Reactions of (chloromethyl)platinum(II) derivatives with nucleophiles. Formation of (dimethylamino)carbene complexes using N,N,N ',N '-tetramethylmethanediamine as nucleophile and the X-ray crystal and molecular structures of cis- (Ph3P)Pt(CH2NMe3)Cl-2 , cis(C,P)- (Ph3P)Pt(CH2CH2C(O)NMe2)Cl , and trans(As,CH2)- (Ph3As)Pt(CHNMe2)(CH2NHMe2)Cl PF6