Selective ligand modification on the periphery of diruthenium compounds: Toward new metal-alkynyl scaffolds

Diruthenium compounds Ru-2(DmAniF)(3)(OAc)Cl (1, DmAniF is N,N'-di(m-methoxyphenyl)-formamidinate) and cis-Ru-2(DmAniF)(2)(OAc)(2)Cl (6) reacted with N,N'-dimethyl-4-iodobenzamidine (HDMBA-I) to furnish new compounds Ru-2(DmAniF)(3)(DMBA-I)Cl (2) and cis-Ru-2(DmAniF)(2)(DMBA-I)(2)Cl (7), respectively. Both compounds 2 and 7 were modified with a terminal alkyne under Sonogashira conditions. Examples reported include 2 cross-coupled with HC (CSiPr3)-Pr-i or HC CFc to yield Ru-2(DmAniF)(3)(DMBA-4-(C2SiPr3)-Pr-i)Cl (3a) or Ru-2(DmAniF)(3)(DMBA-4-C(2)Fc)Cl (3b), respectively, and 7 cross-coupled with HC CFc to yield cis-Ru-2(DMAniF)(2)(DMBA-4-C(2)Fc)(2)Cl (8). The peripherally modified compounds (2, 3a/3b, 7, and 8) were further alkynylated at the axial positions of the Ru-2 core to yield a series of bis-alkynyl adducts: Ru-2(DMAniF)(3)(DMBA-4-(C2SiPr3)-Pr-i)(C4SiMe3)(2) (4a), Ru-2(DmAniF)(3)(DMBA-4-C2Fc)(C4SiMe3)(2) (4b), Ru-2(DmAniF)(3)(DMBA-I)(2)(C4SiMe3)(2) (5), cis-Ru-2(DmAniF)(2)(DMBA-4-C2FC)(2)(C2Ph)(2) (9), and cis-Ru-2(DniAniF)(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.