Lee M. Daniels

Transition metal (Mn, Co) and zinc formamidinate compounds having the basic beryllium acetate structure, and unique isomeric iron compounds

Abstract Oxidation of Co 2 (DPhF) 3 or hydrolysis of Co 2 (DPhF) 4 (DPhF = N , N ′-diphenylformamidinate) gives Co 4 O(DPhF) 6 ( I ). This tetranuclear compound consists of an oxygen atom centered in a tetrahedron of four-coordinate Co atoms with a DPhF bridge along each edge of the tetrahedron. An idealized T d symmetry is also found for zinc, II , and manganese, III , analogs. The latter, Mn 4 O(DPhF) 6 , crystallizes in a disordered fashion so as to appear as two interpenetrating tetrahedra. Two α 4 -O tetrairon compounds, namely, Fe 4 O(DPhF) 6 ( IV ) and Fe 4 O(DBiPhF) 4 ( V ) (DBiPhF = N , N ′-bisbiphenylformamidinate) are also described. These molecules are isomers of the Co, Zn and Mn molecules in that they have the ‘tetrahedron’ of metal atoms badly distorted by a different distribution of the formamidinate ligands. Two opposite FeFe edges are doubly bridged, another two opposite edges are singly bridged and the remaining two edges are unbridged. The lengths of these phree pairs of opposite edges are short, medium and long and the idealized molecular symmetry is only C 2 . Crystal data for I ·toluene at −60°C are: triclinic, space group P 1 , a = 13.426(3), b = 13.491(3), c = 22.600(5) A , α = 99.55(3), β = 95.39(3), γ = 111.80(3)°, Z = 2 . For II · 1.45C 6 H 14 at −60°C: orthorhombic, space group Pbca , a = 23.8113(8), b = 23.406(2), c = 30.956(1) A , Z = 8 . For III at −150°C: trigonal, space group R 3, a = 23.440(1), c = 10.708(1) A , Z = 3 . For IV · 1.5 toluene at −60°C: triclinic, space group P 1 , a = 14.920(3), b = 15.539(3), c = 19.027(4) A , α = 84.63(3), β = 85.67(3), γ = 63.30(3)°, Z = 2 .

Highly distorted diiron(II, II) complexes containing four amidinate ligands. A long and short metal-metal distance

Abstract The reaction of FeCl2(HDPhF)2 (HDPhF = N,N′-diphenylformamidine) with methyllithium in Et2O followed by extraction into solvent mixtures containing THF, toluene and hexanes produces crystals of Fe2(μ-DPhF)4 (I). This dinuclear compound contains four formamidinato bridges but in an arrangement that is highly distorted compared to the known paddle-wheel structures of M2(amidinato)4 molecules. A similar reaction using FeCl2(HDPhBz)2 (HDPhBz = N,N′-diphenylbenzamidine) also gives a distorted molecule Fe2(μ-DPhBz)2(η2-DPhBz)2·2THF (II), in which two amidine groups form bridges between the metal centers while the other two groups chelate to an iron atom each. The FeFe distances are 2.462(2) and 3.124(1) A, respectively. Both compounds I and II have been structurally characterized by X-ray crystallography. At −60°C, crystal data for I are: monoclinic, space group I2/a, a = 18.001(6), b = 10.019(1), c = 25.422(9) A , β = 105.28(1)°, Z = 4 . For II: triclinic, space group P 1 , a = 10.7874(6), b = 13.1756(7), c = 13.4552(8) A , α = 99.89(1), β = 109.405(3), γ = 100.210(7)°, Z = 1 .

Trigonal-lantern dinuclear compounds of diiron(I,II): the synthesis and characterization of two highly paramagnetic Fe2(amidinato)3 species with short metal-metal bonds ☆

Two examples of a new type of trigonal-lantern compound in which a formal Fe23+ unit is bridged by three amidinato groups are formed by reacting FeCl2(HDPhF)2 (HDPhF = N,N′-diphenylformamidine) and FeCl2(HDPhBz)2 (HDPhBz = N,N′-diphenylbenzamidine) with NaEt3BH and methyllithium in THF. The isolated crystalline products, Fe2(amidinato)3, have been structurally characterized by X-ray crystallography at −60°C. Crystal data for Fe2(DPhF)3 (I): monoclinic, space group C2/c, , β = 93.38(1)°, Z = 4; and for Fe2(DPhBz)3·2C6H6 (II): trigonal, space group , a = 11.237(2), . The FeFe bond distances, 2.2318(8) and 2.198(2) A for compounds I and II, respectively, are the shortest known for any diiron compound. The room temperature magnetic susceptibilities of 7.81 and 7.53 B.M. for I and II and the EPR spectrum of I in a toluene glass (10 K) which shows two signals at g values of 1.99 and 7.94 are consistent with the presence of seven unpaired electrons in an axially symmetric environment.

The exceptional structural versatility of 2,2′-dipyridylamine (Hdpa) and its ions [dpa]− and [H2dpa]+

Abstract This report describes several cobalt compounds that contain 2,2′-dipyridylamine (Hdpa) and its ionic forms, dpa− and H2dpa+. It was carried out with the aim of structurally characterizing various coordination modes of such species. The reaction of two equivalents of Hdpa with one equivalent of [Co(H2O)6] (ClO4)2 produces the octahedral complex [Co(Hdpa)2((CH3)2](ClO4)2. Under mild aerobic conditions, Co(II) is oxidized to Co(III) to yield the six-coordinate peroxo bridged compound [Co2(Hdpa)4(μ-O2)(μ-OH)](ClO4)3 · 3acetone (I), the neutral Hdpa ligand chelates to the metal and shows significant puckering of the pyridyl rings. The tetrahedral complex, Co(Hdpa)Cl2 (II), is prepared from the reaction of anhydrous CoCl2 and Hdpa; puckering of the pyridyl groups is significantly smaller than that found for I. The deprotonated ligand reacts with CoCl2 to produce the neutral molecule, Co(dpa)2 (III) in which the dipyridyl groups are almost planar. The reaction of Hdpa and [Co(H2O)6](ClO4)2 in the presence of excess HCl yields the salt, [H2dpa]2[CoCl4] (IV). The crystal structures of I, II, III, and IV are presented. In structures I–III, the ligands chelate to the metal atom through the nitrogen atoms of the pyridyl rings in an anti-anti configuration. The structure of IV is also in an anti-anti configuration with the proton residing between the two nitrogen atoms of the pyridyl rings.

A new class of dinuclear compounds: The synthesis and x-ray structural characterization of tris(μ-diphenyl-formamidinato) diiron

Abstract A new type of dinuclear metal-metal bonded compound is formed by reacting FeCl 2 (HDPhF) 2 , HDPhF=diphenylformamidine, with butyllithium in THF. The isolated crystalline product, Fe 2 (DPhF) 3 , contains the mixed-valent dinuclear unit bridged by only three formamidinato groups. It has been structurally characterized by X-ray crystallography at −60 °C. Crystal data: monoclinic, space group C 2/ c , a = 17.154(4), b = 8.255(1), c = 23.400(5) A, β = 93.38(1)°, Z = 4. The FeFe bond distance is 2.2318(8) A. The EPR spectrum in a toluene glass (10 K) show two signals at g values of 1.99 and 7.94.

Tuning metal-to-metal distances in linear trichromium units

Abstract A series of complexes composed of three chromium atoms linearly arranged and surrounded by four dipyridyl amido anions, dpa, of the type [Cr3(dpa)4]n+, n=2, 3, have been prepared. They show a remarkable variation of the Cr–Cr distances that vary from equal to highly unequal. These complexes are made by reacting CrCl2 and Lidpa, which gives intermediate quadruply bonded Cr2(dpa)4 species (1·CH2Cl2, 2) and then the trinuclear complex [Cr3(dpa)4Cl2] (3·toluene). Compound 3 has chemically equivalent Cr–Cr distances (2.365(2) and 2.345(2) A). The linear, trinuclear complexes [Cr3(dpa)4(CCPh)2] (4) and [Cr3(dpa)4Cl(PF6)] (5·CH2Cl2), obtained from the reaction of 3 and LiCCPh and TlPF6, respectively, show a very different arrangement of the Cr–Cr distances. Whereas the acetylide complex 4 retains a symmetric pair of Cr–Cr–Cr bonds (2.4149(14) and 2.4223(14) A), 5 is very unsymmetrical, with Cr–Cr–Cr distances of 2.0085(13) and 2.6130(12) A. A one-electron oxidation of 3 by various oxidizing agents allows the isolation of [Cr3(dpa)4Cl2]Cl (6·CH2Cl2·THF), [Cr3(dpa)4Cl2]PF6 (7·CH2Cl2·C6H14) and [Cr3(dpa)4Cl2]FeCl4 (8·CH2Cl2). Again there is great variability in the Cr–Cr–Cr unit; the distances vary from totally symmetric in 6 (2.3006(9) and 2.3006(9) A) to moderately different in 7 (2.199(3) and 2.369(3) A) to markedly different in 8 (2.0089(12) and 2.5618(14) A). The latter is best described as containing a quadruply bonded Cr24+ unit and an isolated five-coordinate Cr3+ moiety.

Divalent metal chloride formamidine complexes, M11 = Fe, Co and Pt. syntheses and structural characterization

Abstract The reactions of anhydrous FeCl2, CoCl2 and K2PtCl4 with N,N′-di(p-tolyl)-formamidine (HDTolF) yield crystalline materials which are soluble in common organic solvents. FeCl2(HDTolF)2 (I) and CoCl2(HDTolF)2 (II) have a pseudo-tetrahedral coordination about the metal centre, while [PtCl(HDTolF)3]Cl (III) has a square-planar arrangement of atoms around the platinum atom. The latter reacts with butyllithium to produce PtCl(DTolF) (HDTolF)2 (IV). All compounds reported have been characterized by X-ray crystallography and by various spectroscopic techniques. The facility with which they formand the high purity in which they are isolated, as well as their favourable solubility characteristics, make them attractive starting materials for the preparation of other formamidinato complexes.

Refutation of an alleged example of a disordered but centrosymmetric triboluminescent crystal

Abstract The crystal structure of triboluminescent triethylammonium tetrakis(dibenzoylmethide)-europium has been reinvestigated with the result that crystals previously assigned to the centric space group I2/a actually belong to the non-centric space group Ia.

The use of CoCl2(amidine)2 compounds in the synthesis of tetragonal lantern dicobalt compounds: synthesis, structures and theoretical studies of Co2(DPhF)4 and the oxidized species [Co2(DPhBz)4]+ (DPhF = N,N′-diphenylformamidinate, DPhBz = N,N′-diphenylbenzamidinate)

Abstract CoCl2(PhNC(R)N(H)Ph)2 complexes (R = H and Ph) have been reacted with methyllithium to produce the corresponding lantern-type Co2(amidinato)4 compounds containing cobalt-cobalt bonds of order one. One of them, Co2(DPhBz)4(DPhBz = diphenylbenzamidinato), was oxidized by AgPF6 to yield [Co2(DPhBz)4](PF6·2.4CH2Cl2. Crystal data for Co2(DPhF)4(I) (DPhB = diphenylformamidinato) at 0°C are: monoclinic, space group C2/c, a = 13.927(3), b = 13.678(3), c = 22.855(5) A , β = 91.37(2)°, Z = 4 . For [Co2(DPhBz)4]- (PF6)·2.4CH2Cl2 (II) at −60°C: triclinic, space group P1, a = 13.838(4), b = 13.881(4), c = 19.62(1), A , α=89.7(1), β = 99.76(4), γ = 91.04(4)°, Z = 2 . The metal-to-metal distances are 2.3735(9) A for complex I and 2.322(2) and 2.332(2) A for two crystallographically independent molecules found in complex II. The latter are slightly longer than those found in the parent neutral molecule. The experimental cobalt-to-cobalt separations are in good agreement with those obtained from ab initio quantum chemical calculations.

O-Demethylation reaction at a diruthenium core: synthesis and structural study of two novel diruthenium compounds

Abstract The reaction between Ru2(OAc)4Cl and di(o-methoxyphenyl)formamidine led to the unexpected products trans-Ru2(O2CCH3)2(μ-N,N′-η2-N,O-o-MeOForm)(μ-N,N′-η2-N,O-o-MeOForm′) (1) and Ru2(O2CCH3)(μ-N,N′-o-MeOForm)(μ-N,N′-η2-N,O-o-MeOForm)(μ-N,N′-η2-N,O-o-MeOForm′) (2), where o-MeOForm is di(o-methoxyphenyl)formamidinate, and o-MeOForm′ is the O-demethylation derivative of o-MeOForm, (o-methoxyphenyl)(o-oxyphenyl)formamidinate. Both compounds 1 and 2 were structurally characterized by X-ray diffraction analysis, and are isoelectronic with the previously studied chloro-tetracarboxylatodiruthenium(II,III) and chlorotetrakis(diarylformamidinato)diruthenium(II,III) on the basis of structural and magnetic data.