Synthese und Charakterisierung von Trimethyl(sulfato)platin(IV)Komplexen

Syntheses and Characterization of Trimethyl(sufato)platinum(IV) Complexes [(PtMe₃I)₄] ( 1 ) reacts in benzene/acetone (1 : 1) with excess of freshly precipitated silver sulfate (Pt : Ag = 1 : 2) to give [{[PtMe₃(H₂O)]₂SO₄}_∞] ( 2 ) at working up from acetone (not dried) and water to [{PtMe₃(H₂O)₂}₂SO₄] ( 3 ), respectively. [(PtMe₃I)₄] ( 1 ) reacts with AgBF₄ in the corresponding solvent L to give complexes of the type [PtMe₃L₃]BF₄ (L = Me₂CO 4 , MeOH 5 , MeCN 6 , THF 7 ). The triaqua complex 8 (L = H₂O) has been obtained by reaction of 4 with water. All complexes are characterized by microanalysis and NMR spectroscopy (¹H, ¹³C, ¹⁹⁵Pt). X-ray diffraction analysis of 2 (monoclinic, P2₁) exhibits dinuclear units [Me₃Pt(μ-H₂O)PtMe₃(H₂O)]²⁺ at which oxo ligands of sulfate ions are coordinated in such a way that the crystal is threaded by double chains. The Pt–O bonds to μ-aqua ligand are considerably longer than that to terminal aqua ligand (2.322(9)/2.363(8) vs. 2.234(9) Å). The structural characterization of 3 (triclinic, P 1) reveals [PtMe₃(H₂O)₂]⁺ cations that are bridged by a sulfate ion yielding a dinuclear entity [(H₂O)₂Me₃Pt(μ-SO₄)PtMe₃ · (H₂O)₂]. These entities are linked in the crystal by a network of hydrogen bridges.     

Binuclear platinum(I) complexes with bis(dimethylphosphino)methane ligands: evidence for both short- and long-range NMR trans-influences

The diplatinum(I) complexes or complex ions [Pt₂X₂(μ-dmpm)₂] (X = Cl or I), [Pt₂X(PPh₃)(μ-dmpm)₂]⁺] (X = I, Br or Me), and [Pt₂(PPh₃)₂(μ-dmpm)₂]²⁺, where dmpm = Me₂PCH₂PMe₂, have been prepared and characterized by ¹H and ³¹P NMR spectroscopy. In the linear X-Pt-Pt-Y unit the trans-influence of X is felt primarily at the PtPt bond, but groups X having a very high trans-influence (X = H or Me) can also exert a weaker long-range trans-influence on the PtY bond.     

New biimidazole and bibenzimidazole derivatives: mono and binuclear palladium(II) or platinum(II) complexes and heterobinuclear palladium(II)-rhodium(I) or platinum(II)-rhodium(I) complexes

Novel neutral biimidazolate or bibenzimidazolate palladium(II) and platinum(II) complexes of the type M(NN)₂(dpe) [M = Pd, Pt; (NN)₂^2? = BiIm^2?, BiBzIm^2?. dpe = 1,2-bis(diphenylphosphino) ethane] have been obtained by reacting MCl₂(dpe) with TI₂(NN)₂. Complexes M(NN)₂(dpe) which are Lewis bases react with HClO₄ or [M(dpe)(Me₂CO)₂](ClO₄)₂ to yield, respectively, mononuclear cationic complexes of general formula [M{H₂(NN)₂](dpe) (M = Pd, Pt; H₂(NN)₂ = H₂BiIm, H₂BiBzIm) and homobinuclear palladium(II) or platinum(II) cationic complexes of the type [M₂{μ - (NN)₂}(dpe)₂](ClO₄)₂. Reactions of M(BiBzIm)(dpe) with [Rh(COD) (Me₂CO)_X](ClO₄) render similar heterobinuclear palladium(II)-rhodium(I) and platinum(II)-rhodium(I) cationic complexes, of general formula [(dpe)M(μ-BiBzIm)Rh(COD)](ClO₄) (M = Pd, Pt; COD = 1,5-cyclooctadiene). Di- and mono-carbonyl derivatives [(dpe)M(μ-BiBzIm)Rh(CO)L](ClO₄) (M = Pd, Pt; L = CO, PPh₃) have also been prepared. The structures of the resulting complexes have been elucidated by conductance studies and IR spectroscopy.     

Synthesis and characterization of dinuclear pyrazolato bridged platinum(IV) complexes

Reactions of [PtMe₃(OCMe₂)₃](BF₄) and [(PtMe₃I)₄] with pyrazole (pzH) afforded mononuclear pyrazole platinum(IV) complexes [PtMe₃(pzH)₃](BF₄) (1) and [PtMe₃I(pzH)₂] (2), respectively. The formation of dinuclear pyrazolato bridged platinum(IV) complexes (PPN)[(PtMe₃)₂(μ-pz)₃] (3), (PPN)[(PtMe₃)₂(μ-I)(μ-pz)₂] · 1/2Et₂O (4) and [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (5) was achieved by the reaction of each 1 and 2 with [PtMe₃(OCMe₂)₃](BF₄) in the presence of KOAc followed by reaction with (PPN)Cl (PPN⁺ = bis(triphenylphosphine)iminium cation) and 18C6, respectively. The reaction of complex 4 with AgO₂CCF₃ followed by addition of RSR′ (R/R′ = Me/Me, Me/Ph) resulted in the formation of complexes [(PtMe₃)₂(μ-pz)₂(μ-RSR′)] (R/R′ = Me/Me, 6; Me/Ph, 7). All complexes were characterized unambiguously by microanalysis and NMR (¹H, ¹³C) spectroscopic investigations. Additionally, crystal structures of complexes 3 and 4 as well as DFT calculation are presented. Furthermore, in vitro studies on the anti-proliferative activity of complexes 2 and 5 were carried out.     

Synthese und Kristallstrukturen der Phosphanimin-Komplexe [Cu(μ-HNPEt3)]4(O3S–CF3)4 und [Pt2Me6(μ-I)2(μ-HNPMe3)]

Synthesis and Crystal Structures of the Phosphaneimine Complexes [Cu(μ-HNPEt₃)]₄(O₃S–CF₃)₄ and [Pt₂Me₆(μ-I)₂(μ-HNPMe₃)] The title compounds have been prepared by the reaction of copper(I)triflate with [NiBr(NPEt₃)]₄ in CH₂Cl₂ suspension in the presence of water, and by the reaction of [PtMe₃I]₄ with Me₃SiNPMe₃ in boiling toluene in the presence of cesium fluoride, respectively. According to the crystal structure determinations the cation of the copper complex forms tetrameric units [Cu(HNPEt₃)]₄⁴⁺ with S₄ symmetry with Cu–N bond lengths of 191.6 and 192.1 pm. In the platinum complex the platinum atoms are linked by two μ-I bridging atoms as well as by the μ-N atom of the HNPMe₃ ligand with Pt–N bond lengths of 228.1 and 229.5 pm.     

Platinum(IV) complexes with α,ω-bis(pyrazol-1-yl) alkanediyl and diethyl ether/thioether ligands. Crystal structures of dibromodimethyl[1,2-bis(pyrazol-1-yl)ethane]platinum(IV) and trimethyl-bis[2-(pyrazol-1-yl)ethyl]etherplatinum(IV) tetrafluoroborate

Reactions of the flexible α,ω-bis(pyrazol-1-yl) compounds 1,2-bis(pyrazol-1-yl)ethane (L1), 1,8-bis(pyrazol-1-yl)-n-octane (L2), bis[2-(pyrazol-1-yl)ethyl]ether (L3) and bis[2-(pyrazol-1-yl)ethyl]thioether (L4) with precursor organometallic platinum complexes ([(PtBr₂Me₂)_n], [(PtIMe₃)₄] and [(PtMe₂(cod)]/I₂) are described herein. The spectroscopic characterization of the platinum(IV) products of these reactions [PtBr₂Me₂{pz(CH₂)_mpz}], m = 2 (1) or 8 (2), [PtI₂Me₂{pz(CH₂)₂pz}] (3), [PtMe₃(pzCH₂CH₂OCH₂CH₂pz)][BF₄] (4) and [PtMe₃(pzCH₂CH₂SCH₂CH₂pz)][CF₃SO₃] (5), where ‘pz’ is pyrazol-1-yl, is discussed. Furthermore, solid state structures of 1, a complex with a seven-membered chelate ring, and 4, a complex bearing the neutral κ²N,N′,κO ligand bis[2-(pyrazol-1-yl)ethyl]ether (L3) are reported.     

Organoplatinum(II) complexes with phosphite ligands

The phosphite complexes cis-[PtMe₂L(SMe₂)] in which L = P(OⁱPr)₃, 1a, or L = P(OPh)₃, 1b, were synthesized by the reaction of cis,cis-[Me₂Pt(μ-SMe₂)₂PtMe₂] with 2 equiv. of L. If 4 equiv. of L was used the bis-phosphite complexes cis-[PtMe₂L₂] in which L = P(OⁱPr)₃, 2a, or L = P(OPh)₃, 2b, were obtained. The reaction of cis-[Pt(p-MeC₆H₄)₂(SMe₂)₂] with 2 equiv. of L gave the aryl bis-phosphite complexes cis-[Pt(p-MeC₆H₄)₂L₂] in which L = P(OⁱPr)₃, 2a′, or L = P(OPh)₃, 2b′. Use of 1 equiv. of L in the latter reaction gave the bis-phosphite complex along with the starting complex in a 1:1 ratio.The complexes failed to react with MeI. The reaction of cis,cis-[Me₂Pt(μ-SMe₂)₂PtMe₂] with 2 equiv. of the phosphine PPh₃ gave cis-[PtMe₂(PPh₃)₂] and cis-[PtMe₂(PPh₃)(SMe₂)] along with unreacted starting material. Reaction of cis-[PtMe₂L(SMe₂)], 1a and 1b with the bidentate phosphine ligand bis(diphenylphosphino)methane, dppm = Ph₂PCH₂PPh₂, gave [PtMe₂(dppm)], 8, along with cis-[PtMe₂L₂], 2. The reaction of cis-[PtMe₂L(SMe₂)] with 1/2 equiv. of the bidentate N-donor ligand NN = 4,4′-bipyridine yielded the binuclear complexes [PtMe₂L(μ-NN)PtMe₂L] in which L = P(OⁱPr)₃, 3a, or L = P(OPh)₃, 3b.The complexes were fully characterized using multinuclear NMR (¹H, ¹³C, ³¹P, and ¹⁹⁵Pt) spectroscopy.     

Bis(dimethylphosphino)methane (dmpm) complexes of iron,molybdenum and chromium: X-ray crystal structures of FeCr(CO)6(μ-dmpm)2 and Fe2(CO)4(μ-CO)(μ-dmpm)2

The photolysis of Fe(η¹-dmpm)(dmpm)₂ [dmpm = bis(dimethylphosphino) methane) with Cr(CO)₆ and Fe(CO)₅ under UV irradiation produces FeCr(CO)₆(μ-dmpm)₂, Fe₂(CO)₆(μ-CO)(μ-dmpm) and Fe₂(CO)₄(μ-CO)(μ-dmpm)₂ respectively. The interaction of Mo(CO)₃(MeCN)₃ and (C₇H₈)Cr(CO)₃ with dmpm produces Mo₂(CO)₆(μ-dmpm)₃ and cis-Cr(CO)₂(dmpm)₂ respectively. The X-ray crystal structure of FeCr(CO)₆(μ-dmpm)₂ shows the molecule to contain a trigonal bipyramidal Fe(CO)₃P₂ unit plus a square pyramidal Cr(CO)₃P₂ unit held closely together by the methylene bridges of the dmpm ligands with steric compression between the CO groups causing distortions from ideal geometry in each case. The Cr … Fe distance is 3.111(6) Å and there seems to be little structural evidence of any form of interaction between the 16e Cr(O) centre and the Fe-containing unit. The structure of Fe₂(CO)₄(μ-CO)(μ-dmpm)₂ contains a symmetrical μ₂-carbonyl and a single bond between the two symmetry related (m) iron atoms. The Fe … Fe distance is 2.719(4) Å.     

Carbon‐iodide bond activation by cyclometalated Pt (II) complexes bearing tricyclohexylphosphine ligand: A comparative kinetic study and theoretical elucidation

Cyclometalated Pt (II) complexes [PtMe(C^N)(L)], in which C^N = deprotonated 2,2′‐bipyridine N‐oxide (Obpy), 1 , deprotonated 2‐phenylpyridine (ppy), 2 , deprotonated benzo [h] quinolone (bzq), 3 , and L = tricyclohexylphosphine (PCy₃) were prepared and fully characterized. By treatment of 1–3 with excess MeI, the thermodynamically favored Pt (IV) complexes cis‐[PtMe₂I(C^N)(PCy₃)] (C^N = Obpy, 1a ; ppy, 2a ; and bzq, 3a ) were obtained as the major products in which the incoming methyl and iodine groups adopted cis positions relative to each other. All the complexes were characterized by means of NMR spectroscopy while the absolute configuration of 1a was further determined by X‐ray crystal structure analysis. The reaction of methyl iodide with 1–3 were kinetically explored using UV–vis spectroscopy. On the basis of the kinetic data together with the time‐resolved NMR investigation, it was established that the oxidative addition reaction occurred through the classical S_N2 attack of Pt (II) center on the MeI reagent. Moreover, comparative kinetic studies demonstrated that the electronic and steric nature of either the cyclometalating ligands or the phosphine ligand influence the rate of reaction. Surprisingly, by extending the oxidative addition reaction time, very stable iodine‐bridged Pt (IV)‐Pt (IV) complexes [Pt₂Me₄(C^N)₂(μ‐I)₂] (C^N = Obpy, 1b ; ppy, 2b ; and bzq, 3b ) were obtained and isolated. In order to find a reasonable explanation for the observation, a DFT (density functional theory) computational analysis was undertaken and it was found that the results were consistent with the experimental findings.     

Fumarate,maleate and maleic anhydride complexes of platinum(O)

Dimethyl fumarate (dmf), diethyl fumarate (def), dimethyl maleate (dmm), and maleic anhydride (ma) react with [Pt(cod)₂] (cod = cyclo-octa-1,5-diene) and with [Pt(C₂H₄)₃] to give ‘mixed’ olefin platinum(O) complexes, e.g., [Pt(cod)(def)], [Pt(cod)(ma)], [Pt(C₂H₄)(dmf)₂] or [Pt(C₂H₄)(dmm)₂]. Tris-(olefin)platinum complexes [Pt(def)₃] and [Pt(dmf)₃] have also been obtained.     

Preparation of Dimethyl and Chloro/Methyl Complexes of Platinum(II) Supported by α‐Diimine Ligands: Trends in the Ease of Oxidation to Platinum(IV)

α‐Diimine ligands react with the platinum(II) alkyl complexes [(Me₂S)PtMe₂]₂ and (Me₂S)₂PtClMe to form (RDAB^R′)PtMe₂ and (RDAB^R′)PtClMe (RDAB^R′=RN=CR′−CR′=NR; R=2,6‐Me₂Ph, 2,6‐(CHMe₂)₂Ph, 3,5‐Me₂Ph, 3,5‐(CF₃)₂Ph, C₆H₁₁; R′=Me, H). The oxidation of these complexes with Cl₂, I₂, N‐chlorosuccinimide, [PtCl₆]²⁻ and (TMEDA)PtMe₂I₂ has been investigated. Attempts to determine the oxidation potentials of the Pt^II complexes electrochemically yielded only irreversible one‐electron oxidations. However, a qualitative ordering of increasing difficulty of oxidation has been determined for the series (RDAB^R′)PtMe₂<(RDAB^R′)PtClMe<(RDAB^R′)PtCl₂≪(RDAB^R′)PtMe(solvent)]⁺. The oxidation proceeds via a two‐electron inner‐sphere electron transfer from a bridged binuclear intermediate. The oxidation of (RDAB^R′)PtMe₂ by (TMEDA)PtMe₂I₂ exhibits characteristic third‐order kinetics, first‐order each in [Pt^II], [Pt^IV] and [I⁻]. Oxidation by a one‐electron process in MeCN solution results in a rapid subsequent disproportionation to Pt^IIMe and Pt^IVMe₃ cations with MeCN occupying the fourth or sixth coordination sites. Single‐crystal X‐ray structure determinations for [(2,6‐Me₂PhDAB^Me)PtMe₃(MeCN)]⁺[PtCl₆]_0.5(MeCN) and [(CyDAB^H)PtMe₃(MeCN)]⁺[PtCl₆]_0.5(MeCN) are reported.     

Palladium(II)-, Platin(II)-, Ruthenium(II)-, Rhodium(III)- und Iridium(III)-Komplexe von Desoxyfructosazin

Metal Complexes of Biologically Important Ligands. CIII. [1] Palladium(II), Platinum(II), Ruthenium(II), Rhodium(III), and Iridium(III) Complexes of Desoxyfructosazine The reactions of the pyrazine derivative desoxyfructosazin(pz) with K₂PtCl₄ and with the chlorobridged [M(PR₃)Cl₂]₂ (M = Pd, Pt), [(η⁵-C₅Me₅)MCl₂]₂ and [(η⁶-p-Cymol)RuCl₂]₂ give the watersoluble complexes cis-Cl₂Pt(pz)₂, (R₃P)(Cl)M(pz)M(Cl)(PR₃) (M = Pd, Pt), (η⁵-C₅Me₅)(Cl)₂M(pz)M(Cl)₂(η⁵-C₅Me₅) (M = Rh, Ir), (η⁶-p-Cymol)(Cl₂)Ru(pz)Ru(Cl)₂(η⁶-p-Cymol).     

Six-membered cyclometallated derivatives of platinum(II) derived from 2-benzylpyridines. Crystal and molecular structure of [Pt(L)(Ph3P)Cl] (HL = 2-(1-methylbenzyl)pyridine)

The reaction of K₂[PtCl₄] with 2-(1-methylbenzyl)pyridine, HL, and 2-benzylpyridine, HL', affords the cyclometallated species [{Pt(L)Cl}₂] (1) and [{Pt(L')Cl}₂] (2), respectively. The chloride bridge in complex 1 can be split by neutral or anionic species to give the monomeric, [Pt(L)(Ph₃P)Cl], as two isomers, trans-P-Pt-C (3) and trans-P-Pt-N, (4), [Pt(L)(py)Cl] (5), [Pt(L)(CO)Cl] (6), [Pt(L)(CNCH₂SO₂C₆H₄CH₃-4)Cl] (7), [Pt(L)(acac)] (Hacac = 2,4-pentanedione) (8), [Pt(L)(dppm)][BF₄] (dppm = bis(diphenyl-phosphino)methane) (9), [Pt(L)(dppe)][BF₄] (dppe = bis(diphenylphosphino)ethane) (10) and [Pt(L)(dipy)][BF₄](dipy = 2,2'-dipyridine) (11). Similarly, compound 2, by reaction with Ph₃P, affords [Pt(L')(Ph₃P)Cl], as two isomers, trans-P-Pt-C (12) and trans-P-Pt-N (13). Reaction of compounds 1 or 4 with AgBF₄ in acetonitrile affords [Pt(L)(CH₃CN)₂IBF₄] (14) or [Pt(L)(Ph₃P)-(CH₃CN)][BF₄] (15). From these, [Pt(L)(Ph₃P)₂][BF₄] (16), [Pt(L)(Ph₃P)(CO)][BF₄] (17) and [Pt(L)(Ph₃P)(py)][BF₄] (18), can be obtained by displacement of the coordinated acetonitrile. The new complexes were characterized by IR, ¹H and ³¹P NMR and FAB-MS spectroscopic techniques. The NMR spectra at room temperature of most of the species derived from HL give evidence for the presence in solution of two diastereomers a and b. The structure of one diastereomer of complex 4 has been solved by single crystal X-ray diffraction, 4b. The platinum atom is in an almost square planar geometry with a P-Pt-N trans arrangement: Pt-N = 2.095(3), Pt-C = 1.998(4), Pt-P = 2.226(1) and Pt-Cl = 2.400(1) Å. The six-membered cyclometallated ring is in a boat conformation, with the CH₃ group in an equatorial position, i.e pointing away from the metal. Attempts to obtain [{Pt(L″)Cl}₂] (HL″ = 2-(dimethylbenzyl)pyridine), afforded an insoluble product heavily contaminated by platinum metal; treatment of this crude material with Ph₃P gave [Pt(L″)(Ph₃P)Cl] (19).     

Synthesen und Charakterisierungen der ersten Tris‐ und Tetrakis(trifluormethyl)palladate(II) und ‐platinate(II), [M(CF3)3(PPh3)]— und [M(CF3)4]2— (M = Pd,Pt)

Syntheses and Characterizations of the First Tris and Tetrakis(trifluoromethyl) Palladates(II) and Platinates(II), [M(CF₃)₃(PPh₃)]^— and [M(CF₃)₄]^2— (M = Pd, Pt) Tris(trifluoromethyl)(triphenylphosphino)palladate(II) and platinate(II), [M(CF₃)₃PPh₃]^—, and the tetrakis(trifluoromethyl)metallates, [M(CF₃)₄]^2— (M = Pd, Pt), are prepared from the reactions of [MCl₂(PPh₃)₂] and Me₃SiCF₃ / [Me₄N]F or [I(CF₃)₂]^— salts in good yields. [Me₄N][M(CF₃)₃(PPh₃)] crystallize isotypically in the orthorhombic space group Pnma (no. 62) with Z = 4. The NMR spectra of the new compounds are described.     

SYNTHESIS AND PROPERTIES OF THE FIRST DISULFUR AND DISELENIUM COMPLEXES OF PLATINUM

The reactions of overcrowded platinum(0) complexes [Pt{P(Ar)Me₂}₂] (Ar = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt), 2,6-bis[bis- (trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt)) with elemental sulfur and selenium resulted in the formation of the first platinum disulfur and diselenium complexes, [Pt(S₂){P(Ar)Me₂}₂] (4a (Ar = Tbt), 4b (Ar = Bbt) and [Pt(Se₂){P(Ar)Me₂}₂] (5a (Ar = Tbt), 5b (Ar = Bbt)) respectively. The x-ray crystallographic analyses of 4b and 5b showed a novel three-membered PtE₂ (E = S, Se) ring structure with a square planar geometry around the platinum center. The oxidation of 4b and 5b with an equimolar amount of m-chloroperbenzoic acid or tert-butyl hydroperoxide in dichloromethane yielded the corresponding disulfur and diselenium monoxide complexes [Pt(E₂O){P(Bbt)Me₂}₂] (6 (E = S), 7 (E = Se)). The further reactions of 6 and 7 with an excess of oxidants gave the corresponding O,S-coordinated thiosulfato complex [Pt(S₂ O₃){P(Bbt)Me₂}₂] (8) and the O,O-coordinated selenito complex [Pt(SeO₃){P(Bbt)Me₂}₂] (11), respectively. The dynamic behavior in solution was revealed by the variable-temperature NMR spectroscopy for 4b, 5b, 8, and 11, which indicates the existence of the intramolecular CH···E (E = O, S, Se) interactions between the methine hydrogens of the o-bis(trimethylsilyl)methyl groups and the Pt-bonded chalcogen atoms.     

Unsymmetrical complexes containing the linear tetraphosphine ligand DPPEPM

The tetraphosphine DPPEPM reacts with [PtMe₂(cod)] to produce [PtMe₂(DPPEPM-PP)] (1) in near quantitative yield. On standing in solution, the free P atoms become oxidized to give [PtMe₂(DPPEPM(O)₂-PP)] (1a), which has been characterized by X-ray crystallography. In contrast, reactions of DPPEPM with [MCl₂(cod)] (M = Pd, Pt) yield ionic products of the form [M(DPPEPM-PP)₂]MCl₄ (3, 4). When a solution of the platinum complex was allowed to stand, crystals of [Pt(μ-Cl)(μ-DPPEPM)₂]Cl₃ (5) were obtained. In a third set of reactions, treatment of [PtClR(cod)] (R = Me, Ph) or [PdClMe(cod)] with DPPEPM gives species of the type [MR(DPPEPM-PPP)]Cl (6-8), in which one of the internal P atoms is uncoordinated. Reactions of [PtR₂(DPPEPM-PP)] with or [MCl₂(cod)] (M = Pd, Pt), or of [PtR(DPPEPM-PPP)]Cl with [MCl₂(cod)], lead to unsymmetrical bimetallic complexes. [PtMe₂(μ-DPPEPM)PdCl₂] (11) and [PtClPh(μ-DPPEPM)PdCl₂] (14) have been characterized crystallographically. Trimetallic complexes of the form [{PtR₂(μ-DPPEPM)}₂M][MCl₄] (M = Pd, Pt, 15-17) are produced by reaction of [PtR₂(DPPEPM-PP)] with [MCl₂(cod)].     

Soft Scorpionate Hydridotris(2-mercapto-1-methylimidazolyl) borate) Tungsten-Oxido and -Sulfido Complexes as Acetylene Hydratase Models

A series of W^IV alkyne complexes with the sulfur-rich ligand hydridotris(2-mercapto-1-methylimidazolyl) borate) (Tm^Me) are presented as bio-inspired models to elucidate the mechanism of the tungstoenzyme acetylene hydratase (AH). The mono- and/or bis-alkyne precursors were reacted with NaTm^Me and the resulting complexes [W(CO)(C₂R₂)(Tm^Me)Br] (R=H 1 , Me 2 ) oxidized to the target [WE(C₂R₂)(Tm^Me)Br] (E=O, R=H 4 , Me 5 ; E=S, R=H 6 , Me 7 ) using pyridine-N-oxide and methylthiirane. Halide abstraction with TlOTf in MeCN gave the cationic complexes [WE(C₂R₂)(MeCN)(Tm^Me)](OTf) (E=CO, R=H 10 , Me 11 ; E=O, R=H 12 , Me 13 ; E=S, R=H 14 , Me 15 ). Without MeCN, dinuclear complexes [W₂O(μ-O)(C₂Me₂)₂(Tm^Me)₂](OTf)₂ ( 8 ) and [W₂(μ-S)₂(C₂Me₂)(Tm^Me)₂](OTf)₂ ( 9 ) could be isolated showing distinct differences between the oxido and sulfido system with the latter exhibiting only one molecule of C₂Me₂. This provides evidence that a fine balance of the softness at W is important for acetylene coordination. Upon dissolving complex 8 in acetonitrile complex 13 is reconstituted in contrast to 9 . All complexes exhibit the desired stability toward water and the observed effective coordination of the scorpionate ligand avoids decomposition to disulfide, an often-occurring reaction in sulfur ligand chemistry. Hence, the data presented here point toward a mechanism with a direct coordination of acetylene in the active site and provide the basis for further model chemistry for acetylene hydratase.     

Tripropylarsane Complexes of Palladium(II) and Platinum(II) — Syntheses,Spectroscopy, and Structures

Several palladium(II) and platinum(II) complexes of tripropylarsanes (AsR₃; R = Pr, iPr) with the formulae, [MCl₂(AsR₃)₂], [M₂Cl₂(μ‐Cl)₂(AsR₃)₂], [Pd₂Me₂(μ‐Cl)₂(AsR₃)₂], [Pd₂X₂(μ‐Pz)₂(AsR₃)₂] (X = Cl or Me, Pz = pyrazolate), [Pd₂Cl₂(μ‐Y)₂(AsR₃)₂] (Y = OAc or SPh), [MCl(S₂CNEt₂)(AsR₃)] and [PdCp(Cl)(AsiPr₃)] (M = Pd or Pt) have been prepared. All the complexes have been characterised by elemental analyses, IR and ¹H NMR spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The structures of [Pd₂Me₂(μ‐X)₂(AsiPr₃)₂] (X = Cl or Pz) have been established by single crystal X‐ray diffraction analyses. Both of the complexes have sym‐trans configuration. Strong trans influence of the methyl group is reflected on the Pd—X bond distances.     

The Coordination Chemistry of 1,2-Bis[(diphenylphosphino)methyl]benzene with Nickel(II), Palladium(II), Platinum(II), and Platinum(0) and the X-Ray Crystals Structure of [Pt{1,2-bis[(diphenylphospino)methyl]benzene}(C2H4)]

The preparation of complexes [MX₂( 1 )] (M = Ni, Pd, and Pi; X - Cl, Br, and I; 1 = 1,2-bis[(diphenylphosphino)methyl]benzene). [Pt(OSO₂CH₃)Et( 1 )], [Pt(alkene)( 1 )] (alkene - C₂H₂, and CH₂ = CHCN), and [( 1 )Pt-(μ-H)₂PtH( 1 )][BPh₄] is reported. Their ¹H- and ³¹P-NMR spectra were recorded and used lor structural assignments. The X-ray crystal structure of [Pt(C₂H₄)( 1 )] was determined. It is shown that the P? Pt? P bond angle in this complex differs significantly from those found in related compounds with monodentate phosphines, and that this difference is likely to be due to intramolecular contacts.     

Preparation and characterization of some mixed ligand complexes of platinum(II)

The mixed ligand complexes PtX₂(ER₃)L and PtXY(ER₃)L (where ER₃ = PR₃ or AsMe₃; L = phosphine, arsine; X = Cl; Y = Cl, H or Me) have been prepared and characterized. Reaction of PtMe₂(ER₃)L with HCl yields PtMeCl(ER₃)L, in exclusively one of three possible isomeric forms. Excess tetramethyltin reacts with Pt₂Cl₂(μ-Cl)₂(PMe₂Ph)₂ giving both cis and trans Pt₂(μ-Cl)₂(PMe₂Ph)₂, as identified from the NMR spectra. Cleavage of Pt₂(μ-Cl)₂Me₂(PMe₂Ph)₂ with donor ligands such as AsPh₃, PMe₂ or pyridine, was useful as a synthetic route to the unsymmetrical methylchloro Pt^II derivatives. The reaction of cis-[PtMe₂(PPh₃)(AsPh₃)] with excess dimethylacetylenedicarboxylate (DMA) yielded only one product, which was of the formula trans-[Pt{C(COOCH₃)C(COOCH₃)CH₃}₂(PPh₃)(AsPh₃)], with the alkenyl groups having the same geometry about the CC bond. The use of diethylacetylene-dicarboxylate (DEA) rather than DMA gave a similar product. However, when cis-[PtMe₂(PEt₃)(AsPh₃)] was allowed to react with DMA, two products of the formula trans-[Pt{C(COOCH₃)C(COOCH₃)CH₃}₂(PEt₃)(AsPh₃)] were obtained, with the stereochemistry of both alkenyl groups being either cis or trans.