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CC and CH bond formation in the chemistry of triruthenium clusters
Po/yMron Vol. 7, No. lO/ll, pp. 95-960, Printed in Great Britain
C-C
0277-5387/M S3.00+.00 Q 1988 PagaInan press plc
1988
AND C-H BOND FORMATION IN THE CHEM.ISTRY OF TRIRUTHENIUM CLUSTERS M. J. SAILOR
and D. F. SHRIVER*
Department of Chemistry, Northwestern
University, Evanston, IL 60208, U.S.A.
(Accepted 5 November 1987) Abstract-The p3-acetyl cluster [Ru~(CO),~~-CO)@,-CC(O)CH~)]- (l), readily adds CO to produce the acylketene clusters [Ru~(CO)~@-CO)&~-~~-CH~C(O)CCO)]- and under moderate CO pressures a mobile equilibrium is established between these two species. The phosphine-substituted acetyl cluster [Ru3(CO)8~-CO)(PPh3)(~3-CC(0)CH3)]does not add CO under conditions in which the parent cluster 1 does. The acetyl cluster 1 also reacts with H- or OH-, to produce the complex [Ru~(CO)&CO)~(~~-~~-CHC(O)CH~)]~--, which has been characterized spectroscopically. Mobile C-C and C-H formation is characteristic of these three-metal cluster systems and it is attributed to the variety of multi-site ligandmetal interactions that are possible with a three-metal ensemble.
Recently an extensive chemistry has been observed for the ketenylidene ligand, CCO, in a variety of three-metal clusters, and in particular for anionic ketenylidenes such as [Ru3(CO)&CO),(~,CCO)]2-.‘-5 Several routes to cationic, neutral and anionic ketenylidenes have been devised.‘-” The generation of the CC0 group in these clusters can be described formally as the coupling of a clusterbound carbide atom with a CO molecule. Furthermore, in the anionic ketenylidene clusters the CO group is readily displaced. Thus reaction with alkylating agents,2-5 nucleophiles,i2 or electrophilic metal complexes’3*‘4 can result in scission of the C-C bond of CCO, eqs (l)--(3).
ter [Ru~(CO),~-CO)~~~-~~-CH~C(O)CCO)](2). This compound exists in equilibrium with [Ru~(CO)&~-CO) @3-CC(0)CH3)]- (1) under a CO atmosphere, eq. (4).i5 The acylketene complex 2 reverts to 1 on removal of the CO atmosphere, and it was previously characterized in situ by twodimensional 13C NMR spectroscopy on a highly 13C-enriched sample. I5 In this report we describe some of the factors involved in this C-C bond forming reaction, as well as a related reaction involving C-H bond formation on complex 1.
RESULTS
AND DISCUSSION
[Fe3(C0)9(~3-CCO)]2- + CH3I -,
R&Oh&-CCH3)1-
[CoFe2(C0)9(p3-CCO)]- + PMe3 + [CoFe2(CO)9(~3-CPMe3)]- + CO
(2)
[Fe3(C0)9(~3-CCO)]2- + Cr(C0)3(NCCH3)3 + [CrFe3C(C0),3]2-.
Although the formation of the acylketene moiety 1, an isotopic tracer experiment has shown that the ketenyl CO is derived from an originally clusterbound CO ligand rather than the external carbon monoxide.” Similar CO-insertion reactions have been observed in several osmium carbonyl clusters containing the p-CH2 group.i6 In an attempt to elucidate the factors responsible for the formation of the unusual acylketene cluster 2 of eq. (4), we investigated the reaction of 1 with other ligands. Treatment of the acetyl cluster 1 with PPh3 does not lead to the phosphine-substituted analogue of 2. Rather, simple substitution of phosphine for CO occurs. Thus, reaction of PPh, with 13C-enriched
(1) of 2 is observed on the addition of CO to
(3)
The above reactions demonstrate that the CO of CC0 can be quite labile in these clusters. An unusual example of the lability of the CO moiety of CC0 is provided by the acylketene clus-
*Author to whom correspondence should be addressed.
955
956
M. J. SAILOR
and D. F. SNRZVER
(4)
PPk,
~Ru~(C~)~(~L~-CO)(~~-~C(~)CH~)~in CD2Clz in a sealed NMR tube rcsuhs in a i3C NMR signal for free CO at 183.4 ppm and ~sana~c~s that have been assigned to the phosphine”subst~t~t~ acety~m~thy~id~e cluster 3, eq. (5), Additionally, when a soi~~on of ERu3(Co),(Ct-Co)(PPh~)~~~ C~~)~H~)~- (3) is placed under an atmosphere of CO, we see no s~ctroscopic evidence for reaction. These rest&s suggest that the forward reaction represented by eq. (4) is less favoured for the phospbi~~-subsisted cluster 3 than for the carbony1 complex 1. Similar results are ob~~ned with P(~~~)~ We have pre~ously reported that Hz will also react with [Rn1(~)~(~3-~~)~~~GC(Q)CW3)J-.” Addition of Hz to 1 results in loss of one CO ligand bond, eq. (6). and fo~atio~ of a ear~n-bydro crayon (6) is similar to eq. (4) because in the course of the reaction the oxygen atom of the acetyl
ligand enters into an interaction with the metals, at the expense of a rne~~r~n interaction. The 0 + Ru bonding a~a~~rn~nt apparently is ~rn~~nt in the 6-C and C-H bond foxing recross of use trcatme~t of either of the eqs (4) and (6), products with C~~~S~~~F~ results in ajkylatio~ of the acetyl oxygen atom and d~srup~o~ of the C---C or C-H bond, Znboth cases a ~ny~idene ch&cr is produced (Scheme 1).15 A ~~-~~-C~C(~)C~~~~ga~dcan also be generated by reaction of [Ru~(CO}~~~-CO)(~~c13”cc(o)cH311~ with hyd~de or hydroxide, eq. (7). The di~egati~e compIex 7 has been cbaracte~zed spectroscopically* The con~gnrat~o~ of the cappmg ligand was established by r3C and “H NMR spectra of a sample of 7 that was enriched with s3C.The NMR data are s~rn~zed and compared to two related, previousIy ~~~ac~e~ clusters co~ta~n~~gthe j+-#CHC(0)CHi, liga~d in Table 1. Although the ‘I-f
Chemistry of triruthenium
,o
W,
957
clusters
l-
C’
I
(CO),
2
CH,C
CH,’ i H,C\
CHs
$-OCHa
P 1 (CO), RGpi” ‘Rd (co);
,0-CH3 C
(CO),
’ H (CO),
5
6 Scheme 1.
NMR signal of the unique proton in the CHC(0)CH3 ligand of 7 is more than 2 ppm upfield of the corresponding resonances of the complexes [HRu~(CO),(~~-$-CHC(O)CH~)](8) and H2Ru3 (CO)&-q’-CHC(O)CH,) (9), the associated ‘JcH coupling constant is comparable. The high-field ‘H NMR shift for the unique proton in 7 may be a reflection of the CO ligand disposition, which is
different in 7 than in either of the other two clusters 8 or 9. Although the anionic and neutral complexes [HRu,(CO),~~-~~-CHC(O)CH~)]-~~~H~R~~(CO), (p3-q2-CHC(0)CH3) contain only terminal CO ligands, the IR and 13CNMR data indicate that dinegative [Ru~(CO),~-CO),~~-~~-CHC(O)CH~)]~contains three bridging carbonyl ligands. Presumably the carbonyl ligands of 7 more effectively
1
2-
(7) -
HZ OH-
7
1
Eq. 7
958
M. J. SAILOR and D. F. SHRIVER Table
1. 13C and
‘H NMR shifts and coupling pj-q*-CHC(0)CH3 ligand”
constants
for the
Me
I
13CNMR (ppm) C, C,
Compound
[Rus(W,(L)1*[HRu,(CO),(L)]-b H,Ru,(CO),(L)”
56.9 77.5 74.3
216.1 230.7 239.5
‘H NMR @pm) H, Me 1.46 4.03 4.16
‘J (HZ) C,-C, C,-H,
1.45 1.79 1.99
49 46 43
140 141 143
“L is defined as the p3-q*-C,H,C@(O)Me group. All measurements in CD2C12solution on ‘3C-enriched complexes. ‘Ref. 15.
shield the unique proton, resulting in the higherfield ‘H NMR resonance. With respect to the carbonyl ligand disposition, the isoelectronic series of p3-I$-CHC(0)CH3 clusters 7,8 and 9 is similar to the series of ketenylidene clusters H2Ru3(C0)&.+CCO), ~Ru3(C0).&CCO)]- and [Ru~(CO)~~-CO)~@~-CCO)]~-.~ Presumably the presence of the bridging carbonyl
I
I
280
I
made
groups in the dinegative compounds partially alleviates the high negative charge in these complexes. A set of variable-temperature 13CNMR spectra in the CO-region of 7 is presented in Fig. 1. The lowtemperature spectrum indicates that the molecule possesses a mirror plane that contains the p3-$CHC(0)CH3 ligand (excluding the methyl hydrogens from consideration), a bridging CO, two ter-
I
1
270
210
I
1
200
PPm Fig.
1. Variable-temperature r3C NMR spectrum (100.58 MHz) of [Ru~(CO)&-CO)~&~-~*CHC(O)CH,)]‘-, 7, showing the carbonyl ligand fluxionality.
Chemistry of triruthenium clusters
959
(8) CH,' -
Eq. 8 minal carbonyl ligands and a ruthenium vertex. On barrier to C-C and C-H bond formation and raising the temperature, exchange between all but cleavage is apparently very low. one of the carbonyl ligands becomes fast on the NMR timescale, as evidenced by the broadening of EXPERIMENTAL all but one of the 13C NMR signals for the CO ligands. The unique CO ligand is presumed to be General tram to the 0 + Ru interaction, in line with the All manipulations were carried out under a dry previous interpretation of the VT-13C NMR spectra dinitrogen atmosphere using standard Schlenk and of 8.1S As might be expected, the compounds [HRu3 syringe techniquesI or in a Vacuum Atmospheres (CO)&,-~2-CHC(0)CH3)](8) and H2Ru3 (CO), drybox. Solvents were distilled from the appro@3-q2-CHC(0)CH3) (9) can be synthesized from priate drying agents before use: CH2C12 and [Ru~(C~>,~L-C~)~(~~-~~~_CHC(O)CH~)I~(7) by CD2C12 from P205 ; THF and Et,0 from sodium successive protonation. It is interesting that ad- and benzophenone. The compounds [PPN] [Ru, dition of hydride or hydroxide to 1 results in C-H (C~)~~L~-CO)(CL~-CC(O)CH~)I, [PPNI lBRu3 (CO), (p3-CCO)] and 13C-enriched [PPNl[Ru, (*CO)&,bond formation to generate 7, but that subsequent *CO)(p3-*C*C(0)CH3)] were prepared as deaddition of H+ to 7 occurs at the metal framework rather than the carbon atom. Thus the p3-q2- scribed previously.2 Potassium tri-secbutylboroCHC(0)CH3 moiety is apparently a relatively stable hydride (“K-selectride”, 1.0 M solution in THF, ligand. Another indication of the stability of the Aldrich) and methyllithium (low-halide 1.4 M p3-$-CHC(0)CH3 group is that the cluster solution in Et,O, Aldrich) were used as received. [Ru~(CO),&CO),(~~-?Z_CHC(O)CH~>~’- can also Elemental analyses were performed by Elbach be synthesized by reaction of the ketenylidene clus- Analytical Laboratories. Infrared spectra were obtained on Nicolet 7199 ter [HRu3(C0)&-CCO)]with LiCH3, eq. (8). In Fourier transform or Perkin-Elmer 283 infrared reaction (8) the CH; group is presumed to attack the carbonyl carbon of the CC0 ligand to form a spectrometers. Multinuclear NMR spectra on ‘H, pL,-acetyl ligand. In the course of the trans- 31Pand 13Cwere obtained on either JEOL FX-270 formation, the metal-bound hydride migrates to the or Varian XL-400 NMR spectrometers, and were apical carbon atom of the former pj-CCO ligand. referenced to residual solvent protons, external Apparently, in these anionic clusters the pL3-q2- 20% H3P04 in D20, or the 13CNMR signal of the CHC(0)CH3 ligand is favoured over a p3- solvent carbon atoms, respectively. Unless otherwise noted, the i3C NMR data reported are on 13CCC(0)CH3 moiety. enriched materials. The data for Jcc reported were measured from the i3C-13C satellite peaks from CONCLUDING REMARKS samples ca 30% enriched with i3C. Note that the 13C-enriched starting material [Ru~(*CO)&~In this work we have discussed two related pro*CO)(p3-*C*C(0)CH3)]- was not enriched at the cesses involving the activation of a cluster-bound carbon atom and these can be systematized by the methyl carbon. following formal description. In the pJ-acetyl cluster [Ru~(CO)~(~~-CO)(~&C(O)CH~)]-, the replaceSynthesis and characterization of [PPN] [Ru, ment of a carbon-to-ruthenium bond with an 0 --* (CO),(PPh3)OL3-CC(O)CH3)1,3 Ru interaction can be considered to generate an A 30 mg sample of [PPN][Ru,(*CO),b,“unsaturation” at the capping carbon atom. The carbon can either couple with H to form a p3-q2- *CO)@3-*C*C(0)CH3)] (* denotes 13Cenrichment CHC(0)CH3 ligand, or with CO to form a p2-q2- of ca 20%) and a 6 mg sample of triphenylCH,C(O)CCO moiety. In these anionic clusters, the phosphine, were loaded into a 5 mm NMR tube
960
M. J. SAILOR and D. F. SHRIVER
fitted with a concentric Teflon valve. Approximately 0.5 cm3 of CD,Cl, was vacuum transferred into the tube at liquid nitrogen temperature. ‘H NMR (taken 15 min after sealing and warming the NMR tube) : phenyl protons (PPh3 and [PPN]+) ; 2.41 (s, CH3 of 3) ; 2.36 (s, CH3 of 1) ; 1.87 (s, CH3 of 2) ppm. After 8 h the signals for 1 and 2 had almost disappeared and the only detectable product was species 3. 31P NMR: 35.95 (PPh, of 3); 21.54 ([PPN]+) ; - 5.12 (free PPh3) ppm. 13CNMR (-90°C): 274.6 (& = 7 Hz, p-CO); 212.7 (‘& = 44 Hz, CC(O)CH,) ; 204.1 (Jcr = 10 Hz, 2 CO’s); 199.6 (br, 6CO’s); 193.5 (Jcr = 29 Hz, ‘JcC = 42 Hz, CC(O)CH,) ; 183.4 (dissolved CO) ; 31.4 (CC(O)CH,) ppm. The methyl carbon was unenriched in these experiments ; thus the signal was too weak to discern any associated 13C-13C coupling satellites. IR(vco, THF) :’ 2065(vw), 2035(m), 1982(vs), 1947(sh), 1916(w), 1655(w). There was also a small resonance at 203.3 ppm that was assumed to be an impurity. Reaction of 1 with a five-fold excess of PPh, for two days led to an approximately 1: 1 mixture of 3 and a species with an ‘H NMR resonance at 2.45 ppm, tentatively assigned to a bis-phosphine adduct. Synthesis
and
characterization
of
[PPN12[Ru3
~~~~,~~-~~~,~~~-~‘-~~~(~~~~,)I, 7 A 150 mg sample of [PPN] [RuJ(CO)&-CO) (p3CC(O)CH,)] was dissolved in 2 cm3 of THF. Eight drops of 4 M KOH in methanol solution was added with stirring, at which point the colour of the solution had changed from yellow to red-orange. A solution of 0.2 g of [PPN]Cl in 2 cm3 of methanol was added to the solution, followed by 10 cm3 of Et,O. A red oil was produced, which was separated from the supernatant and extracted into THF. Filtration and addition of diethylether produced 140 mg (69%) of 7 as a yellow powder. Anal. Calc. (found) for Cs4H,01,,P,N2Ru3 : C, 59.70 (59.12) ; H, 3.82 (3.97); P, 7.34 (5.57); Ru, 17.96 (17.75). IR (vco, Nujol): 1988(w), 1932(vs), 1886(m), 1869(m), 18OO(vw), 1741(s). ‘H NMR (CD&, 25°C): 1.46 (lH, CHC(O)CH,); 1.45 (3H, CHC(O)C&) ppm. “C NMR (CD&I,, - 80°C) : 281.2, 268.9 (2 : 1, pCO’s) ; 216.1 (‘JcC = 49 Hz, CHC(O)CH,) ; 207.7, 206.6,205.9,202.7 (2 : 1 : 2 : 1, CO’s) ; 56.1 (‘Jcc = 49 Hz, CHC(O)CH,) ppm. In the proton coupled spectrum the 56.1 ppm peak is split into a doublet, ‘J,-n = 140 Hz. In the ‘H NMR spectrum of 13C-enriched [HRu~(*CO)&*CO)~(~~-$*CH*C(O)CH,)]‘-, ’ 3C satellites of 140 Hz are observed on the 1.46 ppm resonance. Addition of
successive aliquots of HBF4 * Et20 to a sample of 7 in a CD& solution in an NMR tube generates [HRu~(CO)&~-$-CHC(O)CH~)]and H2Ru3 (CO),&3-$-CHC(0)CH3) sequentially, as determined by ‘H NMR. Complex 7 was also produced by addition of K-selectride to a solution of 1 in THF (identified by IR), or alternatively by addition of a LiMe solution to [HRu,(CO)&,-CCO)]in Et,0 at - 78°C. In the latter case the product 7 was identified by IR and ‘H NMR spectroscopy. Acknowledgement-This research was supported by the NSF Synthetic Inorganic and Organometallic Chemistry program.
REFERENCES 1. M. J. Sailor and D. F. Shriver, Organometallics
1985,
4, 1476. 2. M. J. Sailor, C. P. Brock and D. F. Shriver, J. Am. Chem. Sot. 1987,109,6015. 3. M. J. Went, M. J. Sailor, P. L. Bogdan, C. P. Brock and D. F. Shriver, J. Am. Chem. Sot., in press. 4. J. W. Kolis, E. M. Holt, M. A. Drezdzon, K. H. Whitmire and D. F. Shriver, J. Am. Chem. Sot. 1982, 104,6134. 5. J. W. Kolis, E. M. Holt and D. F. Shriver, J. Am. Chem. Sot. 1983,105,7307. 6. D. Seyferth, G. H. Williams and C. L. Nivert, Znorg.
Chem. 1977,4,758. 7. J. B. Keister and T. L. Horling, Znorg. Chem. 1980, 19,2304. 8. J. S. Holmgren and J. R. Shapley, Organometallics 1984, 3, 1322. 9. A. C. Sievert, D. S. Strickland, J. R. Shapley G. R. Steinmetz and G. L. Geoffroy, Organometallics 1982, 1, 214. 10. (a) A. M. Crespi and D. F. Shriver, Organometallics 1986, 5, 1750 ; (b) A. M. Crespi, M. J. Went, S. S. Sunshine and D. F. Shriver, Organometallics 1988, 7, 214.
11. P. L. Bogdan. Ph.D. Thesis, Northwestern University (1987). 12. S. Ching, M. Sabat and D. F. Shriver, J. Am. Chem. Sot. 1987,109,4722.
13. J. W. Kolis, E. M. Holt, J. A. Hriljac and D. F. Shriver, Organometallics 1984, 3, 496. 14. (a) J. A. Hriljac, P. N. Swepston and D. F. Shriver, Organometallics 1985,4, 158 ; (b) J. A. Hriljac, E. M. Holt and D. F. Shriver, Znorg. Chem. 1987,26,2943. 15. M. J. Sailor, M. Sabat and D. F. Shriver, Organometallics, in press. 16. (a) E. D. Morrison, G. R. Steimnetz, G. L. Geoffroy, W. C. Fultz and A. L. Rheingold, J. Am. Chem. Sot. 1984,106,4783 ; (b) E. D. Morrison and G. L. Geoffroy J. Am. Chem. Sot. 1985,107,3541. 17. D. F. Shriver and M. A. Drezdzon, Manipulation of Air-Sensitive Compounds, 2nd edn. John Wiley, New York (1986).
C-C
0277-5387/M S3.00+.00 Q 1988 PagaInan press plc
1988
AND C-H BOND FORMATION IN THE CHEM.ISTRY OF TRIRUTHENIUM CLUSTERS M. J. SAILOR
and D. F. SHRIVER*
Department of Chemistry, Northwestern
University, Evanston, IL 60208, U.S.A.
(Accepted 5 November 1987) Abstract-The p3-acetyl cluster [Ru~(CO),~~-CO)@,-CC(O)CH~)]- (l), readily adds CO to produce the acylketene clusters [Ru~(CO)~@-CO)&~-~~-CH~C(O)CCO)]- and under moderate CO pressures a mobile equilibrium is established between these two species. The phosphine-substituted acetyl cluster [Ru3(CO)8~-CO)(PPh3)(~3-CC(0)CH3)]does not add CO under conditions in which the parent cluster 1 does. The acetyl cluster 1 also reacts with H- or OH-, to produce the complex [Ru~(CO)&CO)~(~~-~~-CHC(O)CH~)]~--, which has been characterized spectroscopically. Mobile C-C and C-H formation is characteristic of these three-metal cluster systems and it is attributed to the variety of multi-site ligandmetal interactions that are possible with a three-metal ensemble.
Recently an extensive chemistry has been observed for the ketenylidene ligand, CCO, in a variety of three-metal clusters, and in particular for anionic ketenylidenes such as [Ru3(CO)&CO),(~,CCO)]2-.‘-5 Several routes to cationic, neutral and anionic ketenylidenes have been devised.‘-” The generation of the CC0 group in these clusters can be described formally as the coupling of a clusterbound carbide atom with a CO molecule. Furthermore, in the anionic ketenylidene clusters the CO group is readily displaced. Thus reaction with alkylating agents,2-5 nucleophiles,i2 or electrophilic metal complexes’3*‘4 can result in scission of the C-C bond of CCO, eqs (l)--(3).
ter [Ru~(CO),~-CO)~~~-~~-CH~C(O)CCO)](2). This compound exists in equilibrium with [Ru~(CO)&~-CO) @3-CC(0)CH3)]- (1) under a CO atmosphere, eq. (4).i5 The acylketene complex 2 reverts to 1 on removal of the CO atmosphere, and it was previously characterized in situ by twodimensional 13C NMR spectroscopy on a highly 13C-enriched sample. I5 In this report we describe some of the factors involved in this C-C bond forming reaction, as well as a related reaction involving C-H bond formation on complex 1.
RESULTS
AND DISCUSSION
[Fe3(C0)9(~3-CCO)]2- + CH3I -,
R&Oh&-CCH3)1-
[CoFe2(C0)9(p3-CCO)]- + PMe3 + [CoFe2(CO)9(~3-CPMe3)]- + CO
(2)
[Fe3(C0)9(~3-CCO)]2- + Cr(C0)3(NCCH3)3 + [CrFe3C(C0),3]2-.
Although the formation of the acylketene moiety 1, an isotopic tracer experiment has shown that the ketenyl CO is derived from an originally clusterbound CO ligand rather than the external carbon monoxide.” Similar CO-insertion reactions have been observed in several osmium carbonyl clusters containing the p-CH2 group.i6 In an attempt to elucidate the factors responsible for the formation of the unusual acylketene cluster 2 of eq. (4), we investigated the reaction of 1 with other ligands. Treatment of the acetyl cluster 1 with PPh3 does not lead to the phosphine-substituted analogue of 2. Rather, simple substitution of phosphine for CO occurs. Thus, reaction of PPh, with 13C-enriched
(1) of 2 is observed on the addition of CO to
(3)
The above reactions demonstrate that the CO of CC0 can be quite labile in these clusters. An unusual example of the lability of the CO moiety of CC0 is provided by the acylketene clus-
*Author to whom correspondence should be addressed.
955
956
M. J. SAILOR
and D. F. SNRZVER
(4)
PPk,
~Ru~(C~)~(~L~-CO)(~~-~C(~)CH~)~in CD2Clz in a sealed NMR tube rcsuhs in a i3C NMR signal for free CO at 183.4 ppm and ~sana~c~s that have been assigned to the phosphine”subst~t~t~ acety~m~thy~id~e cluster 3, eq. (5), Additionally, when a soi~~on of ERu3(Co),(Ct-Co)(PPh~)~~~ C~~)~H~)~- (3) is placed under an atmosphere of CO, we see no s~ctroscopic evidence for reaction. These rest&s suggest that the forward reaction represented by eq. (4) is less favoured for the phospbi~~-subsisted cluster 3 than for the carbony1 complex 1. Similar results are ob~~ned with P(~~~)~ We have pre~ously reported that Hz will also react with [Rn1(~)~(~3-~~)~~~GC(Q)CW3)J-.” Addition of Hz to 1 results in loss of one CO ligand bond, eq. (6). and fo~atio~ of a ear~n-bydro crayon (6) is similar to eq. (4) because in the course of the reaction the oxygen atom of the acetyl
ligand enters into an interaction with the metals, at the expense of a rne~~r~n interaction. The 0 + Ru bonding a~a~~rn~nt apparently is ~rn~~nt in the 6-C and C-H bond foxing recross of use trcatme~t of either of the eqs (4) and (6), products with C~~~S~~~F~ results in ajkylatio~ of the acetyl oxygen atom and d~srup~o~ of the C---C or C-H bond, Znboth cases a ~ny~idene ch&cr is produced (Scheme 1).15 A ~~-~~-C~C(~)C~~~~ga~dcan also be generated by reaction of [Ru~(CO}~~~-CO)(~~c13”cc(o)cH311~ with hyd~de or hydroxide, eq. (7). The di~egati~e compIex 7 has been cbaracte~zed spectroscopically* The con~gnrat~o~ of the cappmg ligand was established by r3C and “H NMR spectra of a sample of 7 that was enriched with s3C.The NMR data are s~rn~zed and compared to two related, previousIy ~~~ac~e~ clusters co~ta~n~~gthe j+-#CHC(0)CHi, liga~d in Table 1. Although the ‘I-f
Chemistry of triruthenium
,o
W,
957
clusters
l-
C’
I
(CO),
2
CH,C
CH,’ i H,C\
CHs
$-OCHa
P 1 (CO), RGpi” ‘Rd (co);
,0-CH3 C
(CO),
’ H (CO),
5
6 Scheme 1.
NMR signal of the unique proton in the CHC(0)CH3 ligand of 7 is more than 2 ppm upfield of the corresponding resonances of the complexes [HRu~(CO),(~~-$-CHC(O)CH~)](8) and H2Ru3 (CO)&-q’-CHC(O)CH,) (9), the associated ‘JcH coupling constant is comparable. The high-field ‘H NMR shift for the unique proton in 7 may be a reflection of the CO ligand disposition, which is
different in 7 than in either of the other two clusters 8 or 9. Although the anionic and neutral complexes [HRu,(CO),~~-~~-CHC(O)CH~)]-~~~H~R~~(CO), (p3-q2-CHC(0)CH3) contain only terminal CO ligands, the IR and 13CNMR data indicate that dinegative [Ru~(CO),~-CO),~~-~~-CHC(O)CH~)]~contains three bridging carbonyl ligands. Presumably the carbonyl ligands of 7 more effectively
1
2-
(7) -
HZ OH-
7
1
Eq. 7
958
M. J. SAILOR and D. F. SHRIVER Table
1. 13C and
‘H NMR shifts and coupling pj-q*-CHC(0)CH3 ligand”
constants
for the
Me
I
13CNMR (ppm) C, C,
Compound
[Rus(W,(L)1*[HRu,(CO),(L)]-b H,Ru,(CO),(L)”
56.9 77.5 74.3
216.1 230.7 239.5
‘H NMR @pm) H, Me 1.46 4.03 4.16
‘J (HZ) C,-C, C,-H,
1.45 1.79 1.99
49 46 43
140 141 143
“L is defined as the p3-q*-C,H,C@(O)Me group. All measurements in CD2C12solution on ‘3C-enriched complexes. ‘Ref. 15.
shield the unique proton, resulting in the higherfield ‘H NMR resonance. With respect to the carbonyl ligand disposition, the isoelectronic series of p3-I$-CHC(0)CH3 clusters 7,8 and 9 is similar to the series of ketenylidene clusters H2Ru3(C0)&.+CCO), ~Ru3(C0).&CCO)]- and [Ru~(CO)~~-CO)~@~-CCO)]~-.~ Presumably the presence of the bridging carbonyl
I
I
280
I
made
groups in the dinegative compounds partially alleviates the high negative charge in these complexes. A set of variable-temperature 13CNMR spectra in the CO-region of 7 is presented in Fig. 1. The lowtemperature spectrum indicates that the molecule possesses a mirror plane that contains the p3-$CHC(0)CH3 ligand (excluding the methyl hydrogens from consideration), a bridging CO, two ter-
I
1
270
210
I
1
200
PPm Fig.
1. Variable-temperature r3C NMR spectrum (100.58 MHz) of [Ru~(CO)&-CO)~&~-~*CHC(O)CH,)]‘-, 7, showing the carbonyl ligand fluxionality.
Chemistry of triruthenium clusters
959
(8) CH,' -
Eq. 8 minal carbonyl ligands and a ruthenium vertex. On barrier to C-C and C-H bond formation and raising the temperature, exchange between all but cleavage is apparently very low. one of the carbonyl ligands becomes fast on the NMR timescale, as evidenced by the broadening of EXPERIMENTAL all but one of the 13C NMR signals for the CO ligands. The unique CO ligand is presumed to be General tram to the 0 + Ru interaction, in line with the All manipulations were carried out under a dry previous interpretation of the VT-13C NMR spectra dinitrogen atmosphere using standard Schlenk and of 8.1S As might be expected, the compounds [HRu3 syringe techniquesI or in a Vacuum Atmospheres (CO)&,-~2-CHC(0)CH3)](8) and H2Ru3 (CO), drybox. Solvents were distilled from the appro@3-q2-CHC(0)CH3) (9) can be synthesized from priate drying agents before use: CH2C12 and [Ru~(C~>,~L-C~)~(~~-~~~_CHC(O)CH~)I~(7) by CD2C12 from P205 ; THF and Et,0 from sodium successive protonation. It is interesting that ad- and benzophenone. The compounds [PPN] [Ru, dition of hydride or hydroxide to 1 results in C-H (C~)~~L~-CO)(CL~-CC(O)CH~)I, [PPNI lBRu3 (CO), (p3-CCO)] and 13C-enriched [PPNl[Ru, (*CO)&,bond formation to generate 7, but that subsequent *CO)(p3-*C*C(0)CH3)] were prepared as deaddition of H+ to 7 occurs at the metal framework rather than the carbon atom. Thus the p3-q2- scribed previously.2 Potassium tri-secbutylboroCHC(0)CH3 moiety is apparently a relatively stable hydride (“K-selectride”, 1.0 M solution in THF, ligand. Another indication of the stability of the Aldrich) and methyllithium (low-halide 1.4 M p3-$-CHC(0)CH3 group is that the cluster solution in Et,O, Aldrich) were used as received. [Ru~(CO),&CO),(~~-?Z_CHC(O)CH~>~’- can also Elemental analyses were performed by Elbach be synthesized by reaction of the ketenylidene clus- Analytical Laboratories. Infrared spectra were obtained on Nicolet 7199 ter [HRu3(C0)&-CCO)]with LiCH3, eq. (8). In Fourier transform or Perkin-Elmer 283 infrared reaction (8) the CH; group is presumed to attack the carbonyl carbon of the CC0 ligand to form a spectrometers. Multinuclear NMR spectra on ‘H, pL,-acetyl ligand. In the course of the trans- 31Pand 13Cwere obtained on either JEOL FX-270 formation, the metal-bound hydride migrates to the or Varian XL-400 NMR spectrometers, and were apical carbon atom of the former pj-CCO ligand. referenced to residual solvent protons, external Apparently, in these anionic clusters the pL3-q2- 20% H3P04 in D20, or the 13CNMR signal of the CHC(0)CH3 ligand is favoured over a p3- solvent carbon atoms, respectively. Unless otherwise noted, the i3C NMR data reported are on 13CCC(0)CH3 moiety. enriched materials. The data for Jcc reported were measured from the i3C-13C satellite peaks from CONCLUDING REMARKS samples ca 30% enriched with i3C. Note that the 13C-enriched starting material [Ru~(*CO)&~In this work we have discussed two related pro*CO)(p3-*C*C(0)CH3)]- was not enriched at the cesses involving the activation of a cluster-bound carbon atom and these can be systematized by the methyl carbon. following formal description. In the pJ-acetyl cluster [Ru~(CO)~(~~-CO)(~&C(O)CH~)]-, the replaceSynthesis and characterization of [PPN] [Ru, ment of a carbon-to-ruthenium bond with an 0 --* (CO),(PPh3)OL3-CC(O)CH3)1,3 Ru interaction can be considered to generate an A 30 mg sample of [PPN][Ru,(*CO),b,“unsaturation” at the capping carbon atom. The carbon can either couple with H to form a p3-q2- *CO)@3-*C*C(0)CH3)] (* denotes 13Cenrichment CHC(0)CH3 ligand, or with CO to form a p2-q2- of ca 20%) and a 6 mg sample of triphenylCH,C(O)CCO moiety. In these anionic clusters, the phosphine, were loaded into a 5 mm NMR tube
960
M. J. SAILOR and D. F. SHRIVER
fitted with a concentric Teflon valve. Approximately 0.5 cm3 of CD,Cl, was vacuum transferred into the tube at liquid nitrogen temperature. ‘H NMR (taken 15 min after sealing and warming the NMR tube) : phenyl protons (PPh3 and [PPN]+) ; 2.41 (s, CH3 of 3) ; 2.36 (s, CH3 of 1) ; 1.87 (s, CH3 of 2) ppm. After 8 h the signals for 1 and 2 had almost disappeared and the only detectable product was species 3. 31P NMR: 35.95 (PPh, of 3); 21.54 ([PPN]+) ; - 5.12 (free PPh3) ppm. 13CNMR (-90°C): 274.6 (& = 7 Hz, p-CO); 212.7 (‘& = 44 Hz, CC(O)CH,) ; 204.1 (Jcr = 10 Hz, 2 CO’s); 199.6 (br, 6CO’s); 193.5 (Jcr = 29 Hz, ‘JcC = 42 Hz, CC(O)CH,) ; 183.4 (dissolved CO) ; 31.4 (CC(O)CH,) ppm. The methyl carbon was unenriched in these experiments ; thus the signal was too weak to discern any associated 13C-13C coupling satellites. IR(vco, THF) :’ 2065(vw), 2035(m), 1982(vs), 1947(sh), 1916(w), 1655(w). There was also a small resonance at 203.3 ppm that was assumed to be an impurity. Reaction of 1 with a five-fold excess of PPh, for two days led to an approximately 1: 1 mixture of 3 and a species with an ‘H NMR resonance at 2.45 ppm, tentatively assigned to a bis-phosphine adduct. Synthesis
and
characterization
of
[PPN12[Ru3
~~~~,~~-~~~,~~~-~‘-~~~(~~~~,)I, 7 A 150 mg sample of [PPN] [RuJ(CO)&-CO) (p3CC(O)CH,)] was dissolved in 2 cm3 of THF. Eight drops of 4 M KOH in methanol solution was added with stirring, at which point the colour of the solution had changed from yellow to red-orange. A solution of 0.2 g of [PPN]Cl in 2 cm3 of methanol was added to the solution, followed by 10 cm3 of Et,O. A red oil was produced, which was separated from the supernatant and extracted into THF. Filtration and addition of diethylether produced 140 mg (69%) of 7 as a yellow powder. Anal. Calc. (found) for Cs4H,01,,P,N2Ru3 : C, 59.70 (59.12) ; H, 3.82 (3.97); P, 7.34 (5.57); Ru, 17.96 (17.75). IR (vco, Nujol): 1988(w), 1932(vs), 1886(m), 1869(m), 18OO(vw), 1741(s). ‘H NMR (CD&, 25°C): 1.46 (lH, CHC(O)CH,); 1.45 (3H, CHC(O)C&) ppm. “C NMR (CD&I,, - 80°C) : 281.2, 268.9 (2 : 1, pCO’s) ; 216.1 (‘JcC = 49 Hz, CHC(O)CH,) ; 207.7, 206.6,205.9,202.7 (2 : 1 : 2 : 1, CO’s) ; 56.1 (‘Jcc = 49 Hz, CHC(O)CH,) ppm. In the proton coupled spectrum the 56.1 ppm peak is split into a doublet, ‘J,-n = 140 Hz. In the ‘H NMR spectrum of 13C-enriched [HRu~(*CO)&*CO)~(~~-$*CH*C(O)CH,)]‘-, ’ 3C satellites of 140 Hz are observed on the 1.46 ppm resonance. Addition of
successive aliquots of HBF4 * Et20 to a sample of 7 in a CD& solution in an NMR tube generates [HRu~(CO)&~-$-CHC(O)CH~)]and H2Ru3 (CO),&3-$-CHC(0)CH3) sequentially, as determined by ‘H NMR. Complex 7 was also produced by addition of K-selectride to a solution of 1 in THF (identified by IR), or alternatively by addition of a LiMe solution to [HRu,(CO)&,-CCO)]in Et,0 at - 78°C. In the latter case the product 7 was identified by IR and ‘H NMR spectroscopy. Acknowledgement-This research was supported by the NSF Synthetic Inorganic and Organometallic Chemistry program.
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