A new triclinic modification of the pyrochlore-type KOs2O6 superconductor

A new modification of KOs2O6, the representative of a new structural type (Pearson symbol aP18, a=5.5668(1)A, b=6.4519(2)A, c=7.2356(2)A, space group P-1, no.2) was synthesized employing high pressure technique. Its structure was determined by single-crystal X-ray diffraction. The structure can be described as two OsO6 octahedral chains relating to each other through inversion and forming big voids with K atoms inside. Quantum chemical calculations were performed on the novel compound and structurally related cubic compound. High-pressure X-ray study showed that cubic KOs2O6 phase was stable up to 32.5(2) GPa at room temperature.Comment: 23 pages, 9 figures,6 tables. Accepted for J. Solid State Che

Manganese thiophene tricarbonyl complexes: Nucleophilic addition to sulfur and synthesis of thiophenium salts

New thiophene manganese derivatives, [(2-R1-C4H3S)Mn(CO)3]+ 1(sil) (R1 = Si(OCH2-CH2)3N) and 1(Mn) (R1 = (C6H6)Mn(CO)3), have been synthesized and their reaction with nucleophiles studied. Except for the Grignard reagent, nucleophiles (Nu- = H-, -CN, -P(O)(OR)2 (R = Me, Ph)) usually attack the C5 position. Grignard reagents attack the sulfur atom to yield manganese S-R-thiophene carbonyls 3. To compare the reactivities of 1(sil) and 1(Mn) with that of (thiophene)Mn(CO)3 + with respect to Grignard reagent addition, the known compounds [(thiophene)Mn(CO)3]+ (thiophene = thiophene, 2-methylthiophene, 2,5-dimethylthiophene) have been synthesized and their reaction with Grignard reagents studied. In all cases, S-R-thiophene manganese carbonyls 3 were obtained as a sole product. Refluxing 3 (R = Ph, p-tolyl, 2-thienyl) with Me3NO in benzene yielded diaryl sulfide. Treatment of 3 with NOBF4 in CH2Cl2 led to S-R-thiophenium-manganese dicarbonyl nitrosyl cations 4. Photolysis of 4 in acetone gave rise to S-R-thiophenium 5 in high yields. The molecular structures of [{2-exo-P(O)(OMe)2??4-C4H 3S}Mn(CO)3] (2(sil,P(O)(OMe)2)), [S-Ph-??4-2-{(??5-C6H 6)Mn(CO)3}SC4H3]Mn(CO)3 (3(Mn,Ph)), and [p-CH3C6H5-S-2-CH3C 4H3] (5(Me,p-tolyl)) have been determined by X-ray studies.close131