REACTIONS OF THE ANIONIC PHENYLPHOSPHINIDENE CLUSTER [OS3-(MU-H)(MU)-PPH)(CO)10]- AND ITS PHENYLPHOSPHIDO ISOMER [OS3-(MU-PHPH)(CO)10]- WITH ELECTROPHILES - CRYSTAL-STRUCTURES OF [OS3H(MU-PMEPH)(CO)10] AND [(OS3H(PPH)(CO)10)2HG]

Deprotonation of [Os3H(mu-PHPh)(CO)10] 3 gives the anion [Os3H(mu-PPh)(CO)10]- 4 containing a nucleophilic phosphorus centre which reacts with H+ to regenerate cluster 3 with the Ph group exo to the Os(CO)4 group as in the starting material. However, Mel reacts with anion 4 at the most accessible side of the mu-PPh ligand to give [Os3H(mu-PMePh)(CO)10] 6 (X-ray structure reported) which has the Ph group endo and the Me group exo to the Os(CO)4 group. Anion 4 reacts with [AuCl(PMe2Ph)] to give [Os3H(mu-PhPAuPMe2Ph)(CO)10] 8 (Ph probably endo) but the thermally generated isomer of 4, [Os3(mu-PHPh)(CO)10]- 5, reacts by the attack of gold at osmium atoms to give [Os3(mu-AuPMe2Ph)(mu-PHPh)(CO)10] 9 (Ph probably endo) which is isometric with 8. Compounds with P-Hg bonds are formed by the reaction of 4 with [HgCl(R)] (R = Et, PhCH2 or ferrocenyl) or with HgX2 (X = Cl, Br or l). The X-ray structure of the Hg-bridged product, [{Os3H(PPh)(CO)10}2Hg], formed from anion 4 and HgX2 or [Fe(C5H5)(C5H4HgCl)], is described. Although the co-ordination of the Hg atom is closely linear [P-Hg-P 171.8(2)-degrees], there are fairly close approaches of O atoms of axial CO ligands to this atom (Hg ... O 2.88 and 2.85 angstrom). The conformations of the two-mu-3-PPh groups are different.