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I i The cationic ortho-metalated imine complexes, (q6-C6~)Ru(R')N=C(R'')C,H,(L) (R = Me, H; R' = Ph, Et, Me; R" = H, Me; L + PMe3, CO), 1, are formed in the reaction of (C6&)RuC12(L) with 2 equiv of imine and 2 equiv of AgBF,. These complexes react with powerful nucleophiles [L~(BUW)~A~H,RL~] via attack at the imine carbon atom, giving the neutral ortho-metalated amide complexes C6R6Ru(R')-NC(R")(Nu)C6H4(L). The nucleophilic attack occurs with high (>98%) diastereoselectivity when the nucleophile differs from the substituent on the imine carbon. The molecular structures of [(qe-C6Me6)Ru(Ph)N=(CH)C,H4(PMe3)] [BF,], la, and (TI~-C,M~~)R~(P~)NC(H)(M~)C,H~(PM~,), 2a, were determined by X-ray diffraction. Com lex l a crystallizes in space group P2,/c (No. 14) with cell parameters a = 10.893 (2) A, b = 14.507 (1) x, c = 17.568 (3) A, p = 100.40 (1)O, 2 = 4, R = 0.025, and R, = 0.028. Com ound 2a crystallizes in space group R , / c (No. 14) with cell parameters a = 16.803 (3) A, b = 9.306 (2) 1, c = 18.077 (3) A, 0 = 109.65 ( 1 ) O , 2 = 4, R = 0.061, and R, = 0.060.7

Die PH‐funktionellen Zweikernkomplexe Fe2(CO)6(PHR)2 (1, R  Me, t‐Bu, Ph, p‐Tol) enthalten die (CO)3Fe‐ und PHR‐Einheiten in einer Anordnung, die den Anbau weiterer Carbonyl‐metall‐Einheiten unter Bildung Phosphiniden‐verbrückter Cluster möglich erscheinen lassen. Sie reagieren demgemäß mit Co2(CO)8 Zu Fe2Co(CO)9(μ3‐PHR)(μ3‐PR) (2, R  Me, Ph) und Fe2Co2(CO)11(μ4‐PR)2 (3, R  Me, Ph), wobei die Cluster 2 keine Zwischenstufen auf dem Wege zu 3 sind. Aus 1 und Fe3(CO)12 entstehen je nach den Bedingungen Fe3(CO)9(μ3‐PR)2 (4, R  Me, Ph, p‐Tol), Fe4(CO)11(μ4‐PR)2 (5, R  Me, t‐Bu, Ph, p‐Tol) und Fe4(CO)12(μ4‐PR)2 (6, R  Me, t‐Bu, Ph, p‐Tol). Die Fe4‐Cluster 5 bilden sich auch aus Fe3(CO)12 und den Fe3‐Clustern 4. Umgekehrt liefern die Cluster 5 durch thermischen Abbau die Cluster 4, wodurch auch die Pt‐Bu‐Verbindung 4 zugänglich wird. Die gesättigten Fe4‐Cluster 6 und die ungesättigten Fe4‐Cluster 5 sind im Vakuum bzw. durch CO‐Zugabe leicht ineinander zu überführen. Von je einem Vertreter der Fe2Co‐Cluster 2, der Fe2Co2‐Cluster 3 (2 Isomere) und der Fe4‐Cluster 5 wurde kristallographisch die Struktur bestimmt.

strongly coupled electronically and are diamagneti~.'~ Generally, Os(1V) complexes are paramagnetic, and spin-orbit coupling within the t : electronic configuration gives rise to internal t : transitions in their near-IR spectra.l6Vz2 The absence of such transitions in the nitrido-bridged complexes is consistent with the diamagnetism, since the diamagnetic ground state will not be affected by spin-orbit coupling. Strong coupling between the osmium centers via the p, and pv orbitals of the N3-ligand gives rise to strong Os=N triple bonds. The molecular orbital description of the bonding (Figure l ) is similar to that initially put forward by Griffith (for other pnitrido c o m p l e~e s )~~ and Dunitz and Orgel (for p o x 0 c o m p l e x e~) .~~ Interactions between the ligand p, and p,, orbitals (e, symmetry) with the e, combinations of the d,, and d,,, metal ion orbitals result in strongly bonding a (e,) and strongly antibonding a* (e,) combinations of orbitals. The antibonding eg (d,,, d,,,) combinations of the d orbitals of the metal ions remain relatively unaffected, as they do not have the correct symmetry to interact with the p orbitals of the bridging nitrido ligand. In this qualitative picture, the eg (d,,, dy,) set of orbitals is the HOMO level and is filled, which gives rise to the observed diamagnetism. The strong tetragonal distortion that is induced by the strong Os=N=Os bonds will result in a further raising of the energy of the antibonding eg (d,,, d,,J combinations, while the bzg (d,z-,,z) and b,, (d,z-$) combinations are lowered in energy. The intensities of the low-energy transitions at 21 500 and 26 000 cm-' suggest that they are d-d in nature, and they (22) Piepho, S. B.; Dickinson, J. R.; Spencer, J. A,: Schatz, P. N. Mol. Phys. (23) Dunitz, J. D.: Orgel, L. E. J . Chem. SOC. 1953, 2594-2596. 1972, 24,609-630.have been assigned as eg (d,,, dYz) -d+z, d,z transitions. An intense metal to ligand charge-transfer eg (d,,, d,,,) -e, (a*) transition that is z-allowed is expected, and this has been assigned to the intense transition at 40 300 cm-I. The nature of the shoulder at 38 000 cm-l is less certain but may be a symmetry-allowed eg (d,,, d, ) -d,z transition or a 6,6* (d,) ---* dxz+ d,z transition.A further intense charge transfer is expected between the 6 (bit) combination of the d,. orbitals and the e, (a*) orbitals. It is anticipated that this trarsition will be lower in intensity than the eg ---*. e, transition, but it is x,y-allowed. Indeed, an intense transition is observed at 52 600 cm-' for transpuns-[(Cl)-(NH3)40sNOs(NH3)4(C1)]3+, and the rising absorption in the far-UV spectrum of [(NH3)50sNOs(NH3)5]5+ indicates that a similar transition occurs here. The charge-transfer transitions of the ruthenium complexes20 are at lower energies than those of their osmium analogues. Since interactions between the ruthenium orbitals and the ligand orbitals are expected to be weaker, the difference in the energy between the e, (a*) and eg orbitals would be lower. This is consistent with the assign...