Synthesis and reactivity of the neutral pyrazolate complexes (see abstract)

Article abstract of DOI:10.1021/om0203835

The synthesis and reactivity of the neutral pyrazolate complexes were presented. Elemental analyses were performed on a Perkin-Elmer 240-B microanalyzer. The results showed the facility with which the platinum substrates form Pt-Ag bonds and the reluctance of Pd to form this kind of bond.

Full text of DOI:10.1021/om0203835

4604
Organometallics 2002, 21, 4604-4610
Syn th esis a n d Rea ctivity of th e Neu tr a l P yr a zola te
Com p lexes [M2{CH2C6H4P (o-tolyl)2-KC,P }2(µ-Rp z)2]
(M ) P d , P t; Rp z ) P z, 3,5-d m p z, 4-Mep z) tow a r d AgClO4.
Molecu la r Str u ctu r e of
[P t2Ag{CH2C6H4P (o-tolyl)2-KC,P }2(µ-4-Mep z)2]ClO4
Larry R. Falvello, J uan Fornie´s,* Antonio Mart´ın, Violeta Sicilia, and
Pablo Villarroya
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received May 13, 2002
The neutral compounds [Pt2{CH2C6H4P(o-tolyl)2-κC,P}2(µ-Rpz)2] (Rpz ) pz (2a ), 3,5-dmpz
(2b), 4-Mepz (2c)) react with AgClO4 in a 1:1 molar ratio to give the trinuclear compounds
[Pt2Ag{CH2C6H4P(o-tolyl)2-κC,P}2(µ-Rpz)2]ClO4 (Rpz ) pz (4a ), 3,5-dmpz (4b), 4-Mepz (4c)),
which contain two Pt-Ag bonds. The reaction of [Pd2{CH2C6H4P(o-tolyl)2-κC,P}2(µ-3,5-dmpz)2]
(3b ) with AgClO4 renders [{Pd2(CH2C6H4P(o-tolyl)2-κC,P)2(µ3-3,5-dmpz-N,N′,C4)2Ag(η2-µ2-
ClO4)}2] (5), a palladium/silver compound with an unprecedented dmpz bridging ligand η1-
bonded to the Ag centers, a coordination mode involving only the C4 atom of each dmpz
ligand.
In tr od u ction
(perhalophenyl)palladate substrates, similar Pd-Ag
derivatives have not been obtained mainly due to trans-
arylation processes2,4 or to a reluctance of the Pd center
to engage in the formation of this type of PdfM donor-
acceptor bond.5
Metal-metal bonding in heteronuclear complexes
containing d8 and d10 metal ions has been known for
some years. A rich chemistry in this area has been
developed in our group, involving the synthesis of
heteronuclear PtII-M compounds1-14 (M ) Ag, Cu, Hg,
Tl, Pb, Sn), which have usually been obtained by
reacting mono- or dinuclear anionic pentahalophenyl
complexes of PtII with the corresponding complexes or
salts of the metal M. In some cases the neutral mono-
or dinuclear platinum complexes have been used for
preparing PtfM derivatives. However, complexes con-
taining PdfM bonds usually cannot be prepared, except
for a few cases in which very long Pd-Ag bonds (if any)
are supported by bridging ligands.15-20 In the case of
Recently we have described the synthesis of the
neutral MII complexes [M(C∧P)(L∧L)] (M ) Pt, Pd; C∧P
) CH2C6H4P(o-tolyl)2-κC,P; L∧L ) S2CNMe2, S2COEt,
acac) and have studied their reactivity toward Hg(II)21,22
and Ag(I)23 salts. We have observed, when M ) Pt, their
ability to form heteronuclear compounds containing
unsupported Pt-Hg donor-acceptor bonds when they
react with Hg(II) salts (HgX2, X ) Br, I). However, the
reactions of the analogous palladium complexes result
in transmetalation (X ) Br), giving rise to dinuclear
compounds with the C∧P group acting as an unprec-
edented bridging ligand between the palladium and
mercury atoms.
(1) Uso´n, R.; Fornie´s, J . Inorg. Chim. Acta 1992, 200, 165-177.
(2) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Ara, I.; Casas, J . M.; Mart´ın,
A. J . Chem. Soc., Dalton Trans. 1991, 2253-2264.
(3) Cotton, F. A.; Falvello, L. R.; Uso´n, R.; Fornie´s, J .; Toma´s, M.;
Casas, J . M.; Ara, I. Inorg. Chem. 1987, 26, 1366.
(4) Fornie´s, J .; Martinez, F.; Navarro, R.; Urriolabeitia, E. P.
Organometallics 1996, 15, 1813-1819.
(5) Fornie´s, J .; Navarro, R.; Toma´s, M.; Urriolabeitia, E. P. Orga-
nometallics 1993, 12, 940-943.
(6) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Cotton, F. A.;
Falvello, L. R. Inorg. Chem. 1987, 26, 3482-3486.
(7) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Cotton, F. A.;
Falvello, L. R. Inorg. Chem. 1989, 28, 2388.
(8) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Cotton, F. A.;
Falvello, L. R.; Llusar, R. Organometallics 1988, 7, 2279.
(9) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M. Angew. Chem.,
Int. Ed. Engl. 1989, 28, 8.
(10) Uso´n, R.; Fornie´s, J .; Menjo´n, B.; Cotton, F. A.; Falvello, L. R.;
Toma´s, M. Inorg. Chem. 1985, 24, 4651.
To explore further the possibilities of preparing Pd-
Ag complexes, we have extended our work to the
synthesis of new neutral dinuclear complexes of PdII and
PtII containing the same C∧P group (C∧P ) CH2C6H4P-
(15) Ebihara, M.; Tsuchiya, M.; Yamada, M.; Tokoro, K.; Kawamura,
T. Inorg. Chim. Acta 1995, 231, 35.
(16) Ebihara, M.; Tokoro, K.; Maeda, M.; Ogami, M.; Imaeda, K.;
Sakurai, K.; Masuda, H.; Kawamura, T. J . Chem. Soc., Dalton Trans.
1994, 3621.
(17) Ardizzoia, G. A.; La Monica, G.; Cenini, S.; Moret, M.; Mascio-
cchi, N. J . Chem. Soc., Dalton Trans. 1996, 1351.
(18) Kickham, J . E.; Loeb, S. J . Organometallics 1995, 14, 3584.
(19) Glaum, M.; Klaui, W.; Skelton, B.; White, A. H. Aust. J . Chem.
1997, 50, 1047.
(20) Uso´n, R.; Uso´n, M. A.; Herrero, S. Inorg. Chem. 1997, 36, 5959.
(21) Falvello, L. R.; Fornie´s, J .; Mart´ın, A.; Navarro, R.; Sicilia, V.;
Villarroya, P. Inorg. Chem. 1997, 36, 6166-6171.
(22) Fornie´s, J .; Mart´ın, A.; Sicilia, V.; Villarroya, P. Organometallics
2000, 19, 1107-1114.
(23) Fornie´s, J .; Mart´ın, A.; Navarro, R.; Sicilia, V.; Villarroya, P.;
Orpen, A. G. J . Chem. Soc., Dalton Trans. 1998, 3721-3726.
(11) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Cotton, F. A.;
Falvello, L. R. Inorg. Chem. 1986, 25, 4519.
(12) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Uso´n, I. Angew. Chem., Int.
Ed. Engl. 1990, 29, 1449-1450.
(13) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Garde, R. J . Am. Chem. Soc.
1995, 117, 1837-1838.
(14) Casas, J . M.; Fornie´s, J .; Mart´ın, A.; Orera, V. M.; Orpen, A.
G.; Rueda, A. J . Inorg. Chem. 1995, 34, 6514-6519.
10.1021/om0203835 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 09/21/2002

Neutral Pyrazolate Complexes of Pd and Pt
Organometallics, Vol. 21, No. 22, 2002 4605
K): δ 1.61 (s, MeC∧P,
3,5-dmpz), 2.22 (s, Me3,5-dmpz), 2.30 (d, 2J HH
(o-tolyl)2-κC,P) and µ-azolato bridging ligands, [{M-
{CH2C6H4P(o-tolyl)2-κC,P}(µ-Rpz)}2] (M ) Pt, Pd; Rpz
) pyrazole (Hpz), 3,5-dimethylpyrazole (H3,5-dmpz),
4-methylpyrazole (H4-Mepz)), and have studied their
reactivity toward AgI species such as AgClO4 and [Ag-
(OClO3)(PPh3)].
The results indicate the facility with which the
platinum substrates form Pt-Ag bonds and the reluc-
tance of Pd to form this type of bond. Some of the results
presented in this paper have been communicated previ-
ously.24
) 16.35 Hz, CH2), 2.75 (s, MeC∧P), 2.96 (d, CH2), 5.58 (s, H4),
6.2-7.5 (m, C6H4). MS (FAB+, CH2Cl2; m/z, %): 1186, 85%
(M+); 1091, 100% [(M - 3,5-dmpz) +].
[{P t {CH2C6H4P (o-t olyl)2-KC,P }(µ-4-Mep z)}2] (2c). This
compound was prepared similarly to 2a : NEt3 (2.5 mL), H4-
Mepz (0.1968 g, 2.396 mmol), [{Pt{CH2C6H4P(o-tolyl)2-κC,P}-
(µ-O2CCH3)}2] (1a ; 0.668 g, 0.599 mmol). Yield of 2c: 0.5762
g, 83%. Anal. Found: C, 51.96; H, 4.29; N. 4.90. Calcd for
C
50H50N4P2Pt2: C, 51.81; H, 4.35; N, 4.83. IR (νmax/cm-1): 465
(m), 476 (m), 485 (m), 531 (m), 565 (m), 588 (m), 629 (m), 747
(s, sh), 818 (m, sh), 1074 (s), 1590 (m). 1H NMR ([2H]-
chloroform, 293 K): δ 1.81 (s, Me4-Mepz), 2.08 (s, MeC∧P), 2.54
2
2
(s, MeC∧P), 3.12 (νA, J PtH ) 46.15 Hz, J HH ) 18.4 Hz, CH2),
Exp er im en ta l Section
2
2
3.38 (νB, J PtH ) 46.15 Hz, J HH ) 18.4 Hz, CH2), 6.2-7.6 (m,
C6H4). MS (FAB+, CH2Cl2; m/z; %): 1157, 20% (M+); 1077,
100% [(M - 4-Mepz)+].
Gen er a l P r oced u r es. Elemental analyses were performed
on a Perkin-Elmer 240-B microanalyzer. IR spectra were
recorded on a Perkin-Elmer 599 spectrophotometer (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.
[{P d {CH2C6H4P (o-tolyl)2-KC,P }(µ-p z)}2] (3a ). This com-
pound was prepared similarly to 2a : NEt3 (2.5 mL), Hpz
(0.1298 g, 1.906 mmol), [{Pd{CH2C6H4P(o-tolyl)2-κC,P}(µ-O2-
CCH3)}2] (0.687 g, 0.733 mmol). Yield of 3a : 0.635 g, 90.8%.
Anal. Found: C, 60.38; H, 4.14; N. 5.93. Calcd for C48H46N4P2-
Pd2: C, 60.45; H, 4.86; N, 5.87. IR (νmax/cm-1): 459 (s), 467
(s), 483 (s), 510 (w), 528 (s), 560 (m), 585 (m), 629 (m), 670
(m), 750 (m), 1050 (m), 1280 (w), 1583 (m), 1592 (m). 1H NMR
([2H]chloroform, 293 K): δ 1.98 (s, MeC∧P), 2.65 (s, MeC∧P), 3.18
(AB, CH2), 5.87 (s, H4), 6.4-7.6 (m, H3, H,5 C6H4). MS (FAB+,
CH2Cl2; m/z; %): 887, 50% [(M - pz)+].
Sa fety Note. Caution! Perchlorate salts are potentially
explosive. Only small amounts of material should be prepared,
and these should be handled with great caution.
Syn th esis. [{Pt{CH2C6H4P(o-tolyl)2-κC,P}(µ-Cl)}2],25 [{Pd-
{CH2C6H4P(o-tolyl)2-κC,P}(µ-O2CCH3)}2],26 and [{Pd{CH2C6H4P-
24
(o-tolyl)2-κC,P}(µ-3,5-dmpz)}2Ag]ClO4 were prepared as de-
scribed elsewhere.
[{P d {CH2C6H4P (o-tolyl)2-KC,P }(µ-3,5-d m p z)}2] (3b). This
compound was prepared similarly to 2a : NEt3 (2.5 mL), H3,5-
dmpz (0.250 g, 2.60 mmol), [{Pd{CH2C6H4P(o-tolyl)2-κC,P}(µ-
O2CCH3)}2] (0.813 g, 0.867 mmol). Yield of 3b: 0.8494 g, 97%.
Anal. Found: C, 61.53; H, 5.16; N, 5.18. Calcd for C52H54N4P2-
Pd2: C, 61.85; H, 5.39; N, 5.50. IR (νmax/cm-1): 457 (s), 476
(s), 487 (s), 509 (m), 531 (s), 565 (s), 588 (s), 672 (w), 747 (s),
[{P t{CH2C6H4P (o-tolyl)2-KC,P }(µ-O2CCH3)}2] (1a ). [{Pt-
{CH2C6H4P(o-tolyl)2-κC,P}(µ-Cl)}2] (0.859 g, 0.800 mmol) and
AgClO4 (0.332 g, 1.60 mmol) were suspended in THF (35 mL)
and allowed to react for 4 h at room temperature in the dark.
The AgCl that formed was filtered off through Celite and the
resulting solution concentrated to ca. 3 mL. Methanol (20 mL)
and KO2CCH3 (0.157 g, 1.60 mmol) were added, and the
mixture was stirred for 15 min. The solid was filtered and
recrystallized from CH2Cl2/n-pentane to give a yellow solid,
1a (0.76 g, 85%). Anal. Found: C, 49.10; H, 4.25. Calcd for
1
755 (s), 775 (s), 1276 (s), 1586 (w). H NMR ([2H]chloroform,
293 K): δ 1.61 (s, MeC∧P), 1.68 (s, Me3,5-dmpz), 2.28 (s, CH2),
2.32 (s, Me3,5-dmpz), 2.83 (s, CH2), 2.87 (s, MeC∧P), 5.57 (s, H4),
6.2-7.5 (m, C6H4,). MS (FAB+, CH2Cl2; m/z; %): 915, 85% [(M
- 3,5-dmpz)+]. 13C NMR: δ 159.96 (d, J CP ) 35.0 Hz, 1C),
147.19 (s, C3(3,5-dmpz)), 145.69 (s, C5(3,5-dmpz)), 142.99 (d,
J CP ) 11.0 Hz, 1C), 142.54(d, J CP ) 15.2 Hz, 1C), 135.48 (d,
J CP ) 54.7 Hz, 1C), 133.75 (d, J CP ) 10.2 Hz, 1C), 133.40 (s,
1C), 132.54 (s, 1C), 132.3-131.9 (m, 2C), 131.49 (d, J CP ) 38.2
Hz, 1C), 130.46 (d, J CP ) 13.3 Hz, 2C), 130.26 (s, 1C), 129.04
(d, J CP ) 22.1 Hz, 1C), 128.2 (d, J CP ) 53.8 Hz, 1C), 125.55
(m, 3C), 103.14 (d, J CP ) 3.2 Hz, C4 (3,5-dmpz)), 28.57 (s, CH2),
C
46H46O4P2Pt2: C, 49.55; H, 4.16. IR (νmax/cm-1): νa(COO) 1580
(vs). 1H NMR ([2H]chloroform, 218 K): δ 2.01 (s, Meacetate), 2.14
2
2
(s, MeC∧P), 2.25 (d, J HH ) 16.0 Hz, CH2, 2H), 2.80 (d, J HH
16.0 Hz, CH2, 2H), 3.08 (s, MeC∧P), 6.4-7.5 (m, C6H4).
)
[{P t {CH2C6H 4P (o-t olyl)2-KC,P }(µ-p z)}2] (2a ). NEt3 (2.5
mL) and Hpz (0.1364 g, 2.00 mmol) were added to a stirred
suspension of [Pt{CH2C6H4P(o-tolyl)2-κC,P}(µ-O2CCH3)}2] (1a ;
0.5588 g, 0.50 mmol) in methanol (35 mL). The mixture was
refluxed for 1 h, and after cooling, the white solid, 2a , was
filtered off and washed with methanol (0.5254 g, 92.7% yield).
Anal. Found: C, 50.89; H, 4.18; N. 4.90. Calcd for C48H46N4P2-
Pt2: C, 50.97; H, 4.10; N, 4.95. IR (νmax/cm-1): 464 (s), 474 (s),
488 (m), 514 (w), 533 (s), 565 (s), 588 (s), 627 (m), 752 (m),
770 (w), 1054 (s), 1280 (s), 1588 (m). 1H NMR ([2H]chloroform,
293 K): δ 2.00 (s, MeC∧P), 2.53 (s, MeC∧P), 3.09 (νA, 2J HH ) 16.2
Hz, CH2), 3.38 (νB, 2J HH ) 16.2 Hz, CH2), 5.93 (s, H4), 6.3-7.8
(m, C6H4). MS (FAB+, CH2Cl2; m/z, %): 1130, 100% (M+); 1063,
90% [(M - pz)+].
3
3
22.34 (d, J CP ) 13.8 Hz, MeC∧P), 21.50 (d, J CP ) 8.3 Hz,
MeC∧P), 14.33 (s, Me3,5-dmpz), 12.61 (s, Me3,5-dmpz).
[{P d {CH2C6H4P (o-tolyl)2-KC,P }(µ-4-Mep z)}2] (3c). This
compound was prepared similarly to 2a : NEt3 (2.5 mL), H4-
Mepz (0.1364 g, 1.661 mmol), [{Pd{CH2C6H4P(o-tolyl)2-κC,P}-
(µ-O2CCH3)}2] (0.500 g, 0.533 mmol). Yield of 3c: 0.4546 g,
87%. Anal. Found: C, 60.87; H, 5.44; N, 5.59. Calcd for
C
50H50N4P2Pd2: C, 61.17; H, 5.13 N, 5.70. IR (νmax/cm-1): 458
(m), 468 (m), 481 (m), 509 (m), 526 (m), 560 (m), 584 (w), 630
1
(m), 748 (s), 762 (s), 816 (s, sh), 1074 (s), 1585 (m). H NMR
[{P t{CH2C6H4P (o-tolyl)2-KC,P }(µ-3,5-d m p z)}2] (2b). This
compound was prepared similarly to 2a : NEt3 (4.5 mL), H3,5-
dmpz (0.451 g, 4.69 mmol), [Pt{CH2C6H4P(o-tolyl)2-κC,P}(µ-
O2CCH3)}2] (1a ; 1.7436 g, 1.564 mmol). Yield of 2b: 1.4946 g,
80.5%. Anal. Found: C, 52.20; H, 4.95; N. 4.55. Calcd for
([2H]chloroform, 293 K): δ 1.78 (s, Me4-Mepz), 2.09 (s, MeC∧P),
2
2
2.64 (s, MeC∧P), 3.15 (νA, J HH ) 15.0 Hz, CH2), 3.23 (νB, J HH
) 15.0 Hz, CH2), 6.2-7.5 (m, C6H4). MS (FAB+, CH2Cl2; m/z;
%): 901, 40% [(M - 4-Mepz)+].
C
52H54N4P2Pt2: C, 52.61; H, 4.58; N, 4.71. IR (νmax/cm-1): 454
[{P t{CH2-C6H4-P (o-tolyl)2-KC,P }(µ-pz)}2Ag]ClO4 (4a). Ag-
ClO4 (0.037 g, 0.18 mmol) was added to a solution of [{Pt-
{CH2C6H4P(o-tolyl)2-κC,P}(µ-pz)}2] (2a ; 0.2 g, 0.18 mmol) in
CH2Cl2/OEt2 (20 mL/8 mL), and the mixture was stirred at
room temperature for 40 min in the dark. Then, the solution
was evaporated to dryness and OEt2 (20 mL) and CH2Cl2 (2
mL) were added to the residue, giving rise to a pale yellow
solid, 4a (0.1926 g, 81% yield). Anal. Found: C, 42.77; H, 3.28;
N. 3.94. Calcd for AgC48ClH46N4O4P2Pt2: C, 43.07; H, 3.46;
(s), 470 (s), 481 (w), 504 (w), 527 (s), 561 (m), 584 (s), 671 (m),
1
751 (s, sh), 1274 (m), 1565 (m). H NMR ([2H]chloroform, 293
(24) Falvello, L. R.; Fornie´s, J .; Mart´ın, A.; Navarro, R.; Sicilia, V.;
Villarroya, P. Chem. Commun. 1998, 2429-2430.
(25) Fornie´s, J .; Mart´ın, A.; Navarro, R.; Sicilia, V.; Villarroya, P.
Organometallics 1996, 15, 1826-1833.
(26) Herrmann, W. A.; Brossmer, C.; Ofele, K.; Reisinger, C. P.;
Priermeier, T.; Beller, M.; Fischer, H. Angew. Chem., Int. Ed. Engl.
1995, 34, 1844-1848.
N, 4.10. ΛM ) 89 Ω-1 cm2 mol-1 (10-3 M, MeOH). IR (νmax
/

4606 Organometallics, Vol. 21, No. 22, 2002
Falvello et al.
cm-1): 462 (s), 477 (s), 506 (m), 528 (s), 565 (s), 588 (s), 623
(s), 750 (s), 763 (s), 775 (s), 1098 (vs), 1587 (w). 1H NMR ([2H]-
chloroform, 293 K): δ 1.43 (s, MeC∧P), 2.90 (s, MeC∧P), 3.28 (d,
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 4c‚2CHCl3
empirical formula
unit cell dimensions
a (Å)
b (Å)
c (Å)
C50H50AgClN4O4P2Pt2‚2CHCl3
2
2
2J HH ) 18 Hz, J PtH ) 85.8 Hz, CH2), 4.00, (d, J HH ) 18 Hz,
2J PtH )132 Hz, CH2), 6.34 (s, H4), 6.2-8.0 (m, C6H4, H3, H5).
MS (FAB+, CH2Cl2; m/z; %): 1239, 100% (M+).
14.2550(16)
14.5969(16)
26.869(4)
[{P t {CH 2C6H 4P (o-t olyl)2-KC,P }(µ-3,5-d m p z)}2Ag]ClO4
(4b). AgClO4 (0.0364 g, 0.175 mmol) was added to a solution
of [{Pt{CH2C6H4P(o-tolyl)2-κC,P}(µ-3,5-dmpz)}2] (3a ; 0.2037 g,
0.171 mmol) in CH2Cl2/OEt2 (40 mL/8 mL). After 1 h of stirring
at room temperature in the dark, the solution was evaporated
to dryness and CH2Cl2 (10 mL) was added to the residue. The
filtered solution was evaporated to ca. 2 mL, and the addition
of Et2O (15 mL) gave compound 4b as a pale yellow solid.
Yield: 0.189 g, 79%. Anal. Found: C, 44.93; H, 3.54; N. 3.66.
Calcd for AgC52ClH54N4O4P2Pt2: C, 44.79; H, 3.90; N, 4.02.
â (deg)
97.305(17)
5545.6(11), 4
0.710 73
V (Å3), Z
wavelength (Å)
temp (K)
150(1)
radiation
graphite-monochromated
Mo KR
monoclinic
cryst syst
space group
P21/n
cryst dimens (mm)
0.38 × 0.32 × 0.27
abs coeff (mm-1
)
5.826
transmissn factors
abs cor
diffractometer
0.929, 0.645
ψ scans
Enraf-Nonius CAD4
4.0-50.0 (+h, +k, (l)
ΛM ) 30 Ω-1 cm2 mol-1 (10-3 M, 1,2-dichloroethane). IR (νmax
/
cm-1): 458 (w), 478 (s), 487 (m), 506 (m), 531 (m), 564 (m),
587 (m), 623 (s), 765 (s), 772 (s), 1041 (vs), 1128 (vs), 1589
2θ range for data
collection (deg)
no. of rflns collected
no. of indep rflns
refinement method
goodness of fit on F
1
(w). H NMR ([2H]chloroform, 293 K): δ 1.72 (s, MeC∧P), 1.77
(s, Me3,5-dmpz), 2.28 (s, Me3,5-dmpz), 2.65 (s, MeC∧P), 2.69 (d, 2J HH
10 171
9751 (R(int) ) 0.0376)
full-matrix least squares on F
1.031
2
2
) 17.9 Hz, J PtH ) 96.92 Hz, CH2), 4.01 (d, J HH ) 17.9 Hz,
2J PtH ) 115.8 Hz, CH2), 5.82 (s, H4), 6.0-7.8 (m, C6H4). MS
(FAB+, CH2Cl2; m/z; %): 1295, 100% (M+).
2
2
final R indices (I > 2σ(I))a
R1 ) 0.0375
[{P t{CH2C6H4P (o-tolyl)2-KC,P }(µ-4-Mepz)}2Ag]ClO4 (4c).
To a solution of [{Pt{CH2C6H4P(o-tolyl)2-κC,P}(µ-4-Mepz)}2]
(2c; 0.2087 g, 0.18 mmol) in CH2Cl2 (20 mL) was added AgClO4
(0.045 g, 0.22 mmol) and OEt2 (5 mL), and the mixture was
stirred in the dark at room temperature for 2 h. Then, the
mixture was filtered through Celite and the resulting solution
was evaporated to dryness. The addition of diethyl ether to
the residue gave 4c as a pale yellow solid (0.195 g, 79% yield).
wR2 ) 0.0848
R1 ) 0.0597
R indices (all data)
wR2 ) 0.0928
wR2 ) [∑w(Fo - Fc2)2/∑wFo
]
0.5; R1 ) ∑||Fo| - |Fc||/∑|Fo|.
a
2
4
residual indices given in Table 1. Final difference electron
density maps showed no features above 1 e/Å3 (maximum/
minimum +0.96/-1.46 e/Å3).
Anal. Found: C, 44.08; H, 4.35; N. 4.00. Calcd for AgC50
-
ClH50N4O4P2Pt2: C, 43.95; H, 3.69; N, 4.09. ΛM ) 131 Ω-1 cm2
mol-1 (1.27 × 10-4 M, acetone). IR (νmax/cm-1): 463 (w), 478
(m), 529 (m), 565 (w), 588 (w), 625 (m), 766 (s), 1094 (vs), 1587
(w). 1H NMR ([2H]dichloromethane, 293 K): δ 1.47 (s, MeC∧P),
1.95 (s, Me4-Mepz), 2.90 (s, MeC∧P), 3.21 (d, 2J HH ) 20.0 Hz, 2J PtH
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of th e Com -
p lexes [{M{CH2C6H4P (o-tolyl)2-KC,P }(µ-Rp z)}2] (M
) P t, Rp z ) p z (2a ), 3,5-d m p z (2b), 4-Mep z (2c); M
) P d , Rp z ) p z (3a ), 3,5-d m p z (3b), 4-Mep z (3c)).
Complexes 2a -c and 3a -c have been prepared in good
yield by reaction of the corresponding dinuclear acetate
bridging derivatives, [{M{CH2C6H4P(o-tolyl)2-κC,P}(µ-
O2CCH3)}2] (M ) Pt (1a ), Pd (1b)) with an excess of
pyrazole (Hpz), 3,5-dimethylpyrazole (H3,5-dmpz), or
4-methylpyrazole (H4-Mepz) in refluxing methanol and
in the presence of triethylamine (Scheme 1). Elemental
analyses and IR and NMR data are given in the
Experimental Section. The mass spectra (FAB+) of these
complexes are those expected for the dinuclear formula-
tion. According to this formulation such compounds
could exist as two different isomers: cis and trans. The
31P{1H} NMR spectra of these compounds at room
temperature (20 °C) in CDCl3 display in all cases only
one singlet, which for 2a -c is flanked by the corre-
sponding platinum satellites (J Pt-P ) ca. 4000 Hz)
2
2
) 70.0 Hz, CH2), 3.98 (d, J HH ) 17.9 Hz, J PtH ) 120.0 Hz,
CH2), 5.82 (s, H4), 6.0-7.8 (m, C6H4). MS (FAB+, CH2Cl2; m/z;
%): 1266, 100% (M+).
[{P d{CH2C6H4P (o-tolyl)2-KC,P }(µ-3,5-dm pz)}2Ag]ClO4 (5).
The synthesis and structural NMR data have already been
published.24 ΛM ) 10.7 Ω-1 cm2 mol-1 (10-3 M, 1,2-dichloro-
ethane). IR (νmax/cm-1): 456 (m), 471 (s), 483 (s), 504 (w), 527
(s), 560 (m), 586 (m), 622 (s), 751 (s), 762 (s, sh), 1063 (vs),
1133 (vs), 1585 (m). MS (FAB+, CH2Cl2; m/z; %): 1119, 100%
(M+).
Cr ysta l Str u ctu r e An a lysis of [{P t{CH2C6H4P (o-tolyl)2-
KC,P }(µ-4-Mep z)}2Ag]ClO4‚2CHCl3 (4c‚2CHCl3). Crystal
data and other details of the structure analysis are presented
in Table 1. Suitable crystals of 4c were obtained by slow
diffusion of n-hexane into a solution of 0.025 g of [{Pt-
{CH2C6H4P(o-tolyl)2-κC,P}(µ-4-Mepz)}2Ag]ClO4 in CH2Cl2 (3
mL) and were mounted at the end of a glass fiber. Unit cell
dimensions were determined from 25 centered reflections in
the range 22.0 < 2θ < 31.5°, each centered at four different
goniometer positions. An absorption correction was applied on
the basis of 548 azimuthal scan data.
1
(Table 2). The H NMR spectra (similar experimental
conditions) also confirm the equivalence of the halves
of the molecules (see Experimental Section). In addition,
the presence of only one singlet due to H4 (or to 4-Me)
of both pyrazolate rings indicates that these complexes
have a trans configuration. If these complexes were the
cis isomers, their 1H NMR spectra should show two
signals, as the two rings would be magnetically non-
equivalent. The assignments of the CH3 signals of the
respective molecules were made through NOESY ex-
periments.
The structure was solved by Patterson and Fourier methods.
All refinements were carried out using the program SHELXL-
93.27 All non-hydrogen atoms were assigned anisotropic dis-
placement parameters and refined without positional con-
straints. All hydrogen atoms were constrained to idealized
geometries and assigned isotropic displacement parameters
of 1.2 times the Uiso value of their attached carbon atoms (1.5
times for methyl hydrogen atoms). Full-matrix least-squares
2
refinement of this model against F converged to the final
The 31P and 1H NMR spectra of [{M{CH2C6H4P(o-
tolyl)2-κC,P}(µ-3,5-dmpz)}2] (M ) Pt (2b), Pd, (3b)) in
(27) Sheldrick, G. M. SHELXL 93; University of Go¨ttingen, Go¨ttin-
gen, Germany.

Neutral Pyrazolate Complexes of Pd and Pt
Organometallics, Vol. 21, No. 22, 2002 4607
Sch em e 1
Ta ble 2. 31P {1H} NMR Da ta
complex
δ(P) (ppm)
∆(δ(P)) (ppm)
1J Pt-P (Hz)
∆(1J Pt-P) (Hz)
[{Pt(C∧P)(µ-O2CCH3)}2] (1a )a,b
8.42 (s)
19.39 (s)
18.72 (s)
19.47 (s)
36.60 (s)
35.61 (s)
36.48 (s)
14.10 (s)
9.39 (s)
5311.0
3957.4
4026.9
3951.0
[{Pt(C∧P)(µ-pz)}2] (2a )c
[{Pt(C∧P)(µ-3,5-dmpz)}2] (2b)c
[{Pt(C∧P)(µ-4-Mepz)}2] (2c)c
[{Pd(C∧P)(µ-pz)}2] (3a )c
[{Pd(C∧P)(µ-3,5-dmpz)}2] (3b)c
[{Pd(C∧P)(µ-4-Mepz)}2] (3c)d
[{Pt2(C∧P)2(µ-pz)2Ag] ClO4 (4a )c
[{Pt2(C∧P)2(µ-3,5-dmpz)2Ag] ClO4 (4b)c
[{Pt2(C∧P)2(µ-4-Mepz)2Ag] ClO4 (4c)d
[{Pd2(C∧P)2(µ-3,5-dmpz)2Ag(ClO4)}2] (5)c
-5.29
-9.33
-7.56
2.53
3383.9
3294.9
3342.3
-573.5
-732.0
-608.7
11.91 (s)
39.13 (s)
C∧P ) CH2C6H4P(o-tolyl)2-κC,P. Conditions: CDCl3, 218 K. c Conditions: CDCl3, 293 K. Conditions: CD2Cl2, 293 K.
a
b
d
CDCl3 are temperature-independent (range -60 to 20
°C), indicating that throughout this range only the trans
isomer is present in solution. However, the 31P NMR
spectra of [{M{CH2C6H4P(o-tolyl)2-κC,P}(µ-Rpz)}2] (M
) Pt, Rpz ) pz (2a ), 4-Mepz (2c); M ) Pd, Rpz ) pz
(3a ), 4-Mepz (3c)) at -50 °C show three singlets, two of
them (2a , 17.53 (s), 28.93 (s) ppm; 2c, 17.25 (s), 29.00
(s) ppm; 3a , 34.91 (s), 48.88 (s) ppm; 3c, 34.52 (s), 48.82
(s) ppm) due to the cis isomer, in which the halves of
the molecules are inequivalent, probably due to the
hindered rotation of the o-tolyl groups about the P-C
bonds. The other signal (2a , 17.74 (s) ppm; 2c, 19.00
(s) ppm; 3a , 35.88 (s) ppm; 3c, 35.59 (s) ppm) corre-
sponds to the trans isomer, in which the P-C bond
rotation is not prevented. As the temperature increases,
the intensity of the singlets due to the cis isomer
decreases identically, while the singlet due to the trans
isomer grows, remaining as the only signal observed at
room temperature. This fact indicates (a) that complexes
2a , 3a (Rpz ) pz) and 2c, 3c (Rpz ) 4-Mepz) are present
in solution as a mixture of two isomers (cis and trans),
which interconvert with each other very quickly, prob-
ably through mononuclear species (Scheme 1), and (b)
that the trans isomer is the only species detected at 20
°C. The 1H NMR spectra of 2a ,c and 3a ,c at low temper-
atures are also fully compatible with this behavior.
A crystallographic analysis of 2a at 5 °C reveals a cis
structure for this complex in the solid state. Because of
poor data quality, the results are not suitable for
publication, but the connectivity and the characteristic
boatlike conformation of the six-membered “Pt2N4”
metallacycle can be unambiguously established.
Rea ctivity of th e P la tin u m Der iva tives [{P t-
{CH2C6H4P (o-tolyl)2-KC,P }(µ-Rp z)}2] (Rp z ) p z (2a ),
3,5-d m p z (2b), 4-Mep z (2c)) tow a r d Ag(I) Sp ecies.
[{Pt(C∧P) (µ-Rpz)}2] (Rpz ) pz (2a ), 3,5-dmpz (2b),
4-Mepz (2c)) react with equimolar amounts of AgClO4
in CH2Cl2/OEt2 to afford the complexes [{Pt(C∧P)(µ-
Rpz)}2Ag]ClO4 (Rpz ) pz (4a ), 3,5-dmpz (4b), 4-Mepz
(4c)) in high yield, as indicated in Scheme 2. The

4608 Organometallics, Vol. 21, No. 22, 2002
Falvello et al.
Sch em e 2
reactions of complexes 2a -c with greater quantities of
AgClO4 (molar ratio 1:3) also yield the same compounds,
4a -c, which indicates that complexes 2a -c incorporate
only one silver atom each. Additionally, complexes 2a -c
react with [Ag(OClO3)(PPh3)] in a 1:2 molar ratio to give,
again, compounds 4a -c, with [Ag(PPh3)2]ClO4 as a
byproduct. These compounds (4a -c) are pale yellow air-
and moisture-stable crystalline solids and have been
characterized by analytical and spectroscopic methods
and also by a single-crystal X-ray diffraction study on
compound 4c.
Mass spectra of compounds 4a -c show a high peak
(I ) 100%) corresponding to the cationic species [{Pt-
(C∧P) (µ-Rpz)}2Ag]+ (m/z 1239 (4a ), 1295 (4b), 1266
(4c)). The molar conductivities of the three compounds
are appropriate for 1:1 electrolytes.
The structure of the cation of 4c is shown in Figure
1, together with the atom-labeling scheme and bond
distances and angles. The trinuclear platinum-silver
[Pt2Ag] cation is comprised of the dinuclear platinum
starting material “[Pt2{CH2C6H4P(o-tolyl)2-κC,P}2(µ-4-
Mepz)2]” and a silver cation bonded to both platinum
centers and to two o-tolyl rings through their π electron
density, in such a way that the Ag atom can be
considered to be trapped in the [Pt2] unit.
The platinum fragment is comprised of two “Pt-
{CH2C6H4P(o-tolyl)2-κC,P}” metallacycles bridged by
two 4-Mepz ligands. The Pt‚‚‚Pt separation (3.402(1) Å)
precludes any intermetallic interaction. The six-mem-
bered ring Pt2N4 has, as expected, a boat conformation,
the angle between the two Pt-N-N-Pt fragments
being 75.7°.28 This conformation creates an “open book”
disposition for the square-planar environments of the
two platinum atoms (as in the starting material). The
dihedral angle between the best least-squares planes
of the platinum environments is 97.2°. This disposition
creates an appropriate site for the silver atom to be
located, two Pt-Ag donor-acceptor bonds being estab-
lished. The Pt-Ag bond distances are 2.783(1) Å (Pt-
(1)-Ag) and 2.788(1) Å (Pt(2)-Ag), within the range
found for this kind of donor-acceptor bond.6,8,11,29 The
Pt-Ag vectors are roughly perpendicular to the coor-
dination planes of their respective Pt atoms; the angle
between the Pt-Ag bond and the perpendicular to the
Pt coordination plane has, in both cases, a value of
11.5°.28 This structural parameter is also indicative of
a good orbital overlap to form the Pt-Ag bond.30
The Pt(1)-Ag-Pt(2) angle is 75.28(2)°, similar to
those found in other complexes in which a dinuclear Pt
complex acts as a chelating ligand toward silver, for
instance in [Pt2Ag(µ-Cl)2(C6F5)4(OEt2)]- (Pt(1)-Ag-Pt-
(2) ) 72.15°)6 and [(C6F5)2Pt(µ-OH)(µ-dppm){Ag(PPh3)}-
Pt(C6F5)2]- (Pt(1)-Ag-Pt(2) ) 76.4°).31
The silver atom completes its coordination sphere
with additional interactions to the π electron density of
two o-tolyl groups, one from each C∧P group. Two short
Ag-C distances to each o-tolyl group are observed:
2.498(7) Å (C(37)) and 2.609(7) Å (C(42)) for one o-tolyl
group and 2.528(7) Å (C(16)) and 2.748(1) Å (C(17)) for
the other. The remaining silver-carbon separations are
greater than 3.00 Å, well beyond the limits from 2.42
(28) Nardelli, M. Comput. Chem. 1983, 7, 95.
(29) Uso´n, R.; Fornie´s, J .; Falvello, L. R.; Toma´s, M.; Casas, J . M.;
Mart´ın, A. Inorg. Chem. 1993, 32, 5212-5215.
(30) Aullo´n, G.; Alvarez, S. Inorg. Chem. 1996, 35, 3137.
(31) Casas, J . M.; Falvello, L. R.; Fornie´s, J .; Mart´ın, A. Inorg. Chem.
1996, 35, 7867-7872.

Neutral Pyrazolate Complexes of Pd and Pt
Organometallics, Vol. 21, No. 22, 2002 4609
cates that, despite the η2-arene-Ag coordination, the
aromaticity of the coordinated aryl ring is maintained,
and further suggests a weak Ag-arene interaction.
The 31P{1H} NMR spectra of complexes 4a -c (see
Table 2) show only one singlet between 9 and 15 ppm
flanked by the corresponding 195Pt satellites, indicating
that the halves of the molecule are equivalent in solu-
tion. These signals appear at lower frequencies, and the
195Pt-P coupling constants are smaller, than those ob-
served in the respective starting materials (∆J Pt-P range
570-735 Hz). As was the case in the complexes [Pt-
(C∧P)(S2CZ)HgX(µ-X)]2 (Z ) NMe2, OEt; X ) Br, I),21
[Pt(C∧P)(acac-O,O′)HgI(µ-I)]2, and [{Pt(C∧P)(acac-O,O′)-
HgBr(µ-Br)}2(µ-HgBr2)],22 the decrease observed in the
195Pt-P coupling constant occurs when the Pt atoms are
involved in a Pt to M (M ) Hg, Ag) donor-acceptor bond.
Keeping in mind that the compounds [{Pt(C∧P)(µ-
Rpz)}2] (Rpz ) pz (2a ), 3,5-dmpz (2b), 4-Mepz (2c)) react
with [Ag(OClO3)(PPh3)] in a 1:2 molar ratio to afford
the complexes [{Pt(C∧P)(µ-Rpz)}2Ag]ClO4 (Rpz ) pz
(4a ), 3,5-dmpz (4b), 4-Mepz (4c)), with [Ag(PPh3)2]ClO4
as a byproduct, it is worth emphasizing the following.
The strength of η1-arene- or η2-arene-metal interac-
tions depends on the nature of both the arene and the
complex fragment, but they are normally weak in
nature,41 since this kind of interaction can be broken
easily by weak donor ligands.42-45 Surprisingly, in our
case, the opposite holds, since the PPh3 ligand is
replaced from the coordination sphere of the Ag atom
by the π electron density of two aromatic rings. As a
result, this PPh3 ligand bonds to another Ag atom to
form [Ag(PPh3)2]ClO4 as a byproduct.
Rea ctivity of th e P a lla d iu m Der iva tives [{P d -
{CH2C6H4P (o-tolyl)2-κC,P }(µ-Rp z)}2] (Rp z ) p z (3a ),
3,5-d m p z (3b), 4-Mep z (3c)) tow a r d AgClO4. Com-
plexes 3a ,c do not react with AgClO4 in any molar ratio,
while the reaction of [Pd2(C∧P)2(µ-3,5-dmpz)2] (3b )
with AgClO4 gives [{Pd2(C∧P)2(µ3-3,5-dmpz-N,N′,C4)2Ag-
(µ2-η2-ClO4)}2] (5), as is indicated in Scheme 2.
The molecular structure of 5, determined by X-ray
diffraction, has been communicated.24 The molecule is
represented in Scheme 2. The structure of complex 5 is
completely different from that of the Pt complexes, since
neither Pd-Ag nor o-tolyl arene-Ag interactions are
present.
F igu r e 1. Molecular structure and numbering scheme for
4c. Selected bond lengths (Å) and angles (deg) for 4c‚
2CHCl3: Pt(1)-Ag ) 2.783(1), Pt(2)-Ag ) 2.788(1), Pt-
(1)-P(1) ) 2.229(2), Pt(1)-C(15) ) 2.055(7) Pt(1)-N(1) )
2.070(6), Pt(1)-N(3) ) 2.093(6), Pt(2)-P(2) ) 2.227(2), Pt-
(2)-C(36) ) 2.068(7), Pt(2)-N(2) ) 2.085(5), Pt(2)-N(4)
) 2.068(5), Ag-C(16) ) 2.528(7), Ag-C(17) ) 2.748(1), Ag-
C(37) ) 2.498(7), Ag-C(42) ) 2.609(7); C(15)-Pt(1)-N(1)
) 88.0(3), N(1)-Pt(1)-N(3) ) 87.4(2), C(15)-Pt(1)-P(1) )
84.3(2), N(3)-Pt(1)-P(1) ) 100.43(16), C(15)-Pt(1)-Ag )
87.7(2), N(1)-Pt(1)-Ag ) 99.07(16), N(3)-Pt(1)-Ag )
94.91(15), P(1)-Pt(1)-Ag ) 77.21(5), C(36)-Pt(2)-N(4) )
89.3(3), N(4)-Pt(2)-N(2) ) 86.6(2), C(36)-Pt(2)-P(2) )
84.8(2), N(2)-Pt(2)-P(2) ) 99.75(15), C(36)-Pt(2)-Ag )
86.6(2), N(4)-Pt(2)-Ag ) 96.62(16), N(2)-Pt(2)-Ag )
97.74(16), P(2)-Pt(2)-Ag ) 76.55(5), Pt(1)-Ag-Pt(2) )
75.28(2), Pt(1)-Ag-C(16) ) 79.05(16), Pt(2)-Ag-C(37) )
77.86(16), C(37)-Ag-C(42) ) 31.9(2), C(16)-Ag-C(42) )
120.8(2), C(16)-Ag-C(37) ) 149.5(2), Pt(2)-Ag-C(42) )
100.43(17).
to 2.76 Å observed in previously reported AgI-η-aryl
complexes.32-40 Thus, from the shortest Ag-C distances,
it can be construed than the two o-tolyl groups are η2-
bonded to the silver center. In accord with a common
feature found in complexes with this kind of aryl-metal
interaction36-40 the two o-tolyl rings show asymmetrical
η2-aryl-silver bonds; the corresponding Ag-C lines form
angles with the perpendicular to the aryl ring, of 6.8
and 24.3° for C(16) and C(17) and of 12.1 and 21.3° for
C(37) and C(42), respectively. Longer Ag-C distances
correspond to larger deviations of the Ag atom from the
line perpendicular to the aryl ring, drawn through the
corresponding C atom. The coordinated phenyl groups
maintain their planarity, and the C-C distances in the
rings are equal within experimental error.28 This indi-
The extraordinary structural feature of this compound
is the unprecedented coordination mode of the 3,5-dmpz
groups to Ag+. The silver cation is located in the cleft
between, and approximately equidistant from, the two
3,5-dmpz rings at distances of 2.410(5) and 2.420(5) Å
from the respective C4 atoms (Scheme 2). Thus, both
3,5-dmpz rings are η1-coordinated (C4 ) to the silver
atom. Despite the η1 interaction to the silver center, the
pyrazolato rings maintain their aromaticity, as the bond
distances and angles in the dmpz groups in 5 are very
similar to those observed in uncomplexed “M2L2(µ-pz)2”
(32) Barnes, J . C.; Blyth, C. S. Inorg. Chim. Acta 1985, 98, 181.
(33) Schmidbaur, H.; Bublak, W.; Huber, B.; Reber, G.; Mu¨ller, G.
Angew. Chem., Int. Ed. Engl. 1986, 25, 1089.
(34) Kang, H. C.; Hanson, A. W.; Eaton, B.; Boekelheide, V. J . Am.
Chem. Soc. 1985, 107, 1979.
(35) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T.; Maekawa, M.;
Suenaga, Y.; Sugimoto, K. Inorg. Chem. 1997, 36, 4903.
(36) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T.; Maekawa, M.;
Suenaga, Y.; Ning, G. L.; Kojima, T. J . Am. Chem. Soc. 1998, 120,
8610-8618.
(37) Ning, G. L.; Munakata, M.; Wu, L. P.; Maekawa, M.; Kuroda-
Sowa, T.; Suenaga, Y.; Sugimoto, K. Inorg. Chem. 1999, 38, 1376-
1377.
(38) Batsanov, A. S.; Crabtree, S. P.; Howard, J . A. K.; Lehmann,
C. W.; Kilner, M. J . Organomet. Chem. 1998, 550, 59-61.
(39) Xu, W.; Puddephatt, R. J .; Muir, K. W.; Torabi, A. A. Organo-
metallics 1994, 13, 3054.
(40) Uso´n, R.; Laguna, A.; Laguna, M.; Manzano, B. R.; J ones, P.
G.; Sheldrick, G. M. J . Chem. Soc., Dalton Trans. 1984, 285-292.
(41) Shiu, K. B.; Chou, C. C.; Wang, S. L.; Wei, S. C. Organometallics
1990, 9, 286.
(42) Ca´mpora, J .; Lo´pez, J . A.; Palma, P.; Valerga, P.; Spilner, E.;
Carmona, E. Angew. Chem., Int. Ed. 1999, 38, 147-151.
(43) Falvello, L. R.; Fornie´s, J .; Navarro, R.; Sicilia, V.; Toma´s, M.
J . Chem. Soc., Dalton Trans. 1994, 3143-3148.
(44) Casas, J . M.; Fornie´s, J .; Mart´ın, A.; Menjon, B. Organometallics
1993, 12, 4376-4380.
(45) Casas, J . M.; Fornie´s, J .; Mart´ın, A.; Menjon, B.; Toma´s, M. J .
Chem. Soc., Dalton Trans. 1995, 2949-2954.

4610 Organometallics, Vol. 21, No. 22, 2002
Falvello et al.
Con clu d in g Rem a r k s
The ability of the neutral dinuclear platinum azolato
complexes 2a -c to participate in the formation of
PtfAg bonds is obvious.
The reactivity of the analogous palladium derivatives
toward AgClO4 is much reduced, since two of them do
not allow isolation of any silver adduct and [Pd2(C∧P)2-
(µ-3,5-dmpz)2] (3b) forms a very unusual Pd/Ag adduct
with the silver cation locked into the cleft between the
two dmpz groups through two η1-C4-Ag bonds.
The Pt- and Pd-containing starting materials display
remarkable flexibility in adapting to the coordination
of Ag+. The platinum complexes form two PtfAg
2
donor-acceptor bonds using the dz electron density on
Pt, an interaction that is optimized when Ag lies on the
line perpendicular to the platinum coordination plane.
Together with the constraints imposed by the bridging
pyrazolyl ligands, this leads to a dihedral angle of 82.9°
between the two platinum coordination planes for 4c,
as compared to the value of 69.8° found for the pal-
ladium complex 5, which lacks Pd-Ag bonds. For the
Pd-containing product, the two η1-C-Ag bonds lead to
a dihedral angle of 44.8° between the dmpz rings. This
can be compared to the value of 109.9° for the platinum
complex, in which the dmpz groups do not accommodate
the silver atom (Figure 2).
Ack n ow led gm en t. We thank the Direccio´n General
de Ensen˜anza Superior of Spain for financial support
(Projects PB98-1595-C02-01 and PB98-1593), Prof. R.
Navarro for helpful discussions, and J ose´ M. Saez-
Rocher for some experimental assistance.
F igu r e 2.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
positional and equivalent isotropic displacement parameters,
anisotropic displacement parameters, all bond distances and
bond angles, and hydrogen coordinates and isotropic displace-
ment parameters for the crystal structure of complex 4. This
material is available free of charge via the Internet at
http://pubs.acs.org.
compounds. The mass spectrum (FAB+) of 5 shows the
molecular peak for the cation [Pd2(C∧P)2(µ3-3,5-dmpz-
N,N′C4)2Ag]+ (m/z 1119). The sharp 31P, 1H, and 13C
NMR signals of 5 at room temperature and their
observed shifts with respect to those in the starting
material, 3b, indicate that the silver-η1-dmpz bonds are
present in solution.
OM0203835