Bernhard Walther

Phosphinigsa¨ure-silyl-, -germanyl-, -stannylester des typs (R2PO)nER′4−n

Abstract Phosphinous acid esters of the type (R 2 P O ) n ER′ 4− n (E = Si, Ge, Sn) are prepared by three different methods: 1. reaction of the alkali-phosphinites with R′ 3 ECl, 2. reaction of the sec-phosphine oxides with organochlorosilanes in the presence of triethylamine, 3. reaction of the sec-phosphine oxides with organotin amides. The reactions of these compounds with H 2 O 2 , sulfur, H 2 O, CH 3 I, HgBr 2 , SOCl 2 , CS 2 and isothiocyanates are described and their structure and reactivity are discussed.

New bimetallic Rh―Mo and Rh―W clusters as precursors for selective heterogeneous CO hydrogenation

Abstract The hydrogenation of carbon monoxide on molybdenum- and tugsten-promoted silica-supported rhodium catalysts has been investigated. Whereas preparation according to the conventional impregnation method leads to bimetallic catalysts with substantially increased activity in comparison to monometallic samples, the application of heteronuclear carbonyl clusters as precursors results additionally in an enhanced selectivity towards oxygen-containing products. Fourier transform infrared spectroscopy, hydrogen chemisorption and temperature programmed reduction have been used to characterize the samples. The results indicate that covering of the Rh by promoter oxide species occurs to a certain extent.

Unexpected reaction of [Ni(CO)4-n(R2PCl)n] (n = 1, 2 ; R = But, Cy, Ph) with Na2[Fe2(CO)8]. Synthesis and electronic structure of the anions [Fe2(μ-CO)(CO)6(μ-PR2)]- and their reactions with H+ and [M(PPh3)]+ (M = Cu, Ag, Au)

Treatment of [Ni(CO)4-n(R2PCl)n] (n = 1, 2; R = Bu(t), Cy, Ph) with Na2[Fe2(CO)8] gave, depending on n and R, either the doubly phosphido-bridged complexes [Fe2(CO)6(mu-PR2)2] or the anions [Fe2(mu-CO)(CO)6(mu-PR2)]-. These anions can also be obtained by the reaction of [Fe(CO)4(PR2)]- with either [Fe2(CO)9] or [Fe(CO)5] via the intermediate [Fe2(CO)8(mu-PR2)]-. The electronic structure of the anions [Fe2(mu-CO) (CO)6(mu-PR2)]- has been studied by an EHT calculation which supports their ambident oxygen- or metal-nucleophilicity. The metal-centred nucleophilic reactions of the anion [Fe2(mu-CO)(CO)6(mu-PBu(t)2)]- with H+ and [M(PPh3)]+, (M = Cu, Ag, Au), respectively, are described. The new complexes have been characterized by various spectroscopic methods and the structure of [Fe2{mu-Ag(PPh3)}(mu-CO)(CO)6(mu-PBu(t)2)] has been established by X-ray analysis.

Dialkylthallium(III)-phosphide und -arsenide, eine weitere substanzklasse mit (tix)2-struktureinheit

Abstract Phenyl-substituted primary and secondary dialkylthallium(III) phosphides and arsenides, R 2 Tl—ER′Ph (E = P, As; R′ = Ph, H), can be prepared as easily decomposing compounds from trialkylthalliums or dialkylthalliumdimethylamides and the appropriate phosphines or arsines. They are characterized by spectroscopic methods and chemical reactions. Experiments aiming atthe preparation of dialkylthallium stannides, R 2 Tl—SnR′ 3 , are reported.

Synthesis of [Mo2{μ-Au(PPh3)}Cp2(CO)4(μ-PPh2)] and structural comparison with the dimolybdenum complexes [Mo2Cp2(CO)4(μ-H)(μ-PPh2)] and PPN[Mo2Cp2(CO)4(μ-PPh2)] (PPN = (PPh3)2N+)

Abstract [Mo 2 {μ-Au(PPh 3 )}Cp 2 (CO) 4 (μ-PPh 2 )] ( 4 ) has been synthesized from K[Mo 2 Cp 2 (CO) 4 (μ-PPh 2 )] ( 2 ) and [AuCl(PPh 3 )] and characterized by IR and 31 P NMR spectroscopy. X-ray structures of this cluster and of [Mo 2 Cp 2 (CO) 4 (μ-H)(μ-PPh 2 )] ( 1 ) and PPN[Mo 2 Cp 2 (CO) 4 (μ-PPh 2 )] ( 3 ) have been performed and refined to R = 0.026, 0.037 and 0.025, respectively. In all three complexes two MoCp(CO) 2 fragments are bridged by a PPh 2 group and they are additionally bridged by a hydrogen atom or an AuPPh 3 group in 1 and 4 . The most striking difference in the structures of the doubly-bridged complexes involves the conformation of the central Mo 2 PAu/H unit: it is approximately planar for 1 but strongly folded for 4 .

Synthese, Charakterisierung und Reaktivität heterodinuklearer Komplexe: [(CO)4(μ-PtBu2)Rh(CO)L](Fe-Rh) (L = CO2, HPtBu2), [(CO)3,Co(μ-H)(μ-PtBu2)Rh(CO)(HPtBu2)](Co-Rh)

Abstract [Rh 2 (μ,-Cl),(HP t Bu 2 )4] ( 2 ) reacts with KICo(CO) 4 ] and PPN[FeH(CO) 4 ] to give the heterobinuclear complexes [(CO) 3 Co(μ-H)(μ-P t Bu 2 )Rh(CO)(HP t Bu 2 )] ( 5 ) and [(CO) 4 Fe(μ-P t Bu 2 )Rh (CO)(HP t Bu 2 )] ( 4 ), respectively. Treatment of 5 with KH results in its anion, which is isolated as PPN[(CO) 3 ,Co(μ-P t Bu 2 )Rh(CO)(HP t Bu 2 )] (PPN[ 8 ]). Substitution of one carbonyl ligand on the Co atom occurs with PPh 3 . The structure of the resulting complex [(CO) 2 (PPh 3 )CO(μ-H)(μ-P t Bu 2 )Rh-(CO)(HP t Bu 2)] ( 7 ) has been determined by an X-ray diffraction study. Hydroformulation reactions with these complexes are reported.

Synthesis of triangular [RhM2cp3(CO)n] clusters (M = Ni, n = 2; M = Fe, n = 4; M = Mo, W, n = 6). [RhMo2cp3(CO)6] as catalyst precursor in the CO hydrogenation reaction

Different synthetic routes to triangular clusters [RhM2cp3(CO)n] (M=NJ, n=2; M=Fe, n=4; M= Mo, W, n=6) were studied. The clusters obtained were characterized by spectroscopic means (IR, 1H and 13C NMR, MS). The behaviour of a [RhMo2cp3- (CO)6] cluster-derived catalyst in CO hydrogenation reactions was studied in comparison to appropriate conventionally prepared bimetallic and monometallic catalysts.

Diorganothallium-übergangsmetall-komplexe, R2Tl—Mln

Abstract Diorganothallium transition metal complexes of the general formula R 2 Tl—ML n with ML n = M(CO) 2 LCp (M = Mo, W; L = CO, PPh 3 ) are obtained by protolytic reactions, redistribution reactions or by methatetic reactions, and are characterized spectroscopically and by chemical reactions. For ML n = Cr(CO) 3 Cp, Fe(CO) 2 Cp and Co(CO) 4 R 3 Tl and Tl(ML n ) 3 can always be isolated. In the case of Me 2 Tl—M(CO) 3 Cp (M = Mo, W) variable temperature NMR measurements gave evidence for a symmetrisation—redistribution equilibrium 3 R 2 Tl—ML n —ML n ⇌ R 3 Tl + Tl(ML n , which generally determines the stability of the diorganomthallium transition metal complexes.

Ligandinduzierter abbau von dodecacarbonyltriruthenium mit di-tert-butylphosphin: Synthese, kristallstruktur und strukturdynamik von HRu2(CO)4(PtBU2)(HPtBu2)2

Abstract The reaction of Ru 3 (CO) 12 with HP t Bu 2 leads to the complexes Ru 3 (CO) 9 (HP t Bu 2 ) 3 ( 1 ), HRu 2 (CO) 4 (P t Bu 2 )(HP t Bu 2 ) 2 ( 2 ) and Ru(CO) 3 (HP t Bu) 2 ) 2 ( 3 ). The unsaturated dinuclear complex 2 reversibly takes up carbon monoxide to give the coordinatively saturated compound HRu 2 (CO) 6 (P t Bu 2 )(HP t Bu 2 ) ( 4 ). The molecular structure of 2 has been established by single-crystal X-ray structure analysis; the solid-state structure differs from that in solution.

Interplay of phosphido and phosphine ligands in dinuclear ruthenium complexes: implication in the catalytic hydroformylation of ethylene

The conversion of the diphenylphosphine complex [Ru2(CO)4(µ-O2CEt)2(PPh2H)2]1 into the diphenylphosphido complex [Ru2(CO)6(µ-PPh2)2]2 under a pressure of CO and the conversion of 2 into the ethyldiphenylphosphine complex [Ru2(CO)4(µ-O2CEt)2(PPh2Et)2]3 in the presence of ethylene and water have been studied; high-yield syntheses for the known complex 2 are also reported.