Reactions of Alkynylplatinum(I1) Compounds
Inorganic Chemistry, Vol. 16, No. 9, 1977 2177 Contribution from the Department of Chemistry, Princeton University, Princeton, New Jersey 08540
Reactions of Alkynylplatinum(I1) Compounds with Aprotic Substrates MALCOLM H. CHISHOLM* and LILLIAN A. RANKEL AIC70 17 3M Reactions of alkynylplatinum(I1) compounds trans-PtX(C=CR)L2, where R = H, Me, or CF3,X = C s C R or C1, and L = PMe2Phor AsMe3,with a number of inorganic and organic substrates A-B are reported. Four types of reactions have been observed: (i) oxidative addition to give platinum(1V) alkynyl compounds (A-B = 12, IBr, ICN, CF31,and MeI) where the ease of oxidative addition followed the order R = Me > H > CF3,X = CSCR > C1 and L = AsMe3> PMe2Ph; (ii) insertion into the Pt-C(alkyny1) bond (A-B = (CN)2C==C(CN)2); (iii) attack at the C-C triple bond either to give vinylplatinurn( 11) compounds (A-B = CF3COCI,o-tetrachloroquinone, and NOCI) or to generate a new alkynyl moiety (PtC=CH + (CF3)*C0 P~CECC(OH)(CF,)~);and (iv) formation of 1:l ?r complexes (A-B = (CF,),CO). These reactions are compared with previously reported reactions of methylplatinum(I1) compounds. Platinum(I1) is shown to activate the u-bonded alkynyl ligand toward addition reactions.
Received March 3, 1977
-
> Jpt(IV)-H. These changes in JPt-Hmay be correlated with the change in hybridization of platinum which accompanies oxidative addition, Pt(II)-dsp2 to Pt(IV)-d2sp3, and the relative Pt 6s character in the Pt-L bond.30 We have also noted that vstr(C=C) increases in going from Pt(I1) to Pt(1V). This may be indicative of the relative degree of Pt to CEC a * backbonding, Pt(I1) > Pt(1V). Addition of A-B across the carbon-carbon triple bond leads to the loss of vstr(C=C) in the infrared spectrum and the appearance of a lower energy band, ca. 1600 cm-', associated with the C-C moiety. The coupling constant 4Jpt-H to the L methyl protons remains essentially unchanged in magnitude but Jpt-H to the R protons of the acetylenic substituent is diminished. The latter is consistent with the change from sp to sp2 hybridization in the carbon atom directly bonded to platinum: P t C E C R + AB PtC(A)=C(B)R. Insertion into the Pt-C(acety1ide) bond leads to a loss, or diminuation, of JPt-H to the R protons of the acetylide. 4Jpt-H to the L methyl protons and v,,,(C=C) are little changed. Finally ?r complexation to platinum, which is only possible for A-B unsaturated molecules, causes changes in J p t + and vstr(C=C); the magnitude of these changes is determined largely by the stereochemistry of the adduct. t r ~ n s - P t ( ~ R ) , ( P M e ~ Pwhere h ) ~ , R = H, Me, and CF3, trans-Pt(C~CMe)~(AsMe~)~, and trans-PtCl(C==CMe)(AsMe3)*were reacted with the following substrates: CH31, CF31, Iz, ICN, CH,COCl, CF3COCl, CF3CN, CHz=CH2, CH2=C=CH2, CF2=CF2, P h C e C H , P h C E C P h , M e C E C M e , MeOZCC=CCO2Me, M e C r C C O O H , CF3C=CH, CF3CsCCF3,CO, COz, SO2, ethylene oxide, Results and Discussion MezSO, NOC1, 0- and p-tetrachlorobenzoquinone, tetracyanoethylene (TCNE), PhSSPh, and Hz in the presence of Four types of reactions have been observed: (1) oxidative addition to give platinum(1V) alkynyl compounds; (2) attack palladium black. The various reactions studied are noted in a t the carbon-carbon triple bond either to give vinylic platTable I. Although all combinations of reactants were not inum(I1) compounds containing a PtC(A)=C(B)R moiety or examined we believe our studies are sufficient to note general to generate a new alkynyl moiety, P t m R ' ; (3) insertion into and comparative trends in reactivity, the platinum-carbon bond to give Pt(AB)C=CR; (4) a Analytical and other characterization data for a representative sample of the new compounds are given in Table 11. complexation of an unsaturated AB substrate molecule to The products obtained from a number of reactions were not platinum. subjected to elemental analyses. This was either because the Since elemental analyses cannot distinguish between the above, we comment first on our methods of product analyses compound was not isolated in a spectroscopically pure state or because spectroscopic data were considered unequivocal with which are based predominantly on NMR and infrared regard to the nature of the product. Pertinent 'H N M R data spectroscopy. In the previous paperz9we reviewed the genare recorded in Table 111and infrared data are given in Table erally accepted criteria that exist for the assignment of steIV. reochemistry in PtR(X)L2 compounds (in particular for L = Oxidative Addition. Only Iz, IBr, ICN, CF31, or Me1 has PMe2Ph), based on 'H N M R data. These same arguments been found to react with the alkynylplatinum(I1) compounds hold for stereochemical assignments in the platinum(1V) to give isolable alkynylplatinum(1V) compounds. The relative compounds PtR(X)(A)(B)L2 and a distinction between Pt(I1) ease of oxidative addition of these substrates follows the order and Pt(1V) derivatives is readily apparent from the magnitude of platinum-195 to hydrogen coupling constants. For the L 12, IBr, ICN > CF31 > CH& Significantly CH3COCl was unreactive, although it readily oxidatively adds to alkylmethyl protons 4Jpt(II)-H is ca. 50% larger than 4Jpt(lv)-H. A similar change is observed for the Pt-CR moiety, JP~(II)-H platinum(I1) compounds. CF3COC1, which also very readily
Introduction Platinum has played a prominent role in the development Studies involving alkyl- and of organometallic hydridoplatinum compounds have elucidated many of the fundamental aspects of oxidative a d d i t i ~ n , ~reductive -~ e l i m i n a t i ~ n , ~@-hydrogen -'~ elirninati~n,'~-'~ a-complex formati~n,"-'~and ligand migration (insertion-deinsertion) r e a c t i o n ~ . ~ J ' ~ ~Alkynyl" - ~ ~ and alkenylplatinum compounds of the type Pt(un)zL2and PtX(un)Lz (where un = a a-bonded alkynyl or alkenyl ligand, X = a univalent anionic ligand, e.g., C1-, and L = a neutral donor ligand such as a tertiary have not phosphine or arsine), although readily been extensively studied. Since these compounds contain both inorganic2' and organic sites of unsaturation their reactions pose many interesting synthetic and mechanistic possibilities. Prior to this work we have proposed that their reactions with protic acids and the solvolysis and elimination reactions of a-chlorovinylplatinum(I1) compounds involve platinum-stabilized carbonium ion i n t e r r n e d i a t e ~ . ~ ~InJ ~this J ~ paper we describe the reactions of alkynylplatinum(I1) compounds of the type t r ~ n s - P t ( m R ) ~and L ~trans-PtC1(mR)Lz with a number of inorganic and organic substrates. ( 1 ) Qualitatively we define the relative reactivity of the alkynylplatinum(I1) compounds as a function of R (R = H, Me, and CF3) and L (L = PMe2Ph and AsMe3) for a given substrate. (2) For a given platinum compound we note certain trends in the reactivity of A-B substrate molecules. (3) We make a comparison with the reactivity patterns of methylplatinum(I1) compounds of the type PtMezLzand PtMe(Cl)Lz.
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2178 Inorganic Chemistry, Vol. 16, No. 9, 1977
Malcolm H. Chisholm and Lillian A. Rankel
Table I. Some Reactions of Alkynylplatinum(I1) Compoundsa Pt(C=CMe)X(AsMe,), Substrate CH,I CF,I 1, ICN CH,COCl HC1 HPF,/MeOH CF,CN CH,=CH, CF,=CF, CF,CzCCF, CF,C=CH CH C=CCOOH CH;OOCC-CCOOCH, PhCXH PhC=CPh MeCzCMe SO, CO,
Addn26,28 Alkoxycarbene formnZ6 NR NR NR Polymerizn NR Polymerizn of RC&R
7
NR NR Addn t o C=C and ox addn Reaction
Addn to C=C
Addn to C&
Go -
CI
(PMe,Ph), NR Slow ox addn Ox addn
Addn26'28 Alkoxycarbene formnZ6
AddnZ6 NR26
Complicated NMR NR
Me,SO CF,COCl
CI
Addn t o C=C Alkoxycarbene formn
Pt(C*CF,),-
Ox addn and red elimn Slow ox addn Ox addn
NR Polymerizn NR NR NR NR NR
CH, =C=CH,
NOCl
Dec NR
Addn t o C=C
Addn t o C=C
Slow ox addn
Ox addn and addn t o C=€
Ox addn and addn to C&
Slow ox addn
Addn to C=C
Addn to CIC
NR
CI
NR
OQO CI
CI
,
C F COCF , TCNE PhSSPh H,(Pd on carbon, MeOH/CH,Cl,) a
Ox addn Ox addn Ox addn Ox addn NR Addn" Alkoxycarbene formnZ6 NR
NR Dec NR NR NR
co
x=c1
X=C d M e
Pt(C=CH), (PMe, Ph), Slow ox addn Ox addn Ox addn Ox addn
Pt(C=CMe),(PMe,Ph),
Insertion at p carbon Insertion a t Pt-C= NR NR
adduct Insertion at Pt-C=
n adduct Insertion at Pt-Cr
II
NR NR
Key: ox addn = oxidative addition; red elimn = reductive elimination; NR = no reaction.
Table 11. Analytical and Other Characterization Data for Alkynylplatinum(l1) Compounds and Some of Their Derivatives %C
% other
%H
Compda
Calcd
Found
Calcd
Found
Pt(GCMe),A, Pt(C=CMe),(CH,)IA, Pt(C=CMe), (CF ,)(I)A, Pt(C=CMe),(I) ,A2 Pt(GCMe), (CN)(I)A, Pt(C=CMe)ClA, Pt(C=CH),(CF,)(I)P, R(C-CH), (I) ,P, F't(C=CMe), (C, C1,0, )A, F " X W , ( C , C l , O , ),P, Pt [ C(Cl)=C( COCF ,)MeI2A2 Pt(C=CMe), (TCNE)A, Pt(GCH),(TCNE)P, Pt (C=CMe)(CCl=C(NO)Me)(NO)(Cl)A, P t ( G C H ) , ( CF,COCF ,),P2
28.08 23.81 22.02 18.79 23.44 21.22 35.16 30.98 28.48 37.93 24.70 33.72 48.01 22.3 8 36.59
29.98 25.05 22.16 19.36 23.44 22.16 34.86 29.69 28.72 38.06 24.5 0 33.68 47.81 22.47 37.08
4.71 4.12 3.39 3.13 3.60 4.12 3.35 3.09 3.16 2.39 3.08 3.74 3.69 3.73 2.81
4.80 4.14 3.38 2.98 3.49 4.11 3.41 3.06 2.94 2.57 3.08 3.66 3.72 3.61 2.62
a
Calcd
Found
19.37 (I) 17.90 (I) 33.10 (I)
18.95 16.87 32.80
17.70 32.55 18.68 27.99 9.11 8.74 8.62
17.81 31.93 21.59 28.05 9.11 8.76 8.55
(I) (I) (Cl) (Cl) (Cl) (N) (N)
MP, " C
Color
146-148 dec 128 dec 169 dec 146-148 200 dec 107-109 192-194 120 158 dec 143 140-142 148-152 191 136-140 171-173
White Yellow Yellow Red Yellow Off-white Yellow Red Yellow Yellow Yellow Yellow Yellow Pink White
Key: A = AsMe,; P = PMe,Ph.
oxidatively adds to alkylplatinum(I1) compounds, always reacted to give products of addition to the carbon-arbon triple bond (see later).
For z r u n s - P t ( C ~ C R ) ~compounds L~ we observed the following relative order of ease of oxidative addition: R = Me > H > CF3and L = AsMe, > PMe2Ph. Thus, while I2 readily
Inorganic Chemistry, Vol. 16, No. 9, I977 2179
Reactions of Alkynylplatinum(I1) Compounds H NMR Dataa for Alkynylplatinum(I1) Compounds and Their Derivatives
Table 111.
Ligand A o r P methyls Compdb
Solvent
Pt(C=CMe),A, Pt(C=CMe),(CH,)(I)A, Pt(C=CMe),(CF,)(I)A, Pt(C=CMe), (I), A, Pt(C=CMe),(CN)(I)A, Pt(C=CMe)ClA, Pt(C=CMe)Cl(CF,)(I)A, Pt(C=CMe)Cl(I,)A, Pt(C=CMe), P, Pt(C=CH),P, Pt(C=CH),I,P, Pt(C=CH), (CF,)IP, Pt(C=CCF,),P, Pt(C=CCF ,), I,P,
Benzene Benzene Benzene Benzene Benzene Benzene Benzene Benzene CDCl,
Pt(C(Cl)=C(COCF,)Me),A, Pt(C(Cl)=C(COCF,)Me)ClA, Pt(C=CMe), A,(o-O,C,Cl,)
Benzene Benzene Benzene
P~(C~CH),P,(O-O,C,~,),
Pt(C=CMe)(CCl=C(NO)Me)(NO)(CI)A,
Benzene CH,a,
Pt(C=CMe), ((CF,),CO)A, Pt(C=CMe)CI((CF, ), CO)A, Pt(C=CMe), ((CF,),CO)P, Pt(C=CC(CF, ),OH), P, Pt(C=CMe), (TCNE)A, Pt(C=CMe)Cl(TCNE)A,
Benzene Benzene CH,Cl, Acetone-d, Benzene CH C1,
CDC1, CDCl, CH,Cl, Benzene
,
Acetone-d,
Pt(C=CH),(TCNE)P, a6
in p p m relative to Me,Si; J in Hz.
S
1.37 1.54 1.71 1.87 1.74 1.27 1.57 1.71 2.02 2.05 2.62 2.47 1.93 2.23 1.12 1.06 1.12 0.98 0.93 1.5-1 .o 1.53 1.28 1.20 1.91 1.18 1.13 1.47 1.44 1.47
Compda
,
Pt(C=CCF ,), P, Pt(C=CCF ,), I, P, Pt (C(Cl)=C(COCF,)Me), A, Pt(C(Cl)=C(COCF,)Me)CIA, Pt(C(Cl)=C(COCF,)Me),P, Pt(C=CMe), A,-o-O, C,Cl, Pt(CkCH) P, .20-0, C,Cl, Pt(C=CMe)( CCl=C(NO)Me)(NO)(Cl)A, Pt(C=CMe),((CF,),CO)A, Pt (C=CMe)(Cl)((CF, ), C0)A2 Pt(C=CC(CI: ,), COH),P, Pt(C=CMe), (TCNE)A, Pt(C=CMe)Cl(TCNE)A, Pt(C=CH),(TCNE)P,
,
a
v(C=C)b
-
Otherb
2122 2160 2170 2166
2165, 2150 2122 1968 1998 2005, 2030 2130 2160 1720 v(C=O), 1575,1560, 1540 v(C=C) 1710 v(C=O), 1580, 1520 2130 2180
1728 v(C=O), 1678, 1550 1738, 1575, 1540 1760, 1570 1660, 1620,1500 1875, 1640 1625 1880,1640
2105
Key: A = AsMe,, P = PMe,Ph.
7.5 7.8 7.4 8.6 8.0 8.4
3525 v(OH), 2620 v(OD) 2225, 1560 2210,1550 2220,1980 + 2 cm-'.
reacted with all the alkynylplatinum compounds, Me1 only to give slowly reacted with truns-Pt(C~CMe)~(AsMe~)~ trans-Pt( Me) (I) (C=CMe)2(AsMe3)2. Under comparable conditions tran~-Pt(C=CMe)~(PMe~Ph)~ and Me1 do not react. However, under reflux and in the presence of a large excess of MeI, trans-Pt((=--CMe)2(PMezPh)2 reacted to give tran~-Pt1(C=CMe)(PMe~Ph)~. This reaction could well
Acetylide R
3Jpt-~
S
24.0 16.6 16.4 16.0 17.3 23.6 15.8 15.2 33.0 33.0 17.6 20.2 32.8 20.4 23.5 25.5 23.4 24.7 25 .O
2.00 2.10 2.10 2.46 2.13 2.12 1.95 2.33 1.83 2.13 1.56 1.86
JP-H
Other
Jpt-~
15.2 14.6 14.6 15.0 14.5 22.8 20.8 20.4 16.4 45 33.0 36.4
1.9 2.3 3.6 3.8
2.08 2.10 2.00
15 15
C
15.0
7.8 8.0
8.2
Key: A = AsMe,; P = PMe,Ph.
Table IV. Characteristic Infrared Absorptions for Some Alkynylplatinum(I1) Compounds and Their Derivatives Pt(C=CMe), A, Pt(C=CMe),(CH,)(I)A, Pt(C=CMe),(CF,)(I)A, Pt(C=CMe),(I) ,A, Pt(C=CMe),(CN)(I)A, Pt(C=CMe)ClA, Pt(C=CH),P, Pt(C=CH) I,P, Pt(C=CH),(CF,)IP,
'J+
23.4 23.0 33.8 32.6 25.0 24.0 24.0 30.0
1.98 2.09 1.72 1.69 1.63 2.07 1.94
Very complicated.
2.3
14 14 10 13.6 14
6
JP-H
Jpt-~
1.61
70.4 (Me)
2.12
10 (vinyl R)
5.1 2.15
2.5
39 (vinylH) 6 (vinyl R)
1.28
1.8
10
d
15
1.91 1.74
None
None
Singlet.
proceed via an oxidative addition/reductive elimination sequence, but this has not been demonstrated. tr~ns-PtCl(mCMe)(AsMe~)~ did not react with MeI, cf. the reaction with P t ( m M e ) 2 ( A s M e 3 ) 2above, but did react slowly with CF31 to give oxidative addition. The reactivity order ~rans-Pt(C=CMe)~(AsMe~)~ > trans-PtCl(C= CMe)(AsMe3) has a parallel in the reactivity of methylplatinum(I1) compounds, RMe2L2> PtCl(Me)L2. However, trans-PtMe(C1)L2 compounds do react with Me1 to give oxidative-addition products, e.g., L = PEt, and PMe2Ph.' We conclude that alkynylplatinum(I1) compounds are generally less susceptible to oxidative-addition reactions than their methylplatinum analogues. This may well reflect the electron density on platinum which we expect follows the order Me > -Me > C S H > =CF3. The reactivity order L = AsMe3 > PMe2Ph finds a direct parallel in methylplatinum chemistry. We believe this is largely a kinetic effect. The AsMe3 ligand is less sterically demanding than PMe2Ph and thus their derivatives are more open to attack by substrates. ?r Complexation. Clark and his c o - ~ o r k e r s ~have l - ~ ~found that a number of substituted acetylenes and ethylenes form ?r complexes with PtMeZL2 and PtMe(C1)L2 compounds. These five-coordinated platinum ?r complexes are involved in Pt-C(methy1) insertion reactions and in acetylene polymerization reactions. The alkynylplatinum(I1) compounds in the present study did not form ?r complexes in NMR detectable concentrations. In some cases acetylene polymerization was observed, e.g., CF3C=CH, CF3C=CCF3, and MeO2CCECCO2Me. We find no evidence to support the suggestion that this polymerization occurs via insertion into Pt-C(acety1ide) bonds. Our results may be interpreted in terms of the reaction sequence discussed by Appleton, Clark, and P ~ d d e p h a t tfor ~ ~the polymerization of CF3C=CH by methylplatinum compounds. A number of other unsaturated molecules are known to form ?r complexes with electron-rich group 8 transition metal
2180 Inorganic Chemistry, Vol. 16, No. 9, 1977
complexes, e.g., allene,360 2 , 3 7 C02,38Cs2,39-40 CF3CN,"l S02,"2 and (CF3)2C0.43-45 Of these only hexafluoroacetone forms T complexes with alkynylplatinum compounds. We find that trans-Pt(C~CMe)~(AsMe,)~ and transP ~ C ~ ( C = C M ~ ) ( A S react M ~ ~to) ~form the stable 1:l adducts I and 11. The stereochemistry of I and I1 is readily deduced
Me
Me
I1
I
from the 'H NMR data. Both I and II show only one AsMe3 proton resonance with 3Jpt-H = 23 Hz. I showed two propynyl methyl resonances with differing values of 4Jpt-H. We assign the methyl resonance with 4Jpt-H = 10 Hz to the propynyl ligand trans to the Pt-C bond and the methyl resonance with 4 J n - H = 14 Hz to the ligand trans to the Pt-0 bond. Similarly for I1 the magnitude of 4J&H = 14 Hz for the propynyl protons leads us to suggest that this is trans to the Pt-0 bond. Our proposed stereochemistry for I1 is that expected from trans-influence theories.30 Of course the angle 0-Pt-C of the Pt-O-C(CF,), moiety must be much smaller than 90'; ~ f PtMe( C1) (AsMe3)2( C F,C=CC F3) where the C-Pt-C angle of the PtC2(CF3)2moiety is 37'. The geometry about platinum in I and I1 might be described in terms of either a five- or a six-coordinate model. In any event both compounds are stereochemically rigid on the N M R time scale. Reaction of (CF3)2C0with ethynylplatinum(I1) compounds leads to insertion into the x - H bond and is discussed later. The trifluoropropynylplatinum compound trans-Pt(C= CCF3)2(PMe2Ph)2did not react with (CF3)&0. This observation is consistent with our previously expressed view that the electron density on platinum is sensitive to the acetylenic substituent R and is greater for Me than for CF3; cf. relative ease of oxidative addition. When a large excess of (CF3)2C0 was reacted with tr~ns-Pt(C=CMe)~(AsMe~)~ a platinum-containing compound which was insoluble in benzene and only very sparingly soluble in acetone was formed. This we believe is probably similar to Ni, Pd, and Pt five-membered ringed compounds previously reported43which involve
Malcolm H. Chisholm and Lillian A. Rankel
tr~ns-Pt(C=-CMe)~(AsMe~)~ reacts with 1 equiv of TCNE to the AsMe, to give a platinum compound in which the lJpt-H protons remains unchanged. There are two propynyl methyl resonances: one shows 4Jpt_H = 15 Hz; the other shows no apparent coupling to 195Pt. These observations rule out a complexation of TCNE to platinum and oxidative addition, Le., derivatives of type I11 and VI. Also we discount the formation of an N-bonded ligand, IV, since a marked increase in 4Jpt-H to the propynyl protons would be expected.30 We believe the only reasonable structure consistent with the 'H N M R and infrared data is that of trans-Pt(C=@Me)(C(CN)2C(CN)2CaMe)(AsMe3)2 in which insertion into one Pt-C (acetylide bond) has occurred, i.e., formation of a compound of type V. This is the only example of an insertion into a Pt-C(acety1ide) bond that we have observed for a neutral platinum compound.50 There is a report concerning the insertion of Me02CC=--CC02Me into the Pd-C(acetylide) bond in PdCl(G=CPh)(PEt,),. We believe that the inertness of the Ft-C(acetylide) bond toward insertion reactions, relative to the Pt-C(methy1) bond, is a result of thermodynamic considerations, namely the Pt-C bond strengths.52 Only the highly electron-withdrawing cyano groups of the PtC(CN),C(CN),C=CMe ligand make the insertion thermodynamically favorable. It seems a similar situation may hold chemistry where the driving force for the reaction . in~palladium ~ PdC=CPh + Me02CC=CC02Me PdC(C02Me)= (C02Me)C=CPh comes from the electron-withdrawing substituents on the Pd-vinylic ligand. Addition to the C< Triple Bond. CF3COC1,53o-tetrac h l o r ~ q u i n o n e Br2,56 , ~ ~ , ~and ~ NOC15' are known to oxidatively add to d8 metal complexes. However, in our study we find products of addition to the carbon-carbon triple bond. tr~ns-Pt(-Me)~L~ reacts quantitatively with 2 equiv of CF3COC1to give a platinum(I1) bisvinyl derivative. A number of isomers could be formed depending on the mode of addition: the CF3C0 moiety could add to either the a: or @ carbon and the addition could lead to either cis or trans vinylic isomers. Furthermore if there is restricted rotation about the Pt-C(vinyl) bond, then two further sets of stereoisomers are possible. We believe the addition of the C F 3 C 0 moiety occurs exclusively to the @ carbon but that in solution both cis and trans vinylic isomers are present. In a crystallographic study the presence of the
-
,Me
M/o''*C(CF3)2
\ I c -0 I
(cF3)2
moieties. Pt-C( acetylide) Insertion Reactions. Tetracyanoethylene (TCNE) is known to react with transition metal complexes (i) to give T complexes, e.g., with t r ~ n s - P t M e ( X ) L ~(ii) , ~ ' to give insertion products which may be either C or N bonded to the metal, and48(iii) to undergo oxidative-addition react i o n ~ These . ~ ~ possibilities are shown schematically in 111-VI. CN / C-CN
I
C-CN C 'N
CN
IV
11s CN
I
MC=C(CN)2 MC(CN)2C(CN)2R
V
C I
CI MN=C=C-C(CN
M'I\
isomer was found.58 When tetrachloro-o-quinone forms 1:1 adducts with group 8 transition metal complexes, a decrease in v,,,(C=O) is observed of ca. 200 This is indicative of coordination to the metal as shown in VII.
I
CN
VI
)2R
VIS
However, upon reaction with alkynylplatinum(I1) compounds we observed an increase in vstr(C=O) by ca. 70 cm-'. This we believe rules out complexation to platinum as in VII. When trans-Pt(C=CMe)2(AsMe3)2 was reacted with 1 equiv of 0-02C6C14we obtained a product of addition to one of the propynyl ligands. The exact nature of the product cannot be deduced from 'H NMR data alone. However, we can reasonably formulate the product either as a l,4-addition
Reactions of Alkynylplatinum(I1) Compounds product, VIII, or as a phenyl C-Cl addition product, IX, akin Me
Inorganic Chemistry, Vol. 16, No. 9, 1977 2181 reactions occurred and no pure compounds were isolated from this reaction. In blank experiments MeCECMe was reacted with o02C6C14,TCNE, CF3COCl, and NOCl in benzene. No reaction was observed.
Experimental Section K2PtCl4 was obtained from Mathey Bishop, Inc. CH30D,TCNE, 0-02C6C14,PhCECH, Me02CC=CC02Me, MeC=CC02H, MeCSCMe were from Aldrich; (CFJ2C0, HC=CCF3, CF3C= to that obtained in the reaction with CF3COCl. CCF3, CF2=CF2 were from PCR, Inc.; CH2=CH2, CH3C=CH, and HCECH were from Matheson. Analyses were performed by The evidence in support of VI11 or IX may be summarized Atlantic Microlabs and Chemalytics, Inc. as follows. (1) There are two AsMe3 resonances (6 0.98 and cis-PtC12L; and truns-Pt(C=CR)(X)L2 (where R = H, Me, Ph, 0.93 ppm relative to Me4Si) in the integral ratio 1:l. Both CF,; X = C1, C S C r ; and L = AsMe3, PMe2Ph) were prepared by have similar 3 J h - H values, 24.7 and 25 Hz, respectively. This methods previously described.26 is indicative of a Pt(I1) complex with As trans to As and an Infrared spectra were obtained from Nujol mulls between CsI or absence of a plane of symmetry containing the MeCECPtNaCl plates using a Beckman IR-12 spectrophotometer. 'H NMR (vinyl) moiety. In VI11 such a plane does not exist. For IX were recorded on a Varian A60 or HA100 spectrometer. such a plane need not exist if there is restricted rotation about Pt(C=CMe)2(CF3)(I)(AsMe3)2. Pt(C=CMe)z(AsMe3)2 (0.103 the C(vinyl)-C6C1302 single bond. (2) The only other two g, 0.2 mmol) was dissolved in benzene (0.5 mL) and CF31(1.O mmol) 'Hresonances, 6 2.00 and 2.12 ppm, are readily assigned to was condensed into the reaction tube which was sealed. When the tube warmed to room temperature, a yellow compound crystallized PtCECMe and PtC=CMe moieties on the basis of the from solution. After 3 h, the tube was opened and petroleum ether magnitude of 4JR-H: ' J R e x C H = 15 Hz and 4JptC
