Organometallics 1983,2, 167-169
167
electron clusters are electronically equivalent to the 62Synthesls, Structure, and Spectral Propertles of electron MozFe2clusters described here.21v29 Given the Mo(CO)( RCsR‘)L,X, Complexes range of observed geometries, electron ~ o u n t s , and ’~~~~ isomers within a given electron count,15 it would appear Paul 6. Winston, Sharon J. Nleter Burgmayer, and that any attempt to predict structures and stoichiometries Joseph L. Templeton’ of M4 clusters on the basis of any cluster counting scheme should proceed with utmost caution. Department of Chemistry, University of North Carolina Localized electron counting arguments can also be used Chapel Hill, North Carolina 27514 to derive an 18-electronconfiguration at each metal center in complexes 3 and 4;but, rather surprisingly, different Received July 7, 1982 formal oxidation states must be assigned in order to do so. Assuming each M-M bond and each p C 0 contribute one Summary: The preparation of Mo(C0)(R’C=CR2)electron each to the metal, Cp- contributes six, and each (PEtJ2Br2 (R’ = Ph, R2 = H, 1; R’ = R2 = Me, 2) and the M-S and terminal M-CO bond contribute two, then for structure of 1 are reported as the first members of a new 3 we assign oxidation states of S2, Cp-, Fe+l, and Mo+~. Because of the different roles played by the carbonyl class of formal 16-electron Mo(I1) complexes, Mo(C0)bonded to Mo in the two isomers, the formal oxidation (RCrCR)L2X2. The unique NMR chemical shifts of astates in 4 are FeO and Mo+~.~O These complexes will be donor alkyne ligands have been supplemented by visible the subject of a planned Mossbauer study. spectroscopy and cyclic voltammetry, both convenient A comparison of the M-M and M-S distances in Table probes for studying other electron-deficient complexes I show that the M-M bonds are shorter by 0.02-0.03 A and with a-donor ligands in the coordination sphere. the M-S bonds longer by 0.01-0.05 A, in the butterfly 4a vs. the planar 3b. In both structures, the Mo-Mo bond is surprisingly short compared to the Mo-Fe bond (a Monomeric metal alkyne complexes display a rich difference of about 0.2 A might be expected on the basis chemistry that is inconsistent with an alkyne bonding of atomic radii). Apparently the double sulfide bridge of model which neglects the second alkyne T system.’ the Mo-Mo bond imparts additional bonding character to Communications describing five-coordinateMo(I1) alkyne its orbital m a k e ~ p . ~ ’ complexes,2 structures of alkyne ligands as two- and The generality of the reaction between metal sulfur four-electron donors in closely related complexes ([ Cocomplexes and metal-metal multiple bonds in rational (CzPhz)L3]+ and [ C O ( C ~ P ~ ~ ) L ~ ( C H , Cand N ) ]formation +)~ cluster synthesis is shown by the reaction of 5 with the of a coordinated alkyne from coupling of carbon monoxide M-Mo bond of lb (eq 2). In the formation of the MOqS4 and methylidyne ligands4 have been reported in the first half of 1982 alone. We wish to report here the preparation C~MO(SCH&H(M~)S)~M + OlbC ~ of a new class of alkyne complexes, Mo(CO)(R’C= 5 CP~CP’~MO + ~C3H6 S ~ (2) CR2)L2X2,which hold promise as versatile reagents for 6 expanding the chemistry of group 6 alkyne complexes. A deep blue methylene chloride solution of Mo(CO)*cluster, 6,32the displacement of propylene from 5 by the (PEtJ2Br; with a threefold excess of phenylacetylene was Mo=Mo bonds presumably parallels the analogous disheated at 40 “C for 18 h to yield a dark green-brown soplacement of C3H6by the C=C bonds of acetylene^.^^ lution. Solvent removal and extraction of the residue with Acknowledgment. We thank the National Science diethyl ether produced a light green solution of MoFoundation for support through Grant No. CHE79(CO)(PhC=CH)(PEt3)2Brz(1). Subsequent recrystalli07748-02. P.D.W. thanks the Department of Chemistry zation from ether/toluene yielded analytically pure forest and the donors of the Samuel H. Baer Fellowship for green crystals of 1. An analogous synthesis utilizing a support. We are also grateful to Dr. P. Braunstein for tenfold excess of 2-butyne yielded Mo(CO)(MeC= helpful comments. CMe)(PEtJzBrz (2). Registry No. lb, 83587-35-3;2, 14243-23-3;3b, 83587-36-4; The lH NMR spectrum of 1 revealed a resonance at 13.0 4b, 83603-89-8;5, 81423-61-2;6,83587-37-5; Mo, 7439-98-7;Fe, ppm which was assigned to the acetylenic proton in accord 7439-89-6. with previous NMR observations for six-coordinate terminal (alkyne)molybdenum(II)complexes.6 In conjuncSupplementary Material Available: Tables of fractional tion with the single v(C0) infrared absorption at 1950 coordinates,thermal factor, and observed and calculated structure cm-’ and molecular orbital guideliness established for d4 factors for 3b (12 pages). Ordering information is given on any
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current masthead page. (28) Bender, R.; Braunstein, P.; Dusausoy, Y.; Protas, J. Angew. Chem., Int. Ed. Engl. 1978,17,596; J.Organomet. Chem. 1979,172, C51. (29) Lauher, J. W. J. Organomet. Chem. 1981,213, 25. (30) In this assignment, it is assumed that the *p3-C0*in 4 contributes two electrons to Ma and none to Fe. This carbonyl is best assigned a role as ‘semibridging” since its 13Cresonance falls a t 238 ppm, well within the range for “terminal” Mo-CO carbonyls. (31) Rives, A. B.; Xiao-Zang, Y.; Fenske, R. F. Inorg. Chem. 1982,21, 2286. (32) Complex 6 is generated by heating of a toluene solution of l b and 5 to 65 “C for 48 h followed by cooling and filtering off the product as a violet powder. 6 decomposes in chlorinated solvents after several hours and is sparingly soluble in most common organic solvents. X-ray structure characterization of this species is planned. Cp2Cp’,Mo,S4 (6): mp ca. 330 OC; ‘H NMR (CDC13, 6 7.24) 2.02 (6 H), 5.11 (8 H), 5.17 (10 H) ppm; mass spectrum, m / e (P)* 800, (P - CH3)+785, (P - CH3C6H4)+721.
0276-7333/83/2302-0167$01.50/0
(1) Tatsumi, K.; Hoffmann, R.; Templeton, J. L. Inorg. Chem. 1982, 21, 466. (2) (a) Kamata, M.; Yoshida, T.; Otsuka, S.; Hirotsu, K.; Higuchi, T.; Kido, M.; Tatsumi, K.; Hoffmann, R. Organometallics 1982,1,227. (b) The structure of a square-pyramidal molybdenum(I1) alkyne has also been recently communicated by: De Cian, A.; Colin, J.; Schappacher, M.; Ricard, L.; Weiss, R. J. Am. Chem. SOC.1981, 103, 1850. (3) Capelle, B.; Beauchamp, A. L.; Dartiguenave, M.; Dartiguenave, Y. J. Chem. SOC.,Chem. Commun. 1982, 566. (4) Churchill, M. R.; Wasserman, H. J.; Holmes, S. J.; Schrock, R. R. Organometallics 1982, 1, 766. (5) Moss, J. R.; Shaw, B. L. J. Chem. SOC.A 1970, 595. (6) (a) McDonald, J. W.; Newton, W. E.; Creedy, C. T. C.; Corbin, J. L. J . Organomet. Chem. 1975, 92, C25. (b) Templeton, J. L.; Ward, B. C.; Chen, G. J.-J.; McDonald, J. W.; Newton, W. E. Inorg. Chem. 1981, 20, 1248.
0 1983 American Chemical Society
Organometallics, Vol. 2, No. 1, 1983
1
Communications
NHR of HoCCOIr2-Butm~~IPEt~,lB~l
//II '
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Figure 2. An ORTEP view of Mo(CO)(PbC~H)(PE~)PBrZ (1) showing the atomic labeling scheme.
Figure 1. Variable-temperature lH NMR spectra of Mo(C0)(MeC=CMe)(PEt&Br, (2). monocarbonyl alkyne derivatives a cis colinear Mo(C0)(PhC-CH) fragment was indicated. The two alkyne carbons in 1 appear as triplets in the spectrum with 'JP+.,& coupling constants typical of cis-P-MoC geometries while 31Pcoupling to the carbonyl carbon is too small to resolve (6 224.7 (t, J = 5.2 Hz, PhCECH), 224.8 (t,J = 5.2 Hz, PhC-CH), 230.9 (br s, J =
