Andrzej F. Borowski

Rhodium complexes withN-phenylanthranilic acid. Synthesis, structural investigations and catalytic activity in hydrogenation of some aromatic and heteroaromatic compounds

SummarySyntheses and physico-chemical properties of three complexes obtained from rhodium trichloride andN-phenylanthranilic acid are described. Based on a variety of data the complexes are formulated as macromolecular rhodium compounds linked by carboxylate groups with no coordination through the amine. The catalytic activities of the complexes in hydrogenation of aromatic and heteroaromatic compounds are compared with those of the rhodium complex withN-phenylanthranilic acid described previously by other authors.

Structure and properties of anthranilato- andN-phenylanthranilatorhodium(I) complexes withcis, cis-cycloocta-1,5-diene

SummaryReaction products of [{RhCl(η-COD)}2] (COD=cycloocta-1,5-diene) with sodium salts of anthranilic andN-phenylanthranilic acid have been isolated and their structures and catalytic activities investigated. A monomeric square-planar structure with O-Rh-N bonds is postulated for the anthranilate complex, and a dimeric structure, with carboxylate bridges and without binding of the β-amine nitrogen to rhodium, is postulated for theN-phenylanthranilate. Catalytic activities in hydrogenation of some alkenes, dienes, aromatic and heteroaromatic compounds have been investigated at ambient temperature and pressure. The stability of the complexes under hydrogenation conditions is low and complete saturation has been achieved only forn-alkenes and dienes.

Structures and properties of anthranilato- and N-phenylanthranilato-rhodium(I) complexes containing triphenylphosphine ligands

Abstract The structures of two triphenylphosphine rhodium(I) complexes with anthranilic and N-phenylanthranilic acid, which are active in hdyrogenation of some alkenes, dienes, aromatic and heteroaromatic compounds, are described, together with some of their catalytic properties. A monomeric aminocarboxylate analogue of Wilkinsons catalyst is postulated for the anthranilate complex ( 1 ) and a dimeric structure with carboxylate bridges and two cis -triphenylphosphine molecules coordinated to each rhodium atom is proposed for N-phenylanthranilate ( 2 ). On treatment with hydrogen both complexes give cis -dihydrides, but variable temperature 1 H and 31 P NMR studies of the product derived from 1 reveal that a temperature-dependent equilibrium involving dissociation of PPh 3 occurs. Complexes 1 and 2 are stable under hydrogenation conditions and enable slow hydrogenation of 1-alkenes and cyclohexadienes. For cyclohexadienes some selectivity to cyclohexene formation is observed, especially in DMF. Although the activities of 1 and 2 towards the hydrogenation of arenes and heteroaromatics are generally very low, pyridine can be hydrogenated to piperidine to a substantial degree.

Linkage isomerism in rhodium(I) complexes of mixed anhydrides of diphenylphosphinous and acrylic acids: crystal and molecular structure of [RhCl(PPh3)(Ph2PO2CCHCHMe)]

Reactions of [RhCl(PPh3)3] with mixed anhydrides Ph2PO2CCRCR′R″(R = R′= H, R″= Me or CHCHMe; R = H, R′= R″= Me; R = Me, R′= H, R″= Ph) give complexes [RhCl(PPh3)n(Ph2PO2CCRCR′R″)](n= 1, R = R′= H, R″= Me or CHCHMe; n= 2, R = H, R′= R″= Me; R = Me, R′= H, R″= Ph; R = R′= H, R″= CHCHMe). For n= 1, the mixed anhydride is bound to the metal via the phosphorus atom and the double bond, whilst for n= 2 binding is through phosphorus alone. Treatment of [RhCl(PPh3)n(Ph2PO2CCRCR′R″)] with TlPF6 or AgSbF6 leads in all cases to complexes [Rh(PPh3)2(Ph2PO2CCRCR′R″)]+ in which the mixed anhydride is bound through the phosphorus atom and the carbonyl oxygen atom. Spectroscopic diagnostics for the various different bonding modes are discussed, whilst their occurrence is rationalised largely on steric grounds. The X-ray crystal structure of [RhCl(PPh3)(Ph2PO2CCHCHMe)] is described along with its curious fluxional behaviour. Crystals of this complex are monoclinic (space group P21/n), with a= 19.954(4), b= 13.250(4), c= 11.425(1)A, β= 91.66(2)°, and Z= 4. The structure was obtained from 3 721 observed intensities measured on an automatic diffractometer and refined to an R value of 0.0358. The complex is distorted square planar about rhodium with the co-ordination sites being occupied by the two phosphorus atoms, the chloride, and the CC of the mixed anhydride. The two phosphorus atoms are mutually cis. The CC bond length is 1.393(9)A, and there is significant pyramidalisation at the carbon atoms of the double bond, suggesting a fairly strong interaction between the double bond and the rhodium atom.

Notes. Upon the fluxionality of [RhCl(PPh3)(Ph2PO2CCHCHMe)]

The fluxional behaviour of [RhCl(PPh3)(Ph2PO2CCHCHMe)] observed in the n.m.r. spectra is attributed to the rapid equilibrium between two isomers having mutually cis and trans phosphorus atoms respectively. Thermodynamic parameters for this process are measured and loss of P–P but not Rh–P coupling under fast exchange conditions suggests that Jpp has different signs for the two isomers

Structure of di-μ-N-Phenylanthranilato-di-1, 5-cyclooctadiene dirhodium(I)

Abstract The reaction of [RhCl(COD)]2 (COD = 1,5-cyclooctadiene) with sodium N-phenylanthranilate leads to the formation of the new crystalline rhodium(I) complex [RhFA(COD)]2 (FA = N-phenylanthranilate anion). The compound is a dimer with two N-phenylanthranilate ions bridging and COD ligands terminally bonded to rhodium with an Rh … Rh distance equal to 3.424(3) A. Strong intramolecular hydrogen bonding occurs between the hydrogen of the NH group and the closest carbonyl oxygen in the FA ligands. The crystals are monoclinic, space group P21/c, with a = 11.246(8), b = 14.999(9), c = 21.82(2) A, β = 105.11(6)°. The structure was solved by the heavy-atom method and refined by least squares to R = 0.035 for 4260 diffractometer data.

Hydrogenation of coal-derived liquids in the presence of rhodium complexes

Abstract Hydrogenation of 473–573 K distillate derived from the product of catalytic hydrogenation of coal in the presence of hydrogen-donor solvent and ethyl alcohol and dimethyl-formamide extracts of the tar from low-temperature (fluidized-bed) coal carbonization have been investigated in the presence of rhodium complexes. The complexes used (293–393 K; 0.1–5 MPa) bpth in homogeneous and in immobilized forms are catalytically active in hydrogenation of those coal-derived liquids. However, the increase of H/C atomic ratio is low. The catalysts in the immobilized form have not been deactivated in several catalytic cycles following.

X-Ray crystal structure of the bis(dihydrogen) complex RuH2(H2)2(PCy3)2

RuH2(H2)2(PCy3) 2, the first reported stable bis (dihydrogen) complex crystallizes in the P1 space group; the two dihydrogen ligands lie in the equatorial plane in a mutual cis position and are located trans to the hydride ligands; the H–H distances are ca. 0.85 A, in agreement with the presence of unstretched dihydrogen ligands; these results are compared with previous theoretical calculations using density functional theory.