Amido complex

CHAPTER 4 COVALENT (x-TYPE) LIGANDS BOUND THROUGH METAL-HETEROATOM BONDS 

A comparison of typical properties of early- and late-metal amides. 

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Another route to the amido complexes originates from [(>j-Tp )W(CO) (PhC=CMe)(OTf)l and benzylamine and yields [(i -Tp )W(CO)(PhC=CMe) (NHCH2Ph)] (96JA6916). The latter can be protonated with tetrafluoroboric acid to give the amine derivative [(> -Tp )W(CO)(PhC=CMe)(NH2CH2Ph)](Bp4), and this process can be reversed by -butyllithium. Hydride abstraction by silver tetrafiuoroborate, molecular iodine, or PhsCPEe leads to the cationic imine derivatives [(> -Tp )W(CO)(PhC=CMe)(HN=CHPh)]". -Butyllithium deproto-nates the product and gives the neutral azavinylidene species [(> -Tp )W(CO) (PhC=CMe)(N=CHPh)]. The latter with silver tetrafiuoroborate forms the cationic nitrile species [(j -Tp )W(CO)(PhC=CMe)(N=CPh)](Bp4). 

The C-coordinated thiazolium complexes are the result of the proton-induced cyclization reactions (980M513). Thus, complex 1 on protonation with tetrafiuoroboric acid yields the C-coordinated thiazolium structure 2. In turn, the nitrile complex 3 under these conditions is transformed to the thiazolium cationic species 4. Protonation of the amido complex 5 with tetrafiuoroboric acid also results in a cyclization but it proceeds differently. The amino group of the CONH2 moiety is lost and BF3-framework is coordinated via the carbonyl oxygen in an overall neutral complex 6. 

Different coordination modes of the amidinate ligands were observed when the mixed-ligand amidinato-amido complexes of Ge(II) and Sn(II) were treated... 

Protonolysis of the f/ -styrene zirconium complex Cp Zr(t/ -PhCHCH2) [MeC(NPr )2] with 2 equivalents of Bu NH2 provided a high yield of a novel bis(amido) complex according to Scheme 93. ... 

PhNHC(NPh)2]2Ru(CO)(PPh3) The Ru(n) amido complex (PCP)Ru(CO) (PMesllNHPh) (PCP = CgH3(CH2PBu2)2-2,6) reacts with nitriles under formation... 

Iridium chemistry also holds a rare example of a monodentate guanidinate ligand. The monomeric parent amido complex Cp Ir(PMe3)(Ph)(NH2) cleanly undergoes an insertion reaction on treatment with diisopropylcarbodiimide (Scheme 153). Spectroscopic data and an X-ray structural analysis revealed the presence of a nonchelating guanidinate ligand. ... 

Using the preorganized bis(amidinate) ligands featuring 9,9-dimethyl-xanthene backbones, several new dizirconium complexes have been prepared. For example, hexa(amido) complexes were obtained by reaction of the ligands with 2 equivalents of Zr(NMe2)4 (Scheme 212). ... 

Fig. 2.16 Copper-amido complexes as catalysts for the intermolecular hydroamination of electron-deficient alkenes...

The proposed reaction mechanism involves intermolecular nucleophilic addition of the amido ligand to the olefin to produce a zwitterionic intermediate, followed by proton transfer to form a new copper amido complex. Reaction with additional amine (presnmably via coordination to Cn) yields the hydroamination prodnct and regenerates the original copper catalyst (Scheme 2.15). In addition to the NHC complexes 94 and 95, copper amido complexes with the chelating diphosphine l,2-bis-(di-tert-bntylphosphino)-ethane also catalyse the reaction [81, 82]. 

Complexes 36 undergo a proton exchange reaction with protic reagents for example, a series of monomeric amido complexes are easily prepared using this route [45] (Equation 2.11 in Scheme 2.5). 

The bis amido complex [Au(bipy)(NHC6H4N02-4)2][Pp6] (43) has been similarly obtained by reaction of 40 with p-nitroaniline in acetone solution (Equation 2.14 in Scheme 2.6) [45b]. Complex 40 promotes the stoichiometric oxidation of various amines different from p-nitroaniline. Azotoluene is the main organic product of the... 

Nin-amido complexes such as (117) react with small electrophiles by insertion either in the Ni—N bond (e.g., with C02 to form (118)) or in the N—11 bond. With unsubstituted aryl groups (Ar = Ar = Ph), both a monomeric complex (117) or a dimeric species (119) is formed, depending on the amount of PMe3 added. Using bulky borylamide ligands, an almost linear, two-coordinate Nin complex could be obtained and structurally characterized.467 The N—Ni—N angle in (120) is 167.9°. 

Reduction of Ni11 chloride complexes [NiCl2(L)] (L = various diphosphinomethanes, -ethanes, and -propanes) with, for example, potassium naphthalenide in THF gives the corresponding Ni1 chlorides [NiCl(L)].2368 By treatment of (963) with LiNHAr, a terminal amido complex of Ni1 (964) was prepared (Scheme 13).2369 It contains planar three-coordinate nickel and a planar amido ligand with d(Ni—N) = 1.881(2) A. The P,Ni,P and C,N,H planes are orthogonal with a 91° dihedral angle. 

Scheme 3 summarizes the reductive elimination chemistry of arylpalladium amides. Arylpalladium amido complexes containing PPh3 as the dative ligand were stable enough to isolate, and... 

Alkylnickel amido complexes ligated by bipyridine have been prepared that undergo reductive elimination of V-alkyl amines (Equation (54)).207,208 Unlike the phosphine-ligated palladium arylamides, these complexes underwent reductive elimination only after oxidation to nickel(III). Thermally induced reductive elimination of alkylamines from phosphine-ligated nickel complexes appears to occur after consumption of phosphine by arylazides 209... 

Reaction of dpp-bian with Mg in THF for 30 min reflux gives complex 87 (Ar = 2,6-diisopropylphenyl) which undergoes oxidative addition via m-bond metathesis with PhC=CH to give the black alkynyl amido complex 88. The insertion reaction of 88 with Ph2CO in EtzO yields complex 89. Unexpectedly, hydrogen abstraction to give the radical anion occurs simultaneously with ketone insertion.268... 

Two equiv. of 6,6-di(cyclopropyl)fulvene react at 60 °C over a period of a week with Ca[N(SiMe3)2]2-(THF)2 bis in THF to yield the metallocene 170. The heteroleptic amido complex 171 is detected as an intermediate with 111 and 13C 1H NMR spectroscopy. A 1 1 reaction of the calcium amide and 170 also produces 171 in solution, an equilibrium involving these three derivatives exists (Equation (30)). The calcocene 170 crystallizes at — 20 °C from THF as colorless cuboids. The metal center is surrounded by the four ligands in a distorted tetrahedral manner, and the cyclopentadienyl group and the propylidene fragment are coplanar with each other.393... 

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