A Synthetic and X-ray Crystallographic Study of Zinc and Platinum Complexes of 4,5-Diazafluoren-9-one (Dafone) and Dicobalt Hexacarbonyl Derivatives of 9-Phenylethynyl-4,5-Diazafluoren-9-ol: Chelation versus Monocoordination

• Published in: European Journal of Inorganic Chemistry 2009-08, Vol.2009 (22), p.3250-3258
• Main Authors: Maguire, Linda, Seward, Corey M., Baljak, Sladjana, Reumann, Thea, Ortin, Yannick, Banide, Emilie, Nikitin, Kirill, Müller-Bunz, Helge, McGlinchey, Michael J.
• Format: Article
• Language: English
• Subjects: Asymmetric bonds; Cobalt; Coordination modes; Hydrogen bonds; Metal-nitrogen linkages; Platinum; Zinc
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200900161

Reaction of 4,5‐diazafluoren‐9‐one (dafone, 6) and zinc dichloride yields [(dafone)ZnCl2(H2O)] (11) in which the ZnCl2 moiety is coordinated to a single nitrogen atom and also to a molecule of water. Hydrogen bonding, not only to the uncomplexed nitrogen atom of dafone but also to the ketonic oxygen atom of a neighbouring molecule, leads to a zigzag chain structure. In contrast, reaction with anhydrous zinc iodide forms cis‐(dafone)2ZnI2 (12) in which the metal–nitrogen distances – 2.170(5) and 2.456(5) Å – are significantly different. Dafone, in the presence of dimethyl sulfoxide, reacts with K2PtCl4 to produce square‐planar (dafone)PtCl2(dmso) (13), whereas with K2PtBr6 the octahedral complex (dafone)PtBr4 (14) is formed in which the ligand chelates in a symmetrical fashion. Treatment of dafone with phenylethynyllithium furnishes 9‐phenylethynyl‐4,5‐diazafluoren‐9‐ol (7), which forms a square‐planar nitrogen‐bonded PtCl2 complex, 15. Reaction of 7 with Co2(CO)8 yields the (μ‐alkyne)hexacarbonyldicobalt cluster 17, which undergoes protonation at the nitrogen atom to form 20 rather than at the alcohol to form a cobalt‐complexed propargyl cation. Alkynol 7 also reacts with HBr by addition across the triple bond to form Z‐9‐[(2‐bromo‐2‐phenyl)ethenyl]‐4,5‐diazafluoren‐9‐ol (10). X‐ray crystal structures are reported for 6, 7, 10–15, 17 and 20, and their differing hydrogen‐bonding motifs are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) Complexes of 4,5‐diazafluoren‐9‐one and 9‐phenylethynyl‐4,5‐diazafluoren‐9‐ol with zinc and platinum halides have been characterised. Protonation of (9‐phenylethynyl‐4,5‐diazafluoren‐9‐ol)Co2(CO)6 (17)with HBF4 does not yield a cobalt‐stabilised carbocation 21, but instead protonation occurs at the nitrogen atom to form 20, which gives rise to an intricate hydrogen‐bonding pattern.