More than half a century of intense investigation in coordination compounds has laid a firm foundation for our understanding of the ligand fields in transition-metal complexes. Complexes of the heavier 4d and 5d metals are generally low spin, whereas the spin of 3d metal complexes can be high or low, depending on ligand characteristics. The number and type of donor atoms, ligand substituents, and the presence or absence of chelate rings all influence metal spin states. A combination of data-mining and detailed computational study have quantified recently these empirical observations. In spite of such variety, there are still some types of metal complexes that are rarely observed. The stereospinomers of high-spin, square-planar complexes, for example, are extremely rare because the large separation of the dx2 y2 orbital from the rest of the d-manifold favors low-spin electron configurations for d with n> 4, and four-coordinate compounds are rare for d systems which could have all four low-lying d orbitals half filled. Known d examples include multiple Cr species, a Mn species, and one Nb complex. The rarity of this geometry and spin-state combination is demonstrated by only a handful of examples with late 3d metals. An interesting {NiO2N2} d 8 system is known whose high-spin examples are subtly dependent on ligand substitution. Until the structure was confirmed as tetrameric with octahedral coordination at the Co center, [Co(acac)2] was postulated to have square-planar geometry based on magnetic and spectroscopic data that differed from tetrahedral complexes. A search of the Cambridge Structural Database (V 5.32) for Fe and Co complexes in a fourcoordinate environment with t4 parameter [11] < 0.25 and magnetic susceptibility data revealed five high-spin d Fe complexes with macrocyclic or chelating N4 [12, 13] and O4 [14,15] coordination, and three high-spin d Co complexes 16,17] with varied ligand systems. A complete description of the CSD search and results can be found in the Supporting Information. Herein we report a unique pair of high-spin, square-planar {MO4} species. Our group has prepared several families of homoleptic fluorinated aryloxide and alkoxide complexes of 3d metals. We have extensively investigated the high-spin aryloxide compounds [M(OAr)4] 2 , M = Fe, Co, Ni, and Cu and [M(OAr)5] 2 , M = Fe, in which OAr = OC6F5 or 3,5OC6H3(CF3)2, as well as the high-spin alkoxide compounds [M(OC4F9)3] 1 , M = Fe, Co, Cu and [M(OC4F9)4] 2 , M = Co, Ni. Spectroscopic and computational work have shown that these fluorinated ligands are medium field ligands, on par with OH and F , and stronger than NCO . The electron-withdrawing power of extensively fluorinated ligands reduces the p-donor character of the O atom, such that bridging is not observed and mononuclear species are readily prepared. More recently, we have begun studies of the chelating perfluoropinacolate ligand, ddfp . Magnetic susceptibility and elemental analysis data were reported for K2[M(ddfp)2], (M = Mn, Ni, Cu) for which square-planar geometry was proposed. An octahedral bis-H2O adduct, (Me4N)2[Co(OH2)2(ddfp)2] has been proposed based on elemental analysis data. Despite the relative ease in making the [M(ddfp)2] 2 complexes with first-row transition metals, no examples of M = Co or Fe have been published. We now report a highspin, square-planar Co complex, {K(DME)2}2[Co(ddfp)2] (1), and the analogous high-spin, square-planar Fe complex {K(DME)2}2[Fe(ddfp)2] (2). We also provide a discussion of three other square-planar {MO4} species from the recent literature whose composition and spin-state characteristics clarify the ligand requirements for the highly unusual highspin, square-planar combination in late row 3d metals. Compound 1 has been prepared as pale pink crystals as shown in Equation (1), and is stable in an inert atmosphere and in various organic solvents, but yields a brown oil upon prolonged exposure to air. Iron-containing 2, and the Zn derivative, {K(DME)2}2[Zn(ddfp)2] (3), were similarly prepared as purple-pink, and colorless crystals, respectively. No [*] S. A. Cantalupo, Prof. Dr. L. H. Doerrer Department of Chemistry, Boston University 590 Commonwealth Avenue, Boston, MA 02215 (USA) E-mail: doerrer@bu.edu

High‐Spin Square‐Planar CoII and FeII Complexes and Reasons for Their Electronic Structure

A series of binuclear half-sandwich p-cymene ruthenium complexes bearing oxamidato ligands [(p-cymene)2Ru2(μ-N,N′-bis(aryl)oxamidato)Cl2] (1–3) was synthesized by the reactions of the lithium salts of oxamide with [(p-cymene)RuCl2]2, respectively. Treatment of the binuclear complexes (1–3) with bidentate ligands such as 4,4′-bipyridine (4,4′-bpy) and trans-1,2-bis(4-pyridyl)ethylene (bpe) in the presence of AgOTf (OTf = CF3SO3) gave the corresponding tetranuclear complexes generally formulated as [(p-cymene)4Ru4(μ-N,N′- bis(aryl)oxamidato)2(μ-4,4′-bpy)2](OTf)4 (4a–c) and [(p-cymene)4Ru4(μ-N,N′-bis(aryl)oxamidato)2(μ-bpe)2](OTf)4 (5a–c) in high yields. All compounds (1–3, 4a–5c) have been characterized by NMR and IR spectra and elemental analyses. The molecular structures of 1, 4a and 5a have been determined by single-crystal X-ray analyses. The molecular structures of tetranuclear complexes 4a and 5a showed that two binuclear fragments as building blocks were connected by 4,4′-bpy or bpe to construct a rectangular cavity with the dimensions 5.57 × 11.28 A (4a) and 5.56 × 13.65 A (5a).

Synthesis and characterization of molecular rectangles of half-sandwich p-cymene ruthenium complexes bearing oxamidato ligands

By using the macrocyclic oxamido-copper(II) complex as a building block and N 3 - and Cl- as auxiliary bridged groups, a binuclear complex and two tetranuclear complexes derived from the binuclear species have been prepared by stepwise synthesis and characterized. Their formulas are Cu(μ-exoO 2 )cyclam (1), [Cu(μ-exoO 2 )cyclamCu-(tmen)](ClO 4 ) 2 .H 2 O (2), {[Cu(μ-exoO 2 )cyclamCu(μ-1,3-N 3 ) 0.5 (tmen)] 2 {ClO 4 )4, [Cu(μ-exoO 2 )cyclamCu(μ-1,3-N 3 ) 0.5 (tmen)] 2 -(ClO 4 ) 2 } (3), and [Cu(μ-exoO 2 )cyclamCu(μ-Cl) 0.5 (tmen)] 2 (ClO 4 )3 (4), where tmen = N,N,N'N'-tetramethylethylene-diamine and (exoO 2 )cyclam = 1,4,8,11-tetraazacyclotradecanne-2,3-dione. The structure of complex 1 consists of the neutral copper(II) complex of the [14]N 4 macrocyclic oxamido dianion, and the packing of the molecules along the b orientation results in a novel one-dimensional wavelike chain through weak coordination bonds and hydrogen bonds. The structure of complex 2 consists of binuclear cations, a weakly coordinated water molecule, and perchlorate anions, and the structures of 3 and 4 consist of tetranuclear cations derived from binuclear species through azide and chloride ligands, respectively, and perchlorate anions.

Rational Design of Mono-, Bi-, and Tetranuclear Macrocyclic Oxamido−Metal Complexes via Stepwise Complexation

Two novel oxamido-bridged heterobinuclear copper(II)–manganese(II) complexes derived from macrocylic oxamido compounds incorporating different blocking ligands were synthesized and characterized by IR and electronic spectroscopy. They are of formula [Cu(L)Mn(phen)2](ClO4)2·1.5H2O (1) and [Cu(L)Mn(ntb)](ClO4)2·H2O (2), where L = 1,4,8,11-tetraazacyclotetradecane-2,3-dione, phen = 1,10-phenanthroline and ntb = tris(2-benzimidazolylmethyl)amine. The crystal structures of the two complexes have been determined and they consist of binuclear units in which the copper(II) ion is in a square-planar environment and linked to the manganese(II) ion via the exo–cis oxygen atoms of the oxamido macrocyclic ligand,
with Cu⋯Mn separations of 5.421 (1) and 5.486 A (2), respectively. The packing of the molecules along the a orientation in 2 results in open channels, which were extended into a three-dimensional hydrogen-bonded supramolecular network. The temperature dependence of the magnetic susceptibility for 1 and 2 were analyzed by means of the Hamiltonian, Ĥ
=
−2JŜMnŜCu, leading to J
=
−14.2 and −14.7 cm−1 for 1 and 2, respectively.

Heterobinuclear copper(II)–manganese(II) complexes behaving as three-dimensional supramolecular networks via both macrocyclic oxamido-bridges and hydrogen bonds

Synthesis and magnetism of the first tetranuclear copper(II)–iron(III) complexes of macrocyclic oxamides

Binucleating Macrocyclic (14)N4 Ligands and Their Complexes. Synthesis of the Free Ligand 2,3-Dioxo-5,6:13,14-dibenzo-9,10-(4′,5′-dimethylbenzo)-1,4,8,11-tetraazacyclotetradeca-7,11-diene (L) and of the 7,12-Me2-L Metal Complexes and

D. Christodoulou

Papers

Binucleating Macrocyclic (14)N4 Ligands and Their Complexes. Synthesis of the Free Ligand 2,3-Dioxo-5,6:13,14-dibenzo-9,10-(4′,5′-dimethylbenzo)-1,4,8,11-tetraazacyclotetradeca-7,11-diene (L) and of the 7,12-Me2-L Metal Complexes and