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Half‐Sandwich o ‐ N , N ‐Dimethylaminobenzyl Complexes over the Full Size Range of Group 3 and Lanthanide Metals. Synthesis, Structural Characterization, and Catalysis of Phosphine PH Bond Addition to Carbodiimides
Author(s) -
Zhang WenXiong,
Nishiura Masayoshi,
Mashiko Tomohiro,
Hou Zhaomin
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701300
Subject(s) - chemistry , phosphine , catalysis , medicinal chemistry , lanthanide , ligand (biochemistry) , silylene , metal , amine gas treating , yield (engineering) , stereochemistry , cyclopentadiene , base (topology) , organic chemistry , ion , biochemistry , receptor , mathematical analysis , materials science , mathematics , silicon , metallurgy
The acid‐base reactions between the rare‐earth metal (Ln) tris( ortho ‐ N , N ‐dimethylaminobenzyl) complexes [Ln(CH 2 C 6 H 4 NMe 2 ‐ o ) 3 ] with one equivalent of the silylene‐linked cyclopentadiene‐amine ligand (C 5 Me 4 H)SiMe 2 NH(C 6 H 2 Me 3 ‐2,4,6) afforded the corresponding half‐sandwich aminobenzyl complexes [{Me 2 Si(C 5 Me 4 )(NC 6 H 2 Me 3 ‐2,4,6)}Ln(CH 2 C 6 H 4 NMe 2 ‐ o )(thf)] ( 2 ‐ Ln ) (Ln=Y, La, Pr, Nd, Sm, Gd, Lu) in 60–87 % isolated yields. The one‐pot reaction between ScCl 3 and [Me 2 Si(C 5 Me 4 )(NC 6 H 2 Me 3 ‐2,4,6)]Li 2 followed by reaction with LiCH 2 C 6 H 4 NMe 2 ‐ o in THF gave the scandium analogue [{Me 2 Si(C 5 Me 4 )(NC 6 H 2 Me 3 ‐2,4,6)}Sc(CH 2 C 6 H 4 NMe 2 ‐ o )] ( 2‐Sc ) in 67 % isolated yield. 2 ‐ Sc could not be prepared by the acid‐base reaction between [Sc(CH 2 C 6 H 4 NMe 2 ‐ o ) 3 ] and (C 5 Me 4 H)SiMe 2 NH(C 6 H 2 Me 3 ‐2,4,6). These half‐sandwich rare‐earth metal aminobenzyl complexes can serve as efficient catalyst precursors for the catalytic addition of various phosphine PH bonds to carbodiimides to form a series of phosphaguanidine derivatives with excellent tolerability to aromatic carbon‐halogen bonds. A significant increase in the catalytic activity was observed, as a result of an increase in the metal size with a general trend of La>Pr, Nd>Sm>Gd>Lu>Sc. The reaction of 2‐La with 1 equiv of Ph 2 PH yielded the corresponding phosphide complex [{Me 2 Si(C 5 Me 4 )(NC 6 H 2 Me 3 ‐2,4,6)}La(PPh 2 )(thf) 2 ] ( 4 ), which, on recrystallization from benzene, gave the dimeric analogue [{Me 2 Si(C 5 Me 4 )(NC 6 H 2 Me 3 ‐2,4,6)}La(PPh 2 )] 2 ( 5 ). Addition of 4 or 5 to i PrNCN i Pr in THF yielded the phosphaguanidinate complex [{Me 2 Si(C 5 Me 4 )(NC 6 H 2 Me 3 ‐2,4,6)}La{ i PrNC(PPh 2 )N i Pr}(thf)] ( 6 ), which, on recrystallization from ether, afforded the ether‐coordinated structurally characterizable analogue [{Me 2 Si(C 5 Me 4 )(NC 6 H 2 Me 3 ‐2,4,6)}La{ i PrNC(PPh 2 )N i Pr}(OEt 2 )] ( 7 ). The reaction of 6 or 7 with Ph 2 PH in THF yielded 4 and the phosphaguanidine i PrNC(PPh 2 )NH i Pr ( 3 a ). These results suggest that the catalytic formation of a phosphaguanidine compound proceeds through the nucleophilic addition of a phosphide species, which is formed by the acid‐base reaction between a rare‐earth metal o ‐dimethylaminobenzyl bond and a phosphine PH bond, to a carbodiimide, followed by the protonolysis of the resultant phosphaguanidinate species by a phosphine PH bond. Almost all of the rare earth complexes reported this paper were structurally characterized by X‐ray diffraction studies.