Metal complexes, Ni

Experimental determination of the electron density topology in a non-centrosymmetric transition metal complex [Ni(H3L)] N03][PF6] [H3L = N, N, N"-tris(2-hydroxy-3-... 

The first molecular metal based on single component and electrically neutral metal complex, [Ni(tmdt)2] (tmdt = trimethylenetetrathiafulva-lenedithiolate. Figure 4.17) was reported in 2001. Details of this compound and some other single component molecular conductors are given in Section 4.3.4 and in several review articles. 

The first of these used a non-polar stationary phase containing a chiral metal complex ("Ni-R-Cam"). This phase was developed by a German university (Schurig) and was not a commercial by available. It was therefore discarded. 

Enzymatic, surface-initiated polymerizations of aliphatic polyesters was reported for wider clinical use of aliphatic polyesters 84). The hydroxyl terminated SAM acted as an initiation site for lipase B catalyzed ROP of aliphatic polyesters, such as poly(e-caprolactone) and poly (p-dioxanone) (Scheme 3). Another example of enzymatic SIP is the polymerization of poly (3-hydroxybutyrate) (PHB), where PHB synthase, fused with a His-tag at the N-terminus, was immobilized onto solid substrates through transition-metal complexes, Ni (II)-NTA, and the immobilized PHB synthase catalyzed the polymerization of 3-R-hydroxybutyry 1-coenzyme A (3HB-CoA) to PHB 85). 

When comparing compounds of this family with adjacent metals, M(III), from the same line in the periodic table (e.g. Au and Pt or Cu and Ni), one clearly notes that the unpaired electron of the d metal complexes (Ni and Pt) does not affect the transport properties and the M-I transition occurs in the same way, irrespective of the paramagnetic or diamagnetic character of the M(mnt)J units. The only systematic... 

Pd-cataly2ed reactions of butadiene are different from those catalyzed by other transition metal complexes. Unlike Ni(0) catalysts, neither the well known cyclodimerization nor cyclotrimerization to form COD or CDT[1,2] takes place with Pd(0) catalysts. Pd(0) complexes catalyze two important reactions of conjugated dienes[3,4]. The first type is linear dimerization. The most characteristic and useful reaction of butadiene catalyzed by Pd(0) is dimerization with incorporation of nucleophiles. The bis-rr-allylpalladium complex 3 is believed to be an intermediate of 1,3,7-octatriene (7j and telomers 5 and 6[5,6]. The complex 3 is the resonance form of 2,5-divinylpalladacyclopentane (1) and pallada-3,7-cyclononadiene (2) formed by the oxidative cyclization of butadiene. The second reaction characteristic of Pd is the co-cyclization of butadiene with C = 0 bonds of aldehydes[7-9] and CO jlO] and C = N bonds of Schiff bases[ll] and isocyanate[12] to form the six-membered heterocyclic compounds 9 with two vinyl groups. The cyclization is explained by the insertion of these unsaturated bonds into the complex 1 to generate 8 and its reductive elimination to give 9. 

The preparation of a series of transition metal complexes (Co. Ni. Pd. Pt, Ir. Au. Cu. Ag) with ambident anion (70) and phosphines as ligands has been reported recently (885). According to the infrared and NMR spectra the thiazoline-2-thione anion is bounded through the exocyclic sulfur atom to the metal. The copper and silver complexes have been found to be dimeric. 

Many transition metal complexes including Ni(CO)4 obey the 18 electron rule, which IS to transition metal complexes as the octet rule is to mam group elements like carbon and oxygen It states that... 

Because the electron-counting paradigm incorporates the 18-electron rule when appHed to transition-metal complexes, exceptions can be expected as found for classical coordination complexes. Relatively minor exceptions are found in (Tj -C H )2Fe2C2BgHg [54854-86-3] (52) and [Ni(B2QH22)2] A [11141-32-5] (53). The former Q,n electrons) is noticeably distorted from an idealized stmcture, and the latter is reminiscent of the and complexes discussed above. An extremely deficient electron count is obtained for complexes such as P7036-06-9] which have essentially undistorted... 

As an example of a standardless bulk analysis by SNMS, a measurement of the complex Ni-based Hasteloy metal (NIST SRM 2402) is presented in Figure 3 and Table 1, in which the composition determined from ion-current ratios (not RSF corrected) is compared to the certified chemical composition. 

Although the structure of [SsN] has not been established by X-ray crystallography, the vibrational spectra of 30% N-enriched [SsN] suggest an unbranched [SNSS] (5.22) arrangement of atoms in contrast to the branched structure (Dsh) of the isoelectronic [CSs] and the isovalent [NOs] ion (Section 1.2). Mass spectrometric experiments also support the SNSS connectivity in the gas phase.Many metal complexes are known in which the [SsN] ion is chelated to the metal by two sulfur atoms (Section 7.3.3). Indeed the first such complex, Ni(S3N)2, was reported more than twenty years before the discovery of the anion. It was isolated as a very minor product from the reaction of NiCl2 and S4N4 in methanol. However, some of these complexes, e.g., Cu and Ag complexes, may be obtained by metathetical reactions between the [S3N] ion and metal halides. 

Stability constants of metal complexes of 9-hydroxy-4//-pyrido[l,2-n]pyrimidin-4-one [Ni(II), Co(II), Zn(II), and Cd(II)] were determined by potentiometric and polarographic investigations (93JCC283). The distribution coefficient of risperidone (11) in H20- -octanol at pH 7.4 (log D — 2.04) was determined by an RP-HPLC method (01JMC2490). 

Among the J ,J -DBFOX/Ph-transition(II) metal complex catalysts examined in nitrone cydoadditions, the anhydrous J ,J -DBFOX/Ph complex catalyst prepared from Ni(C104)2 or Fe(C104)2 provided equally excellent results. For example, in the presence of 10 mol% of the anhydrous nickel(II) complex catalyst R,R-DBFOX/Ph-Ni(C104)2, which was prepared in-situ from J ,J -DBFOX/Ph ligand, NiBr2, and 2 equimolar amounts of AgC104 in dichloromethane, the reaction of 3-crotonoyl-2-oxazolidinone with N-benzylidenemethylamine N-oxide at room temperature produced the 3,4-trans-isoxazolidine (63% yield) in near perfect endo selectivity (endo/exo=99 l) and enantioselectivity in favor for the 3S,4J ,5S enantiomer (>99% ee for the endo isomer. Scheme 7.21). The copper(II) perchlorate complex showed no catalytic activity, however, whereas the ytterbium(III) triflate complex led to the formation of racemic cycloadducts. 

Monodentate dipolarophiles such as acrolein, methacrolein, and a-bromoacrolein could be successfully utilized in the l ,J -DBFOX/Ph-transition metal complex-catalyzed asymmetric nitrone cycloadditions [76]. The reactions of N-benzylideneani-line N-oxide with acrolein in the presence of the nickel(II) aqua complex R,R-DBF0X/Ph-Ni(C104)2 3H20 (10mol%) and MS 4 A produced a mixture of two regioisomers (5-formyl/4-formyl regioisomers ca 3 1). However, enantio-... 

It is believed [1135,1136] that the decomposition of metal complexes of salicyaldoxime and related ligands is not initiated by scission of the coordination bond M—L, but by cleavage of another bond (L—L) in the chelate ring which has been weakened on M—L bond formation. Decomposition temperatures and values of E, measured by several non-isothermal methods were obtained for the compounds M(L—L)2 where M = Cu(II), Ni(II) or Co(II) and (L—L) = salicylaldoxime. There was parallel behaviour between the thermal stability of the solid and of the complex in solution, i.e. Co < Ni < Cu. A similar parallel did not occur when (L—L) = 2-indolecarboxylic acid, and reasons for the difference are discussed... 

Transition metal complexes that are easy to handle and store are usually used for the reaction. The catalytically active species such as Pd(0) and Ni(0) can be generated in situ to enter the reaction cycle. The oxidative addition of aryl-alkenyl halides can occur to these species to generate Pd(II) or Ni(II) complexes. The relative reactivity for aryl-alkenyl halides is RI > ROTf > RBr > RC1 (R = aryl-alkenyl group). Electron-deficient substrates undergo oxidative addition more readily than those electron-rich ones because this step involves the oxidation of the metal and reduction of the organic aryl-alkenyl halides. Usually... 

Coordination-catalyzed ethylene oligomerization into n-a-olefins. The synthesis of homologous, even-numbered, linear a-olefins can also be performed by oligomerization of ethylene with the aid of homogeneous transition metal complex catalysts [26]. Such a soluble complex catalyst is formed by reaction of, say, a zero-valent nickel compound with a tertiary phosphine ligand. A typical Ni catalyst for the ethylene oligomerization is manufactured from cyclo-octadienyl nickel(O) and diphenylphosphinoacetic ester ... 

The Lewis bases attached to the central metal atom or ion in a d-metal complex are known as ligands they can be either ions or molecules. An example of an ionic ligand is the cyanide ion. In the hexacyanoferrate(II) ion, [Fe(CN)6]4, the CN- ions provide the electron pairs that form bonds to the Lewis acid Fe2+. In the neutral complex Ni(CO)4, the Ni atom acts as the Lewis acid and the ligands are the CO molecules. 

Note Many of the (substituted hydrazino)quinoxalines covered in this section have been converted into metal complexes, randomly exemplified here. 2-(Pyridin-2-ylhydrazonomethyl)quinoxaline (246) Fe(ll), Ni(ll), and Cu(ll)... 

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