Box-like Heterometallic Macrocycles Derived from Bis-Terpyridine Metalloligands

A series
of [4+2] hexanuclear heterometallic macrocycles, {[Cp*2Ir2(μ-DHNA)]2­[Zn­(pyterpy)2]2(OTf)2}·(OTf)6 (1a), {[Cp*2Ir2(μ-DHNA)]2­[Zn­(pyterpy)2]2}·(SbF6)8 (1a′), {[Cp*2Rh2(μ-DHNA)]2­[Zn­(pyterpy)2]2}·(OTf)8 (1b), {[Cp*2Ir2(μ-DHNA)]2­[Ni­(pyterpy)2]2(OTf)2}·(OTf)6 (2a), {[Cp*2Rh2(μ-DHNA)]2­[Ni­(pyterpy)2]2}·(OTf)8 (2b), {[Cp*2Ir2(μ-DHNA)]2­[Cu­(pyterpy)2]2}·(PF6)4(OTf)4 (3a), and {[Cp*2Rh2(μ-DHNA)]2­[Cu­(pyterpy)2]2}·(PF6)4(OTf)4 (3b), have been
constructed by the self-assembly of half-sandwich organometallic units
[(Cp*2M2(μ-DHNA)­Cl2] (M = Ir
and Rh; Cp* = η5-pentamethylcyclopentadienyl; DHNA
= 6,11-dihydroxy-5,12-naphthacenedione) and the metalloligands [M­(pyterpy)2]2+ (M = Zn, Ni, and Cu; pyterpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine).
Confirmed by single-crystal X-ray analysis, complexes 1a–3b display hexanuclear heterometallic macrocycles
with two box-like cavities. Interestingly, on the basis of the different
combinations of metals, complexes 1a and 2a have the ability to encapsulate two OTf – guest
anions in the molecular cavities, but differ from that of the other
complexes in which all counteranions exist outside the molecular backbones.
In addition, the reaction of [Cp*MCl2]2 (M =
Ir and Rh) and [Ni­(pyterpy)2]­(NO3)2 leads to the formation of [2+1] trinuclear heterometallic linear
molecules {Cp*2Ir2[Ni­(pyterpy)2]­Cl4}­(NO3)2 (4a) and {Cp*2Rh2[Ni­(pyterpy)2]­Cl4}­(NO3)2 (4b), which could be used as a
kind of precursor.