Paramagnetic ruthenium(III) complex, [(C5Me5)RuCl2]n, is prepared by the reaction of RuCl3·H2O with C5Me5H in refluxing ethanol. Treatment of [Cp*RuCl2]n (Cp* = C5Me5) with cyclic dienes or α,ω-bis(diphenylphosphino)alkanes gives diamagnetic Ru(II) complexes, Cp*RuCl(diene) or Cp*RuCl(dipos), respectively. Cationic diene complex of ruthenium is formed by the reaction of Cp*RuCl(2,5-norbornadiene) with AgBF4.

The tetrahydride-bridged complex ( C~M~~) R U (~-H )~R U ( C~M~~)(2) is synthesized by the reaction of [(C5Mes)RuCl212 (1) with LiAlH4, which is characterized as a classical hydride complex on the basis of the 2' 1 value and X-ray diffraction study. In the presence of acid, 2 decomposes to form a coordinatively unsaturated species, which is trapped by the 6-electron ligands to yield the cationic Welectron complexes. Treatment of 2 with ethylene yields (C5Me5)-Ru(CsMe5) (9), structural analogue of the intermediate 8. Thermolysis of 6 in toluene at 60 "C under 1 atm of ethylene generates a dinuclear ruthenacyclopentadiene complex ((25- M~~)R~(CHFCH~)(CM~=CHCH=CM~)R~(CSM~~)(10) as a result of the C-C coupling reaction among the coordinated ethylene and two vinyl ligands. The bis(palky1idene) complex (C6Me5)Ru(pL-CHMe) [pCMe(CH=CHCOMe)Ru(C5Me6) (13) which seems to be a model compound of the intermediate of the cyclometalation leading to 10 is obtained upon heating a divinyl complex (C~M~~)RU(CHFCHCOM~)(CH=CH~)~RU(C~M~~) (12) in refluxing toluene. The ethylene molecule coordinated in 10 inserts into the Ru-C bond of the ruthenacyclopentadiene to form (CsMes)Ru(CMe=CHCH=CMeCH=CH2)(p-H)Ru(CsMe5) (16) when 10 is heated in toluene at 110 "C. Regioselective insertion of a,P-unsaturated ketones into the Ru-C bond of the ruthenacycle giving (C5Me5)Ru(CMe=CHCH=CMeCR1=CCOR2) (p-H)Ru(C5Me5) (17, R1 = H, R2 = Me; 18, R1, R2 = (CH2)2; 19, R', R2 = (CH2)3) is demonstrated in the thermolysis of 10 in the presence of methyl vinyl ketone, cyclopentenone, and cyclohexenone. The molecular structures of several of the products are determined by single-crystal X-ray diffraction studies. Crystal data for 2: space group P 2 / a , a = 12.291(2) A, b = 8.521(1) A, c = 10.053(2) A, = 108.52(1)", V = 998.3(3) A3, and Dcdcd = 1.585 g cm3 for Z = 2. Least-squares refinement based on 2391 reflections converged to R = 0.0220 and R, = 0.0220. Crystal data for 6: space group PI, a = 11.335(2) A, b = 14.315(2) A, c = 8.401(2) A, a = 95.09(2)", p = 117,18(1)", y = 94.36(1)", v = 1197.4(6) A3, and D d c d = 1.538 g cm3 for z = 2. Least-squares refinement based on 2621 reflections converged to R = 0.0900 and R, = 0.1581. Crystal data for 9: space group Pbca, a = 17.876(2) A, b = 20.896(2) A, c = 17.690(2) A, V = 6608(1) g cm3, andDcdcd = 1.529 g cm3 for Z = 8. Least-squares refinement based on 2186 reflections converged to R = 0.057 and R, = 0.040. Crystal data for 10: space group P21/n, a = 14.882(2) A, b = 19.718(4) A, c = 8.794(1) A, = 92.30(2)", v = 2578.5(8) A3, and Dcdcd = 1.496 g ~m -~ for z = 4. Least-squares refinement based on 5731 reflections converged to R = 0.044 and R, = 0.041. Crystal data for 13: space group P21/a, a = 17.210(6) A, b = 9.693(6) A, c = 16.037(7) A, p = 100.366(3)", V = 2632(2) A3, andDdcd = 1.506 g ~m -~ for Z = 4. Least-squares refinement based on 3781 reflections converged to R = 0.037 and R, = 0.035. Crystal data for 16: space group E 1 / a , a = 18.814(2) A, b = 9.212(5) A, c = 15.068(5) A, p = 100.31(2)O, V = 2569(2)...

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A coordinated reciprocal interaction between epithelium and mesenchyme is involved in salivary gland morphogenesis. The submandibular glands (SMGs) of Wnt1-Cre/R26R mice have been shown positive for mesenchyme, whereas the epithelium is ␤-galactosidase-negative, indicating that most mesenchymal cells are derived from cranial neural crest cells. Platelet-derived growth factor (PDGF) receptor ␣ is one of the markers of neural crest-derived cells. In this study, we analyzed the roles of PDGFs and their receptors in the morphogenesis of mouse SMGs. PDGF-A was shown to be expressed in SMG epithelium, whereas PDGF-B, PDGFR␣, and PDGFR␤ were expressed in mesenchyme. Exogenous PDGF-AA and -BB in SMG organ cultures demonstrated increased levels of branching and epithelial proliferation, although their receptors were found to be expressed in mesenchyme. In contrast, short interfering RNA for Pdgfa and -b as well as neutralizing antibodies for PDGF-AB and -BB showed decreased branching. PDGF-AA induced the expression of the fibroblast growth factor genes Fgf3 and -7, and PDGF-BB induced the expression of Fgf1, -3, -7, and -10, whereas short interfering RNA for Pdgfa and Pdgfb inhibited the expression of Fgf3, -7, and -10, indicating that PDGFs regulate Fgf gene expression in SMG mesenchyme. The PDGF receptor inhibitor AG-17 inhibited PDGF-induced branching, whereas exogenous FGF7 and -10 fully recovered. Together, these results indicate that fibroblast growth factors function downstream of PDGF signaling, which regulates Fgf expression in neural crest-derived mesenchymal cells and SMG branching morphogenesis. Thus, PDGF signaling is a possible mechanism involved in the interaction between epithelial and neural crest-derived mesenchyme.

The triruthenium hexahydride complex [{(η 5 -C 5 Me 5 )Ru} 3 (µ-H) 6 ](BF 4 ) reacted with NaBH 3 X (X ) H, CN) to yield the novel trinuclear µ 3 -borylene complex {(η 5 -C 5 Me 5 )Ru} 3 (µ-H) 3 (µ 3 -BX), and the µ 3 -BH derivative was converted into a µ 3 -B(OR) analogue (R ) Me, Et) upon treatment with MeOH and EtOH, respectively. In the reaction of the µ 3 -BH analogue with benzothiophene, a µ 3 -thiaruthenacyclohexadiene complex formed via carbon-sulfur bond cleavage was isolated, and its structure was determined by an X-ray diffraction study.

NÀH bond activation of amines has attracted increasing attention owing to its applicability to the synthesis of various amino compounds, and the development of a new and effective reaction system for the activation of ammonia must be one of the most important research targets in connection with the transformation of abundant and inexpensive ammonia into a useful amino compound.[1] However, successful examples of activation of the NÀH bond of ammonia are still rare because of both the high NÀH bond dissociation energy ( % 104 AE 2 kcal mol À1 ) [2] and the difficulty in forming an NÀH s complex.[3]The groups of Milstein [1g, i, j] and Hartwig [1k, q] showed independently that some mononuclear iridium(i) complexes exhibited activity towards oxidative addition of ammonia. A highly unsaturated 14 e species with T-shaped geometry was proposed as a reactive intermediate for the NÀH bond cleavage on the basis of kinetic studies.[1q] Some complexes containing a d 0 metal center, such as [Cp* 2 MH 2 ] (M = Zr, Hf; Cp* = pentamethylcyclopentadiene), [1b, c, e] [Cp* 2 ScR], [1f] and [(neopentyl) 3 Ta = C(H)(tBu)], [1h] also activated ammonia to generate amido and nitrido complexes. There have, thus far, been examples of bimetallic oxidative addition to ammonia. A trinuclear carbonyl cluster, [Os 3 (CO) 11 (L)] (L = c-C 6 H 8 or CH 3 CN), effectively activates ammonia with the participation of the two osmium centers to produce the m-amido complex [Os 3 (CO) 10 (m-H)(m-NH 2 )]. [1a, d] A multimetallic system may work more efficiently for bond activation than a monometallic complex owing to the cooperative action of the metal centers. Each metal center would be allotted a part as a binding site and an activation site, and the transition state of the bond-activation step may, therefore, be stabilized.

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