Organometallics 1995,14, 589-591
589
Partial Desulfurization of a Coordinated Xanthate and Concomitant Sulfur Insertion into a Molybdenum-Acetyl Bond Leopoldo Contreras, Antonio Pizzano, Luis Shnchez,* and Ernest0 Carmona" Departamento de Quimica Inorganica-Instituto de Ciencia de Materiales, Universidad de Sevilla-Consejo Superior de Investigaciones Cientificas, Apdo 553, 41071 Sevilla, Spain
Angeles Monge and Caridad Ruiz Instituto de Ciencia de Materiales, Sede D, Consejo Superior de Investigaciones Cientificas, Serrano 113,28006 Madrid, Spain, and Facultad de Ciencias Quimicas, Universidad Complutense, 28040 Madrid, Spain Received September 19, 1994@ Summary: The acetyls Mo(C(O)Me)(SzCOR)(CO)(PMe3)2 undergo partial desulfurization of the ligated xanthate and coupling of the resulting S atom with the acetyl group to furnish complexes containing coordinated alkoxythiocarbonyl and monothioacetate ligands, Mo(SOCMe)($-C(S)OMe)(CO)(PMe3)2.Metathetical replacement of the MeCOS- ligand by ROCSz- affords Mo(S2COR)($-C(S)OR)(CO)(PMe3)2,which can be prepared in a one-pot synthesis from Mo($-C(0)Me)Cl(CO)(PMe& and 2 equiv of KSzCOR. The structure of the t-Bu derivative has been determined by X-ray crystallography.
are presently known. In this contribution we wish to describe an unusual reaction that entails the coupling of a Mo-bound acetyl ligand, C(O)Me,with a sulfur atom derived from a coordinated xanthate, &COR. Apart from their inherent interest in M-acyl chemistry, reactions of this type that form or break C-S bonds are of academic and industrial r e l e ~ a n c e . ~ Solutions of the acyl-xanthate complexes8Mo(C(0)Me)(S2COR)(CO)(PMe&(1;R = Me, i-Pr) rearrange readily to the alkoxythiocarbonyl derivatives 2 when stirred at room temperature over a period of 1-2 days. As shown in eq 1,the process involves partial desul-
The acyl ligand is an important organometallic functionality.' While many investigations have focused on the synthetic and structural aspects of this entity, comparatively less attention has been devoted to its reaction chemistry. In recent years, however, the need to understand the intermediary role of transition-metal acyls in many stoichiometricand catalytic reactions2has motivated a number of reactivity studies. Of particular interest are those processes that involve the coupling of the acyl with other unsaturated groups, which, a t least in a formal sense, can be considered as insertion reactions. Transformations of M-acyls that involve also olefins or alkynes: CO,4 alkylidenes? and other groups6
Mo(C(O)Me)(S,COR)(CO)(PMe,),20 "C
Abstract published in Advance ACS Abstracts, December 1,1994. (1)(a)Durfee, L. D.; Rothwell, I. P. Chem. Rev.1988,88,1059. (b) Cutler, A. R.; Hanna, P. K.; Vites, J. C. Chem. Rev. 1988,88,1363. (2)(a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley: New York, 1988. (b) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransitwn Metal Chemistry; University Science Books: Mill Valley, CA, 1987. (c) Davies, S. Organotransition Metal Chemistry: Applications to Organic Synthesis. Pergamon Press: Oxford, U.K., 1982. (3)See for example: (a) Brookhart, M.; R k , F. C.; DeSimone, J. M.; Barborak, J. C. J. A m . Chem. SOC.1992,114,5894. (b) van Asselt, R.; Gielens, E. E. C. G.;Riilke, R. E.;Vrieze, K.; Elsevier, C. J. J.A m . Chem. SOC.1994,116,976. (c) van ksselt, R.; Gielens, E. E. C. G.; Riilke, R. E.; Elsevier, C. J. J. Chem. Soc., Chem. Commun. 1993,1203. (d) Brumbaugh, J. S.; Whittle, R. R.; Parvez, M.; Sen, A. Organometallics 1990,9,1735.(e) Carmona.,E.;Gutibrrez-Puebla, E.; Monge, A.; Marin, J. M.; Paneque, M.; Poveda, M. L. Organometallics 1989, 8, 967. (0 Guram, A. S.; Guo, Z.; Jordan, R. F. J. Am. Chem. SOC. 1993,115,4902. (g) Curtis, M. D.; Real, J.; Hirpo, W.; Butler, W. M. Organometallics lsw),9,66. (4)Sheridan, J. B.; Johnson, J. R.; Handwerker, B. M.; Geoffroy, G. L. Organometallics 1988,7,2404. (5)Adams, H.; Bailey, N. A.; Tattershall, C. E.; Winter, M. J. J. Chem. SOC.,Chem. Commun. 1991,912. (6)(a) Han, S.-H.; Song, J.-S.; Macklin, P. D.; Nguyen, S. T.; Geoffroy, G. L.; Rheingold, G. L. Organometallics 1989,8,2127. (b) Yang, G.-M.; Lee, G.-H.; Peng, S.-M.; Liu, R.-S. J. Chem. SOC.,Chem. Commun. 1991,478.(c)Hart, I. H.; Jeffery, J. C.; Lowry, R. M.; Stone, F. G. A. Angew. Chem., Int. Ed. Engl. 1988,27,1703. @
-
1
Mo(r2-SOCMe)(q2-C(S)OR)(CO)(PMe,), (1) 2
furization of a coordinated xanthate ligandgJOto an alkoxythiocarbonyl fragment with subsequent incorporation of the S atom into the acyl groupl1J2 to yield a (7) (a)Schuman, S. C.; Shalit, H. Catal. Rev.1970,4,245.(b) Riaz, U.; Cumow, 0. J.; Curtis, M. D. J.Am. Chem. SOC.1994,116,4357. (c) Delgado, E.; Emo, A. T.; Jeffery, J. C.; Simmons, N. D.; Stone, F. G. A. J. Chem. SOC.,Dalton Trans. 1986,1323. (8)Contreras, L.;Monge, A.; Pizzano, A.; Ruiz, C.; SBnchez, L.; Carmona, E. Organometallics 1992,11,3971.These compounds have been shown to exist in solution as equilibrium mixtures that contain n
n
mainly the +acyl (Mo(C(0)Me))and the agostic (Mo(C(O)Me))isomeric structures. (9)Although the cleavage of one or both of the C-S bonds of a coordinated dithiocarbamate is a known process,1° the analogus transformation of a coordinated xanthate is a much rarer reaction. (10)(a)Herrick, R. S.; Nieter-Burgmayer, S. J.; Templeton, J. L. J. Am. Chem. SOC.1983,105, 2599. (b) Brower, D. C.; Tonker, T. L.; Morrow, J. R.; Rivers, D. S.; Templeton, J. L. Organometallics 1986, 5,1093.(c) Gilleti, P. F.; Femec, D. A.; Keen, F. I.; Brown, T. M. Inorg. Chem. 1992,31,4008.(d) Hitchcock, P. B.; Lappert, M. F.; McGeary, M. J. J.Am. Chem. SOC.1990,112,5658.(e) Hitchcock, P. B.; Lappert, M. F.; McGeary, M. J. Organometallics 1990,9, 2645. (0 Coffey, T. A.; Forster, G. D.; Hogarth, G. J. Chem. Soc., Chem. Commun. 1993, 1524. (g) Ricard, L.;Estienne, J.; Weiss, R. Inorg. Chem. 1973,12, 2182. (h) M a y , A.;McDermott, G. A,; Dorries, A. M.; Holder, A. K.; Fultz, W. C.; Rheingold, A. L. J. Am. Chem. SOC.1988,108,310. (11)The related insertion of a sulfur atom into a V(+C(N-t-Bu)Mes) linkage has been described recently by Floriani and co-workers. See: Vivanco, M.; Ruiz, J.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1993,12,1802. (12)Some complexes of alkoxythiocarbonyl ligands are known, and two of them'bab have been structurally characterized by X-ray methods. See: (a) Robert, P.; Le Bozec, H.; Dixneuf, P. H.; Hartsock, F.; Taylor, N. J.; Carty, A. J . Organometallics 1982, 1, 1148. (b) Samb, A.; Demerseman, B.; Dixneuf, P. H.; Mealli, C. Organometallics 1988,7, 26. (c) Critchlow, P. B.; Robinson, S. D. Inorg. Chem. 1978,17,1903. (d) Esteruelas, M. A.; Oro, L. A,; Ruiz, N. Inorg. Chem. 1993,32,3793.
0276-733319512314-0589$09.00/0 0 1995 American Chemical Society
Communications
590 Organometallics, Vol. 14,No. 2, 1995
monothiocarboxylate ligand. The reactions are not, however, clean and produce in addition small amounts (less than 5% by IH and 31P{1H} NMR) of other unidentified species. This and the high solubility of compounds 2 in common organic solvents have precluded their isolation in a pure crystalline form. Evidence for the proposed formulation for 2 comes from spectroscopic data. The alkoxythiocarbonyl ligand gives rise to a strong IR absorption at ca. 1270 cm-l, close to the value of 1290 cm-l found by Dixneuf and co-workers in the iron complex Fe(q2-C(S)OMe)(CO)(P(OM~)~)(P~~PCH=C(~-BU)S).~~~ In addition, the Mo-bound alkoxythiocarbonyl carbon gives rise t o a triplet ( 2 J ~= p 20 Hz) at the very low-field chemical shift value of ca. 290 ppm. This suggests considerable carbenoid character (structure C,see below). Reactivity studies provide supplementary, and moreover unequivocal, corroboration of the structure of compounds 2. Interaction of these complexes with 1 equiv of a xanthate salt, KS&OR, proceeds13 with metathetical replacement of the monothiocarboxylate ligand by the xanthate, as depicted in eq 2 for the isopropyl derivative 2b.The liberated KSOCMe salt has
c52
c53
Figure 1. ORTEP diagram of Mo(S2CO-t-Bu)(q2-C(S)O-tBu)(CO)(PMe3)2(3~).
of the corresponding bidxanthate) Mo(S2COR)dCO)(PMe3)213also being formed. Complex 3c has been structurally characterized by X-ray cry~tallography,~~ and an ORTEP diagram is shown in Figure 1. The coordination polyhedron around MO(~~-OSCM~)(~~-C(S)O-Z-P~)(CO)(PM~~)~ molybdenum is a distorted octahedron, with the two 2b PMe3 ligands axial and the carbonyl, the bidentate KS,co-i-FT xanthate, and the C(S)OR ligands all equatorial. While the S atom of the last group is on the equatorial plane, MO(S,C~-~-P~)(~~-C(S)O-~-P~)(CO)(PM~~)~ its carbon atom is slightly raised above this plane, 3b making the coordination of the q2-C(S)ORfragment in KSOCMe (2) complexes of this type closely reminiscent of that of the related q2-C(0)R ligand.lJ5 The Mo-C4 distance of been isolated and identified by comparison of its IR and 2.018(3) A, while somewhat longer than the Mo-CO lH and 13C{lH} NMR spectra with those of an authentic separation of 1.914(3) 8,,is significantly shorter than sample. Complex 3b is a red crystalline solid that the value of 2.3-2.4 8, typically found in Mo(I1)-alkyl exhibits 4 C S ) at ca. 1270 cm-l and d(Mo-C(S)O-i-Pr) complexes.16 This result denotes considerable n-bonding at 295 ppm ( t , 2 J C p = 19 Hz). The observation of within the Mo-q2-C(S)OR linkage and, hence, an imvirtually coupled triplets for the PMe3 groups, in both portant contribution of the carbene resonance structure the lH and 13C{lH} NMR spectra, and of a carbonyl C, which is also in accord with the very low-field resonance at ca. 245 ppm (t, 2Jcp= 15 Hz) are in accord chemical shift characteristic of this Mo-bound carbon with structure A for these compounds.
+
(13) In the presence of an excess of the xanthate ( 2 2 equiv) the bis(xanthate) Mo(SzCOR)2(CO)(PMe3)zand other unidentified species are also formed. See: Carmona, E.; Contreras, L.; Shchez, L. J.; GutiBrrez-Puebla, E.; Monge, A. J. Chem. SOC.,Dalton Trans. 1989, 2003. (14) Crystal- data for 3c: C ~ , H ~ & O O ~ P Z M, S ~=, 542.5, triclinic, space group P1,a = 9.619(3)A,b = 10.794(2) A,c = 14.736(2) A,a = 75.64(1)",9, = 83.45(1)', y = 111.10(2)0,V = 1347(3) A3, 2 = 2, D, = 1.34 g ~ m - p(Mo ~ , Ka)= 8.281 cm-' (graphite monochromated), 1 = 0.710 69 A, F(OO0) = 564. Data were collected on an Enraf-Nonius bMe3 CAD-4difiactometer at 295 K. The intensities were corrected for Lorentz and polarization effects. Scattering factors for neutral atoms and anomalous dispersion correction for Mo were taken from ref 22. A Of the 7856 unique reflections, 5941 with Z 2 2 d n were used in refinement. The structure was solved by Patterson and Fourier methods. An empirical absorption correctionZSwas applied at the end The reaction chemistry summarized in eqs 1 and 2 of the isotropic refinement. Final refinement with fixed isotropic suggests compounds of type 3 may be prepared in a onefactors and coordinates for H atoms gave RF= 0.032 andR(w)F= 0.034. pot procedure by treatment of the starting acetyl Mo(q2Most of the calculations were carried out with the X-Ray80 system.z4 (15) (a) Carmona, E.; Marin, J. M.; Poveda, M. L.; Shchez, L. J.; C(O)Me)Cl(CO)(PMe&with ca. 2.2 equiv of KS2COR. Rogers, R. D.; Atwood, J. L. J. Chem. SOC.,Dalton Trans. 1985, 1003. Equation 3 exemplifies this synthetic methodology for (b) Carmona, E.; Shchez, L. J.; Marin, J. M.; Poveda, M. L.; Atwood, J. L.; Rester, R. D.; Rogers, R. D. J.Am. Chem. SOC.1984,106,3214. (c) Desmond, T.; Lalor, F. J.; Ferguson, G.; Ruhl, B.; Parvez, M. J. J. Chem. SOC.,Chem. Commun. l985,55. (d) Curtis, M. D.; Shiu, K.-B.; 1986, 108, 1550. (e) Carmona, E.; Butler, W. M. J.Am. Chem. SOC. Muiioz, M. A.; Rogers, R. D. h o g . Chem. 1988, 27, 1598. (0Rusik, MO(S,CO-~-BU)(~~-C(S)O-~-BU)(CO)(PM~~)~ (3) C. A.; Collins, M. A.; Gamble, A. S; Tonker, T. L.; Templeton, J. L. J. 3c Am. Chem. SOC.1989,111,2550. (16) (a) Carmona, E.; Wilkinson, G.; Rogers, R. D.; Hunter, W. E.; Zaworotko, M. J.; Atwood, J. L. J. Chem.-Soc., Dalton Trans. 1980, the t-Bu derivative 3c. Moderate yields of compounds 229. (b) Girolami, G. S.; Mainz, V. V.; Andersen, R. A.; Vollmer, S. H.; Day, V. W. J.Am. Chem. SOC.1981,103,3953. 3 (30-40%) can be obtained in this way, small amounts
PMe3 I
Organometallics, Vol. 14,No.2, 1995 591
Communications
A
atom. The C4-S3 bond length of 1.670(4) is midway between expected values for related C-S (ca. 1.55 A) and C-S bonds (1.79-1.86 A).17
Mo
/rR-
\
/ioR
Mo\ ' S
' S
University of Sevilla for free access to its analytical and NMR facilities. Supplementary Material Available: Crystallographic tables giving details of the structure determination, crystal and refinement data, bond distances and angles, fractional coordinates, and thermal parameters for 3c (7 pages). Ordering information is given on any current masthead page. OM940729E
(18) Spectroscopic data for selected compounds are as follows. 2b: 'H NMR (CsD6) 6 4.84 (heptet (h), CH i-Pr, lH), 2.00 (t, SOCMe, J I I ~ = 2.8 Hz, 3H), 1.46 (t,PMe3, J a p p ~ = p 3.8 Hz, 18H), 1.05 (d, CH3, kPr, As might be expected, the propensity of the above 6H); 31P{1H}NMR (CsDs) 6 7.7 6 ; 13C{lH} NMR (CsD6) 6 295.0 (t, C(S)O-i-Pr,J c p = 20 Hz), 247.4 (t, CO, J c p = 14 Hz), 217.2 (t, SOCMe, acyls to undergo insertion of a sulfur atom also maniJ c p = 5 Hz), 89.6 (s, CHI, 34.8 (s, SOCMe), 21.6 (s, CH3 GPr), 16.7 (t, fests itself during the course of reactivity studies. Thus, PMe3, J , c p = 12 Hz); IR (Nujol mull) 1805 s (v(CO)), 1624 w and 1518 m (gOCMe), 1271 s, 1155 s, and 1093 s (C(S)O-i-Pr)cm-l. 3b: when carbon monoxide is bubbled through solutions at lH NMR (C6D6) 6 5.37 (h, CH i-Pr xant, lH), 4.90 (h, CH i-Pr, lH), -20 "C, complexes 1 add one molecule of CO and convert 1.51 (t, PMe3, J , p ~ =p 3.8 Hz, 18H), 1.08 (d, CH3 i - b , 6H), 1.07 (d, into the alkoxythiocarbonyl derivatives 4 (eq 4). The CH3 i-Pr, 6H); 3PP{1H}NMR (C6D6) 6 5.3 s; I3C{lH} NMR (C6Ds) 6 297.0 (t, C(S)O-i-Pr,J c p = 19 Hz), 241.3 (t, CO, JCP = 15 Hz), 220.5 (t, co SzCO-i-Pr, J c p = 7 Hz), 89.2 (s, CH), 74.2 ( 8 , CH xant), 21.6 (9, CH3 Mo(C(O)M~)(S,COR>(CO>(PM~~)~ i-Pr),21.4 ( 8 , CH3i-Pr), 16.5 (t, PMe3, JaPpcp = 12 Hz); IR (Nujol mull) 1801 (v(CO)),1271 (C(S)O-i-Pr),1221, 1093, and 1043 (SZCO-i-Pr) la,b cm-1. Anal. Calcd for C ~ ~ H ~ Z M O OC,~ 35.0; P ~ S H, ~ : 6.2. Found: C, Mo(~~-SOCM~)(~~-C(S)OR)(CO),(PM~~), (4) 35.4; H, 6.2. 30: lH NMR (C&) 6 1.51 (t, PMe3 Ja p~ = 3.8 Hz, 18H), 1.47 ( 8 , t-Bu, 9H), 1.44 ( 8 , t-Bu, 9H); 31P{1H}' d R (C&) 6 6.2 4a,b S; 13C{lH] NMR (C&) 6 293.4 (t, C(S)O-t-Bu,JCP = 19 Hz), 242.3 (t, CO, Jcp = 15 Hz), 220.2 (t, SzCO-t-Bu, J c p = 7 Hz), 91.4 ( 6 , CMe3), 86.9 (s, CMe3), 28.1 (s, CMe3), 27.3 ( 8 , CMe3), 16.6 (t, PMe3, JaPpcp = 12 Hz); IR (Nujol mull) 1790 s (v(CO)),1278 s (C(S)O-t-Bu),1237,1131, Mo-)i12-C(S)OMe entity exhibits spectroscopic properand 1048 (SzCO-t-Bu)cm-l. Anal. Calcd for C ~ ~ H ~ ~ M O O ~C,P37.6; ZSS: tiesl8 analogous to those of the related complexes 2 and H, 6.6. Found C, 37.2; H, 6.6 4b: lH NMR (C7D8, -30 "C) 6 5.05 (h, 3. However, the monothioacetate ligand gives rise t o = 9.5 Hz, 9H), CH i-Pr, lH), 2.63 (s, SOCMe, 3H), 1.17 (d, PMe3, JHP = 7.4 Hz, 9H); 31P{1H}NMR 1.08 (d, CH3 i-Pr, 6H), 1.04 (d, PMe3, JHP an IR absorption a t 1620 cm-l, indicative of Mo-ql(C7D8, -30 "C) 6 -0.9 (d, J p p = 15 Hz), -16.3 (d); 13C{lH} NMR SC(0)Me coordination.lg Compounds 4 exist in solution (acetone&, -90 "C; low field signals not observed) 6 90.1 ( 8 , CH), 36.0 as a mixture of several isomeric species whose charac(s, SOCMe), 22.3 (8,CH3 i-Pr), 18.6 (d, PMe3, JCP = 28 H d , 13.9 (d, PMe3, J c p = 23 Hz); 13C{lH} NMR (C6D6) 6 284.4 (br t, C(S)O-i-Pr, teristics are presently under investigation.20 When they Jcp = 10 Hz), 234.0 (dd, CO, J c p = 25, 14 Hz), 216.8 (dd, CO, JCP = stand a t room temperature under nitrogen, compounds 58, 18 Hz), 213.1 ( 8 , SOCMe), 90.3 ( 6 , CH), 35.5 (s, SOCMe), 21.6 (s, CH3 ;-PI-), 18.7 (d, PMe3, J c p = 27 Hz), 14.4 (d, PMe3, JCP = 21 Hz); IR 4 slowly lose CO with concomitant change in the (Nujol mull) 1966 and 1887 s (v(CO)), 1286 s (SOCMe), 1142 s and coordination mode of the SOCMe ligand from q 1 to q2, 1088 s (C(S)O-i-Pr)cm-l. Anal. Calcd for C14HzsMo04PzSz: C, 34.8; thereby affording the already described monocarbonyl H, 5.8. Found: C, 34.9; H, 5.7. (19) (a) El-Hinnawi, M. A.; Al-Ajlouni, A. M.; AbuNasser, J. S.; species 2. Powell, A. K.; Vahrenkamp, H. J . Organomet. Chem. 1989,359, 79. In summary, we have shown that the xanthate(b) El-Hinnawi, M. A.; Sumadi, M. L.; Esmadi, F. T.; Jibril, I.; Imhof, W.: Huttner. G. J. Oreanomet. Chem. 1989. 377. 373. (c) Hunter. J. acetyl complexes Mo(C(O)Me)(S2COR)(CO)(PMe& (1) A.;'Lindsell, E.; McCuiough, K. J.; Parr, R. A.; Scholes, M. L. J . Chem. undergo partial desulfurization of the coordinated xanSOC.,Dalton Trans. 1990, 2145. thate and insertion of the sulfur atom into the Mo-acyl (20) When solutions of 4a,b are maintained below -20 "C, NMR studies show the presence of only one isomer with inequivalent cis bond to yield complexes containing alkoxythiocarbonyl PMe3 groups. When they are warmed to 0 "C, these species are and monothioacetate ligands. Although compounds 1 partially, although irreversibly, transformed into an equilibrium exist in solution as equilibrium mixtures of the isomeric mixture of isomers whose precise nature is at present under investigation. 72 and agostic acyl formulations, the well-known elec(21) (a) Arnold, J.; Tilley, T. D.; Rheingold, A. L. J . Am. Chem. SOC. trophilicity of the M-bound y2-acylcarbon21suggests the 1986, 108, 5355. (b) Arnold, J.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J.; Arif, A. M. J . Am. Chem. SOC.1989, 111, 149. (c) Arnold, J.; former is the active species in this transformation. Tilley, T. D.; Rheingold, A. L; Geib, S. J. Znog. Chem. 1987,26,2556. (d)Bonnesen, P. V.; Yau, P. K. L.; Hersh, W. H. Organometallics 1987, Acknowledgment. We thank the Direccibn General 6,1587. (e) Tikkanen, W.; Ziller, J. W. Organometallics 1991,10,2266. (0 Karsch, H. H.; Midler, G.; m g e r , C. J. Organomet. Chem. 1986, de Investigacibn Cientifica y TBcnica (Grant No. PB91273,195. (g) Berg, F. J.; Petersen, J. L. Organometallics 1989,8,2461. 0612-(203-01) and Junta de Andalucia for the award of (22) International Tables for X-Ray Crystallography; Kynoch research fellowships. Thanks are also due to the Press: Birmingham, U.K., 1974; Vol. IV. (23) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158. (24) Stewart, J. M. The X-Ray80 System; Computer Science Center, (17) Rickard, C. E. F.; Roper, W. R.; Salter, D. M.; Wright, L. J . University of Maryland: College Park, MD, 1985. Organometallics 1992, 11, 3931 and references therein.
B
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