Synthesis of heterobridged (μ-C=CR)(μ-X) (X = PPh2, PPh2O) platinum-rhodium or platinum-iridium dimers

Article abstract of DOI:10.1021/ic9900049

The synthesis and full characterization of a series of heterobimetallic mixed-bridge alkynyl/phosphido platinum-rhodium and alkynyl/phosphinite platinum-rhodium and platinum-iridium complexes is presented.

Full text of DOI:10.1021/ic9900049

3116
Inorg. Chem. 1999, 38, 3116-3125
Synthesis of Heterobridged (µ-CtCR)(µ-X) (X ) PPh2, PPh2O) Platinum-Rhodium or
Platinum-Iridium Dimers
Larry R. Falvello, Juan Fornie´s,* and Antonio Mart´ın
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-Consejo Superior de Investigaciones Cient´ıficas, 50009 Zaragoza, Spain
Julio Go´mez, Elena Lalinde,* M. Teresa Moreno, and Jorge Sacrista´n
Departamento de Qu´ımica, Universidad de La Rioja, 26001 Logron˜o, Spain
ReceiVed January 6, 1999
The synthesis and full characterization of a series of heterobimetallic mixed-bridge alkynyl/phosphido platinum-
rhodium and alkynyl/phosphinite platinum-rhodium and platinum-iridium complexes is presented. Treatment
of trans-[Pt(C6F5)(CtCR)(PPh2H)2] [2; R ) t-Bu (a), Ph (b)] [generated through the rupture of the homobridged
trans,sym-[Pt(µ-κCR:η2-CtCR)(C6F5)(PPh2H)]2 (1) with PPh2H] or cis-[Pt(CtCR)2(PPh2H)2] with rhodium
acetylacetonate species [Rh(acac)L2] (L2 ) COD, 2CO) in acetone produces the corresponding alkynyl/
diphenylphosphido-bridged complexes trans,cis-[(C6F5)(PPh2H)Pt(µ-κCR:η2-CtCR)(µ-PPh2)RhL2] [L2 ) COD
(3), 2CO (4a)] and cis,cis-[(CtCR)(PPh2H)Pt(µ-κCR:η2-CtCR)(µ-PPh2)RhL2] [L2 ) COD (5), 2CO (6a)]. The
related mixed alkynyl/phosphinite complexes [{(PPh2O)2H}Pt(µ-κCR:η2-CtCR)(µ-κP,κO-PPh2O)ML2] [ML2 )
RhCOD (7), Rh(CO)2 (8), IrCOD (9)] can be prepared by reacting [Pt(CtCR){(PPh2O)2H}(PPh2OH)] with
[M(acac)L2] (M ) Rh, Ir). The molecular structure of 6a, determined by X-ray diffraction, shows that the alkynyl
ligand is σ-bonded to platinum and η2-bonded to the rhodium center with a platinum-rhodium distance of 3.142-
(1) Å. Complex 6a (C38H39O2P2PtRh) crystallizes in the triclinic system, space group P1h: a ) 11.427(2) Å, b )
12.882(2) Å, c ) 14.692(2) Å, R ) 99.098(14)°, â ) 108.339(12)°, γ ) 113.11(2)°, V ) 1787.2(4) Å3, and Z
) 2.
process.1d,5 In contrast, derivatives containing a heterobridged
system of the type (µ-CtCR)(µ-X) are less common,6 and in
Introduction
particular, a very limited number of mixed-bridge µ-phosphido
During the past decade, a large number of studies involving
1b,c,7
LnM(µ-CtCR)(µ-PR′2)M′Ln
or µ-phosphinite LnM(µ-Ct
the preparation and chemistry of homo- and heterobinuclear
complexes containing alkynyl bridging ligands have been
reported.1 Much attention has been paid to doubly alkynyl
bridged (µ-CtCR)2 complexes2 because of their implication in
C-C alkynide coupling processes,2e,3 as well as C-C bond
cleavage in butadiyne ligands induced by metal centers.2f,4
Binuclear complexes with a single µ-CtCR moiety have also
been studied, particularly because of their relevance as model
species for the well-known acetylene-vinylidene tautomerism
8
CR)(µ-PR′2O)M′Ln binuclear complexes have been reported.
The main synthetic method for the preparation of homobime-
tallic compounds of this type is based on the P-C(alkyne) bond
cleavage reactions starting from phosphinoalkyne (PR′2CtCR)
or alkynylphosphine oxides [PR′2CtCR(O)], respectively, and
metal carbonyls. The only heterobimetallic complex structurally
described to date, [Cp2Ti(µ-κCR:η2-CtCPh)(µ-PPh2)Ni(PPh3)],7f
was unexpectedly produced by treatment of the tweezer-like
complex [Cp2Ti(µ-κCR:η2-CtCSiMe3)(µ-κCR:η2-CtCPh)Ni-
(PPh3)] with PPh3; in this reaction, one Ph group of PPh3 is
selectively coupled with the CtCSiMe3 fragment to give
(1) (a) Nast, R. Coord. Chem. ReV. 1982, 47, 89. (b) Carty, A. J. Pure
Appl. Chem. 1982, 54, 113. (c) Sappa, E.; Tiripicchio, A.; Braunstein,
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Bull. Chem. Soc. Jpn. 1995, 68, 420. (e) Fornie´s, J.; Lalinde, E. J.
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10.1021/ic9900049 CCC: $18.00 © 1999 American Chemical Society
Published on Web 06/11/1999

Synthesis of Heterobridged Pt-Rh or Pt-Ir Dimers
Inorganic Chemistry, Vol. 38, No. 13, 1999 3117
PhCtCSiMe3, and the remaining PPh2 fragment leads to the
final heterobridged Ti-Ni mixed complex.
Scheme 1
We are interested in these types of systems because phosphido
and phosphinite bridges are very useful as strongly bound yet
flexible ligands capable of stabilizing and maintaining the
integrity of the binuclear fragments during chemical transforma-
tions.9 Thus, it has been demonstrated that multisite-bound
unsaturated ligands in binuclear phosphido-bridged complexes
can be successfully derivatized with nucleophilic reagents,
affording new C-C, C-N, C-P, or C-S bonds without
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12, 3618. (e) Heeres, H. J.; Nijholf, J.; Teuben, J. H.; Rogers, R. D.
Organometallics 1993, 12, 2609. (f) Duchateau, R.; van Wee, C. T.;
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destroying the µ-PR2 bridge.1b,7c,10 However, several recently
reported transformations involving phosphido ligands set limits
on their use for framework-stabilizing since they do not
invariably behave as innocent bridging ligands.11
Following our studies on the chemistry of alkynyl platinum
complexes and phosphido polynuclear complexes, we are now
exploring the possibilities of mixed phosphido-alkynyl or
phosphinite-alkynyl bridges to stabilize heterobinuclear plati-
num complexes. With that purpose we have recently synthe-
sized12 heteroleptic platinum alkynyl complexes containing the
acid ligands PPh2H or PPh2OH which can be used as precursors
for bi- or polynuclear derivatives by simple deprotonation
processes. We present here the conditions for the formation of
a series of platinum-rhodium (µ-CtCR)(µ-PPh2) and platinum-
rhodium and platinum-iridium (µ-CtCR)(µ-PPh2O) (R ) t-Bu,
Ph) dibridged complexes by reaction of trans-[Pt(C6F5)(CtCR)-
(PPh2H)2] (generated through the rupture of the homobridged
trans,sym-[Pt(µ-κCR:η2-CtCR)(C6F5)(PPh2H)]2 with PPh2H),
cis-[Pt(CtCR)2(PPh2H)2], and [Pt(CtCR){(PPh2O)2H}(PPh2-
OH)] with rhodium or iridium acetylacetonate species [M(acac)-
L2] (L2 ) COD, M ) Rh, Ir; L2 ) 2CO, M ) Rh) (Scheme 2).
Results and Discussion
(7) (a) Smith, W. F.; Yule, J.; Taylor, N. J.; Paik, H. N.; Carty, A. J.
Inorg. Chem. 1977, 16, 1593. (b) Cherkas, A. A.; Randall, L. H.;
MacLaughlin, S. A.; Mott, G. N.; Taylor, N. J.; Carty, A. J.
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D.; Taylor, N. J.; Carty, A. J. J. Chem. Soc., Chem. Commun. 1995,
2165. (d) Blenkiron, P.; Corrigan, J. F.; Pilette, D.; Taylor, N. J.; Carty,
A. J. Can. J. Chem. 1996, 74, 2349. (e) Hogarth, G.; Redmond, S. P.
J. Organomet. Chem. 1997, 534, 221. (f) Pulst, S.; Arndt, P.; Baumann,
W.; Tillack, A.; Kempe, R.; Rosenthal, U. J. Chem. Soc., Chem.
Commun. 1995, 1753. (g) Carty, A. J.; Cherkas, A. A.; Randall, L. H.
Polyhedron 1988, 7, 1045. (h) Doherty, S.; Elsegood, M. R. J.; Clegg,
W.; Ward, M. F.; Waugh, M. Organometallics 1997, 16, 4251. (i)
The mixed [FeRu(CO)6(µ-κCR:η2-CtC-t-Bu)(µ-PPh2)] (δ(P) 137.6)
has been also reported (ref 15, page 565). For M4 species made up
of two M(µ-CtCR)(µ-PR2)M see: (j) Daran, J.-C.; Jeannin, Y.;
Kristiansson, O. Organometallics 1985, 4, 1882. (k) Blenkiron, P.;
Enright, G. D.; Low, P. J.; Corrigan, J. F.; Taylor, N. J.; Chi, Y.;
Saillard, J.-Y.; Carty, A. J. Organometallics 1998, 17, 2447. (l) Adams,
C. J.; Bruce, M. I.; Skelton, B. W.; White, A. H. J. Organomet. Chem.
1993, 450, C9.
Heterobinuclear (µ-CtCR)(µ-PPh2) Complexes. Our initial
efforts were concentrated on the use of the very stable platinum
species trans-[Pt(CtCR)2(PPh2H)2]12 as precursors for the
synthesis of heterobridged (µ-CtCR)(µ-PPh2) complexes.
However, all of our attempts to synthesize heterobridged mixed
(10) (a) Cherkas, A. A.; Carty, A. J.; Sappa, E.; Pellinghelli, M. S.;
Tiripicchio, A. Inorg. Chem. 1987, 26, 3201. (b) Cherkas, A. A.;
Randall, L. H.; Taylor, N. J.; Mott, G. N.; Yule, J. E.; Guinamant, J.
L.; Carty, A. J. Organometallics 1990, 9, 1677 and references therein.
(c) Cherkas, A. A.; Doherty, S.; Cleroux, M.; Hogarth, G.; Randall,
L. H.; Breckenridge, S. M.; Taylor, N. J.; Carty, A. J. Organometallics
1992, 11, 1701 and references therein. (d) Hogarth, G.; Lavender, M.
H.; Shukri, K. Organometallics 1995, 14, 2325. (e) Carty, A. J.;
Hogarth, G.; Enright, G.; Frapper, G. Chem. Commun. 1997, 1883.
(f) Chi, Y.; Carty, A. J.; Blenkiron, P.; Delgado, E.; Enright, G. D.;
Wang, W.; Peng, S.-M.; Lee, G.-H. Organometallics 1996, 15, 5269.
(11) (a) Regragui, R.; Dixneuf, P. H.; Taylor, N. J.; Carty, A. J.
Organometallics 1990, 9, 2234. (b) Brown, M. P.; Buckett, J.; Harding,
M. M.; Lynden-Bell, R. M.; Mays, M. J.; Woulfe, K. W. J. Chem.
Soc., Dalton Trans. 1991, 307. (c) Etienne, M.; Mathieu, R.; Lugan,
N. Organometallics 1993, 12, 140. (d) Falvello, L. R.; Fornie´s, J.;
Fortun˜o, C.; Mart´ın, A.; Mart´ınez-Sarin˜ena, A. P. Organometallics
1997, 16, 5849.
(8) Fogg, D. E.; Taylor, N. J.; Meyer, A.; Carty, A. J. Organometallics
1987, 6, 2252.
(9) (a) Leoni, P.; Pasquali, M.; Pieri, G.; Albinati, A.; Pregosin, P. S.;
Ru¨egger, H. Organometallics 1995, 14, 3143. (b) Braunstein, P.; de
Jesu´s, E.; Tiripicchio, A.; Ugozzoli, F. Inorg. Chem. 1992, 31, 411.
(c) Powell, J.; Sawyer, J. F.; Smith, S. J. J. Chem. Soc., Dalton Trans.
1992, 2793. (d) Leoni, P.; Pasquali, M.; Fortunelli, A.; Germano, G.;
Albinati, A. J. Am. Chem. Soc. 1998, 120, 9564. (e) Shyu, S.-G.; Hsiao,
S.-M.; Lin, K.-J.; Gau, H.-M. Organometallics 1995, 14, 4300. (f)
Falvello, L. R.; Fornie´s, J.; Fortun˜o, C.; Mart´ınez, F. Inorg. Chem.
1994, 33, 6242.
(12) (a) Falvello, L. R.; Fornie´s, J.; Lalinde, E.; Mart´ın, A.; Moreno, M.
T.; Sacrista´n, J. Chem. Commun. 1998, 141. (b) Falvello, L. R.;
Fornie´s, J.; Go´mez, J.; Lalinde, E.; Mart´ın, A.; Moreno, M. T.;
Sacrista´n, J. Chem.sEur. J. 1999, 5, 474.

3118 Inorganic Chemistry, Vol. 38, No. 13, 1999
Falvello et al.
Scheme 2
the reaction system 2/[Rh(acac)(CO)2] is more complicated due
to the much slower formation of the analogous dimers 4 and
especially because of their low stability in solution. Thus,
monitoring by NMR spectroscopy indicates that the formation
of 4a in acetone at 20 °C needs approximately 48 h for
completion. In that period a dark solution is formed, from which
4a can be isolated only as an oily residue (with traces of
impurity) which has been characterized spectroscopically in
solution. However, the related phenylethynyl complex 4b could
not be obtained; the reaction between 2b and [Rh(acac)(CO)2]
affords a complex mixture of products in which the expected
4b could not be detected.
In contrast to the results with trans bis alkynyl derivatives
described above, reactions involving the corresponding cis-[Pt-
(CtCR)2(PPh2H)2] substrates with [Rh(acac)L2] in acetone at
-20 °C resulted in the precipitation of cis,cis-[(CtCR)(PPh2H)-
Pt(µ-κCR:η2-CtCR)(µ-PPh2)RhL2] [L2 ) COD, 5a (orange),
5b (yellow); L2 ) 2CO, 6a (yellow)] in good yields (Scheme
2, ii). These complexes are moderately stable in the solid state
(-30 °C), but seem to be very unstable in solution. Compound
6a is always obtained with small amounts of the dinuclear
derivative [Pt(CtC-t-Bu)(µ-PPh2)(PPh2H)]212b as determined by
NMR spectroscopy (1H and 31P{1H}). Crystallization of the
mixture at low temperature in different solvents gave yellow
crystals of 6a and white crystals of the binuclear product, which
were separated by hand. Again, however, under similar reaction
conditions the analogous phenylethynyl complex 6b could not
be obtained. In the reaction mixture only the precursor cis-[Pt-
(CtCR)2(PPh2H)2] and undefined rhodium-phosphine com-
plexes were detected.
Attempts to prepare the iridium-containing binuclear ana-
logues also failed. The NMR spectra (CDCl3) of the mixture
obtained by reacting 2 or cis-[Pt(CtCR)2(PPh2H)2] and 1 equiv
of [Ir(acac)COD] reveal that the mononuclear complexes are
always present in solution (after 24 h for 2a, 12 h for 2b, 4 h
for cis t-Bu, 3 h for cis Ph), together with unidentified phosphine
complexes. The relatively small amounts of these latter species
and the very low stability of the reaction mixtures precluded
their isolation and identification.
platinum compounds by deprotonation of trans-[Pt(CtCR)2-
(PPh2H)2] with [ML2(acac)] (L2 ) COD, M ) Rh, Ir; L2 )
2CO, M ) Rh) were unsuccessful. We have only found evidence
of reaction for the systems R ) t-Bu/[Rh(acac)COD] and R )
Ph/[M(acac)L2] (M ) Rh, Ir, L2 ) COD, M ) Rh, L ) CO).
However, the results of these reactions are not clear. The
processes are very slow, and after prolonged reaction (∼24 h),
in all cases, substantial amounts of the starting materials are
still present together with complex mixtures of undefined
1
compounds as detected by NMR spectroscopy (31P and H).
Mononuclear platinum species of the type trans-[Pt(C6F5)-
(CtCR)(PPh2H)2] (2), stabilized by two mutually trans PPh2H
ligands were next chosen as precursors. These complexes were
prepared as shown in Scheme 1. By treating trans-[Pt(CtCR)2-
(PPh2H)2] [R ) t-Bu (a), Ph (b)] with cis-[Pt(C6F5)2(thf)2] in
CH2Cl2 at room temperature2h,13 the binuclear complexes trans,-
sym-[Pt(µ-κCR:η2-CtCR)(C6F5)(PPh2H)]2 (1a, 1b) were ob-
tained in moderate (62% 1a) or low yield (42% 1b); and in
agreement with previous findings,2h,13 treatment of complexes
1 with PPh2H in CH2Cl2 results in bridge cleavage to give the
desired mononuclear trans-[Pt(C6F5)(CtCR)(PPh2H)2] (2a, 2b).
These complexes are isolated as white (1a, 2a) or beige (1b,
2b) solids, the tert-butyl derivatives being more stable than the
phenylethynyl homologues. The products were characterized by
the usual means (Tables 1 and 2 and Experimental Section).
As shown in Scheme 2, step i (see Experimental Section),
treatment of the resulting mononuclear complexes trans-[Pt-
(C6F5)(CtCR)(PPh2H)2] (2) with 1 equiv of [Rh(acac)COD]
in acetone at 20 °C readily afforded in good yields the
heterobinuclear derivatives trans,cis-[(C6F5)(PPh2H)Pt(µ-κCR:
η2-CtCR)(µ-PPh2)RhCOD] (3a, 3b) as orange microcrystalline
solids. These solids are moderately air-stable, but in solution
the products decompose in a few hours’ time. The evolution of
The heterobinuclear complexes 3-6 have been identified by
IR and NMR spectroscopic techniques, mass spectrometry, and
elemental analyses (except 4a). Furthermore, the structure of
6a was confirmed by X-ray crystallography (see below).
Complexes 3 show in their IR spectra characteristic absorptions
in the expected range for bridging alkynyl ligands, and in the
cis alkynyl binuclear complexes, only 5b shows a medium ν-
(CtC) absorption at 2108 cm-1, indicative of the presence of
a terminal alkynyl ligand. The ν(CO) bands in complexes 4a
and 6a appear in the same region as those observed in the
starting material [Rh(acac)(CO)2] [(2067, 2012 cm-1 (vs)],
suggesting that the “Rh(CO)2” fragment does not suffer
significant electronic changes in the final products. The separa-
tion between the two bands (∆ν ) 64 cm-1, 6a) is consistent
with a cis formulation of the carbonyl ligands.14
Relevant 31P{1H} NMR data are given in Table 1. The spectra
exhibit two well-separated signals with platinum satellites for
all compounds. In each one, the resonance which appears at a
position similar (δ -3.85 to -10.42) to that observed in the
corresponding precursor is assigned to the secondary phosphine
(PAPh2H). This signal appears as a doublet [except 5b (singlet)]
with a bridge phosphorus coupling constant [2J(PA-PX(B))], as
(14) Browning, J.; Goggin, P. L.; Goodfellow, R. J.; Norton, M. G.; Rattray,
A. J. M.; Taylor B. F.; Mink, J. J. Chem. Soc., Dalton Trans. 1977,
2061.
(13) Berenguer, J. R.; Fornie´s, J.; Lalinde, E.; Mart´ınez, F.; Sanchez, L.;
Serrano, B. Organometallics 1998, 17, 1640.

Synthesis of Heterobridged Pt-Rh or Pt-Ir Dimers
Inorganic Chemistry, Vol. 38, No. 13, 1999 3119
1
1
Table 1. 31P{1H} NMR in CDCl3 at 20 °C for Complexes 3-9 (J in Hz), J(Pt-P) in Brackets and J(Rh-P) in Parentheses
compound
δPA
δPX(B)
2J(PA-PX(B)
)
3a, trans,cis-[(C6F5)(PPh2H)Pt(µ-κCR:η2-CtC-t-Bu)(µ-PPh2)RhCOD]
-5.80 (d)
[2379]
-8.76 (d)
[2252]
-10.42 (d)
[2457]
-3.85 (d)
[2882]
-6.25 (s)
[2701]
-5.25 (d)
[2793]
36.75 (dd)
[1720], (114)
0.1
328
3b, trans,cis-[(C6F5)(PPh2H)Pt(µ-κCR:η2-CtCPh)(µ-PPh2)RhCOD]
4a, trans,cis-[(C6F5)(PPh2H)Pt(µ-κCR:η2-CtC-t-Bu)(µ-PPh2)Rh(CO)2]a
5a, cis,cis-[(CtC-t-Bu)(PPh2H)Pt(µ-κCR:η2-CtC-t-Bu)(µ-PPh2)RhCOD]
5b, cis,cis-[(CtCPh)(PPh2H)Pt(µ-κCR:η2-CtCPh)(µ-PPh2)RhCOD]
6a, cis,cis-[(CtC-t-Bu)(PPh2H)Pt(µ-κCR:η2-CtC-t-Bu)(µ-PPh2)Rh(CO)2]
326
339
14.5
b
[1720], (101)
21.57 (dd)
[1697], (80)
-4.12 (dd)
[1342], (99)
-46.95 (d)
[1363], (105)
-14.26 (dd)
[1364], (79)
18
δPA
δPB
δPX
2J(PA-PX)
2J(PB-PX)
2J(PA-PB)
7a, [{(PPh2O)2H}Pt(µ-κCR:η2-CtC-t-Bu)(µ-κP,κO-PPh2O)RhCOD]
7b, [{(PPh2O)2H}Pt(µ-κCR:η2-CtCPh)(µ-κP,κO-PPh2O)RhCOD]
8a, [{(PPh2O)2H}Pt(µ-κCR:η2-CtC-t-Bu)(µ-κP,κO-PPh2O)Rh(CO)2]a
8b, [{(PPh2O)2H}Pt(µ-κCR:η2-CtCPh)(µ-κP,κO-PPh2O)Rh(CO)2]a
9a, [{(PPh2O)2H}Pt(µ-κCR:η2-CtC-t-Bu)(µ-κP,κO-PPh2O)IrCOD]
9b, [{(PPh2O)2H}Pt(µ-κCR:η2-CtCPh)(µ-κP,κO-PPh2O)IrCOD]
73.88
[2120]
76.68
[2151]
79.65
[2104]
81.34
[2144]
78.38
[2086]
94.14
[2285]
68.38
[2341]
70.28
[2308]
69.70
[2354]
70.29
[2297]
68.87
[2400]
73.15
[2344]
74.63
[3044]
74.56
[3002]
72.59
[3049]
72.40
[3024]
71.55
[3077]
73.12
[2938]
21.8
22.2
20.8
19.4
20.8
24.4
28.1
414
25.1
26.9
27.0
27.2
29.1
402
403
392
404
397
a Only characterized spectroscopically in solution. b It is not resolved.
expected, lower for the cis complexes (5-6a, 0-18 Hz) than
for the trans (3-4a, 326-339 Hz). The other signal which is
observed in complexes 5 and 6a at lower frequencies (δ -4.12
to -46.95) and for complexes 3 and 4a at higher frequencies
(δ 0.1-36.75) is unambiguously assigned to the phosphido
bridging groups (PX,B) due to additional splitting by rhodium
coupling, clearly lower in the dicarbonyl complexes [1J(Rh-
P) ∼ 80 Hz] than in the cyclooctadiene compounds (99-114
Hz, 3, 5). The chemical shifts of these µ-phosphido ligands15
are in agreement with the platinum-rhodium separation of
3.142(1) Å found in the solid state for complex 6a, which is
approximately halfway between that expected for a conventional
Pt(II)-Rh(I) bond16 (strong deshielding) and that for a non-
bonding distance (P resonance significantly shielded). Com-
parison of the values of the 1J(Pt-P) coupling constants suggests
that the bridging phosphido ligand exerts a larger trans influence
than the alkynyl bridging ligand [1J(Pt-PA) 2252-2457, 3, 4a,
vs 2701-2882, 5, 6a] and that the terminal alkynyl possesses
a stronger trans influence than does PPh2H [1J(Pt-PX) 1342-
resonances in 3 and 5 (see Table 2 and Experimental Section).
Notwithstanding, the proton spectra display (even at low
temperature) only two olefinic resonances, clearly suggesting
the existence of a fluxional process (presumably a rapid ring
inversion of the central metallacycle) which would average the
endo and exo protons of the diolefin.
The low-temperature (-50 °C) 19F NMR spectrum (see
Experimental Section) of 3a shows that the five fluorine atoms
of the C6F5 ligand are inequivalent, confirming not only the
bent conformation of the Pt(µ-CtCR)(µ-PPh2)Rh core (as
observed in solid state for 6a) but also that the rotation of the
C6F5 groups is hindered. At higher temperatures, the two ortho
fluorine signals (as well the two meta fluorine signals) collapse
to give broad unresolved signals (at +20 °C) or sharp signals
(at +50 °C), suggesting dynamic behavior. At 20 °C, com-
pounds 3b and 4a exhibit (3b even at -50 °C) the same pattern
as 3a at high temperature. Since the platinum fragment is rather
similar in the three complexes,17 this further suggests that the
equivalence of ortho and meta fluorine atoms is attained by
means of a rapid intramolecular inversion of the central
metallacycle.
1
1364 Hz, 5, 6a, Vs J(Pt-PX) 1697-1720 Hz in 3-4a]. The
terminal P-H protons in these complexes give rise to 1H NMR
signals (dd) ranging from 5.12 to 6.52 ppm, which show
coupling to phosphorus nuclei [AMX system, 1J(PA-H) 370-
385 Hz, 3J(PX-H) 3.0-16.7 Hz] and an additional Pt-H
coupling in the range 27-35 Hz. The asymmetry of the
µ-CtCR/µ-PPh2 system is inferred from the COD (1H and 13C)
13C{1H} analyses for 3b and 4a were rendered impossible
by low solubility (3b) or low stability (4a). For the rest of the
complexes the most useful information comes from the CR and
Câ alkynyl carbon resonances which appear in the expected
range (δ CR/Câ 73.6-103.2/111.7-122.4). Although 195Pt
(15) Carty, A. J.; McLaughlin, S. A.; Nucciarone, D. in Phosphorus-31
NMR Spectroscopy in Stereochemical Analysis: Organic Compounds
and Metal Complexes; Verkade, J. G., Quin, L. D., Eds.; VCH:
Deerfield Beach, FL, 1987; Vol. 8, Chapter 16. See also refs 18-22.
(16) Tanase, T.; Toda, H.; Kobayashi, K.; Yamamoto, Y. Organometallics
1996, 15, 5272 and references therein.
(17) It should be noted that the equivalence of the two halves of the C6F5
ligand can also be achieved by a free rotation of this group about the
Pt-Cipso linkage. However, in these species, the rotation of the C6F5
ligand is expected to have similar energetic barriers in the three
complexes: Casares, J. A.; Espinet, P.; Mart´ınez-Ilarduya, J. M.; Lin,
Y.-S. Organometallics 1997, 16, 770.

Table 2. 1H NMR Dataa for the Complexes (J in Hz)
δ(COD)
Ta
compd (°C)
δ(t-Bu)
δ(PPh2H)
1J(P-H)b 3J(P-H) δ(O‚‚‚H‚‚‚O)
δ(Ph)
dCH
CH2
1a
20
0.65 (s, 18H)
6.35 (d, 2H) ∼408
7.72 (m, 8H), 7.39 (m, 12H)
[38]
1b
20
c
c
[46]
d
7.78 (m, 4H), 7.39-6.67 (m, 26H)
2a
2b
3a
20
20
20
0.89 (s, 9H)
0.88 (s, 9H)
6.42 (2H)d
c
6.26 (dd, 1H) 370
[33]
7.68 (br, 8H), 7.33 (br, 12H)
7.68-6.88 (m, 25H)
7.71 (m, 4H), 7.36 (m, 10H), 7.16 (m, 6H)
c
3.0
4.62 (s, 2H), 3.95 (br, 2H)
2.24 (br, 4H), 1.96 (br, 4H)
-50 0.85 (s, 9H)
c
c
c
c
c
c
c
12
c
7.87, 7.59, 7.37, 6.90 (br)
7.75-6.84 (m, 25H)
7.67-6.79 (m, 25H)
7.84, 7.57, 7.30
4.43 (br, 3H), 3.31 (br, 1H)
4.42 (s, 2H), 3.78 (s, 2H)
4.36 (s, br, 2H), 3.57 (s, br, 2H)
2.5, 1.9 (vbr), 1.5 (br)
2.35, 2.16, 2.04, 1.8
2.35, 2.19, 2.04, 1.93
3b
4ae
5a
20
-50
20
0.96 (s, 9H)
6.52 (dd, 1H) 385
[35]
4.6
(m, 20H)
20
1.11 (s, br, 18H) 5.48 (dd, 1H) 375
[28]
14.9
15
7.88 (m, 4H), 7.34 (m, 10H), 7.15 (m, 6H)
5.45 (br, 2H), 3.61 (br, 2H)
5.53 (s, 2H), 3.36 (br, 2H)
5.43 (s, 2H), 3.71 (br, 2H)
4.68 (s, br, 2H), 3.42 (s, br, 2H)
4.58 (s, 2H), 3.28 (s, 2H)
2.26 (br, 4H), 1.99 (br, 4H)
2.23 (m, 4H), 1.99 (m, 4H)
2.26 (m, 4H), 2.01 (m, 4H)
2.27 (m, 4H), 1.98 (m, 4H)
2.34 (br, 4H), 1.95 (br, 4H)
-50 1.15 (s, 9H)
1.11 (s, 9H)
+50 1.12 (s, 9H)
1.11 (s, 9H)
20
5.43 (dd, 1H) 376
7.86 (m, 4H), 7.37 (m, 10H), 7.20 (m, 6H)
7.89 (m, 4H), 7.35 (m, 10H), 7.14 (m, 6H)
f
5.51 (dd, 1H) 376
[27]
14.3
16.1
15.9
16.7
5b
5.62 (dd, 1H) 376
7.88 (m, 4H), 7.52 (m, 4H), 7.36 (m, 6H),
7.12 (m, 16H)
7.87 (m, 4H), 7.52 (m, 4H), 7.38 (m, 6H),
7.19 (m, 16H)
[31.5]
-50
5.61 (dd, 1H) 377
f
5.12 (dd, 1H) 379
[28]
6a
7a
20
20
1.11 (s, 9H),
1.08 (s, 9H)
1.08 (s, 9H)
7.67 (m), 7.21-7.48 (m), 7.09 (m, 20H)
17.2 (br)
15.5 (br)
8.26 (m, 2H), 8.12 (m, 2H), 7.55-7.21
(m, 18H), 7.01 (m), 6.94 (m) (4H), 6.62
(m, 2H), 6.46 (m, 2H)
4.86 (m, 1H), 4.32 (m, 1H),
3.18 (m, 1H)
2.64 (m, 2H),g 2.46 (m, 1H),
2.19 (m, 1H), 1.97 (m, 2H),
1.79 (m, 1H), 1.45 (m, 1H),
1.35 (m, 1H)
2.39 (m, 2H), 2.07 (m, 2H),
1.74 (m, 2H), 1.53 (m, 2H),
1.25 (m, 1H), 0.86 (m, 1H)
7b
20
7.77, 7.55, 7.34, 7.05, 6.61 (m, 35H)
4.67 (s, br, 1H), 2.57 (s, br, 1H)h
8ae
8be
9a
20
20
20
0.83 (s, 9H)
1.01 (s, 9H)
f
7.97-6.96 (m), 6.7 (t), 6.49 (t) (30H)
7.84 (m, 3H), 7.6-7.05 (m, 30H), 7.86 (d, 2H)
8.17 (m), 8.06 (m), 7.53-6.52 (m) (30H)
15.5 (br)
f
4.73 (s, br, 1H), 4.00 (s, br, 1H),
2.99 (s, br, 1H), 2.79 (s, br, 1H)
2.20 (m, 2H), 1.84 (m, 2H),
1.49 (m, 2H), 1.24 (m, 2H)
9b
20
f
7.53 (m), 7.38-7.07 (m), 6.81 (m) (35H)
4.35 (s, 1H), 3.74 (s, 2H), 2.53 (s, 1H) 2.23, 1.97, 1.84, 1.54 (m, 8H)
b
2
1
1
a In CDCl3, chemical shifts are reported relative to SiMe3 as external reference.
J
in brackets. c The δ(PPh2H) and J(P-H) cannot be determined even with a H{31P} NMR experiment for 1b
195
Pt-H
and 2b. d AA′XX′ system, N ) J(P-H) + J(P′-H) ) 392.5 Hz. e Only characterized spectroscopically in solution. f Not observed. g 2 H, 1 CH2, + 1 dCH. h Two olefinic protons overlap in the CH2
1
3
region.

Synthesis of Heterobridged Pt-Rh or Pt-Ir Dimers
Inorganic Chemistry, Vol. 38, No. 13, 1999 3121
Table 3. Selected Bond Distances (Å) and Angles (deg) for
Complex cis,cis-[(CtC-t-Bu)(PPh2H)Pt(µ-κCR:η2-CtC-t-Bu)-
(µ-PPh2)Rh(CO)2] (6a)
Pt(1)-C(1)
Pt-P(2)
2.012(5)
2.256(2)
3.142(1)
1.925(7)
2.323(2)
1.138(7)
1.216(8)
Pt-C(7)
2.014(6)
2.297(1)
1.830(6)
2.312(6)
2.418(6)
1.125(7)
1.192(8)
Pt-P(1)
Pt-Rh
Rh-C(37)
Rh-C(1)
Rh-C(2)
O(2)-C(38)
C(7)-C(8)
Rh-C(38)
Rh-P(1)
O(1)-C(37)
C(1)-C(2)
C(1)-Pt-C(7)
C(7)-Pt-P(2)
C(7)-Pt-P(1)
C(37)-Rh-C(38)
C(1)-Rh-P(1)
C(38)-Rh-C(1)
Pt-C(1)-C(2)
Pt-C(1)-Rh
95.5(2)
87.5(2)
171.2(2)
92.9(3)
71.3(1)
103.5(2)
167.9(5)
92.9(2)
174.9(6)
C(1)-Pt-P(2)
C(1)-Pt-P(1)
P(2)-Pt-P(1)
C(37)-Rh-P(1)
Pt-P(1)-Rh
C(38)-Rh-C(2)
C(1)-C(2)-C(3)
C(8)-C(7)-Pt
175.5(2)
77.4(2)
99.4(1)
91.4(2)
85.7(1)
88.1(2)
164.5(6)
173.5(5)
C(7)-C(8)-C(9)
Figure 1. Molecular structure of cis,cis-[(CtC-t-Bu)(PPh2H)Pt(µ-κCR:
η2-CtC-t-Bu)(µ-PPh2)Rh(CO)2] (6a) showing the atom-numbering
scheme. Hydrogen atoms are omitted for clarity.
atoms retain the normal four-coordinate planar coordination
geometry with no metal-metal bond [Rh‚‚‚Rh 3.717(1) Å]
while in the other isomer one rhodium is planar and the other
is tetrahedral and the dimer has a Rh-Rh distance of 2.761 Å,
consistent with the presence of a single Rh-Rh bond.
The platinum-rhodium distance [3.142(1) Å] in 6a is clearly
longer, and the angle at the bridging phosphorus atom [85.71-
(5)°] is rather less acute than those found for conventional Pt-
Pt or Rh-Rh metal-metal bonds supported by closed M(µ-
PPh2)M bridge bonding11d,19a,20,21 (i.e., [Pt4(µ-PPh2)4(C6F5)4(CO)2],
Pt(3)-Pt(2,4) 2.699(1), 2.688(1) Å; Pt-P-Pt 71.9(1)-73.5-
(1)°;11d [(PEt3)2Rh(µ-PPh2)2RhCOD], Rh-Rh 2.752(1), Rh-
P-Rh 73.4(1), 74.16(4)° 21a). However, the distance is still
markedly shorter than those expected for a complete nonbonding
metal-metal interaction20,22 (i.e., [Pt(CtC-t-Bu)(µ-PPh2)-
(PPh2H)]2, Pt‚‚‚Pt 3.649(1) Å, P-Pt-P 103.2(1)°;12b [Rh(µ-
PPh2)(dppe)]2, Rh‚‚‚Rh 3.471(1) Å, Rh-P-Rh 94.7(1)° 22a). In
fact, similar PPh2 bridged metal-metal (Pt‚‚‚Pt or Rh‚‚‚Rh)
distances were considered as intermediate between bonding and
nonbonding in triplatinum21c and trirhodium19a clusters, with
angles at the phosphorus atom ranging from 81.1(1)° to 89.0-
(1)°.
satellites are not observed, CR or Câ resonances can be assigned
unambiguously on the basis of carbon-trans and carbon-cis
phosphorus coupling constants. The assignment as CR/Câ
terminal or bridging has been tentatively carried out by assuming
larger coupling of µ-CRtCâR to terminal PA than of terminal
σ-CRtCâR to bridging PX. With this assumption in mind, we
observe small upfield shifts for CR signals relative to the
precursors [cis-[Pt(CtCR)2(PPh2H)2] δCR 84.3 (R ) t-Bu); 99.9
(R ) Ph)] upon η2 coordination of the CtCR ligands to
rhodium, as was previously found for related complexes.2i,18
For 6a, the two CO signals [trans (δ 186.1) and cis (δ 185.0)
to µ-PPh2-] could be easily identified due to their significantly
different coupling constants to the rhodium and phosphorus
centers [1J(C-Rh)/2J(C-P) 58.8/92.6 trans to µ-P, 78.9/10.8
1
cis to µ-P]. Again, comparison of J(Rh-C) confirms that the
bridging µ-PPh2 group exerts a larger trans influence than does
the µ-CtC-t-Bu (η2-bonded).
The structure of 6a was established by an X-ray diffraction
study (see Figure 1 and Table 3). As was deduced on the basis
of NMR studies, the molecule possesses a central folded Pt(µ-
CtC-t-Bu)(µ-PPh2)Rh core. The platinum atom completes its
usual square planar coordination with one PPh2H molecule and
one CtC-t-Bu terminal group. The geometry about the rho-
dium(I) is also essentially square planar with the remaining two
coordination sites being occupied by two carbonyl ligands. The
dihedral angle formed by the corresponding metal coordination
planes is 71.6°. The stabilization of the Rh(µ-PPh2)(CO)2
fragment with a square planar coordination at the Rh(I) center
on the binuclear species is particularly significant.19 It has been
previously noted that the tendency of the Rh center in the Rh-
(µ-PPh2)(CO)2 unit to adopt a tetrahedral geometry is presum-
ably the reason for its giving rise to a number of oligomeric
products of the types [Rh3(µ-PPh2)3(CO)n] (n ) 5, 7, 9) and
[Rh4(µ-PPh2)4(CO)6].19a The simple dimer [Rh(µ-PPh2)(CO)2]2
is not known, and as far as we know, the most closely related
species structurally characterized are the two isomers of [Rh-
(µ-Pt-Bu2)(CO)2]2 (A and B).20 In one isomer (A) both rhodium
In comparison with other alkynyl platinum-rhodium systems,
the Pt(II)-Rh(I) bond length [3.142(1) Å] in 6a is clearly longer
than that found in [(PPh3)2Pt(µ-H)(µ-κCR:η2-CtCPh)RhCp*-
(PMe3)]2+ [2.826(1) Å]6j but shorter than those observed for
neutral Pt(II)-Rh(III) systems such as [(PEt3)Cp*Rh(µ-κCR:
η2-CtC-t-Bu)(µ-Cl)Pt(C6F5)2] [3.371(1) Å] or [(PEt3)Cp*Rh-
(µ-κCR:η2-CtCSiMe3)(µ-2κCR:η2-CtCSiMe3)Pt(C6F5)2] [3.554-
(1) Å].2i
The M-P (phosphido) distances [Pt-P ) 2.297(1) Å, Rh-P
) 2.323(2) Å] are comparable to those reported for related
complexes.11d,19-22 The alkynyl ligand bridges the metal centers
(21) (a) Meek, D. W.; Kreter, P. E.; Christoph, G. G. J. Organomet. Chem.
1982, 231, C53. (b) Alonso, E.; Fornie´s, J.; Fortun˜o, C.; Mart´ın, A.;
Orpen, G. Chem. Commun. 1996, 231. (c) Bender, R.; Braunstein, P.;
Dedieu, A.; Ellis, P. D.; Huggins, B.; Harvey, P. D.; Sappa, E.;
Tiripicchio, A. Inorg. Chem. 1996, 35, 1223. (d) Leoni, P.; Manetti,
S.; Pasquali, M.; Albinati, A. Inorg. Chem. 1996, 35, 6045. (e) Jones,
R. A.; Wright, T. C. Organometallics 1983, 2, 1842.
(22) (a) Fultz, W. C.; Rheingold, A. L.; Kreter, P. E.; Meek, D. W. Inorg.
Chem. 1983, 22, 860. (b) Fornie´s, J.; Fortun˜o, C.; Navarro, R.;
Mart´ınez, F.; Welch, A. J. J. Organomet. Chem. 1990, 394, 643. (c)
Kourkine, I. V.; Chapman, M. B.; Gluek, D. S.; Eichele, K.;
Wasylishen, R. E.; Yap, G. P. A.; Liable-Sands, L. M.; Rheingold,
A. L. Inorg. Chem. 1996, 35, 1478 and references therein. (d) Alonso,
E.; Fornie´s, J.; Fortun˜o, C.; Toma´s, M. J. Chem. Soc., Dalton Trans.
1995, 3777.
(18) Ara, I.; Berenguer, J. R.; Fornie´s, J.; Lalinde, E. Organometallics 1997,
16, 3921.
(19) (a) Haines, R. J.; Steen, N. D. C. T.; English, R. B. J. Chem. Soc.,
Dalton Trans. 1984, 515. See also: (b) Summerville, R. H.; Hoffmann,
R. J. Am. Chem. Soc. 1976, 98, 7240.
(20) Jones, R. A.; Wright, T. C.; Atwood, J. L.; Hunter, W. E. Organo-
metallics 1983, 2, 470.

3122 Inorganic Chemistry, Vol. 38, No. 13, 1999
Falvello et al.
in the most commonly observed σ-π-mode in which the R-C
atom is bonded to platinum [Pt-C 2.012(5) Å] and the
unsaturated CtC bond is unsymmetrically η2-bonded to the
rhodium center [Rh-C(1) 2.312(6), Rh-C(2) 2.418(6) Å]. The
two CtC distances are identical within experimental error
[C(1)tC(2) ) 1.216(8) Å, C(7)tC(8) ) 1.192(8) Å]. As
expected, there is a marked deviation from linearity in the
alkynyl bridging group, with angles at CR and Câ 167.9(5)°/
164.5(6)° smaller than in the alkynyl terminal group 173.5(5)°/
174.9(6)°.
of strong O‚‚‚H‚‚‚O hydrogen bonds.12b,23b,24 Although the
presence of an alkynyl bridging ligand is only observed in the
1
IR spectrum of 9b (2019 cm-1), the H NMR spectra of tert-
butyl derivatives exhibit the expected singlet due to CtC-t-Bu
with the appropriate integration ratio. The presence of a central
bent core is unambiguously inferred from the asymmetry of the
COD ligand in solution. Thus, complexes 9 clearly display at
20 °C four nonequivalent olefinic and four aliphatic signals in
the proton spectra. In complexes 7, although is not possible to
assign separately the olefinic and aliphatic protons because these
overlap each other, the integration is correct for the 12 protons.
Similarly, 13C{1H} NMR spectroscopy at -50 °C on 7a reveals
four olefinic doublet resonances produced by coupling to 103Rh
[δ range 89.9-69.1; J(C-Rh) 14.2-10.9 Hz] and four singlet
signals for the aliphatic carbons (δ 34.3-27.3). The η2-bonded
alkyne signals at 86.9 ppm (CR) and 113.4 (Câ) are seen as
doublets of multiplets although the 195Pt satellites are not
observed despite prolonged accumulation.
All complexes display in their 31P{1H} NMR spectra the
expected ABX pattern with platinum satellites. The signal due
to the central phosphorus atom trans to µ-CtCR (range 71.55-
74.63) appears as a triplet due to similar cis 2J(PX-PA,B) (19.4-
29.1 Hz) coupling and is easily identified. The remaining PA
(73.88-94.14) and PB (68.38-73.15) signals due to mutually
trans phosphorus atoms exhibit a dd splitting pattern with a large
two-bond trans PA-PB coupling (392-414 Hz). The high-
frequency signal, which experiences larger shifts upon changing
the ML2 unit (i.e., δ 73.88, 7a, vs δ 79.65, 8a) is tentatively
assigned to the phosphinite bridging ligand (PA); and the low-
frequency signal, which appears closer to PX, is assigned to the
other phosphorus atom of the mixed chelating PPh2O-H‚‚‚
OPPh2 system.
The Rh-CO distance trans to the CtC triple bond [Rh-
C(37) 1.830(6) Å] is significantly shorter than the corresponding
distance trans to the phosphido ligand [Rh-C(38) 1.925(7) Å],
reflecting not only the asymmetric disposition of the bridging
ligands but also the stronger trans influence of the phosphido
ligand, in keeping with the NMR data (see above).
Heterobinuclear (µ-CtCR)(µ-PPh2O) Derivatives. Recent-
ly12b we have described the synthesis of unusual mononuclear
alkynyl-phosphinite complexes of the type [Pt(CtCR)-
{(PPh2O)2H}(PPh2OH)] stabilized by two molecules of hy-
droxyphosphine; and we have shown that these complexes can
be totally deprotonated by lithium hydroxide, yielding unusual
sandwiched [Pt(CtCR)(PPh2O)3Li2(H2O)(THF)]2 compounds
formed by self-assembly of the resulting (alkynyl)tris(diphen-
ylphosphinite)platinate(II) fragments with the lithium ions. For
comparative purposes, we have now studied the reactivity of
these hydroxy phosphine complexes toward the [M(acac)L2]
substrates. As is summarized in Scheme 2, step iii, treatment
of [Pt(CtCR){(PPh2O)2H}(PPh2OH)], in acetone (R ) t-Bu)
or thf (R ) Ph), at low temperature (-20 °C) with 1 equiv of
[M(acac)L2] [M ) Rh, Ir; L2 ) COD, (CO)2] results in the
formation of binuclear complexes [{(PPh2O)2H}Pt(µ-κCR:η2-
CtCR)(µ-κP,κO-PPh2O)ML2] (M ) Rh, L2 ) COD, 7a, 7b;
L2 ) 2CO, 8a, 8b; M ) Ir, L2 ) COD, 9a, 9b) in moderate to
good yield (59-73%). The cyclooctadiene complexes are
isolated as solids (yellow/orange) after the usual workup.
However, complexes 8a and 8b are extremely soluble even in
solvents such as n-hexane, pentane, or diethyl ether and hence
the final oily residues (pure 8a and 8b by 31P NMR) are only
characterized spectroscopically.
In summary, the reactivity of several mononuclear alkynyl
platinum complexes stabilized by acidic molecules (PPh2H or
PPh2OH) toward deprotonating metal complexes [M(acac)L2]
(M ) Rh, Ir) has been studied. We have found that only the
σ-alkynyl complexes trans-[Pt(C6F5)(CtCR)(PPh2H)2] (2), cis-
[Pt(CtCR)2(PPh2H)2], and [Pt(CtCR){(PPh2O)2H}(PPh2OH)]
(R ) t-Bu, Ph) are suitable precursors for heterobridged (µ-
CtCR)(µ-X) (X ) PPh2, PPh2O) derivatives through simple
deprotonation processes. In addition, formation of either het-
erobridged rhodium or iridium-platinum binuclear complexes
[{(PPh2O)2H}Pt(µ-κCR:η2-CtCR)(µ-κP,κO-PPh2O)ML2] (7-
9) is only straightforward starting from [Pt(CtCR){(PPh2O)2H}-
(PPh2OH)]. The reactions of the platinum precursors containing
PPh2H with the rhodium or iridium acetylacetonate complexes
[M(acac)L2] greatly depend on the nature of the metal, the
ligands, and the alkynyl organic substituent R. Thus, only the
expected heterobridged binuclear Pt-Rh complexes [X(PPh2H)-
Pt(µ-κCR:η2-CtCR)(µ-PPh2)RhL2] [X ) C6F5 (3, 4a), CtCR
(5, 6a) can be isolated starting from [Rh(acac)L2]. The influence
of the alkynyl substituent seems to be decisive in the final
stability of the dimers (CtC-t-Bu > CtCPh), and in the case
of L ) CO, only when R ) t-Bu are the final complexes easily
formed (4a, 6a). The structure of cis,cis-[(CtC-t-Bu)(PPh2H)-
Pt(µ-κCR:η2-CtC-t-Bu)(µ-PPh2)Rh(CO)2] (6a) has been solved
by an X-ray diffraction study, and to our knowledge, this is
just the second report of a heterobimetallic complex stabilized
by a (µ-CtCR)(µ-PPh2) bridging system.
Attempts at growing suitable crystals of any of these
heterobridged (µ-CtCR)(µ-PPh2O) complexes 7-9 for an
X-ray analysis were unsuccessful. However, their characteriza-
tion by microanalysis (except 8), spectroscopic means (IR,
NMR, see Tables 1 and 2), and mass spectrometry is straight-
forward; the lack of solubility for 7b and 9 and stability for 8
prevented their identification by 13C NMR spectroscopy. All
complexes show the expected peak corresponding to the
molecular ion in their FAB(+) mass spectra together with peaks
derived from the loss of the COD ligand or M(COD) fragment
as well as the Pt{(PPh2O)2H} unit (7a, 7b, 9a). Their IR spectra
showed absorptions in the P-O stretching region (range 1029-
962 cm-1), and the lack of bands due to ν(O-H) in the normal
region is consistent with the presence of symmetrical hydrogen
bond formation as has been previously described.12b,23 Com-
1
plexes 7 and 8b clearly exhibit in their H NMR at 20 °C a
broad downfield signal (δ 15.5-17.2), confirming the presence
(23) (a) Roundhill, D. M.; Sperline, R. P.; Beaulieu, W. B. Coord. Chem.
ReV. 1978, 26, 263. (b) Carty, A. J.; Jacobson, S. E.; Simpson, R. T.;
Taylor, N. J. J. Am. Chem. Soc. 1975, 97, 7254. (c) Dixon, K. R.;
Rattray, A. D. Can. J. Chem. 1971, 49, 3997. (d) Cornock, M. C.;
Gould, R. O.; Jones, C. L.; Stephenson, T. A. J. Chem. Soc., Dalton
Trans. 1977, 1307.
(24) See: R. F.; Curtis, Ch. J.; McConnell, K. W.; Santhanam, S.; Strub,
W. M.; Ziller, J. W. Inorg. Chem. 1997, 36, 4151 and references
therein.

Synthesis of Heterobridged Pt-Rh or Pt-Ir Dimers
Inorganic Chemistry, Vol. 38, No. 13, 1999 3123
CRtCâ-t-Bu, 1J(Pt-C) ∼ 910], 31.5 [s, C(CH3)3], 28.9 [s, CMe3, 3J(Pt-
Experimental Section
1
C) ) 19.1]. 31P{1H}NMR: δ -6.15, J(Pt-P) ) 2656.
General methods and instrumentation have been described pre-
viously.12b The starting materials trans,cis-[Pt(CtCR)2(PPh2H)2], [Pt-
(CtCR){(PPh2O)2H}(PPh2OH)] (R ) t-Bu, Ph),12b cis-[Pt(C6F5)2-
(thf)2],25 [Rh(acac)(CO)2],26a and [M(acac)(COD)]26b,c (M ) Rh, Ir) were
prepared as described elsewhere.
Preparation of trans,sym-[Pt(µ-κCR:η2-CtCR)(C6F5)(PPh2H)]2 (R
) t-Bu, 1a; R ) Ph, 1b). A colorless solution of trans-[Pt(CtC-t-
Bu)2(PPh2H)2] (0.401 g, 0.549 mmol) in CH2Cl2 (15 mL) was treated
with 0.370 g (0.549 mmol) of cis-[Pt(C6F5)2(thf)2], and the resulting
yellow solution was stirred for 20 min. Then, the solvent was evaporated
to a small volume (ca. 2 mL) and treated with cold ethanol (∼5 mL)
to give 0.297 g of complex 1a. Concentration of the mother liquors
and cooling to -30 °C afforded an additional fraction (0.133 g, 62%
yield).
2b. Anal. Calcd for C38F5H27P2Pt: C, 54.62; H, 3.26. Found: C,
54.21; H, 3.07. EI-MS (apci+): m/z 920 ([Pt(C6F5)(PPh2H)3]+, 100),
836 ([M + 1]+, 13), 735 ([M - CtCPh]+, 26). IR (νmax/cm-1): 2099
(w) (CtC), 782 (w) (C6F5)X-sens.
19F NMR at 20 °C: δ -116.9 [dm,
Fo, 3J(Pt-Fo) ) 274], -162.1 (t, Fp), -163.9 (m, Fm). The low stability
of this complex prevented the acquisition of the 13C NMR spectrum.
1
31P{1H}NMR: δ -6.53, J(Pt-P) ) 2621.
Preparation of trans,cis-[(C6F5)(PPh2H)Pt(µ-κCR:η2-CtCR)(µ-
PPh2)RhCOD] (R ) t-Bu, 3a; R ) Ph, 3b). To a solution of trans-
[Pt(C6F5)(CtC-t-Bu)(PPh2H)2] (2a) (0.150 g, 0.184 mmol) in acetone
(15 mL) was added a stoichiometric amount of [Rh(acac)COD] (0.057
g, 0.184 mmol). The resulting orange solution was stirred for 4 h and
concentrated to small volume (2 mL) to give a microcrystalline orange
solid, which was filtered off and washed with cold acetone (2 × 2
mL) (0.123 g, 65% yield).
The phenyl complex 1b was prepared in a similar way using the
appropriate starting materials trans-[Pt(CtCPh)2(PPh2H)2] (0.400 g,
0.520 mmol) and cis-[Pt(C6F5)2(thf)2] (0.350 g, 0.520 mmol) (0.0288
g, 42% yield).
Complex 3b was prepared similarly as an orange solid by using the
appropriate starting materials [2b (0.100 g, 0.120 mmol) and [Rh(acac)-
COD] (0.037 g, 0.12 mmol)], after 3 h of stirring, evaporation to small
volume (ca. 2 mL), and treatment with n-hexane (10 mL) (0.078 g,
62% yield).
3a. Anal. Calcd for C44F5H42P2PtRh: C, 51.52; H, 4.13. Found: C,
51.26; H, 3.70. MS: m/z 1025 ([M]+, 242), 917 ([M - COD]+, 17),
813 ([M - Rh(COD) - 1]+, 20), 590 ([Pt(PPh2)Rh(COD) - 1]+, 50),
1a. Anal. Calcd for C48F10H40P2Pt2: C, 45.80; H, 3.20. Found: C,
45.50; H, 3.14. MS: m/z 1089 ([M - C6F5 - 2]+, 24), 1007 ([M -
C6F5 - CtC-t-Bu - 3]+, 16), 922 ([M - 2C6F5 - 2]+, 19), 842 ([M
- 2C6F5 - CtC-t-Bu - 1]+, 15), 760 ([Pt2(PPh2)2]+, 29), 681 ([Pt2-
(PPh2)PPh - 2]+, 63), 629 ([M/2]+, 24), 604 ([Pt2(PPh2)P - 2]+, 100),
528 ([Pt(C6F5)2 - 1]+, 73), 377 ([PtPPh2 - 3]+, 25). IR (νmax/cm-1):
512 ([Pt(PPh2)PRh - 2]+, 100), 436 ([Pt(PPh)PRh - 1]+, 62). IR (νmax
/
a weak band at 2310 was tentatively assigned to PH, 2007 (m) (Ct
cm-1): 2022 (w) (CtC), 787 (s) (C6F5)X-sens 19F NMR at -50 °C: δ
.
3
C), 786 (s) (C6F5)X-sens
.
19F NMR at 20 °C: δ -116.2 [d, Fo, J(Pt-
-113.4, -116.2 [s, br, Fo, 3J(Pt-Fo) ) 343, 320], -163.3 (s, Fp),
-164.6, -164.8 (overlapping of two Fm). At 20 °C: δ -115.2 [br, Fo,
Pt satellites are observed but 3J(Pt-Fo) cannot be calculated], -164.0
Fo) ) 263], -161.6 (t, Fp), -164.3 (m, Fm). A similar pattern was
3
observed at -50 °C: -116.5 [d, br, Fo, J(Pt-Fo) ) 250], -160.7 (t,
Fp), -163.5 (br, Fm).13C{1H} NMR at 20 °C: δ 147.3 [dd, 1J(C-F) ∼
3
2
(t, Fp), -165.2 (m, Fm). At +50 °C: δ -115.3 [s, Fo, J(Pt-Fo) )
231, J(C-F) ∼ 16.8, C6F5], 136.8 (dm, “J” ∼ 235, C6F5), 133.3 [d,
362], -164.2 (t, Fp), -165.3 (m, Fm). 13C{1H} NMR at -50 °C: δ
2J(C-P) ) 11.1, Co, PPh2H], 130.9 (s, Cp, PPh2H), 128.05 [d, J(C-
3
1
2
P) ) 11.6, Cm, PPh2H], 127.5 [d, 1J(C-P) ) 67.9, Cipso, PPh2H], 121.4
[d, J(C-P) ) 21.6], 87.5 (m) (CR,Câ, Pt satellites are not observed),
31.1 [s, br, C(CH3)3], 30.2 (s, CMe3). 31P{1H}NMR: δ -12.93, 1J(Pt-
P) ) 3866.
146.4 [dd, J(C-F) ∼ 210, J(C-F) ∼ 20, C6F5], 137.4-130.5 (br,
overlapping of C6F5 and Ph groups), 128.4 [d, J(C-P) ) 9.9 Hz], 126.9
(s, br) (Ph), 119.0 [m, J(Pt-Câ) ) 243, Câ, CRtCâ-t-Bu)], CR is not
2
observed, 94.1, 91.3, 71.2, 69.4 (br, dCH, COD), 37.3, 32.7 (CH2,
COD), 31.9 [s, br, C(CH3)3], 30.6 (s, CMe3), 28.2, 26.1 (CH2, COD).
3b. Anal. Calcd for C46F5H38P2PtRh: C, 52.83; H, 3.66. Found: C,
52.26; H, 3.66. MS: m/z 936 ([M - COD - 1]+, 17), 813 ([M -
Rh(COD) - 1]+, 19), 512 ([Pt(PPh2)PRh - 2]+, 100), 436 ([Pt(PPh)-
PRh - 1]+, 64). IR (νmax/cm-1): 2328 (w) (PH), 2020 (w) (CtC),
1b. Anal. Calcd for C52F10H32P2Pt2: C, 48.08; H, 2.48. Found: C,
48.50; H, 2.78. MS: m/z 1220 ([M - Ph]+, 20), 1130 ([M - C6F5]+,
15), 798 ([Pt(C6F5)2(CtCPh)(PPh2H) - F]+, 45), 719 ([Pt(C6F5)2(Ct
CPh)(PPh) - F - 1]+, 100), 603 ([Pt2(PPh2)P - 3]+, 40), 529 ([Pt-
(C6F5)2]+, 35), 377 ([PtPPh2 - 3]+, 85). IR (νmax/cm-1): 2345 (w)
(tentatively assigned to PH), 2020 (w) (CtC), 799 (s) (C6F5)X-sens.19F
782 (m) (C6F5)X-sens.
19F NMR at 20 °C: δ -114.8 [dm, Fo, 3J(Pt-Fo)
3
) 340], -163.7 (t, Fp), -165.1, (m, Fm). A similar spectrum is observed
at -50 °C. Compound 3b is not soluble enough for 13C NMR studies.
Reactions of trans-[Pt(C6F5)(CtCR)(PPh2H)2] and [Rh(acac)-
(CO)2]. Formation of trans,cis-[(C6F5)(PPh2H)Pt(µ-κCR:η2-CtC-t-
Bu)(µ-PPh2)Rh(CO)2] (4a). [Rh(acac)(CO)2] (0.046 g, 0.18 mmol) was
added to a solution of trans-[Pt(C6F5)(CtC-t-Bu)(PPh2H)2] (2a) (0.146
g, 0.179 mmol) in acetone (15 mL). The initial orange solution
progressively turned dark brown. After 48 h of stirring at 20 °C, the
resulting solution was evaporated to dryness, giving an oily brown
residue, which was identified as 4a by 31P{1H} NMR.
NMR at 20 °C: δ -118.3 [dm, Fo, J(Pt-Fo) ) 254], -161.9 (t, Fp),
-164.4 (m, Fm). The 13C NMR spectrum could not be recorded due to
the very low stability of 1b in solution. 31P{1H}NMR: δ -13.45, 1J(Pt-
P) ) 3827.
Preparation of trans-[Pt(C6F5)(CtCR)(PPh2H)2] (R ) t-Bu, 2a;
R ) Ph, 2b). (PPh2H 120 µL, 0.659 mmol) was added to a solution of
trans,sym-[Pt(µ,κCR:η2-CtC-t-Bu)(C6F5)(PPh2H)]2 (1a) (0.425 g, 0.338
mmol) in CH2Cl2 (10 mL), and the mixture was stirred for 45 min.
The solution was evaporated to a small volume (ca. 2 mL), and addition
of cold ethanol (3 mL) gave 2a as a white solid (0.479 g, 87% yield).
Complex 2b (56% yield) was prepared in a similar way by using 1b
(0.35 g, 0.270 mmol) and 98.1 µL of PPh2H (0.539 mmol) as starting
materials, but in this case the solvent was evaporated and the final
residue was treated with n-hexane.
The reaction is slow, and we observed the presence of starting
materials (by 31P{1H} NMR spectroscopy) until ∼48 h of reaction.
Because of this long reaction period some decomposition also takes
place.
2a. Anal. Calcd for C36F5H31P2Pt: C, 53.01; H, 3.83. Found: C,
52.73; H, 3.54. MS: m/z 815 ([M]+, 44), 734 ([M - CtC-t-Bu]+,
82), 647 ([M - C6F5 - 1]+, 33), 566 ([Pt(PPh2)2 + 1]+, 100), 379
([PtPPh2 - 1]+, 40). IR (νmax/cm-1): 2352 (w) (PH), (CtC) not
The reaction between [Rh(acac)(CO)2] (0.044 g, 0.17 mmol) and
2b (0.142 g, 0.170 mmol) in acetone (25 mL) at 20 °C renders after 7
h of stirring a green solid (rhodium starting material), and the 31P{1H}
NMR of the solution shows 2b (traces) and considerable quantities of
decomposition products. In thf, 2b is detected in the solution even after
48 h of stirring, together with an unidentified mixture of products.
4a. It contains traces of impurity. MS: m/z 973 ([M]+, 49), 947 ([M
- CO + 2]+, 52), 812 ([M - Rh(CO)2 - 2]+, 72), 737 ([M - Rh-
(CO)2 - Ph + 1], 93), 512 ([Pt(PPh2)PRh - 2]+, 100), 436 ([Pt(PPh)-
PRh - 1]+, 75). IR (νmax/cm-1): 2059 (s), 2000 (s, br) (CtC, CO),
observed, 788 (s) (C6F5)X-sens
.
19F NMR at 20 °C: δ -116.6 [dm, Fo,
3J(Pt-Fo) ) 274], -162.7 (t, Fp), -164.3 (m, Fm).13C{1H} NMR at 20
1
2
°C: δ 146.8 [dd, J(C-F) ∼ 222, J(C-F) ∼ 22, C6F5], 133.5 (dm,
“J” ∼258, C6F5), 133.6 (s, Co, PPh2H), 130.4 (s, Cp, PPh2H), 128.1 (s,
Cm, PPh2H), 122.0 [s, Câ, CRtCâ-t-Bu, 2J(Pt-C) ) 250], 81.2 [m, CR,
(25) Uso´n, R.; Fornie´s, J.; Toma´s, M.; Menjo´n, B. Organometallics 1985,
4, 1912.
(26) (a) Varshavskii, Yu. S.; Cherkasova, T. G. Russ J. Inorg. Chem. 1967,
12, 899. (b) Bonatti, F.; Wilkinson, G. J. Chem. Soc. 1964, 3156. (c)
Robinson, S. R.; Shaw, B. L. J. Chem. Soc. 1965, 4997.
791 (m) (C6F5)X-sens.
19F NMR at 20 °C: δ -115.0 [dm, Fo, 3J(Pt-Fo)
) 343], -164.6 (t, Fp), -165.4 (m, Fm). The very low stability of this
complex in solution prevented its characterization by 13C NMR
spectroscopy.

3124 Inorganic Chemistry, Vol. 38, No. 13, 1999
Falvello et al.
Preparation of cis,cis-[(CtCR)(PPh2H)Pt(µ-κCR:η2-CtCR)(µ-
PPh2)RhCOD] (R ) t-Bu, 5a; R ) Ph, 5b). To a yellow solution of
cis-[Pt(CtC-t-Bu)2(PPh2H)2] (0.200 g, 0.274 mmol) in acetone (10 mL)
was added [Rh(acac)COD] (0.085 g, 0.274 mmol) at -20 °C. The
resulting brown solution was allowed to warm to 20 °C, and after 1 h
of stirring, an orange solid started to precipitate. Stirring was continued
for 4 h, and then the resulting solid was filtered off and washed with
cold acetone (2 × 2 mL). This solid was identified as cis,cis-[(CtC-
t-Bu)(PPh2H)Pt(µ-κCR:η2-CtC-t-Bu)(µ-PPh2)RhCOD] (5a) (0.196 g,
76% yield).
cm-1): 2340 (m) (PH) [CtC: not assigned because of overlap with
ν(CO)], 2066 (vs), 2002 (vs) (CO) with additional shoulders at 2035,
2020, and 1956, some of them probably also due to ν(CtC). 13C{1H}
1
NMR at -50 °C: δ 186.1 [dd, CtO trans to P, J(C-Rh) ) 58.8,
2J(C-P) ) 92.6], 185.0 [dd, CtO cis to P, 1J(C-Rh) ) 78.9, 2J(C-
P) ) 10.8], 134.8 [d, Co, J(C-P) ) 11.1, PPh2-], 134.0 [d, Co, J(C-
2
P) ) 10.5, PPh2H], 130.5 (s, Cp, PPh2H), 129.6 [Ci, J(Pt-C) ) 47],
129.0 (s, Cp, PPh2-), 128.3 [d, Cm, J(C-P) ) 10.6, PPh2H], 127.7 [d,
Cm, J(C-P) ) 10.5, PPh2-], 121.5 [dm, Câ, CRtCâ-t-Bu (b), “J(C-
P)” ) 36.8], 120.4 [“d”, Câ, CRtCâ-t-Bu (t), 3J(C-Ptrans) ) 26.5], 84.6
[dd, CR, CRtCâ-t-Bu (t), 2J(C-Ptrans) ) 110.7, 2J(C-Pcis) ) 18.0], 73.6
Complex 5b was prepared similarly as a yellow solid by using the
appropriate starting materials, cis-[Pt(CtCPh)2(PPh2H)2] (0.200 g,
0.260 mmol) and [Rh(acac)COD] (0.081 g, 0.26 mmol) (0.173 g, 68%
yield).
2
2
[dd, CR, CRtCâ-t-Bu (b), J(C-Ptrans) ) 139.4, J(C-Pcis) ) 28.9],
32.3, 31.8 [s, C(CH3)3 (b and t)], 31.6, 29.0 [s, CMe3 (b and t)].
Preparation of [{(PPh2O)2H}Pt(µ-κCR:η2-CtCR)(µ-κP,κO-PPh2O)-
RhCOD] (R ) t-Bu, 7a; R ) Ph, 7b). A suspension of [Pt(CtC-t-
Bu){(PPh2O)2H}(PPh2OH)] (0.150 g, 0.17 mmol) in acetone (20 mL)
was cooled to -40 °C and treated with [Rh(acac)COD] (0.053 g, 0.17
mmol). The mixture was stirred for 3 h while being warmed to 20 °C,
and then the resulting cloudy pale-yellow solution was filtered through
Celite. Partial evaporation of the solvent and addition of n-hexane (5
mL) gave 7a as a yellow-orange solid (0.109 g, 59% yield).
Complex 7b was obtained as a yellow solid in a similar way by
reaction of the appropriate starting materials [Pt(CtCPh){(PPh2O)2H}-
(PPh2OH)] (0.150 g, 0.166 mmol) and [Rh(acac)COD] (0.0516 g, 0.166
mmol) in thf (20 mL) for 5 h from -25 to 20 °C (0.135 g, 73% yield).
7a. Anal. Calcd for C50H52O3P3PtRh: C, 55.00; H, 4.80. Found: C,
54.68; H, 4.36. MS: m/z 1091 ([M]+, 40), 982 ([M - COD - 1]+,
100), 882 ([Pt(CtC-t-Bu){(PPh2O)2H}(PPh2OH) + 1]+, 33), 599 ([Pt-
{(PPh2O)2H} + 1]+, 20). IR (νmax/cm-1): 1029 (sh), 1011 (m), 994
(m), 979 (s) (PO).13C{1H} NMR at -50 °C: δ 142.2 [dd, 1,3J(C-P) )
48.6; 12.6], 140.2 [dd, 1,3J(C-P) ) 50.6; 15.2], 139.4 [dd, 1,3J(C-P)
) 46.6, 12.9], 138.1 [dd, 1,3J(C-P) ) 68.8, 17.4], 136.3 [dd, 1,3J(C-
P) ) 46.9, 15.9] (Ci, PPh2O-, {PPh2O}H), 133.9 [d, Co, J(C-P) )
13.1], 132.8 [d, Co, J(C-P) ) 11.2], 131.1 [d, Co, J(C-P) ) 8.3],
130.8 (m), 130.3 (s, Cp), 129.6 (s, Cp), 129.3 [d, Cm, J(C-P) ) 10.2],
128.8 (s, Cp), 127.9 [d, J(C-P) ) 11.2, Cm], 127.6 (m, Cm), 127.1 [d,
Cm, J(C-P) ) 9.3], 126.7 [d, Cm, J(C-P) ) 8.5] (PPh2OH and
PPh2O-), 113.4 [dm, Câ, CRtCâ-t-Bu, 3J(C-P) ) 28.1], 89.9 [d, J(C-
Rh) ) 14.2, dCH, COD], 86.9 [dm, CR, CRtCâ-t-Bu, 2J(C-P) )
114.1], 80.6 [d, J(C-Rh) ) 11.5], 75.0 [d, J(C-Rh) ) 10.9], 69.1 [d,
J(C-Rh) ) 11.6] (dCH, COD), 34.3, 32.7, 28.8, 27.3 (s, CH2, COD),
30.7 [s, C(CH3)3], 30.5 (s, CMe3).
5a. Anal. Calcd for C44H51P2PtRh: C, 56.23; H, 5.47. Found: C,
55.87; H, 5.60. MS: m/z 858 ([M - CtC-t-Bu]+, 28), 831 ([M -
COD]+, 23), 591 ([Pt(PPh2)Rh(COD)]+, 32), 512 ([Pt(PPh2)PRh - 2]+,
100), 436 ([Pt(PPh)PRh - 1]+, 68), 405 ([Pt(PPh)Rh - 1]+, 29), 359
([PtP2Rh - 1]+, 31). IR (νmax/cm-1): 2358 (w) (tentatively assigned
to PH). 13C{1H} NMR at -50 °C: δ 135.0 (m), 134.8 (s, br), 134.4 (s,
br) (Ph), 134.0 [d, Co, J(C-P) ) 10.1, PPh2H], 130.2 (s, Cp, PPh2H),
130.1 (s, Ph), 129.4 (s, Ph), 128.3 [d, Cm, J(C-P) ) 10.3, PPh2H],
128.1 (s, Ph), 127.4 [d, Cm, J(C-P) ) 9.3, PPh2-], 122.4 [dd, Câ, CRt
Câ-t-Bu (b), 3J(C-Ptrans) ) 31.0, 3J(C-Pcis) ) 9.1], 120.4 [d, Câ, CRt
Câ-t-Bu (t), 3J(C-Ptrans) ) 24.9], 95.5 (s, br, dCH, COD, trans to P),
87.4 [dd, CR, CRtCâ-t-Bu (t), 2J(C-Ptrans) ) 104.2, 2J(C-Pcis) ) 16.5],
83.2 [dd, CR, CRtCâ-t-Bu (b), 2J(C-Ptrans) ) 142.1, 2J(C-Pcis) ) 36.4],
72.0 [d, J(C-Rh) ) 13.1, dCH, COD, trans to CtC-t-Bu], 32.8 [s,
CMe3 (b), CH2, COD], 32.5, 32.0 [s, C(CH3)3 (b and t)], 29.4 (s, CH2,
COD), 29.1 [s, CMe3 (t)].
5b. Anal. Calcd for C48H43P2PtRh: C, 58.84; H, 4.42. Found: C,
59.30; H, 3.95. MS: m/z 871 ([M - COD]+, 33), 770 ([M - COD -
CtCPh]+, 12), 590 ([Pt(PPh2)Rh(COD) - 1]+, 37), 512 ([Pt(PPh2)-
PRh - 2]+, 100), 436 ([Pt(PPh)PRh - 1]+, 86), 404 ([Pt(PPh)Rh -
2]+, 43), 359 ([PtP2Rh - 1]+, 40). IR (νmax/cm-1): 2108 (m) (CtC).
13C{1H} NMR at -50 °C: δ 135.4 (m), 134.4 (d), 134.1 (s), 133.7 (s),
131.1 (s), 130.9 (s), 130.6 (s), 128.9 (s), 128.5 (d), 128.1 (s), 127.6
(d), 127.3 (s), 127.0 (s), 125.0 (s), (Ph), 113.4 [dd, Câ, CRtCâPh (b),
3
3J(C-Ptrans) ) 32.9, J(C-Pcis) ) 8.5], 111.7 [d, Câ, CRtCâPh (t),
3J(C-Ptrans) ) 26.7], 103.2 [dd, CR, CRtCâPh (t), 2J(C-Ptrans) ) 102.8,
2J(C-Pcis) ) 17.8], 100.3 (s, br, dCH, COD trans to P), 86.6 [dd, CR,
CRtCâPh (b), 2J(C-Ptrans) ) 145.1, 2J(C-Pcis) ) 39.9], 73.3 [d, J(C-
Rh) ) 12.9, dCH, COD trans to CtCPh], 32.4 (br, CH2, COD), 28.5
(s, CH2, COD).
7b. Anal. Calcd for C52H48O3P3PtRh: C, 56.17; H, 4.35. Found: C,
56.05; H, 4.58. MS: m/z 1112 ([M + 1]+, 33), 1003 ([M - COD]+,
100), 902 ([M - COD - CtCPh]+, 35), 599 ([Pt{(PPh2O)2H} + 1]+,
18). IR (νmax/cm-1): 2019 (w) (CtC), 1028 (sh), 1010 (m), 996 (m),
974 (s) (PO). Its low solubility prevented characterization by 13C NMR
spectroscopy.
Reactions of [Pt(CtCR){(PPh2O)2H}(PPh2OH)] (R ) t-Bu; R
) Ph) with [Rh(acac)(CO)2]. Formation of 8a and 8b. A cooled
(-20 °C) suspension of [Pt(CtC-t-Bu){(PPh2O)2H}(PPh2OH)] (0.125
g, 0.142 mmol) in acetone was treated with [Rh(acac)(CO)2] (0.0402
g, 0.156 mmol) and stirred for 2 h while the mixture warmed to 20 °C.
The resulting yellow solution was filtered through Celite, and the solvent
was removed in a vacuum to give an oily residue very soluble in
common precipitating solvents, which was characterized spectroscopi-
cally (see Tables 1 and 2) as [{(PPh2O)2H}Pt(µ-κCR:η2-CtC-t-Bu)-
(µ-κP,κO-PPh2O)Rh(CO)2] (8a). Its very low stability in solution
prevented its characterization by 13C NMR spectroscopy.
The analogous reaction with the phenyl starting material (0.100 g,
0.111 mmol of [Pt(CtCPh){(PPh2O)2H}(PPh2OH)]) and 0.034 g, 0.13
mmol of [Rh(acac)(CO)2] was carried out in thf (25 mL). The initial
suspension dissolved slowly, and after 1 h, the resulting yellow solution
was filtered through Celite and the solvent removed in a vacuum to
give [{(PPh2O)2H}Pt(µ-κCR:η2-CtCPh)(µ-κP,κO-PPh2O)Rh(CO)2] (8b)
as an oily residue, which was characterized spectroscopically (Tables
1 and 2).
Preparation of [{(PPh2O)2H}Pt(µ-κCR:η2-CtCR)(µ-κP,κO-PPh2O)-
IrCOD] (R ) t-Bu, 9a; R ) Ph, 9b). Complexes 9a and 9b were
prepared as orange solids in a similar way to 7a and 7b, respectively,
starting from [Pt(CtC-t-Bu){(PPh2O)2H}(PPh2OH)] (0.150 g, 0.170
Reactions of cis-[Pt(CtCR)2(PPh2H)2] (R ) t-Bu; R ) Ph) with
[Rh(acac)(CO)2]. Preparation of cis,cis-[(CtC-t-Bu)(PPh2H)Pt(µ-
κCR:η2-CtC-t-Bu)(µ-PPh2)Rh(CO)2] (6a). [Rh(acac)(CO)2] (0.18 g,
0.69 mmol) was added to a stirred solution of cis-[Pt(CtC-t-Bu)2-
(PPh2H)2] (0.50 g, 0.70 mmol) in acetone (20 mL) at -20 °C, and the
mixture was stirred for 30 min and then allowed reach 20 °C. In a few
minutes a yellow solid started to precipitate, and after 1 h of stirring
the solid was filtered and washed with cold acetone (2 × 2 mL), 0.41
g (67% yield). The 31P{1H} NMR spectrum of this solid shows it to be
the complex cis,cis-[(CtC-t-Bu)(PPh2H)Pt(µ-κCR:η2-CtC-t-Bu)(µ-
PPh2)Rh(CO)2] (6a) impurified with traces of the binuclear complex
[Pt(CtC-t-Bu)(µ-PPh2)(PPh2H)]2.12b
The reaction of cis-[Pt(CtCPh)2(PPh2H)2] (0.100 g, 0.130 mmol)
with [Rh(acac)(CO)2] (0.035 g, 0.13 mmol) in acetone (10 mL) at -10
°C was monitored by 31P{1H} NMR spectroscopy. After 2 h, a dark-
brown solution was observed, with 31P NMR indicating the presence
of considerable amounts of starting material cis-[Pt(CtCPh)2(PPh2H)2]
plus weak signals at δ -5.08 (d, J ) 14.5) and -11.83 (d, J ) 21.4).
Similar results were observed when the reaction was carried out in a
1:2 ratio (Pt:Rh) for 40 min at 20 °C.
6a. Anal. Calcd for C38H39O2P2PtRh: C, 51.42; H, 4.43. Found: C,
+
50.91; H, 4.64. MS: m/z 1294 ([Pt(CtC-t-Bu)(µ-PPh2)(PPh2H)]2
)
A+, 56), 1213 ([A - CtC-t-Bu]+, 100), 1108 ([A - PPh2H]+, 22),
1026 ([A - CtC-t-Bu - PPh2H - 1]+, 35), 946 ([Pt2(PPh2)2(PPh2H)]+,
57), 887 ([M]+, 18), 871 ([M - O]+, 89), 689 ([Rh(µ-PPh2)(CO)2]2
)
+
B+ + 1, 28), 635 ([B - 2CO + 3]+, 63), 605 ([B - 3CO + 1]+, 41),
512 ([Pt(PPh2)PRh - 2]+, 68), 436 ([Pt(PPh)PRh - 1]+, 68). IR (νmax
/

Synthesis of Heterobridged Pt-Rh or Pt-Ir Dimers
Inorganic Chemistry, Vol. 38, No. 13, 1999 3125
mmol) and [Ir(acac)COD] (0.068 g, 0.17 mmol) for 9a (0.143 g, 71%
yield) and [Pt(CtCPh){(PPh2O)2H}(PPh2OH)] (0.125 g, 0.139 mmol)
and [Ir(acac)COD] (0.055 g, 0.14 mmol) for 9b (0.122 g, 73% yield).
Longer reaction times (7 h, 9a, and 24 h, 9b) were required.
9a. Anal. Calcd for C50H52O3P3PtIr: C, 50.84; H, 4.44. Found: C,
50.75; H, 4.36. MS: m/z 1181 ([M + 1]+, 10), 1073 ([M - COD -
1]+, 23), 882 ([Pt(CtC-t-Bu){(PPh2O)2H}(PPh2OH) + 1]+, 100), 599
([Pt{(PPh2O)2H} + 1]+, 42). IR (νmax/cm-1): 1028 (sh), 1012 (s), 996
(m), 962 (s) (PO).
9b. Anal. Calcd for C52H48O3P3PtIr: C, 52.00; H, 4.03. Found: C,
52.51; H, 4.79. MS: m/z 1201 ([M + 1]+, 5), 1093 ([M - COD +
1]+, 11), 399 ([Pt(PPh2OH) + 2]+, 100). IR (νmax/cm-1): 2339 (w)
(PH), 2019 (w) (CtC), 1027 (sh), 1014 (m), 997 (m), 965 (m) (PO).
The very low solubility of 9a and 9b prevented their characterization
by 13C NMR.
X-ray Crystallography of 6a. Crystals of 6a suitable for X-ray
analysis were obtained by slow diffusion of n-hexane into a chloroform
solution of 6a at -30 °C. Important crystal data and data collection
parameters are listed in Table 4. A crystal of 6a was mounted at the
end of a quartz fiber and held in place with a fluorinated oil. All
diffraction measurements were made at 150(1) K on an Enraf-Nonius
CAD4 diffractometer, using graphite-monochromated Mo KR X-
radiation. Unit cell dimensions were determined from 25 centered
reflections in the range 22.3° < 2θ < 31.5°. Diffracted intensities were
measured in a hemisphere of reciprocal space for 4.0° < 2θ < 50.0°
by ω scans. Three check reflections remeasured after every 3 h showed
no decay of the crystal over the period of data collection. An absorption
correction was applied on the basis of 370 azimuthal scan data
(maximum and minimum transmission coefficients were 0.908 and
0.677). The structure was solved by Patterson methods. All non-
hydrogen atoms were assigned anisotropic displacement parameters and
refined without positional constraints. The hydrogen atoms of the
complex were constrained to idealized geometries and assigned isotropic
displacement parameters 1.2 times the Uiso value of their parent carbon
atoms (1.5 times for the methyl hydrogen atoms). Full-matrix least-
Table 4. Crystallographic Data for cis,cis-[(CtC-t-Bu)(PPh2H)-
Pt(µ-κCR:η2-CtC-t-Bu)(µ-PPh2)Rh(CO)2] (6a)
empirical formula
fw
temp (K)
wavelength (Å)
space group
unit cell dimens
a (Å)
C38H39O2P2PtRh
887.63
150(1)
0.710 73
P1h
11.427(2)
b (Å)
c (Å)
12.882(2)
14.692(2)
R (deg)
99.098(14)
108.339(12)
113.11(2)
1787.2(4)
2
1.65
4.49
â (deg)
γ (deg)
vol (Å3)
Z
F
calc (Mg/m3)
abs coeff (mm-1
)
final R indicesa [I > 2σ(I)]
R indicesa (all data)
R1 ) 0.0320, wR2 ) 0.0661
R1 ) 0.0458, wR2 ) 0.0708
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) ∑[w(Fo - Fc2)2/∑w(Fo )2]1/2
.
squares refinement of this model against F2 converged to final residual
indices given in Table 4. A final difference electron density map showed
no peaks above 1 e Å-3 (largest difference peak 0.62; largest difference
hole -0.66). Least-squares calculations were carried out using the
program SHELXL-93.27
Acknowledgment. We thank the Direccio´n General de
Ensen˜anza Superior (Spain) (Projects PB95-0003-C02-01-02 and
PB95-0792) and the University of La Rioja (Project API-99/
B17 and a grant for J.G.) for financial support.
Supporting Information Available: An X-ray crystallographic file,
in CIF format, for complex 6a. This material is available free of charge
via the Internet at http://pubs.acs.org.
(27) Sheldrick, G. M. SHELXL-93, a program for crystal structure
determination; University of Go¨ttingen: Go¨ttingen, Germany, 1993.
IC9900049