Synthetic and spectroscopic studies of some new organophosphorus (111) and (v) compounds

Abstract

The acceptor properties of some halogenated organophosphorus (V) compounds towards chloride, pyridine, 2,2'-bipyridine and 1,10-phenanthroline have been investigated by means of 31p n.m.r. spectroscopy. It was found that C(_6)F(_5)PCl(_4) forms a six-coordinate anionic species C(_6)F(_5)PCl(_5)(^-) with R(_4)NCl which dissociates in solution. CCl(_3)PCl(_4) also show acceptor properties towards R(_4)NCl, but a stable adduct was only formed with Pr(_4)NCl in PhNO(_2), where no dissociation was observed. In CH(_2)Cl(_2), decomposition occurred in which CCl(_3)PCl(_2) was detected. In contrast, C(_2)Cl(_5)PCl(_4) only showed temporary formation of the adduct with Et(_4)NCl in CH(_2)Cl(_2), followed by decomposition, but it did not do so with R(_4)NCl (R=n-Pr, n-Bu or n-Pe) either in CH(_2)Cl(_2) or PhNO(_2), where only decomposition products were observed. As expected, the higher members of the series R(_4)PCl(_3) (R=C(_6)F(_5) or CCI(_3)) and (C(_6)F(_5))(_3)^PCl(_2) did not form adducts with R(_4)NCl, either in CH(_2)Cl(_2) or PhNO(_2). RPCl(_4) (R=C(_6)F(_5) or CCl(_3)) react with pyridine to give RPCl(_4).py, but no adduct was found with bidentate ligands (L). In contrast, the complexes [C(_2)Cl(_5)PCl(_3)L](^+)Cl(^-)were isolated. RPCl(_3)(^+)x(^-) (R=C(_6)F(_5) and CCl(_3); X=SbCl(_6) and BCl(_4)) also form adducts with L, giving six-coordinate cationic species [RPCl(_3)L](^+)X(^-) which exist in two isomeric forms in solution but only one isomer is dominant when the solid is isolated. The ionic compound [C(_6)F(_5)PBr(_3)][BBr(_4)] was isolated, but attempts to establish the chemical shift for the six-coordinate species with bidentate ligands L failed. Organophosphorus (111) halides (C(_6)F(_5)(_n)PCl(_3-n) (X=C1,Br, n=l, 2) and pseudohalides (C(_6)F(_5))(_n)PX(_3-n) (X=NCS, n=l;X=CN, n=2) show acceptor properties towards Y(^-) (Y=C1, Br, I and NCS) to form four-coordinate phosphoranides[(C(_6)F(_5))(_n)PX(_3-n)Y](^-), which all proved to be very unstable. Substitution reactions occurred with CN(^-) or NCS(^-) for (C(_6)F(_5))(_n)PX(_3-n) (X=C1, Br) and with CN(^-) for C(_6)F(_5)P(NCS)(_2). No acceptor properties were observed towards CI(^-), Br(^-), I(^-), CN(^-) or NCS(^-) ions for CCl(_3)PCl(_2) and (C(_6)F(_5)(_2)PNCS, whereas the compounds RP(NCS)(_2), (R=Me, Et or Ph) are thermally unstable and their Lewis acid behaviour could not be investigated. Substitution reactions occurred between AgNCS and RPCl(_3)(^+)x(^-) (R=Me or Ph, X=SbCl(_6); R=C(_6)F(_5), X=SbCl(_6) or BCl(_4)),giving [RPCl(_3-n)(NCS)(_n)](^+) (l<n<3), but with AgCN only MePCl(_3-n)(CN)(_n)(^+) (2<n<3) were detected in solution. Reaction of C(_6)F(_5)PCl(_3)(^+)x(^-) (X=SbCl(_6) or BCl(_4)) with LiN(_3) gave[C(_6)F(_5)PC1(_3-n)(N(_3)(_n)](^+)X(^-)) which were detected in solution only. In the C(_6)F(_5)PCl(_3)BCl(_4)/NCS(^-) , CN(^-) and N(_3)(^-) systems, substitution also occurred at the BC1(_4)(^-) anion, and the BC1(_4-n)Y(_n)(^-) species were detected in solution by means of (^11)B n.m.r. Decomposition occurred on addition of M(^+)NCS(^-) (M=Ag, Li or Et(_4)N) to RPCl(_4) or RPCl(_5)(^-) (R=Me, Ph or Et) solutions to give RPCl(_2), RPSCl(_2) and RPS(NCS)(_2), while substitution occurred with [C(_6)F(_5)PCl(_5)](^-) giving [C(_6)F(_5)PCl(_5-n)(NCS)(_n)](^-) (n = 1 and 2), followed by decomposition to C(_6)F(^5)PCl(_2), C9_6)F(_5)P-(NCS)(_2), C(_6)F(_5)PS(NCS)(_2) and C(_6)F(_5)PS(CN)(_2). Conversely, the cyano-derivatives RPCl(_5-n)(CN)(_n)(^-) (R=Et, l<n<5; R=C(_6)F(_5), l<n<4 and R=CCl(_3), l<n<3) were detected in solution and the complexes [Pr(_4)N][EtP(CN)(_5)], [R(_4)N][C(_6)F(_5)PCl(CN)(_4)] (R=Et or Pr) and [Pr(_4)N][CCl(_3)PCl(_5-n)(CN)(_n)] (n=2 and 3) were isolated .