Abstract:Die a-Aminosiiur~pter-Platink~mpiexe cis-CiiPt( NHzCHRCOz-Eth (R = H. Mc, CWfiHMe:) wtzm sich mit furt-Butylhypochlurit m den N-Chlor-~-amin~uusiiureezler-vcrbiadun~n trans-~~P~~~~~~l~H R C O~E t~ um. bA1kylidea-1,3-o~~oizolidin-2J-, dim vird an (Ph3P)?Pt(C2H4) in Ahhiingigkeit von den Substituentea %bcr die C-GDoppef-oder die NH-Bindung addiert. Dk Struktur &v H drido-bnido-Komplexes wiaw4J%,~HIh -bestimmt. bC -----% ( ZD C!HPhmO)o 0 (4c) wude durch ~~t a i~s t r u k~u r a n~l y~ In Fortfuhrung unserer Arbeit… Show more
“…The Pt center is in a square-planar environment with the two phosphines in trans position [PPtP = 167.56(5)°]. The hydride at Pt was unambiguously located in the difference Fourier map, with a rather short Pt–H distance of 1.41(4) Å . The NHC(O)Ph amide fragment bridges the Pt and Al centers.…”
Reaction of the geminal PAl ligand [Mes2PC(═CHPh)AltBu2] (1) with [Pt(PPh3)2(ethylene)] affords the T-shape Pt complex [(1)Pt(PPh3)] (2). X-ray diffraction analysis and DFT calculations reveal the presence of a significant Pt→Al interaction in 2, despite the strain associated with the four-membered cyclic structure. The Pt···Al distance is short [2.561(1) Å], the Al center is in a pyramidal environment [Σ(C-Al-C) = 346.6°], and the PCAl framework is strongly bent (98.3°). Release of the ring strain and formation of X→Al interactions (X = O, S, H) impart rich reactivity. Complex 2 reacts with CO2 to give the T-shape adduct 3 stabilized by an O→Al interaction, which is a rare example of a CO2 adduct of a group 10 metal and actually the first with η(1)-CO2 coordination. Reaction of 2 with CS2 affords the crystalline complex 4, in which the PPtP framework is bent, the CS2 molecule is η(2)-coordinated to Pt, and one S atom interacts with Al. The Pt complex 2 also smoothly reacts with H2 and benzamide PhCONH2 via oxidative addition of H-H and H-N bonds, respectively. The ensuing complexes 5 and 7 are stabilized by Pt-H→Al and Pt-NH-C(Ph) = O→Al bridging interactions, resulting in 5- and 7-membered metallacycles, respectively. DFT calculations have been performed in parallel with the experimental work. In particular, the mechanism of reaction of 2 with H2 has been thoroughly analyzed, and the role of the Lewis acid moiety has been delineated. These results generalize the concept of constrained geometry TM→LA interactions and demonstrate the ability of Al-based ambiphilic ligands to participate in TM/LA cooperative reactivity. They extend the scope of small molecule substrates prone to such cooperative activation and contribute to improve our knowledge of the underlying factors.
“…The Pt center is in a square-planar environment with the two phosphines in trans position [PPtP = 167.56(5)°]. The hydride at Pt was unambiguously located in the difference Fourier map, with a rather short Pt–H distance of 1.41(4) Å . The NHC(O)Ph amide fragment bridges the Pt and Al centers.…”
Reaction of the geminal PAl ligand [Mes2PC(═CHPh)AltBu2] (1) with [Pt(PPh3)2(ethylene)] affords the T-shape Pt complex [(1)Pt(PPh3)] (2). X-ray diffraction analysis and DFT calculations reveal the presence of a significant Pt→Al interaction in 2, despite the strain associated with the four-membered cyclic structure. The Pt···Al distance is short [2.561(1) Å], the Al center is in a pyramidal environment [Σ(C-Al-C) = 346.6°], and the PCAl framework is strongly bent (98.3°). Release of the ring strain and formation of X→Al interactions (X = O, S, H) impart rich reactivity. Complex 2 reacts with CO2 to give the T-shape adduct 3 stabilized by an O→Al interaction, which is a rare example of a CO2 adduct of a group 10 metal and actually the first with η(1)-CO2 coordination. Reaction of 2 with CS2 affords the crystalline complex 4, in which the PPtP framework is bent, the CS2 molecule is η(2)-coordinated to Pt, and one S atom interacts with Al. The Pt complex 2 also smoothly reacts with H2 and benzamide PhCONH2 via oxidative addition of H-H and H-N bonds, respectively. The ensuing complexes 5 and 7 are stabilized by Pt-H→Al and Pt-NH-C(Ph) = O→Al bridging interactions, resulting in 5- and 7-membered metallacycles, respectively. DFT calculations have been performed in parallel with the experimental work. In particular, the mechanism of reaction of 2 with H2 has been thoroughly analyzed, and the role of the Lewis acid moiety has been delineated. These results generalize the concept of constrained geometry TM→LA interactions and demonstrate the ability of Al-based ambiphilic ligands to participate in TM/LA cooperative reactivity. They extend the scope of small molecule substrates prone to such cooperative activation and contribute to improve our knowledge of the underlying factors.
“…If the cis/trans isomerization is kinetically inhibited, the trans -hydrido−amido complexes are stable and can be isolated. Examples of structurally characterized hydrido−amido complexes are given in Scheme . , 18 Crystallographically Charactarized Hydrido−Amido Complexes: 1 , 2 , 3 , 4 , 5 , 6 , 7 , and 8 215 …”
Section: Activation Of the N−h Bond By Late
Transition
Metalsmentioning
ContentsI. Introduction 675 II. Mechanism and Coordination Chemistry 676 1. Activation of the Olefin 677 a. Stoichiometric Use of Transition Metals 677 b. Making the Reaction Catalytic 679 2. N−H Activation by Alkali Metals 680 3. Activation of the N−H Bond by Early Transition Metals, Lanthanides, and Actinides 681 4. Activation of the N−H Bond by Late Transition Metals 684 III. Synthetic Applications of Catalytic Aminations 686 1. Aminations Catalyzed by Zeolites 686 2. Aminations Assisted by Alkali Metals 686 a. Ethylene 686 b. Aliphatic Olefins 687 c. Styrenes 688 d. 1,3-Butadienes 689 3. Aminations Catalyzed by Transition Metals 690 a. Palladium-Catalyzed Aminations of Olefins 690 b. Other Catalytic Oxidative Aminations of Olefins 693 c. Amination of Allenes 693 d. Intramolecular Amination of Alkynes 694 e. Intramolecular Amination of Alkenes 695 f. Tandem Cyclization Reactions of Aminoalkynes and -alkenes 697 g. Intermolecular Hydroamination Reactions 698 IV. Summary and Conclusions 699 V. Acknowledgments 700 VI. References 700
“…The reaction of Pt(COD) 2 and PEt 3 with tert ‐butyl Gly‐NCA afforded insertion of platinum into the N–H bond to give the hydrido‐amide complex 11 (Scheme ) 113. Previously, the analogous oxidative addition has been observed in the reaction of (C 2 H 4 )Pt(PPh 3 ) 2 with unsaturated Leuch ’s anhydrides 114. The metal‐mediated ring‐opening polymerization of NCAs has been covered in excellent reviews115–117 and NCAs have been proposed as intermediates in the prebiotic synthesis of amino acids and peptides96 (see also chapter 11).…”
Section: Synthesis Of Polypeptides By Controlled Transition Metal‐mentioning
The formation of peptide bonds in the neighborhood of metal ions is reviewed. The metal ions can function as activating and catalytic groups; they can act as templates. Metal ions can play a role as stabilizing spectators when peptides are formed within their ligands and they are able to protect the amino or carboxylate group of amino
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