The first alkynethiolate derivatives of bis(substituted cyclopentadienyl)titanium(IV) and their role in the synthesis of heterobimetallic compounds. Crystal structures of [Ti(η5-C5H4SiMe3)2(SCCBut)2] and [(η5-C5H4SiMe3)(SCCBut)Ti(μ-η5∶κ-P-C5H4PPh2)(μ-SCCBut)Pt(C6F5)2] †