles
5a
5c
5a
5c
Re(1)-Re(2)
Re(1)-Cl
4.333
4.460
Re(1)-Cl-Re(2)
P(1)-Re(1)-Cl
P(1)-Re(1)-C(4)
C(2)-Re(1)-Cl
C(1)-Re(1)-C(3)
P(2)-Re(2)-Cl
P(2)-Re(2)-C(6)
C(8)-Re(2)-Cl
C(5)-Re(2)-C(7)
128.2(2)
84.8(2)
123.85(2)
86.87(2)
178.62(8)
177.31(9)
173.97(10)
87.66(2)
176.13(8)
178.23(7)
174.35(12)
2.421(4)
2.510(4)
2.03(2)
1.95(2)
2.01(2)
1.94(2)
2.397(5)
2.493(3)
1.98(2)
1.92(2)
1.96(2)
1.91(2)
2.5264(5)
2.5371(6)
1.997(2)
1.908(3)
1.997(3)
1.939(3)
2.5285(7)
2.5277(6)
2.006(2)
1.960(3)
1.990(2)
1.915(3)
Re(1)-P(1)
Re(1)-C(1)
Re(1)-C(2)
Re(1)-C(3)
Re(1)-C(4)
Re(2)-Cl
176.5(5)
177.9(6)
178.8(6)
83.93(14)
178.0(5)
170.7(5)
177.6(7)
Re(2)-P(2)
Re(2)-C(5)
Re(2)-C(6)
Re(2)-C(7)
Re(2)-C(8)
washed once with cold hexane (5 mL) and dried in a vacuum to provide
1.10 g of 1b (81% yield). Colorless prisms suitable for X-ray diffraction
studies were obtained by recrystallization from cyclohexane/hexane (1/
5) at -30 °C. Complexes 1a and 1c were prepared analogously to 1b
and isolated as white solids in 91% and 83% yields, respectively.
Colorless prisms of 1c suitable for X-ray diffraction studies were
obtained by recrystallization from cyclohexane/hexane (1/2) at -30
°C. Data for 1b. Anal. Calcd for C13H21O4ClPRe: C, 31.61; H, 4.29.
Found: C, 32.05; H, 4.31. 1H NMR (CD2Cl2) 2.56 (d of septets, JHP
9.2, JHH ) 7.2, 3H, CH), 1.35 (dd, JHP ) 14.1, JHH ) 7.2, 18H, CH3).
)
13C{1H} NMR (CD2Cl2) 188.16 (d, JHP ) 9.2, CO), 184.93 (d, JHP
)
5.0, CO), 183.55 (d, JHP ) 53.0, CO), 25.40 (d, JCP ) 23.6, iPr), 19.85
i
(s, Pr). Data for 1c. Anal. Calcd for C22H33ClO4PRe: C, 43.03; H,
5.42. Found: C, 42.75; H, 5.26. 1H NMR (CD2Cl2) 2.24 (m, 1H, PCy3),
2.00 (m, 2H, PCy3), 1.87 (m, 2H, PCy3), 1.52 (m, 2H, PCy3), 1.74 (m,
1H, PCy3), 1.31 (m, 3H, PCy3). 13C{1H} NMR (CD2Cl2) 188.49 (d,
JCP ) 8.8, CO), 185.20 (d, JCP ) 6.7, CO), 183.67 (d, JCP ) 52.5,
CO), 34.91 (d, JCP ) 21.7, Cy), 30.03 (s, Cy), 28.02 (d, JCP ) 10.4,
Cy), 26.72 (s, Cy).
Figure 8. ORTEP diagram for [cis-Re(CO)4(PiPr3)(NC5F5)][BArF], 6;
BArF not shown (50% probability ellipsoids).
Photochemical Preparation of 1b and 1c. Re(CO)5Cl (1.88 g, 5.20
mmol) and PiPr3 (0.834 g, 5.20 mmol) were weighed into a Schlenk
flask and CH2Cl2 (50 mL) and cyclohexane (50 mL) were added. The
reaction mixture was placed approximately two inches from a 450 W
lamp (which was inserted in a quartz water cooled jacket) and
photolized for 1.5 h with stirring, after which time a pale yellow solution
was obtained. The volatiles were removed under vacuo, and the resulting
white residue was dissolved in hot cyclohexane (50 mL). The solution
was filtered hot through a frit under Ar to remove any unreacted Re-
(CO)5Cl and then concentrated to a volume of 5 mL. Hexanes (10 mL)
were added, and the solution was concentrated until crystals began to
form. Storage in a freezer (-30 °C) for 10 h afforded white crystals,
which were washed once with cold hexane (5 mL) and dried in a
vacuum to provide 1.98 g of 1b (77% yield). Complex 1c was prepared
similarly from phosphine and Re(CO)5Cl, and isolated in 78% yield.
Table 6. Selected Bond Distances and Angles for
Pentafluoropyridine Complex 6
Distances (Å)
Re(1)-(P1)
Re(1)-N(1)
Re(1)-C(1)
Re(1)-C(2)
Re(1)-C(3)
Re(1)-C(4)
2.534(1)
2.319(5)
2.002(7)
1.919(6)
2.004(7)
1.982(7)
N(1)-C(14)
C(14)-C(15)
C(15)-C(16)
C(16)-C(17)
C(17)-C(18)
C(18)-N(1)
1.327(8)
1.382(9)
1.365(11)
1.365(11)
1.376(9)
1.332(8)
Angles (deg)
P(1)-Re(1)-N(1)
92.79(12)
P(1)-Re(1)-C(4)
C(3)-Re(1)-C(1)
N(1)-Re(1)-C(2)
176.9(2)
175.0(2)
173.5(2)
114.7(5)
i
Preparation of cis-Re(CO)4(PR3)(CH3) (R ) Ph (2a), Pr (2b),
Cy (2c)). An aliquot of MeLi (0.72 mL, 1.4 M) was added to a stirred
and cooled (-78 °C) solution of 1b (0.500 g, 1.01 mmol) in Et2O (50
mL). The reaction mixture was stirred for 5 min, then slowly warmed
to room temperature and stirred for 30 min. To the resulting pale yellow
reaction mixture was added CH2Cl2 (0.50 mL) to quench any unreacted
MeLi. The solvents were removed under vacuum and the residue was
chromatographed on SiO2 (15 g) eluting with hexanes/benzene (10/1).
The first fraction was collected, and removal of volatiles provided 2b
as a white solid (0.30 g, 62% yield). Compounds 2a and 2c were
prepared analogously to 2b from MeLi and 1a or 1c and isolated as
white solids in 55% and 48% yields, respectively. Data for 2b. Anal.
Calcd for C14H24O4PRe: C, 35.51; H, 5.11. Found: C, 35.51; H, 4.91.
1H NMR (CD2Cl2) 2.33 (d of sept, JHP ) 8.8, JHH ) 7.2, 3H, iPr), 1.27
C(18)-N(1)-C(14)
[BArF]19 were prepared according to literature procedures. The Re-
(CO)5Cl and all phosphines were purchased from Strem Chemicals and
used as supplied, MeLi was purchased from Aldrich in Et2O solution
(1.4 M). Characterization data for 1a and 2a have been reported
elsewhere.10,12
i
Preparation of cis-Re(CO)4(PR3)Cl for R ) Ph (1a), Pr (1b),
Cy (1c). Re(CO)5Cl (1.00 g, 2.76 mmol) and PiPr3 (0.449 g, 2.80 mmol)
were weighed into a Schlenk flask, and CHCl3 (100 mL) was added.
The reaction mixture was gently refluxed for 15 h with stirring, after
which time the clear and colorless solution was obtained. The
chloroform was removed under vacuo and the resulting white residue
was dissolved in hot cyclohexane (30 mL). The solution was filtered
hot through a frit under Ar to remove any unreacted Re(CO)5Cl, and
then concentrated to a volume of 5 mL. Hexanes (10 mL) were added
and the solution concentrated until white crystal began to form. Storage
in a freezer (-30 °C) for 10 h afforded white crystals, which were
i
(dd, JHP ) 13.7, JHH 7.2, 18H, Pr), -0.45 (d, JHP ) 6.3, CH3, 3H).
13C{1H} NMR (CD2Cl2) 193.81 (d, JCP ) 10.2, CO), 189.37 (d, JCP
)
47.0, CO), 188.46 (d, JCP ) 7.2, CO), 26.02 (d, JCP ) 22.4, iPr), 19.78
i
(s, Pr), -34.30 (d, JCP ) 8.2, CH3). Data for 2c. Anal. Calcd for
C23H36O4PRe: C, 46.53; H, 6.11. Found: C, 46.67; H, 5.95. 1H NMR
(CD2Cl2) 2.01 (m, 3H, Cy), 1.89 (m, 12H, Cy), 1.72 (br s, 3H, Cy),

Re Complexes with Weakly Coordinating Solvent Ligands
Inorganic Chemistry, Vol. 38, No. 1, 1999 123
1.46 (m, 6H, Cy), 1.29 (m, 9H, Cy), -0.49 (d, JHP ) 6.4, 3H, CH3).
13C{1H} (CD2Cl2) 194.10 (d, JCP ) 9.5, CO), 189.59 (d, JCP ) 47.3,
CO), 188.51 (d, JCP ) 9.3, CO), 35.55 (d, JCP ) 20.5, Cy), 29.93 (s,
Cy), 28.13 (d, JCP ) 10.1, Cy), 26.90 (s, Cy), -34.28 (d, JCP ) 8.5,
CH3).
) 2.5, Ph), 130.01 (d, JCP ) 10.6, Ph). Data for 5b. Anal. Calcd for
C58H54BClF24O8P2Re2: C, 38.37; H, 3.00. Found: C, 38.37; H, 2.98.
1H NMR (CD2Cl2) 7.73 (s, 8H, BArF), 7.57 (s, 4H, BArF), 2.47 (m,
i
i
6H, Pr), 1.33 (dd, JHH ) 7.5, JHP ) 15.0, 36H, Pr). 31C{1H} NMR
(CD2Cl2) 187.45 (d, JCP ) 8.4, CO), 183.94 (d, JCP ) 46.7, CO), 181.95
i
i
(d, JCP ) 6.8, CO), 26.03 (d, JCP ) 24.0, Pr), 19.85 (s, Pr). Data for
5c. Anal. Calcd for C76H78BClF24O8P2Re2: C, 44.40; H, 3.82. Found:
C, 44.76; H, 3.99. 1H NMR (CD2Cl2) 7.73 (s, 8H, BArF), 7.57 (s, 4H,
BArF), 1.1-2.3 (m, 66H, Cy). 31C{1H} NMR (CD2Cl2) 187.90 (d, JCP
) 8.5, CO), 184.36 (d, JCP ) 45.8, CO), 182.34 (d, JCP ) 6.2, CO),
35.66 (d, JCP ) 21.9, Cy), 30.33 (s, Cy), 28.01 (d, JCP ) 10.7, Cy),
26.40 (s, Cy).
Preparation of [cis-Re(CO)4(PR3)(OEt2)][BArF] (R ) Ph (3a),
iPr (3b), Cy (3c)). Compound 2a (0.200 g, 0.347 mmol) was added to
a 20 mL flask and dissolved in Et2O (7 mL). Subsequent addition of
[H(OEt2)2][BArF] (0.354 g, 0.500 mmol) with stirring resulted in fast
evolution of methane. The pale yellow reaction mixture was stirred
for 5 min before the addition of hexanes (2 mL). The solution was
stored at -30 °C overnight to give colorless crystals of 3a which were
washed twice with hexanes (5 mL) and dried in vacuo (0.502 g, 97%
yield). Compounds 3b and 3c were prepared in analogous fashion from
[H(OEt2)2][BArF] and 2b or 2c and isolated in 91% and 89% yields,
respectively. Data for 3a. Anal. Calcd for C58H37BF24O5PRe: C, 46.51;
Preparation of [cis-Re(CO)4(PiPr3)(NC5F5)][BArF] (6). Solid
[Ph3C][BArF] (0.057 g, 0.052 mmol) was added to a solution of 2b
(0.025 g, 0.052 mmol) in 2 mL NC5F5 to provide a clear, yellow
solution. Hexanes (5 mL) were added, and the solution was stored at
room temperature overnight, after which time clear, colorless crystals
which were suitable for X-ray crystallographic studies had formed. The
solution was pipetted off, and the crystals were washed twice with
hexanes and dried in vacuo to provide 0.048 g of 6 (62% yield). Anal.
Calcd for C50H33BF29NO4PRe: C, 40.28; H, 2.23; N, 0.94. Found: C,
39.97; H, 2.45; N, 1.14. 1H NMR (NC5F5) 7.68 (s, 8H, BArF), 7.27 (s,
1
H, 2.49. Found: C, 46.40; H, 2.36. H NMR (CD2Cl2, -73 °C) 7.73
(s, 8H, BArF), 7.3-7.6 (m, 19H, Ph, BArF), 3.53 (q, 6.9 Hz, 4H Et2O),
0.98 (t, 6.9 Hz, 6H, Et2O). 13C{1H} NMR (CD2Cl2, -73 °C) 187.0 (d,
JCP ) 9.3, CO), 183.51 (d, JCP ) 5.2, CO), 183.11 (d, JCP ) 51.2,
CO), 132.9 (br s, Ph), 132.3 (br s, Ph), 129.6 (br s, Ph), 127.6 (d, JCP
1
) 44.6, i-Ph), 77.13 (br s, OEt2), 12.82 (br s, OEt2). H NMR (CD2-
i
Cl2) 7.73 (s, 8H, BArF), 7.3-7.6 (m, 19H, Ph, BArF), 3.71 (q, 7.1 Hz,
4H Re-OEt2), 1.12 (t, 7.1 Hz, 6H, Re-OEt2). Data for 3b. Anal. Calcd
for C49H43BF24O5PRe: C, 42.16; H, 3.11. Found: C, 41.80; H, 3.13.
1H NMR (CD2Cl2) 7.73 (s, 8H, BArF), 7.56 (s, 4H, BArF), 4.10 (br,
4H, Re-OEt2), 2.46 (m, 3H, iPr), 1.30 (m, 24H, iPr + Re-OEt2). Data
for 3c. Anal. Calcd for C58H55BF24O5PRe: C, 45.95; H, 3.66. Found:
C, 45.93; H, 3.44. 1H NMR (CD2Cl2) 7.73 (s, 8H, BArF), 7.56 (s, 4H,
BArF), 4.00 (br, 4H, Re-OEt2), 0.8-2.2 (br m, Cy + Re-OEt2).
Preparation of [cis-Re(CO)4(PR3)(ClCH2Cl)][BArF] (R ) Ph (4a),
iPr (4b), Cy (4c)). A solution of [Ph3C][BArF] (0.481 g, 0.434 mmol)
in CH2Cl2 (5 mL) was added dropwise via cannula to a stirred solution
of 2a (0.250 g, 0.434 mmol) in CH2Cl2 (15 mL). After 15 min of
stirring, the yellow solution was concentrated to ca. 5 mL in vacuo
and hexanes (20 mL) were added. The reaction mixture was further
concentrated to 10 mL and allowed to stand for 1 h, providing yellow
microcrystals. The solution was syringed off, and the product washed
with hexanes and dried in vacuo (0.53 g, 81% yield). Complexes 4b
and 4c were prepared analogously to the PPh3 analogue in 92% and
80% yields, respectively, from 2b and 2c. Data for 4a. Anal. Calcd for
C55H29BCl2F24PO4Re: C, 43.79; H, 1.94. Found: C, 44.15; H, 1.75.
1H NMR (CD2Cl2) 7.72 (s, 8H, BArF), 7.3-7.7 (m, 19H, Ph, BArF).
4H, BArF), 2.50 (m, 3H, Pr), 1.34 (dd, JHH ) 7.2, JHP ) 15.0, 18H,
iPr).
X-ray Structures of 1b, 1c, and 5a. Crystals of each complex were
each mounted from a pool of mineral oil under argon gas flow on a
thin glass fiber with silicon grease, and placed under a liquid nitrogen
stream on a Siemens P4/PC diffractometer. The lattice parameters were
optimized from a least-squares calculation on 25 carefully centered
reflections of high Bragg angle. The data were collected using ω scans
with a 0.82° (1b), 0.86° (1c), and 1.24° (5a) scan range. Three check
reflections monitored every 97 reflections shoed no systematic variation
of intensities. Lattice determination and data collection for 1a and 1c
were performed using the SHELXTL PC Version 4.2/360 software.
Lattice determination and data collection for 5a was carried out using
XSCANS Version 210b software. All data reduction, including Lorentz
and poarization corrections and structure solution and graphics were
performed using SHELXTL PC Version 4.2/360 software. The structure
refinements were performed using SHELX 93 software.20 All data were
corrected for absorption using either the ellipsoidal (1a, 1c) or laminar
(5a) options in the XEMP facility of SHELXTL PC.
The structures were solved using Patterson and difference Fourier
techniques. These solutions yielded the rheneium atoms and the majority
of all other non-hydrogen atom positions. Subsequent Fourier synthesis
gave all remaining non-hydrogen atom positions. An occupational
disorder in 1c between Cl(1) and the C(4)-O(4) carbonyl group was
modeled, with each site at one-half occupancy for chlorine and one-
half occupancy for carbonyl. The phenyl rings of the triphenylphosphine
ligands 5a were refined as rigid bodies with the C-C distances fixed
at 1.39 Å. All hydrogen atoms were fixed in positions of ideal geometry,
with a C-H distances of 0.97 Å (sp3) or 0.93 Å (sp2) and refined using
the riding model in the HFIX facility in SHELX 93. These idealized
hydrogen atoms had their isotropic temperature factors fixed at 1.2 times
(1c, 5a and methylene of 1b) or 1.5 times (1b methyl) the equiv
isotropic U of the carbon atom they were bonded to.
13C{1H} NMR (CD2Cl2) 184.86 (d, JCP ) 9.0, CO), 182.64 (d, JCP
)
44, CO), 181.89 (d, JCP ) 6.8, CO), 133.50 (d, JCP ) 2.0, Ph), 133.46
(d, JCP ) 10.6, Ph), 130.61 (d, JCP ) 10.6, Ph), iPh not observed. Data
for 4b. Anal. Calcd for C46H35BCl2F24O4PRe: C, 39.28; H, 2.51.
Found: C, 39.27; H, 2.63. 1H NMR (CD2Cl2) 7.72 (s, 8H, BArF), 7.57
(s, 4H, BArF), 2.45 (m, 3H, iPr), 1.34 (dd, JHH ) 7.2, JHP ) 15.0, 18H,
iPr). 13C{1H} NMR (CD2Cl2) 185.85 (d, JCP ) 8.2, CO), 181.14 (d,
JCP ) 6.7, CO), 180.93 (d, JCP ) 39.4, CO), 26.84 (d, JCP ) 24.7, iPr),
i
19.92 (s, Pr). Data for 4c. Anal. Calcd for C55H47BCl2F24PO4Re: C,
43.27; H, 3.10. Found: C, 43.62; H, 3.53. 1H NMR (CD2Cl2) 7.72 (s,
8H, BArF), 7.53 (s, 4H, BArF), 1.0-2.1 (m, 33H, PCy3). 13C{1H} NMR
(CD2Cl2) 185.95 (d, JCP ) 8.9, CO), 181.10 (d, JCP ) 6.4, CO), 180.68
(d, JCP ) 41, CO), 35.78 (d, JCP ) 23, Cy), 30.10 (s, Cy), 27.35 (d, JCP
) 11.4, Cy), 25.78 (s, Cy).
X-ray Structure of 4b, 5c, and 6. Crystals of 4b, 5c, and 6 were
mounted from a pool of mineral oil under argon gas flow on a thin
glass fiber with silicon grease, and placed under a liquid nitrogen stream
on a Bruker P4/CCD/PC diffractometer. The lattice parameters were
determined using 185 (4b), 66 (5c), and 75 (6) reflections. A hemisphere
of data was collected using a combination of æ and ω scans, with 30
s frame exposures and 0.3° frame widths. Data collection and initial
indexing and cell refinement was performed using SMART21 sofltware.
Frame integration and final cell parameter calculation were carried out
Preparation of {[cis-Re(CO)4(PR3)]2(µ-Cl)}{BArF} (R ) Ph (5a),
iPr (5b), Cy (5c)). Diethyl ether (5 mL) was added to a vial containing
1a (0.052 g, 0.087 mmol), 2a (0.050 g, 0.087 mmol) and [H(OEt2)2]-
[BArF] (0.088 g, 0.087 mmol). The colorless solution was stirred for 5
min, and then hexanes (3 mL) were added. The solution was stored at
room temperature for 5 h, providing needles of 5a which were washed
with hexanes and dried in vacuo (0.135 g, 77% yield). Complexes 5b
and 5c were prepared analogously from [H(OEt2)2][BArF], and the
corresponding chloride and methyl compounds and isolated in 62%
and 77% yields, respectively. Data for 5a. Anal. Calcd for C76H42-
BClF24O8P2Re2: C, 45.20; H, 2.10. Found: C, 45.43; H, 2.44. 1H NMR
(CD2Cl2) 7.73 (s, 8H, BArF), 7.3-7.6 (m, 34H, Ph + BArF). 31C{1H}
NMR (CD2Cl2) 186.07 (d, JCP ) 9.5, CO), 184.80 (d, JCP ) 50.4, CO),
181.26 (d, JCP ) 6.5, CO), 133.68 (d, JCP ) 10.6, Ph), 132.70 (d, JCP
(20) XSCANS and SHELXTL PC are products of Siemens Analytical X-ray
Instruments, Inc., 6300 Enterprise Lane, Madison, WI 53719. SHELX-
93 is a program for crystal structure refinement written by G. M.
Sheldrick, University of Go¨ttingen, Germany, 1993.
(21) SMART, Version 4.210; Bruker Analytical X-ray Systems, Inc.: 6300
Enterprise Lane, Madison, WI 53719, 1996.

124 Inorganic Chemistry, Vol. 38, No. 1, 1999
Huhmann-Vincent et al.
using SAINT22 software. The final cell parameters were determined
using a least-squares fit to 7627 (4b), 5670 (5c), and 8192 (6)
reflections. The data were corrected for absorption using the SADABS23
program. Decay of reflection intesitiy was not observed.
For 5c, several disordered fluoride atoms were refined in two positions,
with the sum of their site occupancy factors tied to one. One fluoride
atom was refined in three positions, with each atom having its
occupancy fixed at one-third. Three disordered cyclohexyl carbon atoms
were refined in two positions, with their site ocupancy factors set to
one-half. Hydrogen atoms were not placed on disordered cyclohexyl
carbon atoms (vide infra) or the carbon atoms they were bonded to.
The final refinement included anisotropic temperature factors on all
non-hydrogen atoms (except the disordered fluoride and carbon atoms
in 5c). Structure solution and graphics were performed using SHELXTL
PC.24 SHELX-93 was used for structure refinement and creation of
publication tables.20
The structure were solved using Patterson and difference Fourier
techniques. The initial solutions revealed Re and the majority of all
other non-hydrogen atom positions. The remaining atomic positions
were determined from subsequent Fourier synthesis. All hydrogen atom
positions were fixed in ideal positions. The C-H distances were fixed
at 0.93, 0.96, 0.97 and 0.98, and 0.97 Å for aromatic, methyne,
methylene, and methyl hydrogen atoms, respectively. The hydrogen
atoms were refined using a riding model, with their isotropic temper-
ature factors set to 1.2 (aromatic, methyne, methylene) or 1.5 (methyl)
times the equiv isotropic U of the carbon atom they were bonding to.
For 4b, the methylene chloride ligand was disordered. As a result
of this disorder, the carbon atom C(5) and nonbonded chlorine atom
Cl(2) were each refnined as two one-half occupancy atom positions.
Acknowledgment. This work is supported by the Depart-
ment of Energy, Office of Basic Energy Sciences, Chemical
Sciences Division. J.H.-V is grateful to the Director of the Los
Alamos National Laboratory for postdoctoral funding.
Supporting Information Available: X-ray crystallographic files,
in CIF format, for the structure determinations of complexes 1b, 1c,
4b, 5a, 5c, and 6 are available on the Internet only. Access information
is given on any current masthead page.
(22) SAINT, Version 4.05; Bruker Analytical X-ray Systems, Inc.: 6300
Enterprise Lane, Madison, WI 53719, 1996.
(23) First release; Sheldrick, G. M. SADABS; University of Go¨ttingen:
Germany.
(24) SHELXTL PC, Version 5.03; Bruker Analytical X-ray Systems, Inc.:
6300 Enterprise Lane, Madison, WI 53719, 1994.
IC980912Q