Bis-ortho-chelated diaminoaryl platinum compounds with σ-acetylene substituents. Investigations into their stability and subsequent construction of multimetallic systems. The crystal structure of [(μ2-[(η2-NCN)Pt(η 1-CO)C≡CSiMe3])Co2(CO)6] (NCN = 2,6-bis[(dimethylamino)methyl]phenyl)

Article abstract of DOI:10.1021/om000272a

A series of related platinum σ-acetylide complexes {Pt}C≡CR ({Pt} = [Pt(C₆H₃{Me₂NCH₂} ₂-2,6)]⁺) were prepared by reacting lithium acetylides with {Pt}Cl (1) in order to investigate the stability of the Pt-acetylide σ-bond and their possible application in the assembly of multimetallic compounds containing the {Pt} "pincer" unit. This may be achieved by η²-coordination of the acetylide or by incorporating a second ligating site in the acetylide anion. Both of these approaches are demonstrated herein. {Pt}C≡CSiMe₃ (2) was reacted with [M][BF₄] ([M] = [Cu(NCMe)₄], Ag) and different forms of Cu(I) halides. Only with the former was the formation of stable π-coordinated M(I) compounds observed. [(η²-[{Pt}C≡CSiMe₃]₂)-Cu][BF ₄] exhibits η²-coordination of both acetylenic units to a formal Cu(I) metal center, thus forming a heterotrimetallic compound. In the presence of halide ions, 2 undergoes cleavage of the Pt-C≡C σ-bond with concomitant formation of {Pt}X (X = Cl or I). The reaction of 2 with Co₂(CO)₈ leads via π-coordination to the formation of a trimetallic dicobaltatetrahedrane. The structure of [(μ²-[(η²-NCN)Pt(η ¹-CO)C≡CSiMe₃])Co₂(CO)₆] in the solid state shows that one ortho-CH₂NMe₂ substituent of the NCN ligand is no longer coordinated to the Pt metal center. Instead, a CO ligand coordinates trans to the Pt-N bond, yielding a metal center with four different ligand donor atoms. Attempts to obtain related Pt(IV) acetylides by reaction of 2 with CuCl₂ resulted in the formation of {Pt}Cl₃, [CuX]_n, and [CuC≡CSiMe₃]_n. The reaction with I₂ gave neither a Pt(IV) diiodide nor a Pt(II) η₁-I₂ complex, but instead led to Pt-C(acetylide) bond cleavage and formation of {Pt}I and IC≡CSiMe₃. The reaction of {Pt}C≡CC₆H₄CN-4 with [{Pt}H₂O][BF₄] and {Ru}N≡N{Ru} ({Ru} = [RuCl₂(C₅H₃N{CH₂NMe ₂}₂-2,6)]) gives air-stable well-defined bimetallic compounds. In contrast, the reaction of {Pt}C≡CC₆H₄CN-4 with [AuCl₃]₂ or Au(CO)Cl leads to the formation of a gold mirror, NCC₆H₄(C≡C)₂C₆H₄CN, and {Pt}Cl₃ or {Pt}Cl, respectively. Cyclic voltammetry studies with representative Pt-acetylides show irreversible oxidative processes which are shifted to a more negative potential upon substitution of Cl by acetylide.

Full text of DOI:10.1021/om000272a

3296
Organometallics 2000, 19, 3296-3304
Bis-or th o-ch ela ted Dia m in oa r yl P la tin u m Com p ou n d s
w ith σ-Acetylen e Su bstitu en ts. In vestiga tion s in to Th eir
Sta bility a n d Su bsequ en t Con str u ction of Mu ltim eta llic
System s. Th e Cr ysta l Str u ctu r e of
[(µ2-[(η2-NCN)P t(η1-CO)CtCSiMe3])Co2(CO)6] (NCN )
2,6-Bis[(d im eth yla m in o)m eth yl]p h en yl)
Stephan Back,†,‡ Robert A. Gossage,‡ Martin Lutz,§ Ignacio del R´ıo,
Anthony L. Spek,§ Heinrich Lang,† and Gerard van Koten*,‡
Institut fu¨r Chemie, Lehrstuhl Anorganische Chemie, Technische Universita¨t Chemnitz,
Strasse der Nationen 62, 09111 Chemnitz, Germany; and Debye Institute,
Department of Metal-Mediated Synthesis, and Bijvoet Center for Biomolecular Research,
Department of Crystal and Structural Chemistry, Utrecht University, Padualaan 8,
3584 CH Utrecht, The Netherlands
Received March 29, 2000
A series of related platinum σ-acetylide complexes {Pt}CtCR ({Pt} ) [Pt(C6H3{Me2NCH2}2-
2,6)]+) were prepared by reacting lithium acetylides with {Pt}Cl (1) in order to investigate
the stability of the Pt-acetylide σ-bond and their possible application in the assembly of
multimetallic compounds containing the {Pt} “pincer” unit. This may be achieved by η2-
coordination of the acetylide or by incorporating a second ligating site in the acetylide anion.
Both of these approaches are demonstrated herein. {Pt}CtCSiMe3 (2) was reacted with
[M][BF4] ([M] ) [Cu(NCMe)4], Ag) and different forms of Cu(I) halides. Only with the former
was the formation of stable π-coordinated M(I) compounds observed. [(η2-[{Pt}CtCSiMe3]2)-
Cu][BF4] exhibits η2-coordination of both acetylenic units to a formal Cu(I) metal center,
thus forming a heterotrimetallic compound. In the presence of halide ions, 2 undergoes
cleavage of the Pt-CtC σ-bond with concomitant formation of {Pt}X (X ) Cl or I). The
reaction of 2 with Co2(CO)8 leads via π-coordination to the formation of a trimetallic
dicobaltatetrahedrane. The structure of [(µ2-[(η2-NCN)Pt(η1-CO)CtCSiMe3])Co2(CO)6] in the
solid state shows that one ortho-CH2NMe2 substituent of the NCN ligand is no longer
coordinated to the Pt metal center. Instead, a CO ligand coordinates trans to the Pt-N bond,
yielding a metal center with four different ligand donor atoms. Attempts to obtain related
Pt(IV) acetylides by reaction of 2 with CuCl2 resulted in the formation of {Pt}Cl3, [CuX]n,
and [CuCtCSiMe3]n. The reaction with I2 gave neither a Pt(IV) diiodide nor a Pt(II) η1-Ι2
complex, but instead led to Pt-C(acetylide) bond cleavage and formation of {Pt}I and
ICtCSiMe3. The reaction of {Pt}CtCC6H4CN-4 with [{Pt}H2O][BF4] and {Ru}NtN{Ru}
({Ru} ) [RuCl2(C5H3N{CH2NMe2}2-2,6)]) gives air-stable well-defined bimetallic compounds.
In contrast, the reaction of {Pt}CtCC6H4CN-4 with [AuCl3]2 or Au(CO)Cl leads to the
formation of a gold mirror, NCC6H4(CtC)2C6H4CN, and {Pt}Cl3 or {Pt}Cl, respectively. Cyclic
voltammetry studies with representative Pt-acetylides show irreversible oxidative processes
which are shifted to a more negative potential upon substitution of Cl by acetylide.
In tr od u ction
resulting complexes and catalytic properties of these
“pincer” metal compounds.3 Recently, we reported that
the Pt-carbon bond in the pincer halide complex 1 (cf.
Chart 1) possesses a surprising stability and remains
inert to protonation by water or diluted acids under
certain conditions.4 This opened the possibility to pre-
pare para-functionalized NCN Pt-X complexes, e.g., A
or B, which can be used as building blocks for the
The organometallic chemistry of the potentially η3-
chelating, monoanionic diaminoaryl ligand NCN {NCN
) [2,6-(Me2NCH2)2C6H3]-},1 in addition to the related
diphosphino-2 and disulfido-aryl anions,2 has been
extensively investigated due to the stability of the
* To whom correspondence should be addressed. E-mail:
g.vankoten@chem.uu.nl.
(2) For examples see: (a) Dani, P.; Karlen, T.; Gossage, R. A.;
Smeets, W. J . J .; Spek, A. L.; van Koten, G. J . Am. Chem. Soc. 1997,
119, 11317. (b) Loeb, S. J .; Shimizu, G. K. H.; Wisner, J . H. Organo-
metallics 1998, 17, 2324. (c) Vigalok, A.; Rybtchinski, B.; Shimon, L.
J . W.; Ben-David, Y.; Milstein, D. Organometallics 1999, 18, 895.
(3) For example see: Kleij, A. W.; Kleijn, H.; J astrzebski, J . T. B.
H.; Spek, A. L.; van Koten, G. Organometallics 1999, 18, 277.
† Technische Universita¨t Chemnitz.
‡ Debye Institute, Department of Metal-Mediated Synthesis.
§ Bijvoet Center for Biomolecular Research, Department of Crystal
and Structural Chemistry.
(1) (a) van Koten, G. Pure Appl. Chem. 1989, 61, 1681. (b) Rietveld,
M. H. P.; Grove, D. M.; van Koten, G. New J . Chem. 1997, 21, 751.
10.1021/om000272a CCC: $19.00 © 2000 American Chemical Society
Publication on Web 07/25/2000

Bis-ortho-chelated Diaminoaryl Pt Complexes
Organometallics, Vol. 19, No. 17, 2000 3297
Ch a r t 1
systems will allow for the investigation of possible
metal-metal interactions along the organic fragments
and hence evaluate these complexes as “nano-conduct-
ing” materials.
Resu lts a n d Discu ssion
P r ep a r a tion a n d Ch a r a cter iza tion of Mon op la t-
in u m Acetylid es. Reaction of {Pt}Cl (1)4 with in situ
prepared lithium acetylides (eq 1) at -78 °C leads to
(1)
assembly of larger molecules3,5 or H-bonded networks
which offer a high degree of directionality.6 These can
serve as model compounds for molecules that exhibit
qualities that are necessary for application (i) in liquid
crystalline materials (due to their rigid-rod-like struc-
ture),7 (ii) as compounds with high hyperpolarizabili-
ties,8 and (iii) as models for electronic conduction along
conjugated organometallic chains.9
One of these possible molecules is represented as C,
which is built up by repeating units of zwitterionic-type
D. We choose a stepwise approach, since a direct route
to obtain compounds such as C is unknown. Also, an
important factor for the construction of polymeric
compounds such as C is the stability of the Pt-C
σ-bonds. Therefore, we focused this work on the syn-
thesis of model complexes based on 1, which contain
solely one Pt σ-acetylide. Here, the formation, stability,
and electrochemical behavior of Pt σ-acetylides can be
studied. Furthermore, these Pt acetylides can be func-
tionalized to incorporate a second reactive site. This
allows the assembly of bimetallic molecules in which the
{Pt} ({Pt} ) [Pt(C6H3{Me2NCH2}2-2,6)]+) unit can be
connected to a second transition metal (TM) complex
fragment via a conjugated system. Another possibility
to form multimetallic assemblies is given by the CtC
unit itself. Here, transition metals (TMs) such as Cu(I)
or Ag(I) can be attached via η2-coordination. Examples
of such complexes are known.10,11 These multimetallic
the formation of platinum acetylides 2-5. These com-
plexes can be isolated as pure materials in 20-80%
yield.
1
The most representative spectroscopic data (IR, H,
and 13C {1H} NMR) of these compounds are given in
Table 1.
In comparison with the νCtC values of free acety-
lenes,12 the IR spectra of compounds 3-5 all exhibit ca.
35 cm-1 lower values (Table 1). For complex 2 this νCtC
band is observed at 2018 cm-1. In the sharp and well-
1
resolved H NMR spectra of the acetylides 2-5, singlet
resonances of the CH2NMe2 methyl and CH2 protons
are generally shifted (in comparison with 1) by about
0.1 ppm to lower field with coupling constants (3J PtH
)
between 38 and 44 Hz (Table 1). In the 13C{1H} NMR
spectra, the 13C resonances of the NCN ligand are
shifted by 15-20 ppm (Cipso) and ca. 3 ppm for the ortho-
carbon atoms, respectively. The δ 13C(CtC) of the two
acetylenic carbon atoms are found in regions that are
typical for Pt acetylides. Due to the low intensity of the
Cipso of the aryl [C(1)] and acetylide ligands, 195Pt-C
satellite resonances could not be detected.
(4) (a) Grove, D. M.; van Koten, G.; Louwen, J . N.; Noltes, J . G.;
Spek, A. L.; Ubbels, H. J . C. J . Am. Chem. Soc. 1982, 104, 6609. (b)
Albrecht, M.; Gossage, R. A.; Spek, A. L.; van Koten, Chem. Eur. J .,
submitted. (c) Osakada, K.; Yamamoto, T, Coord. Chem. Rev., in press.
(5) (a) Davies, P. J .; Grove, D. M.; van Koten, G. Organometallics
1997, 16, 800. (b) Lagunas, M. C.; Gossage, R. A.; Spek, A. L.; van
Koten, G. Organometallics 1998, 17, 731. (c) Steenwinkel, P.; Grove,
D. M.; Veldman, N.; Spek, A. L.; van Koten, G. Organometallics 1998,
17, 5647. (d) Kleij, A. M.; Kleijn, H.; J astrzebski, J . T. B. H.; Smeets,
W. J . J .; Spek, A. L.; van Koten, G. Organometallics 1998, 18, 268. (e)
Steenwinkel, P.; J ames, S. L.; Gossage, R. A.; Grove, D. M.; Kooijman,
H.; Smeets, W. J . J .; Spek, A. L.; van Koten, G. Organometallics 1998,
17, 4680.
(6) J ames, S. L.; Verspui, G.; Spek, A. L.; van Koten, G. Chem.
Commun. 1996, 1309.
(7) for examples see: (a) Kaharu, T.; Matsubara, H.; Takahashi, S.
J . Mater. Chem. 1991, 1, 145. (b) Abe, A.; Kimura, N.; Tabata, S.
Macromolecules 1991, 24, 6238.
(8) (a) Kanis, D. R.; Ratner, M. A.; Marks, T. J . Chem. Rev. 1994,
94, 195. (b) Sponsler, M. B. Organometallics 1995, 14, 1920.
(9) For examples see: (a) Coat, F.; Lapinte, C. Organometallics 1996,
15, 477. (b) Astruc, D. Acc. Chem. Res. 1997, 30, 383. (c) Brady, M.;
Weng, W.; Zhou, Y.; Seyler, J . W.; Amoroso, A.; Arif, A. M.; Bo¨hme,
M.; Frenking, G.; Gladysz, J . A. J . Am. Chem. Soc. 1997, 119, 775. (d)
Belanzoni, P.; Re. N.; Sgamellotti, A.; Floriani, C. J . Chem. Soc., Dalton
Trans. 1998, 1825.
Rea ction s of {P t}CtCSiMe3 (2). Knowledge of the
stability of the metal-carbon bonds in compounds such
as 2 in the presence of various TM complexes such as
Cu reagents is necessary for two reasons: (i) when the
CtC unit is used for the construction of multimetallic
systems containing, for example, a Cu(I) metal center
13
and (ii) when larger Pt acetylides are created based
on 1.14 We were concerned that the use of functionalized
acetylenes in organolithium reactions might lead to
(11) For examples see: (a) Fornie´s, J .; Lalinde, E.; Mart´ın, A.;
Moreno, M. T. J . Organomet. Chem. 1995, 490, 179. (b) Fornie´s, J .;
Lalinde, E. J . Chem. Soc., Dalton Trans. 1996, 2587.
(12) Dale, J . Properties of Acetylenic Compounds. In Chemistry of
Acetylenes; Viehe, H. G., Ed.; Marcel Dekker: New York, 1969.
(13) For example see: Yamazaki, S.; Deeming, A. J .; Hursthouse,
M. B.; Malik, K. M. A. Inorg. Chim. Acta 1995, 235, 147.
(14) Cu(I)-catalyzed reactions to form stable metal acetylides are
well known and have recently been applied to the preparation of
acetylene TM complexes such as (η5-C5H5)Ni(PPh3)CtCCtCH15 or
(bipy)Pt(CtCR)2.16
(10) For examples see: Lang, H.; Ko¨hler, K.; Blau, S. Coord. Chem.
Rev. 1995, 143, 113.

3298 Organometallics, Vol. 19, No. 17, 2000
Back et al.
Ta ble 1. Rep r esen ta tive IR a n d 1H a n d 13C{1H} NMR Sp ectr oscop ic Da ta of th e P la tin u m Acetylid es 3-5 a s
Well a s of {P t}Cl (1) for Com p a r ison
1H (3J PtH [Hz])
13C {1H} (J PtC [Hz])
compound
IR [cm-1
]
NMe2
CH2
Cipso(Pt)
Cipso(CH2)
PtCtC
PtCtC
1
2
3
4
5
3.08 (38.0)
3.15 (43.3)
3.21 (41.3)
3.21 (41.1)
3.19 (41.8)
4.01 (45.9)
4.08 (43.4)
4.14 (42.6)
4.11 (43.0)
4.12 (41.3)
145.2
159.6
165.5
166.6
166.1
143.3 (76.4)
146.2 (56.4)
146.0
146.1
146.0 (58.3)
2018
2071
2076
2079
110.6
107.5
103.3
106.0
138.9
133.8
138.2
136.5
CuCl entity in 10 is shielded against a possible η2-
coordination of 2 by the bis-η2-chelation of the titanocene
bis(acetylide) unit. Thus, in the case of 10 the chloride
ion is not available for subsequent formation of 1. To
see if the Pt-acetylide 2 is stable under similar condi-
tions in the absence of free halide sources, it has been
reacted with [Cu(NCMe)4][BF4] or Ag[BF4], respectively.
In these cases (Scheme 1), all spectroscopic data point
toward retention of the Pt-acetylide bond and a reac-
tion of the alkyne bond resulting in the formation of the
heterotrimetallic complexes 8 (M ) Cu) or 9 (M ) Ag).
Most informative data are derived from the IR spectra
(KBr) and involve a shift of the νC≡C vibration from 2018
cm-1 (2) to 1918 cm-1 (8) or 1947 cm-1 (9). This indicates
a bond weakening of the CtC entity upon η2-coordina-
Sch em e 1
19
tion of the triple bond to the M(I) center. Also, in the
case of complex 8, absorption bands typical for η1-
coordinated acetonitriles (ca. 2200-2300 cm-1) are
1
absent.20 Compared to 2, the H NMR spectra of 8 or 9
do not exhibit significant changes upon η2-coordination
of the respective M(I) center. However, in the 13C{1H}
NMR spectrum of 9 two doublets are observed for the
reactions at sites other than the acetylenic unit (i.e.,
poor chemoselectivity).
Thus, we carried out a series of experiments to
address the stability and reactivity of the Pt-acetylide
bond (Scheme 1). As model compound, the prototypical
Pt-acetylide {Pt}CtCSiMe3 (2) was used.
1
η2-coordinated Pt-CRtCâ unit at 113.8 ppm (Câ, J AgC
) 17 Hz) and 151.3 ppm (CR,1J AgC ) 19 Hz).
At -30 °C, crystals of 8 were grown from a THF/Et2O
solution. Preliminary X-ray crystallographic results
suggest a tetrahedral environment around the Cu(I)
center with two {Pt}CtCSiMe3 entities coordinated via
their CtC triple bonds. Similar complexes containing
this structural motif have been prepared earlier.21 The
crystal packing of 8 displays large channel-like cavities
in which the [BF4] ions and solvent molecules are
disordered. This restricts a more detailed crystal-
lographic analysis.
In conclusion these results suggest that the reaction
of 2 with Cu(I) halides is likely to proceed via interme-
diates in which the Cu(I) halide in some stage of the
process becomes η2-bonded to the acetylide unit. This
situation leads to ligand exchange and hence the forma-
tion of compounds 1 and 7, respectively. However, it
must be recalled that the cleavage experiment of 2 with
[n-Bu4N]Cl points to a crucial role of the nucleophilic
halide ion in the Pt-C bond cleavage process. It
moreover underlines the strong trans-influence of the
central C(sp2) anion of the NCN ligand. As a direct
consequence of this observation, Cu(I) halide-catalyzed
reactions cannot be used with 1 to form other Pt(II)
monoacetylides.
First the stability of 2 toward [CuX]n (X ) Cl, I) was
tested, since these salts are likely intermediates in
Cu(I)-mediated reactions at the acetylene fragment. As
can be deduced from Scheme 1, treatment of 2 with
equimolar amounts of [CuX]n leads to virtually quan-
titative formation of {Pt}Cl (1) or {Pt}I (6, identified
by 1H NMR)4 and of a yellow precipitate, which was
subsequently identified as [CuCtCSiMe3]n (7).16 For-
mation of 1 was also observed when [n-Bu4N]Cl was
added to a solution of 2. Interestingly, this result points
toward a crucial role of the halide ions in these reac-
tions. Thus, it can be concluded that the bonding of {Pt}
to Cl (or I) is favored over a {Pt} σ-acetylide bond (as in
2), cf. ref 4b. Furthermore, this implies that the applied
Cu(I) halides are likely solubilized in the course of the
reaction. Examples of Cu(I) complexes containing metal-
bound acetylides are well known and usually incorpo-
rate a Cu2Cl2 unit with each of the Cu(I) centers η2-
coordinated to an alkyne.10 Various reactions were
carried out to test this hypothesis. No reaction was
observed when equimolar amounts of {Pt}CtCSiMe3 (2)
were reacted with [(η5-C5H4SiMe3)2Ti(CtCSiMe3)2]CuCl
(10) in THF (25 °C, 12 h).18 Obviously, the monomeric
(18) Lang, H.; Herres, M.; Ko¨hler, K.; Blau, S.; Weinmann, S.;
Weinmann, M.; Rheinwald, G.; Imhof, W. J . Organomet. Chem. 1995,
505, 85.
(15) Gallagher, J . F.; Butler, P.; Manning, A. R. Acta Crystallogr.
1998, C54, 342.
(16) Lang, H.; del Villar, A.; Rheinwald, G. J . Organomet. Chem.
1999, submitted and literature cited therein.
(19) Manna, J .; J ohn, K. D.; Hopkins, M. D. Adv. Organomet. Chem.
1995, 32, 79.
(20) Storhoff, B. N.; Lewis, H. C. Coord. Chem. Rev. 1977, 23, 1.
(21) For example see: Bruce, M. I.; Clark, R.; Howard, J .; Woodward,
P. J . Organomet. Chem. 1972, 42, C107.
(17) Sladkov, A. M.; Gol’ding, I. R. Russ. Chem. Rev. 1979, 48, 868.

Bis-ortho-chelated Diaminoaryl Pt Complexes
Organometallics, Vol. 19, No. 17, 2000 3299
The successful formation of multimetallic complex 8
and 9, using non-halide-containing transition metal
complexes, prompted us to react 2 with other halogen-
less complexes which are known to coordinate acetylene
derivatives. A classical example of this is Co2(CO)8,
which upon reaction with alkynes leads to the formation
of dicobaltatetrahedranes.22 The result of the reaction
of 2 with Co2(CO)8 is presented in eq 2. After workup,
complex 11 is obtained as a dark-brown solid, which is
stable at ambient temperature under a nitrogen atmo-
sphere.
F igu r e 1. Displacement ellipsoid drawing (50% prob-
ability level) of 11 with molecular geometry and atom-
numbering scheme.
tation of the spectroscopic data for the compound in
solution (vide supra). Selected bond lengths and angles
are presented in Table 2.
(2)
The coordination environment around the Pt center
reveals a slightly distorted square-planar geometry. The
distance Pt(1)-C(1) [2.062(4) Å] is in the range of other
known Pt-aryl bonds, e.g., that reported by Brune et
al. (ca. 2.06 Å)24 or in [cis-(PPh3)2Pt(CO2H)(C6H5)]
[2.071(8) Å].25 This bond is longer, however, than that
in η3-coordinated NCN compounds such as [PtCl-
{C6H2(Me2NCH2)2-2,6-(CtCH)-4}] [1.911(12) Å].6 This
mirrors the change in the coordination mode of the NCN
ligand from η3-N,C,N to η2-N,C. The distance of the
noncoordinating nitrogen N1 to the carbonyl group is
small [N1-C18 2.726(4) Å; N1-O1 2.990(4) Å], but the
nitrogen lone pair does not point in the direction of this
group, so there is no direct binding interaction. The bond
length of Pt to the carbonyl carbon atom [Pt(1)-C(18)
1.844(4) Å] resembles other previously reported Pt-
carbonyl distances [ref 23, 1.842(16) Å; ref 26, 1.82(2)
Å]. The other bond lengths of the tetrahedrane frame-
work [Co(1)-Co(2) 2.4896(9) Å; Co(1)-C(13) 2.069(4);
Co(1)-C(14) 2.008(4) Å] and the C-O distances of the
carbonyl ligands attached to Co are in accordance with
earlier published values.22 Interestingly, the bond dis-
tance of Pt to the tetrahedrane unit [Pt(1)-C(13) 2.084-
(4) Å] does not have the value expected for a Pt bound
to sp-hybridized carbon atoms (around 1.9 Å).27 In fact,
it features separations detected for bonds between Pt
and sp2-hybridized28 or even sp3-hybridized carbon
centers.29 Also, the bond length C(13)-C(14) [1.325(5)
Å] of the former CtC unit of 4 is in agreement with
the expected change in hybridization of these carbon
atoms upon binding to the Co2 carbonyl unit. Actually,
this distance resembles that of CdC double bonds,22
which is supported by the aforementioned shift of the
C-C stretching mode. The Si(1)-C(14) [1.858(4) Å] bond
1
The H NMR spectrum of 11 is consistent with the
presence of one coordinated and one noncoordinated
CH2NMe2 unit. The former shows J PtH couplings on both
the CH2 and NMe2 protons, due to Pt-N coordination.
The resonance signals of the free CH2NMe2 group
appear in the region typical for the free [NCN]H ligand
[2.21 ppm (NMe2), 3.44 ppm (CH2)]. The IR spectrum
of 11 displays the expected bands of the CO ligands
(1980-2075 cm-1).22 The band at 2075 cm-1 is assigned
to the νCtO vibration of CO coordinated to Pt, although
this value is slightly lower than that reported for, for
example, [(η2-C6H4{CH2NMe2}-2)Pt(CO)I].23 The related
complex [{Pt}CO]+, in which the CO ligand is η1-
coordinated trans to C(1) of the aryl, has a CO mode at
2086 cm-1 4
Hence, the trans-influence of NMe2 is
.
stronger than that of the aryl carbanion of the NCN
ligand. The vibration mode of the CtC unit was
detected at 1558 cm-1, a region that is typical for
dicobalt-bound acetylenes and strongly indicates a
weakening of the CtC bond due to coordination.22
Taking into account the spectroscopic evidence, com-
pound 11 is the first example of a Pt-NCN complex
where a Pt-N coordination has been replaced by an
incoming monodentate ligand, in this case CO.
Thermogravimetric analysis (TGA) and differential
scanning calorimetry (DSC) have been used to study the
liberation of the Pt-centered CO molecule from com-
pound 11. In the TGA plot, a weight loss of 3.5% is
observed at 105 °C. This loss corresponds with the
liberation of one molecule CO per formula unit of 11.
Further heating causes slow degradation. The DSC
experiment reveals that the liberation of CO is exother-
mic (105 °C, ∆H ) 65 ( 5 kJ mol-1). Thus, these data
indicate that 11 is the kinetic reaction product.
(24) (a) Wiege, M.; Brune, H. A.; Klein, H. P.; Thewald, U. Z.
Naturforsch. 1982, 37b, 718. (b) Brune, H. A.; Wiege, M.; Debaerde-
maker, T. Z. Naturforsch. 1984, 39b, 359.
(25) Bennett, M. A.; Robertson, G. B.; Rokicki, A.; Wickramasinghe,
W. A. J . Am. Chem. Soc. 1988, 110, 7098.
(26) Grassi, M.; Meille, S. V.; Muscso, A.; Pontellini, R.; Sironi, A.
J . Chem. Soc., Dalton Trans. 1989, 615.
From a pentane solution of 11 (-40 °C), crystals
suitable for an X-ray crystal diffraction study have been
obtained. The molecular structure of 11 in the solid state
is shown in Figure 1. It fully corroborates the interpre-
(22) (a) Dickson, R. S.; Fraser, P. J . Adv. Organomet. Chem. 1974,
12, 323. (b) Seyferth, D.; Kugita, T.; Rheingold, A.; Yap, G. P. A.
Organometallics 1995, 14, 5632.
(23) Avshu, A.; O’Sullivan, R. D.; Parkins, A. W.; Alcock, N. W.;
Countryman, R. M. J . Chem. Soc., Dalton Trans. 1983, 1619.
(27) For example see: Su¨nkel, K. H. J . Organomet. Chem. 1988,
348, C12.
(28) Stang, P. J .; Kowalski, M. H. J . Am. Chem. Soc. 1989, 111, 3356.
(29) Manojlovic-Muir, L.; Muir, K. W.; Frew, A. A:; Ling, S. S. M.;
Thomson, M. A.; Puddephatt, R. J . Organometallics 1984, 3, 1637.

3300 Organometallics, Vol. 19, No. 17, 2000
Ta ble 2. Selected Bon d Len gth s [Å] a n d An gles [d eg] for 11a
bond lengths
Back et al.
angles
Pt1-C1
2.062(4)
2.112(3)
2.084(4)
1.844(4)
2.4896(9)
2.069(4)
2.008(4)
1.775(5)
3.416(3)
1.863(4)
O1-C18
O2-C19
N2-C10
N1-C7
C13-C14
Si1-C14
N1-C18
N1-O1
1.126(4)
1.139(5)
1.494(5)
1.450(5)
1.325(5)
1.858(4)
2.726(4)
2.990(4)
N2-Pt1-C18
C1-Pt1-C13
C13-Co1-C14
C7-N1-C8
171.68(14)
Pt1-N2
Pt1-C13
Pt1-C18
Co1-Co2
Co1-C13
Co1-C14
Co1-C22
Pt1-N1
Si1-C15
173.76(14)
37.89(14)
109.3(3)
114.2(3)
109.7(3)
157.1(3)
150.9(3)
172.4(3)
169.1(2)
N1-C7-C6
N2-C10-C2
Pt1-C13-C14
Si1-C14-C13
Pt1-C18-O1
Pt1-C1-C4
a
Standard deviation in units of the last significant figure in parentheses.
Sch em e 2
Sch em e 3
length lies in the range expected for Si-C(sp) or Si-
C(sp2) distances.30 The angles N(2)-Pt(1)-C(18) [171.68-
(14)°] and C(1)-Pt(1)-C(13) [173.76(14)°] are those of
a distorted square-planar coordination. The Pt(1)-C(1)-
C(4) angle of 169.1(2)° reflects also the η2-N,C coordina-
tion mode of the NCN framework, which leads to a tilt
of the Pt-C bond away from the bulky (i.e., noncoordi-
nating) ortho-CH2NMe2 substituent.5e
Previously, the reaction of {Pt}Cl (1) with either 2
equiv of CuCl2 or an excess of Cl2(g) has been investi-
gated, which results in the clean formation of Pt(IV)-
NCN pincer complex {Pt}Cl3.31 To investigate if related
Pt(IV) monoacetylides could be synthesized, {Pt}Ct
CSiMe3, 2, was reacted with a 2-fold excess of CuCl2
(Scheme 2).
During the course of this reaction an orange precipi-
tate was formed while the supernatant solution turned
intensely yellow. By IR spectroscopy, the precipitate was
identified as the Cu(I) acetylide 7. Evaporation of the
solution to dryness yielded a yellow compound, which
was identified as the previously characterized Pt(IV)
complex {Pt}Cl3 (12). Traces of the butadiyne Me3Si-
(CtC)2SiMe3 could not be detected. This result indicates
that initially oxidation of the Pt(II) center to Pt(IV)
takes place followed by a ligand exchange between the
resulting Cu(I) chloride and an intermediate Pt(IV)
acetylide.
Me-4 successfully gave cis-{Pt}(C6H4Me-4)I2.32 However,
the only products formed in this reaction of 2 with I2
were {Pt}I (6) and ICtCSiMe3 (13).33 Both were identi-
1
fied by their respective IR and H NMR spectra. Thus,
the preparation of Pt(IV) acetylides via this route is not
a viable option. It is likely that also in these reactions
the halide effect (reaction with [CuCl]n) plays a domi-
nant role and leads to cleavage of the Pt-acetylide bond.
Coor d in a tion Ch em istr y of {P t}CtCC6H4CN (4).
The replacement of the SiMe3 substituent by a func-
tionalized arene, e.g., a 4-benzonitrile substituent as in
compound 4, permits the construction of heterobime-
tallic systems in which the two metals are connected in
a linear, one-dimensional fashion to each other. The
capability of nitriles to form linear complexes is already
well established.20 Typically, the CN unit has the
potential for η1-N-coordination, which leads to the
formation of linear bridges between two metal atoms.
Accordingly, 4 was reacted with equimolar amounts of
[{Pt}‚H2O][BF4] (14)4 or 0.5 equiv of [Ru]NtN[Ru]
(15) ({Ru} ) [η3-mer-(2,6-{Me2NCH2}2C5H3N}RuCl2])34
(Scheme 3). In another approach, 4 was also reacted
with Au(CO)Cl or [Au2Cl6], which are known for their
ability to form linear molecular aggregates (Scheme 3).
Furthermore, 2 was reacted with 1 equiv of I2 to see
if the oxidation product {Pt(IV)}(CtCSiMe3)I2 could be
obtained. A similar reaction in the case of {Pt}C6H4-
(32) Van Beek, J . A. M.; van Koten, G.; Smeets, W. J . J .; Spek, A.
L. J . Am. Chem. Soc. 1986, 108, 5010.
(33) Walton, D. R. M.; Webb, M. J . J . Organomet. Chem. 1972, 37,
41.
(30) Corey, J . Y. In The Chemistry of Organic Silicon Com-
pounds; Patai, S., Rappoport, Z., Eds.; Wiley Interscience: New York,
1989.
(31) Van Beek, J . A. M.; van Koten, G.; Wehmann-Ooyevaar, I. C.
M.; Smeets, W. J . J .; van der Sluis, P.; Spek, A. L. J . Chem. Soc., Dalton
Trans. 1991, 883.
(34) Abbenhuis, R. A. T. M.; del R´ıo, I.; Bergshoef, M. M.; Boersma,
J .; Veldman, N.; Spek, A. L.; van Koten, G. Inorg. Chem. 1998, 37,
1749.

Bis-ortho-chelated Diaminoaryl Pt Complexes
Organometallics, Vol. 19, No. 17, 2000 3301
Ta ble 3. Com p a r ison of Electr och em ica l Da ta of
The reaction of 4 in CH2Cl2 solution with equimolar
amounts of ionic 14 leads to the formation of the
monocationic bis-Pt complex 16 in virtually quantitative
yield. Here, both Pt-containing units are orientated in
a head-to-head fashion. With the neutral dinitrogen-
bridged bis-Ru compound 15, formation of neutral
bimetallic 17 occurs following liberation of N2. Here, the
reaction can be followed visually by the change of the
reaction mixture from brown to an intense red color and
can be monitored by following the νCN, which changes
from 2220 cm-1 (4) to 2248 cm-1 (16). For neutral
heterobimetallic 17 the νCN is found at lower frequency
(2198 cm-1), which is an unusual result for η1-bound
nitriles.20 This shift to lower wavenumbers can be
explained by the different back-bonding properties of
the neutral {Ru} fragment in 17 and the cationic {Pt}+
fragment in 16. The 1H and 13C{1H} NMR spectra of
16 and 17 show well-resolved signals for the organic
groups present. The 1H NMR spectrum of 17 shows
singlets for the CH2 and NMe2 protons of the {Ru}
fragment, which indicates that the Pt-cyanide ligand
4 is coordinated trans to the pyridine-N of the {Ru}
fragment with the Cl ligands in trans-position. This
interpretation is corroborated by X-ray crystal data
obtained for {Ru}NCPh, which can be considered as a
model for 17.35 In contrast to the results of the reactions
of {Pt}-acetylide fragments with Cu(I) and Cu(II)
halides, the presence of halides in {Ru} fragments does
not result in Pt-Ct bond cleavage. Therefore, other TM
complexes known to form linear assemblies were inves-
tigated, e.g., of Au(I), since a number of linear Au(I)-
nitrile or isonitrile complexes are known.36 The reaction
of Au(CO)Cl (CH2Cl2) with equimolar amounts of 4 in
the temperature range -78 to -40 °C leads to the
immediate formation and precipitation of an intermedi-
ate, which was surmised to be the η1-adduct of 4 to
AuCl, i.e., 18, through substitution of CO by the nitrile
group (Scheme 3). The formation of this intermediate
can be followed by IR spectroscopy. The CO vibration
Com p ou n d s 1, 2, 4, 17, a n d {Ru }NCP h a
oxidation
Pt
Ru
∆E [mV]
compound
E
ox [V]
E1/2
{Pt}Cl
{Pt}CtÌSiMe3
{Pt}CtCC6H4CN-4
{Pt}CtCC6H4CN{Ru}
{Ru}NCPh
1
2
4
0.76
0.55
0.50
0.48
17
0.31
0.32
50
70
a
Cyclic voltammograms have been recorded in the presence of
[n-Bu4N] [PF6] (c ) 0.1 mol dm-3) at 25 °C under N2; scan rate
100 mV s-1; potentials are referenced to FcH/FcH+ (E1/2
)
0.00 V).
The reaction of [Au2Cl6] with nitriles typically yields
air-stable Au(III) nitrile adducts.42 However, reaction
of this Au(III) species with equimolar amounts of
compound 4 (-78 °C, CH2Cl2) leads again, after im-
mediate formation of a brown precipitate, to the buildup
of a gold mirror on the walls of the reaction flask after
ca. 2 min. Workup of the reaction mixture yields the
Pt(IV) compound 1231 and the butadiyne 19.41
Electr och em ical Beh avior of Mon on u clear P lati-
n u m Acetylid es. The preparation of the Pt acetylides
2-5 and the study of their reactivity have revealed that
the Pt σ-acetylide bond is not stable to halogen-contain-
ing oxidants such as CuCl2, I2, or Au2Cl6. As the mono-
anionic NCN ligand stabilizes transition metals in high
oxidation states,31,32 it is of interest to study if Pt(IV)
acetylides can be detected electrochemically. Also, par-
tial oxidation of oligometallic compounds offers the op-
portunity to form stable mixed-valence compounds. This
has been observed in, for example, the bis-Ru complex
4+ 5c
{(terpy)Ru[2,6-(Me2NCH2)2C6H2]}2
or the bis-Pt
compound {(MeCN)Pt[2,6-(Me2NCH2)2C6H2]}2
.
4+ 5b There,
oxidation of the metal centers did not affect the ligand
framework. Therefore, representative examples of the
Pt acetylides presented above were subjected to cyclo-
voltammetric investigation, and the results were com-
pared to the values obtained for 1 (Table 3).
(2158 cm-1 37
loses intensity, and the stretching band
)
of the nitrile is shifted to higher wavenumbers, i.e., from
2220 to 2248 cm-1. This is fully consistent with η1-
coordination of CN to Au.20 Unfortunately, intermediate
18 could not be isolated. With the reaction still incom-
plete, upon raising the temperature above -40 °C, a
gold mirror begins to appear on the walls of the reaction
vessel. This observation can be explained by a group-
exchange reaction between 18, which leads again to
{Pt}Cl (1) and the corresponding Au(I)-acetylide (cf. the
reactions with [CuCl]n above). Oxidative coupling of two
acetylide units then leads to the formation of the 1,4-
butadiyne derivative 19 (which can be isolated as an
off-white solid) and formation of Au(0). Compound 19
was identified by IR and 1H NMR spectroscopy.38 In
addition, 1H NMR investigation of the reaction mixture
shows the presence of 1.4
All oxidative processes are irreversible in THF solu-
tion and are shifted from +0.76 V (1) by ca. 200 mV to
more negative potentials. This mirrors the substitution
of the Cl ligand by an acetylide (Table 3). An interpreta-
tion is that the electron density on the Pt center has
increased and thus it is easier to oxidize. The measure-
ment of the total current of the cathodic process for
compound 2 suggests that during the oxidation two
electrons are removed irreversibly from the Pt center,
thus forming a Pt(IV) species. However, reductive
processes could not be observed in this system. The
electrochemical study of the mixed-metal complex 17
clearly shows that attachment of the {Ru} fragment to
the Pt system does not alter the electrochemical proper-
ties of the latter metal. Also, comparison with the
aforementioned benzonitrile complex {Ru}NCPh (E1/2
35
(35) del R´ıo, I.; Back, S.; Hannu, M. S.; Rheinwald, G.; Lang, H.;
van Koten, G. Inorg. Chim. Acta 1999, submitted.
(36) (a) Fenske, G. P.; Mason, W. R. Inorg. Chem. 1974, 13, 1783.
(b) J ia, G.; Puddephatt, J .; Vittal, J . J .; Payne, N. C. Organometallics
1993, 12, 263. (c) Mathieson, T. J .; Langdon, A. G.; Milestone, N. B.;
Nicholson, B. K. Chem. Commun. 1998, 371.
) 0.32V, ∆E ) 70 mV)
reveals that the oxidation
potential Ru(II)/Ru(III) is not influenced by the remote
(39) Sheldrick, G. M. SHELXL97. Program for crystal structure
refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(40) Spek, A. L. PLATON. A multipurpose crystallographic tool;
Utrecht University: Utrecht, The Netherlands, 1999.
(37) Dell’Amico, D. B.; Calderazzo, F. Gazz. Chim. Ital. 1973, 103,
1099.
(38) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Gualiardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J . Appl. Crystallogr. 1999, 32, 115.
(41) Kurihara, T.; Ebisawa, F.; Tabei, H. J pn. Kokai Tokkyo Koho
J P 60,217,213 [85,217,213], 30 Oct 1985.
(42) Kharasch, M. S.; Beck, T. M. J . Am. Chem. Soc. 1934, 56, 2057.

3302 Organometallics, Vol. 19, No. 17, 2000
Back et al.
solvent as the internal reference signal. FAB mass spectra
were recorded at the Department of Mass Spectrometry,
Bijvoet Center, Utrecht University, on a J EOL J MS SX/SX
102A four-sector mass spectrometer operating at 10 kV ac-
celerating voltage. Melting points were determined on a Bu¨chi
melting point apparatus. Microanalyses were performed by H.
Kolbe, Mikroanalytisches Laboratorium, Mu¨lheim/Ruhr, Ger-
many. Electrochemical measurements were carried out by
cyclic voltammetry in a solution of NBu4PF6 (0.1 mol dm-3) in
THF at 25 °C, using a standard three-electrode cell on a
Princeton Applied Research EG&G 263A analyzer. All poten-
tials were referenced to the ferrocene/ferrocenium couple,
{Pt} unit. This contrasts with recent findings obtained
for a related Ti-Ru system.43
Con clu sion s
A series of Pt monoacetylides of the form {Pt}CtCR
({Pt} ) [Pt(C6H3{Me2NCH2}2-2,6)]+) have been synthe-
sized and fully characterized. The crystal structure
determination of {Pt}CtCC6H2I-1-(CH2NMe2)2-3,5 (6)
exhibits a rigid-rod-like arrangement. The acetylenic
unit is designed to carry different functionalities which
enable the construction of oligometallic complexes.
Stability studies have been carried out on the prototypi-
cal complex {Pt}CtCSiMe3 (2). This has revealed that
the CtCSiMe3 unit is easily substituted by halide ions.
In the case of reactions with Cu(I) halides, this likely
proceeds via the formation of an η2-coordinated inter-
mediate. The accessibility of this has been shown by the
assembly of M(I)-bridged dimeric structures [{η2-[{Pt}
CtCSiMe3]}2M][BF4] (8, M ) Cu; 9, M ) Ag). The
structure of this compound has been confirmed by an
X-ray crystal structure analysis. The coordination abil-
ity of the CtC unit was used for the synthesis of
heterotrimetallic [(µ2-[(η2-NCN)Pt(η1-CO)CtCSiMe3])-
Co2(CO)6] (11). Here, an unprecedented lowering of the
hapticity of an η3-coordinated NCN ligand was observed
upon coordination of an incoming monodentate CO. TGA
and DSC studies revealed that 11 is the kinetic product
of the reaction. The construction of Pt(IV) monoacetyl-
ides using CuCl2 or I2 could not be achieved. Instead,
cleavage of the Pt-acetylide σ-bond was observed and,
in the case of CuCl2, the formation of {Pt}Cl3. The
attachment of the functionalized Pt acetylide {Pt}
CtCC6H4CN-4 (4) to {Ru}, {Pt}, AuCl, or AuCl3 has
been carried out successfully via the η1-coordination of
the -CtN functionality. However, both of the gold
adducts decompose at low temperatures, and this
leads to the formation of the butadiyne NCC6H4
(CtC)2C6H4CN (19) via oxidative coupling and {Pt}Cl
or {Pt}Cl3, respectively. Cyclic voltammetric studies of
representative examples reveal that the irreversible
two-electron Pt(II)/Pt(IV) oxidation is shifted to a more
negative potential relative to {Pt}Cl (1). This is indica-
tive of an increase in electron density on the Pt-core
upon substitution of Cl by an acetylide. The coordination
of a Ru-containing complex fragment does not alter the
electrochemical properties of the Pt core. Also, no
influence of the Pt center on the electrochemical behav-
ior of this Ru complex fragment has been observed. This
indicates that the Pt-acetylides presented here can be
used for the construction of multimetallic compounds
but they are of limited scope.
which was defined to have E1/2 ) 0.00 V.
4
Gen er a l R em a r k s. {Pt}Cl (1),
C6H3(CH2NMe2)2-2,6-
(CtCH)-4,6 HCtCC6H4CN-4,44 HCtCC5H4N-4,45 [Cu(NCMe)4]-
[BF4],46 [(η5-C5H4SiMe3)2Ti(CtCSiMe3)2]CuCl (10),18 [{Pt}‚
H2O][BF4] (14),4 {Ru}NtN{Ru} (15),34 Au(CO)Cl,37 and
[Au2Cl6]37 were prepared following literature procedures. All
other materials were commercially available and used as
received.
Syn t h esis of {P t }CtCSiMe3 (2). To
a solution of
LiCtCSiMe3 (320 mg, 3.1 mmol) in Et2O (200 mL) was added
{Pt}Cl (1) (1.28 g, 3.1 mmol) at - 78 °C. The cooling bath was
then removed, and after stirring (24 h, 25 °C), all volatiles were
evaporated in vacuo. The residue was extracted with pentane
(2 × 40 mL) and then with benzene (3 × 40 mL). Concentration
of the combined benzene extracts to ca. 5 mL was followed by
addition of pentane (150 mL). This lead to the precipitation of
4 as an off-white solid (960 mg, 65% yield based on 1). Mp:
[°C] > 200. IR (KBr): [cm-1] 2018 (s) [νC≡C]. 1H NMR (300
3
MHz) (CDCl3): [δ] 0.13 (s, 9 H, SiMe3), 3.15 (s, J HPt ) 44 Hz,
3
12 H, NMe2), 4.07 (s, J HPt ) 41 Hz, 4 H, CH2), 6.7-7.1 (m, 3
H, C6H3). 13C{1H} NMR (75 MHz) (CDCl3): [d] 1.4 (SiMe3), 55.8
2
(NMe2), 80.0 (s, J CPt ) 42 Hz, CH2), 110.6 (PtCtC), 118.5 (s,
3J CPt ) 18 Hz, CH/C6H3), 128.3 (CH/C6H3), 138.9 (PtCtC),
146.2 (s, 2J CPt ) 56 Hz, iC/C6H3), 159.6 (iC/C6H3). Electrospray-
MS [m/z (rel int)]: 851 (20) {M+ + [C12H19N2Pt]}, 483 (10) M+,
386 (100) {M+ - [C5H9Si]}. Anal. Calcd for C17H28N2PtSi
(483.60): C, 42.22; H, 5.84; N, 5.79. Found: C, 42.14; H, 5.94;
N, 5.72.
Syn th esis of {P t}CtCC6H3(CH2NMe2)2-3,5 (3). HCt
CC6H3(CH2NMe2)2-3,5 (250 mg, 1.2 mmol) was dissolved in
Et2O (150 mL), and the solution was cooled to - 78 °C. Then
n-BuLi (0.8 mL, 1.6 M) was added, and the solution was stirred
for 3 h. Then 1 (510 mg, 1.2 mmol) was added, and the reaction
mixture was allowed to warm to 25 °C. After 24 h, all volatile
materials were removed in vacuo. The residue was extracted
with pentane (4 × 30 mL) and with Et2O (3 × 40 mL).
Separation from undissolved material was effected by cen-
trifugation. Evaporation to dryness of the collected Et2O
extracts yielded 5 (300 mg, 40% yield based on 1) as an off-
white solid. Mp: [°C] 150 (dec). IR (KBr): [cm-1] 2076 (s) [νC≡C].
1H NMR (300 MHz) (CDCl3): [δ] 2.22 (s, 12 H, NMe2), 3.23 (s,
3
3J HPt ) 46 Hz,12 H, NMe2), 3.38 (s, 4 H, CH2), 4.11 (s, J HPt
)
48 Hz, 4 H, CH2), 6.8-7.1 (m, 3 H, C6H3), 7.23 (s, 2 H, C6H2).
13C{1H} NMR (75 MHz) (CDCl3): [δ] 45.4 (NMe2), 56.0 (NMe2),
64.3 (CH2), 80.0 (CH2), 107.7 (PtCtC), 118.5 (CH/C6H3), 125.3
(iC/C6H3), 127.6 (CH/C6H3), 131.2 (CH/C6H2), 136.8 (PtCtC),
138.1 (iC/C6H2), 146.1 (iC/C6H3), 166.5 (iC/C6H3). FAB-MS [m/z
(rel int)]: 601 (50) M+, 385 (100) {[C12H19N2Pt]+}, 217 (10)
{[C14H17N2]+}, 215 (10) {[C14H15N2]+}. Anal. Calcd for C26H38N4-
Pt (601.70): C, 51.90; H, 6.37; N, 9.31. Found: C, 52.11; H,
6.32; N, 9.22.
Exp er im en ta l Section
Gen er a l Meth od s. All reactions were carried out under an
atmosphere of dry nitrogen using standard Schlenk tech-
niques. Tetrahydrofuran (THF) and diethyl ether (Et2O) were
purified by distillation from sodium/benzophenone ketyl; pen-
tane was purified by distillation from calcium hydride. Infrared
spectra were obtained with a Mattson Galaxy Series FTIR
5000. 1H and 13C{1H} NMR spectra were recorded on a Bruker
AC 300 spectrometer. Chemical shifts are reported in δ units
(parts per million) downfield from tetramethylsilane with the
Syn th esis of {P t}CtCC6H4CtN-4 (4). To a Et2O solution
(100 mL) of LiCtCC6H4CN-4 (110 mg, 0.8 mmol) was added
1 (340 mg, 0.8 mmol) at - 78 °C. After gradual warming to 25
(44) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N.
Synthesis 1980, 627.
(45) Della Ciana, L.; Haim, A. J . Heterocyclic Chem. 1984, 21, 607.
(46) (a) Kubas, G. J . Inorg. Synth. 1979, 19, 90. (b) J ones, P. G.;
Gespo, O. Acta Crystallogr. 1998, C54, 18.
(43) Back, S.; Gossage, R. A.; Rheinwald, G.; del R´ıo, I.; Lang, H.;
van Koten, G. J . Organomet. Chem. 1999, in press.

Bis-ortho-chelated Diaminoaryl Pt Complexes
Organometallics, Vol. 19, No. 17, 2000 3303
°C and stirring for 24 h, all volatile material was removed in
vacuo. The brown residue was extracted with CH2Cl2 (3 × 50
mL) and then separated from undissolved material by cen-
trifugation. After evaporation of the CH2Cl2 solution, the
resulting solid was washed with ethyl acetate (3 × 10 mL) to
yield 7 (250 mg, 60% yield based on 1) as an off-white solid.
Mp: [°C] > 200. IR (KBr): [cm-1] 2220 (s) [νCN], 2071 (s) [νC≡C].
based on 2. Mp: [°C] 115 (dec). IR (KBr): [cm-1] 1947 (s) [νC≡C],
1257 (s) [νC≡Si]. 1H NMR (300 MHz) (CDCl3): [δ] 0.27 (s, 18 H,
3
3
SiMe3), 3.15 (s, J HPt ) 41.6 Hz, 24 H, NMe2), 4.09 (s, J HPt
)
48.2 Hz, 4 H, CH2), 6.8-7.1 (m, 3 H, C6H3). 13C{1H} NMR (75
MHz) (CDCl3): [δ] 1.60 (SiMe3), 56.3 (NMe2), 79.4 (CH2), 113.8
(d, 1J ) 17 Hz, PtCtC), 119.3 (CH/C6H3), 125.2 (CH/C6H3),
145.4 (iC/C6H3), 151.3 (d, 1J AgC ) 19 Hz, PtCt), 163.3 (iC/C6H3).
Anal. Calcd for C34H56AgBF4N4Pt2Si2 (1163.90): C, 35.09; H,
5.02; N, 4.81; Si, 4.83. Found: C, 34.86; H, 5.10; N, 4.89; Si,
4.91.
Syn t h esis of {µ2-[(η1-NCN)P t (η1-CO)CtCSiMe3][Co2-
(CO)6]} (11). A toluene/pentane solution (40 mL, 1:1) of Co2-
(CO)8 (85 mg, 0.2 mmol) and 2 (100 mg, 0.2 mmol) was stirred
at 0 °C (2 h). All volatiles were then evaporated, and the
residue was extracted with pentane (3 × 20 mL). The pentane
extracts were filtered through Celite. Concentration to ca. 10
mL and crystallization (-20 °C) yielded 11 as dark crystals
(50 mg, 30% yield based on 2). Mp: [°C] 125 (dec). IR (KBr):
[cm-1] 2075, 2026, 1990 (s) [νCÃ]. 1H NMR (300 MHz)
3
1H NMR (300 MHz) (CDCl3): [δ] 3.21 (s, J HPt ) 41 Hz, 12 H,
3
NMe2), 4.14 (s, J HPt ) 43 Hz, 4 H, CH2), 6.7-7.1 (m, 3 H,
C6H3), 7.4-7.5 (m, 4 H, C6H4). 13C{1H} NMR (75 MHz)
(CDCl3): [δ] 56.0 (NMe2), 80.0 (CH2), 107.2 (CN), 107.5 (PtCt
C), 118.7 (CH/C6H3), 119.7 (iC/C6H4), 125.3 (CH/C6H3), 129 (iC/
C6H4), 131.6 (CH/C6H4), 131.9 (CH/C6H4), 133.8 (PtCtC), 146.0
(iC/C6H3), 165.5 (iC/C6H3). FAB-MS [m/z (rel int)]: 512 (30)
{[M + H]+}, 511 (10) M+, 389 (100) {[C12H19N2Pt]+}, 58 (50)
{[C3H8N]+}. Anal. Calcd for C21H23N3Pt (512.53): C, 49.21; H,
4.52; N, 8.20. Found: C, 49.08; H, 4.60; N, 8.23.
Syn th esis of {P t}CtCC5H4N-4 (5). Experimental condi-
tions and workup were the same as for the preparation of
compound 7. Specific experimental details: 4-LiCtCC5H4N
(190 mg, 1.8 mmol), {Pt}Cl (1) (750 mg, 1.8 mmol). Yield: 600
(CDCl3): [δ] 0.36 (s, 9 H, SiMe3), 2.21 (s, 6 H, NMe2), 2.86 (s,
3
3J HPt ) 38 Hz, 6 H, NMe2), 3.44 (s, 2 H, CH2), 4.19 (s, J HPt
)
mg, 68% yield based on 1. Mp: [°C] > 200. IR (KBr): [cm-1
]
34 Hz, 2 H, CH2), 6.9-7.2 (m, 3 H, C6H3). Anal. Calcd for
C24H28Co2N2O7PtSi (769.53): C, 36.14; H, 3.54; N, 3.51; Si,
3.52. Found: C, 36.02; H, 3.60; N, 3.38; Si, 3.61.
1
3
2079 (s) [νC≡C]. H NMR (300 MHz) (CDCl3): [δ] 3.19 (s, J HPt
3
) 42 Hz, 12 H, NMe2), 4.12 (s, J HPt ) 39 Hz, 4 H, CH2), 6.8-
7.1 (m, 3 H, C6H3), 7.1-7.2 (m, 2 H, C5H4N), 8.3-8.4 (m, 2 H,
C5H4N). 13C{1H} NMR (75 MHz) (CDCl3): [δ] 56.0 (NMe2), 79.9
(CH2), 106.0 (PtCtC), 118.7 (CH/C6H3), 123.7 (CH/C6H3), 125.0
(iC/C6H3), 126.2 (CH/C5H4N), 136.5 (PtCtC), 146.3 (iC/C6H3),
149.1 (CH/C5H4N), 166.1 (iC/C6H3). Anal. Calcd for C19H23N3-
Pt (488.50): C, 46.72; H, 4.75; N, 8.60. Found: C, 46.58; H,
4.86; N, 8.66.
Rea ction of {P t}CtCSiMe3 (2) w ith [Cu Cl]n . To a
suspension of [CuCl]n (20 mg, 0.2 mmol) in CH2Cl2 (30 mL)
was added {Pt}CtCSiMe3 (2) (100 mg, 0.2 mmol). After 1 h
stirring at 25 °C, the orange suspension was separated by
centrifugation. Subsequently, the supernatant liquid was
concentrated to 5 mL. Addition of 30 mL of pentane gave an
off-white precipitate. By 1H NMR spectroscopy, this was
identified as 1.4 The precipitate was identified as 7 by IR
spectroscopy.
Cr ysta l Str u ctu r e Deter m in a tion of 11. C24H28Co2N2O7-
PtSi, fw ) 797.52, black plate, 0.63 × 0.45 × 0.25 mm3,
monoclinic, P21/c, a ) 10.0863(13) Å, b ) 17.4645(15) Å, c )
16.437(2) Å, â ) 96.188(10)°, V ) 2878.5(6) Å3, Z ) 4, F )
1.840 g cm -3, 13 921 measured reflections, 6597 unique
reflections (Rint ) 0.0538). Absorption correction based on
ψ-scans (PLATON, µ ) 6.071 mm-1, 0.58-0.99 transmission),
341 refined parameters, no restraints. R (I>2σ(I)): R1 )
0.0268, wR2 ) 0.0489. R (all data): R1 ) 0.0398, wR2 )
0.0520. S ) 1.054. Intensities were measured on an Enraf-
Nonius CAD4T diffractometer with rotating anode (Mo KR, λ
) 0.71037 Å) at a temperature of 100 K up to a resolution of
(sin θ/λ)max ) 0.65 Å-1. The structure was solved with direct
methods (SIR9738) and refined with the program SHELXL9739
against F2 of all reflections. Non-hydrogen atoms were refined
freely with anisotropic displacement parameters. Hydrogen
atoms were refined as rigid groups. The drawing, structure
calculations, and checking for higher symmetry were per-
formed with the program PLATON.40
Rea ction of {P t}CtCSiMe3 (2) w ith Cu Cl2. {Pt}Ct
CSiMe3 (4) (50 mg, 0.1 mmol) and CuCl2 (30 mg, 0.2 mmol)
were dissolved in methanol (30 mL). After 3 h (25 °C), the
initially green solution had turned into a yellow suspension.
After evaporation of all volatile material, the residue was
extracted with CH2Cl2 (3 × 20 mL) and separated by centrifu-
gation. Concentration of the CH2Cl2 extracts to ca. 5 mL and
addition of 30 mL of pentane resulted in the precipitation of
12 as a yellow solid, which was identified by 1H NMR
spectroscopy.31
Rea ction of {P t}CtCSiMe3 (2) w ith [Cu I]n . Experimen-
tal conditions and workup were the same as for the reaction
of {Pt}CtCSiMe3 (2) with [CuCl]n. Specific experimental
details: 2 (80 mg, 0.2 mmol), [CuI]n (30 mg, 0.2 mmol), 30 mL
of CH2Cl2. By 1H NMR spectroscopy, the precipitate formed
after addition of pentane was identified as 6.4
Rea ction of {P t}CtCSiMe3 (2) w ith {[Ti](CtCSiMe3)2}-
Cu Cl (10). To a THF solution (30 mL) of 10 (60 mg, 0.1 mmol)
was added 2 (40 mg, 0.1 mmol). After stirring (12 h, 25 °C) all
volatile material was evaporated. IR and 1H NMR spectra
reveal solely the presence of the starting materials.
Syn th esis of ({η2-{P t}CtCSiMe3}2Cu )[BF 4] (8). [Cu-
(MeCN)4][BF4] (20 mg, 0.06 mmol) and 2 (60 mg, 0.12 mmol)
were brought together in a reaction flask. After addition of
CH2Cl2 (30 mL), the reaction mixture was stirred for 2 h.
Concentration to ca. 5 mL and cooling to - 40 °C (48 h)
resulted in the precipitation of 8 (55 mg, 80% yield based on
Rea ction of {P t}CtCSiMe3 (2) w ith I2. A THF solution
(20 mL) of I2 (50 mg, 0.2 mmol) and 2 (95 mg, 0.2 mmol) was
stirred for 2 h (0 °C). The THF was then removed under
reduced pressure, and the resulting dark brown residue was
extracted with pentane (3 × 10 mL) and CH2Cl2 (2 × 10 mL).
After concentration of the combined pentane extracts, the
2) as an off-white solid. Mp: [°C] 155 (dec). IR (KBr): [cm-1
1918 (s) [νC≡C]. 1H NMR (300 MHz) (CDCl3): [δ] 0.28 (s, 18 H,
]
3
3
1
SiMe3), 3.16 (s, J HPt ) 37.7 Hz, 24 H, NMe2), 4.12 (s, J HPt
)
resulting residue was identified (IR, H NMR) as ICtCSiMe3
39 Hz, 4 H, CH2), 6.8-7.1 (m, 3 H, C6H3). 13C{1H} NMR (75
MHz) (CDCl3): [δ] 1.0 (SiMe3), 56.1 (NMe2), 79.3 (CH2), 118.8
(PtCtC), 119.5 (CH/C6H3), 125.4 (CH/C6H3), 145.8 (iC/C6H3),
162.6 (PtCt), 163.3 (iC/C6H3). Anal. Calcd for C34H56BCuF4N4-
Pt2Si2 (1117.55): C, 36.54; H, 5.05; N, 5.01. Found: C, 36.64;
H, 5.02; N, 5.08.
(13). Concentration of the combined CH2Cl2 extracts yielded
a dark solid, which was subsequently identified (1H NMR, FAB
MS) as 6.
Syn th esis of [({P t}CtCC6H4CtN-4){P t}][BF4] (16). Com-
pound 4 (90 mg, 0.2 mmol) and {{Pt}H2O}BF4 (14) (115 mg,
0.2 mmol) were dissolved in CH2Cl2 (50 mL). After 24 h (25
°C), the solution was concentrated to 5 mL, and 50 mL of
pentane was added. Complex 16 (190 mg, 95% yield based on
4) precipitated as an off-white solid. Mp: [°C] > 200. IR
(KBr): [cm-1] 2248 (s) [νCN], 2071 (s) [νC≡C]. 1H NMR (300 MHz)
Syn th esis of ({η2-{P t}CtCSiMe3}2Ag)[BF 4] (9). All han-
dlings were carried out under the exclusion of light; all other
experimental procedures were as described for the preparation
of 8. Specific experimental details: Ag[BF4] (20 mg, 0.1 mmol),
2 (90 mg, 0.2 mmol), CH2Cl2 (10 mL). Yield: 100 mg, 90%
3
(CDCl3): [δ] 3.21 (s, J HPt ) 40.1 Hz, 12 H, NMe2), 3.26 (s,

3304 Organometallics, Vol. 19, No. 17, 2000
Back et al.
3
3J HPt ) 39.8 Hz, 12 H, NMe2), 4.25 (s, J HPt ) 41.2 Hz, 4 H,
solution was evaporated to dryness and the resulting residue
was extracted with pentane (2 × 10 mL) and CH2Cl2 (3 × 5
mL). After concentration of the combined pentane extracts,
the remaining solid was identified as NtCC6H4(CtC)2C6H4Ct
N (19).41 The remaining residue after concentration of the
combined CH2Cl2 extracts was identified as 1.
Rea ction of {P t}CtCC6H4CtN-4 (4) w ith [Au 2Cl6]. At
-78 °C, [Au2Cl6] (40 mg, 0.13 mmol) was brought into a
CH2Cl2 solution (20 mL) of 4 (65 mg, 0.13 mmol). Immediately,
a yellow precipitate formed. After 2 min stirring, the yellow
suspension turned brown (green in transparent light) and a
gold mirror appeared on the walls of the reaction vessel. After
20 min, the solvent was removed under reduced pressure and
the residue was then extracted with pentane (2 × 10 mL) and
with CH2Cl2 (2 × 10 mL). The combined pentane extracts were
concentrated, and the residue was identified (IR, 1H NMR) as
NtCC6H4(CtC)2C6H4CtN (19).41 After concentration of the
combined CH2Cl2 extracts, the remaining residue was identi-
fied (1H NMR) as 12.31
3
CH2), 4.32 (s, J HPt ) 40.8 Hz, 4 H, CH2), 6.8-7.2 (m, 6 H,
C6H3), 7.7-8.0 (m, 4 H, C6H4). 13C{1H} NMR (75 MHz)
(CDCl3): [δ] 55.0 (NMe2), 57.0 (NMe2), 77.9 (CH2), 80.0 (CH2),
108.5 (PtCtC), 111.5 (CN), 120.0 (CH/C6H3), 120.4 (CH/C6H3),
121.8 (iC/C6H4), 126.0 (iC/C6H3), 126.3 (CH/C6H3), 132.8 (CH/
C6H4), 133.1 (iC/C6H4), 135.0 (CH/C6H4), 146.3 (iC/C6H3), 147.4
(iC/C6H3), 163.9 (iC/C6H3)a). FAB-MS [m/z (rel int)]: 898 (40)
[M - BF4]+, 798 (60) [C25H38N3Pt2]+, 386 (100) [C12H19N2Pt]+.
Anal. Calcd for 16: C, 40.21; H, 4.29; N, 7.10. Found: C, 40.39;
H, 4.36; N, 6.97.
Syn th esis of ({P t}CtCC6H4CtN-4){Ru } (17). In CH2Cl2
(20 mL), 4 (50 mg, 0.1 mmol) and {Ru}NtN{Ru} (15) (37 mg,
0.05 mmol) were dissolved. After stirring (3 h, 25 °C), all
volatile materials were evaporated and the residue was
extracted with Et2O (6 × 20 mL). Evaporation of the combined
Et2O extracts gave 17 (40 mg, 60% yield based on 4) as a red
solid. Mp: [°C]. IR (KBr): [cm-1] 2198 (s) [νCN], (s) [νC≡C]. H
1
NMR (300 MHz) (CDCl3): [δ] (s, 3J HPt ) 40.1 Hz, 12 H, NMe2),
3
(s, J HPt ) 41.2 Hz, 4 H, CH2), (m, 6 H, C6H3), (m, 4 H, C6H4).
13C{1H} NMR (75 MHz) (CDCl3): [δ] (NMe2), (NMe2), (CH2),
(CH2), (PtCtC), (CN), (CH/C6H3), (CH/C6H3), (iC/C6H4), (iC/
C6H3), (CH/C6H3), (CH/C6H4), (iC/C6H4), (CH/C6H4), (iC/C6H3),
(iC/C6H3), (iC/C6H3). Anal. Calcd for 17: C, 43.78; H, 4.82; N,
9.57. Found: C, 43.69; H, 4.95; N, 9.38.
Ack n ow led gm en t. Were are grateful to the Volks-
wagenstiftung and Utrecht University for financial
support. The authors would like to thank the Depart-
ment of Mass Spectrometry for the recording of the mass
spectra. We are very grateful to Mrs. H. Pruiksma and
Dr. P. Steenwinkel for valuable help.
Rea ction of {P t}CtCC6H4CtN-4 (4) w ith Au (CO)Cl. To
a solution of 4 (155 mg,0.3 mmol) in CH2Cl2 (20 mL) was added
Au(CO)Cl (80 mg, 0.3 mmol) (-78 °C). The reaction mixture
was then gradually warmed to -40 °C, during which time it
turned into a yellowish suspension. Monitoring via IR spec-
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data collection and refinement details, positional and thermal
parameters, and bond distances and angles for 11. This
material is available free of charge via the Internet at
http://pubs.acs.org.
troscopy reveals the development of a band at 2248 cm-1
indicating the formation of 18. When the temperature rose to
over -40 °C, a gold mirror started to appear on the walls of
the reaction flask. After 20 min of stirring, the reaction
,
OM000272A