The studies described in this paper show that hydrocarbon oligomers are alternatives for low molecular weight alkane solvents. These oligomeric solvents are nontoxic, nonvolatile, and recyclable alternatives to heptane in thermomorphic solvent mixtures that use a polar solvent such as methanol, aqueous ethanol, or DMF or in biphasic mixtures that use acetonitrile. Regardless of which polar solvent is used, hydrocarbon oligomers like poly(α-olefin)s (PAOs) exhibit very low leaching into the polar phase. UV-visible spectroscopy studies show that these solvents have the solubility properties of heptane. For example, PAOs dissolve heptane soluble dyes and quantitatively separate them from polar phases in thermomorphic solvent mixtures. PAOs either as pure solvents or as additives in heptane act as antileaching agents, decreasing the already low leaching of such dyes into a polar phase in heptane/polar solvent mixtures. These oligomeric hydrocarbon solvents were also compared to heptane in studies of azo dye isomerization. The results show that thermal isomerization of an azo dye occurs at the same rate in heptane and a PAO. Further studies of carboxylic acid promoted dye isomerization in heptane and a PAO show that low molecular weight and oligomeric carboxylic acids are kinetically equivalent at accelerating this isomerization. The results suggest that these and other hydrocarbon oligomers behave as solvents like their low molecular weight nonpolar hydrocarbon solvents and that they can be substituted successfully for conventional solvents like heptane.

The (dippe)palladium(0) fragment generated from [(dippe)Pd(μ-H)] 2 (1) has been shown to form an intermediate η 2 -nitrile complex with acetonitrile (dippe)Pd(η 2 -C,N-CH 3 CN-BEt 3 ) (2a) in the presence of BEt 3 [(dippe = bisdiisopropylphosphino)ethane)]. On introducing a solution of 2a to 1 equiv of BPh 3 , rapid formation of (dippe)Pd(η 2 -C,N-CH 3 CNBPh 3 ) (2a′) is observed. Heating 2a′ at 100°C in THF-d 8 results in the C−CN activation product 3a′, (dippe)Pd(CH 3 )(CNBPh 3 ). Reaction of 1 with benzonitrile in the presence of BEt 3 gives the C−CN activation product (dippe)Pd(Ph)(CN-BEt 3 ) (3b) exclusively. The complexes 2a, 2a′, 3a′, and 3b were characterized by 1 H, 31 P{ 1 H}, and 13 C{ 1 H} NMR spectroscopy, elemental analysis, IR spectroscopy, and X-ray diffraction.I nterest in the carbon−carbon bond activation of alkyl, allyl, and aryl nitriles has risen due to potential industrial 1 and organic synthesis applications. 2 Recently, the complexes [(dippe)Ni(μ-H)] 2 and [(dippe)PtH] 2 (dippe = bisdiisopropylphosphino)ethane) have been employed in stoichiometric activation of nitriles in our group in collaboration with Garcı́a. 3,4 These complexes furnish a reactive 14-electron (dippe)M 0 (M = Ni, Pt) fragment that can cleave the C−CN bond in the nitriles. Garcı́a and co-workers have since expanded [(dippe)Ni(μ-H)] 2 studies by providing the first catalytic example of low-valent nickel additions of alcohols to aryl, alkyl, and heteroatomic nitriles. 5 As an extension to the studies with group 10 hydride dimers in our group, we wanted to investigate the palladium hydride dimer, [(dippe)Pd(μ-H)] 2 (1), in the activation of the C−CN bond in nitriles. Complex 1 has been shown to be effective in cleaving the carbon−sulfur bonds in thiophenes and thioethers. 6 Herein, we report Lewis acid assisted C−CN cleavage to form (dippe)palladium(II) intermediate complexes that are crucial in cross-coupling, hydrodecyanation, and cycloaddition reactions. 7 Complex 1, [(dippe)Pd(μ-H)] 2 , 6,8 is generated in situ when a (dippe)PdCl 2 suspension in THF is treated with 2 equiv of potassium triethylborohydride with the loss of KCl/BEt 3 (Scheme 1). After filtration to remove the KCl salt, the filtrate is treated with an excess of acetonitrile, causing a color change from intense dark red to light transparent orange. A pair of doublet resonances at δ 75.63 (d, 2 J P-P = 25.0 Hz) and 61.77 (d, 2 J P-P = 25.0 Hz) is observed in the 31 P{ 1 H} NMR spectrum, consistent with asymmetrically η 2 -coordinated (dippe)Pd(0) complexes. 9 The 13 C{ 1 H} NMR spectrum of 2a in THF shows a distinct downfield shift of the CN to δ 149.70 compared to δ 117 in free acetonitrile. The 11 B{ 1 H} NMR spectrum shows a resonance at δ −13.2, the region for BEt 3 complexes. 10 Attempts to isolate 2a as a solid by removing solvent in vacuo results in 2a decomposing to [(μ-dippe)Pd] 2 , 11 which has the characteristic signal at δ 33 in the 31 P{ 1 H} NMR spectrum. However, X-ray quality crystals grew from the THF solution of 2a at room temperature ove...