Platinum(0) complexes of 3-arylthiete 1,1-dioxides

3-Phenyl- and 3-p-bromophenyl-thiete 1,1-dioxides react with [Pt(trans-stilbene)(PPh₃)₂] and [Pt(AsPh₃)₄] to give the complexes [Pt($\text{CHCrCH}{}_2\text{S}$O₂)(MPh₃)₂] (R  Ph, p-BrC₆H₄; M P, As).     

Platinum(II) complexes ofN-alkylphenothiazines

Summary The synthesis and physical properties of eight square-planar platinum(II) complexes, [PtLCl₂] (L =N-alkylphenothiazine) are reported. Analytical, conductometric, spectral (electronic, i.r. and¹H n.m.r.) and thermal data for the complexes are discussed.     

Platinum(II) hydrazido complexes

Reaction of 1,2-dimethylhydrazine with the platinum hydroxo complex [(dppp)Pt(mu-OH)](2)(BF(4))(2) gives the bridging 1,2-dimethylhydrazido(-2) product [(dppp)(2)Pt(2)(mu-eta(2):eta(2)-MeNNMe)](BF(4))(2) 1. Crystals of 1.CH(2)Cl(2) from CH(2)Cl(2)/Et(2)O are monoclinic (C/2) with a = 19.690(1), b = 18.886(1), c = 17.170 (1) A, and beta = 92.111(1) degrees. Treatment of [(dppp)Pt(mu-OH)](2)(OTf)(2) with 1,1-dimethylhydrazine gives [(dppp)(2)Pt(2)(mu-OH)(mu-NHNMe(2))](OTf)(2) 2. Crystals of 2.CH(2)Cl(2) from CH(2)Cl(2)/Et(2)O are triclinic (P-1) with a = 12.910 (3), b = 13.927(3), c = 17.5872 (3) A, alpha = 87.121(3), beta = 89.997(4), and gamma = 84.728(3) degrees. Reaction of [(dppp)Pt(mu-OH)](2)(OTf)(2) with 1 equiv of phenylhydrazine in CH(2)Cl(2) gives [(dppp)(2)Pt(2)(mu-OH)(mu-NHNHPh)](OTf)(2) 3. Two equivalents of phenylhydrazine with [(dppp)Pt(mu-OH)](2)(X)(2) gives [(dppp)Pt(mu-NHNHPh)](2)(X)(2) 4 (X = BF(4), OTf). Crystals of 3.ClCH(2)CH(2)Cl from ClCH(2)CH(2)Cl/(i)()Pr(2)O are monoclinic (P2(1)/n) with a = 20.990(2), b = 13.098(1), c = 25.773 (2) A, and beta = 112.944(2) degrees. Crystals of 4(X = BF(4)).ClCH(2)CH(2)Cl(.)()2((t)()BuOMe) from ClCH(2)CH(2)Cl/(t)()BuOMe are monoclinic (C2/m) with a = 30.508(1), b = 15.203(1), c = 19.049 (1) A, and beta = 118.505(2) degrees.     

Synthesis of electron-rich platinum centers: Platinum0(carbene)(alkene)2 complexes

The synthesis and molecular structure of the zero-valent platinum-mono-carbene-bis-alkene complexes [Pt⁰(NHC)(dimethyl fumarate)₂] (NHC = 1,3-dimesityl-imidazol-2-ylidene (1a); 1,3-dimesityl-dihydroimidazol-2-ylidene (2a); diphenyl-dihydroimidazol-2-ylidene (2b) are described. Two routes have been evaluated for the synthesis of 1a and 2a, involving reaction of a zero-valent platinum compound either with an isolated carbene ligand, or with an in situ generated carbene ligand. The in situ method proved to be easier and gave similar yields of about 50% after crystallization. Attempts have been made to synthesize similar compounds with N-phenyl and N-alkyl groups, of which the latter met with little success. However, (1,3-diphenyl-dihydroimidazol-2-ylidene)-bis(η²-dimethyl fumarate) platinum(0) (2b) could be obtained in 49% yield, after crystallization, from the appropriate Wanzlick dimer.Compound 1a reacts with H₂ and D₂ in sequences of oxidative addition, migration–insertion involving dimethyl fumarate, and reductive elimination to form neutral hydrido platinum (II) carbene complexes, probably containing a metallacyclic (R)–CO … Pt unit.     

Interaction of Dinitrogentrioxide with Platinum(0) and Palladium(0) Complexes

Dinitrogentrioxide reacts with tetrakis(triphenylphosphine) platinum and palladium under nitrogen to give dinitrobis(triphenylphosphine) platinum(II) and palladium(II) complexes, respectively. In the presence of oxygen these reactions afford the formation of nitro-nitrato complexes of platinum(II) and palladium(II). The products are characterized by the elemental analyses, i.r. spectra, conductivity and magnetic measurements.     

Platinum(II) complexes containing 2-(alkenyl)pyridines

The ligands 2-(allyl)pyridine(APy), and 2-(1-methallyl)pyridine (1-MAPy) react with [Pt₂X₄(PEt₃)₂] (X = Cl or Br), in acetone solution to give complexes of the type [PtX(PEt₃)L] [PtX₃(PEt₃)], (L = APy or 1-MAPy), which contain a bidentate 2-(alkenyl)pyridine, whereas the same reaction in benzene solution gives trans-[PtBr₂(PEt₃)L], (L = APy or 1-MAPy), which contains a monodentate 2-(alkenyl)pyridine; ¹H NMR spectra indicate that both types of product undergo olefin exchange in solution. The same reaction with 2-(3-methallyl)-pyridine [2-(2-butenyl)pyridine] (3-MAPy), 2-(3,3-dimethylallyl)pyridine [2-(3-methyl-2-butenyl)pyridine] (3,3-DMAPy), and 2-(3-butenyl)pyridine (BPy), in either acetone or benzene solution, gives only trans-[PtBr₂(PEt₃)L]. The reaction of trans-[PtBr₂(PEt₃)L] (L = APy or 3-MAPy) with AgClO₄ gives [PtBr(PEt₃)L]ClO₄. Complexes of the type [PtCl₂L], which contain bidentate 2-(alkenyl)pyridines, result on reaction of L = APy, 3-MAPy, 3,3-DMAPy, BPy, MBPy with [Pt₂Cl₄(C₂H₄)₂].     

Bis‐NHC Chelate Complexes of Nickel(0) and Platinum(0)

For a long time d¹⁰‐ML₂ fragments have been known for their potential to activate unreactive bonds by oxidative addition. In the development of more active species, two approaches have proven successful: the use of strong σ‐donating ligands leading to electron‐rich metal centers and the employment of chelating ligands resulting in a bent coordination geometry. Combining these two strategies, we synthesized bis‐NHC chelate complexes of nickel(0) and platinum(0). Bis(1,5‐cyclooctadiene)nickel(0) and ‐platinum(0) react with bisimidazolium salts, deprotonated in situ at room temperature, to yield tetrahedral or trigonal‐planar bis‐NHC chelate olefin complexes. The synthesis and characterization of these complexes as well as a first example of C? C bond activation with these systems are reported. Due to the enforced cis arrangement of two NHCs, these compounds should open interesting perspectives for bond‐activation chemistry and catalysis.     

Trifluoromethylselenato(0) and trifluoromethyltellurato(0) complexes of platinum(II)

The series of cis/trans-trifluoromethylselenato complexes [Pt(SeCF₃)_2 − xCl_x(PPh₃)₂] (x = 0, 1) was identified by NMR spectroscopic methods. While in acetonitrile solution spectra are dominated by the resonances of the cis derivatives, those of pure cis-[Pt(SeCF₃)₂(PPh₃)₂] indicate cis-trans-isomerisation in CH₂Cl₂ solution. In contrast, exchange reactions of cis-[PtCl₂(PPh₃)₂] and [NMe₄]TeCF₃ only gave evidence for cis isomers. Molecular structures of cis- and trans-[Pt(SeCF₃)₂(PPh₃)₂] and cis-[Pt(TeCF₃)₂(PPh₃)₂] are discussed in comparison with related compounds.     

Platinum(II) pyridine-2-thiolate and -selenolate complexes

The reaction of [Pt₂X₂(-Cl)₂(PR₃)₂] with NaSpy or NaSepy gave complexes of the type [PtX(Epy)(PR₃)]_n (X=Cl or Ar; E=S or Se; PR₃=PEt₃, PMe₂Ph, PMePh₂ or PPh₃; n=1 or 2) which were characterized by elemental analysis and by ¹H, ³¹P{¹H}, ¹⁹⁵Pt{¹H} n.m.r. spectroscopy. When X=Cl a dynamic equilibrium between [Pt₂Cl₂(-Spy)₂(PR₃)₂] and [PtCl(k-S,N-Spy)(PR₃)] species exists in CHCl₃ solution. The aryl derivatives, X=Ar, exist exclusively as dimers (n=2) with predominantly SN bridging. The [Pt(Spy)₂ (PPh₃)₂] complex, prepared by reacting [PtCl₂ (PPh₃)₂] with NaSpy, dissociates in CHCl₃ to [Pt(k-S,N-Spy) (Spy)(PPh₃)] and PPh₃ at room temperature.     

Platinum(II) complexes containing the 3,3-dimethylglutarimidate ligand

Reaction of cis-[PtCl₂(PPh₃)₂] with excess 3,3-dimethylglutarimide (dmgH) and sodium chloride in refluxing methanol gives the mono-imidate complex cis-[PtCl(dmg)(PPh₃)₂], which was structurally characterized. The plane of the imidate ligand is approximately perpendicular to the platinum coordination plane which, coupled with restricted rotation about the Pt–N bond, results in inequivalent methyl groups and CH₂ protons of the dmg ligand in the room temperature ¹H NMR spectrum. These observations were corroborated by a theoretical study using density functional theory methods. The analogous bromide complex cis-[PtBr(dmg)(PPh₃)₂] can be prepared by replacing NaCl with NaBr in the reaction mixture.     

Platinum(II) iodide complexes with propan-1-amine

Summary Thecis-[PtPra₂I₂],trans-[PtPra₂I₂], [PtPra₃I]I, [PtPra₄]I₂ and [PtPra₄]I₂ · 2H₂O (Pra = propan-1-amine) complexes have been prepared and characterized by elemental analyses, i.r. and¹H n.m.r. spectra and t.g., d.t.g. and d.t.a. measurements. Thermal degradation of the 13 and 14 complexes yieldstrans-[PtPra₂I₂] as an intermediate, whereascis-[PtPra₂I₂] isomerizes totrans without decomposition. The¹H n.m.r. spectra of the 12 and 14 species in deuteriated solvents are characteristic of the stoichiometry and geometry, whereas the spectra of [PtPra₃I]I indicate a general instability of this complex in solution, owing to easy decomposition to give trans-[PtPra₂I₂].     

Platinum(II) halide complexes with propan-1-amine

Summary The complexescis-[PtPra₂X₂],trans-[PtPra₂X₂], [PtPra₃X]X, [PtPra₄]X₂ and [PtPra₄]X₂ · 2H₂O, where Pra= propan-1-amine and X=Cl or Br, have been prepared with good yields and characterized by thermal analysis and i.r. and¹H n.m.r. spectroscopy. The best methods to obtain the pure products are discussed. The TG and DTA data are reported for all the complexes; in particular the thermal degradation of the 13 and 14 bromo-derivatives allows to isolate the intermediatetrans-[PtPra₂Br₂]. The i.r. spectra are characteristic of geometry and stoichiometry, as the¹H n.m.r. spectra ofcis-[PtAm₂Br₂],trans-[PtAm₂Br₂], [PtAm₃Br]Br and [PtAm₄]Br₂ (Am=propan-1-amine or hexan-1-amine) in deuteriated benzene, acetone and chloroform.     

Platinum(II) and palladium(II) complexes with substituted pyrimidines

Summary Platinum(II) and Palladium(II) complexes with 2-mercaptopyrimidine, 2-thiocytosine (4-aminopyrimidine 2-thione), and isocytosine (2-amino-4-hydroxy pyrimidine) were prepared and characterised by elemental analysis, conductivity data, i.r.,¹H n.m.r. and¹³C n.M.r. spectral studies. 2-Mercaptopyrimidine and 2-thiocytosine are coordinated to the metal ion through N(3) and C₂S, thus forming a four-membered chelate ring. Isocytosine acts as a monodentate ligand and coordinates to the metal ion through N(1). All the complexes are non-electrolytes.     

Flexible Platinum(0) Coordination to a Ditungsten Ethanediylidyne

The lithiocarbyne [W(≡CLi)(CO)₂(Tp*)] (Tp*=hydrotris(3,5‐dimethylpyrazol‐1‐yl)borate) reacts with [PtCl₂(L₂)] (L₂=1,5‐cyclo‐octadiene, norbornadiene) to furnish ditungsten ethanediylidyne complexes, [W₂{μ‐C₂Pt(L₂)}(CO)₄(Tp*)₂], wherein a trigonal platinum(0) center unsymmetrically ligates one W≡C bond in the solid state but rapidly shimmies between the two W≡C bonds in solution. The η⁴‐dienes are displaced by monodentate CO or isocyanide ligands to provide derivatives where both W≡C bonds coordinate to a single Pt⁰ center, attended by significant distortion of the WCCW spine.     

Strongly luminescent palladium(0) and platinum(0) diphosphine complexes

The synthesis, structure, and photoluminescence of palladium(0) and platinum(0) complexes containing biarydiphosphines, biphep (biphep = 2,2'-bis(diphenylphosphino)-1,1'-biphenyl) and binap (binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) have been studied. X-ray structure analysis of [Pt(biphep)(2)] revealed the distorted-tetrahedral geometry of the complex. The photophysical properties of the three complexes [Pd(biphep)(2)], [Pt(biphep)(2)], and [Pd(binap)(2)] were investigated and compared with that of the previously reported [Pt(binap)(2)] complex. The [Pd(biphep)(2)] complex shows the strongest luminescence with a high quantum yield (38%) and a long lifetime (3.2 micros) in a toluene solution at room temperature. The luminescence should be due to metal-to-ligand charge transfer excited states. At room temperature, radiative rate constants of the four complexes show similar values. The difference in the luminescent properties should reflect the different nonradiative rate constants of the complexes. The temperature-dependence of the luminescence spectra and lifetime of the complexes were also discussed.     

A Square‐Planar Complex of Platinum(0)

The Pt⁰ complex [Pt(PPh₃)(Eind₂‐BPEP)] with a pyridine‐based PNP‐pincer‐type phosphaalkene ligand (Eind₂‐BPEP) has a highly planar geometry around Pt with ∑(Pt)=358.6°. This coordination geometry is very uncommon for formal d¹⁰ complexes, and the Pd and Ni homologues with the same ligands adopt distorted tetrahedral geometries. DFT calculations reveal that both the Pt and Pd complexes are M⁰ species with nearly ten valence electrons on the metals whereas their atomic orbital occupancies are evidently different from one another. The Pt complex has a higher occupancy of the atomic 6s orbital because of strong s–d hybridization due to relativistic effects, thereby adopting a highly planar geometry reflecting the shape and orientation of the partially unoccupied orbital.     

Platinum(II) complexes of hydrazides of aspartic and glutamic acids

Mononuclear platinum(II) complexes of the hydrazides of aspartic and glutamic acids have been synthesized and studied. The 1:1 complexes are of the type [Pt(HL)Cl₂]·3H₂O, while the 1:2 complexes are [Pt(HL)₂]Cl₂·3H₂O. In DMF solutions the water molecules are substituted completely by DMF, while in 1:1 (v/v) water-DMF solutions complexes with one DMF and two water molecules are formed. The complexes are characterized using spectroscopic methods (IR, electronic spectra, ESCA), DTA, elemental analysis and titration curves, on the basis of which the ligands are thought to coordinate through the amino- and the hydrazide groups, the carboxylic one remaining deprotonated and non-coordinated.