Organometallic chemistry of carbon-nitrogen multiple bonds. 3. Reaction of tris(triphenylphosphine)platinum(0) with dimethylmethyleniminium chloride. X-ray structures of the products [(Ph3P)PtCH2N(CH3)2CH2N(CH3)2(Cl)]Cl and cis-[(Ph3P)Pt[CHN(CH3)2]Cl2]