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In this study, two [PCP] pincer silylene cobalt(I) complexes [((Ph2POCH2)2CH)Co(PMe3)(SiCl((NtBu)2CAr))] (Ar = Ph (2) and 4-MePh (3)) were synthesized through the substitution reaction of the [PCP] pincer cobalt(I) complex [((Ph2POCH2)2CH)Co(PMe3)2] (1) with silylene ligands: SiCl((NtBu)2CAr) (Ar = Ph (L1) and 4-MePh (L2)). The reaction of complex 2 with CO afforded the carbonyl silylene cobalt(I) complex [((Ph2POCH2)2CH)Co(CO)(SiCl((NtBu)2CPh))] (4), while complex 2 reacted with CH3I to give rise to cobalt(II) iodide [((Ph2POCH2)2CH)Co(I)(PMe3)] (6). With a catalyst loading of 2 mol%, complex 6 displayed efficient catalytic activity for hydrosilylation of alkenes by using Ph2SiH2 as the hydrogen source under mild conditions. The molecular structures of complexes 2, 3, 4 and 6 were determined by single crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Polyfluorinated aryl imines 2,4,5-R1,R2,R3-C6H2-HC=N-1-C10H7 (R1 = F, R2 = F, R3 = H (1); R1 = F, R2 = H, R3 = F (2) and R1 = F, R2 = F, R3 = F (3)) and F5C6-HC=N-1-C10H7 (7) reacted with CoMe(PMe3)4 to give rise to hydrido [CNC]-pincer cobalt(iii) complexes (2,4,5-R1,R2,R3-C6H-HC=N-1-C10H6)Co(H)(PMe3)2 (R1 = F, R2 = F, R3 = H (4); R1 = F, R2 = H, R3 = F (5); R1 = F, R2 = F, R3 = F (6)) and (F4C6-HC=N-1-C10H6)Co(H)(PMe3)2 (8) via selective C–F/C–H bond activation. Penta-coordinate dicarbonyl cobalt(i) complexes (2,4,5-R1,R2,R3-C6H-HC=N-1-C10H7)Co(CO)2(PMe3) (R1 = F, R2 = H, R3 = F (9); R1 = F, R2 = F, R3 = F (10)) were obtained from reactions of hexa-coordinate cobalt(iii) complexes 5 and 6 with carbon monoxide through reductive elimination. Cobalt(iii) halides (2,4,5-R1,R2,R3-C6H-HC=N-1-C10H6)Co(i)(PMe3)2 (R1 = F, R2 = F, R3 = H (11); R1 = F, R2 = H, R3 = F (12); R1 = F, R2 = F, R3 = F (13)) and (2,4,5-R1,R2,R3-C6H-HC=N-1-C10H6)Co(Br)(PMe3)2 (R1 = F, R2 = F, R3 = H (14); R1 = F, R2 = H, R3 = F (15); R1 = F, R2 = F, R3 = F (16)) were prepared by the interaction between hydrido cobalt(iii) complexes 4–6 and MeI or EtBr. The molecular configurations of complexes 4, 8, and 11 were determined by single crystal X-ray diffraction. We then confirmed that the four hydrido cobalt(iii) complexes 4–6 and 8 could be used as catalysts for reduction of aldehydes and ketones. Complex 8 is the best catalyst among the four complexes and can selectively catalyze the carbonyl groups of α,β-unsaturated aldehydes and ketones. [ABSTRACT FROM AUTHOR]

A series of phosphorus‐chalcogen chelated hydrido iron (II) complexes 1–7, (o‐(R'2P)‐p‐R‐C6H4Y)FeH (PMe3)3 (1: R = H, R' = Ph, Y = O; 2: R = Me, R' = Ph, Y = O; 3: R = H, R' = iPr, Y = O; 4: R = Me, R' = iPr, Y = O; 5: R = H, R' = Ph, Y = S; 6: R = Me, R' = Ph, Y = S; 7: R = H, R' = Ph, Y = Se), were synthesized. The catalytic performances of 1–7 for dehydration of amides to nitriles were explored by comparing three factors: (1) different chalcogen coordination atoms Y; (2) R' group of the phosphine moiety; (3) R substituent group at the phenyl ring. It is confirmed that 5 with S as coordination atom has the best catalytic activity and 7 with Se as coordination atom has the poorest catalytic activity among complexes 1, 5 and 7. Electron‐rich complex 4 is the best catalyst among the seven complexes and the dehydration reaction was completed by using 2 mol% catalyst loading at 60 °C with 24 hr in the presence of (EtO)3SiH in THF. Catalyst 4 has good tolerance to many functional groups. Among the seven iron complexes, new complexes 3 and 4 were obtained via the O‐H bond activation of the preligands o‐iPr2P(C6H4)OH and o‐iPr2P‐p‐Me‐(C6H4)OH by Fe(PMe3)4. Both 3 and 4 were characterized by spectroscopic methods and X‐ray diffraction analysis. The catalytic mechanism was experimentally studied and also proposed. [ABSTRACT FROM AUTHOR]

Four NHC [CNN] pincer nickel (II) complexes, [iPrCNN (CH2)4‐Ni‐Br] (5a), [nBuCNN (CH2)4‐Ni‐Br] (5b), [iPrCNN (Me)2‐Ni‐Br] (6a) and [nBuCNN (Me)2‐Ni‐Br] (6b), bearing unsymmetrical [C (carbene)N (amino)N (amine)] ligands were synthesized by the reactions of [CNN] pincer ligand precursors 4 with Ni (DME)Cl2 in the presence of Et3N. Complexes 5a and 5b are new and were completely characterized. The transfer hydrogenation of ketones catalyzed by the four pincer nickel complexes were explored. Complexes 5a and 6a have better catalytic activity than 5b and 6b. With a combination of NaOtBu/iPrOH/80 °C and 2% catalyst loading of 5a, 77–98% yields of aromatic alcohols could be obtained. [ABSTRACT FROM AUTHOR]