14653-44-2Relevant articles and documents
Stabilization of low-valent Ni(CO)-building blocks by [Ti] (C≡CR)2; reaction behavior of {[Ti](C≡CR)2}Ni(CO) towards triphenylphosphane and phosphites
Lang, H.,Meichel, E.,Stein, Th.,Weber, C.,Kralik, J.,et al.
, p. 150 - 160 (2008/10/08)
The preparation of heterobimetallic transition metal complexes of the type {[Ti](C≡CR)2}Ni(CO) {R = SiMe3: 3a, [Ti] = (η5-C5H5)2Ti; 3b: [Ti] = (Ti) a late (Ni) transition metal is present, is described. Additionally, the reaction chemistry of 3a and 3c towards P(OR′)3 (4a, R′ = CH3; 4b, R′ = C6H5; 4c, R′ = C6H4Me-2; 4d, R′ = C6H4tBu-2) is reported. In these reactions the nickel-bound carbonyl ligand is replaced by P(OR′) 3 producing {[Ti](C≡CSiMe3)2Ni[P (OR′)3] {[Ti] = (η5-C5 H5)2Ti: 5a, R′ = CH3; 5b, R′ = C6H5; 5c, R′ = C6 H4Me-2; [Ti] = (η5-C5H 4SiMe3)2Ti: 5d, R′ = CH3; 5e, R′ = C6H5} along with Ni(CO)2[P(OR′)3]2 (6a, R′ = C6H5; 6b, R′ = C6H 4Me-2; 6c, R′ = C6H4 tBu-2). It appeared that the latter reaction strongly depends on the sterical demand, Tolman cone angle, of the respective phosphites used: while, in the reaction of 3a or 3c with 4a selectively 5a and 5d is formed, with more bulky substituents R′, e.g. R′ = C6H5 and C6H 4Me-2, complexes 5b and 5c along with 6a and 6b are produced. Changing to even more sterical demanding groups such as R′ = C6H4tBu-2 than exclusively 6c is formed. The dynamic behaviour of 5 in solution is discussed. When 3a is treated with equimolar amounts of PPh3 (7) the titanium-nickel alkynyl species [Ti](μ-η1:η 2-C≡CSiMe3)Ni(PPh3)(μ-η 1:η2-C≡CSiMe3) {8a, [Ti] = (η5-C5H5)2Ti} is accessible via an alkynyl-transfer reaction from titanium to nickel. However, on treatment of 3c with 7 no reaction occurs. Arguments for the different behaviour of 3a-3c towards 4 and 7 will be presented. The result of the X-ray structure analysis of complexes 5d and 5e are reported. Both complex crystallize in the monoclinic space group P21/n. Cell parameters for 5d: a = 10.9390(10), b = 15.585(4), c = 22.950(3) A , β = 92.861(7)°, V = 3907.7(14) A 3, Z = 4 and δ = 1.189 g mol-1. 5e: a = 17.694(9), b = 22.620(10), c = 24.510(10) A , β = 103.90(4)°, V = 9523(8) A 3, Z = 8 and δ = 1.236 g mol-1. In both complexes a low-valent Ni[P(OR′)3] building block (5d, R′ = CH3; 5e, R′ = C6H5) is stabilised by the chelating effect of the organometallic ?-tweezer [Ti](C≡CSiMe3) 2, giving rise to a trigonal-planar environment at the nickel atom. The early (Ti) and late (Ni) transition metal centers are thereby bridged via the ?- and ?-bound alkynyl groups Me3 SiC≡C. The influence of the different sterical demanding phosphites onto the [Ti](C≡CSiMe3)2 framework will be discussed. 2002 Elsevier Science B.V. All rights reserved.
Kinetics and mechanism of the reactions of di-μ-carbonyl-bis(cyclopentadienyl)dinickel(0) with monodentate ligands
Ellgen, Paul C.
, p. 232 - 239 (2008/10/08)
The ligands carbon monoxide, triphenylarsine, triphenyl phosphite, triphenylphosphine, ethyldiphenylphosphine, and tri-n-butylphosphine react with di-μ-carbonyl-bis(cyclopentadienyl)dinickel(0) to give nickelocene and diliganddicarbonylnickel(0) (eq 1). The kinetics of these reactions have been studied by following the carbonyl region infrared spectra of reaction mixtures or by manometric observation of carbon monoxide absorption. Complicated behavior is observed with tri-n-butylphosphine. The dependence on carbon monoxide concentration was not studied, but reaction according to (1) is much slower than the rate reported for carbon monoxide exchange. For the other ligands studied, a second-order rate law, first order in each reactant, is observed: -d[Ni2(CO)2(C5H5)2]/dt = k[Ni2(CO)2(C5H5)2][L]. The reaction mechanism is discussed. A complex mechanism can be shown to be quantitatively consistent with the data for the reaction with tri-n-butylphosphine.
