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

Reaction of 4,5‐diazafluoren‐9‐one (dafone, 6 ) and zinc dichloride yields [(dafone)ZnCl 2 (H 2 O)] ( 11 ) in which the ZnCl 2 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) 2 ZnI 2 ( 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 K 2 PtCl 4 to produce square‐planar (dafone)PtCl 2 (dmso) ( 13 ), whereas with K 2 PtBr 6 the octahedral complex (dafone)PtBr 4 ( 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 PtCl 2 complex, 15 . Reaction of 7 with Co 2 (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)