Multifunctionality of Organometallic Quinonoid Metal Complexes: Surface Chemistry, Coordination Polymers, and Catalysts

Abstract

Quinonoid metal complexes have potential applications in surface chemistry, coordination polymers, and catalysts. Although quinonoid manganese tricarbonyl complexes have been used as secondary building units (SBUs) in the formation of novel metal-organometallic coordination networks and polymers, the potentially wider applications of these versatile linkers have not yet been recognized. In this Account, we focus on these diverse new applications of quinonoid metal complexes, and report on the variety of quinonoid metal complexes that we have synthesized. Through the use of [(η(6)-hydroquinone)Mn(CO)3](+), we are able to modify the surface of Fe3O4 and FePt nanoparticles (NPs). This process occurs either by the replacement of oleylamine with neutral [(η(5)-semiquinone)Mn(CO)3] at the NP surface, or by the binding of anionic [(η(4)-quinone)Mn(CO)3](-) upon further deprotonation of [(η(5)-semiquinone)Mn(CO)3] at the NP surface. We have demonstrated chemistry at the intersection of surface-modified NPs and coordination polymers through the growth of organometallic coordination polymers onto the surface modified Fe3O4 NPs. The resulting magnetic NP/organometallic coordination polymer hybrid material exhibited both the unique superparamagnetic behavior associated with Fe3O4 NPs and the paramagnetism attributable to the metal nodes, depending upon the magnetic range examined. By the use of functionalized [(η(5)-semiquinone)Mn(CO)3] complexes, we attained the formation of an organometallic monolayer on the surface of highly ordered pyrolitic graphite (HOPG). The resulting organometallic monolayer was not simply a random array of manganese atoms on the surface, but rather consisted of an alternating "up and down" spatial arrangement of Mn atoms extending from the HOPG surface due to hydrogen bonding of the quinonoid complexes. We also showed that the topology of metal atoms on the surface could be controlled through the use of quinonoid metal complexes. A quinonoid rhodium complex showed catalytic activity in Suzuki-Miyaura type reaction. As a result of the excellent stability of the homogeneous catalyst [(quinone)Rh(COD)](-) in water, we also successfully demonstrated catalyst recycling in 1,2- and 1,4-addition reactions. The compound [(quinone)Ir(COD)](-) showed significantly poorer catalytic activity in 1,4-addition reactions. Following upon the excellent coordination ability of the quinonoid rhodium complexes to metal centers, we synthesized organometallic coordination polymer nanocatalysts and silica gel-supported quinonoid rhodium catalysts, the latter using a surface sol-gel technique. The resulting heterogeneous catalysts showed activity in the stereospecific polymerization of phenylacetylene.

ZnO Nanoparticles Embedded on a Reduced Graphene Oxide Nanosheet (ZnO−NPs@r‐GO) as a Proficient Heterogeneous Catalyst for a One‐Pot A3‐Coupling Reaction

“…All of the aforesaid systems have been proposed to demonstrate more or less highly active and -selective products due to the presence of easily accessible active sites. [17][18][19][20][21][22][23][24][25][26][27][28][29][30] However, these systems are often regarded as imprecise with many impediments, including agglomeration of active sites; the contamination of toxic metal is also found along with the product which is comparatively detrimental one when dealing with the synthesis of biological products. In this regard, the non-recoverable catalyst from the product is the key challenging task in the research field.…”

Theoretical Investigations of Electronic Structure and Magnetic and Optical Properties of Transition-Metal Dinuclear Molecules

“…In addition, metal–organic quinonoid molecules are potential building blocks in coordination polymers as well as many other materials which are useful for catalysis, surface chemistry, and molecular spintronics. 7 , 8 In transition-metal-quinonoid (TM-quinonoid), the valence electrons are primarily from the partially filled d-orbitals of the TM. Therefore, they can be stabilize in various spin-state configurations depending on the local environment of the TM present in the molecule.…”

The Ferraquinone–Ferrahydroquinone Couple: Combining Quinonic and Metal-Based Reactivity

“…Other reports from our group described phenoxonium cations as well as quinone methides stabilized by transition metals. − A number of organometallic species are known that contain o - and p -quinonic moieties − in their ligand framework, but in no other case is the metal center an integral part of the quinonic system. − On the basis of our earlier findings, we intended to prepare a corresponding complex of earth-abundant iron, ferraquinone 1 , with its hydrogenated counterpart, the ferrahydroquinone 2 , and to investigate the general reactivity of the resulting redox couple toward the activation of small molecules (Scheme ).…”