Single-molecule magnets: preparation and properties of low symmetry [Mn4O3(O2CPh-R)4(dbm)3] complexes with S = 9/2.

The preparation and properties of [Mn(4)O(3)(O(2)CPh-R)(4)(dbm)(3)] (R = H, p-Me, p-OMe, and o-Cl; dbm(-) is the anion of dibenzoylmethane) single-molecule magnets (SMMs) with virtual C(S) symmetry are reported. They were prepared by controlled potential electrolysis in 26-80% yields. The structures comprise a distorted-cubane core of virtual C(S) symmetry, in contrast to the other, more common complexes of this type with virtual C(3)(V) symmetry.

Single-molecule magnets: a large Mn30 molecular nanomagnet exhibiting quantum tunneling of magnetization.

The largest single-molecule magnet (SMM) to date has been prepared and studied. Recrystallization of known [Mn(12)O(12)(O(2)CCH(2)Bu(t))(16)(H(2)O)(4)] (1; 8Mn(III), 4Mn(IV)) from CH(2)Cl(2)/MeNO(2) causes its conversion to [Mn(30)O(24)(OH)(8)(O(2)CCH(2)Bu(t))(32)(H(2)O)(2)(MeNO(2))(4)] (2; 3Mn(II), 26Mn(III), Mn(IV)). The structure of 2 consists of a central, near-linear [Mn(4)O(6)] backbone, to either side of which are attached two [Mn(13)O(9)(OH)(4)] units.

Single-molecule magnets: novel Mn(8) and Mn(9) carboxylate clusters containing an unusual pentadentate ligand derived from pyridine-2,6-dimethanol.

The reactions of the Mn(III)(3) and Mn(II)Mn(III)(2) complexes [Mn(3)O(O(2)CEt)(6)(py)(3)][ClO(4)] and [Mn(3)O(O(2)CEt)(6)(py)(3)] with pyridine-2,6-dimethanol (pdmH(2)) afford the mixed-valence Mn(II)(6)Mn(III)(2) octanuclear complex [Mn(8)O(2)(py)(4)(O(2)CEt)(8)(L)(2)][ClO(4)](2) (1) and the Mn(II)(7)Mn(III)(2) enneanuclear complex [Mn(9)(O(2)CEt)(12)(pdm)(pdmH)(2)(L)(2)] (2), respectively. Both compounds contain a novel pentadentate ligand, the dianion of (6-hydroxymethylpyridin-2-yl)-(6-hydroxymethylpyridin-2-ylmethoxy)methanol (LH(2)), which is the hemiacetal formed in situ from the Mn-assisted oxidation of pdmH(2). Complex 1 crystallizes in the monoclinic space group P2(1)/n with the following cell parameters at -160 degrees C: a = 16.

Single-molecule magnets: a new family of Mn(12) clusters of formula [Mn(12)O(8)X(4)(O(2)CPh)(8)L(6)].

The reaction of (NBu(n)(4))[Mn(8)O(6)Cl(6)(O(2)CPh)(7)(H(2)O)(2)] (1) with 2-(hydroxymethyl)pyridine (hmpH) or 2-(hydroxyethyl)pyridine (hepH) gives the Mn(II)(2)Mn(III)(10) title compounds [Mn(12)O(8)Cl(4)(O(2)CPh)(8)(hmp)(6)] (2) and [Mn(12)O(8)Cl(4)(O(2)CPh)(8)(hep)(6)] (3), respectively, with X = Cl. Subsequent reaction of 3 with HBr affords the Br(-) analogue [Mn(12)O(8)Br(4)(O(2)CPh)(8)(hep)(6)] (4). Complexes 2.

Bridging nitrate groups in [Mn(4)O(3)(NO(3))(O(2)CMe)(3)(R(2)dbm)(3)] (R = H, Et) and [Mn(4)O(2)(NO(3))(O(2)CEt)(6)(bpy)(2)](ClO(4)): acidolysis routes to tetranuclear manganese carboxylate complexes.

New synthesis procedures are described to tetranuclear manganese carboxylate complexes containing the [Mn(4)O(2)](8+) or [Mn(4)O(3)X](6+) (X(-) = MeCO(2)(-), F(-), Cl(-), Br(-), NO(3)(-)) core. These involve acidolysis reactions of [Mn(4)O(3)(O(2)CMe)(4)(dbm)(3)] (1; dbm is the anion of dibenzoylmethane) or [Mn(4)O(2)(O(2)CEt)(6)(dbm)(2)] (8) with HX (X(-) = F(-), Cl(-), Br(-), NO(3)(-)); high-yield routes to 1 and 8 are also described. The X(-) = NO(3)(-) complexes [Mn(4)O(3)(NO(3))(O(2)CR)(3)(R'(2)dbm)(3)] (R = Me, R' = H (6); R = Me, R' = Et (7); R = Et, R' = H (12)) represent the first synthesis of the [Mn(4)O(3)(NO(3))](6+) core, which contains an unusual eta(1):mu(3)-NO(3)(-) group.

[Co(4)O(4)](4+) Cubane Core as a Brønsted Base: Preparation and Properties of [Co(4)O(3)(OH)(O(2)CR)(2)(bpy)(2)](3+) and [Co(4)O(2)(OH)(2)(O(2)CR)(2)(bpy)(2)](4+) Salts.

The preparation and properties are described of complexes resulting from the mono- and diprotonation of the [Co(4)O(4)](4+) unit to give products containing [Co(4)O(3)(OH)](5+) and [Co(4)O(2)(OH)(2)](6+), respectively. Treatment of [Co(4)O(4)(O(2)CC(6)H(4)-p-OMe)(2)(bpy)(4)](2+) (bpy = 2,2'-bipyridine) in MeCN with 70% perchloric acid leads to isolation of [Co(4)O(2)(OH)(2)(O(2)CC(6)H(4)-p-OMe)(2)(bpy)(4)](ClO(4))(4) (5) in 61% yield. Treatment of [Co(4)O(4)(O(2)CC(6)H(4)-p-Me)(2)(bpy)(4)](2+) in MeCN with an acidic solution of (NH(4))(3)[Ce(NO(3))(6)] leads to isolation of [Co(4)O(3)(OH)(O(2)CC(6)H(4)-p-Me)(2)(bpy)(4)][Ce(NO(3))(6)] (6) in 96% yield.

Dinuclear (d(3)-d(3)) Diolate Complexes of Molybdenum and Tungsten. 3.(1) Bridging and Chelating Isomers of M(2)(NMe(2))(2)(O approximately approximately CHMe approximately approximately O)(2), Where O approximately approximately CHMe approximately approximately O Is the Dianion of 2,2'-Ethylidenebis(4,6-di-tert-butylphenol). Kinetic versus Thermodynamic Considerations.

Hydrocarbon solutions of Mo(2)(NMe(2))(6) and 2,2'-ethylidenebis(4,6-di-tert-butylphenol), HO approximately approximately CHMe approximately approximately OH (2 equiv), react to give a mixture of two isomers, A and B, of formula Mo(2)(NMe(2))(2)(O approximately approximately CHMe approximately approximately O)(2). Both A and B are shown to contain the bridging &mgr;-O approximately approximately CHMe approximately approximately O ligands. They are diastereomers differing with respect to the positioning of the CHMe moiety as a result of ring closure with elimination of HNMe(2).

Single-Molecule Magnets: Different Rates of Resonant Magnetization Tunneling in Mn Complexes.

Two new molecular magnets, the dodecanuclear manganese complexes of the type [Mn O (O CR) (H O) ] (known for R = CH , new for R = o-ClC H , o-BrC H ) have contributed to a better quantum mechanical understanding of single-molecule magnets. For instance, appreciable differences in the steps seen in the magnetization hysteresis loops of these high-spin clusters are attributed to changes in the rates of magnetization tunneling from one complex to another.

Reaction of Nitrogen Chelates with the [Rh(2)](4+) Core: Bis-Chelate Products and Demonstration of Reversible, Chelate-Based Reduction Processes.

The preparations and properties are described of a series of [Rh(2)](4+) complexes possessing carboxylates and N-based chelates as ligands. Treatment of Rh(2)(O(2)CR)(4)(MeOH)(2) (R = Me (1), Et (2), Ph (3) or CF(3) (4)) with 2 equiv of 2,2'-bipyridine (bpy) in refluxing MeCN leads to the [Rh(2)(O(2)CR)(2)(bpy)(2)](2+) cation (in complexes 5-9). Reaction of 1 with 1,10-phenanthroline (phen), 4,4'-dimethyl-2,2'-bipyridine (Me(2)bpy), 4,4'-diphenyl-2,2'-bipyridine (Ph(2)bpy), and 4,7-diphenyl-1,10-phenanthroline (Ph(2)phen) leads to the analogous cations of complexes 10-13.

Reactivity of RuCl(2)(CO)(P(t)()Bu(2)Me)(2) toward H(2) and Brønsted Acids: Aggregation Triggered by Protonation and Phosphine Loss.

Reaction of H(2) with RuCl(2)(CO)L(2) (L = P(t)()Bu(2)Me) in benzene forms RuHCl(CO)L(2) and HCl. The latter reacts with RuCl(2)(CO)L(2) to give [LH][Ru(2)Cl(5)(CO)(2)L(2)] and [LH]Cl. The Ru(2)Cl(5)(CO)(2)L(2)(-) ion is detected (NMR) as several isomers, and is shown by X-ray diffraction to have a face-shared bioctahedral structure: LCl(OC)Ru(&mgr;-Cl)(3)Ru(CO)ClL(-).

Magnetochemical Properties and Reactions of Vanadium(III) Thiolate Complexes: Preparation of (NEt(4))(3)[V(3)Cl(6)(edt)(3)] and Mixed-Valence (NEt(4))[V(2)(edt)(4)] (edt = Ethane-1,2-dithiolate).

Reactions of the previously reported dinuclear vanadium(III) thiolate anion [V(2)(edt)(4)](2)(-) (edtH(2) = ethane-1,2-dithiol) are described. Treatment of (NEt(4))(2)[V(2)(edt)(4)] (1) in MeCN with equimolar (C(12)H(8)S(2))BF(4) (C(12)H(8)S(2)(+) = the thianthrenium radical cation) results in a one-electron oxidation and isolation of the V(III),V(IV) complex (NEt(4))[V(2)(edt)(4)] (2). The same product can also be obtained by controlled-potential electrolysis of 1 at -0.

Tetranuclear and Pentanuclear Vanadium(IV/V) Carboxylate Complexes: [V(4)O(8)(NO(3))(O(2)CR)(4)](2-) and [V(5)O(9)X(O(2)CR)(4)](2-) (X = Cl(-), Br(-)) Salts.

The syntheses and properties of tetra- and pentanuclear vanadium(IV,V) carboxylate complexes are reported. Reaction of (NBzEt(3))(2)[VOCl(4)] (1a) with NaO(2)CPh and atmospheric H(2)O/O(2) in MeCN leads to formation of (NBzEt(3))(2)[V(5)O(9)Cl(O(2)CPh)(4)] 4a; a similar reaction employing (NEt(4))(2)[VOCl(4)] (1b) gives (NEt(4))(2)[V(5)O(9)Cl(O(2)CPh)(4)] (4b). Complex 4a.