Reactivity of Monomeric N→Ge Coordinated Germanium(II) Hydrides

Abstract

Monomeric organogermanium(II) hydrides {(LGeH)M-(CO) 5 } (M = Cr (1), W (2), L = [2-(CH 2 NEt 2 )-4,6-tBu 2 -C 6 H 2 ] -) were treated with ortho-quinones and terminal alkyne HC≡CCO 2 Me to give {[(LH)Ge(κ 2 -O 2 -3,5-tBu 2 C 6 H 2 )]M(CO) 5 } (M = Cr (3), W (4)), {[(LH)Ge(κ 2 -O 2 -3,4,5,6-Cl 4 C 6 )]M(CO) 5 } (M = Cr (5), W (6)) and {[LGeCH=CH(COOMe)]Cr(CO) 5 } (11). These reactions proceeded as catalyst-free reductions of C=O and C≡C bonds. Experimental data demonstrated zwitterionic character of Ge(II) complexes 3-6, where the 1,3,2-benzodioxagermylenolato anion involving the GeO 2 C 2 five membered ring coordinates the M(CO) 5 frag- [a]

Molecular Main Group Metal Hydrides

“… Five years later, the Jambor group prepared the arylamine-chelated Ge­(II) hydrides [{2,4,6-(Et 2 NCH 2 ) t Bu 2 C 6 H 2 }­GeH·M­(CO) 5 ] [M = Cr ( 960 ), W ( 961 )], participated in cyanide/hydride exchange with t BuNC, as a cyanide equivalent, to yield the corresponding cyano complexes [{2,4,6-(Et 2 NCH 2 ) t Bu 2 C 6 H 2 }­GeCN·M­(CO) 5 ] [M = Cr ( 962 ), W ( 963 )] and t BuH (Scheme ). The same group reported the cycloaddition of orthoquinones to the Ge­(II) centers in 960 and 961 , a process that is accompanied by migration of a hydrogen atom from Ge to the pendant −NEt 2 group; the resulting products ( 964 – 967 ) were shown to exist in equilibrium with tautomeric hydroxides, as shown to the right of Scheme . The Cr­(CO) 5 -supported germanium­(II) hydride [{2,4,6-(Et 2 NCH 2 ) t Bu 2 C 6 H 2 }­GeH·Cr­(CO) 5 ] ( 960 ) could hydrogermylate HCCC­(O)­OMe to give the alkenyl product [{2,4,6-(Et 2 NCH 2 ) t Bu 2 C 6 H 2 }­Ge­{C­(H)=CH­(C­(O)­OMe)}·Cr­(CO) 5 ] ( 968 ) .…”

“…The same group reported the cycloaddition of orthoquinones to the Ge­(II) centers in 960 and 961 , a process that is accompanied by migration of a hydrogen atom from Ge to the pendant −NEt 2 group; the resulting products ( 964 – 967 ) were shown to exist in equilibrium with tautomeric hydroxides, as shown to the right of Scheme . The Cr­(CO) 5 -supported germanium­(II) hydride [{2,4,6-(Et 2 NCH 2 ) t Bu 2 C 6 H 2 }­GeH·Cr­(CO) 5 ] ( 960 ) could hydrogermylate HCCC­(O)­OMe to give the alkenyl product [{2,4,6-(Et 2 NCH 2 ) t Bu 2 C 6 H 2 }­Ge­{C­(H)=CH­(C­(O)­OMe)}·Cr­(CO) 5 ] ( 968 ) . Recently, Ruzicka and coworkers prepared a series of dimeric hydridoborate Ge­(II) complexes {[{2,4,6-(Et 2 NCH 2 ) t Bu 2 C 6 H 2 }­GeH­(R)]­[Li­(THF) 2 ]} 2 (R = Ph ( 970 ), n Bu ( 971 ), and t Bu ( 972 )) according to the procedure outlined at the bottom of Scheme ; notably, the phenylated germanide {[{2,4,6-(Et 2 NCH 2 ) t Bu 2 C 6 H 2 }­GeH­(Ph)]­[Li­(THF) 2 ]} 2 ( 970 ) can be used as a soluble source of hydride for the reduction of ketonic and imine substrates …”

“…1155 The same group reported the cycloaddition of orthoquinones to the Ge(II) centers in 960 and 961, a process that is accompanied by migration of a hydrogen atom from Ge to the pendant −NEt 2 group; the resulting products (964− 967) were shown to exist in equilibrium with tautomeric hydroxides, as shown to the right of Scheme 146. 1156 The Cr(CO) (970) can be used as a soluble source of hydride for the reduction of ketonic and imine substrates. 29 Kinjo and coworkers prepared the isolable germaborene complex [{MesBN(Ad)CHCHC(SiMe 3 ) 2 }GeB−N-(SiMe 3 ) 2 ] (973) and showed that this species could activate H 2 in a step-wise fashion, to first yield the formal 1,2-addition of H 2 across the GeB π-bond to form 974 (at room temperature), followed by hydrogenolysis at 60 °C of the remaining Ge−B single bond to afford the dihydrogermane 975 and H 2 BN(SiMe 3 ) 2 as end-products (Scheme 147).…”

“…3 Si) 2 CH}Sb(H)-Sb(H)-{CH(SiMe 3 ) 2 }] (1158) by reaction of alkyl dichlorostibine {(Me 3 Si) 2 CH}SbCl 2(1156) withLi[AlH 4 ] (eq 98) 1249. When a solution of 1156 in Et 2 O was added to Li[AlH 4 ], the expected primary stibine {(Me 3 Si) 2 CH}SbH 2(1157) was isolated as a colorless liquid in a 69% yield; however, when the order of addition is reversed, [{(Me 3 Si) 2 CH}Sb(H)-Sb(H)-{CH(SiMe 3 ) 2 }] (1158) was isolated in a 83% yield.…”

(N),C,N‐Coordinated Heavier Group 13–15 Compounds: Synthesis, Structure and Applications

“…In the case of N ‐coordinated germylenes, the monomeric complexes {(Ar CN *GeH)M(CO) 5 } (M=Cr, W) with the terminal Ge−H bond were prepared . These compounds were reacted with ortho ‐quinones or terminal alkyne HC≡CCO 2 Me (Scheme ) and the reduction of C=O and C≡C bonds was observed without catalyst providing {[(Ar CN * H )Ge(κ 2 ‐O 2 ‐3,5‐ t Bu 2 C 6 H 2 )]M(CO) 5 }, {[(Ar CN * H )Ge(κ 2 ‐O 2 ‐3,4,5,6‐Cl 4 C 6 )]M(CO) 5 } (M= Cr, W) or {[Ar CN *GeCH=CH(COOMe)]Cr(CO) 5 } (Scheme ) . In contrast, the reaction with t BuNC provided {(Ar CN *GeCN)M(CO) 5 } (M=Cr, W) as the product of the C−N bond cleavage …”