Complex Insertion Research Articles

Insertion of Imines and Carbon Monoxide into Manganese−Alkyl Bonds: Synthesis and Structure of a Manganese−α-Amino Acid Derivative

Two new routes have been developed to generate manganese-chelated amides from imine and carbon monoxide building blocks. The reaction of (CO)5MnR (R = CH3, Ph) with (p-tolyl)(R1)NR2 (R1 = H, tBu; R2 = alkyl, H) results in the generation of the cyclometalated imine complexes (CO)4Mn[η2-4-CH3-2-(C(R1)NR2)-C6H3] in 50−84% isolated yield. However, when the reaction of (p-tolyl)(H)CNCH3 with (CO)5MnCH3 is performed in the presence of AlCl3, the product of sequential carbon monoxide and imine insertion is generated in 35% yield: (CO)4Mn[η2-C(H)(p-tolyl)N(CH3)COCH3]. The addition of PPh3 to the latter complex results in replacement of a carbonyl ligand and formation of the isolable fac-(CO)3(PPh3)Mn[η2-C(H)(p-tolyl)N(CH3)COCH3]. In an alternative route to metal-bound amides, the oxidative addition of the N-acyl iminium salt (p-tolyl(H)CN(CH3)COPh+Cl- to (CO)5Mn-Na+ has been found to lead to the generation of the product of subsequent CO insertion, (CO)4Mn[η2-COC(H)(p-tolyl)N(CH3)COPh]. The latter represents the first example of a acyl-bound transition-metal-chelated α-amino acid complex and has been characterized by X-ray crystallography. Preliminary reactivity studies demonstrate that (CO)4Mn[η2-COC(H)(p-tolyl)N(CH3)COPh] reacts with PPh3 to generate the unchelated cis-(CO)4(PPh3)Mn[COC(H)(p-tolyl)N(CH3)COPh], while reaction with NaBH4 leads to the liberation of the amide (p-tolyl)CH2N(CH3)COPh, rather than the amino acid residue.

Syntheses and reactions of metal carbonyl complexes containing the trimethylsilylmethyl ligand; CO insertion reactions assisted by the trimethylsilylmethyl groups

Trimethylsilylmethyl complexes of ruthenium and tungsten, Cp(CO),RuCH2SiMe3 (1) (Cp = η5-C5H5) and Cp(CO)3WCH2SiMe3 (2) were prepared by reactions of ClMgCH2SiMe3 with CP(CO)2RuCl and Cp(CO)3 WCl respectively, in ether at low temperature. The complex (CO)5ReCH2SiMe3 (3) was prepared by reaction of ICH2SiMe3 with NaRe(CO)5 in THF. In contrast to the severe conditions required for the CO insertion reactions of Cp(CO)2RuCH3 and Cp(CO)3WCH3, carbonylation reactions of 1 and 2 with PPh3 took place readily under mild conditions and gave two acyl complexes Cp(CO)3(PPh3)RuC(O)CH3 (4) and Cp(CO),(PPh3)WC(O)CH3 (5) respectively. The reaction of 3 with PPh3 in CD3CN retained the trimethylsilyl group and gave both the acyl product (CO)4(PPh3)ReC(O)CH2SiMe3 (6) and the substitution product (CO)4(PPh3)ReCH2SiMe3 (7). The CO insertion reactions of these three complexes are believed to be assisted by the MCSi angles being rather larger. The RuCSi angle of 1 is 119°.Complexes 1 and 5 · 1.5C6H6 were confirmed by X-ray crystallography: Crystal data for 1: space group P1, a = 6.933(1)°, b = 8.455(1) Å, c = 12.001(1) Å, α = 105.88(1)°, β = 98.41(1)°, γ = 92.55(1) °, V = 666.7 Å3, Z = 2; R(F) = 0.0296, Rw(F) = 0.0254, based on 4586 reflections with I > 3σ(I). Crystal data for 5: space group P1, a = 8.922 (2) Å, b = 13.496(2) Å, c = 13.925(2) Å, α = 102.94(1)°, β = 109.71(2)°, γ = 87.13(1)°, V = 1537.9 Å3, Z = 2; R(F) = 0.0253, Rw(F) = 0.0190, based on 4596 reflections with I > 3σ(I). The other complexes were characterized by spectroscopic studies.

Synthesis, X-ray structure and rearrangement of nitrogen ylides obtained upon alkyne and CO insertion reactions into aminocarbene complexes of chromium

The aminocarbene complexes (CO)5CrC(R1)N(R2R3)1[R1= H, Me, Ph, R2= Me, R2R3=(CH2)5, R3= Me, cyclopropyl] react with diphenylacetylene to give nitrogen ylides 5 which were fully characterized by an X-ray analysis carried out on 5a[(CO)3CrR2R3N(C16H10OR1)–(R1= H, R2= R3=(CH2)5] and which lead, upon nitrogen to carbon migrations of alkyl groups R2 and R3, to the expected lactams (e.g.8 and 9) C16H10ONR1R2R3.

First intramolecular alkyne–CO insertion reactions in aminocarbene complexes of chromium: formation of condensed heterocycles following extensive hydrogen migrations

The aminocarbene complexes (CO)5CrC(Me)[N(Me)(CH2)3CCPh](6) and (CO)5CrC[graphic omitted][(CH2)3CCMe](14) lead, upon heating in benzene, to the polycyclic triple bond and CO inserted products C15H15NO (12) and C12H15NO (19) through multiple C–H activations.

ChemInform Abstract: Reactions of (CO)2(η5‐C5H5)Fe Alkyls and Ph3C+BF4‐ : A Search for Hydrogen‐Atom Abstraction Following One‐Electron‐Transfer.

AbstractOn treatment of (III) with (IV) under N2, β‐hydride abstraction occurs to give the complexes (V).

Reactions of (CO) 2(η 5-C 5H 5)Fe Alkyls and Ph 3C + BF 4: A Search for Hydrogen-Atom Abstraction following One-Electron-Transfer

The reaction products of Ph 3C +BF 4 - ( 2) and (CO) 2 - (η 5-C 5H 5)Fe-(2-cyclopropylethyl) (1), -neopentyl ( 10), and -(1-norbornyl-carbinyl) (13) under N 2 and under CO have been determined in an effort to detect evidence of hydrogen-atom abstraction from the 17e, Fe(III) cation-radical intermediate produced by one-electron transfer to the starting cation. None was observed. Labeling studies reveal that migratory CO insertion to produce (CO) 2(η 5-C 5H 5)FeCO(2-cyclo-propylethyl) ( 8) is accompanied by β- not α-hydride abstraction to form [(CO) 2(η 5-C 5H 5)Fe(η 2-cyclopropylethene)] +BF 4 -(3) when 1 reacts with 2 under CO. The insertion is catalytic in 2. Hydrogen is not lost from 10 or 13 under these conditions; the acyl complexes (CO) 2(η 5-C 5H 5)FeCOCH 2-C(CH 3) 3 ( 11), 71%, or (CO) 2(η 5-C 5H 5)FeCO(1-norbornylcarbinyl) (14), 80%, respectively, are the only organometallic products.