Syntheses, characterization and facial-meridional isomerism of tungsten tricarbonyl diphosphine complexes

Article abstract of DOI:10.1039/a704416j

The complexes fac-[W(CO)₃(η²-dppf)(η¹-dppm)] 4f, fac-[W(CO)₃(η²-dppm)(η¹-dppf)] 5f, fac-[W(CO)₃(η²-dppf)-(η¹-dppe)] 6f, fac-[W(CO)₃(η²-dppe)(η¹-dppf)] 7f, fac-[W(CO)₃(η²-dppm)(η¹-dppe)] 8f and fac-[W(CO)₃(η²-dPpe)-(η¹-dppm)] 9f have been prepared by treating fac-[W(CO)₃(η²-diphos)(NCMe)] 1-3 [diphos = 1,1′-bis(diphenylphosphino)ferrocene (dppf), dppm (Ph₂PCH₂PPh₂) or dppe (Ph₂PCH₂CH₂PPh₂)] with the corresponding diphosphines. The initially afforded facial isomers are converted into the meridional forms (4m-9m) in a subsequent, slow rearrangement process through opening of the chelated diphosphine ligand. A five-co-ordinate, square-pyramidal intermediate is presumed. In contrast, acid-assisted facial-meridional isomerization of 4f and 6f is likely via a seven-co-ordinate hydrido species. The new compounds have been characterized by elemental analyses and IR, mass and NMR spectroscopy.

Full text of DOI:10.1039/a704416j

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Syntheses, characterization and facial–meridional isomerism of
tungsten tricarbonyl diphosphine complexes
Sodio C. N. Hsu and Wen-Yann Yeh*
Department of Chemistry, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
The complexes fac-[W(CO)3(η2-dppf)(η1-dppm)] 4f, fac-[W(CO)3(η2-dppm)(η1-dppf)] 5f, fac-[W(CO)3(η2-dppf)-
(η1-dppe)] 6f, fac-[W(CO)3(η2-dppe)(η1-dppf)] 7f, fac-[W(CO)3(η2-dppm)(η1-dppe)] 8f and fac-[W(CO)3(η2-dppe)-
(η1-dppm)] 9f have been prepared by treating fac-[W(CO)3(η2-diphos)(NCMe)] 1–3 [diphos = 1,1Ј-bis(diphenyl-
phosphino)ferrocene (dppf), dppm (Ph2PCH2PPh2) or dppe (Ph2PCH2CH2PPh2)] with the corresponding
diphosphines. The initially afforded facial isomers are converted into the meridional forms (4m–9m) in a
subsequent, slow rearrangement process through opening of the chelated diphosphine ligand. A five-co-ordinate,
square-pyramidal intermediate is presumed. In contrast, acid-assisted facial–meridional isomerization of 4f and
6f is likely via a seven-co-ordinate hydrido species. The new compounds have been characterized by elemental
analyses and IR, mass and NMR spectroscopy.
The d6 metal tricarbonyl complexes, M(CO)3L3, exhibit facial
(fac) and meridional (mer) isomers.1–6 When L is a good σ
donor and poor π acceptor relative to CO the fac isomer is
expected to be more stable electronically to achieve stronger M
to CO back donation. On the other hand, the mer isomer is less
sterically encumbered and is favored when L contains bulky
groups.7 Several studies regarding their isomerization have been
reported. For example, Rousche and Dobson8 studied the
thermolysis of fac-[Mo(CO)3(η2-dppe){P(OPri)3}] (dppe = Ph2-
PCH2CH2PPh2) at 120 ЊC leading to mer-[Mo(CO)3(η2-dppe)-
{P(OPri)3}] via dissociation/association of the P(OPri)3 ligand.
Darensbourg et al.9 observed that on prolonged standing a
solution of fac-[W(CO)3(13CO)(η2-dppm)] (dppm = Ph2PCH2-
PPh2) at room temperature afforded a mixture of facial and
meridional isomers, presumably undergoing an intramolecular
CO rearrangement process. Schenk and Hilpert10 found an
interesting reaction of fac-[Mo(CO)3(η2-dppm)(NCMe)] and
dppe giving fac-[Mo(CO)3(η2-dppe)(η1-dppm)] with switch of
the chelate ligand, but no subsequent isomerization of this
compound was indicated. In contrast, Krishnamurthy and co-
workers11 revealed that treating fac-[Mo(CO)3(NCMe){η2-Ph2-
PN(Pri)PPh(dmpz)}] (dmpz = 3,5-dimethylpyrazol-1-yl) with
dppe produced fac- and mer-[Mo(CO)3{η2-Ph2PN(Pri)-
PPh(dmpz)}(η1-dppe)], in which the four-membered diphos-
phazane ring was retained and the dppe was co-ordinated in an
η1 fashion. In these reactions, however, a plausible isomeriz-
ation mechanism involving opening the η2-diphosphine ring
was ignored.
under dried nitrogen. The complexes fac-[W(CO)3(η2-dppf)-
(NCMe)]12 1 and fac-[W(CO)3(η2-dppm)(NCMe)]9 2 were
prepared by literature methods. 1,1Ј-Bis(diphenylphosphino)-
ferrocene (dppf) was prepared from ferrocene and chloro-
diphenylphosphine as described.13 Trimethylphosphine (1.0 
in toluene), methyldiphenylphosphine, triphenylphosphine,
dppm, dppe and tetrafluoroboric acid (54% in Et2O) from
Aldrich were used without further purification. Solvents were
dried over appropriate agents under nitrogen and distilled
before use. Thin-layer chromatographic (TLC) plates were pre-
pared from silica gel (Merck). Infrared spectra were recorded
with a 0.1 mm path CaF2 solution cell on a Hitachi I-2001
1
spectrometer, H and 31P NMR spectra on a Varian VXR-300
spectrometer at 300 and 121.4 MHz, respectively, and fast atom
bombardment (FAB) mass spectra on a VG Blotch-5022 spec-
trometer. Elemental analyses were performed at the National
Science Council Regional Instrumentation Center at the
National Chung-Hsing University, Taichung, Taiwan.
Preparation of fac-[W(CO)3(ç2-dppe)(NCMe)] 3
The complex [W(CO)3(NCMe)3] (500 mg, 1.28 mmol) and dppe
(510 mg, 1.28 mmol) were placed in a Schlenk flask (50 cm3)
containing a magnetic stirring bar. The flask was capped with a
rubber septum, evacuated and backfilled with nitrogen. After
adding dichloromethane (15 cm3), the solution was stirred at
ambient temperature for 5 h, forming a yellow precipitate. The
supernatant was removed via a cannula and the solids washed
with diethyl ether (50 cm3) and then dried under vacuum. The
complex fac-[W(CO)3(η2-dppe)(NCMe)] 3 was afforded in
86% yield (780 mg, 1.10 mmol). Mass spectrum (FAB): m/z 707
(Mϩ, 184W), 666 (Mϩ Ϫ CH3CN) and 666 Ϫ 28n (n = 1–3); IR
We recently prepared the complexes fac-[W(CO)3(η2-dppf)-
(PMe3)] and fac-[W(CO)3(η2-dppf)(PPh2X)] [dppf = 1,1Ј-
bis(diphenylphosphino)ferrocene, X = H or OH], which did not
lead to the meridional isomers upon heating.12 Apparently their
geometries are not sterically congested enough to surpass the
electronic advantages. We then investigated the analogous
complexes with bulky diphosphines. This paper presents results
concerning the syntheses and facial–meridional isomerism
of a series of complexes of the type [W(CO)3(η2-diphos)-
(η1-diphosЈ)] (diphos = diphosphine). It appears that the
chelated diphosphine ligand is opened up to facilitate the
isomerization reaction.
(1,2-C2H4Cl2, cmϪ1): ν(CO) 1932vs, 1838s and 1822s. 31P-{1H}
1
NMR (CD2Cl2, 20 ЊC): δ 46.25 (s; with 183W satellites, JWP
=
226 Hz). 1H NMR (CD2Cl2, 20 ЊC): δ 1.97 (s, 3 H, NCMe), 2.59
(m, 4 H, CH2) and 7.30–7.80 (m, 20 H, Ph).
Reaction of complex 1 and dppm
The complex fac-[W(CO)3(η2-dppf)(NCMe)] 1 (50 mg, 0.058
mmol) and dppm (25 mg, 0.065 mmol) were placed in a Schlenk
flask (50 cm3) containing a magnetic stirring bar. The flask was
fitted with a rubber septum, evacuated and backfilled with
nitrogen. After adding dichloromethane (15 cm3), the solution
was stirred at ambient temperature for 20 h. The mixture was
dried under vacuum and the residue separated by TLC, eluting
Experimental
General methods
Reactions were performed on a double-manifold Schlenk line
J. Chem. Soc., Dalton Trans., 1998, Pages 125–132
125

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with CH2Cl2–n-hexane (1:1, v/v). Three bands were obtained
according to the order of appearance: yellow [W(CO)4-
(η2-dppf)] (trace amount), yellow mer-[W(CO)3(η2-dppm)-
(η1-dppf)] 5m (28 mg, 40%) and yellow fac-[W(CO)3(η2-dppf)-
(η1-dppm)] 4f (30 mg, 43%).
Complex 5m (Found: C, 61.23; H, 4.37. C62H50FeO3P4W
requires C, 61.71; H, 4.18%): mass spectrum (FAB) m/z 1206
(Mϩ); IR (1,2-C2H4Cl2, cmϪ1) ν(CO) 1966w, 1864s and
1838 (sh); 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ Ϫ25.0 (dd, JPP = 31
and 24; with 183W satellites, JWP = 180, dppm), Ϫ16.69 (s, dppf),
Ϫ11.56 (dd, JPP = 31 and 67; with 183W satellites, JWP = 244,
dppm) and 22.96 (dd, JPP = 24 and 67, with 183W satellites,
JWP = 302 Hz, dppf); 1H NMR (CD2Cl2, 20 ЊC) δ 3.75 (s, 2 H),
4.00 (s, 2 H), 4.26 (s, 2 H), 4.30 (s, 2 H, C5H4), 5.04 (t, 2 H,
JPH = 9 Hz, CH2) and 7.00–7.70 (m, 40 H, C6H5).
mmol) was treated with dppf (80 mg, 0.14 mmol) by the same
method as described above (60 h). Three products were isolated:
yellow [W(CO)4(η2-dppe)] (32 mg, 33%), yellow mer-
[W(CO)3(η2-dppe)(η1-dppf)] 7m (45 mg, 26%) and yellow
fac-[W(CO)3(η2-dppe)(η1-dppf)] 7f (50 mg, 29%).
Complex 7m (Found: C, 61.82; H, 4.40. C63H52FeO3P4W
requires C, 61.99; H, 4.29%): mass spectrum (FAB) m/z 1221
(Mϩ) and 1221 Ϫ 28n (n = 1–3); IR (1,2-C2H4Cl2, cmϪ1) ν(CO)
1965w and 1859s; 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ 47.10 (dd,
JPP = 12, 69; with 183W satellites, JWP = 271, dppe), 38.79
(dd, JPP = 15, 12; with 183W satellites, JWP = 216, dppe), 18.32
(dd, JPP = 15, 69; with 183W satellites, JWP = 295 Hz, dppf) and
1
Ϫ17.03 (s, dppf); H NMR (CD2Cl2, 20 ЊC) δ 2.38 (br, 4 H,
C2H4), 3.71 (s, 2 H), 3.95 (s, 2 H), 4.17 (s, 2 H), 4.23 (s, 2 H,
C5H4) and 6.90–7.70 (m, 40 H, C6H5).
Complex 4f (Found: C, 61.50; H, 4.19. C62H50FeO3P4W
requires C, 61.71; H, 4.18%): mass spectrum (FAB) m/z 1206
(Mϩ), 822 (Mϩ Ϫ dppm) and 822 Ϫ 28n (n = 1–3); IR (1,2-
C2H4Cl2, cmϪ1): ν(CO) 1938s, 1842s and 1826 (sh); 31P-{1H}
NMR (CD2Cl2, 20 ЊC) δ Ϫ24.16 (d, JPP = 23, dppm), 8.17 (dt,
JPP = 23, 26; with 183W satellites, JWP = 214, dppm) and 16.91 (d,
Complex 7f (Found: C, 61.85; H, 4.22. C63H52FeO3P4W
requires C, 61.99; H, 4.29%): mass spectrum (FAB) m/z 1221
(Mϩ) and 1221 Ϫ 28n (n = 1–3); IR (1,2-C2H4Cl2, cmϪ1) ν(CO)
1935s and 1840s; 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ 33.68 (d,
JPP = 22; with 183W satellites, JWP = 220, dppe), 8.02 (t, JPP = 22;
with 183W satellites, JWP = 213 Hz, dppf) and Ϫ17.26 (s, dppf);
1H NMR (CD2Cl2, 20 ЊC) δ 2.48 (br, 4 H, C2H4), 3.83 (s, 2 H),
3.97 (s, 2 H), 4.27 (s, 2 H), 4.62 (s, 2 H, C5H4) and 6.60–7.70 (m,
40 H, C6H5).
1
JPP = 26; with 183W satellites, JWP = 230 Hz, dppf); H NMR
(CD2Cl2, 20 ЊC) δ 3.08 (s, 2 H), 3.95 (s, 2 H), 4.27 (s, 2 H), 4.46
(s, 2 H, C5H4), 4.68 (s, 2 H, CH2) and 6.90–7.50 (m, 40 H,
C6H5).
Reaction of complex 2 and dppe
Reaction of complex 2 and dppf
Complex fac-[W(CO)3(η2-dppm)(NCMe)] 2 (100 mg, 0.144
mmol) was treated with dppe (60 mg, 0.15 mmol) for 50 h at
28 ЊC by the same method as described above. Yellow mer-
[W(CO)3(η2-dppe)(η1-dppm)] 9m (70 mg, 46%) and yellow fac-
[W(CO)3(η2-dppe)(η1-dppm)] 9f (58 mg, 38%) were obtained by
TLC. Two intermediates corresponding to fac-[W(CO)3(η2-
dppm)(η1-dppe)] 8f and mer-[W(CO)3(η2-dppm)(η1-dppe)] 8m
were detected by 31P NMR spectroscopy during the reaction.
However, attempts to isolate them failed, leading only to 9m
and 9f.
The complex fac-[W(CO)3(η2-dppm)(NCMe)] 2 (20 mg, 0.023
mmol) and dppf (50 mg, 0.09 mmol) and CD2Cl2 (2 cm3) were
placed in a dry NMR tube under nitrogen. The reaction was
carried out at ambient temperature and monitored by 31P NMR
spectroscopy. The resonances corresponding to fac-[W(CO)3-
(η2-dppm)(η1-dppf)] 5f were detected initially. However, only
5m (17 mg, 0.014 mmol, 61%) was obtained after separation by
TLC. Attempts to isolate 5f in pure form have been unsuccess-
ful. Complex 5f: 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ Ϫ22.46 (d,
JPP = 22, dppm), Ϫ17.03 (s, dppf) and 12.96 (t, JPP = 22 Hz,
dppf).
Complex 8f: 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ Ϫ21.85 (d,
JPP = 22, dppm), Ϫ12.53 (d, JPP = 36, dppe) and 15.08 (dt,
JPP = 22, 36 Hz, dppe).
Complex 8m: 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ Ϫ24.60 (dd,
JPP = 23, 30, dppm), Ϫ12.35 (dd, JPP = 30, 66, dppm), Ϫ12.06
(d, JPP = 39, dppe) and 25.67 (ddd, JPP = 23, 39, 66 Hz,
dppe).
Reaction of complex 1 and dppe
The reaction of fac-[W(CO)3(η2-dppf)(NCMe)] 1 (50 mg, 0.058
mmol) and dppe (25 mg, 0.063 mmol) was carried out (5 h) and
worked up in a fashion similar to that of 1 and dppm. Three
products were obtained in order of appearance on the TLC
plate: yellow [W(CO)4(η2-dppf)] (trace amount), yellow fac-
[W(CO)3(η2-dppf)(η1-dppe)] 6f (38 mg, 54%) and yellow
fac, fac-[{W(CO)3(η2-dppf)}2(η1 :η1-dppe)] 6ff (25 mg, 42%).
Complex 6f (Found: C, 61.72; H, 4.39. C63H52FeO3P4W
requires C, 61.99; H, 4.29%): mass spectrum (FAB) m/z 1220
(Mϩ), 1220 Ϫ 28n (n = 1–3), 822 (Mϩ Ϫ dppe) and 822 Ϫ 28n
(n = 1–3); IR (1,2-C2H4Cl2, cmϪ1) ν(CO) 1938s, 1842s and
1826 (sh); 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ Ϫ12.49 (d, JPP = 31,
dppe), 9.14 (dt, JPP = 31, 27; with 183W satellites, JWP = 211,
dppe) and 16.0 (d, JPP = 27; with 183W satellites, JWP = 227 Hz,
dppf); 1H NMR (CD2Cl2, 20 ЊC) δ 1.82 (m, 2 H), 2.35 (m, 2 H,
C2H4), 3.91 (s, 2 H), 4.24 (s, 2 H), 4.45 (s, 2 H), 4.67 (s, 2 H,
C5H4) and 6.90–7.50 (m, 40 H, C6H5).
Complex 6ff (Found: C, 58.92; H, 3.87. C100H80Fe2O6P6W2
requires C, 58.79; H, 3.95%): mass spectrum (FAB) m/z 1220
[Mϩ Ϫ W(CO)3(dppf)] and 822 [Mϩ Ϫ W(CO)3(dppf)(dppe)];
IR (1,2-C2H4Cl2, cmϪ1) ν(CO) 1938s, 1842s and 1828 (sh); 31P-
{1H} NMR (CD2Cl2, 20 ЊC) δ 15.0 (t, JPP = 27; with 183W satel-
lites, JWP = 232, dppe) and 17.33 (d, JPP = 27; with 183W satel-
lites, JWP = 230 Hz, dppf); 1H NMR (CD2Cl2, 20 ЊC) δ 2.48 (br,
4 H, C2H4), 3.97 (s, 4 H), 4.24 (s, 4 H), 4.49 (s, 4 H), 4.73 (s, 4 H,
C5H4) and 6.80–7.50 (m, 60 H, C6H5).
Complex 9m (Found: C, 61.67; H, 4.46. C54H46O3P4W
requires C, 61.73; H, 4.41%): mass spectrum (FAB) m/z 1050
(Mϩ) and 1050 Ϫ 28n (n = 1–3); IR (1,2-C2H4Cl2, cmϪ1) ν(CO)
1966w and 1860s; 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ 47.85 (dd,
JPP = 11, 69; with 183W satellites, JWP = 273, dppe), 40.18
(dd, JPP = 15, 11; with 183W satellites, JWP = 220, dppe), 16.47
(ddd, JPP = 15, 42, 69; with 183W satellites, JWP = 293, dppm)
1
and Ϫ25.92 (d, JPP = 42 Hz, dppm); H NMR (CD2Cl2, 20 ЊC)
δ 2.41 (m, 4 H, C2H4), 3.02 (br, 2 H, CH2) and 6.90–7.70 (m,
40 H, C6H5).
Complex 9f (Found: C, 61.65; H, 4.45. C54H46O3P4W requires
C, 61.73; H, 4.41%): mass spectrum (FAB) m/z 1050 (Mϩ) and
1050 Ϫ 28n (n = 1–3); IR (1,2-C2H4Cl2, cmϪ1) ν(CO) 1938s and
1844s; 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ 36.99 (d, JPP = 22; with
183W satellites, JWP = 225, dppe), 6.89 (dt, JPP = 30, 22; with 183
W
satellites, JWP = 215, dppm) and Ϫ25.61 (d, JPP = 30 Hz, dppm);
1H NMR (CD2Cl2, 20 ЊC) δ 2.55 (m, 4 H, C2H4), 2.79 (br, 2 H,
CH2) and 6.70–7.70 (m, 40 H, C6H5).
Reaction of complex 1 and PPh3
Complex fac-[W(CO)3(η2-dppf)(NCMe)] 1 (50 mg, 0.058 mmol)
was treated with PPh3 (16 mg, 0.06 mmol) for 20 h by the same
method as described above. Three products were isolated:
yellow mer-[W(CO)3(η2-dppf)(PPh3)] 12f (2 mg, 3%), yellow
[W(CO)4(η2-dppf)] (14 mg, 28%) and yellow fac-[W(CO)3-
(η2-dppf)(PPh3)] 12m (16 mg, 26%).
Reaction of complex 3 and dppf
The complex fac-[W(CO)3(η2-dppe)(NCMe)] 3 (100 mg, 0.141
126
J. Chem. Soc., Dalton Trans., 1998, Pages 125–132

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Complex 12m (Found: C, 60.67, H, 4.45. C55H43FeO3P3W
requires C, 60.91; H, 4.00%): IR (1,2-C2H4Cl2, cmϪ1) ν(CO)
1965w, 1856s and 1840 (sh); 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ
15.16 (dd, JPP = 23, 11; with 183W satellites, JWP = 224), 20.72
(dd, JPP = 23, 66; with 183W satellites, JWP = 286) and 28.66 (dd,
JPP = 66, 11; with 183W satellites, JWP = 282 Hz); 1H NMR
(CD2Cl2, 20 ЊC) δ 3.98–4.40 (m, 8 H, C5H4) and 6.80–7.60 (m,
35 H, C6H5).
Complex 12f (Found: C, 60.99; H, 3.92. C55H43FeO3P3W
requires C, 60.91; H, 4.00%): mass spectrum (FAB) m/z 1084
(Mϩ), 822 (Mϩ Ϫ PPh3) and 822 Ϫ 28n (n = 1–3); IR (1,2-
C2H4Cl2, cmϪ1) ν(CO) 1940s, 1846s and 1828 (sh); 31P-{1H}
NMR (CD2Cl2, 20 ЊC) δ 16.26 (d, JPP = 28; with 183W satellites,
JWP = 224) and 19.05 (t, JPP = 28; with 183W satellites, JWP = 210
Hz); 1H NMR (CD2Cl2, 20 ЊC) δ 3.90 (s, 2 H), 4.26 (s, 2 H), 4.53
(s, 2 H), 4.80 (s, 2 H, C5H4) and 6.80–7.60 (m, 35 H, C6H5).
The material from the yellow band gave mer-[W(CO)3(η2-
dppf)(η1-dppm)] 4m (14 mg, 78%) (Found: C, 61.42; H, 4.22.
C62H50FeO3P4W requires C, 61.71; H, 4.18%): mass spectrum
(FAB) m/z 1205 (Mϩ), 1205 Ϫ 28n (n = 1–3) and 821 (Mϩ Ϫ
dppm); IR (1,2-C2H4Cl2, cmϪ1) ν(CO) 1961w and 1853s; 31P-
{1H} NMR (CD2Cl2, 20 ЊC) δ 21.66 (dd, JPP = 23, 66; with 183
W
satellites, JWP = 288, dppf), 16.83 (dd, JPP = 23, 33; with 183W
satellites, JWP = 230, dppf), 14.66 (ddd, JPP = 33, 38, 66; with
183W satellites, JWP = 275, dppm) and Ϫ25.06 (d, JPP = 38 Hz,
1
dppm); H NMR (CD2Cl2, 20 ЊC) δ 3.23 (br, 2 H, CH2), 4.12
(br, 4 H, C5H4), 4.21 (br, 4 H, C5H4) and 6.80–7.70 (m, 40 H,
C6H5).
Complex 6f in the presence of acid. Isomerization of fac-
[W(CO)3(η2-dppf)(η1-dppe)] 6f (20 mg, 0.016 mmol) in the
presence of an excess amount of HBF4 was carried out and
worked up in a fashion identical to that above. Yellow mer-
[W(CO)3(η2-dppf)(η1-dppe)] 6m (12 mg, 60%) was obtained as
the major product. Mass spectrum (FAB): m/z 1221 (Mϩ), 823
Reaction of complex 1 and PPh2Me
Complex 1 (50 mg, 0.058 mmol) was treated with PPh2Me (12
mg, 0.06 mmol) for 20 h by the method described above. Three
products were isolated: yellow [W(CO)4(η2-dppf)] (2 mg, 4%),
yellow mer-[W(CO)3(η2-dppf)(PPh2Me)] 13m (4 mg, 7%) and
yellow fac-[W(CO)3(η2-dppf)(PPh2Me)] 13f (52 mg, 88%).
Complex 13m (Found: C, 58.50; H, 4.23. C50H41FeO3P3W
requires C, 58.75; H, 4.01%): mass spectrum (FAB) m/z 1022
(Mϩ), 994 (Mϩ Ϫ CO), 822 (Mϩ Ϫ PPh2Me) and 822 Ϫ 28n
(n = 1–3); IR (1,2-C2H4Cl2, cmϪ1) ν(CO) 1960w, 1852s and
1842 (sh); 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ 1.50 (dd, JPP = 13,
65; with 183W satellites, JWP = 272), 17.62 (dd, JPP = 13, 23; with
(Mϩ Ϫ dppe) and 823 Ϫ 28n (n = 1–3); IR (1,2-C2H4Cl2, cmϪ1
)
ν(CO) 1960w and 1854s; 31P-{1H} NMR (CD2Cl2, 20 ЊC)
δ 21.53 (dd, JPP = 23, 66; with 183W satellites, JWP = 291, dppf),
18.27 (ddd, JPP = 33, 34, 66; with 183W satellites, JWP = 273,
dppe), 16.26 (dd, JPP = 23, 34; with 183W satellites, JWP = 225,
1
dppf) and Ϫ13.45 (d, JPP = 34 Hz, dppe); H NMR (CD2Cl2,
20 ЊC) δ 1.62 (m, 2 H), 2.36 (m, 2 H, C2H4), 4.12 (s, 2 H), 4.18
(s, 2 H), 4.22 (s, 2 H), 4.24 (s, 2 H, C5H4) and 6.60–7.80 (m,
40 H, C6H5).
183W satellites, JWP = 224) and 21.35 (dd, JPP = 23, 65; with 183
satellites, JWP = 292 Hz); H NMR (CD2Cl2, 20 ЊC) δ 1.65 (d,
3 H, JPH = 7, Me), 4.16 (s, 2 H), 4.25 (br, 4 H), 4.28 (s, 2 H,
C5H4) and 7.00–7.70 (m, 30 H, C6H5).
W
Reactions of complex 4f
1
With dppe. The complex (23 mg, 0.019 mmol) and dppe (75
mg, 0.19 mmol) were placed in a Schlenk flask (50 cm3) contain-
ing a magnetic stirring bar. The flask was fitted with a rubber
septum, evacuated, and backfilled with nitrogen. After intro-
ducing dichloromethane (15 cm3), the solution was stirred at
ambient temperature for 48 h. The mixture was then dried
under vacuum and the residue separated by TLC, eluting with
CH2Cl2–n-hexane (1:1, v/v). Three products were isolated in
order of appearance on the TLC plate: yellow mer-[W(CO)3-
(η2-dppm)(η1-dppf)] 5m (11 mg, 48%), yellow fac-[W(CO)3-
(η2-dppf)(η1-dppe)] 6f (60 mg, 25%) and yellow fac-
[W(CO)3(η2-dppf)(η1-dppm)] 4f (50 mg, 21%).
Complex 13f (Found: C, 58.52; H, 4.13. C50H41FeO3P3W
requires C, 58.75; H, 4.01%): mass spectrum (FAB) m/z 1022
(Mϩ), 994 (Mϩ Ϫ CO), 822 (Mϩ Ϫ PPh2Me) and 822 Ϫ 28n
(n = 1–3); IR (1,2-C2H4Cl2, cmϪ1) ν(CO) 1938s, 1846s and
1830 (sh); 31P-{1H} NMR (CD2Cl2, 20 ЊC) δ Ϫ3.71 (t, JPP = 27;
with 183W satellites, JWP = 228) and 19.83 (d, JPP = 27; with 183
satellites, JWP = 216 Hz); H NMR (CD2Cl2, 20 ЊC) δ 1.90 (d,
3 H, JPH = 5 Hz, Me), 3.99 (s, 2 H), 4.28 (s, 2 H), 4.50 (s, 2 H),
4.73 (s, 2 H, C5H4) and 7.00–7.60 (m, 30 H, C6H5).
W
1
Isomerizations
With PMe3. A Schlenk flask (50 cm3) was charged with fac-
[W(CO)3(η2-dppf)(η1-dppm)] 4f (10 mg, 0.008 mmol) and 1,2-
dichloroethane (10 cm3) under nitrogen. A toluene solution of
PMe3 (12 µl, 0.012 mmol) was introduced by a microsyringe.
The mixture was stirred at ambient temperature for 30 h. The
solvents were removed under vacuum and the residue separated
by TLC, eluting with n-hexane–dichloromethane (1:1, v/v).
The known complex fac-[W(CO)3(η2-dppf)(PMe3)]12 10f (6 mg,
83%) and 5m (1 mg, 10%) were obtained.
Complexes 4f and 7f. Typically, an NMR tube was charged
with fac-[W(CO)3(η2-dppf)(η1-dppm)] 4f (15 mg) and CD2Cl2
(2 cm3) under nitrogen. The isomerization was carried out at
room temperature and monitored by 31P NMR spectroscopy. It
was complete after 72 h, showing only the resonances for 5m.
Isomerization of complex 7f to give 7m takes 1 week to com-
plete at room temperature, but only 3 h are required at 80 ЊC.
Complexes 4m and 6m. A typical reaction: a Schlenk flask (50
cm3) was charged with mer-[W(CO)3(η2-dppf)(η1-dppm)] 4m
(40 mg) and 1,2-dichloroethane (10 cm3). The flask was placed
in an oil-bath at 80 ЊC and the reaction was monitored by IR
spectroscopy in the CO stretching region. The spectra showed
no further change after 6 h. The solvent was evaporated under
vacuum and the residue separated by TLC, affording 5m in 90%
yield. Isomerization of complex 6m was carried out at 80 ЊC,
producing 7m in 71% yield. No reaction was observed at am-
bient temperature.
With CO. A two-necked flask (100 cm3) was equipped with a
magnetic stir bar. One neck was connected to an oil bubbler and
the other had an inlet tube for introduction of carbon mon-
oxide gas into the solution. A solution of fac-[W(CO)3(η2-
dppf)(η1-dppm)] 4f (20 mg, 0.017 mmol) in 1,2-dichloroethane
(10 cm3) was transferred to the flask and saturated with CO gas.
The mixture was stirred at ambient temperature for 48 h with
slow bubbling of CO through the solution. The mixture was
dried under vacuum and the residue separated by TLC. The
known complex [W(CO)4(η2-dppf)]14 11 (10 mg, 70%) and 5
(3 mg, 15%) were obtained.
Complex 4f in the presence of acid. The complex (18 mg,
0.015 mmol) and dichloromethane (10 cm3) were placed in a
Schlenk flask (50 cm3) containing a magnetic stirring bar and a
rubber septum. An ether solution of HBF4 (20 µl, excess) was
added via a syringe. The mixture was stirred at ambient tem-
perature for 2 h, and evacuated under vacuum. The residue was
subjected to TLC, eluting with CH2Cl2–n-hexane (1:1, v/v).
Results and Discussion
Preparation of compound 3
The syntheses of fac-[W(CO)3(η2-dppf)(NCMe)]12 1 and fac-
J. Chem. Soc., Dalton Trans., 1998, Pages 125–132
127

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O
C
O
C
P
P
P
Fc
W
C
O
P
4m
heat
H+ cat.
O
C
O
C
O
C
P
P
O
O
C
C
P
P
O
C
C
P
P
P
slow
C
P
P
Fc
W
Fc
W
P
W
O
P
N
C
Me
O
Fc
C
O
P
5m
1
4f
fast
P
O
C
O
C
Fc
O
O
C
P
C
P
P
P
W
W
P
P
C
C
O
O
N
C
Me
Fc
P
2
5f
Scheme 1
Preparation and isomerization of complexes 4f and 5f
O
C
The complex fac-[W(CO)3(η2-dppf)(η1-dppm)] 4f is initially
afforded from the reaction of fac-[W(CO)3(η2-dppf)(NCMe)] 1
and dppm at ambient temperature. Isomerization of 4f readily
takes place at 25 ЊC to give mer-[W(CO)3(η2-dppm)(η1-dppf)]
5m together with a switch of the chelate ligand from dppf to
dppm. Complete transformation from 4f to 5m takes 72 h at
25 ЊC, but only 4 h are required at 50 ЊC. In the presence of acid,
however, mer-[W(CO)3(η2-dppf)(η1-dppm)] 4m is obtained as
the sole product. Compound 4m is indefinitely stable at room
temperature, but it slowly converts into 5m in hot 1,2-dichloro-
ethane solution (80 ЊC). The other isomer fac-[W(CO)3(η2-
dppm)(η1-dppf)] 5f is not isolable but only detected by 31P
NMR spectroscopy as an intermediate during the reaction of
fac-[W(CO)3(η2-dppm)(NCMe)] 2 and dppf, leading to 5m. The
results are summarized in Scheme 1.
It is obvious that complexes 4f and 5f are the kinetic products
of the reactions, while 5m is most stable thermodynamically.
However, when dppe, PMe3 or CO is present, 5m is obtained
together with fac-[W(CO)3(η2-dppf)(η1-dppe)] 6f, fac-
[W(CO)3(η2-dppf)(PMe3)] 10f and [W(CO)4(η2-dppf)] 11,
respectively (Scheme 2). This indicates that substitution of the
η1-diphosphine ligand is a competitive reaction. Nevertheless,
once the meridional isomer is formed, it is quite resistant to
ligand dissociation, such that 5m does not react with PMe3 at
50 ЊC.
O
C
C
P
P
Fc
W
P
O
P
4f
L
O
C
O
C
O
O
C
C
C
P
P
P
P
P
Fc
+
W
W
O
L
C
O
P
Fc
dppe
PMe3
CO
6f
5m
L =
10f
11
Scheme 2
[W(CO)3(η2-dppm)(NCMe)]9 2 have been previously described.
The analogous complex fac-[W(CO)3(η2-dppe)(NCMe)] 3 is
prepared in a similar fashion by treating [W(CO)3(NCMe)3]
with equimolar dppe at room temperature. The IR spectrum of
3 in the carbonyl region resembles those recorded for 1 and 2,
indicating similar structures. The 31P NMR spectrum of 3 dis-
plays one resonance at δ 46.25, which is significantly downfield
from those recorded for 1 (δ 22.4) and 2 (δ Ϫ11.06).
The different reactivity between complexes 4f and 5f can be
rationalized in terms of the structures of parent compounds 1
and 2. Since the dppf ligand of 1 can modify its steric bite by
twisting the cyclopentadienyl rings, the phenyl groups and the
NCMe ligand are staggered.12 However, the four-membered
dppm ring of 2 constrains the phenyl groups to being eclipsed
to the axial NCMe and CO ligands.9 So compound 5f would
128
J. Chem. Soc., Dalton Trans., 1998, Pages 125–132

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Scheme 3. The results closely resemble the reactions with
O
C
dppm shown above, except that a dimetallic complex fac, fac-
[{W(CO)3(η2-dppf)}2(η1 :η1-dppe)] 6ff is produced and both 6f
and 7f are isolable. Standing a solution of pure 6f at 25 ЊC
yields 7m and 6ff, but under acidic conditions 6m is obtained
solely without forming the dimetallic species. It is apparent that
eliminating a dppe ligand from 6f is essential to give 6ff, while
6m is resistant to ligand dissociation. Furthermore, no isomeri-
zation of 6ff is evidenced. This is contrary to the reaction of
fac-[Mo(CO)3(NCMe){η2-Ph2PN(Pri)PPh(dmpz)}] and dppe
to produce mer,mer-[{Mo(CO)3[η2-Ph2PN(Pri)PPh(dmpz)]}2-
(η1 :η1-dppe)].11
O
O
C
C
P
P
Fc
W
N
C
Me
1
P
P
On the other hand, treating fac-[W(CO)3(η2-dppe)(NCMe)] 3
with dppf at room temperature produces [W(CO)4(η2-dppe)]
(33%), fac-[W(CO)3(η2-dppe)(η1-dppf)] 7f (29%) and mer-
[W(CO)3(η2-dppe)(η1-dppf)] 7m (26%). It is likely compound 7f
is afforded initially, following by isomerization to give 7m as
well as disproportionation to yield the W(CO)4 complex.
O
C
O
C
O
O
C
P
C
O
C
P
W
P
Fc
W
P
P
P
Preparation and isomerization of complex 8f
C
O
Fc
P
The acetonitrile ligand of fac-[W(CO)3(η2-dppm)(NCMe)] 2 is
readily replaced by dppe, but leading to fac-[W(CO)3(η2-
dppe)(η1-dppm)] 9f and mer-[W(CO)3(η2-dppe)(η1-dppm)] 9m
(Scheme 4). Phosphorus-31 NMR spectroscopy has been
applied to assess the progress of reaction. The spectrum of
reaction mixture after 2 h shows the presence of fac-
[W(CO)3(η2-dppm)(η1-dppe)] 8f along with small quantities of
mer-[W(CO)3(η2-dppm)(η1-dppe)] 8m and 9f. The quantities of
8f, 8m and 9f are about equal in 24 h. After 3 d, 9f and 8m are
present as the major products together with a minor amount of
8f and 9m. Although this transformation is slow, attempts to
isolate all the components by TLC only afford 9f and 9m. It is
probable that the conversion of 8 into 9 is accelerated by acid
contaminant on the silica gel. Schenk and Hilpert10 previously
reported an analogous reaction of fac-[Mo(CO)3(η2-dppm)-
(NCMe)] and dppe to yield fac-[Mo(CO)3(η2-dppe)(η1-dppm)],
where the four-membered chelate ring of dppm is opened up
to leave an η1-co-ordinated dppm while a more stable
five-membered chelate ring is formed by dppe. The ultimate
formation of 9m indicates the operation of ring strains in
determining the products.
O
C
P
Fc
W
P
P
C
O
6f
C
O
H+ cat.
6ff
O
C
O
C
O
O
P
C
C
P
P
P
P
Fc
W
W
P
P
C
O
Fc
C
O
P
7m
6m
O
C
O
C
Reaction of complex 1 and bulky monophosphine
O
O
C
C
P
C
P
P
Treatment of fac-[W(CO)3(η2-dppf)(NCMe)] 1 with PPh3 and
PPh2Me affords fac-[W(CO)3(η2-dppf)(PPh3)] 12f and fac-
[W(CO)3(η2-dppf)(PPh2Me)] 13f, respectively, which then
rearrange to give mer-[W(CO)3(η2-dppf)(PPh3)] 12m and mer-
[W(CO)3(η2-dppf)(PPh2Me)] 13m. The analogous complexes
fac-[W(CO)3(η2-dppf)(L)] (L = PMe3, PPh2H, or PPh2OH) are
stable under similar conditions.12 Obviously, the energy barrier
for fac → mer transformation is reduced as the steric bulk of
the ligands increases.
+
W
P
W
P
P
C
O
Fc
O
C
O
P
Fc
P
O
C
O
O
7f
C
C
P
W
P
Characterization of new compounds
N
Compounds 5f, 8m and 8f cannot be isolated in a pure form and
were characterized only by 31P NMR spectroscopy. The remain-
ing complexes form crystalline solids and give satisfactory
analyses (C, H). Their FAB mass spectra display the molecular
ion and ions corresponding to successive loss of three car-
bonyls. The IR spectra in the carbonyl region for the facial
isomers show three strong bands, presumably due to a dis-
rupted C3 symmetry for the W(CO)3 group, while the meri-
dional geometry is indicated by one weak and two medium to
strong absorption bands.2–6,9,15
C
Me
3
Scheme 3
sustain stronger steric repulsions between phosphine ligands
than 4f and is more susceptible to isomerization.
Identification of these new complexes is unambiguously sub-
stantiated by 31P NMR spectroscopy. Their spectra are assigned
on the basis of chemical shifts and coupling patterns.2–4,10,16 In
general, the facial isomers have a plane of symmetry and would
Preparation and isomerization of complexes 6f and 7f
Reactions of fac-[W(CO)3(η2-dppf)(NCMe)] 1 with dppe and
its subsequent isomerization processes are summarized in
J. Chem. Soc., Dalton Trans., 1998, Pages 125–132
129

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O
C
P
P
O
C
O
C
O
O
O
C
P
P
C
P
P
C
C
P
P
W
P
W
W
P
C
C
O
O
O
N
C
Me
P
P
9f
8f
2
O
C
O
C
O
C
P
P
O
C
P
P
W
W
P
P
C
O
C
O
P
P
8m
9m
Scheme 4
parison. For 4f a doublet signal at δ 16.91 and a doublet of
doublets at δ 8.17 accompanied by 183W satellites are assigned
to the co-ordinated dppf and dppm moieties, respectively, and
an upfield doublet resonance at δ Ϫ24.16 without 183W satellites
is assigned to the pendant dppm group. On the other hand, 4m
and 5m display three complex resonances for the co-ordinated
phosphines due to coupling between the inequivalent phos-
phorus atoms and to the 183W atom.
The co-ordination shifts, ∆ = δmonodentate Ϫ δfree ligand, and
chelation shifts, ∆R = δchelate Ϫ δmonodentate, of the diphosphine
ligands are of interest in these complexes. The co-ordination
shifts for dppm, dppe and dppf are comparable, averaging ϩ32,
ϩ24 and ϩ28 ppm, respectively. In contrast, the chelation shifts
are more diverse, where the four-membered dppm rings are
shielded (Ϫ30 ppm), the five-membered dppe rings are
deshielded (ϩ25 ppm) and the dppf rings are only slightly
affected (ϩ5 ppm). Although the theoretical aspects of the ring
contribution remain elusive, Garrou17 has proposed the general
utility of ∆ and ∆R for structural assignments of transition-
metal phosphine complexes.
Possible isomerization mechanism
The facial–meridional isomerism may be reasonably accounted
for by the reaction sequence shown in Scheme 5. Apparently,
three bulky phosphines in a facial arrangement cause consid-
erable steric repulsions, leading to ready dissociation of the
η1-disphosphine ligand to give I, or opening up the η2-
disphosphine ring to give II. The resulting square-pyramidal
intermediates could then undergo site exchange, presumably
through a trigonal-bipyramidal transient with one of the
diphosphine ligands at the axial position and ring closing to
yield the final products.18,19 Alternatively, an associative mech-
anism to generate a seven-co-ordinate, 20-electron intermediate
[W(CO)3(η2-diphos)(η2-diphosЈ)] seems improbable based on
the steric considerations.
Since isomerization of complex 4f produces 5m solely with-
out forming 4m, the site-exchange rate for II should be much
faster than that for I. One possible explanation is the ring con-
straints of I increasing the energy separation between the more
stable square-pyramidal and less stable trigonal-bipyramidal
structures. Furthermore, adding PMe3 to a solution of 4f does
not give [W(CO)3(η1-dppm)(η1-dppf)(PMe3)] or [W(CO)3(η2-
dppm)(PMe3)]. This means that, once the intermediate II is
Fig. 1 The 31P-{1H} NMR spectra of (a) fac-[W(CO)3(η2-dppf)(η1-
dppm)] 4f, (b) mer-[W(CO)3(η2-dppm)(η1-dppf)] 5m and (c) mer-
[W(CO)3(η2-dppf)(η1-dppm)] 4m in CD2Cl2 solution
display two 31P resonances for the co-ordinated phosphines and
one resonance for the pendant phosphine group, while the
meridional isomers present four resonance signals. Typical
spectra of 4f, 4m and 5m are illustrated in Fig. 1 for com-
130
J. Chem. Soc., Dalton Trans., 1998, Pages 125–132

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P
P
+
L
P
P
x
x
W
W
L
4f
6f
10f , 11
+
y
P
P
6ff
P
P
I
y
P
x
x
x
P
P
P
P
P
P
x
W
W
W
P
W
P
P
P
P
P
P
P
y
y
y
y
III
II
IV
P
x
P
x
x
P
P
P
P
P
W
W
P
W
P
P
P
y
P
y
y
P
5m
7m
4f
6f
8f
5f
5m
7m
9m
9f
7f
9f
Scheme 5
PMe3 or CO concentration at a pressure close to 1 atm (ca.
101 325 Pa). This clearly indicates that the rate-determining
step is fission of the W᎐dppm bond.
x
x
P
P
P
P
P
W
x
W
y
W
P
P
P
P
Rearrangement of complex 4m to 5m, 6m to 7m and 8m to
9m probably occurs via the pathway shown in Scheme 6. It is
apparent the ability of diphosphine ligands to form a chelate
ring is dppe > dppm > dppf. The five-membered dppe ring is
obviously preferable to the strained, four-membered dppm ring.
On the other hand, though the chelated dppf ligand presents
little ring strain, its large bite angle (ca. 98Њ)12 combined with
the steric bulk of the phenyl groups could impose strong steric
interactions with the adjacent ligands. This makes dppf less
favorable as a chelate ligand than dppm.
P
P
y
y
P
4m
6m
8m
5m
7m
9m
Scheme 6
+
P
P
Vila and Shaw20 previously reported a trace of acid-induced
rapid interconversion between the facial and meridional iso-
mers of [W(CO)3(η2-dppm)(PEt3)] and a hydrido intermediate,
[WH(CO)3(η2-dppm)(PEt3)]ϩ, was evidenced.20 It is likely that
protonation of complex 4f or 6f generates a fluxional seven-co-
ordinate species, which then undergoes fast intramolecular
rearrangement by placing the η1-diphosphine ligand trans to
the η2-disphosphine group to reduce steric crowding. Sub-
sequent deprotonation of this species could afford the meri-
dional isomer (Scheme 7). A pseudo-three-fold rotation is likely
involved to account for this facile rearrangement. It has been
shown that the energy barrier for a ligand three-fold rotation
decreases dramatically as the co-ordination number of the
metal changes from six to seven.21
+ H+
x
x
W
H
W
P
P
P
P
P
P
y
y
+
P
P
– H+
x
x
W
W
H
P
P
P
P
y
y
P
P
Acknowledgements
We are grateful for support of this work by the National
Science Council of Taiwan, Grant No. NSC 85-2113-M110-020.
4m
6m
4f
6f
Scheme 7
formed, the subsequent site exchange and ring-closing pro-
cesses must be very rapid.
References
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s
observed to be first order in metal substrate and zero order in
J. Chem. Soc., Dalton Trans., 1998, Pages 125–132
131

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132
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