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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.

The reaction of cadmium salts with various amounts of the tridentate NS 2 -chelating ligands 1-(2-mercapto-acetophenone)-4-triphenylmethylthiosemicarbazone (H 2 L 1 ) and 1-(5-mercapto-3-methyl-1-phenylpyrazole-4-carboxaldehyde)-4-triphenyl-methylthiosemicarbazone (H 2 L 2 ) in the presence of bases like N-methylimidazole (N±MeIm), pyridine (py) or triethylamine (Et 3 N) provided a series of novel mono-, di-, tri-and heptanuclear cadmium complexes. They are of the general formulas [CdL 1 (N±MeIm)] 2 (1), [CdL 1 (py)] 2 (2), [CdL 2 (N±MeIm)] 2 (3), [CdL 2 (py) 3 ]0 .25 C 6 H 14´0 .5 py (4), [Et 3 NH] 2 [Cd 3 L 2 4 ]´7 MeOH (5), [Et 3 NH] 2 [Cd 3 L 1 4 ] (6) and [Et 3 NH] 2 [Cd 7 L 2 8 ]´14 MeOH (7). The compounds were characterized by elemental analysis, IR-and 1 H-NMR-spectroscopy. Single-crystal X-ray struc-ture analyses are reported for the complexes 2, 4, 5 and 7. While 2 has a dimeric structure where each cadmium ion is pentacoordinated in a N 2 S 3 -environment, 4 consists of a monomeric cadmium center with distorted octahedral N 4 S 2coordination. The complexes 5 and 7 exhibit new structural types for tri-and heptanuclear cadmium compounds. It is shown that sulfur bridging might proceed via arylthiolates, iminothiolates or even both functions of the ligand. Aggregation is influenced by various factors like solvents, counterions and ligand properties.Koordinationsverhalten tridentater NS 2 -Donor-Liganden mit Cadmium: Synthese und Kristallstrukturen neuer Komplexverbindungen Inhaltsu È bersicht. Die Reaktion von Cadmiumsalzen mit unterschiedlichen Mengen der dreifach chelatisierenden Liganden 1-(2-Mercapto-acetophenon)-4-triphenylmethylthiosemicarbazon (H 2 L 1 ) und 1-(5-Mercapto-3-methyl-1phenylpyrazole-4-carboxaldehyde)-4-triphenylmethylthiosemicarbazone (H 2 L 2 ) in Gegenwart verschiedener Basen wie N-Methylimidazol (N±MeIm), Pyridin (py) oder Triethylamin (Et 3 N) ergab eine Reihe neuer mono-, di-, triund heptanuklearer Cadmiumkomplexe mit folgenden Strukturformeln: [CdL 1 (N±MeIm)] 2 (1), [CdL 1 (py)] 2 (2), [CdL 2 (N±MeIm)] 2 (3), [CdL 2 (py) 3 ]´0.25 C 6 H 14´0 .5 py (4), [Et 3 NH] 2 [Cd 3 L 2 4 ]´7 MeOH (5), [Et 3 NH] 2 [Cd 3 L 1 4 ] (6) und [Et 3 NH] 2 [Cd 7 L 2 8 ]´14 MeOH (7). Die Verbindungen wurden durch Elementaranalysen, IR-und 1 H-NMR-Spektroskopie charakterisiert. Ro È ntgenstrukturanalysen wurden fu È r die Komplexe 2, 4, 5 und 7 durchgefu È hrt. Wa È hrend 2 eine dimere Struktur hat, in der jedes Cadmiumatom in einer N 2 S 3 -Umgebung fu È nffach koordiniert ist, ist 4 ein Monomer mit einer verzerrt oktaedrischen N 4 S 2 -Koordination. 5 und 7 stellen neue Strukturtypen fu È r tri-und heptanukleare Cadmiumkomplexe dar. Die Verbru È ckung durch die Schwefelatome geschieht einerseits nur u È ber die Aryl-oder Iminothiolate und andererseits u È ber beide Funktionen des Liganden. Der Umfang der Aggregation wird dabei durch verschiedene Faktoren wie Lo È sungsmittel, Gegenionen und Ligandeigenschaften beeinfluût.

365; eigene Analysen der Strukturdaten zeigen das Vorliegen von Dimeren, die durch vier Wasserstoffbriickenwie in 1 -verknupft sind: b) H. Gods, B.