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Peter W Roesky

Publications and source records attributed to Peter W Roesky.

18 recordsLinked to original sources
PubMed2006

Reactions of potassium bis(phosphinimino)methanide with group 11 compounds.

Transmetalation of the potassium methanide complex, K{CH(PPh2NSiMe3)2}, with [(Ph3P)2CuI] afforded the corresponding copper complex [{CH(PPh2NSiMe3)2}CuPPh3] (1), whereas the reaction of K{CH(PPh2NSiMe3)2} with [Ph3PAuCl] resulted in the dinuclear gold complex [(Ph3PAu)2{C(PPh2NSiMe3)2}] (2). The solid-state structure of 1 shows the formation of a six-membered metallacycle (N1-P1-C1-P2-N2-Cu) that has a twist boat conformation. In contrast, compound 2 is an alpha,alpha-diaurated species, in which the two gold atoms are coordinated in a linear fashion onto the ligand backbone. Photoluminescence measurements show that the latter compound has a strong violet emission.

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PubMed2006

Yttrium and lanthanide complexes having a chiral phosphanylamide in the coordination sphere.

The chiral phosphanylamides {N(R-CHMePh)(PPh(2))}(-) and {N(S-CHMePh)(PPh(2))}(-) were introduced into rare earth chemistry. Transmetalation of the enantiomeric pure lithium compounds Li{N(R-CHMePh)(PPh(2))} (1a) and Li{N(S-CHMePh)(PPh(2))} (1b) with lanthanide bis(phosphinimino)methanide dichloride [{CH(PPh(2)NSiMe(3))(2)}LnCl(2)](2) in a 2:1 molar ratio in THF afforded the enantiomeric pure complexes [{CH(PPh(2)NSiMe(3))(2)}Ln(Cl){eta(2)-N(R-CHMePh)(PPh(2))}] (Ln = Er (2a), Yb (3a), Lu (4a)) and [{CH(PPh(2)NSiMe(3))(2)}Ln(Cl){eta(2)-N(S-CHMePh)(PPh(2))}] (Ln = Er (2b), Yb (3b), Lu (4b)). The solid-state structures of 2a and 3a,b were established by single-crystal X-ray diffraction. Attempts to synthesize compounds 3 in a one-pot reaction starting from K{CH(PPh(2)NSiMe(3))(2)}, YbCl(3), and 1 resulted in the lithium chloride incorporated complex [{(Me(3)SiNPPh(2))(2)CH}Yb(mu-Cl)(2)LiCl(THF)(2)] (5). In an alternative approach to give chiral rare earth compounds in a one-pot reaction 1a or 1b was reacted with LnCl(3) and K(2)C(8)H(8) to give the enantiomeric pure cyclooctatetraene compounds [{eta(2)-N(R-CHMePh)(PPh(2))}Ln(eta(8)-C(8)H(8))] (Ln = Y (6a), Er (7a), Yb (8)) and [{eta(2)-N(S-CHMePh)(PPh(2))}Ln(eta(8)-C(8)H(8))] (Ln = Y (6b), Er (7b)). The structures of 6a,b, 7a, and 8 were confirmed by single-crystal X-ray diffraction in the solid state.

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PubMed2006

Syntheses and structures of strontium, barium, and europium bis(diphosphanylamido) complexes.

Bis(diphosphanylamido) complexes of strontium and europium, [{(Ph(2)P)(2)N}(2)M(THF)(3)] (M = Sr (1), Eu (2)), have been prepared by reaction of [K(THF)(n)()][N(PPh(2))(2)] (n = 1.25, 1.5) and MI(2). The single-crystal X-ray structures of compounds 1 and 2 always show a eta(2) coordination of the ligand via the nitrogen and one phosphorus atom. In solution, a dynamic behavior of the ligand is observed, which is caused by the rapid exchange of the two different phosphorus atoms. As a result of the radius of the larger ion, treatment of [K(THF)(n)()][N(PPh(2))(2)] with BaI(2) gives the coordination polymer [{(Ph(2)P)(2)N}(2)Ba(THF){(Ph(2)P)(2)N}K](n)() (3). Two of the three {(Ph(2)P)(2)N}(-) ligands of compound 3 bind to the metal in eta(2) (N, P) while the third shows a heteroallylic (P, P) coordination mode. In the solid state, the infinite chain is formally held together by pi coordination of the phenyl rings to the potassium atoms.

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PubMed2005

Lanthanide hydroxide cubane clusters anchoring ferrocenes: model compounds for fixation of organometallic fragments on a lanthanide oxide surface.

The reaction of the lanthanide trichloride hexahydrates [LnCl(3).6H(2)O] (Ln = Yb, Lu) with two equivalents of benzoylferrocenoylmethane resulted in the tetranuclear lanthanide hydroxo clusters [Ln(4)(mu(3)-OH)(4)(FcacacPh)(8)] (Ln = Yb (1), Lu (2); FcacacPh = benzoylferrocenoylmethanide). Compounds 1 and 2 are made up of a distorted tetranuclear lanthanide Ln(4)O(4) cubane core consisting of four mu(3)-oxygen atoms while the eight FcacacPh ligands build up the peripheral part of the cluster. These compounds contain the maximum number of ferrocene units anchored to any molecular metal-heteroatom framework reported so far and for which the X-ray structures are known.

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PubMed2005

Lanthanide-potassium wheels.

Mixed potassium-lanthanide wheel-shaped-structured, hexanuclear coordination oligomers of composition [(eta5-C5H5)Ln(NPh2)2{N(PPh2)2}2K2(THF)4]2 (Ln = Er (1a), Yb (1b)) and an octanuclear coordination polymer of composition [(eta5-C5H5)Sm(NPh2)2{N(PPh2)2}K]infinity (2) were synthesized. All presented compounds can be obtained in moderate yields in a one-pot procedure, in which the potassium salts KNPh2 and [K(THF)(n)N(PPh2)2] as well as NaC5H5 are reacted with anhydrous samarium, erbium, and ytterbium trichloride in THF.

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PubMed2005

Zirconium complexes having a chiral phosphanylamide in the co-ordination sphere.

The chiral phosphanylamido ligand, (N(CHMePh)(PPh2))-, has been introduced into co-ordination chemistry. As starting material the oily amines HN(R-*CHMePh)(PPh2)(1a) and HN(S-*CHMePh)(PPh2)(1b) were used. To reconfirm their absolute structure, 1b was oxidized with H2O2 in air to obtain HN(S-*CHMePh)(P(O)Ph2)(2) as a solid compound. The solid-state structure of 2 was established by single-crystal X-ray diffraction. The lithium salts of both enantiomers Li(N(R-*CHMePh)(PPh2))(3a) and Li(N(S-*CHMePh)(PPh2))(3b) were prepared by deprotonation reaction of 1a,b. Compounds 3a,b were further reacted with zirconocen dichloride to give the chiral metallocenes [(eta5-C5H5)2Zr(Cl)(eta2-N(R-*CHMePh)(PPh2))](4a) and [(eta5-C5H5)2Zr(Cl)(eta2-N(S-*CHMePh)(PPh2))](4b). In an alternative approach to give chiral zirconium compounds, the neutral amine 1b was reacted with [(PhCH2)4Zr] to give the enantiomeric pure complex [(PhCH2)3Zr(eta2-N(S-*CHMePh)(PPh2))](5). The solid-state structures of all zirconium complexes were determined by single-crystal X-ray diffraction.

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PubMed2005

Yttrium and lanthanide complexes with various P,N ligands in the coordination sphere: synthesis, structure, and polymerization studies.

Yttrium and lanthanide complexes with different P,N ligands in the coordination sphere have been synthesized. First the chloride complexes [{CH(PPh2NSiMe3)2}Ln{(Ph2P)2N}Cl] (Ln = Y (1 a), La (1 b), Nd (1 c), Yb (1 d)) having the bulky [CH(PPh2NSiMe3)2]- and the flexible [(Ph2P)2N]- ligands in the same molecule were prepared by three different synthetic pathways. Compounds 1 a-d can be obtained by reaction of [{[CH(PPh2NSiMe3)2]LnCl2}2] with [K(thf)nN(PPh2)2] (n = 1.25, 1.5) or by treatment of [{(Ph2P)2N}LnCl2(thf)3] with K[CH(PPh2NSiMe3)2]. Furthermore, a one-pot reaction of K[CH(PPh2NSiMe3)2] with LnCl3 and [K(thf)nN(PPh2)2] leads to the same products. Single-crystal X-ray structures of 1 a-d show that the conformation of the six-membered metallacycle (N1-P1-C1-P2-N2-Ln) which is formed by chelation of the [CH(PPh2NSiMe3)2]- ligand to the lanthanide atom is influenced by the ionic radius of the central metal atom. In solution dynamic behavior of the [(Ph2P)2N]- ligand is observed, which is caused by rapid exchange of the two different phosphorus atoms. Further reaction of 1 b with KNPh2 resulted in [{(Me3SiNPPh2)2CH}La{N(PPh2)2}(NPh2)] (2). Compounds 1 a-d and 2 are active in the ring-opening polymerization of epsilon-caprolactone and the polymerization of methyl methacrylate. In some cases high molecular weight polymers with good conversions and narrow polydispersities were obtained. In both polymerizations the catalytic activity depends on the ionic radius of the metal center.

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PubMed2004

Ytterbium and samarium bis(diphosphanylamides): syntheses and structures of lanthanide complexes having two [(Ph2P)2N]- ligands in the coordination sphere.

Bis(diphosphanylamide) complexes of the lanthanides have been synthesized. Two approaches to obtain these compounds are shown. Reaction of YbCl3 with a slight excess of [K(THF)n][N(PPh2)2] gives [((Ph2P)2N)2 YbCl(THF)2], which can be further reacted with K(C5Me5) to give the corresponding pentamethylcyclopentadienyl complex [((Ph2P)2N)2Yb(C5Me5)]. In a second approach to bis(diphosphanylamide) complexes of the lanthanides, Na(C(5)H(5)) was treated with SmCl3 to generate [(C5H5)SmCl2(THF)3] in situ. Further reaction with 2 equiv of [K(THF)n][N(PPh2)2] gave the desired complex [((Ph2P)2N)2Sm(C5H5)(THF)].

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PubMed2004

Yttrium and lanthanide diphosphanylamides: syntheses and structures of complexes with one [(Ph2P)2N]- ligand in the coordination sphere.

Treatment of the recently reported potassium salt [K(thf)(n)][N(PPh(2))(2)] (n=1.25, 1.5) with anhydrous yttrium or lanthanide trichlorides in THF leads after crystallization from THF/n-pentane (1:2) to the monosubstituted diphosphanylamide complexes [LnCl(2)[(Ph(2)P)(2)N](thf)(3)] (Ln=Y, Sm, Er, Yb). The single-crystal X-ray structures of these complexes show that the metal atoms are surrounded by seven ligands in a distorted pentagonal bipyramidal arrangement, in which the chlorine atoms are located in the apical positions. The diphosphanylamide ligand is always eta(2)-coordinated through the nitrogen atom and one phosphorus atom. Further reaction of [SmCl(2)[(Ph(2)P)(2)N](thf)(3)] with K(2)C(8)H(8) or reaction of [LnI(eta(8)-C(8)H(8))(thf)(3)] with [K(thf)(n)][N(PPh(2))(2)] in THF gives the corresponding cyclooctatetraene complexes [Ln[(Ph(2)P)(2)N](eta(8)-C(8)H(8))(thf)(2)] (Ln=La, Sm). The single crystals of these compounds contain enantiomerically pure complexes. Both compounds adopt a four-legged piano-stool conformation in the solid state. The structures of the A and the C enantiomers were established by single-crystal X-ray diffraction. The more soluble bistrimethylsilyl cyclooctatetraene complex [Y[(Ph(2)P)(2)N](eta(8)-1,4-(Me(3)Si)(2)C(8)H(6))(thf)(2)] was obtained by transmetallation of Li(2)[1,4-(Me(3)Si)(2)C(8)H(6)] with anhydrous yttrium trichloride in THF followed by the addition of one equivalent of [K(thf)(n)][N(PPh(2))(2)]. The (89)Y NMR signal of the complex is split up into a triplet, supporting other observations that the phosphorus atoms are chemically equivalent in solution and, thus, dynamic behavior of the ligand in solution can be anticipated.

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PubMed2004

Nitrophenolate as a building block for lanthanide chains, layers, and clusters.

Potassium o-nitrophenolate (1) was reacted with various lanthanide trichlorides under different reaction conditions. By using the smaller lanthanides and working under rigorous exclusion of air, infinite chains of composition [(THF)4[K(o-O2N-C6H4-O)4Ln]4]n (Ln = Y (2a), Er (2b), Lu (2c)) were obtained. Using the same conditions but performing the crystallization under air, tetradecanuclear clusters of composition H18[Ln14(micro-eta2-o-O2N-C6H4-O)8(eta2-o-O2N-C6H4-O)16(micro4-O)2(micro3-O)16] (Ln = Dy (3a), Er (3b), Tm (3c), Yb (3d)) were isolated. Using larger center metals such as samarium, europium, and terbium and working under rigorous exclusion of air, infinite layers of composition [[K2(o-O2N-C6H4-O)5Tb]n] (4) and [[K2(o-O2N-C6H4-O)5Ln)]n] (Ln = Sm (5a), Eu (5b)) were obtained. In 4 the layers have a closer packing than those in compound 5. The closer packing is a result of the increased coordination number of the lanthanide metal and the potassium atoms. In contrast, the more open structures of 5 results in channels which are rectangular through the layers. All compounds reported including 1 have been investigated by single-crystal X-ray diffraction.

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PubMed2002

Homoleptic lanthanide complexes of chelating bis(phosphanyl)amides: synthesis, structure, and ring-opening polymerization of lactones.

Treatment of the bis(phosphanyl)amide (Ph2P)2NH with KH in boiling THF followed by crystallization from THF/n-pentane leads to [K(thf)n][N(PPh2)2] (n = 1.25, 1.5). Reaction of [K(thf)n][N(PPh2)2] with anhydrous yttrium or lanthanide trichlorides in a 3:1 molar ratio afforded homoleptic bis(phosphanyl)amide complexes [Ln[N(PPh2)2]3] (Ln = Y, Er) as large crystals in good yields. [Ln[N(PPh2)2]3] can also be obtained by reaction of the homoleptic bis(trimethylsilyl)amides of Group 3 metals and lanthanides [Ln[N(SiMe3)2]3] (Ln = Y, La, Nd) with three equivalents of (Ph2P)2NH in boiling toluene. The single-crystal X-ray structures of these complexes always show eta 2 coordination of the ligand. Dynamic behavior of the ligand is observed in solution and is caused by rapid exchange of the two different phosphorus atoms. [Ln[N(PPh2)2]3] was used as catalyst for the polymerization of epsilon-caprolactone. Significant differences in terms of correlation of theoretical and experimental molecular weights as well as polydispersities were observed depending on the nature of Ln. On the basis of the crystal structure of the heteroleptic complex [Lu[N(PPh2)2]3(thf)], we suggest that in the initiation step of epsilon-caprolactone polymerization the lactone adds to the lanthanide atom to form a sevenfold coordination sphere around the central atom.

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