Journal of Chemical Crystallography, Vol. 33, Nos. 5/6, June 2003 ( C  2003) Caged phosphite complexes of copper(I) halides Jenine R. Cole, (1) Megan E. Dellinger, (1) T. Jason Johnson, (1) Bryn A. Reinecke, (1) Robert D. Pike, (1)∗ William T. Pennington, (2) Mariusz Krawiec, (2) and Arnold L. Rheingold (3) Received August 2, 2002 The coordination chemistry of the caged phosphites 4-methyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2]octane (MeCage) and 4-nitro-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane (NO 2 Cage) with copper(I) halides is reported. Reactions of CuX = CuCl, CuBr, and CuI with the phosphite ligands afford complexes of the type [CuX(MeCage)] 4 , [CuX(NO 2 Cage)] 4 , [CuX(MeCage) 2 ] 2 , [CuX(NO 2 Cage) 2 ] 2 , and [CuX(MeCage) 3 ]. Recrystallization of [CuBr(NO 2 Cage) 2 ] 2 in MeCN produced [CuBr(NO 2 Cage)(NCMe)] 2 . Three X-ray crystal structures are reported: [CuCl(MeCage)] 4 ( I − 4, a = 13.4292(5) ˚ A, b = 13.4292(5) ˚ A, c = 9.4641(5) ˚ A, V = 1706.79(13) ˚ A 3 , Z = 2), [CuBr(MeCage) 2 ] 2 ( I 4 1 /a, a = 19.5751(17) ˚ A, b = 19.5751(17) ˚ A, c = 16.4513(15) ˚ A, V = 6303.9(10) ˚ A 3 , Z = 8), and [CuBr(NO 2 Cage)(NCMe)] 2 ( P 2 1 /c, a = 9.0506(4) ˚ A, b = 15.2428(7) ˚ A, c = 8.8673(4) ˚ A, β = 109.7640(10) ◦ , V = 1151.24(9) ˚ A 3 , Z = 2). KEY WORDS: Copper(I); halide; phosphite; cubane; tetramer; dimer. Introduction The caged phosphite 4-methyl-2,6,7-trioxa- 1-phosphabicyclo[2.2.2]octane (MeCage) has been known for over 40 years. 1 However, it has found surprisingly limited use as a ligand in coor- dination chemistry. 2 The ligand is of interest as a result of its combination of strong π -acceptor na- ture (exceeding that of P(OPh) 3 ) and its very small cone angle of 101 ◦ . 3 An analogous ligand, 4- nitro-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane (NO 2 Cage), which has been virtually unstudied (1) Department of Chemistry, College of William and Mary, Williamsburg, Virginia 23187. (2) Department of Chemistry, Clemson University, Clemson, South Carolina. (3) Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware. ∗ To whom correspondence should be addressed. E-mail: rdpike@wm.edu to date, 4 should prove to be an even stronger π -acceptor than MeCage due to inductive electron-withdrawal by the nitro group. The foregoing combination of electronic and steric characteristics should make the caged phos- phites excellent ligands for the soft copper(I) ion. A previous study has shown that excess MeCage reacts with CuY 2 (Y = NO 3 , ClO 4 ) in acetonitrile solution to reduce the copper, pro- ducing [Cu(MeCage) 4 ]Y. 5 Solutions of the latter species proved to be conductive; however, no 341 1074-1542/03/0600-0341/0 C  2003 Plenum Publishing Corporation