Zirconium and titanium complexes with side-chain functionalized cyclopentadienyl ligands

Abstract

The present review summarizes the results of studies of Zr and Ti complexes based on chelating side chain functionalized cyclopentadienyl ligands, which were synthesized by the author of the present review and co workers. The coordination ability of the functional groups is considered. Dynamic processes that occur in half sandwich complexes in solutions were studied by NMR spectroscopy. Emphasis is given to the reduction reactions of side chain functionalized zirconocene dichlorides, as well as to the structures and properties of the reaction products depending on the nature of the heteroatomic substituent.The present review summarizes data on Zr and Ti complexes with chelating cyclopentadienyl ligands con taining a functional (heteroorganic) group C 5 R 4 CH 2 CH 2 X (R = H and X = PMe 2 , PPh 2 , P(O)Ph 2 , or P(S)Ph 2 ; R = Me and X = OMe, SMe, NMe 2 , PMe 2 , or PPh 2 ) or C 5 Me 4 CH 2 (2 Py) in the side chain. The types of sand wich and half sandwich complexes I-IV that were syn thesized and investigated are given below.The fundamental and applied interest in studying these compounds is associated with an important feature of these ligands. Thus, these ligands contain two coordina tion sites of different nature, viz., the cyclopentadienyl ring strongly bound to the metal atom and the functional group capable of being involved in the reversible coordi nation. Due to this feature, the ligands are very attractive for the catalyst design, in particular, in the α olefin poly merization, which has stimulated extensive studies in this field from the late 1980s (see the reviews 1-6 ).The presence or absence of the coordination interac tion between the chelating functional group and the metal atom is one of the key factors responsible for the chemi cal, including catalytic, behavior of complexes with side chain functionalized cyclopentadienyl ligands. The coordination ability of chelating heteroatomic functional groups was studied in sufficient detail (primarily by X ray diffraction) for metal complexes in the crystalline state,

Nickel(II) and Palladium(II) Complexes with η5:κ1(N)-Coordinated Dicarbollide Ligands Containing Pendant Pyridine Group

“…First, via the reaction of the tetramethylammonium salt of nido-carborane with 2-pyridylsulfenyl chloride in a mixture of acetonitrile and acetic acid, the N-protonated derivative [9-(HNC5H4-2′-S)-7,8-C2B9H11] (H [1]) was obtained, which was then converted to the cesium salt Cs[9-(NC5H4-2′-S)-7,8-C2B9H11] (Cs [1]) via treatment with CsOH in aqueous acetone (Scheme 1). The obtained carboranes were characterized using methods of 1 H, 13 C, and 11 B NMR and IR spectroscopy and mass spectrometry (See Supplementary Materials, Figure S1-S70 and Table S1). The 11 B NMR spectrum of Cs [1] in acetone-d6 contains a singlet at −3.1 ppm and seven doublets at −6.8, −15.6, −18.4, −22.5, −24.3, −30.6, and −37.8 ppm with an integral intensity ratio of 1:1:1:2:1:1:1:1, which is significantly different from the spectrum of the N-protonated form H[1] [51], indicating a rather strong interaction between the carborane cage and the pyridine ring.…”

“…The obtained carboranes were characterized using methods of 1 H, 13 C, and 11 B NMR and IR spectroscopy and mass spectrometry (See Supplementary Materials, Figure S1-S70 and Table S1). The 11 B NMR spectrum of Cs [1] in acetone-d 6 contains a singlet at −3.1 ppm and seven doublets at −6.8, −15.6, −18.4, −22.5, −24.3, −30.6, and −37.8 ppm with an integral intensity ratio of 1:1:1:2:1:1:1:1, which is significantly different from the spectrum of the N-protonated form H[1] [51], indicating a rather strong interaction between the carborane cage and the pyridine ring.…”

“…Previously, this approach was used for the synthesis of various alkylsulfenyl derivatives of orthoand nido-carboranes including those containing various functional groups [75][76][77][78][79]. The obtained carboranes were characterized using methods of 1 H, 13 C, and 11 B NMR and IR spectroscopy and mass spectrometry (See Supplementary Materials). In the 1 H NMR spectrum of 4 in acetone-d6, the signal of the methylene group appears as a singlet at 4.42 ppm, whereas in the spectrum of Cs [5], the signals of the methylene group appear as two doublets at 4.13 and 3.89 ppm ( 2 JHH = 12.8 Hz) due to chirality of the C-monosubstituted nido-carborane cage that causes protons to become diastereotopiс and magnetically inequivalent.…”

“…After the removal of endo-hydrogen from nido-carborane, the resulting dicarbollide anion [nido-1,2-C 2 B 9 H 11 ] 2can act as a ligand similar to a cyclopentadienyl one [3][4][5][6][7][8]. It is known that transition metal complexes with cyclopentadienyl ligands containing pendant donor groups are good catalysts for various organic reactions [9][10][11][12][13][14][15][16], and some of them are also promising luminescent materials [17,18]. One such pendant substituent is the pyridyl group [19,20].…”

Organozirconium Complex with Keggin-Type Mono-Aluminum-Substituted Silicotungstate: Synthesis, Molecular Structure, and Catalytic Performance for Meerwein–Ponndorf–Verley Reduction

“…To explore POMs that could be used as supports for grafting reactions, we focused on the aluminum-substituted POMs and successfully synthesized an organozirconium(IV)-supported polyoxometalate, [-PW11Al(OH)O39ZrCp2]2 6− (Cp =  5 -C5H5 − ) (P-Al-Zr), by a grafting reaction of -Keggin mono-aluminum-substituted phosphotungstate with a bis( 5cyclopentadienyl)zirconium(IV) fragment [25]. Although the chemistry of organometallic moieties possessing  5 -cyclopentadienyl ligands has rapidly expanded [26][27][28] In this study, we focused on the use of the tetra-n-butylammonium/potassium salt of - Cp2Zr(OTf)2THF (OTf = CF3SO3 − ) were synthesized by previously published methods [25,37]. All the reagents and solvents were obtained and used as received from commercial sources.…”