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Asymmetric cyclopropanation of alkenes by aryldiazoacetates was achieved using the readily-available racemic (diene)rhodium complex in combination with the chiral oxazoline-phenol ligand, which acts as the chiral poison and selectively inhibits one of the enantiomers of the catalyst. This approach eliminates a common problematic step of the synthesis of chiral catalysts.

The catalytic activity of cyclobutadiene rhodium complexes was investigated in various transformations of alkynes. Complexes [Rh(C4Et4)Hal]n (at 1 mol% loading) were found to promote hydrosilylation of 1-octyne selectively giving 1-Z-, 1-E-, or 2-Et3Si-1-octene depending on the nature of the halide ligand and the presence of additional ligand PPh3. Complex [Rh(C4Et4)(p-xylene)]+ (1 mol%) also efficiently catalyzed the polymerization of phenylacetylene. At the same time, we found that various cyclobutadiene rhodium complexes do not catalyze the Diels–Alder reaction, alkyne hydration, and 1,4-addition of boronic acids to cyclohexanone. New complexes [Rh(C4Et4)(PPh3)2]BF4 and [Rh(C4Et4)(C10H8)]PF6 were also synthesized and their structures were established by X-ray diffraction. [ABSTRACT FROM AUTHOR]

[Display omitted] Rhodium complex based on 9-(p-methoxybenzyl)-1,2,3,4- tetrahydrofluorenyl ligand was found to be an efficient catalyst for various C–H annulation reactions such as couplings of benzoic acids with alkynes, pivaloyl hydroxamate with alkenes, or the tandem reaction of p -anisaldehyde and p-toluidine with tolane. The catalyst demonstrated higher catalytic performance than the unsubstituted analog due to the stabilization of the rhodium–tetrahydrofluorenyl bond. Tetrahydrofluorenyl rhodium complexes also effectively catalyzed the synthesis of tetramethyl thiophene-2,3,4,5- tetracarboxylate from elemental sulfur and dimethyl acetylenedicarboxylate. [ABSTRACT FROM AUTHOR]

The rhodium complex [(C5H2tBu2CH2tBu)RhCl2]2 with an asymmetric cyclopentadienyl ligand was prepared in 95% yield by the reaction of [(cod)RhCl]2 with tert-butylacetylene in the presence of AlCl3. A similar reaction in the presence of InBr3 gave the cationic fulvene complex [(C5H2tBu2 = CHtBu)Rh(cod)]InBr4 (70%), which can add alcohols ROH and produce more bulky catalysts [(C5H2tBu2CH(OR)tBu)RhCl2]2. The enantiomers of these planar-chiral complexes were separated by thin-layer chromatography in the presence of L-phenylglycinol. The complexes catalyze the reactions of arylhydroxamates with alkenes giving dihydroisoquinolones in excellent yields (80–90%), but with moderate enantioselectivity (typically 20–50% ee). [ABSTRACT FROM AUTHOR]

A rhodium(II)-catalyzed reaction of cyclic nitronates (5,6-dihydro-4H-1,2-oxazine N-oxides) with vinyl diazoacetates proceeds as a [3+3]-annulation producing bicyclic unsaturated nitroso acetals (4a,5,6,7-tetrahydro-2H-[1,2]oxazino[2,3-b][1,2]oxazines). Optimization of reaction conditions revealed the use of Rh(II) octanoate as the preferred catalyst in THF at room temperature, which allows the preparation of target products in good yields and excellent diastereoselectivity. Under basic conditions, namely, the combined action of DBU and alcohol, these nitroso acetals undergo ring contraction of an unsaturated oxazine ring into the corresponding pyrrole. Both transformations can be performed in a one-pot fashion, thus constituting a quick approach to oxazine-annulated pyrroles from available starting materials, such as nitroalkenes, olefins, and diazo compounds. [ABSTRACT FROM AUTHOR]

This work demonstrates the influence of the catalyst and alkyne nature on the regioselectivity of rhodium-catalyzed annulation of alkoxy-substituted benzoic acids (such as 3-methoxybenzoic, 3,4-dimethoxybenzoic, and piperonylic acids) with alkynes. Here, X-ray diffraction and DFT calculation data gave evidence that the observed regioselectivity is provided by both steric and coordination effects of methoxy groups. The latter is the result of weak non-covalent C–H⋯O interactions with the supporting ligand rather than with the rhodium atom. We believe that these results are also valid for other reactions of the C-H activation of methoxy-substituted arene compounds. [ABSTRACT FROM AUTHOR]

An efficient protocol has been developed for the synthesis of larger condensed arenes from aromatic hydrocarbons and internal alkynes. This protocol uses readily available [CpRhI2 ]n as a catalyst and Cu(OAc)2 as an oxidant and proceeds smoothly through undirected double C–H activation. The addition of trifluoroacetic acid has a crucial positive impact on the reaction selectivity and the yields of the target products. In contrast to the previously reported catalytic systems, the new conditions allow the use of both dialkyl- and diarylacetylenes with the same high efficiency. [ABSTRACT FROM AUTHOR]

Diene rhodium complexes are important catalysts in modern organic synthesis. Herein, we report a new approach to such complexes with the uncommon planar chirality. The synthesis is achieved by face‐selective coordination of the prochiral 2,5‐disubstituted‐1,4‐benzoquinones (R2‐Q) with rhodium precursors containing the chiral auxiliary ligand S‐salicyl‐oxazoline (S‐Salox). Such coordination leads to the formation of (R,R‐R2‐Q)Rh(S‐Salox) complexes in high yields and with exceptional diastereoselectivity (d. r.>20 : 1). Subsequent replacement of the auxiliary ligand provides various benzoquinone rhodium complexes with retention of the planar chirality. Combined theoretical and experimental studies show that due to their electron‐withdrawing nature benzoquinones bind metals stronger than the related 1,4‐cyclohexadiene, but weaker than other common diene ligands, such as cyclooctadiene. [ABSTRACT FROM AUTHOR]

A new method for the synthesis of chiral diene rhodium catalysts is introduced. The readily available racemic tetrafluorobenzobarrelene complexes [(R2‐TFB)RhCl]2 were separated into two enantiomers via selective coordination of one of them with the auxiliary S‐salicyl‐oxazoline ligand. One of the resulting chiral complexes with an exceptionally bulky diene ligand [(R,R‐iPr2‐TFB)RhCl]2 was an efficient catalyst for the asymmetric insertion of diazoesters into B−H and Si−H bonds giving the functionalized organoboranes and silanes with high yields (79–97 %) and enantiomeric purity (87–98 % ee). The stereoselectivity of separation via auxiliary ligand and that of the catalytic reaction was predicted by DFT calculations. [ABSTRACT FROM AUTHOR]

On the basis of the 1,2,3,4‐tetrahydrofluorenyl ligand, a simple approach was developed to new effective rhodium catalysts for the construction of C−C and C−N bonds. The halide compounds [(η5‐tetrahydrofluorenyl)RhX2]2 (2 a: X=Br; 2 b: X=I) were synthesized by treatment of the bis(ethylene) derivative (η5‐tetrahydrofluorenyl)Rh(C2H4)2 (1 a) with halogens. An analogous reaction of the cyclooctadiene complex (η5‐tetrahydrofluorenyl)Rh(cod) (1 b) with I2 is complicated by the side formation of [(cod)RhI]2. The reaction of 2 b with 2,2′‐bipyridyl leads to cation [(η5‐tetrahydrofluorenyl)Rh(2,2′‐bipyridyl)I]+ (3). The halide abstraction from 2 a,b with thallium or silver salts allowed us to prepare sandwich compounds with incoming cyclopentadienyl, dicarbollide and mesityleneligands [(η5‐tetrahydrofluorenyl)RhCp]+ (4), (η5‐tetrahydrofluorenyl)Rh(η‐7,8‐C2B9H11) (5), and [(η5‐tetrahydrofluorenyl)Rh(η‐mesitylene)]2+ (6). The structures of 1 b, 2 b ⋅ 2I2, 3PF6, 4TlI4, 5, and [(cod)RhI]2 were determined by X‐ray diffraction. Compounds 2 a,b efficiently catalyze the oxidative coupling of benzoic acids with alkynes to selectively give isocoumarins or naphthalenes, depending on the reaction temperature. Moreover, they showed moderate catalytic activity in other annulations of alkynes with aromatic compounds (such as benzamide, acetanilide, etc.) which proceed through CH activation. Compound 2 b also effectively catalyzes the reductive amination of aldehydes and ketones in the presence of carbon monoxide and water via water‐gas shift reaction, giving amines in high yields (67–99 %). [ABSTRACT FROM AUTHOR]

A new chiral cyclopentadiene CpmyrH was synthesized from the natural terpene (R)‐myrtenal in 5 steps and about 40 % total yield. The key step was the reaction of vinyl‐dibromocyclopropane derivative with MeLi which provided the diene CpmyrH via Skattebøl rearrangement. The reaction of CpmyrH with [(cod)Rh(OAc)]2 gave the rhodium(I) complex (Cpmyr)Rh(cod) and subsequent oxidation with halogens X2 gave the rhodium(III) complexes [(Cpmyr)RhX2]2 (X = Br, I). Complex (Cpmyr)Rh(cod) in combination with benzoyl peroxide catalyzed the C–H activation of O‐pivaloyl‐phenylhydroxamic acid and its subsequent annulation with alkenes giving dihydroisoquinolones with high yield (70–90 %) but moderate enantioselectivity (16–36 % ee). [ABSTRACT FROM AUTHOR]

Abstract Bis(indenyl)-rhodium and -iridium complexes [(η5-indenyl)M(η5-C 9 H 2 R 5)]PF 6 (2a : M = Rh, R = H; 2b : M = Ir, R = H; 3 : M = Rh, R = Me) were synthesized by reactions of iodides [(η5-indenyl)MI 2 ] n (1a , b) with indenes in the presence of AgPF 6. The structures of 2a SbF 6 and 2b PF 6 were determined by X-ray diffraction. They have fully eclipsed geometry, in which the bridgehead carbon atoms of the indenyl ligands are arranged close to each other. Experimental and DFT calculation data showed that the strength of the M−indenyl bond in the bis(indenyl) compounds decreases in the following row: Ir > Co > Rh. Graphical abstract Image 1 Highlights • A straightforward approach to bis(indenyl)-rhodium and -iridium complexes was developed. • X-ray diffraction suggested that they have a fully eclipsed cisoid conformation. • Correlation of 13C NMR chemical shifts with bond dissociation energy was proposed. [ABSTRACT FROM AUTHOR]

Catalytic reaction of arylhydroxamic acids with alkenes represents a convenient method for preparation of biologically active dihydroisoquinolones. Here, the rhodium(III) complex [(C5H2tBu2CH2tBu)RhCl2]2, which allows one to carry out such reactions with high regioselectivity to obtain 4‐substituted dihydroisoquinolones in 72–97 % yields, is described. The regioselectivity is provided by the bulky cyclopentadienyl ligand of the catalyst, which is formed through a [2+2+1] cyclotrimerization of tert‐butylacetylene. The catalytic reaction tolerates various distant functional groups in alkenes, but is inhibited by bulky (e.g., tBu) or strongly coordinating (e.g., imidazolyl) substituents. Some of the prepared dihydroisoquinolones effectively inhibit growth of phytopathogenic fungi. Regioselective synthesis of biologically active dihydroisoquinolones was achieved by using rhodium(III) catalyst with bulky cyclopentadienyl ligand, which was formed from three tert‐butylacetylenes. [ABSTRACT FROM AUTHOR]

Reaction of the thallium salt Tl[7,8-Me 2 -10-SMe 2 -7,8- nido -C 2 B 9 H 8 ] with [(cod)RhCl] 2 in THF furnishes new rhodacarborane 1,2-Me 2 -3,3-(cod)-8-SMe 2 -3,1,2 -closo -RhC 2 B 9 H 8 ( 1 ). The latter undergoes 1,2 → 1,7 carbon atom isomerization upon reflux in o -xylene for 5 h producing complex 1,8-Me 2 -2,2-(cod)-11-SMe 2 -2,1,8- closo -RhC 2 B 9 H 8 ( 2 ). Reaction of complex 2 with 1 equiv of I 2 in benzene results in a loss of the cod ligand and formation of product 3 , consisting of cationic [(1,8-Me 2 -11-SMe 2 - closo -2,1,8-RhC 2 B 9 H 8 ) 2 I 3 ] + ( 3a + ) and anionic [(1,8-Me 2 -11-SMe- closo -2,1,8-RhC 2 B 9 H 8 ) 2 I 3 ] − ( 3b – ) iodide species. In contrast, unisomerized analog 3,3-(cod)-8-SMe 2 - closo- 3,1,2-RhC 2 B 9 H 10 reacts with I 2 affording dimeric iodide [3,3-I 2 -8-SMe 2 - closo- 3,1,2-RhC 2 B 9 H 10 ] 2 ( 5 ). The structures of 2 and 5 were determined by a single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Abstract: The rapid development of enantioselective C−H activation reactions has created a demand for new types of catalysts. Herein, we report the synthesis of a novel planar‐chiral rhodium catalyst [(C5H2tBu2CH2tBu)RhI2]2 in two steps from commercially available [(cod)RhCl]2 and tert‐butylacetylene. Pure enantiomers of the catalyst were obtained through separation of its diastereomeric adducts with natural (S)‐proline. The catalyst promoted enantioselective reactions of aryl hydroxamic acids with strained alkenes to give dihydroisoquinolones in high yields (up to 97 %) and with good stereoselectivity (up to 95 % ee). [ABSTRACT FROM AUTHOR]

Polyhedral rearrangement of iridacarborane 1,2-Me2-3,3-(cod)-4-SMe2-3,1,2-closo-IrC2B9H8 (1) proceeds in a solution at RT and affords a product of 1,2 → 1,7 isomerization 1,8-Me2-2,2-(cod)-7-SMe2-2,1,8-closo-IrC2B9H8 (2). Rhodium derivative 1,2-Me2-3,3-(cod)-4-SMe2-3,1,2-closo-RhC2B9H8 (3) is significantly more stable toward heating than iridium complex 1 and isomerizes at 110 °C by 1,2 → 1,2 and 1,2 → 1,7 reaction schemes with 1,2 → 1,2 being the predominant route forming 1,2-Me2-4,4-(cod)-8-SMe2-4,1,2-closo-RhC2B9H8 (4) and 1,8-Me2-2,2-(cod)-7-SMe2-2,1,8-closo-RhC2B9H8 (5). Complexes 4 and 5 were characterized by 11B{¹H}-11B{¹H} COSY NMR spectrometry. A mechanism of 1,2 → 1,2 isomerization of 3 to 4 was proposed on the basis of DFT calculations. Reaction of the thallium salt Tl[7,8-Me2-9-SMe2-7,8-nido-C2B9H8] (CarbTl) with [Cp*RuCl]4 in THF furnishes new ruthenacarborane 1,2-Me2-3-(Cp*)-4-SMe2-3,1,2-closo-RuC2B9H8 (6). Heating of 6 at 80 and 144 °C leads to the partial and complete decomposition, respectively. Interaction of CarbTl with [Cp*IrCl2]2 in the presence of TlPF6 provides two new Ir(III) complexes [1,2-Me2-3-(Cp*)-4-SMe2-3,1,2-closo-IrC2B9H8]PF6 (7PF6) and 1,2-Me2-3-(Cp*)-4-SMe-3,1,2-closo-IrC2B9H8 (8) both stable upon heating in boiling tetrachloroethane (146 °C). A new 10-substituted charge-compensated carborane [7,8-Me2-10-SMe2-7,8-nido-C2B9H9] (9) was synthesized via an interaction of dicarbollide dianion [7,8-Me2-7,8-nido-C2B9H9]2- with dimethyl sulfide and acetaldehyde in acidic media. Thallium salt of 9 Tl[7,8-Me2-10-SMe2-7,8-nido-C2B9H8] (10) reacts with [(cod)IrCl]2 furnishing positional isomer of 1 with a symmetrical emplacement of SMe2 substituent complex 1,2-Me2-3,3-(cod)-8-SMe2-3,1,2-closo-IrC2B9H8 (11). Iridacarborane 11 requires elevated temperatures to undergo cage isomerization and converts upon heating at 110 °C to two new compounds 1,8-Me2-2,2-(cod)-11-SMe2-2,1,8-closo-IrC2B9H8 (12) and 1,2-Me2-4,4-(cod)-9-SMe2-4,1,2-closo-IrC2B9H8 (13) as a result of 1,2 → 1,7 and 1,2 → 1,2 rearrangements respectively with 13 being the minor product. The structures of 2, 6, 7PF6, 8, 10, 12, and 13 were determined by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Room temperature reactions of the rhodium and iridium bromides (η-9-SMe 2 -7,8-Me 2 -7,8-C 2 B 9 H 8 )MBr 2 (M = Rh ( 1a ), Ir ( 1b )) with CpTl give the dicarbollide thioether complexes (η-9-SMe-7,8-Me 2 -7,8-C 2 B 9 H 8 )MCp ( 2a,b ), as a result of demethylation of the SMe 2 substituent. These reactions are accompanied by transformation of cage structure from pseudocloso to closo . Refluxing of the sulfonium derivatives [(η-9-SMe 2 -7,8-Me 2 -7,8-C 2 B 9 H 8 )MCp] + ( 3a , b ) with [Bu 4 N]Br also affords 2a , b . In the same manner ruthenacarboranes [(η-9-SMe 2 -7,8-C 2 B 9 H 10 )Ru(η-C 6 H 6 )] + ( 4a ) and [(η-10-SMe 2 -7,8-C 2 B 9 H 10 )Ru(η-C 6 H 6 )] + ( 4b ) react with halide ions giving the thioether complexes (η-9-SMe-7,8-C 2 B 9 H 10 )Ru(η-C 6 H 6 ) ( 5a ) and (η-10-SMe-7,8-C 2 B 9 H 10 )Ru(η-C 6 H 6 ) ( 5b ). Dependence of the demethylation rate on the nature of halide ion and solvent was studied both experimentally and theoretically. The structures of 2a and 3a PF 6 were determined by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Cyclobutadiene rhodium complexes bear high potential for applications in organometallic synthesis and catalysis. We have found that the cyclobutadiene complexes with substitutionally labile p-xylene ligands [(C4R4)Rh( p-xylene)]+ can be synthesized in one step from the commercially available bis(ethylene) complex [{(C2H4)2RhCl}2], p-xylene, and internal alkynes. The replacement of p-xylene by various ligands provides a general access to other [(C4R4)Rh] compounds, such as [(C4R4)RhCl] x, [(C4R4)RhL3]+, [(C4R4)Rh(C5H5)], and [(C4R4)Rh(arene)]+. Complex [(C4Et4)Rh( p-xylene)]+ also catalyzes an unusual cycloisomerization of a 1,11-dien-6-yne into a bicyclic diene. [ABSTRACT FROM AUTHOR]

In the original article, Scheme 5 describes the reaction of O-Boc-phenylhydroxamic acid with a mixture of alkenes, Scheme 6 describes the reaction of O-Boc- and O-Piv-phenylhydroxamic acid with styrene. For example, reaction of B 1 a b with an equimolar mixture of allyl alcohol, styrene and myrcene proceed selectively in the presence of the catalyst B 5 b to give 4-CH SB 2 sb OH-substituted product B 4 e b in 89 % yield (Scheme 5). Indeed, we observed that the reaction of O-Boc-phenylhydroxamic acid B 1 a b with styrene in the presence of the classical catalyst [Cp*RhCl SB 2 sb ] SB 2 sb gives only the 3-benzylisoindolin-1-one B 4 p b , while similar reaction of O-pivaloyl-phenylhydroxamic acid B 1 b b produced the 3-substituted structural isomer B 3 p b (Scheme 6). [Extracted from the article]

Keywords: chirality; diene ligands; quinones; rhodium EN chirality diene ligands quinones rhodium 1 1 1 03/31/22 20220328 NES 220328 B Chiral rhodium complexes b are widely used in asymmetric catalysis. Cover Feature: Planar Chiral Rhodium Complexes of 1,4-Benzoquinones (Chem. Eur. J. 18/2022) Chirality, diene ligands, quinones, rhodium. [Extracted from the article]

Reaction of two molecules of o‐diphenylphosphino‐tolane with RhCl(PPh3)3 produces the metallacycle complex with C4Rh(P3)Cl core. Further addition of tolane leads to 2+2+2‐cycloaddition and gives the cationic complex [Rh(Ph2P−C6H4−C6Ph4−C6H4−PPh2)]Cl, in which the metal is coordinated to C6Ph4 aromatic ring as well to two chelating PPh2 groups. The resulting bulky terphenyl‐diphosphine ligand with phosphorous atoms locked in cis‐position can be decoordinated from rhodium by a strong and non‐hindered ligand tBuNC. Peculiar structures of all the compounds were studied by the X‐ray diffraction. [ABSTRACT FROM AUTHOR]

The tetrahedral clusters [(C 4 Me 4)CoRh 3 Cpʹ 3 (μ 3 -CO) 3 ]+ (2 ; Cpʹ = C 5 H 4 Me) and [(Ph 3 P)AuRh 3 Cpʹ 3 (μ 2 -CO) 3 ]+ (3) were synthesized by reactions of Rh 3 Cpʹ 3 (μ 2 -CO) 3 (1b) with metalloelectrophiles [(C 4 Me 4)Co]+ (generated from [(C 4 Me 4)Co(C 6 H 6)]+ under visible-light irradiation) and [(Ph 3 P)Au]+ (generated from (Ph 3 P)AuCl/Tl+). They were isolated as salts with PF 6 − anion, and the structures of 2 PF 6 and 3 PF 6 were determined by X-ray diffraction. The structural data gave evidence that the coordination of [(C 4 Me 4)Co]+ occurs to the face of 1b with the CO ligands, while the [(Ph 3 P)Au]+ species reacts with the opposite face of 1b. The latter interaction is accompanied by elongation of the Rh–Rh bonds within the rhodium triangle by 0.1 Å. DFT calculations (at the BP86/TZP level) revealed that the selectivity of the metalloelectrophile coordination is determined by orbital control. Image 1 • New heteronuclear tetrahedral CoRh 3 and AuRh 3 clusters were synthesized. • The triangular rhodium cluster showed dual reactivity towards metalloelectrophiles [(C 4 Me 4)Co]+ and [(Ph 3 P)Au]+. • The [(C 4 Me 4)Co]+ and [(Ph 3 P)Au]+ species prefer π- and σ-bonding, respectively. • The selectivity of the metalloelectrophile coordination is determined by orbital control. [ABSTRACT FROM AUTHOR]

[Display omitted] Porous metal–organic framework ZIF-8 materials containing incorporated rhodium (Rh@ZIF-8) and rhodium chloride (RhCl 3 @ZIF-8) nanoparticles were obtained and tested as a catalytic reaction vessel in the reactions of hydroformylation of 1-decene and styrene. Catalytic tests with Rh@ZIF-8 showed that the selectivity and conversion of the hydroformylation reaction depended on the size of the substrate molecule. The incorporation of catalytic nanoparticles into the pores of a metal–organic framework opens up new possibilities for regioselective hydroformylation. [ABSTRACT FROM AUTHOR]

A page of a coloring book shows the molecules of hydroxamic acid and alkene at the fork of the road. The signpost with a traditional weathervane figure—the cyclopentadienyl rhodium catalyst—directs the reaction to the right to give the 4‐substituted dihydroisoquinolones. For more information, see the Full Paper by D. S. Perekalin et al. on page 16570 ff. [ABSTRACT FROM AUTHOR]

Sandwich Complexes The center of the stained glass represents the top view of the cyclobutadiene rhodium benzene complex [(C4H4)Rh(C6H6)]+. This sandwich compound not only shows the geometric beauty (circle inscribed in a square inscribed in a hexagon!) but also provides an entry to the world of the cyclobutadiene rhodium complexes through replacement of benzene by various ligands. Details of this research is reported by A. R. Kudinov and co ‐ workers in their Communication on page 16344 ff. [ABSTRACT FROM AUTHOR]

The cyclobutadiene rhodium complex [(C 4 Et 4 )RhCl] 2 (generated from [(C 4 Et 4 )Rh(p-xylene)]PF 6 and BnNEt 3 Cl) catalyzes the reaction of methyl α-diazophenylacetate with R n X-H compounds to give the insertion products methyl 2-R n X-2-phenylacetates in 70–90% yields (R n X-H = methanol, tert -butylamine, 2,6-diisopropylaniline, morpholine, diallylamine, triethylsilane, triethylamine-borane). The stoichiometric reaction of [(C 4 Et 4 )RhI] 2 with methyl α-diazophenylacetate gives the intermediate complex (C 4 Et 4 ) 2 Rh 2 (μ-I) 2 (μ-1-carboxymethyl-1-phenylmethylene), which has a binuclear structure with bridging iodide and carbene ligands. This result indicates that catalytically active carbene species may have more complex structures than the commonly assumed L n M=CR 2 . [ABSTRACT FROM AUTHOR]

In a search for an active catalyst for CH-activation reactions we have synthesized the half-sandwich rhodium complexes with a cyclohexadienyl ligand. In particular, the reaction of [(cyclooctene) 2 RhCl] 2 with 1,3,5,5-tetramethylcyclohexadiene followed by addition of bromine gave the cyclohexadienyl polybromide complex [(η 5 -C 6 H 3 Me 4 )RhBr 3 ] n ( 1 ) in 73% yield. Treatment of 1 with ethylene converted it into the Rh(III) bromide complex [(η 5 -C 6 H 3 Me 4 )RhBr 2 ] 2 ( 2 ), which is analogous to the classical catalyst [Cp*RhCl 2 ] 2 . The reaction of 2 with 2 equiv. of 2-electron ligands L produced the expected adducts (η 5 -C 6 H 3 Me 4 )RhBr 2 L (L =  t BuNC, pyridine, P(OMe) 3 , PPh 3 ) in 80–90% yields. On the other hand, the reactions of 1 or 2 with excess of t BuNC led to complete replacement of the cyclohexadienyl ligand. The complex 2 was found to be inactive as catalyst (at 10 mol-% loading) for reactions of diphenylacetylene with benzoic acid, acetanilide, O-Boc-phenylhydroxamic acid, or benzophenone oxime. The absence of catalytic activity was attributed to the displacement of the cyclohexadienyl ligand. [ABSTRACT FROM AUTHOR]

Reaction of bis( p -tolyl-propargyl)-tosylamide with [(cod)RhCl] 2 in the presence of CO gives the cyclopentadienone complex [(Cpd’)Rh(CO)Cl] n (Cpd’ = TsN(CH 2 ) 2 C 4 (Tol) 2 CO). Its dissolution in DMSO or pyridine leads to decarbonylation and formation of the adducts (Cpd’)Rh(DMSO) 2 Cl and (Cpd’)Rh(Py) 2 Cl. The reaction of [(Cpd’)Rh(CO)Cl] n with AgPF 6 and p -xylene produces the sandwich arene complex [(Cpd’)Rh( p -xylene)]PF 6 , in which the arene can be substituted by t BuNC ligand to give [(Cpd’)Rh( t BuNC) 3 ]PF 6 . The arene complex acts as an efficient catalyst for the reductive amination of carbonyl compounds in the presence of CO as deoxygenation agent, producing various amines in 75–85% yields. [ABSTRACT FROM AUTHOR]

Reaction of dimethylamine adduct of 1-methyl-3-borolene with [(C 2 H 4 ) 2 RhCl] 2 gives the triple-decker complex (η-C 4 H 4 BMe)Rh(μ-η:η-C 4 H 4 BMe)Rh(η-C 4 H 4 BMe) ( 1a ) in 62% yield and trace amount (<1%) of the hybrid rhodacyclopentadienyl/borole triple-decker complex (η-C 4 H 4 BMe)Rh(μ-η:η-C 4 H 4 Rh{(μ-η:η-C 4 H 4 BMe)Rh(η-C 4 H 4 BMe)})Rh(η-C 4 H 4 BMe) ( 2 ). The structure of 2 was determined by X-ray diffraction. In the presence of Cu(OAc) 2 , 1a and (η-C 4 H 4 BPh)Rh(μ-η:η-C 4 H 4 BPh)Rh(η-C 4 H 4 BPh) ( 1b ) catalyze the oxidative coupling of benzoic acid with diphenylacetylene selectively giving 1,2,3,4-tetraphenylnaphtalene in 50–90% yields. Analogous reactions of benzoic acid with 1-phenyl-1-butyne catalyzed by 1a and [CpRhI 2 ] 2 regioselectively give 1,4-diethyl-2,3-diphenylnaphthalene. The related dicationic triple-decker complexes [(9-SMe 2 -7,8-C 2 B 9 H 10 )Rh(μ-η:η-C 4 H 4 BPh)Rh(9-SMe 2 -7,8-C 2 B 9 H 10 )] 2+ ( 3 ) and [Cp*Rh(μ-η:η-C 4 H 4 BPh)IrCp*] 2+ ( 4 ) were also tested as catalysts. [ABSTRACT FROM AUTHOR]

The halide complexes TpRhCl 2 (MeOH) and TpMe2RhI 2 (CO) (Tp = hydrotris-(pyrazolyl)borate; TpMe2 = hydrotris-(3,5-dimethylpyrazolyl)borate) were synthesized by reactions of RhCl 3 with K[Tp] in methanol and TpMe2Rh(CO) 2 with iodine, respectively. Reactions of TpMe2RhCl 2 (MeOH) and TpMe2RhI 2 (CO) with 1,10-phenanthroline afford the phenanthroline derivatives [TpMe2Rh(phen)X]+ (X = Cl, I). The structures of TpRhCl 2 (MeOH) and TpRhI 2 (CO) were determined by X-ray diffraction. Tris(pyrazolyl)borate rhodium complexes effectively catalyze the reductive amination and the reductive esterification of aldehydes in the presence of carbon monoxide. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Indenyl-ligated rhodium(III) catalyst [(η 5 -indenyl)RhX 2 ] n ( 1 ) is reported for the synthesis of alkylated amines via catalytic reductive amination using carbon monoxide as a reducing agent. Water as a solvent was found to be the best media for the reaction. Complex 1 was synthesized via a high-yielding procedure based on the reaction of bis(ethylene) derivative (η 5 -indenyl)Rh(C 2 H 4 ) 2 with iodine. [ABSTRACT FROM AUTHOR]