Gordon K. Anderson

Platinum(II) complexes of unsymmetrical, potentially bidentate ligands

Preparation des complexes [PtCl(Ph 2 PCH 2 CH 2 OMe) 2 ] + et [Pt(Ph 2 PCH 2 CH 2 OMe) 2 ] 2+ . Spectres RMN de 31 P et 1 H

Substitution reactions of (diphosphine)palladium(II) and -platinum(II) chloride and triflate complexes

Abstract The triflate complexes [Pd(OTf)2L2] (L2 = dppm, dppe, dppp) and [Pt(OTf)2(dppp)] are prepared by reaction of the corresponding chloride with methyl triflate. The chloropalladium complexes [PdCl2L2] do not react with PPh3, but with PBu3 substitution of one chloride takes place, whereas [PtCl2(dppp)] reacts with either PPh3 or PBu3. The triflate complexes [M(OTf)2L2] (M = Pd, Pt; L2 = dppm, dppe, dppp) react with either PPh3 or PBu3 by substitution of one or both triflate ligands, although in CDCl3 the system is complicated by reaction with the solvent. [Pt(cod)(dppp)][OTf]2 reacts with PPh3 or PBu3 by attack of the phosphine on one of the double bonds of cyclooctadiene.

Chemistry at diplatinum centers

Publisher Summary This chapter describes dimeric complexes containing unsupported metal–metal bonds, followed by those bridged by simple ligands, such as halides or hydrides, then a number of compounds with bridging organic fragments. The number and variety of dimeric complexes have increased tremendously, however, with the availability of several bidentate ligands of a bite size suitable to coordinate in a bridging fashion. Most notable among these is bis(dipheny1phosphino) methane (dppm), and the remarkable versatility of this ligand has prompted the development of a number of analogs of dppm. Dppm and related ligands have been used to support dimeric complexes, containing platinum in the formal oxidation states 0, I, II, III, or IV. These ligands confer substantial stability on the diplatinum system, such that substitution, oxidative addition, and reductive elimination reactions within a dimeric framework can be investigated.

Platinum and rhodium complexes in which diphenylphosphino (methylthio) methane acts as a monodentate, chelated or bridging ligand

Reaction of [PtCl2(cod)] with Ph2PCH2SCH3 yields cis-[PtCl2(Ph2PCH2-SCH3)2] which, on treatment with AgBF4, is converted to [PtC](Ph2PCH2SCH3)2]-BF4, in which one of the ligands is chelated. With [Pt(dba)2], cis-[Pt(Cl2(Ph2PCH2-SCH3)2] reacts to give the platinum(I) complex [Pt2Cl2(μ-Ph2PCH2SCH3)2], which contains a platinum-platinum bond. The terminal chlorides may be replaced by iodide, but the complex is cleaved by carbon monoxide. [Rh2(μ-Cl)2(CO)4] reacts with Ph2PCH2SCH3 to produce [Rh2Cl2(CO)2(μ-Ph2PCH2SCH3)2], whereas with Ph2PCH2CH2SCH3 it yields [RhCl(CO)(Ph2PCH2CH2SCH3)]. A ligand exchange reaction occurs between cis-[PtCl2(Ph2SCH3)2] and [Rh2(μ-Cl)2(CO)4] to give cis-[PtCl2(CO)(Ph2PCH2SCH3)] and [Rh2Cl2(CO)2(μ-Ph2PCH2SCH3)2].

The crystal structures of the complexes [M(C6H4NNPh)(η5-C5H5)], M = Ni, Pd and Pt

Abstract The compounds [M(C 6 H 4 NNPh)(η 5 -C 5 H 5 )] (M = Ni, 1a ; M = Pd, 1b ; M = Pt, 1c ) display the unexpected reactivity pattern Pd > Pt > Ni on treatment with monotertiary phosphines. Their structures, determined by X-ray diffraction, provide no help in explaining this reactivity pattern but do illustrate the effects of differing metal size and polarisability. In particular, 1b and 1c display highly distorted M-η 5 -C 5 H 5 geometries: MC(η 5 -C 5 H 5 ) distances range from 2.167(3) to 2.408(3) A for 1b and 2.153(7)-2.367(8) A for 1c . The NiC(η 5 -C 5 H 5 ) distances in 1a are more regular: 2.036(5)-2.148(5) A. 1a is monoclinic, space group P 2 1 / n , with a 9.502(1), b 16.155(2), c 18.659(3) A, β 99.16(1)°, Z = 8, R = 0.037 for refinement of 361 parameters using 3072 unique intensities. 1b is monoclinic, space group P 2 1 / a , a 7.046(1), b 14.897(2), c 13.709(2) A, β 101.66(1)°, Z =4, R 0.022 for refinement of 237 parameters from 3099 unique intensities. 1c is isomorphous and isostructural with 1b , a 6.993(2), b 14.846(3), c 13.709(4) A, β 101.92(2) °. R = 0.027 for refinement of 181 parameters from 2818 unique intensities.

Hydride-bridged dipalladium complexes containing diphosphine ligands

Abstract A series of hydride-bridged dipalladium complexes supported by bis(diphenylphosphino) methane (dppm) ligands has been prepared. The complexes [Pd 2 R 2 (μ-H) (μ.-dppm) 2 ] PF 6 (R = Me, Et, Bu, CH 2 SiMe 3 , Ph) were generated by reduction, using NaBH 3 CN, of the corresponding halide-bridged species. The products are thermally stable, yellow solids, and they have been characterized by 1H and 31 P[ 1 H] NMR spectroscopy. The ethyl complex [Pd2Et2(μ-H) (μ-dppm)2]PF 6 has been characterized further by X-ray crystallography. It crystallizes in the monoclinic space group P21 lc with a=10.6160 ( I ), 6=12.8637 (1 ), c=25.3739 (3) A, β=97.479 (1 )° and Z=2. The cation adopts an A-frame structure, with a Pd-Pd distance of 2.9933 (7) A.

Reactions of diphosphineplatinum(II) oxalate complexes with phenylacetylene. Formation of phenylalkynylplatinum complexes

Abstract [Pt(C 2 O 4 )(dppe)] reacts thermally with PhCCH to produce [Pt(CCPh) 2 (dppe)], which has been prepared by alternative routes. Similar treatment of [Pt(C 2 O 4 )(dppm)] initially produces [Pt(CCPh) 2 (dppm)], which rearranges to give cis , cis -[Pt 2 (CCPh) 4 (μ-dppm) 2 ]. Reaction of [PtCl 2 (dppm)] with PhCCH/KOH/18-crown-6, or with (PhCC)SnMe 3 , gives [Pt(CCPh) 2 (dppm)], which may be converted to the cis , cis -dimer by addition of oxalic acid. Ultraviolet irradiation or refluxing with a trace amount of dppm converts [Pt(CCPh) 2 (dppm)] to trans , trans -[Pt 2 (CCPh) 4 (μ-dppm) 2 ], but the cis , cis -dimer is stable under these conditions. [Pt(C 2 O 4 )L 2 ] (L = PPh 3 , PEt 3 ) complexes also react thermally with PhCCH to yield [Pt(CCPh) 2 L 2 ] species.

Oxidative degradation of the ascorbate anion in the presence of platinum and palladium. Formation and structures of platinum and palladium oxalate complexes

Abstract The reactions of [Pt(NO3)2(dppm)] (dppm=bis(diphenylphosphino)methane) and cis-[Pt(NO3)2(PEt3)2] with sodium ascorbate are described. Complexes containing O,O-coordinated ascorbate ligands are formed initially, but on standing further oxidation and cleavage of the ligand occur to produce the corresponding oxalate complexes. The reactions were monitored by NMR spectroscopy, and reactions of [Pt(NO3)2(dppm)] with oxalic acid or calcium threonate also produced [Pt(C2O4)(dppm)]. Reactions of [PtMe(Me2CO)(dppe)]+ or [PdMe(Me2CO)(P∩P)]+ (P∩P=dppe, dppp) with sodium ascorbate result in cleavage of the MC bond and oxidation of ascorbate to again produce metal oxalate derivatives. The solid state structures of [Pt(C2O4)(dppm)]·Me2CO, [Pd(C2O4)(dppe)]·H2O and [Pd2(μ-C2O4)(dppp)2][BF4]2·2Me2CO, determined by X-ray crystallography, are described.

Photochemical reactions of diphosphineplatinum(II) oxalate complexes

Irradiation at 254 nm of CH3CN/C6H6 or PhCN solutions of [Pt(C2O4)(dppe)] produces 2 equiv. of CO2, and in the presence of PhCl or PhI yields [PtX2(dppe)] (X  Cl, I). With CO or PhCCPh the products are [Pt(CO)2 (dppe)] or [Pt(PhCPh)(dppe)], but in the latter case extended photolysis yields [PtPh(CCPh)(dppe)]. Photolysis in the presence of H2 gives a mixture of the [Pt2H3(dppe)2]+ and [Pt3H3(dppe)3]+ cations. Simple elimination of CO2 does not occur in all cases, as illustrated by the formation of [pt(CO2Me)2(dppe)] when [Pt(C2O4)(dppe)] is photolyzed in the presence of methanol. Photochemical reactions of the related complexes [Pt(C2O4)L2] (L2  dppm, dcpe) are also described.

Synthesis and reactions of platinum(IV) complexes with sodium ascorbate

The platinum(IV) complexes [PtCl2(OH)2(N S N )] (N S N� /en, N ,N -dmen, N ,N ?-dmen) were prepared by oxidation of [PtCl2(N S N )] with hydrogen peroxide. The complexes were characterized by multinuclear NMR and infrared spectroscopy, as well as microanalysis. The reactions of these compounds with sodium ascorbate were monitored spectroscopically. Reduction of the platinum(IV) complexes by sodium ascorbate occurred only slowly. An oxalatoplatinum(IV) complex [Pt(C2O4)Cl(OH)(N ,N dmen)]/H2O was isolated from the reaction of [PtCl2(OH)2(N ,N -dmen)] and sodium ascorbate and characterized by an X-ray diffraction study. # 2002 Elsevier Science B.V. All rights reserved.