Influence of the terminal ligands on the redox properties of the {Pt2(mu-S)2} core in [Pt2(Ph2X(CH2)2XPh2)2(mu-S)2] (X = P or As) complexes and on their reactivity towards metal centres, protic acids and organic electrophiles

In order to explore possible ways for modulating the unusually rich chemistry shown by complexes of formula [L2Pt(mu-S)2PtL2] we have studied the influence of the nature of the terminal ligand L on the chemical properties of the {Pt2(mu-S)2} core. The systematic study we now report allows comparison of the behaviour of [Pt2(dpae)2(mu-S)2](dpae = Ph2As(CH2)2AsPh2) (1) with the already reported analogue [Pt2(dppe)2(mu-S)2](dppe = Ph2P(CH2)2PPh2). Complex 1 as well as the corresponding multimetallic derivatives [Pt(dpae){Pt2(dpae)2(mu-S)2}](BPh4)2 2, [M{Pt2(dpae)2(mu-S)2}2]X2 (M = Cu(II), X = BF4 3; M = Zn(II), X = BPh4 4; M = Cd(II), X = ClO4 5; M = Hg(II), X = Cl 6 or X2 = Cl(1.5)[HCl2](0.5) 6') have been characterized in the solid phase and in solution. Comparison of structural parameters of 1 and 3-6' with those of the corresponding phosphine analogues, together with the results of the electrochemical study for 1, allow us to conclude that replacement of dppe by dpae causes a decrease in basicity of the {Pt2(mu-S)2} core. The study of the reactivity of 1 towards CH2Cl2 and protic acids has led to the structural characterization of [Pt(dpae)(S2CH2)] 9 and [PtCl2(dpae)] 10. Moreover, comparison with the reactivity of [Pt2(dppe)2(mu-S)2] indicates that the stability of the intermediate species as well as the nature of the final products in both multistep reactions are sensitive to the nature of the terminal ligand.     

利用DFT方法探究一类自组装[Pt2M4（C≡CH）8]（M=Cu，Ag）簇合物的电子结构和光谱性质

应用TD．DFT（time－dependent density functional theory）并PCMfpolarizable continuum model）模型研究了一类自组装的[Pt2M4（C＇≡CH）8]（M=Cu,Ag）簇合物的电子结构和光谱性质．应用DFT（density functional theory）方法优化了该簇合物的基态及激发态结构．综合计算结果,得到与试验结果相一致的结构与光谱特点．[Pt2Ag4（C≡CH）8]具有呈D4和D4h对称性的两个稳定的基态几何结构．Pt－M距离预示弱相互作用的存在．Cu—Cu距离大于俩个Cu原子的范德华半径和而Ag－Ag间距与俩个Ag原子的范德华半径和差别不大．激发过程使得Pt…M,Ag…Ag作用增强,虽然Cu…Cu距离也相应缩短,但是其仍大于范德华半径之和．[Pt2Cu4（C≡CH）8]、[Pt2Ag4（C≡CH）8]（A）和（B）的最低能吸收在450、365和375nm处,发射在611、431和435nm处．红外可见谱范围内,[Pt2M4（C≡CH）8]的吸收波带都有Cu或Ag成分的贡献,所以没有ILCT或MPtLCT跃迁特征出现（ILCT：intraligand charge transfer;MLCT：metal-to—ligand charge transfer）．由于最低能吸收和发射具有不同的跃迁特征,所以发射不是来自于最低能吸收．[Pt2Ag4（C≡CH）8]簇合物的MM相互作用在激发态增强,发射光谱具有显著的ILCT特点,这也是[Pt2Ag4（C≡CH）8]的发射波长相对于其对应的同配体前躯体[Pt（C≡CH）4]^2-有少许蓝移的原因．     

Preparation, properties and structures of the first series of organometallic Pt(II) and Pt(IV) complexes with stibine co-ligands

The planar Pt(II) monomers [PtMe2(L-L)] and [(PtMe2)2(L'-L')2] dimers (L-L = R2Sb(CH2)3SbR2, o-C6H4(CH2SbMe2)2; L'-L' = R2SbCH2SbR2; R = Me or Ph) are obtained in good yield via reaction of [PtMe2(SMe2)2] with L-L or L'-L' in benzene. The Pt(iv) stibines, [PtMe3(L-L)I] (L-L = R2Sb(CH2)3SbR2, o-C6H4(CH2SbMe2)2 or 2 x SbPh3, SbMePh2 or SbMe2Ph) are obtained by treatment of [PtMe3I] with L-L in chloroform. These represent the first series of stable Pt(IV) stibine complexes. All of the products have been characterised by 1H, 13C{1H}, 195Pt NMR spectroscopy, electrospray mass spectrometry and analysis. Crystal structure determinations on [PtMe3{R2Sb(CH2)3SbR2}I], [PtMe3{o-C6H4(CH2SbMe2)2}I] and [PtMe3(SbPh3)2I] confirm the distorted octahedral environment at Pt, with fac Me groups and mutually cis Sb donor atoms. The Sb-Pt-Sb angle in the seven-membered chelate ring of the o-C6H4(CH2SbMe2)2 complex is ca. 96 degrees , compared to <90 degrees in the complexes with six-membered chelates. The C1-distibines R2SbCH2SbR2 afford only the dinuclear [(PtMe3)2(mu-R2SbCH2SbR2)(mu-I)2] in which the stibine ligand and two I atoms bridge two Pt atoms giving an edge sharing bioctahedral geometry which has been confirmed by a crystal structure analysis. The Pt(II) species undergo oxidative addition with MeI to give the corresponding Pt(IV) species, while the Pt(IV) species reductively eliminate ethane upon thermolysis.     

Synthesis and characterisation of transition metal halide complexes of the xylyl-distibine, 1,2-bis(dimethylstibanylmethyl)benzene

Complexes of the title ligand with Cu(I), Ag(I), Au(I), Pd(II), Pt(II), Rh(III), and rare examples with Ni(II) and Co(III) have been prepared and characterised by analysis, IR, UV-vis, 1H, 63Cu and 59Co NMR spectroscopy and ES+ mass spectrometry as appropriate. The structures of [Cu[1,2-C6H4(CH2SbMe2)2]2]BF4, [PtCl2[1,2-C6H4(CH2SbMe2)2]], [M[1,2-C6H4(CH2SbMe2)2]2][PF6]2 (M = Pd or Pt), and [NiI[1,2-C6H4(CH2SbMe2)2]2]ClO4 have been determined, and the varying chelate bite and conformations of the xylyl backbone in these structures are discussed. Despite the unfavourable seven-membered chelate ring and the large soft antimony donors, 1,2-C6H4(CH2SbMe2)2 proves to be a surprisingly good ligand for late transition metals in medium oxidation states.     

The first example of macrocycles containing butterfly transition metal cluster cores via novel tandem reactions

A novel type of double butterfly, two mu-CO-containing dianions {[(mu-CO)Fe2(CO)6]2[mu-SCH2(CH2OCH2)nCH2S-mu]}2- (m1, n = 2, 3), has been synthesized from dithiol HSCH2(CH2OCH2)nCH2SH (n = 2, 3), Fe3(CO)12, and Et3N in THF at room temperature. While dianions m1 react in situ with CS2 followed by treatment with dihalide 1,4-(BrCH2)2C6H4 or 1,4-I(CH2)4I to give macrocyclic clusters [mu-SCH2(CH2OCH2)nCH2S-mu](mu-CS2ZCS2-mu)[Fe2(CO)6]2 (1a, n = 2, Z = 1,4-(CH2)2C6H4; 1b, n = 3, Z = (CH2)4), reactions of dianions m1 with (mu-S2)Fe2(CO)6 followed by treatment with dihalide 1,4-I(CH2)4I afford macrocyclic clusters [mu-SCH2(CH2OCH2)nCH2S-mu]{[Fe2(CO)6]2(mu4-S)}2[mu-S(CH2)4S-mu] (2a, n = 2; 2b, n = 3). The crystal structures of 1a and 2b are described.     

Synthesis, characterisation and speciation studies of heterobimetallic pyridinehydroxamate-bridged Pt(II)/M(II) complexes (M = Cu, Ni, Zn). Crystal structure of a novel heterobimetallic 3-pyridinehydroxamate-bridged Pt(II)/Cu(II) wave-like coordination polymer

The reaction of cis-[Pt(NH3)2(3-pyhaH)2]2+ (3-pyhaH = 3-pyridinehydroxamic acid) and cis-[Pt(NH3)2(4-pyhaH)2]2+ (4-pyhaH = 4-pyridinehydroxamic acid) with Cu(II), Ni(II) or Zn(II) in aqueous solution affords novel heterobimetallic pyridinehydroxamate-bridged complexes, {cis-[Pt(NH3)2(mu-3-pyha)M(mu-3-pyha)].SO4.xH2O}n and {cis-[Pt(NH3)2(mu-4-pyha)M(mu-4-pyha)].SO4.xH2O}n respectively. The crystal and molecular structure of one of these, {cis-[Pt(NH3)2(mu-3-pyha)Cu(mu-3-pyha)]SO4.8H2O}n 3a, has been determined and was found to be a novel heterobimetallic wave-like coordination polymer, the structure of which contains interlinked pyridinehydroxamate-bridged repeating units of Pt(II) and Cu(II) ions in slightly distorted square-planar N4 and O4 coordination environments respectively and extensive hydrogen-bonding through the Pt ammines and the deprotonated hydroxamate O and via the O of the SO4(2-) counterions and the H(N) of the hydroxamate moiety. Spectrophotometric and speciation studies on the other heterobimetallic systems confirm that very similar species are being formed in solution and based on elemental analysis and spectroscopic results analogous complexes are formed in the solid-state. In this paper, we report the first examples of coordination polymers incorporating both Pt(II)/Cu(II), Pt(II)/Ni(II) and Pt(II)/Zn(II) and containing pyridinehydroxamic acids as bridging scaffolds.     

Halide addition/abstraction in phosphido derivatives: isolation of the thallium and silver intermediates

Reaction of unsaturated (44e (-) skeleton) [PdPt 2(mu-PPh 2) 2(mu-P 2Ph 4)(R F) 4] 4 with Br (-) produces the saturated (48e (-) skeleton) complex [NBu 4][(R F) 2Pt(mu-PPh 2)(mu-Br)Pd(mu-PPh 2)(mu-P 2Ph 4)Pt(R F) 2] 5 without any M-M' bond. Attempts to eliminate Br (-) of 5 with Ag (+) in CH 2Cl 2 as a solvent gives a mixture of [(R F) 2Pt (III)(mu-PPh 2) 2Pt (III)(R F) 2] and some other unidentified products as a consequence of oxidation and partial fragmentation. However, when the reaction of 5 with Ag (+) is carried out in CH 3CN, no oxidation is observed but the elimination of Br (-) and the formation of [(R F) 2(CH 3CN)Pt(mu-PPh 2)Pd(mu-PPh 2)(mu-P 2Ph 4)Pt(R F) 2] 6 (46e (-) skeleton), a complex with a Pt-Pd bond, takes place. It is noteworthy that the reaction of 5 with TlPF 6 in CH 2Cl 2 does not precipitate TlBr but forms the adduct [(R F) 2PtTl(mu-PPh 2)(mu-Br)Pd(mu-PPh 2)(mu-P 2Ph 4)Pt(R F) 2] 7 with a Pt-Tl bond. Likewise, 5 reacts with [AgOClO 3(PPh 3)] in CH 2Cl 2 forming the adduct [AgPdPt 2(mu-Br)(mu-PPh 2) 2(mu-Ph 2P-PPh 2)(R F) 4(PPh 3)] 8, which contains a Pt-Ag bond. Both adducts are unstable in a CH 3CN solution, precipitating TlBr or AgBr and yielding the unsaturated 6. The treatment of [NBu 4] 2[(R F) 2Pt(mu-PPh 2) 2Pd(mu-PPh 2) 2Pt(R F) 2] in CH 3CN with I 2 (1:1 molar ratio) at 233 K yields a mixture of 4 and 6, which after recrystallization from CH 2Cl 2 is totally converted in 4. If the reaction with I 2 is carried out at room temperature, a mixture of the isomers [NBu 4][(R F) 2Pt(mu-PPh 2)(mu-I)Pd(mu-PPh 2)(mu-P 2Ph 4)Pt(R F) 2] 9 and [NBu 4][(R F)(PPh 2R F)Pt(mu-PPh 2)(mu-I)Pd(mu-PPh 2) 2Pt(R F) 2] 10 are obtained. The structures of the complexes have been established on the bases of NMR data, and the X-ray structures of 5- 8 have been studied. The relationship between the different complexes has been studied.     

Effect of Synthesis Conditions on the Molecular and Crystal Structures of Heterometallic 1D-Polymeric Acetate Complexes with the {Dy2Co}n Motif

Russian Journal of Coordination Chemistry - New heterometallic 1D-polymeric acetate complexes with the {Dy2Co}n motif of the metallic framework, [Dy2Co(CH3COOO)8(H2O)4]n ? 6nH2O (I) and...     

Structural comparisons of silver(I) complexes of third-generation ligands built from tridentate (o-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)) versus bidentate poly(1-pyrazolyl)methane units (o-C(6)H(4)[CH(2)OCH(2)CH(pz)(2)](2)) (pz = pyrazolyl ring)

The new bitopic, bis(1-pyrazolyl)methane-based ligand o-C6H4[CH2OCH2CH(pz)2]2 (L2, pz = pyrazolyl ring) is prepared from the reaction of (pz)2CHCH2OH (obtained from the reduction of (pz)2CHCOOH with BH3.S(CH3)2) with NaH, followed by the addition of alpha,alpha'-dibromo-o-xylene. The reaction of L2 with AgPF6 or AgO3SCF3 yields {o-C6H4[CH2OCH2CH(pz)2]2(AgPF6)}n or {o-C6H4[CH2OCH2CH(pz)2]2(AgO3SCF3)}n, respectively. Both compounds in the solid state have tetrahedral silver(I) centers arranged in a 1D coordination polymer network. The analogous ligand based on tris(1-pyrazolyl)methane units, o-C6H4[CH2OCH2C(pz)3]2 (L3), reacts with AgO3SCF3 to form a similar coordination polymer, {o-C6H4[CH2OCH2C(pz)3]2(AgO3SCF3)}n. In this case, each tris(pyrazolyl)methane unit in L3 adopts the kappa2-kappa0 bonding mode. Crystallization of a 3:1 mixture of AgO3SCF3 and L3 yields {o-C6H4[CH2OCH2C(pz)3]2(AgO3SCF3)2}n, in which the tris(1-pyrazolyl)methane units adopt a kappa2-kappa1 coordination mode.     

Ni(II), Pd(II) and Pt(II) complexes of PNP and PSP tridentate amino-phosphine ligands

The ligands D((CH(2))(2)NHPiPr(2))(2) (D = NH 1, S 2) react with (dme)NiCl(2) or (PhCN)(2)MCl(2) (M = Pd, Pt) to give complexes of the form [D((CH(2))(2)NHPiPr(2))(2)MX]X (X = Cl, I; M = Ni, Pd, Pt) which were converted to corresponding iodide derivatives by reaction with Me(3)SiI. Reaction of 1 or 2 with (COD)PdMeCl affords facile routes to [κ(3)P,N,P-NH((CH(2))(2)NHPiPr(2))(2)PdMe]Cl (8a) and [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)PdMe]Cl (9a) in high yields. An alternative synthetic approach involves oxidative addition of MeI to a M(0) precursor yielding [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)NiMe]I (10), [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MMe]I (M = Pd 8b Pt 11) and [κ(3)P,S,P-S(CH(2)CH(2)NHPiPr(2))(2)MMe]I (M = Pd 9b, Pt 12). Alternatively, use of NEt(3)HCl in place of MeI produces the species [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MH]X (X = Cl, M = Ni 13a, Pd 14a, Pt 16a). The analogs containing 2; [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)MH]X (M = Pd, X = PF(6)15: M = Pt, X = Br, 17a, PF(6)17b) were also prepared in yields ranging from 74-93%. In addition, aryl halide oxidative addition was also employed to prepare [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MC(6)H(4)F]Cl (M = Ni 18, Pd 19) and [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)Pd(C(6)H(4)F)]Cl (20). Crystal structures of 3a, 4a, 5a, 6a, 8a, 9a, 14b and 16b are reported.     

Cyclometallated Pt(II) and Pd(II) complexes with a trithiacrown ligand

We report the synthesis and full characterization for a series of cyclometallated complexes of Pt(II) and Pd(II) incorporating the fluxional trithiacrown ligand 1,4,7-trithiacyclononane ([9]aneS3). Reaction of [M(C insertion mark N)(micro-Cl)]2 (M = Pt(II), Pd(II); C insertion mark N = 2-phenylpyridinate (ppy) or 7,8-benzoquinolinate (bzq)) with [9]aneS3 followed by metathesis with NH4PF6 yields [M(C insertion mark N)([9]aneS3)](PF6). The complexes [M(C insertion mark P)([9]aneS3)](PF6) (M = Pt(II), Pd(II); Cinsertion markP = [CH2C6H4P(o-tolyl)2-C,P]-) were synthesized from their respective [Pt(C insertion mark P)(micro-Cl)]2 or [Pd(C insertion mark P)(micro-O2CCH3)]2 (C insertion mark P) starting materials. All five new complexes have been fully characterized by multinuclear NMR, IR and UV-Vis spectroscopies in addition to elemental analysis, cyclic voltammetry, and single-crystal structural determinations. As expected, the coordinated [9]aneS3 ligand shows fluxional behavior in its NMR spectra, resulting in a single 13C NMR resonance despite the asymmetric coordination environment of the cyclometallating ligand. Electrochemical studies reveal irreversible one-electron metal-centered oxidations for all Pt(II) complexes, but unusual two-electron reversible oxidations for the Pd(II) complexes of ppy and bzq. The X-ray crystal structures of each complex indicate an axial M-S interaction formed by the endodentate conformation of the [9]aneS3 ligand. The structure of [Pd(bzq)([9]aneS3)](PF6) exhibits disorder in the [9]aneS3 conformation indicating a rare exodentate conformation as the major contributor in the solid-state structure. DFT calculations on [Pt([9]aneS3)(ppy)](PF6) and [Pd([9]aneS3)(ppy)](PF6) indicate the HOMO for both complexes is primarily dz2 in character with a significant contribution from the phenyl ring of the ppy ligand and p orbital of the axial sulfur donor. In contrast, the calculated LUMO is primarily ppy pi* in character for [Pt([9]aneS3)(ppy)](PF6), but dx2-y2 in character for [Pd([9]aneS3)(ppy)](PF6).     

Comproportionation reaction and hindered rotation of coordinated pyridine rings in an acetate-bridged tetraplatinum(II) cluster with pyridine-based ligands in the cluster plane

A series of pyridine-substituted derivatives of octaacetatotetraplatinum(II), [Pt4(CH3COO)8-n(L)2n]n+ (L= 4-dimethylaminopyridine (dmap), pyridine (py), 4-cyanopyridine (cpy); n = 1-4) were prepared, and the tetra- and octasubstituted forms (n = 2 and 4) were isolated. 1HNMR spectra showed that this type of cluster undergoes a comproportionation reaction. Reactions between clusters in which n = 0 and 2, n = 0 and 4, and n = 2 and 4 afforded Pt4 clusters with n = 1, 2, and 3, respectively, as a main product in acetonitrile. The dmap-substituted clusters, trans-[Pt4(CH3COO)6(dmap)4](ClO4)2 x 3CH3NO2 (3a(ClO4)2 x 3CH3NO2) and [Pt4(CH3COO)4(dmap)8](ClO4)4 x 4 H2O (5a(ClO4)4-4H2O), have been structurally characterized. Both 3a and 5a have a square-planar cluster core comprised of four PtII ions, and all eight out-of-plane coordination sites are occupied by acetate ligands in a bridging mode. In 5a, all of the in-plane sites are occupied by dmap ligands. In 3a, four dmap ligands occupy the coordination sites at the two mutually opposite edges of the square planar cluster skeleton, giving a trans tetrasubstituted form of [Pt4(CH3COO)8-] (1). In octasubstituted 5a, adjacent dmap ligands are so closely arranged that the Pt-N distances (2.20(3), 2.30(3) A) are longer than those in tetrasubstituted 3a (2.13(1), 2.15(1) A) and related Pt4 clusters. Furthermore, rotation of the dmap ligand about the Pt-N bond in 5a was restricted, and the rate constant of the rotation was 4.5s(-1) at 20 degrees C from dynamic NMR study. Cluster [Pt4(CH3COO)5(dmap)6]3+ (4a) also exhibited similar hindered rotation with the rate constants of 2.0s(-1), 12s(-1) and approximately 10(4)s(-1) at 20 degrees C depending on the coordination sites of the dmap ligands in 4a.     

Conformation changes and luminescent properties of Au-Ln (Ln = Nd, Eu, Er, Yb) arrays with 5-ethynyl-2,2'-bipyridine

Reaction of polymeric gold(I) acetylide species (bpyC[triple bond]CAu)n (bpyC[triple bond]CH = 5-ethynyl-2,2'-bipyridine) with diphosphine ligands Ph2P(CH2)nPPh2 (n = 2-6) or 1,1'-bis(diphenylphosphino)-ferrocene (dppf) in dichloromethane induces isolation of binuclear gold(I) complexes (bpyC[triple bond]CAu)2{mu-Ph2P(CH2)nPPh2} or (bpyC[triple bond]CAu)2(mu-dppf). Complexation of Ln(hfac)3 (hfac = hexafluoroacetylacetonate, Ln = Nd, Eu, Er, Yb) subunits to the binuclear gold(I) complexes through 2,2'-bipyridyl chelation gives the corresponding Au4Ln4 or Au2Ln2 heteropolynuclear complexes. Noticeably, upon formation of the Au4Ln4 arrays by complexation of (bpyC[triple bond]CAu)2(mu-Ph2P(CH2)4PPh2) (3) with Ln(hfac)3 units, trans-conformation in 3 transforms dramatically to the cis-arranged form due to the strong driving force from ligand-unsupported Au-Au contacts between two Au2Ln2 subunits. In contrast, cis-conformation in (bpyC[triple bond]CAu)2(mu-dppf) (6) stabilized by Au-Au interactions is reversed to the trans-oriented form upon formation of Au2Ln2 arrays by introducing Ln(hfac)3 units through 2,2-bipyridyl chelation. The binuclear gold(I) complexes show bright blue luminescence featured by ligand-centered pi --> pi* (C[triple bond]Cbpy) states together with low-energy emission at 500-540 nm, associated with 3(pi-->pi*) excited states, mixed probably with some characteristic from (Au-Au) --> (C[triple bond]Cbpy) 3MMLCT transition. For Au4Ln4 or Au2Ln2 complexes, sensitized lanthanide luminescence is achieved by energy transfer from Au-acetylide chromophores with lifetimes in the sub-millisecond range for EuIII complexes, whereas in the microsecond range for near-infrared emitting NdIII, ErIII, and YbIII species.     

A new series of luminescent phosphine stabilised platinum ethynyl complexes

A series of cis-platinum ethynyl complexes with the general formula cis-[Pt(dppe)(C[triple bond]CR)2](dppe = 1,2-bis(diphenylphosphino)ethane; R = C6H4-p-NO2 1, C6H4-p-CH3 2, C6H4-p-C[triple bond]CH 3 and C6H4-p-C6H4-p-C[triple bond]CH 4) have been prepared by the coupling reaction of cis-[Pt(dppe)Cl2] with two equivalents of the appropriate alkyne. The new complexes have been fully characterized by spectroscopic techniques, and the cis square planar arrangement at the platinum centre has been confirmed by single-crystal X-ray diffraction studies of complexes 1, 2 and 4. The absorption spectra of the complexes 1-4 are dominated by a pi-->pi* band that contains some platinum (n + 1) p orbital character. The position of the band is dependent on the electron donating or withdrawing properties of the ethynyl substituents, R. Complex 1 displays a triplet emission in the green, at room temperature, while complexes 2-4, display singlet emissions in the blue. Again, the difference can be attributed to the nature of the R substituents.     

Reduction of (imine)Pt(IV) to (imine)Pt(II) complexes with carbonyl-stabilized phosphorus ylides

A novel method is reported for generation of the difficult-to-obtain (imine)Pt(II) compounds that involves reduction of the corresponding readily available Pt(IV)-based imines by carbonyl-stabilized phosphorus ylides, Ph3P=CHCO2R, in nonaqueous media. The reaction between neutral (imino)Pt(IV) compounds [PtCl4[NH=C(Me)ON=CR1R2]2] [R1R2 = Me2, (CH2)4, (CH2)5, (Me)C(Me)=NOH], [PtCl4[NH=C(Me)ONR2]2] (R = Me, Et, CH2Ph), (R1 = H; R2 = Ph or C6H4Me; R3 = Me) as well as anionic-type platinum(IV) complexes (Ph3PCH2Ph)[PtCl5[NH=C(Me)ON=CR2]] [R2 = Me2, (CH2)4, (CH2)5] and 1 equiv of Ph3P=CHCO2R (R = Me, Et) proceeds under mild conditions (ca. 4 h, room temperature) to give selectively the platinum(II) products (in good to excellent isolated yields) without further reduction of the platinum center. All thus prepared compounds (excluding previously described Delta4-1,2,4-oxadiazoline complexes) were characterized by elemental analyses, FAB mass spectrometry, IR and 1H, 13C[1H], 31P[1H] and 195Pt NMR spectroscopies, and X-ray single-crystal diffractometry, the latter for [PtCl2[NH=C(Me)ON=CMe2]2] [crystal system tetragonal, space group P4(2)/n (No. 86), a = b = 10.5050(10) A, c = 15.916(3) A] and (Ph3PCH2CO2Me)[PtCl3(NCMe)] [crystal system orthorhombic, space group Pna2(1) (No. 33), a = 19.661(7) A, b = 12.486(4) A, c = 10.149(3) A]. The reaction is also extended to a variety of other Pt(II)/Pt(IV) couples, and the ylides Ph3P=CHCO2R are introduced as mild and selective reducing agents of wide applicability for the conversion of Pt(IV) to Pt(II) species in nonaqueous media, a route that is especially useful in the case of compounds that cannot be prepared directly from Pt(II) precursors, and for the generation of systematic series of Pt(II)/Pt(IV) complexes for biological studies.     

Luminescent one- and two-dimensional extended structures and a loosely associated dimer based on platinum(II)-thallium(I) backbones

Neutralization reactions between (NBu4)2[ trans-Pt(C 6F5)2(CN)2] 1 and (NBu4)2[cis-Pt(C6F5)2(CN)2] 2 with TlPF 6 have been carried out, and the resulting structures of [trans,trans,trans-Tl2{Pt(C6F5)2(CN)2}.(CH3COCH3) ] n [4.(CH3COCH3)2] n and {Tl[Tl{cis-Pt(C6F5)2(CN)2}].(H2O)} n [5.(H2O)] n have been determined by X-ray crystallography. Remarkably, the change from trans to cis geometry on the platinum substrate causes a significant decrease in the Pt(II)...Tl(I) metallophilic interaction. Thus, the platinum center in the trans fragment easily connects with two Tl(I) ions forming a distorted pseudo-octahedron PtTl2, which generates a final two-dimensional layered structure by secondary additional intermolecular Tl(I)...N(CN) interactions. However, the [cis-Pt(C6F5)2(CN)2] (2-) fragment interacts strongly with just one Tl center leading to an extended helical [-Pt-Tl-Pt-Tl-] n(n-) chain. In this case, the second thallium center neutralizes the anionic chain mainly through Tl...N(CN) ( intra) and Tl...F(C 6F 5) (intra and inter)actions. The reaction of TlPF 6 with the monoanionic fragment (NBu4)[cis-Pt(C6F5)2(CN)(PPh2C[triple bond]CPh)] 3 yields the discrete associated dimer [Tl{cis-Pt(C6F5)2(CN)(PPh2C[triple bond]CPh)}] 2 [ 6] 2. Dimer [ 6] 2 could be described as two square pyramids with the thallium atoms in the apical positions, connected through Tl...N(cyano) interactions. The final heteropolynuclear Pt-Tl complexes, except 4 at room temperature, show bright emission in the solid state when irradiated with UV-vis radiation, in contrast to the precursors 1 and 3, which are not luminescent. This difference indicates that the emissions in 4- 6 are presumably related to the interaction between the metal centers. The Pt-Tl bonding interactions and, consequently, the emissive properties are lost in solution at room temperature, as shown by the conductivity and NMR measurements. However, variable-concentration luminescence measurements in glassy acetonitrile solutions indicate the formation of different aggregates with different degrees of Pt...Tl interactions for 4 and 5 and a dimeric structure similar to that observed in solid state for 6.     

Electrochemical and theoretical study of the redox properties of transition metal complexes with [Pt2S2] cores

The oxidation processes undergone by the [Pt2(mu-S)2] core in [Pt2(P[intersection]P)2(mu-S)2](P[intersection]P = Ph2P(CH2)nPPh2, n= 2,3) complexes have been analysed on the basis of electrochemical measurements. The experimental results are indicative of two consecutive monoelectronic oxidations after which the [Pt2(mu-S)2] core evolves into [Pt2(mu-S2)]2+, containing a bridging disulfide ligand. However, the instability of the monoxidised [Pt2(P[intersection]P)2(mu-S)2]+ species formed initially, which converts into [Pt3(P[intersection]P)3(mu-S)2]2+, hampered the synthesis and characterisation of the mono and dioxidised species. These drawbacks have been surpassed by means of DFT calculations which have also allowed the elucidation of the structural features of the species obtained from the oxidation of [Pt2(P[intersection]P)2(mu-S)2] compounds. The calculated redox potentials corresponding to the oxidation processes are consistent with the experimental data obtained. In addition, calculations on the thermodynamics of possible processes following the degradation of [Pt2(P[intersection]P)2(mu-S)2]+ are fully consistent with the concomitant formation of monometallic [Pt(P[intersection]P)S2)] and trimetallic [Pt3(P[intersection]P)3(mu-S)2]2+ compounds. Extension of the theoretical study on the [Pt2Te2] core and comparisons with the results obtained for [Pt2S2] have given a more general picture of the behaviour of [Pt2X2](X = chalcogenide) cores subject to oxidation processes.     

Synthesis, spectroscopic, and structural studies on transition metal complexes involving homoleptic tripodal selenoether and telluroether coordination

The reaction of [MCl2(NCMe)2] (M = Pd or Pt) with 2 molar equiv of MeC(CH2ER)3 (E = Se, R = Me; E = Te, R = Me or Ph) and 2 molar equiv of TlPF6 affords the bis ligand complexes [M(MeC(CH2ER)3)2][PF6]2. The crystal structure of [Pt(MeC(CH2SeMe)3)2][PF6]2 (C16H36F12P2PtSe6, a = 12.272(10) A, b = 18.563(9) A, c = 15.285(7) A, beta = 113.18(3) degrees, monoclinic, P2(1)/n, Z = 4) confirms distorted square planar Se4 coordination at Pt(II), derived from two bidentate tripod selenoethers with the remaining arm not coordinated and directed away from the metal center. Solution NMR studies indicate that these species are fluxional and that the telluroether complexes are rather unstable in solution. The octahedral bis tripod complexes [Ru(MeC(CH2SMe)3)2][CF3-SO3]2 and [Ru(MeC(CH2TePh)3)2][CF3SO3]2 are obtained from [Ru(dmf)6][CF3SO3]3 and tripod ligand in EtOH solution. The thioether complex (C18H36F6O6RuS8, a = 8.658(3) A, b = 11.533(3) A, c = 8.659(2) A, alpha = 108.33(2) degrees, beta = 91.53(3) degrees, gamma = 106.01(2) degrees, triclinic, P1, Z = 1) is isostructural with its selenoether analogue, involving two facially coordinated trithioether ligands in the syn configuration. NMR spectroscopy confirms that this configuration is retained in solution for all of the bis tripod Ru(II) complexes. These low-spin d6 complexes show unusually high ligand field splittings. The hexaselenoether Rh(III) complex [Rh(MeC(CH2SeMe)3)2][PF6]3 was obtained by treatment of [Rh(H2O)6]3+ with 2 molar equiv of MeC(CH2SeMe)3 in aqueous MeOH in the presence of excess PF6- anion, while the iridium(III) analogue [Ir(MeC(CH2SeMe)3)2][PF6]3 was obtained via the reaction of the Ir(I) precursor [IrCl(C8H14)2]2 with the selenoether tripod in MeOH/aqueous HBF4. NMR studies reveal different invertomers in solution for both the Rh and Ir species. The Cu(I) complexes [Cu(MeC(CH2ER)3)2]PF6 were obtained from [Cu(NCMe)4]PF6 and tripod ligand in CH2Cl2 solution. The corresponding Ag(I) species [Ag(MeC(CH2TeR)3)2]CF3SO3 (R = Me or Ph) were obtained from Ag[CF3SO3] and tripod telluroether. In contrast, a similar reaction with 2 molar equiv of MeC(CH2SeMe)3 afforded only the 1:1 complex [Ag(MeC(CH2SeMe)3)]CF3SO3. The structure of this species (C9H18AgF3O3SSe3, a = 8.120(3) A, b = 15.374(3) A, c = 14.071(2) A, beta = 93.86(2) degrees, monoclinic, P2(1)/n, Z = 4) reveals a distorted trigonal planar geometry at Ag(I) derived from one bidentate selenoether and one monodentate selenoether. These units are then linked to adjacent Ag(I) ions to give a one-dimensional linear chain cation.     

Preparation and coordinating properties of {CH2(o-C6H4CH2SbMe2)}2, a novel wide-angle cis-chelating distibine

The unique wide-angle distibine, {CH2(o-C6H4CH2SbMe2)}2, has been prepared indirectly by reaction of Me2SbCl with the di-Grignard formed unexpectedly by coupling of o-C6H4(CH2MgCl)2 in concentrated thf solution, and directly by treatment of the {CH2(o-C6H4CH2MgCl)}2 with Me2SbCl. The very oxygen-sensitive distibine has been characterised by 1H and 13C{1H} NMR spectroscopy and high-resolution EIMS. Oxidation of with Br2 gives the air-stable tetrabromide {CH2(o-C6H4CH2SbMe2Br2)}2. Surprisingly, shows a very strong tendency to function as a cis-chelate, e.g. to Pt(IV) in the complex [PtMe3I], forming an 11-membered ring and providing a stable Pt(IV) stibine complex, the crystal structure of which shows the Sb-Pt-Sb angle to be 95.96(1) degrees. The yellow Pt(II) complex [PtCl2] is obtained from reaction of [PtCl2(MeCN)2] with and IR spectroscopic data and a crystal structure determination confirm the Cl ligands are mutually cis in this species. Reaction of [W(CO)4(piperidine)2] with in refluxing EtOH gives [W(CO)4], the IR spectrum of which shows four nu(CO) bands, also consistent with cis-Sb2 coordination. The cis-chelation is also confirmed by single-crystal X-ray structure determinations of two polymorphs of [W(CO)4].     

The π-acceptor effect in the substitution reactions of tridentate N-donor ligand complexes of platinum(ii): a detailed kinetic and mechanistic study

The nucleophilic substitution reactions of complexes [Pt{4'-(2'-CH(3)-phenyl)-2,2':6',2'-terpyridine}Cl]CF(3)SO(3), [CH(3)PhPtCl], [Pt{4'-(2'-CH(3)-phenyl)-6-(3'-isoquinoyl)-2,2'bipyridine}Cl]SbF(6), [CH(3)PhisoqPtCl], [Pt{2-(2'-pyridyl)-1,10-phenanthroline}Cl]Cl, [pyPhenPtCl], and [Pt(terpyridine)Cl](+), [PtCl] with a series of nucleophiles: thiourea (TU), N,N-dimethylthiourea (DMTU), N,N,N,N-tetramethylthiourea (TMTU), I(-), Br(-), and SCN(-) were studied in 0.1 M LiCF(3)SO(3) in methanol (in the presence of 10 mM LiCl). The reactivity of the investigated complexes follows the order pyPhenPtCl > PtCl > CH(3)PhPtCl > CH(3)PhisoqPtCl. The lability of the chloride ligand is dependent on the strength of π-backbonding properties of the spectator ligands around the platinum centre. The experimental data is strongly supported by DFT calculations. The dependence of the second-order rate constants on concentration of the nucleophiles as well as the large negative values reported for the activation entropy (ΔS(?)) confirmed an associative mechanism of substitution.