SUBSTITUTION OF CHLORIDE IN [PTCL2(PET(3))(2)] BY THE CHIRAL ANIONIC LIGAND [MO(CO)(5)(PPHH)](-) TO GIVE MIXED PLATINUM-MOLYBDENUM COMPOUNDS AND A P-31(H-1) NMR ANALYSIS OF THEIR FLUXIONALITY - X-RAY CRYSTAL-STRUCTURE OF [PTCL(PET(3))(2)(MU-PPHH)(MO(CO)(5))] AND TRANS-[PT(PET(3))(2)(MU-PPH)(2)(MO(CO)(5))(2)]

Deprotonation of the primary phosphine complex [Mo(CO)(5)(PPhH(2))] ge nerated [Mo(CO)(5)(PPhH)](-), a chiral anionic ligand which reacted re adily with cis- or trans-[PtCl2(PEt(3))(2)] via facile nucleophilic su bstitution of one or both chloride ligands to afford trans-[PtCl(PEt(3 ))(2)(mu-PPhH){Mo(CO)(5)}] (1) and cis- and trans-[Pt(PEt(3))(2)(mu-PP hH)(2){MO(CO)(5)}(2)] (2), respectively. These are rare examples of he terometallic complexes containing primary phosphido bridges, Compound 1 can be described either as the square-planar Pt-II complex with the anionic ligand PPhH{Mo(CO)(5)}(-) or as the Pt-Mo phosphido-bridged di mer trans- [PtCl(PEt(3))(2)(mu-PPhH){Mo(CO)(5)}]. As a phosphido-bridg ed heterobimetallic 1 possesses an exceptionally large Pt-P-Mo angle [ 120.9(1)degrees] reflecting the long Pt-Mo nonbonding interaction (4.5 Angstrom). Compound 2 can correspondingly be described either as a ph osphido-bridged PtMo2 trimer or a square-planar arrangement of two neu tral PEt(3) and two anionic PPhH {Mo(CO)(5)} ligands at Pt. The low-te mperature P-31{H-1} NMR spectrum of 1 showed several ABXY spin systems together with their associated ABXYM (M = Pt-195) counterparts and va riable-temperature studies revealed the dynamic interconversion of sev eral rotametric isomers arising from restricted relation about the Pt- P mu bond. The P-31{H-1} NMR spectrum of trans-2 shows its two possibl e RR/SS and meso diastereoisomers, the latter existing in clearly iden tifiable rotameric forms which interconvert slowly at -75 degrees C. W e note very different values between (2)J(P-P) and (1)J(Pt-195-P) for th, anionic ligands [PPhH{Mo(CO)(5)}](-) and PEt(3), unattributable to bond length variation but which must reflect reduced s-orbital contri bution to the Pt-P bond of the anionic phosphines PPhH {Mo(CO)(5)}. (C ) 1997 Elsevier Science Ltd.