Dimethyl and Cationic 1,4-Diazabutadiene Complexes of Platinum(II)

Abstract

The reaction of the 1,4-diazabutadiene ligand glyoxal bis(2-(methoxymethyl)-4,6-di-tert-butylphenyl)diimine (L) with the platinum complex Pt2Me4(SMe2)2 yields two isomers of the complex PtMe2 L (2a,b) that have been isolated and characterized. The isomers exhibit distorted-square-planar coordination geometries about the central Pt(II) ion and differ only in the relative orientation of the methoxymethyl and tert-butyl substituents with respect to the coordination plane of the complex. Isomerization between 2a and 2b is promoted by heating solutions of either form of the complex in benzene or chloroform. Upon prolonged refluxing in chloroform, 2a,b react with chloroform to yield the methyl chloro derivative PtMeClL, which is also obtained as syn and anti isomers (3a,b). Cationic solvento complexes [PtMe(S)L]BF4 (4 and 5, S = MeCN, pyridine) are generated by halide abstraction from 3 using AgBF4. In the presence of selected olefins such as ethylene and acrylonitrile, halide abstraction from 3 by AgBF4 or methyl group abstraction from 2a and 2b by the strong Lewis acid B(C6F5)3 yields the cationic α-olefin complexes [PtMe(CH2CHR)L]+ (R = H, CN; 6 and 7 for the BF4 salt, 8 and 9 for the MeB(C6F5)3 salt). All new compounds have been characterized by IR and NMR spectroscopy. Molecular structures of 2a,b, and 3a were determined by X-ray single-crystal diffraction.

Synthesis and characterization of novel Pd(II) and Pt(II) complexes with 5-ring chelating iminoylcarbene ligands

“…Deviations from the ideal 90°L-Pt-L 0 angles are however significant, ranging from 77.4°for the N(1)-Pt(1)-C(4) chelate bite angle, to 100.0°for the C(4)-Pt(1)-C(2) angle. These observations are consistent with previous structural studies on functionalized diimine (j 2 -N,N)PtMe 2 complexes [39,40]. The imidazole ring and the 5-membered chelate ring are essentially coplanar.…”

“…Thus, although considerable differences were seen between the two 2 J(Pt-H) coupling constants in 6, only a slight trans effect difference is exerted on the two Pt-Me bond distances. The Pt-N(imine) bond length of 2.126(3) Å is in the range found in (diimine)PtMe 2 complexes [39,40], ranging from 2.094 to 2.138 Å . No 5-ring chelated (j 2 -carbene)PtMe 2 or (j 2 -carbene)PtCl 2 crystal structures have been reported for comparison, but differences in the cis and trans M-X (X = halide, Me) distances are found in other functionalized carbenes [20,44].…”

“…The PtMe distance trans to the carbene, Pt(1)-C(1), is 2.071(5) Å , and the Pt-Me distance cis to imine-N is 2.051(4) Å . These values are in the range 2.037-2.079 Å spanned by Pt-Me bonds in three (diimine)PtMe 2 complexes [39,40,42] and a number of recently reported pyridinium-derived cyclometalated Pt methyl complexes [43]. Thus, although considerable differences were seen between the two 2 J(Pt-H) coupling constants in 6, only a slight trans effect difference is exerted on the two Pt-Me bond distances.…”

Synthesis, Characterization, and Protonation Reactions of Ar‐BIAN and Ar‐BICAT Diimine Platinum Diphenyl Complexes

“…These differences reflect the increased steric demands of the 2,6-dimethyl-substituted systems and appear to be a common feature for N,NЈ-diaryl-substituted (N-N)PtX 2 complexes where similar trends in dihedral angles have been reported. [15,36,44,45,54,60,[62][63][64][65][66][67] This empha-sizes the steric hindrance imposed by the 2,6-dimethyl-substituted N-aryl groups: The perpendicular orientation of these N-aryl groups with respect to the coordination plane causes the methyl groups to sterically block the access to Pt from above and below the coordination plane. This has a pronounced effect on the qualitative protonation rates and on the stabilities of the Pt II π-benzene complexes, as discussed earlier.…”

Synthesis and Reactivity of Square‐Planar PtII–η1‐Hydrocarbyl Complexes Containing cis‐Coordinated Olefin or Alkyne

“…Unsymmetrical N,N-chelates were used to isolate ethylene and acrylonitrile complexes I-34 to I-36, by using a procedure analogous to that reported in Scheme 5. [17,18] Alternatively, the same complexes were obtained by reacting the dimethyl precursor with B(C 6 F 5 ) 3 , giving rise to B(C 6 F 5 ) 3 -www.eurjic.org…”