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 (O2NN)-N-tBu' and (O2NN)-N-Me' are reported [(H2O2NN)-N-R' = (2-C5H4N)CH2N(2-HO-3,5-C6H2R2)(2) where R = Bu-t or Me] along with some comparative studies with the tridentate amino-bis(phenolate) ligand (O2N)-N-tBu ((H2O2N)-N-tBu = (PrN)-Pr-n(2-HO-3,5-(C6H2Bu2)-Bu-t)(2)). Reaction of (Na2O2NN)-N-tBu' with ScCl3 and pyridine in THF gave monomeric Sc((O2NN)-N-tBu')Cl(py) (2), whereas (Na2O2NN)-N-Me' gave the dimeric phenoxy-bridged Sc-2((O2NN)-N-Me')(2)Cl-2 (3) Reaction of (Na2O2NN)-N-tBu' and YCl3 in neat pyridine gave the chloride-bridged, seven-coordinate dimer Y-2((O2NN)-N-tBu')(2)(mu-Cl)(2)(py)(2) (4). Reaction of M(CH2SiMe3)(3)(THF)(2) (M = Sc or Y) with (H2O2NN)-N-tBu' afforded M((O2NN)-N-tBu')(CH2SiMe3)(THF). The one-pot reaction of ScCl3 with (Na2O2NN)-N-R' (R = Bu-t or Me) and Li[PhC(NSiMe3)(2)] gave the fluxional benzamidinate derivatives Sc((O2NN)-N-R'){PhC(NSiMe3)(2)}. Treatment of Ti(NMe2)(4) with (H2O2NN)-N-R' gave the corresponding Ti((O2NN)-N-R')(NMe2)(2) (R = Bu-t (11) or Me): 11 in turn reacts with HS-4-C6H4Me to give Ti((O2NN)-N-tBu')(NMe2)(S-4-C6H4Me). One-pot reactions of TiCl2(THF)(2) with MeLi (2 equiv) followed by (H2O2NN)-N-R' affords Ti((O2NN)-N-R')Cl-2 (R = Bu-t (9) or Me (10)), which are cleanly methylated with MeMgBr to yield the corresponding Ti((O2NN)-N-R')Me-2 (R = Bu-t (14) or Me (15)). The terminal imidotitanium compounds Ti((O2NN)-N-tBu')(NR)(py) (R = Bu-t or 2,6-C6H3Me2) were formed from the respective Ti(NR)Cl-2(py)(3) reagents and (Na2O2NN)-N-tBu', and these react with CO2 by imido group transfer to yield the mu-oxo dimer Ti-2((O2NN)-N-tBu')(2)-(mu-O)(2) (18) and RNCO. The related five-coordinate compounds Ti((O2N)-N-tBu)(NR)(py) (R = Bu-t, 2,6-C6H3Me2 (20) or 2,6-(C6H3Pr2)-Pr-i (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(Ar-F)(3) or [CPh3][B(Ar-F)(4)] (ArF = C6F5) gave the fluxional, dimeric phenoxy-bridged cations [Ti-2((O2NN)-N-R')(2)Me-2](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.