Expansion of iridaborane clusters by addition of monoborane. Novel metallaboranes and mechanistic detail.

This work reports the results of a thermally driven cluster expansion of arachno-1-{eta5-C5Me5IrH2}B3H7, 1, with BH3.THF. In addition to the previously reported product, arachno-1-{eta5-C5Me5IrH}B4H9, 2, formed at lower temperatures, reaction at 100 degrees C permits the isolation of four new iridaboranes.

Metallaborane reactivity. A stoichiometric mechanism for the insertion of two alkynes into an iridaborane framework via a disposable molybdenum chaperone.

Building on earlier work that showed the formation of [1-Cp*-2,2,2-(CO)3-2-THF-nido-1,2-IrMoB(4)H(8)], 2, from the reaction of [1-Cp*-arachno-1-IrB(4)H(10)], 1, with (arene)Mo(CO)3, the stoichiometric mechanism for the generation of [1-Cp*-5,6,7,8-(R)4-nido-1,5,6,7,8-IrC(4)B(3)H(3)], 8, from the reaction of 2 with RCCR, R = Me, Ph, has been identified. For R = Me, the major product in solution is [1-Cp*-5,6,7,8-(CH3)4-closo-1,5,6,7,8-IrC(4)B(3)H(3)Mo(CO)3], 7, which is in equilibrium with 8. The equilibrium 8 + Mo(THF)3(CO)3 <==> 7 + 3THF is characterized by DeltaH = 8 kcal/mol and DeltaS = 34 cal/mol K.

Properties of a mixed-valence (Fe(II))2(Fe(III))2 square cell for utilization in the quantum cellular automata paradigm for molecular electronics.

The di-mixed-valence complex [{(eta(5)-C5H5)Fe(eta(5)-C5H4)}4(eta(4)-C4)Co(eta(5)-C5H5)]2+, 1(2+), has been evaluated as a molecular four-dot cell for the quantum cellular automata paradigm for electronic devices. The cations 1(1+) and 1(2+) are prepared in good yield by selective chemical oxidation of 1(0) and are isolated as pure crystalline materials. The solid-state structures of 1(0) and 1(1+) and the midrange- and near-IR spectra of 1(0), 1(1+), 1(2+), and 1(3+) have been determined.

Dependence of field switched ordered arrays of dinuclear mixed-valence complexes on the distance between the redox centers and the size of the counterions.

trans-[(H(2)NCH(2)CH(2)C triple bond N)(dppe)(2)Ru(C triple bond C)(6)Ru(dppe)(2)(N triple bond CCH(2)CH(2)NH(2))][PF(6)](2), 2[PF(6)](2), a derivative of trans-[Cl(dppe)(2)Ru(C triple bond C)(6)Ru(dppe)(2)Cl] functionalized for binding to a silicon substrate, has been prepared and characterized spectroscopically, electrochemically, and with a solid state, single-crystal structure determination. Covalent binding via reaction of one amine group to a boron-doped, smooth Si-Cl substrate is verified by XPS measurements and surface electrochemistry. Vertical orientation is demonstrated by film thickness measurements.

Condensed metallaborane clusters: synthesis and structure of Fe2(CO)6(eta5-C5Me5RuCO)(eta5-C5Me5Ru)B6H10.

Mild pyrolysis of (eta5-C5Me5Ru)2B6H12 with Fe2(CO)9 yields the 12 skeletal electron pair (sep) Fe2(CO)6(eta5-C5Me5RuCO)(eta5-C5Me5Ru)B6H10 cluster; the title compound represents a novel class of hybrid multiple cluster in which a Fe2B2 tetrahedron has been fused to a ruthenaborane substrate.

Cooperative metal-boron interactions in the reaction of nido-1,2-(Cp*RuH)2B3H7, Cp* = eta5-C5Me5, with HC(triple bond)CPh.

Products of the reaction of nido-1,2-(CpRuH)(2)B(3)H(7), 1, and phenylacetylene demonstrate the ways in which cluster metal and main group fragments can combine with an alkyne. Observed at 22 degrees C are (a) reduction to mu-alkylidene Ru-B bridges (isomers nido-1,2-(CpRu)(2)(1,5-mu-C{Ph}Me)B(3)H(7), 2, and nido-1,2-(CpRu)(2)(1,5-mu-C{CH(2)Ph}H)B(3)H(7), 3), (b) reduction to exo-cluster alkyl substituents on boron (nido-1,2-(CpRuH)(2)-3-CH(2)CH(2)Ph-B(3)H(6), 4), (c) cluster insertion with extrusion of a BH(2) fragment into an exo-cluster bridge (nido-1,2-(CpRu)(2)(mu-H)(mu-BH(2))-4-or-5-Ph-4,5-C(2)B(2)H(5), 5), (d) combined insertion with BH(2) extrusion and reduction (nido-1,2-(CpRu)(2)(mu-H)(mu-BH(2))-3-CH(2)CH(2)Ph-5-Ph-4,5-C(2)B(2)H(4), 6), (e) insertion and loss of borane with and without reduction (nido-1,2-(CpRu)(2)-5-Ph-4,5-C(2)B(2)H(7), 7, and isomers nido-1,2-(CpRu)(2)-3-CH(2)CH(2)Ph-4-(and-5-)Ph-C(2)B(2)H(6), 8 and 9), and (f) insertion and borane loss plus reduction (nido-1,2-(CpRu)(2)-3-(trans-CH=CHPh)-5-Ph-4,5-C(2)B(2)H(6), 10). Along with 7, 8, and 10, the reaction at 90 degrees C generates products of insertion and nido- to closo-cluster closure (closo-4-Ph-1,2-(CpRuH)(2)-4,6-C(2)B(2)H(3), 11, closo-1,2-(CpRuH)(2)-3-CH(2)CH(2)Ph-5-Ph-7-CH(2)CH(2)Ph-4,5-C(2)B(3)H(2), 12, closo-1,2-(CpRuH)(2)-5-Ph-4,5-C(2)B(3)H(4), 13, and isomers closo-1,2-(CpRuH)(2)-3-and-7-CH(2)CH(2)Ph-5-Ph-4,5-C(2)B(3)H(3), 14 and 15).

Synthesis and characterization of hypoelectronic rhenaboranes. Analysis of the geometric and electronic structures of species following neither borane nor metal cluster electron-counting paradigms.

The reaction of (CpReH(2))(2)B(4)H(4) with monoborane leads to the sequential formation of (CpRe)(2)B(n)()H(n)() (n = 7-10, 1-4). These species adopt closed deltahedra with the same total connectivities as the closo-borane anions [B(n)()H(n)()](2)(-), n = 9-12, but with flattened geometries rather than spherical shapes. These rhenaborane clusters are characterized by high metal coordination numbers, Re-Re cross-cluster distances within the Re-Re single bond range, and formal cluster electron counts three skeletal electron pairs short of that required for a canonical closo-structure of the same nuclearity.

Ruthenacarboranes from the reaction of nido-1,2-(Cp*RuH)2B3H7 with HC [triple bond] CCO2Me, Cp* = eta5-C5Me5. Hydrometalation, alkyne incorporation, and functional group modification via cooperative metal-boron interactions within a metallaborane cluster framework.

Reaction of nido-1,2-(Cp*RuH)2B3H7, 1, and methyl acetylene monocarboxylate under kinetic control generates nido-1,2-(Cp*Ru)2(mu-C[[CO2Me]Me])B3H7 (a pair of geometric isomers, 3 and 5) and nido-1,2-(Cp*Ru)2(1,3-mu-C[[CH2CO2Me]H])B3H7, 4, which display the first examples of exo-cluster mu-alkylidene Ru-B bridges generated by hydrometalation of an alkyne on the cluster framework. Both 3 and 5, but not 4, rearrange into arachno-2,8-mu(C)-5-eta1(O)-Me[CO2Me]C-1,2-(Cp*Ru)2B3H7, 2, in which an unprecedented intramolecular coordination of the carbonyl oxygen atom of the alkyne substituent to a boron framework site opens the ruthenaborane skeleton. Compound 2, in turn, is an intermediate in the formation of the ruthenacarborane nido-1,2-(Cp*Ru)2-3-OH-4-OMe-5-Me-4,5-C2B2H5, 12, in which the carbonyl-oxygen double bond has been cleaved as its oxygen atom inserts into a B-H bond and the carbonyl carbon inserts into the metallaborane framework.

Molecular quantum cellular automata cells. Electric field driven switching of a silicon surface bound array of vertically oriented two-dot molecular quantum cellular automata.

The amine functionality of the linker on the dinuclear complex [trans-Ru(dppm)(2)(Ctbd1;CFc)(NCCH(2)CH(2)NH(2))][PF(6)] reacts with Si-Cl bonds of a chlorinated, highly B doped Si (111) surface to yield Si-N surface-complex bonds. The surface bound complex is constrained to a near vertical orientation by the chain length of the linker as confirmed by variable angle XPS. Oxidation of the dinuclear complex with ferrocenium ion or electrochemically generates a stable, biased Fe(III)-Ru(II) mixed-valence complex on the surface.

Molecular QCA cells. 2. Characterization of an unsymmetrical dinuclear mixed-valence complex bound to a Au surface by an organic linker.

Utilization of binary information encoded in the charge configuration of quantum-dot cells (the quantum-dot cellular automata, QCA, paradigm) requires surface-bound molecule-sized dots for room temperature operation. Molecular QCA cells are mixed-valence complexes, and the evaluation of a surface-bound unsymmetrical, heterobinuclear, two-dot, Fe-Ru molecular QCA cell is described. The tailed complex, trans-[Ru(dppm)(2)(C[triple bond]CFc)(N[triple bond]CCH(2)CH(2)-NH(2))][PF(6)] (dppm = methylbis(diphenylphosphane), Fc = (eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4))), is covalently modified with the molecular adapter, HS(CH(2))(10)COOH, for binding to a Au surface.

Molecular QCA cells. 1. Structure and functionalization of an unsymmetrical dinuclear mixed-valence complex for surface binding.

Utilization of binary information encoded in the charge configuration of quantum-dot cells (the quantum-dot cellular automata, QCA, paradigm) requires molecule-sized dots for room temperature operation. Molecular QCA cells are mixed-valence complexes, and the evaluation and functionalization of an unsymmetrical heterobinuclear, two-dot, Fe-Ru molecular QCA cell is described. The solid state structures of trans-RuCl(dppm)(2)(C[triple bond]CFc) (1) (dppm = methylbis(diphenylphosphane), Fc = (eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4))) and mixed-valence [trans-RuCl(dppm)(2)(C[triple bond]CFc)][BF(4)] (1a) as well as XPS and spectroscopic data suggest class II behavior suitable for the intended application.

Building blocks for the molecular expression of quantum cellular automata. Isolation and characterization of a covalently bonded square array of two ferrocenium and two ferrocene complexes.

The suitability of [{(eta5-C5H5)Fe(eta5-C5H4)}4(eta4-C4)Co(eta5-C5H5)][PF6]2, [1][PF6]2, for use as a molecular quantum cellular automata (QCA) cell is demonstrated. To this end the structure of 1 in the solid state and the conversion of 1 to mono- and dicationic mixed-valence complexes have been accomplished. The latter compounds have been isolated as pure materials and characterized by IR, EPR, and Mössbauer spectroscopies and single-crystal XRD (monocation only) and magnetic susceptibility measurements.

Facile hydrometalation of alkynes by nido-1,2-(CpRuH)(2)B(3)H(7) yielding novel Ru-B edge-bridging alkylidenes. Stepwise conversion of HCtbd1;CC(O)OMe into nido-1,2-(CpRuH)(2)-3-HOB-4-MeC-5-MeOC-BH(3), Cp = eta(5)-C(5)Me(5).

The reaction of the alkyne HCCC(O)OMe with 7 sep 1,2-(Cp*RuH)2B3H7 leads to hydroboration plus hydroruthenation to produce nido-1,3-mu-Me{C(O)OMe}C-1,2-(Cp*Ru)2B3H7, a compound with an exocluster ruthenium-boron mu-alkylidene that exists in two isomeric forms. Both isomers undergo rearrangement with intramolecular chelation of the carbonyl oxygen at a boron site, thereby opening the cluster and generating arachno-2,3,-mu(C)-5-eta1(O)-Me{C(O)OMe}C-1,2-(Cp*Ru)2B3H7. Further heating leads to deoxygenation of the carbonyl fragment by a boron center concurrent with insertion of the carbon atom into the metallaborane cage to give nido-1,2-(Cp*RuH)2-3-HOB-4-MeC-5-MeOC-BH3.

2,2'-commo-Bis[2-ruthena-nido-1-(η-pentamethylcyclopentadienyl)ruthenahexaborane(12)]: An Unusual Ruthenaborane Related to Ruthenocene and Exhibiting a Linear Triruthenium Fragment.

An isomer of a sandwich complex, compound 1 has been prepared from nido-[1,2-{Cp*Ru}BH] and structurally characterized. Owing to the connection of the two dimetallahexaborane cages, the three metals form a linear array. The environment of the unique central Ru atom is different from that normally found in metallaboranes.

Clusters as Ligands. 4. Synthesis, Structure, and Characterization of the Tungsten(II)-Tungsten(III) Cluster Carboxylate {[Na][W(2){OOCCCo(3)(CO)(9)}(2)(OOCCF(3))(4)(THF)(2)]}(2).

The reaction of W(2)(OOCCF(3))(4) with (CO)(9)Co(3)CCOOH and Na[OOCCF(3)] in a nonpolar solvent mixture leads to the formation of the cluster of clusters {[Na][W(2){OOCCCo(3)(CO)(9)}(2)(OOCCF(3))(4)(THF)(2)]}(2), 1, in 40% yield. The structure of 1.3C(6)H(5)CH(3) in the solid state corresponds to a dimer of W(2) dinuclear complexes (monoclinic P2(1)/c, a = 15.