Synthesis and structure of new neutral bimetallic platinum hydride complexes

Article abstract of DOI:10.1021/om970581+

The reactions of mononuclear hydride complexes trans-[PtHXL₂] with the solvated species Cis-[Pt(C₆F₅)₂(thf)₂] constitute a simple methodology to high-yield synthesis of dinuclear compounds with a mixe

Full text of DOI:10.1021/om970581+

5392
Organometallics 1997, 16, 5392-5405
Articles
Syn th esis a n d Str u ctu r e of New Neu tr a l Bim eta llic
P la tin u m Hyd r id e Com p lexes
Irene Ara,† Larry R. Falvello,† J uan Fornie´s,*,† Elena Lalinde,*,‡
Antonio Mart´ın,† Francisco Mart´ınez,† and M. Teresa Moreno‡
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-Consejo Superior de Investigaciones Cientı´ficas, 50009 Zaragoza,
Spain, and Departamento de Quı´mica, Universidad de La Rioja, 26001 Logron˜o, Spain
Received J uly 9, 1997X
The reactions of mononuclear hydride complexes trans-[PtHXL2] with the solvated species
cis-[Pt(C6F5)2(thf)2] constitute a simple methodology to high-yield synthesis of dinuclear
compounds with a mixed bridging system H/X. Thus, trans-[Pt(CtCPh)H(PPh3)2] reacts
readily with cis-[Pt(C6F5)2(thf)2] to give trans-[(C6F5)(PPh3)Pt(µ-H)(µ-CtCPh)Pt(C6F5)(PPh3)]
(1b), containing (X-ray) a µ-η1:η2-CtCPh alkynyl ligand. trans-[Pt(C6F5)H(PPh3)2] reacts
with cis-[Pt(C6F5)2(thf)2] under mild conditions to afford initially the 1:1 adduct trans,cis-
[(C6F5)(PPh3)Pt(µ-H)(µ(P)-η2-PPh3)Pt(C6F5)2] (2a ), which finally rearranges quantitatively
to form cis-[(C6F5)(PPh3)Pt(µ-H)(µ-C6F5)Pt(C6F5)(PPh3)] (2c). The crystal structures of 2a ,
a compound displaying an unusual PPh3 bridging ligand via the P donor atom and an η2-
phenyl interaction, and 2c with a mixed pentafluorophenyl/hydride bridged system are
reported. Similar hydride/chloride bridged diplatinum complexes [(C6F5)LPt(µ-H)(µ-Cl)Pt-
(C6F5)L] (3, L ) PPh3; 4, L ) PEt3), are also quantitatively formed by treatment of trans-
[PtClHL2] with cis-[Pt(C6F5)2(thf)2] in CHCl3. Both complexes are obtained as trans isomers
(3b and 4b), but their NMR data in CD3COCD3 indicate that they are present as a mixture
of trans (3b, 4b) and cis (3c, 4c) isomers. Slow crystallization of 3b (CH2Cl2/hexane) in the
presence of light gave crystals of the cis isomer 3c (X-ray), which is also quantitatively formed
by photolysis of 3b. The presence of hydride bridging ligands in all complexes 1-4 is
1
unambiguously confirmed by H NMR spectroscopy.
In tr od u ction
common type the platinum atoms are linked only by
hydride ligands, and examples of both singly (µ-H)4 and
doubly (µ-H)24dfhi,5 hydride bridged derivatives are known.
Hydride-bridged complexes containing other bridging
ligands, the latter contributing to the reinforcement of
the stability of the dinuclear unit, are also known; the
most representative are the cationic bis(diphenylphos-
phino)methane-bridged A-frame species of type [Pt2X2-
(µ-H)(µ-dppm)2]+ (X ) halide, hydride, alkyl, aryl,
alkynyl).6 In contrast, examples of diplatinum com-
plexes containing a mixed-bridge system of the type
Bimetallic hydride-bridged complexes are an interest-
ing family of compounds because of their structural
features and reactivity, particularly as related to their
catalytic activity.1 Since the report of the first neutral
doubly hydride bridged diplatinum complexes [Pt(µ-H)-
RL2]2 (R ) H, SiR′3, GeR′3, L ) phosphine),2 which were
shown to be very efficient catalysts for the hydrosilyl-
ation and hydrogermylation of alkenes and alkynes,3
several types of homodinuclear hydride-bridged plati-
num compounds have been reported. In the most
† Universidad de Zaragoza-Consejo Superior de Investigaciones
Cient´ıficas.
(4) (a) Bracher, G.; Grove, D. M.; Venanzi, L. M.; Bachechi, F.; Mura,
P.; Zambonelli, L. Angew. Chem., Int. Ed. Engl. 1978, 17, 778. (b)
Minghetti, G.; Banditelli, G.; Bandini, A. L. J . Organomet. Chem. 1977,
139, C80. (c) Tulip, T. H.; Yamagata, T.; Yoshida, T.; Wilson, R. D.;
Ibers, J . A.; Otsuka, S. Inorg. Chem. 1979, 18, 2239. (d) Grove, D. M.;
van Koten, G.; Ubbels, H. J . C. J . Am. Chem. Soc. 1982, 104, 4285. (e)
Carmona, D.; Thouvenot, R.; Venanzi, L. M.; Bachechi, F.; Zambonelli,
L. J . Organomet. Chem. 1983, 250, 589. (f) Paonessa, R. S.; Trogler,
W. C. Inorg. Chem. 1983, 22, 1038. (g) Carmona, D.; Chaloupka, S.;
J ans, J .; Thouvenot, R.; Venanzi, L. M. J . Organomet. Chem. 1984,
275, 303. (h) Paonessa, R. S.; Prignano, A. L.; Trogler, W. C. Organo-
metallics 1985, 4, 647. (i) Bandini, A. L.; Banditelli, G.; Cinellu, M.
A.; Sanna, G.; Minghetti, G.; Demartin, F.; Manassero, M. Inorg. Chem.
1989, 28, 404. (j) Bergamini, P.; Sostero, S.; Traverso, O.; Venanzi, L.
M. Inorg. Chem. 1990, 29, 4376. (k) Bachechi, F. Acta Crystallogr. 1993,
C49, 460. (l) Bachechi, F.; Mura, P.; Zambonelli, L. Acta Crystallogr.
1993, C49, 2072. (m) Schwartz, D. J .; Andersen, R. A. J . Am. Chem.
Soc. 1995, 117, 4014. (n) Hill, G. S.; Puddephatt, R. J . J . Am. Chem.
Soc. 1996, 118, 8745. (o) Albinati, A.; Chaloupka, S.; Eckert, J .;
Venanzi, L. M.; Wolfer, M. K. Inorg. Chim. Acta 1997, 259, 305.
‡ Universidad de La Rioja.
X Abstract published in Advance ACS Abstracts, November 1, 1997.
(1) (a) Venanzi, L. M. Coord. Chem. Rev. 1982, 43, 251. (b) Hlatki,
G. G.; Crabtree, R. H. Coord. Chem. Rev. 1985, 65, 1; Comments Inorg.
Chem. 1985, 4, 229. (c) Chaloupka, S.; Venanzi, L. M. Inorg. Synth.
1990, 27, 30. (d) Boag, N. M.; Browning, J .; Crocker, C.; Goggin, P. L.;
Goodfellow, R. J .; Murray, M.; Spencer, J . L. J . Chem. Res., Synop.
1978, 228; J . Chem. Res., Miniprint 1978, 2962. (e) Albinati, A.;
Chaloupka, S.; Demartin, F.; Koetzle, T. F.; Ruegger, H.; Venanzi, L.
M.; Wolfer, M. K. J . Am. Chem. Soc. 1993, 115, 168 and references
quoted therein.
(2) (a) Green, M.; Howard, J . A. K.; Proud, J .; Spencer, J . L.; Stone,
F. G. A.; Tsipis, A. C. J . Chem. Soc., Chem. Commun. 1976, 671. (b)
Ciriano, M.; Green, M.; Howard, J . A. K.; Proud, J .; Spencer, J . L.;
Stone, F. G. A.; Tsipis, C. A. J . Chem. Soc., Dalton Trans. 1978, 801.
(3) Green, M.; Spencer, J . L.; Stone, F. G. A.; Tsipis, C. A. J . Chem.
Soc., Dalton Trans. 1977, 1519-1525, 1525-1529. (b) Tsipis, C. A. J .
Organomet. Chem. 1980, 188, 53-61; 1980, 187, 427-446.
S0276-7333(97)00581-5 CCC: $14.00 © 1997 American Chemical Society

Neutral Bimetallic Platinum Hydride Complexes
Organometallics, Vol. 16, No. 25, 1997 5393
Pt(µ-H)(µ-X)Pt are relatively scarce.7-9 As far as we are
aware, only three dimeric derivatives with a mixed
hydride/phosphide bridging system have been reporteds
[{(PPh2POHOPPh2)Pt}2(µ-H)(µ-PPh2)],8c [L2Pt(µ-H)(µ-
Resu lts a n d Discu ssion
It is now well-established that cis-[Pt(C6F5)2(thf)2]11
is an excellent precursor to a variety of mono-,12a-g di-
12h-m
,
and polymetallic12n-q complexes containing the
PR′2)PtLR]+ (L ) PPh3, R′ ) R ) Ph;8a,b L ) PHBut ,
2
“cis-Pt(C6F5)2” fragment, since the two thf groups are
easily replaced by other ligands.12 In the preparation
of di- and polynuclear derivatives much of the effort with
cis-[Pt(C6F5)2(thf)2] has focused on the study of its
reactivity toward metallo species with potentially bridg-
ing groups in cis positions and, probably because of that,
the reactions always proceed with stereoretention. The
reactivity of cis-[Pt(C6F5)2(thf)2] toward metallo species
with the potentially bridging ligands in a relative trans
disposition has been scarcely explored,13ab but we re-
cently noted the different behavior of cis-[Pt(C6F5)2(thf)2]
toward neutral bis(alkynyl) mononuclear platinum
complexes.13a Thus (Scheme 1), while the reactions with
cis-[Pt(CtCR)2(PPh3)2] take place, as expected, with
retention of the cis geometry around both platinum
centers, yielding asymmetric complexes cis,cis-[{L2Pt-
(µ-CtCR)2}Pt(C6F5)2]12i (Scheme 1i), the analogous
reactions with the trans derivatives result in a redis-
R′ ) But, R ) H8d)sin addition to several cationic
derivatives [Pt2(µ-H)(µ-X)(L-L)2]+ synthesized by Ming-
hetti et al.,4i,7 which are formally diplatinum(I) species.
A serendipitous preparation of [Pt2(µ-H)(µ-S)(dppe)2]PF6
has also been reported.9a,b Our interest in platinum
hydride complexes arises from the reported unexpected
formation of a µ-phenylethenylidene-bridged diplatinum
complex by direct reaction between the alkynyl-hydride
mononuclear complexes trans-[Pt(CtCPh)H(PPh3)2] and
cis-[Pt(C6F5)2(thf)(CO)].10 In this paper we report the
synthesis and structural characterization of novel neu-
tral diplatinum complexes [Pt2(µ-X)(µ-H)(C6F5)2L2] (L )
PPh3, X ) CtCPh (1b), C6F5 (2c), Cl (3b,c); L ) PEt3,
X ) Cl (4b,c)) displaying three new mixed hydride
bridging systems. These complexes are obtained in
quantitative yield from simple reactions of cis-[Pt(C6F5)2-
(thf)2] with mononuclear hydride species trans-[PtXHL2].
In addition, we also report the isolation of an unexpected
intermediate isomeric precursor in the formation of 2c,
trans,cis-[(C6F5)(PPh3)Pt(µ-H)(µ-(P)-η2-PPh3)Pt(C6F5)2]
(2a ), which displays (X-ray) an unusual µ(P)-η2-tri-
phenylphosphine bridging ligand.
tribution of ligands and the ultimate formation of the
13a
symmetric trans-[Pt(CtCR)(C6F5)(PPh3)]2
(Scheme
1ii). Therefore, we considered it of interest to explore
this synthetic approach to dinuclear derivatives con-
taining a mixed bridging system, and in view of the
rather small number of hydride-bridged diplatinum
complexes of the type Pt(µ-H)(µ-X)Pt we sought first to
utilize this strategy with mononuclear hydride com-
plexes of the type trans-[PtHXL2] (X ) CtCPh, Cl,
C6F5). In all cases, the reactions with cis-[Pt(C6F5)2-
(thf)2] lead to the formation of dimetallic hydride-
bridged complexes, as is observed by NMR spectroscopy.
R ea ct ion of cis-[P t (C6F 5)2(t h f)2] w it h tr a n s-
[P t (CtCP h )H (P P h 3)2]. Treatment of trans-[Pt-
(CtCPh)H(PPh3)2] with cis-[Pt(C6F5)2(thf)2] in CHCl3 at
room temperature affords trans-[(C6F5)(PPh3)Pt(µ-H)-
(µ(σ,π)η2-CtCPh)Pt(C6F5)(PPh3)] (1b), isolated in 75%
yield, which is the first example of a diplatinum complex
with a mixed µ-H, µ-CtCPh bridging system (Scheme
(5) (a) Bracher, G.; Grove, D. M.; Pregosin, P. S.; Venanzi, L. M.
Angew. Chem., Int. Ed. Engl. 1979, 18, 155; Angew. Chem. 1979, 91,
169. (b) Paonessa, R. S.; Trogler, W. C. J . Am. Chem. Soc. 1982, 104,
3529. (c) Bachechi, F.; Bracher, G.; Grove, D. M.; Kellenberger, B.;
Pregosin, P. S.; Venanzi, L. M.; Zambonelli, L. Inorg. Chem. 1983, 22,
1031. (d) Knobler, C. B.; Kaesz, H. D.; Minghetti, G.; Bandini, A. L.;
Banditelli, G.; Bonati, F. Inorg. Chem. 1983, 22, 2324. (e) Packett, D.
L.; Syed, A.; Trogler, W. C. Organometallics 1988, 7, 159. (f) Car-
michael, D.; Hitchcock, P. B.; Nixon, J . F.; Pidcock, A. J . Chem. Soc.,
Chem. Commun. 1988, 1554. (g) Aime, S.; Gobetto, R.; Bandini, A. L.;
Banditelli, G.; Minghetti, G. Inorg. Chem. 1991, 30, 316. (h) Bennett,
B. L.; Roddick, D. M. Inorg. Chem. 1996, 35, 4703 and references given
therein. (i) Mole, L.; Spencer, J . L.; Litster, S. A.; Redhouse, A. D.;
Carr, N.; Orpen, A. G. J . Chem. Soc., Dalton Trans. 1996, 2315.
(6) (a) Brown, M. P.; Puddephatt, R. J .; Rashidi, M.; Seddon, K. R.
J . Chem. Soc., Dalton Trans. 1978, 516; Inorg. Chim. Acta 1977, 23,
L27. (b) Brown, M. P.; Cooper, S. J .; Frew, A. A.; Manojlovic-Muir, L.;
Muir, K. W.; Puddephatt, R. J .; Thomson, M. A. J . Chem. Soc., Dalton
Trans. 1982, 299; J . Organomet. Chem. 1980, 198, C33. (c) Azam, K.
A.; Puddephatt, R. J . Organometallics 1983, 2, 1396. (d) Azam, K. A.;
Brown, M. P.; Cooper, S. J .; Puddephatt, R. J . Organometallics 1982,
1, 1183. (e) Grossel, M. C.; Batson, R. J .; Moulding, R. P.; Seddon, K.
K. J . Organomet. Chem. 1986, 304, 391. (f) Langrick, C. R.; Pringle,
P. G.; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1985, 1015. (g)
Anderson, G. K. Adv. Organomet. Chem. 1993, 35, 1. (h) Xu, C.;
Anderson, G. K. Organometallics 1994, 13, 3981. (i) Xu, C.; Anderson,
G. K. Organometallics 1996, 15, 1760.
(7) (a) Minghetti, G.; Bandini, A. L.; Banditelli, G.; Bonati, F. J .
Organomet. Chem. 1979, 179, C13. (b) Minghetti, G.; Bandini, A. L.;
Banditelli, G.; Bonati, F.; Szostak, R.; Strouse, C. E.; Knobler, C. B.;
Kaesz, H. D. Inorg. Chem. 1983, 22, 2332. (c) Minghetti, G.; Albinati,
A.; Banditelly, G. Angew. Chem., Int. Ed. Engl. 1985, 24, 120.
(8) (a) J ans, J .; Naegeli, R.; Venanzi, L. M.; Albinati, A. J . Organo-
met. Chem. 1983, 247, C37. (b) Siedle, A. R.; Newmark, R. A.; Gleason,
W. B. J . Am. Chem. Soc. 1986, 108, 767. (c) van Leeuven, P. W. N. M.;
Roobeek, C. F.; Frijns, J . H. G.; Orpen, A. G. Organometallics 1990, 9,
1211. (d) Leoni, P.; Manetti, S.; Pascuali, M. Inorg. Chem. 1995, 34,
749.
(11) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B. Organometallics
1985, 4, 1912.
(12) (a) Casas, J . M.; Falvello, L. R.; Fornie´s, J .; Mart´ın, A. Inorg.
Chem. 1996, 35, 56 and references given therein. (b) Casas, J . M.;
Fornie´s, J .; Mart´ın, A.; Menjo´n, B.; Toma´s, M. J . Chem. Soc., Dalton
Trans. 1995, 2949. (c) Casas, J . M.; Fornie´s, J .; Mart´ın, A.; Menjo´n,
B. Organometallics 1993, 12, 4376. (d) Fornie´s, J .; Menjo´n, B.; Go´mez,
N.; Toma´s, M. Organometallics 1992, 11, 1187. (e) Uso´n, R.; Fornie´s,
J .; Toma´s, M.; Menjo´n, B.; Welch, A. J . J . Organomet. Chem. 1986,
304, C24. (f) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B.; Fortun˜o,
C.; Welch, A. J .; Smith, D. E. J . Chem. Soc., Dalton Trans. 1993, 275.
(g) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B. Organometallics 1986,
5, 1581. (h) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Navarro,
R. J . Chem. Soc., Dalton Trans. 1989, 169. (i) Fornie´s, J .; Go´mez-Saso,
M. A.; Lalinde, E.; Mart´ınez, F.; Moreno, M. T. Organometallics 1992,
11, 2873. (j) Berenguer, J . R.; Falvello, L. R.; Fornie´s, J .; Lalinde, E.;
Toma´s, M. Organometallics 1993, 12, 6. (k) Fornie´s, J .; Lalinde, E.;
Mart´ın, A.; Moreno, M. T.; Welch, A. J . J . Chem. Soc. Dalton Trans.
1995, 1333. (l) Delgado, E.; Fornie´s, J .; Herna´ndez, E.; Lalinde, E.;
Mansilla, N.; Moreno, M. T. J . Organomet. Chem. 1995, 494, 261. (m)
Amador, U.; Delgado, E.; Fornie´s, J .; Herna´ndez, E.; Lalinde, E.;
Moreno, M. T. Inorg. Chem. 1995, 34, 5279. (n) Fornie´s, J .; Mart´ınez,
F.; Navarro, R.; Urriolabeitia, E. P.; Welch, A. J . J . Chem. Soc., Dalton
Trans. 1995, 2805. (o) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B.;
Welch, A. J . Organometallics 1988, 7, 1318. (p) Uso´n, R.; Fornie´s, J .;
Toma´s, M.; Menjo´n, B.; Carnicer, J .; Welch, A. J . J . Chem. Soc., Dalton
Trans. 1990, 151. (q) Fornie´s, J .; Lalinde, E.; Mart´ın, A.; Moreno, M.
T. J . Chem. Soc., Dalton Trans. 1994, 135.
(9) (a) Capdevila, M.; Gonza´lez-Duarte, P.; Mira, I.; Sola, J .; Glegg,
W. Polyhedron 1992, 12, 3091. (b) Glegg, W.; Capdevila, M.; Gonza´lez-
Duarte, P.; Sola, J . Acta Crystallogr. 1996, B52, 270. (c) The species
[(L-L)2Pt2(µ-Cl)(µ-H)]2+ (L-L ) (C6H11)2PCH2CH2P(C6H11)2) has also
been noted to be formed (1H, 31P) by crystallization of [Pt(C7H11)(L-
L)]+ in chlorinated solvents: Carr, N.; Dunne, B. J .; Mole, L.; Orpen,
A. G.; Spencer, J . L. J . Chem. Soc., Dalton Trans. 1991, 863.
(10) Ara, I.; Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Toma´s, M.
Organometallics 1996, 15, 1014.
(13) (a) Berenguer, J . R.; Fornie´s, J .; Mart´ınez, F.; Cubero, J . C.;
Lalinde, E.; Moreno, M. T.; Welch, A. J . Polyhedron 1993, 12, 1797.
(b) Uso´n, R.; Fornie´s, J .; Uso´n, M. A.; Mas, M. L. Inorg. Chim. Acta
1990, 168, 59.

5394 Organometallics, Vol. 16, No. 25, 1997
Ara et al.
Sch em e 1
2, i). Species in which the metal centers are connected
only through a mixed µ-H, µ-CtCR bridging system are
rather rare.14 When the reaction is monitored by NMR
spectroscopy, it is observed that the formation of
complex 1b is immediate (1 or 2 min) and complete; no
other compound is present in solution (1H, 31P, and 19F
NMR). Complex 1b is indefinitely stable both in the
solid state and in solution and has been characterized
by microanalysis and IR and NMR spectroscopy; finally,
a definitive structural assignment has been established
by X-ray crystallography. In the IR spectrum of 1b a
weak absorption at 2018 cm-1, which we assign to
ν(CtC), indicates the presence of a bridging alkynyl
ligand.12i,q,13a We have made no attempts to locate the
IR absorption of the bridging hydride, as it is well-
known that such absorptions (∼1600 cm-1) are usually
weak and often difficult to assign.15 The 19F NMR
spectrum (see Experimental Section) shows two sets of
signals (2Fo, Fp, 2Fm), confirming that the two C6F5
groups are inequivalent. The dimeric nature of the
unambiguously assigned by observing the 31P NMR
spectrum while decoupling only the triphenylphosphine
protons. With this treatment, the downfield signal
(δ[P(1)] 29.21) clearly splits into a doublet (J ≈ 73 Hz)
by the large expected coupling to the trans bridging
hydride. The resonance centered at δ 11.3 is not
affected and is therefore assigned to the PPh3 ligand
1
(P(2)) which is cis to the hydride ligand. The H NMR
spectrum unequivocally demonstrates the presence of
a bridging hydride ligand. It exhibits in the high-field
region (see Figure 1) one hydride resonance at -7.44
ppm with different coupling constants to the two in-
equivalent 31P nuclei (2J H-P(1)(trans) ) 74.2 Hz, 2J H-P(2)(cis)
) 14.5 Hz). Moreover, this resonance shows two dif-
ferent sets of 195Pt satellites, which establishes that this
hydride, not observed in the X-ray crystal structure (see
below), bridges the two platinum atoms. The whole
resonance has roughly the appearance of a quintet (1:
8:18:8:1) of multiplets (dd central (18) and outer (1)
signals and overlapping of dd for the remaining (4:4)),
thus proving the presence of a Pt2(µ-H) group.4n,6a,b The
1
complex is apparent from the 31P and H NMR spectra,
1
each of which consists of the superposition of three
subspectra, arising from the three different isotopomeric
combinations of platinum nuclei having different nuclear
spins (Pt/Pt 43.8%,195Pt/Pt 22.4%, Pt/195Pt 22.4% and
195Pt/195Pt 11.4%, the percentages arising from the
33.8% natural abundance of 195Pt). The 31P NMR
spectrum shows, as expected, two resonances, each
exhibiting short and long platinum satellites (δ[P(1)]
29.21, 1J Pt(1)-P(1) ) 3843 and J Pt(2)-P(1) ) 101 Hz; δ[P(2)]
magnitudes of both J Pt-H values (562 and 515 Hz,
respectively) are in the range previously found in other
hydride-diplatinum derivatives.4-8 In the 13C NMR
spectrum the acetylenic carbon signals are observed at
108.7 and 124.9 ppm for CR and Câ, respectively, which
compares well with the values given for dinuclear
derivatives of other metals containing an analogous µ-H,
µ-CtCR mixed bridging system.14 In order to determine
the structure of 1b, an X-ray diffraction study of a single
crystal has been carried out. A view of the skeleton of
the molecule is shown in Figure 2, and selected bond
distances and angles are listed in Table 2. As can be
seen, the heavy-atom skeleton confirms its dinuclear
nature formed by two Pt(C6F5)(PPh3) units connected
by the alkynyl ligand which is σ-bonded to Pt(1) (Pt(1)-
C(1) ) 1.98(2) Å)and unsymmetrically η2-bonded to Pt(2)
with the R-carbon atom closer to Pt(2) (Pt(2)-C(1) )
2.23(1) Å) than the Câ atom (Pt(2)-C(2) ) 2.35(1) Å).
This type of asymmetry is opposite to that found in the
neutral doubly alkynyl bridged complex [Pt(µ(σ)-η2-
CtCPh)(C6F5)(PPh3)]2,13a and in accord with this struc-
tural feature, the Pt(1)-C(1)-Pt(2) angle (83.8(5)°) is
1
11.30, J Pt(2)-P(2) ) 3590 and J Pt(1)-P(2) ≈ 30 Hz with
J P(1)-P(2) ≈ 0), in agreement with the presence of two
inequivalent phosphorus nuclei (see Table 1 for nuclei
labeling). Resonances due to P(1) and P(2) have been
(14) (a) Nubel, P. O.; Brown, T. L. Organometallics 1984, 3, 29. (b)
Top, S.; Gunn, M.; J aouen, G.; Vaissermann, J .; Daran, J . C.;
McGlinchey, M. J . Organometallics 1992, 11, 1201. (c) Cao, D. H.;
Stang, P. J .; Arif, A. M. Organometallics 1995, 14, 2733. (d) Bruce, M.
I.; Low, P. J .; Skelton, B. W.; White, A. H. J . Organomet. Chem. 1996,
515, 65. (e) Wu, H.-L.; Lu, G.-L.; Chi, Y.; Farrugia, L. J .; Peng, S.-M.;
Lee, G.-H. Inorg. Chem. 1996, 35, 6015. (f) Schaverien, C. J . Organo-
metallics 1994, 13, 69. (g) Top, S.; Gunn, M.; J aouen, G.; Vaissermann,
J .; Daran, J . C.; Thornback, J . R. J . Organomet. Chem. 1991, 414, C22.
(15) Kaesz, H. D.; Saillant, R. B. Chem. Rev. 1972, 72, 231. See also
ref 5h.

Neutral Bimetallic Platinum Hydride Complexes
Organometallics, Vol. 16, No. 25, 1997 5395
Ta ble 1. 31P a n d 1H NMR Da ta a
1H
2J H-P(1)(trans) J H-P(2)(cis) J Pt-H J Pt-H
31P
δ(H)
δ (other)
2
1
1
1
1bb 29.21 (P(1), J Pt(1)-P(1) ) 3843, J Pt(2)-P(1) ) 101)
-7.44
74.2
14.5
562
515 7.63-7.21 (m, 35H, Ph)
1
11.30 (P(2), J Pt(2)-P(2) ) 3590, J Pt(1)-P(2) ) 30)
J P(1)-P(2) ≈ 0
2a c 17.77 (P(A),d J Pt(1)-P(A) ) 2573)
-10.75e
535
623
8.15, 7.5 (m, 30H, Ph)f
1
1
12.22 (P(B), J Pt(1)-P(B) ) 2553, J Pt(2)-P(B) ) 166.4)
2J P(A)-P(B) ) 386.2
2cb 18.23 (1J Pt-P ) 3825, J Pt-P ) 112)
-8.32g
-9.33
7.33, 7.07 (m, 30H, Ph)
566 7.54-7.27 (m, 30H, Ph)
2
1
3bh 17.34 (P(1), J Pt(1)-P(1) ) 3859, J Pt(2)-P(1) ) 94.9)
81.7
75.2
i
i
642
1
i
11.96 (P(2), J Pt(2)-P(2) ) 4403, J Pt(1)-P(2)
)
3ch 10.6 (1J Pt-P ) 4513, J Pt-P
)
-10.84g
-9.9j
575
592
7.29, 7.06 (m, 30H, Ph)
1.88 (m, 6H), 1.6 (m, 6H)
(CH2, PEt3); 1.08 (m, 9H),
0.95 (m, 9H) (CH3, PEt3)
2
i
1
4b 16.10 (P(1), J Pt(1)-P(1) ) 3609, J Pt(2)-P(1) ) 98.2)
1
i
15.55 (P(2), J Pt(2)-P(2) ) 4151, J Pt(1)-P(2)
)
4ck 13.75 (1J Pt-P ) 4085, J Pt-P ) 23.3)
-11.96g
590
2
4
i
5
8.48 (1J Pt-P ) 4491, J Pt-P
)
In CDCl3; J in Hz. The same spectral pattern is observed both at -50 °C and in CD3COCD3. c In HDA. J Pt(2)-P(A) not resolved.
a
b
d
e Quintuplet (1:8:18:8:1), the same pattern is observed at -85 °C. f Data at -85 °C: δ 8.66, 8.43, 8.23, 8.1, 7.85, 7.55, 7.47, 7.19, 6.32 (all
g
h
i
j
k
broad). Quintuplet (1:8:18:8:1). The same spectra (1H and 31P) are observed at -50 °C. Not resolved. Quintuplet of doublets. Data
1
1
from a mixture of 4b and 4c (2:1) in CD3COCD3; in CDCl3 δ(P) 11.86, J Pt-P ) 4169 Hz, δ(H) -12.09, J Pt-H ) 583 Hz.
F igu r e 1. High-field region of the 1H NMR spectrum of [trans-(C6F5)(PPh3)Pt(µ-H)(µ-CtCPh)Pt(C6F5)(PPh3)] (1b) in CDCl3
at 20 °C; J values are in hertz.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for tr a n s-[(C6F 5)(P P h 3)P t-
(µ-H)(µ-CtCH)P t(C6F 5)(P P h 3)] (1b)
Pt(1)-C(1)
Pt(1)-P(1)
Pt(2)-C(33)
Pt(2)-P(2)
C(1)-C(2)
1.98(2)
Pt(1)-C(9)
Pt(1)-Pt(2)
Pt(2)-C(1)
Pt(2)-C(2)
C(2)-C(3)
2.08(2)
2.262(3)
2.048(13)
2.247(4)
1.23(2)
2.8159(10)
2.232(13)
2.354(12)
1.44(2)
C(1)-Pt(1)-C(9)
C(9)-Pt(1)-P(1)
C(9)-Pt(1)-Pt(2)
166.9(5)
91.9(4)
114.9(4)
C(1)-Pt(1)-P(1)
C(1)-Pt(1)-Pt(2)
P(1)-Pt(1)-Pt(2)
C(33)-Pt(2)-P(2)
C(33)-Pt(2)-C(2)
101.2(4)
52.0(4)
153.23(9)
88.7(4)
C(33)-Pt(2)-C(1) 113.8(5)
C(1)-Pt(2)-P(2)
P(2)-Pt(2)-C(2)
C(1)-Pt(2)-Pt(1)
C(2)-Pt(2)-Pt(1)
C(2)-C(1)-Pt(2)
C(1)-C(2)-C(3)
157.3(4)
171.5(3)
44.2(4)
75.2(3)
80.0(8)
82.9(5)
C(33)-Pt(2)-Pt(1) 157.8(3)
P(2)-Pt(2)-Pt(1)
C(2)-C(1)-Pt(1)
Pt(1)-C(1)-Pt(2)
113.08(9)
163.8(11)
83.8(5)
163.6(13)
F igu r e 2. Drawing of the crystal structure of trans-[(C6F5)-
(PPh3)Pt(µ-H)(µ-CtCH)Pt(C6F5)(PPh3)] (1b), showing the
atom-labeling scheme.
P atoms of the PPh3 ligands and the Cipso carbon atoms
of the terminal C6F5 groups are also contained in this
plane. The least-squares coordination planes (Pt(1),
C(1), C(9), P(1) for Pt(1) and Pt(2), C(33), P(2), C(1,2)
(C(1,2) ) midpoint of C(1)-C(2)) for Pt(2)) are almost
coplanar, forming a dihedral angle of 3.52(7)°.
Although the hydride has not been located directly
from the final difference Fourier map, its position as a
bridging ligand between the two platinum atoms and
more acute than that observed in [Pt(µ(σ)-η2-CtCPh)-
(C6F5)(PPh3)]2 (112.5(2)°). The acetylenic fragment
deviates from linearity (angles at CR and Câ ∼163°),
adopting a trans-bent arrangement. The C(1)-C(2) and
Pt(1)-Pt(2) vectors form an angle of 35.77(3)°, but the
Pt(1)-Pt(2)-C(1)-C(2) core is roughly planar and the

5396 Organometallics, Vol. 16, No. 25, 1997
Ara et al.
Ta ble 3. P t-P t Dista n ces, Nu m ber of Electr on s in th e Br id ge, a n d Nu m ber of Tota l Electr on s in Bin u clea r
Hyd r id o-Br id ged P la tin u m (II) Com p lexes
electrons in
the bridge
total
electron
Pt(1)-Pt(2) (Å)
ref
[(PEt3)2PhPt(µ-H)PtY(PEt3)2]+
2
30
3.238(1) (Y ) Ph)
4e
4a
2
3.093(1) (Y ) H)
2.692(3)
[Pt(µ-H)(SiEt3)(PEt3)]2
4
4
4
28
28
30
[{(C6F5)(PPh3)Pt}2(µ-H)(µ-C6F5)] (2c)
2.6742(7)
this work
5c
5c
5d
this work
this work
this work
8c
8b
8a
[(PEt3)2Pt(µ-H)2PtX(PEt3)2]+
2.819(1) (X ) Ph)
2.826(1) (X ) H)
2.728(1)
[(dppe)Pt(µ-H)2PtH(dppe)]+
4
6
6
6
6
6
30
30
30
30
30
30
[{(C6F5)(PPh3)Pt}2(µ-H)(µ-CtCPh)] (1b)
[(C6F5)(PPh3)Pt(µ-H)(µ-PPh3)Pt(C6F5)2] (2a )
[(C6F5)(PPh3)Pt(µ-H)(µ-Cl)Pt(C6F5)(PPh3)] (3c)
[{(PPh2POHOPPh2)Pt}2(µ-H)(µ-PPh2)]
[(PPh3)2Pt(µ-H)(µ-PPh2)PtPh(PPh3)]Z
2.8159(10)
2.7593(6)
2.907(1)
2.885(1) (Z ) HC(SO2CF3)2)
2.889(3) (Z ) BF4)
2.912(2)
[(dppe)Pt(µ-H)(µ-S)Pt(dppe)]+
6
30
2.774(1)
9
approximately trans to P(1) is quite clear from the NMR
spectroscopic data. Moreover, the Pt(1)-Pt(2) vector
does not bisect the P-Pt-Cipso angle of the Pt(C6F5)-
(PPh3) units, which is also consistent with the presence
of a bridging H ligand. The Pt(1)-Pt(2)-C(33) (157.8(3)°)
and P(1)-Pt(1)-Pt(2) (153.23(9)°) angles are substan-
tially larger than the corresponding Pt(2)-Pt(1)-C(9)
(114.9(4)°) and P(2)-Pt(2)-Pt(1) (113.08(9)°) ones, thus
reflecting a considerable bending of both P(2)Ph3 and
C6F5 (with C(9)) ligands toward the less sterically
demanding bridging hydride ligand. The relative value
of the long-range platinum-phosphorus coupling ob-
served (J Pt(2)-P(1) ) 101 Hz and J Pt(1)-P(2) ≈ 30 Hz,
respectively) can be readily understood on the basis of
this structural feature. It is reasonable that P(2) shows
smaller long-range coupling to Pt(1) as a result of the
considerable deviation of the angle Pt(1)-Pt(2)-P(2)
(113.08(9)°) from linearity. Both Pt-P(1,2) bond dis-
tances (2.262(3), 2.247(4) Å), which span the range
usually observed for PtII-P bonds,12i,13a are identical
within experimental error, even though the correspond-
ing trans bridging ligands are different. Thus, in this
complex, the two bridging groups (µ-H and µ-C2R) seem
to exhibit similar trans influences. If the µ-hydride
ligand is treated as a two-electron anionic donor and
the alkynyl bridging group is assumed to be a four-
electron anionic donor, then the platinum atoms are in
the formal oxidation state +2 and the total valence
electron count sums to 30 electrons. This implies a
three-center-two-electron bond for Pt-H-Pt, which is
consistent with the Pt(1)-Pt(2) distance of 2.816(1) Å.
Table 3 reports the observed distances in some dinuclear
platinum(II) hydride compounds. As can be seen, the
Pt-Pt distance in the present compound is significantly
shorter than that observed in 30-electron monohydride-
bridged diplatinum complexes such as [(PEt3)2XPt(µ-
H)PtY(PEt3)2]+ (X ) Y ) Ph 3.238(1) Å;4e X ) Ph, Y )
H, 3.093(1) Å4a (Table 3)) and [Pt2(CH3)2(µ-H)(µ-dppm)2]
(2.93 Å)6b and is more in line with those reported for
dihydride-bridged compounds such as [(PEt3)2Pt(µ-
H)2PtX(PEt3)]+ (X ) Ph, 2.819(1) Å; X ) H, 2.826(1) Å5c)
and [(dppe)Pt(µ-H)2PtH(dppe)]+ (2.728(1) Å) and similar
to 30 e- diplatinum hydride species in which a mixed
bridging system exists (see Table 3). However, the Pt-
Pt separation in this complex (1b) is considerably longer
than those found in [Pt(µ-H)(SiEt3)(PEt3)]2 (2.692(3)Å)2
and 2c (2.6742(7) Å), both with a total valence electron
count of 28 e-. This structural fact is in accord with
recent qualitative molecular orbital calculations, carried
out for systems of this type, which suggest the existence
of through-ring metal-metal interactions for 6- or
4-framework-electron count (FEC, number of electrons
in the bridging system).16 Consistent with these theo-
retical calculations, the platinum-platinum distance in
1b with FEC ) 6 is longer than in [Pt(µ-H)(SiEt3)-
(PEt3)]2 (Table 3) and 2c (2.6742(7) Å) both with a
framework electron count of 4. As expected, a further
lengthening of this Pt‚‚‚Pt separation is observed in 32-
electron diplatinum complexes such as the well-known
doubly halide (∼3.5 Å)17 or doubly alkynyl bridged
dimers [Pt(µ(σ)-η2-CtCPh)(C6F5)(PPh3)]2 (3.65 Å),13a
[(dppe)Pt(µ-CtCPh)2Pt(C6F5)2] (3.27 Å),12i and [Pt(µ(σ)-
2-
η2-CtCPh)(C6F5)2]2 (3.43 Å) with FEC ) 8.12i
R ea ct ion of cis-[P t (C6F 5)2(t h f)2] w it h tr a n s-
[P t(C6F 5)H(P P h 3)2]. Although the ability of C6F5
ligands to act as 3c-2e-bridging ligands between plati-
num or palladium centers has been reported recently,
this group has seldom been seen to act as a bridging
ligand. In fact, the only examples reported have been
the anionic species [MM′(µ-C6F5)2(C6F5)4]2- (M, M′ ) Pd,
18b
Pt)12h,18a and [Pt2(µ-X)(µ-C6F5)(C6F5)4]- (X ) C6F5 or
1,8-naphthyridine (napy)18c), and it is worth noting that
attempts to prepare other palladium or platinum de-
rivatives containing a mixed µ-Xµ-C6F5 (X ) Cl, Br, I)
bridging system have been unsuccessful.12h Bearing
this in mind, and with the aim of preparing a dinuclear
neutral derivative with a mixed µ-Hµ-C6F5 bridging
system, we investigated the reaction between cis-
[Pt(C6F5)2(thf)2] and trans-[Pt(C6F5)H(PPh3)2].
Addition of cis-[Pt(C6F5)2(thf)2] to a colorless solution
of trans-[Pt(C6F5)H(PPh3)2] in CHCl3 at room temper-
ature results in the immediate precipitation of a white
microcrystalline solid in 71% yield, trans,cis-[(C6F5)-
(PPh3)Pt(µ-H)(µ(P)-η2-PPh3)Pt(C6F5)2]‚CHCl3 (2a‚CHCl3)
(path ii, Scheme 2), which has been characterized by
elemental analysis, spectroscopic methods, and X-ray
diffraction analysis. Suitable crystals for an X-ray study
of complex 2a were grown by slow diffusion of n-hexane
into a dichloromethane solution of 2a at low tempera-
(16) Aullo´n, G.; Alemany, P.; Alvarez, S. J . Organomet. Chem. 1994,
478, 75.
(17) (a) Watkins, S. F. J . Chem. Soc. A 1970, 168. (b) Anderson, G.
K.; Cross, R. J .; Manojlovic-Muir, L.; Muir, K. W.; Salomon, T. J .
Organomet. Chem. 1979, 170, 385.
(18) (a) Uso´n, R.; Fornie´s, J ., Toma´s, M.; Casas, J . M.; Cotton, F.
A.; Falvello, L. R.; Llusar, R. Organometallics 1988, 7, 2279. (b) Uso´n,
R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Cotton, F. A.; Falvello, L. R.;
Feng, X. J . Am. Chem. Soc. 1993, 115, 4145. (c) Ara, I.; Casas, J . M.;
Fornie´s, J .; Rueda, A. J . Inorg. Chem. 1996, 35, 7345.

Neutral Bimetallic Platinum Hydride Complexes
Organometallics, Vol. 16, No. 25, 1997 5397
a
Sch em e 2
complex molecule is unambiguously established and the
geometric parameters are reasonable.
Clearly, the most interesting feature of this complex
is the presence of a triphenylphosphine (P(1)Ph3) acting
as a bridging ligand with P bonded to the Pt(2)C6F5P(2)-
Ph3 fragment and η2-bonded via the C(25) and C(30)
carbon atoms of the C(25-30) phenyl ring to the cis-
Pt(C6F5)2 fragment. Although the position of the hy-
dride ligand could not be located with certainty, its
location as a bridging ligand is confirmed by the 1H
NMR spectrum (see below); it also seems clear from the
position of the heavy atoms that could be located trans
to the carbon atom C(13) bonded to Pt(2) and close to
the bisectrix of the P(1)-Pt(2)-P(2) angle (173.0(2)°).
The different magnitudes of the C-Pt-Pt angles (C(7)-
Pt(1)-Pt(2) ) 167.1(4)°; C(13)-Pt(2)-Pt(1) ) 157.7(4)°)
suggest that the µ-H bridge is slightly asymmetric.
Both the position of the heavy atoms and the inferred
position of the hydride indicate that the formation of
complex 2a proceeds with the retention of the original
configuration about the platinum centers. Thus, un-
expectedly the precursor trans-[Pt(C6F5)H(PPh3)2] acts
as a metallo chelating ligand toward the “cis-Pt(C6F5)2”
fragment. This is in contrast with previous reports,
which showed that mononuclear platinum hydride
complexes [PtHRL2] react with coordinatively unsat-
urated metal fragments LnMS, yielding dinuclear de-
F igu r e 3. Drawing of the crystal structure of cis-[(C6F5)-
(PPh3)Pt(µ-H)(µ(P)-η2-PPh3)Pt(C6F5)2] (2a ), showing the
atom-labeling scheme.
ture (-40 °C). A drawing of the molecular structure is
shown in Figure 3, and selected bond distances and
angles are listed in Table 4. It should be noted that
the dinuclear complex shows a disorder over two posi-
tions related by a pseudo binary axis, affecting the
quality of the crystallographic results (see Experimental
Section). Despite this fact, the connectivity of the

5398 Organometallics, Vol. 16, No. 25, 1997
Ara et al.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for tr a n s,cis-[(C6F 5)(P P h 3)P t-
(µ-H)(µ(P )-η2-P P h 3)P t(C6F 5)2] (2a )
Pt(1)-C(1)
Pt(1)-C(25)
Pt(1)-Pt(2)
Pt(2)-P(2)
P(1)-C(19)
P(1)-C(25)
P(2)-C(49)
C(25)-C(26)
C(26)-C(27)
C(28)-C(29)
1.94(2)
2.42(2)
2.972(2)
2.291(4)
1.80(2)
1.81(2)
1.81(2)
1.41(2)
1.39(2)
1.37(2)
Pt(1)-C(7)
Pt(1)-C(30)
Pt(2)-C(13)
Pt(2)-P(1)
P(1)-C(31)
P(2)-C(37)
P(2)-C(43)
C(25)-C(30)
C(27)-C(28)
C(29)-C(30)
2.01(2)
2.517(15)
2.02(2)
2.302(4)
1.81(2)
1.80(2)
1.81(2)
1.42(2)
1.39(3)
1.42(2)
C(1)-Pt(1)-C(7)
C(7)-Pt(1)-C(25)
C(7)-Pt(1)-C(30)
C(7)-Pt(1)-Pt(2)
C(13)-Pt(2)-P(1)
87.9(7)
92.5(6)
91.0(6)
167.1(4)
92.7(5)
C(1)-Pt(1)-C(25) 167.4(6)
C(1)-Pt(1)-C(30) 159.4(6)
C(1)-Pt(1)-Pt(2) 104.9(5)
F igu r e 4. High-field region of the 1H NMR spectrum of
[trans,cis-(C6F5)(PPh3)Pt(µ-H)(µ(P)-η2-PPh3)Pt(C6F5)2] (2a )
in CD3COCD3 at 20 °C. The signal denoted with an asterisk
is due to a small amount of 2c; J is in hertz.
C(13)-Pt(2)-P(2)
P(2)-Pt(2)-P(1)
93.9(5)
173.0(2)
P(2)-Pt(2)-Pt(1) 102.33(13)
C(13)-Pt(2)-Pt(1) 157.7(4)
P(1)-Pt(2)-Pt(1)
70.74(11) C(19)-P(1)-C(31) 103.1(7)
all C-C distances (1.37(2)-1.42(2) Å) and angles within
this group are identical within 3σ. This indicates that
the loss of aromaticity in the ring upon coordination is
negligible, as has been previously suggested in other (η2-
aryl)platinum interactions.20 In contrast to complex 1b,
this 1:1 adduct 2a is not planar and the best least-
squares planes around Pt(1) [Pt(1),C(1),C(7) and mid-
point of C(25)-C(30)) and Pt(2) (Pt(2),C(13),P(1),P(2))
form a dihedral angle of 35.2(1)°.
C(19)-P(1)-C(25) 107.5(8)
C(19)-P(1)-Pt(2) 114.0(5)
C(25)-P(1)-Pt(2) 107.0(5)
C(37)-P(2)-C(43) 106.5(8)
C(37)-P(2)-Pt(2) 108.0(6)
C(43)-P(2)-Pt(2) 113.9(5)
C(31)-P(1)-C(25) 103.3(8)
C(31)-P(1)-Pt(2) 120.9(5)
C(37)-P(2)-C(49) 106.5(8)
C(49)-P(2)-C(43) 105.3(8)
C(49)-P(2)-Pt(2) 115.9(5)
rivatives RL2Pt(µ-H)MLn stabilized only by a single
bridging hydride ligand.1a,e,4d-g,o,19 In this case, the
presence of two labile solvent molecules in cis-[Pt(C6F5)2-
(thf)2] and the ability of the “cis-Pt(C6F5)2” fragment to
stabilize η2-phenyl interactions20 seem to favor the
formation of this unusual 1:1 adduct. As far as we
know, this is the first crystallographic example char-
acterized with the PPh3 molecule acting as a µ(P)-η2
bridging ligand, though examples of µ(P)-η6 PPh3 ligands
have been reported previously.21 It is noteworthy that
only slight structural differences between the terminal
(P(2)Ph3) and bridging (P(1)Ph3) triphenylphosphine
ligands are observed. Thus, both triphenylphosphine
ligands have comparable P-C(phenyl) bond distances
(range 1.80(2)-1.81(2) Å) and angles at the phosphorus
atoms (range 107.0(5)° for C(25)-P(1)-Pt(2) to 120.9(5)°
for C(31)-P(1)-Pt(2)) and the Pt-P distances are
identical within experimental error (Pt(2)-P(1) ) 2.302(4)
Å; Pt(2)-P(2) ) 2.291(4) Å). However, as expected, the
η2 coordination of one phenyl group on P(1) to Pt(2) has
a perceptible effect on the P-Pt(2)-Pt(1) angles (P(1)-
Pt(2)-Pt(1) ) 70.7(1)° versus P(2)-Pt(2)-Pt(1) )
102.3(1)°). The Pt(1)-C distances for this η2-Pt(1)
interaction are almost equal within experimental error
(Pt(1)-C(25) ) 2.42(2) Å, Pt(1)-C(30) ) 2.517(15) Å)
and are similar to related (η2-aryl)platinum interac-
tions20 and, as expected from the geometry of PtII-olefin
systems, the C(25)-C(30) vector forms an angle of
2.5(1)° with the normal to the Pt(1),C(1),C(7) plane. It
should be noted that in spite of the η2-coordination to
Pt(1) the phenyl ring C(25)-C(30) remains planar and
Finally, considering the µ-PPh3 ligand as a four-
electron donor, we arrive at a total valence electron
count of 30 electrons. This is consistent with the Pt(1)-
Pt(2) distance of 2.972(2) Å, which is comparable to
those observed in similar diplatinum species (30 e-)
listed in Table 3.
The NMR data for 2a in CD3COCD3 (Table 1 and
Experimental Section) are in keeping with its dinuclear
nature. Thus, the 31P NMR spectrum confirms the
presence of two different PPh3 groups. It exhibits a
central AB quartet (δ[P(A)] 17.77, δ[P(B)] 12.22) with
a large coupling constant between the two phosphorus
nuclei (2J P(A)-P(B) ) 386.2 Hz), surrounded by a pair of
AB subspectra (simply “copies” of the central multiplet),
the separation of which gives a direct measure of both
195Pt-P(A,B) coupling constants [1J Pt-P(A) ) 2573 Hz and
1J Pt-P(B) ) 2553 Hz). Moreover, the high-field signal (δ
12.22) also exhibits a long-range platinum coupling
2J Pt-P(B) of 166.4 Hz, confirming that, in spite of the use
of a donor solvent, the dinuclear structure is retained
1
in solution. The H NMR spectrum at room tempera-
ture (see Figure 4) shows in the high-field region a
1
resonance centered at -10.75 ppm (1J Pt(1)-H ≈ J Pt(2)-H
≈ 535 Hz) with the typical appearance of a bridging
hydride ligand: a quintet of relative intensity 1:8:18:
1
8:1 where the signals are separated by /2J Pt-H. The
signals of this quintet are broad, probably due to
unresolved coupling to the two mutually cis PPh3
ligands. Only two broad multiplets centered at 8.15 and
7.5 ppm due to PPh3 ligands are observed in the
aromatic region, and the broadness of these resonances
led us to examine its spectrum at low temperature.
When the system is cooled to -85 °C, a complex pattern
with nine broad resonances is observed in the aromatic
region. One of them appears clearly shifted to lower
frequency (6.32 ppm) and could be tentatively assigned
to the ortho proton of the phenyl ring involved in the η2
interaction, in agreement with similar shifts to higher
(19) (a) Albinati, A.; Demartin, F.; Venanzi, L. M.; Wolfer, M. K.
Angew. Chem., Int. Ed. Engl. 1988, 27, 563. (b) Albinati, A.; Lehner,
H.; Venanzi, L. M.; Wolfer, M. Inorg. Chem. 1987, 26, 3933. (c)
McGilligan, B. S.; Venanzi, L. M.; Wolfer, M. Organometallics 1987,
6, 946. (d) Crespo, M.; Sales, J .; Sola´ns, X. J . Chem. Soc., Dalton Trans.
1989, 1089.
(20) (a) Casas, J . M.; Fornie´s, J .; Mart´ın, A.; Menjo´n, B.; Toma´s, M.
J . Chem. Soc., Dalton Trans. 1995, 2949. (b) Alonso, E., Fornie´s, J .;
Fortun˜o, C.; Mart´ın, A.; Orpen, A. G. J . Chem. Soc., Chem. Commun.
1996, 231. (c) Casas, J . M.; Fornie´s, J .; Mart´ın, A.; Menjo´n, B.
Organometallics 1993, 12, 4376. (d) Fornie´s, J .; Menjo´n, B.; Go´mez,
N.; Toma´s, M. Organometallics 1992, 11, 1187.
(21) (a) Robertson, G. B.; Whimp, P. O. J . Organomet. Chem. 1973,
60, C11. (b) Luck, R.; Morris, R. H.; Sawyer, J . F. Organometallics
1984, 3, 1009.

Neutral Bimetallic Platinum Hydride Complexes
Organometallics, Vol. 16, No. 25, 1997 5399
F igu r e 5. 19F NMR spectrum of [cis-(C6F5)(PPh3)Pt(µ-H)(µ-C6F5)Pt(C6F5)(PPh3)] (2c) in CDCl3 at 20 °C.
field observed in other η2-aryl interactions.22 However,
no 195Pt satellites were observed in any of these signals
and we also noted that the hydride region remained
essentially unchanged in the temperature range (+15
to -85 °C). The 19F NMR spectrum is also temperature-
dependent, suggesting the existence of a dynamic
process. The 19F NMR spectra registered in the range
+15 to -85 °C confirm the presence of three nonequiva-
lent C6F5 groups. However, for the structure found in
the solid state, one would expect to see inequivalence
of the ortho and meta fluorine atoms within each C6F5
group. Even at low temperature (-85 °C) the spectrum
shows the expected two ortho and two meta fluorine
signals for only two of the three C6F5 rings (see
Experimental Section). Thus, in the ortho fluorine
region five resonances (-113.1 (d), -113.4 (br), -117.7
(d), -118.0 (d), 118.6 (d)) of relative intensity 1:1:1:1:2
are observed at -85 °C, and we tentatively assign the
lower frequency signal (-118.6), which remains un-
changed at higher temperatures, to the ortho fluorine
atoms of the C6F5 group bonded to Pt(2). The remaining
resonances, assigned to the cis-Pt(1)(C6F5)2 fragment,
suggest that at low temperature the Pt(1) coordination
plane does not act as a mirror plane. When the
temperature is raised, these four ortho fluorine reso-
nances broaden, coalesce at ca. -20 °C, and finally
collapse at room temperature to only one signal centered
at -115.4 ppm. A similar behavior is observed for the
meta fluorine atoms, but for these signals two different
meta fluorine resonances are observed at room temper-
ature, suggesting that the coincidence of the two ortho
fluorine atoms on each C6F5 ligand is accidental. This
pattern suggests that on the NMR time scale a mirror
plane is present at room temperature in the fragment
Pt(C6F5)2. The simplicity of the aromatic region at room
temperature would suggest that the η2 interaction is lost
in solution or at least dynamic exchange of the interac-
tion of Pt(1) with the three phenyl rings on P(1) is easily
established. The simplest process that is consistent
with these observations and that explains the mirror
planes developed on the platinum coordination planes
is a rapid inversion of the central dimetallacycle.
However, the simple rotation of the C6F5 rings about
their respective Pt-C bonds cannot be excluded, al-
though this process, as has been noted previously, is
severely hindered in square-planar platinum or pal-
ladium complexes.23
The adduct 2a is only sparingly soluble in CHCl3 but
on stirring gradually dissolves, yielding a yellow solu-
tion; over a period of approximately 28 h at room
temperature 2a completely rearranges to the isomeric
derivative cis-[(C6F5)(PPh3)Pt(µ-H)(µ-C6F5)Pt(C6F5)(PPh3)]
(2c; Scheme 2). In the conversion of 2a to 2c no
intermediates were detected by monitoring the isomer-
ization by 1H and 31P NMR spectroscopy (CDCl3). It
seems, therefore, that the reaction of cis-[Pt(C6F5)2(thf)2]
with trans-[Pt(C6F5)H(PPh3)2] gives 2a as the kinetic
product, which then transforms into the thermodynami-
cally favored complex 2c. We note that if the isomer-
ization process is conducted in CD3COCD3, in addition
to 2a and 2c we always observe the presence (1H and
31P NMR) of small but at first increasing amounts of
trans-[Pt(C6F5)H(PPh3)2], which eventually disappears.
This fact suggests that 2a probably dissociates partially
in this solvent and that the exchange between free and
coordinated [Pt(C6F5)H(PPh3)2] which probably occurs
is slow on the NMR time scale. Alternatively, complex
2c can easily be obtained by refluxing an equimolecular
mixture of cis-[Pt(C6F5)2(thf)2] and trans-[Pt(C6F5)H-
(PPh3)2] in CHCl3 for 30 min. Concentration of the
resulting deep yellow solution to small volume and
addition of n-hexane gives 2c in nearly quantitative
yield (92%) as a bright yellow solid (iii, Scheme 2). The
NMR data of 2c indicate that the formation of the
expected diplatinum complex with the mixed bridging
system Pt(µ-H)(µ-C6F5)Pt has taken place. Thus, the
1H NMR spectrum shows a diagnostic resonance for µ-H
2
at δ -8.32 (J Pt(1)-H ≈ J Pt(2)-H ≈ 623 Hz, J P-H not
resolved) with a pattern similar to that observed for 2a .
The 19F NMR spectrum, which provides additional
structural information, is presented in Figure 5. As can
be seen, it shows six multiplet signals due to ortho
(isochronous), and para and meta fluorine atoms (iso-
chronous) of one bridging (A, B, and C) and two
equivalent terminal (D, E, and F) C6F5 ligands, as
indicated by their relative intensities as well as the
relative intensity of the platinum satellites observed for
both of the higher frequency signals (ortho fluorine
region, A and D). The resonances due to the C6F5
bridging ligand (-107.15 ppm, 2Fo; -136.7ppm, Fp;
-160.6 ppm, 2Fm) appear at higher frequencies than
(22) Akita, M.; Hua, R.; Oku, T.; Tanaka, M.; Moro-oka, Y. Organo-
metallics 1996, 15, 4162.
(23) Casares, J . A.; Espinet, P.; Mart´ınez-Ilarduya, J . M.; Lin, Y.-
H. Organometallics 1997, 16, 770 and references therein.

5400 Organometallics, Vol. 16, No. 25, 1997
Ara et al.
angles formed by the C6F5 rings and the central Pt2C(1)
plane are 89.5(2.7)° (bridging) and 40.55(4)° (terminal).
The Pt-C(5) terminal distance (2.033(8) Å) is within the
usual range for platinum pentafluorophenyl complexes,
and it is shorter than the Pt-C6F5 bridging distance
(Pt(1)-C(1) ) 2.194(8) Å), as previously found for [Pt2(µ-
C6F5)2(C6F5)4]n- (n ) 1,18b 218a). The bond angles around
the platinum centers are 91.3(3)° for C(1)-Pt(1)-C(5)
and 91.8(2)° for P(1)-Pt(1)-C(5). The Pt-Pt vector
does not bisect the PPh3-Pt-C6F5(terminal) fragment;
the P(1)-Pt(1)-Pt(1a) angle (124.78(15)°) is less obtuse
than C(5)-Pt(1)-Pt(1a) (143.4(2)°), indicating a notable
bending of the bulky PPh3 ligands toward the less
demanding hydride bridging ligand, which again was
not located in the X-ray study. The Pt(1)-C(1)-Pt(1a)
angle is very acute (75.1(3)°), as required by the short
Pt(1)-Pt(1a) bond distance of 2.6742(7) Å. This dis-
tance is in accord with the presence of two three-center-
two-electron bridges between the platinum centers (total
valence electron count 28 e-) but is clearly shorter than
those previously found in the anion [(C6F5)2Pt(µ-C6F5)2-
Pt(C6F5)2]2- (2.714(1) Å)18a and in the neutral complex
[(PEt3)(SiEt3)Pt(µ-H)2Pt(SiEt3)(PEt3)]2 (2.692(3) Å), both
with similar FEC values of 4.16
F igu r e 6. Drawing of the crystal structure of cis-[(C6F5)-
(PPh3)Pt(µ-H)(µ-C6F5)Pt(C6F5)(PPh3)] (2c), showing the
atom-labeling scheme.
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for cis-[(C6F 5)(P P h 3)P t-
(µ-H)(µ-C6F 5)P t(C6F 5)(P P h 3)] (2c)a
R ea ct ion of cis-[P t (C6F 5)2(t h f)2] w it h tr a n s-
[P tClHL2]. Similar dinuclear derivatives containing a
mixed chloride-hydride bridging system can also be
obtained by treatment of cis-[Pt(C6F5)2(thf)2] with trans-
[PtClHL2] (see Scheme 2). Thus, the reactions between
trans-[PtClHL2] (L ) PPh3, PEt3) and cis-[Pt(C6F5)2-
(thf)2] in CHCl3 yield almost immediately (1-2 min;
NMR spectroscopy) the corresponding trans dinuclear
isomers [(C6F5)LPt(µ-H)(µ-Cl)Pt(C6F5)L] (3b, L ) PPh3;
4b, L ) PEt3). Both complexes are isolated as white
solids in high yields (3b, 85%; 4b, 73%) and have been
characterized by elemental analyses and spectroscopic
methods (see Experimental Section and Table 1). The
NMR spectra of 3b and 4b are very similar to those
observed for compound 1b, confirming that they are the
corresponding trans isomers. The 19F NMR spectra of
both compounds show signals corresponding to two
nonequivalent C6F5 rings, ruling out the alternative cis
isomers, which should display equivalent C6F5 groups.
As expected, the 31P NMR spectra also display two
different singlet resonances (3b, 17.34 and 11.96 ppm;
4b, 16.10 and 15.55 ppm), indicating nonequivalent
phosphorus environments. Selective decoupling of the
phosphine (but not hydride) protons in their 31P NMR
spectra split only the downfield signals (17.34 ppm for
3b and 16.10 ppm for 4b) into a doublet (J ≈ 83.0),
consistent with hydride ligand trans to phosphorus.
Therefore, these signals, which exhibit long-range (94.9
Hz, 3b; 98.2 Hz, 4b) and short-range (3859 Hz, 3b; 3609
Hz, 4b) 195Pt coupling, are assigned to phosphorus
nuclei (P(1)) trans to hydride while the resonances at
11.96 ppm (1J Pt(2)-P(2) ) 4403 Hz) for 3b and at 15.5 ppm
(J Pt(2)-P(2) ) 4151 Hz) for 4b are assigned to the
phosphine ligands (P(2)) cis to H. It is worth mentioning
that the 1J Pt-P(1) coupling constants (in these derivatives
and in complex 1b) are very large, in agreement with
previous observations4n,6a,8c indicating that the µ-H
ligands exert a much weaker trans influence than do
the terminal hydrides. In addition, the presence of a
hydride ligand is evidenced by an upfield doublet
resonance centered at δ -9.33 for 3b and at δ -9.9 for
Pt(1)-C(5)
Pt(1)-P(1)
C(1)-C(2)
C(3)-C(4)
C(6)-C(7)
C(8)-C(9)
2.033(8)
2.228(2)
1.383(9)
1.374(10)
1.369(12)
1.305(2)
Pt(1)-C(1)
Pt(1)-Pt(1a)
C(2)-C(3)
C(5)-C(6)
C(7)-C(8)
C(9)-C(10)
2.194(8)
2.6742(7)
1.380(11)
1.373(12)
1.360(2)
1.393(12)
C(5)-Pt(1)-C(1)
C(1)-Pt(1)-P(1)
C(1)-Pt(1)-Pt(1a)
C(2)-C(1)-C(2a)
C(2)-C(1)-Pt(1)
C(10)-C(5)-C(6)
91.3(3)
C(5)-Pt(1)-P(1)
91.8(2)
173.27(8) C(5)-Pt(1)-Pt(1a) 143.4(2)
52.4(2)
114.7(10) C(2)-C(1)-Pt(1a)
119.0(4)
115.4(8)
P(1)-Pt(1)-Pt(1a) 124.78(5)
111.7(4)
75.1(3)
Pt(1a)-C(1)-Pt(1)
a
Symmetry transformation used to generate equivalent atoms:
-x + 3/2, -y, z.
those of the terminal C6F5 groups, in accord with similar
observations previously reported for anionic diplatinum
derivatives containing bridging and terminal C6F5
ligands.12h,18 The equivalence of the two terminal C6F5
groups in the complex indicates a mutually cis disposi-
tion in the dinuclear structure. As expected, the two
PPh3 ligands are also equivalent. The 31P NMR spec-
trum exhibits only a singlet signal (δ 18.23, Pt-Pt
isotopomer ∼44%, A2 spin system) flanked by platinum
satellites due to short-range (1J Pt-P ) 3825 Hz) and
long-range (2J Pt-P ) 112 Hz) coupling to near and far
195Pt atoms (195Pt-Pt and Pt-195Pt ≈ 45%, AA′X spin
systems J AA′
)
3J P-P′ ≈ 0). Only the most intense
signals due to the third isotopomer (195Pt-195Pt ≈ 11%,
1
AA′XX′ spin system) and separated by N ) J Pt-P
+
2J Pt-P are observed in the spectrum. These lines fall
1
1
outside the J Pt-P doublet, indicating that J Pt-P and
2J Pt-P are of the same sign.24 Although the two isomers
A (PPh3 ligands trans to µ-C6F5) and B (C6F5 ligands
trans to µ-C6F5) are compatible with these spectroscopic
data, the structure of 2c (Figure 6, Table 5) was shown
to be A by X-ray crystallography. The Cipso(C1) and
Cpara (C4) atoms of the C6F5 bridging group lie on a
crystallographic 2-fold axis, and thus, the two platinum
atoms are in identical environments. The dihedral
(24) Kiffen, A. A.; Masters, C.; Visser, J . P. J . Chem. Soc., Dalton
Trans. 1975, 1311.

Neutral Bimetallic Platinum Hydride Complexes
Organometallics, Vol. 16, No. 25, 1997 5401
4b with 195Pt satellites (1J Pt-H ) 642 and 566 Hz for
1
1
3b and J Pt(1)-H ≈ J Pt(2)-H ≈ 592 for 4b). The doublet
structure arises from coupling with the trans phospho-
rus P(1) only (2J H-P(1) ) 81.7 Hz for 3b and J H-P
)
2
75.2 Hz for 4b), as has been confirmed by the selective
decoupling (phosphine protons) 31P NMR experiment
mentioned above. In addition to the NMR evidence, the
mass spectra of 3b and 4b show the expected molecular
ion peaks (see Experimental Section), confirming the
dinuclear nature of both complexes.
Attempts to obtain crystals of compound 3b by slow
diffusion of n-hexane into a CH2Cl2 solution of 3b in
the presence of light unexpectedly yield colorless crys-
tals of the cis isomer 3c, which has been characterized
by microanalysis and spectroscopic methods and, fur-
thermore, by X-ray crystallography (see below). How-
ever, no isomerization is observed if the solution is kept
in the dark, suggesting that the isomerization process
is probably induced photochemically. This conclusion
is further confirmed by the fact that complex 3b (trans
isomer) is thermally stable in CHCl3 at reflux but is
quantitatively isomerized to the cis isomer (3c) upon
photolysis (30 min, 125 W, Hg lamp). The isomerization
is reversible, and a CDCl3 solution of 3c rearranges to
a mixture of 3b and 3c isomers (2:1 ratio after 10 days
at room temperature). We have also observed that the
trans isomer 3b slowly transforms into a mixture of the
3b and 3c isomers in CD3COCD3. A 2:1 (3b/3c) ratio
has been detected after 8 h, and the mixture remains
unchanged after 7 days. It should be noted, however,
that prolonged photolysis (14 h, 125 W, Hg lamp) of a
solution of complex 3b yields the dinuclear doubly
chloride-bridged complex [Pt(µ-Cl)(C6F5)(PPh3)]2 (5; δ(P)
8.48, J Pt-P ) 4491 Hz), as characterized by comparison
with the NMR spectrum of another sample prepared by
treating [trans-PtCl2(PPh3)2] with cis-[Pt(C6F5)2(thf)2]
(see Experimental Section). A similar behavior is
observed in CD3COCD3 for complex 4b, which re-
arranges into a mixture of 4b and 4c (a 2:1 ratio is
observed in 2 h). Irradiation of a CH2Cl2 solution of 4b
(125 W, Hg lamp) for 30 min also yields a mixture of
4b and 4c (ratio 1.2:1) which remains unchanged after
50 min. Due to the similar solubilities of 4b and 4c we
have not been able to isolate 4c in pure form, but its
spectroscopic data can easily be extracted (1H and 31P
NMR (Table 1), 19F (Experimental Section)) from the
NMR spectra of the mixture.
F igu r e 7. Drawing of the crystal structure of cis-[(C6F5)-
(PPh3)Pt(µ-H)(µ-Cl)Pt(C6F5)(PPh3)] (3c), showing the atom-
labeling scheme.
Ta ble 6. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for cis-[(C6F 5)(P P h 3)P t-
(µ-H)(µ-Cl)P t(C6F 5)(P P h 3)] (3c)
Pt(1)-Pt(2)
Pt(1)-P(1)
Pt(2)-C(7)
Pt(2)-Cl(1)
P(1)-C(25)
P(2)-C(37)
P(2)-C(31)
2.759(1)
2.204(2)
2.018(9)
2.342(2)
1.802(10)
1.802(10)
1.805(9)
Pt(1)-C(1)
Pt(1)-Cl(1)
Pt(2)-P(2)
P(1)-C(19)
P(1)-C(13)
P(2)-C(43)
2.005(8)
2.349(2)
2.197(2)
1.792(10)
1.821(9)
1.803(9)
C(1)-Pt(1)-P(1)
P(1)-Pt(1)-Cl(1)
P(1)-Pt(1)-Pt(2)
C(7)-Pt(2)-Cl(1)
C(7)-Pt(2)-Pt(1)
Pt(2)-Cl(1)-Pt(1)
88.6(2)
C(1)-Pt(1)-Cl(1)
92.(2)
175.27(9) C(1)-Pt(1)-Pt(2) 146.6(2)
124.68(7) C(7)-Pt(2)-P(2)
89.9(2)
143.9(2)
72.07(7)
95.9(2)
172.52(9)
P(2)-Pt(2)-Cl(1)
P(2)-Pt(2)-Pt(1) 120.03(7)
environments and have mutually cis dispositions of both
the two C6F5 groups and the two PPh3 ligands. The
compound can be described as formed by two distorted-
square-planar Pt(II) units having as terminal ligands
the C6F5 and PPh3 moieties, with bridging chloride and
hydride ligands. Even though it is not possible to locate
the hydrogen atom, its bridging position is unequivocally
defined by the NMR data (see above). The C(7)Pt(2)P(2)
and Pt(1)C(1)P(1) atoms and the bridging Cl(1) atom
are essentially in the same plane; the dihedral angle
between the platinum coordination planes is only 6.3(2)°.
The P-Pt-Pt angles (124.68(7) and 120.03(7)°) are
similar to those observed in 2c, indicating a similar
bending of the PPh3 ligands toward the hydride bridging
atom.
In both of the cis dinuclear derivatives, 3c and 4c,
the resonance due to the hydride bridging ligand is
observed as a binomial quintet (couplings to cis phos-
phorus nuclei are not resolved) centered at slightly
higher field than that observed for the corresponding
trans isomers (3c, δ -10.84 vs -9.33 for 3b; 4c, δ
-11.96 vs -9.9 for 4b). However, the magnitude of the
platinum coupling constants (1J Pt-H ) 575 Hz (3c), 590
Hz (4c)) is comparable to that observed in 3b and 4b
(see Table 1). The 31P NMR spectra consist, as expected,
of a singlet resonance (δ(P) 10.6 (3c), 13.75 (4c)) flanked
by a single set of short-range-coupling platinum satel-
lites (4513 Hz, 3c; 4085 Hz, 4c); the 19F NMR spectra
reveal that the two C6F5 groups are equivalent (see
Experimental Section). Complex 3c has been charac-
terized by an X-ray crystal structure analysis (Figure 7
and Table 6). The molecule, as anticipated, is a dimer
in which the platinum centers are in identical chemical
The bridging chloride ligand is nearly symmetrically
bound to both platinum centers, and the Pt-Cl dis-
tances (Pt(2)-Cl(1) ) 2.342(2) Å, Pt(1)-Cl(1) ) 2.349(2)
Å) are comparable to those found in other doubly
chloride-bridged diplatinum complexes.25 The Pt-P
distances (Pt(2)-P(2) ) 2.197(2) Å, Pt(1)-P(1) ) 2.204(2)
Å) are significantly shorter than those found in 1b and
2c, in keeping with the very low trans influence of the
chloride bridging ligand.26 The Pt(1)-Cl(1)-Pt(2) angle
is very acute (72.07(7)°)snotably smaller than those
(25) Kukushkin, V. Y.; Belski, V. K.; Konovalov, V. E.; Shifrina, R.
R.; Moiseev, A. I.; Vlasova, R. A. Inorg. Chim. Acta 1991, 183, 57 and
references therein.
(26) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.

5402 Organometallics, Vol. 16, No. 25, 1997
Ara et al.
found in bis(µ-chloro) complexes12p,17,25,27 (ca. 96°) but
comparable to those found in other dinuclear complexes
containing the mixed bridging system µ-Cl, µ-H28 (ca.
73°). In accord with this, the platinum-platinum
distance is very short (2.7593(6) Å), near the lower end
of the range of distances found in related µ-H diplati-
num derivatives with a total valence electron count of
30 e- (see Table 3). Notwithstanding, the Pt-Pt
distance in this complex with FEC ) 6 is, as expected,
a bit longer than in 2c (2.6742(7) Å) or in [Pt(µ-H)-
(SiEt3)(PEt3)]2 (2.692(3) Å), both with framework elec-
tron counts of 4.
leading to µ-PPh2 and often to Pt-phenyl linkages have
been reported previously,8ab,30 and metalation of a
phenyl ring of the PPh3 ligand has also been observed.31
In this context, the structure of 2a provides an indica-
tion that such P-C or C-H bond cleavages could take
place via the formation of intermediate species in which
the PPh3 behaves as a four-electron ligand by using the
P atom and an η2-phenyl interaction. Related η2-arene-
metal interactions are believed to occur prior to C(sp2)-E
(E ) H, F) bond cleavages.32 It is also worth noting that
P-C bond cleavage reactions induced by transition-
metal centers have received considerable attention
because of their potential role in the deactivation of
phosphine-containing homogeneous catalysts.33
Con clu sion
Although no similar adducts have been detected (even
at temperatures as low as -50 °C) between the plati-
num substrates trans-[PtHXL2] (X ) CtCR, Cl) and cis-
[Pt(C6F5)2(thf)2], the intermediacy of η2-phenyl interac-
tions in the ligand redistribution pathway cannot be
ruled out. It is remarkable that these reactions proceed
instantaneously, giving the isomeric derivative 1b, 3b,
or 4b, and are essentially quantitative. This result is
in contrast with the drastic conditions needed in the
synthesis, for instance, of dinuclear [Pt(µ-Cl)Cl(PR3)]2
derivatives, which have been prepared by refluxing
[PtCl2(PR3)2] with PtCl2 in solvents such as xylene/
naphthalene,34a tetrachloroethane,34b and p-chloro-
toluene34c or more recently by refluxing the Zeise dimer
[Pt(µ-Cl)Cl(C2H4)]2 with the appropriate phosphine in
toluene or tetrachloroethane.34d Similar drastic condi-
tions (refluxing toluene, 5 h) are required in the forma-
tion of [Pt(µ-Cl)(C6F5)(tht)]2 by reaction of [Pt(C6F5)2-
(tht)2] and PtCl2.35 It is clear that in all these reactions
the formation of the final products necessarily implies
the migration of ligands between the two platinum
centers. However, even though in the synthesis of the
diplatinum complexes 1-4 a precursor much more
soluble and reactive than PtCl2 (cis-[Pt(C6F5)2(thf)2]) is
used, the hydride ligand seems to play a prominent role,
since the analogous reaction between trans-[PtCl2(PR3)2]
and cis-[Pt(C6F5)2(thf)2] to give 5 also requires longer
reaction times for completion (24 h, reflux).
This work provides a simple method for the prepara-
tion of a series of diplatinum complexes with unusual
µ-H, µ-X (X ) CtCR, C6F5, Cl) mixed bridging systems.
It has been demonstrated that the overall transforma-
tion of trans-[Pt(C6F5)H(PPh3)2] and cis-[Pt(C6F5)2(thf)2]
to the thermodynamically more stable dinuclear deriva-
tive cis-[(C6F5)(PPh3)Pt(µ-H)(µ-C6F5)Pt(C6F5)(PPh3)] (2c)
proceeds through the initial formation of a reasonably
stable intermediate, 2a , which has been shown (X-ray)
to contain an unexpected bridging PPh3 ligand exhibit-
ing a µ(P)-η2-phenyl bonding mode. The PPh3 ligand is
a very common 2 e- P-bonded ligand in coordination
chemistry. To the best of our knowledge, this is the first
example in which this group acts as a four-electron
bridging ligand between two metal centers with P
bonding to one metal center and η2-aryl bonding to the
second metal. µ(P)-η6-aryl PPh3 bridging complexes are
also a rather rare class of compounds,21 though more
examples have been reported for η6-aryl arene deriva-
tives in which the phosphine is bonded via M-π-arene
bonds alone without any M-P interactions.29 Examples
of fragmentation of P-C bonds on platinum substrates
(27) (a) Goel, A. B.; Goel, S.; Vanderveer, D. Inorg. Chim. Acta 1981,
54, L267. (b) Albinati, A.; Naegeli, R.; Ostoja, K. H. A.; Pregosin, P.
S.; Ruegger, H. Inorg. Chim. Acta 1983, 76, L231. (c) Clark, H. C.;
Ferguson, G.; Goel, A. B.; Ruhl, B. L. Organometallics 1984, 3, 15. (d)
Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Cotton, F. A.; Falvello,
L. R. Inorg. Chem. 1987, 26, 3482. (e) Phillips, I. G.; Ball, R. G.; Cavell,
R. G. Inorg. Chem. 1988, 27, 4038. (f) Alyea, E. C.; Ferguson, G.; Malito,
J .; Ruhl, B. L. Organometallics 1989, 8, 1188. (g) Vila, J . M.; Gayoso,
M.; Pereira, M. T.; Romar, A.; Ferna´ndez, J . J . J . Organomet. Chem.
1991, 401, 385. (h) Stang, P.; Huang, Y.-H.; Arif, A. M. Organometallics
1992, 11, 231. (i) King, S. A.; Engen, D. V.; Fisher, H. E.; Schwartz, J .
Organometallics 1991, 10, 1195. (j) Rashidi, M.; Fakhroeian, Z.;
Puddephatt, R. J . J . Organomet. Chem. 1991, 406, 261.
(28) (a) Albinati, A.; Lehner, H.; Venanzi, L. M. Inorg. Chem. 1985,
24, 1483. (b) Lehner, H.; Matt, D.; Togui, A.; Thouvenot, R.; Venanzi,
L. M.; Albinati, A. Inorg. Chem. 1984, 23, 4254. (c) Churchill, M. R. In
Transition Metal Hydrides; Bau, R., Ed.; Advances in Chemistry Series
167; American Chemical Society: Washington, DC, 1978; p 36. (d)
Robinson, S. D.; Sahajpal, A.; Tocher, D. J . Chem. Soc., Dalton Trans.
1995, 3497.
(31) (a) Clark, H. C.; Hine, K. E. J . Organomet. Chem. 1976, 105,
C32. (b) Rice, N. C.; Oliver, J . D. J . Organomet. Chem. 1978, 145, 121.
(c) Bennett, M. A.; Perry, D. E.; Bhargava, S. K.; Ditzel, E. J .;
Robertson, G. B.; Willis, A.-C. J . Chem. Soc., Chem. Commun. 1987,
1613. (d) Canty, A. J .; Minchin, N. J .; Patrick, J . M.; White, A. H. J .
Chem. Soc., Dalton Trans. 1983, 1253. (e) Scheffknecht, C.; Rhomberg,
A.; Mu¨ller, E. P.; Peringer, P. J . Organomet. Chem. 1993, 463, 245. (f)
Chakravarty, A. R.; Cotton, F. A.; Tocher, D. A. Inorg. Chem. 1984,
23, 4697. (g) Chakravarty, A. R.; Cotton, F. A.; Tocher, D. A.
Organometallics 1985, 4, 8. (h) J anowicz, A. H.; Bergman, R. G. J .
Am. Chem. Soc. 1983, 105, 3929. (i) Cole-Hamilton, D. J .; Wilkinson,
G. J . Chem. Soc., Dalton Trans. 1979, 1283; 1977, 797. (j) Cole-
Hamilton, D. J .; Wilkinson, G. Nouv. J . Chim. 1977, 1, 141. (k) Werner,
H.; Gotzig, J . J . Organomet. Chem. 1985, 284, 73.
(29) Morris, M. J . In Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press:
Oxford, U.K., 1995; Vol. 5, Chapter 8, p 529.
(32) (a) J ones, W. D.; Feher, F. J . Acc. Chem. Res. 1989, 22, 91; J .
Am. Chem. Soc. 1986, 108, 4814; 1984, 106, 1650; 1982, 104, 4240. (b)
Griffits, D. C.; Young, G. B. Organometallics 1989, 8, 875 and
references therein. (c) Faller, J . W.; Smart, C. J . Organometallics 1989,
8, 602. (d) Stoutland, P. O.; Bergman, R. G. J . Am. Chem. Soc. 1988,
110, 5732. (e) Lin, C.-H.; Li, C.-S.; Cheng, C.-H. Organometallics 1994,
13, 18. (f) Belt, S. T.; Dong, L.; Duckett, S. B.; J ones, W. D.; Partridge,
M. G.; Perutz, R. N. J . Chem. Soc., Chem. Commun. 1991, 266. (g)
J ones, W. D.; Partridge, M. G.; Perutz, R. N. J . Chem. Soc., Chem.
Commun. 1991, 264. See also references given in ref 12b-d.
(33) (a) Garrou, P. E. Chem. Rev. 1985, 85, 171. (b) Dubois, R. A.;
Garrou, P. E. Organometallics 1986, 5, 466.
(34) (a) Goodfellow, R. J .; Venanzi, L. M. J . Chem. Soc. 1965, 7533.
(b) Smithies, A. C.; Schmidt, P.; Orchin, M. Inorg. Synth. 1970, 12,
240. (c) Baratta, W.; Pregosin, P. S. Inorg. Chim. Acta 1993, 209, 85.
(d) Boag, N. M.; Ravetz, M. S. J . Chem. Soc., Dalton Trans. 1995, 3473.
(35) Uso´n, R.; Fornie´s, J .; Espinet, P.; Alfranca, G. Synth. React.
Inorg. Met.-Org. Chem. 1980, 10, 579.
(30) (a) Taylor, N. J .; Chieh, P. C.; Carty, A. J . Chem. Soc., Chem.
Commun. 1975, 448. (b) Gillar, R. D.; Ugo, R.; Cariati, F.; Cenini, S.;
Bonati, F. Chem. Commun. 1966, 869. (c) Ugo, R.; La Monica, G.;
Cariati, F.; Cenini, S.; Conti, F. Inorg. Chim. Acta 1970, 4, 390. (d)
Ugo, R.; Cenini, S.; Pilbrow, M.; Deibl, B.; Scheider, G. Inorg. Chim.
Acta 1976, 18, 113. (e) Blake, D. M.; Nyman, C. J . J . Chem. Soc., Dalton
Trans. 1969, 483. (f) Blake, D. M.; Nyman, C. J . J . Am. Chem. Soc.
1970, 92, 5359. (g) Tolman, C. A.; Seidel, W. C.; Gerlach, D. H. J . Am.
Chem. Soc. 1972, 94, 2669. (h) Durkin, T. P.; Schram, E. P. Inorg.
Chem. 1972, 11, 1048, 1054. (i) Glockling, F.; McBride, T.; Pollock, R.
J . I. J . Chem. Soc., Chem. Commun. 1973, 650. (j) Evans, D. G.;
Hughes, G. R.; Mingos, D. M. P.; Bassett, J .-M.; Welch, A. J . J . Chem.
Soc., Chem. Commun. 1980, 1255. (k) Bender, R.; Braunstein, P.;
Dedieu, A.; Ellis, P. D.; Huggins, B.; Harvey, P. D.; Sappa, E.;
Tiripicchio, A. Inorg. Chem. 1996, 35, 1223.

Neutral Bimetallic Platinum Hydride Complexes
Organometallics, Vol. 16, No. 25, 1997 5403
yellow. Concentration of the solution to small volume (∼2 mL)
and treatment with n-hexane afforded 2c as a bright yellow
solid; yield 92%. Anal. Calcd for C54H31F15P2Pt2: C, 45.77;
H, 2.21. Found: C, 45.72; H, 2.20. EI-MS (FAB+): molecular
peak not observed, m/ z 1081 ([M - 2C6F5], 51%), 1004
([Pt2(C6F5)(PPh2)(PPh3)]+, 100%), 529 ([Pt(C6F5)2]+, 29%), 456
([Pt(PPh3)]+, 65%), 378 ([Pt(PPh2) - 2H]+, 79%). IR (cm-1):
Exp er im en ta l Section
Gen er a l Meth od s. All reactions were carried out under
N2 using dried solvents purified by known procedures and
distilled prior to use. IR spectra were recorded on a Perkin-
Elmer 883 spectrometer from Nujol mulls between polyethyl-
ene sheets. NMR spectra were recorded on a Bruker ARX 300
spectrometer. Chemical shifts are reported in ppm relative
to external standards (SiMe4, CFCl3, and 85% H3PO4). Ele-
mental analyses were carried out with a Perkin-Elmer 240C
ν(C6F5)X-sens 795 (vs, br). 19F NMR (CDCl3; at 20 °C):
δ
3
-107.15 (s, br, 2Fo, J Pt-F ) 217 Hz, C6F5 bridging) -118.0
o
3
(d, 4Fo, J Pt-F ) 335 Hz, C6F5 terminal) -136.7 (1Fp, C6F5
o
microanalyzer and the mass spectra on
a VG Autospec
bridging) -160.6 (m, 2Fm, C6F5 bridging), -161.5 (t, 2Fp, C6F5
terminal), -163.5 (m, 4Fm, C6F5 terminal). The same spectral
pattern is observed at -50 °C. 13C NMR (CDCl3; 20 °C): δ
158.7 (br), 155.3 (br), 147.5 (br), 144.1 (br), 138.4 (br), 138 (br),
spectrometer. The starting complexes trans-[PtXHL2] (L )
PPh3, X ) CtCPh,36a C6F5,36b Cl;36c L ) PEt3, X ) Cl36d), trans-
[PtCl2(PPh3)2],37 and cis-[Pt(C6F5)2(thf)2]11 were prepared as
described elsewhere.
(C6F5), 133.6 (m, Co, Ph), 130.7 (s, Cp, Ph), 129.6 (d, Ci, J P-C
62 Hz, Ph), 127.8 (m, Cm, Ph).
)
P r ep a r a tion of tr a n s-[(C6F 5)(P P h 3)P t(µ-H)(µ-CtCP h )-
P t(C6F 5)(P P h 3)] (1b). To a CHCl3 solution (20 mL) of trans-
[Pt(CtCPh)H(PPh3)2] (0.113 g, 0.138 mmol) was added cis-
[Pt(C6F5)2(thf)2] (0.093 g, 0.138 mmol), and the mixture was
stirred at room temperature for 1 h. The resulting solution
was evaporated to dryness, and the residue was treated with
methanol, yielding 1b (yield 75%) as a white solid. Anal.
Calcd for C56H36P2F10Pt2: C, 49.79; H, 2.69. Found: C, 49.48;
H, 2.87. EI-MS (FAB+): molecular peak not observed, m/ z
1081 ([Pt2(C6F5)(PPh3)2]+, 15%), 719 ([Pt(PPh3)2]+, 35%), 528
([Pt(C6F5)2]+, 47%), 456 ([Pt(PPh3)]+, 55%). IR (cm-1): ν(CtC)
2018 (w), ν(C6F5)X-sens 797 (m), 784 (m).38 19F NMR (CDCl3;
20 °C): δ -116.4 (dm, 3J Pt-F ) 286 Hz, 2Fo), -118.7 (d, 3J Pt-F
P r ep a r a t ion of tr a n s-[(C6F 5)(P P h 3)P t (µ-H )(µ-Cl)P t -
(C6F 5)(P P h 3)] (3b). cis-[Pt(C6F5)2(thf)2] (0.178 g, 0.264 mmol)
was added to a solution of trans-[PtClH(PPh3)2] (0.200 g, 0.264
mmol) in CHCl3 (10 mL). The mixture was stirred for 10 min,
and then the solution was evaporated to dryness. Addition of
methanol (5 mL) caused the separation of 3b as a white solid
(85% yield). Anal. Calcd for C48H31F10P2ClPt2: C, 44.85; H,
2.43. Found: C, 45.01; H, 2.46. EI-MS (FAB+): m/ z 1283
([M - H]+, 3%), 1081 ([M - H -Cl - C6F5]+, 15%), 719
([Pt(PPh3)2]+, 17%), 528 ([Pt(C6F5)2, 25%), 456 ([Pt(PPh3)],
82%), 378 ([PtPPh2 - 2H], 100%). IR (cm-1): ν(C6F5)X-sens 806
(vs), 795 (s), ν(Pt-Cl) 320 (m with sh). 19F NMR (CDCl3; 20
o
o
) 345 Hz, 2Fo), -163.5 (m, 1Fp), -164.3 (m, 2Fm), -164.7 (t,
1Fp), -165.3 (m, 2Fm). The same spectral pattern was
observed at -50 °C. 13C NMR (CDCl3, -50 °C): δ 147.2-137.3
(C6F5), 134.1 (d, J C-P ) 11.8 Hz), 133.6 (d, J C-P ) 11.2 Hz)
(Co, PPh3), 131.0, 130.9 (Cp, PPh3), 130.1 (d, J C-P ) 61 Hz),
129.1 (d, J C-P ) 65 Hz) (Ci, PPh3), 128.8, 128.6 (s, Ph), 127.8
(m, Cm, PPh3), 127.4 (s, Ph), 124.9 (d, J C-P ) 3.3 Hz, tentatively
assigned to Câ, CRtCâPh), 108.7 (d, J C-P ) 21.7 Hz, CR,
CRtCâPh) (195Pt satellites not observed).
3
3
°C): δ -117.4 (d, 2Fo, J Pt-F ) 339 Hz) -118.3 (d, 2Fo, J Pt-F
o
o
) 412 Hz), -161.3 (t, Fp), -163.5 (t, Fp), -163.9 (m, 2Fm),
-164.9 (m, 2Fm). The same pattern is observed at -50 °C.
13C NMR (CDCl3): δ 148.6-134.8 (br, C6F5), 133.9 (d, 2J P-C
11.5 Hz), 133.5 (d, J P-C ) 11.31 Hz) (Co, Ph, PPh3), 130.96,
130.94 (Cp, Ph, PPh3), 129.1 (d, 1J P-C ) 67.3 Hz), 128.9 (d, 1J P-C
) 60.9) (Cipso, Ph, PPh3), 127.9 (m, Cm, Ph, PPh3).
)
2
P r ep a r a tion of cis-[(C6F 5)(P P h 3)P t(µ-H)(µ-Cl)P t(C6F 5)-
(P P h 3)] (3c). Meth od i. Colorless crystals of 3c (30 mg) are
obtained by slow diffusion (15 days) of n-hexane into a CH2Cl2
solution of 3b (50 mg) at room temperature in the presence of
sunlight. We note that, if the mixture is kept in the freezer,
only crystals of 3b are obtained.
P r ep a r a tion of tr a n s,cis-[(C6F 5)(P P h 3)P t(µ-H)(µ(P )-η2-
P P h 3)P t (C6F 5)2] (2a ). To a colorless solution of trans-
[Pt(C6F5)H(PPh3)2] (0.150 g, 0.169 mmol) in CHCl3 (5 mL) was
added cis-[Pt(C6F5)2(thf)2] (0.114 g, 0.169 mmol), immediately
giving a pale yellow solution. After a few (1-2) minutes of
stirring a white solid precipitates. The mixture was stirred
for 30 min, and then the resulting white microcrystalline solid
(2a ‚CHCl3) was filtered off; yield 71%. Anal. Calcd for
C55H32F15Cl3P2Pt2: C, 43.00; H, 2.03. Found: C, 43.20; H, 2.08.
EI-MS (FAB+): molecular peak not observed, m/ z 1082 ([M
- 2C6F5]+, 20%), 1005 ([Pt2(C6F5)(PPh2)(PPh3)]+, 28%), 888
([Pt(C6F5)H(PPh3)2]+, 40%), 720 ([PtH(PPh3)2]+, 85%), 529
([Pt(C6F5)2]+, 21%), 456 ([Pt(PPh3)]+, 68%), 378 ([Pt(PPh2) -
2H]+, 88%). IR (cm-1): ν(C6F5)X-sens 804 (s), 793 (vs). 19F NMR
Meth od ii. A solution of 3b (0.12 g, 0.09 mmol) in CH2Cl2
(150 mL) was irradiated through Pyrex glass, at room tem-
perature under an argon atmosphere, using a medium-
pressure mercury lamp (125 W) for 30 min until the complete
transformation of starting product (monitored by 31P and 1H
NMR). The solution was evaporated under reduced pressure
to small volume and was treated with hexane, giving pure 3c
as a white solid (80% yield). Anal. Calcd for C48H31F10P2-
ClPt2: C, 44.85; H, 2.43. Found: C, 45.10; H, 2.63. EI-MS
(FAB+): m/ z 1283 ([M - H]+, 7%), 1081 ([M - H - Cl -
C6F5]+, 17%), 719 ([Pt(PPh3)2]+, 15%), 528 ([Pt(C6F5)2]+, 25%),
456 ([PtPPh3]+, 75%), 378 ([Pt(PPh2) - 2H]+, 100%). IR (cm-1):
ν(C6F5)X-sens 806 (vs), 798 (vs), ν(Pt-Cl) 316 (s). 19F NMR
3
(CD3COCD3; 20 °C) δ -115.4 (s, br, 4Fo, J Pt-F ≈ 408 Hz),
o
3
-117.7 (d, 2Fo, J Pt-Fo ≈ 326 Hz), -162.97, -163.05 (overlap-
ping of two t, 2Fp), -163.2 (t, 1Fp), -163.7 (m, 2Fm), -164.8
(m, 2Fm), -165.8 (m, 2Fm). 19F NMR (CD3COCD3; -85 °C): δ
3
(CDCl3; 20 °C): δ -117.7 (d, Fo, J Pt-F ) 323 Hz), -161.3 (t,
o
3
3
-113.1 (d, 1Fo, J Pt-F ≈ 477 Hz), -113.4 (s, br, 1Fo, J Pt-F
≈
o
o
Fp), -163.9 (m, Fm). The same pattern is observed at -50 °C.
P r ep a r a t ion of tr a n s-[(C6F 5)(P E t 3)P t (µ-H )(µ-Cl)P t -
(C6F 5)(P Et3)] (4b). Complex 4b is obtained in a similar way
to complex 3b, with trans-[PtClH(PEt3)2] (0.139 g, 0.297 mmol)
and cis-[Pt(C6F5)2(thf)2] (0.200 g, 0.297 mmol) as starting
materials; yield 72%. Anal. Calcd for C24H31F10P2ClPt2: C,
28.91; H, 3.03. Found: C, 28.91; H, 3.00. EI-MS (FAB+): m/ z
995 ([M - 2H]+, 20%), 829 ([M - C6F5]+, 30%). IR (cm-1):
ν(C6F5)X-sens 805 (vs), 792 (s), ν(Pt-Cl) 305 (m). 19F NMR
363 Hz), -117.7(d, 1Fo), -118.0 (d, 1Fo); -118.6 (d, 2Fo, 3J Pt-F
o
≈ 296 Hz), -161.8 (m, 3Fp), -162.7 (m, 1Fm), -163.2 (m, 2Fm),
-164.1 (m, 1Fm), -165.0 (m, 2Fm). The 13C NMR spectrum
could not be recorded due to the low solubility of the complex.
P r ep a r a t ion of cis-[(C6F 5)(P P h 3)P t (µ-H )(µ-C6F 5)P t -
(C6F 5)(P P h 3)] (2c). To a solution of cis-[Pt(C6F5)2(thf)2] (0.200
g, 0.297 mmol) in CHCl3 (30 mL) was added trans-[Pt(C6F5)H-
(PPh3)2] (0.262 g, 0.297 mmol). The mixture was refluxed for
30 min, and the colorless solution gradually turned deep
3
(CDCl3): δ -117.3 (d, 2Fo, J Pt-F ) 354 Hz), -117.7 (d, 2Fo,
o
3J Pt-F ) 447 Hz), -160.2 (t, Fp), -161.2 (t, Fp), -163.2 (m,
o
(36) (a) Furlani, A.; Licoccia, S.; Russo, M. V.; Chiesi-Villa, A.;
Guastini, C. J . Chem. Soc., Dalton Trans. 1982, 2449. (b) Crespo, M.;
Sales, J .; Sola´ns, X.; Font-Altaba, M. J . Chem. Soc., Dalton Trans.
1988, 1617. (c) Bailar, J . C.; Itatani, H. Inorg. Chem. 1965, 4, 1618.
(d) Phillips, J . R.; Trogler, W. C. Inorg. Synth. 1992, 29, 189.
(37) Gavinato, G.; Toniolo, L. Inorg. Chim. Acta 1981, 52, 39.
(38) Maslowsky, E., J r. Vibrational Spectra of Organometallic
Compounds; Wiley: New York, 1977; p 437, and references therein.
2Fm), -163.7 (m, 2Fm).
Mixtu r e of 4b a n d 4c. A solution of 4b (0.100 g, 0.100
mmol) in CH2Cl2 (150 mL) was irradiated through Pyrex glass,
at room temperature under an argon atmosphere, using a
medium-pressure mercury lamp (125 W) for 30 min. The NMR
spectra of the resulting solution indicates the presence of a

5404 Organometallics, Vol. 16, No. 25, 1997
Ara et al.
Ta ble 7. Cr ysta l Da ta a n d Str u ctu r e Refin em en t P a r a m eter s for Com p lexes 1b, 2a , 2c, a n d 3c
complex
1b‚0.5CH2Cl2
2a ‚1.25CH2Cl2
2c‚C7H8
3c
empirical formula
unit cell dimens
a (Å)
b (Å)
c (Å)
C
56H36F10P2Pt2‚0.5CH2Cl2 C54H31F15P2Pt2‚1.25CH2Cl2 C54H31F15P2Pt2‚C7H8
C48H31ClF10P2Pt2
33.589(7)
11.181(2)
28.843(6)
90
112.10(3)
90
10 036(4), 8
0.710 73
210(1)
graphite monochrom
Mo KR
monoclinic
C2/c
20.007(3)
13.8247(9)
20.179(3)
17.279(3)
17.512(4)
18.338(4)
90
90
90
5549(2), 4
0.710 73
210
graphite monochrom
Mo KR
orthorhombic
Pnna
19.717(2)
17.212(3)
25.108(3)
90
90
90
8521(2), 8
0.710 73
200(1)
graphite monochrom
Mo KR
orthorhombic
Pbca
R (deg)
90
â (deg)
111.412(15)
90
5196(1), 4
0.710 73
γ (deg)
V (Å3), Z
wavelength (Å)
temp (k)
radiation
150(1)
graphite monochrom
Mo KR
monoclinic
P21/c
cryst syst
space group
cryst dimens (mm)
0.23 × 0.22 × 0.19
0.40 × 0.30 × 0.20
0.51 × 0.26 × 0.24
0.54 × 0.22 × 0.14
abs coeff (mm-1
)
5.820
5.662
5.184
6.777
transmissn factors
abs corr
diffractometer
0.379, 0.255
ψ scans
Siemens STOE/AED2
4-48 (+h,+k,(l)
7782
0.854, 0.435
ψ scans
Enraf Nonius CAD4
4-50 ((h,+k,+l)
9417
0.223, 0.191
ψ scans
Siemens STOE/AED2
4-50 (+h,+k,+l)
5410
0.973, 0.652
ψ scans
Siemens P4
3.5-52 (+h,+k,-l)
9805
2θ range (deg)
no. of rflns collected
no. of indep rflns
refinement method
7571 (R(int) ) 0.0503)
9111 (R(int) ) 0.0446)
4888 (R(int) ) 0.00)
8274 (R(int) ) 0.0471)
full-matrix least-squares full-matrix least-squares
full-matrix least-squares full-matrix least-squares
on F2
1.116
on F2
1.026
on F2
1.37
on F2
0.978
goodness of fit on F2 a
final R indices (I > 2σ(I)]a R1 ) 0.050, wR2 ) 0.130 R1 ) 0.068, wR2 ) 0.156
R1 ) 0.039, wR2 ) 0.100 R1 ) 0.047, wR2 ) 0.068
R1 ) 0.069, wR2 ) 0.135 R1 ) 0.113, wR2 ) 0.099
R indices (all data)
R1 ) 0.082, wR2 ) 0.176 R1 ) 0.138, wR2 ) 0.193
a
2
2
2
R1 ) ∑(|Fo| - |Fc|)/∑|Fo|; wR2 ) [∑w(Fo - Fc2)2/∑wFo
]
1/2; goodness of fit ) [∑w(Fo - Fc2)2/(Nobs - Nparam)]1/2; w ) [σ2(Fo) + (g1P)2 +
g2P]-1; P ) [max(Fo2;0) + 2Fc2]/3.
mixture of 4b and 4c in a 1.2:1 ratio. The mixture remained
unchanged when irradiated under similar conditions for an
additional time of 20 min. 4c: 19F NMR (CDCl3) δ -117.3
positional restraints, except for the dichloromethane solvent
molecule Cl(3)-C(56)-Cl(4), for which interatomic distances
were restrained to 1.72 Å; the carbon atom C(56) was refined
isotropically. The hydrogen atoms were constrained to ideal-
ized geometries and assigned isotropic displacement param-
eters equal to 1.2 times the Uiso value of their respective parent
carbon atoms. One of the dichloromethane solvent molecules,
Cl(3)-C(56)-Cl(4), was refined with a partial occupancy of
0.25. The dinuclear Pt complex shows a disorder over two
positions related by a pseudo binary axis located at (1/4, y, 1/4).
The disorder arises because the periphery of the molecule has
a shape that approximates to 2-fold symmetry, with the local
symmetry axis parallel to the crystallographic b axis. At the
center of the molecule, however, the approximate 2-fold
symmetry is broken by a significant inclination of the Pt-Pt
vector away from the pseudo-2-fold axis. One of the sets of
positions is clearly in the majority (87%), and thus, only the
positions of the heavy metal atoms of the minor component
could be identified from the electron density maps. The
addition of these atoms (Pt(1′) and Pt(2′)) significantly im-
proves the model (R1 ) 0.0682 and wR2 ) 0.1559 with Pt(1′)
and Pt(2′) in the model as compared to R1 ) 0.0949, wR2 )
0.2301 and the largest nonassigned electron density peak of
16.27 e Å-3 without these atoms). The midpoints between the
(Fo, J Pt-F ) 360 Hz), -159.9 (t, Fp), -163.2 (m, Fm).
o
P r ep a r a tion of [P t(µ-Cl)(C6F 5)(P P h 3)]2 (5). Meth od i.
The synthesis of 5 was performed as described for 3c (method
ii) by ultraviolet irradiation of 3b through Pyrex glass, but
with increased reaction time (14 h) (71% yield).
Meth od ii. A mixture of trans-[PtCl2(PPh3)2] (0.100 g, 0.126
mmol) and cis-[Pt(C6F5)2(thf)2] (0.057 g, 0.085 mmol) in CH2Cl2
(40 mL) was refluxed for 24 h. The resulting yellow solution
was concentrated to 2 mL, and then ethanol (10 mL) was added
to give 5 as a beige solid which was isolated by filtration and
air-dried (68% yield). Anal. Calcd for C48H30F10P2Cl2Pt2: C,
43.68; H, 2.29. Found: C, 44.03; H, 2.31. EI-MS (FAB+): m/ z
1318 ([M]+, 30%). IR (cm-1): ν(C6F5)X-sens 812 (vs), ν(Pt-Cl)
285 (m), 280 (sh), 262 (m). 19F NMR (CDCl3): δ -120.1 (d,
3
4Fo, J Pt-F ) 400 Hz), -161.75 (t, 2Fp), -164.4 (m, 4Fm).
o
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 1b. Crystal
data and other details of the structure analysis are presented
in Table 7. A crystal of 1b was mounted at the end of a glass
fiber and held in place with an epoxy resin adhesive. Unit
cell dimensions were determined from 20 centered reflections
in the range 21 < 2θ < 30°. Three check reflections re-
measured after 45 min showed no decay over the period of data
collection. The structure was solved by direct methods. All
non-hydrogen atoms were assigned anisotropic displacement
parameters and refined without positional restraints. The
dichloromethane solvent molecule Cl(1)-C(57)-Cl(2) was
refined isotropically, with a partial occupancy of 0.5. No
attempts to locate the hydride ligand were made.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 2a . Crystal
data and other details of the structure analysis are presented
in Table 7. A crystal of 2a was mounted at the end of a quartz
fiber and held in place with a fluorinated oil. Unit cell
dimensions were determined from 25 centered reflections in
the range 14.6 < 2θ < 31.1°. Three check reflections re-
measured after every 3 h showed no decay of the crystal over
the period of data collection. The structure was solved by
Patterson methods. All non-hydrogen atoms were assigned
anisotropic displacement parameters and refined without
1
two platinum congeners of each set lie very near to (1/4, y, /4)
and define a line parallel to the b axis of the unit cell. This
line also passes near the positions of the atoms C(13), C(16),
and F(16), the midpoint between the two phosphorus atoms
P(1) and P(2), and the midpoints of the atom pairs C(14)-
C(18), C(15)-C(17), F(14)-F(18) and F(15)-F(17). This line
is the false symmetry axis which relates the two disordered
molecules. For the atom Pt(2) and the ligands bonded to it,
the disorder does not generate separate atomic sites, since this
part of the molecule has approximately the symmetry of the
pseudo-binary rotation axis, and thus no disorder is seen here.
In contrast, the pentafluorophenyl groups bonded to the atom
Pt(1), and Pt(1) itself, do not comply with this symmetry
element; thus, they show more pronounced disorder. Since
the ratio of the disorder is 87/13, as mentioned above only the
heavy atom of the minor component (Pt(1′)) at this end of the
molecule has enough electron density to be clearly identified.

Neutral Bimetallic Platinum Hydride Complexes
Organometallics, Vol. 16, No. 25, 1997 5405
The result is such that in the final density maps there are a
good number of peaks with density higher than 1 e/Å3 (15
peaks, maximum 1.38 e/Å3; largest difference hole -2.29 e/Å3),
which cannot be successfully assigned but which likely cor-
respond to the carbon and fluorine atoms of the minor
component of the disorder. Despite the disorder, the con-
nectivity of the complex molecule is unambiguously estab-
lished, and the geometric parameters are coherent. No
attempts to locate the hydride ligand were made.
of data collection. The structure was solved by Patterson
methods. All non-hydrogen atoms were refined with aniso-
tropic displacement parameters. The hydrogen atoms were
constrained to idealized geometries and assigned isotropic
displacement parameters of 1.2 times the Uiso values of their
respective parent carbon atoms. No attempts to locate the
hydride ligand were made.
All calculations were performed on a local area VAX cluster
(VAX/VMS V5.5) with the SHELXTL-PLUS39 and SHELXL9340
software packages.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 2c. Crystal
data and other details of the structure analysis are presented
in Table 7. A crystal of 2c was mounted at the end of a glass
fiber and held in place with an epoxy resin adhesive. Unit
cell dimensions were determined from 18 centered reflections
in the range 22 < 2θ < 25°. Three check reflections re-
measured after every 45 min showed no decay over the period
of data collection. The structure was solved by direct methods.
All non-hydrogen atoms were assigned anisotropic displace-
ment parameters and refined without positional restraints,
except for the toluene solvent molecule (C(29)-C(33)), for
which the interatomic distance C(29)-C(30) was restrained
to 1.50 Å. No attempts to locate the hydride ligand were made.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 3c. Crystal
data and other details of the structure analysis are presented
in Table 7. A selected crystal of 3c was fixed with epoxy on
top of a glass fiber and transferred to the cold stream of the
low-temperature device of the diffractometer. Data were
collected by the ω-scan method. Three check reflections
measured at regular intervals showed no decay over the period
Ack n ow led gm en t. We thank the Direccio´n General
de Ensen˜anza Superior for financial support (Spain,
Projects PB 95-0003-C0 1-2 and PB 95-0792).
Su p p or tin g In for m a tion Ava ila ble: Tables of all 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 structures of complexes 1b,
2a , 2c, and 3c (31 pages). Ordering information is given on
any current masthead page.
OM970581+
(39) SHELXTL-PLUS Software Package for the Determination of
Crystal Structures, Release 4.0; Siemens Analytical X-Ray Instru-
ments, Inc., Madison, WI, 1990.
(40) Sheldrick, G. M. SHELXL-93, a Program for Crystal Structure
Refinement; University of Go¨ttingen, Go¨ttingen, Germany, 1993.