Complexes from ring opening of Lawesson's Reagent and phosphorus-phosphorus coupling

Article abstract of DOI:10.1021/om020933z

At ambient temperature the reaction of [CpCr(CO)₃]₂ (1; Cp = η⁵-C₅H₅) with 1 mol equiv of Lawesson's reagent, Ar₂P₂S₄ (2; Ar = C₆H₄OCH₃), for 3 h led to the isolation of brown crystals of Cp₂Cr₂(CO)₅(SPAr) (3), dark red solids of Cp₂Cr₂(CO)₅(S₂PAr) (4), deep blue solids of Cp₂Cr₂(S₂P(O)Ar)₂ (5), greenish yellow solids of CpCr(CO)₃H (9), and deep green crystals of Cp₂Cr₂(CO)₄S (10) with yields of 5, 11, 20, 7, and 8%, respectively; a similar reaction at 90°C for 2 h gave 5 (36%), CpCr(CO)₂(SP(H)Ar) (6) as red crystals (9%), [CpCr(CO)₂(SPAr)]₂ (cis-7) as dark brown crystalline solids (14%), and its isomer trans-7 as dark red crystals (5%), together with 9 (4%) and 10 (11%). The ambient-temperature reaction of [Cp*Cr(CO)₃]₂ (1*; Cp* = η⁵-C₅Me₅) yielded the Cp* analogues of 4, 5, 9, and 10, i.e., 4*, 5*, 9*, and 10* with yields of 51, 17, 6, and 8%, respectively. The thermolysis of Cp*₂Cr₂(CO)₅(S₂PAr) (4*) resulted in the isolation of Cp*Cr(CO)₂(SP(H)Ar) (6*), Cp*₂Cr₂(CO)₄(SPAr) (8*), and Cp*₂-Cr₂(S₂P(O)Ar)₂ (5*) with yields of 7, 14, and 13%, respectively. A NMR spectral study demonstrated that thermolytic degradation of complex 3 or its reaction with sulfur or Lawesson's reagent (2) led to the formation of cis-7; cis- and trans-7 were found to interconvert under elevated temperatures, giving 4:1 equilibrium mixtures at 80°C both isomers react with 1 to re-form 3. The solid-state structures of all the above-mentioned complexes have been characterized by single-crystal X-ray diffraction analysis. Complexes 3 and 8* contain the phosphinothioylidene ligand in different coordination modes. The analogous structures of complexes 4/4* reveal a bridging dithiophosphorane ligand, being η²(S,S′) coordinated to a Cp/Cp*Cr(CO)₂ moiety and η¹(P) coordinated to a Cp/Cp*Cr(CO)₃ moiety. The similar molecular structures of 5 and 5* contain an eight-membered ring, comprising two CpCr/ Cp*Cr units and two [S₂P(O)Ar] moieties. Complexes 6/6* contain a rare η²-arylthioxophosphane ligand. The complexes cis- and trans-7 are conformers of a P-P-bonded dimer.

Full text of DOI:10.1021/om020933z

Organometallics 2003, 22, 1645-1656
1645
Com p lexes fr om Rin g Op en in g of La w esson ’s Rea gen t
a n d P h osp h or u s-P h osp h or u s Cou p lin g
Zhiqiang Weng, Weng Kee Leong, J agadese J . Vittal, and Lai Yoong Goh*
Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 119260
Received November 12, 2002
At ambient temperature the reaction of [CpCr(CO)3]2 (1; Cp ) η5-C5H5) with 1 mol equiv
of Lawesson’s reagent, Ar2P2S4 (2; Ar ) C6H4OCH3), for 3 h led to the isolation of brown
crystals of Cp2Cr2(CO)5(SPAr) (3), dark red solids of Cp2Cr2(CO)5(S2PAr) (4), deep blue solids
of Cp2Cr2(S2P(O)Ar)2 (5), greenish yellow solids of CpCr(CO)3H (9), and deep green crystals
of Cp2Cr2(CO)4S (10) with yields of 5, 11, 20, 7, and 8%, respectively; a similar reaction at
90 °C for 2 h gave 5 (36%), CpCr(CO)2(SP(H)Ar) (6) as red crystals (9%), [CpCr(CO)2(SPAr)]2
(cis-7) as dark brown crystalline solids (14%), and its isomer trans-7 as dark red crystals
(5%), together with 9 (4%) and 10 (11%). The ambient-temperature reaction of [Cp*Cr(CO)3]2
(1*; Cp* ) η5-C5Me5) yielded the Cp* analogues of 4, 5, 9, and 10, i.e., 4*, 5*, 9*, and 10*
with yields of 51, 17, 6, and 8%, respectively. The thermolysis of Cp*2Cr2(CO)5(S2PAr) (4*)
resulted in the isolation of Cp*Cr(CO)2(SP(H)Ar) (6*), Cp*2Cr2(CO)4(SPAr) (8*), and Cp*2-
Cr2(S2P(O)Ar)2 (5*) with yields of 7, 14, and 13%, respectively. A NMR spectral study
demonstrated that thermolytic degradation of complex 3 or its reaction with sulfur or
Lawesson’s reagent (2) led to the formation of cis-7; cis- and trans-7 were found to interconvert
under elevated temperatures, giving 4:1 equilibrium mixtures at 80 °C; both isomers react
with 1 to re-form 3. The solid-state structures of all the above-mentioned complexes have
been characterized by single-crystal X-ray diffraction analysis. Complexes 3 and 8* contain
the phosphinothioylidene ligand in different coordination modes. The analogous structures
of complexes 4/4* reveal a bridging dithiophosphorane ligand, being η2(S,S′) coordinated to
a Cp/Cp*Cr(CO)2 moiety and η1(P) coordinated to a Cp/Cp*Cr(CO)3 moiety. The similar
molecular structures of 5 and 5* contain an eight-membered ring, comprising two CpCr/
Cp*Cr units and two [S2P(O)Ar] moieties. Complexes 6/6* contain a rare η2-arylthioxophos-
phane ligand. The complexes cis- and trans-7 are conformers of a P-P-bonded dimer.
In tr od u ction
complexes M[N(SiMe3)2]2, M(ButNCH2CH2NBut), and
M[(SPAr)2]2 (M ) Ge, Sn).2h In these reactions, the
metal center has coordinated to fragments from Lawes-
son’s reagent as shown in Chart 1.
Lawesson’s reagent, (p-methoxyphenyl)thionophos-
phine sulfide (2), is an efficient S-donor agent for the
conversion of carbonyl to thiocarbonyl compounds.1
In the context of our interest in the chemistry of
[CpCr(CO)3]2 (1) with S- and/or P-containing com-
pounds, we have chosen to investigate the reactivity of
1 toward the P2S4 central ring component of 2. To date,
we have studied 1-initiated interchalcogen cleavage in
a variety of systems, viz. in homopolynuclear inorganic
compounds,3 in organic substrates, e.g. Ph2E2 (E ) S,
Se, Te),4 in bis(phosphorodithioato)disulfanes, (R2P-
Although thionation reactions of Lawesson’s reagent
toward organic substrates are well-documented, its
reactivity with transition-metal compounds has so far
been little studied. We found in the literature only a
limited number of reactions, viz. those with (i) the
carbonyl complexes Cp2Mo2(CO)4,2a (Cp)2Ti(CO)2,2b and
Fe2(CO)9,2c (ii) the group 10 compounds MCl2,2d K2-
MCl4,2d and (PR3)2MCl2 (M ) Ni, Pd, Pt),2e Pt(C2H4)-
(PPH3)2,2f and NiCl2 in the presence of 1,3-dialkylimi-
dazolidine-2-thione-4,5-dione,2g and (iii) the group 14
(2) (a) Alper, H.; Einstein, F. W. B.; Petrignani, J .-F.; Willis, A. C.
Organometallics 1983, 2, 1422. (b) Zank, G. A.; Rauchfuss, T. B.
Organometallics 1984, 3, 1191. (c) Kruger, G. J .; Lotz, S.; Linford, L.;
Dyk, M. V.; Raubenheimer, H. G. J . Organomet. Chem. 1985, 280, 241.
(d) Aragoni, M. C.; Arca, M.; Demartin, F.; Devillanova, F. A.; Graiff,
C.; Isaia, F.; Lippolis, V.; Tiripicchio, A.; Verani, G. Eur. J . Inorg. Chem.
2000, 2239. (e) Wood, P. T.; Woollins, J . D. Transition Met. Chem. 1987,
12, 403. (f) J ones, R.; Williams, D. J .; Wood, P. T.; Woollins, J . D.
Polyhedron 1987, 6, 539. (g) Arca, M.; Cornia, A.; Devillanova, F. A.;
Fabretti, A. C.; Isaia, F.; Lippolis, V.; Verani, G. Inorg. Chim. Acta
1997, 262, 81. (h) Carmalt, C. J .; Clyburne, J . A. C.; Cowley, A. H.;
Lomeli, V.; McBurnett, B. G. Chem. Commun. 1998, 243.
(3) Goh, L. Y. Coord. Chem. Rev. 1999, 185-186, 257 and references
therein.
* To whom correspondence should be addressed. E-mail: chmgohly@
nus.edu.sg.
(4) (a) Goh, L. Y.; Tay, M. S.; Mak, T. C. W.; Wang, R.-J . Organo-
metallics 1992, 11, 1711. (b) Goh, L. Y.; Tay, M. S.; Lim, Y. Y.; Mak,
T. C. W.; Zhou, Z.-Y J . Chem. Soc., Dalton Trans. 1992, 1239. (c) Goh,
L. Y.; Tay, M. S.; Chen, W. Organometallics 1994, 13, 1813.
(1) (a) Cheraksov, R. A.; Kutrev, G. A.; Pudovik, N. Tetrahedron
1985, 41, 2567. (b) Cava, M. P.; Levinson, M. I. Tetrahedron 1985, 41,
5061.
10.1021/om020933z CCC: $25.00 © 2003 American Chemical Society
Publication on Web 03/20/2003

1646 Organometallics, Vol. 22, No. 8, 2003
Ch a r t 1. Coor d in a tion of F r a gm en ts fr om 2a
Weng et al.
a
M ) metal fragment.
i
(S)S-)2 (R ) Ph5a and PrO,5b respectively), in teraalkyl-
thiuram disulfanes (R2NC(S)S-)2,6 and very recently in
dibenzothiazolyl disulfane, (-SCSN(C6H4))2.7a For chal-
cogen-pnicogen bond cleavage, our previous work had
dealt with the closo polyhedra P4E3 (E ) S,8a Se8b) and
the polymeric Sb2S3.8c In this present study, the four-
membered P2S2 ring with doubly bonded S substituents
on P presents a different class of S- and P-containing
substrates that we envisage will possess rich reactivity
features with 1. These are described in this paper.
a silica gel column (2 × 10 cm) prepared in n-hexane. Elution
under slight pressure gave five fractions: (i) a dark green
eluate in n-hexane/toluene (4:1, 10 mL), from which was
obtained green solids (ca. 26 mg), the 1H NMR spectra of which
indicated the presence of an approximately 1:2 molar mixture
of CpCr(CO)3H (9; estimated 7 mg, 0.03 mmol, 7% yield) and
unreacted 1 (estimated 19 mg, 0.05 mmol, 19% recovery); (ii)
a green eluate in n-hexane/toluene (1:1, 4 mL), from which
was obtained [CpCr(CO)2]2S (10) as deep green crystals (8 mg,
0.02 mmol, 8% yield); (iii) a brown eluate in toluene (5 mL),
which on concentration gave dark brown crystals of Cp2Cr2-
(CO)5(SPAr) (3; 7 mg, 0.01 mmol, 5% yield); (iv) a red eluate
in toluene (8 mL), which yielded the dark red solid Cp2-
Cr2(CO)5(S2PAr) (4; 15 mg, 0.03 mmol, 11% yield); (v) a blue
eluate in toluene/THF (1:1, 15 mL), which yielded a deep blue
solid of Cp2Cr2(S2P(O)Ar)2 (5; 34 mg, 0.05 mmol, 20%). A deep
blue band remained unmoved on the top of the column.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All reactions were carried out
using conventional Schlenk techniques under an inert atmo-
sphere of nitrogen or under argon in an M. Braun Labmaster
130 inert gas system. NMR spectra were measured on Bruker
ACF300 300 MHz FT NMR spectrometers (1H at 300.14 MHz,
13C at 75.43 MHz, and 31P at 121.49 MHz); 1H and 13C chemical
shifts were referenced to residual C6H6 in C6D6 and 31P
chemical shifts to external H3PO4. IR spectra were measured
in the range 4000-400 cm-1 on a BioRad FTS-165 FTIR
instrument. Mass spectra were obtained on a Finnigan Mat
95XL-T spectrometer. Elemental analyses were performed by
the in-house microanalytical laboratory. [CpCr(CO)3]2 (1) and
[Cp*Cr(CO)3]2 (1*) were prepared according to literature
procedures.9 Lawesson’s reagent (98% purity) was used as
supplied by Fluka Chemical Co. All solvents were dried over
sodium/benzophenone and distilled before use. Silica gel
(Merck Kieselgel 60, 230-400 mesh) was dried at 140 °C
overnight before chromatographic use.
(b) At 90 °C. A deep green mixture of [CpCr(CO)3]2 (1; 201
mg, 0.50 mmol) and 2 (202 mg, 0.50 mmol) in toluene (10 mL)
was stirred at 90 °C for 2 h. The resultant dark brown product
mixture was filtered to remove an uncharacterizable insoluble
dark green compound (ca. 20 mg). The filtrate was concen-
trated to ca. 3 mL and loaded onto a silica gel column (2 × 15
cm) prepared in n-hexane. Elution gave six fractions: (i) a
yellow eluate in n-hexane/toluene (5:1, 8 mL), from which was
obtained greenish yellow solids of CpCr(CO)3H (9; 9 mg, 0.04
mmol, 4%); (ii) a green eluate in n-hexane/toluene (2:1, 8 mL),
from which was obtained [CpCr(CO)2]2S (10; 21 mg, 0.06 mmol,
11% yield); (iii) a red eluate in toluene (10 mL), which gave
red crystals of CpCr(CO)2(SP(H)Ar) (6; 31 mg, 0.09 mmol, 9%
yield); (iv) a reddish brown eluate in toluene (15 mL), which
yielded a dark brown crystalline solid of [CpCr(CO)2(SPAr)]2
(cis-7; 48 mg, 0.07 mmol, 14% yield); (v) a red eluate in toluene
(10 mL), which on concentration yielded a dark red solid of
[CpCr(CO)2(SPAr)]2 (trans-7; 18 mg, 0.026 mmol, 5% yield);
(vi) a deep blue eluate in toluene/THF (4:1, 10 mL), which
yielded a deep blue solid of Cp2Cr2(S2P(O)Ar)2 (5; 121 mg, 0.18
mmol, 36% yield). A deep blue band remained unmoved on
the top of the column.
Rea ction of [Cp Cr (CO)3]2 (1) w ith La w esson ’s Re-
a gen t. (a ) At Am bien t Tem p er a tu r e. A deep green mixture
of [CpCr(CO)3]2 (1; 100 mg, 0.25 mmol) and Lawesson’s reagent
(2; 101 mg, 0.25 mmol) in toluene (8 mL) was stirred at
ambient temperature for 4 h. The resultant greenish brown
product mixture was concentrated to 4 mL and filtered to
remove unreacted 2 (ca. 30 mg). The filtrate was loaded onto
Rea ction of [Cp *Cr (CO)3]2 (1*) w ith La w esson ’s Re-
a gen t a t Am bien t Tem p er a tu r e. A deep purple mixture of
[Cp*Cr(CO)3]2 (1*; 135 mg, 0.25 mmol) and 2 (101 mg, 0.25
mmol) in toluene (8 mL) was stirred at ambient temperature
for 3 h. The resultant reddish brown product mixture was
filtered to remove an uncharacterizable blue compound (7 mg).
The filtrate was concentrated to 3 mL and loaded onto a silica
gel column (2 × 8 cm) prepared in n-hexane. Elution gave four
fractions: (i) a yellow eluate in n-hexane/toluene (4:1, 5 mL),
from which was obtained greenish yellow crystals of Cp*Cr-
(CO)3H10 (9*; 8 mg, 0.03 mmol, 6% yield); (ii) a green eluate
in n-hexane/toluene (2:1, 4 mL), from which was obtained dark
green crystals of Cp*2Cr2(CO)4S (10*; 10 mg, 0.02 mmol, 8%
yield); (iii) a reddish brown eluate in toluene (10 mL), which
(5) (a) Goh, L. Y.; Leong, W. K.; Leung, P. H.; Weng, Z.; Haiduc, I.
J . Organomet. Chem. 2000, 607, 64. (b) Goh, L. Y.; Weng, Z.; Leong,
W. K.; Haiduc, I.; Lo, K. M.; Wong, R. C. S. J . Organomet. Chem. 2001,
631, 67.
(6) (a) Goh, L. Y.; Weng, Z.; Leong, W. K.; Leung, P. H. Angew.
Chem., Int. Ed. 2001, 40, 3236. (b) Goh, L. Y.; Weng, Z.; Leong, W. K.;
Leung, P. H. Organometallics 2002, 21, 4398. (c) Goh, L. Y.; Weng, Z.;
Hor, T. S. A.; Leong, W. K. Organometallics 2002, 21, 4408.
(7) (a) Goh, L. Y.; Weng, Z.; Leong, W. K.; Vittal, J . J . J . Am. Chem.
Soc. 2002, 124, 8804. (b) Goh, L. Y.; Weng, Z.; Leong, W. K.; Vittal, J .
J .; Haiduc, I. Organometallics 2002, 21, 5287.
(8) (a) Goh, L. Y.; Chen, W.; Wong, R. C. S.; Karaghiosoff, K.
Organometallics 1995, 14, 3886. (b) Goh, L. Y.; Chen, W.; Wong, R. C.
S. Organometallics 1999, 18, 306. (c) Goh, L. Y.; Chen, W.; Wong, R.
C. S. Chem. Commun. 1999, 1481.
(9) (a) Manning, A. R.; Hackett, P.; Birdwhistell, R.; Soye, P. Inorg.
Synth. 1990, 28, 148. (b) Watkins, W. C.; J aeger, T.; Kidd, C. E.;
Fortier, S.; Baird, M. C.; Kiss, G.; Roper, G. C.; Hoff, C. D. J . Am.
Chem. Soc. 1992, 114, 907.
(10) J aeger, T. J .; Baird, M. C. Organometallics 1988, 7, 2074.

Ring Opening of Lawesson’s Reagent
Organometallics, Vol. 22, No. 8, 2003 1647
yielded a brown solid of Cp*2Cr2(CO)5(S2PAr) (4*; 92 mg, 0.13
mmol, 51% yield); (iv) a blue eluate in toluene/THF (1:1, 15
mL), which yielded a deep blue solid of Cp*2Cr2(S2P(O)Ar)2 (5*;
34 mg, 0.04 mmol, 17% yield).
Calcd for C14H12CrO3PS: C, 48.9; H, 3.8; S, 9.3. Found: C,
49.4; H, 3.7; S, 9.2. MS FAB+ (m/z): 344 [M]+, 288 [M - 2CO]+.
HR-MS ESI+ (m/z): for [M]+ 343.9731 (found), 343.9728
(calcd).
Da ta for 6*. IR (KBr, ν(CO)/cm-1): 1942 s, 1870 s. 1H NMR
(C6D6): δ 1.58 (d, J ) 1 Hz, 15H, C5(CH3)5), 6.55 (dd, J ) 8
Hz, 2H, C6H4), 7.31 (m, 2H, C6H4), 3.11 (s, 3H, OCH3), 5.40
(d, J ) 384 Hz, 1H, PH). 13C NMR (C6D6): δ 101.6 (C5(CH3)5),
163.1 (C6H4), 134.4 (d, J ) 14 Hz, C6H4), 123.1 (d, J ) 58 Hz,
C6H4), 115.6 (d, J ) 14 Hz, C6H4), 55.4 (OCH3), 10.8 (C5(CH3)5),
257.9 (d, J ) 46 Hz, CO), 252.5 (d, J ) 8 Hz, CO). 31P NMR
(C6D6; proton-coupled): δ 50.4 (d, J ) 384 Hz). Anal. Calcd
for C19H23CrO3PS: C, 55.1; H, 5.6. Found: C, 55.2; H, 5.6. MS
FAB+ (m/z): 414 [M]+, 358 [M - 2CO]+. HR-MS ESI+ (m/z):
for [M]+ 414.0513 (found), 414.0511 (calcd).
Da ta for cis-7. IR (KBr, ν(CO)/cm-1): 1944 s, 1883 s. 1H
NMR (C6D6): δ 4.12 (s, 10H, C5H5), 6.79 (d, J ) 8 Hz, 4H,
C6H4), 8.03 (m, 4H, C6H4), 3.22 (s, 6H, OCH3). 13C NMR
(C6D6): δ 91.0 (C5H5), 163.4 (C6H4), 136.1 (C6H4), 122.9 (C6H4),
114.6 (t, J ) 6 Hz, C6H4), 55.5 (OCH3), 257.5 (CO), 249.1 (CO).
31P NMR (C6D6): δ 80.3. Anal. Calcd for C28H24Cr2O6P2S2‚
1/2C4H8O: C, 49.9; H, 3.9. Found: C, 49.8; H, 3.8. MS FAB+
(m/z): 686 [M]+, 630 [M - 2CO]+, 574 [M - 4CO]+.
Th er m olysis of Cp *2Cr 2(CO)5(S2P Ar ) (4*). A reddish
brown solution of Cp*2Cr2(CO)5(S2PAr) (4*; 120 mg, 0.17 mmol)
in toluene (5 mL) was stirred at 90 °C for 10 min. The resultant
greenish brown product mixture was loaded onto a silica gel
column (2 × 8 cm) prepared in n-hexane. Elution gave four
fractions. (i) This fraction was a yellow eluate in n-hexane/
toluene (4:1, 5 mL), from which was obtained 9* (4 mg, 0.02
mmol, 4% yield). (ii) A green eluate in n-hexane/toluene (1:1,
8 mL) was the second fraction from the column, from which
was obtained 10* (20 mg, 0.04 mmol, 23% yield). (iii) A reddish
brown eluate in toluene (10 mL) was obtained, which gave
1
brown solids (24 mg), the H NMR spectra of which indicated
the presence of a 1:3 molar mixture of 6* and 8*. This mixture
was extracted with n-hexane/toluene (1:2, 2 × 3 mL), leaving
behind on the walls of the flask a dark red solid of Cp*2Cr2-
(CO)4(SPAr) (8*; ca. 16 mg, 0.03 mmol, 14% yield). The
combined extracts were concentrated to dryness, yielding red
crystalline solids of Cp*Cr(CO)2(SP(H)Ar) (6*; ca. 5 mg, 0.01
mmol, 7% yield). (iv) A blue eluate in toluene/THF (1:1, 15
mL) was obtained, which yielded a deep blue solid of Cp*2Cr2-
(S2P(O)Ar)2 (5*; 18 mg, 0.02 mmol, 13% yield). A deep blue
band remained unmoved on the top of the column.
Da ta for tr a n s-7. IR (KBr, ν(CO)/cm-1): 1952 s, 1886 s.
1H NMR (C6D6): δ 4.31 (s, 10H, C5H5), 6.75 (d, J ) 8 Hz, 4H,
C6H4), 7.95 (m, 4H, C6H4), 3.21 (s, 6H, OCH3). 13C NMR
(C6D6): δ 91.0 (C5H5), 163.3 (d, J ) 16 Hz, C6H4), 137.4 (t,
J ) 8 Hz, C6H4), 135.3 (t, J ) 10 Hz, C6H4), 115.9 (t, J ) 6 Hz,
C6H4), 114.4 (t, J ) 6 Hz, C6H4), 55.5 (OCH3), 259.8 (CO), 248.8
Da ta for 3. IR (KBr, ν(CO)/cm-1): 2015 s, 1958 s, 1942 s,
1
1921 s, 1848 s. H NMR (C6D6): δ 4.29 (s, 5H, C5H5), 4.21 (s,
5H, C5H5), 6.54 (dd, J ) 8 Hz, 2H, C6H4), 7.78 (t, J ) 9 Hz,
2H, C6H4), 3.15 (s, 3H, OCH3). 13C NMR (C6D6): δ 94.1, 91.4
(C5H5), 160.9 (C6H4), 142.3 (C6H4), 132.0 (d, J ) 12 Hz, C6H4),
114.2 (d, J ) 10 Hz, C6H4), 55.3 (OCH3), 264.2 (CO), 255.0 (d,
J ) 8 Hz, CO), 243.3 (d, J ) 13 Hz, CO), 238.2 (d, J ) 36 Hz,
CO). 31P NMR (C6D6): δ 74.7. Anal. Calcd for C22H17Cr2O6PS:
C, 48.5; H, 3.2. Found: C, 48.8; H, 3.2. MS FAB+ (m/z): 544
[M]+, 460 [M - 3CO]+, 404 [M - 5CO]+. HR-MS FAB+ (m/z):
for [M]+ 543.9296 (found), 543.9294 (calcd).
Da ta for 4. IR (toluene, ν(CO)/cm-1): 2017 s, 1947 br, 1880
br. 1H NMR (C6D6): δ 4.60 (s, 5H, C5H5), 4.53 (br, ν1/2 ) 36
Hz, 5H, C5H5), 8.31 (br, 2H, C6H4), 6.84 (br, 2H, C6H4), 3.22
(s, 3H, OCH3). 13C NMR (C6D6): δ 95.5, 95.0 (C5H5), 132.7
(C6H4), 130.8 (C6H4), 114.0 (d, J ) 11 Hz, C6H4), 55.3 (OCH3).
31P NMR (C6D6): δ 169.1. Anal. Calcd for C22H17Cr2O6PS2‚
1/4C7H8: C, 47.6; H, 3.2. Found: C, 47.1; H, 3.2. MS FAB+
(m/z): 576 [M]+, 520 [M - 2CO]+, 436 [M - 5CO]+.
(CO). 31P NMR (C6D6): δ 85.2. Anal. Calcd for C28H24
-
Cr2O6P2S2: C, 49.0; H, 3.5. Found: C, 49.5; H, 3.5. MS FAB+
(m/z): 686 [M]+, 630 [M - 2CO]+, 574 [M - 4CO]+.
Da ta for 8*. IR (KBr, ν(CO)/cm-1): 1959 s, 1888 s. 1H NMR
(C6D6): δ 1.32 (s, 30H, C5(CH3)5), 6.83 (d, J ) 8 Hz, 2H, C6H4),
7.92 (m, 2H, C6H4), 3.29 (s, 3H, OCH3). 13C NMR (C6D6): δ
102.3 (C5(CH3)5), 163.7 (C6H4), 137.6 (C6H4), 130.8 (C6H4), 114.1
(C6H4), 55.5 (OCH3), 10.8 (C5(CH3)5), 260.4 (t, J ) 24 Hz, CO),
250.2 (CO). 31P NMR (C6D6): δ 85.2. Anal. Calcd for C31H37
-
Cr2O5PS: C, 56.7; H, 5.7. Found: C, 56.0; H, 5.5. MS FAB+
(m/z): 656 [M]+, 600 [M - 2CO]+, 544 [M - 4CO]+.
Da ta for 9 a n d 9*. 1H NMR (C6D6): 9, δ 4.02 (s, C5H5),
-5.58 (s, CrH); 9*, δ 1.57 (s, C5(CH3)5), -5.58 (s, CrH).
Da ta for 10 a n d 10*. 1H NMR (C6D6): 10, δ 4.36 (s, C5H5);
10*, δ 1.63 (s, C5(CH3)5).
Da ta for 4*. IR (KBr, ν(CO)/cm-1): 2001 s, 1947 s, 1928 s,
1919 s, 1854 s. 1H NMR (C6D6): δ 1.78 (s, 15H, C5(CH3)5), 1.52
(s, 15H, C5(CH3)5), 6.77 (d, J ) 8 Hz, 2H, C6H4), 8.20 (m, 2H,
C6H4), 3.21 (s, 3H, OCH3). 13C NMR (C6D6): δ 105.4 (C5(CH3)5),
103.9 (C5(CH3)5), 161.2 (C6H4), 146.7 (d, J ) 26 Hz, C6H4), 130.7
(d, J ) 11 Hz, C6H4), 113.1 (d, J ) 11 Hz, C6H4), 55.3 (OCH3),
11.2 (C5(CH3)5), 10.2 (C5(CH3)5), 274.5 (CO), 245.5 (CO), 245.3
(CO), 239.9 (CO), 239.3 (CO). 31P NMR (C6D6): δ 184.7. Anal.
Calcd for C32H37Cr2O6PS2‚1/2C7H8: C, 55.9; H, 5.4; S, 8.4.
Found: C, 55.4; H, 5.8; S, 8.6. MS FAB+ (m/z): 716 [M]+, 660
[M - 2CO]+, 576 [M - 5CO]+.
NMR-Tu be Rea ction s. The following reactions were car-
ried out in C6D6 (0.5 mL) in septum-capped 5 mm tubes under
argon at ca. 80 °C for 40 min (unless otherwise specified),
1
followed by H NMR spectral scans.
(i) Reaction of [CpCr(CO)2]2(Cr≡Cr) with 2: a deep green
mixture of [CpCr(CO)2]2(CrtCr) (4 mg, 0.01 mmol) and 2
(4 mg, 0.01 mmol).
(ii) Reaction of [CpCr(CO)3]2 (1) with 2: a deep green mixture
of 1 (4 mg, ca. 0.01 mmol) and 2 (4 mg, 0.01 mmol).
(iii) Cothermolysis of [CpCr(CO)2(SPAr)]2 (cis-7) with 1: a
brown mixture of cis-7 (7 mg, 0.01 mmol) and 1 (4 mg, 0.01
mmol).
Da ta for 5. 1H NMR (C6D6): δ 4.31 (s, C5H5), 17.6 (br, C6H4),
10.02 (br, C6H4), 3.33 (br, OCH3). Anal. Calcd for C24H24
-
(iv) Cothermolysis of [CpCr(CO)2(SPAr)]2 (trans-7) with
1: a brown mixture of trans-7 (7 mg, 0.01 mmol) and 1 (4 mg,
0.01 mmol).
Cr2O4P2S4‚1/4C7H8: C, 44.6; H, 3.8. Found: C, 44.3; H, 3.7. MS
FAB+ (m/z): 672 [M + 2H]+.
Da ta for 5*. 1H NMR (C6D6): δ 1.59 (s, C5(CH3)5), 16.7 (br,
(v) Thermolysis of [CpCr(CO)2(SPAr)]2 (cis-7): a red-brown
solution of cis-7 (7 mg, 0.01 mmol).
C6H4), 10.0 (br, C6H4), 3.32 (br, OCH3). Anal. Calcd for C34H44
-
Cr2O4P2S4‚1/2C7H8: C, 52.5; H, 5.6. Found: C, 52.1; H, 5.6. MS
FAB+ (m/z): 812 [M + 2H]+.
(vi) Thermolysis of [CpCr(CO)2(SPAr)]2 (trans-7): a red
solution of trans-7 (7 mg, 0.01 mmol).
Da ta for 6. IR (toluene, ν(CO)/cm-1) 1958 s, 1886 s. 1H NMR
(C6D6): δ 4.33 (s, 5H, C5H5), 6.56 (d, J ) 8 Hz, 2H, C6H4), 7.24
(m, 2H, C6H4), 3.12 (s, 3H, OCH3), 5.89 (d, J ) 403 Hz, 1H,
PH). 13C NMR (C6D6): δ 90.2 (C5H5), 163.4 (C6H4), 134.4 (d, J
) 14 Hz, C6H4), 120.8 (C6H4), 115.7 (d, J ) 12 Hz, C6H4), 55.4
(OCH3), 255.6 (d, J ) 45 Hz, CO), 250.7 (d, J ) 10 Hz, CO).
31P NMR (C6D6; proton coupled): δ 38.7 (d, J ) 403 Hz). Anal.
(vii) Thermolysis of Cp2Cr2(CO)5(SPAr) (3): a reddish brown
solution of 3 (6 mg, 0.01 mmol).
(viii) Reaction of Cp2Cr2(CO)5(SPAr) (3) with S8: a reddish
brown solution of 3 and S8 (3 mg, 0.01 mmol) in C6D6 (0.5 mL)
was shaken up for 10 min and kept at ambient temperature
for 1 h.

1648 Organometallics, Vol. 22, No. 8, 2003
Weng et al.

Sch em e 1. Rea ction P r od u cts a n d Th eir Isola ted Yield sa
a
In this scheme, the pentagonal ring with the inner circle is Cp/Cp*. Reaction conditions: (i) 4 h at ambient temperature; (ii) 2 h at 90 °C. N.D. ) not detected.

1650 Organometallics, Vol. 22, No. 8, 2003
Ta ble 2. Yield s (%) of P r od u ctsa
products
Weng et al.
reaction
3
4
5
6
cis-7
trans-7
8*
9
10
1 + 2 at room temp/3 h
1 + 2 at 90 °C/2 h
1* + 2 at room temp/3 h
thermolysis of 4* at 90 °C/10 min
5
0
11
0
(51)
N.D.
20
36
(17)
(13)
0
9
0
0
5
(0)
b
0
0
(0)
(14)
7
4
(6)
(4)
8
14
(0)
b
11
(8)
(23)
N.D.
N.D.
N.D.
(7)
a
b
Values in parentheses are the products from Cp* analogues. N.D. ) not detected. A trace was observed in the NMR spectrum of the
product mixture but was lost in the chromatographic separation.
(ix) Reaction of Cp2Cr2(CO)5(SPAr) (3) with 2: a reddish
brown solution of 3 and 2 (3 mg, 0.01 mmol) in C6D6 (0.5 mL)
was shaken up for 10 min and kept at ambient temperature
for 2 h.
(x) Thermolysis of CpCr(CO)2(SP(H)Ar) (6): a dark red
solution of 6 (8 mg, 0.02 mmol) in toluene-d8 (0.5 mL) was
maintained at ca. 110 °C, and its proton NMR spectrum was
scanned at intervals up to 2 h.
by inference 4 also) was thermally labile. The thermoly-
sis of Cp*2Cr2(CO)5(S2PAr) (4*) at 90 °C for 10 min
yielded 5*, cherry red Cp*Cr(CO)2(SP(H)Ar) (6*), and
dark red solids of Cp*2Cr2(CO)4(SPAr) (8*) (14%),
together with 9* and 10*. A small amount of 7* (ca. 6%)
was seen (1H NMR δ 1.53 (Cp*), 3.26 (OMe); 31P NMR
δ 88.9) in the crude product solution but was lost in the
chromatographic process. The data depicted in Scheme
1 are also tabulated in Table 2 for a clearer comparison.
Cr ysta l Str u ctu r e An a lyses. Diffraction-quality single
crystals were obtained at -29 °C as follows: from solutions
in toluene layered with hexane, 3 as dark brown irregular
polyhedra, 4 and 4* as dark red needles, 8* as red rhombuses
after 2-4 days, and trans-7 as dark red needles after 5 days;
from solutions in THF layered with hexane, 5 and 5* as deep
blue prisms after 4 and 7 days, respectively, 6 and 6* as red
rhombuses after 3 days, and cis-7 as dark brown prisms after
5 days. The crystals were mounted on quartz fibers. X-ray data
were collected on a Bruker AXS APEX diffractometer, equipped
with a CCD detector, using Mo KR radiation (λ ) 0.710 73 Å).
The data were corrected for Lorentz and polarization effcts
with the SMART suite of programs11 and for absorption effects
with SADABS.12 Structure solution and refinement were
carried out with the SHELXTL suite of programs.13 The
structure was solved by direct methods to locate the heavy
atoms, followed by difference maps for the light non-hydrogen
atoms. The Cp and alkyl hydrogens were placed in calculated
positions. The data collection and processing parameters are
given in Table 1.
The molecular structures of 3 and 4 suggest that they
both originate from a common intermediate, the radical
species 2A, shown in Scheme 2, formed via interaction
•
of CpCr(CO)3 (1A), the incumbent monomer of 1, and
the “monomer” of 2. Rauchfuss had demonstrated that
the mechanism for the thiation of organic carbonyls by
Lawesson’s reagent involves monomeric ArPS2 inter-
mediates into which 2 reversibly cleaves (route i).14 In
the situation here the radical 1A is likely to play a
dominant role in cleaving the P2S4 central unit of 2,
forming directly the moiety 2A (route ii). Further
reaction of 2A with 1A then generates 3 and 10 (route
iii) and compound 4 (route iv), as well as compound 5
by dimerization with elimination of CO (route v), as
illustrated. In the absence of oxygen or water, we
surmise that the O atom in the eight-membered ring
in 5/5* originates from a CO ligand. Unfortunately,
evidence for this is difficult to obtain and we have not
been successful in identifying any compound with a CS
ligand. The formation of hydride 9 has been observed
in many reactions of 1 with various substrates, and
experimental evidence has ruled out the solvent as the
source of the hydridic H.4c,8a,b,15 It is probable that the
source is coordinated Cp, considering that we have
observed in crude product solutions, as well as in some
of the chromatographed fractions, several low-intensity
unassignable peaks between δ 4.17 and 5.37. These fall
in the same Cp region where resonances have been
reported for the crystallographically characterized tri-
nuclear Cp2M2M′(µ-η1:η5-C5H4)(CO)6 (M ) Mo and
M′ ) W) complexes, which were obtained from photolytic
C-H cleavage of Cp2M2(CO)6, along with the hydrides
CpM(H)(CO)3 and Cp2M2(µ-H)2(CO)4.16
Resu lts a n d Discu ssion
P r od u cts a n d Rea ction P a th w a ys. The product
mixture from the reaction of [CpCr(CO)3]2 (1) with 1 mol
equiv of Lawesson’s reagent (2) in toluene varied with
reaction conditions, as shown in Scheme 1. Thus, from
a reaction at ambient temperature for 4 h were isolated
dark brown crystals of Cp2Cr2(CO)5(SPAr) (3), dark red
solids of Cp2Cr2(CO)5(S2PAr) (4), deep blue solids of Cp2-
Cr2(S2P(O)Ar)2 (5), yellowish green solids of CpCr-
(CO)3H (9), and deep green crystals of Cp2Cr2(CO)4S (10)
in yields shown in the scheme. From a similar reaction
of [Cp*Cr(CO)3]2 (1*), the analogue of 3 was not de-
tected. The same reaction performed at 90 °C for 2 h
gave 5, 9, and 10, together with new products, viz., red
crystals of CpCr(CO)2(SP(H)Ar) (6) and dark brown
crystalline solids of [CpCr(CO)2(SPAr)]2 (cis-7) and its
isomer trans-7 as dark red crystals, but the ambient-
temperature products 3 and 4 were not detected.
However, an NMR-tube reaction in C6D6 for 60 min at
80 °C did show the presence of 3, in admixture with
5-7, 9 and 10, in an approximate molar ratio of 9:2:4:
3:2:5, respectively. Indeed, it was found that 4* (and
The thermolytic products of 4* are in agreement with
the occurrence of homolytic cleavage, followed by cou-
pling reactions, as proposed in Scheme 3; thus a Cr-P
bond scission (route a) will give the P-centered radical
•
4A* and the Cr-centered radical Cp*Cr(CO)3 (1A*),
while P-S bond cleavage (route b) together with Cr-S
bond scission (route c) will yield the P-centered radical
3A* and the S-centered radical Cp*Cr(CO)2S•. It is
(11) SMART, version 5.1; Bruker Analytical X-ray Systems, Madi-
son, WI, 2000.
(12) Sheldrick, G. M. SADABS, a Program for Empirical Absorption
Correction; University of Go¨ttingen, Go¨ttingen, Germany, 2000.
(13) SHELXTL, version 5.03; Bruker Analytical X-ray Systems,
Madison, WI, 1997.
(14) Rauchfuss, T. B.; Zank, G. A. Tetrahedron Lett. 1986, 27, 3445.
(15) Goh, L. Y.; Tay, M. S. Unpublished observations, 1992.
(16) Alvarez, M. A.; Garcia, M. E.; Riera, V.; Ruiz, M. A.; Bois, C.;
J eannin, Y. J . Am. Chem. Soc. 1995, 117, 1324.

Ring Opening of Lawesson’s Reagent
Organometallics, Vol. 22, No. 8, 2003 1651
Sch em e 2a
a
Legend: Ar ) C6H4OCH3; [\ ] ) bond cleavage.
Sch em e 3a
a
Routes a-c are bond scissions.

1652 Organometallics, Vol. 22, No. 8, 2003
Weng et al.
Sch em e 4a
a
Legend: (i) ∆, S8 or 2.
Sch em e 5
envisaged that coupling of the latter with 1A* ac-
companied by loss of a CO ligand will yield 10*, while
it is possible for 3A* to generate 7*, 8*, and 6* by
dimerization via P-P coupling, coupling with 1A*, and
abstraction of H from a hydrogen source, respectively.
This source is likely to be Cp*Cr(CO)3H (9*), which is
also one of the products in this reaction, considering that
it was demonstrated experimentally that a deuteride
analogue of 6* was not formed from a thermolytic
reaction in benzene-d6 or toluene-d8, thus ruling out
abstraction of D (or H) from solvent. As mentioned
above, in the absence of oxygen or water, the most
probable source of O in the O-containing eight-mem-
bered metallacyclic complex 5* seems to be a carbonyl
ligand of the P-centered radical 4A*.
The low yield of 3 from the ambient-temperature
reaction, together with its noticeable absence among the
products from the reaction at 90 °C, and also from the
ambient-temperature reaction of [Cp*Cr(CO)3]2, points
to its thermal lability. Indeed, this was confirmed by
NMR-tube reactions in C6D6, which showed that 3
thermally degraded or reacted with S8 or Lawesson’s
reagent at ambient temperature, giving cis-7 (12-15%),
10 (ca. 8%), and a trace amount of Cp4Cr4S4; it was also
demonstrated that cis- or trans-7 can be transformed
back to 3 with 80% conversion by interaction with 1 for
40 min at 80 °C. In addition, it was observed that cis-
or trans-7 in solution reached a 4:1 equilibrium mixture
after 40 min at 80 °C. These interconversions, as
presented in Scheme 4, explain the variation of products
with reaction temperatures and the preponderance of
isolated cis-7 over trans-7.
Although 7 may be considered as a dimer of 6 with
H2 elimination, an NMR-tube reaction showed that
heating 6 for 2 h in refluxing toluene-d8 gave only Cp4-
Cr4S4 (ca. 13% yield) and other insoluble noncharacter-
izable compounds. It is probable that the formation of
7 is initiated by a homolytic cleavage of a Cr-P bond
•
in 3, generating CpCr(CO)3 (1A) and the phosphi-
nothioylidene radical 3A, which then undergoes P-P
bond coupling to give 7. This proposition is supported
by (i) the reversal of the transformation by addition of
1, and (ii) the ambient-temperature facilitation of the
process by elemental sulfur or Lawesson’s reagent,
which as effective scavengers for 1A drives the reaction
toward formation of 7. We noted that Cowley et al. had
recently reported the only other case of P-P coupling
in a reaction involving 2, as illustrated in Scheme 5.2h
Under such thermolytic conditions, 1 will also un-
dergo decarbonylation to [CpCr(CO)2]2(CrtCr).17 The
reactivity of the latter complex with 2 was therefore
investigated; an NMR tube reaction in benzene-d6
demonstrated that reaction was complete after 30 min
at 80 °C, producing mainly 5, 6, and 9.
P r op er ties a n d Sp ectr a l Ch a r a cter istics. In the
solid state, 3, 4*, 5-7, and 8* are stable in air for a few
hours, while 4 is unstable in air or argon. In solution,
(17) Hackett, P.; O’Neill, P. S.; Manning, A. R. J . Chem. Soc., Dalton
Trans. 1974, 1625.

Ring Opening of Lawesson’s Reagent
Organometallics, Vol. 22, No. 8, 2003 1653
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 3-5*
3
4
4*
5
5*
Bond Lengths (Å)
Cr(1)-P(1)
Cr(2)-P(1)
Cr(1)-S(1)
Cr(1)-S(2)
Cr(1)-O(11A)
P(1)-S(1)
2.3391(17)
2.4722(17)
2.466(2)
2.451(2)
2.472(3)
2.477(3)
2.4400(15)
2.4901(14)
2.4882(13)
2.3723(15)
2.3758(15)
1.959(3)
2.0338(18)
2.0288(18)
1.509(4)
1.795(5)
1.361(6)
1.425(7)
2.3862(10)
2.3951(10)
1.989(3)
2.0346(12)
2.0343(12)
1.523(3)
1.789(4)
1.353(4)
1.427(5)
2.025(2)
2.034(3)
2.029(3)
2.0441(15)
2.0403(16)
P(1)-S(2)
P(1)-O(11)
P(1)-C(31)
C(34)-O(34)
C(37)-O(34)
1.848(6)
1.362(7)
1.414(10)
1.824(9)
1.387(11)
1.409(14)
1.828(4)
1.373(5)
1.407(5)
Bond Angles (deg)
78.80(8)
87.56(10)
S(1)-Cr(1)-S(2)
P(1)-S(1)-Cr(1)
P(1)-S(2)-Cr(1)
Cr(1)-P(1)-Cr(2)
C(31)-P(1)-S(2)
C(31)-P(1)-S(1)
S(2)-P(1)-S(1)
C(31)-P(1)-Cr(2)
S(1)-P(1)-Cr(2)
S(2)-P(1)-Cr(2)
O(1A)-Cr(1)-S(1)
O(1A)-Cr(1)-S(2)
O(1)-P(1)-C(31)
O(1)-P(1)-S(1)
O(1)-P(1)-S(2)
P(1)-O(1)-Cr(1A)
C(34)-O(34)-C(37)
77.57(4)
85.99(6)
86.12(5)
83.99(5)
85.03(6)
85.05(6)
83.47(3)
85.37(4)
85.14(4)
61.85(6)
131.64(7)
108.5(2)
87.54(10)
107.9(3)
108.6(3)
101.28(13)
111.2(3)
113.93(11)
113.29(12)
106.26(16)
106.68(15)
99.54(7)
107.46(14)
117.83(7)
118.03(6)
109.39(17)
109.40(17)
102.88(7)
109.65(12)
108.21(12)
102.94(5)
108.13(18)
116.06(8)
100.10(11)
98.27(12)
105.7(2)
114.27(16)
115.11(16)
144.9(2)
97.70(8)
98.88(8)
105.26(15)
115.12(11)
115.51(11)
145.05(16)
118.0(3)
120.2(6)
118.4(9)
117.7(4)
118.9(4)
3, 5, 6/6*, and 7 remain unchanged for 30 min in air,
but 4/4* and 8* are very air-sensitive.
1H NMR spectrum (4, δ 4.60 and 4.53; 4*, δ 1.78 and
1.52) and in the 13C NMR spectrum (4, δ 95.5 and 95.0;
4*, δ 11.2 and 10.2 (Me), δ 105.4 and 103.9 for the ring
C’s). A single 31P signal is seen at δ 169.1. The aryl-
thioxophosphane complexes 6/6* possess the Cp/Cp*-
(Me) resonances at δ 4.33 and 1.58, respectively, in the
1H NMR spectrum and at δ 90.2, and 10.8, 101.6,
respectively, in the 13C NMR spectrum. The PH proton
resonances are found at δ 5.89 for 6 and δ 5.40 for 6*,
with strong coupling to the P atom (J ) 403 Hz for 6;
J ) 384 Hz for 6*). The complexes cis-7 and trans-7 both
display equivalent Cp resonances which are observed
at δ 4.12 and 4.31, respectively, in the 1H NMR
spectrum and δ 91.0 for both in the 13C NMR spectrum.
The 31P signal is observed at δ 80.3 for cis-7 and δ 85.2
for trans-7.
Except for the paramagnetic 32-electron Cr(III) com-
pounds 5 and 5*, all the others are diamagnetic 18-
electron (mononuclear) or 36-electron (dinuclear) Cr(II)
compounds. The NMR spectra of complex 3 show Cp
proton resonances at δ 4.29 and 4.21 and 13C resonances
at δ 94.1 and 91.4, consistent with the molecular
structure, which possesses Cp rings in different molec-
ular environments. The 31P signal is seen at δ 74.7.
Likewise, 4/4* each possess two Cp resonances in the
F igu r e 1. Molecular structure of 3 (H atoms are omitted).
F igu r e 2. Molecular structure of 4* (H atoms are omitted).
Thermal ellipsoids are drawn at the 50% probability level.
Thermal ellipsoids are drawn at the 50% probability level.

1654 Organometallics, Vol. 22, No. 8, 2003
Weng et al.
F igu r e 3. Molecular structure of 5* (H atoms are omitted). Thermal ellipsoids are drawn at the 50% probability level.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 6-8*
6
6*
cis-7
trans-7
8*
Bond Lengths (Å)
Cr(1)-P(1)
Cr(2)-P(1)
Cr(1)-S(1)
Cr(2)-S(1)
P(1)-S(1)
P(1)-P(1A)
P(1)-C(8)
C(11)-O(3)
C(14)-O(3)
2.2607(8)
2.5116(8)
2.0093(11)
2.2704(11)
2.2699(8)
2.5207(8)
2.2730(13)
2.4962(15)
2.3681(18)
2.3753(19)
2.5001(18)
2.4900(17)
2.031(2)
2.5079(12)
2.0021(14)
2.0024(9)
2.2097(13)
1.803(2)
1.365(3)
1.423(3)
2.0003(15)
2.219(2)
1.809(4)
1.369(5)
1.423(6)
1.794(3)
1.361(4)
1.420(5)
1.805(4)
1.364(5)
1.422(5)
1.814(6)
1.369(8)
1.421(8)
Bond Angles (deg)
P(1)-Cr(1)-S(1)
P(1)-Cr(2)-S(1)
Cr(1)-S(1)-Cr(2)
P(1)-S(1)-Cr(1)
P(1)-S(1)-Cr(2)
S(1)-P(1)-Cr(1)
S(1)-P(1)-Cr(2)
Cr(1)-P(1)-Cr(2)
C(8)-P(1)-S(1)
C(8)-P(1)-Cr(1)
C(8)-P(1)-Cr(2)
C(8)-P(1)-P(1A)
S(1)-P(1)-P(1A)
P(1A)-P(1)-Cr(1)
C(11)-O(3)-C(14)
49.46(3)
49.24(4)
49.07(2)
49.32(4)
49.23(5)
49.28(5)
104.44(6)
62.00(6)
62.42(6)
68.77(7)
68.30(7)
112.50(7)
111.4(2)
122.1(2)
121.0(2)
58.76(3)
71.78(3)
59.19(4)
71.57(5)
58.92(3)
72.01(3)
59.52(5)
71.16(5)
116.18(10)
130.32(9)
115.21(14)
126.16(13)
116.25(8)
123.84(8)
114.71(14)
128.91(13)
104.77(8)
108.22(5)
126.05(5)
117.8(2)
104.20(14)
110.65(6)
121.50(6)
118.0(4)
118.5(3)
118.1(3)
116.6(5)
The carbonyl stretching frequencies in the infrared
spectrum in complexes 3, 4, 4*, 6, 6*, cis-7, trans-7, and
8* are observed in the range for terminal carbonyls.
Cr ysta l Str u ctu r es. The molecular structures of all
the isolated complexes have been determined. The
ORTEP diagrams for 3, 4*, 5, 6, cis-7 and trans-7, and
8* are shown in Figures 1-6, respectively. Selected bond
parameters of the complexes 3-5 and 6-8* are given
in Tables 3 and 4, respectively.
The structure of the molecule of 3 (Figure 1) contains
a phosphinothioylidene ligand bridging two CpCr(CO)n
(n ) 2, 3) moieties. Except for the absence of a Cr-Cr
bond, the structure resembles closely that of the Mo
complex Cp2Mo2(CO)4(SPAr).2a The two Cr-P bond
distances (2.3391(17) and 2.4722(17) Å) are significantly
different, the shorter being for Cr(1)-P(1), which are
also bridged by a S ligand. The Cr-S bond (2.466(2) Å)
is slightly shorter than that (2.5155(7) Å) in the complex
CpCr(CO)2(SPMe2).7b The P-S bond distance (2.025(2)
Å) shows some double-bond character (PdS
)
1.926(1)-1.966(2) Å; P-S ) 2.122(1) Å).18
The structures of the molecules of 4 and 4* are
similar; the ORTEP diagram of 4* is shown in Figure
2. The molecule contains a bridging dithiophosphorane
ligand, being η2(S,S′) coordinated to a Cp*Cr(CO)2
moiety and η1(P) coordinated to a Cp*Cr(CO)3 moiety.
The Cr-P bond length (2.4400(15) Å) falls between
(18) (a) Fluck, E.; Gonza´lez, G.; Peters, K.; von Schnering, H. G. Z.
Anorg. Allg. Chem. 1981, 473, 51. (b) Kerr, K. A.; Boorman, P. M.;
Misener, B. S.; Van Roode, J . H. G. Can. J . Chem. 1977, 55, 3081.

Ring Opening of Lawesson’s Reagent
Organometallics, Vol. 22, No. 8, 2003 1655
F igu r e 4. Molecular structure of 6. Thermal ellipsoids are
drawn at the 50% probability level.
F igu r e 6. Molecular structure of 8* (H atoms are omitted).
Thermal ellipsoids are drawn at the 50% probability level.
in the double-cubane complex Cp6Cr8S4(OH)(SN(C6H4))2-
(SNC2(C6H4))2 (2.085(5) and 2.079(4) Å).7a
The analogous structures of 6 (Figure 4) and 6* each
contain a Cp/Cp*Cr moiety bonded to two CO groups
and a η2-arylthioxophosphane ligand, which is rarely
encountered; the only example that we found in the
literature is in the complex [Os(η2-SP(H)Me)(CO)2-
(PPh3)2]+, obtained by methylation of [Os(η2-SPH)(CO)2-
(PPh3)2] by Roper et al.20 The Cr-P bond (2.2607(8) Å
in 6 and 2.2704(11) Å in 6*) is comparable to those of
η2-thiophosphinito complexes CpCr(CO)2(SPR2) (R )
Me, 2.2704(6) Å; R ) Et, 2.2738(18) Å) that we have
previously reported.7b However, it is significantly shorter
than those of 3 (2.3391(17) and 2.4722(17) Å). The Cr-S
bond distances (2.5116(8) Å in 6 and 2.5079(12) Å in
6*) are indicative of a single Cr-S bond. The P-S bond
distance (2.0093(11) Å in 6 and 2.0021(14) Å in 6*) lies
between that of a P-S and a PdS bond.18
F igu r e 5. Molecular structures of cis- and trans-7 (H
atoms are omitted). Thermal ellipsoids are drawn at the
50% probability level.
The molecular structures of 7 (Figure 5) reveal a
bridging P-P bond, with cis and trans orientations
of the CpCr(CO)2 moieties and different conforma-
tions of the bridging [-SPAr]2 ligand. The P-P bond
(2.2097(13) Å in cis-7 and 2.219(2) Å in trans-7) is
comparable to that of [(SPAr)2]2Ge (2.220(2) Å),2h the
only other known compound possessing a similar P-P-
bonded component from Lawesson’s reagent. The Cr-S
bond (2.5207(8) Å in cis-7 and 2.4962(15) Å in trans-7),
Cr-P bond (2.2699(8) Å in cis-7 and 2.2730(13) Å in
trans-7), and P-S bond (2.0024(9) Å in cis-7 and
2.0003(15) Å in trans-7) are similar to those found in 6,
indicating that the P-P bond in the SPAr ligand does
not have any significant effect on the corresponding
bond parameters of these complexes.
those of the corresponding bonds in 3. The two Cr-S
bond distances (2.4901(14) and 2.4882(13) Å) are very
close but longer than that in 3. The two P-S bond
distances (2.0441(15) and 2.0403(16) Å) are also very
similar.
The molecular structures of 5 and 5* (Figure 3) are
analogous, containing an eight-membered ring, com-
prised of two Cp/Cp*Cr and two [S2P(O)Ar] moieties,
with a center of symmetry in the center of the ring.
The two Cr(1)-S(1) and Cr(1)-S(2) bond lengths
(2.3862(10) and 2.3951(10) Å, respectively) are almost
equivalent, as are the two P(1)-S(1) and P(1)-S(2) bond
lengths (2.0346(12) and 2.0343(12) Å, respectively). The
P-O bond possesses double-bond character, its bond
In the molecular structure of 8* (Figure 6), a η4-
phosphinothioylidene ligand bridges two Cp*Cr(CO)2
(19) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960.
(20) Bohle, D. S.; Rickard, C. E. F.; Roper, W. R. Angew. Chem.,
Int. Ed. Engl. 1988, 27, 302.
length (1.523(3) Å) being comparable with the PdO
3- 19
distance (1.56 Å) found in PO4
.
The Cr(1)-O(11A)
bond length (1.989(3) Å) is comparable with those found

1656 Organometallics, Vol. 22, No. 8, 2003
Weng et al.
units. The two Cr-P bond distances (2.3681(18) and
2.3753(19) Å) are significantly longer than those found
in 6 and 7, while the Cr-S bond distances (2.5001(18)
and 2.4900(17) Å) are comparable. The P-S bond
distance (2.031(2) Å) shows no significant difference
from those found in 6 and 7.
coupling and hydrogen and oxygen abstraction reac-
tions.
Ack n ow led gm en t. Support from the Academic Re-
search Fund (Grant No. R-143-000-077-112) of the
National University of Singapore and a research schol-
arship to Z.W. are gratefully acknowledged. We also
thank Ms. G. K. Tan for technical assistance.
Su p p or tin g In for m a tion Ava ila ble: For structures of 3,
4, 4*, 5, 5*, 6, 6*, cis-7, trans-7, and 8*, complete listings of
bond lengths and angles, ORTEP diagrams, and tables of
atomic coordinates and equivalent isotropic displacement
parameters, anisotropic displacement parameters, hydrogen
coordinates, and isotropic displacement parameters. This
material is available free of charge via the Internet at
http://pubs.acs.org.
Con clu sion
•
The 17-electron Cp/Cp*Cr(CO)3 species has reacted
with Lawesson’s reagent or its monomer unit to gener-
ate the primary products 3 and 4. A diverse mixture of
complexes was obtained from secondary thermolytic
•
and/or Cp/Cp*Cr(CO)3 -initiated homolytic cleavage of
P-S, Cr-P, and Cr-S bonds, followed by radical
OM020933Z