The oligophosphanylamine ligand 1,1,4,7,10,10-hexakis(diphenylphosphanyl)triethylenetetramine (1) was obtained from the reaction of triethylenetetramine with six equivalents of chlorodiphenylphosphine in good yield. Ligand 1 was treated with three equivalents of [Cr(CO) 4 (MeCN) 2 ], [Mo(CO) 4 (nbd)] (nbd = norbornadiene), or [W(CO) 4 (MeCN) 2 ] in toluene to give the trinuclear tetracarbonyl complexes [{M(CO2307 Scheme 2. Synthesis of hexaphosphanylamine 1 and trinuclear group 6 metal tetracarbonyl complexes 2-4.

Polyphosphoric acid (PPA), a powerful dehydrating agent, has been widely used to perform several important organic reactions and thus has played an important role in the synthesis of organic compounds and natural products. The present micro review describes briefly the use of PPA (i) in the cyclization of acids on the aromatic ring (ii) in acetylation and isopropylation on the aromatic ring, (iii)hydrolysis of esters, (iv) cleavage of epoxides and (v) synthesis of heterocyclic compounds.

A series of related acetylacetonate–carbonyl–rhodium compounds substituted by functionalized phosphines has been prepared in good to excellent yields by the reaction of [Rh(acac)(CO)2] (acac is acetylacetonate) with the corresponding allyl-, cyanomethyl- or cyanoethyl-substituted phosphines. All compounds were fully characterized by 31P, 1H, 13C NMR and IR spectroscopy. The X-ray structures of (acetylacetonato-κ2 O,O′)(tert-butylphosphanedicarbonitrile-κP)carbonylrhodium(I), [Rh(C5H7O2)(CO)(C8H13N2)] or [Rh(acac)(CO)(tBuP(CH2CN)2}] (2b), (acetylacetonato-κ2 O,O′)carbonyl[3-(diphenylphosphanyl)propanenitrile-κP]rhodium(I), [Rh(C5H7O2)(C15H14N)(CO)] or [Rh(acac)(CO){Ph2P(CH2CH2CN)}] (2h), and (acetylacetonato-κ2 O,O′)carbonyl[3-(di-tert-butylphosphanyl)propanenitrile-κP]rhodium(I), [Rh(C5H7O2)(C11H22N)(CO)] or [Rh(acac)(CO){tBu2P(CH2CH2CN)}] (2i), showed a square-planar geometry around the Rh atom with a significant trans influence over the acetylacetonate moiety, evidenced by long Rh—O bond lengths as expected for poor π-acceptor phosphines. The Rh—P distances displayed an inverse linear dependence with the coupling constants J P-Rh and the IR ν(C[triple-bond]O) bands, which accounts for the Rh—P electronic bonding feature (poor π-acceptors) of these complexes. A combined study from density functional theory (DFT) calculations and an evaluation of the intramolecular H...Rh contacts from X-ray diffraction data allowed a comparison of the conformational preferences of these complexes in the solid state versus the isolated compounds in the gas phase. For 2b, 2h and 2i, an energy-framework study evidenced that the crystal structures are mainly governed by dispersive energy. In fact, strong pairwise molecular dispersive interactions are responsible for the columnar arrangement observed in these complexes. A Hirshfeld surface analysis employing three-dimensional molecular surface contours and two-dimensional fingerprint plots indicated that the structures are stabilized by H...H, C...H, H...O, H...N and H...Rh intermolecular interactions.

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