Reactivity of rhodium-β-diketonato cyclooctadiene derivatives with mono- and di-phosphines. Synthesis, structural and spectroscopic characterization of Rh(I) and Rh(III) species containing unsymmetrical β-diketonate and P-donor ligands

Synthesis, characterization and structures of cyclic organorhodium complexes of the type [Rh{CH(SO₂Ph)CH₂CH₂YR₂-κC,κY}L₂] (YR₂ = PPh₂, NMe₂; L₂ = diphosphine, cyclooctadiene)

Reactions of dinuclear chloridorhodium(I) complexes [(RhL₂)₂(μ-Cl)₂] (L₂ = P[symbol: see text]P: Me₂P(CH₂)₂PMe₂, dmpe, 7a; Ph₂PCH₂PPh₂, dppm, 7b; Ph₂P(CH₂)₂PPh₂, dppe, 7c; Ph₂P(CH₂)₃PPh₂, dppp, 7d; L₂ = cycloocta-1,5-diene, cod, 5) with lithiated γ-phosphino- and γ-aminofunctionalized propyl phenyl sulfones (Li[CH(SO₂Ph)CH₂CH₂PPh₂], 2; Li[CH(SO₂Ph)CH₂CH₂NMe₂], 4) led to the formation of organorhodium inner complexes of the type [Rh{CH(SO₂Ph)CH₂CH₂PPh₂-κC,κP}(P[symbol: see text]P)] (8a-d), [Rh{CH(SO₂Ph)CH₂CH₂NMe₂-κC,κN}(P[symbol: see text]P)] (9a-d), [Rh{CH(SO₂Ph)CH₂CH₂PPh₂-κC,κP}(cod)]·LiCl (11·LiCl) and [Rh{CH(SO₂Ph)CH₂CH₂NMe₂-κC,κN}(cod)]·LiCl (12·LiCl), respectively. Single-crystal X-ray diffraction analysis of 9c·THF, 11 and 12 exhibited in all three compounds a distorted square planar coordination of the rhodium atoms having bidentately coordinated neutral co-ligands (cod, 11, 12; dppe, 9c) and anionic α-phenylsulfonyl γ-phosphinopropyl (κC,κP; 11) and γ-aminopropyl ligands (κC,κN; 12, 9c), thus being typical organorhodium inner complexes. Furthermore, organorhodium inner complexes of type 8 were obtained in reactions of the dinuclear chloridobridged rhodium complexes [(RhL₂)₂(μ-Cl)₂] (L₂ = P[symbol: see text]P, 7a-d; cod, 5; (C₂H₄)₂, 6) with the (non-lithiated) γ-phosphinofunctionalized propyl phenyl sulfone PhSO₂CH₂CH₂CH₂PPh₂ (1) resulting in the formation of complexes having the sulfone κP coordinated ([RhClL₂-(Ph₂PCH₂CH₂CH₂SO₂Ph-κP)] (L₂ = P[symbol: see text]P, 10a-d; cod, 13; (C₂H₄)₂, 14) which were deprotonated (10a-d, 13) at the α-C atom with lithium diisopropyl amide (LDA) in a subsequent reaction. Single-crystal X-ray diffraction analysis of 10c (P[symbol: see text]P = dppe) revealed the expected square-planar coordination geometry of Rh. The identities of all rhodium complexes have been unambiguously proved by microanalyses and NMR spectroscopy (¹H, ¹³C, ³¹P).

Synthesis, Molecular Structure (X-ray and DFT), and Solution Behavior of Titanium 4-Acyl-5-pyrazolonates. Correlations with Related Antitumor β-Diketonato Derivatives

Previously reported structure-activity relationships have shown two features for effective antitumor activity of titanium beta-diketone complexes: (a) ligand asymmetry and (b) the presence of planar substitutents on the ligand. Mono- and dinuclear derivatives, studied with diffraction and DFT methods show that (a) is consistent with different Ti-O(beta-diketonato) bond lengths, which are longer than Ti-O(oxo) and Ti-O(alkoxy) ones. pi-pi features observed in dinuclear derivatives correlate with strong reactivity of related complexes with DNA and support DNA intercalation by such planar groups, in agreement with (b). Large variation for Ti-O bond lengths and Ti-O-C bond angles in the ethoxy moiety is associated with the titanium withdrawing effect and oxygen bonding s character; it is confirmed through exploration of the Cambridge crystallographic database. This ethoxy geometrical flexibility also suggests versatile accommodation in protein pockets and/or other biological targets. Electrospray ionization mass spectrometry (ESI-MS) spectra show formation of di- and trinuclear Ti-4-acyl-5-pyrazolonato cationic oligomers. Hydrolysis/oligomerization is also described by NMR results.

Synthesis, Reactivity, Spectroscopic Characterization, X-ray Structures, PGSE, and NOE NMR Studies of (η5-C5Me5)-Rhodium and -Iridium Derivatives Containing Bis(pyrazolyl)alkane Ligands

Rhodium(III) and iridium(III) complexes containing bis(pyrazolyl)methane ligands (pz = pyrazole, L' in general; specifically, L1 = H2C(pz)2, L2 = H2C(pzMe2)2, L3 = H2C(pz4Me)2, L4 = Me2C(pz)2), have been prepared in a study exploring the reactivity of these ligands toward [Cp*MCl(mu-Cl)]2 dimers (M = Rh, Ir; Cp* = pentamethylcyclopentadienyl). When the reaction was carried out in acetone solution, complexes of the type [Cp*M(L')Cl]Cl were obtained. However, when L1 and L2 ligands have been employed with excess [Cp*MCl(mu-Cl)]2, the formation of [Cp*M(L')Cl][Cp*MCl3] species has been observed. PGSE NMR measurements have been carried out for these complexes, in which the counterion is a cyclopentadienyl metal complex, in CD2Cl2 as a function of the concentration. The hydrodynamic radius (rH) and, consequently, the hydrodynamic volume (VH) of all the species have been determined from the measured translational self-diffusion coefficients (Dt), indicating the predominance of ion pairs in solution. NOE measurements and X-ray single-crystal studies suggest that the [Cp*MCl3]- approaches the cation, orienting the three Cl-legs of the "piano-stool" toward the CH2 moieties of the bis(pyrazolyl)methane ligands. The reaction of 1 equiv of [Cp*M(L')Cl]Cl or [Cp*M(L')Cl][Cp*MCl3] with 1 equiv of AgX (X = ClO4 or CF3SO3) in CH2Cl2 allows the generation of [Cp*M(L')Cl]X, whereas the reaction of 1 equiv of [Cp*M(L')Cl] with 2 equiv of AgX yields the dicationic complexes [Cp*M(L')(H2O)][X]2, where single water molecules are directly bonded to the metal atoms. The solid-state structures of a number of complexes were confirmed by X-ray crystallographic studies. The reaction of [Cp*Ir(L')(H2O)][X]2 with ammonium formate in water or acetone solution allows the generation of the hydride species [Cp*Ir(L')H][X].

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.