Reactivity of [M(C∧P)(S2C-R)] (M = Pd, Pt; C∧P = CH2-C6H4-P(o-tolyl)2-κ C,P,- R = NMe2, OEt) toward HgX2 (X = Br, I). (see abstract)

Article abstract of DOI:10.1021/ic970584e

The reaction of the complexes [Pt(C∧P)(S₂C-R)] (C∧P = CH₂-C₆H₄-P(o-tolyl)_2-κC,P, R = NMe₂, OEt) with an equimolar amount of HgX₂ (X = Cl, Br) gives the tetranuclear derivatives [

Full text of DOI:10.1021/ic970584e

6166
Inorg. Chem. 1997, 36, 6166-6171
Reactivity of [M(C∧P)(S2C-R)] (M ) Pd, Pt; C∧P ) CH2-C6H4-P(o-tolyl)2-KC,P; R )
NMe2, OEt) toward HgX2 (X ) Br, I). X-ray Crystal Structures of
[Pt{CH2-C6H4P(o-tolyl)2-KC,P}(S2CNMe2)HgI(µ-I)]2 and
[PdBr(S2COEt){µ-P(o-tolyl)2-C6H4-CH2-}HgBr]‚0.5HgBr2‚C2H4Cl2
Larry R. Falvello, Juan Fornie´s,* Antonio Mart´ın, Rafael Navarro, Violeta Sicilia, and
Pablo Villarroya
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-CSIC, Facultad de Ciencias, E-50009 Zaragoza, Spain
ReceiVed May 15, 1997X
The reaction of the complexes [Pt(C∧P)(S2C-R)] (C∧P ) CH2-C6H4-P(o-tolyl)2-κC,P, R ) NMe2, OEt) with an
equimolar amount of HgX2 (X ) Cl, Br) gives the tetranuclear derivatives [Pt(C∧P)(S2C-R)HgX(µ-X)]2 [R )
NMe2, X ) Br (3), I (4); R ) OEt, X ) Br (5), I (6)] containing PtfHg donor-acceptor bonds. The reaction
of [Pd(C∧P)(S2CNMe2)] with HgI2 affords the complex [Pd(C∧P)(S2CNMe2)HgI(µ-I)]2 (9) similar to the complexes
3-6; by contrast the reaction of [Pd(C∧P)(S2C-R)] (R ) NMe2, OEt2) with HgBr2 leads to the corresponding
dinuclear complexes [PdBr(S2C-R)(µ-C∧P)HgBr] [R ) NMe2 (10), OEt (11)] with the didentate C∧P
cyclometalating ligand, -CH2-C6H4-P(o-tolyl)2-C,P (resulting from the C-H activation of the P(o-tolyl)3) acting
in an unprecedented bridging mode. Compound 4 (C24H26HgI2NPPtS2) crystallizes in the triclinic system, space
group P1h: a ) 9.5755(11) Å, b ) 11.1754(12) Å, c ) 14.504(2) Å, R ) 84.826(5)°, â ) 81.611(7)°, γ )
68.606(9)°, V ) 1428.5(3) Å3, and Z ) 1. Compound 11‚0.5 HgBr2‚C2H4Cl2 (C24H25Br2HgOPPdS2‚0.5
HgBr2‚C2H4Cl2) crystallizes in the monoclinic system, space group P21/c: a ) 15.571(2) Å, b ) 10.7425(10) Å,
c ) 19.655(2) Å, â ) 94.741(12)°, V ) 3276.5(5) Å3, and Z ) 4.
Introduction
I) with organoplatinum(II) compounds have been found to
proceed differently: In some cases, oxidative addition of HgX2
to PtII renders compounds containing a PtIV-Hg covalent bond,
as seems to occur in the reaction of cis-[PtMe2(Ph2Me2phen)]
with HgX2 (X ) Cl, Br, I),9 and in other cases the oxidative
addition process is followed by a reductive elimination so that
the platinum substrate acts as an alkylating agent toward the
Hg center, as happens in the reactions of cis-[PtMe2(PPhMe2)2]
and cis-[PtMe2(bpy)] with HgCl2.14 As far as we know, no
examples of PtIIfHgX2 adducts have yet been prepared by
reacting the Pt substrate with HgX2. In comparison to the
situation with platinum, the chemistry of PdII derivates with
HgX2 is much less developed.15
Metal-metal bonding in heteronuclear complexes containing
d8 and d10 metal ions has been known for some years.1 We
have developed chemistry for PtII and AgI using mono- or
dinuclear anionic pentahalophenyl complexes of Pt(II) as Lewis
bases,2 and, more recently, heteronuclear PtfHg complexes
obtained from this kind of Pt(II) substrates have also been
reported.3
The ability of mercury to form heterodimetallic complexes
with transition metal complex fragments is well-known.4 Some
of these products have been prepared by reaction of HgX2 (X
) Cl, Br, I) with d8 transition metals,5-13 and the resulting
complexes can be divided into those with a covalent metal-
metal bond5-9 (type I) and those with a metal to metal donor-
acceptor bond10-13 (type II). Reactions of HgX2 (X ) Cl, Br,
We have previously reported the reactivity of [Pt{CH2-C6H4-
P(o-tolyl)2-κC,P}(S2C-R)] (R ) NMe2, OEt) toward halogens
(Cl2, Br2, I2) to give the Pt(IV) compounds [Pt{CH2-C6H4-P(o-
tolyl)2-κC,P}(S2C-R)X2] (R ) NMe2, OEt; X ) Cl, Br, I) as a
result of the oxidative addition of X2 to the Pt(II) substrates.16
Since Hg(II) salts are able to add oxidatively to d8 metal
fragments affording heteronuclear complexes containing metal-
metal bonds, we have extended this work to the study of the
reactivity of such mononuclear Pt(II) complexes [Pt{CH2-C6H4-
P(o-tolyl)2-κC,P}(S2C-R)] (R ) NMe2, OEt) toward HgX2 (X
) Br, I) and additionally to a study of similar Pd(II) complexes.
As a result of this work, we report here the synthesis, structural
characterization, and NMR studies of new mixed Pt-Hg and
Pd-Hg complexes.
X Abstract published in AdVance ACS Abstracts, December 1, 1997.
(1) (a) Coffey, E.; Lewis, J.; Nyholm, R. S. J. Chem. Soc. 1964, 1741.
(b) Kuyper, J.; Vrieze, K. J. Organomet. Chem. 1976, 107, 129.
(2) (a) Uso´n, R.; Fornie´s, J. AdV. Organomet. Chem. 1988, 28, 219. (b)
Uso´n, R.; Fornie´s, J. Inorg. Chim. Acta 1992, 198-200, 165.
(3) Uso´n, R.; Fornie´s, J.; Falvello, L. R.; Ara, I.; Uso´n, I. Inorg, Chim.
Acta 1993, 212, 105.
(4) Gade, L. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 24.
(5) Brotherton, P. D.; Raston, C. L.; White, A. H.; Wild, S. B. J. Chem.
Soc., Dalton Trans. 1976, 1799.
(6) Tiripicchio, A.; Lahoz, F. J.; Oro, L. A.; Pinillos, M. T. J. Chem.
Soc., Chem. Commun. 1984, 936.
(7) Einstein, F. W. B.; Yan, X.; Zhang, X.; Sutton, D. J. Organomet.
Chem. 1992, 439, 221.
(8) Brekau, U.; Werner, H. Organometallics 1990, 9, 1067.
(9) Kuyper, J. Inorg. Chem. 1978, 17, 1458.
(10) Faraone, F.; Schiavo, S. L.; Bruno, G.; Bombieri, G. J. Chem. Soc.,
Chem. Commun. 1984, 6.
(11) Faraone, F.; Tresoldi, G.; Loprete, G. A. J. Chem. Soc., Dalton Trans.
1979, 933.
(12) Nowell, I. W.; Russell, D. R. J. Chem. Soc., Dalton Trans. 1972, 2393.
(13) Faraone, F.; Bruno, G.; Tresoldi, G.; Faraone, G.; Bombieri, G. J.
Chem. Soc., Dalton Trans. 1981, 1651.
(14) (a) Cross, R. J.; Wardle, R. J. Chem. Soc. A 1970, 840. (b) Jawad, J.
K.; Puddephatt, R. J. J. Chem. Soc, Chem. Commun. 1977, 892. (c)
Jawad, J. K.; Puddephatt, R. J. Inorg. Chim. Acta 1978, 31, L391.
(15) Barr, R. M.; Goldstein, M.; Hairs, N. D.; McPartlin, M.; Markwell,
A. J. J. Chem. Soc., Chem. Commun. 1974, 221.
(16) Fornie´s, J.; Mart´ın, A.; Navarro, R.; Sicilia, V.; Villarroya, P.
Organometallics 1996, 15, 1826.
S0020-1669(97)00584-3 CCC: $14.00 © 1997 American Chemical Society

Reactivity of [M(C∧P)(S2C-R)] toward HgX2
Inorganic Chemistry, Vol. 36, No. 27, 1997 6167
orange solution was evaporated to dryness. Addition of n-pentane (30
mL) to the residue afforded compound 6 as an orange solid (yield:
0.162 g, 70%). IR data (cm-1): C∧P, 450 (w), 479 (m), 490 (m), 512
(w), 526 (s), 568 (m), 599 (s), 756 (s), 788 (s),1574 (m), 1605 (m);
-S2COEt, 1024 (vs), 1135 (s), 1278 (vs). 1H NMR: C∧P, 3.71 (s,2H)
(2JPt-H ) 97.30 Hz, 85.10 Hz) (-CH2-Pt), 2.40 (s), 2.69 (s) (CH3-
C6H4), 6.8-7.6 (m) (C6H4); -S2COEt, 4.64 (q), 1.49 (t) (3JH-H ) 7.10
Hz). Anal. Calcd for C48H50I4Hg2O2P2Pt2S4: C, 26.84; H, 2.35.
Found: C, 26.64; H, 2.28.
Experimental Section
Elemental analyses were performed on a Perkin-Elmer 240-B micro-
analyzer. IR spectra were recorded on a Perkin-Elmer 599 spectro-
photometer (Nujol mulls between polyethylene plates in the range 200-
4000 cm-1). NMR spectra were recorded on either a Varian XL-200
or a Varian Unity 300 NMR spectrometer using the standard references.
[Pd(OOCCH3)2],17 [Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)] (1)16
and [Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2COEt)] (2)16 were prepared as
described elsewhere.
[Pd{CH2-C6H4-P(o-tolyl)2-KC,P}(S2CNMe2)] (7). To a stirred
suspension of [Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(µ-Cl)]2 (0.475 g, 0.53
mmol) in tetrahydrofuran (THF, 30 mL) was added AgClO4 (0.221 g,
1.07 mmol), and the mixture was stirred at room temperature for 15
min. The AgCl precipitated was filtered off, and the resulting solution
was evaporated almost to dryness. The residue was treated with 30
mL of methanol, and the addition of NaS2CNMe2‚2H2O (0.191 g, 1.07
mmol) to the solution gave a yellow solid 7, which was filtered off
and washed with MeOH and n-pentane (yield: 0.534 g, 94%). IR data
(cm-1): C∧P, 445 (s), 461 (s), 468 (s), 480 (s), 509 (s), 525 (s), 558
(s), 578 (s), 754 (vs), 761 (vs),1581 (m); -S2CNMe2, 1531 (vs) (ν(C-
N)), 974 (s) (ν(C-S)). 1H NMR: C∧P, 3.38 (s) (-CH2-Pd), 2.44 (s),
2.74 (s) (CH3-C6H4), 6.7-7.4 (m) (C6H4); -S2CNMe2, 3.29 (s), 3.34
(s). Anal. Calcd for C24H26NPPdS2: C, 54.39; H, 4.94; N, 2.64.
Found: C, 53.95; H, 4.33; N, 2.88.
[Pd{CH2-C6H4-P(o-tolyl)2-KC,P}(S2COEt)] (8). To the solution
resulting from the treatment of [Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(µ-Cl)]2
(0.469 g, 0.53 mmol) with AgClO4 (0.218 g, 1.05 mmol), in THF (20
mL), after elimination of the AgCl, was added KS2COEt (0.169 g, 1.05
mmol), and the mixture was stirred for 15 min at room temperature.
After filtration the solution was evaporated to dryness, n-hexane (25
mL) was added, and the solution was concentrated to a small volume
(5 mL). The resulting suspension was cooled at 5 °C to afford a yellow
solid which was recrystallized from CH2Cl2/n-hexane (-20 °C),
compound 8 (yield: 0.4253 g, 76%). IR data (cm-1): C∧P, 461 (s),
470 (s), 478 (s), 511 (s), 527 (s), 559 (s), 579 (s), 752 (vs), 761 (vs),
1583 (m),1591 (w); -S2COEt, 1030 (s), 1203 (s). 1H NMR: C∧P,
3.48 (s) (-CH2-Pd), 2.39 (s), 2.66 (s) (CH3-C6H4), 6.6-7.4 (m) (C6H4);
-S2COEt, 4.56 (q), 1.39 (t) (3JH-H ) 7.20 Hz). Anal. Calcd for
C24H25OPPdS2: C, 54.20; H, 4.75. Found: C, 54.49; H, 4.76.
[Pd{CH2-C6H4-P(o-tolyl)2-KC,P}(S2CNMe2)HgI(µ-I)] (9). To a
yellow solution of compound 7 (0.216 g, 0.41 mmol) in CH2Cl2 (25
mL) was added an equimolar amount of HgI2 (0.185 g, 0.41 mmol)
and OEt2 (45 mL). The mixture was stirred for 1 h, and the resulting
yellow solid 9 was filtered off and dried in vacuo. An additional
amount of compound 9 was obtained from the resulting solution by
evaporation almost to dryness and addition of n-pentane (20 mL) to
the residue (total yield: 0.36 g, 90%). IR data (cm-1): C∧P, 451 (s),
471 (s), 481 (s), 500 (m), 520 (s), 559 (m), 584 (m), 751 (vs), 758
(vs), 1584 (m), 1591 (m); -S2CNMe2, 1549 (vs) (ν(C-N)), 971 (vs)
(ν(C-S)). 1H NMR: C∧P, 3.59 (s) (-CH2-Pd), 2.50 (s), 2.70 (s) (CH3-
C6H4), 6.8-7.5 (m) (C6H4); -S2CNMe2, 3.44 (s, 6H). Anal. Calcd
for C48H52Hg2I4N2P2Pd2S4: C, 29.28; H, 2.66; N, 1.42. Found: C,
29.33; H, 2.59; N, 1.47.
Safety Note. Caution! Perchlorate salts are potentially explosive.
Only small amounts of material should be prepared, and these should
be handled with great caution.
[Pd{CH2-C6H4-P(o-tolyl)2-KC,P}(µ-OOCCH3)]2.18 A mixture of
[Pd(OOCCH3)2] (1.216 g, 5.42 mmol) and P(o-tolyl)3 (1.649 g, 5.42
mmol) was refluxed in Me2CO (45 mL) for 1 h. The dark green
precipitate was filtered off and recrystallized from CH2Cl2/Et2O
(yield: 2.012 g, 79%).
[Pd{CH2-C6H4-P(o-tolyl)2-KC,P}(µ-Cl)]2. To a solution of [Pd-
{CH2-C6H4-P(o-tolyl)2-κC,P}(µ-OOCCH3)]2 (0.119 g, 2.38 mmol) in
MeOH/CH2Cl2 (25:25 mL) was added LiCl (0.202 g, 4.77 mmol), and
a dark green solid precipitated immediately. The solid was filtered
off, washed with Et2O, and dried in vacuo (yield: 1.06 g, 99.7%). IR
data (cm-1): C∧P, 460 (vs), 470 (vs), 513 (s), 523 (vs), 560 (vs), 581
(vs), 753 (vs, br), 1568 (w),1583 (m), 1590 (m); ν(Pd-Cl), 247 (s),
289 (s). Anal. Calcd for C42Cl2H40P2Pd2: C, 56.65; H, 4.53. Found:
C, 56.34; H, 4.17.
[Pt{CH2-C6H4-P(o-tolyl)2-KC,P}(S2CNMe2)HgX(µ-X)]2 (X ) Br
(3), I(4)). X ) Br (3). To a pale yellow solution of compound 1 (0.2
g, 0.32 mmol) in CH2Cl2 (15 mL) was added HgBr2 (0.116 g, 0.32
mmol), and the color of the solution turned orange immediately. The
mixture was stirred for 10 min; then, the solvent was evaporated to
dryness, and n-hexane (20 mL) was added to the residue (yield: 0.275
g, 87%). IR data (cm-1): C∧P, 456 (s), 474 (s), 488 (m), 504 (m),
528 (s), 562 (m), 586 (s), 758 (s), 774 (s), 1584 (w), 1595 (w);
-S2CNMe2, 1554 (vs) (ν(C-N)), 968 (m) (ν(C-S)). 1H NMR: C∧P,
3.94 (s, 2H) (2JPt-H ) 85.30 Hz, 75.80 Hz) (-CH2-Pt), 2.37 (s), 2.61
(s) (CH3-C6H4), 6.8-7.6 (m) (C6H4); -S2CNMe2, 3.33 (s), 3.34 (s).
Anal. Calcd for Br4C48H52Hg2N2P2Pt2S4: C, 29.44; H, 2.68; N, 1.43.
Found: C, 29.25; H, 2.64; N, 1.42.
X ) I (4). Compound 1 (0.151 g, 0.24 mmol) and HgI2 (0.111 g,
0.24 mmol) in CH2Cl2 (25 mL) were reacted for 40 min. The solution
was filtered and evaporated to dryness, whereupon addition of n-pentane
(20 mL) gave compound 4 as an orange solid (yield: 0.228 g, 87%).
IR data (cm-1): C∧P, 456 (s), 473 (s), 486 (s), 503 (m), 528 (s), 562
(s), 585 (s), 756 (s), 762 (s), 773 (s),1584 (w), 1592 (w); -S2CNMe2,
1552(vs) (ν(C-N)), 969 (m) (ν(C-S)). 1H NMR: C∧P, 3.88 (s, 2H)
(2JPt-H ) 95.20 Hz, 70.34 Hz) (-CH2-Pt), 2.37 (s), 2.64 (s) (CH3-
C6H4), 6.8-7.8 (m) (C6H4); -S2CNMe2, 3.32 (s), 3.37 (s). Anal. Calcd
for C48H52Hg2I4N2P2Pt2S4: C, 26.86; H, 2.44; N, 1.31. Found: C,
26.73; H, 2.39; N, 1.29.
[Pt{CH2-C6H4-P(o-tolyl)2-KC,P}(S2COEt)HgX(µ-X)]2 (X ) Br (5),
I(6)). X ) Br (5). To a yellow solution of compound 2 (0.218 g,
0.35 mmol) in CH2Cl2 (25 mL) was added HgBr2 (0.127 g, 0.35 mmol);
the color of the solution turned to a brighter yellow. The mixture was
stirred for 5 min and the solution evaporated to dryness. Addition of
n-pentane (30 mL) to the residue afforded compound 5 as a yellow
solid (yield: 0.29 g, 84%). IR data (cm-1): C∧P, 464 (m), 482 (m),
492 (m), 510 (w), 529 (s), 569 (m), 597 (s), 758 (s), 779 (s),1579 (w),-
1597 (w), 1602 (w); -S2COEt, 1022 (vs), 1126 (s), 1275 (vs). 1H
NMR: C∧P, 3.98 (s, 2H) (2JPt-H ) 103.44 Hz, 72.41 Hz) (-CH2-Pt),
2.39 (s), 2.65 (s) (CH3-C6H4), 6.8-7.6 (m) (C6H4); -S2COEt, 4.70 (q),
1.53 (t) (3JH-H ) 7.10 Hz). Anal. Calcd for Br4C48H50Hg2O2P2Pt2S4:
C, 29.41; H, 2.57. Found: C, 29.12; H, 2.47.
[PdBr(S2CNMe2){µ-P(o-tolyl)2-C6H4-CH2-}HgBr] (10). To a yel-
low solution of compound 7 (0.15 g, 0.28 mmol) in CH2Cl2 (25 mL)
at -25 °C was added an equimolar amount of HgBr2 (0.102 g, 0.28
mmol), whereupon the color of the solution turned orange. After 40
min of stirring, the mixture was filtered, and the resulting solution was
evaporated to dryness. Addition of Et2O (-20 °C) to the residue
rendered a yellow solid, 10 (yield: 0.195 g, 77%). IR data (cm-1):
C∧P, 442 (m), 461 (s), 478 (s), 501 (m), 522 (m), 537 (s), 551 (m),
568 (s), 754 (vs), 1591 (m); -S2CNMe2, 1554 (vs) (ν(C-N)), 970 (vs)
(ν(C-S)). 1H NMR: C∧P, 3.43 (d, 1H) 3.72 (d, 1H, 2JH-H ) 9.1 Hz)
(-CH2-Pd), 1.52 (s), 1.76 (s) (CH3-C6H4), 6.8-7.6 (m, 11H), 9.12 (d,
1H) (C6H4); -S2CNMe2, 3.12 (s), 3.28 (s). Anal. Calcd for
Br2C24H26HgNPPdS2: C, 32.37; H, 2.94; N, 1.57. Found: C, 32.17;
H, 2.90; N, 1.62.
X ) I (6). Complex 6 was prepared in a similar way. Compound
2 (0.135 g, 0.22 mmol) and HgI2 (0.099 g, 0.22 mmol) were mixed in
CH2Cl2/OEt2 (10/40 mL) for 30 min. After filtration the resulting
[PdBr(S2COEt){µ-P(o-tolyl)2-C6H4-CH2-}HgBr] (11). To a solu-
tion of compound 8 (0.125 g, 0.24 mmol) in CHCl3 (30 mL) at -30
°C was added HgBr2 (0.17 g, 0.47 mmol); the color of the solution
turned orange. After 2 h, the mixture was filtered through celite and
the filtrate was evaporated almost to dryness. Addition of cold
n-pentane (-20 °C) to the residue afforded compound 11 as a yellow
(17) Heyn, B.; Hipler, B.; Kreisel, G.; Schreer, H.; Walther, D. Anorga-
nische Synthesechemie; Springer-Verlag: Berlin, 1986; p 142.
(18) This complex was prepared recently by Herrmann in a different way:
Herrmann, W. A.; Brossmer, Ch.; O¨ fele, K.; Reisinger, C.-P.;
Priermeier, T.; Beller, M.; Fischer, H. Angew. Chem., Int. Ed. Engl.
1995, 34, 1844.

6168 Inorganic Chemistry, Vol. 36, No. 27, 1997
Falvello et al.
Table 1. Crystallographic Data for [Pt{CH2-C6H4P(o-tolyl)2-κC,
P}(S2CNMe2)HgI(µ-I)]2 (4) and [PdBr(S2COEt){µ-P(o-tolyl)2-
C6H4-CH2-}HgBr]‚0.5 HgBr2‚C2H4Cl2 (11‚0.5 HgBr2‚C2H4Cl2)
Scheme 1
4
11‚0.5 HgBr2‚C2H4Cl2
empirical formula
C48H52Hg2I4N2P2Pt2S4 C24H25Br2HgOPPdS2
‚0.5 HgBr2‚C2H4Cl2
1348.72
143(1)
fw
2146.13
273(1)
temp (K)
wavelength (Å)
space group
unit cell dimensions
a (Å)
b (Å)
c (Å)
0.710 73
P1h
P21/c
9.5755(11)
11.1754(12)
14.504(2)
84.826(5)
81.611(7)
68.606(9)
1428.5(3)
1
15.571(2)
10.7425(10)
19.655(2)
90
94.741(12)
90
3276.5(5)
4
2.37
R (deg)
â (deg)
γ (deg)
vol (Å3)
Z
F
calc (Mg/m3)
2.50
abs coeff (mm-1
final R indicesa
[I > 2σ(I)]
)
12.64
R ) 0.0351,
Rw ) 0.0371
11.58
R ) 0.0410,
Rw2 ) 0.0848
R ) 0.0735,
Rw2 ) 0.0964
R indicesa (all data) R ) 0.0839,
Rw ) 0.0501
2
2
a R ) Σ ||Fo| - |Fc||/Σ|Fo|; Rw ) [Σw(|Fo| - |Fc|)2/Σw|Fo| ]1/2; Rw
CAD4 diffractometer, using graphite monochromated Mo KR X-
radiation. Unit cell dimensions were determined from 25 centered
reflections in the range 23.6 < 2θ < 31.8°. Diffracted intensities were
measured in a unique quadrant of reciprocal space for 4.0 < 2θ <
50.0° by ω/θ scans. Three check reflections remeasured after every 3
h showed no decay of the crystal over the period of data collection.
An absorption correction was applied on the basis of 555 azimuthal
scan data (maximum and minimum transmission coefficients were 0.854
and 0.435). Lorentz and polarization corrections were applied. The
structure was solved by Patterson and Fourier methods. All non-
hydrogen atoms were assigned anisotropic displacement parameters and
refined without positional constraints. The hydrogen atoms were
constrained to idealized geometries and assigned isotropic displacement
parameters 1.2 times the Uiso value of their parent carbon atoms (1.5
times for the methyl hydrogen atoms). The carbon atoms of the 1,2-
dichloroethane solvent molecule are disordered over two sets of
positions (partial occupancy 0.5) and were refined with a common set
of anisotropic thermal parameters. Full-matrix least squares refinement
of this model against F2 converged to final residuals given in Table 1.
Final difference electron density maps showed three peaks above 1 e
Å-3 (1.24, 1.19, and 1.06 e Å-3; largest difference hole, -1.22) lying
within 1.06 Å of the mercury atoms. Least squares calculations were
carried out using the program SHELXL-93.19b Residuals are defined
in ref 19b.
2
2
) [Σ[w(Fo - Fc2)2]/Σ[w(Fo )2]]1/2
.
solid (yield: 0.159 g, 76%). IR data (cm-1): C∧P, 458 (s), 478 (s),
501 (m), 521 (s), 534 (s), 560 (s), 580 (s), 755 (vs, sh), 1563 (m),
1589 (m); -S2COEt, 1021 (vs, br), 1234 (vs, br). 1H NMR (218 K):
2
C∧P, 3.38 (d, 1H), 3.76 (d, 1H, JH-H ) 10.8 Hz) (-CH2-Pd), 1.54
(s), 1.76 (s) (CH3-C6H4), 6.7-7.6 (m, 11H), 9.04 (d, 1H) (C6H4);
-S2COEt, 4.65 (q), 1.42 (t) (3JH-H ) 7.10 Hz). Anal. Calcd for
Br2C24H25HgOPPdS2: C, 32.34; H, 2.83. Found: C, 31.98; H, 2.81.
Crystal Structure Determination of [Pt{CH2-C6H4-P(o-tolyl)2-
KC,P}(S2CNMe2)HgI(µ-I)]2 (4). Important crystal data and data
collection parameters for complex 4 are listed in Table 1.
A
parallelepiped-shaped crystal mounted on the tip of a glass fiber with
epoxy cement was used for geometric and intensity data collection.
All diffraction measurements were made at room temperature on a
Siemens STOE/AED2 four circle diffractometer. Lattice dimensions
and type were determined by routine procedures and verified by
oscillation photography. Cell constants were refined from 2θ values
of 70 reflections including Friedel pairs (17.3 < 2θ < 35.7°). Diffracted
intensities were measured in a unique hemisphere of reciprocal space
for 4.0 < 2θ < 50.0° by ω scans. During intensity data collection,
three monitor reflections were measured at regular intervals, and they
did not vary appreciably in intensity during the course of data collection.
A measured absorption correction was applied on the basis of complete
Ψ-scans of reflections with diffractometer angle ø near 90°. The
structure of compound 4 was solved by direct methods and developed
and refined in a series of alternating difference Fourier maps and least
squares analyses using all data and the program package SHELXTL-
PLUS.19a All non-hydrogen atoms were refined anisotropically. All
hydrogen atoms were included in calculated positions and refined as
riding atoms (C-H, 0.96 Å; U ) 0.0917 Å3). Final difference electron
density maps showed no peaks above 1 e Å-3 (largest peak, 0.84 e
Å-3; largest difference hole, -0.77 e Å-3). Residuals and other final
refinement parameters are listed in Table 1. Residuals are defined in
ref 19a.
Results and Discusion
Reactivity of Complexes [Pt{CH2-C6H4-P(o-tolyl)2-KC,P}-
(S2CR)] [R ) NMe2 (1), OEt (2)] toward HgX2 (X ) Br, I).
The reactions of [Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CR)] (R )
NMe2 (1), OEt (2)) with HgX2 (X ) Br, I) (1:1 molar ratio) in
dichloromethane afford the tetranuclear complexes [Pt{CH2-
C6H4-P(o-tolyl)2-κC,P}(S2CR)HgX(µ-X)]2 in high yields as air
stable solids (Scheme 1a).
The IR spectra of complexes 3 and 4 show several absorptions
corresponding to the Me2NCS2- ligand in a bidentate coordina-
tion mode20 (see Experimental Section). The values of the νst-
(CN) [1554 cm-1 (3), 1552 cm-1 (4)] suggest a pronounced
degree of C-N double bonding, even more so than in the
starting complex (1543 cm-1). The IR spectra of complexes 5
and 6 also show the typical absorptions of the EtOCS2- group.20
Figure 1 shows the molecular structure of compound 4 with
the atom numbering scheme. General crystallographic informa-
tion is collected in Table 1. Relevant bond distances and angles
are listed in Table 2.
Crystal Structure Determination of [PdBr(S2COEt){µ-P(o-tolyl)2-
C6H4-CH2-}HgBr]‚0.5 HgBr2‚C2H4Cl2 (11‚0.5HgBr2‚C2H4Cl2). Crys-
tal data and other details of the structure analysis are presented in Table
1. A crystal of compound 11‚0.5 HgBr2‚C2H4Cl2 was mounted at the
end of a quartz fiber and glued in place with epoxy adhesive. All
diffraction measurements were made at 143(1) K on an Enraf-Nonius
(19) (a) SHELXTL-PLUS Software Package for the Determination of
Crystal Structures, Release 4.0; Siemens Analytical X-ray Instruments,
Inc.: Madison, WI, 1990. (b) Sheldrick, G. M. SHELXL-93, a program
for crystal structure determination; University of Go¨ttingen: Go¨ttin-
gen, Germany, 1993.
(20) Coucouvanis, D. Progress in Inorganic Chemistry; John Wiley &
Sons: New York, 1979; Vol. 26, p 424.

Reactivity of [M(C∧P)(S2C-R)] toward HgX2
Inorganic Chemistry, Vol. 36, No. 27, 1997 6169
covalent bond: [(2-Me2NCH2-C6H4)2(µ-MeCO2)PtHg(O2CMe)],
2.513(1) Å;24 [(PPh3)2R-Pt-Hg-R], 2.637(1) Å;25a [PhCH[HgPt-
(Ph3P)2Br]COOC10H19], 2.499 Å;25b [N(CH2CH2PPh2)3Pt-
(HgMe)]BPh4, 2.531(1) Å;25c [PtCl(HgMe)(dmphen)(Z-MeO2-
CCHdCHCO2Me)], 2.558 (1) Å.25d
It is noteworthy that, in complex 4, the PtfHg bond is not
supported by any bridging ligand, especially considering that
the basic Pt complex [Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2-
CNMe2)] used as starting material contains two S atoms with
pairs of electrons capable of forming a Hg-S bond. Mercury,
furthermore, has a well-known affinity for sulfur.26 The absence
of bridging ligands between the Pt and Hg centers makes
compound 4 different from the other complexes exhibiting PtII
to HgII donor bonds.22,23
From the point of view of the Hg(II), the complex can be
considered as a dimer of stoicheiometry [HgIL(µ-I)]2, L being
the complex [Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)] with
the Pt acting as the donor atom. Each Hg atom is located in a
very distorted tetrahedral environment, the Hg-I terminal
distance [2.661(1) Å] being shorter than the Hg-I bridging ones,
which are in turn very different from each other [Hg-I(2),
2.766(2) Å, Hg-I(2′), 3.041(1) Å], in keeping with the structures
of other [LHgX(µ-X)]2 complexes.27,28 The Hg-I(2)sHg′-
I(2′) fragment is planar and the angles I(2)-Hg-I(2′) and Hg-
I(2)-Hg′ are nearly 90°.
Figure 1. Drawing of the crystal structure of [[Pt{CH2-C6H4P(o-tolyl)2-
κC,P}(S2CNMe2)HgI(µ-I)]2 (4), showing the atom labeling scheme.
Atoms are represented by their 50% probability ellipsoids.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
[Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)HgI(µ-I)]2 (4)
Although the literature contains numerous reports of 1:1
complexes of mercuric halides with neutral ligands such as
[HgX(Me3SiCH2SeMe)(µ-X)]2 (X ) Cl, Br, I),27a [HgI(Ph3-
PC5H4)(µ-I)]2,27b [HgCl(PBu3)(µ-Cl)]2,28a or [Ph3PCHCOC6H5-
HgX2]2 (X ) Cl, I)28d showing discrete centrosymmetric halogen
bridged dimeric structures, to our knowledge, there is none in
which the neutral ligand is a metal complex with the metal center
acting as donor atom, as in this case.
Pt-Hg
2.768(1)
2.246(4)
2.341(5)
1.707(14)
2.661(1)
3.041(1)
Pt-C(21)
Pt-S(1)
C(22)-N
C(22)-S(2)
Hg-I(2)
2.081(14)
2.413(4)
1.315(21)
1.733(14)
2.766(2)
Pt-P
Pt-S(2)
C(22)-S(1)
Hg-I(1)
Hg-I(2′)
S(1)-Pt-S(2)
S(1)-Pt-P
P-Pt-C(21)
S(2)-Pt-C(21)
S(1)-C(22)-N
S(2)-C(22)-N
C(22)-N-C(23)
Hg-I(2)-Hg′
73.9(1)
107.5(1)
84.6(4)
C(22)-N-C(24)
Pt-Hg-I(1)
Pt-Hg-I(2)
Pt-Hg-I(2′)
I(1)-Hg-I(2)
I(1)-Hg-I(2′)
I(2)-Hg-I(2′)
122.1(13)
113.8(1)
112.4(1)
109.5(1)
122.7(1)
105.0(1)
89.5(1)
In agreement with the molecular symmetry observed in the
crystal, the 31P{1H} NMR spectra of complexes 3-6 (see Table
3) show only one singlet at about 25 ppm with the corresponding
195Pt satellites. The P-Pt coupling constants in these complexes
are smaller than those of the starting materials (see Table 3) in
the range of about 200-400 Hz.
94.0(4)
125.5(1)
122.2(10)
121.9(13)
90.5(1)
The tetranuclear complex 4 can be regarded as being formed
by two “Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)HgI2” units
bridged by two I atoms and related to each other by a center of
symmetry.
As can be seen, each unit contains one unsupported Pt-Hg
bond. In each unit the five-coordinated Pt atom is located at
the center of the base of a square pyramid with the Hg atom in
the apical position. The angle between the Pt-Hg vector and
the perpendicular to the Pt basal plane [Pt, C(21), P, S(1), S(2)]
is 9.19°.21
1
The H NMR spectra of complexes 3-6 in CDCl3 at room
temperature (20 °C) also confirm the equivalence of the two
halves of the molecule in each case. These spectra show a
common pattern due to the cyclometalated group “Pt{CH2-C6H4-
P(o-tolyl)2-κC,P}” (see Experimental Section): (a) The CH3
groups of the o-tolylphosphine appear as two singlets indicating
(23) Krumm, M.; Zangrando, E.; Randaccio, L.; Menzer, S.; Danzmann,
A.; Holthenrich, D.; Lippert, B. Inorg. Chem. 1993, 32, 2183.
(24) (a) van der Ploeg, A. F. M. J.; van Koten, G.; Vrieze, K.; Spek, A.
L.; Duisenberg, A. J. M. J. Chem. Soc., Chem. Commun. 1980, 469.
(b) van der Ploeg, A. F. M. J.; van Koten, G.; Vrieze, K.; Spek, A. L.
Inorg. Chem. 1982, 21, 2014.
(25) (a) Rossell, O.; Seco, M.; Torra, I.; Solans, X.; Font-Altaba, M. J.
Organomet. Chem. 1984, 270, C63. (b) Suleimanov, G. Z.; Bashilov,
V. V.; Musaev, A. A.; Sokolov, V. I.; Reutov, O. A. J. Organo-
met. Chem. 1980, 202, C61. (c) Ghilardi, C. A.; Midollini, S.; Moneti,
S.; Orlandini, A.; Scapacci, G.; Dakternieks, D. J. Chem. Soc., Chem.
Commun. 1989, 1686. (d) Cucciolito, E.; Giordano, F.; Panunzi, A.;
Rufo, F.; de Felice, V. J. Chem. Soc., Dalton Trans. 1993, 3421.
(26) (a) Christou, G.; Folting, K.; Huffman, J. C. Polyhedron 1984, 3, 1247.
(b) Bond, A. M.; Colton, R.; Hollenkamp, A. F.; Hoskins, B. F.;
McGregor, K. J. Am. Chem. Soc. 1987, 109, 1969.
(27) (a) Chadha, R. K.; Drake, J. E.; McManus, N. T.; Mislankar, A. Can.
J. Chem. 1987, 65, 2305. (b) Baenziger, N. C.; Flynn, R. M.; Swenson,
D. C. Acta Crystallogr. 1978, B34, 2300.
(28) (a) Bell. N. A.; Goldstein, M.; Jones, T.; Nowell, I. W. Inorg. Chim.
Acta 1980, 43, 87. (b) van Enckevort, W. J. P.; Beurskens, P. T.;
Menger, E. M.; Bosman, W. P. Cryst. Struct. Commun. 1977, 6, 417.
(c) Castineiras, A.; Arquero, A.; Masaguer, J. R.; Mart´ınez-Carrera,
S.; Garc´ıa Blanco, S. Anorg. Allg. Chem. 1986, 539, 219. (d)
Kalyanasundari, M.; Panchanatheswaran, K.; Robinson, W. T.; Wen,
H. J. Organomet. Chem. 1995, 491, 103.
Bond distances and angles corresponding to the “Pt{CH2-
C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)” fragment are similar to
those observed in the Pt(II) complex which is used as starting
material.16
The Pt-Hg distance [2.768(1) Å] and the geometry around
the Pt center are similar to these observed in [{2,6-(Me2NCH2)2-
C6H3}Pt(µ-{(p-tol)NC(H)N(iPr)}HgBrCl] [2.8331(7) Å],22 trans-
[(CH3NH2)2Pt(1,5-diMeC-)2Hg](NO3)2‚0.5 H2O [2.765(1) Å],23
trans-[(CH3NH2)2Pt(1-MeC-)2HgCl(NO3)] [2.835(1) Å],23 and
trans-[(CH3NH2)2Pt(1-MeC-)2Hg](NO3)2 [2.785(1) Å],23 for
which the Pt-Hg interaction has been described as a PtfHg
donor bond with both metals in a formal oxidation state of 2.
In contrast, the Pt-Hg distance is clearly different from the
distances observed in mixed Pt-Hg compounds displaying a
(21) Nardelli, M. Comput. Chem. 1983, 7, 95.
(22) van der Ploeg, A. F. M. J.; van Koten, G.; Vrieze, K.; Spek, A. L.;
Duisenberg, A. J. M. Organometallics 1982, 1, 1066.

6170 Inorganic Chemistry, Vol. 36, No. 27, 1997
Falvello et al.
Table 3. 31P{1H} NMRa Data for Complexes 1-11
their inequivalence; (b) the signals corresponding to the CH2-
1JPt-P ∆1JPt-P
Pt group are isochronous, showing however different values of
2
195
J
Pt-H; (c) the aromatic hydrogens give several multiplets
complex
δP (ppm)
(Hz)
(Hz)
between 6.5 and 7.8 ppm. The main difference observed with
respect to the starting complex is the δ value of the CH2-Pt
signal together with the Pt-H coupling constant.
[Pt(C∧P)(S2CNMe2)] (1)
[Pt(C∧P)(S2COEt)] (2)
24.70 (s) 3969.4
23.73 (s) 4083.8
[Pt(C∧P)(S2CNMe2)HgBr(µ-Br)]2 (3) 26.06 (s) 3594.93 374.5c
25.69 (s) 3681.10 288.3c
25.16 (s) 3745.80 338.0d
24.63 (s) 3862.75 221.0d
35.58 (s)
35.93 (s)
36.76 (s)
Square-pyramidal compounds containing PtIIfHgII donor
bonds (type II) have been proposed as intermediates in the
formation of species with covalent Pt-Hg bonds (type I).24
However, we have not observed the subsequent formation of
type I complexes from compounds 3-6 (type II).
[Pt(C∧P)(S2CNMe2)HgI(µ-I)]2 (4)
[Pt(C∧P)(S2COEt)HgBr(µ-Br)]2 (5)
[Pt(C∧P)(S2COEt)HgI(µ-I)]2 (6)
[Pd(C∧P)(S2CNMe2)] (7)
[Pd(C∧P)(S2COEt)] (8)
[Pd(C∧P)(S2CNMe2)HgI(µ-I)]2 (9)
[PdBr(S2CNMe2)(µ-P∧C)HgBr] (10)b 20.24 (s)
The reactions of compounds 3-6 with PPh3 in 1:2 molar ratio
afford the starting Pt(II) complexes [Pt{CH2-C6H4-P(o-tolyl)2-
κC,P}(S2CR)] [R ) NMe2 (1), OEt (2)] as a result of the
cleavage of the PtIIfHgII bond rather than of the dihalogen
bridging system (eq 1).
[PdBr(S2COEt)(µ-P∧C)HgBr] (11)b
20.71 (s)
a C∧P, CH2-C6H4-P(o-tolyl)2-κC,P; external reference H3PO4, 85%;
CDCl3; room temperature. b 218 K. c ∆1JPt-P
)
1JPt-P(1) - JPt-P
.
1
1
1
d ∆1JPt-P ) JPt-P(2) - JPt-P
.
Reactivity of [Pd{CH2-C6H4-P(o-tolyl)2-KC,P}(S2CR)] [R
) NMe2 (7), OEt (8)] toward HgX2 (X ) Br, I). The reactions
of [Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CR)] (R ) NMe2 (7),
OEt (8)) with HgX2 (X ) Br, I) proceed differently depending
on the nature of X and the S2CR- ligands.
[Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CR)HgX(µ-X)]2 +
2PPh3 f 2[Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CR)] +
[HgX(PPh3)(µ-X)]2
R ) NMe2, OEt; X ) Br, I (1)
The reactivity of the platinum(II) complexes [Pt{CH2-C6H4-
P(o-tolyl)2-κC,P}(S2CR)] [R ) NMe2 (1), OEt (2)] toward HgX2
prompted us to study the reactions of the analogous palladium-
(II) complexes with the aim of preparing the corresponding
derivatives with PdfHg bonds.
Synthesis and Characterization of [Pd{CH2-C6H4-P(o-
tolyl)2-KC,P}(S2CR)] (R ) NMe2 (7), OEt (8)). These
compounds have been prepared similarly to the previously
reported platinum analogues.16
Solutions resulting from the reaction of [Pd{CH2-C6H4-P(o-
tolyl)2-κC,P}(µ-Cl)]2 with AgClO4 (1:2 molar ratio) in THF at
room temperature, presumably containing the [Pd{CH2-C6H4-
P(o-tolyl)2-κC,P}(THF)2]ClO4 species, react with equimolar
amounts of sodium dimethyldithiocarbamate (NaS2CNMe2‚2H2O)
and potassium ethylxanthate (KS2COEt) to give the mononuclear
complexes [Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)] (7) and
[Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(S2COEt)] (8) as air stable
solids (see Experimental Section; eqs 2 and 3).
[Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)] (7) reacts with
HgI2 at room temperature in a 1:1 molar ratio to give [Pd{CH2-
C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)HgI(µ-I)]2 (9) in a very high
yield (Scheme 1b), whereas the xanthate complex [Pd{CH2-
C6H4-P(o-tolyl)2-κC,P}(S2COEt)] (8) does not react with HgI2
under similar conditions or even when the reactants are refluxed
in diethyl ether for several hours (Scheme 1c). The structure
of 9 has been assigned on the bases of the similarities of its IR
and 31P{1H} and 1H NMR spectra with its platinum-containing
analogues, [Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)HgBr(µ-
Br)]2 (3) and [Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)HgI-
(µ-I)]2 (4).
HgBr2 reacts with both complexes 7 and 8, giving similar
complexes although different from the one obtained in the
reaction with HgI2. Treatment of dichloromethane solutions of
[Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CR)] [R ) NMe2 (7), OEt
(8)] with HgBr2 at low temperature (-25 °C) affords the air
stable solids [PdBr(S2CNMe2){µ-P(o-tolyl)2-C6H4-CH2-}HgBr]
(10) and [PdBr(S2COEt){µ-P(o-tolyl)2-C6H4-CH2-}HgBr] (11)
in high yields (Scheme 1d). As can be seen in Figure 2,
compounds 10 and 11 are the result of transmetalation processes
in which Pd-Br and C-Hg bonds are formed. These reac-
tions have to be performed at low temperature [-25 °C and
-30 °C] in order to avoid the formation of an unidentified
byproduct which appears as an impurity (δP ) 42 ppm) in
products 10 and 11 when the reactions are carried out at room
temperature.
[Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(µ-Cl)]2 +
2AgClO4 f 2AgCl + 2[Pd{CH2-C6H4-P(o-tolyl)2-κC,P}
(THF)2]ClO4 (2)
[Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(THF)2]ClO4 +
MS2C-R f [Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(S2C-R)] +
MClO4
R ) NMe2 (7), OEt (8) (3)
The similarities of the IR and 1H NMR spectra of compounds
7 and 8 to those of the analogous Pt complexes [Pt{CH2-C6H4-
P(o-tolyl)2-κC,P}(S2CR)] [R ) NMe2 (1), OEt (2)] suggest a
similar structure for all of them, consisting of square-planar
mononuclear complexes with bidentate chelating ligands. As
in the Pt derivatives 1 and 2, the hindered rotation of the P-Cipso
bonds at room temperature causes the inequivalence of the two
CH3 groups of the o-tolylphosphine. The ∆G# values at the
coalescence temperature of the methyl resonances, for the
P-Cipso bond rotation process in complexes 7 (∆G#319K ) 64.2
The geometry of the binuclear palladium-mercury complex
[PdBr(S2COEt){µ-P(o-tolyl)2-C6H4-CH2-}HgBr] (11), as deter-
mined by X-ray diffraction studies, is illustrated in Figure 2
together with the atomic numbering scheme. General crystal-
lographic information is collected in Table 1. Relevant bond
distances and angles are listed in Table 4.
As can be seen, the molecule contains one palladium and
one mercury atom bridged by the bidentate “P(o-tolyl)2-C6H4-
CH2-” group, the Pd-Hg distance being 3.098(1) Å.
The palladium atom is located in a distorted square-planar
environment formed by one bromine, two sulfur atoms of the
ethylxanthate ligand, and the P of the bidentate bridging group;
the S(1) atom is 0.159 Å away from the best plane21 defined
by Pd, Br(1), S(1), S(2), and P. The angles around the palladium
center between cis ligand bonds range from 74.9(1) to 97.6-
(1)°, distortion which can be mainly due to the small bite angle
KJ mol-1) and 8 (∆G#
) 63.2 KJ mol-1) have been
313K
calculated using the approximation to Eyring’s equation,29 and
they are very similar to the values found for the analogous
platinum derivates 1 and 2.
(29) Gu¨nther, H. NMR Spectroscopy: An Introduction; John Wiley &
Sons: Chichester, U.K., 1980.

Reactivity of [M(C∧P)(S2C-R)] toward HgX2
Inorganic Chemistry, Vol. 36, No. 27, 1997 6171
[PdBr(S2CR){µ-P(o-tolyl)2-C6H4-CH2-}HgBr] a [Pd
{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CR)] + HgBr2 (4)
The 31P{1H} NMR spectra of [PdBr(S2CR){µ-P(o-tolyl)2-
C6H4-CH2-}HgBr] [R ) NMe2 (10), OEt (11)] at room
temperature show in both cases two signals, one due to complex
10 or 11, respectively, and the other corresponding to the starting
material 7 or 8, respectively.
The spectrum of complex 10 at -55 °C does not show the
signal corresponding to the starting material, while the spectrum
of complex 11 at -55 °C shows the two signals observed at
room temperature. The disappearence of the signal due to the
starting material (at -55 °C) requires that HgBr2 be added to
the above mentioned solution of 11. All these facts suggest
that complexes 10 and 11 dissociate in solution at room
temperature (10) or even low temperature (11) (eq 4).
As can be seen from the 31P{1H} NMR data (Table 3), the
new disposition of the C∧P group, which now acts as a bridge
between the Pd and Hg atoms, leads to an important change in
the position of the 31P signal (about 15 ppm) with respect to
the cases in which this ligand acts as a chelate at the Pd center
(complexes 7-9). The new arrangement also causes important
Figure 2. Drawing of the crystal structure of [PdBr(S2COEt){µ-P(o-
tolyl)2-C6H4-CH2-}HgBr] (11), showing the atom labeling scheme.
Atoms are represented by their 50% probability ellipsoids.
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
[PdBr(S2COEt){µ-P(o-tolyl)2-C6H4-CH2-}HgBr]‚0.5 HgBr2‚C2H4Cl2
(11‚0.5HgBr2‚C2H4Cl2)
Pd-Br(1)
Pd-S(1)
Pd-Hg
Hg-C(10)
S(2)-C(1)
O-C(2)
2.454(1)
2.288(3)
3.098(1)
2.106(10)
1.706(10)
1.489(14)
Pd-P
2.305(2)
2.389(2)
2.460(1)
1.693(10)
1.299(11)
1.35(2)
Pd-S(2)
Hg-Br(2)
S(1)-C(1)
O-C(1)
1
changes in the H NMR spectrum, especially in the signals
corresponding to the -CH2- group, which appears as an AX
system with a 2JH-H close to 10 Hz, and also for those of CH3-
C6H4, which are shifted to lower δ by almost 1 ppm.
The formation of complexes 10 and 11 takes place as a result
of a transmetalation process. Cleavage of platinum carbon σ
bonds by electrophiles such as HgCl2 have been observed
previously.14b,c These reactions result in alkyl or aryl transfer
from the platinum substrate to mercury and the formation of
organomercurials (eq 5).
C(2)-C(3)
S(1)-Pd-P
Br(1)-Pd-P
94.93(9) S(1)-Pd-S(2)
92.58(7) S(2)-Pd-Br(1)
74.90(9)
97.62(7)
C(5)-C(10)-Hg(1) 109.5(6)
C(10)-Hg(1)-Br(2) 171.1(3)
S(1)-C(1)-S(2)
S(2)-C(1)-O
113.7(5)
120.5(7)
S(1)-C(1)-O
C(1)-O-C(2)
125.8(8)
116.5(9)
of the chelate xanthate ligand (74.1°).30 Pd-S distances are
different, with Pd-S(2) [2.389(2) Å] longer than Pd-S(1)
[2.288(3) Å], probably because of the higher trans influence of
the P ligand compared to the bromide. The Pd-P distance
[2.305(2) Å] is slightly longer than that observed in the
“R-M” + HgCl2 f “Cl-M” + RHgCl
(5)
In our case, although the cleavage of the Pd-C σ bond takes
place, the bidentate nature of the C,P-cyclometalated ligand leads
to the formation of Pd-Hg complexes with the ligand acting
as a bridge between the two metal centers.
Dirhodium(II) compounds with metalated arylphosphines
acting as bridges between the two metal centers have been
reported, with the phosphines forming three-atom bridges.33 The
formation of a four-atom bridge between two metal centers is
very rare due to the stability of the five-membered metallocycles,
and as far as we know only one such compound s[(C6F5)(8-
mq)Pd(µ-8-mq)Pd(C6F5)(phen)] (8-mq ) 8-quinolylmethyl)s
containing a C,N metalated ligand (8-mq) with a four-atom
bridge has previously been reported.34
18
complexes [Pd{CH2-C6H4-P(o-tolyl)2-κC,P}(µ-OOCCH3)]2
and [Pt{CH2-C6H4-P(o-tolyl)2-κC,P}(S2CNMe2)]16 in which the
C∧P ligand acts as a chelate.
The xanthate ligand is essentially planar and almost coplanar
with the Pd coordination plane (dihedral angle 6.3°). The C-S
bond lengths [1.693(10), 1.706(10) Å] are very similar to those
observed in other complexes with chelating xanthate ligands,31
but the C-O distance [1.489(14) Å] is longer than those
normally observed in this type of complexes and is as long as
a typical C-O single bond.31
The Hg atom is located at 3.098(1) Å from the Pd atom and
is close to the perpendicular to the Pd coordination plane; the
angle between the perpendicular to the palladium coordination
plane and the Pd-Hg vector is 17.5°. The Hg is coordinated
to a Br and to the C donor atom of the bridging “P(o-tolyl)2-
C6H4-CH2-” group in almost a linear mode [C(10)-Hg-Br-
(2) ) 171.1(3)°] as is usual for RHgX compounds.32 The Hg-
Br5,27b and the Hg-C3,25 distances are similar to those found in
other organometallic Hg complexes.
The present results show the greater capacity of Pt(II), as
compared to Pd(II), for the formation of donor-acceptor metal-
metal bonds, as well as the predisposition of Hg to bond to
carbon.
Acknowledgment. We thank the Direccio´n General de
Ensen˜anza Superior (Spain) for financial support (Projects PB95-
0003-CO2-01 and PB95-0792).
The compound [PdBr(S2COEt){µ-P(o-tolyl)2-C6H4-CH2-}-
HgBr] (11) crystallizes with 0.5 molecules of HgBr2. The
presence of HgBr2 in the crystal can be explained in terms of
the equilibrium represented in eq 4. The fact that complexes
10 and 11 dissociate in solution according to eq 4 is confirmed
by the 31P{1H} NMR data.
Supporting Information Available: For the crystal structure of
4, full tables of crystallographic data, atomic coordinates, thermal
parameters, and bond lengths and angles (5 pages). X-ray crystal-
lographic files, in CIF format, for complex 11‚0.5HgBr2‚C2H4Cl2 are
available on the Internet only. Ordering and access information is given
on any current masthead page.
IC970584E
(30) Uso´n, R.; Fornie´s, J.; Falvello, L. R.; Toma´s, M.; Ara, I.; Uso´n, I.
Inorg. Chim. Acta 1995, 232, 35.
(31) Orpen, G.; Brammer, L.; Allen, F. H.; Kennard, O. Watson, D. G.;
Taylor, R. J. Chem. Soc., Dalton Trans. 1989, S1.
(33) Estevan, F.; Gonza´lez, G.; Lahuerta, P.; Mart´ınez, M.; Peris, E.; van
Eldik, R. J. Chem. Soc., Dalton Trans. 1996, 1045.
(34) Fornie´s, J.; Navarro, R.; Sicilia, V.; Toma´s, M. Organometallics 1990,
9, 2422.
(32) Cotton, F. A.; Wilkinson, G. AdVanced Inorganic Chemistry, 5th ed.;
John Wiley & Sons: New York, 1988; p 618.