Triple Bonding to Germanium:  Characterization of the Transition Metal Germylynes (η⁵-C₅H₅)(CO)₂M⋮Ge-C₆H₃-2,6-Mes₂(M = Mo, W; Mes = −C₆H₂-2,4,6-Me₃) and (η⁵-C₅H₅)(CO)₂M⋮Ge-C₆H₃-2,6-Trip₂(M = Cr, Mo, W; Trip = −C₆H₂-2,4,6-i-Pr₃) and the Related Single Bonded Metallogermylenes (η⁵-

Abstract

The synthesis and characterization of several m-terphenyl stabilized germylyne transition metal complexes and related metallogermylenes are reported. The reaction of Na[M(η 5 -C 5 H 5 )(CO) 3 ] (M ) Cr, or W) with Ge(Cl)C 6 H 3 -2,6-Trip 2 (Trip ) -C 6 H 2 -2,4,6-i-Pr 3 ) below room temperature affords the metallogermylenes (η 5 -C 5 H 5 )(CO) 3 M-G ¨e-C 6 H 3 -2,6-Trip 2 (M ) Cr, 1; W, 5). However, for the analogous reaction with Na[Mo(η 5 -C 5 H 5 )(CO) 3 ], the metallogermylene was not isolated. Instead, the germylyne complex (η 5 -C 5 H 5 )(CO) 2 MotGe-C 6 H 3 -2,6-Trip 2 (3) was obtained directly with elimination of carbon monoxide. The corresponding chromium and tungsten compounds (η 5 -C 5 H 5 )(CO) 2 MtGe-C 6 H 3 -2,6-Trip 2 (M ) Cr, 2; W, 6) could be obtained by refluxing 1 or 5 in toluene or by photolysis. The related germylyne (η 5 -C 5 H 5 )(CO) 2 Wt Ge-C 6 H 3 -2,6-Mes 2 (7), as well as the recently reported molybdenum analogue (η 5 -C 5 H 5 )(CO) 2 MotGe-C 6 H 3 -2,6-Mes 2 (4), which was the first example of a triply bonded germanium species, are also described. All compounds were characterized by 1 H and 13 C NMR, UV-vis, and IR spectroscopy, and by C, H analysis. The X-ray crystal structures of 1-3, 5, and 7 have also been determined. The MtGe (M ) Cr, Mo, W) triple bonds in the germylynes are typically ca. 0.4 Å shorter than the M-Ge single bonds in the metallogermylenes. In addition, angles at germanium in the germylynes are nearly linear (range 170.9(3)-175.99(6)°) whereas in the metallogermylenes the corresponding angles are 114.7(6) and 117.8(2)°, consistent with the presence of a lone pair at germanium. The synthesis of the series of compounds 1-7 has enabled, for the first time, a comparison of single and triple bond lengths between closely related species involving the same coordination number and substituents at the heavier group 14 element.

Theoretical investigation of M≡E bonds in transition metal–ylidyne complexes trans-[H(PMe3)4M≡ER] (M = Mo, W; E = Si, Ge, Sn, Pb; R = Mes, Xylyl)

“…The first successful attempts to synthesis of the higher homologs of metalecarbyne complexes were made by power and coworkers when they isolated numerous metalegermylidyne complexes [(h 5 -C 5 H 5 )(CO) 2 MhGeR] (M ¼ Cr, Mo, W; R ¼ C 6 H 3 -2,6-Mes 2 , C 6 H 3 -2,6-Trip 2 ) [17,18]. Tilley et al reported a complex compound [(h 5 -C 5 Me 5 )(Me 3 P) 2 RuSi{(bipy)-(SC 6 H 4 -4-Me)}][OTf] 2 which can be formally described as a silylyne complex, but it has four-coordinated silicon [19].…”

Synthesis and characterization of new, modified terphenyl ligands: Increasing the rotational barrier for flanking rings

“…Their use has resulted in the stabilization of many new compound classes including the first crystalline heavier group 14 radicals (GeAr # ) 3 [24], the multiply bonded species Na 2 Ar * MMAr * (M = Ge, Sn) [25] or [K(THF) 6 ][Ar * SnSnAr * ] [26], Cp(CO) 2 M"GeAr # (M = Mo, W) [27], Cp(CO) 2 M"GeAr * (M = Cr, Mo, W) [28], trans-[Cl(PMe 3 ) 4 W"SnAr * ] [29], trans-[Br(PMe 3 ) 4 Mo" PbAr * ] [30], alkene and alkyne analogs of groups 13 and 14 elements Na 2 [Ar * GaGaAr * ] [31] and Ar 0 MMAr 0 (M = Al [21], Ga [32], In [33], Ge [17], Sn [18], Pb [19]) or the hydride (Ar * SnH) 2 [13]. Attempts to extend the range of such compounds to include boron or silicon species such as ArBBAr or ArSiSiAr have encountered problems with activation of the substituents on the flanking aryls that yield products incorporating boron [34][35][36] or silicon [37][38][39][40][41][42][43] in the rings rather than the desired multiply bonded species.…”

ipso-and para-Functionalization of meta-terphenyl ligands with substituted methyl groups: Unusual head-to-tail coupling of terphenyl moieties

“…Bulky meta-terphenyl ligands have been shown to be effective for the stabilization of numerous compounds with low coordination numbers [1][2][3][4][5][6][7], previously unknown multiple bonds [8][9][10][11][12], or heavier main group element compounds with unpaired electrons [13][14][15][16]. Usually the terphenyl ligand is attached directly to the reactive center through the ipso carbon of the central aryl ring and steric protection is provided by the flanking aryls attached at positions ortho to this carbon.…”