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Monomeric and dimeric ruthenium-TCNQ complexes containing phosphine ligands (TCNQ = 7,7,8,8-tetracyanoquinodimethane)
PolyhedronVol. 15, No. 2~ pp. 211 217. 1996
~
Pergamon 0277-5387(95)00275-8
Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 027%5387/96 $9.50 ~-0.00
MONOMERIC AND DIMERIC RUTHENIUM-TCNQ COMPLEXES CONTAINING PHOSPHINE LIGANDS (TCNQ = 7,7,8,8-TETRACYANOQUINODIMETHANE) L. BALLESTER,* M. C. BARRAL, R. JIMI~NEZ-APARICIO and B. OLOMBRADA Departamento de Quimica Inorg~inica, Facultad de Ciencias Quimicas, Universidad Complutense, Ciudad Universitaria, 28040 Madrid, Spain
(Received 15 March 1995; accepted 25 May 1995) Abstract--Treatment of [Ru(CO)2(PPh3)z(THF)2] (BF4)2 with LiTCNQ (TCNQ = 7,7,8,8tetracyanoquinodimethane) in dichloromethane at reflux resulted in the formation of [Ru(CO)2(PPh3)2(TCNQ)]BF4 (1). The synthesis of the carbonylhydride compound [RuH(CO)(PPh3)2(TCNQ)]2 (2) was carried out by reaction of RuHCI(CO)(PPh3)3 and T C N Q or from [RuH(CO)(PPh3)2(CH3CN)2]PF6 and LiTCNQ. The preparation of compounds with diphosphines [Ru(dppe)2(TCNQ)]zTCNQ(C104) (3) and [Ru(dppm)3 TCNQ]C104 (4) is also described. In all cases substitution reactions of labile ligands occurred with formation of compounds with a-coordinated TCNQ. From IR, UV-vis, 1H and 31p N M R spectroscopy and FAB mass spectrometric determinations, monomeric and dimeric compounds are proposed.
The reactivity of the conjugated polynitriles, T C N X (tetracyanoethylene, T C N E ; 7,7,8,8-tetracyanoquinodimethane, TCNQ), towards organometallic compounds, in a low or normal oxidation state, offers interesting possibilities because of the T C N X acceptor properties and their capacity to act as mono- or polydentate ligands. Different R u - T C N E compounds obtained from metal complexes and T C N E have been reported. 2 Their properties are very dependent on the electronic characteristics of the metallic fragment. The number of R ~ T C N Q compounds are scarce and we are interested in the reactivity of T C N Q towards [RuL,] 2+ fragments with different coordination environments. Because of the planarity of T C N Q '~ (0 < 6 < 2) units we are focusing the influence of their relative position in the solid array on the formed solid properties. Kaim and co-workers 2c have reported the reactivity of the very stable R u - - R u bonded compounds towards T C N Q ° or T C N Q ° LiTCNQ.
* Author to whom correspondence should be addressed.
They have obtained complexes with T C N Q a-coordinated in a monodentate fashion and complexes which contain both monodentate and uncoordinated TCNQ. Spectroscopic studies in solution have permitted them to distinguish both T C N Q units. From our preliminary results on the formation of the stacked dimeric compound 3 [Ru(PPh3)2(# 2TCNQ)]2 and on the first a-bonded N i - T C N Q complex, 4 [NiLR(TCNQ)2] (L R = 1,8-R2-1,3,6, 8,10,13-hexaazacyclotetradecane, R = C2H4OH, C2H5, CH2C6Hs) , we have extended this study to the new Ru I1 complex [Ru(CO)2(PPh3)2(THF)2] BF4 and the ones described previously, [Ru(H) (CO) (PPh3)z(CHsCN)2I (PF6)2, Ru(H)(C1)(CO) (PPh3)3 and [Ru(P--P)s(C1Oa)]C104 [P--P = 1,2bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)methane (dppm)]. In order to facilitate the a-coordination of T C N Q - , we have used these complexes with anionic groups (BF4, P F 6 , C I O g ) and with labile ligands (THF, CH3CN, C104). We report here monomeric and dimeric compounds containing [Ru(PPh3)2 (L)2]2+ (L = H, CO) or [Ru(P--P),] 2+ (x = 2, P - - P = dppe; x = 3, P - - P = dppm) fragments.
211
L. BALLESTER et al.
212
On the basis of the fully characterized 3 [Ru (PPh3)2(/.t2-TCNQ)]2 and from spectroscopic measurements and mass spectrometric determinations, we propose different coordination environments for ruthenium atoms. Related studies in which the starting Ru l~ complexes [Ru (PPh3)2(S--S)2 ] (S--S = S2COR, S2CNR2) contain the fragment [Ru(PPh3)2] 2+ and very inert bidentate ligands are in progress. 5 RESULTS AND DISCUSSION The synthetic procedure is shown in Scheme 1.
Complexes 1 and 2 The reactions (Scheme 1) of carbonylphosphine complexes of Ru" with LiTCNQ occur with total substitution of labile ligands and total or partial replacement of non-coordinated PF6 or BF4 anions. In the case of [Ru(CO)2(PPh3)2(th02](BF4)2, the excess of PPh3 plays a very important role giving the complex 3 [Ru(PPh3)2(#2-TCNQ)]2, whereas in the absence of PPh 3 the complex [Ru(CO)2 (PPh3)2(TCNQ)]BF4 (1) is formed. From the starting complex [RuH(CO)(PPh3) 2 (CH3CN)2]PF6, a complete replacement of CH3-CN and PF6 occurs to give complex [RuH (CO)(PPh3)2(TCNQ)]2 (2). This compound can also be obtained from T C N Q and the neutral corn-
plex RuHCI(CO)(PPh3)3, in which the substitution of the labile C1 and PPh3 ligands occurs.
Physicalproperties. The IR spectra of complexes 1 and 2 (Table 1) show the characteristic vibrations for the radical anion TCNQ=. As pointed out by Lunelli and Pecile, 6 it is possible to determine whether T C N Q 2-, T C N Q - , T C N Q '~- (0 < 6 < 1) or T C N Q ' (or a combination of these possibilities) is present by examining its IR spectra in the region of 800-880 cm- ~. Complexes I and 2 present only one absorption around 830 cm t. This is a clear indication that T C N Q - is present. With respect to the v(CN) bands, we have observed that no T C N Q ~ or T C N Q 2- is present, and two or three v(CN) bands are observed in the range corresponding to T C N Q . The number and intensity of these bands are very dependent not only on the T C N Q status, but also on the symmetry of the R u - T C N Q complex. As reported, 3 free D2/, symmetry species show a maximum of two such IR bands. The r/I-coordinated T C N Q molecules or ions should exhibit four bands, the highest energy band being the weakest. For the monomeric complex [Ru(CO)2(PPh3)2(TCNQ)]BF4, two characteristic absorptions for the r/l-coordinated T C N Q are observed, similar to those 5 corresponding to [Ru (PPh3)(S2COR)2(TCNQ)]. The Aq activated modes at 1578 (v3), 1355 (v4), 1175 (vs), 722 (v7), 620 (vs) and 325 (Vg) cm ~ are observed, indicating that dimerized (TCNQ)22 is present in the solid state.
RuC~(CO)2(PI'%)2 AgBF4 [
I
PPh3(execss) LiTCNQ
" ['Ru(PPh3)2(TCNQ)12
0ee ref.3)
IRu(CO)2(PPt~)2(t~021(BF4)2
I
LiTCNQ
[Ru(H)(CO)(PPh3)2(CH3CN)2](PF¢)
L IRu(CO)20,pa3)20"C~rQ)I03F4) (I) LiT(~Q [Ru(H)(CO)(PPI~)2(TCNQ)I2
IRu0~)o(coxPP%h
IRu(dpl~h(CIO~)](ClO4)
lRu(dPVmh(CZO,)l(OO,) '
TC-~Q LiTCNQ
LiTCNQ
(2)
1 . IRu(@P%ffCNQ)12(TCNQ)(OO,)
m,Ru(dppm)3('I'CNQ)(,CIO4)
(4)
Scheme 1. Reactions of carbonylphosphine complexes of Ru" with LiTCNQ or TCNQ.
O)
Ruthenium-TCNQ complexes
213
Table 1. IR vibrational frequencies (cm -~) of ruthenium complexes"
Aq modes Compound
v(CN)
Y3
Y4
Y5
Y7
Y8
v9
6(CH)
TCNQ
2197s 2166m 2200sh 2170s 2140m 2180m 2140m 2200sh 2180s 2160sh 2190s 2145s
1578
1355
1175
722
620
325
820w
1575
1355
1175
722
620
325
830w
1575
1355
1175
722
620
325
1578
1355
1175
722
620
325
840w 810w 850w 810w
1575
1355
1175
722
620
325
1575
1355
1175
722
620
325
[Ru(PPh3)2(~2-TCNQ)]2 h
! 2
3
2190s 2140sh
850sh 830w 810sh 825w
"KBr disc. hSee ref. 3.
Broad and intense bands are found in the regions of 1000-833,625-555 and 400-333 nm, assigned to a CT1, LE~ and L E f in dimerized T C N Q complexes. Complexes 1-3 are highly insoluble in normal organic solvents. The electronic spectra in D M S O or D M F show absorptions in the same region. As pointed out by K a i m and co-workers 2° in [(L')~Ru2(TCNQ)](BPh4), the spectrum of coordinated T C N Q - is similar to that of free T C N Q - , but the bands are less well structured and less intense. In our case we can propose that in solution T C N Q is dissociated. Only in the case of very dilute solutions ( ~ 1 0 -5 M) do the spectra present the characteristic absorptions of completely dissociated T C N Q - , with e(394 nm)/e(842 nm) ~ 0.6. Charge transfer Ru ~ zr*(CO) absorptions are in the region 475~J~90 nm. The presence of (TCNQ)22- fragments formed by intermolecular dimerization, similar to that observed 4 in Ni(LR)(TCNQ)2, or intramolecular dimerization, as shown by the crystal structure of the complex 3 [Ru(PPh3)2(#2-TCNQ)]2, are responsible for the spectroscopic properties described. The kH N M R spectra of these compounds show a very low resolution typical of paramagnetic compounds, suggesting the dissociation of paramagnetic T C N Q ~. The FAB mass spectrum of [Ru(CO)2 (PPh3)2(TCNQ)]BF4 (1) does not show the peak corresponding to the intact cation [Ru(CO)2 (PPh3)2(TCNQ)] +. The high-mass peak (m/z = 848) could correspond to [Ru(CO)2(PPh3)2
(TCNQ-CCN)]+. Further decomposition of this cation forms the fragment [Ru(CO)2(PPh3)2] + ; the loss of two CO groups leads to the [Ru (PPh3)2] + fragment. The base peak ion (rn/z = 364) in the spectrum is formed by loss of PPh3 of this last fragment to give [Ru(PPh3)] ÷. Other peaks corresponding to the fragmentation of the coordinated PPh 3 ligand are also observed. The FAB mass spectrometric data of this compound suggest that [Ru(CO)2(PPh3)2(TCNQ)]BF4 is a mononuclear species. The FAB mass spectrum of [RuH(CO)(PPh3)2 (TCNQ)]2 (2) shows several peaks containing the Ru(PPh3)2 unit, such as [Ru(PPh3)2(TCNQ)] + (m/z = 830) and [Ru(PPh3)2(CO)(TCNQ)] ÷ (m/z = 858). Other peaks at higher mass of the m o n o m e r compound are also observed, such as {[Ru(PPh3)2(CO)]2TCNQ} + ( m / z - - 1512). The presence of these peaks seems to indicate the dimeric nature of the compound. Because of the failure in all attempts to obtain suitable crystals for X-ray structure determination of complexes 1 and 2, we suggest a monomeric or dimeric nature on the basis of the experimental data obtained. In the case of complex 1, we propose a monomeric structure with pentacoordinate Ru n centres. The coupling of two [Ru(CO)2(PPh3)2 (TCNQ)] ÷ cations through T C N Q ligands gives intermolecular ( T C N Q ) f - fragments (Fig. 1), similar to that found 4 in Ni(LR)(TCNQ)2. For compound 2 we propose a dimeric structure with hexacoordinate Ru H atoms. The parent compound
L. BALLESTER et al.
214
that the solid complexes contain TCNQ in dimerized form. Complex 4 shows a sharp absorption at 825 cm -~, whereas in the case of complex 3 an absorption at 830 cm ~ with shoulders at 850 and NC C N ~ CO 810 cm -j is observed. Complexes 3 and 4 present a very different behaviour in solution. Complex 4 decomposes instantaneously to produce a very high concentration of paramagnetic species, which precludes 1H and 3~p N M R studies. Complex 3 presents a higher stability and although the 1H N M R spectrum shows a low oc P resolution, mono- and bidentate dppe ligands are observed. Thus, a broad signal at 2.82 ppm corresponding to the methylene protons of chelated dppe is observed ; a singlet at 1.55 ppm, assigned to P ~ ~ ' - C N ~ C O methylene protons of a monodentate dppe ligand, is also observed. The presence of monodentate and chelated dppe is confirmed by the 3~p N M R spectrum. This spectrum displays signals to monoI --No--G dentate dppe at -14.70 ppm (uncoordinated phosphorus atom) and to 45.20 ppm (coordinated phosphorus atom); the chelated dppe shows a doublet centred at 43.29 ppm. These signals are Fig. 1. Proposed structures for [Ru(CO)2(PPh3)2 similar to those observed 8 for the starting com(TCNQ)]BF4 (1) and [RuH(CO)(PPh3)2(TCNQ)]2 pound [Ru(dppe)3(C104)]C104. (2). The UV-vis spectrum of complex 3 in DMSO solution shows charge transfer absorptions at very low energies, whose shape indicates new maxima of 2, [Ru(H)(CO)(PPh3)2(CH3CN)2]PF6, has the below 1000 nm. This spectrum excludes the exisPPh3 ligands in trans positions and the CO and tence of free T C N Q - in solution, as happens in the hydride ligands in cis positions. The spectroscopic dppm complex and in complexes 1 and 2, indicating data of 2 suggest the same stereochemistry for the an extensive electronic delocalization, as found 9 in [RuH(CO)(PPh3)2] moieties which are bonded [(RezCI4(dppm)2)2(#-TCNQ)] and in polynuclear by intramolecular (TCNQ)2:- fragments, similar TCNE complexes. 2 The solid state spectrum shows to that found in the complex 3 [Ru(PPh3)2 characteristic bands of higher electronic delocaliz(#2-TCNQ)]2, giving [RuH(CO)(PPh3)2(TCNQ)]2 ation than in complex 2. The FAB mass spectrum of 3 does not show a (Fig. 1). Complexes 1 and 2 are diamagnetic in the solid molecular peak. However, peaks corresponding to the state and show paramagnetic behaviour in solution, fragments [Ru(TCNQ)] + (m/z = 306), [Ru(dppe)] + (m/z=500) and [Ru(dppe)2] + (m/z=898) are indicating TCNQ ~ dissociation. We have tried to produce shorter ring-ring dis- observed. No peaks containing C104 groups are tances by introducing new TCNQ molecules in present, which is expected if the CIO4- group is order to improve the electrical conductivity, but all a counterion in the compound; however, from attempts were unsuccessful, probably due to the this group chlorine atoms can be generated and peaks containing chlorine atoms are also observed, bulky PPh3 ligands. such as [Ru(dppe)2C1] + (m/z = 933), Ru(dppe)2Cl (TCNQ) (m/z= 1137) and [Ru(dppe)zCl]2TCNQ Complexes 3 and 4 (m/z = 2072). The formation of chloro ligand from From [Ru(P--P)3(C10,)]C104 ( P - - P = d p p e , the C104 anion has been observed in both mass dppm) and LiTCNQ, we have obtained (Scheme 1) spectra and chemical reactions of ruthenium comtwo different compounds containing uncoordinated pounds/ ° Due to the presence of the C104- group in C104- [1190 and 620 cm 1, v(CIO) and di(OC10), 3 the chlorine atoms could be generated in the FAB respectively] .8 process, leading to the formation of stable fragments In the IR spectra, the main absorptions for containing chlorine atoms. In fact, the base peak of TCNQ units (Table 1) are in the same regions as the spectrum corresponds to the fragment those observed for complexes 1 and 2, indicating Ru(dppe)2Cl (m/z = 933). co P
P NC~CN
1
P
P
Ruthenium-TCNQ complexes On the basis of these data, we propose for complex 3 a hexacoordinate RuP3N3 environment. Each ruthenium atom is bonded to one dppe monodentate and one dppe chelate; these Ru(dppe)2 moieties are bridged by (TCNQ)22- fragments, giving dinuclear units of the type [Ru(dppe)2 (TCNQ)]2, which are also bridged by other TCNQ molecules leading to infinite chains (Fig. 2). In the case of complex 4 the arrangement of the dppm ligands is analogous to the starting compound with two chelate and one monodentate dppm ligands. The sixth coordination site of the Ru H atom is occupied by one TCNQ ligand. According to the experimental data, the [Ru(dppm)3(TCNQ)] + cations dimerize through TCNQ ligands, leading to (TCNQ)22 fragments giving [Ru(dppm)3(TCNQ)]22+ (Fig. 2). Complexes 3 and 4 are diamagnetic. The electrical conductivity of 3 (5.13 × 10 -6 ~-)-i c m - l ) is in the same range as that for the complex3 [Ru(PPh3)2(/~2-TCNQ)] 2. In summary, a-bonded TCNQ-Ru complexes were obtained from different starting Ru I1 phosphine complexes. We propose hexa- or pentacoordinated Ru u compounds. The formation of intramolecular (TCNQ)22- fragments, as in complexes 2 and 3,
215
intermolecular (TCNQ)22- interactions, as in complexes 1 and 4, or electronically delocalized bridging TCNQ, as in complex 3, explain the diamagnetic behaviour.
EXPERIMENTAL All reactions were carried out in an inert atmosphere, using standard Schlenk techniques. Solvents were purified and distilled by standard methods. The starting materials [RuC12(CO)2 (PPh3)2] , [Ru(H)(Cl)(fO)(PPh3)3] , [Ru(H)(CO) (PPh3)2(CH3CN)2] (PF6)2, [Ru(dppe)3(CIO4)] (C104) and [Ru(dppm)3(C104)] (C104) were prepared according to the literature. TM RuCI3" 3H20 and all ligands used were purchased from commercial sources. IR spectra were recorded as KBr discs on a Perkin-Elmer 1330 IR spectrophotometer. ~H and 31p{IH} NMR spectra were recorded on a Varian VXR-300S spectrometer, using CDC13 as solvent. ~H NMR chemical shifts are reported in ppm relative to TMS ; 31p chemical shifts are reported in ppm relative to external 85% H3PO4. FAB mass spectra were recorded on a VG AutoSpec spectrometer. Electronic spectra were recorded on a gbc UV-vis 911 spectrophotometer in the region 1000-280 nm, and on a Kontron Uvi-
f--p
P
NC
PINe
pJ 3
NC---"~
P~..-p~ p ~
~
CN
P
Fig. 2. Proposed structures for [Ru(dppe)2(TCNQ)]2TCNQ(C104) (3) and [Ru(dppm)3TCNQ]C104
(4).
216
L. BALLESTER et al.
kon 280 spectrophotometer in the range of 900-190 nm, equipped with diffuse reflectance accessory and BaSO4 as diluent. Elemental analyses for carbon, hydrogen and nitrogen were performed in the Microanalytical Service of the Complutense University of Madrid. Synthesis of [Ru(CO)2(PPh3)2(THF)2] (BF4)2 RuC12(CO)2(PPh3) 2 (0.5 g, 0.65 mmol) was dissolved in T H F (40 cm 3) and AgBF4 (0.28 g, 1.3 mmol) was added. The mixture was stirred at room temperature for ca 12 h, producing a white precipitate of AgC1. The solution was filtered over celite and then concentrated under reduced pressure and layered with petroleum ether (40-60°C). The white solid [Ru(CO)2(PPh3)z(THF)z](BF4)2 was filtered, washed with diethyl ether and dried in a stream of nitrogen. Found: C, 54.9; H, 4.5. Calc. for [Ru(CO)z(PPh3)2(THF)z](BF4)2: C, 55.3; H, 4.6%. Synthesis of [Ru(CO)2(PPh3)2(TCNQ)]BF4 (1) To a solution of [Ru(CO)2(PPh3)2(THF)2](BF4)2 (1 g, 1 mmol) in dichloromethane was added LiTCNQ (0.42 g, 2 mmol). The mixture was stirred at reflux for 6 h, giving a dark green solution. The solution was concentrated under reduced pressure, leaving [Ru(CO)2(PPh3)2(TCNQ)]BF4 as a green solid, which was filtered and washed twice with methanol and diethyl ether, and dried in t'~acuo. Found: C, 61.4; H, 3.6; N, 5.7. Calc. for [Ru (CO)2(PPh3)2(TCNQ)]BF4: C, 61.7; H, 3.5; N, 5.8%. 2 .... (nm, DMSO) : 399, 420, 475, 743, 761, 842. MS: m/z 848 ( M + - C C N ) , 821 [ M + - C (CN)2], 682 [Ru(PPh3)2(CO2)] +, 654 [Ru(PPh3)2 (CO)] +, 626 [Ru(PPh3)2] +, 549 [Ru(PPh3) (PPh2)] +, 364 [Ru(PPh3)] +. Synthesis of [RuH(CO)(PPh3)2(TCNQ)]2 (2) Method (a): from RuHCI(CO)(PPh3)3 and TCNQ. To a heated suspension of T C N Q (0.06 g, 0.3 mmol) in ethanol was added a suspension of RuHCI(CO)(PPh3)3 in ethanol. The mixture was stirred at reflux for 5 h, giving a green solid, which was filtered and washed with acetonitrile and ethanol. Method (b): from [RuH(CO) (PPh3)2 (CH3CN)z]PF6 and LiTCNQ. To a solution of [RuH(CO)(PPh3)2(CH3CN)2]PF6 (0.3 g, 0.34 mmol) in dichloromethane was added a solution of LiTCNQ (0.07 g, 0.34 mmol) in ethanol. The mixture was stirred at room temperature for 2 days, giving a green solid, which was filtered and washed
with CH2Cl2-ethanol. Found: C, 68.6; H, 4.2; N, 6.6. Calc. for [RuH(CO)(PPh3)2(TCNQ)]2: C, 68.5; H, 4.1; N, 6.5%. Zmax/(nm, D M S O ) : 399, 420, 490, 743, 761,842. MS: m/z 1555, 1529, 1512 {[Ru(PPh3)2(CO)]2TCNQ}+, 1293 (1555-PPh3), 1267 (1529-PPh3), 1248 (1510-PPh3), 912, 858 [Ru(PPh3)2(CO)TCNQ] +, 830 [Ru(PPh3)2 TCNQ] +, 754, 654 [Ru(PPh3)2(CO)] +, 626 [Ru(PPh3)2] +, 549 [Ru(PPh3) (PPh2)] +, 364 [Ru(PPh3)] + . Synthesis of[Ru(dppe)2(TCNQ)]2TCNQ(CI04) (3) To a solution of [Ru(dppe)3(C104)]C104 (1 g, 0.7 mmol) in chloroform was added a solution of LiTCNQ (0.28 g, 1.4 mmol) in ethanol. The reaction mixture was stirred at reflux for 7 h. The solution was cooled to room temperature, giving a green precipitate which was filtered, washed with ethanol and dried in vacuo. Found : C, 67.3 ; H, 4.5 ; N, 6.6. Calc. for [Ru(dppe)2(TCNQ)]zTCNQ(CIO4): C, 67.05; H, 4.3; N, 6.7%. •max (nm, D M S O ) : 420, 761,842. M S : m / z 2072 {[Ru(dppe)2C1]2TCNQ} +, 1137 [Ru(dppe)2ClYCNQ]+, 933 [Ru(dppe)2C1] +, 898 [Ru(dppe)2] +, 500 [Ru(dppe)] +, 306 [RuTCNQ] + . Synthesis of [Ru(dppm)3TCNQ]C104 (4) To a solution of [Ru(dppm)3(C104)]C104 (1 g, 0.7 mmol) in chloroform was added a solution of LiTCNQ (0.14 g, 0.7 mmol) in ethanol. The mixture was stirred at reflux for 6 h. After cooling, petroleum ether was added, giving a dark green solid, which was filtered, washed with ethanol and dried in vacuo. Found: C, 66.7; H, 4.3; N, 3.5. Calc. for [Ru(dppm)3TCNQ]C104: C, 67.1; H, 4.5; N, 3.6%. Acknowled#ements--We are grateful to the Direcci6n General de Investigaci6n Cientifica y T6cnica (DGICYT, Spain) for financial support (projects PB90/0020 and PB91/0402). REFERENCES
W. Kaim and M. Moscherosh, Coord. Chem. Rev. 1994, 129, 157. 2. (a) S. I. Amer, T. P. Dasgupta and P. M. Henry, Inor#. Chem. 1983, 22, 1970 ; (b) M. Moscherosh and W. Kaim, Inor#. Chim. Acta 1993, 206, 229; (c) S. E. Bell, J. S. Field, R. I. Haines, M. Moscherosh, W. Matheis and W. Kaim, Inor9. Chem. 1992, 31, 3269 ; (d) E. Lindner, R. M. Jansen, H. A. Mayer, W. Hiller and R. Fawzi, Or#anometallics 1989, 8, 2355; (e) F. G. Moers and J. P. Launghout, J. lnorg. Nucl. Chem. 1977, 39, 591 ; (f) M. I. Bruce, T. W. Hambley, M. 1.
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B. Taqui Khan, M. Satyanarayan Reddy and K. Veera Reddy, J. Chem. Soc., Dalton Trans. 1985, 2603. 9. S. L. Bartley and K. R. Dunbar, Angew. Chem., Int. Edn Engl. 1991, 30, 448. 10. (a) C. A. Bignozzi, O. Bortolini, O. Curcuruto and M. Hamdan, Rapid Commun. Mass Spectrom. 1994, 8, 706; (b) A. M. Echavarren, J. L6pez, A. Santos, A. Romero, J. A. Hermoso and A. Vegas, Oryanometallics 1991, 10, 2371. 11. (a) T. A. Stephenson and G. Wilkinson, J. Inorg. Nucl. Chem. 1966, 28, 945 ; (b) G. W. Parshall, Inorg. Synth. 1974, 15, 48; (c) B. E. Cavit, K. R. Grundy and W. R. Roper, J. Chem. Soc., Chem. Commun. 1972, 60.
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MONOMERIC AND DIMERIC RUTHENIUM-TCNQ COMPLEXES CONTAINING PHOSPHINE LIGANDS (TCNQ = 7,7,8,8-TETRACYANOQUINODIMETHANE) L. BALLESTER,* M. C. BARRAL, R. JIMI~NEZ-APARICIO and B. OLOMBRADA Departamento de Quimica Inorg~inica, Facultad de Ciencias Quimicas, Universidad Complutense, Ciudad Universitaria, 28040 Madrid, Spain
(Received 15 March 1995; accepted 25 May 1995) Abstract--Treatment of [Ru(CO)2(PPh3)z(THF)2] (BF4)2 with LiTCNQ (TCNQ = 7,7,8,8tetracyanoquinodimethane) in dichloromethane at reflux resulted in the formation of [Ru(CO)2(PPh3)2(TCNQ)]BF4 (1). The synthesis of the carbonylhydride compound [RuH(CO)(PPh3)2(TCNQ)]2 (2) was carried out by reaction of RuHCI(CO)(PPh3)3 and T C N Q or from [RuH(CO)(PPh3)2(CH3CN)2]PF6 and LiTCNQ. The preparation of compounds with diphosphines [Ru(dppe)2(TCNQ)]zTCNQ(C104) (3) and [Ru(dppm)3 TCNQ]C104 (4) is also described. In all cases substitution reactions of labile ligands occurred with formation of compounds with a-coordinated TCNQ. From IR, UV-vis, 1H and 31p N M R spectroscopy and FAB mass spectrometric determinations, monomeric and dimeric compounds are proposed.
The reactivity of the conjugated polynitriles, T C N X (tetracyanoethylene, T C N E ; 7,7,8,8-tetracyanoquinodimethane, TCNQ), towards organometallic compounds, in a low or normal oxidation state, offers interesting possibilities because of the T C N X acceptor properties and their capacity to act as mono- or polydentate ligands. Different R u - T C N E compounds obtained from metal complexes and T C N E have been reported. 2 Their properties are very dependent on the electronic characteristics of the metallic fragment. The number of R ~ T C N Q compounds are scarce and we are interested in the reactivity of T C N Q towards [RuL,] 2+ fragments with different coordination environments. Because of the planarity of T C N Q '~ (0 < 6 < 2) units we are focusing the influence of their relative position in the solid array on the formed solid properties. Kaim and co-workers 2c have reported the reactivity of the very stable R u - - R u bonded compounds towards T C N Q ° or T C N Q ° LiTCNQ.
* Author to whom correspondence should be addressed.
They have obtained complexes with T C N Q a-coordinated in a monodentate fashion and complexes which contain both monodentate and uncoordinated TCNQ. Spectroscopic studies in solution have permitted them to distinguish both T C N Q units. From our preliminary results on the formation of the stacked dimeric compound 3 [Ru(PPh3)2(# 2TCNQ)]2 and on the first a-bonded N i - T C N Q complex, 4 [NiLR(TCNQ)2] (L R = 1,8-R2-1,3,6, 8,10,13-hexaazacyclotetradecane, R = C2H4OH, C2H5, CH2C6Hs) , we have extended this study to the new Ru I1 complex [Ru(CO)2(PPh3)2(THF)2] BF4 and the ones described previously, [Ru(H) (CO) (PPh3)z(CHsCN)2I (PF6)2, Ru(H)(C1)(CO) (PPh3)3 and [Ru(P--P)s(C1Oa)]C104 [P--P = 1,2bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)methane (dppm)]. In order to facilitate the a-coordination of T C N Q - , we have used these complexes with anionic groups (BF4, P F 6 , C I O g ) and with labile ligands (THF, CH3CN, C104). We report here monomeric and dimeric compounds containing [Ru(PPh3)2 (L)2]2+ (L = H, CO) or [Ru(P--P),] 2+ (x = 2, P - - P = dppe; x = 3, P - - P = dppm) fragments.
211
L. BALLESTER et al.
212
On the basis of the fully characterized 3 [Ru (PPh3)2(/.t2-TCNQ)]2 and from spectroscopic measurements and mass spectrometric determinations, we propose different coordination environments for ruthenium atoms. Related studies in which the starting Ru l~ complexes [Ru (PPh3)2(S--S)2 ] (S--S = S2COR, S2CNR2) contain the fragment [Ru(PPh3)2] 2+ and very inert bidentate ligands are in progress. 5 RESULTS AND DISCUSSION The synthetic procedure is shown in Scheme 1.
Complexes 1 and 2 The reactions (Scheme 1) of carbonylphosphine complexes of Ru" with LiTCNQ occur with total substitution of labile ligands and total or partial replacement of non-coordinated PF6 or BF4 anions. In the case of [Ru(CO)2(PPh3)2(th02](BF4)2, the excess of PPh3 plays a very important role giving the complex 3 [Ru(PPh3)2(#2-TCNQ)]2, whereas in the absence of PPh 3 the complex [Ru(CO)2 (PPh3)2(TCNQ)]BF4 (1) is formed. From the starting complex [RuH(CO)(PPh3) 2 (CH3CN)2]PF6, a complete replacement of CH3-CN and PF6 occurs to give complex [RuH (CO)(PPh3)2(TCNQ)]2 (2). This compound can also be obtained from T C N Q and the neutral corn-
plex RuHCI(CO)(PPh3)3, in which the substitution of the labile C1 and PPh3 ligands occurs.
Physicalproperties. The IR spectra of complexes 1 and 2 (Table 1) show the characteristic vibrations for the radical anion TCNQ=. As pointed out by Lunelli and Pecile, 6 it is possible to determine whether T C N Q 2-, T C N Q - , T C N Q '~- (0 < 6 < 1) or T C N Q ' (or a combination of these possibilities) is present by examining its IR spectra in the region of 800-880 cm- ~. Complexes I and 2 present only one absorption around 830 cm t. This is a clear indication that T C N Q - is present. With respect to the v(CN) bands, we have observed that no T C N Q ~ or T C N Q 2- is present, and two or three v(CN) bands are observed in the range corresponding to T C N Q . The number and intensity of these bands are very dependent not only on the T C N Q status, but also on the symmetry of the R u - T C N Q complex. As reported, 3 free D2/, symmetry species show a maximum of two such IR bands. The r/I-coordinated T C N Q molecules or ions should exhibit four bands, the highest energy band being the weakest. For the monomeric complex [Ru(CO)2(PPh3)2(TCNQ)]BF4, two characteristic absorptions for the r/l-coordinated T C N Q are observed, similar to those 5 corresponding to [Ru (PPh3)(S2COR)2(TCNQ)]. The Aq activated modes at 1578 (v3), 1355 (v4), 1175 (vs), 722 (v7), 620 (vs) and 325 (Vg) cm ~ are observed, indicating that dimerized (TCNQ)22 is present in the solid state.
RuC~(CO)2(PI'%)2 AgBF4 [
I
PPh3(execss) LiTCNQ
" ['Ru(PPh3)2(TCNQ)12
0ee ref.3)
IRu(CO)2(PPt~)2(t~021(BF4)2
I
LiTCNQ
[Ru(H)(CO)(PPh3)2(CH3CN)2](PF¢)
L IRu(CO)20,pa3)20"C~rQ)I03F4) (I) LiT(~Q [Ru(H)(CO)(PPI~)2(TCNQ)I2
IRu0~)o(coxPP%h
IRu(dpl~h(CIO~)](ClO4)
lRu(dPVmh(CZO,)l(OO,) '
TC-~Q LiTCNQ
LiTCNQ
(2)
1 . IRu(@P%ffCNQ)12(TCNQ)(OO,)
m,Ru(dppm)3('I'CNQ)(,CIO4)
(4)
Scheme 1. Reactions of carbonylphosphine complexes of Ru" with LiTCNQ or TCNQ.
O)
Ruthenium-TCNQ complexes
213
Table 1. IR vibrational frequencies (cm -~) of ruthenium complexes"
Aq modes Compound
v(CN)
Y3
Y4
Y5
Y7
Y8
v9
6(CH)
TCNQ
2197s 2166m 2200sh 2170s 2140m 2180m 2140m 2200sh 2180s 2160sh 2190s 2145s
1578
1355
1175
722
620
325
820w
1575
1355
1175
722
620
325
830w
1575
1355
1175
722
620
325
1578
1355
1175
722
620
325
840w 810w 850w 810w
1575
1355
1175
722
620
325
1575
1355
1175
722
620
325
[Ru(PPh3)2(~2-TCNQ)]2 h
! 2
3
2190s 2140sh
850sh 830w 810sh 825w
"KBr disc. hSee ref. 3.
Broad and intense bands are found in the regions of 1000-833,625-555 and 400-333 nm, assigned to a CT1, LE~ and L E f in dimerized T C N Q complexes. Complexes 1-3 are highly insoluble in normal organic solvents. The electronic spectra in D M S O or D M F show absorptions in the same region. As pointed out by K a i m and co-workers 2° in [(L')~Ru2(TCNQ)](BPh4), the spectrum of coordinated T C N Q - is similar to that of free T C N Q - , but the bands are less well structured and less intense. In our case we can propose that in solution T C N Q is dissociated. Only in the case of very dilute solutions ( ~ 1 0 -5 M) do the spectra present the characteristic absorptions of completely dissociated T C N Q - , with e(394 nm)/e(842 nm) ~ 0.6. Charge transfer Ru ~ zr*(CO) absorptions are in the region 475~J~90 nm. The presence of (TCNQ)22- fragments formed by intermolecular dimerization, similar to that observed 4 in Ni(LR)(TCNQ)2, or intramolecular dimerization, as shown by the crystal structure of the complex 3 [Ru(PPh3)2(#2-TCNQ)]2, are responsible for the spectroscopic properties described. The kH N M R spectra of these compounds show a very low resolution typical of paramagnetic compounds, suggesting the dissociation of paramagnetic T C N Q ~. The FAB mass spectrum of [Ru(CO)2 (PPh3)2(TCNQ)]BF4 (1) does not show the peak corresponding to the intact cation [Ru(CO)2 (PPh3)2(TCNQ)] +. The high-mass peak (m/z = 848) could correspond to [Ru(CO)2(PPh3)2
(TCNQ-CCN)]+. Further decomposition of this cation forms the fragment [Ru(CO)2(PPh3)2] + ; the loss of two CO groups leads to the [Ru (PPh3)2] + fragment. The base peak ion (rn/z = 364) in the spectrum is formed by loss of PPh3 of this last fragment to give [Ru(PPh3)] ÷. Other peaks corresponding to the fragmentation of the coordinated PPh 3 ligand are also observed. The FAB mass spectrometric data of this compound suggest that [Ru(CO)2(PPh3)2(TCNQ)]BF4 is a mononuclear species. The FAB mass spectrum of [RuH(CO)(PPh3)2 (TCNQ)]2 (2) shows several peaks containing the Ru(PPh3)2 unit, such as [Ru(PPh3)2(TCNQ)] + (m/z = 830) and [Ru(PPh3)2(CO)(TCNQ)] ÷ (m/z = 858). Other peaks at higher mass of the m o n o m e r compound are also observed, such as {[Ru(PPh3)2(CO)]2TCNQ} + ( m / z - - 1512). The presence of these peaks seems to indicate the dimeric nature of the compound. Because of the failure in all attempts to obtain suitable crystals for X-ray structure determination of complexes 1 and 2, we suggest a monomeric or dimeric nature on the basis of the experimental data obtained. In the case of complex 1, we propose a monomeric structure with pentacoordinate Ru n centres. The coupling of two [Ru(CO)2(PPh3)2 (TCNQ)] ÷ cations through T C N Q ligands gives intermolecular ( T C N Q ) f - fragments (Fig. 1), similar to that found 4 in Ni(LR)(TCNQ)2. For compound 2 we propose a dimeric structure with hexacoordinate Ru H atoms. The parent compound
L. BALLESTER et al.
214
that the solid complexes contain TCNQ in dimerized form. Complex 4 shows a sharp absorption at 825 cm -~, whereas in the case of complex 3 an absorption at 830 cm ~ with shoulders at 850 and NC C N ~ CO 810 cm -j is observed. Complexes 3 and 4 present a very different behaviour in solution. Complex 4 decomposes instantaneously to produce a very high concentration of paramagnetic species, which precludes 1H and 3~p N M R studies. Complex 3 presents a higher stability and although the 1H N M R spectrum shows a low oc P resolution, mono- and bidentate dppe ligands are observed. Thus, a broad signal at 2.82 ppm corresponding to the methylene protons of chelated dppe is observed ; a singlet at 1.55 ppm, assigned to P ~ ~ ' - C N ~ C O methylene protons of a monodentate dppe ligand, is also observed. The presence of monodentate and chelated dppe is confirmed by the 3~p N M R spectrum. This spectrum displays signals to monoI --No--G dentate dppe at -14.70 ppm (uncoordinated phosphorus atom) and to 45.20 ppm (coordinated phosphorus atom); the chelated dppe shows a doublet centred at 43.29 ppm. These signals are Fig. 1. Proposed structures for [Ru(CO)2(PPh3)2 similar to those observed 8 for the starting com(TCNQ)]BF4 (1) and [RuH(CO)(PPh3)2(TCNQ)]2 pound [Ru(dppe)3(C104)]C104. (2). The UV-vis spectrum of complex 3 in DMSO solution shows charge transfer absorptions at very low energies, whose shape indicates new maxima of 2, [Ru(H)(CO)(PPh3)2(CH3CN)2]PF6, has the below 1000 nm. This spectrum excludes the exisPPh3 ligands in trans positions and the CO and tence of free T C N Q - in solution, as happens in the hydride ligands in cis positions. The spectroscopic dppm complex and in complexes 1 and 2, indicating data of 2 suggest the same stereochemistry for the an extensive electronic delocalization, as found 9 in [RuH(CO)(PPh3)2] moieties which are bonded [(RezCI4(dppm)2)2(#-TCNQ)] and in polynuclear by intramolecular (TCNQ)2:- fragments, similar TCNE complexes. 2 The solid state spectrum shows to that found in the complex 3 [Ru(PPh3)2 characteristic bands of higher electronic delocaliz(#2-TCNQ)]2, giving [RuH(CO)(PPh3)2(TCNQ)]2 ation than in complex 2. The FAB mass spectrum of 3 does not show a (Fig. 1). Complexes 1 and 2 are diamagnetic in the solid molecular peak. However, peaks corresponding to the state and show paramagnetic behaviour in solution, fragments [Ru(TCNQ)] + (m/z = 306), [Ru(dppe)] + (m/z=500) and [Ru(dppe)2] + (m/z=898) are indicating TCNQ ~ dissociation. We have tried to produce shorter ring-ring dis- observed. No peaks containing C104 groups are tances by introducing new TCNQ molecules in present, which is expected if the CIO4- group is order to improve the electrical conductivity, but all a counterion in the compound; however, from attempts were unsuccessful, probably due to the this group chlorine atoms can be generated and peaks containing chlorine atoms are also observed, bulky PPh3 ligands. such as [Ru(dppe)2C1] + (m/z = 933), Ru(dppe)2Cl (TCNQ) (m/z= 1137) and [Ru(dppe)zCl]2TCNQ Complexes 3 and 4 (m/z = 2072). The formation of chloro ligand from From [Ru(P--P)3(C10,)]C104 ( P - - P = d p p e , the C104 anion has been observed in both mass dppm) and LiTCNQ, we have obtained (Scheme 1) spectra and chemical reactions of ruthenium comtwo different compounds containing uncoordinated pounds/ ° Due to the presence of the C104- group in C104- [1190 and 620 cm 1, v(CIO) and di(OC10), 3 the chlorine atoms could be generated in the FAB respectively] .8 process, leading to the formation of stable fragments In the IR spectra, the main absorptions for containing chlorine atoms. In fact, the base peak of TCNQ units (Table 1) are in the same regions as the spectrum corresponds to the fragment those observed for complexes 1 and 2, indicating Ru(dppe)2Cl (m/z = 933). co P
P NC~CN
1
P
P
Ruthenium-TCNQ complexes On the basis of these data, we propose for complex 3 a hexacoordinate RuP3N3 environment. Each ruthenium atom is bonded to one dppe monodentate and one dppe chelate; these Ru(dppe)2 moieties are bridged by (TCNQ)22- fragments, giving dinuclear units of the type [Ru(dppe)2 (TCNQ)]2, which are also bridged by other TCNQ molecules leading to infinite chains (Fig. 2). In the case of complex 4 the arrangement of the dppm ligands is analogous to the starting compound with two chelate and one monodentate dppm ligands. The sixth coordination site of the Ru H atom is occupied by one TCNQ ligand. According to the experimental data, the [Ru(dppm)3(TCNQ)] + cations dimerize through TCNQ ligands, leading to (TCNQ)22 fragments giving [Ru(dppm)3(TCNQ)]22+ (Fig. 2). Complexes 3 and 4 are diamagnetic. The electrical conductivity of 3 (5.13 × 10 -6 ~-)-i c m - l ) is in the same range as that for the complex3 [Ru(PPh3)2(/~2-TCNQ)] 2. In summary, a-bonded TCNQ-Ru complexes were obtained from different starting Ru I1 phosphine complexes. We propose hexa- or pentacoordinated Ru u compounds. The formation of intramolecular (TCNQ)22- fragments, as in complexes 2 and 3,
215
intermolecular (TCNQ)22- interactions, as in complexes 1 and 4, or electronically delocalized bridging TCNQ, as in complex 3, explain the diamagnetic behaviour.
EXPERIMENTAL All reactions were carried out in an inert atmosphere, using standard Schlenk techniques. Solvents were purified and distilled by standard methods. The starting materials [RuC12(CO)2 (PPh3)2] , [Ru(H)(Cl)(fO)(PPh3)3] , [Ru(H)(CO) (PPh3)2(CH3CN)2] (PF6)2, [Ru(dppe)3(CIO4)] (C104) and [Ru(dppm)3(C104)] (C104) were prepared according to the literature. TM RuCI3" 3H20 and all ligands used were purchased from commercial sources. IR spectra were recorded as KBr discs on a Perkin-Elmer 1330 IR spectrophotometer. ~H and 31p{IH} NMR spectra were recorded on a Varian VXR-300S spectrometer, using CDC13 as solvent. ~H NMR chemical shifts are reported in ppm relative to TMS ; 31p chemical shifts are reported in ppm relative to external 85% H3PO4. FAB mass spectra were recorded on a VG AutoSpec spectrometer. Electronic spectra were recorded on a gbc UV-vis 911 spectrophotometer in the region 1000-280 nm, and on a Kontron Uvi-
f--p
P
NC
PINe
pJ 3
NC---"~
P~..-p~ p ~
~
CN
P
Fig. 2. Proposed structures for [Ru(dppe)2(TCNQ)]2TCNQ(C104) (3) and [Ru(dppm)3TCNQ]C104
(4).
216
L. BALLESTER et al.
kon 280 spectrophotometer in the range of 900-190 nm, equipped with diffuse reflectance accessory and BaSO4 as diluent. Elemental analyses for carbon, hydrogen and nitrogen were performed in the Microanalytical Service of the Complutense University of Madrid. Synthesis of [Ru(CO)2(PPh3)2(THF)2] (BF4)2 RuC12(CO)2(PPh3) 2 (0.5 g, 0.65 mmol) was dissolved in T H F (40 cm 3) and AgBF4 (0.28 g, 1.3 mmol) was added. The mixture was stirred at room temperature for ca 12 h, producing a white precipitate of AgC1. The solution was filtered over celite and then concentrated under reduced pressure and layered with petroleum ether (40-60°C). The white solid [Ru(CO)2(PPh3)z(THF)z](BF4)2 was filtered, washed with diethyl ether and dried in a stream of nitrogen. Found: C, 54.9; H, 4.5. Calc. for [Ru(CO)z(PPh3)2(THF)z](BF4)2: C, 55.3; H, 4.6%. Synthesis of [Ru(CO)2(PPh3)2(TCNQ)]BF4 (1) To a solution of [Ru(CO)2(PPh3)2(THF)2](BF4)2 (1 g, 1 mmol) in dichloromethane was added LiTCNQ (0.42 g, 2 mmol). The mixture was stirred at reflux for 6 h, giving a dark green solution. The solution was concentrated under reduced pressure, leaving [Ru(CO)2(PPh3)2(TCNQ)]BF4 as a green solid, which was filtered and washed twice with methanol and diethyl ether, and dried in t'~acuo. Found: C, 61.4; H, 3.6; N, 5.7. Calc. for [Ru (CO)2(PPh3)2(TCNQ)]BF4: C, 61.7; H, 3.5; N, 5.8%. 2 .... (nm, DMSO) : 399, 420, 475, 743, 761, 842. MS: m/z 848 ( M + - C C N ) , 821 [ M + - C (CN)2], 682 [Ru(PPh3)2(CO2)] +, 654 [Ru(PPh3)2 (CO)] +, 626 [Ru(PPh3)2] +, 549 [Ru(PPh3) (PPh2)] +, 364 [Ru(PPh3)] +. Synthesis of [RuH(CO)(PPh3)2(TCNQ)]2 (2) Method (a): from RuHCI(CO)(PPh3)3 and TCNQ. To a heated suspension of T C N Q (0.06 g, 0.3 mmol) in ethanol was added a suspension of RuHCI(CO)(PPh3)3 in ethanol. The mixture was stirred at reflux for 5 h, giving a green solid, which was filtered and washed with acetonitrile and ethanol. Method (b): from [RuH(CO) (PPh3)2 (CH3CN)z]PF6 and LiTCNQ. To a solution of [RuH(CO)(PPh3)2(CH3CN)2]PF6 (0.3 g, 0.34 mmol) in dichloromethane was added a solution of LiTCNQ (0.07 g, 0.34 mmol) in ethanol. The mixture was stirred at room temperature for 2 days, giving a green solid, which was filtered and washed
with CH2Cl2-ethanol. Found: C, 68.6; H, 4.2; N, 6.6. Calc. for [RuH(CO)(PPh3)2(TCNQ)]2: C, 68.5; H, 4.1; N, 6.5%. Zmax/(nm, D M S O ) : 399, 420, 490, 743, 761,842. MS: m/z 1555, 1529, 1512 {[Ru(PPh3)2(CO)]2TCNQ}+, 1293 (1555-PPh3), 1267 (1529-PPh3), 1248 (1510-PPh3), 912, 858 [Ru(PPh3)2(CO)TCNQ] +, 830 [Ru(PPh3)2 TCNQ] +, 754, 654 [Ru(PPh3)2(CO)] +, 626 [Ru(PPh3)2] +, 549 [Ru(PPh3) (PPh2)] +, 364 [Ru(PPh3)] + . Synthesis of[Ru(dppe)2(TCNQ)]2TCNQ(CI04) (3) To a solution of [Ru(dppe)3(C104)]C104 (1 g, 0.7 mmol) in chloroform was added a solution of LiTCNQ (0.28 g, 1.4 mmol) in ethanol. The reaction mixture was stirred at reflux for 7 h. The solution was cooled to room temperature, giving a green precipitate which was filtered, washed with ethanol and dried in vacuo. Found : C, 67.3 ; H, 4.5 ; N, 6.6. Calc. for [Ru(dppe)2(TCNQ)]zTCNQ(CIO4): C, 67.05; H, 4.3; N, 6.7%. •max (nm, D M S O ) : 420, 761,842. M S : m / z 2072 {[Ru(dppe)2C1]2TCNQ} +, 1137 [Ru(dppe)2ClYCNQ]+, 933 [Ru(dppe)2C1] +, 898 [Ru(dppe)2] +, 500 [Ru(dppe)] +, 306 [RuTCNQ] + . Synthesis of [Ru(dppm)3TCNQ]C104 (4) To a solution of [Ru(dppm)3(C104)]C104 (1 g, 0.7 mmol) in chloroform was added a solution of LiTCNQ (0.14 g, 0.7 mmol) in ethanol. The mixture was stirred at reflux for 6 h. After cooling, petroleum ether was added, giving a dark green solid, which was filtered, washed with ethanol and dried in vacuo. Found: C, 66.7; H, 4.3; N, 3.5. Calc. for [Ru(dppm)3TCNQ]C104: C, 67.1; H, 4.5; N, 3.6%. Acknowled#ements--We are grateful to the Direcci6n General de Investigaci6n Cientifica y T6cnica (DGICYT, Spain) for financial support (projects PB90/0020 and PB91/0402). REFERENCES
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B. Taqui Khan, M. Satyanarayan Reddy and K. Veera Reddy, J. Chem. Soc., Dalton Trans. 1985, 2603. 9. S. L. Bartley and K. R. Dunbar, Angew. Chem., Int. Edn Engl. 1991, 30, 448. 10. (a) C. A. Bignozzi, O. Bortolini, O. Curcuruto and M. Hamdan, Rapid Commun. Mass Spectrom. 1994, 8, 706; (b) A. M. Echavarren, J. L6pez, A. Santos, A. Romero, J. A. Hermoso and A. Vegas, Oryanometallics 1991, 10, 2371. 11. (a) T. A. Stephenson and G. Wilkinson, J. Inorg. Nucl. Chem. 1966, 28, 945 ; (b) G. W. Parshall, Inorg. Synth. 1974, 15, 48; (c) B. E. Cavit, K. R. Grundy and W. R. Roper, J. Chem. Soc., Chem. Commun. 1972, 60.