Synthetic, Structural and Spatial Studies of Rhenium Compounds

Abstract

<p>A new concept, Virtual Radii, is introduced to define the non-bonding interactions of ligating atoms in the coordination sphere of six coordinated transition metal compounds. The interactions of structural parameters in the coordination sphere and their chemical consequences are discussed within the bounds of a systematic study of Vinual Radii and Solid Angle Factors were extracted for six coordinated rhenium compounds with the use of the Cambridge Structural Database, recent publications, and structures determined in this study.</p> <p>Thirteen structures were determined to answer chemical questions as well as to provide additional data for the spatial studies. The questions were: i. What was the real structure of the compound formulated as K[Re₂O₂H(CO)₈] by Hieber and Schuster? ii. Is the cyanide ion bonded to the rhenium atom through the nitrogen atom in the compound "K₂[ReN(NC)₄]∙H₂O" as proposed in the literature? iii. Is it possible to synthesize some new neutral or monocationic rhenium or technetium species with ligands that contain pyrazole?</p> <p>Reactions of Re(CO)₅CI and KOH under various conditions produced several products. The structures of five of them, KRe₃(CO)₉(OMe)₄ (3A), Re₄(CO)₁₂(OH)₂(OEt)₂∙2EtOH (3B), Re₄(CO)₁₂(OH)₄∙8H₂O (3C), KRe₂(CO)₆(OH)₃∙2H₂O(3D), KRe₃(CO)₉(OH)₄ (3E), were determined by single-crystal X-ray diffraction methods. The structure of 3D clarified question (i).</p> <p>X-ray crystal structure determination of (AsPh₄)₂[ReN(CN)₄(H₂O)]∙5H₂O (4B) indirectly answered question (ii) and showed that the literature was wrong.</p> <p>As part of the basic research on the development of new radiopharmaceuticals, new compounds with pyrazole-containing ligands, ReO(HBPz₃)(NCS)₂ (5A), ReO(HBPz₃)(PzOCMe₂)∙ReO₄ (5B), ReOCl₂(PPh₃)(PzOCMe₂) (5C), ReOCl₂(PPh3)(PzOCHMe)∙0.5CHOCHO (5D), Re₂O₃Cl₂(PPh₃)₂(Pz)₂∙CHCl₃ (5E), Re₂O₃Cl₂(3,5-Me₂-Pz)₂(3,5-Me₂-HPz)₂ (5F) were prepared and characterized. The investigations were extended to new compounds [ReOCl₂(PPh₃)L]∙2H₂O (5G) and [TcOL₂(HL)]TcO₄ (5H), where HL was 4-hydroxymethyl-1,5-dimethyl-imidazole. The X-ray crystal structures of all compounds, except 5A, were determined.</p>