An unusual reaction product from a 1,3-diborolene and tetracarbonylnickel. Structure of a bis(allyl)nickel complex

The bis(allyl)nickel complex (η³-3-vinyl-2,4,5,6-tetraethyl-1-oxa-2,6-diboracyclohexenyl)(η³-2,3,4,5,6-pentaethyl-1-oxa-2,6-diboracyclohexenyl)nickel(IV) is formed by initial insertion of CO from Ni(CO)₄ into the five-membered 1,3-diborolene I, to give a six-membered ring. Subsequent exchange of the CHCH₃ group of I for the oxygen atom of the inserted CO and migration of a hydrogen atom from the

group of one ring to that of the other results in formation of the bis1-oxa-2,6-diboracyclohexenyl]nickel, IV, having one vinyl and nine ethyl substituents. An X-ray structural analysis of IV shows the non-planarity of the C₃B₂O rings; the boron and oxygen atoms lie 0.4 and 0.7 Å, respectively, away from the best plane through the allyl carbon atoms. IV crystallizes in the space group P2₁/n with a = 9.065(2), b = 16.264(3), c = 10.187(2) Å, β = 104.28(1)°, and Z = 2.