Supramolecular chemistry of half-sandwich organometallic building blocks based on RuCl2(p-cymene)Ph2PCH2Y

A new series of neutral organometallic building blocks based on piano-stool ruthenium(II) complexes, RuCl2(p-cymene)Ph2PCH2Y [Y = -NHC6H4(2-CO2H) (2a), -NHC6H4(3-CO2H) (2b), -NHC6H3(3-CO2H)(6-OCH3) (2c), -NHC6H4(4-CO2H) (2d), -NHC6H3(2-CO2H)(4-OH) (2e), -NHC6H3(3-OH)(4-CO2H) (2f), -NHC6H3(2-CO2H)(5-CO2H) (2g) and -OH (2h)], were synthesised in high yields (>88%) from {RuCl2(p-cymene)}2 and the appropriate phosphines 1a–1h. The new tertiary phosphine 1b was prepared by Mannich condensation of NH2C6H4(3-CO2H) with Ph2PCH2OH in MeOH. Solution NMR (31P{1H}, 1H), FT-IR and microanalytical data are in full agreement with the proposed structures. Single crystal X-ray studies confirm that, in each case, compounds 2a, 2b and 2d–2h have piano-stool arrangements with typical Ru–P, Ru–Cl and Ru–Ccentroid bond lengths. From our crystallographic studies, factors that influence the supramolecular assemblies of these ruthenium(II) complexes include: (i) the type of functional group present, (ii) the geometric disposition of the –N(H)CH2PPh2, –CO2H and –OH groups around the central benzene scaffold, and (iii) the solvents used in the recrystallisations. Hence in isomers 2a and 2b, molecules are associated into head-to-tail dimer pairs through classical intermolecular O–H⋯O hydrogen bonding. This feature is also observed in isomer 2d but dimer pairs are further associated to give a 1-D chain through assisted intermolecular N–H⋯Cl hydrogen bonding. The additional 4-hydroxo group in 2e promotes a ladder arrangement via intermolecular O–H⋯O and O–H⋯Cl hydrogen bonding. In contrast the isomeric compound 2f does not show head-to-tail O–H⋯O hydrogen bonding but instead O–H⋯Cl and N–H⋯O intermolecular hydrogen bonding is observed. Depending on the choice of solvent (MeOH or DMSO), 2g forms extended networks based on chains (2g · DMSO · 1.5MeOH) or tapes (2g · 3MeOH). In 2h, a single intramolecular O–H⋯Cl hydrogen bond is observed for each independent molecule. The X-ray structure of one representative tertiary phosphine, 1f, has also been determined.