Gerd Rheinwald

Bis(alkynyl) transition metal complexes, R1CC[M]CCR2, as organometallic chelating ligands; formation of μ,η1(2)-alkynyl-bridged binuclear and oligonuclear complexes

Abstract The reaction chemistry of bis(alkynyl)metal complexes towards different metal centers (electron-rich or electron-poor) to give alkynyl-bridged binuclear and oligonuclear species is described. Different coordination modes of the alkynyl ligands are found in these systems, depending upon the nature of the alkynyl substituents and the metal centers involved. The interconversion of these structures, as well as the factors affecting the preference for one coordination mode over another, is discussed.

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

Hydrogen activation by arene ruthenium complexes in aqueous solution. Part 2. Build-up of cationic tri- and tetra-nuclear ruthenium clusters with hydrido ligands

The low-pressure hydrogenation of the hydrolysis mixture of [Ru2(η6-C6H6)2Cl4] in water (1.5 atm, 20 °C) led, in the presence of NaClO4, to the oxo-capped trinuclear cluster cation [Ru3(η6-C6H6)3(µ-Cl)(µ3-O)(µ-H)2]+1 which crystallized as the perchlorate salt. The chloro-capped trinuclear cluster cation [Ru3(η6-C6H2Me-1,2,4,6)3(µ3-Cl)H3]2+2, crystallized as the dichloride, was accessible from the durene derivative [Ru2(η6-C6H2Me-1,2,4,6)2Cl4] by high-pressure hydrogenation (60 atm, 55 °C) in water. In hot aqueous solution, the chloro-capped cluster 2 underwent hydrolysis to give the oxo-capped cluster [Ru3(η6-C6H2Me4-1,2,4,6)3(µ3-O)H3]+3. In the presence of NaBF4, the low-pressure hydrogenation (1.5 atm, 20 °C) of the hydrolysis mixture of [Ru2(η6-C6H6)2Cl4] led to the tetranuclear tetrahydrido cluster cation [Ru4(η6-C6H6)4H4]2+4 which precipitated as the tetrafluoroborate salt. Under high-pressure conditions (60 atm, 55 °C) and in the absence of an additional salt, the hexahydrido cluster cation [Ru4(η6-C6H6)4H6]2+5 was formed and obtained as the dichloride. By analogy, the p-cymene derivative [Ru2(η6-C6H4MePri-p)2Cl4] gave [Ru4(η6-C6H4MePri-p)4H6]2+6. In contact with air, the hexahydrido clusters 5 and 6 were transformed into the corresponding tetrahydrido clusters [Ru4(η6-C6H6)4H4]2+4 and [Ru4(η6-C6H4MePri-p)4H4]2+7. The hexahydrido cluster 5 is capable of hydrogenating fumarie acid to give succinic acid and 4; the latter adds molecular hydrogen to regenerate the hexahydrido species 5. The crystal and molecular structures of the cluster salts [Ru3(η6-C6H6)3(µ-Cl)(µ3-O)(µ-H)2]ClO4(cation 1), [Ru3(η6-C6H2Me4-1,2,4,6)3(µ3-O)H3]BF4(cation 3), [Ru4(η6-C6H6)4H4]Cl2(cation 4) and [Ru4(η6-C6H4MePri-p)4H6][ClO4]2(cation 6) have also been determined.

Five- and six-membered ring Group 14 chalcogenides of the types (Me2ME)3 (M=Si, Ge, Sn), E(Si2Me4)2E, Me4Si2(E)2MRx (MRx=C(CH2)5, SiMe2, GeMe2, SnMe2, SnPh2, BPh) and [Me4Si2(E)2SiMe]2 (E=S, Se, Te)

Abstract The reactions of Me 2 MCl 2 (M=Si, Ge, Sn) with either H 2 S/NEt 3 or Li 2 E (E=Se, Te) yielded the six-membered-ring compounds (Me 2 ME) 3 . Similarly the treatment of ClMe 2 SiSiMe 2 Cl ( 1 ) with H 2 S/NEt 3 or Li 2 E resulted in the formation of E(Si 2 Me 4 ) 2 E. Mixed species E(Si 2 Me 4 ) 2 E′ could be obtained by reaction with mixtures of Li 2 E and Li 2 E′ or in the presence of traces of moisture (E′=O). Reactions of 1:1 mixtures of Me 2 MCl 2 and 1 with Li 2 E resulted in exclusive or at least preferred formation of five-membered rings Me 4 Si 2 (E) 2 MMe 2 . A carbon analogue, Me 4 Si 2 (S) 2 C(CH 2 ) 5 , was obtained from 1 and (HS) 2 C(CH 2 ) 5 . Boron could also be introduced in these ring systems, starting from PhBCl 2 and 1 the compounds PhB(E) 2 Si 2 Me 4 (E=S, Se) could be synthesized. Mixtures of 1 and Cl 2 MeSiSiMeCl 2 yielded, on treatment either with H 2 S/NEt 3 or Li 2 E (E=Se, Te), the bis(cyclopentyl) compounds [Me 4 Si 2 (E) 2 SiMe] 2 . All products have been characterized by multinuclear NMR ( 1 H, 11 B, 13 C, 29 Si, 77 Se, 119 Sn, 125 Te) measurements including coupling constants. Trends of chemical shifts and coupling constants are discussed. The crystal structures of E(Si 2 Me 4 ) 2 E (E=S, Se) and [Me 4 Si 2 (S) 2 SiMe] 2 are reported.

New chalcogen derivatives of silicon possessing adamantane and noradamantane structures

Abstract The reaction of Si 2 Cl 4 Me 2 ( 1 ) with Li 2 Se in THF yields exclusively the noradamantane (MeSi) 4 Se 5 ( 4 ). The sulfur analogue (MeSi) 4 S 5 ( 3 ) could be obtained from 1 , MeSiCl 3 , H 2 S and NEt 3 . Reactions of the disilylmethane CH 2 (SiMeCl 2 ) 2 ( 5c ) with either H 2 S/NEt 3 or Li 2 E (E=Se, Te) produced the new adamantanes (MeSi) 4 (CH 2 ) 2 E 4 (E=S ( 6 ), Se ( 7 ) and Te ( 8 )). Similar reactions of mixtures of 1 and 5c resulted in the formation of the noradamantanes (MeSi) 4 (CH 2 )E 4 (E=S ( 9 ), Se ( 10 )). All compounds were characterized by multinuclear NMR spectroscopy. The crystal structures of 3 , 6 , 7 , 8 ·CDCl 3 and 9 are reported.

Tris(pyrazolyl)methanesulfonate (Tpms) − A Versatile Alternative to Tris(pyrazolyl)borate in Rhodium(I) Chemistry

Thallium(I) tris(pyrazol-1-yl)methanesulfonate (TlTpms) has been prepared as a new versatile precursor for Tpms complexes. TlTpms readily reacts with the rhodium(I) complexes [Rh(LL)Cl]2 [LL = (CO)2, cod, nbd] to give the corresponding TpmsRh(LL) complexes [LL = (CO)2 (2a), cod (3), and nbd (4)]. In solution, 2a reversibly forms the binuclear complex TpmsRh(µ-CO)3RhTpms (2b). 3 and 4 react with CO to form 2a. TpmsRh(CO)(PR3) complexes [PR3 = PPh3 (5a), PMe3 (5b), PCy3 (5d), P(Ph)2(PhSO3K) (5e)] have been obtained by reaction of 2a with the corresponding phosphanes. The solid-state structures of 2a, 3, 4, and 5a have been determined by X-ray analysis. 2a, 3, and 5a have square-planar geometries with the Tpms ligand coordinating in a κ2 mode. The non-coordinating pyrazole ring faces either away from (structure 2a) or towards the rhodium atom (structures 3 and 5a). 4 has a trigonal-bipyramidal coordination geometry with a genuine κ3-bonded Tpms ligand. The non-rigid behaviour of the (Tpms)rhodium complexes has been followed by variable-temperature NMR studies. IR studies on 2a and 5a−e show that Tpms is a weakly donating ligand, comparable to the Tp and Tp ligands. Compound 5e is soluble and stable in dilute acids, showing that Tpms, unlike the Tp ligand, is hydrolytically stable.

Heterometallic early–late π-tweezer complexes: their synthesis, electrochemical behaviour and the solid-state structures of (η5-C5H4SiMe3)2Ti(CCPh)2 and [(η5-C5H4SiMe3)2Ti(CCPh)2]Pd(PPh3)

The reaction of [Ti](CCPh)2 (1) {[Ti]=(η5-C5H4SiMe3)2Ti} with equimolar amounts of CuBr, Ni(PPh3)3 or Pd(PPh3)4 produces the heterobimetallic early–late transition metal complexes of general type {[Ti](CCPh)2}MX [2: MX=CuBr, 3: MX=Ni(PPh3), 4: MX=Pd(PPh3)} in which the respective transition metal atoms are linked by σ,π-bound alkynyl ligands. The solid-state structure of 1 and 4 is reported. In heterobimetallic 4 the Pd(0) centre possesses a trigonal–planar environment caused by the two η2-coordinated Me3SiCC ligands and the datively bonded PPh3 group. The PPh3 moiety is thereby located out of the best Ti(CCSi)2Pd plane. Comparative cyclic voltammetric studies on complexes 1–4 as well as {[Ti](CCPh)2}Ni(CO), for comparison, are presented. These studies reveal a strong influence of the η2-coordinated low-valent transition metal complex fragments MX on the reduction behaviour of the Ti(IV) centre.

Synthesis, electrochemistry and electronic spectra of tetranuclear bis(η2-alkynyl) transition-metal complexes. The molecular structure of [(η5-C5H4SiMe3)2Ti(CCFc)2]CuBr

Abstract Tetrametallic complexes of type {[Ti](CCFc) 2 }MX (M=Cu: 2a, X=Cl; 2b , X=Br; 2c : X=OTf; M=Ag: 3a , X=Cl; 3b , X=BF 4 ; [Ti]=(η 5 -C 5 H 4 SiMe 3 ) 2 Ti, Fc=(η 5 -C 5 H 4 )Fe(η 5 -C 5 H 5 ), OTf=OSO 2 CF 3 ) were synthesised by the reaction of trinuclear [Ti](CCFc) 2 ( 1 ) with one equivalent of [MX] (M=Cu, Ag; X=Cl, Br, OTf, BF 4 ). The solid-state structure of {[Ti](CCFc) 2 }CuBr ( 2b ) displays a three-coordinate Cu(I) centre with two η 2 -coordinated CCFc units and a η 1 -bound Br ligand. The Fc groups are both positioned on one side of the Ti(CC) 2 Cu plane, while the Br ligand points towards the opposite side and is located 0.2566(57) A out of this array. The electronic spectra of complexes 2b (M=Cu) and 3a (M=Ag) show a bathochromic shift of λ max upon η 2 -coordination of the FcCC units in 1 to the M(I) centre in 2b or 3a . Cyclic voltammetric studies reveal a behaviour dependent on M(I). In the case of Cu(I), the Ti σ-acetylide bonds are retained upon oxidation of the remote Fc units, while with Ag(I) immediate TiC CC σ-bond cleavage is observed.

PENTA-COORDINATED CHLOROSILANES: REACTION CHEMISTRY, STRUCTURE AND BONDING

The synthesis and reaction behavior of the penta-coordinated chlorosilanes [C 6 H 4 CH 2 N(CH 3 ) 2 -2]Si(Cl)(R)(R′) [ 3a : R=R′=Cl; 3b : R=R′=CH 3 ; 3c : R=C1, R′=CH 3 ; 3d : R=Cl, R′=CHCH 2 ; 3e : R=CH 3 , R′=CHCH 2 ] are discussed. Compounds 3a–e can be obtained by the reaction of LiC 6 H 4 CH 2 N(CH 3 ) 2 -2 ( 1 ) with stoichiometric amounts of (R)(R′)SiCl 2 ( 2 ) in high yields and give access to a versatile reaction chemistry on substitution of the chlorine atoms by many of the diverse nucleophiles used. Hydrolysis of compound 3d produces oligomeric {[C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)SiO} n ( 4a ), whereas 3e yields the disiloxane {[C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)(CH 3 )Si} 2 O ( 4b ). Alcoholysis of compounds 3d and 3e in presence of NEt 3 affords [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)(CH 3 )Si(OCH 3 ) ( 5a ) or [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)Si(OR) 2 [ 5b : R=CH 3 , 5c : R=C 2 H 5 , 5d : R= i C 3 H 7 ], respectively. Compound 5b can be transferred to the difluorosilane derivative [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)SiF 2 ( 6 ) by its reaction with BF 3 *O(C 2 H 5 ) 2 , while treatment with LiAlH 4 produces the silane [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)SiH 2 ( 7a ). Moreover, hypervalent silanes are accessible by the reaction of chloro-functionalized 3d or 3e with LiAlH 4 whereby compounds [C 6 H 4 CH 2 N(CH 3 ) 2 ](H 2 CCH)Si(H)(R) ( 7a : R=H; 7b : R=CH 3 ) are formed in good yields. Metathesis reaction of compounds 3b–e with LiR reagents [R=CCR′, NHC 6 H 2 (CH 3 ) 3 -2,4,6, P(C 6 H 5 ) 2 ] produces [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 3 )(R)(SiCCR′) [reaction of 3b or 3e with LiCCR′; 8a : R=CH 3 , R′=C 6 H 5 ; 8b : R=CH 3 , R′=Si(CH 3 ) 3 ; 8c : R=CHCH 2 , R′=C 6 H 5 ; 8d : R=CHCH 2 , R′=Si(CH 3 ) 3 ], [C 6 H 4 CH 2 N(CH 3 ) 2 -2](R)Si(CCR′) 2 [reaction of 3c or 3d with LiCCR′; 9a : R=CH 3 , R′=C 6 H 5 ; 9b : R=CHCH 2 , R′=C 6 H 5 ; 9c : R=CHCH 2 , R=Si(CH 3 ) 3 ], [C 6 H 4 CH 2 N(CH 3 ) 2 -2](H 2 CCH)Si[HNC 6 H 2 (CH 3 ) 3 -2,4,6] 2 [reaction of 3d with LiNHC 6 H 2 (CH 3 ) 3 -2,4,6; 10 ] or [C 6 H 4 CH 2 N(CH 3 ) 2 -2](H 2 CCH)Si[P(C 6 H 5 ) 2 ] 2 [reaction of 3d with LiP(C 6 H 5 ) 2 ; 11 ]. The solid state structures of 3c and 3d are reported. Complex 3c crystallizes in the monoclinic space group P 2 1 / c with a =8.918(5), b =11.557(3), c =12.830(7) A; β =108.17(4)°, V =1256(5) A 3 and Z =4; 3d crystallizes in the monoclinic space group P 2 1 with a =6.625(3), b =8.574(6), c =11.281(8) A; β =88.16(5)°, V =640.5(7) A 3 and Z =2. The central silicon atom in compounds 3c and 3d shows an essentially distorted trigonal-bipyramidal coordination sphere, with the axial positions occupied by the nitrogen donor atom and one chloro ligand. Dynamic 1 H-NMR studies confirm that the same geometry is adopted in solution.

Ruthenium carbonyl complexes with polyfunctional phosphine ligands

Abstract Reactions of Ru 3 (CO) 12 with the polyfunctional phosphinestris (2-thienyl)phosphine and tris(diethylamino)phosphine have been investigated. The reaction of the former phosphine with Ru 3 (CO) 12 yields, inter alia, the complexes Ru 3 (CO) 10 [P(C 4 H 3 S) Ru 3 (CO) 10 [P(C 4 H 3 S) 3 ] 2 ( 1 ) and Ru(CO) 3 [P(C 4 H 3 S) 3 ] 2 ( 2 ), both of which have been characterized by X-ray diffraction studies. In 1 the two polyfunctional phosphine ligands are coordinated equatorially via their phosphorus atoms to two adjacent metal atoms of the Ru 3 triangle. In 2 the phosphorus atoms of two P(C 4 H 3 S) 3 ligands occupy the axial positions of the trigonal bipyramidal coordination sphere around the ruthenium atom. The six thienyl substituents are arranged in an eclipsed conformation, with all sulphur atoms pointing preferentially towards the center of the molecule. The reaction of Ru 3 (CO) 12 with an excess of P(NEt 2 ) 3 yields the disubstituted cluster Ru 3 (CO) 10 [P(NEt 2 ) 3 ] 2 ( 3 ). The IR spectrum of 3 reveals the presence of bridging carbonyl ligands, distinguishing 3 from all previously known clusters of this type.