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Vinylsilanes are very useful building blocks in organic synthesis and have widespread applications in life sciences and materials chemistry. Here we describe the potential of complex cis‐[Fe(PCP‐iPr)(CH2CH2CH3)(CO)2] as an effective catalyst for the hydrosilylation of both terminal and internal alkynes with SiPhH3 to give vinylsilanes. The reactions were typically performed with a catalyst loading of 1 mol% for 24 h at 70 °C. The catalytic reaction is initiated by migratory insertion of a CO ligand into the Fe─alkyl bond to yield an acyl intermediate, which reacts with silanes to form the 16e− Fe(II) silyl catalyst [Fe(PCP‐iPr)(SiPhH2)(CO)]. In the case of aliphatic terminal alkynes good regioselectivity (anti‐Markovnikov addition) toward the thermodynamically more stable β‐(E)‐vinylsilanes in ratios of up to 10:90 was achieved, while for aromatic alkynes the selectivities were poor with ratios of β‐(Z)‐ to β‐(E)‐vinylsilanes of about 40:60. With internal unsymmetrical alkynes, the two possible regioisomers of the syn‐addition of SiPhH3 were obtained in different ratios with no clear trend toward one regioisomer. Internal symmetrical alkynes yielded exclusively the respective syn‐products in high yields. Mechanistic investigations including deuterium labelling studies were undertaken to provide a reasonable reaction mechanism. [ABSTRACT FROM AUTHOR]

Efficient hydrogenations of terminal alkenes with molecular hydrogen catalyzed by well‐defined bench stable Mn(I) complexes containing an N‐heterocyclic carbene‐based PCP pincer ligand are described. These reactions are environmentally benign and atom economic, implementing an inexpensive, earth abundant non‐precious metal catalyst. A range of aromatic and aliphatic alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation proceeds at 100 °C with catalyst loadings of 0.25–0.5 mol %, 2.5–5 mol % base (KOtBu) and a hydrogen pressure of 20 bar. Mechanistic insight into the catalytic reaction is provided by means of DFT calculations. [ABSTRACT FROM AUTHOR]

Treatment of [Co2(CO)8] with the ipso-substituted P(C-X)PY ligands (X = Br, Cl; R = iPr, tBu) bearing Y = NH and CH2 linkers under solvothermal conditions affords the five-coordinate Co(I) and Co(III) complexes [CoI(PCPY-R)(CO)2] and [CoIII(PCPY-R)X2]. The later are paramagnetic exhibiting a solution magnetic moment in the range of 3.0–3.3 μB which is consistent with a d6 intermediate spin system corresponding to two unpaired electrons. In the case of P(C-X)PY ligands (X = Br, Cl; R = tBu; Y = NH) the formation of the square planar Co(II) complex [Co(PCPNH-tBu)X] was favored. This complex gives rise to a magnetic moment of 1.8 μB being consistent with a d7 low spin system corresponding to one unpaired electron. All complexes are characterized by means of spectroscopic techniques (NMR, IR), HR-MS. Representative complexes were also characterized by X-ray crystallography. [ABSTRACT FROM AUTHOR]

A new pyrazole-derived PCP pincer ligand featuring a 1-methylpyrazole backbone tethered to two di(isopropyl)phosphine moieties via phenylene spacers (P(CH)P-iPr) was prepared. When reacting the ligand with group six carbonyl complexes [M(CO)6] (M = Cr, Mo, W) at 130 °C, complexes of the type [M(κ2PN-PCP-iPr)(CO)4] were obtained featuring a κ2P,N-bound ligand with a pendant phosphine arm. Upon an increase of the reaction temperature to 150 °C, in the case of molybdenum, the formation of the complex [Mo(κ3PCP-PCP-iPr)(CO)3] was observed featuring a weak Mo–C bond. DFT calculations reveal that there is no agostic η2-C–H interaction. Treatment of [Mn2(CO)10], [Fe2(CO)9], [Co2(CO)8] and [Ni(COD)2] afforded complexes [Mn(κ3PCP-PCP-iPr)(CO)3], [Fe(κ3PCP-PCP-iPr)(H)(CO)2], [Co(κ3PCP-PCP-iPr)(CO)2] and [Ni(κ3PCP-PCP-iPr)(H)], respectively, where the PCP ligand is coordinated in the typical meridional κ3-fashion. Postfunctionalization of the anionic PCP pincer ligand was possible via N-methylation of the second nitrogen atom of the pyrazole unit with the oxonium salt [Me3O]BF4. Treatment of [Mn(κ3PCP-PCP-iPr)(CO)3] and [Fe(κ3PCP-PCP-iPr)(H)(CO)2] with [Me3O]BF4 resulted in the formation of the cationic complexes [Mn(κ3PCP-PCPMe-iPr)(CO)3]+ and [Fe(κ3PCP-PCPMe-iPr)(Cl)(CO)2]+. In the case of the latter, the chloride ligand seems to originate from the solvent CH2Cl2 undergoing a hydride chloride exchange. All complexes were characterized by means of 1H, 13C{1H}, and 31P{1H} NMR spectroscopy, IR spectroscopy and HR-MS. In addition, the structures of representative complexes were determined by X-ray crystallography. [ABSTRACT FROM AUTHOR]