A multidentate phosphite ligand comprising a backbone which comprises a substituted or unsubstituted spirobiindane compound and at least two organophosphite groups chemically bonded to the backbone, wherein the organophosphite groups are alkyl phosphite groups or wherein the organophosphite groups are aryl phosphite groups, wherein the aryl moieties on the aryl phosphite groups are phenyl rings substituted with one or more C.sub.1-C.sub.4 alkyl groups; or which comprises a substituted or unsubstituted spirodifluorene compound and at least two organophosphite groups chemically bonded to the backbone.

A ligand which contains arsenic and has the formula (I): where n is 2 and the ligand is bidentate; each X is O or NH; and Ar.sup.1 and Ar.sup.2 may be the same or different and each is an aryl group, provided that each Ar.sup.1 group connected to the same As atom may be combined to form a single aryl group.

A bidentate phosphite ligand which comprises a backbone having an a,a,a,a-tetrahydrocarbyl-1,3-dioxolane-4,5-dimethanol structure in which the hydrogen atoms of the hydroxyl groups on the methanol substituents have each been replaced by a P(OR.sup.1).sub.2 group, where R.sup.1 is an aryl radical and wherein the 1,3-dioxolane ring in the ,,,-tetrahydrocarbyl-1,3-dioxolane-4,5-dimethanol backbone is optionally substituted at the 2-position with one or more alkyl groups. When combined with a transition metal, such as nickel, the ligand provides a catalyst complex useful in hydrocyanation and other reactions.

A ligand which contains arsenic and has the formula (I): where n is 2 and the ligand is bidentate; each X is O or NH; and Ar.sup.1 and Ar.sup.2 may be the same or different and each is an aryl group, provided that each Ar.sup.1 group connected to the same As atom may be combined to form a single aryl group.

The present invention relates to air stable, binary Ni(0)-olefin complexes and their use in organic synthesis.