Orthopalladation of iminophosphoranes: synthesis, structure and study of stability

The reaction of Pd(OAc)(2) with polyfunctional iminophosphoranes Ph(3)P=NCH(2)CO(2)Me (1a), Ph(3)P=NCH(2)C(O)NMe(2) (1b), Ph(3)P=NCH(2)CH(2)SMe (1c) and Ph(3)P=NCH(2)-2-NC(5)H(4) (1d), gives the orthopalladated dinuclear complex [Pd(mu-Cl){C(6)H(4)(PPh(2)=NCH(2)CO(2)Me-kappa-C,N)-2}](2) (2a) and the mononuclear derivatives [PdCl{C(6)H(4)(PPh(2)=NCH(2)CONMe(2)-kappa-C,N,O)-2}] (2b), [PdCl{C(6)H(4)(PPh(2)=NCH(2)CH(2)SMe-kappa-C,N,S)-2}] (2c) and [PdCl{C(6)H(4)(PPh(2)=NCH(2)-2-NC(5)H(4)-kappa-C,N,N)-2}] (2d). The reaction implies the activation of a C-H bond in a phenyl ring of the phosphonium group, this fact being worthy of note due to the strongly deactivating nature of the phosphonium unit. The palladacycle containing the metallated carbon atom is remarkably stable toward the coordination of incoming ligands, while that formed by the iminic N atom and another heteroatom (O, 2a and 2b; S, 2c; N, 2d) is less stable and the resulting complexes can be considered as hemilabile. The X-ray crystal structures of the cyclopalladated [Pd(mu-Cl){C(6)H(4)(PPh(2)=NCH(2)CO(2)Me-kappa-C,N)-2}](2) (2a), [PdCl{C(6)H(4)(PPh(2)=NCH(2)-2-NC(5)H(4)-kappa-C,N,N)-2}] (2d), [Pd{C(6)H(4)(PPh(2)=NCH(2)CONMe(2)-kappa-C,N,O)-2}(NCMe)](ClO(4)) (7b) and [Pd{C(6)H(4)(PPh(2)NCH(2)CONMe(2)-kappa-C,N,O)-2}(py)](ClO(4)) (3b), and the coordination compound cis-[Pd(Cl)(2)(Ph(3)P=NCH(2)CH(2)SMe-kappa-N,S)] (8) are also reported.     

Regioselective functionalization of iminophosphoranes through Pd-mediated C-H bond activation: C-C and C-X bond formation

The orthopalladation of iminophosphoranes [R(3)P=N-C(10)H(7)-1] (R(3) = Ph(3) 1, p-Tol(3) 2, PhMe(2) 3, Ph(2)Me 4, N-C(10)H(7)-1 = 1-naphthyl) has been studied. It occurs regioselectively at the aryl ring bonded to the P atom in 1 and 2, giving endo-[Pd(μ-Cl)(C(6)H(4)-(PPh(2=N-1-C(10)H(7))-2)-κ-C,N](2) (5) or endo-[Pd(μ-Cl)(C(6)H(3)-(P(p-Tol)(2)=N-C(10)H(7)-1)-2-Me-5)-κ-C,N](2) (6), while in 3 the 1-naphthyl group is metallated instead, giving exo-[Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7). In the case of 4, orthopalladation at room temperature affords the kinetic exo isomer [Pd(μ-Cl)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (11exo), while a mixture of 11exo and the thermodynamic endo isomer [Pd(μ-Cl)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (11endo) is obtained in refluxing toluene. The heating in toluene of the acetate bridge dimer [Pd(μ-OAc)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (13exo) promotes the facile transformation of the exo isomer into the endo isomer [Pd(μ-OAc)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (13endo), confirming that the exo isomers are formed under kinetic control. Reactions of the orthometallated complexes have led to functionalized molecules. The stoichiometric reactions of the orthometallated complexes [Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7), [Pd(μ-Cl)(C(6)H(4)-(PPh(2)[=NPh)-2)](2) (17) and [Pd(μ-Cl)(C(6)H(3)-(C(O)N=PPh(3))-2-OMe-4)](2) (18) with I(2) or with CO results in the synthesis of the ortho-halogenated compounds [PhMe(2)P=N-C(10)H(6)-I-8] (19), [I-C(6)H(4)-(PPh(2)=NPh)-2] (21) and [Ph(3)P=NC(O)C(6)H(3)-I-2-OMe-5] (23) or the heterocycles [C(10)H(6)-(N=PPhMe(2))-1-(C(O))-8]Cl (20), [C(6)H(5)-(N=PPh(2)-C(6)H(4)-C(O)-2]ClO(4) (22) and [C(6)H(3)-(C(O)-1,2-N-PPh(3))-OMe-4]Cl (24).     

Synthesis and structure of tetranuclear orthometallated Pd(II) complexes derived from bis-iminophosphoranes

The reaction of Pd(OAc)2 with bis-iminophosphoranes Ph3P=NCH2CH2CH2N=PPh3 (1a), [C6H4(C(O)N=PPh3)2-1,3] (1b) and [C6H4(C(O)N=PPh3)2-1,2] (1c), gives the orthopalladated tetranuclear complexes [{Pd(mu-Cl){C6H4(PPh2=NCH2-kappa-C,N)-2}}2CH2]2 (2a) [{Pd(mu-OAc){C6H4(PPh2=NC(O)-kappa-C,N)-2}}2C6H4-1',3']2 (2b) and [{Pd(mu-OAc){C6H4(PPh2=NC(O)-kappa-C,N)-2}}2C6H4-1',2']2 (2c). The reaction takes place in CH2Cl2 for 1a, but must be performed in glacial acetic acid for 1b and 1c. The process implies in all cases the activation of a C-H bond on a Ph ring of the phosphonium group, with concomitant formation of endo complexes. This is the expected behaviour for 1a, but for 1b and 1c reverses the exo orientation observed in other ketostabilized iminophosphoranes. The influence of the solvent in the orientation of the reaction is discussed. The dinuclear acetylacetonate complexes [{Pd(acac-O,O'){C6H4(PPh2=NCH2-kappa-C,N)-2}}2CH2] (3a), [{Pd(acac-O,O'){C6H4(PPh2=NC(O)-kappa-C,N)-2}}2C6H4-1',3'] (3b) and [{Pd(acac-O,O'){C6H4(PPh2=NC(O)-kappa-C,N)-2}}2C6H4-1',2'] (3c) have been obtained from the halide-bridging tetranuclear derivatives. The X-ray crystal structure of [3c.4CHCl3] is also reported.     

Metal-promoted synthesis of amidines containing the model nucleobases 1-methylcytosine and 9-methyladenine

The amidine complexes cis-[L(2)PtNH==C(R){1-MeCy(-2H)}]NO(3) (R = Me, 1a; Ph, 1b, Me(3)C, 1c; Ph(2)(H)C, 1d) and cis-[L(2)PtNH==C(R){9-MeAd(-2H)}]NO(3) (R = Me, 2a; Ph, 2b; Me(3)C, 2c; Ph(2)(H)C, 2d), are formed when cis-[L(2)Pt(μ-OH)](2)(NO(3))(2) (L = PPh(3)) reacts with 1-methylcytosine (1-MeCy) and 9-methyladenine (9-MeAd) in solution of MeCN, PhCN, Me(3)CCN and Ph(2)(H)CCN. Reaction of 1a,b and 2a,b with HCl affords the protonated amidines [NH(2)==C(R){1-MeCy(-H)}]NO(3) (R = Me, 3a; Ph, 3b) and [NH(2)==C(R){9-MeAd(-H)}]NO(3) (R = Me, 4a; Ph, 4b) and cis-(PPh(3))(2)PtCl(2) in quantitative yield. Treatment of 3b and 4b with NaOH allows the isolation of the neutral benzimidamides NH(2)-C(Ph){1-MeCy(-2H)} (5b) and NH(2)-C(Ph){9-MeAd(-2H)} (6b). In the solid state 3b shows a planar structure with the hydrogen atom on N(4) cytosine position involved in a strong H-bond with the NO(3)(-) ion. Intermolecular H-bonds between the oxygen of the cytosine ring and one of the H atoms of the amidine-NH(2) group allow the dimerization of the molecule. A detailed analysis of the spectra of 3b in DMF-d(7) at -55 °C indicates the presence of an equilibrium between the species [NH(2)==C(R){1-MeCy(-H)}]NO(3) and [NH(2)==C(R){1-MeCy(-H)}](2)(NO(3))(2), exchanging with trace amounts of water at 25 °C. [(15)N,(1)H]-HMBC experiments for 5b and 6b indicate that the amino tautomer H(2)N-C(Ph){nucleobase(-2H)}, is the only detectable in solution and such structure has been confirmed in the solid state. The reaction of 5b and 6b with cis-L(2)Pt(ONO(2))(2) (L = PPh(3)), in chlorinated solvents, determines the immediate appearance of a pale yellow colour due to the coordination of the neutral amidine, likely in its imino form HN==C(Ph){nucleobase(-H)}, to give the adducts cis-[L(2)PtNH==C(Ph){nucleobase(-H)}](2+). In fact, addition of "proton sponge" leads to the immediate deprotonation of the amidine ligand with formation of the starting complexes 1b and 2b.     

Bis(2-diphenylphosphinoxynaphthalen-1-yl)methane: transition metal chemistry, Suzuki cross-coupling reactions and homogeneous hydrogenation of olefins

Transition metal complexes of bis(2-diphenylphosphinoxynaphthalen-1-yl)methane (1) are described. Bis(phosphinite) 1 reacts with Group 6 metal carbonyls, [Rh(CO)2Cl]2, anhydrous NiCl2, [Pd(C3H5)Cl]2/AgBF4 and Pt(COD)I2 to give the corresponding 10-membered chelate complexes 2, 3 and 5-8. Reaction of 1 with [Rh(COD)Cl]2 in the presence of AgBF4 affords a cationic complex, [Rh(COD){Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappaP,kappaP}]BF4 (4). Treatment of 1 with AuCl(SMe2) gives mononuclear chelate complex, [(AuCl){Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappaP,kappaP}] (9) as well as a binuclear complex, [Au(Cl){mu-Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappaP,kappaP}AuCl] (10) with ligand 1 exhibiting both chelating and bridged bidentate modes of coordination respectively. The molecular structures of 2, 6, 7, 9 and 10 are determined by X-ray studies. The mixture of Pd(OAc)2 and effectively catalyzes Suzuki cross-coupling reactions of a range of aryl halides with aryl boronic acid in MeOH at room temperature or at 60 degrees C, giving generally high yields even under low catalytic loads. The cationic rhodium(I) complex, [Rh(COD){Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappaP,kappaP}]BF4 (4) catalyzes the hydrogenation of styrenes to afford the corresponding alkyl benzenes in THF at room temperature or at 70 degrees C with excellent turnover frequencies.     

Formation of P-C bonds under unexpectedly mild conditions. Phosphoryl migration and metal coordination of diphenylphosphinomethyl-oxazolines and -thiazolines

The heterocycles 2-methyl-2-oxazoline (mox) and 2-methyl-2-thiazoline (mth) react with Ph2PCl under mild conditions, in the presence of NEt3 which promotes their phosphorylation by stabilization of their enamino tautomers mox(e) and mth(e), respectively, and which also behaves as HCl scavenger. Depending on the reaction conditions, three different phosphine ligands were obtained in good yields from mox: the monophosphine Ph2PCH2C=NCH2CH2O (1ox) and the isomeric diphosphines Ph2PCH=COCH2CH2NPPh2 (2ox) (X-ray structure) and (Ph2P)2CHC=NCH2CH2O (3ox). The formation of these ligands involves phosphoryl migration reactions, which were studied by NMR spectroscopy. The synthesis and the X-ray structures of the corresponding diphenylphosphinothiazolines Ph2PCH2C=NCH2CH2S (1th) and Ph2CH=CSCH2CH2NPPh2 (2th) are also reported but the thiazoline analog of the geminal diphosphine 3ox was not observed. The metal complexes [Pt(3ox-H)2] x 4 CH2Cl2 (4 x 4 CH2Cl2), [Pt(Me)I(1ox)] (5), [Pt(Me)2(1ox)] (7), [Pd(dmba-C,N)(1th)]OTf x 0.25 Et2O (8 x 0.25 Et2O), [Pd(dmba-C,N)(1th-H)] (9), and [9 x {Pd(dmba-C,N)Cl}] x 2.5 C6H6 (10 x 2.5 C6H6) have been prepared and structurally characterized by X-ray diffraction.     

NMR studies on the novel heterobimetallic complexes [M(dppm)(Ph(2)PCH(2)PPh(2)PPPP) {Pt(PPh3)2}]OTf (M = Rh, Ir) derived from the stepwise activation of white phosphorus

The solution structures of the novel heterobimetallic complexes [Ir(dppm)(Ph(2)PCH(2)PPh(2)PPPP){Pt(PPh(3))2}]OTf and [Rh(dppm)(Ph(2)PCH(2)PPh(2)PPPP){Pt(PPh(3))(2)}]OTf derived from the reaction of Rh and Ir--P(5) precursors with [Pt(C2H4)(PPh3)2] have been unambiguously assigned on the basis of 1H NMR and 31P{1H} NMR data. The results are in agreement with the regio-selective insertion of the {Pt(PPh3)2} moiety resulting in a new pentaphosphorus topology which agrees with the formal formation of a unique phosphonium(+)-tetraphosphabutadienide(2-) ligand.     

Synthesis and structural characterization of configurational isomers of tungsten-palladium complexes with bridging diphenyl(dithioalkoxycarbonyl)phosphine as a ligand and phosphine transfer from tungsten to palladium

Treatment of the complex [W(CO)5[PPh2(CS2Me)]] (2) with [Pd(PPh3)4] (1) affords binuclear complexes such as anti-[(Ph3P)2Pd[mu-eta 1,eta 2-(CS2Me)PPh2]W(CO)5] (3), syn-[(Ph3P)2Pd[mu-eta 1,eta 2-(CS2Me)PPh2]W(CO)5] (4), and trans-[W(CO)4(PPh3)2] (5). In 3 and 4, respectively, the W and Pd atoms are in anti and syn configurations with respect to the P-CS2 bond of the diphenyl(dithiomethoxycarbonyl)phosphine ligand, PPh2(CS2Me). Complex 3 undergoes extensive rearrangement in CHCl3 at room temperature by transfer of a PPh3 ligand from Pd to W, eliminating [W(CO)5(PPh3)] (7), while the PPh2CS2Me ligand transfers from W to Pd to give [[(Ph3P)Pd[mu-eta 1,eta 2-(CS2Me)PPh2]]2] (6). In complex 6, the [Pd(PPh3)] fragments are held together by two bridging PPh2(CS2Me) ligands. Each PPh2(CS2Me) ligand is pi-bonded to one Pd atom through the C=S linkage and sigma-bonded to the other Pd through the phosphorus atom, resulting in a six-membered ring. Treatment of Pd(PPh3)4 with [W(CO)5[PPh2[CS2(CH2)nCN]]] (n = 1, 8a; n = 2, 8b) in CH2Cl2 affords syn-[(Ph3P)2Pd[mu-eta 1,eta 2-[CS2(CH2)nCN]PPh2]W(CO)5] (n = 1, 9a; n = 2, 9b). Similar configurational products syn-[(Ph3P)2Pd[mu-eta 1,eta 2-(CS2R)PPh2]W(CO)5] (R = C2H5, C3H5, C2H4OH, C3H6CN, 11a-d) are synthesized by the reaction of Pd(PPh3)4 with [W(CO)5[PPh2(CS2R)]] (R = C2H5, C3H5, C2H4OH, C3H6CN, 10a-d). Although complexes 11a-d have the same configuration as 9a,b, the SR group is oriented away from Pd in the former and near Pd in the latter. In these complexes, the diphenyl(dithioalkoxycarbonyl)phosphine ligand is bound to the two metals through the C=S pi-bonding and to phosphorus through the sigma-bonding. All of the complexes are identified by spectroscopic methods, and the structures of complexes 3, 6, 9a, and 11d are determined by single-crystal X-ray diffraction. Complexes 3, 9, and 11d crystallize in the triclinic space group P1 with Z = 2, whereas 6 belongs to the monoclinic space group P2/c with Z = 4. The cell dimensions are as follows: for 3, a = 10.920(3) A, b = 14.707(5) A, c = 16.654(5) A, alpha = 99.98(3) degrees, beta = 93.75(3) degrees, gamma = 99.44(3) degrees; for 6, a = 15.106(3) A, b = 9.848(3) A, c = 20.528(4) A, beta = 104.85(2) degrees; for 9a, a = 11.125(3) A, b = 14.089(4) A, c = 17.947(7) A, alpha = 80.13(3) degrees, beta = 80.39(3) degrees, gamma = 89.76(2) degrees; for 11d, a = 11.692(3) A, b = 13.602(9) A, c = 18.471(10) A, alpha = 81.29(5) degrees, beta = 80.88(3) degrees, gamma = 88.82(1) degrees.     

Synthesis and structure of orthopalladated complexes derived from prochiral iminophosphoranes and phosphorus ylides

The iminophosphorane Ph₂MePNPh (1) reacts with Pd(OAc)₂ to give the orthopalladated [Pd(μ-Cl){C₆H₄(PPh(Me)NPh-κ-C,N)-2}]₂ (2) as the racemic mixture, which reacts with Tl(acac) to give [Pd(acac){C₆H₄(PPh(Me)NPh-κ-C,N)-2}] (3). The X-ray structure of (3) has been determined by diffraction methods. The phosphorus ylide Ph₂MePCHC(O)Ph (5) reacts with Pd(OAc)₂ to give the dinuclear [Pd(μ-Cl){C₆H₄(PPh(Me)CHC(O)Ph-κ-C,C)-2}]₂ (6) as a mixture of isomers. Complex (6) reacts with Tl(acac), PPh₃ or AgClO₄/dppe giving the mononuclear derivatives [Pd(acac){C₆H₄(PPh(Me)CHC(O)Ph-κ-C,C)-2}] (7), [PdCl{C₆H₄(PPh(Me)CHC(O)Ph-κ-C,C)-2}PPh₃] (8) and [Pd{C₆H₄(PPh(Me)CHC(O)Ph-κ-C,C)-2}(dppe-P,P′)](ClO₄) (9), as mixtures of stereoisomers with high diastereomeric excess.     

Chelate and pincer carbene complexes of rhodium and platinum derived from hexaphenylcarbodiphosphorane, Ph3P=C=PPh3

The reaction of [(cod)RhCl]2 with Ph3P=C=PPh3 (1) gave the bidentate Rh(I) carbene complex, (cod)Rh[eta2-C{P(C6H4)Ph2}{PPh3}] (2), in which one of the Ph groups in 1 underwent orthometalation to form the chelate. Displacement of cod by 2 equiv of PMe3 transformed 2, via a second orthometalation event, into the Rh(III) C,C,C pincer carbene complex, HRh(PMe3)2[eta3-C{P(C6H4)Ph2}2] (3). The reaction of [Me2Pt(SMe2)]2 with 1 led directly to the analogous C,C,C pincer carbene complex of Pt(II), (Me2S)Pt[eta3-C{P(C6H4)Ph2}2] (4). DFT calculations on a model form of 3 suggest a net single sigma-bonding interaction between Rh and an sp2-hybridized carbene center, with a HOMO that is predominantly carbene pz in character.     

Interactions of Rh(III)-dihydrido-bis(phosphine) complexes with semicarbazones

Interaction of cis,trans,cis-[Rh(H)2(PR3)2(acetone)2]PF6 complexes (R = aryl or R3 = Ph2Me, Ph2Et) under H2 with E-semicarbazones gives the Rh(III)-dihydrido-bis(phosphine)-semicarbazone species cis,trans-[Rh(H)2(PR3)2{R'(R' ')C=N-N(H)CONH2}]PF6, where R' and R' ' are Ph, Et, or Me. The complexes are generally characterized by elemental analysis, 31P{1H} NMR, 1H NMR, and IR spectroscopies, and MS. X-ray analysis of three PPh3 complexes reveals chelation of E-semicarbazones by the imine-N atom and the carbonyl-O atom. In contrast, the corresponding reaction of [Rh(H)2(PPhMe2)2(acetone)2]PF6 with acetophenone semicarbazone gives the ortho-metalated-semicarbazone species cis-[RhH(PPhMe2)2{o-C6H4(Me)C=N-N(H)CONH2}]PF6. The X-ray structure of E-propiophenone semicarbazone is also reported. Rhodium-catalyzed, homogeneous hydrogenation of semicarbazones was not observed even at 40 atm H2.     

Electron-transfer-catalyzed rearrangement of unsymmetrically substituted diiron dithiolate complexes related to the active site of the [FeFe]-hydrogenases

Novel asymmetrically substituted azadithiolate compounds [Fe2(CO)4(kappa2-dppe){micro-SCH2N(R)CH2S}] (R=iPr, 1a; CH2CH2OCH3, 1b; CH2C6H5, 1c) have been synthesized by treatment of [Fe2(CO)6(micro-adt)] [adt=SCH2N(R)CH2S, with R=iPr, CH2CH2OCH3, CH2C6H5] with dppe (dppe=Ph2PCH2CH2PPh2) in refluxing toluene in the presence of Me3NO. 1a-c have been characterized by single-crystal X-ray diffraction analyses. The electrochemical investigation of 1a-c and of [Fe2(CO)4(kappa2-dppe)(micro-pdt)] (1d) [pdt=S(CH2)3S] in MeCN- and THF-[NBu4][PF6] has demonstrated that the electrochemical reduction of 1a-d gives rise to an Electron-transfer-catalyzed (ETC) isomerization to the symmetrical isomers 2a-d where the dppe ligand bridges the iron centers. Compounds 2a-d were characterized by IR and NMR spectroscopy, elemental analysis, and X-ray crystallography for 2a.     

Synthesis, structures and reactions of lithium complexes of [(o-RCHC6H4)PPh2=NSiMe3]-(R = H, SiMe3) ligands

N-Trimethylsilyl o-methylphenyldiphenylphosphinimine, (o-MeC6H4)PPh2=NSiMe3 (1), was prepared by reaction of Ph2P(Br)=NSiMe3 with o-methylphenyllithium. Treatment of 1 with LiBun and then Me3SiCl afforded (o-Me3SiCH2C6H4)PPh2=NSiMe3 (2). Lithiations of both 1 and 2 with LiBu(n) in the presence of tmen gave crystalline lithium complexes [Li{CH(R)C6H4(PPh(2=NSiMe3)-.tmen](3, R = H; 4, R = SiMe3). From the mother liquor of 4, traces of the tmen-bridged complex [Li{CH(SiMe3)C6H4(PPh2=NSiMe3)-2}]2(mu-tmen) (5) were obtained. Reaction of 2 with LiBun in Et2O yielded complex [Li{CH(SiMe3)C6H4(PPh2=NSiMe3)-2}.OEt2] (6). Reaction of lithiated with Me2SiCl2 in a 2:1 molar ratio afforded dimethylsilyl-bridged compound Me2Si[CH2C6H4(PPh2=NSiMe3)-2]2 (7). Lithiation of 7 with two equivalents of LiBun in Et2O yielded [Li2{(CHC6H4(PPh2=NSiMe3)-2)2SiMe2}.0.5OEt2](8.0.5OEt2). Treatment of 4 with PhCN formed a lithium enamide complex [Li{N(SiMe3)C(Ph)CHC6H4(PPh2=NSiMe3)-2}.tmen] (9). Reaction of two equivalents of 5 with 1,4-dicyanobenzene gave a dilithium complex [{Li(OEt2)2}2(1,4-{C(N(SiMe3)CHC6H4(PPh2=NSiMe3)-2}2C6H4)] (10). All compounds were characterised by NMR spectroscopy and elemental analyses. The structures of compounds 2, 3, 5, 6 and 9 have been determined by single crystal X-ray diffraction techniques.     

Nitrile-amidine coupling at Pt(IV) and Pt(II) centers. An easy entry to imidoylamidine complexes

Treatment of trans-[PtCl4(RCN)2] (R = Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(=NH)NHPh in a suspension of MeCN (R = Me), CHCl3 (R = Et, Ph), or in CHCl3 solution (R = NEt2) results in the formation of the imidoylamidine complexes trans-[PtCl4{NH=C(R)N=C(Ph)NHPh}2] (1-4) isolated in good yields (66-84%). The reaction of soluble complexes 3 and 4 with 2 equiv of Ph3P=CHCO2Me in CH2Cl2 (40 degrees C, 5 h) leads to dehydrochlorination resulting in a chelate ring closure to furnish the platinum(IV) chelates [PtCl2{NH=C(R)NC(Ph)=NPh}2] (R = Ph, 5; R = NEt2, 6), accordingly, and the phosphonium salt [Ph3PCH2CO2Me]Cl. Treatment of 5 with 3 equiv of Ph3P=CHCO2Me at 50 degrees C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt{NH=C(NEt2)NC(Ph)=NPh}2] (15). The reduction can be achieved within several minutes, when Ph2PCH2CH2PPh2 in CDCl3 is used. When the platinum(II) complex trans-[PtCl2(RCN)2] is reacted with 2 equiv of the amidine, the imidoylamidinato complexes [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) and [PhC(=NH)NHPh] x HCl (7) are formed. The reaction of trans-[PtCl2(RCN)2] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) with 2 more equiv of the amidine yields the complex bearing two chelate rings [Pt{NH=C(R)NC(Ph)=NHPh}2] (12-15). The treatment of cis-[PtCl2(RCN)2] (R = Me, Et) with the amidine gives ca. 50-60% yield of [PtCl2{NH=C(R)NHC(Ph)=NHPh}] (16 and 17). All of the platinum compounds were characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; 1H, 13C{1H}, and 195Pt NMR spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC(=NH)NHPh do not react in the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile-amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of them exhibiting luminescent properties.     

A systematic study on the synthesis, reactivity and structure of ortho-palladated aryloximes, including the first cyclopalladated aryloximato and iminoaryloxime complexes

Complexes [Pd{C,N-Ar{C(Me)=NOH}-2}(μ-Cl)](2) (1) with Ar = C(6)H(4), C(6)H(3)NO(2)-5 or C(6)H(OMe)(3)-4,5,6, were obtained from the appropriate oxime, Li(2)[PdCl(4)] and NaOAc. They reacted with neutral monodentate C-, P- or N-donor ligands (L), with [PPN]Cl ([PPN] = Ph(3)P=N=PPh(3)), with Tl(acac) (acacH = acetylacetone), or with neutral bidentate ligands N^N (tetramethylethylenediamine (tmeda), 4,4'-di-tert-butyl-2,2'-bipyridine ((t)Bubpy)) in the presence of AgOTf or AgClO(4) to afford complexes of the types [Pd{C,N-Ar{C(Me)=NOH}-2}Cl(L)] (2), [PPN][Pd{C,N-Ar{C(Me)=NOH}-2}Cl(2)] (3), [Pd{C,N-Ar{C(Me)=NOH}-2}(acac)] (4) or [Pd{C,N-Ar{C(Me)=NOH}-2}(N^N)]X (X = OTf, ClO(4)) (5), respectively. Complexes 1 reacted with bidentate N^N ligands in the presence of a base to afford mononuclear zwitterionic oximato complexes [Pd{C,N-Ar{C(Me)=NO}-2}(N^N)] (6). Dehydrochlorination of complexes 2 by a base yielded dimeric oximato complexes of the type [Pd{μ-C,N,O-Ar{C(Me)[double bond, length as m-dash]NO}-2}L](2) (7). The insertion of XyNC into the Pd-C(aryl) bond of complex 2 produced the mononuclear iminoaryloxime derivative [Pd{C,N-C(=NXy)Ar{C(Me)=NOH}-2}Cl(CNXy)] (8) which, in turn, reacted with [AuCl(SMe(2))] to give [Pd{μ-N,C,N-C(=NXy)Ar{C(Me)=NOH}-2}Cl](2) (9) with loss of XyNC. Some of these complexes are, for any metal, the first containing cyclometalated aryloximato (6, 7) or iminoaryloxime (8, 9) ligands. Various crystal structures of complexes of the types 2, 3, 6, 7, 8 and 9 have been determined.     

Reactivity of niobium(v) and tantalum(v) halides with carbonyl compounds: synthesis of simple coordination adducts, C-H bond activation, C=O protonation, and halide transfer

The metal halides of Group 5 MX(5) (M = Nb, Ta; X = F, Cl, Br) react with ketones and acetylacetones affording the octahedral complexes [MX(5)(ketone)] () and [TaX(4){kappa(2)(O)-OC(Me)C(R)C(Me)O}] (R = H, Me, ), respectively. The adducts [MX(5)(acetone)] are still reactive towards acetone, acetophenone or benzophenone, giving the aldolate species [MX(4){kappa(2)(O)-OC(Me)CH(2)C(R)(R')O}] (). The syntheses of (M = Ta, X = F, R = R' = Ph) and (M = Ta, X = Cl, R = Me, R' = Ph) take place with concomitant formation of [(Ph(2)CO)(2)-H][TaF(6)], and [(MePhCO)(2)-H][TaCl(6)], respectively. The compounds [acacH(2)][TaF(6)], and [TaF{OC(Me)C(Me)C(Me)O}(3)][TaF(6)], have been isolated as by-products in the reactions of TaF(5) with acacH and 3-methyl-2,4-pentanedione, respectively. The molecular structures of, and have been ascertained by single crystal X-ray diffraction studies.     

A thermally stable and sterically unprotected terminal electrophilic phosphinidene complex of cobalt and its conversion to an eta(1)-phosphirene

The terminal chloroaminophosphido complex [Co(CO)3(PPh3){P(Cl)NiPr2}] is formed via reaction of K[Co(CO)4] with iPr2NPCl2 in the presence of triphenylphosphine. Chloride abstraction by aluminum trichloride leads to the first terminal phosphinidene complex of cobalt, [Co(CO)3(PPh3)(PNiPr2)][AlCl4]. The electrophilicity of the phosphinidene was demonstrated by its reaction with diphenylacetylene to form the phosphirene complex [Co(CO)3(PPh3){P(NiPr2)C(Ph)C(Ph)}][AlCl4].     

Synthesis and reactivity of silylated tetrathiafulvalenes

Novel organosilylated tetrathiafulvalenes (TTFs) possessing Si-H or Si-Si bonds have been synthesised. The crystal structures of several derivatives have been determined by X-ray diffraction, including that of dimeric (Si(2)Me(4))(TTF)(2) () incorporating a diatomic SiMe(2)-SiMe(2) linker. Cyclic voltammetry measurements in all cases show two oxidation waves. DFT calculations were performed to rationalize the absence of an electronic communication between the two TTF moieties of through the disilanyl spacer. The reactivity of the Si-H bond has been exploited to prepare the dinuclear complex [{Ru(CO)(4)}(2){mu-(Me(2)Si)(4)TTF}] (), starting from Ru(3)(CO)(12) and TTF(SiMe(2)H)(4) (). Treatment of with 2 equiv. of PPh(3) or dppm results in selective substitution of a CO ligand trans to a SiMe(2) group to afford mer-[{Ru(PPh(3))(CO)(3)}(2){mu-(Me(2)Si)(4)TTF}] () and mer-[{Ru(CO)(3)}(2)(eta(1)-dppm){mu-(Me(2)Si)(4)TTF}] (). Attempts to transform the Si-H bonds of some TTF(SiMe(2)H)(n) (n = 1, 2) into Si-O functions using stoichiometric amounts of water in the presence of tris(dibenzylideneacetone)dipalladium(0) were unsuccessful. Quantitative cleavage of the C(TTF)-Si bond was observed instead of formation of TTF-based-siloxanes. Essays of catalytic bis-silylation of phenylacetylene with and TTF(SiMe(2)-SiMe(3)) () in the presence of Pd(OAc)(2)/1,1,3,3-tetramethylbutylisocyanide failed. Again, cleavage of the C(TTF)-Si bond was noticed.     

Highly metallized polymers: synthesis, characterization, and lithographic patterning of polyferrocenylsilanes with pendant cobalt, molybdenum, and nickel cluster substituents

High molecular weight, soluble, air- and moisture-stable, highly metallized (>25 wt% metal) polyferrocenylsilanes (PFS) [Fe(eta-C5H4)2Si(Me){Co2(CO)6C2Ph}]n (Co-PFS), [Fe(eta-C5H4)2Si(Me){Mo2-Cp2(CO)4C2Ph}]n (Mo-PFS), and [Fe(eta-C5H4)2Si(Me){Ni2Cp2C2Ph}]n (Ni-PFS) containing pendant cobalt, molybdenum, and nickel clusters, respectively, have been prepared via macromolecular clusterization of an acetylide-substituted PFS [Fe(eta-C5H4)2Si(Me)C(triple bond)CPh]n with [Co(2)(CO)8], [{MoCp(CO)(2)}2], or [{NiCp(CO)}2]. The extent of clusterization achieved was in the range of 70-75%. All three highly metallized polymers were demonstrated to function as negative-tone resists in electron-beam lithography, while Co-PFS and Mo-PFS were successfully patterned by UV-photolithography, allowing the fabrication of micron-sized bars, dots, and lines. These studies suggest that the highly metallized polymers may be useful in the fabrication of patterned arrays of alloy nanoparticles for both materials science and catalytic applications.     

Kinetic and thermodynamic aspects of the regioselective addition of bifunctional hydroxylaminooxime-type HO-nucleophiles to Pt-complexed nitriles

The coupling between coordinated propiononitriles in trans-[PtCln(EtCN)2] (n = 2, 4) and the 1,2-hydroxylaminooximes HON(H)CMe2C(R)=NOH (R = Ph 1, Me 2) proceeds smoothly in CHCl(3) at ca. 40-45 degrees C and gives trans-[PtCln{NH=C(Et)ON(H)CMe2C(R)=NOH}2] (n = 2, R = Ph 5, Me 6; n = 4, R = Ph 7, Me 8) in 80-85% isolated yields. The reaction is highly regioselective, and both spectroscopic (IR; FAB+-MS; 1D 1H, 13C{1H}, and 195Pt NMR; and 2D 1H,13C HMQC, 1H,13C HMBC, and 1H,15N HMQC NMR) and X-ray data for 6-8 suggest that the addition proceeds exclusively via the hydroxylamine moiety of the 1,2-hydroxylaminooxime species; the existence of an oxime group remote from the nucleophile was also confirmed. Heating of 6 in air leads to its conversion to the unusual nitrosoalkane complex [PtCl2{HON=C(Me)C(Me)2N=O}] (9), whereas in the case of 5, only the metal-free salt [H3NC(Me)2C(Ph)=NOH]2(NO3)Cl.H2O (10) was isolated. To compare the kinetic aspects and trends in the addition of both types of nucleophiles (oximes and hydroxylamines; for the latter, see our recent work: Inorg. Chem. 2005, 44, 2944) to coordinated nitriles, a kinetic study of the addition of HON=C(CH2Ph)2 to [Ph3PCH2Ph][PtCl5(EtCN)] (11) to give [Ph(3)PCH(2)Ph][PtCl(5){NH=C(Et)ON=C(CH2Ph)2}] (12) was performed. The calculated rate constant k2 of 3.9 x 10(-6) M(-1) s(-1) at -20 degrees C for the addition of the oxime indicates that the hydroxylamine is, by a factor 1.7 x 10(4), more reactive toward the addition to nitriles than the oxime. Results of the synthetic, kinetic, and theoretical (at the B3LYP level of theory) studies have demonstrated that the high regioselectivity of the reactions of the 1,2-hydroxylaminooximes with ligated nitriles is both kinetically and thermodynamically controlled.