Cyclopentadienyl nitrosyl compounds of chromium: aqueous solution chemistry, pi bonding and nitric oxide loss

{The compiler [Cr(eta-C5H5)(NO)(2)(CF3SO3)] 1 was synthesised in order to explore the relationship between a-donor ligands and nitrosyl lability and to investigate the aqueous chemistry of the [Cr(eta-C5H5)(NO)(2)](+) fragment. Treatment of 1 with sigma-donor ligands gave [Cr(eta-C5H5)(NO)(2)(L)][CF3SO3] salts. Potentiometric titrations and H-1 NMR spectroscopic studies of 1 provided evidence for the existence of [Cr(eta-C5H5)(NO)(2)-(H2O)](+) and [Cr(eta-C5H5)(NO)(2)-(OH)] in aqueous solution. When generated in sitic, [Cr(eta-C5H5)(NO)(2)-(OH)] reacted with acetylacetone, pyridinecarboxylic acid, or salicylaldehyde to form paramagnetic, mononitrosyl complexes which were independently synthesised from the mononitrosyl precursor [Cr(eta-C5H5)(NO)-(mu-I)](2). The solid-state molecular structures of [Cr(eta-C5Me5)(NO)(2)(CF3SO3)] 2, [Cr(eta-C5H5)(NO)(2)(N2C5H7)] 9 and [Cr(eta-C5H4)(NO)(O2C5H7)] 10 were determined by X-ray crystallography. Crystals of 2 are monoclinic