Michael Geprägs

Catalytic activity of cationic diphospalladium(II) complexes in the alkene/CO copolymerization in organic solvents and water in dependence on the length of the alkyl chain at the phosphine ligands

Abstract A series of diphos ligands CH2(CH2PR2)2 (1a–x) (a–g: R=(CH2)nOH, n=1, 3–8; h–k: R=(CH2)nCH(CH2OH)2, n=3–6; l–u: R=CnH2n+1, n=1–8, 10, 14; v–x: R=CH(CH3)2, (CH2)2CH(CH3)2, (CH2)3CH(CH3)2, ( Scheme 1 Download : Download high-res image (228KB) Download : Download full-size image Scheme 1 . ), provided with functionalities of different polarity, was prepared photochemically by hydrophosphination of the corresponding 1-alkenes with H2P(CH2)3PH2 or reaction of Grignard reagents with Cl2P(CH2)3PCl2. The water-soluble palladium complexes [(R2P(CH2)3PR2)Pd(OAc)2] (2a–k) were obtained by reaction of Pd(OAc)2 with the ligands 1a–k in ethanol–acetonitrile. Treatment of PdCl2(NCC6H5)2 with 1l–x afforded the dichloropalladium(II) complexes [(R2P(CH2)3PR2)PdCl2] (3l–x). Upon chloride abstraction with AgBF4 in dichloromethane–acetonitrile the dicationic palladium(II) complexes [(R2P(CH2)3PR2)Pd(NCCH3)2][BF4]2 (4l–x) are formed. The structure of 4n (R=n-Pr) was investigated by an X-ray structural analysis. In particular the water-soluble complexes 2c–k proved to be highly active in the carbon monoxide/ethene copolymerization under biphasic conditions (water–toluene). In the presence of an emulsifier and methanol as activator the catalytic activity increased by a factor of about three. Also higher olefins could be successfully incorporated into the copolymerization with CO and the terpolymerization with ethene and CO. The catalytic activity of the dicationic complexes 4l–x in the propene or 1-hexene/CO copolymerization strongly depends on the length of the alkyl chain R. At 25°C a maximum is achieved in the case of 4q (R=nHex) which is five times more active than the corresponding catalyst with the dppp-ligand. This maximum is shifted to 4t (R=n-C10H21) if the temperature is raised to 60°C. The 1-alkene/CO copolymers are distinguished by their regioregular microstructure and their ultra high molecular weights. Compared to the sulfonated dppp-SO3 catalyst the water-soluble complexes 2c,e,f,h are responsible for a higher 1-hexene incorporation in the terpolymerization of ethene with 1-hexene and CO.

Reactions of ether-phosphine ruthenium hydride complexes with carbon disulfide and phenylacetylene: crystal structures of Ru(CO) Cl(P ∼ O)3(η2-S2CH and Ru(CO) Cl(P ∼ O)2(η2-S2CH)

The dithioformato complexes RuCl(P ∼ O)3(η2CH) (2ab) and RuCl(P ⋒ O(P ∼ O)(η2-S2CH) (3ab) are accessible by insertion of CS2 into the RuH bond of the (ether-phosphine)(hydrido)ruthenium complexes RuCl(P ⋒ O)(P ∼ O)2 (1a,b) [P ∼ O = η1(P)-coordinated, P ⋒ O = η2 (O,P)-chelated; O,P = diphenyl(2-methoxyethyl)phosphone (a), (1,3-dioxan-2-methyl) diphenylphosphine (b)]. Treatment of 2a, 3a and 2b, 3b with carbon monoxide in CH2Cl2 results in the formation of the carbonyl complexes Ru(CO)Cl(P ∼ O)2(η2S2CH) (4a,b). The structures of 2a and 4a were determined by single crystal X-ray diffraction analyses. Crystal data for 2a: space group Pca21 with a = 17.578(4) A, b = 14.215(3) A, c = 17.934(4) A, V = 4481(2) A3, Z = 4. The structure was refined to R = 0.037, wR = 0.082. Crystal data for 4a: space group P1/n with a = 12.009(2) A, b = 17.143(4) A, c = 16.510(4) A, β = 107.92(2)°, V = 3234(1) A3, Z = 4. The structure was refined to R = 0.035, wR = 0.087. 1a,b react with phenylacetylene to give the acetylide complexes RuCl(P ⋒ O(P ∼ O)2(CCPh) 5a,b with evulition of dihydrogen. Carbonylation of 5a yields the cis-η1(P-coordinated complex RuCl(P ⋒ O(P ∼ O)2(CCPh) (6). If chloride is abstracted from Ru(CO) Cl(P ∼ O)2(η2-S2CH) (4a) with AgBF4 in THF the P ⋒ O-chelated complex Ru(CO) Cl(P ∼ O)2(η2-S2CH][BF4] (4) is obtained. Upon reaction of 7 with PhCCH the RuO bond is cleaved and instead of an η1-vinylidene species the acetylide complex Ru(CO) Cl(P ∼ O)2(η2-S2CH) (8) is formed.