Cationic Carbonyl Complexes Research Articles

Ligand Rearrangement and Hemilability in Rhodium(I) and Iridium(I) Complexes Bearing Terphenyl Phosphanes

The synthesis of a series of cationic rhodium(I) and iridium(I) compounds stabilized by sterically demanding phosphanes that contain a terphenyl substituent PMe2Ar′ (Ar′ = 2,6‐diarylphenyl) is described. Salt metathesis of metal precursors [MCl(COD)(PMe2Ar′)] (M = Rh, Ir; COD = cyclooctadiene) with NaBArF {BArF = B[3,5‐C6H3(CF3)2]4} resulted in a series of cationic complexes in which the loss of the chlorido ligand is compensated by the appearance of relatively weak π interactions with one of the flanking aryl rings of the terphenyl substituent. The same experiments carried out with carbonyl complexes [MCl(CO)2(PMe2Ar′)] led to the corresponding cationic carbonyl complexes, the CO‐induced rearrangement reactivity of which was investigated, both experimentally and computationally. The differences in reactivity between rhodium and iridium complexes and as a result of varying the sterics of terphenyl phosphanes are discussed.

Light-triggered carbon monoxide delivery with Al-MCM-41-based nanoparticles bearing a designed manganese carbonyl complex.

A photoactive manganese carbonyl complex namely, fac-[Mn(pqa)(CO)3]ClO4 (abbreviated as {Mn-CO}, pqa = (2-pyridylmethyl)(2-quinolylmethyl)amine) has been incorporated in the pores of 60 nm mesoporous Al-MCM-41 nanoparticles. Strong electrostatic interactions with the negatively charged walls of the aluminosilicate host entrap the cationic carbonyl complex in the resulting material {Mn-CO}@Al-MCM-41 which has been characterized by various physical techniques and chemical analysis. The sample morphology and microstructure of the material have been established by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results of powder X-ray diffraction (PXRD) data and the SEM-EDX elemental maps of Si, O, Al and Mn confirm that the carbonyl complex is within the pores of the nanoparticles. The 2% manganese content of {Mn-CO}@Al-MCM-41, determined by acid digestion followed by inductively coupled plasma-optical emission spectroscopy (ICP-OES), indicates efficient loading of the carbonyl complex in the nanoparticles. In biological buffer solutions, less than 2% leaching of {Mn-CO} from the nanoparticles was noted within a period of 24 h. When exposed to a broadband visible light source (λ > 350 nm), {Mn-CO}@Al-MCM-41 rapidly releases CO, as confirmed by the reduced myoglobin assay. The utility of light-induced CO delivery by {Mn-CO}@Al-MCM-41 has been established by its capacity to relax rat aorta muscle rings in tissue bath experiments.

Synthesis of cationic rhodium(I) and iridium(I) carbonyl complexes of tetradentate P(CH2CH2PPh2)3 ligand: An implication of steric inhibition and catalytic hydroformylation reaction

New cationic carbonyl complexes of the type [M(CO)L]Cl (1) [M=Rh (a) and Ir (b); L=P(CH2CH2PPh2)3] have been synthesized and characterized by various spectroscopic techniques including the single crystal X-ray diffraction. Both the complexes crystallize in trigonal bipyramidal symmetry with the metal at the centre. Two strong intermolecular hydrogen bonds are observed in 1a. Despite the high trans effect of the CO group, the symmetrical tetradentate phosphine ligand bonded strongly to the metal centre through all sites and thereby expelling the Cl− ion outside the coordination sphere. The complexes are very stable and inert towards the oxidative addition (OA) of small molecules like CH3I, C2H5I and I2 at room as well as higher temperature. However, the complexes show catalytic activity towards the hydroformylation of alkene to the corresponding aldehydes under the reaction conditions: pressure 35±2bar, temperature 80±2°C, 500rpm and time 5–8h. The yields of the aldehyde products are in the ranges 55–75%. The complexes exhibited dissociation of weaker MP bond under the above reaction conditions to form a vaccant coordination site for initiation of the catalytic cycle.

Cyclometalated Iridium Complexes of Bis(Aryl) Phosphine Ligands: Catalytic C–H/C–D Exchanges and C–C Coupling Reactions

This work details the synthesis and structural identification of a series of complexes of the (η(5)-C5Me5)Ir(III) unit coordinated to cyclometalated bis(aryl)phosphine ligands, PR'(Ar)2, for R' = Me and Ar = 2,4,6-Me3C6H2, 1b; 2,6-Me2-4-OMe-C6H2, 1c; 2,6-Me2-4-F-C6H2, 1d; R' = Et, Ar = 2,6-Me2C6H3, 1e. Both chloride- and hydride-containing compounds, 2b-2e and 3b-3e, respectively, are described. Reactions of chlorides 2 with NaBArF (BArF = B(3,5-C6H3(CF3)2)4) in the presence of CO form cationic carbonyl complexes, 4(+), with ν(CO) values in the narrow interval 2030-2040 cm(-1), indicating similar π-basicity of the Ir(III) center of these complexes. In the absence of CO, NaBArF forces κ(4)-P,C,C',C″ coordination of the metalated arm (studied for the selected complexes 5b, 5d, and 5e), a binding mode so far encountered only when the phosphine contains two benzylic groups. A base-catalyzed intramolecular, dehydrogenative, C-C coupling reaction converts the κ(4) species 5d and 5e into the corresponding hydrido phosphepine complexes 6d and 6e. Using CD3OD as the source of deuterium, the chlorides 2 undergo deuteration of their 11 benzylic positions whereas hydrides 3 experience only D incorporation into the Ir-H and Ir-CH2 sites. Mechanistic schemes that explain this diversity have come to light thanks to experimental and theoretical DFT studies that are also reported.

Tuning Cluster Reactivity by Charge State and Composition: Experimental and Theoretical Investigation of CO Binding Energies to AgnAum+/− (n + m = 3)

Temperature-dependent gas-phase reaction kinetics measurements and equilibrium thermodynamics under multicollision conditions in conjunction with ab initio DFT calculations were employed to determine the binding energies of carbon monoxide to triatomic silver-gold binary cluster cations and anions. The binding energies of the first CO molecule to the trimer clusters increase with increasing gold content and with changing charge from negative to positive. Thus, the reactivity of the binary clusters can be sensitively tuned by varying charge state and composition. Also, multiple CO adsorption on the clusters was investigated. The maximum number of adsorbed CO molecules was found to strongly depend on cluster charge and composition as well. Most interestingly, the cationic carbonyl complex Au(3)(CO)(4)(+) is formed at cryogenic temperature, whereas for the anion, only two CO molecules are adsorbed, leading to Au(3)(CO)(2)(-). All other trimer clusters adsorb three CO molecules in the case of the cations and are completely inert to CO in our experiment in the case of the anions.

Some new cationic di- and tricarbonyl complexes of technetium(I)

Some new low-valent, cationic complexes of technetium-99 have been prepared. Oxidation of Tc2(CO)10 (1) with NOPF6 in acetonitrile gave [Tc(CH3CN)(CO)5]PF6 (2) quantitatively. This complex constitutes a useful precursor for cationic carbonyl complexes, as exemplified by a variety of reactions with bi- and tridentate ligands from which air-stable, water-soluble complexes of type [LTc(CO)3]+ (L = 1,4,7-triazacyclononane, 1,4,7-trimethyl-1,4,7-triazacyclononane and 1,4,7-trithiacyclononane) have been isolated and characterized. A series of mixed complexes of technetium(I) of general formula {Tc(N,N)[P(OR)3]2(CO)2}PF6 (N,N = 2,2′-bipyridine, 4,4′-dimethyl-2,2′-bipyridine and R = methyl, isopropyl) has also been prepared.

V(CO)7+: A capped octahedral structure completes the 18-electron rule

Abstract Molecular structures, relative energies, vibrational spectra and bond dissociation energies of the seven-coordinate, 18-valence-electron vanadium carbonyl complex, V ( CO ) 7 + , are predicted theoretically. A C3v symmetry capped octahedral structure is found to be the global minimum and predicted CO vibrational frequencies range from 2023 to 2122 cm−1, generally consistent with experiment for known cationic carbonyl complexes. The lowest energy structure of V ( CO ) 6 + is also determined, a triplet D3d structure. The resulting bond dissociation energy, De, for CO ligand loss is predicted to be 11 kcal mol−1 with B3LYP, in good agreement with experiment, while BP86 and MP2 predict much higher values of 30 and 39 kcal mol−1.

An Iron Carbonyl Approach to the Influenza Neuraminidase Inhibitor Oseltamivir.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Naphthyl-Based PCP Platinum Complexes. Nucleophilic Activation of Coordinated CO and Synthesis of a Pt(II) Formyl Complex

A series of naphthyl-based PCP Pt(II) complexes was synthesized and characterized. A single-crystal X-ray study of (PCP)PtCl (2) reveals stacking of the aromatic units between each pair of molecules of 2. Chloride abstraction from 2 under nitrogen atmosphere leads to formation of the unsaturated cationic complex [(PCP)Pt]+BF4- (3), with the metal center being stabilized by the counteranion (3a) or by the solvent (3b). Abstraction of the chloride ligand from 2 under CO atmosphere leads to formation of the cationic carbonyl complex [(PCP)Pt(CO)]+BF4- (4), containing an electrophilic carbonyl ligand. The latter is attacked by nucleophiles (MeO- and H-) to give the platinum carbomethoxy complex 5 and a rare platinum formyl complex, 6. Stabilized by the bulky bis-chelating tridentate pincer-type system, the formyl complex 6 was isolated and characterized. Complex 6 is more stable than the previously reported platinum formyls. At room temperature complex 6 is slowly converted (during days) into a hydride complex, 7.

Reactivity and stability of platinum(ii) formyl complexes based on PCP-type ligands. The significance of sterics

The synthesis and characterization of several Pt(ii) complexes, including formyl complexes, based on the PCP-type pincer ligands C(6)H(4)[CH(2)P(iPr)(2)](2) ((iPr)PCP) and C(6)H(4)[CH(2)P(tBu)(2)](2) ((tBu)PCP) are described. The chloride complex ((iPr)PCP)PtCl (6) and the unsaturated cationic complexes [(PCP)Pt](+)X(-) (X = OTf(-), BF(4)(-)) (1, 7), based on both PCP ligands, were prepared and the latter reacted with carbon monoxide to give the corresponding cationic carbonyl complexes [(PCP)Pt(CO)](+)X(-) (X = OTf(-), BF(4)(-)) (2, 8a). Hydride nucleophilic attack on both carbonyl complexes resulted in rare neutral platinum formyl complexes ((iPr)PCP)Pt(CHO) (3) and ((tBu)PCP)Pt(CHO) (9). Complex 3 undergoes decarbonylation to the corresponding hydride complex within hours at room temperature, while the bulkier complex 9 is more stable and undergoes complete decarbonylation only after 3-4 d. This observation demonstrates the very significant steric effect of the ligand on stabilization of the corresponding formyl complexes. Reaction of complex 9 with triflic acid resulted in the carbonyl complex [((tBu)PCP)Pt(CO)](+) OTf(-) (8b) with liberation of H(2), an unusual transformation for a metal formyl. Reaction with methyl triflate resulted in the Fischer carbene-type complex, the methoxy-methylidene [((tBu)PCP)Pt(CHOCH(3))](+)OTf(-) (11). The X-ray structures of complexes 2, 6, 8a and 11 were determined.

Synthesis and Characterization of a Novel Heteroditopic Macrocyclic System – Monometallic Nickel(II) and Uranyl Complexes and Their Corresponding Heterobimetallic Carbonylrhodium(I) Complexes

AbstractA novel heteroditopic macrocyclic ligand system for selective coordination of two different transition metal ions has been obtained in the form of monometallic salen complexes of NiII (LNi, 1) and uranyl (LUO2, 2). The system is characterized by the presence of a dianionic, tetradentate salen donor system (N2O2) derived from cis‐1,2‐diaminocyclohexane and of a neutral, tridentate 2,6‐bis(alkylthiomethyl)pyridine group (NS2). The two binding sites are connected by two oxyethyl chains. The synthetic procedure involves the coupling of the disodium salt of 2,6‐bis(mercaptomethyl)pyridine with two equivalents of 3‐(2‐bromoethoxy)‐2‐(2‐propenyloxy)benzaldehyde. Removal of the protecting allyl groups from the reaction product (I) by palladium catalysis yields the ligand synthon 2,6‐bis[2‐(3‐formyl‐2‐hydroxyphenyl)oxyethyl]thiomethylpyridine (II). The monometallic macrocyclic complexes 1 and 2, obtained by metal‐templated synthesis from cis‐1,2‐diaminocyclohexane, ligson II, and the corresponding NiII or uranyl acetate salts, respectively, in the presence of barium bis(trifluoroacetate), have been fully characterized by spectroscopic techniques in solution and by X‐ray diffraction analyses in the solid state. Both complexes react readily at room temperature with [Rh(CO)2Cl]2 in methanol to form the bimetallic cationic carbonyl complexes [LNiIIRh(CO)]PF6 (3) and [LUO2Rh(CO)]PF6 (4) upon addition of NH4PF6. Two conformers of complex 3 are observed in solution by IR and NMR spectroscopy, in a 5:1 ratio in [D2]dichloromethane, which exhibit a fluxional behavior and are shown to interconvert above room temperature in [D3]acetonitrile. The carbonylrhodium group in the bimetallic systems reacts further with methyl iodide in dichloromethane solution to form oxidative‐addition products. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Ligand Electronic Effects on Late Transition Metal Polymerization Catalysts

A series of bis-(aryl)-α-diimine ligands were synthesized bearing a range of electron-donating and -withdrawing substituents to systematically investigate the ligand electronic effects on late transition metal olefin polymerization catalysts. Their palladium(II) complexes were prepared and characterized. Electronic perturbations were verified by analysis of the 1H and 13C NMR chemical shifts of the corresponding methyl chloride complexes and the CO stretching frequencies of the corresponding cationic carbonyl complexes, which were found to correlate strongly with the Hammet substituent constant (σp) of the substituent on the ligand. The palladium(II) complexes of the functionalized α-diimine ligands were employed in the polymerization of ethylene and the copolymerization of ethylene with methyl acrylate. For ethylene homopolymerization, higher molecular weight was obtained with catalysts bearing more strongly electron-donating ligands. It was observed for the first time that the ligand electronic structur...

Cationic carbonyl complexes of rhodium(I) and rhodium(III): syntheses, vibrational spectra, NMR studies, and molecular structures of tetrakis(carbonyl)rhodium(I) heptachlorodialuminate and -gallate, [Rh(CO)4][Al2Cl7] and [Rh(CO)4][Ga2Cl7

Dimeric rhodium(I) bis(carbonyl) chloride, [Rh(CO)(2)(mu-Cl)](2), is found to be a useful and convenient starting material for the syntheses of new cationic carbonyl complexes of both rhodium(I) and rhodium(III). Its reaction with the Lewis acids AlCl(3) or GaCl(3) produces in a CO atmosphere at room temperature the salts [Rh(CO)(4)][M(2)Cl(7)] (M = Al, Ga), which are characterized by Raman spectroscopy and single-crystal X-ray diffraction. Crystal data for [Rh(CO)(4)][Al(2)Cl(7)]: triclinic, space group Ponemacr; (No. 2); a = 9.705(3), b = 9.800(2), c = 10.268(2) A; alpha = 76.52(2), beta = 76.05(2), gamma = 66.15(2) degrees; V = 856.7(5) A(3); Z = 2; T = 293 K; R(1) [I > 2sigma(I)] = 0.0524, wR(2) = 0.1586. Crystal data for [Rh(CO)(4)][Ga(2)Cl(7)]: triclinic, space group Ponemacr; (No. 2); a = 9.649(1), b = 9.624(1), c = 10.133(1) A; alpha = 77.38(1), beta = 76.13(1), gamma = 65.61(1) degrees; V = 824.4(2) A(3); Z = 2; T = 143 K; R(1) [I > 2sigma(I)] = 0.0358, wR(2) = 0.0792. Structural parameters for the square planar cation [Rh(CO)(4)](+) are compared to those of isoelectronic [Pd(CO)(4)](2+) and of [Pt(CO)(4)](2+). Dissolution of [Rh(CO)(2)Cl](2) in HSO(3)F in a CO atmosphere allows formation of [Rh(CO)(4)](+)((solv)). Oxidation of [Rh(CO)(2)Cl](2) by S(2)O(6)F(2) in HSO(3)F results in the formation of ClOSO(2)F and two seemingly oligomeric Rh(III) carbonyl fluorosulfato intermediates, which are easily reduced by CO addition to [Rh(CO)(4)](+)((solv)). Controlled oxidation of this solution with S(2)O(6)F(2) produces fac-Rh(CO)(3)(SO(3)F)(3) in about 95% yield. This Rh(III) complex can be reduced by CO at 25 degrees C in anhydrous HF to give [Rh(CO)(4)](+)((solv)); addition of SbF(5) at -40 degrees C to the resulting solution allows isolation of [Rh(CO)(4)][Sb(2)F(11)], which is found to have a highly symmetrical (D(4)(h)()) [Sb(2)F(11)](-) anion. Oxidation of [Rh(CO)(2)Cl](2) in anhydrous HF by F(2), followed in a second step by carbonylation in the presence of SbF(5), is found to be a simple, straightforward route to pure [Rh(CO)(5)Cl][Sb(2)F(11)](2), which has previously been structurally characterized by us. All new complexes are characterized by vibrational and NMR spectroscopy. Assignment of the vibrational spectra and interpretation of the structural data are supported by DFT calculations.

Synthesis, Characterization, and Reactivity toward MeI of Carbonyl Rh(I) Complexes Containing a PNO Hydrazonic Ligand

The reaction of the potentially tridentate hydrazonic ligand 2-(diphenylphosphino)benzaldehyde benzoylhydrazone (HL, 1) with Rh2(CO)4Cl2 in diethyl ether led to the isolation of Rh(HL)(CO)Cl (2), where the neutral ligand was PN bidentate. Addition of Et3N or NaOMe caused the deprotonation of the ligand, with the consequent formation of the three-coordinated carbonyl Rh(I) complex Rh(L)(CO) (3), which was X-ray characterized. The 2 → 3 conversion was reversible, as it was found that 2 could be regenerated by bubbling a stoichiometric amount of HCl into an ethereal solution of 3. On treating a solution of 2 with silver triflate, the cationic carbonyl complex [Rh(HL)(CO)](CF3SO3) (4) was obtained, where the neutral ligand showed a tridentate PNO behavior. All the complexes were allowed to react with MeI at room temperature. Complex 2 led to two different acetyl stereoisomers Rh(HL)(MeCO)ClI (5), where the neutral ligand coordinated in a PNO fashion. Complex 3 led to different products depending on the reaction solvent; thus the pentacoordinated acetyl complex Rh(L)(MeCO)I (8) and the solvated octahedral acetyl complex [Rh(L)(MeCO)(THF)I](THF) (9) were isolated in CH2Cl2 and in THF, respectively; the X-ray structure of 9 is reported. On carrying out the reaction in Et2O, the immediate precipitation of the hexacoordinated methylcarbonyl complex Rh(L)(CO)(Me)I (7) was observed, which rapidly rearranged into 8 after dissolution in CH2Cl2 or CHCl3. Finally, the reaction between 4 and MeI formed the cationic PNO coordinated acetyl complex [Rh(HL)(MeCO)I](CF3SO3) (10). All the oxidative addition reactions were monitored by liquid IR spectroscopy.

Synthesis and reaction of ruthenium(II) complexes containing heteroatom donor (O, N, and P) tethered to η6-arene ring

Synthesis of ruthenium(II) complexes chelated by the η6-arene ring and a pendent donor atom (O, N, and P) is described. The alcohol-containing η6-arene ruthenium complexes [Ru{η6-C6H5(CH2)3OH}(PR3)Cl2] (1a R=Ph; 1b R=Et) and [Ru{η6-C6H5(CH2)3OH}L2Cl]BF4 (2a L2=2,2′-bipyridine; 2b L2=1,10-phenanthroline; 2c L2=2,2-bis[4(R)-phenyl-1,3-oxazolon-2-yl]propane, (R)-bpop) were prepared by treatment of [Ru{η6-C6H5(CH2)3OH}Cl2]2 with tertiary phosphines or N,N′-chelate ligands/NaBF4, respectively. Addition of 1 equiv. of AgBF4 to a solution of complexes 1 or 2 gave alcohol chelate complexes [Ru{η6:η1-C6H5(CH2)3OH}(PR3)Cl]BF4 (3a–b) or [Ru{η6:η1-C6H5(CH2)3OH}L2](BF4)2 (4a–c), respectively. Although stable in MeOH, the alcohol-Ru chelate bond of 3 and 4 was cleaved by Cl− ion. Treatment of 4 with bases (OH−, R3N) led to abstraction of the hydroxy proton to give alkoxy chelate complexes [Ru{η6:η1-C6H5(CH2)3O}L2]BF4 (5a–c). In CH2Cl2 acidity of the hydroxy proton in 4c was revealed to be comparable to that of N-methylbenzylammonium cation (pKa in H2O, ca. 11). Amino chelate complexes [Ru{η6:η1-C6H5(CH2)nNH2}(PPh3)Cl]BF4 (7an=3; 7bn=2) were prepared by treatment of ammonium complexes [Ru{η6-C6H5(CH2)nNH3Cl}(PPh3)Cl2] (6an=3; 6bn=2) with 1 equiv. of NaOH and NaBF4. 7 were stable to the attack of Cl− ion. In contrast, the similar treatment of dimethylammonium derivative [Ru{η6-C6H5(CH2)3NMe2HCl}(PPh3)Cl2] (8) with KOH gave a non-chelate complex [Ru{η6-C6H5(CH2)3NMe2}(PPh3)Cl2] (9). Phosphorous chelate complexes [Ru{η6:η1-C6H5(CH2)3OPPR2}Cl2] (10a R=Ph; 10b R=iPr) were prepared by reaction of [Ru{η6-C6H5(CH2)3OH}Cl2]2, PPR2Cl, and EtNiPr2. Treatment of 10b with AgBF4 and CO (1 atm) gave the cationic carbonyl complex [Ru{η6:η1-C6H5(CH2)3OPiPr2}(CO)Cl]BF4 (11).

Synthesis and reactivities of the indenyl-ruthenium cluster [( η5-C 9H 7)Ru( μ-SEt)] 3: indenyl effect in the trinuclear ruthenium cluster

The triruthenium cluster with bridging ethanethiolato and indenyl ligands [( η 5-C 9H 7)Ru( μ-SEt)] 3 ( 2) was synthesized by heating the mononuclear indenyl complex [( η 5-C 9H 7)Ru(SEt)(PPh 3) 2] ( 1a) in toluene. Cluster 2 reacted with MeI to afford the S-methylated cluster [( η 5-C 9H 7) 3Ru 3( μ-SEt) 2( μ-SEtMe)]I·CH 2Cl 2 ( 4a) with high stereoselectivity through the attack of MeI on the axial SEt group from the equatorial side. The PF 6 − salt of the cationic cluster [( η 5-C 9H 7) 3Ru 3( μ-SEt) 2( μ-SEtMe)][PF 6] was further converted into the cationic carbonyl complex [( η 5-C 9H 7) 2Ru 2( μ-SEt)(CO) 4][PF 6] ( 5) by treatment with CO at 50°C. The crystal structures of 4a and 5 were determined by X-ray diffraction study. When a THF solution of 2 was allowed to contact with atmospheric pressure of CO at room temperature, the trinuclear carbonyl cluster [( η 5-C 9H 7) 3Ru 3( μ-SEt) 3( μ-CO)(CO)] ( 6) and the dinuclear carbonyl complex [( η 5-C 9H 7)Ru( μ-SEt)(CO)] 2 ( 7) were obtained. The structures of 6 and 7 were also crystallographically determined. Furthermore, cluster 2 was oxidized in refluxing CHCl 3 to give [( η 5-C 9H 7)Ru(SEt)Cl] n ( 9). The Cp analogue of 2, [CpRu( μ-SEt)] 3, failed to react with CO and CHCl 3, and the hapticity change of the indenyl ligand in 2 is considered to be crucial for the initial interaction of 2 with CO and CHCl 3. These reactions provide rare examples of the indenyl ligand effect in a multinuclear complex.

The reduction and oxidation of cationic carbonyl complexes of manganese with phosphoniodithioformate: X-ray crystal structure of [Mn(CO) 4(S 2CPCy 3)]ClO 4

Manganese carbonyl complexes of the types behaviour have been studied by cyclic voltammetry and controlled potential electrolysis, showing that they undergo one-electron reduction and one-electron oxidation at potentials that depend mainly on the number of carbonyls. The results have been explained on the basis on an MO study at an EH level carried out on the model complexes [Mn(CO) 4(S 2CPH 3)] + ( 1b), fac-[Mn(CO) 3PH 3(S 2CPH 3)] + ( 2d), cis,trans-[Mn(CO) 2(PH 3) 2(S 2CPH 3)] + ( 3d), mer-[Mn(CO) 3PH 3(S 2CPH 3)] + ( 4), trans,cis-[Mn(CO) 2(PH 3) 2(S 2CPH 3)] + ( 5), and cis,cis-[Mn(CO) 2(PH 3) 2(S 2CPH 3)] + ( 6).

Cationic platinum(II) complexes: platinum–alkyl bond cleavage by a powerful Lewis acid

Treatment of [PtCl(Me)(dbbipy)] or [PtCl2(dbbipy)](dbbipy = 4,4′-di-tert-butyl-2,2′-bipyridine) with AgX (X = SO3CF3 or O2CCF3) gave the complexes [PtMe(SO3CF3)(dbbipy)]1, [Pt(SO3CF3)2(dbbipy)]2 and [Pt(O2CCF3)2(dbbipy)]5. The complexes [PtCl(SO3CF3)(dbbipy)]3 and [PtMe(O2CCF3)(dbbipy)]4 were prepared by the addition of HX to [PtCl2(dbbipy)] or [PtMe2(dbbipy)], respectively. Complex 1 reacted with CO to give the cationic carbonyl complex [PtMe(CO)(dbbipy)][SO3CF3]6a, which reacted with NEt2H to give an equilibrium with the corresponding carbamyl complex [Pt(CONEt2)Me(dbbipy)]7. In the first example of alkyl-ligand abstraction from a late-transition-metal complex by the powerful Lewis acid B(C6F5)3, the complexes [PtMeL(dbbipy)][BMe(C6F5)3](L = CO 6b or C2H48) were readily prepared from [PtMe2(dbbipy)] and B(C6F5)3 in the presence of L.

Synthesis, stability and reactivity of cationic carbonyl complexes of rhodium(I)

Trans-[RhCl(CO)L2] (L = PPh3, AsPh3 or PCy3) react with AgBF4 in CH2Cl2 to give the novel species [Rh-(CO)L2]+ [BF4]−.nCH2Cl2 (n = 1/2 or 1 1/2) (1–3), which we believe to be stabilised by weak solvent interaction. The corresponding stibine compound cannot be isolated by the same process, instead [Rh(CO)2(SbPh3)3]+ [BF4]− (7) is formed when the reaction is carried out in the presence of CO. When reactions designed to prepare [Rh(CO)L2]+ [BF4]− are performed in the presence of CO, or [Rh(CO)L2]+ [BF4]− complexes are reacted with CO, [Rh(CO)2L2]+ [BF4]− (L = PPh3, AsPh3 or PCy3) (4–6) are formed. If Me2CO is used as solvent in the preparation of [Rh(CO)L2]+ [BF4]− (L = PPh3 or AsPh3), then the products are the four-coordinate [Rh(CO)L2-(Me2CO)]+ [BF4]− (8,9) species. The complexes have been characterised by i.r., 31P and 1H n.m.r. spectroscopy and elemental analyses.

Synthesis and properties of the ruthenium vinylidene and acetylide complexes containing 1,1′-bis(diphenylphosphino)ferrocene

RuCl(dppf)(η-C 5H 5) was treated with NH 4PF 6 in acetonitrile to give the cationic complex [Ru(CH 3CN)(dppf)(q-C 5H 5)]PF 6 in good yield, in which no sbonding interaction between iron and ruthenium atoms was found. The reaction of RuCl (dppf) (η-C 5H 5) with terminal acetylene in the presence of NH 4PF 6 gave the corresponding vinylidene complexes, which were converted on treatment with base or alumina to the corresponding acetylide complexes. A similar reaction with methyl propiolate at room temperature gave the corresponding vinyl ether complex rather than the acetylide complex as a main product, and a novel degradation reaction to the cationic carbonyl complex was also observed.