Facile two-step construction of a novel tetrathiamacrotricycle

Article abstract of DOI:10.1021/om040126v

Summary: The reactions of [Os(CO)(CA)(PPh₃)₃] (A = O, S) with 4,7,10-trithiatrideca-2,11-diyne provide cyclopentadienone and cydopentadienethione complexes, the latter affording a novel polythioether macrotricyclic ligand on subsequent treatment with dimethylacetylene- dicarboxylate.

Full text of DOI:10.1021/om040126v

Organometallics 2005, 24, 2027-2029
2027
Facile Two-Step Construction of a Novel
Tetrathiamacrotricycle
Anthony F. Hill,* Madeleine Schultz, and Anthony C. Willis
Research School of Chemistry, Institute of Advanced Studies, Australian National University,
Canberra, Australian Capital Territory, Australia
Received October 13, 2004
Summary: The reactions of [Os(CO)(CA)(PPh3)3] (A ) O,
S) with 4,7,10-trithiatrideca-2,11-diyne provide cyclo-
pentadienone and cyclopentadienethione complexes, the
latter affording a novel polythioether macrotricyclic
ligand on subsequent treatment with dimethylacetylene-
dicarboxylate.
parable to those for 2a. As in the formation of 2a, no
intermediates were observed, suggesting that the rate-
limiting step occurs early in the mechanism. The
reaction of 1 with 4 was next investigated. Although no
reaction ensues at room temperature, heating the
reagents in benzene under reflux results in the forma-
tion of a new complex, which we suggest is 2c, the
thiocarbonyl analogue of 2b, albeit on the basis of
somewhat limited spectroscopic and microanalytical
data.8 The complex is essentially insoluble in all the
common organic solvents with which it does not react
with (vide infra), a property that compromised the
acquisition of spectroscopic data. Most notable among
the spectroscopic data obtained were (i) the loss of
infrared activity attributable to a terminal thiocarbonyl
ligand and (ii) a 1H NMR spectrum that is reminiscent
of those for 2a2 and 2b. Attempts to obtain 13C{1H}
NMR data from solutions of 2c in CD2Cl2 were thwarted
by a slow reaction with the solvent to provide the salt
[Os(CO)(PPh3){ClCD2SC(CMedCSC2H4)2S}]Cl (d2-5‚
Cl), which was characterized as both the d2 and fully
protio derivative.8 The complex 5+ features a cyclopen-
tadienyl ligand that is part of a macrobicyclic ligand
with a pendant thioether coordinated to osmium(II).
Cyclopentadienethione complexes remain a rare class
of compound,9 and both reports point toward the sulfur
atoms being strongly nucleophilic; the oxidative cleav-
age of ruthenocenyl disulfide provides the binuclear
complex [Ru(µ-SdC5H4)(η-C5H5)]22+, in which the thiones
act as donors to adjacent ruthenium centers,9a while the
cobalt complex [Co(η4-SdC5Ph4)(η-C5H5)] is readily alky-
lated at sulfur.9b
The reactions of 2c with a range of electrophilic
alkylating agents will be discussed elsewhere;10 however
these and the formation of 5‚Cl suggest that the thione
group in 2c is particularly nucleophilic. The reaction of
2c with the electrophilic alkyne dimethylacetylenedi-
carboxylate (DMAD) was therefore investigated. There
is limited precedent for the reaction of ene-thiones with
activated alkynes; however in general these proceed via
[4+2] cycloaddition.11 This route is prevented for 2c,
which is unable to achieve the requisite S-cis ene-thione
geometry. The product of the reaction of 2c with DMAD
was identifed as the complex 6 of a novel macrotricyclic
ligand arising from the [2+3] coupling of the alkyne
with the thione and carbon center R to the thione. The
reaction proceeds under mild conditions and provides
only one regioisomer, which was unambiguously identi-
fied by crystallographic analysis (Figure 1).8 Two mecha-
nistic routes appear plausible (Scheme 2); either (a) a
We have recently been concerned with the metal-
mediated reactions of 4,7,10-trithiatrideca-2,11-diyne
(1),1,2 motivated by the simple concept that the many
and various metal-mediated alkyne coupling protocols
currently available might be applied to polythioether
R,ω-diynes to provide access to a variety of functional-
ized polythiamacrocycles. Initial studies based on [RhCl-
(PPh3)3] were discouraging in that they demonstrated
a remarkable lability of the S-C(sp) bonds.1 However,
studies based on the complex [Ru(CO)2(PPh3)3] proved
more fruitful, providing the novel macrocyclic cyclopen-
tadienone complex [Ru(CO)(PPh3){η4-κ-S-OdC(CMed
CSC2H4)2S}] (2a).2 The facility (ambient conditions) of
this [1+2+2] CO/alkyne co-cyclization reaction contrasts
markedly with the behavior of [Ru(CO)2(PPh3)3] toward
diphenylacetylene, which only provides coupled products
under prolonged forcing conditions.3 The ease of forma-
tion of 2a also precluded the observation of any inter-
mediates; however, our suggested mechanism drew
upon precedent from the reactions of [Os(CO)(CS)-
(PPh3)3] with ethyne4 and diphenylacetylene5 for which
metallacyclohexadienethione (“osmabenzene”) and met-
allacyclobutenethione products were isolated. We have
therefore investigated the reactions of 1 with the
complexes [Os(CO)(CA)(PPh3)3] (A ) O 3,6 S, 47). The
products of these reactions not only reinforce our
proposal but provide access to a complex of an unprec-
edented tricyclic tetrathioether macrocyclic ligand.
Reassuringly, the reaction of [Os(CO)2(PPh3)3]6 with
1 was found to proceed in an identical manner to the
ruthenium analogue, albeit under more forcing condi-
tions (refluxing benzene). Data for the product [Os(CO)-
(PPh3){η4-κ-S-OdC(CMedCSC2H4)2S}] (2b)8 were com-
* To whom correspondence should be addressed. E-mail: a.hill@
anu.edu.au.
(1) Caldwell, L. M.; Edwards, A. J.; Hill, A. F.; Neumann, H.;
Schultz, M. Organometallics 2003, 22, 2531.
(2) Hill, A. F.; Rae, A. D.; Schultz, M.; Willis, A. C. Organometallics
2004, 23, 81.
(3) Hill, A. F.; Schultz, M.; Willis, A. C. Organometallics 2004, 23,
5729.
(4) Elliott, G. P.; Roper, W. R.; Waters, J. M. J. Chem. Soc., Chem.
Commun. 1982, 811.
(5) Elliot, G. P.; Roper, W. R. J. Organomet. Chem. 1983, 250, C5.
(6) Cavit, W. R.; Grundy, K. R.; Roper, W. R. J. Chem. Soc., Chem.
Commun. 1972, 60.
(7) Collins, T. J.; Grundy, K. R.; Roper, W. R. J. Organomet. Chem.
1982, 231, 161.
10.1021/om040126v CCC: $30.25 © 2005 American Chemical Society
Publication on Web 03/31/2005

2028 Organometallics, Vol. 24, No. 9, 2005
Communications
concerted [2+3] cycloaddition or alternatively (b) a two-
step sequence involving initial nucleophilic attack by
(8) Characterizational data (‘@δX)’ indicates 2-D correlations to
nucleus X; 1H (300), 13C (75), and 31P (121 MHz) NMR: CD2Cl2, 298
K): (a) 2b: A mixture of 1 (60 mg, 0.30 mmol) and 3 (230 mg, 0.30
mmol) in benzene (5 mL) was heated under reflux for 30 min and then
left to cool slowly. The resulting yellow precipitate was isolated by
filtration, washed with ethanol and hexane, and dried in vacuo.
Yield: 60 mg (28%). Mp: 220 °C. IR Nujol: 1908 ν(OsCO), 1577 ν(Cd
O) cm-1. CH2Cl2: 1918 ν(OsCO), 1558 ν(CdO) cm-1 1H NMR: 7.6,
.
7.43 (m × 2, 15 H, C6H5), 4.03 (ddd, 1 H, JHH ) 15, 12, 2.4, @δC
29.0, @δH ) 2.68, 1.78, 1.20), 2.92 (ddd, 1 H, JHH ) 12, 3, 3, @δC
43.2, @δH ) 2.45, 2.16, 1.98), 2.68 (ddd, 1 H, JHH ) 15, 3, 4, @δC
)
)
)
29.0), 2.45 (ddd, 1 H, JHH ) 13, 3, 3, @δC ) 26.9), 2.16 (ddd, 1 H, JHH
) 15, 15, 3, @δC ) 26.9), 1.98 (ddd, 1 H, JHH ) 3, remaining component
of resonance obscured by CH3 resonance, @δC ) 43.2), 1.78 (ddd, 1 H,
JHH ) 15, 5, 2, @δC ) 19.0), 1.20 (ddd, 1 H, JHH ) 12, 3, 3, @δC
)
19.0). 13C{1H} NMR: δ 189.5 (RuCO), 135.1 (d, JPC ) 54.1, C1(C6H5),
133.9 (d, JPC ) 11.2, C2,6(C6H5), 133.9 (d, JPC ) 2, C4(C6H5), 128.6 (d,
JPC ) 10.5, C3,5(C6H5), 93.12, 85.0, 76.8, 73.7 (C4CdO), 43.2, 29.0, 26.9,
18.9 (SCH2), 9.92, 8.62 (CH3), quarternary ketonic carbon resonance
not unequivocally identified. 31P{1H}: δ 11.94 (C6D6), 11.89 (CD2Cl2).
FAB-MS (nba): m/z ) 741 [HM]+, 712 [M - CO]+. Anal. Found: C,
48.54; H, 4.00; N, 0.00; S, 12.67; P, 3.80. Calcd for C30H29O2OsPS3: C,
48.76; H, 3.96; N, 0.00; S, 13.02; P, 4.19. (b) 2c: A mixture of 4 (600
mg, 0.57 mmol) and 1 (138 mg, 0.60 mmol) in benzene (10 mL) was
heated under reflux for 30 min and then left to cool. The brown solid
that precipitated was isolated by filtration, washed with thf and
hexane, and dried in vacuo. Yield: 225 mg (52%). 1H NMR: δ 7.6-7.2
(m, 15 H, C6H5), 4.15 (ddd, 1 H, JHH ) 15, 13, 1.8 @δC ) 27.5), 3.01
(ddd, 1 H, JHH ) 14, 2.3, 2.3, @δC ) 42.2), 2.79 (ddd, 1 H, JHH ) 15,
4.4, 3.3, @δC ) 27.5), 2.43 (ddd, 1 H, JHH ) 14, 2.7, 2.7, @δC ) 26.0),
2.29 (d, 3 H, JHP ) 1.8, CH3 @δC ) 12.4, pseudo-trans to CO), 2.16
(ddd, 1H, JHH ) 13, 13, 2.7, @δC ) 26.0), 2.05 (ddd, 1 H, JHH ) 15, 15,
3.6 @δC ) 42.2), 1.94 (ddd, 1 H, JHH ) 16, 3.9, 2.4 @δC ) 19.0), 1.14
(ddd, 1 H, JHH ) 12, 12, 2.7 @δC ) 19.0), 1.12 (d, 3 H, JHP ) 2.4 Hz,
CH3 @δC ) 11.4, pseudo-trans to PPh3). 13C{1H} NMR: δ 130.0 (C2Cd
S), 133-128 (m, PPh3), 111, 102 (CMe × 2), 83, 77 (C2C-S × 2), 42.2
Figure 1. Molecular geometry of 6 in the crystal of 6‚C6H12
(50% probability ellipsoids, hydrogen atoms omitted and
phenyl groups simplified). Selected bond lengths (Å) and
angles (deg): Os1-S2 2.3685(8), Os1-P1 2.3335(9), Os1-
C3 2.202(3), Os1-C8 2.236(3), Os1-C9 2.236(3), Os1-C11
2.158(3), Os1-C12 1.874(4), S1-C3 1.770(3), S1-C4 1.818-
(4), S3-C7 1.820(4), S3-C8 1.765(3), S4-C11 1.794(3),
C2-C3 1.544(5), C2-C11 1.530(5), C3-C8 1.462(5), C8-
C9 1.409(5), C9-C11 1.479(5), S2-Os1-P1 94.27(3), S2-
Os1-C12 92.06(11).
(CH2 R to δC ) 26.0), 27.5 (CH2 R to δC )19.0), 26.0 (CH2 R to δC
)
42.2), 19.0 (CH2 R to δC ) 27.5), 12.4 (CH3 pseudo-trans to CO), 11.4
(CH3 pseudo-trans to P) (OsCO not observed). 31P{1H} NMR: δ 6.25.
IR Nujol: 1930 (νCO) cm-1. FAB-MS (nba): m/z ) 756 [M]+. NB 13C-
{1H} NMR data inferred from two-dimensional spectra due to reaction
with CD2Cl2. (c) 5‚Cl: Yield: 80% (spectr. quant.). Mp: 170-175 °C.
the thione at the alkyne to provide a zwitterionic
intermediate that collapses via C-C bond formation. At
present we have no evidence to differentiate between
the two mechanisms, but note that the thermal [4+2]
cycloaddition reaction of DMAD with thiobenzophenone
is purported to proceed via a zwitterionic intermediate.11b
Of interest is the regiospecificity displayed in the
exclusive formation of 6, in that C-C bond formation
occurs pseudo-trans to the phosphine ligand. The dis-
placement of the pendant thioether in 2a requires
forcing conditions (110 °C), and so we are disinclined
to invoke direct participation of the osmium center via
coordinatively unsaturated intermediates. Since the
phosphine, carbonyl, and thioether ligands are distal to
the sites for ring formation, it would appear that the
regioselectivity arises entirely from frontier orbital
controlled electronic effects.
1H NMR: δ 7.53-7.25 (m, 15 H, C6H5), 4.69 4.59 (AB, 1H × 2, 2JHH
)
12, CH2Cl), 4.37 (ddd, 1 H, JHH ) 13, 12, 2.2 @δC ) 28.3), 3.37 (m, 1
H, @δC ) 25.6), 3.32 (m, 1 H, @δC ) 42.8), 3.18 (ddd, 1H, JHH ) 16,
3.6, 2.7, @δC ) 28.3), 3.07 (ddd, 1H, JHH ) 15, 2.0, 1.9, @δC ) 16.9),
2.67 (ddd, 1 H, JHH ) 14, 3.6, 2.3, @δC ) 25.6), 2.50 (d, 3 H, JHP ) 1.6,
CH3 @δC ) 11.8), 2.01 (ddd, 1 H, 15, 13, 3.3, @δC ) 42.8), 1.67 (d, 3H,
JHP ) 2.3 Hz, CH3 @δC ) 11.2), 0.96 (m, 1 H, @δC ) 16.9). 13C{1H}
NMR: δ 179.6 (d, 2JCP ) 9.5, OsCO), 133.5 [d, 2JCP ) 11, C2, 6(C6H5)],
1
131.9 [s, C4(C6H5)], 130.8 [d, JCP ) 59, C1(C6H5)], 129.1 [d, JCP ) 11,
C3,5(C6H5)], 118.1, 109.2 (CCH3 × 2), 88.5, 86.5 (dCSCH2CH2 × 2),
82.5 (CSCH2Cl), 42.8 (CH2, R to δC ) 25.6), 28.3 (CH2, R to δC ) 16.9),
25.6 (CH2, R to δC ) 42.8), 16.9 (CH2, R to δC ) 28.3), 11.8 (s, CH3),
11.2 (s, CH3). 31P{1H} NMR: δ 0.91 (s). IR Nujol: 1951; CH2Cl2: 1968
cm-1. APCI-MS: m/z ) 805 [5]+. 6: A mixture of 2c (100 mg, 0.13
mmol) and DMAD (25 µL, 0.20 mmol) in dichloromethane (5 mL) was
stirred for 15 min and then diluted with ethanol to precipitate a tan
solid, which was isolated by filtration and dried in vacuo. Yield: 70
mg (59%). Mp: 150-155 °C (dec). IR CH2Cl2: 1912s (OsCO), 1724br
(CdO); Nujol: 1918s (OsCO), 1719m (CdO) cm-1 1H NMR (CD2Cl2,
.
The molecular geometry of 6 in a crystal of the
cyclohexane monosolvate is depicted in Figure 1. The
osmium center has a pseudo-piano-stool geometry with
unremarkable Os, P1, C12, and S2 interligand angles
and bond lengths. Interest focuses on the macrocycle
which is best described as a cyclopentadiene coordinated
tetrahapto to zerovalent osmium. Coordination of a 1,3-
butadiene fragment to a metal center typically results
in an increase in electron delocalization and reduction
in the degree of 1,3-diene bond length alternation. This
is particularly evident in 6, to the extent that it is the
298 K) (300 MHz): δ 7.43-7.19 (m, 15 H, C6H5), 4.31 (ddd, 1 H, JHH
) 13, 13, 2.1, @δC ) 27.6), 3.69 (s, 3 H, OCH3), 3.68 (s, 3 H, OCH3),
2.78 (m, 3 H, @δC ) 44.9, 32.3, 27.6), 2.20 (m, 2 H, @δC ) 44.9, 32.3),
1.64 (ddd, 1 H, JHH ) 14, 13, 3.6, @δC ) 17.9), 1.58 (d, 3 H, JHP ) 3.0,
CCH3, @δC ) 12.4), 1.43 (d, 3 H, JHP ) 0.9, CCH3, @δC ) 20.4), 1.26
(ddd, 1 H, JHH ) 14, 12, 3.3 Hz, @δC ) 17.9). 13C{1H} NMR (121 MHz,
see Figure 1 for designations): δ 164.8, 163.9 (CO2 × 2), 150.2 (CCO2),
1
2
135.8 [d, JCP ) 76, C1(C6H5)], 134.0 [d, JCP ) 18, C2,6(C6H5)] 130.2
4
[d, JCP ) 3, C4(C6H5)], 128.6 [d, JCP ) 16 Hz, C3,5(C6H5)], 103.3 (C9),
85.74, 85.18 (C3,8), 59.8 (C2), 52.73, 52.02 (OCH3 × 2), 52.2 (C11), 44.9,
32.3, 27.6 (CH2), 20.4 (CH3), 17.9 (CH2), 12.4 (CH3). 31P{1H} NMR (121
MHz): δ 8.5. ESI-MS: 899 [M]+, 757 [M - DMAD]+. Crystal data for
2. C6H12: C42H47O5OsPS4, Mw ) 981.27, monoclinic, P21/n (#14), a )
12.6976(2) Å, b ) 9.8747(1) Å, c ) 33.4827(4) Å, â ) 98.5399(5)°, V )
4151.68(9) Å3, Z ) 4, Fcalc ) 1.570 g cm-3, T ) 200 K, colorless needle,
9591 independent measured reflections [2θ e 55°], R1 ) 0.0235, wR2
)
0.0261, 6524 absorption-corrected reflections [I
>
3σ(I)], 467
(11) (a) Tominaga, Y.; Morita, Y.; Matsuda, Y.; Kobayashi, G. Chem.
Pharm. Bull. 1975, 23, 2390. (b) Gotthardt, H.; Nieberl, S. Liebigs Ann.
Chem. 1980, 867. (c) Gotthardt, H.; Nieberl, S.; Do¨necke, J. Liebigs
Ann. Chem. 1980, 873. (d) Okuma, K.; Shiki, K.; Sonoda, S.; Koga, Y.;
Shioji, K.; Kitamura, T.; Fujiwara, Y.; Yokomori, Y. Bull. Chem. Soc.
Jpn. 2000, 73, 155. (e) Ohmura, H.; Motoki, S. Bull. Chem. Soc. Jpn.
1984, 57, 1131. (f) Jutzi, P.; Schwartzen, K.-H.; Mix, A.; Stammler,
H.-G.; Neumann, B. Chem. Ber. 1993, 126, 415.
parameters, CCDC 247964.
(9) Sato, M.; Sensui, M.-A. Chem. Lett. 1996, 991. (b) Lee, J.-C.;
Tomita, I.; Endo, T. Chem. Lett. 1998, 121. (c) For a general review of
the organometallic chemistry of thiones and thioaldehydes see: Fis-
cher, H.; Stumpf, R.; Roth, G. Adv. Organomet. Chem.1998, 43, 125.
(10) Hill, A. F.; Rae, A. D.; Schultz, M.; Willis, A. C. Manuscript in
preparation.

Communications
Organometallics, Vol. 24, No. 9, 2005 2029
Scheme 1a
overall bonding description should be considered. Con-
sistent with this perspective, we note that the bonds
from osmium to C3 and C11 are significantly shorter
than those to C8 and C9 (8σ and 18σ, respectively).
Tethering of the pendant thioether (S2) does not appear
to induce any strain on the cyclopentadiene coordina-
tion, given that Os-C8 and Os-C9 are not significantly
different in length.
In conclusion, a complex tricyclic polythioether mac-
rocycle has been constructed in two steps. The question
of generality arises, with respect to both the potential
range of dipolarophiles and the range of R,ω diynes that
might be similarly co-cyclized. While we have not yet
investigated the latter, preliminary studies of the former
have been somewhat disappointing. This is not through
any flaw in the basic principle, but rather through the
practical caveat that we have not yet identified a
nonreactive solvent in which 2c is sufficiently soluble
for study. For the strongly electrophilic dipolarophile
DMAD, the reaction with 2c is sufficiently rapid in CH2-
Cl2 that no 5‚Cl is observed. With the, albeit limited,
range of alternative dipolarophiles investigated in dichlo-
romethane12 either mixtures of compounds were ob-
tained or, more commonly, formation of 5‚Cl predomi-
nated. Nevertheless, variation in the co-ligands and
alkyne substitution should be possible to enhance the
solubility of analogues of 2c. Thus, the synthesis of 6
at least indicates a conceptual approach to macrocycle
synthesis that offers much potential for development.
a
L ) PPh3, DMAD ) dimethylacetylenedicarboxylate, * )
proposed intermediate.
Scheme 2. (a) Concerted vs (b) Zwitterionic
Routes for the Cycloaddition of DMAD to 2c
Acknowledgment. We wish to gratefully acknowl-
edge W. R. Roper, L. J. Wright, and P. Johns for helpful
discussions and for access to facilities at the University
of Auckland for preliminary studies.
Supporting Information Available: Full details of the
crystal structure analysis of 6‚C6H12 (CCDC247964). This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM040126V
(12) Preliminary studies (31P NMR, CD2Cl2) indicate that tetracya-
noethylene leads to a mixture of at least four as yet unidentified
species; methylbutynoate provides predominately d2-5‚Cl with a small
amount of an adduct presumed to be an analogue of 6 but with
undefined regiochemistry; maleic anhydride, dimethylmaleate, and
dimethylfumarate failed to compete with the solvent, resulting in
C8-C9 bond length of 1.409(5) Å that is by far the
shortest in the ring. While ring strain and substituent
bulk may well be factors, the contribution of a σ,σ′,π-
but-2-ene-1,4-diyl osmium(II) canonical form to the
exclusive formation of d2-5‚Cl,
a disappointing result given the
possibility of these educts forming two further stereogenic centers in
the hypothetical adducts.