PURPOSE: To prepare the subject compound useful as a raw material for various homogeneous platinum catalysts and as an additive for silicone resins in high pulity and yield by adding platinous chloride to benzonitrile, thermally reacting the compounds with each other, hot-filtering the reaction solution, cooling the filtrate to crystallize the reaction product, and subsequently filtering the resultant crystals.

CONSTITUTION: Benzonitrile is reacted with platinous chloride at 100°C in a hot water bath to make into solution. The solution is filtered at 90-100°C and the filtrate is cooled to a temperature of -10-5°C for ≥2hr to produce crystals. The crystals are filtered and washed with petroleum ether at approximately 5°C to provide the objective compound.