The iron hydride complexes bearing a Si−H or a Ge−H functional group in a ligand [2,5-SiPh 3 -3,4-butylene-(η 5 -C 4 COEEt 2 H)]Fe(CO) 2 H (E = Si (4), Ge (5)) and [2,5-SiPh 3 -3,4-butylene-(η 5 -C 4 COSiMe 2 OSiMe 2 H)]Fe(CO) 2 H (6), were synthesized in the reaction of the iron acetonitrile complex [2,5-SiPh 3 -3,4-butylene-(η 4 -C 4 CO)]Fe(CO) 2 (NCCH 3 ) (3) with Et 2 EH 2 or HSiMe 2 OSiMe 2 H. These complexes did not hydrogenate a polar unsaturated bond in either ketones or aldehydes but did hydrogenate a nonpolar unsaturated bond in alkynes and alkenes to give alkenes and alkanes selectively. These complexes also catalyzed a transfer hydrogenation reaction from isopropyl alcohol (IPA) to alkynes and alkenes.T he hydrogenation reaction of unsaturated bonds promoted by a transition-metal catalyst is one of the most fundamental transformations in organic synthesis. Most hydrogenation reactions promoted by a transition-metal catalyst proceed via insertion of an unsaturated bond (R 2 CX, where X stands for CR′ 2 , NR′, O) into a metal−hydrogen bond to give M−X−CHR 2 followed by a coupling of the X−CHR 2 moiety and a hydride on M which is produced in the reaction of M with H 2 (Figure 1a). A metal−ligand bifunctional catalyst is another type of hydrogenation catalyst and is effective for catalytic hydrogenation of unsaturated organic compounds in the presence of H 2 and for a transfer hydrogenation reaction from HCOOH or isopropyl alcohol (IPA) as alternative hydrogen sources. The Shvo complex was the first example of a metal−ligand bifunctional catalyst that has Ru−H and O−H functional groups. 1 Since its discovery in 1986, various types of metal− ligand bifunctional complexes have been developed. 2−5 These complexes are characterized by two kinds of active hydrogen atoms: one bonded to a metal as a hydride and the other bonded to an oxygen or a nitrogen atom in its ligand as an acidic proton.
All manipulations were carried out using standard Schlenk techniques under a nitrogen atmosphere. Methyl iron complex CpFe(CO) 2 (Me) (1) 1 and Et 3 SnH 2 were prepared according to the literature methods. Benzene, hexane, ether and THF were distilled from sodium and benzophenone prior to use and stored under nitrogen. The other chemicals except ( c Hex) 2 GeH 2 and (PhCH 2 ) 2 GeH 2 were purchased. NMR spectra ( 1 H, 13 C{ 1 H} and 29 Si{ 1 H}) were recorded on a JEOL JNM-AL 400 spectrometer. 1 H and 13 C{ 1 H} NMR data were referred to residual peaks of solvent as an internal standard. Peak positions of the 29 Si{ 1 H} NMR spectra were referenced to an external Me 4 Si. IR spectra were recorded on a Perkin Elmer FTIR-Spectrum one.Elemental analysis data were obtained on a Perkin−Elmer 2400 CHN elemental analyzer. Highresolution mass spectra (HRMS) were recorded on a JMS-700T spectrometer. Characterizations of cyclotrigermoxanes were carried out by SYNAPT G2 High Definition Mass Spectrometry (SYNAPT TM HDMS TM ), and the analysis of MS revealed that no other oligomers or polymers were formed in the cyclization of secondary germane.With secondary germanes, Et 2 GeH 2 , n Bu 2 GeH 2 , and Ph 2 GeH 2 can be purchased, but ( c Hex) 2 GeH 2 , and (PhCH 2 ) 2 GeH 2 have not been prepared to date. Therefore, we newly prepared and identified as follows.
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