59307-41-4Relevant academic research and scientific papers
Die Best?ndigkeit von (η5-C5H4R)2Ti(CCR′) 2 in Abh?ngigkeit von den elektronischen Eigenschaften der Cyclopentadienyl-Liganden. Die Festk?rperstruktur von (η5-C5H5)(η5-C 5H4SiMe3)Ti(CCSiMe3)2
Lang,Meichel,Stein,Back,Hovestreydt
, p. 71 - 78 (2007/10/03)
The synthesis of the titanocene dichlorides (η5-C5H5)(η5-C 5H4SiMe3)TiCl2 (3) and (η5-C5H4CO2R) 2TiCl2 (8a, R=CH3; 8b, R=CH2CH3), which contain either electron-donating or electron-withdrawing substituents at the cyclopentadienyl fragments is discussed. While the reaction of 8a or 8b with LiCCR′ in different stoichiometric ratios leads only to product mixtures from which no pure components could be isolated, treatment of 3 with two equivalents of LiCCR′ (9a, R′=C6H5; 9b, R′=tBu; 9c, R′=SiMe3) selectively produces the bis(alkinyl) titanocenes (η5-C5H5)(η5-C 5H4SiMe3)Ti(CCR′)2 (10a, R′=C6H5; 10b, R′=tBu; 10c, R′=SiMe3). However, it was found that when complex 10c is stirred in tetrahydrofuran solutions, Me3SiCC is eliminated and Me3SiCC-CCSiMe3 (11) along with [(η5-C5H5)(η5-C 5H4SiMe3)Ti(CCSiMe3)]2 (12) is formed.The solid-state structure of (η5-C5H5)(η5-C 5H4SiMe3)Ti(CCSiMe3)2 (10c) is reported. Complex 10c crystallises in the monoclinic space group Pc with two independent molecules in the asymmetric unit and with the cell constants a=20.8131(6), b=10.6615(3), c=12.2543(4) A?, β=101.12(3)°, V=2668.14(14) A?3 and Z=4. 10c exhibits a pseudotetrahedrally coordination sphere around the Ti(IV) centre comprised of the two σ-bonded alkynyl ligands Me3SiCC and the η5-coordinated cyclopentadienyl moieties C5H5 as well as C5H4SiMe3.
Zur Umsetzung von Bis(alkinyl)-Titanocenen mit übergangsmetall-Verbindungen von Cu(II), Pd(II), Pt(II), Fe(III) und Au(III)
Frosch,Back,K?hler,Lang
, p. 226 - 232 (2007/10/03)
The reaction behaviour of the bis(alkynyl) titanocenes [Ti](CCR1)(CCR2) {[Ti]=(η5-C5H4SiMe3) 2Ti; 1: R1=R2=Fc, Fc=(η5-C5H4)Fe(η5-C 5H5); 5a: R1=R2=SiMe3; 5b: R1=R2=C6H5; 5c: R1=SiMe3, R2=C6H5} towards MX2 (M=Pd, Pt; X=Cl; M=Cu; X=Cl, Br, OAc, acac) and MCl3 (M=Fe, Au) is described. All reactions are dominated by redox processes. Generally, the reaction of 1 or 5a-5c with AuCl3 or MCl2 (M=Cu, Pd, Pt) produces the titanocene dichloride [Ti]Cl2 (3a) along with the corresponding butadiynes R1CC-CCR2 (4: R1=R2=Fc; 7a: R1=R2=SiMe3; 7b: R1=R2=C6H5; 7c: R1=SiMe3, R2=C6H5) and M(0) (M=Cu, Au, Pd, Pt). As key intermediates the heterobimetallic tweezer complexes {[Ti](CCR1)(CCR2)}MCl2 (M=Cu, Pd, Pt) are formed. These reactions are strongly solvent dependent. While {[Ti](CCFc)2}CuCl2 (2) is readily formed as the main product when 1 is reacted with CuCl2 in diethyl ether, it is found that 2 affords 3a, 4 and Cu(0) on prolonged stirring in tetrahydrofuran. In contrast, complexes 5a-5c produce with equimolar amounts of CuX2 (X=Cl, Br) the compounds [Ti]X2 (3a: X=Cl, 3b: X=Br), R1CC-CCR2 (7a: R1=R2=SiMe3; 7b: R1=R2=C6H5; 7c: R1=SiMe3, R2=C6H5), {[Ti](CCR1)(CCR2)}CuX (6a: R1=R2=SiMe3, X=Cl; 6b: R1=R2=SiMe3, X=Br; 6c: R1=R2=C6H5, X=Cl; 6d: R1=SiMe3; R2=C6H5, X=Cl) as well as 1/n[CuX]n (X=Cl, Br). However, when 5a is treated with Cu(OAc)2 or Cu(acac)2 in a 1:1 ratio, heterobimetallic {[Ti](CCSiMe3)2}CuX (6e: X=OAc, 6f: X=acac) is the only isolated species. Possible mechanisms for the reactions presented are described.
Trigonal-planar-coordinated organogold(I) complexes stabilized by organometallic 1,4-diynes: Reaction behavior, structure, and bonding
K?hler, Katrin,Silverio, Sandro J.,Hyla-Kryspin, Isabella,Gleiter, Rolf,Zsolnai, Laszlo,Driess, Alexander,Huttner, Gottfried,Lang, Heinrich
, p. 4970 - 4979 (2008/10/08)
The reaction of the bis(alkynyl) titanocenes [Ti](C≡CR1)(C≡CR2) ([Ti] = (η5-C5H4SiMe3)2-Ti; 1a R1 = R2 = SiMe3; 1b R1 = R2 = tBu; 1c R1 = SiMe3, R2 = tBu) with (C5H5N)AuCl3 (2), LAuCl (5a, L = PPh3; 5b, L = SMe2) as well as (Me2S)AuR3 (6b, R3 = C≡CSiMe3; 6c, R3 = C≡C4Bu; 6d, R3 = C6H2(CF3)3-2,4,6; 6e, R3 = Me) is described. Treatment of [Ti](C≡CSiMe3)2 (1a) with (C5H5N)AuCl3 (2) produces [Ti]Cl2 (3) and Me3SiC≡C-C≡CSiMe3 (4a) together with Au(0). However, the linear two-coordinated gold(I) chlorides LAuCl (5a,b) react with 1a to afford different products, depending on the Lewis bases applied. While in the reaction of the Ph3P donor-stabilized gold(I) chloride 5a, the titanocene dichloride (3) along with (Ph3P)AuC≡CSiMe3 (6a) is obtained, with the appropriate Me2S donor-stabilized molecule 5b, the titanocene dichloride (3) along with the heterobimetallic tweezer molecule {[Ti]-(C≡CSiMe3)2}AuC≡CSiMe3 (7a) is formed. A possible mechanism for the different chemical behavior is discussed. Likewise, molecules of the latter type (compounds 7a-e) can be synthesized in much better yields by the reaction of [Ti](C≡CR1)(C≡CR2) (1a-c) with (Me2S)-AuR3 (6b-e). In the heterobimetallic titanium-gold complexes {[Ti](C≡CR1)(C≡CR2)}AuR3 (7a, R1 = R2 = SiMe3, R3 = C≡CSiMe3; 7b, R1 = R2 = tBu, R3 = C≡CtBu; 7c, R1 = SiMe3, R2 = tBu, R3 = C≡CSiMe3; 7d, R1 = R2 = SiMe3, R3 = C6H2(CF3)3-2,4,6; 7e, R1 = R2 = SiMe3, R3 = Me), a low-valent monomeric organogold(I) moiety in a trigonal-planar environment is present, which is stabilized by the chelating effect of the organometallic π-tweezer bis(alkynyl) titanocene. The thermolysis of selected organogold(I) complexes affords, on elimination of the bis(alkynyl) titanocene fragment, the coupling products R3-R3 (4) and gold films. The X-ray structure analyses of compounds 7a, 7b, and 7d are reported. It is found that in all compounds short titanium-gold bond lengths are present (7a, 3.007(2) A?; 7b, 2.975(1) A?; 7d, 2.995(1) A?). Calculations show that the complexation of the Au-R3 monomers with the organometallic π-tweezer bis(alkynyl) titanocene is described by a four-center two-electron bond. The monomeric organogold(I) moieties are stabilized by a synergetic in-plane donation and back-donation of electron density between the bis(alkynyl) titanocene and the Au-R3 species. A direct donor-acceptor Au-Ti interaction contributes to this stabilization.
