Synthesis, Structures, and Reactions of Titanium, Scandium, and Yttrium Complexes of Diamino-bis(phenolate) Ligands: Monomeric, Dimeric, Neutral, Cationic, and Multiply Bonded Derivatives

New groups 3 and 4 organometallic and coordination compounds supported by the
tetradentate diamino-bis(phenolate) ligands O2tBuNN‘ and O2MeNN‘ are reported [H2O2RNN‘
= (2-C5H4N)CH2N(2-HO-3,5-C6H2R2)2 where R = tBu or Me] along with some comparative
studies with the tridentate amino-bis(phenolate) ligand O2tBuN (H2O2tBuN = nPrN(2-HO-3,5-C6H2tBu2)2). Reaction of Na2O2tBuNN‘ with ScCl3 and pyridine in THF gave monomeric
Sc(O2tBuNN‘)Cl(py) (2), whereas Na2O2MeNN‘ gave the dimeric phenoxy-bridged Sc2(O2MeNN‘)2Cl2 (3). Reaction of Na2O2tBuNN‘ and YCl3 in neat pyridine gave the chloride-bridged,
seven-coordinate dimer Y2(O2tBuNN‘)2(μ-Cl)2(py)2 (4). Reaction of M(CH2SiMe3)3(THF)2 (M
= Sc or Y) with H2O2tBuNN‘ afforded M(O2tBuNN‘)(CH2SiMe3)(THF). The one-pot reaction of
ScCl3 with Na2O2RNN‘ (R = tBu or Me) and Li[PhC(NSiMe3)2] gave the fluxional benzamidinate derivatives Sc(O2RNN‘){PhC(NSiMe3)2}. Treatment of Ti(NMe2)4 with H2O2RNN‘
gave the corresponding Ti(O2RNN‘)(NMe2)2 (R = tBu (11) or Me); 11 in turn reacts with HS-4-C6H4Me to give Ti(O2tBuNN‘)(NMe2)(S-4-C6H4Me). One-pot reactions of TiCl4(THF)2 with
MeLi (2 equiv) followed by H2O2RNN‘ affords Ti(O2RNN‘)Cl2 (R = tBu (9) or Me (10)), which
are cleanly methylated with MeMgBr to yield the corresponding Ti(O2RNN‘)Me2 (R = tBu
(14) or Me (15)). The terminal imidotitanium compounds Ti(O2tBuNN‘)(NR)(py) (R = tBu or
2,6-C6H3Me2) were formed from the respective Ti(NR)Cl2(py)3 reagents and Na2O2tBuNN‘,
and these react with CO2 by imido group transfer to yield the μ-oxo dimer Ti2(O2tBuNN‘)2(μ-O)2 (18) and RNCO. The related five-coordinate compounds Ti(O2tBuN)(NR)(py) (R = tBu,
2,6-C6H3Me2 (20) or 2,6-C6H3iPr2 (21)) were prepared in an analogous manner. These do not
give identifiable metal products with CO2. Treatment of the dimethyl compounds 14 or 15
with B(ArF)3 or [CPh3][B(ArF)4] (ArF = C6F5) gave the fluxional, dimeric phenoxy-bridged
cations [Ti2(O2RNN‘)2Me2]2+, which show very sluggish 1-hexene polymerization behavior.
The compounds 2, 3, 4, 11, 9, 10, 16, 18, 20, and 21 have been crystallographically
characterized.