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2-Aminoalkylpyridines [H2N(CH2)nC5H4N] (n = 1 or 2) react with [IrHCl{(PPh2(o-C6H4CO))2H}] (1a) in THF to afford hydridoirida-β-ketoimines [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CN(CH2)nC5H4N))H}] (2, n = 1; 3, n = 2) with intramolecular N-H···O hydrogen bonding and a dangling pyridine. In protic media 2–3 transform into [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4C=N(CH2)nC5H4N))] (4, n = 1; 5, n = 2) containing new terdentate PCN ligands in a facial disposition with the phosphorus atom trans to H and an iminoacyl fragment trans to the other phosphorus atom. The formation of 4–5 requires breaking of the hydrogen bond, isomerization, and dehydrochlorination of an intermediate iminium-acyl species to allow the coordination of the nitrogen atom of pyridine to iridium. The reaction of 1a with the N-substituted N-methylaminomethylpyridine allows the synthesis of [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4C=N(CH3)CH2C5H4N))]ClO4 (6) containing a PCN ligand with an iminium-acyl moiety trans to phosphorus. The reaction of [IrH2{(PPh2(o-C6H4CO))2H}] (1b) with 2-(aminoalkyl)pyridines [H2N(CH2)nC5H4N] (n = 1 or 2) in MeOH requires the presence of KOH to afford the hydrido derivatives [IrH(PPh2(o-C6H4CO))2(NH2(CH2)nC5H4N,κNH2)] (7, n = 1; 8, n = 2) were the ligands are amino-coordinated with a dangling pyridine. The reaction occurs with hydrogen evolution and transfer of hydrogen from a hydroxyl in the solvent to iridium. Single-crystal X-ray diffraction analysis was performed on 3, 4, 6, and 8.

2-Aminopyridines (H2NC5H3RN) react with [IrH2{(PPh2(o-C6H4CO))2H}] (1) in refluxing methanol to afford [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CHNHC5H3RN))] (R = H (2), R = CH3 (3)) containing new terdentate PCN ligands in a facial disposition with the phosphorus atom trans to H and the new alkyl fragment trans to the other phosphorus atom. The formation of 2 and 3 requires imination of the hydroxycarbene moiety in 1, iridium to carbon hydrogen transfer, and coordination of the nitrogen atom of pyridine to iridium. In refluxing methanol the reaction of 1 with the N-substituted 2-(methylamino)pyridine leads to [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4C(OH)N(CH3)C5H4N))] (4), containing a PCN ligand with a hydroxyalkyl moiety trans to phosphorus and the nitrogen atom of pyridine trans to hydride. By performing this reaction in the presence of KOH, complex [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4C(OCH3)N(CH3)C5H4N))] (5), with a methoxyalkyl moiety in the PCN ligand and similar stereochemistry to that of 2 and 3, is obtained. In chl...

The reaction of [RhCl(COD)]2 (COD = 1,5-cyclooctadiene) with PPh2(o-C6H4CHO) (Rh/P = 1:1) in the presence of 4-methylpyridine (4-pic) or isoquinoline (iquin) leads to hydridoacyl complexes [RhHCl(PPh2(o-C6H4CO))L2] (L = 4-pic, 1; iquin, 2). Their reaction with diphenylphosphine oxide affords neutral complexes [RhHCl{(PPh2(o-C6H4CO))(PPh2O)H}L] (L = pyridine (py), 4; 4-pic, 5; iquin, 6) with trans P-ligands belonging to a formally PCP pincer ligand due to the formation of a O---H---O hydrogen bond between the oxygen atom of the diphenylphosphinous acid and the oxygen atom of the coordinated acyl. The reaction of 4 with chelating N-donors (LL) leads to displacement of pyridine and chloride to afford cationic [RhH{(PPh2(o-C6H4CO))(PPh2O)H}(LL)]BPh4 (LL = 2,2′-bipyridine, 7; biacetyldihydrazone, 8; biacetyloximehydrazone, 9; 2-aminomethylpyridine, 10), which undergo cleavage of the O---H---O hydrogen bond in solution. Complex 9, containing a nonsymmetric ligand, exists in solution as an equimolar mixture of t...

The reaction of the platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) with quinoline-8-carbaldehyde (C9H6NCHO) in MeOH/H2O (Pt/C9H6NCHO = 1/2) leads to the cleavage of the chloride bridges in 1 with acetaldehyde displacement and to the formation of the acetylacyl(hydroxyalkyl)platinum(IV) complex [Pt(COMe)Cl(C9H6NCO-κN,κC)(C9H6NCHOH-κN,κC)] (3) as a single diastereomer (OC-6-46). Water-assisted activation of the OC–H bond of one aldehyde and H transfer to the oxygen atom of the second aldehyde occurs. In the presence of sodium methoxide, dehydrochlorination of the platinum starting material affords the dinuclear [Pt2(C9H6NCO-κN,κC)2(μ-COMe)2] (4) with acetyl bridges in a head-to-tail fashion. Pyridine or tetrahydrofuran fail to cleave the acetyl bridges, which are readily cleaved by triphenylphosphane to afford the mononuclear [Pt(C9H6NCO-κN,κC)(COMe)(PPh3)] (5) with the two acyl groups in cis positions. The reaction of the diacetylbis(amine)platinum(II) complexes [Pt(COMe)2(NH2R)2] (R = CH2Ph (2a), Et (2b))...

Unprecedented metallapyrazoles [IrH2{Ph2P(o-C6H4)CNNHC(o-C6H4)PPh2}] (3) and [IrHCl{Ph2P(o-C6H4)CNNHC(o-C6H4)PPh2}] (4) were obtained by the reaction of the irida-β-ketoimine [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNNH2))H}] (2) in MeOH heated at reflux in the presence and absence of KOH, respectively. In solution, iridapyrazole 3 undergoes a dynamic process due to prototropic tautomerism with an experimental barrier for the exchange of ΔGcoal⧧ = 53.7 kJ mol–1. DFT calculations agreed with an intrapyrazole proton transfer process assisted by two water molecules (ΔG = 63.1 kJ mol–1). An X-ray diffraction study on 4 indicated electron delocalization in the iridapyrazole ring. The reaction of the irida-β-diketone [IrHCl{(PPh2(o-C6H4CO))2H}] (1) with H2NNRR′ in aprotic solvents gave irida-β-ketoimines [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNNRR′))H}] (R = R′ = Me (5); R = H, R′ = Ph (8)), which can undergo N–N bond cleavage to afford the acyl–amide complex [IrHCl(PPh2(o-C6H4CO))(PPh2(o-C6H4C(O)N(CH3)2))-κP,κO] (6) o...

The acylhydridorhodium(III) complex [RhHCl{PPh2(o-C6H4CO)}(py)2] (1) reacts with 8-quinolinecarbaldehyde (C9H6NCHO) to afford mixed diacyl [RhCl(C9H6NCO){PPh2(o-C6H4CO)}(py)] (2) with acyl groups trans to chlorine and to pyridine. Complex 1 undergoes displacement of pyridine by 2-(aminomethyl)pyridine (ampy) or diphosphanes to give hydridoacyl neutral [RhHCl{PPh2(o-C6H4CO)}(LL)] [LL = ampy (3), bis(diphenylphosphanyl)methane (dppm, 5), 1,3-bis(diphenylphosphanyl)propane (dppp, 6), 1,2-bis(diphenylphosphanyl)ethane (dppe, 7)] with hydride trans to chloride. Complex 3 exchanges hydride with chloride to give [Rh(Cl)2{PPh2(o-C6H4CO)}(ampy)] (4). The reaction of 2 with bidentate N-donor ligands yields cationic mixed diacyl [Rh(C9H6NCO){PPh2(o-C6H4CO)}(NN)]+ species [NN = 2,2′-bipyridine (bipy, 8), ampy (9)]. Neutral or cationic diacyl complexes that contain two acylquinoline fragments can be obtained by the reaction of dimer [Rh(μ-Cl)(C9H6NCO)2]2 (10) with pyridine to give [Rh(Cl)(C9H6NCO)2(py)] (11) or with bidentate N- or P-donor ligands (LL) to afford [Rh(C9H6NCO)2(LL)]+ [LL = dppm (12), dppe (13), dppp (14), 1,4-bis(diphenylphosphanyl)butane (15), ampy (16), 8-aminoquinoline (17), biacetyldihydrazone (18), bipy (19)] with the acyl groups trans to LL. Complex 11 is highly fluxional in solution. At low temperatures, the acylquinoline chelate opens to allow an intramolecular exchange between 11a and 11b (ΔH‡ = 10.1 ± 0.2 kcal mol–1 and ΔS‡ = 1.0 ± 0.1 cal K–1 mol–1), and pyridine dissociation occurs at room temperature. All the complexes were characterized spectroscopically. Single crystal X-ray diffraction analysis was performed on 2.

The dihydridoirida-β-diketone [IrH2{(PPh2(o-C6H4CO))2H}] (2) has been used as a homogeneous catalyst for the hydrolysis of ammonia- or amine-boranes to generate up to 3 equivalents of hydrogen in the presence of air. When using 0.5 mol% loading of 2, dimethylamine-borane is hydrolysed completely within 8 min at 30 °C and maintains its activity in consecutive runs. Ammonia-borane or tert-butylamine-borane is hydrolysed completely within 32 or 25 min respectively. Triethylamine-borane fails to be hydrolysed. Kinetic studies suggest a sequence of two consecutive first-order reactions, in which an intermediate builds up and finally falls, with the first step being the rate controlling step. ΔH1(‡) are in the range 65-85 kJ mol(-1) and negative values of ΔS1(‡) are obtained. A multinuclear NMR study of the catalyzed reaction shows the formation of a resting state (A) of the active catalyst proposed to be of the hydridodiacyl type [IrH(PPh2(o-C6H4CO))2(solvent)] with a hydride trans to the acyl group. In the absence of substrate a dormant species (B) is formed. By the reaction of hydridoirida-β-diketones with ammonia, the hydridoirida-β-ketoimine [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNH))H}] (3) and the hydridobis(acylphosphane)aminoiridium(III) complex [IrH(PPh2(o-C6H4CO))2(NH3)] (4), with a hydride trans to phosphane, are formed. Aromatic amines such as aniline or anisidines afford cationic [IrH{(PPh2(o-C6H4CO))2H}(C6H4RNH2)]ClO4 (R = H (6); p-MeO (7); o-MeO (8)) hydridoirida-β-diketones with a coordinated amine group trans to the hydride. The dormant species B is proposed to be of the hydridobis(acylphosphine)aminoiridium(III) type with a hydride trans to the amine group.