Synthesis and co-ordination chemistry of a new tripodal phosphine alcohol

Abstract

The tripodal phosphine alcohol CH₃C(CH₂PPh₂)₂(CH₂OH)(dpmp) was prepared and its co-ordination chemistry towards Group 6 metal carbonyls and a manganese(I) complex studied. In [M(CO)₄(dpmp-P,P′)](M = Cr, Mo or W), the tripodal ligand behaves as a bidentate ligand with the hydroxyl site unco-ordinated. Reaction of dpmp with [Mn(CO)₅Br] gave a stereoisomeric mixture of products, anti,fac-[Mn(CO)₃Br(dpmp-P,P′)]4a and syn,fac-[Mn(CO)₃Br(dpmp-P,P′)]4b Treatment of 4a or 4b with silver hexafluorophosphate yielded a facial complex fac-[Mn(CO)₃(dpmp-P,P′,O)]PF₆6. Complex 6 reacted with the anions X (X = Br, I, N₃ or SCN) stereospecifically to give syn,fac-[Mn(CO)₃X(dpmp-P,P′)],(X = Br 4b, I 5b, N₃8b or NCS 9b). X-Ray crystal structures of complexes 4b, 6 and 9b were determined. The crystal structure of complex 9b is the first of a manganese thiocyanate complex containing carbonyl ligands. Both the bond angles [Mn–N–C 170.4(5), N–C–S 175.0(6)°] and the distances [C–N 1.143(8), S–C 1.637(7)Å] of 9b clearly demonstrated the nature of the Mn–NCS bond, which is consistent with spectral data. Comparison of the co-ordination chemistry of dpmp with CH₃C(CH₂PPh₂)₂(CH₂OCH₃) is discussed.