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

Abstract

New groups 3 and 4 organometallic and coordination compounds supported by the tetradentate diamino-bis(phenolate) ligands O2 tBuNN‘ and O2 MeNN‘ are reported [H2O2 RNN‘ = (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 O2 tBuN (H2O2 tBuN = nPrN(2-HO-3,5-C6H2 tBu2)2). Reaction of Na2O2 tBuNN‘ with ScCl3 and pyridine in THF gave monomeric Sc(O2 tBuNN‘)Cl(py) (2), whereas Na2O2 MeNN‘ gave the dimeric phenoxy-bridged Sc2(O2 MeNN‘)2Cl2 (3). Reaction of Na2O2 tBuNN‘ and YCl3 in neat pyridine gave the chloride-bridged, seven-coordinate dimer Y2(O2 tBuNN‘)2(μ-Cl)2(py)2 (4). Reaction of M(CH2SiMe3)3(THF)2 (M = Sc or Y) with H2O2 tBuNN‘ afforded M(O2 tBuNN‘)(CH2SiMe3)(THF). The one-pot reaction of ScCl3 with Na2O2 RNN‘ (R = tBu or Me) and Li[PhC(NSiMe3)2] gave the fluxional benzamidinate derivatives Sc(O2 RNN‘){PhC(NSiMe3)2}. Treatment of Ti(NMe2)4 with H2O2 RNN‘ gave the corresponding Ti(O2 RNN‘)(NMe2)2 (R = tBu (11) or Me); 11 in turn reacts with HS-4-C6H4Me to give Ti(O2 tBuNN‘)(NMe2)(S-4-C6H4Me). One-pot reactions of TiCl4(THF)2 with MeLi (2 equiv) followed by H2O2 RNN‘ affords Ti(O2 RNN‘)Cl2 (R = tBu (9) or Me (10)), which are cleanly methylated with MeMgBr to yield the corresponding Ti(O2 RNN‘)Me2 (R = tBu (14) or Me (15)). The terminal imidotitanium compounds Ti(O2 tBuNN‘)(NR)(py) (R = tBu or 2,6-C6H3Me2) were formed from the respective Ti(NR)Cl2(py)3 reagents and Na2O2 tBuNN‘, and these react with CO2 by imido group transfer to yield the μ-oxo dimer Ti2(O2 tBuNN‘)2(μ-O)2 (18) and RNCO. The related five-coordinate compounds Ti(O2 tBuN)(NR)(py) (R = tBu, 2,6-C6H3Me2 (20) or 2,6-C6H3 iPr2 (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(O2 RNN‘)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.

Synthesis, structure and catalytic behavior of yttrium complexes bearing a diaminobis(phenolate) ligand

“…The present result is quite different from that of the reported diaminobis(phenolate) yttrium chloride L' YCl [L'=(2-C 5 H 4 )-CH 2 N{CH 2 -(2-OC 6 H 2 t Bu 2 -3,5)} 2 ], in which the Y -Cl bond was inactive for substitution with LiN(SiMe 3 ) 2 or lithium alkyls [11] . These results revealed that the sidearm donor has a great effect on the reactivity of Ln-Cl bond of diaminobis(phenolate) rare-earth complexes.…”

“…The central metal atom is coordinated 6 times by two oxygen atoms and two nitrogen atoms from the diaminobis(phenolate) ligand, one THF molecule, and one chlorine atom in a distorted octahedron. The overall coordination geometry is similar to the geometries of LLnCl(THF) (Ln = Yb , Er) [15] and L'ScCl(py) [L' =(2-C 5 H 4 )-CH 2 N{CH 2 -(2-OC 6 H 2 -t Bu 2 -3, 5)} 2 ], but different from the geometry of [L'Y(µ-Cl) (py)] 2 [11] , in which each metal center is seven-coordinate. In [11] and LLnCl [15] , when the differences in ionic radii are considered.…”

“…The overall coordination geometry is similar to the geometries of LLnCl(THF) (Ln = Yb , Er) [15] and L'ScCl(py) [L' =(2-C 5 H 4 )-CH 2 N{CH 2 -(2-OC 6 H 2 -t Bu 2 -3, 5)} 2 ], but different from the geometry of [L'Y(µ-Cl) (py)] 2 [11] , in which each metal center is seven-coordinate. In [11] and LLnCl [15] , when the differences in ionic radii are considered. The Y-Cl bond length of 2.562 Å in complex 1 is in agreement with the data found in the other monomeric yttrium chlorides and, apparently shorter than the corresponding bond length in the dimeric [L'Y(µ-Cl)(py)] 2 (2.766 Å) [11] , and comparable to the corresponding value in LLnCl [15] when differences in ionic radii are also considered.…”

“…In [11] and LLnCl [15] , when the differences in ionic radii are considered. The Y-Cl bond length of 2.562 Å in complex 1 is in agreement with the data found in the other monomeric yttrium chlorides and, apparently shorter than the corresponding bond length in the dimeric [L'Y(µ-Cl)(py)] 2 (2.766 Å) [11] , and comparable to the corresponding value in LLnCl [15] when differences in ionic radii are also considered. The Y-N(2) bond length of 2.546(6) Å in complex 1 is shorter than the bond length presented in [L'Y(µ-Cl)(py)] 2 , and the Y-N(1) bond length of 2.520(5) Å is in accordance with the corresponding value in [L'Y(µ-Cl)(py)] 2 [11] .…”

“…In general, the metathesis of yttrium halides with lithium amides or alkyls should be a convenient method for the synthesis of yttrium complexes bearing various initiating groups. However, only one paper reported the synthesis of yttrium chloride supported by diaminobis(phenolate) ligand, but the reported yttrium chloride is inactive for many halide substitution reactions [11] .…”