A composition contains (A) a hydrosilylation reaction catalyst and (B) an aliphatically unsaturated compound having an average, per molecule, of one or more aliphatically unsaturated organic groups capable of undergoing hydrosilylation reaction. The composition is capable of reacting via hydrosilylation reaction to form a reaction product, such as a silane, a gum, a gel, a rubber, or a resin. Ingredient (A) contains a metal-ligand complex that can be prepared by a method including reacting a metal precursor and a ligand.

The purpose of the present invention is to provide a branched organopolysiloxane that has excellent compatibility with polar oils and the like and that can serve as a substitute for conventional low-molecular-weight siloxanes. Furthermore provided is a production method with which the branched organopolysiloxane is easily obtained at high purity.

A branched organopolysiloxane represented by formula (1)

##STR00001##

(in the formula, R.sup.1 is independently a C1-3 alkyl group, R.sup.2 independently represent a C2 or C3 alkyl group, R.sup.3 independently represent a C1-3 alkyl group, n is 1 or 2, and m is an integer of 0-3 when n=1 but is 0 or 1 when n=2; additionally, the bonding order of the siloxane units is not limited to the above, and the bonding state of the siloxane units may be block or random).

Provided is a fluorene compound having a sulfonic acid ester structure and an allyl group, the compound being represented by formula (1).

##STR00001##

(In the formula, R.sup.1 each independently are a hydrogen atom or a methyl group. R.sup.2 each independently are a C1-20 hydrocarbyl group, some or all of the hydrogen atoms of which may be substituted by a halogen atom, a nitro group, or a cyano group, and an ester bond or an ether bond may be present between the carbon-carbon bonds thereof.)