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Mono-and digerma[n]metallocyclophanes (n ) 1, 2) [(η 6 ,η 6′ -dimethyldiphenylgermane)M] (M ) Cr, 17; V, 18 • ), [(η 6 ,η 6′ -tetraphenylgermane)M] (M ) Cr, 20; V, 21 • ), and [(1,1,2,2tetramethyl-1,2-di-η 6 ,η 6′ -phenyldigermane)Cr] (24) were synthesized by means of lithiation and subsequent reaction with dichlorodimethylgermane or dichlorodiphenylgermane. Metalligand cocondensation of bromodimethylphenylgermane with chromium atoms followed by reductive coupling with lithium naphthalide gave the digermane complex 24. Additionally, the nonbridged derivatives [bis(trimethylgermyl-η 6 -benzene)M] (M ) Cr, 10d; V, 11 • ), [(trimethylgermyl-η 6 -benzene)(η 6 -benzene)Cr] (10m), and [bis(triphenylgermyl-η 6 -benzene)M] (M ) Cr, 14; V, 15 • ) were prepared and characterized by 1 H-and 13 C-NMR (10m, 10d, 14, 17, 20), cyclic voltammetry (CV) (10d, 11 • , 14, 15 • , 18 • , 21 • , 24), and EPR spectroscopy (10d •+ , 11 • , 14 •+ , 15 • , 18 • , 21 • , 24 •+ ). Crystals of 20 were subjected to a structure determination by X-ray diffraction, which disclosed a bending of the sandwich axis from linearity by 14.4°. The strain exerted on the coordinated benzene ring forces a pyramidal structure on the ipso-C leading to a markedly shielded 13 C-NMR resonance. An EPR spectroscopic investigation of the vanadium derivatives reveals an increasing metal to ligand spin delocalization and the appearance of orthorhombic g and A tensors on bending the sandwich axis. While the redox potentials are virtually unaffected, when passing from the unstrained vanadium complexes 11 • and 15 • to the germa[1]vanadocyclophanes 18 • and 21 • , the transient monocationic species of the latter are destabilized dramatically. No evidence of ring-opening polymerization was observed on heating 18 • to 165 °C. Instead, metal-ligand cleavage occurs.

Catalytic hydrocracking of 4-(1-naphthylmethyl)bibenzyl (NMBB) predominantly yielded naphthalene and 4-methylbibenzyl. Various iron compounds were examined as catalyst precursors. Sulfur addition to most catalyst precursors led to substantially higher catalyst activity and higher conversion. NMBB was also treated with sulfur in the absence of iron compounds, in concentrations of 1.2-3.4 wt %, corresponding to the conditions present in reactions with added iron compounds. Increasing sulfur concentrations led to higher NMBB conversions. Furthermore, sulfur had a permanent effect on the reactor walls. A black sulfide layer formed on the surface which could not be removed mechanically. The supposed noncatalytic reactions done in the same reactor but after experiments with added sulfur showed higher conversions than comparable experiments done in new reactors. This wall catalytic effect can be reduced by treating the sulfided reactors with hydrochloric acid. The results of this work demonstrate the significant effect of sulfur addition and sulfur-induced residual wall effects on carbon-carbon bond cleavage and hydrogenation of aromatics.

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Bay-K-8644 (1) reagiert mit Pyidiniumbromidperbromid (PBPB) zurn anellierlen I.4-Dihydmpyridin (DHP)-lacton 7 und der qridiniumverbindung 8; rnit UV A-Licht entstehen danlus die 3-mdinole 10 und 11. Aus dem Diester-1.4-DHP 2 k6nnen mit PBPB das Monolacton 12, das Bislacton I3 und das Dibmmmethylderivat 14 isoliert werden. Das zu 1 isomere 1.2-DHP 4 liefert mit PBPB nur das Oxidationsprodukt 17, wtihrend das Diester-l.2-DHP 5 auSer dem Pyridin (Py) 18 zu den anellienen I&DHP-lactonen 19 und 24 Nhrt. Aus 24 wird durch Solvolyse 25 erhaIten. Ale DHP wer&n zu den konespondierenden Pyidinen dehydriert Durch anodische Oxidation werden die Halbstufenpotentiale Nr das System DHP/Py bestimmt, deren Awgigkeit von strukturellen Parametern wird diskutiert Bei der polampphischen Bestimmung des pyridinbislactons 16 entsteht in zweielektroniger Reaktion das IPDHP 13, was durch priipamive kathodische Reduktion bewiesen wird.Anellated Lactones from Bay-K-8644 and Dihydropyrldlne By-ProductsIn the Hantsch Synthesis Bay-K-8644 (1) reacts with pyridiniumbromide perbromide (PBPB) to yield the anellated 1.4-dihydro~dine @HP) laaone 7 and the pyridinium compound 8. whose irradiation with UV A-light leads to the 3-pyridinoles 10 and 11. The monolactone 12. the bislactone I3 and the dibromomethyl derivative 14 can be isolated h m the diester-l.4-DHP 2 with PBPB. The IJ-DHP 4, isomeric to 1. with PBPB only gives the oxidation product 17. while the diester-l.2-DHP 5 leads to the pyridine (Py) 18 as well as to the anellated 1.2-DHP-lactones 19 and 24.25 is obtained from 24 by solvolysis. All DHPs are dehydrogenated to the corresponding pyridines. The half-wave potentials of the DHP/Py system are determined by anodic oxidation and relationships to structural parameters are discussed. The 1.4-DHP I3 is formed in a two elecmnic reaction from the pyridine lactone 16 by polarographic assay. which is proven by preparative cathodic reduction Bei der Hantzsch-Synthese des Calcium-Agonisten Bay-K-8644 (1) entstehen als Nebenprodukte die symmetrischen 1 PDihydropyridine (DHP). der Diester 2 und die Dinitroverbindung 3, sowie die isomeren 12-DHP 4-62). COOMe NOz Schema 1Die Umsetzung der DHP-Ester 1.2,4 und 5 mit Pyridiniumbromidperbmmid (PBPB) hat sich als einfacher Zugang zu anellierten DHP-Lactonen bew&*').Aus 2 ist bereits sowohl das anellierte MonolactonU) als auch das Bislacton') dargestellt worden. Die Dehydrierungsprodukte der DHP-Lactone k6nnen als Neben-Metaboliten der DHP-Ester aufmten'). FUr die Nitro-DHF-Lactone sind Untersuchungen zur photochemischen Stabilitd) von Interesse.Bei der Reaktion von Bay-K-8644 (1) mit PBPB und Pyridin unter Young-Bedingungen3) werden zwei gelbe Produkte erhalten, von denen eines wasserlUslich ist und in alkalischer Usung eine tiefrote Farbe annimmt. Die im Vergleich zurn Fdukt schwerer 1Usliche gelbe Substanz enveist sich aufgrund der spektroskopischen Daten als das Nitro-1.4-DHP-Lacton 7.In einer kWich emhienenen Arbeit*) Uber die calciumagonistische Wirkung von Bay-K-8644 und vemandter Verbindungen wird da...