Didentate phosphine ligands with alkenyl and alkynyl linker units as building blocks for dendrimer fixation

Abstract

Using diethyl-2-methylmalonate as a starting material, the two diphosphines HC᎐ ᎐ ᎐ CCH 2 C(CH 3 )(CH 2 PPh 2 ) 2 (7) and H 2 C᎐ ᎐ CHCH 2 C(CH 3 )(CH 2 PPh 2 ) 2 (13), containing alkynyl and alkenyl unit in the ligand backbone were prepared in multistep syntheses. These two ligands were employed in the synthesis of [{(CH 3), all of which were characterized by X-ray diffraction. Reaction of Si[(CH 2 ) 3 SiMe 2 Cl] 4 (= "G[0]-[Cl] 4 ") with four molar equivalents of the in situ lithiated alkynyl diphosphine 7 cleanly yielded the four-fold functionalized derivative G[0]-[C᎐ ᎐ ᎐ CCH 2 C(CH 3 )(CH 2 PPh 2 ) 2 ] 4 (15) which was converted to the metallated derivative G[0]-[C᎐ ᎐ ᎐ CCH 2 -C(CH 3 )(CH 2 PPh 2 ) 2 PdCl 2 ] 4 (16). Since the fixation of the alkenyl-functionalized diphosphine ligand 13 to the SiHsilane Si[(CH 2 ) 3 SiMe 2 H] 4 (= "G[0]-[H] 4 ") by Pt-catalyzed hydrosilation proved to be unsuccessful due to the negative interference of the phosphine with Karstedt's catalyst, the chloro-substituted precursor of 13, H 2 C᎐ ᎐ CHCH 2 C(CH 3 )-(CH 2 Cl) 2 (12) was used. Hydrosilation of G[0]-[H] 4 with four molar equivalents of 12 readily gave the functionalized dendrimer G[0]-[CH 2 CH 2 CH 2 C(CH 3 )(CH 2 Cl) 2 ] 4 (17) which was then reacted with eight equivalents of LiPPh 2 to yield the phosphinated derivative G[0]-[CH 2 CH 2 CH 2 C(CH 3 )(CH 2 PPh 2 ) 2 ] 4 (18). Scheme 1 Synthesis of the alkynyl diphosphine 7 from diethyl-2methylmalonate. DALTON

Synthesis and Charge/Discharge Properties of Polyacetylenes Carrying 2,2,6,6‐Tetramethyl‐1‐piperidinoxy Radicals

“…4-Carboxy-TEMPO (TCI), 4-hydroxy-TEMPO (TCI), l-Glutamic acid-a,g-dimethyl ester hydrochloride (l-HGluA C H T U N G T R E N N U N G (OMe)-OMe·HCl) (Watanabe Chemical Industries, Ltd), propargyl alcohol (Aldrich), propargylamine (Aldrich), N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC·HCl; Eiweiss Chemical Corporation), 4-dimethylaminopyridine (DMAP; Wako) were purchased and used without further purification. 4-Carboxy-2,2,6,6-tetramethyl-1-piperidinoxy N-propargylamide, [17] 4-carboxy-2,2,6,6-tetramethyl-1-piperidinoxy propargyl ester, [17] 1-pentyne-4,4-dimethanol, [20] 4-ethynylbenzoic acid, [21] N-(4-ethynyl benzoyl)-l-aspartic acid methyl ester, [22] and [Rh [23] were synthesized according to previous reports.…”

A Trithiol Protio-Ligand and Its Fixation to the Periphery of a Carbosilane Dendrimer as Scaffolds for Polynuclear Rhodium and Iridium Complexes and Metallodendrimers

“…Moreover, this methodology involves the formation of Si−C bonds between the core dendrimer and the precursor of the ligand, which led to very robust and thermally stable constructs. Parallel strategies have been used to couple a tripod-based phosphine ligand to carbosilane dendrimers, although some of these relied on the formation of Si−O bonds, which are more susceptible to the hydrolysis.

4 Attachment of a Tripod Ligand Precursor to Carbosilane Dendrimers a a i = Karstedt's catalyst, THF; ii = KSCN, DMF; iii = LiAlH 4 , Et 2 O.

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Phosphines and Related Tervalent Phosphorus Systems

“…384 Imine formation with o-diphenylphosphinobenzaldehyde has also been used for the surface functionalisation of dendritic primary alkylamines, giving dendrimeric P,N ligands. 385 Aminal-and thioacetal-like cyclocondensations of o-diphenylphosphinobenzaldehyde with chiral amino-amides, disecondary amines, and 3-hydroxypropanethiols has afforded new chiral phosphines, e.g., (162), 386,387 and (163). 388,389 Imine formation from enantiopure 2-formyl-1-phosphanorbornadiene has been utilised to give the new chiral phosphinoimines (164).…”

“…161 Metallophosphide routes have been applied to the preparation of a wide range of di-, tri-and tetra-phosphines bearing additional donor or other reactive functional groups. Findeis and Gade have described the synthesis of a series of di-and triphosphines bearing alkenyl, alkynyl 162,163 and hydroxyalkyl groups, 164 e.g., (82), these acting as linkers for the synthesis of phosphino-functional dendrimers and related catalyst systems. Various chiral oxo-and oxy-functional diphosphines, e.g., (83), have been prepared from the camphor system.…”