Nucleophilic displacement reactions of cis-bis((2,2′-biphenylylene)phosphochloridite ester)tetracarbonylmolybdenum(0). The first example of an unusual hydrolysis reaction yielding unsymmetrically substituted products

Article abstract of DOI:10.1021/om030411z

Ligands containing groups derived from bis(aryl)diols are widely used in asymmetric catalysis; however, few studies of the conformations of these ligands in transition-metal complexes have been reported. In this paper, the nucleophilic displacement reactions of cis-Mo(CO)₄(2,2′-C₁₂H₈O₂ PCl)₂ (1) have been used to prepare a variety of complexes with [1,3,2]-dioxaphosphepin ligands, and the conformations of these ligands have been studied by NMR spectroscopy and X-ray crystallography. The nucleophilic substitution reactions yield both the expected disubstituted complexes cis-Mo(CO)₄(2,2′-C₁₂H₈O₂ PXR)₂ (XR = NPrⁿ (2), OMe (4), SC₆H₄ -4-Me (6)) and the unexpected hydrolysis products [R′₃NH] [cis-Mo(CO)₄(2,2′-C₁₂H₈O₂PO)(2 ,2′-C₁₂H₈O₂PXR)] (R′₃ = PrⁿH₂, XR = NPrⁿ, 3; R′₃ = Et₃; XR = OMe, 5). NMR studies have demonstrated that the hydrolysis product is the major product when more than a minute amount of water is present, even in the presence of a large excess of the nucleophiles. This reaction is complete in approximately 90 min at 25°C. A very surprising feature of this reaction is that substitution of one chloride in 1 by the RX^- nucleophile greatly enhances the rate of substitution of the second chloride either by water or by another RX^- nucleophile. NMR studies of the [1,3,2]dioxaphosphepin complexes in chloroform-d solution suggest that the R* and S* enantiomers of the ligands interconvert via a low-energy pathway. Crystal structures of the complexes demonstrate that both the R*S* diastereomer (1) and racemic mixtures of the R*R* and S*S* diastereomers (2-4) are observed in the solid state. These results suggest that bulkier biaryl groups are needed to prevent the racemization of the [1,3,2]dioxaphosphepin ligands in solution.

Full text of DOI:10.1021/om030411z

4198
Organometallics 2003, 22, 4198-4205
Nu cleop h ilic Disp la cem en t Rea ction s of
cis-Bis((2,2′-bip h en ylylen e)p h osp h och lor id ite
ester )tetr a ca r bon ylm olybd en u m (0). Th e F ir st Exa m p le of
a n Un u su a l Hyd r olysis Rea ction Yield in g
Un sym m etr ica lly Su bstitu ted P r od u cts
Houston Byrd,*,† J eremiah D. Harden,† J ennifer M. Butler,‡
Michael J . J ablonsky,‡ and Gary M. Gray*,‡
Department of Biology, Chemistry & Mathematics, The University of Montevallo, Station 6480,
Montevallo, Alabama 35115, and Department of Chemistry, The University of Alabama at
Birmingham, 201 Chemistry Building, 1530 3rd Avenue South,
Birmingham, Alabama 35204-1240
Received J une 2, 2003
Ligands containing groups derived from bis(aryl)diols are widely used in asymmetric
catalysis; however, few studies of the conformations of these ligands in transition-metal
complexes have been reported. In this paper, the nucleophilic displacement reactions of cis-
Mo(CO)4(2,2′-C12H8O2PCl)2 (1) have been used to prepare a variety of complexes with [1,3,2]-
dioxaphosphepin ligands, and the conformations of these ligands have been studied by NMR
spectroscopy and X-ray crystallography. The nucleophilic substitution reactions yield both
the expected disubstituted complexes cis-Mo(CO)4(2,2′-C12H8O2PXR)2 (XR ) NPrn (2), OMe
(4), SC6H4-4-Me (6)) and the unexpected hydrolysis products [R′3NH][cis-Mo(CO)4(2,2′-
C12H8O2PO)(2,2′-C12H8O2PXR)] (R′3 ) PrnH2, XR ) NPrn, 3; R′3 ) Et3; XR ) OMe, 5). NMR
studies have demonstrated that the hydrolysis product is the major product when more than
a minute amount of water is present, even in the presence of a large excess of the
nucleophiles. This reaction is complete in approximately 90 min at 25 °C. A very surprising
feature of this reaction is that substitution of one chloride in 1 by the RX- nucleophile greatly
enhances the rate of substitution of the second chloride either by water or by another RX-
nucleophile. NMR studies of the [1,3,2]dioxaphosphepin complexes in chloroform-d solution
suggest that the R* and S* enantiomers of the ligands interconvert via a low-energy pathway.
Crystal structures of the complexes demonstrate that both the R*S* diastereomer (1) and
racemic mixtures of the R*R* and S*S* diastereomers (2-4) are observed in the solid state.
These results suggest that bulkier biaryl groups are needed to prevent the racemization of
the [1,3,2]dioxaphosphepin ligands in solution.
In tr od u ction
A number of ligands containing [1,3,2]dioxaphos-
phepin groups (Figure 1) derived from bis(aryl)diols
such as 2,2′-biphenol are currently used in asymmetric
catalysis. Such ligands include symmetrical bis([1,3,2]-
dioxaphosphepin) ligands,1-3 asymmetrical bidentate
phosphine-[1,3,2]dioxaphosphepin ligands,4,5 and mon-
odentate [1,3,2]dioxaphosphepin ligands.6 The axially
chiral diaryl backbone in the [1,3,2]dioxaphosphepin
F igu r e 1. General structure of a [1,3,2]dioxaphosphepin
ligand derived from bis(aryl)diols such as 2,2′-biphenol.
groups should result in C2 symmetry at the phosphorus;
however, recent studies of ligands containing [1,3,2]-
dioxaphosphepin groups derived from 2,2′-biphenol sug-
gested that there is a low-energy pathway to inversion
of the biphenyl group, even when the ligand is coordi-
nated to an inert metal center.7 This suggests that the
rational design of [1,3,2]dioxaphosphepin ligands for
asymmetric catalysts requires a better understanding
of the factors that affect the conformations of [1,3,2]-
dioxaphosphepin groups.
* To whom correspondence should be addressed. E-mail: gmgray@
uab.edu (G.M.G.); byrdh@montevallo.edu (H.B.).
† The University of Montevallo.
‡ The University of Alabama at Birmingham.
(1) Hariharasarma, M.; Watkins, C. L.; Gray, G. M. Organometallics
2000, 19, 1232 and references therein.
(2) Billig, E.; Abatjoglou, A. G.; Bryant, D. R. (UCC) U.S. Patent
4,769,498, 1988.
(3) (a) Cuny, G. D.; Buchwald, S. L. J . Am. Chem. Soc. 1993, 115,
2066. (b) J ohnson, J . R.; Cuny, G. D.; Buchwald, S. L. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1760.
(4) (a) Deerenberg, S.; Kamer, P. C. J .; van Leeuwen, P. W. N. M.
Organometallics 2000, 19, 2065. (b) Sua´rez, A.; Me´ndez-Rojas, M. A.;
Pizzano, A. Organometallics 2002, 21, 4611.
(5) (a) Sakai, N.; Mano, S.; Nozaki, K.; Takaya, H. J . Am. Chem.
Soc. 1993, 115, 7033. (b) Nozaki, K.; Ojima, I. Catalytic Asymmetric
Synthesis; Ojima, I., Ed.; Wiley-VCH: New York, 2000; Chapter 7.
(6) Reetz, M. T.; Mehler, G. Angew. Chem., Int. Ed. 2000, 39, 3889.
(7) Hariharasarma, M.; Lake, C. H.; Watkins, C. L.; Gray, G. M.
Organometallics 1999, 18, 2593 and references therein.
10.1021/om030411z CCC: $25.00 © 2003 American Chemical Society
Publication on Web 08/29/2003

Nucleophilic Displacement Reactions
Organometallics, Vol. 22, No. 21, 2003 4199
There have been few studies of the conformations of
[1,3,2]dioxaphosphepin ligands in transition-metal com-
plexes, in large part because relatively few of these
ligands have been prepared.7 It should be possible to
prepare complexes of [1,3,2]dioxaphosphepin ligands
with a variety of functional groups using the nucleo-
philic displacement reactions of transition-metal-coor-
dinated 2-chloro-[1,3,2]dioxaphosphepin ligands. Such
reactions with chlorophosphines8-17 and chlorophosphi-
tes derived from aliphatic diols18-20 are a versatile
method for the formation of complexes with unusual
phosphorus-donor ligands. The coordination of the
ligand to the transition metal stabilizes the phosphorus-
(III) oxidation state while maintaining a reactive phos-
phorus center. This allows the introduction of functional
groups that are often unstable in the free ligands.
F igu r e 2. Reaction scheme for the formation of cis-Mo-
(CO)4(2,2′-C12H8O2PCl)2.
The structural characterization of a series of com-
plexes of [1,3,2]dioxaphosphepin ligands would also be
of aid in the development of databases for computational
organometallic chemistry. Cundari has recently been
computationally modeling the cone angle effects of
phosphine ligands21 that were initially empirically
measured by Tolman.22 However, his modeling was less
successful for phosphites, due to the difficulty in ac-
curately describing the P-O bonds. Additional struc-
tural data for phosphite complexes could lead to better
modeling of the steric effects in these complexes.
Exp er im en ta l Section
All reactions and purifications were carried out under high-
purity nitrogen. All starting materials were reagent grade and
were purified by sublimation or distillation before use. All
solvents were dried and distilled immediately prior to use.
Tetrahydrofuran (THF) and triethylamine were distilled from
sodium/benzophenone under high-purity nitrogen. Hexanes
were distilled from calcium hydride under high-purity nitro-
gen. Deuterated NMR solvents (chloroform-d, dichloromethane-
d2) were opened and stored under a nitrogen atmosphere at
all times. cis-Mo(CO)4nbd and 2,2′-biphenylylenephosphochlo-
ridite ester were synthesized using literature procedures.23,24
Because of the wide applications of [1,3,2]dioxaphos-
phepin ligands in catalysis and the need for accurate
data for computational studies, we have begun to pre-
pare and structurally characterize transition-metal com-
plexes with a variety of [1,3,2]dioxaphosphepin ligands.
In this paper, we describe the synthesis (Figure 2) of
the tetracarbonylmolybdenum(0) complex of (2,2′-biphe-
nylylene)phosphochloridite ester, Mo(CO)4(2,2′-C12-
H8O2PCl)2 (1), and nucleophilic displacement reactions
of the chlorides in this complex by N-, O-, and S-
nucleophiles. The solution conformations of the products
have been characterized by multinuclear NMR spectro-
scopy, and the solid-state conformations of 1 and of three
of the substitution products have been determined. The
cis coordination of the [1,3,2]dioxaphosphepin ligands
in 1 allows for interesting noncovalent interactions, and
the rates of the chloride substitution reactions provide
insight into the effect of the phosphite backbone.20
All one-dimensional 31P{1H}, 13C{1H}, and H NMR spectra
1
of the compounds were recorded using a Bruker ARX-300 NMR
spectrometer with a quad (1H, 13C, 19F, 31P) 5 mm probe. The
31P{1H} NMR spectra were referenced to external 85% phos-
phoric acid, and both the 13C and the 1H NMR spectra were
referenced to internal TMS. Two-dimensional 1H-1H Cosy-
45, 13C{1H} HMBC, and 13C{1H} HMQC spectra were recorded
using a Bruker DRX-400 NMR spectrometer. Biphenoxy rings
were equivalent in all disubstituted complexes and are num-
bered so that the carbon bonded to oxygen is C1 and the
bridging carbon is C6.
Elemental analyses were performed by Atlantic Microlabs,
Norcross, GA. A solvent of crystallization is included in the
calculated analysis only if the solvent was observed in the H
1
NMR spectrum of the analytical sample.
IR spectra of these complexes were performed on a Nicolet
Nexus 470 FT-IR spectrometer. The compounds were dissolved
in ethyl acetate (0.05 g/mL), and 5-6 drops were placed on a
NaCl plate. The ethyl acetate was evaporated by blowing N2
over the plate, leaving a film of the compound. The IR spectra
of these films were taken at 4 cm-1 resolution and 16 scans.
cis-Mo(CO)4(2,2′-C12H8O2P Cl)2 (1). A solution of 3.77 g
(15.1 mmol) of 2,2′-biphenylylenephosphochloridite ester, 2.26
g (7.53 mmol) of Mo(CO)4nbd, and 50 mL of dry hexanes in a
Schlenk flask was stirred at room temperature overnight,
during which time a white solid slowly precipitated from the
solution. The solution was cooled to -5 °C for several hours,
and then the precipitate was collected, washed with hexanes,
and placed under high vacuum at room temperature overnight.
This procedure produced 5.14 g (96.7%) of crude 1. The crude
1 was purified by recrystallization from a dichloromethane/
hexanes mixture to give analytically pure 1 as colorless
crystals. Anal. Calcd for C28H16Cl2O8P2Mo: C, 47.42; H, 2.28.
(8) Kraihanzel, C. S. J . Organomet. Chem. 1974, 73, 137 and
references therein.
(9) J ohanssen, G.; Stelzer, O.; Unger, E. Chem. Ber. 1975, 108, 1259.
(10) Ledner, P. W.; Beck, W.; Theil, G. Inorg. Chim. Acta 1976, 20,
L11.
(11) Gray, G. M.; Kraihanzel, C. S. J . Organomet. Chem. 1978, 146,
23.
(12) Gray, G. M.; Kraihanzel, C. S. J . Organomet. Chem. 1980, 187,
51.
(13) Noth, H.; Reith, H.; Thorn, V. J . Organomet. Chem. 1978, 159,
165.
(14) Lindner, E.; Wuhrmann, J . C. Chem. Ber. 1981, 114, 2272.
(15) Wong, E. H.; Bradley, F. C. Inorg. Chem. 1981, 20, 2333.
(16) Treichel, P. M.; Rosenheim, L. D. Inorg. Chem. 1981, 20, 1539.
(17) Gray, G. M. Inorg. Chim. Acta 1984, 81, 157.
(18) Bartish, C. M.; Kraihanzel, C. S. Inorg. Chem. 1973, 12, 391.
(19) Gray, G. M.; Box, J . W.; Whitten, J . E. Inorg. Chim. Acta 1986,
116, 21.
Found: C, 47.48; H, 2.22. 31P{1H} NMR (chloroform-d):
δ
192.45 (s). 13C{1H} NMR (carbonyl and aromatic carbons,
(20) Gray, G. M.; Box, J . W.; Whitten, J . E. Inorg. Chim. Acta 1986,
120, 25.
(21) Cooney, K. D.; Cundari, T. R.; Hoffman, N. W.; Pittard, K. A.;
Temple, M. D.; Zaho, T. J . Am. Chem. Soc., in press.
(22) Tolman, C. A. Chem. Rev. 1977, 77, 313.
(23) Ehrl, W.; Ruck, R.; Vahrenkamp, H. J . Organomet. Chem. 1973,
56, 285.
(24) Verizhnikov, L. V.; Kirpichnikov, P. A. Zh. Obshch. Khim. 1966,
37, 1355.

4200 Organometallics, Vol. 22, No. 21, 2003
Byrd et al.
2
2
chloroform-d): δ 209.53 (trans CO, aq, | J (PC) + J (P′C)| )
(chloroform-d): δ 7.17-7.40 (m, 16H, Ar), 3.54 (aq, 6H, CH3,
2
3
41 Hz), 204.81 (cis CO, t, | J (PC)| ) 13 Hz), 149.71 (aq, C1,
| J (PH) + 5J (P′H)| ) 7 Hz). IR: νCO (cm-1) 2027 (s), 1929 (sh),
2
4
| J (PC) + J (P′C)| ) 11 Hz), 122.85 (bs, C2), 126.84 (s, C3,),
1910 (s).
129.93 (s, C4), 130.64 (s, C5), 130.57 (s, C6). 1H NMR (aromatic
The crude 5 was purified by recrystallization from a dichlo-
romethane/hexanes mixture to give analytically pure 5 as a
white powder. Anal. Calcd for C35H35NO10P2Mo: C, 53.37; H,
4.49; N, 1.78. Found: C, 53.21; H, 4.54; N, 1.81. 31P{1H} NMR
3
carbons, chloroform-d): δ 7.16 (bdd, H2, | J (HH)| ) 8 Hz,
4
3
3
| J (HH)| ) 2 Hz), 7.28 (bddd, H3, | J (HH)| ) | J (HH)| ) 8 Hz,
4
3
3
| J (HH)| ) 2 Hz), 7.34 (ddd, H4, | J (HH)| ) | J (HH)| ) 8 Hz,
4
3
4
2
| J (HH)| ) 2 Hz), 7.45 (dd, H5, | J (HH)| ) 8 Hz, | J (HH)| ) 2
(chloroform-d): δ 179.02 (d, POCH3, | J (PP)| ) 51 Hz), 160.20
Hz). IR: νCO (cm-1) 2055 (s), 1975 (sh) 1947 (s).
2
1
(d, PO-, | J (PP)| ) 51 Hz). H NMR (chloroform-d): δ 7.00-
2
cis-Mo(CO)4(2,2′-C12H8O2P NHCH2CH2CH3)2 (2) an d [CH3-
CH2CH2NH3] [cis-Mo(CO)4(2,2′-C12H8O2P NHCH2CH2CH3)-
(2,2′-C12H8O2P O)] (3). Excess n-propylamine (2.0 mL), which
had been distilled from KOH, was added via cannula transfer
to a solution of 0.50 g (0.71 mmol) of 1 in 10 mL of dry THF.
The mixture was stirred at room temperature over the
weekend and then was filtered to remove the n-propylammo-
nium chloride. The solution was rotary evaporated to dryness,
leaving a white solid. The solid was stirred in hot hexanes
overnight to completely separate compound 2 (soluble) from
compound 3 (insoluble) and then filtered. The filtrate was
evaporated to dryness to yield 0.27 g (51%) of crude 2. The
hexanes-insoluble solid was washed with hexanes and dried
under vacuum to yield 0.081 g (15%) of crude 3.
7.54 (m, 16H, Ar), 3.59 (d, 3H, OCH3, | J (PH)| ) 11 Hz), 2.61
3
3
(q, 6H, NCH2, | J (HH)| ) 7 Hz), 0.929 (t, 9H, CH3, | J (HH)| )
7 Hz).
cis-Mo(CO)4{2,2′-C12H8O2P SC6H4-4-CH3}2 (6). A solution
of 0.15 g (1.4 mmol) of dry thiocresol in 10 mL of THF was
added via cannula transfer to a solution of 0.50 g (0.71 mmol)
of 1 in 10 mL of dry THF. Next, 2.0 mL of dry triethylamine
was added via cannula transfer. The mixture was stirred at
room temperature overnight and then filtered to remove the
triethylammonium chloride precipitate. The filtrate was evapo-
rated to dryness, and the white solid residue was stirred in
hot hexanes overnight. The insoluble portion of the solid was
removed by filtration, and the filtrate was evaporated to
dryness to yield 0.13 g (21%) of crude 6. The crude 6 was
purified by recrystallization from a dichloromethane/hexanes
mixture to give analytically pure 6 as a white solid. Anal. Calcd
for C42H30O8P2S2Mo: C, 57.01; H, 3.42. Found: C, 57.16; H,
3.48. 31P{1H} NMR (chloroform-d): δ 213.29 (s). 13C{1H} NMR
The crude 2 was purified by recrystallization from a dichlo-
romethane/hexanes mixture to give analytically pure 2 as
colorless crystals. Anal. Calcd for C34H32N2O8P2Mo: C, 54.12;
H, 4.27; N, 3.71. Found: C, 54.17; H, 4.24; N, 3.66. 31P{1H}
NMR (chloroform-d): δ 175.71 (s). 13C{1H} NMR (carbonyl,
aromatic and aliphatic carbons, chloroform-d): δ 210.82 (trans
2
(carbonyl, chloroform-d): δ 213.12 (trans CO, aqueous, | J (PC)
2
2
1
+ J (P′C)| ) 35 Hz), 207.55 (cis CO, t, | J (PC)| ) 12 Hz). H
NMR (chloroform-d): δ 6.80-7.40 (m, 24H, Ar), 2.23 (s, 6H,
CH3).
CO, aq, | J (PC) + 2J (P′C)| ) 27 Hz), 206.33 (cis CO, t, | J (PC)|
2
2
2
4
) 13 Hz), 149.83 (aq, C1, | J (PC) + J (P′C)| ) 9 Hz), 121.28
(s, C2), 124.15 (s, C3,), 128.24 (s, C4), 128.77 (s, C5), 129.37
31P {1H} NMR Stu d ies of th e Rea ction of 1 w ith n -
P r op yla m in e. A 0.028 M solution of 1 in tetrahydrofuran-d8
was prepared in an NMR tube, and its 31P{1H} NMR spectrum
was taken. Then, a 2.5-fold excess of n-propylamine was added
to the NMR tube, and NMR spectra were taken at intervals
until the 31P NMR resonance of 1 had disappeared. The NMR
temperature was 298 K.
X-r a y Da ta Collection a n d Solu tion . Suitable single
crystals of 1-4 were mounted on glass fibers with epoxy
cement and aligned upon an Enraf-Nonius CAD4 single-crystal
diffractometer under aerobic conditions. Standard peak search
and automatic indexing routines followed by least-squares fits
of 25 accurately centered reflections resulted in accurate unit
cell parameters. The space groups of the crystals were assigned
on the basis of systematic absences and intensity statistics.
All data collection was carried out using the CAD4-PC
software,25 and details of the data collections are given in Table
1. The analytical scattering factors of the complex were
corrected for both ∆f ′ and i∆f ′′ components of anomalous
dispersion. All data were corrected for the effects of absorption
and for Lorentz and polarization effects.
All crystallographic calculations were performed with the
Siemens SHELXTL-PC program package.26 The Mo and P
positions were located using the Patterson method and the
remainder of the non-hydrogen atoms was located in difference
Fourier maps. Full-matrix refinement of the positional and
anisotropic thermal parameters for all non-hydrogen atoms
versus F2 was carried out. All hydrogen atoms were placed in
calculated positions with the appropriate molecular geometry
and d(C-H) ) 0.96 Å. The isotropic thermal parameter
associated with each hydrogen atom was fixed equal to 1.2
times the Ueq value of the atom to which it was bound. The
correct enantiomer for 1 was chosen on the basis of its Flack
parameter. Selected bond lengths for complexes 1-4 are given
in Table 2, selected bond angles for complexes 1-4 are given
1
(s, C6), 42.63 (s, CH2), 24.10 (s, CH2) 9.89 (s, CH3). H NMR
(chloroform-d): δ 7.18-7.44 (m, 16H, Ar), 3.57 (m, 2H, NH),
3
2.59 (m, 4H, NHCH2) 1.24 (tq, 4H, CH2CH3, | J (HH)| )
3
3
| J (HH)| ) 7 Hz)), 0.64 (t, 6H, CH3, | J (HH)| ) 7 Hz). IR: νCO
(cm-1) 2036 (s), 1943 (sh), 1918 (s).
The crude 3 was purified by recrystallization from a dichlo-
romethane/hexanes mixture to give analytically pure 3 as
colorless crystals. Anal. Calcd for C34H34N2O9P2Mo: C, 52.29;
H, 4.19; N, 3.63. Found: C, 52.46; H, 4.47; N, 3.70. 31P{1H}
2
NMR (chloroform-d): δ 175.97 (d, PN, | J (PP)| ) 43 Hz), 165.61
(d, PO-, | J (PP)| ) 43 Hz). H NMR (chloroform-d): δ 7.23-
7.50 (m, 16H, Ar), 2.52 (M, 2H, NHCH2), 2.24 (m, 2H,
NH2CH2), 1.35 (m, 2H, CH2CH3), 1.18 (m, 2H, CH2CH3), 0.67
2
1
3
3
(t, 3H, CH3, | J (HH)| ) 7 Hz), 0.61 (t, 3H, CH3, | J (HH)| ) 7
Hz). IR: νCO (cm-1) 2022 (s), 1924 (sh), 1900 (s).
cis-Mo(CO)4(2,2′-C12H8O2P OCH3)2 (4) a n d [(C2H5)3NH]-
[cis-Mo(CO)4(2,2′-C12H8O2P OCH3)(2,2′-C12H8O2P O)] (5). A
mixture of 3.0 mL of methanol and 2.0 mL of triethylamine
was added via cannula transfer to a solution of 0.50 g (0.71
mmol) of 1 in 10 mL of dry THF. The mixture was stirred at
room temperature overnight and then was filtered to remove
the triethylammonium chloride precipitate. The filtrate was
evaporated to dryness to yield a white solid residue. The solid
was stirred in hot hexanes overnight to completely separate
compound 4 (soluble) from compound 5 (insoluble) and then
filtered. The filtrate was evaporated to dryness to yield 0.40 g
(81%) of crude 4. The hexanes-insoluble solid was washed with
hexanes and dried under high vacuum to yield 0.069 g (12%)
of crude 5.
The crude 4 was purified by recrystallization from a dichlo-
romethane/hexanes mixture to give analytically pure 4 as
colorless crystals. Anal. Calcd for C30H22O10P2Mo: C, 51.48;
H, 3.14. Found: C, 51.36; H, 3.43. 31P{1H} NMR (chloroform-
d): δ 173.04 (s). 13C{1H} NMR (carbonyl, aromatic, and
aliphatic carbons, chloroform-d): δ 209.80 (trans CO, aq,
2
2
2
| J (PC) + J (P′C)| ) 33 Hz), 205.23 (cis CO, t, | J (PC)| ) 14
(25) CAD4-PC Version 1.2; Enraf-Nonius, Delft, The Netherlands,
1988.
(26) Sheldrick, G. M. SHELXTL NT version 5.10; Bruker AXS,
Madison, WI, 1999.
Hz), 148.83 (aq, C1, | J (PC) + 4J (P′C)| ) 9 Hz), 121.11 (s, C2),
2
124.40 (s, C3), 128.36 (s, C4), 129.03 (s, C5), 127.25 (s, C6),
53.17 (aqueous CH3, | J (PC) + 4J (P′C)| ) 8 Hz). 1H NMR
2

Nucleophilic Displacement Reactions
Organometallics, Vol. 22, No. 21, 2003 4201
Ta ble 1. Exp er im en ta l Da ta of Cr ysta llogr a p h ic
Stu d ies of Com p ou n d s 1-4
1
2
3
4
formula
C
28H16Cl2-
MoO8P2
C
34H32Mo-
N2O8P2
C
34H34Mo-
N2O9P2
C
30H22Mo-
O
10P2
mol wt
space group
a (Å)
b (Å)
c (Å)
709.19
P212121
12.258(3)
13.050(3)
18.478(4)
90
90
90
4
1.594
0, 13
-1, 14
-19, 0
754.50
P1h
772.51
P1h
700.36
P21/n
8.6520(17)
18.725(4)
19.165(4)
90
100.45(3)
90
4
1.523
-9, 9
-20, 0
-1, 20
10.586(2)
13.129(3)
13.309(3)
78.87(3)
67.79(3)
81.41(3)
2
10.765(2)
12.138(2)
15.511(3)
91.91(3)
103.86(3)
114.31(3)
2
R (deg)
â (deg)
γ (deg)
Z
d
h
k
calcd (g/cm3)
max, hmin
max, kmin
1.496
1.447
-11, 11
-14, 1
14, 14
-10, 11
-13, 1
l
max, lmin
-16, 16
2θ limits (deg) 1.91-22.46 2.09-22.47 2.14-22.48 2.16-22.47
no. of rflns
measd
2391
5054
5416
4409
no. of indep
rflns measd
Rint (%)
scan type
abs cor
2359
4360
4624
3983
2.54
2.13
3.96
4.06
F igu r e 3. Reaction scheme for the nucleophilic substitu-
tion reactions. All reactions were carried out at room
temperature in dry THF with dry triethylamine or propyl-
amine as a base.
ω-2θ
none
0.781
ω-2θ
empirical
0.541
ω-2θ
empirical
0.515
ω-2θ
none
0.590
abs coeff
(mm-1
)
no. of variables 371
435
437
391
extinction coeff 0.0055(3)
0.0202(10) 0.0004(4)
0.0015(2)
5.11 (2σ)
10.46 (2σ)
0.990
Ta ble 4. Selected Tor sion An gles (d eg) a n d Th eir
R, %
Rw, %
GOF
3.14 (2σ)
7.17 (2σ)
1.073
3.08 (2σ)
7.91 (2σ)
1.106
4.35 (2σ)
10.58 (2σ)
1.042
Esd s for Com p ou n d s 1-4
1
2
3
4
C6-C1-O1-P1
C7-C12-O2-P1
C18-C13-O3-P2
C19-C24-O4-P2
P1-Mo-P2-X
-75.3(7)
-73.7(8)
73.6(8)
67.8(9)
152.41(12) 12.69(14)
78.1(3)
72.3(4)
74.6(3)
74.3(3)
70.5(6) 73.9(9)
81.4(6) 70.19(9)
75.8(6) 72.2(9)
78.1(6) 75.9(9)
6.4(2) 87.4(3)
Ta ble 2. Selected Bon d Dista n ces (Å) w ith Th eir
Esd s for Com p ou n d s 1-4
1
2
3
4
Mo-P1
Mo-P2
X-P1
2.406(2)
2.4048(19)
2.059(3)
2.056(3)
1.614(5)
1.595(5)
1.621(5)
1.602(5)
2.006(9)
2.030(9)
2.071(9)
2.048(9)
1.134(10)
1.134(9)
1.131(9)
1.173(10)
2.4610(11)
2.4671(12)
1.617(4)
1.631(3)
1.632(2)
1.643(2)
1.635(2)
1.633(2)
2.018(4)
2.005(4)
2.040(4)
2.024(4)
1.135(4)
1.131(4)
1.140(4)
1.143(4)
2.4670(18)
2.4460(17)
1.513(4)
1.638(5)
1.664(4)
1.652(4)
1.634(4)
1.639(4)
1.988(8)
1.976(7)
1.995(8)
2.050(8)
1.155(8)
1.156(7)
1.153(8)
1.128(7)
2.444(2)
2.432(2)
1.575(5)
1.591(7)
1.622(5)
1.613(5)
1.592(5)
1.624(6)
1.132(9)
1.997(10)
2.028(9)
2.027(8)
1.132(9)
1.152(9)
1.137(9)
1.133(8)
P2-Mo-P1-X
-77.44(11) 98.19(17) 164.8(2) 83.5(3)
in Figure 2. The 31P{1H} NMR spectrum of the hexanes-
insoluble product contained a single resonance at 192.45
ppm due to 1 and did not exhibit a resonance at 179.89
ppm that would have indicated the presence of unre-
acted free ligand of the product. The fact that a single,
sharp 31P NMR resonance is observed for 1 suggests
that the diastereomers of the complex are interconvert-
ing rapidly at ambient temperature.
Nu cleop h ilic Disp la cem en t Rea ction s of th e
Ch lor id e Gr ou p s in 1. The general reaction scheme
for the nucleophilic displacement reactions is shown in
Figure 3. The starting material, 1, was reacted with a
stoichiometric amount of dry triethylamine and of the
dried and purified nucleophile in dry THF, except when
the nucleophile was n-propylamine, where only an
excess of the n-propylamine was used.27 Two products
were observed for each reaction. In each case, the two
products were readily separated, due to the fact that
only the major product was soluble in hot hexanes. It
should be noted that NMR studies indicate that these
nucleophilic substitution reactions are complete after
90 min. They were typically set up to run overnight or
over the weekend as a matter of convenience.
X-P2
O1-P1
O2-P1
O3-P2
O4-P2
C25-Mo
C26-Mo
C27-Mo
C28-Mo
C25-O5
C26-O6
C27-O7
C28-O8
Ta ble 3. Selected Bon d An gles (d eg) w ith Th eir
Esd s for Com p ou n d s 1-4
1
2
3
4
C25-Mo-C26
C25-Mo-C27
C25-Mo-C28
C26-Mo-C27
C26-Mo-C28
C27-Mo-C28
C25-Mo-P1
C25-Mo-P2
C26-Mo-P1
C26-Mo-P2
C27-Mo-P1
C27-Mo-P2
C28-Mo-P1
C28-Mo-P2
P1-Mo-P2
90.5(4)
89.3(4)
91.0(4)
89.9(4)
90.3(4)
179.6(4)
179.3(3)
91.5(3)
88.8(2)
174.9(3)
90.7(2)
85.4(2)
89.0(2)
94.4(3)
89.23(7)
89.60(15)
85.62(14)
85.36(14)
92.38(15)
87.79(14)
170.97(13)
175.43(10)
89.58(10)
85.94(11)
177.26(11)
93.60(11)
90.17(11)
95.42(10)
89.54(10)
94.93(4)
86.6(3)
91.1(3)
92.6(3)
93.0(3)
93.2(3)
172.9(3)
170.93(18)
91.00(18)
84.6(2)
177.4(2)
91.6(2)
88.05(19)
85.7(2)
85.83(19)
97.74(6)
90.7(3)
90.8(3)
91.2(3)
88.2(3)
88.5(3)
176.2(4)
176.4(2)
89.2(2)
92.9(3)
177.5(2)
89.0(2)
94.3(3)
89.2(2)
89.0(2)
87.23(8)
The assignments of the products were made on the
basis of their 31P{1H} NMR spectra and were confirmed
by elemental analyses. The major and expected product
was one in which both chloride groups were displaced
by the nucleophile. The 31P{1H} NMR resonances of
these complexes are singlets due to the equivalent
in Table 3, and selected torsion angles for complexes 1-4 are
given in Table 4.
Resu lts a n d Discu ssion
(27) THF and triethylamine were dried over Na-benzophenone and
were not used until a deep purple color was observed for at least 24 h.
Propylamine was first placed over KOH for 24 h and then refluxed
and distilled from CaH2.
Syn t h esis of cis-Mo(CO)4(2,2′-C12H 8O2P Cl)2 (1).
The reaction scheme for the preparation of 1 is shown

4202 Organometallics, Vol. 22, No. 21, 2003
Byrd et al.
chemical environments of the phosphorus nuclei. The
minor products were those in which one chloride group
had been replaced by the nucleophile and the other
chloride group had been replaced by a hydroxy group.
The 31P{1H} NMR resonances of these complexes are
two doublets, due to the inequivalent chemical environ-
ments of the phosphorus nuclei.
It was somewhat surprising that two products were
obtained from these reactions, because previous reac-
tions of similarly dried nucleophiles with the related
complex cis-Mo(CO)4(Ph2PCl)2 have not been observed
to yield hydrolysis products.11,12 This suggests that 1 is
particularly susceptible to hydrolysis and that only very
small amounts of water are required for hydrolysis to
occur.
To better understand the unexpected formation of the
hydrolysis products, the reactions of 1 with excesses of
“dry”27 and “wet”28 n-propylamine were followed by 31P-
{1H} NMR spectroscopy. Selected NMR spectra for the
reaction of 1 with “dry” n-propylamine are shown in
Figure 4. The 31P{1H} NMR resonances of the hydrolysis
product, 3 (doublets at 180.62 and 169.27 ppm), were
observed first, apparently from residual water in the
“dry” n-propylamine and tetrahydrofuran-d8. The for-
mation of 3 was completed after 10 min, and then the
31P{1H} NMR resonance of the disubstitution product,
2 (singlet at 183.27 ppm), began to appear. The disub-
stitution reaction was completed after 90 min. The
amount of the hydrolysis product does not change
during the formation of the disubstituted product, which
suggests that the two products are formed by different
mechanisms.
The reaction of 1 with “wet” n-propylamine was
similar to that of 1 with “dry” n-propylamine. The
hydrolysis product, 3, was observed after 5 min, while
the 31P NMR resonance of the disubstitution product,
2, did not appear until after 15 min. The major product
was 3 (91% from integration of the 31P{1H} NMR
1
resonances), although a H NMR spectrum of the “wet”
n-propylamine showed that less than 5% water was
present in the “wet” n-propylamine. These spectra
clearly indicate that the reaction to form the hydrolysis
product, 3, is significantly more rapid than is the
reaction to form the disubstitution product, 2, and that
the products of the two reactions do not interconvert.
F igu r e 4. 31P NMR of the reaction of cis-Mo(CO)4(2,2′-
C
12H8O2PCl)2 (compound 1) with “dry” propylamine. Spec-
tra were taken at various timed intervals. The two doublets
at 180.62 and 169.27 ppm are assigned to the hydrolysis
product, compound 3. The singlet at 183.27 ppm is assigned
to the disubstituted propylamine, compound 2. The arrows
(a) indicate the formation of resonances due to the inter-
mediate species. Both resonances disappear by the end of
the reaction.
Small resonances due to a monosubstituted interme-
diate (doublet at 197.57 ppm partially obscured by the
2
resonance of 1; doublet at 180.43 ppm, | J (PP′)| ) 44
Hz) are observed in the 31P{1H} NMR spectra of both
the “dry” and “wet” reaction mixtures. The chemical
shifts of the 31P{1H} NMR resonances of the intermedi-
ate suggest that it is cis-Mo(CO)4(2,2′-C12H8O2PNHPrn)-
(2,2′-C12H8O2PCl). This is consistent with n-propylamine
both being a better nucleophile and having a much
higher concentration than the water.
significantly more rapidly than does the substitution of
a chloride in 1 by n-propylamine. The more rapid
reaction of the intermediate with water explains why
the concentration of the intermediate is lower in the
reaction with “wet” n-propylamine than in the reaction
with “dry” n-propylamine. Additional studies will be
needed to determine the mechanism that gives rise to
the more rapid nucleophilic substitution reactions of the
intermediate complex, but it seems likely that this will
involve interactions between the 2-(n-propylamino)-
1,3,2-dioxaphosphepin ligand and the incoming nucleo-
phile and possibly with the adjacent 2-chloro-1,3,2-
dioxaphosphephin ligand.
The low concentration of the intermediate in each
reaction and the observation that the intensities of both
of the doublets 3 increase at the same rate suggests that
the substitution of the chloride in the monosubstituted
intermediate by either water or n-propylamine occurs
(28) n-Propylamine was used without drying. A 1H NMR spectrum
of n-propylamine in chloroform-d gave the expected integration for the
four n-propylamine resonances (2:2:2:3), indicating that only a small
amount of water (<5%) was present.

Nucleophilic Displacement Reactions
Organometallics, Vol. 22, No. 21, 2003 4203
F igu r e 7. ORTEP drawing of the molecular structure of
the major conformer of 3. Thermal ellipsoids are drawn at
the 25% probability level, and hydrogen atoms are omitted
for clarity. Hydrogen bonding is shown by the dotted line.
F igu r e 5. ORTEP drawing of the molecular structure of
the major conformer of 1. Thermal ellipsoids are drawn at
the 25% probability level, and hydrogen atoms are omitted
for clarity.
the heteroatom bound to the phosphorus. Similar trends
in 31P NMR chemical shifts of the [1,3,2]dioxaphospho-
rinane ligands in Mo(CO)5{RXP(OCH2CMe2CH2O)} and
Mo(CO)5{RXP(OCH2CH2CHMeO)} complexes have pre-
viously been observed, but not in the 31P NMR chemical
shifts of Ph2PXR ligands in Mo(CO)5(Ph2PXR) and cis-
Mo(CO)4(Ph2PXR)2 complexes.19,20
Each of the disubstituted complexes, 1, 2, 4, and 6,
exhibits a 31P{1H} NMR resonance that is a sharp
singlet. This indicates either that only the R*S* con-
formation is present in solution or that the R* and S*
conformations32 of the rings are rapidly interconverting
in solution. The second explanation seems most likely
on the basis of previous work1 and because both R*S*
and R*R*/S*S* conformations are found in the solid-
state conformations of the complexes.
All of the resonances of the carbons and hydrogens
in 1 have been assigned using 2D NMR spectroscopy.
A 1H-1H COSY-45 NMR experiment was run to deter-
1
1
mine the H-1H coupling, and the H-13C connectivity
was determined using a 1H{13C} HMBC NMR experi-
ment. 1H{13C} HMQC was used to assign protons to
their respective carbons. For compounds 2 and 4, the
13C NMR spectra in the aromatic region are similar to
that of 1, and the assignment has been made in a
F igu r e 6. ORTEP drawing of the molecular structure of
the major conformer of 2. Thermal ellipsoids are drawn at
the 25% probability level, and hydrogen atoms are omitted
for clarity. Hydrogen bonding is shown by the dotted line.
NMR Spectr oscopic Ch ar acter ization of th e Com -
p lexes. The chemical shifts of 13C{1H} NMR resonances
and the magnitudes of the C-P coupling constants of
the CO ligands are consistent with the [1,3,2]dioxaphos-
phepin ligands being oriented in a cis geometry. The
13C{1H} NMR resonances for the carbonyls cis to both
[1,3,2]dioxaphosphepin ligands (cis-CO) are observed
between 204 and 208 ppm. Each resonance is a triplet
1
consistent fashion. The H NMR spectra of 2 and 4 in
the aromatic region are less clearly defined, and no
attempt has been made to assign the aromatic 1H
resonances of these complexes.
X-r a y Cr yst a l St r u ct u r es for Com p ou n d s 1-4.
The molecular structures of 1-4 have been determined
and are shown in Figures 5-8, respectively. The coor-
dination environment of the molybdenum in each com-
plex is a slightly distorted octahedron. The distortion
seems to be dictated by the position of the nucleophile
(XR). For compounds 1 and 4, the XR groups are
2
with | J (PC)| between 12 and 14 Hz. The 13C{1H} NMR
resonances of the carbonyls trans to one of the phos-
phepin ligands (trans-CO) are farther downfield be-
tween 209 and 213 ppm. Each of these resonances is
an apparent quintet (A portion of an AXX′ spin sys-
2
2
tem29) with a | J (PC) + J (P′C)| value between 27 and
(29) Redfield, D. A.; Nelson, J . H.; Cary, L. W. Inorg. Nucl. Chem.
Lett. 1974, 10, 727.
(30) Pregosin, P. S.; Kunz, R. W. NMR Basic Princ. Prog. 1979, 16,
47.
(31) Gorenstein, D. G. Phosphorus-31 NMR, Principles and Applica-
tions; Academic Press: New York, 1984; pp 7-8.
(32) Throughout this paper, R* and S* are used to refer to the
relative conformations of the 2,2′-biphenyl groups. The first conforma-
tion referred to in a molecule is designated R* by convention.
41 Hz.
The chemical shifts of the 31P{1H} NMR resonances
of 1, 2, 4, and 6 are extremely sensitive to the nature of
the nucleophile that is bound to the P atom.30,31 How-
ever, the chemical shift of the 31P{1H} NMR resonance
does not appear to be related to the electronegativity of

4204 Organometallics, Vol. 22, No. 21, 2003
Byrd et al.
F igu r e 8. ORTEP drawing of the molecular structure of
the major conformer of 4. Thermal ellipsoids are drawn at
the 25% probability level, and hydrogen atoms are omitted
for clarity.
Ta ble 5. P la n es Used To Defin e th e
Seven -Mem ber ed P h osp h ep in Rin gs for
Com p ou n d s 1-4
compd
space group
plane
angle
value, deg
1
P212121
1. O1-P1-O2
2. O1-C1-C6
3. O2-C12-C7
1-2
1-3
2-3
59.1
51.1
47.7
1: O3-P2-O4
2: O3-C13-C18
3: O4-C24-C19
1-2
1-3
2-3
55.8
51.1
45.2
2
3
4
P1h
1: O1-P1-O2
2: O1-C1-C6
3: O2-C12-C7
1-2
1-3
2-3
58.8
54.1
45.9
1: O3-P2-O4
2: O3-C13-C18
3: O4-C24-C19
1-2
1-3
2-3
56.6
55.3
46.0
P1h
1: O1-P1-O2
2: O1-C1-C6
3: O2-C12-C7
1-2
1-3
2-3
54.4
62.4
48.5
1: O3-P2-O4
2: O3-C13-C18
3: O4-C24-C19
1-2
1-3
2-3
57.5
60.3
47.4
P21/n
1: O1-P1-O2
2: O1-C1-C6
3: O2-C12-C7
1-2
1-3
2-3
57.0
53.7
47.0
F igu r e 9. ORTEP rendition of both enantiomers of the
phosphepin rings in 1. Thermal ellipsoids are drawn at the
50% probability level, and hydrogen atoms are omitted for
clarity.
1: O3-P2-O4
2: O3-C13-C18
3: O4-C24-C19
1-2
1-3
2-3
55.4
58.8
46.8
sponding difference in the C-O bond lengths of the
carbonyl ligands. These observations have been reported
by a number of authors, and one example is given in
ref 33.
oriented “outside” of the P1-Mo-P2 bite angle, and this
angle is slightly less than 90°. In contrast, compounds
2 and 3 have one XR group oriented “inside” of the P1-
Mo-P2 bite angle, and this angle is greater than 90°
in both complexes. The orientations of the XR groups
in 2 and 3 may be due to hydrogen bonding, although
the hydrogen bonding in the two complexes is quite
different. In 2, hydrogen bonding between the amine
proton of the n-propylamino group and one of the
oxygens of the adjacent phosphepin ring is observed. In
contrast, hydrogen bonding occurs between the am-
monium proton of the n-propylammonium cation and
the anionic phosphito oxygen in 3.
The conformations of the seven-membered phos-
phepin rings 1-4 are defined by the angles between the
least-squares planes through O1, P1, and O2 (plane 1),
through O1, C1, and C6 (plane 2) and through O2, C12,
and C7 (plane 3). These angles are summarized in Table
5 and are similar for all of the phosphepin ligands in
1-4, with the angles between plane 1 and either plane
2 or plane 3 being between 55.3 and 62.4° and the angles
between planes 2 and 3 being between 45.9 and 48.5°.
This narrow range of interplanar angles indicates that
the phosphepin rings have a strongly preferred confor-
mation that is not significantly affected by either
hydrogen-bonding or crystal-packing forces.
The carbonyls trans to the phosphepin ligands in 1-4
have shorter Mo-C bonds than do the carbonyls trans
to carbonyls. This is consistent with the phosphepin
ligands being better σ-donors and/or poorer π-acceptors
than the carbonyl ligands. However, there is no corre-
(33) Gray, G. M.; Fish, F. P.; Srivastava, D. K.; Varshney, A.; van
der Woerd, M. J .; Ealick, S. E. J . Organomet. Chem. 1990, 385, 49.

Nucleophilic Displacement Reactions
Organometallics, Vol. 22, No. 21, 2003 4205
The most interesting aspect of the conformation of the
phosphepin ligands in 1-4 is that the twist of the 2,2′-
biphenoxy groups causes each of the ligands to be chiral
and the complexes, which contain two ligands, to be
diastereomeric. Figure 9 shows a rendition of both
enantiomers of the phosphepin rings in 1. The chirality
of the ligands can be determined from the torsion angles
about the C-O bonds of the 2,2′-biphenoxy groups,
given in Table 4. The conformation of the phosphepin
ring requires the torsion angles about the two C-O
bonds to have the same sign, and the similar conforma-
tions of the phosphepin ligands requires the torsion
angles to have approximately the same magnitudes.
When both ligands in a complex have the same signs
for the C-O torsion angles, as is the case for 2-4, the
complex is the R*R*/S*S* diastereomer.32 In contrast,
when the torsion angles for the C-O bonds of the two
ligands have opposite signs, as is the case for 1, the
complex is the R*S* diastereomer. It is interesting that
complexes 2-4 crystallize in centrosymmetric space
groups with both the R*R* and S*S* enantiomers
present in the crystal while complex 1, which is the
meso diastereomer (R*S* configuration), crystallizes in
a noncentrosymmetric P212121 space group. This is
counterintuitive and demonstrates the importance of
crystal-packing forces in the determination of the space
groups of crystals. It is important to note that, because
the [1,3,2]dioxaphosphepin groups of all of the com-
plexes racemize rapidly in solution, the observation of
a particular diastereomer in the solid state does not
necessarily reflect the distribution of diastereomers in
solution.
in the presence of nitrogen bases yield both the desired
disubstituted products cis-Mo(CO)4(2,2′-C12H8O2PXR)2
and the unexpected hydrolysis products [R3NH][cis-Mo-
(CO)4(2,2′-C12H8O2PXR)(2,2′-C12H8O2PO)]. The relative
yields of the two products depend on the amount of
water that is present in reactions, with excess water
giving exclusively the hydrolysis product. Although
NMR studies indicate that the R* and S* enantiomers
of these ligands interconvert rapidly in solution, the use
of bulkier biaryl groups with fixed conformations should
allow the generation of unique diastereomeric com-
plexes. The ability to cleanly generate the hydrolysis
product should allow diastereomeric complexes with
chemically inequivalent phosphepin ligands to be pre-
pared in high yields. The use of the appropriate nucleo-
philes will allow the ligands to interact via hydrogen-
bonding interactions, which could generate further
asymmetry in the complexes in both the solution and
solid states.
Ack n ow led gm en t. We thank the NSF-REU Sum-
mer Research Program (Grant No. CHE-9820282) at
UAB for funding of part of this research. J .M.B. thanks
the Chemistry Department of the University of Alabama
at Birmingham for a graduate teaching assistantship.
H.B. thanks the University of Montevallo for a sabbati-
cal semester.
Su p p or tin g In for m a tion Ava ila ble: Tables giving ex-
perimental data for the crystallographic studies, bond dis-
tances, bond angles, positional parameters, anisotropic ther-
mal coordinates, and hydrogen atom coordinates for compounds
1-4. This material is available free of charge via the Internet
at http://pubs.acs.org.
Con clu sion s
The reactions of cis-Mo(CO)4(2,2′-C12H8O2PCl)2 (1)
with HXR (X ) NH, O, S; R ) alkyl, aryl) nucleophiles
OM030411Z