Reactions of tetracyanoethylene with transition-metal acetylides: synthesis and structure of Rh(CCPh) [η2-C2(CN)4] (NCMe)(PPh3)2

The title complex was obtained from the adduct of C₂(CN)₄ and Rh(CCPh)-(CO)(PPh₃)₂ by simple substitution of CO in refluxing acetonitrile. Crystals of the complex are orthorhombic, with a 10.058(2), b 20.008(4), c 21.594(5) Å, space group P2₁2₁2₁, Z  4. The rhodium has approximate trigonal bipyramidal coordination, with apical NCMe and C₂Ph ligands: RhC₂Ph, 1.939(18); RhC(olefinic), 2.151, 2.157(19); RhN, 2.051(16); RhP, 2.377, 2.397(6) Å.     

Relative stabilities of acyl- and formyl-rhodium complexes

The various complexes RhCl₂(COR)(PPh₃)₂ and/or RhRCl₂CO(PPh₃)₂ (R  H, Me, Et, n-Pr, CH₂Cl, CH₂Ph, CH₂CH₂Ph, Cl) are generated in solution, and factors affecting the positions of equilibrium between the five-coordinate and six-coordinate isomers are discussed. The complex RhCl₂(COMe)[(Ph₂P)₂(CH₂)₃] is far more stable with respect to isomerization to a six-coordinate methyl isomer than are any of the triphenylphosphine complexes studied.     

The formation of alkyne and alkynyl complexes by reaction of 1-alkynes with trans-[M(N2)2(PH2PCH2CH2PPh2)2] (M  Mo OR W) and with [Mo(Ph2PCH2PPh2)3]: X-ray structure of trans-[Mo(CCPh)2(PH2PCH2CH2PPh2)2]

Reaction of RCCH (R  Ph, CO₂Meor CO₂Et) with trans-[M(N₂)₂(dppe)₂] (M  Mo or W; dppe  Ph₂PCH₂CH₂PPh₂) or [Mo(dppm)₃] (dppm  Ph₂PCH₂PPh₂) gives the alkyne complexes [M(RCCH)₂(diphos)₂] (diphos  dppe, M  Mo, R = Ph; dihpos  dppm, M  Mo, R  Ph or CO₂Me) and the alkynyl complexes trans-[M(cCR)₂(dppe)₂], [MH₂(CCR)₂ (dppe)₂] (M  Mo or W. R  Ph, CO₂Me or CO₂Et) and cis-[WH(CCCO₂Me)(dppe)₂]: the X-ray structure of trans-[Mo(CCPh)₂(dppe)₂] is reported.     

Crystal structure of (η5-pentamethylcyclo-pentadienyl)(methyldiphenylphosphite-P)dichlororhodium(III)

The molecule (η⁵-pentamethylcyclopentadienyl)(methyldiphenylphosphinite-P)dichlororhodium(III), [(η⁵-C₅Me₅)RhCl₂(PPh₂OMe)], crystallizes in the monoclinic crystal system in space group P2₁/c with unit cell parameters a = 16.056(3) Å, b = 9.4331(18) Å, c = 15.745(3) Å, β = 108.330(4)°, V = 2263.8(7) ų and Z = 4. There is three-legged piano stool geometry about Rh. The Rh-P distance of 2.278(2) Å is shorter than those of [(η⁵-C₅Me₅)RhCl₂(PPh₂OR)] where R is an aryl group, and longer than those found in [(η⁵-C₅Me₅)RhCl₂{PPh(OR)₂}]. The structure reveals significant distortion of the pentamethylcyclopentadienyl towards ′η³,η²-enyl-ene′ coordination.     

Synthesis and reactivity of formamidinato rhodium(I) complexes

The syntheses of [Rh(diol)(formamidine)]₂ complexes (diol  cycloocta-1,5-diene (1); diol  norbornadiene (2); formamidine  N,N′-di-p-tolylformamidine) are reported. These complexes are dimeric and contain the bridging formamidino ligand. They react with CO, dppe and PPh₃ with displacement of the diene ligand to yield the known [Rh(CO)₂(formamidine)]₂, [Rh(dppe)₂]⁺ and [Rh(PPh₃)₂(formamidine)], respectively; the last complex, in which the formamidine acts as a chelating ligand, was isolated only as the O₂ adduct. With HCl or HBF₄ aqueous 1 and 2 do not form hydrides but instead the formamidino cation [p-tolyl-NHCHNHtolyl-p]⁺ and the complexes [Rh(diol)X]₂ (X  Cl, F); a possible scheme for the reaction with HCl is proposed. The [Rh(C₈H₁₂)(formamidine)]₂ complex reacts with heterocumulenes as CS₂, SO₂, PhNCS and PhNCO with diene displacement; the only product isolated was [Rh(CS₂)₂(formamidine], to which a polymeric structure is assigned.     

The reaction of trihydrobistriphenylphosphine iridium IrH3(PPh3)2 with diazonium salts

The reaction of IrH₃(PPh₃)₂ with p-substituted aryldiazonium salts gives the compounds [IrH₂(NHNC₆H₄R)(PPh₃)₂]⁺BF₄^- at low temperature (-10°C) and the o-metalated complexes [I$\text{rH(NHN}$C₆H₃R)(PPh₃)₂]⁺BF₄^- (R  F, OCH₃) at 40–50°C. The reactions of the o-metalated complexes with CO, PPh₃, NaI and HCl have been studied.     

Remarks on the process of homogeneous carbonylation of rhodium compounds by N,N-dimethylformamide

Reductive carbonylation of rhodium(III) chloride complexes, commercial RhCl₃ · nH₂O neutralized with BaCO₃, (Me₂NH₂)₂[RhCl₅(DMF)], (PPh₄)[RhCl₄(H₂O)₂], RhCl₃(DMF)₃, RhCl₃(CH₃CN)₃, RhCl₃(CH₃CN)₂(DMF), [Rh(CO)₂Cl₃]₂, and rhodium(I) complex, Rh(PPh₃)₃Cl, by N,N-dimethylformamide (DMF) is studied. The data obtained support the conception of direct carbonyl group transfer from DMF molecule to the Rh metal center. The mechanistic scheme of carbonylation process is refined and discussed with regard of new experimental results.     

Bis-aryldiazo complexes of manganese

The first bis-aryldiazo complexes containing manganese of the type MnX(N₂Ph)₂(PPh₃)₂ and Mn(CO)(N₂Ph)₂(PPh₃)₂⁺PF₆^? have been prepared from Mn(CO)₂(N₂Ph)(PPh₃)₂ (X  Cl, Br, NCO). In addition, the mixed aryldiazonitrosyl analogues and the dinitrosyl analogues have been prepared in order to compare their spectroscopic properties with the bis-aryldiazo complexes. The preparation of the rhenium complex Re(CO)₂(N₂Ph)(PPh₃)₂ is also reported.     

The syntheses,crystal, molecular and electronic structures of two polymorphs of [ReCl2(N2COPh)(C3N2H4)(PPh3)2] and [ReCl2(N2COPh)(py)(PPh3)2] complexes

The [ReCl₂(η²-N₂COPh–N^′,O)(PPh₃)₂] complex reacts with pyridine and pyrazole to give [ReCl₂(N₂COPh)(py)(PPh₃)₂] and [ReCl₂(N₂COPh)(C₃N₂H₄)(PPh₃)₂], respectively. Two monoclinic polymers of [ReCl₂(N₂COPh)(C₃N₂H₄)(PPh₃)₂] and [ReCl₂(N₂COPh)(py)(PPh₃)₂] have been characterized by IR, UV–Vis, ¹H NMR, magnetic measurements and X-ray structure.     

The chemistry of hetero-allene and -allylic derivatives with rhodium and iridium III. Elimination of hetero-allene molecules from rhodium(I)-hetero-allylic-phosphine complexes. The first complex with η2-coordinated Ph2PS−

Carbon monoxide causes elimination of the hetero-allene molecules ptolNNptol and PhNCO in Rh(PPh₃)₂[Ph₂PC(Nptol)Nptol] and Rh(PPh₃)₂[Ph₂PC(NPh)O], respectively. The resulting complex in both cases is [Rh(CO)₂(PPh₂)(PPh₂)]_n.In the reaction of RhCl(PPh₃)₃ with Ph₂P(S)C(Nptol)NHptol or Ph₂P(S)C(O)NHPh in the presence of a base, a similar elimination occurs yielding the liberated heterocumulene and Rh(PPh₃)₂(SPPh₂). This complex is the first example of a specieswith a side-on coordinated Ph₂PS-moiety. We have also prepared this compound and other species, containing η₂SPPh₂, via direct interaction of RhCl(PPh₃)₃ and IrCl(PPh₃)₂(C₈H₁₄) with Ph₂P(S)H. Upon reaction with CO, the chelating PPh₂ group is displaced by CO to give complexes with an end-on coordinated Ph₂PS^? ligand.Finally, Rh(PPh₃)₂(SPPh₂) incorporates three moles of PhNCS, one by insertion and two by disproportionation, to yield Rh(PPh₃)(PhNC)(PhNCS₂)[Ph₂P(S)C(S)NPh].     

Fulvene—platinum complexes: x-ray crystal structure of [Pt(η2-C5H4CPh2)(PPh3)2]

Bis(cycloocta-1,5-diene)platinum reacts with 2,3,4,5-tetraphenylfulvene to afford the complex [Pt(η²-CH₂C₅Ph₄)(cod)] (cod  C₈H₁₂) in which the metal atom is coordinated to the exo-cyclic double bond of the fulvene. Related compounds [Pt(η²-CH₂C₅Ph₄L₂] (L  PPh₃, PMePh₂, PMe₂Ph, AsPh₃ or CNBu^t have also been prepared and characterised. Reaction of the complexes [Pt(C₂H₄)₂(L)] (L  P(cyclo-C₆H₁₁)₃, PPh₃ or AsPh₃) with 2,3,4,5-tetraphenylfulvene yields the compounds [Pt(C₂H₄)(η²-CH₂C₅PH₄)(L)]. NMR data for the new species are reported and discussed. 6,6-Diphenylfulvene reacts with [Pt(cod)₂] and PPh₃ ($\text{1}\text{2}$ mol ratio) to give the complex [Pt(η²-C₅H₄CPh₂)-(PPh₃)₂] in which the metal atom is bonded to carbon atoms C(2) and C(3) of the fulvene ring. This was established by an X-ray diffraction study. Crystals are monoclinic, space group P2₁/n, with Z  4 in a unit cell of dimensions a  13.761(4), b  21.653(13), c  17.395(6) Å, β,  104.46(2)°. The structure has been solved and refined to R  0.064 (R′  0.064) for 3139 independent diffracted intensifies measured at room temperature. The platinum atom is in a trigonal environment formed by the two ligated phosphorus atoms and the CC bond of the fulvene which is elongated to 1.52(3) Å. The c₅ fulvene ring is planar, and makes an angle of 108° with the coordination plane around the platinum. In this plane the metal atom is slightly asymmetrically bonded with PtC 2.15(2) and 2.24(2) Å, and PtP 2.280(6) and 2.301(6) Å.     

Synthesis,spectroscopic investigation,structural characterization,and DFT calculations of [ReX2(N2COPh)(CH3PhCN)(PPh3)2] (X=Cl,Br)

Reactions of [ReX₂(η ²-N₂COPh-N′,O)(PPh₃)₂] with 3-methylbenzonitrile give two iso-structural complexes, [ReX₂(N₂COPh)(CH₃PhCN)(PPh₃)₂] (X?=?Cl, Br). The crystal and molecular structures of [ReCl₂(N₂COPh)(CH₃PhCN)(PPh₃)₂] (1) and [ReBr₂(N₂COPh)(CH₃PhCN)(PPh₃)₂]?·?CH₂Cl₂ (2) were determined. The electronic structures were examined with density functional theory (DFT). The spin-allowed electronic transitions were calculated with the time-dependent DFT method, and the UV-Vis spectrum has been discussed.     

The unusual inhibition of a dirhodium tetraphosphine-based bimetallic hydroformylation catalyst by PPh3

The addition of even small amounts of PPh₃ to the dirhodium tetraphosphine hydroformylation catalyst generated from 〚rac-Rh₂(nbd)₂(et,ph-P4)〛(BF₄)₂ (nbd = norbornadiene; et,ph-P4 = Et₂CH₂CH₂(Ph)PCH₂P(Ph)CH₂CH₂PEt₂) causes a dramatic drop in the aldehyde linear-to-branched regioselectivity (25:1 to 3:1) in acetone solvent (90 °C, 6.1 bar, 1-hexene). Catalytic results are presented for differing amounts of added PPh₃ along with comparisons to the monometallic Rh catalyst family, HRh(CO)_x(PPh₃)_y (x = 1–3; y = 3 – x), generated from PPh₃ and Rh(acac)(CO)₂ (acac = acetylacetonate). The results point to the extremely effective inhibition of the regioselective bimetallic hydroformylation mechanism and the formation of an inefficient monometallic catalyst cycle, but not fragmentation to generate free HRh(CO)(PPh₃)₂ catalysts.     

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.     

An experimental and density functional study of the Sb–C bond activation and organo-Rh bond formation from the spontaneous decay of [RhCl3(SbPh3)3]

The reaction of RhCl₃ with SbPh₃ that produces mer-[RhCl₃(SbPh₃)₃] 1 and trans,mer-[RhCl₂(Ph)(SbPh₃)₃] 2 [A. Cavaglioni, R. Cini, J. Chem. Soc., Dalton Trans. (1997) 1149 (and references cited therein)], as well as the transformation of 1 to 2, was studied in details using the UV–Vis spectroscopy and density functional approaches. We elucidated the mechanism of Sb–C(Ph) bond activation and Rh–C(Ph) bond formation during these processes. Experimental studies show that the first step of the reaction of RhCl₃ with SbPh₃ is the formation of 1, which later rearranges to complex 2 via a concerted mechanism. The transition state associated with this transformation includes the Rh(III) center (hepta-coordinate) that interacts with three Cl^? ligands, two Sb-centers of SbPh₃ ligands, and one Sb–Ph bond of the third SbPh₃ ligand. The Cl^? ligand, trans to Sb, bridges Rh and Sb atom from the third SbPh₃ ligand. A possible pathway involving rhodium(I) intermediate species was also taken into account. The calculated geometry parameters of models of complexes 1 and 2 are in good agreement with the available X-ray data. Presented relative energies of the studied reactions are in good agreement with the relative yields of 1 and 2.     

Rhodium(I) complexes with bis(pyrazolyl)methane ligands. Crystal structure of [Rh(COD)(CH2(Pz)2)]ClO4·12 C2H4Cl2

The synthesis and properties of neutral and cationic complexes of general formulae [{RhCl(diolefin)}₂(CH₂(pz)₂)], [Rh(CO)₂ (CH₂(pz)₂)][RhCl₂(CO)₂], (Rh(diolefin)(CH₂(pz)₂)]ClO₂, [{Rh(diolefin)(PPh₃)}₂(CH₂(pz)₂)](ClO₄)₂, [Rh(CO)₂(CH₂(pz)₂)]ClO₄ and [Rh(CO)(CH₂(pz)₂)(PPh₃)]ClO₄ are described. The NMR spectra of [Rh(COD)(CH₂(pz)₂)]ClO₄ complexes are discussed. X-ray structural analysis of [Rh(COD)(CH₂(Pz)₂)]ClO₄ · $\text{1}\text{2}$C₂H₄Cl₂ is presented; the final R factor is 0.061 for 2436 observed data, recorded with Cu-K_α, not corrected for absorption and with the sample inside a capillary. The Rh atom presents a distorted square planar coordination in a mononuclear arrangement. The COD ring has a twisted boat conformation, and the two halves of the CH₂(Pz)₂ moiety, which are quite similar to one another, form an angle of 47.2(4)°.     

Tetracarbonyl group 6 complexes containing secondary and tertiary phosphines

The mixed ligand tetracarbonyl derivatives, cis-M(CO)₄(PPh₂H)(PPh₃) (M  Cr, Mo, W) and cis-W(CO)₄(PPh₂H)(L) (L  PEt₃, PEt₂Ph, PEtPh₂) have been prepared from the reaction of M(CO)₅PPh₂H with L in THF in the presence of potassium t-butoxide. These reactions are accompanied in most instances by the formation of [W(CO)₅PPh₂]⁻, [(OC)₅M(μ-PPh₂)M(CO)₅]⁻, [(OC)₅M(μ-PPh₂)-M(CO)₄(PPh₂H)]⁻, [(OC)₄M(μ-PPh₂)₂M(CO)₄]²⁻, (OC)₄M(μ-PPh₂)₂M(CO)₄, and cis-M(CO)₄(PPh₂H)₂.     

Molybdenum and tungsten complexes with the heteroallyl-like Ph2P(O)C(S)NR− (R  Me,Ph) as ligand. X-ray structural analysis of Mo(CO)2(PPh3)(Ph2P(O)C(S)NPh)2 · CH2Cl2; A 4 : 3 piano-stool configuration

Ph₂P(O)C(S)N(H)R (R  Me, Ph) reacts with M(CO)₃(η⁵-C₅H₅)Cl (M  Mo, W) in the presence of Et₃N to give M(CO)₂(η⁵-C₅H₅)(Ph₂P(O)C(S)NR). The deprotonated ligand coordinates in a bidentate manner through N and S to give a four-membered ring system. M(CO)₃(PPh₃)₂Cl₂ (M  Mo, W) reacts with Ph₂P(O)C(S)N(H)R (R  Me, Ph) in the presence of Et₃N to give complexes in which the central metal atoms are seven coordinate through two ligands bonded via O and S to form five-membered ring systems, one PPh₃, and two CO groups. The complexes were characterised by elemental analyses, IR, ¹H NMR, and ³¹P NMR spectroscopy, and an X-ray structural analysis of Mo(CO)₂(PPh₃)(Ph₂P(O)C(S)NPh)₂ · CH₂Cl₂.     

Synthesis and characterization of novel platinum group metal complexes of bis[2-(diphenylphosphino)ethyl]amine

A mixed donor tridentate ligand bis[2-(diphenylphosphino)ethyl]amine (DPEA) was synthesized in its hydrochloride form by a modified procedure and characterized by ¹H, ¹³C and ³¹P NMR spectral data. Reaction of RhCl(CO)(PPh₃)₂ with DPEA · HCl and NaBPh₄ in methanol gave the cationic Rh(I) complex [Rh(DPEA)PPh₃IBPh₄ but the reaction of IrCl(CO)(PPh₃)₂ with DPEA · HCl in boiling benzene gave a unique complex, [Ir(H)(Cl)(CO)(DPEA)]Cl, in which five different donor atoms are coordinated to the single Ir(III) ion. A neutral, RH(III) complex of the composition [RhCl₃(DPEA)] was prepared by the reaction of RhCl₃ · xH₂O with DPEA · HCl in methanol. Reaction of PdCl₂(COD) with DPEA · HCl in benzene or methanol gave the cationic complex [PdCl(DPEA)]Cl the above reaction conducted in benzene-acetone-methanol mixture gave the 1:2 complex [Pd(DPEA)₂]Cl₂. A novel trinuclear Pt(II) complex of the composition [Pt₃Cl₃(DPEA)₃]Cl₃ was prepared by the reaction of K₂PtCl₄ and DPEA · HCl in water-acetone mixture. Reaction of K₂PtCl₄, DPEA · HCl and NH₄PF₆ in water ethanol mixture gave the binuclear, cationic complex, [Pt₂(DPEA)₃](PF₆)₄. All the complexes were characterized by elemental analysis, conductivity, ¹H and ³¹P NMR spectral data.