Small Molecule Activation by POCOP‐Nickel Complexes

Abstract

This contribution describes the reactivities of CO2 , CO, O2 , and ArNC with the pincer-type complexes [(κ(P) ,κ(C) ,κ(P') -POC sp 3OP)NiX] (POC sp 3OP=(R2 POCH2 )2 CH; R=iPr; X=OSiMe3 , NArH; Ar=2,6-iPr2 C6 H3 ). Reaction of the amido derivative with CO2 and CO leads to a simple insertion into the NiN bond to give stable carbamate and carbamoyl derivatives, respectively, the pincer ligand backbone remaining intact in both cases. In contrast, the analogous reactions with the siloxide derivative produced kinetically labile insertion products that either revert to the starting material (in the case of CO2 ) or react further to give the mixed-valent, dinickel species [(POC sp 3OP)Ni(II) {μ,κ(O) ,κ(P) ,κ(P') -OCOCH(CH2 CH2 OPR2 )2 }Ni(0) (CO)2 ]. The zero-valent center in the latter compound is ligated by a new ligand arising from transformation of the POC sp 3OP ligand backbone. The carbonylation and carboxylation of the siloxido derivative also produced minor quantities of a side-product identified as the trinickel species, [{(η(3) -allyl)Ni(μ(O) ,κ(P) -R2 PO)2 }2 Ni], arising from total dismantling of the POC sp 3OP ligand. Similar reactivities were observed with isonitrile, ArNC: reaction with the siloxido derivative resulted in a complex sequence of steps involving initial insertion, a 1,3-hydrogen shift, and an Arbuzov rearrangement to give [Ni(CNAr)4 ] and a methacrylamide based on fragments of the POC sp 3OP ligand. Oxygenation of the amido and siloxido derivatives led to the phosphinate derivative, [(POC sp 3OP)Ni(OP(O)R2 )], arising from oxidative transformation of the original ligand frame; the reaction with the Ni-NHAr derivative also gave ArHNP(O)R2 through a complex NP bond-forming reaction.

A Silyl-Nickel Moiety as a Metal–Ligand Cooperative Site

“…The solid-state structure of 6b reveals that a carbamate moiety is clearly bound to a distorted square-planar nickel­(II) ion (τ 4 = 0.20 and 0.23; Figure b). There are only three crystallographically characterized terminal nickel­(II) carbamato species reported in the literature. ,, The Ni–O bond lengths of 1.948(1) Å in 6a and 1.999(2) and 2.031(2) Å in 6b (Table ) are similar to that of (MeSiP 2 )­Ni­[OC­(O)­NHMes] [1.948(1) Å] and in the range of the typical Ni–O bond length found in other four-coordinate nickel complexes. ,− …”

“…There are only three crystallographically characterized terminal nickel(II) carbamato species reported in the literature. 48,95,96 Because CO 2 addition is much faster with a nickel amido species than a nickel phenyl species, 3 might undergo its transformation to 2 via Si−N bond cleavage and Si−C bond formation, which is consequently followed by CO 2 reaction with a nickel amide species to generate 6. To test whether or not the transformation of 3 to 2 is possible, a solution of 3a without 2a was prepared by the following method.…”

Recent Advances in the Chemistry of Metal Carbamates

“…The scenario changed over the last 15 years, as several carbamato complexes obtained by this methodology were reported, and especially organometallic species. These include late d-block metals such as iridium [190,191], nickel [192][193][194][195][196][197], palladium [198,199], gold [200] and zinc [201][202][203][204], f-block metals cerium [134] and uranium [205][206][207][208][209] and p-block metals tin [210] and gallium [211,212]. Furthermore, in situ-formed amide complex of Zn(II) and alkyl-amide of Mg(II) were mixed under carbon dioxide atmosphere to afford a heterobimetallic Zn/Mg alkyl-carbamato derivative [213].…”

Study of the Reactivity of the [(PE1CE2P)Ni(II)] (E1, E2 = O, S) Pincer System with Acetonitrile and Base: Formation of Cyanomethyl and Amidocrotononitrile Complexes versus Ligand Decomposition by P–S Bond Activation

“…The molecular structure shows the Ni center in distorted square-planar coordination geometry. The Ni1–N1 bond distance was found to be 1.9022(12) Å. PCP Ni amide complexes are comparably rare. − …”