Use of Michael additions to (Ph₂P)₂CCH₂complexes to prepare thiophene- and pyrrole-functionalised metal–phosphine complexes

Abstract

The complex [Pd(O,CMe),(vdpp)]1 a [vdpp = (Ph,P), C=CH,] undergoes nucleophilic addition at the double bond with primary alcohols to afford [Pd(O,CMe),{(Ph,P),CHCH~OR}] 2 [R = Me, Et, CH,CH,C,H,S-3 or CH,C6H,(OMe),-3,4]. These were not isolated pure, but metathesis with Nal gave the corresponding diiodides 3, which were isolated, and have been fully characterised by microanalysis and infrared and NMR ('H and 31P-(1H}) spectroscopies. By using 2-(3-thieny1)ethanol as the nucleophile, the complex [Pdl,{( Ph,P),CHCH,OCH2CH,C,H,S-3}]3c was obtained, and its electrochemistry examined. The reactivity of the double bond in 1 a towards other potential weak nucleophiles has been examined. In particular, pyrrole underwent electrophilic addition with 1 a t o give, after work-up with Nal, [Pdl,{( Ph,P),CHCH,C,H,NH}] 4b. Proton NMR spectroscopy established that 4b was a mixture of 2and 3-pyrrole isomers (ca. 3: 1). The complexes [MClJvdpp)] (M = Pd lc or Pt I d ) were less reactive, but underwent addition with alcohols in the presence of NEt, as catalyst t o afford [MCI,{(Ph,P),CHCH,OR}]

Unusually Stable Four-Membered Chelate Rings in Nickel(II), Palladium(II), and Platinum(II) Complexes with the Ligand 2,2-Bis(diphenylphosphino)propane (2,2-dppp). Crystal and Molecular Structure of [PdI2(2,2-dppp)]·0.8CH2Cl2

“…The addition of nucleophiles to the double bond of chelated (Ph 2 P) 2 CCH 2 has been demonstrated as a route to coordinated, functionalized diphosphines of the type (Ph 2 P) 2 CHCH 2 X ( X = −NHR, −NR 2 , −OR, −C⋮CR, etc. ), − and we have used this reaction to prepare redox-active Ru II complexes for oxide surface modification 26 and for incorporation into conjugated polymers …”

Strong Activation of the Double Bond in (PPh2)2CCH2. Novel Synthesis of Gold(III) Methanide Complexes by Michael Addition Reactions

“…Although the double bond in uncoordinated vinylidenebis(diphenylphosphine) is not normally susceptible to nucleophilic attack, it has been shown that complexation to a metal center activates the double bond in such a manner that various nucleophiles can be added by Michael-type reactions. − In these processes, the nucleophile HNu is added to complexes [M]−(PPh 2 ) 2 CCH 2 to give the products [M]−(PPh 2 ) 2 CH−CH 2 Nu. However, reactions in which the addition takes place only at the terminal carbon atom of the double bond, thus affording species of the type [M]−(PPh 2 ) 2 C−CH 2 Nu in which the central carbon atom can be regarded as a methanide carbon, are unknown.…”

Complexes of 2,3-bis(diphenylphosphino)propene with PtII, PdII and RuII: synthesis, characterisation and rearrangements to complexes of cis-1,2-bis(diphenylphosphino)propene

“…Pd II , Pt II , Pt IV ) than by co-ordination to M 0 (M = Cr, Mo or W). 5, 6 It was therefore of interest to investigate the co-ordination chemistry of 2,3-dpppn with Pd II , Pt II and Ru II , and to investigate whether the co-ordinated ligand would undergo nucleophilic addition. In this paper, we report the syntheses and characterisation of neutral and cationic 2,3-dpppn complexes of these metals, and some chemistry of the coordinated ligand.…”