Paul-Gerhard Lassahn

Structural Study and Solution Integrity of Dioxomolybdenum(VI) Complexes with Tridentate Schiff Base and Azole Ligands

Four new molybdenum complexes (Mo VI O2(L 1 )(Him)) (1), (Mo VI O2(L 1 )(3-MepzH) (2), (Mo VI O2(L 2 )(3-MepzH)) (3), and ((Mo VI O2)2(µ-L 3 )(MeOH)2 )( 4) were synthesized and characterized by IR, NMR, ESI-MS, and single-crystal structure analysis (H2L 1 2-(salicylideneamino)-2-methyl-1-propanol, H2L 2 2-(3- methoxysalicylideneamino)-2-methyl-1-propanol, H4L 3 1,7- bis(salicylidene)dihydrazide malonic acid, Him imidazole and 3- MepzH 3-methylpyrazole). In all four structures the molyb- denum atom has a distorted octahedral coordination with the three meridional donor atoms from the Schiff base di- or tetraanion (L 1,2 ) 2 /(L 3 ) 4 and one oxo group occupying the sites of the equa- torial plane. The other oxo group and the azole or methanol mol- ecule occupy the apical sites. In 1-3 two centrosymmetrically related

Coordination chemistry of dinucleating P2N2S ligands: preparation and characterization of cationic palladium complexes.

The thioethers (4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylimino)methyl)phenyl)(tert-butyl)sulfane (tBuL3) and (4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylamino)methyl)phenyl)(tert-butyl)sulfane (tBuL4) react readily with [Pd(NCMe)2Cl2] to give the dinuclear palladium thiophenolate complexes [(L3)Pd2(Cl)2]+ and [(L4)Pd2(micro-Cl)]2+ (HL3=2,6-bis((2-(diphenylphosphino)ethylimino)methyl)-4-tert-butylbenzenethiol, HL4=2,6-bis((2-(diphenylphosphino)ethylamino)methyl)-4-tert-butylbenzenethiol). The chlorides in could be replaced by neutral (MeCN) and anionic ligands (NCS-, N3-, I-, CN-) to give the dinuclear PdII complexes [(L3)Pd2(NCMe)2]3+, [(L3)Pd2(SCN)2]+, [(L3)Pd2(N3)2]+, [(L3)Pd2(I)2]+, and [(L3)Pd2(CN)2]+. The acetonitrile ligands in are readily hydrated to give the corresponding amidato complex [(L3)Pd2(NHCOMe)]2+. All complexes were isolated as perchlorate salts and studied by infrared, 1H, and 31P NMR spectroscopy. In addition, complexes [ClO4].EtOH, [ClO4]2, [ClO4], [ClO4].EtOH, and [ClO4]2.MeCN.MeOH have been characterized by X-ray crystallography. The dipalladium complex was found to catalyse the vinyl-addition polymerization of norbornene in the presence of MAO (methylalumoxane) and B(C6F5)3/AlEt3.

Dinuclear nickel(II) and palladium(II) complexes in combination with different co-catalysts as highly active catalysts for the vinyl/addition polymerization of norbornene

Dinuclear nickel(II) and palladium(II) complexes with Schiff-base ligands (derived form salicylaldehyde condensed with 2-amino-1-alcohols or from 2-hydroxy-5-methylisophthaldialdehyde and pyridine-2-carboxaldehyde condensed with semicarbazide, thiosemicarbazide, carbonodihydrazide, or thiocarbonodihydrazide) can be activated with the co-catalysts methylalumoxane (MAO) or tris(pentafluorophenyl)borane/triethylaluminium, B(C6F5)3/AlEt3 for the vinyl/addition polymerization of norbornene to reach activities of up to 2.4 · 107 gpolymer/mol(metal)·h (molar ratios metal:AlMAO = 1:100, metal:borane:AlEt3 = 1:9:10). Polymer characterization by GPC gave molar mass distributions of Mw/Mn ≈ 2, thereby indicating a coordination polymerization with a single-site character of the active species.

Borane Activators for Nickel Catalysts for Olefin Polymerization

Abstract Activation of Ni(acetylacetonate)2 and Ni(2-ethylhexanoate)2 with B(C6F5)3 and B(C6F5)3/ triethylaluminium leads to highly active catalyst systems for the vinyl polymerization of norbomene.

Transfer of the fluorous Biphasic concept to the palladium-catalyzed addition polymerization of norbornene

Abstract Two perfluorinated palladium(II) pre-catalysts of the type (ArF3P)2PdCl2 (ArF = m-C8F17-C2H4- C6H4 - and p-C7F15-CH2-O-C6H4-) could be highly activated with the co-catalyst B(C6F5)3/AlEt3 or methylalumoxane (MAO) for the vinyl/addition polymerization of norbornene. Their recycling was studied by using the FBS concept (Fluorous Biphasic System).

Palladium(II) salts containing [PdCl4]2− and [Pd2Cl6]2− ions as pre-catalysts for the vinyl-polymerization of norbornene—evidence for the in situ formation of PdCl2 as the active species

The polymerization behaviour of a new series of palladium(II) pre-catalysts in the vinyl-polymerization of norbornene has been investigated. Compounds containing [PdCl4]2− or [Pd2Cl6]2− anions and the organic cations [K(18-crown-6)]+, [H3O(18-crown-6)]+, [Ph3PCH2C(O)CH3]+ or [Him]+ (im = imidazole) can be activated with the Lewis acids methylalumoxane (MAO), tris(pentafluorophenyl)borane, B(C6F5)3 or a combination of B(C6F5)3/triethylaluminum (TEA). The catalytic systems show very high norbornene polymerization activities of up to 107 gpolymer molPd−1 h−1. In the case of an activation with B(C6F5)3 alone it is possible to obtain soluble palladium-catalyzed poly(norbornene)s which exhibit a fully saturated polymer backbone and a molar mass (Mn) between 8 × 103 and 3 × 105 g mol−1. The activation process of the pre-catalyst [Ph3PCH2C(O)CH3]2[Pd2Cl6] (2C) in combination with B(C6F5)3 can be followed by multinuclear (1H, 13C, 19F and 31P) NMR investigations and points to the in situ formation of PdCl2 which then represents the active species for the polymerization process. The X-ray structure of compound 2C is reported.