Interactions intramoleculaires. XXI—Constantes de couplage et interactions gauches avec un groupement t-butyle (molécules cyclohexaniques deutériées)

Different isotopic modifications of deuterated products of 1-t-butlyl-4-methoxycarbonyl cyclohexene (d₄-3,3,6,6), cis- and trans-3-methyl-4-cyanocyclohexene (d₃-3,6,6), cis- and trans-3-methyl-4-cyanocyclohexene (d₃,6,6), cis- and trans-3-t-butyl-4-methoxycarbonylcyclohexene (d₃,-3,6,6) are shown by nuclear magnetic resonance spectral analysis. By comparison of ³J and ⁴J coupling constants of model molecules and molecules with large gauche interactions, we obtain proof that the latter are in a chair conformation with moderate cycle deformations.     

Conformation et spectrométrie de R.M.N.: II

The four isomeric 3-dimethylamino-trans-2-decalols-1,1,4,4-d₄ have been synthesised. Examination of PMR spectra of these compounds allows us to confirm the ‘flattened-chair’ conformation for the cis N(CH₃)₂^a OH^e isomer, whereas the remaining three conserve the double chair conformation. The same type of flattening is also observed in the case of the diaxial quaternary ammonium salt and is even more marked in the cis N(CH₃)₃^a OH^e isomer resulting in a ‘twist-chair’ conformation.     

Reaction of Carbon Anions With Iron α,β-Unsaturated Ketimine Complexes

Complexes (η⁴-PhCH=CHCR=NPh)Fe(CO)₃, where R=H(1a) and CH₃ were synthesized in excellent yield from the reaction of the corresponding α,β-unsaturated ketimines with excess Fe₂(CO)₉. Reaction of la with (Ph)₂CHLi and (CH₃)₂(NC)CLi at ?78°C or ambient temperature followed by acid quenching gave trans-PhCH=CHCHRNHPh, where R=CHPH₂ and C(CH₃)₂CN, respectively, in good yield. In the presence of 1 atm. of CO the reaction of 1a with (CH₃)₂(NC)CLi, followed by CuCl₂ oxidation resulted in the formation of a carbamyl choride, trans-PhCH=CHCH[C(CH₃)₂CN]N(Ph)COCl. This species was converted to a carbamate compound trans-PhCH=CHCH[C(CH₃)₂ - CN]N(Ph)COOCH₃ in MeOH in the presence of Ag⁺.     

Interactions intramoleculaires: XXII—Constantes de couplage, équilibres conformationnels et interactions gauches avec un groupement t-butyle (molécules cyclohexéniques deutériées)

The NMR parameters are determined for a series of disubstituted (R = CH₃, (CH₃)₃C; X = COOCH₃, CN) and specifically deuterated cyclohexenes. The ³ J(HH), ³J(HD), ⁴J(HH) and ⁵ J(HH) coupling constants are used to evaluate the conformational equilibria. Three of the five compounds with an allylic t-butyl substituent, are conformationally heterogeneous; these equilibria, and those between stereoisomers are used for an analysis of this phenomenon, carried out within the framework of the hypothesis of additivity of conformational free energies and gauche interactions.     

Cyanoalkyl Complexes of Platinum (II). I. Preparation and Spectroscopic Properties

The oxidative addition of XRCN to PtL₄ yields cis-and/or trans-PtX(RCN)L₂ (X = Cl, Br; R = (CH₂)_n, n = 1, 2, 3; L = PPh₃, PPh₂CH₃, AsPh₃). L is readily displaced by more basic phosphines or by a diphosphine. In each case the trans complex is the thermodynamically more stable isomer and cis-trans isomerization catalyzed by free L occurs in dichloromethane. Insertion of CO in the σ Pt? C bond takes place quantitatively in the case of cyanoethyl and cyanopropyl. Abstraction of X by AgBF₄ gives cis or trans cationic complexes with N-bonded CN group.     

Syntheses of Unique Bicyclophostones and Unexpected Difference in the Reaction of Lawesson's Reagent vs. P2S5 with Cis-Bicyclophostone (1)

Abstract

The purpose of this study was to synthesize trans-l and determine the equilibriurr constant with cis-1. Oniy the synthesis¹ and x-ray structure² of the cis isomer have bcen reported. Four prior synthetic routes to make the vans isomer³ gave only cis product. For example, intrarmolecular ring closure of the cis or trains isomers of 4 (R= (CH₂)₃OH) with LiH or thermal closure of the cis or trans 4 (R= (CH₂)₂) gave only cis-1. Since both iosmers of 1,8-dioxabicyclo[4.4.0] decane are known and readily equilibrate (57% cis and 43% trans), the apparent inaccessibility of trans-1 attracted our attention. Thc preparation of trans-1 was achieved by treatment of cis-1 with Lawesson's reagent (LR) to provide cis-2. followed by oxidation with m-chloroperbenzoic acid/trifluoroacetic acid to give a 5:1 mixture of cis:trans 1, respectively. An unexpected formation of the sulfur analogue of 1 was observed on treatment of cis-1 with P₂S₅/pyridine at reflux temperatures to give a 1.6:1 mixture of cis:trans 3, respectively. Thermal quilibration of 1 at 204°C provided an equilibrium ratio of 99.5% cis and 0.5% of the trans isomer. However, equilibration of 3 at 250°C led to 82.2:17.8 ratio in favor of the cis isomr. These results are consistent with semiemperical MO calculations. The stereochemical outcome on treatment of 4 with LR was also investigated. X-ray structures for six compounds: trans-1, cis-2, cis and trans-3; cis-4 (R=Ph), and cis-5, (R = Ph) wen determined.     

Kinetics,mechanism, and stereochemistry of Diels-Alder reactions of CN-substituted ethenes with cyclohexa-1, 3-diene in the gas phase

The kinetics of the Diels-Alder additions of CH₂ = CHCN, CH₂ = C(CH₃) CN, and cis- and trans-CH₃CH = CHCN to cyclohexa-1, 3-diene have been studied in the gas phase. The stereochemistry of these reactions is discussed. In terms of a biradical mechanism, a minimum value of 4.1 ± 0.8 kcal mol^?1 for the stabilizing effect of a CN group vis-à-vis a methyl group is shown to fit the experimental activation energies.     

Thermal isomerization of ruthenium hydride compounds containing asymmetric bidentate pyrrole‐imine ligands

A series of ruthenium hydride compounds containing substituted bidentate pyrrole‐imine ligands were synthesized and characterized. Reacting RuHCl(CO)(PPh₃)₃ with one equivalent of [C₄H₃NH(2‐CH=NR)] in ethanol in the presence of KOH gave compounds {RuH(CO)(PPh₃)₂[C₄H₃N(2‐CH=NR)]} where trans‐Py‐Ru‐H 1, R = CH₂CH₂C₆H₉; cis‐Py‐Ru‐H 2, R = Ph‐2‐Me; and cis‐Py‐Ru‐H 3, R = C₆H₁₁. Heating trans‐Py‐Ru‐H 1 in toluene at 70°C for 12 hr resulted a thermal conversion of the trans‐Py‐Ru‐H 1 into its cis form, {RuH(CO)(PPh₃)₂[C₄H₃N(2‐CH=NCH₂CH₂C₆H₉)]} (cis‐Py‐Ru‐H 1) in very high yield. The ¹H NMR spectra of trans‐Py‐Ru‐H 1, cis‐Py‐Ru‐H 2, cis‐Py‐Ru‐H 3, and cis‐Py‐Ru‐H 1 all show a typical triplet at ca. δ–11 for the hydride. The trans and cis form indicate the relative positions of pyrrole ring and hydride. The geometries of trans‐Py‐Ru‐H 1, cis‐Py‐Ru‐H 1, and cis‐Py‐Ru‐H 3 are relatively similar showing typical octahedral geometries with two PPh₃ fragments arranged in trans positions.     

Interactions intramoléculaires. XXVII—Etudes structurales en série bicyclo[4.1.0]heptanique (effets d'anisotropie sur les déplacements chimiques du proton; constantes de couplage et équilibres conformationnels)

All the ¹H n.m.r. parameters of the following derivatives of 1,6-dimethylbicyclo[4.1.0]heptane are determined: 3,4-dimethoxycarbonyl (3 diastereoisomers), cis- and trans-3-methoxycarbonyl-2,2,5,5-d₄, cis- and trans-3-methyl-3-methoxycarbonyl; the cis- and trans-1,5,5-trimethylbicyclo[4.1.0]-3-heptanols are studied in the same way. The different chemical shifts are correlated with the aid of a collection of empiral increments. The conformational equilibria are determined from the vicinal coupling constants; the conformational free energies of the COOCH₃ group are evaluated; the part played by gauche interactions is considered.     

Conformational analysis: XIV—A 1H n.m.r. conformational study of methyl substituted 2-oxo-1,3,2-dioxathians to confirm the predominance of chair forms in the trimethylene sulphite series

Seven isomeric 4,5,6-trimethyl-2-oxo-1,3,2-dioxathians, cis-4-trans-6-dimethyl-r-2-oxo-1,3,2-dioxathian and two isomeric 4,5,5,6-tetramethyl-2-oxo-1,3,2-dioxathians were prepared and their ¹H n.m.r. spectra analysed. The values of the vicinal coupling constants reported earlier for the cis-4-trans-6 compound were shown to be erroneous. In all cases the values of the vicinal coupling constants (and those of the chemical shifts) are indicative of a single chair conformation or a chair-chair equilibrium, in contrast to earlier reports on the significant contribution of twist forms but in agreement with an electron diffraction study. The chair form is ? 31 kJ mol^?1 thermochemically more stable than the twist form.     

Cyanoalkyl complexes of transition metals . : II. Preparation and properties of some platinum complexes containing phosphorus as a donor atom

cis-PtCl(CH₂CN)(PPh₃)₂ was obtained by the reaction of Pt(PPh₃)₄ with ClCH₂CN in acetone. A solution of Pt(PPh₃)₄ and ClCH₂CN in benzene was heated under reflux to give trans-PtCl(CH₂CN)(PPh₃)₂. The reaction of the trans-isomer with Br^?, I^?, Ph₂PCH₂CH₂ PPh₂, Ph₂PCH₂CH₂AsPh₂ and cisPh₂PCHCHPPh₂ has been examined. The trans-influence of a ligand trans to the CH₂CN group seems to be indicated by the ²J(PtH) of the CH₂CN protons. The τ values of trans-PtX(CH₂CN)(PPh₃)₂ and PtX(CH₂ CN)(PP) (X = Cl, Br, I) are related by a linear function.     

Le diméthyl- et le diéthyl-tétracarbonylosmium Synthèse et réactivité

The sodium salt Na₂[Os(CO)₄] has been obtained in high yields by the reduction of either OsH₂(CO)₄ or Os₃(CO)₁₂ with sodium sand in the presence of catalytic amounts of 2, 2′-bipyridyle. The reaction of Na₂[Os(CO)₄] with alkylating agents such as methyl and ethyl iodide produces OsR₂(CO)₄ (R = CH₃, C₂H₅). NMR. and IR. spectra indicate a cis-octahedral structure of symmetry C_2v for these new alkyl compounds. Bromine breaks one osmium-carbon bond in cis-Os(CH₃)₂(CO)₄ to give cis-OsCH₃Br(CO)₄, whereas in cis-Os(C₂H₅)₂(CO)₄ both ethyl groups are easily displaced by bromine to give cis-OsBr₂(CO)₄. Under CO pressure and at elevated temperature cis-Os(CH₃)₂(CO)₄ is converted to Os(CO)₅ and ethane. With cis-Os(C₂H₅)₂(CO)₄ two CO are inserted in osmium-carbon bonds to give . NMR. and IR. data suggest a cis-configuration for this derivative and the possibility of the presence of rotational isomers.     

Investigations on organoantimony compounds : XVII. Preparation and properties of heterocyclic trans-dichloro-β-diketonato-cis-diorganoantimony(V) compounds. Influence of stereochemistry on β-diketonate ligand exchange reactions in octahedral dichloro-β-diketonatodiorganoantimony(V) compounds

A series of heterocyclic trans-dichloro-β-diketonato-cis-diorganoantimony(V) compounds of the type R₂SbCl₂X (R₂ = (CH₂)₄, (CH₂)₅, o,o′−C₆H₄C₆H₄, o,o′−C₆H₄CH₂C₆H₄; X = Acac, Dpm) has been synthesized. The stereochemistry of these compounds has been deduced from PMR spectroscopic and molecular dipole moment data. Since the cis-dichloro-β-diketonato-trans-diorganoantimony(V) compounds R₂SbCl₂Acac (R = Me, Et, Ph) were known previously, a set of both cis- and trans-diorgano main group organometallic complexes has thus been made available, which allows a comparative study of the influence of stereochemistry on the strength of metal—ligand interactions in this type of octahedral d¹⁰ metal complex. β-Diketonate—ligand exchange reactions have been studied by PMR spectroscopy, and a marked influence of stereochemistry observed. trans-Dichloro-β-diketonato-cis-diorganoantimony(V) compounds undergo ligand exchange only slowly, if at all, whereas cis-dichloro-β-diketonato-trans-diorganoantimony(V) compounds react instantaneously. Both PMR chemical shift data and IR spectroscopic data point to the occurrence of a stronger antimony-β-diketonate interaction in trans-dichloro-β-diketonato-cis-diorganoantimony than in cis-dichloro-β-diketonato-trans-diorganoantimony compounds. This can be understood in terms of the hybridization of the antimony valence orbitals. The results are in line with the assumption that Sb---O bond rupture is the rate-determining step in β-diketonate ligand exchange.     

Die Kristallstruktur von cis‐ und trans‐N‐iso‐Propylamidodimethylindium, [(CH3)2In‐N(H)iC3H7]2

The Crystal Structure of cis‐ and trans‐N‐iso‐Propylamidodimethyl Indium, [(CH₃)₂In‐N(H)ⁱC₃H₇]₂ According to the X‐ray structure determination [(CH₃)₂In‐N(H)ⁱC₃H₇]₂ (prepared from InMe₃ (Me = CH₃) and H₂NⁱPr (ⁱPr = CH(CH₃)₂) crystallizes in the monoclinic space group P2₁/n with 3 dimeric trans as well as 3 dimeric cis isomers per unit cell. The centrosymmetric form has a planar In₂N₂ core with In—N bonds of 222.1(4) and 222.9(5) pm, respectively, the skeleton of the cis isomer with In—N bonds of 221.4(4) pm is slightly folded (13.7°). Some ¹H, ¹³C NMR, IR, and Raman data are reported.     

1H-NMR-Spektroskopische Untersuchungen an isomeren Alkendiinen

¹H NMR spectra of several aliphatic and phenyl substituted alkenediynes have been obtained. Chemical shifts and coupling constants of these compounds are discussed in conjunction with some compounds described in the literature. Chemical shifts of the protons from isomeric alkenediynes R? C?C? C?C? CH?CH₂, R? CH?CH? C?C? C?CH and R? CH?CH? C?C? C?C? CH₃ (R = H, alkyl, C₆H₅, C₆H₄OCH₃-p) are well correlated with cis/trans-isomerism and electronic effects of substituents at the C?C bond. The coupling constants were found to be only slightly dependent on the substitution at the double bond. We could resolve couplings over a maximum of eight bonds in the alkenediyne system.     

Trägerfixierte Organometallkomplexe. VI. Charakterisierung und Reaktivität Polysiloxan-gebundener (Ether-phosphan)ruthenium(II)-Komplexe

Supported Organometallic Complexes. VI. Characterization und Reactivity of Polysiloxane-Bound (Ether-phosphane)ruthenium(II) Complexes The ligands PhP(R)CH₂D [R = (CH₃O)₃Si(CH₂)₃; D = CH₂OCH₃ ( 1b ); D = tetrahydrofuryl ( 1c ); D = 1,4-dioxanyl ( 1d )] have been used to synthesize (ether-phosphane)ruthenium(II) complexes, which have been copolymerized with Si(OEt)₄ to yield polysiloxane-bound complexes. The monomers cis,cis,trans-Cl₂Ru(CO)₂(P ～ O)₂ ( 3b ) and HRuCl(CO)(P ～ O)₃ ( 5b ) were treated with NaBH₄ to form cis,cis,trans-H₂Ru(CO)₂(P ～ O)₂ ( 4b ) and H₂Ru(CO)(P ～ O)₃ ( 6b ), respectively (P ～ O = η¹-P coordinated; = η²- coordinated). Addition of Si(OEt)₄ and water leads to a base catalyzed hydrolysis of the silicon alkoxy-functions and a precipitation of the immobilized counterparts 4b ′, 6b ′. The polysiloxane matrix resulting by this new sol gel route has been described under quantitative aspects by ²⁹Si CP-MAS NMR spectroscopy. 4b ′ reacts with carbon monoxide to form Ru(CO)₃(P ～ O)₂ ( 7b ′). Chelated polysiloxane-bound complexes Cl₂Ru( )₂ ( 9c ′, d ′) and Cl₂Ru( )(P ～ O)₂ ( 10b ′, c ′) have been synthesized by the reaction of 1b–c with Cl₂Ru(PPh₃)₃ ( 8 ) followed by a copolymerization with Si(OEt)₄. The polysiloxane-bound complexes 9c ′, d ′ and 10b ′, c ′ react with one equivalent of CO to give Cl₂Ru(CO)( )(P ～ O) ( 12b ′– d ′). Excess CO leads to the all-trans-complexes Cl₂Ru(CO)₂(P ～ O)₂ ( 14b ′– d ′), which are thermally isomerized to cis,cis,trans- 3b ′– d ′. The chemical shift anisotropy of ³¹P in crystalline Cl₂Ru( )₂ ( 9a , R = Ph, D = CH₂OCH₃) has been compared with polysiloxane-bound 9d ′ indicating a non-rigid behavior of the complexes in the matrix.     

Stereochemistry of alkyl 3-substituted 4-halotetrahydro-2-oxo-3-furancarboxylates: 2—1H and 13C NMR spectra

The ¹H NMR parameters of methyl 3-substituted cis-4-halotetrahydro-2-oxo-3-furancarboxylates are reported, with assignments of the ring protons based on solvent-induced changes in the vicinal trans coupling constants, ³J(H-4, H-5). Preferred conformations, ce with a pseudo-equatorial halogen for the cis isomers and ta with a pseudo-axial halogen for the trans isomers, have been suggested on comparison of the magnitudes of J(trans) and J(gem) in both series. The ³J(¹³CH₃, H-4) values measured for methyl cis-4-bromotetrahydro-3-methyl-3-furancarboxylate, methyl trans-4-bromotetrahydro-3-methyl-3-furancarboxylate and trans-3,4-dibromodihydro-3-methyl-2(3H)-furanone have confirmed the stereochemical assignments.     

Base hydrolysis of mono-alkylsubstituted chloropentaamminecobalt(III) complexes

Summary The preparation of the series ofcis- andtrans-[Co(NH₃)₄(RNH₂)Cl]²⁺ complexes (withcis, R = Me orn-Pr andtrans, R = Me, Et,n-Pr,n-Bu ori-Bu) is described. The u.v-visible spectra indicate a decrease of the ligand field on increasing chain length. Infrared spectra show an enhanced Co-Cl bond strength compared to the pentaammine. Partial molar volumes of the complex cations do not reveal steric compression. From proton exchange studies in D₂O it follows that [Co(NH₃)₅Cl]²⁺ and thecis- andtrans-[Co(NH₃)₄-(CH₃NH₂)C1]²⁺ complexes exchange the amine protons on the grouptrans to the chloro faster than those on thecis. A coordinated methylamine group exchanges its amine protons slower than a corresponding NH₃ group in the parent pentaammine, but the methyl introduction accelerates the exchange of the other NH₃ groups. The aquation of thetrans-alkylamine complexes (studied at 52° C) is acceleratedca. 10 times compared to the parent pentaammine, irrespective of the nature of the alkyl group. Thecis complexes do not show this acceleration of aquation. In base hydrolysis (studied at 25° C) thecis complexes are the most reactive (a factor 20 over the parent ion). Thecis/trans product ratio in base hydrolysis and the competition ratio in the presence of azide ions were calculated from the 500 MHz¹H n.m.r. spectra, which display distinctly different alkyl resonances for each individual complex. Thecis ions react under stereochemical retention of configuration; thetrans compounds give 10±1%trans tocis rearrangement. The ionic strength (4 mol dm^–3) and the pH do not affect this result. The same product ratio is obtained in methanol-water and DMSO-water mixtures. Ammoniation in liquid ammonia gives the same ratios as in base hydrolysis, base-catalyzed solvolysis in neat methylamine gives stereochemical retention for both thecis- andtrans-methylamine ion. The product competition ratio (Co-N₃)/(Co-OH₂) for thecis compounds and the bulkier amines (R =n- andi-Bu), 15–25% at 1 mol dm^–3N ₃ ^– , isca. twice that of thetrans compounds and the pentaammine. The results are interpreted in the classical conjugate base mechanism, and discussed in the context of current ideas about stereochemistry of base hydrolysis.Prof. C. R. Píriz Mac-Coll from Uruguay is a guest at the Free University of Amsterdam.     

Die thermische Umlagerung von 2-(Buta-1′,3′-dienyl)-phenolen in 2-Alkyl-2H-chromene; Beispiele für aromatische [1,7a]- und [1,5s]sigmatropische Wasserstoffverschiebungen

2-(1′-cis,3′-cis-)- and 2-(1′-cis,3′-trans-Penta-1′,3′-dienyl)-phenol (cis, cis- 4 and cis, trans- 4 , cf. scheme 1) rearrange thermally at 85–110° via [1,7 a] hydrogen shifts to yield the o-quinomethide 2 (R ? CH₃) which rapidly cyclises to give 2-ethyl-2H-chromene ( 7 ). The trans formation of cis, cis- and cis, trans- 4 into 7 is accompanied by a thermal cis, trans isomerisation of the 3′ double bond in 4. The isomerisation indicates that [1,7 a] hydrogen shifts in 2 compete with the electrocyclic ring closure of 2 . The isomeric phenols, trans, trans- and trans, cis- 4 , are stable at 85–110° but at 190° rearrange also to form 7 . This rearrangement is induced by a thermal cis, trans isomerisation of the 1′ double bond which occurs via [1, 5s] hydrogen shifts. Deuterium labelling experiments show that the chromene 7 is in equilibrium with the o-quinomethide 2 (R ? CH₃), at 210°. Thus, when 2-benzyl-2H-chromene ( 9 ) or 2-(1′-trans,3′-trans,-4′-phenyl-buta1′,3′-dienyl)-phenol (trans, trans- 6 ) is heated in diglyme solution at >200°, an equilibrium mixture of both compounds (～ 55% 9 and 45% 6 ) is obtained.     

Reactivity of cationic methyl rhodium(III) complexes cis-[Rh(β-diket)(PPh3)2(CH3)(CH3CN)][BPh4] toward ligands of different character: pyridine, carbon monoxide, and triphenylphosphine

Cationic methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(Py)][BPh₄] (1) as a single isomer with Py in the trans to PPh₃ position, is formed upon the reaction of cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] with pyridine in methylene chloride solution.Complex 1 was characterized by elemental analysis and by ³¹P{¹H} and ¹H NMR spectra.Cationic pentacoordinate acetyl complexes, trans-[Rh(Acac)(PPh₃)₂(COCH₃)][BPh₄] (2) and trans-[Rh(BA)(PPh₃)₂(COCH₃)][BPh₄] (3), are prepared by action of carbon monoxide on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄], respectively, in methylene chloride solutions.Complexes 2 and 3 were characterized by elemental analysis and by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR. According to NMR data, 2 and 3 in solution are non-fluxional trigonal bipyramids with β-diketonate and acetyl ligands in the equatorial plane and axial phosphines.In solutions, 2 and 3 gradually isomerize into octahedral methyl carbonyl complexes trans-[Rh(Acac)(PPh₃)₂(CO)(CH₃)][BPh₄] (4) and trans-[Rh(BA)(PPh₃)₂(CO)(CH₃)][BPh₄] (5), respectively.Complexes 4 and 5 were characterized by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR, without isolation.Upon the action of PPh₃ on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)] [BPh₄], reductive elimination of the methyl ligand as a phosphonium salt, [CH₃PPh₃][BPh₄], occurs to give square planar rhodium(I) complexes [Rh(Acac)(PPh₃)₂] and[Rh(BA)(PPh₃)₂], respectively. The reaction products were identified in the reaction mixtures by ³¹P{¹H} and ¹H NMR.