Utilizing Steric Bulk to Stabilize Molybdenum Aminogermylyne and Aminogermylene Complexes Jamie Hicks, † Terrance J. Hadlington, † Christian Schenk, †,‡ Jiaye Li, † and Cameron Jones* ,† † School of Chemistry, Monash University, P.O. Box 23, Melbourne, Victoria, 3800, Australia ‡ Im Neuenheimerfeld 270, Anorganische Chemie, Universitä t Heidelberg, 69120, Heidelberg, Germany *S Supporting Information ABSTRACT: Two extremely bulky bis(aryl)amines, HN(Ar*)- (Ph) (HL Ph ) and HN(Ar*)(Mes) (HL Mes ) (Ar* =C 6 H 2 {C(H)- Ph 2 } 2 Me-2,6,4; Mes = mesityl), have been prepared by palladium- catalyzed cross-coupling reactions and structurally characterized. These have been utilized in the preparation of the amido- germanium(II) chlorides, [L Ph GeCl] and [L Mes GeCl]. Reactions of these, and the known complex, [L′GeCl] (L′ = -N(Ar*)(SiMe 3 )), with Na[CpMo(CO) 3 ] have afforded the first examples of structurally characterized two-coordinate molybdenum substituted germylenes, [Cp(CO) 3 MoGeN(Ar*)(R)] (R = SiMe 3 or Ph). The former readily eliminates a molecule of CO when heated or irradiated with UV light to give an unprecedented amino- germylyne complex, [Cp(CO) 2 MoGeN(Ar*)(SiMe 3 )]. The spectroscopic and structural data for this complex, in combination with the results of computational studies, show that this compound is best viewed as having a bent Mo-Ge “triple” bond, with little multiple bond character to its Ge-N interaction. Computational studies have also indicated that the Mo-Ge-N bending in the complex is due to the extreme steric bulk of its amido substituent. ■ INTRODUCTION The chemistry of transition-metal carbyne complexes, L n M CR, is extensively developed and such species have found numerous synthetic and other applications. 1 In recent years, considerable efforts have been made to extend this work to the preparation of heavier group 14 analogues of this important compound class, viz. the transition-metal tetrelynes L n MER (E = Si, Ge, Sn, or Pb), and to investigate their chemistry. 2 These studies have largely been restricted to the group 6 metals, and examples of complexes are now known that incorporate triple bonds between those metals and all of the heavier group 14 elements. In all cases, sterically bulky aryl or alkyl substituents are required to kinetically stabilize the ME bonds of the complexes. It is interesting to note that, whereas complexes of the type, L n MER, invariably have essentially linear MEC fragments, the closely related heavier alkyne analogues, REER, have trans-bent CEE fragments and decreasing EE bond orders (ranging from below 3 to close to 1) as the group is descended. 3 Related to carbyne complexes are transition-metal amino- carbynes, L n MCNR 2 . However, as these have planar amino substituents, their bonding typically exhibits a significant contribution from their 2-azavinylidene canonical form, L n - MCN + R 2 . 4 While this can affect the π-acidity and reactivity of the aminocarbyne ligand relative to that of organocarbynes, transition-metal aminocarbyne complexes do have synthetic value. Because of this, and because of the increasing interest in transition-metal tetrelynes, we sought to prepare examples of closely related aminotetrelyne complexes, L n MENR 2 , which, to the best of our knowledge, are unknown. At the outset of this study, it was clear that amino substituents of considerable steric bulk would be required to stabilize these target molecules. In this respect, we have recently developed an extremely bulky class of amido ligands, for example, N(Ar*)(SiMe 3 ) L′ (Ar*= C 6 H 2 {C(H)Ph 2 } 2 Me- 2,6,4), 5 which we believed would fit the bill. These ligands have allowed us entry to a variety of unprecedented low coordinate group 13 and 14 metal amide complexes, which include one-coordinate group 13 metal(I) amides, [L′M:] (M = Ga, In, or Tl), 6 monomeric chloro-tetrelenes [L′ECl] (E = Ge or Sn), 5 a singly bonded amido-digermyne [L′Ge-GeL′], 7 the low coordinate metal(II) cations [L′E:] + (E = Ge or Sn), 8 and the acyclic boryl-germylene [L′Ge{B(DAB)}] (DAB = {DipNCH} 2 ; Dip = C 6 H 3 Pr i 2 -2,6). 9 Here, we report the use of such bulky amides in the preparation of the first example of a transition-metal aminotetrelyne, and two related metallo- germylene complexes. ■ RESULTS AND DISCUSSION The first report of a transition-metal germylyne complex, [Cp(CO) 2 MoGeAr′] (Ar′ =C 6 H 3 Mes 2 -2,6; Mes = mesityl), came from the group of Power. 2a This compound was readily prepared via the elimination of NaCl and CO below 0 °C in the reaction of the terphenyl substituted chloro-germylene, [Ar′GeCl], with Na[CpMo(CO) 3 ]. Considering that we have previously shown that our bulky amide ligands, for example, L′, have similar steric profiles and stabilizing properties to Received: November 26, 2012 Article pubs.acs.org/Organometallics © XXXX American Chemical Society A dx.doi.org/10.1021/om301144h | Organometallics XXXX, XXX, XXX-XXX