62
D.A. Brown et al. / Journal of Organometallic Chemistry 592 (1999) 61–68
trifluoroacetic acid in nonpolar solvents. For example,
fac-Mn(CO)3(dppp)CH2OC(O)CF3 (3) was prepared
from the reaction of the methoxymethyl complex, fac-
Mn(CO)3(dppp)CH2OCH3 with trifluoroacetic acid in a
9:1 mixture of hexane and benzene, Eq. (1):
complexes 4 and 5 show a doublet of doublets and a
triplet for the two sets of terminal carbonyls. However,
the 13C-NMR spectra of the manganese complexes 2
and 3 show broad resonances for the terminal car-
1
bonyls. As expected, the H- and 13C-NMR spectra of
6 exhibit one triplet for the methylene protons and
methylene carbon of CH2I group.
fac-Mn(CO)3(dppp)CH2OCH3+CF3COOH
3+CH3OH
(1)
2.4. X-ray structures of 1, 5 and 7
Complex 3 was isolated by evaporating the solvents.
A small amount of the corresponding tetracarbonyl
trifluoroacetate salts, [M(CO)4{Ph2P(CH2)nPPh2}]-
[CF3CO2], where, M=Mn, Re and n=2, 3, were also
produced during the preparations of 2–5. Fractional
crystallizations in methylene chloride–hexane led to the
isolation of pure 2–5.
The conformations and atomic numbering schemes
for 1, 5 and 7 are shown in Figs. 1–3, respectively.
Crystal data for 1, 5 and 7 were obtained under the
conditions summarized in Table 2.
Selected bond lengths and angles for 1 are compiled
in Table 3. The Re atom in 1 is octahedrally coordi-
nated to four carbonyls, triphenylphosphine and the
trifluoroacetoxymethyl group. The rhenium–carbon
2.2. Synthesis of the iodomethyl complexes,
fac-Mn(CO)3(dppp)CH2I (6) and
cis-Re(CO)4(PPh3)CH2I (7)
,
(ReꢀC(5)) bond length of 2.267 (8) A for the tri-
fluoroacetoxymethyl ligand in 1 is similar to the bond
length observed for related rhenium methyl complexes
Complex 6 was prepared from the reaction of the
corresponding methoxymethyl complex, fac-Mn(CO)3-
(dppp)CH2OCH3 with (CH3)3SiI [5,6] Eq. (2):
[7]. The ReꢀC 2ꢀO bond angle of 113.6(4)° is slightly
CH
larger than the Re(1)ꢀC(9)ꢀO(20) bond angle of 111.0
(2)° in [{LRe(NO)(CO)}2(m-CH2OCH2)]I2 (where, L=
1,4,7-triazacyclononane) [8]. Thus, the methylene car-
bon in 1 is slightly distorted from tetrahedral geometry.
Selected bond lengths and angles for 5 are compiled
in Table 4. The Re atom in 5 is octahedrally coordi-
nated to three carbonyls, dppp [1,3-bis(diphenylphos-
phino)propane] and the trifluoroacetoxymethyl group.
The rhenium–carbon (Re(1)ꢀC(4)) bond length of
fac-Mn(CO)3(dppp)CH2OCH3+(CH3)3SiI
6+(CH3)3SiOCH3
(2)
The solvent and the volatile (CH3)3SiOCH3 were evapo-
rated to obtain an impure solid residue of 6. Crystal-
lization of 6 from CH2Cl2–hexane at −35°C yielded
light-yellow crystalline 6. The synthesis and spectral
characterization of 7 were reported previously [5].
,
2.242(3) A for the trifluoroacetoxymethyl ligand in 5 is
,
very similar to the bond lengths of 2.267 (8) A observed
2.3. Spectral studies
,
in 1 (vide supra), 2.214(15) A in [NEt4]2[Re3(m-H)3-
2
,
(m3-h -CH2O)(CO)9] [9], 2.225(7) A in [NEt4][ fac-
¸¹¹¹¹¹¹¹¹¹¹º
The IR spectral data for the complexes 1–6 are given
in Section 3. The IR spectrum of 1 shows four strong
stretching frequencies (w(CꢁO)s) expected for cis ge-
ometry and each of compounds 2–5 shows three strong
w(CꢁO)s expected for facial geometry of the terminal
carbonyls. Compounds 1–5 exhibit a medium intensity
w(CꢂO) in the 1770–1760 cm−1 region for the CꢂO of
(CO3)ReP(C6H5)2(o-C6H4C(H)OCꢂO)] [10] and 2.24–
»¹¹¹¹¹¹¹¹¹¹¹¹¹¹¼
,
2.55 A in related rhenium methyl complexes [7]. The
ReꢀCCH2ꢀO bond angle of 108.3(2)° in 5 is only slightly
larger than the Re(2)ꢀC(19)ꢀO(20) bond angle of
107.0(2)° in [{LRe(NO)(CO)}2(m-CH2OCH2)]I2 [8] and
the Re(1)ꢀCꢀO bond angle of 106.0(8)° in [NEt4]2-
[Re3(m-H)3(m3-h2-CH2O)(CO)9] [9] and appreciably
smaller than the ReꢀCCH2ꢀO bond angle of 113.6(4)° in
1.
1
the ꢀOC(O)CF3 group. The H- and 13C-NMR spectral
1
data are listed in Table 1. As expected, the H- and
13C-NMR spectral data of 1 exhibit one doublet in each
case for the methylene protons and methylene carbon
coupled to phosphorus. Similarly, the 1H- and 13C-
NMR spectral data of 2–5 show one triplet in each
case associated with the methylene protons and
methylene carbons. The 13C-NMR spectra of 1–5 ex-
hibit a quartet with 1J(CF):285 Hz for the CF3
carbon and a quartet with 2J(CF):40 Hz for the
OC(O) carbon. The 13C-NMR spectrum of 1 exhibits
three doublets for the terminal carbonyls as observed
for the analogous cis disubstituted manganese and rhe-
nium tetracarbonyl complexes [5] and both rhenium
Selected bond lengths and angles for 7 are compiled
in Table 5. The Re atom in 7 is octahedrally coordi-
nated to four carbonyls, triphenylphosphine and the
iodomethyl group. The ReꢀCCH bond length of 2.38(8)
2
,
A is longer than the corresponding bond length of
2
,
,
2.267(8) A in 1, 2.214(15) A in [NEt4]2[Re3(m-H)3(m3-h -
,
A in [NEt4][ fac-
CH2O)(CO)9] [9] and 2.225(7)
¸¹¹¹¹¹¹¹¹¹¹º
(CO3)ReP(C6H5)2(o-C6H4C(H)OCꢂO)] [10]. However,
»¹¹¹¹¹¹¹¹¹¹¹¹¹¹¼
,
larger rhenium–carbon bond lengths of 2.55 A have
been observed in some rhenium methyl complexes (vide
supra). It has been suggested for analogous manganese
Brown, Damon A.
