Organometallics 1983, 2, 183-184
183
Laboratoire de Chimie de Coordination was supported by the CNRS (Greco-CO). Registry No. 1, 83704-63-6; 3, 83704-64-7; 4, 83704-65-8; 5, 83704-66-9;Co, 7440-48-4; Mo, 7439-98-7; [PdCldppmIz,8370467-0; NaCo(CO)4,14878-28-5;NaMo(CO)&p, 12107-35-6;NaW(CO)&p, 12107-36-7;~FWIS-P~[MO(CO)~CP]~(P~CN)~, 83704-681; PtCl,(dppe), 14647-25-7;W, 7440-33-7;Pd, 7440-05-3;Pt, 744006-4. Supplementary Material Available: Tables of the positional and thermal parameters and their estimated standard deviations for compounds 1 and 5 (6 pages). Ordering information is given on any current masthead page.
Basic Cluster Reactions. 3.' Hetero Site Reactivities in Ru,Co,(CO),,
Figure 1. Molecular structure of H , R U ~ C O ~ ( C(1): O ) ~small ~ circles, CO ligands. H atoms were located but not refined. Bond lengths (pm): Rul-Ru2 = 290.4 ( l ) , Rul-Col = 266.6 (l), Rul-Co2 = 266.3 (l), Ru2-Col = 264.3 (l),Ru2-Co2 = 265.3 (l), C0l-C02 = 254.6 ( l ) , Rul-H1 = 190, Ru2-Hl = 177, Ru2-H2 = 196, Col-H2 = 173, C02-H2 = 180.
isolated in 76% yield by cooling the solution to 4 "C. 3-Hexyne reacted equivalently. Znstitut fur Anorganische Chemie der Universitat Freiburg H2RuzCoz(CO)i2 RU~CO~(CO)~~(P~&~) 0-7800 Freiburg, Germany 1 2 Received July 8, 1982 The compositions of both new clusters were determined by FD mass spectra. The reaction sites were deduced for Summary: Two metal-specific reactions have been ob1 from NMR data" and established for 1 and 2 by crystal served for the tetrahedral cluster Ru,CO,(CO),~ under very structure analyses.12 The hydrogen positions in 1 were mild conditions. Hydrogen reacts at the ruthenium atoms located from difference Fourier maps as well as by Orpen's to form H,Ru,Co,(CO),,. Alkynes insert between the coH searching program.13 Figures 1 and 2 give the overall balt atoms to form Ru,Co,(CO),,(R,C,). molecular structures and important bond lengths. The cluster core geometries and ligand distributions are normal The advantages of mixed-metal clusters in studying in both cases. There is a striking similarity (including unit cluster reactivity and molecular dynamics as well as their cell dimensions) between 1 and Co4(CO)1214 or HFeCo3catalytic potential due to the their possible different site (CO)12,15whereas 2 is intermediate between CO~(CO)~,-,reactivities have been ~ t r e s s e d . ~However, ?~ few reactions (R2C2)16and Ru4(CO)12(R2C2). l7 of mixed-metal clusters have been found yet to underline The structures show that the preferred reaction sites thk2y4 In particular, we are not aware of such a cluster have been used. The acetylene in 2 has been inserted for which reactions with simple substrates a t different between the two cobalt atoms, thereby opening the cluster specific locations in the cluster core have been r e p ~ r t e d . ~ and forming a closo Ru2C02C2core. The hydrogen atoms We have now observed that the ternary metal carbonyl in 1 are associated with the ruthenium atoms. one of them R U ~ C O ~ ( Cpossesses O ) ~ ~ ~hetero site reactivity. The two reagents chosen were hydrogen and internal (10) RuZCo2(CO)ll(Ph2C2)(2): green-black crystals; mp 194 "C dec; acetylenes, both well established in cluster chemistry.'~~ IR (cyclohexane) 2090 (w), 2052 (vs), 2047 (s), 2019 (m), 2006 (w), 1881 (w). 1861 (w) cm-': 'H NMR (CDC1,) multiolet centered at 7.07 m m . From their different reactivities toward simple clusters of And. Calcd for [C;5H10C02011R~2]: 37.24; H, 1.25. Found: C, g6.94; cobalt and ruthenium one could expect that hydrogen H, 0.80. would prefer the ruthenium sites and acetylenes would (11) Upon cooling of CDzClzsolutions of 1 the broad 'H NMR resoprefer the cobalt sites in a mixed cobalt-ruthenium cluster. nance sharpens and moves to high field. At -60 O C when the low solubility of 1 limits further cooling there is a sharp signal at -20.36 ppm This was observed. Both reactions proceeded in n-hexane which we associate with a Ru-Ru edge bridging hydrogen because of the a t 45-50 "C. Stirring of R U ~ C O ~ ( Cfor O )3 ~h~under an strong broadening effect of the quadrupolar cobalt nuclei. The second atmosphere of H2 produced black 1: isolated in 78% yield signal to be expected to the low field side of this which would have to be with a Ru/Co or Co/Co bridging hydrogen is too broad to be by crystallization from toluene. Reaction of R U ~ C O ~ ( C O ) ~associated ~ observed. with diphenylacetylene for 4 h yielded dark green 2,1° (12) Crystals of 1 were obtained from toluene and those of 2 from Eckehart Roland and Heinrich Vahrenkamp'
e,
(1)Part 2: Vahrenkamp, H.; Wolters, D. Organometallics 1982,1,874. (2) Gladfelter, W. L.; Geoffroy, G. L. Adu. Organomet. Chem. 1980, 18, 207. (3) Vahrenkamp, H. Philos. Trans. R. SOC. London, in press. (4) Cf. Richter, F.; Vahrenkamp, H. Organometallics 1982, 1, 756. (5) Among the few reactions of mixed-metal clusters with different substrates are the nonspecific reactions of H2FeRu3(C0)13with Hz and alkynes: Knox, S. A. R.; Koepke, J. W.; Andrews, M. A.; Kaesz, H. D. J.Am. Chem. SOC. 1975,97,3942. Fox, J. R.; Gladfelter, W. L.; Geoffroy, G. L.; Tavanaiepour, I.; Abdel-Mequid, S.; Day, V. W. Inorg. Chem. 1981, 20, 3230. (6) Roland, E.; Vahrenkamp, H. Angew. Chem. 1981,93,714;Angew. Chem., Int. Ed. Engl. 1981,20,679. (7) Humphries, H. P.; Kaesz, H. D. Prog. Inorg. Chem. 1979,25,145. (8) Deemine, A. J., In "Transition Metal Clusters": Johnson, B. F. G., Ed.; Wiley: New York, 1980; p 391. (9) HzRuzCoz(CO)lz(1): black crystals; m p 175 OC dec; IR (CHClJ 2082 (s), 2058 (vs), 2050 (sh), 2032 (sh), 1880 (w), 1868 (sh) 2112 (vw), cm-'; 'H NMR (CD,Cl,) broad resonance at -18.8 ppm. Anal. Calcd for [C12H2C02012R~2]: C, 21.90; H , 0.31. Found: C, 22.22; H , 0.08.
hexane. The crystal quality was checked by Weissenberg photographs; all other measurements were done on a Nonius CAD 4 diffractometer. 1: monoclinic, space group R 1 / c , 2 = 4, a = 930.4 (1) pm, b = 1153.0 (2) pm, c = 1664.2 (4) pm, fi = 91.28 (2)'. 2: monoclinic, space group PZ1/c, 2 = 4, a = 922.6 (4) pm, b = 1168.8 (1)pm, c = 2398.1 (3) pm, p = 93.77 (2)". The structures were solved by direct methods. Full matrix refinement (anisotropic for all non-hydrogen atoms, phenyl groups in 2 as rigid bodies with H atoms isotropic, H atoms in 1 located but not refined) using unit weights resulted in R values of 0.040 for 1 and 0.036 for 2. All details of the crystallographic work are documented in the supplementary material: Table A contains all crystallographic data, Tables B and C list all atomic parameters, Tables D and E all bond lengths and angles for both compounds, Tables F and G give the FJF, listings, and Figures A and B show the detailed molecular structures and atom numbering schemes. (13) Orpen, A. G. J . Chem. Soc., Dalton Trans. 1980, 2509. (14) Wei, C. H. Inorg. Chem. 1969,8, 2384. (15) Cf. Huie, B. T.; Knobler, C. B.; Kaesz, H. D. J . Am. Chem. SOC. 1978, 100, 3059. (16) Dahl, L. F.; Smith, D. L. J. Am. Chem. SOC.1962, 84, 2450. (17) Johnson, B. F. G.; Lewis, J.; Reichert, B. E.; Schorpp, K. T.; Sheldrick, G. M. J. Chem. SOC.,Dalton Trans. 1977, 1417.
0276-7333/83/2302-0183$01.50/0 0 1983 American Chemical Society
Organometallics 1983,2, 184-185
184
stannylcuprates enter into a dynamic equilibrium with ethyl butynoate. The equilibrium can be driven to the product side only with protons as electrophiles. The stannylcuprates are protonated by trifluoroacetic acid (100 % ) and acetic acid (-50%) but not by methanol. Thus, contrary to intuition, the conjugate acid of a stannylcuprate has a pKa of -5.
Piers discovered that stannylcuprates can be added to alkynoate esters.lB2 When the reaction was carried out at low temperature, it was found to produce the E ester (1) stereospecifically and exclusively.
b
Figure 2. Molecular structure of RuzCoz(CO)ll(PhzCz)(2): small circles, CO ligands and C atoms of PhzCz. Bond lengths (pm): Rul-Ru2 = 275.7 (l), Rul-Col = 260.7 (l), RuS-Col = 258.7 (l), Rul-Co2 = 261.4 (l), Ru2-Co2 = 257.2 (l),C0l-C02 = 352.4 (1). Acetylenic ligand distances (pm): Rul-C = 216.6 (3), Col-C = 210.1 (3), C02-C = 210.2 (3) (front C), Ru2-C = 227.8 (3), Col-C = 204.8 (3), Co2-C = 202.4 (3) (rear C), C-C = 143.2 (5).
occupying the "best" position bridging the Ru-Ru edge and the other one bridging a RuCo2 face.'* Both reactions are basic steps of substrate activation by clusters. And in both products the reactive sites for the respective reagent are still available. The relation of these observations to bimetallic catalysis is obvious. Subsequent reactions such as the expulsion of H2 from 1 by adding CO or the addition of acetylenes to 1 and of hydrogen to 2 suggest themselves. These reactions require more forcing conditions, thereby leading to complicated product mixtures. Further work in optimizing and extending the model character of the Ru2C02clusters is in progress.
R3Sn(L)CuLi"
t
-
R'C E C - C O z E t
A
1
Piers also noted that the quenching reagent (MeOH) could be added concurrently with the alkynoate to the stannylcuprate without sacrifice in yield or stereoselectivity but did not comment further on this observation. When we tried to apply this reaction to the preparation of compounds of general formula 2, by addition of an electrophile (Y-C1 or Y-Br) to cuprate A at -78 "C, followed by quenching with methanol, we were surprised to observe the results tabulated in Table I. The salient R'
P
'c=c
Z
E
'
\v
E3S/ n
2, y = Br, R,Sn, HgCl
Acknowledgment. This work was supported by the Fonds der Chemischen Industrie and by the Rechenzentrum der Universitat Freiburg.
features were that (a) only protons seemed to quench A efficiently, something that Piers had also observed when Registry No. 1, 83830-89-1; 2, 83830-90-4; R u , C O ~ ( C O ) ~ ~ , he tried to trap A with various organic electrophiles (CH,I, 78456-90-3; Hz,1333-74-0; PhzC2, 501-65-5; CO, 7440-48-4; Ru, ketones, et^),^ and (b) even though formation of A is es7440-18-8; 3-hexyne, 928-49-4. sentially complete in ca. 15 min at -78 to -48 "C, substantial amounts of alkynoate were recovered when powSupplementary Material Available: Listings of the complete erful electrophiles such as bromine or mercuric chloride crystallographic details, all positional and anisotropic thermal were used. parameters, all bond lengths and angles, observed and calculated To account for these observations, we were forced to structure factors, and complete molecular drawings with atom numbering for both structures (47 pages). Ordering information suggest two unprecedented phenomena: (1)addition of is given on any current masthead page. "R3Sn(L)CuLi" to CH,C=C-CO2Et is reversible and (2) the conjugate acid of "R3Sn(L)Cu-Li+" ("R,Sn(L)CuH", R = Me, Bu) is a relatively strong acid (or conversely (18)A "better" position for H2, e.g., Ru-Ru bridging or RuPCo "R,Sn(L)Cu-Li+" is a very weak base in THF). This is bridging, seems unlikely due to steric reasons. depicted in Scheme I. Scheme I R3SnLi t CuLBr
Two Unprecedented Observations in Organocuprate Chemistry: Reverslbllity of Addition to an Alkyne and Low pK, of a Stannylcuprate
-
"R3SnLCuLi"
H3C,
S. D. Cox and F. Wudl'
"R3Sn(L)CuLi" t
MeCEC-COPEt
Bell Laboratories Murray Hill, New Jersey 07974
"R3Sn(L)CuLi"
/c=C R3Sn t
Received August 17, 1982 H3C,
Summary: The addiiion of organocuprates to unsaturated carbonyl-substituted systems is assumed always to proceed irreversibly and stereospecifically and to proceed probably via electron transfer. Here we report that
* To whom correspondence should be addressed at the Department of Physics, University of California, Sank Barbara, CA 93106.
0276-7333/83/2302-0l84$01.50/0
( 2)
i = P h S . "PhzP(OZ)", Me23 - 3 r
/c=c
R3Sn
/COZE~
t >C"LI
Ht
MeOH
-
-
h3C
YR
\
/c=c GjSr
COZEt / \ L-CULI
(3)
(4) / \
COzEt
(5) H
L
(1)Piers, E.; Morton, H. E. J. Org. C h e n . 1980, 45, 4263. (2) Piers, E.; Chong, J. M.; Morton, H. E. Tetrahedron Lett. 1981,22, 4905.
(3) Piers, E.; Chong, J. M. J. Org. Chem. 1982, 47, 1602.
0 1983 American Chemical Society
