Syntheses and structures of six and seven-coordinate diene complexes of molybdenum and tungsten(II). The crystal and molecular structures of [WBr 2(CO) 2(PMePh 2)(norbornadiene)] and [WBr 2(CO)(NCCHCH 2)(norbornadiene)]

• Published in: Journal of organometallic chemistry Vol. 592; no. 2; pp. 168 - 179
• Main Authors: Davidson, Jack L, Richtzenhein, Heiko, Thiebaut, Benedicte J.S, Landskron, Kai, Rosair, Georgina M
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.12.1999
• Subjects: Crystal structures; Norbornadiene; Seven coordination; Six coordination; Synthesis; Tungsten; Seven coordination; Crystal structures; Synthesis; Six coordination; Tungsten; Norbornadiene
• DOI: 10.1016/S0022-328X(99)00509-4
• ISSN: 0022-328X

Reactions of [WI 2(CO) 3(NCMe) 2] with norbornadiene (NBD) and 1,5-cycloctadiene (COD) give six-coordinate dicarbonyls [WI 2(CO) 2(NBD)] and [WI 2(CO) 2(COD)], respectively. The related dibromo complex [WBr 2(CO) 2(NBD)] reacts with tertiary phosphines L to give unstable seven-coordinate adducts [WBr 2(CO) 2(L)(NBD)] (L=PPh 3, PMePh 2, PEt 3), which in the case of L=PMePh 2 was shown to undergo CO loss to give the six-coordinate derivative [WBr 2(CO)(PMePh 2)(NBD)]. X-ray diffraction studies of [WBr 2(CO) 2(PMePh 2)(NBD)] reveal a seven-coordinate structure (distorted pentagonal bipyramid) with the diene CC bonds on the pentagonal plane lying approximately parallel to the WCO axes. Reactions of [WBr 2(CO) 2(NBD)] with organonitriles NCR at room temperature afford CO substitution products (R=Me, Pr i , Ph, C 6H 4Me-4, CHCH 2) directly with no evidence for seven-coordinate intermediates. [WBr 2(CO) 2(COD)] and acetonitrile similarly give [WBr 2(CO)(NCMe)(COD)]. X-ray diffraction studies of [WBr 2(CO)(NCCHCH 2)(NBD)] confirmed a distorted octahedral structure where the carbonyl lies trans to the acrylonitrile ligand.