Ring slippage in indenyl derivatives of molybdenum and tungsten

Ring slippage of the indenyl occurs upon dissolution of the complexes [eta(5)-IndM(CO)(2)L(2)]BF4 (M = Mo or W; L = NCMe or dimethylformamide) in an excess of L, to give [(eta(3)-Ind)M(CO)(2)L(3)]BF4. Other ring-slipped complexes synthesized are [(eta(3)-Ind)Mo(CO)(2)L(3)]BF4 (L(3) = HC(pz)(3), [HB(pz)(3)](-), Me(3)tacn or {en(NCMe)}). Addition of NCMe or an excess of L failed to give ring slippage in [eta(5)-IndMo(CO)(2)L(2)]BF4 (L(2) = bipy, dppe, (PMe(3))(2), {P(OMe)(3)}(2) or triphos). NMR and X-ray studies reveal a large folding of the eta(3)-indenyl ring. The structure complex [(eta(3)-Ind)W(CO)(2)(NCMe)(3)]BF4 (5) was determined by X-ray analysis.