.eta.3 and .eta.6 Bridging cations in the N,N,N',N'',N''-pentamethyldiethylenetriamine-solvated complexes of benzylpotassium and benzylrubidium: an x-ray, NMR, and MO study

Abstract

The metalation of toluene (PhCH3) with a 1: 1 mixtureof n-BuLi/MOtBu (M = K, Rb) at ambient temperature affords orange-red powders of benzylpotassium or benzylrubidium. On addition of N,N,N',N",N"-pentamethyldiethylenetriamine (PMDTA) the precipitates dissolve to give burgundy-red solutions, from which needles of [PhCH2K-PMDTA.O.5PhCH3ln (1) or [PhCH2RbPMDTA], (2) areobtained. X-ray analysis reveals that 1 incorporates half a molecule of toluene per asymmetric unit. In both 1 and 2, the 73 and 76 interaction of one M+ cation with two benzyl fragments gives rise to the formation of polymeric chains. The coordination sphere of the cations is completed by one chelating triamine ligand. M O calculations predict multihapto metal carbon interactions to become more important from Li to Cs and substantiate the solid-state results. Ab initio calculations on three different polymers suggest that the array present in the crystal structure is the most stable. The gated decoupled 13C NMR spectrum of 1 in THF-dg solution reveals a IJ(I3C,lH) coupling constant for the benzylic carbon atom which may be interpreted in terms of a mainly planar configuration of the CH2-group in solution.

Exploiting σ/π Coordination Isomerism to Prepare Homologous Organoalkali Metal (Li, Na, K) Monomers with Identical Ligand Sets

“…Mimicking 1 and 2, the Me 6 TREN ligand in 3 ligates to the cation in a h 4 manner via its four nitrogen lone pairs, with the coordinative saturation successfully preventing polymerization such as that previously found for the PMDETA- [28] or THF-solvated [29] derivatives of benzylpotassium. Remarkably, the potassium cation shows no interaction with the CH 2 arm [K···C a separation distance = 3.893(4) ] but rather has slipped round accompanied by its multidentate Lewis donor scaffold to bind exclusively to the delocalized p system of the aromatic ring [3.097(4)-3.250(4) , av 3.156 ] resulting in a naked CH 2 head.…”

“…(2) ]. [28] The bulkier triaryl-substituted Ph 3 CK·PMDETA·THF shows no KÀC a interaction but this may also be due to extensive electron delocalization promoted by the presence of two other aromatic rings.…”

Terminal, Anionic Carbide, Nitride, and Phosphide Transition‐Metal Complexes as Synthetic Entries to Low‐Coordinate Phosphorus Derivatives

“…À salts, the anion was protonated to provide the methylidyne complex [HCMo(NtBuAr) 3 ] in high yield. After recrystallization of the methylidyne complex, deprotonation with benzylpotassium [23] led smoothly to the desired potassium salts in pure form (Scheme 1).…”

Alkali metal derivatives of an ortho-phenylene diamine

“…n-Butyl lithium was purchased from Aldrich and was used as received. The compounds PDAH2, 19 [MCH2C6H5] (M = Na-Cs), [41][42][43][44] and [MOC8H17] (M = Rb, Cs) 35 were prepared by literature procedures.…”