Antonio Tiripicchio

Pyrazolate bridged dinuclear rhodium complexes. X-ray structure of [Rh(Pz)(CO)P(OPh)3]2

Abstract The synthesis and properties of complexes of general formulae [Rh(Pz)(CO)L] 2 (Pz = pyrazolate ion, L = phosphorus donor ligand), [Rh(Pz)(diolefin)] 2 and [Rh(Pz)(C 2 H 4 ) 2 ] 2 are reported. The crystal structure of the novel complex [Rh(Pz)(CO)P(OPh) 3 ] 2 has been determined by X-ray methods. The crystals are triclinic, space group P 1 , with Z = 2 in a unit cell of dimensions a 14.061(10), b 17.140(13), c 9.937(7) A, α 102.19(7), β 10.9.55(8), γ 75.14(8)°. The structure has been solved by Patterson and Fourier methods and refined by full-matrix least-squares to R = 0.058 for 2514 independent observed reflections. The structure consists of discrete dimeric complexes in which each rhodium is in nearly square-planar arrangement, being bonded to a carbon atom of a carbonyl group, to a phosphorus of a triphenylphosphite ligand and to two nitrogen atoms of pyrazolate ligands bridging the metal atoms. The dihedral angle between the two square planes of 86.2° gives a bent configuration to the molecule in which the carbonyls and the phosphite ligands are in a trans arrangement.

Chiral Phosphoramidite Ligands Based on 8‐Chloroquinoline and Their Rhodium(III), Palladium(II), and Platinum(II) Complexes

The new chiral ligands 2-butyl-8-chloro-1-(4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cyclohepten-6-yl)-1,2-dihydroquinoline (BIPHENPHOSHQUIN, 3) and 2-butyl-8-chloro-1-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yl)-1,2-dihydroquinoline (BINAPHOSHQUIN, 4; 4a: SaRC, 4b: SaSC) have been synthesized starting from the rigid backbone of 8-chloroquinoline. The reactions of 3 and 4 with rhodium(I), palladium(II), and platinum(II) substrates are reported. The reaction of 3 with [Rh(CO)2Cl]2 in a 2:1 molar ratio in hexane afforded a binuclear chloro-bridged rhodium(III) species by intramolecular oxidative addition of the C–Cl bond of ligand 3 across the rhodium(I) centers. The rhodium(III) complex 5, incorporating the enantiomers SaRC-3 and RaSC-3, has been fully characterized by X-ray diffractometry. Reactions of [Pd(PhCN)2Cl2] with the ligands 3 and 4a in 1:2 molar ratio in toluene afforded the products cis-[Pd(3)2Cl2] (9) and cis-[Pd(4a)2Cl2] (10). Similarly, reaction of [Pt(COD)I2] with 4a in a 1:2 molar ratio afforded the complex cis-[Pt(4a)2I2] (11). An X-ray analysis has been carried out to obtain information on the effect of the ligand 4a on the overall structure of 11.

Topologically Unique Heterometallic CuII/Li Coordination Polymers Self-Assembled from N,N-bis(2-Hydroxyethyl)-2-aminoethanesulfonic Acid Biobuffer: Versatile Catalyst Precursors for Mild Hydrocarboxylation of Alkanes to Carboxylic Acids

The facile aqueous medium reactions of copper(II) nitrate with BES biobuffer [(HOCH(2)CH(2))(2)N(CH(2)CH(2)SO(3)H), hereinafter referred as H(3)bes] in the presence of various benzenecarboxylic acids [benzoic (Hba), 3-hydroxybenzoic (Hhba), and 3,5-dihydroxybenzoic (Hdhba) acid] and lithium hydroxide gave rise to the self-assembly generation of three new heterometallic Cu(II)/Li materials, [Li(H(2)O)(4)][Cu(4)(μ(2)-Hbes)(4)(μ(2)-ba)]·H(2)O (1) and [Cu(4)(μ(3)-Hbes)(4)(L){Li(H(2)O)(2)}](n)·3nH(2)O {L = μ(2)-hba (2) and μ(2)-dhba (3)}. They were isolated as air-stable crystalline solids and fully characterized by infrared (IR) and UV-vis spectroscopy and electrospray ionization (ESI)-MS(±), elemental, thermal, and single-crystal X-ray diffraction analyses. The latter revealed that 1-3 have comparable packing patterns and unit cell parameters, being composed of similar [Cu(4)(μ-Hbes)(4)(μ-carboxylate)](-) cores and [Li(H(2)O)(4)](+) cations (in 1) or [μ-Li(H(2)O)(2)](+) groups (in 2 and 3), which are arranged into discrete 0D aggregates in 1 or infinite 3D noninterpenetrating metal-organic networks in 2 and 3. The topological analysis of the coordination polymers 2 and 3 disclosed the trinodal 3,3,4-connected underlying nets with an unprecedented topology defined by the point symbol of (4.6.8)(4)(4(2).6)(2)(6(2).16(2).18(2)), further simplification of which resulted in the binodal 4,4-connected nets with the pts (PtS) topology. Apart from representing very rare examples of coordination compounds derived from H(3)bes, 1-3 feature solubility in water and were applied as efficient and versatile catalyst precursors for the mild (60 °C) single-pot hydrocarboxylation, by CO and H(2)O, of various gaseous, linear, and cyclic C(n) (n = 2-9) alkanes into the corresponding C(n+1) carboxylic acids, in H(2)O/MeCN medium under homogeneous conditions and in the presence of potassium peroxodisulfate. Total yields (based on alkane) of carboxylic acids up to 78% were achieved, which are remarkable in the field of alkane functionalization under mild conditions, especially for a C-C bond formation reaction in aqueous acid-solvent-free medium.

Spectral Properties and Crystal Structure of Bis(μ-thiocyanato-N,S)bis(thiocyanato-N)-tetrakis(5,7-dimethyl[1,2,4]triazolo[1,5-α]pyrimidine-N3)dicopper(II) and of Tetrakis(5,7-dimethyl[1,2,4]triazolo[1,5-α]pyrimidine-N3)platinum(II)hexa(thiocyanato-S)platinate(IV).

Abstract The preparation, spectroscopic studies and the crystal structure of Cu(dmtp) 2 (NCS) 2 ( I ) and Pt(dmtp) 4 Pt(SCN) 6 ( II ) (dmtp stands for the 5,7-dimethyl[1,2,4]triazolo[1,5- a ] pyrimidine ligand) are described. Crystals of I are monoclinic, space group C 2/ c , with a = 19.088(7), b = 11.516(8), c = 20.118(7) A, β = 104.51(4)°, Z = 28; crystals of II are monoclinic, space group P 2 1 / n , with a = 16.914(8), b = 11.474(9), c = 11.893(7) A, β = 91.52(4)°, Z = 2. The structures of I and II have been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares to R = 0.044 for I and 0.051 for II . The structure of I consists of centrosymmetric dimers [Cu(dmtp) 2 (NCS) 2 ] 2 , in which the copper atoms, bridged by two thiocyanate groups, are in a square pyramidal arrangement involving two isothiocyanate nitrogen atoms and two triazole nitrogen atoms from two dmtp ligands in the basal plane and a thiocyanate sulphur atom from the centrosymmetric complex in the apical position. The structure of II consists of square planar [Pt(dmtp) 2 ] 2+ cations, in which the platinum atom is bound to four triazole nitrogen atoms from dmtp ligands and of octahedral [Pt(SCN) 6 ] 2− anions with the metal bound to sulphur atoms of thiocyanate anions.

Four-versus five-co-ordination in palladium(II) and platinum(II) complexes containing 2,9-dimethyl-1,10-phenanthroline (dmphen). Crystal structures of [PtCl2(dmphen)] and [Pt(η2-C2H4)Cl2(dmphen)]

The four-co-ordinate complexes with 2,9-dimethyl-1,10-phenanthroline [MX2(dmphen)](M = Pt, X2= Cl21, ClBr 2, Br23, or I24; M = Pd, X2= Cl25, ClBr 6, Br27 or I28) have been prepared for the first time. The crystal structure of [PtCl2(dmphen)]1, has been determined by X-ray diffraction methods. The complex has a square-planar geometry around the metal and the steric interaction between the methyl groups of dmphen and the cis chlorine ligands causes a narrowing of the Cl–Pt–Cl angle [85.8(1)°], a displacement of the two chlorine atoms from the N–Pt–N plane [0.286(4) and 0.372(4)A respectively], a bending of the phenanthroline (ca. 17°), and a rotation of the overall ligand plane with respect to the platinum co-ordination plane (ca. 28°). All interligand steric constraints are released in the five-co-ordinate complexes obtained from the four-co-ordinate species by direct uptake of olefins, [M(η2-olefin)X2(dmphen)](olefin = ethylene, a; propene, b; but-1-ene, c; cis-but-2-ene, d; trans-but-2-ene, e; or styrene, f). The structure of [Pt(η2-C2H4)Cl2(dmphen)]1a, has been determined by X-ray diffraction methods. The complex has a trigonal-bipyramidal geometry around the Pt atom; the phenanthroline ligand and the olefinic carbons occupy the equatorial plane while the two chlorine atoms are in axial positions. Bond distances and angles are similar to those found in other five-co-ordinate complexes of platinum(II). The rate of uptake of olefin by the four-co-ordinate complexes, the equilibrium constant (Kf) of the formation reaction [MX2(dmphen)]+ olefin ⇌[M(η2-olefin)X2(dmphen)], and the activation energy for olefin rotation in the five-co-ordinate complexes have been measured for different olefins and halogen ions. The uptake, in chloroform, takes place in a one-step process and the reaction rate increases by a factor of 104 going from the chloro 1 to the iodo 4 complex. The equilibrium constant for the formation reaction decreases by a factor of 103 going from ethylene to trans-but-2-ene and increases by a factor of 102 going from the chloro 1 to the iodo 4 species. The activation energy for olefin rotation (ethylene and propene)(ca. 20.5 kcal mol–1) is higher than any reported value for platinum complexes and does not appear to depend upon the nature of the halogen atoms.

Chiral modification of trinuclear ruthenium clusters with proline and cysteine derivatives. Synthesis, crystal structure, and catalytic properties of [(μ2-H)Ru3(CO)10- (μ2,η2-OCNCH2CH2CH2CHCH2OCH3)] and [(μ2-H)Ru3(CO)9(μ3,η2-NCCH2CH2CHCH2OCH3)]

Abstract Proline and cysteine derivatives have been used for the chiral modification of the trinuclear ruthenium cluster system. Whereas proline derivatives yield carbamoyl Ru3 clusters by NH activation, the cysteine derivatives react by SH activation to give mercapto Ru3 clusters. The chiral methoxymethyl pyrrolydine carbamoyl clusters catalyse the enantioselective isomerization of nerol to give citronellal with an enantiomeric excess of 12.4%. The structures of [(μ2-H)Ru3(CO)10(μ2,η2- OC NCH 2 CH 2 CH 2 C HCH2OCH3)] (R-2) and [(μ2-H)Ru3(CO)9(μ3,η2- NCCH 2 CH 2 C HCH2OCH3)] (S-3) have been determined by X-ray diffraction methods. Crystals of R-2 are monoclinic, space group P21 with Z = 2, in a unit cell of dimensions a = 8.662(4), b = 18.234(4), c = 7.662(2) A, β = 94.87(2)°. Crystals of S-3 are monoclinic, space group P21 with Z = 2 in a unit cell of dimensions a = 8.881(4), b = 16.720(6), c = 7.567(3) A, β = 112.15(2)°. Both structures have been solved by direct and Fourier methods and refind by full-matrix least-squares to R = 0.0581 (R-2) and R = 0.0239 (S-3) for 2366 (R-2) and 2454 (S-3) observed reflections. The structure of R-2 consists of a ruthenium triangle of unequal edges with both the hydride and carbamoyl ligands bridging the longest edge; the carbamoyl ligand interacts through the carbon and oxygen atoms. The structure of S-3 shows a metal triangle of unequal edges in which the dehydrogenated substituted pyrrolidine ligand interacts with all three Ru atoms through the C and N atoms of the imine group to form two σ-bonds with the two metals defining the longest edge (bridged also by the hydride ligand) and a π-bond with the third one.

Simple, high-yields syntheses of nickel-osmium clusters. spectroscopic characterization of the new (η-C5H5)NiOs3(CO)9(μ2-H)3. The reactivity of (η-C5H5)NiOs3(CO)9(μ2-H)3 and (η-C5H5)3Ni3Os3(CO)9 towards H2, CO, alkynes and alkenes

Abstract The complexes (η-C5H5)NiOs3(CO)9(μ2-H)3 and (η-C5H5)3 Ni3Os3(CO)9 can be obtained in high yield by treating Os3(CO)12 or H2Os3(CO)10 with [(η-C5H5)-Ni(CO)]2 in refluxing hydrocarbons. The course of the reactions and the yields of the products can be modified by carrying out the reaction under nitrogen, hydrogen or carbon monoxide atmospheres. A preliminary report of an X-ray study of the hexametallic, 87 e− cluster was presented. The new tetrametallic derivative was characterized by spectroscopic techniques; a tetrahedral, tri-hydridic structure is proposed for this complex. The reactions of the heterometallic nickel-osmium complexes towards ligands, in particular alkenes and alkynes, are discussed. A preliminary investigation of homogeneous hydrogenation of these substrates is reported.

The Reactivity of HRu3(CO)9C2BUt. The Synthesis and crystal structure of (PPH3)AuRu3(CO)9C2BUt, a new ruthenium-gold cluster

Abstract The (PPh 3 )AuRu 3 (CO) 9 C 3 Bu t complex has been obtained by reacting (PPh 3 )AuCl with the anionic complex [Ru 3 (CO) 9 C 2 Bu t ] − , prepared from the hydride HRu 3 (CO) 9 C 2 Bu t with a new procedure. The crystal structure of this heterometallic complex, as acetone solvate, has been determined by X-ray methods: it crystallizes in the orthorhombic space group F dd2, with 16 molecules in a unit cell of dimensions a = 33.64(2), b = 48.38(2), c = 9.23(1) A. The structure has been solved from diffractometer data by direct and Patterson methods, and refined by full-matrix least-squares to R = 0.068 for 1628 observed reflections. The complex consists of a AuRu 3 cluster in a butterfly arrangement with the Au atom on a wingtip. The Au atom of the Au(PPh 3 ) group bridges one side of the ruthenium triangle and practically substitutes the hydride ligand of the HRu 3 (CO) 9 C 2 -Bu t complex, maintaining the basic features of the Ru 3 (CO) 9 C 2 Bu t framework virtually unchange.

The reactions of ruthenium carbonyl and alkyne-carbonyl complexes with nickelocene, [(η-C5H5)Ni(CO)]2 and (η-C5H5)2Ni2(RC2R′). Cyrstal structures of two isostructural heterometallic trinuclear clusters, (η-C5H5)2Ni2Ru(CO)3(C2Ph2) and (η-C5H5)2Ni2Fe(CO)3(C2Ph2)

The reactions of nickelocene, [(η-C5H5)Ni(CO)]2 and (η-C5H5)2Ni2(RC2R”) (R = H, R′ = But; R = R′ = Et, Ph) with Ru3(CO)12, H4Ru4(CO)12, HRu3(CO)9C2But and HRu3(CO)9(C6H9) are reported and compared with those of the iron carbonyls and alkyne-carbonyls. Some new products have been identified and characterized by spectroscpic analyses. The isostructural trimetallic (η-C5H5)2Ni2Fe(CO)3(C2Ph2) (V) and (η-C5H5)2Ni2Ru(CO)3(C2Ph2) (Va) have been studied by X-ray methods. Crystals of V and Va are monoclinic, space group Cc. Unit cell parameters for V are: a = 9.334(8), b = 26.717(13), c = 9.143(8)A, β = 95.15(7)°, and for Va: a = 9.201(9), b = 27.076(15), c = 9.303(8) A, β = 94.94(7)°. Both structures have been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R = 0.049 for V and 0.044 for Va. The complexes consist of a triangular cluster formed by two Ni and one Fe atoms and two Ni and one Ru atoms, respectively. A cyclopentadienyl ligand is η-bonded to each Ni atom and three terminal carbonyls are attached to the unique metal atom. The diphenylacetylene, σ-bonded to the Ni atoms and π-bonded to Fe or Ru atom, lies almost parallel to the NiNi side of the cluster. The clusters are considerably smaller in size than other complexes of comparable structure. The elongation of the acetylenic CC bond is different in the two complexes V and Va, although the alkyne—metal interactions are comparable.

Pyrazolate thiocarbonylrhodium complexes. X-ray structure of [Rh(μ-3,5-Me2Pz)(CS)(PPh3)]2

Abstract The preparation and properties of complexes of general formulae [Rh(CS)-(HL)(PR3)2]ClO4 (HL = pyrazole (HPz), 3-methylpyrazole (H3-MePz), 3,5-dimethylpyrazole (H3,5-Me2Pz), PR3 = triphenylphosphine, tricyclohexylphosphine) and [(PR3)2(CS)Rh(μ-Pz)AuPPh3]ClO4 are reported. Complexes of the first set react with potassium hydroxide to give [Rh(μ-L)(CS)(PPh3)2 or RhPz(CS)(PR3)2 complexes. The structure of the complex [Rh(3,5-Me2Pz)(CS)(PPh3)]2 has been determined by X-ray diffraction methods. The crystals are monoclinic, space group P21/c, with Z = 4 in a unit cell of dimensions a = 12.700(11), b = 17.217(16), c = 23.041(18) A, β = 116.55(8)°. The structure has been solved by Patterson and Fourier methods and refined by full-matrix least-squares to R = 0.059 for 1978 independent reflections. The structure consists of dimeric complexes, in which each rhodium atom is in a square-planar environment being bonded to a carbon atom of a thiocarbonyl ligand, a phosphorus atom of a triphenylphosphine molecule and to two nitrogen atoms of pyrazolate ligands bridging the metal atoms. The dihedral angle of 71.1° between such two square planes leads to a bent configuration with an intramolecular rhodium-rhodium distance of 3.220 A. The thiocarbonyl and triphenylphosphine ligands are in a trans disposition.