Reactions of homoleptic (alkyl isocyanide)molybdenum(II) cations [Mo(CNR)7]2+ with 2,2'-bipyridine and related ligands (N-N). Substitution chemistry and dealkylation to form cyano-bridged complexes of the type [{Mo(CNCMe3)4(N-N)}2(.mu.-CN)](PF6)3