Tellurium-bridged manganese carbonyl clusters: synthesis and structural transformations of [Te4Mn3(CO10]-, [Te2Mn3(CO)9]2-, [Te2Mn3(CO)9]-, and [Te2Mn4(CO)12]2-

The reactions of appropriate ratios of K2TeO3 and [Mn2(CO)10)] in superheated methanol solutions lead to a series of novel cluster anions [Te4Mn3(CO)10] (1), [Te2Mn3(CO)9]2- (2), [Te2Mn3(CO)9]- (3), and [Te2Mn4(CO)12]2- (4). When cluster 1 is treated with [Mn2(CO)10]/KOH in methanol, paramagnetic cluster 2 is formed in moderate yield. Cluster 2 is oxidized by [Cu(MeCN)4]BF4 to give the closo-cluster [Te2Mn3(CO)9]- (3), while treatment of 2 with [Mn2(CO)10]/KOH affords the closo-cluster 4. IR spectroscopy showed that cluster 1 reacted with [Mn2(CO)10] to give cluster 4 via cluster 2. Clusters 1-4 were structurally characterized by spectroscopic methods or/and X-ray analyses. The core structure of 1 can be described as two [Mn(CO)3] groups doubly bridged by two Te2 fragments in a mu2-eta2 fashion. Both [Mn(CO)3] groups are further coordinated to one [Mn(CO)4] moiety. Cluster 2 is a 49 e- species with a square-pyramidal core geometry. While cluster 3 displays a trigonal-bipyramidal metal core, cluster 4 possesses an octahedral core geometry.     

Syntheses and reactivity studies of solvated dirhenium acetonitrile complexes

Fully and partially solvated triply-bonded [Re2]4+ complexes have been synthesized and their X-ray structures are described. A fully solvated dirhenium salt with BArf [tetrakis(3,5-bis(trifluoromethyl)phenyl)borate] as the counter anion [Re2(CH3CN)10][BArf]4 () has been characterized. The solubility of the complex in CH2Cl2 and THF in addition to CH3CN offers the possibility of improved reactivity. The structure of [Re2(micro-O)(CH3CN)10][BF4]4 () that possesses a linear [Re(III)-O-Re(III)]4+ unit is reported. Protonation reactions of cis-Re2Cl2(dppm)2(O2CCH3)2 and trans-Re2Cl4(dppm)2 with HBF4.Et2O in acetonitrile afforded cis and trans [Re2(dppm)2(CH3CN)6][BF4]4 ( and ), respectively. Prolonging the reaction time, however, does not lead to fully solvated complex [Re2(CH3CN)10][BF4]4. The neutral nitrogen donor ligands pynp (2-(2-pyridyl)-1,8-naphthyridine) and tznp (2-(2-thiazolyl)-1,8-naphthyridine) react readily with [Re2(CH3CN)10][BF4]4 to provide trans-[Re2(pynp)2(CH3CN)4][BF4]4 and trans-[Re2(tznp)2(CH3CN)4][BF4]4. The X-ray structures trans-[Re2(pynp)2(CH3CN)4][BF4]4 () and trans-[Re2(tznp)2(CH3CN)4][BF4]3[PF6] () have been determined.     

Borane reaction chemistry. Alkyne insertion reactions into boron-containing clusters. Products from the thermolysis of [6,9-(2-HC[triple bond]C-C5H4N)2-arachno-B10H12

The stirring of [ortho-(HC[triple bond]C)-C(5)H(4)N] with [nido-B(10)H(14)] in benzene affords [6,9-{ortho-(HC[triple bond]C)-C(5)H(4)N}(2)-arachno-B(10)H(12)] 1 in 93% yield. In the solid state, 1 has an extended complex three-dimensional structure involving intramolecular dihydrogen bonding, which accounts for its low solubility. Thermolysis of 1 gives the known [1-(ortho-C(5)H(4)N)-1,2-closo-C(2)B(10)H(11)] 2 (13%), together with new [micro-5(N),6(C)-(NC(5)H(4)-ortho-CH(2))-nido-6-CB(9)H(10)] 3 (0.4%), [micro-7(C),8(N)-(NC(5)H(4)-ortho-CH(2))-nido-7-CB(10)H(11)] (0.4%) , 4 binuclear [endo-6'-(closo-1,2-C(2)B(10)H(10))-micro-(1(C),exo-6'(N))-(ortho-C(5)H(4)N)-micro-(exo-8'(C),exo-9'(N))-(ortho-(CH(2)CH(2))-C(5)H(4)N)-arachno-B(10)H(10)] (0.5%) 5, and [exo-6(C)-endo-6(N)-(ortho-(CH[double bond]CH)-C(5)H(4)N)-exo-9(N)-(ortho-(HC[triple bond]C)-C(5)H(4)N)-arachno-B(10)H(11)] 6. An improved solvent-free route to 2 is also presented. This set of compounds features an increasing cluster incorporation of the ethynyl moiety, initially by an effective internal hydroboration, affording an arachno to nido and then a nido to arachno:closo sequence of cluster geometry. An alternative low-temperature route to internal hydroboration is demonstrated in the room temperature reaction of [closo-B(11)H(11)][N(n)Bu(4)](2) with CF(3)COOH and [ortho-(HC[triple bond]C)-C(5)H(4)N], which gives [micro-1(C),2(B)-[ortho-C(5)H(4)N-CH(2)]-closo-1-CB(11)H(10)] 7 (40%) in which one carbon atom is incorporated into the cluster; a similar reaction with [ortho-(N[triple bond]C)-C(5)H(4)N] affords [N(n)Bu(4)][7-(ortho-N[triple bond]C-C(5)H(4)N)-nido-B(11)H(12)], 8 (68%) and stirring [ortho-(N[triple bond]C)-C(5)H(4)N] with [nido-B(10)H(14)] quantitatively affords the cyano analogue of 1, [6,9-{ortho-(N[triple bond]C)-C(5)H(4)N}(2)-arachno-B(10)H(12)] 9. All compounds were characterised by single-crystal X-ray diffraction analysis and NMR spectroscopy.     

Assembly of a new family of mercury(II) zwitterionic thiolate complexes from a preformed compound [Hg(Tab)2](PF6)2 [Tab = 4-(trimethylammonio)benzenethiolate

Reactions of Hg(OAc)2 with 2 equiv of TabHPF6 [TabH = 4-(trimethylammonio)benzenethiol] in MeCN/MeOH afforded a mononuclear linear complex [Hg(Tab)2](PF6)2 (1). By using 1 as a precursor, a new family of mercury(II) zwitterionic thiolate complexes, [Hg2(Tab)6](PF6)4.2MeCN (2.2MeCN), [Hg(Tab)2(SCN)](PF6) (3), [Hg(Tab)2(SCN)2] (4), [Hg(Tab)I2] (5), {[Hg(Tab)2]4[HgI2][Hg2I6]}(PF6)2(NO3)4 (6), [Hg(Tab)2][HgI4] (7), [Hg(Tab)2][HgCl2(SCN)2] (8), [Tab-Tab]2[Hg3Cl10] (9), and [Hg2(Tab)6]3(PF6)Cl11 (10), were prepared and characterized by elemental analysis, IR spectra, UV-vis spectra, 1H NMR, and single-crystal X-ray crystallography. The [Hg2(Tab)6]4+ tetracation of 2 or 10 contains an asymmetrical Hg2S2 rhomb with an inversion center lying on the midpoint of the Hg...Hg line. The Hg atom of the [Hg(Tab)2]2+ dication of 3 is coordinated to one SCN-, forming a rare T-shaped coordination geometry, while in 4, the Hg atom of [Hg(Tab)2]2+ is coordinated to two SCN-, forming a seesaw-shaped coordination geometry. Through weak secondary Hg...S coordinations, each cation in 3 is further linked to afford a one-dimensional zigzag chain. The trigonal [Hg(Tab)I2] molecules in 5 are held together by weak secondary Hg...I and Hg...S interactions, forming a one-dimensional chain structure. In 6, the four [Hg(Tab)2]2+ dications, one HgI2 molecule, one [Hg2I6]2- dianion, one PF6-, and four NO3- anions are interconnected by complicated secondary Hg...I and Hg...O interactions, forming a scolopendra-like chain structure. The secondary Hg...I interactions, [Hg(Tab)2]2+ and [HgI4]2- in 7, are combined to generate a one-dimensional chain structure, while [Hg(Tab)2]2+ and [HgCl2(SCN)2]2- in 8 are interconnected by secondary Hg...N interactions to form a one-dimensional zigzag chain structure. Compound 9 consists of two [Tab-Tab]2+ dications and one [Hg3Cl10]4- tetraanion. The facile approach to the construction of 2-8 and 10 from 1 may be applicable to the mimicking of a coordination sphere of the Hg sites of metallothioneins.     

A novel bornane synthesis by an old idea

Aiming at a synthesis of spiro[2.4]hepta-4,6-dienes with a carbon substituent at C-4, we investigated solvolysis reactions of the thiatricycle 2, obtained from spiro[2.4]hepta-4,6-diene (1) and thiophosgene by [4 + 2] cycloaddition. With methanol or ethanol a mixture of the esters 7 and 8 was formed. Desulfurization of the thionoesters 8 gave methyl and ethyl spiro[2.4]hepta-4,6-diene-4-carboxylate (10a,b). The corresponding alcohol (11) was prepared from 10b by LiAlH(4) reduction. Ethenetetracarbonitrile combined with the 4-substituted spiro[2.4]hepta-4,6-dienes to give the [4 + 2] cycloadducts 12a-c. Diels-Alder reaction between 11 and 2-chloroacrylonitrile afforded the spiro(bicyclo[2.2.1]hept-5-ene-7,1'-cyclopropane) derivative 14a that was transformed in three steps to rac-10-hydroxycamphor (17). This synthesis of a bornane derivative opens opportunity for variations and thus may find further applications.     

Synthesis, crystal structure, and magnetic studies of one-dimensional cyano-bridged Ln3+-Cr3+ complexes with bpy as a blocking ligand

The reaction of Ln(NO3)3.aq with K3[Cr(CN)6] and 2,2'-bipyridine (bpy) in a water/ethanol solution led to two families of complexes: 4 one-dimensional (1D) complexes of the formula trans-[Cr(CN)4(mu-CN)2Ln(H2O)3(bpy)2]n.4nH2O.3.5nbpy (Ln3+ = La, Ce, Pr, and Nd) and 10 1D complexes of the formula trans-[Cr(CN)4(mu-CN)2Ln(H2O)4(bpy)]n.3.5nH2O.1.5nbpy (Ln3+ = Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The structures for the fourteen complexes [LaCr]n (1), [CeCr]n (2), [PrCr]n (3), [NdCr]n (4), [NdCr]n (4'), [SmCr]n (5), [EuCr]n (6), [TbCr]n (7), [DyCr]n (8), [HoCr]n (9), [ErCr]n (10), [TmCr]n (11), [YbCr]n (12), and [LuCr]n (13) have been solved. Complexes 1-4 crystallize in the orthorhombic space group Pbam and are isomorphous; complexes 4'-13 crystallize in the triclinic space group PI and are isomorphous. The X-ray structural characterization of complexes 1-4 shows the presence of a discrete decameric water cluster built around a cyclic hexameric core stabilized by the solid-state structure, which represents another new mode of association of water molecules. The Ln3+-Cr3+ magnetic interaction is negligible in 6 and 12, antiferromagnetic in 2, 4', 7, 8, 9, 10, and 11, and unresolved for 3. The complex 5 is a ferrimagnet because its magnetic studies suggest the onset of a very weak ferromagnetic three-dimensional ordering.     

The fixation of bis(2-pyridylimino)isoindolato (BPI) ligands to dendritic carbosilanes

Bis(2-pyridylimino)isoindolato (BPI) ligands, containing an alkynyl linker unit which allows their fixation to carbosilane dendrimers and dendrons, were synthesized by reaction of 4-nitrophthalodinitrile with 4-butynol giving the phthalodinitrile derivative containing the linker. These were subsequently reacted with two molar equivalents of 2-amino-4-methylpyridine and 2-amino-4-(t)butylpyridine yielding the respective BPI protioligands 2a and 2b. Lithiation with LDA and reaction with Si-Cl or Si-OTf (OTf=triflate) end groups in core or peripheral positions of dendritic carbosilanes gave the endodendrally and expdendrally functionalized dendrimers. Among these the first and second generation dendrimers [G-1](8-exo)-4-[C[triple bond, length as m-dash]CCH2CH2O]-10-MeBPI (8), [G-1]12-exo-4-[C[triple bond, length as m-dash]CCH2CH2O]-10-MeBPI (9) and [G-2](16-exo)-4-[C[triple bond, length as m-dash]CCH2CH2O]-10-MeBPI (10) were synthesized and fully characterized. The functional dendrimers were metallated by reaction with [(PhCN)2PdCl2] in dichloromethane to give the corresponding pallada-dendrimers.     

Metal telluride clusters composed of niobocene carbonyl, telluride, and cobalt carbonyl units: syntheses, structures, and reactivity

Abstract: The reaction of [Cp#2NbTe2H] (1#; Cp# = Cp* (C5Me5) or Cp(x) (C5Me4Et)) with two equivalents of [Co2(CO)8] gives a series of cobalt carbonyl telluride clusters that contain different types of niobocene carbonyl fragments. At 0 degrees C, [Cp#2NbTe2CO3(CO)7] (2#) and [Co4Te2(CO)10] (3) are formed which disappear at higher temperatures: in boiling toluene a mixture of [cat2][Co9Te6(CO)8] (5#) (cat= [Cp#2Nb(CO)2]+) and [cat2][Co11Te7(CO)10] (6#) is formed along with [cat][Co(CO)4] (4#). Complexes 6# transform into [cat][Co11Te7(CO)10] (7#) upon interaction with HPF6 or wet SiO2. The molecular structures of 2(Cp(x)), 4(Cp(x)), 5(Cp*), 6(Cp*) and 7(Cp*) have been determined by X-ray crystallography. The structure of the neutral 2(Cp(x)) consists of a [Co3(CO)6Te2] bipyramid which is connected to a [(C5Me4Et)2Nb(CO)] fragment through a mu4-Te bridge. The ionic structures of 4(Cp(x)), 5(Cp*), 6(Cp*) and 7(Cp*) each contain one (4, 7) or two (5, 6) [Cp#2Nb(CO)2]+ cations. Apart from 4, the anionic counterparts each contain an interstitial Co atom and are hexacapped cubic cluster anions [Co9Te6(CO)8]2- (5) or heptacapped pentagonal prismatic cluster anions [Co11Te7(CO)10]n- (n=2: [6]2- , n=1: [7]-), respectively. Electrochemical studies established a reversible electron transfer between the anionic clusters [Co11,Te7(CO)10]- and [Co11Te7(CO)10]2in 6# and 7# and provided evidence for the existence of species containing [Co11Te7(CO),0] and [Co11Te7(CO)0]3-. The electronic structures of the new clusters and their relative stabilities are examined by means of DFT calculations.     

Propellanes. Part LXXVIII. Preparation of Several Triaza[3.3.3]propellanes and an Oxadiaza[3.3.3]propellane

3,7,10-Tribenzyl-3,7,10-triaza[3.3.3]propellane ( 4a ), 3,7-dibenzyl-10-phenyl-3,7,10-triaza[3.3.3]propellane ( 4c ), 3,7-dibenzyl-10-(p-tolyl)-3,7,10-triaza[3.3.3]propellane ( 4b ), and 3-oxa-7,10-diaza[3.3.3]propellane ( 6 ) have been prepared.     

Influence of hydrogen bonding on the assembly of six-membered vanadium borophosphate cluster anions: synthesis and structures of (NH4)2(C2H10N2)6[Sr(H2O)5]2[V2P2BO12](6)10H2O, (NH4)2(C3H12N2)6[Sr(H2O)4]2[V2P2BO12](6)17H2O, and (NH4)3(C4H14N2)4 5[Sr(H2O)5]2[Sr(H2O)4][V2P2BO12]6 10H2O

Three new strontium vanadium borophosphate compounds, (NH4)2(C2H10N2)6[Sr(H2O)5]2[V2P2BO12]6 10H2O (Sr-VBPO1) (1), (NH4)2(C3H12N2)6[Sr(H2O)4]2[V2P2BO12]6 17H2O (Sr-VBPO2) (2), and (NH4)3(C4H14N2)4.5[Sr(H2O)5]2[Sr(H2O)4][V2P2BO12]6 10H2O (Sr-VBPO3) (3) have been synthesized by interdiffusion methods in the presence of diprotonated ethylenediamine, 1,3-diaminopropane, and 1,4-diaminobutane. Compound 1 has a chain structure, whereas 2 and 3 have layered structures with different arrangements of [(NH4) [symbol: see text] [V2P2BO12]6] cluster anions within the layers. Crystal data: (NH4)2(C2H10N2)6[Sr(H2O)5]2[V2P2BO12]6 10H2O, monoclinic, space group C2/c (no. 15), a = 21.552(1) A, b = 27.694(2) A, c = 20.552(1) A, beta = 113.650(1) degrees, Z = 4; (NH4)2(C3H12N2)6[Sr(H2O)4]2[V2P2BO12]6 17H2O, monoclinic, space group I2/m (no. 12), a = 15.7618(9) A, b = 16.4821(9) A, c = 21.112(1) A, beta = 107.473(1) degrees, Z = 2; (NH4)3(C4H14N2)4.5[Sr(H2O)5]2[Sr(H2O)4] [V2P2BO12]6 10H2O, monoclinic, space group C2/c (no. 15), a = 39.364(2) A, b = 14.0924(7) A, c = 25.342(1) A, beta = 121.259(1) degrees, Z = 4. The differences in the three structures arise from the different steric requirements of the amines that lead to different amine-cluster hydrogen bonds.     

Chemistry of 1,2,3-thiadiazole. IV. Synthesis of [1]benzoxepino-[3,4-d][1,2,3]thiadiazole, [1]benzothiepino-[3,4-d][1,2,3]thiadiazole, [1]benzoxepino[4,3-d][1,2,3]thiadiazole, [1]benzoxepino[4,3-d]oxazole and [1]benzoxepino[4,3-d]oxazole. Four novel heterocycles

Starting from the readily available 4-bromomethy-5-carbethoxy 1,2,3-thiadiazole (V), 5-bromomethy-4-carbethoxy-1,2,3-thiadiazole (IX) and ethyl 2-aryl-5-bromomethyloxazole-4-carboxylate (XIV), 4,10-dihydro-10-oxo[1]benzoxepino[3,4-d][1,2,3]thiadiazole (Ia), 4,10-dihydro-10-oxo[1]benzothiepino[3,4-d][1,2,3]thiadiazole (Ib), 4,10-dihydro-4-oxo[1]benzothiepino[4,3-d] [1,2,3]thiazole (II), 2-aryl-4,10-dihydro-4-oxo[1]benzoxepino[4,3-d]oxazoles (XIXa-XIXc) and 2-aryl-4,10-dihydro-4-oxo[1]benzothiepino[4,3-d]oxazoles (XIXd-XIXf) were prepared.     

Chlorine anion encapsulation by molecular capsules based on cucurbit[5]uril and decamethylcucurbit[5]uril

Three barrel-shaped artificial molecular capsules 1-3, based on normal cucurbit[5]uril (Q[5]) and decamethylcucurbit[5]uril (Me10Q[5]), were synthesized and structurally characterized by single-crystal X-ray diffraction. Encapsulation of a chlorine anion in the cavity of a Q[5] or Me10Q[5] to form closed a molecular capsule with the coordinated metal ions or coordinated metal ions and water molecules in the crystal structures of these compounds is common. The three complexes [Pr2(C30H30N20O10)Cl3(H2O)13]3+ 3 Cl- x 5 H2O (1), [Sr2(C40H50N20O10)(H2O)4Cl]3+ 3 Cl- x 2 (HCl) 19 H2O (2) and [K(C40H50N20O10)(H2O)Cl] x [Zn(H2O)2Cl2] x [ZnCl4]2- x 2 (H3O)+ x 8 H2O (3) all crystallize as isolated molecular capsules.     

Syntheses and characterizations of palladium-based molecular triangle/square compounds and hybrid composites with polyoxometalates

Syntheses and characterizations of a Pd-based molecular triangle and square and hybrid composites with polyoxometalates are examined. The equilibrium between the Pd-based molecular triangle [(en*)Pd(4,4'-bpy)]3(NO3)6 and square [(en*)Pd(4,4'-bpy)]4(NO3)8 largely depends on the solvents, and both compounds have successfully been isolated: [(en*)Pd(4,4'-bpy)]3(NO3)6.3.5DMSO, monoclinic Cc (No. 9), a = 19.8210(2) A, b = 34.3667(5) A, c = 27.5484(4) A, beta = 89.9420(10) degrees , V = 18765.5(4) A3; [(en*)Pd(4,4'-bpy)]4(NO3)8, monoclinic C2/c (No. 15), a = 45.6921(16) A, b = 8.7721(8) A, c = 36.719(3) A, beta = 126.509(2) degrees , V = 11829.4(14) A3. The reactions of the Pd-based molecular triangle/square with [W6O19]2-, [W10O32]4-, and [alpha-SiW12O40]4- form [[(en*)Pd(4,4'-bpy)]4[ supersetW6O19]][W6O19]3, [[(en*)Pd(4,4'-bpy)]4[ supersetW6O19]](NO3)6, [[(en*)Pd(4,4'-bpy)]4[ supersetW10O32]][W10O32], [(en*)Pd(4,4'-bpy)]4[W10O32]2, and [(en*)Pd(4,4'-bpy)]4[alpha-SiW12O40]2. The molecular square does not encapsulate the largest [alpha-SiW12O40]4-, but it does encapsulate [W6O19]2- and [W10O32]4-. The isolation of [W6O19]2- and [alpha-SiW12O40]4- from the mixture by use of the molecular square is possible by utilizing the quite different solubility of [[(en*)Pd(4,4'-bpy)]4[ supersetW6O19]](NO3)6 and [(en*)Pd(4,4'-bpy)]4[alpha-SiW12O40]2 formed in DMSO. The size-selective encapsulation property of supramolecules may open the new way to rationalize isolation methods of the useful polyoxometalates.     

Cucurbit[10]uril

Melamine diamine 1 is able to displace CB[5] from the CB[10].CB[5] complex resulting in CB[10].12 and precipitated CB[5].1. We were able to isolate free CB[10] by treatment of CB[10].1 with acetic anhydride followed by washing with MeOH, DMSO, and water. The spacious cavity of CB[10] is able to complex large guests, including a cationic calix[4]arene derivative in its 1,3-alternate form (CB[10].1,3-alt-3). The addition of adamantane carboxylic acid (4) to CB[10].3 triggers a conformational change during the formation of termolecular complex CB[10].cone-3.4.     

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.     

Copper(I) alkynyl clusters, [Cu(x+y)(hfac)(x)(C[triple chemical bond]CR)(y)], with Cu(10)-Cu(12) cores

The facile syntheses and the structures of five new Cu(I) alkynyl clusters, [Cu(12)(hfac)(8)(C[triple chemical bond]CnPr)(4)(thf)(6)]xTHF (1), [Cu(12)(hfac)(8)(C[triple chemical bond]CtBu)(4)] (2), [Cu(12)(hfac)(8)(C[triple chemical bond]CSiMe(3))(4)] (3), [Cu(10)(hfac)(6)(C[triple chemical bond]CtBu)(4)(diethyl ether)]/[Cu(10)(hfac)(6)(C[triple chemical bond]CtBu)(3)(C[triple chemical bond]CnPr)(diethyl ether)] (4) and [Cu(10)(hfac)(6)(C[triple chemical bond]CtBu)(4)(diethyl ether)] (5) are reported, in which hfacH=1,1,1,5,5,5-hexafluoropentan-2,4-dione. The first independent molecule found in the crystals of 4 (4 a) proved to be chemically identical to 5. The Cu(10) and Cu(12) cores in these clusters are based on a central "square" Cu(4)C(4) unit. Whilst the connectivities of the Cu(10) or Cu(12) units remain identical the geometries vary considerably and depend on the bulk of the alkynyl group, weak coordination of ether molecules to copper atoms in the core and CuO intramolecular contacts formed between Cu-hfac units on the periphery of the cluster. Similar intermolecular contacts and interlocking of Cu-hfac units are formed in the simple model complex [Cu(2)(hfac)(2)(HC[triple chemical bond]CtBu)] (6). When linear alkynes, C(n)H(2n+1)C[triple chemical bond]CH, are used in the synthesis and non-coordinating solvents are used in the workup, further association of the Cu(4)C(4) cores occurs and clusters with more than eighteen copper atoms are isolated.     

Synthesis and conformational evaluation of p-tert-butylthiacalix[4]arene-crowns

Bridging of p-tert-butylthiacalix[4]arene afforded 1,3-dihydroxythiacalix[4]arene-monocrown-5 (3b), 1,2-alternate thiacalix[4]arene-biscrown-4 and -5 (4a,b), and 1,3-alternate thiacalix[4]arene-biscrown-5 and -6 (5a,b), depending on the metal carbonates and oligoethylene glycol ditosylates used. Starting from 1,3-dialkylated thiacalix[4]arenes, the corresponding bridging reaction gave 1,3-alternate, partial-cone, and cone conformers 10-19, depending on the substituents present. Temperature-dependent studies revealed that the conformationally flexible 1,3-dimethoxythiacalix[4]arene-crowns 10a-c exclusively occupy the 1,3-alternate conformation. Demethylation exclusively gave the cone 1,3-dihydroxythiacalix[4]arene-crowns (3a,c), which could not be obtained by direct bridging of thiacalix[4]arene. The different structures were assigned on the basis of several X-ray crystal structures and extensive 2-D (1)H NMR studies.     

Main-group-element calix[4]arenes: variable coordination and conformational isomerism at phosphorus and silicon

Treatment of calix[4]arene (1b) with trichloromethylsilane yields two conformers of calix[4]SiMe(OH), the cone 2b-C and the partial cone 2b-PC. These are isolated and structurally characterized, and their thermodynamic activation parameters are determined in solution [Ea = 117(3) kJ/mol, delta H = 5(4) kJ/mol]. Similar parameters are found for the p-tert-butylcalix[4]arene analogues 2a-C and 2a-PC. Deprotonation of 2b with butyllithium yields calix[4]SiMe(OLi) (8b). The structure of 8b is solvent dependent: 8b contains a five-coordinate silicon in THF and a four-coordinate silicon in benzene. Similar behavior is found for the p-tert-butylcalix[4]arene analogues. The five-coordinate phosphorus analogue of the anion in 8, p-tert-butylcalix[4]PMe (11a), is synthesized from the phosphonium triflate salt p-tert-butylcalix[4]PMe(OH)OTf (10a(OTf)) via treatment with butyllithium. The structure of 11a shows the geometry around phosphorus to be very close to a pure trigonal bipyramid. The X-ray structure of 10a(OTf) cannot be obtained, but its iodide analogue 10a(T) is synthesized and structurally characterized. The cation in 10a(I) adopts the partial cone conformation in the solid state, similar to 2b-PC. Treatment of 8b with methyl trifluoromethanesulfonate yields the methyl phenyl ether calix[4]SiMe(OMe) (3b). This species and its p-tert-butyl analogue 3a are structurally characterized. Both adopt the partial cone conformation. The SiMe group in 3b can be removed via treatment with fluoride to yield the monomethylated calix[4]arene 4b in 50-60% overall yield based on 1b.     

Synthesis,Characterization and Reactions of 4‐Hydrazino‐2‐methylpyrimidino[4′5′:4,5]thiazolo[3,2‐a]benzimidazole

4‐Hydrazino‐2‐methylpyrimidino[4′,5′:4,5]thiazolo[3,2‐a]benzimidazole ( 4 ) was obtained from hydrazinolysis of the 4‐chloro derivative 3 with hydrazine hydrate. The hydrazino derivative 4 was further cyclized to the corresponding pyrazole 5 , pyrazolone 6 and 5‐methyl‐1,2,4‐triazolo[1″,5″:3′,4′]pyrimidino[5′,6′:5,4]‐thiazolo[3,2‐a]benzimidazole ( 9 ) and 5‐methy‐1,2,4‐triazolo[4″,3″:3′,4′]pyrimidino[5′,6′:5,4]thiazolo‐[3,2‐a]benzimidazole ( 10 ), respectively. The triazolo derivative 10 was isomerized to the triazolo derivative 9 under a variety of reaction conditions.     

Functional [6]pericyclynes: synthesis through [14+4] and [8+10] cyclization strategies

Critical analysis of possible strategies for the synthesis of novel carbo-benzene derivatives suggests several [(18-n)+n] routes for the preparation of hexaoxy[6]pericyclyne precursors. Beyond the previously attempted [9+9] symmetrical scheme (n=9), the a priori most selective strategies are those for which n=1, 4, 7, 10, 13, and 16. They involve a cyclizing double-propargylation of a C(18-n) omega-bis-terminal-skipped oligoyne containing (19-n)/3 triple bonds with a C(n) omega-dicarbonyl-skipped oligoyne containing (n-1)/3 triple bonds. To complement the previously used [11+7] strategy, the [14+4] and [8+10] strategies were thus explored. They proved to be efficient, affording seven novel hexaoxy[6]pericyclynes corresponding to six different substitution patterns. These compounds were obtained in 7-15 steps as mixtures of stereoisomers. Thus, by using dibenzoylacetylene as the C(4) electrophile, a [14+4] strategy allowed the synthesis of two hexaphenyl representatives with two or four free carbinol vertices. This approach also afforded tetraphenyl representatives in which the two remaining carbinoxy vertices were substituted with either two alkynyl or one 4-anisyl and one 4-pyridyl groups. By using the hexacarbonyldicobalt complex of butynedial as the C(4) electrophile, a [14+4] strategy also allowed the isolation of a tetraphenylhexaoxy[6]pericyclyne with two adjacent unsubstituted carbinol vertices. A regioisomer with two opposite unsubstituted carbinol vertices was obtained through an [8+10] strategy and its oxidation afforded the corresponding pericyclynedione. Several attempts at synthesizing diphenylhexaoxy[6]pericyclynes with four unsubstituted carbinoxy vertices are described. Only an [8+10] strategy allowed the generation of a fragile diphenylhexaoxy[6]pericyclyne with four adjacent unsubstituted carbinoxy vertices, which could be partly characterized. These results show that the synthesis of the nonsubstituted hexahydroxy[6]pericyclyne, the ring carbo-mer of [6]cyclitol, is a difficult challenge.