Syntheses, spectroscopic characteristics and thermolytic rearrangements of bis-[(trimethylgermyl)methyl]platinum(II) and bis-[(trimethylstannyl)methyl]platinum(II) complexes

The preparations and spectroscopic characteristics are reported of a series of (trimethylgermyl)methyl- and (trimethylstannyl)methylplatinum(II) complexes with diene and P-donor ancillary ligands, cis-Pt(CH₂GeMe₃)₂L₂ (L = PPh₃ or PPh₂Me; L₂ = dppe or cod) and cis-Pt(CH₂SnMe₃)₂L₂ (L = PPh₃; L₂ =cod). Thermolysis of toluene solutions of cis-Pt(CH₂GeMe₃)₂(PPh₃)₂ leads to cis-Pt(Me)(CH₂GeMe₂CH₂GeMe₃)(PPh₃)₂ via β-alkyl migration, after (non-rate-limiting) phosphine dissociation. Estimated activation parameters (ΔH_{298 K}^‡ = 126 ± 3 kJ mol⁻¹, ΔS^‡ = + 17 ± 7 J mol⁻¹ K⁻¹ and hence Δ_{298 K}^‡ = 121 ± 5 kJ mol⁻¹) suggest that this system is more migration labile than its silicon analogue, primarily as a result of a lower activation enthalpy. While cis-Pt(CH₂GeMe₃)₂(PPh₂Me)₂ reacts similarly but less readily, Pt(CH₂GeMe₃)₂(dppe)₂ is inert at operable temperatures. Thermolysis of Pt(CH₂GeMe₃)₂(cod) generates 1,1,3,3,-tetramethyldi-1,3-germacyclobutane as the major organogermanium product, while from cis-Pt(CH₂SnMe₃)₂(PPh₃)₂, 1,1,3,3-tetramethyldi-1,3-stannacyclobutane predominates. Mechanistic implications are discussed.     

Intermolecular propargyl/allenyl group transfer from Pd(II) to Pt(0) and Pt(II) to Pd(0). Key reaction in metal-catalyzed isomerization between propargyl and allenyl metal complexes

Isomerization of phenyl-substituted propargylplatinum(II) complex, trans-Pt(CH₂CCPh)(Cl)(PPh₃)₂ (1) to allenyl complex, trans-Pt(CPh=C=CH₂)(Cl)(PPh₃)₂ (2) was found to be catalyzed by zerovalent complex Pd(PPh₃)₄. The reaction was proposed to proceed through the transfer of the propargyl/allenyl ligand both from Pt(II) to Pd(0) and Pd(II) to Pt(0). The former transfer, which seemingly has a thermodynamic disadvantage, has unambiguously been confirmed to take place; treatment of 1 with Pd(PPh₃)₄ or a mixture of Pd₂(dba)₃ and PPh₃ resulted in the formation of Pd(I) complex, Pd₂(μ-PhCCCH₂)(μ-Cl)(PPh₃)₂ which lies in equilibrium with a mixture of propargyl/allenylpalladium(II) and Pd(0) complexes.     

Synthesis of a tripalladium cluster containing an η:η:η-bridging butadienyl ligand stabilized by a zwitterionic structure

An η¹-butadienyl complex [trans-η¹-CH₂=C(Me)C=CH₂Pd(PPh₃)₂Cl] (1) reacted with [(μ-η²:η²-1,3-butadiene)Pd₂(PPh₃)(μCl)Cl] (2) to result in displacement of the diene ligand of 2 accompanied by exchange of PPh₃ of 1 with Cl anion of 2 producing a butadienyl tripalladium cluster [(μ-CH₂=C(Me)C=CH₂)Pd(PPh₃)Cl₂ · Pd₂(PPh₃)₂(μ-Cl)] (3) stabilized by the zwitterionic structure in moderate yield. The X-ray structure analysis of 3 revealed rigid binding of [Pd₂(PPh₃)₂(μ-Cl)]⁺ and [CH₂ =C(Me)C=CH₂Pd(PPh₃)Cl₂]⁻ through the π-bond coordination of the butadienyl group to the dipalladium cation.     

Attempts at stepwise reduction of the carbon-nitrogen triple bond of a nitrile at two metal centres: study of the reactivity of [(CO)(PPh3)2Re( (μ-NCHPh)Ru(PPh3) 2(PhCN)] towards tetrafluoroboric acid and dihydrogen

The reaction of [(CO)PPh₃)₂Re(μ-H)₂(μ-NCHPh)Ru(PPh₃)₂(PhCN)] (2) with HBF₄-Me₂O generates [(CO)PPh₃)₂Re(μ- H)₂(μ,η¹,η²HNCHPh)Ru(PPh₃)₂(PhCN)][BF₄] (3). Monitoring the reaction by NMR spectroscopy shows the intermediate formation of [(CO)(PPh₃)₂ HRe(μ-H)₂(μ-NCHPh)Ru(PPh₃)₂(PhCN)][BF₄] (4). Attempted reduction of the imine ligand by a nucleophile (H⁻ or CN⁻) failed, regenerating 2. Under dihydrogen at 50 atm, 3 is slowly transformed into [(CO)(PPh₃)₂HRe(μ-H)₃Ru(PPh₃)₂(PhCN)][BF₄] (5) with liberation of benzyl amine.     

Preparation and characterization of ruthenium(II), rhodium(III) and iridium(III) complexes of isocyanide bearing the azo group

Reactions of [(η⁶-arene)RuCl₂]₂ (1) (η⁶-arene=p-cymene (1a), 1,3,5-Me₃C₆H₃ (1b), 1,2,3-Me₃C₆H₃ (1c) 1,2,3,4-Me₄C₆H₂(1d), 1,2,3,5-Me₄C₆H₂ (1e) and C₆Me₆ (1f)) or [Cp*MCl₂]₂ (M=Rh (2), Ir (3); Cp*=C₅Me₅) with 4-isocyanoazobenzene (RNC) and 4,4′-diisocyanoazobenzene (CN–R–NC) gave mononuclear and dinuclear complexes, [(η⁶-arene)Ru(CNC₆H₄N=NC₆H₅)Cl₂] (4a–f), [Cp*M(CNC₆H₄N=NC₆H₅)Cl₂] (5: M=Rh; 6: M=Ir)_, [{(η⁶-arene)RuCl₂}₂{μ-CNC₆H₄N=NC₆H₄NC}] (8a–f) and [(Cp*MCl₂)₂(μ-CNC₆H₄N=NC₆H₄NC)}] (9: M=Rh; 10: M=Ir)_, respectively. It was confirmed by X-ray analyses of 4a and 5 that these complexes have trans-forms for the ---N=N--- moieties. Reaction of [Cp*Rh(dppf)(MeCN)](PF₆)₂ (dppf=1,1′-bis (diphenylphosphino)ferrocene) with 4-isocyanoazobenzene gave [Cp*Rh(dppf)(CNC₆H₄N=NC₆H₅)](PF₆)₂ (7), confirmed by X-ray analysis. Complex 8b reacted with Ag(CF₃SO₃), giving a rectangular tetranuclear complex 11b, [{(η⁶-1,3,5-Me₃C₆H₃)Ru(μ-Cl}₄(μ-CNC₆H₄N=NC₆H₄NC)₂](CF₃SO₃)₄ bridged by four Cl atoms and two μ-diisocyanoazobenzene ligands. Photochemical reactions of the ruthenium complexes (4 and 8) led to the decomposition of the complexes, whereas those of 5, 7, 9 and 10 underwent a trans-to-cis isomerization. In the electrochemical reactions the reductive waves about −1.50 V for 4 and −1.44 V for 8 are due to the reduction of azo group, [---N=N---]→[---N=N---]²⁻. The irreversible oxidative waves at ca. 0.87 V for the 4 and at ca. 0.85 V for 8 came from the oxidation of Ru(II)→Ru(III).     

Synthesis of Re-Ru heterobimetallic polyhydride complexes. Study of the influence of ligands bonded to the monometallic precursors on the nature of the isolated binuclear complexes

The reaction of K[H₆ReL₂] with [RuHCl(CO)(PPh₃)_3−x {P(OPrⁱ}₃)_x](L₂ = (PMePh₂)₂, dppe, (AsPh₃)₂, or (PPh₃)₂; x = 0, 1 or 2) leads to [L₂(CO)HRe(μ-H)₃RuH(PPh₃)_2−y{P(OPrⁱ)₃}_y] (x = 0 or 1, Y = 0; X = 2, Y = 1(L₂ = PPh₃)) in a first step. Under the reaction conditions most of these complexes react rapidly with the liberated phosphine giving [L₂(CO)Re(μ-H)₃Ru(PPh₃)_3−y- {P(OPrⁱ)₃}_y] (L₂ = (PMePh₂)₂ or dppe, Y = 0; L₂ = (PPh₃)₂, Y = 1) as the only iso complexes. The structure of [(PMePh₂)₂(CO)Re(μ-H)₃Ru(PPh₃)₃] has been establishedby X-ray structure analysis. The complex [(PPh₃)₂(CO)Re(μ-H)₃Ru(PPh₃)₂(P(OPrⁱ)₃)] reacts with molecular hydrogen under pressure to generate [L₂(CO)HRe(μ-H)₃RuH(PPh₃)(P(OPrⁱ)₃) as the sole product.     

Intervalence electron transfer through a thiolate bridge ligand: a Fe–S–R–Fe mixed valence complex

The reaction of Cp(dppe)FeI with the ligands 2,2′- and 4,4′-dithiobispyridine (S₂(Py)₂) give the mononuclear or binuclear complexes of the type [Cp(dppe)Fe-S₂(Py)₂]PF₆, [Cp(dppe)Fe---SPy]PF₆ or [{Cp(dppe)Fe}₂-μ-SPy](PF₆)₂ depending on the reaction condition. Reaction of Cp(dppe)FeI with dithiobispyridines in presence of TlPF₆ as halide abstractor and using CH₂Cl₂ as a solvent gives the complexes [Cp(dppe)Fe-4,4′-S₂(Py)₂)₂]PF₆ (1) and [CpFe(dppe)-2,2′-S₂(Py)₂]PF₆ (2) whereas the same reaction using CH₃OH as a solvent and NH₄PF₆ as the halide abstractor leads to the formation of the Fe^III–thiolate complex [Cp(dppe)Fe-2,2′-SPy]PF₆ (3) and the mixed-valence complex [Cp(dppe)Fe^III-μSPy-Fe^II(dppe)Cp](PF₆)₂ (4). Magnetic and ESR measurements are in agreement with one unpaired electron delocalized between them. Mössbauer data indicate clearly the presence of two different iron sites, each one of the N-bonded and S-bonded iron atoms, with intermediate oxidation state Fe^II---Fe^III. An electron transfer intervalence absorption was observed for this complex at 780 nm (in CH₂Cl₂). By applying the Hush theory the intervalence parameters were obtained; =0.028, H_ab=361 cm⁻¹ which indicate Class II Robin–Day. Estimation of the rate electron transfer affords a value k_th=6.5×10⁶ s⁻¹. Solvent effect on the intervalence transition follow the Hush prediction for high dielectric constants solvents which permit the evaluation of the outer and inner-sphere reorganizational parameters, which were analyzed and discussed. The electronic interaction parameters compare well with those found for electron transfer in metalloproteins.     

Heterobimetallic Mo---Sn complexes. Reactions of [Mo(CO)3(CH3CN)2(Cl)(SnRCl2)] (R = Me, Ph) with 4(4-XC6H4)3 (X = Cl, F, H, Me, MeO)

Three families of heterobimetallic compounds were obtained by reaction of [Mo(CO)₃(CH₃CN)₂(Cl)(SnRCl₂)] (R = Ph, Me) with P(4-XC₆H₄)₃ (X = Cl, F, H, Me, MeO). The type of compound obtained dependent on the solvent and concentration of the starting compound. So, [Mo(CO)₂(CH₃COCH₃)₂(PPh₃)(Cl)(SnRCl₂)]·nCH₃COCH₃ (R = Ph, n = 0.5; R = Me, n = 1) (type I) and [Mo(CO)₃{P(4-XC₆H₄)₃}(μ-Cl)(SnRCl₂)]₂ (R = Ph, X = Cl, F, H, Me, MeO; R = Me, X = Cl, F) (type II) were isolated from acetone solution in ca 0.05 M and 0.1 M concentrations, respectively. However, [Mo(CO)₃(CH₃CN) {P(4-XC₆H₄)₃}(Cl)(SnRCl₂)] (R = Ph, X = H; R = Me, X = Cl, F, H) (type III) were obtained from dichloromethane solution independently of the concentration used. All new complexes showed a seven-coordinate environment at molybdenum, containing Mo---Cl and Mo---Sn bonds. Mössbauer spectra indicated a four-coordination at tin for type III complexes.     

New rhodium---ruthenium heterobimetallic complexes with bridging bi- or tri-dentate phosphine ligands

The mononuclear chelated complex [RuCl(Cp)(η²-dppa)] has been synthesised and reacted with [Rh₂Cl₂(CO)₄] to form the heterobimetallic complex [(Cp)Ru(μ-CO)₂{(μ-Ph₂PN(H)PPh₂}RhCl₂]. Complexes of [RuCl(Cp){(PPh₂)₂CHCH₂PPh₂}] have been reacted with [Rh₂Cl₂(CO)₄] or [RhCl(CO)₂(p-toluidene)]. Characterisation of these new ruthenium complexes was carried out using ³¹P-NMR, FAB mass spectroscopy, elemental analysis and IR spectrophotometry.     

Synthesis and characterization of trimetallic complexes with a borazine core

Treatment of [Cp*Ru(dppe)]⁺ with B-triethynyl-N-trimethylborazine and piperidine produces the trimetallic complex [Cp*Ru(dppe)(CC)]₃B₃N₃Me₃, the structure of which has been confirmed by X-ray diffraction. Reaction of RuHCl(CO)(PPh₃)₃ with B-triethynyl-N-trimethylborazine produces the trimetallic complex [RuCl(CO)(PPh₃)₂(CH=CH)]₃B₃N₃Me₃.     

Studies on organolanthanide complexes : LXIII. Synthesis, spectroscopic and X-ray crystallographic characterization of new early organolanthanide, organoyttrium hydride and organoholmium hydroxide complexes

Organolanthanide chloride complexes [(CH₃OCH₂CH₂C₅H₄)₂Ln(μ-Cl)]₂ (Ln = La, Pr, Ho and Y) react with excess NaH in THF at 45°C to give the dimeric hydride complexes [(CH₃OCH₂CH₂C₅H₄)₂Ln(μ-H)]₂, which have been characterized by IR, ¹H NMR, MS and XPS spectroscopy, elemental analyses and X-ray crystallography. [(CH₃OCH₂CH₂C₅H₄)₂Y(μ-H)]₂ crystallizes from THF/n-hexane at −30°C, in the triclinic space group P1 with a = 8.795(2) Å, b = 11.040(1) Å, c = 16.602(2) Å, = 93.73(1)°, β = 91.82(1)°, γ = 94.21(1)°, D_c = 1.393 gcm⁻³ for Z = 2 dimers. However, crystals of [(CH₃OCH₂CH₂C₅H₄)₂Ho(μ-OH)]₂ were obtained by recrystallization of holmium hydride in THF/n-hexane at −30°C, in the orthorhombic space group Pbca with a = 11.217(2) Å, b = 15.865(7) Å, c = 17.608(4) Å, D_c = 1.816 gcm⁻³ for Z = 4 dimers. In the complexes of yttrium and holmium, each Ln atom of the dimers is coordinated by two substituted cyclopentadienyl ligands, one oxygen atom and two hydrogen atoms (for the Y atom) or two hydroxyl groups (for the Ho atom) to form a distorted trigonal bipyramid if the C(η⁵)-bonded cyclopentadienyl is regarded as occupying a single polyhedral vertex.     

Mononuclear Pt(II) and Pd(II) 1,4-dithiolato complexes. Crystal structures of [Pt((−) DIOS) (PPh3)2] and [Pd(S(CH2) 4S)(Ph2P(CH2) 3PPh2)]. Application in styrene hydroformylation

Addition of 1,4-dithiols to dichloromethane solutions of [PtCl₂(P-P)] (P-P = (PPh₃)₂, Ph₂P(CH₂)₃PPh₂, Phd₂P(CH₂)₄PPh₂; 1,4-dithiols = HS(CH₂)₄SH, (−)DIOSH₂ (2,3-O-isopropylidene-1,4-dithiol-l-threitol), BINASH₂ (1,1′-dinaphthalene-2,2′-dithiol)) in the presence of NEt₃ yielded the mononuclear complexes [Pt(1,4-dithiolato)(P-P)]. Related palladium(II) complexes [Pd(dithiolato)(P-P)] (P-P=Ph₂P(CH₂)₃PPh₂, Ph₂P(CH₂)₄PPh₂; dithiolato = ⁻S(CH₂)₄S⁻, (−)-DIOS) were prepared by the same method. The structure of [Pt((−)DIOS)(PPh₃)₂] and [Pd(S(CH₂)₄S)(Ph₂P(CH₂)₃PPh₂)] complexes was determined by X-ray diffraction methods. Pt—dithiolato—SnC1₂ systems are active in the hydroformylation of styrene. At 100 atm and 125°C [Pt(dithiolate)(P-P)]/SnCl₂ (Pt:Sn = 20) systems provided aldehyde conversion up to 80%.     

Synthesis and characterization of hydroxo, pyrazolato and carboxylato derivatives of the PdR(PPh3)moiety (R = C6F5 or C6Cl5)

The hydroxo-complexes [{PdR(PPh₃)(μ-OH)}₂] (R = C₆F₅ or C₆Cl₅) have been obtained by reaction of the corresponding [{PdR(PPh₃)(μ-Cl)}2] complexes with NBu₄OH in acetone. In this solvent, the reaction of the hydroxo-bridged complexes with pyrazole (Hpz) and 3,5-dimethylpyrazole (Hdmpz) in 1:2 molar ratio leads to the formation of the new complexes [{Pd(C₅F₅)(PPh₃)(μ-azolate)}2] and [{Pd(C₆Cl₅)(PPh₃)}₂(μ-OH)(μ-azolate)] (azolate = pz or dmpz). The reaction of the bis(μ-hydroxo) complexes with Hpz and Hdmpz in acetone in 1:1 molar ratio has also been studied, and the resulting product depends on the organic radical (C₆F₅ or C₆Cl₅) as well as the azolate (pz or dmpz). The identity of the isomer obtained has been established in every case by NMR (¹H, ¹⁹F and ³¹P) spectroscopy. The reaction of the bis(μ-hydroxo) complexes with oxalic (H₂Ox) and acetic (HOAc) acids yields the binucle ar complexes [{PdR(PPh₃)}2(μ-Ox)] (R = C₆F₅ or C₆Cl₅) and [{Pd(C₆F₅)(PPh₃)(μ-OAc)}2], respectively. [{Pd(C₆F₅)(PPh₃)(μ-OH)}₂] reacts with PPh₃ in acetone in 1:2 ratio giving the mononuclear complex trans-[Pd(C₆F₅) (OH)(PPh₃)₂], whereas the pentachlorophenylhydroxo complex does not react with PPh₃, even under forcing conditions.     

Synthesis and X-ray crystal structures of [Ph2PMe2][(η-C5H4Bu)2Li] and [(η-C5H4Bu)2Yb(Cl)CH2P(Me)Ph2]

The interaction of [(η⁵-C₅H₄Bu^t)₂YbCl · LiCl] with one equivalent of Li[(CH₂) (CH₂)PPh₂] in tetrahydrofuran gave [Ph₂PMe₂][(η⁵-C₅H₄Bu^t)₂Li] (1) and [(η⁵-C₅H₄Bu^t)₂Yb(Cl)CH₂P(Me)Ph₂] (2) in 10% and 30% yields, respectively. 1 could also be prepared in 70% yield from the reaction of [Ph₂PMe₂][CF₃SO₃] with two equivalents of (C₅H₄Bu^t)Li. Both compounds have been fully characterized by analytical, spectroscopic and X-ray diffraction methods. The solid state structure of 1 reveals a sandwich structure for the [(η⁵-C₅H₄Bu^t)₂Li]⁻ anion.     

Synthesis and properties of some diruthenium acetate compounds

The compound [Ru₂(μ-O₂CCH₃)₄(THF)₂]BF₄ (I) containing the Ru₂⁵⁺ unit was prepared by reaction of Ru₂Cl(μ-O₂CCH₃)₄ with AgBF₄ in THF. This compound, in contrast with Ru₂Cl(μ-O₂CCH₃)₄, is soluble in several polar organic solvents and reacts in THF with OPPh₃ and PPh₃ giving [Ru₂(μ-O₂CCH₃)₄(OPPh₃)₂]BF₄·CH₂Cl₂ (II) and [Ru(μ-O₂CCH₃)(O₂CCH₃)(PPh₃)]_n (III), respectively. The complex II has been also obtained as hexafluorophosphate [Ru₂(μ-O₂CCH₃)₄(OPPh₃₂]PF₆·CH₂Cl₂ (IV) by treatment of Ru₂Cl(μ-O₂CCH₃)₄ with an excess of NOPF₆ and PPh₃ in methanol. In this reaction the triphenylphosphine oxide is generated by oxidation of the triphenylphosphine.     

Highly stereoselective reduction of methyl ketone complexes of the chiral Lewis acid [(η-C5H5)Re(NO)(PPh3)] by K(s-C4H9)3BH; synthesis of optically active secondary alcohols and derivatives

Reaction of optically active ketone complexes (+)-(R)-[(η⁵-C₅H₅)Re(NO)-(PPh₃)(η¹-O=C(R)(CH₃)]⁺ BF₄⁻ (R = CH₂CH₃, CH(CH₃)₂m C(CH₃)₃, C₆H₅) with K(s-C₄H₉)₃BH gives alkoxide complexes (+)-(RS)-(η⁵-C₅H₅)Re(NO)(PPh₃)-(OCH(R)CH₃) (73–90%) in 80–98% de. The alkoxide ligand is then converted to Mosher esters (93–99%) of 79–98% de.     

Synthesis, structure and hydrogenation catalytic activity of [Ru3(μ3,η-ampy)(μ,η:η-PhC=CHPh)(CO)6(PPh3) (Hampy = 2-amino-6-methylpyridine)

The compound [RU₃(μ₃,η²- -ampy)(μ₃η¹:η²-PhC=CHPh)(CO)₆(PPh₃)₂] (1) (ampy = 2-amino-6-methylpyridinate) has been prepared by reaction of [RU₃(η-H)(μ₃,η²- ampy) (μ,η¹:η²-PhC=CHPh)(CO)₇(PPh₃)] with triphenylphosphine at room temperature. However, the reaction of [RU₃(μ-H)(μ₃, η² -ampy)(CO)₇(PPh₃)₂] with diphenylacetylene requires a higher temperature (110°C) and does not give complex 1 but the phenyl derivative [RU₃(μ₃,η²-ampy)(μ,η ¹:η² -PhC=CHPh)(μ,-PPh₂)(Ph)(CO)₅(PPh₃)] (2). The thermolysis of complex 1 (110°C) also gives complex 2 quantitatively. Both 1 and 2 have been characterized by0 X-ray diffraction methods. Complex 1 is a catalyst precursor for the homogeneous hydrogenation of diphenylacetylene to a mixture of cis- and trans -stilbene under mild conditions (80°C, 1 atm. of H₂), although progressive deactivation of the catalytic species is observed. The dihydride [RU₃(μ-H)₂(μ ₃,η²-ampy)(μ,η¹:η²- PhC=CHPh)(CO)₅(PPh₃)₂] (3), which has been characterized spectroscopically, is an intermediate in the catalytic hydrogenation reaction.     

Synthesis, characterization and the unpleasantly disordered crystal structure of Ir(Ome)(CO)(PPh3)2(SO4)

The adducts of O₂ and SO₂ with trans-MeOIr(CO)(PPh₃)₂ are formed in equilibria and have been characterized. Reaction of the SO₂ adduct, Ir(OMe)(SO₂)(CO)(PPh₃)₂ with dioxygen leads to the sulfato complex, Ir(Ome)(CO)(PPh₃)₂(SO₄), the structure of which has been determined. Ir(Ome)(CO)(PPh₃)₂(SO₄) crystallizes in the monoclinic system with a 11.958(2), b 14.163(3), c 12.231(2) Å, β 118.365(12)°, V 1822.7(6) ų and Z = 2. Diffraction data for 2θ = 4.5–45.0° (Mo-K) were collected with a Syntex P2₁ diffractometer and the structure was solved (assuming space group P2₁/m and an unpleasant 2-fold disordered model) and refined to R = 4.8% for all 2512 independent data (R = 3.5% for those 2042 data with ¦F_O¦ > 6σ(¦F¦)). The iridium(III) atom has a distorted octahedral coordination sphere with trans PPh₃ ligands and a cis-chelating bidentate O,O′-SO₄ group; the structure is completed by mutually cis OMe and CO ligands.     

Synthesis, characterization of new Rh---Co mixed-metal clusters and reactions of clusters containing [Rh2Co2C2] core with 1-alkynes and/or carbon monoxide

Six new cluster derivatives [Rh₂Co₂(CO)₆(μ-CO)₄(μ₄,η²-HCCR)] (R=FeCp₂ 1, CH₂OH 2, (CH₃O)C₁₀H₆CH(CH₃)COOCH₂CCH 3) and [RhCo₃(CO)₆(μ-CO)₄(μ₄,η²-HCCR)] (R=FeCp₂ 4, CH₂OH 5, (CH₃O)C₁₀H₆CH(CH₃)COOCH₂CCH 6) were obtained by the reactions of [Rh₂Co₂(CO)₁₂] and [RhCo₃(CO)₁₂] with substituted 1-alkyne ligands HCCR [R=FeCp₂ 7, CH₂OH 8, (CH₃O)C₁₀H₆CH(CH₃) COOCH₂CCH 9] in n-hexane at room temperature, respectively. Alkynes insert into the Co---Co bond of the tetranuclear clusters to give butterfly clusters. [Rh₂Co₂(CO)₆(μ-CO)₄(μ₄,η²-HCCFeCp₂)] (1) was characterized by a single-crystal X-ray diffraction analysis. Reactions of 1, 2 with 7, 8 and ambient pressure of carbon monoxide at 25 °C gave two known cluster complexes [Co₂(CO)₆(μ₂, η²-HCCR)] (R=FeCp₂ 10, CH₂OH 11), respectively. All clusters were characterized by element analysis, IR and ¹H-NMR spectroscopy.     

Structures of propionaldehyde, butyraldehyde, and pivalaldehyde complexes of the chiral rhenium fragment [(η-C5H5)Re(NO)(PPh3)]

The crystal structures of propionaldehyde complex (RS,SR)-(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHCH₂CH₃)]⁺ PF₆⁻ (1b⁺ PF₆^s−; monoclinic, P2₁/c (No. 14), a = 10.166 (1) Å, b = 18.316(1) Å, c = 14.872(2) Å, β = 100.51(1)°, Z = 4) and butyraldehyde complex (RS,SR)-[(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHCH₂CH₂CH₃)]⁺ PF₆⁻ (1c⁺PF₆⁻; monoclinic, P2₁/a (No. 14), a = 14.851(1) Å, b = 18.623(3) Å, c = 10.026(2) Å, β = 102.95(1)°, Z = 4) have been determined at 22°C and −125°C, respectively. These exhibit C O bond lengths (1.35(1), 1.338(5) Å) that are intermediate between those of propionaldehyde (1.209(4) Å) and 1-propanol (1.41 Å). Other geometric features are analyzed. Reaction of [(η⁵-C₅H₅)Re(NO)(PPh₃)(ClCH₂Cl)]⁺ BF₄⁻ and pivalaldehyde gives [(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHC(CH₃)₃)]⁺BF₄⁻ (81%), the spectroscopic properties of which establish a π C O binding mode.