1. Field of the Invention
The present invention relates to novel platinum/olefin complexes, and, more especially, to platinum/alkenylcyclohexene complexes useful as hydrosilylation catalysts, to the preparation thereof and to organopolysiloxane compositions comprising such catalytic complexes.
2. Description of the Prior Art
Numerous platinum compounds and complexes have to date been proposed to this art for promoting the addition reaction of an organohydropolysiloxane containing .tbd.SiH groups to a diorganopolysiloxane containing hydrocarbon radicals which are alkylenically unsaturated, to form an addition product comprising an added silicon-carbon bond.
This addition reaction can be expressed schematically as follows: ##STR2##
One of the first such catalysts was chloroplatinic acid, as described in U.S. Pat. No. 2,823,218, or platinum metal arranged on a finely divided carrier, as described in U.S. Pat. No. 2,970,150.
In U.S. Pat. Nos. 3,159,601 and 3,159,602, platinum/ olefin complexes were proposed with a view to reducing the disadvantages inherent in the use of finely divided platinum or of chloroplatinic acid, said disadvantages relating to the poisoning of the catalyst and to its excessively low reactivity. In U.S. Pat. No. 3,220,972, the reaction products of platinum derivatives with alcohols, aldehydes and ethers were also proposed as a catalyst for the same purpose.
More recently, complexes of platinum and vinylsiloxane, which have been treated with a base and in which the ratio of halogen to platinum is between 0, or a decimal number close to 0, and approximately 1, have been proposed. See U.S. Pat. Nos. 3,715,334, 3,775,432 and 3,814,730.
European Pat. No. 57,459 describes platinum/styrene complexes which have been treated with a base and in which the ratio of halogen to platinum (calculated in gram-atoms of platinum and of halogen) is greater than 1, but less than 4.
The platinum complexes described above have admittedly enabled advances in the state of the art, but they have at least one of the following disadvantages:
(1) they are unstable and display low catalytic activity after a relatively short storage time, on the order of 1 month or less;
(2) they display insufficient activity at low concentrations; and
(3) they, especially those described in said '459 European patent, are particularly difficult to produce in a simple and reproducible manner.