M(CO)6 (M = Cr, Mo, W) derivatives of (o-anisyl)diphenylphosphine, bis(o-anisyl)phenylphosphine tris(o-anisyl)phosphine and (p-anisyl)bis(o-anisyl)phosphine

Article abstract of DOI:10.1016/s0020-1693(00)00190-0

Aromatic tertiary phosphine ligands having ortho-methoxy substituents reacted with Group 6 metal carbonyls to form complexes with monodentate bonding through the phosphorus atom. One tungsten hexacarbonyl derivative with two P-bonded phosphine ligands was also formed. The complexes were characterized by X-ray crystallography, ¹H, ¹³C{¹H} and ³¹P{¹H) NMR spectroscopy, IR spectroscopy and elemental analysis. The steric properties of the ligands were studied by molecular modelling methods. Metal-phosphorus bond distances correlate with cone angles of the phosphines. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/s0020-1693(00)00190-0

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 307 (2000) 47–56
M(CO)6 (M=Cr, Mo, W) derivatives of
(o-anisyl)diphenylphosphine, bis(o-anisyl)phenylphosphine
tris(o-anisyl)phosphine and (p-anisyl)bis(o-anisyl)phosphine
Leeni Hirsivaara a,*, Lucia Guerricabeitia a, Matti Haukka b, Pekka Suomalainen b,
Riitta H. Laitinen a, Tapani A. Pakkanen b, Jouni Pursiainen a
a Department of Chemistry, Uni6ersity of Oulu, PO Box 3000, FIN-90401 Oulu, Finland
b Department of Chemistry, Uni6ersity of Joensuu, PO Box 111, FIN-80101 Joensuu, Finland
Received 18 February 2000; accepted 24 May 2000
Abstract
Aromatic tertiary phosphine ligands having ortho-methoxy substituents reacted with Group 6 metal carbonyls to form
complexes with monodentate bonding through the phosphorus atom. One tungsten hexacarbonyl derivative with two P-bonded
1
phosphine ligands was also formed. The complexes were characterized by X-ray crystallography, H, 13C{1H} and 31P{1H) NMR
spectroscopy, IR spectroscopy and elemental analysis. The steric properties of the ligands were studied by molecular modelling
methods. Metal–phosphorus bond distances correlate with cone angles of the phosphines. © 2000 Elsevier Science S.A. All rights
reserved.
Keywords: Crystal structures; Metal complexes; Carbonyl complexes; Phosphine complexes
We report the preparation and characterization of a
series of Group 6 metal carbonyl complexes with phos-
1. Introduction
phorus–oxygen heterodonor ligands: (o-anisyl)-
diphenylphosphine (PPh2(o-MeOPh) (1), bis(o-anisyl)-
The coordination chemistry of phosphines is an es-
sential part of organometallic chemistry and especially
phenylphosphine
(PPh(o-MeOPh)2),
and
tris-
of homogeneous organometallic catalysis [1]. Com-
plexes of the type [Cr(CO)5L] have been used to esti-
mate the steric and electronic properties of the
phosphine ligands [2]. Therefore, systematic studies of
these complexes gives information that helps classifica-
tion of new phosphines. Cone angles based on X-ray
structural data or mathematical models are important
for describing the steric restrictions [2]. The electronic
properties of the ligand also have important effects on
the coordination chemistry of the metal complex. 31P
NMR spectroscopy has been widely used in
organometallic chemistry since the chemical shift is
extremely sensitive to the electronic, steric and geomet-
ric environments of the 31P nuclei [3].
(o-anisyl)phosphine (P(o-MeOPh)3), and
a
chrom-
ium complex with a bis(o-anisyl)(p-anisyl)phosphine
(P(o-MeOPh)2(p-MeOPh)) ligand. Complexes of the
type [M(CO)5(L)] are easily formed, with bonding oc-
curring via the phosphorus atom. Also cis-
[W(CO)4(PPh2(o-MeOPh)2] (3b) has been isolated. No
chelation through the oxygen atom is observed in these
complexes. There have been some NMR or IR studies
[4–8], in which complexes of the type [Cr(CO)5L],
where L is aryl phosphine, are reported. The crystal
structures of the complexes [Cr(CO)5(P(o-MeOPh)3]
(7),
[MO(CO)5(P(o-MeOPh)3]
(8)
and
trans-
[W(CO)4{PPh2(o-MeOPh)}2]·1/4CH2Cl2 have been
published [9,10]. The complexes in this study were
characterized with multinuclear NMR, IR and X-ray
analysis. The lowest energy conformations of the lig-
ands were determined by ab initio calculations and
* Corresponding author. Fax: +358-8-553 1603.
E-mail address: leeni.hirsivaara@oulu.fi (L. Hirsivaara).
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00190-0

48
L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
were compared with the solid state complex structures.
Correlations between M–P bond lengths and cone an-
gles and steric properties of the ligands are discussed.
pounds 4, 5 and 10 hydrogens were located from the
difference Fourier map and refined isotropically (com-
pounds 4 and 5: Uiso=0.06 for aromatic hydrogens,
Uiso=0.08 for methyl hydrogens). Crystallographic
data are summarized in Table 1 and selected bond
lengths and angles in Tables 3 and 4.
2. Experimental
All reactions were carried out with standard Schlenk
techniques under a nitrogen atmosphere. Solvents and
commercial reagents were used as received. The
chromium, molybdenum and tungsten hexacarbonyl
were obtained from Aldrich, trimethylamine-N-oxide
dihydrate was from Fluka Chemica, dichloromethane
(99.8%) from FF Chemicals and hexane (95%) from
Lab Scan. The ligands PPh2(o-MeOPh), PPh(o-
MeOPh)2, P(o-MeOPh)3, and P(o-MeOPh)2(p-MeOPh)
were prepared according to methods described previ-
ously [11,12].
2.3. Computational details
Gaussian 94 [20] and Sybyl [21] programs were used
in modelling. For geometry optimizations at Hartree–
Fock level the 3-21G* basis set was used. In confor-
mational analysis the single point energies were
calculated with the gridsearch method of Sybyl, and
final geometries were determined with the HF/3-21G*
method. For cone angle determinations the metal–
,
phosphorus distance 2.28 A and the van der Waals
,
radii of hydrogen 1.2 A were used. As for free ligands
a dummy metal atom was used.
2.1. Spectroscopy
2.4. Synthetic procedure
NMR spectra were recorded on a Bruker DPX 400
spectrometer at room temperature in CDCl3 (D 99.8
%, 0.03 % TMS, CIL). H NMR: resonance frequency
Metal carbonyl, ligand and trimethylamine-N-oxide
dihydrate [22] were dissolved in dichloromethane with
a molar ratio of 1:1:2, and the resulting yellow solu-
tion was stirred at room temperature for 3 h. The
solvent was removed in vacuo, and the product was
purified by column chromatography using silica gel 60
as the stationary phase. Mixtures of dichloromethane
and hexane were used as eluent. The first colourless
fraction was unreacted metal carbonyl, and the sec-
ond, yellow fraction, was the complex. If unreacted
ligand was present, it was the last fraction. Crystals
were grown from dichloromethane–hexane mixtures
by slow evaporation at room temperature.
1
400.1 MHz, reference SiMe4. 13C{1H} NMR: reso-
nance frequency 100.6 MHz, CDCl3 set to 77.0 ppm.
31P{1H} NMR: resonance frequency 162.0 MHz, ex-
ternal standard 85% H3PO4. Two dimensional HSQC
NMR were also measured. IR spectra were recorded
on a Bruker IFS 66 spectrometer in dichloromethane
(99.8%).
2.2. X-ray crystallography
X-ray diffraction data were collected with a Nonius
Kappa CCD diffractometer using Mo Ka radiation
,
(u=0.71073 A) and ƒ-scan or combined ƒ/ꢀ-scan
data collection mode with a Collect [13] data collec-
tion program. Denzo and Scalepack [14] programs
were used for cell refinements and data reduction.
Structures 2 and 3b were solved by the Patterson
method with use of SHELXS97 program [15]. All other
structures were solved by direct methods using
SHELXS97 or SIR97 [16] programs with the WinGX
[17] graphical user interface, or by using the SHELXTL
v5.1 [18] program package. In all cases the structure
refinements were carried out with SHELXL97 [19]. A
semi-empirical absorption correction, based on equiva-
lent reflections (XPREP in SHELXTL), was applied to 3a,
3b, 6 and 9 (Tmin/Tmax was 0.22596/0.29621, 0.22912/
0.32775, 0.20183/0.33385 and 0.21893/0.30011 respec-
tively). For compounds 1, 2, 3a, 3b, 6 and 9 the
hydrogens were constrained to ride on their parent
2.4.1. [Cr(CO)5PPh2(o-MeOPh)] (1)
Cr(CO)6 (247 mg, 1.12 mmol), PPh2(o-MeOPh) (238
mg, 1.12 mmol) and (CH3)3NO·2H2O (250 mg, 2.25
mmol) were dissolved in 20 ml of dichloromethane.
After purification complex 1a was isolated as a yellow
solid (162 mg, 30%). Anal. Found: C, 59.17; H, 3.27.
CrC24H17O6P requires: C, 59.51; H, 3.54%. IR: w(CO)
1
(cm−1) 2062s, 1982m, 1937vs. H NMR (ppm): l CH3
3.71(s), H8 6.97(m), H10 6.95(m), H11 6.86(m),
H9,H13–H23 7.36–7.50(m). 13C{1H} NMR (ppm): l
1
CH3 54.53(s), C6 122.20 (d, JCP 36.2 Hz), C7 159.59
2
1
(d, JCP 6.2 Hz), C8 110.77 (d, JCP 4.1 Hz), C9 132.20
1
3
(d, JCP 0.7 Hz), C9 120.96 (d, JCP 7.2 Hz), C11
2
1
132.05 (d, JCP 4.1 Hz), C12,C18 134.76 (d, JCP 37.6
Hz), C13,C17,C19,C23 133.10 (d, JCP 11.5 Hz),
C14,C16,C20,C22 128.33 (d, JCP 9.7 Hz), C15,C21
129.87 (d, JCP 1.9 Hz). CO(cis) 217.25 (d, JCP 13.8
2
3
1
2
,
,
atom (C–H=0.95 A or C–H=0.93 A, Uiso=1.2(Ceq)
2
,
for aromatic hydrogens and C–H=0.98 A or C–H=
Hz); CO(trans) 222.10 (d, JCP 6.8 Hz). See Fig. 1 for
,
0.96 A, Uiso=l.5(Ceq) for methyl H atoms). For com-
numbering scheme.

L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
49

50
L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
2.4.2. [Mo(CO)5{PPh2(o-MeOPh)}] (2)
6.93(m), H9,H15,H20–H22 7.36–7.45(m), H19,H23
7.58(m). 13C{1H} NMR (ppm): CH3 54.45(s), C6,C12
122.05 (d, JCP 36.9 Hz), C7,C3 159.50 (d, JCP 6.6 Hz),
MO(CO)6 (257 mg, 0.97 mmol), PPh2(o-MeOPh)
(285 mg, 0.97 mmol) and (CH3)3NO·2H2O (216 mg,
1.95 mmol) were dissolved in 20 ml of dichloromethane.
After purification complex 2 was isolated as a pale
yellow solid (361 mg, 70%). Anal. Found: C, 54.46; H,
3.03. MOC24H17O6P requires: C, 54.56; H, 3.24%. IR:
1
2
3
4
C8,C14 110.80 (d, JCP 4.3 Hz), C9,C15 131.80 (d, JCP
3
1.2 Hz), C10,C16 120.46 (d, JCP 7.2 Hz), C11,C17
132.57 (d, JCP 4.1 Hz), C18 133.50 (d, JCP 37.3 Hz),
2
1
2
C19,C23 134.26 (d, JCP 11.9 Hz), C20,C22 128.21 (d,
w(CO) (cm−1) 2071s, 1990m, 1943vs. H NMR: CH3
3JCP 9.7 Hz), C21 129.96 (d, JCP 2.0 Hz). CO(cis)
1
1
2
2
3.69(s), H8 6.96(m), H10 6.93(m), H11 6.79(m),
217.53 (d, JCP 13.8 Hz), CO(trans) 222.88 (d, JCP 6.4
H9,H13–H23 7.37–7.49(m). 13C{1H} NMR (ppm):
Hz). See Fig. 3 for numbering scheme.
1
CH3 54.57(s), C6 122.52 (d, JCP 35.2 Hz), C7 159.54
1
3
(d, JCP 6.5 Hz), C8 110.67 (d, JCP 3.9 Hz), C9 132.10
2.4.5. [Mo(CO)5(PPh(o-MeOPh)2)] (5)
4
3
(d, JCP 0.2 Hz), C1O 120.90 (d, JCP 7.1 Hz), C11
MO(CO)6 (252 mg, 0.96 mmol), PPh(o-MeOPh)2
(308 mg, 0.96 mmol) and (CH3)3NO·2H2O (318 mg,
2.87 mmol) were dissolved in 25 ml of dichloromethane.
After purification complex 5 was isolated as a pale
yellow solid (428 mg, 80%). Anal. Found: C, 54.11; H,
3.26. MOC25H19O7P requires: C, 53.78; H, 3.43%. IR:
2
1
132.04 (d, JCP 1.2 Hz), C12,C18 134.74 (d, JCP 36.5
Hz), C13,17,19,23 133.27 (d, 2JCP 13.1 Hz),
3
C14,C16,C20,C22 128.33 (d, JCP 9.7 Hz), C15,C21
129.85 (d, JCP 1.9 Hz). CO(cis) 206.17 (d, JCP 9.1 Hz),
CO(trans) 210.93 (d, JCP 23.2 Hz). See Fig. 1 for
1
2
2
1
numbering scheme.
w(CO) (cm−1) 2070s, 1985m, 1939vs. H NMR: CH3
3.67(s), H11,H17 6.84(m), H10,H16 6.90(m), H18,H14
6.93(m), H19,H15,H20–H22 7.36–7.45(m), H19,H23
7.56(m). 13C{1H} NMR (ppm): CH3 54.54(s), C6,C12
2.4.3. [W(CO)5{PPh2(o-MeOPh)}] (3a) and
[W(CO)4{PPh2(o-MeOPh)}2] (3b)
1
2
W(CO)6 (258 mg, 0.73 mmol), PPh2(o-MeOPh) (214
mg, 0.73 mmol) and (CH3)3NO·2H2O (163 mg, 1.47
mmol) were dissolved in 20 ml of dichloromethane, a
mixture of complexes 3a and 3b was formed. In column
chromatography complex 3a came out from the column
before 3b. 3b was difficult to separate from the free
ligand. By using column chromatography again with a
2:1 mixture of dichloromethane and hexane, almost
pure 3b was gained. After separations, complexes were
isolated as yellow solids 3a (152 mg, 34 %), 3b (20 mg,
6%). 3a: Anal. Found: C, 46.94; H, 2.83. WC24H17O6P
requires: C, 46.78; H, 2.78%. IR: w(CO) (cm−1) 2070s,
122.01 (d, JCP 35.4 Hz), C7,C13 159.61 (d, JCP 7.0
3
Hz), C8,C14 110.76 (d, JCP 3.9 Hz), C9,C15 131.71(s),
1
C10,C16 120.50 (d, JCP 7.1 Hz), C11,C17 132.61 (d,
1
2JCP 4.8 Hz), C8 133.59 (d, JCP 36.3 Hz), C19,C23
134.33 (d, 2JCP 13.8 Hz), C20,C22 128.18 (d, 3JCP 9 Hz),
2
C21 129.88 (d ,1JCP 1.8 Hz). CO(cis) 206.45 (d, JCP 9.5
2
Hz), CO(trans) 211.86 (d, JCP 24.1 Hz). See Fig. 3 for
numbering scheme.
2.4.6. [W(CO)5(PPh(o-MeOPh)2)] (6)
W(CO)6 (237 mg, 0.67 mmol), PPh(o-MeOPh)2 (217
mg, 0.67 mmol) and (CH3)3NO·2H2O (224 mg, 2.02
mmol) were dissolved in 20 ml of dichloromethane.
After purification complex 6 was isolated as a pale
yellow solid (175 mg, 40 %). Anal. Found: C, 46.62; H,
2.82. WC25H19O7P requires: C, 46.46; H, 2.96%. IR:
1
1979m, 1934vs. H NMR: CH3 3.69(s), H11 6.79(m),
H10 6.95(m), H8 6.98(m), H9,H13–H23 7.38–7.49(m).
13C{1H} NMR (ppm): CH3 54.66(s), C6 121.98 (d, JCP
1
2
3
41.3 Hz), C7 159.65 (d, JCP 6.1 Hz), C8 110.72 (d, JCP
4
3
1
4.2 Hz), C9 132.27 (d, JCP 1.2 Hz), C10 120.90 (d, JCP
w(CO) (cm−1) 2069s, 1976m, 1932vs. H NMR: CH3
2
7.6 Hz), C11 132.12 (d, JCP 4.8 Hz), C12,C18 134.44
3.67(s), H11,H17 6.84(m), H10,H16 6.92(m), H8,H14
6.93(m), H9,H15,H20–H22 7.37–7.45(m), H19,H23 7.5
6(m). 13C{1H} NMR (ppm): CH3 54.64(s), C6,C12
(d, 1JCP 42.6 Hz), C13,C17,C19,C23 133.38 (d, 2JCP 12.5
3
Hz), C14,C16,C20,C22 128–38 (d, JCP 10.0 Hz),
1
2
1
2
C15,C21 130.07 (d, JCP 2.0 Hz). CO(cis) 197.76 (d JCP
121.47 (d, JCP 41.6 Hz), C7,C13 159.70 (d, JCP 6.3
2
3
7.8 Hz), CO(trans) 199.80 (d, JCP 22.4 Hz). See Fig. 1
Hz), C8,C14 110.85 (d, JCP 4.3 Hz), C9,C15 131.95 (d,
for numbering scheme. 3b: IR: w(CO) (cm−1) 2018m,
4JCP 0.7 Hz), C10,C16 120.47 (d, JCP 7.7 Hz), C11,C17
3
2
1
1979m, 1907sh, 1890vs.
132.74 (d, JCP 5.1 Hz), C18 133.30 (d, JCP 42.1 Hz),
2
C19,C23 134.52 (d, JCP 13.1 Hz), C20,C22 128.24 (d,
1
2.4.4. [Cr(CO)5(PPh(o-MeOPh)2)] (4)
3JCP 10.3 Hz), C21 130.10 (d, JCP 2.0 Hz). CO(cis)
2
2
Cr(CO)6 (203 mg, 0.92 mmol), PPh(o-MeOPh)2 (298
mg, 0.92 mmol) and (CH3)3NO·2H2O (308 mg, 2.77
mmol) were dissolved in 20 ml of dichloromethane.
After purification complex 4 was isolated as a pale
yellow solid (227 mg, 47 %). Anal. Found: C, 58.09; H,
3.55. CrC25H19O7P requires: C, 58.04; H, 3.70%. IR:
198.27 (d, JCP 7.7 Hz), CO(trans) 200.69 (d, JCP 22.8
Hz). See Fig. 3 for numbering scheme.
2.4.7. [Cr(CO)5(P(o-MeOPh)3)] (7)
Cr(CO)6 (256 mg, 1.16 mmol), P(o-MeOPh)3 (410
mg, 1.16 mmol) and (CH3)3NO·2H2O (259 mg, 2.33
mmol) were dissolved in 25 ml of dichloromethane.
After purification complex 7 was isolated as a yellow
1
w(CO) (cm−1) 2068s, 1979m, 1935vs. H NMR: CH3
3.68(s), H11,H17 6.85(m), H10,H16 6.91(m), H18,H14

L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
51
solid (173 mg, 27%). Anal. Found: C, 57.34; H, 3.50.
CrC26H21O8P requires: C, 57.36; H, 3.89%. IR: w(CO)
3.89%. IR: w(CO) (cm−1) 2060s, 1980m, 1934vs. 1H
NMR: o-CH3 3.69(s); p-CH3 3.83(s), H11,H17
6.82(m), H8,H10,H14,H16,H20,H22 6.87–6.94(m),
H9,H15 7.41(m), H19,H23 7.50(m). 13C{1H} NMR
(ppm): p-CH3 55.20(s); p-CH3 54.45(s); C8,C14 110.75
1
(cm−1) 2059s, 1979m, 1932vs. H NMR: CH3 3.56(s),
H8,H14,H20
6.87(m),
H10,H16,H22
6.95(m),
H11,H17,H23 7.36(m), H9,H15,H2 7.38(m). 13C{1H}
NMR (ppm): CH3 54.39(s), C6,C12,C13 120.73 (d, 1JCP
(d, JCP 4.4 Hz); C20,C22 113.82 (d, JCP 10.8 Hz),
3
1
2
3
37.1 Hz), C7,C13,C19 159.77 (d, JCP 4.3 Hz),
C1O,C16 120.39 (d, JCP 7.1 Hz); C6,C12 122.54 (d,
C8,C14,C20 110.96 (d, 3JCP 3.9 Hz), C9,C15,C21 131.56
1JCP 37.2 Hz), C18 123.98 (d, JCP 41.4 Hz), C9,C15
1
4
3
4
2
(d, JCP 1.1 Hz), C10,C16,C22 119.90 (d, JCP 9.2 Hz),
131.65 (d, JCP 1.0 Hz); C11,C17 132.39 (d, JCP 3.6
C11,C17,C21 134.58 (d, 2JCP 9.4 Hz). CO(cis) 217.76 (d,
Hz), C19,C23 136.00 (d, JCP 13.4 Hz); C7,C13 159.42
2
2JCP 13.8 Hz); CO(trans) 223.41 (d, JCP 6.4 Hz). See
(d, JCP 6.8 Hz), C21 160.93 (d, JCP 1.7 Hz), CO(cis)
2
2
4
2
1
Fig. 4 for numbering scheme.
217.62 (d, JCP 14.1 Hz), CO(trans) 222.96 (d, JCP 6.5
Hz). See Fig. 5 for numbering scheme.
2.4.8. [Mo(CO)5(P(o-MeOPh)3)] (8)
MO(CO)6 (253 mg, 0.96 mmol), P(o-MeOPh)3 (337
mg, 0.96 mmol) and (CH3)3NO·2H2O (213 mg, 1.91
mmol) were dissolved in 25 ml of dichloromethane.
After purification complex 8 was isolated as a pale
yellow solid (386 mg, 69%). Anal. Found: C, 53.19; H,
3.33. MOC26H21O8P requires: C, 53.08; H, 3.60%. IR:
3. Results and discussion
3.1. Reactions
The reaction between equimolar amounts of Group 6
metal hexacarbonyl and the phosphine ligand in
dichloromethane at room temperature in the presence
of Me3NO·2H2O [22] produced a monodentate phos-
phorus-bound complex [M(CO)5(L)], where M=Cr,
Mo or W, and L=phosphine ligand [23]. In addition,
tungsten hexacarbonyl showed a tendency also to form
a tetracarbonyl complex with two phosphine ligands in
cis positions. No evidence of phosphorus-oxygen bound
multidentate complexes was seen. A few complexes with
bonding via phosphorus and oxygen have been pre-
pared earlier, but through very different reaction path-
ways [24–28].
1
w(CO) (cm−1) 2068s, 1983m, 1938vs. H NMR: CH3
3.56(s), H18,H14,H20 6.87(m), H10,H16,H22 6.95(m),
H11,H17,H23 7.31(m), H19,H15,H21 7.40(m). 13C{1H}
NMR (ppm): CH3 54.51(s), C6,C12,C18 120.75 (d, 1JCP
2
35.8 Hz), C7,C13,C19 159.95 (d, JCP 5.0 Hz),
C8,C14,C20 110.95 (d, 3JCP 3.7 Hz), C9,C15,C21 131.50
4
3
(d, JCP 1.1 Hz), C10,C16,C22 120.01 (d, JCP 9.1 Hz),
2
C11,C17,C23 134.70 (d, JCP 10.3 Hz). CO(cis) 206.66
(d, 2JCP 9.1 Hz); CO(trans) 212.58 (d, 2JCP 24.5 Hz). See
Fig. 4 for numbering scheme.
2.4.9. [W(CO)5(P(o-MeOPh)3)] (9)
W(CO)6 (254 mg, 0.72 mmol), P(o-MeOPh)3 (254
mg, 0.72 mmol) and (CH3)3NO·2H2O (241 mg, 2.16
mmol) were dissolved in 25 ml of dichloromethane.
After purification complex 9 was isolated as a yellow
solid (124 mg, 27 %). Anal. Found: C, 46.49; H, 3.24.
WC26H21O8P requires: C, 46.18; H, 3.13%. IR: w(CO)
The reaction procedure was also carried out using a
metal–ligand ratio of 1:2 using PPh2(o-MeOPh) ligand.
There was spectroscopic evidence of the formation of
chromium
and
molybdenum
analogues
of
[M(CO)4{PPh2(o-MeOPh)}2]. These complexes, how-
ever, could not be isolated from the free ligand. This
possibly reflects a tendency for gradual decomposition
of the [M(CO)4{PPh2(o-MeOPh)}2] complexes.
Coordination of the corresponding phosphines con-
taining methylthio groups instead of methoxy groups
has shown mainly bidentate bonding through the P and
S atoms, only Cr(CO)6 has also formed a monodentate
phosphorus bound analogue with the ligand [o-
(methylthio)phenyldiphenylphosphine] [23].
1
(cm−1) 2067s, 1976m, 1930vs. H NMR: CH3 3.55(s),
H8,H14,H20
6.87(m),
H10,H16,H22
6.96(m),
H11,H17,H23 7.32(m), H9,H15,H2, 7.39(m). 13C{1H}
NMR (ppm): CH3 54.57(s), C6,C12,C18 120.26 (d, 1JCP
42.2 Hz), C7,C13,C19 159–92 (d, JCP 4.3 Hz),
2
1
C8,C14,C20 34 110.03 (d, JCP 4.0 Hz), C9,C15,C21
1
1
131.72 (d, JCP 1.1 Hz), C10,C16,C22 119.96 (d, JCP
2
9.7 Hz), C11,C17,C23 135.04 (d, JCP 10.3 Hz). CO(cis)
2
2
198.67 (d, JCP 7.3 Hz), CO(trans) 201.30 (d, JCP 23.2
Hz). See Fig. 4 for numbering scheme.
3.2. Conformational analysis of the ligands
2.4.10. [Cr(CO)5{P(o-MeOPh)2(p-MeOPh)}] (10)
The equilibrium geometries of PPh2(o-MeOPh),
PPh(o-MeOPh)2, and P(o-MeOPh)3 ligands were first
determined by optimizing the structures with the ab
initio Hartree–Fock method using a 3-21G* basis set.
Starting from the initial geometries, conformational
analysis was carried out by rotating the torsional angles
of three phenyl rings. The unsubstituted phenyl ring(s)
Cr(CO)6 (203 mg, 0.91 mmol), P(o-MeOPh)2(p-
MeOPh) (320 mg, 0.91 mmol) and (CH3)3NO·2H2O
(207 mg, 1.86 mmol) were dissolved in 25 ml of
dichloromethane. After purification complex 10 was
isolated as a yellow solid (144 mg, 29 %). Anal. Found:
C, 57.18 H, 3.89. CrC26H21O8P requires: C, 57.36; H,

52
L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
were rotated 180° while the substituted phenyl ring(s)
were rotated 360° by increments of 20°, resulting in up
to 6000 different conformers. Based on contour maps
of the potential energy surface of resulting conformers,
20 to 40 local minima were identified and subsequently
optimized with the HF/3-21G* method. The energies of
the minima in relation to the ground state are presented
in Table 2. The number of low lying conformers in-
creases in proportion to the degree of substitution of
the ligand.
num compounds tend to have slightly longer bonds
around the metal centre than tungsten compounds
[23,29].
3.4. Steric and electronic properties of the ligands and
complexes
The steric crowding of free and coordinated ligands
was measured using Tolman’s semicone angle method
for unsymmetrical phosphines [2,30]. The cone angles
of the free ligands were calculated for the ground states
and for the low lying conformations. As shown in
Table 2, the cone angles are widest for the ground
states and become narrower for the higher energy con-
formers, giving an indication of the energy demands of
the steric repulsion. A comparison of the calculated
cone angles of the free ligands and the structurally
determined angles of the complexes is given in Table 5.
The cone angles in the Cr, Mo and W complexes are
similar, and close to the values of the low energy
conformations of the free ligands. In the lowest energy
conformations, the maximum semicone angles are al-
ways determined by the o- or m-hydrogen atoms of the
phenyl rings, or by one of the hydrogens in an –OCH3
3.3. Crystal structures
The structures of the complexes were determined
using a single-crystal X-ray diffraction study. Tables 3
and 4 show selected bond distances and angles. The
crystal structures are shown in Figs. 1–5. Octahedral
symmetry around the metal centre is shown, in which
the phosphine ligand has replaced one (1–10) or two
(3b) of the carbonyl ligands.
The bond lengths of the monosubstituted complexes
are closely related. The complexes of chromium car-
bonyl have the shortest metal to ligand bond distances
due to the small atomic radius of chromium. Molybde-
Table 2
Low lying conformations and corresponding cone angles of ligands
Conformation
DE (kJ mol−1)/[ (°)
PPh2(o-MeOPh)
PPh(o-MeOPh)2
P(o-MeOPh)3
conf 1 a
conf 2
conf 3
conf 4
conf 5
conf 6
0
8.9
12.6
166
156
153
0
8.7
10.6
32.9
183
174
169
165
0
81
12.1
30 5
31.4
36.5
205
188
197
177
169
169
a Global minimum.
Table 3
a
,
Metal–carbon, metal–phosphorus and carbon–oxygen bond lengths (A) in compounds 1–6, 9, 10
[1]
[2]
[3a]
[3b]
[4]
[5]
[6]
[9]
[10]
M(1)–C(1)
M(1)–C(2)
M(1)–C(3)
M(1)–C(4)
M(1)–C(5)
M(1)–P(1)
M(1)–P(2)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
C(4)–O(4)
C(5)–O(5)
1.890(4)
1.916(4)
1.903(4)
1.874(4)
1.903(4)
2.3868(11)
2.038(6)
2.047(6)
2.029(5)
2.016(5)
2.057(5)
2.5386(13)
2.041(4)
2.035(4)
2.032(4)
1.994(3)
2.046(3)
2.5539(7)
2.028(2)
2.021(2)
1.983(2)
1.980(2)
1.894(2)
1.896(2)
1.887(2)
1.859(2)
1.907(2)
2.4235(5)
2.037(2)
2.056(3)
2.042(2)
1.999(2)
2.043(2)
2.5680(5)
2.034(3)
2.047(3)
2.046(3)
1.988(3)
2.040(3)
2.5608(6)
2.057(4)
2.018(4)
2.036(4)
1.980(4)
2.042(4)
2.5751(8)
1.892(2)
1.897(2)
1.892(2)
1.858(2)
1.905(2)
2.4217(6)
2.5661(6)
2.5618(6)
1.142(3)
1.141(3)
1.151(3)
1.148(3)
1.147(4)
1.138(4)
1.14](4)
1.151(4)
1.141(4)
1.128(7)
1.121(6)
1.133(6)
1.130(6)
1.138(5)
1.141(4)
1.136(4)
1.137(4)
1.148(4)
1.137(3)
1.137(3)
1.142(2)
1.146(3)
1.145(3)
1.135(3)
1.136(3)
1.127(3)
1.137(3)
1.135(3)
1.124(3)
1.140(4)
1.130(4)
1.131(4)
1.141(4)
1.132(4)
1.135(5)
1.143(4)
1.145(5)
1.150(4)
1.137(4)
1.150(3)
1.146(3)
1.145(3)
1.151(3)
1.146(3)
a [1] [Cr(CO)5(PPh2(o-MeOPh)]; [2] [Mo(CO)5{PPh2(o-MeOPh)}]; [3a] [W(CO)5{PPh2(o-MeOPh)}]; [3b] [W(CO)4{PPh2(o-MeOPh)}2]; [4]
[Cr(CO)5(PPh(o-MeOPh)2)]; [5] [Mo(CO)5(PPh(o-MeOPh)2)]; [6] [W(CO)5(PPh(o-MeOPh)2)]; [7] [Cr(CO)5(P(o-MeOPh)3)], see ref. [9]; [8]
[MO(CO)5(P(o-MeOPh)3)], see ref. [9]; [9] [W(CO)5(P(o-MeOPh)3)]; [10] [Cr(CO)5{P(o-MeOPh)2(p-MeOPh)}].

L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
53
Table 4
Selected bond angles (°) for compounds 1–6, 9, 10
[1]
94.48(11)
87.49(11)
91.77(11)
[2]
91.56(15)
88.96(14)
94.93(14)
175.64(15)
86.71(13)
[3a]
91.88(9)
88.92(10)
92.96(12)
176.58(9)
89.69(8)
[3b]
84.13(6)
92.62(7)
83.50(7)
164.75(8)
[4]
95.88(6)
89.37(6)
93.03(6)
175.31(6)
86.14(6)
[5]
93.19(6)
95.58(7)
89.55(6)
176.00(6)
95.22(7)
[6]
91.89(11)
87.81(8)
91.71(9)
[9]
88.55(11)
89.29(11)
93.24(11)
178.36(11)
93.91(11)
[10]
95.11(7)
90.94(7)
85.52(6)
174.97(7)
90.20(7)
P(1)–M(1)–C(1)
P(1)–M(1)–C(2)
P(1)–M(1)–C(3)
P(1)–M(1)–C(4) 175.81(12)
177.96(11)
91.73(8)
P(1)–M(1)–C(5)
P(1)–M(1)–P(2)
P(2)–M(1)–C(1)
P(2)–M(1)–C(2)
P(2)–M(1)–C(3)
P(2)–M(1)–C(4)
88.30(11)
108.35(2)
89.85(7)
85.61(8)
166.80(7)
85.87(8)
C(1)–M(1)–C(2) 174.84(16)
C(1)–M(1)–C(3) 85.74(15)
C(1)–M(1)–C(4) 88.91(15)
C(1)–M(1)–C(5) 90.12(16)
C(2)–M(1)–C(3) 89.44(15)
C(2)–M(1)–C(4) 89.34(15)
C(2)–M(1)–C(5) 94.71(15)
C(3)–M(1)–C(4) 90.94(16)
C(3)–M(1)–C(5) 175.85(16)
C(4)–M(1)–C(5) 89.22(15)
176.3(2)
86.2(2)
91.3(2)
89.3(2)
90.1(2)
88.4(2)
94.4(2)
88.5(2)
175.3(2)
90.06(19)
177.98(12)
87.06(15)
91.53(13)
88.21(13)
94.75(14)
87.67(13)
89.94(12)
87.12(15)
174.65(12)
90.51(12)
173.30(10)
97.31(10)
90.59(10)
173.28(9)
84.23(10)
86.86(9)
91.56(10)
91.33(9)
88.18(8)
92.97(9)
91.03(9)
175.62(10)
89.98(9)
176.62(10)
90.95(9)
90.63(9)
84.71(11)
92.20(9)
90.67(9)
92.25(11)
89.18(8)
173.71(9)
86.33(9)
175.43(13)
86.46(15)
90.15(15)
93.97(14)
88.99(13)
90.15(13)
90.60(12)
88.35(13)
176.52(11)
88.19(12)
176.81(14)
89.20(15)
92.95(15)
90.45(16)
93.27(15)
99.23(15)
87.36(15)
86.13(15)
172.83(14)
86.73(15)
173.93(9)
86.44(10)
88.19(9)
88.10(10)
94.54(10)
85.90(9)
91.40(9)
90.91(9)
172.74(9)
93.70(9)
88.11(11)
93.98(11)
82.99(10)
group. For the higher energy conformations, the cone
angle diminishes, when the substituted phenyl ring(s)
rotates in a way so that the –OCH3 group is located
inside the cone, and no longer determines the maximum
cone angle. The ground state conformation of the
PPh2(o-MeOPh) ligand was found to correspond best
to the geometry of the coordinated ligand in all the
Group 6 transition metal (Cr, Mo,W) complexes. Hav-
ing only one substituent group, the PPh2(o-MeOPh)
ligand does not experience a great deal of either elec-
tronic or steric strain from equatorial carbonyl groups
and can therefore lie near its free lowest energy confor-
mation. In complexes 4 and 5, the PPh(o-MeOPh)2
ligand was also observed to have geometry similar to
the lowest energy conformation of PPh(o-MeOPh)2. On
the contrary, in the corresponding tungsten complex
the other –OCH3 group in the substituted phenyl ring
lies inside the cone which is a similar arrangement to
that found in conformations 2 and 3 of PPh(o-
MeOPh)2. The most sterically crowded P(o-MeOPh)3
ligand seems to experience a lot of strain when coordi-
nated to transition metals (Cr, W), evidenced by the
wide deviation in the cone angles of low lying conform-
ers and coordinated ligand. When bound to the metal,
P(o-MeOPh)3 interacts with equatorial carbonyl
groups, resulting in comparatively low cone angle val-
ues of 176 and 172° for 7 and 9 respectively. The mean
CPC angle, however, is larger in both complexes than
in the ground state conformation of the free ligand.
Variations of M–P bond distances can depend on
both the electronic and steric properties of the ligands.
Cr–P bonds lengthen in the order PPh2(o-MeOPh)B
PPh(o-MeOPh)2BP(o-MeOPh)3, the Mo–P and W–P
distances show similar trends. In Scheme 1 cone angles
of both the ligands and the complexes are plotted as a
function of Cr–P bond lengths. Calculated cone angle
Fig. 1. Crystal structure of complex 2. The structures and numbering
of 1 and 3a are similar.
Fig. 2. Crystal structure of complex 3b.

54
L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
values for free ligands correlate well with the Cr–P
distances, but in the case of complexes, the conforma-
tions of the ligands have changed due to steric stress
not giving so good correlation. There are previous
investigations [29,31] that support the observation
that the lengthened M–P bond reflects increased
steric restrictions of the ligand.
Small substituents in para position can be used to
alter only the electronic properties of the ligand.
However, the cone angle is slightly increased due to
substitution of the para methoxy group, as it affects
the orientation of the phenyl ring.
The electronic properties of the ligand refer to the
electronic character of the metal–ligand bond [2]. Ac-
cording to the empirical equation of Tolman [32], the
basicities of the ligands in this study increase in the
order PPh2(o-MeOPh)BPPh(o-MeOPh)2BP(o-MeO-
Ph)2(p-MeOPh)BP(o-MeOPh)3. The Cr–P bond dis-
tances of complexes 1, 4, 7 and 10 lengthen monoton-
ically with increasing basicity of the ligand, indicating
that it is difficult to draw a line between the elec-
tronic and steric effects.
Fig. 3. Crystal structure of complex 4. The structures and numbering
of 5 and 6 are similar.
Disubstituted tungsten derivative 3b has longer W–
P bonds than its monosubstituted analogue 3a, which
can be explained by increased steric crowding caused
by the two ligands in cis positions. W–P bonds of
,
trans-[W(CO)4{PPh2(o-MeOPh)}2] are 2.489(2) A [10],
shorter than in both 3a and 3b, which is probably
due to the relative trans influences of the phosphine
and carbonyl ligands [33]. In monodentate complexes,
M–C bond distances of carbonyl ligands trans to
phosphines are shortened, reflecting similar electronic
effects. All of the W–C bonds in derivative 3a are
slightly longer than those of the disubstituted tung-
sten derivative 3b.
Fig. 4. Crystal structure of complex 9. The structures and numbering
of 7 and 8 are similar.
Complexation causes slight changes in the bond an-
gles around the metal centre, resulting in deviation
from the ideal octahedral symmetry, but no striking
effects are observed, except in the case of complex 3b
in which a wide P(l)–M–P(2) bond angle (108.36°) is
observed. This wide bond angle between phosphine
ligands agrees with the long M–P distances attributed
to steric crowding.
3.5. Spectroscopic data
The 1H NMR, 13C{1H} NMR and IR data are
presented in the experimental section. The 31P{1H}
NMR data are presented in Table 6.
In the 1H and 13C NMR spectra, the chemical
shifts of the phosphines correlate well with the shifts
of the complexes. The chemical shifts of the o-OCH3
groups of the ligands are marginally shielded due to
coordination, the shielding difference increasing with
the increasing number of o-methoxy groups. For
complex 10, the o-OCH3 groups are shielded while
Fig. 5. Crystal structure of complex 10.

L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
55
Table 5
Cone angle data for free and coordinated ligands
Ligand
Free ligand
(X-ray)
Free ligand
(HF-3-21G*)
Flexibility range
(HF 3-21G*)
Coordinated ligands (X-ray)
Cr(CO)5L
Mo(CO)5L
W(CO)5L
PPh2(o-MeOPh)
PPh(o-MeOPh)2
P(o-MeOPh)3
P(o-MeOPh)2 (p-OmePh)
162
166
183
205
185
153–166
165–183
169–205
59
73
176
180
158
72
57
160
172
Table 6
31P{1H} chemical shifts (ppm) and 31P coordination shifts (Dl=
Dlcomplex−Dl1igand
)
Complex or ligand
l(P)
Dl(P)
PPh2(o-MeOPh)
PPh(o-MeOPh)2
P(o-MeOPh)3
P(o-MeOPh)(p-OMePh)
1
−15.6
−26.7
−37.9
−27.7
52.7
68.3
48.1
30.6
74.9
51.0
33.4
80.1
59.7
40.7
71.1
2
3a
4
5
6
7
8
9
10
32.5
15.0
48.2
24.3
6.7
42.2
21.8
2.8
43.3
In the 31P{1H} NMR spectra Table 6 the signals
move to higher frequencies due to coordination of
phosphorus to the metal centre. These coordination
shifts (Dl=l(complex)−l(ligand)) clearly increase
from tungsten to molybdenum to chromium [23,37].
The coordination shifts also increase with an increasing
amount of ortho methoxy groups. The 31P chemical
shifts of the complexes decrease in the same order.
A comparison of 31P NMR shifts of chromium car-
bonyl complexes 1, 4, 7, 10, [Cr(CO)5(P(p-MeOPh)3)]
[4] and [Cr(CO)5(PPh3)] [6] reveals, that the l31Pcomplex
is probably effected by both the electronic and steric
properties of the ligand, since the chemical shift corre-
lates quite well with both increasing basicity (Tolman)
and increasing steric crowding of the ligands. In the
previous investigations concerning the complexes of
type [Cr(CO)5(phosphine)], the l31Pcomplex has been
governed either by the simultaneous effects of elec-
tronegativity, steric hindrance and p-bonding [38], or is
dominated by steric effects[4,39] depending on the na-
ture of the phosphine ligands.
Scheme 1. Cone angle data for free and coordinated ligands as a
function of Cr–P bond length.
p-OCH3 is deshielded. This may indicate some weak
interaction between the oxygen atom or atoms in ortho
positions, and the metal centre [24].
The 13C NMR spectra of the carbonyl ligands in-
clude two signals, a more shielded doublet for cis
carbonyls and a less shielded, smaller doublet for trans
2
carbonyl. The JCP coupling constants of the complexes
1–9 are consistent with the previous investigations: for
chromium derivatives ꢀJꢀcis\ꢀJꢀtrans, and for molybde-
num and tungsten derivatives ꢀJꢀcisBꢀJꢀtrans [34–36].

56
L. Hirsi6aara et al. / Inorganica Chimica Acta 307 (2000) 47–56
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4. Supplementary material
mination, University of Go¨ttingen, Germany, 1997.
[16] A. Altomare, C. Cascarano, C. Giacovazzo, A. Guagliardi,
A.G.G. Molitemi, M.C. Burna, G. Polidori, M. Camalli, R.
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[17] L.J. Farrugia, WinGX v. 6, A Windows Program for Crystal
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[18] G.M. Sheldrick, SHELXTL Version 5. 1, Bruker Analytical X-ray
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[19] G.M. Sheldrick, SHELXL97, Program for Crystal Structure Refin-
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Crystallographic data (excluding structure factors)
for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre, CCDC Nos. 124116–124124. Copies of the
data can be obtained free of charge on application to
The Director, CCDC, 12 Union Road, Cambridge,
CB2 IEZ, UK (fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
The Inorganic Materials Chemistry Graduate Pro-
gram supported by The Ministry of Education in Fin-
land is acknowledged for financial support.
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