Browsing by Author "Browning, Jane"

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    Coordination chemistry of [CH2(PPh2) (P(Y)R2)] and [CH(PPh2)(P(Y)R2)]−, Y = S or Se, R = Ph or tBu: rhodium, iridium and ruthenium complexes; 13C 31P, and 77 Se NMR studies; and the crystal and molecular structures of [Ir(cod)CH2(PPh2)(P(S)tBu2)-P,S]BF4 · CHCl3, [Rh(cod)CH2(PPh2)(P(S)tBu2)-P,SClO4 · CH2Cl2 [Rh(cod)CH(PPh2) (P(S)Ph2)-P,S] and [RuCl2(p-cymene)CH2(PPh2)(P(S) Ph2) -P] · CH2Cl2
    (1992) Browning, Jane; Bushnell, Gordon W.; Dixon, Keith R.; Hilts, Robert
    Reactions of the chloro-bridged complexes, [M2Cl2(cod)2], M  Ir or Rh, COD  cyclooctadiene, with CH2(PPh2)(P(Y)R2), Y  S or Se, R  Ph or tBu, provide a synthetic route to the cations, [M(cod)(CH2(PPh2)(P(Y)R2)-P,S]+, which are isolated as fluoroborate or perchlorate salts. Treatment of these products with sodium hydride results in facile deprotonation to the neutral complexes, [M(cod)CH(PPh2)(P(Y)Ph2)-P,S)], and when Y  S, the neutral complexes are also accessible via reactions of [M2Cl2(cod)2] with Li[CH(PPh2)(P(S)R2)]. Reactions of the cations, [M(cod)CH2(PPh2)(P(S)tBu2)-P,S)]+ with other ligands, Lg  (CO)2, (CNtBu)2, or bis(diphenylphosphino)methane (dppm), result in displacement of cod to form [M(Lg)(CH2(PPh2)(P(S)tBu2)-P,S]+. Ruthenium complexes of CH2(PPh2)(P(S)Ph2) are accessiblevia similar bridge cleavage reactions using [Ru2Cl4L2], L  benzene or p-cymene. These complexes are characterized by complete 13C, 31P, and 77Se nuclear magnetic resonance (NMR) studies and by four crystal structure determinations. The complexes [Ir(cod)(CH2(PPh2)(P(S)tBu2)-P,S]BF4·CHCl3 (1), [Rh(cod)(CH2(PPh2)(P(S)tBu2)-P,S]ClO4·CH2Cl2 (2), [Rh(cod)(CH(PPh2)(P(S)Ph2-P,S] (3) and [RuCl2(p-cymene)(CH2(PPh2)(P(S)Ph2)-P]· CH2Cl2 (4) crystallize in the P (No. 2) space group (Z  2) with respective unit cells: a = 12.307(7) Å, b = 14.743(8) Å, c = 10.877(6) Å, α =74.42(5)°, β = 107.65(6)°, γ = 105.47(5)°; a = 12.163(1) Å, b = 14.56(1) Å, c = 10.560(1) Å, α = 77.69(1)°, β = 74.54(1)°, γ = 77.01(1)°; a = 10.650(4) Å, b = 13.327(4) Å, c = 10.419(3) Å, α = 90.60(3)°, β = 102.64(3)°, γ = 83.15(3)°; a = 11.217(2) Å, b 17.124(3) Å, c = 10.412(2) Å, α = 90.58(1)°, β = 112.29(2)°, γ = 97.53(2)°. Complexes 1–3 all contain bidentate P,S-bonded ligands occupying two coordination positions of an approximately square planar metal centre. In each case, the coordination is completed by two double bonds of a cod ligand. In contrast, complex 4 contains a monodentate P-bonded ligand.
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    Coordination chemistry of [CH{P(S)Ph2}2]−: x-ray diffraction studies of S,S-chelate complexes of iridium and rhodium
    (1992) Browning, Jane; Bushnell, Gordon W.; Dixon, Keith R.; Hilts, Robert
    Reactions of the chloro-bridged complexes, [M2Cl2(cod)2], M  Ir or Rh, with CHR(P(S)Ph2)2, R  H or Me, provide a synthetic route to the cations, [M(cod){CHR(P(S)Ph2)2-S,S}]+, which are isolated as fluoroborate or perchlorate salts. Treatment of these products with sodium hydride results in facile deprotonation to the neutral complexes, [M(cod){CR(P(S)Ph2)2-S,S}], and when R  H, the neutral complexes are also accessible via reactions of [M2Cl2(cod)2] with Li[CH{P(S)Ph2)2]. The complexes, [Ir(cod){CH(P(S)Ph2)2-S,S}], and [Rh(cod){CH(P(S)Ph2)2-S,S}], crystallize in the P1 (No. 2) space group (Z = 2) with respective unit cells: a = 11.570(4), b = 15.122(2), c = 9.919(3) Å, α = 79.86(4), β = 64.87(3), γ = 97.94(4)°; and α = 11.571(16), b = 15.078(2), c = 9.869(2) Å, α = 100.16(1), β = 64.97(1), γ = 82.10(1)°. Both structures consist of puckered 6-membered rings formed by coordination of the disulfide ligands via two sulfur atoms to the metal center. The rings lie in distorted boat conformations with the prows occupied by one sulfur and one phosphorus and the metal atoms in one side.
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    Multimode coordination chemistry of [R2P(X)CHnP(Y)R'2](2-n)- ligands (X, Y = O, S, Se; n = 1, 2). Synthesis and phosphorus-31 NMR spectroscopy of platinum complexes
    (1992) Berry, David E.; Browning, Jane; Dixon, Keith R.; Hilts, Robert; Pidcock, Alan
    Reactions of the bis(phosphine chalcogenides) CH2|P(X)R2l|P(Y)R'2l (X, Y = O, S, Se) and their derived anions [CH|P-(X)R2)lP(Y)R'2l]" with chloroplatinum complexes PtCl42", [Pt2Cl4(PEt3)2], or [Pt2Cl2(PEt3)4]2+ result in a wide variety of coordination complexes. For example, when R = R' = Ph and X = Y = S, the following are all accessible in high yield: [PtCl(PEt3){CH2(P(S)Ph2)2-S^|]+, [PtCl(PEt3)iCH(P(S)Ph2)2-C,S|], [PtCl(PEt3)|CH(P(S)Ph2)2-S^|], [Pt(PEt3)2|CH2(P(S)-Ph2)2)-5^i]2+, [Pt(PEt3)2(CH(P(S)Ph2)2-C,S|]+, [PtCl2lCH2(P(S)Ph2)2-S^l], [Pt|CH2(P(S)Ph2)2-.S„S|2]2+, and [Pt(CH(P-(S)R2)2-C^|2]· A more limited range of complexes is also reported for X = Y = O, X = Y = Se, and X = O, Y = S. In general, the ligands exhibit at least five different coordination modes: (i) Bidentate X,Y coordination of neutral ligands; (ii) bidentate X,Y coordination of the anionic ligands; (iii) bidentate C,X coordination of the anions in a strained four-membered ring; (iv) monodentate C coordination of the anions; (v) complex C,S bridging mode involving a dianionic ligand and two metal centers. Interconversion reactions and characteristic 31P NMR spectroscopy are described for all of the coordination modes, including dynamic NMR studies of the C,X modes. These last modes all exhibit some degree of fluxional behavior, involving an exchange of coordinated and noncoordinated P=X groups in essentially a classic “bimolecular” substitution reaction, except that the incoming ligand is actually part of one of the existing ligands.
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    Platinum and palladium complexes of [R2PCH2P(Y)R′2] and [R2PCHP(Y)R′2]− ligands, Y = O,S, or Se: 13C, 31P, 77Se, and 195Pt nuclear magnetic resonance studies and the crystal and molecular structures of trans-[PtCl(PEt3){But2PCH2P(O)Me2}][ClO4] and trans-PtCl(PEt3){Ph2PCH2P(S)But2}|[ClO4]
    (1988) Berry, David E.; Browning, Jane; Dixon, Keith R.; Hilts, Robert
    Reactions of the bisphosphine monochalcogenides, [Ph2PCH2P(Y)R2], Y = O, S, or Se, R = Ph, Pri, or But, with the chloro-bridged dimers [M2Cl4(PR′3)2], M = Pd or Pt, R′ = Et or Bun, in the presence of either NaClO4or NaBF4yield perchlorate and fluoroborate salts of the complex cations cis- and trans-[PtCl(PR′3){Ph2PCH2P(Y)R2}]+. In many cases both cisand transisomers (defined by the relative orientation of the two M—P bonds) are obtained and the precise isomer distribution is a sensitive function of the substituents. Corresponding neutral complexes, cis- and trans-[PtCl(PR′3){Ph2PCHP(Y)R2}], can be synthesized either by deprotonation of the cations using NaH or by use of the salts Li[Ph2PCHP(Y)R2] in the initial bridge cleavage reactions. These and related complexes are characterized by complete 13C, 31P, 77Se, and 195Pt NMR studies and by two crystal structure determinations. The complexes I, trans-[PtCl(PEt3){But2PCH2P(O)Me2}][ClO4], and II, trans-[PtCl(PEt3){Ph2PCH2P(S)But2}][ClO4], crystallize in the monoclinic space group P21/c, respective cell dimensions: a = 15.579(2), b = 13.590(3), c = 13.578(1) Å;β= 105.96(1)°; and a = 14.002(4), b = 16.366(5), c = 15.524(5) Å; β = 106.01 (3)°. Complete X-ray diffraction studies show that both complexes contain closely square planar platinum centres with the R2PCH2P(Y)R′2ligands coordinated via phosphorus and the Y atom so as to form five-membered chelate rings. The molecular dimensions suggest that the bond to sulphur is stronger than that to oxygen and exerts a larger transinfluence.
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    Reactivity of coordinated [Ph2PCHP(S)Ph2]- and [Ph2P(S)CHP(S)Ph2]-: two-center, regiospecific reactivity in rhodium and iridium complexes and formation of a disubstituted methylene bridge between platinum atoms
    (1988) Browning, Jane; Dixon, Keith R.; Hilts, Robert
    Reaction of methyl iodide with [Ir(Ph,P(S)-CHP(S)Ph,](cod)] occurs in a regiospecific sequence to form first [Ir{Ph,P(S)CHMeP(S)Ph,](cod)] I and only subsequently [IrMeI(Ph,P(S)CHMeP(S)Ph,](cod)] I. For [Rh-(Ph,PCHP(S)Ph,](cod)] the addition sequence is reversed. [Pt(Ph,P(S)CHP(S)Ph,)(MeOcod)] shows both ligand and metal site reactivity in transforming a novel dimer, [Pt,{Ph,P(S)CP(S)Ph,)(MeOcod),] , containing a quaternary carbon bridge between two platinum centers. The bridging carbon is part of four-member C,S chelate rings at both platinums.
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    Synthesis and structural characterisation of tris(diphenylthiophosphinoyl)methane and tris(diphenylthiophosphinoyl)methanide complexes of rhodium and iridium; X-ray structures of [Rh(C8H12){η2-C(P(S)Ph2)3-S,S}] and [Ir(CO)2{gh2-C(P(S)Ph2)3-S,S}]
    (1990) Browning, Jane; Dixon, Keith R.; Hilts, Robert; Meanwell, Neil J.
    Reactions of [MCl(cod)]2, M = Rh or Ir, cod = cyclooctadiene, with CH{P(S)Ph2}3 give the complex cations, [M(cod){CH(P(S)Ph2)3}]+, which are isolated in high yield as BF4− or ClO4− salts. These are the first reported examples of CH{P(S)Ph2}3 complexes in which the methine proton is retained after coordination. The high acidity of this proton is demonstrated by easy deprotonation to corresponding [M(cod){C(P(S)Ph2)3}] complexes. The 31P NMR spectrum of [Rh(cod){CH(P(S)Ph2)3}]BF4 remains a single line to −100°C whereas that of [Rh(cod){C(P(S)Ph2)3}] is resolved into two resonances at −60°C, suggesting that the former complex is 5-coordinate with an η3 (S,S,S) ligand and the latter 4-coordinate, η2 (S,S). The 4-coordinate structure is confirmed by X-ray diffraction studies of [Rh(cod){C(P(S)Ph2)3}] and [Ir(CO)2{C(P(S)Ph2)3}] which both show approximately square planar metal centers, η2 ligands with the third sulfur non-coordinated (“dangling”), and trigonal planar geometry at the central carbon of the tris(phosphinesulfide) ligand. [Rh(cod){C(P(S)Ph2)3}] and [Ir(CO)2{C(P(S)Ph2)3}] crystallize in the Pbca space group (Z = 8) with respective unit cells: a = 20.427(4) Å, b = 16.931(2) Å, c = 23.138(3) Å; and a = 22.140(6) Å, b = 22.317(5) Å, c = 14.792(3) Å. Line shape analysis for a variable temperature 31P NMR study of [Rh(cod){C(P(S)Ph2)3}] gives ΔGo‡ 46 ± 2 kJ mol−1 for the dynamic exchange of coordinated and non-coordinated sulfur.