Mixed-Ligand Approach to Design of Heterometallic Single-Source Precursors with Discrete Molecular Structure

Abstract

Heterometallic single-source precursors for the Pb/Fe = 1:1 oxide materials, PbFe(β-dik)4 (β-dik = hexafluoroacetylacetonate (hfac, 1), acetylacetonate (acac, 2), and trifluoroacetylacetonate (tfac, 4)), have been isolated by three different solid-state synthetic methods. The crystal structures of heterometallic diketonates 1, 2, and 4 were found to contain polymeric chains built on alternating [Fe(β-dik)2] and [Pb(β-dik)2] units that are held together by bridging M-O interactions. Heterometallic precursors are highly volatile, but soluble only in coordinating solvents, in which they dissociate into solvated homometallic fragments. In order to design the heterometallic precursor with a proper metal/metal ratio and with a discrete molecular structure, we used a combination of two different diketonate ligands. Heteroleptic complex Pb2Fe2(hfac)6(acac)2 (5) has been obtained by optimized stoichiometric reaction of an addition of homo-Fe(acac)2 to heterometallic Pb2Fe(hfac)6 (3) diketonate that can be run in solution on a high scale. The combination of two ligands with electron-withdrawing and electron-donating groups allows changing the connectivity pattern within the heterometallic assembly and yields the precursor with a discrete tetranuclear structure. In accord with its molecular structure, heteroleptic complex 5 is soluble even in noncoordinating solvents and was found to retain its heterometallic structure in solution. Thermal decomposition of heterometallic precursors in air at 750 °C resulted in the target Pb2Fe2O5 oxide, a prospective multiferroic material. Prolonging the annealing time or increasing the decomposition temperature leads to another phase-pure lead-iron oxide PbFe12O19 that is a representative of the important family of magnetic hexaferrites.

Metal–Organic Derivatives with Fluorinated Ligands as Precursors for Inorganic Nanomaterials

“…153 Utilizing the reaction between two metal carboxylates or β-diketonates, mostly unsolvated and with at least one of them being coordinatively unsaturated, Dikarev et al reported the synthesis of unligated heterometallic derivatives of the main group and the transition metals. 154 67,69,159 They have also utilized solid-state redox reaction between M(hfac) 3 (M = Bi, Mn) and either transition metals, M′, or their complex, M′(hfac) 2 , to give homoleptic heterometallics of different stoichiometries 160,161 (Scheme 10).…”

“…In the presence of weakly coordinating 160 The trinuclear structure of Pb 2 Fe(hfac) 6 resembles the above structure, except that the former exhibits strong interactions between the trimetallic fragments to afford infinite zigzag polymeric chains. 67 The mixed-ligand complex [Pb 2 Fe 2 (hfac) 6 (acac) 2 ] is a discrete cyclic tetramer consisting of two [Fe(hfac) 2 ] and two [Pb(acac)(hfac)] fragments ( Figure 34). Each Fe atom features two additional bridging interactions to the oxygens of the acac ligands on both lead atoms, thus achieving an octahedral coordination.…”

“…Each Pb atom also has two additional contacts with oxygens of the neighboring [Fe(hfac) 2 ] units. 67 The structure of [LnF(hfac) 3 K(diglyme)] 2 (Ln = Nd, Eu, Sm) is comprised of two Ln 2 K triangles, which share the common Ln···Ln edge (Figure 35). 383 The three metals in each triangle are connected by (i) one triply bridging fluoride ligand, (ii) oxygen atoms from the two bridging hfac ligands on one edge, and (iii) an oxygen from the another bridging hfac ligand on the other edge.…”

“…Heterometallic Derivatives. In comparison to the homometallic β-diketonates, for which a plethora of structures have been reported, only a few heterometallic derivatives containing fluorinated β-diketonate moieties are known,67−69,159−161,390−395 the chelating character of the ligand being the main reason behind this. The infinite chain structures of [CsM(hfac) 4 ] (M = Y, 390 Dy, Er, 391 Eu, Am 392 ), [KM(hfac) 4 ] (M = Dy, Er 391 ), [NaM(hfac) 3 ] (M = Mn, Fe, Co, Ni), 67−69 and [M′Mn(hfac) 3 ] (M′ = K, 393 In 161 ) consist of an alternating arrangement of M(hfac) 4 − /M(hfac) 3…”

Synthesis and characterization of {[CuI3Sn2(OBut)6]+[CuII(hfac)3]−} – A heterometallic cluster with unique triangular copper(I) core

“…Our recent work is centered at application of a mixed-ligand combination approach that allows one to effectively change bridging connectivity pattern http://dx.doi.org/10.1016/j.ica.2014.08.045 0020-1693/Ó 2014 Elsevier B.V. All rights reserved. within the heterometallic assembly thus opening broad opportunities to design new volatile heterometallic precursors [16]. Combining metal b-diketonates and alkoxides for the preparation of heterometallic complexes is quite an attractive direction that has been studied extensively [17].…”