Stabilization of high oxidation states by rigid bidentate nitrogen ligands: synthesis and characterization of diorgano-and triorganopalladium(IV) and cationic triorganoplatinum(IV) complexes van Asselt, R.; Rijnberg, E.; Elsevier, C.J. Published in: Organometallics DOI:10.1021/om00014a049Link to publication Citation for published version (APA):van Asselt, R., Rijnberg, E., & Elsevier, C. J. (1994). Stabilization of high oxidation states by rigid bidentate nitrogen ligands: synthesis and characterization of diorgano-and triorganopalladium(IV) and cationic triorganoplatinum(IV) complexes. Organometallics, 13, 706-720. DOI: 10.1021/om00014a049 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Dimethylpalladium(I1) and (di)methylplatinum(II) complexes containing the rigid bidentate nitrogen ligands his@-toly1imino)acenaphthene @Tol-BIAN) and bis(pheny1imino)camphane (Ph-BIC) readily undergo oxidative addition of a variety of (organic) halides, to give the corresponding octahedral diorgano-and triorganopalladium(1V) and -platinum(IV) complexes. The palladium complexes PdMeZ(R)X(NN) (RX = MeI, PhCHZBr; NN = pTol-BIAN, Ph-BIC) were synthesized and isolated a t 20 "C and were fully characterized. Reductive elimination from these complexes in chloroform obeyed first order kinetics and was slower than for other reported triorganopalladium(1V) complexes. The new diorganopalladium(1V) complexes PdMe212(NN), synthesized via oxidative addition of diiodine to PdMeANN) are much less stable than the triorganopalladium(1V) complexes studied. PtMez(R)X@Tol-BIAN) (RX = MeI, PhCHZBr, EtI, PhCH(Me)Br, MeC(O) Cl, 12) and Pt(Me)I(R)X(pTol-BIAN) (RX = MeI, PhCHZBr, 12) were obtained via oxidative addition to PtMez WTol-BIAN) and Pt(Me)I@Tol-BIAN), respectively. Reaction of PtMez(R)X(pTol-BIAN) with AgS03CF3 led to the formation of remarkably stable five-coordinate [PtMe2(R)pTol-BIAN)1SO3CF3 complexes (R = Me, CHzPh, C(O)Me), which were fully characterized and can be isolated and kept at 20 "C. The complexes are very stable toward reductive elimination, e.g. in CDCl3 and CD3CN [PtMedCHZPh)(pTol-BIAN)]SO&F3 was stable for at least 7 days a t 20 "C or 40 h at 50 "C. The analogous complex [PtMe&HzPh)(phen)IS03CF3 was also stable a t 50 "C in CD3CN for a t least 40 h, whereas [PtMez(CHZPh) @T...

A new enantiomerically pure S,N-chelated zinc bis(aminoarenethiolate), (R,R)-Zn(SC 6 H 4 C-(Me)HNMe 2-2) 2 ((R,R)-3b), has been synthesized by the reaction of the (R)-trimethylsilyl aminoarenethiolate species (R)-2b with ZnCl 2 in a 2:1 molar ratio. (R,R)-3b is an efficient catalyst for the addition of dialkylzinc compounds to aliphatic and aromatic aldehydes to give the corresponding secondary alcohols in nearly quantitative yields with optical purities of 69-99% ee under mild reaction conditions. Although excellent selectivities were obtained with this simple ligand containing only one stereogenic (carbon) center, further modifications of the amino substituents were studied. Cyclic N(CH 2) 4 or N(CH 2) 5 amino-substituted aminoarenethiolate ligands considerably enhanced the reaction rates, resulting in shorter reaction times and higher ee's. The mechanism of these 1,2-addition reactions has the general characteristics as reported by Noyori et al. This conclusion is based on the synthesis, isolation, and characterization (X-ray, 1 H and 13 C NMR) of the enantiopure zinc bis-(aminoarenethiolate) and organozinc aminoarenethiolate intermediates and on monitoring of the reaction process. We present evidence for an interpretation of the binding in the product-forming key intermediate complex in terms of an organozinc cation/anion pair. The possibility that the very efficient transfer of chiral information in this compact complex may be due to a combination of the shortness of the Zn-N coordinate bonds with concomitant η 2 bonding of the aldehyde substrate is discussed. The solid-state structure of the zinc bis-(aminoarenethiolate) (R,R)-Zn(SC 6 H 4 C(Me)HNMe 2-2) 2 is reported.

Homoleptic lithium zincates with intramolecular Li-N coordination, i.e., Li(thf) n Zn-(C 6 H 4 CH 2 NMe 2 -2) 3 (n ) 0 (1); n ) 1 (1(thf))) and Li 2 Zn(C 6 H 4 CH 2 NMe 2 -2) 4 (2) have been prepared by reacting [Li(C 6 H 4 CH 2 NMe 2 -2)] 4 with Zn(C 6 H 4 CH 2 NMe 2 -2) 2 . In the solid state 1(thf) is a monomer containing a distorted tetrahedral zinc atom. The zinc is surrounded by three monoanionic C 6 H 4 CH 2 NMe 2 -2 (dmba) ligands, which all show a different bonding mode: η 1 -C bonding to zinc and nitrogen coordination to lithium; η 1 ,µ 2 -C bridge bonding to zinc and lithium with Li-N coordination; and C,N-chelate bonded to zinc. One thf coordinates to lithium. In the solid state, 2 is a monomeric dilithium tetraarylzincate complex containing a tetrahedral zinc atom. The four dmba ligands are all similarly η 1 ,µ 2 -C bridgebonded to zinc and lithium, and each lithium is four-coordinate by two additional Li-N bonds. The reaction of LiCH 2 SiMe 3 and Zn(C 6 H 4 CH 2 NMe 2 -2) 2 did not give a mixed zincate complex but the respective homoleptic zincate complexes instead. Both homoleptic and in situ prepared mixed zincate complexes react readily with 2-cyclohexen-1-one, but the product composition shows that the in situ prepared zincate disproportionates into the corresponding homoleptic zincates prior to reaction.

Organozinc radicals, [RZn-t-BuDABl *, which are considered to be key intermediates in the regioselective alkylation reactions of R2Zn compounds with 1,4-di-tert-butyl-l,4-diaza-1,3-butadiene (t-BuDAB), have been prepared via independent routes in good yield either from the reaction of K(t-BuDAB) with RZnCl or by the thermal conversion of stable RzZn-t-BuDAB complexes (R = Me, CH2SiMe3). In solution the [RZn-t-BuDAB]' radicals are in equilibrium with their C-C coupled dimers, which were isolated as solids. A preliminary X-ray diffraction study of one such dimer, 6a, shows the stereoselective coupling of two Me&iCHzZn-t-BuDAB moieties by a C-C bond. The [RZn-t-BuDABI. radicals are reactive toward alkyl halides, like allyl and benzyl bromide, as well as a-and ,&substituted halo esters, producing C-alkylated products in good yield. The reactions with the halo esters give, after a subsequent ring closure reaction, heterocyclic products, Le. B-lactams (with good to excellent diastereoselectivity, de 60-90 % ) and 2-pyrrolidinones.

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