Chromium and Molybdenum Pentacarbonyl Complexes of Phosphinocarbodithioates: Synthesis, Molecular Structure and Behaviour in RAFT Polymerisation

Synthesis of S-Alkyl Phosphinocarbodithioates with Switch between P(III) and P(V) Derivatives

Simple and effective synthetic pathways are described to prepare compounds R₂P(X)C(S)SCH(Me)Ph with the P atom either in the oxidation state V [R/X = t-Bu/O (6), Ph/S, (7), t-Bu/S (8), t-Bu/Se (9)] or III [R/X = Ph/BH₃ (4), t-Bu/BH₃ (5), t-Bu/lone pair (10)]. Compound 9 is the first example of carbodithioate ester with a P = Se group, and for the first time, a phosphinocarboditioate with a free phosphine function (compound 10) is described. Stabilization of the latter crucially depends on the steric protection by the t-Bu groups since an analogous derivative with R = Ph is observable but too unstable for isolation. Compound 10 can be reversibly protonated to yield the [t-Bu₂PHC(S)SCH(Me)Ph]⁺ cation (10-H⁺), which was isolated as a BF₄^- salt. A few interconversion processes resulting in the facile addition/removal or exchange of the X group in this family of compounds are also described. The oxidation state of the phosphorus atom and the nature of an electron-withdrawing group have a significant impact on the spectral properties.

Manganese phosphinocarbodithioate for RAFT polymerisation with sunlight-induced chain end post-treatment

A new manganese complex of the formula Cp(CO)₂MnP(Ph)₂C(S)SCH(CH₃)Ph is an efficient RAFT agent for the preparation of SH-terminated polymers by simple visible light photocleavage of the organometallic end-group.

RAFT Polymerization with Triphenylstannylcarbodithioates (Sn-RAFT)

A new range of tin-based reversible addition-fragmentation chain-transfer (RAFT) agents is described and evaluated for the polymerization of acrylamides, methyl acrylate and styrene. These organometallic compounds are highly reactive reversible transfer agents which allow an efficient control of the polymerization of substituted acrylamide monomers, whereas RAFT control for methyl acrylate and styrene polymerization is contaminated by side reactions at prolonged reaction times. ¹¹⁹Sn NMR is shown to be an informative instrument for the monitoring of Sn-RAFT-mediated polymerizations.

Unexpected fragmentation of bis(triarylstannanethiocarbonyl)disulfides, formation and X-ray structure of triarylstannyl triarylstannanecarbodithioates

The synthesis of bis(triarylstannanethiocarbonyl)disulfides was attempted by oxidation of lithium triaryl stannane carbodithioates with molecular iodine. Unexpectedly, the desired compounds are highly unstable and undergo subsequent fragmentation giving triarylstannyl triarylstannanecarbodithioates. The proposed mechanism for this transformation assumes intramolecular nucleophilic substitution with formation of six-membered ring transition complex, stabilized by interaction between tin and thiocarbonyl sulfur atom. Obtained compounds were identified by mass-spectrometry and NMR spectroscopies, and their structures were analyzed by X-ray diffraction. These molecules show the existence of intramolecular non-bonding interactions between the sulfur atoms of the thiocarbonyl moieties and tin atoms. These interactions reflect the tin - sulfur affinity and are the main driving force in the fragmen tation of bis(triphenylstannanethiocarbonyl)disulfides.

Electronic structure predictions of the properties of non-innocent P-ligands in group 6B transition metal complexes

Neutral group 6B (Cr, Mo, W) pentacarbonyl complexes M(CO)5-L possessing various P-ligands such as phosphines, phosphaalkenes, and phospha-quinomethanes can form radical cations and anions under redox conditions. There is significant interest in whether the radical site is localized on the metal or on a "non-innocent" ligand. Density functional theory was used to predict whether the radicals of the complexes behave as metal or ligand-centered radicals and whether these compounds could form in solution or as an ion pair with various oxidizing and reducing agents. The quinone-like ligands are predicted to be ligand centered radicals when they are anions and metal centered radicals when they are cations. The predicted reaction energies for single electron transfer (SET) reactions involving the quinone like ligands are negative or near thermoneutral for both radicals in polar solutions and as solid state ion pairs. The energetics of the SET reactions can be controlled by the nature of L, the nature of the oxidizing/reducing agent, and the solvent polarity. Such complexes could be used as flexible catalysts for single electron transfer reactions.

Living Radical Polymerization by the RAFT Process – A Third Update

This paper provides a third update to the review of reversible deactivation radical polymerization (RDRP) achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of reversible addition-fragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379). The first update was published in November 2006 (Aust. J. Chem. 2006, 59, 669) and the second in December 2009 (Aust. J. Chem. 2009, 62, 1402). This review cites over 700 publications that appeared during the period mid 2009 to early 2012 covering various aspects of RAFT polymerization which include reagent synthesis and properties, kinetics and mechanism of polymerization, novel polymer syntheses, and a diverse range of applications. This period has witnessed further significant developments, particularly in the areas of novel RAFT agents, techniques for end-group transformation, the production of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.