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Platinum-Acetylene complexes II. Implications of high resolution nuclear magnetic resonance spectra
163
PLATINUM-ACETYLENE III. IMPLICATIONS OF RESONANCE SPECTRA
COMPLMES HIGH RESOLUTION
NUCLEAR
MAGNETIC
JOHN H. NELSON*, J. J_ R. REED* ANDH. B. JONASSENRichardson Chemistry Laboratory, Deparlment of Chemistry, Tulane Wnicersily, New Orleans, Louiskmu 70118 (US.A.) and
Esso Research and Engineering Laboratories,
Humble Oil and Refining Cornpan>, Baytown, Texas (U.S.A.)
(Received November 19th, 1970)
SUMMARY
High resolution PMR spectra were recorded on ten zerovalent platinum complexes of terminal acetylenic alcohols and methylacetylenic alcohols. The results indicate that the complexes are essentially planar in solution, that the methylacetylenic alcohol complexes dissociate and that these complexes undergo oxidative addition reactions with the solvent (CDC13).
INTRODUCTION
In an earlier publication the preparation and characterization of several platinum acetylene complexes were reported l. One important and interesting part of this work was the proton NMR spectra of the complexes wherein the chemical shift of the complexed acetylenic hydrogen showed it to be in the region where olefinic protons are normally found. We interpreted this resonance on the basis of 60 MHz spectra as theX part of an AA’MX multiplet ; this is borne out by the 100 MHzspectra. However, only four lines of the anticipated twelve line spectrum were observed at the lower resolution; therefore new coupling constants were determined. In addition to the previously reported complexes we have preparedcomplexes ofmethyl acetylenic a]cohols for comparison. EXPERIMENTAL
The compounds 2-methyl-3-pentyne-2-01 and 1-propynylcyclohexanol ob-. tained from Farchan Research Laboratories were used without further purifications. The acetylenes l,l-diphenyl-2-butyne-l-01* and 1-propynyl-3,35,5_tetramethylcy* Department of Chemistry, University of Nevada, Rena, Nevada 89507. fir Esso Research and Engineering Laboratories. ** Tulane University, author to whom correspondent should be adressed. .I_ Organometaf. Gem., 29 (1971) 163468
164
J. H. NEUON,
J. J. R. REED, H. B. JONASSEN
clohexanol were prepared from the appropriate ketone and propynyllithium (Foote Chemical Company). The method used for preparing complexes has been previously reportedl- The new complexes were characterized by IR, PMR and elemental analyses (Tables 1 and 2). The 100 MHzPMR spectra were obtained with a Varian Associates HA-100 spectrometer operated in the field sweep mode and calibrated by the audio oscillation side band technique_The samples for NMR were dissolved in N, degassed CDCls under nitrogen, fntered through glass wool into the NMR tubes, purged with nitrogen and sealed. The chemical shifts and coupling constants are recorded in Table 2. TABLE EL-~-AL
1 AXAL.YSES
Acetylene
Ahi
PI-NSICAL
“0
OF THE
v(cGc)
Av(GC)
M-p.“
(cm-‘)
(cm- ‘)
CC)
COMPLEXES
(ph$‘)$‘t(acectykne)
Aualysls found &alcd.) (%) C
H
P
5.82 (5.70)
6.90 (6.77)
1789
446
145-147
64.25 (64.50)
1782
452
146-147
63.89
a-i cy-cd
PROPERTIES
6
(63.50)
(E,
61.65 (61.67)
(4.93)
7.75 (7.57)
66.28 (66.20)
4.72 (4.67)
6.69 (6.57)
OH
CHX-C&-CHS
1799
421
138-141
dH, YH CH,-C=C-C-Ph
1799
458
l&l
16&161
4.95
a All complexes melted with decomposition to red liquids. b Found : Pt, 2228. Calcd. : Pt, 22.42% REZWL.lS AND DISCUSSION
-Many complexes ofthe type (RJP)2M(Un); M = Ni, Pd, Pt and Un is an olefm or acetylene, have been prepared and characterized and the bonding in these complexes has led to much discussion3-g. The NMR spectra of these complexes have been particularly useful in the structural assignment due to the presence of lg5Pt (I = l/2, 34% natural abundance) coupling in both the proton and fluorine NMR. The coupling constantsJ and chemical shifts r of the various nuclei are such that many of the spectra can be interpreted by simple fmt order analyses. However, only two reports of 100 MHz PMR spectra for complexes of this type have appeareds9”. The chemical shift and coupling constant data for the complexes is given in Table 2. A typical spectrum is shown in Fig. 1. The conclusions which can be drawn from these spectra are the following: The chemical shift values of the acetylenic protons (Table 2) demonstrate that the complexed acetylene is spectroscopically equivalent to an olefin as its proton appears in the region where olefmic protons are J_ Orgcurametal_Chem, 29 (1971) 163-168
PLATINUM-ACETYLENE
165
COMPLEXE% III
-OH Fig. 1.100 MHz PMR spectrum of (PH.P),Pt(H-C&-C-Ph) panded acetylene hydrogen r&C-H
I
in CDCI, solution at 329 The inset is the ex-
ill resonance showing the AAWX multiplet. The large resonance is the
unresolved multipletof the phenylgroups.
Fig. 2. Representation of the coupling for CK-H and C=C-CHJ type (PPh,),Pt(R-C=C-H) and (PPh&Pt(R-C=C-CH&
protons of platinum complexes of the
normally found 12. This is in agreement with the spectral shifts observed in the infrared and the lengthening of the C-C bond determined by X-ray structure measurements13. Recently” it was shown by 60 MHz PMR studies on the complex (PPh&Pt(H-CJ_ OrgnnomernL Chem, 29 (1971) 163468
s:
?
g
g 6 *r a
s
5’ 0 a
I Ph
OH
-.--_I
2.74
2.83
2.74
2.75
2.x0
-.-
9.18”
8a42 9,07 9,28
8.91’
9.09”
8.X0”
9.20,
8.98”
8.75”
8.75’
8.16’ 8S8 8075 8082
8.60
3.55
3.78
3,78
3,72
3.74
8.34s
8.71
-
8072 9,23d
8.09
8.46”
8.49”
2.70 X.75” 9.17c
8.32”
2.70
2.70
8850”
2368
3.76
T(OH)
58
63.5
62
60
63
59.5
___-_.
J(Pt-C&-H)
01: ‘TIlli ‘I’Yl’li (P)13P),l’l(llcetylc~lc)
5(CeC-II)
OF COMI’LEXES
36
40
40.5
38
--. J(P1-ckc-CN,) ---.-...F--
22 23.25
IO IO,25
2
1.5
2
8
8
8
22.25
22 IO
IO
22.75
22
10
10
JO’,,,-1-I) JPvm-HI
” Center ofu broad unrcsolvcd multiplct. * J(Pt-CH,) =6 Hz. ’ J(Pt-H)= I.5 Hz for the ethyl group mclllyl hydrogens. d J(Pt-Cl&) =4 Hz, ’ J(PL-CHI) =3 Hz. f J(PkOH)=4 Hz. DJ(Pt-OH)=6 Hz. ” J(Pt-OH)=8 Hz. ’ J(Pt-OH)=9 Hz.
cH,-CsC
cti,-CFdC-C-Ph
OH
OH
6h
I
OH
I CHI
-4-l
CH,-C=C-C-CH,
CH,-CreC
H-CeC-C-Ph
H-crc
1’ values
100 MHz PMR DATA FOR SA’IIJRATEI~ CD& SOLUTIONS (ppni) relative to TMS interrinl standurd ..--r(Pl1) Acetylene W-M W,) ---H-C~C-C~OH)Wl,12 8.68” ?,I0
TABLE 2
”
E !?
g
F ??
6
P
LI
w
PLATINUM~ACFXYLENE
COMPLEXES.
167
III
S-H) that the acetylenic.hydrogen resonances were obscured by the phenyl proton resonances and these authors used perdeuteriotriphenylphosphine in place of triphenylphosphine as a ligand because of this. This is not the case for complexes of terminal acetylenes as is shown by the fact that all twelve of the anticipated lines due to the CEC-H proton are clearly observed to the high geld side of the phenyl resonancesat 100 MHz for these complexes. The coupling scheme for the acetylenic and methylacetylenic protons can be analyzed as follows : These protons are the X part of AAMX and AA’MX, multiplets *respectively which should contain twelve lines as shown in Fig. 2. There are two satellite lines due to coupling with lg5Pt and one line due to the uncoupled resonance in the relative intensity ratio of 1/4/l. These three lines are then further split by the nonequivalent cis- and trans-phosphorus atoms to give an apparent triplet of double doublets or twelve lines with relative intensities 1,,,,,,,,,,9 1 1 14 4 4 4 1 1 1 1. The complexes of this type which have been studied by X-ray have been found to be essentially planar in the solid state14- 17_Recent molecular orbital calculations have shown that this is the energetically favored configuration ‘p**l 8. The observation of non-equivalent coupling5*1 O to the cis- and trans-phosphorus atoms implies the same structure in solution as in the solid state. Distinctive cis- and truns-coupling to the phosphorus atoms also implies that the rate of rotation of the acetylene is very slow on the NMR time scale (with an upper limit of ca. 1.2 see-‘) based on the magnitude of J(P-H). Furthermore, the phosphorus-phosphorus couplin, 0 should be and is very small. The presence of free acetylene in solutions of the complex (Ph,P),Pt [(CH,),C(OH)C=C-CH,j further complicates the spectra_ The observation of separate resonances due to free and complexed acetylene implies a slow rate of ligand displacement. Furthermore, the concentration of free acetylene increases with increasing temperature, demonstrating that the displacement is temperature dependent. The spectra indicate that the reaction is not a simple dissociation reaction as the spectrum of a sample after a temperature cycle does not appear the same as that of one before a temperature cycle. Rather, an irreversible oxidative addition reaction involving the solvent most likely has occurred5 : (R,P)zPt(acetylene)
+CDCl,
-.
(R,P),PtCI(CDCl,)
+Acetylene
The complex (Ph,P),PtCl(CHCl,) has been isolated and characterized5 from the reaction of (Ph3P),Pt(Ph-C=C-CH3) and it was clearly shown that the carbonchlorine bond had been broken with concurrent formation of platinum-chlorine and platinum-carbon bonds Such reactions are similar to those which the zerovalent complexes M(Ph,P)4, (M = Pd, Pt) undergo with halocarbons’3*‘g-‘2-and offer chemical evidence confuming that the complexes of the type M(RsP)z(Un) are indeed zerovalent1v7-*. The solutions of all the complexes of dialkylacetylenes contain free acetylene but the solutions of the monoalkyl complexes do not. This suggests that the monoalkylacetylene complexes are more stable toward oxidative addition. This is in line with the predictions of the molecular orbital bonding model8*‘3 as the monosubstituted acetylenes should be better x-acceptors than the disubstituted acetylenes_ The spectrum of the 1-propynyl-3;3,5,5tetrðylcyclohexanol complex possesses separate resonances for the axial and equatorial methyls on the cyclohexane ring demonstrating that the ring is not inverting in this complex. This is to be expected from the size of the ring substituents. In addition to this, the presence of free acetylene J.
Urgohomerai_ Chem, 29 (1971) 163-168
165
J. H. NELSON,
J. J. R. REED,
H. B. JONASSEN
in solution makes it difficult to specifically assign the ring methylene resonances. The magnitudes of the platinum hydrogen coupling constants are very similar to those observed for analogous systems 13_It is of interest to note that J(Pt-H) of analogous olefm and acetylene complexes are very similar in magnitude with the acetylene complexes usually displaying very slightly larger couplings. The results of the molecular orbital calculations on systems’* of the type described in this work suggested that it might be possible to observe rotation of the coordinated acetylene about the metal-acetylene bond in the NMR spectra as observed in divalent complexes23-2g_ No evidence was found for rotation in the temperature range - 60” to + 60” in CDC13. However, since halocarbon solvents oxidative-
ly add, the observation of this rotation in these solvents at elevated temperatures may be impossible. Nevertheless, it may be possible to observe rotation-at elevated temperatures in nonreactive solvents and work is in progress to clarify this point. ACKNOWLEDGEMENTS
We wish to acknowledge the financial support of the Esso Research Laboratories, Humble Oil and Refining Company, Baton Rouge, Louisiana.
REFERENCES I 2 3 4 5 6 7 8 9 10 I1 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29
J. H. Nnso~, H. B. JONAXS~?~ AND D. M. RO~XDHILL, Znorg. Chem., 8 (1969) 2591. C. U. PInMAN AND G. A. OLAH, J. Amer. Chem. Sot., 87 (1965) 5632. J- A. MCGINNEIY AND J. k IBFRS, Chem. Commun., (1968) 235: G. T. B~INKE AND K. NA~OTO, Znorg. Chem., 7 (1968) 2030. E. 0. GREAVES, C. J. Loa AND P. M. MAINS, Can. J. Chem., 46 (1968) 3879. J. P. COLL~~ANAE~DJ. W. KANG, J. Amer. Chem. Sot., 89 (1967) 844. J. H. NELSON, K. S. WHEELOCK.L. C. CUSACHSAED Ii. B. JONASSEN, C/rem. Commun.. (1969) 1019. J. H. NELSON,K. S. WHEELOCIC, L. C. CusAcw. Ah?) H. B. JONASEEN,J.Amer. Chem. SOL, 91(1969) 7005. R. CRIER, J. Amer. Chem. SOL, 86 (1964) 217. E- 0. GREXVES.R- BRUCEAhn P. M. MAITLIS. Chem. Commrm., (1967) 860. C. D. Cooe AND K. Y. WAN, J. Amer. Chem. Sot., 92 (1970) 2595. J. W. EMSLEY,J. FEENEYh%= L. H. SUTCLIFFE,High Resolution Nuclear Magnetic Resatmance Specimscopy, Pergamon, New York, N.Y.. 1966. J. H. Naso~ AND H. B. JONASSEX,Coord. C/~em. Ra-., 6 (1971) 27. J. 0. GL~NVILLE, J. M. STRVART AND S. 0. GR~I, J. Organometaf. Chem., 1 (1967) 9. C. PANA~ONI, G. Bohmu%& U. BELL~C~ AND W. H. BADDLEY,J. Amer. Chem. Sot., 90 (1968) 798. W. DREISQGAhD H. DIETRICH,Acra Cry~fdogr., Sect. B. 24 (1968) 108. C. D. COOK, C. H. Koo, S. C. NY~URG AND M. T. SHIOMI, Chem. Commun., (1967) 426. K. S. WHEEXOCK, J. H. NRSON, L. C. CUSACHS AND H. B. JONASSEX, J. Amer. Chew Sot., 92 (1970) 5110. H. C. Cra~~c AND W. S. TSANG, J. Amer. Chem. Sot., 89 (1967) 529. W. J. Buhm AND R. D. W. KE?+~~%II-& J. C&em. Sot. A, (1969) 2062. M. GREEN, R. B. L. OSBORN, A. J. REZX AND F. G. A. STONE,J. Chem. Sot. A, (1968) 2525. W. H. BADDLEYAND L. M. V~ANZI, Znorg. Chem., 5 (1966) 33. B. F. G. JOHNSON,C. HOLLOWAY, G. HULLFI. Ah?> J. Lms, Cjzem. Commzm., (1967) 1143. S. F. A. KEITLE, J. Chem. Sot., (I 965) 6664. M. ORCHIN AND P. J. SC~IIDT, Inorg. Chim. Acta Reus., 2’(1968) 123. R. cRa_ J. Amer. Chem. Sot., 86 (1964) 217. T. A. WEIL, P_ J. SCK~T AND M. ORCH~, Ztzorg. Che.m., 8 (1969) 2138. S. MARICIC. C. R. REDPA’IHAND J. A. S. ShfiTH, J. Chem. Sot., (1963) 4905. G. J. ERSKINE AND R. S. NYHOLM, J. Chem. Sot. A, (1967) 1260. M. A. Bm,
J. Organometal.
Chem,
29 (1971) 163-168
PLATINUM-ACETYLENE III. IMPLICATIONS OF RESONANCE SPECTRA
COMPLMES HIGH RESOLUTION
NUCLEAR
MAGNETIC
JOHN H. NELSON*, J. J_ R. REED* ANDH. B. JONASSENRichardson Chemistry Laboratory, Deparlment of Chemistry, Tulane Wnicersily, New Orleans, Louiskmu 70118 (US.A.) and
Esso Research and Engineering Laboratories,
Humble Oil and Refining Cornpan>, Baytown, Texas (U.S.A.)
(Received November 19th, 1970)
SUMMARY
High resolution PMR spectra were recorded on ten zerovalent platinum complexes of terminal acetylenic alcohols and methylacetylenic alcohols. The results indicate that the complexes are essentially planar in solution, that the methylacetylenic alcohol complexes dissociate and that these complexes undergo oxidative addition reactions with the solvent (CDC13).
INTRODUCTION
In an earlier publication the preparation and characterization of several platinum acetylene complexes were reported l. One important and interesting part of this work was the proton NMR spectra of the complexes wherein the chemical shift of the complexed acetylenic hydrogen showed it to be in the region where olefinic protons are normally found. We interpreted this resonance on the basis of 60 MHz spectra as theX part of an AA’MX multiplet ; this is borne out by the 100 MHzspectra. However, only four lines of the anticipated twelve line spectrum were observed at the lower resolution; therefore new coupling constants were determined. In addition to the previously reported complexes we have preparedcomplexes ofmethyl acetylenic a]cohols for comparison. EXPERIMENTAL
The compounds 2-methyl-3-pentyne-2-01 and 1-propynylcyclohexanol ob-. tained from Farchan Research Laboratories were used without further purifications. The acetylenes l,l-diphenyl-2-butyne-l-01* and 1-propynyl-3,35,5_tetramethylcy* Department of Chemistry, University of Nevada, Rena, Nevada 89507. fir Esso Research and Engineering Laboratories. ** Tulane University, author to whom correspondent should be adressed. .I_ Organometaf. Gem., 29 (1971) 163468
164
J. H. NEUON,
J. J. R. REED, H. B. JONASSEN
clohexanol were prepared from the appropriate ketone and propynyllithium (Foote Chemical Company). The method used for preparing complexes has been previously reportedl- The new complexes were characterized by IR, PMR and elemental analyses (Tables 1 and 2). The 100 MHzPMR spectra were obtained with a Varian Associates HA-100 spectrometer operated in the field sweep mode and calibrated by the audio oscillation side band technique_The samples for NMR were dissolved in N, degassed CDCls under nitrogen, fntered through glass wool into the NMR tubes, purged with nitrogen and sealed. The chemical shifts and coupling constants are recorded in Table 2. TABLE EL-~-AL
1 AXAL.YSES
Acetylene
Ahi
PI-NSICAL
“0
OF THE
v(cGc)
Av(GC)
M-p.“
(cm-‘)
(cm- ‘)
CC)
COMPLEXES
(ph$‘)$‘t(acectykne)
Aualysls found &alcd.) (%) C
H
P
5.82 (5.70)
6.90 (6.77)
1789
446
145-147
64.25 (64.50)
1782
452
146-147
63.89
a-i cy-cd
PROPERTIES
6
(63.50)
(E,
61.65 (61.67)
(4.93)
7.75 (7.57)
66.28 (66.20)
4.72 (4.67)
6.69 (6.57)
OH
CHX-C&-CHS
1799
421
138-141
dH, YH CH,-C=C-C-Ph
1799
458
l&l
16&161
4.95
a All complexes melted with decomposition to red liquids. b Found : Pt, 2228. Calcd. : Pt, 22.42% REZWL.lS AND DISCUSSION
-Many complexes ofthe type (RJP)2M(Un); M = Ni, Pd, Pt and Un is an olefm or acetylene, have been prepared and characterized and the bonding in these complexes has led to much discussion3-g. The NMR spectra of these complexes have been particularly useful in the structural assignment due to the presence of lg5Pt (I = l/2, 34% natural abundance) coupling in both the proton and fluorine NMR. The coupling constantsJ and chemical shifts r of the various nuclei are such that many of the spectra can be interpreted by simple fmt order analyses. However, only two reports of 100 MHz PMR spectra for complexes of this type have appeareds9”. The chemical shift and coupling constant data for the complexes is given in Table 2. A typical spectrum is shown in Fig. 1. The conclusions which can be drawn from these spectra are the following: The chemical shift values of the acetylenic protons (Table 2) demonstrate that the complexed acetylene is spectroscopically equivalent to an olefin as its proton appears in the region where olefmic protons are J_ Orgcurametal_Chem, 29 (1971) 163-168
PLATINUM-ACETYLENE
165
COMPLEXE% III
-OH Fig. 1.100 MHz PMR spectrum of (PH.P),Pt(H-C&-C-Ph) panded acetylene hydrogen r&C-H
I
in CDCI, solution at 329 The inset is the ex-
ill resonance showing the AAWX multiplet. The large resonance is the
unresolved multipletof the phenylgroups.
Fig. 2. Representation of the coupling for CK-H and C=C-CHJ type (PPh,),Pt(R-C=C-H) and (PPh&Pt(R-C=C-CH&
protons of platinum complexes of the
normally found 12. This is in agreement with the spectral shifts observed in the infrared and the lengthening of the C-C bond determined by X-ray structure measurements13. Recently” it was shown by 60 MHz PMR studies on the complex (PPh&Pt(H-CJ_ OrgnnomernL Chem, 29 (1971) 163468
s:
?
g
g 6 *r a
s
5’ 0 a
I Ph
OH
-.--_I
2.74
2.83
2.74
2.75
2.x0
-.-
9.18”
8a42 9,07 9,28
8.91’
9.09”
8.X0”
9.20,
8.98”
8.75”
8.75’
8.16’ 8S8 8075 8082
8.60
3.55
3.78
3,78
3,72
3.74
8.34s
8.71
-
8072 9,23d
8.09
8.46”
8.49”
2.70 X.75” 9.17c
8.32”
2.70
2.70
8850”
2368
3.76
T(OH)
58
63.5
62
60
63
59.5
___-_.
J(Pt-C&-H)
01: ‘TIlli ‘I’Yl’li (P)13P),l’l(llcetylc~lc)
5(CeC-II)
OF COMI’LEXES
36
40
40.5
38
--. J(P1-ckc-CN,) ---.-...F--
22 23.25
IO IO,25
2
1.5
2
8
8
8
22.25
22 IO
IO
22.75
22
10
10
JO’,,,-1-I) JPvm-HI
” Center ofu broad unrcsolvcd multiplct. * J(Pt-CH,) =6 Hz. ’ J(Pt-H)= I.5 Hz for the ethyl group mclllyl hydrogens. d J(Pt-Cl&) =4 Hz, ’ J(PL-CHI) =3 Hz. f J(PkOH)=4 Hz. DJ(Pt-OH)=6 Hz. ” J(Pt-OH)=8 Hz. ’ J(Pt-OH)=9 Hz.
cH,-CsC
cti,-CFdC-C-Ph
OH
OH
6h
I
OH
I CHI
-4-l
CH,-C=C-C-CH,
CH,-CreC
H-CeC-C-Ph
H-crc
1’ values
100 MHz PMR DATA FOR SA’IIJRATEI~ CD& SOLUTIONS (ppni) relative to TMS interrinl standurd ..--r(Pl1) Acetylene W-M W,) ---H-C~C-C~OH)Wl,12 8.68” ?,I0
TABLE 2
”
E !?
g
F ??
6
P
LI
w
PLATINUM~ACFXYLENE
COMPLEXES.
167
III
S-H) that the acetylenic.hydrogen resonances were obscured by the phenyl proton resonances and these authors used perdeuteriotriphenylphosphine in place of triphenylphosphine as a ligand because of this. This is not the case for complexes of terminal acetylenes as is shown by the fact that all twelve of the anticipated lines due to the CEC-H proton are clearly observed to the high geld side of the phenyl resonancesat 100 MHz for these complexes. The coupling scheme for the acetylenic and methylacetylenic protons can be analyzed as follows : These protons are the X part of AAMX and AA’MX, multiplets *respectively which should contain twelve lines as shown in Fig. 2. There are two satellite lines due to coupling with lg5Pt and one line due to the uncoupled resonance in the relative intensity ratio of 1/4/l. These three lines are then further split by the nonequivalent cis- and trans-phosphorus atoms to give an apparent triplet of double doublets or twelve lines with relative intensities 1,,,,,,,,,,9 1 1 14 4 4 4 1 1 1 1. The complexes of this type which have been studied by X-ray have been found to be essentially planar in the solid state14- 17_Recent molecular orbital calculations have shown that this is the energetically favored configuration ‘p**l 8. The observation of non-equivalent coupling5*1 O to the cis- and trans-phosphorus atoms implies the same structure in solution as in the solid state. Distinctive cis- and truns-coupling to the phosphorus atoms also implies that the rate of rotation of the acetylene is very slow on the NMR time scale (with an upper limit of ca. 1.2 see-‘) based on the magnitude of J(P-H). Furthermore, the phosphorus-phosphorus couplin, 0 should be and is very small. The presence of free acetylene in solutions of the complex (Ph,P),Pt [(CH,),C(OH)C=C-CH,j further complicates the spectra_ The observation of separate resonances due to free and complexed acetylene implies a slow rate of ligand displacement. Furthermore, the concentration of free acetylene increases with increasing temperature, demonstrating that the displacement is temperature dependent. The spectra indicate that the reaction is not a simple dissociation reaction as the spectrum of a sample after a temperature cycle does not appear the same as that of one before a temperature cycle. Rather, an irreversible oxidative addition reaction involving the solvent most likely has occurred5 : (R,P)zPt(acetylene)
+CDCl,
-.
(R,P),PtCI(CDCl,)
+Acetylene
The complex (Ph,P),PtCl(CHCl,) has been isolated and characterized5 from the reaction of (Ph3P),Pt(Ph-C=C-CH3) and it was clearly shown that the carbonchlorine bond had been broken with concurrent formation of platinum-chlorine and platinum-carbon bonds Such reactions are similar to those which the zerovalent complexes M(Ph,P)4, (M = Pd, Pt) undergo with halocarbons’3*‘g-‘2-and offer chemical evidence confuming that the complexes of the type M(RsP)z(Un) are indeed zerovalent1v7-*. The solutions of all the complexes of dialkylacetylenes contain free acetylene but the solutions of the monoalkyl complexes do not. This suggests that the monoalkylacetylene complexes are more stable toward oxidative addition. This is in line with the predictions of the molecular orbital bonding model8*‘3 as the monosubstituted acetylenes should be better x-acceptors than the disubstituted acetylenes_ The spectrum of the 1-propynyl-3;3,5,5tetrðylcyclohexanol complex possesses separate resonances for the axial and equatorial methyls on the cyclohexane ring demonstrating that the ring is not inverting in this complex. This is to be expected from the size of the ring substituents. In addition to this, the presence of free acetylene J.
Urgohomerai_ Chem, 29 (1971) 163-168
165
J. H. NELSON,
J. J. R. REED,
H. B. JONASSEN
in solution makes it difficult to specifically assign the ring methylene resonances. The magnitudes of the platinum hydrogen coupling constants are very similar to those observed for analogous systems 13_It is of interest to note that J(Pt-H) of analogous olefm and acetylene complexes are very similar in magnitude with the acetylene complexes usually displaying very slightly larger couplings. The results of the molecular orbital calculations on systems’* of the type described in this work suggested that it might be possible to observe rotation of the coordinated acetylene about the metal-acetylene bond in the NMR spectra as observed in divalent complexes23-2g_ No evidence was found for rotation in the temperature range - 60” to + 60” in CDC13. However, since halocarbon solvents oxidative-
ly add, the observation of this rotation in these solvents at elevated temperatures may be impossible. Nevertheless, it may be possible to observe rotation-at elevated temperatures in nonreactive solvents and work is in progress to clarify this point. ACKNOWLEDGEMENTS
We wish to acknowledge the financial support of the Esso Research Laboratories, Humble Oil and Refining Company, Baton Rouge, Louisiana.
REFERENCES I 2 3 4 5 6 7 8 9 10 I1 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29
J. H. Nnso~, H. B. JONAXS~?~ AND D. M. RO~XDHILL, Znorg. Chem., 8 (1969) 2591. C. U. PInMAN AND G. A. OLAH, J. Amer. Chem. Sot., 87 (1965) 5632. J- A. MCGINNEIY AND J. k IBFRS, Chem. Commun., (1968) 235: G. T. B~INKE AND K. NA~OTO, Znorg. Chem., 7 (1968) 2030. E. 0. GREAVES, C. J. Loa AND P. M. MAINS, Can. J. Chem., 46 (1968) 3879. J. P. COLL~~ANAE~DJ. W. KANG, J. Amer. Chem. Sot., 89 (1967) 844. J. H. NELSON, K. S. WHEELOCK.L. C. CUSACHSAED Ii. B. JONASSEN, C/rem. Commun.. (1969) 1019. J. H. NELSON,K. S. WHEELOCIC, L. C. CusAcw. Ah?) H. B. JONASEEN,J.Amer. Chem. SOL, 91(1969) 7005. R. CRIER, J. Amer. Chem. SOL, 86 (1964) 217. E- 0. GREXVES.R- BRUCEAhn P. M. MAITLIS. Chem. Commrm., (1967) 860. C. D. Cooe AND K. Y. WAN, J. Amer. Chem. Sot., 92 (1970) 2595. J. W. EMSLEY,J. FEENEYh%= L. H. SUTCLIFFE,High Resolution Nuclear Magnetic Resatmance Specimscopy, Pergamon, New York, N.Y.. 1966. J. H. Naso~ AND H. B. JONASSEX,Coord. C/~em. Ra-., 6 (1971) 27. J. 0. GL~NVILLE, J. M. STRVART AND S. 0. GR~I, J. Organometaf. Chem., 1 (1967) 9. C. PANA~ONI, G. Bohmu%& U. BELL~C~ AND W. H. BADDLEY,J. Amer. Chem. Sot., 90 (1968) 798. W. DREISQGAhD H. DIETRICH,Acra Cry~fdogr., Sect. B. 24 (1968) 108. C. D. COOK, C. H. Koo, S. C. NY~URG AND M. T. SHIOMI, Chem. Commun., (1967) 426. K. S. WHEEXOCK, J. H. NRSON, L. C. CUSACHS AND H. B. JONASSEX, J. Amer. Chew Sot., 92 (1970) 5110. H. C. Cra~~c AND W. S. TSANG, J. Amer. Chem. Sot., 89 (1967) 529. W. J. Buhm AND R. D. W. KE?+~~%II-& J. C&em. Sot. A, (1969) 2062. M. GREEN, R. B. L. OSBORN, A. J. REZX AND F. G. A. STONE,J. Chem. Sot. A, (1968) 2525. W. H. BADDLEYAND L. M. V~ANZI, Znorg. Chem., 5 (1966) 33. B. F. G. JOHNSON,C. HOLLOWAY, G. HULLFI. Ah?> J. Lms, Cjzem. Commzm., (1967) 1143. S. F. A. KEITLE, J. Chem. Sot., (I 965) 6664. M. ORCHIN AND P. J. SC~IIDT, Inorg. Chim. Acta Reus., 2’(1968) 123. R. cRa_ J. Amer. Chem. Sot., 86 (1964) 217. T. A. WEIL, P_ J. SCK~T AND M. ORCH~, Ztzorg. Che.m., 8 (1969) 2138. S. MARICIC. C. R. REDPA’IHAND J. A. S. ShfiTH, J. Chem. Sot., (1963) 4905. G. J. ERSKINE AND R. S. NYHOLM, J. Chem. Sot. A, (1967) 1260. M. A. Bm,
J. Organometal.
Chem,
29 (1971) 163-168