Shoichiro Yamada

ADVANCEMENT IN STEREOCHEMICAL ASPECTS OF SCHIFF BASE METAL COMPLEXES

Abstract The object of the paper is to look back upon the development of coordination chemistry in the past several decades, during the career of the author, and possibly see how and through what accomplishments the present coordination chemistry has been built up. For the sake of space available, the paper will focus on the stereochemical aspects of Schiff base metal complexes. Those findings which are remarkable from a historical point of view are chosen and discussed. There is other work I would like to include, but must omit for lack of space. The paper is divided for convenience into the two parts dealing with Schiff base ligands of types (A) and (B): (A) Salen and multidentate ligands derived from Salen, and (B) bidentate N-substituted salicylidene-aminates. The main subjects to be discussed include: (A) non-planar Salen in metal complexes, effects of the polymethylene chain between the two imine nitrogen atoms on the structure of metal complexes, the first synthetic sexadentate metal chelates, possibility of trigonal-prismatic configuration for sexadentate chelates, dioxygen adducts of Co(Salen) and analogous complexes. (B) Anomalous solution paramagnetism of Ni(II) complexes, isomerism in the Ni(II) and Cu(II) complexes with Schiff base ligands and 5-coordination of Co(II) and Ni(II).

Red and green forms of nickel(II) complexes of schiff bases obtained from 3-methoxysalicylaldehyde and 4-halogenoanilines

Abstract Crystals of two forms were prepared for complexes of the type Ni(3CH 3 OSAL.4YPh) 2 , where YPh denotes a chlorophenyl or bromophenyl. Bis-(N-aryl-3-methoxysalicylideneiminato)nickel(II) is abbreviated as Ni(3CH 3 OSAL.aryl) 2 . The two forms of the chloro-series take a structure similar to that of the corresponding forms of the bromo-series. Since both the forms are paramagnetic with a magnetic moment corresponding to two unpaired electrons, the squareplanar configuration is excluded. The electronic spectrum, together with the magnetic moment, indicates that the green crystals (Form II) consist of associated, polymeric species, in which the nickel(II) ions are six-coordinated. In a similar way, it is concluded that the nickel(II) ions in the red crystals (Form I) are five-coordinated. Possible structures for the two forms are discussed.

Dioxomolybdenum(VI) complexes with schiff bases obtained from salicylaldehyde derivatives and polymethylenediamines

New dioxomolybdenum(VI) complexes have been synthesized with quadridentate Schiff bases derived from salicylaldehyde derivatives and polymethylenediamines. On the basis of infrared and proton magnetic resonance spectra, it is concluded that the MoO2 group in them has cis structure, in which the quadridentate bis(salicylaldehyde)polymethylenediiminates assume non-planar coordination instead of planar one.

Copper (II) complexes with a subnormal magnetic moment

In the course of the study about copper(II) complexes of Schiff bases of type I1 obtained from salicylaldehyde derivatives and alkanol amines, we have isolated some interesting compounds, which have a subnormal magnetic moment.

Oxomolubdenum complexes with schiff bases obtained from salicylaldehyde derivatives and alkyl- and aryl-amines

Abstract With N-alkyl- and N-aryl-salicylaldiminates (abbreviated as X-Sal-R) as ligands, new molybdenum (V) and molybdenum(VI) complexes of the following three types have been synthesized by reactions of dioxobis(ring-substituted salicylaldehydato)molybdenum(VI) with various alkyl- and aryl-amines: (1) MoO 2 (X-Sal_R) 2 , yellow; (2) MoO 2 (X-Sal-R), red; (3) Mo 2 O 3 (H-Sal_R) 4 , purple. Infrared spectra indicate that the complexes of type (1) are six-coordinate with a cis-MoO 2 group. The complexes of type (2) are considered to be multinuclear molybdenum(V) complexes. The complex of type (3), which shoes a characteristic UV spectrum, is similar to the acetylacetonato analogue, and is possibly binuclear with one oxygen atom as a bridge.

A hierarchical algorithm for one-dimensional gate assignment based on contraction of nets

A one-dimensional gate assignment algorithm based on hierarchical contraction of nets is proposed. In this algorithm, a special feature of multiterminal nets plays an important role, namely that if the gates can be arranged such that the nets with fewer terminals are shorter, the chip area will be much reduced. The algorithm consists of two phases, hierarchical contraction of nets and partial gate assignment. In the first phase, the original problem is partitioned to multiple levels with the basis on contraction of multiterminal nets, and in the next phase, the gates at each level are placed close to one another. Experimental results on logic circuits are shown which are superior to those obtained by the method presented by T. Fujii, et al. (ibid., vol.CAD-6, no.3, p.159-64, March 1987). >

Dioxotungsten(Vl) complexes with neutral schiff bases as ligands

Abstract The reaction of WO 2 Ct 2 with various N-arylsalicylaldimines (abbreviated as (Sal-R)H) has yielded tungsten(VI) complexes of the type WO 2 Cl 2 [(Sal-R)H] 2 It is very likely that these complexes involve the neutral Schiff bases, which are coordinated as unidentate ligands to tungsten(VI) ion. Infrared spectra indicate that the tungstenyl group WO 2 2+ in these complexes has a cis-configuration.

The crystal structure of the eight-coordinated erbium(III) complex with the tetradentate ligand N,N′-ethylene-bis(salicylaldimine)

Abstract The crystal structure of Er(III)(salen)2(pipH) [salen=N,N′-ethylene-bis(salicylaldimine),pipH= piperidinium] has been determined by X-ray diffraction. The structure of the compound consists of [Er(salen)2]−1 anions and pipH+ cations. In the complex anion the erbium(III) ion is eight-coordinated by the donor atoms of two tetradentate salen ligands, forming a distorted square antiprism with approximate D2 symmetry. The ErO and ErN distances average respectively 2.270 and 2.511 A. This is the first structural determination of a lanthanide element complex with a tetradentate ligand.

Placement of Circuit Modules Using a Graph Space Approach

This paper deals with the problem of automated placement of electronic components in a circuit layout by using a graph-space approach. In this approach, the relationships of connections among modules in a given electronic circuit are represented by a hypergraph. Then by using a graph-space approach, the vertices (representing the modules) are mapped into the graph space such that the distance between vertices in the space reflects the weights (the number of wires) of edges between vertices of the original hypergraph. On the basis of this placement in graph-space, the modules are assigned to grids on the printed-circuit board so as to minimize the total wire length. Simulation results show this technique yields a better assignment than the one derived from a hand-optimized layout and from an accepted automated-design method.

Chromium(III) complexes containing N,N′-ethylene-bis(salicylideneiminate) as a ligand

Abstract Numerous six-coordinate chromium(III) complexes with N,N′-ethylene-bis(salicylideneiminate) (abbreviated as Salen) have been synthesized. The complexes obtained are [Cr(Salen)L2]X. nH2O (X=Cl or NCS; L=H2O, NH3, CH3NH2, C2H5NH2, n-C3H7NH2, n-C4H9NH2, and pyridine), K[Cr(CN)2Salen)], [CR(ONO)Salen(H2O)], [CrCl(Salen)py], and [Cr(Salen)(H2O)py]Cl. The complexes of the type [Cr(Salen)(H2O)2]X have been obtained by a reaction of chromium(III) chloride hexahydrate with N,N′-ethylene-bis(salicylideneimine) in ethylene glycol-water-methanol at about 120°, by a reaction of NH4[Cr(NCS)4(NH3)2]. H2O with N,N′-ethylene-bis(salicylidenimine) in methanol, and by Collmans modified method using anhydrous chromium(III) chloride in tetrahydrofuran. The other complexes have been derived from [Cr(Salen)(H2O)2]X. The nitrite ion in [Cr(ONO)Salen(H2O)] is bound with the chromium(III) ion through the oxygen atom.