2,2′-Bipyrimidine transition metal complexes: Synthesis, reaction chemistry and solid state structures

2,2′-Bipyrimidine metal complexes with Ti, Mo, Fe, Ru, Pt, Ag, and Cu transition metal atoms have been synthesized and structurally characterized. These molecules were prepared by following synthesis methodologies. The reaction of 2,2′-bipyrimidine (1; bipym) with {[Ti](μ-σ,π-CCSiMe3)2}AgOTf ([Ti] = (η5-C5H4SiMe3)2Ti, OTf = OSO2CF3) (2) in a 1:1 molar ratio gave [{[Ti](μ-σ,π-CCSiMe3)2}Ag(bipym)]OTf (3) which on further treatment with another equivalent of 2 produced [({[Ti](μ-σ,π-CCSiMe3)2}Ag)2(μ-1,2,3,4-bipym)](OTf)2 (4). As consequence thereof, the coordination number of Ag(I) was changed from 3 to 4. A platinum–bipym complex with two acetylide substituents was accessible by the gradual reaction of 1 with K2[PtCl4] (5) and two equivalents of HCCR (7a, R = SiMe3; 7b, R = Fc; 7c, R = Rc; Fc = (η5-C5H4)(η5-C5H5)Fe; Rc = (η5-C5H4)(η5-C5H5)Ru) in di-iso-propylamine and in presence of [CuI]. Originating from cis-[(bipym)Pt(CCR)2] (8a, R = SiMe3; 8b, R = Fc; 8c, R = Rc) diverse multinuclear complexes with two, three or four different transition metals could be obtained. These are: [((CO)4Mo)(μ-1,2,3,4-bipym)Pt(CCFc)2] (10), [(AgClO4)(μ-1,2,3,4-bipym){[Pt(μ-σ,π-CCFc)2]AgOClO3}] (12), [(McCC)2Pt(μ-1,2,3,4-bipym)({[Ti](μ-σ,π-CCSiMe3)2}M)]X (15a, Mc = Fc, M = Cu, X = PF6; 15b, Mc = Rc, M = Cu, X = PF6; 15c, Mc = Fc, M = Ag, X = ClO4), and [(McCC)2Pt(μ-1,2,3,4-bipym)PtCl2] (17). Like other organometallic Pt–Ag tweezer complexes, compound 12 decomposed to give FcCC–CCFc (13). During prolonged stirring of 15a and 15b, respectively, [(McCC)2Pt(μ-1,2,3,4-bipym)({[Ti](μ-σ,π-CCSiMe3)(μ-σ,π-CCH)}M)]X (15′a, M = Cu, X = PF6; 15′b, M = Cu, X = PF6) was formed.The structures of 8b, 8c, 15a′, and 15b′ in the solid state are reported. All complexes exhibit the anticipated planar dinuclear Pt–M structure (M = Pt, Cu, Ag) with the 2,2′-bipyrimidine unit in a μ-1,2,3,4-bridging mode.Electrochemical investigations were carried out with 8a, 8b, and 8c and show that no significant influence of R on the bipym redox potentials exists. The typical redox behavior for the bipym, ferrocene, ruthenocene units and platinum were observed.

The synthesis, characterization and electrochemical behavior of diverse transition metal complexes with the 2,2′-bipyrimidine connecting unit is discussed.Figure optionsDownload as PowerPoint slide