Binding of propylene oxide to porphyrin- and salen-M(III) cations, where M = Al, Ga, Cr, and Co

The binding of propylene oxide (PO) to a series of metal cations LM(III)(+), where for L = tetraphenylporphyrin (TPP) M = Al, Ga, Cr, and Co, and for L = (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexenediamine (salen) M = Al and Cr, was studied in the gas phase by electrospray tandem mass spectroscopy, and the relative stabilities of LM(PO)(2)(+) and LM(PO)(+) cations were determined. The chromium(III) and aluminum(III) cations most tenaciously bind PO, and for M = Al, coordination to the TPP ligated metal center was favored relative to salen. For (TPP)M(PO)(2)(+), the dissociation of PO followed the order M = Al > Cr, but for (TPP)M(PO)(+) the dissociation was M = Cr > Al. The single-crystal structural determinations on (R,R-salen)AlOCHMe(S)CH(2)Cl.0.5PO and (R,R-salen)AlO(2)CMe.1.5py grown in neat PO and pyridine, respectively, reveal five-coordinate aluminum(III) centers with the alkoxide/acetate ligands in the axial position of a square-based pyramid. These results are discussed in terms of the reactivity of these metal complexes in ring-opening polymerizations and copolymerizations with PO and CO(2), respectively.     

Mechanistic insight into the initiation step of the coupling reaction of oxetane or epoxides and CO2 catalyzed by (salen)CrX complexes

The most active and robust current catalysts for the copolymerization of carbon dioxide and epoxides or oxetanes, (salen)CrX in conjunction with PPNX (PPN(+) = (Ph3P)2N(+)) or n-Bu4NX (X = Cl, N3, CN, NCO), are characterized both in solution by infrared spectroscopy and in the solid-state by X-ray crystallography. All anions (X) afford six-coordinate chromium(III) PPN(+) or n-Bu4N(+) salts composed of trans-(salen)CrX2(-) species. Of the X groups investigated in (salen)CrX, chloride is easily displaced by the others, that is, the reaction of (salen)CrCl with 2 equiv of N3(-), CN(-), or NCO(-) quantitatively provide (salen)Cr(N3)2(-), (salen)Cr(CN)2(-), and (salen)Cr(NCO)2(-), respectively. On the other hand, addition of less than 2 equiv of azide to (salen)CrCl leads to a Schlenk (ligand redistribution) equilibrium of the three possible anions both in solution and in the solid-state as shown by X-ray crystallography and electrospray ionization mass spectrometry. It was further demonstrated that all trans-(salen)CrX2(-) anions react with the epoxide or oxetane monomers in TCE (tetrachloroethane) solution to afford an equilibrium mixture containing (salen)CrX x monomer, with the oxetane adduct being thermodynamically more favored. The ring-opening steps of the bound cyclic ether monomers by X(-) were examined, revealing the rate of ring-opening of the epoxides (cyclohexene oxide and propylene oxide) to be much faster than of oxetane, with propylene oxide faster than cyclohexene oxide. Furthermore, both X anions in (salen)CrX2(-) were shown to be directly involved in monomer ring-opening.     

Studies of the carbon dioxide and epoxide coupling reaction in the presence of fluorinated manganese(III) acacen complexes: kinetics of epoxide ring-opening

Five-coordinate manganese(III) complexes of N, N'-bis(trifluoroacetylacetone)-1,2-ethylenediimine (tfacacen) have been synthesized and structurally characterized by X-ray crystallography. The presence of the electron-withdrawing -CF3 substituents enhances the electrophilicity of the metal center in these (tfacacen)MnX (X=Cl, N3, NCO, NCS) derivatives when compared with their (acacen)MnX (acacen=N, N'-bis(acetylacetone)-1,2-ethylenediimine) analogs. This is demonstrated by the increased propensity of the Mn(III) center in the tfacacen complexes to bind a sixth ligand. Binding studies were performed utilizing the upsilonN3 stretching frequency in (tfacacen)MnN3, which is sensitive to the coordination of a ligand at the vacant axial site. Of importance, cyclohexene oxide was shown to readily bind to (tfacacen)MnN3, thereby providing an opportunity for directly monitoring the dependence of the epoxide ring-opening process on the metal complex concentration. In this instance, as has been amply demonstrated in the (salen)CrX case, the ring opening of cyclohexene oxide was found to be second-order in [(tfacacen)MnN3], with an activation energy of 71.0+/-6.0 kJ/mol. In the presence of strongly coordinating anions or amine bases, the rate of epoxide ring opening by (tfacacen)MnN3 was greatly retarded. The manganese cyanate and thiocyanate complexes were examined in an effort to develop other initiators for epoxide ring opening which provide readily accessible infrared spectroscopic probes. Indeed, the thiocyanate ligand was found to be well-suited for monitoring the epoxide ring-opening reaction by infrared spectroscopy.     

Ring‐opening polymerization of (Macro)lactones by highly active mononuclear salen–aluminum complexes bearing cyclic β‐ketoiminato ligand

In this contribution, we explored the catalytic ring‐opening polymerization (ROP) of (macro)lactones using salen–aluminum complexes bearing cyclic β‐ketoiminato ligand. The effects of bridge moiety and ring size in the benzocyclane skeleton on the catalytic activity of these complexes were thoroughly investigated. Complex 5 with 2,2‐dimethylpropylene bridge and five‐membered cyclane ring can efficiently catalyze the ROP of ω‐pentadecalactone (ω‐PDL), showing higher catalytic activity (turnover frequency [TOF] up to 309.2 h^?1) than the typical Al‐salen analogs bearing salicylaldiminato ligand (TOF = 227.2 h^?1). Thus, polyethylene‐like polyester with high‐molecular weight (up to 164.5 kg/mol) could be easily prepared under optimal conditions. In addition, complex 5 can also catalyze the ROP of lactide (LA) and ε‐caprolactone (ε‐CL) with extremely high activity (TOF is high up to 147.6 h^?1 and 4752 h^?1, respectively). Here, we demonstrated a rare mono‐nuclear salen‐Al complex that can prompt the ROP of (macro)lactones with unprecedentedly high efficiency. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 973–981     

^31P NMR Studies on the Ligand Dissociation of Trinuclear Molybde-num Cluster Compounds

A series of carboxylate-substituted trinudear molybdenum dus-ter compounds formulated as Mo3S4(DTP)3(RCO2)(L), where RffiH, CH3, C2H5, CH2Cl, CCl3, R^1C6H4(R^1 is the group on the benzene ring of aromatic carboxylate ), L=pyridine,CH3CN, DMF, have been synthesized by the ligand substitu-tion reaction. The dissociation of the loosely-coordinated ligand L from the cluster core was studied by ^31p NMR. The dissocia-tion process of L is related to the solvent, temperature, and acidity of carboxylate groups, so as to affect the solution struc-ture and reactive properties of the duster. The long-distance in-teraction between ligands RCO2 and L is transported by Mo3S4 core.     

Concerning the mechanism of the ring opening of propylene oxide in the copolymerization of propylene oxide and carbon dioxide to give poly(propylene carbonate)

The reactions between (TPP)AlX, where TPP = tetraphenylporphyrin and X = Cl, O(CH(2))(9)CH(3), and O(2)C(CH(2))(6)CH(3), and propylene oxide, PO, have been studied in CDCl(3) and have been shown to give (TPP)AlOCHMeCH(2)X and (TPP)AlOCH(2)CHMeX compounds. The relative rates of ring opening of PO follow the order Cl > OR > O(2)CR, but in the presence of added 4-(dimethylamino)pyridine, DMAP (1 equiv), the order is changed to O(2)CR > OR. From studies of kinetics, the ring opening of PO is shown to be first order in [Al]. Carbon dioxide inserts reversibly into the Al-OR bond to give the compound (TPP)AlO(2)COR, and this reaction is promoted by the addition of DMAP. The coordination of DMAP to (TPP)AlX is favored in the order O(2)C(CH(2))(6)CH(3) > O(2)CO(CH(2))(9)CH(3) > O(CH(2))(9)CH(3). The microstructure of the poly(propylene carbonate), PPC, formed in the reactions between (TPP)AlCl/DMAP and (R,R-salen)CrCl and rac-PO/S-PO/R-PO and CO(2), has been investigated by (13)C [(1)H] NMR spectroscopy. The ring opening of PO is shown to proceed via competitive attack on the methine and methylene carbon atoms, and furthermore attack at the methine carbon occurs with both retention and inversion of stereochemistry. On the basis of these results, the reaction pathway leading to ring opening of PO can be traced to an interchange associative mechanism, wherein coordination of PO to the electrophilic aluminum atom occurs within the vicinity of the Al-X bond (X = Cl, OR, O(2)CR, or O(2)COR). The role of DMAP is two-fold: (i) to labilize the trans Al-X bond toward heterolytic behavior, and (ii) to promote the insertion of CO(2) into the Al-OR bond.     

Photochemistry of a chiral salen aluminum complex in nonconventional solvents: use of imidazolium ionic liquids and chiral alcohols

The photochemistry of a chiral (salen)aluminum(III) chloride complex has been studied in nonconventional solvents, namely, two imidazolium ionic liquids differing on the hydrophobicity (hydrophilic BF(4)(-) or hydrophobic PF(6)(-) counter anions) and in chiral 2-butanols (R and S). Upon 355 nm laser excitation, the same transient absorption spectrum (with some solvatochromic shift in lambda(max)) was recorded in all cases and assigned to the (salen)Al(II) complex with radicaloid character at the metal atom. This intermediate arises from the photoinduced homolytic cleavage of the apical Al-Cl bond. The half-life of this radicaloid Al(II) species varies depending on the solvent, indicating that its reactivity is governed by the nature of the ionic liquid and also on the R or S configuration of the chiral alcohol.     

Mechanistic investigations of cooperative catalysis in the enantioselective fluorination of epoxides

This report describes mechanistic studies of the (salen)Co- and amine-cocatalyzed enantioselective ring opening of epoxides by fluoride. The kinetics of the reaction, as determined by in situ (19)F NMR analysis, are characterized by apparent first-order dependence on (salen)Co. Substituent effects, nonlinear effects, and reactivity with a linked (salen)Co catalyst provide evidence for a rate-limiting, bimetallic ring-opening step. To account for these divergent data, we propose a mechanism wherein the active nucleophilic fluorine species is a cobalt fluoride that forms a resting-state dimer. Axial ligation of the amine cocatalyst to (salen)Co facilitates dimer dissociation and is the origin of the observed cooperativity. On the basis of these studies, we show that significant improvements in the rates, turnover numbers, and substrate scope of the fluoride ring-opening reactions can be realized through the use of a linked salen framework. Application of this catalyst system to a rapid (5 min) fluorination to generate the unlabeled analog of a known PET tracer, F-MISO, is reported.     

Titanium-salen complexes as initiators for the ring opening polymerisation of rac-lactide

A family of bis(iso-propoxide) titanium(IV) complexes supported by tetradentate Schiff base (salen) ligands has been synthesised and characterised, including a structural determination of N,N'-bis(6'-methylenimino-2',4'-di-tert-butylphenoxy)cyclohexyl-(1R,2R)-diamino titanium(IV) bis(iso-propoxide). Their suitability for initiating the ring-opening polymerisation of rac-lactide has been investigated. Polymerisation activities are shown to correlate with the electronic properties of the substituents within the salen ligand. In contrast to aluminium-salen initiators, electron-withdrawing substituents on the Schiff base ligand have a detrimental influence upon polymerisation activities, whereas the use of electron-donating alkoxy-functionalized ligands has allowed the highest recorded activity to date for a titanium-based initiator.     

Mechanistic studies of the copolymerization reaction of oxetane and carbon dioxide to provide aliphatic polycarbonates catalyzed by (Salen)CrX complexes

Chromium salen derivatives in the presence of anionic initiators have been shown to be very effective catalytic systems for the selective coupling of oxetane and carbon dioxide to provide the corresponding polycarbonate with a minimal amount of ether linkages. Optimization of the chromium(III) system was achieved utilizing a salen ligand with tert-butyl groups in the 3,5-positions of the phenolate rings and a cyclohexylene backbone for the diimine along with an azide ion initiator. The mechanism for the coupling reaction of oxetane and carbon dioxide has been studied. Based on binding studies done by infrared spectroscopy, X-ray crystallography, kinetic data, end group analysis done by (1)H NMR, and infrared spectroscopy, a mechanism of the copolymerization reaction is proposed. The formation of the copolymer is shown to proceed in part by way of the intermediacy of trimethylene carbonate, which was observed as a minor product of the coupling reaction, and by the direct enchainment of oxetane and CO 2. The parity of the determined free energies of activation for these two processes, namely 101.9 kJ x mol (-1) for ring-opening polymerization of trimethylene carbonate and 107.6 kJ x mol (-1) for copolymerization of oxetane and carbon dioxide supports this conclusion.     

Metal-assisted ring-closing/opening process of a chiral tetrahydroquinazoline

The ring-chain tautomerism of a 2-aryl-1,2,3,4-tetrahydroquinazoline has been exploited to induce reversible changes in the aminal-imine equilibrium, as desired, by coordination of a suitable metal ion. This process was studied by NMR and UV-vis spectroscopies, X-ray crystallography, and molecular modeling approach. The results obtained show that the imine H(2)L(i) undergoes a selective ring-closing reaction upon complexation with Ni(2+). As a result, complexes of the type Ni(HL(a))(2) are obtained, whose chirality arises from the chiral ligand H(2)L(a) and the helicity of the structure. Hence, helical enantiomers form the following racemates: [Δ-C(R,R)N(S,S),Λ-C(S,S)N(R,R)]-Ni(HL(a))(2)·2HOAc and [Δ,Λ-C(S,R)N(R,S)]-Ni(HL(a))(2)·4MeOH. In contrast to the situation observed for Ni(2+), the cyclic tautomer of the ligand, H(2)L(a), undergoes a selective ring-opening reaction upon complex formation with Pd(2+), ultimately yielding Pd(HL(i))(2)·MeOH, in which the open-chain imine ligand is bidentate through the N,O donor set of the quinoline residue. Density functional theory calculations were conducted to provide insight into the different behavior of both coordinated metals (Ni(2+) and Pd(2+)) and to propose a mechanism for the metal-assisted opening/closing reaction of the tetrahydroquinazoline ring.     

Synthesis and Immortal ROP of L-Lactide Using Copper Complex

In the present work, the -ONNO- tetradentate Schiff base ligand N, N′-bis (2-hydroxy-3-methoxybenzaldehyde) propylenediamine, [HMBPD] was synthesized. Further, complexation of this ligand with copper [HMBPD-Cu] was carried out and their reactivity for the ring-opening polymerization (ROP) of lactide (LA) has been studied. This monomeric copper complex is prepared by the reactions of copper solution with one molar equivalent of HMBPD Schiff-base ligand in ethanol under nitrogen atmosphere. This copper complex has been characterized by different spectroscopic methods, which showed square planner geometry. The copper complex is highly active towards ROP of LA. The rate of polymerization is heavily dependent on the initiator used. The copper complex allows controlled ring-opening polymerization as shown by the linear relationship between the percentage conversion and the number-average molecular weight. On the basis of literature reports, a mechanism for ROP of lactide has been proposed.     

Mechanistic studies of the copolymerization reaction of aziridines and carbon monoxide to produce poly-beta-peptoids

The coupling of carbon monoxide and aziridines has been shown to be selective for comonomer-alternating enchainment in the presence of PhCH2C(O)Co(CO)4 to afford poly-beta-peptoids. In this article, we have investigated the mechanistic aspects of the reaction of CO and N-butylaziridine by means of in situ infrared spectroscopy employing CH3C(O)Co(CO)3L (L = PPh3 (1) and P(o-tolyl)3 (2)) as precatalysts. Precatalyst 1 exists in solution under catalytic conditions as an equilibrium mixture of 1 and CH3C(O)Co(CO)4, and affords both poly-beta-butylalanoid and the corresponding lactam. By way of contrast, precatalyst 2 which possesses the sterically bulky and labile P(o-tolyl)3 ligand, affords only the acyl cobalt tetracarbonyl species in solution during catalysis with concomitant selective production of the copolymer. Kinetic studies conducted with precatalyst 2 showed the coupling reaction to have a first order dependence on catalyst, a first order dependence on N-butylaziridine, and only a slight dependence on the concentration of CO over the pressure range 17-69 bar. The working mechanistic model for the copolymerization reaction involves first aziridine insertion into the cobalt-acyl bond, rate determining ring opening by the cobaltate species, followed by the migratory CO insertion.     

Surfactant Mediated Cationic and Anionic Suspension Polymerization of PEG-Based Resins in Silicon Oil: Beaded SPOCC 1500 and POEPOP 1500

A novel surfactant has been synthesized for use in cationic and anionic ring-opening suspension polymerization of PEG-based macromonomers in silicon oil. A polymer of acrylate esters containing pentamethyldisiloxane and PEG was prepared by radical polymerization. The surfactant can stabilize an emulsion of PEG-based macromonomers, initiator, and solvent in silicon oil such that polymer beads are obtained by ring-opening polymerization, initiated either by a Lewis acid (cationic ring opening) or potassium tert-butoxide (anionic ring opening). The average bead size could be controlled by varying the stirring rate and the amount of surfactant and solvent. The surfactant does not interfere with the polymerization and can be removed together with residual silicon oil by a simple washing procedure.     

Silver complexes of cyclic hexachlorotriphosphazene

The first solid-state structures of complexed P3N3X6 (X = halogen) are reported for X = Cl. The compounds were obtained from P3N3Cl6 and Ag[Al(OR)4] salts in CH2Cl2/CS2 solution. The very weakly coordinating anion with R = C(CF3)3 led to the salt Ag(P3N3Cl6)2+[Al(OR)4]- (1), but the more strongly coordinating anion with R' = C(CH3)(CF3)2 gave the molecular adduct (P3N3Cl6)AgAl(OR')4 (3). Crystals of [Ag(CH2Cl2)(P3N3Cl6)2]+[Al(OR)4]- (2), in which Ag+ is coordinated by two phosphazene and one CH2Cl2 ligands, were isolated from CH2Cl2 solution. The three compounds were characterized by their X-ray structures, and 1 and 3 also by NMR and vibrational spectroscopy. Solution and solid-state 31P NMR investigations in combination with quantum chemically calculated chemical shifts show that the 31P NMR shifts of free and silver-coordinated P3N3Cl6 differ by less than 3 ppm and indicate a very weakly bound P3N3Cl6 ligand in 1. The experimental silver ion affinity (SIA) of the phosphazene ligand was derived from the solid-state structure of 3. The SIA shows that (PNCl2)3 is only a slightly stronger Lewis base than P4 and CH2Cl2, while other ligands such as S8, P4S3, toluene, and 1,2-Cl2C2H4 are far stronger ligands towards the silver cation. The energetics of the complexes were assessed with inclusion of entropic, thermal, and solvation contributions (MP2/TZVPP, COSMO). The formation of the cations in 1, 2, and 3 was calculated to be exergonic by delta(r)G(degrees)(CH2Cl2) = -97, -107, and -27 kJ mol(-1), respectively. All prepared complexes are thermally stable; formation of P3N3Cl5+ and AgCl was not observed, even at 60 degrees C in an ultrasonic bath. Therefore, the formation of P3N3Cl5+ was investigated by quantum chemical calculations. Other possible reaction pathways that could lead to the successful preparation of P3N3X5+ salts were defined.     

Stereoselective synthesis of a chiral ferrosalen ligand using an aromatization strategy

A new chiral salen ligand based on two ferrocenyl groups is designed. Unlike known salen ligands, of which chirality originates from central and axial chiral centers, the chirality of this ligand comes from the planar chiral ferrocenyl groups. The ligand is synthesized stereoselectively using a novel aromatization strategy starting from a ferrocene derivative, which was readily prepared using a known chiral auxiliary approach.     

Synthesis of Al complexes containing phenoxy-imine ligands and their use as the catalyst precursors for efficient living ring-opening polymerisation of epsilon-caprolactone

Al complexes containing phenoxy-imine ligands of type, Me2Al[O-2-R1-6-(R2N=CH)C6H3] [R1 = Me, R2 = 2,6-iPr2C6H3 (1a), tBu (1b); R1 = tBu, R2 = 2,6-iPr2C6H3 (2a), tBu (2b), cyclohexyl (2c), adamantyl (2d), C6H5 (2e), 2,6-Me2C6H3 (2f), C6F5 (2g)] have been prepared in high yields from AlMe3 by treating with 1.0 equiv. of 2-R1-6-(R2N=CH)C6H3OH in n-hexane. Structures for 1a, 1b, 2a-e and 2g were determined by X-ray crystallography, and these complexes have a distorted tetrahedral geometry around Al; both the Al-O and the Al-N bond distances were influenced by substituents in both the aryloxo and the imino groups. Me2Al[mu2-O-2-(R2N=CH)C6H4](AlMe3) [R2 = 2,6-iPr2C6H3 (3a), tBu (3b)] were prepared exclusively by reaction of AlMe3 with 2-(R2N=CH)C6H4OH, and these complexes form a distorted tetrahedral geometry around each Al centre with additional AlMe3 coordinating to the oxygen in the phenoxy-imine ligand. Complexes 1a, 1b and 2a-g were tested as catalyst precursors for ring-opening polymerisation (ROP) of epsilon-caprolactone (CL) in the presence of (n)BuOH (1.0 equiv. to Al), and their catalytic activities were strongly influenced by the imino substituent (R2). The efficient ROP has been achieved using the C6F5 analogue (2g), with the ROP taking place in a living manner.     

Imidazopyridinium and pyridopyrimidium bromides: synthesis and hydrolysis

The reactions of symmetrical and unsymmetrical 2,2'-dipyridylamines with 1,2-dibromoethane and 1,3-dibromopropane give imidazopyridinium and pyridopyrimidium bromides, respectively. These acetone/CH(2)Cl(2)-insoluble, highly fluorescent quaternary ammonium salts undergo addition/ring opening upon treatment with methanolic KOH to give pyridin-2-one derivatives. A sequential N,N-dialkylation/ring-opening hydrolysis/N,N-dialkylation/ring-opening hydrolysis strategy was developed for the construction of unsymmetrical bis(pyridin-2-ones).     

Synthesis and characterisation of lanthanide phenolate compounds and their catalytic activity towards ring-opening polymerisation of cyclic esters

Five new heteroleptic lanthanide(III) phenolate compounds have been synthesised in high yield, four via a transamination reaction between Ln(N(SiMe(3))2)3 and two equivalents of the phenol, HOC(6)H(2)(2,4-Bu(t))-6-CH(2)N(Me)CH(2)CH(2)NMe(2) [corrected] (LH) in thf {L(2)LnN(SiMe(3))2 where Ln = La (1); Nd (2); Sm (3); Yb (4)}. The fifth compound, [L(2)La][BPh(4)] 5 was formed by conversion of 1 by treatment with one equivalent of [Et(3)NH][BPh(4)] in toluene. Compound 3 was subjected to a single-crystal X-ray analysis and revealed a five-coordinate, distorted trigonal bipyramidal samarium(III) metal centre where each phenolate ligand is bidentate coordinating through the phenolate oxygen and nitrogen yielding six-membered chelate rings. Compound 1 exhibited fluxional behaviour in C(4)D(8)O solution which was temperature dependent. All five compounds were assessed as catalyst precursors towards the ring-opening polymerisation of both L-lactide and epsilon-caprolactone. These polymerisation studies revealed that catalysts containing larger lanthanide metals were more efficacious than those with smaller lanthanide metals. Furthermore, replacement of the [N(SiMe(3))2] initiating group in 1 with [BPh(4)] in 5 reduced catalytic activity by this compound. Detailed kinetics analysis of the ring-opening polymerisation of L-lactide by compound 1, the most efficacious catalyst precursor analysed in this study, revealed the following rate law: -d[LA]/dt = k[LA](2)[1](1) which is second order in lactide and first order in catalyst. End-group analysis by ESI mass spectrometry revealed the presence of phenolate end-groups and lactide cycles, the latter formed by intra-molecular, intrachain transesterification.     

Syntheses, structures, and reactivity of new pentamethylcyclopentadienyl-rhodium(III) and -iridium(III) 4-acyl-5-pyrazolonate complexes

New [CpM(Q)Cl] complexes (M = Rh or Ir, Cp = pentamethylcyclopentadienyl, HQ = 1-phenyl-3-methyl-4R(C=O)-pyrazol-5-one in general, in detail HQ(Me), R = CH(3); HQ(Et), R = CH(2)CH(3); HQ(Piv), R = CH(2)-C(CH(3))(3); HQ(Bn), R = CH(2)-(C(6)H(5)); HQ(S), R = CH-(C(6)H(5))(2)) have been synthesized from the reaction of [CpMCl(2)](2) with the sodium salt, NaQ, of the appropriate HQ proligand. Crystal structure determinations for a representative selection of these [CpM(Q)Cl] compounds show a pseudo-octahedral metal environment with the Q ligand bonded in the O,O'-chelating form. In each case, two enantiomers (S(M)) and (R(M)) arise, differing only in the metal chirality. The reaction of [CpRh(Q(Bn))Cl] with MgCH(3)Br produces only halide exchange with the formation of [CpRh(Q(Bn))Br]. The [CpRh(Q)Cl] complexes react with PPh(3) in dichloromethane yielding the adducts CpRh(Q)Cl/PPh(3) (1:1) which exist in solution in two different isomeric forms. The interaction of [CpRh(Q(Me))Cl] with AgNO(3) in MeCN allows generation of [CpRh(Q(Me))(MeCN)]NO(3).3H(2)O, whereas the reaction of [CpRh(Q(Me))Cl] with AgClO(4) in the same solvent yields both [CpRh(Q(Me))(H(2)O)]ClO(4) and [CpRh(Cl)(H(2)O)(2)]ClO(4); the H(2)O molecules derive from the not-rigorously anhydrous solvents or silver salts.