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Synthesis and Characterization of Thermally Robust Amidinato Group 13 Hydride Complexes
Author(s) -
Cole Marcus L.,
Jones Cameron,
Junk Peter C.,
Kloth Marc,
Stasch Andreas
Publication year - 2005
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.200500278
Subject(s) - chemistry , denticity , amidine , hydride , medicinal chemistry , ligand (biochemistry) , stereochemistry , imine , quinuclidine , chelation , bridging ligand , reactivity (psychology) , steric effects , metal , crystallography , crystal structure , inorganic chemistry , organic chemistry , medicine , biochemistry , receptor , alternative medicine , pathology , catalysis
The reactivity of two sterically bulky amidines, ArNC(R)N(H)Ar (Ar=2,6‐diisopropylphenyl; R=H (HFiso); t Bu, (HPiso)) towards LiMH 4 , M=Al or Ga, [AlH 3 (NMe 3 )], and [GaH 3 (quin)] (quin=quinuclidine) has been examined. This has given rise to a variety of very thermally stable aluminum and gallium hydride complexes. The structural motif adopted by the prepared complexes has been found to be dependent upon both the amidinate ligand and the metal involved. The 1:1 reaction of HFiso with LiAlH 4 yielded dimeric [{AlH 3 (μ‐Fiso)Li(OEt 2 )} 2 ]. Amidine HFiso reacts in a 1:1 ratio with [AlH 3 (NMe 3 )] to give the unusual hydride‐bridging dimeric complex, [{AlH 2 (Fiso)} 2 ], in which the Fiso − ligand is nonchelating. The equivalent reaction with the bulkier amidine, HPiso, yielded a related hydride‐bridging complex, [{AlH 2 (Piso)} 2 ], in which the Piso − ligand is chelating. In contrast, the treatment of [GaH 3 (quin)] with one equivalent of HFiso afforded the four‐coordinate complex [GaH 2 (quin)(Fiso)], in which the Fiso − ligand acts as a localized monodentate amido–imine ligand. The 2:1 reactions of HFiso with [AlH 3 (NMe 3 )] or [GaH 3 (quin)] gave the monomeric complexes [MH(Fiso) 2 ], which are thermally robust and which exhibit chelating amidinate ligands. In contrast, HPiso did not give 2:1 complexes in its reactions with either of the Group 13 trihydride precursors. For sake of comparison, the reactions of [AlH 3 (NMe 3 )] and [GaH 3 (quin)] with the bulky carbodiimide ArNCNAr and the thiourea Ar(H)NC(S)N(H)Ar were examined. These last reactions afforded the five‐coordinate thioureido complexes, [MH{N(Ar)C[N(H)(Ar)]S} 2 ], M=Al or Ga.