The room temperature reaction of NiBr(2)(NCCH(3))(x) with the pincer-type ligand POCHOP(Ph) gave the new pincer complex (POCOP(Ph))NiBr (1, POCOP(Ph) = κ(P), κ(C), κ(P)-2,6-{Ph(2)PO}(2)C(6)H(3)). Complex 1 reacts with AgX to give the analogous Ni-X derivatives (X = CN, 2; OSO(2)CF(3), 3; OC(O)CH(3), 4; ONO(2), 5), whereas complex 3 reacts with phenylacetylene and NEt(3) to give the Ni-CCPh derivative 6. On the other hand, reaction of 1 or 3 with RLi or RMgI did not afford the desired Ni-R derivatives, giving instead the corresponding iodo and hydroxo derivatives. Complexes 1-6 have been characterized by NMR, IR, and UV-Vis spectroscopy and X-ray crystallography. The solid state structural and IR data indicate that Ni-C(sp) interaction is dominated by ligand-to-metal σ-donation in 2 and 6. Cyclic voltammetry measurements indicate that complexes 3 and 4 display reversible redox behaviour (Ni(II)/Ni(III)); comparison of the E(0)(1/2) values for these complexes and their POCOP(i-Pr) analogues shows that both the X ligands and the P-substituent have a considerable impact on the ease of oxidation in this family of complexes.

This report describes the catalytic activity of the pincer-type complex {κ P ,κ C ,κ P -2,6-(Ph2PO)2C6H3}Ni(OSO2CF3) (1) in the anti-Markovnikov addition of aliphatic and aromatic amines and alcohols to acrylonitrile, crotonitrile, and methacrylonitrile. The influence of additives on the catalytic activities was investigated, and it was found that substoichiometric quantities of water promoted the C–N bond forming reactions catalyzed by 1, especially the reactions involving aromatic amines; in comparison, NEt3 had a less dramatic impact. The opposite pattern was observed for the alcoholysis of acrylonitrile promoted by 1: water had no beneficial effect on these reactions, while NEt3 proved to be a potent promoter. Another important difference between these reactions is that hydroamination works better with more nucleophilic amines, whereas the alcoholysis reactions work well with ArOH, CF3CH2OH, and ArCH2OH but not at all with the more nucleophilic aliphatic alcohols methanol, ethanol, and 2-propanol. Both hydroamination and alcoholysis proceed much better with acrylonitrile in comparison to its Me-substituted derivatives crotonitrile and methacrylonitrile. Under optimized conditions, precatalyst 1 promotes conjugate additions to acrylonitrile with catalytic turnover numbers of up to 100 (hydroamination) or higher (alcoholysis). Spectroscopic studies have established that the main Ni-containing species in the hydroamination reactions is a cationic adduct in which the olefinic substrate is bound to the Ni center via its nitrile moiety; this binding activates the double bond toward an outer-sphere nucleophilic attack by the amine (Michael addition). The solid-state structures of the cationic nitrile adducts [{κ P ,κ C ,κ P -2,6-(Ph2PO)2C6H3}Ni(NCR)][OSO2CF3] (R = Me (2a), CH2CH2N(H)Ph (2e)), which can be regarded as model complexes for the species involved in the hydroamination catalysis, have been elucidated. Also reported are the solid-state structures of the charge-neutral compound {κ P ,κ C ,κ P -2,6-(i-Pr2PO)2C6H3}Ni(OSO2CF3) and an octahedral Ni(II) species resulting from the aerobic/hydrolytic oxidation of 1.

Different structures and reactivities have been observed with the unsymmetrical pincertype complex (5,6-POCOP´)Ni(II)Br and its various derivatives compared to their analogous symmetrical 5,5-POCOP systems, thus serving to establish the importance of the size and degree of flexibility in the metallacycle rings. AbstractThis report describes the synthesis and characterization of a family of unsymmetrical pincer complexes of nickel(II) featuring both 5-and 6-membered nickelacycles. The room temperature reaction of NiBr 2 (NCCH 3 ) x with the bis(phosphinite) ligand 1-(i-Pr 2 PO),3-(i-Pr 2 POCH 2 )-C 6 H 4 (POCHOP´) results in direct nickelation at the 2-position of the aromatic ring to give (5,6-POCOP´)NiBr (5,6-POCOP´ = {κ P ,κ C ,κ P´-2-(i-Pr 2 PO),6-(i-Pr 2 POCH 2 )-C 6 H 3 }). This complex undergoes salt metathesis reactions with M´X to give the corresponding charge neutral derivatives (5,6-POCOP´)NiX (X = OSO 2 CF 3 , OSO 2 (4-CH 3 -C 6 H 4 ), CH 3 , and C≡CCH 3 ), whereas abstraction of the bromide by AgBPh 4 in acetonitrile gave the cationic derivative [(5,6-POCOP´)Ni(NCCH 3 )][BPh 4 ]. The new complexes have been characterized by multinuclear NMR spectroscopy and X-ray diffraction studies. The reactivities of the new complexes (5,6-POCOP´)NiX (X= Br, OSO 2 CF 3 ) have been explored briefly to establish the nucleophilicity of the X ligand and the substitutional lability of the phosphinite moiety in the 6-membered cycle.

The mol­ecule of the title complex, [Ni(C30H23O2P2)(OH)], adopts a slightly distorted square-planar geometry around NiII defined by the coordination of the two mutually trans P atoms, the Csp 2 atom of the pincer ligand and the O atom of the hydroxide ligand. The largest distortions from ideal geometry are reflected in the smaller than usual P—Ni—P [163.95 (3)°] and P—Ni—C [82.06 (6)°] angles. The OH ligand does not form intra- or inter­molecular hydrogen bonds.