Coordination Chemistry of 4-Methyl-2,6,7-trioxa-1-phosphabicyclo[2,2,1]heptane: Preparation and Characterization of Ru(II) Complexes

The complexes TpRu­[P­(OCH2)2(OCCH3]­(PPh3)Cl (2) [Tp = hydridotris­(pyrazolyl)­borate; P­(OCH2)2(OCCH3) (1) = (4-methyl-2,6,7-trioxa-1-phosphabicyclo­[2,2,1]­heptane] and TpRu­(L)­(PPh3)Cl [L = P­(OCH2)3CEt (3), PMe3 (4) or P­(OMe)3 (5)], (η6-C6H6)­Ru­(L)­Cl2 [L = PPh3 (6), P­(OMe)3 (7), PMe3 (8), P­(OCH2)3CEt (9), CO (10) or P­(OCH2)2(OCCH3) (11)] and (η6-p-cymene)­Ru­(L)­Cl2 [L = P­(OCH2)3CEt (12), P­(OCH2)2(OCCH3)­P­(OCH2)2(OCCH3) (13), P­(OMe)3 (14) or PPh3 (15)] have been synthesized, isolated, and characterized by NMR spectroscopy, cyclic voltammetry, mass spectrometry, and, for some complexes, single crystal X-ray diffraction. Data from cyclic voltammetry and solid-state structures have been used to compare the properties of (1) with other phosphorus-based ligands as well as carbon monoxide. Data from the solid-state structures of Ru­(II) complexes show that P­(OCH2)2(OCCH3) has a cone angle of 104°. Cyclic voltammetry data reveal that the Ru­(II) complexes bearing P­(OCH2)2(OCCH3) have more positive Ru­(III/II) redox potentials than analogous complexes with the other phosphorus ligands; however, the Ru­(III/II) potential for (η6-C6H6)­Ru­[P­(OCH2)2(OCCH3)]­Cl2 is more negative compared to the Ru­(III/II) potential for the CO complex (η6-C6H6)­Ru­(CO)­Cl2. For the Ru­(II) complexes studied herein, these data are consistent with the overall donor ability of 1 being less than other common phosphines (e.g., PMe3 or PPh3) or phosphites [e.g., P­(OCH2)3CEt or P­(OMe)3] but greater than carbon monoxide.