Coordination of Piano‐Stool Complexes to a Hydrogen‐Bonded Rosette‐Type Assembly

Abstract

A new melamine (ME)–barbituric acid (BA) rosette‐type system has been prepared and characterized. The introduction of a pyridyl group on the barbituric acid moiety allows coordination of metal ions at the periphery of the ME3·BA3 rosette. Reactions of 1.5 equiv. of [Ru(cym)Cl2]2 (cym = p‐cymene) or [M(Cp*)Cl2]2 (Cp* = pentamethylcyclopentadienyl; M = Rh, Ir) with the rosette afford the corresponding ME3·[BA{Ru(cym)Cl2}]3 and ME3·[BA{M(Cp*)Cl2}]3 assemblies. The neutral metal‐containing rosettes ME3·[BA{Ru(cym)Cl2}]3 and ME3·[BA{Rh(Cp*)Cl2}]3 can also be obtained by adding the mononuclear complexes [BA{Ru(cym)Cl2}] and [BA{Rh(Cp*)Cl2}] to N,N′‐bis(4‐tert‐butylphenyl)melamine in chloroform. In addition, the triphenylphosphine derivatives [Ru(cym)(PPh3)Cl2] or [M(Cp*)(PPh3)Cl2] react with ME3·BA3 in the presence of silver triflate to generate the ionic rosette‐type assemblies ME3·[BA{Ru(cym)(PPh3)Cl}+]3·3CF3SO3– and ME3·[BA{M(Cp*)(PPh3)Cl}+]3·3CF3SO3–, respectively.

Using a Hydrogen‐Bonded Rosette‐Type Scaffold to Generate Heteronuclear Metalla‐Assemblies

“…5‐Butyl‐5‐(pyridin‐4‐ylmethyl)pyrimidine‐2,4,6‐trione (BApy) and N‐ (4‐ tert ‐butylphenyl) ‐N′ ‐(pyridin‐4‐ylmethyl)melamine (MEpy) have been prepared according to published methods. The pyridyl‐containing derivatives react with the dinuclear complexes [Ru(cym)Cl 2 ] 2 (cym = p ‐cymene) and [Rh(Cp*)Cl 2 ] 2 (Cp* = pentamethylcyclopentadienyl) to give the corresponding mononuclear piano‐stool complexes (MEpyRu), (MEpyRh), (BApyRu), and (BApyRh) (see Figure ).…”

“…As previously shown, trinuclear systems can be prepared by mixing a metal‐containing unit with the corresponding metal‐free component (Scheme ), thus giving rise to four trinuclear rosettes; (MEpy) 3 · (BApyRu) 3 , (MEpyRu) 3 · (BApy) 3 , (MEpy) 3 · (BApyRh) 3 , and (MEpyRh) 3 · (BApy) 3 . As in the (ME) 3 · (BApyRu) 3 rosette, the diffusion coefficient of these trinuclear systems is about 4 × 10 –10 m 2 s –1 , which corresponds to a hydrodynamic radius (R H ) of more than 10 Å.…”

“…Materials and Methods: All solvents were dried before use following standard procedures and all reactions were manipulated under an inert atmosphere. 5‐Butyl‐5‐(pyridin‐4‐ylmethyl)pyrimidine‐2,4,6‐trione (BApy), N‐ (4‐ tert ‐butylphenyl) ‐N′ ‐(pyridin‐4‐ylmethyl)melamine (MEpy), [Ru(cym)Cl 2 ] 2 , [Rh(Cp*)Cl 2 ] 2 , BApyRu, and BApyRh were prepared according to published methods. All other reagents were commercially available and used as received.…”

“…Last year, we used a pyridyl‐containing barbituric acid derivative, 5‐butyl‐5‐(pyridin‐4‐ylmethyl)pyrimidine‐2,4,6‐trione (BApy), in combination with N , N′ ‐bis(4‐ tert ‐butylphenyl)melamine (ME), to generate a (ME) 3 · (BApy) 3 rosette structure with three coordination sites at the periphery of the hexameric rosette . Arene ruthenium and cyclopentadienyl rhodium and iridium piano‐stool complexes were coordinated to the rosette, giving rise to neutral and cationic trinuclear systems (Figure ).…”

“…Molecular structures of neutral (left) and ionic (right) hexameric rosettes incorporating three piano‐stool complexes …”