NO-Donor Ligands

Abbasi, B. G. Bhat, and R. S. Singh, Inorg. Nuclear Ckem. Letters, 1976, 12, 391. 

Kokoszka, Inorg. Ckim. Acta, 1976,19, 51. 

Wakajima, K. Matsumoto, K. Tanaka, and T. Tanaka, J. Inorg. Nuclear Chem., 1975, 37, 2463. 

Reinprecht, and G. C. Vogel, Inorg. Nuclear Chem. Letters, 1976,12, 399. 

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Figure 5-54. Transimination may provide a method for the preparation of imines which are not readily accessible by other methods. This reaction illustrates a way of making NO donor ligands without the need for nucleophilic attack of amine on a co-ordinated 1,3-diketonate.

H2 ean no longer be ignored in understanding the valenee states of the XY moleeules. This situation arises quite naturally in systems involving transition metals, where interaetions between empty metal or metal ion orbitals and 2-eleetron donor ligands are ubiquitous. 

Similar behaviour is found in many other carboxylates of Cu as well as their adducts in which axial water is replaced by other O-or A -donor ligands. In spite of a continuous flow of work on these compounds there is still no general agreement as to the actual mechanism of the interaction nor on possible correlations of its magnitude with relevant... 

Schrock-type carbenes are nucleophilic alkylidene complexes formed by coordination of strong donor ligands such as alkyl or cyclopentadienyl with no 7T-acceptor ligand to metals in high oxidation states. The nucleophilic carbene complexes show Wittig s ylide-type reactivity and it has been discussed whether the structures may be considered as ylides. A tantalum Schrock-type carbene complex was synthesized by deprotonation of a metal alkyl group [38] (Scheme 7). 

When L = 4-CNC5H4N (PK3 = 1.86), 2-CIC5H4N (pK = 2.81), or 4-PhCOC5H4N (pKj = 3.35) [Hg2L2] [C10412 can be isolated as solids. However, under the same conditions the more basic unsubstituted pyridine (pK, = 5.21) leads to disproportionation, and no complex can be isolated. Complexes of Hg(I) of these more basic substituted pyridines can be prepared under a N2 atmosphere in MeOH at -70°C. Table 1 shows some Hg(I) complexes prepared with N-donor ligands. The majority contain an Hg2 ion with each atom coordinated to one or two N atoms as in I or II. 

Recently, an abstract has been published 83) of a kinetic study of reactions of RMn(CO)3L2 (L = P donor ligand) with CO. No data were disclosed, however. 

The Ni111 state is more easily attained with the NOS donor-set ligand (75a) (i 1/2 = +0.75V vs. SCE) compared to the N02 analogue (75b), the latter showing only an ill-defined anodic... 

The unsymmetric phenolato-derived ligand (749) bearing a tridentate N20 donor set and a bidentate NO donor set has produced a trinuclear Ni11 complex that incorporates two unusual... 

A T structure with the strongest ct-donor D trans to the empty site (I in Scheme 1) is preferred in the case of three pure cr-donor ligands. The presence of a ir-acceptor ligand also makes the T structure more stable. When one of the ligands is a tt-donor, X, a Y structure of type II (Scheme 1) is observed. This structure permits the formation of a w bond between the empty metal d orbital and the lone pair of X. No such tt bond is present in the T structure since all symmetry adapted d orbitals are filled. This partial M—X multiple bond stabilizes Y over T. 

When the structures for many ligands (e.g., H20, NH3, C032-, and C2042-) are drawn, there is no question as to which atom is the electron pair donor. Ligands such as CO and CN normally bond to metals by donation of an electron pair from the carbon atom. It is easy to see why this is so when the structures are drawn for these species and the formal charges are shown. 

Not only do palladium complexes catalyze reactions of Eq. (58), but nickel complexes were also effective (51) and formed the same products. Complexes such as Fe(CO)5 and Fe2(CO)8 were ineffective. Cobalt carbonyl, and tris-triphenylphosphinerhodium chloride were effective even at room temperature, but no 2 1 adducts were made. With both palladium and nickel, the activity of the catalyst and the distribution of products between 1 1 and 2 1 adducts is greatly dependent on the nature of the donor ligands on the metal. 

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