Organometallics 1995, 14, 1536-1538
1536
High-Nuclearity Ruthenium Carbonyl Cluster Chemistry. 2.l Reaction of [Ru2@-H)@-NC5H4)2 (c0)4 (NC5H5)21 [RulO@-H)@6-c)(c0)241 with Triphenylphosphine: Stepwise Apical Substitution on a “Giant Tetrahedral” Cluster Marie P. Cifuentes Department of Chemistry, University of New England, Armidale, NSW 2351, Australia
Mark G. Humphrey* Department of Chemistry, Australian National University, Canberra, ACT 0200, Australia
Brian W. Skelton and Allan H. White Department of Chemistry, University of Western Australia, Nedlands, W A 6009, Australia Received October 28, 1994@ Summary: The (hydrido)(carbido)decaruthenium cluster anion LRuldp-H)(p&)(CO)d- reacts with triphenylphosphine in a stepwise manner to afford [Ruldp-H)(ps-C)(C0)2*-dPPh3)J- (x = 1-4)) with initial ligand displacement on the apical ruthenium associated with the hydride ligand and subsequent ligand substitution at the other apices; the location of the phosphine substituent of the monosubstituted cluster anion [Ruldp-H)(ps-C)(C0)23(PPh3)1- has been confirmed by a single crystal X-ray dipaction study.
(C0)4(NC~H5)21+ salt’ and have been investigating its reactivity toward nucleophiles. We report herein its behavior toward triphenylphosphine. In sharp contrast to the osmium system, nucleophilic substitution of [Rulo@-H)Cu6-C)(C0)24]-occurs in a stepwise manner under exceptionally mild conditions to afford a unique series of (hydrido)(carbido)decarutheniumcluster anions containing from one t o four phosphine ligands.
Introduction
Results and Discussion
High nuclearity carbonyl clusters of transition metals are ideal models for metal crystallites with chemisorbed ligands; their chemistry is therefore of fundamental importance. The chemistry of the “giant tetrahedral” cluster [oS~O~6-c)(co)24]2has been reported in depth;2 a range of electrophiles can be added, but the cluster is reported to have a “remarkable resistance to ... nucleophiles”,2d requiring Os-Os cleavage by halogens and harsh reaction conditions. The development of highnuclearity ruthenium cluster chemistry has lagged behind that of its extensively investigated heavier congener osmium, primarily due to the lack of facile, high-yielding syntheses. However, where comparative studies between ruthenium and osmium systems have been possible (e.g. carbonylation), the ruthenium clusters have shown greatly enhanced r e a ~ t i v i t y . ~ We ~~~ have recently developed a near quantitative synthesis
* To whom correspondence should be addressed. Abstract published in Advance ACS Abstracts, February 1,1995. (1)Part 1: Cifuentes, M. P.; Humphrey, M. G.; Skelton, B. W.; White, A. H. Organometallics 1993,12, 4272. (2) (a)Braga, D.; Henrick, K.; Johnson, B. F. G.; Lewis, J.; McPartlin, M.; Nelson, W. J. H.; Puga, J. J. Chem. SOC.,Chem. Commun. 1982, 1083. (b) Dearing, V.; Drake, S. R.; Johnson, B. F. G.; Lewis, J.; McPartlin, M.; Powell, H. R. J. Chem. Soc., Chem. Commun. 1988, 1331. (c) Drake, S. R.; Henrick, K.; Johnson, B. F. G.; Lewis, J.; McPartlin, M.; Morris, J. J . Chem. SOC.,Chem. Commun. 1986,928. (d) Goudsmit, R. J.; Jackson, P. F.; Johnson, B. F. G.; Lewis, J.; Nelson, W. J. H.; Puga, J.; Vargas, M. D.; Braga, D.; Henrick, K.; McPartlin, M.; Sironi, A. J . Chem. SOC.,Dalton Trans. 1985,1795. (e) Cifuentes, M. P.; Humphrey, M. G. In Comprehensive Organometallic Chemistry II; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: Oxford, U.K., 1995, Volume 7, Chapter 16. (3) Coston, T.; Lewis, J.; Wilkinson, D.; Johnson, B. F. G. J . Organomet. Chem. 1991,407,C13. @
of the (hydrido)(carbido)decaruthenium cluster anion [ R U ~ O C ~ - H ) C ~ ~ - C ) ( CasO )its ~ ~ I[-R U ~ ( M - H ) ( U - N C ~ H ~ ) ~ -
Addition of an approximately equimolar amount of PPh3 t o [ R ~ ~ C ~ - H ) C ~ - N C ~ H ~ ) ~ ( C O ) ~ ( N C ~ H ~ ) ~ I [ R U ~ O (f&c)(c0)241 (1) a t room temperature results in an immediate change in the IR spectrum. Crystallization from CHzClz affords green-black needles of [Ru~@-H)-
(~-NC~H~)~(CO)~(NC~H~)~I[RU~O(~-H)(~
(PPh3)](2) in high yield. In similar reactions, addition of 2-4 equiv of PPh3 to 1 a t room temperature has afforded the bis- and tris(phosphine1-substituted decaruthenium complexes [ R U ~ ~ L - H ) C U - N C ~ H ~ ) ~ ( C O ) ~ (NC~H~)~I[RU~O~-H)C~-C)(CO)~~(PP~~)~I(~ and [Ruzb-
H)(~-NC~H~)~(CO)~(NC~H~)ZI[RU~O( C)(C0)21(PPh3)31(41, respectively. Formation of the tetrakis-substituted cluster anion, [Ru&-H)&-C)(C0)20(PPh3)41-(51, requires addition of a 12-fold excess of the ligand and reaction in refluxing acetone for 2 h. Spectroscopic data of the resultant product is consistent with a bis(phosphine)-substituted diruthenium cation [RU~C~-H)C~-NC~H~)~(CO)~(PP~~)~~+, where the a-bound pyridines of the cation precursor have been replaced; a-pyridine often has a “lightly stabilizing” role in polynuclear ~ h e m i s t r ybut , ~ in this system substitution a t the “giant tetrahedral” cluster anion apices is so facile that it occurs before replacement of the a-bound pyridines of the cluster cation. In contrast to the unsubstituted cluster, the mono- (2) and bis(phosphine)substituted (3)clusters are relatively stable as solids in air, and in solution under a n inert atmosphere. The (4) Cifuentes, M. P.; Humphrey, M. G.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 1994,406,211.
0276-733319512314-1536$09.00/0 0 1995 American Chemical Society
Notes
Organometallics, Vol. 14, No. 3, 1995 1537
t r i d p h o s p h i n e h b s t i t u t e d cluster 4 forms 3 slowly at room temperature, the PPh3 conceivably being replaced by CO scavenged from slight decomposition of t h e cluster anion or cation, chemistry which is mirrored in t h e FAB MS of 4 where [M - PPhs COI- is observed. The initial site of ligand substitution was inferred from spectroscopic data and sclbsequently confirmed through an X-ray crystallographic study of 2; complexes 3-5 have been spectroscopically characterized. The lH NMR spectrum of 2 shows a doublet signal M H P ) 7 Hzl due to the metal-bound hydride of the anion, and the 13C{lH}NMR spectrum shows carbonyl signals in the ratio 3:3:6:2:9 (low field to high field), suggesting substitution on t h e apical ruthenium atom associated with t h e bridging hydride ligand (Lewis and co-workers have previously assigned upfield carbonyl resonances to apical site^).^ The molecular structure of t h e anion of 2 is shown in Figure 1. The metal framework has a tetracapped octahedral geometry, with the interstitial carbide sitting in the octahedral cavity, the same core structure a s that observed in the unsubstituted parent compound. The structural study confirms substitution of a n apical carbonyl by the triphenylphosphine, although bond length and angle data do not allow confirmation of the spectroscopically-assigned hydride ligand site. The 31P{1H} NMR spectra of complexes 2-5 show signal ratios consistent with successive apical substitutions of the decaruthenium anion and the expected upfield shifts of the signals as the electron density at the anion is increased.
+
( 5 ) Bailey, P. J.; Duer, M. J.; Johnson, B. F. G.; Lewis,J.; Conole, G.; McPartlin, M.; Powell, H. R.; Anson, C . E.J. Organomet. Chem. 1990,383, 441.
These results demonstrate (i) that high-nuclearity group 8 cluster chemistry can embrace nucleophilic as well as electrophilic reagents and (ii) that reactions on high-nuclearity clusters can proceed with control of extent and specificity under very mild conditions. This chemistry is now being extended to a wide variety of nucleophilic reagents.
Experimental Section
~RUZ~-H~~-NC~H~~Z~CO~~~NC~H~ (1) was synthesized by the literature pr0cedure.l Triphenylphosphine (Hopkin and Williams) was used as received. Petroleum ether refers to the fraction with boiling point between 60 and 80 "C. Reactions were carried out using Schlenk techniques6 under an atmosphere of dry nitrogen; subsequent workup was carried out without any precautions to exclude air. IR spectra were recorded using a Perkin-Elmer model 1600 Fourier transform spectrophotometer with CaFz optics. NMR spectra were recorded on a Varian Gemini 300 spectrometer (lH spectra at 300 MHz, 13C at 75 MHz and 31P at 121MHz) in acetone-& unless otherwise stated. References for the 'H and 13C NMR spectra were set to residual solvent peaks; the latter were proton decoupled. The 31PNMR spectra were recorded using approximately 0.2 M Cr(acac)j as a relaxation agent, or a recycle delay of 40 s; they are reported relative to external 85% &Po4 at 0.0 ppm and are proton decoupled. Mass spectra were recorded using a VG ZAF3 2SEQ instrument (30 kV Cs+ ions, current 1 mA, accelerating potential 8 kV, 3-nitrobenzyl alcohol matrix) at the Australian National University; peaks were recorded as mlz. Thin layer chromatography(tlc) was on glass plates (20 x 20 cm) coated with Merck GF254 silica gel (0.5 mm) using 1:l acetone/ (6) Shriver, D. F.; Drezdzon, M. A. The Manipulation ofAir Sensitive Compounds, 2nd ed.; John Wiley and Sons: New York, 1986.
1538 Organometallics, Vol. 14,No. 3, 1995
Notes
to unknown products. Reactions using up to 4-fold equivalents petroleum ether as eluent. Cluster 1was not isolated; rather, of PPh3 (with respect to complete conversion of the triruthecalculated yields for reactions involving 1 assume complete conversion of its triruthenium precursor Ru~@-H)@-NC~H~)- nium precursor to a product containing a decaruthenium anion and a diruthenium cation) resulted in the formation of both (coho. the bis- and tris-substituted decaruthenium cations in yields Reactions of 1 with PPh. (a) One Equivalent-Synof up to 30% each. thesis of [Ru~(~~-H)(I~-NC~H~)~(CO)~(NCSHS)~I[RU~OC~-H)(c) 12-fold Excess-Synthesis of [Ru2(lr-H)@c-NC&)2(Ice-C)(CO)~(PPh)l (2). Triphenylphosphine (7 mg, 0.027 (5). Triphmmol) was added to a stirred solution of [Ru~@-H)@-NC~H&- (CO)~(PP~)~~[RU~~~~-H)~~-C)(CO)~O~(PP~ enylphosphine (140 mg, 0.534 mmol) was added to a solution (C0)4(NC5Hs)zl[Ruio@-H)@6-C)(C0)243(1,63 mg, 0.027 of 1 [from R U ~ ~ - H ) @ - N C ~ H ~ ) (118 C Omg, ) ~ O0.178 , "011 in in acetone (20 mL). An IR spectrum at this stage showed acetone (20 mL) and the mixture heated at reflux for 2 h. complete consumption of 1. The solution was taken to dryness Purification by tlc afforded one main green band which was and crystallized from CHzClz at -20 "C to give green-black crystallized from acetoneln-butanol to afford a green-black needles identified as 2 (45 mg, 0.018 mmol, 65%). IR (CH2microcrystalline solid identified as 5 (58 mg, 0.016 mmol, 36%). Clz), v(C0)lcm-': 2077 (w), 2047 (s), 2016 (m), 2000 (m). 'H IR (CH&12), v(CO)/cm-l: 2050 (w), 2024 (w), 1996 (s), 1972 NMR (CDC13): 6 8.13 (m, 6H), 7.82 (m, 2H), 7.59 (m, 8H), 7.41 (m, 15H),6.89 (m, 2H), -10.93 (s,Ruz-H), -11.68 [d, lH, JH-P (m sh). lH NMR: 6 7.69-6.82 (m, 90H), -11.54 (m, lH, J H - p = 7 Hz, Rulo-H), -12.65 (t, J H - p = 11 Hz, RUZ-H). 31P = 7 Hz, Rulo-H]. 13C NMR (CDC13): 6 378.8 G6-C); 197.2, NMR: 6 47.9 (s,3P, RuloP), 40.4 (8,lP, RuioP), 26.7, 25.0 (1: 194.0 (ratio 1:1, Ru2CO); 210.5, 210.0, 207.9, 199.3 (d, Jc-P = 1, Ru2P). Positive ion FAB MS: mlz 997 (997, M+).Negative 9 Hz), 190.3 (ratio 3:3:6:2:9, RuloCO); 174.9, 153.9, 153.1, ion FAB MS: mlz 2633 (2633, M-1. Anal. Calcd for C143H100140.2, 139.0, 135.7, 133.5 (d, Jc-p = 11 Hz), 130.5, 128.5 (d, N ~ O ~ ~ P ~ RC,U47.33; I Z : H, 2.78; N, 0.76. Found: C, 48.34; H, J c - p = 10 Hz), 126.3, 121.6 (aromatic carbons). 31PNMR: 6 2.69; N, 0.37. 44.4. Positive ion FAB MS: mlz 630 (630, M+). Negative ion Crystal Data for 2: C~,&&OZ~PRU~~, a = 21.625(5) A, b FAB MS: mlz 1930 (1930, M-1. And. Calcd for C66H36N4= 14.80(1)A, c = 12.387(4) A, a = 81.73(4)", p = 80.07(2)", y 027PRu12: C, 30.97; H, 1.38;N, 2.19. Found: C, 31.10; H, 1.32; = 88.53(2)", V = 3864 A3,D,(2= 2) = 2.20 g ~ m -p~~ ~ ; = 23.7 N, 2.18. cm-l; specimen 0.20 x 0.12 x 0.08 mm; A*min,max (Gaussian (b)2-4-fold Excess of PPh. Triphenylphosphine (45 mg, correction) = 1.20, 1.34; 28" = 50"; Nindept) = 13 664, 0.172 mmol) was added to a solution of 1 [from Rua@-H)@N(obs) ( I =- 3dI)) = 3226; R = 0.075, R , (statistical weights) NC5H4)(CO)lo,200 mg, 0.172 mmol] in acetone (20 mL) and = 0.067; T -295 K, unique difl'ractometer data, 28/8 scan the mixture stirred for 90 min. An IR spectrum indicated the mode, monochromatic Mo K a radiation, 1 = 0.71073 A. presence of some mono-PPb-substituted decaruthenium anion, Considerable difficulties imposed by small specime: size, so a further portion of PPh3 was added (7 mg, 0.198 mmol) pseudocentrosymmetric symmetry (triclinic, P1, quasi-Pl), and and the solution stirred for 30 min. The solution was taken crystal decomposition during data collection (-60%; data to dryness in vacuo; tlc of the resulting black residue afforded rescaled) resulted in the adoption of a model with considerable a number of brown-green bands. The first green band was constraints (anisotropic thermal parameter refinement for Ru found to contain a minor amount of the bis-PPh3-substituted and P only; (z,y , z , U1& estimated; refinement of sixanion [RU~O@-H)@~-C)(CO)~~(PP~~)Z]identified by IR, NMR, membered rings as rigid bodies). The determination is inferior and negative ion FAB mass spectra, although the cation could and is useful only inasmuch as it determines general nonnot be identified (positive ion FAB MS: mlz 769). The second hydrogen atom disposition and connectivity, establishing the green band was isolated as a green-black solid by trituration with petroleum ether and identified as [RUZ@-H)@-NCSH~)Z- location of the PPh3 substituent on the anionic cluster. Hydrido species were not located. (CO)~(NC~H~)ZI[RU~O@-H)@~-C)(CO)Z~(PP~)~I (3,70 mg, 0.0250 mmol, 33%). IR (CH&12), Y(C0)lcm-l: 2064 (m), 2041 (s), 2011 (s sh), 2006 (s), 1990 (9). lH NMR (CDC13): 6 8.14 (m, 6H), Acknowledgment. We thank the Australian Re7.82 (m, 2H), 7.60 (m, 2H), 7.41 (m, 36H), 6.93 (m, 2H), -10.93 search Council for support of this work and Johnson(8,Ruz-H), -11.69 (d, lH, J H - p = 7 Hz, Rule-H). 31PNMR: Matthey Technology Centre for the loan of ruthenium 6 52.1, 43.0 (1:l). Positive ion FAB MS: mlz 630 (630, M+). salts. M.P.C. holds a UNE Postgraduate Research Negative ion FAB MS: mlz 2165 (2165, M-). The contents of Scholarship. M.G.H. is an ARC Australian Research the third green band were identified as [Ruz@-H)@-NC~H~)Z- Fellow. ( C ~ ~ ~ ( N C ~ H ~ ~ Z ~ ~ R ~(4, ~ 25 O mg, ~ -0.008 H ~ @ ~ - C ~ ~ C ~ ~ Z ~ ~ P P ~ ~ ~ ~ ~ mmol, 11%).IR (CH2C12), v(C0)lcm-l: 2063 (w), 2040 (m), Supplementary Material Available: Tables of crystal2013 (s), 2000 (vs), 1985 (m sh). IH NMR: 6 8.15 (m, 6H), lographic data, atomic coordinates and isotropic displacement 7.69-7.48 (m, 57H), -10.75 (6, Ruz-H), -11.54 (d, lH, JH-P parameters for all atoms, anisotropic displacement parameters = 7 Hz, Rule-H). 31P NMR: 6 50.0 (s, 2P), 41.9 (s, 1P). for ruthenium and phosphorus atoms and all bond distances Positive ion FAB MS: mlz 630 (630, M+). Negative ion FAB and angles (39 pages). Ordering information is given on any MS: mlz 2399 (2399, M-). Attempts t o crystallize these current masthead page. samples for analyses proved unsuccessful; repurification by OM9408268 tlc resulted in further conversion of the diruthenium cation
