Synthesis, crystal structure, and properties of MnNCN, the first carbodiimide of a magnetic transition metal

Synthesis, single-crystal structure determination, and magnetic properties are reported for manganese carbodiimide, MnNCN. The presumably unstable but inert phase adopts the trigonal system (R3m) with a = 3.3583(4) A, c = 14.347(2) A, V = 140.13(3) A3, and Z = 3. Divalent manganese is octahedrally coordinated by nitrogen atoms at 2.26 A, and the NCN(2-) unit adopts the linear [N=C=N](2-) carbodiimide shape with two C=N double bonds of 1.23 A. MnNCN contains high-spin Mn(II) with five unpaired electrons and behaves like an antiferromagnet with an ordering temperature below 30 K.     

Versuche zur Herstellung eines «Bis(triasterans)» und Synthese des heterocyclischen (Tricyclo[4.4.1.01,6]undeca-3,8-dien-11,11-dimethyl)sulfits

Tentative Synthesis of ‘Bis(triasterane)’ and Synthesis of the Heterocyclic (Tricyclo[4.4.1.0^1,6]undeca-3,8-diene-11,11-dimethyl)sulfite The synthesis of the bis(triasterane) ( 1 ) has been tried; the reaction of ‘isotetraline’ (1,4,5,8-Tetrahydronaphthalene; 2 ) with diazomalonate yielded the tricyclic systems 5 and 6 , and not 4 . Hydrolysis of 5 gave the monocarboxylic acid 7 , and not the dicarboxylic acid 9 . The latter could be obtained from the dibromoderivative 8 , but 9 couldn't be converted to the acyl chloride 10 . The reduction of 9 with LiAlH₄ yielded the crystalline diol 11 , which was cyclized with SOCl₂ to the heterocycle 12 . The spectral data of the new compounds 5, 6, 7, 11 and 12 are reported and discussed.     

Etude théorique de derives substitués du benzène

Résumé Dans les conditions explicitées lors du premier article de cette série, la méthode semi-empirique de Pariser-Parr-Pople est appliquée à l'étude électronique des dialcoxybenzènes symétriques. Le calcul met en évidence l'influence de la position relative des substituants sur les potentiels d'ionisation, le déplacement des bandes électroniques du benzène et les intensités des bandes d'absorption. Pour les dérivés ortho et para, ce travail met en évidence l'existence d'un transfert électronique lors de l'excitation jusqu'aux deux premiers singulets excités, alors qu'un phénomène analogue se produit pour les quatre premiers singulets des composés méta. Enfin la réactivité chimique des positions substituables de ces molécules est discutée.

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Theoretical study of substituted benzenesII. Symmetrical dialkoxybenzenes

In the conditions we gave in the first paper, the semi empirical Pariser-Parr-Pople's method has been applied for the electronic study of symetrical dialkoxybenzenes. These calculations show the effect of the substituants position on ionization potentials, spectroscopic shifts on benzene absorption bands and corresponding intensities. This work indicates that the excitation to the first and second singlet induces an electronic transfer from the heteroatom in the case of ortho and para derivatives; for meta compounds, the same phenomenon occurs for the four first singlets. At last, the reactivity of substituable positions is discussed.

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Zusammenfassung Die im Teil I erfolgte Untersuchung der Monoalkoxybenzole wurde auf die entsprechenden Dialkoxyverbindungen ausgedehnt, wobei sich zeigt, wie Ionisierungspotentiale, Absorptions- und IntensitÄtsverschiebungen von der gegenseitigen Lage der Substituenten abhÄngen. Die ersten zwei SingulettübergÄnge zeigen im Fall der ortho- und para-Verbindungen Ladungsübergang; im Fall der meta-Verbindungen sind es die ersten vier.

     

Some general results concerning the critical exponents of percolation processes

Summary In this paper we will give some results concerning the critical exponents of percolation processes which are valid for any model. These results show that in several respects the behavior which occurs for percolation on the binary tree provides bounds on one side for what happens in general. These results and their proofs are closely related to their analogues for the Ising model.Alfred P. Sloan Fellow. This work partially supported by NSF grant MCS 80-02732.     

The application of C-N.M.R. spectroscopy to the determination of the stereochemistry of Diels-Alder adducts

Long-range (³J) ¹³C-H coupling is a reliable probe to evaluate the stereochemistry of cycloaddition products. The method is best applied to carbonyl containing adducts but not restricted to them. Several structures have been revised and new ones evaluated.