Dilithiation of Bis(benzene)molybdenum and Subsequent Isolation of a Molybdenum-Containing Paracyclophane

Abstract

The homoleptic sandwich complex bis(benzene)molybdenum, [Mo(eta6-C6H6)2], was successfully dilithiated by employing an excess of BuLi in the presence of N,N,N',N'-tetramethylethylenediamine (up to 6 equiv each) at slightly elevated temperatures furnishing the highly reactive, ring metalated species [Mo(eta6-C6H5Li)2].tmeda in high yields. Alternatively, this compound was synthesized upon prolonged sonication with 5 equiv of tBuLi/tmeda without heating. An X-ray crystal structure determination revealed a symmetrical, dimeric composition in the solid state, i.e., a formula of [Mo(eta6-C6H5Li)2]2.(thf)6, where the six-membered rings are connected by two pairs of bridging lithium atoms. The synthesis of an elusive ansa-bridged complex failed in the case of a [1]bora and a [1]sila bridge due to the thermal lability of the resulting compounds. Instead, reverse addition of the dilithio precursor to an excess of the appropriate element dihalide facilitated the isolation of several unstrained, 1,1'-disubstituted derivatives, namely, [Mo{eta6-C6H5(BN(SiMe3)2X)}2] (X = Cl, Br) and [Mo{eta6-C6H5(SiiPr2Cl)}2], respectively. However, the incorporation of a less congesting [2]sila bridge was accomplished. In addition to the formation of [Mo{(eta6-C6H5)2Si2Me4}], a molybdenum-containing paracylophane complex was isolated and characterized by means of crystal structure analysis. The ancillary formation of 1 equiv of bis(benzene)molybdenum strongly suggests that this species is generated by deprotonation of the ansa-bridged complex by the dilithiated precursor and subsequent reaction with a second equivalent of the disilane.

Intramolecular Activation of a Disila[2]molybdenocenophanedihydride: Synthesis and Structure of a [1],[1]Metalloarenophane

“…[6d, 8] Irradiation of a solution of 1 in [D 6 ]benzene afforded 3 with concomitant evolution of gaseous H 2 . Monitoring the reaction by 1 H NMR spectroscopy revealed the absence of any soluble byproducts, thus indicating quantitative conversion.…”

Insertion of [Pt(PEt3)2] into a Strained Si−C Bond of Diphenylsila[1]molybdarenophane

“…The rms deviation from a plane of the five atoms Pt1, P1, P2, C1, and Si1 is 0.0599 Å , with the largest individual deviation of 0.0717(14) Å found for P2, illustrating a planar coordination of the d 8 metal cation. The Si atom is in a distorted tetrahedral environment, with angles spanning from 98.9(2)°(C7-Si1-C13) to 117.56 (16)…”

“…Independent of our work, Braunschweig et al had attempted the synthesis of sila[1]molybdarenophanes using Ph 2 SiCl 2 , iPr 2 SiCl 2 , and Me 2 SiCl 2 before but did not find any direct evidence for the formation of the targeted species. 16 Only in the case of iPr 2 SiCl 2 had a product been identified, the 1,1 0 -disubstituted bis(benzene)molybdenum derivative [{(CliPr 2 Si)C 6 H 5 } 2 Mo], and its synthesis was subsequently optimized. We had shown that species 1 can be obtained, with the main impurities presumably being 1,1 0 -disubstitued bis(benzene)molybdenum species.…”

Dichlorodiisopropylsilane

“…26-28 For example, the bis(benzene)molybdenum complex was metalated with 2 equiv t-BuLi to give the diionic intermediate 10, which was subjected to react with i-Pr 2 SiCl 2 to give complex 11; the yield of the latter step is 37% (eq 10). 28 …”