Substitution Of Compounds Research Articles

Alkylindium(I) vs Carbon Monoxide Bridges in Binuclear Iron Carbonyl Complexes: A Theoretical Study

Polynuclear iron carbonyl complexes have been prepared only recently, in which bridging carbonyl ligands were replaced by isolobal monoalkylindium groups. A theoretical analysis of the compounds (CO)3Fe(μ-CO)3-x(μ-InCH3)xFe(CO)3 (x = 0, 1, 2, 3) shows the specific influence of a stepwise substitution of CO by RIn(I) fragments on their electronic, structural, and bonding properties. This influence is determined by the order of the σ donor [RIn(I) ≫ CO(bridge)] and π acceptor [RIn(I) < CO(bridge) ≪ CO(terminal)] capabilities of these ligands.

A Convenient Synthesis of Thiazolo [ 3,2-a } - &amp; Triazolo [ 4,3-a ]- Pyrimidines &amp; Pyrimido [ 2,1-c ] Triazine Derivatives

Alkylation of 4-oxo-6-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine- 5-carbonitrile (1) gave the S-alkyl derivatives (2b,c). Compound (2c) could be cyclised into 3-methyl-5-oxo-5H-7- phenylthiazolo[ 3,2-a] pyrimidine-6-carboxamide (3). Further substitution of compounds (2a,b) yielded the N3-Substituted pyrimidine derivatives (7a-e). Desulphunisation of each of compounds (2a,b) with benzhydrazide resulted in the formation of 2-(2-benzoylhydrazino)- pyrimidine derivative (9) , which could be converted into the triazolo[4,3-a] pyrimidine (11). Each of compounds (2a,b) reacted with semicarbazide to produce directly the dioxotriazolopyrimidine derivative (14). Treatment of the 2-hydrazinopyrimidine derivative (10) with chloroacetyl chloride afforded the pyrimido[2,1-c]triazine derivative (16). Its isomeric compound (17) could be also prepared. The structures of the newly synthesized compounds were proved by chemical routes and spectral studies.

Phosphinsubstituierte chelatliganden: XXI. Reversibel substitution von tetracarbonyl(phosphinothioformamid)-komplexen, (CO) 4M( ) M  Cr, Mo, W), mit triorganophosphinen, -arsinen und -stibinen

To investigate the substitution of octahedral, neutral P,S-chelate complexes, the tetracarbonyl(phosphinothioformamide) compounds (CO) 4 MSC(NR 1R 2)P Ph 2 (M  Cr ( 1), Mo ( 2), W ( 3); R 1  Me, R 2  H ( A), R 1  Ph, R 2  H ( B) and R 1  R 2  Me ( C)) were treated with the ligands PPh 3 ( a), AsPh 3 ( b), SbPhP 3 ( b), ( c), PEt 3 ( d) and P(OMe) 3 ( e)_. Unlike the corresponding phosphinothioformimidate complexes with an anionic chelate ligand, no CO substitution occurs, but a nucleophilic cleavage of the metalsulfur bond under formation of the cis, trans-isomeric complexes with unindentage ligands. The position of the equilibrium depends on steric and kinetic factors. A further equilibrium of the cis-substituted complex and the previous chelate complex is established resulting from the reversible substitution process with increasing kinetic lability from tungsten to chromium. A dissociative mechanism of the chromium complexes starting from the trans form is also discussed. The tungsten complex 3aC shows ideal reversible conditions with complete re-chelation unaffected by isomerisation.