Ligandengestützte Kopplung metallorganischer Reaktionszentren

Abstract

Elektronenreservoir‐Verhalten, die Bildung gemischtvalenter RhII/RhI‐Spezies und die Aufspaltung der Redoxprozesse durch “Kommunikation” zwischen den Redoxzentren wurden bei der ersten systematischen Untersuchung zur ligandengestützten Kopplung zweier äquivalenter Redox‐(ECE)‐Reaktionszentren festgestellt (siehe Schema rechts; E = Elektronentransfer; C = chemischer Schritt, hier die Chloridabspaltung; Cp* = C5Me5; L = mehrzähniger Ligand).

Directed Reduction of Six‐Membered Nitrogen Heterocycles—Selective Formation of Polynuclear Titanium Complexes

“…[18a] The formation of 8 is particularly surprising, since pyrazine (6) is considered to be a typical bridging ligand and no defined CÀC coupling at metal centers has been described to date for this heterocycle. [19] For the investigations described herein, we employed a novel synthetic method, in which metal-linked complexes of polyvalent N-donor ligands are formed from readily accessible building blocks. The good solubility of the starting materials 1 and 2 allows a smooth separation of the (in most cases) sparingly soluble products.…”

“…Structure of 10 in the crystal (50 % probability, without H atoms). Selected bond lengths [] and angles [8] at the terminal Ti5 and Ti7 centers as well as at the chelate positions Ti6 and Ti8: Ti5-N9 2.193(6), Ti5-N8 2.205(6), Ti6-N10 2.155(6), Ti6-N11 2.157(5), Ti7-N12, 2.182(6), Ti7-N13 2.190(6), Ti8-N15 2.153(6), Ti8-N14 2.158(6), N9-C67 1.334(9), N9-C68 1.430(9), N10-C67 1.272(9), N10-C70a 1.569(15), N11-C84 1.301(9), N11-C81a 1.468(9), N12-C84 1.367(8), N12-C83 1.378(9), N13-C95 1.361(9), N13-C96 1.415(9), N14-C95 1.313(9), N14-C98a 1.552(10), N15-C112 1.317(9), N15-C109a 1.496(11), N16-C112 1.338(9), N16-C111 1.422(8), C68-C69 1.302(11), C69-C70a 1.529(18), C70a-C81a 1.602(19), C81a-C82 1.420(9), C82-C83 1.306(10), C96-C97 1.287(11), C97-C98a 1.502(12), C98a-C109a 1.500(14); N9-Ti5-N8 82.0(2), Ct-Ti5-Ct 131.72, N10-Ti6-N11 75.4(2), Ct-Ti6-Ct 133.48, N12-Ti7-N13 83.4(2), Ct-Ti7-Ct 131.88, N15-Ti8-N14 75.8(2), Ct-Ti8-Ct 135,16; Ct = ring centroid of the carbon atoms of the respective Cp ring.…”

Titanium‐Based Molecular Squares and Rectangles: Syntheses by Self‐Assembly Reactions of Titanocene Fragments and Aromatic N‐Heterocycles

“…The concept of self-assembly occupies a key position in this field, and a multitude of supramolecular compounds have been synthesized by combining simple building blocks to form two-and three-dimensional structures. [1][2][3] Owing to their electronic and steric versatility, aromatic N-heterocycles play a prominent role as classical ligands in coordination compounds, [4,5] as bridging ligands in binuclear derivatives, [6][7][8] and as building blocks for supramolecular compounds. [9][10][11][12][13][14][15][16][17] In addition to their ability to connect metal centers by forming ligand-metal bonds, they provide the opportunity of p backbonding and thereby may affect delocalization and transport of electrons.…”

Selenol Nitrosation and Se‐Nitrososelenol Homolysis: A Reaction Path with Possible Biochemical Implications

“…The splitting pattern ( Figure 1) can be simulated reasonably well if coupling to selenium (a( 77 Se) = 30 G) and to two nitrogen atoms (a( 14 N) = 7.6 G) is assumed. [16,17] The valency of selenium in 5 may be compared to that in [C 6 H 4 N 2 SeW-(CO) 5 ]C À , [18] the {W(CO) 5 } complex of the cyclic radical anion C 6 H 4 N 2 SeC À ( Figure 2) After about 20 min at room temper- In contrast to selenol 4 a, trisylthiol 3 a was not attacked by tert-butylnitrite or by isopentylnitrite at À78 8C. Nitrosation at 5-10 8C led to relatively stable S-…”