A comparison of the ligating properties of the mixed P/O- and P/S-donor ligands Ph2P(CH2)2O(CH2)2O(CH2)2PPh2 and Ph2P(CH2)2S(CH2)2S(CH2)2PPh2 with Group 6 and 7 carbonyls

[M(CO)4(nbd)] (M=Cr or Mo) react with L1 (Ph2P(CH2)2O(CH2)2O(CH2)2PPh2) to give the trans-[Cr(CO)4(L1)] and cis-[Mo(CO)4(L1)] respectively, both of which show coordination of L1 through the P atoms only, giving 11-membered ring metallocyclic complexes. The crystal structure of [Mo(CO)4(L1)] confirms the cis-geometry of the product. The cis-[W(CO)4(L1)] is obtained similarly from [W(CO)4(TMPA)]. Prolonged reaction of [MnCl(CO)5] with L1 affords mer-trans-[MnCl(CO)3(L1)], with L1 functioning as a trans chelate via the phosphine functions. The kinetic product fac-[MnCl(CO)3(L1)] is obtained when short reaction times are used. In contrast, [ReBr(CO)5] reacts with L1 to give [ReBr(CO)3(L1)] as a mixture of geometric isomers. Both 1:1 and 2:1 M:L2 (L2=Ph2P(CH2)2S(CH2)2S(CH2)2PPh2) may be obtained for M=Mn(I) or Mo(0). The [MnCl(CO)3(L2)] exists in solution as the fac isomer with L2 functioning as a bidentate P,S-donor ligand giving a five-membered chelate ring and with the remaining thioether and phosphine functions uncoordinated. Addition of a further equivalent of [MnCl(CO)5] affords the binuclear fac-[{MnCl(CO)3}2(μ2-L2)], with symmetrical P,S-chelation to each metal centre. Similar behaviour is seen for Mo, thus cis-[{Mo(CO)4}2(μ2-L2)] involves P,S-chelation to each Mo(0) ion. The related 1:1 species cis-[Mo(CO)4(L2)] exists as a mixture of two compounds each with bidentate L2 coordination, the P2-chelate (11-membered ring metallocycle) and P,S-coordinated (five-membered chelate ring) species. The new compounds are characterised by microanalyses, IR, 1H-, 13C{1H}-, 31P{1H}-, 55Mn-NMR spectroscopy and mass spectrometry as appropriate. The different ligating properties of the related compounds L1 and L2 are discussed.