Phosphine exchange reactions involving cis-[Pt(PPh3)2(Bcat)2] (cat = 1,2-O2C6H4) and the oxidative addition of 1,2-B2Cl2(NMe2)2 to Pt0

Abstract

The reaction between the platinum(II) bis(boryl) complex cis-[Pt(PPh3)2(Bcat)2] (cat = 1,2-O2C6H4) and the tertiary phosphines PMe3, PEt3, PMe2Ph, PMePh2 and dcpe [1,2-bis(dicyclohexylphosphino)ethane] and the phosphite P(OEt)3 afforded the new complexes cis-[Pt(PR3)2(Bcat)2] (PR3 = PMe3, PEt3, PMe2Ph or PMePh2), cis-[Pt(dcpe)(Bcat)2] and cis-[Pt{P(OEt)3}2(Bcat)2]. With PCy3 the mixed phosphine species cis-[Pt(PCy3)(PPh3)(Bcat)2] is the major product and was characterised by X-ray crystallography. With P(OMe)3 reductive elimination of B2(cat)2 and the formation of platinum(>0>) products occurs exclusively whereas with dmpe [1,2-bis(dimethylphosphino)ethane] the only identifiable product is the platinum(II) species [Pt(dmpe)2]Cl2. With dppm [bis(diphenylphosphino)methane] a reaction occurs to give a product assigned the structure cis-[Pt(dppm)(Bcat)2] or [Pt2(dppm)2(Bcat)4] but two binuclear products were isolated as minor products, namely [Pt2(PPh3)(µ-dppm)2(Bcat)(µ-Bcat)] and [Pt2(κ1-dppm)(µ-dppm)2(Bcat)(µ-Bcat)]. Both compounds were characterised by X-ray crystallography and shown to contain unusual semi-bridging Bcat groups. The reaction between [Pt(PPh3)2(η-C2H4)] and the diborane(4) compound 1,2-B2Cl2(NMe2)2 is also described which results in B–B bond oxidative addition yielding cis-[Pt(PPh3)2{BCl(NMe2)}2] and a complex to which this bis(boryl) subsequently rearranges, namely trans-[PtCl(PPh3)2{BCl(NMe2)}]. Both of these complexes were characterised by X-ray crystallography and have geometries typical of cis-bis(boryl) and trans-boryl chloride complexes respectively.