Synthesis and reactivity of platinacycloalkanes

Angewandte Chemie International Edition, 2007

Metallacycloalkanes are an important class of compounds which have been known for many years to be key intermediates in useful catalytic reactions. For example, metallacyclobutanes are known to be present in the alkene metathesis reaction. More recently, metallacycloheptanes were first implicated, then proven to be involved in ethylene trimerization. There has been interesting discussion and a belief that the formation of nine-membered and other larger metallacycloalkane rings is unlikely.

Dalton Transactions, 2014

A new series of platinacyclopentanes (2a-2f ) and platinacycloheptanes (3a-3f ) of the type [Pt(N^P)(CH 2 ) n ] (n = 4, 6) were obtained by the reaction of [Pt(COD)(CH 2 ) n ] with the appropriate iminophosphine ligand (1a-1f). These complexes were characterised using a variety of spectroscopic and analytical techniques. X-ray structure analysis of complex 2a revealed a slightly distorted square planar geometry around platinum as a consequence of the ring strain imposed by the [P,N] chelate ring formed and the metallocycloalkane. Thermal decomposition analyses of the platinacycloalkanes revealed that the platinacyclopentanes are markedly stable, with the decomposition reaction requiring temperatures higher than 100°C to occur. The major products obtained from the thermal decomposition reactions were 1-butene (for platinacyclopentanes) and 1-hexene (for platinacycloheptanes). † CCDC 973798. For crystallographic data in CIF or other electronic format see

A new series of platinacyclopentanes (2a-2f ) and platinacycloheptanes (3a-3f ) of the type [Pt(N^P)(CH 2 ) n ] (n = 4, 6) were obtained by the reaction of [Pt(COD)(CH 2 ) n ] with the appropriate iminophosphine ligand (1a-1f). These complexes were characterised using a variety of spectroscopic and analytical techniques. X-ray structure analysis of complex 2a revealed a slightly distorted square planar geometry around platinum as a consequence of the ring strain imposed by the [P,N] chelate ring formed and the metallocycloalkane. Thermal decomposition analyses of the platinacycloalkanes revealed that the platinacyclopentanes are markedly stable, with the decomposition reaction requiring temperatures higher than 100°C to occur. The major products obtained from the thermal decomposition reactions were 1-butene (for platinacyclopentanes) and 1-hexene (for platinacycloheptanes). † CCDC 973798. For crystallographic data in CIF or other electronic format see

Journal of Organometallic Chemistry, 1999

The complexes [Pt(CH 2 CH 2 CH 2 CH 2)(NN)], 1a (NN=2,2%-bipyridyl) and 1b (NN = 1,10-phenanthroline), react with dibromoalkanes Br(CH 2) n Br (n=3-6) to give new platina(IV)cyclopentane complexes fully characterized as [PtBr(CH 2 CH 2 CH 2-CH 2){(CH 2) n Br}(NN)]. When n= 2, complexes 1 react with Br(CH 2) 2 Br to give binuclear complexes [Pt 2 Br 2 (CH 2 CH 2-CH 2 CH 2) 2 {v-(CH 2) 2 }(NN) 2 ]. All the reactions proceed by the S N 2 mechanism and rates of reactions follow the sequence n= 2 6 \3 \4 $5. The trend of reactivity is discussed in terms of chain lengths of dibromides and 1 J(Pt-C) values of bond between Pt and polymethylene chain in the platina(IV)cyclopentane complexes.

Journal of Organometallic Chemistry, 2006

SMe 2 ] (5d) containing a [C,N] ligand, from which triphenylphosphine derivatives 6c and 6d were also prepared. In all cases, metallation took place to yield five-membered endo-metallacycles and formation of seven-membered or of exo-metallacycles was not observed. The reactions of 3a, 3b, 6c and 6d with methyl iodide were studied in acetone and gave the corresponding cyclometallated platinum (IV) compounds. All compounds were characterised by NMR spectroscopy and compounds 3b, 4a, 6c and 6d were also characterised crystallographically.

Organometallics, 1996

Reaction of the sodium bis(iminophosphoranyl)alkanide compounds Na[CR′′(PPh 2 dNC 6 H 4 R′-4) 2 ] (1a, R′′) H, R′) CH 3 ; 1b, R′′) H, R′) OCH 3 ; 1c, R′′) CH 3 , R′) CH 3) with M 2 X 4-(PR 3) 2 (M) Pt, Pd; X) Cl, Br; PR 3) PEt 3 , PMe 2 Ph) yields the four-membered metallacycles MX(PR 3){CR′′(PPh 2 dNC 6 H 4 R′-4) 2 } (2a-f, M) Pt; 3a-c, M) Pd), containing the bis-(iminophosphoranyl)alkanide ligand coordinated in a σ-C,σ-N chelating fashion. The molecular structure of 2e (X) Cl, PR 3) PMe 2 Ph, R′′) CH 3 , R′) CH 3) has been determined by X-ray crystallography. The 1,1-bis(iminophosphoranyl)ethanide ligand (1c) in 2e is σ-C,σ-N-chelated toward the square-planar-surrounded Pt, with N coordinated trans to PMe 2 Ph (Pt-N) 2.132(4) Å) and C trans to Cl (Pt-C) 2.116(4) Å), resulting in a puckered M-N-P-C metallacycle and one noncoordinated phosphinimine moiety. In solution the complexes 2 and 3 undergo a dynamic process, involving an intermediate (for 2) or fast (for 3) N,N′ exchange of coordinated and noncoordinated PdN groups. Heating (to 60-80°C) or prolonged stirring of solutions of the kinetically obtained four-membered metallacycles 2 and 3 gives the orthometalated complexes PtX(PR 3){2-C 6 H 4 PPh(NHC 6 H 4 R′-4)CHPPh 2 d NC 6 H 4 R′-4} (4a-d,f) and PdCl(PR 3){2-C 6 H 4 PPh(dNC 6 H 4 Me-4)CHPPh 2 NHC 6 H 4 Me-4} (5a,c). The X-ray crystal structure of 4a (X) Cl, PR 3) PEt 3 , R′) CH 3) has been determined. The new mononuclear orthometalated Pt complexes 4 contain a σ-C,σ-C′ coordinated [2-C 6 H 4-PPh(NHC 6 H 4 R-4′)CR′′PPh 2 dNC 6 H 4 R′-4]-ligand, in which the ortho-H (Ph) has shifted to a bridge position between the two noncoordinating nitrogen atoms. The four-membered platinacycles 2a,b and the orthometalated platinacycles 4a,b react with 1 equiv of HBF 4 or CF 3 COOH to give 6a,b and 7a,b, respectively, by protonation of the noncoordinated PdNC 6 H 4 R′-4 groups only. Addition of CO 2 to 2a,d and 4c,f results in an aza-Wittig reaction, giving PtCl(PR 3){CH(PPh 2 dNC 6 H 4 R′-4)(PPh 2 dO)} (8a,d) and PtX(PR 3){2-C 6 H 4 PPh(dO)-CHPPh 2 NHC 6 H 4 R′-4} (9c,f), respectively, together with aryl isocyanate and bis(aryl)carbodiimide.

Journal of Organometallic Chemistry, 2000

The chemistry of alkynyl and alkyne ligands in platinum complexes of different oxidation states is described. The review focuses on the synthetic aspects of mono-and polynuclear compounds and on the reactivity of o-alkynyl and rc-alkyne species in different stoichiometric reactions such as insertion, addition of nucleophiles and electrophiles, rearrangements and isomerization processes and also some catalytic additions of heteroatoms (B, Si, S) across the C=C triple bond. The relevant features of polynuclear complexes bearing the C=C group in dendrimers and organometallic polymers are briefly reported.

Inorganica Chimica Acta, 1985

Propene complexes, cis-[PtCl,(PRa)($-C3H6)], are formed quickly and in good yield by the reaction of [Pt(n3-C,Hs)Cl(PR,)]

Journal of Organometallic Chemistry, 2005

Oxidative addition reactions of Cl 2 C@PR (R = 2,4,6-tris(trifluoromethyl)phenyl (Ar) or 2,6-bis(trifluoromethyl)phenyl (Ar 0) with Pt(PPh 3) 4 yield the cis and trans (at platinum) complexes [PtCl(ClC@PAr)(PPh 3) 2 ] and [PtCl(ClC@PAr 0)(PPh 3) 2 ]. All starting materials and intermediates have been characterised by NMR spectroscopy. The crystal and molecular structures of the transplatinum complexes have been determined by single-crystal X-ray diffraction at low temperature.