Browsing by Author "Chivers, Tristram"

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    Coordination chemistry of unsaturated cyclic and acyclic PNS and PNSe ligands
    (1994) Chivers, Tristram; Hilts, Robert
    This review is primarily concerned with the synthesis, structure and fluxional behaviour of cyclic and acyclic chalcogen-nitrogen systems containing phosphorus (V) or phosphorus (III). The cyclic Ph4P2N4S2R− and Ph4P2N4S2−2 anions (and their selenium analogues) are versatile ligands for both early and late transition metals. Mono-, di-, tri- and tetradentate bonding modes have been established for the eight-membered P2N4S2 ring in these inorganic heterocycles. Ligation occurs through sulphur (or selenium) and/or nitrogen, while the coordinatively saturated phosphorus (V) centres serve as an informative probe of fluxional processes. By contrast, coordination occurs exclusively through phosphorus in both the cyclic and acyclic phosphorus (III) systems.
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    Formation, x-ray structure, and deprotonation of an S,S'-methylene-bridged P2N4S2 ring
    (1992) Chivers, Tristram; Cowie, Martin; Edwards, Mark; Hilts, Robert
    There is an extensive chemistry of binary sulfur-nitrogen (S- N) anions, several of which are shown only in coordination complexes with metals. Although there is polarographic evidence for the formation of S4N4(2-) at low temperatures, this dianion has only been characterized in Ira and Pt5b complexes as a tridentate (N,S,S’) ligand formed by insertion of the metal into an S-N bond of S4N4. Anions of diphosphadithiatetrazocines 1 are unknown, but Pt0 or Pd0 compounds readily undergo oxidative addition with these norganic heterocycles to give ŋ2- S4ZS1-metal complexes.(6)
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    Group 4 metal complexes of Ph4P2N4S2R- anions: preparation, structure and reactions with electrophiles
    (1994) Chivers, Tristram; Hilts, Robert; Parvez, Masood; Vollmerhaus, Rainer
    The reaction of [Li(Ph4P2N4S2R)THF]2 (R = Me, 'Bu, Ph, CH2PPI12) with the metallocene dihalides MCp2Cl2 (M = Ti, Zr, Hf) in THF produces complexes of the type MCp2Cl(Ph4P2N4S2R) in which the Ph4P2N4S2R" anion is bonded to the metal in an n* 12-N,S fashion as demonstrated by an X-ray structural determination of ZrCp2Cl-(Ph4P2N4S2‘Bu) (2a). Crystals of 2a are triclinic, space group Pi, with a = 12.439(4) Á, b =18.200(5) Á, c = 10.370(2) A, a = 100.40(2)°, ß = 106.65(2)°, y = 72.53(2)°, V= 2136(1) A3, and Z = 2. The final R and R„ values were 0.054 and 0.061, respectively. The dimensions of the three-membered ZrNS ring are d(Zr-S) = 2.634(2) A,
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    Preliminary communication: preparation and structure of a ruthenium dicarbonyl derivative of the P2N4S2 ring
    (1994) Chivers, Tristram; Hilts, Robert; Parvez, Masood
    The reaction of Ru(CO)4(C2H4) or Ru(CO)5 with 1,5-Ph4P2N4S2 in CH2Cl2/hexane at 23°C produces the dimer [Ru(CO)2(Ph4 P2N4S2)]2 (2), which was shown by X-ray crystallography to have a centrosymmetric structure in which the P2N4S2 ring is attached to one ruthenium atom through two (geminal) nitrogen atoms and the remote sulfur atom and serves as a bridge to the other ruthenium atom via the second sulfur atom. Crystals of 2 ·2(CH2Cl2) are triclinic, space group P (No. 2), a = 12.901(1) Å, b = 13.072(1) Å, c = 10.123(1) Å, α = 100.88(1)°, β = 98.90(1)°, γ = 67.50(1)°, V = 1542.4(3) Å, Z = 1 with final R and Rw values of 0.040 and 0.027, respectively.
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    Preparation and 31P NMR characterization of N-bonded complexes of platinum(II) with a phosphadithiatriazine: x-ray structure of trans-PtCl2(Pet3)(η1-N-Ph2PS2N3)
    (1992) Chivers, Tristram; Hilts, Robert; Krouse, Ian H.
    The reaction of Ph2PS2N3 with [Pt2(μ-Cl)2(PEt3)4][BF4]2 or [PtCl2(PEt3)]2, in dichloromethane at 23° C produces the 1:1 adducts cis-[PtCl(PEt3)2(Ph2PS2N3)][BF4], 3, and trans-[PtCl2(PEt3)(Ph2PS3N2)], 4, respectively, in good yields. The 31P NMR data for 3 and 4 indicate that (i) the platinum is attached to a nitrogen atom adjacent to phosphorus in both these adducts, (ii) the PEt3 ligands in 3 are in mutually cis positions, and (iii) the PEt3 ligand in 4 is trans to the heterocyclic nitrogen. These structural features were confirmed by an X-ray analysis of 4. Crystals of 4 are monoclinic, space group P21/c, with a = 14.920(3) Å, b = 8.966(5) Å, c = 19.103(5) Å, β = 109.32(2)°, V = 2411.6(16) Å3, and Z = 4. The least-squares refinement with anisotropic thermal parameters for all non-hydrogen atoms converged at R = 0.050 and Rw = 0.053. The Pt—N bond length is 2.122(15) Å and the coordinated nitrogen atom is lifted ca. 0.63(2) Å out of the plane containing the other heterocyclic ring atoms. The attachment of a platinum(II) centre to the PN3S2 ring perturbs the S—N bond lengths significantly. The S—N distance involving the coordinated nitrogen is 1.672(16) Å, while the other S—N distances are 1.631(19), 1.555(19), and 1.562(19) Å, indicative of a localized sulfur diimide (-N=S=N-) structure. The UV–visible spectra of 3 and 4 in CH2Cl2 exhibit absorption bands at 514 and 528 nm, respectively, but dissociation of these adducts to give the free ligand Ph2PS2N3 occurs readily in dilute solution.
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    Preparation and nuclear magnetic resonance characterization of N-bonded complexes of platinum(II) with phosphorus-nitrogen rings containing three-coordinate chalcogens: x-ray structure of [PtCl2(PEt3)]2(Ph4P2N4Se2Et2)
    (1993) Chivers, Tristram; Doxsee, Daniel D.; Hilts, Robert; Parvez, Masood
    The reaction of 1,5-Ph4P2N4S2Ph2 with [PtCl2CPEt3)]2 in chloroform at 60 °C produces the 1:1 adduct trans-PtCl2(PEt3)(Ph4P2N4S2Ph2) in which the platinum is attached to a nitrogen atom on the basis of 31P nmr spectroscopy. By contrast, the corresponding reactions of 1,5-Ph4P2N4Se2R2 (R = Me, Et, Ph) produce the 2:1 adducts [PtCl2(PEt3)]2(Ph4P2N4Se2R2) (7a, R = Me; 7b, R = Et; 7c, R = Ph) which have been characterized by 1H, 31P and 77Se nmr spectroscopy and, in the case of 7b, by X-ray crystallography. Crystals of 7b are monoclinic, space group C2/c, with a = 27.803(7) Å, b = 12.378(7) Å, c = 15.752(8) Å, β = 115.49(2)°, V = 4893(3) Å3, and Z = 4. The least-squares refinement with anisotropic thermal parameters for all non-hydrogen atoms converged at R = 0.037 and Rw = 0.022. The platinum centres in 7b are attached to distal nitrogen atoms of the disordered P2N4Se2 ring. The reaction of the six-membered ring Ph4P2N3SPh with [PtCl2(PEt3)]2 in dichloromethane at 23 °C occurs in a regiospecific manner to give the 1:1 adduct PtCl2(PEt3)(Ph4P2N3SPh) in which, on the basis of 31P nmr spectroscopy, the platinum is coordinated to a nitrogen atom between phosphorus and sulfur.
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    Preparation and phosphorus-31 and selenium-77 NMR spectra of platinum and palladium complexes of a P2N4Se2 ring
    (1993) Chivers, Tristram; Doxsee, Daniel D.; Hilts, Robert; Parvez, Masood
    The reaction of 1,5-Ph4P2N4Se2 with Pt(PPh&(CH2=CH2) or Pd(PPh3)l in toluene at 0 OC produces the 92- Se,Se'-bonded complexes M(PPh3)2( 1,5-Ph4P~N4Sez) (2a, M = Pt; 2b, M = Pd) characterized by their 3IP and "Se NMR spectra. Simulation of the 77Se NMR spectra gave detailed coupling information for 2a and 2b. Heating 2a or 2b in boiling toluene produces the corresponding ~2-Se,N-p,r11-Se'-bonded dimers [M(PPh3)( 1,5-Ph&N4- Sez)12 (3a, M = Pt; 3b, M = Pd). Variable-temperature 31P NMR spectra of 3a reveal a fluxional process which is proposed to involve a [ 1,3]-metallotropic shift. The reaction of 1,5-Ph4P2N4Se2 with [PtC12(PEt3)]2 in CHzCl2 produces the #-N-bonded adducts [PtClZ(PEt3)],(1,5-Ph4PzN4Se2) (4a, n = 1; 5, n = 2). The two PtC12(PEt3) groups in 5 are attached to distal nitrogen atoms of the P2N4Se2 ring, which retains a folded structure with d(Se-Se) = 2.594 A. Treatment of 4a with Pt(PPh3)2(CHyCH2) produces the pZ,s3-Se,Se',N-bonded complex Pt(PPh3)z( 1,s- PhP2Nfie2) [PtC12(PEt3)] identified by "PNMR spectroscopy. Reaction of [Li[Ph&NBe2Ph](THF)]z, generated from the combination of 1,5-Ph4P~N4Sez and phenyllithium in THF, with cis-PtCl~(PEt3)~ yields the +Se-bonded complex trans-PtCl(PEt3)z(PhdP2N&e2Ph)(7a). Variable temperature 31P NMR spectra of 7a reveal a two-site exchange process involving the two PEt3 ligands, which is proposed to occur via rotation about the PtSe bond. Line-fitting analysis yielded the thermodynamic parameters for this process.
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    Preparation, spectroscopic and structural characterization of η1-N and η2-Se,Se′ complexes of a P2N4Se2 ring
    (1992) Chivers, Tristram; Doxsee, Daniel D.; Hilts, Robert; Meetsma, Auke; Parvez, Masood; Grampel, Johan C. van de
    The reaction of 1,5-Ph4P2N4Se2, 1, prepared by the treatment of Ph2PN2(SiMe3)3 with a mixture of SeCl4 and Se2Cl2 in acetonitrile, with [PtCl2(PEt3)]2 gives the adducts [PtCl2(PEt3)]n[η1-N-Ph4P2N4Se2](2, n- 1; 3, n- 2) in which the P2N4Se2 ring is shown by an X-ray structural determination of 3 to contain a transannular Se–Se interaction; the oxidative addition of 1 or 2 to Pt(C2H4)(PPh3)2 produces the corresponding η2-Se,Se′ complexes.
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    Ruthenium carbonyl complexes of the bridging tetradentate ligands Ph4P2N4S2 and Ph4P2N4S2Me
    (1995) Chivers, Tristram; Hilts, Robert; Parvez, Masood; Ristic Petrovic, Dusan
    The reaction of Ru(CO)4(C2H4) or Ru(CO)5 with 1,5-Ph4P2N4S2 in CH2Cl2-hexane at 23 °C produces the dimer [Ru(CO)2(Ph4P2N4S2)]2 (4) in 54% and 11% yields, respectively. The treatment of 4 with methyl triflate (1:1 molar ratio) in dichloromethane yields the mono(N-methylated) derivative [Ru2(CO)4(Ph4P2N4S2)(Ph4P2N4S2Me)][CF3SO3] (5) or, in a 1:2 molar ratio, the dimethylated derivative [Ru(CO)2(Ph4P2N4S2Me)]2[CF3SO3]2, which exists as a ca. equal mixture of two symmetrical isomers on the basis of 1H and 31P NMR, and IR spectra. The reaction of 4 with two equivalents of Me3NO in the presence of acetonitrile generates [Ru(CO)(CH3CN)(Ph4P2N4S2)]2, which is also formed as a mixture of isomers in a ratio of ca. 2:1 on the basis of 1H and 31P NMR, and IR spectra. The X-ray structure of 4•CH2Cl2 shows that the P2N4S2 ring is bonded to one ruthenium through two (geminal) nitrogen atoms and the remote sulfur atom while the second sulfur atom acts as a bridge to the other ruthenium. The crystals of 4•CH2Cl2 are triclinic, space group with a = 12.901(1) Å, b = 13.072(1) Å, c = 10.123(1) Å, α = 100.88(1)°, β = 98.90(1)°,γ = 67.50(1)°, V = 1542.4(3) Å3, and Z = 2. The final R and Rw, values were 0.040 and 0.027, respectively. The X-ray structure of 5 reveals that N-methylation does not significantly perturb the bonding between the heterocyclic ligand and ruthenium. The crystals of 5 are triclinic, space group with a = 12.912(6) Å, b = 13.435(7) Å, c = 9.948(3) Å, α = 105.04(3)°, β = 102.85(3)°, γ = 70.74(4)°, V = 1555(1) Å3, and Z = 2. The final R and Rw values were 0.063 and 0.071, respectively. Keywords: ruthenium, tetradentate ligand, P2N4S2 ring.
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    S,S'-diorgano derivatives of the 1,5-Ph4P2N4S2 ring: lithium halide adducts, conformational isomerism, and N-methylation
    (1995) Chivers, Tristram; Gao, Xiaoliang; Hilts, Robert; Parvez, Masood; Vollmerhaus, Rainer
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    Solid state and solution structures of dimeric organolithium derivatives of a P2N4S2 ring
    (1993) Chivers, Tristram; Edwards, Mark; Hilts, Robert; Parvez, Masood; Vollmerhaus, Rainer
    An X-ray structural determination of the dimer [Li(Ph4P2N4S2Ph)-THFl2 (THF = tetrahydrofuran) reveals a step-shaped structure; 7Li and 31P NMR investigations of [Li(Ph4P2N4S2R)-THFl2 (R = Me, But, Ph), as a function of temperature and concentration, in THF solution show that this dimer is fluxional and indicate the presence of a second dimeric species.
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    Synthesis and reactions of alkali metal derivatives of the Ph4P2N4S22- dianion: x-ray structure of Cp*Rh(.eta.3-Ph4P2N4S2-N,S,S')
    (1995) Chivers, Tristram; Edwards, Mark; Gao, Xiaoliang; Hilts, Robert; Parvez, Masood; Vollmerhaus, Rainer
    The reaction of 1,5-PhP2N& with 2 molar equiv of M[BEt3H] in THF produces {M2[Ph4P2N4S2]}fl (4a, M = Li; 4b, M = Na; 4c, M = K) in quantitative yields with the concomitant evolution of H2 gas. The lithium and sodium derivatives are obtained as insoluble, yellow powders, whereas (K2[Ph4P2N4&]},, (6(31P) = 33.5 ppm) is soluble in THF when formed initially. The reaction of (Na2[Ph4P2N4&]}, with CH212 in THF yields Ph4P2N4S2- CH2 (Sa) in excellent yields. The methylene-bridged compound Sa is readily deprotonated by LiN(SiMe3)z in THF, and the subsequent addition of Me1 produces Ph4P2N4S2CHMe (a).In a similar way, Sb can be deprotonated and methylated to give Ph4P2N4S2CMe2. The reaction of {N~Z[P~P~N~S~]),, with (Cp*RhC12)2 in THF affords Cp*Rh(Ph&N4S2) (6), which can also be produced by the oxidative addition of 1,5-Ph&N& to Cp*Rh(C2H&. The X-ray structure of 6 reveals that the heterocyclic P2N& ligand is bonded to Rh in a tridentate (v3-N,S,S') fashion with d(Rh-N) = 2.135(5) A. Crystals of 6 are triclinic, space group Pi with a = 10.167(1) A, b = 17.972(2) A, c = 9.377(1) A, a= 100.24(1)", /? = 93.19(1)", y = 95.35(1)", V= 1674.2(3) A3, and Z= 2. The final R and R, values were 0.045 and 0.058, respectively. The treatment of {M~[P~I&N&])~ with a variety of other electrophiles, e.g. ICH2CH21, PhCHBr2, CHI3, CBr4, Me2SiCl2, Me2SnCl2, PhPCl2, S2C12, GeC4, or FeBr2, regenerates the folded ring system 1,5-PhP2N&.
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    Synthesis, properties and bishomoaromaticity of the first tetrahalogenated derivative of a 1,5- diphosphadithiatetrazocine: a combined experimental and computational investigation
    (2010) Chivers, Tristram; Hilts, Robert; Jin, Peng; Chen, Zhongfang; Lu, Xin
    The first example of a tetrahalogenated derivative of a diphosphadithiatetrazocine, 1,5-Cl2P(NSN)2PCl2 (3), was synthesized by cyclocondensation of a 2:1 mixture of SCl2 and SO2Cl2 with Cl2P(NSiMe3)N(SiMe3)2 in CH2Cl2. The heterocycle 3 was isolated as an orange, moisture-sensitive, thermally labile solid and characterized by mass spectrometry, 31P NMR, and UV−visible spectroscopy. The low-field 31P NMR chemical shift (93.7 ppm) is indicative of a cross-ring S---S interaction in the eight-membered P2N4S2 ring, and this conclusion is supported by density-functional computations. Compound 3 exhibits unusual physical properties compared with those of the known tetraalkyl or aryl derivatives; mild heating (90 °C) produces an orange rubbery material. The bishomoaromatic character of the diphosphadithiatetrazocine 1,5-R2P(NSN)2PR2 (R = Me, Cl, F) is evinced by the negative nucleus-independent chemical shift (NICS) values, and the through-space bishomoconjugation in the eight-membered ring decreases with increasing electronegativity of the substituents attached to the P atoms.
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    Zirconium-assisted functionalizations of an unsaturated phosphorus-nitrogen-sulfur heterocycle
    (1994) Chivers, Tristram; Hilts, Robert; Parvez, Masood