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A highly efficient multitasking FeOCN composite was synthesized in a single step by the fast heating of an Fe(III) salt and urea. The composite was confirmed by various spectroscopic and analytical techniques which include XRD, FTIR, Raman, FESEM, and XPS analysis. The composite was then investigated for various organic transformations and it was found to be excellent for the hydroformylation of 1‐octene in toluene under 50 bar syngas pressure at 95 °C. The composite was also found to be significantly active for the hydration reactions of alkynes and nitriles under acid‐ and base‐free conditions. The hydration reactions were performed in aqueous methanol at 120 °C and an excellent yield of regioselective products was obtained under optimized reaction conditions. [ABSTRACT FROM AUTHOR]

The synthesis and characterisation of two new water‐soluble RhI mononuclear 1,4‐diazabutadiene (DADs) complexes of general formula: [Rh(DADs‐R)(COD)], where (DADs = sulfonated‐tagged–1,4‐diazabutadiene, COD = cyclooctadiene; and R = H or C10H8), are described. The rhodium(I) complexes were obtained via a complexation reaction of [Rh(COD)(MeCN)2]BF4 with the sulfonated α‐diimine (DAD) ligands, which were previously obtained from a Schiff base condensation reaction of 4‐aminophenol with either 1,2‐ethanedione or acenapthenequinone. All rhodium complexes and their precursor ligands were characterised using 1H NMR, 13C NMR, FT‐IR spectroscopy and mass spectrometry. Their performance as catalyst precursors in the hydroformylation of 1‐octene was assessed and compared to those of the non‐sulfonated RhI mononuclear 1,4‐diazabutadiene (DAD) complexes. Utilisation of the water soluble [Rh(DADs‐R)(COD)] lead to high conversions and regioselectivity (linear/branched aldehyde ratio) in the aqueous biphasic hydroformylation of 1‐octene. Additionally, the catalysts were recovered by phase separation and are reusable over four consecutive catalytic runs without significant loss in catalytic activity. [ABSTRACT FROM AUTHOR]

This review provides an overview of recent developments in the area of aqueous biphasic hydroformylation of higher olefins using metal catalysts and surfactants, cosolvents, thermoregulated ligands, cyclodextrins, and most importantly emerging water-soluble nonphosphine ligands. Water-soluble phosphine ligands have been widely explored for aqueous biphasic hydroformylation; however, phosphines are generally expensive and are prone to oxidation hence the recent interest in exploring other ligands. Various approaches have been used to introduce hydrophilicity to the ligands. The catalytic activity of monometallic and heterobimetallic systems containing nonphosphine ligands in aqueous biphasic media is emphasized in this review. [ABSTRACT FROM AUTHOR]

The synthesis of cationic bimetallic 'pseudo-paddlewheel' dirhodium(II,II) acetato-bipyridyl complexes of the type [Rh 2 (OAc) 2 (bis-4,4′-R-bipy) 2 ]2+ containing either acetate (AcO-) or hexafluorophosphate (PF 6 - ) counter ions is described. In both series, the 4 and 4′ positions of each bipyridyl ligand are substituted such that R = H, CF 3 or OMe (complexes 1 - 3 for AcO- and 4 - 6 for PF 6 - derivatives). As catalyst precursors for the hydroformylation reaction, the complexes were initially evaluated using 1-octene as a substrate. The complex which displayed the greatest chemoselectivity toward aldehydes was evaluated further as a catalyst precursor for the hydroformylation of styrene, cyclohexene and 7-tetradecene as substrates. A correlation between product distributions in terms of chemo- and regioselectivity in the hydroformylation reaction versus axial site interaction is delineated. Recyclability was achieved through suitable modification of the substituent and counter ion, culminating in a simplistic method of post-catalytic precursor collection with minimal reduction of the catalytic activity over 5 cycles. [Display omitted] • Discrete set of dirhodium(II,II) acetato-bipyridyl complexes were synthesised. • Evaluated as catalyst precursors in the hydroformylation reaction. • Trends involving axial interactions were delineated. • Good conversions were obtained across a range of olefinic substrates. • Catalysts can be effectively recycled with no degradation. [ABSTRACT FROM AUTHOR]

A series of organometallic dendrons containing N,O-salicylaldimine entities at the focal point were synthesised by reacting the N,O-salicylaldimine-functionalised Fréchet dendrons (G0, G1 and G2) with a [Rh(μ-Cl)(η2:η2-COD)]2 dimer to yield the corresponding Rh(COD) [COD = cyclooctadiene] complexes. These Rh(COD) complexes were exposed to an atmosphere of CO to yield a new class of rhodium carbonyl organometallic dendrons with Rh(CO)2 units at the focal point. All the compounds were characterised using standard spectroscopic and analytical techniques, these include nuclear magnetic resonance, infrared spectroscopy, mass spectrometry and single-crystal X-ray diffraction for compounds 1, 4 and 7. All of the complexes were evaluated in the hydroformylation of 1-octene, with excellent conversion and chemoselectivity towards aldehydes. The G0-(CO)2 catalyst precursor (7) was active in the hydroformylation of 1-octene, styrene, 7-tetradecene, methyl oleate, triolein, d-limonene and R-citronellal. The conversion and chemoselectivity towards aldehydes for 7-tetradecene, methyl oleate, triolein and d-limonene were promising. Across a particular dendron series, an increase in chemoselectivity was observed due to the dendritic effect. Mercury drop tests were performed for the G0-analogues and these confirm that the hydroformylation can be attributed to a combination of homogeneous and heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

The synthesis of water-soluble rhodium(I) salicylaldiminato and salicylhydrazonic complexes has been achieved employing two preparative routes. Schiff base condensation between 6A-deoxy-6A-amino-β-CD or 6A-deoxy-6A-hydrazino-β-CD and 5-sodiosulfonato-2-hydroxybenzaldehyde (sulfonated salicylaldehyde) (1) or 5-sodiosulfonato-3-tert-butyl-2-hydroxybenzaldehyde (sulfonated tBu-salicylaldehyde) (2) led to the formation of the corresponding imine or hydrazone ligands (3, 4, 5 and 6). Reaction of [Rh(COD)2+BF4−] with these new ligands in an alkaline solution formed the corresponding rhodium complexes quantitatively. These rhodium(I) complexes could also be prepared in one-pot by mixing, in stoichiometric proportions, the modified β-CDs with the sulfonated salicylaldehyde and with the rhodium precursor in an alkaline solution at room temperature. These rhodium complexes were applied as catalysts in the aqueous biphasic hydroformylation of 1-decene as a model reaction. [ABSTRACT FROM AUTHOR]

Monometallic and heterobimetallic complexes of Rh(I) bearing chelating N, O-bidentate aryl- and ferrocenyl-derived ligands have been synthesised via Schiff base condensation reactions, and characterised fully using 1H NMR, 13C{1H} NMR and Fourier transform infrared spectroscopies, elemental analysis and mass spectrometry. The new monometallic and heterobimetallic complexes were evaluated as potential catalyst precursors in the hydroformylation of 1-octene at 95°C and 40 bar. The ferrocenylimine mononuclear compounds were inactive in the hydroformylation experiments. The Rh(I) monometallic and the ferrocene-Rh(I) heterobimetallic pre-catalysts displayed good activity and conversion of 1-octene as well as outstanding chemoselectivity towards aldehydes in the hydroformylation reaction. [ABSTRACT FROM AUTHOR]

A series of rhodium(I)-1,2,3-triazol-5-ylidene (trz) complexes are described, containing either a novel triarylated trz ligand A' (N1, N3-arylated, C4-ferrocenyl) {complexes 1, [Rh(A')Cl(cod)]; 4, [Rh(A')Cl(CO)2]}, or N3-alkylated triazolylidenes with a C4-ferrocenyl {2, [Rh(B')Cl(cod)]; 5, [Rh(B')Cl(CO)2]} or C4-phenyl substituent {3, [Rh(C')Cl(cod)]; 6, [Rh(C')Cl(CO)2]}. The free mesoionic carbene (MIC) A' is structurally characterized and its electronic properties evaluated by employing the complex [Pd(Br)2(iPr2-bimy)(A')] (7) in an NMR spectroscopic analysis method. The redox activity of A' is exploited, and the chemically oxidized precursor Aox and complex 4ox are isolated. The mesoionic carbene complexes 1-3, as well as in situ oxidized 1ox, are used as homogeneous catalysts for the hydroformylation of 1-octene for the first time, and the influence of chemical oxidation of the catalyst on the activity and chemoand regioselectivity of the catalyst precursor 1 is evaluated. [ABSTRACT FROM AUTHOR]

A series of water-soluble Rh(I) mononuclear complexes of general formula: [Rh(sulphsal-X-R)(COD)] [sulphsal = sulphonated salicylaldimine, COD = cyclooctadiene; where R = H, Cl, CH3 and X = H, tBu] have been synthesized. All the compounds were characterised using various spectroscopic and analytical techniques such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, single crystal X-ray diffraction (for complex 10) and mass spectrometry. All the compounds display excellent water-solubility at room temperature and were tested as catalyst precursors in the aqueous biphasic hydroformylation of 1-octene. The catalysts could be easily recovered by phase separation and were used up to 5 times without any significant loss in activity and 1-octene conversion. Very high yields of the expected aldehydes were obtained without addition of any phase transfer agents, co-solvents or hydrophobic ligands. Excellent aldehyde chemoselectivity is observed for all the catalysts but this varied each time the catalysts were recycled, with the formation of a small amount of internal olefins. ICP-OES and mercury poisoning experiments show that a combination of homogeneous catalysis and catalysis mediated by nanoparticles is taking place in these systems. [ABSTRACT FROM AUTHOR]

Water-soluble mononuclear ruthenium complexes containing monodentate P-donor ligands [1,3,5-triaza-7-phosphaadamantane (PTA) and P(OMe)3], together with a mononuclear bidentate salicylaldimine ruthenium-arene complex, were synthesized from a water-soluble dimeric ruthenium(II)-arene precursor. These complexes were used as catalyst precursors in the aqueous biphasic hydroformylation of 1-octene. Hydroformylation reactions with these Ru-arene complexes showed that the complexes are active hydroformylation catalyst precursors in water. The catalyst precursors convert 1-octene into a range of products, which include aldehydes and alcohols, as well as isomerization and hydrogenation products. The less basic the ligand, the more it favoured the production of aldehydes. The relative basicity of the ligands P(OMe)3, PTA and the N, O-chelating ligand was elucidated by cyclic voltammetry and supported by DFT calculations. The catalysts show good recyclability without a significant decrease in 1-octene conversion. All of the catalysts could be reused three times. [ABSTRACT FROM AUTHOR]

Chitosan-supported Rh complexes were prepared in a stable form to form new catalysts and have been characterized using elemental analysis, UV-vis, FT-IR, ICP-MS, PXRD, solid state 31P and 13C NMR spectroscopy and TEM. Mononuclear Rh(i) complexes (as models for the heterogenized catalysts) were also prepared via the Schiff-base condensation reaction and the crystal structure of the cyclohexyl iminophosphine Rh(i) complex was elucidated. The chitosan-supported Rh complexes and mononuclear analogues are active catalysts in the hydroformylation of 1-octene with optimal reaction conditions realized at 75 °C and 30 bar syngas pressure. Under these conditions, 1-octene conversion to the desired linear aldehydes was observed and the best selectivity in this regard was shown by the supported iminophosphine-based rhodium catalyst. Overall, the supported catalysts showed similar chemo- and regioselectivities in comparison to their mononuclear counterparts but where more stable, being reused up to four times without loss of activity and selectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mono- and dinuclear Rh(I) complexes based on alkylated-sulfonated scaffolds have been prepared. • The complexes were characterized using several spectroscopic and analytical techniques. • The complexes were evaluated as catalyst precursors for the hydroformylation of 1-octene. • The dinuclear complex showed higher conversion rates. The synthesis of two water-soluble Rh(I) complexes, a disulfonated diimine mononuclear complex and a tetrasulfonated tetraimine binuclear complex, is reported. The reaction of the N,N -donor ligands containing the sulfonated alkyl substituents with [Rh(COD)(MeCN) 2 ]BF 4 led to the formation of the corresponding water-soluble Rh(I) complexes. The complexes were fully characterised using an array of analytical techniques such as NMR, infrared spectroscopy and mass spectrometry. The complexes were evaluated as catalyst precursors in the aqueous biphasic hydroformylation of 1-octene. Both catalyst precursors are highly active as hydroformylation precatalysts showing high conversions of 1-octene and good aldehyde chemoselectivity with no hydrogenation products (alkanes or alcohols) observed. The binuclear complex gave higher quantitative conversions compared to the mononuclear rhodium complex. Additionally, the catalysts were recovered by phase separation and reused over four catalytic runs, notably with a significant drop in conversion after each cycle. [ABSTRACT FROM AUTHOR]

A series of mono- and multivalent phosphorus-based ligands was synthesised by the lower-rim benzylation of the water-soluble ligand, 1,3,5-triaza-7-phosphaadamantane (PTA). These ligands were used to prepare mono-, bi- and trinuclear Rh(I) complexes whose catalytic activity, product selectivity and recyclability were evaluated in the aqueous biphasic hydroformylation of 1-octene. [ABSTRACT FROM AUTHOR]

Two mononuclear rhodium complexes, Rh(I)-1,5-cyclooctadiene and Rh(III)-pentamethylcyclopentadienyl, and a bimetallic Rh(I)-Rh(III) mixed-valence complex were synthesised. The complexes were fully characterised using an array of analytical techniques which included NMR and infrared spectroscopy, single-crystal X-ray diffractometry, elemental analysis, and mass spectrometry. These complexes were evaluated as catalyst precursors in the hydroformylation of olefins. All catalyst precursors were active in the hydroformylation of 1-octene under optimised conditions. The rhodium complexes generally showed chemoselectivity towards the formation of linear aldehydes. The electrochemical behaviour of the rhodium complexes was examined using cyclic voltammetry. [ABSTRACT FROM AUTHOR]

A series of fluorocarbon-containing salicylaldimine and iminophosphine Schiff base ligands and their Rh(I) complexes were synthesized. The synthesized ligands and complexes were characterized using different analytical and spectroscopic techniques including ( 1 H, 13 C{ 1 H}, 31 P{ 1 H} and 19 F{ 1 H} NMR spectroscopy), FT-IR spectroscopy, mass spectrometry (ESI and EI), and elemental analysis. In addition, single crystal X-ray diffraction was also used for characterization for complexes 1 and 2 . Consequently, the Rh(I) synthesized complexes were evaluated as catalyst precursors in the hydroformylation of 1-octene. The hydroformylation results showed that the iminophosphine and salicylaldimine-based catalyst precursors are active and selective under mild conditions, converting 1-octene to mostly aldehydes. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of poly(propyleneimine)-iminopyridyl and iminophosphine rhodium(I) metallodendrimers, with rhodium coordinated to monodentate (N-donor) and chelating, heterobidentate (P,N) moieties respectively located on the periphery, has been accomplished in order to evaluate their potential as hydroformylation catalysts. Related mononuclear complexes were obtained in a similar manner to model the multinuclear complexes. The multinuclear rhodium(I) complexes were found to be effective catalyst precursors in the hydroformylation of 1-octene, achieving higher conversions, faster reaction rates and slightly enhanced catalytic activity when compared with analogous mononuclear rhodium complexes. Hydroformylation reactions using the tetra- and octanuclear rhodium complexes generally show a chemoselective formation of aldehydes, together with a small amount of isomerisation products. [Copyright &y& Elsevier]

• Core-functionalised dendritic rhodium(I) precatalysts were evaluated for olefin hydroformylation. • Precatalysts show good yields and aldehyde chemoselectivity. • Higher generation dendritic precatalysts gave better regioselectivity, favouring linear aldehydes. • Mercury drop experiments suggest a combination of homogeneous and heterogeneous catalysis. Rhodium(I) poly(aryl ether)-based, core-functionalised alpha-diimine metallodendrimers were investigated as catalyst precursors in the rhodium-catalysed hydroformylation of terminal olefins, 1-octene and styrene. The electronic environment across the metallodendrimer series was probed using cyclic voltammetry. The electrochemical behaviour of the metallodendrimers show irreversible and quasi-reversible electrochemical behaviour in the range 0.0–2.0 V at a scan rate of 100 mV s−1. All the catalyst precursors (C1 - C6) gave excellent conversions of the respective substrates with good chemoselectivity under the investigated conditions. In general, the higher dendritic catalysts C5 and C6 gave better regioselectivity, favouring linear aldehydes. [ABSTRACT FROM AUTHOR]

• Water-soluble Rhodium(I) precatalysts were evaluated for olefin hydroformylation. • Catalysts can be recycled using an aqueous biphasic strategy. • The trinuclear precatalyst shows greater stability. • Precatalysts show good activity and aldehyde chemoselectivity. Water-soluble, sulfonated, salicylaldiminato-aryl ether mono- (7) and trimeric (8) ligands were prepared and reacted with the [Rh(μ-Cl)(η2:η2−COD)] 2 dimer to yield the corresponding water-soluble mononuclear (9) and trinuclear (10) Rh(I) complexes. These rhodium complexes were evaluated and are active as catalyst precursors in the aqueous biphasic hydroformylation of 1-octene and styrene. Optimal conditions were realised, using 1-octene as a model substrate, at 85 °C and a syngas pressure of 50 bar, where the best activity and chemoselectivity for aldehydes was obtained. Catalyst recycling was successfully conducted over 5 cycles in a biphasic medium, with a gradual loss in catalytic performance for both complexes. However, the dendrimer-stabilised trinuclear precatalyst (10) showed improved recyclability during "neat", aqueous monophasic hydroformylation experiments, while the mononuclear precatalyst (9) showed a reduced overall performance. Both precatalysts showed sustained catalytic activity (> 450 h−1) and a total bias towards aldehyde chemoselectivity during the aqueous biphasic hydroformylation of styrene. [ABSTRACT FROM AUTHOR]

• Mononuclear Rh(I) metallacycles based on alkylated-PTA scaffolds have been prepared. • The complexes were characterized using several spectroscopic and analytical techniques. • The complexes were evaluated as catalyst precursors for the aqueous biphasic (water-toluene) hydroformylation of 1-octene. • The precatalysts are chemoselective towards aldehydes but show poor recyclability. A series of rhodium(I) metallacycles based on alkylated PTA complexes were synthesised and fully characterised using a range of spectroscopic and analytical techniques. These mononuclear Rh(I) complexes were evaluated in the aqueous biphasic (water-toluene) hydroformylation of 1-octene, showing chemoselectivity to aldehydes. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Rhodium(I) monometallic and heterobimetallic precatalysts evaluated for post-metathesis product 7-tetradecene hydroformylation. • High turnover numbers up to 4310 towards predominantly alkyl-branched aldehydes products. • Heterobimetallic precatalyst showed improved hydroformylation performance under mild reaction conditions. • Precatalysts remain active over at least three consecutive reaction cycles. Abstract The rhodium-catalysed hydroformylation of the post-metathesis product 7-tetradecene using aryl- (1) and ferrocenyl- (2) Schiff base derived precatalyst complexes was investigated. It was found that the reaction temperature (75–115 °C), pressure (30–60 bar, CO/H 2 = 0.5–2) and 7-tetradecene-to-precatalyst molar ratio (1000:1–6000:1) had a significant influence on the hydroformylation performance. Turnover numbers up to 4310 were observed and the selectivity data show a temperature and pressure-dependent conversion of 7-tetradecene to the primary branched aldehyde product 2-hexylnonanal and isomeric branched aldehydes. A cooperative effect between rhodium and ferrocene was observed as hydroformylation performance results obtained with the heterobimetallic precatalysts (2) differ from that achieved using the monometallic catalyst system (1) under mild reaction conditions. Both precatalysts performed optimally at a temperature of around 95 °C. Lifetime studies with the precatalysts were conducted and the precatalysts were found to remain active over at least three consecutive reaction cycles. [ABSTRACT FROM AUTHOR]

New examples of the rare class of rhodium(I) ferrocenyl Fischer carbene complexes 1-8, [Rh(LL)Cl{C(XR)Fc}] [LL = cod, (CO)2, (CO, PR3) (R = Ph, Cy or OPh), and (CO, AsPh3); XR = OEt or NHnPr] were prepared, and the electronic effects of coligands and alkoxy vs aminocarbene substituents were investigated by spectroscopic and electrochemical methods. The molecular structures of complexes 1, 2, and 4-6 were confirmed by single-crystal X-ray diffraction. The use of the complexes 1-8 as homogeneous catalysts for the hydroformylation of 1-octene was demonstrated, and the influence of the carbene substituents and coligands on the activity and regioselectivity of the catalysts evaluated. Finally, the stability of the Rh-Ccarbene bond of complex 1 under hydroformylation conditions was confirmed with 13C NMR experiments. [ABSTRACT FROM AUTHOR]

Water-soluble complexes based on monosodium 5-sulfonato salicylaldimine ( 3 ) and 3- t butyl-5-sulfonatosalicylaldimine have been synthesised via sulfonation and Schiff base condensation reactions. The ligand ( 3 ) and the new water-soluble mononuclear 5-sulfonatosalicylaldimine-ferrocenylimine complexes ( 4 and 5 ) have been synthesised and characterised fully using 1 H NMR, 13 C{ 1 H} NMR, and FT-IR spectroscopy, elemental analysis as well as mass spectrometry. Subsequently, the Rh(I) heterobimetallic complexes ( 6 and 7 ) were synthesised from [RhCl(COD)] 2 (COD = 1,5-cyclooctadiene) and the ferrocenylimine metalloligands ( 4 and 5 ) and characterised using various analytical and spectroscopic techniques. These complexes were applied as catalyst precursors in aqueous biphasic hydroformylation reactions. Optimal conditions were established at 95 °C (40 bar), showing the best chemoselectivity for aldehydes. The mononuclear ferrocenyl pre-catalysts ( 4 and 5 ) were inactive in the aqueous-biphasic hydroformylation of 1-octene. The heterobimetallic catalyst precursors ( 6 and 7 ) displayed good activity and could be recycled for at least 4 runs under the investigated conditions for the aqueous biphasic hydroformylation of 1-octene. [ABSTRACT FROM AUTHOR]

The use of metallodendrimers in various applications such as catalysis and biology has highlighted the potential for the development of polynuclear metal-based complexes. This review provides a more focused overview of the developments in the application of metallodendrimers as catalysts for the hydroformylation reactions involving olefins. Specific attention is drawn to the influence of these dendritic scaffolds on the activity as well as the chemo- and regioselectivity afforded by the catalyst itself. We furthermore emphasize the recyclability of the rhodium-bearing metallodendrimers via heterogenization of homogeneous catalysts. Recyclable and reusable catalyst precursors are attractive in championing the sustainable use of mineral resources, especially where rare, expensive, and fast-depleting metals such as rhodium are of prime importance. [Display omitted] • A review of metallodendrimers for hydroformylation is presented. • This covers both heterogeneous and homogeneous metallodendrimers. • Distinction is made between core- and peripheral-functionalised dendrimers. • Strategies for recycling are touted. [ABSTRACT FROM AUTHOR]

The preparation of a series of rhodium(I) complexes coordinated by various electronically tuneable Fischer carbene (FC) ligands, is reported. The Rh(I) metal complexes' electronic properties could readily be modulated by variation of a p - N,N- dimethylaniline moiety with a ruthenocenyl substituent, or alternatively, substituting the carbene O -heteroatom for an amino-group. The electronic properties of the complexes were evaluated, and it was determined from the Tolman electronic parameters that the donor-ability of the FC ligands are comparable to N -heterocyclic carbenes. Furthermore, the facile control of the electronic properties of the complexes was demonstrated by mild oxidation of a ferrocenyl aminocarbene rhodium(I) complex, yielding the corresponding ferrocenium rhodium(I) complex cation. Finally, the complexes were evaluated as catalyst precursors for the hydroformylation of 1-octene. RhI Fischer carbene complexes are evaluated in the hydroformylation of 1-octene, with tailoring of the catalyst performance allowed by the tuning of the electronic properties of the electron-donating Fischer carbene ligands. Image 1 •The manuscript describes the synthesis and spectroscopic and structural characterisation of new Fischer carbene complexes of rhodium(I), containing ferrocenyl, ruthenocenyl, or p- N,N -dimethylaniline substituents. • The catalytic performance of the rhodium(I) Fischer carbene complexes in the hydroformylation of 1-octene was evaluated. • Chemical oxidation of the ferrocenyl aminocarbene rhodium(I) complex was investigated as a possible redox-switchable catalyst. • Improved catalytic activity (turnover frequency) was observed for ruthenocenyl Fischer carbene complexes, while improved regioselectivity (linear aldehyde formation) was achieved by the dimethylaniline Fischer carbene complexes. [ABSTRACT FROM AUTHOR]

• Fréchet-type dendrons containing a chelating N,P -iminophosphine entity at the focal point have been prepared. • Neutral Rh(I) organometallic dendrons were synthesized by reacting the N,P -iminophosphine dendrons with [Rh(μ-Cl)(CO) 2 ] 2. • The complexes were characterised using several spectroscopic and analytical techniques. • The complexes were evaluated as catalyst precursors in the hydroformylation of 1-octene but showed poor conversion. Fréchet-type dendrons containing a chelating N,P -iminophosphine entity at the focal point were synthesized by reacting an N,P -iminophosphine Schiff base with the appropriate bromido-Fréchet dendron (G 0 , G 1 or G 2) via a Williamson-ether reaction. Neutral Rh(I) organometallic dendrons were synthesized by reacting the N,P -iminophosphine dendron with [Rh(μ-Cl)(CO) 2 ] 2. The ligands and complexes were characterised using NMR and IR spectroscopy, mass spectrometry, elemental analysis and the G 0 analogue was characterised using single-crystal X-ray diffraction. All complexes were evaluated as catalyst precursors for the hydroformylation of 1-octene. [ABSTRACT FROM AUTHOR]

• Rhodium-salicylaldimine precatalysts evaluated for olefin hydroformylation. • Catalysts can be reused using organic solvent nanofiltration. • Both catalysts have an activation of 62 kJ mol−1. • Observed rate constants compare favourably with a modified rate model. Rh(I)-salicylaldimine-triazole mononuclear (6) and trinuclear (7) complexes based on an aryl-ether scaffold were investigated as precatalysts in the rhodium-catalysed hydroformylation of the terminal olefin, 1-octene, and internal olefins, 7-tetradecene and 4-octene. The complexes generally show good catalytic activity in the hydroformylation of 1-octene at temperatures ranging from 75 °C to 95 °C and syngas pressures of 20 to 40 bar. The precatalysts have excellent stability and could be reused several times using organic solvent nanofiltration under optimum conditions of 85 °C and 40 bar. Kinetic studies using catalyst precursor 6 were investigated by evaluating the effect of temperature, syngas total pressure and catalyst loading on the rate of hydroformylation. The activation energy for the hydroformylation of 1-octene was calculated to be 62 kJ mol−1 and the experimental rate constants were found to be in good agreement with the predicted rate data obtained using a modified fundamental mechanism-based rate model. [ABSTRACT FROM AUTHOR]