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SunzmaryThe reaction of carbon dioxide with dicyclopentadienyldiphenyltitanium leads to carboxylation of the phenyl ring and to metallocycle formation; the molecular structure of the compound has been determined by an X-ray study.Pbcu. The structure was determined by the heavy atom method and refined by least-squares (full-matrix, isotropic temperature factors). A t the present stage of refinement R = 0.13 for GU. 800 independent reflexions. The molecular structure (Figure) is in full agreement with the formulation CARBON DIOXIDE is known to react with transition metal compounds (excluding carbonate formation) either with the formation of complexes112 or with insertion of CO, into the metal-hydrogen bond., 9 4 We have now investigated the reaction of bis-(n-cyclopentadieny1)diphenyltitanium with carbon dioxide (80--90"; CO, bubbled through a solution in xylene) , which gave diamagnetic, air-stable, red crystals, m.p. 192-195" (decomp.), (35%) soluble in acetone and benzene, but insoluble in ether or light petroleum. The i.r. spectrum shows Ph and C5H5 absorptions and also bands a t 880m, 1130s, 1280vs, 1620s, and 1660vs cm-l; lH n.m.r. spectrum: 6 6 . 6 7 . 5 5 (phenyl) and 6-45 (C5H5) p.p.m. (relative areas 4 : 10).Heating of the compound with dilute H2S04 (1 : 1) gives benzoic acid and the action of BF, in methanol (100"; 3 h) gives methylbenzoate (70%). Pyrolysis a t 200" gives CO,, benzene, and cyclopentadiene. These data, together with elemental analyses, its molecular weight, and its mass spectrum support the formulation as structure (I). J-We carried out an X-ray study to investigate the mode of CO, co-ordination. Crystals of (I) are orthorhombic. Crystal data: u = 13.744(2), b = 14.410(2), c = 13.774(2) A; D, = 1-46, D, = 1.46 g crn4 for 2 = 8, space group

Mechanisms of intramolecular transformations of carbanions generated from 2-aza-1,3,5-trienes by the action of potassium tert-butoxide, which could lead to homo-or heteroannular azacycloheptadienes, were studied by quantum-chemical methods in terms of the density functional theory. The corresponding gradient channels were localized for model 1-methylsulfanyl-1-(cyclopentylideneamino)-and 1-methylsulfanyl-1-(cyclohexylideneamino)buta-1,3-dien-2-ols. Analysis of the kinetic and thermodynamic parameters showed that carbanion generated from N-cyclopentylidenebuta-1,3-dien-1-amine undergoes rearrangement mainly into homoannular azacycloheptadiene and that analogous N-cyclohexylidene derivative gives rise to heteroannular isomer. The results of calculations were consistent with the experimental data. * For communication XV, see [1].Seven-membered nitrogen-containing heterocycles constitute structural fragments of many natural and synthetic biologically active compounds which have found wide applications in medicine and pharmacology [2]. Increased interest in these compounds stimulated search for rational ways of their synthesis, including the synthesis of new derivatives. We recently showed that 2-aza-1,3,5-trienes I available in one preparative step from α-lithiated allenes (e.g., methoxyallene or protected allenyl alcohol) and s-alkyl isothiocyanates (e.g., isopropyl isothiocyanate) (Scheme 1) [3] by the action of potassium tert-butoxide in tetrahydrofuran-dimethyl sulfoxide are readily (-30°C, 30 min) transformed into previously unknown 4,5-dihydro-3H-azepines II (Scheme 2); these results were briefly reported in [4,5].

The thermolysis and reactions of the polymeric high spin Mn II and Fe II complexes [Mn(µ OOCBu t ) 2 (HOEt)] n (1) and [Fe(µ OOCBu t ) 2 ] n (3) with pivalic acid and o phenylenedi amines 1,2 (NH 2 ) 2 C 6 H 2 R 2 (R = H or Me) were studied. The synthesis of compound 1 per formed with a deficiency of pivalate anions affords the antiferromagnetic chloropivalate poly mer {(MeCN)(HOOCBu t )(H 2 O)Mn 5 Cl(OH)(OOCBu t ) 8 •MeCN} n . The reaction of 1 with an excess of pivalic acid produces the antiferromagnetic polymer [Mn 4 (OOCBu t ) 8 (HOOCBu t ) 2 ] n . The analogous reaction of pivalic acid with polymer 3 gives the mononuclear complex Fe(η 1 OOCBu t ) 2 (η 1 HOOCBu t ) 4 containing the high spin iron(II) atom as the major product. Study of the reactions of 3 with a deficiency (<1 : 1) and an excess (>1 : 1) of diamines demonstrated that the polymer {[(η 2 (NH 2 ) 2 C 6 H 4 ) 2 Fe(µ OOCBu t ) 2 ][Fe 2 (µ OOCBu t ) 4 ]• •2MeCN} n is generated as the major product in the former case, whereas the mononuclear complexes Fe(η 1

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