Synthesis and Reactivity of Boron‐, Silicon‐, and Tin‐Bridged ansa‐Cyclopentadienyl–Cycloheptatrienyl Titanium Complexes (Troticenophanes)

Abstract

A novel one-pot method was developed for the preparation of [Ti(η(5)-C(5)H(5))(η(7)-C(7)H(7))] (troticene, 1) by reaction of sodium cyclopentadienide (NaCp) with [TiCl(4)(thf)(2)], followed by reduction of the intermediate [(η(5)-C(5)H(5))(2)TiCl(2)] with magnesium in the presence of cycloheptatriene (C(7)H(8)). The [n]troticenophanes 3 (n=1), 4, 8, 10 (n=2), and 11 (n=3) were synthesized by salt elimination reactions between dilithiated troticene, [Ti(η(5)-C(5)H(4)Li)(η(7)-C(7)H(6)Li)]⋅pmdta (2) (pmdta = N,N',N',N'',N''-pentamethyldiethylenetriamine), and the appropriate organoelement dichlorides Cl(2)Sn(Mes)(2) (Mes = 2,4,6-trimethylphenyl), Cl(2)Sn(2)(tBu)(4), Cl(2)B(2)(NMe(2))(2), Cl(2)Si(2)Me(4), and (ClSiMe(2))(2)CH(2), respectively. Their structural characterization was carried out by single-crystal X-ray diffraction and multinuclear NMR spectroscopy. The stanna[1]- and stanna[2]troticenophanes 3 and 4 represent the first heteroleptic sandwich complexes bearing Sn atoms in the ansa bridge. The reaction of 3 with [Pt(PEt(3))(3)] resulted in regioselective insertion of the [Pt(PEt(3))(2)] fragment into the Sn-C(ipso) bond between the tin atom and the seven-membered ring, which afforded the platinastanna[2]troticenophane 5. Oxidative addition was also observed upon treatment of 4 with elemental sulfur or selenium, to produce the [3]troticenophanes [Ti(η(5)-C(5)H(4)SntBu(2))(η(7)-C(7)H(6)SntBu(2))E] (6: E=S; 7: E=Se). The B-B bond of the bora[2]troticenophane 8 was readily cleaved by reaction with [Pt(PEt(3))(3)] to form the corresponding oxidative addition product [Ti(η(5)-C(5)H(4)BNMe(2))(η(7)-C(7)H(6)BNMe(2))Pt(PEt(3))(2)] (9). The solid-state structures of compounds 5, 6, and 9 were also determined by single-crystal X-ray diffraction.

Synthesis, Reactivity and Ring‐Opening Polymerization of a Tin‐Bridged ansa‐Cycloheptatrienyl‐Cyclopentadienyl Titanium Sandwich Complex

“…The 13 C NMR spectrum displays three and four signals for the C 5 H 4 and C 7 H 6 carbon atoms with the ipso-carbon atoms appearing at δ = 97.2 and 87.0 ppm, respectively. [5b,22,23] The results indicate, however, a less strained structure for 2 compared with the SiMe 2 (λ max = 663 nm) [24b,24c] and SnMes 2 (λ max = 667 nm) [27] analogues. The 119 Sn NMR spectrum of the bridging tin atom in 2 shows a single resonance at δ = -50.2 ppm, which is slightly upfield shifted compared with that reported for [(η 5 -C 5 H 4 )Fe(η 5 -C 5 H 4 )]SntBu 2 (δ = -23.7 ppm).…”

“…[25b] The stanna [1]troticenophane was successfully synthesized by using sterically demanding mesityl substituents, which provide here the necessary steric protection for the isolation of the desired complex, because attempts to prepare analogous compounds by using less bulky methyl or n-butyl substituents at the tin atom afforded oily mixtures of unidentified products. [27] Furthermore, di-tert-butylstanna [1]ferrocenophane polymerizes much more rapidly than the dimesityl derivative (see above), which indicated that the tBu 2 Sn moiety in the bridge is more appropriate for ROP than Mes 2 Sn. [27] Furthermore, di-tert-butylstanna [1]ferrocenophane polymerizes much more rapidly than the dimesityl derivative (see above), which indicated that the tBu 2 Sn moiety in the bridge is more appropriate for ROP than Mes 2 Sn.…”

Preparation and characterization of Cp-functionalized cycloheptatrienyl–cyclopentadienyl titanium sandwich complexes (troticenes)

“…The magnetically equivalent Cht carbon atoms in the 13 C NMR spectra of 2, 3, 6, 7, 9, 10 and 12 are observed as singlet resonances between 85.5 (9) and 89.1 ppm (12). These values are close to that reported for the C 7 H 7 carbon NMR signal in troticene (86.4 ppm) [26]. The 13 C NMR resonance for the quaternary tBu carbon atoms in 3 is found at 36.0 ppm with 1 J( 13 Ce 117/ 119 Sn) ¼ 423.7/402.3 Hz, which falls in the expected range for a four-coordinate tin atom [33].…”

“…Recent developments involved the use of nBuLi/pmdta (pmdta ¼ N,N 0 ,N 0 ,N 00 ,N 00 -pentamethyldiethylenetriamine), affording [(h 7 -C 7 H 6 Li)Ti(h 5 -C 5 H 4 Li)]$pmdta (1a), which can conveniently be isolated as a dimeric species in crystalline form ( Fig. 2) and subsequently be employed for the preparation of troticenyldiphosphanes such as [(h 7 -C 7 H 6 PPh 2 )Ti(h 5 -C 5 H 4 PPh 2 )] (dppti) [25] and various boron-, silicon-and tin-bridged [1]-and [2]troticenophanes [26].…”

Singular Metal Activation of Diboron Compounds

“…[131][132][133][134] Conversely, oxidative addition of the BdB bond within [2]borametalloarenophanes 38 was reported to proceed smoothly and in high yields with platinum(0) phosphine complexes to give the corresponding bis(boryl)platinum(II) complexes 39 (Scheme 37). [135][136][137] Subsequent addition of these complexes to alkynes gave the ansa-bis(boryl)alkene products.…”