178
Organometallics 1986, 5 , 178-180
and PI6 isomer ( p = Wl0, WI1, WIz as shown). The physical properties of CpTi.SiWgV3O4t-further indicate the strong, covalent CpTi3+ attachment to the close-packed, surface oxygens of SiWgV30,,7-. Although CpTi(CH3CN),(N03), is quite sensitive to even atmospheric moisture, once supported, CpTi43iWgV30404-is stable to the atmosphere for >1 month either in the solid state or in CH,CN solution (by solution 51V and la3W NMR). An orange CH3CN solution of ( B ~ , N ) ~ [ c p T i s SiW9V3040]passes unaltered (IH NMR, IR) through a Amberlyst 15 cation-exchange column while a control shows t h a t organometallic cations like CpTi(CH3CN),3+(N03)33are retained on the top of the column. Conversely, all the color of the anionic CpTi4iWgV30404remains with an Amberlyst A-27 anion-exchange column in the C1- form, with no visible CpTiC13elution from this top band. Preliminary experiments indicate that it will be possible to prepare SiW9V3Oa7-supported TiCF+, a more reactive, better catalyst precursor, and that CpTi*P2W15V30626and CpTi.1,4,9-PWgV3O42-can be prepared;7fthese latter two complexes will allow a comparison of 1,2,3 (or A-type) vs. 1,4,9 (or B-type) trivanadium-substituted polyoxoanions. These experiments, continuing attemptsI7 at obtaining crystals of CpTi.SiW9V3O42-suitable for X-ray crystall ~ g r a p h yand , ~ ~ other experiments aimed at using polyoxoanion-supported Ti4+as Ziegler-Natta polymerization and olefin epoxidation catalysts will be reported in due course. Acknowledgment. Support from NSF Grant CHE8313459 and from Dreyfus Teacher-Scholar, Alfred P. Sloan, and Guggenheim (1984-1985) fellowships to R.G.F. are gratefully acknowledged. High-resolution fast-atombombardment mass spectra were obtained in the Mass Spectrometry Laboratory, School of Chemical Sciences, University of Illinois at Urbana-Champaign, supported in part by a grant from the National Institute of General Medical Sciences (GM27029), and with the assistance of Professor K. S. Suslick, whose help it is a pleasure to acknowledge. The ZAB-SE mass spectrometer was purchased in part with grants from the Division of Research Resources, National Institutes of Health (RR01575), the National Science Foundation (PCM 81-21494), and the National Institute of General Medical Sciences (GM27029). Supplementary Material Available: A plot of the ultracentrifugation, sedimentation equilibrium molecular weight measurement in CH&N for (BU,N)~[C~T~.S~W~V,O~] (1page). Ordering information is given on any current masthead page. (16)(a) Massart, R.; Contant, R.; Fruchart, J. M. Ciabrini, J. P.; Fournier, M. Inorg. Chem. 1977,16,2916.(b) Herv6, G.;TCz6, A.Inorg. Chem. 1977,16,2115.(c) See also ref l e and the discussion and references therein. (17) Day, V. W.; Finke, R. G.; Rapko, B., experiments in progress.
Photoinduced Ring Expansion of a Cyclobutyllron a Complex: An Example of Rearrangement of an Alkyl Group from Saturated Carbon to a Transition Metal To Give a Carbene Complex Yngve Stenstrram and W. M. Jones" Department of Chemistry, University of Florida Gainesville, Florida 326 1 1 Received September 20, 1985
Summary: Photolysis of either dicarbonyl(q5-cyclopentadienyl)( l-methoxycyclobutane-l-carbonyl)iron (8) or
its corresponding a-complex d i c a r b ~ n y I ( ~ ~ - c y c l o pentadienyl)(l-methoxycyclobuty1)iron (9) gives the rearranged carbene complex 11. The carbene complex reacts with CO at room temperature and low pressure (ca. 6.5 atm) to give the ring-contracted dicarbonyl(q5-cyclopentadienyl)(2-methoxycyclobutyl)iron(12). Photolysis of 12 regenerates the carbene complex 11. I t is suggested that these rearrangements involve both rearrangement from saturated carbon to iron to give a carbene complex and its reverse.
Theory predicts that the rearrangements generalized in the following equation should be facile.' M-C-
I
f--,
M=C
I
I
R
R
I
/
'
And, indeed, rearrangement in both directions in which hydrogen is the rearranging group are now c o m m o n p l a ~ e ~ ~ ~ as are rearrangements of both alkyl and aryl groups from metal to carbene carbon4 (rearrangement from right to left). In contrast, rearrangement of alkyl groups from saturated carbon to metal to give new carbene complexes are exceedingly rare5 and aryl rearrangement has yet to be reported. We recently reported that photolysis of 1 or 2 gives 5 for which we suggested the mechanism outlined in Scheme I.6p8 We further suggested that the driving force for this rearrangement is a combination of relief of ring strainaa (5 is less strained than 3) and stabilization of the carbene (5 is stabilized by electron donation from the methoxy more than 3), a suggestion that is consistent with Green's hypothesis that the paucity of 1,2-rearrangements of alkyl or aryl groups from saturated carbon to metals is thermodynamic in rigi in.^^^ (1)Berke, H.; Hoffmann, R. J . Am. Chem. SOC.1978, 100, 7224. Goddard. R. J.: Hoffmann. R.; Temmis, E. D. J . Am. Chem. SOC.1980, 102,7667. (2)Schrock, R. R. Acc. Chem. Res. 1979,12,98.Schultz, A. J.; Williams, J. M.; Schrock, R. R.; Rupprecht, J. A.; Fellmann, J. J. Am. Chem. SOC. 1979,101, 1593. Canestrani, M.;Green, M. L. H. J . Chem. Soc., Dalton Trans. 1982,1789. Calderon, N.;Lawrence, J. P.; Ofstead, E. A. Adu. Organomet. Chem. 1979,17,449.Foley, P.; Whitesides, G. J. Am. Chem. SOC.1979,101,2732.Empsall, H. D.;Hyde, E. M.; Markham, M.; McDonald, W. S.; Norton, M. C.; Shaw, B. L.; Weeks, B. J. Chem. SOC., Chem. Commun. 1977,589.Kemball, C. Catal. Rev. 1971,5,33.Light, J. R. C.; Zeiss, H. H. J . Organomet. Chem. 1970,21,391. Sneedon, R. P.A,; Zeiss, H. H. J. Organomet.Chem. 1971,26,101.Farady, L.; Marko, L. J . Organomet. Chem. 1972,43,51. Ahmed, K. J.; Chisholm, M. H.; Rothwell, I. P.; Huffman, J. C. J . Am. Chem. SOC.1982, 104, 6453. Chamberlain, L. R.; Rothwell, A. P.; Rothwell, I. P. J . Am. Chem. SOC. 1984,106,1847. Green, J. C.; Green, M. L. H.; Morley, C. P. Organometallics 1985,4,1302. (3)Cooper, N. J.; Green, M. L. H. J . Chem. Soc., Dalton Trans. 1979, 1121. (4)Thorn, D. L.; Tulip, T. H. J. A m . Chem. SOC.1981,103,5984. Thorn, D.L.Organometallics 1985,4,192.Hayes, J. C.; Pearson, G. D. N.; Cooper, N. J. J . Am. Chem. SOC.1981,103,4648. Jernakoff, P.; Cooper, N. J. J . Am. Chem. SOC.1984,106,3026.Hayes, J. C.; Cooper, N. J. J . Am. Chem. SOC.1982,104,5570. Threlkel, R. S.;Bercaw, J. E. J . Am. Chem. SOC.1981,103,2650. Barger, P.T.; Bercaw, J. E. Organometallics 1984,3,278.van Leeuwen, P. W. N. M.; Roobeek, C. F.; Huis, R. J. Organomet. Chem. 1977,142,243.Taggle, R. M.; Weaver, D. L. J . Am. Chem. SOC.1970,92,5523. (5)Prior to our first report6 on this subject, in only one case7 had evidence accrued for such a rearrangement and in no case had the rearranged carbene been isolated and characterized. (6)Lisko, J. R.; Jones, W. M. Organometallics 1 9 6 4 ,944. ( 7 ) Miyashita, A.; Grubbs, R. H. J. Am. Chem. SOC.1978,100,7418. (8)An alternate possibility is a photoinduced single step rearrangement from 2 to 5. However, we consider this to be unlikely in view of the results reported herein. (a) Bly (Bly, R. S.; Hossain, M. M.; Lebioda, L. J . Am. Chem. SOC.1985,107,5549) has recently suggested relief of ring strain as a driving force for rearrangement of alkyl from carbon to the carbene carbon of an iron(I1) alkylidene.
0276-7333/86/2305-0178$01.50/0 0 1986 American Chemical Society
Organometallics, Vol. 5, No. 1, 1986 179
Communications
Scheme 111'
Scheme I CP
b( - kFp ..1
c-
\
'
OMe
Fe-CO
hi
hr
G O F p
\
OMe
'
\
'
2
1
OMe
3
CY + d OMe
OMe
Fe-Cp
"//
co
12
mFp*eF;
FP
\
13
11
( i ) 6.5 a t m CO, C,D,, 25 'C, 4-50 h ; (ii) h v , C,D,, -CO; (iii) MeOH (excess), Na,CO,, 2 h.
chromatography over silica gel (230-400 mesh; methylene chloridehexane, 6040 v/v, and then ethyl acetate-hexane, 5050 v/v). 5 Photolysis of a benzene solution of 8 under a N2 atmosphere with a 450-W Hanovia medium-pressure lamp Fp.CpFe(CO)p followed by flash chromatography over silica gel (230-400 mesh; EtOAc-hexane, 1090 v/v) yielded 11 as a dark red, Scheme 11' extremely air-sensitive oil (48% isolated, 55% NMR). The OMe structure is based on MS, IR, and 'H and 13C NMR.15 The Ico2H d C O 2 H i i i , i v JCOFp most characteristic features are the relatively low-field U U U methoxy methyl (6 3.72) in the 'H NMR, the relatively 6 7 8 high-field methylene carbon (6 13.6 ppm) bonded to iron and the very low-field carbene carbon (6 344.28) in the 13C OMe NMR, the single CO resonance in the 13C NMR, and the single terminal CO absorption and the absence of bridging carbonyl in the IR. \ 9 L J OMe When photolysis of the acyl complex 8 was followed by 10 11 'H NMR, along with other resonances, a new resonance grew in at 6 3.00 and then gradually disappeared. This was ' (i) 3 equiv of L D A , THF, 25 'C, 16 h, t h e n 0,, 20 'C, 2 h ; (ii) 3 equiv of NaH, 3 equiv of MeI, THF, 36 h , assigned to the methoxy of the a-complex 9, an assignment Kugelrohr distillation; (iii) (COCI),, Et,O, 1 0 h ; (iv) KFp, that was confirmed by isolation (flash chromatography THF, 0 "C 25 'C, 1 2 h ; ( v ) h v , C,D,, -CO; (vi) over silica gel, 230-400 mesh; ethyl acetate-hexane, 10:90 [(PPh,),RhCl],, CH,CN, 50 h. v/v) from an incomplete reaction.16 The same compound was also prepared by chemical decarbonylation of 8 with Cyclobutane is nearly as strained as cyclopropanelO and [ (Ph3P)2RhC1]2.17Photolysis of the u-complex also gave the strain in 5 and 11 should be comparable. We therefore 11 as the major product. reasoned that if the rearrangement in Scheme I were To explore the reversibility of rearrangement of 9 to 11, driven by relief of strain and carbene stabilization, then a sample of the latter was dissolved in benzene-de and photolysis of the methoxycyclobutane 8 might also lead sealed in an NMR tube under 6.5 atm of CO (ca. 10 molar to rearrangement. At this time we report that this is equiv). After less than 4 h at room temperature the color indeed the case. of the solution had changed to light orange and both NMR As in the cyclopropane system? we began with the acyl ('H and 13C)and TLC indicated that a single new comcomplex 8 which was synthesized as depicted in Scheme pound had formed in practically quantitative yield.l8 To 11. Reacting cyclobutanecarboxylic acid with 3 equiv of our surprise, the new compound, which was isolated by LDA followed by O2 in a slight modification of previously flash chromatography over silica gel (230-400 mesh; ethyl published procedures" gave a quantitative yield of a-hyacetate-hexane, 20:80 v/v), was not the starting a-complex droxycyclobutanecarboxylic acid. The crude acid was but was an isomer. This isomer was characterized by methylated12to give 713in 80% overall yield. Reaction of chemical analysis, spectral characteristics, and alternate 7 with oxalyl chloride gave the acid chloride which was synthesis (Scheme 111) and is assigned structure 12.19,20 converted to the acyl complex 814in 71 70yield after flash
-
-
-+
(9)The contribution of strain relief to the exothermicity of the conversion of 3 to 4 in this mechanism is not known and, in fact, if carbocycles were used as models the change in strain would actually retard the reaction since cyclobutene is a bit more strained than cyclopropane.1° However, cyclobutene is probably a poor model and, regardless, the metallocyclopentenone 5 i$ certainly less strained than the cyclopropane in 3. (10)Greenberg, A.; Liebman, J. F. "Strained Organic Molecules"; Academic Press: New York, 1978. (11)Moersch, G . W.; Zwiesler, M. L. Synthesis 1971,647.Kouen, D. A.; Silbert, L. S.; Pfeffer, P. E. J. Org. Chem. 1975,40, 3253. (12)Stoochnoff, B. A.; Benoiton, N. L. Tetrahedron Lett. 1973,21. (13)1-Methoxycyclobutanecarboxylic acid (7):mp 68-69 "C; IR (KBr) 3200-2500, 1695,1415,1300,1230,1125,1025,945,755 cm-'; 'H NMR (100MHz, CDC1,) 6 1.8-2.5 (m, 6 HI, 3.24 (s, 3 H), 10.24 ( 8 , 1 H); 13C NMR (25MHz, CDCI,) 6 12.91 (CH,), 30.50 (CHZ X 2),52.29 (CH,O), 79.97 (C-0), 178.96 (C=O). (14)Dicarbonyl~~5-cyclopentadienyl~(l-methoxycyclobutyl-lcarbony1)iron (8): mp 52-53 OC; IR (CDCI,) 2005,1960,1640 cm-'; 'H NMR (60 MHz, C&) 6 1.1-2.4(m, 6 H), 2.85 (s, 3 H), 4.35 (s, 5 H); 13C NMR (25MHz, c& 6 11.91 (CHZ), 28.77 (CHp X 2),51.10(CH,O), 86.67 (Cp), 92.62 (C-O), 215.92 (terminal CO), 256.66 (bridging CO); mass spectrum, m / e 290 (M+),262 (M+ - CO), 234 (M+ - 2CO), 205 (FpCO+), 85 (M+ - FpCO, 100%). Anal. Calcd for C13H1,Fe04:C, 53.82;H, 4.86. Found: C, 53.87;H, 4.90.
(15)l-Carbonyl-l-(~5-cyclopentadienyl)-2-methoxy-l-ferracyclouentene (111: IR (CDCL) 1925 cm-': 'H NMR (100MHz. CD.1 6 1.6-2.6 im, 6 H); 3.67 (8, 3 H), i.26 (s, 5 Hj; 13C NMR (25MHZ, 666,) 6 13.58 (CHJ, 30.05 (CH,), 60.17 (CHZ), 64.36 (CHqO), 84.92 (Cp), 222.64 (CO), 344.28 (carbene 6);mass spectrum, m / e 234 (M'), 206 (M+ - CO), 152, 122 (FeCpH+, loo%), 121 (FeCp+). While indefinitely stable in carefully degassed solvents, removal of the solvent gives a nearly black oil that was too unstable to permit reliable elemental analyses. (16)Di~arbonyl(~~-cyclopentadienyl)( 1-methoxycyclobut-1-y1)iron(9): IR (CDCl,) 2005,1960cm-'; 'H NMR (60MHz, C6D6)6 1.1-2.4 (m, 6 H), 3.00 ( ~ , H), 3 4.22 (5, 5 H); 13CNMR (25MHz, C&) 6 15.63 (CHz),46.33 (CHZ X 2), 51.79 (CH,O), 87.36 (Cp), 95.64 (C-0),218.45 ( C O ) . The compound was too unstable for reliable elemental analyses. (17)Kuhlmann, E. J.;Alexander, J. J. J. Organomet. Chem. 1979,174, 81. (18)When the reaction was run with only 1.5 molar equiv of CO (6.5 atm), the reaction required about 50 h to reach completion but the resultant reaction mixture was the same. (19)Dicarbonyl(~5-cyclopentadienyl)(trans-2-methoxycyclobut-l-yl)iron (12): IR (CDCl3) 2000, 1945 cm-'; 'H NMR (100 MHz, C&6) 6 1.3-1.7(m, 1 H), 1.8-2.2 (m, 3 H), 2.3-2.6(m, 1 H), 3.07 ( 8 , 3 H), 3.4-3.7 (m, 1 H), 4.27 ( 8 , 5 H); 13C NMR (25 MHz, C,jD6) 6 27.22 (CHz), 28.00 (CH), 33.65 (CH,), 55.00 (CH,O), 84.92 (Cp), 88.24(CH), 217.47 (CO), 217.86 (CO); mass spectrum, m / e 262 (M+),234 (M+ - CO), 206 (M+ 2CO), 177 (Fp+),85 (M+ - FpCO, 100%). Anal. Calcd for Cl1Hl4FeO2: C, 54.99;H, 5.38. Found: C, 54.91;H, 5.41.
180
Organometallics 1986,5, 180-182 field of 7 T; therefore acknowledgment is made to the Instrument Program, Chemistry Division, National Science Foundation, for financial assistance in the purchase of the instrument.
Scheme IV
co 11
OMe
OMe
10
9
it "Fe-Cp \
\
14
cO
15
"Fe-1 l i / \
co co 12
Equally surprising, the reaction is reversible; photolysis of 12 regenerates the carbene complex 11 as the primary product. A reasonable mechanism for the interconversion of 11 and 12 is suggested in Scheme IV. The significant features and evidence to date for this mechanism are as follows: (1) The first step is a thermally induced reverse of the proposed 1,2-rearrangement,a reaction that must be occurring even in the absence of added CO since the only sensible role of the carbon monoxide is to trap 15. Evidence for this equilibrium is the finding that treatment of 11 with a trace of CD,O- in CD,OD led to rapid exchange of four ring hydrogens (followed by slower exchange of methoxide) despite the fact that only the two at C3 should be acidic. Exchange of four hydrogens would be expected if 11 were in thermal equilibrium with 10 since C3 and C5 become equivalent in the latter. (2) If 11 and 10 equilibrate at room temperature (as suggested by the deuterium exchange) but not rapidly enough for 11 to show fluxionality in the lH NMR, the maximum energy separating 10 from 11 can be no more than about 25 kcal/mol nor less than about 15 kcal/mol. (3) The equilibrium between 10 and 15 must favor the latter and/or CO attack on 15 must be faster than on 10 because 12 was observed to the exclusion of 9 (probably for steric reasons). (4) This mechanism requires exclusive trans stereochemistry in 12 which is observed. In conclusion it should be noted that conversion of 10 to 11 is the first example of rearrangement of alkyl from saturated carbon to metal in which the primary rearrangement product has been isolated. It also shows that the special bonding in the cyclopropane ring of 3 is not required for rearrangement to occur.
Acknowledgment. This work was partially supported by the National Science Foundation to whom the authors are grateful. Acknowledgment is also made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research. The support from the Norway-America Association for Thanks to Scandinavia Scholarship to Y.S. is greatly acknowledged. High-field NMR spectra were obtained on a Nicolet NT-300 spectrometer, operating at a (20) Assignment of the trans stereochemistry is based on the knownz1 trans addition of nucleophiles to Fp+ *-complexes. However the cis isomer has not been synthesized for final confirmation. (21) Davies, S.G. "OrganotransitionMetal Chemistry: Applications to Organic Synthesis";Pergamon Press: New York, 1982; pp 128-135. Lennon, P.; Madhavarao, M.; Rosan, A.; Rosenblum, M. J. Organomet. Chem. 1976, 108.93. (22) Careful examination of the 'H NMR from photolysis of 8 reveals the growth and decline of a small resonance correspondingto the methoxy methyl of 12, which could also be isolatad in small quantities as an impure sample from an incomplete reaction mixture.
Regiospeclflc Reactions of Cobalt-Rhodium Mixed-Metal Clusters. Unprecedented, Facile and Reversible Tetranuclear-Dlnuclear Transformations Invoking Diphenylacetylene and/or Carbon Monoxide Istvh 1. Horvbth" Department of Industrial and Engineering Chemistry Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zurich, Switzerland
LBszld Zsolnai and Gottfrled Huttner FakuM fur Chemie der Universitat Konstanz Postfach 5560 0-7750 Konstanz, Federal Republic of Germany Received October 2, 1985
Summary: Co,Rh,(CO),, (1)reacts with alkynes (RC,R, R = C6F5(2a), R = Ph (2b)) via specific insertion into the cobalt-cobalt bond to give CO,R~,(CO),,(~,-~~-RC,R) (3a,b). 3a was characterized by a single-crystal X-ray diffraction analysis: space group P2,lc (No. 14), a = 11.286 (8) A, b = 17.37 (1) A, c = 16.65 (1) A, fl = 126.32 ( 5 ) O , V = 2630 (5) A3, Z = 4, D,,, = 2.43 g l cm3. A total of 2479 reflections ( I 1 20) of 3215 reflections were used to give RF = 5.2% and RFz = 5.6%. Reaction of 3a with CO and 2a results in regiospecific fragmentation to give COR~(CO),(I.L-~*-F,C~~*C~F~) (4a) exclusively. 3b undergoes facile, reversible, and regiospecific fragmentation when treated with PhC2Ph(2b) and carbon monoxide to give C O R ~ ( C O ) ~ ( ~ - ~ ~ - P(4b). ~C,P~) Medium-pressure in situ IR studies have revealed that 3b reacts with carbon monoxide in a reversible and regiospecific reaction to give the 1:l mixture of CoRh(CO), (5) and 4b.
The chemistry of mixed-metal cluster compounds is of current interest.' The reactions of mixed-metal clusters and alkynes can result in either substitution or degradation of the cluster to lower nuclearity complexes.2 Two interesting questions arise. First, at which site does the substitution take place, and second, what is the metal distribution in the fragmentation products. Reversible fragmentation of transition-metal clusters involving ligand addition and elimination is rarely observed, and the few studied examples are limited to clusters containing only carbonyl and hydride ligand^.^ We now wish to report a facile, reversible, and regiospecific frag(3a) affected mentation of Co2Rh2(CO)lo(~4-~z-PhCzPh) by diphenylacetylene and/or carbon monoxide. The reaction of Co2Rhz(CO)lz(lI4 and 1equiv of alkyne (1) Gladfelter, W.L.;Geoffroy, G. L. Adu. Organomet. Chem. 1980, 18, 207. Roberts, D. A.; Geoffroy, G . L. In "Comprehensive Organometallic Chemistrv":Wilkinson. G.. Stone. F. G. A.. Abel.. E... Eds.:. Pergamon Press: ELsford, NY, 19821 Chapkr 40. (2) Sappa, E.;Tiripicchio,A.; Braunstein, P. Chem. Reu. 1983,83,203. (3) Whyman, R. J. Chem. SOC.,Dalton Trans. 1972,1375. Whyman, R. J . Chem. SOC.,Chem. Commun. 1970, 1194. Ungvbry, F. J . Organomet. Chem. 1972,36,363. Oldani, F.; Bar, G. J. Organomet. Chem. 1983, 246, 309.
0276-7333/86/2305-0180$01.50/0 0 1986 American Chemical Society
