Synthesis and characterization of amidate bridged dimeric and oligomeric platinum complexes having short platinum-platinum interactions

A number of pivalamidate bridged dinuclear [PtII2(RNH2)4(NHCOtBu)2]2+, [PtIII2LL (RNH2)4(NHCOtBu)2]n+ (2RNH2 = 2NH3, 1,2-ethylenediamine, 1,2-diaminocyclohexane; L, L' = NO3-, H2O, or ketonate), trinuclear [{PtII(dap)(NHCOtBu)2}2PdIII]3+ (dap = 1,2-diaminopropane), tetranuclear [{PtII2(NH3)2(DACH)(NHCOtBu)2}2]4+ (DACH = 1,2-diaminocyclohexane), pentanuclear [{Pt2(C5H7O)(NH3)2Cl2(NHCOtBu)2}2PtCl4], and hexanuclear [Pt2(NH3)2(en)(NHCOtBu)2Pt(NO2)4]2 platinum complexes containing Pt(II)-Pt(II), Pt(II)-Pt(III), Pt(II)-Pd(III), and Pt(III)-Pt(III) interactions have been prepared and structurally characterized. The Pt-Pt interactions are characteristic of covalent, dative, or orbital symmetric Pt-Pt bonds. The dimeric Pt(III) complexes are able to activate C-H bonds of ketones to afford ketonate platinum(III) complexes. The Pt-Pt bonds are either doubly amidate-bridged or ligand unsupported. Their distances are 2.99-3.22 A for Pt(II)-Pt(II), 2.59-2.72 A for Pt(III)-Pt(III), 2.98 A for Pt(II)-Pt(III), and 2.66 A for Pt(II)-Pd(III) bonds depending on the oxidation states of the two metals and the ancillary ligands.     

From a trinuclear platinum(III) phosphido derivative to a platinum(II) cluster: formation of a P-C bond

Reaction of the trinuclear Pt(III)-Pt(III)-Pt(II) [(C6F5)2Pt(III)(mu-PPh2)2Pt(III)(mu-PPh2)2Pt(C6F5)2] (2) derivative with NBu4Br or NBu4I results in the formation of the trinuclear Pt(II) complexes [NBu4][(PPh2C6F5)(C6F5)Pt(mu-PPh2)(mu-X)Pt(mu-PPh2)2Pt(C6F5)2] [X = I (3), Br (4)] through an intramolecular PPh2/C6F5 reductive coupling and the formation of the phosphine PPh2C6F5. The trinuclear Pt(II) complex [(PPh2C6F5)(C6F5)Pt(mu-PPh2)Pt(mu-PPh2)2Pt(C6F5)2] (5), which displays two Pt-Pt bonds, can be obtained either by halide abstraction in 4 or by refluxing of 2 in CH2Cl2. This latter process also implies an intramolecular PPh2/C6F5 reductive coupling. Treatment of complex 5 with several ligands (Br-, H-, and CO) results in the incorporation of the ligand to the cluster and elimination of one (X = H-) or both (X = Br-, CO) Pt-Pt bonds, forming the trinuclear complexes [NBu4][(PPh2C6F5)(C6F5)Pt(mu-PPh2)(mu-X)Pt(mu-PPh2)2Pt(C6F5)2] [X = Br (6), H (7)] or [(PPh2C6F5)(C6F5)Pt(mu-PPh2)2Pt(mu-PPh2)(CO)Pt(C6F5)2(CO)] (8). The structures of the complexes have been established on the basis of 1H, 19F, and 31P NMR data, and the X-ray structures of the complexes 2, 3, 5, and 7 have been established. The chemical relationship between the different complexes has also been studied.     

Synthesis and characterisation of triselenocarbonate [CSe3]2- complexes

[Pt(CSe3)(PR3)2] (PR3= PMe3, PMe2Ph, PPh3, P(p-tol)3, 1/2 dppp, 1/2 dppf) were all obtained by the reaction of the appropriate metal halide containing complex with carbon diselenide in liquid ammonia. Similar reaction with [Pt(Cl)2(dppe)] gave a mixture of triselenocarbonate and perselenocarbonate complexes. [{Pt(mu-CSe3)(PEt3)}4] was formed when the analogous procedure was carried out using [Pt(Cl)2(PEt3)2]. Further reaction of [Pt(CSe3)(PMe2Ph)2] with [M(CO)6] (M = Cr, W, Mo) yielded bimetallic species of the type [Pt(PMe2Ph)2(CSe3)M(CO)5] (M = Cr, W, Mo). The dimeric triselenocarbonate complexes [M{(CSe3)(eta5-C5Me5)}2] (M = Rh, Ir) and [{M(CSe3)(eta6-p-MeC6H4(i)Pr)}2] (M = Ru, Os) have been synthesised from the appropriate transition metal dimer starting material. The triselenocarbonate ligand is Se,Se' bidentate in the monomeric complexes. In the tetrameric structure the exocyclic selenium atoms link the four platinum centres together.     

Facile insertion and halogen migration reactions of the hexaphosphapentaprismane cage P6C4tBu4 with zerovalent and divalent platinum complexes

The hexaphosphapentaprismane P(6)C(4)(t)Bu(4) undergoes specific insertion of the zerovalent platinum fragment [Pt(PPh(3))(2)] into the unique P-P bond between the 5-membered rings to afford [Pt(PPh(3))(2)P(6)C(4)(t)Bu(4)]. A similar reaction with the Pt(ii) complexes [{PtCl(2)(PMe(3))}(2)] and [PtCl(2)(eta(4)-COD)] results in both insertion and chlorine migration reactions. The complexes [Pt(PPh(3))(2)P(6)C(4)(t)Bu(4)], trans-[PtCl(PMe(3))P(6)C(4)(t)Bu(4)Cl], cis-,trans-[{PtCl(2)(PMe(3))}micro-{P(6)C(4)(t)Bu(4)}{PtCl(2)(PMe(3))}], [{PtClP(6)C(4)(t)Bu(4)Cl}(2)] and cis-[PtClP(6)C(4)(t)Bu(4)Cl(P(6)C(4)(t)Bu(4))] have been structurally characterized by single crystal X-ray diffraction and multinuclear NMR studies.     

Platinum(II) complexes with pi-conjugated, naphthyl-substituted, cyclometalated ligands (RC N N): structures and photo- and electroluminescence

The crystal structures and photophysical properties of mononuclear [(RC N N)PtX](ClO4)n ((RC N N)=3-(6'-(2'-naphthyl)-2'-pyridyl)isoquinolinyl and derivatives; X=Cl, n=0; X=PPh(3) or PCy(3), n=1), dinuclear [(RC N N)2Pt2(mu-dppm)](ClO4)2 (dppm=bis(diphenyphosphino)methyl) and trinuclear [(RC N N)3Pt3(mu-dpmp)](ClO4)3 (dpmp=bis(diphenylphosphinomethyl)phenylphosphine) complexes are presented. The crystal structures show extensive intra- and/or intermolecular pipi interactions; the two (RC N N) planes of [(RC N N)2Pt2(mu-dppm)](ClO4)2 (R=Ph, 3,5-tBu2Ph or 3,5-(CF3)2Ph) are in a nearly eclipsed configuration with torsion angles close to 0 degrees. [(RC N N)PtCl], [(RC N N)2Pt2(mu-dppm)](ClO4)2, and [(RC N N)3Pt3(mu-dpmp)](ClO4)3 are strongly emissive with quantum yields of up to 0.68 in CH2Cl2 or MeCN solution at room temperature. The [(RC N N)PtCl] complexes have a high thermal stability (T(d)=470-549 degrees C). High-performance light-emitting devices containing [(RC N N)PtCl] (R=H or 3,5-tBu2Ph) as a light-emitting material have been fabricated; they have a maximum luminance of 63,000 cd m(-2) and CIE 1931 coordinates at x=0.36, y=0.54.     

Stable diplatinum complexes with functional thiolato bridges from dialkylation of [Pt2(mu-S)2(P-P)2] [P-P=2 x PPh3, Ph2P(CH2)3PPh2

The normally robust monoalkylated complexes [Pt(2)(mu-S)(mu-SR)(PPh(3))(4)](+) can be activated towards further alkylation. Dialkylated complexes [Pt(2)(mu-SR)(2)(P-P)(2)](2+) (P-P=2 x PPh(3), Ph(2)P(CH(2))(3)PPh(2)) can be stabilized and isolated by the use of electron-rich and aromatic halogenated substituents R [e.g. 3-(2-bromoethyl)indole and 2-bromo-4'-phenylacetophenone] and 1,3-bis(diphenylphosphino)propane [Ph(2)P(CH(2))(3)PPh(2) or dppp] which enhances the nucleophilicity of the {Pt(2)(mu-S)(2)} core. This strategy led to the activation of [Pt(2)(mu-S)(mu-SR)(PPh(3))(4)](+) towards R-X as well as isolation and crystallographic elucidation of [Pt(2)(mu-SC(10)H(10)N)(2)(PPh(3))(4)](PF(6))(2) (2a), [Pt(2)(mu-SCH(2)C(O)C(6)H(4)C(6)H(5))(2)(PPh(3))(4)](PF(6))(2) (2b), and a range of functionalized-thiolato bridged complexes such as [Pt(2)(mu-SR)(2)(dppp)(2)](PF(6))(2) [R= -CH(2)C(6)H(5) (8a), -CH(2)CHCH(2) (8b) and -CH(2)CN (8c)]. The stepwise alkylation process is conveniently monitored by Electrospray Ionisation Mass Spectrometry, allowing for a direct qualitative comparison of the nucleophilicity of [Pt(2)(mu-S)(2)(P-P)(2)], thereby guiding the bench-top synthesis of some products observed spectroscopically.     

Unsymmetrical platinum(II) phosphido derivatives: oxidation and reductive coupling processes involving platinum(III) complexes as intermediates

Reaction of the trinuclear [NBu 4] 2[(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(R F) 2] ( 1, R F = C 6F 5) with HCl results in the formation of the unusual anionic hexanuclear derivative [NBu 4] 2[{(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(mu-Cl)} 2] ( 4, 96 e (-) skeleton) through the cleavage of two Pt-C 6F 5 bonds. The reaction of 4 with Tl(acac) yields the trinuclear [NBu 4][(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(acac)] ( 5, 48 e (-) skeleton), which is oxidized by Ag (+) to form the trinuclear compound [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(acac)][ClO 4] ( 6, 46 e (-) skeleton) in mixed oxidation state Pt(III)-Pt(III)-Pt(II), which displays a Pt-Pt bond. The reduction of 6 by [NBu 4][BH 4] gives back 5. The treatment of 6 with Br (-) (1:1 molar ratio) at room temperature gives a mixture of the isomers [(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-Br)Pt(mu-PPh 2) 2Pt(acac)], having Br trans to R F ( 7a) or Br cis to R F ( 7b), which are the result of PPh 2/C 6F 5 reductive coupling. The treatment of 5 with I 2 (1:1 molar ratio) yields the hexanuclear [{(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-I)Pt(mu-PPh 2) 2Pt(mu-I)} 2] ( 8, 96 e (-) skeleton), which is easily transformed into the trinuclear compound [(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-I)Pt(mu-PPh 2) 2Pt(I)(PPh 3)] ( 9, 48 e (-) skeleton). Reaction of [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(NCMe) 2] ( 10) with I 2 at 213 K for short reaction times gives the trinuclear platinum derivative [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(I) 2] ( 11, 46e skeleton) in mixed oxidation state Pt(III)-Pt(III)-Pt(II) and with a Pt-Pt bond, while the reaction at room temperature and longer reactions times gives 8. The structures of the complexes have been established by multinuclear NMR spectroscopy. In particular, the (195)Pt NMR analysis, carried out also by (19)F- (195)Pt heteronuclear multiple-quantum coherence, revealed an unprecedented shielding of the (195)Pt nuclei upon passing from Pt(II) to Pt(III). The X-ray diffraction structures of complexes 4, 5, 6, 9, and 11 have been studied. A detailed study of the relationship between the complexes has been carried out.     

Syntheses and ligand interconversions of copper(II) derivatives of the metalloligand [Pt2(mu-S)2(PPh3)4

The reactivity of the metalloligand [Pt2(micro-S)2(PPh3)4] towards a variety of copper(II)-ligand systems has been studied. Reaction of [Pt2(mu-S)2(PPh3)4] with copper(II) halide complexes [CuCl2L](L = 2,2'-bipyridine and 1,10-phenanthroline) gave trinuclear dicationic products [Pt2(mu-S)2(PPh3)4CuL]2+, and the 8-hydroxyquinolinate (hq) complex [Cu(hq)2] gave [Pt2(mu-S)2(PPh3)4Cu(hq)]+, isolated as their BPh4- or PF6- salts. Related cationic complexes with other ancillary amine ligands (1,2-diaminoethane, 1,2-diaminopropane, 1,2-diaminocyclohexane) were obtained by reactions of [Pt2(mu-S)2(PPh3)4] with CuCl2 and the amine. In contrast, reaction of [Pt2(mu-S)2(PPh3)4] with CuCl2 and NH3 in methanol gave the intensely blue methoxy-bridged dicopper complex [{Pt(2)(mu-S)2(PPh3)4Cu(OMe)}2]2+, isolated as its hexafluorophosphate salt. Copper beta-diketonate complexes reacted with [Pt2(mu-S)2(PPh3)4] giving [Pt2(mu-S)2(PPh3)4Cu(beta-diketonate)]+PF6- complexes, with the CH3COCHCOCH3(acac) and CF3COCHCO(2-thienyl)(tta) derivatives characterised by X-ray structure determinations. The local Cu(II) environment ranges from distorted square-planar to an intermediate form of square-planar and tetrahedral. The beta-diketonate derivatives show varying stability towards methanolysis, giving [{Pt2(mu-S)2(PPh3)4Cu(OMe)}2]2+.     

Tetranuclear platinum phosphido complexes with different structures

The addition of [NBu4]Br or [NBu4][BH4] to solutions of [Pt4(mu-PPh2)4(C6F5)4(CO)2] yields the complexes [NBu4]2[Pt4(mu-PPh2)4(mu-X)2(C6F5)4] (X=Br, H,) in which the two CO groups have been replaced by two anionic, bridging X ligands. The total valence electron counts are 64 and 60, respectively; thus, complex does not require Pt-Pt bonds, while two metal-metal bonds are present in, as their NMR spectra confirm. Also, the NMR spectra indicate a nonsymmetrical "Pt(mu-PPh2)2Pt(mu-PPh2)(mu-X)Pt(mu-PPh2)(mu-X)Pt" disposition for and. Treatment of with HX (X=Cl, Br) yields the complexes [NBu4]2[Pt4(mu-PPh2)4(mu-H)2(C6F5)3X] (X=Cl, Br,). These complexes react with [Ag(OClO 3)PPh3] with displacement of the halide and formation of [NBu4][Pt4(mu-PPh2)4(mu-H)2(C6F5)3PPh3]. Complexes maintain the same basic skeleton as, with two Pt-Pt bonds. Complex is, however, an isomer of the symmetric [NBu4]2[{(C6F5)2Pt(mu-PPh2)2Pt(mu-Br)}2], which has been prepared by a metathetical process from the well-known [NBu4]2[{(C6F5)2Pt(mu-PPh2)2Pt(mu-Cl)}2]. The comparison of the X-ray structures of and confirms the different disposition of the bridging ligands, and their main structural differences seem to be related to the size of Br- and its position in the skeleton.     

Synthesis, structural characterization, and photophysical properties of palladium and platinum(II) complexes containing 7,8-benzoquinolinate and various phosphine ligands

A series of mononuclear cyclometalated benzo[h]quinolinate platinum and palladium(II) complexes with phosphine ligands, namely, [M(bzq)ClL] (L=PPh2H, Pt 1, Pd 2; PPh2CCPh, Pt 3, Pd 4), [Pt(bzq)(PPh2H)(PPh2CCPh)]ClO4 5, [Pt(bzq)(PPh2C(Ph)=C(H)PPh2)]ClO4 6, and [Pt(bzq)(CCPh)(PPh2CCPh)] (7a, 7b), were synthesized. The X-ray crystal structures of 1, 6.CH3COCH3.1/2CH3(CH2)4CH3, and 7b.CH3COCH3 have been determined. In 1, the metalated carbon atom and the P atom are mutually cis, whereas in 7b they are trans located. For complex 6, C and N are crystallographically indistinguishable. Reaction of [Pt(bzq)(mu-Cl)]2 with PPh2H and excess of NEt3 leads to the phosphide-bridge platinum dimer [Pt(bzq)(mu-PPh2)]2 8 (X-ray). Moderate pi-pi intermolecular interactions and no evident Pt-Pt interactions are found in 1, 7b, and in 8. All of the complexes exhibit absorption bands at high energy due to the intraligand transitions (1IL pi --> pi) and absorptions at lower energy which are attributed to MLCT (5d) pi --> pi (CLambdaN) transition. Platinum complexes show strong luminescence in both solid state and frozen solutions. The influence of the coligands on the photophysics of the platinum complexes has been examined by absorption and emission spectroscopy.     

Thiolate bridging and metal exchange in adducts of a zinc finger model and Pt(II) complexes: biomimetic studies of protein/Pt/DNA interactions

To provide precedents for the possible interactions of platinum DNA adducts with zinc finger proteins, the complexes [Pt(dien)Cl]Cl (dien = diethylenetriamine) and [Pt(terpy)Cl]Cl (terpy = 2,2':6',2'-terpyridine) were exposed to the N,N'-bis(2-mercaptoethyl)-1,4-diazacycloheptanezinc(II) dimer, [Zn(bme-dach)]2, and the products defined by electrospray ionization mass spectrometry (ESI-MS), X-ray crystallography and (195)Pt NMR spectroscopy. The presence of a leaving chloride in both platinum(II) complexes facilitates electrophilic substitution involving sulfur-containing zinc finger synthetic models or, as in previous studies, zinc finger peptidic sequences. Monitored via ESI-MS, both reactants yielded evidence for Zn-(mu-SR)-Pt bridges followed by zinc ejection from the N2S2 coordination sphere and subsequent formation of a trimetallic Zn-(mu-SR)2-Pt-(mu-SR)2-Zn-bridged species. The isolation of Zn-(mu-SR)-Pt-bridged species [(Zn(bme-dach)Cl)(Pt(dien))]Cl is, to our knowledge, the first Zn-Pt bimetallic thiolate-bridged model demonstrating the interaction between Zn-bound thiolates and Pt(2+). In the case of the [Pt(terpy)Cl]Cl reaction with the [Zn(bme-dach)]2, ESI-MS analysis further suggests metal exchange by formation of [Zn(terpy)Cl](+), whereas the [Pt(dien)Cl]Cl reaction does not yield the corresponding [Zn(dien)Cl](+) ion. Direct synthesis of the Zn-Pt thiolate-bridged species and the Pt(N2S2) chelate, where Pt has displaced the Zn from the chelate core, permitted the isolation of X-ray-quality crystals to confirm the bridging and metal-exchanged structures. The ESI-MS, (195)Pt NMR spectroscopy, and molecular structures of the di- and trinuclear complexes will be discussed, as they provide insight into the metal-exchange mechanism.     

Solution and solid-state dynamics of metal-coordinated white phosphorus

The dynamic behavior in solution of eight mono-hapto?tetraphosphorus transition metal-complexes, trans-[Ru(dppm)(2) (H)(η(1) -P(4) )]BF(4) ([1]BF(4) ), trans-[Ru(dppe)(2) (H)(η(1) -P(4) )]BF(4) ([2]BF(4) ), [CpRu(PPh(3) )(2) (η(1) -P(4) )]PF(6) ([3]PF(6) ), [CpOs(PPh(3) )(2) (η(1) -P(4) )]PF(6) ([4]PF(6) ), [Cp*Ru(PPh(3) )(2) (η(1) -P(4) )]PF(6) ([5]PF(6) ), [Cp*Ru(dppe)(η(1) -P(4) )]PF(6) ([6]PF(6) ), [Cp*Fe(dppe)(η(1) -P(4) )]PF(6) ([7]PF(6) ), [(triphos)Re(CO)(2) (η(1) -P(4) )]OTf ([8]OTf), and of three bimetallic Ru(μ,η(1:2) -P(4) )Pt species [{Ru(dppm)(2) (H)}(μ,η(1:2) -P(4) ){Pt(PPh(3) )(2) }]BF(4) ([1-Pt]BF(4) ), [{Ru(dppe)(2) (H)}(μ,η(1:2) -P(4) ){Pt(PPh(3) )(2) }]BF(4) ([2-Pt]BF(4) ), [{CpRu(PPh(3) )(2) )}(μ,η(1:2) -P(4) ){Pt(PPh(3) )(2) }]BF(4) ([3-Pt]BF(4) ), [dppm=bis(diphenylphosphanyl)methane; dppe=1,2-bis(diphenylphosphanyl)ethane; triphos=1,1,1-tris(diphenylphosphanylmethyl)ethane; Cp=η(5) -C(5) H(5) ; Cp*=η(5) -C(5) Me(5) ] was studied by variable-temperature (VT) NMR and (31) P{(1) H} exchange spectroscopy (EXSY). For most of the mononuclear species, NMR spectroscopy allowed to ascertain that the metal-coordinated P(4) molecule experiences a dynamic process consisting, apart from the free rotation about the M?P(4) axis, in a tumbling movement of the P(4) cage while remaining chemically coordinated to the central metal. EXSY and VT (31) P?NMR experiments showed that also the binuclear complex cations [1-Pt](+) -[3-Pt](+) are subjected to molecular motions featured by the shift of each metal from one P to an adjacent one of the P(4) moiety. The relative mobility of the metal fragments (Ru vs. Pt) was found to depend on the co-ligands of the binuclear complexes. For complexes [2]BF(4) and [3]PF(6) , MAS, (31) P?NMR experiments revealed that the dynamic processes observed in solution (i.e., rotation and tumbling) may take place also in the solid state. The activation parameters for the dynamic processes of complexes 1(+) , 2(+) , 3(+) , 4(+) , 6(+) , 8(+) in solution, as well as the X-ray structures of 2(+) , 3(+) , 5(+) , 6(+) are also reported. The data collected suggest that metal-coordinated P(4) should not be considered as a static ligand in solution and in the solid state.     

Stereoselective preparation, structures, and reactivities of phosphine-bridged mixed-metal trinuclear and pentanuclear complexes with tris[2-(diphenylphosphino)ethyl]phosphine

The phosphine-bridged linear trinuclear and pentanuclear complexes with Pd(II)-Pt(II)-Pd(II), Ni(II)-Pt(II)-Ni(II), and Rh(III)-Pd(II)-Pt(II)-Pd(II)-Rh(III) metal-ion sequences were almost quantitatively formed by the stepwise phosphine-bridging reaction of the terminal phosphino groups of tris[2-(diphenylphosphino)ethyl]phosphine (pp3), which is the tetradentate bound ligand of the starting Pd(II) and Ni(II) complexes. The solid-state structures of the trinuclear complexes were determined by X-ray structural analyses, and the structures of the polynuclear complexes in solution were characterized by NMR spectroscopy. The trans and cis isomers of the trinuclear and pentanuclear complexes, which arise from the geometry around the Pt(II) center, were selectively obtained simply by changing the counteranion of the starting complexes: the tetrafluoroborate salts, [MX(pp3)](BF4) [M = Pd(II) or Ni(II), X = Cl- or 4-chlorothiophenolate (4-Cltp-)], gave only the trans isomers, and the chloride salt, [PdCl(pp3)]Cl, gave only the cis isomers. The formation of the trinuclear complex with the 4-Cltp- and chloro ligands, trans-[Pt(4-Cltp)2{PdCl(pp3)}2](BF4)2, proceeded with exchange between the thiolato ligand in the starting Pd(II) complex, [Pd(4-Cltp)(pp(3))](BF4), and the chloro ligands in the starting Pt(II) complex, trans-[PtCl2(NCC6H5)2], retaining the trans geometry around the Pt(II) center. In contrast, the formation reaction between [PdCl(pp3)]Cl and trans-[PtCl2(NCC6H5)2] was accompanied by the trans-to-cis geometrical change on the Pt(II) center to give the trinuclear complex, cis-[PtCl2{PdCl(pp3)}2]Cl2. The mechanisms of these structural conversions during the formation reactions were elucidated by the 31P NMR and absorption spectral changes. The differences in the catalytic activity for the Heck reaction were discussed in connection with the bridging structures of the polynuclear complexes in the catalytic cycle.     

Highly luminescent half-lantern cyclometalated platinum(II) complex: synthesis, structure, luminescence studies, and reactivity

The half-lantern compound [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)}(2)]·Me(2)CO (1) was obtained by reaction of equimolar amounts of potassium 2-mercaptobenzothiazolate (KC(7)H(4)NS(2)) and [Pt(bzq)(NCMe)(2)]ClO(4). The Pt(II)···Pt(II) separation in the neutral complex [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)}(2)] is 2.910 (2) ?, this being among the shortest observed in half-lantern divalent platinum complexes. Within the complex, the benzo[h]quinoline (bzq) groups lie in close proximity with most C···C distances being between 3.3 and 3.7 ?, which is indicative of significant π-π interactions. The reaction of 1 with halogens X(2) (X(2) = Cl(2), Br(2), or I(2)) proceeds with a two-electron oxidation to give the corresponding dihalodiplatinum(III) complexes [{Pt(bzq)(μ-C(7)H(4)NS(2)-κN,S)X}(2)] (X = Cl 2, Br 3, I 4). Their X-ray structures confirm the retention of the half-lantern structure and the coordination mode of the bzq and the bridging ligand μ-C(7)H(4)NS(2)-κN,S. The Pt-Pt distances (Pt-Pt = 2.6420(3) ? 2, 2.6435(4) ? 3, 2.6690(3) ? 4) are shorter than that in 1 because of the Pt-Pt bond formation. Time dependent-density functional theory (TD-DFT) studies performed on 1 show a formal bond order of 0 between the metal atoms, with the 6p(z) contribution diminishing the antibonding character of the highest occupied molecular orbital (HOMO) and being responsible for an attractive intermetallic interaction. A shortening of the Pt-Pt distance from 2.959 ? in the ground state S(0) to 2.760 ? in the optimized first excited state (T(1)) is consistent with an increase in the Pt-Pt bond order to 0.5. In agreement with TD-DFT calculations, the intense, structureless, red emission of 1 in the solid state and in solution can be mainly attributed to triplet metal-metal-to-ligand charge transfer ((3)MMLCT) [dσ*(Pt-Pt) → π*(bzq)] excited states. The high quantum yields of this emission measured in toluene (44%) and solid state (62%) at room temperature indicate that 1 is a very efficient and stable (3)MMLCT emitter, even in solution. The high luminescence quantum yield of its red emission, added to its neutral character and the thermal stability of 1, make it a potential compound to be incorporated as phosphorescent dopant in multilayer organic light-emitting devices (OLEDs).     

Chemistry and electrochemistry of the heterodinuclear complex ClPd(dppm)2PtCl: a M-M' bond providing site selectivity

The heterodinuclear d(9)-d(9) title compound 1, whose crystal structure has been solved, reacts with dppm [bis(diphenylphosphino)methane] in the presence of NaBF4 to generate the salt [ClPd(mu-dppm)2Pt(eta(1)-dppm)][BF4] (2a), which contains a Pt-bound dangling dppm ligand. 2a has been characterized by 1H and 31P NMR, Fourier transform Raman [nu(Pd-Pt) = 138 cm(-1)], and UV-vis spectroscopy [lambda(max)(dsigma-dsigma*) = 366 nm]. In a similar manner, [ClPd(mu-dppm)2Pt(eta(1)-dppm=O)][BF4] (2b), ligated with a dangling phosphine oxide, has been prepared by the addition of dppm=O. The molecular structure of 2b has been established by an X-ray diffraction study. 2a reacts with 1 equiv of NaBH4 to form the platinum hydride complex [(eta(1)-dppm)Pd(mu-dppm)2Pt(H)][BF4] (3). Both 2a and 3 react with an excess of NaBH4 to provide the mixed-metal d(10)-d(10) compound [Pd(mu-dppm)3Pt] (4). The photophysical properties of 4 were studied by UV-vis spectroscopy [lambda(max)(dsigma-dsigma*) = 460 nm] and luminescence spectroscopy (lambda(emi) = 724 nm; tau(e) = 12 +/- 1 micros, 77 K). The protonation of 1 and 4 leads to [ClPd(mu-dppm)2(mu-H)PtCl]+ (5) and 3, respectively. Stoichiometric treatment of 1 with cyclohexyl or xylyl isocyanide yields [ClPd(mu-dppm)2Pt(CNC6H11)]Cl (6a) and [ClPd(mu-dppm)2Pt(CN-xylyl)]Cl (6b) ligated by terminal-bound CNR ligands. In contrast, treatment of 1 with the phosphonium salt [C[triple bond]NCH2PPh3]Cl affords the structurally characterized A-frame compound [ClPd(mu-dppm)2(mu-C=NCH2PPh3)PtCl]Cl (6c), spanned by a bridging isocyanide ligand. The electrochemical reduction of 2a at -1.2 V vs SCE, as well as the reduction of 5 in the presence of dppm, leads to a mixture of products 3 and 4. Further reduction of 3 at -1.7 V vs SCE generates 4 quantitatively. The reoxidation at 0 V of 4 in the presence of Cl- ions produces back complex 2a. The whole mechanism of the reduction of 1 has been established.     

Reaction of BH4- with [Mo2Cp2(mu-SMe)n] species to give tetrahydroborato, hydrido or dimetallaborane compounds: control of product by ancillary ligands

The reaction of mono- or dichloro-dimolybdenum(III) complexes [Mo2Cp2(mu-SMe)2(mu-Cl)(mu-Y)] (Cp=eta5-C5H5; 1, Y=SMe; 2, Y=PPh2; 3, Y=Cl) with NaBH4 at room temperature gave in high yields tetrahydroborato (8), hydrido (9) or metallaborane (12) complexes depending on the ancillary ligands. The correct formulation of derivatives and has been unambigously determined by X-ray diffraction methods. That of the hydrido compound 9 has been established in solution by NMR analysis and confirmed by an X-ray study of the mu-azavinylidene derivative [Mo2Cp2(mu-SMe)2(mu-PPh2)(mu-N=CHMe)] (10) obtained from the insertion of acetonitrile into the Mo-H bond of 9. Reaction of NaBH4 with nitrile derivatives, [Mo2Cp2(mu-SMe)4-n(CH3CN)2n]n+(5, n=1; 6 n=2), afforded the tetrahydroborato compound 8, together with a mu-azavinylidene species [Mo2Cp2(mu-SMe)3(mu-N=CHMe)](14), when n=1, and the metallaborane complex 12, together with a mixed borohydrato-azavinylidene derivative [Mo2Cp2(mu-SMe)2(mu-BH4)(mu-N=CHMe)] (13), when n=2. The molecular structures of these complexes have been confirmed by X-ray analysis. Preparations of some of the starting complexes (3 and 4) are also described, as are the molecular structures of the precursors [Mo2Cp2(mu-SMe)2(mu-X)(mu-Y)] (1, X/Y=Cl/SMe; 2, X/Y=Cl/PPh2; 4, X/Y=SMe/PPh2).     

Olefin metatheses in metal coordination spheres: versatile new strategies for the construction of novel monohapto or polyhapto cyclic, macrocyclic, polymacrocyclic, and bridging ligands

The broad applicability of the title reaction is established through studies of neutral and charged, coordinatively saturated and unsaturated, octahedral and square planar rhenium, platinum, rhodium, and tungsten complexes with cyclopentadienyl, phosphine, and thioether ligands which contain terminal olefins. Grubbs' catalyst, [Ru(=CHPh)(PCy3)2(Cl)2], is used at 2-9 mol% levels (0.0095-0.00042 M, CH2-Cl2). Key data are as follows: [(eta5-C5H4(CH2)6CH=CH2)Re(NO)(PPh3)-(CH3)], intermolecular metathesis (95 %); [(eta5-C5H5)Re(NO)(PPh3)(E(CH2CH=CH2)2)]+ TfO (E=S, PMe, PPh), formation of five-membered heterocycles (96-64%; crystal structure E = PMe); [(eta5-C5Me5)Re(NO)(PPh((CH2)6CH=CH2)2)(L)]n+ nBF4-(L/n = CO/1, Cl/0), intramolecular macrocyclization (94-89%; crystal structure L= Cl); fac-[(CO)3Re(Br)(PPh2(CH2)6CH=CH2)2] and cis-[(Cl)2Pt(PPh2(CH2)6CH=CH2)2], intramolecular macrocyclizations (80-71%; crystal structures of each and a hydrogenation product); cis-[(Cl)2Pt(S(R)(CH2)6CH= CH2)2], intra-/intermolecular macrocyclization (R=Et, 55%/24%; tBu, 72%/ <4%); trans-[(Cl)(L)M(PPh2(CH2)6CH=CH2)2] (M/L = Rh/CO, Pt/C6F5) intramolecular macrocyclization (90-83%; crystal structure of hydrogenation product, M=Pt); fac-[W(CO)3(PPh((CH2)6CH=CH2)2)3], intramolecular trimacrocyclization (83 %) to a complex mixture of triphosphine, diphosphine/ monophosphine, and tris(monophosphine) complexes, from which two isomers of the first type are crystallized. The macrocycle conformations, and basis for the high yields, are analyzed.     

One-dimensional phosphinite platinum chains based on hydrogen bonding interactions and phosphinite tetranuclear platinum(II)-thallium(I) complexes

The mononuclear pentafluorophenyl platinum complex containing the chelated diphenylphosphinous acid/diphenylphosphinite system [Pt(C(6)F(5)){(PPh(2)O)(2)H}(PPh(2)OH)] 1 has been prepared and characterised. 1 and the related alkynyl complex [Pt(C[triple bond, length as m-dash]CBu(t)){(PPh(2)O)(2)H}(PPh(2)OH)] 2 form infinite one-dimensional chains in the solid state based on intermolecular O-H[dot dot dot]O hydrogen bonding interactions. Deprotonation reactions of [PtL{(PPh(2)O)(2)H}(PPh(2)OH)] (L = C(6)F(5), C[triple bond, length as m-dash]CBu(t), C[triple bond, length as m-dash]CPh 3) with [Tl(acac)] yields tetranuclear Pt(2)Tl(2) complexes [PtL{(PPh(2)O)(2)H}(PPh(2)O)Tl](2) (L = C(6)F(5) 4, C[triple bond, length as m-dash]CBu(t), C[triple bond, length as m-dash]CPh ). The structure of the tert-butylalkynyl derivative , established by X-ray diffraction, shows two anionic discrete units [Pt(C[triple bond, length as m-dash]CBu(t)){(PPh(2)O)(2)H}(PPh(2)O)](-) joined by two Tl(i) centres via Tl-O and Pt-Tl bonds. Despite the existence of Pt-Tl interactions, they do not show luminescence.     

Mixed-metal assemblies containing multiply bonded dirhenium species linked through thiocyanate- and cyanide-containing bridging units

The lability of the terminal Re-Cl bond that is cis to the bridging CO ligand in the edge-sharing bioctahedral complexes Re(2)(mu-Cl)(mu-CO)(mu-PP)(2)Cl(3)(L), where PP = Ph(2)PC(=CH(2))PPh(2) (dppE) when L = CO (1) and PP = Ph(2)PCH(2)PPh(2) (dppm) when L = CO (2) or XyINC (3), has been exploited in the preparation of mixed-metal Re(4)Pd(2), Re(2)Ag, Re(2)W, Re(2)Pt, and Re(2)Rh assemblies, in which the dirhenium units are bound to the other metals through NCS or CN bridges. These complexes, which retain the Re=Re bonds of the parent dirhenium complexes, comprise the novel centrosymmetric complex [Re(2)Cl(3)(mu-dppE)(2)(CO)(2)(mu-NCS)](2)Pd(2)(mu-SCN)(mu-NCS)Cl(2) (9), and the trimetallic complexes Re(2)Cl(3)(mu-dppE)(2)(CO)(2)[(mu-NC)Ag(CN)] (10), Re(2)Cl(3)(mu-dppE)(2)(CO)(2)[(mu-NC)W(CO)(5)] (11), [Re(2)Cl(3)(mu-dppE)(2)(CO)(2)[(mu-NC)Pt(CN)(CN-t-Bu)(2)]]PF(6) (12), [Re(2)Cl(3)(mu-dppE)(2)(CO)(2)[(mu-N(CN)(2))Rh(CO)(PPh(3))(2)]]O(3)SCF(3) (13), and Re(2)Cl(3)(mu-dppm)(2)(CO)(2)[(mu-NC)W(CO)(5)] (16). The identities of 9 and 16 have been established by X-ray crystallography, and all complexes characterized by IR and NMR spectroscopy and cyclic voltammetry. The reactions of the dicarbonyl complex 1, and the isomeric pair of complexes Re(2)Cl(4)(mu-dppm)(2)(CO)(CNXyl), which have edge-sharing bioctahedral (ESBO) (3) and open bioctahedral (OBO) (4) geometries, with Na[N(CN)(2)] and K[C(CN)(3)] have been used to prepare complexes in which the uncoordinated CN groups have the potential to coordinate other mono- or dimetal units to form extended arrays. The complexes which have been prepared and characterized are the monosubstituted species Re(2)Cl(3)(X)(mu-dppE)(2)(CO)(2) (X = N(CN)(2) (14) or C(CN)(3) (15)) and Re(2)Cl(3)(X)(mu-dppm)(2)(CO)(CNXyl) (X = N(CN)(2) (17) or C(CN)(3) (18) with ESBO structures; X = N(CN)(2) (19) or C(CN)(3) (20) with OBO structures), of which 15, 18, and 20 have been characterized by single-crystal X-ray structure determinations. The substitutional labilities of the Re-Cl bonds in the complexes Re(2)Cl(4)(mu-dppm)(2)(CO) (5), Re(2)Cl(4)(mu-dppm)(2)(CNXyl) (6), and Re(2)Cl(4)(mu-dppm)(2) (7) toward Na[N(CN)(2)] and K[C(CN)(3)] have also been explored and the complexes Re(2)Cl(3)(X)(mu-dppm)(2)(CO) (X = N(CN)(2) (21) or C(CN)(3) (22)), Re(2)Cl(3)(X)(mu-dppm)(2)(CNXyl) (X = N(CN)(2) (23) or C(CN)(3) (24)), Re(2)Cl(2)(X)(2)(mu-dppm)(2)(CNXyl) (X = N(CN)(2) (25) or C(CN)(3) (26)), Re(2)[N(CN)(2)](4)(mu-dppm)(2) (27), and Re(2)[C(CN)(3)](4)(mu-dppm)(2) (28) isolated in good yield. Single-crystal X-ray structure determinations of 24, 26, and 27 have shown that the Re-Re triple bonds present in the starting materials 5-7 are retained in these products.     

Experimental and Theoretical Studies of Two New Trinuclear Ni(II) Asymmetric Salamo-Based Complexes

Russian Journal of General Chemistry - Two new trinuclear Ni(II) complexes, [{Ni(L)(DMF)(μ-OAc)}2Ni] (1) and [{Ni(L)(EtOH)(μ-OAc)}2Ni]·2CH2Cl2 (2), have been successfully synthesized...