Synthesis, spectroscopy, structure, and reactivity of bis-azapentadienyl–ruthenium–phosphine complexes [1]

• The first examples of bis-(η3-azapentadienyl)RuL2 complexes have been synthesized and characterized.
• The complexes adopt a variety of structural motifs, which differ in the orientation of the azapentadienyl ligands.
• Dynamic interconversions between these structural types are observed.
• The azapentadienyl nitrogens are the preferred sites of electrophilic attack.

We report the synthesis, spectroscopy, structure, and reactivity of the first examples of bis-azapentadienyl–ruthenium complexes. The parent compound, [(1,2,3-η3)-(5-tert-butylazapentadienyl)]2Ru(PPh3)2 (1), is produced by reacting Cl2Ru(PPh3)3 with two equivalents of potassium tert-butylazapentadienide. Treatment of 1 with CNCMe3, P(OMe)3, PMe3, or PEt3 (L) in THF at room temperature yields single-ligand substitution products [(1,2,3-η3)-(5-tert-butylazapentadienyl)]2Ru(PPh3)(L) (2, L = CNCMe3; 3, L = P(OMe)3; 4, L = PMe3; 5, L = PEt3), and the double-ligand substitution product, [(1,2,3-η3)-(5-tert-butylazapentadienyl)]2Ru(PEt3)2 (6). Other double-ligand substitution products, [(1,2,3-η3)-(5-tert-butylazapentadienyl)]2Ru(L)2 (7, L = PMe3; 8, L = P(OMe)3), are obtained when 1 is treated with PMe3 or P(OMe)3 in THF at reflux. Compounds 7 and 8 exist in solution as equilibrium mixtures of two structural isomers. Electron-rich compounds 6 and 7 react with triflic acid to generate dicationic products,{[(1,2,3-η3)-(CH2CHCHCHN(H)(CMe3)]2Ru(L)2}2+(−O3SCF3)2 (9, L = PEt3; 10, L = PMe3), in which both azapentadienyl nitrogen atoms have been protonated. All of the compounds reported herein have been characterized by NMR spectroscopy, and the structures of 2, 3, 4, 6, and 9 have been confirmed by single-crystal X-ray diffraction.

The first examples of bis-(η3-azapentadienyl)RuL2 complexes have been synthesized, and a variety of structural motifs have been observed by NMR and X-ray diffraction. Treatment of electron-rich members of this family with triflic acid leads to protonation at both azapentadienyl nitrogen centres.Figure optionsDownload as PowerPoint slide