Synthesis of molybdenum arene complexes containing amide-derived heterodifunctional P,O ligands

Article abstract of DOI:10.1039/b105957m

The reactions of the amide-derived ligands Ph₂PN(R)C(O)CH₃ (R = H, CH₃) with the molybdenum arene complexes [Mo(η³-C₃H₅)(μ-Cl)(η ⁶-C₆H₅R)]₂ (R =

Full text of DOI:10.1039/b105957m

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Synthesis of molybdenum arene complexes containing
amide-derived heterodifunctional P,O ligands
Neale G. Jones,a Malcolm L. H. Green,*a Ino Vei,a Andrew Cowley,a Xavier Morise*b
and Pierre Braunstein*b
a Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford,
UK OX1 3QR. E-mail: Malcolm.Green@chemistry.oxford.ac.uk
b Université Louis Pasteur (UMR 7513 CNRS), 4 rue Blaise Pascal, F-67070 Strasbourg,
France. E-mail: morise@chimie.u-strasbg.fr; braunst@chimie.u-strasbg.fr
Received 5th July 2001, Accepted 2nd January 2002
First published as an Advance Article on the web 26th February 2002
The reactions of the amide-derived ligands Ph2PN(R)C(O)CH3 (R = H, CH3) with the molybdenum arene
complexes [Mo(η3-C3H5)(µ-Cl)(η6-C6H5R)]2 (R = H, CH3) have been investigated. A series of complexes in which
the functional ligand displays η1-phosphine, η2-acetamidophosphine and η2-phosphinoiminolate coordination
have been synthesised and characterised. The crystal structures of the cationic compounds [Mo(η3-C3H5)(η6-C6H6)-
{Ph2PN(R)C(O)CH3-κ2P,O}][PF6] (R = H, CH3) have been determined. The first example of a structurally
3
6
2
ؒؒ ؒؒ
characterised phosphinoiminolate complex [Mo(η -C3H5)(η -C6H6){Ph2PN᎐C(᎐O)CH3-κ P,O}] is also reported.
(Scheme 1) as a purple solid, in moderate yield. The characteris-
ing data for 1, and all other new compounds 2–4 described in
this paper, are given in Table 1.
Introduction
Heterodifunctional chelating ligands which combine a soft
phosphine donor with a hard oxygen functionality are well
known and the chemistry of their various transition metal
complexes widely studied, in particular with respect to their
role in homogeneous catalysis and their potentially hemilabile
behaviour.1–3
The 31P-{1H} NMR spectrum of 1 shows a peak at δ 78.1
ppm which corresponds to a downfield shift of 57 ppm relative
to the free ligand (δ 21.6 ppm in CDCl3)10 and this is consistent
with coordination of the phosphorus atom to the Mo()
centre.14 The IR spectrum confirmed that the carbonyl frag-
ment was not coordinated to the metal centre (νco 1698 cmϪ1 vs.
1715 cmϪ1 for the free ligand in CH2Cl2).10
In recent times, heterodifunctional ligands possessing P–N
bonds have emerged as an interesting class of ligands. For
example, comparisons between the reactivity of the related
ligands, bis(diphenylphosphino)methane (dppm) and bis-
(diphenylphosphino)amine (dppa) have been reported.4–7 The
reactions of a P,N mixed donor ligand Ph2PN(H)Py with vari-
ous late transition metal complexes have also been described.8,9
The amide-derived ligands, Ph2PN(R)C(O)CH3 (R = H,
CH3)10 and Ph2PN(H)C(O)R (R = Ph, NH2, 3-pyridyl)11,12
represent new difunctional P,O ligands for late transition metal
complexes. The acetamide-derived P,O donor ligands have been
observed to be more effective chelating ligands than Ph2PCH2-
C(O)Ph. These have also been found to act as efficient stabil-
ising ligands for cationic Pd complexes and have allowed the
direct observation and characterisation of intermediates in the
sequential insertion of CO, ethene, CO and ethene or methyl-
acrylate into a Pd-methyl bond.13
However, the reaction between L1 and the dinuclear complex
[Mo(η3-C3H5)(µ-Cl)(η6-C6H6)]2 in ethanol yielded a dark red
solution. The 31P-{1H} NMR spectrum of the mixture showed
a signal at δ 119.4 ppm, which corresponds to a downfield
shift of ca. 40 ppm compared to the 31P chemical shift of 1.
Furthermore, in the IR spectrum the νco vibration occurred at
1602 cmϪ1. These data suggest a chelating coordination mode
of the P,O ligand, as already observed in Pd complexes,10 and
formation of the cationic complexes [Mo(η3-C3H5){Ph2PNHC-
(O)CH3-κ2P,O}(η6-C6H6)]Cl. Indeed, after the reaction mixture
was treated with an excess of ammonium hexafluorophosphate,
orange–red crystals of [Mo(η3-C3H5){Ph2PNHC(O)CH3-κ2-
P,O}(η6-C6H6)][PF6] 2a were obtained in 33% yield (Scheme 1).
The toluene analogue of 2a [Mo(η3-C3H5){Ph2PNHC(O)CH3-
κ2P,O}(η6-C6H5CH3)][PF6] 2b, was also obtained as orange–
red crystals (31% yield) in a similar manner from L1 and
[Mo(η3-C3H5)(µ-Cl)(η6-C6H5CH3)]2 (Scheme 1). Complexes
2a,b both crystallised with one equivalent of ethanol in the
crystal lattice.
The early transition metal chemistry of the phosphine
ligands containing a carbonyl group, such as a ketone, ester or
amide function, is relatively underdeveloped. However, half-
sandwich molybdenum complexes of the amidophosphine
14
Ph2PCH2C(O)NPh2 and the keto-functionalised N-pyrrolyl-
The 1H NMR spectra of 2a,b showed a resonance assignable
to the NH proton and this is significantly shifted to low field
(2a δ 10.46 ppm, 2b δ 11.60 ppm, free ligand δ 6.15 ppm in
CDCl3).10 The observed shift is consistent with the amide pro-
ton undergoing hydrogen bonding with an ethanol molecule.
The presence of hydrogen bonding between the NH and the
OH of the ethanol solvent was confirmed from the crystal
structure of 2aؒC2H5OH.
X-Ray quality crystals of 2a were grown via the slow cooling
of a hot ethanol solution of the cationic complex. The mole-
cular structure of 2aؒC2H5OH is given in Figs 1 and 2. Selected
bond distances and angles are listed in Table 2.
phosphine Ph2PNC4H3{C(O)CH3}-215 have been recently
reported. Here we describe the chemistry of heterodifunctional
acetamido P,O donor ligands with molybdenum() arene
complexes.
Results and discussion
The reaction between [Mo(η3-C3H5)(µ-Cl)(η6-C6H5CH3)]2 and
N-(diphenylphosphino)acetamide L1 in toluene resulted in
cleavage of the chloro-bridged dimer to afford the phosphine
adduct [Mo(η3-C3H5)Cl(η6-C6H5CH3){Ph2PNHC(O)CH3}] 1
DOI: 10.1039/b105957m
J. Chem. Soc., Dalton Trans., 2002, 1487–1493
This journal is © The Royal Society of Chemistry 2002
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Fig. 2 Packing diagram of [Mo(η3-C3H5)(η6-C6H6){Ph2PNHC(O)-
CH3-κ2P,O}][PF6]ؒC2H5OH 2aؒC2H5OH (50% thermal ellipsoids),
viewed along the 100 axis. Hydrogen atoms have been omitted for clarity.
centred chirality are present in the unit cell. The average L–M–
L angle of 89.2Њ and the average arene centroid–Mo–L angle of
124.5Њ, are similar to those observed in other molybdenum
three-legged piano stool structures.16,17 The Mo-ligand bond
lengths and angles are within the expected ranges.17–20
The structural features of the acetamide-based P,O ligand are
similar to those observed in the crystal structure of the square
planar cationic palladium() complex [Pd(CH3){PPh2NH-
C(O)CH3-κ2P,O}{PPh2NHC(O)CH3}][O3SCF3].10
Scheme 1
However, the bite angle of the ligand L1 is slightly smaller in
the Mo() complex (75.39(4)Њ) compared with that in the
square planar Pd() complex (80.5(1)Њ). Yet it is similar to the
PCCO bite angles of 74.76(4) and 74.37(9)Њ observed in
[MoCpCl3{Ph2PCH2C(O)NPh2-κ2P,O}] and [MoCp*Cl3{Ph2-
PCH2C(O)NPh2-κ2P,O}][BF4], respectively.10
The cations of 2a form channels which lie approximately
along the x axis and the hexafluorophosphate anions are inter-
spersed between the C(10)–C(15) phenyl rings of the PPh2
groups on adjacent molecules. The ethanol molecules occupy
the spaces between adjacent C(4)–C(9) phenyl groups of the
PPh2 fragment (Fig. 2).
The hydrogen bonding between the ethanol oxygen and the
amide proton is confirmed from the crystal structure, with an
O ؒ ؒ ؒ N distance of 2.82 Å. The O–H–N angle of approxi-
mately 164Њ is also consistent with a hydrogen bond. Similar
hydrogen bonding between the amide proton and ethanol
solvate molecules was observed in the crystal structure of
[NiCl(EtOH)L2]Cl[NiCl2L2] (L = {Ph2PN(H)C(O)Ph}).11
A
hydrogen bonding interaction between the amide proton and
the amide oxygen of an adjacent molecule was also observed in
the crystal structure of the free ligand Ph2PNHC(O)CH3
(N ؒ ؒ ؒ O 2.83 Å, N–H–O 173.7Њ).10
Fig. 1 Molecular structure of the cation in [Mo(η3-C3H5)(η6-C6H6)-
{Ph2PNHC(O)CH3-κ2P,O}][PF6]ؒC2H5OH 2aؒC2H5OH. (50% thermal
ellipsoids). Hydrogen atoms and ethanol have been omitted for clarity.
The η6-benzene ligand of 2a adopts an inverted boat
conformation.20–23 Two carbon atoms [C(19) and C(22)] are
pushed away from the metal centre, resulting in a dihedral
fold angle (θ) of 9.8Њ at the C(19)–C(22) vector. The observed
The cationic compound 2a adopts a three-legged piano stool
structure, with the Mo-allyl centroid vector taken as one of the
legs of the stool. The two enantiomers resulting from the metal-
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Table 1 Analytical and spectroscopic data
Compound and analytical dataa
NMRb and IRc data
1
[Mo(η3-C3H5)Cl{Ph2PNHC(O)CH3}-
(η6-C6H5CH3)] Purple solid C 56.3 (56.8),
H 5.3 (5.4), N 2.8 (2.8)
1Hd: 8.37 (d, JHP = 18, 1H, NH ), 7.87–7.08 (m, 10H, Ph2P), 4.35 (m, 1H, Tol ), 4.29 (m, 1H,
Tol ), 4.26 (m, 1H, allyl Hc), 3.79 (m, 2H, Tol ), 3.67 (t, JHH = 5.7, 1H, Tol ), 3.09 (dd, JHH = 3,
JHH = 6, 1H, allyl Ht), 2.81 (dd, JHH = 3, JHH = 8, 1H, allyl Ht), 1.73 (s, 3H, C(O)CH3), 1.68
(m, 1H, allyl Ht), 1.46 (s, 3H, tolCH3), 1.01 (t, JHH = 7.7, 1H, allyl Ht).
13C-{1H}d: 170.6 (d, JPC = 12.7, NC(O)CH3), 136.0 (d, JPC = 43.7, Ph), 131.9 (d, JPC = 10.9,
Ph), 131.5 (unknown–under 131.9 peak), 129.9 (d, JPC = 14.5, Ph), Ph resonances obscured
by solvent, 115.3 (s, tol), 100.3 (s, tol), 97.0 (s, tol), 94.4 (s, tol), 93.2 (s, tol), 92.5 (s, tol), 81.8
(s, allyl Cc), 52.9 (s, allyl Ct), 43.5 (d, JPC = 6, C(O)CH3, 24.3 (s, allyl Ct), 19.0 (s, tolCH3).
31P-{1H}d: 78.1 (s, –PPh2).
IR: 1698 (s, νco).
2a
2b
3a
3b
[Mo(η3-C3H5){Ph2PNHC(O)CH3-κ2P,O}-
(η6-C6H6)][PF6] Red crystals C 45.6
(46.2), H 4.5 (4.8), N 2.2 (2.2)
1He: 10.46 (br, 1H, NH ), 8.01–7.97 (m, 2H, Ph), 7.84–7.77 (m, 2H, Ph), 7.70–7.58 (m, 6H,
Ph), 5.10 (d, JHP = 1.2, 6H, C6H6), 3.57 (m, 2H, HOCH2CH3), 3.47–3.32 (m, 2H, allyl Hc and
Ht), 2.49 (d, JHP = 0.7, 3H, C(O)CH3), 2.02 (m, 1H, allyl Ht), 1.76 (m, 1H, allyl Ht), 1.13
(t, JHH = 7.0, 3H, HOCH2CH3), 1.11 (m, 1H, allyl Ht).
13C-{1H}e: 210.0 (s, NC(O)CH3), 135.7 (d, JPC = 43.5, Ph), 131.9 (s, Ph), 131.8 (s, Ph), 131.65
(d, JPC = 11.2, Ph), 130.6 (d, JPC = 11.2, Ph), 129.9 (d, JPC = 9.9, Ph), 129.6 (d, JPC = 9.9, Ph),
129.0 (apparent s, Ph), 99.4 (s, C6H6), 79.8 (s, allyl Cc), 48.7 (s, allyl Ct), 42.5 (s, C(O)CH3),
22.3 (s, allyl Ct).
31P-{1H}e: 119.4 (s, Ph2PN), Ϫ143.2 (sept, JPF = 708, PF6).
IR: 1602 (s, νco).
[Mo(η3-C3H5){Ph2PNHC(O)CH3-κ2P,O}-
(η6-C6H5CH3)][PF6] Red crystals C 47.2
(47.1), H 4.8 (5.0), N 2.1 (2.1)
1Hg: 11.60 (br d, JHP = 3.4, 1H, NH ), 7.89 (m, 2H, Ph), 7.76–7.61 (m, 10H, Ph), 5.30–5.22
(m, 2H, tol), 4.77 (t, JHH = 5.6, 1H, tol), 4.67 (d, JHH = 4.4, 1H, tol), 4.61 (t, JHH = 6.0, 1H,
tol), 3.22 (m, 1H, allyl Hc), 2.99 (m, 1H, allyl Ht), 2.37 (s, 3H, amide CH3), 1.90 (m, 1H, allyl
Ht), 1.56 (s, 3H, tol-CH3), 1.54 (m, 1H, allyl Ht), 0.84 (m, 1H, allyl Ht).
13C-{1H}g: 186.8 (s, CO), 134.9 (d, JCP = 42.7, PPh2), 131.0 (s, PPh2), 130.9 (s, PPh2), 130.8
(s, PPh2), 129.8 (s, PPh2), 129.1 (d, JCP = 9.3, PPh2), 128.8 (d, JCP = 10.2, PPh2), 119.4 (s, Tol ),
102.7 (s, Tol ), 98.3 (s, Tol ), 97.4 (s, Tol ), 96.6 (s, Tol ), 93.3 (s, Tol ), 91.4 (s, allyl Cc), 77.6
(s, allyl Ct), 41.4 (s, C(O)CH3), 22.1 (s, allyl Ct), 18.9 (s, tolCH3).
31P-{1H}g: 118.5 (s, Ph2PN), Ϫ143.1 (sept, JPF = 713, PF6).
IR: 1602 (s, νco).
[Mo(η3-C3H5){Ph2PN(CH3)C(O)-
1He: 7.92–7.85 (m, 4H, Ph2PN), 7.74–7.67 (m, 6H, Ph2PN), 5.06 (d, JHH = 1, 6H, C6H6), 3.56
(m, 1H, allyl Hc), 3.26 (dd, J = 8.4, J = 2.6, 1H, allyl Ht), 3.22 (d, JHP = 4, 3H, NCH3, 2.46
(s, 3H, COCH3), 1.98 (dd, JHH = 3, JHH = 6.5, 1H, allyl Ht), 1.50 (m, 1H, allyl Ht), 1.06
(m, 1H, allyl Ht).
CH3-κ2P,O} (η6-C6H6)][PF6] Orange–Red
crystals C 46.7 (46.7), H 4.4 (4.4), N 2.3 (2.3)
13C-{1H}e: 189.3 (d, JPC = 18, NC(O)CH3), 133.3 (d, JPC = 41, Ph), 132.5 (d, JPC = 10, Ph),
132.1 (d, JPC = 8, Ph), 131.7 (s, Ph), 131.6 (s, Ph), 130.1 (d, JPC = 10, Ph), 129.8 (d, JPC = 9.5,
Ph), 125.9 (d, JPC = 37.6, Ph), 80.0 (s, allyl), 48.8 (s allyl), 42.9 (d, JPC = 4.2, C(O)CH3), 37.3
(d, JPC = 4.3, NCH3), 22.7 (s, allyl).
31P-{1H}e: 150.5 (s, Ph2PN), Ϫ143.1 (sept, JFP = 708, PF6).
IR: 1580, 1570 (s, νco).
[Mo(η3-C3H5){Ph2PN(CH3)C(O)-
CH3-κ2P,O}(η6-C6H5CH3)][PF6]
Orange–Red crystals C 47.5 (47.6), H 4.6
(4.6), N 2.2 (2.2)
1He: 7.94–7.82 (m, 4H, Ph2PN), 7.75–7.66 (m, 6H, Ph2PN), 5.34 (d, JHH = 5.3, 1H, tol), 5.09
(m, 1H, tol), 4.77 (d, JHH = 5.3, 1H, tol), 4.69 (m, 1H, tol), 4.59 (t, JHH = 6.2, 1H, tol), 3.58
(m, 1H, allyl Hc), 3.25 (d, JHP = 3.8, 3H, NCH3), 3.05 (dd, JHH = 2.7, JHH = 8.5, 1H, allyl Ht),
2.51 (s, 3H, C(O)CH3), 2.02 (dd, JHH = 3.3, JHH = 6.4, 1H, allyl Ht), 1.67 (s, 3H, tolCH3), 1.49
(m, 1H, allyl Ht), 0.91 (t, JHH = 7.1, allyl Ht).
13C-{1H}e: 188.3 (d, JCP = 17.7, CO), 132.4 (d, JCP = 40.2, PPh2), 131.7 (s, PPh2), 131.6
(s, PPh2), 131.2 (d, JCP = 12.1, PPh2), 130.6 (d, JCP = 11.4, PPh2), 129.3 (d, JCP = 9.4, PPh2),
129.0 (d, JCP = 8.7, PPh2). 125.1 (d, JCP = 37.5, PPh2), 119.7 (s, Tol ), 102.9 (s, Tol ).
31P-{1H}e: 151.0 (s, Ph2PN), Ϫ143.1 (sept, JFP = 708, PF6).
IR: 1580, 1568 (s, νco).
3
6
1Hf: 7.96 (m, 3H, Ph), 7.83 (m, 3H, Ph), 7.18–7.02 (m, 4H, Ph), 4.14 (s, 6H, C6H6), 3.49
(m, 1H, allyl Hc), 2.86 (dd, JHH = 2.6, JHH = 7.8, 1H, allyl Ht), 2.33 (s, 3H, C(O)CH3), 2.26
(m, 1H, allyl Ht), 1.83 (m, 1H, allyl Ht), 0.48 (m, 1H, allyl Ht).
ؒؒ ؒؒ
4a
4b
[Mo(η -C3H5)(η -C6H6){Ph2PN᎐C(᎐O)-
CH3-κ2P,O}] Orange crystals
13C-{1H}f: 186.8 (d, JCP = 8, C᎐N), 130.7 (d, JCP = 8.6, PPh2), 129.6 (d, JCP = 10.4, PPh2),
ؒؒ
128.6 (d, JCP = 1.7, PPh2), 128.5 (d, JCP = 1.8, PPh2), 127.7 (d, JCP = 8.7, PPh2), 127.3 (d, JCP
=
9.2, PPh2), 95.8 (s, C6H6), 76.8 (s, allyl Cc), 46.6 (s, allyl Ct), 40.3 (d, JCP = 5.4, C(O)CH3), 22.7
(d, JCP = 12.4, allyl Ct).
31P-{1H}f: 107.6 (s, Ph2PN)
IR: 1506 (w, νCN ϩ νCO).
3
6
ؒؒ ؒؒ
[Mo(η -C3H5)(η -C6H6){Ph2PN᎐C(᎐O)-
CH3-κ2P,O}] Orange crystals C 61.4 (61.2),
H 5.8 (5.6), N 2.9 (3.0)
1Hf: 7.84–7.78 (m, 2H, Ph2PN), 7.66–7.60 (m, 2H, Ph2PN), 7.46–7.34 (m, 6H, Ph2PN),
4.85–4.79 (m, 2H, tol), 4.22 (m, 1H, tol), 4.17–4.10 (m, 2H, tol), 2.92 (m, 1H, allyl Hc), 2.48
(dd, JHH = 2.5, JHH = 8, 1H, allyl Ht), 2.12 (d, JHP = 1, 3H, COCH3), 1.73 (m, 1H, allyl Ht),
1.52 (m, 1H, allyl Ht), 1.44 (s, 3H, tolCH3), 0.30 (m, 1H, allyl Ht).
13
1
f
ؒؒ
C-{ H} : 186.4 (s, C᎐N), 140.9 (d, JPC = 43, Ph2PN), 134.6 (d, JPC = 40, Ph2PN), 130.7
(d, JPC = 9.7, Ph2PN), 129.5 (d, JPC = 9.7, Ph2PN), 128.5 (d, JPC = 2, Ph2PN), 128.4 (d, JPC
=
2.6, Ph2PN), 127.7 (d, JPC = 8.5, Ph2PN), 127.3 (d, JPC = 9.6, Ph2PN), 119.1 (s, tol), 102.0
(s, tol), 95.8 (s, tol), 94.9 (d, JPC = 3, tol), 88.6 (d, JPC = 2.4, tol), 86.6 (s, tol), 75.8 (s, allyl Cc),
46.8 (s, COCH3), 40.2 (d, JPC = 5.2, allyl Ct), 23.2 (d, JPC = 13.3, allyl Ct), 18.5 (s, tolCH3).
31P-{1H}f: 107.6 (s, Ph2PN)
IR: 1506 (w, νCN ϩ νCO
)
a Calculated values given in parentheses. b NMR data are given as chemical shift (δ) (multiplicity, relative intensity, J/Hz, assignment). c Nujol mull.
d Recorded in C6D6. e Recorded in d6-acetone. f Recorded in CD2Cl2. g Recorded in d6-dmso.
fold angle is consistent with other observed distortions in
(CH3)2}2(η6-C6H5CH3)]20 displayed inverted boat distortion of
the arene ligand with fold angles 9.6 and 10.9Њ,22 respectively.
The distortion of the arene ligand is also reflected in the
molybdenum arene complexes. For example, the complexes
23
[Mo(µ-SCH3)2(η6-C6H5CH3)]2[PF6]2
and [Mo(CH3)2{PPh-
J. Chem. Soc., Dalton Trans., 2002, 1487–1493
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Table 2 Selected bond lengths (Å) and angles (Њ) for 2aؒC2H5OH
Mo(1)–C(16)
Mo(1)–C(17)
Mo(1)–C(18)
Mo(1)–Cent(allyl)
Mo(1)–C(average)
2.255(2)
2.194(2)
2.257(2)
1.980
Mo(1)–C(19)
Mo(1)–C(20)
Mo(1)–C(21)
Mo(1)–C(22)
Mo(1)–C(23)
Mo(1)–C(24)
Mo(1)–Cent(bz)
Mo(1)–C(average)
2.359(2)
2.256(2)
2.292(2)
2.366(2)
2.275(2)
2.295(2)
1.827
2.234
Mo(1)–P(1)
Mo(1)–O(1)
2.4316(5)
2.1930(15)
2.307
Cent(bz)–Mo(1)–Cent(allyl)
Cent(bz)–Mo(1)–O(1)
Cent(bz)–Mo(1)–P(1)
131.26
120.01
122.32
Cent(allyl)–Mo(1)–O(1)
Cent(allyl)–Mo(1)–P(1)
O(1)–Mo(1)–P(1)
94.47
97.71
75.39(4)
P(1)–N(1)
N(1)–C(2)
C(2)–O(1)
1.7160(17)
1.340(3)
1.250(3)
P(1)–N(1)–C(2)
N(1)–C(2)–O(1)
118.07(15)
121.36(19)
carbon–carbon bond distances, with two bonds [C(20)–C(21) =
1.433(4), C(23)–C(24) = 1.437(4) Å] longer than the others
[average = 1.40(4) Å].
arene and allyl ligands. Since the complex is chiral at the
molybdenum centre, exchanging the positions of the benzene
and allyl ligands produces the other enantiomer (enantiomers
A and B). However, the molecule exists in its racemic form and
crystallises in an achiral space group. The observed disorder is
due to distortion in the crystal packing, with 40% of enantio-
mer A occupying sites otherwise occupied by enantiomer B and
vice versa.
The reaction between N-(diphenylphosphino)-N-methyl-
acetamide L2 and the dinuclear complexes [Mo(η3-C3H5)(µ-Cl)-
(η6-C6H5R)]2 (R = H, CH3) in ethanol also yielded a dark red
solution from which orange–red crystals of [Mo(η3-C3H5)-
{Ph2PN(CH3)C(O)CH3-κ2P,O}(η6-C6H5R)][PF6] 3a (R = H),
3b (R = CH3) were obtained in 42–64% yields after addition of
an excess of ammonium hexafluorophosphate (Scheme 1).
The 31P-{1H} NMR and IR spectra of 3a,b were consistent
with the P,O ligand coordinating as a bidentate ligand to form
a cationic Mo() complex (Table 1).
X-Ray quality crystals of 3a were grown via the slow cooling
of a hot ethanol solution of the cationic complex. The crystal
structure of the complex 3a has been determined and the
molecular structure is shown in Fig 3. Selected bond distances
and angles are presented in Table 3.
The reaction between L1, [Mo(η3-C3H5)(µ-Cl)(η6-C6H5R)]2
(R = H, CH3) and an excess of sodium methoxide in ethanol
yielded a dark red solution from which orange crystals of
3
6
2
ؒؒ ؒؒ
[Mo(η -C3H5)(η -C6H5R){Ph2PN᎐C(᎐O)CH3-κ P,O}] 4a (R =
H), 4b (R = CH3) were isolated in 75 and 30% yield for 4a and
4b, respectively (Scheme 1).
A 31P-{1H} NMR resonance at δ 107.6 ppm was observed for
both complexes. The IR spectra of 4a,b exhibited a band at
1506 cmϪ1 which was ascribed to a νCN ϩ νCO vibration. These
data are consistent with the formation of an η2-phosphino-
iminolate complex (Table 1).
X-Ray quality crystals of 4a were grown from a concentrated
dichloromethane–pentane solution at Ϫ20 ЊC. The molecular
structure of complex 4a is given in Fig. 4. Selected bond
Fig. 3 Molecular structure of the cation in [Mo(η3-C3H5){Ph2PN-
(CH3)C(O)CH3-κ2P,O}(η6-C6H6)][PF6] 3a (50% thermal ellipsoids).
Hydrogen atoms have been omitted for clarity. The benzene and allyl
groups are disordered over common sites (see text).
The cationic complex adopts a three-legged piano stool
structure, as observed for the crystal structure of 2a. Similarly,
the two enantiomers, resulting from the metal-centred chirality
are present in the unit cell. The Mo–ligand bond lengths and
angles are within expected ranges.17–20
As for the complex 2a, the molecules pack in such a way to
generate chains along the x axis (100) of the crystal. The hexa-
fluorophosphate anions occupy spaces between the allyl ligands
of adjacent molecules along the chain.
3
6
ؒؒ ؒؒ
Fig. 4 Molecular structure of [Mo(η -C3H5)(η -C6H6){PhP2N᎐C(᎐O)-
CH3-κ2P,O}] 4a (50% thermal ellipsoids). Hydrogen atoms have been
omitted for clarity. The benzene and allyl groups are disordered over
two sites equivalent by symmetry (see text).
distances and angles are presented in Table 4. The neutral
complex 4a adopts a three-legged piano stool structure, as
observed for the crystal structures of 2a and 3a and likewise, the
The crystal structure of 3a displayed some disorder of the
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Table 3 Selected bond lengths (Å) and angles (Њ) for 3a
Mo(1)–C(102)
Mo(1)–C(103)
Mo(1)–C(104)
Mo(1)–Cent(allyl)
Mo(1)–C(average)
2.263(6)
2.225(6)
2.293(6)
2.014
Mo(1)–C(201)
Mo(1)–C(202)
Mo(1)–C(203)
Mo(1)–C(204)
Mo(1)–C(205)
Mo(1)–C(206)
Mo(1)–Cent(bz)
Mo(1)–C(average)
2.314(8)
2.247(6)
2.238(5)
2.320(5)
2.289(8)
2.253(8)
1.782
2.264
Mo(1)–P(1)
Mo(1)–O(1)
2.4123(12)
2.161(3)
2.280
Cent(bz)–Mo(1)–Cent(allyl)
Cent(bz)–Mo(1)–O(1)
Cent(bz)–Mo(1)–P(1)
129.06
116.42
123.24
Cent(allyl)–Mo(1)–O(1)
Cent(allyl)–Mo(1)–P(1)
O(1)–Mo(1)–P(1)
99.48
99.17
75.29(9)
P(1)–N(1)
N(1)–C(1)
C(1)–O(1)
1.735(4)
1.347(6)
1.251(6)
P(1)–N(1)–C(1)
N(1)–C(1)–O(1)
N(1)–C(3)
116.4(3)
120.7(4)
1.482(6)
Table 4 Selected bond lengths (Å) and angles (Њ) for 4a
Mo(1)–C(4*)
Mo(1)–C(5*)
Mo(1)–C(6*)
Mo(1)–Cent(allyl)
Mo(1)–C(average)
2.302(5)
2.231(4)
2.248(4)
2.007
Mo(1)–C(1)
Mo(1)–C(2)
Mo(1)–C(3)
Mo(1)–C(4)
Mo(1)–C(5)
Mo(1)–C(6)
Mo(1)–Cent(bz)
Mo(1)–C(average)
2.383(7)
2.294(7)
2.292(7)
2.302(5)
2.231(4)
2.248(4)
1.825
2.26
Mo(1)–P(1)
Mo(1)–O(1)
2.4471(14)
2.152(4)
2.29
Cent(bz)–Mo(1)–Cent(allyl)
Cent(bz)–Mo(1)–O(1)
Cent(bz)–Mo(1)–P(1)
132.88
112.73
123.23
Cent(allyl)–Mo(1)–O(1)
Cent(allyl)–Mo(1)–P(1)
O(1)–Mo(1)–P(1)
99.35
97.76
73.8(1)
P(1)–N(1)
N(1)–C(7)
C(7)–O(1)
1.679(4)
1.298(7)
1.291(6)
P(1)–N(1)–C(7)
N(1)–C(7)–O(1)
C(7)–C(8)
113.6(3)
125.9(5)
1.508(7)
enantiomers, resulting from the metal-centred chirality, are
present in the unit cell. The Mo-ligand bond lengths and angles
are within expected ranges. This is the first example of a struc-
turally characterised η2-phosphinoiminolate complex. The
metallacyclic fragment, Mo(1)–P(1)–N(1)–C(7)–O(1), is planar
and the methyl carbon [C(8)] is also lying in this plane.
The results described here present the first investigations
into the chemistry of acetamide derived ligands with a middle
transition metal species.
Experimental
Deprotonation of the phosphino–acetamide complex 2a to
give the corresponding phosphinoiminolate complex 4a has
little effect upon the Mo–P bond length [2.4471(14) Å vs.
2.4316(5) and 2.4123(12) Å for 2a and 3a, respectively] or the
P–Mo–O bite angle of the chelating ligand [73.8(1) vs. 75.39(4)
and 75.29(9)Њ for 2a and 3a, respectively]. However a shortening
of the Mo–O [2.152(4)], P–N [1.679(4)] and N–C [1.298(7) Å]
bonds and a lengthening of the C–O [1.291(6) Å] bond is
observed. These observed changes are consistent with the for-
mation of a phosphinoiminolate ligand.
Because the molecule lies on a mirror plane defined by
Mo(1)–P(1)–N(1)–C(7)–O(1), the allyl and arene groups are
inevitably 50% disordered over the two equivalent sites. The
atoms of the allyl group essentially overlap (in the disorder)
three of the arene carbons, so that these appear at full occu-
pancy in the list of atomic coordinates.
General
All manipulations of air- and/or moisture sensitive materials
were performed under an inert atmosphere of argon using
standard Schlenk line techniques, or in an inert atmosphere dry
box containing dinitrogen. Solvents were dried over the
appropriate drying agent and distilled under nitrogen. Deuter-
ated solvents were dried over the appropriate drying agent and
vacuum distilled prior to use.
The compounds [Mo(η3-C3H5)(µ-Cl)(η6-C6H5R)]2 (R = H,
CH3)24 and Ph2PN(R)C(O)CH3 (R = H, CH3)10 were prepared
according to previously published methods.
NMR spectra were recorded on a Varian Mercury 300 (1H,
13C and 31P at 300.17, 75.48 and 121.51 MHz respectively)
spectrometer at room temperature in d6-acetone, d6-dimethyl-
sulfoxide or d2-dichloromethane. They were referenced intern-
ally using the residual protio solvent (1H) and solvent (13C)
resonances and measured relative to tetramethylsilane (1H and
13C; δ 0 ppm). 31P NMR were referenced externally to 85%
H3PO4 (δ 0 ppm). Elemental analyses were provided by the
microanalytical department, Inorganic Chemistry Laboratory,
University of Oxford. Infrared spectra were recorded as a mull
in Nujol on a Perkin Elmer 1600 Series FTIR spectrometer.
Conclusion
A series of arene molybdenum complexes in which the amide-
derived ligands Ph2PN(R)C(O)CH3 (R = H, CH3) display
η1-phosphine, η2-acetamidophosphine and η2-phosphino-
iminolate coordination have been synthesised and characterised.
The X-ray crystal structure determination of the phosphino-
Preparations
3
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ؒؒ ؒؒ
iminolate complex [Mo(η -C3H5)(η -C6H6){PhP2N᎐C(᎐O)CH3-
κ2P,O}] represents the first structurally characterised example
of this class of chelating ligand. The crystal structures of the
cationic compounds [Mo(η3-C3H5)(η6-C6H6){Ph2PN(R)C(O)-
CH3-κ2P,O}][PF6] (R = H, CH3) have also been determined.
[Mo(ꢀ3-C3H5)Cl(ꢀ6-C6H5CH3){Ph2PNHC(O)CH3}] 1. [Mo-
(η3-C3H5)(µ-Cl)(η6-C6H5CH3)]2 (167 mg, 0.32 mmol) and
Ph2PN(H)C(O)CH3 (160 mg, 0.66 mmol) were combined as
solids and dissolved in toluene (20 ml). The reaction mixture
J. Chem. Soc., Dalton Trans., 2002, 1487–1493
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Table 5 Crystal data and structure refinement for compounds 2a, 3a and 4a
2a
3a
4a
Empirical formula
M
Crystal system
Space group
C25H31F6MoNO2P2
649.40
Monoclinic
P21/n
C24H27F6MoNOP2
617.36
Monoclinic
P21/c
C23H24MoNOP
457.36
Orthorhombic
Cmca
a/Å
b/Å
c/Å
10.8978(2)
18.1501(3)
14.0945(3)
104.2295(6)
2702.3
11.4697(5)
13.7585(8)
16.5254(9)
105.4(1)
2513.8
14.8887(8)
16.5295(8)
16.1773(9)
90
3981.3
8
β/Њ
U/Å3
Z
4
4
T /K
150
0.67
150
0.71
150
0.75
µ/mmϪ1
Reflections collected
Independent reflections
6343
5053
5979
3076
2362
1511
R
Rw
0.0311
0.0392
0.0417
0.0471
0.0356
0.0387
was stirred at 65 ЊC for 3 h. The resulting dark red–purple
solution was filtered and the filtrate reduced to small volume in
vacuo. The product was precipitated by addition of pentane,
isolated by filtration and dried in vacuo. Complex 1 (145 mg,
0.29 mmol, 45%) was obtained as a pale purple solid.
solution in methanol, 3 ml) was added and the reaction mixture
stirred at 65 ЊC for 2 h. The solvent was removed in vacuo and
the residue extracted with dichloromethane (30 ml). The solvent
was removed in vacuo and the resulting red–orange residue
washed with cold hexane (10 ml). Complex 4a (134 mg, 0.30
mmol, 75%) was obtained as an orange solid.
[Mo(ꢀ3-C3H5){Ph2PNHC(O)CH3-ꢁ2P,O}(ꢀ6-C6H6)][PF6] 2a.
[Mo(η3-C3H5)(µ-Cl)(η6-C6H6)]2 (151 mg, 0.30 mmol) and Ph2-
PN(H)C(O)CH3 (150 mg, 0.62 mmol) were combined as solids
and suspended in ethanol (20 ml). The reaction mixture was
stirred at 60–70 ЊC for 4 h. The resulting orange–red solution
was filtered into a solution of ammonium hexafluorophosphate
(200 mg) in ethanol (5 ml). The reaction was allowed to stand at
room temperature for 2 h and then cooled at Ϫ20 ЊC for 1 h.
The resulting precipitate was isolated by filtration and dried in
vacuo. Complex 2a (121 mg, 0.2 mmol, 33%) was obtained as an
orange–red crystalline solid.
3
6
2
ؒؒ ؒؒ
[Mo(ꢀ -C3H5)(ꢀ -C6H5CH3){Ph2PN᎐C(᎐O)CH3-ꢁ P,O}] 4b.
[Mo(η3-C3H5)(µ-Cl)(η6-C6H5CH3)]2 (166 mg, 0.31 mmol) and
Ph2PN(H)C(O)CH3 (160 mg, 0.66 mmol) were combined as
solids and suspended in ethanol (20 ml). Excess sodium meth-
oxide (30% solution in methanol, 3 ml) was added and the
reaction stirred at room temperature for 2 h. The solvent was
removed in vacuo and the residue extracted with hexane (2 × 60
ml). The combined extracts were reduced to small volume
and cooled to Ϫ20 ЊC overnight. The product was isolated by
filtration and dried in vacuo. Complex 4b (85 mg, 0.18 mmol,
30%) was obtained as an orange crystalline solid.
[Mo(ꢀ3-C3H5){Ph2PNHC(O)CH3-ꢁ2P,O}(ꢀ6-C6H5CH3)][PF6]
2b. This compound was prepared in a manner similar to 2a,
starting from [Mo(η3-C3H5)(µ-Cl)(η6-C6H5CH3)]2 (140 mg, 0.26
mmol) and Ph2PN(H)C(O)CH3 (130 mg, 0.53 mmol). However,
the reaction was carried out at room temperature. Complex 2b
(100 mg, 0.16 mmol, 31%) was obtained as a red crystalline
solid.
Crystallography
Data were collected on a Nonius KappaCCD diffractometer
with Mo-Kα radiation (λ = 0.71069 Å). The images were
processed with DENZO25 and SCALEPACK26 programs. All
solution, refinement and graphical calculations were performed
using CRYSTALS27 and CAMERON28 software packages.
In each case, a single crystal was encased in perfluoropoly-
ether oil and mounted atop a glass fibre. The fibre, secured in a
goniometer head, was placed under a stream of cold nitrogen
maintained at 150 K and data collected.
[Mo(ꢀ3-C3H5){Ph2PN(CH3)C(O)CH3-ꢁ2P,O}(ꢀ6-C6H6)][PF6]
3a. [Mo(η3-C3H5)(µ-Cl)(η6-C6H6)]2 (105 mg, 0.21 mmol) and
Ph2PN(CH3)C(O)CH3 (120 mg, 0.47 mmol) were combined as
solids and suspended in ethanol (20 ml). The reaction mixture
was stirred at 60–70 ЊC for 4 h. The resulting orange–red sol-
ution was filtered into a solution of ammonium hexafluoro-
phosphate (200 mg) in ethanol (5 ml). The reaction was allowed
to stand at room temperature overnight. The resulting preci-
pitate was isolated by filtration and dried in vacuo. Complex 3a
(167 mg, 0.27 mmol, 64%) was obtained as an orange crystal-
line solid.
The structure was solved using the program SIR9229
and refined using full-matrix least-squares on all F data
(CRYSTALS). All non-hydrogen atoms were refined aniso-
tropically and hydrogen atoms were included in calculated pos-
itions with isotropic thermal parameters. All calculations were
carried out on a Pentium personal computer.
A Chebychev polynomial weighting scheme30 with the
parameters 1.06, 0.469 and 0.735 was applied to the crystal
structure of compound 2a giving a final R factor of 0.0311 and
Rw = 0.0392 with a maximum residual electron density of 0.84 e
[Mo(ꢀ3-C3H5){Ph2PN(CH3)C(O)CH3-ꢁ2P,O}(ꢀ6-C6H5CH3)]-
[PF6] 3b. This compound was prepared in a manner similar to
3a, starting from [Mo(η3-C3H5)(µ-Cl)(η6-C6H5CH3)]2 (140 mg,
0.26 mmol) and Ph2PN(CH3)C(O)CH3 (140 mg, 0.54 mmol).
However, the reaction was carried out at room temperature.
Complex 3b (142 mg, 0.22 mmol, 42%) was obtained as a red
crystalline solid.
Å
Ϫ3. A similar weighting scheme was applied to the structure of
3a using the parameters 0.688, 0.249 and 0.403. This yielded a
final R factor of 0.0417, Rw = 0.0471 with a maximum residual
electron density of 0.63 e ÅϪ3. A similar weighting scheme was
applied to the structure of 4a using the parameters 0.507,
0.0919 and 0.212. This yielded a final R factor of 0.0356, Rw =
0.0387 with a maximum residual electron density of 0.64 e ÅϪ3
The crystallographic data are given in Table 5.
CCDC reference numbers 169296–169298.
.
3
6
2
ؒؒ ؒؒ
[Mo(ꢀ -C3H5)(ꢀ -C6H6){Ph2PN᎐C(᎐O)CH3-ꢁ P,O}] 4a. [Mo-
(η3-C3H5)(µ-Cl)(η6-C6H6)]2 (100 mg, 0.20 mmol) and Ph2PN-
(H)C(O)CH3 (105 mg, 0.43 mmol) were combined as solids and
suspended in ethanol (20 ml). Excess sodium methoxide (30%
See http://www.rsc.org/suppdata/dt/b1/b105957m/ for crys-
tallographic data in CIF or other electronic format.
1492
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14 J. M. Camus, D. Morales, J. Andrieu, P. Richard, R. Poli, P.
Acknowledgements
Braunstein and F. Naud, J. Chem. Soc., Dalton Trans., 2000, 2577.
15 C. D. Andrews, A. D. Burrows, J. M. Lynam, M. F. Mahon and
M. T. Palmer, New J. Chem., 2001, 25, 824.
16 F. Abugideiri, J. C. Fettinger, D. W. Keogh and R. Poli,
Organometallics, 1996, 15, 4407.
17 M. T. Ashby, V. S. Asirvatham, A. S. Kowalski and M. A. Khan,
Organometallics, 1999, 18, 5004.
18 C. P. Mehnert, A. N. Chernaga and M. L. H. Green, J. Organomet.
Chem., 1996, 513, 247.
We thank Dr David Watkin for assistance with the crys-
tallography. We also wish to thank the University of Sydney,
Australia and The King’s School, Sydney, Australia for finan-
cial support (N. G. J), the Centre National de la Recherche
Scientifique/Royal Society cooperation programme (X. M.,
N. G. J) and the A.G. Leventis Foundation (I. V) for financial
support.
19 P. W. Jolly, C. Krüger, C. C. Romão and M. J. Romão,
Organometallics, 1984, 3, 936.
20 J. L. Atwood, W. E. Hunter, R. D. Rogers, E. Carmona-Guzman
and G. Wilkinson, J. Chem. Soc., Dalton Trans., 1979, 1519.
21 W. E. Silverthorn, C. Couldwell and K. Prout, J. Chem. Soc., Chem.
Commun., 1978, 1009.
22 P. A. Wexler, D. E. Wigley, J. B. Koerner and T. A. Albright,
Organometallics, 1991, 10, 2319.
References
1 C. S. Slone, D. A. Weinberger and C. A. Mirkin, Prog. Inorg. Chem.,
1999, 48, 233.
2 A. Bader and E. Lindner, Coord. Chem. Rev., 1991, 108, 27.
3 P. Braunstein and F. Naud, Angew. Chem., Int. Ed., 2001, 40,
681.
4 I. Bachert, I. Bartusseck, P. Braunstein, E. Guillon, J. Rosé and
G. Kickelbick, J. Organomet. Chem., 1999, 588, 144.
5 P. Braunstein, R. Hasselbring, A. Tiripicchio and F. Ugozzoli,
J. Chem. Soc., Chem. Commun., 1995, 37.
6 P. Braunstein, R. Hasselbring, A. DeCian and J. Fischer, Bull. Soc.
Chim. Fr., 1995, 132, 691.
7 J. T. Mague, J. Cluster Sci., 1995, 6, 217.
8 L. K. Peterson and E. W. Ainscough, Inorg. Chem., 1970, 9, 2699.
9 S. M. Aucott, A. M. Z. Slawain and J. D. Wollins, J. Chem. Soc.,
Dalton Trans., 2000, 2559.
10 P. Braunstein, C. Frison, X. Morise and R. D. Adams, J. Chem. Soc.,
Dalton Trans., 2000, 2205.
23 L. J. Radonovich, F. J. Koch and T. A. Albright, Inorg. Chem., 1980,
19, 3373.
24 M. L. H. Green and W. E. Silverthorn, J. Chem. Soc., Dalton Trans.,
1973, 301.
25 Z. Otwinowski, in DENZO©, Department of Molecular Biophysics
and Biochemistry, Yale University, New Haven, CT, US, 1993.
26 Z. Otwinowski, in SCALEPACK©, Department of Molecular
Biophysics and Biochemistry, Yale University, New Haven, CT, US,
1993.
27 D. J. Watkin, C. K. Prout, J. R. Carruthers and P. W. Betteridge, in
Crystals Issue 10, Chemical Crystallography Laboratory, University
of Oxford, UK, 1996.
28 D. J. Watkin, C. K. Prout and L. J. Pearce, CAMERON, Chemical
Crystallography Laboratory, University of Oxford, UK, 1996.
29 A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M. C.
Burla, G. Polidori and M. Camalli, J. Appl. Crystallogr., Sect. A,
1994, 27, 435.
11 P. Bhattacharyya, T. Q. Ly, A. M. Z. Slawin and J. D. Woollins,
Polyhedron, 2001, 20, 1803.
12 T. Q. Ly, A. M. Z. Slawin and J. D. Woollins, Polyhedron, 1999, 18,
1761.
13 P. Braunstein, C. Frison and X. Morise, Angew. Chem., Int. Ed.,
2000, 39, 2867.
30 R. Carruthers and D. J. Watkin, Acta Crystallogr., Sect. A, 1979, 35,
698.
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