DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 13–14 13 Coupling and disproportionation reactions of ethyne on ruthenium carbonyl clusters: molecular structures of Ru5(Ï4-CHCHCCH2)- (CO)15 and Ru6(Ï-H)(Ï4-C)(Ï4-CCMe)(Ï-CO)(CO)16† Michael I. Bruce,a Brian W. Skelton,b Allan H. White b and Natasha N. Zaitseva a a Department of Chemistry, University of Adelaide, Adelaide, South Australia 5005. E-mail: mbruce@chemistry.adelaide.edu.au b Department of Chemistry, University of Western Australia, Nedlands, Western Australia 6907 Received 6th October 1998, Accepted 13th November 1998 Thermolysis of Ru3(Ï3-C2H2)(Ï-CO)(CO)9 1 (50 8C, 6 h) has given Ru5(Ï4-CHCHCCH2)(CO)15 3 and Ru6(Ï-H)(Ï4-C)- (Ï4-CCMe)(Ï-CO)(CO)16 4, both characterised by X-ray crystallography; in 3, coupling of two ethyne molecules occurred, likely with prior isomerisation of one to vinylidene, whereas in 4, two molecules of ethyne disproportionate to carbide and methylethynyl.Reactions of alkynes with ruthenium cluster carbonyls are rich sources of complexes with unusual structures.1,2 Reactions of the simplest alkyne, ethyne, with Ru3(CO)12 have been known since the 1960s, when the carbonyl was used to catalyse the synthesis of hydroquinone from C2H2, CO and H2.3 The complex Ru3(CO)11(h-C2H2), prepared from Ru3H(m-H)(CO)11 and ethyne at low temperatures,4 is converted to Ru3(m3-C2H2)- (m-CO)(CO)9 1 at room temperature. In turn, heating 1 in pentane (bp 36 8C) for 1 h gave Ru3(m-H)(m3-C2H)(CO)9 2 in 91% yield.5 We have been interested to find reactions in which further coupling of the cluster-bonded alkyne or alkynyl ligands might occur.With this objective in mind, we examined the thermolysis of 1 in more detail. When 1 (160 mg, 0.26 mmol) is heated in hexane (50 ml) at 50 8C for 6 h, only 78 mg (50%) of 2 is isolated. Other products, isolated in between 1 and 12% yield, include Ru4(m4-C2H2)- (CO)12, Ru5(m4-CCH2)(CO)15 and Ru6(m4-CCH2)2(CO)16, containing either ethyne or its tautomer, vinylidene.6 The structures of two other complexes have special interest and form the subjects of this work.The complexes can be separated readily by preparative TLC (silica gel, hexane–C6H6 4:1). The complexes Ru5(m4-CHCHCCH2)(CO)15 3‡ and Ru6(m-H)(m4-C)- (m3-CCMe)(m-CO)(CO)16 4‡ were isolated in 6–8% yields from the fractions with Rf 0.19 and 0.25, respectively. Both complexes were characterised by single-crystal X-ray structure determinations.§ Fig. 1 is a plot of a molecule of 3, selected bond parameters being given in the caption. The cluster core is a C3Ru4 pentagonal bipyramid, one carbon of which is linked via a CH2 C C (OC)3Ru Ru(CO)3 Ru (CO)3 H H C O (OC)3Ru Ru C H H (CO)3 Ru (CO)3 C Ru1 Ru4 (CO)2 C1 C3 C4 Ru5(CO)4 (OC)3 Ru3 (CO)3 Ru6(CO)3 (OC)3Ru5 Ru2(CO)3 C1 Ru3(CO)3 C2 Me H C12 C(0) (OC)3Ru4 Ru1 1 2 3 O 4 (OC)3Ru2 C2 H H CO H2 group to the fifth Ru atom, which is also bonded to Ru(4).Atoms Ru(1,2,3) each have three terminal CO ligands; the Ru(5)(CO)4 group takes the place of the third CO group on Ru(4) [angles Ru(3)–Ru(4)–Ru(5) 94.42(8), Ru(1)–Ru(4)–C(41) 112.6(6)8]. Atoms Ru(1,3) are s-bonded to C(1) and C(3), respectively; the strain inherent in the four-membered C(3)– C(4)–Ru(5)–Ru(4) ring is evidenced by the internal angle at C(4) being only 98(1)8. Three carbons C(1,2,3) of the organic ligand are coplanar with Ru(1) and Ru(3) and interact equally with Ru(2) and Ru(4) in a p-type bond.This cluster is best described as an Ru-spiked Ru4C3 system with 76 cluster valence electrons (c.v.e.). A plot of 4 is given in Fig. 2, the caption containing selected bond parameters. In this hexanuclear cluster, the Ru6 core can be described as a butterfly, to a hinge atom of which an Ru2 unit is attached. The cleft of the butterfly carries a carbon atom and the hinge vector is bridged by a CO ligand. This structural feature has been described previously in Ru4C(m-CO)(CO)12 7 and comparable structural parameters are similar.Apart from Ru(1), which has only one CO, all Ru atoms carry three terminal CO ligands. The Ru(2)–Ru(3) vector is bridged by a hydrogen atom, but as found in other hydrido–alkynyl Ru3 complexes, is not particularly lengthened as a result. The m4-CCMe is bonded to Ru(1) and Ru(4) via C(1) and to Ru(2,3) via both carbons. As judged by the C(1)–C(2) separation of Fig. 1 Plot of a molecule of Ru5(m4-CHCHCCH2)(CO)15 3 showing atom numbering scheme.Bond lengths: Ru(1)–Ru(2) 2.834(3), Ru(1)– Ru(3) 2.807(3), Ru(1)–Ru(4) 2.849(2), Ru(2)–Ru(3) 2.782(3), Ru(3)– Ru(4) 2.874(2), Ru(4)–Ru(5) 2.815(2), Ru(1)–C(1) 2.09(1), Ru(2)– C(1,2,3), 2.24(2), 2.20(2), 2.45(2), Ru(3)–C(3) 2.13(1), Ru(4)–C(1,2,3) 2.25(2), 2.23(2), 2.24(2), Ru(5)–C(4) 2.17(2), C(1)–C(2) 1.43(2), C(2)– C(3) 1.43(2), C(3)–C(4) 1.47(2) Å. Bond angles: C(1)–C(2)–C(3) 121(1), C(2)–C(3)–C(4) 117(1), Ru(5)–C(4)–C(3) 98(1), Ru(4)–Ru(5)–C(4) 78.7(4)8.14 J.Chem. Soc., Dalton Trans., 1999, 13–14 1.308(6) Å and the angle C(1)–C(2)–C(3) of 136.6(5)8, this ligand is a m4-alkynyl group, similar to that found in Ru3Pt- (m-H)(m4-C2But)(CO)9(dppe), for example.8 The c.v.e. count is 90. The spectroscopic properties of 3 and 4 are consistent with their solid-state structures. Their IR n(CO) spectra contain respectively ten and eleven terminal CO absorptions, while a band at 1887 cm21 in the spectrum of 4 is assigned to the bridging CO ligand.In the 1H NMR spectrum of 3, no high-field signals were detected; signals at d 5.84, 9.64 and at 3.01 and 4.12 were assigned to protons in C(1) and C(2) and to the CH2 group, respectively. For 4, the Me resonance is at d 1.65, while a singlet at d 219.3 confirms the presence of the cluster-bound hydride. The organic ligands in 3 and 4 are formed by coupling of two C2H2 ligands of the original complex 1, with concomitant cluster expansion and hydrogen migration from C(3) to C(4).In 3, the latter process is reminiscent of the common alkyne to vinylidene isomerisation that is widespread in mononuclear and cluster chemistry. For example, conversion of ethyne to vinylidene on an Os3 cluster has been described by Deeming.9 Subsequent cluster-mediated coupling of the vinylidene with ethyne would give the C4 ligand. The course of this reaction is not obvious, dimerisation of the Ru3 cluster being accompanied by considerable rearrangement and loss of one ruthenium atom.The formation of 4 requires a more fundamental change, three of the four hydrogens of two ethyne molecules ending up on the same carbon atom [C(3)], while the fourth is attached to the cluster. Further, disproportionation of the two alkynes, an uncommon process on Group 8 carbonyl clusters, results in formation of the novel carbido cluster. This reaction may be related to the cleavage of alkynes by Co3(m3-CO)2Cp3, for example.10 In conclusion, we have demonstrated the occurrence of two novel reactions of ethyne on an Ru3 cluster leading to com- Fig. 2 Plot of a molecule of Ru6(m-H)(m4-C)(m3-CCMe)(m-CO)(CO)16 4 showing atom numbering scheme. Bond lengths: Ru(1)–Ru(2) 2.8303(8), Ru(1)–Ru(3) 2.8076(8), Ru(1)–Ru(4) 2.8341(7), Ru(1)–Ru(5) 2.7543(7), Ru(1)–Ru(6) 2.8272(7), Ru(2)–Ru(3) 2.7819(9), Ru(4)–Ru(5) 2.8373(8), Ru(5)–Ru(6) 2.8258(8), Ru(1)–C(0) 2.123(4), Ru(4)–C(0) 1.955(4), Ru(5)–C(0) 2.144(5), Ru(6)–C(0) 1.911(4), Ru(1)–C(1) 2.027(4), Ru(2)–C(1) 2.304(5), Ru(2)–C(2) 2.143(5), Ru(3)–C(1) 2.251(5), Ru(3)–C(2) 2.247(5), Ru(4)–C(1) 2.297(4), C(1)–C(2) 1.308(6) Å.Bond angles: Ru(1)–C(0)–Ru(5) 80.4(2), Ru(4)–C(0)–Ru(6) 174.9(3), Ru(4)–C(1)–C(2) 135.5(4), C(1)–C(2)–C(3) 136.6(5)8. plexes containing acyclic C4 (in 3) or carbide and methylethynyl ligands (in 4) which do not have counterparts in the chemistry of mono- or di-substituted alkynes on Group 8 metal carbonyl clusters.Acknowledgements We thank the Australian Research Council for support of this work and Johnson Matthey plc, Reading, for a generous loan of RuCl3?nH2O. Notes and references † Dedicated to Warren Roper on the occasion of his 60th birthday, in recognition of his outstanding contributions to organometallic chemistry. ‡ Selected spectroscopic data. For 3. IR (cyclohexane); n(CO) 2116w, 2079m, 2057m, 2049s, 2041s, 2033s, 2017m, 2010m, 1986w (br), 1953w cm21. 1H NMR (CDCl3): d 3.01 [d, 1H, J(HH) 7, CH2], 4.12 [d, 1H, J(HH) 7, CH2], 5.84 [d, 1H, J(HH) 5.4 Hz, CH], 9.64 (d, 1H, CH).For 4. IR (cyclohexane): n(CO) 2081s, 2077s, 2072m, 2062vs, 2047m, 2036m, 2027m, 2019m, 1992w, 1985w, 1945w (br), 1887w (br) cm21. 1H NMR (CDCl3): d 219.3 (s, 1H, RuH), 1.65 (s, 3H, Me). § Crystal data for 3: red crystal, Ru5(m4-CHCHCCH2)(CO)15 3 º C19H4O15P2Ru5, M = 977.6, monoclinic, space group P21/c, a = 11.517(8), b = 14.792(11), c = 16.503(18) Å, b = 113.41(7)8, V = 2580 Å3, Z = 4, rc = 2.516 g cm23, F(000) = 1832. Crystal dimensions: 0.05 × 0.24 × 0.32 mm, m(Mo-Ka) = 29.3 cm21, A* (min, max) = 1.15, 1.96.N = 4511, No [I > 3s(I)] = 3179; R = 0.061, Rw = 0.067. For 4: dark red crystal, Ru6(m-H)(m4-C)(m4-CCMe)(m-CO)(CO)16 (4) º C21H4O17Ru6, M = 1134.7, monoclinic, space group C2/c, a = 34.595(9), b = 9.534(2), c = 19.461(4) Å, b = 108.97(2)8, V = 6070 Å3, Z = 8, rc = 2.483 g cm23, F(000) = 4240. Crystal dimensions: 0.08 × 0.58 × 0.23 mm, m(Mo-Ka) = 29.8 cm21, A* (min, max) = 1.26, 1.81.N = 5329, No [I > 3s(I)] = 4521; R = 0.027, Rw = 0.031. Unique diVractometer data sets were measured at ca. 295 K to 2qmax = 508 (CAD4 diVractometer, 2q–q scan mode; monochromatic Mo-Ka radiation, l = 0.71073 Å); N independent reflections were obtained No being considered ‘observed’ and used in the full-matrix least squares refinements after Gaussian absorption correction. Anisotropic thermal parameters were refined for the non-hydrogen atoms; (x, y, z, Uiso)H were included constrained at estimated values for 3 and refined in 4.The precision of the determination for 3 was adversely aVected by the use of a split crystal. CCDC reference number 186/1245. See http://www.rsc.org/suppdata/dt/1999/13/ for crystallographic files in .cif format. 1 M. I. Bruce, in Comprehensive Organometallic Chemistry, eds. G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon, Oxford, 1982, vol. 4, p. 858. 2 A. K. Smith, in Comprehensive Organometallic Chemistry II, eds. E. W. Abel, F. G. A. Stone and G. Wilkinson, Elsevier, Oxford, 1995, vol. 7, p. 772. 3 P. Pino, G. Braca, G. Sbrana and A. Cuccuru, Chem. Ind. (London), 1968, 1732. 4 S. Aime, W. Dastru, R. Gobetto, L. Milone and A. Viale, Chem. Commun., 1997, 267. 5 S. Aime, R. Gobetto, L. Milone, D. Osella, L. Violano, A. J. Arce and Y. De Sanctis, Organometallics, 1991, 10, 2854. 6 M. I. Bruce, N. N. Zaitseva, B. W. 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