Syntheses of functionalized ferratricarbadecaboranyl complexes

The reactions of nitriles (RCN) with arachno-4,6-C(2)B(7)H(12)(-) provide a general route to functionalized tricarbadecaboranyl anions, 6-R-nido-5,6,9-C(3)B(7)H(9)(-), R = C(6)H(5) (2(-)), NC(CH(2))(4) (4(-)), (p-BrC(6)H(4))(Me(3)SiO)CH (6(-)), C(14)H(11) (8(-)), and H(3)BNMe(2)(CH(2))(2) (10(-)). Further reaction of these anions with (eta(5)-C(5)H(5))Fe(CO)(2)I yields the functionalized ferratricarbadecaboranyl complexes 1-(eta(5)-C(5)H(5))-2-C(6)H(5)-closo-1,2,3,4-FeC(3)B(7)H(9) (3), 1-(eta(5)-C(5)H(5))-2-NC(CH(2))(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (5), 1-(eta(5)-C(5)H(5))-2-[(p-BrC(6)H(4))(Me(3)SiO)CH]-closo-1,2,3,4-FeC(3)B(7)H(9) (7), 1-(eta(5)-C(5)H(5))-2-C(14)H(11)-closo-1,2,3,4-FeC(3)B(7)H(9) (9), and 1-(eta(5)-C(5)H(5))-2-H(3)BNMe(2)(CH(2))(2)-closo-1,2,3,4-FeC(3)B(7)H(9) (11). Reaction of 11 with DABCO (triethylenediamine) resulted in removal of the BH(3) group coordinated to the nitrogen of the side chain, giving 1-(eta(5)-C(5)H(5))-2-NMe(2)(CH(2))(2)-closo-1,2,3,4-FeC(3)B(7)H(9) (12). Crystallographic studies of complexes 3, 5, 7, 9, and 11 confirmed that these complexes are ferrocene analogues in which a formal Fe(2+) ion is sandwiched between the cyclopentadienyl and tricarbadecaboranyl monoanionic ligands. The metals are eta(6)-coordinated to the puckered six-membered face of the tricarbadecaboranyl cage, with the exopolyhedral substituents bonded to the low-coordinate carbon adjacent to the iron.     

Controlled direct synthesis of C-mono- and C-disubstituted derivatives of [3,3'-Co(1,2-C2B9H11)2]- with organosilane groups: theoretical calculations compared with experimental results

Mono- and dilithium salts of [3,3'-Co(1,2-C(2)B(9)H(11))(2)](-), (1(-)), react with different chlorosilanes (Me(2)SiHCl, Me(2)SiCl(2), Me(3)SiCl and MeSiHCl(2)) with an accurate control of the temperature to give a set of novel C(c)-mono- (C(c) = C(cluster)) and C(c)-disubstituted cobaltabis(dicarbollide) derivatives with silyl functions: [1-SiMe(2)H-3,3'-Co(1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))](-) (3(-)); [1,1'-mu-SiMe(2)-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (4(-)); [1,1'-mu-SiMeH-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (5(-)); [1-SiMe(3)-3,3'-Co(1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))](-) (6(-)) and [1,1'-(SiMe(3))(2)-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (7(-)). In a similar way, the [8,8'-mu-(1',2'-C(6)H(4))-1,1'-mu-SiMe(2)-3,3'-Co(1,2-C(2)B(9)H(9))(2)](-) (8(-)); [8,8'-mu-(1',2'-C(6)H(4))-1,1'-mu-SiMeH-3,3'-Co(1,2-C(2)B(9)H(9))(2)](-) (9(-)) and [8,8'-mu-(1',2'-C(6)H(4))-1-SiMe(3)-3,3'-Co(1,2-C(2)B(9)H(9))(1',2'-C(2)B(9)H(10))](-) (10(-)) ions have been prepared from [8,8'-mu-(1',2'-C(6)H(4))-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (2(-)). Thus, depending on the chlorosilane, the temperature and the stoichiometry of nBuLi used, it has been possible to control the number of substituents on the C(c) atoms and the nature of the attached silyl function. All compounds were characterised by NMR and UV/Vis spectroscopy and MALDI-TOF mass spectrometry; [NMe(4)]-3, [NMe(4)]-4 and [NMe(4)]-7 were successfully isolated in crystalline forms suitable for X-ray diffraction analyses. The 4(-) and 8(-) ions, which contain one bridging -mu-SiMe(2) group between each of the dicarbollide clusters, were unexpectedly obtained from the reaction of the monolithium salts of 1(-) and 2(-), respectively, with Me(2)SiHCl at -78 degrees C in 1,2-dimethoxyethane. This suggests that an intramolecular reaction has taken place, in which the acidic C(c)-H proton reacts with the hydridic Si-H, with subsequent loss of H(2). Some aspects of this reaction have been studied by using DFT calculations and have been compared with experimental results. In addition, DFT theoretical studies at the B3 LYP/6-311G(d,p) level of theory were applied to optimise the geometries of ions 1(-)-10(-) and calculate their relative energies. Results indicate that the racemic mixtures, rac form, are more stable than the meso isomers. A good concordance between theoretical studies and experimental results has been achieved.     

Azatricarbaborane 7-t-Bu-arachno-7,1,5,12-NC3B8H12 and Parent Tricarbaboranes nido-[5,6,9-C3B7H10]- and -5,6,9-C3B7H11

The neutral azatricarbaborane 7-t-Bu-arachno-7,1,5,12-NC(3)B(8)H(12), isolated as a side product (yield 2%) from the new synthesis of 7-t-BuNH2-nido-7,8,9-C(3)B(8)H(10) (yield 70%), can be easily converted to the first parent representatives of the 10-vertex nido family of tricarbaboranes, [5,6,9-C(3)B(7)H(10)]- and 5,6,9-C(3)B(7)H(11).     

Chemistry of mangana- and rhenatricarbadecaboranyl tricarbonyl complexes: evidence for an associative mechanism of ligand substitution involving an eta6-eta4 cage-slippage process analagous to eta5-eta3-cyclopentadienyl ring-slippage

The reaction of the tricarbadecaboranyl anion, 6-Ph-nido-5,6,9-C(3)B(7)H(9)(-), with M(CO)(5)Br [M = Mn, Re] or [(eta(6)-C(10)H(8))Mn(CO)(3)(+)]BF(4)(-) yielded the half-sandwich metallatricarbadecaboranyl analogues of (eta(5)-C(5)H(5))M(CO)(3) [M = Mn, Re]. For both 1,1,1-(CO)(3)-2-Ph-closo-1,2,3,4-MC(3)B(7)H(9) [M = Mn (2) and Re (3)], the metal is eta(6)-coordinated to the puckered six-membered open face of the tricarbadecaboranyl cage. Reactions of 2 and 3 with isocyanide at room temperature produced complexes 8-(CNBu(t))-8,8,8-(CO)(3)-9-Ph-nido-8,7,9,10-MC(3)B(7)H(9) [M = Mn (4), Re (5)], having the cage eta(4)-coordinated to the metal. Photolysis of 4 and 5 then resulted in the loss of CO and the formation of 1-(CNBu(t))-1,1-(CO)(2)-2-Ph-closo-1,2,3,4-MC(3)B(7)H(9) [M = Mn, Re (6)], where the cage is again eta(6)-coordinated to the metal. Reaction of 2 and 3 with 1 equiv of phosphine at room temperature produced the eta(6)-coordinated monosubstituted complexes 1,1-(CO)(2)-1-P(CH(3))(3)-2-Ph-closo-1,2,3,4-MC(3)B(7)H(9) [M = Mn (7), Re (9)] and 1,1-(CO)(2)-1-P(C(6)H(5))(3)-2-Ph-closo-1,2,3,4-MC(3)B(7)H(9) [M = Mn (8), Re (10)]. NMR studies of these reactions at -40 degrees C showed that substitution occurs by an associative mechanism involving the initial formation of intermediates having structures similar to those of the eta(4)-complexes 4 and 5. The observed eta(6)-eta(4) cage-slippage is analogous to the eta(5)-eta(3) ring-slippage that has been proposed to take place in related substitution reactions of cyclopentadienyl-metal complexes. Reaction of 9 with an additional equivalent of P(CH(3))(3) gave 8,8-(CO)(2)-8,8-(P(CH(3))(3))(2)-9-Ph-nido-8,7,9,10-ReC(3)B(7)H(9) (11), where the cage is eta(4)-coordinated to the metal. Photolysis of 11 resulted in the loss of CO and the formation of the disubstituted eta(6)-complex 1-CO-1,1-(P(CH(3))(3))(2)-2-Ph-closo-1,2,3,4-ReC(3)B(7)H(9) (12).     

New palladium-catalyzed cross-coupling routes to carbon functionalized metallatricarbadecaboranes

A general method for the synthesis of cage-carbon-functionalized cyclopentadienyl iron and cyclopentadienyl ruthenium tricarbadecaboranyl complexes has been developed that employs palladium-catalyzed Sonogashira, Heck, and Stille cross-coupling reactions directed at a cage-carbon haloaryl substituent. The key Li(+)[6-(p-XC(6)H(4))-nido-5,6,9-C(3)B(7)H(9)(-)] (X = I (1), Br (2), Cl (3)) haloaryl-tricarbadecaboranyl anionic ligands were synthesized in high yields via the reaction of the arachno-4,6-C(2)B(7)H(12)(-) anion with the corresponding p-halobenzonitriles (p-XC(6)H(4)-CN). The reactions of the salts 1-3 with (η(5)-C(5)H(5))Fe(CO)(2)I and (η(5)-C(5)H(5))Ru(CH(3)CN)(3)PF(6) were then used to produce the haloaryl complexes 1-(η(5)-C(5)H(5))-2-(p-XC(6)H(4))-closo-1,2,3,4-MC(3)B(7)H(9) (M = Fe, X = I (4), Br (5), Cl (6) and M = Ru, X = I (7), Br (8), Cl (9)). The sonication-promoted Sonogashira coupling reactions of 4 with terminal alkynes catalyzed by Pd(dppf)(2)Cl(2)/CuI yielded the alkynyl-linked derivatives 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = (PhC≡C)- (10), (CH(3)CH(2)C(O)OCH(2)C≡C)- (11), ((η(5)-C(5)H(5))Fe(η(5)-C(5)H(4)C≡C))- (12)). Heck reactions of 4 with terminal alkenes catalyzed by Pd(OAc)(2) yielded the alkene-functionalized products 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = (PhCH(2)CH═CH)- (13), (CH(3)(CH(2))(2)CH═CH)- (14)), while the Stille cross-coupling reactions of 4 with organotin compounds catalyzed by Pd(PPh(3))(2)Cl(2) afforded the complexes 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = Ph- (15), (CH(2)═CH)- (16), (CH(2)═CHCH(2))- (17)). These reactions thus provide facile and systematic access to a wide variety of new types of functionalized metallatricarbadecaboranyl complexes with substituents needed for potential metallocene-like biomedical and/or optoelectronic applications.     

Silver as an exopolyhedral auxiliary to the rhenacarborane anion [Re(CO)3(eta5-7,8-C2B9H11)]-

The rhenacarborane salt Cs[Re(CO)3(eta5-7,8-C2B9H11)] (1) has been used to synthesize the tetranuclear metal complex [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-Ph2P(CH2)2PPh2]] (3) where two [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] fragments have been shown by X-ray crystallography to be bridged by a single 1,2-bis(diphenylphosphino)ethane ligand. Reaction of 1 with Ag[BF4] in the presence of the ligands bis- or tris(pyrazol-1-yl)methane yields the complexes [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa2-CH2(C3H3N2-1)2]] (4) or [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-kappa1,kappa2-CH(C3H3N2-1)3]] (5), respectively. From X-ray studies, the former comprises a Re-Ag bond bridged by the carborane cage and with the bis(pyrazol-1-yl)methane coordinating the silver(I) center in an asymmetric kappa(2) mode. Complex 5 was unexpectedly found to contain a tris(pyrazol-1-yl)methane bridging two [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] fragments in a kappa1,kappa2 manner. Treatment of 1 with Ag[BF4] in the presence of 2,2'-dipyridyl and 2,2':6',2' '-terpyridyl yields [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa2-(C5H4N-2)(2)]] (6) and [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa3-C5H3N(C5H4N-2)2-2,6]] (7). The X-ray structure determination of 7 revealed an unusual pentacoordinated silver(I) center, asymmetrically ligated by a kappa3-2,2':6',2' '-terpyridyl molecule. The same synthetic procedure using N,N,N',N'-tetramethylethylenediamine gave a tetranuclear metal complex [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-Me2N(CH2)2NMe2]2] (8) which is believed, in the solid state, to be bridged between the silver atoms by two of the diamine molecules. The salt 1 with Ag[BF4] in the absence of any added ligand gave the tetrameric cluster [ReAg[mu-5,6,10-(H)3-eta5-7,8-C2B9H8](CO)3]4 (9) where, in the solid state, four [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] units are held together by long interunit B-H right harpoon-up Ag bonds.     

Ten-vertex polyhedral azametallaborane chemistry: a unique nido-6,9 to nido-6,8-cluster isomerization

Reaction of the [arachno-4-NB(8)H(12)](-) anion with [RhCl(2)(eta(5)-C(5)Me(5))](2) in CH(2)Cl(2) at room temperature affords a mixture of red '6,9' isomer [9-(eta(5)-C(5)Me(5))-nido-6,9-NRhB(8)H(11)] () and its yellow '6,8' isomer, [8-(eta(5)-C(5)Me(5))-nido-6,8-NRhB(8)H(11)] (). Under the same conditions, reactions of with [IrCl(2)(eta(5)-C(5)Me(5))](2) and [RuCl(2)(eta(6)-MeC(6)H(4)-4-(iso)Pr)](2) give the '6,8' isomers, yellow [8-(eta(5)-C(5)Me(5))-nido-6,8-NIrB(8)H(11)] () and red [8-(eta(6)-MeC(6)H(4)-4-(iso)Pr)-nido-6,8-NRuB(8)H(11)] (), respectively. In contrast, [IrCl(PPh(3))(3)] yields orange [9,9-(PPh(3))(2)-9-H-nido-6,9-NIrB(8)H(11)] (), which exhibits the '6,9' configuration. Compound isomerizes quantitatively in solution to give . At high temperatures, compound gives the yellow '6,8' species, [8,8-(PPh(3))(2)-8-H-nido-6,8-NIrB(8)H(11)] (), in low yields. Possible mechanisms for the unprecedented 6,9 --> 6,8 isomerization are discussed.     

Palladium-Catalyzed Coupling of Ethynylated p-Carborane Derivatives: Synthesis and Structural Characterization of Modular Ethynylated p-Carborane Molecules

Methodology leading to a new class of rodlike p-carborane derivatives is described, involving the palladium-catalyzed coupling of B-iodinated p-carboranes with terminal alkynes. The products of these reactions contain an alkyne substituent at a boron vertex of the p-carborane cage. Reaction of closo-2-I-1,12-C(2)B(10)H(11) (1) with closo-2-(C&tbd1;CH)-1,12-C(2)B(10)H(11) (3) in the presence of pyrrolidine and catalytic quantities of bis(triphenylphosphine)palladium dichloride and cupric iodide yields 1,2-(closo-1',12'-C(2)B(10)H(11)-2'-yl)(2) acetylene (4). Oxidative coupling of 3 in the presence of cupric chloride in piperidine affords 1,4-(closo-1',12'-C(2)B(10)H(11)-2'-yl)(2)-1,3-butadiyne (5). Reaction of 2 molar equiv. of closo-2,9-I(2)-1,12-C(2)B(10)H(10) (6) withcloso-2,9-(C&tbd1;CH)(2)-1,12-C(2)B(10)H(10) (7) in the presence of pyrrolidine and catalytic quantities of bis(triphenylphosphine)palladium dichloride and cupric iodide yields closo-2,9-(closo-2'-I-9'-C&tbd1;C-1',12'-C(2)B(10)H(10))(2)-1,12-C(2)B(10)H(10) (8), a rigid, iodine-terminated carborod trimer in which the p-carborane cages are linked at the 2 and 9 B-vertices by alkyne (C&tbd1;C) bridges. The molecular structures of 5 and the previously described closo-2,9-(C&tbd1;CSiMe(3))(2)-1,12-C(2)B(10)H(10) (9) have been determined by X-ray crystallography. Crystallographic data are as follows: for 5, monoclinic, space group P2/a, a = 12.352(6) ?, b = 14.169 (6) ?, c = 12.384(5) ?, beta = 109.69(2) degrees, V = 2041 ?(3), Z = 4, R = 0.098, R(w)( )()= 0.135; for 9, monoclinic, space group C2/m, a = 22.111(4) ?, b = 7.565(2) ?, c = 6.943(2) ?, beta = 107.871(8) degrees, V = 1105 ?(3), Z = 2, R = 0.059, R(w)( )()= 0.090.     

Direct and facile synthesis of carbon substituted alkylhydroxy derivatives of cobalt bis(1,2-dicarbollide), versatile building blocks for synthetic purposes

Reactions of lithiated cobalt bis(1,2-dicarbollide)(1(-)) anion (1(-)) in presence of paraformaldehyde, ethylene oxide or trimethylene oxide led to the substitution of 1(-) at the C-atoms resulting in the high yield formation of monosubstituted alkylhydroxy derivatives [(1-HO(CH(2))(n)-1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))-3,3'-Co(III)](-) (n = 1-3) isolated as caesium salts (Cs2, Cs3, Cs4) along with disubstituted products of general formulation [(HO(CH(2))(n)-1,2-C(2)B(9)H(10))(2)-3,3'-Co(III)](-) (n = 1-3) (Cs5, Cs6 and Cs7). Disubstituted compounds are in fact a mixture of diastereoisomers denoted as 1,1'-anti(rac-), 1,2'-syn- and in case of Cs6 and Cs7 also 1,2-vicinal-isomer, from which only the anti-isomer could be isolated in pure form in case of shorter chain compounds Cs5 and Cs6. All these alkylhydroxy derivatives can serve as versatile precursors for the generation of a variety of functional molecules. Thus, reaction of Me(3)NH4 with NaH and one equivalent of POCl(3) provided after hydrolysis the phosphorylated [(1-(HO)(2)P(O)OC(3)H(6)-1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))-3,3'-Co(III)](-) derivative, isolated in the form of trimethylammonium salt, Me(3)NH8 as the main product whereas reaction with half of the equivalent produces a high yield of phosphoric acid diester (Me(3)NH)(2)9 comprising in its structure two cages connected via propyl spacers to the central part. The calcium salt Ca(10)(2) of bridged ion [μ-(HOP(O)(OC(3)H(6))(2))-(1,2-C(2)B(9)H(10))(2)-3,3'-Co(III)](-) resulted from reaction of Me(3)NH7 with NaH and one equivalent of POCl(3) followed by hydrolysis and addition of CaCl(2). All new compounds were characterized by multinuclear NMR spectroscopy and mass spectrometry and the structure of Me(3)NH3 and that of the respective salts of the pure anti-stereoisomer of dialkylhydroxy derivatives Cs5 and Me(3)NH6 were established by X-ray crystallography.     

Dimethylsulfide-dicarbaborane chemistry. Isolation and characterisation of isomers [9-(SMe2)-nido-7,8-C2B9H10-X-Me] (where X = 1, 2, 3 and 4) and some related compounds. An unusual skeletal rearrangement

Oxidative coupling by FeCl(3) of the [nido-7,8-C(2)B(9)H(11)-9-Me](-) anion 1a with SMe(2) yields a mixture of four isomers of 9-(SMe(2))-nido-7,8-C(2)B(9)H(10)-X-Me, where X = 1, 2, 3 and 4 (compounds 2a, 2b, 2c and 2d respectively). On high dilution of the reaction mixture, the 9-(SMe(2))-nido-7,8-C(2)B(9)H(10)-10-Me 2e isomer is also isolated in a low yield. The isomers are separated by HPLC, and are identified and characterised by NMR spectroscopy and by single-crystal X-ray diffraction analyses of 2c and 2d. The formation of the products implies an unexpected cluster rearrangement, which is discussed in terms of dsd and vertex-flip reaction pathways. Two additional isomers, 9-(SMe(2))-nido-7,8-C(2)B(9)H(10)-5-Me 2f and 9-(SMe(2))-nido-7,8-C(2)B(9)H(10)-6-Me 2g occur when [nido-7,8-C(2)B(9)H(11)-5-Me](-) 1b is used as the starting substrate, in a reaction in which no cluster rerarrangement is observed. The corresponding bromide, [nido-7,8-C(2)B(9)H(11)-5-Br](-) 1c, behaves similarly, forming only 9-(SMe(2))-nido-7,8-C(2)B(9)H(10)-5-Br 2h and 9-(SMe(2))-nido-7,8-C(2)B(9)H(10)-6-Br 2i.     

The [2,5,12-C3B8H15]- anion, the first representative of the eleven-vertex hypho family of tricarbaboranes

In one synthetic step from the readily available 9-Me(2)SCH(2)-nido-7,8-C(2)B(9)H(11) (compound 1), the first representative of the eleven-vertex hypho family of tricarbaboranes, [2,5,12-C(3)B(8)H(15)][X] (X=[NMe4]+ or [PPh4]+) (compound 2), has been isolated in 32% yield and structurally characterised by single-crystal X-ray diffraction, multi-nuclear NMR spectroscopy, mass spectrometry, and computational methods. Both [NMe4]+ or [PPh4]+ salts of anion 2 were found to undergo degradative conversion to the [hypho-6,7-C(2)B(6)H(13)]- anion (anion 3) in alkaline medium. The [PPh4]+ salt of anion 2 converted quantitatively to the [6-CH3-arachno-5,10-C(2)B(8)H(12)]- anion (anion 4) if passed through a silica column or to the neutral 5-CH3-arachno-6,9-C(2)B(8)H(13) (compound 5) on treatment of its [NMe4]+ salt with dilute HCl. Moreover, the reaction of compound 2 with [RhCl2(C(5)Me(5))]2 afforded the eleven-vertex ruthenadicarbaborane [1-C(5)Me(5)-4-CH(3)-closo-1,2,3-RhC(2)B(8)H(9)] (compound 8). All these reactions resulted in an extrusion of one of the cluster carbon atoms into an exoskeletal position.     

Carboracycles: Macrocyclic Compounds Composed of Carborane Icosahedra Linked by Organic Bridging Groups

A family of macrocyclic compounds are described, together with their precursors. These cycles are composed of icosahedral carboranes linked via their carbon vertices through 1,3-trimethylene, alpha,alpha'-1,3-xylylene, or alpha,alpha'-2,6-lutidylene groups. The compounds cyclo-(1,3-trimethylene-1',2'-closo-1',2'-C(2)B(10)H(10))(4) (6a), cyclo-(1,3-trimethylene-1',2'-closo-9',12'-dimethyl-1',2'-C(2)B(10)H(8))(4) (6b), cyclo-(1,3-trimethylene-1',2'-closo-1',2'-C(2)B(10)H(10))(3) (9), cyclo-(alpha,alpha'-1,3-xylylene-1',2'-closo-1',2'-C(2)B(10)H(10))(2) (11a), cyclo-(alpha,alpha'-1,3-xylylene-1',7'-closo-1',7'-C(2)B(10)H(10))(2) (11b), cyclo-(alpha,alpha'-1,3-xylylene-1',7'-closo-9',10'-dimethyl-1,7-C(2)B(10)H(8))(2) (11c), cyclo-(alpha,alpha'-1,3-xylylene-1',2'-closo-1',2'-C(2)B(10)H(10))(4) (12), cyclo-(alpha,alpha'-1,3-xylylene-1',7'-closo-1',7'-C(2)B(10)H(10))(3) (13), cyclo-(alpha,alpha'-2,6-lutidylene-1',7'-closo-1',7'-C(2)B(10)H(10))(2) (19), and cyclo-(alpha,alpha'-2,6-lutidylene N-oxide-1',7'-closo-1',7'-C(2)B(10)H(10))(2) (20) have been synthesized. The structures of 6a, 6b, 9, 11a, 11b, 11c, 12, and 19 have been determined by X-ray crystallography. Crystal data: for 6a, triclinic, space group P&onemacr;, a = 11.131(2) ?, b = 12.642(2) ?, c = 12.996(2) ?, alpha = 84.383(6) degrees, beta = 65.884(6) degrees, gamma = 97.292(5) degrees, Z = 1, R = 0.079; for 6b, monoclinic, space group P2(1)/a, a = 13.500(2) ?, b = 31.141(3) ?, c = 13.831(2) ?, beta = 99.90(1) degrees, Z = 2, R = 0.097; for 11a, monoclinic, space group C2/c, a = 14.5682(8) ?, b = 14.5046(8) ?, c = 16.1998(8) ?, beta = 95.631(2) degrees, Z = 4, R = 0.081; for 11b, monoclinic, space group P2(1)/n, a = 11.650(2) ?, b = 10.606(2) ?, c = 11.730(2) ?, beta = 104.951(6) degrees, Z = 2, R = 0.069; for 11c, orthorhombic, space group Pbca, a = 12.532(2) ?, b = 14.271(2) ?, c = 18.143(3) ?, Z = 4, R = 0.076; for 19, orthorhombic, space group Pcab (No. 61, standard setting Pbca), a = 11.0428(6) ?, b = 11.3785(6) ?, c = 22.533(1) ?, Z = 4, R = 0.074.     

Enantioselective self-assembly of bimetallic [Mn(II) (delta)-Cr(III)(C2O4)3]- and [Mn(II) (lambda)-Cr(III)(C2O4)3]- layered anionic networks templated by the optically active (Rp)- and (Sp)-[1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5]+ ions

The ferrocenic ammonium (Rp)- and (Sp)-[1-CH2NR(3-)-2-CH3-C5H3Fe-C5H5] iodide salts with R=CH3, C2H5, n-C3H7, n-C4H9, were synthesized starting from the (Rp)- and (Sp)-[1-CH2N(CH3)2-2-CH3-C5H3Fe-C5H5] amines obtained in their optically active forms through asymmetric cyclopalladation of [C5H5Fe-C5H4CH2N(CH3)2]. 1H NMR studies of these planar chiral 1,2-disubstituted ferrocenic ammonium iodide salts in the presence of the (Delta)-(tris(tetrachlorobenzenediolato)phosphate(V) anion), [(Delta)-Trisphat] support the formation of specific diastereomeric ion pairs. Such intermolecular interactions can be related to the self-assembly of the two-dimensional optically active compounds [[(Sp)-1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5][Mn (Delta)-Cr(C2O4)3]] and [[(Rp)-1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5][Mn (Lambda)-Cr(C2O4)3]] starting from the resolved (Rp)- and (Sp)-[1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5]+ ion associated to the racemic anionic building block rac-[Cr(C2O4)3]3- and Mn2+. Both enantiomeric forms of the networks behave as ferromagnets with a Curie temperature of 5.7 K.     

Metallacarboranes as building blocks for polyanionic polyarmed aryl-ether materials

Polyanionic species have been obtained in high yield by a new route in the ring-opening reaction of cyclic oxonium [3,3'-Co(8-C4H8O2-1,2-C2B9H10)(1',2'-C2B9H11)] (2) by using carboxylic acids, Grignard reagents, and thiocarboranes as nucleophiles. The crystal structures of Na3(H2O)(C2H5OH)[1',3',5'-{3,3'-Co(8-O(CH2CH2O)2-1,2-C2B9H10)(1',2'-C2B9H11)}3-C6H3] and Na(H2O)[3,3'-Co(8-O(CH2CH2O)2C(O)CH3-1,2-C2B9H10)(1',2'-C2B9H11)] show that the chain contributes three or two oxygen atoms for coordination to Na(+), and interestingly, the [3,3'-Co(1,2-C2B9H11)2](-) moiety provides extra B-H coordination sites. These B-H...Na interactions in the solid state have also been confirmed by dynamic NMR studies in solution. These new polyanionic compounds that contain multiple carborane or metallacarborane clusters at their periphery may prove useful as new classes of boron neutron capture therapy compounds with enhanced water solubility and as a core to make a new class of dendrimers.     

Syntheses, characterizations, and coordination chemistry of the 10-vertex phosphadicarbaboranes 6-R-arachno-6,8,9-PC2B7H11 and 6-R-arachno-6,5,7-PC2B7H11

The 10-vertex phosphadicarbaboranes, 6-R-arachno-6,8,9-PC(2)B(7)H(11) (1) (R = Ph 1a or Me 1b) and 6-R-arachno-6,5,7-PC(2)B(7)H(11) (2) (R = Ph 2a or Me 2b) have been synthesized using in situ dehydrohalogenation reactions of RPCl(2) (R = Ph or Me) with the arachno-4,5-C(2)B(7)H(13) and arachno-4,6-C(2)B(7)H(13) carboranes, respectively. X-ray crystallographic determinations in conjunction with DFT/GIAO/NMR calculations and NMR spectroscopic studies have established that both 1 and 2 have open cage structures based on an icosahedron missing two vertexes. The two isomeric compounds differ in the positions of the carbons and bridging hydrogens on the open face. Studies of the reactions of 2a with BH(3).THF, S(8), and hydrogen peroxide demonstrated that 2a shows strong donor properties yielding the compounds endo-6-H(3)B-exo-6-Ph-arachno-6,5,7-PC(2)B(7)H(11) (3), endo-6-S-exo-6-Ph-arachno-6,5,7-PC(2)B(7)H(11) (4), and endo-6-O-exo-6-Ph-arachno-6,5,7-PC(2)B(7)H(11) (5) in which the BH(3), S, and O substitutents are bonded to an electron lone pair localized at the phosphorus endo-position. The reaction of 2a with an excess of S(8) results in the loss of a framework boron to produce the unique open-cage compound micro(7,8)-[HS(Ph)P]-hypho-7,8-C(2)B(6)H(11) (6). 2a also formed the donor complexes cis-(eta(1)-[6-Ph-arachno-6,5,7-PC(2)B(7)H(11)])(2)PtBr(2) (7) and trans-(eta(1)-[6-Ph-arachno-6,5,7-PC(2)B(7)H(11)])(2)PdBr(2) (8) in which the metal fragment is bonded in an eta(1)-fashion at the phosphorus endo-position. In these complexes, 2a is functioning as a two-electron sigma donor to the metals and can thus be considered as an analogue of the PR(3) ligands in the classical cis-(PPh(3))(2)PtBr(2) and trans-(PPh(3))(2)PdBr(2) coordination complexes. Although 1a did not show the donor properties exhibited by 2a, its dianion 6-Ph-6,8,9-PC(2)B(7)H(9)(2)(-) (1a(2)()(-)()) readily formed eta(4)-coordinated complexes with late transition metals including 8-Ph-7-(Ph(3)P)(2)-nido-7,8,10,11-PtPC(2)B(7)H(9) (9), 7-Ph-11-(eta(5)-C(5)H(5))-nido-11,7,9,10-CoPC(2)B(7)H(9) (10), and commo-Ni-(7-Ni-8'-Ph-nido-8',10',11'-PC(2)B(7)H(9))(7-Ni-8-Ph-nido-8,10,11-PC(2)B(7)H(9)) (11).     

Synthesis and characterization of cyano-substituted carborane-based compounds. Molecular structure of [1-(4-C7H7)-12-(C5H3-3-(CN)-3,4-(CH3)2)-C2B10H10

The reaction of cyanogen chloride with [1-(4-C(7)H(7))-12-(C(5)H(3)-3,4-(CH(3))(2))-C(2)B(10)H(10)] (7) was found to yield two new C(5)-substituted carborane cluster-based compounds, [1-(4-C(7)H(7))-12-(C(5)H(2)-3-(CN)-3,4-(CH(3))(2))-C(2)B(10)H(10)] (8) and [1-(4-C(7)H(7))-12-(C(5)H-2,4-(CN)(2)-3,4-(CH(3))(2))-C(2)B(10)H(10)] (9). This cyano-substitution pattern is in contrast to the known substitution for the analogous organic quinarene[5.6.7] system. The observed unique cluster-based products may be understood by a combination of steric and electronic effects. Compounds 8 and 9 were characterized by complete multinuclear NMR, (1)H-(1)H COSY NMR, (1)H-(13)C HMQC NMR, FTIR, UV-Vis, IR, MS data and a single crystal analysis for 8 [X-ray data for 8: C(17)H(25)B(10)N, monoclinic, space group P2(1)/n with cell constants a = 8.6794(17) ?, b = 11.021(2) ?, c = 43.175(9) ?, β = 91.00(3)°, V = 4129.2(14) ?(3), Z = 8, R(1) = 0.0729, wR(2) = 0.1464].     

Syntheses and structural characterizations of endo-eta(1)-, exo-eta(1)-, eta(4)-, eta(5)-, and eta(6)-metallaphosphamonocarbaborane complexes derived from a versatile new polyborane ligand: exo-6-R-arachno-6,7-PCB(8)H(12)

Deprotonation of the phosphamonocarbaborane, exo-6-R-arachno-6,7-PCB(8)H(12) (R = Ph 1a or Me 1b), yields exo-6-R-arachno-6,7-PCB(8)H(11)(-), which when reacted with appropriate transition-metal reagents affords new metallaphosphamonocarbaborane complexes in which the metals adopt endo-eta(1), exo-eta(1), eta(4), eta(5), or eta(6) coordination geometries bonded to the formal R-arachno-PCB(8)H(11)(-), R-arachno-PCB(8)H(10)(2-), R-arachno-PCB(8)H(9)(3-), or R-nido-PCB(8)H(9)(-) ligands. The reaction of exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11)(-) (1a-) with Mn(CO)(5)Br generated the eta(1)-sigma product exo-6-[Mn(CO)(5)]-endo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11) (2) having the [Mn(CO)(5)] fragment in the thermodynamically favored exo position at the P6 cage atom. On the other hand, reaction of 1a- with (eta(5)-C(5)H(5))Fe(CO)(2)I resulted in the formation of two products, an eta(1)-sigma complex endo-6-[(eta(5)-C(5)H(5))Fe(CO)(2)]-exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11) (3) having the (eta(5)-C(5)H(5))Fe(CO)(2) fragment attached at the endo-P6 position and an eta(6)-closo complex, 1-(eta(5)-C(5)H(5))-2-(C(6)H(5))-closo-1,2,3-FePCB(8)H(9) (4a). Rearrangement of the endo-compound 3 to its exo-isomer 5 was observed upon photolysis of 3. Synthesis of the methyl analogue of 4a, 1-(eta(5)-C(5)H(5))-2-CH(3)-closo-1,2,3-FePCB(8)H(9) (4b), along with a double-insertion product, 1-CH(3)-2,3-(eta(5)-C(5)H(5))(2)-2,3,1,7-Fe(2)PCB(8)H(9) (6), containing two iron atoms eta(5)-coordinated to a formal R-arachno-PCB(8)H(9)(3-), was achieved by reaction of exo-6-CH(3)-arachno-6,7-PCB(8)H(11)(-) (1b-) with FeCl(2) and Na(+)C(5)H(5)(-). Complexes 4a and 4b can be considered ferrocene analogues, in which an Fe(II) is sandwiched between C(5)H(5)(-) and 6-R-nido-6,9-PCB(8)H(9)(-) anions. Reaction of exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11)(-) (1a-) with cis-dichlorobis(triphenylphosphine)platinum (II) afforded two compounds, an eta(1)-sigma complex with the metal fragment again in the endo-P6 position, endo-6-[cis-(Ph(3)P)(2)PtCl]-exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11) (7) and an eta(4)-complex, 7-(C(6)H(5))-11-(Ph(3)P)(2)-nido-11,7,8-PtPCB(8)H(10) (8) containing the formal R-arachno-PCB(8)H(10)(2)(-) anion. The structures of compounds 2, 3, 4a, 4b, 6, 7, and 8 were crystallographically confirmed.     

Preparations, structures, and electrochemical studies of aryldiazene complexes of rhenium: syntheses of the first heterobinuclear and heterotrinuclear derivatives with bis(diazene) or bis(diazenido) bridging ligands

The mono- and binuclear aryldiazene complexes [Re(C6H5N=NH)(CO)5-nPn]BY4 (1-5) and [(Re(CO)5-nPn)2-(mu-HN=NAr-ArN=NH)](BY4)2 (6-12) [P = P(OEt)3, PPh(OEt)2, PPh2OEt; n = 1-4; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-(2-CH3)C6H3-C6H3(2-CH3), 4,4'-C6H4-CH2-C6H4; Y = F, Ph) were prepared by reacting the hydride species ReH(CO)5-nPn with the appropriate mono- and bis(aryldiazonium) cations. These compounds, as well as other prepared compounds, were characterized spectroscopically (IR; 1H, 31P, 13C, and 15N NMR data), and 1a was also characterized by an X-ray crystal structure determination. [Re(C6H5N=NH)(CO)(P(OEt)3)4]BPh4 (1a) crystallizes in space group P1 with a = 15.380(5) A, b = 13.037(5) A, c = 16.649(5) A, alpha = 90.33(5) degrees, beta = 91.2(1) degrees, gamma = 89.71(9) degrees, and Z = 2. The "diazene-diazonium" complexes [M(CO)3P2(HN=NAr-ArN identical to N)](BF4)2 (13-15, 17) [M = Re, Mn; P = PPh2OEt, PPh2OMe, PPh3; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4] and [Re(CO)4(PPh2OEt)(4,4'-HN=NC6H4-C6H4N identical to N)](BF4)2 (16b) were synthesized by allowing the hydrides MH(CO)3P2 or ReH(CO)4P to react with equimolar amounts of bis(aryldiazonium) cations under appropriate conditions. Reactions of diazene-diazonium complexes 13-17 with the metal hydrides M2H2P'4 and M2'H(CO)5-nP"n afforded the heterobinuclear bis(aryldiazene) derivatives [M1(CO)3P2(mu-HN=NAr-ArN=NH)M2HP'4](BPh4)2 (ReFe, ReRu, ReOs, MnRu, MnOs) and [M1(CO)3P2(mu-HN=NAr-ArN=NH)M2'(CO)5-nP"n](BPh4)2 (ReMn, MnRe) [M1 = Re, Mn; M2 = Fe, Ru, Os; M2' = Mn, Re; P = PPh2OEt, PPh2OMe; P',P" = P(OEt)3, PPh(OEt)2; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4; n = 1, 2]. The heterotrinuclear complexes [Re(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N=NH)M(P(OEt)3)4(mu-4,4'-HN=NC6H4- C6H4N=NH)Mn(CO)3(PPh2OEt)2](BPh4)4 (M = Ru, Os) (ReRuMn, ReOsMn) were obtained by reacting the heterobinuclear complexes ReRu and ReOs with the appropriate diazene-diazonium cations. The heterobinuclear complex with a bis(aryldiazenido) bridging ligand [Mn(CO)2(PPh2OEt)2(mu-4,4'-N2C6H4-C6H4N2)Fe(P(OEt)3)4]BPh4 (MnFe) was prepared by deprotonating the bis(aryldiazene) compound [Mn(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N=NH)Fe(4- CH3C6H4CN)(P(OEt)3)4](BPh4)3. Finally, the binuclear compound [Re(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N2)Fe(CO)2(P(OPh)3)2](BPh4)2 (ReFe) containing a diazene-diazenido bridging ligand was prepared by reacting [Re(CO)3(PPh2OEt)2(4,4'-HN=NC6H4-C6H4N identical to N)]+ with the FeH2(CO)2(P(OPh)3)2 hydride derivative. The electrochemical reduction of mono- and binuclear aryldiazene complexes of both rhenium (1-12) and the manganese, as well as heterobinuclear ReRu and MnRu complexes, was studied by means of cyclic voltammetry and digital simulation techniques. The electrochemical oxidation of the mono- and binuclear aryldiazenido compounds Mn(C6H5N2)(CO)2P2 and (Mn(CO)2P2)2(mu-4,4'-N2C6H4-C6H4N2) (P = PPh2OEt) was also examined. Electrochemical data show that, for binuclear compounds, the diazene bridging unit allows delocalization of electrons between the two different redox centers of the same molecule, whereas the two metal centers behave independently in the presence of the diazenido bridging unit.     

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). The clusters with an exo-cluster bridging BH(2) groups are shown to be intermediates by demonstrating that the major products 5 and 6 rearrange to 13 and convert to 14, respectively. 14 then isomerizes to 15, thus connecting low- and high-temperature products. Finally, all available information shows that the high reactivity of 1 with alkynes can be associated with the "extra" two Ru-H hydrides on the framework of 1 which are required to meet the nido-cluster electron count.     

Synthesis and characterization of novel monocarbollide exo-closo-(pi-arene)biruthenacarboranes [(PPh3)mClRu(eta6-C6H5R)Ru'CB10H11-n(OMe)n] (where R = H, m = 2, n = 1; R = mu-PPh2, m = 1, n = 0, 1)

The monocarbon carborane [Cs][nido-7-CB(10)H(13)] reacts with the 16-electron [RuCl(2)(PPh(3))(3)] in a solution of benzene/methanol in the presence of N,N,N',N'-tetramethylnaphthalene-1,8-diamine as the base to give a series of 12-vertex monocarbon arene-biruthenacarborane complexes of two types: [closo-2-[7,11-exo-RuClPPh(3)(mu,eta(6)-C(6)H(5)PPh(2))]-7,11-(mu-H)(2)-2,1-RuCB(10)H(8)R] (5, R = H; 6, R = 6-MeO; 7, R = 3-MeO) and [closo-2-(eta(6)-C(6)H(6))-10,11,12-[exo-RuCl(PPh(3))(2)]-10,11,12-(mu-H)(3)-2,1-RuCB(10)H(7)R(1)] (8a, R(1) = 6-MeO; 8b, R(1) = 3-MeO, inseparable mixture of isomers) along with trace amounts of 10-vertex mononuclear hypercloso/isocloso-type complexes [2,2-(PPh(3))(2)-2-H-3,9-(MeO)(2)-2,1-RuCB(8)H(7)] (9) and [2,5-(Ph(3)P)-2-Cl-2-H-3,9-(MeO)(2)-2,1-RuCB(8)H(6)] (10). Binuclear ruthenacarborane clusters of both series were characterized by a combination of analytical and multinuclear NMR spectroscopic data and by single-crystal X-ray diffraction studies of three selected complexes, 6-8. In solution, isomers 8a,b have been shown to undergo the isomerization process through the scrambling of the exo-[RuCl(PPh(3))(2)] fragment about two adjacent triangular cage boron faces B(7)B(11)B(12) and B(8)B(9)B(12).