Carbene Complexes Based on Dilithium Methandiides

Abstract

In the last 15 years, methandiide ligands have given access to a new class of carbene complexes with unique electronic properties. The metal-carbon interactions in these complexes cover a range of bonding situations, from highly polar interactions to metal-carbon double bonds. This flexibility has allowed the isolation of complexes with metals covering the whole periodic table, including metals that had long been reluctant to form multiple bonds with carbon atoms. Thus, recent years have seen the revelation of many unusual carbene species with interesting reactivities. In this microreview, we focus on the latest developments in the chemistry of me-

Methanediide Formation via Hydrogen Elimination in Magnesium versus Aluminium Hydride Complexes of a Sterically Demanding Bis(iminophosphoranyl)methanediide

“…Three-coordinated Mg complexes with terminal nBu-groups are rare and are best described for the β-diketiminate class of ligand that allows some comparison with the sterics of HL − . Comparable monomeric complexes of [{HC(RCNAr) 2 }MgnBu] with an overall molecular structure similar to 1 were found for R = Me and Ar = 2,6-(Ph 2 CH) 2 -4-MeC 6 H 2 (≡ Ar*) [27], and R = tBu and Ar = Dip [28]. For the respective complex with R = Me and Ar = Dip [29] and smaller β-diketiminates, molecular structures with bridging nBu groups and four-coordinate Mg centres were found.…”

“…For the respective complex with R = Me and Ar = Dip [29] and smaller β-diketiminates, molecular structures with bridging nBu groups and four-coordinate Mg centres were found. Thus, the steric profile of HL − , at least when coordinated to Mg, can be approximately compared with [{HC(tBuCNDip) 2 were found for R = Me and Ar = 2,6-(Ph2CH)2-4-MeC6H2 (≡ Ar*) [27], and R = tBu and Ar = Dip [28]. For the respective complex with R = Me and Ar = Dip [29] In analogy to the synthesis of a sterically less hindered methanediide Mg complex of type B (M = Mg, E = NSiMe3) [16], which was synthesized at 140 °C using MgnBu2, we heated [HLMgnBu] 1 to various high temperatures (up to 200 °C) though only obtained a complex product mixture were found for R = Me and Ar = 2,6-(Ph2CH)2-4-MeC6H2 (≡ Ar*) [27], and R = tBu and Ar = Dip [28].…”

“…Complexes of methanediides (methandiides) that derive from P-oxidized bis(diphenylphosphino)methane species with electropositive metals have especially attracted widespread interest in recent years [2][3][4][5][6][7][8]. In these complexes, the dianionic bis(diphenylphosphoranyl)methanediide fragment A shows overall delocalization of the charge across the EPCPE fragment with a simplified charge distribution as shown in Figure 1.…”

“…This delocalization allows the deprotonation of both hydrogen atoms of the central CH 2 unit of the substituted "methane" pro-ligand with suitable strong bases. Methanediides show several bonding modes containing typically one or two coordinated metal centres [2][3][4][5][6][7][8]. Over the past years, several examples of alkaline earth metal complexes of substituted bis(phosphoranyl)methanides and -methanediides have been forthcoming [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] that show several coordination types B-E, see Figure 1.…”

Synthesis and Characterization of a Sulfonyl- and Iminophosphoryl-Functionalized Methanide and Methandiide

“…This is mainly due to their applicability as ligands for the preparation of carbene-type complexes by simple salt metathesis reactions [1][2][3]. Thereby, methandiides revealed to be highly efficient ligand systems stabilizing a variety of carbene complexes with main group metals [4][5][6][7], early and late transition metals [8][9][10][11][12] as well as lanthanides and actinides [13][14][15][16].…”