Charlotte K. Broder

1H NMR and X-ray crystallographic analysis of 1,2-bis(4,6-diethylthio-1H-pyrazolo[3,4-d]pyrimidin-1-yl)ethane and its ‘propylene linker’-analog: molecular recognition versus crystal engineering ☆

Abstract Proton NMR analysis on newly synthesized 1,2-bis(4,6-diethylthio-1H-pyrazolo[3,4-d]pyrimidin-1-yl)ethane, 2c , and 1,2-bis(4,6-diethylthio-1H-pyrazolo[3,4-d]pyrimidin-1-yl)propane, 2d , showed intramolecular stacking in solution. X-Ray crystallography on 2c and 2d , however, confirmed the presence of such intramolecular stacking only in case of the ‘propylene linker’ compound, 2d , while the ‘ethylene linker’ compound, 2c , was devoid of it.

Halogen trimer synthons in crystal engineering: low-temperature X-ray and neutron diffraction study of the 1:1 complex of 2,4,6-tris(4-chloro- phenoxy)-1,3,5-triazine with tribromobenzene

The title complex has been studied using low-temperature X-ray (150 K) and neutron (100 K) diffraction. Molecules of the triazine host form a two-dimensional hexagonal network mediated by trigonally symmetric Cl(3) synthons having Cl.Cl interactions of 3.441 (3) A, a C-Cl.Cl angle of 165 degrees and a Cl.Cl-C angle of 105 degrees, close to the ideal values of 180 and 90 degrees, respectively. The guest molecules are of an appropriate size to fit the hexagonal networks and interact with the host via C-H.pi (phenyl) and C-Br.pi (phenyl) interactions which stabilize the overall structure. Both C-donor bond vectors are directed more closely towards the mid-point (X) of an individual aromatic bond, rather than the ring centroid, with H.X 2.817 (9) A and C-H.X 174.0 (9) degrees, and Br.X 3.353 (4) A and C-Br.X 158.1 (2) degrees.

Insertion and cleavage reactions of [closo-3,1,2-Ta(NMe2)3(C2B9H11)] with nitriles, phenols and thiols; structural characterisation of N,N-dimethylamidinate ligands

The tantalum complex [closo-3,1,2-Ta(NMe2)3(C2B9H11)] underwent insertion into the NC bond of acetonitrile and p-fluorobenzonitrile to give the N,N-dimethylacetamidinate complex [closo-3,1,2-Ta{NC(Me)NMe2}3(C2B9H11)], and p-fluoro-N,N-dimethylbenzamidinate, [closo-3,1,2-Ta{NC(C6H4F)NMe2}3(C2B9H11)], respectively. Attempted re-crystallisation of the latter from chlorinated solvents led to [closo-3,1,2-Ta{NC(C6H4F)NMe2}2Cl(C2B9H11)], in which one amidinate ligand has been replaced by a chloride. [closo-3,1,2-Ta(NMe2)3(C2B9H11)] reacts with cyclohexylisocyanide to give [Ta(NMe2)2{η2-N(Cy)CNMe2}(C2B9H11)]. The structures of the novel N,N-dialkylamidinate complexes have been determined by single crystal X-ray diffraction, and reveal the extensive delocalisation and strong π-donor character of the amidinate ligands. The M–N bonds of [closo-3,1,2-Ta(NMe2)3(C2B9H11)] are cleaved by protic reagents, and it reacts with 2,6-dimethylphenol to give [closo-3,1,2-Ta(OC6H3Me2-2,6)3(C2B9H11)] and with benzenethiol to give the charge-compensated complex [closo-3-Ta(SC6H5)4(9-NHMe2-1,2-C2B9H10)] where the β-boron of the C2B3 face bears a NHMe2+ substituent. The structures of the last two compounds have also been determined.

Synthesis, structure and reactivity of 1-(α-C,α′-halo-o-xylyl)-2-trialkylsilyl-1,2-dicarbaboranes

Treating Li[tBuMe2Si-1,2-C2B10H10] with excess α,α′-dihalo-o-xylenes, 1,2-C6H4(CH2X)2 (X = Br, Cl), generates only 1-(α-C,α′-halo-o-xylyl)-2-(tert-butyldimethylsilyl)-1,2-dicarba-closo-dodecaboranes, 1-{o-(XCH2C6H4CH2)}-2-tBuMe2Si-1,2-C2B10H10 (X = Cl 1a, Br 1b). The structures of both 1a and 1b were determined by single crystal X-ray diffraction. Reaction of either 1a or 1b with nBuLi or MeLi affords the substituted ethane, (2-tBuMe2Si-1,2-C2B10H10-1-o-CH2C6H4)2C2H42 whereas reaction with tBuHNLi affords the substituted ethene (2-tBuMe2Si-1,2-C2B10H10-1-o-CH2C6H4)2C2H23; both structures were confirmed by X-ray diffraction. Cleavage of the carborane–silicon bond in 1a or 1b by Bu4NF gives dihydronaphthocarborane, 4, which has been structurally characterised.

A highly functionalized ferrocenylpyrazolo[2,3-a]pyridine.

The crystal structure of [2-(4-bromophenyl)-4-cyano-5-ferrocenylpyrazolo[2,3-a]pyridin-7-yl]acetonitrile, C(26)H(17)N(4)FeBr or [Fe(C(5)H(5))(C(21)H(12)BrN(4))], shows that the pyrazolopyridine ring system (PP), the bromophenyl ring (BP) and the cyclopentadiene ring (Cp) are nearly planar. The PP ring system is twisted out of the plane of the BP and Cp rings by about 20 degrees.