Synthesis, characterisation and crystal structures of new water-soluble 1-alkanaminedicarbonyl(η5-cyclopentadienyl)ruthenium(II) tetrafluoroborate complex salts

New water-soluble 1-alkanaminedicarbonyl(η5-cyclopentadienyl)ruthenium(II) tetrafluoroborate complex salts, [CpRu(CO)2NH2R]+BF4− (Cp = η5-C5H5) (R = CH3 1, C2H5 2, C3H7 3, C4H9 4, C5H11 5 and C6H13 6), were synthesised by the reaction of the organometallic Lewis acid, [CpRu(CO)2]+BF4, with slight excesses of 1-alkanamines, RNH2, in dry methylene chloride at room temperature and pressure. These compounds are reported for the first time and have been fully characterised by IR, electrospray ionisation mass spectroscopy, 1H and 13C NMR spectroscopy, and elemental analysis. Spectral data show that the n-alkanamines are σ-bonded to the metal centre via the nitrogen atom. Complexes 2–5 were characterised by single crystal X-ray diffraction and all four cationic species feature a “pseudo-octahedral three-legged piano stool” structure in which the ruthenium centre is coordinated through a sigma bond to the amine N atom and two carbonyl ligands at the base of the stool and the cyclopentadienyl ring in the apex of the stool. IR studies showed that peaks of the νCO stretching vibrations shifted slightly to lower frequency as the carbon chain length increased. The melting point and percentage yields were observed to generally decrease with increase in n-value.