Novel neutral antimony(V) complexes were isolated as crystalline materials and characterized by IR and NMR spectroscopy: o-amidophenolate complexes [4,6-di-tert-butyl-N-(2,6-dimethylphenyl)-o-amidophenolato]triphenylantimony(V) (Ph3Sb[AP-Me], 1) and [4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-amidophenolato]triphenylantimony(v) (Ph3Sb[AP-iPr], 2); catecholate complexes (3,6-di-tert-butyl-4-methoxycatecholato)triphenylantimony(V) (Ph3Sb[(MeO)Cat], 3), its methanol solvate 3CH3OH (4); (3,6-di-tert-butyl-4,5-di-methoxycatecholato)triphenylantimony(V) (Ph3Sb[(MeO)2Cat], 5) and its acetonitrile solvate 5CH3CN (6). Complexes 1-7 were synthesized by oxidative addition of the corresponding o-iminobenzoquinones or o-benzoquinones to Ph3Sb. In the case of the phenanthrene-9,10-diolate (PhenCat) ligand, two different complexes were isolated: Ph3Sb[PhenCat] (7) and [Ph4Sb]+[Ph2Sb(PhenCat)2]- (8). Complexes 7 and 8 were found to be in equilibrium in solution. Molecular structures of 2, 4, 6, and 8 were determined by X-ray crystallography. Complexes 1-7 reversibly bind molecular oxygen to yield Ph3Sb[L-Me]O2 (9), Ph3Sb[L-iPr]O2 (10), Ph3Sb[(MeO)L']O2 (11), Ph3Sb[(MeO)2L']O2 (12) and Ph3Sb[PhenL']O2 (13), which contain five-membered trioxastibolane species (where L is the O,O',N-coordinated derivative of a 1-hydroperoxy-6-(N-aryl)-iminocyclohexa-2,4-dienol, and L' the O,O',O''-coordinated derivative of 6-hydroperoxy-6-hydroxycyclohexa-2,4-dienone). Complexes 9-13 were characterized by IR and 1H NMR spectroscopy and X-ray crystallography.

Dioxygen binds reversibly to the non‐transition‐metal complex 1 to form the spiroendoperoxide 2 (see scheme). Complexes 1 and 2 were characterized by NMR, IR, and UV/Vis spectroscopies, and their molecular structures were determined by X‐ray crystallography.

The coordination chemistry of new fluorinated dialkoxy-diimino ligands onto Al(III) centers has been studied. Diimino-diols) react selectively with AlMe 3 , AlMe 2 Cl, and Al(OiPr) 3 to give the corresponding complexes {ON Et NO}AlX (X ) Me, 1; Cl, 2; OiPr, 3), {ON Cy NO}AlX (X ) Me, 5; Cl, 6; OiPr, 7), and { Me ON Et NO}AlX (X ) Me, 8; Cl, 9) with concomitant alkane or alcohol elimination, respectively. Single-crystal X-ray diffraction studies revealed that complexes 2, 5, 7, 8, and 9 are mononuclear in the solid state with distorted trigonal-bipyramidal to square-pyramidal geometries. Complexes 1-9 were also characterized in CD 2 Cl 2 solution by 1 H, 13 C, and 19 F NMR spectroscopy. Only one symmetric isomer was observed for complexes 1-7, but mixtures of two isomers (one symmetric, one dissymmetric on the NMR time scale) were observed for complexes 8 and 9. The Al-OiPr complexes 3 and 7 are effective initiators for the ring-opening polymerization of ε-caprolactone and racemic lactide, giving polymers with high molecular weights (M n up to 37 500 g mol -1 ) and relatively narrow polydispersities (M w /M n ) 1.08-1.91). The PLAs produced, both under slurry or melt conditions, with either achiral complex 3 or chiral complex 7, have a highly isotactic-enriched stereoblock microstructure (P meso ) 0.87).

The reaction of fluorous imino-alcohols {ON(R1,R2)}H (R(1) = Me, Ph; R(2) = Ph, CH(2)Ph, cyclohexyl, piperidinyl) with Zn(N(SiMe(3))(2))(2) (1 or 0.5 equiv) systematically led to bis(ligand) complexes Zn{ON(R1,R2)}(2) (1-9), which were isolated in 84-88% yield. Imino-alcohols {ON(R1,R2)}H react selectively with ZnEt(2) to give the corresponding complexes {ON(R1,R2)}ZnEt (4-7), in 74-78% yield. The stability of complexes 4-7 appears to be controlled by the nature of the substituent at the imine N atom: a phenyl group leads to slow ligand redistribution while alkyl-type substituents (benzyl, cyclohexyl, piperidinyl) prevent this disproportionation. Treatment of 5 with isopropanol afforded {ON(Ph,Bn)}Zn(OiPr) (8) in modest yield, due to rapid ligand redistribution. Complexes 1-8 were authenticated by elemental analysis, (1)H, (19)F and (13)C NMR spectroscopy in solution, and single-crystal X-ray diffraction studies for 1, 3, 5, 7 and 8. In situ combinations of {ON(Ph,Bn)}ZnEt (5)/BnOH and Zn{ON(Ph,Bn)}(2) (2)/BnOH are active systems for the ROP of racemic lactide and beta-butyrolactone at 20-50 degrees C, yielding atactic polylactide and poly(3-hydroxybutyrate) with good molecular weight control (M(n) up to 20,700 g/mol) and relatively narrow molecular weight distributions (M(w)/M(n) = 1.06-1.57). These binary systems also allow the immortal ROP of lactide and beta-butyrolactone, using excess alcohol (up to 5 equiv) vs the Zn catalyst.

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Scandium, yttrium and lanthanum amido complexes supported by tridentate bis(ortho-silyl-substituted naphtholate)-donor ligands ({ONO(SiPh3)}(2-) and {ONO(SitBuMe2)}(2-), donor = 2,6-pyridine; {OSO(SiPh3)}(2-), donor = 2,5-thiophene) have been prepared in high yields (72-96%) by reaction of the corresponding pro-ligand {OZO(SiR3)}H(2) and Ln[N(SiHMe(2))(2)](3)(THF)(n) precursor. The solid-state structures of {ONO(SiPh3)}La[N(SiHMe(2))(2)](THF) (3), {ONO(SitBuMe2)}Ln[N(SiHMe(2))(2)](THF) (Ln = Sc, 4; Y, 5) and {OSO(SiPh3)}Ln[N(SiHMe(2))(2)](THF) (Ln = Sc, 7; La, 9) have been determined by single-crystal X-ray diffraction studies. In all five complexes, the naphtholate rings twist in the same direction from the plane of the pyridine or thiophene linker, to give rise to C(s)-symmetric (non crystallographic) structures. Compounds are 1-9 single-site initiators for the ring-opening polymerization (ROP) of racemic lactide (rac-LA) at 20 degrees C, affording poly(lactides)s (PLAs) with relatively narrow polydispersities and molecular weights in good agreement with calculated values. When carried out in THF, the polymerizations afforded heterotactic-enriched PLAs (P(r) up to 0.93), while atactic polymers are formed in toluene. Compounds 1-3 and 7-9, having o-SiPh(3) substituents on the naphtholate rings, are also active for the ROP of racemic beta-butyrolactone at 20-50 degrees C, to form syndiotactic-enriched poly(3-hydroxybutyrate)s (PHBs) (P(r) up to 0.87) when using toluene as the solvent, whereas atactic polymers were obtained in THF. The nature of the metal center (Sc, Y, La), the central linker in the ligand framework (pyridine, thiophene), and the ortho-silyl substituent (SiPh(3), SiMe(2)tBu) significantly affect the degree of stereocontrol in those polymerizations.

The coordination chemistry of the dianionic fluorous dialkoxy-diimino ligand {OC(CF 3 ) 2 -CH 2 C(Me)dNCH 2 CH 2 NdC(Me)CH 2 C(CF 3 ) 2 O} 2-({ON Et NO} 2-) onto Y(III) and La(III) centers has been studied. The diimino-diol {ON Et NO}H 2 reacts with 1 equiv of Y(N(SiHMe 2 ) 2 ) 3 • 2THF to afford {ON Et NO}Y(N(SiHMe 2 ) 2 )(THF) (1). Complex 1 slowly decomposes in solution, forming as yet undefined products, but could be stabilized by further reaction with 1 equiv of (R)-(+)-tert-butyl lactate, to give selectively [{ON Et NO}Y((R)-tBu-lactate)] 2 (2) in 78% yield. A single-crystal diffraction study revealed that 2 is dinuclear in the solid state, with bridging µ,κ 2 O,O,O-lactate units and tetracoordinated {ON Et NO} units. The same geometry is retained in THF-d 8 solution, as indicated by 1 H, 13 C, and 19 F NMR spectroscopy. Reaction of {ON Et NO}H 2 with 1 equiv of La(N(SiHMe 2 ) 2 ) 3 • 2THF or La(N(SiMe 3 ) 2 ) 3 systematically yielded {ON Et NO}La{ON Et NOH} (3), which was characterized by single-crystal X-ray diffraction and NMR studies. Complex 2 is an effective initiator for the controlled-"living" ring-opening polymerization of rac-lactide and rac-β-butyrolactone, giving atactic polymers with high molecular weights (M n up to 55 000 g mol -1 ) that match well the calculated values and relatively narrow polydispersities (M w /M n ) 1.06-1.60). The immortal ROP of rac-lactide appears feasible by combining complex 2 with 5 equiv of 2-propanol.