SYNTHESES AND STRUCTURES OF [M(CO)5(B2H4.2P(CH3)3)] AND [M(CO)4(B2H4.2P(CH3)3)] (M = CR, MO, W)

Photochemical reactions of M(CO)6 (M = Cr, Mo, W) with B2H4.2P(CH3)3 (1) gave two types of new complexes: [M(CO)5-{B2H4.2P(CH3)3}) (2) (M = Cr, W) and [M(CO)4{B2H4.2P(CH3)3}] (3) (M = Cr, Mo, W). Structures of both types of complexes were characterized by spectroscopic measurements as well as X-ray structure analyses. B2H4.2P(CH3)3 acts as a unidentate ligand in 2, whereas it acts as a bidentate chelate in 3. Both 2 and 3 are the first examples of the coordination of 1 to metals other than d10 metals, and moreover complexes 2 are the first examples of complexes with a single M-H-B attachment between polyboranes and metals. Crystals of [Cr(CO)5{B2H4.2P(CH3)3}] (2a) belong to the monoclinic space group P2(1)/n, with a = 18.510 (4) angstrom, b = 10.669 (3) angstrom, c = 10.278 (2) angstrom, beta = 93.79 (3)-degrees, V = 2025.3 (9) angstrom3, Z = 4, and R(F(o)) = 0.079 for 2153 reflections with \F(o)\ greater-than-or-equal-to 3-sigma(F(o)). Those of [W(CO)5{B2H4.2P(CH3)3}] (2c) are isomorphous with 2a: a = 18.613 (3) angstrom, b = 10.581 (2) angstrom, c = 10.363 (3) angstrom, beta = 93.61 (2)-degrees, V = 2036.9 (7) angstrom3, Z = 4, and R(F(o)) = 0.048 for 1323 reflections with \F(o)\ greater-than-or-equal-to 3-sigma(F(o)). Crystals of [Cr(CO)4{B2H4.2P(CH3)3}] (3a) belong to the orthorhombic space group P2(1)nb, with a = 9.416 (1) angstrom, b = 21.068 (3) angstrom, c = 9.112 (1) angstrom, V = 1807.6 (4) angstrom3, Z = 4, and R(F(o)) = 0.051 for 1808 reflections with \F(o)\ greater-than-or-equal-to 3-sigma(F(o)). Those of [W(CO)4{B2-H4.2P(CH3)3}] (3c) are isomorphous with 3a: a = 9.425 (1) angstrom, b = 21.141 (5) angstrom, c = 9.177 (1) angstrom, V = 1828.6 (6) angstrom3, Z = 4, and R(F(o)) = 0.060 for 1666 reflections with \F(o)\ greater-than-or-equal-to 3-sigma(F(o)).