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 O<INF>2</INF>^tBuNN‘ and O<INF>2</INF>^MeNN‘ are reported [H<INF>2</INF>O<INF>2</INF>^RNN‘ = (2-C<INF>5</INF>H<INF>4</INF>N)CH<INF>2</INF>N(2-HO-3,5-C<INF>6</INF>H<INF>2</INF>R<INF>2</INF>)<INF>2</INF> where R = ^tBu or Me] along with some comparative studies with the tridentate amino-bis(phenolate) ligand O<INF>2</INF>^tBuN (H<INF>2</INF>O<INF>2</INF>^tBuN = ⁿPrN(2-HO-3,5-C<INF>6</INF>H<INF>2</INF>^tBu<INF>2</INF>)<INF>2</INF>). Reaction of Na<INF>2</INF>O<INF>2</INF>^tBuNN‘ with ScCl<INF>3</INF> and pyridine in THF gave monomeric Sc(O<INF>2</INF>^tBuNN‘)Cl(py) (<BO>2</BO>), whereas Na<INF>2</INF>O<INF>2</INF>^MeNN‘ gave the dimeric phenoxy-bridged Sc<INF>2</INF>(O<INF>2</INF>^MeNN‘)<INF>2</INF>Cl<INF>2</INF> (<BO>3</BO>). Reaction of Na<INF>2</INF>O<INF>2</INF>^tBuNN‘ and YCl<INF>3</INF> in neat pyridine gave the chloride-bridged, seven-coordinate dimer Y<INF>2</INF>(O<INF>2</INF>^tBuNN‘)<INF>2</INF>(μ-Cl)<INF>2</INF>(py)<INF>2</INF> (<BO>4</BO>). Reaction of M(CH<INF>2</INF>SiMe<INF>3</INF>)<INF>3</INF>(THF)<INF>2</INF> (M = Sc or Y) with H<INF>2</INF>O<INF>2</INF>^tBuNN‘ afforded M(O<INF>2</INF>^tBuNN‘)(CH<INF>2</INF>SiMe<INF>3</INF>)(THF). The one-pot reaction of ScCl<INF>3</INF> with Na<INF>2</INF>O<INF>2</INF>^RNN‘ (R = ^tBu or Me) and Li[PhC(NSiMe<INF>3</INF>)<INF>2</INF>] gave the fluxional benzamidinate derivatives Sc(O<INF>2</INF>^RNN‘){PhC(NSiMe<INF>3</INF>)<INF>2</INF>}. Treatment of Ti(NMe<INF>2</INF>)<INF>4</INF> with H<INF>2</INF>O<INF>2</INF>^RNN‘ gave the corresponding Ti(O<INF>2</INF>^RNN‘)(NMe<INF>2</INF>)<INF>2</INF> (R = ^tBu (<BO>11</BO>) or Me); <BO>11</BO> in turn reacts with HS-4-C<INF>6</INF>H<INF>4</INF>Me to give Ti(O<INF>2</INF>^tBuNN‘)(NMe<INF>2</INF>)(S-4-C<INF>6</INF>H<INF>4</INF>Me). One-pot reactions of TiCl<INF>4</INF>(THF)<INF>2</INF> with MeLi (2 equiv) followed by H<INF>2</INF>O<INF>2</INF>^RNN‘ affords Ti(O<INF>2</INF>^RNN‘)Cl<INF>2</INF> (R = ^tBu (<BO>9</BO>) or Me (<BO>10</BO>)), which are cleanly methylated with MeMgBr to yield the corresponding Ti(O<INF>2</INF>^RNN‘)Me<INF>2</INF> (R = ^tBu (<BO>14</BO>) or Me (<BO>15</BO>)). The terminal imidotitanium compounds Ti(O<INF>2</INF>^tBuNN‘)(NR)(py) (R = ^tBu or 2,6-C<INF>6</INF>H<INF>3</INF>Me<INF>2</INF>) were formed from the respective Ti(NR)Cl<INF>2</INF>(py)<INF>3</INF> reagents and Na<INF>2</INF>O<INF>2</INF>^tBuNN‘, and these react with CO<INF>2</INF> by imido group transfer to yield the μ-oxo dimer Ti<INF>2</INF>(O<INF>2</INF>^tBuNN‘)<INF>2</INF>(μ-O)<INF>2</INF> (<BO>18</BO>) and RNCO. The related five-coordinate compounds Ti(O<INF>2</INF>^tBuN)(NR)(py) (R = ^tBu, 2,6-C<INF>6</INF>H<INF>3</INF>Me<INF>2</INF> (<BO>20</BO>) or 2,6-C<INF>6</INF>H<INF>3</INF>ⁱPr<INF>2</INF> (<BO>21</BO>)) were prepared in an analogous manner. These do not give identifiable metal products with CO<INF>2</INF>. Treatment of the dimethyl compounds <BO>14</BO> or <BO>15</BO> with B(Ar^F)<INF>3</INF> or [CPh<INF>3</INF>][B(Ar^F)<INF>4</INF>] (Ar^F = C<INF>6</INF>F<INF>5</INF>) gave the fluxional, dimeric phenoxy-bridged cations [Ti<INF>2</INF>(O<INF>2</INF>^RNN‘)<INF>2</INF>Me<INF>2</INF>]²⁺, which show very sluggish 1-hexene polymerization behavior. The compounds <BO>2</BO>, <BO>3</BO>, <BO>4</BO>, <BO>11</BO>, <BO>9</BO>, <BO>10</BO>, <BO>16</BO>, <BO>18</BO>, <BO>20</BO>, and <BO>21</BO> have been crystallographically characterized.