Karel Baše

The partition of amines between water and an organic solvent phase

Abstract The partition of a series of protonated amines (aniline, benzylamine, 2-phenylethylamine and related compounds) between water and nitrobenzene was investigated using electrochemical approaches (cyclic voltammetry and differential pulse stripping voltammetry) which made it possible to infer the transport and thermodynamic parameters of the partition process. Micromolar concentrations of the protonated amines in the aqueous phase can be determined by DPSV at the electrolyte hanging drop electrode. The function of an amine as the proton acceptor in the facilitated proton transfer across the water/organic solvent phase was discussed.

The Preparation and Structures of New Nido-Platinaheteroboranes

Abstract Treatment of 4-XB8H12 (X=CH2, NH and S) hetero-boranes1–3 with Pt(PPh3)4 produced new ten-vertex platinaheteroboranes, 9,9-(PPh3)2-6,9-XPtB8H10 which are isoelectronic with nido-6-CB9H13. Their molecular structures were determined by single crystal X-ray studies. ESCA spectra were measured to estimate the influence of heteroborane ligands on central Pt atoms.

Synthesis of the new 6-carba-nido-dodecahydrodecaborate(–1) and 4-carba-nido-nonaborane(14)

Reduction of 6-Me3N-6-CB9H11(I) to 6-CB9H12–(II) and hydrolytic degradation of (II) to 4-CB8H14(III), the first monocarbaborane belonging to the arachno-series, are described; structures for these compounds are proposed on the basis of their genesis and n.m.r. spectra.

Synthesis and X-ray structure of 4-azanonaborane(13)(4-NB8H13)

Addition of NaNO2 to B10H14 in tetrahydrofuran, followed by acidification with HCl afforded the first uncharged 4-NB8H13 azaborane, the structure of which was determined by X-ray diffraction.

Polyhedral iridamonocarbaborane chemistry. Two ten-vertex arachno-6,9-iridacarbadecaboranes and some related ten-vertex carbaborane chemistry. Comparative nuclear magnetic resonance studies and the molecular structure of [asym-9-(CO)-9,9-(PPh3)2-9-H-arachno-9,6-IrCB8H12]

Reaction of trans-[IrCl(CO)(PPh3)2] with [NMe4][nido-6-CB9H12] in solution resulted in the formation in low yields of two isomers (sym and asym) of [9-(CO)-9,9-(PPh3)2-9-H-arachno-9,6-IrCB8H12]. These new air-stable yellow compounds differ in the arrangement of the exopolyhedral {(CO)(PPh3)2H} ligand group on the metal atom. Single-crystal X-ray diffraction analysis on the asym isomer confirmed the molecular constitution. Crystals were monoclinic, space group Cc, with a= 1 112.7(2), b= 2 184.7(3), c= 1 553.2(2) pm, β= 94.06(1)°, and Z= 4; 3 265 observed data [I > 2.0σ(I)]; R= 0.0183, R′= 0.0187. The cluster structure is of arachno ten-vertex ‘boat’ configuration, with the {Ir(CO)(PPh3)2} and {CH2 centres occupying the “prow” positions 9 and 6, and with the Ir–H hydrogen atom being endo over the cluster open face. N.m.r. spectroscopy permits assignment of the cluster 11B and 1H parameters and thence comparison with the equivalent parameters of the analogues [B10H14]2–, [6-CB9H14]–, 6,9-C2B8H14, and [5-(η5-C5H5)-5,6,9-CoC2B7H11], in order to assess the comparative effects of replacement of boron by carbon and metal centres in the basic ten-vertex arachno[B10H14]2– cluster type. Preparative details for [arachno-6-CB9H14]– are given.

Degradative insertion reactions of nido-7,9-C2B9H–12.Synthesis and properties of 4-thia -6,8-dicarba-arachno-nonborane (10),4,6,8-SC2B6H10

The reaction of 7,9-C2B9H–12(1)with NaNO2and Na2SO3in dilute hydrochloric acid affords 6,8-C2B7H13(2)and the new thiacarbaborane 4,6,8-SC2B6H10(3)the structure of which is proposed on the basis of 1H and 11B n.m.r. spectra.

The structure of the arachno-[B10H13CN]2– anion; an example of endo substitution in the decaborane(14) framework

The cyano group in [B10H13CN]2– occupies an endo-position with respect to the cage in both solution (n.m.r.) and solid (X-ray crystallography) states, indicating a general pathway for the formation of heteroboranes.

A novel eleven-vertex closo-type azametallaborane: [1-(η6-MeC6H4-4-Pri)-closo-1,2-RuNB9H10]

Reaction between nido-6-NB9H12 and [(η6-MeC6H4-4-Pri)RuCl2]2 in tetrahydrofuran yields a variety of azaruthenaboranes of which one is the novel closo-type eleven-vertex species [1-(η6-MeC6H4-4-Pri)-closo-1,2-RuNB9H10].

Synthesis of 6-aza-nido-decaborane(12) and its derivatives

The aza-nido-borane 6-NB9H12(1) has been prepared by treatment of the reaction intermediate formed in the reaction of B10H14 and NaNO2 in tetrahydrofuran with concentrated H2SO4; hydrolysis of compound (1) afforded arachno-4-NB8H13(2) and the addition of Lewis bases produced the arachno-9-L-6-NB9H12(3) compounds [L = Me2S (3a), MeCN (3b), and PPh3(3c)].