Lourdes Ibarlucea

Rhodium(I) complexes with bidentate nitrogen heterocycles and their reactions with tin (II) chloride and carbon monoxide

SummaryCleavage of [{Rh(diolefin)Cl}2] by bidentate heterocyclic chelating ligands (LL) has been studied, and diolefin neutral, ionic or ion-pair type compounds are formed depending on the ligands and/or the Rh: (LL) ratio employed. When the reactions are performed in media saturated with CO and with Rh: (LL)=2∶1, only carbonylated ion-pair complexes are formed. The diolefin compounds react with tin(II) chloride yielding species containing trichlorostannato-groups. Subsequent reaction with CO leads to displacement of the diolefin and formation of the corresponding dicarbonyl species.

Reaction of [RhCl(CO)2]2 or [RhCl(COD)]2 with o-(diphenylphosphino)benzaldehyde. Formation of hemiaminals in the subsequent reaction with dihydrazones

Abstract [RhCl(CO) 2 ] 2 reacts with o -(diphenylphosphino)benzaldehyde (PCHO) to afford a monocarbonylated rhodium(I) complex containing P-monodentate PCHO, trans -[RhCl(CO)(PCHO) 2 ] ( 1 ) while [RhCl(COD)] 2 undergoes the oxidative addition of one PCHO, with displacement of 1,5-cyclooctadiene, and coordination of the second PCHO molecule as P-(σ-aldehyde) chelate to give [RhH(PCO)Cl(PCHO)] ( 2 ) which contains trans P-atoms. Compound 2 reacts with H 2 NNCHCHNNH 2 (gdh) to give selectively a complex [RhH(PCO)(Pgdh)] + containing a stable hemiaminal in a new tridentate ligand, Pgdh, coordinated via the imino nitrogens and the phosphorus and the atom. The reaction of Rh(COD)(gdh)Cl with PCHO gives a mixture of the hemiaminal containing compound and the hydroxyalkyl complex [Rh(PCO)(PCHOH)(gdh)] + which contains trans P-atoms and is formed from precursors containing cis P-atoms. The transformation of the hemiaminal group in [RhH(PCO)(PNN)] + (PNN=Pgdh or Ppvdh (pvdh, H 2 NNCHC(CH 3 )NNH 2 )) into imine to give new tridentate PaNN ligands in complexes [RhH(PCO)(PaNN)] + has also been studied.

Rhodium(I) complexes containing aliphatic diamine ligands

Abstract The reaction of [Rh(diolefin)Cl]2 and aliphatic diamines (LL) in 2 1 ratio, gave either the ion-pair species [Rh(diolefin)(LL)]+ [Rh(diolefin)Cl2]− or neutral pentacoordinated [Rh(Cl)(diolefin)(LL)] complexes depending on the degree of N-substitution in the ligands. When the reactions were performed in solutions saturated with CO only ion-pair [Rh(CO)2(LL)]+ [Rh(CO)2Cl2]− complexes were obtained; these carbonyl derivatives show some metal-metal interaction. Reaction of [Rh(NBD)Cl]2 with ethylenediamine and triphenylphosphine gives pentacoordinated [Rh(NBD)(en)(PPh3)]+ species.

Rhodium(I) complexes with 2-(aminoalkyl)pyridines or 2-(2-aminomethyl)-1-methylpyrrol. Crsytal structure of RhCl(C8H12)(C7N2H12) and [Rh(C8H12)(C7N2H10)][Rh(C8H12)Cl2]

Abstract [Rh(L 2 )Cl] 2 (L 2 = COD, NBD; L = CO) complexes react with 2-(2-aminoethyl)-1-methylpyrrol to give only neutral tetracoordinated RhCl(L 2 )(aempyr) species, irrespective of the stoichiometric rations employed. In solution, dynamic behaviour through pentacoordinated compounds is observed. The X-ray structure of RhCl(COD)(C 7 N 2 H 12 ) indicates coordination through the primary amino group. Aminopyridines such as 2-(2-aminoethyl)pyridine or 2-(aminomethyl)pyridine afford, from the 1:2 reaction pentacoordinated RhCl(L 2 )(LL′) compounds or ionic [Rh(L 2 )(LL′)] + species. The cationic species show association processes in solution. From the 1:1 reaction Rh 2 (L 2 )Cl 2 (LL′) complexes are obtained. When LL′ = 2-(2-aminoethyl)pyridine the X-ray diffraction indicates an ionic structure [Rh(C 8 H 12 )(C 7 H 2 H 10 )[Rh(C 8 H 12 )Cl 2 ] in the solid state. In solution, evidence of an equilibrium between this species and the corresponding dimer [Rh(C 8 H 12 )Cl] 2 (μ-C 7 N 2 H 10 ) is observed.

Rhodium(I) complexes with diimines. 1H and 119Sn NMR study of the trichlorostannato compounds

Abstract Reactions of [RhL 2 Cl] 2 (L 2 COD or NBD, LCO) with α-diimines, RN:C(CH 3 )C(CH 3 ):NR′(LL); RR′NH 2 (bdh); RNH 2 , R′OH (boh); RR′N(CH 3 ) 2 (bdnh) or RR′C 6 H 5 (bda) or with 2,2′-biquinoline (biqui) and SnCl 2 afford trichlorostannato complexes. Rh(SnCl 3 )(NBD)(LL) compounds are neutral and according to their 1 H and 119 Sn NMR spectra undergo tin halide dissociation and intramolecular rearrangements. Rh(SnCl 3 )(COD)(LL) are ionic or neutral and also undergo SnCl 3 − or SnCl 2 dissociation. In the absence of SnCl 2 , [RhL 2 Cl] 2 dimers react with α-diimines to give fluxional pentacoordinated [Rh(Cl)L 2 (LL)] complexes (L 2 COD or NBD) irrespective of the stoichiometric ratios employed, or ion-pair [RhL 2 (LL)] + [RhL 2 Cl 2 ] − compounds (LCO).

Rhodium(I) complexes with unsymmetric aliphatic diamines. Crystal structure of [Rh(C8H12)(C7N2H16)][RhCl2(C8H12)] and [Rh(C8H12)(C7N2H16)]ClO4

Abstract Reactions of [Rh(COD)Cl]2 with unsymmetric aliphatic diamines (LL′) have been studied. The 1:1 ligand:dimer reactions yield ionic products [Rh(C8H12)(LL′)][RhCl2(C8H12)] that in solution are in equilibrium with the respective binuclear compounds {[RhCl2(C8H12)]2(μ-LL′)}. The X-ray structure of [Rh(C8H12)(C7N2H16)][RhCl2(C8H12)] is presented. When the reactions are performed in media saturated with CO, carbonylated ion-pair complexes are obtained. The 2:1 ligand:dimer reactions afford neutral tetracoordinated [Rh(COD)(LL′)Cl] compounds bonded through the primary amino group, and show rapid interchange of olefinic protons at room temperature. The synthesis and properties of cationic complexes of general formulae [Rh(COD)(LL′)]Cl2 and [Rh(CO)(PPh3)(LL′)]CO4 are also discussed. Cyclooctadiene compounds show association processes in acetone solution, though they are monomeric in the solid state. The X-ray structure of [Rh(C8H12)(C7N2H16)]ClO4 indicates the existence of hydrogen bonding between the oxygens in the perchlorate anion and the primary amino group in the cation.

Formation of new acylhydride rhodium(III) complexes and hydroxyalkyl derivatives in the reaction of rhodium(I) compounds containing dinitrogen donor ligands with o-(diphenylphosphino)benzaldehyde

Abstract The complexes Rh(COD)(NN)Cl (NN=2,2′-bipyridine or 1,10-phenanthroline derivatives) react with o-(diphenylphosphino)benzaldehyde (PCHO) (Rh–PCHO=1:1) to give acylhydride [Rh(Cl)(H)(PCO)(NN)] species. When this reaction is performed in the presence of SnCl2, neutral trichlorostannate compounds with phosphorus trans to tin [Rh(SnCl3)(H)(PCO)(NN)] are obtained and the complexes containing bipyridine derivatives undergo deinsertion of SnCl2 from the RhCl bond in solution. The oxidative addition of PCHO to Rh(COD)(NN)Cl in the presence of PPh3 gives cationic species [Rh(H)(PCO)(PPh3)(NN)]+ containing mutually trans phosphorus atoms. The reaction of Rh(COD)(NN)Cl with PCHO (Rh–PCHO=1:2) affords cationic complexes [Rh(H)(PCO)(PCHO)(NN)]+ where PCHO behaves as P-monodentate ligand and contains a free aldehyde group. The aldehyde group in [Rh(H)(PCO)(PCHO)(bipy)]+, may undergo the insertion reaction into the RhH bond to give the hydroxyalkyl derivative [Rh(PCO)(PCHOH)(bipy)]+.

Formation of 18e− and 16e− Acyl(η3-cyclooctenyl)rhodium(III) Complexes in the Reaction of Cationic (Cycloocta-1,5-diene)rhodium(I) Compounds with 2-(Diphenylphosphino)benzaldehyde

The reaction of cationic diolefinic rhodium(I) complexes with 2-(diphenylphosphino)benzaldehyde (pCHO) was studied. [Rh(cod)2]ClO4 (cod=cycloocta-1,5-diene) reacted with pCHO to undergo the oxidative addition of one pCHO with (1,2,3-η)cyclooct-2-en-1-yl (η3-C8H13) formation, and the coordination of a second pCHO molecule as (phosphino-κP)aldehyde-κO(σ-coordination) chelate to give the 18e− acyl(allyl)rhodium(III) species [Rh(η3-C8H13)(pCO)(pCHO)]ClO4 (see 1). Complex 1 reacted with [Rh(cod)(PR3)2]ClO4 (R=aryl) derivatives 3–6 to give stable pentacoordinated 16e− acyl[(1,2,3-η)-cyclooct-2-en-1-yl]rhodium(III) species [Rh(η3-C8H13)(pCO)(PR3)]ClO47–10. The (1,2,3-η)-cyclooct-2-en-1-yl complexes contain cis-positioned P-atoms and were fully characterized by NMR, and the molecular structure of 1 was determined by X-ray crystal diffraction. The rhodium(III) complex 1 catalyzed the hydroformylation of hex-1-ene and produced 98% of aldehydes (n/iso=2.6).

Rhodium complexes with diimines derived from glyoxal: crystal structure of [Rh(SnCl3)(NBD)(GCH)] (NBD = norbornadiene; GCH = gloxal bis(cyclohexylimine)

Abstract [{Rh(L 2 )Cl} 2 ] (L 2 ≡ COD, or norbornadiene (NBD)) react with α-diimines (LL) derived from glyoxal, irrespective of the stoichiometric ratios employed, to give [Rh 2 (L 2 )Cl 2 (LL)] when L 2 ≡ COD or [Rh(Cl)(L 2 )(LL)] when L 2 = NBD. Solutions of COD compounds contain dinuclear [{Rh(COD)(Cl)} 2 (μ-LL)] species with bridging LL groups and ionic [Rh(COD)(LL)] + [Rh-(COD)Cl 2 ] − species, in temperature-dependent ratios. The NBD compounds are pentacoordinated in the solid state and undergo rearrangements in solution. When the reactions are performed in the presence of SnCl 2 , pentacoordinated [Rh(SnCl 3 )-(diolefin)(LL)] are obtained, which in solution undergo SnCl 3 − dissociation. The molecular structure of [Rh(SnCl 3 )(NBD)(GCH)] (GCH = glyoxalbis(cyclohexylimine)) has been determined by an X-ray diffraction study. It is best described as distorted square pyramidal with the equatorial positions occupied by the diolefin and the diimine respectively, and the SnCl 3 fragment in the apical position.

Isolation of [Rh(diolefin)X2]- species and their reactions with P- or N-donor ligands, tin(II) halides and carbon monoxide

Abstract Anionic [Rh(diolefin)X2]− species (X = Cl, Br) have been prepared and their reactions studied. The reactions with monodentate ligands led to neutral tetracoordinated complexes, and with N-donor bidentate ligands (Rh : LL = 2 : 1) gave Rh(X)(diolefin)(LL), [Rh(diolefin)(LL)]+[Rh(diolefin)X2]−, or [Rh(diolefin)(LL)]X compounds, depending on the nature of LL or X. Reactions with carbon monoxide involved diolefin displacement. A trichlorostannato complex was obtained from the [Rh(COD)Cl2]− species. Reactions of [Rh(COD)Br]2 with bidentate N-donor ligands were also studied.