Synthesis and characterisation of dialkyltin 2,3-bis(diphenylphosphino)maleic acid adducts

The novel dialkyltin 2,3-bis(diphenylphosphino)maleic acid adducts (R2Sn)(O,O′-dpmaa) [1a, R = Me; 1b, R = Bu; dpmaa = bis(diphenylphosphino)maleic acid] were synthesised from dpmaa and R2SnCl2 or Bu2SnO. They were fully characterised by elemental analysis, IR- and multinuclear NMR-spectroscopies as well as X-ray crystallography [in the case of 1a as its Ph2P(O)(CH2)2P(O)Ph2 adduct]. Both were found to be cyclic trimers in the solid state that dissolve in the case of 1b into an equilibrium mixture of oligomers.