The molecular modeling methods have found wide acceptance in the fields of organic chemistry and biochemistry. This study introduces a new algorithm to overcome the special problems encountered when extending standard force fields to metal-organic and inorganic complexes. The extension can easily be incorporated in common modeling programs. The application to the complexes of Cu(II) in square-planar coordination validates the approach. A general parametrization for Cu(II) consistent with the TRIPOS 5.2 force field is developed on the basis of the X-ray structures of 27 complexes with nitrogen-and oxygen-coordinated copper. The metal environment can be calculated to better than 2 pm for the bond lengths and 2°for the bond angles. Some larger deviations for the torsion angles can be attributed to the intermolecular interactions in the crystal.
Reaction of 1,3-dicyanotetrafluorobenzene with 2 equiv of (trimethylsilyl)iminophosphoranes gave the disubstituted derivatives 4,6-(CN)(2)C(6)F(2)-1,3-AB: 1, A = B = (N=PPh(3)); 2, A = B = (N=PPh(2)Me); and 3, A = (N=PPh(3)), B = (N=PPh(2)Me). Monosubstituted compounds of the type 2,4-(CN)(2)C(6)F(3)-1-A; notably 4, A = (N=PPh(3)), and 5, A = (N=PPh(2)Me), were readily obtained by reaction of 1 molar equiv of the silylated iminophosphorane with the cyanofluoro aromatic. Substitution of the fluorine para to the CN group(s) occurs in all cases. Reactions of 1,2- and 1,4-dicyanotetrafluorobenzene with (trimethylsilyl)iminophosphoranes gave only monosubstituted derivatives 3,4-(CN)(2)C(6)F(3)-1-A (6, A = (N=PPh(3)), and 7, A = (N=PPh(2)Me)) and 2,5-(CN)(2)C(6)F(3)-1-A (8, A = (N=PPh(3)), and 9, A = (N=PPh(2)Me)), respectively, as the result of electronic deactivation of the second substitutional point. 1, 4,6-(CN)(2)C(6)F(2)-1,3-(N=PPh(3)), 2, 4,6-(CN)(2)C(6)F(2)-1,3-(N=PPh(2)Me)(2), and 3, 4,6-(CN)(2)C(6)F(2)-1-(N=PPh(3))-3-(N=PPh(2)Me) have been structurally characterized. For 1 (at 21 degrees C), monoclinic, C2/(c) (No. 15), a = 15.289(2) Å, b = 10.196(1) Å, c = 23.491(6) Å, beta = 91.63(2) degrees, V = 3660(2) Å(3), and Z = 4. The P=N bond length is 1.579(2) Å and the P(V)-N-C(phenyl) angle is 134.0(2) degrees. For 2, (at 21 degrees C) monoclinic, C2/(c) (No. 15), a = 18.694(2) Å, b = 8.576(1) Å, c = 40.084(4) Å, beta = 94.00(1) degrees, V = 6411(2) Å(3), and Z = 8. The P(1)=N(1) bond length is 1.570(4) Å, the P(2)=N(2) bond length is 1.589(3) Å, the P(1)-N(1)-C(14) angle is 131.6(3) degrees, and the P(2)-N(2)-C(16) angle is 131.3(3) degrees. For 3, (at -80 degrees C) monoclinic, P2(1)/c (No. 14), a = 9.210(1) Å, b = 18.113(2) Å, c = 20.015(2) Å, beta = 100.07(1) degrees, V = 3287(2) Å(3), and Z = 4. The P(1)=N(1) bond length (PPh(3) group) is 1.567(4) Å, the P(2)=N(2) bond length (PPh(2)Me group) is 1.581(5) Å, the P(1)-N(1)-C(1) angle is 140.4(4) degrees, and the P(2)-N(2)-C(3) angle is 129.4(4) degrees. These new multifunctional chelating ligands readily react with [Rh(cod)Cl](2) and AgClO(4) to give cationic Rh(I) complexes in which the imine and/or the nitrile groups are coordinated to the Rh center.
Metal Complexes of Unsymmetrically Bridged IN4] Macrocycles: Synthesis, Structure and Redox BehaviourMetal complexes M-5a (M = Cu, Ni, CO, Fe, and I-Fe") of 6,13-Di(ethoxycarbonyl)-7,12-dimethyl-benzo[ b]-l,4,8,11tetraaza-cyclotetradeca-2,5,7,11,13-pentaene and the free ligand H2-5a have been synthesized. The crystals of Cu-5a . H20 and Ni-5a . H 2 0 consist of planar complex molecules which are linked by H bridges between the water molecules and the peripheric ester groups to give 1D chains. The average M-N-distances are equal for both complexes (Cu 1.928, Ni 1.924 A), being unexpectedly large for the nickel complex. 'The redox properties of all the new compounds as well as some acetyl derivatives M-5b have been examined by cyclic voltammetry and compared with those of the previously re-ported symmetrically phenylene (M-4) and ethylene (M-6) bridged derivatives. All complexes give a reversible single electron reduction which clearly shows the increasing electron density around the central atom in the order M-4 < M-5 < M-6. Like the carbonyl substituted tetraazaannulenes M-4 the copper complexes Cu-5 give two, the cobalt complexes CO-5 three, and the iron complex Fe-5a probably four reversible single electron oxidations. They can be attributed to the species [M"'L-I']+, (M"L0J2+, [M"1Lo]3f, and [Fe1VLo]4+ with Lo being a "non innocent" neutral 1,2-quinodiimine ligand. Very surprisingly, since in contrast to Ni-4 and Ni-6, the nickel complexes Ni-5 gave no reversible oxidation. Makrocyclisch [Ni-1-koordinierte Chelatkomplexe der 3d-Elemente wirken als Aktivzentren vieler Biokatalysatoren. Beispiele sind das allen Hamenzymen zugrunde liegende Eisenporphyrin 1, das Corrin 2 der B12-Enzyme und das Dihydrocorphingeriist 3 des Cofaktors F 430[']. Obwohl sie fur unterschiedlichste Prozesse der biologischen Stoff-und Energiewandlung funktionsoptimiert sind, zeigen sie eine Reihe ubereinstimmender Strukturmotive, die offenbar gunstige Voraussetzungen fur eine Steuerung der katalytischen Eigenschaften biecen: Das Zentraiion bildet mit dem Bquatorial koordinierten, anionischen [N4]-Liganden mindestens zwei konjugiert-ungesattigte Chelatsechsringe aus. Hinsichtlich des x-Elektronensystems und der Ringgliederzahl m des inneren Makrocyclus sowie der Ladung z des Ligandanions bestehen charakteristische Unterschiede (1: 18 n; m = 16, z = -2; 2: 14 x; m = 15, z = -1; 3: 12 x; m = 16, z = -1). Die fur das Design biomimetischer Katalysatoren wichtige Frage, wie derartige Strukturmerkmale das katalytische Leistungsvermogen und die dafur entscheidenden Eigenschaften solcher Komplexe beeinflussen, 1al3t sich bisher kaum beantworten. Vor 30 Jahren erhielten wir uber eine Templatsynthese erstmals Komplexe des ,,Tetraaza[14]annulen6'-Typs 4, die sich von cyclischen 2:2-Kondensationsprodukten aus p-Dicarbonylverbindungen und 1,2-Phenylendiamin ableitenL'1. Sie unterscheiden sich vom inneren Makrocyclus des Por-1 4 4-8 I R' R2 R3 2 R2 5 X=C2H, p 3 R3&R1 / N \ A X M X ' 6 phyrinsystems nur durch das Fehlen zweier Methingruppen (16 n; m = 14...
COMMUNICATIONSMW but a measure of the hydrodynamic volume. Thus, by SEC using randomly coiled polystyrene standards, the number average molecular weights (M,) of rigid-rod polymers are usually greatly overestimated relative the actual molecular weights. Accordingly, the SEC-determined M , values of the octamer 20 ( M , = 2800, actual MW =1981) and the 16-mer 23 ( M , = 6650, actual MW = 3789) are much greater than the actual MWs. These results further confirm the formation of the 16-mer 23. Also, as predicted, the monomer 2, dimer 8, and tetramer 14 have M , values that are reasonably close to the actual MWs (slope = 1 .O in Fig. 3) because they are in the low M W region, in which the polystyrene standards are not coiled. In all cases, the SEC-determined values of M,/M, are 1.04-1.07. Thus Figure 3 can serve as a useful calibration chart for very rigid linear oligomers as they compare to polystyrene standards by SEC. 0 . I. Paynter, D.
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