3683
Organometallics 1996, 14, 3683-3692
Organotransition-MetalMetallacarboranes. 39. Arene-CappedRuthenium-Carborane Tetradecker Sandwich Complexes1 Peter Greiwe,? Michal Sabat, and Russell N. Grimes" Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901 Received March 27, 1995@
A new family of C2B3-bridgedtetradecker sandwich complexes, having cymene rather than cyclopentadienyl end rings, has been synthesized via reactions of metal ions with nido-(pC H M ~ ~ C ~ H ~ M ~ ) R U ( E ~ ~anions C ~ Bthat ~H~ are - isoelectronic ~ - Y ) - analogues of the nido-($CsMes)Co(Et2C2B3H3-5-Y)- synthons employed in earlier work. Bridge-deprotonation of CyRu(Et2C2B3H4-5-Y) (Cy =p-isopropyltoluene; 3,Y = Me; 6, Y = Cl), followed by treatment with C0C12 in THF and separation of the products on silica in air, afforded the tetradecker sandwiches [ C ~ R U ( ~ , ~ - E ~ ~ C ~ B(8a, ~ HY ~ -=~Me; - Y8b, ) IY~=CC1) O as the major products, isolated as air-stable paramagnetic green crystals in 40% and 55% yield, respectively. In addition, the minor products C ~ R ~ ( E ~ ~ C ~ B ~ H & L M ~ ) C O ( E ~ ~ C(8c) ~ Band ~ H CyRu~-~-E~)RUC~ (Et2C2B3H2-5-C1)Co(Et2C2B3H3)RuCy (8d)were obtained. The formation of 8b proceeds via a cobalt-protonated diamagnetic complex [ C ~ R U ( ~ , ~ - E ~ ~ C ~ B ~ (7b) H ~ -which ~ - Cwas ~)I~COH isolated and characterized; 8a is assumed to form via an analogous intermediate 7a although this species was not isolated. A similar reaction of 3- with NiCl2 gave moderately air-stable, (9). Reactions of the anion of the B(4,5,6)diamagnetic [CyRu(2,3-EtzCzB3Hz-5-Me)]2Ni trimethyl complex CyRu(Et2CzBaMeaHz)with CoCl2 and NiCl2 generated the corresponding (10)and [CyRu(2,3-EtzCzB3Me3)12Ni (11) tetradecker products [CyRu(2,3-Et2C2B3Me3)12Co in low yields. The new compounds were characterized via lH and/or 13C NMR, IR, Wvisible, and mass spectra, supported by X-ray crystal structure determinations on 8a, 8c, and 9, which established the tetradecker sandwich geometry. The proton NMR spectrum of paramagnetic 8a was completely assigned via the technique of correlated spectroscopy, involving generation of the diamagnetic anion 8a- via stepwise reduction of the neutral compound. Crystal data for 8a: R u ~ C O C ~ C ~ ~ .space & H ~group ~ , Pi (triclinic);a = 13.631(5) b = 16.447(5) c = 9.008(3) a = 100.07(3)",p = 108.12(3)", y = 94.03(3)"; 2 = 2; R = 0.038 for 5527 independent reflections. Crystal data for 8c: R U ~ C O ~ C ~ ~ Bspace J & Ogroup , P21/n (monoclinic); a = 12.781(3) b = 11.120(4) c = 26.214(4) A, p = 96.71'; 2 = 4; R = 0.031 for 3052 observed reflections. Cr stal data for 9: R U Z N ~ C ~ ~ B space S H ~group ~ , Pi (triclinic); a = 12.577(7)A, b = 14.330(6) c = 11.671(7) A, a = 113.24(4)', p = 111.71(4)", y = 83.24(4)'; 2 = 2; R = 0.028 for 4073 independent reflections.
A,
A,
A, A,
A,
i,
Introduction
Scheme 1
Transition metal sandwiches incorporating planar C2B3 carborane rings form an extensive family of wellcharacterized organometallic complexes having 2-6 decks, many of which exhibit remarkable oxidative and thermal stability and are readily soluble in organic solvent^.^,^ Within this group, tetradecker sandwiches of the type [ C ~ * C O ( R R ' C ~ B ~ H(Scheme ~X)~~M 1; Cp* = v5-C5Me5) have been an object of detailed synthetic, structural, spectroscopic, and electrochemical investiVisiting graduate student from the University of Bielefeld, Germany, 1993-1994. The assistance of Professor Peter Jutzi in arranging this visit is gratefully acknowledged. Abstract published in Advance ACS Abstracts, July 1, 1995. (1)(a)Part 38: Stockman, K. E.; Houseknecht, K. L.; Boring, E. A,; Sabat, M.; Finn, M. G.; Grimes, R. N. Organometallics, in press. (b) Part 37: Stephan, M.; Muller, P.; Zenneck, U.; Pritzkow, H.; Siebert, W.; Grimes, R. N. Inorg. Chem. 1995,34,2058. (c) Part 36: Houseknecht, K. L.; Stockman, K. E.; Sabat, M.; Finn, M. G.; Grimes, R. N. J.Am. Chem. SOC.1995,1163. (d) Part 35: Stephan, M.; Hauss, J.; Zenneck, U.; Siebert, W.; Grimes, R. N. Inorg. Chem. 1994,33,4211. (2)Recent reviews: (a)Grimes, R. N. Chem. Rev. 1992,92,251. (b) Grimes, R. N. In Current Topics in the Chemistry ofBoron; Kabalka, G. W., Ed.; Royal Society of Chemistry: Cambridge, 1994; 269. '
* co
* I
M = Co, Ni, Ru
X = H , CI, Br, I , M e , C ( 0 ) M e . C H 2 C s C M e R. R ' = o l k y l , H
gat ion^.^^-^ As shown in Scheme 1,these complexes are prepared via metal-stacking reactions involving nido[Cp*Co(RRC2B3H&)I- anions (generated by bridgedeprotonation of the neutral species) and transition metal cations a t room t e m p e r a t ~ r e .This ~ ~ synthetic
0 1995 American Chemical Society Q276-7333/95/2314-3683$Q9.QQ/Q
Greiwe et al.
3684 Organometallics, Vol. 14,No. 8, 1995
Scheme 2
"
"
Ld&-''
n-chlorosuccinimide
Ru
A,
I Ru
THF
I
&
&
1
5 Scheme 3 I
3 6
-
w e t TMEDA
b , 6h
Ru I
/-e=6
I
Y=Me Y = C l
&.
7a Y = Me ( n o t isolated)
7b Y
= CI
route exploits the availability of the double-decker Cp*Co(RRCzB3H&) starting material^,^ which are routinely prepared in multigram quantity and are readily derivatized via substitution on the carborane ring.5 Moreover, by employing bifunctional complexes that contain two Co(RR'CzB3H&) units connected by multicyclic hydrocarbons such as (C5H4)Z (fulvalene) or ( C ~ M ~ ~ ) Z Cthis & , approach has been exploited in the synthesis of linked multisandwich 01igomers.~~ It is apparent that other classes of stable carborane(3)(a)Piepgrass, K.W.; Meng, X.; Holscher, M.; Sabat, M.; Grimes, R. N. Inorg. Chem. 1992,31,5202. (b) Meng, X.;Sabat, M.; Grimes, R. N. J . A m . Chem. Soc. 1993,115,6143. (c) Pipal, J. R.; Grimes, R. N. Organometallics 1993,12, 4452. (d) Pipal, J. R.; Grimes, R. N. Organometallics 1993,12,4459. (e)Wang, X.;Sabat, M.; Grimes, R. N. J . A m . Chem. Soc. 1994,116,2687. (4)Davis, J. H., Jr.; Sinn, E.; Grimes, R. N. J . Am. Chem. Soc. 1989, 111, 4776. (5)(a) Piepgrass, K. W.; Grimes, R. N. Organometallics 1992,11, 2397. (b) Piepgrass, K.W.; Stockman, K. E.; Sabat, M.; Grimes, R. N. Organometallics 1992,11, 2404. (c) Benvenuto, M. A.; Grimes, R. N. Inorg. Chem. 1992,31,3897.(d) Benvenuto, M.A.; Sabat, M.; Grimes, R. N. Inorg. Chen. 1992,31,3904.
8~
Y , Y ' = Me
8b
Y,Y' = C I
8c
Y = Me, Y ' = Et
8d
Y = CI, Y' = H
bridged tetradeckers should be accessible as well, and one would expect their electronic structures and properties to differ significantly from those of the wellestablished Cp*Co-end-capped series. We were particularly interested in multideckers capped by arene ligands, which one would expect to be more reactive, hence more readily tailorable, than the relatively inert Cp* groups. With this in mind, and also in order t o explore possible alternative strategies for constructing multisandwich oligomers, we have developed a route t o a new class of tetradeckers having Ru(arene) end units that are isoelectronic and isolobal with CoCp*. This paper describes the preparation and structural characterization of several such species.
Results and Discussion Synthesis and Derivitization of Ruthenacarborane Double-Decker Complexes. The starting point for this chemistry is the cymene-ruthenacarborane CyRu(EtzCzB4H4)(Cy = p-isopropyltoluene) 1, a
Organometallics, Vol. 14, No. 8, 1995 3685
Organotransition-MetalMetallacarboranes
C o r r e l a t e d P r o t o n NMR D a t a on 8 a / 8 a ’
- t
6 5 r
3 2 1
0 -1 -2
-3 -4
-5 0.0
I
I
I
I
I
I
I
1
I
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
80 1 -fp 80‘ Figure 1. Correlation diagram for ‘HNMR spectra of 8d8a- in CDCls. Values of 6 (vertical axis) are plotted vs 1 - f, Cf, is the mole fraction of the paramagnetic component). colorless, slightly air-sensitive oil first prepared by The synthesis of 8b was accompanied by a paramagDavis et al.4 (Scheme 2). Decapitation of this species netic monochloro product identified as CyRu(EtzCzBsH2with TMEDA affords nido-CyRu(Et2CzB3H5)(21, an air~ - C ~ ) C O ( E ~ ~ C ~ B(8d). ~ H ~The ) R proposed U C ~ structures for these compounds are consistent with mass spectrostable colorless complex that can be deprotonated and alkylated to yield mono- t o tri-B-alkyl derivatives (e.g., scopic and W-visible evidence, and X-ray diffraction 3 and 4h6 In the present work, the closo complex 1 was studies of 8a and 8c (vide infra) confirmed the tetrato generate regiotreated with n-chlor~succinimide~~ decker sandwich geometry. The dichloro complex 8b specifically (80%yield) the pale yellow B(5)-C1complex is generated via an isolable intermediate, 7b, a dark 5, which in turn was converted in refluxing TMEDA to brown diamagnetic 42-electron tetradecker complex the nido species nido-CyRu(EtzCzB3H4-5-Cl) (6),a colorcontaining a formal Co(III)H4+unit that was characterless air-stable compound (Scheme 2). All of these ized from NMR and mass spectra. The proton spectrum double-decker ruthenacarborane sandwich species are of this complex contains a high-field peak at 6 -6.66 and a much smaller signal at -8.31, both of which are oils at room temperature, readily separated via column chromatography on silica and characterized via multicharacteristic of metal-bound protons and can be nuclear NMR and mass spectroscopy. assigned3bto Co-H and Ru-H hydrogens. This supSynthesis of Tetradecker Sandwich Complexes. ports the likely possibility that isomers arising from protonation at two different metal sites are present in As shown in Scheme 3, complexes 3 and 6 were bridgesolution; indeed, the “extra” proton may in fact migrate deprotonated and reacted with 0.5 equiv of CoC12, between two or three metal centers, but the available producing in each case a dark orange-brown solution data do not allow more definitive assignment. Converthat turned green on exposure to air. Chromatographic sion of 7b t o 8b with loss of the metal-bound proton separation of products on silica in air gave, respectively, occurred quantitatively, with no decomposition, on the paramagnetic dimethyl and dichloro products [CyRuexposure to silica in air. The synthesis of 8a from 3 is (E~~C~B~H~-~ - YY) = I ~Me; C O8b,Y = Cl). A minor (8a, assumed to follow a similar path via formation of a side product of the synthesis of 8a,having a mass 14 protonated intermediate 7a as shown, but the latter units higher than the latter complex, was identified by compound was not isolated. X-ray crystallography as a B(5)-methyl, B(5’)-ethyl The lH NMR spectra of 8a and 8b indicate that both derivative (8c). The formation of this species implies species are paramagnetic, consistent with 41-valencethe presence of small amounts of a B(5)-ethyl precursor electron (vel systems, and this was verified by the complex, which may be generated from a [Cp*Coobservation of ESR signals (X-band at - 115 K in frozen (Et2C2B3H4-5-CH211- tautomer of the deprotonated 3CH2C12) indicating a single unpaired electron in each anion and Me1 during the synthesis of 3.6 Evidence of case. The presence of cobalt hyperfine structure in the such tautomerism in an analogous system is seen in the ~ -treatC H ~ P P spectra ~ ~ ) of both compounds establishes that the unpaired preparation of C ~ * C O ( E ~ ~ C ~ B ~ H ~ -via electron is at least partially associated with cobalt, ment of the [ C ~ * C O ( E ~ ~ C ~ B ~ H ~anion - ~ - Mwith ~)Icorresponding t o formal oxidation states of Co(IV) and PPh~cl.~ Ru(I1) in these species. This does not, however, preclude (6) Davis, J. H., Jr.; Attwood, M. 1990, 9, 1171.
D.; Grimes, R. N. Organometallics
( 7 )Wang, X. Ph.D. Thesis, University of Virginia, 1995.
Greiwe et al.
3686 Organometallics,Vol. 14, No. 8,1995
Scheme 4 I
Ru
3
&.
9 c7
1 ) t-BuLi
2) MCl2
0 2 , H2O c
M C9E
C2R9
the possibility of some degree of electron-delocalization over the three metal centers, as has been seen in other multidecker systems. For example, the ESR spectrum of the closely related 29-electron cobalt-ruthenium a fully triple-decker cation [CYRU(E~~C~B~H~)COCP*I+, electron-delocalized species, exhibits cobalt hyperfine splitting;8 yet, in the spectra of several 41-electron CoCoCo CaB3-bridged tetradecker sandwiches that are also evidently electron-delocalized, on the basis of electrochemical data, no such feature is observed.3c The proton NMR spectrum of 8a was completely assigned via correlation with the spectrum of its 42electron diamagnetic anion 8a-,obtained by stepwise reduction of the neutral compound on repeated contact with a potassium mirror in the NMR tube as described in earlier publication^.^^^^-^ Least-squares plots of chemical shift vs 1- f p (fp = mole fraction of the paramagnetic component) for the distinguishable proton signals in 8a are shown in Figure 1. The chemical shifts of the paramagnetic neutral complex and the diamagnetic monoanion correspond to f p = 1and 0, respectively. The B-methyl signal was not clearly observed in the paramagnetic spectra and is omitted from the diagram; this resonance was, however, identified in the spectrum of the monoanion as a singlet a t 6 0.81. The trends evident in these plots can be compared with those found in earlier work on Cp*Co-end-capped carborane-bridged multidecker s a n d w i ~ h e s . l In ~ *the ~ ~latter ~ ~ species, the protons closest to the Paramagnetic metal centeds) tend to be most strongly affected by redox processes, exhibit(8)Merkert, J.; Davis, J. H., Jr.; Geiger, W.; Grimes, R. N. J. Am. Chem. SOC.1992,114,9846, ( 9 )(a) Stephan, M.; Davis, J. H., Jr.; Meng, X.; Chase, K. P.; Hauss, J.; Zenneck, U.; Pritzkow, H.; Siebert, W.; Grimes, R. N. J.Am. Chem. SOC.1992, 114, 5214. (b) Koehler, F. H.; Zenneck, U.; Edwin, J.; Siebert, W. J . Organomet. Chem. 1981, 208, 137. (c) Zwecker, J.; Kuhlmann, T.; Pritzkow, H.; Siebert, W.; Zenneck, U. Organometallics 1988, 7 , 2316.
C2R7
C2R10
Figure 2. Molecular structure of [CyRu(Et2C2B3H2-5Me)lzCo (8a).
'
ing the steepest slopes in the 6 vs f p plots; conversely, the signals arising from the more remote protons generate nearly flat plots, showing little effect of the added electron. One finds similar correlations in the present case: the largest shifts observed on reduction occur in the isopropyl CH and ring proton resonances (plots A, G, and H), while the signals arising from the isopropyl CH3 and ethyl CH3 protons (E and F, respectively), which are more remote from the metals, are shifted only slightly. On the other hand, it is remarkable that the cymene tolyl (D)proton resonance is essentially unchanged in the paramagnetic vs diamagnetic species, in contrast to the isopropyl (A) signal, despite comparable RU-HD and RU-HA average distances. Conceivably, this effect can be accounted for by restricted rotation of the isopropyl group that holds hydrogen A in an orientation allowing significant interaction with the nearest metal (ruthenium), as shown; similar interactions of the individual D protons might be, in effect, averaged out by free rotation of the tolyl group and hence not observed. Since the A protons are relatively far from cobalt, their sensitivity to the redox state of the complex suggests that some of the unpaired spin density is delocalized from the formal Co(IV) center onto the Ru atoms in 8a,i.e., there is a partially occupied MO having both Co and Ru character. This would be consistent with the finding of cobalt hyperfine splitting in the ESR spectrum of 8a, mentioned earlier, and also fits the pattern observed in the fully delocalized paramagnetic
Organometallics, Vol. 14,No.8,1995 3687
Organotransition-MetalMetallacarboranes
CIA10
C l R 5A C1
CIR3 IR9B
C1Ri0C1R3
\ 86
ii
M
C3E
NI
C8E
C9E
C8E
c2
w
C2R9
C2R6
C2R5
C2A9
Figure 4. Molecular structure of [ C Y R U ( ~ , ~ - E ~ ~ C ~ B ~ H ~ 5-Me)IzNi (9). C2RIO
Figure 3. Molecular structure of CyRu(Et2C2B3H2-5-Me)CO(Et2CzB3H2-5-Et)RuCy ( 8 ~ ) . Co-Ru triple-decker cation referred to above. The nature and extent of electron-delocalizationin these and other carborane-bridged multidecker sandwich systems are subjects of continuing investigations. Treatment of the B(5)-methyldouble-decker complex 3 with NiC12 following deprotonation produced a dark greenish-brown solution which 0x1 workup via silica chromatography afforded the Ru-Ni-Ru tetradecker sandwich 9, obtained in low yield as a dark green solid (Scheme 4). This compound is moderately air-stable, undergoing degradation on standing in air over several weeks. Characterization via lH and 13CNMR, U V , IR, and mass spectra supported the proposed structure, and the tetradecker geometry was confirmed by a singlecrystal X-ray diffraction study. In order to probe steric inhibition of the tetradecker stacking reaction, we examined the reactivity of a peralkylated synthon, the B(4,5,6)-trimethylcomplex 4, toward metal reagents. Previous work involving formation of C2B3-bridged tetra decker^^^ has not included substrates of this type in which all of the carborane ring atoms contain substituents, and it was of interest to see whether metal coordination is blocked in such cases. Accordingly, 4 was deprotonated with n-butyllithium and treated with CoC12 or NiC12, which produced color changes similar to those obtained with the monosubstituted species as described above. Workup in air as before gave, in each case, a mixture of starting material
(ca. 50%recovered) and one main product characterized as a hexamethyl derivative, 10 or 11. The slow formation and relatively low isolated yields of 10 and 11 (17% and 9%, respectively, based on 4 consumed) suggest that the alkyl groups do indeed sterically hinder the coordination of the carborane ring to metal ions. Electron donation from the alkyl substituents may also be an inhibiting factor, since previous studies have demonstrated that the construction of stable tetradecker sandwiches via metal stacking reacions - ~ -isXfacilitated )~by tions of C P * C O ( E ~ ~ C ~ B ~ H ~ Nevertheless, the electron-withdrawing X characterization data do support the proposed tetradecker structures for 10 and 11,making these the first examples of fully substituted tetradecker sandwich metallacarboranes. Significantly, 10 and 11 are considerably less stable than the less substituted species 7-9, rapidly decomposing on silica in air. X-ray Crystallographic Studies of 8a,c and 9. The molecular geometries of these complexes are depicted in Figures 2-4, data collection parameters and crystal data are presented in Table 1, bond distances and bond angles are listed in Tables 2-4, and tables of positional parameters as well as mean plane calculations are deposited as supporting information. The molecular structural parameters of the three complexes 8a,c and 9 can be compared with those obtained earlier on several CoCp*-cappedtetra decker^.^^ As summarized in Table 5, the main features of these complexes display a basic similarity despite the variation in metals, substituent groups on boron, end ligands, and numbers of valence electrons. In all cases, the metals are essentially centered over the C2B3 rings to
3688 Organometallics, Vol. 14, No. 8, 1995
Greiwe et al.
Table 1. Experimental X-ray Diffraction Parameters and Crystal Data empirical formula fw cryst color, habit cryst dimens (mm3) space group a,A b,A
c, A
a, deg
A deg Y ,deg
v, A3
z
cm-' (Mo Ka) transmissn factors Dcalcd, g 20max,deg reflns measd reflns obsd [I > 3dI)l R
{i,
RW
largest peak in final diff map, e h-3
Sa
8C
9
R u ~ C O C5BsH5g ~C~~ 835.2 black prism 0.46 x 0.32 x 0.28 Pi 13.631(5) 16.447(5) 9.008(3) 100.07(3) 108.12(3) 94.03(3) 1873 2 13.13 0.63-1.00 1.481 50.0 6898 5527 0.038 0.062 1.17
RuzCozCaaBsHso 806.8 black prism 0.46 x 0.36 x 0.32 P2 lln 12.781(3) 11.120(4) 26.214(4)
Ru2NiC&&8 792.53 dark green plate 0.38 x 0.28 x 0.18 P1 12.577(7) 14.330(6) 11.671(7) 113.24(4) 111.71(4) 83.24(4) 1795 2 13.60 0.68-1.00 1.466 46.0 4868 4073 0.028 0.042 0.52
which they are coordinated, i.e., there are no cases of significant "ring slippage" in these systems. The intramolecular metal-metal distances (allowing for the larger covalent radius of Ru compared to Co and Nil, carborane C -C bond lengths, and metal-ring distances are closely similar in all of the structures. Each stack is appreciably bent in the center, as measured by the deviation of the M-M'-M angle from linearity, but the degree of bending varies significantly, and 14" in 9, a from 15" in the 40 ve Co-Ru-Co 42 ve Ru-Ni-Ru system, t o as little as 5-6" in the 41 ve Ru-Co-Ru species 8a and 8c. In all cases seen thus far, the bending is such as to increase the interligand distance between the Et-C-C-Et units on opposing carborane rings, although the steric interaction between these groups is also reduced in some instances by mutual rotation away from each other. This effect is also seen in the dihedral angles subtended by the four ring planes, which again exhibit their largest values in the Ru-centered sandwich. As discussed elsewhere, the nonparallel ring orientations in carborane-bridged multideckers can be ascribed t o electronic causes related to the binding of the metal centers to the heterocyclic C2B3 carborane rings. In the case of the 40-electron ruthenium-centered system, it is proposed that electrondeficiency at the formal Ru(1V) center produces closer Ru-boron contact and thus exacerbates the bending effect.3a The wide variation in the rotational twist in these molecules defies simple rationalization, and may well be as much (or more) influenced by crystal-packing effects as by intramolecular steric or electronic factors. For example, in the Co-M'-Co series one sees a much smaller twist (27")in the B,B'-diacetyl species than in the corresponding dichloro derivatives (75"),despite the considerably greater steric demands of acetyl vs chloro groups. In solution, relatively free rotation of the ring ligands on the intermetallic axes is assumed; NMR evidence, for example, is consistent in all cases with time-averaged CzUsymmetry in which the four carborane C-ethyl groups are equivalent (except in the inherently asymmetric trichloro CoRuCo complex). These findings do not reveal any particularly striking pattern of structural differences between the (arene)-
96.71 3700 4 12.56 0.94-1.00 1.448 46.0 5470 3052 0.031 0.042 0.82
Ru-capped complexes reported in this paper and their Cp*Co-capped analogues. Based on this very limited set of avk-lable stru&res, together with their close physical and chemical resemblance, one suspects that the stacked systems assembled from CZB3 ring ligands and the formally isoelectronic (cymene)Ru and Cp*Co units are not grossly dissimilar. It will be interesting to see if this impression is borne out as studies of tetradecker and other multidecker sandwich systems are extended to a broader range of compositions and molecular geometries. Experimental Section Instrumentation. 13C(75.5 MHz) and *H(300 MHz) NMR spectra were acquired on a GE QE300 spectrometer, and U V vis spectra were recorded on a Hewlett-Packard 8452A diode array spectrophotometer with an HP Vectra computer interface. Infrared spectra were obtained on microcrystalline films on NaCl plates. Unit-resolution mass spectra of the bimetallic starting complexes la-f and 2a-c were obtained on a Finnegan MAT 4600 GC/MS spectrometer using perfluorotributylamine (FC43)as a calibration standard. I n all cases, strong parent envelopes were observed, and the calculated and observed unit-resolution spectral patterns were in close agreement. Elemental analyses were obtained on a Perkin-Elmer 2400 CHN Analyzer using cyclohexanone-2,4-dinitrophenylhydrazone as a standard. In some cases, satisfactory microanalyses could not be obtained, but elemental composition and sample punty were established via combined multinuclear and mass spectra. Materials and Procedures. Dichloromethane and nhexane were anhydrous grade and were stored over 4A molecular sieves prior to use. THF was distilled from sodiumbenzophenone immediately prior to use. Column chromatography was conducted on silica gel 60 (Merck), and thick-layer chromatography was carried out on precoated silica gel plates (Merck). Unless otherwise indicated, all syntheses were conducted under vacuum or an atmosphere of argon. Workup of products was conducted in air using benchtop procedures. The complex (CyRuClz)z was prepared by the method of Bennett and Smith,loand the building-block compounds 1, 2, and 4 were obtained via literature routes4a6 (10)Bennett, M. A,; Smith, A. K. J . Chem. SOC.,Dalton Trans. 1974, 233.
Organotransition-Metal Metallacarboranes
Organometallics, Vol. 14, No. 8, 1995 3689
Table 2. Bond Distances and Selected Bond Angles for [CyRu(Et2C2B3H2-5-Me)l&o(8a) Ru(l)-C(2) Ru( 1)- C(3 Ru(l)-C(lRl) Ru( 1)- C(1R2) Ru(l)-C(lR3) Ru( 1)-C(1R4) Ru(l)-C(lR5) Ru( 1)-C( 1R6) Ru( 1)-B(4) Ru( 1)- B(5 ) Ru( 1)-B(6) Ru(2)-C(8) Ru(2)- C(9) Ru(2)-C(2Rl) Ru(2)-C(2R2) Ru(2)-C(2R3) Ru(2)-C(2R4) Ru(2)-C(2R5) Ru(2)-C(2R6) Ru(2)-B(10) Ru(21- B(11) Ru(2)-B(12) Co-C(2) co-c(3) Co-C(8) Co-C(9) CO-B(4) CO-B(5) Co-B(6) Co-B(l0) Co-B( 11) Co-B(l2) Cl(l)-C(lS) Cl(B)-C(lS) C(2M)-C(2) C(2M)-C(2E) C(2)-C(3)
Bond Distances, A 2.193(4) C(2)-B(6) 2.205(4) C(3M)-C(3) 2.265(5) C(3M)-C(3E) 2.248(4) C(3)-B(4) 2.239(4) C(7)-B(5) 2.216(4) C(8)-C(8M) 2.180(4) C(8)-C(9) 2.202(5) C(8)-B(12) 2.207(5) C(8M)-C(8E) 2.234(5) C(9M)-C(9) 2.244(5) C(9M)-C(9E) 2.194(4) C(9)-B(10) 2.194(4) C(lO)-B(ll) 2.273(4) C(lRl)-C(lRB) 2.211(4) C(lRl)-C(lRG) 2.204(4) C(lRl)-C(lR7) 2.227(4) C(lR2)-C(lR3) 2.232(4) C(1R3)-C( 1R4) 2.262(4) C(lR4)-C(lR5) 2.237(5) C(lR4)-C(lR8) 2.226(5 ) C(lR5)-C(lR6) 2.202(5) C(1R8)-C(1R9) 2.179(4) C(lRS)-C(lRlO) 2.103(4) C(2Rl)-C(2R2) 2.090(4) C(2Rl)-C(2R6) 2.174(4) C(2Rl)-C(2R7) 2.057(5 C(2R2)-C(2R3) 2.099(5) C(2R3)-C(2R4) 2.132(5) C(2R4)-C(2R5) 2.140(5) C(2R4)-C(2R8) 2.098(5) C(2R5)-C(2R6) 2.068(5) C(2RS)-C(2R9) 1.85(2) C(2R8)-C(2R10) 1.63(2) B(4)-B(5) 1.515(6) B(5)-B(6) 1.502(7) B(lO)-B(ll) 1.464(6) B(ll)-B(12)
1.569(6) 1.513(6) 1.510(7) 1.596(6) 1.587(6) 1.512(6) 1.472(5) 1.573(6) 1.526(6) 1.502(6) 1.534(6) 1.551(7) 1.577(7) 1.409(8) 1.420(7) 1.502(7) 1.421(7) 1.409(6) 1.426(7) 1.520(7) 1.412(7) 1.536(6) 1.519(7) 1.414(7) 1.412(7) 1.531(6) 1.430(7) 1.433(6) 1.410(7) 1.513(6) 1.420(6) 1.505(7) 1.542(6) 1.783(7) 1.751(7) 1.747(7) 1.783(7) 114.2(3) 128.8(3) 131.9(3) 114.6(4) 119.3(4) 112.9(4) 127.7(3) 105.6(4) 129.0(4) 130.5(4) 100.4(3) 107.3(4) 64.4(2) 130.3(4) 128.9(4) 100.8(4) 104.8(3
Synthesis of CyRu(2,3-Et&zB4H+Cl) (5). A 200-mg (0.55 mmol) sample of 1 was dissolved in ca. 60 mL of THF and placed in a 3-neck 100-mL flask which was fitted with a water-cooled condenser and a sidearm tip-tube charged with 150 mg (1.1mmol) ofN-chlorosuccinimide (NCS) and attached to an argon line and purged with argon. The NCS was tipped into the THF solution, and the mixture was refluxed for ca. 10 h under a flow of argon. The solution was stripped of solvent on a rotary evaporator, and the residue was taken up in 1:2 hexane/CH&le and chromatographed on a silica column, affording one pale yellow major band, 5, which was isolated in 80% yield (0.44 mmol) as a pale yellow oil. Minor bands were identified via mass spectroscopy as dichloro and trichloro derivatives of 1. This reaction is very sensitive to temperature, concentration, and the NCS:1 ratio and requires continual monitoring by spot TLC analysis. MS: base peak at mlz 400, cutoff at mlz 405, corresponding to calcd spectrum for RuClC16B4H27. 'H NMR (CDC13,ppm relative to TMS): 5.335
Table 3. Bond Distances and Selected Bond Angles for
CyRu(Et2C2B~H2-5-Me)Co(Et2CzB3H2-5-Et)RuCy (8c) Bond Distances. A Ru(l)-C(2) Ru(1)- C(3) Ru(l)-C(lRl) Ru(1)- C(1R2) Ru(1)- C(1R3) Ru(l)-C(lR4) Ru(1)- C(1R5) Ru( 1)- C(1R6) Ru(1)-B(4) Ru(1)-B(5) Ru(l)-B(6) Ru(2)-C(8) Ru(2)-C(9) Ru(2)-C(2Rl) Ru(2)- C(2R2) Ru(2)- C(2R3) Ru(2)- C(2R4) Ru(2)-C(2R5) Ru(2)-C(2R6) Ru(2)-B( 10) Ru(21-B( 11) Ru(2)-B( 12 Co-C(2) Co-c(3) Co-C(8) Co-C(9) CO-B(4) CO-B(5) Co-B(6) Co-B(l0) Co-B( 11) Co-B(l2) C(2)-C(2M) C(2)-C(3) C(2)-B(6) C(2M)-C(2E) C(3M)-C(3) C(3M)-C(3E)
2.194(5) 2.191(5) 2.277(6) 2.255(8) 2.177(8) 2.199(9) 2.182(7) 2.229(6) 2.218(6) 2.220(7 2.221(6) 2.186(5) 2.208(5) 2.292(6) 2.211(5) 2.199(6) 2.232(5) 2.199(5) 2.234(6) 2.255(7) 2.237(7) 2.198(6) 2.110(5) 2.177(5) 2.084(5) 2.169(5) 2.128(7) 2.073(6) 2.048(6) 2.127(6) 2.110(6) 2.024(6) 1.522(7) 1.493(7) 1.559(8) 1.499(8) 1.499(7) 1.52(1)
1.562(8) 1.506(9) 1.584(8) 1.507(7) 1.461(7) 1.576(7) 1.505(7) 1.507(7) 1.559(8) 1.506(7 1.36(1) 1.378(8) 1.54(1) 1.31(1) 1.569(7) 1.37(1) 1.51(1) 1.57(1) 1.432(8) 1.43(2) 1.15(2) 1.53(2) 1.86(2) '1.410(8) 1.428(8) 1.476(9) 1.425(8) 1.417(7) 1.417(7) 1.499(7) 1.405(8) 1.518(8) 1.512(8) 1.720(8) 1.749(9) 1.741(9) 1.783(8)
114.9(4) 132.9(4) 128.4(4) 120.1(4) 112.5(4) 127.4(5) 114.5(4) 107.3(5) 131.1(4) 101.7(4) 127.4(4) 10584) 108.4(4) 130.1(5) 130.5(5) 99.4(4) 106.1(4) d (CsH4),5.303 d ( C G H ~2.65 ) , m (CHMe**),2.30 m (ethyl CH2), 2.14 s (cymene tolyl CH3), 1.26 d (CH*MeZ), 1.18m (ethyl CH3). 13C NMR (CDC13, ppm vs TMS): 107.9 (unsubstituted cymene ring carbons), 96.9 (unsubstituted cymene ring carbons), 84.2 (substituted cymene ring carbons), 81.7 (substituted cymene ring carbons), 31.9 (C*HMed, 24.3 (cymene tolyl CHd, 23.5 (ethyl CHz), 19.8 (isopropyl CH3), 15.9 (ethyl CH3). Synthesis of nido-CyRu(2,3-EtzCzBsH4-5-C1)(6). Complex 5 was decapitated in wet TMEDA (refluxing for 6 h) via the previously described procedure,5d affording 6 in 65%-70% yield a s a pale yellow oil following chromatography on silica. MS: base peak at mlz 390, cutoff at mlz 395, corresponding to calcd spectrum for RuClC16B3H28. 'H NMR (CDC13, ppm relative to TMS): 5.32 m (CsHd, 2.71 m (CH*MeZ), 2.21 s (cymene tolyl CH3), 2.05 m (ethyl CHd, 1.90 m (ethyl CHd,
Greiwe et al.
3690 Organometallics, Vol. 14, No. 8, 1995
Table 4. Bond Distances and Selected Bond Angles for [CyRu(2,3-Et&zBsH2-5-Me)I~Ni (9) Ru( 11- C(2) Ru( 1)-C(3 Ru( 1)-C(1R1) Ru(lI-C(lR2) Ru( 1)-C( 1R3) Ru( 1)-C( 1R4) Ru(lI-C(lR5) Ru(l)-C(lR6) Ru(l)-B(4) Ru(1)-B(5) Ru( 1)-B(6) Ru(2)-C(8) Ru(2)-C(9) Ru(2)-C(2Rl) Ru(2)-C(2R2) Ru(2 1- C(2R3) Ru(2)-C(2R4) Ru(2)-C(2R5) Ru(2)- C(2R6) Ru(21-B( 10) Ru(21-B( 11) Ru(2)-B( 12) Ni-C(2) Ni-C(3) Ni-C(8) Ni-C(S) Ni-B(4) Ni-B(5) Ni-B(6) Ni-B(10) Ni-B( 11) Ni-B( 12) C(2M)-C(2) C(2M)-C(2E) C(2)-C(3) C(2)-B(6)
Bond Distances, A 2.225(4) C(3M)-C(3) C(3M)-C(3E) 2.239(4) 2.268(4) C(3)-B(4) 2.198(4) C(7)-B(5) C(8M)-C(8) 2.167(4) C(8M)-C(8E) 2.209(4) 2.238(4) C(8)-C(9) C(8)-B(12) 2.252(4) C(9M)-C(9) 2.236(4) C(9M)-C(9E) 2.184(5) C(9)-B(10) 2.196(5 C(lO)-B(ll) 2.240(4) 2.221(4) C(lRl)-C(lR2) C(lRl)-C(lRG) 2.225(4) 2.194(4) C(lRl)-C(lR7) C(lR2)-C(lR3) 2.187(4) C(lR3)-C(lR4) 2.247(4) 2.262(4) C(lR4)-C(lR5) C(lR4)-C(lR8) 2.239(4) C(1R5)-C( 1R6) 2.215(4) C(lR8)-C(lR9) 2.186(4) C(lR8)-C(lRlO) 2.245(5) C(2Rl)-C(2R2) 2.173(4) C(2Rl)-C(2R6) 2.192(4) C(2Rl)-C(2R8) 2.187(4) 2.175(4) C(2R2)-C(2R3) 2.117(4) C(2R3)-C(2R4) C(2R4)-C(2R5) 2.064(4) 2.062(4) C(2R4)-C(2R7) C(2R5)-C(2R6) 2.061(5) 2.077(5) C(2R8)-C(2R9) C(2R8)-C(2R10) 2.109(5) 1.502(5) B(4)-B(5) 1.506(5) B(5)-B(6) B(lO)-B(ll) 1.465(5) B(111-B( 12) 1.559(6)
1.518(5) 1.525(5) 1.553(6) 1.593(6) 1.526(5) 1.529(5) 1.450(5) 1.564(6) 1.521(5) 1.515(6) 1.558(6) 1.587(6) 1.411(6) 1.418(5) 1.509(6) 1.388(6) 1.434(5) 1.421(5) 1.509(6) 1.415(6) 1.524(6) 1.510(6) 1.438(5) 1.418(5) 1.503(5) 1.421(5) 1.422(6) 1.408(5) 1.498(5) 1.420(5) 1.548(6) 1.528(6 1.755(6) 1.795(6) 1.822(6) 1.762(6)
orange-brown. The mixture was warmed to room temperature and stirred overnight, after which it was opened to the air, causing a color change t o dark green. The solution was stripped of solvent, and the residue was washed with CHzClz through a 2-cm silica column. The filtrate was evaporated to dryness and the residue was chromatographed in 2 : l hexane1 CHzClZ, giving a pale green band of unreacted 3 (190 mg, 40% recovery) and two dark green, nearly black bands. The first of these bands, which had a mass spectral parent ion (base peak) at mlz 808, was identified via X-ray crystallography as 8c, 25 mg (0.031 mmol, 8.6% yield based on 3 consumed). The second band, having a parent ion a t mlz 794, was 8a, 108 mg (0.136 mmol, 37.8%). The proton NMR spectrum of paramagnetic 8a was assigned via correlation with that of its diamagnetic anion 8a- (vide supra and supporting information). lH NMR (CDC13, ppm relative to TMS) for 8a: 13.06 (CH*Me2), 8.94 (ethyl CHz), 6.74 (ethyl CH2), 1.70 (CHMe*2), -0.02 (ethyl CH3), -1.36 (C&4), -4.19 (C6H4). For K+8a-in THF-da: 4.34 m (C6H4),4.26 m (C6H4),2.98 m (ethyl CH2), 2.34 m (CH*MeZ), 2.19 m (ethyl CHz), 1.37 t (ethyl CH3), 1.06 d (CHMe*2),0.81 s (B-CH3). IR (cm-') for 8a: 2960 vs, 2925 vs, 2874 vs, 2495 vs, 1445 s, 1372 s, 1283 s, 1112 m, 1069 s, 1031 m, 874 m, 809 s; for 8c, 2960 vs, 2926 vs, 2868 m, 2507 s, 2469 s, 2361 m, 2343 m,1447 m,1374 m,1283 m , 1 1 5 1 w , 1 1 1 2 m,1069 s, 1031 m, 940 w, 888 w, 856 w, 813 m. UV-visible absorptions (nm) for 8a: 318 (loo%), 594 (10%); for 8c, 320 (loo%), 594 (11%). Anal. Calcd for RuzCoC34BsHsa (8a): C, 51.51; H, 7.37. Found: C, 51.99; H, 7.19.
Synthesisof [ C ~ R U ( ~ , ~ - E ~ ~ C ~ B & I(7b), ~ - ~[Cy-C~)I~COH RU(~,~-E~~CZB~H~-~-C~)I&O (8b),and CyRu(Et2C2B3Hz-5Cl)Co(Et&zB&Ia)RuCy (8d). Following the same procedure
as in the preceding synthesis, 225 mg (0.56 mmol) of 6 in 50 mL of THF was deprotonated with 1.06 mmol of tert-butyllithium and reacted with 40 mg (0.30 mmol) of CoC12 (added a t -78 "C). After the solution had been stirred overnight a t room temperature, the mixture was opened to the air and worked up as before. Chromatography on silica with 2:l Bond Angles, deg 132.7(3) 114.3(3) CH2Clz/hexane gave three bands, the first of which was light 129.0(3) 133.7(3) brown unreacted 6 (70 mg, 0.18 mmol). The second band was 120.6(3) 128.0(3) dark brown diamagnetic 7b (90 mg, 0.11 mmol, 55% based on 126.4(3) 120.5(3) 6 consumed). The last band eluted was red-orange paramag113.0(3) 113.9(3) netic 8d (40 mg, 0.05 mmol, 25%), whose mass spectrum 115.1(3) 125.6(3) (parent base peak a t mlz 801) indicated a monochlorinated 119.1(3) 113.9(3) tetradecker, Le., with one less C1 atom than 8b. 114.2(3) 107.0(3) 126.7(3) 130.0(3) Exposure of 7b in the same solvent mixture to air on a silica 132.8(2) 126.8(3) TLC plate for 36 h resulted in complete conversion of that 129.9(3j 99.5(3) compound to green paramagnetic 8b, with no decomposition. 115.1(3) 106.3(3) MS for 7b: base peak at mlz 835, cutoff at mlz 842 corre133.0(3) 105.7(3) sponding to calcd spectrum for RuzCoClzC32B,&3. 'H NMR 129.7(2) 131.7(3) (CDCl3, ppm relative to TMS): 4.86 m (C&I4),2.84 m (CH*Me2), 119.8(3) 125.8(3) 2.16 m (ethyl CHZ)1.96 s (cymene tolyl CH31, 1.41 t (ethyl 125.8(3) 130.7(3) CHz), 1.16 d (CHMe*2),-6.66 s (Co-H), -8.31 s (Ru-H?). 13C 114.4(3) 106.8(3) NMR (cDc13, ppm vs TMS): 106.8 (unsubstituted cymene ring carbons), 96.4 (unsubstituted cymene ring carbons), 83.8 1.26 d (CHMe*z),1.07 m (CH~CHZ).13C NMR (CDC13, ppm vs (substituted cymene ring carbons), 81.1 (substituted cymene TMS): 112.1 (unsubstituted cymene ring carbons), 101.3 ring carbons), 31.7 (C*HMe2),27.2 (tolyl CH3),23.4 (ethyl CH2), (unsubstituted cymene ring carbons), 89.2 (substituted cymene 19.4 (isopropyl CH3), 16.1 (ethyl CH3). IR (cm-l): 2961 vs, ring carbons), 86.5 (substituted cymene ring carbons), 32.0 2926 vs, 2870 vs, 2515 vs, 1476 m, 1447 s, 1377 s, 1319 w, (C*HMe2), 25.5 (cymene tolyl CH3), 23.7 (ethyl CHz), 20.0 1279 w, 1055 w, 1032 w, 947 s, 847 m, 804 vs, 733 w. W(isopropyl CH3), 17.3 (ethyl CH3). visible (nm) for 8b: 324 (loo%), 590 (10%). Anal. Synthesis of [ C ~ R ~ ( Z , ~ - E ~ ~ C ~ B ~(8a) H~and ~-M~) I Z Cabsorptions O C~RU(E~&B~HZ-~-M~)CO(E~ZCZB~ (8c). H ~ -A~ - E ~Calcd ) R Ufor C ~Ru2CoClzC32BsH52 (8b): C, 46.11; H, 6.29. Found: C, 45.93; H, 6.89. 475-mg (1.22 mmol) sample of 3 was dissolved in ca. 75 mL of MS for 8d: base peak a t mlz 801, cutoff a t mlz 807 THF and placed in a 3-neck 100-mL flask containing a stir H~~. corresponding to calcd spectrum for R u z C O C ~ C ~ Z B SWbar which was fitted with a septum and a sidearm tip-tube visible absorptions (nm): 316 (loo%), 448 (lo%), 738 (4%). IR charged with 75 mg (0.58 mmol) of anhydrous CoClz and (cm-l): 2961 vs, 2925 vs, 2868 s, 2515 vs, 2361 vs, 1458 m, attached t o a vacuum line. Under argon, the mixture was 1375 s, 1319 w, 1262 w, 1055 w, 1032 w, 941 s, 889 m, 810 s, cooled t o -60 "C and 0.7 mL of 1.7 M (1.19 mmol) tert669 m. butyllithium was added via syringe, producing a n immediate color change from pale yellow to canary yellow. The solution Synthesis of [ C ~ R U ( ~ , ~ - E ~ & B ~ H Z(9)~ . Using -M~)I~N~ was warmed t o room temperature, stirred for 30 min, and a n apparatus and procedure identical to that employed in the cooled to 0 "C, and the cobalt salt was added via rotation of preparation of 8a, a 390-mg (1.06 mmol) sample of 3 was the sidearm. As it slowly dissolved, the color changed to dark dissolved in ca. 75 mL of THF and deprotonated with 1.14
Organometallics, Vol. 14,No.8,1995 3691
Organotransition-MetalMetallacarboranes
Table 5. Comparison of Tetradecker Sandwich Structures
ref no. of valence electrons
a
a
a
41
41
42
M-M'-M angle (deg)d dihedral angles (degy ring 1-ring 2 ring 2-ring 3 ring 3-ring 4 ring 1-ring 4 rotational twist (deg)f M - M distances (A) carborane C-C distances (A) M'-CzB3 distances (AF M-CzB3 distances (AF M-C, ring distances (AF
175
174
4.3 8.0 3.2 14.5 95 3.32, 3.32 1.46, 1.47 1.60, 1.59 1.73, 1.72 1.72, 1.73
4.1 9.1 3.4 15.1 98 3.31, 3.32 1.46, 1.49 1.58, 1.59 1.73, 1.73 1.72, 1.72
b 42
b 40
166
b 42 (Co-Ni- COT 41 (CO-CO- .COY 172
171
165
7.4 16.2 6.4 29.2 48 3.33,3.33 1.47, 1.45 1.60, 1.60 1.73, 1.73 1.71, 1.71
6.4 9.4 5.1 20.4 75 3.19, 3.19 1.47, 1.48 1.61, 1.62 1.58, 1.58 1.67, 1.68
4.5 11.8 3.7 20.0 27 3.18, 3.19 1.44, 1.49 1.62, 1.62 1.57, 1.58 1.67, 1.68
5.0 22.1 6.6 33.7 89 3.30, 3.30 1.47, 1.46 1.76, 1.75 1.56, 1.55 1.69, 1.69
This work. Reference 3a. Isomorphous structures. M = central metal, M = outer metals. e Top and bottom rings are 1 and 4, respectively, in each structure. f Dihedral angle between M'-BB-M and M'-Bll-M planes. 8 Metal-ring perpendicular vectors. mmol of tert-butyllithium a t -60". After warming to 0 "C, 75 mg (0.58 mmol) of NiClz was added from the sidearm and the reaction mixture turned green and finally dark greenish brown. After the mixture had been stirred overnight at room temperature, the solution was opened to the air and worked up as in the synthesis of 8a. Chromatography on silica in 1:l hexane1CHzClz gave a colorless band of unreacted 3 (175 mg, 45% recovery) and a major green band, as well as several smaller bands that were not collected. Further chromatography of the major band in 2 5 1 hexanelCHzClz afforded a major green fraction and three smaller bands, two green and one brown. The major band was dark green crystalline 9 (50 mg, 0.063 mmol, 22% yield based on 3 consumed), a moderately air-stable diamagnetic complex t h a t decomposes in air over several weeks. MS: base peak at mlz 793, cutoff at mlz 800 corresponding to calcd spectrum for RuzNiC34B6Hs~. Anal. Calcd for RuzNiC34B6Hs~:C, 51.53; H, 7.38. Found: C, 51.97; H, 7.55. 'H NMR (CDC13, ppm relative to TMS): 4.77 m (C6H4), 2.54 m (CH*MeZ), 2.29 m (ethyl CHZ)1.96 s (cymene tolyl CH3), 1.27 t (ethyl CH3), 1.21 s (B-CHs), 1.16 d (CHMe*Z). 13C NMR (CDC13, ppm vs TMS): 106.8 (unsubstituted cymene ring carbons), 95.8 (unsubstituted cymene ring carbons), 82.8 (substituted cymene ring carbons), 80.1 (substituted cymene ring carbons), 32.2 (C*HMeZ),23.7 (tolyl CH3), 23.4 (ethyl CHz), 19.5 (isopropyl CH3), 15.7 (ethyl CH3). IR (cm-'): 2961 vs, 2926 vs, 2870 vs, 2515 vs, 1476 m, 1447 s, 1377 s, 1319 w, 1279 w, 1055 w, 1032 w, 947 s, 847 m, 804 vs, 733 w. UVvisible absorptions (nm): 338 (loo%),386 (45%), 606 (5%),656 (6%).
Synthesis of [C~RU(~,~-E~ZCZB~M~~)IZCO (10)and [CyRu(2,3-EtzC&Mes)]~Ni (11). The above procedure was employed using 200 mg (0.50 mmol) of 4, 0.50 mmol of tertbutyllithium, and 33 mg (0.25 mmol) of CoClz in ca. 50 mL of THF. Following deprotonation of the carborane complex, CoC12 was added a t -78 "C and the mixture was allowed to warm overnight, producing a color change to brownish-green. The solvent was stripped off, and the residue was dissolved in hexane and filtered through a standard medium-porosity frit under vacuum (the product decomposes on silica or alumina). A mass spectrum revealed the presence of the hexamethyl product 10 (mlz 849) and a n unidentified minor product (mlz 656). Unreacted 4 ('50% recovery) and the lower
MW product were removed by sublimation in vacuo, leaving behind nonvolatile paramagnetic 10 as a dark green oil (18 mg, 0.02 mmol, ca. 17%). MS: base peak a t mlz 849, cutoff at mlz 855 corresponding to calcd spectrum for Ru~CoC3&36&6. IR (cm-l): 2961 vs, 2926 vs, 2870 vs, 2486 m, 2361 vs, 1456 vs, 1375 s, 1292 vs, 1261 w, 1152 w, 1082 s, 1053 s, 1030 s, 966 w, 872 vs, 801 vs, 741 w, 667 m. UV-visible absorptions (nm): 334 (loo%), 792 (7%). The same method was followed using 600 mg (1.50 mmol) of 4, 1.5 mmol of tert-butyllithium, and 98 mg (0.75 mmol) of NiClt in ca. 50 mL of THF. A similar workup procedure was employed except that the final filtration was done in CHzClz solution, giving 11 as a dark green oil (28 mg, 0.033 mmol, ca. 9%) with 50% recovery of starting complex 4. MS: base peak a t mlz 849, cutoff a t mlz 855 corresponding t o calcd spectrum for R U Z N ~ C ~ ~ B SIR H S(em-'): ~. 2959 vs, 2924 vs, 2868 vs, 1456 m, 1375 w, 1294 m, 1261 m, 1091 s, 1028 s, 864 m, 801 s. UV-visible absorptions (nm): 298 (35%), 360 (loo%),718 (5%). X-ray Structure Determinations. Diffraction data were collected on a Rigaku AJXGS diffractometer at -100, -120, and -110 "C for 8a, 812,and 9, respectively, using Mo K a radiation (1= 0.710 69 A). Details of the data collections and structure determinations are listed in Table 1. For each crystal, the intensities of three standard reflections were monitored, showing no significant variation. Empirical absorption corrections were applied following 1~ scanning of several reflections (transmission factors are reported in Table 1). All calculations were performed on a VAX station 3520 computer employing the TEXSAN 5.0 crystallographic software package." The structures were solved by direct methods in SIR88.12 Full-matrix least-squares refinement with anisotropic thermal displacement parameters was carried out for each structure, and the results are summarized in Table 1. The crystal lattice of 8a contained two molecules of dichloromethane solvent per molecule of the complex, and hightemperature factors indicated t h a t the molecular positions (11)TEXSAN 6.0: Single Crystal Structure Analysis Software. Molecular Structure Corporation: The Woodlands, TX 77381;1989. (12)SIR88: Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.; Polidori, G.; Spagna, R.; Viterbo, D. J . Appl. Crystallogr. 1989,22, 389.
Greiwe et al.
3692 Organometallics, Vol. 14, No. 8, 1995 were only partially populated. In the final cycles, these atoms were refined using population parameters of 0.5 and isotropic thermal parameters. In compound 8c ring C(lRl)-C(lRlO) was disordered; consequently, these carbon atoms were refined with isotropic thermal parameters. In addition, difference Fourier maps showed that the isopropyl group on this ring was disordered between two orientations. The carbon atoms belonging to these orientations were refined with occupancy factors of 0.6 and 0.4 for groups C(lRSA)-C(lRlOA) and C(lRSB)-C(lRlOB), respectively. The final difference Fourier maps for 8c and 9 were essentially featureless. The map for 8a showed a peak ca. 1.1e/A3 high located in the vicinity of one of the disordered solvent molecules.
Acknowledgment. This work was supported by the National Science Foundation, Grant No. CHE 9322490, and the US. Army Research Oflice. We thank Dr. Yaning Wang for recording the ESR spectra and Dr. Eric Houser for the elemental analyses. Supporting Information Available: Tables of atomic coordinates, isotropic and anisotropic displacement parameters, and calculated mean planes for 8a,c and 9 (15 pages). Ordering information is given on any current masthead page.
OM9502244
