Selective Ligand Modification on the Periphery of Diruthenium Compounds: Toward New Metal-Alkynyl Scaffolds

Diruthenium compounds Ru2(DmAniF)3(OAc)Cl (1, DmAniF is N,N‘-di(m-methoxyphenyl)formamidinate) and cis-Ru2(DmAniF)2(OAc)2Cl (6) reacted with N,N‘-dimethyl-4-iodobenzamidine (HDMBA-I) to furnish new compounds Ru2(DmAniF)3(DMBA-I)Cl (2) and cis-Ru2(DmAniF)2(DMBA-I)2Cl (7), respectively. Both compounds 2 and 7 were modified with a terminal alkyne under Sonogashira conditions. Examples reported include 2 cross-coupled with HC⋮CSiiPr3 or HC⋮CFc to yield Ru2(DmAniF)3(DMBA-4-C2SiiPr3)Cl (3a) or Ru2(DmAniF)3(DMBA-4-C2Fc)Cl (3b), respectively, and 7 cross-coupled with HC⋮CFc to yield cis-Ru2(DmAniF)2(DMBA-4-C2Fc)2Cl (8). The peripherally modified compounds (2, 3a/3b, 7, and 8) were further alkynylated at the axial positions of the Ru2 core to yield a series of bis-alkynyl adducts: Ru2(DmAniF)3(DMBA-4-C2SiiPr3)(C4SiMe3)2 (4a), Ru2(DmAniF)3(DMBA-4-C2Fc)(C4SiMe3)2 (4b), Ru2(DmAniF)3(DMBA-I)(C4SiMe3)2 (5), cis-Ru2(DmAniF)2(DMBA-4-C2Fc)2(C2Ph)2 (9), and cis-Ru2(DmAniF)2(DMBA-I)2(C2Ph)2 (10). All compounds reported were characterized with voltammetric, vis−NIR, and NMR (whenever applicable) techniques. Molecular structures of compounds 1, 4a, 5, 6, 9, and 10 were established through X-ray diffraction studies.