Reactions of M(CO)5X (M = Mn, Re; X = Cl, Br) with {Ph2PCH2}3CCH3 (P3) and {Ph2P(CH2)2}3P (P3P'): Synthetic, spectroscopic, electroche

Article abstract of DOI:10.1021/ic0000294

The reactions of M(CO)₅X (M = Mn, Re; X = Cl, Br) with {Ph₂PCH₂}₃CCH₃ (P₃) and {Ph₂P(CH₂)₂}₃P (P₃P') are investigated, and the product

Full text of DOI:10.1021/ic0000294

4696
Inorg. Chem. 2000, 39, 4696-4703
Reactions of M(CO)5X (M ) Mn, Re; X ) Cl, Br) with {Ph2PCH2}3CCH3 (P3) and
{Ph2P(CH2)2}3P (P3P′): Synthetic, Spectroscopic, Electrochemical, and Electrospray Mass
Spectrometric Studies
Alan M. Bond,*,† Ray Colton,† Adrian van den Bergen,† and Jacky N. Walter‡
Department of Chemistry, Monash University, Clayton, Victoria 3168, Australia, and School of
Chemistry, La Trobe University, Bundoora, Victoria 3083, Australia
ReceiVed January 6, 2000
The reactions of M(CO)5X (M ) Mn, Re; X ) Cl, Br) with {Ph2PCH2}3CCH3 (P3) and {Ph2P(CH2)2}3P (P3P′)
are investigated, and the products are characterized by IR, NMR (31P and 13C), and electrospray mass spectrometric
(ESMS) techniques. With P3, the major products are fac-M(CO)3(η2-P3)X (syn and anti isomers) and cis,fac-
M(CO)2(η3-P3)X, and with P3P′, the major product for each metal is cis,mer-M(CO)2(η3-P3P′)X, but cis-[M(CO)2-
(η4-P3P′)]X and fac-[Re(CO)3(η3-P3P′)]X are also characterized. Addition of MeI to those complexes containing
pendant phosphine groups produces the corresponding phosphonium cations without affecting the remainder of
the molecule. On the voltammetric time scale, electrochemical oxidation of cis,fac-Mn(CO)2(η3-P3)X yields the
corresponding 17e cation cis,fac-[Mn(CO)2(η3-P3)X]+, but on the longer time scale of exhaustive electrolysis or
chemical oxidation, the product is fac-[Mn(CO)3(η3-P3)]+. In contrast, the rhenium cation cis,fac-[Re(CO)2(η3-
P3)X]+ is stable on the synthetic time scale, but upon oxidation of cis,fac-Re(CO)2(η3-P3)X with NOBF4, the
final product is the 18e [Re(CO)(NO)(η3-P3)X]+. cis,mer-Mn(CO)2(η3-P3P′)X is reversibly oxidized to cis,mer-
[Mn(CO)2(η3-P3P′)X]+ on the voltammetric time scale, but on the longer synthetic time scale, the product isomerizes
to trans-[Mn(CO)2(η3-P3P′)X]+, which can be reduced to trans-Mn(CO)2(η3-P3P′)X. Upon voltammetric oxidation,
the corresponding rhenium complexes show an initial irreversible response associated with the pendant phosphine
group prior to the reversible oxidation of the metal on the synthetic time scale; spectroscopic data indicate formation
of cis,mer-Re(CO)2(η3-P3P′O)X. The complex cis,mer-[Re(CO)2(η3-P3P′Me)X]+ shows only the reversible metal
oxidation response. ESMS data are obtained directly for the methylated cationic complexes, and neutral complexes
are either oxidized or adducted with sodium ions to produce cationic species.
Introduction
Manganese carbonyl halide complexes containing the poten-
tially tridentate ligand {Ph2PCH2}3CCH3 (P3; structure 1) have
syn, 2
1
been reported by Ellermann and co-workers.1 Reaction between
Mn2(CO)10 and P3 with subsequent addition of HX and
irradiation of the solution with UV light gave fac-Mn(CO)3-
(η2-P3)X (X ) Cl, Br). Liu and co-workers2 showed that two
stereoisomers of fac-Mn(CO)3(η2-P3)Br exist. Separation of the
syn isomer (structure 2; uncoordinated phosphorus atom on the
same side of the six-membered chelate ring as the bromide)
anti, 3
was achieved, but the anti isomer (structure 3) was not isolated
in a pure form. It was found1,2 that when fac-Mn(CO)3(η2-P3)X
was refluxed in polar solvents, cis-Mn(CO)2(η3-P3)X formed.
fac-Re(CO)3(η2-P3)Cl was prepared from Re2(CO)10 and P3 in
dichloromethane under photolytic conditions.3 fac-Re(CO)3(η2-
P3O)Cl, in which the pendant phosphorus atom is oxidized, was
characterized as a minor product.4 cis-Re(CO)2(η3-P3)Cl has
been prepared by the reaction of Re(PPh3)(N2COPh)Cl2 with
* Corresponding author. Fax: 613-9905-1338. E-mail: Alan.Bond@
sci.monash.edu.au.
† Monash University.
‡ La Trobe University.
(1) Ellermann, J.; Lindner, H. A.; Moll, M. Chem. Ber. 1979, 112, 3441.
(2) Liu, S. T.; Wang, H. E.; Yiin, L. M.; Tsai, S. C.; Liu, K. J.; Wang, Y.
M.; Cheng, M. C.; Peng, S. M. Organometallics 1993, 12, 2277.
(3) Lin, S. C.; Cheng, C. P.; Lee, T. Y.; Lee, T. J.; Peng, S. M. Acta
Crystallogr. 1986, C42, 1733.
(4) Liu, L. K.; Lin, S. C.; Cheng, C. P. Acta Crystallogr. 1988, C44, 1402.
10.1021/ic0000294 CCC: $19.00 © 2000 American Chemical Society
Published on Web 09/26/2000

M(CO)5X Reactions with P3 and P3P′ Compounds
Table 1. IR Data (20 °C) for Dichloromethane Solutions of the P3 Complexes and Their Derivatives
CO (cm-1
Inorganic Chemistry, Vol. 39, No. 21, 2000 4697
ν
)
syn
anti
complex
fac-Mn(CO)3(η2-P3)Cl
2029
2028
2029
2028
2036
2036
2036
2036
1962
1963
1962
1963
1958
1961
1958
1960
1904
1903
1904
1903
1893
1894
1894
1894
2029
2028
2029
2028
2035
2035
2036
2036
1962
1962
1962
1963
1957
1959
1958
1959
1909
1909
1909
1908
1899
1899
1899
1898
fac-Mn(CO)3(η2-P3)Br
fac-[Mn(CO)3(η2-P3Me)Cl]I
fac-[Mn(CO)3(η2-P3Me)Br]I
fac-Re(CO)3(η2-P3)Cl
fac-Re(CO)3(η2-P3)Br
fac-[Re(CO)3(η2-P3Me)Cl]I
fac-[Re(CO)3(η2-P3Me)Br]I
ν
CO (cm-1
)
ν
CO (cm-1
)
complex
complex
cis-Mn(CO)2(η3-P3)Cl
cis-Mn(CO)2(η3-P3)Br
cis-Re(CO)2(η3-P3)Cl
cis-[Re(CO)2(η3-P3)Cl]BF4
1953
1953
1958
2037
1894
1893
1895
1931
cis-Re(CO)2(η3-P3)Br
1952
2036
2044
2044
1893
1930
cis-[Re(CO)2(η3-P3)Br]BF4
cis-[Re(CO)(NO)(η3-P3)Cl]BF4
cis-[Re(CO)(NO)(η3-P3)Br]BF4
1778 (νNO
)
)
1778 (νNO
Table 2. 31P NMR Data (22 °C) for Dichloromethane Solutions of
P3 in refluxing benzene under carbon monoxide.5 With the
potentially quadridentate ligand {Ph2P(CH2)2}3P (P3P′; structure
4) only the reaction with Mn(CO)5Br in refluxing benzene to
give cis-Mn(CO)2(η3-P3P′)Br has been reported.6
the P3 Complexes and Their Derivativesa
31P δ (ppm)
syn
anti
complex
fac-Mn(CO)3(η2-P3)Cl
fac-Mn(CO)3(η2-P3)Br
30.4 (2) -28.2 (1) 30.4 (2) -29.0 (1)
28.0 (2) -28.4 (1) 28.0 (2) -29.2 (1)
fac-[Mn(CO)3(η2-P3Me)Cl]I 32.6 (2) 17.1 (1) 29.9 (2) 17.1 (1)
fac-[Mn(CO)3(η2-P3Me)Br]I 29.3 (2) 17.0 (1) 27.3 (2) 17.0 (1)
fac-Re(CO)3(η2-P3)Cl
fac-Re(CO)3(η2-P3)Br
fac-[Re(CO)3(η2-P3)Cl]I
fac-[Re(CO)3(η2-P3)Br]I
-12.4 (2) -29.3 (1) -12.3 (2) -30.4 (1)
-15.8 (2) -28.6 (1) -15.4 (2) -29.7 (1)
-9.7 (2) 17.3 (1) -13.1 (2) 16.8 (1)
-13.5 (2) 16.9 (1) -16.3 (2) 16.4 (1)
31P δ (ppm)
complex
4
cis-Mn(CO)2(η3-P3)Cl
cis-Mn(CO)2(η3-P3)Br
cis-Re(CO)2(η3-P3)Cl
cis-Re(CO)2(η3-P3)Br
67.1 (1)
69.0 (1)
1.6 (1) -19.1 (2)
0.7 (1) -21.6 (2)
22.0 (2)
21.2 (2)
In this study, fac-M(CO)3(η2-P3)X, cis-M(CO)2(η3-P3)X, and
M(CO)2(η3-P3P′)X (M ) Mn, Re; X ) Cl, Br) and related
compounds have been prepared from the direct reactions of
M(CO)5X with P3 and P3P′. Reactions with methyl iodide have
been investigated for species with a pendant phosphorus atom,
and the products of all reactions have been characterized by
spectroscopic and electrospray mass spectrometric (ESMS)
techniques. Electrochemical and chemical oxidation reactions
have been explored for many of the compounds. These studies
have led to the characterization of a new and extensive series
of 17e species whose reactivities can be compared with those
of their 18e unoxidized counterparts.
cis-[Re(CO)(NO)(η3-P3)Cl]BF4 -11.3 (1) -24.4 (1) -27.3 (1)
cis-[Re(CO)(NO)(η3-P3)Br]BF4 -14.3 (1) -27.7 (1) -30.5 (1)
a Numbers in parentheses are relative intensities of the resonances.
are similar to those in the literature7 and are due to the presence of the
syn and anti isomers of fac-Mn(CO)3(η2-P3)Br. The solid products were
obtained by removing the solvent under vacuum. Fractional recrystal-
lization from either dichloromethane/hexane or chloroform/hexane
solutions yielded the syn isomer as the first product, while the more
soluble anti isomer was isolated from the filtrate and recrystallized
several times by dissolution in dichloromethane and fractional precipita-
tion with hexane. Total yield: 90 ( 5%. The corresponding chloro
derivatives were prepared similarly.
Experimental Section
Materials. All solvents were of analytical reagent grade. Manganese
and rhenium carbonyls, P3, P3P′, NOBF4, and “magic blue”, (BrC6H4)3-
NSbCl6 (Strem), were used as supplied. The pentacarbonyl halides were
prepared by the interactions of the carbonyls with halogens.7 All
preparations were performed under a nitrogen atmosphere.
Syntheses. A. Complexes Containing P3. Spectroscopic data for
complexes containing P3 are given in Tables1 and 2. ESMS was used
to determine molecular formulas, and data for the intact ions are
summarized in Table 3.
(ii) fac-[Mn(CO)3(η2-P3Me)X]I. These compounds were prepared
by the addition of 1 equiv amounts of methyl iodide to 0.7 g of each
isomer of fac-Mn(CO)3(η2-P3)X, and the products were isolated by
evaporation of the solutions. Total yield: 95 ( 2%. Several recrys-
tallizations from dichloromethane/hexane yielded analytically pure
crystals. The IR spectra indicate that the carbonyl bands are virtually
unaffected by the methylation, whereas the 31P NMR resonances of
the originally pendant phosphorus atoms shift to the higher frequencies
characteristic of phosphonium derivatives.8 ESMS gives the intact ion
in each case (Table 3).
(i) fac-Mn(CO)3(η2-P3)X. A 0.5-0.7 g sample of Mn(CO)5Br and
P3 (1:1 mole ratio) were reacted in refluxing chloroform for 3 h. The
IR spectrum showed three strong carbonyl bands, and the 31P NMR
spectrum showed two resonances near the signal of the free P3 ligand
and another two overlapping signals at higher frequency. These spectra
(iii) cis-Mn(CO)2(η3-P3)X. A 0.5-0.7 g sample of Mn(CO)5Cl or
Mn(CO)5Br and P3 (1:1 mole ratio) were reacted in refluxing chloroform
for 30 h. Upon cooling, an orange solid precipitated and was collected
by filtration. IR and 31P NMR data agree with the literature values.1
Yield: 85 ( 5%.
(5) Chatt, J.; Dilworth, J. R.; Gunz, H. P.; Leigh, G. J. J. Organomet.
Chem. 1974, 64, 245.
(6) King, R. B.; Kapoor, R. N.; Saran, M. S.; Kapoor, P. N. Inorg. Chem.
1971, 10, 1851.
(7) Colton, R.; McCormick, M. J. Aust. J. Chem. 1976, 29, 1657.
(8) Colton, R.; Harvey, J.; Traeger, J. C. Org. Mass Spectrom. 1992, 27,
1030.

4698 Inorganic Chemistry, Vol. 39, No. 21, 2000
Bond et al.
Table 3. Electrospray Mass Spectrometric Data (Intact Ions Only)
complex
additive
ion
m/z
fac-[Mn(CO)3(η2-P3Me)Cl]I
fac-[Mn(CO)3(η2-P3Me)Br]I
fac-[Re(CO)3(η2-P3Me)Cl]I
fac-[Re(CO)3(η2-P3Me)Br]I
cis-Mn(CO)2(η3-P3)Cl
[Mn(CO)3(P3Me)Cl]+
[Mn(CO)3(P3Me)Br]+
[Re(CO)3(P3Me)Cl]+
[Re(CO)3(P3Me)Br]+
[Mn(CO)3(P3)]+
813
859
945
989
763
763
902
904
948
781
831
877
941
913
971
963
1007
NOBF4
NOBF4
magic blue
NOBF4
NOBF4
cis-Mn(CO)2(η3-P3)Br
[Mn(CO)3(P3)]+
cis-Re(CO)2(η3-P3)Cl
[Re(CO)2(P3)Cl]+
cis-Re(CO)2(η3-P3)Cl
[Re(CO)(NO)(P3)Cl]+
[Re(CO)(NO)(P3)Br]+
[Mn(CO)2(P3P′)]+
cis-Re(CO)2(η3-P3)Br
cis-[Mn(CO)2(η4-P3P′)]Br
cis,mer-[Mn(CO)2(η3-P3P′Me)Cl]PF6
cis,mer-[Mn(CO)2(η3-P3P′Me)Br]PF6
fac-[Re(CO)3(η3-P3P′)]Br
cis-[Re(CO)2(η4-P3P′)]Br
cis,mer-Re(CO)2(η3-P3P′)Cl
cis,mer-[Re(CO)2(η3-P3P′Me)Cl]I
cis,mer-[Re(CO)2(η3-P3P′Me)Br]PF6
[Mn(CO)2(P3P′Me)Cl]+
[Mn(CO)2(P3P′Me)Br]+
[Re(CO)3(P3P′)]+
[Re(CO)2(P3P′)]+
NaOAc
[Na + Re(CO)2(P3P′)Cl]+
[Re(CO)2(P3P′Me)Cl]+
[Re(CO)2(P3P′Me)Br]+
Table 4. IR Data (20 °C) for Dichloromethane Solutions of the
P3P′ Complexes and Their Derivatives
only with the formulation cis-[Mn(CO)2(η4-P3P′)]Br (structure 5). The
ν
CO (cm-1
)
complex
cis-[Mn(CO)2(η4-P3P′)]Cl
1949
1936
2035
1893
1969
1939
1948
1937
2033
1893
1967
1940
1964
2036
1940
1942
1942
1963
2037
1942
1943
1943
1891
1858
1967
cis,mer-Mn(CO)2(η3-P3P′)Cl
cis,mer-[Mn(CO)2(η3-P3P′)Cl]+
trans-Mn(CO)2(η3-P3P′)Cl
trans-[Mn(CO)2(η3-P3P′)Cl]+
cis,mer-[Mn(CO)2(η3-P3P′Me)Cl]PF6
cis-[Mn(CO)2(η4-P3P′)]Br
1849
1891
1862
1965
cis,mer-Mn(CO)2(η3-P3P′)Br
cis,mer-[Mn(CO)2(η3-P3P′)Br]+
trans-Mn(CO)2(η3-P3P′)Br
trans-[Mn(CO)2(η3-P3P′)Br]+
cis,mer-[Mn(CO)2(η3-P3P′Me)Br]PF6
cis-[Re(CO)2(η4-P3P′)]Cl
5
ES mass spectrum gave a strong peak for the intact ion [Mn(CO)2-
(P3P′)]+ (m/z 781). The filtrate from the reaction mixture was evaporated
to a small volume and cooled, which resulted in the precipitation of
orange crystals. The IR spectrum indicated a cis-dicarbonyl geometry,
agreeing with the literature,6 and the 31P NMR spectrum was consistent
only with η3 coordination of the P3P′ ligand. The 13C NMR spectrum
of the bromo complex (two resonances) identified the compound as
cis,mer-Mn(CO)2(η3-P3P′)Br (structure 6). Yield: 75 ( 5%. Similar
results were obtained for the corresponding chloro compounds.
1851
1905
1959
1857
1862
1867
1905
1958
1860
1864
1869
fac-[Re(CO)3(η3-P3P′)]Cl
cis,mer-Re(CO)2(η3-P3P′)Cl
cis,mer-Re(CO)2(η3-P3P′O)Cl
cis,mer-[Re(CO)2(η3-P3P′Me)Cl]I
cis-[Re(CO)2(η4-P3P′)]Br
fac-[Re(CO)3(η3-P3P′)]Br
cis,mer-Re(CO)2(η3-P3P′)Br
cis,mer-Re(CO)2(η3-P3P′O)Br
cis,mer-[Re(CO)2(η3-P3P′Me)Br]I
(iv) Rhenium Complexes. Reactions between 0.5-0.7 g of Re-
(CO)5X and P3 (1:1 mole ratio) under conditions similar to those given
for the manganese complexes, except that the dicarbonyl complexes
required the use of the higher boiling solvent xylene, yielded products
or mixtures of isomers analogous to those produced in the cases of the
rhenium complexes. Isomers were separated by chromatography on
silica using dichloromethane as the eluent, and all solids were
recrystallized using dichloromethane/hexane. Total yield: 85 ( 5%.
A crystal structure determination for one isomer of fac-Re(CO)3(η2-
P3)Cl was reported in the literature;3 however, the 31P NMR resonances
for this complex were given as δ -11.26 and -11.43 ppm and attributed
to the two signals of a single isomer of fac-Re(CO)3(η2-P3)Cl. It seems
that the syn and anti isomers were both present in the solution, but the
resonances of the pendant phosphorus atoms were not reported. fac-
[Re(CO)3(η2-P3Me)X]I compounds were prepared by procedures analo-
gous to those described above for their manganese counterparts.
B. Complexes Containing P3P′. Spectroscopic data for the P3P′
complexes are summarized in Tables 4 and 5, and ESMS data, in Table
3.
6
(ii) cis, mer-[Mn(CO)3(η3-P2P′Me)X]PF6. Addition of excess MeI
to a solution containing 0.1 g of cis,mer-Mn(CO)2(η3-P3P′)Cl in
dichloromethane methylated the pendant phosphine. The iodide salt
was isolated by evaporation of the solution. Yield: 90 ( 3%. IR and
31P NMR spectra indicated no other change in this reaction, and the
ES mass spectrum of the product gave a strong peak at m/z 831,
attributable to the intact anion [Mn(CO)2(P3P′)Cl]+. An acetone solution
of this compound was passed through an ion exchange column that
had been pretreated with KPF6 to replace the electrochemically active
-
iodide ion with the PF6 ion.
(i) cis-Mn(CO)2(η4-P3P) and cis, mer-Mn(CO)3(η3-P2P′)X. A 0.5-
0.7 g sample of Mn(CO)5Br and P3P′ (1:1 mole ratio) were reacted in
refluxing xylene until a pale yellow precipitate began to form (about 2
h). After cooling of the solution and collection of the solid by filtration
(yield 10 ( 3%), the solid was dissolved in dichloromethane. The
resultant solution exhibited two strong carbonyl stretches consistent
with a cis-dicarbonyl geometry and a 31P NMR spectrum consistent
(iii) Reaction between Re(CO)5X and P3P′. A 0.5-0.7 g sample
of Re(CO)5X and P3P′ (1:1 mole ratio) were reacted in refluxing
mesitylene for 3-5 h. The 31P NMR spectrum of the mesitylene solution
then showed numerous peaks, indicating the presence of several species.
Successive additions of hexane to the solution resulted in the formation
of white precipitates which were recrystallized several times from
dichloromethane/hexane to yield three compounds. The least soluble

M(CO)5X Reactions with P3 and P3P′ Compounds
Inorganic Chemistry, Vol. 39, No. 21, 2000 4699
Table 5. 31P and 13C NMR Data (22 °C) for Dichloromethane Solutions of the P3P′ Complexes and Their Derivatives (ppm)
31P δ (CH2Cl2)
13C δ (CDCl3)
complex
P′
P2
P1
CO
cis,mer-Mn(CO)2(η3-P3P′)Cl
122.1
138.2
126.8
155.2
121.7
141.3
127.5
79.5
79.5
85.8
114.1
67.7
77.5
86.1
69.9
87.0
82.4
84.9
70.6
86.2
37.8
37.9
39.5
26.3
27.9
35.2
35.1
37.1
-14.2
-13.9
24.0
224.7a
trans-Mn(CO)2(η3-P3P′)Cl
cis,mer-[Mn(CO)2(η3-P3P′Me)Cl]PF6
cis-[Mn(CO)2(η4-P3P′)]Br
79.3
cis,mer-Mn(CO)2(η3-P3P′)Br
trans-Mn(CO)2(η3-P3P′)Br
-14.2
-14.0
24.9
-14.1
34.3
23.7
31.0
-13.8
-14.0
31.4
232.5, 231.3
cis,mer-[Mn(CO)2(η3-P3P′Me)Br]PF6
cis,mer-Re(CO)2(η3-P3P′)Cl
cis,mer-Re(CO)2(η3-P3P′O)Cl
cis,mer-[Re(CO)2(η3-P3P′Me)Cl]I
cis-[Re(CO)2(η4-P3P′)]Br
195.6, 201.9 (d, J(C,P) ) 58 Hz)
fac-[Re(CO)3(η3-P3P′)]Br
cis,mer-Re(CO)2(η3-P3P′)Br
cis,mer-Re(CO)2(η3-P3P′O)Br
cis,mer-[Re(CO)2(η3-P3P′Me)Br]I
194.8, 201.2 (d, J(C,P) ) 56 Hz)
77.5
84.4
23.6
a May be two overlapping peaks.
compound in the mesitylene/hexane and dichloromethane/hexane
mixtures showed IR and 31P NMR spectra similar to those observed
for cis-[Mn(CO)2(η4-P3P′)]Br (5), suggesting that the compound is cis-
[Re(CO)2(η4-P3P′)]Br. ESMS data confirmed the presence of the [Re-
(CO)2(P3P′)]+ cation. The IR and 31P NMR spectra of a dichloromethane
solution of the second compound (bromo) are very similar to those for
fac-[Re(CO)3(η3-P2P′)]Br11 (except for an additional NMR resonance
due to the pendant phosphine), suggesting the product is fac-[Re(CO)3-
(η3-P3P′)]Br (structure 7). ESMS data confirm the presence of [Re-
Anal. Found (calcd) for [Mn(CO)2(η3-P3Me)Cl]I: C, 57.7 (57.9); H,
4.7 (4.6). Found (calcd) for Re(CO)3(η2-P3)Br: C, 54.1 (54.2); H, 3.9
(4.0); P, 9.3 (9.5). Found (calcd) for Mn(CO)3(η2-P3)Cl‚0.67CH2Cl2:
C, 63.0 (62.7); H, 4.5 (4.8), Cl, 9.7 (9.7). Found (calcd) for [Re(CO)3-
(η2-P3Me)Br]I‚CH3I: C, 43.6 (43.9); H, 3.1 (3.6); P, 7.9 (7.4). Found
(calcd) for [Mn(CO)2(η4-P3P′)]Cl‚CHCl3: C, 58.0 (57.6), H, 4.8 (4.8).
Found (calcd) for [Re(CO)2(η4-P3P′)]Br: C, 53.9 (53.2); H, 4.7 (4.3);
Br, 8.1 (8.1).
Electrochemical Methods. Conventional voltammetric measure-
ments were typically obtained with 1.0 mM solutions of the compound
in dichloromethane (0.1 M Bu4NPF6) using a Cypress Systems
(Lawrence, KS) Model CYSY-1 computer-controlled electrochemical
system or a BAS (Bioanalytical Systems, West Lafayette, IN) 100A
electrochemical analyzer. The working electrode was a glassy carbon
disk (radius 0.5 mm), the auxiliary electrode was a platinum wire, and
the reference electrode was Ag/AgCl (saturated LiCl in dichloromethane
(0.1 M Bu4NPF6)) separated from the test solution by a salt bridge.
The reversible voltammetry of an approximately 1.0 mM ferrocene (Fc)
solution in the same solvent was used as a reference redox couple, and
all potentials are quoted relative to Fc+/Fc. Near-steady-state voltam-
mograms were recorded using a 12.5 µm radius platinum microdisk
electrode. Solutions were purged with solvent-saturated nitrogen before
voltammetric measurements and then maintained under an atmosphere
of nitrogen during measurements.
7
(CO)3(P3P′)]+ (m/z 941). The least soluble compound in the mixture is
identified as cis,mer-Re(CO)2(η3-P3P′)Br. Total yield: 80 ( 5%.
(iv) cis, mer-[Re(CO)2(η3-P3P′Me)X]I. Samples (0.1 g) of cis,mer-
Re(CO)2(η3-P3P′)X were reacted with excess MeI in dichloromethane
solutions, and the products were isolated by evaporating the solutions.
Yield: 90 ( 5%. The IR and 31P NMR data indicate that only the
pendant phosphorus atoms were affected by the reactions. The iodide
anion was exchanged with PF6- to obtain the bromo complex used in
electrochemical studies. ES mass spectra confirmed the presence of
[Re(CO)2(P3P′Me)X]+ ions (m/z 963 (Cl), 1007 (Br)).
Bulk electrolysis experiments were undertaken with the BAS 100A
electrochemical analyzer using a large platinum basket working
electrode, a platinum gauze auxiliary electrode separated from the test
solution by a salt bridge, and the same reference electrode as used in
the voltammetric studies. Coulometric determinations gave n values
of 1 ( 0.1 per molecule for all oxidations.
Spectroscopic Methods. NMR spectra were recorded on a Bruker
AM 300 spectrometer, 31P at 121.496 MHz in dichloromethane and
13C at 75.469 MHz in CDCl3 solution. The high-frequency positive
convention is used for 31P and 13C chemical shifts with external 85%
H3PO4 and internal TMS references, respectively. Infrared spectra were
recorded on a Perkin-Elmer FT-IR 1720X or a Perkin-Elmer 1430 IR
spectrometer.
Analysis of Solids. 31P NMR data for dichloromethane solutions of
the compounds showed no evidence for phosphine ligand impurities
or any other diamagnetic phosphine-containing impurities. Voltammetric
analysis was used to confirm the presence or absence (<0.1%) of free
halide. 13C and 1H NMR data obtained for deuterated acetonitrile
solutions revealed the presence of dichloromethane, chloroform, or MeI
as appropriate in many of the solid samples. Crystal structures on related
compounds also have revealed11 the presence of solvent.
Electrospray Mass Spectrometry. Electrospray mass spectra of
cationic complexes were obtained with a VG Bio-Q triple-quadrupole
mass spectrometer using a water/methanol/acetic acid (50:50:1) mobile
phase. Solutions of the compounds (2.0 mM in dichloromethane) were
mixed, if necessary, with oxidant or sodium acetate as described under
Results and Discussion. A mixed solution, diluted 1:10 with methanol,
was immediately injected directly into the spectrometer via a Rheodyne
injector fitted with a 10 µL loop. A Phoenix 20 micro LC syringe pump
delivered the solution to the vaporization nozzle of the electrospray
source at a flow rate of 5 µL min-1. Nitrogen was used as the drying
gas and for nebulization with flow rates of approximately 3 L min-1
and 100 mL min-1, respectively. The potential on the first skimmer
(B1) was usually 40 V. Peaks were identified by the most abundant
Representative elemental microanalyses for a range of new com-
pounds prepared in this work were performed by Chemsearch,
University of Otago, New Zealand, and provided the following data.
(9) Bond, A. M.; Colton, R.; Gable, R. W.; Mackay, M. F.; Walter, J. N.
Inorg. Chem. 1997, 36, 1181.
(10) Bond, A. M.; Grabaric, B. S.; Grabaric, Z. Inorg. Chem. 1978, 17,
1013.
(11) (a) Bond, A. M.; Colton, R.; Jackowski, J. J. Inorg. Chem. 1975, 14,
274. (b) Bond, A. M.; Colton, R.; McCormick, M. J. Inorg. Chem.
1977, 16, 155. (c) Bond, A. M.; Carr, S. W.; Colton, R. Inorg. Chem.
1984, 23, 2343.

4700 Inorganic Chemistry, Vol. 39, No. 21, 2000
Bond et al.
facial geometry. Process 2 involves further oxidation to an
unstable 16e Mn(III) species
Voltammetric data for these and all other complexes studied
are listed in Table 6. For all compounds in this paper, couple 1
will refer to the reversible one-electron oxidation of the metal
(18e h 17e) and process 2 will refer to further irreversible
oxidation of the metal complex.
(ii) Bulk Electrolysis and Electrospray Mass Spectrom-
etry. Bulk electrolysis of a dichloromethane solution (0.4 M
NBu4ClO4) of cis-Mn(CO)2(η3-P3)Cl was undertaken at 0.100
V (i.e., slightly more positive than Epox of couple 1) at a platinum
gauze electrode. The amount of charge passed indicated a one-
electron process, as expected. Surprisingly, a near-steady-state
voltammogram of the oxidized solution obtained at a platinum
microdisk electrode did not indicate the presence of the oxidized
component of couple 1, demonstrating that cis-[Mn(CO)2(η3-
P3)Cl]+ is not stable on the longer synthetic time scale. The IR
spectrum of the oxidized solution shows two carbonyl absorp-
tions at 2031 and 1961 cm-1
.
A 2 mM solution of cis-Mn(CO)2(η3-P3)Cl in acetone (2 mM
NBu4PF6) was electrolyzed at room temperature exhaustively.
(These nonstandard conditions were selected to minimize the
amount of supporting electrolyte required, since excessive
amounts of ionic species depress the intensities of peaks in
electrospray mass spectra.) The ES mass spectrum of the
resultant solution shows the intact ion [Mn(CO)3(P3)]+ at m/z
763, confirming that this cation is produced upon oxidation of
cis-Mn(CO)2(η3-P3)Cl.
Figure 1. (a) Oxidative cyclic voltammogram recorded at a glassy
carbon macrodisk electrode (scan rate 200 mV s-1) at 20 °C for a 1.0
mM solution of cis-Mn(CO)2(η3-P3)Cl in dichloromethane (0.1 M Bu4-
NPF6). (b) Voltammogram for similar conditions over an extended
potential range.
mass in the isotopic mass distribution. In all cases, the agreement
between experimental and theoretical isotopic mass patterns was
excellent.
Chemical oxidations of cis-Mn(CO)2(η3-P3)Cl and cis-Mn-
(CO)2(η3-P3)Br with NOBF4 also led to the observation of [Mn-
(CO)3(P3)]+ in the ES mass spectra. The IR data for the oxidized
solutions also are consistent with the formation of the cation
[Mn(CO)3(η3-P3)]+, and the IR spectral patterns indicate that
the carbonyl ligands have a facial geometry. Thus, fac-[Mn-
(CO)3(η3-P3)]+ is generated by either electrochemical or chemi-
cal oxidation of cis-Mn(CO)2(η3-P3)X.
Results and Discussion
Electrochemical Studies of P3 Complexes. A. Manganese
Dicarbonyl Complexes. (i) Cyclic Voltammetry. Figure 1a
shows an oxidative cyclic voltammogram recorded at a glassy
carbon electrode (scan rate 200 mV s-1) for a 1.0 mM solution
of cis-Mn(CO)2(η3-P3)Cl in dichloromethane (0.1 M NBu4PF6)
at 20 °C. A reversible couple is observed at E r1/2 ) -0.020 V
(couple 1) (E r1/2 ) reversible half-wave potential), and second
and subsequent cycles are similar. The separation, ∆Ep, between
the oxidation peak potential (Epox) and the reduction peak
potential (Epred) is 85 mV. A similar value is observed under
these conditions for the known one-electron reversible couple
Fc+/Fc. At more positive potentials, an irreversible response at
0.885 V (process 2) is apparent (Figure 1b). This response
remains irreversible for the temperature range -60 to +20 °C
and for scan rates of 100-50 000 mV s-1. A near-steady-state
voltammogram recorded at a platinum microdisk electrode for
the first oxidation process indicates that it involves one electron
by comparison of its limiting current with that for the first
oxidation of an equimolar solution of fac-Mn(CO)3(η2-dpe)Br
(dpe ) Ph2P(CH2)2PPh2), which is known to be a one-electron
process.10 Thus, redox couple 1 is assigned to the reaction
A possible mechanism leading to [Mn(CO)3(η3-P3)]+ involves
the initial formation of cis-[Mn(CO)2(η3-P3)Cl]+ as in eq 1. It
is well-known12 that where isomerization cannot occur for the
17e species, as in this case, reactions involving disproportion-
ation usually occur:
2 cis-[Mn(CO)2(η3-P3)Cl]+ f cis-Mn(CO)2(η3-P3)Cl +
cis-[Mn(CO)2(η3-P3)Cl]2+ (3)
The voltammetric studies have shown 16e cis-[Mn(CO)2(η3-
P3)Cl]2+ to be unstable, and it presumably decomposes with
evolution of carbon monoxide, which probably reacts with
further 17e cis-[Mn(CO)2(η3-P3)Cl]+ to give fac-[Mn(CO)3(η3-
P3)]+.
B. Rhenium Dicarbonyl Complexes. (i) Cyclic Voltam-
metry. An oxidative cyclic voltammogram (scan rate 200 mV
s-1) of a 1.0 mM solution of cis-Re(CO)2(η3-P3)Cl in dichloro-
methane (0.1 M NBu4PF6) at 20 °C (Figure 2a) shows a
cis-Mn(CO)2(η3-P3)Cl h
cis-[Mn(CO)2(η3-P3)Cl]+ + e- (couple 1) (1)
(12) (a) Bond, A. M.; Bowden, J. A.; Colton, R. Inorg. Chem. 1974, 13,
602. (b) Bond, A. M.; Colton, R.; Kevekordes, J. E.; Panagiotidou, P.
Inorg. Chem. 1987, 26, 1430.
The usual isomerization to trans+, after oxidation to a 17e
species,11 is not observed because P3 can only coordinate in a

M(CO)5X Reactions with P3 and P3P′ Compounds
Inorganic Chemistry, Vol. 39, No. 21, 2000 4701
Table 6. Voltammetric Data Recorded at a Glassy Carbon Macrodisk Electrode (Scan Rate 200 mV s-1) for 1.0 mM Solutions in
Dichloromethane (0.1 M Bu4NPF6) at 20 °Ca
potentials (V vs Fc+/0
)
E r1/2
∆Ep (mV)
ox
red
complex
couple
Ep
Ep
cis-Mn(CO)2(η3-P3)Cl
1
0.025
0.890
0.065
0.920
0.375
1.040
0.385
1.030
0.195
-0.390
0.265
0.225
-0.350
0.295
0.560
0.610
0.485
0.560
0.615
0.485
0.635
0.500
-0.060
-0.025
0.290
-0.020
85
irrev 2
1
irrev 2
1
irrev 2
1
irrev 2
1
3
1
1
3
1
irrev
1
4
cis-Mn(CO)2(η3-P3)Br
cis-Re(CO)2(η3-P3)Cl
cis-Re(CO)2(η3-P3)Br
cis,mer-Mn(CO)2(η3-P3P′)Cl
0.020
0.330
0.340
90
85
90
0.295
0.105
-0.470
0.175
0.135
-0.435
0.205
0.150
-0.430
0.220
0.180
-0.395
0.250
90
80
90
90
85
90
cis,mer-[Mn(CO)2(η3-P3P′Me)Cl]PF6
cis,mer-Mn(CO)2(η3-P3P′)Br
cis,mer-[Mn(CO)2(η3-P3P′Me)Br]PF6
cis,mer-Re(CO)2(η3-P3P′)Cl
0.520
0.410
0.565
0.450
90
75
cis,mer-Re(CO)2(η3-P3P′)Br
irrev
1
4
1
4
0.525
0.410
0.540
0.430
0.570
0.450
0.590
0.465
90
75
95
70
cis,mer-[Re(CO)2(η3-P3P′Me)Br]PF6
a Epox ) oxidation peak potential; Epred ) reduction peak potential; ∆Ep ) separation in reduction and oxidation peak potentials; Er1/2 ) reversible
ox
half-wave potential, which is approximately equal to the reversible formal potential and is calculated as (Ep + Epred)/2.
compound. Similar voltammograms were obtained for cis-Re-
(CO)2(η3-P3)Br, and the voltammetric data are summarized in
Table 6.
(ii) Bulk Electrolysis. Bulk oxidation of a solution of cis-
Re(CO)2(η3-P3)Cl in dichloromethane (0.4 M NBu4PF6) at 20
°C was undertaken at 0.450 V at a platinum gauze electrode. A
near-steady-state voltammogram of the colorless solution before
the oxidation is shown in Figure 2b. After electrolysis, the
amount of charge passed indicated a one-electron process and
the solution was observed to be a red color. A near-steady-
state voltammogram (Figure 2c) of the red solution shows a
response with an Er1/2 value and a limiting current identical to
those for process 1 of the colorless solution before electrolysis.
However, the sign of the current indicates that the oxidized
species of redox couple 1 is present in solution. A cyclic
voltammogram of this solution shows that both processes 1 and
2 remain after bulk oxidation. The IR spectrum of the oxidized
solution displays two carbonyl bands which occur at higher
frequencies than those of the neutral precursors and are
consistent with the formation of cis-[Re(CO)2(η3-P3)Cl]+.
Similar results were obtained for the bromo complex, except
that a purple solution was produced by the electrolysis. Thus,
cis-[Re(CO)2(η3-P3)X]+ appears stable on the synthetic time
scale, unlike cis-[Mn(CO)2(η3-P3)X]+.
Figure 2. (a) Oxidative cyclic voltammogram recorded at a glassy
carbon macrodisk electrode (scan rate 200 mV s-1) at 20 °C for a 1.0
mM solution of cis-Re(CO)2(η3-P3)Cl in dichloromethane (0.1 M Bu4-
(iii) Chemical Oxidation. NOBF4 was added to a dichloro-
methane solution of cis-Re(CO)2(η3-P3)Br. The colorless solu-
tion immediately became purple, and the IR spectrum confirmed
the presence of cis-[Re(CO)2(η3-P3)Br]+. The addition of hexane
to the dichloromethane solution led to isolation of the purple
solid. A similar reaction for the chloro complex produced a red
solid. When a dichloromethane solution of cis-Re(CO)2(η3-P3)X
was stirred with NOBF4 for 1-2 h, the purple or red solution
was replaced by a brownish solution. A solid product obtained
by adding hexane to the solution was purifed by recrystallization
from dichloromethane/hexane several times. The IR spectrum
of the brown dichloromethane solution of the bromo complex
shows a carbonyl band at 2044 cm-1, while an absorption
observed at 1778 cm-1 is attributed to a nitrosyl stretch. The
NPF6). (b) Near-steady-state voltammogram (scan rate 10 mV s-1
)
recorded at a platinum microdisk electrode (radius 12.5 µm) at 20 °C
for a 1.0 mM solution of cis-Re(CO)2(η3-P3)Cl in dichloromethane (0.4
M Bu4NPF6) before electrolysis. (c) Near-steady-state voltammogram
of the same solution after subsequent exhaustive oxidative electrolysis.
reversible couple at Er1/2 ) 0.335 V (couple 1). Upon a scan to
more positive potentials, an irreversible oxidation response at
1.040 V (process 2, not shown) also is detected. The current
obtained for a near-steady-state voltammogram of this solution
indicates that process 1 is a one-electron process. Thus, the
voltammetry is similar to that of the analogous manganese

4702 Inorganic Chemistry, Vol. 39, No. 21, 2000
Bond et al.
31P NMR spectrum shows three resonances of similar intensities.
The formulation [Re(CO)(NO)(P3)Br]+ is confirmed by elec-
trospray mass spectrometry. The nitrosyl and carbonyl ligands
have a cis relationship by necessity, since the P3 ligand requires
a facial geometry. There is only one isomer of [Re(CO)(NO)-
(η3-P3)Br]+ that conforms to these conditions, and this is shown
in structure 8. Spectroscopic data are similar for the chloro
8
complex, and these species are characterized as cis-[Re(CO)-
(NO)(η3-P3)X]BF4.
Electrochemical Studies of P3P′ Complexes. A. Manganese
Complexes. (i) Cyclic Voltammetry. An oxidative cyclic
voltammogram of a 1.0 mM solution of cis,mer-Mn(CO)2(η3-
P3P′)Cl in dichloromethane (0.1 M NBu4PF6) at 20 °C shows a
reversible redox couple at Er1/2 ) 0.150 V (couple 1). Analysis
of a near-steady-state voltammogram recorded at a platinum
microdisk electrode also indicates that process 1 involves one
electron per molecule. Redox couple 1 is therefore assigned to
the reaction
Figure 3. Near-steady-state voltammograms (scan rate 10 mV s-1
)
recorded at a platinum microdisk electrode (radius 12.5 µm) at 20 °C
for a 1.0 mM solution of cis,mer-Mn(CO)2(η3-P3P′)Cl in dichloro-
methane (0.4 M Bu4NClO4): (a) before electrolysis; (b) after exhaustive
oxidative electrolysis at a platinum gauze electrode; (c) after subsequent
exhaustive reductive electrolysis.
passed during the reductive electrolysis, and the solution became
red. A near-steady-state voltammogram indicates that the
compound giving rise to process 3 now is in its reduced form
(Figure 3c). The IR spectrum of the reduced solution shows a
carbonyl band at 1893 cm-1, and the compound present is
assigned as 18e trans-Mn(CO)2(η3-P3P′)Cl. The 31P NMR
spectrum of the dichloromethane solution shows three peaks
(intensity 1:2:1) at δ 138.2, 69.9, and -13.9 ppm; the signal at
δ -13.9 ppm is attributed to the pendant phosphorus atom. The
resonances of the coordinated phosphorus atoms occur at
positions similar to those for the signals of trans-Mn(CO)2(η3-
P2P′)Cl.12 Redox couple 3 therefore is assigned as
cis,mer-Mn(CO)2(η3-P3P′)Cl h
cis,mer-[Mn(CO)2(η3-P3P′)Cl]+ + e- (couple 1) (4)
A similar response was observed for cis,mer-Mn(CO)2(η3-P3P′)-
Br in dichloromethane, and the data are summarized in Table
6.
Cyclic voltammograms of 1.0 mM solutions of cis,mer-[Mn-
(CO)2(η3-P3P′Me)X]PF6 in dichloromethane or acetone (0.1 M
NBu4PF6) at 20 °C show a single reversible oxidative response,
in each case again assigned to couple 1.
(ii) Bulk Electrolysis. Exhaustive bulk oxidative electrolysis
of a solution of cis,mer-Mn(CO)2(η3-P3P′)Cl in dichloromethane
(0.4 M NBu4ClO4) at 20 °C was undertaken at 0.300 V (slightly
more positive than the potential for process 1) at a platinum
gauze working electrode. Upon completion of the electrolysis,
the charge passed indicated a one-electron process and the
solution which initially was yellow had changed to orange. A
reductive cyclic voltammogram of the resultant solution indi-
cates that process 1 now is absent; however a reversible response
is observed at Er1/2 ) -0.430 V (couple 3). Parts a and b of
Figure 3 show voltammograms obtained at a microdisk platinum
electrode under near-steady-state conditions before and after
oxidation. The sign of the current indicates that, after electroly-
sis, the compound giving rise to process 3 is in its oxidized
form. The IR spectrum of this solution shows a single carbonyl
band at 1969 cm-1 which is identical to the position of the single
carbonyl stretch of the known9 compound trans-[Mn(CO)2(η3-
P2P′)Cl]+ (P2P′ ) (PPh2CH2CH2)2PPh). Thus, it seems likely
that trans-[Mn(CO)2(η3-P3P′)Cl]+ is present in the oxidized
solution.
trans-Mn(CO)2(η3-P3P′)Cl h
trans-[Mn(CO)2(η3-P3P′)Cl]+ + e- (couple 3) (5)
Thus, on the longer time scale, the usual partial square scheme
involving isomerization of cis,mer+ to the electronically more
favorable13 trans+ is observed:
There is no indication of isomerization of trans0 to cis,mer0.
Bulk electrolysis of a solution of cis,mer-Mn(CO)2(η3-P3P′)Br
produced analogous results.
Bulk reduction of the orange solution was carried out at
-0.570 V (slightly more negative than the potential of process
3). A one-electron process was determined from the charge
(13) Mingos, D. M. P. J. Organomet. Chem. 1979, 179, C29.

M(CO)5X Reactions with P3 and P3P′ Compounds
Inorganic Chemistry, Vol. 39, No. 21, 2000 4703
B. Rhenium Complexes. (i) Cyclic Voltammetry. Electro-
chemical studies were undertaken only for the complexes cis,-
mer-Re(CO)2(η3-P3P′)X and cis,mer-[Re(CO)2(η3-P3P′Me)Br]-
PF6. A cyclic voltammogram of a 1.0 mM solution of cis,mer-
Re(CO)2(η3-P3P′)Br in dichloromethane (0.1 M NBu4PF6) at
20 °C (scan rate 200 mV s-1) shows an oxidative response at
0.560 V which is shown to be irreversible when the scan
direction is reversed immediately after this process. This process
is designated as “irrev” in Table 6. Scanning to more positive
potentials reveals that this irreversible process appears as a
reversible one-electron couple to be detected on second and
subsequent cycles:
cis,fac-Re(CO)2(η3-P3P′O)X h
cis,fac-[Re(CO)2(η3-P3P′O)X]+ + e- (couple 4) (9)
Voltammetric data are summarized in Table 6.
(ii) Bulk Electrolysis. Exhaustive oxidative bulk electrolysis
of a solution of cis,mer-Re(CO)2(η3-P3P′)Br in dichloromethane
(0.4 M NBu4ClO4) at 20 °C was conducted at 0.500 V (platinum
gauze working electrode). The solution remained colorless
throughout the electrolysis, and the amount of charge passed
corresponded to a two-electron process, as expected for a
reaction involving oxidation of the pendant phosphorus atom.
A cyclic voltammogram of the oxidized solution reveals only
process 1 on the forward scan, while couples 1 and 4 are present
in second and subsequent cycles. The IR spectrum of the
oxidized solution shows two carbonyl IR bands, similar to those
of the complex before electrolysis, while the 31P NMR spectrum
shows three resonances (ratio 1:2:1), two of which occur at
positions similar to those of cis,mer-Re(CO)2(η3-P3P′)Br. How-
ever, the third signal, due to the pendant phosphorus atom, has
shifted to higher frequency. Similar spectra are obtained for a
solution of cis,mer-Re(CO)2(η3-P3P′)Cl after electrolysis, and
the data strongly suggest that the complexes cis,mer-Re(CO)2-
(η3-P3P′O)X are formed in the bulk electrolysis experiments.
An oxidative cyclic voltammogram of a 1.0 mM solution of
cis,mer-[Re(CO)2(η3-P3P′Me)Br]PF6 in dichloromethane (0.1 M
NBu4PF6) at 20 °C shows a reversible couple at Er1/2 ) 0.590
V (couple 1), and the reverse scan displays a reduction response
(process 4′) which is shown to be reversible in a second cycle.
A cyclic voltammogram obtained in acetone solution is similar
to that obtained in dichloromethane, but process 4′ is enhanced
in acetone. These voltammograms appear similar to those
obtained for cis,mer-Re(CO)2(η3-P2P′)Br,12 since the pendant
phosphorus is methylated and thus cannot be oxidized, unlike
the situation for cis,mer-Re(CO)2(η3-P3P′)Br.
shoulder on a voltammogram for a reversible couple at Er1/2
)
0.570 V (couple 1). The reverse scan and subsequent cycles
show an additional weak reversible couple at 0.450 V (couple
4). Cyclic voltammograms of the chloro complex show similar
features. The potential of the first irreversible oxidation indicates
that it could be either ligand or metal based, since the oxidation
of the free P3P′ ligand occurs at a similar potential. As evidenced
later, the irreversible process involves oxidation of the pendant
phosphorus atom from P(III) to P(V), as observed for the
complexes cis,mer-Re(CO)2(η1-dpm)(η2-dpm)X (dpm ) Ph2-
PCH2PPh2).14 The overall process involves reaction with traces
of water:
cis,mer-Re(CO)2(η3-P3P′)X + H2O f
cis,mer-Re(CO)2(η3-P3P′O)X + 2H+ + 2e- (7)
The reversible couple at 0.570 V (couple 1) is attributed to the
usual one-electron oxidation of the metal center:
cis,mer-Re(CO)2(η3-P3P′O)X h
cis,mer-[Re(CO)2(η3-P3P′O)X]+ + e- (couple 1) (8)
Couple 4 is only a weak feature and has not been fully
characterized, but by analogy with the similar behavior of cis,-
mer-Re(CO)2(η3-P2P′)X, it is probably associated with some
initial isomerization of the oxidized cis,mer+ cation to the
isomeric cis,fac+ cation, which then enables the following
Acknowledgment. We are indebted to the Australian
Research Council for financial support, and J.N.W. thanks the
Australian Commonwealth Government for a Postgraduate
Research Award.
(14) Walter, J. N. Ph.D. Thesis, La Trobe University, 1998.
IC0000294