Polyhedron Vol. 7, No. 1, pp. 5741.1988 Printed in Great Britain 0277-5387/88 $3.W + .OO 0 I988 E’eqanton Jcumals Ltd zyxwvuts X-RAY CRYSTAL STRUCTURE OF 2,3,7,8,12,13,17,1& OCT~~LPORP~~ATOPLAT~~I) (PtOEP): POTENTIAL FOR CORRELATION OF MESO-CARBON BOND-ANGLE @,,J WITH ONE-BOND 13C~Eso-1H~ETHINE COUPLING CONSTANT IN SOME DIAMAGNETIC METAL COMPLEXES OF OEP LIONEL R. ~GROM* School of Inorganic and Physical Chemistry, Kingston Polytechnic, Penrhyn Road, Kingston-upon-Thames KTl 2EE, U.K. and RICHARD N. SHEPPARD, ALEXANDRA M. Z. SLAWIN and DAVID J. WILLIAMS Department of Chemistry, Imperial College of Science and Technology, Exhibition Road, London SW7 2AZ, U.K. (Received 7 April 1987 ; accepted 24 July 1987) Abstract-The X-ray crystal structure of the title compound is reported. Crystals of PtOEP are triclinic, a = 8.165(l), b = 10.042(2), c = 10.069(2) A, a = 84.42(2), j? = 81.02(l), y = 67.05(l)“, space group PI, 2 = 1. The structure was refined on 2009 independent reflections to R = 0.018. Compa~sons of c~s~lo~aphically-dete~in~ C,-C,,,,,-C0 bond angle (&) of PtOEP and other diamagnetic metalloporphyrins, with the one-bond 13Cmeso-tHmethine coupling constant (‘J) indicate a possible inverse relationship provided the macrocycle remains planar. For Ag(III)OEP+CLO; and H40EP2+, an increase in ‘J, by about 10 Hz, is attributed to delocalization of central positive charge onto the porphyrin meso-carbons, via the porphyrin a-system. The consequences this may have for the bio- logical f~ctioning of haemoproteins are discussed. NMR spectroscopy has proved invaluable in the study of porphyrins and metalloporphyrins.’ Recently, we described the use of proton-coupled “C-NMR in elucidating “through-space” intra- molecular interactions in dihydroxo-5,10,15,20-tet- traphenylporphyrinatotin(IV).’ Also, measurement of the 13C -*Hmethine meso one-bond coupling constant (‘J) in 2,3,7,8,17,18-octaethylpo~hy~natoplati- num(I1) (PtOEP)3 raised the question whether ‘J might correlate with the C,C,,,,,--C,(&) bond angle in this and other metalloOEPs. In order to investigate this, we have determined the X-ray crystal structure of PtOEP and ‘J coupling constants for other diamagnetic metalloOEPs. We report this data here. *Author to whom correspondence should be addressed. EXPERIMENTAL X-ray studies PtOEP was prepared and purified by literature methods. 3,4 Bright orange-red crystals, suitable for X-ray crystallography, were grown by slow evap- oration of a dilute ethanol solution of PtOEP. Crystal data. C36H44N4Pt, triclinic, u = 8.165(l), b = 10.042(2), c = 10.069(2) A, o! = 84.42(2), j? = 81.02(l), y = 67.05(l)“, U = 750 A3, space group Pi, 2 = 1, M = 727.8, D, = 1.62 g cm- 3, ~(CU-K,) = 90 cm- ‘, F(OO0) = 366. Measurements. Refined unit cell parameters were obtained by centring 20 reflections on a Nicolet R3m diffractometer. Using the w-scan measuring routine, 2009 independent reflections (6 < 58”) were measured with Cu-K, radiation (graphite mono- chromator), all of which had IF01 > a(jF& and were 57