Lithium cyclopentadienide adds to a variety of isocyanates [R−NCO, R = tert-butyl (a), n-butyl (b), cyclohexyl (c), phenyl (d), 3-pyridyl (e), 2-tetrahydropyranyl (f), adamantyl (g)] to yield the monocarbamoyl-substituted cyclopentadienides C5H4CONHR- 3 admixed with varying amounts of the respective 1,2-dicarbamoyl-substituted C5H3(CONHR)2 - systems 4 and a corresponding quantity of the C5H5 - starting material. Subsequent treatment of these reaction mixtures with anhydrous FeCl2 gave the 1,1‘-dicarbamoylferrocenes 6 and the corresponding monocarbamoylferrocenes 5, which were easily separated by chromatography. The carbamoylferrocenes 5b, 5c, and 6d were characterized by X-ray crystal structure analyses. The (N-phenyl- and (N-adamantylcarbamoyl)cyclopentadienides were treated with CpTiCl3 to give the carboxamide-substituted titanocene dichloride complexes [Cp(C5H4CONHR)TiCl2] 8a (R = Ph) and 8b (R = adamantyl), respectively. Complex 8b was also characterized by X-ray diffraction. The valine ester-derived isocyanate reacts with lithium cyclopentadienide to give the N-valinyl-substituted carbamoylcyclopentadienide 3h. Subsequent treatment with FeCl2 or FeCl2/CpLi, respectively, produces the 1,1‘-difunctionalized ferrocene 6h or the monofunctionalized ferrocene 5h. Both complexes were characterized by X-ray crystal structure analyses.

The high reactivity of 1,2,4,5-tetrazines 1 relative to donor-substituted C N multiple bondsci1 such as in the hydrazones 2 or cyanamides 3 makes amine-substituted triazines 4 and 5 respectively, surprisingly readily accessible by Diels-Alder addition with inverse electron demandl2]. We have found that the C=N functionality in isocyanides 6 behaves differently: the reaction of la-c with benzyl isocyanide 6 is the first example of a synthesis in which five-membered heterocycles result from a [4 + I]cycloaddition and subsequent [4+ 2]cycloreversion. as 9c (m.p. = 180-181 "C, carbon tetrachloride, yield 75%) are obtained after concentration; crystals of 9b (m. p. = 220°C, ethyl acetate, yield 70%) precipitate out after a short time. lla, b: 9a is completely hydrolyzed to l l a (m. p. = 185 C, ethyl acetate, yield 95%) by addition of water. 9b is hydrolyzed by heating for a short time in conc. hydrochloric acid. Treatment of the hydrochloride with an aqueous solution of potassium carbonate led quantitatively to l l b (m.p.=208"C, ethanol).-9 and 11 gave correct C,H,N analysis results and appropriate spectra (MS, In the initial step, the previously only rarely achieved[31 [4+ l]cycloaddition of 6 to 1, in which the azine system is s-cis-fixed, should dominate over a [4 + 2lcycloaddition.The non-isolable tetraazanorbornadienimine derivative 7, whose high angular strain causes elimination of nitrogen via a [4 + 2]cy~loreversion[~~ in a rapid subsequent reaction, is formed; the resulting energy-rich diazacyclopentadienonimine derivative 8 rapidly tautomerizes to the aromatic pyrazole 9. Hydrolysis of 9a-c leads quantitatively to the pharmacologically interesting aminopyrazoles lla-c. The structures of l l a and l l b were confirmed by independent synthesi~'~]. Hence, e.g., condensation of 12a and 13a also led, after transesterification to l l a , although in considerably lower yield. Procedure 9a-c: la-c (5 mmol) is dissolved in 20 mL of anhydrous dichloromethane, and a solution of 6 (5 mmol) in 10 mL of dichloromethane added dropwise at ca. 0°C; the mixture is left to react until the red color of 1 has disappeared. 9a (m. p. = 161 " C , ethyl acetate, yield 65%) as well A Novel Anionic Five-Coordinate Tris(trichlorostannato)platinum(n) Complex**By Albert0 A fbinati, Ralph Nageli. Heinz Riiegger. and Paul S . Pregosin* Trichlorostannato complexes of platinum(i1) are recognized as useful hydrogenation and hydroformylation catalysts"'. Although the exact composition of the active species is not clear, it is known that the catalyst functions optimally when the ratio Sn : Pt exceeds five, and therefore poly(trich1orostannato) derivatives may be important intermediates. We have recently shown that mono-and bis(trichlorostannato)platinum(lr) complexes containing either tertiary phosphane or arsane ligands are stable in soI~t i o n~~.~] , and now report the synthesis and characterization of the anion

4ß•", -H20, 45H [(tpy)(bpy)RuII;(N02)]+ -2», 4H2oj|+2H+, -H20 t(t py Hbpy )R uX ( +)33+ C(tpy)(bpy)RuIII(NH3)]3+ [(tpy)(bpy)RuXI(NO• )]Z+ 2H*. +»"|-2Hi, C(tpy)(bpy)RuIV=NH2+ 11* +•", +H ,-H20 -, *H20 (slow) C(tpy)(bpy)RuXI(NH0H)]2+ C(tpy)(bpy)Ru(NO)l -•", -II 24 ==*• C(tpy)(bpy)Ru (NHO)] 4«-,4H'lations of the intermediates proposed here which differ with regard to water content, e.g., [(tpy)(bpy)Ru!I(NH20)]2+ vs. [(tpy)-(bpy)Osv=N]2+, may be profound with regard to both electronic structure and reactivity characteristics. For example, the spectral properties of [(tpy)(bpy)RuIV=NH]2+ are essentially those of the high-oxidation-state oxo complex [(tpy)(bpy)Rulv=0]2+, which features an absence of visible absorption bands.1 lb The "reductive hydration" reaction [(tpy)(bpy)RuIV=NH]2+ + H2G -» [(tpy)(bpy)RuII(NH2OH)]2+ produces a typical complex of Ru(II) having intense metal to ligand charge-transfer (MLCT) absorption bands (ir*(bpy) <-dTr(Run)) at nearly the same energy as for the ammine complex [(tpy)(bpy)Ru(NH3)]2+.u The presence or absence of hydrated-dehydrated pairs like MIV-NH2+/Mn-NH2OH2+, Mv= N2+/Mn-NH202+, and MIV=N+/M"-NH02+ may depend on the pH, the metal, and the ligand environment involved, and we hope to learn how to control this chemistry in a systematic way.In Schemes I and II an attempt has been made to summarize our best guesses as to the mechanistic details for the nitro-ammine interconversion for the Ru and Os complexes in the pH range 2-6. Acknowledgment is made to the National Institutes of Health under Grant No. 5-RO1-GM32296-02 for support of this research.

The complex formation reactions of Mn2+, Fe2+, Co2+, and Ni2+ with 2,2'-bipyridine and 2,2':6',2"-terpyridine in aqueous solution were studied as a function of metal ion and ligand concentrations for pressures up to 100 MPa. The corresponding volumes of activation range from -3.4 ± 0.7 (for Mn2+) to +6.7 ± 0.2 cm3 mol"1 11(for Ni2+) and parallel the earlier reported data for solvent exchange for the equated metal ions. This study is the first to report an activation volume for a complex formation reaction involving Fe2+, viz. +3.5 ± 0.5 cm3 mol"1 for the reaction with terpyridine. The results are discussed in reference to data for closely related systems and in terms of a changeover in the nature of the ligand-exchange process, i.e. from I, to Id, along the first-row transition-metal elements. 15 0.02 0.15-0.30 10-%,d M'1 s'1 7.8 ± 0.4 8.0 ± 0.3 8.0 ± 0.2 8.1 ± 0.3 8.3 ± 0.2 -1.3 ± 0.3 0.1-0.5 0.015-0.03 10'%, M'1 s'1 8.2 ± 0.4 8.3 ± 0.4 8.5 ± 0.6 8.7 ± 0.4 9.5 ± 0.4 -3.4 ± 0.7 k" s'1 4.3 ± 1.4 4.9 ± 1.4 5.6 ± 1.9 6.1 ± 1.3 5.8 ± 1.3 -7.7 ± 2.2 Fe terpy 25 0.02 0.20 b b C-1 *obsd> S 14.4 ± 0.3 13.9 ± 0.8 13.3 ± 0.8 12.5 ± 0.2 12.8 ± 0.4 +3.5 ± 0.7 0.02 0.30 23.3 ± 1.6 22.6 ± 0.5 22.3 ± 0.8 20.8 ± 0.9 20.6 ± 0.7 +3.3 ± 0.4 0.2 0.02 24.0 ± 0.9 21.1 ± 0.8 21.4 ± 1.5 19.6 ± 0.3 18.3 ± 0.4 +4.3 ± 1.2 0.4 0.02 31.2 ± 1.2 30.2 ± 1.2 29.5 ± 1.4 29.0 ± 1.0 26.9 ± 0.7 +3.5 ± 0.6 0.6 0.02 45 ± 4 45 ± 4 44 ± 4 42 ± 4 40 ± 2 + 3.4 ± 0.6 Co terpy 25 0.015-0.03 0.175-0.50 © 4.5 ± 0.3 4.4 ± 0.2 4.3 ± 0.2 4.1 ± 0.1 3.7 ± 0.2

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