The reactions of cis-PtCl2(PR3)2 (R = OPh, OMe) with 1 equiv. of lithium phosphoranide generated from a bis(naphth-1,8-diyl-8-oxy)phosphorane lead to the formation of cis-monophosphoranido complexes with high stereospecificity. The reaction of cis-PtCl2(PMe3)2 with 1 equiv. of the lithium phosphoranide afforded a trans-monophosphoranido complex, exclusively. Hitherto unknown trans-bis(phosphoranido)platinum(II) complexes were obtained as major products in the reactions of cis-PtCl2(PR3)2 (R = OPh, OMe, Me) with an excess of the lithium phosphoranide. The stereochemistry was confirmed by X-ray structural analysis of the bis(phosphoranido) complex bearing triphenyl phosphites. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)