Synthesis and characterization of chair and boat forms of fac-Re(CO)3(P3)(X) [P3 = η2-CH3C(CH2PPh2)3, X = Br, Cl]

Article abstract of DOI:10.1021/om001018l

The syntheses of complexes having the general formula fac-Re(CO)₃(η²-triphos)X (triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane; 1 and 2, X = Br; 5 and 6, X = Cl) from reactions of Re(CO)₅X and triphos are described. The X-ray structure of 1 shows that the six-membered metallacyclic ring (ReP₂C₃) adopts a chair conformation like the known complex 5, while structural data for 2 and 6 indicate boat forms for the metallacyclic rings. This represents the first identification of boat forms of these complexes. The pendant phosphines in compounds 1 and 2 can be oxidized, yielding compounds 3 and 4, respectively. The X-ray structure of 4 retains the boat form of its precursor and the properties of 3 are different, suggesting that the ring conformation was retained here also. Thermolysis reactions of 5 and 6 were conducted to probe for differences in the ease of decarbonylation and conversion to the known η³-coordinated complex, 7. The boat complex 6 is converted more readily to 7; there is no evidence for any thermal conversion of 6 to 5.

Full text of DOI:10.1021/om001018l

1456
Organometallics 2001, 20, 1456-1461
Syn th esis a n d Ch a r a cter iza tion of Ch a ir a n d Boa t F or m s
of fa c-Re(CO)3(P 3)(X) [P 3 ) η2-CH3C(CH2P P h 2)3,
X ) Br , Cl]
Dorothy H. Gibson,* Haiyang He, and Mark S. Mashuta
Department of Chemistry and Center for Chemical Catalysis, University of Louisville,
Louisville, Kentucky 40292
Received November 28, 2000
The syntheses of complexes having the general formula fac-Re(CO)3(η2-triphos)X (triphos
) 1,1,1-tris(diphenylphosphinomethyl)ethane; 1 and 2, X ) Br; 5 and 6, X ) Cl) from
reactions of Re(CO)5X and triphos are described. The X-ray structure of 1 shows that the
six-membered metallacyclic ring (ReP2C3) adopts a chair conformation like the known complex
5, while structural data for 2 and 6 indicate boat forms for the metallacyclic rings. This
represents the first identification of boat forms of these complexes. The pendant phosphines
in compounds 1 and 2 can be oxidized, yielding compounds 3 and 4, respectively. The X-ray
structure of 4 retains the boat form of its precursor and the properties of 3 are different,
suggesting that the ring conformation was retained here also. Thermolysis reactions of 5
and 6 were conducted to probe for differences in the ease of decarbonylation and conversion
to the known η3-coordinated complex, 7. The boat complex 6 is converted more readily to 7;
there is no evidence for any thermal conversion of 6 to 5.
In tr od u ction
instances, the formation of species with η2-coordination
of the triphos has been implicated from 31P NMR
spectral data or oxidation of the pendant phosphine.6-8
In some cases, this species was observed to exhibit two
forms.7-9 Since we are interested in catalysts and
catalytic intermediates in CO2 reduction processes,10 we
sought synthetic methods for new rhenium(I) complexes
with bidentate triphos ligands. We found that chair and
boat isomers of the six-membered metallacyclic ring
(ReP2C3) formed by η2-coordination of triphos to rhe-
nium were present in products with the general formula
fac-Re(CO)3(η2-triphos)X (X ) Br, Cl); see Chart 1
(phenyl groups have been omitted for clarity). This is
the first identification of boat isomers in this series.
Herein we report the synthesis and characterization of
all four complexes and the phosphine oxide derivatives
of two of them.
Transition metal complexes with the tripodal poly-
phosphine ligand CH3C(CH2PPh2)3 (1,1,1-tris(diphe-
nylphosphinomethyl)ethane: triphos) have received
attention in recent years due to their high catalytic
activity in a wide range of reactions such as hydrogena-
tion and hydroformylation of olefins.1 Triphos, with
electronic properties resembling the cyclopentadienyl
anion, is able to form stable complexes with metals in
a variety of oxidation states by occupying three facial
sites at the metal centers.2 Complexes with the Re(CO)2-
(η3-triphos) fragment were reported several years ago3
and demonstrated interesting reactivities.4 While triph-
os could form complexes in η3-fashion, dissociation of
one phosphine, known as “arm-off” dissociation, has
been implicated in some catalytic reactions.5 In several
(1) (a)Bianchini, C.; Meli, A.; Moneti, S.; Oberhauser, W.; Vizza, F.;
Herrera, V.; Fuentes, A.; Sanchez-Delgado, R. A. J . Am. Chem. Soc.
1999, 121, 7071. (b) Bianchini, C.; Herrera, V.; J imenez, M. V.; Meli,
A.; Sanchez-Delgado, R. A.; Vizza, F. J . Am. Chem. Soc. 1995, 117,
8567. (c) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Zanobini, F.
Coord. Chem. Rev. 1992, 120, 193. (d) Bianchini, C.; Meli, A.; Peruzzini,
M.; Vizza, Frediani P.; Ramirez, J . A Organometallics 1990, 9, 226.
(e) Aoki, T.; Crabtree, R. H. Organometallics 1993, 12, 294.
(2) (a) Mayer, H. A.; Kaska, W. C. Chem. Rev. 1994, 94, 1239. (b)
Siwajek, M. J .; Ding, Y.; Fanwick, P. E.; Walton, R. A. J Clust. Sci.
2000, 11, 243. (c) Costello, M. T.; Fanwick, P. E.; Green, M. A.; Walton,
R. A. Inorg. Chem. 1992, 31, 2359. (d) Bergamini, P.; Debiani, F. F.;
Marvelli, L.; Mascellani, N.; Peruzzini, M.; Rossi, R.; Zanello, P. New
J . Chem. 1999, 23, 207.
(3) Bianchini, C.; Marchi, A.; Marvelli, L.; Peruzzini M.; Romerosa,
A.; Rossi, R.; Vacca, A. Organometallics 1995, 14, 3203.
(4) (a) Bianchini, C.; Mantovani, N.; Marchi, A.; Marvelli, L.; Masi,
D.; Peruzzini, M.; Rossi, R.; Romerosa, A. Organometallics 1999, 18,
4501. (b)Bianchini, C.; Marchi, A.; Marvelli, L.; Peruzzini, M.; Rome-
rosa, A. Rossi, R. Organometallics 1996, 15, 3804.
Resu lts a n d Discu ssion
1. Syn th esis a n d Sp ectr a l P r op er ties of Com -
p lexes 1-6. Reaction of Re(CO)5Br with triphos for 7
h in refluxing methanol produced a white precipitate,
which was collected from the cooled mixture. Examina-
tion of the NMR spectra of the product indicated the
presence of two compounds, which could be separated
(6) Kiss, G.; Horvath, I. T. Organometallics 1991, 10, 3798.
(7) Thaler, E. G.; Folting, K.; Caulton, K. G. J . Am. Chem. Soc. 1990,
112, 2664.
(8) (a) Brandt, K.; Sheldrick, W. S. Inorg. Chim. Acta 1998, 267,
39. (b) Landgrafe, C.; Sheldrick, W. S.; Su¨dfeld, M. Eur. J . Inorg. Chem.
1998, 407.
(5) (a) Ott, J .; Venanzi, L. M.; Ghilardi, C. A.; Midollini, S.;
Orlandini, A. J . Organomet. Chem. 1985, 291, 89. (b) Bianchini, C.
Masi, D.; Meli, A.; Peruzzini, M.; Zanobini, F. J . J . Am. Chem. Soc.
1988, 110, 6411. (c) Rauscher, D. J .; Thaler, E. G.; Huffman, J . C.;
Caulton, K. G. Organometallics 1991, 10, 2209.
(9) Hussain, Z. I.; de Souza, A. L. A. B.; Whiteley, M. W. J .
Organomet. Chem. 1997, 544, 121.
(10) (a) Gibson, D. H.; Yin, X. L. J . Am. Chem. Soc. 1998, 120, 11200.
(b) Gibson, D. H.; Ding, Y.; Sleadd, B. A.; Franco, J . O.; Richardson, J .
F.; Mashuta, M. S. J . Am. Chem. Soc. 1996, 118, 11984.
10.1021/om001018l CCC: $20.00 © 2001 American Chemical Society
Publication on Web 02/27/2001

Chair and Boat Forms of fac-Re(CO)3(P3)(X)
Organometallics, Vol. 20, No. 7, 2001 1457
Ch a r t 1
uncoordinated phosphorus, at δ 2.35, are correlated with
the carbon resonance at δ 51.86 and the methyl protons
at δ 0.32 are correlated with the carbon resonance at δ
30.24.
The chair and boat isomers are stable in the solid form
and in solution at room temperature. Also, these com-
plexes are stable toward oxygen even in solution.
However, when 1 or 2 was dissolved in ether, traces of
the corresponding phosphine oxide complexes (3 and 4)
were detected. It appears that peroxide impurities in
the solvent may be responsible for the oxidation. Treat-
ing 1 and 2 with tert-butyl hydroperoxide afforded near
quantitative conversions into 3 and 4, respectively. The
31P NMR spectrum of 3 and 4 showed that the reso-
nances for the phosphine oxides shifted greatly (to δ
25.36 and 24.54 for 3 and 4, respectively), while those
for the coordinated phosphines were changed only
slightly. The 13C NMR chemical shifts of 3 and 4 exhibit
little variation as compared with those in 1 and 2. The
1H NMR spectra for 3 and 4 are very similar to those of
1 and 2, except for the methylene resonances adjacent
to the pendant phosphorus ligands, which shift down-
field slightly and change from broad singlets to doublets.
The synthesis and structure of fac,chair-Re(CO)3(η2-
triphos)Cl (5) has been reported previously.12 The
complex was prepared in low yield by photolysis of a
solution of Re2(CO)10 and triphos in dichloromethane.12a
The 31P NMR spectrum was reported to consist of two
singlets at δ -11.26 and -11.43 in a ratio of 2:1, which
the authors assigned to 5. In view of the 31P NMR
spectral properties of the bromo derivatives, it seemed
unlikely to us that either single chloro complex would
exhibit these resonances. We carried out the synthesis
of Re(CO)3(η2-triphos)Cl by refluxing Re(CO)5Cl with
triphos in MeOH overnight; a white precipitate formed
readily because of differences in their solubility in
acetone. The insoluble complex 1 shows H resonances
1
at δ 3.54 (d), 2.42 (dd), 2.35 (s) for the CH2 groups and
a single resonance at δ 0.32 for the CH3 group; the 13C
NMR spectrum showed a triplet at δ 192.40 and a
slightly overlapped doublet of triplets at δ 189.41 for
the carbonyl groups in addition to resonances for the
triphos ligand (see Experimental Section). Complex 2
displays resonances at δ 3.41 (dd), 2.66 (dd), 1.83 (s)
for the CH2 groups and a resonance at δ 1.03 for the
CH3 group in CD2Cl2; the 13C NMR spectrum showed a
triplet at δ 190.89 and an overlapped doublet of triplets
at δ 189.91 in addition to resonances for the triphos
ligand (see Experimental Section). Integration of CH3
1
groups in the H NMR spectrum of the crude mixture
indicated that it was composed of 54% 1 and 46% 2. The
IR spectrum of 1 showed strong bands for the carbonyl
ligands at 2028, 1952, and 1891 cm-1, and the spectrum
of 2 showed strong bands at 2030, 1949, and 1909 cm-1
;
these patterns are consistent with facial arrangements
of the carbonyl ligands in each compound.11 Elemental
analyses were in agreement with the formulation of both
compounds as Re(CO)3(triphos)Br, suggesting η2-coor-
dination of the triphos ligand. The two isomers showed
very similar 31P NMR spectra; each consisted of two
singlets (δ -14.71 and -27.69 for 1 and δ -14.26 and
-28.89 for 2) with relative ratios of 2:1, respectively.
The high-field resonances in the 31P spectra of both
compounds are close to that of free triphos (δ -25.86
ppm in CD2Cl2) and are assigned to the noncoordinated
phosphorus atom. This assignment is also supported by
their COSY (1H-1H correlation) and HSQC (1H-13C
correlation) spectra. The COSY spectrum of 2 (in CD2-
Cl2) shows correlation of the proton resonances at δ 2.66
and 3.41, identifying these as the diastereotopic protons
of the methylene carbons bound to the coordinated
phosphorus ligands. The HSQC spectrum of 2 shows
correlation of both of these proton resonances with the
carbon resonance at δ 34.96, while the proton resonance
at δ 1.83 is correlated with the carbon resonance at δ
45.53 (CH2 adjacent to the uncoordinated phosphorus)
and the proton resonance at δ 1.03 (methyl protons)
correlates with the carbon resonance at δ 34.32. The
COSY spectrum of 1 was obtained initially in CD2Cl2
and suggests that the proton resonances at δ 3.54 and
2.42 are correlated. The spectrum was also obtained in
toluene-d8, which allowed better separation of the close
resonances at δ 2.35 and 2.42; in toluene, these are at
δ 2.19 and 2.29 and the correlation is clear. The HSQC
spectrum of 1 (in CD2Cl2) showed that both resonances
at δ 2.42 and 3.54 correlate with the carbon resonance
at δ 34.71, while the methylene protons adjacent to the
1
during this time. As expected, the H NMR spectrum
of the crude mixture was very similar to that of the
bromo complexes, even in the composition, revealing a
54% to 46% ratio of two compounds. The two isomers
were separated by trituration with ether; the minor
isomer is soluble, while the major isomer is almost
1
insoluble. Compounds 5 and 6 exhibit IR and H, 13C,
and 31P NMR spectra that are very similar to the
corresponding bromo derivatives 1 and 2 (see Experi-
mental Section) and appeared to have η2-coordinated
triphos ligands. The boat form of the metallacyclic ring
in 6 was confirmed for this isomer by X-ray crystal-
lography (see discussion below). The 31P NMR spectrum
of 5 showed resonances at δ -10.49 and -27.39 in a
ratio of 2:1. The 31P NMR spectrum of 6 showed
resonances at δ -10.32 and -28.39 in a ratio of 2:1.
Thus, the 31P NMR spectral data reported previously
appear to represent the lower field resonances of a
mixture containing both 5 and 6.
The phosphine oxide derivative of 6 was reported
previously as a minor product from the reaction that
produced 5;12b the compound was structurally charac-
terized, although its origin was not detailed. However,
this supports our conclusion that the previous synthesis
of 5 probably also produced 6.
A few generalizations can be made about the spectral
properties of these compounds. The IR spectra of all of
(12) (a) Lin, S. C.; Cheng, C. P.; Lee, T. Y.; Lee, T. J . Peng, S. M.
Acta Crystallogr. 1986, C42, 1733. (b) Liu, L. K.; Lin, S. C.; Cheng, C.
P. Acta Crystallogr. 1988, C44, 1402.
(11) Bond, A. M.; Colton, R.; McDonald, M. E. Inorg. Chem. 1978,
17, 2842.

1458 Organometallics, Vol. 20, No. 7, 2001
Gibson et al.
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t P a r a m eter s for Com p lexes 1, 2, 4, a n d 6
1
2
4
6
empirical formula
fw
C
44H39BrO3P3Re
C44H39BrO3P3 Re‚0.7CH2Cl2
1034.22
C44H39BrO4P3 Re‚C6H14
1062.83
C44H39ClO3P3Re‚1.4CH2Cl2
1046.39
974.77
temp, K
wavelength, Å
cryst syst
space group
a, Å
293(2)
0.71073
triclinic
P1h
triclinic
P1h
triclinic
P1h
monoclinic
P21/n
14.630(4)
15.309(4)
21.382(7)
90
99.78(3)
90
4719.3(16)
4
9.837(2)
9.867(2)
21.297(7)
77.66(3)
83.09(3)
83.11(3)
1995.2(7)
2
1.623
4.206
2.10-24.97
7241
11.090(2)
14.560(3)
14.690(3)
103.27(3)
91.48(3)
105.09(3)
2219.8(8)
2
11.088(5)
14.868(6)
15.044(6)
74.82(3)
73.21(4)
89.95(3)
2284(2)
2
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
D
calcd, g/cm3
1.547
3.867
2.08-26.48
9685
1.545
3.683
2.04-24.97
8473
1.473
2.928
2.06-23.00
10349
abs coeff, mm-1
θ range, deg
no. reflns measd
no. unique (Rint
)
7032 (0.0258)
0.0297, 0.0692
1.023
9173 (0.0162)
0.0292, 0.0758
1.051
8011 (0.0345)
0.0449, 0.1236
1.149
6212 (0.0251)
0.0352, 0.0806
1.068
R1, wR2a (I > 2σΙ)
GOF
max diff peak, e/Å3
1.257
1.103
1.322
0.807
R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo2)2]}1/2
.
a
2
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 1
Ta ble 3. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 2.
Bond Distances
Bond Distances
Re-C(1)
Re-C(2)
Re-C(3)
1.949(5)
1.894(5)
1.944(5)
Re-Br
Re-P(1)
Re-P(2)
2.6414(9)
2.4624(14)
2.4931(14)
Re-C(1)
Re-C(2)
Re-C(3)
1.943(4)
1.902(4)
1.949(5)
Re-Br
Re-P(1)
Re-P(2)
2.6489(8)
2.4639(12)
2.4634(11)
Bond Angles
Bond Angles
C(1)-Re-P(1)
C(2)-Re-P(1)
C(3)-Re-P(1)
C(1)-Re-P(2)
C(2)-Re-P(2)
C(3)-Re-P(2)
C(1)-Re-C(2)
C(1)-Re-C(3)
C(2)-Re-C(3)
89.13(14)
96.37(15)
171.27(15)
170.82(15)
100.24(14)
92.27(15)
88.8(2)
Br-Re-C(1)
Br-Re-C(2)
Br-Re-C(3)
Br-Re-P(1)
Br-Re-P(2)
P(1)-Re-P(2)
86.85(16)
174.78(14)
84.98(15)
86.38(4)
84.26(4)
88.03(4)
C(1)-Re-P(1)
C(2)-Re-P(1)
C(3)-Re-P(1)
C(1)-Re-P(2)
C(2)-Re-P(2)
C(3)-Re-P(2)
C(1)-Re-C(2)
C(1)-Re-C(3)
C(2)-Re-C(3)
94.13(13)
92.29(14)
175.75(12)
173.12(13)
97.53(13)
90.61(13)
89.34(18)
89.86(18)
89.23(18)
Br-Re-C(1)
Br-Re-C(2)
Br-Re-C(3)
Br-Re-P(1)
Br-Re-P(2)
P(1)-Re-P(2)
85.82(13)
173.77(12)
86.84(13)
91.97(4)
87.35(4)
85.26(4)
89.2(2)
92.2(2)
Ta ble 4. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 4
the chair complexes (1, 3, and 5) show two strong
carbonyl bands above 1900 cm-1 and one strong band
slightly below this frequency. All boat complexes (2, 4,
and 6) show three strong bands above 1900 cm-1. In
the 1H NMR spectra, the methyl resonances of the
triphos ligand appear at less than 1 ppm in all chair
complexes, while those of the boat complexes appear at
more than 1 ppm.
Bond Distances
Re-C(1)
Re-C(2)
Re-C(3)
Re-Br
1.945(7)
1.896(8)
1.956(8)
2.6523(9)
Re-P(1)
Re-P(2)
P(3)-O(4)
2.4674(18)
2.4655(18)
1.474(7)
Bond Angles
95.9(2)
C(1)-Re-P(1)
C(2)-Re-P(1)
C(3)-Re-P(1)
C(1)-Re-P(2)
C(2)-Re-P(2)
C(3)-Re-P(2)
C(1)-Re-C(2)
C(1)-Re-C(3)
C(2)-Re-C(3)
Br-Re-C(1)
Br-Re-C(2)
Br-Re-C(3)
Br-Re-P(1)
Br-Re-P(2)
P(1)-Re-P(2)
86.5(2)
174.6(2)
88.2(2)
91.35(5)
87.15(5)
85.27(6)
91.6(2)
175.2(2)
173.6(3)
97.6(3)
89.9(2)
88.6(4)
88.9(3)
89.3(3)
Solid -Sta te Str u ctu r es of Com p ou n d s 1, 2, 4, a n d
6. The structures of the compounds were determined
by X-ray crystallography. Data collection parameters are
given in Table 1. Selected bond distances and angles of
these complexes are listed in Tables 2-5. The Re atom
in all four complexes is octahedrally coordinated to three
carbonyl ligands (in a facial arrangement), two phos-
phorus atoms of triphos, and a halide atom. There are
two unusual characteristics for these complexes: (a) the
conformations of the metallacyclic rings (ReP2C3) formed
by η2-coordination of the triphos to rhenium and (b) the
orientation of the pendant phosphine group with respect
to the halide atom.
diphosphine ligands, fac-Re(CO)3(P2)X (X ) Br or Cl).13
The equatorial Re-CO bonds are slightly longer than
the axial Re-CO, consistent with the phosphines’
greater trans influence. The six-membered ring formed
by Re, P(1), C(4), C(5), C(6), and P(2) exhibits a chair
(13) (a) Schibli, R.; Katti, K. V.; Volkert, Barnes, C. L. Inorg. Chem.
1998, 37, 5306. (b) Yang, K. Y.; Bott, S. G. Richmond, M. G.
Organometallics 1995, 14, 2387. (c) Miller, T. M.; Ahmed, K. J .;
Wrighton, M. S. Inorg. Chem. 1989, 28, 2347. (d) Gutmann, T.
Dombrowski, E.; Burzlaff, N. Schenk, W. A. J . Organomet. Chem. 1998,
552, 91. (e) Mague, J . T. Acta Crystallogr. C 1994, 50, 1391. (f) Graziani,
R.; Casellato, U. Acta Crystallogr. C 1996, 52, 850. (g) Miller, T. M.;
Ahmed, K. J .; Wrighton, M. S. Inorg. Chem. 1989, 28, 2347.
The ORTEP view of 1 is shown in Figure 1. The bond
distances of Re-CO, 1.894(5), 1.944(5), and 1.949(5) Å,
Re-P, 2.4624(14) and 2.4931(14) Å, and Re-Br, 2.6414-
(9) Å, are unexceptional when compared with other
structurally characterized rhenium complexes with

Chair and Boat Forms of fac-Re(CO)3(P3)(X)
Organometallics, Vol. 20, No. 7, 2001 1459
Ta ble 5. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 6
Bond Distances
Re-C(1)
Re-C(2)
Re-C(3)
1.942(8)
1.892(9)
1.940(9)
Re-Cl
Re-P(1)
Re-P(2)
2.511(2)
2.482(2)
2.4545(18)
Bond Angles
91.7(3)
C(1)-Re-P(1)
C(2)-Re-P(1)
C(3)-Re-P(1)
C(1)-Re-P(2)
C(2)-Re-P(2)
C(3)-Re-P(2)
C(1)-Re-C(2)
C(1)-Re-C(3)
C(2)-Re-C(3)
Cl-Re-C(1)
Cl-Re-C(2)
Cl-Re-C(3)
Cl-Re-P(1)
Cl-Re-P(2)
P(1)-Re-P(2)
90.6(3)
177.1(2)
88.7(3)
82.08(6)
92.65(6)
86.02(6)
99.3(3)
170.6(3)
175.7(3)
90.0(2)
93.0(2)
86.8(4)
89.9(3)
90.0(4)
F igu r e 2. ORTEP drawing of 2 with thermal ellipsoids
shown at the 50% probability level.
F igu r e 1. ORTEP drawing of 1 with thermal ellipsoids
shown at the 50% probability level.
conformation with P(1), C(4), C(6), and P(2) at the base
(mean deviation 0.0135 Å); deviations of Re and C(5)
from the least-squares plane defined by P(1), C(4), C(6),
and P(2) are -1.063 and +0.708 Å, respectively. The
P(1)-Re(1)-P(2) angle, 88.03(4)°, is significantly larger
than those in the Re(CO)2(η3-triphos) fragment3 (aver-
age value 85.1°) but closer to those of Re(CO)3(dppp)X
(X ) O, C; dppp ) 1, 3-bis(diphenylphosphino)propane)
with an average of 88.5°,14 which exhibit the chair
conformation exclusively. The pendant phosphine group
adopts a position syn to Br and below the six-membered
metallacyclic ring. This arrangement avoids steric
crowding between the phenyl groups of the pendant
phosphine and those of the coordinated P(1) and P(2).
There are a number of bond angles that are distorted
with respect to octahedral geometry: C(2)-Re-P(1) and
C(2)-Re-P(2) are both greater than 90°, resulting in
Br-Re-P(1) and Br-Re-P(2) angles that are com-
pressed well below 90°. Also, C(2)-Re-Br is compressed
to less than 175°, and C(1)-Re-P(2) is compressed even
lower.
F igu r e 3. ORTEP drawing of 4 with thermal ellipsoids
shown at the 50% probability level.
and P(2) clearly exhibits a boat conformation in the solid
state. Re(1), P(1), C(5), and C(6) form the base of the
boat (mean deviation 0.0002 Å), while P(2) and C(4) are
out of this plane; deviations of P(2) and C(4) from the
base are +0.977 and +0.619 Å, respectively. The P(1)-
Re(1)-P(2) angle, 85.26(4)°, is significantly smaller than
that in 1 but close to that typical of the Re(CO)2(η3-
triphos) fragment (see discussion above). The pendant
phosphine group adopts an anti position with respect
to Br and syn to C(2)-O(2). Again, the shortest Re-
C(carbonyl) bond is the one trans to Br. The C(2)-Re-
P(2) bond angle is enlarged, resulting in slight com-
pression of the Br-Re-P(2) angle, but greater compres-
sion of the C(1)-Re-P(2) and C(1)-Re-Br angles. The
pendant phosphorus is anti to the Br, and the P(3)-
C(43)-C(5) angle is 116.9(3)°.
The ORTEP view of 4 is shown in Figure 3 and clearly
shows that the pendant phosphorus has been oxidized.
The Re-CO bond distances, 1.945(7), 1.896(8), and
1.956(8) Å, and those of Re-P, 2.4674(18) and 2.4655-
(18) Å, and Re-Br, 2.6523(9) Å, are similar to those in
2. Again, Re, P(1), C(5), and C(6) form the base of the
boat with P(2) and C(4) out of this plane by 0.9727 and
0.6336 Å, respectively. As in 1 and 2, the shortest Re-
C(carbonyl) bond distance is the one trans to the
halogen atom. Oddly, the shortest Re-C(carbonyl) bond
The ORTEP view of 2 is shown in Figure 2. The bond
distances of Re-CO, 1.902(4), 1.943(4), and 1.949(5) Å,
Re-P, 2.4634(11) and 2.4639(12) Å, and Re-Br, 2.6489-
(8) Å, are close to those of 1. The six-membered metal-
lacyclic ring formed by Re(1), P(1), C(4), C(5), C(6),
(14) (a) Williams, M. T.; McEachin, C.; Becker, T. M.; Ho, D. M.;
Mandal, S. K. J . Organomet. Chem. 2000, 599, 308. (b) Brown, D. A.;
Mandal, S. K.; Ho, D. M.; Becker, T. M.; Orchin, M. J . Organomet.
Chem. 1999, 592, 61. (c) Mandal, S. K.; Ho, D. M.; Orchin, M. J .
Organomet. Chem. 1992, 439, 53.

1460 Organometallics, Vol. 20, No. 7, 2001
Gibson et al.
Exp er im en ta l Section
Gen er a l Ma ter ia ls a n d Meth od s. All reactions were
carried out under a nitrogen atmosphere. Reagent grade
dichloromethane, methanol, acetone, pentane, and hexane
were used as received. Ether and THF were refluxed over
sodium benzophenone and freshly distilled prior to use. Re-
(CO)5Cl and Re(CO)5Br were prepared according to the litera-
ture procedure.15 The 1,1,1-tris(diphenylphosphinomethyl)-
ethane (triphos) and tert-butyl hydroperoxide were used as
received from Aldrich. 1H, 13C, and 31P NMR were recorded
1
on a Varian INOVA-500 and a Bruker AMX-500; the H and
13C chemical shifts (ppm) were referenced to residual protons
and carbons, respectively, in the deuterated solvents; the 31P
chemical shifts were determined using H3PO4 (85%) as the
external standard. Infrared spectra were obtained by the
DRIFTS16 technique and were recorded on a ATI Mattson RS-1
FT-IR instrument by means of a Graseby Specac Inc. “Mini-
Diff” accessory as KCl dispersions. Melting points were
determined on
a Thomas-Hoover capillary melting point
apparatus and are uncorrected. Elemental analyses were
performed by Midwest Microlab, Indianapolis, IN.
F igu r e 4. ORTEP drawing of 6 with thermal ellipsoids
shown at the 50% probability level.
P r ep a r a t ion of fa c,ch a ir -R e(CO)3(η2-t r ip h os)Br (1)
a n d fa c,boa t-R e(CO)3(η2-t r ip h os)Br (2). A suspension of
triphos (1.88 g, 3 mmol) with Re(CO)5Br (1.23 g, 3 mmol) in
100 mL of MeOH was refluxed for 7 h at 85 °C. After cooling,
the precipitate was collected, washed with MeOH, then dried
distance in the chloro derivative reported previously12b
is not the one trans to Cl. There are angle deviations
from octahedral geometry present in 4, too, but these
are diminished as compared to the distortions in 2. The
presence of the P(3)-O(4) bond increases the P(3)-
C(43)-C(5) angle to 120.3(5)°, apparently due to steric
crowding between O(4) and the methyl group at C(5).
1
to produce a white solid (2.27 g, yield 78%). H NMR analysis
showed that the solid was composed of 54% 1 and 46% 2. The
two isomers can be separated easily by trituration with
acetone; isomer 2 is soluble in acetone, while isomer 1 is almost
insoluble. Further purification was done by recrystallization
from CH2Cl2-Et2O.
The ORTEP view of 6 is shown in Figure 4 and shows
a boat form for the metallacyclic ring. The Re-C bond
distances, 1.892(9), 1.942(8), and 1.940(9) Å, are similar
to those in the bromide with this ring conformation (2),
and, again, the shortest Re-C bond is the one trans to
the halogen. The atoms Re, P(2), C(4), and C(5) are
coplanar (deviation is 0.0001 Å), and P(1) and C(6) are
out of this plane, 0.9211 and 0.6414 Å, respectively. As
in 2, the pendant phosphorus is anti to the halogen.
There are numerous angular distortions around the
metal center here, also: C(2)-Re-P(1) is large, resulting
in a compressed P(1)-Re-Cl angle and a C(3)-Re-P(1)
angle that, at 170.6(3)°, is far less than 180°. Thermoly-
sis reactions of the chair and boat isomers 5 and 6 were
conducted to determine how readily these η2-forms
might be decarbonylated and converted to the fully
chelated form and to see if there were differences in the
ease of conversion of the chair and boat forms. In 5,12a
as in the corresponding bromide (1), the pendant
phosphorus ligand is syn to the halogen atom, whereas,
in 6, the pendant phosphorus is anti to the halogen (and
syn to a CO). In accord with expectations based on these
differences in geometry, the solid-state thermolysis of
6 proceeds more easily than that of 5, although both
require high temperatures for conversion to the η3-
coordinated compound, 7, which has been characterized
previously.3 Compound 5 showed no conversion to 7
after 4.5 h at 180 °C, but was fully converted to 7 after
1 h at 245 °C. About one-third of a sample of compound
6 was converted to 7 after 4.5 h at 180 °C. A second
sample was heated to 220 °C for 20 min and showed
complete conversion to 7. Solution thermolysis of 6 was
attempted in refluxing toluene; after 7 h, approximately
half of the sample had converted to 7. In no case
involving the thermolysis of 6 was there any evidence
of its conversion to 5.
Com p ou n d 1. Anal. Calcd for C44H39BrO3P3Re: C, 54.21;
H, 4.03. Found: C, 53.87; H, 4.27. IR νCO: 2028 (s), 1952 (s),
1
1891 (s) cm-1. H NMR (CD2Cl2): δ 7.79-7.26 (30H, m), 3.54
(2H, d), 2.42 (2H, dd), 2.35 (s, 2H), 0.32 (3H, s). 13C NMR (CD2-
Cl2): δ 192.40 (t), 189.41 (dt), 139.43-128.15 (m), 51.86 (dt),
40.05 (d); 34.71 (dd), 30.24 (d). 31P NMR (CD2Cl2): δ -14.71
(2), -27.69 (1).
Com p ou n d 2. Anal. Calcd for C44H39BrO3P3Re: C, 54.21;
H, 4.03. Found: C, 54.31; H, 4.10. IR νCO: 2030 (s), 1949 (s),
1
1909 (s) cm-1. H NMR (CD2Cl2): δ 7.63-7.00 (30H, m), 3.41
(2H, dd), 2.66 (2H, dd),1.83 (2H, s), 1.03 (3H, s). 13C NMR (CD2-
Cl2): δ 190.89 (t), 189.91 (dt), 139.56-128.30 (m), 45.53 (d),
39.24 (d); 34.96 (td), 34.32 (m). 31P NMR (CD2Cl2): δ -14.26
(2), -28.89 (1).
P r ep a r a tion of fa c,ch a ir -Re(CO)3(η2-tr ip h os oxid e)Br
(3). To 10 mL of THF containing 1 (0.20 g) was added tert-
butyl hydroperoxide (5.5 M, 80 µL). After standing for 3 h, the
solution was concentrated almost to dryness, then MeOH was
added to precipitate the product, 0.19 g (94% yield). Anal.
Calcd for C44H39BrO4P3Re‚H2O: C, 52.39; H, 4.10. Found: C,
52.32; H, 3.97. IR νCO: 2026 (s), 1948 (s) and 1896 (s) cm-1
.
1H NMR (CD2Cl2): δ 7.74-7.34 (30 H, m), 3.54 (2 H, d), 2.67
(2H, dd), 2.47 (2H, d), 0.60 (3H, s). 13C NMR (CD2Cl2): δ 191.74
(t), 189.52 (dt), 137.20-128.23 (m), 48.45 (dt), 40.28 (s, br),
34.74 (m), 31.25 (m). 31P NMR (CD2Cl2): δ 25.36 (1), -15.02
(2).
P r ep a r a tion of fa c,boa t-Re(CO)3(η2-tr ip h os oxid e)Br
(4). To 3 mL of THF containing 2 (0.10 g) was added tert-butyl
hydroperoxide (5.5 M, 30 µL). The solution was allowed to
stand for 3 h, then pentane (30 mL) was added to precipitate
5 (0.10 g, yield 98%), mp 175-177 °C. Anal. Calcd for C44H39
BrO3P3Re: C, 53.34; H, 3.97. Found: C, 52.98; H, 3.95. IR
CO: 2029 (s), 1962 (s), 1911 (s) cm-1 1H NMR (CD2Cl2): δ
-
ν
.
7.63-7.26 (30H, m), 3.52 (2H, dd), 2.88 (2H, dd), 1.95 (2H, d),
(15) Schmidt, S. P.; Trogler, W. C.; Basolo, F. Inorg. Synth. 1990,
28, 160.
(16) Griffiths, P. W.; de Haseth, J . A. Fourier Transform Infrared
Spectroscopy; Wiley: New York, 1986; Chapter 5.

Chair and Boat Forms of fac-Re(CO)3(P3)(X)
Organometallics, Vol. 20, No. 7, 2001 1461
1.22 (3H, s). 13C NMR (CD2Cl2): δ 190.97 (t), 189.83 (dt),
136.30-128.33 (m), 43.16 (d), 39.58 (d); 35.23 (td), 34.51 (m).
31P NMR (CD2Cl2): δ 24.54 (1), -14.40 (2).
using the Bruker SHELXTL (version 5.1019) software package.
ORTEP diagrams for 4 and 6 were generated from ORTEP-
3.20 Hydrogen atom positions were calculated using a riding
model with U(H) ) 1.2Ueq (attached atom) for the phenyl and
methylene H’s. For methyl groups, the torsion angle that
defines its orientation was allowed to refine, and these
hydrogen atoms were assigned U(H) ) 1.5Ueq (attached carbon
atom). Scattering and anomalous dispersion factors were taken
from Cromer and Waber.21
P r ep a r a tion of fa c,ch a ir -Re(CO)3(η2-tr ip h os)Cl (5) a n d
fa c,boa t-Re(CO)3(η2-tr ip h os)Cl (6). A suspension of triphos
(0.94 g, 1.5 mmol) with Re(CO)5Cl (0.55 g, 1.5 mmol) in 50
mL of MeOH was refluxed overnight. After cooling, the
precipitate was collected, washed with MeOH, then dried to
produce a white solid (1.23 g, yield 87%). 1H NMR analysis
showed that the solid was composed of 54% 5 and 46% 6. The
two isomers can be separated easily by trituration with ether;
isomer 6 is soluble in ether, while isomer 5 is almost insoluble.
Further purification was done by recrystallization in CH2Cl2-
pentane.
For structure 1, the final anisotropic full-matrix least-
squares refinement (based on F2) for 470 variables using 7032
(all) data converged at R1 ) 0.0446 and wR2 ) 0.0745. For
structure 2, the final anisotropic full-matrix least-squares
refinement (based on F2) for 497 variables using 9173 (all) data
converged at R1 ) 0.0384 and wR2 ) 0.0793. For structure 4,
the final anisotropic full-matrix least-squares refinement
(based on F2) for 567 variables using 8011 (all) data converged
at R1 ) 0.0577 and wR2 ) 0.1292. The hexane solvate present
in this structure has numerous sites of disorder, which were
adequately modeled as follows. A half-occupancy set of six
carbon atoms C(70)-C(75) refined anisotropically were used
to model one portion of the disorder in the hexane. C(70), C(81),
and C(82) (refined anisotropically at one-half occupancy) in
combination with C(83A), C(75), and C(85A) (refined isotro-
pically at one-quarter occupancy) comprise the second set of
atoms in the hexane disorder. Similarly, a third set of atoms
C(70), C(81), C(82), C(83B), C(74), and C(85B) were employed
to model the final site of disorder in the hexane. For structure
6, the final anisotropic full-matrix least-squares refinement
(based on F2) for 551 variables using 6212 (all) data converged
at R1 ) 0.0642 and wR2 ) 0.0878. There are two fractional
(0.7) dichloromethane solvate molecules present in this struc-
ture which contain disorder. The first solvent molecule was
modeled with Cl(4a) and C(70), both refined anisotropically
at 0.70 occupancy with the site of disorder involving the second
chlorine atom: Cl(5a) (0.40) and Cl(5b) (0.30). The second
solvent molecule was modeled with one carbon atom, C(60) at
0.70 occupancy, one set one chlorine atoms Cl(2a) and Cl(3a)
at 0.40 occupancy, and the second set of chlorine atoms at 0.30
occupancy.
Com p ou n d 5. Anal. Calcd for C44H39ClO3P3Re: C, 56.80;
H, 4.23. Found: C, 56.57; H, 4.27. IR νCO: 2026 (s), 1945 (s),
1
1892 (s) cm-1. H NMR (CD2Cl2): δ 7.81-7.36 (30H, m), 3.44
(2H, d), 2.38 (4H, m), 0.44 (3H, s). 13C NMR (CD2Cl2) δ 192.54
(t), 190.42 (dt), 139.48-128.29 (m), 51.39 (dt), 39.91 (d); 34.23
(dd), 30.41 (d). 31P NMR (CD2Cl2): δ -10.49 (2), -27.39(1).
Com p ou n d 6. Anal. Calcd for C44H39ClO3P3Re: C, 56.80;
H, 4.23. Found: C, 56.71; H, 4.35. IR νCO: 2028 (s), 1945 (s),
1907 (m) cm-1. 1H NMR (CD2Cl2): δ 7.66-7.02 (30H, m), 3.35
(2H, dd), 2.61 (2H, dd), 1.94 (2H, s), 1.05 (3H, s). 13C NMR
(CDCl3): δ 190.68 (t), 190.10 (dt), 138.98-128.14 (m), 46.06
(dt), 38.77 (d); 34.46 (td), 33.67 (m). 31P NMR (CD2Cl2):
δ
-10.32 (2), -28.39 (1).
Th er m olysis of 5. A sample of 5 (0.02 g) was placed in a
Schlenk tube and then heated in an oil bath, under nitrogen,
for 4.5 h at 180 °C. Spectral analysis of the sample after this
time showed only compound 5. A second sample (0.02 g) was
heated, in the same way, to 245 °C for 1 h. NMR analysis of
the sample showed that all of 5 had been converted to a new
compound whose spectral properties are consistent with those
reported for Re(CO)2(η3-triphos)Cl3 (7): IR (KCl, DRIFTS) νCO
1946 (s) and 1884 (s) cm-1; 1H NMR (CD2Cl2) δ 7.58-7.05 (30H,
m), 2.50 (6H, m), 1.49 (3H, s). Lit.3 IR (KBr): 1948 (s) and
1
1887 (s) cm-1; H NMR (CD2Cl2) δ 2.48 (6Η, m), 1.45 (3H, q).
Th er m olysis of 6. A sample of 6 (0.02 g) was heated, as
described for 5, for 4.5 h at 180 °C. Spectral analysis of the
sample showed that approximately one-third of 6 had been
converted to 7. A second sample was heated, in the same way,
at 220 °C for 20 min; spectral analysis then showed that all of
6 had been converted to 7. In solution in toluene (10 mL), a
new sample of 6 (0.20 g) was refluxed for 7 h. After evaporation
to dryness, spectral analysis showed that approximately half
of 6 had been converted to 7.
X-r a y Cr ysta l Str u ctu r es of 1, 2, 4, a n d 6. A colorless
block crystal of 1 was obtained by diffusion of ether into a CH2-
Cl2 solution of the compound. A colorless block crystal of 2 was
grown from a CH2Cl2-Et2O solution of compound maintained
at 0 °C. A thin colorless needle crystal of 4 was produced by
diffusion of hexane into a benzene solution of the compound.
A colorless block crystal of 6 was formed by layering a CH2Cl2
solution of the compound with pentane.
Ack n ow led gm en t. Support of this work by the
United States Department of Energy, Office of Science,
Office of Basic Energy Sciences, is gratefully acknowl-
edged.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data, positional and isotropic thermal parameters,
anisotropic displacement parameters, H atom positional pa-
rameters, bond distances and bond angles for 1, 2, 4, and 6.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM001018L
(19) SHELXTL 5.10: Program Library for Structure Solution and
Molecular Graphics; Bruker Analytical X-ray Systems: Madison, WI,
1997.
(20) Farrugia, L. J . ORTEP-3 for Windows. J . Appl. Crystallogr.
1997, 30, 565.
(21) a) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. IV,
Table 2.2A. (b) Creagh, D. C.; Hubbell, J . H. International Tables for
X-ray Crystallography; Kluwer Academic Publishers: Boston, MA,
1992; Vol. C, Table 4.2.6.8.
All data were collected on an Enraf-Nonius CAD4 diffrac-
tometer at 293 K. Crystallographic data are outlined in Table
1. The structures were solved by direct methods17 and refined18
(17) SHELXS-90: Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(18) SHELXL-97: Sheldrick, G. M. Program for the Refinement of
Crystal Structures; University of Go¨ttingen: Germany, 1997.