Chemistry of di-and tri-metal complexes with bridging carbene or carbyne ligands. Part 37. Methylene group transfer to carbon–metal multiple bonds; crystal structures of [TiW{µ-C(C<sub>6</sub>H<sub>4</sub>Me-4)Ch<sub>2</sub>}(µ-CO)(CO)(η-C<sub>5</sub>H<sub>5</sub>)<sub>3</sub>] and [PtW{µ-C(C<sub>6</sub>H<sub>4</sub>Me-4)CH<sub>2</sub>}(CO)<sub>2</sub>(PMe<sub>3</sub>)<sub>2</sub>(η-C<sub>5</sub>H<sub>5</sub>)]