[1]Molybdarenophanes:  Strained Metallarenophanes with Aluminum, Gallium, and Silicon in Bridging Positions

Abstract

The first [1]molybdarenophanes were synthesized and structurally characterized. The aluminum and gallium compounds [(Me2Ntsi)Al(eta6-C6H5)2Mo] (2a) and [(Me2Ntsi)Ga(eta6-C6H5)2Mo] (2b) [Me2Ntsi = C(SiMe3)2(SiMe2NMe2)] were obtained from [Mo(LiC6H5)2].TMEDA and (Me2Ntsi)ECl2 [E = Al, Ga] in analytical pure form with isolated yields of 74% (2a) and 52% (2b). The silicon-bridged species [Ph2Si(eta6-C6H5)2Mo] (2c) was synthesized from [Mo(LiC6H5)2].TMEDA and Ph2SiCl2. Compound 2c was isolated as a crystalline material in an approximately 90% overall purity, from which a single crystal was used for X-ray analysis. The molecular structures of all three [1]molybdarenophanes 2a-c were determined by single-crystal X-ray analysis. The ring-tilt angle alpha was found to be 18.28(17), 21.24(10), and 20.23(29) degrees for 2a, 2b, and 2c, respectively. Variable temperature NMR measurements of 2a and 2b (-80 to 80 degrees C; 500 MHz) showed a dynamic behavior of the gallium species 2b but not of compound 2a. The dynamic behavior of 2b was rationalized by assuming that the Ga-N donor bond breaks, inversion at the nitrogen atom occurs, and a rotation of the Me2Ntsi ligand takes place followed by a re-formation of the Ga-N bond on the other side of the gallium atom. The analysis of the signals of meta and ortho protons of 2b gave approximate values of DeltaG not equal of 59.6 and 59.1 kJ mol-1, respectively. Compound 2b reacted with [Pt(PEt3)3] to give the ring-open product [(eta6-C6H6)Mo{eta6-C6H5[GaPh(Me2Ntsi)]}] (3b). The molecular structure of 3b was deduced from a single-crystal X-ray determination. The formation of the unexpected platinum-free product 3b can be rationalized by assuming that benzene reacted with 2b in a 1:1 ratio. Through a series of 1H NMR experiments with 2b it was shown that small amounts of donor molecules (e.g., THF) in benzene are needed to form 3b; in the absence of a donor molecule, 2b is thermally stable.

Understanding the Reactivity of Strained Sandwich Compounds with Aluminum or Gallium in Bridging Positions: Experiments and DFT Calculations

“…For example, for [1]chromarenophanes the difference is 1.4°[Al: 11.81(9)°; Ga: 13.24(13)°], 10c whereas for [1]molybdarenophanes, equipped with the same bridging moiety E(Me 2 Ntsi) (Chart 2), the difference amounts to 3.0°[Al: 18.28(17)°; Ga: 21.24(10)°]. 11 The measured difference of only 0.6°for [1]ruthenocenophanes 7a and 7b is surprisingly small [Al: 20.31 (19)°; Ga: 20.91 (19)°]. 12 Based on the difference of 3.0°found for [1]molybdarenophanes, the calculated difference of 3.3°for 7a and 7b matches with the expectation better than the experimentally determined difference of only 0.6°.…”

Synthesis and Reactivity of a Strained Silicon‐Bridged [1]Ferrocenophanium Ion

“…[2a, 3] An interesting class of ferrocene derivatives is represented by [n]ferrocenophanes. [5] Despite the large and rapidly increasing number of existing strained [n]ferrocenophanes, [6] only species with two or more atoms in the bridge, such as the 17-electron carbon-bridged [2]ferrocenophanium ions in 1 and 2, have been successfully synthesized by oxidation and isolated as stable salts. [5] Despite the large and rapidly increasing number of existing strained [n]ferrocenophanes, [6] only species with two or more atoms in the bridge, such as the 17-electron carbon-bridged [2]ferrocenophanium ions in 1 and 2, have been successfully synthesized by oxidation and isolated as stable salts.…”

“…[4] Among these, the most explored are strained silicon-bridged [1]ferrocenophanes or sila[1]ferrocenophanes, because of their diverse reactivity and ability to be converted into polyferrocenylsilanes (PFSs) by a variety of ring-opening polymerization (ROP) methods. [5] Despite the large and rapidly increasing number of existing strained [n]ferrocenophanes, [6] only species with two or more atoms in the bridge, such as the 17-electron carbon-bridged [2]ferrocenophanium ions in 1 and 2, have been successfully synthesized by oxidation and isolated as stable salts. [7] To date, only electrochemical studies of the one-electron oxidation of [1]ferrocenophanes have been reported.…”

The galla[1]ferrocenophane {[dimethyl(2-pyridyl)silyl]bis(trimethylsilyl)methyl-κ2C,N}(ferrocene-1,1′-diyl)gallium(III)

“…A related galla[1]ferrocenophane was published by Lund et al (2006). For related literature, see: Bellas & Rehahn (2007) ;Foucher et al (1992); Herbert et al (2007); Lund et al (2007); Osborne & Whiteley (1975); Schachner et al (2005aSchachner et al ( , 2007.…”