Orthogonal Coordination Chemistry of PTA toward Ru(II) and Zn(II) (PTA = 1,3,5-Triaza-7-phosphaadamantane) for the Construction of 1D and 2D Metal-Mediated Porphyrin Networks.

This work demonstrates that PTA (1,3,5-triaza-7-phosphaadamantane) behaves as an orthogonal ligand between Ru(II) and Zn(II), since it selectively binds through the P atom to ruthenium and through one or more of the N atoms to zinc. This property of PTA was exploited for preparing the two monomeric porphyrin adducts with axially bound PTA, [Ru(TPP)(PTA-κ)] (, TPP = -tetraphenylporphyrin) and [Zn(TPP)(PTA-κ)] (). Next, we prepared a number of heterobimetallic Ru/Zn porphyrin polymeric networks-and two discrete molecular systems-mediated by -bridging PTA in which either both metals reside inside a porphyrin core, or one metal belongs to a porphyrin, either Ru(TPP) or Zn(TPP), and the other to a complex or salt of the complementary metal (i.e., -[RuCl(CO)(PTA-κ)] (), -[RuCl(PTA-κ)] (), Zn(CHCOO), and ZnCl). The molecular compounds , , -[{RuCl(PTA-κ)}{Zn(TPP)}] (), and [{Ru(TPP)(PTA-κ)(PTA-κ)}{ZnCl(OH)}] (), as well as the polymeric species [{Ru(TPP)(PTA-κ)}{Zn(TPP)}] (), -[{RuCl(CO)(PTA-κ)}{Zn(TPP)}] (), -[{RuCl(PTA-κ)}{Zn(TPP)}] (), and [{Ru(TPP)(PTA-κ)}{Zn(CHCOO)(CHOH)(OH)}] (), were structurally characterized by single crystal X-ray diffraction. Compounds , , , and are the first examples of solid-state porphyrin networks mediated by PTA. In , , , , and the bridging PTA has the κ binding mode, whereas in the 2D polymeric layers of it has the triple-bridging mode κ,2. The large number of compounds with the six-coordinate Zn(TPP) (the three polymeric networks of , and , out of five compounds) strongly suggests that the stereoelectronic features of PTA are particularly well-suited for this relatively rare type of coordination. Interestingly, the similar 1D polymeric chains and have different shapes (zigzag in vs "Greek frame" in ) because the {-Ru(PTA-κ)} fragment bridges two Zn(TPP) units with geometry in and with geometry in . Orthogonal "Greek frame" 1D chains make the polymeric network of . Having firmly established the binding preferences of PTA toward Ru(II) and Zn(II), we are confident that in the future a variety of Ru/Zn solid-state networks can be produced by changing the nature of the partners. In particular, there are several inert Ru(II) compounds that feature two or more P-bonded PTA ligands that might be exploited as connectors of well-defined geometry for the rational design of solid-state networks with Zn-porphyrins (or other Zn compounds).