110
Organometallics 1986, 5 , 110-113
Excitation Wavelength Dependence of Photodissociation and the Secondary Laser Pulse Photolysis of Dimanganese Decacarbonylt Takayoshi Kobayashi, la Hiroyuki Ohtani,'avdHisanao Noda,lbShosuke Teratani," Hiroshi Yamazaki,lb and Katsutoshi Yasufukulc Department of Physics, the University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan, Institute of Physical and Chemical Research, Wako-shi, Saitama 35 1, Japan, and Tokyo Gakugei University, Koganei-shi, Tokyo 184, Japan Received May 22, 1985
The transient spectroscopy technique was applied for the determination of the quantum yields for the following two processes, and their dependences on the excitation wavelength were found. The quantum yield for process I, Yl,increases with the excitation wavelength while that of process 11, Yz,decreases. The ratio R = Y l / Y 2obtained for different excitation wavelengths (Aex) is as follows: R = 0.19 f 0.05 (Aex = 266 nm), R = 0.43 f 0.02 (Aex = 337 nm), and R = 1.1f 0.2 (Aex = 355 nm). The sum of Yl and Y2were
€ €
(I)
2.Mn (C0)5
MnZ(CO),o
MnZ(CO),
MnZ(C0)g
+
CO
(111
.Mn(C0)5 t .Mn(C0I4
(111)
Mn2(CO)e t CO
(IV)
found to be unity for 355-, 337-, and 266-nm excitations. These results =e discussed in terms of the properties of their excited states. Using two Q-switched Nd:YAG lasers, the following successive photolysis of Mn2(CO)9 by the second pulse was found to result in further CO elimination (process IV).
Introduction The photochemistry of Mn,(CO),o in solution has been studied by a number of groups and is generally taken as a prototype for photoreactions of organometallic compounds containing metal-metal bond^.^-^ However, recently two primary photochemical reaction pathways in the photolysis of Mnz(CO)lo have been established: metal-metal bond cleavage to produce .M~I(CO)~ radicals (eq 1)and dissociativeloss of CO to give h4r1,(CO)~without metal-metal bond cleavage (eq 2 ) . These have been
[CpFe(CO)z]Z1l and R U ~ ( C O ) , ~ . ' ~ ~ ~ ~ In this paper, we report the first known real-time measurement of the branching ratio between the two processes 1 and 2 at different excitation wavelengths by means of nanosecond spectroscopy. Furthermore double-flash experiment on Mn2(CO)loin cyclohexane is reported to clarify the photochemistry of the ligand-unsaturated intermediate Mn2(C0)9.In the double-flash study, the first flash (355 nm, 5-ns fwhm) is used to produce Mnz(C0)9 and ~ M n ( c 0and ) ~ the second flash (532 nm, 20-ns fwhm) is used to excite Mnz(CO)g.
(1)
2.Mn(C0)5
Experimental Section Materials. Mnz(CO)lowas synthesized by the method deand purified by sublimation. Cycloscribed in the literat~re'~ demonstrated by flash photolysis with UV-vis detectionk7 hexane stored on a K-Na alloy was volumetrically added to the or IR detection8 and by conventional photolysis in lowsample compartment in vacuo. The sample solutions were detemperature mat rice^.^ The IR spectroscopic s t u d i e ~ ~ * ~ have revealed that Mnz(CO)ghas an unsymmetrically (1) (a) Departmentof Physics, the University of Tokyo. (b)Institute bridged CO in solvents which have no coordinating ability. of Physical and Chemical Research. (c) Tokyo Gakugei University. (d) Visiting research fellow from Hamamatsu Photonics K.K. to the DeIn the framework of a simple one-electron diagram of partment of Physics, the University of Tokyo. the dinuclear metal carbony1,'O M2(CO)lo,the photoexci(2) Geoffroy, G. L.; Wrighton, M. S. "Organometallic Photochemistry"; tation of a metal-metal bonding (a)electron to the antiAcademic Press: New York, 1978. Geoffroy, G. L. J. Chem. Educ. 1983, 60, 861. bonding u* orbital results in metal-metal bond cleavage (3)Wegman, R. W.; Olsen, R. J.; Gard, D. R.; Faulkner, L. R.; Brown, (eq 1). However, as these findings show, the u o* exT. L. J . Am. Chem. SOC. 1981,103,6089. citation also causes dissociation of the metal-CO bond (eq (4)Wrighton, M. S.;Ginley, D. S. J. Am. Chem. SOC.1975,97,2065. 2) as well as process 1. Thus, it is of great interest to study (5)Yesaka, H.; Kobayashi, T.; Yasufuku, K.; Nagakura, S. Reza Kagaku Kenkyu 1981,3,97;J . Am. Chem. SOC.1983,105,6249. the effect of excitation wavelength on the two primary (6)Rothberg, L. J.; Cooper, N. J.; Peters, K. S.; Vaida, V. J . Am. processes. Only two reports have appeared so far on the Chem. SOC.1982,104, 3536. dependence of wavelength on quantum yields for CO (7) Herrick, R. S.; Brown, T. L. Inorg. Chem. 1984,23,4550. (8)Church, S.P.; Herman, H.; Grevels, F.-W.; Schaffner, K. J. Chem. photodissociation and metal-metal bond cleavage in Mnn(C0)io
h
v
l
(2)
MnZ(CO)g t CO
-
+Thiswork was supported in part by a Grant-in-Aid from the Ministry of Education, Science and Culture of Japan, Toray Science and Technology Foundation, and Kurata Science Foundation to T.K. This work was in part supported by grants of "Solar energy conversion by means of photosynthesis" given to Riken (IPCR) by the Science and Technology Agency.
0276-7333/86/2305-0l10$01.50/0
SOC.,Chem. Commun. 1984,785. (9) Hepp, A. F.; Wrighton, M. S. J . Am. Chem. SOC.1983,105,5934. (10) Levenson, R. A.; Gray, H. B. J . Am. Chem. SOC.1975,97,6042. (11) Tyler, D. R.; Schmidt, M. A,; Gray, H. B. J . Am. Chem. SOC. 1983, 105,6018. (12)Malito, J.; Markiewicz, S.; Poe, A. Inorg. Chem. 1981,21, 4337. (13)Desroslers, M. F.;Ford, P. C. Organometallics 1982, I , 1715. (14)King, R. B.;Stokes, J. C.; Korenowski, T. F. J. Organomet. Chem. 1968,11, 641.
0 1986 American Chemical Society
Organometallics, Vol. 5, No. 1, 1986 111
Photolysis of Dimanganese Decacarbonyl
Table 1. Quantum Yields of Processes 1 and 2, Y , and Y 2 , Respectively, and t h e Excitation Wavelength ha,!' h.,/nm 266 337 347c 355 PM
L
F
L SC
5 L
F LAMP
Figure 1. Block diagram of nanosecond time-resolved spectroscopy apparatus. The symbols for the abbreviation are as follows: TRG, main trigger circuit; DL, digital delay circuit; BS, beam splitter; F, filter; M, mirror; L, lens; S, mechanical shutter; SC, sample cell; MC, monochromator; PM, photomultiplier; TR, transient recorder; I/O, input/output unit; FD, floppy disk driver; $2, microcomputer; PLT, X-Y plotter.
Atb 5 ns 10 ns 25 ps 5 ns
solvent cyclohexane cyclohexane ethanol cyclohexane
Y,
YZ
0.16 f 0.02 0.30 f 0.02 0.33d 0.49 f 0.05
0.84 f 0.10 0.70 f 0.00 0.67d 0.44 f 0.03
'Reference 20. Excitation pulse width (fwhm). Reference 6. dCalculated on the assumption that their sum of Y , and Yz is equal to unity.
ciation processes of Mn2(CO)loin cyclohexane. The absorbance with A, at 800 nm is due to the photogenerated radicals which decay in the following recombination process (1B). The second-order rate constant, kl, in cyclo-
kl
0.04 .
I
2.Mn(CO),
.
0 02
0.00
1 ~~
400
500
600
700
800
Wavelength/ nm
F i g u r e 2. Transient difference absorption spectra of Mnz(CO)lo in cyclohexane 3 (open circles) and 30 c(s (closed circles) after excitation. Excitation wavelengths are 355 (top) and 266 nm (bottom). gassed after five freeze-thaw cycles and were hermetically sealed. Then, Ar or CO gas was admitted through a side arm with a Teflon stopcock. Excitation Wavelength Dependence on the Q u a n t u m Yield. A nanosecond spectroscopic experiment was performed at 20-22 "C with the fourth (266 nm, 5-11s fwhm, 0.1 MW) and third (355 nm, 5-11s fwhm, 0.4 MW) harmonics of a Q-switched Nd:YAG laser (Quanta-Ray, DCR-1A). T h e concentrations of Mnz(CO)loin cyclohexane are 8 X mol dm-3 for the 266-nm excitation and 4 x mol dm-3 for the 337- and 355-nm excitations. T h e intensity of the probe light was detected with a photomultiplier (Hamamatsu Photonics, R666S), and the output signal of the photomultiplier was digitized with a transient recorder (Iwatsu, DM901) and was averaged with a microcomputer (NEC, PC8001). Double-Flash Experiment. The excitation light sources of the first and the second flashes are a third harmonic (355 nm, 5-ns fwhm, 0.4 MW) of the $-switched Nd:YAG laser (QuantaRay, DCR-1A) and a second harmonic (532 nm, 20-11s fwhm, 0.6 MW) of a Q-switched Nd:YAG laser (Quantel, YG472), respectively. The time interval of the two excitation light pulses was adjusted by a digital delay circuit with a time resolution of 10 ns.I5 Figure 1 shows the block diagram of the nanosecond time-resolved double-flash excitation apparatus. The two excitation beams are colinear t o each other.
Results and Discussion Excitation Wavelength Dependence. Figure 2 shows the excitation wavelength dependence on the photodisso(15)Kobayashi, T.; Koshihara, S. Chem. Phys. Lett. 1984,104, 174.
Mn,(CO)lo
(1B)
hexane was estimated for both 266- and 355-nm excitations to be 8.5 X lo8 mol-l dm3 s-l, which is very close to the previously reported value for the 337-nm excitation (8.8 X lo8mol-' dm3 s-~).~ The photogenerated Mn2(CO)gand .Mn(CO)5do not appreciably disappear within 30 ns after excitation. Therefore the present nanosecond experiment allows the direct real-time observation of the initial amounts of both primary photoproducts under the conditions without the subsequent bimolecular recombination reaction of .MII(CO)~(process 1B) and/or a probable secondary photoreaction of Mn2(C0)916 The absorbance at 500 nm is due to MII~(CO)~,, and the bimolecular rate constant for the reaction of Mn2(C0)9 with CO has been estimated to be on the order of lo5+ mol-l dm3 s-1.5-8 The quantum yield, Yl or Yz,is determined from the comparison of the absorbance change at 500 nm due to Mn2(C0)9or that at 780 nm due to .Mn(CO), with that of benzophenone in the triplet state at 530 nm as a standard." In this experiment the photolyses of benzophenone and Mn2(CO)lowere performed under the same optical geometry, excitation density, and absorbance at the excitation wavelength. The molar extinction coefficient of Mn,(CO)g at 500 nm was taken to be 900 mol-l dm3 cm-' from both the reported value^.^!^ The molar extinction coefficient of .Mn(CO)5at 780 nm (e780) was determined to be 800 mol-l dm3 cm-' from both the reported spectral shape and €830 value.18 Here c830 was taken to be 875 mol-l dm3 cm-' which is an averaged value of em's reported by Waltz et al. (800 f 80 mol-' dm3cm-')l9 and by Walker et al. (950 mol-' dm3cm-l).18 The measured quantum yields are shown in Table I.2o It is noted that the sum of Yl and Yzis unity for each excitation wavelength. The value Yl thus estimated increases with the excitation wavelength as shown in Table I. The electronic absorption spectrum of Mnz(CO)lohas been assigned as ~
(16) (a) The experiment of excitation by pulses longer than 1 ~s or by
ordinary light sources may suffer from a possible subsequent reaction following CO cleavage (eq 2) as follows:'6b Mn,(CO)9
-
.Mn(CO)5+ .Mn(C0)4
(b) Coville, N. J.; Stolzenberg, A. M.; Muetterties, E. L. J . Am. Chem. SOC.1983,105, 2499.
(17)Bensasson, R.;Land, E. J. Trans. Faraday SOC.1971,67, 1904. (18)Walker, H. W.; Herrick, R. S.: Olsen, R. J.; Brown, T. L. Inorp. Chem. 1984,23,3748. (19)Waltz, W. L.;Hackelberg, 0.;Dorfman, L. M.; Wojciki, A. J. Am. Chem. SOC.1978,100,7259. (20) (a) The ratio Y l / Y 2has been preliminary reported.20b In this paper the measurement of the quantum yields has been improved. (b) Kobayashi, T.; Yasufuku, K.; Iwai, J.; Yesaka, H.; Noda, H.; Ohtani, H. Coord. Chem. Rev. 1985,64, 1.
112 Organometallics, Vol. 5, No. 1, 1986
Kobayashi et al.
I
z a
I
0.000
t h
I 4 50
500
550
600
650
Wavelength/nm
Figure 3. Transient absorption spectra of Mn2(CO),oin cyclohexane following 355-nm excitation: curve 1, 5 p s before the second pulse (532-nm) excitation; curve 2,3 ps after the second pulse excitation; curve 3, difference spectrum of curve 2 minus
curve 1.
follows: 374 nm (d?r-a*), 336 nm (u-u*), 303 nm (u-T*), and 266 nm (da-r*co).lo This clearly shows that the rate of the internal conversion is smaller than the reaction rate. The value Y l /Y2shows that in the case of the d?r T * ~ excitation, metal-CO cleavages are more efficient than metal-metal fissions by a factor of 5. It is worth mentioning that the CO cleavage occurs as efficiently as radical formation even by the lower energy u* excitation. Thus both the o-u* (337 nm) excitation and the d?m*co (266 nm) excitation have reaction channels to (1) and (2). However it should also be noted that the irradiation of light induces the fission of the metal-metal bond. This is in contrast with the thermal reaction in which the absence of metal-metal bond cleavage has recently been verified.16" A different value of Y l / Y2 (about 2) was estimated by the competition reaction methodg and a flash photolysis with a 35-ps pulses7 We consider that their experiments may have suffered from complications due to a stationary or longer pulse excitation by polychromatic lamp whose spectrum extends to the longer wavelength region. Kidd and Brown measured the total quantum yield for the disappearance of Mn2(CO)loto be 0.81-0.94 by the photolysis of Mn2(CO)lowith the stationary light irradiation at 350 nm in the presence of phosphorus bases (P).21 Their results can be reinterpreted along with our new results obtained by the 355-nm excitation as follows. The disappearance yield of Mn2(CO)lofor reaction 3 is estimated to be 0.44 in our recent study. The difference
-
Mnz(CO)g+ P
+
Mnz(C0)9P
(3)
between the disappearance yield of Mn2(CO)lo(0.814.94) and the residue yield of 0.374.50 is interpreted by invoking mechanism 4 suggested by Kidd and Brown.21 S M ~ ( C O+)P~ Mn(CO),P + CO (4) +
They also reported that the yield for the disappearance of MII~(CO)~, decreases to 0.66-0.76 in the presence of both phosphorus bases and CO. The result can be explained as follows. Reaction 3 competes with the back reaction of process 2 which reproduces Mn2(CO)lofrom Mn2(C0)9 and externally adds CO. Double-Flash Excitation. Figure 3 shows the transient absorption of Mn2(CO)loin cyclohexane under 1atm of Ar following double-flash excitation. The secondary excitation of the sample by the 532-nm light pulse was performed 30 I.LS after the first excitation by the 355-nm (21) Kidd,
D.R.;Brown, T. L. J . Am. Chem. SOC.1978, 100, 4095.
0
9 a
0.000
I
v
- 0.005' 3b
I
50
40
60
70
tlus
Figure 4. Kinetics of the absorbance change of Mn2(CO),, in cyclohexane, A(t; double-flash)- A@; single flash (355 nm)). The ~ 532-nm light was irradiated at the sample solution 30 p s after the 355-nm excitation pulse: (a) under 1atm of Ar measured at 500 nm, (b) under 1 atm of CO measured at 500 nm, and (c) under 1 atm of Ar measured at 780 nm.
excitation light pulse. Curves 1 and 2 show the transient absorption spectra 5 ps before and 3 ps after the second excitation, respectively. Curve 3 shows the difference absorption spectrum (curve 2 minus curve 1). The spectrum resembles the absorption due to Mn2(CO)g.Therefore, the decrease in the absorbance around 500 nm is caused by the disappearance of Mn2(CO)ginduced by the second excitation light at 532 nm. On analogy with the photoreaction of Mn2(CO),,, eq 5 and 6 may be the two possible processes. In process 6, there may be other disproportionations such as MII~(CO)~ + 2CO and Mn2(CO)6 3CO and so on. Mn2(C0)9
-
+
+
--c
*Mn(C0)5
t *Mn(C0)4
(5)
532 nm
MnZ(C0)e t CO
(6)
Parts a and b of Figure 4 show the kinetics of the absorbance changes, A(t;double flash) - A(t;single flash (355 nm)), of Mn2(CO),, in cyclohexane under 1 atm of Ar and CO, respectively, at 500 nm. The intense spikes at 30 I.LS shown in parts a and b of Figure 4 are due to scatterings of the 532-nm excitation light. The 355-nm excitation was performed 30 ps before the 532-nm excitation. The absorbance change due to the disappearance of Mn2(CO)9is smaller under 1atm of CO than Ar, since the back reaction of process 6 may be rapid due to higher CO concentration. Figure 4c shows the kinetics of the absorbance change at 780 nm. If cleavage of the Mn-Mn bond of Mn2(CO)g takes place, the radical -Mn(CO),is expected as one of the species in process 5.16aHowever, no detectable signal was observed at 780 nm where the molar extinction coefficient of .Mn(CO)5is nearly equal to that of Mn2(C0)9at 500 nm. The molar concentration (C,)of -Mn(CO),formed through process 5 is estimated to be 3 x lo4 mol dm-3 by assuming that the absorbance change shown in Figure 4b is solely due to the loss of Mn2(C0)9by process 5. The expected absorbance change due to the formation of -Mn(CO),thus which is lower than the detectable should be 7 x absorbance change (0.001; see Figure 4c). The ratio of the quantum yield for processes 5 and 6, Y5/Ye, is estimated
Organometallics 1986,5, 113-117 from eq 7 and 8. Here the upper limit of C5 is 3 y5/ y6 = C5/C6
X
lo*
(7)
(8) C5 + c6 1 AA(t)/~5m(Mn2(Co)9)1 mol dm-3 and c6 is the molar concentration of Mn2(C0)& The equality relationship in (8)is satisfied when Mn2(CO)8 and other species such as Mn2(C0)7do not have absorptions at that wavelength. Inequality in (8) is due to any absorbance of these species. The optical path length (1) is 0.3 cm in this double-pulse experiment. The absorbance change, AA(t) (0.002),is shown in Figure 4a. The ratio Y 5 / Y 6is therefore estimated to be lower than 0.7. The yield for process 5, which was proposed by Coville et al.,l& is, therefore, concluded to be low even if it is present. The major process in Mn2(CO)gphotolysis is not the cleavage
113
of the metal-metal bond but of the Mn-CO bond (process 6). The steady-state irradiation at low temperature is in progress to clarify the products of the photoreaction of Mn2(CO)9. The recombination of Mn2(CO), with CO following the second flash has not been studied because of the complicated kinetics and the small absorbance change. Advanced studies will be published in another paper.
Acknowledgment. We wish to express thanks to Prof. A. Poe for his helpful discussions on the wavelength dependence. They also thank Mr. J. Iwai for his help in the early stage of the study. Registry No. Mnz(CO)lo,10170-69-1; Mn(C0)5, 54832-42-7; Mn2(CO)9,86728-79-2; Mn(C0I4, 71518-80-4; CO, 630-08-0.
A New General Route to Diphosphenes via Germylated Compounds Claude Couret, Jean Escudie, Henri Ranaivonjatovo, and Jacques SatgQ" Laboratoire de Chimie des Organomin&aux, UA du CNRS No. 4 77, Universitg Paul Sabatier, 3 1062 Toulouse. France Received April 10, 1985
Several (trichlorogermy1)phosphinesRP(H)GeCl, (3) are prepared by two different routes: (i) from primary phosphines RPH2 and germanium tetrachloride and (ii) from dichlorophosphines RPClz and the dichlorogermylene-dioxane complex, GeC12.C4H802.Subsequent addition of 3 to an excess of DBU (1,5diazabicyclo[5.4.0]undec-5-ene)affords the corresponding diphosphenes RP=PR. This method appears conveniently and generally applicable to the synthesis of diphosphenes. This reaction involves formation of chlorophosphine intermediates RP(H)Cl (2). Stable diphosphenes IC,bis(2,4,6-tri-tert-butylphenyl)diphosphene, and le, bis[bis(trimethylsilyl)methyl]diphosphene, can be isolated in excellent yield. Unstable dienophilic diphosphenes were characterized by cycloaddition with 1,3-dienes. Cycloadduct 12d, obtained by reaction of di-tert-butyldiphosphenewith cyclopentadiene,is a clean precursor of di-tert-butyldiphosphene, Id.
Introduction Since the report by Yoshifuji et al. describing the synthesis and characterization of the first stable compound with a P=P bond, bis(2,4,6-tri-tert-butylphenyl)diphosphene,l this new class of unsaturated compounds has been of current interest.2-10 (1) (a) Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotau, K.; Higuchi, T., J . Am. Chem. Soc. 1981,103,4587; (b) Ibid. 1982,104,6167. (2) For recent reviews see: Cowley, A. H. Polyhedron 1984,3,389-432. Cowley, A. H.; Kilduff, J. E.; Lasch, J. G.; Mehrotra, S. K.; Norman, N. C.; Pakulski, M.; Whittlesey, B. R.; Atwood, J. L.; Hunter, W. E. Inorg.
Chem. 1984,23, 2582-2593. (3) Smit, C. N.; Van der Knaap, T. A.; Bickelhaupt, F. Tetrahedron Lett. 1983, 24, 2031. (4) Cowley, A. H.; Kilduff, J. E.; Newman, T. H.; Pakulski, M. J. Am. Chem. SOC.1982,104,5820. Cowley, A. H.; Kilduff, J. E.; Pakulski, M.; Stewart, C. A. Ibid. 1983, 105, 1655. (5) (a) Bertrand, G.; Couret, C.; EscudiB, J.; Majid, S.;Majoral, J. P. Tetrahedron. Lett. 1982,23, 3567. (b) Couret, C.; Escudi6, J.; Satg6, J. Ibid. 1982,23, 4941. Escudi6, J.; Couret, C.; Ranaivonjatovo, H.; Satg6, J.; Jaud, J. Phosphorus Sulfur 1983, 17, 221. Niecke, E.; Ruger, R. Angew. Chem. 1983,95,154; Angew. Chem., Int. Ed. Engl. 1983,22,155. Niecke, E.; Ruger, R.; Lysek, M.; Pohl, S.; Schoeller, W. Angew. Chem. 1983,95,495;Angew. Chem.,Int. Ed. Engl. 1983,22,486; Angew. Chem. Suppl. 1983, 639. Schmidt, H.; Wirkner, C.; Issleib, K. 2.Chem. 1983, 23,67. Cetinkaya, B.; Hudson, A.; Lappert, M. F.; Goldwhite, H. J. Chem. Soc., Chem. Commun. 1982, 609, 691.
Diphosphenes have been obtained by several routes from reactions of the corresponding dichlorophosphines with various reagents: magnesium,l*, odium,^ or lithium derivatives: bis(trimethylsiiyl)mercury,6divalent species of group IVA7 (14),30primary phosphines (dehydrochlorination in the presence of amines),8and silylphosphines (dechlorosilylation).3~9 However, although all these methods are convenient for the preparation of some kinds of diphosphenes, there is currently no generally applicable methodology for the preparation of all diphosphenes. In a preceding paper, we described the synthesis of bis[bis(trimethylsilyl)methyl]diphosphene via organogermanium compounds,1° which is presently the only existing route to this diphosphene. Herein, we describe the (6) Romanenko, V. D.;Klebalskii, E. 0.; Markovskii, L. N. Zh. Obshch. Khim. 1984,54, 465. (7) Veith, M.; Huch, V.; Majoral, J. P.; Bertrand, G.; Manuel, G. Tetrahedron Lett. 1983, 24, 4219. (8) (a) Cowley, A. H.; Kilduff, J. E.; Mehrotra, N. C.; Norman, N. C.; Pakulski, M. J. Chem. SOC., Chem. Commun. 1983, 528. (b) Yoshifuji, M.; Shibayama, K.; Inamoto, N.; Matsushita, T.; Nishimoto, K. J. Am. Chem. Soc. 1983,105, 2495. (9) EscudiB, J.; Couret, C.; Andriamizaka, J. D.; Satg6, J. J . Organomet. Chem. 1982,228 C76. (10) Escudi6, J.; Couret, C.; Ranaivonjatovo, H.; Satg6, J. J. Chem. Soc., Chem. Commun. 1984, 24, 1621.
0276-7333/86/2305-0113$01.50/00 1986 American Chemical Society
