Cationic Group 4 Metallocene–(o‐Phosphanylaryl)oxido Complexes: Synthetic Routes to Transition‐Metal Frustrated Lewis Pairs

Abstract

Synthetic routes to cationic group 4 metallocene-(o-phosphanylaryl)oxido compounds of the type [Cp R 2 M(O ∧ PR 2 )]-[WCA] (M = Ti, Zr, Hf; WCA = weakly coordinating anion) are described. The neutral mono-methyl complexes [Cp R 2 ZrMe(O ∧ PR 2 )] 1-6 [Cp R = Cp (1-3) or Cp* (4); O ∧ PR 2 = o-OC 6 H 4 (PtBu) 2 (1 and 4), OCMe 2 CH 2 (PtBu) 2 (2) or OC(CF 3 ) 2 -CH 2 (PtBu) 2 (3)] are prepared by protonolysis of [Cp R 2 ZrMe 2 ] by the parent alcohol. The remaining methyl group in such complexes is best removed by protonolysis with [DTBP]-[B(C 6 F 5 ) 4 ] (DTBP = 2,6-di-tert-butylpyridinium) to yield the desired cationic complexes 7 and 8 in the case of 1 and 4. In Eur. J. Inorg. Chem. 2012, 1546-1554

Frustrated Lewis Pairs

“…179 This situation is highly reminiscent of bifunctional transition metal catalysts. In this regard it is also important to draw attention to transition metal based FLPs in which metal centers with pendant donors activate a range of small molecule substrates, which has been explored by the groups of Wass [126][127][180][181][182][183] and Erker 128-129,184-188 among others. 130 The concept of FLPs has also been exploited to describe a variety of systems that activate small molecules.…”

Insertion Reactions of Neutral Phosphidozirconocene Complexes as a Convenient Entry into Frustrated Lewis Pair Territory

“…Until recently, intramolecular Zr + /P FLPs were synthesised by the following methods: 1) protonolysis of a Zr−Me bond with a functionalised phosphane followed by Zr + formation with a suitable electrophile [Scheme , Eq. (1)];–, or 2) insertion of a phosphaalkyne into the Zr−Me bond of a zirconocene cation [Scheme , Eq. (2)] ,,.…”

Unexpected Selective Methyl Group Abstractions from SiMe3 Moieties of CH2SiMe3 Ligands To Give New Cationic Titanium Complexes

“…[21,22] As ac onsequence of the methyl group abstraction from the SiMe 3 functionalg roup, two signals for the two remaining methyl groups at the silicon atom are observed, localized at d 1 H = À0. 27 Figure S19). Althought he low-field shift in the 29 Si NMR spectrum of above 40 ppm in comparison with that of complex 2 is significant, for silylium ions, more pronounced low-field shifts are observed, even when they are donor-stabilized (Scheme 4).…”

“…[12c-f,27] The 1 H/15 NHMBC spectrumo fc omplex 6a reveals coupling of the nitrogen signal with ac hemical shift of 323.1 ppm to one of the signals of the methyleneg roup (d 1 H = 3.03 ppm (d, H,H = 10.9 Hz, 1H)/d 13 C{ 1 H} = 76.9 ppm) and to both methyl groups of the remaining SiMe 2 moiety (d 1 H = À0.46 and 0.27 ppm/d 13 C{ 1 H} = 4.5 and 8.8 ppm), which proves the occurred ring closure (see the Supporting Information, Figures S42 and S48). The shift to lower field in the 13 C{ 1 H} NMR spectrum of the TiCH 2 unit of over 45 ppm in comparison with that of the starting complex 5a underlines the changed chemical environment.…”