Controlling Catenation in Germanium(I) Chemistry through Hemilability

Abstract

We present anovel approach for constructing chains of Group 14 metal atoms linked by unsupported metal-metal bonds that exploits hemilabile ligands to generate unsaturated metal sites.T he formation/nature of catenated species (oligodimetallynes) can be controlled by the use of (acidic/basic) "protecting groups" and through variation of the ligand scaffold.Reduction of Ar NiPr2 GeCl (Ar NiPr2 = 2,6-( i Pr 2 NCH 2 ) 2 C 6 H 3 )-featuring hemilabile N i Pr 2 donors-yields (Ar NiPr2 Ge) 4 (2), which contains at etrameric Ge 4 chain. 2 represents an ovel type of al inear homo-catenated Ge I compound featuring unsupported E À Eb onds.T rapping experiments reveal that ak ey structural component is the central two-way Ge = Ge donor-acceptor bond:r eactions with IMe 4 and W(CO) 5 (NMe 3 )g ive the base-or acid-stabilized digermynes (Ar NiPr2 Ge(IMe 4 )) 2 ( 4)and (Ar NiPr2 Ge{W(CO) 5 }) 2 (5), respectively.The use of smaller N-donors leads to stronger Ge-N interactions and quenchingo fc atenation behaviour: reduction of Ar NEt2 GeCl gives the digermyne (Ar NEt2 Ge) 2 , while the unsymmetrical system Ar NEt2 GeGeAr NiPr2 dimerizes to give tetranuclear (Ar NEt2 GeGeAr NiPr2 ) 2 through aggregation at the N i Pr 2 -ligated Ge I centres.

Reversible Uptake of CO2 by Pincer Ligand Supported Dimetallynes

“… Exploiting hemi‐lability in dimetallynes to control access to two‐coordinate Group 14 metal centres: applications in a) catenation; [13] b) reversible E−H bond activation; [14] and c) reversible CO 2 capture (this work).…”

“…In recent work we have begun to probe the applications of low‐valent main group complexes featuring hemi‐labile ancillary donors. Within Group 14 chemistry, such ligands offer a means of manipulating access to the reactive metal centres found in two‐coordinate metallylenes [13, 14] . This approach can be exploited i) to generate extended chains of Ge I centres akin to oligo‐acetylenes through the formation of Lappert‐type double bonds between “decomplexed” metal centres (Scheme 2a); [13, 15] and ii) to facilitate reversible bond activation via oxidative addition/reductive elimination at Sn I (Scheme 2b) [14] …”

“…The reactions of the pincer‐ligand supported dimetallynes (Ar E) 2 ( 1 ‐Ge 2 (E=Ge); [13] 1 ‐Sn 2 (E=Sn, see Supporting Information); where Ar =C 6 H 3 (CH 2 NEt 2 ) 2 ‐2,6) with CO 2 proceed rapidly at −30 °C, leading to the loss of the distinctive colour associated with the starting material (orange/red, respectively). The pale yellow (E=Ge) or colourless (E=Sn) products are characterized by an additional low‐field 13 C NMR resonance (at δ C =206.0 and 220.6 ppm, respectively), [8, 12] and, in the case of the tin system, by the appearance of two new 119 Sn resonances at δ Sn =80.9 and 90.4 ppm (cf.…”