Formation of (diphenylphosphino)naphthalenes by double insertion of (alkynyl)diphenylphosphines into nickel(0)-benzyne complexes

(Alkynyl)diphenylphosphines Ph2PC=CR (R = H, Me, Ph, PPh2) undergo double insertion into the nickel(0)-benzyne bond of the complexes [Ni{(1,2-eta)-4,5-X2C6H2}(PEt3)(2)] (X = H (1a), F (1b)) to give mixtures of nickel(0) complexes containing (diphenylphosphino)-naphthalenes, which in some cases are formed with high regioselectivity. Bromination of the mixtures of nickel(0) complexes obtained from Ph2PC=CR (R = Me, Ph) and 1a or 1b gives in high yield the chelate NiBr2 complexes [NiBr2{6,7-X2C10H2-1,4-Y-2-2,3-(PPh2)(2)}] (X = H, Y = Me (6a), Ph (11a); X = F, Y = Me (6b), Ph (11b)), from which the corresponding 1,4-disubstituted 2,3-naphthylenebis(diphenylphosphines) 12a, 13a, 12b, and 13b can be liberated by treatment with NaCN in DMSO at 60 degrees C or dimethylglyoxime/ammonia at room temperature. Derivatives in which only one of the phosphorus atoms is oxidized, 6,7-X2C10H2-,1,4-Me-2-2-PPh2-3-P(O)PPh2 (X = H (15a), F (15b)), have also been prepared. The regioselectivity of the reactions of Ph2PC=CH with 1b is poorer than that of Ph2PC=CR (R = Me, Ph), and products with a 1,3-substitution pattern predominate. Reaction of Ph2PC=CPPh2 (dppa) with 1a gives, after addition of bromine, a pair of isomers in which NiBr2 is attached to the phosphorus atoms at the 2,3- and 1,2-positions, respectively, of the tetrakis(tertiary phosphine) species C10H4-1,2,3,4-(PPh2)(4) (19). The molecular structures of complexes 11b and [NiBr2{C10H4-1,2,3-(PPh2)(3)-4-{P(O)Ph-2}-kappa P-1,P-2}] (18), and of a disordered 73:27 mixture of the bis(diphenylphosphine oxides) C10H4-1,4-(PPh2)(2)-2,3{P(O)Ph-2}(2) (20) and C10H4-1,2-(PPh2)(2)-3,4-{P(O)Ph-2}(2) (21) obtained by partial oxidation of 19, have been determined by single-crystal X-ray diffraction. The regioselectivities of the insertions of Ph2PC=CMe and Ph2PC=CH into 1a and 1b are similar to those of MeC=CCO2Me and HC=CCO2Me, respectively, and factors that influence them are discussed.