Supporting Information. Polymerization of Lactide

Similar documents
Supporting Information

Simple Solution-Phase Syntheses of Tetrahalodiboranes(4) and their Labile Dimethylsulfide Adducts

Ziessel a* Supporting Information (75 pages) Table of Contents. 1) General Methods S2

David L. Davies,*, 1 Charles E. Ellul, 1 Stuart A. Macgregor,*, 2 Claire L. McMullin 2 and Kuldip Singh. 1. Table of contents. General information

Electronic Supplementary Information

Supporting Information

Syntheses and Structures of Mono-, Di- and Tetranuclear Rhodium or Iridium Complexes of Thiacalix[4]arene Derivatives

Synthesis of Vinyl Germylenes

Supporting Information

Chiral Sila[1]ferrocenophanes

Supporting Information

Selective Reduction of Carboxylic acids to Aldehydes Catalyzed by B(C 6 F 5 ) 3

Reversible 1,2-Alkyl Migration to Carbene and Ammonia Activation in an NHC-Zirconium Complex.

Reversible dioxygen binding on asymmetric dinuclear rhodium centres

Supporting information

A Facile Route to Rare Heterobimetallic Aluminum-Copper. and Aluminum-Zinc Selenide Clusters

Supporting Information

Supporting Information

The oxide-route for the preparation of

Catalytic hydrogenation of liquid alkenes with a silica grafted hydride. pincer iridium(iii) complex: Support for a heterogeneous mechanism

Phosphirenium-Borate Zwitterion: Formation in the 1,1-Carboboration Reaction of Phosphinylalkynes. Supporting Information

Hassan Osseili, Debabrata Mukherjee, Klaus Beckerle, Thomas P. Spaniol, and Jun Okuda*

Salan ligands assembled around chiral bipyrrolidine: predetermination of chirality around octahedral Ti and Zr. centres

Electronic Supplementary Information

2-(2 -pyridyl)-4,6-diphenylphosphinine versus 2-(2 -pyridyl)-4,6- diphenylpyridine: An evaluation of their coordination chemistry towards Rh(I)

1,4-Dihydropyridyl Complexes of Magnesium: Synthesis by Pyridine. Insertion into the Magnesium-Silicon Bond of Triphenylsilyls and

Supporting Information for: Kinetic Analysis of the Immortal Ring-Opening Polymerization of Cyclic. Esters: A Case Study with Tin(II) Catalysts

Electronic Supplementary Information (ESI)

Electronic Supplementary Information

Supporting Information

Structural Elucidation of Sumanene and Generation of its Benzylic Anions

Active Trifluoromethylating Agents from Well-defined Copper(I)-CF 3 Complexes

A Highly Reactive Scandium Phosphinoalkylidene Complex: C H and H H Bonds Activation

A Clipped [3]Rotaxane Derived From Bis-nor-seco-Cucurbit[10]uril

Supporting Information

White Phosphorus is Air-Stable Within a Self-Assembled Tetrahedral Capsule

Stoichiometric Reductions of Alkyl-Substituted Ketones and Aldehydes to Borinic Esters Lauren E. Longobardi, Connie Tang, and Douglas W.

A Ladder type Iron(II) Coordination Polymer with Cooperative Spin Transition

Supporting Information for the Article Entitled

Electronic Supplementary Information for: Gram-scale Synthesis of a Bench-Stable 5,5 -Unsubstituted Terpyrrole

Supporting Information for. an Equatorial Diadduct: Evidence for an Electrophilic Carbanion

Cationic scandium aminobenzyl complexes. synthesis, structure, and unprecedented catalysis of copolymerization of 1-hexene and dicyclopentadiene

Supporting Information

Supporting Information

Supporting Information

Carbon monoxide and carbon dioxide insertion chemistry of f-block N-heterocyclic carbene complexes. Experimental details and characterising data

Supporting Information

Electronic Supplementary Information. Pd(diimine)Cl 2 Embedded Heterometallic Compounds with Porous Structures as Efficient Heterogeneous Catalysts

Supporting Information

Binuclear Rare-Earth Polyhydride Complexes Bearing both

Supporting Information Reagents. Physical methods. Synthesis of ligands and nickel complexes.

Supporting Information

,

Supporting Information

Supporting Information

Electronic Supplementary Information

Supporting Information

Supporting Information

Supporting Information Borata-alkene Derivatives Conveniently Made by Frustrated Lewis Pair Chemistry

Supporting Information

An Efficient Total Synthesis and Absolute Configuration. Determination of Varitriol

Efficient Magnesium Catalysts for the Copolymerization of Epoxides and CO 2 ; Using Water to Synthesize Polycarbonate Polyols

Supporting Information

Total Synthesis of Gonytolides C and G, Lachnone C, and. Formal Synthesis of Blennolide C and Diversonol

Supporting Information. Molecular Iodine-Catalyzed Aerobic α,β-diamination of Cyclohexanones with 2- Aminopyrimidine and 2-Aminopyridines

Supporting information. A Brønsted Acid-Catalyzed Generation of Palladium Complexes: Efficient Head-to-Tail Dimerization of Alkynes.

Diastereoselectivity in the Staudinger reaction of. pentafluorosulfanylaldimines and ketimines

Aziridine in Polymers: A Strategy to Functionalize Polymers by Ring- Opening Reaction of Aziridine

Supplementary Information: Selective Catalytic Oxidation of Sugar Alcohols to Lactic acid

Halogen bonded dimers and ribbons from the self-assembly of 3-halobenzophenones Patricia A. A. M. Vaz, João Rocha, Artur M. S. Silva and Samuel Guieu

SUPPLEMENTARY INFORMATION

Living polymerization of arylisocyanide initiated by phenylethynyl palladium(ii) complex

Supporting Information

Supporting Information

Supporting Information

Reversible Enolization of!-amino Carboxamides by Lithium Hexamethyldisilazide. Anne J. McNeil and David B. Collum*

Electronic Supplementary Information

Supporting Information for

Halogen halogen interactions in diiodo-xylenes

Supporting Information

Coordination Behaviour of Calcocene and its Use as a Synthon for Heteroleptic Organocalcium Compounds

Transformations: New Approach to Sampagine derivatives. and Polycyclic Aromatic Amides

Prabhat Gautam, Bhausaheb Dhokale, Shaikh M. Mobin and Rajneesh Misra*

The First Asymmetric Total Syntheses and. Determination of Absolute Configurations of. Xestodecalactones B and C

An unprecedented 2D 3D metal-organic polyrotaxane. framework constructed from cadmium and flexible star-like

Supporting information for the manuscript. Synthesis and Structure of Nitride-Bridged Uranium(III) Complexes

Aggregation-induced emission enhancement based on 11,11,12,12,-tetracyano-9,10-anthraquinodimethane

Supporting Information

Electronic Supplementary Information

Optimizing Ion Transport in Polyether-based Electrolytes for Lithium Batteries

Supporting Information

Supporting Information. for. Synthetic routes to [Au(NHC)(OH)] (NHC = N- heterocyclic carbene) complexes

Stoichiometry-Controlled FeP Nanoparticles from Single Source Precursor.

A Mixed Crystal Lanthanide Zeolite-like Metal-Organic. Framework as a Fluorescent Indicator for Lysophosphatidic. Acid, a Cancer Biomarker

Supporting Information

Supporting Information

Supporting Information

Straightforward Synthesis of Enantiopure (R)- and (S)-trifluoroalaninol

Supporting Information

oligomerization to polymerization of 1-hexene catalyzed by an NHC-zirconium complex

Transcription:

Supporting Information Dinuclear vs. Mononuclear Complexes: Accelerated, Metal-dependent Ring-Opening Polymerization of Lactide Mickael ormand, a Thierry Roisnel, b Jean-François Carpentier, a* and Evgeny Kirillov a* 1. Synthetic procedures and analytical data 2. MR spectra Figure S1. 1 H MR spectrum (500 MHz, C 6 D 6, 298 K) of [{O pipebn }H] 2 (II). Figure S2. 13 C{ 1 H} MR spectrum (125 MHz, C 6 D 6, 298 K) of [{O pipebn }H] 2 (II). Figure S3. 1 H MR spectrum (500 MHz, C 6 D 6, 298 K) of [{O pipebn }AlMe 2 ] 2 (II Al 2 ). Figure S4. 13 C{ 1 H} MR spectrum (125 MHz, C 6 D 6, 298 K) of [{O pipebn }AlMe 2 ] 2 (II Al 2 ). Figure S5. 1 H MR spectrum (500 MHz, C 6 D 6, 298 K) of [{O pipebn }In(CH 2 SiMe 3 ) 2 ] 2 (II In 2 ). Figure S6. 13 C{ 1 H} MR spectrum (125 MHz, C 6 D 6, 298 K) of [{O pipebn }In(CH 2 SiMe 3 ) 2 ] 2 (II In 2 ). Figure S7. 1 H MR spectrum (400 MHz, C 6 D 6, 298 K) of {O pipebn } Ph H (I Ph ). Figure S8. 13 C{ 1 H} MR spectrum (100 MHz, C 6 D 6, 298 K) of {O pipebn } Ph H (I Ph ). Figure S9. 1 H MR spectrum (400 MHz, C 6 D 6, 298 K) of {O pipebn } Ph AlMe 2 (I Ph Al). Figure S10. 13 C{ 1 H} MR spectrum (100 MHz, C 6 D 6, 298 K) of {O pipebn } Ph AlMe 2 (I Ph Al). 3. Crystallographic data Figure S11. Molecular structure of the bimetallic complex II-In 2. Table S1. Summary of Crystal and Refinement Data for Complexes II-Al 2 and II-In 2. 1

4. Kinetic data Figure S12. Plot of rac-la conversion (%) vs. time (s) for the binary system [Al]/iPrOH at different temperatures. Figure S13. Plot of rac-la conversion (%) vs. time (s) for the binary system II Al 2 /iproh at different temperatures. Figure S14. Plot of rac-la conversion (%) vs. time (s) at 110 C, at different concentrations of catalyst/initiator, with the binary system II Al 2 /iproh. Figure S15. Plot of ln(k app ) vs. ln([al]) for ROP of rac-la by the binary system II Al 2 /iproh at 110 C. Figure S16. Plot of ln(k app /T) vs. 1/T for ROP of rac-la by the binary systems I SiPh3 Al and II Al 2 /iproh, [rac-la] 0 = 2.0 M in toluene. Figure S17. Semi-logarithmic plots for ROP of rac-la at 110 C with [rac-la] 0 = 2.0 M in toluene for the binary systems [In]/iPrOH. Figure S18. Plot of M n vs. Conversion (%) for ROP with the binary systems I SiPh3 Al and II Al 2 /iproh. 5. References and notes 2

Experimental Part General Considerations. All manipulations were performed under a purified argon atmosphere using standard Schlenk techniques or in a glove box. Solvents were distilled from a/benzophenone (THF, Et 2 O) or a/k alloy (toluene, hexane and pentane) under argon, degassed thoroughly and stored under argon prior to use. Deuterated solvents were stored over a/k alloy (benzene-d 6, toluene-d 8, THF-d 8 ; >99.5% D, Eurisotop) or CaH 2 (CD 2 Cl 2 ) and vacuum-transferred just before use. CDCl 3 was dried over a mixture of 3 and 4 Å molecular sieves. 2,9-Dicarboxyaldehyde-1,8-bisphenol, 1 2-hydroxybiphenyl-3-carbaldehyde 2 and precursors I SiPh3 M (M = Al, In) 3 were prepared using literature procedures. Racemic lactide (rac-la) was received from Acros. Purification of rac-la required a three-step procedure involving first a recrystallization from a hot, concentrated iproh solution (80 C), followed by two subsequent recrystallizations in hot toluene (100 C). After purification, rac-la was stored at a temperature of 30 C in the glove-box. Other starting materials were purchased from Acros, Strem and Alfa and used as received. Instrumentation and Measurements. MR spectra of complexes were recorded on Bruker Avance DRX 400 and AM-500 spectrometers in Teflon-valved MR tubes at 25 ºC unless otherwise indicated. 1 H and 13 C MR chemical shifts are reported in ppm vs. SiMe 4 and were determined by reference to the residual solvent peaks. Assignment of resonances for organometallic complexes was made from 2D 1 H 13 C HMQC and HMBC MR experiments. Elemental analyses (C, H, ) were performed using a Flash EA1112 CHS Thermo Electron apparatus and are the average of two independent determinations. Size exclusion chromatography (SEC) analyses of PLAs were performed in THF (1.0 ml.min 1 ) at 20 C using a Polymer Laboratories PL-GPC 50 plus apparatus equipped with two ResiPore 300 7.5 mm columns, and RI and Dual angle LS (PL-LS 45/90) detectors. The number-average molecular masses (M n ) and polydispersity index (M w /M n ) of the polymers were 3

calculated with reference to a universal calibration vs. polystyrene standards. Reported experimental SEC molar mass values (M n,sec ) for PLA samples were corrected by a factor of 0.58, 4 as previously established. Unless otherwise stated, the SEC traces of the polymers all exhibited a unimodal, and usually symmetrical, peak. The microstructure of PLAs was determined by homodecoupling 1 H MR spectroscopy at 20 C in CDCl 3 on a Bruker AC-500 spectrometer. Crystal Structures Determination. Diffraction data were collected at 100(2) K using a Bruker APEX CCD diffractometer with graphite-monochromatized MoKα radiation (λ = 0.71073 Å). A combination of ω and φ scans was carried out to obtain at least a unique data set. The crystal structures were solved by direct methods, remaining atoms were located from difference Fourier synthesis followed by full-matrix least-squares refinement based on F2 (programs SIR97 and SHELXL-97) 5 with the aid of the WIGX program. 6 In most cases, many hydrogen atoms could be found from the Fourier difference analysis. Other hydrogen atoms were placed at calculated positions and forced to ride on the attached atom. The hydrogen atom contributions were calculated but not refined. All non-hydrogen atoms were refined with anisotropic displacement parameters. The locations of the largest peaks in the final difference Fourier map calculation as well as the magnitude of the residual electron densities were of no chemical significance. Crystal data and details of data collection and structure refinement for the different compounds are given in Annexes. [{O pipebn }H] 2 (II). A solution of 2,9-dicarboxyaldehyde-1,8-bisphenol (1.00 g, 4.13 mmol), 4-amino-1-benzylpiperidine (2.30 g, 12.4 mmol) and PTSA (cat., ca. 2 mg) in benzene (20 ml) was stirred under reflux with a Dean-Stark apparatus at 120 C for 48 h. Volatiles were removed under vacuum and the resulting solid recrystallized in methanol (ca. 20 ml). The resulting material was filtered, washed with cold methanol (30 ml) and dried in vacuo to give II as a yellow solid (2.03 g, 84%). 1 H MR (500 MHz, C 6 D 6, 298 K): δ 1.49 (m, 4H, CH 2 pip), 1.53-1.60 (m, 4H, CH 2 pip), 1.95 (m, 4H, CH 2 pip), 2.59 (m, 4H, CH 2 pip), 2.75 (m, 2H, CH 4

pip), 3.28 (s, 4H, CH 2 Ph), 6.87 (t, J H-H = 7.6 Hz, 2H, Haro), 6.96-6.97 (dd, J H-H = 1.7 and 5.9 Hz, 2H, Haro), 7.10-7.13 (m, 2H, Haro), 7.21 (t, J H-H = 7.6 Hz, 4H, Haro), 7.33-7.34 (m, 4H, Haro), 7.70-7.71 (dd, 2 J = 1.75 and 5.7 Hz, 2H, Haro), 7.81 (s, 2H, ArCH=), 14.10 (s, 2H, ArOH). 13 C{ 1 H} MR (125 MHz, C 6 D 6, 298 K): δ 33.33 (CH 2 pip), 51.28 (CH 2 pip), 62.97 (CH 2 Ph), 64.93 (CH pip), 117.60, 119.14, 126.54, 126.84, 128.15, 128.75, 130.58, 134.70, 139.32 (Caro), 159.56 (ipso-c phenol), 163.03 (ArCH=). Anal. calcd. for C 38 H 42 4 O 2: C, 77.78; H, 7.21;, 9.55; found: C, 77.16; H, 7.26;, 9.87. Mp: 253 C. [{O pipebn }AlMe 2 ] 2 (II Al 2 ). A solution of [{O pipebn }H] 2 (II) (1.00 g, 1.70 mmol) in toluene (ca. 10 ml) was added to a solution of AlMe 3 (0.341 ml of a 1.0 M solution in n- heptane, 3.41 mmol) in toluene (ca. 10 ml). The reaction mixture was stirred at room temperature for 24 h. Then, volatiles were removed under vacuum and the resulting material washed with n-hexane (ca. 10 ml), and dried in vacuo to give II Al 2 as a yellow solid (1.15 g, 96%). 1 H MR (500 MHz, C 6 D 6, 298 K): δ 0.29 (s, 12H, Al(CH 3 ) 2 ), 1.39 (m, 4H, CH 2 pip), 1.57 (td, J H-H = 1.9 and 9.9 Hz, 4H, CH 2 pip), 1.74-1.81 (qd, J H-H = 3.5 and 3.75 Hz, 4H, CH 2 pip), 2.62-2.64 (m, 4H, CH 2 pip), 2.74 (tt, J H-H = 4.1 and 12 Hz, 2H, CH pip), 3.25 (s, 4H, CH 2 Ph), 6.66-6.72 (m, 4H, Haro), 7.10-7.13 (tt, J H-H = 1.3 and 7.3 Hz, 2H, Haro), 7.18-7.21 (m, 4H, Haro), 7.30-7.31 (m, 4H, Haro), 7.36 (s, 2H, ArCH=), 7.87 (dd, J H-H = 2.1 and 5 Hz, 2H, Haro). 13 C{ 1 H} MR (125 MHz, C 6 D 6, 298 K) :δ 7.91 (Al(CH 3 ) 2 ), 32.51 (CH 2 pip), 52.19 (CH 2 pip), 62.57 (CH 2 Ph), 65.11 (CH pip), 116.55, 119.54, 127.09, 128.29, 128.73, 130.16, 134.10, 138.70, 139.30 (Caro), 162.18 (ArC O Al), 169.34 (ArCH=). Anal. calcd. for C 42 H 52 Al 2 4 O 2: C, 72.18; H, 7.50;, 8.02; found: C, 72.52; H, 7.12;, 8.22. [{O pipebn }In(CH 2 SiMe 3 ] 2 (II In 2 ). A solution of [{O pipebn }H] 2 (II) (0.083 g, 0.142 mmol) in toluene (5 ml) and In(CH 2 SiMe 3 ) 3 (0.117 g, 0.283 mmol) in toluene (2 ml) was stirred at 90 C for 18 h. Then, volatiles were removed in vacuo, n-hexane (ca. 10 ml) was vacuum-condensed in and the resulting solution was filtered off. The filtrate was concentrated under vacuum to give II In 2 as a bright yellow solid (0.092 g, 56%). 1 H MR (500 MHz, 5

C 6 D 6, 298 K): δ 0.19 (d, 2 J H-H = 12.5 Hz, 4H, CHHSiMe 3 ), 0.12 (d, 2 J H-H = 12.5 Hz, 4H, CHHSiMe 3 ), 0.20 (s, 36H, Si(CH 3 ) 3 ), 1.43 (m, 4H, CH 2 pip), 1.65 (td, J H-H = 1.3 and 10.2 Hz, 4H, CH 2 pip), 1.77 (qd, J H-H = 3.5 and 12 Hz, 4H, CH 2 pip), 2.56 (tt, J H-H = 3.9 and 11.6 Hz, 2H, CH pip), 2.70 (m, 4 H, CH 2 pip), 3.28 (s, 4 H, CH 2 Ph), 6.78 (t, J H-H = 7.8 Hz, 2H, Haro), 6.86-6.88 (dd, J H-H = 2.0 and 8.0 Hz, 2H, Haro), 7.09 (tt, J H-H = 1.8 and 7.3 Hz, 2H, Haro), 7.16-7.19 (m, 4H, Haro), 7.30 (m, 4H, Haro), 7.54 (s, 2H, CH=), 7.91 (dd, J H-H = 2.0 and 7.2 Hz, 2H, Haro). 13 C{ 1 H} MR (125 MHz, C 6 D 6, 298 K): δ 2.24 (CH 2 Si(CH 3 ) 3 ), 2.70 (Si(CH 3 ) 3 ), 34.07 (CH 2 pip), 52.05 (CH 2 pip), 62.74 (CH 2 Ph), 68.92 (CH pip), 114.00, 118.74 127.12, 128.32, 128.80, 132.55, 135.31, 138.52, 138.61 (Caro), 167.84 (ArC O In), 169.86 (ArCH=). Anal. calcd. for C 54 H 84 In 2 4 O 2 Si 4 : C, 55.76; H, 7.28;, 4.82; found: C, 56.19 ; H, 7.37;, 5.04. O Bn OH MgCl2 (2 equiv) Et 3 (2 equiv) paraformaldehyde (3 equiv) OH H -benzyl- 4-aminopiperidine (1.2 equiv) OH THF, 70 C, 16 h 90% MeOH, 70 C, 3 h 20% I Ph Scheme 1. Synthetic route toward the phenol-imine pro-ligand (O Ph pipebn }H (I Ph ). {O pipebn } Ph H (I Ph ). A solution of 2-hydroxybiphenyl-3-carbaldehyde (2.30 g, 11.7 mmol), -benzyl-4-aminopiperidine (2.60 g, 13.9 mmol) in methanol (30 ml) was stirred [without catalyst] under reflux for 3 h. The reaction mixture was allowed to cool to room temperature, and volatiles were removed under vacuum till the apparition of a precipitate. The suspension was then stored at 30 C for 24 h. The precipitate was filtered off, washed with cold methanol (3 20 ml) and dried in vacuo to give I Ph as a yellow solid (0.303 g, 20%). 1 H MR 6

(400 MHz, C 6 D 6, 298 K): δ 1.44-1.50 (m, 2H, CH 2 pip), 1.57-1.62 (m, 2H, CH 2 pip), 1.96 (t, J H- H = 9.2 Hz, 2H, CH 2 pip), 2.61-2.63 (m, 2H, CH 2 pip), 2.76 (m, 1H, CH pip), 3.31 (s, 2H, CH 2 Ph), 6.80 (t, J H-H = 7.5 Hz, 1H, Haro), 6.91-6.93 (dd, J H-H = 1.6, 7.6 Hz, 1H, Haro), 7.21 (t, J H-H = 7.6 Hz, 2H, Haro), 7.28 (t, J H-H = 7.8 Hz, 2H, Haro), 7.33-7.37 (m, 3H, Haro), 7.80-7.81 (m, 3H, Haro and ArCH=), 14.31 (s, 1H, ArOH). 13 C{ 1 H} MR (100 MHz, C 6 D 6, 298 K): δ 33.33 (CH 2 pip), 51.29 (CH 2 pip), 62.99 (CH 2 Ph), 64.97 (CH pip), 118.24, 119.23, 128.77, 129.64, 130.51, 130.51, 133.14, 138.21, 139.19 (Caro), 159.10 (ipso-c phenol), 163.00 (ArCH=). Anal. calcd. C 25 H 26 2 O: C, 81.05; H, 7.07;, 7.56; found: C, 80.88; H, 7.10;, 7.49. {O pipebn } Ph AlMe 2 (I Ph Al). A solution of {O pipebn } Ph H (I Ph ) (0.053 g, 0.140 mmol) in toluene (ca. 3 ml) was added to a solution of AlMe 3 (0.140 ml of a 1.0 M solution in n- heptane, 0.140 mmol) in toluene (ca. 3 ml). The reaction mixture was stirred at room temperature for 18 h. Then, volatiles were removed under vacuum and the resulting material washed with n-hexane (ca. 5 ml), and dried in vacuo to give I Ph Al as a yellow solid (0.042 g, 70%). 1 H MR (400 MHz, C 6 D 6, 298 K): δ 0.47 (s, 6H, Al(CH 3 ) 2 ), 1.22 (m, 2H, CH 2 pip), 1.43 (t, 3 J H-H = 10.8 Hz, 2H, CH 2 pip), 1.62 (m, 2H, CH 2 pip), 2.47 (m, 2H, CH 2 pip), 2.61 (m, 1H, CH pip), 3.11 (s, 2H, CH 2 Ph), 6.49 (t, J H-H = 7.6 Hz, 1H, Haro), 6.57 (m, 1H, Haro), 6.64 (m, 2H, Haro), 7.04-7.16 (m, 6H, Haro), 7.26 (s, 1H, Haro), 7.28 (s, 1H, ArCH=), 7.60 (s, 1H, Haro), 7.62 (s, 1H, Haro). 13 C{ 1 H} MR (100 MHz, C 6 D 6, 298 K): δ 9.17 (Al(CH 3 ) 2 ), 31.47 (CH 2 pip), 51.10 (CH 2 pip), 61.51 (CH 2 Ph),64.31 (CH pip), 116.05, 118.51, 127.27, 128.39, 132.74, 132.91, 136.45, 137.37, 137.57 (Caro), 160.76 (ArC O Al), 168.20 (ArCH=). Anal. calcd. C 27 H 31 Al 2 O: C, 76.03; H, 7.33;, 6.57; found: C, 76.35; H, 7.49;, 6.51. General Procedure for Kinetic Studies of ROP of racemic Lactide. Each polymerization experiment was conducted in a Teflon valve-sealed Schlenk flask as previously described. After a given time period, the reaction was quenched with H 2 O (ca. 0.5 ml of a 10 7

wt% H 2 O solution in THF). The monomer (LA) conversion was calculated from 1 H MR spectra of the crude reaction mixture in CDCl 3, from the integration (Int.) ratio Int. polymer /[Int. polymer +Int. monomer ], using the methyl hydrogen resonances for PLA at δ 1.49 ppm and for LA at δ 1.16 ppm. Then, the polymer was separated from the crude reaction mixture by filtration and was re-precipitated 3 times with excess pentane (ca. 15 ml). The polymer was then dried under vacuum till constant weight. The microstructure of PLAs was determined by homodecoupling 1 H MR spectroscopy (methine region) at 20 C in CDCl 3 on a Bruker AC-500 spectrometer. 8

2.01 1.94 1.89 3.83 3.77 2.00 2.00 2.01 4.00 1.98 3.94 3.84 4.02 3.90 14.1079 7.8187 7.7191 7.7156 7.7042 7.7007 7.3478 7.3452 7.3313 7.3300 7.2281 7.2134 7.2010 7.1980 7.1543 7.1337 7.1191 6.9787 6.9752 6.9633 6.9599 6.8931 6.8780 6.8629 3.2877 3.0278 2.7765 2.7683 2.7598 2.7513 2.7430 2.6085 2.5967 2.5853 1.9545 1.5819 1.5744 1.5635 1.5571 1.4912 1.4720 0.2915 a HO OH f c' b d' c d e * 13.5 12.5 11.5 10.5 9.5 9.0 8.5 8.0 7.5 7.0 f1 (ppm) 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Figure S1. 1 H MR spectrum (500 MHz, C 6 D 6, 298 K) of [{O pipebn }H] 2 (II). * stands for grease. 9

163.0387 159.5652 139.3354 134.7219 130.5998 128.7666 128.1686 127.9778 127.8789 127.7917 127.6861 127.5972 127.4936 126.8583 126.5621 119.1617 117.6192 64.9395 62.9865 51.2893 33.3387 * 170 160 150 140 130 120 110 100 90 f1 (ppm) 80 70 60 50 40 30 20 Figure S2. 13 C{ 1 H} MR spectrum (125 MHz, C 6 D 6, 298 K) of [{O pipebn }H] 2 (II). * stands for residual signal of C 6 D 6. 10

a Me Me Al O b c d O c' Al d' Me Me f e Figure S3. 1 H MR spectrum (500 MHz, C 6 D 6, 298 K) of [{O pipebn }AlMe 2 ] 2 (II Al 2 ). * stands for grease. 11

Figure S4. 13 C{ 1 H} MR spectrum (125 MHz, C 6 D 6, 298 K) of [{O pipebn }AlMe 2 ] 2 (II Al 2 ). * stands for residual signal of C 6 D 6. 12

SiMe 3SiMe3 In a O b c O c' d In d' e f SiMe 3 SiMe 3 g Figure S5. 1 H MR spectrum (500 MHz, C 6 D 6, 298 K) of [{O pipebn }In(CH 2 SiMe 3 ) 2 ] 2 (II In 2 ). * stands for signal of residual C 6 D 6. 13

169.8493 167.8271 138.6068 138.5083 135.3034 132.5488 128.7723 128.2788 127.9609 127.8618 127.7734 127.6691 127.5791 127.4766 127.1124 118.7401 114.0000 68.9250 62.7478 52.0556 34.0754 2.7056 2.2479 * 170 160 150 140 130 120 110 100 90 80 f1 (ppm) 70 60 50 40 30 20 10 0 Figure S6. 13 C{ 1 H} MR spectrum (125 MHz, C 6 D 6, 298 K) of [{O pipebn }In(CH 2 SiMe 3 ) 2 ] 2 (II In 2 ). * stands for residual signal of C 6 D 6. 14

1.00 3.14 7.98 0.88 1.34 1.32 2.24 1.21 2.34 2.22 4.80 14.3129 7.8005 7.3566 7.3384 7.2872 7.2193 7.1504 6.9153 6.9113 6.7968 3.3121 2.6397 2.6251 2.6111 1.9826 1.9597 1.9367 1.6217 1.5983 1.5444 1.5022 1.4786 0.2885 OH * ** 13.5 12.5 11.5 10.5 9.5 9.0 8.5 8.0 7.5 7.0 6.5 f1 (ppm) 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Figure S7. 1 H MR spectrum (400 MHz, C 6 D 6, 298 K) of {O pipebn } Ph H (I Ph ). * and ** stand for signals of residual C 6 D 6 and grease, respectively. 15

163.0028 159.1099 139.1997 133.1452 130.5198 129.6455 128.7797 119.2308 118.2480 62.9962 51.2925 33.3390 * ** 160 150 140 130 120 110 100 90 80 f1 (ppm) 70 60 50 40 30 20 10 0 Figure S8. 13 C{ 1 H} MR spectrum (100 MHz, C 6 D 6, 298 K) of {O pipebn } Ph H (I Ph ). * and ** stand for signals of residual C 6 D 6 and grease, respectively. 16

O Me Al Me Figure S9. 1 H MR spectrum (400 MHz, C 6 D 6, 298 K) of {O pipebn } Ph AlMe 2 (I Ph Al). * stands for signal of C 6 D 6. 17

Figure S10. 13 C{ 1 H} MR spectrum (100 MHz, C 6 D 6, 298 K) of {O pipebn } Ph AlMe 2 (I Ph Al). * stands for signal of C 6 D 6. 18

Figure S11. Molecular structure of the dinuclear complex II-In 2 (all hydrogen atoms are omitted for clarity; ellipsoids drawn at 50% level). 19

Table S1. Summary of Crystal and Refinement Data for Complexes II-Al 2 and II-In 2. II-Al 2 II-In 2 Empirical formula C 336 H 416 Al 16 32 O 16 C 54 H 84 In 2 4 O 2 Si 4 Formula weight 5590.69 1163.25 Crystal system Orthorhombic Triclinic Space group F 2 d d P -1 a, Å 15.3906(12) 10.335(3) b, Å 41.213(3) 14.576(4) c, Å 55.854(4) 20.959(6) α, deg 90 95.297(13) β, deg 90 99.709(11) γ, deg 90 95.859(12) Volume, Å 3 35428(5) 3076.5(15) Z 4 2 Density, g.m -3 1.048 1.256 Abs. coeff., mm -1 0.101 0.866 F(000) 11968 1212 Crystal size, mm 0.6 x 0.09 x 0.08 0.6 x 0.3 x 0.13 θ range, deg 1.23 to 27.54 2.92 to 27.62 Limiting indices 20 h 13, 53 k 53, 72 l 72 13 h 9, 18 k 18, 27 l 27 Reflec. Collected 76390 34709 Refle. Unique [I>2σ(I)] 18553 (17458) 13984 (9503) Data/restrains/ param. 18553 / 1 / 909 13984 / 0 / 575 Goodness-of-it on F 2 0.925 1.021 R 1 [I>2σ(I)] (all data) 0.0686 (0.1326) 0.044 (0.0894) wr 2 [I>2σ(I)] (all data) 0.1463 (0.1677) 0.0763 (0.1028) Largest diff. e.a -3 0.622 and 0.313 1.458 and -0.863 20

Figure S12. Plot of rac-la conversion (%) vs. time (s) for the binary system [Al]/iPrOH at different temperatures: (a) mononuclear systems; conditions: toluene, [rac-la] 0 /[Al]/[iPrOH] 0 = 500:1:5 ([rac-la] 0 = 2.0 M; [Al] 0 = 4.0 mm; [iproh] 0 = 20 mm). I SiPh3 Al: 90 C, k app = 3.4 ± 0.2 10 4 s 1, R 2 = 0.964; 100 C, k app = 5.9 ± 0.4 10 4 s 1, R 2 = 0.976; 110 C, k app = 1.1 ± 0.2 10 3 s 1, R 2 = 0.965; 120 C, k app = 2.1 ± 0.2 10 3 s 1, R 2 = 0.975. I Ph Al: 110 C, k app = 2.5 ± 0.1 10 3 s 1, R 2 = 0.996; (b) dinuclear system; conditions: toluene, [rac-la] 0 /[Al]/[iPrOH] 0 = 1000:2:10 ([rac-la] 0 = 2.0 M; [Al] 0 = 4.0 mm; [iproh] 0 = 20 mm). II Al 2 : 90 C, k app = 4.7 ± 0.4 10 3 s 1, R 2 = 0.985; 100 C, k app = 8.3 ± 0.6 10 3 s 1, R 2 = 0.989; + 110 C, k app = 1.2 ± 0.1 10 2 s 1, R 2 = 0.985; * 120 C, k app = 2.2 ± 0.2 10 2 s 1, R 2 = 0.987. 21

Figure S13. Plot of rac-la conversion (%) vs. time (s) for the binary system II Al 2 /iproh at different temperatures: conditions: toluene, [rac-la] 0 /[Al]/[iPrOH] 0 = 1000:4:10 ([rac-la] 0 = 2.0 M; [Al] 0 = 8.0 mm; [iproh] 0 = 20 mm). 90 C, k app = 6.0 ± 0.6 10 3 s 1, R 2 = 0.979; 100 C, k app = 9.3 ± 0.7 10 3 s 1, R 2 = 0.985; 110 C, k app = 1.8 ± 0.1 10 2 s 1, R 2 = 0.989; 120 C, k app = 3.0 ± 0.2 10 2 s 1, R 2 = 0.988. 22

Figure S14. Plot of rac-la conversion (%) vs. time (s) at 110 C, at different concentrations of catalyst/initiator, with the binary system II Al 2 /iproh. Conditions: toluene, [rac- LA] 0 /[Al]/[iPrOH] 0 = 1000:n:50 ([rac-la] 0 = 2.0 M; [iproh] 0 = 100 mm). n = 4 ([Al] 0 = 8.0 m M), k app = 3.0 ± 0.2 10 2 s 1, R 2 = 0.991; n = 8 ([Al] 0 = 16.0 mm), k app = 6.0 ± 0.1 10 2 s 1, R 2 = 0.999; n = 20 ([Al] 0 = 40.0 mm), k app = 1.1 ± 0.1 10 1 s 1, R 2 = 0.973. Figure S15. Plot of ln(k app ) vs. ln([al]) for ROP of rac-la by the binary system II Al 2 /iproh at 110 C, [rac-la] 0 = 2.0 M, [iproh] 0 = 100 mm in toluene and [Al] 0 = 4.0 mm, 8.0 mm, 16.0 mm and 40.0 mm. 23

Figure S16. Plot of ln(k app /T) vs. 1/T for ROP of rac-la by the binary systems I SiPh3 Al and II Al 2 /iproh, [rac-la]0 = 2.0 M in toluene. I SiPh3 Al; H = 16.4(1) kcal mol 1, S = - 29(4) cal mol 1 K 1, G 298 = 25.2(1) kcal mol 1, R 2 = 0.996. II-Al 2 (1000:2:10); H = 13.5(1) kcal mol -1, S = 32(5) cal mol -1 K -1, G 298 = 23.1(1) kcal mol 1, R 2 = 0.990. II-Al 2 (1000:4:10); H = 14.8(1) kcal mol 1, S = 29(5) cal mol 1 K 1, G 298 = 23.2(1) kcal mol 1, R 2 = 0.993. 24

Figure S17. Semi-logarithmic plots for ROP of rac-la at 110 C with [rac-la] 0 = 2.0 M in toluene for the binary systems: I SiPh3 In, [rac-la] 0 /[In]/[iPrOH] 0 = 500:1:10, k app = 0.70 ± 0.05 10 3 M -1 s 1, R 2 = 0.983; II-In 2, [rac-la] 0 /[In]/[iPrOH] 0 = 1000:2:20, k app = 0.8 ± 0.1 10 3 M -1 s 1, R 2 = 0.996. 25

Figure S18. Plot of M n vs. conversion (%) for ROP with the binary systems I SiPh3 Al and II Al 2 /iproh, [rac-la] 0 = 2.0 M in toluene at 110 C: I SiPh3 Al, [rac-la] 0 /[Al]/[iPrOH] 0 = 500:1:5; II-Al 2, [rac-la] 0 /[Al]/[iPrOH] 0 = 1000:2:10. References and notes 1 2 3 4 5 6 H.-C. Zhang, W.-S. Huang, L. Pu, J. Org. Chem. 2001, 66, 481-487. T. V. Hansen, L. Skattebol, Organic Syntheses, 2005, 82, 20, 64-68. M. ormand, V. Dorcet, E. Kirillov, J.-F. Carpentier, Organometallics, 2012, 32, 1694 1709. A. Kowalski, A. Duda, S. Penczek, Macromolecules 1998, 31, 2114-2122. (a) A. Altomare, M. C. Burla, M. Camalli, G.Cascarano, C. Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R. Spagna, J. Appl. Cryst. 1999, 32, 115-119. (b) G. M. Sheldrick, SHELXS-97, Program for the Determination of Crystal Structures, University of Goettingen (Germany), 1997. (c) G. M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structures, University of Goettingen (Germany), 1997. (d) G. M. Sheldrick, Acta Cryst.2008, 64, 112-122. L. J. Farrugia, J. Appl. Cryst. 1999, 32, 837. 26